Science.gov

Sample records for detector dynamic range

  1. Large dynamic range radiation detector and methods thereof

    DOEpatents

    Marrs, Roscoe E [Livermore, CA; Madden, Norman W [Sparks, NV

    2012-02-14

    According to one embodiment, a radiation detector comprises a scintillator and a photodiode optically coupled to the scintillator. The radiation detector also includes a bias voltage source electrically coupled to the photodiode, a first detector operatively electrically coupled to the photodiode for generating a signal indicative of a level of a charge at an output of the photodiode, and a second detector operatively electrically coupled to the bias voltage source for generating a signal indicative of an amount of current flowing through the photodiode.

  2. A large dynamic range readout design for the plastic scintillator detector of DAMPE

    NASA Astrophysics Data System (ADS)

    Zhou, Yong; Sun, Zhiyu; Yu, Yuhong; Zhang, Yongjie; Fang, Fang; Chen, Junling; Hu, Bitao

    2016-08-01

    A large dynamic range is required by the Plastic Scintillator Detector (PSD) of DArk Matter Particle Explorer (DAMPE) to detect particles from electron to heavy ions with Z ≤ 20. To expand the dynamic range, the readout design based on the double-dynodes signal extraction from the photomultiplier tube has been proposed and adopted by PSD. To verify this design, a prototype detector module has been constructed and tested with cosmic ray and relativistic ion beam. The results match with the estimation and the readout unit could easily cover the required dynamic range of about 4 orders of magnitude.

  3. High dynamic range CMOS-based mammography detector for FFDM and DBT

    NASA Astrophysics Data System (ADS)

    Peters, Inge M.; Smit, Chiel; Miller, James J.; Lomako, Andrey

    2016-03-01

    Digital Breast Tomosynthesis (DBT) requires excellent image quality in a dynamic mode at very low dose levels while Full Field Digital Mammography (FFDM) is a static imaging modality that requires high saturation dose levels. These opposing requirements can only be met by a dynamic detector with a high dynamic range. This paper will discuss a wafer-scale CMOS-based mammography detector with 49.5 μm pixels and a CsI scintillator. Excellent image quality is obtained for FFDM as well as DBT applications, comparing favorably with a-Se detectors that dominate the X-ray mammography market today. The typical dynamic range of a mammography detector is not high enough to accommodate both the low noise and the high saturation dose requirements for DBT and FFDM applications, respectively. An approach based on gain switching does not provide the signal-to-noise benefits in the low-dose DBT conditions. The solution to this is to add frame summing functionality to the detector. In one X-ray pulse several image frames will be acquired and summed. The requirements to implement this into a detector are low noise levels, high frame rates and low lag performance, all of which are unique characteristics of CMOS detectors. Results are presented to prove that excellent image quality is achieved, using a single detector for both DBT as well as FFDM dose conditions. This method of frame summing gave the opportunity to optimize the detector noise and saturation level for DBT applications, to achieve high DQE level at low dose, without compromising the FFDM performance.

  4. Investigation of the dynamic range of calorimeter scintillation detector for space gamma-ray telescope

    NASA Astrophysics Data System (ADS)

    Runtso, M. F.; Naumov, P. Yu; Naumov, P. P.; Solodovnikov, A. A.

    2016-02-01

    An arrangement of the GAMMA-400 space gamma-ray telescope that currently is under the ground testing, suggests implementation of fast two-layer calorimeter scintillation detector system S3 with large dynamic range for electromagnetic showers detection in the main operation mode of the device. The S3 constructive features are demonstrated. The experimental method and basic diagram of the ground prototype dynamic range investigation are described.

  5. Dual-exposure technique for extending the dynamic range of x-ray flat panel detectors.

    PubMed

    Sisniega, A; Abella, M; Desco, M; Vaquero, J J

    2014-01-20

    This work presents an approach to extend the dynamic range of x-ray flat panel detectors by combining two acquisitions of the same sample taken with two different x-ray photon flux levels and the same beam spectral configuration. In order to combine both datasets, the response of detector pixels was modelled in terms of mean and variance using a linear model. The model was extended to take into account the effect of pixel saturation. We estimated a joint probability density function (j-pdf) of the pixel values by assuming that each dataset follows an independent Gaussian distribution. This j-pdf was used for estimating the final pixel value of the high-dynamic-range dataset using a maximum likelihood method. The suitability of the pixel model for the representation of the detector signal was assessed using experimental data from a small-animal cone-beam micro-CT scanner equipped with a flat panel detector. The potential extension in dynamic range offered by our method was investigated for generic flat panel detectors using analytical expressions and simulations. The performance of the proposed dual-exposure approach in realistic imaging environments was compared with that of a regular single-exposure technique using experimental data from two different phantoms. Image quality was assessed in terms of signal-to-noise ratio, contrast, and analysis of profiles drawn on the images. The dynamic range, measured as the ratio between the exposure for saturation and the exposure equivalent to instrumentation noise, was increased from 76.9 to 166.7 when using our method. Dual-exposure results showed higher contrast-to-noise ratio and contrast resolution than the single-exposure acquisitions for the same x-ray dose. In addition, image artifacts were reduced in the combined dataset. This technique to extend the dynamic range of the detector without increasing the dose is particularly suited to image samples that contain both low and high attenuation regions.

  6. Dual-exposure technique for extending the dynamic range of x-ray flat panel detectors

    NASA Astrophysics Data System (ADS)

    Sisniega, A.; Abella, M.; Desco, M.; Vaquero, J. J.

    2014-01-01

    This work presents an approach to extend the dynamic range of x-ray flat panel detectors by combining two acquisitions of the same sample taken with two different x-ray photon flux levels and the same beam spectral configuration. In order to combine both datasets, the response of detector pixels was modelled in terms of mean and variance using a linear model. The model was extended to take into account the effect of pixel saturation. We estimated a joint probability density function (j-pdf) of the pixel values by assuming that each dataset follows an independent Gaussian distribution. This j-pdf was used for estimating the final pixel value of the high-dynamic-range dataset using a maximum likelihood method. The suitability of the pixel model for the representation of the detector signal was assessed using experimental data from a small-animal cone-beam micro-CT scanner equipped with a flat panel detector. The potential extension in dynamic range offered by our method was investigated for generic flat panel detectors using analytical expressions and simulations. The performance of the proposed dual-exposure approach in realistic imaging environments was compared with that of a regular single-exposure technique using experimental data from two different phantoms. Image quality was assessed in terms of signal-to-noise ratio, contrast, and analysis of profiles drawn on the images. The dynamic range, measured as the ratio between the exposure for saturation and the exposure equivalent to instrumentation noise, was increased from 76.9 to 166.7 when using our method. Dual-exposure results showed higher contrast-to-noise ratio and contrast resolution than the single-exposure acquisitions for the same x-ray dose. In addition, image artifacts were reduced in the combined dataset. This technique to extend the dynamic range of the detector without increasing the dose is particularly suited to image samples that contain both low and high attenuation regions.

  7. High Dynamic Range Pixel Array Detector for Scanning Transmission Electron Microscopy.

    PubMed

    Tate, Mark W; Purohit, Prafull; Chamberlain, Darol; Nguyen, Kayla X; Hovden, Robert; Chang, Celesta S; Deb, Pratiti; Turgut, Emrah; Heron, John T; Schlom, Darrell G; Ralph, Daniel C; Fuchs, Gregory D; Shanks, Katherine S; Philipp, Hugh T; Muller, David A; Gruner, Sol M

    2016-02-01

    We describe a hybrid pixel array detector (electron microscope pixel array detector, or EMPAD) adapted for use in electron microscope applications, especially as a universal detector for scanning transmission electron microscopy. The 128×128 pixel detector consists of a 500 µm thick silicon diode array bump-bonded pixel-by-pixel to an application-specific integrated circuit. The in-pixel circuitry provides a 1,000,000:1 dynamic range within a single frame, allowing the direct electron beam to be imaged while still maintaining single electron sensitivity. A 1.1 kHz framing rate enables rapid data collection and minimizes sample drift distortions while scanning. By capturing the entire unsaturated diffraction pattern in scanning mode, one can simultaneously capture bright field, dark field, and phase contrast information, as well as being able to analyze the full scattering distribution, allowing true center of mass imaging. The scattering is recorded on an absolute scale, so that information such as local sample thickness can be directly determined. This paper describes the detector architecture, data acquisition system, and preliminary results from experiments with 80-200 keV electron beams.

  8. Dynamic range extension of SiPM detectors with the time-gated operation.

    PubMed

    Vilella, Eva; Diéguez, Angel

    2014-05-19

    The silicon photomultiplier (SiPM) is a novel detector technology that has undergone a fast development in the last few years, owing to its single-photon resolution and ultra-fast response time. However, the typical high dark count rates of the sensor may prevent the detection of low intensity radiation fluxes. In this article, the time-gated operation with short active periods in the nanosecond range is proposed as a solution to reduce the number of cells fired due to noise and thus increase the dynamic range. The technique is aimed at application fields that function under a trigger command, such as gated fluorescence lifetime imaging microscopy.

  9. Dynamic range considerations for EUV MAMA detectors. [Extreme UV Multianode Microchannel Array

    NASA Technical Reports Server (NTRS)

    Illing, Rainer M. E.; Bybee, Richard L.; Timothy, J. G.

    1990-01-01

    The multianode microchannel array (MAMA) has been chosen as the detector for two instruments on the ESA/NASA Solar Heliospheric Observatory. The response of the MAMA to the two extreme types of solar spectra, disk and corona, have been modeled with a view toward evaluating dynamic range effects present. The method of MAMA operation is discussed, with emphasis given to modeling the effect of electron cloud charge spreading to several detector anodes and amplifiers (n-fold events). Representative synthetic EUV spectra have been created. The detector response to these spectra is modeled by dissecting the input photon radiation field across the detector array into contributions to the various amplifier channels. The results of this dissection are shown for spectral regions across the entire wavelength region of interest. These results are used to identify regions in which total array photon counting rate or individual amplifier rate may exceed the design limits. This allows the design or operational modes to be tailored to eliminate the problem areas.

  10. Large dynamic range 64-channel ASIC for CZT or CdTe detectors

    NASA Astrophysics Data System (ADS)

    Glasser, F.; Villard, P.; Rostaing, J. P.; Accensi, M.; Baffert, N.; Girard, J. L.

    2003-08-01

    We present a customized 64-channel ASIC, named ALIX, developed in a 0.8 μm CMOS technology. This circuit is dedicated to measure charges from semi-conductor X-ray detectors like Cadmium Zinc Telluride (CZT) or Cadmium Telluride CdTe. The specificity of ALIX is to be able to measure charges over a very large dynamic range (from 10 fC to 3 nC), and to store eight measurements in a very short time (from every 250 ns to a few ms). Up to eight images are stored inside the ASIC and each image can be read out in 64 μs. A new acquisition sequence can then be started. Two analog readouts are available, one for the X-ray signal and one for the offset and afterglow measurement in case of pulsed X-rays. The outputs are converted into digital values by two off-chip 14 bits Analog-to-Digital Converters (ADC). A first version of ALIX has been tested with CZT and CdTe detectors under high-energy pulsed X-ray photons (20 MeV, 60 ns pulses every 250 ns). We will present the different results of linearity and signal-to-noise ratio. A second version of ALIX has been designed with some corrections. Electrical tests performed on 85 ASICS showed that the corrections were successful. We are now able to integrate them behind a 64×32 pixels 1 mm pitch CZT detector. Such an ASIC could also be used for strip detectors where a large dynamic range and a fast response are necessary.

  11. Evaluation of detector dynamic range in the x-ray exposure domain in mammography: a comparison between film-screen and flat panel detector systems.

    PubMed

    Cooper, Virgil N; Oshiro, Thomas; Cagnon, Christopher H; Bassett, Lawrence W; McLeod-Stockmann, Tyler M; Bezrukiy, Nikita V

    2003-10-01

    Digital detectors in mammography have wide dynamic range in addition to the benefit of decoupled acquisition and display. How wide the dynamic range is and how it compares to film-screen systems in the clinical x-ray exposure domain are unclear. In this work, we compare the effective dynamic ranges of film-screen and flat panel mammography systems, along with the dynamic ranges of their component image receptors in the clinical x-ray exposure domain. An ACR mammography phantom was imaged using variable mAs (exposure) values for both systems. The dynamic range of the contrast-limited film-screen system was defined as that ratio of mAs (exposure) values for a 26 kVp Mo/Mo (HVL=0.34 mm Al) beam that yielded passing phantom scores. The same approach was done for the noise-limited digital system. Data from three independent observers delineated a useful phantom background optical density range of 1.27 to 2.63, which corresponded to a dynamic range of 2.3 +/- 0.53. The digital system had a dynamic range of 9.9 +/- 1.8, which was wider than the film-screen system (p<0.02). The dynamic range of the film-screen system was limited by the dynamic range of the film. The digital detector, on the other hand, had an estimated dynamic range of 42, which was wider than the dynamic range of the digital system in its entirety by a factor of 4. The generator/tube combination was the limiting factor in determining the digital system's dynamic range.

  12. Flat panel X-ray detector with reduced internal scattering for improved attenuation accuracy and dynamic range

    DOEpatents

    Smith, Peter D.; Claytor, Thomas N.; Berry, Phillip C.; Hills, Charles R.

    2010-10-12

    An x-ray detector is disclosed that has had all unnecessary material removed from the x-ray beam path, and all of the remaining material in the beam path made as light and as low in atomic number as possible. The resulting detector is essentially transparent to x-rays and, thus, has greatly reduced internal scatter. The result of this is that x-ray attenuation data measured for the object under examination are much more accurate and have an increased dynamic range. The benefits of this improvement are that beam hardening corrections can be made accurately, that computed tomography reconstructions can be used for quantitative determination of material properties including density and atomic number, and that lower exposures may be possible as a result of the increased dynamic range.

  13. Imaging X-ray detector front-end with high dynamic range: IDeF-X HD

    NASA Astrophysics Data System (ADS)

    Gevin, O.; Lemaire, O.; Lugiez, F.; Michalowska, A.; Baron, P.; Limousin, O.; Delagnes, E.

    2012-12-01

    Presented circuit, IDeF-X HD (Imaging Detector Front-end) is a member of the IDeF-X ASICs family for space applications. It has been optimized for a half millimeter pitch CdTe or CdZnTe pixelated detector arranged in 16×16 array. It is aimed to operate in the hard X-ray range from few keV up to 250 keV or more. The ASIC has been realized in AMS 0.35 μm CMOS process. The IDeF-X HD is a 32 channel analog front-end with self-triggering capability. The architecture of the analog channel includes a chain of charge sensitive amplifier with continuous reset system and non-stationary noise suppressor, adjustable gain stage, pole-zero cancellation stage, adjustable shaping time low pass filter, baseline holder and peak detector with discriminator. The power consumption of the IDeF-X HD is 800 μW per channel. With the in-channel variable gain stage the nominal 250 keV dynamic range of the ASIC can be extended up to 1 MeV anticipating future applications using thick sensors. Measuring the noise performance without a detector at the input with minimized leakage current (programmable) at the input, we achieved ENC of 33 electrons rms at 10.7 μs peak time. Measurements with CdTe detector show good energy resolution FWHM of 1.1 keV at 60 keV and 4.3 keV at 662 keV with detection threshold below 4 keV. In addition, an absolute temperature sensor has been integrated with resolution of 1.5 °C.

  14. Dynamic-Range Compression For Infrared Imagery

    NASA Technical Reports Server (NTRS)

    Cheng, Li-Jen; Liu, Hua-Kuang

    1989-01-01

    Photorefractive crystals covering detectors prevent saturation. To make full use of information in image, desirable to compress dynamic range of input intensity to within region of approximately linear response of detector. Dynamic-range compression exhibited by measurements of attenuation in photorefractive GaAs. Effective dynamic-range-compressor plate, film, or coating reduces apparent contrast of scene imaged on detector plane to within dynamic range of detectors; original image contrast or intensity data recovered subsequently in electronic image processing because range-compression function and inverse known.

  15. Towards a microchannel-based X-ray detector with two-dimensional spatial and time resolution and high dynamic range.

    PubMed

    Adams, Bernhard W; Mane, Anil U; Elam, Jeffrey W; Obaid, Razib; Wetstein, Matthew; Chollet, Matthieu

    2015-09-01

    X-ray detectors that combine two-dimensional spatial resolution with a high time resolution are needed in numerous applications of synchrotron radiation. Most detectors with this combination of capabilities are based on semiconductor technology and are therefore limited in size. Furthermore, the time resolution is often realised through rapid time-gating of the acquisition, followed by a slower readout. Here, a detector technology is realised based on relatively inexpensive microchannel plates that uses GHz waveform sampling for a millimeter-scale spatial resolution and better than 100 ps time resolution. The technology is capable of continuous streaming of time- and location-tagged events at rates greater than 10(7) events per cm(2). Time-gating can be used for improved dynamic range.

  16. Towards a microchannel-based X-ray detector with two-dimensional spatial and time resolution and high dynamic range

    SciTech Connect

    Adams, Bernhard W.; Mane, Anil; Elam, Jeffrey; Obaid, Razib; Wetstein, Matthew J.

    2015-09-01

    X-ray detectors that combine two-dimensional spatial resolution with a high time resolution are needed in numerous applications of synchrotron radiation. Most detectors with this combination of capabilities are based on semiconductor technology and are therefore limited in size. Furthermore, the time resolution is often realised through rapid time-gating of the acquisition, followed by a slower readout. Here, a detector technology is realised based on relatively inexpensive microchannel plates that uses GHz waveform sampling for a millimeter-scale spatial resolution and better than 100 ps time resolution. The technology is capable of continuous streaming of time- and location-tagged events at rates greater than 10(7) events per cm(2). Time-gating can be used for improved dynamic range.

  17. Long range alpha particle detector

    DOEpatents

    MacArthur, D.W.; Wolf, M.A.; McAtee, J.L.; Unruh, W.P.; Cucchiara, A.L.; Huchton, R.L.

    1993-02-02

    An alpha particle detector capable of detecting alpha radiation from distant sources. In one embodiment, a high voltage is generated in a first electrically conductive mesh while a fan draws air containing air molecules ionized by alpha particles through an air passage and across a second electrically conductive mesh. The current in the second electrically conductive mesh can be detected and used for measurement or alarm. The detector can be used for area, personnel and equipment monitoring.

  18. The dynamic range of LZ

    NASA Astrophysics Data System (ADS)

    Yin, J.

    2016-02-01

    The electronics of the LZ experiment, the 7-tonne dark matter detector to be installed at the Sanford Underground Research Facility (SURF), is designed to permit studies of physics where the energies deposited range from 1 keV of nuclear-recoil energy up to 3,000 keV of electron-recoil energy. The system is designed to provide a 70% efficiency for events that produce three photoelectrons in the photomultiplier tubes (PMTs). This corresponds approximately to the lowest energy threshold achievable in multi-tonne time-projection chambers, and drives the noise specifications for the front end. The upper limit of the LZ dynamic range is defined to accommodate the electroluminescence (S2) signals. The low-energy channels of the LZ amplifiers provide the dynamic range required for the tritium and krypton calibrations. The high-energy channels provide the dynamic range required to measure the activated Xe lines.

  19. A method for the dynamic range extension of a pixelated Silicon detector beam profilometer based on the incomplete reset mechanism

    NASA Astrophysics Data System (ADS)

    Caccia, M.; Santoro, R.; Antonello, M.

    2017-03-01

    The SUCIMA collaboration, within a project supported by the European Commission in the Fifth Framework Program, developed a sensor for non-disruptive real-time beam profilometry for hadron therapy centres. The sensor, named MIMOTERA, has been used at different European facilities, imaging beams by direct impact on the sensor and by the detection of secondary electrons emitted by thin targets. In 2015, the detector has been thinned to 50 μm, integrated in a high vacuum and cryogenic temperature compliant assembly and successfully commissioned as antiproton beam monitor for the AEbar gIS experiment at CERN. The detector contributed to the optimisation of the experiment functionality providing the shape and position of the beam on a spill-by-spill basis. However, it failed in measuring the fluctuations of the beam intensity because the deposited energy exceeded the full well capacity and saturated the output signal. In order to recover this information, a method was developed based on the persistence of the signal in a series of frames that follows the one corresponding to the beam impact, due to the incomplete sensor reset. A laboratory test that makes use of a laser with tuneable intensity was designed and the method was qualified. This paper reports the description of the procedure and the main outcomes.

  20. Fan-less long range alpha detector

    DOEpatents

    MacArthur, D.W.; Bounds, J.A.

    1994-05-10

    A fan-less long range alpha detector is disclosed which operates by using an electrical field between a signal plane and the surface or substance to be monitored for air ions created by collisions with alpha radiation. Without a fan, the detector can operate without the possibility of spreading dust and potential contamination into the atmosphere. A guard plane between the signal plane and the electrically conductive enclosure and maintained at the same voltage as the signal plane, reduces leakage currents. The detector can easily monitor soil, or other solid or liquid surfaces. 2 figures.

  1. Enabling photon counting detectors with dynamic attenuators

    NASA Astrophysics Data System (ADS)

    Hsieh, Scott S.; Pelc, Norbert J.

    2014-03-01

    Photon-counting x-ray detectors (PCXDs) are being investigated as a replacement for conventional x-ray detectors because they promise several advantages, including better dose efficiency, higher resolution and spectral imaging. However, many of these advantages disappear when the x-ray flux incident on the detector is too high. We recently proposed a dynamic, piecewise-linear attenuator (or beam shaping filter) that can control the flux incident on the detector. This can restrict the operating range of the PCXD to keep the incident count rate below a given limit. We simulated a system with the piecewise-linear attenuator and a PCXD using raw data generated from forward projected DICOM files. We investigated the classic paralyzable and nonparalyzable PCXD as well as a weighted average of the two, with the weights chosen to mimic an existing PCXD (Taguchi et al, Med Phys 2011). The dynamic attenuator has small synergistic benefits with the nonparalyzable detector and large synergistic benefits with the paralyzable detector. Real PCXDs operate somewhere between these models, and the weighted average model still shows large benefits from the dynamic attenuator. We conclude that dynamic attenuators can reduce the count rate performance necessary for adopting PCXDs.

  2. Wide range radioactive gas concentration detector

    DOEpatents

    Anderson, David F.

    1984-01-01

    A wide range radioactive gas concentration detector and monitor which is capable of measuring radioactive gas concentrations over a range of eight orders of magnitude. The device of the present invention is designed to have an ionization chamber which is sufficiently small to give a fast response time for measuring radioactive gases but sufficiently large to provide accurate readings at low concentration levels. Closely spaced parallel plate grids provide a uniform electric field in the active region to improve the accuracy of measurements and reduce ion migration time so as to virtually eliminate errors due to ion recombination. The parallel plate grids are fabricated with a minimal surface area to reduce the effects of contamination resulting from absorption of contaminating materials on the surface of the grids. Additionally, the ionization chamber wall is spaced a sufficient distance from the active region of the ionization chamber to minimize contamination effects.

  3. Wide-range nuclear magnetic resonance detector

    NASA Technical Reports Server (NTRS)

    Sturman, J. C.; Jirberg, R. J.

    1972-01-01

    Compact and easy to use solid state nuclear magnetic resonance detector is designed for measuring field strength to 20 teslas in cryogenically cooled magnets. Extremely low noise and high sensitivity make detector applicable to nearly all types of analytical nuclear magnetic resonance measurements and can be used in high temperature and radiation environments.

  4. The solid state detector technology for picosecond laser ranging

    NASA Technical Reports Server (NTRS)

    Prochazka, Ivan

    1993-01-01

    We developed an all solid state laser ranging detector technology, which makes the goal of millimeter accuracy achievable. Our design and construction philosophy is to combine the techniques of single photon ranging, ultrashort laser pulses, and fast fixed threshold discrimination while avoiding any analog signal processing within the laser ranging chain. The all solid state laser ranging detector package consists of the START detector and the STOP solid state photon counting module. Both the detectors are working in an optically triggered avalanche switching regime. The optical signal is triggering an avalanche current buildup which results in the generation of a uniform, fast risetime output pulse.

  5. High dynamic range subjective testing

    NASA Astrophysics Data System (ADS)

    Allan, Brahim; Nilsson, Mike

    2016-09-01

    This paper describes of a set of subjective tests that the authors have carried out to assess the end user perception of video encoded with High Dynamic Range technology when viewed in a typical home environment. Viewers scored individual single clips of content, presented in High Definition (HD) and Ultra High Definition (UHD), in Standard Dynamic Range (SDR), and in High Dynamic Range (HDR) using both the Perceptual Quantizer (PQ) and Hybrid Log Gamma (HLG) transfer characteristics, and presented in SDR as the backwards compatible rendering of the HLG representation. The quality of SDR HD was improved by approximately equal amounts by either increasing the dynamic range or increasing the resolution to UHD. A further smaller increase in quality was observed in the Mean Opinion Scores of the viewers by increasing both the dynamic range and the resolution, but this was not quite statistically significant.

  6. High dynamic range infrared radiometry and imaging

    NASA Technical Reports Server (NTRS)

    Coon, Darryl D.; Karunasiri, R. P. G.; Bandara, K. M. S. V.

    1988-01-01

    The use is described of cryogenically cooled, extrinsic silicon infrared detectors in an unconventional mode of operation which offers an unusually large dynamic range. The system performs intensity-to-frequency conversion at the focal plane via simple circuits with very low power consumption. The incident IR intensity controls the repetition rate of short duration output pulses over a pulse rate dynamic range of about 10(6). Theory indicates the possibility of monotonic and approx. linear response over the full dynamic range. A comparison between the theoretical and the experimental results shows that the model provides a reasonably good description of experimental data. Some measurements of survivability with a very intense IR source were made on these devices and found to be very encouraging. Evidence continues to indicate that some variations in interpulse time intervals are deterministic rather than probabilistic.

  7. Streak camera dynamic range optimization

    SciTech Connect

    Wiedwald, J.D.; Lerche, R.A.

    1987-09-01

    The LLNL optical streak camera is used by the Laser Fusion Program in a wide range of applications. Many of these applications require a large recorded dynamic range. Recent work has focused on maximizing the dynamic range of the streak camera recording system. For our streak cameras, image intensifier saturation limits the upper end of the dynamic range. We have developed procedures to set the image intensifier gain such that the system dynamic range is maximized. Specifically, the gain is set such that a single streak tube photoelectron is recorded with an exposure of about five times the recording system noise. This ensures detection of single photoelectrons, while not consuming intensifier or recording system dynamic range through excessive intensifier gain. The optimum intensifier gain has been determined for two types of film and for a lens-coupled CCD camera. We have determined that by recording the streak camera image with a CCD camera, the system is shot-noise limited up to the onset of image intensifier nonlinearity. When recording on film, the film determines the noise at high exposure levels. There is discussion of the effects of slit width and image intensifier saturation on dynamic range. 8 refs.

  8. Small long-range alpha detector (LRAD) with computer readout

    SciTech Connect

    MacArthur, D.W.; Allander, K.S.; Bounds, J.A.; Butterfield, K.B.

    1991-10-01

    The small long-range alpha detector developed by N-2 was described in detail in the Los Alamos publication LA-12073-MS, Long-Range Alpha Detector,'' published in 1991. Since publication of that report, a computerized data acquisition system has been added to the LRAD detector. In addition to detailing the new data acquisition system, we discuss new data generated with the enhanced system, including measurements of (1) ultimate sensitivity; (2) detector linearity; (3) ion lifetime; and (4) characteristics. Furthermore, we have expanded our understanding of ion recombination and statistical noise effects in the LRAD and have addressed them here as well as several proposed applications. 6 refs., 30 figs.

  9. A Wide Dynamic Range Tapped Linear Array Image Sensor

    NASA Astrophysics Data System (ADS)

    Washkurak, William D.; Chamberlain, Savvas G.; Prince, N. Daryl

    1988-08-01

    Detectors for acousto-optic signal processing applications require fast transient response as well as wide dynamic range. There are two major choices of detectors: conductive or integration mode. Conductive mode detectors have an initial transient period before they reach then' i equilibrium state. The duration of 1 his period is dependent on light level as well as detector capacitance. At low light levels a conductive mode detector is very slow; response time is typically on the order of milliseconds. Generally. to obtain fast transient response an integrating mode detector is preferred. With integrating mode detectors. the dynamic range is determined by the charge storage capability of the tran-sport shift registers and the noise level of the image sensor. The conventional net hod used to improve dynamic range is to increase the shift register charge storage capability. To achieve a dynamic range of fifty thousand assuming two hundred noise equivalent electrons, a charge storage capability of ten million electrons would be required. In order to accommodate this amount of charge. unrealistic shift registers widths would be required. Therefore, with an integrating mode detector it is difficult to achieve a dynamic range of over four orders of magnitude of input light intensity. Another alternative is to solve the problem at the photodetector aml not the shift, register. DALSA's wide dynamic range detector utilizes an optimized, ion implant doped, profiled MOSFET photodetector specifically designed for wide dynamic range. When this new detector operates at high speed and at low light levels the photons are collected and stored in an integrating fashion. However. at bright light levels where transient periods are short, the detector switches into a conductive mode. The light intensity is logarithmically compressed into small charge packets, easily carried by the CCD shift register. As a result of the logarithmic conversion, dynamic ranges of over six orders of

  10. Alternating current long range alpha particle detector

    DOEpatents

    MacArthur, Duncan W.; McAtee, James L.

    1993-01-01

    An alpha particle detector, utilizing alternating currents, whcih is capable of detecting alpha particles from distinct sources. The use of alternating currents allows use of simpler ac circuits which, in turn, are not susceptible to dc error components. It also allows the benefit of gas gain, if desired. In the invention, a voltage source creates an electric field between two conductive grids, and between the grids and a conductive enclosure. Air containing air ions created by collision with alpha particles is drawn into the enclosure and detected. In some embodiments, the air flow into the enclosure is interrupted, creating an alternating flow of ions. In another embodiment, a modulated voltage is applied to the grid, also modulating the detection of ions.

  11. Alternating current long range alpha particle detector

    DOEpatents

    MacArthur, D.W.; McAtee, J.L.

    1993-02-16

    An alpha particle detector, utilizing alternating currents, which is capable of detecting alpha particles from distinct sources. The use of alternating currents allows use of simpler ac circuits which, in turn, are not susceptible to dc error components. It also allows the benefit of gas gain, if desired. In the invention, a voltage source creates an electric field between two conductive grids, and between the grids and a conductive enclosure. Air containing air ions created by collision with alpha particles is drawn into the enclosure and detected. In some embodiments, the air flow into the enclosure is interrupted, creating an alternating flow of ions. In another embodiment, a modulated voltage is applied to the grid, also modulating the detection of ions.

  12. Enhancement of concentration range of chromatographically detectable components with array detector mass spectrometry

    SciTech Connect

    Enke, Christie

    2013-02-19

    Methods and instruments for high dynamic range analysis of sample components are described. A sample is subjected to time-dependent separation, ionized, and the ions dispersed with a constant integration time across an array of detectors according to the ions m/z values. Each of the detectors in the array has a dynamically adjustable gain or a logarithmic response function, producing an instrument capable of detecting a ratio of responses or 4 or more orders of magnitude.

  13. Wide dynamic range beam profile monitor

    SciTech Connect

    Lee, D.M.; Brown, D.; Hardekopf, R.; Bilskie, J.R.; van Dyck, O.B.V.

    1985-01-01

    An economical harp multiplexer system has been developed to achieve a wide dynamic range. The harp system incorporates a pneumatically actuated harp detector with ceramic boards and carbon wires; a high-sensitivity multiplexer packaged in a double-wide NIM module; and flat, shielded ribbon cable consisting of individual twisted pairs. The system multiplexes 30 wires in each of the x and y planes simultaneously and operates with or without computer control. The system has operated in beams of 100 nA to 1 mA, 1- to 120-Hz repetition rate, with a signal-to-noise ratio of greater than 10/1.

  14. Wide dynamic range beam profile monitor

    SciTech Connect

    Lee, D.M.; van Dyck, O.B.; Bilskie, J.R.; Brown, D.; Hardekopf, R.

    1985-10-01

    An economical harp multiplexer system has been developed to achieve a wide dynamic range. The harp system incorporates a pneumatically actuated harp detector with ceramic boards and carbon wires; a high-sensitivity multiplexer packaged in a double-wide NIM module; and flat, shielded ribbon cable consisting of individual twisted pairs. The system multiplexes 30 wires in each of the x and y planes simultaneously and operates with or without computer control. The system has operated in beams of 100 nA to 1 mA, 1- to 120-Hz repetition rate, with a signal-to-noise ratio of greater than 10/1.

  15. Simple dynamic electromagnetic radiation detector

    NASA Technical Reports Server (NTRS)

    Been, J. F.

    1972-01-01

    Detector monitors gamma dose rate at particular position in a radiation facility where a mixed neutron-gamma environment exists, thus determining reactor power level changes. Device also maps gamma intensity profile across a neutron-gamma beam.

  16. Multi-dimensional position sensor using range detectors

    DOEpatents

    Vann, Charles S.

    2000-01-01

    A small, non-contact optical sensor uses ranges and images to detect its relative position to an object in up to six degrees of freedom. The sensor has three light emitting range detectors which illuminate a target and can be used to determine distance and two tilt angles. A camera located between the three range detectors senses the three remaining degrees of freedom, two translations and one rotation. Various range detectors, with different light sources, e.g. lasers and LEDs, different collection options, and different detection schemes, e.g. diminishing return and time of flight can be used. This sensor increases the capability and flexibility of computer controlled machines, e.g. it can instruct a robot how to adjust automatically to different positions and orientations of a part.

  17. High-dynamic-range neutron time-of-flight detector used to infer the D(t,n)(4)He and D(d,n)(3)He reaction yield and ion temperature on OMEGA.

    PubMed

    Forrest, C J; Glebov, V Yu; Goncharov, V N; Knauer, J P; Radha, P B; Regan, S P; Romanofsky, M H; Sangster, T C; Shoup, M J; Stoeckl, C

    2016-11-01

    Upgraded microchannel-plate-based photomultiplier tubes (MCP-PMT's) with increased stability to signal-shape linearity have been implemented on the 13.4-m neutron time-of-flight (nTOF) detector at the Omega Laser Facility. This diagnostic uses oxygenated xylene doped with diphenyloxazole C15H11NO + p-bis-(o-methylstyryl)-benzene (PPO + bis-MSB) wavelength shifting dyes and is coupled through four viewing ports to fast-gating MCP-PMT's, each with a different gain to allow one to measure the light output over a dynamic range of 1 × 10(6). With these enhancements, the 13.4-m nTOF can measure the D(t,n)(4)He and D(d,n)(3)He reaction yields and average ion temperatures in a single line of sight. Once calibrated for absolute neutron sensitivity, the nTOF detectors can be used to measure the neutron yield from 1 × 10(9) to 1 × 10(14) and the ion temperature with an accuracy approaching 5% for both the D(t,n)(4)He and D(d,n)(3)He reactions.

  18. High-dynamic-range neutron time-of-flight detector used to infer the D(t,n)4He and D(d,n)3He reaction yield and ion temperature on OMEGA

    NASA Astrophysics Data System (ADS)

    Forrest, C. J.; Glebov, V. Yu.; Goncharov, V. N.; Knauer, J. P.; Radha, P. B.; Regan, S. P.; Romanofsky, M. H.; Sangster, T. C.; Shoup, M. J.; Stoeckl, C.

    2016-11-01

    Upgraded microchannel-plate-based photomultiplier tubes (MCP-PMT's) with increased stability to signal-shape linearity have been implemented on the 13.4-m neutron time-of-flight (nTOF) detector at the Omega Laser Facility. This diagnostic uses oxygenated xylene doped with diphenyloxazole C15H11NO + p-bis-(o-methylstyryl)-benzene (PPO + bis-MSB) wavelength shifting dyes and is coupled through four viewing ports to fast-gating MCP-PMT's, each with a different gain to allow one to measure the light output over a dynamic range of 1 × 106. With these enhancements, the 13.4-m nTOF can measure the D(t,n)4He and D(d,n)3He reaction yields and average ion temperatures in a single line of sight. Once calibrated for absolute neutron sensitivity, the nTOF detectors can be used to measure the neutron yield from 1 × 109 to 1 × 1014 and the ion temperature with an accuracy approaching 5% for both the D(t,n)4He and D(d,n)3He reactions.

  19. Analysis of the TMI-2 source range detector response

    SciTech Connect

    Carew, J.F.; Diamond, D.J.; Eridon, J.M.

    1980-01-01

    In the first few hours following the TMI-2 accident large variations (factors of 10-100) in the source range (SR) detector response were observed. The purpose of this analysis was to quantify the various effects which could contribute to these large variations. The effects evaluated included the transmission of neutrons and photons from the core to detector and the reduction in the multiplication of the Am-Be startup sources, and subsequent reduction in SR detector response, due to core voiding. A one-dimensional ANISN slab model of the TMI-2 core, core externals, pressure vessel and containment has been constructed for calculation of the SR detector response and is presented.

  20. Development of a wide-range tritium-concentration detector

    SciTech Connect

    Jun, F.; Zhe, L.; Shicheng, L.; Jiangfeng, S.; Deli, L.

    2015-03-15

    According to the requirements of the tritium related systems of the TBM (Test Blanket Module) for monitoring the on-line tritium concentration, a wide-range tritium-concentration detector has been developed to measure the tritium concentration in the range of 10{sup 4} Bq/ml - 5*10{sup 8} Bq/ml. This detector is combined with a low-memory helium ionization chamber. The weak current signal collected in the ionization chamber is converted to the voltage signal by an I-V converter. The minimum weak current which the detector could be measured is 10{sup -14} A. The performance of the background current and the current response linearity of the prototype have been tested. The test result indicates that the linear response of the current signal of the prototype without connecting the ionization chamber is good. The linear correlation coefficient is R{sup 2} = 0.998.

  1. Wind dynamic range video camera

    NASA Technical Reports Server (NTRS)

    Craig, G. D. (Inventor)

    1985-01-01

    A television camera apparatus is disclosed in which bright objects are attenuated to fit within the dynamic range of the system, while dim objects are not. The apparatus receives linearly polarized light from an object scene, the light being passed by a beam splitter and focused on the output plane of a liquid crystal light valve. The light valve is oriented such that, with no excitation from the cathode ray tube, all light is rotated 90 deg and focused on the input plane of the video sensor. The light is then converted to an electrical signal, which is amplified and used to excite the CRT. The resulting image is collected and focused by a lens onto the light valve which rotates the polarization vector of the light to an extent proportional to the light intensity from the CRT. The overall effect is to selectively attenuate the image pattern focused on the sensor.

  2. HIGH DYNAMIC-RANGE HIGH SPEED LINAC CURRENT MEASUREMENTS

    SciTech Connect

    Deibele, Craig Edmond; Curry, Douglas E; Dickson, Richard W

    2012-01-01

    It is desired to measure the linac current of a charged particle beam with a consistent accuracy over a dynamic range of over 120 dB. Conventional current transformers suffer from droop, can be susceptible to electromagnetic interference (EMI), and can be bandwidth limited. A novel detector and electronics were designed to maximize dynamic range of about 120 dB and measure rise-times on the order of 10 nanoseconds.

  3. A Wide Range Neutron Detector for Space Nuclear Reactor Applications

    SciTech Connect

    Nassif, Eduardo; Sismonda, Miguel; Matatagui, Emilio; Pretorius, Stephan

    2007-01-30

    We propose here a versatile and innovative solution for monitoring and controlling a space-based nuclear reactor that is based on technology already proved in ground based reactors. A Wide Range Neutron Detector (WRND) allows for a reduction in the complexity of space based nuclear instrumentation and control systems. A ground model, predecessor of the proposed system, has been installed and is operating at the OPAL (Open Pool Advanced Light Water Research Reactor) in Australia, providing long term functional data. A space compatible Engineering Qualification Model of the WRND has been developed, manufactured and verified satisfactorily by analysis, and is currently under environmental testing.

  4. Wide-range radioactive-gas-concentration detector

    DOEpatents

    Anderson, D.F.

    1981-11-16

    A wide-range radioactive-gas-concentration detector and monitor capable of measuring radioactive-gas concentrations over a range of eight orders of magnitude is described. The device is designed to have an ionization chamber sufficiently small to give a fast response time for measuring radioactive gases but sufficiently large to provide accurate readings at low concentration levels. Closely spaced parallel-plate grids provide a uniform electric field in the active region to improve the accuracy of measurements and reduce ion migration time so as to virtually eliminate errors due to ion recombination. The parallel-plate grids are fabricated with a minimal surface area to reduce the effects of contamination resulting from absorption of contaminating materials on the surface of the grids. Additionally, the ionization-chamber wall is spaced a sufficient distance from the active region of the ionization chamber to minimize contamination effects.

  5. Dynamics of laser interferometric gravitational wave detectors

    NASA Astrophysics Data System (ADS)

    Rakhmanov, Malik

    2000-11-01

    Dynamics of fields and mirrors in the new laser interferometric gravitational wave detectors is described. The dynamics of fields is formulated in terms of difference equations, which take into account the large delay due to the light transit time in the interferometer arm cavities. Solutions of these field equations are found in both transient and steady-state regimes. The solutions for fields in the transient regime can be used for the measurement of the parameters of Fabry-Perot cavities. The solutions for fields in the steady-state regime can be used for the analysis of noise performance of Fabry-Perot cavities. The dynamics of the mirrors is described in terms of two normal coordinates: the cavity length and its center of mass. Such dynamics is strongly affected by the radiation pressure of light circulating in the cavity. The forces of radiation pressure are nonlinear and nonconservative. These two effects introduce instabilities and give rise to a violation of conservation of energy for the motion of the suspended mirrors. Analytical calculations and numerical simulations of the dynamics are done with applications to the Laser Interferometer Gravitational-Wave Observatory (LIGO). The dynamics of signal recycling and power recycling interferometers is analyzed using the field equations. The response of the interferometers to the input laser field and motion of its mirrors is calculated. Several basic transfer functions are found. These correspond to either a single or a nested cavity. A nested cavity appears either in the dynamics of the differential mode in signal recycling interferometers or in the dynamics of the common mode of power recycling interferometers. The poles of transfer functions of these nested cavities are found. The response of the interferometers to gravitational waves is described: the analysis is done in the rest frame of a local observer which is a natural coordinate system of the detector. This response is given by the interferometer

  6. High dynamic range infrared thermography by pixelwise radiometric self calibration

    NASA Astrophysics Data System (ADS)

    Ochs, M.; Schulz, A.; Bauer, H.-J.

    2010-03-01

    A procedure is described where the response function of each pixel of an InSb detector is determined by radiometric self-calibration. With the present approach no knowledge of the spectral characteristics of the IR system is required to recover a quantity which is linear with the incident irradiance of the object. The inherent detector non-uniformity is corrected on the basis of self-calibrated scaled irradiance. Compared to the standard two-point non-uniformity correction procedure - performed with the detector signal - only two NUC-tables are required for arbitrary integration times. Images obtained at various exposures are fused to a single high dynamic range image. The procedure is validated with synthetic data and its performance is demonstrated by measurements performed with a high resolution InSb FPA.

  7. Active Dendrites Enhance Neuronal Dynamic Range

    PubMed Central

    Gollo, Leonardo L.; Kinouchi, Osame; Copelli, Mauro

    2009-01-01

    Since the first experimental evidences of active conductances in dendrites, most neurons have been shown to exhibit dendritic excitability through the expression of a variety of voltage-gated ion channels. However, despite experimental and theoretical efforts undertaken in the past decades, the role of this excitability for some kind of dendritic computation has remained elusive. Here we show that, owing to very general properties of excitable media, the average output of a model of an active dendritic tree is a highly non-linear function of its afferent rate, attaining extremely large dynamic ranges (above 50 dB). Moreover, the model yields double-sigmoid response functions as experimentally observed in retinal ganglion cells. We claim that enhancement of dynamic range is the primary functional role of active dendritic conductances. We predict that neurons with larger dendritic trees should have larger dynamic range and that blocking of active conductances should lead to a decrease in dynamic range. PMID:19521531

  8. 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.

  9. Single and double grid long-range alpha detectors

    DOEpatents

    MacArthur, D.W.; Allander, K.S.

    1993-03-16

    Alpha particle detectors capable of detecting alpha radiation from distant sources. In one embodiment, a voltage is generated in a single electrically conductive grid while a fan draws air containing air molecules ionized by alpha particles through an air passage and across the conductive grid. The current in the conductive grid can be detected and used for measurement or alarm. Another embodiment builds on this concept and provides an additional grid so that air ions of both polarities can be detected. The detector can be used in many applications, such as for pipe or duct, tank, or soil sample monitoring.

  10. Single and double grid long-range alpha detectors

    DOEpatents

    MacArthur, Duncan W.; Allander, Krag S.

    1993-01-01

    Alpha particle detectors capable of detecting alpha radiation from distant sources. In one embodiment, a voltage is generated in a single electrically conductive grid while a fan draws air containing air molecules ionized by alpha particles through an air passage and across the conductive grid. The current in the conductive grid can be detected and used for measurement or alarm. Another embodiment builds on this concept and provides an additional grid so that air ions of both polarities can be detected. The detector can be used in many applications, such as for pipe or duct, tank, or soil sample monitoring.

  11. High dynamic range holographic data storage media

    NASA Astrophysics Data System (ADS)

    Askham, Fred; Ayres, Mark R.; Urness, Adam C.

    2015-08-01

    Holographic data storage (HDS) employs the physics of holography to record digital data in three dimensions in a highly stable photopolymer medium. The photopolymer medium must provide the essential characteristics of low scatter and high dynamic range while maintaining low recording induced physical shrinkage and long archival lifetimes. In this article, we report on media advancements employing Akonia's DREDTM technology which provide a 5x increase in media dynamic range with unchanged media shrinkage. We also discuss the implications of these results for photopolymer media mechanistic models.

  12. High Dynamic Range Digital Imaging of Spacecraft

    NASA Technical Reports Server (NTRS)

    Karr, Brian A.; Chalmers, Alan; Debattista, Kurt

    2014-01-01

    The ability to capture engineering imagery with a wide degree of dynamic range during rocket launches is critical for post launch processing and analysis [USC03, NNC86]. Rocket launches often present an extreme range of lightness, particularly during night launches. Night launches present a two-fold problem: capturing detail of the vehicle and scene that is masked by darkness, while also capturing detail in the engine plume.

  13. Nonperturbative short-range dynamics in TMDs

    SciTech Connect

    Weiss, Christian

    2013-05-01

    This presentation covers: deep inelastic processes and transverse momentum distributions; chiral symmetry breaking, including the physical picture, the dynamical model, and parton distributions; partonic structures, including transverse momentum distributions, coordinate space correlator, and short range correlations; and measurements of semi-inclusive deep inelastic scattering, correlations, and multi-parton processes in pp interactions.

  14. The Dynamic Range of Human Lightness Perception

    PubMed Central

    Radonjić, Ana; Allred, Sarah R.; Gilchrist, Alan L.; Brainard, David H.

    2011-01-01

    Summary Natural viewing challenges the visual system with images that have a dynamic range of light intensity (luminance) that can approach 1,000,000:1 and that often exceeds 10,000:1 [1, 2]. The range of perceived surface reflectance (lightness), however, can be well-approximated by the Munsell matte neutral scale (N 2.0/ to N 9.5/), consisting of surfaces whose reflectance varies by about 30:1. Thus, the visual system, must map a large range of surface luminance onto a much smaller range of surface lightness. We measured this mapping in images with a dynamic range close to that of natural images. We studied simple images that lacked segmentation cues that would indicate multiple regions of illumination. We found a remarkable degree of compression: at a single image location, a stimulus luminance range of 5905:1 can be mapped onto an extended lightness scale that has a reflectance range of 100:1. We characterized how the luminance-to-lightness mapping changes with stimulus context. Our data rule out theories that predict perceived lightness from luminance ratios or Weber contrast. A mechanistic model connects our data to theories of adaptation and provides insight about how the underlying visual response varies with context. PMID:22079116

  15. Adaptive optimal spectral range for dynamically changing scene

    NASA Astrophysics Data System (ADS)

    Pinsky, Ephi; Siman-tov, Avihay; Peles, David

    2012-06-01

    A novel multispectral video system that continuously optimizes both its spectral range channels and the exposure time of each channel autonomously, under dynamic scenes, varying from short range-clear scene to long range-poor visibility, is currently being developed. Transparency and contrast of high scattering medium of channels with spectral ranges in the near infrared is superior to the visible channels, particularly to the blue range. Longer wavelength spectral ranges that induce higher contrast are therefore favored. Images of 3 spectral channels are fused and displayed for (pseudo) color visualization, as an integrated high contrast video stream. In addition to the dynamic optimization of the spectral channels, optimal real-time exposure time is adjusted simultaneously and autonomously for each channel. A criterion of maximum average signal, derived dynamically from previous frames of the video stream is used (Patent Application - International Publication Number: WO2009/093110 A2, 30.07.2009). This configuration enables dynamic compatibility with the optimal exposure time of a dynamically changing scene. It also maximizes the signal to noise ratio and compensates each channel for the specified value of daylight reflections and sensors response for each spectral range. A possible implementation is a color video camera based on 4 synchronized, highly responsive, CCD imaging detectors, attached to a 4CCD dichroic prism and combined with a common, color corrected, lens. Principal Components Analysis (PCA) technique is then applied for real time "dimensional collapse" in color space, in order to select and fuse, for clear color visualization, the 3 most significant principal channels out of at least 4 characterized by high contrast and rich details in the image data.

  16. Photon Counting Detectors for the 1.0 - 2.0 Micron Wavelength Range

    NASA Technical Reports Server (NTRS)

    Krainak, Michael A.

    2004-01-01

    We describe results on the development of greater than 200 micron diameter, single-element photon-counting detectors for the 1-2 micron wavelength range. The technical goals include quantum efficiency in the range 10-70%; detector diameter greater than 200 microns; dark count rate below 100 kilo counts-per-second (cps), and maximum count rate above 10 Mcps.

  17. Integration of Dynamic Models in Range Operations

    NASA Technical Reports Server (NTRS)

    Bardina, Jorge; Thirumalainambi, Rajkumar

    2004-01-01

    This work addresses the various model interactions in real-time to make an efficient internet based decision making tool for Shuttle launch. The decision making tool depends on the launch commit criteria coupled with physical models. Dynamic interaction between a wide variety of simulation applications and techniques, embedded algorithms, and data visualizations are needed to exploit the full potential of modeling and simulation. This paper also discusses in depth details of web based 3-D graphics and applications to range safety. The advantages of this dynamic model integration are secure accessibility and distribution of real time information to other NASA centers.

  18. Performance optimization of detector electronics for millimeter laser ranging

    NASA Technical Reports Server (NTRS)

    Cova, Sergio; Lacaita, A.; Ripamonti, Giancarlo

    1993-01-01

    The front-end electronic circuitry plays a fundamental role in determining the performance actually obtained from ultrafast and highly sensitive photodetectors. We deal here with electronic problems met working with microchannel plate photomultipliers (MCP-PMTs) and single photon avalanche diodes (SPADs) for detecting single optical photons and measuring their arrival time with picosecond resolution. The performance of available fast circuits is critically analyzed. Criteria for selecting the most suitable electronics are derived and solutions for exploiting the detector performance are presented and discussed.

  19. Dynamic range of hypercubic stochastic excitable media

    NASA Astrophysics Data System (ADS)

    Assis, Vladimir R. V.; Copelli, Mauro

    2008-01-01

    We study the response properties of d -dimensional hypercubic excitable networks to a stochastic stimulus. Each site, modeled either by a three-state stochastic susceptible-infected-recovered-susceptible system or by the probabilistic Greenberg-Hastings cellular automaton, is continuously and independently stimulated by an external Poisson rate h . The response function (mean density of active sites ρ versus h ) is obtained via simulations (for d=1,2,3,4 ) and mean-field approximations at the single-site and pair levels (∀d) . In any dimension, the dynamic range and sensitivity of the response function are maximized precisely at the nonequilibrium phase transition to self-sustained activity, in agreement with a reasoning recently proposed. Moreover, the maximum dynamic range attained at a given dimension d is a decreasing function of d .

  20. Coarsening dynamics of zero-range processes

    NASA Astrophysics Data System (ADS)

    Godrèche, Claude; Drouffe, Jean-Michel

    2017-01-01

    We consider a class of zero-range processes exhibiting a condensation transition in the stationary state, with a critical single-site distribution decaying faster than a power law. We present the analytical study of the coarsening dynamics of the system on the complete graph, both at criticality and in the condensed phase. In contrast with the class of zero-range processes with critical single-site distribution decaying as a power law, in the present case the role of finite-time corrections is essential for the understanding of the approach to scaling.

  1. Backwards compatible high dynamic range video compression

    NASA Astrophysics Data System (ADS)

    Dolzhenko, Vladimir; Chesnokov, Vyacheslav; Edirisinghe, Eran A.

    2014-02-01

    This paper presents a two layer CODEC architecture for high dynamic range video compression. The base layer contains the tone mapped video stream encoded with 8 bits per component which can be decoded using conventional equipment. The base layer content is optimized for rendering on low dynamic range displays. The enhancement layer contains the image difference, in perceptually uniform color space, between the result of inverse tone mapped base layer content and the original video stream. Prediction of the high dynamic range content reduces the redundancy in the transmitted data while still preserves highlights and out-of-gamut colors. Perceptually uniform colorspace enables using standard ratedistortion optimization algorithms. We present techniques for efficient implementation and encoding of non-uniform tone mapping operators with low overhead in terms of bitstream size and number of operations. The transform representation is based on human vision system model and suitable for global and local tone mapping operators. The compression techniques include predicting the transform parameters from previously decoded frames and from already decoded data for current frame. Different video compression techniques are compared: backwards compatible and non-backwards compatible using AVC and HEVC codecs.

  2. Enhanced dynamic range x-ray imaging.

    PubMed

    Haidekker, Mark A; Morrison, Logan Dain-Kelley; Sharma, Ajay; Burke, Emily

    2017-03-01

    X-ray images can suffer from excess contrast. Often, image exposure is chosen to visually optimize the region of interest, but at the expense of over- and underexposed regions elsewhere in the image. When image values are interpreted quantitatively as projected absorption, both over- and underexposure leads to the loss of quantitative information. We propose to combine multiple exposures into a composite that uses only pixels from those exposures in which they are neither under- nor overexposed. The composite image is created in analogy to visible-light high dynamic range photography. We present the mathematical framework for the recovery of absorbance from such composite images and demonstrate the method with biological and non-biological samples. We also show with an aluminum step-wedge that accurate recovery of step thickness from the absorbance values is possible, thereby highlighting the quantitative nature of the presented method. Due to the higher amount of detail encoded in an enhanced dynamic range x-ray image, we expect that the number of retaken images can be reduced, and patient exposure overall reduced. We also envision that the method can improve dual energy absorptiometry and even computed tomography by reducing the number of low-exposure ("photon-starved") projections.

