Science.gov

Sample records for 5-to-25 element tuned

  1. RF tuning element

    NASA Technical Reports Server (NTRS)

    McGrath, William R. (Inventor); Lubecke, Victor M. (Inventor)

    1992-01-01

    A device for tuning a circuit includes a substrate, a transmission line on the substrate that includes first and second conductors coupled to a circuit to be tuned, and a movable short-circuit for varying the impedance the transmission line presents to the circuit to be tuned. The movable short-circuit includes a dielectric layer disposed atop the transmission line and a distributed shorting element in the form of a conductive member that is configured to be slid along at least a portion of the transmission line atop the dielectric layer. The conductive member is configured to span the first and second conductors of the transmission line and to define at least a first opening that spans the two conductors so that the conductive member includes first and second sections separated by the first opening. The first and second sections of the conductive member combine with the first and second conductors of the transmission line to form first and second low impedance sections of transmission line, and the opening combines with the first and second conductors of the transmission line and the dielectric layer to form a first high impedance section of transmission line intermediate the first and second low impedance sections. Each of the first low impedance section and the first high impedance section have a length along the transmission line of approximately one-quarter wavelength, thus providing a periodic variation of transmission line impedance. That enhances reflection of rf power.

  2. Phased waveguide array with fixed tuning elements

    SciTech Connect

    Motley, R.W.; Bernabei, S.; Hooke, W.M.; Paoloni, F.J.

    1980-04-01

    The waveguide grill excites both penetrating lower hybrid waves and surface plasma waves. Quarter wavelength tuning elements attached to the sides of a twin waveguide are shown to reduce the surface wave component by a factor of approx. 3..

  3. A single-element tuning fork piezoelectric linear actuator.

    PubMed

    Friend, James R; Satonobu, Jun; Nakamura, Kentaro; Ueha, Sadayuki; Stutts, Daniel S

    2003-02-01

    This paper describes the design of a piezoelectric tuning-fork, dual-mode motor. The motor uses a single multilayer piezoelectric element in combination with tuning fork and shearing motion to form an actuator using a single drive signal. Finite-element analysis was used in the design of the motor, and the process is described along with the selection of the device's materials and its performance. Swaging was used to mount the multilayer piezoelectric element within the stator. Prototypes of the 25-mm long bidirectional actuator achieved a maximum linear no-load speed of 16.5 cm/s, a maximum linear force of 1.86 N, and maximum efficiency of 18.9%.

  4. Tuning the mechanical behaviour of structural elements by electric fields

    NASA Astrophysics Data System (ADS)

    Di Lillo, Luigi; Raither, Wolfram; Bergamini, Andrea; Zündel, Manuel; Ermanni, Paolo

    2013-06-01

    This work reports on the adoption of electric fields to tune the mechanical behaviour of structural elements. A mechanical characterization procedure, consisting of double lap joint and 3-point bending tests, is conducted on copper-polyimide laminates while applying electric fields of varying intensity. Field dependence and, thus, adaptability of shear strength and bending stiffness are shown as a function of the overlapping length and interfaces number, respectively. Further, the impact of remaining charges is investigated in both testing configurations. The findings herein lay the foundation for the implementation of electro-adaptive components in structural applications.

  5. Design of fast tuning elements for the ITER ICH system

    SciTech Connect

    Swain, D.W.; Goulding, R.H.

    1996-05-01

    The coupling between the ion cyclotron (IC) antenna and the ITER plasma (as expressed by the load resistance the antenna sees) will experience relatively fast variations due to plasma edge profile modifications. If uncompensated, these will cause an increase in the amount of power reflected back to the transmitter and ultimately a decrease in the amount of radio frequency (rf) power to the plasma caused by protective suppression of the amount of rf power generated by the transmitter. The goals of this task were to study several alternate designs for a tuning and matching (T&M) system and to recommend some research and development (R&D) tasks that could be carried out to test some of the most promising concepts. Analyses of five different T&M configurations are presented in this report. They each have different advantages and disadvantages, and the choice among them must be made depending on the requirements for the IC system. Several general conclusions emerge from our study: The use of a hybrid splitter as a passive reflected-power dump [``edge localized mode (ELM)-dump``] appears very promising; this configuration will protect the rf power sources from reflected power during changes in plasma loading due to plasma motion or profile changes (e.g., ELM- induced changes in the plasma scrape-off region) and requires no active control of the rf system. Trade-offs between simplicity of design and capability of the system must be made. Simple system designs with few components near the antenna either have high voltages over considerable distances of transmission lines, or they are not easily tuned to operate at different frequencies. Designs using frequency shifts and/or fast tuning elements can provide fast matching over a wide range of plasma loading; however, the designs studied here require components near the antenna, complicating assembly and maintenance. Capacitor-tuned resonant systems may offer a good compromise.

  6. Finite Element Analysis of Electrically Excited Quartz Tuning Fork Devices

    PubMed Central

    Oria, Roger; Otero, Jorge; González, Laura; Botaya, Luis; Carmona, Manuel; Puig-Vidal, Manel

    2013-01-01

    Quartz Tuning Fork (QTF)-based Scanning Probe Microscopy (SPM) is an important field of research. A suitable model for the QTF is important to obtain quantitative measurements with these devices. Analytical models have the limitation of being based on the double cantilever configuration. In this paper, we present an electromechanical finite element model of the QTF electrically excited with two free prongs. The model goes beyond the state-of-the-art of numerical simulations currently found in the literature for this QTF configuration. We present the first numerical analysis of both the electrical and mechanical behavior of QTF devices. Experimental measurements obtained with 10 units of the same model of QTF validate the finite element model with a good agreement. PMID:23722828

  7. An adjustable RF tuning element for microwave, millimeter wave, and submillimeter wave integrated circuits

    NASA Technical Reports Server (NTRS)

    Lubecke, Victor M.; Mcgrath, William R.; Rutledge, David B.

    1991-01-01

    Planar RF circuits are used in a wide range of applications from 1 GHz to 300 GHz, including radar, communications, commercial RF test instruments, and remote sensing radiometers. These circuits, however, provide only fixed tuning elements. This lack of adjustability puts severe demands on circuit design procedures and materials parameters. We have developed a novel tuning element which can be incorporated into the design of a planar circuit in order to allow active, post-fabrication tuning by varying the electrical length of a coplanar strip transmission line. It consists of a series of thin plates which can slide in unison along the transmission line, and the size and spacing of the plates are designed to provide a large reflection of RF power over a useful frequency bandwidth. Tests of this structure at 1 GHz to 3 Ghz showed that it produced a reflection coefficient greater than 0.90 over a 20 percent bandwidth. A 2 GHz circuit incorporating this tuning element was also tested to demonstrate practical tuning ranges. This structure can be fabricated for frequencies as high as 1000 GHz using existing micromachining techniques. Many commercial applications can benefit from this micromechanical RF tuning element, as it will aid in extending microwave integrated circuit technology into the high millimeter wave and submillimeter wave bands by easing constraints on circuit technology.

  8. The Temporal Tuning of the Drosophila Motion Detectors Is Determined by the Dynamics of Their Input Elements.

    PubMed

    Arenz, Alexander; Drews, Michael S; Richter, Florian G; Ammer, Georg; Borst, Alexander

    2017-04-03

    Detecting the direction of motion contained in the visual scene is crucial for many behaviors. However, because single photoreceptors only signal local luminance changes, motion detection requires a comparison of signals from neighboring photoreceptors across time in downstream neuronal circuits. For signals to coincide on readout neurons that thus become motion and direction selective, different input lines need to be delayed with respect to each other. Classical models of motion detection rely on non-linear interactions between two inputs after different temporal filtering. However, recent studies have suggested the requirement for at least three, not only two, input signals. Here, we comprehensively characterize the spatiotemporal response properties of all columnar input elements to the elementary motion detectors in the fruit fly, T4 and T5 cells, via two-photon calcium imaging. Between these input neurons, we find large differences in temporal dynamics. Based on this, computer simulations show that only a small subset of possible arrangements of these input elements maps onto a recently proposed algorithmic three-input model in a way that generates a highly direction-selective motion detector, suggesting plausible network architectures. Moreover, modulating the motion detection system by octopamine-receptor activation, we find the temporal tuning of T4 and T5 cells to be shifted toward higher frequencies, and this shift can be fully explained by the concomitant speeding of the input elements.

  9. Tuned electronic, optical and mechanical properties of pristine and hetero nanotubes of group IV elements (C, Si and Ge)

    NASA Astrophysics Data System (ADS)

    Chandel, Surjeet Kumar; Kumar, Arun; Sharma, Raman; Ahluwalia, P. K.

    2015-09-01

    Density functional theory has been used to investigate the structural, electronic, optical and mechanical properties of pristine nanotubes of carbon, silicon, germanium and their hetero nanotubes having armchair conformation with chirality (6,6). In the pristine nanotubes it is found that the cohesive energy per atom is more for CNT as compared to other nanotubes under investigation. However, in hetero systems under study its value is highest for SiCNT system and least for GeCNT. GeNT and SiGeNT have been observed to be more puckered in comparison to other systems. All the pristine and heteronanotubes in our study are found to be semiconducting in nature, except GeNT, which is found to be metallic in nature with a conductance of 2G0, indicating GeNT to be an ideal material for ballistic transport. Three different types of hetero nanotubes have wide band gap spectrum which opens up an arena for band gap selective engineered devices. The band gap for SiCNT and GeCNT lie in the visible region, while the band gap for other systems lie in the infrared region. The tuning of electronic band structure by means of compression, tensile strain and external electric field indicates that the band gap can be altered considerably. There is a band gap closure under both compression and expansion at a certain value in all the cases except SiCNT, revealing that its band gap can be varied considerably. The decreasing order of tensile strength is CNT > SiCNT > GeCNT > SiNT > GeNT > SiGeNT. The effective mass of holes decreases for pristine systems on the application of compression. Under no strain the effective mass of electrons is generally found to be larger than holes in hetero systems, while it is reverse in pristine systems. In case of unstrained systems, we generally observed that the more the effective mass of electron, the more is the band gap in the corresponding system. Electronic band structure and corresponding total and partial DOS for pristine and heteronanotubes. In the

  10. Beam tuning

    SciTech Connect

    Pardo, R.C.; Zinkann, G.P.

    1995-08-01

    A program for configuring the linac, based on previously run configurations for any desired beam was used during the past year. This program uses only a small number of empirical tunes to scale resonator fields to properly accelerate a beam with a different charge-to-mass (q/A) ratio from the original tune configuration. The program worked very well for the PII linac section where we can easily match a new beam`s arrival phase and velocity to the tuned value. It was also fairly successful for the Booster and ATLAS sections of the linac, but not as successful as for the PII linac. Most of the problems are associated with setting the beam arrival time correctly for each major linac section. This problem is being addressed with the development of the capacitive pickup beam phase monitor discussed above. During the next year we expect to improve our ability to quickly configure the linac for new beams and reduce the time required for linac tuning. Already the time required for linac tuning as a percentage of research hours has decreased from 22% in FY 1993 to 15% in the first quarter of FY 1995.

  11. A monochromator for tuning the photon energy range 600 eV and 6000 eV with a single dispersing optical element (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Jark, Werner H.

    2016-09-01

    Recently it was found that reflection gratings of standard quality, which can be used at lower energy soft X-rays with photon energies of the order of 300 eV, diffract also efficiently X-rays with photon energies of the order of 5 keV, when these gratings are operated at grazing angle of incidence in the extreme off-plane configuration [1]. Consequently a grating employed in the extreme off-plane configuration has the capability to provide monochromatic radiation in the photon energy range from below 1 keV to far above 2 keV, where one usually switches for the same purpose between the diffraction at surface structures and the diffraction in bulk structures. Such an operation scheme requires rather complex mechanical structures. The present study will show that the tuning of diffraction gratings in the conical diffraction configuration can cover the indicated and even more extended tuning ranges employing a rather simple mechanical structure. Infact such a grating can be mounted together with a plane mirror in a pseudo channel-cut crystal monochromator configuration, i.e. with almost parallel surfaces and with fixed gap between them. The photon energy is then tuned simply by varying the angle of grazing incidence onto the pair of optics. Like in a double crystal monochromator scheme the monochromatic beam will exit from the configuration parallel to the incident beam with in most cases negligibly varying displacement in the plane of incidence. The optical performance data will be discussed depending on the properties of some state-of-the-art synchrotron radiation sources. [1] W. Jark and D. Eichert, Opt. Express 23, 22753 (2015).

  12. Fine-tuning key parameters of an integrated reactor system for the simultaneous removal of COD, sulfate and ammonium and elemental sulfur reclamation.

    PubMed

    Yuan, Ye; Chen, Chuan; Liang, Bin; Huang, Cong; Zhao, Youkang; Xu, Xijun; Tan, Wenbo; Zhou, Xu; Gao, Shuang; Sun, Dezhi; Lee, Duujong; Zhou, Jizhong; Wang, Aijie

    2014-03-30

    In this paper, we proposed an integrated reactor system for simultaneous removal of COD, sulfate and ammonium (integrated C-S-N removal system) and investigated the key parameters of the system for a high level of elemental sulfur (S(0)) production. The system consisted of 4 main units: sulfate reduction and organic carbon removal (SR-CR), autotrophic and heterotrophic denitrifying sulfide removal (A&H-DSR), sulfur reclamation (SR), and aerated filter for aerobic nitrification (AN). In the system, the effects of key operational parameters on production of elemental sulfur were investigated, including hydraulic retention time (HRT) of each unit, sulfide/nitrate (S(2-)-S/NO3(-)-N) ratios, reflux ratios between the A&H-DSR and AN units, and loading rates of chemical oxygen demand (COD), sulfate and ammonium. Physico-chemical characteristics of biosulfur were studied for acquiring efficient S(0) recovery. The experiments successfully explored the optimum parameters for each unit and demonstrated 98% COD, 98% sulfate and 78% nitrogen removal efficiency. The optimum HRTs for SR-CR, A&H-DSR and AN were 12h, 3h and 3h, respectively. The reflux ratio of 3 could provide adequate S(2-)-S/NO3(-)-N ratio (approximately 1:1) to the A&H-DSR unit for obtaining maximum sulfur production. In this system, the maximum production of S(0) reached 90%, but only 60% S(0) was reclaimed from effluent. The S(0) that adhered to the outer layer of granules was deposited in the bottom of the A&H-DSR unit. Finally, the microbial community structure of the corresponding unit at different operational stage were analyzed by 16S rRNA gene based high throughput Illumina MiSeq sequencing and the potential function of dominant species were discussed.

  13. PERI auto-tuning.

    SciTech Connect

    Chame, J.; Chen, C.; Dongarra, J.; Hall, M.; Hollingsworth, J. K.; Hovland, P.; Moore, S.; Seymour, K.; Shin, J.; Tiwari, A.; Williams, S.; You, H.; Bailey, D. H.

    2008-01-01

    The enormous and growing complexity of today's high-end systems has increased the already significant challenges of obtaining high performance on equally complex scientific applications. Application scientists are faced with a daunting challenge in tuning their codes to exploit performance-enhancing architectural features. The Performance Engineering Research Institute (PERI) is working toward the goal of automating portions of the performance tuning process. This paper describes PERI's overall strategy for auto-tuning tools and recent progress in both building auto-tuning tools and demonstrating their success on kernels, some taken from large-scale applications.

  14. Tuning the engine

    PubMed Central

    2012-01-01

    In the last years post-transcriptional regulation (PTR) of gene expression has been increasingly recognized to be a powerful and general determinant of the quantitative changes in proteomes, and therefore a driving force for cell phenotypes. By means of networks of trans-factors on one hand, and cis-elements found primarily in untranslated regions (UTRs) of mRNA on the other hand, mRNA availability to translation and translation rates are tightly controlled and can be rapidly tuned according to the changing state of the cell. A number of dedicated resources and tools, including databases and predictive algorithms, have been proposed as bioinformatics aids for the study of this fundamental layer of gene expression regulation. Their use, however, is rendered difficult by heterogeneity and fragmentation. This review aims to locate these resources in their proper space, classifying them according to their goals, limitations and integration capabilities and, in the end, to provide the user with an initial toolbox for the bioinformatic analysis of post-transcriptional regulation of gene expression. The accompanying website, available at www.ptrguide.org, lists all resources, provides summary and features for each one and will be regularly updated in the future. PMID:22995832

  15. Tuning method for microresonators and microresonators made thereby

    DOEpatents

    Henry, Michael David; Olsson, Roy H.; Greth, Karl Douglas; Young, Travis Ryan; Nguyen, Janet; Stevens, James E.

    2015-12-01

    A micromechanical resonator is disclosed. The resonator includes a resonant micromechanical element. A film of annealable material can be deposited on a facial surface of the element. The resonance of the element can be tuned by annealing the deposited film. Also disclosed are methods of applying a film on a resonator and annealing the film, thereby tuning one or more resonant properties of the resonator.

  16. Tuned borehole gravity gradiometer

    SciTech Connect

    Lautzenhiser, T.V.; Nekut, A.G. Jr.

    1986-04-15

    A tuned borehole gravity gradiometer is described for detecting variations in gravity gradient which consists of: a suspended dipole mass system having symmetrically distributed dipole masses and suspension means for suspending the dipole masses such that the gravity gradient to be measured produces an angular displacement about a rotation axis of the dipole mass system from a reference position; and tuning means with the dipole mass system for selectively varying the sensitivity to angular displacements with respect to the rotation axis of the dipole mass system to variations in gravity gradient, wherein the tuning means includes means for selectively varying the metacentric height of the dipole mass system.

  17. TUNE: Compiler-Directed Automatic Performance Tuning

    SciTech Connect

    Hall, Mary

    2014-09-18

    This project has developed compiler-directed performance tuning technology targeting the Cray XT4 Jaguar system at Oak Ridge, which has multi-core Opteron nodes with SSE-3 SIMD extensions, and the Cray XE6 Hopper system at NERSC. To achieve this goal, we combined compiler technology for model-guided empirical optimization for memory hierarchies with SIMD code generation, which have been developed by the PIs over the past several years. We examined DOE Office of Science applications to identify performance bottlenecks and apply our system to computational kernels that operate on dense arrays. Our goal for this performance-tuning technology has been to yield hand-tuned levels of performance on DOE Office of Science computational kernels, while allowing application programmers to specify their computations at a high level without requiring manual optimization. Overall, we aim to make our technology for SIMD code generation and memory hierarchy optimization a crucial component of high-productivity Petaflops computing through a close collaboration with the scientists in national laboratories.

  18. Automatic Tuning of AN Aculight Optical Parametric Oscillator

    NASA Astrophysics Data System (ADS)

    Morrison, A. M.; Liang, T.; Douberly, G. E.

    2011-06-01

    We have automated the tuning of a continuous wave, singly resonant optical parametric oscillator (Lockheed-Martin Aculight ARGOS 2400-SF-15). This OPO is capable of producing >1 Watt of continuously tunable idler output between 2.3 and 3.9 μm. We will discuss a simple algorithm and its implementation that synchronizes the tuning of three separate OPO tuning elements, which allows for several hundred wavenumbers of efficient, automatic, continuous tuning. Continuous feedback from a wavemeter (Bristol Instruments 621A) limits the frequency resolution to ˜10 MHz.

  19. Structural Composites With Tuned EM Chirality

    DTIC Science & Technology

    2014-12-23

    AFRL-OSR-VA-TR-2015-0018 STRUCTURAL COMPOSITES WITH TUNED EM CHIRALITY Siavouche Nemat Nasser UNIVERSITY OF CALIFORNIA SAN DIEGO Final Report 12/23...REPORT Grant/Contract  Title:        STRUCTURAL  COMPOSITES  WITH  TUNED  EM   CHIRALITY     Grant  No.:  FA9550-­‐09-­‐1...structural   composites  with   tunable   chiral   elements   has   produced   some   impressive   results   in   the

  20. Magnetic tuning of electrically resonant metamaterial with inclusion of ferrite

    NASA Astrophysics Data System (ADS)

    Kang, Lei; Zhao, Qian; Zhao, Hongjie; Zhou, Ji

    2008-10-01

    We experimentally demonstrate a magnetic tuning of electrically resonant metamaterial (EMM) at microwave frequencies by introducing microwave ferrite rods into the periodic array of electrically resonant element. Different from those based on controlling the capacitance of equivalent LC circuit, this tunability arises from a mechanism of magnetically tuning the inductance of resonant element via the active ambient effective permeability. For magnetic fields from 0 to 5000 Oe, resonance frequency of the EMM can be continuously and reversibly tuned in a range of about 800 MHz. The active effective permittivity has also been investigated through the simulated scattering parameters.

  1. Complier-Directed Automatic Performance Tuning (TUNE) Final Report

    SciTech Connect

    Chame, Jacqueline

    2013-06-07

    TUNE was created to develop compiler-directed performance tuning technology targeting the Cray XT4 system at Oak Ridge. TUNE combines compiler technology for model-guided empirical optimization for memory hierarchies with SIMD code generation. The goal of this performance-tuning technology is to yield hand-tuned levels of performance on DOE Office of Science computational kernels, while allowing application programmers to specify their computations at a high level without requiring manual optimization. Overall, TUNE aims to make compiler technology for SIMD code generation and memory hierarchy optimization a crucial component of high-productivity Petaflops computing through a close collaboration with the scientists in national laboratories.

  2. Field flatness tuning of TM110 mode cavities with closely spaced modes

    SciTech Connect

    Leo Bellantoni et al.

    2003-10-31

    Superconducting cavities for the CKM RF separated kaon beamline at Fermilab have modes that are closely spaced compared to the resonance bandwidths when warm, and this complicates the field flatness (warm) tuning process. Additionally, it is necessary to maintain the azimuthal orientation of the mode during the tuning deformations. the authors present two analytic techniques to warm-tune cavities with overlapping modes, a finite-element analysis of the tuning process, the design of a warm tuner which maintains mode polarization, and the results of tuning a cavity in which initial manufacturing variations caused the desired {pi} and nearby {pi}-1 modes to be indistinguishable before field flatness tuning.

  3. Tuning the Blend

    ERIC Educational Resources Information Center

    Schaffhauser, Dian

    2012-01-01

    "Tuning the blend" is a phrase that educators hear a lot these days. It refers to finding the correct balance of online activities and face-to-face instruction in hybrid--or blended--courses. Finding a mix that meets the needs of both faculty and students requires experimentation, experience, and constant tweaking. And, as with coffee, the same…

  4. Electronically Tuned Microwave Oscillator

    NASA Technical Reports Server (NTRS)

    Lakshminarayana, Mysore

    1987-01-01

    Features include low phase noise and frequency stability. Bias-tuned, low-phase-noise microwave oscillator circuit based on npn bipolar transistor and dielectric resonator. Operating at frequency of about 8.4 GHz, oscillator adjusted to give low phase noise, relatively flat power output versus frequency, and nearly linear frequency versus bias voltage.

  5. Tuning toward Completion

    ERIC Educational Resources Information Center

    Kolb, Marcus; Kalina, Michelle; Chapman, Adina

    2013-01-01

    The Obama administration and the Lumina Foundation have been the principal drivers focusing the nation on increasing the number of high-quality degrees and credentials. Tuning, a faculty-driven process for defining clear student learning outcomes--what a student should know, understand, and be able to do--is one of the ways to support this goal.

  6. Active impedance metasurface with full 360° reflection phase tuning

    PubMed Central

    Zhu, Bo O.; Zhao, Junming; Feng, Yijun

    2013-01-01

    Impedance metasurface is composed of electrical small scatters in two dimensional plane, of which the surface impedance can be designed to produce desired reflection phase. Tunable reflection phase can be achieved by incorporating active element into the scatters, but the tuning range of the reflection phase is limited. In this paper, an active impedance metasurface with full 360° reflection phase control is presented to remove the phase tuning deficiency in conventional approach. The unit cell of the metasurface is a multiple resonance structure with two resonance poles and one resonance zero, capable of providing 360° reflection phase variation and active tuning within a finite frequency band. Linear reflection phase tuning can also be obtained. Theoretical analysis and simulation are presented and validated by experiment at microwave frequency. The proposed approach can be applied to many cases where fine and full phase tuning is needed, such as beam steering in reflectarray antennas. PMID:24162366

  7. Electronically tuned optical filters

    NASA Technical Reports Server (NTRS)

    Castellano, J. A.; Pasierb, E. F.; Oh, C. S.; Mccaffrey, M. T.

    1972-01-01

    A detailed account is given of efforts to develop a three layer, polychromic filter that can be tuned electronically. The operation of the filter is based on the cooperative alignment of pleochroic dye molecules by nematic liquid crystals activated by electric fields. This orientation produces changes in the optical density of the material and thus changes in the color of light transmitted through the medium. In addition, attempts to improve materials and devices which employ field induced changes of a cholesteric to a nematic liquid crystal are presented.

  8. Tuning Broadband Microwave Amplifiers

    SciTech Connect

    Alaniz, Gabriel

    2003-09-05

    The PEP-II/DA {Phi} NE/ALS longitudinal feedback systems are complex wide bandwidth systems requiring analog, digital and microwave circuits. The solid-state amplifier is one of the components in the microwave circuit that is required to suppress the coupled bunch instabilities that exist in the PEP-II accelerator. The suppression is achieved by using an antenna as a kicker structure that provides an electric field in order to increase or decrease the energy of particles passing through the structure. The amplifier is made up of sixteen 30 to 35W microstrip GaAs FET modules that are combined to obtain 500W over a bandwidth of 850MHz to 1850MHz. The amplifier malfunctioned causing a reduction in the functionality and power output of the individual GaAs FET modules. The amplifier must be repaired. After repair, the amplifier must be tuned to optimize the gain while maintaining proper power output. The amplifier is tuned using microstrip circuit techniques. A variety of microstrip methods are used to obtain the proper line impedance. The result is a working amplifier that operates efficiently.

  9. The dynamics and tuning of orchestral crotales

    NASA Astrophysics Data System (ADS)

    Deutsch, Bradley M.; Ramirez, Cherie L.; Moore, Thomas R.

    2004-10-01

    An experimental and theoretical investigation of the acoustic and vibrational properties of orchestral crotales within the range C6 to C8 is reported. Interferograms of the acoustically important modes of vibration are presented and the frequencies are reported. It is shown that the acoustic spectra of crotales are not predicted by assuming that they are either thin circular plates or annular plates clamped at the center, despite the physical resemblance to these objects. Results from finite element analysis are presented that demonstrate how changing the size of the central mass affects the tuning of the instruments, and it is concluded that crotales are not currently designed to ensure optimal tuning. The possibility of using annular plates as crotales is also investigated and the physical parameters for such a set of instruments are presented. .

  10. Tuning and scanning control system for high resolution alexandrite lasers

    NASA Technical Reports Server (NTRS)

    Smith, James C.; Schwemmer, Geary K.

    1988-01-01

    An alexandrite laser is spectrally narrowed and tuned by the use of three optical elements. Each element provides a successively higher degree of spectral resolution. The digitally controlled tuning and scanning control servo system simultaneously positions all three optical elements to provide continuous high resolution laser spectral tuning. The user may select manual, single, or continuous modes of automated scanning of ranges up to 3.00/cm and at scan rates up to 3.85/cm/min. Scanning over an extended range of up to 9.999/cm may be achieved if the highest resolution optic is removed from the system. The control system is also capable of being remotely operated by another computer or controller via standard RS-232 serial data link.

  11. Nanoplasmonics tuned "click chemistry".

    PubMed

    Tijunelyte, I; Guenin, E; Lidgi-Guigui, N; Colas, F; Ibrahim, J; Toury, T; Lamy de la Chapelle, M

    2016-04-07

    Nanoplasmonics is a growing field of optical condensed matter science dedicated to optical phenomena at the nanoscale level in metal systems. Extensive research on noble metallic nanoparticles (NPs) has emerged within the last two decades due to their ability to keep the optical energy concentrated in the vicinity of NPs, in particular, the ability to create optical near-field enhancement followed by heat generation. We have exploited these properties in order to induce a localised "click" reaction in the vicinity of gold nanostructures under unfavourable experimental conditions. We demonstrate that this reaction can be controlled by the plasmonic properties of the nanostructures and we propose two physical mechanisms to interpret the observed plasmonic tuning of the "click" chemistry.

  12. Nanoplasmonics tuned ``click chemistry''

    NASA Astrophysics Data System (ADS)

    Tijunelyte, I.; Guenin, E.; Lidgi-Guigui, N.; Colas, F.; Ibrahim, J.; Toury, T.; Lamy de La Chapelle, M.

    2016-03-01

    Nanoplasmonics is a growing field of optical condensed matter science dedicated to optical phenomena at the nanoscale level in metal systems. Extensive research on noble metallic nanoparticles (NPs) has emerged within the last two decades due to their ability to keep the optical energy concentrated in the vicinity of NPs, in particular, the ability to create optical near-field enhancement followed by heat generation. We have exploited these properties in order to induce a localised ``click'' reaction in the vicinity of gold nanostructures under unfavourable experimental conditions. We demonstrate that this reaction can be controlled by the plasmonic properties of the nanostructures and we propose two physical mechanisms to interpret the observed plasmonic tuning of the ``click'' chemistry.Nanoplasmonics is a growing field of optical condensed matter science dedicated to optical phenomena at the nanoscale level in metal systems. Extensive research on noble metallic nanoparticles (NPs) has emerged within the last two decades due to their ability to keep the optical energy concentrated in the vicinity of NPs, in particular, the ability to create optical near-field enhancement followed by heat generation. We have exploited these properties in order to induce a localised ``click'' reaction in the vicinity of gold nanostructures under unfavourable experimental conditions. We demonstrate that this reaction can be controlled by the plasmonic properties of the nanostructures and we propose two physical mechanisms to interpret the observed plasmonic tuning of the ``click'' chemistry. Electronic supplementary information (ESI) available: NMR study on reaction initiation, SERS spectra and temperature calculations. See DOI: 10.1039/c5nr09018k

  13. Differential Resonant Ring YIG Tuned Oscillator

    NASA Technical Reports Server (NTRS)

    Parrott, Ronald A.

    2010-01-01

    A differential SiGe oscillator circuit uses a resonant ring-oscillator topology in order to electronically tune the oscillator over multi-octave bandwidths. The oscillator s tuning is extremely linear, because the oscillator s frequency depends on the magnetic tuning of a YIG sphere, whose resonant frequency is equal to a fundamental constant times the DC magnetic field. This extremely simple circuit topology uses two coupling loops connecting a differential pair of SiGe bipolar transistors into a feedback configuration using a YIG tuned filter creating a closed-loop ring oscillator. SiGe device technology is used for this oscillator in order to keep the transistor s 1/f noise to an absolute minimum in order to achieve minimum RF phase noise. The single-end resonant ring oscillator currently has an advantage in fewer parts, but when the oscillation frequency is greater than 16 GHz, the package s parasitic behavior couples energy to the sphere and causes holes and poor phase noise performance. This is because the coupling to the YIG is extremely low, so that the oscillator operates at near the unloaded Q. With the differential resonant ring oscillator, the oscillation currents are just in the YIG coupling mechanisms. The phase noise is even better, and the physical size can be reduced to permit monolithic microwave integrated circuit oscillators. This invention is a YIG tuned oscillator circuit making use of a differential topology to simultaneously achieve an extremely broadband electronic tuning range and ultra-low phase noise. As a natural result of its differential circuit topology, all reactive elements, such as tuning stubs, which limit tuning bandwidth by contributing excessive open loop phase shift, have been eliminated. The differential oscillator s open-loop phase shift is associated with completely non-dispersive circuit elements such as the physical angle of the coupling loops, a differential loop crossover, and the high-frequency phase shift of the n

  14. Varactor tuned transistor oscillators /Survey/

    NASA Astrophysics Data System (ADS)

    Deriugin, I. A.; Kitaev, Iu. I.; Solodovnikov, N. P.

    1981-03-01

    Major developments in the theory and technology of varactor tuned solid state oscillators are surveyed on the basis of data appearing in periodical and patent literature. Attention is given to problems in general theory, modulation characteristics, transient processes occurring during tuning, stability properties, and circuit fabrication aspects.

  15. Plasmonic color tuning

    NASA Astrophysics Data System (ADS)

    Lee, Byoungho; Yun, Hansik; Lee, Seung-Yeol; Kim, Hwi

    2016-03-01

    In general, color filter is an optical component to permit the transmission of a specific color in cameras, displays, and microscopes. Each filter has its own unchangeable color because it is made by chemical materials such as dyes and pigments. Therefore, in order to express various colorful images in a display, one pixel should have three sub-pixels of red, green, and blue colors. Here, we suggest new plasmonic structure and method to change the color in a single pixel. It is comprised of a cavity and a metal nanoaperture. The optical cavity generally supports standing waves inside it, and various standing waves having different wavelength can be confined together in one cavity. On the other hand, although light cannot transmit sub-wavelength sized aperture, surface plasmons can propagate through the metal nanoaperture with high intensity due to the extraordinary transmission. If we combine the two structures, we can organize the spatial distribution of amplitudes according to wavelength of various standing waves using the cavity, and we can extract a light with specific wavelength and amplitude using the nanoaperture. Therefore, this cavity-aperture structure can simultaneously tune the color and intensity of the transmitted light through the single nanoaperture. We expect that the cavity-apertures have a potential for dynamic color pixels, micro-imaging system, and multiplexed sensors.

  16. Tuning of Pectin Methylesterification

    PubMed Central

    Sénéchal, Fabien; L'Enfant, Mélanie; Domon, Jean-Marc; Rosiau, Emeline; Crépeau, Marie-Jeanne; Surcouf, Ogier; Esquivel-Rodriguez, Juan; Marcelo, Paulo; Mareck, Alain; Guérineau, François; Kim, Hyung-Rae; Mravec, Jozef; Bonnin, Estelle; Jamet, Elisabeth; Kihara, Daisuke; Lerouge, Patrice; Ralet, Marie-Christine; Pelloux, Jérôme; Rayon, Catherine

    2015-01-01

    Pectin methylesterases (PMEs) catalyze the demethylesterification of homogalacturonan domains of pectin in plant cell walls and are regulated by endogenous pectin methylesterase inhibitors (PMEIs). In Arabidopsis dark-grown hypocotyls, one PME (AtPME3) and one PMEI (AtPMEI7) were identified as potential interacting proteins. Using RT-quantitative PCR analysis and gene promoter::GUS fusions, we first showed that AtPME3 and AtPMEI7 genes had overlapping patterns of expression in etiolated hypocotyls. The two proteins were identified in hypocotyl cell wall extracts by proteomics. To investigate the potential interaction between AtPME3 and AtPMEI7, both proteins were expressed in a heterologous system and purified by affinity chromatography. The activity of recombinant AtPME3 was characterized on homogalacturonans (HGs) with distinct degrees/patterns of methylesterification. AtPME3 showed the highest activity at pH 7.5 on HG substrates with a degree of methylesterification between 60 and 80% and a random distribution of methyl esters. On the best HG substrate, AtPME3 generates long non-methylesterified stretches and leaves short highly methylesterified zones, indicating that it acts as a processive enzyme. The recombinant AtPMEI7 and AtPME3 interaction reduces the level of demethylesterification of the HG substrate but does not inhibit the processivity of the enzyme. These data suggest that the AtPME3·AtPMEI7 complex is not covalently linked and could, depending on the pH, be alternately formed and dissociated. Docking analysis indicated that the inhibition of AtPME3 could occur via the interaction of AtPMEI7 with a PME ligand-binding cleft structure. All of these data indicate that AtPME3 and AtPMEI7 could be partners involved in the fine tuning of HG methylesterification during plant development. PMID:26183897

  17. iTunes U: An Opportunity for Students

    ERIC Educational Resources Information Center

    Germany, Lisa

    2011-01-01

    Purpose: The aim of this paper is to demonstrate that, with a bit of creative thinking, elements of certain university-wide projects (in this case study, establishing an iTunes U site) can be incorporated into student studies and assessment as real-world learning opportunities. Design/methodology/approach: Describes three different approaches…

  18. Neuromechanical tuning of nonlinear postural control dynamics

    NASA Astrophysics Data System (ADS)

    Ting, Lena H.; van Antwerp, Keith W.; Scrivens, Jevin E.; McKay, J. Lucas; Welch, Torrence D. J.; Bingham, Jeffrey T.; DeWeerth, Stephen P.

    2009-06-01

    Postural control may be an ideal physiological motor task for elucidating general questions about the organization, diversity, flexibility, and variability of biological motor behaviors using nonlinear dynamical analysis techniques. Rather than presenting "problems" to the nervous system, the redundancy of biological systems and variability in their behaviors may actually be exploited to allow for the flexible achievement of multiple and concurrent task-level goals associated with movement. Such variability may reflect the constant "tuning" of neuromechanical elements and their interactions for movement control. The problem faced by researchers is that there is no one-to-one mapping between the task goal and the coordination of the underlying elements. We review recent and ongoing research in postural control with the goal of identifying common mechanisms underlying variability in postural control, coordination of multiple postural strategies, and transitions between them. We present a delayed-feedback model used to characterize the variability observed in muscle coordination patterns during postural responses to perturbation. We emphasize the significance of delays in physiological postural systems, requiring the modulation and coordination of both the instantaneous, "passive" response to perturbations as well as the delayed, "active" responses to perturbations. The challenge for future research lies in understanding the mechanisms and principles underlying neuromechanical tuning of and transitions between the diversity of postural behaviors. Here we describe some of our recent and ongoing studies aimed at understanding variability in postural control using physical robotic systems, human experiments, dimensional analysis, and computational models that could be enhanced from a nonlinear dynamics approach.

  19. Tuning Forks and Monitor Screens.

    ERIC Educational Resources Information Center

    Harrison, M. A. T.

    2000-01-01

    Defines the vibrations of a tuning fork against a computer monitor screen as a pattern that can illustrate or explain physical concepts like wave vibrations, wave forms, and phase differences. Presents background information and demonstrates the experiment. (Author/YDS)

  20. Manganite films: Tuning phase diagrams

    NASA Astrophysics Data System (ADS)

    Mihailovic, Dragan

    2016-09-01

    Strain engineering can tune a manganite film into an antiferromagnetic insulating state whose extreme photo-susceptibility allows for the ordinary ferromagnetic metal state to then be transiently realized.

  1. Cochlear microphonic broad tuning curves

    NASA Astrophysics Data System (ADS)

    Ayat, Mohammad; Teal, Paul D.; Searchfield, Grant D.; Razali, Najwani

    2015-12-01

    It is known that the cochlear microphonic voltage exhibits much broader tuning than does the basilar membrane motion. The most commonly used explanation for this is that when an electrode is inserted at a particular point inside the scala media, the microphonic potentials of neighbouring hair cells have different phases, leading to cancelation at the electrodes location. In situ recording of functioning outer hair cells (OHCs) for investigating this hypothesis is exceptionally difficult. Therefore, to investigate the discrepancy between the tuning curves of the basilar membrane and those of the cochlear microphonic, and the effect of phase cancellation of adjacent hair cells on the broadness of the cochlear microphonic tuning curves, we use an electromechanical model of the cochlea to devise an experiment. We explore the effect of adjacent hair cells (i.e., longitudinal phase cancellation) on the broadness of the cochlear microphonic tuning curves in different locations. The results of the experiment indicate that active longitudinal coupling (i.e., coupling with active adjacent outer hair cells) only slightly changes the broadness of the CM tuning curves. The results also demonstrate that there is a π phase difference between the potentials produced by the hair bundle and the soma near the place associated with the characteristic frequency based on place-frequency maps (i.e., the best place). We suggest that the transversal phase cancellation (caused by the phase difference between the hair bundle and the soma) plays a far more important role than longitudinal phase cancellation in the broadness of the cochlear microphonic tuning curves. Moreover, by increasing the modelled longitudinal resistance resulting the cochlear microphonic curves exhibiting sharper tuning. The results of the simulations suggest that the passive network of the organ of Corti determines the phase difference between the hair bundle and soma, and hence determines the sharpness of the

  2. Adaptive Self-Tuning Networks

    NASA Astrophysics Data System (ADS)

    Knox, H. A.; Draelos, T.; Young, C. J.; Lawry, B.; Chael, E. P.; Faust, A.; Peterson, M. G.

    2015-12-01

    The quality of automatic detections from seismic sensor networks depends on a large number of data processing parameters that interact in complex ways. The largely manual process of identifying effective parameters is painstaking and does not guarantee that the resulting controls are the optimal configuration settings. Yet, achieving superior automatic detection of seismic events is closely related to these parameters. We present an automated sensor tuning (AST) system that learns near-optimal parameter settings for each event type using neuro-dynamic programming (reinforcement learning) trained with historic data. AST learns to test the raw signal against all event-settings and automatically self-tunes to an emerging event in real-time. The overall goal is to reduce the number of missed legitimate event detections and the number of false event detections. Reducing false alarms early in the seismic pipeline processing will have a significant impact on this goal. Applicable both for existing sensor performance boosting and new sensor deployment, this system provides an important new method to automatically tune complex remote sensing systems. Systems tuned in this way will achieve better performance than is currently possible by manual tuning, and with much less time and effort devoted to the tuning process. With ground truth on detections in seismic waveforms from a network of stations, we show that AST increases the probability of detection while decreasing false alarms.

  3. A Wave Traveling over a Hopf Instability Shapes the Cochlear Tuning Curve

    NASA Astrophysics Data System (ADS)

    Magnasco, Marcelo O.

    2003-02-01

    The tuning curve of the cochlea measures how intense an input is required to elicit a given output level as a function of the frequency. It is a fundamental object of auditory theory, for it summarizes how to identify sounds on the basis of the cochlear output. A simple model is presented showing that only two elements are sufficient for establishing the cochlear tuning curve: a broadly tuned traveling wave, moving unidirectionally from high to low frequencies, and a set of mechanosensors poised at the threshold of an oscillatory (Hopf) instability. These two components generate the various frequency-response regimes needed for a cochlear tuning curve with a high slope.

  4. Tuning sperm chemotaxis.

    PubMed

    Guerrero, Adán; Wood, Christopher D; Nishigaki, Takuya; Carneiro, Jorge; Darszon, Alberto

    2010-10-01

    Sperm chemotaxis is a long-term puzzle and most of our knowledge comes from studying marine animals that are external fertilizers. Sperm are attracted by diffusible chemical factors (chemoattractants) released from the egg which redirect their swimming paths towards their source. This redirection is driven by increases in flagellar curvature that correlate with transient flagellar Ca(2+) increases. Recent experimental and modelling results provide insights into the signal flow underlying the translation of an external chemical gradient into an intracellular molecular and motor response. A fundamental element of sea-urchin sperm chemotaxis lies in the ability of these cells to suppress Ca(2+)-mediated increases in flagellar curvature while experiencing an increasing chemoattractant gradient. The article considers this new evidence and summarizes the known underlying cellular mechanisms and behavioural strategies that sperm use to locate and fertilize the oocyte.

  5. A novel optical tuning technology

    NASA Astrophysics Data System (ADS)

    Miron, Nicolae

    2007-02-01

    A novel optical tuning technology based on new non-resonant interferometer (Optune interferometer) is described. This interferometer has a totally reflective layer either parallel with a partially reflective layer or tilted with a small angle, with an adjustable air gap between them. An input fiber optic collimator delivers a free space collimated beam that is incident first on the totally reflective layer at a small incidence angle. This beam bounces many times between the two reflective layers. An output fiber optic collimator collects all the beams going through the partially reflective layer making them to interfere at the entrance aperture of the output fiber. The optical configuration has no resonant frequencies. A broadband signal at the input is available at the output as a comb with even spacing. Any arbitrary wavelength can be selected by adjusting accurately the gap size. Tuning across 90 nm range could require less than 10 μm change of the gap size. Some properties of Optune interferometer are: 240 nm tuning range, no tuning holes, 0.2 ms / 100 nm tuning speed, 1 pm tuning accuracy, 0.15 nm bandwidth, 1 dB insertion loss, 45 dB contrast, 0.2 dB flatness, 0.15 dB polarization dependent loss. Optune interferometer can be used either for filtering or for generating optical wavelengths in a broad range of applications such as optical monitoring of structures (FBG and Brillouin technologies), and in optical communications. U.S. Patent No. 7,002,696 covers Optune interferometer and also optical tuning technology based on it.

  6. Tuning a Tetrahertz Wire Laser

    NASA Technical Reports Server (NTRS)

    Qin, Qi; Williams, Benjamin S.; Kumar, Sushil; Reno, John L.; Hu, Qing

    2009-01-01

    Tunable terahertz lasers are desirable in applications in sensing and spectroscopy because many biochemical species have strong spectral fingerprints at terahertz frequencies. Conventionally, the frequency of a laser is tuned in a similar manner to a stringed musical instrument, in which pitch is varied by changing the length of the string (the longitudinal component of the wave vector) and/ or its tension (the refractive index). However, such methods are difficult to implement in terahertz semiconductor lasers because of their poor outcoupling efficiencies. Here, we demonstrate a novel tuning mechanism based on a unique 'wire laser' device for which the transverse dimension w is much much less than lambda. Placing a movable object close to the wire laser manipulates a large fraction of the waveguided mode propagating outside the cavity, thereby tuning its resonant frequency. Continuous single-mode redshift and blueshift tuning is demonstrated for the same device by using either a dielectric or metallic movable object. In combination, this enables a frequency tuning of approximately equal to 137 GHz (3.6%) from a single laser device at approximately equal to 3.8 THz.

  7. Tuning a terahertz wire laser

    NASA Astrophysics Data System (ADS)

    Qin, Qi; Williams, Benjamin S.; Kumar, Sushil; Reno, John L.; Hu, Qing

    2009-12-01

    Tunable terahertz lasers are desirable in applications in sensing and spectroscopy because many biochemical species have strong spectral fingerprints at terahertz frequencies. Conventionally, the frequency of a laser is tuned in a similar manner to a stringed musical instrument, in which pitch is varied by changing the length of the string (the longitudinal component of the wave vector) and/or its tension (the refractive index). However, such methods are difficult to implement in terahertz semiconductor lasers because of their poor outcoupling efficiencies. Here, we demonstrate a novel tuning mechanism based on a unique `wire laser' device for which the transverse dimension w is <<λ. Placing a movable object close to the wire laser manipulates a large fraction of the waveguided mode propagating outside the cavity, thereby tuning its resonant frequency. Continuous single-mode redshift and blueshift tuning is demonstrated for the same device by using either a dielectric or metallic movable object. In combination, this enables a frequency tuning of ~137 GHz (3.6%) from a single laser device at ~3.8 THz.

  8. Dual mode tuning strategy of a slightly asymmetric ring.

    PubMed

    Park, Han Gil; Kang, Yeon June; Kim, Seock Hyun

    2008-03-01

    Clear beats with proper periods in the first and the second vibration modes are very important factors for the sound of the Korean bell. In this study, the Korean bell is expressed as a circular ring with multiple point masses and a dual mode tuning strategy for clear beat with proper period. For the dual mode tuning, a dual mode equivalent ring model is composed with two point masses, which satisfies the mode pair conditions of the first mode and second mode simultaneously. By adding a suitable amount of additional masses to the dual mode equivalent ring model at appropriate positions, a clear beat with proper period in both of the two important modes is generated. The position and amount of the additional masses are determined analytically. Analytical tuning results are compared and verified with those of the finite element analysis.

  9. Color-tuned channelrhodopsins for multiwavelength optogenetics.

    PubMed

    Prigge, Matthias; Schneider, Franziska; Tsunoda, Satoshi P; Shilyansky, Carrie; Wietek, Jonas; Deisseroth, Karl; Hegemann, Peter

    2012-09-14

    Channelrhodopsin-2 is a light-gated ion channel and a major tool of optogenetics. It is used to control neuronal activity via blue light. Here we describe the construction of color-tuned high efficiency channelrhodopsins (ChRs), based on chimeras of Chlamydomonas channelrhodopsin-1 and Volvox channelrhodopsin-1. These variants show superb expression and plasma membrane integration, resulting in 3-fold larger photocurrents in HEK cells compared with channelrhodopsin-2. Further molecular engineering gave rise to chimeric variants with absorption maxima ranging from 526 to 545 nm, dovetailing well with maxima of channelrhodopsin-2 derivatives ranging from 461 to 492 nm. Additional kinetic fine-tuning led to derivatives in which the lifetimes of the open state range from 19 ms to 5 s. Finally, combining green- with blue-absorbing variants allowed independent activation of two distinct neural cell populations at 560 and 405 nm. This novel panel of channelrhodopsin variants may serve as an important toolkit element for dual-color cell stimulation in neural circuits.

  10. Integrated tuned vibration absorbers: a theoretical study.

    PubMed

    Gardonio, Paolo; Zilletti, Michele

    2013-11-01

    This article presents a simulation study on two integrated tuned vibration absorbers (TVAs) designed to control the global flexural vibration of lightly damped thin structures subject to broad frequency band disturbances. The first one consists of a single axial switching TVA composed by a seismic mass mounted on variable axial spring and damper elements so that the characteristic damping and natural frequency of the absorber can be switched iteratively to control the resonant response of three flexural modes of the hosting structure. The second one consists of a single three-axes TVA composed by a seismic mass mounted on axial and rotational springs and dampers, which are arranged in such a way that the suspended mass is characterized by uncoupled heave and pitch-rolling vibrations. In this case the three damping and natural frequency parameters of the absorber are tuned separately to control three flexural modes of the hosting structure. The simulation study shows that the proposed single-unit absorbers produce, respectively, 5.3 and 8.7 dB reductions of the global flexural vibration of a rectangular plate between 20 and 120 Hz.

  11. Color-tuned Channelrhodopsins for Multiwavelength Optogenetics

    PubMed Central

    Prigge, Matthias; Schneider, Franziska; Tsunoda, Satoshi P.; Shilyansky, Carrie; Wietek, Jonas; Deisseroth, Karl; Hegemann, Peter

    2012-01-01

    Channelrhodopsin-2 is a light-gated ion channel and a major tool of optogenetics. It is used to control neuronal activity via blue light. Here we describe the construction of color-tuned high efficiency channelrhodopsins (ChRs), based on chimeras of Chlamydomonas channelrhodopsin-1 and Volvox channelrhodopsin-1. These variants show superb expression and plasma membrane integration, resulting in 3-fold larger photocurrents in HEK cells compared with channelrhodopsin-2. Further molecular engineering gave rise to chimeric variants with absorption maxima ranging from 526 to 545 nm, dovetailing well with maxima of channelrhodopsin-2 derivatives ranging from 461 to 492 nm. Additional kinetic fine-tuning led to derivatives in which the lifetimes of the open state range from 19 ms to 5 s. Finally, combining green- with blue-absorbing variants allowed independent activation of two distinct neural cell populations at 560 and 405 nm. This novel panel of channelrhodopsin variants may serve as an important toolkit element for dual-color cell stimulation in neural circuits. PMID:22843694

  12. PID Tuning Using Extremum Seeking

    SciTech Connect

    Killingsworth, N; Krstic, M

    2005-11-15

    Although proportional-integral-derivative (PID) controllers are widely used in the process industry, their effectiveness is often limited due to poor tuning. Manual tuning of PID controllers, which requires optimization of three parameters, is a time-consuming task. To remedy this difficulty, much effort has been invested in developing systematic tuning methods. Many of these methods rely on knowledge of the plant model or require special experiments to identify a suitable plant model. Reviews of these methods are given in [1] and the survey paper [2]. However, in many situations a plant model is not known, and it is not desirable to open the process loop for system identification. Thus a method for tuning PID parameters within a closed-loop setting is advantageous. In relay feedback tuning [3]-[5], the feedback controller is temporarily replaced by a relay. Relay feedback causes most systems to oscillate, thus determining one point on the Nyquist diagram. Based on the location of this point, PID parameters can be chosen to give the closed-loop system a desired phase and gain margin. An alternative tuning method, which does not require either a modification of the system or a system model, is unfalsified control [6], [7]. This method uses input-output data to determine whether a set of PID parameters meets performance specifications. An adaptive algorithm is used to update the PID controller based on whether or not the controller falsifies a given criterion. The method requires a finite set of candidate PID controllers that must be initially specified [6]. Unfalsified control for an infinite set of PID controllers has been developed in [7]; this approach requires a carefully chosen input signal [8]. Yet another model-free PID tuning method that does not require opening of the loop is iterative feedback tuning (IFT). IFT iteratively optimizes the controller parameters with respect to a cost function derived from the output signal of the closed-loop system, see [9

  13. Apparatuses and methods for tuning center frequencies

    DOEpatents

    Wojciechowski, Kenneth; Olsson, Roy H.

    2016-02-23

    Apparatuses and methods for tuning center frequencies are described herein. Examples of tuning described herein including tuning using feedback from the resonator. Variable gain feedback for tuning of acoustic wave resonators is provided in some examples. An example apparatus may include a resonator and a feedback loop. The resonator may be configured to receive a tuning signal and to provide a feedback signal. The feedback signal may be based on the tuning signal. The feedback loop may be configured to receive the feedback signal from the resonator. The feedback loop further may be configured to provide the tuning signal to actively tune a center frequency of the resonator. The tuning signal may be based on the feedback signal.

  14. Tuning the DARHT Axis-II linear induction accelerator focusing

    SciTech Connect

    Ekdahl, Carl A.

    2012-04-24

    Flash radiography of large hydrodynamic experiments driven by high explosives is a well-known diagnostic technique in use at many laboratories, and the Dual-Axis Radiography for Hydrodynamic Testing (DARHT) facility at Los Alamos produces flash radiographs of large hydrodynamic experiments. Two linear induction accelerators (LIAs) make the bremsstrahlung radiographic source spots for orthogonal views of each test. The 2-kA, 20-MeV Axis-I LIA creates a single 60-ns radiography pulse. The 1.7-kA, 16.5-MeV Axis-II LIA creates up to four radiography pulses by kicking them out of a longer pulse that has a 1.6-{mu}s flattop. The Axis-II injector, LIA, kicker, and downstream transport (DST) to the bremsstrahlung converter are described. Adjusting the magnetic focusing and steering elements to optimize the electron-beam transport through an LIA is often called 'tuning.' As in all high-current LIAs, the focusing field is designed to be as close to that of the ideal continuous solenoid as physically possible. In ideal continuous solenoidal transport a smoothly varying beam size can easily be found for which radial forces balance, and the beam is said to be 'matched' to the focusing field. A 'mismatched' beam exhibits unwanted oscillations in size, which are a source of free energy that contributes to emittance growth. This is undesirable, because in the absence of beam-target effects, the radiographic spot size is proportional to the emittance. Tuning the Axis-II LIA is done in two steps. First, the solenoidal focusing elements are set to values designed to provide a matched beam with little or no envelope oscillations, and little or no beam-breakup (BBU) instability growth. Then, steering elements are adjusted to minimize the motion of the centroid of a well-centered beam at the LIA exit. This article only describes the design of the tune for the focusing solenoids. The DARHT Axis-II LIA was required to be re-tuned after installing an accelerator cell to replace a failed

  15. Self-tuning regulators. [adaptive control research

    NASA Technical Reports Server (NTRS)

    Astrom, K. J.

    1975-01-01

    The results of a research project are discussed for self-tuning regulators for active control. An algorithm for the self-tuning regulator is described as being stochastic, nonlinear, time variable, and not trivial.

  16. Tuning in the bullfrog ear.

    PubMed Central

    Lewis, E R

    1988-01-01

    When electrical resonances were observed in acoustic sensory cells of lower vertebrates, the hearing research community was presented with the exciting possibility that tuning in the ears of those animals might be explained directly in terms of familiar molecular devices. It is reported here that in the frog sacculus, where electrical resonances have been observed in isolated hair cells, the effects of those resonances are completely obscured in the tuning properties of the sacculus in the intact ear. This observation has important implications not only for students of the ear, but for reductionist biologists in general. All of the dynamic properties of a system of connected, bidirectional processes are consequences of all of those processes at once; in such a system, the properties of an experimentally isolated subsystem may be totally obscured in the operation of the system as a whole. PMID:3258166

  17. 21 CFR 882.1525 - Tuning fork.

    Code of Federal Regulations, 2014 CFR

    2014-04-01

    ... 21 Food and Drugs 8 2014-04-01 2014-04-01 false Tuning fork. 882.1525 Section 882.1525 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES NEUROLOGICAL DEVICES Neurological Diagnostic Devices § 882.1525 Tuning fork. (a) Identification. A tuning...

  18. 21 CFR 882.1525 - Tuning fork.

    Code of Federal Regulations, 2012 CFR

    2012-04-01

    ... 21 Food and Drugs 8 2012-04-01 2012-04-01 false Tuning fork. 882.1525 Section 882.1525 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES NEUROLOGICAL DEVICES Neurological Diagnostic Devices § 882.1525 Tuning fork. (a) Identification. A tuning...

  19. 21 CFR 882.1525 - Tuning fork.

    Code of Federal Regulations, 2010 CFR

    2010-04-01

    ... 21 Food and Drugs 8 2010-04-01 2010-04-01 false Tuning fork. 882.1525 Section 882.1525 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES NEUROLOGICAL DEVICES Neurological Diagnostic Devices § 882.1525 Tuning fork. (a) Identification. A tuning...

  20. 21 CFR 882.1525 - Tuning fork.

    Code of Federal Regulations, 2013 CFR

    2013-04-01

    ... 21 Food and Drugs 8 2013-04-01 2013-04-01 false Tuning fork. 882.1525 Section 882.1525 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES NEUROLOGICAL DEVICES Neurological Diagnostic Devices § 882.1525 Tuning fork. (a) Identification. A tuning...

  1. 21 CFR 882.1525 - Tuning fork.

    Code of Federal Regulations, 2011 CFR

    2011-04-01

    ... 21 Food and Drugs 8 2011-04-01 2011-04-01 false Tuning fork. 882.1525 Section 882.1525 Food and Drugs FOOD AND DRUG ADMINISTRATION, DEPARTMENT OF HEALTH AND HUMAN SERVICES (CONTINUED) MEDICAL DEVICES NEUROLOGICAL DEVICES Neurological Diagnostic Devices § 882.1525 Tuning fork. (a) Identification. A tuning...

  2. JEM's 2009 Tune-up

    PubMed Central

    2009-01-01

    Scientific journals, like cars, require periodic tune-ups to keep them running smoothly. Effective immediately, several changes to the JEM publication policies will take effect. Our aim is to address policy issues that have arisen over the past several years and, more broadly, to maintain the quality and integrity of the research we publish. The upcoming changes to JEM policies and the impetus behind them are outlined here.

  3. Eighth-Grade Violinists' Instrument Tuning Ability: A Comparison of Pitch Perception and Tuning Accuracy

    ERIC Educational Resources Information Center

    Hopkins, Michael T.

    2015-01-01

    The purpose of this study was to explore the relationship between eighth-grade violinists' pitch perception and instrument tuning skill. The perceptual task was a researcher-developed computer-based Violin Tuning Perception Test. The instrument tuning task involved tuning two violins, one mistuned flat and the other mistuned sharp. Participants (N…

  4. Optimization methods for passive damper placement and tuning

    NASA Technical Reports Server (NTRS)

    Milman, M. H.; Chu, C. C.

    1992-01-01

    The effectiveness of viscous elements in introducing damping in a structure is a function of several variables, including their number, their location in the structure, and their physical properties. In this paper several optimization problems are posed to optimize these variables. The paper investigates various metrics to define the optimization problem, and compares the damping profiles that are obtained. Both discrete and continuous optimization problems are formulated and solved, corresponding, respectively, to the problems of placement of damping elements and to the tuning of their parameters. The paper particularly emphasizes techniques to make feasible the large scale problems resulting from the optimization formulations. Numerical results involving a lightly damped tested structure are presented.

  5. Thermo-optically tuned photonic resonators with concurrent electrical connection and thermal isolation

    DOEpatents

    Lentine, Anthony L.; Kekatpure, Rohan Deodatta; Zortman, William A.; Savignon, Daniel J.

    2016-06-14

    A photonic resonator system is designed to use thermal tuning to adjust the resonant wavelength of each resonator in the system, with a separate tuning circuit associated with each resonator so that individual adjustments may be made. The common electrical ground connection between the tuning circuits is particularly formed to provide thermal isolation between adjacent resonators by including a capacitor along each return path to ground, where the presence of the capacitor's dielectric material provides the thermal isolation. The use of capacitively coupling necessarily requires the use of an AC current as an input to the heater element (conductor/resistor) of each resonator, where the RMS value of the AC signal is indicative of the amount of heat that is generated along the element and the degree of wavelength tuning that is obtained.