  3. Large dynamic range relative B1+ mapping

    PubMed Central

    Hess, Aaron T.; Aljabar, Paul; Malik, Shaihan J.; Jezzard, Peter; Robson, Matthew D.; Hajnal, Joseph V.; Koopmans, Peter J.

    2015-01-01

    Purpose Parallel transmission (PTx) requires knowledge of the B1+ produced by each element. However, B1+ mapping can be challenging when transmit fields exhibit large dynamic range. This study presents a method to produce high quality relative B1+ maps when this is the case. Theory and Methods The proposed technique involves the acquisition of spoiled gradient echo (SPGR) images at multiple radiofrequency drive levels for each transmitter. The images are combined using knowledge of the SPGR signal equation using maximum likelihood estimation, yielding an image for each channel whose signal is proportional to the B1+ field strength. Relative B1+ maps are then obtained by taking image ratios. The method was tested using numerical simulations, phantom imaging, and through in vivo experiments. Results The numerical simulations demonstrated that the proposed method can reconstruct relative transmit sensitivities over a wide range of B1+ amplitudes and at several SNR levels. The method was validated at 3 Tesla (T) by comparing it with an alternative B1+ mapping method, and demonstrated in vivo at 7T. Conclusion Relative B1+ mapping in the presence of large dynamic range has been demonstrated through numerical simulations, phantom imaging at 3T and experimentally at 7T. The method will enable PTx to be applied in challenging imaging scenarios at ultrahigh field. Magn Reson Med 76:490–499, 2016. © 2015 The Authors. Magnetic Resonance in Medicine published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine. This is an open access article under the terms of the Creative Commons Attribution License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited. PMID:26308375

  4. Dual Transition Edge Sensor Bolometer for Enhanced Dynamic Range

    NASA Technical Reports Server (NTRS)

    Chervenak, J. A.; Benford, D. J.; Moseley, S. H.; Irwin, K. D.

    2004-01-01

    Broadband surveys at the millimeter and submillimeter wavelengths will require bolometers that can reach new limits of sensitivity and also operate under high background conditions. To address this need, we present results on a dual transition edge sensor (TES) device with two operating modes: one for low background, ultrasensitive detection and one for high background, enhanced dynamic range detection. The device consists of a detector element with two transition temperatures (T(sub c)) of 0.25 and 0.51 K located on the same micromachined, thermally isolated membrane structure. It can be biased on either transition, and features phonon-limited noise performance at the lower T(sub c). We measure noise performance on the lower transition 7 x 10(exp -18) W/rt(Hz) and the bias power on the upper transition of 12.5 pW, giving a factor of 10 enhancement of the dynamic range for the device. We discuss the biasable range of this type of device and present a design concept to optimize utility of the device.

  5. Development of a stacked detector system for the x-ray range and its possible applications

    NASA Astrophysics Data System (ADS)

    Maier, Daniel; Limousin, Olivier; Meuris, Aline; Pürckhauer, Sabina; Santangelo, Andrea; Schanz, Thomas; Tenzer, Christoph

    2014-07-01

    We have constructed a stacked detector system operating in the X-ray range from 0.5 keV to 250 keV that consists of a Si-based 64×64 DePFET-Matrix in front of a CdTe hybrid detector called Caliste-64. The setup is operated under laboratory conditions that approximate the expected environment of a space-borne observatory. The DePFET detector is an active pixel matrix that provides high count-rate capabilities with a near Fanolimited spectral resolution at energies up to 15 keV. The Caliste-64 hard X-ray camera consists of a 1mm thick CdTe crystal combined with very compact integrated readout electronics, constituting a high performance spectro-imager with event-triggered time-tagging capability in the energy range between 2 keV and 200 keV. In this combined geometry the DePFET detector works as the Low Energy Detector (LED) while the Caliste-64 - as the High Energy Detector (HED) - detects predominantly the high energetic photons that have passed the LED. In addition to the individual optimization of both detectors, we use the setup to test and optimize the performance of the combined detector system. Side-effects like X-ray fluorescence photons, electrical crosstalk, and mutual heating have negative impacts on the data quality and will be investigated. Besides the primary application as a combined imaging detector system with high sensitivity across a broad energy range, additional applications become feasible. Via the analysis of coincident events in both detectors we can estimate the capabilities of the setup to be used as a Compton camera and as an X-ray polarimeter - both desirable functionalities for use in the lab as well as for future X-ray missions.

  6. Fast range measurement of spot scanning proton beams using a volumetric liquid scintillator detector

    PubMed Central

    Hui, CheukKai; Robertson, Daniel; Alsanea, Fahed; Beddar, Sam

    2016-01-01

    Accurate confirmation and verification of the range of spot scanning proton beams is crucial for correct dose delivery. Current methods to measure proton beam range using ionization chambers are either time-consuming or result in measurements with poor spatial resolution. The large-volume liquid scintillator detector allows real-time measurements of the entire dose profile of a spot scanning proton beam. Thus, liquid scintillator detectors are an ideal tool for measuring the proton beam range for commissioning and quality assurance. However, optical artefacts may decrease the accuracy of measuring the proton beam range within the scintillator tank. The purpose of the current study was to 1) develop a geometric calibration system to accurately calculate physical distances within the liquid scintillator detector, taking into account optical artefacts; and 2) assess the accuracy, consistency, and robustness of proton beam range measurement using the liquid scintillator detector with our geometric calibration system. The range of the proton beam was measured with the calibrated liquid scintillator system and was compared to the nominal range. Measurements were made on three different days to evaluate the setup robustness from day to day, and three sets of measurements were made for each day to evaluate the consistency from delivery to delivery. All proton beam ranges measured using the liquid scintillator system were within half a millimeter of the nominal range. The delivery-to-delivery standard deviation of the range measurement was 0.04 mm, and the day-to-day standard deviation was 0.10 mm. In addition to the accuracy and robustness demonstrated by these results when our geometric calibration system was used, the liquid scintillator system allowed the range of all 94 proton beams to be measured in just two deliveries, making the liquid scintillator detector a perfect tool for range measurement of spot scanning proton beams. PMID:27274863

  7. Ultra-wide Range Gamma Detector System for Search and Locate Operations

    SciTech Connect

    Odell, D. Mackenzie Odell; Harpring, Larry J.; Moore, Frank S. Jr.; French, Phillip J.; Gordon, John R.

    2005-10-26

    Collecting debris samples following a nuclear event requires that operations be conducted from a considerable stand-off distance. An ultra-wide range gamma detector system has been constructed to accomplish both long range radiation search and close range hot sample collection functions. Constructed and tested on a REMOTEC Andros platform, the system has demonstrated reliable operation over six orders of magnitude of gamma dose from 100's of uR/hr to over 100 R/hr. Functional elements include a remotely controlled variable collimator assembly, a NaI(Tl)/photomultiplier tube detector, a proprietary digital radiation instrument, a coaxially mounted video camera, a digital compass, and both local and remote control computers with a user interface designed for long range operations. Long range sensitivity and target location, as well as close range sample selection performance are presented.

  8. Detectors for high resolution dynamic pet

    SciTech Connect

    Derenzo, S.E.; Budinger, T.F.; Huesman, R.H.

    1983-05-01

    This report reviews the motivation for high spatial resolution in dynamic positron emission tomography of the head and the technical problems in realizing this objective. We present recent progress in using small silicon photodiodes to measure the energy deposited by 511 keV photons in small BGO crystals with an energy resolution of 9.4% full-width at half-maximum. In conjunction with a suitable phototube coupled to a group of crystals, the photodiode signal to noise ratio is sufficient for the identification of individual crystals both for conventional and time-of-flight positron tomography.

  9. Picosecond dynamics of a silicon donor based terahertz detector device

    SciTech Connect

    Bowyer, Ellis T.; Li, Juerong; Litvinenko, K. L.; Murdin, B. N. E-mail: yuxm@pku.edu.cn; Villis, B. J.; Erfani, Morteza; Matmon, Guy; Aeppli, Gabriel; Ortega, Jean-Michel; Prazeres, Rui; Dong, Li; Yu, Xiaomei E-mail: yuxm@pku.edu.cn

    2014-07-14

    We report the characteristics of a simple complementary metal-oxide-semiconductor compatible terahertz detector device with low response time (nanoseconds) determined using a short-pulse, high intensity free-electron laser. The noise equivalent power was 1 × 10{sup −11} W Hz{sup −1/2}. The detector has an enhanced response over narrow bands, most notably at 9.5 THz, with a continuum response at higher frequencies. Using such a device, the dynamics of donors in silicon can be explored, a system which has great potential for quantum information processing.

  10. Silicon field-effect transistors as radiation detectors for the Sub-THz range

    SciTech Connect

    But, D. B. Golenkov, O. G.; Sakhno, N. V.; Sizov, F. F.; Korinets, S. V.; Gumenjuk-Sichevska, J. V.; Reva, V. P.; Bunchuk, S. G.

    2012-05-15

    The nonresonance response of silicon metal-oxide-semiconductor field-effect transistors (Si-MOSFETs) with a long channel (1-20 {mu}m) to radiation in the frequency range 43-135 GHz is studied. The transistors are fabricated by the standard CMOS technology with 1-{mu}m design rules. The volt-watt sensitivity and the noise equivalent power (NEP) for such detectors are estimated with the calculated effective area of the detecting element taken into account. It is shown that such transistors can operate at room temperature as broadband direct detectors of sub-THz radiation. In the 4-5 mm range of wavelengths, the volt-watt sensitivity can be as high as tens of kV/W and the NEP can amount to 10{sup -11} - 10{sup -12}W/{radical}Hz . The parameters of detectors under study can be improved by the optimization of planar antennas.

  11. Detectors for in vivo range and dose verification in proton therapy

    NASA Astrophysics Data System (ADS)

    Alarcon, R.; Blyth, D.; Galyaev, E.; Holmes, J.; Ice, L.; Randall, G.; Bues, M.; Fatyga, M.

    2016-09-01

    Particle detection instrumentation to address the in vivo verifications of proton dose and range is under development as part of a proton therapy research program focused on patient quality assurance. For in vivo proton range verification, a collimated gamma detector array is under construction to indirectly measure the position of the Bragg peak for each proton beam spot to within 1-2 mm precision. For dose flux verification, a proton fluence detector based on the technology of the Micromegas is under construction. This detector has an active area of about 100 cm2, coordinate resolution of better than 1 mm, and handling of incident proton beam fluxes of 109-1013 particles/s.

  12. Saturation and Dynamic Range of Microchannel Plate-Based X-Ray Imagers

    SciTech Connect

    ,

    2012-05-04

    This paper describes recent advances in Monte Carlo simulations of microchannel plate (MCP)–based x-ray detectors, a continuation of ongoing work in this area. A Monte Carlo simulation model has been developed over the past several years by National Security Technologies, LLC (NSTec). The model simulates the secondary electron emission process in an MCP pore and includes the effects of gain saturation. In this work we focus on MCP gain saturation and dynamic range. We have performed modeling and experimental characterizations of L/D = 46, 10-micron diameter, MCP-based detectors. The detectors are typically operated by applying a subnanosecond voltage pulse, which gates the detector on. Agreement between the simulations and experiment is very good for a variety of voltage pulse waveforms ranging in width from 150 to 300 ps. The results indicate that such an MCP begins to show nonlinear gain around 5 × 10^4 electrons per pore and hard saturation around 105 electrons per pore. The simulations show a difference in MCP sensitivity vs voltage for high flux of photons producing large numbers of photoelectrons on a subpicosecond timescale. Simulations and experiments both indicate an MCP dynamic range of 1 to 10,000, and the dynamic range depends on how the voltage is applied.

  13. High dynamic range imaging for the detection of motion

    NASA Astrophysics Data System (ADS)

    Hay, Jeffrey Robert

    High dynamic range imaging involves imaging at a bit depth higher than the typical 8-12 bits offered by standard video equipment. We propose a method of imaging a scene at high dynamic range, 14+ bits, to detect motion correlated with changes in the measured optical signal. Features within a scene, namely edges, can be tracked through a time sequence and produce a modulation in light levels associated with the edge moving across a region being sampled by the detector. The modulation in the signal is analyzed and a model is proposed that allows for an absolute measurement of the displacement of an edge. In addition, turbulence present in the received optical path produces a modulation in the received signal that can be directly related to the various turbulent eddy sizes. These features, present in the low frequency portion of the spectrum, are correlated to specific values for a relative measurement of the turbulence intensity. In some cases a single element sensor is used for a measurement at a single point. Video technology is also utilized to produce simultaneous measurements across the entire scene. Several applications are explored and the results discussed. Key applications include: the use of this technique to analyze the motions of bridges for the assessment of structural health, non-contact methods of measuring the blood pulse waveform and respiration rate of an individual(s), and the imaging of turbulence, including clear air turbulence, for relative values of intensity. Resonant frequencies of bridges can be measured with this technique as well as eddies formed from turbulent flow.

  14. Displacement response, detection limit, and dynamic range of fiber-optic lever sensors

    NASA Technical Reports Server (NTRS)

    He, Gang; Cuomo, Frank W.

    1991-01-01

    The authors present the evaluation of the displacement response, detection limit, and dynamic range of fiber-optic lever sensors in a general format to establish their dependence on fiber sizes, optoelectronic detector specifications, input power, and other relevant parameters. The formations for the normalized reflected optical power change are derived for the evaluation of the optimal sensor response, the linearity range, and the minimum detectable displacement. The theoretical models are verified by an experiment which determines sensor response, modulation index, reflected optical power change, and linear response range through dynamic measurement. The application of this theoretical model to the study of a fiber-optic microphone for acoustic pressure detection is considered.

  15. Conductance measurement circuit with wide dynamic range

    NASA Technical Reports Server (NTRS)

    Mount, Bruce E. (Inventor); Von Esch, Myron (Inventor)

    1994-01-01

    A conductance measurement circuit to measure conductance of a solution under test with an output voltage proportional to conductance over a 5-decade range, i.e., 0.01 uS to 1000 uS or from 0.1 uS to 10,000 uS. An increase in conductance indicates growth, or multiplication, of the bacteria in the test solution. Two circuits are used each for an alternate half-cycle time periods of an alternate squarewave in order to cause alternate and opposite currents to be applied to the test solution. The output of one of the two circuits may be scaled for a different range optimum switching frequency dependent upon the solution conductance and to enable uninterrupted measurement over the complete 5-decade range. This circuitry provides two overlapping ranges of conductance which can be read simultaneously without discontinuity thereby eliminating range switching within the basic circuitry. A VCO is used to automatically change the operating frequency according to the particular value of the conductance being measured, and comparators indicate which range is valid and also facilitate computer-controlled data acquisition. A multiplexer may be used to monitor any number of solutions under test continuously.

  16. Servomotor and Controller Having Large Dynamic Range

    NASA Technical Reports Server (NTRS)

    Alhorn, Dean C.; Howard, David E.; Smith, Dennis A.; Dutton, Ken; Paulson, M. Scott

    2007-01-01

    A recently developed micro-commanding rotational-position-control system offers advantages of less mechanical complexity, less susceptibility to mechanical resonances, less power demand, less bulk, less weight, and lower cost, relative to prior rotational-position-control systems based on stepping motors and gear drives. This system includes a digital-signal- processor (DSP)-based electronic controller, plus a shaft-angle resolver and a servomotor mounted on the same shaft. Heretofore, micro-stepping has usually been associated with stepping motors, but in this system, the servomotor is micro-commanded in response to rotational-position feedback from the shaft-angle resolver. The shaft-angle resolver is of a four-speed type chosen because it affords four times the resolution of a single-speed resolver. A key innovative aspect of this system is its position-feedback signal- conditioning circuits, which condition the resolver output signal for multiple ranges of rotational speed. In the preferred version of the system, two rotational- speed ranges are included, but any number of ranges could be added to expand the speed range or increase resolution in particular ranges. In the preferred version, the resolver output is conditioned with two resolver-to-digital converters (RDCs). One RDC is used for speeds from 0.00012 to 2.5 rpm; the other RDC is used for speeds of 2.5 to 6,000 rpm. For the lower speed range, the number of discrete steps of RDC output per revolution was set at 262,144 (4 quadrants at 16 bits per quadrant). For the higher speed range, the number of discrete steps per revolution was set at 4,096 (4 quadrants at 10 bits per quadrant).

  17. Extension of the Focusable Mass Range in Distance-of-Flight Mass Spectrometry with Multiple Detectors

    SciTech Connect

    Gundlach-Graham, Alexander W.; Dennis, Elise; Ray, Steven J.; Enke, Christie G.; Carado, Anthony J.; Barinaga, Charles J.; Koppenaal, David W.; Hieftje, Gary M.

    2012-11-15

    Since the underlying theory of Distance-of-Flight Mass Spectrometry (DOFMS) was reported in 2007,[1] laboratory results[2, 3] have proven its practical viability. However, these previous implementations of DOFMS considered ion detection only over narrow DOF-detection windows, with 25-mm being the greatest detection length explored. These small mass windows cannot be used to evaluate how DOFMS focusing performs over greater DOF detection lengths and mass ranges. In the present study, we expand on previous studies by placing two spatially selective ion detectors along the detection plane of the DOFMS instrument. Ion signals are simultaneously collected from both DOF detectors in order to simulate DOFMS performance with a longer spatially selective ion detector.

  18. Inertial Range Dynamics in Boussinesq Turbulence

    NASA Technical Reports Server (NTRS)

    Rubinstein, Robert

    1996-01-01

    L'vov and Falkovich have shown that the dimensionally possible inertial range scaling laws for Boussinesq turbulence, Kolmogorov and Bolgiano scaling, describe steady states with constant flux of kinetic energy and of entropy respectively. These scaling laws are treated as similarity solutions of the direct interaction approximation for Boussinesq turbulence. The Kolmogorov scaling solution corresponds to a weak perturbation by gravity of a state in which the temperature is a passive scalar but in which a source of temperature fluctuations exists. Using standard inertial range balances, the renormalized viscosity and conductivity, turbulent Prandtl number, and spectral scaling law constants are computed for Bolgiano scaling.

  19. High resolution Cerenkov and range detectors for balloon-borne cosmic-ray experiment

    NASA Technical Reports Server (NTRS)

    Ahlen, S. P.; Cartwright, B. G.; Tarle, G.

    1975-01-01

    A combination of an active Cerenkov detector and passive range detectors is proposed for the high resolution measurement of isotopic composition in the neighborhood of iron in the galactic cosmic rays. A large area (4,300 sq cm) Cerenkov counter and passive range detectors were tested. Tests with heavy ions (2.1 GeV/amu C-12, 289 MeV/amu Ar-40, and 594 MeV/amu Ne-20) revealed the spatial uniformity of response of the Cerenkov counter to be better than 1% peak-to-peak. Light collection efficiency is independent of projectile energy and incidence angle to within at least 0.5%. Passive Lexan track recorders to measure range in the presence of the nuclear interaction background which results from stopping particles through 0.9 interaction lengths of matter were also tested. It was found that nuclear interactions produce an effective range straggling distribution only approximately 75% wider than that expected from range straggling alone. The combination of these tested techniques makes possible high mass resolution in the neighborhood of iron.

  20. A range extender hybrid electric vehicle dynamic model

    SciTech Connect

    Powell, B.K.; Pilutti, T.E.

    1994-12-31

    This paper describes a dynamic model possessing the key system components of a Range Extender Hybrid Electric Vehicle. The model is suitable for dynamic analysis, control law synthesis, and prototype simulation.

  1. Noise and dynamical gain studies of GaAs photoconductive detectors

    NASA Astrophysics Data System (ADS)

    Vilcot, J. P.; Decoster, D.; Raczy, L.; Constant, M.

    1984-03-01

    Noise mesurements on N-type GaAs planar photoconductive detectors have been made over the 10 MHz-1.5 GHz frequency range. The dynamical gains of the devices were calculated from noise data and compared with the values obtained using picosecond measurements. In the gigahertz frequency domain, the photodetectors have an internal current gain as observed in the avalanche photodiodes, but no excess factor has been found.

  2. Determining the dynamic range of MCPs based on pore size and strip current

    NASA Astrophysics Data System (ADS)

    Hunt, C.; Adrian, M. L.; Herrero, F.; James, P.; Jones, H. H.; Rodriguez, M.; Roman, P.; Shappirio, M.

    2010-12-01

    Micro-Channel Plates (MCPs) are used as detectors for almost all detectors measuring particles (both ions, electrons and neutrals) below 30 keV. Recent advances in the manufacturing technology of the MCPs have increased the number of options one has when selecting plates for an instrument. But it is not clear how many of these options affect the performance of the MCPs. In particular the dynamic range is not a clear cut calculation to make from the strip current. There is also some evidence that pore size and coating play a role. We measured the dynamic range and pulse height distribution of MCPs detector chevron stacks with a wide variety of strip currents from the low “normal” range in the EDR range. We also looked at the effects of varying the pore size from 25 microns to 10 microns, partial plating of the MCP surface and coating one surface on each MCP with gold rather than the standard zinc chromium. We will show how the dynamic range and pulse height distributions vary vs. strip current, pore size, and surface plating configurations.

  3. Research on high dynamic range information capture of GEO camera

    NASA Astrophysics Data System (ADS)

    Huang, Sijie; Chen, Fansheng; Gong, Xueyi

    2014-07-01

    A high dynamic range imaging method of GEO staring imaging is proposed based on radiance simulation of GEO remote sensing targets and analysis of foreign and domestic remote sensing payload characteristics. Due to the high temporal resolution of GEO staring imaging, multiple exposure method is used and image sequences are captured with different integration times; Then a high dynamic range image is obtained after fusion with the contrast of neighborhood pixel values being the weighting factor. Finally experiments are done in lab with visible plane array 2048*2048 imaging system for verifying multiple exposure test. It can be proved that using multiple exposure capture fusion method can obtain an 11 bit high dynamic range image. The essence of the method is that it sacrifices time resolution in exchange for high dynamic range, which overcomes the defect of small dynamic range of single exposure and is of practical significance in terms of GEO high dynamic range information capture.

  4. Radon monitoring using long-range alpha detector-based technology

    SciTech Connect

    Bolton, R.D.

    1994-11-01

    Long-Range Alpha Detector (LRAD) technology is being studied for monitoring radon gas concentrations. LRAD-based instruments collect and measure the ionization produced in air by alpha decays. These ions can be moved to a collection grid via electrostatic ion-transport design collected approximately 95% of the radon produced ions, while instruments using an airflow transport design collected from 44% to 77% of these ions, depending on detector geometry. The current produced by collecting this ionization is linear with respect to {sup 222}Rn concentration over the available test range of 0.07 to 820 pCi/L. In the absence of statistical limitations due to low radon concentrations, the speed of response of LRAD-based instruments is determined by the air exchange rate, and therefore changes in radon concentration can be detected in just a few seconds. Recent tests show that at radon concentrations below 20 pCi/L current pulses produced by individual alpha decays can be counted, thus improving detector sensitivity and stability even further. Because these detectors are simple, rugged, and do not consume much power, they are natural candidates for portable, battery operation.

  5. Dynamic range measurement and calibration of SiPMs

    NASA Astrophysics Data System (ADS)

    Bretz, T.; Hebbeker, T.; Lauscher, M.; Middendorf, L.; Niggemann, T.; Schumacher, J.; Stephan, M.; Bueno, A.; Navas, S.; Ruiz, A. G.

    2016-03-01

    Photosensors have played and will continue to play an important role in high-energy and Astroparticle cutting-edge experiments. As of today, the most common photon detection device in use is the photomultiplier tube (PMT). However, we are witnessing rapid progress in the field and new devices now show very competitive features when compared to PMTs. Among those state-of-the-art photo detectors, silicon photomultipliers (SiPMs) are a relatively new kind of semiconductor whose potential is presently studied by many laboratories. Their characteristics make them a very attractive candidate for future Astroparticle physics experiments recording fluorescence and Cherenkov light, both in the atmosphere and on the ground. Such applications may require the measurement of the light flux on the sensor for the purpose of energy reconstruction. This is a complex task due to the limited dynamic range of SiPMs and the presence of thermal and correlated noise. In this work we study the response of three SiPM types in terms of delivered charge when exposed to light pulses in a broad range of intensities: from single photon to saturation. The influence of the pulse time duration and the SiPM over-voltage on the response are also quantified. Based on the observed behaviour, a method is presented to reconstruct the real number of photons impinging on the SiPM surface directly from the measured SiPM charge. A special emphasis is placed on the description of the methodology and experimental design used to perform the measurements.

  6. SU-E-T-641: Proton Range Measurements Using a Geometrically Calibrated Liquid Scintillator Detector

    SciTech Connect

    Hui, C; Robertson, D; Alsanea, F; Beddar, S

    2015-06-15

    Purpose: The purpose of this work is to develop a geometric calibration method to accurately calculate physical distances within a liquid scintillator detector and to assess the accuracy, consistency, and robustness of proton beam range measurements when using a liquid scintillator detector system with the proposed geometric calibration process. Methods: We developed a geometric calibration procedure to accurately convert pixel locations in the camera frame into physical locations in the scintillator frame. To ensure accuracy, the geometric calibration was performed before each experiment. The liquid scintillator was irradiated with spot scanning proton beams of 94 energies in two deliveries. A CCD camera was used to capture the two-dimensional scintillation light profile of each of the proton energies. An algorithm was developed to automatically calculate the proton range from the acquired images. The measured range was compared to the nominal range to assess the accuracy of the detector. To evaluate the robustness of the detector between each setup, the experiments were repeated on three different days. To evaluate the consistency of the measurements between deliveries, three sets of measurements were acquired for each experiment. Results: Using this geometric calibration procedure, the proton beam ranges measured using the liquid scintillator system were all within 0.3mm of the nominal range. The average difference between the measured and nominal ranges was −0.20mm. The delivery-to-delivery standard deviation of the proton range measurement was 0.04mm, and the setup-to-setup standard deviation of the measurement was 0.10mm. Conclusion: The liquid scintillator system can measure the range of all 94 beams in just two deliveries. With the proposed geometric calibration, it can measure proton range with sub-millimeter accuracy, and the measurements were shown to be consistent between deliveries and setups. Therefore, we conclude that the liquid scintillator

  7. Logarithmic circuit with wide dynamic range

    NASA Technical Reports Server (NTRS)

    Wiley, P. H.; Manus, E. A. (Inventor)

    1978-01-01

    A circuit deriving an output voltage that is proportional to the logarithm of a dc input voltage susceptible to wide variations in amplitude includes a constant current source which forward biases a diode so that the diode operates in the exponential portion of its voltage versus current characteristic, above its saturation current. The constant current source includes first and second, cascaded feedback, dc operational amplifiers connected in negative feedback circuit. An input terminal of the first amplifier is responsive to the input voltage. A circuit shunting the first amplifier output terminal includes a resistor in series with the diode. The voltage across the resistor is sensed at the input of the second dc operational feedback amplifier. The current flowing through the resistor is proportional to the input voltage over the wide range of variations in amplitude of the input voltage.

  8. Intercomparison of experimental and theoretical ranges of heavy ions in plastic track detectors

    NASA Astrophysics Data System (ADS)

    Virk, H. S.; Randhawa, G. S.; Sharma, S. K.

    1996-01-01

    In the present study, CR-39 and Lexan polycarbonate plastic track detectors have been exposed to various heavy ion beams, i.e. ,238U, b,208Pb, u,197Au, a,139La, e132Xe and b93Nb (energy range from 5.6 to 18.0 MeV/u), from the UNILAC accelerator at GSI, Darmstadt. After exposure, the irradiated samples were etched under optimum etching conditions. The total etchable ranges of these heavy ions have been determined experimentally using a Carl Zeiss binocular microscope. In order to check the validity of the various stopping power and range formulations in this energy range, the experimentally determined range values have been compared with the theoretically computed values from the Benton and Henke, Mukherjee and Nayak, Ziegler et al. and Hubert et al. formulations.

  9. Short range laser obstacle detector. [for surface vehicles using laser diode array

    NASA Technical Reports Server (NTRS)

    Kuriger, W. L. (Inventor)

    1973-01-01

    A short range obstacle detector for surface vehicles is described which utilizes an array of laser diodes. The diodes operate one at a time, with one diode for each adjacent azimuth sector. A vibrating mirror a short distance above the surface provides continuous scanning in elevation for all azimuth sectors. A diode laser is synchronized with the vibrating mirror to enable one diode laser to be fired, by pulses from a clock pulse source, a number of times during each elevation scan cycle. The time for a given pulse of light to be reflected from an obstacle and received is detected as a measure of range to the obstacle.

  10. Dynamic range studies and improvements for multiplexed photonic Doppler velocimetry

    NASA Astrophysics Data System (ADS)

    Miller, Edward Kirk; Lee, Kevin; Larson, Eric; Daykin, Edward

    2017-01-01

    We present studies of the dynamic range achievable with multiplexed photonic Doppler velocimetry (MPDV) measurements, and we demonstrate some techniques to extend the dynamic range. Improved dynamic range for MPDV measurements is needed in order to track the velocity of the free surface behind a cloud of ejecta, so we have undertaken theoretical and experimental studies of factors affecting dynamic range, particularly in cases where the large number of MPDV probe points precludes high illumination power on each channel. To quantify the potential dynamic range of a given MPDV configuration, we introduce a metric called the frequency-domain number of bits, FNOB, which is less stringent than the formally defined equivalent number of bits (ENOB). This new metric is simple to compute in the lab, and it is well suited to conventional PDV analysis, which does not require digitizer phase coherence beyond tens of nanoseconds.

  11. A full range detector for the HIRRBS high resolution RBS magnetic spectrometer

    SciTech Connect

    Skala, Wayne G.; Haberl, Arthur W.; Bakhru, Hassaram; Lanford, William

    2013-04-19

    The UAlbany HIRRBS (High Resolution RBS) system has been updated for better use in rapid analysis. The focal plane detector now covers the full range from U down to O using a linear stepper motor to translate the 1-cm detector across the 30-cm range. Input is implemented with zero-back-angle operation in all cases. The chamber has been modified to allow for quick swapping of sample holders, including a channeling goniometer. A fixed standard surface-barrier detector allows for normal RBS simultaneously with use of the magnetic spectrometer. The user can select a region on the standard spectrum or can select an element edge or an energy point for collection of the expanded spectrum portion. The best resolution currently obtained is about 2-to-3 keV, probably representing the energy width of the incoming beam. Calibration is maintained automatically for any spectrum portion and any beam energy from 1.0 to 3.5 MeV. Element resolving power, sensitivity and depth resolution are shown using several examples. Examples also show the value of simultaneous conventional RBS.

  12. True coincidence summing corrections for an extended energy range HPGe detector

    SciTech Connect

    Venegas-Argumedo, Y.; Montero-Cabrera, M. E.

    2015-07-23

    True coincidence summing (TCS) effect for natural radioactive families of U-238 and Th-232 represents a problem when an environmental sample with a close source-detector geometry measurement is performed. By using a certified multi-nuclide standard source to calibrate an energy extended range (XtRa) HPGe detector, it is possible to obtain an intensity spectrum slightly affected by the TCS effect with energies from 46 to 1836 keV. In this work, the equations and some other considerations required to calculate the TCS correction factor for isotopes of natural radioactive chains are described. It is projected a validation of the calibration, performed with the IAEA-CU-2006-03 samples (soil and water)

  13. Wide Dynamic Range Front-end Electronics for Beam Current and Position Measurement

    SciTech Connect

    Rawnsley, W. R.; Potter, R. J.; Verzilov, V. A.; Root, L.

    2006-11-20

    An Analog Devices log detector, AD8306, and a Digital Signal Processor (DSP), ADSP-21992, have been found useful for building wide dynamic range, accurate and inexpensive front-end electronics to measure and process the RF signals from TRIUMF's beam monitors. The high-precision log detector has a useful dynamic range of over 100 dB. The 160 MHz mixed-signal DSP is used to digitize the log detector output, linearize it via a lookup table, perform temperature compensation, and remove the variable duty cycle 1 kHz pulse structure of the beam. This approach has been applied to two types of devices in a 500 MeV proton beamline. The 0.1% DC to CW total current monitor is based on a capacitive pickup resonant at 46.11 MHz, the second harmonic of the bunch frequency. The DSP software provides low pass filtering, calculates the antilog of the data and passes the output to a CAMAC input register. The BPM electronics process data from inductive pickup loops. The DSP controls a GaAs switch which multiplexes signals from four adjacent pickups to a single log detector. The DSP performs difference-over-sum or log-ratio data analysis along with averaging over an arbitrary number of samples.

  14. Uncalibrated stereo rectification and disparity range stabilization: a comparison of different feature detectors

    NASA Astrophysics Data System (ADS)

    Luo, Xiongbiao; Jayarathne, Uditha L.; McLeod, A. Jonathan; Pautler, Stephen E.; Schlacta, Christopher M.; Peters, Terry M.

    2016-03-01

    This paper studies uncalibrated stereo rectification and stable disparity range determination for surgical scene three-dimensional (3-D) reconstruction. Stereoscopic endoscope calibration sometimes is not available and also increases the complexity of the operating-room environment. Stereo from uncalibrated endoscopic cameras is an alternative to reconstruct the surgical field visualized by binocular endoscopes within the body. Uncalibrated rectification is usually performed on the basis of a number of matched feature points (semi-dense correspondence) between the left and the right images of stereo pairs. After uncalibrated rectification, the corresponding feature points can be used to determine the proper disparity range that helps to improve the reconstruction accuracy and reduce the computational time of disparity map estimation. Therefore, the corresponding or matching accuracy and robustness of feature point descriptors is important to surgical field 3-D reconstruction. This work compares four feature detectors: (1) scale invariant feature transform (SIFT), (2) speeded up robust features (SURF), (3) affine scale invariant feature transform (ASIFT), and (4) gauge speeded up robust features (GSURF) with applications to uncalibrated rectification and stable disparity range determination. We performed our experiments on surgical endoscopic video images that were collected during robotic prostatectomy. The experimental results demonstrate that ASIFT outperforms other feature detectors in the uncalibrated stereo rectification and also provides a stable stable disparity range for surgical scene reconstruction.

  15. Cryocooled terahertz photoconductive detector system with background-limited performance in 1.5–4 THz frequency range

    SciTech Connect

    Aoki, Makoto; Hiromoto, Norihisa

    2015-10-15

    We describe a 4-K-cryocooled dual-band terahertz (THz) photoconductive detector system with background-limited performance. The detector system comprises two THz photoconductive detectors covering a response in a wide frequency range from 1.5 to 4 THz, low noise amplifiers, optical low-pass filters to eliminate input radiation of higher frequencies, and a mechanical 4 K Gifford-McMahon refrigerator that provides practical and convenient operation without a liquid He container. The electrical and optical performances of the THz detector system were evaluated at a detector temperature of 4 K under 300 K background radiation. We proved that the detector system can achieve background-limited noise-equivalent-power on the order of 10{sup −14} W/Hz{sup 1/2} in the frequency range from 1.5 to 4 THz even if the vibration noise of the mechanical refrigerator is present.

  16. Monolithic single-photon detectors and time-to-digital converters for picoseconds time-of-flight ranging

    NASA Astrophysics Data System (ADS)

    Markovic, Bojan; Tisa, Simone; Tosi, Alberto; Zappa, Franco

    2011-03-01

    We present a novel "smart-pixel" able to measure and record in-pixel the time delay (photon timing) between a START (e.g. given by laser excitation, cell stimulus, or LIDAR flash) and a STOP (e.g. arrival of the first returning photon from the fluorescence decay signal or back reflection from an object). Such smart-pixel relies of a SPAD detector and a Timeto- Digital Converter monolithically designed and manufactured in the same chip. Many pixels can be laid out in a rows by columns architecture, to give birth to expandable 2D imaging arrays for picoseconds-level single-photon timing applications. Distance measurements, by means of direct TOF detection (used in LIDAR systems) provided by each pixel, can open the way to the fabrication of single-chip 3D ranging arrays for scene reconstruction and intelligent object recognition. We report on the design and characterization of prototype circuits, fabricated in a 0.35 μm standard CMOS technology containing complete conversion channels, "smart-pixel" and ancillary electronics with 20 μm active area diameter SPAD detector and related quenching circuitry. With a 100 MHz reference clock, the TDC provides timeresolution of 10 ps, dynamic range of 160 ns and very high conversion linearity.

  17. A wide dynamic range x-ray streak camera system

    SciTech Connect

    Niu Lihong; Yang Qinlao; Niu Hanben; Liao Hua; Zhou Junlan; Ding Yunkun

    2008-02-15

    An x-ray streak camera with wide dynamic range and a large slit photocathode of 30 mm length has been developed and calibrated. In order to achieve wide dynamic range, a conventional streak tube has been improved and the camera system has been designed without microchannel plate electron amplifier. As a result, a dynamic range of 922 is achieved in a single shot mode with laser pulse of 30 ps (full width at half maximum) at time resolution of better than 31 ps.

  18. Superconducting nanowire single photon detector at 532 nm and demonstration in satellite laser ranging.

    PubMed

    Li, Hao; Chen, Sijing; You, Lixing; Meng, Wengdong; Wu, Zhibo; Zhang, Zhongping; Tang, Kai; Zhang, Lu; Zhang, Weijun; Yang, Xiaoyan; Liu, Xiaoyu; Wang, Zhen; Xie, Xiaoming

    2016-02-22

    Superconducting nanowire single-photon detectors (SNSPDs) at a wavelength of 532 nm were designed and fabricated aiming to satellite laser ranging (SLR) applications. The NbN SNSPDs were fabricated on one-dimensional photonic crystals with a sensitive-area diameter of 42 μm. The devices were coupled with multimode fiber (ϕ = 50 μm) and exhibited a maximum system detection efficiency of 75% at an extremely low dark count rate of <0.1 Hz. An SLR experiment using an SNSPD at a wavelength of 532 nm was successfully demonstrated. The results showed a depth ranging with a precision of ~8.0 mm for the target satellite LARES, which is ~3,000 km away from the ground ranging station at the Sheshan Observatory.

  19. SCD's uncooled detectors and video engines for a wide-range of applications

    NASA Astrophysics Data System (ADS)

    Fraenkel, A.; Mizrahi, U.; Bikov, L.; Giladi, A.; Shiloah, N.; Elkind, S.; Kogan, I.; Maayani, S.; Amsterdam, A.; Vaserman, I.; Duman, O.; Hirsh, Y.; Schapiro, F.; Tuito, A.; Ben-Ezra, M.

    2011-06-01

    Over the last decade SCD has established a state of the art VOx μ-Bolometer product line. Due to its overall advantages this technology is penetrating a large range of systems. In addition to a large variety of detectors, SCD has also recently introduced modular video engines with an open architecture. In this paper we will describe the versatile applications supported by the products based on 17μm pitch: Low SWaP short range systems, mid range systems based on VGA arrays and high-end systems that will utilize the XGA format. These latter systems have the potential to compete with cooled 2nd Gen scanning LWIR arrays, as will be demonstrated by TRM3 system level calculations.

  20. Dynamics of Quantum Matter with Long-Range Entanglement

    DTIC Science & Technology

    2013-06-07

    REPORT Final Report: Dynamics of quantum matter with long-range entanglement. 14. ABSTRACT 16. SECURITY CLASSIFICATION OF: Recent experiments on...ultracold atoms in optical lattices have opened a remarkable new window on the dynamics of quantum matter with long-range entanglement. The simplest...paradigm of this is the boson superfluid-insulator quantum phase transition in two spatial dimensions. This project will study the theoretical

  1. Detectors

    DOEpatents

    Orr, Christopher Henry; Luff, Craig Janson; Dockray, Thomas; Macarthur, Duncan Whittemore; Bounds, John Alan; Allander, Krag

    2002-01-01

    The apparatus and method provide techniques through which both alpha and beta emission determinations can be made simultaneously using a simple detector structure. The technique uses a beta detector covered in an electrically conducting material, the electrically conducting material discharging ions generated by alpha emissions, and as a consequence providing a measure of those alpha emissions. The technique also offers improved mountings for alpha detectors and other forms of detectors against vibration and the consequential effects vibration has on measurement accuracy.

  2. Intercomparison of experimental and theoretical ranges of heavy ions in plastic track detectors

    NASA Astrophysics Data System (ADS)

    Randhawa, G. S.; Sharma, S. K.; Virk, H. S.

    1996-01-01

    In the present study, CR-39 and Lexan polycarbonate plastic track detectors have been exposed to various heavy ion beams, i.e. 238U, 208Pb, 197Au, 139La, 132Xe and 93Nb (energy range from 5.6 to 18.0 MeV/u), from the UNILAC accelerator at GSI, Darmstadt. After exposure, the irradiated samples were etched under optimum etching conditions. The total etchable ranges of these heavy ions have been determined experimentally using a Carl Zeiss binocular microscope. In order to check the validity of the various stopping power and range formulations in this energy range, the experimentally determined range values have been compared with theoretically computed values from the Benton and Henke [Nucl. Instr. and Meth. 67 (1969) 87], Mukherjee and Nayak [Nucl. Instr. and Meth. 159 (1979) 421], Ziegler et al. [Stopping power and range of ions in solids, vol. 1 (Pergamon, New York, 1985); Nucl. Instr. and Meth. B 35 (1988) 215] and Hubert et al. [Nucl. Instr. and Meth. B 36 (1989) 357] formulations.

  3. Range image segmentation using Zernike moment-based generalized edge detector

    NASA Technical Reports Server (NTRS)

    Ghosal, S.; Mehrotra, R.

    1992-01-01

    The authors proposed a novel Zernike moment-based generalized step edge detection method which can be used for segmenting range and intensity images. A generalized step edge detector is developed to identify different kinds of edges in range images. These edge maps are thinned and linked to provide final segmentation. A generalized edge is modeled in terms of five parameters: orientation, two slopes, one step jump at the location of the edge, and the background gray level. Two complex and two real Zernike moment-based masks are required to determine all these parameters of the edge model. Theoretical noise analysis is performed to show that these operators are quite noise tolerant. Experimental results are included to demonstrate edge-based segmentation technique.

  4. Large Area Imaging Detector for Long-Range, Passive Detection of Fissile Material

    SciTech Connect

    Ziock, K P; Craig, W W; Fabris, L; Lanza, R C; Gallagher, S; Horn, B P; Madden, N W

    2003-10-29

    Recent events highlight the increased risk of a terrorist attack using either a nuclear or a radiological weapon. One of the key needs to counter such a threat is long-range detection of nuclear material. Theoretically, gamma-ray emissions from such material should allow passive detection to distances greater than 100 m. However, detection at this range has long been thought impractical due to fluctuating levels of natural background radiation. These fluctuations are the major source of uncertainty in detection and mean that sensitivity cannot be increased simply by increasing detector size. Recent work has shown that this problem can be overcome through the use of imaging techniques. In this paper we describe the background problems, the advantages of imaging and the construction of a prototype, large-area (0.57 m{sup 2}) gamma-ray imager to detect nuclear materials at distances of {approx}100 m.

  5. Large Area Imaging Detector for Long-Range, Passive Detection Of Fissile Material

    SciTech Connect

    Ziock, K P; Craig, W W; Fabris, L; Lanza, R C; Gallagher, S; Horn, B P; Madden, N W

    2004-07-30

    Recent events highlight the increased risk of a terrorist attack using either a nuclear or a radiological weapon. One of the key needs to counter such a threat is long-range detection of nuclear material. Theoretically, gamma-ray emissions from such material should allow passive detection to distances greater than 100 m. However, detection at this range has long been thought impractical due to fluctuating levels of natural background radiation. These fluctuations are the major source of uncertainty in detection and mean that sensitivity cannot be increased simply by increasing detector size. Recent work has shown that this problem can be overcome through the use of imaging techniques. In this paper we describe the background problems, the advantages of imaging and the construction of a prototype, large-area (0.57 m{sup 2}) gamma-ray imager to detect nuclear materials at distances of {approx}100 m.

  6. A low-noise large dynamic-range readout suitable for laser spectroscopy with photodiodes

    NASA Astrophysics Data System (ADS)

    Pullia, A.; Sanvito, T.; Potenza, M. A.; Zocca, F.

    2012-10-01

    An original low-noise large dynamic-range readout system for optical light spectroscopy with PIN diodes is presented. The front-end circuit is equipped with a smart device for automatic cancellation of the large dc offset brought about by the photodiode current. This device sinks away the exact amount of dc current from the preamplifier input, yielding auto zeroing of the output-voltage offset, while introducing the minimum electronic noise possible. As a result the measurement dynamic-range is maximized. Moreover, an auxiliary inspection point is provided which precisely tracks the dc component of the photodiode current. This output allows for precise beam alignment and may also be used for diagnostic purposes. The excellent gain stability and linearity make the circuit perfectly suited for optical-light pulse spectroscopy. Applications include particle sizing in the 100 nm range, two-dimensional characterization of semiconductor detectors, ultra-precise characterization of laser beam stability, confocal microscopy.

  7. Real-time high dynamic range laser scanning microscopy

    PubMed Central

    Vinegoni, C.; Leon Swisher, C.; Fumene Feruglio, P.; Giedt, R. J.; Rousso, D. L.; Stapleton, S.; Weissleder, R.

    2016-01-01

    In conventional confocal/multiphoton fluorescence microscopy, images are typically acquired under ideal settings and after extensive optimization of parameters for a given structure or feature, often resulting in information loss from other image attributes. To overcome the problem of selective data display, we developed a new method that extends the imaging dynamic range in optical microscopy and improves the signal-to-noise ratio. Here we demonstrate how real-time and sequential high dynamic range microscopy facilitates automated three-dimensional neural segmentation. We address reconstruction and segmentation performance on samples with different size, anatomy and complexity. Finally, in vivo real-time high dynamic range imaging is also demonstrated, making the technique particularly relevant for longitudinal imaging in the presence of physiological motion and/or for quantification of in vivo fast tracer kinetics during functional imaging. PMID:27032979

  8. Real-time high dynamic range laser scanning microscopy

    NASA Astrophysics Data System (ADS)

    Vinegoni, C.; Leon Swisher, C.; Fumene Feruglio, P.; Giedt, R. J.; Rousso, D. L.; Stapleton, S.; Weissleder, R.

    2016-04-01

    In conventional confocal/multiphoton fluorescence microscopy, images are typically acquired under ideal settings and after extensive optimization of parameters for a given structure or feature, often resulting in information loss from other image attributes. To overcome the problem of selective data display, we developed a new method that extends the imaging dynamic range in optical microscopy and improves the signal-to-noise ratio. Here we demonstrate how real-time and sequential high dynamic range microscopy facilitates automated three-dimensional neural segmentation. We address reconstruction and segmentation performance on samples with different size, anatomy and complexity. Finally, in vivo real-time high dynamic range imaging is also demonstrated, making the technique particularly relevant for longitudinal imaging in the presence of physiological motion and/or for quantification of in vivo fast tracer kinetics during functional imaging.

  9. High-dynamic-range pixel architectures for diagnostic medical imaging

    NASA Astrophysics Data System (ADS)

    Karim, Karim S.; Yin, Sherman; Nathan, Arokia; Rowlands, John A.

    2004-05-01

    One approach to increase pixel signal-to-noise ratio (SNR) in low noise digital fluoroscopy is to employ in-situ pixel amplification via current-mediated active pixel sensors (C-APS). Experiments reveal a reduction in readout noise and indicate that an a-Si C-APS, coupled together with an established X-ray detection technology such as amorphous selenium (a-Se), can meet the stringent requirements (of < 1000 noise electrons) for digital X-ray fluoroscopy. A challenge with the C-APS circuit is the presence of a small-signal input linearity constraint. While using such a pixel amplifier for real-time fluoroscopy (where the exposure level is small) is feasible, the voltage change at the amplifier input is much higher in chest radiography or mammography due to the larger X-ray exposure levels. The larger input voltage causes the C-APS output to be non-linear thus reducing the pixel dynamic range. In addition, the resulting larger pixel output current causes the external column amplifier to saturate further reducing the pixel dynamic range. In this research, we investigate two alternate amplified pixel architectures that exhibit higher dynamic range. The test pixels are designed and simulated using an a-Si TFT model implemented in Verilog-A and results indicate a linear performance, high dynamic range, and a programmable circuit gain via choice of supply voltage and sampling time. These high dynamic range pixel architectures have the potential to enable a large area, active matrix flat panel imager (AMFPI) to switch instantly between low exposure, fluoroscopic imaging and higher exposure radiographic imaging modes. Lastly, the high dynamic range pixel circuits are suitable for integration with on-panel multiplexers for both gate and data lines, which can further reduce circuit complexity.

  10. Frequency-Modulated, Continuous-Wave Laser Ranging Using Photon-Counting Detectors

    NASA Technical Reports Server (NTRS)

    Erkmen, Baris I.; Barber, Zeb W.; Dahl, Jason

    2014-01-01

    Optical ranging is a problem of estimating the round-trip flight time of a phase- or amplitude-modulated optical beam that reflects off of a target. Frequency- modulated, continuous-wave (FMCW) ranging systems obtain this estimate by performing an interferometric measurement between a local frequency- modulated laser beam and a delayed copy returning from the target. The range estimate is formed by mixing the target-return field with the local reference field on a beamsplitter and detecting the resultant beat modulation. In conventional FMCW ranging, the source modulation is linear in instantaneous frequency, the reference-arm field has many more photons than the target-return field, and the time-of-flight estimate is generated by balanced difference- detection of the beamsplitter output, followed by a frequency-domain peak search. This work focused on determining the maximum-likelihood (ML) estimation algorithm when continuous-time photoncounting detectors are used. It is founded on a rigorous statistical characterization of the (random) photoelectron emission times as a function of the incident optical field, including the deleterious effects caused by dark current and dead time. These statistics enable derivation of the Cramér-Rao lower bound (CRB) on the accuracy of FMCW ranging, and derivation of the ML estimator, whose performance approaches this bound at high photon flux. The estimation algorithm was developed, and its optimality properties were shown in simulation. Experimental data show that it performs better than the conventional estimation algorithms used. The demonstrated improvement is a factor of 1.414 over frequency-domainbased estimation. If the target interrogating photons and the local reference field photons are costed equally, the optimal allocation of photons between these two arms is to have them equally distributed. This is different than the state of the art, in which the local field is stronger than the target return. The optimal

  11. Real-time extended dynamic range imaging in shearography

    SciTech Connect

    Groves, Roger M.; Pedrini, Giancarlo; Osten, Wolfgang

    2008-10-20

    Extended dynamic range (EDR) imaging is a postprocessing technique commonly associated with photography. Multiple images of a scene are recorded by the camera using different shutter settings and are merged into a single higher dynamic range image. Speckle interferometry and holography techniques require a well-modulated intensity signal to extract the phase information, and of these techniques shearography is most sensitive to different object surface reflectivities as it uses self-referencing from a sheared image. In this paper the authors demonstrate real-time EDR imaging in shearography and present experimental results from a difficult surface reflectivity sample: a wooden panel painting containing gold and dark earth color paint.

  12. Real-Time Local Range On-Demand and Dynamic Regional Range Images

    SciTech Connect

    Tsap, L.V.

    2000-02-22

    This paper presents a new approach to a gesture tracking system using real-time range on-demand. The system represents a gesture-controlled interface for interactive visual exploration of large data sets. The paper describes a method performing range processing only when necessary and where necessary. Range data is processed only for non-static regions of interest. This is accomplished by a set of filters on the color, motion, and range data. The speedup achieved is between 41% and 54%. The algorithm also includes a robust skin color segmentation insensitive to illumination changes. Selective range processing results in dynamic regional range images (DRRIs). This development is also placed in a broader context of a biological visual system emulation, specifically redundancies and attention mechanisms.

  13. Real-Time Local Range On-Demand for Tracking Gestures and Dynamic Regional Range Images

    SciTech Connect

    Tsap, L.V.

    2000-05-30

    This paper presents a new approach to a gesture-tracking system using real-time range on-demand. The system represents a gesture-controlled interface for interactive visual exploration of large data sets. The paper describes a method performing range processing only when necessary and where necessary. Range data is processed only for non-static regions of interest. This is accomplished by a set of filters on the color, motion, and range data. The speedup achieved is between 41% and 54%. The algorithm also includes a robust skin-color segmentation insensitive to illumination changes. Selective range processing results in dynamic regional range images (DRRIs). This development is also placed in a broader context of a biological visual system emulation, specifically redundancies and attention mechanisms.

  14. Phase Preserving Dynamic Range Compression of Aeromagnetic Images

    NASA Astrophysics Data System (ADS)

    Kovesi, Peter

    2014-05-01

    Geoscientific images with a high dynamic range, such as aeromagnetic images, are difficult to present in a manner that facilitates interpretation. The data values may range over 20000 nanoteslas or more but a computer monitor is typically designed to present input data constrained to 8 bit values. Standard photographic high dynamic range tonemapping algorithms may be unsuitable, or inapplicable to such data because they are have been developed on the basis of statistics of natural images, feature types found in natural images, and models of the human visual system. These algorithms may also require image segmentation and/or decomposition of the image into base and detail layers but these operations may have no meaning for geoscientific images. For geological and geophysical data high dynamic range images are often dealt with via histogram equalization. The problem with this approach is that the contrast stretch or compression applied to data values depends on how frequently the data values occur in the image and not on the magnitude of any data features themselves. This can lead to inappropriate distortions in the output. Other approaches include use of the Automatic Gain Control algorithm developed by Rajagopalan, or the tilt derivative. A difficulty with these approaches is that the signal can be over-normalized and perception of the overall variations in the signal can be lost. To overcome these problems a method is presented that compresses the dynamic range of an image while preserving local features. It makes no assumptions about the formation of the image, the feature types it contains, or its range of values. Thus, unlike algorithms designed for photographic images, this algorithm can be applied to a wide range of scientific images. The method is based on extracting local phase and amplitude values across the image using monogenic filters. The dynamic range of the image can then be reduced by applying a range reducing function to the amplitude values, for

  15. The design and imaging characteristics of dynamic, solid-state, flat-panel x-ray image detectors for digital fluoroscopy and fluorography.