  6. New tuning method for PID controller.

    PubMed

    Shen, Jing-Chung

    2002-10-01

    In this paper, a tuning method for proportional-integral-derivative (PID) controller and the performance assessment formulas for this method are proposed. This tuning method is based on a genetic algorithm based PID controller design method. For deriving the tuning formula, the genetic algorithm based design method is applied to design PID controllers for a variety of processes. The relationship between the controller parameters and the parameters that characterize the process dynamics are determined and the tuning formula is then derived. Using simulation studies, the rules for assessing the performance of a PID controller tuned by the proposed method are also given. This makes it possible to incorporate the capability to determine if the PID controller is well tuned or not into an autotuner. An autotuner based on this new tuning method and the corresponding performance assessment rules is also established. Simulations and real-time experimental results are given to demonstrate the effectiveness and usefulness of these formulas.

  7. Electrostatic Tuning of Cellular Excitability

    PubMed Central

    Börjesson, Sara I.; Parkkari, Teija; Hammarström, Sven; Elinder, Fredrik

    2010-01-01

    Abstract Voltage-gated ion channels regulate the electric activity of excitable tissues, such as the heart and brain. Therefore, treatment for conditions of disturbed excitability is often based on drugs that target ion channels. In this study of a voltage-gated K channel, we propose what we believe to be a novel pharmacological mechanism for how to regulate channel activity. Charged lipophilic substances can tune channel opening, and consequently excitability, by an electrostatic interaction with the channel's voltage sensors. The direction of the effect depends on the charge of the substance. This was shown by three compounds sharing an arachidonyl backbone but bearing different charge: arachidonic acid, methyl arachidonate, and arachidonyl amine. Computer simulations of membrane excitability showed that small changes in the voltage dependence of Na and K channels have prominent impact on excitability and the tendency for repetitive firing. For instance, a shift in the voltage dependence of a K channel with −5 or +5 mV corresponds to a threefold increase or decrease in K channel density, respectively. We suggest that electrostatic tuning of ion channel activity constitutes a novel and powerful pharmacological approach with which to affect cellular excitability. PMID:20141752

  8. Tuning magnetofluidic spreading in microchannels

    NASA Astrophysics Data System (ADS)

    Wang, Zhaomeng; Varma, V. B.; Wang, Z. P.; Ramanujan, R. V.

    2015-12-01

    Magnetofluidic spreading (MFS) is a phenomenon in which a uniform magnetic field is used to induce spreading of a ferrofluid core cladded by diamagnetic fluidic streams in a three-stream channel. Applications of MFS include micromixing, cell sorting and novel microfluidic lab-on-a-chip design. However, the relative importance of the parameters which govern MFS is still unclear, leading to non-optimal control of MFS. Hence, in this work, the effect of various key parameters on MFS was experimentally and numerically studied. Our multi-physics model, which combines magnetic and fluidic analysis, showed excellent agreement between theory and experiment. It was found that spreading was mainly due to cross-sectional convection induced by magnetic forces, and can be enhanced by tuning various parameters. Smaller flow rate ratio, higher magnetic field, higher core stream or lower cladding stream dynamic viscosity, and larger magnetic particle size can increase MFS. These results can be used to tune magnetofluidic spreading in microchannels.

  9. Breakpoint Tuning in DCT-Based Nonlinear Layered Video Codecs

    NASA Astrophysics Data System (ADS)

    Cuenca, Pedro; Orozco-Barbosa, Luis; Delicado, Francisco; Garrido, Antonio

    2004-12-01

    Many studies have been conducted to evaluate the benefits of using layered video coding schemes as a means to improve the robustness of video communications systems. In this paper, we study a frame-aware nonlinear layering scheme for the transport of a DCT-based video over packet-switched networks. This scheme takes into account the relevance of the different elements of the video sequence composing the encoded video sequence. Throughout a detailed study over a large set of video streams, we show that by properly tuning the encoding parameters, it is feasible to gracefully degrade or even maintain the video quality while reducing the amount of data representing the video sequence. We then provide the major guidelines to properly tune up the encoding parameters allowing us to set the basis towards the development of more robust video communications systems.

  10. Timoshenko beam with tuned mass dampers and its design curves

    NASA Astrophysics Data System (ADS)

    Chen, Yung-Hsiang; Huang, Yen-Hui

    2004-12-01

    The structural analysis and design of a Timoshenko beam with tuned mass dampers (or TMDs) under a harmonic excitation are presented. The dynamic-stiffness matrix of a Timoshenko-beam element is employed to study the dynamic responses for the whole frequency range. A proposed simplified two-degree-of-freedom system and Hartog's method are employed to study the dynamic characteristics of TMDs. Some important formulas for the design parameters (such as the mass ratio and stiffness ratio at the tuned frequency, the optimal damping ratio of TMDs, and their upper limits) and a series of the design charts are presented for practical applications, if the beam-own damping is absent and all TMDs are identical.

  11. Tune-out wavelengths for the alkaline-metal atoms

    NASA Astrophysics Data System (ADS)

    Wei-Wei, Yu; Rong-Mei, Yu; Yong-Jun, Cheng; Ya-Jun, Zhou

    2016-02-01

    An approximation formula is developed to determine the tune-out wavelengths for the ground states of the alkaline-metal atoms lithium, sodium and cesium from the existing relativistic reduced matrix elements and experimental energies. The first longest tune-out wavelengths for Li, Na, and Cs are 670.971 nm, 589.557 nm, and 880.237 nm, respectively. This is in good agreement with the previous high precise results of 670.971626 nm, 589.5565 nm, and 880.25 nm from the relativistic all-order many-body perturbation theory (RMBPT) calculation [Phys. Rev. A 84 043401 (2011)]. Project supported by the National Natural Science Foundation of China (Grant Nos. 11304063 and 11174066) and the Youth Foundation of Liaoning Normal University, China (Grant No. LS2014L002).

  12. POET: Parameterized Optimization for Empirical Tuning

    SciTech Connect

    Yi, Q; Seymour, K; You, H; Vuduc, R; Quinlan, D

    2007-01-29

    The excessive complexity of both machine architectures and applications have made it difficult for compilers to statically model and predict application behavior. This observation motivates the recent interest in performance tuning using empirical techniques. We present a new embedded scripting language, POET (Parameterized Optimization for Empirical Tuning), for parameterizing complex code transformations so that they can be empirically tuned. The POET language aims to significantly improve the generality, flexibility, and efficiency of existing empirical tuning systems. We have used the language to parameterize and to empirically tune three loop optimizations-interchange, blocking, and unrolling-for two linear algebra kernels. We show experimentally that the time required to tune these optimizations using POET, which does not require any program analysis, is significantly shorter than that when using a full compiler-based source-code optimizer which performs sophisticated program analysis and optimizations.

  13. Self tuning scalar tensor black holes

    NASA Astrophysics Data System (ADS)

    Charmousis, Christos; Iosifidis, Damianos

    2015-04-01

    Studying a certain sub class of higher order Horndeski (scalar-tensor) theories we discuss a method discovered recently permitting analytic black hole solutions with a non trivial and regular scalar field. One of the solutions found has de Sitter asymptotics and self tunes the bulk cosmological constant. Using the aforementioned method we find and analyse new black hole solutions which can also have de Sitter asymptotics. By looking at small deviations of the integration constant responsible for self tuning we discuss the robustness of the self tuning mechanism. We find that neighboring solutions to the one previously found present also self tuning properties with unaltered effective cosmological constant.

  14. Auto-tuning of cascade control systems.

    PubMed

    Song, Sihai; Cai, Wenjian; Wang, Ya-Gang

    2003-01-01

    In this paper, a novel auto-tuning method for a cascade control system is proposed. By employing a simple relay feedback test, both inner and outer loop model parameters can be simultaneously identified. Consequently, well-established proportional-integral-derivative (PID) tuning rules can be applied to tune both loops. Compared with existing methods, the new method is simpler and yet more effective. It can be directly integrated into commercially available industrial auto-tuning systems. Some examples are given to illustrate the effectiveness and robustness of the proposed method.

  15. Tune measurement methods of the Tevatron

    SciTech Connect

    Cheng-Yang Tan; Xiaolong Zhang; Paul Lebrun

    2003-06-10

    We will discuss several methods for measuring the tunes in the Tevatron. These methods can be separated into three classes: active, passive and hybrid. In the active method, the beam is tickled in order to obtain a frequency response. In the passive method, a Schottky detector which uses a resonant stripline is used to measure the Schottky spectrum of the beam. In the hybrid method, we tickle the beam using kickers, or the Tevatron Electron Lens (TEL) in order to bring the tune signal above the noise floor of the Schottky detectors. An automatic tune fitting algorithm is also under development which allows us to measure the tune without human intervention.

  16. Neuromechanical tuning of nonlinear postural control dynamics

    PubMed Central

    Ting, Lena H.; van Antwerp, Keith W.; Scrivens, Jevin E.; McKay, J. Lucas; Welch, Torrence D. J.; Bingham, Jeffrey T.; DeWeerth, Stephen P.

    2009-01-01

    Postural control may be an ideal physiological motor task for elucidating general questions about the organization, diversity, flexibility, and variability of biological motor behaviors using nonlinear dynamical analysis techniques. Rather than presenting “problems” to the nervous system, the redundancy of biological systems and variability in their behaviors may actually be exploited to allow for the flexible achievement of multiple and concurrent task-level goals associated with movement. Such variability may reflect the constant “tuning” of neuromechanical elements and their interactions for movement control. The problem faced by researchers is that there is no one-to-one mapping between the task goal and the coordination of the underlying elements. We review recent and ongoing research in postural control with the goal of identifying common mechanisms underlying variability in postural control, coordination of multiple postural strategies, and transitions between them. We present a delayed-feedback model used to characterize the variability observed in muscle coordination patterns during postural responses to perturbation. We emphasize the significance of delays in physiological postural systems, requiring the modulation and coordination of both the instantaneous, “passive” response to perturbations as well as the delayed, “active” responses to perturbations. The challenge for future research lies in understanding the mechanisms and principles underlying neuromechanical tuning of and transitions between the diversity of postural behaviors. Here we describe some of our recent and ongoing studies aimed at understanding variability in postural control using physical robotic systems, human experiments, dimensional analysis, and computational models that could be enhanced from a nonlinear dynamics approach. PMID:19566271

  17. Tuning innate immunity by translation.

    PubMed

    Rauscher, Robert; Ignatova, Zoya

    2015-12-01

    In multicellular organisms, the epithelia is a contact surface with the surrounding environment and is exposed to a variety of adverse biotic (pathogenic) and abiotic (chemical) factors. Multi-layered pathways that operate on different time scales have evolved to preserve cellular integrity and elicit stress-specific response. Several stress-response programs are activated until a complete elimination of the stress is achieved. The innate immune response, which is triggered by pathogenic invasion, is rather harmful when active over a prolonged time, thus the response follows characteristic oscillatory trajectories. Here, we review different translation programs that function to precisely fine-tune the time at which various components of the innate immune response dwell between active and inactive. We discuss how different pro-inflammatory pathways are co-ordinated to temporally offset single reactions and to achieve an optimal balance between fighting pathogens and being less harmful for healthy cells.

  18. Tuning universality far from equilibrium

    PubMed Central

    Karl, Markus; Nowak, Boris; Gasenzer, Thomas

    2013-01-01

    Possible universal dynamics of a many-body system far from thermal equilibrium are explored. A focus is set on meta-stable non-thermal states exhibiting critical properties such as self-similarity and independence of the details of how the respective state has been reached. It is proposed that universal dynamics far from equilibrium can be tuned to exhibit a dynamical transition where these critical properties change qualitatively. This is demonstrated for the case of a superfluid two-component Bose gas exhibiting different types of long-lived but non-thermal critical order. Scaling exponents controlled by the ratio of experimentally tuneable coupling parameters offer themselves as natural smoking guns. The results shed light on the wealth of universal phenomena expected to exist in the far-from-equilibrium realm. PMID:23928853

  19. Birefringence of solid-state laser media: broadband tuning discontinuities and application to laser line narrowing

    SciTech Connect

    Krasinski, J.S.; Band, Y.B.; Chin, T.; Heller, D.F.; Morris, R.C.; Papanestor, P.

    1989-04-15

    Spectral consequences that result from using birefringent media with broadband gain inside of laser cavities containing polarizing elements are described. We show that the laser intensity is modulated as a function of the output frequency unless the cavity elements are carefully aligned so that their polarization axis coincides with a principal optical axis of the gain medium. Analysis of the tuning characteristics of a birefringent polarization-dependent gain medium is exploited to provide a simple method for line narrowing the laser output. By introduction of an intracavity birefringent compensator the narrow-band output can be continuously tuned. Experimental results for alexandrite lasers are presented.

  20. Active noise control using noise source having adaptive resonant frequency tuning through stiffness variation

    NASA Technical Reports Server (NTRS)

    Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor); Renshaw, Anthony A. (Inventor); Hedeen, Robert A. (Inventor)

    1995-01-01

    A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of a noise radiating element is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating element is tuned by a plurality of force transmitting mechanisms which contact the noise radiating element. Each one of the force transmitting mechanisms includes an expandable element and a spring in contact with the noise radiating element so that excitation of the element varies the spring force applied to the noise radiating element. The elements are actuated by a controller which receives input of a signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the elements and causes the spring force applied to the noise radiating element to be varied. The force transmitting mechanisms can be arranged to either produce bending or linear stiffness variations in the noise radiating element.

  1. Temporal tuning in the bat auditory cortex is sharper when studied with natural echolocation sequences

    PubMed Central

    Beetz, M. Jerome; Hechavarría, Julio C.; Kössl, Manfred

    2016-01-01

    Precise temporal coding is necessary for proper acoustic analysis. However, at cortical level, forward suppression appears to limit the ability of neurons to extract temporal information from natural sound sequences. Here we studied how temporal processing can be maintained in the bats’ cortex in the presence of suppression evoked by natural echolocation streams that are relevant to the bats’ behavior. We show that cortical neurons tuned to target-distance actually profit from forward suppression induced by natural echolocation sequences. These neurons can more precisely extract target distance information when they are stimulated with natural echolocation sequences than during stimulation with isolated call-echo pairs. We conclude that forward suppression does for time domain tuning what lateral inhibition does for selectivity forms such as auditory frequency tuning and visual orientation tuning. When talking about cortical processing, suppression should be seen as a mechanistic tool rather than a limiting element. PMID:27357230

  2. Two-level tuning of fuzzy PID controllers.

    PubMed

    Mann, G I; Hu, B G; Gosine, R G

    2001-01-01

    Fuzzy PID tuning requires two stages of tuning; low level tuning followed by high level tuning. At the higher level, a nonlinear tuning is performed to determine the nonlinear characteristics of the fuzzy output. At the lower level, a linear tuning is performed to determine the linear characteristics of the fuzzy output for achieving overall performance of fuzzy control. First, different fuzzy systems are defined and then simplified for two-point control. Non-linearity tuning diagrams are constructed for fuzzy systems in order to perform high level tuning. The linear tuning parameters are deduced from the conventional PID tuning knowledge. Using the tuning diagrams, high level tuning heuristics are developed. Finally, different applications are demonstrated to show the validity of the proposed tuning method.

  3. Novel tune diagnostics for the Tevatron

    SciTech Connect

    Tan, Cheng-Yang; /Fermilab

    2005-04-01

    In the Tevatron collider, protons and antiprotons share the same beam pipe. This poses a challenge in the measurement of tunes for both species simultaneously because of the possibility of signal contamination from the other species. The tune of each bunch is also very different because of beam-beam effects from parasitic crossing points. This means that the tune diagnostics must be able to differentiate between protons and anti-protons, it also has to measure tunes from each bunch. There are three different tune pickups used in the Tevatron: 1.7 GHz Schottky pickups, 21.4 MHz Schottky pickups and baseband pickups. These devices will be discussed in detail in this paper.

  4. An automatic data system for vibration modal tuning and evaluation

    NASA Technical Reports Server (NTRS)

    Salyer, R. A.; Jung, E. J., Jr.; Huggins, S. L.; Stephens, B. L.

    1975-01-01

    A digitally based automatic modal tuning and analysis system developed to provide an operational capability beginning at 0.1 hertz is described. The elements of the system, which provides unique control features, maximum operator visibility, and rapid data reduction and documentation, are briefly described; and the operational flow is discussed to illustrate the full range of capabilities and the flexibility of application. The successful application of the system to a modal survey of the Skylab payload is described. Information about the Skylab test article, coincident-quadrature analysis of modal response data, orthogonality, and damping calculations is included in the appendixes. Recommendations for future application of the system are also made.

  5. Laser with rapid tuning of the spectrum shape.

    PubMed

    Parkhomenko, Y N; Galkin, O N; Gorbenko, O V; Sokolov, V A

    1998-11-20

    We have studied a laser system with quick electronic tuning of the spectrum shape and continuous distribution. The proposed method is based on separate control of phase and amplitude spatial distributions of resonator transmittance. Evolution of the spectral function of the diffractively coupled dispersive resonators and the model for the formation of the resonator with the spectral function given by its moments are studied theoretically. The synthesis of continuous spectra is investigated experimentally in the laser with a novel control element including a spatial acousto-optic modulator and a tunable lens telescope.

  6. An automatically tuning intrusion detection system.

    PubMed

    Yu, Zhenwei; Tsai, Jeffrey J P; Weigert, Thomas

    2007-04-01

    An intrusion detection system (IDS) is a security layer used to detect ongoing intrusive activities in information systems. Traditionally, intrusion detection relies on extensive knowledge of security experts, in particular, on their familiarity with the computer system to be protected. To reduce this dependence, various data-mining and machine learning techniques have been deployed for intrusion detection. An IDS is usually working in a dynamically changing environment, which forces continuous tuning of the intrusion detection model, in order to maintain sufficient performance. The manual tuning process required by current systems depends on the system operators in working out the tuning solution and in integrating it into the detection model. In this paper, an automatically tuning IDS (ATIDS) is presented. The proposed system will automatically tune the detection model on-the-fly according to the feedback provided by the system operator when false predictions are encountered. The system is evaluated using the KDDCup'99 intrusion detection dataset. Experimental results show that the system achieves up to 35% improvement in terms of misclassification cost when compared with a system lacking the tuning feature. If only 10% false predictions are used to tune the model, the system still achieves about 30% improvement. Moreover, when tuning is not delayed too long, the system can achieve about 20% improvement, with only 1.3% of the false predictions used to tune the model. The results of the experiments show that a practical system can be built based on ATIDS: system operators can focus on verification of predictions with low confidence, as only those predictions determined to be false will be used to tune the detection model.

  7. Algorithms to Automate LCLS Undulator Tuning

    SciTech Connect

    Wolf, Zachary

    2010-12-03

    Automation of the LCLS undulator tuning offers many advantages to the project. Automation can make a substantial reduction in the amount of time the tuning takes. Undulator tuning is fairly complex and automation can make the final tuning less dependent on the skill of the operator. Also, algorithms are fixed and can be scrutinized and reviewed, as opposed to an individual doing the tuning by hand. This note presents algorithms implemented in a computer program written for LCLS undulator tuning. The LCLS undulators must meet the following specifications. The maximum trajectory walkoff must be less than 5 {micro}m over 10 m. The first field integral must be below 40 x 10{sup -6} Tm. The second field integral must be below 50 x 10{sup -6} Tm{sup 2}. The phase error between the electron motion and the radiation field must be less than 10 degrees in an undulator. The K parameter must have the value of 3.5000 {+-} 0.0005. The phase matching from the break regions into the undulator must be accurate to better than 10 degrees. A phase change of 113 x 2{pi} must take place over a distance of 3.656 m centered on the undulator. Achieving these requirements is the goal of the tuning process. Most of the tuning is done with Hall probe measurements. The field integrals are checked using long coil measurements. An analysis program written in Matlab takes the Hall probe measurements and computes the trajectories, phase errors, K value, etc. The analysis program and its calculation techniques were described in a previous note. In this note, a second Matlab program containing tuning algorithms is described. The algorithms to determine the required number and placement of the shims are discussed in detail. This note describes the operation of a computer program which was written to automate LCLS undulator tuning. The algorithms used to compute the shim sizes and locations are discussed.

  8. Design of a Slender Tuned Ultrasonic Needle for Bone Penetration

    NASA Astrophysics Data System (ADS)

    Cleary, Rebecca; Mathieson, Andrew; Wallace, Robert; Simpson, Hamish; Lucas, Margaret

    This paper reports on an ultrasonic bone biopsy needle, particularly focusing on design guidelines applicable for any slender tuned ultrasonic device component. Ultrasonic surgical devices are routinely used to cut a range of biological tissues, such as bone. However the realisation of an ultrasonic bone biopsy needle is particularly challenging. This is due to the requirement to generate sufficient vibrational amplitude capable of penetrating mineralised tissue, while avoiding flexural vibrational responses, which are known to reduce the performance and reliability of slender ultrasonic devices. This investigation uses finite element analysis (FEA) to predict the vibrational behaviour of a resonant needle which has dimensions that match closely to an 8Gx4inch bone marrow biopsy needle. Features of the needle, including changes in material and repeated changes in diameter, have been included and systematically altered to demonstrate that the location of and geometry of these features can significantly affect the resonant frequency of bending and torsional modes of vibration while having a limited effect on the frequency and shape of the tuned longitudinal mode. Experimental modal analysis was used to identify the modal parameters of the selected needle design, validating the FEA model predictions of the longitudinal mode and the close flexural modes. This verifies that modal coupling can be avoided by judicious small geometry modifications. Finally, the tuned needle assembly was driven under typical operational excitation conditions to demonstrate that an ultrasonic biopsy needle can be designed to operate in a purely longitudinal motion.

  9. Tuning superconductivity by carrier injection

    NASA Astrophysics Data System (ADS)

    Müller, Paul

    2011-03-01

    All high-Tc cuprates are stacking sequences of Cu O2 layers and charge reservoir layers consisting of metal oxides. Upon doping the Cu O2 layers, antiferromagnetic order is destroyed and metallic conductivity is established. Usually doping is achieved by a non-stoichiometric composition of the charge reservoir layer. However, we already have shown that we can change the carrier concentration of Bi 2 Sr 2 CaCu 2 O8 + δ single crystals by current injection along the c- axis. Critical temperature, c-axis resistivity and critical current of intrinsic Josephson junctions can be tuned in a large range from underdoping to extreme overdoping. This effect is persistent up to annealing temperatures of approximately 270 K. Using current injection at higher bias, we were able to reduce the carrier concentration again. We investigated in detail the superconducting properties by performing macroscopic quantum tunneling experiments of intrinsic Josephson junctions. The experiments have been carried out repeatedly on samples, whose properties were changed only by current injection. An exponential increase of the critical current density with hole concentration was observed. At the same time, the capacitance of intrinsic Josephson junctions increased significantly. Finally, only by current injection, we were able to convert into the superconducting state a nonsuperconducting, oxygen depleted sample. This work was done in collaboration with Y. Koval, X.Y. Jin, S. Probst, Y. Simsek, C. Steiner (Universität Erlangen), H. B. Wang (NIMS, Tsukuba), and G. Behr, B. Büchner (IFW Dresden).

  10. 2-Shock layered tuning campaign

    NASA Astrophysics Data System (ADS)

    Masse, Laurent; Dittrich, T.; Khan, S.; Kyrala, G.; Ma, T.; MacLaren, S.; Ralph, J.; Salmonson, J.; Tipton, R.; Los Alamos Natl Lab Team; Lawrence Livermore Natl Lab Team

    2016-10-01

    The 2-Shock platform has been developed to maintain shell sphericity throughout the compression phase of an indirect-drive target implosion and produce a stagnating hot spot in a quasi 1D-like manner. A sub-scale, 1700 _m outer diameter, and thick, 200 _m, uniformly Silicon doped, gas-filled plastic capsule is driven inside a nominal size 5750 _m diameter ignition hohlraum. The hohlraum fill is near vacuum to reduce back-scatter and improve laser/drive coupling. A two-shock pulse of about 1 MJ of laser energy drives the capsule. The thick capsule prevents ablation front feed-through to the imploded core. This platform has demonstrated its efficiency to tune a predictable and reproducible 1-D implosion with a nearly round shape. It has been shown that the high foot performance was dominated by the local defect growth due to the ablation front instability and by the hohlraum radiation asymmetries. The idea here is to take advantage of this 2-Shock platform to design a 1D-like layered implosion and eliminates the deleterious effects of radiation asymmetries and ablation front instability growth. We present the design work and our first experimental results of this near one-dimensional 2-Shock layered design. This work was performed under the auspices of the Lawrence Livermore National Security, LLC, (LLNS) under Contract No. DE-AC52-07NA27344.

  11. Ionic liquid tunes microemulsion curvature.

    PubMed

    Liu, Liping; Bauduin, Pierre; Zemb, Thomas; Eastoe, Julian; Hao, Jingcheng

    2009-02-17

    Middle-phase microemulsions formed from cationic dioctadecyldimethylammonium chloride (DODMAC), anionic sodium dodecylsulfate (SDS), n-butanol, and n-heptane were studied. An ionic liquid (IL), 1-butyl-3-methylimidazolium tetrafluoroborate ([bmim][BF4]), was employed as the electrolyte in the aqueous media instead of inorganic salts usually used in microemulsion formulation. Studies have been carried out as a function of the concentrations of [bmim][BF4], n-butanol, total surfactant (cDODMAC+SDS), and temperature on the phase behavior and the ultralow interfacial tensions in which the anionic component is present in excess in the catanionic film. Ultralow interfacial tension measurements confirmed the formation of middle-phase microemulsions and the necessary conditions for stabilizing middle-phase microemulsions. Electrical conductivity, small-angle X-ray scattering (SAXS), and small-angle neutron scattering (SANS) experiments were also performed, indicating that the typical heptane domain size has an average radius of 360 A and the ionic liquid induces softening of the charged catanionic film. Most interestingly, the IL concentration (cIL) is shown to act as an effective interfacial curvature-control parameter, representing a new approach to tuning the formulation of microemulsions and emulsions. The results expand the potential uses of ILs but also point to the design of new ILs that may achieve superefficient control over interfacial and self-assembly systems.

  12. A STUDY OF RAPID CAVITY TUNING.

    SciTech Connect

    ZHAO, Y.

    2001-07-12

    An FFAG moot likely requires rapid cavity tuning. The cavity must also have a very high gradient. To satisfy both the high power and rapid tuning requirements is a big challenge. Detailed investigation of the possibility is addressed. Included are general thoughts, dual-loop and simple loop analyses, and a study of using ferrite or PIN diodes. Also proposed is a phase control scheme, which may be a better solution if the needed components can be developed. Finally, an energy analysis reveals the difficult of high power tuning.

  13. Automated tuning of an eight-channel cardiac transceive array at 7 tesla using piezoelectric actuators

    PubMed Central

    Keith, Graeme A; Rodgers, Christopher T; Hess, Aaron T; Snyder, Carl J; Vaughan, J Thomas; Robson, Matthew D

    2015-01-01

    Purpose Ultra-high field (UHF) MR scanning in the body requires novel coil designs due to B1 field inhomogeneities. In the transverse electromagnetic field (TEM) design, maximum B1 transmit power can only be achieved if each individual transmit element is tuned and matched for different coil loads, which requires a considerable amount of valuable scanner time. Methods An integrated system for autotuning a multichannel parallel transmit (pTx) cardiac TEM array was devised, using piezoelectric actuators, power monitoring equipment and control software. The reproducibility and performance of the system were tested and the power responses of the coil elements were profiled. An automated optimization method was devised and evaluated. Results The time required to tune an eight-element pTx cardiac RF array was reduced from a mean of 30 min to less than 10 min with the use of this system. Conclusion Piezoelectric actuators are an attractive means of tuning RF coil arrays to yield more efficient B1 transmission into the subject. An automated mechanism for tuning these elements provides a practical solution for cardiac imaging at UHF, bringing this technology closer to clinical use. Magn Reson Med 73:2390–2397, 2015. © 2014 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. PMID:24986525

  14. Thermodynamically Tuned Nanophase Materials for reversible Hydrogen storage

    SciTech Connect

    Ping Liu; John J. Vajo

    2010-02-28

    This program was devoted to significantly extending the limits of hydrogen storage technology for practical transportation applications. To meet the hydrogen capacity goals set forth by the DOE, solid-state materials consisting of light elements were developed. Many light element compounds are known that have high capacities. However, most of these materials are thermodynamically too stable, and they release and store hydrogen much too slowly for practical use. In this project we developed new light element chemical systems that have high hydrogen capacities while also having suitable thermodynamic properties. In addition, we developed methods for increasing the rates of hydrogen exchange in these new materials. The program has significantly advanced (1) the application of combined hydride systems for tuning thermodynamic properties and (2) the use of nanoengineering for improving hydrogen exchange. For example, we found that our strategy for thermodynamic tuning allows both entropy and enthalpy to be favorably adjusted. In addition, we demonstrated that using porous supports as scaffolds to confine hydride materials to nanoscale dimensions could improve rates of hydrogen exchange by > 50x. Although a hydrogen storage material meeting the requirements for commercial development was not achieved, this program has provided foundation and direction for future efforts. More broadly, nanoconfinment using scaffolds has application in other energy storage technologies including batteries and supercapacitors. The overall goal of this program was to develop a safe and cost-effective nanostructured light-element hydride material that overcomes the thermodynamic and kinetic barriers to hydrogen reaction and diffusion in current materials and thereby achieve > 6 weight percent hydrogen capacity at temperatures and equilibrium pressures consistent with DOE target values.

  15. Accurate Guitar Tuning by Cochlear Implant Musicians

    PubMed Central

    Lu, Thomas; Huang, Juan; Zeng, Fan-Gang

    2014-01-01

    Modern cochlear implant (CI) users understand speech but find difficulty in music appreciation due to poor pitch perception. Still, some deaf musicians continue to perform with their CI. Here we show unexpected results that CI musicians can reliably tune a guitar by CI alone and, under controlled conditions, match simultaneously presented tones to <0.5 Hz. One subject had normal contralateral hearing and produced more accurate tuning with CI than his normal ear. To understand these counterintuitive findings, we presented tones sequentially and found that tuning error was larger at ∼30 Hz for both subjects. A third subject, a non-musician CI user with normal contralateral hearing, showed similar trends in performance between CI and normal hearing ears but with less precision. This difference, along with electric analysis, showed that accurate tuning was achieved by listening to beats rather than discriminating pitch, effectively turning a spectral task into a temporal discrimination task. PMID:24651081

  16. Tune control in the Fermilab Main Injector

    SciTech Connect

    G. Wu et al.

    1999-04-16

    We describe methods used to measure and control tunes in the Fermilab Main Injector (FMI). Emphasis is given to software implementation of the operator interface, to the front-end embedded computer system, and handling of hysteresis of main dipole and quadrupole magnets. Techniques are developed to permit control of tune of the Main Injector through several acceleration cycles: from 8.9 GeV/c to 120 GeV/c, from 8.9 GeV/c to 150 GeV/c, and from 150 GeV/c to 8.9 GeV/c. Systems which automate the complex interactions between tune measurement and the variety of ramping options are described. Some results of tune measurements and their comparison with the design model are presented.

  17. Tuning the Response in Disordered Networks

    NASA Astrophysics Data System (ADS)

    Pashine, Nidhi; Rocks, Jason W.; Bischofberger, Irmgard; Goodrich, Carl P.; Nagel, Sidney R.; Liu, Andrea J.

    The fact that amorphous materials are structurally different from crystals has important consequences for how the properties of a disordered structure can be tuned. We have used jamming as a method to create spring networks in both two and three dimensions. By selectively removing a small percentage of bonds, we can tune the network to have a desired response. For example, we can tune the network's Poisson ratio anywhere between the auxetic and incompressible limits. We can also produce a targeted response at a local scale; by perturbing the positions of pair of particles at one point we can tune in a desired response a large distance away. This response is similar to the allosteric regulation in proteins where a reaction at one site activates another site of the protein molecule. Experimentally, we have successfully demonstrated such mechanical networks in 2D (by laser cutting) or in 3D (3D printing).

  18. Accurate guitar tuning by cochlear implant musicians.

    PubMed

    Lu, Thomas; Huang, Juan; Zeng, Fan-Gang

    2014-01-01

    Modern cochlear implant (CI) users understand speech but find difficulty in music appreciation due to poor pitch perception. Still, some deaf musicians continue to perform with their CI. Here we show unexpected results that CI musicians can reliably tune a guitar by CI alone and, under controlled conditions, match simultaneously presented tones to <0.5 Hz. One subject had normal contralateral hearing and produced more accurate tuning with CI than his normal ear. To understand these counterintuitive findings, we presented tones sequentially and found that tuning error was larger at ∼ 30 Hz for both subjects. A third subject, a non-musician CI user with normal contralateral hearing, showed similar trends in performance between CI and normal hearing ears but with less precision. This difference, along with electric analysis, showed that accurate tuning was achieved by listening to beats rather than discriminating pitch, effectively turning a spectral task into a temporal discrimination task.

  19. Crack identification through scan-tuning of vibration characteristics using piezoelectric materials

    NASA Astrophysics Data System (ADS)

    Zhao, Shengjie; Wu, Nan; Wang, Quan

    2017-02-01

    This research develops a frequency-based methodology with a scan vibration tuning process for crack identification in beam-type structures coupled with piezoelectric materials. Piezoelectric sensor and actuator patches are mounted on the surface of the host beam synchronously to generate feedback excitations for a tuning process by applying a feedback voltage output from the piezoelectric sensors. The feedback excitations can adjust the stiffness at local section of the beam covered by piezoelectric patches so as to tune its natural vibration mode shapes to amplify the natural frequency change due to the existence of the crack. Piezoelectric patches located at different positions of the beam are activated one by one to realize the scan-tuning process. The crack is identified since the natural frequency change is magnified by the piezoelectric sensor and actuator located at the crack position. Theoretical and finite element models of the scan-tuned beam structures coupled with piezoelectric materials are established. From simulation results, the crack existence and location can be effectively detected through the scan-tuning process with 25% natural frequency change due to a crack located at the middle of the beam. Further parameter studies are conducted to study the effects of the crack location and size on the detection sensitivity.

  20. Model-independent particle accelerator tuning

    SciTech Connect

    Scheinker, Alexander; Pang, Xiaoying; Rybarcyk, Larry

    2013-10-21

    We present a new model-independent dynamic feedback technique, rotation rate tuning, for automatically and simultaneously tuning coupled components of uncertain, complex systems. The main advantages of the method are: 1) It has the ability to handle unknown, time-varying systems, 2) It gives known bounds on parameter update rates, 3) We give an analytic proof of its convergence and its stability, and 4) It has a simple digital implementation through a control system such as the Experimental Physics and Industrial Control System (EPICS). Because this technique is model independent it may be useful as a real-time, in-hardware, feedback-based optimization scheme for uncertain and time-varying systems. In particular, it is robust enough to handle uncertainty due to coupling, thermal cycling, misalignments, and manufacturing imperfections. As a result, it may be used as a fine-tuning supplement for existing accelerator tuning/control schemes. We present multi-particle simulation results demonstrating the scheme’s ability to simultaneously adaptively adjust the set points of twenty two quadrupole magnets and two RF buncher cavities in the Los Alamos Neutron Science Center Linear Accelerator’s transport region, while the beam properties and RF phase shift are continuously varying. The tuning is based only on beam current readings, without knowledge of particle dynamics. We also present an outline of how to implement this general scheme in software for optimization, and in hardware for feedback-based control/tuning, for a wide range of systems.

  1. An optimal tuning strategy for tidal turbines

    NASA Astrophysics Data System (ADS)

    Vennell, Ross

    2016-11-01

    Tuning wind and tidal turbines is critical to maximizing their power output. Adopting a wind turbine tuning strategy of maximizing the output at any given time is shown to be an extremely poor strategy for large arrays of tidal turbines in channels. This `impatient-tuning strategy' results in far lower power output, much higher structural loads and greater environmental impacts due to flow reduction than an existing `patient-tuning strategy' which maximizes the power output averaged over the tidal cycle. This paper presents a `smart patient tuning strategy', which can increase array output by up to 35% over the existing strategy. This smart strategy forgoes some power generation early in the half tidal cycle in order to allow stronger flows to develop later in the cycle. It extracts enough power from these stronger flows to produce more power from the cycle as a whole than the existing strategy. Surprisingly, the smart strategy can often extract more power without increasing maximum structural loads on the turbines, while also maintaining stronger flows along the channel. This paper also shows that, counterintuitively, for some tuning strategies imposing a cap on turbine power output to limit loads can increase a turbine's average power output.

  2. An optimal tuning strategy for tidal turbines.

    PubMed

    Vennell, Ross

    2016-11-01

    Tuning wind and tidal turbines is critical to maximizing their power output. Adopting a wind turbine tuning strategy of maximizing the output at any given time is shown to be an extremely poor strategy for large arrays of tidal turbines in channels. This 'impatient-tuning strategy' results in far lower power output, much higher structural loads and greater environmental impacts due to flow reduction than an existing 'patient-tuning strategy' which maximizes the power output averaged over the tidal cycle. This paper presents a 'smart patient tuning strategy', which can increase array output by up to 35% over the existing strategy. This smart strategy forgoes some power generation early in the half tidal cycle in order to allow stronger flows to develop later in the cycle. It extracts enough power from these stronger flows to produce more power from the cycle as a whole than the existing strategy. Surprisingly, the smart strategy can often extract more power without increasing maximum structural loads on the turbines, while also maintaining stronger flows along the channel. This paper also shows that, counterintuitively, for some tuning strategies imposing a cap on turbine power output to limit loads can increase a turbine's average power output.

  3. Revisiting fine-tuning in the MSSM

    NASA Astrophysics Data System (ADS)

    Ross, Graham G.; Schmidt-Hoberg, Kai; Staub, Florian

    2017-03-01

    We evaluate the amount of fine-tuning in constrained versions of the minimal supersymmetric standard model (MSSM), with different boundary conditions at the GUT scale. Specifically we study the fully constrained version as well as the cases of non-universal Higgs and gaugino masses. We allow for the presence of additional non-holomorphic soft-terms which we show further relax the fine-tuning. Of particular importance is the possibility of a Higgsino mass term and we discuss possible origins for such a term in UV complete models. We point out that loop corrections typically lead to a reduction in the fine-tuning by a factor of about two compared to the estimate at tree-level, which has been overlooked in many recent works. Taking these loop corrections into account, we discuss the impact of current limits from SUSY searches and dark matter on the fine-tuning. Contrary to common lore, we find that the MSSM fine-tuning can be as small as 10 while remaining consistent with all experimental constraints. If, in addition, the dark matter abundance is fully explained by the neutralino LSP, the fine-tuning can still be as low as ˜ 20 in the presence of additional non-holomorphic soft-terms. We also discuss future prospects of these models and find that the MSSM will remain natural even in the case of a non-discovery in the foreseeable future.

  4. Tuning of nanogap size in high tensile stress silicon nitride thin films.

    PubMed

    Günay-Demirkol, Anıl; Kaya, İsmet İ

    2012-05-01

    High tensile stress suspended structures are demanded for high mechanical quality factor applications. However, high tensile stress causes distortion of the original shapes by contracting, buckling, and bending the suspended structures. We demonstrate a method to compensate for the shape deformation of suspended structures due to intrinsic tensile stress after they are released. With a new design, the distance between two suspended structures after wet etch can easily be tuned by a single fabrication beyond the lithographic resolution limits. The technique is simulated by finite element analysis and experimentally implemented to demonstrate a gap tuning capability with 2.4 nm standard error.

  5. Tuning of nanogap size in high tensile stress silicon nitride thin films

    NASA Astrophysics Data System (ADS)

    Günay-Demirkol, Anıl; Kaya, İsmet İ.

    2012-05-01

    High tensile stress suspended structures are demanded for high mechanical quality factor applications. However, high tensile stress causes distortion of the original shapes by contracting, buckling, and bending the suspended structures. We demonstrate a method to compensate for the shape deformation of suspended structures due to intrinsic tensile stress after they are released. With a new design, the distance between two suspended structures after wet etch can easily be tuned by a single fabrication beyond the lithographic resolution limits. The technique is simulated by finite element analysis and experimentally implemented to demonstrate a gap tuning capability with 2.4 nm standard error.

  6. Tune-out wavelengths of alkali-metal atoms and their applications

    SciTech Connect

    Arora, Bindiya; Safronova, M. S.; Clark, Charles W.

    2011-10-15

    Using first-principles calculations, we identify ''tune-out'' optical wavelengths, {lambda}{sub zero}, for which the ground-state frequency-dependent polarizabilities of alkali-metal atoms vanish. Our approach uses high-precision, relativistic all-order method in which all single, double, and partial triple excitations of the Dirac-Fock wave functions are included to all orders of perturbation theory. We discuss the use of tune-out wavelengths for sympathetic cooling in two-species mixtures of alkali metals with group II and other elements of interest. Special cases in which these wavelengths coincide with strong resonance transitions in a target system are identified.

  7. Elemental ZOO

    NASA Astrophysics Data System (ADS)

    Helser, Terry L.

    2003-04-01

    This puzzle uses the symbols of 39 elements to spell the names of 25 animals found in zoos. Underlined spaces and the names of the elements serve as clues. To solve the puzzle, students must find the symbols that correspond to the elemental names and rearrange them into the animals' names.

  8. Software Controls For Automated Feedback Tuning

    NASA Astrophysics Data System (ADS)

    Lazarski, K.; Alkire, R. W.; Duke, N. E. C.; Rotella, F. J.

    2004-05-01

    The Structural Biology Center (SBC) beamlines have been designed to take full advantage of the highly intense radiation available at Argonne's Advance Photon Source for crystallography experiments. In order to facilitate the delivery of an intense, stable x-ray beam to crystallographic samples, new beam position stabilization software has been developed. Using the beam-position monitor developed by Alkire, Rosenbaum and Evans, the position of the beam is corrected in real time by applying changes to the monochromator tune using DC servomotors. Real-time monitoring tools were developed, in addition to the technique of selecting the reference trigger points. A user interface for feedback tuning has been developed in conjunction with real-time monitoring and interacting with data acquisition at the bending-magnet beamline (19BM) of the SBC. Preliminary results showed positional stability of the beam to better than 1 μrad in tune.

  9. Resonant tuning fork detector for electromagnetic radiation.

    PubMed

    Pohlkötter, Andreas; Willer, Ulrike; Bauer, Christoph; Schade, Wolfgang

    2009-02-01

    A mechanical quartz microresonator (tuning fork) is used to detect electromagnetic radiation. The detection scheme is based on forces created due to the incident electromagnetic radiation on the piezoelectric tuning fork. A force can be created due to the transfer of the photon momentum of the incident electromagnetic radiation. If the surfaces of the tuning fork are nonuniformly heated, a second force acts on it, the so-called photophoretic force. These processes occur for all wavelengths of the incident radiation, making the detector suitable for sensing of ultraviolet, visible, and mid-infrared light, even THz-radiation. Here the detector is characterized in the visible range; noise analysis is performed for 650 nm and 5.26 microm. A linear power characteristic and the dependence on pulse lengths of the incoming light are shown. Examples for applications for the visible and mid-infrared spectral region are given by 2f and absorption spectroscopy of oxygen and nitric oxide, respectively.

  10. Localized electrical fine tuning of passive microwave and radio frequency devices

    DOEpatents

    Findikoglu, Alp T.

    2001-04-10

    A method and apparatus for the localized electrical fine tuning of passive multiple element microwave or RF devices in which a nonlinear dielectric material is deposited onto predetermined areas of a substrate containing the device. An appropriate electrically conductive material is deposited over predetermined areas of the nonlinear dielectric and the signal line of the device for providing electrical contact with the nonlinear dielectric. Individual, adjustable bias voltages are applied to the electrically conductive material allowing localized electrical fine tuning of the devices. The method of the present invention can be applied to manufactured devices, or can be incorporated into the design of the devices so that it is applied at the time the devices are manufactured. The invention can be configured to provide localized fine tuning for devices including but not limited to coplanar waveguides, slotline devices, stripline devices, and microstrip devices.

  11. A PI tuning rule for integrating plus dead time processes with parametric uncertainty.

    PubMed

    Mercader, Pedro; Baños, Alfonso

    2017-03-01

    A novel method to tune a Proportional-Integral (PI) compensator for an integrating plus dead time (IPDT) process, in presence of interval parametric uncertainty, is presented. The design is based on optimization of load disturbance rejection with constraints on the magnitude of the sensitivity and complementary sensitivity functions, that must be satisfied for any element belonging to a set of plants. Instead of solving this problem with a brute force approach (grid the uncertainty set), we prove that this problem can be solved by considering only two plants. That lets us to obtain a tuning rule, after using some approximations. To conclude, some examples will be given in order to elucidate the usefulness of the proposed tuning rule.

  12. Model-independent particle accelerator tuning

    DOE PAGES

    Scheinker, Alexander; Pang, Xiaoying; Rybarcyk, Larry

    2013-10-21

    We present a new model-independent dynamic feedback technique, rotation rate tuning, for automatically and simultaneously tuning coupled components of uncertain, complex systems. The main advantages of the method are: 1) It has the ability to handle unknown, time-varying systems, 2) It gives known bounds on parameter update rates, 3) We give an analytic proof of its convergence and its stability, and 4) It has a simple digital implementation through a control system such as the Experimental Physics and Industrial Control System (EPICS). Because this technique is model independent it may be useful as a real-time, in-hardware, feedback-based optimization scheme formore » uncertain and time-varying systems. In particular, it is robust enough to handle uncertainty due to coupling, thermal cycling, misalignments, and manufacturing imperfections. As a result, it may be used as a fine-tuning supplement for existing accelerator tuning/control schemes. We present multi-particle simulation results demonstrating the scheme’s ability to simultaneously adaptively adjust the set points of twenty two quadrupole magnets and two RF buncher cavities in the Los Alamos Neutron Science Center Linear Accelerator’s transport region, while the beam properties and RF phase shift are continuously varying. The tuning is based only on beam current readings, without knowledge of particle dynamics. We also present an outline of how to implement this general scheme in software for optimization, and in hardware for feedback-based control/tuning, for a wide range of systems.« less

  13. Turbine bucket natural frequency tuning rib

    DOEpatents

    Wang, John Zhiqiang; Norton, Paul Francis; Barb, Kevin Joseph; Jacala, Ariel Caesar-Prepena

    2002-01-01

    A tuning rib is added preferably in the aft cavity of a cored turbine bucket to alter the bucket's natural frequencies. The tuning rib may be a solid rib or a segmented rib and is particularly suited for altering high order frequency modes such as 2T, 4F and 1-3S. As such, detrimental crossings of natural bucket frequencies and gas turbine stimuli can be avoided to thereby improve the reliability of a gas turbine without impacting other features of the bucket that are important to the performance of the gas turbine.

  14. The nonlinear piezoelectric tuned vibration absorber

    NASA Astrophysics Data System (ADS)

    Soltani, P.; Kerschen, G.

    2015-07-01

    This paper proposes a piezoelectric vibration absorber, termed the nonlinear piezoelectric tuned vibration absorber (NPTVA), for the mitigation of nonlinear resonances of mechanical systems. The new feature of the NPTVA is that its nonlinear restoring force is designed according to a principle of similarity, i.e., the NPTVA should be an electrical analog of the nonlinear host system. Analytical formulas for the NPTVA parameters are derived using the homotopy perturbation method. Doing so, a nonlinear generalization of Den Hartog’s equal-peak tuning rule is developed for piezoelectric vibration absorbers.

  15. Fine-tuning in DBI inflationary mechanism

    SciTech Connect

    Chen, Xingang

    2008-12-15

    We show a model-independent fine-tuning issue in the DBI inflationary mechanism. DBI inflation requires a warp factor h small enough to sufficiently slow down the inflation. On the other hand, the Einstein equation in extra dimensions under the inflationary background deforms the warp space on the IR side. Generically these two locations coincide with each other, spoiling the DBI inflation. The origin and tuning of this 'h problem' is closely related, through the AdS/CFT duality, to those of the well-known '{eta} problem' in the slow-roll inflationary mechanism.

  16. A systematic approach for precision electrostatic mode tuning of a MEMS gyroscope

    NASA Astrophysics Data System (ADS)

    Hu, Z. X.; Gallacher, B. J.; Burdess, J. S.; Bowles, S. R.; Grigg, H. T. D.

    2014-12-01

    In this paper a systematic approach to precision electrostatic frequency tuning of the operational modes of a MEMS ring vibratory gyroscope is presented. In both rate and rate integrating gyroscopes the frequency split between the two modes of vibration which detect the Coriolis acceleration is one of the principal factors in determining the sensitivity and noise floor of the sensor. In high precision applications in the defence/aerospace sector a frequency split of the order of 10 mHz or less is highly desirable. In the ground-breaking Hemispherical Resonator Gyroscope (HRG) electrostatic tuning has been employed as a tuning mechanism. However, a description of the procedure is not available in the literature. The tuning scheme described here involves assessing mode mistuning by the ratio of the in-phase and quadrature components of the response to an external force that has similar properties to the gyroscopic force resulting from Coriolis action, and choosing the tuning voltages so that independent modification of the elements of the system stiffness matrix can be achieved. Experiments on a commercially available gyroscope with a natural frequency of 14 kHz show that the frequency split can be reduced from 1.5 Hz to 6 mHz. This represents a frequency precision of better than 1 part in a million.

  17. Optimal tuning and calibration of bendable mirrors with slope measuring profilers

    SciTech Connect

    McKinney, Wayne; Kirschman, Jonathan; MacDowell, Alastair; Warwick, Tony; Yashchuk, Valeriy

    2009-06-22

    We describe a technique to optimally tune and calibrate bendable x-ray optics for sub-micron focusing. The focusing is divided between two elliptically cylindrical reflecting elements, a Kirkpatrick-Baez (KB) pair. Each optic is shaped by applying unequal bending couples to each end of a flat mirror. The developed technique allowsoptimal tuning of these systems using surface slope data obtained with a slope measuring instrument, the long trace profiler (LTP). Due to the near linearity of the problem, the minimal set of data necessary for the tuning of each bender, consists of only three slope traces measured before and after a single adjustment of each bending couple. The data are analyzed with software realizing a method of regression analysis with experimentally found characteristic functions of the benders. The resulting approximation to the functional dependence of the desired shape provides nearly final settings. Moreover, the characteristic functions of the benders found in the course of tuning, can be used for retuning to a new desired shape without removal from the beamline and re-measuring. We perform a ray trace, using profiler data for the finally tuned optics, predicting the performance to be expected during use of the optics on the beamline.

  18. Extension of IMC tuning correlations for non-self regulating (integrating) processes.

    PubMed

    Arbogast, Jeffrey E; Cooper, Douglas J

    2007-06-01

    The filter term of a PID with Filter controller reduces the impact of measurement noise on the derivative action of the controller. This impact is quantified by the controller output travel defined as the total movement of the controller output per unit time. Decreasing controller output travel is important to reduce wear in the final control element. Internal Model Control (IMC) tuning correlations are widely published for PI, PID, and PID with Filter controllers for self regulating processes. For non-self regulating (or integrating) processes, IMC tuning correlations are published for PI and PID controllers but not for PID with Filter controllers. The important contribution of this work is that it completes the set of IMC tuning correlations with an extension to the PID with Filter controller for non-self regulating processes. Other published correlations (not based upon the IMC framework) for PID with Filter controllers fix the filter time constant at one-tenth the derivative time regardless of the model of the process. In contrast, the novel IMC correlations presented in this paper calculate a filter time constant based upon the model of the process and the user's choice for the closed-loop time constant. The set point tracking and disturbance rejection performance of the proposed IMC tunings is demonstrated using simulation studies and a bench-scale experimental system. The proposed IMC tunings are shown to perform as well as various PID correlations (with and without a filter term) while requiring considerably less controller action.

  19. An automated method of tuning an attitude estimator

    NASA Technical Reports Server (NTRS)

    Mason, Paul A. C.; Mook, D. Joseph

    1995-01-01

    Attitude determination is a major element of the operation and maintenance of a spacecraft. There are several existing methods of determining the attitude of a spacecraft. One of the most commonly used methods utilizes the Kalman filter to estimate the attitude of the spacecraft. Given an accurate model of a system and adequate observations, a Kalman filter can produce accurate estimates of the attitude. If the system model, filter parameters, or observations are inaccurate, the attitude estimates may be degraded. Therefore, it is advantageous to develop a method of automatically tuning the Kalman filter to produce the accurate estimates. In this paper, a three-axis attitude determination Kalman filter, which uses only magnetometer measurements, is developed and tested using real data. The appropriate filter parameters are found via the Process Noise Covariance Estimator (PNCE). The PNCE provides an optimal criterion for determining the best filter parameters.

  20. Electro-Optic Diffraction Grating Tuned Laser.

    DTIC Science & Technology

    The patent concerns an electro - optic diffraction grating tuned laser comprising a laser medium, output mirror, retro-reflective grating and an electro - optic diffraction grating beam deflector positioned between the laser medium and the reflective diffraction grating. An optional angle multiplier may be used between the electro - optic diffraction grating and the reflective grating.

  1. Does Face Inversion Change Spatial Frequency Tuning?

    ERIC Educational Resources Information Center

    Willenbockel, Verena; Fiset, Daniel; Chauvin, Alan; Blais, Caroline; Arguin, Martin; Tanaka, James W.; Bub, Daniel N.; Gosselin, Frederic

    2010-01-01

    The authors examined spatial frequency (SF) tuning of upright and inverted face identification using an SF variant of the Bubbles technique (F. Gosselin & P. G. Schyns, 2001). In Experiment 1, they validated the SF Bubbles technique in a plaid detection task. In Experiments 2a-c, the SFs used for identifying upright and inverted inner facial…

  2. Efficient receiver tuning using differential evolution strategies

    NASA Astrophysics Data System (ADS)

    Wheeler, Caleb H.; Toland, Trevor G.

    2016-08-01

    Differential evolution (DE) is a powerful and computationally inexpensive optimization strategy that can be used to search an entire parameter space or to converge quickly on a solution. The Kilopixel Array Pathfinder Project (KAPPa) is a heterodyne receiver system delivering 5 GHz of instantaneous bandwidth in the tuning range of 645-695 GHz. The fully automated KAPPa receiver test system finds optimal receiver tuning using performance feedback and DE. We present an adaptation of DE for use in rapid receiver characterization. The KAPPa DE algorithm is written in Python 2.7 and is fully integrated with the KAPPa instrument control, data processing, and visualization code. KAPPa develops the technologies needed to realize heterodyne focal plane arrays containing 1000 pixels. Finding optimal receiver tuning by investigating large parameter spaces is one of many challenges facing the characterization phase of KAPPa. This is a difficult task via by-hand techniques. Characterizing or tuning in an automated fashion without need for human intervention is desirable for future large scale arrays. While many optimization strategies exist, DE is ideal for time and performance constraints because it can be set to converge to a solution rapidly with minimal computational overhead. We discuss how DE is utilized in the KAPPa system and discuss its performance and look toward the future of 1000 pixel array receivers and consider how the KAPPa DE system might be applied.

  3. Understanding the Fine Tuning in Our Universe

    ERIC Educational Resources Information Center

    Cohen, Bernard L.

    2008-01-01

    It is often stated that the physical properties of our universe are "fine tuned"--that is, they must be almost exactly as they are to make the development of intelligent life possible. The implications of this statement, called the "anthropic principle," have been widely discussed in a philosophical context, but the scientific basis for the…

  4. Fine-Tuning Your Ensemble's Jazz Style.

    ERIC Educational Resources Information Center

    Garcia, Antonio J.

    1991-01-01

    Proposes instructional strategies for directors of jazz groups, including guidelines for developing of skills necessary for good performance. Includes effective methods for positive changes in ensemble style. Addresses jazz group problems such as beat, tempo, staying in tune, wind power, and solo/ensemble lines. Discusses percussionists, bassists,…

  5. Dreams, mnemonics, and tuning for criticality.

    PubMed

    Pearlmutter, Barak A; Houghton, Conor J

    2013-12-01

    According to the tuning-for-criticality theory, the essential role of sleep is to protect the brain from super-critical behaviour. Here we argue that this protective role determines the content of dreams and any apparent relationship to the art of memory is secondary to this.

  6. Tuning Knobs for the NLC Final Focus

    SciTech Connect

    Nosochkov, Yuri

    2002-06-18

    Compensation of optics errors at the Interaction Point (IP) is essential for maintaining maximum luminosity at the NLC. Several correction systems (knobs) using the Final Focus sextupoles have been designed to provide orthogonal compensation of linear and the second order optics aberrations at IP. Tuning effects of these knobs on the 250 GeV beam were verified using tracking simulations.

  7. Natural tuning: towards a proof of concept

    NASA Astrophysics Data System (ADS)

    Dubovsky, Sergei; Gorbenko, Victor; Mirbabayi, Mehrdad

    2013-09-01

    The cosmological constant problem and the absence of new natural physics at the electroweak scale, if confirmed by the LHC, may either indicate that the nature is fine-tuned or that a refined notion of naturalness is required. We construct a family of toy UV complete quantum theories providing a proof of concept for the second possibility. Low energy physics is described by a tuned effective field theory, which exhibits relevant interactions not protected by any symmetries and separated by an arbitrary large mass gap from the new "gravitational" physics, represented by a set of irrelevant operators. Nevertheless, the only available language to describe dynamics at all energy scales does not require any fine-tuning. The interesting novel feature of this construction is that UV physics is not described by a fixed point, but rather exhibits asymptotic fragility. Observation of additional unprotected scalars at the LHC would be a smoking gun for this scenario. Natural tuning also favors TeV scale unification.

  8. Observation of cosmic ray positrons from 5 to 25 GeV

    NASA Technical Reports Server (NTRS)

    Golden, R. L.; Mauger, B. G.; Horan, S.; Badhwar, G. D.; Lacy, J. L.; Zipse, J. E.; Daniel, R. R.; Stephens, S. A.

    1985-01-01

    The positron data gathered in conjunction with electron data published elsewhere is reported. The basic recognition scheme was to look for low mass positive particles that cause a cascade in a 7 radiation length shower counter. The mass criteria is imposed by selecting particles that were accompanied by Cherenkov light but whose rigidity was below the proton Cherenkov threshold. Thus the proton Cherenkov threshold represents an upper limit to the range of the experiment.

  9. Application of a system modification technique to dynamic tuning of a spinning rotor blade

    NASA Technical Reports Server (NTRS)

    Spain, C. V.

    1987-01-01

    An important consideration in the development of modern helicopters is the vibratory response of the main rotor blade. One way to minimize vibration levels is to ensure that natural frequencies of the spinning main rotor blade are well removed from integer multiples of the rotor speed. A technique for dynamically tuning a finite-element model of a rotor blade to accomplish that end is demonstrated. A brief overview is given of the general purpose finite element system known as Engineering Analysis Language (EAL) which was used in this work. A description of the EAL System Modification (SM) processor is then given along with an explanation of special algorithms developed to be used in conjunction with SM. Finally, this technique is demonstrated by dynamically tuning a model of an advanced composite rotor blade.

  10. Logic elements for reactor period meter

    DOEpatents

    McDowell, William P.; Bobis, James P.

    1976-01-01

    Logic elements are provided for a reactor period meter trip circuit. For one element, first and second inputs are applied to first and second chopper comparators, respectively. The output of each comparator is O if the input applied to it is greater than or equal to a trip level associated with each input and each output is a square wave of frequency f if the input applied to it is less than the associated trip level. The outputs of the comparators are algebraically summed and applied to a bandpass filter tuned to f. For another element, the output of each comparator is applied to a bandpass filter which is tuned to f to give a sine wave of frequency f. The outputs of the filters are multiplied by an analog multiplier whose output is 0 if either input is 0 and a sine wave of frequency 2f if both inputs are a frequency f.

  11. Elemental health

    SciTech Connect

    Tonneson, L.C.

    1997-01-01

    Trace elements used in nutritional supplements and vitamins are discussed in the article. Relevant studies are briefly cited regarding the health effects of selenium, chromium, germanium, silicon, zinc, magnesium, silver, manganese, ruthenium, lithium, and vanadium. The toxicity and food sources are listed for some of the elements. A brief summary is also provided of the nutritional supplements market.

  12. Active noise control using noise source having adaptive resonant frequency tuning through stress variation

    NASA Technical Reports Server (NTRS)

    Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor); Renshaw, Anthony A. (Inventor); Hedeen, Robert A. (Inventor)

    1995-01-01

    A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of a noise radiating element is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating element is tuned by an expandable ring embedded in the noise radiating element. Excitation of the ring causes expansion or contraction of the ring, thereby varying the stress in the noise radiating element. The ring is actuated by a controller which receives input of a feedback signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the ring, causing the ring to expand or contract. Instead of a single ring embedded in the noise radiating panel, a first expandable ring can be bonded to one side of the noise radiating element, and a second expandable ring can be bonded to the other side.