    PubMed

    Cowen, A R; Davies, A G; Sivananthan, M U

    2008-10-01

    Dynamic, flat-panel, solid-state, x-ray image detectors for use in digital fluoroscopy and fluorography emerged at the turn of the millennium. This new generation of dynamic detectors utilize a thin layer of x-ray absorptive material superimposed upon an electronic active matrix array fabricated in a film of hydrogenated amorphous silicon (a-Si:H). Dynamic solid-state detectors come in two basic designs, the indirect-conversion (x-ray scintillator based) and the direct-conversion (x-ray photoconductor based). This review explains the underlying principles and enabling technologies associated with these detector designs, and evaluates their physical imaging characteristics, comparing their performance against the long established x-ray image intensifier television (TV) system. Solid-state detectors afford a number of physical imaging benefits compared with the latter. These include zero geometrical distortion and vignetting, immunity from blooming at exposure highlights and negligible contrast loss (due to internal scatter). They also exhibit a wider dynamic range and maintain higher spatial resolution when imaging over larger fields of view. The detective quantum efficiency of indirect-conversion, dynamic, solid-state detectors is superior to that of both x-ray image intensifier TV systems and direct-conversion detectors. Dynamic solid-state detectors are playing a burgeoning role in fluoroscopy-guided diagnosis and intervention, leading to the displacement of x-ray image intensifier TV-based systems. Future trends in dynamic, solid-state, digital fluoroscopy detectors are also briefly considered. These include the growth in associated three-dimensional (3D) visualization techniques and potential improvements in dynamic detector design.

  16. The Dynamic Range of Ultra-High Resolution Cryogenic Gamma-ray Spectrometers

    SciTech Connect

    Ali, S; Terracol, S F; Drury, O B; Friedrich, S

    2005-08-10

    We are developing high-resolution cryogenic gamma-ray spectrometers for nuclear science and non-proliferation applications. The gamma-ray detectors are composed of a bulk superconducting Sn foil absorber attached to multilayer Mo/Cu transition-edge sensors (TES). The energy resolution achieved with a 1 x 1 x 0.25 mm{sup 3} Sn absorber is 50 -90eV for {gamma}-rays up to 100 keV and it decreases for large absorber sizes. We discuss the trade-offs between energy resolution and dynamic range, as well as development of TES arrays for higher count rates and better sensitivity.

  17. Research of time discrimination circuits for PMT signal readout over large dynamic range in LHAASO WCDA

    NASA Astrophysics Data System (ADS)

    Ma, C.; Zhao, L.; Dong, R.; Jiang, Z.; Chu, S.; Gao, X.; Liu, S.; An, Q.

    2016-11-01

    In the readout electronics of the Water Cerenkov Detector Array (WCDA) in the Large High Altitude Air Shower Observatory (LHAASO), both high-resolution charge and time measurement are required over a dynamic range from 1 photoelectron (P.E.) to 4000 P.E. for the PMT signal readout. In this paper, we present our work on the design of time discrimination circuits in LHAASO WCDA, especially on improvement to reduce the circuit dead time. Several approaches were studied through analysis and simulations, and actual circuits were designed and tested in the laboratory to evaluate the performance. Test results indicate that a time resolution better than 500 ps RMS is achieved in the whole large dynamic range, and the circuit dead time is successfully reduced to less than 200 ns.

  18. Temporal image stacking for noise reduction and dynamic range improvement

    NASA Astrophysics Data System (ADS)

    Atanassov, Kalin; Nash, James; Goma, Sergio; Ramachandra, Vikas; Siddiqui, Hasib

    2013-03-01

    The dynamic range of an imager is determined by the ratio of the pixel well capacity to the noise floor. As the scene dynamic range becomes larger than the imager dynamic range, the choices are to saturate some parts of the scene or "bury" others in noise. In this paper we propose an algorithm that produces high dynamic range images by "stacking" sequentially captured frames which reduces the noise and creates additional bits. The frame stacking is done by frame alignment subject to a projective transform and temporal anisotropic diffusion. The noise sources contributing to the noise floor are the sensor heat noise, the quantization noise, and the sensor fixed pattern noise. We demonstrate that by stacking images the quantization and heat noise are reduced and the decrease is limited only by the fixed pattern noise. As the noise is reduced, the resulting cleaner image enables the use of adaptive tone mapping algorithms which render HDR images in an 8-bit container without significant noise increase.

  19. High speed high dynamic range high accuracy measurement system

    SciTech Connect

    Deibele, Craig E.; Curry, Douglas E.; Dickson, Richard W.; Xie, Zaipeng

    2016-11-29

    A measuring system includes an input that emulates a bandpass filter with no signal reflections. A directional coupler connected to the input passes the filtered input to electrically isolated measuring circuits. Each of the measuring circuits includes an amplifier that amplifies the signal through logarithmic functions. The output of the measuring system is an accurate high dynamic range measurement.

  20. Log amplifier instrument measures physiological biopotentials over wide dynamic range

    NASA Technical Reports Server (NTRS)

    Kado, R. T.

    1970-01-01

    To record biopotentials with extreme dynamic ranges, biopotential inputs are capacitatively coupled to a miniature, low power, solid-state signal conditioner consisting of a two-stage differential preamplifier that has a low noise figure. The ouput of the preamplifier uses diodes to provide an overall gain which is nearly logarithmic.

  1. Calibration of semiconductor detectors in the 200-8500 keV range at VNIIM.

    PubMed

    Tereshchenko, Evgeny E; Moiseev, Nikolay

    2012-09-01

    At the ionising radiation department of the D.I. Mendeleyev Institute for Metrology, a semiconductor detector was calibrated in the energy range 200-8500 keV using (n,2γ) and (n,γ) reactions. Separate cylindrical targets (77 mm diameter and 10mm height) were made from mercuric sulphate, sodium chloride and metallic titanium. A (252)Cf spontaneous fission neutron source, placed in 150 mm diameter polyethylene ball, was used to generate thermal neutrons. The optimal target dimensions were determined taking into account the thermal neutron cross-sections and gamma-radiation attenuations in the target materials. The influence of the background radiation induced by neutrons from the walls, floors and ceilings was also taken into account. The shapes of the efficiency curves for point and volume sources in the 200-8500 keV range have been investigated. The experimental results are in good agreement with Monte-Carlo calculations. The emission rate of the 6.13 MeV photons from a (238)Pu-(13)C source was determined with an expanded uncertainty, U(c), of 10% (k=2).

  2. Validating plastic scintillation detectors for photon dosimetry in the radiologic energy range

    SciTech Connect

    Lessard, Francois; Archambault, Louis; Plamondon, Mathieu; and others

    2012-09-15

    Purpose: Photon dosimetry in the kilovolt (kV) energy range represents a major challenge for diagnostic and interventional radiology and superficial therapy. Plastic scintillation detectors (PSDs) are potentially good candidates for this task. This study proposes a simple way to obtain accurate correction factors to compensate for the response of PSDs to photon energies between 80 and 150 kVp. The performance of PSDs is also investigated to determine their potential usefulness in the diagnostic energy range. Methods: A 1-mm-diameter, 10-mm-long PSD was irradiated by a Therapax SXT 150 unit using five different beam qualities made of tube potentials ranging from 80 to 150 kVp and filtration thickness ranging from 0.8 to 0.2 mmAl + 1.0 mmCu. The light emitted by the detector was collected using an 8-m-long optical fiber and a polychromatic photodiode, which converted the scintillation photons to an electrical current. The PSD response was compared with the reference free air dose rate measured with a calibrated Farmer NE2571 ionization chamber. PSD measurements were corrected using spectra-weighted corrections, accounting for mass energy-absorption coefficient differences between the sensitive volumes of the ionization chamber and the PSD, as suggested by large cavity theory (LCT). Beam spectra were obtained from x-ray simulation software and validated experimentally using a CdTe spectrometer. Correction factors were also obtained using Monte Carlo (MC) simulations. Percent depth dose (PDD) measurements were compensated for beam hardening using the LCT correction method. These PDD measurements were compared with uncorrected PSD data, PDD measurements obtained using Gafchromic films, Monte Carlo simulations, and previous data. Results: For each beam quality used, the authors observed an increase of the energy response with effective energy when no correction was applied to the PSD response. Using the LCT correction, the PSD response was almost energy independent, with

  3. Dynamic Range Across Music Genres and the Perception of Dynamic Compression in Hearing-Impaired Listeners.

    PubMed

    Kirchberger, Martin; Russo, Frank A

    2016-02-10

    Dynamic range compression serves different purposes in the music and hearing-aid industries. In the music industry, it is used to make music louder and more attractive to normal-hearing listeners. In the hearing-aid industry, it is used to map the variable dynamic range of acoustic signals to the reduced dynamic range of hearing-impaired listeners. Hence, hearing-aided listeners will typically receive a dual dose of compression when listening to recorded music. The present study involved an acoustic analysis of dynamic range across a cross section of recorded music as well as a perceptual study comparing the efficacy of different compression schemes. The acoustic analysis revealed that the dynamic range of samples from popular genres, such as rock or rap, was generally smaller than the dynamic range of samples from classical genres, such as opera and orchestra. By comparison, the dynamic range of speech, based on recordings of monologues in quiet, was larger than the dynamic range of all music genres tested. The perceptual study compared the effect of the prescription rule NAL-NL2 with a semicompressive and a linear scheme. Music subjected to linear processing had the highest ratings for dynamics and quality, followed by the semicompressive and the NAL-NL2 setting. These findings advise against NAL-NL2 as a prescription rule for recorded music and recommend linear settings.

  4. Dynamic Range Across Music Genres and the Perception of Dynamic Compression in Hearing-Impaired Listeners

    PubMed Central

    Kirchberger, Martin

    2016-01-01

    Dynamic range compression serves different purposes in the music and hearing-aid industries. In the music industry, it is used to make music louder and more attractive to normal-hearing listeners. In the hearing-aid industry, it is used to map the variable dynamic range of acoustic signals to the reduced dynamic range of hearing-impaired listeners. Hence, hearing-aided listeners will typically receive a dual dose of compression when listening to recorded music. The present study involved an acoustic analysis of dynamic range across a cross section of recorded music as well as a perceptual study comparing the efficacy of different compression schemes. The acoustic analysis revealed that the dynamic range of samples from popular genres, such as rock or rap, was generally smaller than the dynamic range of samples from classical genres, such as opera and orchestra. By comparison, the dynamic range of speech, based on recordings of monologues in quiet, was larger than the dynamic range of all music genres tested. The perceptual study compared the effect of the prescription rule NAL-NL2 with a semicompressive and a linear scheme. Music subjected to linear processing had the highest ratings for dynamics and quality, followed by the semicompressive and the NAL-NL2 setting. These findings advise against NAL-NL2 as a prescription rule for recorded music and recommend linear settings. PMID:26868955

  5. High-dynamic-range scene compression in humans

    NASA Astrophysics Data System (ADS)

    McCann, John J.

    2006-02-01

    Single pixel dynamic-range compression alters a particular input value to a unique output value - a look-up table. It is used in chemical and most digital photographic systems having S-shaped transforms to render high-range scenes onto low-range media. Post-receptor neural processing is spatial, as shown by the physiological experiments of Dowling, Barlow, Kuffler, and Hubel & Wiesel. Human vision does not render a particular receptor-quanta catch as a unique response. Instead, because of spatial processing, the response to a particular quanta catch can be any color. Visual response is scene dependent. Stockham proposed an approach to model human range compression using low-spatial frequency filters. Campbell, Ginsberg, Wilson, Watson, Daly and many others have developed spatial-frequency channel models. This paper describes experiments measuring the properties of desirable spatial-frequency filters for a variety of scenes. Given the radiances of each pixel in the scene and the observed appearances of objects in the image, one can calculate the visual mask for that individual image. Here, visual mask is the spatial pattern of changes made by the visual system in processing the input image. It is the spatial signature of human vision. Low-dynamic range images with many white areas need no spatial filtering. High-dynamic-range images with many blacks, or deep shadows, require strong spatial filtering. Sun on the right and shade on the left requires directional filters. These experiments show that variable scene- scenedependent filters are necessary to mimic human vision. Although spatial-frequency filters can model human dependent appearances, the problem still remains that an analysis of the scene is still needed to calculate the scene-dependent strengths of each of the filters for each frequency.

  6. Molecular dynamics simulations of bubble nucleation in dark matter detectors.

    PubMed

    Denzel, Philipp; Diemand, Jürg; Angélil, Raymond

    2016-01-01

    Bubble chambers and droplet detectors used in dosimetry and dark matter particle search experiments use a superheated metastable liquid in which nuclear recoils trigger bubble nucleation. This process is described by the classical heat spike model of F. Seitz [Phys. Fluids (1958-1988) 1, 2 (1958)PFLDAS0031-917110.1063/1.1724333], which uses classical nucleation theory to estimate the amount and the localization of the deposited energy required for bubble formation. Here we report on direct molecular dynamics simulations of heat-spike-induced bubble formation. They allow us to test the nanoscale process described in the classical heat spike model. 40 simulations were performed, each containing about 20 million atoms, which interact by a truncated force-shifted Lennard-Jones potential. We find that the energy per length unit needed for bubble nucleation agrees quite well with theoretical predictions, but the allowed spike length and the required total energy are about twice as large as predicted. This could be explained by the rapid energy diffusion measured in the simulation: contrary to the assumption in the classical model, we observe significantly faster heat diffusion than the bubble formation time scale. Finally we examine α-particle tracks, which are much longer than those of neutrons and potential dark matter particles. Empirically, α events were recently found to result in louder acoustic signals than neutron events. This distinction is crucial for the background rejection in dark matter searches. We show that a large number of individual bubbles can form along an α track, which explains the observed larger acoustic amplitudes.

  7. Molecular dynamics simulations of bubble nucleation in dark matter detectors

    NASA Astrophysics Data System (ADS)

    Denzel, Philipp; Diemand, Jürg; Angélil, Raymond

    2016-01-01

    Bubble chambers and droplet detectors used in dosimetry and dark matter particle search experiments use a superheated metastable liquid in which nuclear recoils trigger bubble nucleation. This process is described by the classical heat spike model of F. Seitz [Phys. Fluids (1958-1988) 1, 2 (1958), 10.1063/1.1724333], which uses classical nucleation theory to estimate the amount and the localization of the deposited energy required for bubble formation. Here we report on direct molecular dynamics simulations of heat-spike-induced bubble formation. They allow us to test the nanoscale process described in the classical heat spike model. 40 simulations were performed, each containing about 20 million atoms, which interact by a truncated force-shifted Lennard-Jones potential. We find that the energy per length unit needed for bubble nucleation agrees quite well with theoretical predictions, but the allowed spike length and the required total energy are about twice as large as predicted. This could be explained by the rapid energy diffusion measured in the simulation: contrary to the assumption in the classical model, we observe significantly faster heat diffusion than the bubble formation time scale. Finally we examine α -particle tracks, which are much longer than those of neutrons and potential dark matter particles. Empirically, α events were recently found to result in louder acoustic signals than neutron events. This distinction is crucial for the background rejection in dark matter searches. We show that a large number of individual bubbles can form along an α track, which explains the observed larger acoustic amplitudes.

  8. Managing Dynamic Range for Visualization of Astronomical Data

    NASA Astrophysics Data System (ADS)

    Hurt, R. L.

    2005-12-01

    The steps involved in transforming one or more astronomical FITS datasets into a print-friendly picture are similar to the photographer's role in taking a photograph. For many images, a key step is compressing dynamic range so that it can be viewed in print or onscreen. Since astronomical datasets can span many magnitudes of dynamic range, they must generally be transformed by the application of a stretch function to render into viewable 8-bit graphics. Many tools for this exist, including the Photoshop FITS LIberator which has a flexible system for stretching data. The quality of the final product can be improved by a proper understanding the characteristics of common stretch functions and how to renormalize the datasets through background subtraction and scaling. This paper will present a practical overview of these topics and show how stretch functions can be used most effectively.

  9. Fluorescence-based Broad Dynamic Range Viscosity Probes.

    PubMed

    Dragan, Anatoliy; Graham, August E; Geddes, Chris D

    2014-03-01

    We introduce two new fluorescent viscosity probes, SYBR Green (SG) and PicoGreen (PG), that we have studied over a broad range of viscosity and in collagen solutions. In water, both dyes have low quantum yields and excited state lifetimes, while in viscous solvents or in complex with DNA both parameters dramatically (300-1000-fold) increase. We show that in log-log scale the dependence of the dyes' quantum yield vs. viscosity is linear, the slope of which is sensitive to temperature. Application of SG and PG, as a fluorescence-based broad dynamic range viscosity probes, to the life sciences is discussed.

  10. Linear dynamic range enhancement in a CMOS imager

    NASA Technical Reports Server (NTRS)

    Pain, Bedabrata (Inventor)

    2008-01-01

    A CMOS imager with increased linear dynamic range but without degradation in noise, responsivity, linearity, fixed-pattern noise, or photometric calibration comprises a linear calibrated dual gain pixel in which the gain is reduced after a pre-defined threshold level by switching in an additional capacitance. The pixel may include a novel on-pixel latch circuit that is used to switch in the additional capacitance.

  11. Infrared predetection dynamic range compression via photorefractive crystals

    NASA Technical Reports Server (NTRS)

    Liu, Hua-Kuang; Cheng, Li-Jen

    1988-01-01

    The theoretical basis and practical implementation of a predetection dynamic-range compression technique for IR sensor systems are discussed. The approach takes advantage of the nonlinear intensity dependence of the gain coefficient in photorefractive crystals. Its feasibility is demonstrated in numerical computations using the experimental data of Cheng and Partovi (1986) on two-wave mixing in GaAs at 1.15 micron wavelength.

  12. High Dynamic Range Characterization of the Trauma Patient Plasma Proteome

    PubMed Central

    Liu, Tao; Qian, Wei-Jun; Gritsenko, Marina A.; Xiao, Wenzhong; Moldawer, Lyle L.; Kaushal, Amit; Monroe, Matthew E.; Varnum, Susan M.; Moore, Ronald J.; Purvine, Samuel O.; Maier, Ronald V.; Davis, Ronald W.; Tompkins, Ronald G.; Camp II, David G.; Smith, Richard D.

    2007-01-01

    SUMMARY While human plasma represents an attractive sample for disease biomarker discovery, the extreme complexity and large dynamic range in protein concentrations present significant challenges for characterization, candidate biomarker discovery, and validation. Herein, we describe a strategy that combines immunoaffinity subtraction and subsequent chemical fractionation based on cysteinyl peptide and N-glycopeptide captures with 2D-LC-MS/MS to increase the dynamic range of analysis for plasma. Application of this “divide-and-conquer” strategy to trauma patient plasma significantly improved the overall dynamic range of detection and resulted in confident identification of 22,267 unique peptides from four different peptide populations (cysteinyl peptides, non-cysteinyl peptides, N-glycopeptides, and non-glycopeptides) that covered 3654 different proteins with 1494 proteins identified by multiple peptides. Numerous low-abundance proteins were identified, exemplified by 78 “classic” cytokines and cytokine receptors and by 136 human cell differentiation molecules. Additionally, a total of 2910 different N-glycopeptides that correspond to 662 N-glycoproteins and 1553 N-glycosylation sites were identified. A panel of the proteins identified in this study is known to be involved in inflammation and immune responses. This study established an extensive reference protein database for trauma patients, which provides a foundation for future high-throughput quantitative plasma proteomic studies designed to elucidate the mechanisms that underlie systemic inflammatory responses. PMID:16684767

  13. High Dynamic Range Characterization of the Trauma Patient Plasma Proteome

    SciTech Connect

    Liu, Tao; Qian, Weijun; Gritsenko, Marina A.; Xiao, Wenzhong; Moldawer, Lyle L.; Kaushal, Amit; Monroe, Matthew E.; Varnum, Susan M.; Moore, Ronald J.; Purvine, Samuel O.; Maier, Ronald V.; Davis, Ronald W.; Tompkins, Ronald G.; Camp, David G.; Smith, Richard D.

    2006-06-08

    While human plasma represents an attractive sample for disease biomarker discovery, the extreme complexity and large dynamic range in protein concentrations present significant challenges for characterization, candidate biomarker discovery, and validation. Herein, we describe a strategy that combines immunoaffinity subtraction and chemical fractionation based on cysteinyl peptide and N-glycopeptide captures with 2D-LC-MS/MS to increase the dynamic range of analysis for plasma. Application of this ''divide-and-conquer'' strategy to trauma patient plasma significantly improved the overall dynamic range of detection and resulted in confident identification of 22,267 unique peptides from four different peptide populations (cysteinyl peptides, non-cysteinyl peptides, N-glycopeptides, and non-glycopeptides) that covered 3654 nonredundant proteins. Numerous low-abundance proteins were identified, exemplified by 78 ''classic'' cytokines and cytokine receptors and by 136 human cell differentiation molecules. Additionally, a total of 2910 different N-glycopeptides that correspond to 662 N-glycoproteins and 1553 N-glycosylation sites were identified. A panel of the proteins identified in this study is known to be involved in inflammation and immune responses. This study established an extensive reference protein database for trauma patients, which provides a foundation for future high-throughput quantitative plasma proteomic studies designed to elucidate the mechanisms that underlie systemic inflammatory responses.

  14. A method for the evaluation of wide dynamic range cameras

    NASA Astrophysics Data System (ADS)

    Wong, Ping Wah; Lu, Yu Hua

    2012-01-01

    We propose a multi-component metric for the evaluation of digital or video cameras under wide dynamic range (WDR) scenes. The method is based on a single image capture using a specifically designed WDR test chart and light box. Test patterns on the WDR test chart include gray ramps, color patches, arrays of gray patches, white bars, and a relatively dark gray background. The WDR test chart is professionally made using 3 layers of transparencies to produce a contrast ratio of approximately 110 dB for WDR testing. A light box is designed to provide a uniform surface with light level at about 80K to 100K lux, which is typical of a sunny outdoor scene. From a captured image, 9 image quality component scores are calculated. The components include number of resolvable gray steps, dynamic range, linearity of tone response, grayness of gray ramp, number of distinguishable color patches, smearing resistance, edge contrast, grid clarity, and weighted signal-to-noise ratio. A composite score is calculated from the 9 component scores to reflect the comprehensive image quality in cameras under WDR scenes. Experimental results have demonstrated that the multi-component metric corresponds very well to subjective evaluation of wide dynamic range behavior of cameras.

  15. Highly mobile laser ranging facilities of the Crustal Dynamics Project

    NASA Technical Reports Server (NTRS)

    Coates, R. J.

    1984-01-01

    Technical specifications, performance, and applications of the NASA transportable laser ranging systems (TLRS-1 and -2) for use in the Crustal Dynamics Program are described. TLRS-1 is truck-mounted, with the laser deployed through the roof. Interacting with the LAGEOS satellite, TLRS has a photoelectric receiver for gathering data on the roundtrip time of the laser beam for calculations of the range gate. The laser has a 0.1 nsec pulse at 3.5 mJ/pulse. Range is measured to within an error of 9 cm. The TLRS-2 version is configured for ease of air transport and modular breakdown and assembly. It has been activated on Easter Island. TLRS-3 and -4 are in development to serve as mobile units in South America and the Mediterranean area.

  16. Fast parallel algorithms for short-range molecular dynamics

    SciTech Connect

    Plimpton, S.

    1993-05-01

    Three parallel algorithms for classical molecular dynamics are presented. The first assigns each processor a subset of atoms; the second assigns each a subset of inter-atomic forces to compute; the third assigns each a fixed spatial region. The algorithms are suitable for molecular dynamics models which can be difficult to parallelize efficiently -- those with short-range forces where the neighbors of each atom change rapidly. They can be implemented on any distributed-memory parallel machine which allows for message-passing of data between independently executing processors. The algorithms are tested on a standard Lennard-Jones benchmark problem for system sizes ranging from 500 to 10,000,000 atoms on three parallel supercomputers, the nCUBE 2, Intel iPSC/860, and Intel Delta. Comparing the results to the fastest reported vectorized Cray Y-MP and C90 algorithm shows that the current generation of parallel machines is competitive with conventional vector supercomputers even for small problems. For large problems, the spatial algorithm achieves parallel efficiencies of 90% and the Intel Delta performs about 30 times faster than a single Y-MP processor and 12 times faster than a single C90 processor. Trade-offs between the three algorithms and guidelines for adapting them to more complex molecular dynamics simulations are also discussed.

  17. High dynamic range hyperspectral imaging for camouflage performance test and evaluation

    NASA Astrophysics Data System (ADS)

    Pearce, D.; Feenan, J.

    2016-10-01

    This paper demonstrates the use of high dynamic range processing applied to the specific technique of hyper-spectral imaging with linescan spectrometers. The technique provides an improvement in signal to noise for reflectance estimation. This is demonstrated for field measurements of rural imagery collected from a ground-based linescan spectrometer of rural scenes. Once fully developed, the specific application is expected to improve the colour estimation approaches and consequently the test and evaluation accuracy of camouflage performance tests. Data are presented on both field and laboratory experiments that have been used to evaluate the improvements granted by the adoption of high dynamic range data acquisition in the field of hyperspectral imaging. High dynamic ranging imaging is well suited to the hyperspectral domain due to the large variation in solar irradiance across the visible and short wave infra-red (SWIR) spectrum coupled with the wavelength dependence of the nominal silicon detector response. Under field measurement conditions it is generally impractical to provide artificial illumination; consequently, an adaptation of the hyperspectral imaging and re ectance estimation process has been developed to accommodate the solar spectrum. This is shown to improve the signal to noise ratio for the re ectance estimation process of scene materials in the 400-500 nm and 700-900 nm regions.

  18. Nonlinear tuning of microresonators for dynamic range enhancement.

    PubMed

    Saghafi, M; Dankowicz, H; Lacarbonara, W

    2015-07-08

    This paper investigates the development of a novel framework and its implementation for the nonlinear tuning of nano/microresonators. Using geometrically exact mechanical formulations, a nonlinear model is obtained that governs the transverse and longitudinal dynamics of multilayer microbeams, and also takes into account rotary inertia effects. The partial differential equations of motion are discretized, according to the Galerkin method, after being reformulated into a mixed form. A zeroth-order shift as well as a hardening effect are observed in the frequency response of the beam. These results are confirmed by a higher order perturbation analysis using the method of multiple scales. An inverse problem is then proposed for the continuation of the critical amplitude at which the transition to nonlinear response characteristics occurs. Path-following techniques are employed to explore the dependence on the system parameters, as well as on the geometry of bilayer microbeams, of the magnitude of the dynamic range in nano/microresonators.

  19. Nonlinear tuning of microresonators for dynamic range enhancement

    PubMed Central

    Saghafi, M.; Dankowicz, H.; Lacarbonara, W.

    2015-01-01

    This paper investigates the development of a novel framework and its implementation for the nonlinear tuning of nano/microresonators. Using geometrically exact mechanical formulations, a nonlinear model is obtained that governs the transverse and longitudinal dynamics of multilayer microbeams, and also takes into account rotary inertia effects. The partial differential equations of motion are discretized, according to the Galerkin method, after being reformulated into a mixed form. A zeroth-order shift as well as a hardening effect are observed in the frequency response of the beam. These results are confirmed by a higher order perturbation analysis using the method of multiple scales. An inverse problem is then proposed for the continuation of the critical amplitude at which the transition to nonlinear response characteristics occurs. Path-following techniques are employed to explore the dependence on the system parameters, as well as on the geometry of bilayer microbeams, of the magnitude of the dynamic range in nano/microresonators. PMID:26345078

  20. Generation of high-dynamic range image from digital photo

    NASA Astrophysics Data System (ADS)

    Wang, Ying; Potemin, Igor S.; Zhdanov, Dmitry D.; Wang, Xu-yang; Cheng, Han

    2016-10-01

    A number of the modern applications such as medical imaging, remote sensing satellites imaging, virtual prototyping etc use the High Dynamic Range Image (HDRI). Generally to obtain HDRI from ordinary digital image the camera is calibrated. The article proposes the camera calibration method based on the clear sky as the standard light source and takes sky luminance from CIE sky model for the corresponding geographical coordinates and time. The article considers base algorithms for getting real luminance values from ordinary digital image and corresponding programmed implementation of the algorithms. Moreover, examples of HDRI reconstructed from ordinary images illustrate the article.

  1. Low Power, Wide Dynamic Range Carbon Nanotube Vacuum Gauges

    NASA Technical Reports Server (NTRS)

    Kaul, Anupama B.; Manohara, Harish M.

    2008-01-01

    This slide presentation presents carbon nanotube vacuum pressure sensor gauges that operate at low power and exhibit a wide-dynamic range based on microelectromechanical systems (MEMS) technology. The fabrication facility, and the formation process are shown. Pressure sensitivity was found to increase rapidly as the bias power was increased. In addition, by etching part of the thermal SiO2 beneath the tubes and minimizing heat conduction through the substrate, pressure sensitivity was extended toward lower pressures. Results are compared to a conventional thin film meander resistor, which was fabricated and whose pressure response was also measured for comparative purposes.

  2. The MOLDY short-range molecular dynamics package

    NASA Astrophysics Data System (ADS)

    Ackland, G. J.; D'Mellow, K.; Daraszewicz, S. L.; Hepburn, D. J.; Uhrin, M.; Stratford, K.

    2011-12-01

    We describe a parallelised version of the MOLDY molecular dynamics program. This Fortran code is aimed at systems which may be described by short-range potentials and specifically those which may be addressed with the embedded atom method. This includes a wide range of transition metals and alloys. MOLDY provides a range of options in terms of the molecular dynamics ensemble used and the boundary conditions which may be applied. A number of standard potentials are provided, and the modular structure of the code allows new potentials to be added easily. The code is parallelised using OpenMP and can therefore be run on shared memory systems, including modern multicore processors. Particular attention is paid to the updates required in the main force loop, where synchronisation is often required in OpenMP implementations of molecular dynamics. We examine the performance of the parallel code in detail and give some examples of applications to realistic problems, including the dynamic compression of copper and carbon migration in an iron-carbon alloy. Program summaryProgram title: MOLDY Catalogue identifier: AEJU_v1_0 Program summary URL:http://cpc.cs.qub.ac.uk/summaries/AEJU_v1_0.html Program obtainable from: CPC Program Library, Queen's University, Belfast, N. Ireland Licensing provisions: GNU General Public License version 2 No. of lines in distributed program, including test data, etc.: 382 881 No. of bytes in distributed program, including test data, etc.: 6 705 242 Distribution format: tar.gz Programming language: Fortran 95/OpenMP Computer: Any Operating system: Any Has the code been vectorised or parallelized?: Yes. OpenMP is required for parallel execution RAM: 100 MB or more Classification: 7.7 Nature of problem: Moldy addresses the problem of many atoms (of order 10 6) interacting via a classical interatomic potential on a timescale of microseconds. It is designed for problems where statistics must be gathered over a number of equivalent runs, such as

  3. Enhanced dynamic range fringe projection for micro-structure characterization

    NASA Astrophysics Data System (ADS)

    Samara, Ayman Mohammad

    We present a solution for one of the main limitations in classical interferometry and fringe projection, which is the dynamic range limitation. The technique is based on real time inverse fringe projection to enhance the dynamic range and increase the vertical resolution without the need of prior information about the test object or the system parameters. The object's form optical path difference map is first measured, and then used to generate inverse fringes to optically filter the low spatial frequency form. The surface finish can then be measured without the impact of the form. A stereo microscope-based fringe projection system was designed, constructed, and used to illustrate the technique. The system was also used to characterize solder bumps with an uncertainty of approximately 10%. Individual solder bumps were also characterized using Zygo's NewView(TM) scanning white light interferometer (SWLI), and the results were compared to measurements on Intel's bump metrology tool. The results show that the SWLI has the lowest uncertainty and maximum repeatability but the lowest measurement speed. Intel's tool has a repeatability of approximately 1% and a measurement speed of about 10 minutes per 100,000 bumps, making it suitable for high volume process control.

  4. Assessment of resolution and dynamic range for digital cinema

    NASA Astrophysics Data System (ADS)

    Fenimore, Charles P.; Nikolaev, A. I.

    2003-05-01

    The proponents of digital cinema seek picture quality exceeding that of the best film-based presentation. Quantifying the performance of systems for the presentation of high quality imagery presents several challenges. One is that the dynamic range and the resolution may not be simply related to the nominal characteristics of bit-depth and pixel counts. We review some of the measurement methods that have been applied to determining these characteristics. One of the presumed advantages of high bit depth systems is to reduce the visibility of image banding. Non-uniformity of the display can be compensated in test pattern design to enable the measurement of banding contrast. The subjective assessment of banding is compared to a contrast-weighted model of just noticeable image differences. Applied to a class of image banding test patterns, the metric relates dynamic range to contouring. The model produces an estimate of the visibility threshold for image contouring in a 10-bit system, superior to a simple Weber model. These measurement issues will continue to be challenges as d-cinema systems improve.

  5. Flicker reduction in tone mapped high dynamic range video

    NASA Astrophysics Data System (ADS)

    Guthier, Benjamin; Kopf, Stephan; Eble, Marc; Effelsberg, Wolfgang

    2011-01-01

    In order to display a high dynamic range (HDR) video on a regular low dynamic range (LDR) screen, it needs to be tone mapped. A great number of tone mapping (TM) operators exist - most of them designed to tone map one image at a time. Using them on each frame of an HDR video individually leads to flicker in the resulting sequence. In our work, we analyze three tone mapping operators with respect to flicker. We propose a criterion for the automatic detection of image flicker by analyzing the log average pixel brightness of the tone mapped frame. Flicker is detected if the difference between the averages of two consecutive frames is larger than a threshold derived from Stevens' power law. Fine-tuning of the threshold is done in a subjective study. Additionally, we propose a generic method to reduce flicker as a post processing step. It is applicable to all tone mapping operators. We begin by tone mapping a frame with the chosen operator. If the flicker detection reports a visible variation in the frame's brightness, its brightness is adjusted. As a result, the brightness variation is smoothed over several frames, becoming less disturbing.

  6. A dynamic attenuator improves spectral imaging with energy-discriminating, photon counting detectors.

    PubMed

    Hsieh, Scott S; Pelc, Norbert J

    2015-03-01

    Energy-discriminating, photon counting (EDPC) detectors have high potential in spectral imaging applications but exhibit degraded performance when the incident count rate approaches or exceeds the characteristic count rate of the detector. In order to reduce the requirements on the detector, we explore the strategy of modulating the X-ray flux field using a recently proposed dynamic, piecewise-linear attenuator. A previous paper studied this modulation for photon counting detectors but did not explore the impact on spectral applications. In this work, we modeled detection with a bipolar triangular pulse shape (Taguchi et al., 2011) and estimated the Cramer-Rao lower bound (CRLB) of the variance of material selective and equivalent monoenergetic images, assuming deterministic errors at high flux could be corrected. We compared different materials for the dynamic attenuator and found that rare earth elements, such as erbium, outperformed previously proposed materials such as iron in spectral imaging. The redistribution of flux reduces the variance or dose, consistent with previous studies on benefits with conventional detectors. Numerical simulations based on DICOM datasets were used to assess the impact of the dynamic attenuator for detectors with several different characteristic count rates. The dynamic attenuator reduced the peak incident count rate by a factor of 4 in the thorax and 44 in the pelvis, and a 10 Mcps/mm (2) EDPC detector with dynamic attenuator provided generally superior image quality to a 100 Mcps/mm (2) detector with reference bowtie filter for the same dose. The improvement is more pronounced in the material images.

  7. Increasing Linear Dynamic Range of a CMOS Image Sensor

    NASA Technical Reports Server (NTRS)

    Pain, Bedabrata

    2007-01-01

    A generic design and a corresponding operating sequence have been developed for increasing the linear-response dynamic range of a complementary metal oxide/semiconductor (CMOS) image sensor. The design provides for linear calibrated dual-gain pixels that operate at high gain at a low signal level and at low gain at a signal level above a preset threshold. Unlike most prior designs for increasing dynamic range of an image sensor, this design does not entail any increase in noise (including fixed-pattern noise), decrease in responsivity or linearity, or degradation of photometric calibration. The figure is a simplified schematic diagram showing the circuit of one pixel and pertinent parts of its column readout circuitry. The conventional part of the pixel circuit includes a photodiode having a small capacitance, CD. The unconventional part includes an additional larger capacitance, CL, that can be connected to the photodiode via a transfer gate controlled in part by a latch. In the high-gain mode, the signal labeled TSR in the figure is held low through the latch, which also helps to adapt the gain on a pixel-by-pixel basis. Light must be coupled to the pixel through a microlens or by back illumination in order to obtain a high effective fill factor; this is necessary to ensure high quantum efficiency, a loss of which would minimize the efficacy of the dynamic- range-enhancement scheme. Once the level of illumination of the pixel exceeds the threshold, TSR is turned on, causing the transfer gate to conduct, thereby adding CL to the pixel capacitance. The added capacitance reduces the conversion gain, and increases the pixel electron-handling capacity, thereby providing an extension of the dynamic range. By use of an array of comparators also at the bottom of the column, photocharge voltages on sampling capacitors in each column are compared with a reference voltage to determine whether it is necessary to switch from the high-gain to the low-gain mode. Depending upon

  8. Dynamic range of safe electrical stimulation of the retina

    NASA Astrophysics Data System (ADS)

    Butterwick, Alexander F.; Vankov, Alexander; Huie, Phil; Palanker, Daniel V.

    2006-02-01

    Electronic retinal prostheses represent a potentially effective approach for restoring some degree of sight in blind patients with retinal degeneration. However, levels of safe electrical stimulation and the underlying mechanisms of cellular damage are largely unknown. We measured the threshold of cellular damage as a function of pulse duration, electrode size, and number of pulses to determine the safe range of stimulation. Measurements were performed in-vitro on embryonic chicken retina with saline-filled glass pipettes for stimulation electrodes. Cellular damage was detected using Propidium Iodide fluorescent staining. Electrode size varied from 115μm to 1mm, pulse duration from 6μs to 6ms, and number of pulses from 1 to 7,500. The threshold current density was independent of electrode sizes exceeding 400μm. With smaller electrodes the current density was scaling reciprocal to the square of the pipette diameter, i.e. acting as a point source so that the damage threshold was determined by the total current in this regime. The damage threshold current measured with large electrodes (1mm) scaled with pulse duration as t -0.5, which is characteristic of electroporation. For repeated electrical pulsed exposure on the retina the threshold current density varied between 0.059 A/cm2 at 6ms to 1.3 A/cm2 at 6μs. The dynamic range of safe stimulation, i.e. the ratio of damage threshold to stimulation threshold was found to be duration-dependent, and varied from 10 to 100 at pulse durations varying between 10μs to 10ms. Maximal dynamic range of 100 was observed near 1ms pulse durations.

  9. Image sensor with high dynamic range linear output

    NASA Technical Reports Server (NTRS)

    Yadid-Pecht, Orly (Inventor); Fossum, Eric R. (Inventor)

    2007-01-01

    Designs and operational methods to increase the dynamic range of image sensors and APS devices in particular by achieving more than one integration times for each pixel thereof. An APS system with more than one column-parallel signal chains for readout are described for maintaining a high frame rate in readout. Each active pixel is sampled for multiple times during a single frame readout, thus resulting in multiple integration times. The operation methods can also be used to obtain multiple integration times for each pixel with an APS design having a single column-parallel signal chain for readout. Furthermore, analog-to-digital conversion of high speed and high resolution can be implemented.

  10. Dynamic range in the C. elegans brain network

    NASA Astrophysics Data System (ADS)

    Antonopoulos, Chris G.

    2016-01-01

    We study external electrical perturbations and their responses in the brain dynamic network of the Caenorhabditis elegans soil worm, given by the connectome of its large somatic nervous system. Our analysis is inspired by a realistic experiment where one stimulates externally specific parts of the brain and studies the persistent neural activity triggered in other cortical regions. In this work, we perturb groups of neurons that form communities, identified by the walktrap community detection method, by trains of stereotypical electrical Poissonian impulses and study the propagation of neural activity to other communities by measuring the corresponding dynamic ranges and Steven law exponents. We show that when one perturbs specific communities, keeping the rest unperturbed, the external stimulations are able to propagate to some of them but not to all. There are also perturbations that do not trigger any response. We found that this depends on the initially perturbed community. Finally, we relate our findings for the former cases with low neural synchronization, self-criticality, and large information flow capacity, and interpret them as the ability of the brain network to respond to external perturbations when it works at criticality and its information flow capacity becomes maximal.

  11. Impact of Infrared Lunar Laser Ranging on Lunar Dynamics

    NASA Astrophysics Data System (ADS)

    Viswanathan, Vishnu; Fienga, Agnès; Manche, Hervé; Gastineau, Mickael; Courde, Clément; Torre, Jean-Marie; Exertier, Pierre; Laskar, Jacques; LLR Observers : Astrogeo-OCA, Apache Point, McDonald Laser Ranging Station, Haleakala Observatory, Matera Laser Ranging Observatory

    2016-10-01

    Since 2015, in addition to the traditional green (532nm), infrared (1064nm) has been the preferred wavelength for lunar laser ranging at the Calern lunar laser ranging (LLR) site in France. Due to the better atmospheric transmission of IR with respect to Green, nearly 3 times the number of normal points have been obtained in IR than in Green [ C.Courde et al 2016 ]. In our study, in addition to the historical data obtained from various other LLR sites, we include the recent IR normal points obtained from Calern over the 1 year time span (2015-2016), constituting about 4.2% of data spread over 46 years of LLR. Near even distribution of data provided by IR on both the spatial and temporal domain, helps us to improve constraints on the internal structure of the Moon modeled within the planetary ephemeris : INPOP [ Fienga et al 2015 ]. IERS recommended models have been used in the data reduction software GINS (GRGS,CNES) [ V.Viswanathan et al 2015 ]. Constraints provided by GRAIL, on the Lunar gravitational potential and Love numbers have been taken into account in the least-square fit procedure. New estimates on the dynamical parameters of the lunar core will be presented.

  12. Dynamic-range tests for a gamma-ray sensor

    SciTech Connect

    Byrd, R.C.; Longmire, J.L.; Moss, C.E.

    1995-01-01

    The task of detecting and characterizing intense bursts of nuclear radiation requires an instrument capable of operating reliably over wide extremes of signal intensity. Developing techniques for testing and calibrating such a detector involves a combination of experimental measurements, data analyses, and computer simulations. The results of these efforts provide important insight into the instrument`s behavior in the laboratory and in its eventual application. For the present case, such studies not only verify the proper operation of the existing detector, but they also provide the basis for future improvements in its performance.

  13. Satellite laser ranging using superconducting nanowire single-photon detectors at 1064  nm wavelength.

    PubMed

    Xue, Li; Li, Zhulian; Zhang, Labao; Zhai, Dongsheng; Li, Yuqiang; Zhang, Sen; Li, Ming; Kang, Lin; Chen, Jian; Wu, Peiheng; Xiong, Yaoheng

    2016-08-15

    Satellite laser ranging operating at 1064 nm wavelength using superconducting nanowire single-photon detectors (SNSPDs) is successfully demonstrated. A SNSPD with an intrinsic quantum efficiency of 80% and a dark count rate of 100 cps at 1064 nm wavelength is developed and introduced to Yunnan Observatory in China. With improved closed-loop telescope systems (field of view of about 26''), satellites including Cryosat, Ajisai, and Glonass with ranges of 1600 km, 3100 km, and 19,500 km, respectively, are experimentally ranged with mean echo rates of 1200/min, 4200/min, and 320/min, respectively. To the best of our knowledge, this is the first demonstration of laser ranging for satellites using SNSPDs at 1064 nm wavelength. Theoretical analysis of the detection efficiency and the mean echo rate for typical satellites indicate that it is possible for a SNSPD to range satellites from low Earth orbit to geostationary Earth orbit.

  14. Temporal artifacts in flat dynamic x-ray detectors

    NASA Astrophysics Data System (ADS)

    Overdick, Michael; Solf, Torsten; Wischmann, Hans-Aloys

    2001-06-01

    Flat X-ray detectors based on CsI:Tl scintillators and amorphous silicon photodiodes are known to exhibit temporal artefacts (ghost images) which decay over time. Previously, these temporal artefacts have been attributed mainly to residual signals from the amorphous silicon photodiodes. More detailed experiments presented here show that a second class of effects, the so-called gain effects, also contributes significantly to the observed temporal artefacts. Both the residual signals and the photodiode gain effect have been characterized under various exposure conditions in the study presented here. The results of the experiments quantitatively show the decay of the temporal artefacts. Additionally, the influence of the detector's reset light on both effects in the photodiode has been studied in detail. The data from the measurements is interpreted based on a simple trapping model which suggests a strong link between the photodiode residual signals and the photodiode gain effect. For the residual signal effect a possible correction scheme is described. Furthermore, the relevance of the remaining temporal artefacts for the applications is briefly discussed for both the photodiode residual signals and the photodiode gain effect.

  15. Effect of competing short-range attraction and long-range repulsion on the dynamics of globular particle suspensions

    NASA Astrophysics Data System (ADS)

    Riest, Jonas; Naegele, Gerhard

    2015-03-01

    The dynamic clustering of globular particle suspensions exhibiting competing short-range attraction and long-range repulsion such as protein solutions has gained a lot of interest in the last years. We investigate the influence of clustering on the phase behavior, and in particular on the dynamics of globular particle systems. To this end, we explore various pair potential models by a combination of static and dynamic analytic calculation methods in conjunction with Molecular Dynamics and Monte Carlo simulations. Our results show that the cluster peak (intermediate-range-order peak) is present also in the hydrodynamic function characterizing the short-time dynamics. Moreover, an enhanced short-range attraction leads to a larger sedimentation velocity and a smaller self-diffusion coefficient. Our results are useful also for technical applications, such as in the ultrafiltration of proteins.

  16. Dynamic flat panel detector versus image intensifier in cardiac imaging: dose and image quality.

    PubMed

    Vano, E; Geiger, B; Schreiner, A; Back, C; Beissel, J

    2005-12-07

    The practical aspects of the dosimetric and imaging performance of a digital x-ray system for cardiology procedures were evaluated. The system was configured with an image intensifier (II) and later upgraded to a dynamic flat panel detector (FD). Entrance surface air kerma (ESAK) to phantoms of 16, 20, 24 and 28 cm of polymethyl methacrylate (PMMA) and the image quality of a test object were measured. Images were evaluated directly on the monitor and with numerical methods (noise and signal-to-noise ratio). Information contained in the DICOM header for dosimetry audit purposes was also tested. ESAK values per frame (or kerma rate) for the most commonly used cine and fluoroscopy modes for different PMMA thicknesses and for field sizes of 17 and 23 cm for II, and 20 and 25 cm for FD, produced similar results in the evaluated system with both technologies, ranging between 19 and 589 microGy/frame (cine) and 5 and 95 mGy min(-1) (fluoroscopy). Image quality for these dose settings was better for the FD version. The 'study dosimetric report' is comprehensive, and its numerical content is sufficiently accurate. There is potential in the future to set those systems with dynamic FD to lower doses than are possible in the current II versions, especially for digital cine runs, or to benefit from improved image quality.

  17. Dynamic flat panel detector versus image intensifier in cardiac imaging: dose and image quality

    NASA Astrophysics Data System (ADS)

    Vano, E.; Geiger, B.; Schreiner, A.; Back, C.; Beissel, J.

    2005-12-01

    The practical aspects of the dosimetric and imaging performance of a digital x-ray system for cardiology procedures were evaluated. The system was configured with an image intensifier (II) and later upgraded to a dynamic flat panel detector (FD). Entrance surface air kerma (ESAK) to phantoms of 16, 20, 24 and 28 cm of polymethyl methacrylate (PMMA) and the image quality of a test object were measured. Images were evaluated directly on the monitor and with numerical methods (noise and signal-to-noise ratio). Information contained in the DICOM header for dosimetry audit purposes was also tested. ESAK values per frame (or kerma rate) for the most commonly used cine and fluoroscopy modes for different PMMA thicknesses and for field sizes of 17 and 23 cm for II, and 20 and 25 cm for FD, produced similar results in the evaluated system with both technologies, ranging between 19 and 589 µGy/frame (cine) and 5 and 95 mGy min-1 (fluoroscopy). Image quality for these dose settings was better for the FD version. The 'study dosimetric report' is comprehensive, and its numerical content is sufficiently accurate. There is potential in the future to set those systems with dynamic FD to lower doses than are possible in the current II versions, especially for digital cine runs, or to benefit from improved image quality.

  18. Testing the Equivalence Principle in an Einstein Elevator: Detector Dynamics and Gravity Perturbations

    NASA Technical Reports Server (NTRS)

    Hubbard, Dorthy (Technical Monitor); Lorenzini, E. C.; Shapiro, I. I.; Cosmo, M. L.; Ashenberg, J.; Parzianello, G.; Iafolla, V.; Nozzoli, S.

    2003-01-01

    We discuss specific, recent advances in the analysis of an experiment to test the Equivalence Principle (EP) in free fall. A differential accelerometer detector with two proof masses of different materials free falls inside an evacuated capsule previously released from a stratospheric balloon. The detector spins slowly about its horizontal axis during the fall. An EP violation signal (if present) will manifest itself at the rotational frequency of the detector. The detector operates in a quiet environment as it slowly moves with respect to the co-moving capsule. There are, however, gravitational and dynamical noise contributions that need to be evaluated in order to define key requirements for this experiment. Specifically, higher-order mass moments of the capsule contribute errors to the differential acceleration output with components at the spin frequency which need to be minimized. The dynamics of the free falling detector (in its present design) has been simulated in order to estimate the tolerable errors at release which, in turn, define the release mechanism requirements. Moreover, the study of the higher-order mass moments for a worst-case position of the detector package relative to the cryostat has led to the definition of requirements on the shape and size of the proof masses.

  19. Optimization of detectors positioning with respect to flying dynamics for future formation flight missions

    NASA Astrophysics Data System (ADS)

    Civitani, Marta; Djalal, Sophie; Chipaux, Remi

    2009-08-01

    In a X-ray telescope in formation flight configuration, the optics and the focal-plane detectors reside in two different spacecraft. The dynamics of the detector spacecraft (DSC) with respect to the mirror spacecraft (MSC, carrying the mirrors of the telescope) changes continuously the arrival positions of the photons on the detectors. In this paper we analyze this issue for the case of the SIMBOL-X hard X-ray mission, extensively studied by CNES and ASI until 2009 spring. Due to the existing gaps between pixels and between detector modules, the dynamics of the system may produce a relevant photometric effect. The aim of this work is to present the optimization study of the control-law algorithm with respect to the detector's geometry. As the photometric effect may vary depending upon position of the source image on the detector, the analysis-carried out using the simuLOS (INAF, CNES, CEA) simulation tool-is extended over the entire SIMBOL-X field of view.

  20. Automatic dynamic range adjustment for ultrasound B-mode imaging.

    PubMed

    Lee, Yeonhwa; Kang, Jinbum; Yoo, Yangmo

    2015-02-01

    In medical ultrasound imaging, dynamic range (DR) is defined as the difference between the maximum and minimum values of the displayed signal to display and it is one of the most essential parameters that determine its image quality. Typically, DR is given with a fixed value and adjusted manually by operators, which leads to low clinical productivity and high user dependency. Furthermore, in 3D ultrasound imaging, DR values are unable to be adjusted during 3D data acquisition. A histogram matching method, which equalizes the histogram of an input image based on that from a reference image, can be applied to determine the DR value. However, it could be lead to an over contrasted image. In this paper, a new Automatic Dynamic Range Adjustment (ADRA) method is presented that adaptively adjusts the DR value by manipulating input images similar to a reference image. The proposed ADRA method uses the distance ratio between the log average and each extreme value of a reference image. To evaluate the performance of the ADRA method, the similarity between the reference and input images was measured by computing a correlation coefficient (CC). In in vivo experiments, the CC values were increased by applying the ADRA method from 0.6872 to 0.9870 and from 0.9274 to 0.9939 for kidney and liver data, respectively, compared to the fixed DR case. In addition, the proposed ADRA method showed to outperform the histogram matching method with in vivo liver and kidney data. When using 3D abdominal data with 70 frames, while the CC value from the ADRA method is slightly increased (i.e., 0.6%), the proposed method showed improved image quality in the c-plane compared to its fixed counterpart, which suffered from a shadow artifact. These results indicate that the proposed method can enhance image quality in 2D and 3D ultrasound B-mode imaging by improving the similarity between the reference and input images while eliminating unnecessary manual interaction by the user.

  1. Resolution and Mass Range Performance in Distance-of-Flight Mass Spectrometry with a Multichannel Focal-Plane Camera Detector

    SciTech Connect

    Graham, Alexander W.; Ray, Steven J.; Enke, Christie G.; Felton, Jeremy A.; Carado, Anthony J.; Barinaga, Charles J.; Koppenaal, David W.; Hieftje, Gary M.

    2011-10-05

    Distance-of-flight mass spectrometry (DOFMS) is a velocity-based mass-separation technique in which ions are separated in space along the plane of a spatially selective detector. In the present work, a solid-state charge-detection array, the focal-plane camera (FPC), was incorporated into the DOFMS platform. Use of the FPC with our DOFMS instrument resulted in improvements in analytical performance, usability, and versatility over a previous generation instrument that employed a microchannel-plate/phosphor DOF detector. Notably, FPC detection provided resolution improvements of at least a factor of two, with typical DOF linewidths of 300 {micro}m (R(FWHM)=1000). Merits of solid-state detection for DOFMS are evaluated and methods to extend the DOFMS mass range are considered.

  2. Resolution and Mass Range Performance in Distance-of-flight Mass Spectrometry with a Multichannel Focal-Plane Camera Detector.

    SciTech Connect

    Graham, Alexander W.; Ray, Steven J.; Enke, Christie G.; Felton, Jeremy A.; Carado, Anthony J.; Barinaga, Charles J.; Koppenaal, David W.; Hieftje, Gary M.

    2011-11-15

    Distance-of-flight mass spectrometry (DOFMS) is a velocity-based mass-separation technique in which ions are separated in space along the plane of a spatially selective detector. In the present work, a solid-state charge-detection array, the focal-plane camera (FPC), was incorporated into the DOFMS platform. Use of the FPC with our DOFMS instrument resulted in improvements in analytical performance, usability, and versatility over a previous generation instrument that employed a microchannel-plate/phosphor DOF detector. Notably, FPC detection provided resolution improvements of at least a factor of 2, with typical DOF linewidths of 300 μm (R((fwhm)) = 1000). The merits of solid-state detection for DOFMS are evaluated, and methods to extend the DOFMS mass range are considered.

  3. New fabrication techniques for high dynamic range tunneling sensors

    NASA Astrophysics Data System (ADS)

    Chang, David T.; Stratton, Fred P.; Kubena, Randall L.; Vickers-Kirby, Deborah J.; Joyce, Richard J.; Schimert, Thomas R.; Gooch, Roland W.

    2000-08-01

    We have developed high dynamic range (105-106 g's) tunneling accelerometers1,2 that may be ideal for smart munitions applications by employing both surface and bulk micromachining processing techniques. The highly miniaturized surface-micromachined devices can be manufactured at very low cost and integrated on chip with the control electronics. Bulk-micromachined devices with Si as the cantilever material should have reduced long-term bias drift as well as better stability at higher temperatures. Fully integrated sensors may provide advantages in minimizing microphonics for high-g applications. Previously, we described initial test results using electrostatic forces generated by a self-test electrode located under a Au cantilever3. In this paper, we describe more recent testing of Ni and Au cantilever devices on a shaker table using a novel, low input voltage (5 V) servo controller on both printed wiring board and surface-mount control circuitry. In addition, we report our initial test results for devices packaged using a low-temperature wafer-level vacuum packaging technique for low-cost manufacturing.

  4. High dynamic range coherent imaging using compressed sensing.

    PubMed

    He, Kuan; Sharma, Manoj Kumar; Cossairt, Oliver

    2015-11-30

    In both lensless Fourier transform holography (FTH) and coherent diffraction imaging (CDI), a beamstop is used to block strong intensities which exceed the limited dynamic range of the sensor, causing a loss in low-frequency information, making high quality reconstructions difficult or even impossible. In this paper, we show that an image can be recovered from high-frequencies alone, thereby overcoming the beamstop problem in both FTH and CDI. The only requirement is that the object is sparse in a known basis, a common property of most natural and manmade signals. The reconstruction method relies on compressed sensing (CS) techniques, which ensure signal recovery from incomplete measurements. Specifically, in FTH, we perform compressed sensing (CS) reconstruction of captured holograms and show that this method is applicable not only to standard FTH, but also multiple or extended reference FTH. For CDI, we propose a new phase retrieval procedure, which combines Fienup's hybrid input-output (HIO) method and CS. Both numerical simulations and proof-of-principle experiments are shown to demonstrate the effectiveness and robustness of the proposed CS-based reconstructions in dealing with missing data in both FTH and CDI.

  5. Method for increasing the dynamic range of mass spectrometers

    DOEpatents

    Belov, Mikhail; Smith, Richard D.; Udseth, Harold R.

    2004-09-07

    A method for enhancing the dynamic range of a mass spectrometer by first passing a sample of ions through the mass spectrometer having a quadrupole ion filter, whereupon the intensities of the mass spectrum of the sample are measured. From the mass spectrum, ions within this sample are then identified for subsequent ejection. As further sampling introduces more ions into the mass spectrometer, the appropriate rf voltages are applied to a quadrupole ion filter, thereby selectively ejecting the undesired ions previously identified. In this manner, the desired ions may be collected for longer periods of time in an ion trap, thus allowing better collection and subsequent analysis of the desired ions. The ion trap used for accumulation may be the same ion trap used for mass analysis, in which case the mass analysis is performed directly, or it may be an intermediate trap. In the case where collection is an intermediate trap, the desired ions are accumulated in the intermediate trap, and then transferred to a separate mass analyzer. The present invention finds particular utility where the mass analysis is performed in an ion trap mass spectrometer or a Fourier transform ion cyclotron resonance mass spectrometer.

  6. Quantitative high dynamic range beam profiling for fluorescence microscopy

    SciTech Connect

    Mitchell, T. J. Saunter, C. D.; O’Nions, W.; Girkin, J. M.; Love, G. D.

    2014-10-15

    Modern developmental biology relies on optically sectioning fluorescence microscope techniques to produce non-destructive in vivo images of developing specimens at high resolution in three dimensions. As optimal performance of these techniques is reliant on the three-dimensional (3D) intensity profile of the illumination employed, the ability to directly record and analyze these profiles is of great use to the fluorescence microscopist or instrument builder. Though excitation beam profiles can be measured indirectly using a sample of fluorescent beads and recording the emission along the microscope detection path, we demonstrate an alternative approach where a miniature camera sensor is used directly within the illumination beam. Measurements taken using our approach are solely concerned with the illumination optics as the detection optics are not involved. We present a miniature beam profiling device and high dynamic range flux reconstruction algorithm that together are capable of accurately reproducing quantitative 3D flux maps over a large focal volume. Performance of this beam profiling system is verified within an optical test bench and demonstrated for fluorescence microscopy by profiling the low NA illumination beam of a single plane illumination microscope. The generality and success of this approach showcases a widely flexible beam amplitude diagnostic tool for use within the life sciences.

  7. High Dynamic Range Beam Imaging with Two Simultaneously Sampling CCDs

    SciTech Connect

    Evtushenko, Pavel E.; Douglas, David R.

    2013-06-01

    Transverse beam profile measurement with sufficiently high dynamic range (HDR) is a key diagnostic to measure the beam halo, understand its sources and evolution. In this contribution we describe our initial experience with the HDR imaging of the electron beam at the JLab FEL. On contrary to HDR measurements made with wire scanners in counting mode, which provide only two or three 1D projections of transverse beam distribution, imaging allows to measure the distribution itself. That is especially important for non-equilibrium beams in the LINACs. The measurements were made by means of simultaneous imaging with two CCD sensors with different exposure time. Two images are combined then numerically in to one HDR image. The system works as an online tool providing HDR images at 4 Hz. An optically polished YAG:Ce crystal with the thickness of 100 {micro}m was used for the measurements. When tested with a laser beam images with the DR of about 10{sup 5} were obtained. With the electron beam the DR was somewhat smaller due to the limitations in the time structure of the tune-up beam macro pulse.

  8. High Dynamic Range Beam Imaging with Two Simultaneously Sampling CCDs

    SciTech Connect

    Evtushenko, Pavel; Douglas, David R.; Legg, Robert A.; Tennant, Christopher D.

    2013-05-01

    Transverse beam profile measurement with sufficiently high dynamic range (HDR) is a key diagnostic to measure the beam halo, understand its sources and evolution. In this contribution we describe our initial experience with the HDR imaging of the electron beam at the JLab FEL. On contrary to HDR measurements made with wire scanners in counting mode, which provide only two or three 1D projections of transverse beam distribution, imaging allows to measure the distribution itself. That is especially important for non-equilibrium beams in the LINACs. The measurements were made by means of simultaneous imaging with two CCD sensors with different exposure time. Two images are combined then numerically in to one HDR image. The system works as an online tool providing HDR images at 4 Hz. An optically polished YAG:Ce crystal with the thickness of 100 {micro}m was used for the measurements. When tested with a laser beam images with the DR of about 10{sup 5} were obtained. With the electron beam the DR was somewhat smaller due to the limitations in the time structure of the tune-up beam macro pulse.

  9. Dynamic range of atomically thin vibrating nanomechanical resonators

    SciTech Connect

    Wang, Zenghui; Feng, Philip X.-L.

    2014-03-10

    Atomically thin two-dimensional (2D) crystals offer attractive properties for making resonant nanoelectromechanical systems (NEMS) operating at high frequencies. While the fundamental limits of linear operation in such systems are important, currently there is very little quantitative knowledge of the linear dynamic range (DR) and onset of nonlinearity in these devices, which are different than in conventional 1D NEMS such as nanotubes and nanowires. Here, we present theoretical analysis and quantitative models that can be directly used to predict the DR of vibrating 2D circular drumhead NEMS resonators. We show that DR has a strong dependence ∝10log(E{sub Y}{sup 3/2}ρ{sub 3D}{sup -1/2}rtε{sup 5/2}) on device parameters, in which strain ε plays a particularly important role in these 2D systems, dominating over dimensions (radius r, thickness t). This study formulizes the effects from device physical parameters upon DR and sheds light on device design rules toward achieving high DR in 2D NEMS vibrating at radio and microwave frequencies.

  10. Threshold contrast detail detectability measurement of the fluoroscopic image quality of a dynamic solid-state digital x-ray image detector.

    PubMed

    Davies, A G; Cowen, A R; Kengyelics, S M; Bury, R F; Bruijns, T J

    2001-01-01

    Solid-state digital x-ray imaging detectors of flat-panel construction will play an increasingly important role in future medical imaging facilities. Solid-state detectors that will support both dynamic (including fluoroscopic) and radiographic image recording are under active development. The image quality of an experimental solid-state digital x-ray image detector operating in a continuous fluoroscopy mode has been investigated. The threshold contrast detail detectability (TCDD) technique was used to compare the fluoroscopic imaging performance of an experimental dynamic solid-state digital x-ray image detector with that of a reference image intensifier television (IITV) fluoroscopy system. The reference system incorporated Plumbicon TV. Results were presented as a threshold detection index, or H(T)(A), curves. Measurements were made over a range of mean entrance air kerma (EAK) rates typically used in conventional IITV fluoroscopy. At the upper and mid EAK rate range (440 and 220 nGy/s) the solid-state detector outperformed the reference IITV fluoroscopy system as measured by TCDD performance. At the lowest measured EAK rate (104 nGy/s), the solid-state detector produces slightly inferior TCDD performance compared with the reference system. Although not statistically significant at this EAK rate, the difference will increase as EAK is lowered further. Overall the TCDD results and early clinical experiences support the proposition that a current design of dynamic solid-state detector produces image quality competitive with that of modern IITV fluoroscopy systems. These findings encourage the development of compact and versatile universal x-ray imaging systems based upon solid-state detector technology to support R & F and vascular/interventional applications.

  11. Multiple-gain-ranging readout method to extend the dynamic range of amorphous silicon flat-panel imagers

    NASA Astrophysics Data System (ADS)

    Roos, Pieter G.; Colbeth, Richard E.; Mollov, Ivan; Munro, Peter; Pavkovich, John; Seppi, Edward J.; Shapiro, Edward G.; Tognina, Carlo A.; Virshup, Gary F.; Yu, J. Micheal; Zentai, George; Kaissl, Wolfgang; Matsinos, Evangelos; Richters, Jeroen; Riem, Heinrich

    2004-05-01

    The dynamic range of many flat panel imaging systems are fundamentally limited by the dynamic range of the charge amplifier and readout signal processing. We developed two new flat panel readout methods that achieve extended dynamic range by changing the read out charge amplifier feedback capacitance dynamically and on a real-time basis. In one method, the feedback capacitor is selected automatically by a level sensing circuit, pixel-by-pixel, based on its exposure level. Alternatively, capacitor selection is driven externally, such that each pixel is read out two (or more) times, each time with increased feedback capacitance. Both methods allow the acquisition of X-ray image data with a dynamic range approaching the fundamental limits of flat panel pixels. Data with an equivalent bit depth of better than 16 bits are made available for further image processing. Successful implementation of these methods requires careful matching of selectable capacitor values and switching thresholds, with the imager noise and sensitivity characteristics, to insure X-ray quantum limited operation over the whole extended dynamic range. Successful implementation also depends on the use of new calibration methods and image reconstruction algorithms, to insure artifact free rebuilding of linear image data by the downstream image processing systems. The multiple gain ranging flat panel readout method extends the utility of flat panel imagers and paves the way to new flat panel applications, such as cone beam CT. We believe that this method will provide a valuable extension to the clinical application of flat panel imagers.

  12. Calibration and GEANT4 Simulations of the Phase II Proton Compute Tomography (pCT) Range Stack Detector

    SciTech Connect

    Uzunyan, S. A.; Blazey, G.; Boi, S.; Coutrakon, G.; Dyshkant, A.; Francis, K.; Hedin, D.; Johnson, E.; Kalnins, J.; Zutshi, V.; Ford, R.; Rauch, J. E.; Rubinov, P.; Sellberg, G.; Wilson, P.; Naimuddin, M.

    2015-12-29

    Northern Illinois University in collaboration with Fermi National Accelerator Laboratory (FNAL) and Delhi University has been designing and building a proton CT scanner for applications in proton treatment planning. The Phase II proton CT scanner consists of eight planes of tracking detectors with two X and two Y coordinate measurements both before and after the patient. In addition, a range stack detector consisting of a stack of thin scintillator tiles, arranged in twelve eight-tile frames, is used to determine the water equivalent path length (WEPL) of each track through the patient. The X-Y coordinates and WEPL are required input for image reconstruction software to find the relative (proton) stopping powers (RSP) value of each voxel in the patient and generate a corresponding 3D image. In this Note we describe tests conducted in 2015 at the proton beam at the Central DuPage Hospital in Warrenville, IL, focusing on the range stack calibration procedure and comparisons with the GEANT~4 range stack simulation.

  13. Design and operational experience of a microwave cavity axion detector for the 20–100μeV range

    DOE PAGES

    Al Kenany, S.; Anil, M. A.; Backes, K. M.; ...

    2017-02-09

    We describe a dark matter axion detector designed, constructed, and operated both as an innovation platform for new cavity and amplifier technologies and as a data pathfinder in the 5-25 GHz range (~20-100 eV). The platform is small but flexible to facilitate the development of new microwave cavity and amplifier concepts in an operational environment. The experiment has recently completed its first data production; it is the first microwave cavity axion search to deploy a Josephson parametric amplifier and a dilution refrigerator to achieve near-quantum limited performance.

  14. Dynamic analysis and optimal design of exposure device of laser detector based on a virtual prototype

    NASA Astrophysics Data System (ADS)

    Xu, Da; Zhao, Jian-xun; Hu, Jun-biao; Li, Hua; Wang, Chuan-you; Li, Bing-wei

    2009-07-01

    The dynamical simulation model of the exposure device of laser detector is built up in ADAMS software. Aiming at optimizing the movement law of the pole and minimizing the maximal value of load of key parts, the influences of the spring stiffness coefficient,the damping coefficient, preload of spring and the mass of pole on the optimal goal are discussed. The virtual prototype of the exposure device of laser detector has been optimized and the optimized parameters are obtained. In order to choose the electromotor and material, intensity of key parts is checked based on ANSYS. And the problem of TQC is solved effectively by this way.

  15. Study of heavy ion range in different solid state nuclear track detector materials

    NASA Astrophysics Data System (ADS)

    Diwan, P. K.; Singh, Lakhwant; Singh, Gurinder; Kumar, Shyam

    2000-03-01

    The range of several heavy ions as 238U, 208Pb, 197Au, 139La, 58Ni and 56Fe in sodalime glass; 197Au and 58Ni in muscovite mica and Lexan polycarbonate; 209Bi and 197Au in CR-39 have been determined experimentally. The calculations of range for these projectile-target combinations have been made using the Benton and Henke [10], Mukherjee and Nayak [11], Ziegler et al. [12] and Hubert et al. [14] semiempirical formulations. Finally a comparison has been made with the experimental results.

  16. Improving the off-axis spatial resolution and dynamic range of the NIF X-ray streak cameras (invited)

    NASA Astrophysics Data System (ADS)

    MacPhee, A. G.; Dymoke-Bradshaw, A. K. L.; Hares, J. D.; Hassett, J.; Hatch, B. W.; Meadowcroft, A. L.; Bell, P. M.; Bradley, D. K.; Datte, P. S.; Landen, O. L.; Palmer, N. E.; Piston, K. W.; Rekow, V. V.; Hilsabeck, T. J.; Kilkenny, J. D.

    2016-11-01

    We report simulations and experiments that demonstrate an increase in spatial resolution of the NIF core diagnostic x-ray streak cameras by at least a factor of two, especially off axis. A design was achieved by using a corrector electron optic to flatten the field curvature at the detector plane and corroborated by measurement. In addition, particle in cell simulations were performed to identify the regions in the streak camera that contribute the most to space charge blurring. These simulations provide a tool for convolving synthetic pre-shot spectra with the instrument function so signal levels can be set to maximize dynamic range for the relevant part of the streak record.

  17. A 1-channel 3-band wide dynamic range compression chip for vibration transducer of implantable hearing aids.

    PubMed

    Kim, Dongwook; Seong, Kiwoong; Kim, Myoungnam; Cho, Jinho; Lee, Jyunghyun

    2014-01-01

    In this paper, a digital audio processing chip which uses a wide dynamic range compression (WDRC) algorithm is designed and implemented for implantable hearing aids system. The designed chip operates at a single voltage of 3.3V and drives a 16 bit parallel input and output at 32 kHz sample. The designed chip has 1-channel 3-band WDRC composed of a FIR filter bank, a level detector, and a compression part. To verify the performance of the designed chip, we measured the frequency separations of bands and compression gain control to reflect the hearing threshold level.

  18. Improving the off-axis spatial resolution and dynamic range of the NIF X-ray streak cameras (invited).

    PubMed

    MacPhee, A G; Dymoke-Bradshaw, A K L; Hares, J D; Hassett, J; Hatch, B W; Meadowcroft, A L; Bell, P M; Bradley, D K; Datte, P S; Landen, O L; Palmer, N E; Piston, K W; Rekow, V V; Hilsabeck, T J; Kilkenny, J D

    2016-11-01

    We report simulations and experiments that demonstrate an increase in spatial resolution of the NIF core diagnostic x-ray streak cameras by at least a factor of two, especially off axis. A design was achieved by using a corrector electron optic to flatten the field curvature at the detector plane and corroborated by measurement. In addition, particle in cell simulations were performed to identify the regions in the streak camera that contribute the most to space charge blurring. These simulations provide a tool for convolving synthetic pre-shot spectra with the instrument function so signal levels can be set to maximize dynamic range for the relevant part of the streak record.

  19. Development of a longer range standoff millimetre wave radar concealed threat detector

    NASA Astrophysics Data System (ADS)

    Bowring, Nicholas J.; Southgate, Matthew J.; Andrews, David A.; Rezgui, Nacer D.; Harmer, Stuart W.; O'Reilly, Dean

    2013-05-01

    A millimeter wave (75 - 110 GHz) polarimetric radar system (MiRTLE) has been developed for the detection of threat objects, such as guns, knives, or explosive devices, which have been concealed under clothing upon the human body. The system uses a Gaussian lens antenna to enable operation at stand-off ranges up to 25 meters. By utilizing ultra-wideband Swept Frequency Continuous Wave Radar very high range resolution (~ 10mm) is realized. The system is capable of detecting objects positioned in front of the body and of measuring the range of a target. By interpretation of the scattered waveform, the presence of a wide spectrum of threat items concealed on the human body may be detected. Threat detection is autonomously rendered by application of a neural network to the scattered time domain, polarimetric radar returns and the system may be taught to alarm or reject certain classes of objects; this allows for highly specific or broad spectrum threat detection. The radar system is portable and operator steerable allowing standoff monitoring of moving human targets in real time. Rapid (1ms) sweep times and fast signal acquisition and processing allow decisions to be made at video frame rates (30 fps) and integrated directly to a video feed providing the operator with a field of view and facilitating aiming. Performance parameters for detection of guns and simulated explosive devices are presented for ranges up to 25 meters.

  20. Blocked impurity band detectors applied to tunable diode laser spectroscopy in the 8- to 28-micron range

    NASA Technical Reports Server (NTRS)

    Sirota, J. M.; Reuter, Dennis C.; Mumma, Michael J.

    1993-01-01

    A novel tunable diode laser spectrometer operating at 8-28 microns is described. A blocked impurity band Si:As chip is employed as detector. This device operates in this wavelength range with high detectivity and adequate frequency response for the high-sensitivity techniques used. A combination of sweep averaging and second-harmonic detection at 22 kHz yielded signal-to-noise ratios of 1200 at wavelengths above 20 microns. The sensitivity and spectral resolution achieved are an order of magnitude better than those of Fourier instruments in this range, with an improvement in instrument time response of about 3000. Several molecular bands of CO2 and N2O are observed for what is, to our knowledge, the first time with this instrument. Examples of spectral line measurements are presented.

  1. An LC-IMS-MS Platform Providing Increased Dynamic Range for High-Throughput Proteomic Studies

    SciTech Connect

    Baker, Erin Shammel; Livesay, Eric A.; Orton, Daniel J.; Moore, Ronald J.; Danielson, William F.; Prior, David C.; Ibrahim, Yehia M.; Lamarche, Brian L.; Mayampurath, Anoop M.; Schepmoes, Athena A.; Hopkins, Derek F.; Tang, Keqi; Smith, Richard D.; Belov, Mikhail E.

    2010-02-05

    A high-throughput approach and platform using 15 minute reversed-phase capillary liquid chromatography (RPLC) separations in conjunction with ion mobility spectrometry-mass spectrometry (IMS-MS) measurements was evaluated for the rapid analysis of complex proteomics samples. To test the separation quality of the short LC gradient, a sample was prepared by spiking twenty reference peptides at varying concentrations from 1 ng/mL to 10 µg/mL into a tryptic digest of mouse blood plasma and analyzed with both a LC-Linear Ion Trap Fourier Transform (FT) MS and LC-IMS-TOF MS. The LC-FT MS detected thirteen out of the twenty spiked peptides that had concentrations ≥100 ng/mL. In contrast, the drift time selected mass spectra from the LC-IMS-TOF MS analyses yielded identifications for nineteen of the twenty peptides with all spiking level present. The greater dynamic range of the LC-IMS-TOF MS system could be attributed to two factors. First, the LC-IMS-TOF MS system enabled drift time separation of the low concentration spiked peptides from the high concentration mouse peptide matrix components, reducing signal interference and background, and allowing species to be resolved that would otherwise be obscured by other components. Second, the automatic gain control (AGC) in the linear ion trap of the hybrid FT MS instrument limits the number of ions that are accumulated to reduce space charge effects, but in turn limits the achievable dynamic range compared to the TOF detector.

  2. A simulation study investigating a radiation detector utilizing the prompt gamma range verification technique for proton radiotherapy

    NASA Astrophysics Data System (ADS)

    Lau, Andrew David

    Proton therapy has shown to be a viable therapy for radiation oncology applications. The advantages of using protons as compared to photons in the treatments of diseases with radiation are numerous including the ability to deliver overall lower amounts of lethal radiation doses to the patient. This advantage is due to the fundamental interaction mechanism of the incident therapeutic protons with the patient, which produces a characteristic dose-distribution unique only to protons. Unlike photons, the entire proton beam is absorbed within the patent and the dose-distribution's maximum occurs near the end of the proton's path. Protons deliver less dose on the skin and intervening tissues, tighter dose conformality to the disease site, as well as no dose past the target volume, sparring healthy tissue distally in the patient. Current research in proton therapy is geared towards minimizing proton range uncertainty and monitoring in-vivo the location of the proton's path. Monitoring the beam's path serves also to verify which healthy structures/tissues were irradiated and whether the target volume has met the prescription dose. Among the many techniques used for in-vivo proton monitoring, the technique based on the emitted secondary particles, specifically the Prompt Gamma (PG) method, can be used for clinical implementation. This work focuses on developing a radiation detector system for using the PG method by investigating the characterizing the secondary particle field emitted from plastic and water phantoms as well as a radiation detector based on glass materials that exploits the Cherenkov phenomenon.

  3. Predicted image quality of a CMOS APS X-ray detector across a range of mammographic beam qualities

    NASA Astrophysics Data System (ADS)

    Konstantinidis, A.

    2015-09-01

    Digital X-ray detectors based on Complementary Metal-Oxide- Semiconductor (CMOS) Active Pixel Sensor (APS) technology have been introduced in the early 2000s in medical imaging applications. In a previous study the X-ray performance (i.e. presampling Modulation Transfer Function (pMTF), Normalized Noise Power Spectrum (NNPS), Signal-to-Noise Ratio (SNR) and Detective Quantum Efficiency (DQE)) of the Dexela 2923MAM CMOS APS X-ray detector was evaluated within the mammographic energy range using monochromatic synchrotron radiation (i.e. 17-35 keV). In this study image simulation was used to predict how the mammographic beam quality affects image quality. In particular, the experimentally measured monochromatic pMTF, NNPS and SNR parameters were combined with various mammographic spectral shapes (i.e. Molybdenum/Molybdenum (Mo/Mo), Rhodium/Rhodium (Rh/Rh), Tungsten/Aluminium (W/Al) and Tungsten/Rhodium (W/Rh) anode/filtration combinations at 28 kV). The image quality was measured in terms of Contrast-to-Noise Ratio (CNR) using a synthetic breast phantom (4 cm thick with 50% glandularity). The results can be used to optimize the imaging conditions in order to minimize patient's Mean Glandular Dose (MGD).

  4. The piecewise-linear dynamic attenuator reduces the impact of count rate loss with photon-counting detectors

    NASA Astrophysics Data System (ADS)

    Hsieh, Scott S.; Pelc, Norbert J.

    2014-06-01

    Photon counting x-ray detectors (PCXDs) offer several advantages compared to standard energy-integrating x-ray detectors, but also face significant challenges. One key challenge is the high count rates required in CT. At high count rates, PCXDs exhibit count rate loss and show reduced detective quantum efficiency in signal-rich (or high flux) measurements. In order to reduce count rate requirements, a dynamic beam-shaping filter can be used to redistribute flux incident on the patient. We study the piecewise-linear attenuator in conjunction with PCXDs without energy discrimination capabilities. We examined three detector models: the classic nonparalyzable and paralyzable detector models, and a ‘hybrid’ detector model which is a weighted average of the two which approximates an existing, real detector (Taguchi et al 2011 Med. Phys. 38 1089-102 ). We derive analytic expressions for the variance of the CT measurements for these detectors. These expressions are used with raw data estimated from DICOM image files of an abdomen and a thorax to estimate variance in reconstructed images for both the dynamic attenuator and a static beam-shaping (‘bowtie’) filter. By redistributing flux, the dynamic attenuator reduces dose by 40% without increasing peak variance for the ideal detector. For non-ideal PCXDs, the impact of count rate loss is also reduced. The nonparalyzable detector shows little impact from count rate loss, but with the paralyzable model, count rate loss leads to noise streaks that can be controlled with the dynamic attenuator. With the hybrid model, the characteristic count rates required before noise streaks dominate the reconstruction are reduced by a factor of 2 to 3. We conclude that the piecewise-linear attenuator can reduce the count rate requirements of the PCXD in addition to improving dose efficiency. The magnitude of this reduction depends on the detector, with paralyzable detectors showing much greater benefit than nonparalyzable detectors.

  5. The piecewise-linear dynamic attenuator reduces the impact of count rate loss with photon-counting detectors.

    PubMed

    Hsieh, Scott S; Pelc, Norbert J

    2014-06-07

    Photon counting x-ray detectors (PCXDs) offer several advantages compared to standard energy-integrating x-ray detectors, but also face significant challenges. One key challenge is the high count rates required in CT. At high count rates, PCXDs exhibit count rate loss and show reduced detective quantum efficiency in signal-rich (or high flux) measurements. In order to reduce count rate requirements, a dynamic beam-shaping filter can be used to redistribute flux incident on the patient. We study the piecewise-linear attenuator in conjunction with PCXDs without energy discrimination capabilities. We examined three detector models: the classic nonparalyzable and paralyzable detector models, and a 'hybrid' detector model which is a weighted average of the two which approximates an existing, real detector (Taguchi et al 2011 Med. Phys. 38 1089-102). We derive analytic expressions for the variance of the CT measurements for these detectors. These expressions are used with raw data estimated from DICOM image files of an abdomen and a thorax to estimate variance in reconstructed images for both the dynamic attenuator and a static beam-shaping ('bowtie') filter. By redistributing flux, the dynamic attenuator reduces dose by 40% without increasing peak variance for the ideal detector. For non-ideal PCXDs, the impact of count rate loss is also reduced. The nonparalyzable detector shows little impact from count rate loss, but with the paralyzable model, count rate loss leads to noise streaks that can be controlled with the dynamic attenuator. With the hybrid model, the characteristic count rates required before noise streaks dominate the reconstruction are reduced by a factor of 2 to 3. We conclude that the piecewise-linear attenuator can reduce the count rate requirements of the PCXD in addition to improving dose efficiency. The magnitude of this reduction depends on the detector, with paralyzable detectors showing much greater benefit than nonparalyzable detectors.

  6. Cortical dynamics of visual motion perception: short-range and long-range apparent motion.

    PubMed

    Grossberg, S; Rudd, M E

    1992-01-01

    This article describes further evidence for a new neural network theory of biological motion perception. The theory clarifies why parallel streams V1----V2, V1----MT, and V1----V2----MT exist for static form and motion form processing among the areas V1, V2, and MT of visual cortex. The theory suggests that the static form system (Static BCS) generates emergent boundary segmentations whose outputs are insensitive to direction-of-contrast and to direction-of-motion, whereas the motion form system (Motion BCS) generates emergent boundary segmentations whose outputs are insensitive to direction-of-contrast but sensitive to direction-of-motion. The theory is used to explain classical and recent data about short-range and long-range apparent motion percepts that have not yet been explained by alternative models. These data include beta motion, split motion, gamma motion and reverse-contrast gamma motion, delta motion, and visual inertia. Also included are the transition from group motion to element motion in response to a Ternus display as the interstimulus interval (ISI) decreases; group motion in response to a reverse-contrast Ternus display even at short ISIs; speed-up of motion velocity as interflash distance increases or flash duration decreases; dependence of the transition from element motion to group motion on stimulus duration and size, various classical dependencies between flash duration, spatial separation, ISI, and motion threshold known as Korte's laws; dependence of motion strength on stimulus orientation and spatial frequency; short-range and long-range form-color interactions; and binocular interactions of flashes to different eyes.

  7. Verification of proton range, position, and intensity in IMPT with a 3D liquid scintillator detector system

    PubMed Central

    Archambault, L.; Poenisch, F.; Sahoo, N.; Robertson, D.; Lee, A.; Gillin, M. T.; Mohan, R.; Beddar, S.

    2012-01-01

    Purpose: Intensity-modulated proton therapy (IMPT) using spot scanned proton beams relies on the delivery of a large number of beamlets to shape the dose distribution in a highly conformal manner. The authors have developed a 3D system based on liquid scintillator to measure the spatial location, intensity, and depth of penetration (energy) of the proton beamlets in near real-time. Methods: The detector system consists of a 20 × 20 × 20 cc liquid scintillator (LS) material in a light tight enclosure connected to a CCD camera. This camera has a field of view of 25.7 by 19.3 cm and a pixel size of 0.4 mm. While the LS is irradiated, the camera continuously acquires images of the light distribution produced inside the LS. Irradiations were made with proton pencil beams produced with a spot-scanning nozzle. Pencil beams with nominal ranges in water between 9.5 and 17.6 cm were scanned to irradiate an area of 10 × 10 cm square on the surface of the LS phantom. Image frames were acquired at 50 ms per frame. Results: The signal to noise ratio of a typical Bragg peak was about 170. Proton range measured from the light distribution produced in the LS was accurate to within 0.3 mm on average. The largest deviation seen between the nominal and measured range was 0.6 mm. Lateral position of the measured pencil beam was accurate to within 0.4 mm on average. The largest deviation seen between the nominal and measured lateral position was 0.8 mm; however, the accuracy of this measurement could be improved by correcting light scattering artifacts. Intensity of single proton spots were measured with precision ranging from 3 % for the smallest spot intensity (0.005 MU) to 0.5 % for the largest spot (0.04 MU). Conclusions: Our LS detector system has been shown to be capable of fast, submillimeter spatial localization of proton spots delivered in a 3D volume. This system could be used for beam range, intensity and position verification in IMPT. PMID:22380355

  8. Home range dynamics, habitat selection, and survival of Greater Roadrunners

    USGS Publications Warehouse

    Kelley, S.W.; Ransom, D.; Butcher, J.A.; Schulz, G.G.; Surber, B.W.; Pinchak, W.E.; Santamaria, C.A.; Hurtado, L.A.

    2011-01-01

    Greater Roadrunners (Geococcyx californianus) are common, poorly studied birds of arid and semi-arid ecosystems in the southwestern United States. Conservation of this avian predator requires a detailed understanding of their movements and spatial requirements that is currently lacking. From 2006 to 2009, we quantified home-range and core area sizes and overlap, habitat selection, and survival of roadrunners (N= 14 males and 20 females) in north-central Texas using radio-telemetry and fixed kernel estimators. Median home-range and core-area sizes were 90.4 ha and 19.2 ha for males and 80.1 ha and 16.7 ha for females, respectively. The size of home range and core areas did not differ significantly by either sex or season. Our home range estimates were twice as large (x??= 108.9 ha) as earlier published estimates based on visual observations (x??= 28-50 ha). Mean percent overlap was 38.4% for home ranges and 13.7% for core areas. Male roadrunners preferred mesquite woodland and mesquite savanna cover types, and avoided the grass-forb cover type. Female roadrunners preferred mesquite savanna and riparian woodland cover types, and avoided grass-forb habitat. Kaplan-Meier annual survival probabilities for females (0.452 ?? 0.118[SE]) were twice that estimated for males (0.210 ?? 0.108), but this difference was not significant. Mortality rates of male roadrunners were higher than those of females during the spring when males call from elevated perches, court females, and chase competing males. Current land use practices that target woody-shrub removal to enhance livestock forage production could be detrimental to roadrunner populations by reducing availability of mesquite woodland and mesquite savanna habitat required for nesting and roosting and increasing the amount of grass-forb habitat that roadrunners avoid. ??2011 The Authors. Journal of Field Ornithology ??2011 Association of Field Ornithologists.

  9. Characterization of BSA unfolding and aggregation using a single-capillary viscometer and dynamic surface tension detector.

    PubMed

    Bramanti, Emilia; Ferrari, Carlo; Angeli, Valeria; Onor, Massimo; Synovec, Robert E

    2011-10-15

    A dynamic surface tension detector (DSTD) has been equipped with an additional pressure sensor for simultaneous viscosity measurements, as a detector for flow injection analysis. The viscosity measurement is based on a single capillary viscometer (SCV) placed in parallel configuration with the DSTD. The viscometer in the optimized conditions consists of a PEEK capillary (i.d.=0.25 mm, L=75 cm) kept at constant temperature using a thermostatic bath, which leads on the two sides to the two arms of a differential piezoelectric pressure transducer with a range of 0-35 psi. The DSTD, described previously, measures the changing pressure across the liquid/air interface of 2 μL drops repeatedly forming at the end of a capillary. SCV performance has been evaluated by measuring dynamic viscosity of water/glycerol mixtures analysed in flow injection and comparing the results with the values reported in the literature. The detection limits of SCV and DSTD, calculated as 3σ of the blank, were 0.012 cP and 0.6 dyn cm(-1), respectively. The FI-SCV-DSTD system has been applied to the study of temperature-induced denaturation/aggregation process in bovine serum albumin (BSA). The results have been supported and discussed with respect to BSA conformational analysis performed using Fourier Transform infrared spectroscopy.

  10. The dynamics of biogeographic ranges in the deep sea.

    PubMed

    McClain, Craig R; Hardy, Sarah Mincks

    2010-12-07

    Anthropogenic disturbances such as fishing, mining, oil drilling, bioprospecting, warming, and acidification in the deep sea are increasing, yet generalities about deep-sea biogeography remain elusive. Owing to the lack of perceived environmental variability and geographical barriers, ranges of deep-sea species were traditionally assumed to be exceedingly large. In contrast, seamount and chemosynthetic habitats with reported high endemicity challenge the broad applicability of a single biogeographic paradigm for the deep sea. New research benefiting from higher resolution sampling, molecular methods and public databases can now more rigorously examine dispersal distances and species ranges on the vast ocean floor. Here, we explore the major outstanding questions in deep-sea biogeography. Based on current evidence, many taxa appear broadly distributed across the deep sea, a pattern replicated in both the abyssal plains and specialized environments such as hydrothermal vents. Cold waters may slow larval metabolism and development augmenting the great intrinsic ability for dispersal among many deep-sea species. Currents, environmental shifts, and topography can prove to be dispersal barriers but are often semipermeable. Evidence of historical events such as points of faunal origin and climatic fluctuations are also evident in contemporary biogeographic ranges. Continued synthetic analysis, database construction, theoretical advancement and field sampling will be required to further refine hypotheses regarding deep-sea biogeography.

  11. High Dynamic Range Complex Impedance Measurement System for Petrophysical Usage

    NASA Astrophysics Data System (ADS)

    Chen, R.; He, X.; Yao, H.; Tan, S.; Shi, H.; Shen, R.; Yan, C.; Zeng, P.; He, L.; Qiao, N.; Xi, F.; Zhang, H.; Xie, J.

    2015-12-01

    Spectral induced polarization method (SIP) or complex resistivity method is increasing its application in metalliferous ore exploration, hydrocarbon exploration, underground water exploration, monitoring of environment pollution, and the evaluation of environment remediation. And the measurement of complex resistivity or complex impedance of rock/ore sample and polluted water plays a fundamental role in improving the application effect of SIP and the application scope of SIP. However, current instruments can't guaranty the accuracy of measurement when the resistance of sample is less than 10Ω or great than 100kΩ. A lot of samples, such as liquid, polluted sea water, igneous rock, limestone, and sandstone, can't be measured with reliable complex resistivity result. Therefore, this problem projects a shadow in the basic research and application research of SIP. We design a high precision measurement system from the study of measurement principle, sample holder, and measurement instrument. We design input buffers in a single board. We adopt operation amplifier AD549 in this system because of its ultra-high input impedance and ultra-low current noise. This buffer is good in acquiring potential signal across high impedance sample. By analyzing the sources of measurement error and errors generated by the measurement system, we propose a correction method to remove the error in order to achieve high quality complex impedance measurement for rock and ore samples. This measurement system can improve the measurement range of the complex impedance to 0.1 Ω ~ 10 GΩ with amplitude error less than 0.1% and phase error less than 0.1mrad when frequency ranges as 0.01 Hz ~ 1 kHz. We tested our system on resistors with resistance as 0.1Ω ~ 10 GΩ in frequency range as 1 Hz ~ 1000 Hz, and the measurement error is less than 0.1 mrad. We also compared the result with LCR bridge and SCIP, we can find that the bridge's measuring range only reaches 100 MΩ, SCIP's measuring range

  12. Dynamic range compression with ProteoMiner™: principles and examples.

    PubMed

    Li, Lei

    2015-01-01

    One of the main challenges in proteomics investigation, protein biomarker research, and protein purity and contamination analysis is how to efficiently enrich and detect low-abundance proteins in biological samples. One approach that makes the detection of rare species possible is the treatment of biological samples with solid-phase combinatorial peptide ligand libraries, ProteoMiner. This method utilizes hexapeptide bead library with huge diversity to bind and enrich low-abundance proteins but remove most of the high-abundance proteins, therefore compresses the protein abundance range in the samples. This work describes optimized protocols and highlights on the successful application of ProteoMiner to protein identification and analysis.

  13. Calibration and assessment of channel-specific biases in microarray data with extended dynamical range

    PubMed Central

    Bengtsson, Henrik; Jönsson, Göran; Vallon-Christersson, Johan

    2004-01-01

    Background Non-linearities in observed log-ratios of gene expressions, also known as intensity dependent log-ratios, can often be accounted for by global biases in the two channels being compared. Any step in a microarray process may introduce such offsets and in this article we study the biases introduced by the microarray scanner and the image analysis software. Results By scanning the same spotted oligonucleotide microarray at different photomultiplier tube (PMT) gains, we have identified a channel-specific bias present in two-channel microarray data. For the scanners analyzed it was in the range of 15–25 (out of 65,535). The observed bias was very stable between subsequent scans of the same array although the PMT gain was greatly adjusted. This indicates that the bias does not originate from a step preceding the scanner detector parts. The bias varies slightly between arrays. When comparing estimates based on data from the same array, but from different scanners, we have found that different scanners introduce different amounts of bias. So do various image analysis methods. We propose a scanning protocol and a constrained affine model that allows us to identify and estimate the bias in each channel. Backward transformation removes the bias and brings the channels to the same scale. The result is that systematic effects such as intensity dependent log-ratios are removed, but also that signal densities become much more similar. The average scan, which has a larger dynamical range and greater signal-to-noise ratio than individual scans, can then be obtained. Conclusions The study shows that microarray scanners may introduce a significant bias in each channel. Such biases have to be calibrated for, otherwise systematic effects such as intensity dependent log-ratios will be observed. The proposed scanning protocol and calibration method is simple to use and is useful for evaluating scanner biases or for obtaining calibrated measurements with extended dynamical

  14. Dynamic range in small-world networks of Hodgkin-Huxley neurons with chemical synapses

    NASA Astrophysics Data System (ADS)

    Batista, C. A. S.; Viana, R. L.; Lopes, S. R.; Batista, A. M.

    2014-09-01

    According to Stevens' law the relationship between stimulus and response is a power-law within an interval called the dynamic range. The dynamic range of sensory organs is found to be larger than that of a single neuron, suggesting that the network structure plays a key role in the behavior of both the scaling exponent and the dynamic range of neuron assemblies. In order to verify computationally the relationships between stimulus and response for spiking neurons, we investigate small-world networks of neurons described by the Hodgkin-Huxley equations connected by chemical synapses. We found that the dynamic range increases with the network size, suggesting that the enhancement of the dynamic range observed in sensory organs, with respect to single neurons, is an emergent property of complex network dynamics.

  15. Protein dynamics in a broad frequency range: Dielectric spectroscopy studies

    SciTech Connect

    Nakanishi, Masahiro; Sokolov, Alexei P.

    2014-09-17

    We present detailed dielectric spectroscopy studies of dynamics in two hydrated proteins, lysozyme and myoglobin. We emphasize the importance of explicit account for possible Maxwell-Wagner (MW) polarization effects in protein powder samples. Combining our data with earlier literature results, we demonstrate the existence of three major relaxation processes in globular proteins. To understand the mechanisms of these relaxations we involve literature data on neutron scattering, simulations and NMR studies. The faster process is ascribed to coupled protein-hydration water motions and has relaxation time similar to 10-50 Ps at room temperature. The intermediate process is similar to 10(2)-10(3) times slower than the faster process and might be strongly affected by MW polarizations. Based on the analysis of data obtained by different experimental techniques and simulations, we ascribe this process to large scale domain-like motions of proteins. The slowest observed process is similar to 10(6)-10(7) times slower than the faster process and has anomalously large dielectric amplitude Delta epsilon similar to 10(2)-10(4). The microscopic nature of this process is not clear, but it seems to be related to the glass transition of hydrated proteins. The presentedresults suggest a general classification of the relaxation processes in hydrated proteins. (c) 2014 Elsevier B.V. All rights reserved.

  16. Protein dynamics in a broad frequency range: Dielectric spectroscopy studies

    DOE PAGES

    Nakanishi, Masahiro; Sokolov, Alexei P.

    2014-09-17

    We present detailed dielectric spectroscopy studies of dynamics in two hydrated proteins, lysozyme and myoglobin. We emphasize the importance of explicit account for possible Maxwell-Wagner (MW) polarization effects in protein powder samples. Combining our data with earlier literature results, we demonstrate the existence of three major relaxation processes in globular proteins. To understand the mechanisms of these relaxations we involve literature data on neutron scattering, simulations and NMR studies. The faster process is ascribed to coupled protein-hydration water motions and has relaxation time similar to 10-50 Ps at room temperature. The intermediate process is similar to 10(2)-10(3) times slower thanmore » the faster process and might be strongly affected by MW polarizations. Based on the analysis of data obtained by different experimental techniques and simulations, we ascribe this process to large scale domain-like motions of proteins. The slowest observed process is similar to 10(6)-10(7) times slower than the faster process and has anomalously large dielectric amplitude Delta epsilon similar to 10(2)-10(4). The microscopic nature of this process is not clear, but it seems to be related to the glass transition of hydrated proteins. The presentedresults suggest a general classification of the relaxation processes in hydrated proteins. (c) 2014 Elsevier B.V. All rights reserved.« less

  17. Ecological change, range fluctuations and population dynamics during the Pleistocene.

    PubMed

    Hofreiter, Michael; Stewart, John

    2009-07-28

    Apart from the current human-induced climate change, the Holocene is notable for its stable climate. In contrast, the preceding age, the Pleistocene, was a time of intensive climatic fluctuations, with temperature changes of up to 15 degrees C occurring within a few decades. These climatic changes have substantially influenced both animal and plant populations. Until recently, the prevailing opinion about the effect of these climatic fluctuations on species in Europe was that populations survived glacial maxima in southern refugia and that populations died out outside these refugia. However, some of the latest studies of modern population genetics, the fossil record and especially ancient DNA reveal a more complex picture. There is now strong evidence for additional local northern refugia for a large number of species, including both plants and animals. Furthermore, population genetic analyses using ancient DNA have shown that genetic diversity and its geographical structure changed more often and in more unpredictable ways during the Pleistocene than had been inferred. Taken together, the Pleistocene is now seen as an extremely dynamic era, with rapid and large climatic fluctuations and correspondingly variable ecology. These changes were accompanied by similarly fast and sometimes dramatic changes in population size and extensive gene flow mediated by population movements. Thus, the Pleistocene is an excellent model case for the effects of rapid climate change, as we experience at the moment, on the ecology of plants and animals.

  18. WE-D-BRF-03: Proton Beam Range Verification with a Single Prompt Gamma-Ray Detector

    SciTech Connect

    Verburg, J; Testa, M; Cascio, E; Bortfeld, T; Lu, H; Seco, J

    2014-06-15

    Purpose: To present an experimental study of a novel range verification method for scanned and scattered proton beams. Methods: A detection system consisting of an actively shielded lanthanum(III)bromide scintillator and a one-sided lead collimator was used to measure prompt gamma-rays emitted during the delivery of proton beams to a water phantom and an anthropomorphic head phantom. The residual proton range at the collimator position was determined by comparing gamma-ray intensities while the proton energy was modulated to the distal end of the target. We used a clinical field to deliver a 50 cGy dose to a 12 cm diameter target in the water phantom and to a 175 cc tumor-shaped target in the head phantom. The detector signals were acquired with a custom data acquisition system enabling energy and time-of-flight discrimination of prompt gamma-rays. Results: Range deviations were detected with a statistical accuracy of ± 0.2 mm and ± 1.4 mm at 90% confidence level, respectively for the water and head phantom. We obtained a time resolution of 1 ns FWHM and an energy resolution < 2% FWHM for the main gamma lines from proton-induced nuclear reactions with carbon and oxygen. This allowed for an accurate separation of the prompt gamma-rays from neutron-induced background. Conclusion: Proton range deviations can be detected with millimeter accuracy using a single prompt gamma-ray measurement point acquired during the delivery of a few proton energy layers to the distal part of the target. The method is also feasible in the presence of background radiation from passively scattered proton beam delivery.

  19. Holarctic genetic structure and range dynamics in the woolly mammoth.

    PubMed

    Palkopoulou, Eleftheria; Dalén, Love; Lister, Adrian M; Vartanyan, Sergey; Sablin, Mikhail; Sher, Andrei; Edmark, Veronica Nyström; Brandström, Mikael D; Germonpré, Mietje; Barnes, Ian; Thomas, Jessica A

    2013-11-07

    Ancient DNA analyses have provided enhanced resolution of population histories in many Pleistocene taxa. However, most studies are spatially restricted, making inference of species-level biogeographic histories difficult. Here, we analyse mitochondrial DNA (mtDNA) variation in the woolly mammoth from across its Holarctic range to reconstruct its history over the last 200 thousand years (kyr). We identify a previously undocumented major mtDNA lineage in Europe, which was replaced by another major mtDNA lineage 32-34 kyr before present (BP). Coalescent simulations provide support for demographic expansions at approximately 121 kyr BP, suggesting that the previous interglacial was an important driver for demography and intraspecific genetic divergence. Furthermore, our results suggest an expansion into Eurasia from America around 66 kyr BP, coinciding with the first exposure of the Bering Land Bridge during the Late Pleistocene. Bayesian inference indicates Late Pleistocene demographic stability until 20-15 kyr BP, when a severe population size decline occurred.

  20. Modeling diverse range of potassium channels with Brownian dynamics.

    PubMed Central

    Chung, Shin-Ho; Allen, Toby W; Kuyucak, Serdar

    2002-01-01

    Using the experimentally determined KcsA structure as a template, we propose a plausible explanation for the diversity of potassium channels seen in nature. A simplified model of KcsA is constructed from its atomic resolution structure by smoothing out the protein-water boundary and representing the atoms forming the channel protein as a homogeneous, low dielectric medium. The properties of the simplified and atomic-detail models, deduced from electrostatic calculations and Brownian dynamics simulations, are shown to be qualitatively similar. We then study how the current flowing across the simplified model channel changes as the shape of the intrapore region is modified. This is achieved by increasing the radius of the intracellular pore systematically from 1.5 to 5 A while leaving the dimensions of the selectivity filter and inner chamber unaltered. The strengths of the dipoles located near the entrances of the channel, the carbonyl groups lining the selectivity filter, and the helix macrodipoles are kept constant. The channel conductance increases steadily as the radius of the intracellular pore is increased. The rate-limiting step for both the outward and inward current is the time it takes for an ion to cross the residual energy barrier located in the intrapore region. The current-voltage relationship obtained with symmetrical solutions is linear when the applied potential is less than approximately 100 mV but deviates slightly from Ohm's law at higher applied potentials. The nonlinearity in the current-voltage curve becomes less pronounced as the radius of the intracellular pore is increased. When the strengths of the dipoles near the intracellular entrance are reduced, the channel shows a pronounced inward rectification. Finally, the conductance exhibits the saturation property observed experimentally. We discuss the implications of these findings on the transport of ions across the potassium channels and membrane channels in general. PMID:12080118

  1. A per-pixel Log2ADC for high dynamic range, 1000FPS digital focal plane arrays (DFPA)

    NASA Astrophysics Data System (ADS)

    Petilli, Eugene

    2016-09-01

    Intrinsix has developed a Digital Focal Plane Array (DFPA) architecture based on a novel piecewise linear Log2 ADC (LADC) with "lossless" analog compression which enables ultra-high dynamic range ROICs that use less power than other extended dynamic range technologies. The LADC provides dynamic range of 126dB with a constant 75dB SNR over the entire frame. The companding 13bit mantissa, 3bit radix per pixel LADCs compress the 21bit signals into efficient 16 bit data words. The Read Out IC (ROIC) is compatible with most IR and LWIR detectors including two-color SLS (photodiode) and uBolometers. The DFPA architecture leverages two (staggered frame prime and redundant) MIPI CSI-3 interfaces to achieve full HD DFPA at 1000 frames/sec; an equivalent uncompressed data rate of 100Gb/sec. The LADC uses direct injection into a moderate sized integrating capacitor and several comparators create a stream of multi-bit data values. These values are accumulated in an SRAM based log2ALU and the radix of the ALU is combined with the data to generate a feedback current to the integrating capacitor, closing the delta loop. The integration time and a single pole low pass IIR filter are configurable using control signals to the log2ALU. The feedback current is at least partially generated using PWM for high linearity.

  2. Characterization of HZC XP1805 photomultiplier tube for LHAASO-WCDA with a high dynamic range base

    NASA Astrophysics Data System (ADS)

    Zhao, X.; Tang, Z.; Li, C.; Li, X.; Zha, W.; Chen, H.; Zhang, Y.; Shao, M.; Sun, Y.; Zhou, Y.

    2016-10-01

    The Water Cherenkov Detector Array (WCDA) for the Large High Altitude Air Shower Observatory (LHAASO) will employ 3000 large-sized hemisphere photomultiplier tubes (PMTs) to collect the Cherenkov light produced by shower particles crossing water. The PMTs require not only good single photoelectron (SPE) resolution and small transit time spread (TTS), but also good linearity up to 4000 photoelectrons. XP1805 PMT produced by Hainan Zhanchuang Photonics Technology Co., Ltd (HZC), China, with a production line imported from Photonis (France) is a good candidate for LHAASO-WCDA readout. In this paper, the design of a high dynamic range base for XP1805 is presented. The SPE responses and non-linearity of XP1805 with the high dynamic range base are measured. These results show that HZC XP1805 with the designed base is well qualified for LHAASO-WCDA, with peak-to-valley ratio greater than 2, TTS around 3 ns, dynamic range (non-linearity within 5%) over 1500 and 5300 photoelectrons for anode and the 6th dynode output, respectively, at PMT gain of 3 × 106 with the inciting light pulse width of 6.4 ns.

  3. Holarctic genetic structure and range dynamics in the woolly mammoth

    PubMed Central

    Palkopoulou, Eleftheria; Dalén, Love; Lister, Adrian M.; Vartanyan, Sergey; Sablin, Mikhail; Sher, Andrei; Edmark, Veronica Nyström; Brandström, Mikael D.; Germonpré, Mietje; Barnes, Ian; Thomas, Jessica A.

    2013-01-01

    Ancient DNA analyses have provided enhanced resolution of population histories in many Pleistocene taxa. However, most studies are spatially restricted, making inference of species-level biogeographic histories difficult. Here, we analyse mitochondrial DNA (mtDNA) variation in the woolly mammoth from across its Holarctic range to reconstruct its history over the last 200 thousand years (kyr). We identify a previously undocumented major mtDNA lineage in Europe, which was replaced by another major mtDNA lineage 32–34 kyr before present (BP). Coalescent simulations provide support for demographic expansions at approximately 121 kyr BP, suggesting that the previous interglacial was an important driver for demography and intraspecific genetic divergence. Furthermore, our results suggest an expansion into Eurasia from America around 66 kyr BP, coinciding with the first exposure of the Bering Land Bridge during the Late Pleistocene. Bayesian inference indicates Late Pleistocene demographic stability until 20–15 kyr BP, when a severe population size decline occurred. PMID:24026825

  4. Estimability and simple dynamical analyses of range (range-rate range-difference) observations to artificial satellites. [laser range observations to LAGEOS using non-Bayesian statistics

    NASA Technical Reports Server (NTRS)

    Vangelder, B. H. W.

    1978-01-01

    Non-Bayesian statistics were used in simulation studies centered around laser range observations to LAGEOS. The capabilities of satellite laser ranging especially in connection with relative station positioning are evaluated. The satellite measurement system under investigation may fall short in precise determinations of the earth's orientation (precession and nutation) and earth's rotation as opposed to systems as very long baseline interferometry (VLBI) and lunar laser ranging (LLR). Relative station positioning, determination of (differential) polar motion, positioning of stations with respect to the earth's center of mass and determination of the earth's gravity field should be easily realized by satellite laser ranging (SLR). The last two features should be considered as best (or solely) determinable by SLR in contrast to VLBI and LLR.

  5. NASA’s new High Dynamic Range Camera Records Rocket Test

    NASA Video Gallery

    This is footage of Orbital ATK’s QM-2 solid rocket booster test taken by NASA’s High Dynamic Range Stereo X (HiDyRS-X) camera. HiDyRS-X records high speed, high dynamic range footage in multiple ex...

  6. Blocked impurity band detectors applied to tunable diode laser spectroscopy in the 8- to 28-micron range

    NASA Technical Reports Server (NTRS)

    Sirota, J. Marcos; Reuter, Dennis C.; Mumma, Michael J.

    1993-01-01

    Blocked impurity band (BIB) detectors have allowed extension of highly sensitive tunable diode laser (TDL) spectroscopy to over 20 micron spectral region. BIB detectors present low noise equivalent power. Here the apparatus and its components are described and an example of molecular spectra is presented.