  13. Application of genetic algorithms to tuning fuzzy control systems

    NASA Technical Reports Server (NTRS)

    Espy, Todd; Vombrack, Endre; Aldridge, Jack

    1993-01-01

    Real number genetic algorithms (GA) were applied for tuning fuzzy membership functions of three controller applications. The first application is our 'Fuzzy Pong' demonstration, a controller that controls a very responsive system. The performance of the automatically tuned membership functions exceeded that of manually tuned membership functions both when the algorithm started with randomly generated functions and with the best manually-tuned functions. The second GA tunes input membership functions to achieve a specified control surface. The third application is a practical one, a motor controller for a printed circuit manufacturing system. The GA alters the positions and overlaps of the membership functions to accomplish the tuning. The applications, the real number GA approach, the fitness function and population parameters, and the performance improvements achieved are discussed. Directions for further research in tuning input and output membership functions and in tuning fuzzy rules are described.

  14. Evolutionary Computation Applied to the Tuning of MEMS Gyroscopes

    NASA Technical Reports Server (NTRS)

    Keymeulen, Didier; Fink, Wolfgang; Ferguson, Michael I.; Peay, Chris; Oks, Boris; Terrile, Richard; Yee, Karl

    2005-01-01

    We propose a tuning method for MEMS gyroscopes based on evolutionary computation to efficiently increase the sensitivity of MEMS gyroscopes through tuning and, furthermore, to find the optimally tuned configuration for this state of increased sensitivity. The tuning method was tested for the second generation JPL/Boeing Post-resonator MEMS gyroscope using the measurement of the frequency response of the MEMS device in open-loop operation.

  15. Tuning of fault tolerant control design parameters.

    PubMed

    DeLima, Pedro G; Yen, Gary G

    2008-01-01

    This paper presents two major contributions in the field of fault tolerant control. First, it gathers points of concern typical to most fault tolerant control applications and translates the chosen performance metrics into a set of six practical design specifications. Second, it proposes initialization and tuning procedures through which a particular fault tolerant control architecture not only can be set to comply with the required specifications, but also can be tuned online to compensate for a total of twelve properties, such as the noise rejection levels for fault detection and diagnosis signals. The proposed design is realized over a powerful architecture that combines the flexibility of adaptive critic designs with the long term memory and learning capabilities of a supervisor. This paper presents a practical design procedure to facilitate the applications of a fundamentally sound fault tolerant control architecture in real-world problems.

  16. Tuning ferromagnetism by varying ion beam profiles

    NASA Astrophysics Data System (ADS)

    Hariwal, Rajesh V.; Malik, Hitendra K.; Asokan, K.

    2017-02-01

    Present study demonstrates a novel technique to tune the ferromagnetism at room temperature by varying the ion beam profiles from 3 to 7 mm during Carbon ion implantation in ZnO matrix and keeping other beam parameters constant. The interaction of implanted C ions with host ZnO matrix at different profiles result in variable ferromagnetism from 0.75 to 3.0  ×  10‑4 emu gm‑1 due to difference in the induced radiation pressure. Similar variation is also observed in the optical bandgap from 3.35 to 3.24 eV for different beam profiles. This study shows that the material properties can be tuned and controlled by the variation of beam profiles during the ion implantation.

  17. I Tune, You Tube, We Rule

    NASA Astrophysics Data System (ADS)

    Shida, R. Y.; Gater, W.

    2007-10-01

    The website YouTube was created in 2005 and has rapidly become one of the most popular entertainment websites on the internet. It is riding the online video wave today like few other online companies and is currently more popular than the video sections of either Yahoo or Google. iTunes, a digital media application created by Apple in 2001, where one can download and play music and videos, has had a similar success. There is little doubt that they both represent important communication channels in a world heavily influenced by online media, especially among teenagers and young adults. As science communicators we can use this direct route to a younger audience to our advantage. This article aims to give a taste of these applications with a few selected examples demonstrating that both YouTube and iTunes are excellent tools to teach and inspire the general public.

  18. Tuning strain in flexible graphene nanoelectromechanical resonators

    NASA Astrophysics Data System (ADS)

    Guan, Fen; Kumaravadivel, Piranavan; Averin, Dmitri V.; Du, Xu

    2015-11-01

    The structural flexibility of low dimensional nanomaterials offers unique opportunities for studying the impact of strain on their physical properties and for developing innovative devices utilizing strain engineering. A key towards such goals is a device platform which allows the independent tuning and reliable calibration of the strain. Here, we report the fabrication and characterization of graphene nanoelectromechanical resonators (GNEMRs) on flexible substrates. Combining substrate bending and electrostatic gating, we achieve the independent tuning of the strain and sagging in graphene and explore the nonlinear dynamics over a wide parameter space. Analytical and numerical studies of a continuum mechanics model, including the competing higher order nonlinear terms, reveal a comprehensive nonlinear dynamics phase diagram, which quantitatively explains the complex behaviors of GNEMRs.

  19. Optical fiber grating tuning device and application

    NASA Astrophysics Data System (ADS)

    Luo, Fei; Yeh, T.

    2008-12-01

    A new design for tuning optical fiber grating is proposed. The fiber grating is placed in the grooves between a pair of slides, in which one end of the fiber is bonded on the bottom slide, and the other end of the fiber is bonded on the top slide, the grating section of the fiber is confined in grooves, so that the fiber grating is remaining straight without buckling during axial compressive force applied to the fiber. An actuator is used for driving slide to apply force on fiber to axially compress or stretch the fiber grating. The wavelength of the fiber grating is tuned according to applied stress on the fiber. The applications of the device include tunable fiber laser, tunable fiber filter etc.

  20. Musician's and Physicist's View on Tuning Keyboard Instruments

    ERIC Educational Resources Information Center

    Lubenow, Martin; Meyn, Jan-Peter

    2007-01-01

    The simultaneous sound of several voices or instruments requires proper tuning to achieve consonance for certain intervals and chords. Most instruments allow enough frequency variation to enable pure tuning while being played. Keyboard instruments such as organ and piano have given frequencies for individual notes and the tuning must be based on a…

  1. Thiadiazoloquinoxalines: tuning physical properties through smart synthesis.

    PubMed

    Dallos, Timea; Hamburger, Manuel; Baumgarten, Martin

    2011-04-15

    The synthesis of π-conjugated acceptors based on thiadiazoloquinoxaline (TQ) derivatives is described. Apart from reporting on the functionalization of the TQ core, the influence of the substituents was studied by UV-vis absorption and emission spectroscopy, cyclic voltammetry measurements, and DFT calculations. By changing the donor as well as the π-spacer, a fine-tuning of the photo- and electrochemical properties was achieved.

  2. Resistive Fine Tuning of Resonant Circuit

    NASA Technical Reports Server (NTRS)

    Mclyman, C. W.

    1985-01-01

    Simple fixed-inductance/fixed-capacitance tank circuit modified for fine adjustment of resonant frequency by addition of small inductance with potentiometer across it. Additional winding built into full winding as integral part or added externally. Technique provides quick way of tuning reactance out of power-transformer circuit to maximize power transfer or to adjust frequency of oscillator. Applications include rotary transformers, servo amplifiers, and analog computer modules.

  3. Turbine blade with tuned damping structure

    DOEpatents

    Campbell, Christian X.; Messmann, Stephen J.

    2015-09-01

    A turbine blade is provided comprising: a root; an airfoil comprising an external wall extending radially from the root and having a radially outermost portion; and a damping structure. The external wall may comprise first and second side walls joined together to define an inner cavity of the airfoil. The damping structure may be positioned within the airfoil inner cavity and coupled to the airfoil so as to define a tuned mass damper.

  4. Parameterizing loop fusion for automated empirical tuning

    SciTech Connect

    Zhao, Y; Yi, Q; Kennedy, K; Quinlan, D; Vuduc, R

    2005-12-15

    Traditional compilers are limited in their ability to optimize applications for different architectures because statically modeling the effect of specific optimizations on different hardware implementations is difficult. Recent research has been addressing this issue through the use of empirical tuning, which uses trial executions to determine the optimization parameters that are most effective on a particular hardware platform. In this paper, we investigate empirical tuning of loop fusion, an important transformation for optimizing a significant class of real-world applications. In spite of its usefulness, fusion has attracted little attention from previous empirical tuning research, partially because it is much harder to configure than transformations like loop blocking and unrolling. This paper presents novel compiler techniques that extend conventional fusion algorithms to parameterize their output when optimizing a computation, thus allowing the compiler to formulate the entire configuration space for loop fusion using a sequence of integer parameters. The compiler can then employ an external empirical search engine to find the optimal operating point within the space of legal fusion configurations and generate the final optimized code using a simple code transformation system. We have implemented our approach within our compiler infrastructure and conducted preliminary experiments using a simple empirical search strategy. Our results convey new insights on the interaction of loop fusion with limited hardware resources, such as available registers, while confirming conventional wisdom about the effectiveness of loop fusion in improving application performance.

  5. Tuning Your Priors to the World

    PubMed Central

    Feldman, Jacob

    2013-01-01

    The idea that perceptual and cognitive systems must incorporate knowledge about the structure of the environment has become a central dogma of cognitive theory. In a Bayesian context, this idea is often realized in terms of “tuning the prior”—widely assumed to mean adjusting prior probabilities so that they match the frequencies of events in the world. This kind of “ecological” tuning has often been held up as an ideal of inference, in fact defining an “ideal observer.” But widespread as this viewpoint is, it directly contradicts Bayesian philosophy of probability, which views probabilities as degrees of belief rather than relative frequencies, and explicitly denies that they are objective characteristics of the world. Moreover, tuning the prior to observed environmental frequencies is subject to overfitting, meaning in this context overtuning to the environment, which leads (ironically) to poor performance in future encounters with the same environment. Whenever there is uncertainty about the environment—which there almost always is—an agent's prior should be biased away from ecological relative frequencies and toward simpler and more entropic priors. PMID:23335572

  6. Tuned Chamber Core Panel Acoustic Test Results

    NASA Technical Reports Server (NTRS)

    Schiller, Noah H.; Allen, Albert R.

    2016-01-01

    This report documents acoustic testing of tuned chamber core panels, which can be used to supplement the low-frequency performance of conventional acoustic treatment. The tuned chamber core concept incorporates low-frequency noise control directly within the primary structure and is applicable to sandwich constructions with a directional core, including corrugated-, truss-, and fluted-core designs. These types of sandwich structures have long, hollow channels (or chambers) in the core. By adding small holes through one of the facesheets, the hollow chambers can be utilized as an array of low-frequency acoustic resonators. These resonators can then be used to attenuate low-frequency noise (below 400 Hz) inside a vehicle compartment without increasing the weight or size of the structure. The results of this test program demonstrate that the tuned chamber core concept is effective when used in isolation or combined with acoustic foam treatments. Specifically, an array of acoustic resonators integrated within the core of the panels was shown to improve both the low-frequency absorption and transmission loss of the structure in targeted one-third octave bands.

  7. Tuning your priors to the world.

    PubMed

    Feldman, Jacob

    2013-01-01

    The idea that perceptual and cognitive systems must incorporate knowledge about the structure of the environment has become a central dogma of cognitive theory. In a Bayesian context, this idea is often realized in terms of "tuning the prior"-widely assumed to mean adjusting prior probabilities so that they match the frequencies of events in the world. This kind of "ecological" tuning has often been held up as an ideal of inference, in fact defining an "ideal observer." But widespread as this viewpoint is, it directly contradicts Bayesian philosophy of probability, which views probabilities as degrees of belief rather than relative frequencies, and explicitly denies that they are objective characteristics of the world. Moreover, tuning the prior to observed environmental frequencies is subject to overfitting, meaning in this context overtuning to the environment, which leads (ironically) to poor performance in future encounters with the same environment. Whenever there is uncertainty about the environment-which there almost always is-an agent's prior should be biased away from ecological relative frequencies and toward simpler and more entropic priors.

  8. How viruses hijack the ERAD tuning machinery.

    PubMed

    Noack, Julia; Bernasconi, Riccardo; Molinari, Maurizio

    2014-09-01

    An essential step during the intracellular life cycle of many positive-strand RNA viruses is the rearrangement of host cell membranes to generate membrane-bound replication platforms. For example, Nidovirales and Flaviviridae subvert the membrane of the endoplasmic reticulum (ER) for their replication. However, the absence of conventional ER and secretory pathway markers in virus-induced ER-derived membranes has for a long time hampered a thorough understanding of their biogenesis. Recent reports highlight the analogies between mouse hepatitis virus-, equine arteritis virus-, and Japanese encephalitis virus-induced replication platforms and ER-associated degradation (ERAD) tuning vesicles (or EDEMosomes) that display nonlipidated LC3 at their cytosolic face and segregate the ERAD factors EDEM1, OS-9, and SEL1L from the ER lumen. In this Gem, we briefly summarize the current knowledge on ERAD tuning pathways and how they might be hijacked for viral genome replication. As ERAD tuning components, such as SEL1L and nonlipidated LC3, appear to contribute to viral infection, these cellular pathways represent novel candidate drug targets to combat positive-strand RNA viruses.

  9. Elemental Education.

    ERIC Educational Resources Information Center

    Daniel, Esther Gnanamalar Sarojini; Saat, Rohaida Mohd.

    2001-01-01

    Introduces a learning module integrating three disciplines--physics, chemistry, and biology--and based on four elements: carbon, oxygen, hydrogen, and silicon. Includes atomic model and silicon-based life activities. (YDS)

  10. Superheavy Elements

    ERIC Educational Resources Information Center

    Tsang, Chin Fu

    1975-01-01

    Discusses the possibility of creating elements with an atomic number of around 114. Describes the underlying physics responsible for the limited extent of the periodic table and enumerates problems that must be overcome in creating a superheavy nucleus. (GS)

  11. Element 117

    ScienceCinema

    None

    2016-09-30

    An international team of scientists from Russia and the United States, including two Department of Energy national laboratories and two universities, has discovered the newest superheavy element, element 117. The team included scientists from the Joint Institute of Nuclear Research (Dubna, Russia), the Research Institute for Advanced Reactors (Dimitrovgrad), Lawrence Livermore National Laboratory, Oak Ridge National Laboratory, Vanderbilt University, and the University of Nevada, Las Vegas.

  12. Element 117

    SciTech Connect

    2010-04-08

    An international team of scientists from Russia and the United States, including two Department of Energy national laboratories and two universities, has discovered the newest superheavy element, element 117. The team included scientists from the Joint Institute of Nuclear Research (Dubna, Russia), the Research Institute for Advanced Reactors (Dimitrovgrad), Lawrence Livermore National Laboratory, Oak Ridge National Laboratory, Vanderbilt University, and the University of Nevada, Las Vegas.

  13. Numerical performance analysis of quartz tuning fork-based force sensors

    NASA Astrophysics Data System (ADS)

    Dagdeviren, Omur E.; Schwarz, Udo D.

    2017-01-01

    Quartz tuning fork-based force sensors where one prong is immobilized onto a holder while the other one is allowed to oscillate freely (‘qPlus’ configuration) are in widespread use for high-resolution scanning probe microscopy applications. Due to the small size of the tuning forks (≈3 mm) and the complexity of the sensor assemblies, the reliable and repeatable manufacturing of the sensors has been challenging. In this paper, we investigate the contribution of the amount and location of the epoxy glue used to attach the tuning fork to its holder on the sensor’s performance. Towards this end, we use finite element analysis to model the entire sensor assembly and to perform static and dynamic numerical simulations. Our analysis reveals that increasing the thickness of the epoxy layer between prong and holder results in a decrease of the sensor’s spring constant, eigenfrequency, and quality factor while showing an increasing deviation from oscillation in its primary modal shape. Adding epoxy at the sides of the tuning fork also leads to a degradation of the quality factor even though in this case, spring constant and eigenfrequency rise in tandem with a lessening of the deviation from its ideal modal shape.

  14. Continuous and reversible tuning of the disorder-driven superconductor–insulator transition in bilayer graphene

    PubMed Central

    Lee, Gil-Ho; Jeong, Dongchan; Park, Kee-Su; Meir, Yigal; Cha, Min-Chul; Lee, Hu-Jong

    2015-01-01

    The influence of static disorder on a quantum phase transition (QPT) is a fundamental issue in condensed matter physics. As a prototypical example of a disorder-tuned QPT, the superconductor–insulator transition (SIT) has been investigated intensively over the past three decades, but as yet without a general consensus on its nature. A key element is good control of disorder. Here, we present an experimental study of the SIT based on precise in-situ tuning of disorder in dual-gated bilayer graphene proximity-coupled to two superconducting electrodes through electrical and reversible control of the band gap and the charge carrier density. In the presence of a static disorder potential, Andreev-paired carriers formed close to the Fermi level in bilayer graphene constitute a randomly distributed network of proximity-induced superconducting puddles. The landscape of the network was easily tuned by electrical gating to induce percolative clusters at the onset of superconductivity. This is evidenced by scaling behavior consistent with the classical percolation in transport measurements. At lower temperatures, the solely electrical tuning of the disorder-induced landscape enables us to observe, for the first time, a crossover from classical to quantum percolation in a single device, which elucidates how thermal dephasing engages in separating the two regimes. PMID:26310774

  15. In Situ Electrochemical Oxidation Tuning of Transition Metal Disulfides to Oxides for Enhanced Water Oxidation

    PubMed Central

    2015-01-01

    The development of catalysts with earth-abundant elements for efficient oxygen evolution reactions is of paramount significance for clean and sustainable energy storage and conversion devices. Our group demonstrated recently that the electrochemical tuning of catalysts via lithium insertion and extraction has emerged as a powerful approach to improve catalytic activity. Here we report a novel in situ electrochemical oxidation tuning approach to develop a series of binary, ternary, and quaternary transition metal (e.g., Co, Ni, Fe) oxides from their corresponding sulfides as highly active catalysts for much enhanced water oxidation. The electrochemically tuned cobalt–nickel–iron oxides grown directly on the three-dimensional carbon fiber electrodes exhibit a low overpotential of 232 mV at current density of 10 mA cm–2, small Tafel slope of 37.6 mV dec–1, and exceptional long-term stability of electrolysis for over 100 h in 1 M KOH alkaline medium, superior to most non-noble oxygen evolution catalysts reported so far. The materials evolution associated with the electrochemical oxidation tuning is systematically investigated by various characterizations, manifesting that the improved activities are attributed to the significant grain size reduction and increase of surface area and electroactive sites. This work provides a promising strategy to develop electrocatalysts for large-scale water-splitting systems and many other applications. PMID:27162978

  16. High precision tune and coupling measurements and tune/coupling feedback in RHIC

    SciTech Connect

    Minty, M.; Curcio, A.; Dawson, C.; Degen, C.; Luo, Y.; Marr, G.; Martin, B.; Marusic, A.; Mernick, K.; Oddo, P.; Russo, T.; Schoefer, V.; Schroeder, R.; Schulthiess, C.; Wilinski, M.

    2010-08-01

    Precision measurement and control of the betatron tunes and betatron coupling in RHIC are required for establishing and maintaining both good operating conditions and, particularly during the ramp to high beam energies, high proton beam polarization. While the proof-of-principle for simultaneous tune and coupling feedback was successfully demonstrated earlier, routine application of these systems has only become possible recently. Following numerous modifications for improved measurement resolution and feedback control, the time required to establish full-energy beams with the betatron tunes and coupling regulated by feedback was reduced from several weeks to a few hours. A summary of these improvements, select measurements benefitting from the improved resolution and a review of system performance are the subject of this report.

  17. Band gap tuning in transition metal oxides by site-specific substitution

    DOEpatents

    Lee, Ho Nyung; Chisholm, Jr., Matthew F; Jellison, Jr., Gerald Earle; Singh, David J; Choi, Woo Seok

    2013-12-24

    A transition metal oxide insulator composition having a tuned band gap includes a transition metal oxide having a perovskite or a perovskite-like crystalline structure. The transition metal oxide includes at least one first element selected form the group of Bi, Ca, Ba, Sr, Li, Na, Mg, K, Pb, and Pr; and at least one second element selected from the group of Ti, Al, V, Cr, Mn, Fe, Co, Ni, Cu, Zr, Nb, Mo, Ru, Rh, Hf, Ta, W, Re, Os, Ir, and Pt. At least one correlated insulator is integrated into the crystalline structure, including REMO.sub.3, wherein RE is at least one Rare Earth element, and wherein M is at least one element selected from the group of Co, V, Cr, Ni, Mn, and Fe. The composition is characterized by a band gap of less of 4.5 eV.

  18. Orientation tuning of the spatial-frequency-tuned mechanisms of the red-green channel.

    PubMed

    Pandey Vimal, R L

    1997-10-01

    Significant orthogonal masking for color stimuli [Invest. Ophthalmol. Visual Sci. 34, 782 (No. 405-54) (1993)] but not for achromatic stimuli [J. Opt. Soc. Am. A 1, 226 (1984)] under sustained presentation led us to investigate the orientation tuning of the spatial-frequency- (SF-) tuned color mechanisms. The Red-Green channel was isolated from the achromatic channel by the minimum flicker technique and from the Yellow-Blue channel by the hue cancellation technique. Contrast sensitivity functions, threshold elevation versus mask orientation curves (measured by orientation masking), and threshold elevation versus mask contrast curves were measured by the method of constant stimuli and a two-interval forced-choice technique on two normal observers. Test targets were spatially localized (D6), vertical color patterns, and masks were sinusoidal color patterns oriented 15 degrees-90 degrees from the vertical in 15 degrees steps and had the same SF's as those of test patterns. Mask contrasts were varied between 1.2% and 60%. The orientation tuning curves of the SF-tuned color mechanisms were extracted by obtaining the best fit to contrast sensitivity and threshold elevation data simultaneously at a given SF with use of the masking model. Results show that threshold elevations depend on test SF, mask SF, mask orientation, and mask contrast. Half-bandwidths at half-height (with respect to 15 degrees from the vertical) of threshold elevation versus mask orientation curves range from 90 degrees to 29 degrees depending on SF's. The slopes of threshold elevation versus mask contrast curves range from 0.76 to 0.29 on octave-octave coordinates depending on SF's. Orientation half-bandwidths at half-height of orientation tuning curves of the SF-tuned color mechanisms (1) range from 79 degrees to 28 degrees and (2) average from 68 degrees to 30 degrees for SF's 0.063-8 cycles per degree (cpd). Data suggest that the orientation tuning curves of the SF-tuned chromatic mechanisms are

  19. Automatic tuning of the reinforcement function

    SciTech Connect

    Touzet, C.; Santos, J.M.

    1997-12-31

    The aim of this work is to present a method that helps tuning the reinforcement function parameters in a reinforcement learning approach. Since the proposal of neural based implementations for the reinforcement learning paradigm (which reduced learning time and memory requirements to realistic values) reinforcement functions have become the critical components. Using a general definition for reinforcement functions, the authors solve, in a particular case, the so called exploration versus exploitation dilemma through the careful computation of the RF parameter values. They propose an algorithm to compute, during the exploration part of the learning phase, an estimate for the parameter values. Experiments with the mobile robot Nomad 200 validate their proposals.

  20. Tuning quantum correlations with intracavity photonic crystals

    SciTech Connect

    Castro, Maria M. de; Gomila, Damia; Zambrini, Roberta; Garcia-March, Miguel Angel

    2011-09-15

    We show how to tune quantum noise in nonlinear systems by means of periodic spatial modulation. We prove that the introduction of an intracavity photonic crystal in a multimode optical parametric oscillator inhibits and enhances light quantum fluctuations. Furthermore, it leads to a significant noise reduction in field quadratures, robustness of squeezing in a wider angular range, and spatial entanglement. These results have potential benefits for quantum imaging, metrology, and quantum information applications and suggest a control mechanism of fluctuations by spatial modulation of interest also in other nonlinear systems.

  1. Underground tuning: quantitative regulation of root growth.

    PubMed

    Satbhai, Santosh B; Ristova, Daniela; Busch, Wolfgang

    2015-02-01

    Plants display a high degree of phenotypic plasticity that allows them to tune their form and function to changing environments. The plant root system has evolved mechanisms to anchor the plant and to efficiently explore soils to forage for soil resources. Key to this is an enormous capacity for plasticity of multiple traits that shape the distribution of roots in the soil. Such root system architecture-related traits are determined by root growth rates, root growth direction, and root branching. In this review, we describe how the root system is constituted, and which mechanisms, pathways, and genes mainly regulate plasticity of the root system in response to environmental variation.

  2. Stretchable Binary Fresnel Lens for Focus Tuning

    NASA Astrophysics Data System (ADS)

    Li, Xueming; Wei, Lei; Poelma, René H.; Vollebregt, Sten; Wei, Jia; Urbach, Hendrik Paul; Sarro, Pasqualina M.; Zhang, Guo Qi

    2016-05-01

    This paper presents a tuneable binary amplitude Fresnel lens produced by wafer-level microfabrication. The Fresnel lens is fabricated by encapsulating lithographically defined vertically aligned carbon nanotube (CNT) bundles inside a polydimethyl-siloxane (PDMS) layer. The composite lens material combines the excellent optical absorption properties of the CNT with the transparency and stretchability of the PDMS. By stretching the elastomeric composite in radial direction, the lens focal length is tuned. Good focusing response is demonstrated and a large focus change (≥24%) was achieved by stretching lenses up to 11.4%.

  3. Stretchable Binary Fresnel Lens for Focus Tuning.

    PubMed

    Li, Xueming; Wei, Lei; Poelma, René H; Vollebregt, Sten; Wei, Jia; Urbach, Hendrik Paul; Sarro, Pasqualina M; Zhang, Guo Qi

    2016-05-03

    This paper presents a tuneable binary amplitude Fresnel lens produced by wafer-level microfabrication. The Fresnel lens is fabricated by encapsulating lithographically defined vertically aligned carbon nanotube (CNT) bundles inside a polydimethyl-siloxane (PDMS) layer. The composite lens material combines the excellent optical absorption properties of the CNT with the transparency and stretchability of the PDMS. By stretching the elastomeric composite in radial direction, the lens focal length is tuned. Good focusing response is demonstrated and a large focus change (≥24%) was achieved by stretching lenses up to 11.4%.

  4. Dynamic functional tuning of nonlinear cortical networks

    NASA Astrophysics Data System (ADS)

    Stetter, Martin

    2006-03-01

    The mammalian neocortex is a highly complex and nonlinear dynamic system. One of its most prominent features is an omnipresent spontaneous neuronal activity. Here the possible functional role of this global background for cognitive flexibility is studied in a prototypic mean-field model area. It is demonstrated that the level of global background current efficiently controls the stimulus-response threshold and the stability and properties of short-term memory states. Moreover, it can dynamically gate arbitrary cortical subnetworks, when applied to parts of the area as a weak bias signal. These results suggest a central functional role of the level of background activation: the dynamic functional tuning of neocortical circuits.

  5. Pre - big bang inflation requires fine tuning

    SciTech Connect

    Turner, Michael S.; Weinberg, Erick J.

    1997-10-01

    The pre-big-bang cosmology inspired by superstring theories has been suggested as an alternative to slow-roll inflation. We analyze, in both the Jordan and Einstein frames, the effect of spatial curvature on this scenario and show that too much curvature --- of either sign --- reduces the duration of the inflationary era to such an extent that the flatness and horizon problems are not solved. Hence, a fine-tuning of initial conditions is required to obtain enough inflation to solve the cosmological problems.

  6. Stretchable Binary Fresnel Lens for Focus Tuning

    PubMed Central

    Li, Xueming; Wei, Lei; Poelma, René H.; Vollebregt, Sten; Wei, Jia; Urbach, Hendrik Paul; Sarro, Pasqualina M.; Zhang, Guo Qi

    2016-01-01

    This paper presents a tuneable binary amplitude Fresnel lens produced by wafer-level microfabrication. The Fresnel lens is fabricated by encapsulating lithographically defined vertically aligned carbon nanotube (CNT) bundles inside a polydimethyl-siloxane (PDMS) layer. The composite lens material combines the excellent optical absorption properties of the CNT with the transparency and stretchability of the PDMS. By stretching the elastomeric composite in radial direction, the lens focal length is tuned. Good focusing response is demonstrated and a large focus change (≥24%) was achieved by stretching lenses up to 11.4%. PMID:27139747

  7. Nonlinear analysis of a family of LC tuned inverters. [dc to square wave circuits for power conditioning

    NASA Technical Reports Server (NTRS)

    Lee, F. C. Y.; Wilson, T. G.

    1974-01-01

    A family of four dc-to-square-wave LC tuned inverters are analyzed using singular point. Limit cycles and waveshape characteristics are given for three modes of oscillation: quasi-harmonic, relaxation, and discontinuous. An inverter in which the avalanche breakdown of the transistor emitter-to-base junction occurs is discussed and the starting characteristics of this family of inverters are presented. The LC tuned inverters are shown to belong to a family of inverters with a common equivalent circuit consisting of only three 'series' elements: a five-segment piecewise-linear current-controlled resistor, linear inductor, and linear capacitor.

  8. Linking Behavioral and Neurophysiological Indicators of Perceptual Tuning to Language

    PubMed Central

    Fava, Eswen; Hull, Rachel; Bortfeld, Heather

    2011-01-01

    Little is known about the neural mechanisms that underlie tuning to the native language(s) in early infancy. Here we review language tuning through the lens of type and amount of language experience and introduce a new manner in which to conceptualize the phenomenon of language tuning: the relative speed of tuning hypothesis. This hypothesis has as its goal a characterization of the unique time course of the tuning process, given the different components (e.g., phonology, prosody, syntax, semantics) of one or more languages as they become available to infants, and biologically based maturational constraints. In this review, we first examine the established behavioral findings and integrate more recent neurophysiological data on neonatal development, which together demonstrate evidence of early language tuning given differential language exposure even in utero. Next, we examine traditional accounts of sensitive and critical periods to determine how these constructs complement current data on the neural mechanisms underlying language tuning. We then synthesize the extant infant behavioral and neurophysiological data on monolingual, bilingual, and sensory deprived tuning, thereby scrutinizing the effect of these three different language profiles on the specific timing, progression, and outcome of language tuning. Finally, we discuss future directions researchers might pursue to further understand this aspect of language development, advocating our relative speed of tuning hypothesis as a useful framework for conceptualizing the complex process by which language experience works together with biological constraints to shape language development. PMID:21866226

  9. Otoacoustic Estimation of Cochlear Tuning: Validation in the Chinchilla

    PubMed Central

    Guinan, John J.; Oxenham, Andrew J.

    2010-01-01

    We analyze published auditory-nerve and otoacoustic measurements in chinchilla to test a network of hypothesized relationships between cochlear tuning, cochlear traveling-wave delay, and stimulus-frequency otoacoustic emissions (SFOAEs). We find that the physiological data generally corroborate the network of relationships, including predictions from filter theory and the coherent-reflection model of OAE generation, at locations throughout the cochlea. The results support the use of otoacoustic emissions as noninvasive probes of cochlear tuning. Developing this application, we find that tuning ratios—defined as the ratio of tuning sharpness to SFOAE phase-gradient delay in periods—have a nearly species-invariant form in cat, guinea pig, and chinchilla. Analysis of the tuning ratios identifies a species-dependent parameter that locates a transition between “apical-like” and “basal-like” behavior involving multiple aspects of cochlear physiology. Approximate invariance of the tuning ratio allows determination of cochlear tuning from SFOAE delays. We quantify the procedure and show that otoacoustic estimates of chinchilla cochlear tuning match direct measures obtained from the auditory nerve. By assuming that invariance of the tuning ratio extends to humans, we derive new otoacoustic estimates of human cochlear tuning that remain mutually consistent with independent behavioral measurements obtained using different rationales, methodologies, and analysis procedures. The results confirm that at any given characteristic frequency (CF) human cochlear tuning appears sharper than that in the other animals studied, but varies similarly with CF. We show, however, that the exceptionality of human tuning can be exaggerated by the ways in which species are conventionally compared, which take no account of evident differences between the base and apex of the cochlea. Finally, our estimates of human tuning suggest that the spatial spread of excitation of a pure tone

  10. Mercury, elemental

    Integrated Risk Information System (IRIS)

    Mercury , elemental ; CASRN 7439 - 97 - 6 Human health assessment information on a chemical substance is included in the IRIS database only after a comprehensive review of toxicity data , as outlined in the IRIS assessment development process . Sections I ( Health Hazard Assessments for Noncarcinoge

  11. Element Research.

    ERIC Educational Resources Information Center

    Herald, Christine

    2001-01-01

    Describes a research assignment for 8th grade students on the elements of the periodic table. Students use web-based resources and a chemistry handbook to gather information, construct concept maps, and present the findings to the full class using the mode of their choice: a humorous story, a slideshow or gameboard, a brochure, a song, or skit.…

  12. A comparison of the linear tuning properties of two classes of axons in the bullfrog lagena.

    PubMed

    Cortopassi, K A; Lewis, E R

    1998-01-01

    Various vertebrate inner-ear end organs appear to have switched their sensory function between equilibrium sensing and acoustic sensing over the courses of various lines of evolution. It is possible that all that is required to make this transition is to provide an end organ with access to the appropriate stimulus mode and frequency range. If, as we believe, however, the adaptive advantage of an acoustic sensory system lies in its ability to sort the total acoustic input into components that correspond to individual acoustic sources, and the adaptive advantage of an equilibrium sensory system lies in its ability to compute the total orientation and motion of the head without regard to the individual sources contributing to that orientation and motion, then it is easy to argue that the differences between acoustic and equilibrium sensors should be more profound than simply access to the appropriate stimuli. Effective signal-sorting requires high resolution in both time and frequency; to achieve this resolution, a peripheral tuning structure must be one of high dynamic order (i.e., constructed from multiple independent energy storage elements). If the peripheral tuning structure simply converts head acceleration to head displacement, velocity, or jerk (i.e., provides one or two steps of integration or differentiation with respect to time, where one energy storage element per step is required), then high dynamic order is inappropriate. Because the bullfrog lagena possesses both acoustic and equilibrium sensitive regions, it is especially suited for comparing these two sensor types and addressing the question of dynamic order of tuning. In this paper we report observations of the linear tuning properties of bullfrog lagenar primary afferent nerve fibers obtained by stimulating the lagena with random, dorsoventral micromotion over the frequency range from 10 Hz to 1.0 kHz. Tuning curves obtained by reverse correlation analysis and discrete Fourier transformation were

  13. Tuning the Magnetic Properties of Nanoparticles

    PubMed Central

    Kolhatkar, Arati G.; Jamison, Andrew C.; Litvinov, Dmitri; Willson, Richard C.; Lee, T. Randall

    2013-01-01

    The tremendous interest in magnetic nanoparticles (MNPs) is reflected in published research that ranges from novel methods of synthesis of unique nanoparticle shapes and composite structures to a large number of MNP characterization techniques, and finally to their use in many biomedical and nanotechnology-based applications. The knowledge gained from this vast body of research can be made more useful if we organize the associated results to correlate key magnetic properties with the parameters that influence them. Tuning these properties of MNPs will allow us to tailor nanoparticles for specific applications, thus increasing their effectiveness. The complex magnetic behavior exhibited by MNPs is governed by many factors; these factors can either improve or adversely affect the desired magnetic properties. In this report, we have outlined a matrix of parameters that can be varied to tune the magnetic properties of nanoparticles. For practical utility, this review focuses on the effect of size, shape, composition, and shell-core structure on saturation magnetization, coercivity, blocking temperature, and relaxation time. PMID:23912237

  14. Grating tuned unstable resonator laser cavity

    DOEpatents

    Johnson, Larry C.

    1982-01-01

    An unstable resonator to be used in high power, narrow line CO.sub.2 pump lasers comprises an array of four reflectors in a ring configuration wherein spherical and planar wavefronts are separated from each other along separate optical paths and only the planar wavefronts are impinged on a plane grating for line tuning. The reflector array comprises a concave mirror for reflecting incident spherical waves as plane waves along an output axis to form an output beam. A plane grating on the output axis is oriented to reflect a portion of the output beam off axis onto a planar relay mirror spaced apart from the output axis in proximity to the concave mirror. The relay mirror reflects plane waves from the grating to impinge on a convex expanding mirror spaced apart from the output axis in proximity to the grating. The expanding mirror reflects the incident planar waves as spherical waves to illuminate the concave mirror. Tuning is provided by rotating the plane grating about an axis normal to the output axis.

  15. RF cavities with transversely biased ferrite tuning

    SciTech Connect

    Smythe, W.R.; Brophy, T.G.; Carlini, R.D.; Friedrichs, C.C.; Grisham, D.L.; Spalek, G.; Wilkerson, L.C.

    1985-10-01

    Earley et al. suggested that ferrite tuned rf cavities have lower ferrite power dissipation if the ferrite bias field is perpendicular rather than parallel to the rf magnetic field. A 50-84 MHz cavity has been constructed in which ferrite can be biased either way. Low power measurements of six microwave ferrites show that the magnetic Q's of these ferrites under perpendicular bias are much higher than under parallel bias, and that the high Q region extends over a much wider range of rf permeability. TDK Y-5 ferrite was found to have a magnetic Q of 10,800, 4,800, 1,200 and 129 at rf permeabilities of 1.2, 2.4, 3.7 and 4.5, respectively. Measurements of perpendicularly biased ferrite at various power levels were made in a coaxial line cavity. The Q of Y-5 ferrite was found to decrease by less than a factor of 2 as the power density in the ferrite was increased to 1.3 W/cmT. A cavity design for a 6 GeV, high current, rapid cycling synchrotron using transversely biased ferrite tuning is described.

  16. Cloverleaf microgyroscope with electrostatic alignment and tuning

    NASA Technical Reports Server (NTRS)

    Challoner, A. Dorian (Inventor); Gutierrez, Roman C. (Inventor); Tang, Tony K. (Inventor)

    2007-01-01

    A micro-gyroscope (10) having closed loop output operation by a control voltage (V.sub.ty), that is demodulated by a drive axis (x-axis) signal V.sub.thx of the sense electrodes (S1, S2), providing Coriolis torque rebalance to prevent displacement of the micro-gyroscope (10) on the output axis (y-axis) V.sub.thy.about.0. Closed loop drive axis torque, V.sub.tx maintains a constant drive axis amplitude signal, V.sub.thx. The present invention provides independent alignment and tuning of the micro-gyroscope by using separate electrodes and electrostatic bias voltages to adjust alignment and tuning. A quadrature amplitude signal, or cross-axis transfer function peak amplitude is used to detect misalignment that is corrected to zero by an electrostatic bias voltage adjustment. The cross-axis transfer function is either V.sub.thy/V.sub.ty or V.sub.tnx/V.sub.tx. A quadrature signal noise level, or difference in natural frequencies estimated from measurements of the transfer functions is used to detect residual mistuning, that is corrected to zero by a second electrostatic bias voltage adjustment.

  17. Passive vibration tuning with neural networks

    NASA Astrophysics Data System (ADS)

    DiDomenico, Eric D.

    1994-05-01

    Neural network control of flexible structures demonstrates better settling time and energy dissipation than linear design methods. Optimal tuning of passive vibration absorbers for reduced order control is examined using linear and non-linear cases. Quasi-Newton (BFGS) and simplex optimization methods improved the Den Hartog parameters where unsupervised LMS or backpropagation techniques were unstable. Lessons on unsupervised training for dynamic system control are illustrated by examining convergence to the solution in `error space' (parameters vs. cost). Spring stiffness and passive damping of a reaction mass actuator (RMA) are `tuned' for best disturbance rejection using total energy as a cost function. A single neuron using two weights (one for damping and the other for the spring coefficient) improved beam energy over the Den Hartog parameters for the linear bi-modal case. The non-linear case demonstrates even better performance. A multiple layer network is then demonstrated for both the linear and non-linear cases. Optimization techniques improved linear system parameters when initiated at the linear solutions. Lab data for the linear single neuron case validates model fidelity.

  18. Fast tuning of superconducting microwave cavities

    SciTech Connect

    Sandberg, M.; Wilson, C. M.; Persson, F.; Johansson, G.; Shumeiko, V.; Bauch, T.; Duty, T.; Delsing, P.

    2008-11-07

    Photons are fundamental excitations of electromagnetic fields and can be captured in cavities. For a given cavity with a certain size, the fundamental mode has a fixed frequency f which gives the photons a specific 'color'. The cavity also has a typical lifetime {tau}, which results in a finite linewidth {delta}f. If the size of the cavity is changed fast compared to {tau}, and so that the frequency change {delta}f>>{delta}f, then it is possible to change the 'color' of the captured photons. Here we demonstrate superconducting microwave cavities, with tunable effective lengths. The tuning is obtained by varying a Josephson inductance at one end of the cavity. We show data on four different samples and demonstrate tuning by several hundred linewidths in a time {delta}t<<{tau}. Working in the few photon limit, we show that photons stored in the cavity at one frequency will leak out from the cavity with the new frequency after the detuning. The characteristics of the measured devices make them suitable for different applications such as dynamic coupling of qubits and parametric amplification.

  19. Small-amplitude synchrotron tune near transition

    SciTech Connect

    Ng, K.Y.; /Fermilab

    2010-05-01

    The separatrices of the rf buckets near transition are mapped when the synchronous phase is neither 0 or {pi}. The small-amplitude synchronous tune is derived when the rf frequency is changed. Synchrotron radiation is present in all electron storage ring. As a result, the synchronous phase is always offset from {phi}{sub s} = {pi} to compensate for the power loss. Even for proton storage rings with negligible synchrotron radiation, the synchronous phase is also required to be offset from {phi}{sub s} = 0 or {pi} slightly to compensate for beam loading. Thus for all storage rings operating near transition, beam particles reside in accelerating buckets instead of stationary bucket. It is of interest to map these buckets and see how they evolve near transition. When the rf frequency is varied, the closed orbit is pushed radially inward or outward. The momentum of the particle synchronous with the rf is thus changed. By measuring the small-amplitude synchrotron tune as a function of the rf frequency, the lowest first few orders of the slip factor can be inferred. Here, we derive this relationship up to the lowest first three orders of the slip factor when the particle velocity is not ultra-relativistic.

  20. Tuning bilayer twist using chiral counterions

    NASA Astrophysics Data System (ADS)

    Oda, R.; Huc, I.; Schmutz, M.; Candau, S. J.; Mackintosh, F. C.

    1999-06-01

    From seashells to DNA, chirality is expressed at every level of biological structures. In self-assembled structures it may emerge cooperatively from chirality at the molecular scale. Amphiphilic molecules, for example, can form a variety of aggregates and mesophases that express the chirality of their constituent molecules at a supramolecular scale of micrometres (refs 1-3). Quantitative prediction of the large-scale chirality based on that at themolecular scale remains a largely unsolved problem. Furthermore, experimental control over the expression of chirality at the supramolecular level is difficult to achieve: mixing of different enantiomers usually results in phase separation. Here we present an experimental and theoretical description of a system in which chirality can be varied continuously and controllably (`tuned') in micrometre-scale structures. We observe the formation of twisted ribbons consisting of bilayers of gemini surfactants (two surfactant molecules covalently linked at their charged head groups). We find that the degree of twist and the pitch of the ribbons can be tuned by the introduction of opposite-handed chiral counterions in various proportions. This degree of control might be of practical value; for example, in the use of thehelical structures as templates for helical crystallization of macromolecules,.

  1. Tuning light focusing with liquid crystal infiltrated graded index photonic crystals

    NASA Astrophysics Data System (ADS)

    Rezaei, B.; Giden, I. H.; Kurt, H.

    2017-01-01

    We perform numerical analyses of tunable graded index photonic crystals based on liquid crystals. Light manipulation with such a photonic medium is explored and a new approach for active tuning of the focal distance is proposed. The graded index photonic crystal is realized using the symmetry reduced unit element in two-dimensional photonic crystals without modifying the dielectric filling fraction or cell size dimensions. By applying an external static electric field to liquid crystals, their refractive indices and thus, the effective refractive index of the whole graded index photonic crystal will be changed. Setting the lattice constant to a=400 nm yields a tuning of 680 nm for focal point position. This property can be used for designing an electro-optic graded index photonic crystal-based flat lens with a tunable focal point. Future optical systems may have benefit from such tunable graded index lenses.

  2. Spectral tuning of a locally bent microfiber taper interferometer with a nanosized liquid crystal overlay.

    PubMed

    Luo, Haimei; Wang, Changjing; Ji, Yinghua; Yuan, Wen; Zhang, Guoping; Wang, Yifan; Hong, Zehua; Wang, Xianping

    2016-09-10

    In this paper, the tuning characteristics of locally bent microfiber taper covered with a nanosized high-refractive-index liquid crystal (LC) layer under different temperatures and electric field intensities have been theoretically analyzed and experimentally investigated. A locally bent microfiber taper interferometer with a waist diameter of ∼3.72  μm is fabricated by using the flame brushing technique, followed by bending the transition region of the taper to form a modal interferometer and later by placing a ∼200  nm LC layer over the uniform taper waist region. Experimental results indicate that a high-efficiency thermal or electric tuning of an LC-coated locally bent microfiber taper interferometer could be achieved. This suggests a potential application of this device as tunable all-fiber photonic devices, such as filters, modulators, and sensing elements.

  3. FUEL ELEMENT

    DOEpatents

    Fortescue, P.; Zumwalt, L.R.

    1961-11-28

    A fuel element was developed for a gas cooled nuclear reactor. The element is constructed in the form of a compacted fuel slug including carbides of fissionable material in some cases with a breeder material carbide and a moderator which slug is disposed in a canning jacket of relatively impermeable moderator material. Such canned fuel slugs are disposed in an elongated shell of moderator having greater gas permeability than the canning material wherefore application of reduced pressure to the space therebetween causes gas diffusing through the exterior shell to sweep fission products from the system. Integral fission product traps and/or exterior traps as well as a fission product monitoring system may be employed therewith. (AEC)

  4. Small Commercial Building Re-tuning: A Primer

    SciTech Connect

    Cort, Katherine A.; Hostick, Donna J.; Underhill, Ronald M.; Fernandez, Nicholas; Katipamula, Srinivas

    2013-09-30

    To help building owners and managers address issues related to energy-efficient operation of small buildings, DOE has developed a Small Building Re-tuning training curriculum. This "primer" provides additional background information to understand some of the concepts presented in the Small Building Re-tuning training. The intent is that those who are less familiar with the buidling energy concepts will review this material before taking the building re-tuning training class.

  5. Heading Tuning in Macaque Area V6

    PubMed Central

    Fan, Reuben H.; Liu, Sheng; DeAngelis, Gregory C.

    2015-01-01

    Cortical areas, such as the dorsal subdivision of the medial superior temporal area (MSTd) and the ventral intraparietal area (VIP), have been shown to integrate visual and vestibular self-motion signals. Area V6 is interconnected with areas MSTd and VIP, allowing for the possibility that V6 also integrates visual and vestibular self-motion cues. An alternative hypothesis in the literature is that V6 does not use these sensory signals to compute heading but instead discounts self-motion signals to represent object motion. However, the responses of V6 neurons to visual and vestibular self-motion cues have never been studied, thus leaving the functional roles of V6 unclear. We used a virtual reality system to examine the 3D heading tuning of macaque V6 neurons in response to optic flow and inertial motion stimuli. We found that the majority of V6 neurons are selective for heading defined by optic flow. However, unlike areas MSTd and VIP, V6 neurons are almost universally unresponsive to inertial motion in the absence of optic flow. We also explored the spatial reference frames of heading signals in V6 by measuring heading tuning for different eye positions, and we found that the visual heading tuning of most V6 cells was eye-centered. Similar to areas MSTd and VIP, the population of V6 neurons was best able to discriminate small variations in heading around forward and backward headings. Our findings support the idea that V6 is involved primarily in processing visual motion signals and does not appear to play a role in visual–vestibular integration for self-motion perception. SIGNIFICANCE STATEMENT To understand how we successfully navigate our world, it is important to understand which parts of the brain process cues used to perceive our direction of self-motion (i.e., heading). Cortical area V6 has been implicated in heading computations based on human neuroimaging data, but direct measurements of heading selectivity in individual V6 neurons have been lacking. We

  6. Tune tracking with a PLL in the Tevatron

    SciTech Connect

    Tan, C.Y.

    2005-11-01

    The Tevatron tune tracker is based on the idea that the phase of the transverse frequency response of the beam can be measured quickly and accurately enough so that the phase at the betatron tune resonance can be tracked by a phase locked loop (PLL). In this paper, a mathematical model of this idea is discussed and is used as the basis for the realization of the tune tracker hardware. The tune tracker has been successfully tested under different beam conditions and is now operational in the Tevatron.

  7. ADVANCES TOWARDS THE MEASUREMENT AND CONTROL LHC TUNE AND CHROMATICITY

    SciTech Connect

    CAMERON, P.; CUPOLO, J.; DEGEN, C.; DELLAPENNA, A.; HOFF, L.; MEAD, J.; SIKORA, R.

    2005-06-06

    Requirements for tune and chromaticity control in most superconducting hadron machines, and in particular the LHC, are stringent. In order to reach nominal operation, the LHC will almost certainly require feedback on both tune and chromaticity. Experience at RHIC has also shown that coupling control is crucial to successful tune feedback. A prototype baseband phase-locked loop (PLL) tune measurement system has recently been brought into operation at RHIC as part of the US LHC Accelerator Research Program (LARP). We report on the performance of that system and compare it with the extensive accumulation of data from the RHIC 245MHz PLL.

  8. A Numerical Optimization Approach for Tuning Fuzzy Logic Controllers

    NASA Technical Reports Server (NTRS)

    Woodard, Stanley E.; Garg, Devendra P.

    1998-01-01

    This paper develops a method to tune fuzzy controllers using numerical optimization. The main attribute of this approach is that it allows fuzzy logic controllers to be tuned to achieve global performance requirements. Furthermore, this approach allows design constraints to be implemented during the tuning process. The method tunes the controller by parameterizing the membership functions for error, change-in-error and control output. The resulting parameters form a design vector which is iteratively changed to minimize an objective function. The minimal objective function results in an optimal performance of the system. A spacecraft mounted science instrument line-of-sight pointing control is used to demonstrate results.

  9. Bandwidth and threshold calculations for angle-tuned parametric oscillators.

    NASA Technical Reports Server (NTRS)

    Basu, R.; Steier, W. H.

    1972-01-01

    The bandwidth of angle-tuned optical parametric oscillators, in some cases, is limited by the noncolinear interaction of the pump, signal, and idler beams, which results when the nonlinear material is rotated relative to the pump beam. To determine this bandwidth, a theoretical expression for the pump power threshold is derived in the near field limit taking into account double refraction for a noncolinear interaction. Angle tuning can be done by (1) rotating the crystal and mirrors as a unit, or by (2) rotating the crystal only. Expressions for determining the tuning rate and threshold increase for both tuning methods are derived.

  10. Giant Bragg Wavelength Tuning of Tunable Hollow Waveguide Bragg Reflector

    NASA Astrophysics Data System (ADS)

    Sakurai, Yasuki; Matsutani, Akihiro; Sakaguchi, Takahiro; Koyama, Fumio

    2005-09-01

    We demonstrate a giant Bragg wavelength tuning with a grating loaded hollow waveguide Bragg reflector. An air-core thickness change of a hollow waveguide enables us to achieve a large propagation constant change over few tens percent, which would be useful for various tunable optical devices. Our observed Bragg-wavelength tuning range is over 160 nm at an air-core thickness change from 10.7 to 1.8 μm, which corresponds to a propagation constant change of over 10%. This is the record large tuning value ever reported in conventional tuning schemes such as thermo-optic or electro-optic effects.

  11. Fine tuning points of generating function construction for linear recursions

    NASA Astrophysics Data System (ADS)

    Yolcu, Bahar; Demiralp, Metin

    2014-10-01

    Recursions are quite important mathematical tools since many systems are mathematically modelled to ultimately take us to these equations because of their rather easy algebraic natures. They fit computer programming needs quite well in many circumstances to produce solutions. However, it is generally desired to find the asymptotic behaviour of the general term in the relevant sequence for convergence and therefore practicality issues. One of the general tendencies to find the general term asymptotic behaviour, when its ordering number grows unboundedly, is the integral representation over a generating function which does not depend on individual sequence elements. This is tried to be done almost for all types of recursions, even though the linear cases gain more importance than the others because they can be more effectively investigated by using many linear algebraic tools. Despite this may seem somehow to be rather trivial, there are a lot of theoretical fine tuning issues in the construction of true integral representations over true intervals on real axis or paths in complex domains. This work is devoted to focus on this issue starting from scratch for better understanding of the matter. The example cases are chosen to best illuminate the situations to get information for future generalization even though the work can be considered at somehow introductory level.

  12. Photon induced L3 vacancy alignment at tuned photon energies

    NASA Astrophysics Data System (ADS)

    Bansal, Himani; Kaur, Gurpreet; Tiwari, Manoj K.; Mittal, Raj

    2016-04-01

    Photon induced L3 X-ray measurements for Lα/Lℓ cross-section ratios in elements, 66 ⩽ Z ⩽ 83, at tuned photon energies on synchrotron Beamline-16 at Indus-2, India have been used to study the effect of Coster-Kronig (CK) transitions and photon energies on alignment of L3 vacancies. Certainty and reliability of the measurements were checked from comparison of measured Lα and Lℓ fluorescence cross-sections at E1 excitation with available theoretical/empirical/experimental values that required additional measurements for source, geometry and efficiency factor S0GɛLα/ℓ in the used set-up. Fall/rise trend of the ratios with energy for different Z's was found to resemble the off/on-set pattern of CK transitions as pointed out by Bambynek et al. and Campbell. Evaluated alignment parameter A2 values are very much within the limits, 0.05

  13. Maximum likelihood tuning of a vehicle motion filter

    NASA Technical Reports Server (NTRS)

    Trankle, Thomas L.; Rabin, Uri H.

    1990-01-01

    This paper describes the use of maximum likelihood parameter estimation unknown parameters appearing in a nonlinear vehicle motion filter. The filter uses the kinematic equations of motion of a rigid body in motion over a spherical earth. The nine states of the filter represent vehicle velocity, attitude, and position. The inputs to the filter are three components of translational acceleration and three components of angular rate. Measurements used to update states include air data, altitude, position, and attitude. Expressions are derived for the elements of filter matrices needed to use air data in a body-fixed frame with filter states expressed in a geographic frame. An expression for the likelihood functions of the data is given, along with accurate approximations for the function's gradient and Hessian with respect to unknown parameters. These are used by a numerical quasi-Newton algorithm for maximizing the likelihood function of the data in order to estimate the unknown parameters. The parameter estimation algorithm is useful for processing data from aircraft flight tests or for tuning inertial navigation systems.

  14. Spatial tuning of a RF frequency selective surface through origami

    NASA Astrophysics Data System (ADS)

    Fuchi, Kazuko; Buskohl, Philip R.; Bazzan, Giorgio; Durstock, Michael F.; Joo, James J.; Reich, Gregory W.; Vaia, Richard A.

    2016-05-01

    Origami devices have the ability to spatially reconfigure between 2D and 3D states through folding motions. The precise mapping of origami presents a novel method to spatially tune radio frequency (RF) devices, including adaptive antennas, sensors, reflectors, and frequency selective surfaces (FSSs). While conventional RF FSSs are designed based upon a planar distribution of conductive elements, this leaves the large design space of the out of plane dimension underutilized. We investigated this design regime through the computational study of four FSS origami tessellations with conductive dipoles. The dipole patterns showed increased resonance shift with decreased separation distances, with the separation in the direction orthogonal to the dipole orientations having a more significant effect. The coupling mechanisms between dipole neighbours were evaluated by comparing surface charge densities, which revealed the gain and loss of coupling as the dipoles moved in and out of alignment via folding. Collectively, these results provide a basis of origami FSS designs for experimental study and motivates the development of computational tools to systematically predict optimal fold patterns for targeted frequency response and directionality.

  15. Riboswitch function: Flipping the switch or tuning the dimmer?

    SciTech Connect

    Baird, Nathan J.; Kulshina, Nadia; Ferré D'Amaré, Adrian R.

    2010-10-08

    Riboswitches are structured mRNA elements involved in gene regulation that respond to the intracellular concentration of specific small molecules. Binding of their cognate ligand is thought to elicit a global conformational change of the riboswitch, in addition to modulating the fine structure of the binding site. X-ray crystallography has produced detailed descriptions of the three-dimensional structures of the ligand-bound conformations of several riboswitches. We have employed small-angle X-ray scattering (SAXS) to generate low-resolution reconstructions of the ligand-free states of the ligand-binding domains of riboswitches that respond to thiamine pyrophosphate (TPP), and cyclic diguanylate (c-di-GMP), a bacterial second messenger. Comparison of the SAXS reconstructions with the crystal structures of these two riboswitches demonstrates that the RNAs undergo dramatic ligand-induced global conformational changes. However, this is not an universal feature of riboswitches. SAXS analysis of the solution behavior of several other riboswitch ligand-binding domains demonstrates a broad spectrum of conformational switching behaviors, ranging from the unambiguous switching of the TPP and c-di-GMP riboswitches to complete lack of switching for the flavin mononucleotide (FMN) riboswitch. Moreover, the switching behavior varies between examples of the same riboswitch from different organisms. The range of observed behaviors suggests that in response to the evolutionary need for precise genetic regulation, riboswitches may be tuned to function more as dimmers or rheostats than binary on/off switches.

  16. An Engineered Metal Sensor Tunes the Kinetics of Synaptic Transmission

    PubMed Central

    Evans, Chantell S.; Ruhl, David A.

    2015-01-01

    The Ca2+ sensor synaptotagmin-1 (syt-1) regulates neurotransmitter release by interacting with anionic phospholipids. Here we test the idea that the intrinsic kinetics of syt–membrane interactions determine, in part, the time course of synaptic transmission. To tune the kinetics of this interaction, we grafted structural elements from the slowest isoform, syt-7, onto the fastest isoform, syt-1, resulting in a chimera with intermediate kinetic properties. Moreover, the chimera coupled a physiologically irrelevant metal, Sr2+, to membrane fusion in vitro. When substituted for syt-1 in mouse hippocampal neurons, the chimera slowed the kinetics of synaptic transmission. Neurons expressing the chimera also evinced rapid and efficient Sr2+ triggered release, in contrast to the weak response of neurons expressing syt-1. These findings reveal presynaptic sensor–membrane interactions as a major factor regulating the speed of the release machinery. Finally, the chimera failed to clamp the elevated spontaneous fusion rate exhibited by syt-1 KO neurons, indicating that the metal binding loops of syt-1 regulate the two modes of release by distinct mechanisms. SIGNIFICANCE STATEMENT In calcium, synaptotagmin-1 triggers neurotransmitter release by interacting with membranes. Here, we demonstrate that intrinsic properties of this interaction control the time course of synaptic transmission. We engineered a “chimera” using synaptotagmin-1 and elements of a slower isoform, synaptotagmin-7. When expressed in neurons, the chimera slowed the rate of neurotransmitter release. Furthermore, unlike native synaptotagmin-1, the chimera was able to function robustly in the presence of strontium–a metal not present in cells. We exploited this ability to show that a key function of synaptotagmin-1 is to penetrate cell membranes. This work sheds light on fundamental mechanisms of neurotransmitter release. PMID:26311762

  17. Interphase tuning for stronger and tougher composites

    PubMed Central

    Livanov, Konstantin; Yang, Lin; Nissenbaum, Asaf; Wagner, H. Daniel

    2016-01-01

    The development of composite materials that are simultaneously strong and tough is one of the most active topics of current material science. Observations of biological structural materials show that adequate introduction of reinforcements and interfaces, or interphases, at different scales usually improves toughness, without reduction in strength. The prospect of interphase properties tuning may lead to further increases in material toughness. Here we use evaporation-driven self-assembly (EDSA) to deposit a thin network of multi-wall carbon nanotubes on ceramic surfaces, thereby generating an interphase reinforcing layer in a multiscale laminated ceramic composite. Both strength and toughness are improved by up to 90%, while keeping the overall volume fraction of nanotubes in a composite below 0.012%, making it a most effective toughening and reinforcement technique. PMID:27230418

  18. Dynamic range tuning of graphene nanoresonators

    NASA Astrophysics Data System (ADS)

    Parmar, Marsha M.; Gangavarapu, P. R. Yasasvi; Naik, A. K.

    2015-09-01

    From sensing perspective, smaller electromechanical devices, in general, are expected to be more responsive to the stimuli. This enhanced performance, however, is contingent upon the noise sources remaining unchanged and the onset of nonlinear behavior not being precipitated by miniaturization. In this paper, we study the effect of strain on the nonlinearities and dynamic range in graphene nanoresonators. The dynamic response and the onset of nonlinearity in these devices are sensitive both to the electrostatic field used to actuate the device and the strain. By tuning the strain of the device by two orders of magnitude, we observe an enhancement of 25 dB in the dynamic range leading to a mass resolution of 100 yoctogram. The increase in dynamic range in our devices is modeled as a combined effect of strain and partial cancellation of elastic and electrostatic nonlinearities.