  7. Dynamic chest radiography: flat-panel detector (FPD) based functional X-ray imaging.

    PubMed

    Tanaka, Rie

    2016-07-01

    Dynamic chest radiography is a flat-panel detector (FPD)-based functional X-ray imaging, which is performed as an additional examination in chest radiography. The large field of view (FOV) of FPDs permits real-time observation of the entire lungs and simultaneous right-and-left evaluation of diaphragm kinetics. Most importantly, dynamic chest radiography provides pulmonary ventilation and circulation findings as slight changes in pixel value even without the use of contrast media; the interpretation is challenging and crucial for a better understanding of pulmonary function. The basic concept was proposed in the 1980s; however, it was not realized until the 2010s because of technical limitations. Dynamic FPDs and advanced digital image processing played a key role for clinical application of dynamic chest radiography. Pulmonary ventilation and circulation can be quantified and visualized for the diagnosis of pulmonary diseases. Dynamic chest radiography can be deployed as a simple and rapid means of functional imaging in both routine and emergency medicine. Here, we focus on the evaluation of pulmonary ventilation and circulation. This review article describes the basic mechanism of imaging findings according to pulmonary/circulation physiology, followed by imaging procedures, analysis method, and diagnostic performance of dynamic chest radiography.

  8. Dynamic range compression in the honey bee auditory system toward waggle dance sounds.

    PubMed

    Tsujiuchi, Seiya; Sivan-Loukianova, Elena; Eberl, Daniel F; Kitagawa, Yasuo; Kadowaki, Tatsuhiko

    2007-02-21

    Honey bee foragers use a "waggle dance" to inform nestmates about direction and distance to locations of attractive food. The sound and air flows generated by dancer's wing and abdominal vibrations have been implicated as important cues, but the decoding mechanisms for these dance messages are poorly understood. To understand the neural mechanisms of honey bee dance communication, we analyzed the anatomy of antenna and Johnston's organ (JO) in the pedicel of the antenna, as well as the mechanical and neural response characteristics of antenna and JO to acoustic stimuli, respectively. The honey bee JO consists of about 300-320 scolopidia connected with about 48 cuticular "knobs" around the circumference of the pedicel. Each scolopidium contains bipolar sensory neurons with both type I and II cilia. The mechanical sensitivities of the antennal flagellum are specifically high in response to low but not high intensity stimuli of 265-350 Hz frequencies. The structural characteristics of antenna but not JO neurons seem to be responsible for the non-linear responses of the flagellum in contrast to mosquito and fruit fly. The honey bee flagellum is a sensitive movement detector responding to 20 nm tip displacement, which is comparable to female mosquito. Furthermore, the JO neurons have the ability to preserve both frequency and temporal information of acoustic stimuli including the "waggle dance" sound. Intriguingly, the response of JO neurons was found to be age-dependent, demonstrating that the dance communication is only possible between aged foragers. These results suggest that the matured honey bee antennae and JO neurons are best tuned to detect 250-300 Hz sound generated during "waggle dance" from the distance in a dark hive, and that sufficient responses of the JO neurons are obtained by reducing the mechanical sensitivity of the flagellum in a near-field of dancer. This nonlinear effect brings about dynamic range compression in the honey bee auditory system.

  9. Monte Carlo simulations of high-speed, time-gated microchannel-plate-based x-ray detectors: Saturation effects in dc and pulsed modes and detector dynamic rangea)

    NASA Astrophysics Data System (ADS)

    Kruschwitz, Craig A.; Wu, Ming; Moy, Ken; Rochau, Greg

    2008-10-01

    We present here results of continued efforts to understand the performance of microchannel plate (MCP)-based, high-speed, gated, x-ray detectors. This work involves the continued improvement of a Monte Carlo simulation code to describe MCP performance coupled with experimental efforts to better characterize such detectors. Our goal is a quantitative description of MCP saturation behavior in both static and pulsed modes. A new model of charge buildup on the walls of the MCP channels is briefly described. The simulation results are compared to experimental data obtained with a short-pulse, high-intensity ultraviolet laser, and good agreement is found. These results indicate that a weak saturation can change the exponent of gain with voltage and that a strong saturation leads to a gain plateau. These results also demonstrate that the dynamic range of a MCP in pulsed mode has a value of between 102 and 103.

  10. Computerized methods for determining respiratory phase on dynamic chest radiographs obtained by a dynamic flat-panel detector (FPD) system.

    PubMed

    Tanaka, Rie; Sanada, Shigeru; Kobayashi, Takeshi; Suzuki, Masayuki; Matsui, Takeshi; Matsui, Osamu

    2006-03-01

    Chest radiography using a dynamic flat-panel detector with a large field of view can provide sequential chest radiographs during respiration. These images provide information regarding respiratory kinetics, which is effective for diagnosis of pulmonary diseases. For valid analysis of respiratory kinetics in diagnosis of pulmonary diseases, it is crucial to determine the association between the kinetics and respiratory phase. We developed four methods to determine the respiratory phase based on image information associated with respiration and compared the results in dynamic chest radiographs of 37 subjects. Here, the properties of each method and future tasks are discussed. The method based on the change in size of the lung gave the most stable results, and that based on the change in distance from the lung apex to the diaphragm was the most promising method for determining the respiratory phase.

  11. Flat panel detector-based cone beam CT for dynamic imaging: system evaluation

    NASA Astrophysics Data System (ADS)

    Ning, Ruola; Conover, David; Yu, Yong; Zhang, Yan; Cai, Weixing; Yang, Dong; Lu, Xianghua

    2006-03-01

    The purpose of this study is to characterize a newly built flat panel detector (FPD)-based cone beam CT (CBCT) prototype for dynamic imaging. A CBCT prototype has been designed and constructed by completely modifying a GE HiSpeed Advantage (HSA) CT gantry, incorporating a newly acquired large size real-time FPD (Varian PaxScan 4030CB), a new x-ray generator and a dual focal spot angiography x-ray tube that allows the full coverage of the detector. During data acquisition, the x-ray tube and the FPD can be rotated on the gantry over Nx360 degrees due to integrated slip ring technology with the rotation speed of one second/revolution. With a single scan time of up to 40 seconds , multiple sets of reconstructions can be performed for dynamic studies. The upgrade of this system has been completed. The prototype was used for a series of preliminary phantom studies: different sizes of breast phantoms, a Humanoid chest phantom and scatter correction studies. The results of the phantom studies demonstrate that good image quality can be achieved with this newly built prototype.

  12. Experimental Study of Three-Nucleon Dynamics in the Dp Breakup Collisions Using the WASA Detector

    NASA Astrophysics Data System (ADS)

    Kłos, B.; Ciepał, I.; Jamróz, B.; Khatri, G.; Kistryn, S.; Kozela, A.; Magiera, A.; Parol, W.; Skwira-Chalot, I.; Stephan, E.

    2017-03-01

    Until recently, all calculations of breakup observables were carried out in a non-relativistic regime. The relativistic treatment of the breakup reaction in 3 N system is quite a new achievement. The detailed study of various aspects of few-nucleon system dynamics in medium energy region, with a particular emphasis on investigation of relativistic effects and their interplay with three nucleon force (3NF) becomes feasible with increasing available energy in the three nucleon system. Therefore an experiment to investigate the ^1H(d, pp)n breakup cross section using a deuteron beam of 300, 340, 380 and 400 MeV and the WASA detector has been performed at COSY-Jülich. The almost 4π geometry of the WASA detector gives an unique possibility to study variety of kinematic configurations, which reveal different sensitivity to aspects of dynamics of the three nucleon system. The main steps of the analysis, including energy calibration, PID, normalization and efficiency studies, and their impact on the final accuracy of the result, are discussed.

  13. Evidence for an unusual dynamical-arrest scenario in short-ranged colloidal systems

    NASA Astrophysics Data System (ADS)

    Foffi, G.; Dawson, K. A.; Buldyrev, S. V.; Sciortino, F.; Zaccarelli, E.; Tartaglia, P.

    2002-05-01

    Extensive molecular dynamics simulation studies of particles interacting via a short-ranged attractive square-well potential are reported. The calculated loci of constant diffusion coefficient D in the temperature-packing fraction plane show a reentrant behavior, i.e., an increase of diffusivity on cooling, confirming an important part of the high volume-fraction dynamical-arrest scenario earlier predicted by theory for particles with short-ranged potentials. The more efficient localization mechanism induced by the short-range bonding provides, on average, additional free volume as compared to the hard-sphere case and results in faster dynamics.

  14. A Supra-Thermal Energetic Particle detector (STEP) for composition measurements in the range approximately 20 keV/nucleon to 1 MeV/nucleon

    NASA Technical Reports Server (NTRS)

    Mason, G. M.; Gloeckler, G.

    1981-01-01

    A detector system is described, employing a time-of-flight versus residual energy technique which allows measurement of particle composition (H-Fe), energy spectral and anisotropies in an energy range unaccessible with previously flown sensors. Applications of this method to measurements of the solar wind ion composition are discussed.

  15. A supra-thermal energetic particle detector /STEP/ for composition measurements in the range of about 20 keV/nucleon to 1 MeV/nucleon

    NASA Technical Reports Server (NTRS)

    Mason, G. M.; Gloeckler, G.

    1981-01-01

    A novel detector system is described, employing a time-of-flight versus residual energy technique which allows measurement of particle composition (H-Fe), energy spectra and anisotropies in an energy range unaccessible with previously flown sensors. Applications of this method to measurements of the solar wind ion composition are also discussed.

  16. In-line ion detector

    SciTech Connect

    Becker, R.; Kester, O.

    2008-02-15

    An in-line particle detector (IPD) uses secondary electrons for the detection of multiply charged ions with low to medium energy (10-10 keV). The ion detector does not physically intercept the ion beam line and is fully transparent to ions without applied voltages. The activation of the detector is performed by applying appropriate voltages to electrodes, which avoids any physical movement. Equipped with a channel electron multiplier, single particle counting is possible as well as measurement of currents. This detector therefore has a large dynamical range from about 10{sup -17} to 10{sup -3} A. The basic principle also allows for ion beam diagnostics.

  17. Ultrafast Optical Beam Deflection in a Planar Waveguide for High Dynamic Range Recording at Picosecond Resolution

    SciTech Connect

    Sarantos, C H; Heebner, J E

    2008-07-02

    We report the latest performance of an ultrafast, all-optical beam deflector based on a prism array imprinted in a planar waveguide. The deflector enables single-shot, high dynamic range optical recording with picosecond resolution.

  18. How interactions between animal movement and landscape processes modify range dynamics and extinction risk

    EPA Science Inventory

    Range dynamics models now incorporate many of the mechanisms and interactions that drive species distributions. However, connectivity continues to be studied using overly simple distance-based dispersal models with little consideration of how the individual behavior of dispersin...

  19. Dynamic Range of Vertical Cavity Surface Emitting Lasers in Multimode Links

    SciTech Connect

    Lee, H.L.T.; Dalal, R.V.; Ram, R.J.; Choquette, K.D.

    1999-07-07

    The authors report spurious free dynamic range measurements of 850nm vertical cavity surface emitting lasers in short multimode links for radio frequency communication. For a 27m fiber link, the dynamic range at optimal bias was greater than 95dB-Hz{sup 2/3} for modulation frequencies between 1 and 5.5 GHz, which exceeds the requirements for antenna remoting in microcellular networks. In a free space link, they have measured the highest dynamic range in an 850nm vertical cavity surface emitting laser of 113dB-Hz{sup 2/3} at 900MHz. We have also investigated the effects of modal noise and differential mode delay on the dynamic range for longer lengths of fiber.

  20. Linking traits to energetics and population dynamics to predict lizard ranges in changing environments.

    PubMed

    Buckley, Lauren B

    2008-01-01

    I present a dynamic bioenergetic model that couples individual energetics and population dynamics to predict current lizard ranges and those following climate warming. The model predictions are uniquely based on first principles of morphology, life history, and thermal physiology. I apply the model to five populations of a widespread North American lizard, Sceloporus undulatus, to examine how geographic variation in traits and life histories influences ranges. This geographic variation reflects the potential for species to adapt to environmental change. I then consider the range dynamics of the closely related Sceloporus graciosus. Comparing predicted ranges and actual current ranges reveals how dispersal limitations, species interactions, and habitat requirements influence the occupied portions of thermally suitable ranges. The dynamic model predicts individualistic responses to a uniform 3 degrees C warming but a northward shift in the northern range boundary for all populations and species. In contrast to standard correlative climate envelope models, the extent of the predicted northward shift depends on organism traits and life histories. The results highlight the limitations of correlative models and the need for more dynamic models of species' ranges.

  1. Wide-Dynamic-Range Analog-to-Digital Conversion for HFDF.

    DTIC Science & Technology

    1986-11-01

    FIELD GROUP SUB-GROUP High-frequency direction finder (HFDF), lasers , fiber optics, switches, a. ,~esed~cea~ ad .Ab4 digitization, noise/jammer...dynamic-range digitization of wideband HFDF data, using a synchronously driven laser /fiber-optic system. Development activity reported is in the areas...dynamic- range digitization of wideband HFDF data, using a synchronously driven laser /fiber-optic system. The background of the concept and previous work

  2. Long-range micro-pulse aerosol lidar at 1.5  μm with an upconversion single-photon detector.

    PubMed

    Xia, Haiyun; Shentu, Guoliang; Shangguan, Mingjia; Xia, Xiuxiu; Jia, Xiaodong; Wang, Chong; Zhang, Jun; Pelc, Jason S; Fejer, M M; Zhang, Qiang; Dou, Xiankang; Pan, Jian-Wei

    2015-04-01

    A micro-pulse lidar at eye-safe wavelength is constructed based on an upconversion single-photon detector. The ultralow-noise detector enables using integration technique to improve the signal-to-noise ratio of the atmospheric backscattering even at daytime. With pulse energy of 110 μJ, pulse repetition rate of 15 kHz, optical antenna diameter of 100 mm and integration time of 5 min, a horizontal detection range of 7 km is realized. In the demonstration experiment, atmospheric visibility over 24 h is monitored continuously, with results in accordance with the weather forecasts.

  3. Statistical treatment of photon/electron counting: extending the linear dynamic range from the dark count rate to saturation.

    PubMed

    Kissick, David J; Muir, Ryan D; Simpson, Garth J

    2010-12-15

    An experimentally simple photon counting method is demonstrated providing 7 orders of magnitude in linear dynamic range (LDR) for a single photomultiplier tube (PMT) detector. In conventional photon/electron counting methods, the linear range is dictated by the agreement between the binomially distributed measurement of counted events and the underlying Poisson distribution of photons/electrons. By explicitly considering the log-normal probability distribution in voltage transients as a function of the number of photons present and the Poisson distribution of photons, observed counts for a given threshold can be related to the mean number of photons well beyond the conventional limit. Analytical expressions are derived relating counts and photons that extend the linear range to an average of ∼11 photons arriving simultaneously with a single threshold. These expressions can be evaluated numerically for multiple thresholds extending the linear range to the saturation point of the PMT. The peak voltage distributions are experimentally shown to follow a Poisson weighted sum of log-normal distributions that can all be derived from the single photoelectron voltage peak-height distribution. The LDR that results from this method is compared to conventional single photon counting (SPC) and to signal averaging by analog to digital conversion (ADC).

  4. Design of pixel electronics based on asynchronous self-reset approach with floating-point output representation for high dynamic range imagers

    NASA Astrophysics Data System (ADS)

    Nascetti, A.; Valerio, P.

    2011-01-01

    A readout circuit suitable for multi-channel preamplifiers for pixellated detectors, hybrid detectors or thin film on asic imagers, for applications requiring large dynamic range such as computed tomography is discussed. The circuit implements an asynchronous self-reset with residue conversion scheme combined with a floating point representation of the input current. This solution allows to reach a very high dynamic range with good linearity while ensuring a compact output format. In particular, in the present implementation the input current range extends from 50 fA up to 820 nA corresponding to a 144 dB dynamic range which is equivalent to a 24-bit code. However the proposed scheme only uses 16 output bits for the floating point representation with 12-bit constant relative resolution: 12 bits serve for the output value itself and 4 for storing the position of the transition point between integer and fractional part. In addition, an analytical study of the achievable imaging performances shows that no significant degradation of the SNR is expected for the 12-bit constant relative resolution implementation with respect to the full 24-bit resolution scheme. Finally, the main building blocks of the circuit are analyzed in detail and their characteristics are put in relationship with the overall system performances.

  5. The dynamic time-over-threshold method for multi-channel APD based gamma-ray detectors

    NASA Astrophysics Data System (ADS)

    Orita, T.; Shimazoe, K.; Takahashi, H.

    2015-03-01

    t- Recent advances in manufacturing technology have enabled the use of multi-channel pixelated detectors in gamma-ray imaging applications. When obtaining gamma-ray measurements, it is important to obtain pulse height information in order to avoid unnecessary events such as scattering. However, as the number of channels increases, more electronics are needed to process each channel's signal, and the corresponding increases in circuit size and power consumption can result in practical problems. The time-over-threshold (ToT) method, which has recently become popular in the medical field, is a signal processing technique that can effectively avoid such problems. However, ToT suffers from poor linearity and its dynamic range is limited. We therefore propose a new ToT technique called the dynamic time-over-threshold (dToT) method [4]. A new signal processing system using dToT and CR-RC shaping demonstrated much better linearity than that of a conventional ToT. Using a test circuit with a new Gd3Al2Ga3O12 (GAGG) scintillator and an avalanche photodiode, the pulse height spectra of 137Cs and 22Na sources were measured with high linearity. Based on these results, we designed a new application-specific integrated circuit (ASIC) for this multi-channel dToT system, measured the spectra of a 22Na source, and investigated the linearity of the system.

  6. Comparison of multialkali and GaAs photocathode detectors for Joint European Torus edge light detection and ranging Thomson scattering profiles

    NASA Astrophysics Data System (ADS)

    Kempenaars, M.; Nielsen, P.; Pasqualotto, R.; Gowers, C.; Beurskens, M.

    2004-10-01

    The Joint European Torus (JET) tokamak has two light detection and ranging (LIDAR) Thomson scattering systems, one for the core and one dedicated to the edge Te and ne profiles. The LIDAR scheme is unique to JET and is envisaged for use on ITER. The system's spatial resolution is defined by the convolution product of its components: laser pulse duration, detector response time, and digitizer speed. The original multialkali photocathode microchannel plate photomultipliers dictated the response time, resulting in a 12 cm spatial resolution along the line of sight. In the edge LIDAR system, this is improved by aligning the line of sight with the flux surfaces, thus improving the effective spatial resolution to 2 cm depending on the plasma configuration. To meet demands for better edge gradient resolution, an upgrade to higher quantum efficiency detectors was proposed. Four GaAs photocathode detectors have been procured, two of which surpass expectations. These detectors are shown to have a more than two times higher effective quantum efficiency and their response time is at least twice as fast as the multialkali detectors. Combined with a fast digitizer this improves the spatial resolution by a factor of two, down to one centimeter effective, depending on plasma configuration.

  7. Comparison of multialkali and GaAs photocathode detectors for Joint European Torus edge light detection and ranging Thomson scattering profiles

    SciTech Connect

    Kempenaars, M.; Nielsen, P.; Pasqualotto, R.; Gowers, C.; Beurskens, M.

    2004-10-01

    The Joint European Torus (JET) tokamak has two light detection and ranging (LIDAR) Thomson scattering systems, one for the core and one dedicated to the edge T{sub e} and n{sub e} profiles. The LIDAR scheme is unique to JET and is envisaged for use on ITER. The system's spatial resolution is defined by the convolution product of its components: laser pulse duration, detector response time, and digitizer speed. The original multialkali photocathode microchannel plate photomultipliers dictated the response time, resulting in a 12 cm spatial resolution along the line of sight. In the edge LIDAR system, this is improved by aligning the line of sight with the flux surfaces, thus improving the effective spatial resolution to 2 cm depending on the plasma configuration. To meet demands for better edge gradient resolution, an upgrade to higher quantum efficiency detectors was proposed. Four GaAs photocathode detectors have been procured, two of which surpass expectations. These detectors are shown to have a more than two times higher effective quantum efficiency and their response time is at least twice as fast as the multialkali detectors. Combined with a fast digitizer this improves the spatial resolution by a factor of two, down to one centimeter effective, depending on plasma configuration.

  8. Dynamic Engagement of Human Motion Detectors across Space–Time Coordinates

    PubMed Central

    2014-01-01

    Motion detection is a fundamental property of the visual system. The gold standard for studying and understanding this function is the motion energy model. This computational tool relies on spatiotemporally selective filters that capture the change in spatial position over time afforded by moving objects. Although the filters are defined in space–time, their human counterparts have never been studied in their native spatiotemporal space but rather in the corresponding frequency domain. When this frequency description is back-projected to spatiotemporal description, not all characteristics of the underlying process are retained, leaving open the possibility that important properties of human motion detection may have remained unexplored. We derived descriptors of motion detectors in native space–time, and discovered a large unexpected dynamic structure involving a >2× change in detector amplitude over the first ∼100 ms. This property is not predicted by the energy model, generalizes across the visual field, and is robust to adaptation; however, it is silenced by surround inhibition and is contrast dependent. We account for all results by extending the motion energy model to incorporate a small network that supports feedforward spread of activation along the motion trajectory via a simple gain-control circuit. PMID:24948800

  9. Dynamic Electrothermal Model of a Sputtered Thermopile Thermal Radiation Detector for Earth Radiation Budget Applications

    NASA Technical Reports Server (NTRS)

    Weckmann, Stephanie

    1997-01-01

    The Clouds and the Earth's Radiant Energy System (CERES) is a program sponsored by the National Aeronautics and Space Administration (NASA) aimed at evaluating the global energy balance. Current scanning radiometers used for CERES consist of thin-film thermistor bolometers viewing the Earth through a Cassegrain telescope. The Thermal Radiation Group, a laboratory in the Department of Mechanical Engineering at Virginia Polytechnic Institute and State University, is currently studying a new sensor concept to replace the current bolometer: a thermopile thermal radiation detector. This next-generation detector would consist of a thermal sensor array made of thermocouple junction pairs, or thermopiles. The objective of the current research is to perform a thermal analysis of the thermopile. Numerical thermal models are particularly suited to solve problems for which temperature is the dominant mechanism of the operation of the device (through the thermoelectric effect), as well as for complex geometries composed of numerous different materials. Feasibility and design specifications are studied by developing a dynamic electrothermal model of the thermopile using the finite element method. A commercial finite element-modeling package, ALGOR, is used.

  10. Dynamical phase transitions and Loschmidt echo in the infinite-range XY model.

    PubMed

    Žunkovič, Bojan; Silva, Alessandro; Fabrizio, Michele

    2016-06-13

    We compare two different notions of dynamical phase transitions in closed quantum systems. The first is identified through the time-averaged value of the equilibrium-order parameter, whereas the second corresponds to non-analyticities in the time behaviour of the Loschmidt echo. By exactly solving the dynamics of the infinite-range XY model, we show that in this model non-analyticities of the Loschmidt echo are not connected to standard dynamical phase transitions and are not robust against quantum fluctuations. Furthermore, we show that the existence of either of the two dynamical transitions is not necessarily connected to the equilibrium quantum phase transition.

  11. Dynamic Range for Speech Materials in Korean, English, and Mandarin: A Cross-Language Comparison

    ERIC Educational Resources Information Center

    Jin, In-Ki; Kates, James M.; Arehart, Kathryn H.

    2014-01-01

    Purpose: The purpose of this study was to identify whether differences in dynamic range (DR) are evident across the spoken languages of Korean, English, and Mandarin. Method: Recorded sentence-level speech materials were used as stimuli. DR was quantified using different definitions of DR (defined as the range in decibels from the highest to the…

  12. Breathing chest radiography using a dynamic flat-panel detector combined with computer analysis.

    PubMed

    Tanaka, Rie; Sanada, Shigeru; Suzuki, Masayuki; Kobayashi, Takeshi; Matsui, Takeshi; Inoue, Hitoshi; Yoshihisa, Nakano

    2004-08-01

    Kinetic information is crucial when evaluating certain pulmonary diseases. When a dynamic flat-panel detector (FPD) can be used for a chest examination, kinetic information can be obtained simply and cost-effectively. The purpose of this study was to develop methods for analyzing respiratory kinetics, such as movement of the diaphragm and lung structures, and the respiratory changes in x-ray translucency in local lung fields. Postero-anterior dynamic chest radiographs during respiration were obtained with a modified FPD, which provided dynamic chest radiographs at a rate of 3 frames/s. Image registration for correction of physical motion was followed by measurement of the distance from the lung apex to the diaphragm. Next, we used a cross-correlation technique to measure the vectors of respiratory movement in specific lung areas. Finally, the average pixel value for a given local area was calculated by tracing the same local area in the lung field. This method of analysis was used for six healthy volunteers and one emphysema patient. The results reported here represent the initial stage in the development of a method that may constitute a new method for diagnosing certain pulmonary diseases, such as chronic obstructive pulmonary disease, fibroid lung, and pneumonia. A clinical evaluation of our method is now in progress.

  13. High dynamic range compression and detail enhancement of infrared images in the gradient domain

    NASA Astrophysics Data System (ADS)

    Zhang, Feifei; Xie, Wei; Ma, Guorui; Qin, Qianqing

    2014-11-01

    To find the trade-off between providing an accurate perception of the global scene and improving the visibility of details without excessively distorting radiometric infrared information, a novel gradient-domain-based visualization method for high dynamic range infrared images is proposed in this study. The proposed method adopts an energy function which includes a data constraint term and a gradient constraint term. In the data constraint term, the classical histogram projection method is used to perform the initial dynamic range compression to obtain the desired pixel values and preserve the global contrast. In the gradient constraint term, the moment matching method is adopted to obtain the normalized image; then a gradient gain factor function is designed to adjust the magnitudes of the normalized image gradients and obtain the desired gradient field. Lastly, the low dynamic range image is solved from the proposed energy function. The final image is obtained by linearly mapping the low dynamic range image to the 8-bit display range. The effectiveness and robustness of the proposed method are analyzed using the infrared images obtained from different operating conditions. Compared with other well-established methods, our method shows a significant performance in terms of dynamic range compression, while enhancing the details and avoiding the common artifacts, such as halo, gradient reversal, hazy or saturation.

  14. Large aperture at low cost three-dimensional time-of-flight range sensor using scanning micromirrors and synchronous detector switching.

    PubMed

    Bogatscher, Siegwart; Streck, Andreas; Fox, Maik; Meinzer, Sebastian; Heussner, Nico; Stork, Wilhelm

    2014-03-10

    In this article the problem of achieving fast scanning of a time-of-flight range sensor with a large optical receiver aperture at low system cost is targeted. The presented approach to solve this problem consists of a micromirror-based transmitter unit and a receiver unit consisting of a large aperture lens system with a small field of view and a detector array. A concept, which is called synchronous detector switching, is applied to the detector array. Thereby electronic steering of the small receiver field of view is possible. The overall approach is compared to alternative approaches, and the underlying concept of synchronous detector switching is demonstrated experimentally in an implementation of a three-dimensional time-of-flight range sensor. It is theoretically shown that the presented concept is potentially cheaper than the alternative approaches for applications with a field of view of less than 60×60°. After a discussion of the strengths and limitations of the approach, its effect on broader scientific issues is outlined.

  15. Spatial resolution of synchrotron x-ray microtomography in high energy range: Effect of x-ray energy and sample-to-detector distance

    NASA Astrophysics Data System (ADS)

    Seo, D.; Tomizato, F.; Toda, H.; Uesugi, K.; Takeuchi, A.; Suzuki, Y.; Kobayashi, M.

    2012-12-01

    Spatial resolution of three-dimensional images obtained by synchrotron X-ray microtomography technique is evaluated using cyclic bar patterns machined on a steel wire. Influences of X-ray energy and the sample-to-detector distance on spatial resolution were investigated. High X-ray energies of 33-78 keV are applied due to the high X-ray absorption of transition metals. Best spatial resolution of about 1.2 μm pitch was observed at the sample-to-detector distance range of 20-110 mm and at the energy range of 68-78 keV. Several factors such as X-ray scattering and diffraction phenomena affecting the degradation of spatial resolution are also discussed.

  16. High dynamic range imaging pipeline: perception-motivated representation of visual content

    NASA Astrophysics Data System (ADS)

    Mantiuk, Rafal; Krawczyk, Grzegorz; Mantiuk, Radoslaw; Seidel, Hans-Peter

    2007-02-01

    The advances in high dynamic range (HDR) imaging, especially in the display and camera technology, have a significant impact on the existing imaging systems. The assumptions of the traditional low-dynamic range imaging, designed for paper print as a major output medium, are ill suited for the range of visual material that is shown on modern displays. For example, the common assumption that the brightest color in an image is white can be hardly justified for high contrast LCD displays, not to mention next generation HDR displays, that can easily create bright highlights and the impression of self-luminous colors. We argue that high dynamic range representation can encode images regardless of the technology used to create and display them, with the accuracy that is only constrained by the limitations of the human eye and not a particular output medium. To facilitate the research on high dynamic range imaging, we have created a software package (http://pfstools.sourceforge.net/) capable of handling HDR data on all stages of image and video processing. The software package is available as open source under the General Public License and includes solutions for high quality image acquisition from multiple exposures, a range of tone mapping algorithms and a visual difference predictor for HDR images. Examples of shell scripts demonstrate how the software can be used for processing single images as well as video sequences.

  17. Impacts of Land Cover Data Selection and Trait Parameterisation on Dynamic Modelling of Species’ Range Expansion

    PubMed Central

    Heikkinen, Risto K.; Bocedi, Greta; Kuussaari, Mikko; Heliölä, Janne; Leikola, Niko; Pöyry, Juha; Travis, Justin M. J.

    2014-01-01

    Dynamic models for range expansion provide a promising tool for assessing species’ capacity to respond to climate change by shifting their ranges to new areas. However, these models include a number of uncertainties which may affect how successfully they can be applied to climate change oriented conservation planning. We used RangeShifter, a novel dynamic and individual-based modelling platform, to study two potential sources of such uncertainties: the selection of land cover data and the parameterization of key life-history traits. As an example, we modelled the range expansion dynamics of two butterfly species, one habitat specialist (Maniola jurtina) and one generalist (Issoria lathonia). Our results show that projections of total population size, number of occupied grid cells and the mean maximal latitudinal range shift were all clearly dependent on the choice made between using CORINE land cover data vs. using more detailed grassland data from three alternative national databases. Range expansion was also sensitive to the parameterization of the four considered life-history traits (magnitude and probability of long-distance dispersal events, population growth rate and carrying capacity), with carrying capacity and magnitude of long-distance dispersal showing the strongest effect. Our results highlight the sensitivity of dynamic species population models to the selection of existing land cover data and to uncertainty in the model parameters and indicate that these need to be carefully evaluated before the models are applied to conservation planning. PMID:25265281

  18. Calibration of spectral responsivity of IR detectors in the range from 0.6 μm to 24 μm

    NASA Astrophysics Data System (ADS)

    Podobedov, Vyacheslav B.; Eppeldauer, George P.; Hanssen, Leonard M.; Larason, Thomas C.

    2016-05-01

    We report the upgraded performance of the National Institute of Standards and Technology (NIST) facility for spectral responsivity calibrations of infrared (IR) detectors in both radiant power and irradiance measurement modes. The extension of the wavelength range of the previous scale, below 0.8 μm and above 19 μm in radiant power mode as well as above 5.3 μm in irradiance mode, became available as a result of multiple improvements. The calibration facility was optimized for low-level radiant flux. A significantly reduced noise-equivalent-power and a relatively constant spectral response were achieved recently on newly developed pyroelectric detectors. Also, an efficient optical geometry was developed for calibration of the spectral irradiance responsivity without using an integrating sphere. Simultaneously, the upgrade and maintenance of the NIST transfer standards, with an extended spectral range, were supported by spectral reflectance measurements of a transfer standard pyroelectric detector using a custom integrating sphere and a Fourier transform spectrometer. The sphere reflectance measurements performed in a relative mode were compared to a bare gold-coated mirror reference, separately calibrated at the Fourier transform Infrared Spectrophotometry facility to 18 μm. Currently, the reflectance data for the pyroelectric standard, available in the range up to 30 μm, are supporting the absolute power responsivity scale by the propagation of the reflectance curve to the absolute tie-spectrum in the overlapping range. Typical examples of working standard pyroelectric-, Si-, MCT-, InSb- and InGaAs- detectors are presented and their optimal use for scale dissemination is analyzed.

  19. Long-Range Coulomb Effect in Intense Laser-Driven Photoelectron Dynamics

    PubMed Central

    Quan, Wei; Hao, XiaoLei; Chen, YongJu; Yu, ShaoGang; Xu, SongPo; Wang, YanLan; Sun, RenPing; Lai, XuanYang; Wu, ChengYin; Gong, QiHuang; He, XianTu; Liu, XiaoJun; Chen, Jing

    2016-01-01

    In strong field atomic physics community, long-range Coulomb interaction has for a long time been overlooked and its significant role in intense laser-driven photoelectron dynamics eluded experimental observations. Here we report an experimental investigation of the effect of long-range Coulomb potential on the dynamics of near-zero-momentum photoelectrons produced in photo-ionization process of noble gas atoms in intense midinfrared laser pulses. By exploring the dependence of photoelectron distributions near zero momentum on laser intensity and wavelength, we unambiguously demonstrate that the long-range tail of the Coulomb potential (i.e., up to several hundreds atomic units) plays an important role in determining the photoelectron dynamics after the pulse ends. PMID:27256904

  20. Wide dynamic range wavefront sensor using sub-wavelength grating array

    NASA Astrophysics Data System (ADS)

    Liang, Xiaobin; Li, Yanqiu; Liu, Ke

    2015-07-01

    We propose a new zonal wavefront sensor with a very wide dynamic range. The proposed sensor uses a sub-wavelength grating array to subdivide the input wavefront and produce transmitted light spots on CCD. The wavefront tilts are calculated from the transmissions of a sub-wavelength grating array. The dynamic range and resolution of the proposed sensor are respectively decided by the grating parameters and the sub-unit size of the array. So these two performances of the sensor are independent of one another, which enables the realization of wide dynamic range and high resolution simultaneously. We introduce the principle of the sensor by both Rigorous Coupled Wave Analysis and Finite-Difference Time-Domain methods. A simulation is designed to validate our proposed method, and the measurement errors are analyzed. The sensor performs good sensitivity for wide incident angles, which is particularly suitable for spherical input wavefront.

  1. Sorting method to extend the dynamic range of the Shack-Hartmann wave-front sensor

    SciTech Connect

    Lee, Junwon; Shack, Roland V.; Descour, Michael R

    2005-08-10

    We propose a simple and powerful algorithm to extend the dynamic range of a Shack-Hartmann wave-front sensor. In a conventional Shack-Hartmann wave-front sensor the dynamic range is limited by the f-number of a lenslet, because the focal spot is required to remain in the area confined by the single lenslet. The sorting method proposed here eliminates such a limitation and extends the dynamic range by tagging each spot in a special sequence. Since the sorting method is a simple algorithm that does not change the measurement configuration, there is no requirement for extra hardware, multiple measurements, or complicated algorithms. We not only present the theory and a calculation example of the sorting method but also actually implement measurement of a highly aberrated wave front from nonrotational symmetric optics.

  2. Note: All-digital pulse-shrinking time-to-digital converter with improved dynamic range.

    PubMed

    Chen, Chun-Chi; Hwang, Chorng-Sii; Lin, Yi; Chen, Guan-Hong

    2016-04-01

    This paper proposes an all-digital pulse-shrinking time-to-digital converter (TDC) using the offset error cancellation circuitry to widen its dynamic range and to improve its accuracy. Although the TDC based on a pulse-shrinking mechanism can achieve a sub-gate resolution without circuit complexity, it possesses an undesired offset error that results in a nonzero lower bound appeared in its dynamic range and then affects its accuracy. The proposed cancellation circuitry for eliminating the offset error consists of a time adder with a delay line and a time subtractor with an identical delay line. The experimental TDC is implemented on Xilinx field programmable gate arrays and it also functions successfully in improving its dynamic range.

  3. Uncertainty-based Estimation of the Secure Range for ISO New England Dynamic Interchange Adjustment

    SciTech Connect

    Etingov, Pavel V.; Makarov, Yuri V.; Wu, Di; Hou, Zhangshuan; Sun, Yannan; Maslennikov, S.; Luo, Xiaochuan; Zheng, T.; George, S.; Knowland, T.; Litvinov, E.; Weaver, S.; Sanchez, E.

    2014-04-14

    The paper proposes an approach to estimate the secure range for dynamic interchange adjustment, which assists system operators in scheduling the interchange with neighboring control areas. Uncertainties associated with various sources are incorporated. The proposed method is implemented in the dynamic interchange adjustment (DINA) tool developed by Pacific Northwest National Laboratory (PNNL) for ISO New England. Simulation results are used to validate the effectiveness of the proposed method.

  4. Temporal-spatial characteristic evaluation in a dynamic flat-panel detector system

    NASA Astrophysics Data System (ADS)

    Kawashima, H.; Tanaka, R.; Matsubara, K.; Ichikawa, K.; Sakuta, K.; Minami, S.; Hayashi, N.; Sanada, S.; Kawamura, M.; Yamamoto, T.

    2010-04-01

    This report presents the fundamental temporospatial characteristics of a dynamic flat-panel detector (FPD) system. We investigated the relationship between pixel value and X-ray pulse output, and examined reproducibility, dependence on pulse width, tube voltage, and pulse rate. Sequential images were obtained using a direct conversion-type dynamic FPD. The exposure conditions were: 110 kV, 80 mA, 6.3 ms, 7.5 fps, source-to-image distance (SID) 1.5 m. X-ray pulse output was measured using a dosimetry system with a sampling interval of 70 μs, to determine temporal changes in each X-ray pulse output. Temporal changes in pixel value were measured in the obtained images, and the relationship between pixel value and X-ray pulse output was examined. Reproducibility was assessed by comparing the results in two sequential images obtained under the same exposure conditions. Moreover, the relationships and properties were evaluated by changing the pulse width (12 ms and 25 ms), tube voltage (80 kV, 90 kV, and 100 kV), and pulse rate (3.75 fps and 15 fps). The results showed a good correlation between the X-ray pulse output and pixel values. Fluctuation of the pixel value measured in sequential images is thought to be mainly due to changes in X-ray pulse output, and is not caused by FPD.

  5. Dynamic chest radiography with a flat-panel detector (FPD): ventilation-perfusion study

    NASA Astrophysics Data System (ADS)

    Tanaka, R.; Sanada, S.; Fujimura, M.; Yasui, M.; Tsuji, S.; Hayashi, N.; Okamoto, H.; Nanbu, Y.; Matsui, O.

    2011-03-01

    Pulmonary ventilation and blood flow are reflected in dynamic chest radiographs as changes in X-ray translucency, i.e., pixel values. This study was performed to investigate the feasibility of ventilation-perfusion (V/Q) study based on the changes in pixel value. Sequential chest radiographs of a patient with ventilation-perfusion mismatch were obtained during respiration using a dynamic flat-panel detector (FPD) system. The lung area was recognized and average pixel value was measured in each area, tracking and deforming the region of interest. Inter-frame differences were then calculated, and the absolute values were summed in each respiratory phase. The results were visualized as ventilation, blood flow, V/Q ratio distribution map and compared to distribution of radioactive counts on ventilation and perfusion scintigrams. In the results, abnormalities were appeared as a reduction of changes in pixel values, and a correlation was observed between the distribution of changes in pixel value and those of radioactivity counts (Ventilation; r=0.78, Perfusion; r=0.77). V/Q mismatch was also indicated as mismatch of changes in pixel value, and a correlation with V/Q calculated by radioactivity counts (r=0.78). These results indicated that the present method is potentially useful for V/Q study as an additional examination in conventional chest radiography.

  6. [Reproducibility of dynamic chest radiography with a flat-panel detector - respiratory changes in pixel value].

    PubMed

    Kawashima, Hiroki; Tanaka, Rie; Sanada, Shigeru

    2009-06-20

    Dynamic chest radiography using a flat panel detector (FPD) with a large field of view is expected to be a useful pulmonary functional evaluation method based on the respiratory changes in pixel value. For clinical use as a follow-up and therapeutic evaluation tool, the system must have a high degree of reproducibility in measurements of pixel values. The present study was performed to investigate the reproducibility of respiratory changes in pixel values. Dynamic chest radiographs of five normal subjects and one patient were obtained. Imaging was performed twice in each subject. The slope (X-ray translucency variation) was then calculated from the changes in pixel value from distance lung apex-diaphragm, and the slopes of two sequences were compared. The results showed there were no significant differences in changes in pixel value between the two sequences in all normal subject (5 males, p>0.05). The results indicated that the present method has reproducibility for measuring pulmonary function and also has potential as a tool for follow-up and therapeutic evaluation.

  7. Rubicon - a New Diode Array Detector System

    NASA Astrophysics Data System (ADS)

    Schmidt-Kaler, T.; Rudolph, R.; Tug, H.

    A photon-counting system with a 512-channel parallel output digital image tube is presented. Electronics developed separately for each detector channel as well as data aquisition are optimized for low power consumption and high counting rates. This detector, characterized by wide dynamic range, very low noise and high photometric accuracy, is especially suitable for spectrophotometry and calibrations.

  8. Spin segregation via dynamically induced long-range interactions in a system of ultracold fermions

    SciTech Connect

    Ebling, Ulrich; Eckardt, Andre; Lewenstein, Maciej

    2011-12-15

    We investigate theoretically the time evolution of a one-dimensional system of spin-1/2 fermions in a harmonic trap after, initially, a spiral spin configuration far from equilibrium is created. We predict a spin segregation building up in time already for weak interaction under realistic experimental conditions. The effect relies on the interplay between exchange interaction and the harmonic trap, and it is found for a wide range of parameters. It can be understood as a consequence of an effective, dynamically induced long-range interaction that is derived by integrating out the rapid oscillatory dynamics in the trap.

  9. Cost-effective multi-camera array for high quality video with very high dynamic range

    NASA Astrophysics Data System (ADS)

    Keinert, Joachim; Wetzel, Marcus; Schöberl, Michael; Schäfer, Peter; Zilly, Frederik; Bätz, Michel; Fößel, Siegfried; Kaup, André

    2014-03-01

    Temporal bracketing can create images with higher dynamic range than the underlying sensor. Unfortunately, moving objects cause disturbing artifacts. Moreover, the combination with high frame rates is almost unachiev­ able since a single video frame requires multiple sensor readouts. The combination of multiple synchronized side-by-side cameras equipped with different attenuation filters promises a remedy, since all exposures can be performed at the same time with the same duration using the playout video frame rate. However, a disparity correction is needed to compensate the spatial displacement of the cameras. Unfortunately, the requirements for a high quality disparity correction contradict the goal to increase dynamic range. When using two cameras, disparity correction needs objects to be properly exposed in both cameras. In contrast, a dynamic range in­crease needs the cameras to capture different luminance ranges. As this contradiction has not been addressed in literature so far, this paper proposes a novel solution based on a three camera setup. It enables accurate de­ termination of the disparities and an increase of the dynamic range by nearly a factor of two while still limiting costs. Compared to a two camera solution, the mean opinion score (MOS) is improved by 13.47 units in average for the Middleburry images.

  10. Echo-acoustic flow dynamically modifies the cortical map of target range in bats

    NASA Astrophysics Data System (ADS)

    Bartenstein, Sophia K.; Gerstenberg, Nadine; Vanderelst, Dieter; Peremans, Herbert; Firzlaff, Uwe

    2014-08-01

    Echolocating bats use the delay between their sonar emissions and the reflected echoes to measure target range, a crucial parameter for avoiding collisions or capturing prey. In many bat species, target range is represented as an orderly organized map of echo delay in the auditory cortex. Here we show that the map of target range in bats is dynamically modified by the continuously changing flow of acoustic information perceived during flight (‘echo-acoustic flow’). Combining dynamic acoustic stimulation in virtual space with extracellular recordings, we found that neurons in the auditory cortex of the bat Phyllostomus discolor encode echo-acoustic flow information on the geometric relation between targets and the bat’s flight trajectory, rather than echo delay per se. Specifically, the cortical representation of close-range targets is enlarged when the lateral passing distance of the target decreases. This flow-dependent enlargement of target representation may trigger adaptive behaviours such as vocal control or flight manoeuvres.

  11. Functional shoulder radiography with use of a dynamic flat panel detector.

    PubMed

    Sakuda, Keita; Sanada, Shigeru; Tanaka, Rie; Kitaoka, Katsuhiko; Hayashi, Norio; Matsuura, Yukihiro

    2014-07-01

    Our purpose in this study was to develop a functional form of radiography and to perform a quantitative analysis for the shoulder joint using a dynamic flat panel detector (FPD) system. We obtained dynamic images at a rate of 3.75 frames per second (fps) using an FPD system. Three patients and 5 healthy controls were studied with a clinically established frontal projection, with abduction of the arms. The arm angle, glenohumeral angle (G-angle), and scapulothoracic angle (S-angle) were measured on dynamic images. The ratio of the G-angle to the S-angle (GSR) was also evaluated quantitatively. In normal subjects, the G-angle and S-angle changed gradually along with the arm angle. The G-angle was approximately twice as large as the S-angle, resulting in a GSR of 2 throughout the abduction of the shoulder. Changes in G-angle and S-angle tended to be irregular in patients with shoulder disorders. The GSR of the thoracic outlet syndrome, recurrent dislocation of the shoulder joint, and anterior serratus muscle paralysis were 3-7.5, 4-9.5, and 3.5-7.5, respectively. The GSR of the anterior serratus muscle paralysis improved to approximately 2 after orthopedic treatment. Our preliminary results indicated that functional radiography by FPD and computer-aided quantitative analysis is useful for diagnosis of some shoulder disorders, such as the thoracic outlet syndrome, recurrent dislocation of the shoulder joint, and anterior serratus muscle paralysis. The technique and procedures described comprise a simple, functional shoulder radiographic method for evaluation of the therapeutic effects of surgery and/or rehabilitation.

  12. The MIC photon counting detector

    NASA Astrophysics Data System (ADS)

    Fordham, J. L. A.; Bone, D. A.; Oldfield, M. K.; Bellis, J. G.; Norton, T. J.

    1992-12-01

    The MIC (Microchannel plate Intensified CCD (Charge Coupled Device)) detector is an advanced performance Micro Channel Plate (MCP) intensified CCD photon counting detector developed for high resolution, high dynamic range, astronomical applications. The heart of the detector is an MCP intensifier developed specifically for photon counting applications. The maximum detector format is 3072 by 2304 pixels. The measured resolution of the detector system is 18 micrometers FWHM at 490 nm. The detector is linear to approximately 1,000,000 events/detector area/sec on a flat field and linear to count rates up to 200 events/object/s on star images. Two versions of the system have been developed. The first for ground based astronomical applications based around a 40 mm diameter intensifier, was proven in trials at a number of large optical telescopes. The second, specifically for the ESA X-Ray Multi Mirror Mission (XMM), where the MIC has been accepted as the blue detector for the incorporated Optical Monitor (OM). For the XMM-OM, the system is based around a 25 mm diameter intensifier. At present, under development, is a 75 mm diameter version of the detector which will have a maximum format of 6144 by 4608 pixels. Details of the MIC detector and its performance are presented.

  13. MO-F-CAMPUS-T-03: Verification of Range, SOBP Width, and Output for Passive-Scattering Proton Beams Using a Liquid Scintillator Detector

    SciTech Connect

    Henry, T; Robertson, D; Therriault-Proulx, F; Beddar, S

    2015-06-15

    Purpose: Liquid scintillators have been shown to provide fast and high-resolution measurements of radiation beams. However, their linear energy transfer-dependent response (quenching) limits their use in proton beams. The purpose of this study was to develop a simple and fast method to verify the range, spread-out Bragg peak (SOBP) width, and output of a passive-scattering proton beam with a liquid scintillator detector, without the need for quenching correction. Methods: The light signal from a 20×20×20 cm3 liquid scintillator tank was collected with a CCD camera. Reproducible landmarks on the SOBP depth-light curve were identified which possessed a linear relationship with the beam range and SOBP width. The depth-light profiles for three beam energies (140, 160 and 180 MeV) with six SOBP widths at each energy were measured with the detector. Beam range and SOBP width calibration factors were obtained by comparing the depth-light curve landmarks with the nominal range and SOBP width for each beam setting. The daily output stability of the liquid scintillator detector was also studied by making eight repeated output measurements in a cobalt-60 beam over the course of two weeks. Results: The mean difference between the measured and nominal beam ranges was 0.6 mm (σ=0.2 mm), with a maximum difference of 0.9 mm. The mean difference between the measured and nominal SOBP widths was 0.1 mm (σ=1.8 mm), with a maximum difference of 4.0 mm. Finally an output variation of 0.14% was observed for 8 measurements performed over 2 weeks. Conclusion: A method has been developed to determine the range and SOBP width of a passive-scattering proton beam in a liquid scintillator without the need for quenching correction. In addition to providing rapid and accurate beam range and SOBP measurements, the detector is capable of measuring the output consistency with a high degree of precision. This project was supported in part by award number CA182450 from the National Cancer

  14. The Contribution of Matched Envelope Dynamic Range to the Binaural Benefits in Simulated Bilateral Electric Hearing

    ERIC Educational Resources Information Center

    Chen, Fei; Wong, Lena L. N.; Qiu, Jianxin; Liu, Yehai; Azimi, Behnam; Hu, Yi

    2013-01-01

    Purpose: This study examined the effects of envelope dynamic-range mismatch on the intelligibility of Mandarin speech in noise by simulated bilateral electric hearing. Method: Noise-vocoded Mandarin speech, corrupted by speech-shaped noise at 5 and 0 dB signal-to-noise ratios, was presented unilaterally or bilaterally to 10 normal-hearing…

  15. Quantum dot SOA input power dynamic range improvement for differential-phase encoded signals.

    PubMed

    Vallaitis, T; Bonk, R; Guetlein, J; Hillerkuss, D; Li, J; Brenot, R; Lelarge, F; Duan, G H; Freude, W; Leuthold, J

    2010-03-15

    Experimentally we find a 10 dB input power dynamic range advantage for amplification of phase encoded signals with quantum dot SOA as compared to low-confinement bulk SOA. An analysis of amplitude and phase effects shows that this improvement can be attributed to the lower alpha-factor found in QD SOA.

  16. Method and apparatus of high dynamic range image sensor with individual pixel reset

    NASA Technical Reports Server (NTRS)

    Yadid-Pecht, Orly (Inventor); Pain, Bedabrata (Inventor); Fossum, Eric R. (Inventor)

    2001-01-01

    A wide dynamic range image sensor provides individual pixel reset to vary the integration time of individual pixels. The integration time of each pixel is controlled by column and row reset control signals which activate a logical reset transistor only when both signals coincide for a given pixel.

  17. Density matrix renormalization group with efficient dynamical electron correlation through range separation

    SciTech Connect

    Hedegård, Erik Donovan Knecht, Stefan; Reiher, Markus; Kielberg, Jesper Skau; Jensen, Hans Jørgen Aagaard

    2015-06-14

    We present a new hybrid multiconfigurational method based on the concept of range-separation that combines the density matrix renormalization group approach with density functional theory. This new method is designed for the simultaneous description of dynamical and static electron-correlation effects in multiconfigurational electronic structure problems.

  18. Control and dynamic range extension of linear photodiode arrays by a single board computer

    NASA Astrophysics Data System (ADS)

    McGeorge, Scott W.; Salin, Eric D.

    A complete interface for data acquisition and control of Reticon Series arrays utilizing an inexpensive microcomputer (Rockwell AIM-65) is described and with specific application to atomic spectra (ICP), data collection techniques are illustrated that provide a dynamic range extension for intense signals.

  19. Fractional quantum mechanics on networks: Long-range dynamics and quantum transport.

    PubMed

    Riascos, A P; Mateos, José L

    2015-11-01

    In this paper we study the quantum transport on networks with a temporal evolution governed by the fractional Schrödinger equation. We generalize the dynamics based on continuous-time quantum walks, with transitions to nearest neighbors on the network, to the fractional case that allows long-range displacements. By using the fractional Laplacian matrix of a network, we establish a formalism that combines a long-range dynamics with the quantum superposition of states; this general approach applies to any type of connected undirected networks, including regular, random, and complex networks, and can be implemented from the spectral properties of the Laplacian matrix. We study the fractional dynamics and its capacity to explore the network by means of the transition probability, the average probability of return, and global quantities that characterize the efficiency of this quantum process. As a particular case, we explore analytically these quantities for circulant networks such as rings, interacting cycles, and complete graphs.

  20. Numerical analysis for finite-range multitype stochastic contact financial market dynamic systems

    NASA Astrophysics Data System (ADS)

    Yang, Ge; Wang, Jun; Fang, Wen

    2015-04-01

    In an attempt to reproduce and study the dynamics of financial markets, a random agent-based financial price model is developed and investigated by the finite-range multitype contact dynamic system, in which the interaction and dispersal of different types of investment attitudes in a stock market are imitated by viruses spreading. With different parameters of birth rates and finite-range, the normalized return series are simulated by Monte Carlo simulation method and numerical studied by power-law distribution analysis and autocorrelation analysis. To better understand the nonlinear dynamics of the return series, a q-order autocorrelation function and a multi-autocorrelation function are also defined in this work. The comparisons of statistical behaviors of return series from the agent-based model and the daily historical market returns of Shanghai Composite Index and Shenzhen Component Index indicate that the proposed model is a reasonable qualitative explanation for the price formation process of stock market systems.

  1. Fractional quantum mechanics on networks: Long-range dynamics and quantum transport

    NASA Astrophysics Data System (ADS)

    Riascos, A. P.; Mateos, José L.

    2015-11-01

    In this paper we study the quantum transport on networks with a temporal evolution governed by the fractional Schrödinger equation. We generalize the dynamics based on continuous-time quantum walks, with transitions to nearest neighbors on the network, to the fractional case that allows long-range displacements. By using the fractional Laplacian matrix of a network, we establish a formalism that combines a long-range dynamics with the quantum superposition of states; this general approach applies to any type of connected undirected networks, including regular, random, and complex networks, and can be implemented from the spectral properties of the Laplacian matrix. We study the fractional dynamics and its capacity to explore the network by means of the transition probability, the average probability of return, and global quantities that characterize the efficiency of this quantum process. As a particular case, we explore analytically these quantities for circulant networks such as rings, interacting cycles, and complete graphs.

  2. Numerical analysis for finite-range multitype stochastic contact financial market dynamic systems.

    PubMed

    Yang, Ge; Wang, Jun; Fang, Wen

    2015-04-01

    In an attempt to reproduce and study the dynamics of financial markets, a random agent-based financial price model is developed and investigated by the finite-range multitype contact dynamic system, in which the interaction and dispersal of different types of investment attitudes in a stock market are imitated by viruses spreading. With different parameters of birth rates and finite-range, the normalized return series are simulated by Monte Carlo simulation method and numerical studied by power-law distribution analysis and autocorrelation analysis. To better understand the nonlinear dynamics of the return series, a q-order autocorrelation function and a multi-autocorrelation function are also defined in this work. The comparisons of statistical behaviors of return series from the agent-based model and the daily historical market returns of Shanghai Composite Index and Shenzhen Component Index indicate that the proposed model is a reasonable qualitative explanation for the price formation process of stock market systems.

  3. Effects of ADC Nonlinearity on the Spurious Dynamic Range Performance of Compressed Sensing

    PubMed Central

    Tian, Pengwu; Yu, Hongyi

    2014-01-01

    Analog-to-information converter (AIC) plays an important role in the compressed sensing system; it has the potential to significantly extend the capabilities of conventional analog-to-digital converter. This paper evaluates the impact of AIC nonlinearity on the dynamic performance in practical compressed sensing system, which included the nonlinearity introduced by quantization as well as the circuit non-ideality. It presents intuitive yet quantitative insights into the harmonics of quantization output of AIC, and the effect of other AIC nonlinearity on the spurious dynamic range (SFDR) performance is also analyzed. The analysis and simulation results demonstrated that, compared with conventional ADC-based system, the measurement process decorrelates the input signal and the quantization error and alleviate the effect of other decorrelates of AIC, which results in a dramatic increase in spurious free dynamic range (SFDR). PMID:24895645

  4. Nonlinear Dynamics of Bose-Einstein Condensates with Long-Range Interactions

    SciTech Connect

    Wunner, G.; Cartarius, H.; Fabcic, T.; Koeberle, P.; Main, J.; Schwidder, T.

    2008-11-13

    The motto of this paper is: Let's face Bose-Einstein condensation through nonlinear dynamics. We do this by choosing variational forms of the condensate wave functions (of given symmetry classes), which convert the Bose-Einstein condensates via the time-dependent Gross-Pitaevskii equation into Hamiltonian systems that can be studied using the methods of nonlinear dynamics. We consider in particular cold quantum gases where long-range interactions between the neutral atoms are present, in addition to the conventional short-range contact interaction, viz. gravity-like interactions, and dipole-dipole interactions. The results obtained serve as a useful guide in the search for nonlinear dynamics effects in numerically exact quantum calculations for Bose-Einstein condensates. A main result is the prediction of the existence of stable islands as well as chaotic regions for excited states of dipolar condensates, which could be checked experimentally.

  5. Numerical analysis for finite-range multitype stochastic contact financial market dynamic systems

    SciTech Connect

    Yang, Ge; Wang, Jun; Fang, Wen

    2015-04-15

    In an attempt to reproduce and study the dynamics of financial markets, a random agent-based financial price model is developed and investigated by the finite-range multitype contact dynamic system, in which the interaction and dispersal of different types of investment attitudes in a stock market are imitated by viruses spreading. With different parameters of birth rates and finite-range, the normalized return series are simulated by Monte Carlo simulation method and numerical studied by power-law distribution analysis and autocorrelation analysis. To better understand the nonlinear dynamics of the return series, a q-order autocorrelation function and a multi-autocorrelation function are also defined in this work. The comparisons of statistical behaviors of return series from the agent-based model and the daily historical market returns of Shanghai Composite Index and Shenzhen Component Index indicate that the proposed model is a reasonable qualitative explanation for the price formation process of stock market systems.

  6. Maturity of lumped element kinetic inductance detectors for space-borne instruments in the range between 80 and 180 GHz

    NASA Astrophysics Data System (ADS)

    Catalano, A.; Benoit, A.; Bourrion, O.; Calvo, M.; Coiffard, G.; D'Addabbo, A.; Goupy, J.; Le Sueur, H.; Macías-Pérez, J.; Monfardini, A.

    2016-07-01

    This work intends to give the state-of-the-art of our knowledge of the performance of lumped element kinetic inductance detectors (LEKIDs) at millimetre wavelengths (from 80 to 180 GHz). We evaluate their optical sensitivity under typical background conditions that are representative of a space environment and their interaction with ionising particles. Two LEKID arrays, originally designed for ground-based applications and composed of a few hundred pixels each, operate at a central frequency of 100 and 150 GHz (Δν/ν about 0.3). Their sensitivities were characterised in the laboratory using a dedicated closed-cycle 100 mK dilution cryostat and a sky simulator, allowing for the reproduction of realistic, space-like observation conditions. The impact of cosmic rays was evaluated by exposing the LEKID arrays to alpha particles (241Am) and X sources (109Cd), with a read-out sampling frequency similar to those used for Planck HFI (about 200 Hz), and also with a high resolution sampling level (up to 2 MHz) to better characterise and interpret the observed glitches. In parallel, we developed an analytical model to rescale the results to what would be observed by such a LEKID array at the second Lagrangian point. We show that LEKID arrays behave adequately in space-like conditions with a measured noise equivalent power close to the cosmic microwave background photon noise and an impact of cosmic rays smaller with respect to those observed with Planck satellite detectors.

  7. Note: An X-ray powder diffractometer with a wide scattering-angle range of 72° using asymmetrically positioned one-dimensional detectors

    SciTech Connect

    Katsuya, Yoshio; Tanaka, Masahiko; Song, Chulho; Ito, Kimihiko; Kubo, Yoshimi; Sakata, Osami

    2016-01-15

    An X-ray powder diffractometer has been developed for a time-resolved measurement without the requirement of a scattering angle (2θ) scan. Six one-dimensional detector modules are asymmetrically arranged in a vertical line at a designed distance of 286.5 mm. A detector module actually covers a diffraction angle of about 12° with an angular resolution of 0.01°. A diffracted intensity pattern is simultaneously recorded in a 2θ angular range from 1.63° to 74.37° in a “one shot” measurement. We tested the performance of the diffractometer with reference CeO{sub 2} powders and demonstrated diffraction measurements from an operating lithium-air battery.

  8. A reduction for spiking integrate-and-fire network dynamics ranging from homogeneity to synchrony.

    PubMed

    Zhang, J W; Rangan, A V

    2015-04-01

    In this paper we provide a general methodology for systematically reducing the dynamics of a class of integrate-and-fire networks down to an augmented 4-dimensional system of ordinary-differential-equations. The class of integrate-and-fire networks we focus on are homogeneously-structured, strongly coupled, and fluctuation-driven. Our reduction succeeds where most current firing-rate and population-dynamics models fail because we account for the emergence of 'multiple-firing-events' involving the semi-synchronous firing of many neurons. These multiple-firing-events are largely responsible for the fluctuations generated by the network and, as a result, our reduction faithfully describes many dynamic regimes ranging from homogeneous to synchronous. Our reduction is based on first principles, and provides an analyzable link between the integrate-and-fire network parameters and the relatively low-dimensional dynamics underlying the 4-dimensional augmented ODE.

  9. High-resolution, large dynamic range fiber-optic thermometer with cascaded Fabry-Perot cavities.

    PubMed

    Liu, Guigen; Sheng, Qiwen; Hou, Weilin; Han, Ming

    2016-11-01

    The paradox between a large dynamic range and a high resolution commonly exists in nearly all kinds of sensors. Here, we propose a fiber-optic thermometer based on dual Fabry-Perot interferometers (FPIs) made from the same material (silicon), but with different cavity lengths, which enables unambiguous recognition of the dense fringes associated with the thick FPI over the free-spectral range determined by the thin FPI. Therefore, the sensor combines the large dynamic range of the thin FPI and the high resolution of the thick FPI. To verify this new concept, a sensor with one 200 μm thick silicon FPI cascaded by another 10 μm thick silicon FPI was fabricated. A temperature range of -50°C to 130°C and a resolution of 6.8×10-3°C were demonstrated using a simple average wavelength tracking demodulation. Compared to a sensor with only the thick silicon FPI, the dynamic range of the hybrid sensor was more than 10 times larger. Compared to a sensor with only the thin silicon FPI, the resolution of the hybrid sensor was more than 18 times higher.

  10. Acute effect of static and dynamic stretching on hip dynamic range of motion during instep kicking in professional soccer players.

    PubMed

    Amiri-Khorasani, Mohammadtaghi; Abu Osman, Noor A; Yusof, Ashril

    2011-06-01

    The purpose of this study was to examine the effects of static and dynamic stretching within a pre-exercise warm-up on hip dynamic range of motion (DROM) during instep kicking in professional soccer players. The kicking motions of dominant legs were captured from 18 professional adult male soccer players (height: 180.38 ± 7.34 cm; mass: 69.77 ± 9.73 kg; age: 19.22 ± 1.83 years) using 4 3-dimensional digital video cameras at 50 Hz. Hip DROM at backward, forward, and follow-through phases (instep kick phases) after different warm-up protocols consisting of static, dynamic, and no-stretching on 3 nonconsecutive test days were captured for analysis. During the backswing phase, there was no difference in DROM after the dynamic stretching compared with the static stretching relative to the no-stretching method. There was a significant difference in DROM after the dynamic stretching compared with the static stretching relative to the no-stretching method during (a) the forward phase with p < 0.03, (b) the follow-through phase with p < 0.01, and (c) all phases with p < 0.01. We concluded that professional soccer players can perform a higher DROM of the hip joint during the instep kick after dynamic stretching incorporated in warm-ups, hence increasing the chances of scoring and injury prevention during soccer games.

  11. Dynamic Tensile Properties of Iron and Steels for a Wide Range of Strain Rates and Strain

    NASA Astrophysics Data System (ADS)

    Kojima, Nobusato; Hayashi, Hiroyuki; Yamamoto, Terumi; Mimura, Koji; Tanimura, Shinji

    The tensile stress-strain curves of iron and a variety of steels, covering a wide range of strength level, over a wide strain rate range on the order of 10-3 ~ 103 s-1, were obtained systematically by using the Sensing Block Type High Speed Material Testing System (SBTS, Saginomiya). Through intensive analysis of these results, the strain rate sensitivity of the flow stress for the large strain region, including the viscous term at high strain rates, the true fracture strength and the true fracture strain were cleared for the material group of the ferrous metals. These systematical data may be useful to develop a practical constitutive model for computer codes, including a fracture criterion for simulations of the dynamic behavior in crash worthiness studies and of work-pieces subjected to dynamic plastic working for a wide strain rate range.

  12. Implication of high dynamic range and wide color gamut content distribution

    NASA Astrophysics Data System (ADS)

    Lu, Taoran; Pu, Fangjun; Yin, Peng; Chen, Tao; Husak, Walt

    2015-09-01

    High Dynamic Range (HDR) and Wider Color Gamut (WCG) content represents a greater range of luminance levels and a more complete reproduction of colors found in real-world scenes. The current video distribution environments deliver Standard Dynamic Range (SDR) signal. Therefore, there might be some significant implication on today's end-to-end ecosystem from content creation to distribution and finally to consumption. For SDR content, the common practice is to apply compression on Y'CbCr 4:2:0 using gamma transfer function and non-constant luminance 4:2:0 chroma subsampling. For HDR and WCG content, it is desirable to examine if such signal format still works well for compression, and it is interesting to know if the overall system performance can be further improved by exploring different signal formats and processing workflows. In this paper, we will provide some of our insight into those problems.

  13. UMER: An analog computer for dynamics of swarms interacting via long-range forces

    NASA Astrophysics Data System (ADS)

    Kishek, R. A.; Bai, G.; Bernal, S.; Feldman, D.; Godlove, T. F.; Haber, I.; O'Shea, P. G.; Quinn, B.; Papadopoulos, C.; Reiser, M.; Stratakis, D.; Tian, K.; Tobin, C. J.; Walter, M.

    2006-06-01

    Some of the most challenging and interesting problems in nature involve large numbers of objects or particles mutually interacting through long-range forces. Examples range from galaxies and plasmas to flocks of birds and traffic flow on a highway. Even in cases where the form of the interacting force is precisely known, such as the 1/ r2-dependent Coulomb and gravitational forces, such problems present a formidable theoretical and modeling challenge for large numbers of interacting bodies. This paper reports on a newly constructed, scaled particle accelerator that will serve as an experimental testbed for the dynamics of swarms interacting through long-range forces. Primarily designed for intense beam dynamics studies for advanced accelerators, the University of Maryland Electron Ring (UMER) design is described in detail and an update on commissioning is provided. An example application to a system other than a charged particle beam is discussed.

  14. Twenty-year home-range dynamics of a white-tailed deer matriline

    USGS Publications Warehouse

    Nelson, Michael E.; Mech, L. David

    1999-01-01

    We examined the seasonal migration and home-range dynamics of a multigeneration white-tailed deer (Odocoileus virginianus) matriline comprising six females from four generations spanning a 20-year period in northeastern Minnesota. All, from the matriarch to her great-granddaughter, migrated to the same summer and winter ranges, the longest individual record being 14.5 years. Three maternal females concurrently occupied exclusive fawning sites within their ancestral matriarch's summer range, while two nonmaternal females explored new areas and ranged near their mothers. One great-granddaughter expanded her summer range 1 km beyond the matriarch's summer range while essentially vacating half of her ancestors' range and becoming nonmigratory the last 4 years of her life. These data indicate that individual movements of matriline members can potentially expand their ranges beyond the areas occupied by their ancestors through a slow process of small incremental changes. This suggests that the rapid extension of deer range in eastern North America resulted from natal dispersal by yearling deer rather than from the type of home-range expansion reported here.

  15. Requirements on high resolution detectors

    SciTech Connect

    Koch, A.

    1997-02-01

    For a number of microtomography applications X-ray detectors with a spatial resolution of 1 {mu}m are required. This high spatial resolution will influence and degrade other parameters of secondary importance like detective quantum efficiency (DQE), dynamic range, linearity and frame rate. This note summarizes the most important arguments, for and against those detector systems which could be considered. This article discusses the mutual dependencies between the various figures which characterize a detector, and tries to give some ideas on how to proceed in order to improve present technology.

  16. Spatial-temporal population dynamics across species range: From centre to margin

    USGS Publications Warehouse

    Guo, Q.; Taper, M.; Schoenberger, M.; Brandle, J.

    2005-01-01

    Understanding the boundaries of species' ranges and the variations in population dynamics from the centre to margin of a species' range is critical. This study simulated spatial-temporal patterns of birth and death rates and migration across a species' range in different seasons. Our results demonstrated the importance of dispersal and migration in altering birth and death rates, balancing source and sink habitats, and governing expansion or contraction of species' ranges in changing environments. We also showed that the multiple equilibria of metapopulations across a species' range could be easily broken following climatic changes or physical disturbances either local or regional. Although we refer to our models as describing the population dynamics across whole species' range, they should also apply to small-scale habitats (metapopulations) in which species abundance follows a humped pattern or to any ecosystem or landscape where strong central-marginal (C-M) environmental gradients exist. Conservation of both central and marginal populations would therefore be equally important considerations in making management decisions.

  17. Spatial-temporal population dynamics across species range: from center to margin

    USGS Publications Warehouse

    Guo, Q.; Taper, M.L.; Schoenberger, M.; Brandl, J.

    2005-01-01

    Understanding the boundaries of species' ranges and the variations in population dynamics from the centre to margin of a species' range is critical. This study simulated spatial-temporal patterns of birth and death rates and migration across a species' range in different seasons. Our results demonstrated the importance of dispersal and migration in altering birth and death rates, balancing source and sink habitats, and governing expansion or contraction of species' ranges in changing environments. We also showed that the multiple equilibria of metapopulations across a species' range could be easily broken following climatic changes or physical disturbances either or local or regional. Although we refer to our models as describing the population dynamics across whole species' range, they should also apply to small-scale habitats (metapopulations) in which species abundance follows a humped pattern or to any ecosystem or landscape where strong central-marginal (C-M) environmental gradients exist. Conservation of both central and marginal populations would therefore be equally important considerations in making management decisions.

  18. Long-Range Correlations in Stride Intervals May Emerge from Non-Chaotic Walking Dynamics

    PubMed Central

    Ahn, Jooeun; Hogan, Neville

    2013-01-01

    Stride intervals of normal human walking exhibit long-range temporal correlations. Similar to the fractal-like behaviors observed in brain and heart activity, long-range correlations in walking have commonly been interpreted to result from chaotic dynamics and be a signature of health. Several mathematical models have reproduced this behavior by assuming a dominant role of neural central pattern generators (CPGs) and/or nonlinear biomechanics to evoke chaos. In this study, we show that a simple walking model without a CPG or biomechanics capable of chaos can reproduce long-range correlations. Stride intervals of the model revealed long-range correlations observed in human walking when the model had moderate orbital stability, which enabled the current stride to affect a future stride even after many steps. This provides a clear counterexample to the common hypothesis that a CPG and/or chaotic dynamics is required to explain the long-range correlations in healthy human walking. Instead, our results suggest that the long-range correlation may result from a combination of noise that is ubiquitous in biological systems and orbital stability that is essential in general rhythmic movements. PMID:24086274

  19. CMOS Amperometric ADC With High Sensitivity, Dynamic Range and Power Efficiency for Air Quality Monitoring.

    PubMed

    Li, Haitao; Boling, C Sam; Mason, Andrew J

    2016-08-01

    Airborne pollutants are a leading cause of illness and mortality globally. Electrochemical gas sensors show great promise for personal air quality monitoring to address this worldwide health crisis. However, implementing miniaturized arrays of such sensors demands high performance instrumentation circuits that simultaneously meet challenging power, area, sensitivity, noise and dynamic range goals. This paper presents a new multi-channel CMOS amperometric ADC featuring pixel-level architecture for gas sensor arrays. The circuit combines digital modulation of input currents and an incremental Σ∆ ADC to achieve wide dynamic range and high sensitivity with very high power efficiency and compact size. Fabricated in 0.5 [Formula: see text] CMOS, the circuit was measured to have 164 dB cross-scale dynamic range, 100 fA sensitivity while consuming only 241 [Formula: see text] and 0.157 [Formula: see text] active area per channel. Electrochemical experiments with liquid and gas targets demonstrate the circuit's real-time response to a wide range of analyte concentrations.

  20. A high speed, wide dynamic range digitizer circuit for photomultiplier tubes

    SciTech Connect

    Yarema, R.J.; Foster, G.W.; Knickerbocker, K.; Sarraj, M.; Tschirhart, R.; Whitmore, J.; Zimmerman, T.; Lindgren, M.

    1994-06-01

    High energy physics experiments running at high interaction rates frequently require long record lengths for determining a level 1 trigger. The easiest way to provide a long event record is by digital means. In applications requiring wide dynamic range, however, digitization of an analog signal to obtain the digital record has been impossible due to lack of high speed, wide range FADCs. One such application is the readout of thousands of photomultiplier tubes in fixed target and colliding beam experiment calorimeters. A circuit has been designed for digitizing PMT signals over a wide dynamic range (17--18 bits) with 8 bits of resolution at rates up to 53 MHz. Output from the circuit is in a floating point format with a 4 bit exponent and an 8 bit mantissa. The heart of the circuit is a full custom integrated circuit called the QIE (Charge Integrator and Encoder). The design of the QIE and associated circuitry reported here permits operation over a 17 bit dynamic range. Tests of the circuit with a PMT input and a pulsed laser have provided respectable results with little off line correction. Performance of the circuit for demanding applications can be significantly enhanced with additional off line correction. Circuit design, packaging issues, and test results of a multirange device are presented for the first time.

  1. A low background-rate detector for ions in the 5 to 50 keV energy range to be used for radioisotope dating with a small cyclotron

    SciTech Connect

    Friedman, P.G.

    1986-11-25

    Accelerator mass spectrometry in tandem Van de Graaff accelerators has proven successful for radioisotope dating small samples. We are developing a 20 cm diameter 30 to 40 keV cyclotron dedicated to high-sensitivity radioisotope dating, initially for /sup 14/C. At this energy, range and dE/dx methods of particle identification are impossible. Thus arises the difficult problem of reliably detecting 30 to 40 keV /sup 14/C at 10/sup -2/ counts/sec in the high background environment of the cyclotron, where lower energy ions, electrons, and photons bombard the detector at much higher rates. We have developed and tested an inexpensive, generally useful ion detector that allows dark-count rates below 10/sup -4/ counts/sec and excellent background suppression. With the cyclotron tuned near the /sup 13/CH background peak, to the frequency for /sup 14/C, the detector suppresses the background to 6 x 10/sup -4/ counts/sec. For each /sup 14/C ion the detectors grazing-incidence Al/sub 2/O/sub 3/ conversion dynode emits about 20 secondary electrons, which are independently multiplied in separate pores of a microchannel plate. The output signal is proportional to the number of secondary electrons, allowing pulse-height discrimination of background. We have successfully tested the detector with positive /sup 12/C, /sup 23/Na, /sup 39/K, /sup 41/K, /sup 85/Rb, /sup 87/Rb, and /sup 133/Cs at 5 to 40 keV, and with 36 keV negative /sup 12/C and /sup 13/CH. It should detect ions and neutrals of all species, at energies above 5 keV, with good efficiency and excellent background discrimination. Counting efficiency and background discrimination improve with higher ion energy. The detector can be operated at least up to 2 x 10/sup -7/ Torr and be repeatedly exposed to air. The maximum rate is 10/sup 6.4/ ions/sec in pulse counting mode and 10/sup 9.7/ ions/sec in current integrating mode.

  2. Dynamic range compression/expansion of light beams by photorefractive crystals

    NASA Technical Reports Server (NTRS)

    Cheng, Li-Jen (Inventor); Liu, Hua-Kuang (Inventor)

    1988-01-01

    An apparatus is provided which greatly reduces the intensity of bright portions of an image while only moderately reducing the brightness of dimmer portions of the image, to thereby compress the range of light intensities to facilitate detection of the image. The apparatus includes a light detector device formed by a chip of photorefractive material. A 2-D array of light beams from an object to be detected passes through a beam splitter to form two arrays of light beams. The two arrays are directed at different angles against a surface of the chip of photorefractive material, the two arrays of light beams forming coincident images on the surface. One of the 2-D arrays of beams emerging from an opposite surface of the chip has a lower range of intensities, to facilitate detection of the object despite very bright spots in its image. The other array of light beams emerging from the chip has a greater range of intensities than the unprocessed image of the object.

  3. Extended dynamical mean-field study of the Hubbard model with long-range interactions

    NASA Astrophysics Data System (ADS)

    Huang, Li; Ayral, Thomas; Biermann, Silke; Werner, Philipp

    2014-11-01

    Using extended dynamical mean-field theory and its combination with the G W approximation, we compute the phase diagrams and local spectral functions of the single-band extended Hubbard model on the square and simple cubic lattices, considering long-range interactions up to the third nearest neighbors. The longer-range interactions shift the boundaries between the metallic, charge-ordered insulating, and Mott insulating phases, and lead to characteristic changes in the screening modes and local spectral functions. Momentum-dependent self-energy contributions enhance the correlation effects and thus compete with the additional screening effect from longer-range Coulomb interactions. Our results suggest that the influence of longer-range intersite interactions is significant, and that these effects deserve attention in realistic studies of correlated materials.

  4. Singular dynamics and emergence of nonlocality in long-range quantum models

    NASA Astrophysics Data System (ADS)

    Lepori, L.; Trombettoni, A.; Vodola, D.

    2017-03-01

    We discuss how nonlocality originates in long-range quantum systems and how it affects their dynamics at and out of equilibrium. We focus in particular on the Kitaev chains with long-range pairings and on the quantum Ising chain with long-range antiferromagnetic coupling (both having a power-law decay with exponent α). By studying the dynamic correlation functions, we find that for every finite α two different behaviours can be identified, one typical of short-range systems and the other connected with locality violation. The latter behaviour is shown related also with the known power-law decay tails previously observed in the static correlation functions, and originated by modes—having in general energies far from the minima of the spectrum—where particular singularities develop as a consequence of the long-rangedness of the system. We refer to these modes as to ‘singular’ modes, and as to ‘singular dynamics’ to their dynamics. For the Kitaev model they are manifest, at finite α, in derivatives of the quasiparticle energy, the order of the derivatives at which the singularity occurs is increasing with α. The features of the singular modes and their physical consequences are clarified by studying an effective theory for them and by a critical comparison of the results from this theory with the lattice ones. Moreover, a numerical study of the effects of the singular modes on the time evolution after various types of global quenches is performed. We finally present and discuss the presence of singular modes and their consequences in interacting long-range systems by investigating in the long-range Ising quantum chain, both in the deep paramagnetic regime and at criticality, where they also play a central role for the breakdown of conformal invariance.

  5. Territorial Dynamics and Stable Home Range Formation for Central Place Foragers

    PubMed Central

    Potts, Jonathan R.; Harris, Stephen; Giuggioli, Luca

    2012-01-01

    Uncovering the mechanisms behind territory formation is a fundamental problem in behavioural ecology. The broad nature of the underlying conspecific avoidance processes are well documented across a wide range of taxa. Scent marking in particular is common to a large range of terrestrial mammals and is known to be fundamental for communication. However, despite its importance, exact quantification of the time-scales over which scent cues and messages persist remains elusive. Recent work by the present authors has begun to shed light on this problem by modelling animals as random walkers with scent-mediated interaction processes. Territories emerge as dynamic objects that continually change shape and slowly move without settling to a fixed location. As a consequence, the utilisation distribution of such an animal results in a slowly increasing home range, as shown for urban foxes (Vulpes vulpes). For certain other species, however, home ranges reach a stable state. The present work shows that stable home ranges arise when, in addition to scent-mediated conspecific avoidance, each animal moves as a central place forager. That is, the animal's movement has a random aspect but is also biased towards a fixed location, such as a den or nest site. Dynamic territories emerge but the probability distribution of the territory border locations reaches a steady state, causing stable home ranges to emerge from the territorial dynamics. Approximate analytic expressions for the animal's probability density function are derived. A programme is given for using these expressions to quantify both the strength of the animal's movement bias towards the central place and the time-scale over which scent messages persist. Comparisons are made with previous theoretical work modelling central place foragers with conspecific avoidance. Some insights into the mechanisms behind allometric scaling laws of animal space use are also given. PMID:22479510

  6. High dynamic range infrared images detail enhancement based on local edge preserving filter

    NASA Astrophysics Data System (ADS)

    Song, Qiong; Wang, Yuehuan; Bai, Kun

    2016-07-01

    In the field of infrared (IR) image processing, displaying a high dynamic range (HDR) image on a low dynamic range display equipment with a natural visual effect, clear details on local areas and less artifacts is an important issue. In this paper, we present a new approach to display HDR IR images with contrast enhancement. First, the local edge-preserving filter (LEPF) is utilized to separate the image into a base layer and detail layer(s). After the filtering procedure, we use an adaptive Gamma transformation to adjust the gray distribution of the base layer, and stretch the detail layer based on a human visual effect principle. Then, we recombine the detail layer and base layer to obtain the enhance output. Finally, we adjust the luminance of output by applying multiple exposure fusion method. The experimental results demonstrate that our proposed method can provide a significant performance in terms of enhancing details and less artifacts than the state of the arts.

  7. 32-channel pyrometer with high dynamic range for studies of shocked nanothermites

    NASA Astrophysics Data System (ADS)

    Bassett, Will P.; Dlott, Dana D.

    2017-01-01

    A 32-channel optical pyrometer has been developed for studying temperature dynamics of shock-initiated reactive materials with one nanosecond time resolution and high dynamic range. The pyrometer consists of a prism spectrograph which directs the spectrally-resolved emission to 32 fiber optics and 32 photomultiplier tubes and digitizers. Preliminary results show shock-initiated reactions of a nanothermite composite, nano CuO/Al in nitrocellulose binder, consists of three stages. The first stage occurred at 30 ns, right after the shock unloaded, the second stage at 100 ns and the third at 1 μs, and the temperatures ranged from 2100K to 3000K. Time-resolved emission spectra suggest hot spots formed during shock unloading, which initiated the bulk thermite/nitrocellulose reaction.

  8. Introducing a Public Stereoscopic 3D High Dynamic Range (SHDR) Video Database

    NASA Astrophysics Data System (ADS)

    Banitalebi-Dehkordi, Amin

    2017-03-01

    High dynamic range (HDR) displays and cameras are paving their ways through the consumer market at a rapid growth rate. Thanks to TV and camera manufacturers, HDR systems are now becoming available commercially to end users. This is taking place only a few years after the blooming of 3D video technologies. MPEG/ITU are also actively working towards the standardization of these technologies. However, preliminary research efforts in these video technologies are hammered by the lack of sufficient experimental data. In this paper, we introduce a Stereoscopic 3D HDR database of videos that is made publicly available to the research community. We explain the procedure taken to capture, calibrate, and post-process the videos. In addition, we provide insights on potential use-cases, challenges, and research opportunities, implied by the combination of higher dynamic range of the HDR aspect, and depth impression of the 3D aspect.

  9. Note: Increasing dynamic range of digital-to-analog converter using a superconducting quantum interference device

    SciTech Connect

    Nakanishi, Masakazu

    2014-10-15

    Responses of a superconducting quantum interference device (SQUID) are periodically dependent on magnetic flux coupling to its superconducting ring and the period is a flux quantum (Φ{sub o} = h/2e, where h and e, respectively, express Planck's constant and elementary charge). Using this periodicity, we had proposed a digital to analog converter using a SQUID (SQUID DAC) of first generation with linear current output, interval of which corresponded to Φ{sub o}. Modification for increasing dynamic range by interpolating within each interval is reported. Linearity of the interpolation was also based on the quantum periodicity. A SQUID DAC with dynamic range of about 1.4 × 10{sup 7} was created as a demonstration.

  10. Noise-induced dynamical phase transitions in long-range systems.

    PubMed

    Chavanis, Pierre-Henri; Baldovin, Fulvio; Orlandini, Enzo

    2011-04-01

    In the thermodynamic limit, the time evolution of isolated long-range interacting systems is properly described by the Vlasov equation. This equation admits nonequilibrium dynamically stable stationary solutions characterized by a zero order parameter. We show that the presence of external noise sources, such as a heat bath, can reduce their lifetime and induce at a specific time a dynamical phase transition marked by a nonzero order parameter. This transition may be used as a distinctive experimental signature of the temporary existence of nonequilibrium Vlasov-stable states. In particular, we present evidence of a regime characterized by an order parameter pulse. Our analytical results are corroborated by numerical simulations of a paradigmatic long-range model.

  11. A Kalman-filtering approach to high dynamic range imaging for measurement applications.

    PubMed

    Dedrick, Eric; Lau, Daniel

    2012-02-01

    High dynamic range imaging (HDRI) methods in computational photography address situations where the dynamic range of a scene exceeds what can be captured by an image sensor in a single exposure. HDRI techniques have also been used to construct radiance maps in measurement applications; unfortunately, the design and evaluation of HDRI algorithms for use in these applications have received little attention. In this paper, we develop a novel HDRI technique based on pixel-by-pixel Kalman filtering and evaluate its performance using objective metrics that this paper also introduces. In the presented experiments, this new technique achieves as much as 9.4-dB improvement in signal-to-noise ratio and can achieve as much as a 29% improvement in radiometric accuracy over a classic method.

  12. Improvement of dynamic range of filter-less fluorescence sensor with body-biasing technique

    NASA Astrophysics Data System (ADS)

    Moriwaki, Yu; Takahashi, Kazuhiro; Akita, Ippei; Ishida, Makoto; Sawada, Kazuaki

    2015-04-01

    Although fluorescence microscopy is an important technique in biomedical fields, the bulky equipment is disadvantageous in some situations. We have previously proposed a filter-less fluorescence sensor whose operation is based on the light absorption coefficient, which depends on the wavelength in a silicon substrate. In this sensor, the ratio of the excitation light intensity to the fluorescence intensity is as high as 400:1 upon optimizing the impurity concentration and the depth of the p-well region. To improve the dynamic range, herein we use a body-biasing technique to optimize the potential distribution of the sensing area to acquire sufficient photocurrent. Consequently, the dynamic range of the filter-less fluorescence sensor is improved to 800:1 with an 8 V substrate voltage.

  13. Research on temperature distribution of combustion flames based on high dynamic range imaging

    NASA Astrophysics Data System (ADS)

    Zhao, Hui; Feng, Huajun; Xu, Zhihai; Li, Qi

    2007-10-01

    The imaging-based three-color method is widely used in the field of non-contact temperature measurement of combustion flames. In this paper, by analyzing the imaging process of a combustion flame in detail, we re-derivate the three-color method by adopting a theory of high dynamic range imaging. Instead of using white balanced, gamma calibrated or other algorithms applied 8-bit pixel values, we use irradiance values on the image plane; these values are obtained by combining two differently exposed raw images into one high dynamic range irradiance map with the help of the imaging system's response function. An instrumentation system is presented and a series of experiments have been carried out, the results of which are satisfactory.

  14. Enhanced Dynamic Range in N-SQUID Lumped Josephson Parametric Amplifiers

    NASA Astrophysics Data System (ADS)

    Eddins, A.; Levenson-Falk, E. M.; Toyli, D. M.; Vijay, R.; Minev, Z.; Siddiqi, I.

    2014-03-01

    Simultaneously providing high gain and nearly quantum-limited noise performance, superconducting parametric amplifiers (paramps) have been used successfully for high fidelity qubit readout, quantum feedback, and microwave quantum optics experiments. The Lumped Josephson Parametric Amplifier (LJPA) consists of a capacitively shunted SQUID coupled to a transmission line to form a nonlinear resonator. Like other paramps employing a resonant circuit, the LJPA's dynamic range-a potentially key ingredient for multiplexing-is limited. Simple theory predicts that the dynamic range can be increased without any reduction in bandwidth or gain by distributing the resonator nonlinearity over a series array of SQUIDs. We fabricated such array devices with up to 5 SQUIDs and observed a clear increase in the critical power for bifurcation about which parametric gain occurs. We discuss in detail amplifier performance as a function of the number of SQUIDs in the array. This research was supported by the Army Research Office under a QCT grant.

  15. Analysis of quantum Monte Carlo dynamics for quantum adiabatic evolution in infinite-range spin systems

    NASA Astrophysics Data System (ADS)

    Inoue, Jun-Ichi

    2011-03-01

    We analytically derive deterministic equations of order parameters such as spontaneous magnetization in infinite-range quantum spin systems obeying quantum Monte Carlo dynamics. By means of the Trotter decomposition, we consider the transition probability of Glauber-type dynamics of microscopic states for the corresponding classical system. Under the static approximation, differential equations with respect to macroscopic order parameters are explicitly obtained from the master equation that describes the microscopic-law. We discuss several possible applications of our approach to disordered spin systems for statistical-mechanical informatics. Especially, we argue the ground state searching for infinite-range random spin systems via quantum adiabatic evolution. We were financially supported by Grant-in-Aid for Scientific Research (C) of Japan Society for the Promotion of Science, No. 22500195.

  16. Note: Increasing dynamic range of digital-to-analog converter using a superconducting quantum interference device.

    PubMed

    Nakanishi, Masakazu

    2014-10-01

    Responses of a superconducting quantum interference device (SQUID) are periodically dependent on magnetic flux coupling to its superconducting ring and the period is a flux quantum (Φo = h/2e, where h and e, respectively, express Planck's constant and elementary charge). Using this periodicity, we had proposed a digital to analog converter using a SQUID (SQUID DAC) of first generation with linear current output, interval of which corresponded to Φo. Modification for increasing dynamic range by interpolating within each interval is reported. Linearity of the interpolation was also based on the quantum periodicity. A SQUID DAC with dynamic range of about 1.4 × 10(7) was created as a demonstration.

  17. Incongruent range dynamics between co-occurring Asian temperate tree species facilitated by life history traits.

    PubMed

    Zhao, Yun-Peng; Yan, Xiao-Ling; Muir, Graham; Dai, Qiong-Yan; Koch, Marcus A; Fu, Cheng-Xin

    2016-04-01

    Postglacial expansion to former range limits varies substantially among species of temperate deciduous forests in eastern Asia. Isolation hypotheses (with or without gene flow) have been proposed to explain this variance, but they ignore detailed population dynamics spanning geological time and neglect the role of life history traits. Using population genetics to uncover these dynamics across their Asian range, we infer processes that formed the disjunct distributions of Ginkgo biloba and the co-occurring Cercidiphyllum japonicum (published data). Phylogenetic, coalescent, and comparative data suggest that Ginkgo population structure is regional, dichotomous (to west-east refugia), and formed ˜51 kya, resulting from random genetic drift during the last glaciation. This split is far younger than the north-south population structure of Cercidiphyllum (~1.89 Mya). Significant (recent) unidirectional gene flow has not homogenized the two Ginkgo refugia, despite 2Nm > 1. Prior to this split, gene flow was potentially higher, resulting in conflicting support for a priori hypotheses that view isolation as an explanation for the variation in postglacial range limits. Isolation hypotheses (with or without gene flow) are thus not necessarily mutually exclusive due to temporal variation of gene flow and genetic drift. In comparison with Cercidiphyllum, the restricted range of Ginkgo has been facilitated by uncompetitive life history traits associated with seed ecology, highlighting the importance of both demography and lifetime reproductive success when interpreting range shifts.

  18. Human tissue color as viewed in high dynamic range optical spectral transmission measurements.

    PubMed

    Petrov, Georgi I; Doronin, Alexander; Whelan, Harry T; Meglinski, Igor; Yakovlev, Vladislav V

    2012-09-01

    High dynamic range optical-to-near-infrared transmission measurements for different parts of human body in the spectral range from 650 to 950 nm have been performed. Experimentally measured spectra are correlated with Monte Carlo simulations using chromaticity coordinates in CIE 1976 L*a*b* color space. Both a qualitative and a quantitative agreement have been found, paving a new way of characterizing human tissues in vivo. The newly developed experimental and computational platform for assessing tissue transmission spectra is anticipated to have a considerable impact on identifying favorable conditions for laser surgery and optical diagnostics, while providing supplementary information about tissue properties.

  19. Determination of metal ions by fluorescence anisotropy exhibits a broad dynamic range

    NASA Astrophysics Data System (ADS)

    Thompson, Richard B.; Maliwal, Badri P.; Fierke, Carol A.

    1998-05-01

    Recently, we have shown that metal ions free in solution may be determined at low levels by fluorescence anisotropy (polarization) measurements. Anisotropy measurements enjoy the advantages of wavelength ratiometric techniques for determining metal ions such as calcium, because anisotropy measurements are ratiometric as well. Furthermore, fluorescence anisotropy may be imaged in the microscope. An advantage of anisotropy not demonstrated for wavelength ratiometric approaches using indicators such as Fura-2 and Indo-1 is that under favorable circumstances anisotropy-based determinations exhibit a much broader dynamic range in metal ion concentration. Determinations of free Zn(II) in the picomolar range are demonstrated.

  20. Face recognition based on matching of local features on 3D dynamic range sequences

    NASA Astrophysics Data System (ADS)

    Echeagaray-Patrón, B. A.; Kober, Vitaly

    2016-09-01

    3D face recognition has attracted attention in the last decade due to improvement of technology of 3D image acquisition and its wide range of applications such as access control, surveillance, human-computer interaction and biometric identification systems. Most research on 3D face recognition has focused on analysis of 3D still data. In this work, a new method for face recognition using dynamic 3D range sequences is proposed. Experimental results are presented and discussed using 3D sequences in the presence of pose variation. The performance of the proposed method is compared with that of conventional face recognition algorithms based on descriptors.

  1. A convection-driven long-range linear gradient generator with dynamic control.

    PubMed

    Wang, Hao; Chen, Chia-Hung; Xiang, Zhuolin; Wang, Ming; Lee, Chengkuo

    2015-03-21

    We developed a novel gradient generator to achieve long range and linear chemical gradients with a dynamic control function. The length of the gradient can be on the centimetre scale. The gradient profile can be tuned by changing the flow rates. The device can work in both high flow rate regimes with large shear stress and low flow rate regimes with minimum shear stress. The drug screening function was demonstrated by the viability test of PC-9 cancer cells.

  2. Roles of Long-Range Tertiary Interactions in Limiting Dynamics of the Tetrahymena Group I Ribozyme

    PubMed Central

    2015-01-01

    We determined the effects of mutating the long-range tertiary contacts of the Tetrahymena group I ribozyme on the dynamics of its substrate helix (referred to as P1) and on catalytic activity. Dynamics were assayed by fluorescence anisotropy of the fluorescent base analogue, 6-methyl isoxanthopterin, incorporated into the P1 helix, and fluorescence anisotropy and catalytic activity were measured for wild type and mutant ribozymes over a range of conditions. Remarkably, catalytic activity correlated with P1 anisotropy over 5 orders of magnitude of activity, with a correlation coefficient of 0.94. The functional and dynamic effects from simultaneous mutation of the two long-range contacts that weaken P1 docking are cumulative and, based on this RNA’s topology, suggest distinct underlying origins for the mutant effects. Tests of mechanistic predictions via single molecule FRET measurements of rate constants for P1 docking and undocking suggest that ablation of the P14 tertiary interaction frees P2 and thereby enhances the conformational space explored by the undocked attached P1 helix. In contrast, mutation of the metal core tertiary interaction disrupts the conserved core into which the P1 helix docks. Thus, despite following a single correlation, the two long-range tertiary contacts facilitate P1 helix docking by distinct mechanisms. These results also demonstrate that a fluorescence anisotropy probe incorporated into a specific helix within a larger RNA can report on changes in local helical motions as well as differences in more global dynamics. This ability will help uncover the physical properties and behaviors that underlie the function of RNAs and RNA/protein complexes. PMID:24738560

  3. Dynamic Range Enhancement of High-Speed Electrical Signal Data via Non-Linear Compression

    NASA Technical Reports Server (NTRS)

    Laun, Matthew C. (Inventor)

    2016-01-01

    Systems and methods for high-speed compression of dynamic electrical signal waveforms to extend the measuring capabilities of conventional measuring devices such as oscilloscopes and high-speed data acquisition systems are discussed. Transfer function components and algorithmic transfer functions can be used to accurately measure signals that are within the frequency bandwidth but beyond the voltage range and voltage resolution capabilities of the measuring device.

  4. Proposed satellite laser ranging and very long baseline interferometry sites for crustal dynamics investigations

    NASA Technical Reports Server (NTRS)

    Lowman, P. D.; Allenby, R. J.; Frey, H. V.

    1979-01-01

    Recommendations are presented for a global network of 125 sites for geodetic measurements by satellite laser ranging and very long baseline interferometry. The sites were proposed on the basis of existing facilities and scientific value for investigation of crustal dynamics as related to earthquake hazards. Tectonic problems are discussed for North America peripheral regions and for the world. The sites are presented in tables and maps, with bibliographic references.

  5. A visibility matching tone reproduction operator for high dynamic range scenes

    SciTech Connect

    Larson, G.W.; Rushmeier, H.; Piatko, C.

    1997-01-15

    The authors present a tone reproduction operator that preserves visibility in high dynamic range scenes. The method introduces a new histogram adjustment technique, based on the population of local adaptation luminances in a scene. To match subjective viewing experience, the method incorporates models for human contrast sensitivity, glare, spatial acuity and color sensitivity. They compare the results to previous work and present examples the techniques applied to lighting simulation and electronic photography.

  6. The STEIN Particle Detector

    DTIC Science & Technology

    2015-02-27

    associated with solar disturbances, magnetic storms and magnetospheric substorms. AF-STEIN has several distinct advantages over standard detectors flown on...low-earth- orbit (LEO) satellites. AF-STEIN provides the sensitivity, temporal resolution, energy resolution (~1 keV FWHM), dynamic range, and energy...essentially all important suprathermal (~4 to 200 keV) particle populations associated with solar disturbances, magnetic storms and magnetospheric substorms

  7. High sensitive/wide dynamic range, field emission pressure sensor based on fully embedded CNTs

    NASA Astrophysics Data System (ADS)

    Taak, S.; Rajabali, S.; Darbari, S.; Mohajerzadeh, S.

    2014-01-01

    The formation of high sensitivity-wide dynamic range field emission pressure sensors based on carbon nanotubes (CNTs) is reported. In this work, CNTs are grown inside an array of micromachined holes in order to ensure a high sensitivity and a wide dynamic range by allowing anode-cathode proximity while preventing anode-cathode direct contact simultaneously. External pressure is applied to a Si-based flexible anode, which results in consequent variations in emission current, due to electric field changes. Microcavities in this structure have been formed by a Si deep vertical etching process, while the CNTs have been grown by direct current plasma-enhanced chemical vapour deposition. Also, it is demonstrated that a similar fabrication process can be applied to implement a device with an electrically controllable emission current. A high sensitivity of 1.5-13.7 µA kPa-1 (with Vanode/cathode < 100 V) within a dynamic range from around 0.1 to 1 GPa, is measured in this experiment.

  8. Fluorescent Protein Based FRET Pairs with Improved Dynamic Range for Fluorescence Lifetime Measurements

    PubMed Central

    George Abraham, Bobin; Sarkisyan, Karen S.; Mishin, Alexander S.; Santala, Ville; Tkachenko, Nikolai V.; Karp, Matti

    2015-01-01

    Fluorescence Resonance Energy Transfer (FRET) using fluorescent protein variants is widely used to study biochemical processes in living cells. FRET detection by fluorescence lifetime measurements is the most direct and robust method to measure FRET. The traditional cyan-yellow fluorescent protein based FRET pairs are getting replaced by green-red fluorescent protein variants. The green-red pair enables excitation at a longer wavelength which reduces cellular autofluorescence and phototoxicity while monitoring FRET. Despite the advances in FRET based sensors, the low FRET efficiency and dynamic range still complicates their use in cell biology and high throughput screening. In this paper, we utilized the higher lifetime of NowGFP and screened red fluorescent protein variants to develop FRET pairs with high dynamic range and FRET efficiency. The FRET variations were analyzed by proteolytic activity and detected by steady-state and time-resolved measurements. Based on the results, NowGFP-tdTomato and NowGFP-mRuby2 have shown high potentials as FRET pairs with large fluorescence lifetime dynamic range. The in vitro measurements revealed that the NowGFP-tdTomato has the highest Förster radius for any fluorescent protein based FRET pairs yet used in biological studies. The developed FRET pairs will be useful for designing FRET based sensors and studies employing Fluorescence Lifetime Imaging Microscopy (FLIM). PMID:26237400

  9. Seasonal source-sink dynamics at the edge of a species' range

    USGS Publications Warehouse

    Kanda, L.L.; Fuller, T.K.; Sievert, P.R.; Kellogg, R.L.

    2009-01-01

    The roles of dispersal and population dynamics in determining species' range boundaries recently have received theoretical attention but little empirical work. Here we provide data on survival, reproduction, and movement for a Virginia opossum (Didelphis virginiana) population at a local distributional edge in central Massachusetts (USA). Most juvenile females that apparently exploited anthropogenic resources survived their first winter, whereas those using adjacent natural resources died of starvation. In spring, adult females recolonized natural areas. A life-table model suggests that a population exploiting anthropogenic resources may grow, acting as source to a geographically interlaced sink of opossums using only natural resources, and also providing emigrants for further range expansion to new human-dominated landscapes. In a geographical model, this source-sink dynamic is consistent with the local distribution identified through road-kill surveys. The Virginia opossum's exploitation of human resources likely ameliorates energetically restrictive winters and may explain both their local distribution and their northward expansion in unsuitable natural climatic regimes. Landscape heterogeneity, such as created by urbanization, may result in source-sink dynamics at highly localized scales. Differential fitness and individual dispersal movements within local populations are key to generating regional distributions, and thus species ranges, that exceed expectations. ?? 2009 by the Ecological Society of America.

  10. Digital PCR modeling for maximal sensitivity, dynamic range and measurement precision.

    PubMed

    Majumdar, Nivedita; Wessel, Thomas; Marks, Jeffrey

    2015-01-01

    The great promise of digital PCR is the potential for unparalleled precision enabling accurate measurements for genetic quantification. A challenge associated with digital PCR experiments, when testing unknown samples, is to perform experiments at dilutions allowing the detection of one or more targets of interest at a desired level of precision. While theory states that optimal precision (Po) is achieved by targeting ~1.59 mean copies per partition (λ), and that dynamic range (R) includes the space spanning one positive (λL) to one negative (λU) result from the total number of partitions (n), these results are tempered for the practitioner seeking to construct digital PCR experiments in the laboratory. A mathematical framework is presented elucidating the relationships between precision, dynamic range, number of partitions, interrogated volume, and sensitivity in digital PCR. The impact that false reaction calls and volumetric variation have on sensitivity and precision is next considered. The resultant effects on sensitivity and precision are established via Monte Carlo simulations reflecting the real-world likelihood of encountering such scenarios in the laboratory. The simulations provide insight to the practitioner on how to adapt experimental loading concentrations to counteract any one of these conditions. The framework is augmented with a method of extending the dynamic range of digital PCR, with and without increasing n, via the use of dilutions. An example experiment demonstrating the capabilities of the framework is presented enabling detection across 3.33 logs of starting copy concentration.

  11. Long-range correlations improve understanding of the influence of network structure on contact dynamics.

    PubMed

    Peyrard, N; Dieckmann, U; Franc, A

    2008-05-01

    Models of infectious diseases are characterized by a phase transition between extinction and persistence. A challenge in contemporary epidemiology is to understand how the geometry of a host's interaction network influences disease dynamics close to the critical point of such a transition. Here we address this challenge with the help of moment closures. Traditional moment closures, however, do not provide satisfactory predictions close to such critical points. We therefore introduce a new method for incorporating longer-range correlations into existing closures. Our method is technically simple, remains computationally tractable and significantly improves the approximation's performance. Our extended closures thus provide an innovative tool for quantifying the influence of interaction networks on spatially or socially structured disease dynamics. In particular, we examine the effects of a network's clustering coefficient, as well as of new geometrical measures, such as a network's square clustering coefficients. We compare the relative performance of different closures from the literature, with or without our long-range extension. In this way, we demonstrate that the normalized version of the Bethe approximation-extended to incorporate long-range correlations according to our method-is an especially good candidate for studying influences of network structure. Our numerical results highlight the importance of the clustering coefficient and the square clustering coefficient for predicting disease dynamics at low and intermediate values of transmission rate, and demonstrate the significance of path redundancy for disease persistence.

  12. Chroma sampling and modulation techniques in high dynamic range video coding

    NASA Astrophysics Data System (ADS)

    Dai, Wei; Krishnan, Madhu; Topiwala, Pankaj

    2015-09-01

    High Dynamic Range and Wide Color Gamut (HDR/WCG) Video Coding is an area of intense research interest in the engineering community, for potential near-term deployment in the marketplace. HDR greatly enhances the dynamic range of video content (up to 10,000 nits), as well as broadens the chroma representation (BT.2020). The resulting content offers new challenges in its coding and transmission. The Moving Picture Experts Group (MPEG) of the International Standards Organization (ISO) is currently exploring coding efficiency and/or the functionality enhancements of the recently developed HEVC video standard for HDR and WCG content. FastVDO has developed an advanced approach to coding HDR video, based on splitting the HDR signal into a smoothed luminance (SL) signal, and an associated base signal (B). Both signals are then chroma downsampled to YFbFr 4:2:0 signals, using advanced resampling filters, and coded using the Main10 High Efficiency Video Coding (HEVC) standard, which has been developed jointly by ISO/IEC MPEG and ITU-T WP3/16 (VCEG). Our proposal offers both efficient coding, and backwards compatibility with the existing HEVC Main10 Profile. That is, an existing Main10 decoder can produce a viewable standard dynamic range video, suitable for existing screens. Subjective tests show visible improvement over the anchors. Objective tests show a sizable gain of over 25% in PSNR (RGB domain) on average, for a key set of test clips selected by the ISO/MPEG committee.

  13. Detectability of regional lung ventilation with flat-panel detector-based dynamic radiography.

    PubMed

    Tanaka, Rie; Sanada, Shigeru; Okazaki, Nobuo; Kobayashi, Takeshi; Suzuki, Masayuki; Matsui, Takeshi; Matsui, Osamu

    2008-03-01

    This study was performed to investigate the ability of breathing chest radiography using flat-panel detector (FPD) to quantify relative local ventilation. Dynamic chest radiographs during respiration were obtained using a modified FPD system. Imaging was performed in three different positions, ie, standing and right and left decubitus positions, to change the distribution of local ventilation. We measured the average pixel value in the local lung area. Subsequently, the interframe differences, as well as difference values between maximum inspiratory and expiratory phases, were calculated. The results were visualized as images in the form of a color display to show more or less x-ray translucency. Temporal changes and spatial distribution of the results were then compared to lung physiology. In the results, the average pixel value in each lung was associated with respiratory phase. In all positions, respiratory changes of pixel value in the lower area were greater than those in the upper area (P < 0.01), which was the same tendency as the regional differences in ventilation determined by respiratory physiology. In addition, in the decubitus position, it was observed that areas with large respiratory changes in pixel value moved up in the vertical direction during expiration, which was considered to be airway closure. In conclusion, breathing chest radiography using FPD was shown to be capable of quantifying relative ventilation in local lung area and detecting regional differences in ventilation and timing of airway closure. This method is expected to be useful as a new diagnostic imaging modality for evaluating relative local ventilation.

  14. Dynamics and thermodynamics of systems with long-range dipole-type interactions

    NASA Astrophysics Data System (ADS)

    Atenas, Boris; Curilef, Sergio

    2017-02-01

    A Hamiltonian mean field model, where the potential is inspired by dipole-dipole interactions, is proposed to characterize the behavior of systems with long-range interactions. The dynamics of the system remains in quasistationary states before arriving at equilibrium. The equilibrium is analytically derived from the canonical ensemble and coincides with that obtained from molecular dynamics simulations (microcanonical ensemble) at only long time scales. The dynamics of the system is characterized by the behavior of the mean value of the kinetic energy. The significance of the results, compared to others in the recent literature, is that two plateaus sequentially emerge in the evolution of the model under the special considerations of the initial conditions and systems of finite size. The first plateau decays to a different second one before the system reaches equilibrium, but the dynamics of the system is expected to have only one plateau when the thermodynamics limit is reached because the difference between them tends to disappear as N tends to infinity. Hence, the first plateau is a type of quasistationary state the lifetime of which depends on a power law of N and the second seems to be a true quasistationary state as reported in the literature. We characterize the general behavior of the model according to its dynamics and thermodynamics.

  15. MO-A-BRD-01: An Investigation of the Dynamic Response of a Novel Acousto-Optic Liquid Crystal Detector for Full-Field Transmission Ultrasound Breast Imaging

    SciTech Connect

    Rosenfield, J.R.; La Riviere, P.J.; Sandhu, J.S.