  19. Tuning of superconducting niobium nitride terahertz metamaterials.

    PubMed

    Wu, Jingbo; Jin, Biaobing; Xue, Yuhua; Zhang, Caihong; Dai, Hao; Zhang, Labao; Cao, Chunhai; Kang, Lin; Xu, Weiwei; Chen, Jian; Wu, Peiheng

    2011-06-20

    Superconducting planar terahertz (THz) metamaterials (MMs), with unit cells of different sizes, are fabricated on 200 nm-thick niobium nitride (NbN) films deposited on MgO substrates. They are characterized using THz time domain spectroscopy over a temperature range from 8.1 K to 300 K, crossing the critical temperature of NbN films. As the gap frequency (f(g) = 2Δ0/h, where Δ0 is the energy gap at 0 K and h is the Plank constant) of NbN is 1.18 THz, the experimentally observed THz spectra span a frequency range from below f(g) to above it. We have found that, as the resonance frequency approaches f(g), the relative tuning range of MMs is quite wide (30%). We attribute this observation to the large change of kinetic inductance of superconducting film.

  20. Chemical and biological sensing using tuning forks

    DOEpatents

    Tao, Nongjian; Boussaad, Salah

    2012-07-10

    A device for sensing a chemical analyte is disclosed. The device is comprised of a vibrating structure having first and second surfaces and having an associated resonant frequency and a wire coupled between the first and second surfaces of the vibrating structure, wherein the analyte interacts with the wire and causes a change in the resonant frequency of the vibrating structure. The vibrating structure can include a tuning fork. The vibrating structure can be comprised of quartz. The wire can be comprised of polymer. A plurality of vibrating structures are arranged in an array to increase confidence by promoting a redundancy of measurement or to detect a plurality of chemical analytes. A method of making a device for sensing a chemical analyte is also disclosed.

  1. Fine tuning of cytosolic Ca 2+ oscillations

    PubMed Central

    Dupont, Geneviève; Combettes, Laurent

    2016-01-01

    Ca 2+ oscillations, a widespread mode of cell signaling, were reported in non-excitable cells for the first time more than 25 years ago. Their fundamental mechanism, based on the periodic Ca 2+ exchange between the endoplasmic reticulum and the cytoplasm, has been well characterized. However, how the kinetics of cytosolic Ca 2+ changes are related to the extent of a physiological response remains poorly understood. Here, we review data suggesting that the downstream targets of Ca 2+ are controlled not only by the frequency of Ca 2+ oscillations but also by the detailed characteristics of the oscillations, such as their duration, shape, or baseline level. Involvement of non-endoplasmic reticulum Ca 2+ stores, mainly mitochondria and the extracellular medium, participates in this fine tuning of Ca 2+ oscillations. The main characteristics of the Ca 2+ exchange fluxes with these compartments are also reviewed. PMID:27630768

  2. Climatology tuned reflectivity-rain rate relations

    NASA Technical Reports Server (NTRS)

    Short, David A.; Rosenfeld, Daniel; Atlas, David

    1989-01-01

    The climatologically-tuned relationships between reflectivity, Z, and rain rate, R, are examined. A method is presented which selects the Z-R relation that assures that the values of R are weighted according to their climatological frequency of occurrence. The method is an extension of the approach suggested by Calheiros and Zawadski (1987). Also, consideration is given to the method of optimizing Z-R relations by matching hourly gage and radar-deduced rain amounts proposed by Smith et al. (1975). These two methods are described and applied to data from Germany and from the GARP Atlantic Tropical Experiment. The differences in the Z-R relations obtained using the two approaches are discussed.

  3. Tuning quantum properties in bilayer ruthenates

    NASA Astrophysics Data System (ADS)

    Ke, Xianglin

    The mutual coupling among spin, charge, lattice and orbital degrees of freedom in transition-metal oxide materials often leads to the competition of various types of energetic states. This makes such materials dramatically susceptible to external parameters, giving rise to novel physical properties and rich phase diagrams. In this talk, I shall use a bilayer ruthenate, Ca3Ru2O7, as an example to discuss the emergent phenomena achieved by systematically tuning materials magnetic and electronic properties via chemical doping, magnetic field, and pressure. I shall show that this system provides a rare opportunity to investigate the interplay between correlated metal and Mott insulator. This work was done in collaboration with M. Zhu, T. Tao, S. D. Mahanti, Z. Q. Mao, J. Peng, T. Hong, W. Tian, H. Cao, C. R. dela Cruz, D. Singh, and K. Prokes.

  4. Determining Absolute Zero Using a Tuning Fork

    NASA Astrophysics Data System (ADS)

    Goldader, Jeffrey D.

    2008-04-01

    The Celsius and Kelvin temperature scales, we tell our students, are related. We explain that a change in temperature of 1°C corresponds to a change of 1 Kelvin and that atoms and molecules have zero kinetic energy at zero Kelvin, -273°C. In this paper, we will show how students can derive the relationship between the Celsius and Kelvin temperature scales using a simple, well-known physics experiment. By making multiple measurements of the speed of sound at different temperatures, using the classic physics experiment of determining the speed of sound with a tuning fork and variable-length tube, they can determine the temperature at which the speed of sound is zero—absolute zero.

  5. Tuning energy relaxation along quantum Hall channels.

    PubMed

    Altimiras, C; le Sueur, H; Gennser, U; Cavanna, A; Mailly, D; Pierre, F

    2010-11-26

    The chiral edge channels in the quantum Hall regime are considered ideal ballistic quantum channels, and have quantum information processing potentialities. Here, we demonstrate experimentally, at a filling factor of ν(L)=2, the efficient tuning of the energy relaxation that limits quantum coherence and permits the return toward equilibrium. Energy relaxation along an edge channel is controllably enhanced by increasing its transmission toward a floating Ohmic contact, in quantitative agreement with predictions. Moreover, by forming a closed inner edge channel loop, we freeze energy exchanges in the outer channel. This result also elucidates the inelastic mechanisms at work at ν(L)=2, informing us, in particular, that those within the outer edge channel are negligible.

  6. Nonsingular multidimensional cosmologies without fine tuning

    NASA Astrophysics Data System (ADS)

    Bronnikov, Kirill A.; Fabris, Julio C.

    2002-09-01

    Exact cosmological solutions for effective actions in D dimensions inspired by the tree-level superstring action are studied. For a certain range of free parameters existing in the model, nonsingular bouncing solutions are found. Among them, of particular interest can be open hyperbolic models, in which, without any fine tuning, the internal scale factor and the dilaton field (connected with string coupling in string theories) tend to constant values at late times. A cosmological singularity is avoided due to nonminimal dilaton-gravity coupling and, for D>11, due to pure imaginary nature of the dilaton, which conforms to currently discussed unification models. The existence of such and similar solutions supports the opinion that the Universe had never undergone a stage driven by full-scale quantum gravity.

  7. Wireless tuning fork gyroscope for biomedical applications

    NASA Astrophysics Data System (ADS)

    Abraham, Jose K.; Varadan, Vijay K.; Whitchurch, Ashwin K.; Sarukesi, K.

    2003-07-01

    This paper presents the development of a Bluetooth enabled wireless tuning fork gyroscope for the biomedical applications, including gait phase detection system, human motion analysis and physical therapy. This gyroscope is capable of measuring rotation rates between -90 and 90 and it can read the rotation information using a computer. Currently, the information from a gyroscope can trigger automobile airbag deployment during rollover, improve the accuracy and reliability of GPS navigation systems and stabilize moving platforms such as automobiles, airplanes, robots, antennas, and industrial equipment. Adding wireless capability to the existing gyroscope could help to expand its applications in many areas particularly in biomedical applications, where a continuous patient monitoring is quite difficult. This wireless system provides information on several aspects of activities of patients for real-time monitoring in hospitals.

  8. Bandgap tuning of multiferroic oxide solar cells

    NASA Astrophysics Data System (ADS)

    Nechache, R.; Harnagea, C.; Li, S.; Cardenas, L.; Huang, W.; Chakrabartty, J.; Rosei, F.

    2015-01-01

    Multiferroic films are increasingly being studied for applications in solar energy conversion because of their efficient ferroelectric polarization-driven carrier separation and above-bandgap generated photovoltages, which in principle can lead to energy conversion efficiencies beyond the maximum value (˜34%) reported in traditional silicon-based bipolar heterojunction solar cells. However, the efficiency reported so far is still too low (<2%) to be considered for commercialization. Here, we demonstrate a new approach to effectively tune the bandgap of double perovskite multiferroic oxides by engineering the cationic ordering for the case of Bi2FeCrO6. Using this approach, we report a power conversion efficiency of 8.1% under AM 1.5 G irradiation (100 mW cm-2) for Bi2FeCrO6 thin-film solar cells in a multilayer configuration.

  9. Continuous Tuning and Calibration of Vibratory Gyroscopes

    NASA Technical Reports Server (NTRS)

    Hayworth, Ken

    2003-01-01

    A method of control and operation of an inertial reference unit (IRU) based on vibratory gyroscopes provides for continuously repeated cycles of tuning and calibration. The method is intended especially for application to an IRU containing vibratory gyroscopes that are integral parts of microelectromechanical systems (MEMS) and that have cloverleaf designs, as described in several previous NASA Tech Briefs articles. The method provides for minimization of several measures of spurious gyroscope output, including zero-rate offset (ZRO), angle random walk (ARW), and rate drift. These benefits are afforded both at startup and thereafter during continuing operation, in the presence of unknown rotation rates and changes in temperature. A vibratory gyroscope contains a precision mechanically resonant structure containing two normal modes of vibration nominally degenerate in frequency and strongly coupled via a Coriolis term. In the case of the cloverleaf design MEMS gyro, these normal modes of vibration are plate rocking modes. The rocking motion of the plate is described by giving two angles, theta(sub 1) and theta(sub 2). A proof mass consisting of a post orthogonal to the plate ensures a high degree of Coriolis coupling of vibratory energy from one mode into the other under inertial rotation. The plate is driven and sensed capacitively across a few-microns-wide gap, and the normal mode frequencies can be tuned electrostatically by DC voltages applied across this gap. In order to sense rotation, the resonator plate is caused to rock in the theta(sub 1) direction, then any small motions in the theta(sub 2) direction are sensed, rebalanced, and interpreted as inertial rotation. In this scenario, the "drive" has been assigned to the theta(sub 1) direction, and the "sense" has been assigned to the theta(sub 2) direction.

  10. Frequency tuning in the electroreceptive periphery.

    PubMed Central

    Olson, E S; Smullin, L D

    1989-01-01

    Our studies are concerned with the frequency tuning that is provided by the electrical resonance of tuberous electroreceptors. Frequency selectivity had previously been measured in the electroreceptor's afferent fibers, and resonant conductances in the electroreceptor cell membrane had been implicated in producing the selectivity. With transdermal application of sinusoidal current, we measured the frequency dependence of the impedance of small areas of the electroreceptor/skin structure of the weakly electric fish Sternopygus and Eigenmannia, and used our data to make a quantitative linear model of the structure. The qualitative form of the model was proposed by Bennett (1). The quantitative model allows us to estimate the frequency selectivity of the voltage across the innervated membrane of the electroreceptor cells. The frequency selectivity of electroreceptor cell voltage derived from our data are as sharp as the neural selectivity at frequencies close to the most sensitive frequency. Many of our measurements supported the linear system model. However, spontaneous electroreceptor voltage oscillations were detected in some of our specimens, suggesting that the electroreceptors can operate in a regime of active nonlinearity. A simple explanation for the observed oscillations is that they arise when damping in the electroreceptor cell's resonant membrane is negative for a limited span of membrane voltage surrounding the resting voltage. The response of oscillating units to sinusoidal current was compatible with this explanation. We report experimental observations bearing on the consequences of active nonlinearity for the frequency tuning of a resonant system. Images FIGURE 11 FIGURE 4 FIGURE 5 FIGURE 6 FIGURE 11 FIGURE 12 PMID:2765655

  11. Performance Optimization and Auto-Tuning

    SciTech Connect

    Howison, Mark

    2012-10-01

    In the broader computational research community, one subject of recent research is the problem of adapting algorithms to make effective use of multi- and many-core processors. Effective use of these architectures, which have complex memory hierarchies with many layers of cache, typically involves a careful examination of how an algorithm moves data through the memory hierarchy. Unfortunately, there is often a non-obvious relationship between algorithmic parameters like blocking strategies, and their impact on memory utilization, and, in turn, the relationship with runtime performance. Auto-tuning is an empirical method used to discover optimal values for tunable algorithmic parameters under such circumstances. The challenge is compounded by the fact that the settings that produce the best performance for a given problem and a given platform may not be the best for a different problem on the same platform, or the same problem on a different platform. The high performance visualization research community has begun to explore and adapt the principles of auto-tuning for the purpose of optimizing codes on modern multi- and many-core processors. This report focuses on how performance optimization studies reveal a dramatic variation in performance for two fundamental visualization algorithms: one based on a stencil operation having structured, uniform memory access, and the other is ray casting volume rendering, which uses unstructured memory access patterns. The two case studies highlighted in this report show the extra effort required to optimize such codes by adjusting the tunable algorithmic parameters can return substantial gains in performance. Additionally, these case studies also explore the potential impact of and the interaction between algorithmic optimizations and tunable algorithmic parameters, along with the potential performance gains resulting from leveraging architecture-specific features.

  12. FUEL ELEMENT

    DOEpatents

    Howard, R.C.; Bokros, J.C.

    1962-03-01

    A fueled matrlx eontnwinlng uncomblned carbon is deslgned for use in graphlte-moderated gas-cooled reactors designed for operatlon at temperatures (about 1500 deg F) at which conventional metallic cladding would ordlnarily undergo undesired carburization or physical degeneratlon. - The invention comprlses, broadly a fuel body containlng uncombined earbon, clad with a nickel alloy contalning over about 28 percent by' weight copper in the preferred embodlment. Thls element ls supporirted in the passageways in close tolerance with the walls of unclad graphite moderator materlal. (AEC)

  13. Dynamic tuning of chemiresistor sensitivity using mechanical strain

    DOEpatents

    Martin, James E; Read, Douglas H

    2014-09-30

    The sensitivity of a chemiresistor sensor can be dynamically tuned using mechanical strain. The increase in sensitivity is a smooth, continuous function of the applied strain, and the effect can be reversible. Sensitivity tuning enables the response curve of the sensor to be dynamically optimized for sensing analytes, such as volatile organic compounds, over a wide concentration range.

  14. Tuning Engineering Education into the European Higher Education Orchestra.

    ERIC Educational Resources Information Center

    Maffioli, Francesco; Augusti, Giuliano

    2003-01-01

    The 'Bologna Process' promotes fundamental changes throughout European higher education. The EC 'Tuning' project was set up to investigate the feasibility of this process. Summarizes the final report of the Engineering Synergy Group which examined the 'tuning' of engineering education (EE), taking advantage of the work of previous and current…

  15. Grid cell spatial tuning reduced following systemic muscarinic receptor blockade.

    PubMed

    Newman, Ehren L; Climer, Jason R; Hasselmo, Michael E

    2014-06-01

    Grid cells of the medial entorhinal cortex exhibit a periodic and stable pattern of spatial tuning that may reflect the output of a path integration system. This grid pattern has been hypothesized to serve as a spatial coordinate system for navigation and memory function. The mechanisms underlying the generation of this characteristic tuning pattern remain poorly understood. Systemic administration of the muscarinic antagonist scopolamine flattens the typically positive correlation between running speed and entorhinal theta frequency in rats. The loss of this neural correlate of velocity, an important signal for the calculation of path integration, raises the question of what influence scopolamine has on the grid cell tuning as a read out of the path integration system. To test this, the spatial tuning properties of grid cells were compared before and after systemic administration of scopolamine as rats completed laps on a circle track for food rewards. The results show that the spatial tuning of the grid cells was reduced following scopolamine administration. The tuning of head direction cells, in contrast, was not reduced by scopolamine. This is the first report to demonstrate a link between cholinergic function and grid cell tuning. This work suggests that the loss of tuning in the grid cell network may underlie the navigational disorientation observed in Alzheimer's patients and elderly individuals with reduced cholinergic tone.

  16. Grid cell spatial tuning reduced following systemic muscarinic receptor blockade

    PubMed Central

    Newman, Ehren L.; Climer, Jason R.; Hasselmo, Michael E.

    2014-01-01

    Grid cells of the medial entorhinal cortex exhibit a periodic and stable pattern of spatial tuning that may reflect the output of a path integration system. This grid pattern has been hypothesized to serve as a spatial coordinate system for navigation and memory function. The mechanisms underlying the generation of this characteristic tuning pattern remain poorly understood. Systemic administration of the muscarinic antagonist scopolamine flattens the typically positive correlation between running speed and entorhinal theta frequency in rats. The loss of this neural correlate of velocity, an important signal for the calculation of path integration, raises the question of what influence scopolamine has on the grid cell tuning as a read out of the path integration system. To test this, the spatial tuning properties of grid cells were compared before and after systemic administration of scopolamine as rats completed laps on a circle track for food rewards. The results show that the spatial tuning of the grid cells was reduced following scopolamine administration. The tuning of head direction cells, in contrast, was not reduced by scopolamine. This is the first report to demonstrate a link between cholinergic function and grid cell tuning. This work suggests that the loss of tuning in the grid cell network may underlie the navigational disorientation observed in Alzheimer's patients and elderly individuals with reduced cholinergic tone. PMID:24493379

  17. New Directions for IR, the DQP, and Tuning

    ERIC Educational Resources Information Center

    Jankowski, Natasha A.; Marshall, David W.

    2015-01-01

    This concluding essay provides a glimpse to the future and alerts IR professionals to related initiatives as well as provides an update to ongoing work with DQP and Tuning. Pulling from the prior chapters it provides some implications for IR offices to consider, not only in their work with the DQP and Tuning, but in terms of general decision…

  18. Tune shifts due to systematic errors in bend magnets

    SciTech Connect

    Douglas, D.

    1983-12-01

    The presence of systematic error multipoles in bend magnets, persistent currents at low magnet excitation, and saturation effects at high magnet excitation may all lead to tune shifts which could prove detrimental to the operation of the SSC. It is the purpose of this note to report estimates of the magnitude of these tune shifts and the corrector strengths required to circumvent them.

  19. PSO algorithm enhanced with Lozi Chaotic Map - Tuning experiment

    SciTech Connect

    Pluhacek, Michal; Senkerik, Roman; Zelinka, Ivan

    2015-03-10

    In this paper it is investigated the effect of tuning of control parameters of the Lozi Chaotic Map employed as a chaotic pseudo-random number generator for the particle swarm optimization algorithm. Three different benchmark functions are selected from the IEEE CEC 2013 competition benchmark set. The Lozi map is extensively tuned and the performance of PSO is evaluated.

  20. Collider constraints on tuning in composite Higgs models

    NASA Astrophysics Data System (ADS)

    Barnard, James; White, Martin

    2015-10-01

    Two potential sources of tuning exist in composite Higgs models: one comes from keeping the Higgs VEV below the compositeness scale and one comes from keeping the Higgs light after constraints on the top partner masses are applied. We construct a measure that determines whether these tunings are independent or not and combines them appropriately. We perform a comprehensive scan of the parameter space for three explicit models and report the minimum tuning values compatible with existing collider constraints. Tuning values are given as functions of resonance masses and deviations to the Higgs couplings so the effect of future constraints can easily be quantified. The current minimum tuning in the minimal model is 2.5-5% and will be decreased to around 0.8-3.3% if no top partners are observed over the lifetime of the LHC

  1. Vibration absorbers for chatter suppression: A new analytical tuning methodology

    NASA Astrophysics Data System (ADS)

    Sims, Neil D.

    2007-04-01

    Vibration absorbers have been widely used to suppress undesirable vibrations in machining operations, with a particular emphasis on avoiding chatter. However, it is well known that for vibration absorbers to function effectively their stiffness and damping must be accurately tuned based upon the natural frequency of the vibrating structure. For general vibration problems, suitable tuning strategies were developed by Den Hartog and Brock over 50 years ago. However, the special nature of the chatter stability problem means that this classical tuning methodology is no longer optimal. Consequently, vibration absorbers for chatter mitigation have generally been tuned using ad hoc methods, or numerical or graphical approaches. The present article introduces a new analytical solution to this problem, and demonstrates its performance using time domain milling simulations. A 40-50% improvement in the critical limiting depth of cut is observed, compared to the classically tuned vibration absorber.

  2. A Generalized Framework for Auto-tuning Stencil Computations

    SciTech Connect

    Kamil, Shoaib; Chan, Cy; Williams, Samuel; Oliker, Leonid; Shalf, John; Howison, Mark; Bethel, E. Wes; Prabhat,

    2009-05-01

    This work introduces a generalized framework for automatically tuning stencil computations to achieve superior performance on a broad range of multicore architectures. Stencil (nearest-neighbor) based kernels constitute the core of many important scientific applications involving block-structured grids. Auto-tuning systems search over optimization strategies to find the combination of tunable parameters that maximizes computational efficiency for a given algorithmic kernel. Although the auto-tuning strategy has been successfully applied to libraries, generalized stencil kernels are not amenable to packaging as libraries. Studied kernels in this work include both memory-bound kernels as well as a computation-bound bilateral filtering kernel. We introduce a generalized stencil auto-tuning framework that takes a straightforward Fortran expression of a stencil kernel and automatically generates tuned implementations of the kernel in C or Fortran to achieve performance portability across diverse computer architectures.

  3. Tuning the beam: a physics perspective on beam diagnostic instrumentation

    SciTech Connect

    Gulley, Mark S

    2010-01-01

    In a nutshell, the role of a beam diagnostic measurement is to provide information needed to get a particle beam from Point A (injection point) to Point B (a target) in a useable condition, with 'useable' meaning the right energy and size and with acceptable losses. Specifications and performance requirements of diagnostics are based on the physics of the particle beam to be measured, with typical customers of beam parameter measurements being the accelerator operators and accelerator physicists. This tutorial will be a physics-oriented discussion of the interplay between tuning evolutions and the beam diagnostics systems that support the machine tune. This will include the differences between developing a tune and maintaining a tune, among other things. Practical longitudinal and transverse tuning issues and techniques from a variety of proton and electron machines will also be discussed.

  4. Otoacoustic Estimates of Cochlear Tuning: Testing Predictions in Macaque

    NASA Astrophysics Data System (ADS)

    Shera, Christopher A.; Bergevin, Christopher; Kalluri, Radha; Mc Laughlin, Myles; Michelet, Pascal; van der Heijden, Marcel; Joris, Philip X.

    2011-11-01

    Otoacoustic estimates of cochlear frequency selectivity suggest substantially sharper tuning in humans. However, the logic and methodology underlying these estimates remain untested by direct measurements in primates. We report measurements of frequency tuning in macaque monkeys, Old-World primates phylogenetically closer to humans than the small laboratory animals often taken as models of human hearing (e.g., cats, guinea pigs, and chinchillas). We find that measurements of tuning obtained directly from individual nerve fibers and indirectly using otoacoustic emissions both indicate that peripheral frequency selectivity in macaques is significantly sharper than in small laboratory animals, matching that inferred for humans at high frequencies. Our results validate the use of otoacoustic emissions for noninvasive measurement of cochlear tuning and corroborate the finding of sharper tuning in humans.

  5. Spin tune dependence on closed orbit in RHIC

    SciTech Connect

    Ptitsyn, V.; Bai, M.; Roser, T.

    2010-05-23

    Polarized proton beams are accelerated in RHIC to 250 GeV energy with the help of Siberian Snakes. The pair of Siberian Snakes in each RHIC ring holds the design spin tune at 1/2 to avoid polarization loss during acceleration. However, in the presence of closed orbit errors, the actual spin tune can be shifted away from the exact 1/2 value. It leads to a corresponding shift of locations of higher-order ('snake') resonances and limits the available betatron tune space. The largest closed orbit effect on the spin tune comes from the horizontal orbit angle between the two snakes. During RHIC Run in 2009 dedicated measurements with polarized proton beams were taken to verify the dependence of the spin tune on the local orbits at the Snakes. The experimental results are presented along with the comparison with analytical predictions.

  6. Compensating tune spread induced by space charge in bunched beams

    SciTech Connect

    Litvinenko, V.; Wang, G.

    2015-05-03

    The effects of space charge play a significant role in modern-day accelerators, frequently constraining the beam parameters attainable in an accelerator or in an accelerator chain. They also can limit the luminosity of hadron colliders operating either at low energies or with sub-TeV high-brightness hadron beams. The latter is applied for strongly cooled proton and ion beams in eRHIC – the proposed future electron-ion collider at Brookhaven National Laboratory. Using an appropriate electron beam would compensate both the tune shift and the tune spread in the hadron beam in a coasting beam. But these methods cannot compensate space charge tune spread in a bunched hadron beam. In this paper we propose and evaluate a novel idea of using a co-propagating electron bunch with mismatched longitudinal velocity to compensate the space charge induced tune-shift and tune spread.

  7. Tuning optical radiation for visual and nonvisual impact

    NASA Astrophysics Data System (ADS)

    Royer, Michael P.

    2011-12-01

    Spectral tuning---the allocation of radiant energy emitted by a lamp---is a fundamental element of illuminating engineering. Proper placement of optical radiation allows for reduced energy consumption, increased brightness perception, and improved color rendition. It can also result in lamps that have a greater impact on nonvisual human functions such as circadian rhythms, sleep, mood, and cognition. For an architectural lighting system, careful consideration must be given to all of these areas; recent advancements in understanding nonvisual photoreception must be balanced with the traditional emphasis on visual quality and energy efficiency. The three research projects described herein investigated spectral tuning by examining the effects of optical radiation or seeking ideal spectral power distributions. In all three cases, emphasis was placed on developing an architectural lighting system based on red, green, and blue (RGB) light emitting diodes (LEDs) that is capable of providing maximum stimulation to nonvisual systems while maintaining visual quality standards. In particular, the elderly were considered as a target population because they have an increased risk of developing disorders linked to illumination deficits. The three endeavors can be summarized as follows: Light Therapy for Seniors in Long-term Care AIM: To examine the effect of optical radiation on circadian rhythms, sleep, mood, and cognition for frail elderly in a long-term care environment. METHODOLOGY: A double-blind, placebo-controlled clinical trial of light therapy was conducted using circadian-effective short-wavelength (blue) optical radiation to treat a sample of residents recruited for participation without bias for existing medical diagnoses. KEY FINDINGS: Light therapy treatment improved cognitive functioning compared to placebo but no changes were detected in nighttime sleep statistics, reports of daytime sleepiness, circadian rhythms, or depression inventory parameters. Perceived

  8. Tuning magnetism by Kondo effect and frustration

    NASA Astrophysics Data System (ADS)

    Löhneysen, Hilbert V.

    2014-03-01

    Heavy-fermion systems are an ideal playground for studying the quantum phase transition (QPT) between paramagnetic and magnetically ordered ground states arising from the competition between Kondo and RKKY interactions. Two different routes have been identified by various experiments, i. e., the more traditional spin-density-wave (SDW) and the Kondo-breakdown approaches. However, up to now an a-priori assignment of a given system to these different routes has not been possible. Yet another route to quantum criticality not included in the above approaches might be geometric frustration of magnetic moments, a route well known for insulating magnets with competing interactions. First experiments on metallic systems have recently been conducted. In the canonical partially frustrated antiferromagnetic system CePd1-xNixAl, the Néel temperature TN(x) decreases, with TN --> 0 at the critical concentration xc ~ 0.144. The low-temperature specific heat C(T) evolves toward C/ Tα ln(T0/ T) for x -->xc. The unusual T dependence of C/ T is compatible with the Hertz-Millis-Moriya (HMM) scenario of quantum criticality if the quantum-critical fluctuations are two-dimensional in nature. Here two-dimensionality might arise from antiferromagnetic planes that are effectively decoupled by the frustrated Ce atoms in between. An exciting possibility is that the planes of frustrated Ce moments form a two-dimensional spin liquid. In the prototypical heavy-fermion system CeCu6-xAux the experiments by Schröder et al. provided the initial evidence of local quantum criticality. While concentration and pressure tuning of the quantum phase transition (QPT) are described by this scenario, magnetic-field tuning the QPT is in line with the SDW scenario. Elastic neutron scattering experiments on CeCu5.5Au0.5 under hydrostatic pressure p show that at p = 8 kbar, TN and the magnetic propagation vector attain almost the values of CeCu5.7Au0.3. This x - p analogy away from the QPT is highly remarkable

  9. Fine tuning of activity for nanoscale catalysts.

    SciTech Connect

    Strmcnik, D.; van derVliet, D.; Lucas, C.; Karapetrov, G.; Markovic, N.; Stamenkovic, V.; Materials Science Division

    2008-01-01

    Ability to tune the electronic and structural properties of nanocatalysts can potentially lead towards the superior catalytic enhancement that was reported for the Pt{sub 3}Ni(111)-skin surface. Here we report investigation of the extended well-defined surfaces of Pt and PtM alloys (M=Ni,Co,Fe,V,Ti,Re) as well as Pt(hkl) single crystalline surfaces for various catalytic reaction. The electrode surfaces were initially characterized in ultra-high vacuum by AES, LEIS and UPS before controlled transfer into electrochemical environment. Catalytic properties have been determined in three compartment electrochemical cell for oxygen reduction reaction (ORR) by rotational disk electrode technique. The single crystalline surfaces of Pt electrodes have been used to benchmark the activity range that could be expected on pure Pt electrodes. We have proposed that surface modifications induced by the second metal, and consequent catalytic enhancements could occur through the following effects: (1) Electronic effect, due to changes in the metallic d-band center position vs. Fermi level; and (2) Structural effect, which reflects relationship between atomic geometry, and/or surface chemistry, i.e., dissolution - surface roughening. It has been reported that Pt bimetallic alloys, could form surfaces with two different compositions. Due to surface segregation annealed surfaces can form the outermost Pt-skin surface layer, while the lightly sputtered surfaces have the bulk ratio of alloying components and form Pt-skeleton outermost layers as a result of dissolution of non-precious atoms. In principle, different near-surface compositions (Pt-skin, Pt-skeleton and polycrystalline Pt) have been found to have different electronic structures. Modification in Pt electronic properties alters adsorption/catalytic properties of corresponding materials. The most active systems for the electrochemical oxygen reduction reaction (ORR) are established to be the Pt-skin near-surface formation. The

  10. Implosion symmetry tuning with megajoule laser pulses on the National Ignition Facility

    NASA Astrophysics Data System (ADS)

    Kline, J.; Meezan, N.; Dixit, S.; Kyrala, G.; London, R.; Thomas, C.; Callahan, D.; Widmann, K.; Glenzer, S.; Suter, L.; Hinkel, D.; Williams, E.; Dewald, E.; Landen, O.; Edwards, J.; MacGowan, B.; Divol, L.; Haynam, C.; Kalantar, D.; Le Pape, S.; Moody, J.; Ralph, J.; Rosen, M.; Schneider, M.; Young, B.

    2010-11-01

    A key element for indirect drive inertial confinement fusion is tuning the implosion symmetry. Symmetric implosions maximize the transfer of kinetic energy to the hot spot. One technique to measure the drive symmetry is the symcap. A symcap is a surrogate capsule that replaces the DT fuel layer by an equivalent mass of ablator material to mimic the hydrodynamic behavior of the capsule. The symcaps are filled with gas that provides an x-ray self-emission flash upon stagnation and is used to diagnose the radiation drive based on the shape of the emission. Simulations indicate that the shape of the emission flash correlates well with an ignition capsule's core shape. Using this data, the radiation drive in the hohlraum can be tuned to achieve symmetric implosions. The current symmetry campaign sets the initial hohlraum conditions to provide symmetric implosions for the ignition campaign. Experimental results will be presented for symmetry tuning with laser energies up to 1.3 MJ. Work for DOE by LANL (DE-AC52-06NA25396 and by LLNL (DE-AC52-07NA27344).

  11. Simultaneous gains tuning in boiler/turbine PID-based controller clusters using iterative feedback tuning methodology.

    PubMed

    Zhang, Shu; Taft, Cyrus W; Bentsman, Joseph; Hussey, Aaron; Petrus, Bryan

    2012-09-01

    Tuning a complex multi-loop PID based control system requires considerable experience. In today's power industry the number of available qualified tuners is dwindling and there is a great need for better tuning tools to maintain and improve the performance of complex multivariable processes. Multi-loop PID tuning is the procedure for the online tuning of a cluster of PID controllers operating in a closed loop with a multivariable process. This paper presents the first application of the simultaneous tuning technique to the multi-input-multi-output (MIMO) PID based nonlinear controller in the power plant control context, with the closed-loop system consisting of a MIMO nonlinear boiler/turbine model and a nonlinear cluster of six PID-type controllers. Although simplified, the dynamics and cross-coupling of the process and the PID cluster are similar to those used in a real power plant. The particular technique selected, iterative feedback tuning (IFT), utilizes the linearized version of the PID cluster for signal conditioning, but the data collection and tuning is carried out on the full nonlinear closed-loop system. Based on the figure of merit for the control system performance, the IFT is shown to deliver performance favorably comparable to that attained through the empirical tuning carried out by an experienced control engineer.

  12. Bendable X-ray Optics at the ALS: Design, Tuning, Performance and Applications

    SciTech Connect

    Advanced Light Source, Lawrence Berkeley National Laboratory; Yashchuk, Valeriy V.; Church, Matthew N.; Knight, Jason W.; Kunz, Martin; MacDowell, Alastair A.; McKinney, Wayne R.; Tamura, Nabumichi; Warwick, Tony

    2008-09-08

    We review the development at the Advanced Light Source (ALS) of bendable x-ray optics widely used for focusing of beams of soft and hard x-rays. Typically, the focusing is divided in the tangential and sagittal directions into two elliptically cylindrical reflecting elements, the so-called Kirkpatrick-Baez (KB) pair [1]. Because fabrication of elliptical surfaces is complicated, the cost of directly fabricated tangential elliptical cylinders is often prohibitive. This is in contrast to flat optics, that are simpler to manufacture and easier to measure by conventional interferometry. The figure of a flat substrate can be changed by placing torques (couples) at each end. Equal couples form a tangential cylinder, and unequal couples can approximate a tangential ellipse or parabola. We review the nature of the bending, requirements and approaches to the mechanical design, and describe a technique developed at the ALS Optical Metrology Laboratory (OML) for optimal tuning of bendable mirrors before installation in the beamline [2]. The tuning technique adapts a method previously used to adjust bendable mirrors on synchrotron radiation beamlines [3]. However, in our case, optimal tuning of a bendable mirror is based on surface slope trace data obtained with a slope measuring instrument--in our case, the long trace profiler (LTP). We show that due to the near linearity of the bending problem, the minimal set of data, necessary for tuning of two benders, consists of only three slope traces measured before and after a single adjustment of each bending couple. We provide an algorithm that was used in dedicated software for finding optimal settings for the mirror benders. The algorithm is based on the method of regression analysis with experimentally found characteristic functions of the benders. The resulting approximation to the functional dependence of the desired slope shape provides nearly final settings for the benders. Moreover, the characteristic functions of the

  13. Social Cognition in Williams Syndrome: Face Tuning.

    PubMed

    Pavlova, Marina A; Heiz, Julie; Sokolov, Alexander N; Barisnikov, Koviljka

    2016-01-01

    Many neurological, neurodevelopmental, neuropsychiatric, and psychosomatic disorders are characterized by impairments in visual social cognition, body language reading, and facial assessment of a social counterpart. Yet a wealth of research indicates that individuals with Williams syndrome exhibit remarkable concern for social stimuli and face fascination. Here individuals with Williams syndrome were presented with a set of Face-n-Food images composed of food ingredients and in different degree resembling a face (slightly bordering on the Giuseppe Arcimboldo style). The primary advantage of these images is that single components do not explicitly trigger face-specific processing, whereas in face images commonly used for investigating face perception (such as photographs or depictions), the mere occurrence of typical cues already implicates face presence. In a spontaneous recognition task, participants were shown a set of images in a predetermined order from the least to most resembling a face. Strikingly, individuals with Williams syndrome exhibited profound deficits in recognition of the Face-n-Food images as a face: they did not report seeing a face on the images, which typically developing controls effortlessly recognized as a face, and gave overall fewer face responses. This suggests atypical face tuning in Williams syndrome. The outcome is discussed in the light of a general pattern of social cognition in Williams syndrome and brain mechanisms underpinning face processing.

  14. Psychophysical tuning curves at very high frequencies

    NASA Astrophysics Data System (ADS)

    Yasin, Ifat; Plack, Christopher J.

    2005-10-01

    For most normal-hearing listeners, absolute thresholds increase rapidly above about 16 kHz. One hypothesis is that the high-frequency limit of the hearing-threshold curve is imposed by the transmission characteristics of the middle ear, which attenuates the sound input [Masterton et al., J. Acoust. Soc. Am. 45, 966-985 (1969)]. An alternative hypothesis is that the high-frequency limit of hearing is imposed by the tonotopicity of the cochlea [Ruggero and Temchin, Proc. Nat. Acad. Sci. U.S.A. 99, 13206-13210 (2002)]. The aim of this study was to test these hypotheses. Forward-masked psychophysical tuning curves (PTCs) were derived for signal frequencies of 12-17.5 kHz. For the highest signal frequencies, the high-frequency slopes of some PTCs were steeper than the slope of the hearing-threshold curve. The results also show that the human auditory system displays frequency selectivity for characteristic frequencies (CFs) as high as 17 kHz, above the frequency at which absolute thresholds begin to increase rapidly. The findings suggest that, for CFs up to 17 kHz, the high-frequency limitation in humans is imposed in part by the middle-ear attenuation, and not by the tonotopicity of the cochlea.

  15. Mechnical tuning of ionized donors in silicon

    NASA Astrophysics Data System (ADS)

    Franke, David P.; Hrubesch, Florian M.; Kuenzl, Markus; Itoh, Kohei M.; Hoehne, Felix; Dreher, Lukas; Brandt, Martin S.

    2015-03-01

    Ionized donors in silicon have been shown to have extraordinarily long coherence times, exceeding tens of minutes even at room temperature, which, combined with the very advanced state of silicon technology, makes them attractive candidates for the realization of solid state qubits. The corresponding near perfect isolation from their environment, however, renders the individual addressing and coupling of such qubits a major challenge on the way towards a spin quantum computer based on ionized donors. We show that the application of strain to the silicon host crystal leads to shifts of the nuclear spin resonance frequencies of 75As+ due to the nuclear quadrupole interaction with crystal fields. This shift can be larger than the resonance linewidth already for modest strains, as we demonstrate by electrically detected electron nuclear double resonance (ED ENDOR) measurements on arsenic donors in strained silicon. We discuss how quadrupole interactions could allow for the individual addressing of ionized nuclear spins by mechanical tuning of their resonance frequency and, possibly, permit the elastic coupling of nuclear spin qubits to a mechanical resonator.

  16. Tuning a microcavity-coupled terahertz laser

    SciTech Connect

    Castellano, Fabrizio; Bianchi, Vezio; Vitiello, Miriam S.; Li, Lianhe; Zhu, Jingxuan; Linfield, Edmund H.; Giles Davies, A.; Tredicucci, Alessandro

    2015-12-28

    Tunable oscillators are a key component of almost all electronic and photonic systems. Yet, a technology capable of operating in the terahertz (THz)-frequency range and fully suitable for widescale implementation is still lacking. This issue is significantly limiting potential THz applications in gas sensing, high-resolution spectroscopy, hyper-spectral imaging, and optical communications. The THz quantum cascade laser is arguably the most promising solution in terms of output power and spectral purity. In order to achieve reliable, repeatable, and broad tunability, here we exploit the strong coupling between two different cavity mode concepts: a distributed feedback one-dimensional photonic resonator (providing gain) and a mechanically actuated wavelength-size microcavity (providing tuning). The result is a continuously tunable, single-mode emitter covering a 162 GHz spectral range, centered on 3.2 THz. Our source has a few tens of MHz resolution, extremely high differential efficiency, and unprecedented compact and simple design architecture. By unveiling the large potential that lies in this technique, our results provide a robust platform for radically different THz systems exploiting broadly tunable semiconductor lasers.

  17. Wide Tuning Capability for Spacecraft Transponders

    NASA Technical Reports Server (NTRS)

    Lux, James; Mysoor, Narayan; Shah, Biren; Cook, Brian; Smith, Scott

    2007-01-01

    A document presents additional information on the means of implementing a capability for wide tuning of microwave receiver and transmitter frequencies in the development reported in the immediately preceding article, VCO PLL Frequency Synthesizers for Spacecraft Transponders (NPO- 42909). The reference frequency for a PLL-based frequency synthesizer is derived from a numerically controlled oscillator (NCO) implemented in digital logic, such that almost any reference frequency can be derived from a fixed crystal reference oscillator with microhertz precision. The frequency of the NCO is adjusted to track the received signal, then used to create another NCO frequency used to synthesize the transmitted signal coherent with, and at a specified frequency ratio to, the received signal. The frequencies can be changed, even during operation, through suitable digital programming. The NCOs and the related tracking loops and coherent turnaround logic are implemented in a field-programmable gate array (FPGA). The interface between the analog microwave receiver and transmitter circuits and the FPGA includes analog-to-digital and digital-toanalog converters, the sampling rates of which are chosen to minimize spurious signals and otherwise optimize performance. Several mixers and filters are used to properly route various signals.

  18. Social Cognition in Williams Syndrome: Face Tuning

    PubMed Central

    Pavlova, Marina A.; Heiz, Julie; Sokolov, Alexander N.; Barisnikov, Koviljka

    2016-01-01

    Many neurological, neurodevelopmental, neuropsychiatric, and psychosomatic disorders are characterized by impairments in visual social cognition, body language reading, and facial assessment of a social counterpart. Yet a wealth of research indicates that individuals with Williams syndrome exhibit remarkable concern for social stimuli and face fascination. Here individuals with Williams syndrome were presented with a set of Face-n-Food images composed of food ingredients and in different degree resembling a face (slightly bordering on the Giuseppe Arcimboldo style). The primary advantage of these images is that single components do not explicitly trigger face-specific processing, whereas in face images commonly used for investigating face perception (such as photographs or depictions), the mere occurrence of typical cues already implicates face presence. In a spontaneous recognition task, participants were shown a set of images in a predetermined order from the least to most resembling a face. Strikingly, individuals with Williams syndrome exhibited profound deficits in recognition of the Face-n-Food images as a face: they did not report seeing a face on the images, which typically developing controls effortlessly recognized as a face, and gave overall fewer face responses. This suggests atypical face tuning in Williams syndrome. The outcome is discussed in the light of a general pattern of social cognition in Williams syndrome and brain mechanisms underpinning face processing. PMID:27531986

  19. Workshop: Tuning the ‘cough center’

    PubMed Central

    Widdicombe, J.; Tatar, M.; Fontana, G.; Hanacek, J.; Davenport, P.; Lavorini, F.; Bolser, D.

    2011-01-01

    The Workshop considered the mechanisms whereby the ‘cough center’ could be tuned by various afferent inputs. There were particular presentations on the effects of inputs from the nose, mouth, respiratory tract and lungs, cerebral cortex, somatic tissues and the pharynx. From all these sites cough induced from the lungs could be increased or decreased in its strength or modified in its pattern. Thus ‘tuning’ of cough could be due to the interaction of afferent inputs, or to the sensitization or desensitization of brainstem neural pathways. The pattern of response depended on the ‘type’ of cough being studied and, in some instances, on the timing of the sensory input into the brainstem. Cough inputs could also affect various ‘non-cough’ motor outputs from the brain, although this was not the main theme of the Workshop. The main conclusion was that cough is not a stereotyped output from the medullary ‘cough center’, but that its pattern and strength depend on many afferent inputs acting on the ‘cough center’. PMID:21215322

  20. TUNED FINITE-DIFFERENCE DIFFUSION OPERATORS

    SciTech Connect

    Maron, Jason; Low, Mordecai-Mark Mac E-mail: mordecai@amnh.org

    2009-05-15

    Finite-difference simulations of fluid dynamics and magnetohydrodynamics generally require an explicit diffusion operator, either to maintain stability by attenuating grid-scale structure, or to implement physical diffusivities such as viscosity or resistivity. If the goal is stability only, the diffusion must act at the grid scale, but should affect structure at larger scales as little as possible. For physical diffusivities the diffusion scale depends on the problem, and diffusion may act at larger scales as well. Diffusivity can undesirably limit the computational time step in both cases. We construct tuned finite-difference diffusion operators that minimally limit the time step while acting as desired near the diffusion scale. Such operators reach peak values at the diffusion scale rather than at the grid scale, but behave as standard operators at larger scales. These operators will be useful for simulations with high magnetic diffusivity or kinematic viscosity such as in the simulation of astrophysical dynamos with magnetic Prandtl number far from unity, or for numerical stabilization using hyperdiffusivity.

  1. Approaching {lambda} without fine-tuning

    SciTech Connect

    Matarrese, Sabino; Baccigalupi, Carlo; Perrotta, Francesca

    2004-09-15

    We address the fine-tuning problem of dark energy cosmologies which arises when the dark energy density needs to initially lie in a narrow range in order for its present value to be consistent with observations. As recently noticed, this problem becomes particularly severe in canonical quintessence scenarios, when trying to reproduce the behavior of a cosmological constant, i.e., when the dark energy equation of state w{sub Q} approaches -1: these models may be reconciled with a large basin of attraction only by requiring a rapid evolution of w{sub Q} at low redshifts, which is in conflict with the most recent estimates from type Ia Supernovae discovered by Hubble space telescope. Next, we focus on scalar-tensor theories of gravity, discussing the implications of a coupling between the quintessence scalar field and the Ricci scalar ('extended quintessence'). We show that, even if the equation of state today is very close to -1, by virtue of the scalar-tensor coupling the quintessence trajectories still possess the attractive feature which allows to reach the present level of cosmic acceleration starting by a set of initial conditions which covers tens of orders of magnitude; this effect, entirely of gravitational origin, represents a new important consequence of the possible coupling between dark energy and gravity. We illustrate this effect in typical extended quintessence scenarios.

  2. Spiders Tune Glue Viscosity to Maximize Adhesion.

    PubMed

    Amarpuri, Gaurav; Zhang, Ci; Diaz, Candido; Opell, Brent D; Blackledge, Todd A; Dhinojwala, Ali

    2015-11-24

    Adhesion in humid conditions is a fundamental challenge to both natural and synthetic adhesives. Yet, glue from most spider species becomes stickier as humidity increases. We find the adhesion of spider glue, from five diverse spider species, maximizes at very different humidities that matches their foraging habitats. By using high-speed imaging and spreading power law, we find that the glue viscosity varies over 5 orders of magnitude with humidity for each species, yet the viscosity at maximal adhesion for each species is nearly identical, 10(5)-10(6) cP. Many natural systems take advantage of viscosity to improve functional response, but spider glue's humidity responsiveness is a novel adaptation that makes the glue stickiest in each species' preferred habitat. This tuning is achieved by a combination of proteins and hygroscopic organic salts that determines water uptake in the glue. We therefore anticipate that manipulation of polymer-salts interaction to control viscosity can provide a simple mechanism to design humidity responsive smart adhesives.

  3. Design of a Multi-DOF Tuned Mounting Fixture for the Navy’s Mediumweight Shock Machine

    DTIC Science & Technology

    1993-06-01

    undertest since it would not excite the higher resonant frequencies that may be present in the equipment. As noted in Corbell (1992), a finite element...RESPONSE Extending the concept developed by Chalmers and Shaw (1989), Corbell proposed that a two degree-of-freedom (DOF) fixture could be designed for the...can be used to tune the fixture to the required stiffness, K. From the shock spectrum shown in Figure 7, Corbell chose 60 Hz and 155 Hz as the system

  4. Adaptive Prognostics for Rolling Element Bearing Condition

    NASA Astrophysics Data System (ADS)

    Li, Y.; Billington, S.; Zhang, C.; Kurfess, T.; Danyluk, S.; Liang, S.

    1999-01-01

    Rolling element bearing failure is one of the foremost causes of breakdown in rotating machinery. This paper proposes a remaining life adaptation methodology based on mechanistic modeling and parameter tuning. Vibration measurement is used to estimate defect severity by monitoring the signals generated from rotating bearings. Through a defect propagation model and defect diagnostic model, an adaptive algorithm is developed to fine tune the parameters involved in the propagation model by comparing predicted and measured defect sizes. In this manner, the instantaneous rate of defect propagation can be captured despite defect growth behavior variation. Therefore, a precise estimation of the remaining life can be determined. Simulations and experimental results are presented to illustrate the implementation principles and to verify the applicability of the adaptive prognostic methodology.

  5. Nonmonotonic Synaptic Excitation and Imbalanced Inhibition Underlying Cortical Intensity Tuning

    PubMed Central

    Wu, Guangying K.; Li, Pingyang; Tao, Huizhong W.; Zhang, Li I.

    2006-01-01

    Summary Intensity-tuned neurons, characterized by their nonmonotonic response-level function, may play important roles in the encoding of sound intensity-related information. The synaptic mechanisms underlying intensity-tuning remain yet unclear. Here, in vivo whole-cell recordings in rat auditory cortex revealed that intensity-tuned neurons, mostly clustered in a posterior zone, receive imbalanced tone-evoked excitatory and inhibitory synaptic inputs. Excitatory inputs exhibit nonmonotonic intensity-tuning, whereas with tone intensity increments, the temporally-delayed inhibitory inputs increase monotonically in strength. In addition, this delay reduces with the increase of intensity, resulting in an enhanced suppression of excitation at high intensities and a significant sharpening of intensity-tuning. In contrast, non-intensity-tuned neurons exhibit covaried excitatory and inhibitory inputs and the relative time interval between them is stable with intensity increments, resulting in monotonic response-level function. Thus, cortical intensity-tuning is primarily determined by excitatory inputs, and shaped by cortical inhibition through a dynamic control of excitatory and inhibitory timing. PMID:17114053

  6. An efficient automated parameter tuning framework for spiking neural networks.

    PubMed

    Carlson, Kristofor D; Nageswaran, Jayram Moorkanikara; Dutt, Nikil; Krichmar, Jeffrey L

    2014-01-01

    As the desire for biologically realistic spiking neural networks (SNNs) increases, tuning the enormous number of open parameters in these models becomes a difficult challenge. SNNs have been used to successfully model complex neural circuits that explore various neural phenomena such as neural plasticity, vision systems, auditory systems, neural oscillations, and many other important topics of neural function. Additionally, SNNs are particularly well-adapted to run on neuromorphic hardware that will support biological brain-scale architectures. Although the inclusion of realistic plasticity equations, neural dynamics, and recurrent topologies has increased the descriptive power of SNNs, it has also made the task of tuning these biologically realistic SNNs difficult. To meet this challenge, we present an automated parameter tuning framework capable of tuning SNNs quickly and efficiently using evolutionary algorithms (EA) and inexpensive, readily accessible graphics processing units (GPUs). A sample SNN with 4104 neurons was tuned to give V1 simple cell-like tuning curve responses and produce self-organizing receptive fields (SORFs) when presented with a random sequence of counterphase sinusoidal grating stimuli. A performance analysis comparing the GPU-accelerated implementation to a single-threaded central processing unit (CPU) implementation was carried out and showed a speedup of 65× of the GPU implementation over the CPU implementation, or 0.35 h per generation for GPU vs. 23.5 h per generation for CPU. Additionally, the parameter value solutions found in the tuned SNN were studied and found to be stable and repeatable. The automated parameter tuning framework presented here will be of use to both the computational neuroscience and neuromorphic engineering communities, making the process of constructing and tuning large-scale SNNs much quicker and easier.

  7. Frequency Tuning of Collapse-Mode Capacitive Micromachined Ultrasonic Transducer.

    PubMed

    Pekař, Martin; Dittmer, Wendy U; Mihajlović, Nenad; van Soest, Gijs; de Jong, Nico

    2017-02-01

    The information in an ultrasound image depends on the frequency that is used. In a clinical examination it may therefore be beneficial to generate ultrasound images acquired at multiple frequencies, which is difficult to achieve with conventional transducers. Capacitive micromachined ultrasonic transducers (CMUTs) offer a frequency response that is tunable by the bias voltage. In this study we investigate this frequency tunability for ultrasonic imaging. We characterized a CMUT array operated at bias voltages up to three times higher than the collapse-voltage. All elements of the array were connected to a single transmit and receive channel through a bias circuit. We quantified the transmit-receive and transmit sensitivity as a function of frequency for a range of bias voltages. Impulse response measurements show that the center frequency is modifiable between 8.7MHz and 15.3MHz with an applied bias voltage of -50V to -170V. The maximum transmit sensitivity is 52kPa/V at a center frequency of 9.0MHz with an applied bias voltage of -105V. The -3dB transmit range in center frequency accessible with the variable bias voltage is 6.7-15.5MHz. This study shows that a collapse-mode CMUT can operate efficiently at multiple center frequencies when the driving pulse and the bias voltage are optimized. We demonstrate the usefulness of frequency tuning by comparing images at different optimal combinations of driving frequency and bias voltage, acquired by linearly moving the transducer across a tissue mimicking phantom.

  8. A Tuned Single Parameter for Representing Conjunction Risk

    NASA Technical Reports Server (NTRS)

    Plakaloic, D.; Hejduk, M. D.; Frigm, R. C.; Newman, L. K.

    2011-01-01

    Satellite conjunction assessment risk analysis is a subjective enterprise that can benefit from quantitative aids and, to this end, NASA/GSFC has developed a fuzzy logic construct - called the F-value - to attempt to provide a statement of conjunction risk that amalgamates multiple indices and yields a more stable intra-event assessment. This construct has now sustained an extended tuning procedure against heuristic analyst assessment of event risk. The tuning effort has resulted in modifications to the calculation procedure and the adjustment of tuning coefficients, producing a construct with both more predictive force and a better statement of its error.

  9. Development of a self-tuning fuzzy logic controller

    SciTech Connect

    Huang, S.H.; Nelson, R.M.

    1999-07-01

    To avoid the laborious task of modifying control rule sets for fuzzy logic controllers, a novel model-based self-tuning strategy has been developed. The performance of this advanced fuzzy logic controller is measured and analyzed in a linguistic plane. An optimal performance trajectory functions as the control model. The self-tuning strategy improves the performance automatically until it converges to a predetermined optimal global criterion. The experimental results indicate that the actual performance trajectory of the advanced fuzzy controller with the self-tuning strategy has reached the optimal criterion.

  10. Musician's and physicist's view on tuning keyboard instruments

    NASA Astrophysics Data System (ADS)

    Lubenow, Martin; Meyn, Jan-Peter

    2007-01-01

    The simultaneous sound of several voices or instruments requires proper tuning to achieve consonance for certain intervals and chords. Most instruments allow enough frequency variation to enable pure tuning while being played. Keyboard instruments such as organ and piano have given frequencies for individual notes and the tuning must be based on a compromise. The equal temperament is not the only solution, but a special choice. Unequal temperaments produce better results in many cases, because important major thirds and triads are improved. Equal temperament was not propagated by Johann Sebastian Bach, as is often stated in introductory literature on this topic.

  11. Frequency Tuning of Hearing in the Beluga Whale.

    PubMed

    Sysueva, Evgeniya V; Nechaev, Dmitry I; Popov, Vladimir V; Supin, Alexander Y

    2016-01-01

    Data on frequency tuning in odontocetes are contradictory: different authors have reported filter qualities from 2 to almost 50. In this study, frequency tuning was measured in a beluga whale (Delphinapterus leucas) using a rippled-noise test stimulus in conjunction with the auditory evoked potential (AEP) technique. The response to ripple reversions was considered to indicate resolvability of the ripple pattern. The limit of ripple-pattern resolution ranged from 20 to 32 ripples per octave (rpo). A model of interaction of the ripple spectrum with frequency-tuned filters suggests that this resolution limit requires a filter quality of 29-46.

  12. First order tune shift calculations for transverse betatron dynamics

    SciTech Connect

    Garavaglia, T.

    1991-09-01

    An effective Hamiltonian, with non-linear magnetic multipole terms and momentum dispersion contributions, is used to obtain the first order tune-shift results for transverse betatron motion for protons in the Superconducting Super Collider (SSC). This Hamiltonian is represented in terms of action angle variables, and analytical results are obtained using symbolic algebra methods. Mathematical derivations of the transverse multipole expansion and of the transverse betatron equations, using an invariant action and curvilinear coordinates, are given in the appendices. Numerical and graphical tune-space results are given that illustrate the dependence of tune-shifts on injection amplitude and momentum spread. 10 refs., 7 figs.

  13. Electro optical tuning of Tamm-plasmon exciton-polaritons

    NASA Astrophysics Data System (ADS)

    Gessler, J.; Baumann, V.; Emmerling, M.; Amthor, M.; Winkler, K.; Höfling, S.; Schneider, C.; Kamp, M.

    2014-11-01

    We report on electro optical tuning of the emission from GaAs quantum wells resonantly coupled to a Tamm-plasmon mode in a hybrid metal/dielectric structure. The structures were studied via momentum resolved photoluminescence and photoreflectance spectroscopy, and the surface metal layer was used as a top gate, which allowed for a precise tuning of the quantum well emission via the quantum confined Stark effect. By tuning the resonance, we were able to observe the characteristic anticrossing behavior of a polaritonic emission in the strong light-matter coupling regime, yielding a Rabi splitting of (9.2 ± 0.2) meV.

  14. Tuned, driven, and active soft matter

    NASA Astrophysics Data System (ADS)

    Menzel, Andreas M.

    2015-02-01

    One characteristic feature of soft matter systems is their strong response to external stimuli. As a consequence they are comparatively easily driven out of their ground state and out of equilibrium, which leads to many of their fascinating properties. Here, we review illustrative examples. This review is structured by an increasing distance from the equilibrium ground state. On each level, examples of increasing degree of complexity are considered. In detail, we first consider systems that are quasi-statically tuned or switched to a new state by applying external fields. These are common liquid crystals, liquid crystalline elastomers, or ferrogels and magnetic elastomers. Next, we concentrate on systems steadily driven from outside e.g. by an imposed flow field. In our case, we review the reaction of nematic liquid crystals, of bulk-filling periodically modulated structures such as block copolymers, and of localized vesicular objects to an imposed shear flow. Finally, we focus on systems that are "active" and "self-driven". Here our range spans from idealized self-propelled point particles, via sterically interacting particles like granular hoppers, via microswimmers such as self-phoretically driven artificial Janus particles or biological microorganisms, via deformable self-propelled particles like droplets, up to the collective behavior of insects, fish, and birds. As we emphasize, similarities emerge in the features and behavior of systems that at first glance may not necessarily appear related. We thus hope that our overview will further stimulate the search for basic unifying principles underlying the physics of these soft materials out of their equilibrium ground state.

  15. Optimization of the alexandrite laser tuning elements for a water vapor lidar

    NASA Technical Reports Server (NTRS)

    Ponsardin, Patrick; Grossmann, Benoist E.; Higdon, Noah S.; Browell, Edward V.

    1990-01-01

    An overview of some of the developments completed on an alexandrite laser for making water vapor DIAL measurements is presented in this paper. A computer control for active stabilization of the two intracavity etalons has been implemented and recently tested in an aircraft environment. Long-term frequency drift (i.e., 2 hours) of less than 0.7 pm has been observed in the laboratory. An alignment technique to get the optimum free spectral range ratio for the two etalons is also developed.

  16. High-precision measurements of the 87 Rb D-line tune-out wavelength

    NASA Astrophysics Data System (ADS)

    Fallon, Adam; Leonard, Robert; Sackett, Charles

    2016-05-01

    We report a measurement of a light wavelength at which the ac electric polarizability equals zero for 87 Rb atoms in the F = 2 ground hyperfine state. The experiment uses a condensate interferometer to find this ``tune-out'' wavelength for the scalar polarizability, which lies at 790.032388(32) nm. Our result can be used to determine the ratio of matrix elements | < 5 P3 / 2 ∥ d ∥ 5 S1 / 2 > / < 5 P1 / 2 ∥ d ∥ 5 S1 / 2>|2 = 1 . 99221(3) , a 100-fold improvement over previous experimental values. We discuss techniques for accurate determination and control of light polarization as well as progress on measurements of the vector polarizability between the D 1 and D 2 spectral lines. Measurements of tune-out wavelengths and the vector polarizability between multiple lines allows separation of individual contributions to the polarizability from higher-lying states and the core up to ratios of matrix elements. Accurate knowledge of these ratios should serve useful as a theoretical benchmark and in atomic parity violation experiments.