    2014-06-15

    Purpose: To characterize the dynamic response of a novel acousto-optic (AO) liquid crystal detector for high-resolution transmission ultrasound breast imaging. Transient and steady-state lesion contrast were investigated to identify optimal transducer settings for our prototype imaging system consistent with the FDA limits of 1 W/cm{sup 2} and 50 J/cm{sup 2} on the incident acoustic intensity and the transmitted acoustic energy flux density. Methods: We have developed a full-field transmission ultrasound breast imaging system that uses monochromatic plane-wave illumination to acquire projection images of the compressed breast. The acoustic intensity transmitted through the breast is converted into a visual image by a proprietary liquid crystal detector operating on the basis of the AO effect. The dynamic response of the AO detector in the absence of an imaged breast was recorded by a CCD camera as a function of the acoustic field intensity and the detector exposure time. Additionally, a stereotactic needle biopsy breast phantom was used to investigate the change in opaque lesion contrast with increasing exposure time for a range of incident acoustic field intensities. Results: Using transducer voltages between 0.3 V and 0.8 V and exposure times of 3 minutes, a unique one-to-one mapping of incident acoustic intensity to steady-state optical brightness in the AO detector was observed. A transfer curve mapping acoustic intensity to steady-state optical brightness shows a high-contrast region analogous to the linear portion of the Hurter-Driffield curves of radiography. Using transducer voltages between 1 V and 1.75 V and exposure times of 90 s, the lesion contrast study demonstrated increasing lesion contrast with increasing breast exposure time and acoustic field intensity. Lesion-to-background contrast on the order of 0.80 was observed. Conclusion: Maximal lesion contrast in our prototype system can be obtained using the highest acoustic field intensity and the

  16. Psychophysical evaluation of the image quality of a dynamic flat-panel digital x-ray image detector using the threshold contrast detail detectability (TCDD) technique

    NASA Astrophysics Data System (ADS)

    Davies, Andrew G.; Cowen, Arnold R.; Bruijns, Tom J. C.

    1999-05-01

    We are currently in an era of active development of the digital X-ray imaging detectors that will serve the radiological communities in the new millennium. The rigorous comparative physical evaluations of such devices are therefore becoming increasingly important from both the technical and clinical perspectives. The authors have been actively involved in the evaluation of a clinical demonstration version of a flat-panel dynamic digital X-ray image detector (or FDXD). Results of objective physical evaluation of this device have been presented elsewhere at this conference. The imaging performance of FDXD under radiographic exposure conditions have been previously reported, and in this paper a psychophysical evaluation of the FDXD detector operating under continuous fluoroscopic conditions is presented. The evaluation technique employed was the threshold contrast detail detectability (TCDD) technique, which enables image quality to be measured on devices operating in the clinical environment. This approach addresses image quality in the context of both the image acquisition and display processes, and uses human observers to measure performance. The Leeds test objects TO[10] and TO[10+] were used to obtain comparative measurements of performance on the FDXD and two digital spot fluorography (DSF) systems, one utilizing a Plumbicon camera and the other a state of the art CCD camera. Measurements were taken at a range of detector entrance exposure rates, namely 6, 12, 25 and 50 (mu) R/s. In order to facilitate comparisons between the systems, all fluoroscopic image processing such as noise reduction algorithms, were disabled during the experiments. At the highest dose rate FDXD significantly outperformed the DSF comparison systems in the TCDD comparisons. At 25 and 12 (mu) R/s all three-systems performed in an equivalent manner and at the lowest exposure rate FDXD was inferior to the two DSF systems. At standard fluoroscopic exposures, FDXD performed in an equivalent

  17. Invited article: The fast readout low noise camera as a versatile x-ray detector for time resolved dispersive extended x-ray absorption fine structure and diffraction studies of dynamic problems in materials science, chemistry, and catalysis

    NASA Astrophysics Data System (ADS)

    Labiche, Jean-Claude; Mathon, Olivier; Pascarelli, Sakura; Newton, Mark A.; Ferre, Gemma Guilera; Curfs, Caroline; Vaughan, Gavin; Homs, Alejandro; Carreiras, David Fernandez

    2007-09-01

    Originally conceived and developed at the European Synchrotron Radiation Facility (ESRF) as an "area" detector for rapid x-ray imaging studies, the fast readout low noise (FReLoN) detector of the ESRF [J.-C. Labiche, ESRF Newsletter 25, 41 (1996)] has been demonstrated to be a highly versatile and unique detector. Charge coupled device (CCD) cameras at present available on the public market offer either a high dynamic range or a high readout speed. A compromise between signal dynamic range and readout speed is always sought. The parameters of the commercial cameras can sometimes be tuned, in order to better fulfill the needs of specific experiments, but in general these cameras have a poor duty cycle (i.e., the signal integration time is much smaller than the readout time). In order to address scientific problems such as time resolved experiments at the ESRF, a FReLoN camera has been developed by the Instrument Support Group at ESRF. This camera is a low noise CCD camera that combines high dynamic range, high readout speed, accuracy, and improved duty cycle in a single image. In this paper, we show its application in a quasi-one-dimensional sense to dynamic problems in materials science, catalysis, and chemistry that require data acquisition on a time scale of milliseconds or a few tens of milliseconds. It is demonstrated that in this mode the FReLoN can be applied equally to the investigation of rapid changes in long range order (via diffraction) and local order (via energy dispersive extended x-ray absorption fine structure) and in situations of x-ray hardness and flux beyond the capacity of other detectors.

  18. Invited article: The fast readout low noise camera as a versatile x-ray detector for time resolved dispersive extended x-ray absorption fine structure and diffraction studies of dynamic problems in materials science, chemistry, and catalysis

    SciTech Connect

    Labiche, Jean-Claude; Mathon, Olivier; Pascarelli, Sakura; Newton, Mark A.; Ferre, Gemma Guilera; Curfs, Caroline; Vaughan, Gavin; Homs, Alejandro; Carreiras, David Fernandez

    2007-09-15

    Originally conceived and developed at the European Synchrotron Radiation Facility (ESRF) as an 'area' detector for rapid x-ray imaging studies, the fast readout low noise (FReLoN) detector of the ESRF [J.-C. Labiche, ESRF Newsletter 25, 41 (1996)] has been demonstrated to be a highly versatile and unique detector. Charge coupled device (CCD) cameras at present available on the public market offer either a high dynamic range or a high readout speed. A compromise between signal dynamic range and readout speed is always sought. The parameters of the commercial cameras can sometimes be tuned, in order to better fulfill the needs of specific experiments, but in general these cameras have a poor duty cycle (i.e., the signal integration time is much smaller than the readout time). In order to address scientific problems such as time resolved experiments at the ESRF, a FReLoN camera has been developed by the Instrument Support Group at ESRF. This camera is a low noise CCD camera that combines high dynamic range, high readout speed, accuracy, and improved duty cycle in a single image. In this paper, we show its application in a quasi-one-dimensional sense to dynamic problems in materials science, catalysis, and chemistry that require data acquisition on a time scale of milliseconds or a few tens of milliseconds. It is demonstrated that in this mode the FReLoN can be applied equally to the investigation of rapid changes in long range order (via diffraction) and local order (via energy dispersive extended x-ray absorption fine structure) and in situations of x-ray hardness and flux beyond the capacity of other detectors.

  19. Single-crystal CVD diamond detector for low-energy charged particles with energies ranging from 100 keV to 2 MeV

    SciTech Connect

    Yuki Sato; Hiroyuki Murakami; Takehiro Shimaoka; Masakatsu Tsubota; Junichi, H. Kaneko

    2015-07-01

    The performance of a diamond detector made of a single-crystal diamond grown by chemical vapor deposition was studied for charged particles, having energies ranging from 100 keV to 2 MeV. Energy peaks of these low-energy ions were clearly observed. However, we observed that the pulse height for individual incident ion decreases with increasing atomic number of the ions. We estimated the charge collection efficiency of the generated charge carriers by charged particle incident. The charge collection above ∼95% is achieved for helium (He{sup +}) with the energy above 1.5 MeV. On the other hand, the charge collection efficiency for heavy-ions shows wrong values compared with that of He{sup +}, ∼70% for silicon (Si{sup +}) and 35 to 40% for gold (Au{sup 3+}), at the same incident energy range, respectively. (authors)

  20. Long-range protein–water dynamics in hyperactive insect antifreeze proteins

    PubMed Central

    Meister, Konrad; Ebbinghaus, Simon; Xu, Yao; Duman, John G.; DeVries, Arthur; Gruebele, Martin; Leitner, David M.; Havenith, Martina

    2013-01-01

    Antifreeze proteins (AFPs) are specific proteins that are able to lower the freezing point of aqueous solutions relative to the melting point. Hyperactive AFPs, identified in insects, have an especially high ability to depress the freezing point by far exceeding the abilities of other AFPs. In previous studies, we postulated that the activity of AFPs can be attributed to two distinct molecular mechanisms: (i) short-range direct interaction of the protein surface with the growing ice face and (ii) long-range interaction by protein-induced water dynamics extending up to 20 Å from the protein surface. In the present paper, we combine terahertz spectroscopy and molecular simulations to prove that long-range protein–water interactions make essential contributions to the high antifreeze activity of insect AFPs from the beetle Dendroides canadensis. We also support our hypothesis by studying the effect of the addition of the osmolyte sodium citrate. PMID:23277543

  1. Optimizing the dynamic range extension of a radiochromic film dosimetry system

    SciTech Connect

    Devic, Slobodan; Tomic, Nada; Soares, Christopher G.; Podgorsak, Ervin B.

    2009-02-15

    The authors present a radiochromic film dosimetry protocol for a multicolor channel radiochromic film dosimetry system consisting of the external beam therapy (EBT) model GAFCHROMIC film and the Epson Expression 1680 flat-bed document scanner. Instead of extracting only the red color channel, the authors are using all three color channels in the absorption spectrum of the EBT film to extend the dynamic dose range of the radiochromic film dosimetry system. By optimizing the dose range for each color channel, they obtained a system that has both precision and accuracy below 1.5%, and the optimized ranges are 0-4 Gy for the red channel, 4-50 Gy for the green channel, and above 50 Gy for the blue channel.

  2. Effect of long-range hopping and interactions on entanglement dynamics and many-body localization

    NASA Astrophysics Data System (ADS)

    Singh, Rajeev; Moessner, Roderich; Roy, Dibyendu

    2017-03-01

    We numerically investigate the dynamics of entanglement in a chain of spinless fermions with nonrandom but long-range hopping and interactions, and with random on-site energies. For moderate disorder in the absence of interactions, the chain hosts delocalized states at the top of the band which undergo a delocalization-localization transition with increasing disorder. We find an interesting regime in this noninteracting disordered chain where the long-time entanglement entropy scales as S (t )˜lnt and the saturated entanglement entropy scales with system size L as S (L ,t →∞ )˜lnL . We further study the interplay of long-range hopping and interactions on the growth of entanglement and the many-body localization (MBL) transition in this system. We develop an analogy to higher-dimensional short-range systems to compare and contrast such behavior with the physics of MBL in a higher dimension.

  3. Small high-speed dynamic target at close range laser active imaging system

    NASA Astrophysics Data System (ADS)

    Yao, Jun; Wang, Du-yue; Zhang, Zheng; Zhang, Yue; Dai, Qin

    2016-11-01

    In the shooting range measuring, all-weather, high speed, unattended, the new concepts such as the remote control is gradually applied. In this paper, a new type of low cost range measurement system, using FPGA + MCU as electronic control system of laser active illumination and high-speed CMOS camera, data to the rear zone by using optical fiber communications, transmission and realizes the remote control of unmanned, due to the low cost of front-end equipment, can be used as consumables replacement at any time, combined with distributed layout principle, can maximum limit close to the measured with mutilate ability goal, thus to achieve the goal of small high-speed dynamic imaging from close range.

  4. Universal threshold for the dynamical behavior of lattice systems with long-range interactions.

    PubMed

    Bachelard, Romain; Kastner, Michael

    2013-04-26

    Dynamical properties of lattice systems with long-range pair interactions, decaying like 1/r(α) with the distance r, are investigated, in particular the time scales governing the relaxation to equilibrium. Upon varying the interaction range α, we find evidence for the existence of a threshold at α=d/2, dependent on the spatial dimension d, at which the relaxation behavior changes qualitatively and the corresponding scaling exponents switch to a different regime. Based on analytical as well as numerical observations in systems of vastly differing nature, ranging from quantum to classical, from ferromagnetic to antiferromagnetic, and including a variety of lattice structures, we conjecture this threshold and some of its characteristic properties to be universal.

  5. Long-range protein-water dynamics in hyperactive insect antifreeze proteins.

    PubMed

    Meister, Konrad; Ebbinghaus, Simon; Xu, Yao; Duman, John G; DeVries, Arthur; Gruebele, Martin; Leitner, David M; Havenith, Martina

    2013-01-29

    Antifreeze proteins (AFPs) are specific proteins that are able to lower the freezing point of aqueous solutions relative to the melting point. Hyperactive AFPs, identified in insects, have an especially high ability to depress the freezing point by far exceeding the abilities of other AFPs. In previous studies, we postulated that the activity of AFPs can be attributed to two distinct molecular mechanisms: (i) short-range direct interaction of the protein surface with the growing ice face and (ii) long-range interaction by protein-induced water dynamics extending up to 20 Å from the protein surface. In the present paper, we combine terahertz spectroscopy and molecular simulations to prove that long-range protein-water interactions make essential contributions to the high antifreeze activity of insect AFPs from the beetle Dendroides canadensis. We also support our hypothesis by studying the effect of the addition of the osmolyte sodium citrate.

  6. Slow dynamics in many-body quantum systems with long range interactions

    NASA Astrophysics Data System (ADS)

    Santos, Lea; Perez-Bernal, Francisco

    2016-05-01

    In recent experiments with ion traps the range of the interactions between spins-1/2 can be controlled. In the limit of infinite-range interaction the system may be described by the Lipkin model, which exhibits an excited state quantum phase transition (ESQPT). The latter corresponds to a singularity in the spectrum that occurs at the ground state and propagates to higher energies as the control parameter increases beyond the ground state critical point. We show that the evolution of an initial state with energy close to the ESQPT critical point may be extremely slow. This result is surprising, since the dynamics is usually expected to be very fast in systems with long-range interactions. This behavior is justified with the analysis of the structures of the eigenstates. This work was supported by the NSF Grant No. DMR-1147430.

  7. Effects of static and dynamic higher-order optical modes in balanced homodyne readout for future gravitational waves detectors

    NASA Astrophysics Data System (ADS)

    Zhang, Teng; Danilishin, Stefan L.; Steinlechner, Sebastian; Barr, Bryan W.; Bell, Angus S.; Dupej, Peter; Gräf, Christian; Hennig, Jan-Simon; Houston, E. Alasdair; Huttner, Sabina H.; Leavey, Sean S.; Pascucci, Daniela; Sorazu, Borja; Spencer, Andrew; Wright, Jennifer; Strain, Kenneth A.; Hild, Stefan

    2017-03-01

    With the recent detection of gravitational waves (GWs), marking the start of the new field of GW astronomy, the push for building more sensitive laser-interferometric gravitational wave detectors (GWDs) has never been stronger. Balanced homodyne detection (BHD) allows for a quantum-noise (QN) limited readout of arbitrary light field quadratures, and has therefore been suggested as a vital building block for upgrades to Advanced LIGO and third-generation observatories. In terms of the practical implementation of BHD, we develop a full framework for analyzing the static optical high-order modes (HOMs) occurring in the BHD paths related to the misalignment or mode matching at the input and output ports of the laser interferometer. We find the effects of HOMs on the quantum-noise limited sensitivity is independent of the actual interferometer configuration; e.g. Michelson and Sagnac interferometers are affected in the same way. We show that misalignment of the output ports of the interferometer (output misalignment) only affects the high-frequency part of the quantum-noise limited sensitivity (detection noise). However, at low frequencies, HOMs reduce the interferometer response and the radiation pressure noise (back-action noise) by the same amount and hence the quantum-noise limited sensitivity is not negatively affected in that frequency range. We show that the misalignment of the laser into the interferometer (input misalignment) produces the same effect as output misalignment and additionally decreases the power inside the interferometer. We also analyze dynamic HOM effects, such as beam jitter created by the suspended mirrors of the BHD. Our analyses can be directly applied to any BHD implementation in a future GWD. Moreover, we apply our analytical techniques to the example of the speed meter proof-of-concept experiment under construction in Glasgow. We find that for our experimental parameters, the performance of our seismic isolation system in the BHD paths is

  8. In-line process control for laser welding of titanium by high dynamic range ratio pyrometry and plasma spectroscopy

    NASA Astrophysics Data System (ADS)

    Lempe, B.; Taudt, C.; Baselt, T.; Rudek, F.; Maschke, R.; Basan, F.; Hartmann, P.

    2014-02-01

    The production of complex titanium components for various industries using laser welding processes has received growing attention in recent years. It is important to know whether the result of the cohesive joint meets the quality requirements of standardization and ultimately the customer requirements. Erroneous weld seams can have fatal consequences especially in the field of car manufacturing and medicine technology. To meet these requirements, a real-time process control system has been developed which determines the welding quality through a locally resolved temperature profile. By analyzing the resulting weld plasma received data is used to verify the stability of the laser welding process. The determination of the temperature profile is done by the detection of the emitted electromagnetic radiation from the material in a range of 500 nm to 1100 nm. As detectors, special high dynamic range CMOS cameras are used. As the emissivity of titanium depends on the wavelength, the surface and the angle of radiation, measuring the temperature is a problem. To solve these a special pyrometer setting with two cameras is used. That enables the compensation of these effects by calculating the difference between the respective pixels on simultaneously recorded images. Two spectral regions with the same emissivity are detected. Therefore the degree of emission and surface effects are compensated and canceled out of the calculation. Using the spatially resolved temperature distribution the weld geometry can be determined and the laser process can be controlled. The active readjustment of parameters such as laser power, feed rate and inert gas injection increases the quality of the welding process and decreases the number of defective goods.

  9. Demonstration of 136 dB dynamic range capability for a simultaneous dual optical band CAOS camera.

    PubMed

    Riza, Nabeel A; La Torre, J Pablo

    2016-12-26

    For the first time, proposed and demonstrated is a simultaneous dual optical band coded access optical sensor (CAOS) camera design suited for extreme contrast multispectral bright target scenarios. Deploying a digital micromirror devices (DMDs)-based time-frequency agile pixels CAOS-mode within a two point detector spatially and spectrally isolating framework, this imager simultaneously and independently detects pixel selective image information for two different broad spectral bands that further undergo independent spectral image data extraction via finer-tuned wavelength filtering using all-optical or CAOS-mode electronic filters. A proof-of-concept visible-near infrared band CAOS imager is successfully demonstrated using a target scene containing LEDs and engaging narrowband optical filters. In addition, using the CAOS-mode, demonstrated is the RF domain simultaneous color content monitoring of a white light LED image pixel. Also proposed is the use of a higher bit count analog-to-digital converter (ADC) with both range and sampling duration parameter control along with a larger data set electronic DSP to extract higher DSP gain and realize additional noise suppression. Using a 16-bit ADC and 2,097,152 point fast Fourier transform (FFT) digital signal processing (DSP) for a 633 nm laser engaged test target scene that is subject to nearly 7 decades (107) of gradual optical attenuation, the experimental camera demonstrates an agile pixel extreme dynamic range of 136 dB, which is a 56 dB improvement over the previous CAOS-imaging demonstrations.

  10. Three dimensional atmospheric dynamics of terrestrial exoplanets over a wide range of orbital and atmospheric parameters

    NASA Astrophysics Data System (ADS)

    Kaspi, Y.; Showman, A. P.

    2014-04-01

    The recent discoveries of terrestrial exoplanets and super Earths extending over a broad range of orbital and physical parameters, suggests that these planets will span a wide range of climatic regimes. Characterization of the atmospheres of warm super Earths has already begun and will be extended to smaller and more distant planets over the coming decade. The habitability of these worlds may be strongly affected by their three-dimensional atmospheric circulation regimes, since the global climate feedbacks that control the inner and outer edges of the habitable zone-including transitions to Snowballlike states and runaway-greenhouse feedbacks-depend on the equator-to-pole temperature differences, pattern of relative humidity, and other aspects of the dynamics. Here, using an idealized moist atmospheric general circulation model (GCM) including a hydrological cycle, we study the dynamical principles governing the atmospheric dynamics on such planets. We show how the planetary rotation rate, planetary mass, surface gravity, heat flux from a parent star and atmospheric mass affect the atmospheric circulation and temperature distribution on such planets. We elucidate the possible climatic regimes and diagnose the mechanisms controlling the formation of atmospheric jet streams, Hadley cells, and the equator-to-pole temperature differences. Finally, we discuss the implications for understanding how the atmospheric circulation influences the global-scale climate feedbacks that control the width of the habitable zone.

  11. Atmospheric dynamics of terrestrial exoplanets over a wide range of orbital and atmospheric parameters

    NASA Astrophysics Data System (ADS)

    Kaspi, Yohai; Showman, Adam

    2014-05-01

    The recent discoveries of terrestrial exoplanets and super Earths extending over a broad range of orbital and physical parameters, suggests that these planets will span a wide range of climatic regimes. Characterization of the atmospheres of warm super Earths has already begun and will be extended to smaller and more distant planets over the coming decade. The habitability of these worlds may be strongly affected by their three-dimensional atmospheric circulation regimes, since the global climate feedbacks that control the inner and outer edges of the habitable zone--including transitions to Snowball-like states and runaway-greenhouse feedbacks--depend on the equator-to-pole temperature differences, pattern of relative humidity, and other aspects of the dynamics. Here, using an idealized moist atmospheric general circulation model (GCM) including a hydrological cycle, we study the dynamical principles governing the atmospheric dynamics on such planets. We show how the planetary rotation rate, planetary mass, surface gravity, heat flux from a parent star, atmospheric mass and optical thickness affect the atmospheric circulation and temperature distribution on such planets. We elucidate the possible climatic regimes and diagnose the mechanisms controlling the formation of atmospheric jet streams, Hadley cells, and the equator-to-pole temperature differences. Finally, we discuss the implications for understanding how the atmospheric circulation influences the global-scale climate feedbacks that control the width of the habitable zone.

  12. Acute Effects of Different Agonist and Antagonist Stretching Arrangements on Static and Dynamic Range of Motion

    PubMed Central

    Amiri-Khorasani, Mohammadtaghi; Kellis, Eleftherios

    2015-01-01

    Background: Traditionally, stretching exercises are considered as basic components of warm up aiming to prepare the musculoskeletal system for performance and to prevent injuries. Objectives: The purpose of this study was to examine the effects of different agonist and antagonist stretching arrangements within a pre-exercise warm-up on hip static (SROM) and dynamic range of motion (DROM). Materials and Methods: Sixty trained male subjects (Mean ± SD: height, 177.38 ± 6.92 cm; body mass, 68.4 ± 10.22 kg; age, 21.52 ± 1.17 years) volunteered to participate in this study. SROM was measured by V-sit test and DROM captured by a motion analysis system before and after (i) static stretching for both hip flexor and extensor muscles (SFSE), (ii) dynamic stretching for both hip flexor and extensor muscles (DFDE), (iii) static stretching for the hip flexors and dynamic stretching for hip extensors (SFDE), and (iv) dynamic stretching for the hip flexors and static stretching for hip extensors (DFSE). Results: DFSE showed a significantly higher increase in DROM and SROM than the remainder of the stretching protocols (P < 0.05). There were significant differences between DFDE with SFSE and SFDE (P < 0.05) and SFSE showed significant increase as compared to SFDE (P < 0.05). Conclusions: In conclusion, DFSE is probably the best stretching arrangement due to producing more post activation potentiation on agonist muscles and less muscle stiffness in antagonist muscles. PMID:26715975

  13. Territoriality and home-range dynamics in meerkats, Suricata suricatta: a mechanistic modelling approach.

    PubMed

    Bateman, Andrew W; Lewis, Mark A; Gall, Gabriella; Manser, Marta B; Clutton-Brock, Tim H

    2015-01-01

    Multiple approaches exist to model patterns of space use across species, among them resource selection analysis, statistical home-range modelling and mechanistic movement modelling. Mechanistic home-range models combine the benefits of these approaches, describing emergent territorial patterns based on fine-scale individual- or group-movement rules and incorporating interactions with neighbours and the environment. These models have not, to date, been extended to dynamic contexts. Using mechanistic home-range models, we explore meerkat (Suricata suricatta) territorial patterns, considering scent marking, direct group interactions and habitat selection. We also extend the models to accommodate dynamic aspects of meerkat territoriality (territory development and territory shift). We fit models, representing multiple working hypotheses, to data from a long-term meerkat study in South Africa, and we compare models using Akaike's and Bayesian Information Criteria. Our results identify important features of meerkat territorial patterns. Notably, larger groups do not seem to control larger territories, and groups apparently prefer dune edges along a dry river bed. Our model extensions capture instances in which 1) a newly formed group interacts more strongly with its parent groups over time and 2) a group moves its territory core out of aversive habitat. This extends our mechanistic modelling framework in previously unexplored directions.

  14. On metrics for objective and subjective evaluation of high dynamic range video

    NASA Astrophysics Data System (ADS)

    Minoo, Koohyar; Gu, Zhouye; Baylon, David; Luthra, Ajay

    2015-09-01

    In high dynamic range (HDR) video, it is possible to represent a wider range of intensities and contrasts compared to the current standard dynamic range (SDR) video. HDR video can simultaneously preserve details in very bright and very dark areas of a scene whereas these details become lost or washed out in SDR video. Because the perceived quality due to this increased fidelity may not fit the same model of perceived quality in the SDR video, it is not clear whether the objective metrics that have been widely used and studied for SDR visual experience are reasonably accurate for HDR cases, in terms of correlation with subjective measurement for HDR video quality. This paper investigates several objective metrics and their correlation to subjective quality for a variety of HDR video content. Results are given for the case of HDR content compressed at different bit rates. In addition to rating the relevance of each objective metric in terms of its correlation to the subjective measurements, comparisons are also presented to show how closely different objective metrics can predict the results obtained by subjective quality assessment in terms of coding efficiency provided by different coding processes.

  15. An Analog Gamma Correction Scheme for High Dynamic Range CMOS Logarithmic Image Sensors

    PubMed Central

    Cao, Yuan; Pan, Xiaofang; Zhao, Xiaojin; Wu, Huisi

    2014-01-01

    In this paper, a novel analog gamma correction scheme with a logarithmic image sensor dedicated to minimize the quantization noise of the high dynamic applications is presented. The proposed implementation exploits a non-linear voltage-controlled-oscillator (VCO) based analog-to-digital converter (ADC) to perform the gamma correction during the analog-to-digital conversion. As a result, the quantization noise does not increase while the same high dynamic range of logarithmic image sensor is preserved. Moreover, by combining the gamma correction with the analog-to-digital conversion, the silicon area and overall power consumption can be greatly reduced. The proposed gamma correction scheme is validated by the reported simulation results and the experimental results measured for our designed test structure, which is fabricated with 0.35 μm standard complementary-metal-oxide-semiconductor (CMOS) process. PMID:25517692

  16. Numerical study of the dynamics of some long range spin glass models

    NASA Astrophysics Data System (ADS)

    Billoire, Alain

    2015-07-01

    We present results of a Monte Carlo study of the equilibrium dynamics of the one dimensional long-range Ising spin glass model. By tuning a parameter σ , this model interpolates between the mean field Sherrington-Kirkpatrick model and a proxy of the finite dimensional Edward-Anderson model. Activated scaling fits for the behavior of the relaxation time τ as a function of the number of spins N (Namely \\ln (τ )\\propto {{N}\\psi} ) give values of \\psi that are not stable against inclusion of subleading corrections. Critical scaling (τ \\propto {{N}ρ} ) gives more stable fits, at least in the non mean field region. We also present results on the scaling of the time decay of the critical remanent magnetization of the Sherrington-Kirkpatrick model, a case where the simulation can be done with quite large systems and that shows the difficulties in obtaining precise values for dynamical exponents in spin glass models.

  17. Digital camera workflow for high dynamic range images using a model of retinal processing

    NASA Astrophysics Data System (ADS)

    Tamburrino, Daniel; Alleysson, David; Meylan, Laurence; Süsstrunk, Sabine

    2008-02-01

    We propose a complete digital camera workflow to capture and render high dynamic range (HDR) static scenes, from RAW sensor data to an output-referred encoded image. In traditional digital camera processing, demosaicing is one of the first operations done after scene analysis. It is followed by rendering operations, such as color correction and tone mapping. In our workflow, which is based on a model of retinal processing, most of the rendering steps are performed before demosaicing. This reduces the complexity of the computation, as only one third of the pixels are processed. This is especially important as our tone mapping operator applies local and global tone corrections, which is usually needed to well render high dynamic scenes. Our algorithms efficiently process HDR images with different keys and different content.

  18. Simulation of Heavy Lift Airship dynamics over large ranges of incidence and speed

    NASA Technical Reports Server (NTRS)

    Tischler, M. B.; Jex, H. R.; Ringland, R. F.

    1981-01-01

    A nonlinear, multibody, six-degrees-of-freedom digital simulation has been developed to study generic Heavy Lift Airship (HLA) dynamics and control. The basic aerodynamic functions developed to model the hull, tail, and rotor loads continuously over all incidence ranges are reviewed and applied to a Quadrotor HLA with a low fineness ratio hull and a small vee-tail. Trim calculations for a test vehicle suggest control power deficiencies in crosswind stationkeeping for the unloaded vehicle. Gust responses show the importance of correctly calculating loads due to accelerated relative motion of air and hull. Numerically linearized dynamics for the test vehicle show the existence of a divergent yaw mode, and an oscillatory pitch mode whose stability characteristics are sensitive to flight speed. A considerable improvement in the vehicle's stability and response results from a simple multi-axis closed-loop control system operating on the rotors and propeller blades.

  19. An analog gamma correction scheme for high dynamic range CMOS logarithmic image sensors.

    PubMed

    Cao, Yuan; Pan, Xiaofang; Zhao, Xiaojin; Wu, Huisi

    2014-12-15

    In this paper, a novel analog gamma correction scheme with a logarithmic image sensor dedicated to minimize the quantization noise of the high dynamic applications is presented. The proposed implementation exploits a non-linear voltage-controlled-oscillator (VCO) based analog-to-digital converter (ADC) to perform the gamma correction during the analog-to-digital conversion. As a result, the quantization noise does not increase while the same high dynamic range of logarithmic image sensor is preserved. Moreover, by combining the gamma correction with the analog-to-digital conversion, the silicon area and overall power consumption can be greatly reduced. The proposed gamma correction scheme is validated by the reported simulation results and the experimental results measured for our designed test structure, which is fabricated with 0.35 μm standard complementary-metal-oxide-semiconductor (CMOS) process.

  20. Dynamic defectoscopy with flat panel and CdTe Timepix X-ray detectors combined with an optical camera

    NASA Astrophysics Data System (ADS)

    Vavrik, D.; Fauler, A.; Fiederle, M.; Jandejsek, I.; Jakubek, M.; Turecek, D.; Zwerger, A.

    2013-04-01

    Damage of gradually loaded ductile materials involves a number of physical processes which are highly nonlinear and have different intensity and extent. Dynamic defectoscopy (i.e. defectoscopy of time changing damage processes) combining an X-ray/optical imaging system is proposed for online visualization and analysis of the complex behaviour of such materials. A large area flat panel detector with rather long read out time is used for overall observation of slow damage processes. On the other hand, a semiconductor CdTe Timepix detector with small active area allows following the rapid damage processes occurring in the final phase of specimen failure. Optical imaging of the specimen surface was utilized for analysing the specimen deformations.

  1. Atmospheric Dynamics of Terrestrial Exoplanets Over a Wide Range of Orbital and Atmospheric Parameters

    NASA Astrophysics Data System (ADS)

    Kaspi, Yohai; Showman, Adam P.

    2014-11-01

    Since the mid-1990s, nearly 1800 exoplanets have been discovered around other stars. Exoplanet discovery and characterization began with giant planets, but as the observational techniques are advancing the emphasis is gradually shifting to smaller worlds. The recent discoveries of terrestrial exoplanets and super Earths extending over a broad range of orbital and physical parameters suggests that these planets will span a wide range of climatic regimes. Characterization of the atmospheres of warm super Earths has already begun and will be extended to smaller and more distant planets over the coming decade. The habitability of these worlds may be strongly affected by their three-dimensional atmospheric circulation regimes, since the global climate feedbacks that control the inner and outer edges of the habitable zone---including transitions to Snowball-like states and runaway-greenhouse feedbacks---depend on the equator-to-pole temperature differences, pattern of relative humidity, and other aspects of the dynamics. Here, using an idealized moist atmospheric general circulation model (GCM) including a hydrological cycle, we discuss the dynamical principles governing the atmospheric dynamics on such planets. We show how the planetary rotation rate, planetary mass, surface gravity, heat flux from a parent star, optical thickness and atmospheric mass affect the atmospheric circulation and temperature distribution on such planets. Our simulations demonstrate that equator-to-pole temperature differences, meridional heat transport rates, structure and strength of the winds, and the hydrological cycle vary strongly with these parameters, implying that the sensitivity of the planet to global climate feedbacks will depend significantly on the atmospheric circulation. We elucidate the possible climatic regimes and diagnose the mechanisms controlling the formation of atmospheric jet stream, Hadley and Ferrel cells and latitudinal temperature differences. Finally, we will

  2. A single-element, thermal, flow-velocity sensor with wide dynamic range

    NASA Astrophysics Data System (ADS)

    Al-Salaymeh, A.; Durst, F.; Gad-El-Hak, M.

    2001-11-01

    Thermal flow sensors with a wide dynamic range approaching 1:1000 are presently not available in spite of the large demand for such sensors in practical fluid flow measurements. During the last meeting (paper JG4, Bul. Am. Phys. Soc. 45, no. 9, p. 141, 2000), we described such a probe consisting of a minute wire heated using sinusoidal alternating current and two sensing wires acting as resistance thermometers and set parallel to, and at a small distance on either side of, the pulsed wire. Herein we detail the development of a single wire heated using square waves of electrical current. The elimination of the sensing wires reduces the complexity as well as the cost of the sensor and improves its spatial resolution. Unlike time-of-flight sensors, however, the present single-element sensor is sensitive to the physical properties and temperature of the ambient fluid. The present device is suited for measuring slowly-varying unidirectional flows over a very wide dynamic range. For a given current amplitude and frequency, the nominal output of the single sensor is the increase in wire temperature (or resistance) between times just before the leading edge of the current pulse and just after the trailing edge of the pulse. In practice, an integral of the resistance over the pulse duration is computed and averaged over several pulses. This output is a function of the wire’s time constant or thermal inertia and thus of the flow speed as well as the heat convected from the heated wire to the flow. We exploit the fact that the time constant decreases as the flow speed increases while the rate of heat transfer increases. At very low flow speeds, the response is determined almost entirely by the time constant whereas at high speeds the device acts almost like a constant-current hot-wire anemometer. At low speeds, therefore, the wire thermal inertia augments the output signal of the basic hot wire increasing its speed range and sensitivity above that of a conventional hot

  3. Macular SD-OCT Outcome Measures: Comparison of Local Structure-Function Relationships and Dynamic Range

    PubMed Central

    Miraftabi, Arezoo; Amini, Navid; Morales, Esteban; Henry, Sharon; Yu, Fei; Afifi, Abdolmonem; Coleman, Anne L.; Caprioli, Joseph; Nouri-Mahdavi, Kouros

    2016-01-01

    Purpose We tested the hypothesis that the macular ganglion cell layer (GCL) thickness demonstrates a stronger structure-function (SF) relationship and extends the useful range of macular measurements compared with combined macular inner layer or full thickness. Methods Ninety-eight glaucomatous eyes and eight normal eyes with macular spectral domain optical coherence tomography (SD-OCT) volume scans and 10-2 visual fields were enrolled. Inner plexiform layer (IPL), GCL, macular retinal nerve fiber layer (mRNFL), ganglion cell-inner plexiform layer (GCIPL), ganglion cell complex (GCC), and full thickness (FT) measurements were calculated for 8 × 8 arrays of 3° superpixels. Main outcome measures were local structure-function relationships between macular superpixels and corresponding sensitivities on 10-2 fields after adjusting for ganglion cell displacement, dynamic range of measurements, and the change point (total deviation value where macular parameters reached measurement floor). Results Median (interquartile range [IQR]) mean deviation was −7.2 (−11.6 to −3.2) dB in glaucoma eyes. Strength of SF relationships was highest for GCIPL, GCL, GCC, and IPL (ρ = 0.635, 0.627, 0.621, and 0.577, respectively; P ≤ 0.046 for comparisons against GCIPL). Highest SF correlations coincided with the peak of GCL thickness, where the dynamic range was widest for FT (81.1 μm), followed by GCC (65.7 μm), GCIPL (54.9 μm), GCL (35.2 μm), mRNFL (27.5 μm), and IPL (20.9 μm). Change points were similar for all macular parameters (−7.8 to −8.9 dB). Conclusions GCIPL, GCL, and GCC demonstrated comparable SF relationships while FT, GCC, and GCIPL had the widest dynamic range. Measurement of GCL did not extend the range of useful structural measurements. Measuring GCL does not provide any advantage for detection of progression with current SD-OCT technology. PMID:27623336

  4. Bayer patterned high dynamic range image reconstruction using adaptive weighting function

    NASA Astrophysics Data System (ADS)

    Kang, Hee; Lee, Suk Ho; Song, Ki Sun; Kang, Moon Gi

    2014-12-01

    It is not easy to acquire a desired high dynamic range (HDR) image directly from a camera due to the limited dynamic range of most image sensors. Therefore, generally, a post-process called HDR image reconstruction is used, which reconstructs an HDR image from a set of differently exposed images to overcome the limited dynamic range. However, conventional HDR image reconstruction methods suffer from noise factors and ghost artifacts. This is due to the fact that the input images taken with a short exposure time contain much noise in the dark regions, which contributes to increased noise in the corresponding dark regions of the reconstructed HDR image. Furthermore, since input images are acquired at different times, the images contain different motion information, which results in ghost artifacts. In this paper, we propose an HDR image reconstruction method which reduces the impact of the noise factors and prevents ghost artifacts. To reduce the influence of the noise factors, the weighting function, which determines the contribution of a certain input image to the reconstructed HDR image, is designed to adapt to the exposure time and local motions. Furthermore, the weighting function is designed to exclude ghosting regions by considering the differences of the luminance and the chrominance values between several input images. Unlike conventional methods, which generally work on a color image processed by the image processing module (IPM), the proposed method works directly on the Bayer raw image. This allows for a linear camera response function and also improves the efficiency in hardware implementation. Experimental results show that the proposed method can reconstruct high-quality Bayer patterned HDR images while being robust against ghost artifacts and noise factors.

  5. Adaptive uniform grayscale coded aperture design for high dynamic range compressive spectral imaging

    NASA Astrophysics Data System (ADS)

    Diaz, Nelson; Rueda, Hoover; Arguello, Henry

    2016-05-01

    Imaging spectroscopy is an important area with many applications in surveillance, agriculture and medicine. The disadvantage of conventional spectroscopy techniques is that they collect the whole datacube. In contrast, compressive spectral imaging systems capture snapshot compressive projections, which are the input of reconstruction algorithms to yield the underlying datacube. Common compressive spectral imagers use coded apertures to perform the coded projections. The coded apertures are the key elements in these imagers since they define the sensing matrix of the system. The proper design of the coded aperture entries leads to a good quality in the reconstruction. In addition, the compressive measurements are prone to saturation due to the limited dynamic range of the sensor, hence the design of coded apertures must consider saturation. The saturation errors in compressive measurements are unbounded and compressive sensing recovery algorithms only provide solutions for bounded noise or bounded with high probability. In this paper it is proposed the design of uniform adaptive grayscale coded apertures (UAGCA) to improve the dynamic range of the estimated spectral images by reducing the saturation levels. The saturation is attenuated between snapshots using an adaptive filter which updates the entries of the grayscale coded aperture based on the previous snapshots. The coded apertures are optimized in terms of transmittance and number of grayscale levels. The advantage of the proposed method is the efficient use of the dynamic range of the image sensor. Extensive simulations show improvements in the image reconstruction of the proposed method compared with grayscale coded apertures (UGCA) and adaptive block-unblock coded apertures (ABCA) in up to 10 dB.

  6. Method of Improving a Digital Image as a Function of its Dynamic Range

    NASA Technical Reports Server (NTRS)

    Woodell, Glenn (Inventor); Jobson, Daniel J. (Inventor); Rahman, Zia-ur (Inventor)

    2004-01-01

    The present invention is a method of processing a digital image that is initially represented by digital data indexed to represent position on a display. The digital data is indicative of an intensity value I(sub i)(x,y) for each position (x,y) in each i-th spectral band. A classification of the image based on its dynamic range is then defined in each of the image's S spectral bands. The intensity value for each position in each i-th spectral band is adjusted to generate an adjusted intensity value for each position in each i-th spectral band in accordance with SIGMA (sup n)(sub n=1) W(sub n)(log I (sub i)(x,y) - log[I(sub i)(x,y)*F(sub n)(x,y)]), i=1,...,S where W(sub n) is a weighting factor, "*" is the convolution operator and S is the total number of unique spectral bands. For each n, the function F(sub n)(x,y) is a unique surround function applied to each position (x,y) and N is the total number of unique surround functions. Each unique surround function is scaled to improve some aspect of the digital image, e.g., dynamic range compression, color constancy, and lightness rendition. The adjusted intensity value to each position in each i-th spectral band of the image is then filtered with a filter function that is based on the dynamic range classification of the image.

  7. Deeply trapped electrons in imaging plates and their utilization for extending the dynamic range

    NASA Astrophysics Data System (ADS)

    Ohuchi, Hiroko; Kondo, Yasuhiro

    2010-09-01

    The absorption spectra of deep centers in an imaging plate (IP) made of BaFBr 0:85I 0:15:Eu 2+ have been studied in the ultraviolet region. Electrons trapped in deep centers are considered to be the cause of unerasable and reappearing latent images in IPs over-irradiated with X-rays. Deep centers showed a dominant peak at around 320 nm, followed by two small peaks at around 345 and 380 nm. By utilizing deeply trapped electrons, we have attempted to extend the dynamic range of an IP. The IP was irradiated by 150-kV X-rays with doses from 8.07 mGy to 80.7 Gy. Reading out the latent image by the stimulation of Eu 2+ luminescence with a 633-nm He-Ne laser light from a conventional Fuji reader showed a linear relationship with irradiated dose up to 0.8 Gy, but then becoming non-linear. After fully erasing with visible light, unerasable latent images were read out using 635-nm semi-conductor laser light combined with a photon-counting detection system. The dose-response curve so obtained gave a further two orders of magnitude extending the dynamic range up to 80.7 Gy. Comprehensive results indicate that electrons supplied from deep centers to the F centers provided the extended dynamic range after the F centers became saturated. Based on these facts, a model of the excitation of deeply trapped electrons and PSL processes is proposed.

  8. X-ray Dust Halos Seen With Extreme Dynamic Range: What Do We Learn?

    NASA Astrophysics Data System (ADS)

    Smith, Randall

    2008-03-01

    The exquisite angular resolution available with Chandra should allow precision measurements of faint diffuse emission surrounding bright sources, such as the X-ray scattering halos created by interstellar dust. However, the ACIS CCDs suffer from pileup when observing bright sources, and this creates difficulties when trying to extract the scattered halo near the source. The initial study of the X-ray halo around GX13+1 using only the ACIS-I detector done by Smith, Edgar & Shafer (2002) suffered from a lack of sensitivity within 50'' of the source, limiting what conclusions could be drawn. To address this problem, observations of GX13+1 were obtained with the Chandra HRC-I and simultaneously with the RXTE PCA. Combined with the existing ACIS-I data, this allowed measurements of the X-ray halo between 2-1000''. After considering a range of dust models, each assumed to be smoothly distributed with or without a dense cloud along the line of sight, the results show that there is no evidence in this data for a dense cloud near the source, as suggested by Xiang et al. 2005. Finally, although no model leads to formally acceptable results, the Weingartner & Draine (2001) and nearly all of the composite grain models from Zubko, Dwek & Arendt (2004) give poor fits. I thank Dr. Michael Juda of the HRC-I team for providing significant assistance; this work was supported by Chandra Observing Grant GO56144X.

  9. Silicon Photomultiplier-Based Multi-Channel Gamma Ray Detector Using the Dynamic Time-Over-Threshold Method

    NASA Astrophysics Data System (ADS)

    Nakamura, Y.; Shimazoe, K.; Takahashi, H.

    2016-02-01

    Silicon photomultipliers (SiPMs), which are a relatively new type of photon detector, have received more attention in the fields of nuclear medicine and high-energy physics because of their compactness and high gain up to 106. In this work, a SiPM-based multi-channel gamma ray detector with individual read out based on the dynamic time-over-threshold (dToT) method is implemented and demonstrated as an elemental material for large-area gamma ray imager applications. The detector consists of 64 channels of KETEK SiPM PM6660 (6 × 6 mm2 containing 10,000 micro-cells of 60 × 60 μm2) coupled to an 8 × 8 array of high-energy resolution Gd3(Al,Ga)5O12(Ce) (HR-GAGG) crystals (10 × 10 × 10 mm3) segmented by a 1 mm thick BaSO4 reflector. To produce a digital pulse containing linear energy information, the dToT-based read-out circuit consists of a CR-RC shaping amplifier (2.2 μs) and comparator with a feedback component. By modelling the pulse of the SiPM, the light output, and the CR-RC shaping amplifier, the integral-non-linearity (INL) was numerically calculated in terms of the delay time and the time constant of dynamic threshold movement. The experimental results of the averaged INL and energy resolution were 5.8±1.6% and the full-width-at-half-maximum (FWHM) of 7.4±0.9% at 662 keV, respectively. The 64-channel single-mode detector module was successfully implemented, demonstrating potential for its use as an elemental material for large-area gamma ray imaging applications.

  10. Short-range order and dynamics of atoms in liquid gallium

    SciTech Connect

    Mokshin, A. V. Khusnutdinoff, R. M.; Novikov, A. G.; Blagoveshchenskii, N. M.; Puchkov, A. V.

    2015-11-15

    The features of the microscopic structure, as well as one-particle and collective dynamics of liquid gallium in the temperature range from T = 313 to 1273 K, are studied on the p = 1.0 atm isobar. Detailed analysis of the data on diffraction of neutrons and X-rays, as well as the results of atomic dynamics simulation, lead to some conclusions about the structure. In particular, for preset conditions, gallium is in the equilibrium liquid phase showing no features of any stable local crystalline clusters. The pronounced asymmetry of the principle peak of the static structure factor and the characteristic “shoulder” in its right-hand part appearing at temperatures close to the melting point, which are clearly observed in the diffraction data, are due to the fact that the arrangement of the nearest neighbors of an arbitrary atom in the system is estimated statistically from the range of correlation length values and not by a single value as in the case of simple liquids. Compactly located dimers with a very short bond make a significant contribution to the statistics of nearest neighbors. The temperature dependence of the self-diffusion coefficient calculated from atomic dynamics simulation agrees well with the results obtained from experimental spectra of the incoherent scattering function. Interpolation of the temperature dependence of the self-diffusion coefficient on a logarithmic scale reveals two linear regions with a transition temperature of about 600 K. The spectra of the dynamic structure factor and spectral densities of the local current calculated by simulating the atomic dynamics indicate the existence of acoustic vibrations with longitudinal and transverse polarizations in liquid gallium, which is confirmed by experimental data on inelastic scattering of neutrons and X-rays. It is found that the vibrational density of states is completely reproduced by the generalized Debye model, which makes it possible to decompose the total vibrational motion into

  11. Development of a precision, wide-dynamic-range actuator for use in active optical systems

    NASA Technical Reports Server (NTRS)

    Lorell, K. R.; Aubrun, J-N.; Zacharie, D. F.; Perez, E. O.

    1989-01-01

    The design, operation, and performance of a wide-dynamic-range optical-quality actuator are discussed. The actuator uses a closed-loop control system to maintain accurate positioning and has an rms noise performance of 20 nm. A unique force offloading mechanism allows the actuator coil to dissipate less than 3 mW under quiescent conditions. The operation of an experimental segmented optical system that uses 18 of the actuators is examined to show how they are integrated into an actual system.

  12. An atomic magnetometer with autonomous frequency stabilization and large dynamic range

    SciTech Connect

    Pradhan, S. E-mail: pradhans75@gmail.com; Poornima,; Dasgupta, K.; Mishra, S.; Behera, R.

    2015-06-15

    The operation of a highly sensitive atomic magnetometer using elliptically polarized resonant light is demonstrated. It is based on measurement of zero magnetic field resonance in degenerate two level systems using polarimetric detection. The transmitted light through the polarimeter is used for laser frequency stabilization, whereas reflected light is used for magnetic field measurement. Thus, the experimental geometry allows autonomous frequency stabilization of the laser frequency leading to compact operation of the overall device and has a preliminary sensitivity of <10 pT/Hz{sup 1/2} @ 1 Hz. Additionally, the dynamic range of the device is improved by feedback controlling the bias magnetic field without compromising on its sensitivity.

  13. Design and testing of magnetorheological valve with fast force response time and great dynamic force range

    NASA Astrophysics Data System (ADS)

    Kubík, M.; Macháček, O.; Strecker, Z.; Roupec, J.; Mazůrek, I.

    2017-04-01

    The paper deals with design, simulation and experimental testing of a magnetorheological (MR) valve with short response time. The short response time is achieved by a suitable design of an active zone in combination with use of a ferrite material for magnetic circuit. The magneto-static model and the simplified hydraulic model of the MR valve are examined and experimentally verified. The development the MR valve achieves an average response time 4.1 ms and the maximum dynamic force range of eight.

  14. An atomic magnetometer with autonomous frequency stabilization and large dynamic range.

    PubMed

    Pradhan, S; Mishra, S; Behera, R; Poornima; Dasgupta, K

    2015-06-01

    The operation of a highly sensitive atomic magnetometer using elliptically polarized resonant light is demonstrated. It is based on measurement of zero magnetic field resonance in degenerate two level systems using polarimetric detection. The transmitted light through the polarimeter is used for laser frequency stabilization, whereas reflected light is used for magnetic field measurement. Thus, the experimental geometry allows autonomous frequency stabilization of the laser frequency leading to compact operation of the overall device and has a preliminary sensitivity of <10 pT/Hz(1/2) @ 1 Hz. Additionally, the dynamic range of the device is improved by feedback controlling the bias magnetic field without compromising on its sensitivity.

  15. A portable surface plasmon resonance biosensor capable of phase interrogation in a large dynamic range

    NASA Astrophysics Data System (ADS)

    Chen, How-Foo; Chuang, Hsin-Yuan; Chen, Chih-Hang; Chang, Yun-Hsiang

    2014-08-01

    With the development of a point of care (POC) biosensor in mind, a polymer-molding prism with double parabolic surfaces is invented and developed to implement an ultra-compact SPR biosensor with extremely high sensitivity. The polymer molded parabolic prism is cost effective and disposable, thus cross contamination between biological samples can be avoided. A highly sensitive biosensor with a form factor less than 15cm*15cm*5cm was received with a tunable excitation angle of light beam for a large dynamic range. A highly sensitive optical phase interrogation was demonstrated. The biosensor is also compatible to a modern microscopy platform.

  16. Evaluation of High Dynamic Range Photography as a Luminance Mapping Technique

    SciTech Connect

    Inanici, Mehlika; Galvin, Jim

    2004-12-30

    The potential, limitations, and applicability of the High Dynamic Range (HDR) photography technique is evaluated as a luminance mapping tool. Multiple exposure photographs of static scenes are taken with a Nikon 5400 digital camera to capture the wide luminance variation within the scenes. The camera response function is computationally derived using the Photosphere software, and is used to fuse the multiple photographs into HDR images. The vignetting effect and point spread function of the camera and lens system is determined. Laboratory and field studies have shown that the pixel values in the HDR photographs can correspond to the physical quantity of luminance with reasonable precision and repeatability.

  17. Stretching and bending dynamics in triatomic ultralong-range Rydberg molecules

    NASA Astrophysics Data System (ADS)

    Fey, Christian; Kurz, Markus; Schmelcher, Peter

    2016-07-01

    We investigate polyatomic ultralong-range Rydberg molecules consisting of three ground-state atoms bound to a Rydberg atom via s - and p -wave interactions. By employing the finite basis set representation of the unperturbed Rydberg electron Green's function we reduce the computational effort to solve the electronic problem substantially. This method is subsequently applied to determine the potential energy surfaces of triatomic systems in electronic s - and p -Rydberg states. Their molecular geometry and resulting vibrational structure are analyzed within an adiabatic approach that separates the vibrational bending and stretching dynamics. This procedure yields information on the radial and angular arrangement of the nuclei and indicates in particular that kinetic couplings between bending and stretching modes induce a linear structure in triatomic l =0 ultralong-range Rydberg molecules.

  18. Single cluster dynamics for the infinite range O(n) model

    NASA Astrophysics Data System (ADS)

    Brower, R. C.; Gross, N. A.; Moriarty, K. J. M.; Tamayo, P.

    1994-03-01

    This paper presents a study of Wolff's single cluster acceleration algorithm for O( n) models in the infinite range or mean-field limit. Numerical results for n = 2, 3 and 4 are consistent with the complete elimination of critical slowing down. Also a heuristic argument is advanced to support the value of z = 0 for the dynamic critical exponent. A new cluster growth algorithm is formulated for the infinite range model that has optimal efficiency of O(inN) in the system size N for the Swendsen-Wang update scheme. Using an asymptotically correct version of this cluster method, we are able to perform simulations for the Wolff update scheme up to 262,144 spins for 10 5 time steps for the O( N) models.

  19. Quercus suber range dynamics by ecological niche modelling: from the Last Interglacial to present time

    NASA Astrophysics Data System (ADS)

    Vessella, Federico; Simeone, Marco Cosimo; Schirone, Bartolomeo

    2015-07-01

    Ecological Niche Modelling (ENM) is widely used to depict species potential occurrence according to environmental variables under different climatic scenarios. We tested the ENM approach to infer past range dynamics of cork oak, a keystone species of the Mediterranean Biome, from 130 ka to the present time. Hindcasting implications would deal with a better species risk assessment and conservation management for the future. We modelled present and past occurrence of cork oak using seven ENM algorithms, starting from 63,733 spatially unique presence points at 30 arc-second resolution. Fourteen environmental variables were used and four time slices were considered (Last Interglacial, Last Glacial Maximum, mid-Holocene and present time). A threshold-independent evaluation of the goodness-of-fit of the models was evaluated by means of ROC curve and fossil or historical evidences were used to validate the results. Four weighted average maps depicted the dynamics of area suitability for cork oak in the last 130 ka. The derived species autoecology allowed its long-term occurrence in the Mediterranean without striking range reduction or shifting. Fossil and historical post-processing validation support the modelled past spatial extension and a neglected species presence at Levantine until the recent time. Despite the severe climatic oscillation since the Last Glacial Maximum, cork oak potential distribution area experienced limited range changes, confirming its strong link with the Mediterranean Basin. The ecological amplitude of Quercus suber could be therefore adopted as a reference to trace the Mediterranean bioclimate area. A better knowledge of the past events of Mediterranean vegetation, a wider range of study species and environmental determinants are essential to inform us about its current state, its sensitivity to human impact and the potential responses to future changes.