  17. OSKI: A Library of Automatically Tuned Sparse Matrix Kernels

    SciTech Connect

    Vuduc, R; Demmel, J W; Yelick, K A

    2005-07-19

    The Optimized Sparse Kernel Interface (OSKI) is a collection of low-level primitives that provide automatically tuned computational kernels on sparse matrices, for use by solver libraries and applications. These kernels include sparse matrix-vector multiply and sparse triangular solve, among others. The primary aim of this interface is to hide the complex decision-making process needed to tune the performance of a kernel implementation for a particular user's sparse matrix and machine, while also exposing the steps and potentially non-trivial costs of tuning at run-time. This paper provides an overview of OSKI, which is based on our research on automatically tuned sparse kernels for modern cache-based superscalar machines.

  18. Little Known Facts about the Common Tuning Fork.

    ERIC Educational Resources Information Center

    Ong, P. P.

    2002-01-01

    Explains the physical principles of the tuning fork which has a common use in teaching laboratories. Includes information on its vibration, frequency of vibration, elasticity, and reasons for having two prongs. (YDS)

  19. Online automatic tuning and control for fed-batch cultivation

    PubMed Central

    van Straten, Gerrit; van der Pol, Leo A.; van Boxtel, Anton J. B.

    2007-01-01

    Performance of controllers applied in biotechnological production is often below expectation. Online automatic tuning has the capability to improve control performance by adjusting control parameters. This work presents automatic tuning approaches for model reference specific growth rate control during fed-batch cultivation. The approaches are direct methods that use the error between observed specific growth rate and its set point; systematic perturbations of the cultivation are not necessary. Two automatic tuning methods proved to be efficient, in which the adaptation rate is based on a combination of the error, squared error and integral error. These methods are relatively simple and robust against disturbances, parameter uncertainties, and initialization errors. Application of the specific growth rate controller yields a stable system. The controller and automatic tuning methods are qualified by simulations and laboratory experiments with Bordetella pertussis. PMID:18157554

  20. Gain and frequency tuning within the mouse cochlear apex

    NASA Astrophysics Data System (ADS)

    Oghalai, John S.; Gao, Simon; Lee, Hee Yoon; Raphael, Patrick D.; Groves, Andrew K.; Zuo, Jian; Applegate, Brian E.

    2015-12-01

    Normal mammalian hearing requires cochlear outer hair cell active processes that amplify the traveling wave with high gain and sharp tuning, termed cochlear amplification. We have used optical coherence tomography to study cochlear amplification within the apical turn of the mouse cochlea. We measured not only classical basilar membrane vibratory tuning curves but also vibratory responses from the rest of the tissues that compose the organ of Corti. Basilar membrane tuning was sharp in live mice and broad in dead mice, whereas other regions of the organ of Corti demonstrated phase shifts consistent with additional filtering beyond that provided by basilar membrane mechanics. We use these experimental data to support a conceptual framework of how cochlear amplification is tuned within the mouse cochlear apex. We will also study transgenic mice with targeted mutations that affect different biomechanical aspects of the organ of Corti in an effort to localize the underlying processes that produce this additional filtering.

  1. On the Tuning of High-Resolution NMR Probes

    PubMed Central

    Pöschko, Maria Theresia; Schlagnitweit, Judith; Huber, Gaspard; Nausner, Martin; Horničáková, Michaela; Desvaux, Hervé; Müller, Norbert

    2014-01-01

    Three optimum conditions for the tuning of NMR probes are compared: the conventional tuning optimum, which is based on radio-frequency pulse efficiency, the spin noise tuning optimum based on the line shape of the spin noise signal, and the newly introduced frequency shift tuning optimum, which minimizes the frequency pushing effect on strong signals. The latter results if the radiation damping feedback field is not in perfect quadrature to the precessing magnetization. According to the conventional RLC (resistor–inductor–capacitor) resonant circuit model, the optima should be identical, but significant deviations are found experimentally at low temperatures, in particular on cryogenically cooled probes. The existence of different optima with respect to frequency pushing and spin noise line shape has important consequences on the nonlinearity of spin dynamics at high polarization levels and the implementation of experiments on cold probes. PMID:25210000

  2. Gain and frequency tuning within the mouse cochlear apex

    SciTech Connect

    Oghalai, John S.; Raphael, Patrick D.; Gao, Simon; Lee, Hee Yoon; Groves, Andrew K.; Zuo, Jian; Applegate, Brian E.

    2015-12-31

    Normal mammalian hearing requires cochlear outer hair cell active processes that amplify the traveling wave with high gain and sharp tuning, termed cochlear amplification. We have used optical coherence tomography to study cochlear amplification within the apical turn of the mouse cochlea. We measured not only classical basilar membrane vibratory tuning curves but also vibratory responses from the rest of the tissues that compose the organ of Corti. Basilar membrane tuning was sharp in live mice and broad in dead mice, whereas other regions of the organ of Corti demonstrated phase shifts consistent with additional filtering beyond that provided by basilar membrane mechanics. We use these experimental data to support a conceptual framework of how cochlear amplification is tuned within the mouse cochlear apex. We will also study transgenic mice with targeted mutations that affect different biomechanical aspects of the organ of Corti in an effort to localize the underlying processes that produce this additional filtering.

  3. Multiple Tune Jumps to Overcome Horizontal Depolarizing Resonances

    NASA Astrophysics Data System (ADS)

    Huang, H.; Ahrens, L. A.; Bai, M.; Brown, K. A.; Dutheil, Y.; Gardner, C.; Glenn, J. W.; Lin, F.; Mackay, W. W.; Meot, F.; Poblaguev, A.; Ranjbar, V.; Roser, T.; Schoefer, V.; Tepikian, S.; Tsoupas, N.; Yip, K.; Zelenski, A.; Zeno, K.

    2016-02-01

    Imperfection and vertical intrinsic depolarizing resonances have been overcome by the two partial Siberian snakes in the Alternative Gradient Synchrotron(AGS). The relatively weak but numerous horizontal resonances are the main source of polarization loss in the AGS. A pair of horizontal tune jump quads have been used to overcome these weak resonances. The locations of the two quads have to be chosen such that the disturbance to the beam optics is minimum. The emittance growth has to be mitigated for this method to work. In addition, this technique needs very accurate jump timing. Using two partial Siberian snakes, with vertical tune inside the spin tune gap and 80% polarization at AGS injection, polarized proton beam had reached 1.5 × 1011 proton per bunch with 65% polarization. With the tune jump timing optimized and emittance preserved, more than 70% polarization with 2 × 1011 protons per bunch has been achieved.

  4. An improved auto-tuning scheme for PI controllers.

    PubMed

    Mudi, Rajani K; Dey, Chanchal; Lee, Tsu-Tian

    2008-01-01

    Ziegler-Nichols tuned PI and PID controllers are usually found to provide poor performances for high-order and nonlinear systems. In this study, an improved auto-tuning scheme is presented for Ziegler-Nichols tuned PI controllers (ZNPICs). With a view to improving the transient response, the proportional and integral gains of the proposed controller are continuously modified based on the current process trend. The proposed controller is tested for a number of high-order linear and nonlinear dead-time processes under both set-point change and load disturbance. It exhibits significantly improved performance compared to ZNPIC, and Refined Ziegler-Nichols tuned PI controller (RZNPIC). Robustness of the proposed scheme is established by varying the controller parameters as well as the dead-time of the process under control.

  5. Tuning micropillar cavity birefringence by laser induced surface defects

    SciTech Connect

    Bonato, Cristian; Ding Dapeng; Gudat, Jan; Exter, Martin P. van; Thon, Susanna; Kim, Hyochul; Petroff, Pierre M.; Bouwmeester, Dirk

    2009-12-21

    We demonstrate a technique to tune the optical properties of micropillar cavities by creating small defects on the sample surface near the cavity region with an intense focused laser beam. Such defects modify strain in the structure, changing the birefringence in a controllable way. We apply the technique to make the fundamental cavity mode polarization-degenerate and to fine tune the overall mode frequencies, as needed for applications in quantum information science.

  6. Method and apparatus for tuning high power lasers

    DOEpatents

    Hutchinson, Donald P.; Vandersluis, Kenneth L.

    1977-04-19

    This invention relates to high power gas lasers that are adapted to be tuned to a desired lasing wavelength through the use of a gas cell to lower the gain at a natural lasing wavelength and "seeding" the laser with a beam from a low power laser which is lasing at the desired wavelength. This tuning is accomplished with no loss of power and produces a pulse with an altered pulse shape. It is potentially applicable to all gas lasers.

  7. Genetic Algorithm Tuned Fuzzy Logic for Gliding Return Trajectories

    NASA Technical Reports Server (NTRS)

    Burchett, Bradley T.

    2003-01-01

    The problem of designing and flying a trajectory for successful recovery of a reusable launch vehicle is tackled using fuzzy logic control with genetic algorithm optimization. The plant is approximated by a simplified three degree of freedom non-linear model. A baseline trajectory design and guidance algorithm consisting of several Mamdani type fuzzy controllers is tuned using a simple genetic algorithm. Preliminary results show that the performance of the overall system is shown to improve with genetic algorithm tuning.

  8. Laser induced tuning of cholesteric liquid crystal without alignment layers

    NASA Astrophysics Data System (ADS)

    Cheng, M.-C.; Huang, T.-C.; Lee, C.-Y.; Hsiao, Vincent K. S.

    2014-12-01

    We demonstrate a laser induced tuning effect on non-chiral azobenzene-doped CLC (Azo-CLCs) without using orientated substrate. The reversible tuning range is 90 nm under alternative violet (405 nm) and green (532 nm) laser exposure corresponded to the response time of 3 and 15 s, respectively. The current demonstrations may find applications in photoactive micro- or nano-photonic devices where orientated substrate is difficult to be incorporated.

  9. Emissivity Tuned Emitter for RTPV Power Sources

    SciTech Connect

    Carl M. Stoots; Robert C. O'Brien; Troy M. Howe

    2012-03-01

    Every mission launched by NASA to the outer planets has produced unexpected results. The Voyager I and II, Galileo, and Cassini missions produced images and collected scientific data that totally revolutionized our understanding of the solar system and the formation of the planetary systems. These missions were enabled by the use of nuclear power. Because of the distances from the Sun, electrical power was produced using the radioactive decay of a plutonium isotope. Radioisotopic Thermoelectric Generators (RTGs) used in the past and currently used Multi-Mission RTGs (MMRTGs) provide power for space missions. Unfortunately, RTGs rely on thermocouples to convert heat to electricity and are inherently inefficient ({approx} 3-7% thermal to electric efficiency). A Radioisotope Thermal Photovoltaic (RTPV) power source has the potential to reduce the specific mass of the onboard power supply by increasing the efficiency of thermal to electric conversion. In an RTPV, a radioisotope heats an emitter, which emits light to a photovoltaic (PV) cell, which converts the light into electricity. Developing an emitter tuned to the desired wavelength of the photovoltaic is a key part in increasing overall performance. Researchers at the NASA Glenn Research Center (GRC) have built a Thermal Photovoltaic (TPV) system, that utilizes a simulated General Purpose Heat Source (GPHS) from a MMRTG to heat a tantalum emitter. The GPHS is a block of graphite roughly 10 cm by 10 cm by 5 cm. A fully loaded GPHS produces 250 w of thermal power and weighs 1.6 kgs. The GRC system relies on the GPHS unit radiating at 1200 K to a tantalum emitter that, in turn, radiates light to a GaInAs photo-voltaic cell. The GRC claims system efficiency of conversion of 15%. The specific mass is around 167 kg/kWe. A RTPV power source that utilized a ceramic or ceramic-metal (cermet) matrix would allow for the combination of the heat source, canister, and emitter into one compact unit, and allow variation in size

  10. Broad tuning range filtering system with Optune interferometers

    NASA Astrophysics Data System (ADS)

    Miron, Nicolae

    2008-08-01

    An optical system built with two Optune interferometers cascaded according to Vernier principle has attractive tunable band pass filtering properties for numerous applications. Several characteristics of Optune interferometer such as 0.2 dB insertion loss flatness across at least 90 nm interval, no tuning holes across 240 nm tuning range, quasi-periodic free spectral range and 1 dB insertion loss are key parameters to obtain a cascade with 0.1 nm band pass tunable across minimum 90 nm. Several properties of Optune interferometers are analyzed to build a cascade tunable across minimum 90 nm: the relationships between the free spectral ranges, bandwidths and tuning conditions. It is presented also a cascade prototype with two interferometers having 9.72 nm free spectral range and respectively 11.12 nm free spectral range. The cascade band pass is 0.1 nm tunable with 1 pm accuracy to any arbitrary wavelength across 150 nm free spectral range, without any tuning hole. It has 0.125 ms / 100 nm tuning speed, the insertion loss is less than 3 dB, 50 dB contrast, 0.5 dB flatness and 0.2 dB polarization dependent loss. A controller based on digital signal processor monitors the operation of the cascade to achieve optimum tuning performance.

  11. Objective estimates of cochlear tuning by otoacoustic emission analysis

    NASA Astrophysics Data System (ADS)

    Moleti, Arturo; Sisto, Renata

    2003-01-01

    A new method is presented for estimating cochlear tuning starting from measurements of either the transient evoked otoacoustic emission latency or the spontaneous otoacoustic emission minimal spacing. This method could be useful in obtaining indirect information about the tuning curve, particularly for subjects that, like neonates, cannot be studied with psycho-acoustical techniques. Theoretical models of the acoustic transmission along the cochlea based on the transmission line formalism predict a relation between the otoacoustic emission latency and the frequency. This relation depends on the tuning curve, i.e., the frequency dependence of the quality factor of the cochlear resonances. On the other hand, models for the generation of spontaneous emissions based on the concept of coherent scattering from cochlear random inhomogeneities imply an independent relation between the tuning curve and the minimal frequency spacing between spontaneous emissions. In this study, experimental measurements of the otoacoustic emission latency and of the minimal spacing between spontaneous emissions are presented. Theoretical relations are derived, which connect these two measured quantities and the tuning curve. The typically longer latency of neonates implies a higher degree of tuning at high levels of stimulation.

  12. Aircraft interior noise reduction by alternate resonance tuning

    NASA Technical Reports Server (NTRS)

    Gottwald, James A.; Bliss, Donald B.

    1990-01-01

    The focus is on a noise control method which considers aircraft fuselages lined with panels alternately tuned to frequencies above and below the frequency that must be attenuated. An interior noise reduction called alternate resonance tuning (ART) is described both theoretically and experimentally. Problems dealing with tuning single paneled wall structures for optimum noise reduction using the ART methodology are presented, and three theoretical problems are analyzed. The first analysis is a three dimensional, full acoustic solution for tuning a panel wall composed of repeating sections with four different panel tunings within that section, where the panels are modeled as idealized spring-mass-damper systems. The second analysis is a two dimensional, full acoustic solution for a panel geometry influenced by the effect of a propagating external pressure field such as that which might be associated with propeller passage by a fuselage. To reduce the analysis complexity, idealized spring-mass-damper panels are again employed. The final theoretical analysis presents the general four panel problem with real panel sections, where the effect of higher structural modes is discussed. Results from an experimental program highlight real applications of the ART concept and show the effectiveness of the tuning on real structures.

  13. Highly-efficient thermally-tuned resonant optical filters.

    PubMed

    Cunningham, John E; Shubin, Ivan; Zheng, Xuezhe; Pinguet, Thierry; Mekis, Attila; Luo, Ying; Thacker, Hiren; Li, Guoliang; Yao, Jin; Raj, Kannan; Krishnamoorthy, Ashok V

    2010-08-30

    We demonstrate spectral tunability for microphotonic add-drop filters manufactured as ring resonators in a commercial 130 nm SOI CMOS technology. The filters are provisioned with integrated heaters built in CMOS for thermal tuning. Their thermal impedance has been dramatically increased by the selective removal of the SOI handler substrate under the device footprint using a bulk silicon micromachining process. An overall ~20x increase in the tuning efficiency has been demonstrated with a 100 µm radius ring as compared to a pre-micromachined device. A total of 3.9 mW of applied tuning power shifts the filter resonant peak across one free spectral node of the device. The Q-factor of the resonator remains unchanged after the co-integration process and hence this device geometry proves to be fully CMOS compatible. Additionally, after the cointegration process our result of 2π shift with 3.9 mW power is among the best tuning performances for this class of devices. Finally, we examine scaling the tuning efficiency versus device footprint to develop a different performance criterion for an easier comparison to evaluate thermal tuning. Our criterion is defined as the unit of power to shift the device resonance by a full 2π phase shift.

  14. On the sensing and tuning of progressive structural vibration waves.

    PubMed

    Minikes, Adi; Gabay, Ran; Bucher, Izhak; Feldman, Michael

    2005-09-01

    Progressive flexural waves can be generated only in finite structures by fine tuning the excitation and the boundary conditions. The tuning process eliminates the reflected waves arising from discontinuities and edge effects. This work presents and expands two new methods for the identification and tuning of traveling waves. One is a parametric method based on fitting an ellipse to the complex spatial amplitude distribution. The other is a nonparametric method based on the Hilbert transform providing a space-localized estimate. With these methods, an optimization-based tuning of transverse flexural waves in a one-dimensional structure, a vibrating beam, is developed. Existing methods are designed for a single frequency and are based on either combining two vibration modes or mechanical impedance matching. Such methods are limited to a designated excitation frequency determined by a specific configuration of the system. With the proposed methods, structural progressive waves can be generated for a wide range of frequencies under the same given system configuration and can be tuned in real time to accommodate changes in boundary conditions. An analytical study on the nature of the optimal excitation conditions has been carried out, revealing singular configurations. The experimental verification of the sensing and tuning methods is demonstrated on a dedicated laboratory prototype. The proposed methods are not confined to mechanical waves and present a comprehensive approach applicable for other physical wave phenomena.

  15. Tune Variations due to Septum Stray Field F. Pederson &

    SciTech Connect

    Rinolfi, L.

    1986-10-12

    Two types of antiproton instabilities due to trapped ions are harmful in the AA. One is a coherent instability occurring when an ion pocket resonates with a 3-Q mode (hiccups), the other is excitation of 11th and 15th order non-linear resonances due to the non-linear focusing fields from localized ion clouds trapped in uncleared potential well pockets. Accumulation with a good injection yield of antiprotons forces us to locate the tune of the dense core in the general area of the array of 15th order resonances. To avoid harmful blow-up of the dense core the tune is located between the resonances 11Q{sub H} + 4Q{sub V} = 34, 10Q{sub H} + 5Q{sub V} = 34, and 11Q{sub H} = 25, requiring a tune of Q{sub H} = 2.2722 to be maintained with a precision of a few 10{sup -4} (Fig. 4). Different angles of the injection and ejection trajectories require the septum current to be changed from 3860 A during accumulation to 3920 A, during ejection mode. Variations in the septum stray field due to these changes in current cause tune changes in the order of 10{sup -3}. In addition, at a given septum current, a pronounced hysteresis of the stray field causes tune variations of about the same order of magnitude, so also the past history of the septum excitation must be carefully controlled to obtain a reproducible tune.

  16. On the Possibility of Using Nonlinear Elements for Landau Damping in High-Intensity Beams

    SciTech Connect

    Alexahin, Y.; Gianfelice-Wendt, E.; Lebedev, V.; Valishev, A.

    2016-09-30

    Direct space-charge force shifts incoherent tunes downwards from the coherent ones breaking the Landau mechanism of coherent oscillations damping at high beam intensity. To restore it nonlinear elements can be employed which move back tunes of large amplitude particles. In the present report we consider the possibility of creating a “nonlinear integrable optics” insertion in the Fermilab Recycler to host either octupoles or hollow electron lens for this purpose. For comparison we also consider the classic scheme with distributed octupole families. It is shown that for the Proton Improvement Plan II (PIP II) parameters the required nonlinear tune shift can be created without destroying the dynamic aperture.

  17. Frequency tuning of synaptic inhibition underlying duration-tuned neurons in the mammalian inferior colliculus.

    PubMed

    Valdizón-Rodríguez, Roberto; Faure, Paul A

    2017-01-18

    Inhibition plays an important role in creating the temporal response properties of duration-tuned neurons (DTNs) in the mammalian inferior colliculus (IC). Neurophysiological and computational studies indicate that duration selectivity in the IC is created through the convergence of excitatory and inhibitory synaptic inputs offset in time. We used paired tone stimulation and extracellular recording to measure the frequency tuning of the inhibition acting on DTNs in the IC of the big brown bat (Eptesicus fuscus). We stimulated DTNs with pairs of tones differing in duration, onset time, and frequency. The onset time of a short, best duration (BD), probe tone set to the best excitatory frequency (BEF) was varied relative to the onset of a longer duration, non-excitatory (NE) tone whose frequency was varied. When the NE tone frequency was near or within the cell's excitatory bandwidth (eBW), BD tone evoked spikes were suppressed by an onset-evoked inhibition. The offset and duration of the suppression decreased as the NE tone frequency departed from the BEF. We measured the inhibitory frequency response area, best inhibitory frequency (BIF), and inhibitory bandwidth (iBW) of each cell. We found that the BIF closely matched the BEF, but the iBW was broader and usually overlapped the eBW measured from the same cell. These data suggest that temporal selectivity of midbrain DTNs is created and preserved by having cells receive an onset-evoked, constant-latency, broadband inhibition that largely overlaps the cell's excitatory receptive field. We conclude by discussing possible neural sources of the inhibition.

  18. Wide and fast dispersion tuning of a picosecond OPO based on aperiodic quasi-phase matching using an axially chirped volume Bragg grating.

    PubMed

    Descloux, Delphine; Walter, Guillaume; Cadiou, Erwan; Dherbecourt, Jean-Baptiste; Gorju, Guillaume; Melkonian, Jean-Michel; Raybaut, Myriam; Drag, Cyril; Godard, Antoine

    2016-09-01

    We report on a widely tunable synchronously pumped picosecond optical parametric oscillator (OPO) combining an aperiodically poled MgO-doped LiNbO3 crystal as a broadband gain medium and an axially chirped volume Bragg grating as a spectral filtering dispersive element. Translation of the Bragg grating along the beam axis enables wavelength tuning over 215 nm around 3.82 μm and provides spectral narrowing. Rapid continuous tuning over 150 nm in 100 ms is demonstrated.

  19. Neural Tuning Functions Underlie Both Generalization and Interference

    PubMed Central

    Howard, Ian S.; Franklin, David W.

    2015-01-01

    In sports, the role of backswing is considered critical for generating a good shot, even though it plays no direct role in hitting the ball. We recently demonstrated the scientific basis of this phenomenon by showing that immediate past movement affects the learning and recall of motor memories. This effect occurred regardless of whether the past contextual movement was performed actively, passively, or shown visually. In force field studies, it has been shown that motor memories generalize locally and that the level of compensation decays as a function of movement angle away from the trained movement. Here we examine if the contextual effect of past movement exhibits similar patterns of generalization and whether it can explain behavior seen in interference studies. Using a single force-field learning task, the directional tuning curves of both the prior contextual movement and the subsequent force field adaptive movements were measured. The adaptation movement direction showed strong directional tuning, decaying to zero by 90° relative to the training direction. The contextual movement direction exhibited a similar directional tuning, although the effect was always above 60%. We then investigated the directional tuning of the passive contextual movement using interference tasks, where the contextual movements that uniquely specified the force field direction were separated by ±15° or ±45°. Both groups showed a pronounced tuning effect, which could be well explained by the directional tuning functions for single force fields. Our results show that contextual effect of past movement influences predictive force compensation, even when adaptation does not require contextual information. However, when such past movement contextual information is crucial to the task, such as in an interference study, it plays a strong role in motor memory learning and recall. This work demonstrates that similar tuning responses underlie both generalization of movement direction

  20. Autonomous Performance Monitoring System: Monitoring and Self-Tuning (MAST)

    NASA Technical Reports Server (NTRS)

    Peterson, Chariya; Ziyad, Nigel A.

    2000-01-01

    Maintaining the long-term performance of software onboard a spacecraft can be a major factor in the cost of operations. In particular, the task of controlling and maintaining a future mission of distributed spacecraft will undoubtedly pose a great challenge, since the complexity of multiple spacecraft flying in formation grows rapidly as the number of spacecraft in the formation increases. Eventually, new approaches will be required in developing viable control systems that can handle the complexity of the data and that are flexible, reliable and efficient. In this paper we propose a methodology that aims to maintain the accuracy of flight software, while reducing the computational complexity of software tuning tasks. The proposed Monitoring and Self-Tuning (MAST) method consists of two parts: a flight software monitoring algorithm and a tuning algorithm. The dependency on the software being monitored is mostly contained in the monitoring process, while the tuning process is a generic algorithm independent of the detailed knowledge on the software. This architecture will enable MAST to be applicable to different onboard software controlling various dynamics of the spacecraft, such as attitude self-calibration, and formation control. An advantage of MAST over conventional techniques such as filter or batch least square is that the tuning algorithm uses machine learning approach to handle uncertainty in the problem domain, resulting in reducing over all computational complexity. The underlying concept of this technique is a reinforcement learning scheme based on cumulative probability generated by the historical performance of the system. The success of MAST will depend heavily on the reinforcement scheme used in the tuning algorithm, which guarantees the tuning solutions exist.

  1. Squeezing Alters Frequency Tuning of WGM Optical Resonator

    NASA Technical Reports Server (NTRS)

    Mohageg, Makan; Maleki, Lute

    2010-01-01

    Mechanical squeezing has been found to alter the frequency tuning of a whispering-gallery-mode (WGM) optical resonator that has an elliptical shape and is made of lithium niobate. It may be possible to exploit this effect to design reconfigurable optical filters for optical communications and for scientific experiments involving quantum electrodynamics. Some background information is prerequisite to a meaningful description of the squeezing-induced alteration of frequency tuning: The spectrum of a WGM resonator is represented by a comblike plot of intensity versus frequency. Each peak of the comblike plot corresponds to an electromagnetic mode represented by an integer mode number, and the modes are grouped into sets represented by integer mode indices. Because lithium niobate is an electro-optically active material, the WGM resonator can be tuned (that is, the resonance frequencies can be shifted) by applying a suitable bias potential. The frequency shift of each mode is quantified by a tuning rate defined as the ratio between the frequency shift and the applied potential. In the absence of squeezing, all modes exhibit the same tuning rate. This concludes the background information. It has been demonstrated experimentally that when the resonator is squeezed along part of either of its two principal axes, tuning rates differ among the groups of modes represented by different indices (see figure). The differences in tuning rates could be utilized to configure the resonance spectrum to obtain a desired effect; for example, through a combination of squeezing and electrical biasing, two resonances represented by different mode indices could be set at a specified frequency difference something that could not be done through electrical biasing alone.

  2. AGS tune jump system to cross horizontal depolarization resonances overview

    SciTech Connect

    Glenn, J.W.; Ahrens, L.; Fu, W.; Mi, J.L.; Rosas, P.; Schoefer, V.; Theisen, C.; Altinbas, Z.

    2011-03-28

    Two partial snakes overcome the vertical depolarizing resonances in the AGS. But a new type of depolarizing intrinsic resonance from horizontal motion appeared. We reduce these using horizontal tune jumps timed to these resonances. We gain a factor of six in crossing rate with a tune jump of 0.05 in 100 {micro}s. Two quadrapoles, we described in 2009, pulse 42 times, the current matching beam energy. The power supplies for these quads are described in detail elsewhere in this conference. The controls for the Jump Quad system is based on a BNL designed Quad Function Generator. Two modules are used; one for timing, and one to supply reference voltages. Synchronization is provided by a proprietary serial bus, the Event Link. The AgsTuneJump application predicts the times of the resonances during the AGS cycle and calculates the power supply trigger times from externally collected tune and energy versus time data and the Low and High PS voltage functions from a voltage to current model of the power supply. The system was commissioned during runs 09 & 10 and is operational. Many beam effects are described elsewhere. The TuneJump system has worked well and has caused little trouble save for the perturbations in the lattice having such a large effect due to our need to run with the vertical tune within a few thousandths of the integer tune. As these problems were mostly sorted out by correcting the 6th harmonic orbit distortions which caused a large 18 theta beta wave. Also running with minimal chromaticity reduces emittance growth. There are still small beta waves which are being addressed. The timing of the pulses is still being investigated, but as each crossing causes minimal polarization loss, this is a lengthy process.

  3. Shear-mode magnetic force microscopy using a quartz tuning

    NASA Astrophysics Data System (ADS)

    Seo, Yongho; Kim, Kyungho; Jhe, Wonho

    2003-03-01

    In conventional magnetic force microscopy (MFM), the cantilever is employed as a force sensor and optical deflection detection is used to measure its vibration. Micro-fabricated cantilever has such a small spring constant order of 10 N/m. The cantilever has some weak points; unexpected crash occurs because of its low stiffness, high resolution MFM is difficult because the dithering amplitude is large ( ˜ 10 nm), and laser light should be exposed, which is undesirable for low temperature or dark environment. We demonstrate shear-mode magnetic force microscopy using a quartz tuning fork with a spring constant of 1300 N/m. A sharpened cobalt tip is attached to the prong of the tuning fork so that it can be controlled in shear mode. We have obtained high resolution images of recorded magnetization patterns of hard disks with a spatial resolution of 50 nm. The minimum detectable force gradient is an order of 10-4 N/m. There are important advantages in tuning fork based MFM; (i) Because the tuning fork sensor is stiff, the tip will not be pulled by the attractive van der Waals force. So, unexpected crash can be avoided. (ii) Its minimum detectable dithering amplitude is much smaller than that of cantilever, (The spectral noise density of the tuning fork is ˜ 100 fm/ Hz) which supports the high resolution imaging. (iii) As the tuning fork is self-dithering and self-sensing device, one can avoid optical deflection detection and the scanning head is simple and small. (iv) Tuning fork based MFM can be operated in dark and low temperature condition, because no optical source is necessary and dissipated power can be reduced ˜ 1 pW.

  4. AUTOMOTIVE DIESEL MAINTENANCE 1. UNIT VII, ENGINE TUNE-UP--DETROIT DIESEL ENGINE.

    ERIC Educational Resources Information Center

    Human Engineering Inst., Cleveland, OH.

    THIS MODULE OF A 30-MODULE COURSE IS DESIGNED TO DEVELOP AN UNDERSTANDING OF TUNE-UP PROCEDURES FOR DIESEL ENGINES. TOPICS ARE SCHEDULING TUNE-UPS, AND TUNE-UP PROCEDURES. THE MODULE CONSISTS OF A SELF-INSTRUCTIONAL BRANCH PROGRAMED TRAINING FILM "ENGINE TUNE-UP--DETROIT DIESEL ENGINE" AND OTHER MATERIALS. SEE VT 005 655 FOR FURTHER INFORMATION.…

  5. A New Approach to Identify Optimal Properties of Shunting Elements for Maximum Damping of Structural Vibration Using Piezoelectric Patches

    NASA Technical Reports Server (NTRS)

    Park, Junhong; Palumbo, Daniel L.

    2004-01-01

    The use of shunted piezoelectric patches in reducing vibration and sound radiation of structures has several advantages over passive viscoelastic elements, e.g., lower weight with increased controllability. The performance of the piezoelectric patches depends on the shunting electronics that are designed to dissipate vibration energy through a resistive element. In past efforts most of the proposed tuning methods were based on modal properties of the structure. In these cases, the tuning applies only to one mode of interest and maximum tuning is limited to invariant points when based on den Hartog's invariant points concept. In this study, a design method based on the wave propagation approach is proposed. Optimal tuning is investigated depending on the dynamic and geometric properties that include effects from boundary conditions and position of the shunted piezoelectric patch relative to the structure. Active filters are proposed as shunting electronics to implement the tuning criteria. The developed tuning methods resulted in superior capabilities in minimizing structural vibration and noise radiation compared to other tuning methods. The tuned circuits are relatively insensitive to changes in modal properties and boundary conditions, and can applied to frequency ranges in which multiple modes have effects.

  6. A new hybrid gyroscope with electrostatic negative stiffness tuning.

    PubMed

    Yang, Bo; Guan, Yumei; Wang, Shourong; Zou, Qi; Chu, Xian; Xue, Haiyan

    2013-05-30

    A variety of gyroscopes have been extensively studied due to their capability of precision detection of rotation rates and extensive applications in navigation, guidance and motion control. In this work, a new Hybrid Gyroscope (HG) which combines the traditional Dynamically Tuned Gyroscope (DTG) with silicon micromachined technology is investigated. The HG not only has the potentiality of achieving the same high precision as the traditional DTG, but also features a small size and low cost. The theoretical mechanism of the HG with a capacitance transducer and an electrostatic torquer is derived and the influence of the installation errors from the capacitance plate and the disc rotor module is investigated. A new tuning mechanism based on negative stiffness rather than the traditional dynamic tuning is proposed. The experimental results prove that the negative stiffness tuning is practicable and a tuning voltage of as high as 63 V is demonstrated. Due to the decreased installation error, the non-linearity of the scale factor is reduced significantly from 11.78% to 0.64%, as well as the asymmetry from 93.3% to 1.56% in the open loop condition. The rebalancing close-loop control is simulated and achieved experimentally, which proves that the fundamental principle of the HG is feasible.

  7. Unsteady Aerodynamic Model Tuning for Precise Flutter Prediction

    NASA Technical Reports Server (NTRS)

    Pak, Chan-Gi

    2011-01-01

    A simple method for an unsteady aerodynamic model tuning is proposed in this study. This method is based on the direct modification of the aerodynamic influence coefficient matrices. The aerostructures test wing 2 flight-test data is used to demonstrate the proposed model tuning method. The flutter speed margin computed using only the test validated structural dynamic model can be improved using the additional unsteady aerodynamic model tuning, and then the flutter speed margin requirement of 15 % in military specifications can apply towards the test validated aeroelastic model. In this study, unsteady aerodynamic model tunings are performed at two time invariant flight conditions, at Mach numbers of 0.390 and 0.456. When the Mach number for the unsteady model tuning approaches to the measured fluttering Mach number, 0.502, at the flight altitude of 9,837 ft, the estimated flutter speed is approached to the measured flutter speed at this altitude. The minimum flutter speed difference between the estimated and measured flutter speed is -.14 %.

  8. On tune deafness (dysmelodia): frequency, development, genetics and musical background.

    PubMed

    Kalmus, H; Fry, D B

    1980-05-01

    With the aid of the Distorted Tunes Test a group of British adults could be established whose melodic aptitude was below a certain level and whom we called tune deaf. They are only a fraction of those popularly called tone deaf. The Distorted Tunes Test is only slightly correlated with pitch discrimination, short term tonal memory or number memory. In children ability to pass the Distorted Tunes Test develops at greatly varying speeds and to a varying degree, reaching stability in adolescence. Tune deafness has a familial distribution and segregates in a way suggesting an autosomal dominant trait with imperfect penetrance. Some degree of positive assortative mating has been established. Some people, unfamiliar with the British melodies which form the basis of the test, pass it. This indicates the existence of a partly innate and partly acquired competence to judge what is acceptable and what is not, within the tradition of Western popular or classical music. This seems to indicate the existence of some deep structure of tonality, comparable with Chomsky's deep language structure. Asians who have not been much exposed to this kind of music find the task very difficult.

  9. Broad electrical tuning of plasmonic nanoantennas at visible frequencies

    NASA Astrophysics Data System (ADS)

    Hoang, Thang B.; Mikkelsen, Maiken H.

    2016-05-01

    We report an experimental demonstration of electrical tuning of plasmon resonances of optical nanopatch antennas over a wide wavelength range. The antennas consist of silver nanocubes separated from a gold film by a thin 8 nm polyelectrolyte spacer layer. By using ionic liquid and indium tin oxide coated glass as a top electrode, we demonstrate dynamic and reversible tuning of the plasmon resonance over 100 nm in the visible wavelength range using low applied voltages between -3.0 V and 2.8 V. The electrical potential is applied across the nanoscale gap causing changes in the gap thickness and dielectric environment which, in turn, modifies the plasmon resonance. The observed tuning range is greater than the full-width-at-half-maximum of the plasmon resonance, resulting in a tuning figure of merit of 1.05 and a tuning contrast greater than 50%. Our results provide an avenue to create active and reconfigurable integrated nanophotonic components for applications in optoelectronics and sensing.

  10. An Adaptive Kalman Filter using a Simple Residual Tuning Method

    NASA Technical Reports Server (NTRS)

    Harman, Richard R.

    1999-01-01

    One difficulty in using Kalman filters in real world situations is the selection of the correct process noise, measurement noise, and initial state estimate and covariance. These parameters are commonly referred to as tuning parameters. Multiple methods have been developed to estimate these parameters. Most of those methods such as maximum likelihood, subspace, and observer Kalman Identification require extensive offline processing and are not suitable for real time processing. One technique, which is suitable for real time processing, is the residual tuning method. Any mismodeling of the filter tuning parameters will result in a non-white sequence for the filter measurement residuals. The residual tuning technique uses this information to estimate corrections to those tuning parameters. The actual implementation results in a set of sequential equations that run in parallel with the Kalman filter. Equations for the estimation of the measurement noise have also been developed. These algorithms are used to estimate the process noise and measurement noise for the Wide Field Infrared Explorer star tracker and gyro.

  11. An Adaptive Kalman Filter Using a Simple Residual Tuning Method

    NASA Technical Reports Server (NTRS)

    Harman, Richard R.

    1999-01-01

    One difficulty in using Kalman filters in real world situations is the selection of the correct process noise, measurement noise, and initial state estimate and covariance. These parameters are commonly referred to as tuning parameters. Multiple methods have been developed to estimate these parameters. Most of those methods such as maximum likelihood, subspace, and observer Kalman Identification require extensive offline processing and are not suitable for real time processing. One technique, which is suitable for real time processing, is the residual tuning method. Any mismodeling of the filter tuning parameters will result in a non-white sequence for the filter measurement residuals. The residual tuning technique uses this information to estimate corrections to those tuning parameters. The actual implementation results in a set of sequential equations that run in parallel with the Kalman filter. A. H. Jazwinski developed a specialized version of this technique for estimation of process noise. Equations for the estimation of the measurement noise have also been developed. These algorithms are used to estimate the process noise and measurement noise for the Wide Field Infrared Explorer star tracker and gyro.

  12. Tuning Parameters in Heuristics by Using Design of Experiments Methods

    NASA Technical Reports Server (NTRS)

    Arin, Arif; Rabadi, Ghaith; Unal, Resit

    2010-01-01

    With the growing complexity of today's large scale problems, it has become more difficult to find optimal solutions by using exact mathematical methods. The need to find near-optimal solutions in an acceptable time frame requires heuristic approaches. In many cases, however, most heuristics have several parameters that need to be "tuned" before they can reach good results. The problem then turns into "finding best parameter setting" for the heuristics to solve the problems efficiently and timely. One-Factor-At-a-Time (OFAT) approach for parameter tuning neglects the interactions between parameters. Design of Experiments (DOE) tools can be instead employed to tune the parameters more effectively. In this paper, we seek the best parameter setting for a Genetic Algorithm (GA) to solve the single machine total weighted tardiness problem in which n jobs must be scheduled on a single machine without preemption, and the objective is to minimize the total weighted tardiness. Benchmark instances for the problem are available in the literature. To fine tune the GA parameters in the most efficient way, we compare multiple DOE models including 2-level (2k ) full factorial design, orthogonal array design, central composite design, D-optimal design and signal-to-noise (SIN) ratios. In each DOE method, a mathematical model is created using regression analysis, and solved to obtain the best parameter setting. After verification runs using the tuned parameter setting, the preliminary results for optimal solutions of multiple instances were found efficiently.

  13. Tuning the Model Predictive Control of a Crude Distillation Unit.

    PubMed

    Yamashita, André Shigueo; Zanin, Antonio Carlos; Odloak, Darci

    2016-01-01

    Tuning the parameters of the Model Predictive Control (MPC) of an industrial Crude Distillation Unit (CDU) is considered here. A realistic scenario is depicted where the inputs of the CDU system have optimizing targets, which are provided by the Real Time Optimization layer of the control structure. It is considered the nominal case, in which both the CDU model and the MPC model are the same. The process outputs are controlled inside zones instead of at fixed set points. Then, the tuning procedure has to define the weights that penalize the output error with respect to the control zone, the weights that penalize the deviation of the inputs from their targets, as well as the weights that penalize the input moves. A tuning approach based on multi-objective optimization is proposed and applied to the MPC of the CDU system. The performance of the controller tuned with the proposed approach is compared through simulation with the results of an existing approach also based on multi-objective optimization. The simulation results are similar, but the proposed approach has a computational load significantly lower than the existing method. The tuning effort is also much lower than in the conventional practical approaches that are usually based on ad-hoc procedures.

  14. Ionic and neuromodulatory regulation of burst discharge controls frequency tuning.

    PubMed

    Mehaffey, W Hamish; Ellis, Lee D; Krahe, Rüdiger; Dunn, Robert J; Chacron, Maurice J

    2008-01-01

    Sensory neurons encode natural stimuli by changes in firing rate or by generating specific firing patterns, such as bursts. Many neural computations rely on the fact that neurons can be tuned to specific stimulus frequencies. It is thus important to understand the mechanisms underlying frequency tuning. In the electrosensory system of the weakly electric fish, Apteronotus leptorhynchus, the primary processing of behaviourally relevant sensory signals occurs in pyramidal neurons of the electrosensory lateral line lobe (ELL). These cells encode low frequency prey stimuli with bursts of spikes and high frequency communication signals with single spikes. We describe here how bursting in pyramidal neurons can be regulated by intrinsic conductances in a cell subtype specific fashion across the sensory maps found within the ELL, thereby regulating their frequency tuning. Further, the neuromodulatory regulation of such conductances within individual cells and the consequences to frequency tuning are highlighted. Such alterations in the tuning of the pyramidal neurons may allow weakly electric fish to preferentially select for certain stimuli under various behaviourally relevant circumstances.

  15. Tuning the growth for a selective nucleation of chains of Quantum Dots behaving as single photon emitters

    NASA Astrophysics Data System (ADS)

    Latini, V.; Tisbi, E.; Placidi, E.; Patella, F.; Biccari, F.; Gurioli, M.; Vinattieri, A.; Arciprete, F.

    2017-01-01

    Single and two-layer InAs/GaAs(001) samples were grown in a Molecular Beam Epitaxy chamber under critical conditions, leading to the selective growth of self-assembled InAs Quantum Dot chains over mounded GaAs surfaces. Changing the thickness of the spacer layer and the InAs deposition made it possible to tune the nucleation of 2-fold or single chains in the second layer. Finite Element Method simulations evidenced the major role of the strain field in favoring the formation of single stacked chains. On the other hand, tuning properly the As4/In flux ratio contributed to improving the QD ordering along the chains. Microphotoluminescence experiments demonstrated single photon emission properties of the observed QDs. Our growth approach did not degrade the optical quality of the InAs QDs, allowing a significant spatial correlation between the QDs aligned along the chain.

  16. Temperature independent tuning of whispering gallery modes in a cryogenic environment.

    PubMed

    Henze, Rico; Ward, Jonathan M; Benson, Oliver

    2013-01-14

    A new tuning method for tuning whispering gallery modes (WGMs) in a cryogenic environment is presented. Within a home-made exchange gas cryostat the applicability of pressure tuning in microbubbles at liquid nitrogen (LN) temperature is shown. The general thermal shift and tuning behavior of borosilicate microbubbles is theoretically analyzed and compared to experimental data. We show that stress/strain tuning using compressed gas is widely unaffected by system temperature.

  17. Tuning the Hydrogen Storage in Magnesium Alloys

    NASA Astrophysics Data System (ADS)

    Er, Suleyman; de Wijs, Gilles A.; Brocks, Geert

    2011-03-01

    We investigate the hydrogen storage properties of promising magnesium alloys. Mg H2 (7.6 wt % H) would be a very useful storage material if the (de)hydrogenation kinetics can be improved and the desorption temperature is markedly lowered. Using first principles calculations, we show that hydrides of Mg-transition metal (TM) alloys adopt a structure that promotes faster (de)hydrogenation kinetics, as is also observed in experiment. Within the lightweight TMs, the most promising alloying element is titanium. Alloying Mg with Ti alone, however, is not sufficient to decrease the stability of the hydride phases, which is necessary to reduce the hydrogen desorption temperature. We find that adding aluminium or silicon markedly destabilizes Mg-Ti hydrides and stabilizes Mg-Ti alloys. Finally, we show that controlling the structure of Mg-Ti-Al(Si) system by growing it as multilayers, has a beneficial influence on the thermodynamic properties and makes it a stronger candidate for hydrogen storage.

  18. Tuning the sensing range of silicon pressure sensor by trench etching technology

    NASA Astrophysics Data System (ADS)

    Chou, Yu-Tuan; Lin, Hung-Yi; Hu, Hsin-Hua

    2006-01-01

    The silicon pressure sensor has been developed for over thirty years and widely used in automobiles, medical instruments, commercial electronics, etc. There are many different specifications of silicon pressure sensors that cover a very large sensing range, from less than 1 psi to as high as 1000 psi. The key elements of the silicon pressure sensor are a square membrane and the piezoresistive strain gages near the boundary of the membrane. The dimensions of the membrane determine the full sensing range and the sensitivity of the silicon sensor, including thickness and in-plane length. Unfortunately, in order to change the sensing range, the manufacturers need to order a customized epi wafer to get the desired thickness. All masks (usually six) have to be re-laid and re-fabricated for different membrane sizes. The existing technology requires at least three months to deliver the prototype for specific customer requests or the new application market. This research proposes a new approach to dramatically reduce the prototyping time from three months to one week. The concept is to tune the rigidity of the sensing membrane by modifying the boundary conditions without changing the plenary size. An extra mask is utilized to define the geometry and location of deep-RIE trenches and all other masks remain the same. Membranes with different depths and different patterns of trenches are designed for different full sensing ranges. The simulation results show that for a 17um thick and 750um wide membrane, the adjustable range by tuning trench depth is about 45% (from 5um to 10um), and can go to as high as 100% by tuning both the pattern and depth of the trenches. Based on an actual test in a product fabrication line, we verified that the total delivery time can be minimized to one week to make the prototyping very effective and cost-efficient.

  19. Wavelength-swept fiber laser based on acousto-optic tuning method

    NASA Astrophysics Data System (ADS)

    Chen, Ming-hui; Fan, Yun-ping; Zhang, Hao; Tao, Jian-feng; Zheng, Gang

    2016-10-01

    In this study, we have demonstrated a wavelength-swept fiber laser based on an acousto-optic tunable filter(AOTF) as a selective element and a semiconductor optical amplifier(SOA) as a gain medium in an internal fiber ring cavity. The light deriving from one port of the SOA goes through an optical isolator, the AOTF, a fiber coupler and a polarized controller successively, then it goes back to the other port of the SOA to form a ring cavity. The laser output is from another port of the fiber coupler. The laser made by this method is mainly used for swept-source optical coherence tomography(SS-OCT). The application of the SOA provides a sufficiently broad range and can ensure an increased axial resolution of SS-OCT. AOTF offers a wide tuning range, high switching speed and stable operation against vibration for the non-mechanical structure. The proposed wavelength-swept fiber laser ensures a high axial resolution of tomographic images and has a stable laser output. We have discussed the influence of the SOA injection current to the tuning range of the laser. In the SOA injection current of 280 mA, a continuous wavelength tuning range from 1295 to 1370 nm centered at a wavelength of 1330nm is obtained at the sweep rate of 1.06 kHz, and the power of the swept source was 1.14 mW. In addition, for quantitative characterization of the wavelength-swept performance with a AOTF, we have theoretically and experimentally analyzed the influence of the following controllable parameters: injection current, output power and sweeping frequency.

  20. Tuning Ferritin's Band Gap through Mixed Metal Oxide Nanoparticle Formation.

    PubMed

    Olsen, Cameron; Embley, Jacob; Hansen, Kameron; Henrichsen, Andrew; Peterson, J; Colton, John S; Watt, Richard

    2017-03-23

    This study uses the formation of a mixed metal oxide inside ferritin to tune the band gap energy of the ferritin mineral. The mixed metal oxide is composed of both Co and Mn, and is formed by reacting aqueous Co2+ with MnO4- in the presence of apoferritin. Altering the ratio between the two reactants allowed for controlled tuning of the band gap energies. All minerals formed were indirect band gap materials, with indirect band gap energies ranging from 0.52 to 1.30 eV. The direct transitions were also measured, with energy values ranging from 2.71 to 3.11 eV. Tuning the band gap energies of these samples changes the wavelengths absorbed by each mineral, increasing ferritin's potential in solar-energy harvesting. Additionally, the success of using MnO4- in ferritin mineral formation opens the possibility for new mixed metal oxide cores inside ferritin.

  1. Frequency tuning with RFQ temperature in China ADS Injector II

    NASA Astrophysics Data System (ADS)

    Wang, Jing; Huang, Jian-Long; Zhang, Xiao-Qi; Zhang, Bin; He, Yuan; Zhang, Zhou-Li; Shi, Ai-Min

    2016-03-01

    A 162.5 MHz four-vane radio frequency quadruple (RFQ) accelerator has been developed at the Institute of Modern Physics (IMP) for Injector II of the China ADS linac. The RFQ will operate in continuous wave mode at 100 kW. For the designed 10 mA beam, the additional RF power dissipation will induce a very large reflection of power. A water-temperature controlling system will be used to reduce the power reflection by tuning the frequency of the RFQ. The tuning capability of the water temperature is studied under different configurations of cooling water. Simulations and experiment are compared in this paper. The experimental results agree well with simulation using ANSYS. This can be used as a reference to tune the RFQ in beam commissioning. Supported by National Natural Science Foundation of China (91026001)

  2. Multimodal tuned dynamic absorber for split Stirling linear cryocooler

    NASA Astrophysics Data System (ADS)

    Veprik, Alexander; Tuito, Avi

    2016-05-01

    Low size, weight, power and price split Stirling linear cryocooler usually comprises electro-dynamically driven compressor and pneumatically driven expander which are side-by-side fixedly mounted upon the common frame and interconnected by the configurable transfer line. Vibration export produced by such a cryocooler comprises of a pair of tonal forces, the frequency of which essentially equals fixed driving frequency. In vibration sensitive applications, this may result in excessive angular line of sight jitter and translational defocusing affecting the image quality. The authors present Multimodal Tuned Dynamic Absorber, having one translational and two tilting modes essentially tuned to the driving frequency. Dynamic analysis shows that the dynamic reactions (force and moment) produced by such a dynamic absorber are capable of simultaneous attenuation of translational and tilting components of cryocooler induced vibration. The authors reveal the preferable design, the method of fine tuning and outcomes of numerical simulation on attainable performance.

  3. Synchrotron Tune Adjustment by Longitudinal Motion of Quadrupoles

    NASA Astrophysics Data System (ADS)

    Bertsche, K. J.

    1996-05-01

    Adjustment of the tune of a synchrotron is generally accomplished by globally varying the strength of quadrupoles, either in the main quadrupole bus or in a set of dedicated trim quadrupoles distributed around the ring. An alternate scheme for tune control involves varying the strengths of quadrupoles only within a local insert, thereby adjusting the phase advance across this insert to create a "phase trombone." In a synchrotron built of permanent magnets, such as the proposed Fermilab Recycler Ring, tune adjustment may also be accomplished by constructing a phase trombone in which the longitudinal position rather than strength of a number of quadrupoles is adjusted. Design philosophies and performance for such phase trombones will be presented. *Operated by Universities Research Association, Inc., under contract with the US. Department of Energy.

  4. AGS tune jump power supply design and test

    SciTech Connect

    Mi, J.; Glenn, J.W.; Huang, H.; Marneris, I.; Rosas, P.; Sandberg, J.; Tan, Y.; Zhang, W.

    2011-03-28

    A horizontal tune jump system has been installed to overcome the horizontal intrinsic spin resonances, which requires jumping the horizontal tune 0.04 units 82 times, 41 up and 41 down. Two quadruple magnets have been installed in AGS ring to perform this. The pulsed magnet current ranges from about 140A near injection to about 1400A later. The current pulse rise and fall time are around 100uS and flat tops time is around 4mS. These quadruples have separated supplies. This tune jump pulse power supply employees all semiconductor parts as well as the main switches. During dummy load and magnet testing, the test results showed that the power supply could meet the specification. This article will describe some details of power supply simulation, design and testing. Some test waveforms and pictures are presented in this paper.

  5. Tune control improvements on the rapid cycling synchrotron

    SciTech Connect

    Potts, C.; Faber, M.; Gunderson, G.; Knott, M.; Voss, D.

    1981-06-01

    The as-built lattice of the Rapid Cycling Synchrotron (RCS) had two sets of correction sextupoles and two sets of quadrupoles energized by dc power supplies to control the tune and the tune tilt. With this method of powering these magnets, adjustment of tune conditions during the accelerating cycle as needed was not possible. A set of dynamically programmable power supplies has been built and operated to provide the required chromaticity adjustment. The short accelerating time (16.7 ms) of the RCS and the inductance of the magnets dictated large transistor amplifier power supplies. The required time resolution and waveform flexibility indicated the desirability of computer control. Both the amplifiers and controls are described, along with resulting improvements in the beam performance. 5 refs.

  6. Tune-control improvements on the rapid-cycling synchrotron

    SciTech Connect

    Potts, C.; Faber, M.; Gunderson, G.; Knott, M.; Voss, D.

    1981-01-01

    The as-built lattice of the Rapid-Cycling Synchrotron (RCS) had two sets of correction sextupoles and two sets of quadrupoles energized by dc power supplies to control the tune and the tune tilt. With this method of powering these magnets, adjustment of tune conditions during the accelerating cycle as needed was not possible. A set of dynamically programmable power supplies has been built and operated to provide the required chromaticity adjustment. The short accelerating time (16.7 ms) of the RCS and the inductance of the magnets dictated large transistor amplifier power supplies. The required time resolution and waveform flexibility indicated the desirability of computer control. Both the amplifiers and controls are described, along with resulting improvements in the beam performance. A set of octupole magnets and programmable power supplies with similar dynamic qualities have been constructed and installed to control the anticipated high-intensity transverse instability. This system will be operational in the spring of 1981.

  7. Ultrasharp ministop-band edge for subnanometer tuning resolution

    NASA Astrophysics Data System (ADS)

    Shahid, N.; Speijcken, N.; Naureen, S.; Li, M. Y.; Swillo, M.; Anand, S.

    2011-02-01

    We propose and demonstrate a method that enables spectral tuning with subnanometer accuracy, and is based on the transmission ministop-band (MSB) in line-defect multimode photonic crystal (PhC) waveguides. The fabricated MSB filter has ultrasharp edges which show a 30 dB drop in transmission in a 4 nm wavelength span. The use of the ultrasharp MSB edge to (optically) determine PhC fabrication accuracy is demonstrated. The wavelength position of the MSB could be tuned by temperature, with a coefficient of 0.1 nm/°C. The spectral characteristics of the MSB realized in this work are promising for sensing, tuning, and modulation applications.

  8. Multimodal tuned dynamic absorber for split Stirling linear cryocooler

    NASA Astrophysics Data System (ADS)

    Veprik, A.; Tuito, A.

    2017-02-01

    Forthcoming low size, weight, power and price split Stirling linear cryocoolers may rely on electro-dynamically driven single-piston compressors and pneumatically driven expanders interconnected by the configurable transfer line. For compactness, compressor and expander units may be placed in a side-by-side manner, thus producing tonal vibration export comprising force and moment components. In vibration sensitive applications, this may result in excessive angular line of sight jitter and translational defocusing affecting the image quality. The authors present Multimodal Tuned Dynamic Absorber (MTDA), having one translational and two tilting modes essentially tuned to the driving frequency. The dynamic reactions (force and moment) produced by such a MTDA are simultaneously counterbalancing force and moment vibration export produced by the cryocooler. The authors reveal the design details, the method of fine modal tuning and outcomes of numerical simulation on attainable performance.

  9. The Tevatron tune tracker pll - theory, implementation and measurements

    SciTech Connect

    Tan, Cheng-Yang; /Fermilab

    2004-12-01

    The Tevatron tune tracker is based on the idea that the transverse phase response of the beam can be measured quickly and accurately enough to allow us to track the betatron tune with a phase locked loop (PLL). The goal of this paper is to show the progress of the PLL project at Fermilab. We will divide this paper into three parts: theory, implementation and measurements. In the theory section, we will use a simple linear model to show that our design will track the betatron tune under conditions that occur in the Tevatron. In the implementation section we will break down and examine each part of the PLL and in some cases calculate the actual PLL parameters used in our system from beam measurements. And finally in the measurements section we will show the results of the PLL performance.

  10. Tuning and Robustness Analysis for the Orion Absolute Navigation System

    NASA Technical Reports Server (NTRS)

    Holt, Greg N.; Zanetti, Renato; D'Souza, Christopher

    2013-01-01

    The Orion Multi-Purpose Crew Vehicle (MPCV) is currently under development as NASA's next-generation spacecraft for exploration missions beyond Low Earth Orbit. The MPCV is set to perform an orbital test flight, termed Exploration Flight Test 1 (EFT-1), some time in late 2014. The navigation system for the Orion spacecraft is being designed in a Multi-Organizational Design Environment (MODE) team including contractor and NASA personnel. The system uses an Extended Kalman Filter to process measurements and determine the state. The design of the navigation system has undergone several iterations and modifications since its inception, and continues as a work-in-progress. This paper seeks to show the efforts made to-date in tuning the filter for the EFT-1 mission and instilling appropriate robustness into the system to meet the requirements of manned space ight. Filter performance is affected by many factors: data rates, sensor measurement errors, tuning, and others. This paper focuses mainly on the error characterization and tuning portion. Traditional efforts at tuning a navigation filter have centered around the observation/measurement noise and Gaussian process noise of the Extended Kalman Filter. While the Orion MODE team must certainly address those factors, the team is also looking at residual edit thresholds and measurement underweighting as tuning tools. Tuning analysis is presented with open loop Monte-Carlo simulation results showing statistical errors bounded by the 3-sigma filter uncertainty covariance. The Orion filter design uses 24 Exponentially Correlated Random Variable (ECRV) parameters to estimate the accel/gyro misalignment and nonorthogonality. By design, the time constant and noise terms of these ECRV parameters were set to manufacturer specifications and not used as tuning parameters. They are included in the filter as a more analytically correct method of modeling uncertainties than ad-hoc tuning of the process noise. Tuning is explored for the

  11. Tuning of linear ADRC with known plant information.

    PubMed

    Fu, Caifen; Tan, Wen

    2016-11-01

    Linear active disturbance rejection control (ADRC) is known for its simplicity and its performance in disturbance attenuation. Currently, tuning of linear ADRC (LADRC) is via the bandwidth idea. In this paper, tuning of LADRC with known plant information is investigated. It is shown that there are limitations using only two bandwidths to tune the LADRC controllers. To take advantage of the known plant information, a generalized ADRC (GADRC) method is proposed. Then the intrinsic link between the conventional LADRC and GADRC is analyzed. It is shown that the available plant model information used in GADRC can be utilized in the designs of the observer gain and the controller gain of the conventional LADRC. Simulation results demonstrate that with known plant information incorporated, the performance of a conventional LADRC can indeed be improved, especially for unstable, time-delayed and non-minimum phase processes.

  12. Design and robust tuning of control scheme based on the PD controller plus Disturbance Observer and low-order integrating first-order plus dead-time model.

    PubMed

    Matausek, M R; Ribić, A I

    2009-10-01

    This paper presents an effective design and robust tuning method for the control structure based on a series PD controller and a simple Disturbance Observer. All elements of the proposed controller are directly obtained from the low-order Integrating First-Order Plus Dead-Time (IFOPDT) model, used to approximate essential dynamic characteristics of lag-dominant stable, integrating and unstable plants. The structure of the proposed controller is an effective, easy to implement and tune, extension of the series PID controller. For the same robustness, a better disturbance rejection response is obtained by the proposed controller than that of the PID, by adjusting only two parameters with a clear meaning. A comparison with well-tuned PIDs, done by simulations, and the experimental results, obtained on a real thermal power plant, confirm that high performance and robustness are obtained, for dynamic characteristics common to industrial processes.

  13. Rolling-Element Bearings

    NASA Technical Reports Server (NTRS)

    Hamrock, B. J.; Anderson, W. J.

    1983-01-01

    Rolling element bearings are a precision, yet simple, machine element of great utility. A brief history of rolling element bearings is reviewed and the type of rolling element bearings, their geometry and kinematics, as well as the materials they are made from and the manufacturing processes they involve are described. Unloaded and unlubricated rolling element bearings, loaded but unlubricated rolling element bearings and loaded and lubricated rolling element bearings are considered. The recognition and understanding of elastohydrodynamic lubrication covered, represents one of the major development in rolling element bearings.

  14. Control System Design for Automatic Cavity Tuning Machines

    SciTech Connect

    Carcagno, R.; Khabiboulline, T.; Kotelnikov, S.; Makulski, A.; Nehring, R.; Nogiec, J.; Ross, M.; Schappert, W.; Goessel, A.; Iversen, J.; Klinke, D.; /DESY

    2009-05-01

    A series of four automatic tuning machines for 9-cell TESLA-type cavities are being developed and fabricated in a collaborative effort among DESY, FNAL, and KEK. These machines are intended to support high-throughput cavity fabrication for construction of large SRF-based accelerator projects. Two of these machines will be delivered to cavity vendors for the tuning of XFEL cavities. The control system for these machines must support a high level of automation adequate for industrial use by non-experts operators. This paper describes the control system hardware and software design for these machines.

  15. Parameter Tuning Patterns for Random Graph Coloring with Quantum Annealing

    PubMed Central

    Titiloye, Olawale; Crispin, Alan

    2012-01-01

    Quantum annealing is a combinatorial optimization technique inspired by quantum mechanics. Here we show that a spin model for the k-coloring of large dense random graphs can be field tuned so that its acceptance ratio diverges during Monte Carlo quantum annealing, until a ground state is reached. We also find that simulations exhibiting such a diverging acceptance ratio are generally more effective than those tuned to the more conventional pattern of a declining and/or stagnating acceptance ratio. This observation facilitates the discovery of solutions to several well-known benchmark k-coloring instances, some of which have been open for almost two decades. PMID:23166818

  16. Thermally tunable silicon racetrack resonators with ultralow tuning power.

    PubMed

    Dong, Po; Qian, Wei; Liang, Hong; Shafiiha, Roshanak; Feng, Dazeng; Li, Guoliang; Cunningham, John E; Krishnamoorthy, Ashok V; Asghari, Mehdi

    2010-09-13

    We present thermally tunable silicon racetrack resonators with an ultralow tuning power of 2.4 mW per free spectral range. The use of free-standing silicon racetrack resonators with undercut structures significantly enhances the tuning efficiency, with one order of magnitude improvement of that for previously demonstrated thermo-optic devices without undercuts. The 10%-90% switching time is demonstrated to be ~170 µs. Such low-power tunable micro-resonators are particularly useful as multiplexing devices and wavelength-tunable silicon microcavity modulators.

  17. Design of a LC-tuned magnetically suspended rotating gyroscope

    NASA Astrophysics Data System (ADS)

    Jin, Lichuan; Zhang, Huaiwu; Zhong, Zhiyong

    2011-04-01

    A inductor-capacitor (LC) tuned magnetically suspended rotating gyroscope prototype is designed and analyzed. High permeability ferrite cores are used for providing suspension force, and the rotation system is designed using the switched reluctance motor (SRM) principle. According to the LC-tuned principle, magnetic suspension force expression has been derived. The electromagnetic properties of the gyroscope are simulated by the Ansoft Maxwell software. And our result is expected to be able to serve as a prototype of micro-electromechanical system (MEMS) magnetically suspended rotating gyroscope in future practical applications.

  18. Collecting EUV mask images through focus by wavelength tuning

    SciTech Connect

    Goldberg, Kenneth A.; Mochi, Iacopo; Huh, Sungmin

    2009-02-23

    Using an extreme-ultraviolet (EUV) microscope to produce high-quality images of EUV reticles, we have developed a new wavelength tuning method to acquire through-focus data series with a higher level of stability and repeatability than was previously possible. We utilize the chromatic focal-length dependence of a diffractive Fresnel zoneplate objective lens, and while holding the mask sample mechanically still, we tune the wavelength through a narrow range, in small steps. In this paper, we demonstrate the method and discuss the relative advantages that this data collection technique affords.

  19. Piezoelectric-tuned microwave cavity for absorption spectrometry

    DOEpatents

    Leskovar, Branko; Buscher, Harold T.; Kolbe, William F.

    1978-01-01

    Gas samples are analyzed for pollutants in a microwave cavity that is provided with two highly polished walls. One wall of the cavity is mechanically driven with a piezoelectric transducer at a low frequency to tune the cavity over a band of microwave frequencies in synchronism with frequency modulated microwave energy applied to the cavity. Absorption of microwave energy over the tuned frequencies is detected, and energy absorption at a particular microwave frequency is an indication of a particular pollutant in the gas sample.

  20. Tune Evaluation From Phased BPM Turn-By-Turn Data

    SciTech Connect

    Alexahin, Y.; Gianfelice-Wendt, E.; Marsh, W.; /Fermilab

    2010-05-18

    In fast ramping synchrotrons like the Fermilab Booster the conventional methods of betatron tune evaluation from the turn-by-turn data may not work due to rapid changes of the tunes (sometimes in a course of a few dozens of turns) and a high level of noise. We propose a technique based on phasing of signals from a large number of BPMs which significantly increases the signal to noise ratio. Implementation of the method in the Fermilab Booster control system is described and some measurement results are presented.

  1. Tuning NaYF4 Nanoparticles through Alkaline Earth Doping

    PubMed Central

    Chen, Xian; Peng, Dengfeng; Wang, Feng

    2013-01-01

    Phase and size of lanthanide-doped nanoparticles are the most important characteristics that dictate optical properties of these nanoparticles and affect their technological applications. Herein, we present a systematic study to examine the effect of alkaline earth doping on the formation of NaYF4 upconversion nanoparticles. We show that alkaline earth doping has a dual function of tuning particle size of hexagonal phase NaYF4 nanoparticles and stabilizing cubic phase NaYF4 nanoparticles depending on composition and concentration of the dopant ions. The study described here represents a facile and general strategy to tuning the properties of NaYF4 upconversion nanoparticles. PMID:28348353

  2. Tm:germanate Fiber Laser: Tuning And Q-switching

    NASA Technical Reports Server (NTRS)

    Barnes, Norman P.; Walsh, Brian M.; Reichle, Donald J.; DeYoung, R. J.; Jiang, Shibin

    2007-01-01

    A Tm:germanate fiber laser produced >0.25 mJ/pulse in a 45 ns pulse. It is capable of producing multiple Q-switched pulses from a single p ump pulse. With the addition of a diffraction grating, Tm:germanate f iber lasers produced a wide, but length dependent, tuning range. By s electing the fiber length, the tuning range extends from 1.88 to 2.04 ?m. These traits make Tm:germanate lasers suitable for remote sensin g of water vapor.

  3. Optimally tuned resonant negative capacitance for piezoelectric shunt damping based on measured electromechanical impedance

    NASA Astrophysics Data System (ADS)

    Salloum, Rogério; Heuss, Oliver; Götz, Benedict; Mayer, Dirk

    2015-04-01

    In this paper, a new tuning method for shunt damping with a series resistance, inductance and negative capacitance is proposed and its validity is investigated. It is based on the measured electromechanical impedance of a piezoelectric system, which is represented through an equivalent electrical circuit that takes into account the characteristics of the piezoelectric transducer and the host structure. Afterwards, an additional circuit representing the shunt is connected and the Norton equivalent impedance is obtained at the terminals that represent the mechanical mode of interest. During the tuning process, the optimal shunt parameters are found by minimizing the maximum absolute value of the Norton equivalent impedance over a defined frequency range through a numerical optimization. Taking benefit from the analogy between electrical impedance and mechanical admittance, the minimization of different mechanical responses (displacement, velocity or acceleration) is also proposed and the different optimum shunt parameters obtained are compared. In view of real technical applications, this method allows the integration of a real negative capacitance circuit, i.e., a negative impedance converter, rather than an ideal component. It is thus possible to use the impedance of this circuit and optimize the individual component values. Since this method is based on one simple measurement, it can be applied to arbitrary structures without the need of complex dynamic tests or expensive finite elements calculations. Finally, an experimental analysis is carried out in order to compare the damping performance of the proposed method and the conventional analytical method that minimizes a mechanical frequency response function.

  4. Dynamical tuning between nearly perfect reflection, absorption, and transmission of light via graphene/dielectric structures

    PubMed Central

    Linder, Jacob; Halterman, Klaus

    2016-01-01

    Exerting well-defined control over the reflection (R), absorption (A), and transmission (T) of electromagnetic waves is a key objective in quantum optics. To this end, one often utilizes hybrid structures comprised of elements with different optical properties in order to achieve features such as high R or high A for incident light. A desirable goal would be the possibility to tune between all three regimes of nearly perfect reflection, absorption, and transmission within the same device, thus swapping between the cases R → 1, A → 1, and T → 1 dynamically. We here show that a dielectric interfaced with a graphene layer on each side allows for precisely this: by tuning only the Fermi level of graphene, all three regimes can be reached in the THz regime and below. Moreover, we show that the inclusion of cylindrical defects in the system offers a different type of control of the scattering of electromagnetic waves by means of the graphene layers. PMID:27917886

  5. Simplified Approach to Evaluation of Beam-Beam Tune Spread Compression by Electron Lens

    SciTech Connect

    Romanov, A.L.; Valishev, A.A.; Shiltsev, V.; /Fermilab

    2010-05-19

    One of the possible ways to increase luminosity of hadron colliders is the compensation of beam-beam tunespread with an electron lens (EL). At the same time, EL as an additional nonlinear element in the lattice can increase strength of nonlinear resonances so that its overall effect on the beam lifetime will be negative. Time-consuming numerical simulations are often used to study the effects of the EL. In this report we present a simplified model, which uses analytical formulae derived for certain electron beam profiles. Based on these equations the idealized shapes of the compressed tune spread can be rapidly calculated. Obtained footprints were benchmarked against several reference numerical simulations for the Tevatron in order to evaluate the selected configurations. One of the tested criteria was the so-called 'folding' of the compensated footprint, which occurs when particles with different betatron amplitudes have the same tune shift. Also studied were the effects of imperfections, including misalignment of the electron and proton beams, and mismatch of their shapes.

  6. Dynamical tuning between nearly perfect reflection, absorption, and transmission of light via graphene/dielectric structures.

    PubMed

    Linder, Jacob; Halterman, Klaus

    2016-12-05

    Exerting well-defined control over the reflection (R), absorption (A), and transmission (T) of electromagnetic waves is a key objective in quantum optics. To this end, one often utilizes hybrid structures comprised of elements with different optical properties in order to achieve features such as high R or high A for incident light. A desirable goal would be the possibility to tune between all three regimes of nearly perfect reflection, absorption, and transmission within the same device, thus swapping between the cases R → 1, A → 1, and T → 1 dynamically. We here show that a dielectric interfaced with a graphene layer on each side allows for precisely this: by tuning only the Fermi level of graphene, all three regimes can be reached in the THz regime and below. Moreover, we show that the inclusion of cylindrical defects in the system offers a different type of control of the scattering of electromagnetic waves by means of the graphene layers.

  7. Optimal placement of tuning masses for vibration reduction in helicopter rotor blades

    NASA Technical Reports Server (NTRS)

    Pritchard, Jocelyn I.; Adelman, Howard M.

    1988-01-01

    Described are methods for reducing vibration in helicopter rotor blades by determining optimum sizes and locations of tuning masses through formal mathematical optimization techniques. An optimization procedure is developed which employs the tuning masses and corresponding locations as design variables which are systematically changed to achieve low values of shear without a large mass penalty. The finite-element structural analysis of the blade and the optimization formulation require development of discretized expressions for two performance parameters: modal shaping parameter and modal shear amplitude. Matrix expressions for both quantities and their sensitivity derivatives are developed. Three optimization strategies are developed and tested. The first is based on minimizing the modal shaping parameter which indirectly reduces the modal shear amplitudes corresponding to each harmonic of airload. The second strategy reduces these amplitudes directly, and the third strategy reduces the shear as a function of time during a revolution of the blade. The first strategy works well for reducing the shear for one mode responding to a single harmonic of the airload, but has been found in some cases to be ineffective for more than one mode. The second and third strategies give similar results and show excellent reduction of the shear with a low mass penalty.

  8. Out-of-plane nanomechanical tuning of double-coupled one-dimensional photonic crystal cavities.

    PubMed

    Tian, Feng; Zhou, Guangya; Du, Yu; Chau, Fook Siong; Deng, Jie; Akkipeddi, Ramam

    2013-06-15

    We demonstrate tuning of double-coupled one-dimensional photonic crystal cavities by their out-of-plane nanomechanical deformations. The coupled cavities are pulled by the vertical electrostatic force generated by the potential difference between the device layer and the handle layer in a silicon-on-insulator chip, and the induced deformations are analyzed by the finite element method. Applied with a voltage of 12 V, the cavities obtain a redshift of 0.0405 nm (twice the linewidth) for their second-order odd resonance mode and a blueshift of 0.0635 nm (three times the linewidth) for their second-order even resonance mode, which are mainly attributed to out-of-plane relative displacement. Out-of-plane tuning of coupled cavities does not need actuators and corresponding circuits; thus the device is succinct and compact. This working principle can be potentially applied in chip-level optoelectronic devices, such as sensors, switches, routers, and tunable filters.

  9. Active noise control using noise source having adaptive resonant frequency tuning through variable ring loading

    NASA Technical Reports Server (NTRS)

    Pla, Frederic G. (Inventor); Rajiyah, Harindra (Inventor); Renshaw, Anthony A. (Inventor); Hedeen, Robert A. (Inventor)

    1995-01-01

    A noise source for an aircraft engine active noise cancellation system in which the resonant frequency of noise radiating structure is tuned to permit noise cancellation over a wide range of frequencies. The resonant frequency of the noise radiating structure is tuned by a plurality of drivers arranged to contact the noise radiating structure. Excitation of the drivers causes expansion or contraction of the drivers, thereby varying the edge loading applied to the noise radiating structure. The drivers are actuated by a controller which receives input of a feedback signal proportional to displacement of the noise radiating element and a signal corresponding to the blade passage frequency of the engine's fan. In response, the controller determines a control signal which is sent to the drivers, causing them to expand or contract. The noise radiating structure may be either the outer shroud of the engine or a ring mounted flush with an inner wall of the shroud or disposed in the interior of the shroud.

  10. Robust control for a biaxial servo with time delay system based on adaptive tuning technique.

    PubMed

    Chen, Tien-Chi; Yu, Chih-Hsien

    2009-07-01

    A robust control method for synchronizing a biaxial servo system motion is proposed in this paper. A new network based cross-coupled control and adaptive tuning techniques are used together to cancel out the skew error. The conventional fixed gain PID cross-coupled controller (CCC) is replaced with the adaptive cross-coupled controller (ACCC) in the proposed control scheme to maintain biaxial servo system synchronization motion. Adaptive-tuning PID (APID) position and velocity controllers provide the necessary control actions to maintain synchronization while following a variable command trajectory. A delay-time compensator (DTC) with an adaptive controller was augmented to set the time delay element, effectively moving it outside the closed loop, enhancing the stability of the robust controlled system. This scheme provides strong robustness with respect to uncertain dynamics and disturbances. The simulation and experimental results reveal that the proposed control structure adapts to a wide range of operating conditions and provides promising results under parameter variations and load changes.

  11. Discrete Element Modeling

    SciTech Connect

    Morris, J; Johnson, S

    2007-12-03

    The Distinct Element Method (also frequently referred to as the Discrete Element Method) (DEM) is a Lagrangian numerical technique where the computational domain consists of discrete solid elements which interact via compliant contacts. This can be contrasted with Finite Element Methods where the computational domain is assumed to represent a continuum (although many modern implementations of the FEM can accommodate some Distinct Element capabilities). Often the terms Discrete Element Method and Distinct Element Method are used interchangeably in the literature, although Cundall and Hart (1992) suggested that Discrete Element Methods should be a more inclusive term covering Distinct Element Methods, Displacement Discontinuity Analysis and Modal Methods. In this work, DEM specifically refers to the Distinct Element Method, where the discrete elements interact via compliant contacts, in contrast with Displacement Discontinuity Analysis where the contacts are rigid and all compliance is taken up by the adjacent intact material.

  12. Study of the Agglomeration of 5 to 25nm Gold Nanoparticles as a Function of Viscosity and Ionic Concentration

    NASA Astrophysics Data System (ADS)

    Stefankiewicz, Adam; Dobbins, Tabbetha

    2013-03-01

    Gold nanoparticles (AuNPs) attached to carcinoma cells and treated with light irradiation are able to convert the light into heat energy, thus killing those cells. In order to get the particles to the affected area, they may be entered into the circulatory system where the environment is highly viscous and comprised of high salt concentrations. This study examines the aggregation behavior of gold nanoparticles under those conditions. Surface charge creates coulombic repulsion between particles. Likewise, highly viscous solutions will prevent aggregation by limiting the rate of transport of gold through the solution. This study examines the aggregation behavior of gold nanopartilces as a function of viscosity (varied using polyethylene glycol). The study also examines the role of excess ions in the solution (varied using 5-Bromo-4-chloro-3-indolyl phosphate disodium salt). The aggregation phenomena was explored using dynamic light scattering for particle size analysis. Early results are presented here.

  13. TUNING SILICON NANORODS FOR ANODES OF LI-ION RECHARGEABLE BATTERIES

    SciTech Connect

    Au, M.

    2010-11-23

    Silicon is a promising anode material for Li-ion batteries in regarding of high capacity, low cost and safety, but it suffers poor cycling stability due to the pulverization induced by severe volume expansion/shrinkage (297%) during lithium insertion/extraction. In our previous investigation on aluminum nanorods anodes, it is found the selection of substrates in which Al nanorods grown plays the role in prevention of pulverization resulting in the increase of cycling life. Adapting this knowledge, we investigated the Si based nanorods anodes by tuning its composition and element distribution. Our results show that although the Si nanorods demonstrated higher initial anodic capacity of 1500 mAh/g, it diminished after 50 cycles due to morphology change and pulverization. By codepositing Cu, the Si-Cu composite nanorods demonstrated sustainable capacity of 500 mAh/g in 100 cycles attributing to its flexible and less brittle nature.

  14. Composition-tuning in a solid-state electrotransport furnace with active thermal expansion compensation.

    PubMed

    Schmehr, J L; Whitley, W; Huxley, A D

    2016-12-01

    A new solid-state electrotransport (SSE) apparatus for refining ultra-pure single crystals of metallic compounds under ultra-high vacuum is described. The setup employs a novel thermal expansion compensation mechanism to minimize mechanical stress on the sample during refinement with cold clamps for contamination-less purification at elevated temperatures. The apparatus is designed to tune the composition of initially slightly off-stoichiometric samples. The expansion compensation and stress-free operation were tested by recording the thermal expansion of elemental cerium in a treatment up to 655 °C. SSE refinement was then performed on a high-quality single crystal of U6Fe resulting in a 50% increase of its residual resistivity ratio to the highest value obtained for a single crystal to date.

  15. Composition-tuning in a solid-state electrotransport furnace with active thermal expansion compensation

    NASA Astrophysics Data System (ADS)

    Schmehr, J. L.; Whitley, W.; Huxley, A. D.

    2016-12-01

    A new solid-state electrotransport (SSE) apparatus for refining ultra-pure single crystals of metallic compounds under ultra-high vacuum is described. The setup employs a novel thermal expansion compensation mechanism to minimize mechanical stress on the sample during refinement with cold clamps for contamination-less purification at elevated temperatures. The apparatus is designed to tune the composition of initially slightly off-stoichiometric samples. The expansion compensation and stress-free operation were tested by recording the thermal expansion of elemental cerium in a treatment up to 655 °C. SSE refinement was then performed on a high-quality single crystal of U6Fe resulting in a 50% increase of its residual resistivity ratio to the highest value obtained for a single crystal to date.

  16. Eigenmodes of a quartz tuning fork and their application to photoinduced force microscopy

    NASA Astrophysics Data System (ADS)

    Kim, Bongsu; Jahng, Junghoon; Khan, Ryan Muhammad; Park, Sung; Potma, Eric O.

    2017-02-01

    We examine the mechanical eigenmodes of a quartz tuning fork (QTF) for the purpose of facilitating its use as a probe for multifrequency atomic force microscopy (AFM). We perform simulations based on the three-dimensional finite element method and compare the observed motions of the beams with experimentally measured resonance frequencies of two QTF systems. The comparison enabled us to assign the first seven asymmetric eigenmodes of the QTF. We also find that a modified version of single beam theory can be used to guide the assignment of mechanical eigenmodes of QTFs. The usefulness of the QTF for multifrequency AFM measurements is demonstrated through photoinduced force microscopy measurements. By using the QTF in different configurations, we show that the vectorial components of the photoinduced force can be independently assessed and that lateral forces can be probed in true noncontact mode.

  17. Tuning the Electronic Absorption of Protein-Embedded All-trans-Retinal

    SciTech Connect

    Wang, Wenjing; Nossoni, Zahra; Berbasova, Tetyana; Watson, Camille T.; Yapici, Ipek; Lee, Kin Sing Stephen; Vasileiou, Chrysoula; Geiger, James H.; Borhan, Babak

    2014-10-02

    Protein-chromophore interactions are a central component of a wide variety of critical biological processes such as color vision and photosynthesis. To understand the fundamental elements that contribute to spectral tuning of a chromophore inside the protein cavity, we redesigned human cellular retinol binding protein II (hCRBPII) to fully encapsulate all-trans-retinal and form a covalent bond as a protonated Schiff base. The system, using rational mutagenesis designed to alter the electrostatic environment within the binding pocket of the host protein, enabled regulation of the absorption maximum of the pigment in the range of 425 to 644 nanometers. Moreover, with only nine point mutations, the hCRBPII mutants induced a systematic shift in the absorption profile of all-trans-retinal of more than 200 nanometers across the visible spectrum.

  18. Tuning the local temperature during feedback controlled electromigration in gold nanowires

    SciTech Connect

    Xiang, An; Hou, Shimin Liao, Jianhui

    2014-06-02

    Feedback controlled electromigration (FCE) in metallic nanowires has been widely used for various purposes. However, the control of the local temperature during FCE remains a challenge. Here, we report that the environment temperature can be used as a knob to tune the local temperature during FCE in gold nanowires. FCE was performed in gold nanowires at various environment temperatures ranging from 4.2 K to 300 K. We find that the dissipated power normalized by the cross section area of the nano constriction is linearly proportional to the environment temperature. Interestingly, the estimated local maximum temperature parabolically depends on the environment temperature. A minimum in the local temperature can be reached if an appropriate environment temperature is chosen. Our findings are well supported by the finite element simulation. Moreover, the data indicates the coupling between FCE triggering current density and local temperature.

  19. Organic Elemental Analysis.

    ERIC Educational Resources Information Center

    Ma, T. S.; Wang, C. Y.

    1984-01-01

    Presents a literature review on methods used to analyze organic elements. Topic areas include methods for: (1) analyzing carbon, hydrogen, and nitrogen; (2) analyzing oxygen, sulfur, and halogens; (3) analyzing other elements; (4) simultaneously determining several elements; and (5) determing trace elements. (JN)

  20. Educational Tool for Optimal Controller Tuning Using Evolutionary Strategies

    ERIC Educational Resources Information Center

    Carmona Morales, D.; Jimenez-Hornero, J. E.; Vazquez, F.; Morilla, F.

    2012-01-01

    In this paper, an optimal tuning tool is presented for control structures based on multivariable proportional-integral-derivative (PID) control, using genetic algorithms as an alternative to traditional optimization algorithms. From an educational point of view, this tool provides students with the necessary means to consolidate their knowledge on…

  1. Perfect harmony: A mathematical analysis of four historical tunings

    NASA Astrophysics Data System (ADS)

    Page, Michael F.

    2004-10-01

    In Western music, a musical interval defined by the frequency ratio of two notes is generally considered consonant when the ratio is composed of small integers. Perfect harmony or an ``ideal just scale,'' which has no exact solution, would require the division of an octave into 12 notes, each of which would be used to create six other consonant intervals. The purpose of this study is to analyze four well-known historical tunings to evaluate how well each one approximates perfect harmony. The analysis consists of a general evaluation in which all consonant intervals are given equal weighting and a specific evaluation for three preludes from Bach's ``Well-Tempered Clavier,'' for which intervals are weighted in proportion to the duration of their occurrence. The four tunings, 5-limit just intonation, quarter-comma meantone temperament, well temperament (Werckmeister III), and equal temperament, are evaluated by measures of centrality, dispersion, distance, and dissonance. When all keys and consonant intervals are equally weighted, equal temperament demonstrates the strongest performance across a variety of measures, although it is not always the best tuning. Given C as the starting note for each tuning, equal temperament and well temperament perform strongly for the three ``Well-Tempered Clavier'' preludes examined. .

  2. Neuromagnetic evidence of broader auditory cortical tuning in schizophrenia

    PubMed Central

    Rojas, Donald C.; Slason, Erin; Teale, Peter D.; Reite, Martin L.

    2007-01-01

    Deficits in basic auditory perception have been described in schizophrenia. Previous electrophysiological imaging research has documented a structure-function disassociation in the auditory system and altered tonotopic mapping in schizophrenia. The present study examined auditory cortical tuning in patients with schizophrenia. Eighteen patients with schizophrenia and 15 comparison subjects were recorded in a magnetoencephalographic (MEG) experiment of auditory tuning. Auditory cortical tuning at 1 kHz was examined by delivering 1 kHz pure tones in conjunction with pure tones at 5 frequencies surrounding and including 1 kHz. Source reconstruction data were examined for evidence of frequency specificity for the M100 component. There was a significant broadening of tuning in the schizophrenia group evident for the source amplitude of the M100. The frequently reported reduction in anterior-posterior source asymmetry for individuals with schizophrenia was replicated in this experiment. No relationships between symptom severity ratings and MEG measures were observed. This finding suggests that the frequency specificity of the M100 auditory evoked field is disturbed in schizophrenia, and may help explain the relatively poor behavioral performance of schizophrenia patients on simple frequency discrimination tasks. PMID:17851045

  3. Integrating Cache Performance Modeling and Tuning Support in Parallelization Tools

    NASA Technical Reports Server (NTRS)

    Waheed, Abdul; Yan, Jerry; Saini, Subhash (Technical Monitor)

    1998-01-01

    With the resurgence of distributed shared memory (DSM) systems based on cache-coherent Non Uniform Memory Access (ccNUMA) architectures and increasing disparity between memory and processors speeds, data locality overheads are becoming the greatest bottlenecks in the way of realizing potential high performance of these systems. While parallelization tools and compilers facilitate the users in porting their sequential applications to a DSM system, a lot of time and effort is needed to tune the memory performance of these applications to achieve reasonable speedup. In this paper, we show that integrating cache performance modeling and tuning support within a parallelization environment can alleviate this problem. The Cache Performance Modeling and Prediction Tool (CPMP), employs trace-driven simulation techniques without the overhead of generating and managing detailed address traces. CPMP predicts the cache performance impact of source code level "what-if" modifications in a program to assist a user in the tuning process. CPMP is built on top of a customized version of the Computer Aided Parallelization Tools (CAPTools) environment. Finally, we demonstrate how CPMP can be applied to tune a real Computational Fluid Dynamics (CFD) application.

  4. Photo-tuning of highly selective wetting in inverse opals.

    PubMed

    Singleton, Thomas A; Burgess, Ian B; Nerger, Bryan A; Goulet-Hanssens, Alexis; Koay, Natalie; Barrett, Christopher J; Aizenberg, Joanna

    2014-03-07

    Crack-free inverse opals exhibit a sharply defined threshold wettability for infiltration that has enabled their use as colourimetric indicators for liquid identification. Here we demonstrate direct and continuous photo-tuning of this wetting threshold in inverse opals whose surfaces are functionalized with a polymer doped with azobenzene chromophores.

  5. Farm Tractor Tune-Up and Service Specifications.

    ERIC Educational Resources Information Center

    Bryant, J. G.; And Others

    Tune-up and service specifications for 10 major tractor manufacturers are presented in the handbook. In addition, the following tables are included: (1) spark plug heat-range comparisons, (2) freezing protection, (3) pressures for farm tractor tires, (4) use of calcium chloride for liquid weighting, (5) comparisons of American Petroleum Institute…

  6. Adaptive tuning functions arise from visual observation of past movement

    PubMed Central

    Howard, Ian S.; Franklin, David W.

    2016-01-01

    Visual observation of movement plays a key role in action. For example, tennis players have little time to react to the ball, but still need to prepare the appropriate stroke. Therefore, it might be useful to use visual information about the ball trajectory to recall a specific motor memory. Past visual observation of movement (as well as passive and active arm movement) affects the learning and recall of motor memories. Moreover, when passive or active, these past contextual movements exhibit generalization (or tuning) across movement directions. Here we extend this work, examining whether visual motion also exhibits similar generalization across movement directions and whether such generalization functions can explain patterns of interference. Both the adaptation movement and contextual movement exhibited generalization beyond the training direction, with the visual contextual motion exhibiting much broader tuning. A second experiment demonstrated that this pattern was consistent with the results of an interference experiment where opposing force fields were associated with two separate visual movements. Overall, our study shows that visual contextual motion exhibits much broader (and shallower) tuning functions than previously seen for either passive or active movements, demonstrating that the tuning characteristics of past motion are highly dependent on their sensory modality. PMID:27341163

  7. Tuning a fuzzy controller using quadratic response surfaces

    NASA Technical Reports Server (NTRS)

    Schott, Brian; Whalen, Thomas

    1992-01-01

    Response surface methodology, an alternative method to traditional tuning of a fuzzy controller, is described. An example based on a simulated inverted pendulum 'plant' shows that with (only) 15 trial runs, the controller can be calibrated using a quadratic form to approximate the response surface.

  8. Perfect harmony: a mathematical analysis of four historical tunings.

    PubMed

    Page, Michael F

    2004-10-01

    In Western music, a musical interval defined by the frequency ratio of two notes is generally considered consonant when the ratio is composed of small integers. Perfect harmony or an "ideal just scale," which has no exact solution, would require the division of an octave into 12 notes, each of which would be used to create six other consonant intervals. The purpose of this study is to analyze four well-known historical tunings to evaluate how well each one approximates perfect harmony. The analysis consists of a general evaluation in which all consonant intervals are given equal weighting and a specific evaluation for three preludes from Bach's "Well-Tempered Clavier," for which intervals are weighted in proportion to the duration of their occurrence. The four tunings, 5-limit just intonation, quarter-comma meantone temperament, well temperament (Werckmeister III), and equal temperament, are evaluated by measures of centrality, dispersion, distance, and dissonance. When all keys and consonant intervals are equally weighted, equal temperament demonstrates the strongest performance across a variety of measures, although it is not always the best tuning. Given C as the starting note for each tuning, equal temperament and well temperament perform strongly for the three "Well-Tempered Clavier" preludes examined.

  9. Recognizing and naming tunes: memory impairment in the elderly.

    PubMed

    Maylor, E A

    1991-09-01

    Subjects over the age of 50 listened to theme tunes of remote, recent, and frequent television programs. If they recognized the tune, they were asked for the name of the program and for as much information about the program as possible. From the responses to a subsequent questionnaire, it was possible to divide the data according to whether or not the subjects watched the programs. There was no effect of age on the recognition and naming of programs subjects never watched. For programs they watched (a true test of memory), older subjects recognized fewer tunes as familiar and were less able than younger subjects to name the programs with familiar tunes. Neither the amount of exposure nor the delay since exposure had a significant influence on the recognition and naming impairments with age. Older subjects reported less information about programs they watched than younger subjects. In multiple regression analyses, age was a better predictor of performance than measures of current cognitive ability. The results are compared with the effects of age on the recognition and naming of famous faces (Maylor, 1990a). It is argued that the studies together support the view that the information processing rate decreases with age; therefore the elderly are poor at speeded tasks, the most dramatic effects appearing for later components of sequential processes.

  10. Automatic tuning of flexible interventional RF receiver coils.

    PubMed

    Venook, Ross D; Hargreaves, Brian A; Gold, Garry E; Conolly, Steven M; Scott, Greig C

    2005-10-01

    Microcontroller-based circuitry was built and tested for automatically tuning flexible RF receiver coils at the touch of a button. This circuitry is robust to 10% changes in probe center frequency, is in line with the scanner, and requires less than 1 s to tune a simple probe. Images were acquired using this circuitry with a varactor-tunable 1-inch flexible probe in a phantom and in an in vitro porcine knee model. The phantom experiments support the use of automatic tuning by demonstrating 30% signal-to-noise ratio (SNR) losses for 5% changes in coil center frequency, in agreement with theoretical calculations. Comparisons between patellofemoral cartilage images obtained using a 3-inch surface coil and the surgically-implanted 1-inch flexible coil reveal a worst-case local SNR advantage of a factor of 4 for the smaller coil. This work confirms that surgically implanted coils can greatly improve resolution in small-field-of-view (FOV) applications, and demonstrates the importance and feasibility of automatically tuning such probes.

  11. Methodologies and Tools for Tuning Parallel Programs: Facts and Fantasies

    NASA Technical Reports Server (NTRS)

    Yan, Jerry C.; Lum, Henry, Jr. (Technical Monitor)

    1994-01-01

    The need for computing power has forced a migration from serial computation on a single processor to parallel processing on multiprocessors. However, without effective means to monitor (and analyze) program execution, tuning the performance of parallel programs becomes exponentially difficult as program complexity and machine size increase. The recent introduction of performance tuning tools from various supercomputer vendors (Intel's ParAide, TMC's PRISM, CRI's Apprentice, and Convex's CXtrace) seems to indicate the maturity of performance tool technologies and vendors'/customers' recognition of their importance. However, a few important questions remain: What kind of performance bottlenecks can these tools detect (or correct)? How time consuming is the performance tuning process? What are some important technical issues that remain to be tackled in this area? This workshop reviews the fundamental concepts involved in analyzing and improving the performance of parallel and heterogeneous message-passing programs. Several alternative strategies will be contrasted, and for each we will describe how currently available tuning tools (e.g. AIMS, ParAide, PRISM, Apprentice, CXtrace, ATExpert, Pablo, IPS-2) can be used to facilitate the process. We will characterize the effectiveness of the tools and methodologies based on actual user experiences at NASA Ames Research Center. Finally, we will discuss their limitations and outline recent approaches taken by vendors and the research community to address them.

  12. Tuned passive control of combustion instabilities using multiple Helmholtz resonators

    NASA Astrophysics Data System (ADS)

    Zhao, Dan; Morgans, A. S.

    2009-03-01

    In this work, tuned passive control is used to damp unstable combustion systems, with particular emphasis on systems which exhibit multiple unstable modes. Helmholtz resonators are used as passive dampers. The frequency at which they offer maximum damping is varied by altering their geometry; in this work, geometry changes are achieved by varying the area of the Helmholtz resonator neck. For each unstable mode exhibited by the combustion system, a separate Helmholtz resonator has its neck area tuned. Two algorithms are developed, one for identifying the characteristics of all modes present in real time, and another for tuning the neck areas of the Helmholtz resonators. These algorithms are successfully implemented in numerical simulations of a longitudinal combustor exhibiting two unstable modes. The algorithms result in both modes being stabilised as long as two Helmholtz resonators are used. Experiments are then conducted on a Rijke tube with its upper part split into two branches of differing lengths, shaped like a 'Y'. The differing lengths give rise to two unstable modes at different frequencies. A Helmholtz resonator is attached to each branch; the neck area of both can be varied by means of an 'iris' valve, which opens and closes like a camera lens. On implementing the procedure for tuning the neck areas, both unstable modes are stabilised, and stability is maintained for large changes in operating condition. This confirms that the procedure developed is sufficiently robust for use in real combustion systems exhibiting multiple unstable modes.

  13. Tribotronic Tuning Diode for Active Analog Signal Modulation.

    PubMed

    Zhou, Tao; Yang, Zhi Wei; Pang, Yaokun; Xu, Liang; Zhang, Chi; Wang, Zhong Lin

    2017-01-24

    Realizing active interaction with external environment/stimuli is a great challenge for current electronics. In this paper, a tribotronic tuning diode (TTD) is proposed by coupling a variable capacitance diode and a triboelectric nanogenerator in free-standing sliding mode. When the friction layer is sliding on the device surface for electrification, a reverse bias voltage is created and applied to the diode for tuning the junction capacitance. When the sliding distance increases from 0 to 25 mm, the capacitance of the TTD decreases from about 39 to 8 pF. The proposed TTD has been integrated into analog circuits and exhibited excellent performances in frequency modulation, phase shift, and filtering by sliding a finger. This work has demonstrated tunable diode and active analog signal modulation by tribotronics, which has great potential to replace ordinary variable capacitance diodes in various practical applications such as signal processing, electronic tuning circuits, precise tuning circuits, active sensor networks, electronic communications, remote controls, flexible electronics, etc.

  14. NEW APPROACHES: Speed of sound in tuning fork metal

    NASA Astrophysics Data System (ADS)

    Narayanan, V. Anantha; Narayanan, Radha

    1996-11-01

    A procedure to find the speed of sound in tuning fork metal is described. The formula needed is extracted from the literature and explained. Since the equipment needed for this project is readily available in most high school and introductory level college science laboratories, this exercise can be done without any additional cost.

  15. A "Tuned" Mask Learnt Approach Based on Gravitational Search Algorithm.

    PubMed

    Wan, Youchuan; Wang, Mingwei; Ye, Zhiwei; Lai, Xudong

    2016-01-01

    Texture image classification is an important topic in many applications in machine vision and image analysis. Texture feature extracted from the original texture image by using "Tuned" mask is one of the simplest and most effective methods. However, hill climbing based training methods could not acquire the satisfying mask at a time; on the other hand, some commonly used evolutionary algorithms like genetic algorithm (GA) and particle swarm optimization (PSO) easily fall into the local optimum. A novel approach for texture image classification exemplified with recognition of residential area is detailed in the paper. In the proposed approach, "Tuned" mask is viewed as a constrained optimization problem and the optimal "Tuned" mask is acquired by maximizing the texture energy via a newly proposed gravitational search algorithm (GSA). The optimal "Tuned" mask is achieved through the convergence of GSA. The proposed approach has been, respectively, tested on some public texture and remote sensing images. The results are then compared with that of GA, PSO, honey-bee mating optimization (HBMO), and artificial immune algorithm (AIA). Moreover, feature extracted by Gabor wavelet is also utilized to make a further comparison. Experimental results show that the proposed method is robust and adaptive and exhibits better performance than other methods involved in the paper in terms of fitness value and classification accuracy.

  16. Taming parallel I/O complexity with auto-tuning

    DOE PAGES

    Behzad, Babak; Luu, Huong Vu Thanh; Huchette, Joseph; ...

    2013-11-17

    We present an auto-tuning system for optimizing I/O performance of HDF5 applications and demonstrate its value across platforms, applications, and at scale. The system uses a genetic algorithm to search a large space of tunable parameters and to identify effective settings at all layers of the parallel I/O stack. The parameter settings are applied transparently by the auto-tuning system via dynamically intercepted HDF5 calls. To validate our auto-tuning system, we applied it to three I/O benchmarks (VPIC, VORPAL, and GCRM) that replicate the I/O activity of their respective applications. We tested the system with different weak-scaling configurations (128, 2048, andmore » 4096 CPU cores) that generate 30 GB to 1 TB of data, and executed these configurations on diverse HPC platforms (Cray XE6, IBM BG/P, and Dell Cluster). In all cases, the auto-tuning framework identified tunable parameters that substantially improved write performance over default system settings. In conclusion, we consistently demonstrate I/O write speedups between 2x and 100x for test configurations.« less

  17. Parameter tuning of PVD process based on artificial intelligence technique

    NASA Astrophysics Data System (ADS)

    Norlina, M. S.; Diyana, M. S. Nor; Mazidah, P.; Rusop, M.

    2016-07-01

    In this study, an artificial intelligence technique is proposed to be implemented in the parameter tuning of a PVD process. Due to its previous adaptation in similar optimization problems, genetic algorithm (GA) is selected to optimize the parameter tuning of the RF magnetron sputtering process. The most optimized parameter combination obtained from GA's optimization result is expected to produce the desirable zinc oxide (ZnO) thin film from the sputtering process. The parameters involved in this study were RF power, deposition time and substrate temperature. The algorithm was tested to optimize the 25 datasets of parameter combinations. The results from the computational experiment were then compared with the actual result from the laboratory experiment. Based on the comparison, GA had shown that the algorithm was reliable to optimize the parameter combination before the parameter tuning could be done to the RF magnetron sputtering machine. In order to verify the result of GA, the algorithm was also been compared to other well known optimization algorithms, which were, particle swarm optimization (PSO) and gravitational search algorithm (GSA). The results had shown that GA was reliable in solving this RF magnetron sputtering process parameter tuning problem. GA had shown better accuracy in the optimization based on the fitness evaluation.

  18. Tuning Up Your Class: Using Assessment for Optimal Student Performance.

    ERIC Educational Resources Information Center

    Duffy, Donna Killian; Duffy, John J.; Jones, Janet Wright

    1997-01-01

    Describes a schedule for college classroom "preventive maintenance" that focuses on four classroom components: classroom community; students; course content; and faculty. A checklist allows assessment of these components during specific time periods in the semester, and a tune-up kit that includes diagnostic questions, sources of relevant…

  19. Taming parallel I/O complexity with auto-tuning

    SciTech Connect

    Behzad, Babak; Luu, Huong Vu Thanh; Huchette, Joseph; Byna, Surendra; Prabhat, -; Aydt, Ruth; Koziol, Quincey; Snir, Marc

    2013-11-17

    We present an auto-tuning system for optimizing I/O performance of HDF5 applications and demonstrate its value across platforms, applications, and at scale. The system uses a genetic algorithm to search a large space of tunable parameters and to identify effective settings at all layers of the parallel I/O stack. The parameter settings are applied transparently by the auto-tuning system via dynamically intercepted HDF5 calls. To validate our auto-tuning system, we applied it to three I/O benchmarks (VPIC, VORPAL, and GCRM) that replicate the I/O activity of their respective applications. We tested the system with different weak-scaling configurations (128, 2048, and 4096 CPU cores) that generate 30 GB to 1 TB of data, and executed these configurations on diverse HPC platforms (Cray XE6, IBM BG/P, and Dell Cluster). In all cases, the auto-tuning framework identified tunable parameters that substantially improved write performance over default system settings. In conclusion, we consistently demonstrate I/O write speedups between 2x and 100x for test configurations.

  20. Tuning the deposition of molecular graphene nanoribbons by surface functionalization

    NASA Astrophysics Data System (ADS)

    Konnerth, R.; Cervetti, C.; Narita, A.; Feng, X.; Müllen, K.; Hoyer, A.; Burghard, M.; Kern, K.; Dressel, M.; Bogani, L.

    2015-07-01

    We show that individual, isolated graphene nanoribbons, created with a molecular synthetic approach, can be assembled on functionalised wafer surfaces treated with silanes. The use of surface groups with different hydrophobicities allows tuning the density of the ribbons and assessing the products of the polymerisation process.

  1. Spatially selective optical tuning of quantum dot thin film luminescence.

    PubMed

    Chen, Jixin; Chan, Yang-Hsiang; Yang, Tinglu; Wark, Stacey E; Son, Dong Hee; Batteas, James D

    2009-12-30

    Photolithographically generated patterns have been created on immobilized CdSe QD thin films by fine-tuning their optical properties (intensity and emission wavelength) postsynthetically. These optically modified QDs show enhanced selectivity for binding of different ligands, affording the ability to fabricate optically reconfigurable surfaces for display or sensing applications. The patterns may be readily generated with any typical optical lithographic approach.

  2. Broadband and tuned signal recycling with a simple michelson interferometer.

    PubMed

    Gray, M B; Stevenson, A J; Bachor, H A; McClelland, D E

    1998-09-01

    We present experimental data on the frequency response of both broadband and tuned signal recycling with a benchtop Michelson interferometer. These data are in excellent agreement with our simple theoretical model. We use in-line modulation to give a control system that provides a high degree of orthogonality between the two servo loops.

  3. The Doctoral Comprehensive Examination: Fine-Tuning the Process.

    ERIC Educational Resources Information Center

    Loughead, Teri Olisky

    1997-01-01

    Uses Bloom's Taxonomy of Educational Objectives to fine-tune the process of designing, preparing for, evaluating, and providing feedback about the doctoral comprehensive examination. Examines the purpose and objectives of comprehensive examinations, curriculum design, preparation for the exam, test item development, evaluation criteria, and…

  4. Semi-active tuned mass dampers with phase control

    NASA Astrophysics Data System (ADS)

    Chung, Lap-Loi; Lai, Yong-An; Walter Yang, Chuang-Sheng; Lien, Kuan-Hua; Wu, Lai-Yun

    2013-07-01

    The present study aims at proposing an innovative phase control methodology for semi-active tuned mass dampers (SA-TMDs) that intend to minimize the off-tuned problems associated with passive tuned mass dampers (P-TMDs). The phase control algorithm is first developed, the essential of which is to apply the variable friction force to slow down the mass block at specific moments when the phase lag of the SA-TMD with respect to the structure is different from 90°, resulting in the SA-TMD back to the desired phase lag, i.e., -90° phase deviation, so that the SA-TMD has the maximum power flow to reduce the structural vibration. The feasibility of the application of the phase control in SA-TMDs is verified by performing numerical analyses of a simplified Taipei 101 structure model with a SA-TMD subjected to sinusoidal loads and design level wind loads. The numerical simulation results show that the SA-TMD implemented with phase control can enable the mass block to vibrate in a manner with a phase lag close to the -90° when the structure model is under sinusoidal excitations with frequencies different from the structural fundamental mode. The SA-TMD with phase control not only exhibits better performance than the optimal P-TMD in terms of suppressing the structural vibration, but also enhances its robustness, particularly when the SA-TMD is off-tuned to the structure.

  5. Dynamic response of structure with tuned mass friction damper

    NASA Astrophysics Data System (ADS)

    Pisal, Alka Y.; Jangid, R. S.

    2016-12-01

    The effectiveness of tuned mass friction damper (TMFD) in suppressing the dynamic response of the structure is investigated. The TMFD is a damper which consists of a tuned mass damper (TMD) with linear stiffness and pure friction damper and exhibits non-linear behavior. The response of the single-degree-of-freedom (SDOF) structure with TMFD is investigated under harmonic and seismic ground excitations. The governing equations of motion of the system are derived. The response of the system is obtained by solving the equations of motion, numerically using the state-space method. A parametric study is also conducted to investigate the effects of important parameters such as mass ratio, tuning frequency ratio and slip force on the performance of TMFD. The response of system with TMFD is compared with the response of the system without TMFD. It was found that at a given level of excitation, an optimum value of mass ratio, tuning frequency ratio and damper slip force exist at which the peak displacement of primary structure attains its minimum value. It is also observed that, if the slip force of the damper is appropriately selected, the TMFD can be a more effective and potential device to control undesirable response of the system.

  6. HEURISTIC OPTIMIZATION AND ALGORITHM TUNING APPLIED TO SORPTIVE BARRIER DESIGN

    EPA Science Inventory

    While heuristic optimization is applied in environmental applications, ad-hoc algorithm configuration is typical. We use a multi-layer sorptive barrier design problem as a benchmark for an algorithm-tuning procedure, as applied to three heuristics (genetic algorithms, simulated ...

  7. Human face processing is tuned to sexual age preferences

    PubMed Central

    Ponseti, J.; Granert, O.; van Eimeren, T.; Jansen, O.; Wolff, S.; Beier, K.; Deuschl, G.; Bosinski, H.; Siebner, H.

    2014-01-01

    Human faces can motivate nurturing behaviour or sexual behaviour when adults see a child or an adult face, respectively. This suggests that face processing is tuned to detecting age cues of sexual maturity to stimulate the appropriate reproductive behaviour: either caretaking or mating. In paedophilia, sexual attraction is directed to sexually immature children. Therefore, we hypothesized that brain networks that normally are tuned to mature faces of the preferred gender show an abnormal tuning to sexual immature faces in paedophilia. Here, we use functional magnetic resonance imaging (fMRI) to test directly for the existence of a network which is tuned to face cues of sexual maturity. During fMRI, participants sexually attracted to either adults or children were exposed to various face images. In individuals attracted to adults, adult faces activated several brain regions significantly more than child faces. These brain regions comprised areas known to be implicated in face processing, and sexual processing, including occipital areas, the ventrolateral prefrontal cortex and, subcortically, the putamen and nucleus caudatus. The same regions were activated in paedophiles, but with a reversed preferential response pattern. PMID:24850896

  8. Tune Up to Literacy: Original Songs and Activities for Kids

    ERIC Educational Resources Information Center

    Balkin, Al

    2009-01-01

    Encourage literacy with twenty original songs by musician and educator Al Balkin! Children's and school librarians will welcome "Tune Up to Literacy", a handy package of music and activities that musically introduces and reinforces crucial literacy concepts such as the alphabet, vowels, consonants, nouns, verbs, adjectives, sentence construction,…

  9. Tuning ground states and excitations in complex electronic materials

    SciTech Connect

    Bishop, A.R.

    1996-09-01

    Modern electronic materials are characterized by a great variety of broken-symmetry ground states and excitations. Their control requires understanding and tuning underlying driving forces of spin-charge-lattice coupling, critical to macroscopic properties and applications. We report representative model calculations which demonstrate some of the richness of the phenomena and the challenges for successful microscopic modeling.

  10. Hair Cells: Bundles, Tuning, Transduction—A Moderated Discussion

    NASA Astrophysics Data System (ADS)

    Karavitaki, K. Domenica; Ricci, Anthony J.

    2011-11-01

    A discussion moderated by the authors on the topic "Hair Cells: Bundles, Tuning, Transduction" was held on 17 July 2011 at the 11th International Mechanics of Hearing Workshop in Williamstown, Massachusetts. The paper provides an edited transcript of the session.

  11. PID tuning: It`s the method, not the rules

    SciTech Connect

    St. Clair, D.W.; Fruehauf, P.S.

    1994-12-01

    Many authors have written rules for tuning controllers, providing formulas for PID settings based on the results of perturbing the process. This article is not one of those. Instead, the authors approach the subject from the other direction - focusing on the mechanics of just how you go about perturbing the process to get the numbers to use in the formulas. The basic principle of tuning is to set the time and amount parameters of the controller to fit the time and amount parameters (called dynamics) of the process. Tuning procedures show certain dynamic characteristics of the process. When tuning, it`s generally necessary to upset the process. While sophisticated, computer-based ways to learn process dynamics exist, there are two simple time-honored ways: automatic (closed-loop) and manual (open-loop). The key is to upset the process just enough to get the information you need, without getting into trouble. Before tuning a controller, you should have an idea of how fast and how far the process is going to respond to the controller output. You should know and agree on how much change you will allow in the process and in the controller output. You also should know and agree on who is going to do the actual adjusting of the controller settings, and be assured the person know how to do it. You should know, and agree on who is going to switch between manual, and automatic, and who is going to make set point or output changes. You will also need to understand the safety interlocks and any other safety concerns for the process. Record the existing settings and the controller output, in the event you want to return to them. Make sure changes are communicated to all operating people. If a log book is kept for this purpose, use it. 5 figs.

  12. The Fine-Tuning of the Universe for Intelligent Life

    NASA Astrophysics Data System (ADS)

    Barnes, L. A.

    2012-06-01

    The fine-tuning of the universe for intelligent life has received a great deal of attention in recent years, both in the philosophical and scientific literature. The claim is that in the space of possible physical laws, parameters and initial conditions, the set that permits the evolution of intelligent life is very small. I present here a review of the scientific literature, outlining cases of fine-tuning in the classic works of Carter, Carr and Rees, and Barrow and Tipler, as well as more recent work. To sharpen the discussion, the role of the antagonist will be played by Victor Stenger's recent book The Fallacy of Fine-Tuning: Why the Universe is Not Designed for Us. Stenger claims that all known fine-tuning cases can be explained without the need for a multiverse. Many of Stenger's claims will be found to be highly problematic. We will touch on such issues as the logical necessity of the laws of nature; objectivity, invariance and symmetry; theoretical physics and possible universes; entropy in cosmology; cosmic inflation and initial conditions; galaxy formation; the cosmological constant; stars and their formation; the properties of elementary particles and their effect on chemistry and the macroscopic world; the origin of mass; grand unified theories; and the dimensionality of space and time. I also provide an assessment of the multiverse, noting the significant challenges that it must face. I do not attempt to defend any conclusion based on the fine-tuning of the universe for intelligent life. This paper can be viewed as a critique of Stenger's book, or read independently.

  13. Why Cosmic Fine-Tuning Needs to BE Explained

    NASA Astrophysics Data System (ADS)

    Manson, Neil Alan

    Discoveries in modern physics and Big Bang cosmology indicate that if either the initial conditions of the universe or the physical laws governing its development had differed even slightly, life could never have developed. It is for this reason that the universe is said to be ``fine-tuned'' for life. I argue that cosmic fine-tuning, which some want to dismiss as the way things just happen to be, in fact needs to be explained. In Chapter One I provide an overview of the evidence that the universe is fine-tuned for life. In Chapter Two I present a set of sufficient conditions for a fact's needing to be explained. The conditions are that the fact is improbable and that a ``tidy'' explanation of it is available. A tidy explanation of a fact is considerably less improbable than that fact and makes the obtaining of that fact considerably less improbable. Chapters Three, Four, and Five are devoted to showing that cosmic Chapter Three I argue that the universe's being finely tuned for life can meaningfully be considered improbable. In Chapter Four I claim that there is at least one tidy explanation of cosmic fine-tuning: that the universe was created by some sort of extramundane designer. In Chapters Four and Five I respond to three objections. The first is that the design hypothesis is ad hoc. The second is that we have no reason to believe a supernatural designer would prefer life-permitting cosmoi to other possible cosmoi and that our tendency to believe otherwise is the result of anthropocentrism. The third is that the design hypothesis never buys us an explanatory advantage.

  14. Tuning photoluminescence and surface properties of carbon nanodots for chemical sensing

    NASA Astrophysics Data System (ADS)

    Zhang, Zhaomin; Pan, Yi; Fang, Yaning; Zhang, Lulu; Chen, Junying; Yi, Changqing

    2015-12-01

    Obtaining tunable photoluminescence (PL) with improved emission properties is crucial for successfully implementing fluorescent carbon nanodots (fCDs) in all practical applications such as multicolour imaging and multiplexed detection by a single excitation wavelength. In this study, we report a facile hydrothermal approach to adjust the PL peaks of fCDs from blue, green to orange by controlling the surface passivation reaction during the synthesis. This is achieved by tuning the passivating reagents in a step-by-step manner. The as-prepared fCDs with narrow size distribution show improved PL properties with different emission wavelengths. Detailed characterization of fCDs using elemental analysis, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy suggested that the surface chemical composition results in this tunable PL emission. Surface passivation significantly alters the surface status, resulting in fCDs with either stronger surface oxidation or N element doping that ultimately determine their PL properties. Further experiments suggested that the as-prepared orange luminescent fCDs (O-fCDs) were sensitive and specific nanosensing platforms towards Fe3+ determination in a complex biological environment, emphasizing their potential practical applications in clinical and biological fields.Obtaining tunable photoluminescence (PL) with improved emission properties is crucial for successfully implementing fluorescent carbon nanodots (fCDs) in all practical applications such as multicolour imaging and multiplexed detection by a single excitation wavelength. In this study, we report a facile hydrothermal approach to adjust the PL peaks of fCDs from blue, green to orange by controlling the surface passivation reaction during the synthesis. This is achieved by tuning the passivating reagents in a step-by-step manner. The as-prepared fCDs with narrow size distribution show improved PL properties with different emission wavelengths. Detailed

  15. 40 CFR 63.10006 - When must I conduct subsequent performance tests or tune-ups?

    Code of Federal Regulations, 2014 CFR

    2014-07-01

    ... optimization during normal operation, each performance tune-up specified in § 63.10021(e) must be no more than... combustion optimization systems during normal operation, each performance tune-up specified in §...

  16. Stopping the growth of particles to silica-supported mono-nuclear Ru hydride surface species by tuning silica with surface silanes

    SciTech Connect

    Berthoud, Romain; Fenet, Bernard; Lukens, Wayne; Pelzer, Katrin; Basset, Jean-Marie; Candy, Jean-Pierre; Coperet, Christophe

    2007-07-11

    Tuning silica by replacing surface silanols with silanes allows chemical grafting of Ru(COD)(COT) through a covalent Ru-Si bond, as evidenced by elemental analysis, IR spectroscopy and EXAFS. Treatment of these surface species under H2 at 300 oC yields a mononuclear Ru hydride species, without any sintering of the metal according to TEM and EXAFS analyses. This supported system displays catalytic properties different from those of supported Ru particles (2 nm), selectively hydrogenating olefins over aromatics.

  17. Tuning of MEMS Devices using Evolutionary Computation and Open-loop Frequency Response

    NASA Technical Reports Server (NTRS)

    Keymeulen, Didier; Fink, Wolfgang; Ferguson, Michael I.; Peay, Chris; Oks, Boris; Terrile, Richard; Yee, Karl

    2005-01-01

    We propose a tuning method for MEMS gyroscopes based on evolutionary computation that has the capacity to efficiently increase the sensitivity of MEMS gyroscopes through tuning and, furthermore, to find the optimally tuned configuration for this state of increased sensitivity. The tuning method was tested for the second generation JPL/Boeing Post-resonator MEMS gyroscope using the measurement of the frequency response of the MEMS device in open-loop operation.

  18. Trace Elements and Health

    ERIC Educational Resources Information Center

    Pettyjohn, Wayne A.

    1972-01-01

    Summarizes the effects of arsenic, lead, zinc, mercury, and cadmium on human health, indicates the sources of the elements in water, and considers the possibility of students in high schools analyzing water for trace amounts of the elements. (AL)

  19. Element-ary Development.

    ERIC Educational Resources Information Center

    Schamp, Homer W., Jr.

    1989-01-01

    Describes the historic development of the periodic table from the four-element theory to the Lavoisier's table. Presents a table listing the old and new names of chemicals and the Lavoisier's table of elements. Lists two references. (YP)

  20. Nickel Based Electrospun Materials with Tuned Morphology and Composition

    PubMed Central

    Ercolano, Giorgio; Farina, Filippo; Cavaliere, Sara; Jones, Deborah J.; Rozière, Jacques

    2016-01-01

    Nickel is set to play a crucial role to substitute the less-abundant platinum in clean electrochemical energy conversion and storage devices and catalysis. The controlled design of Ni nanomaterials is essential to fine-tune their properties to match these applications. A systematic study of electrospinning and thermal post-treatment parameters has been performed to synthesize Ni materials and tune their morphology (fibers, ribbons, and sponge-like structures) and composition (metallic Ni, NiO, Ni/C, Ni3N and their combinations). The obtained Ni-based spun materials have been characterized by scanning and transmission electron microscopy, X-ray diffraction and thermogravimetric analysis. The possibility of upscaling and the versatility of electrospinning open the way to large-scale production of Ni nanostructures, as well as bi- and multi-metal systems for widened applications. PMID:28335364

  1. Nanoionic devices: Interface nanoarchitechtonics for physical property tuning and enhancement

    NASA Astrophysics Data System (ADS)

    Tsuchiya, Takashi; Terabe, Kazuya; Yang, Rui; Aono, Masakazu

    2016-11-01

    Nanoionic devices have been developed to generate novel functions overcoming limitations of conventional materials synthesis and semiconductor technology. Various physical properties can be tuned and enhanced by local ion transport near the solid/solid interface. Two electronic carrier doping methods can be used to achieve extremely high-density electronic carriers: one is electrostatic carrier doping using an electric double layer (EDL); the other is electrochemical carrier doping using a redox reaction. Atomistic restructuring near the solid/solid interface driven by a DC voltage, namely, interface nanoarchitechtonics, has huge potential. For instance, the use of EDL enables high-density carrier doping in potential superconductors, which can hardly accept chemical doping, in order to achieve room-temperature superconductivity. Optical bandgap and photoluminescence can be controlled for various applications including smart windows and biosensors. In situ tuning of magnetic properties is promising for low-power-consumption spintronics. Synaptic plasticity in the human brain is achieved in neuromorphic devices.

  2. Cosmologically Safe QCD Axion without Fine-Tuning.

    PubMed

    Yamada, Masaki; Yanagida, Tsutomu T; Yonekura, Kazuya

    2016-02-05

    Although QCD axion models are widely studied as solutions to the strong CP problem, they generically confront severe fine-tuning problems to guarantee the anomalous Peccei-Quinn (PQ) symmetry. In this Letter, we propose a simple QCD axion model without any fine-tunings. We introduce an extra dimension and a pair of extra quarks living on two branes separately, which is also charged under a bulk Abelian gauge symmetry. We assume a monopole condensation on our brane at an intermediate scale, which implies that the extra quarks develop chiral symmetry breaking and the PQ symmetry is broken. In contrast to Kim's original model, our model explains the origin of the PQ symmetry thanks to the extra dimension and avoids the cosmological domain wall problem because of chiral symmetry breaking in Abelian gauge theory.

  3. Spatial clustering of tuning in mouse primary visual cortex

    PubMed Central

    Ringach, Dario L.; Mineault, Patrick J.; Tring, Elaine; Olivas, Nicholas D.; Garcia-Junco-Clemente, Pablo; Trachtenberg, Joshua T.

    2016-01-01

    The primary visual cortex of higher mammals is organized into two-dimensional maps, where the preference of cells for stimulus parameters is arranged regularly on the cortical surface. In contrast, the preference of neurons in the rodent appears to be arranged randomly, in what is termed a salt-and-pepper map. Here we revisited the spatial organization of receptive fields in mouse primary visual cortex by measuring the tuning of pyramidal neurons in the joint orientation and spatial frequency domain. We found that the similarity of tuning decreases as a function of cortical distance, revealing a weak but statistically significant spatial clustering. Clustering was also observed across different cortical depths, consistent with a columnar organization. Thus, the mouse visual cortex is not strictly a salt-and-pepper map. At least on a local scale, it resembles a degraded version of the organization seen in higher mammals, hinting at a possible common origin. PMID:27481398

  4. Scanning Probe Microscopy of DNA with a Quartz Tuning Fork

    NASA Astrophysics Data System (ADS)

    King, G. M.; Nunes, G., Jr.

    2001-03-01

    Quartz tuning-forks have recently been put to use as highly sensitive force detectors in atomic force microscopy (AFM).(F.J.Giessibl et al.), Science 289, 422 (2000). In this study we have applied a home-built, tuning-fork based AFM to the investigation of single and double stranded DNA (ssDNA and dsDNA). We operate the microscope in the non-contact mode (typical tip amplitude ~1 nm) with a variety of tips (e.g. Si, Si_3N_4, W). Here we report on recent results showing that the apparent height of plasmid dsDNA on mica substrates depends on both the tip material and imaging frequency shift. This talk will also review our efforts to probe ssDNA with a chemically functionalized tip. Current and future prospects for this dynamic-mode, chemically-sensitive force microscopy technique will be discussed.

  5. Aircraft interior noise reduction by alternate resonance tuning

    NASA Technical Reports Server (NTRS)

    Bliss, Donald B.; Gottwald, James A.; Srinivasan, Ramakrishna; Gustaveson, Mark B.

    1990-01-01

    Existing interior noise reduction techniques for aircraft fuselages perform reasonably well at higher frequencies, but are inadequate at lower frequencies, particularly with respect to the low blade passage harmonics with high forcing levels found in propeller aircraft. A method is being studied which considers aircraft fuselage lined with panels alternately tuned to frequencies above and below the frequency that must be attenuated. Adjacent panels would oscillate at equal amplitude, to give equal source strength, but with opposite phase. Provided these adjacent panels are acoustically compact, the resulting cancellation causes the interior acoustic modes to become cutoff, and therefore be non-propagating and evanescent. This interior noise reduction method, called Alternate Resonance Tuning (ART), is currently being investigated both theoretically and experimentally. This new concept has potential application to reducing interior noise due to the propellers in advanced turboprop aircraft as well as for existing aircraft configurations.

  6. The Magnetically-Tuned Transition-Edge Sensor

    NASA Astrophysics Data System (ADS)

    Sadleir, John E.; Lee, Sang-Jun; Smith, Stephen J.; Busch, Sarah E.; Bandler, Simon R.; Adams, Joseph S.; Eckart, Megan E.; Chervenak, James A.; Kelley, Richard L.; Kilbourne, Caroline A.; Porter, Frederick S.; Porst, Jan-Patrick

    2014-08-01

    We present the first measurements on the proposed magnetically-tuned superconducting transition-edge sensor and compare the modified resistive transition with the theoretical prediction (Sadleir et al., IEEE Trans App Supercond 23:2101405, 2013). A TES's resistive transition is customarily characterized in terms of the unitless device parameters and corresponding to the resistive response to changes in temperature and current respectively. We present a new relationship between measured IV quantities (sensor current and voltage ) and the parameters and and use these relations to confirm we have stably biased a TES with negative parameter with magnetic tuning. Motivated by access to this new unexplored parameter space, we investigate the conditions for bias stability of a TES taking into account both self and externally applied magnetic fields.

  7. Tuning the Engine Skoda 781 for Sport Competitions

    NASA Astrophysics Data System (ADS)

    Ragan, Branislav; Polóni, Marián; Chríbik, Andrej

    2014-12-01

    This article deals with the tuning of a mass-produced engine Skoda 781.136B and its rebuilding into a racing engine. The introduction briefly describes the basic parameters of the massproduced engine. The information is then followed by a detailed description of adjustments to the pipe system, valve timing, cylinder head and crank mechanism. The article presents the benefits in terms of increasing power parameters and there is also a comparison of speed characteristics. The aim of the tuning was to increase the engine power parameters, in particular the torque in the range of 4 000-6 000 min-1, at which the engine most often operates during competitions. The adjustments and optimization of the engine have increased the power parameters in the required range of revolutions by 38-47%.

  8. Wideband fixed-tuned SIS receiver for 200-GHz operation

    NASA Technical Reports Server (NTRS)

    Blundell, Raymond; Tong, Cheuk-Yu E.; Papa, D. Cosmo; Leombruno, R. Louie; Zhang, Xiaolei; Paine, Scott; Stern, Jeffrey A.; Leduc, Henry G.; Bumble, Bruce

    1995-01-01

    We report on the design and development of a heterodyne receiver, designed to cover the frequency range 176-256 GHz. This receiver incorporates a niobium superconductor-insulator-superconductor (SIS) tunnel junction mixer, which, chiefly for reasons of reliability and ease of operation, is a fixed-tuned waveguide design. On-chip tuning is provided to resonate out the junction's geometric capacitance and produce a good match to the waveguide circuit. Laboratory measurements on the first test receiver indicate that the required input bandwidth (about 40%) is achieved with an average receiver noise temperature of below 50 K. Mixer conversion gain is observed at some frequencies, and the lowest measured receiver noise is less than 30 K. Furthermore, the SIS mixer used in this receiver is of simple construction, is easy to assemble and is therefore a good candidate for duplication.

  9. High-speed spectral tuning CARS microscopy using AOTF laser

    NASA Astrophysics Data System (ADS)

    Hashimoto, Mamoru; Iwatsuka, Junichi; Niioka, Hirohiko; Araki, Tsutomu

    2012-03-01

    We have developed a high speed spectral tuning CARS microscopy system using a mode-locked Ti:Sapphire laser with an acousto-optic tunable filter (AOTF) in the cavity. Since the wavelength of the laser is tunable with the applied radio frequency to the AOTF, the wavelength is electrically tunable.The pulse duration of the laser is about 10 ps, tunable range is 800 nm to 930 nm, and the tuning speed is ms order. The laser is synchronized with another mode-locked Ti:Sapphire laser laser our own method using a balance cross-correlator and phase lock loop technique. The synchronized lasers are used for light source of multi-focus CARS microscopy system using a microlens array scanner, and the hyperspectral imaging of adipocyte cells is demonstrated.

  10. Angular tuning of the magnetic birefringence in rippled cobalt films

    NASA Astrophysics Data System (ADS)

    Arranz, Miguel A.; Colino, José M.

    2015-06-01

    We report the measurement of magnetically induced birefringence in rippled Co films. For this purpose, the magneto-optical properties of ion beam eroded ferromagnetic films were studied using Kerr magnetometry and magnetic birefringence in the transmitted light intensity. Upon sufficient ion sculpting, these ripple surface nanostructures developed a defined uniaxial anisotropy in the in-plane magnetization, finely tuning the magnetic birefringence effect. We have studied its dependence on the relative orientation between the ripple direction and the magnetic field, and found this effect to be dramatically correlated with the capability to neatly distinguish the mechanisms for the in-plane magnetization reversal, i.e., rotation and nucleation. This double refraction corresponds univocally to the two magnetization axes, parallel and perpendicular to the ripples direction. We have also observed that tuned birefringence in stack assemblies of rippled Co films, which enables us to technically manipulate the number and direction of refraction axes.

  11. Angular tuning of the magnetic birefringence in rippled cobalt films

    SciTech Connect

    Arranz, Miguel A.; Colino, José M.

    2015-06-22

    We report the measurement of magnetically induced birefringence in rippled Co films. For this purpose, the magneto-optical properties of ion beam eroded ferromagnetic films were studied using Kerr magnetometry and magnetic birefringence in the transmitted light intensity. Upon sufficient ion sculpting, these ripple surface nanostructures developed a defined uniaxial anisotropy in the in-plane magnetization, finely tuning the magnetic birefringence effect. We have studied its dependence on the relative orientation between the ripple direction and the magnetic field, and found this effect to be dramatically correlated with the capability to neatly distinguish the mechanisms for the in-plane magnetization reversal, i.e., rotation and nucleation. This double refraction corresponds univocally to the two magnetization axes, parallel and perpendicular to the ripples direction. We have also observed that tuned birefringence in stack assemblies of rippled Co films, which enables us to technically manipulate the number and direction of refraction axes.

  12. A fuzzy self-tuning PI controller for HVDC links

    SciTech Connect

    Routray, A.; Dash, P.K.; Panda, S.K.

    1996-09-01

    This paper introduces a fuzzy logic-based tuning of the controller parameters for the rectifier side current regulator and inverter side gamma controller in a high voltage direct current (HVDC) system. A typical point-to-point system has been taken with the detailed representation of converters, transmission links transformers, and filters. The current error and its derivative and the gamma error and its derivative are used as the principal signals to adjust the proportional and integral gains of the rectifier pole controller and the inverter gamma controller, respectively, for the optimum system performance under various normal and abnormal conditions. Finally, a comparative study has been performed with and without tuning, to prove the superiority of the proposed scheme.

  13. Cosmologically Safe QCD Axion without Fine-Tuning

    NASA Astrophysics Data System (ADS)

    Yamada, Masaki; Yanagida, Tsutomu T.; Yonekura, Kazuya

    2016-02-01

    Although QCD axion models are widely studied as solutions to the strong C P problem, they generically confront severe fine-tuning problems to guarantee the anomalous Peccei-Quinn (PQ) symmetry. In this Letter, we propose a simple QCD axion model without any fine-tunings. We introduce an extra dimension and a pair of extra quarks living on two branes separately, which is also charged under a bulk Abelian gauge symmetry. We assume a monopole condensation on our brane at an intermediate scale, which implies that the extra quarks develop chiral symmetry breaking and the PQ symmetry is broken. In contrast to Kim's original model, our model explains the origin of the PQ symmetry thanks to the extra dimension and avoids the cosmological domain wall problem because of chiral symmetry breaking in Abelian gauge theory.

  14. Plasmonic nanoparticles tuned thermal sensitive photonic polymer for biomimetic chameleon

    NASA Astrophysics Data System (ADS)

    Yan, Yang; Liu, Lin; Cai, Zihe; Xu, Jiwen; Xu, Zhou; Zhang, Di; Hu, Xiaobin

    2016-08-01

    Among many thermo-photochromic materials, the color-changing behavior caused by temperature and light is usually lack of a full color response. And the study on visible light-stimuli chromic response is rarely reported. Here, we proposed a strategy to design a thermo-photochromic chameleon biomimetic material consisting of photonic poly(N-isopropylacrylamide-co-methacrylic acid) copolymer and plasmonic nanoparticles which has a vivid color change triggered by temperature and light like chameleons. We make use of the plasmonic nanoparticles like gold nanoparticles and silver nanoparticles to increase the sensitivity of the responsive behavior and control the lower critical solution temperature of the thermosensitive films by tuning the polymer chain conformation transition. Finally, it is possible that this film would have colorimetric responses to the entire VIS spectrum by the addition of different plasmonic nanoparticles to tune the plasmonic excitation wavelength. As a result, this method provides a potential use in new biosensors, military and many other aspects.

  15. Betatron tune measurement at the Argonne Rapid-Cycling Synchrotron

    SciTech Connect

    Rauchas, A.V.; Brumwell, F.R.; Cho, Y.; Czyz, W.S.; Gunderson, G.R.; Knott, M.J.; Suddeth, D.E.; Volk, G.J.

    1981-01-01

    In the past, betatron tune measurements at the Rapid Cycling Synchrotron (RCS) were made using a spectrum analyzer for betatron frequency analysis and one of the extraction kicker magnets to induce the coherent betatron motion. This method had several severe limitations: poor signal-to-noise ratio, inability to extract the beam after the measurement and dependence on the horizontal kick coupling into the vertical plane for vertical tune measurements. A new system is presently being constructed which will eliminate these problems. The beam will be kicked by independent horizontal and vertical ferrite pinger magnets. The beam positron data will be digitized and then analyzed by an array-processing computer using the Fast Fourier Transform (FFT). The control system will allow for additional improvements.

  16. Artifical intelligence techniques for tuning linear induction accelerators

    SciTech Connect

    Lager, D.; Brand, H.; Chambers, F.; Coffield, F.; Maurer, W.; Turner, W.

    1991-05-01

    We developed an expert system that acts as an intelligent assistant for tuning particle beam generators called MAESTRO, Model and Expert System Resource for Operators. MAESTRO maintains a knowledge base of the accelerator containing not only the interconnections of the beamline components, but also their physical attributes such as measured magnetic tilts, offsets, and field profiles. MAESTRO incorporates particle trajectory and beam envelope models which are coupled to the knowledge base permitting large numbers of real-time orbit and envelope calculations in the control-room environment. To date we have used this capability in three ways: First, to implement a tuning algorithm for minimizing transverse beam motion. Second, to produce a beam waist with arbitrary radius at the entrance to a brightness diagnostic. And finally, to measure beam energy along the accelerator by fitting orbits to focusing and steering sweeps.

  17. Tuning the Poisson's Ratio of Biomaterials for Investigating Cellular Response

    PubMed Central

    Meggs, Kyle; Qu, Xin; Chen, Shaochen

    2013-01-01

    Cells sense and respond to mechanical forces, regardless of whether the source is from a normal tissue matrix, an adjacent cell or a synthetic substrate. In recent years, cell response to surface rigidity has been extensively studied by modulating the elastic modulus of poly(ethylene glycol) (PEG)-based hydrogels. In the context of biomaterials, Poisson's ratio, another fundamental material property parameter has not been explored, primarily because of challenges involved in tuning the Poisson's ratio in biological scaffolds. Two-photon polymerization is used to fabricate suspended web structures that exhibit positive and negative Poisson's ratio (NPR), based on analytical models. NPR webs demonstrate biaxial expansion/compression behavior, as one or multiple cells apply local forces and move the structures. Unusual cell division on NPR structures is also demonstrated. This methodology can be used to tune the Poisson's ratio of several photocurable biomaterials and could have potential implications in the field of mechanobiology. PMID:24076754

  18. A self-tuning phase-shifting algorithm for interferometry.

    PubMed

    Estrada, Julio C; Servin, Manuel; Quiroga, Juan A

    2010-02-01

    In Phase Stepping Interferometry (PSI) an interferogram sequence having a known, and constant phase shift between the interferograms is required. Here we take the case where this constant phase shift is unknown and the only assumption is that the interferograms do have a temporal carrier. To recover the modulating phase from the interferograms, we propose a self-tuning phase-shifting algorithm. Our algorithm estimates the temporal frequency first, and then this knowledge is used to estimate the interesting modulating phase. There are several well known iterative schemes published before, but our approach has the unique advantage of being very fast. Our new temporal carrier, and phase estimator is capable of obtaining a very good approximation of their temporal carrier in a single iteration. Numerical experiments are given to show the performance of this simple yet powerful self-tuning phase shifting algorithm.

  19. Electric field tuning of band offsets in transition metal dichalcogenides

    NASA Astrophysics Data System (ADS)

    Huang, Dennis; Kaxiras, Efthimios

    2016-12-01

    We use first-principles calculations to investigate the band structure evolution of W X2 /Mo X2 (X = S, Se) heterobilayers under a perpendicular electric field. We characterize the extent to which the type II band alignment in these compounds can be tuned or inverted electrostatically. Our results demonstrate two effects of the stacking configuration. First, different stackings produce different net dipole moments, resulting in band offset variations that are larger than 0.1 eV. Second, based on symmetry constraints that depend on stacking, a perpendicular electric field may hybridize W X2 and Mo X2 bands that cross at the Brillouin zone corner K . Our results suggest that external electric fields can be used to tune the physics of intralayer and interlayer excitons in heterobilayers of transition metal dichalcogenides.

  20. Low Emittance Tuning Studies for SuperB

    SciTech Connect

    Liuzzo, Simone; Biagini, Maria; Raimondi, Pantaleo; Donald, Martin; /SLAC

    2012-07-06

    SuperB[1] is an international project for an asymmetric 2 rings collider at the B mesons cm energy to be built in the Rome area in Italy. The two rings will have very small beam sizes at the Interaction Point and very small emittances, similar to the Linear Collider Damping Rings ones. In particular, the ultra low vertical emittances, 7 pm in the LER and 4 pm in the HER, need a careful study of the misalignment errors effects on the machine performances. Studies on the closed orbit, vertical dispersion and coupling corrections have been carried out in order to specify the maximum allowed errors and to provide a procedure for emittance tuning. A new tool which combines MADX and Matlab routines has been developed, allowing for both corrections and tuning. Results of these studies are presented.

  1. Stop search with acceptable fine-tuning in Susy models

    NASA Astrophysics Data System (ADS)

    Ćiçi, Ali; Ün, Cem Salih; Kirca, Zerrin

    2017-02-01

    Supersymmetry (SUSY) is one of the forefront candidates for the models beyond the Standard Model (SM) in resolving the gauge hierarchy problem by proposing new supersymmetric partners for the SM fields. In SUSY, stop, the supersymmetric partner of top quark, is of a special importance, since it cancels the largest quadratic contributions to the Higgs boson mass from top quark loop. Despite heavy stop mass requirement from the Higgs boson searches and fine-tuning demands, it is still possible to find stops of mass about a few hundred GeV, even as light as top quark. In this study, we search for light stop solutions within the SUSY Grand Unified Theory (GUT) models in light of acceptable fine-tuning and current experimental constraints. Afterwards, we analyze the possible signals through which the implications can be tested at the Large Hadron Collider (LHC) experiments.

  2. The Magnetically-Tuned Transition-Edge Sensor

    NASA Technical Reports Server (NTRS)

    Sadleir, John E.; Lee, Sang-Jun; Smith, Stephen J.; Busch, Sarah E.; Bandler, Simon R.; Adams, Joseph S.; Eckart, Megan E.; Chevenak, James A.; Kelley, Richard L.; Kilbourne, Caroline A.; Porter, Frederick S.; Porst, Jan-Patrick

    2014-01-01

    We present the first measurements on the proposed magnetically-tuned superconducting transition-edge sensor (MTES) and compare the modified resistive transition with the theoretical prediction. A TES's resistive transition is customarily characterized in terms of the unit less device parameters alpha and beta corresponding to the resistive response to changes in temperature and current respectively. We present a new relationship between measured IV quantities and the parameters alpha and beta and use these relations to confirm we have stably biased a TES with negative beta parameter with magnetic tuning. Motivated by access to this new unexplored parameter space, we investigate the conditions for bias stability of a TES taking into account both self and externally applied magnetic fields.

  3. Electrical tuning of an optical antenna (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Brongersma, Mark L.

    2016-09-01

    The scaling of active photonic devices to deep-submicron length-scales has been hampered by the fundamental law of diffraction and the absence of materials with sufficiently strong electrooptic effects. Here, we demonstrate a solid state electro-optical switching mechanism that can operate in the visible spectral range with an active volume that is comparable to the size of the smallest active electronic components. The switching mechanism relies on electrochemically displacing atoms inside the nanometer-scale gap between two crossed metallic wires forming a crosspoint junction. Such junctions afford extreme light concentration and display singular optical behavior upon formation of a conductive channel. We illustrate how this effect can be used to actively tune the resonances of a plasmonic antenna. The tuning mechanism is analyzed using a combination of electrical and optical measurements as well as electron energy loss (EELS) in a scanning transmission electron microscope (STEM).

  4. Podcasting for Language Learning through iTunes U: The Learner's View

    ERIC Educational Resources Information Center

    Rosell-Aguilar, Fernando

    2013-01-01

    iTunes U has become the main worldwide provider of educational podcasts but, despite its popularity, little is known about the type of user who downloads iTunes U language resources, or how those resources are used. This paper presents the results of the first major survey (1891 responses) of users of one of the most successful iTunes U content…

  5. Tuned vibration absorbers with nonlinear viscous damping for damped structures under random load

    NASA Astrophysics Data System (ADS)

    Shum, K. M.

    2015-06-01

    The classical problem for the application of a tuned vibration absorber is to minimize the response of a structural system, such as displacement, velocity, acceleration or to maximize the energy dissipated by tuned vibration absorber. The development of explicit optimal absorber parameters is challenging for a damped structural system since the fixed points no longer exist in the frequency response curve. This paper aims at deriving a set of simple design formula of tuned vibration absorber with nonlinear viscous damping based on the frequency tuning for harmonic load for a damped structural system under white noise excitation. The vibration absorbers being considered include tuned mass damper (TMD) and liquid column vibration absorber (LCVA). Simple approximate expression for the standard deviation velocity response of tuned vibration absorber for damped primary structure is also derived in this study to facilitate the estimation of the damping coefficient of TMD with nonlinear viscous damping and the head loss coefficient of LCVA. The derived results indicate that the higher the structural inherent damping the smaller the supplementary damping provided by a tuned vibration absorber. Furthermore, the optimal damping of tuned vibration absorber is shown to be independent of structural damping when it is tuned using the frequency tuning for harmonic load. Finally, the derived closed-form expressions are demonstrated to be capable of predicting the optimal parameters of tuned vibration absorbers with sufficient accuracy for preliminary design of tuned vibration absorbers with nonlinear viscous damping for a damped primary structure.

  6. Double-tuned single coil probe for nuclear magnetic resonance spectrometer

    SciTech Connect

    McKay, R.A.

    1984-05-01

    A double-tuned single coil probe for a nuclear magnetic resonance spectrometer having improved sensitivity is described comprising a double-tuned circuit means in which the low frequency irradiation is fed to a transmission line through an inductor means. The double-tuned circuit means of the invention may be remotely disposed from the magnetic field which results in greater sensitivity.

  7. Effects of Stimulus Octave and Timbre on the Tuning Accuracy of Secondary School Instrumentalists

    ERIC Educational Resources Information Center

    Byo, James L.; Schlegel, Amanda L.; Clark, N. Alan

    2011-01-01

    To test the effects of octave and timbre on tuning accuracy, four stimuli--B-flat 4 sounded by flute, oboe, and clarinet and B-flat 2 sounded by tuba--functioned as reference pitches for high school wind players (N = 72). The two stimulus octaves combined with participants' assigned tuning notes created soprano, tenor, and bass tuning groups. All…

  8. Teachers' Practices and Beliefs Regarding Teaching Tuning in Elementary and Middle School Group String Classes

    ERIC Educational Resources Information Center

    Hopkins, Michael T.

    2013-01-01

    The purpose of this study was to examine teachers' practices and beliefs related to the teaching of stringed instrument tuning in elementary and middle school group classes. The aspects examined included the following: (a) teachers' beliefs about teaching tuning in their string classes, (b) activities teachers used when teaching tuning in string…

  9. ATCOM: Automatically Tuned Collective Communication System for SMP Clusters

    SciTech Connect

    Wu, Meng-Shiou

    2005-01-01

    Conventional implementations of collective communications are based on point-to-point communications, and their optimizations have been focused on efficiency of those communication algorithms. However, point-to-point communications are not the optimal choice for modern computing clusters of SMPs due to their two-level communication structure. In recent years, a few research efforts have investigated efficient collective communications for SMP clusters. This dissertation is focused on platform-independent algorithms and implementations in this area. There are two main approaches to implementing efficient collective communications for clusters of SMPs: using shared memory operations for intra-node communications, and overlapping inter-node/intra-node communications. The former fully utilizes the hardware based shared memory of an SMP, and the latter takes advantage of the inherent hierarchy of the communications within a cluster of SMPs. Previous studies focused on clusters of SMP from certain vendors. However, the previously proposed methods are not portable to other systems. Because the performance optimization issue is very complicated and the developing process is very time consuming, it is highly desired to have self-tuning, platform-independent implementations. As proven in this dissertation, such an implementation can significantly out-perform the other point-to-point based portable implementations and some platform-specific implementations. The dissertation describes in detail the architecture of the platform-independent implementation. There are four system components: shared memory-based collective communications, overlapping mechanisms for inter-node and intra-node communications, a prediction-based tuning module and a micro-benchmark based tuning module. Each component is carefully designed with the goal of automatic tuning in mind.

  10. Microfluidic tuning of distributed feedback quantum cascade lasers

    NASA Astrophysics Data System (ADS)

    Diehl, Laurent; Lee, Benjamin G.; Behroozi, Peter; Loncar, Marko; Belkin, Mikhail; Capasso, Federico; Aellen, Thierry; Hofstetter, Daniel; Beck, Matthias; Faist, Jerome

    2006-11-01

    In this Letter, we report the tuning of the emission wavelength of a single mode distributed feedback quantum cascade laser by modifying the mode effective refractive index using fluids. A fabrication procedure to encapsulate the devices in polymers for microfluidic delivery is also presented. The integration of microfluidics with semiconductor laser (optofluidics) is promising for new compact and portable lab-on-a-chip applications.

  11. Tuning and synthesis of semiconductor nanostructures by mechanical compression

    DOEpatents

    Fan, Hongyou; Li, Binsong

    2015-11-17

    A mechanical compression method can be used to tune semiconductor nanoparticle lattice structure and synthesize new semiconductor nanostructures including nanorods, nanowires, nanosheets, and other three-dimensional interconnected structures. II-VI or IV-VI compound semiconductor nanoparticle assemblies can be used as starting materials, including CdSe, CdTe, ZnSe, ZnS, PbSe, and PbS.

  12. Tuning of PID controllers for boiler-turbine units.

    PubMed

    Tan, Wen; Liu, Jizhen; Fang, Fang; Chen, Yanqiao

    2004-10-01

    A simple two-by-two model for a boiler-turbine unit is demonstrated in this paper. The model can capture the essential dynamics of a unit. The design of a coordinated controller is discussed based on this model. A PID control structure is derived, and a tuning procedure is proposed. The examples show that the method is easy to apply and can achieve acceptable performance.

  13. ORMOSIL thin films: tuning mechanical properties via a nanochemistry approach.

    PubMed

    Palmisano, Giovanni; Le Bourhis, Eric; Ciriminna, Rosaria; Tranchida, Davide; Pagliaro, Mario

    2006-12-19

    The mechanical properties (hardness and elastic modulus) of organically modified silicate thin films can be finely tuned by varying the degree of alkylation and thus the fraction of six- and four-membered siloxane rings in the organosilica matrix. This opens the way to large tunability of parameters that are of crucial practical importance for films that are finding increasing application in numerous fields ranging from microelectronics to chemical sensing.

  14. Compiler-Driven Performance Optimization and Tuning for Multicore Architectures

    DTIC Science & Technology

    2015-04-10

    Report: Compiler-Driven Performance Optimization and Tuning for Multicore Architectures The widespread emergence of multicore processors as the computing...applications have enjoyed the free-ride of performance improvement with each new processor generation. The reality today is that existing and new...applications must be changed to make them multi-threaded if they are to experience any performance benefits from newer generations of processors . An

  15. Electromechanical tuning of vertically-coupled photonic crystal nanobeams.

    PubMed

    Midolo, L; Yoon, S N; Pagliano, F; Xia, T; van Otten, F W M; Lermer, M; Höfling, S; Fiore, A

    2012-08-13

    We present the design, the fabrication and the characterization of a tunable one-dimensional (1D) photonic crystal cavity (PCC) etched on two vertically-coupled GaAs nanobeams. A novel fabrication method which prevents their adhesion under capillary forces is introduced. We discuss a design to increase the flexibility of the structure and we demonstrate a large reversible and controllable electromechanical wavelength tuning (> 15 nm) of the cavity modes.

  16. Betatron tune measurement at the Argonne rapid cycling synchrotron

    SciTech Connect

    Rauchas, A.V.; Brumwell, F.R.; Cho, Y.; Czyz, W.S.; Gunderson, G.R.; Knott, M.J.; Suddeth, D.E.; Volk, G.J.

    1981-06-01

    Preliminary tests of the new system have been completed using the extraction kicker as a ''pinger'' magnet. Data has been gathered, digitized, and the FFT calculated. The results are within expectations. The new system expands the tune measurement capabilities tremendously. The computer allows for data processing which improves signal-to-noise ratio and further increases resolution. The system will also lend itself to study beam motion other than betatron. 8 refs.

  17. UV-mediated tuning of surface biorepulsivity in aqueous environment.

    PubMed

    Weber, Theresa; Meyerbröker, Nikolaus; Hira, Nuruzzaman Khan; Zharnikov, Michael; Terfort, Andreas

    2014-04-28

    While it is well-known that oligoethylene glycol (OEG) terminated self-assembled monolayers (SAMs) can be deteriorated by UV irradiation in air, we now report that the analogous modification can also be performed in water, opening the opportunity for in situ tuning of biorepulsive properties. Surprisingly, this deterioration also takes place even in the absence of molecular oxygen, resulting in a very selective process.

  18. Choice of Tevatron tune with matched low-. beta. insertions

    SciTech Connect

    Month, M.

    1984-06-20

    The Tevatron lattice, following closely the Main Ring lattice, is made up of approximately 90 FODO cells with six straight sections equally spaced. The straight sections are identical (neglecting the special high-..beta.. straight section used for resonant extraction) providing six-fold symmetry. Each straight section is comprised mainly of a pair of doublets, one at each end, in an antisymmetric configuration. The ..beta..-functions are matched to the building block cells but the dispersion function is not. The ..beta..-function matching implies that the structure is not sensitive to the tune of the sextant (i.e., structure resonances); however, the dispersion mismatch excites off-momentum dipole resonances and the dispersion structure of the ring is therefore sensitive to sextant tunes near an integer. The introduction of low-..beta.. insertions can be accomplished by replacing a standard insertion (expanded somewhat from the doublet pair straight section) with a low-..beta.. insertion. By matching the ends of the replacement units with respect to ..beta..-functions and dispersion function, the full lattice is made insensitive to linear structure resonances. Procedures are described here for introducing into the idealized Tevatron lattice considered here a single matched low-..beta.. insertion at BO, and two matched low-..beta.. insertions at BO and DO. The main consequence is the need for a significant number of independently powered quadrupoles. Another conclusion is related to the choice of tune, where it is found that the arbitrary rule of maintaining a fixed tune for all configurations should be modified.

  19. Give your practice a spring tune-up.

    PubMed

    Aluia, J J

    1995-03-01

    Like your car, your medical practice may need some spring adjustments. Although some of the newer automobiles can travel 100,000 miles between "tune-ups," the business side of your medical practice requires more frequent attention. Many times physicians believe that their practice may run on autopilot, until they begin to see acute signs of problems. Such complacency can often lead to surprises that will ultimately impact your patients, your staff and your bottom-line.

  20. System for tuning a combustor of a gas turbine

    SciTech Connect

    Hughes, Michael John

    2016-12-27

    A system for tuning a combustor of a gas turbine includes a flow sleeve having an annular main body. The main body includes an upstream end, a downstream end, an inner surface and an outer surface. A cooling channel extends along the inner surface of the main body. The cooling channel extends at least partially between the downstream end and the upstream end of the main body.

  1. On the controversy about the sharpness of human cochlear tuning.

    PubMed

    Lopez-Poveda, Enrique A; Eustaquio-Martin, Almudena

    2013-10-01

    In signal processing terms, the operation of the mammalian cochlea in the inner ear may be likened to a bank of filters. Based on otoacoustic emission evidence, it has been recently claimed that cochlear tuning is sharper for human than for other mammals. The claim was corroborated with a behavioral method that involves the masking of pure tones with forward notched noises (NN). Using this method, it has been further claimed that human cochlear tuning is sharper than suggested by earlier behavioral studies. These claims are controversial. Here, we contribute to the controversy by theoretically assessing the accuracy of the NN method at inferring the bandwidth (BW) of nonlinear cochlear filters. Behavioral forward masking was mimicked using a computer model of the squared basilar membrane response followed by a temporal integrator. Isoresponse and isolevel versions of the forward masking NN method were applied to infer the already known BW of the cochlear filter used in the model. We show that isolevel methods were overall more accurate than isoresponse methods. We also show that BWs for NNs and sinusoids equate only for isolevel methods and when the levels of the two stimuli are appropriately scaled. Lastly, we show that the inferred BW depends on the method version (isolevel BW was twice as broad as isoresponse BW at 40 dB SPL) and on the stimulus level (isoresponse and isolevel BW decreased and increased, respectively, with increasing level over the level range where cochlear responses went from linear to compressive). We suggest that the latter may contribute to explaining the reported differences in cochlear tuning across behavioral studies and species. We further suggest that given the well-established nonlinear nature of cochlear responses, even greater care must be exercised when using a single BW value to describe and compare cochlear tuning.

  2. NEUTRONIC REACTOR CONTROL ELEMENT

    DOEpatents

    Beaver, R.J.; Leitten, C.F. Jr.

    1962-04-17

    A boron-10 containing reactor control element wherein the boron-10 is dispersed in a matrix material is describeri. The concentration of boron-10 in the matrix varies transversely across the element from a minimum at the surface to a maximum at the center of the element, prior to exposure to neutrons. (AEC)

  3. Organic Elemental Analysis.

    ERIC Educational Resources Information Center

    Ma, T. S.; Gutterson, Milton

    1980-01-01

    Reviews general developments in computerization and data processing of organic elemental analyses; carbon, hydrogen, and nitrogen analyzers; procedures for determining oxygen, sulfur, and halogens, as well as other nometallic elements and organometallics. Selected papers on trace analysis of nonmetals and determination of metallic elements are…

  4. A tuning method of two degrees of freedom PID controller

    SciTech Connect

    Kasahara, Masato; Kimbara, Akiomi; Kurosu, Shigeru; Matsuba, Tadahiko; Kamimura, Kazuyuki; Murasawa, Itaru; Hashimoto, Yukihiro

    1997-12-31

    This paper proposes a new tuning method when using a two degrees of freedom proportional-integral-derivative (PID) controller. Its control performance for a first-order lag plus deadtime system is shown as an example of the commonly approximated controlled plants in the heating, ventilating, and air-conditioning (HVAC) field. Reference and disturbance input changes to a conventional PID controller do not necessarily give a satisfactory response. To overcome this problem, several two degrees of freedom PID (2 DOF PID) algorithms have been developed to replace the conventional PID controllers. However, when these techniques are applied to real plants, it is not usually easy to obtain a set of optimum tuning parameters. To evaluate the control performance, a comparison is carried out between the two tuning methods--the optimization technique and the partial model matching method--using simulation. Graphs by which the controller parameters can be related to dynamics of a popular plant are developed. The 2 DOF PID control is studied taking into account modeling error due to a change in plant characteristics. It is found that the 2 DOF PID controller designed based on the partial model matching method is robust and useful in simulations where a traditional PID controller would be used.

  5. Electrochemical tuning of the optical properties of nanoporous gold

    NASA Astrophysics Data System (ADS)

    Jalas, D.; Shao, L.-H.; Canchi, R.; Okuma, T.; Lang, S.; Petrov, A.; Weissmüller, J.; Eich, M.

    2017-03-01

    Using optical in-situ measurements in an electrochemical environment, we study the electrochemical tuning of the transmission spectrum of films from the nanoporous gold (NPG) based optical metamaterial, including the effect of the ligament size. The long wavelength part of the transmission spectrum around 800 nm can be reversibly tuned via the applied electrode potential. The NPG behaves as diluted metal with its transition from dielectric to metallic response shifted to longer wavelengths. We find that the applied potential alters the charge carrier density to a comparable extent as in experiments on gold nanoparticles. However, compared to nanoparticles, a NPG optical metamaterial, due to its connected structure, shows a much stronger and more broadband change in optical transmission for the same change in charge carrier density. We were able to tune the transmission through an only 200 nm thin sample by 30%. In combination with an electrolyte the tunable NPG based optical metamaterial, which employs a very large surface-to-volume ratio is expected to play an important role in sensor applications, for photoelectrochemical water splitting into hydrogen and oxygen and for solar water purification.

  6. Electrochemical tuning of the optical properties of nanoporous gold

    PubMed Central

    Jalas, D.; Shao, L.-H.; Canchi, R.; Okuma, T.; Lang, S.; Petrov, A.; Weissmüller, J.; Eich, M.

    2017-01-01

    Using optical in-situ measurements in an electrochemical environment, we study the electrochemical tuning of the transmission spectrum of films from the nanoporous gold (NPG) based optical metamaterial, including the effect of the ligament size. The long wavelength part of the transmission spectrum around 800 nm can be reversibly tuned via the applied electrode potential. The NPG behaves as diluted metal with its transition from dielectric to metallic response shifted to longer wavelengths. We find that the applied potential alters the charge carrier density to a comparable extent as in experiments on gold nanoparticles. However, compared to nanoparticles, a NPG optical metamaterial, due to its connected structure, shows a much stronger and more broadband change in optical transmission for the same change in charge carrier density. We were able to tune the transmission through an only 200 nm thin sample by 30%. In combination with an electrolyte the tunable NPG based optical metamaterial, which employs a very large surface-to-volume ratio is expected to play an important role in sensor applications, for photoelectrochemical water splitting into hydrogen and oxygen and for solar water purification. PMID:28276516

  7. Broad electrical tuning of graphene-loaded plasmonic antennas.

    PubMed

    Yao, Yu; Kats, Mikhail A; Genevet, Patrice; Yu, Nanfang; Song, Yi; Kong, Jing; Capasso, Federico

    2013-03-13

    Plasmonic antennas enable the conversion of light from free space into subwavelength volumes and vice versa, which facilitates the manipulation of light at the nanoscale. Dynamic control of the properties of antennas is desirable for many applications, including biochemical sensors, reconfigurable meta-surfaces and compact optoelectronic devices. The combination of metallic structures and graphene, which has gate-voltage dependent optical properties, is emerging as a possible platform for electrically controlled plasmonic devices. In this paper, we demonstrate in situ control of antennas using graphene as an electrically tunable load in the nanoscale antenna gap. In our experiments, we demonstrate electrical tuning of graphene-loaded antennas over a broad wavelength range of 650 nm (∼140 cm(-1), ∼10% of the resonance frequency) in the mid-infrared (MIR) region. We propose an equivalent circuit model to quantitatively analyze the tuning behavior of graphene-loaded antenna pairs and derive an analytical expression for the tuning range of resonant wavelength. In a separate experiment, we used doubly resonant antenna arrays to achieve MIR optical intensity modulation with maximum modulation depth of more than 30% and bandwidth of 600 nm (∼100 cm(-1), 8% of the resonance frequency). This study shows that combining graphene with metallic nanostructures provides a route to electrically tunable optical and optoelectronic devices.

  8. The Effects of Auditory Contrast Tuning upon Speech Intelligibility

    PubMed Central

    Killian, Nathan J.; Watkins, Paul V.; Davidson, Lisa S.; Barbour, Dennis L.

    2016-01-01

    We have previously identified neurons tuned to spectral contrast of wideband sounds in auditory cortex of awake marmoset monkeys. Because additive noise alters the spectral contrast of speech, contrast-tuned neurons, if present in human auditory cortex, may aid in extracting speech from noise. Given that this cortical function may be underdeveloped in individuals with sensorineural hearing loss, incorporating biologically-inspired algorithms into external signal processing devices could provide speech enhancement benefits to cochlear implantees. In this study we first constructed a computational signal processing algorithm to mimic auditory cortex contrast tuning. We then manipulated the shape of contrast channels and evaluated the intelligibility of reconstructed noisy speech using a metric to predict cochlear implant user perception. Candidate speech enhancement strategies were then tested in cochlear implantees with a hearing-in-noise test. Accentuation of intermediate contrast values or all contrast values improved computed intelligibility. Cochlear implant subjects showed significant improvement in noisy speech intelligibility with a contrast shaping procedure. PMID:27555826

  9. PERI - Auto-tuning Memory Intensive Kernels for Multicore

    SciTech Connect

    Bailey, David H; Williams, Samuel; Datta, Kaushik; Carter, Jonathan; Oliker, Leonid; Shalf, John; Yelick, Katherine; Bailey, David H

    2008-06-24

    We present an auto-tuning approach to optimize application performance on emerging multicore architectures. The methodology extends the idea of search-based performance optimizations, popular in linear algebra and FFT libraries, to application-specific computational kernels. Our work applies this strategy to Sparse Matrix Vector Multiplication (SpMV), the explicit heat equation PDE on a regular grid (Stencil), and a lattice Boltzmann application (LBMHD). We explore one of the broadest sets of multicore architectures in the HPC literature, including the Intel Xeon Clovertown, AMD Opteron Barcelona, Sun Victoria Falls, and the Sony-Toshiba-IBM (STI) Cell. Rather than hand-tuning each kernel for each system, we develop a code generator for each kernel that allows us to identify a highly optimized version for each platform, while amortizing the human programming effort. Results show that our auto-tuned kernel applications often achieve a better than 4X improvement compared with the original code. Additionally, we analyze a Roofline performance model for each platform to reveal hardware bottlenecks and software challenges for future multicore systems and applications.

  10. A-Priori Tuning of Modified Magnussen Combustion Model

    NASA Technical Reports Server (NTRS)

    Norris, A. T.

    2016-01-01

    In the application of CFD to turbulent reacting flows, one of the main limitations to predictive accuracy is the chemistry model. Using a full or skeletal kinetics model may provide good predictive ability, however, at considerable computational cost. Adding the ability to account for the interaction between turbulence and chemistry improves the overall fidelity of a simulation but adds to this cost. An alternative is the use of simple models, such as the Magnussen model, which has negligible computational overhead, but lacks general predictive ability except for cases that can be tuned to the flow being solved. In this paper, a technique will be described that allows the tuning of the Magnussen model for an arbitrary fuel and flow geometry without the need to have experimental data for that particular case. The tuning is based on comparing the results of the Magnussen model and full finite-rate chemistry when applied to perfectly and partially stirred reactor simulations. In addition, a modification to the Magnussen model is proposed that allows the upper kinetic limit for the reaction rate to be set, giving better physical agreement with full kinetic mechanisms. This procedure allows a simple reacting model to be used in a predictive manner, and affords significant savings in computational costs for simulations.

  11. Inversion of residual gravity anomalies using tuned PSO

    NASA Astrophysics Data System (ADS)

    Roshan, Ravi; Singh, Upendra Kumar

    2017-02-01

    Many kinds of particle swarm optimization (PSO) techniques are now available and various efforts have been made to solve linear and non-linear problems as well as one-dimensional and multi-dimensional problems of geophysical data. Particle swarm optimization is a metaheuristic optimization method that requires intelligent guesswork and a suitable selection of controlling parameters (i.e. inertia weight and acceleration coefficient) for better convergence at global minima. The proposed technique, tuned PSO, is an improved technique of PSO, in which efforts have been made to choose the controlling parameters, and these parameters have been selected after analysing the responses of various possible exercises using synthetic gravity anomalies over various geological sources. The applicability and efficacy of the proposed method is tested and validated using synthetic gravity anomalies over various source geometries. Finally, tuned PSO is applied over field residual gravity anomalies of two different geological terrains to find the model parameters, namely amplitude coefficient factor (A), shape factor (q) and depth (z). The analysed results have been compared with published results obtained by different methods that show a significantly excellent agreement with real model parameters. The results also show that the proposed approach is not only superior to the other methods but also that the strategy has enhanced the exploration capability of the proposed method. Thus tuned PSO is an efficient and more robust technique to achieve an optimal solution with minimal error.

  12. A comparison of double-tuned surface coils.

    PubMed

    Fitzsimmons, J R; Brooker, H R; Beck, B

    1989-06-01

    The combined acquisition of proton images and localized spectra is considered essential to the practical application of NMR techniques to human and animal research. Double-tuned surface coils which have been introduced to the literature are intended to address the problem; however, a careful evaluation of available designs is lacking. The "trap" method, the loop gap resonator design, and the transformer-coupled double-tuned design are evaluated here using bench tests of signal intensity and Q as well as signal-to-noise measurements on a 2-T imager/spectrometer. Comparisons are made relative to optimized single-tuned circuits of the same size for both protons at 85 MHz and phosphorus at 34 MHz. The results suggest that the "trap" design and the transformer coupled design are very efficient (98%) in the low-frequency mode (34 MHz) while the loop gap resonator is relatively inefficient (82%). In the high-frequency mode (85 MHz) the loop gap resonator is 75% efficient while the "trap" design and the transformer coupled coil are closer to 50% efficient.

  13. Self tuning scalar fields in spherically symmetric spacetimes

    SciTech Connect

    Appleby, Stephen

    2015-05-01

    We search for self tuning solutions to the Einstein-scalar field equations for the simplest class of 'Fab-Four' models with constant potentials. We first review the conditions under which self tuning occurs in a cosmological spacetime, and by introducing a small modification to the original theory—introducing the second and third Galileon terms—show how one can obtain de Sitter states where the expansion rate is independent of the vacuum energy. We then consider whether the same self tuning mechanism can persist in a spherically symmetric inhomogeneous spacetime. We show that there are no asymptotically flat solutions to the field equations in which the vacuum energy is screened, other than the trivial one (Minkowski space). We then consider the possibility of constructing Schwarzschild de Sitter spacetimes for the modified Fab Four plus Galileon theory. We argue that the only model that can successfully screen the vacuum energy in both an FLRW and Schwarzschild de Sitter spacetime is one containing 'John' ∼ G{sup μ}{sub ν} ∂{sub μ}φ∂{sup ν}φ and a canonical kinetic term ∼ ∂{sub α}φ ∂{sup α}φ. This behaviour was first observed in [1]. The screening mechanism, which requires redundancy of the scalar field equation in the 'vacuum', fails for the 'Paul' term in an inhomogeneous spacetime.

  14. Tuning the Emission Energy of Chemically Doped Graphene Quantum Dots

    PubMed Central

    Noor-Ul-Ain; Eriksson, Martin O.; Schmidt, Susann; Asghar, M.; Lin, Pin-Cheng; Holtz, Per Olof; Syväjärvi, Mikael; Yazdi, G. Reza

    2016-01-01

    Tuning the emission energy of graphene quantum dots (GQDs) and understanding the reason of tunability is essential for the GOD function in optoelectronic devices. Besides material-based challenges, the way to realize chemical doping and band gap tuning also pose a serious challenge. In this study, we tuned the emission energy of GQDs by substitutional doping using chlorine, nitrogen, boron, sodium, and potassium dopants in solution form. Photoluminescence data obtained from (Cl- and N-doped) GQDs and (B-, Na-, and K-doped) GQDs, respectively exhibited red- and blue-shift with respect to the photoluminescence of the undoped GQDs. X-ray photoemission spectroscopy (XPS) revealed that oxygen functional groups were attached to GQDs. We qualitatively correlate red-shift of the photoluminescence with the oxygen functional groups using literature references which demonstrates that more oxygen containing groups leads to the formation of more defect states and is the reason of observed red-shift of luminescence in GQDs. Further on, time resolved photoluminescence measurements of Cl- and N-GQDs demonstrated that Cl substitution in GQDs has effective role in radiative transition whereas in N-GQDs leads to photoluminescence (PL) quenching with non-radiative transition to ground state. Presumably oxidation or reduction processes cause a change of effective size and the bandgap. PMID:28335326

  15. Dynamically tuned magnetostrictive spring with electrically controlled stiffness

    NASA Astrophysics Data System (ADS)

    Scheidler, Justin J.; Asnani, Vivake M.; Dapino, Marcelo J.

    2016-03-01

    This paper presents the design and testing of an electrically controllable magnetostrictive spring that has a dynamically tunable stiffness (i.e., a magnetostrictive Varispring). The device enables in situ stiffness tuning or stiffness switching for vibration control applications. Using a nonlinear electromechanical transducer model and an analytical solution of linear, mechanically induced magnetic diffusion, Terfenol-D is shown to have a faster rise time to stepped voltage inputs and a significantly higher magnetic diffusion cut-off frequency relative to Galfenol. A Varispring is manufactured using a laminated Terfenol-D rod. Further rise time reductions are achieved by minimizing the rod’s diameter and winding the electromagnet with larger wire. Dynamic tuning of the Varispring’s stiffness is investigated by measuring the Terfenol-D rod’s strain response to dynamic, compressive, axial forces in the presence of sinusoidal or square wave control currents. The Varispring’s rise time is \\lt 1 ms for 1 A current switches. Continuous modulus changes up to 21.9 GPa and 500 Hz and square wave modulus changes (dynamic {{Δ }}E effect) up to 12.3 GPa and 100 Hz are observed. Stiffness tunability and tuning bandwidth can be considerably increased by operating about a more optimal bias stress and improving the control of the electrical input.

  16. Alternate Tunings for the Linac Coherent Light Source Photoinjector

    SciTech Connect

    Limborg-Deprey, C.; Emma, P.; /SLAC

    2006-03-17

    The Linac Coherent Light Source (LCLS) is an x-ray free-electron laser (FEL) project based on the SLAC linac. The LCLS Photoinjector beamline has been designed to deliver 10-ps long electron bunches of 1 nC with a normalized projected transverse emittance smaller than 1.2 mm-mrad at 135 MeV. Tolerances and regulation requirements are tight for this tuning. Half of the total emittance at the end of the injector comes from the ''cathode emittance'' which is 0.7 mm-mrad for our nominal 1nC tuning. As the ''cathode emittance'' scales linearly with laser spot radius, the emittance will be dramatically reduced for smaller radius, but this is only possible at lower charge. In particular, for a 0.2 nC charge, we believe we can achieve an emittance closer to 0.4 mm-mrad. This working point will be easier to tune and the beam quality should be much easier to maintain than for the 1 nC case. In the second half of this paper, we discuss optimum laser pulse shapes. We demonstrate that the benefits of the ellipsoidal shapes seem to be important enough so that serious investigations should be carried out in the production of such pulses.

  17. Simulation and Big Data Challenges in Tuning Building Energy Models

    SciTech Connect

    Sanyal, Jibonananda; New, Joshua Ryan

    2013-01-01

    EnergyPlus is the flagship building energy simulation software used to model whole building energy consumption for residential and commercial establishments. A typical input to the program often has hundreds, sometimes thousands of parameters which are typically tweaked by a buildings expert to get it right . This process can sometimes take months. Autotune is an ongoing research effort employing machine learning techniques to automate the tuning of the input parameters for an EnergyPlus input description of a building. Even with automation, the computational challenge faced to run the tuning simulation ensemble is daunting and requires the use of supercomputers to make it tractable in time. In this proposal, we describe the scope of the problem, the technical challenges faced and overcome, the machine learning techniques developed and employed, and the software infrastructure developed/in development when taking the EnergyPlus engine, which was primarily designed to run on desktops, and scaling it to run on shared memory supercomputers (Nautilus) and distributed memory supercomputers (Frost and Titan). The parametric simulations produce data in the order of tens to a couple of hundred terabytes.We describe the approaches employed to streamline and reduce bottlenecks in the workflow for this data, which is subsequently being made available for the tuning effort as well as made available publicly for open-science.

  18. Timing and Tuning for Familiarity of Cortical Responses to Faces

    PubMed Central

    Bobes, Maria A.; Lage Castellanos, Agustin; Quiñones, Ileana; García, Lorna; Valdes-Sosa, Mitchell

    2013-01-01

    Different kinds of known faces activate brain areas to dissimilar degrees. However, the tuning to type of knowledge, and the temporal course of activation, of each area have not been well characterized. Here we measured, with functional magnetic resonance imaging, brain activity elicited by unfamiliar, visually familiar, and personally-familiar faces. We assessed response amplitude and duration using flexible hemodynamic response functions, as well as the tuning to face type, of regions within the face processing system. Core face processing areas (occipital and fusiform face areas) responded to all types of faces with only small differences in amplitude and duration. In contrast, most areas of the extended face processing system (medial orbito-frontal, anterior and posterior cingulate) had weak responses to unfamiliar and visually-familiar faces, but were highly tuned and exhibited prolonged responses to personally-familiar faces. This indicates that the neural processing of different types of familiar faces not only differs in degree, but is probably mediated by qualitatively distinct mechanisms. PMID:24130761

  19. Charge carrier tuning of mid-infrared plasmonic devices

    NASA Astrophysics Data System (ADS)

    Anglin, Kevin

    There is currently a wide variety of passive plasmonic technologies, with applications in the fields of sensing, security, and optical interconnects and computing. Development of a rapidly and broadly tunable plasmonic device would be an enabling technology, giving active control over these traditionally passive devices. The free charge carrier concentration directly affects the dielectric permittivity of a semiconductor, which in turn determines the plasmonic resonance. Metal-oxide-semiconductor capacitors using n-type substrates permit the modulation of free charge carriers in a semiconductor by applying a bias. In this study, MOS-capacitors were fabricated with an extraordinary optical transmission gratings built into the top gate. Tuning of the optical resonance of an EOT spectrum is shown applying a reverse bias across the semiconductor. The oxide layer used was hafnium dioxide, grown by atomic layer deposition. The electrical properties of the hafnia were studied in order to maximize the capabilities of this design. The samples were processed using standard photolithography and wet etching techniques, and characterized by optical microscopy, probe testing, and transmission spectroscopy. Resonant tuning of 30 nm has been demonstrated. The maximum depletion width in the semiconductor limited the effect and prohibited broader tuning.

  20. Filter parameter tuning analysis for operational orbit determination support

    NASA Technical Reports Server (NTRS)

    Dunham, J.; Cox, C.; Niklewski, D.; Mistretta, G.; Hart, R.

    1994-01-01

    The use of an extended Kalman filter (EKF) for operational orbit determination support is being considered by the Goddard Space Flight Center (GSFC) Flight Dynamics Division (FDD). To support that investigation, analysis was performed to determine how an EKF can be tuned for operational support of a set of earth-orbiting spacecraft. The objectives of this analysis were to design and test a general purpose scheme for filter tuning, evaluate the solution accuracies, and develop practical methods to test the consistency of the EKF solutions in an operational environment. The filter was found to be easily tuned to produce estimates that were consistent, agreed with results from batch estimation, and compared well among the common parameters estimated for several spacecraft. The analysis indicates that there is not a sharply defined 'best' tunable parameter set, especially when considering only the position estimates over the data arc. The comparison of the EKF estimates for the user spacecraft showed that the filter is capable of high-accuracy results and can easily meet the current accuracy requirements for the spacecraft included in the investigation. The conclusion is that the EKF is a viable option for FDD operational support.

  1. Tuning nanoparticle structure and surface strain for catalysis optimization.

    PubMed

    Zhang, Sen; Zhang, Xu; Jiang, Guangming; Zhu, Huiyuan; Guo, Shaojun; Su, Dong; Lu, Gang; Sun, Shouheng

    2014-05-28

    Controlling nanoparticle (NP) surface strain, i.e. compression (or stretch) of surface atoms, is an important approach to tune NP surface chemistry and to optimize NP catalysis for chemical reactions. Here we show that surface Pt strain in the core/shell FePt/Pt NPs with Pt in three atomic layers can be rationally tuned via core structural transition from cubic solid solution [denoted as face centered cubic (fcc)] structure to tetragonal intermetallic [denoted as face centered tetragonal (fct)] structure. The high activity observed from the fct-FePt/Pt NPs for oxygen reduction reaction (ORR) is due to the release of the overcompressed Pt strain by the fct-FePt as suggested by quantum mechanics-molecular mechanics (QM-MM) simulations. The Pt strain effect on ORR can be further optimized when Fe in FePt is partially replaced by Cu. As a result, the fct-FeCuPt/Pt NPs become the most efficient catalyst for ORR and are nearly 10 times more active in specific activity than the commercial Pt catalyst. This structure-induced surface strain control opens up a new path to tune and optimize NP catalysis for ORR and many other chemical reactions.

  2. Giant resonance tuning of micro and nanomechanical oscillators

    NASA Astrophysics Data System (ADS)

    Vitorino, Miguel V.; Carpentier, Simon; Panzarella, Alain; Rodrigues, Mario S.; Costa, Luca

    2015-01-01

    We present a method to tune the resonance frequency and the Q-factor of micro and nano-metric mechanical oscillators. A counteracting loop drives a capacitive force applied to the oscillator. The proportional and differential gains are used to shift the resonance frequency up to 75% and to tune the Q-factor of the oscillator, by changing its effective stiffness and damping ratio. The oscillator position is monitored in a large bandwidth with a fiber-optic based interferometer. We applied this simple operational scheme with different oscillators for modifying easily their dynamical properties. Compared to alternative methods requiring external fields, our method can either increase or decrease the resonance frequency in a frequency range much more extended. This opens up a wide range of applications, from force sensors with extremely low elastic constants but high quality factor to tunable energy harvesters or to high-frequency tuning of radio frequency filters. The control scheme can work in different media, and is then suitable to be applied to biological sensors and actuators.

  3. Lightweight linear alternators with and without capacitive tuning

    NASA Technical Reports Server (NTRS)

    Niedra, Janis M.

    1993-01-01

    Permanent magnet excited linear alternators rated tens of kW and coupled to free-piston Stirling engines are presently viewed as promising candidates for long term generation of electric power in both space and terrestrial applications. Series capacitive cancellation of the internal inductive reactance of such alternators was considered a viable way to both increase power extraction and to suppress unstable modes of the thermodynamic oscillation. Idealized toroidal and cylindrical alternator geometries are used for a comparative study of the issues of specific mass and capacitive tuning, subject to stability criteria. The analysis shows that the stator mass of an alternator designed to be capacitively tuned is always greater than the minimum achievable stator mass of an alternator designed with no capacitors, assuming equal utilization of materials ratings and the same frequency and power to a resistive load. This conclusion is not substantially altered when the usually lesser masses of the magnets and of any capacitors are added. Within the reported stability requirements and under circumstances of normal materials ratings, this study finds no clear advantage to capacitive tuning. Comparative plots of the various constituent masses are presented versus the internal power factor taken as a design degree of freedom. The explicit formulas developed for stator core, coil, capacitor, and magnet masses and for the degree of magnet utilization provide useful estimates of scaling effects.

  4. Symmetry tuning for ignition capsules via the symcap technique

    SciTech Connect

    Kyrala, G. A.; Kline, J. L.; Dixit, S.; Glenzer, S.; Kalantar, D.; Bradley, D.; Izumi, N.; Meezan, N.; Landen, O.; Callahan, D.; Weber, S. V.; Holder, J. P.; Glenn, S.; Edwards, M. J.; Koch, J.; Suter, L. J.; Haan, S. W.; Town, R. P. J.; Michel, P.; Jones, O.

    2011-05-15

    Symmetry of an implosion is crucial to get ignition successfully. Several methods of control and measurement of symmetry have been applied on many laser systems with mm size hohlraums and ns pulses. On the National Ignition Facility [Moses et al., Phys. Plasmas 16, 041006 (2009)] we have large hohlraums of cm scale, long drive pulses of 10 s of ns, and a large number of beams with the option to tune their wavelengths. Here we discuss how we used the x-ray self-emission from imploding surrogates to ignition capsules (symcaps) to measure the symmetry of the implosion. We show that symcaps are good surrogates for low order symmetry, though having lower sensitivity to distortions than ignition capsules. We demonstrate the ability to transfer energy between laser beams in a gas-filled hohlraum using wavelength tuning, successfully tuning the lowest order symmetry of the symcaps in different size hohlraums at different laser energies within the specification established by calculations for successful ignition.

  5. Tuning photonic bands in plasma metallic photonic crystals

    NASA Astrophysics Data System (ADS)

    Chaudhari, Mayank Kumar; Chaudhari, Sachin

    2016-11-01

    Introducing plasma in the background provides additional degrees of freedom for tuning dispersion curves of photonic crystals. 2D photonic crystals in triangular lattice arrangements offer more global bandgap regions and thus are of more interest for various applications. The dispersion characteristics of a two-dimensional plasma metallic photonic crystal (PMPC) in square as well as triangular lattice arrangements have been analyzed in this paper using the orthogonal finite difference time domain method. The dispersion characteristics of PMPCs for the range of r/a ratios and plasma frequencies for triangular lattice configuration have been analyzed. On introducing plasma in the background, the photonic bands of PMPC are shifted towards higher normalized frequencies. This shift is more for lower bands and increases with plasma frequency. The cut-off frequency was observed for both TE and TM polarizations in PMPC and showed strong dependence on r/a ratio as well as plasma frequency. Photonic bandgaps of PMPC may be tuned by controlling plasma parameters, giving opportunity for utilizing these PMPC structures for various applications such as fine-tuning cavities for enhanced light-matter interaction, plasmonic waveguides, and Gyrotron cavities.

  6. An improved auto-tuning scheme for PID controllers.

    PubMed

    Dey, Chanchal; Mudi, Rajani K

    2009-10-01

    An improved auto-tuning scheme is proposed for Ziegler-Nichols (ZN) tuned PID controllers (ZNPIDs), which usually provide excessively large overshoots, not tolerable in most of the situations, for high-order and nonlinear processes. To overcome this limitation ZNPIDs are upgraded by some easily interpretable heuristic rules through an online gain modifying factor defined on the instantaneous process states. This study is an extension of our earlier work [Mudi RK., Dey C. Lee TT. An improved auto-tuning scheme for PI controllers. ISA Trans 2008; 47: 45-52] to ZNPIDs, thereby making the scheme suitable for a wide range of processes and more generalized too. The proposed augmented ZNPID (AZNPID) is tested on various high-order linear and nonlinear dead-time processes with improved performance over ZNPID, refined ZNPID (RZNPID), and other schemes reported in the literature. Stability issues are addressed for linear processes. Robust performance of AZNPID is observed while changing its tunable parameters as well as the process dead-time. The proposed scheme is also implemented on a real time servo-based position control system.

  7. Large-scale self-tuning solid-state kinetic energy harvester

    NASA Astrophysics Data System (ADS)

    Pletner, Baruch; Swan, Lukas; Wettels, Nicholas; Joseph, Alain

    2012-04-01

    In recent years there has been a strong emphasis on kinetic (vibration) energy harvesting using smart structure technology. This emphasis has been driven in large part by industry demand for powering sensors and wireless telemetry of sensor data in places into which running power and data cables is difficult or impossible. Common examples are helicopter drive shafts and other rotating equipment. In many instances, available space in these locations is highly limited, resulting in a trend for miniaturization of kinetic energy harvesters. While in some cases size limitations are dominant, in other cases large and even very large harvesters are possible and even desirable since they may produce significantly more power. Examples of large-scale energy harvesting include geomatics, which is the discipline of gathering, storing, processing, and delivering spatially referenced information on vast scales. Geomatics relies on suites of various sensors and imaging devices such as meteorological sensors, seismographs, high-resolution cameras, and LiDAR's. These devices may be stationed for prolonged periods of time in remote and poorly accessible areas and are required to operate continuously over prolonged periods of time. In other cases, sensing and imaging equipment may be mounted on land, sea, or airborne platforms and expected to operate for many hours on its own power. Providing power to this equipment constitutes a technological challenge. Other cases may include commercial buildings, unmanned powered gliders and more. Large scale kinetic energy harvesting thus constitutes a paradigm shift in the approach to kinetic energy harvesting as a whole and as often happens it poses its own unique technological challenges. Primarily these challenges fall into two categories: the cost-effective manufacturing of large and very large scale transducing elements based on smart structure technology and the continuous optimization (tuning) of these transducers for various operating

  8. Integrated tuning fork nanocavity optomechanical transducers with high f M Q M product and stress-engineered frequency tuning

    NASA Astrophysics Data System (ADS)

    Zhang, R.; Ti, C.; Davanço, M. I.; Ren, Y.; Aksyuk, V.; Liu, Y.; Srinivasan, K.

    2015-09-01

    Cavity optomechanical systems are being widely developed for precision force and displacement measurements. For nanomechanical transducers, there is usually a trade-off between the frequency (fM) and quality factor (QM), which limits temporal resolution and sensitivity. Here, we present a monolithic cavity optomechanical transducer supporting both high fM and high QM. By replacing the common doubly clamped, Si3N4 nanobeam with a tuning fork geometry, we demonstrate devices with the fundamental f M ≈ 29 MHz and Q M ≈ 2.2 × 10 5 , corresponding to an fMQM product of 6.35 × 10 12 Hz , comparable to the highest values previously demonstrated for room temperature operation. This high fMQM product is partly achieved by engineering the stress of the tuning fork to be 3 times the residual film stress through clamp design, which results in an increase of fM up to 1.5 times. Simulations reveal that the tuning fork design simultaneously reduces the clamping, thermoelastic dissipation, and intrinsic material damping contributions to mechanical loss. This work may find application when both high temporal and force resolution are important, such as in compact sensors for atomic force microscopy.

  9. Evaluation of Sloped Bottom Tuned Liquid Damper for Reduction of Seismic Response of Tall Buildings

    NASA Astrophysics Data System (ADS)

    Patil, G. R.; Singh, K. D.

    2016-12-01

    Due to migration of people to urban area, high land costs and use of light weight materials modern buildings tend to be taller, lighter and flexible. These buildings possess low damping. This increases the possibility of failure during earthquake ground motion and also affect the serviceability during wind vibrations. Out of many available techniques today, to reduce the response of structure under dynamic loading, Tuned Liquid Damper (TLD) is a recent technique to mitigate seismic response. However TLD has been used to mitigate the wind induced structural vibrations. Flat bottom TLD gives energy back to the structure after event of dynamic loading and it is termed as beating. Beating affects the performance of TLD. Study attempts to analyze the effectiveness of sloped bottom TLD for reducing seismic vibrations of structure. Concept of equivalent flat bottom LD has been used to analyze sloped bottom TLD. Finite element method (EM) is used to model the structure and the liquid in the TLD. MATLAB code is developed to study the response of structure, the liquid sloshing in the tank and the coupled fluid-structure interaction. A ten storey two bay RC frame is analyzed for few inputs of ground motion. A sinusoidal ground motion corresponding to resonance condition with fundamental frequency of frame is analyzed. In the analysis the inherent damping of structure is not considered. Observations from the study shows that sloped bottom TLD uses less amount of liquid than flat bottom TLD. Also observed that efficiency of sloped bottom TLD can be improved if it is properly tuned.

  10. Coarse-fine adaptive tuned vibration absorber with high frequency resolution

    NASA Astrophysics Data System (ADS)

    Wang, Xi; Yang, Bintang; You, Jiaxin; Gao, Zhe

    2016-11-01

    The speed fluctuation of satellite-rotary-mechanisms causes vibration of slightly different frequencies. The critical requirements of satellites need a vibration control device with high frequency resolution to suppress the vibration. This paper presents a coarse-fine adaptive tuned vibration absorber (ATVA) with high frequency resolution. The coarse-fine ATVA which simultaneously satisfies the requirements of high resolution and relatively wide effective bandwidth is capable of tracking the variable exciting frequency adaptively to suppress the vibration of the primary system. The coarse-fine ATVA is divided into a coarse tuning segment and a fine tuning segment. The coarse tuning segment is used to tune the required natural frequency in a relatively wide effective bandwidth and the fine tuning segment can achieve precise tune in a tiny-scale bandwidth. The mathematical model of the coarse tuning and the fine tuning is proposed to design the parameters of the coarse-fine ATVA. The experimental test results indicate the coarse tuning bandwidth of the coarse-fine ATVA is 8.7 Hz to 29 Hz and the minimum resolution of the fine tuning is 0.05 Hz. Moreover, a significant vibration attenuation of 15dB is verified in the effective bandwidth.

  11. Noise reduction in a launch vehicle fairing using actively tuned loudspeakers.

    PubMed

    Kemp, Jonathan D; Clark, Robert L

    2003-04-01

    Loudspeakers tuned as optimal acoustic absorbers can significantly reduce damaging, low frequency, reverberant noise in a full-scale launch vehicle fairing. Irregular geometry, changing payloads, and the compliant nature of the fairing hinder effective implementation of a passively tuned loudspeaker. A method of tuning the loudspeaker dynamics in real time is required to meet the application requirements. Through system identification, the dynamics of the enclosure can be identified and used to tune the dynamics of the loudspeaker for reduction of targeted, high intensity, low-frequency modes that dominate the acoustic response in the fairing. A loudspeaker model with desired dynamics serves as the reference model in a control law designed to tune the dynamics of a non-ideal loudspeaker to act as an optimal tuned absorber. Experimental results indicate that a tuned loudspeaker placed in the nose cone of the fairing significantly reduces acoustic energy and verifies results calculated from the simulation.

  12. Design and Field Implementation of Auto Tuned Virtual Instrumentation Corrosion Controller

    NASA Astrophysics Data System (ADS)

    Gopalakrishnan, J.; Agnihotri, Ganga; Deshpande, D. M.

    2016-06-01

    Corrosion in underground metallic pipeline leads to leakage which is hazardous when oil/natural gas is transported. Rate of corrosion in metal pipeline can be controlled by impressing dc current to the gas pipeline and thereby making metal pipeline to act as cathode of corrosion cell. Proportional integral controllers are used in impressed current cathodic protection application; tuning of proportional and integral constants of these controllers requires expertise. Step open, step close and relay tuning methods are compared; relay tuning provided better results for cathodic protection application. Ziegler-Nichols tuning formulas are used to select tuning parameters based on loop response. Virtual instrumentation is used for design, development, testing and field implementation of auto tuned PI controller. Proposed auto tuned proportional integral impressed current cathodic protection controller precisely controls corrosion in pipeline by selecting optimum proportional and integral constants. Controller effectiveness is cross verified using electrical resistance probe.

  13. Design and Field Implementation of Auto Tuned Virtual Instrumentation Corrosion Controller

    NASA Astrophysics Data System (ADS)

    Gopalakrishnan, J.; Agnihotri, Ganga; Deshpande, D. M.

    2017-02-01

    Corrosion in underground metallic pipeline leads to leakage which is hazardous when oil/natural gas is transported. Rate of corrosion in metal pipeline can be controlled by impressing dc current to the gas pipeline and thereby making metal pipeline to act as cathode of corrosion cell. Proportional integral controllers are used in impressed current cathodic protection application; tuning of proportional and integral constants of these controllers requires expertise. Step open, step close and relay tuning methods are compared; relay tuning provided better results for cathodic protection application. Ziegler-Nichols tuning formulas are used to select tuning parameters based on loop response. Virtual instrumentation is used for design, development, testing and field implementation of auto tuned PI controller. Proposed auto tuned proportional integral impressed current cathodic protection controller precisely controls corrosion in pipeline by selecting optimum proportional and integral constants. Controller effectiveness is cross verified using electrical resistance probe.

  14. Design and tuning of standard additive model based fuzzy PID controllers for multivariable process systems.

    PubMed

    Harinath, Eranda; Mann, George K I

    2008-06-01

    This paper describes a design and two-level tuning method for fuzzy proportional-integral derivative (FPID) controllers for a multivariable process where the fuzzy inference uses the inference of standard additive model. The proposed method can be used for any n x n multi-input-multi-output process and guarantees closed-loop stability. In the two-level tuning scheme, the tuning follows two steps: low-level tuning followed by high-level tuning. The low-level tuning adjusts apparent linear gains, whereas the high-level tuning changes the nonlinearity in the normalized fuzzy output. In this paper, two types of FPID configurations are considered, and their performances are evaluated by using a real-time multizone temperature control problem having a 3 x 3 process system.

  15. End-loaded crossed-slot radiating elements

    NASA Technical Reports Server (NTRS)

    Manshadi, F.

    1991-01-01

    Three cavity-backed crossed-slot antenna configurations are described that offer simple design, easy frequency tuning, light weight, low loss, and low cost. These antennas are designed for mobile satellite (MSAT) vehicle phased-array applications. The slots in these antennas are end-loaded. The end loading makes the slots effectively longer, and hence reduces their resonant frequency. Therefore, relatively small radiating elements can be achieved for large-angle-scanning phased-array antennas. These antennas have good RF characteristics and provide a relatively wide bandwidth without needing external tuning circuits for impedance matching. Measurements for the return loss and the far-field pattern of these antennas are presented.

  16. Systematic tuning of silicon Schottky barrier height by atomic interlayers with low electronegativities

    NASA Astrophysics Data System (ADS)

    Long, Wei

    The Schottky barrier height (SBH) is of great importance to the functionality of semiconductor devices, as it governs the carrier transport across the metal-semiconductor (MS) interface. The presence of the Fermi level (FL) pinning phenomena makes tuning the SBH a difficult goal to achieve. The technique of "partisan interlayer" (PI) was proposed recently to modify the SBH, where stable adsorbate-terminated semiconductor (ATS) surfaces were used to form SBs with subsequently applied metal. When elements with large electronegativities were used to form the ATS, the PI technique was effective in reducing the n-type SBH and increasing the p-type SBH, driven by the expected transfer of charge from the semiconductor to the adsorbates. In this thesis work, elements with electronegativities smaller than that of the semiconductor are used as surface termination. SBHs for Ag, Au and In on Si surfaces are found to increase for the n-type and decrease for the p-type interfaces, by as much as 0.25eV, when Ga, Mg and K are used to terminate the Si surfaces. The present results are thus in agreement with the expected charge transfers from elements with smaller electronegativities to silicon and illustrate the general validity of the PI technique. The chemical stability of these surfaces likely weakens the MS interaction and leads to the (partial) preservation of the surface dipole at the MS interface. However, large degrees of SBH inhomogeneity are observed for diodes on these surfaces, likely due to insufficient stability of these surfaces to completely withstand metal interaction. These results are discussed within the basic models of SBH formation and the implications of these results for SBH control of MS systems are also addressed.

  17. Mechanochemical tuning of myosin-I by the N-terminal region

    PubMed Central

    Greenberg, Michael J.; Lin, Tianming; Shuman, Henry; Ostap, E. Michael

    2015-01-01

    Myosins are molecular motors that generate force to power a wide array of motile cellular functions. Myosins have the inherent ability to change their ATPase kinetics and force-generating properties when they encounter mechanical loads; however, little is known about the structural elements in myosin responsible for force sensing. Recent structural and biophysical studies have shown that myosin-I isoforms, Myosin-Ib (Myo1b) and Myosin-Ic (Myo1c), have similar unloaded kinetics and sequences but substantially different responses to forces that resist their working strokes. Myo1b has the properties of a tension-sensing anchor, slowing its actin-detachment kinetics by two orders of magnitude with just 1 pN of resisting force, whereas Myo1c has the properties of a slow transporter, generating power without slowing under 1-pN loads that would stall Myo1b. To examine the structural elements that lead to differences in force sensing, we used single-molecule and ensemble kinetic techniques to show that the myosin-I N-terminal region (NTR) plays a critical role in tuning myosin-I mechanochemistry. We found that replacing the Myo1c NTR with the Myo1b NTR changes the identity of the primary force-sensitive transition of Myo1c, resulting in sensitivity to forces of <2 pN. Additionally, we found that the NTR plays an important role in stabilizing the post–power-stroke conformation. These results identify the NTR as an important structural element in myosin force sensing and suggest a mechanism for generating diversity of function among myosin isoforms. PMID:26056287

  18. The synthetic elements

    SciTech Connect

    Hoffman, D.C.

    1990-05-01

    Prior to 1940, the heaviest element known was uranium, discovered in 1789. Since that time the elements 93 through 109 have been synthesized and identified and the elements 43, 61, 85, and 87 which were missing form the periodic tables of the 1930's have been discovered. The techniques and problems involved in these discoveries and the placement of the transuranium elements in the periodic table will be discussed. The production and positive identification of elements heavier than Md (Z=101), which have very short half-lives and can only be produced an atom-at-a-time, are very difficult and there have been controversies concerning their discovery. Some of the new methods which have been developed and used in these studies will be described. The prospects for production of still heavier elements will be considered.

  19. Chemistry of superheavy elements.

    PubMed

    Schädel, Matthias

    2006-01-09

    The number of chemical elements has increased considerably in the last few decades. Most excitingly, these heaviest, man-made elements at the far-end of the Periodic Table are located in the area of the long-awaited superheavy elements. While physical techniques currently play a leading role in these discoveries, the chemistry of superheavy elements is now beginning to be developed. Advanced and very sensitive techniques allow the chemical properties of these elusive elements to be probed. Often, less than ten short-lived atoms, chemically separated one-atom-at-a-time, provide crucial information on basic chemical properties. These results place the architecture of the far-end of the Periodic Table on the test bench and probe the increasingly strong relativistic effects that influence the chemical properties there. This review is focused mainly on the experimental work on superheavy element chemistry. It contains a short contribution on relativistic theory, and some important historical and nuclear aspects.

  20. Design of a Four-Element, Hollow-Cube Corner Retroreflector for Satellites by use of a Genetic Algorithm.

    PubMed

    Minato, A; Sugimoto, N

    1998-01-20

    A four-element retroreflector was designed for satellite laser ranging and Earth-satellite-Earth laser long-path absorption measurement of the atmosphere. The retroreflector consists of four symmetrically located corner retroreflectors. Each retroreflector element has curved mirrors and tuned dihedral angles to correct velocity aberrations. A genetic algorithm was employed to optimize dihedral angles of each element and the directions of the four elements. The optimized four-element retroreflector has high reflectance with a reasonably broad angular coverage. It is also shown that the genetic algorithm is effective for optimizing optics with many parameters.

  1. Tuned range separated hybrid functionals for solvated low bandgap oligomers

    SciTech Connect

    Queiroz, Thiago B. de Kümmel, Stephan

    2015-07-21

    The description of charge transfer excitations has long been a challenge to time dependent density functional theory. The recently developed concept of “optimally tuned range separated hybrid (OT-RSH) functionals” has proven to describe charge transfer excitations accurately in many cases. However, describing solvated or embedded systems is yet a challenge. This challenge is not only computational but also conceptual, because the tuning requires identifying a specific orbital, typically the highest occupied one of the molecule under study. For solvated molecules, this orbital may be delocalized over the solvent. We here demonstrate that one way of overcoming this problem is to use a locally projected self-consistent field diagonalization on an absolutely localized molecular orbital expansion. We employ this approach to determine ionization energies and the optical gap of solvated oligothiophenes, i.e., paradigm low gap systems that are of relevance in organic electronics. Dioxane solvent molecules are explicitly represented in our calculations, and the ambiguities of straightforward parameter tuning in solution are elucidated. We show that a consistent estimate of the optimal range separated parameter (ω) at the limit of bulk solvation can be obtained by gradually extending the solvated system. In particular, ω is influenced by the solvent beyond the first coordination sphere. For determining ionization energies, a considerable number of solvent molecules on the first solvation shell must be taken into account. We demonstrate that accurately calculating optical gaps of solvated systems using OT-RSH can be done in three steps: (i) including the chemical environment when determining the range-separation parameter, (ii) taking into account the screening due to the solvent, and (iii) using realistic molecular geometries.

  2. Mobile Learning of Astronomy Through Apple's iTunes U

    NASA Astrophysics Data System (ADS)

    Wagner, Robert M.

    2017-01-01

    Students are using mobile devices such as smartphones and tablets increasingly for their education needs. For the past year and a half, a pilot project has been underway at Harrisburg Area Community College to teach a small number of classes using Apple's iTunes U app. As one of the six colleges and universities selected to pilot the iTunes U app before it was released in January of 2012, Harrisburg Area Community College has been significantly involved in mobile learning for a number of years. The author was able to offer an astronomy course with the initial release which now has nearly 70,000 subscribers around the world. Over the past few semesters, the course has been converted to be used with online credit courses at the college. Students can now complete the vast majority of their assignments on their iPad or iPhone. This allows the online student to not feel tied to their laptop or desktop computer as they can access and work on assignments wherever they might be. More of the course has been able to be moved to the iTunes U app each semester as updates are made to the app with the eventual goal to be able to have the entire course completed through a private course on the app. The flexibility of mobile learning allows for more students to be able to take the course without feeling tied down. Student response has been good. Many students like having the flexibility to be able to access course content on their phones at their convenience.

  3. Tuning magnetism by biaxial strain in native ZnO.

    PubMed

    Peng, Chengxiao; Wang, Yuanxu; Cheng, Zhenxiang; Zhang, Guangbiao; Wang, Chao; Yang, Gui

    2015-07-07

    Magnetic ZnO, one of the most important diluted magnetic semiconductors (DMS), has attracted great scientific interest because of its possible technological applications in optomagnetic devices. Magnetism in this material is usually delicately tuned by the doping level, dislocations, and local structures. The rational control of magnetism in ZnO is a highly attractive approach for practical applications. Here, the tuning effect of biaxial strain on the d(0) magnetism of native imperfect ZnO is demonstrated through first-principles calculations. Our calculation results show that strain conditions have little effect on the defect formation energy of Zn and O vacancies in ZnO, but they do affect the magnetism significantly. For a cation vacancy, increasing the compressive strain will obviously decrease its magnetic moment, while tensile strain cannot change the moment, which remains constant at 2 μB. For a singly charged anion vacancy, however, the dependence of the magnetic moment on strain is opposite to that of the Zn vacancy. Furthermore, the ferromagnetic state is always present, irrespective of the strain type, for ZnO with two zinc vacancies, 2VZns. A large tensile strain is favorable for improving the Curie temperature and realizing room temperature ferromagnetism for ZnO-based native semiconductors. For ZnO with two singly charged oxygen vacancies, 2Vs, no ferromagnetic ordering can be observed. Our work points the way to the rational design of materials beyond ZnO with novel non-intrinsic functionality by simply tuning the strain in a thin film form.

  4. Orientation-tuned surround suppression in mouse visual cortex.

    PubMed

    Self, Matthew W; Lorteije, Jeannette A M; Vangeneugden, Joris; van Beest, Enny H; Grigore, Mihaela E; Levelt, Christiaan N; Heimel, J Alexander; Roelfsema, Pieter R

    2014-07-09

    The firing rates of neurons in primary visual cortex (V1) are suppressed by large stimuli, an effect known as surround suppression. In cats and monkeys, the strength of suppression is sensitive to orientation; responses to regions containing uniform orientations are more suppressed than those containing orientation contrast. This effect is thought to be important for scene segmentation, but the underlying neural mechanisms are poorly understood. We asked whether it is possible to study these mechanisms in the visual cortex of mice, because of recent advances in technology for studying the cortical circuitry in mice. It is unknown whether neurons in mouse V1 are sensitive to orientation contrast. We measured the orientation selectivity of surround suppression in the different layers of mouse V1. We found strong surround suppression in layer 4 and the superficial layers, part of which was orientation tuned: iso-oriented surrounds caused more suppression than cross-oriented surrounds. Surround suppression was delayed relative to the visual response and orientation-tuned suppression was delayed further, suggesting two separate suppressive mechanisms. Previous studies proposed that surround suppression depends on the activity of inhibitory somatostatin-positive interneurons in the superficial layers. To test the involvement of the superficial layers we topically applied lidocaine. Silencing of the superficial layers did not prevent orientation-tuned suppression in layer 4. These results show that neurons in mouse V1, which lacks orientation columns, show orientation-dependent surround suppression in layer 4 and the superficial layers and that surround suppression in layer 4 does not require contributions from neurons in the superficial layers.

  5. FUEL ELEMENT INTERLOCKING ARRANGEMENT

    DOEpatents

    Fortescue, P.; Nicoll, D.

    1963-01-01

    This patent relates to a system for mutually interlocking a multiplicity of elongated, parallel, coextensive, upright reactor fuel elements so as to render a laterally selfsupporting bundle, while admitting of concurrent, selective, vertical withdrawal of a sizeable number of elements without any of the remaining elements toppling, Each element is provided with a generally rectangular end cap. When a rank of caps is aligned in square contact, each free edge centrally defines an outwardly profecting dovetail, and extremitally cooperates with its adjacent cap by defining a juxtaposed half of a dovetail- receptive mortise. Successive ranks are staggered to afford mating of their dovetails and mortises. (AEC)

  6. Tuning surface plasmons in graphene ribbons with liquid crystal layer

    NASA Astrophysics Data System (ADS)

    Reshetnyak, Viktor Yu.; Bunning, Timothy J.; Evans, Dean R.

    2016-09-01

    Surface plasmons in graphene possess stronger mode confinement and lower propagation loss. One way to excite the surface plasmons is placing a periodic array of graphene nano-ribbons on top of a dielectric substrate. However once the system is fabricated it is not possible to change its optical properties. Liquid crystals (LC) are a uniaxial medium with an optical axis easily controlled by external stimuli. We suggest tuning the surface plasmons in an array of graphene ribbons by placing a LC slab on top of the ribbons. A voltage applied to the LC layer shifts the graphene ribbons plasmonic notch and changes its depth.

  7. Investigation of earthquake factor for optimum tuned mass dampers

    NASA Astrophysics Data System (ADS)

    Nigdeli, Sinan Melih; Bekdaş, Gebrail

    2012-09-01

    In this study the optimum parameters of tuned mass dampers (TMD) are investigated under earthquake excitations. An optimization strategy was carried out by using the Harmony Search (HS) algorithm. HS is a metaheuristic method which is inspired from the nature of musical performances. In addition to the HS algorithm, the results of the optimization objective are compared with the results of the other documented method and the corresponding results are eliminated. In that case, the best optimum results are obtained. During the optimization, the optimum TMD parameters were searched for single degree of freedom (SDOF) structure models with different periods. The optimization was done for different earthquakes separately and the results were compared.

  8. Nitrogen-tuned transition metal Co adatom embedded graphene

    NASA Astrophysics Data System (ADS)

    Sun, Jiang; Qian, Jun; Zhai, Min; Liu, Feng; Qi, Chang; Shi, Xinzhi; Wang, Gaofeng; Xiong, Rui; Ye, Shuangli

    2015-10-01

    The distribution of Co in pristine and nitrogen-doped graphene is investigated. The coexistence of Co nanoparticles and Co2+ ions is formed by the deposition process. The distribution of Co can be tuned by nitrogen doping. Raman spectra reveal the presence of different defect types in samples. This result confirms that the surface state can be modified by nitrogen doping. Annealing process demonstrates that nitrogen doping favors a stable Co2+ ion-C network, which supports the geometric stability for the Co-graphene system. Therefore, nitrogen doping can offer an effective method to realize the TM-graphene system, which has potential applications in spintronic devices.

  9. Analysis of the tuning characteristics of microwave plasma source

    NASA Astrophysics Data System (ADS)

    Miotk, Robert; Jasiński, Mariusz; Mizeraczyk, Jerzy

    2016-04-01

    In this paper, we present an analysis of the tuning characteristics of waveguide-supplied metal-cylinder-based nozzleless microwave plasma source. This analysis has enabled to estimate the electron concentration ne and electron frequency collisions ν in the plasma generated in nitrogen and in a mixture of nitrogen and ethanol vapour. The parameters ne and ν are the basic quantities that characterize the plasma. The presented new plasma diagnostic method is particularly useful, when spectroscopic methods are useless. The presented plasma source is currently used in research of a hydrogen production from liquids.

  10. Strain tuning of topological band order in cubic semiconductors

    SciTech Connect

    Feng, wanxiang; Zhu, Wenguang; Weitering, Hanno; Stocks, George Malcolm; Yao, yugui; Xiao, Di

    2012-01-01

    We theoretically explore the possibility of tuning the topological order of cubic diamond/zinc-blende semi- conductors with external strain. Based on a simple tight-binding model, we analyze the evolution of the cubic semiconductor band structure under hydrostatic or biaxial lattice expansion, by which a generic guiding princi- ple is established that biaxial lattice expansion can induce a topological phase transition of small band-gap cubic semiconductors via a band inversion and symmetry breaking at point. Using density functional theory cal- culations, we demonstrate that a prototype topological trivial semiconductor, InSb, is converted to a nontrivial topological semiconductor with a 2% 3% biaxial lattice expansion.

  11. Photoluminescence excitation measurements using pressure-tuned laser diodes

    SciTech Connect

    Bercha, Artem; Ivonyak, Yurii; Mędryk, Radosław; Trzeciakowski, Witold A. Dybała, Filip; Piechal, Bernard

    2015-06-15

    Pressure-tuned laser diodes in external cavity were used as tunable sources for photoluminescence excitation (PLE) spectroscopy. The method was demonstrated in the 720 nm-1070 nm spectral range using a few commercial laser diodes. The samples for PLE measurements were quantum-well structures grown on GaAs and on InP. The method is superior to standard PLE measurements using titanium sapphire laser because it can be extended to any spectral range where anti-reflection coated laser diodes are available.

  12. Analysis of filter tuning techniques for sequential orbit determination

    NASA Technical Reports Server (NTRS)

    Lee, T.; Yee, C.; Oza, D.

    1995-01-01

    This paper examines filter tuning techniques for a sequential orbit determination (OD) covariance analysis. Recently, there has been a renewed interest in sequential OD, primarily due to the successful flight qualification of the Tracking and Data Relay Satellite System (TDRSS) Onboard Navigation System (TONS) using Doppler data extracted onboard the Extreme Ultraviolet Explorer (EUVE) spacecraft. TONS computes highly accurate orbit solutions onboard the spacecraft in realtime using a sequential filter. As the result of the successful TONS-EUVE flight qualification experiment, the Earth Observing System (EOS) AM-1 Project has selected TONS as the prime navigation system. In addition, sequential OD methods can be used successfully for ground OD. Whether data are processed onboard or on the ground, a sequential OD procedure is generally favored over a batch technique when a realtime automated OD system is desired. Recently, OD covariance analyses were performed for the TONS-EUVE and TONS-EOS missions using the sequential processing options of the Orbit Determination Error Analysis System (ODEAS). ODEAS is the primary covariance analysis system used by the Goddard Space Flight Center (GSFC) Flight Dynamics Division (FDD). The results of these analyses revealed a high sensitivity of the OD solutions to the state process noise filter tuning parameters. The covariance analysis results show that the state estimate error contributions from measurement-related error sources, especially those due to the random noise and satellite-to-satellite ionospheric refraction correction errors, increase rapidly as the state process noise increases. These results prompted an in-depth investigation of the role of the filter tuning parameters in sequential OD covariance analysis. This paper analyzes how the spacecraft state estimate errors due to dynamic and measurement-related error sources are affected by the process noise level used. This information is then used to establish

  13. Band gap tuning of nickelates for photovoltaic applications

    NASA Astrophysics Data System (ADS)

    Chang, Lei; Wang, Le; You, Lu; Zhou, Yang; Fang, Liang; Wang, Shiwei; Wang, Junling

    2016-11-01

    Hybrid perovskites have achieved tremendous success as a light absorber in solar cells during the past few years. However, the stability issue casts shadow on their practical applications. Perovskite oxides may offer an alternative. In this study, the metal-insulator transition in perovskite neodymium nickelates (NdNiO3) is systematically tuned by adjusting the oxygen partial pressure during film growth. Room temperature insulating films with different band gaps are obtained. Testing photovoltaic cells have been prepared by combining the nickelates with Nb-doped SrTiO3, and photovoltaic performance has been optimized. Our study offers a new route for designing novel photovoltaic materials.

  14. Anytime query-tuned kernel machine classifiers via Cholesky factorization

    NASA Technical Reports Server (NTRS)

    DeCoste, D.

    2002-01-01

    We recently demonstrated 2 to 64-fold query-time speedups of Support Vector Machine and Kernel Fisher classifiers via a new computational geometry method for anytime output bounds (DeCoste,2002). This new paper refines our approach in two key ways. First, we introduce a simple linear algebra formulation based on Cholesky factorization, yielding simpler equations and lower computational overhead. Second, this new formulation suggests new methods for achieving additional speedups, including tuning on query samples. We demonstrate effectiveness on benchmark datasets.

  15. Tuning the cosmological constant, broken scale invariance, unitarity

    SciTech Connect

    Förste, Stefan; Manz, Paul

    2016-06-10

    We study gravity coupled to a cosmological constant and a scale but not conformally invariant sector. In Minkowski vacuum, scale invariance is spontaneously broken. We consider small fluctuations around the Minkowski vacuum. At the linearised level we find that the trace of metric perturbations receives a positive or negative mass squared contribution. However, only for the Fierz-Pauli combination the theory is free of ghosts. The mass term for the trace of metric perturbations can be cancelled by explicitly breaking scale invariance. This reintroduces fine-tuning. Models based on four form field strength show similarities with explicit scale symmetry breaking due to quantisation conditions.

  16. A Micromechanical Contribution to Cochlear Tuning and Tonotopic Organization

    NASA Astrophysics Data System (ADS)

    Holton, Thomas; Hudspeth, A. J.

    1983-11-01

    The response properties of hair cells and nerve fibers in the alligator lizard cochlea are frequency selective and tonotopically organized with longitudinal position in the organ. The lengths of the hair-cell hair bundles also vary monotonically with longitudinal position. In this study, quantitative measurements were made of the motion of individual hair bundles in an excised preparation of the cochlea stimulated at auditory frequencies. The angular displacement of hair bundles is frequency selective and tonotopically organized, demonstrating the existence of a micromechanical tuning mechanism.

  17. Electric field engineering using quantum-size-effect-tuned heterojunctions

    NASA Astrophysics Data System (ADS)

    Adinolfi, V.; Ning, Z.; Xu, J.; Masala, S.; Zhitomirsky, D.; Thon, S. M.; Sargent, E. H.

    2013-07-01

    A quantum junction solar cell architecture was recently reported that employs colloidal quantum dots (CQDs) on each side of the p-n junction. This architecture extends the range of design opportunities for CQD photovoltaics, since the bandgap can be tuned across the light-absorbing semiconductor layer via control over CQD size, employing solution-processed, room-temperature fabricated materials. We exploit this feature by designing and demonstrating a field-enhanced heterojunction architecture. We optimize the electric field profile within the solar cell through bandgap engineering, thereby improving carrier collection and achieving an increased open circuit voltage, resulting in a 12% improvement in power conversion efficiency.

  18. Optimal Tuning for Disturbance Suppression Mechanism for Model Predictive Control

    NASA Astrophysics Data System (ADS)

    Tange, Yoshio; Nakazawa, Chikashi

    Disturbance suppression is one of most required performances in process control. We recently proposed a new disturbance suppression mechanism applicable for model predictive control in order to enhance disturbance suppression performance for ramp-like disturbances. The proposed method utilized the prediction error of controlled values and generates a disturbance compensation signal by a constant gain feedback. In this paper, we propose an improved version of the disturbance suppression mechanism by applying a low-pass filter and parameter tuning methods by which we can make the mechanism more tolerant to various disturbances such as ramp, step, and other supposable ones. We also show numerical simulation results with an oil distillation tower plant.

  19. Reversible tuning of photonic crystal cavities using photochromic thin films

    NASA Astrophysics Data System (ADS)

    Sridharan, Deepak; Waks, Edo; Solomon, Glenn; Fourkas, John T.

    2010-04-01

    We demonstrate reversible tuning of a photonic crystal cavity resonance using a thin photochromic film composed of spiropyran and polymethylmethacrylate that serves as a photosensitive cladding layer. Exposure of spiropyran to ultraviolet light results in smooth redshift of the cavity resonance that can be reversed by exposure to visible wavelength light. We achieve a reversible resonance shift of up to 2.7 nm, which can be performed locally on individual cavities. The resonance shift over multiple successive UV and visible light exposures is studied to determine the repeatability of the photochromic film.

  20. The spiral staircase: Tonotopic microstructure and cochlear tuning

    NASA Astrophysics Data System (ADS)

    Shera, Christopher A.

    2015-12-01

    Cochlear frequency-position maps are predicted to manifest a staircase-like structure comprising plateaus of nearly constant characteristic frequency separated by abrupt discontinuities. The height and width of the stair steps are determined by parameters of cochlear frequency tuning and vary with location in the cochlea. The step height is approximately equal to the critical band, and the step width matches that of the spatial excitation pattern produced by a low-level pure tone. Stepwise tonotopy is an emergent property arising from wave reflection and interference within the cochlea. Possible relationships between the microstructure of the cochlear map and the tiered tonotopy observed in the inferior colliculus are explored.

  1. Energy Scaling of Spin Tune due to RHIC Snakes

    SciTech Connect

    MacKay,W.W.

    2009-01-02

    For a ring like RHIC with two full Siberian snakes on opposite sides of the ring, the spin tune for a flat orbit will be 1/2 if the snake rotation axes are perpendicular, {Delta}{phi} = {phi}{sub 9}-{phi}{sub 3} = {pi}/2. Here {phi}{sup 9} and {phi}{sub 3} are respectively the direction of the rotation axes of the 9 o'clock and 3 o'clock snakes relative to the design trajectory as shown in Figure 1. If the two snakes are slightly detuned by the same amount such that the rotation axes are no longer perpendicular, then the deviation of the closed-orbit spin tune {nu}{sub 0} from 1/2 is given by {Delta}{nu}{sub 0} {approx_equal} ({Delta}{mu}){sup 2}/4{pi} cosG{gamma}{pi} - 2{Delta}{phi}/{pi} {approx_equal} 2{Delta}{phi}/180{sup o} with G{gamma} at a half integer, and where {Delta}{mu} is the deviation of snake rotation angle from 180{sup o}. It should be noted that there is a sign ambiguity in {Delta}{mu}{sub 0} since a spin tune of 0.495 is also a spin tune of 0.505, depending on the direction taken along the stable spin axis. In order to understand the effect of energy scaling on the snake axis direction, I have integrated the trajectory and spin rotation through a model of a RHIC snake (bi9-snk7) and found the energy (U) dependence of the snake axis angle {phi}{sub 9} and rotation angle {mu} as shown. A {approx_equal} p{sup -2} scaling of errors is typical in helical snakes. To first order, the orbit excursion drops as p{sup -1} and the spin precessions about transverse fields increase as {gamma} giving an approximate cancellation with energy, so we do not expect much change during the field ramp. The next order term which comes in is primarily proportional to p{sup -2}; although naively one might expect a slight effect inversely proportional to the velocity since {gamma}/p {proportional_to} c/{nu} {approx_equal} 1 + 1/2{gamma}{sup 2}.

  2. Microwave absorption by nanoresonator vibrations tuned with surface modification

    NASA Astrophysics Data System (ADS)

    Krivosudský, Ondrej; Cifra, Michal

    2016-08-01

    Elucidating the physical and chemical parameters that govern viscous damping of nanoresonator vibrations and their coupling to electromagnetic radiation is important for understanding the behavior of matter at the nanoscale. Here we develop an analytical model of microwave absorption of a longitudinally oscillating and electrically polar rod-like nanoresonator embedded in a viscoelastic fluid. We show that the slip length, which can be tuned via surface modifications, controls the quality factor and coupling of nanoresonator vibration modes to microwave radiation. We demonstrate that the larger slip length brings the sharper frequency response of the nanoresonator vibration and electromagnetic absorption. Our findings contribute to design guidelines of fluid embedded nanoresonator devices.

  3. General self-tuning solutions and no-go theorem

    SciTech Connect

    Förste, Stefan; Kim, Jihn E.; Lee, Hyun Min E-mail: jihnekim@gmail.com

    2013-03-01

    We consider brane world models with one extra dimension. In the bulk there is in addition to gravity a three form gauge potential or equivalently a scalar (by generalisation of electric magnetic duality). We find classical solutions for which the 4d effective cosmological constant is adjusted by choice of integration constants. No go theorems for such self-tuning mechanism are circumvented by unorthodox Lagrangians for the three form respectively the scalar. It is argued that the corresponding effective 4d theory always includes tachyonic Kaluza-Klein excitations or ghosts. Known no go theorems are extended to a general class of models with unorthodox Lagrangians.

  4. Tuning nonlinear optical absorption properties of WS2 nanosheets

    NASA Astrophysics Data System (ADS)

    Long, Hui; Tao, Lili; Tang, Chun Yin; Zhou, Bo; Zhao, Yuda; Zeng, Longhui; Yu, Siu Fung; Lau, Shu Ping; Chai, Yang; Tsang, Yuen Hong

    2015-10-01

    To control the optical properties of two-dimensional (2D) materials is a long-standing goal, being of both fundamental and technological significance. Tuning nonlinear optical absorption (NOA) properties of 2D transition metal dichalcogenides in a cost effective way has emerged as an important research topic because of its possibility to custom design NOA properties, implying enormous applications including optical computers, communications, bioimaging, and so on. In this study, WS2 with different size and thickness distributions was fabricated. The results demonstrate that both NOA onset threshold, FON, and optical limiting threshold, FOL, of WS2 under the excitation of a nanosecond pulsed laser can be tuned over a wide range by controlling its size and thickness. The FON and FOL show a rapid decline with the decrease of size and thickness. Due to the edge and quantum confinement effect, WS2 quantum dots (2.35 nm) exhibit the lowest FON (0.01 J cm-2) and FOL (0.062 J cm-2) among all the samples, which are comparable to the lowest threshold achieved in graphene based materials, showing great potential as NOA materials with tunable properties.To control the optical properties of two-dimensional (2D) materials is a long-standing goal, being of both fundamental and technological significance. Tuning nonlinear optical absorption (NOA) properties of 2D transition metal dichalcogenides in a cost effective way has emerged as an important research topic because of its possibility to custom design NOA properties, implying enormous applications including optical computers, communications, bioimaging, and so on. In this study, WS2 with different size and thickness distributions was fabricated. The results demonstrate that both NOA onset threshold, FON, and optical limiting threshold, FOL, of WS2 under the excitation of a nanosecond pulsed laser can be tuned over a wide range by controlling its size and thickness. The FON and FOL show a rapid decline with the decrease of size

  5. Organization and trade-off of spectro-temporal tuning properties of duration-tuned neurons in the mammalian inferior colliculus

    PubMed Central

    Morrison, James A.; Farzan, Faranak; Fremouw, Thane; Sayegh, Riziq; Covey, Ellen

    2014-01-01

    Neurons throughout the mammalian central auditory pathway respond selectively to stimulus frequency and amplitude, and some are also selective for stimulus duration. First found in the auditory midbrain or inferior colliculus (IC), these duration-tuned neurons (DTNs) provide a potential neural mechanism for encoding temporal features of sound. In this study, we investigated how having an additional neural response filter, one selective to the duration of an auditory stimulus, influences frequency tuning and neural organization by recording single-unit responses and measuring the dorsal-ventral position and spectral-temporal tuning properties of auditory DTNs from the IC of the awake big brown bat (Eptesicus fuscus). Like other IC neurons, DTNs were tonotopically organized and had either V-shaped, U-shaped, or O-shaped frequency tuning curves (excitatory frequency response areas). We hypothesized there would be an interaction between frequency and duration tuning in DTNs, as electrical engineering theory for resonant filters dictates a trade-off in spectral-temporal resolution: sharp tuning in the frequency domain results in poorer resolution in the time domain and vice versa. While the IC is a more complex signal analyzer than an electrical filter, a similar operational trade-off could exist in the responses of DTNs. Our data revealed two patterns of spectro-temporal sensitivity and spatial organization within the IC: DTNs with sharp frequency tuning and broad duration tuning were located in the dorsal IC, whereas cells with wide spectral tuning and narrow temporal tuning were found in the ventral IC. PMID:24572091

  6. A tuning algorithm for model predictive controllers based on genetic algorithms and fuzzy decision making.

    PubMed

    van der Lee, J H; Svrcek, W Y; Young, B R

    2008-01-01

    Model Predictive Control is a valuable tool for the process control engineer in a wide variety of applications. Because of this the structure of an MPC can vary dramatically from application to application. There have been a number of works dedicated to MPC tuning for specific cases. Since MPCs can differ significantly, this means that these tuning methods become inapplicable and a trial and error tuning approach must be used. This can be quite time consuming and can result in non-optimum tuning. In an attempt to resolve this, a generalized automated tuning algorithm for MPCs was developed. This approach is numerically based and combines a genetic algorithm with multi-objective fuzzy decision-making. The key advantages to this approach are that genetic algorithms are not problem specific and only need to be adapted to account for the number and ranges of tuning parameters for a given MPC. As well, multi-objective fuzzy decision-making can handle qualitative statements of what optimum control is, in addition to being able to use multiple inputs to determine tuning parameters that best match the desired results. This is particularly useful for multi-input, multi-output (MIMO) cases where the definition of "optimum" control is subject to the opinion of the control engineer tuning the system. A case study will be presented in order to illustrate the use of the tuning algorithm. This will include how different definitions of "optimum" control can arise, and how they are accounted for in the multi-objective decision making algorithm. The resulting tuning parameters from each of the definition sets will be compared, and in doing so show that the tuning parameters vary in order to meet each definition of optimum control, thus showing the generalized automated tuning algorithm approach for tuning MPCs is feasible.

  7. The Elements Drawing.

    ERIC Educational Resources Information Center

    Dkeidek, Iyad M.

    2003-01-01

    Presents an educational game designed for first- or second-year high school students who have already studied themes related to the periodic table elements, such as their symbols, electronic configurations, properties, and uses. The game is designed to help students learn the symbols of the elements and their properties or uses in a fun, engaging…

  8. Proceedings of transuranium elements

    SciTech Connect

    Not Available

    1992-01-01

    The identification of the first synthetic elements was established by chemical evidence. Conclusive proof of the synthesis of the first artificial element, technetium, was published in 1937 by Perrier and Segre. An essential aspect of their achievement was the prediction of the chemical properties of element 43, which had been missing from the periodic table and which was expected to have properties similar to those of manganese and rhenium. The discovery of other artificial elements, astatine and francium, was facilitated in 1939-1940 by the prediction of their chemical properties. A little more than 50 years ago, in the spring of 1940, Edwin McMillan and Philip Abelson synthesized element 93, neptunium, and confirmed its uniqueness by chemical means. On August 30, 1940, Glenn Seaborg, Arthur Wahl, and the late Joseph Kennedy began their neutron irradiations of uranium nitrate hexahydrate. A few months later they synthesized element 94, later named plutonium, by observing the alpha particles emitted from uranium oxide targets that had been bombarded with deuterons. Shortly thereafter they proved that is was the second transuranium element by establishing its unique oxidation-reduction behavior. The symposium honored the scientists and engineers whose vision and dedication led to the discovery of the transuranium elements and to the understanding of the influence of 5f electrons on their electronic structure and bonding. This volume represents a record of papers presented at the symposium.

  9. Movies and Literary Elements.

    ERIC Educational Resources Information Center

    Keller, Rodney D.

    Showing ten-minute movie clips can be an effective way to motivate students to read literature and to teach elements of fiction, namely plot, character, setting, symbol, irony, and theme. A clip from "And Then There Were None" may be used to teach various elements of plot, including conflict and the four types of conflict (man vs. man,…

  10. Elemental Food for Thought

    ERIC Educational Resources Information Center

    Cady, Susan

    2005-01-01

    One of the first tasks students learn in chemistry is to pronounce and spell the names of elements and learn their corresponding chemical symbols. Repetitive oral recitation is commonly used to learn this information, but games and puzzles can make this task creative, variable, and fun. Elemental Food for Thought is a puzzlelike activity that…

  11. Fine-tuning the onset of myogenesis by homeobox proteins that interact with the Myf5 limb enhancer.

    PubMed

    Daubas, Philippe; Duval, Nathalie; Bajard, Lola; Langa Vives, Francina; Robert, Benoît; Mankoo, Baljinder S; Buckingham, Margaret

    2015-11-04

    Skeletal myogenesis in vertebrates is initiated at different sites of skeletal muscle formation during development, by activation of specific control elements of the myogenic regulatory genes. In the mouse embryo, Myf5 is the first myogenic determination gene to be expressed and its spatiotemporal regulation requires multiple enhancer sequences, extending over 120 kb upstream of the Mrf4-Myf5 locus. An enhancer, located at -57/-58 kb from Myf5, is responsible for its activation in myogenic cells derived from the hypaxial domain of the somite, that will form limb muscles. Pax3 and Six1/4 transcription factors are essential activators of this enhancer, acting on a 145-bp core element. Myogenic progenitor cells that will form the future muscle masses of the limbs express the factors necessary for Myf5 activation when they delaminate from the hypaxial dermomyotome and migrate into the forelimb bud, however they do not activate Myf5 and the myogenic programme until they have populated the prospective muscle masses. We show that Msx1 and Meox2 homeodomain-containing transcription factors bind in vitro and in vivo to specific sites in the 145-bp element, and are implicated in fine-tuning activation of Myf5 in the forelimb. Msx1, when bound between Pax and Six sites, prevents the binding of these key activators, thus inhibiting transcription of Myf5 and consequent premature myogenic differentiation. Meox2 is required for Myf5 activation at the onset of myogenesis via direct binding to other homeodomain sites in this sequence. Thus, these homeodomain factors, acting in addition to Pax3 and Six1/4, fine-tune the entry of progenitor cells into myogenesis at early stages of forelimb development.

  12. Timing matters: tuning the mechanics of a muscle-tendon unit by adjusting stimulation phase during cyclic contractions.

    PubMed

    Sawicki, Gregory S; Robertson, Benjamin D; Azizi, Emanuel; Roberts, Thomas J

    2015-10-01

    A growing body of research on the mechanics and energetics of terrestrial locomotion has demonstrated that elastic elements acting in series with contracting muscle are critical components of sustained, stable and efficient gait. Far fewer studies have examined how the nervous system modulates muscle-tendon interaction dynamics to optimize 'tuning' or meet varying locomotor demands. To explore the fundamental neuromechanical rules that govern the interactions between series elastic elements (SEEs) and contractile elements (CEs) within a compliant muscle-tendon unit (MTU), we used a novel work loop approach that included implanted sonomicrometry crystals along muscle fascicles. This enabled us to decouple CE and SEE length trajectories when cyclic strain patterns were applied to an isolated plantaris MTU from the bullfrog (Lithobates catesbeianus). Using this approach, we demonstrate that the onset timing of muscle stimulation (i.e. stimulation phase) that involves a symmetrical MTU stretch-shorten cycle during active force production results in net zero mechanical power output, and maximal decoupling of CE and MTU length trajectories. We found it difficult to 'tune' the muscle-tendon system for strut-like isometric force production by adjusting stimulation phase only, as the zero power output condition involved significant positive and negative mechanical work by the CE. A simple neural mechanism - adjusting muscle stimulation phase - could shift an MTU from performing net zero to net positive (energy producing) or net negative (energy absorbing) mechanical work under conditions of changing locomotor demand. Finally, we show that modifications to the classical work loop paradigm better represent in vivo muscle-tendon function during locomotion.

  13. A complex carotenoid palette tunes avian colour vision

    PubMed Central

    Toomey, Matthew B.; Collins, Aaron M.; Frederiksen, Rikard; Cornwall, M. Carter; Timlin, Jerilyn A.; Corbo, Joseph C.

    2015-01-01

    The brilliantly coloured cone oil droplets of the avian retina function as long-pass cut-off filters that tune the spectral sensitivity of the photoreceptors and are hypothesized to enhance colour discrimination and improve colour constancy. Although it has long been known that these droplets are pigmented with carotenoids, their precise composition has remained uncertain owing to the technical challenges of measuring these very small, dense and highly refractile optical organelles. In this study, we integrated results from high-performance liquid chromatography, hyperspectral microscopy and microspectrophotometry to obtain a comprehensive understanding of oil droplet carotenoid pigmentation in the chicken (Gallus gallus). We find that each of the four carotenoid-containing droplet types consists of a complex mixture of carotenoids, with a single predominant carotenoid determining the wavelength of the spectral filtering cut-off. Consistent with previous reports, we find that the predominant carotenoid type in the oil droplets of long-wavelength-sensitive, medium-wavelength-sensitive and short-wavelength-sensitive type 2 cones are astaxanthin, zeaxanthin and galloxanthin, respectively. In addition, the oil droplet of the principal member of the double cone contains a mixture of galloxanthin and two hydroxycarotenoids (lutein and zeaxanthin). Short-wavelength-absorbing apocarotenoids are present in all of the droplet types, providing filtering of light in a region of the spectrum where filtering by hydroxy- and ketocarotenoids may be incomplete. Thus, birds rely on a complex palette of carotenoid pigments within their cone oil droplets to achieve finely tuned spectral filtering. PMID:26446559

  14. Design and tuning of robust PID controller for HVAC systems

    SciTech Connect

    Kasahara, Masato; Matsuba, Tadahiko; Kuzuu, Yoshiaki; Yamazaki, Takanori; Hashimoto, Yukihiro; Kamimura, Kazuyuki; Kurosu, Shigeru

    1999-07-01

    This paper concerns the development of a new design and tuning method for use with robust proportional-plus-integral-plus-derivative (PID) controllers that are commonly used in the heating, ventilating, and air-conditioning (HVAC) fields. The robust PID controller is designed for temperature control of a single-zone environmental space. Although the dynamics of environmental space are described by higher-order transfer functions, most HVAC plants are approximated by first-order lag plus deadtime systems. Its control performance is examined for this commonly approximated controlled plant. Since most HVAC plants are complex with nonlinearity, distributed parameters, and multivariables, a single set of PID gains does not necessarily yield a satisfactory control performance. For this reason, the PID controller must be designed as a robust control system considering model uncertainty caused by changes in characteristics of the plant. The PID gains obtained by solving a two-disk type of mixed sensitivity problem can be modified by contrast to those tuned by the traditional Ziegler-Nichols rule. The results, which are surprisingly simple, are given as linear functions of ratio of deadtime to time constant for robustness. The numerical simulation and the experiments on a commercial-size test plant for air conditioning suggest that the robust PID controller proposed in this paper is effective enough for practical applications.

  15. Antisense transcription as a tool to tune gene expression.

    PubMed

    Brophy, Jennifer A N; Voigt, Christopher A

    2016-01-14

    A surprise that has emerged from transcriptomics is the prevalence of genomic antisense transcription, which occurs counter to gene orientation. While frequent, the roles of antisense transcription in regulation are poorly understood. We built a synthetic system in Escherichia coli to study how antisense transcription can change the expression of a gene and tune the response characteristics of a regulatory circuit. We developed a new genetic part that consists of a unidirectional terminator followed by a constitutive antisense promoter and demonstrate that this part represses gene expression proportionally to the antisense promoter strength. Chip-based oligo synthesis was applied to build a large library of 5,668 terminator-promoter combinations that was used to control the expression of three repressors (PhlF, SrpR, and TarA) in a simple genetic circuit (NOT gate). Using the library, we demonstrate that antisense promoters can be used to tune the threshold of a regulatory circuit without impacting other properties of its response function. Finally, we determined the relative contributions of antisense RNA and transcriptional interference to repressing gene expression and introduce a biophysical model to capture the impact of RNA polymerase collisions on gene repression. This work quantifies the role of antisense transcription in regulatory networks and introduces a new mode to control gene expression that has been previously overlooked in genetic engineering.

  16. Transformation optofluidics for large-angle light bending and tuning.

    PubMed

    Yang, Y; Chin, L K; Tsai, J M; Tsai, D P; Zheludev, N I; Liu, A Q

    2012-10-07

    Transformation optics is a new art of light bending by designing materials with spatially variable parameters for developing wave-manipulation devices. Here, we introduce a transformation optofluidic Y-branch splitter with large-angle bending and tuning based on the design of a spatially variable index. Differing from traditional splitters, the optofluidic splitter is achieved in an inhomogeneous medium by coordinate transformation. The designed bidirectional gradient index (GRIN) distribution can be achieved practically by the convection-diffusion process of liquid flowing streams. The transformation optofluidic splitter can achieve a much larger split angle with little bend loss than the traditional ones. In the experiments, a large tunable split angle up to 30° is achieved by tuning the flow rates, allowing optical signals to be freely transferred to different channels. Besides the symmetrical branch splitting, asymmetrical Y-branch splitting with approximately equal power splitting is also demonstrated by changing the composition of the liquids. The optofluidic splitter has high potential applications in biological, chemical and biomedical solution measurement and detection.

  17. A Verification-Driven Approach to Control Analysis and Tuning

    NASA Technical Reports Server (NTRS)

    Crespo, Luis G.; Kenny, Sean P.; Giesy, Daniel P.

    2008-01-01

    This paper proposes a methodology for the analysis and tuning of controllers using control verification metrics. These metrics, which are introduced in a companion paper, measure the size of the largest uncertainty set of a given class for which the closed-loop specifications are satisfied. This framework integrates deterministic and probabilistic uncertainty models into a setting that enables the deformation of sets in the parameter space, the control design space, and in the union of these two spaces. In regard to control analysis, we propose strategies that enable bounding regions of the design space where the specifications are satisfied by all the closed-loop systems associated with a prescribed uncertainty set. When this is unfeasible, we bound regions where the probability of satisfying the requirements exceeds a prescribed value. In regard to control tuning, we propose strategies for the improvement of the robust characteristics of a baseline controller. Some of these strategies use multi-point approximations to the control verification metrics in order to alleviate the numerical burden of solving a min-max problem. Since this methodology targets non-linear systems having an arbitrary, possibly implicit, functional dependency on the uncertain parameters and for which high-fidelity simulations are available, they are applicable to realistic engineering problems..

  18. Basic and Applied Aspects of Color Tuning of Bioluminescence Systems

    NASA Astrophysics Data System (ADS)

    Ohmiya, Yoshihiro

    2005-09-01

    V. Viviani et al. [Biochemistry 38 (1999) 8271] were the first to succeed in cloning the red-emitting enzyme from the South American railroad worm, which is the only bioluminescent organism known to emit a red-colored light. The application of red bioluminescence has been our goal because the transmittance of longer-wavelength light is superior to that of the other colors for visualization of biological functions in living cells. Now, different color luciferases, which emit with wavelength maxima ranging from 400 to 630 nm, are available and are being used. For example, based on different color luciferases, Nakajima et al. developed a tricolor reporter in vitro assay system based on these different color luciferases in which the expression of three genes can be monitored simultaneously. On the other hand, bioluminescence resonance energy transfer (BRET) is a natural phenomenon caused by the intermolecular interaction between a bioluminescent protein and a fluorophore on a second protein, resulting in the light from the bioluminescence reaction having the spectrum of the fluorophore. Otsuji et al. [Anal. Biochem. 329 (2004) 230] showed that the change in the efficiency of energy transfer in intramolecular BRET can quantify cellular functions in living cells. In this review, I introduce the basic mechanisms of color tuning in bioluminescent systems and new applications based on color tuning in the life sciences.

  19. Learning and tuning fuzzy logic controllers through reinforcements

    NASA Technical Reports Server (NTRS)

    Berenji, Hamid R.; Khedkar, Pratap

    1992-01-01

    This paper presents a new method for learning and tuning a fuzzy logic controller based on reinforcements from a dynamic system. In particular, our generalized approximate reasoning-based intelligent control (GARIC) architecture (1) learns and tunes a fuzzy logic controller even when only weak reinforcement, such as a binary failure signal, is available; (2) introduces a new conjunction operator in computing the rule strengths of fuzzy control rules; (3) introduces a new localized mean of maximum (LMOM) method in combining the conclusions of several firing control rules; and (4) learns to produce real-valued control actions. Learning is achieved by integrating fuzzy inference into a feedforward neural network, which can then adaptively improve performance by using gradient descent methods. We extend the AHC algorithm of Barto et al. (1983) to include the prior control knowledge of human operators. The GARIC architecture is applied to a cart-pole balancing system and demonstrates significant improvements in terms of the speed of learning and robustness to changes in the dynamic system's parameters over previous schemes for cart-pole balancing.

  20. The Effect of NUMA Tunings on CPU Performance

    NASA Astrophysics Data System (ADS)

    Hollowell, Christopher; Caramarcu, Costin; Strecker-Kellogg, William; Wong, Antonio; Zaytsev, Alexandr

    2015-12-01

    Non-Uniform Memory Access (NUMA) is a memory architecture for symmetric multiprocessing (SMP) systems where each processor is directly connected to separate memory. Indirect access to other CPU's (remote) RAM is still possible, but such requests are slower as they must also pass through that memory's controlling CPU. In concert with a NUMA-aware operating system, the NUMA hardware architecture can help eliminate the memory performance reductions generally seen in SMP systems when multiple processors simultaneously attempt to access memory. The x86 CPU architecture has supported NUMA for a number of years. Modern operating systems such as Linux support NUMA-aware scheduling, where the OS attempts to schedule a process to the CPU directly attached to the majority of its RAM. In Linux, it is possible to further manually tune the NUMA subsystem using the numactl utility. With the release of Red Hat Enterprise Linux (RHEL) 6.3, the numad daemon became available in this distribution. This daemon monitors a system's NUMA topology and utilization, and automatically makes adjustments to optimize locality. As the number of cores in x86 servers continues to grow, efficient NUMA mappings of processes to CPUs/memory will become increasingly important. This paper gives a brief overview of NUMA, and discusses the effects of manual tunings and numad on the performance of the HEPSPEC06 benchmark, and ATLAS software.