  20. Dynamic techniques for studies of secular variations in position from ranging to satellites. [using laser range measurements

    NASA Technical Reports Server (NTRS)

    Smith, D. E.; Kolenkiewicz, R.; Agreen, R. W.; Dunn, P. J.

    1974-01-01

    Satellite laser range measurements were applied to the study of latitude variation arising from polar motion, and the solid-earth and ocean tidal distortion of the earth's gravity field. Experiments involving two laser tracking stations were conducted. The relative location of one station with respect to the other was determined by performing simultaneous range measurements to a satellite from two stations several hundred kilometers apart. The application of this technique to the San Andreas Fault Experiment in California is discussed. Future capabilities of spacecraft equipped with laser retroreflectors include: (1) determination of the product of the earth's mass and gravitational constant; (2) measurement of crustal and tectonic motions; (3) determination of the elastic response of the solid-earth tidal forces; (4) measurement of the amplitudes and phase of certain components of the ocean tides; and (5) self-monitoring of the latitude and height variations of the tracking station.

  1. Coarsening dynamics in condensing zero-range processes and size-biased birth death chains

    NASA Astrophysics Data System (ADS)

    Jatuviriyapornchai, Watthanan; Grosskinsky, Stefan

    2016-05-01

    Zero-range processes with decreasing jump rates are well known to exhibit a condensation transition under certain conditions on the jump rates, and the dynamics of this transition continues to be a subject of current research interest. Starting from homogeneous initial conditions, the time evolution of the condensed phase exhibits an interesting coarsening phenomenon of mass transport between cluster sites characterized by a power law. We revisit the approach in Godrèche (2003 J. Phys. A: Math. Gen. 36 6313) to derive effective single site dynamics which form a nonlinear birth death chain describing the coarsening behavior. We extend these results to a larger class of parameter values, and introduce a size-biased version of the single site process, which provides an effective tool to analyze the dynamics of the condensed phase without finite size effects and is the main novelty of this paper. Our results are based on a few heuristic assumptions and exact computations, and are corroborated by detailed simulation data.

  2. a Multi-Beam Radio Transient Detector with Real-Time De-Dispersion Over a Wide DM Range

    NASA Astrophysics Data System (ADS)

    Clarke, N.; D'Addario, L.; Navarro, R.; Trinh, J.

    Isolated, short dispersed pulses of radio emission of unknown origin have been reported and there is strong interest in wide-field, sensitive searches for such events. To achieve high sensitivity, large collecting area is needed and dispersion due to the interstellar medium should be removed. To survey a large part of the sky in reasonable time, a telescope that forms multiple simultaneous beams is desirable. We have developed a novel FPGA-based transient search engine that is suitable for these circumstances. It accepts short-integration-time spectral power measurements from each beam of the telescope, performs incoherent de-dispersion simultaneously for each of a wide range of dispersion measure (DM) values, and automatically searches the de-dispersed time series for pulse-like events. If the telescope provides buffering of the raw voltage samples of each beam, then our system can provide trigger signals to allow data in those buffers to be saved when a tentative detection occurs; this can be done with a latency of tens of ms, and only the buffers for beams with detections need to be saved. In one version of our implementation, intended for the ASKAP array of 36 antennas (currently under construction in Australia), 36 beams are simultaneously de-dispersed for 448 different DMs with an integration time of 1.0 ms. In the absence of such a multi-beam telescope, we have built a second version that handles up to 6 beams at 0.1 ms integration time and 512 DMs. We have deployed and tested this at a 34-m antenna of the Deep Space Network in Goldstone, California. A third version that processes up to 6 beams at an integration time of 2.0 ms and 1,024 DMs has been built and deployed at the Murchison Widefield Array telescope.

  3. Quantum spin dynamics and entanglement in systems with long-range interactions

    NASA Astrophysics Data System (ADS)

    Rey, Ana M.

    One of the fundamental goals of modern quantum sciences is to learn how to control and manipulate non-equilibrium many-body systems and use them to make powerful and improved quantum devices, materials and technologies. However, out-of-equilibrium systems are complex, typically strongly correlated and entangled, and thus to model them we are in an urgent need of new methodologies. In this talk I will discuss new theoretical methods that we have developed to investigate emergent non-equilibrium phenomena in driven-dissipative spin systems interacting via long-range interactions. I will show we can capture the dynamics of correlations and entanglement in close systems and the interplay between dissipation and entanglement in open quantum systems including spin-boson models. As a specific application I will discuss the use of our methods to model the spin dynamics exhibited by arrays of trapped ions with controllable long-range interactions. I will show that our predictions are consistent with recent experimental measurements. I will also discuss new protocols to diagnostic and characterize entanglement based on well-established NMR protocols This work is supported by NSF, ARO, AFOSR-MURI, and NIST.

  4. Design of a full-dynamic-range balanced detection heterodyne gyroscope with common-path configuration.

    PubMed

    Lin, Chu-En; Yu, Chih-Jen; Chen, Chii-Chang

    2013-04-22

    In this article, we propose an optical heterodyne common-path gyroscope which has common-path configuration and full-dynamic range. Different from traditional non-common-path optical heterodyne technique such as Mach-Zehnder or Michelson interferometers, we use a two-frequency laser light source (TFLS) which can generate two orthogonally polarized light with a beat frequency has a common-path configuration. By use of phase measurement, this optical heterodyne gyroscope not only has the capability to overcome the drawback of the traditional interferometric fiber optic gyro: lack for full-dynamic range, but also eliminate the total polarization rotation caused by SMFs. Moreover, we also demonstrate the potential of miniaturizing this gyroscope as a chip device. Theoretically, if we assume that the wavelength of the laser light is 1550nm, the SMFs are 250m in length, and the radius of the fiber ring is 3.5cm, the bias stability is 0.872 deg/hr.

  5. Host-Range Dynamics of Cochliobolus lunatus: From a Biocontrol Agent to a Severe Environmental Threat

    PubMed Central

    Louis, Bengyella; Waikhom, Sayanika Devi; Roy, Pranab; Bhardwaj, Pardeep Kumar; Sharma, Chandradev K.; Singh, Mohendro Wakambam; Talukdar, Narayan Chandra

    2014-01-01

    We undertook an investigation to advance understanding of the host-range dynamics and biocontrol implications of Cochliobolus lunatus in the past decade. Potato (Solanum tuberosum L) farms were routinely surveyed for brown-to-black leaf spot disease caused by C. lunatus. A biphasic gene data set was assembled and databases were mined for reported hosts of C. lunatus in the last decade. The placement of five virulent strains of C. lunatus causing foliar necrosis of potato was studied with microscopic and phylogenetic tools. Analysis of morphology showed intraspecific variations in stromatic tissues among the virulent strains causing foliar necrosis of potato. A maximum likelihood inference based on GPDH locus separated C. lunatus strains into subclusters and revealed the emergence of unclustered strains. The evolving nutritional requirement of C. lunatus in the last decade is exhibited by the invasion of vertebrates, invertebrates, dicots, and monocots. Our results contribute towards a better understanding of the host-range dynamics of C. lunatus and provide useful implications on the threat posed to the environment when C. lunatus is used as a mycoherbicide. PMID:24987680

  6. Dynamics of mtDNA introgression during species range expansion: insights from an experimental longitudinal study

    PubMed Central

    Mastrantonio, V.; Porretta, D.; Urbanelli, S.; Crasta, G.; Nascetti, G.

    2016-01-01

    Introgressive hybridization represents one of the long-lasting debated genetic consequences of species range expansion. Mitochondrial DNA has been shown to heavily introgress between interbreeding animal species that meet in new sympatric areas and, often, asymmetric introgression from local to the colonizing populations has been observed. Disentangling among the evolutionary and ecological processes that might shape this pattern remains difficult, because they continuously act across time and space. In this context, long-term studies can be of paramount importance. Here, we investigated the dynamics of mitochondrial introgression between two mosquito species (Aedes mariae and Ae. zammitii ) during a colonization event that started in 1986 after a translocation experiment. By analyzing 1,659 individuals across 25 years, we showed that introgression occurred earlier and at a higher frequency in the introduced than in the local species, showing a pattern of asymmetric introgression. Throughout time, introgression increased slowly in the local species, becoming reciprocal at most sites. The rare opportunity to investigate the pattern of introgression across time during a range expansion along with the characteristics of our study-system allowed us to support a role of demographic dynamics in determining the observed introgression pattern. PMID:27460445

  7. A Maximum a Posteriori Estimation Framework for Robust High Dynamic Range Video Synthesis

    NASA Astrophysics Data System (ADS)

    Li, Yuelong; Lee, Chul; Monga, Vishal

    2017-03-01

    High dynamic range (HDR) image synthesis from multiple low dynamic range (LDR) exposures continues to be actively researched. The extension to HDR video synthesis is a topic of significant current interest due to potential cost benefits. For HDR video, a stiff practical challenge presents itself in the form of accurate correspondence estimation of objects between video frames. In particular, loss of data resulting from poor exposures and varying intensity make conventional optical flow methods highly inaccurate. We avoid exact correspondence estimation by proposing a statistical approach via maximum a posterior (MAP) estimation, and under appropriate statistical assumptions and choice of priors and models, we reduce it to an optimization problem of solving for the foreground and background of the target frame. We obtain the background through rank minimization and estimate the foreground via a novel multiscale adaptive kernel regression technique, which implicitly captures local structure and temporal motion by solving an unconstrained optimization problem. Extensive experimental results on both real and synthetic datasets demonstrate that our algorithm is more capable of delivering high-quality HDR videos than current state-of-the-art methods, under both subjective and objective assessments. Furthermore, a thorough complexity analysis reveals that our algorithm achieves better complexity-performance trade-off than conventional methods.

  8. Analog Filtering of Large Solvent Signals for Improved Dynamic Range in High-Resolution NMR

    NASA Astrophysics Data System (ADS)

    Redfield, A. G.; Kunz, S. D.

    1998-01-01

    The large solvent signal from samples in H2O solvent still challenges the dynamic range capability of any spectrometer. The solvent signal can be largely removed with a pair of simple resistor-capacitor (RC) high-pass filters when the solvent frequency is set at center band (zero frequency) using quadrature detection, withRC∼ 0.5 ms. However, an ∼0.5-ms transient remains at initial time, which we reduce fourfold for a short time only, just before the A/D converter, by means of a variable-gain amplifier, and later restore with software. This modification can result in a nearly fourfold increase in dynamic range. When we converted to a frequency-shifted mode (A. G. Redfield and S. D. Kunz, 1994,J. Magn. Reson. A108, 234-237) we replaced theRChigh-pass filter with a quadrature feedback notch filter tuned to the solvent frequency (5.06 kHz). This filter is an example of a class of two-input/two-output filters which maintain the spectral integrity (image-free character) of quadrature signals. Digital filters of the same type are also considered briefly. We discuss the implications of these ideas for spectrometer input design, including schemes for elimination of radiation damping, and effects of probe bandwidth on extreme oversampling.

  9. Simultaneous broadband laser ranging and photonic Doppler velocimetry for dynamic compression experiments

    SciTech Connect

    La Lone, B. M. Marshall, B. R.; Miller, E. K.; Stevens, G. D.; Turley, W. D.; Veeser, L. R.

    2015-02-15

    A diagnostic was developed to simultaneously measure both the distance and velocity of rapidly moving surfaces in dynamic compression experiments, specifically non-planar experiments where integrating the velocity in one direction does not always give the material position accurately. The diagnostic is constructed mainly from fiber-optic telecommunications components. The distance measurement is based on a technique described by Xia and Zhang [Opt. Express 18, 4118 (2010)], which determines the target distance every 20 ns and is independent of the target speed. We have extended the full range of the diagnostic to several centimeters to allow its use in dynamic experiments, and we multiplexed it with a photonic Doppler velocimetry (PDV) system so that distance and velocity histories can be measured simultaneously using one fiber-optic probe. The diagnostic was demonstrated on a spinning square cylinder to show how integrating a PDV record can give an incorrect surface position and how the ranging diagnostic described here obtains it directly. The diagnostic was also tested on an explosive experiment where copper fragments and surface ejecta were identified in both the distance and velocity signals. We show how the distance measurements complement the velocity data. Potential applications are discussed.

  10. High dynamic range image compression by optimizing tone mapped image quality index.

    PubMed

    Ma, Kede; Yeganeh, Hojatollah; Zeng, Kai; Wang, Zhou

    2015-10-01

    Tone mapping operators (TMOs) aim to compress high dynamic range (HDR) images to low dynamic range (LDR) ones so as to visualize HDR images on standard displays. Most existing TMOs were demonstrated on specific examples without being thoroughly evaluated using well-designed and subject-validated image quality assessment models. A recently proposed tone mapped image quality index (TMQI) made one of the first attempts on objective quality assessment of tone mapped images. Here, we propose a substantially different approach to design TMO. Instead of using any predefined systematic computational structure for tone mapping (such as analytic image transformations and/or explicit contrast/edge enhancement), we directly navigate in the space of all images, searching for the image that optimizes an improved TMQI. In particular, we first improve the two building blocks in TMQI—structural fidelity and statistical naturalness components—leading to a TMQI-II metric. We then propose an iterative algorithm that alternatively improves the structural fidelity and statistical naturalness of the resulting image. Numerical and subjective experiments demonstrate that the proposed algorithm consistently produces better quality tone mapped images even when the initial images of the iteration are created by the most competitive TMOs. Meanwhile, these results also validate the superiority of TMQI-II over TMQI.

  11. Analog filtering of large solvent signals for improved dynamic range in high-resolution NMR.

    PubMed

    Redfield, A G; Kunz, S D

    1998-01-01

    The large solvent signal from samples in H2O solvent still challenges the dynamic range capability of any spectrometer. The solvent signal can be largely removed with a pair of simple resistor-capacitor (RC) high-pass filters when the solvent frequency is set at center band (zero frequency) using quadrature detection, with RC approximately 0.5 ms. However, an approximately 0.5-ms transient remains at initial time, which we reduce fourfold for a short time only, just before the A/D converter, by means of a variable-gain amplifier, and later restore with software. This modification can result in a nearly fourfold increase in dynamic range. When we converted to a frequency-shifted mode (A. G. Redfield and S. D. Kunz, 1994, J. Magn. Reson. A 108, 234-237) we replaced the RC high-pass filter with a quadrature feedback notch filter tuned to the solvent frequency (5.06 kHz). This filter is an example of a class of two-input/two-output filters which maintain the spectral integrity (image-free character) of quadrature signals. Digital filters of the same type are also considered briefly. We discuss the implications of these ideas for spectrometer input design, including schemes for elimination of radiation damping, and effects of probe bandwidth on extreme oversampling.

  12. Charge-integrating organic heterojunction phototransistors for wide-dynamic-range image sensors

    NASA Astrophysics Data System (ADS)

    Pierre, Adrien; Gaikwad, Abhinav; Arias, Ana Claudia

    2017-02-01

    Solution-processed phototransistors can substantially advance the performance of image sensors. Phototransistors exhibit large photoconductive gain and a sublinear responsivity to irradiance, which enables a logarithmic sensing of irradiance that is akin to the human eye and has a wider dynamic range than photodiode-based image sensors. Here, we present a novel solution-processed phototransistor composed of a heterostructure between a high-mobility organic semiconductor and an organic bulk heterojunction. The device efficiently integrates photogenerated charge during the period of a video frame then quickly discharges it, which significantly increases the signal-to-noise ratio compared with sampling photocurrent during readout. Phototransistor-based image sensors processed without photolithography on plastic substrates integrate charge with external quantum efficiencies above 100% at 100 frames per second. In addition, the sublinear responsivity to irradiance of these devices enables a wide dynamic range of 103 dB at 30 frames per second, which is competitive with state-of-the-art image sensors.

  13. Polarization mosaicing: high dynamic range and polarization imaging in a wide field of view

    NASA Astrophysics Data System (ADS)

    Schechner, Yoav Y.; Nayar, Shree K.

    2003-12-01

    We present an approach for imaging the polarization state of scene points in a wide field of view, while enhancing the radiometric dynamic range of imaging systems. This is achieved by a simple modification of image mosaicking, which is a common technique in remote sensing. In traditional image mosaics, images taken in varying directions or positions are stitched to obtain a larger image. Yet, as the camera moves, it senses each scene point multiple times in overlapping regions of the raw frames. We rigidly attach to the camera a fixed, spatially varying polarization and attenuation filter. This way, the camera motion-induced multiple measurements per scene point are taken under different optical settings. This is in contrast to the redundant measurements of traditional mosaics. Computational algorithms then analyze the data to extract polarization imaging with high dynamic range across the mosaic field of view. We developed a Maximum Likelihood method to automatically register the images, in spite of the challenging spatially varying effects. Then, we use Maximum Likelihood to handle, in a single framework, variable exposures (due to transmittance variations), saturation, and partial polarization filtering. As a by product, these results enable polarization settings of cameras to change while the camera moves, alleviating the need for camera stability. This work demonstrates the modularity of the Generalized Mosaicing approach, which we recently introduced for multispectral image mosaics. The results are useful for the wealth of polarization imaging applications, in addition to mosaicking applications, particularly remote sensing. We demonstrate experimental results obtained using a system we built.

  14. Context-dependent JPEG backward-compatible high-dynamic range image compression

    NASA Astrophysics Data System (ADS)

    Korshunov, Pavel; Ebrahimi, Touradj

    2013-10-01

    High-dynamic range (HDR) imaging is expected, together with ultrahigh definition and high-frame rate video, to become a technology that may change photo, TV, and film industries. Many cameras and displays capable of capturing and rendering both HDR images and video are already available in the market. The popularity and full-public adoption of HDR content is, however, hindered by the lack of standards in evaluation of quality, file formats, and compression, as well as large legacy base of low-dynamic range (LDR) displays that are unable to render HDR. To facilitate the wide spread of HDR usage, the backward compatibility of HDR with commonly used legacy technologies for storage, rendering, and compression of video and images are necessary. Although many tone-mapping algorithms are developed for generating viewable LDR content from HDR, there is no consensus of which algorithm to use and under which conditions. We, via a series of subjective evaluations, demonstrate the dependency of the perceptual quality of the tone-mapped LDR images on the context: environmental factors, display parameters, and image content itself. Based on the results of subjective tests, it proposes to extend JPEG file format, the most popular image format, in a backward compatible manner to deal with HDR images also. An architecture to achieve such backward compatibility with JPEG is proposed. A simple implementation of lossy compression demonstrates the efficiency of the proposed architecture compared with the state-of-the-art HDR image compression.

  15. Reversible dimerization of Aequorea victoria fluorescent proteins increases the dynamic range of FRET-based indicators.

    PubMed

    Kotera, Ippei; Iwasaki, Takuya; Imamura, Hiromi; Noji, Hiroyuki; Nagai, Takeharu

    2010-02-19

    Fluorescent protein (FP)-based Forster resonance energy transfer (FRET) technology is useful for development of functional indicators to visualize second messenger molecules and activation of signaling components in living cells. However, the design and construction of the functional indicators require careful optimization of their structure at the atomic level. Therefore, routine procedures for constructing FRET-based indicators currently include the adjustment of the linker length between the FPs and the sensor domain and relative dipole orientation of the FP chromophore. Here we report that, in addition to these techniques, optimization of the dimerization interface of Aequorea FPs is essential to achieve the highest possible dynamic range of signal change by FRET-based indicators. We performed spectroscopic analyses of various indicators (cameleon, TN-XL, and ATeam) and their variants. We chose variants containing mutant FPs with different dimerization properties, i.e., no, weak, or enhanced dimerization of the donor or acceptor FP. Our findings revealed that the FPs that dimerized weakly yielded high-performance FRET-based indicators with the greatest dynamic range.

  16. Field instrument for simultaneous large dynamic range measurement of atmospheric hydrogen sulfide, methanethiol, and sulfur dioxide.

    PubMed

    Toda, Kei; Ohira, Shin-Ichi; Tanaka, Takayoshi; Nishimura, Tomohiko; Dasgupta, Purnendu K

    2004-03-01

    We describe a membrane-based collection/analysis system that differentially monitors H2S and CH3SH, and to which a conductometric SO2 analyzer using the same collector was coupled. A diffusion scrubber (DS) comprised of a Nafion tube collects H2S selectively while a porous polytetrafluoroethylene (pPTFE) DS collects both H2S and CH3SH. Both gases are measured via their ability to react with fluorescein mercuric acetate (FMA) which results in decreased fluorescence. The limited dynamic range of a negative signal procedure was overcome by using dual DS units comprised of short and long scrubbers, placed serially in the liquid flow line. Different DS designs and membrane materials were investigated. H2S, CH3SH, and SO2 from a biogenic point source were continuously measured, and the H2S/CH3SH data compared well with a standard procedure involving Tedlar bag collection, preconcentration and thermal desorption from a Tenax trap, and measurement by gas chromatography/flame photometric detection. Walkaround portability of the instrument and very large dynamic range measurement of H2S and SO2 were demonstrated around the Mt. Aso volcano.

  17. The Effects of Dynamic Range of Motion Exercises and Static Stretching on Strength and Range of Motion of the Hip Joint.

    ERIC Educational Resources Information Center

    Kanetzke, Carol A.

    The effects of Dynamic Range of Motion (D'ROM) exercises and static stretch on hip flexibility and hip strength were examined. One hundred one male and female college students were divided into three groups: D'ROM, static stretch (ST), and control (C). All subjects were measured before and after treatment for hip flexibility and strength. Two…

  18. AIM results for space-qualified HgCdTe photovoltaic detectors from 0.9-μm to 13-μm spectral range

    NASA Astrophysics Data System (ADS)

    Haiml, M.; Bauer, A.; Bitterlich, H.; Bruder, M.; Hofmann, K.; Lutz, H.; Mai, M.; Nothaft, H.-P.; Rühlich, I.; Wendler, J.; Wiedmann, T.; Wollrab, R.; Ziegler, J.

    2006-09-01

    Remote sensing from space is an emerging market for applications in security, climate research, weather forecast, and global environmental monitoring, to mention a few. In particular, next generation systems demand for large, two-dimensional arrays in the short (SWIR, 0.9-2.5 μm) and the very long wavelength infrared (VLWIR) spectral range up to 15 μm. AIM's developments for space applications benefit from AIM's experiences in high-performance thermal imaging and seeker-head applications. AIM has delivered a 13 μm cut-off demonstrator for a high resolution Fourier-transform imaging spectrometer in limb geometry. For this 256 x 256 VLWIR sensor we measured a responsivity of 100 LSB/K and a noise equivalent temperature difference of 22 mK with 14 bit ADCs at 880 Hz full frame-rate. The substrate and epitaxial layer grown at AIM exhibit very good uniformity and low dark currents. Currently, AIM develops a 1024 x 256 SWIR detector (0.9-2.5 μm) with a capacitance transimpedance amplifier (CTIA) for hyperspectral imaging. The radiation hardness of AIM's FPA technology (MCT sensor and Silicon read-out integrated circuit) has been successfully tested by a total ionization dose (TID) experiment using ESTEC's 60Co γ-source. Our reference module withstands 30 krad TID. For enhanced reliability of the IDCA, AIM has developed a compact 1 W pulse-tube cooler with flexure bearing compressor, which induces also a very low vibration output. In summary, AIM will be able to supply space qualified detector modules covering the spectral range from 0.9 to 13 μm in the near future.

  19. Atmospheric Dynamics of Terrestrial Exoplanets over a Wide Range of Orbital and Atmospheric Parameters

    NASA Astrophysics Data System (ADS)

    Kaspi, Yohai; Showman, Adam P.

    2015-05-01

    The recent discoveries of terrestrial exoplanets and super-Earths extending over a broad range of orbital and physical parameters suggest that these planets will span a wide range of climatic regimes. Characterization of the atmospheres of warm super-Earths has already begun and will be extended to smaller and more distant planets over the coming decade. The habitability of these worlds may be strongly affected by their three-dimensional atmospheric circulation regimes, since the global climate feedbacks that control the inner and outer edges of the habitable zone—including transitions to Snowball-like states and runaway-greenhouse feedbacks—depend on the equator-to-pole temperature differences, patterns of relative humidity, and other aspects of the dynamics. Here, using an idealized moist atmospheric general circulation model including a hydrological cycle, we study the dynamical principles governing the atmospheric dynamics on such planets. We show how the planetary rotation rate, stellar flux, atmospheric mass, surface gravity, optical thickness, and planetary radius affect the atmospheric circulation and temperature distribution on such planets. Our simulations demonstrate that equator-to-pole temperature differences, meridional heat transport rates, structure and strength of the winds, and the hydrological cycle vary strongly with these parameters, implying that the sensitivity of the planet to global climate feedbacks will depend significantly on the atmospheric circulation. We elucidate the possible climatic regimes and diagnose the mechanisms controlling the formation of atmospheric jet streams, Hadley and Ferrel cells, and latitudinal temperature differences. Finally, we discuss the implications for understanding how the atmospheric circulation influences the global climate.

  20. ATMOSPHERIC DYNAMICS OF TERRESTRIAL EXOPLANETS OVER A WIDE RANGE OF ORBITAL AND ATMOSPHERIC PARAMETERS

    SciTech Connect

    Kaspi, Yohai; Showman, Adam P.

    2015-05-01

    The recent discoveries of terrestrial exoplanets and super-Earths extending over a broad range of orbital and physical parameters suggest that these planets will span a wide range of climatic regimes. Characterization of the atmospheres of warm super-Earths has already begun and will be extended to smaller and more distant planets over the coming decade. The habitability of these worlds may be strongly affected by their three-dimensional atmospheric circulation regimes, since the global climate feedbacks that control the inner and outer edges of the habitable zone—including transitions to Snowball-like states and runaway-greenhouse feedbacks—depend on the equator-to-pole temperature differences, patterns of relative humidity, and other aspects of the dynamics. Here, using an idealized moist atmospheric general circulation model including a hydrological cycle, we study the dynamical principles governing the atmospheric dynamics on such planets. We show how the planetary rotation rate, stellar flux, atmospheric mass, surface gravity, optical thickness, and planetary radius affect the atmospheric circulation and temperature distribution on such planets. Our simulations demonstrate that equator-to-pole temperature differences, meridional heat transport rates, structure and strength of the winds, and the hydrological cycle vary strongly with these parameters, implying that the sensitivity of the planet to global climate feedbacks will depend significantly on the atmospheric circulation. We elucidate the possible climatic regimes and diagnose the mechanisms controlling the formation of atmospheric jet streams, Hadley and Ferrel cells, and latitudinal temperature differences. Finally, we discuss the implications for understanding how the atmospheric circulation influences the global climate.

  1. Estimating indices of range shifts in birds using dynamic models when detection is imperfect

    USGS Publications Warehouse

    Clement, Matthew J.; Hines, James E.; Nichols, James D.; Pardieck, Keith L.; Ziolkowski, David J.

    2016-01-01

    There is intense interest in basic and applied ecology about the effect of global change on current and future species distributions. Projections based on widely used static modeling methods implicitly assume that species are in equilibrium with the environment and that detection during surveys is perfect. We used multiseason correlated detection occupancy models, which avoid these assumptions, to relate climate data to distributional shifts of Louisiana Waterthrush in the North American Breeding Bird Survey (BBS) data. We summarized these shifts with indices of range size and position and compared them to the same indices obtained using more basic modeling approaches. Detection rates during point counts in BBS surveys were low, and models that ignored imperfect detection severely underestimated the proportion of area occupied and slightly overestimated mean latitude. Static models indicated Louisiana Waterthrush distribution was most closely associated with moderate temperatures, while dynamic occupancy models indicated that initial occupancy was associated with diurnal temperature ranges and colonization of sites was associated with moderate precipitation. Overall, the proportion of area occupied and mean latitude changed little during the 1997–2013 study period. Near-term forecasts of species distribution generated by dynamic models were more similar to subsequently observed distributions than forecasts from static models. Occupancy models incorporating a finite mixture model on detection – a new extension to correlated detection occupancy models – were better supported and may reduce bias associated with detection heterogeneity. We argue that replacing phenomenological static models with more mechanistic dynamic models can improve projections of future species distributions. In turn, better projections can improve biodiversity forecasts, management decisions, and understanding of global change biology.

  2. Estimating indices of range shifts in birds using dynamic models when detection is imperfect.

    PubMed

    Clement, Matthew J; Hines, James E; Nichols, James D; Pardieck, Keith L; Ziolkowski, David J

    2016-10-01

    There is intense interest in basic and applied ecology about the effect of global change on current and future species distributions. Projections based on widely used static modeling methods implicitly assume that species are in equilibrium with the environment and that detection during surveys is perfect. We used multiseason correlated detection occupancy models, which avoid these assumptions, to relate climate data to distributional shifts of Louisiana Waterthrush in the North American Breeding Bird Survey (BBS) data. We summarized these shifts with indices of range size and position and compared them to the same indices obtained using more basic modeling approaches. Detection rates during point counts in BBS surveys were low, and models that ignored imperfect detection severely underestimated the proportion of area occupied and slightly overestimated mean latitude. Static models indicated Louisiana Waterthrush distribution was most closely associated with moderate temperatures, while dynamic occupancy models indicated that initial occupancy was associated with diurnal temperature ranges and colonization of sites was associated with moderate precipitation. Overall, the proportion of area occupied and mean latitude changed little during the 1997-2013 study period. Near-term forecasts of species distribution generated by dynamic models were more similar to subsequently observed distributions than forecasts from static models. Occupancy models incorporating a finite mixture model on detection - a new extension to correlated detection occupancy models - were better supported and may reduce bias associated with detection heterogeneity. We argue that replacing phenomenological static models with more mechanistic dynamic models can improve projections of future species distributions. In turn, better projections can improve biodiversity forecasts, management decisions, and understanding of global change biology.

  3. BOLUX: A cryogenic electrical-substitution radiometer as high accuracy primary detector in the 150-11,000 eV range

    NASA Astrophysics Data System (ADS)

    Troussel, Ph.; Coron, N.

    2010-03-01

    We have measured the electrical and radiometric properties of a cryogenic absolute radiometer BOLUX (Bolomètre pour l'Utilisation dans le domaine de rayons X). BOLUX is intended for use as a primary detector standard for radiant power measurement of a synchrotron beam from EUV to X-ray spectral ranges. The absolute radiometer uses a composite bolometer with a built-in electrical heating element. The bolometer's absorber, optimized for beam diameter and for X-ray absorption, is coupled both to a Ge doped thermometer and to the electrical resistance calibrator with similar thermal paths so that electrical and radiant heating are equivalent. This device operates between 4 K the liquid helium temperature, and 1.25 K obtained by pumping helium. The main advantage of BOLUX over other radiometers is its portability (weight 12 kg) which means it can be used with any synchrotron beamline. The second advantage is its very small time constant (20 ms) compared with other apparatus (typically a few min). We can use it in DC mode or in AC mode and Alpha sources calibration experiments have already been realized. We have measured synchrotron radiant power at the laboratory of the Physikalisch- Technische Bundesanstalt (PTB) at the Berlin electron storage ring BESSY II. We reported experiments in DC mode and showed the possibility to study the drift and the temporal stability at the exit of a synchrotron beamline. For a helium bath temperature of 1.33 K and in the spectral range of 150 eV-11 keV, we have measured a high limit of detection (in 1 s integrated) to be 10 -10 W, with a DC responsivity of 1.3×10 5 V/W, spatial nonuniformity over 4 mm diameter below 1% and possibility to use over five decades between a few nW and 100 μW with a good linearity (<1%). Typically available radiant power of 50 nW can be measured with a standard uncertainty as low as 1%. BOLUX response has been directly compared with qualified photodiodes [1]; we have observed a standard deviation between

  4. Ionizing radiation detector

    DOEpatents

    Thacker, Louis H.

    1990-01-01

    An ionizing radiation detector is provided which is based on the principle of analog electronic integration of radiation sensor currents in the sub-pico to nano ampere range between fixed voltage switching thresholds with automatic voltage reversal each time the appropriate threshold is reached. The thresholds are provided by a first NAND gate Schmitt trigger which is coupled with a second NAND gate Schmitt trigger operating in an alternate switching state from the first gate to turn either a visible or audible indicating device on and off in response to the gate switching rate which is indicative of the level of radiation being sensed. The detector can be configured as a small, personal radiation dosimeter which is simple to operate and responsive over a dynamic range of at least 0.01 to 1000 R/hr.

  5. Long range dynamics of shallow water: renormalization, modulation and long cycles.

    NASA Astrophysics Data System (ADS)

    Gurarie, David

    2000-11-01

    Long-range dynamics of rotating shallow water (RSW) in the low Rossby-Froude regime, Ro = Fr ll1, exhibits multiscale structure with oscillations on different scales, from fast (gravity), to slower ``eddy turnover" , and yet slower ``long weather cycles". We search for an effective theory, that would ``average" fast oscillations on each scale, to produce higher level ``slow evolution". The principal source of fast gravity waves - dominant linear dispersion, could be eliminated by passing to the amplitude equations. In nonlinear systems, however, it does not remove oscillations completely, but transplants them to nonlinear terms. We implement the Bogoliubov-Mitropolskii averaging (BM) to produce renormalized system (RN-RSW), made of the resonant quadratic part of RSW, plus order(Ro) - cubic, and O(Ro^2) - quartic corrections. Renormalized system evolves on the first slow scale. Next we conduct the detailed analysis of RN-RSW for a single 9D-Lorenz-type triad. The triad system allows to implement second renormalization (from ``first slow" to ``second slow" time), based on its 5 adiabatic invariants: two conserved integrals of QGS-oscillator (a 3D subsystem, solvable in Jacobi elliptic functions), and three wave-intensities. The adiabatic invariants evolve on the second slow scale, and describe slow modulation of the basic QGS (Jacobi) parameters: modulus, period, magnitude. The off-shot of our two-step renormalization (BM followed by ``adiabatic averaging") are ``modulated oscillations" of the vortical and gravity modes. We verify the modulation phenomena by numeric simulations of (i) complete RSW-triad, vs. (ii) renormalized system (RN-RSW), vs. (iii) its ``modulated (adiabatic) approximation". All three show good qualitative agreement in their gross features. The analysis of adiabatic system explains some long range phases of the RSW-dynamics, like nonlinear ``relaxation", and ``intensification" regimes, and pinpoints ``modulation" as the principal long-range

  6. A high dynamic range method for the direct readout of a dynamic phase change in homodyne interferometers

    NASA Astrophysics Data System (ADS)

    Marçal, L. A. P.; Kitano, C.; Higuti, R. T.; Nader, G.; Silva, E. C. N.

    2012-12-01

    Piezoelectric flextensional actuators (PFAs) are an efficient alternative to systems that demand nano-positioning of devices, such as in nanotechnology. Optical techniques constitute an excellent choice for contactless measurement of nano-displacements. In particular, optical interferometry constitutes an adequate choice for characterizing PFAs. There are several types of interferometers, as well as optical phase demodulation methods, used in practice. One interesting class of demodulation methods uses the spectrum of the photo-detected signal and its intrinsic properties when there is a harmonically varying time-domain modulating signal. In this work, a low cost homodyne Michelson interferometer, associated with simple electronic circuits for signal conditioning and acquisition, is used. A novel dynamic phase demodulation method, named Jm&Jm + 2, is proposed, which uses only the magnitude spectrum of the photo-detected signal, without the need to know its phase spectrum. The method is passive, direct, self-consistent, without problems of phase ambiguity and immune to fading, and presents a dynamic range from 0.45 to 100 rad displacements (between 22.6 nm and 5 µm, for λ = 632.8 nm). When applied to the measurement of half-wave voltage in a proof-of-concept Pockels cell, it presents errors smaller than 0.9% when compared to theory. For the estimation of PFA displacement, it allows the measurement of linearity and frequency response curves, with excellent results.

  7. Feasibility of a neutron detector-dosemeter based on single-event upsets in dynamic random-access memories.

    PubMed

    Phillips, G W; August, R A; Campbell, A B; Nelson, M E; Price, J L; Guardala, N A; Moscovitch, M

    2002-01-01

    The feasibility was investigated of a solid-state neutron detector/dosemeter based on single-event upset (SEU) effects in dynamic random-access memories (DRAMs), commonly used in computer memories. Such a device, which uses a neutron converter material to produce a charged particle capable of causing an upset, would be light-weight, low-power, and could be read simply by polling the memory for bit flips. It would have significant advantages over standard solid-state neutron dosemeters which require off-line processing for track etching and analysis. Previous efforts at developing an SEU neutron detector/dosemeter have suffered from poor response, which can be greatly enhanced by selecting a modern high-density DRAM chip for SEU sensitivity and by using a thin 10B film as a converter. Past attempts to use 10B were not successful because the average alpha particle energy was insufficient to penetrate to the sensitive region of the memory. This can be overcome by removing the surface passivation layer before depositing the 10B film or by implanting 10B directly into the chip. Previous experimental data show a 10(3) increase in neutron sensitivity by chips containing borosilicate glass, which could be used in an SEU detector. The results are presented of simulations showing that the absolute efficiency of an SEU neutron dosemeter can be increased by at least a factor of 1000 over earlier designs.

  8. TH-C-BRD-05: Reducing Proton Beam Range Uncertainty with Patient-Specific CT HU to RSP Calibrations Based On Single-Detector Proton Radiography

    SciTech Connect

    Doolan, P; Sharp, G; Testa, M; Lu, H-M; Bentefour, E; Royle, G

    2014-06-15

    Purpose: Beam range uncertainty in proton treatment comes primarily from converting the patient's X-ray CT (xCT) dataset to relative stopping power (RSP). Current practices use a single curve for this conversion, produced by a stoichiometric calibration based on tissue composition data for average, healthy, adult humans, but not for the individual in question. Proton radiographs produce water-equivalent path length (WEPL) maps, dependent on the RSP of tissues within the specific patient. This work investigates the use of such WEPL maps to optimize patient-specific calibration curves for reducing beam range uncertainty. Methods: The optimization procedure works on the principle of minimizing the difference between the known WEPL map, obtained from a proton radiograph, and a digitally-reconstructed WEPL map (DRWM) through an RSP dataset, by altering the calibration curve that is used to convert the xCT into an RSP dataset. DRWMs were produced with Plastimatch, an in-house developed software, and an optimization procedure was implemented in Matlab. Tests were made on a range of systems including simulated datasets with computed WEPL maps and phantoms (anthropomorphic and real biological tissue) with WEPL maps measured by single detector proton radiography. Results: For the simulated datasets, the optimizer showed excellent results. It was able to either completely eradicate or significantly reduce the root-mean-square-error (RMSE) in the WEPL for the homogeneous phantoms (to zero for individual materials or from 1.5% to 0.2% for the simultaneous optimization of multiple materials). For the heterogeneous phantom the RMSE was reduced from 1.9% to 0.3%. Conclusion: An optimization procedure has been designed to produce patient-specific calibration curves. Test results on a range of systems with different complexities and sizes have been promising for accurate beam range control in patients. This project was funded equally by the Engineering and Physical Sciences Research

  9. New approach of financial volatility duration dynamics by stochastic finite-range interacting voter system

    NASA Astrophysics Data System (ADS)

    Wang, Guochao; Wang, Jun

    2017-01-01

    We make an approach on investigating the fluctuation behaviors of financial volatility duration dynamics. A new concept of volatility two-component range intensity (VTRI) is developed, which constitutes the maximal variation range of volatility intensity and shortest passage time of duration, and can quantify the investment risk in financial markets. In an attempt to study and describe the nonlinear complex properties of VTRI, a random agent-based financial price model is developed by the finite-range interacting biased voter system. The autocorrelation behaviors and the power-law scaling behaviors of return time series and VTRI series are investigated. Then, the complexity of VTRI series of the real markets and the proposed model is analyzed by Fuzzy entropy (FuzzyEn) and Lempel-Ziv complexity. In this process, we apply the cross-Fuzzy entropy (C-FuzzyEn) to study the asynchrony of pairs of VTRI series. The empirical results reveal that the proposed model has the similar complex behaviors with the actual markets and indicate that the proposed stock VTRI series analysis and the financial model are meaningful and feasible to some extent.

  10. Acidic range titration of HEWL using a constant-pH molecular dynamics method.

    PubMed

    Machuqueiro, Miguel; Baptista, António M

    2008-07-01

    In this work, we present the first application to a protein of the stochastic constant-pH molecular dynamics (MD) method with the inclusion of proton tautomerism. The acidic titration of HEWL was performed under different conditions. Both generalized reaction field (GRF) and particle mesh Ewald (PME) methods were used in the treatment of the long range electrostatics and, even though the PME simulations revealed to be more stable, the better results were obtained using GRF (pK(a) RMSD of 0.82 for GRF and 1.13 for PME). The results using PME at different dielectric constants (2, 4, and 8) also revealed that there was no significant improvement in pK(a)'s prediction upon increasing the dielectric constant. The secondary structure analysis of HEWL revealed a remarkably stable protein in the acidic pH range. The beta-sheet strands (unlike the alpha-helices) seem to be destabilized upon pH decrease, suggesting that the beta-domain is less stable than the alpha-domain. The four principal alpha-helices were also ordered according to their stability in the acidic pH range and the results (4 < 1 < 2 approximately = 3) were consistent with the ones obtained in thermal denaturation studies.

  11. Neuronal avalanches imply maximum dynamic range in cortical networks at criticality.

    PubMed

    Shew, Woodrow L; Yang, Hongdian; Petermann, Thomas; Roy, Rajarshi; Plenz, Dietmar

    2009-12-09

    Spontaneous neuronal activity is a ubiquitous feature of cortex. Its spatiotemporal organization reflects past input and modulates future network output. Here we study whether a particular type of spontaneous activity is generated by a network that is optimized for input processing. Neuronal avalanches are a type of spontaneous activity observed in superficial cortical layers in vitro and in vivo with statistical properties expected from a network operating at "criticality." Theory predicts that criticality and, therefore, neuronal avalanches are optimal for input processing, but until now, this has not been tested in experiments. Here, we use cortex slice cultures grown on planar microelectrode arrays to demonstrate that cortical networks that generate neuronal avalanches benefit from a maximized dynamic range, i.e., the ability to respond to the greatest range of stimuli. By changing the ratio of excitation and inhibition in the cultures, we derive a network tuning curve for stimulus processing as a function of distance from criticality in agreement with predictions from our simulations. Our findings suggest that in the cortex, (1) balanced excitation and inhibition establishes criticality, which maximizes the range of inputs that can be processed, and (2) spontaneous activity and input processing are unified in the context of critical phenomena.

  12. Averaging of Replicated Pulses for Enhanced-Dynamic-Range Single-Shot Measurement of Nanosecond Optical Pulses

    SciTech Connect

    Marciante, J.R.; Donaldson, W.R.; Roides, R.G.

    2007-10-04

    Measuring optical pulse shapes beyond the dynamic range of oscilloscopes is achieved by temporal pulse stacking in a low-loss, passive, fiber-optic network. Optical pulses are averaged with their time-delayed replicas without introducing additional noise or jitter, allowing for high-contrast pulse-shape measurements of single-shot events. A dynamic-range enhancement of three bits is experimentally demonstrated and compared with conventional multi-shot averaging. This technique can be extended to yield an increase of up to seven bits of additional dynamic range over nominal oscilloscope performance.

  13. MO-FG-303-05: A Feasibility Study of Using a Cherenkov Detector Material with the Prompt Gamma Range Verification Technique in Proton Therapy

    SciTech Connect

    Lau, A; Ahmad, S; Chen, Y

    2015-06-15

    Purpose: To simulate the feasibility of a Cherenkov glass material for the determination of the penetration depth of therapeutic proton beams in water. Methods: Proton pencil beams of various energies incident onto a water phantom with dimensions of 5 x 5 x 30 cm{sup 3} were used for simulation with the Geant4 toolkit. The model used standard electromagnetic packages, packages based on binary-cascade nuclear model, several decay modules (G4Decay, G4DecayPhysics, and G4RadioactiveDecayPhysics), and optical photon components (G4OpticalPhysics). A Cherenkov glass material was modeled as the detector medium (7.2 g of In2O3 + 90 g cladding, density of 2.82 g/cm{sup 3}, Zeff = 33.7, index of refraction n(600 nm) = 1.56, and energy threshold of production Eth = 156 keV ). The emitted secondary particles are analyzed characterizing their timing, energy, and angular distributions. A feasibility analysis was conducted for a simplistic detector system using this material to locate the position of the Bragg Peak. Results: The escaping neutrons have energies ranging from thermal to the incident proton energy and the escaping photons have energies >10 MeV. Photon peaks between 4 and 6 MeV were attributed to originate from direct proton interactions with {sup 12}C (∼ 4.4 MeV) and {sup 16}O (∼ 6 MeV), respectively. The escaping photons are emitted isotropically, while low (≤10 MeV) and high (>10 MeV) neutrons are isotropic and forward-directional, respectively. The emissions of photons are categorized into prompt (∼ns) and delayed (∼min) where the prompt photons include the 4.4 and 6 MeV. The Cherenkov material had on average <2% of neutron interactions while LYSO and BGO scintillators had a minimum of ∼50%. Our simplistic detector system was capable of discerning Bragg Peak locations using a timing discrimination of ∼50 ns. Conclusion: We investigate the viability of using the Cherenkov material for MeV photon detection medium for the prompt gamma technique.

  14. Synchronous digitization for high dynamic range lock-in amplification in beam-scanning microscopy

    NASA Astrophysics Data System (ADS)

    Muir, Ryan D.; Sullivan, Shane Z.; Oglesbee, Robert A.; Simpson, Garth J.

    2014-03-01

    Digital lock-in amplification (LIA) with synchronous digitization (SD) is shown to provide significant signal to noise (S/N) and linear dynamic range advantages in beam-scanning microscopy measurements using pulsed laser sources. Direct comparisons between SD-LIA and conventional LIA in homodyne second harmonic generation measurements resulted in S/N enhancements consistent with theoretical models. SD-LIA provided notably larger S/N enhancements in the limit of low light intensities, through the smooth transition between photon counting and signal averaging developed in previous work. Rapid beam scanning instrumentation with up to video rate acquisition speeds minimized photo-induced sample damage. The corresponding increased allowance for higher laser power without sample damage is advantageous for increasing the observed signal content.

  15. Lossy compression of floating point high-dynamic range images using JPEG2000

    NASA Astrophysics Data System (ADS)

    Springer, Dominic; Kaup, Andre

    2009-01-01

    In recent years, a new technique called High Dynamic Range (HDR) has gained attention in the image processing field. By representing pixel values with floating point numbers, recorded images can hold significantly more luminance information than ordinary integer images. This paper focuses on the realization of a lossy compression scheme for HDR images. The JPEG2000 standard is used as a basic component and is efficiently integrated into the compression chain. Based on a detailed analysis of the floating point format and the human visual system, a concept for lossy compression is worked out and thoroughly optimized. Our scheme outperforms all other existing lossy HDR compression schemes and shows superior performance both at low and high bitrates.

  16. Low-frequency predictability of the Dynamical Extended-Range Forecast Experiment

    NASA Technical Reports Server (NTRS)

    Nogues-Peagle, Julia; Rodgers, Dennis A.; Mo, Kingtse C.

    1992-01-01

    The objective of the study was to analyze data from the Dynamical Extended-Range Forecast Experiment conducted from January 1986 to March 1987, and to evaluate differences between analysis and forecasts with emphasis on the tropical 30-50-day oscillation. The diagnostic toll used is the projection of analysis and forecast data onto the normal modes of a primitive equation model. Examination of zonal-wind anomalies in the tropics shows that the forecast model predicts propagation of intraseasonal variations more accurately for slow propagation rates. The forecast amplitude is generally weaker than the analyzed amplitude. Analyzed kinetic energy and error fields exhibit similar horizontal scales for internal and external modes. External Rossby-mode components maximize in the extratropics while Rossby internal modes exhibit patterns that extend over the entire globe.

  17. Activation of Lumbar Spinal Wide-Dynamic Range Neurons by a Sanshool Derivative

    PubMed Central

    Sawyer, Carolyn M.; Carstens, Mirela Iodi; Simons, Christopher T.; Slack, Jay; McCluskey, T. Scott; Furrer, Stefan; Carstens, E.

    2009-01-01

    The enigmatic sensation of tingle involves the activation of primary sensory neurons by hydroxy-α-sanshool, a tingly agent in Szechuan peppers, by inhibiting two-pore potassium channels. Central mechanisms mediating tingle sensation are unknown. We investigated whether a stable derivative of sanshool—isobutylalkenyl amide (IBA)—excites wide-dynamic range (WDR) spinal neurons that participate in transmission of chemesthetic information from the skin. In anesthetized rats, the majority of WDR and low-threshold units responded to intradermal injection of IBA in a dose-related manner over a >5-min time course and exhibited tachyphylaxis at higher concentrations (1 and 10%). Almost all WDR and low-threshold units additionally responded to the pungent agents mustard oil (allyl isothiocyanate) and/or capsaicin, prompting reclassification of the low-threshold cells as WDR. The results are discussed in terms of the functional role of WDR neurons in mediating tingle sensation. PMID:19164099

  18. Ultra-sensitive all-fibre photothermal spectroscopy with large dynamic range

    PubMed Central

    Jin, Wei; Cao, Yingchun; Yang, Fan; Ho, Hoi Lut

    2015-01-01

    Photothermal interferometry is an ultra-sensitive spectroscopic means for trace chemical detection in gas- and liquid-phase materials. Previous photothermal interferometry systems used free-space optics and have limitations in efficiency of light–matter interaction, size and optical alignment, and integration into photonic circuits. Here we exploit photothermal-induced phase change in a gas-filled hollow-core photonic bandgap fibre, and demonstrate an all-fibre acetylene gas sensor with a noise equivalent concentration of 2 p.p.b. (2.3 × 10−9 cm−1 in absorption coefficient) and an unprecedented dynamic range of nearly six orders of magnitude. The realization of photothermal interferometry with low-cost near infrared semiconductor lasers and fibre-based technology allows a class of optical sensors with compact size, ultra sensitivity and selectivity, applicability to harsh environment, and capability for remote and multiplexed multi-point detection and distributed sensing. PMID:25866015

  19. Protein and water dynamics in bovine serum albumin-water mixtures over wide ranges of composition.

    PubMed

    Panagopoulou, A; Kyritsis, A; Shinyashiki, N; Pissis, P

    2012-04-19

    Dielectric dynamic behavior of bovine serum albumin (BSA)-water mixtures over wide ranges of water fractions, from dry protein until 40 wt % in water, was studied through dielectric relaxation spectroscopy (DRS). The α relaxation associated with the glass transition of the hydrated system was identified. The evolution of the low temperature dielectric relaxation of small polar groups of the protein surface with hydration level results in the enhancement of dielectric response and the decrease of relaxation times, until a critical water fraction, which corresponds to the percolation threshold for protonic conductivity. For water fractions higher than the critical one, the position of the secondary ν relaxation of water saturates in the Arrhenius diagram, while contributions originating from water molecules in excess (uncrystallized water or ice) follow separate relaxation modes slower than the ν relaxation.

  20. Activation of lumbar spinal wide-dynamic range neurons by a sanshool derivative.

    PubMed

    Sawyer, Carolyn M; Carstens, Mirela Iodi; Simons, Christopher T; Slack, Jay; McCluskey, T Scott; Furrer, Stefan; Carstens, E

    2009-04-01

    The enigmatic sensation of tingle involves the activation of primary sensory neurons by hydroxy-alpha-sanshool, a tingly agent in Szechuan peppers, by inhibiting two-pore potassium channels. Central mechanisms mediating tingle sensation are unknown. We investigated whether a stable derivative of sanshool-isobutylalkenyl amide (IBA)-excites wide-dynamic range (WDR) spinal neurons that participate in transmission of chemesthetic information from the skin. In anesthetized rats, the majority of WDR and low-threshold units responded to intradermal injection of IBA in a dose-related manner over a >5-min time course and exhibited tachyphylaxis at higher concentrations (1 and 10%). Almost all WDR and low-threshold units additionally responded to the pungent agents mustard oil (allyl isothiocyanate) and/or capsaicin, prompting reclassification of the low-threshold cells as WDR. The results are discussed in terms of the functional role of WDR neurons in mediating tingle sensation.

  1. Endoscopic system for automated high dynamic range inspection of moving periodic structures

    NASA Astrophysics Data System (ADS)

    Hahlweg, Cornelius; Rothe, Hendrik

    2015-09-01

    In the current paper an advanced endoscopic system for high resolution and high dynamic range inspection of periodic structures in rotating machines is presented. We address the system architecture, short time illumination, special optical problems, such as excluding the specular reflex, image processing, forward velocity prediction and metrological image processing. There are several special requirements to be met, such as the thermal stability above 100°C, robustness of the image field, illumination in view direction and the separation of metallic surface diffuse scatter. To find a compromise between image resolution and frame rate, an external sensor system was applied for synchronization with the moving target. The system originally was intended for inspection of thermal engines, but turned out to be of a more general use. Beside the theoretical part and dimensioning issues, practical examples and measurement results are included.

  2. Increase of the dynamic range of catchup experiments by high-pass filtering

    SciTech Connect

    Erskine, D.J.

    1995-08-01

    The release-catchup shock experiment is an important tool for measuring the speed of sound in compressed matter. The catchup of the release wave to the leading shock is sensitively detected optically, through an indicating fluid which produces light approximately to the 4th power of the shock pressure. However, this sensitivity demands a dynamic range which exceeds the capabilities of our digitizer. The catchup signature lies at the top of a flat pulse, thus any signal clipping is a catastrophic loss of data. We have invented a simple and accurate method for recording the catchup signature that is insensitive to signal clipping. A high pass circuit prior to the digitizer is used with post experiment integration. The insensitivity to clipping allows recording the catchup signature at higher gain, and thus with an improved signal to noise ratio.

  3. Increase of the dynamic range of catchup experiments by high-pass filtering

    SciTech Connect

    Erskine, D.J.

    1996-05-01

    The release-catchup shock experiment is an important tool for measuring the speed of sound in compressed matter. The catchup of the release wave to the leading shock is sensitively detected optically, through an indicating fluid which produces light approximately to the 4th power of the shock pressure. However, this sensitivity demands a dynamic range which exceeds the capabilities of our digitizer. The catchup signature lies at the top of a flat pulse, thus any signal clipping is a catastrophic loss of data. We have invented a simple and accurate method for recording the catchup signature that is insensitive to signal clipping. A high pass circuit prior to the digitizer is used with post experiment integration. The insensitivity to clipping allows recording the catchup signature at higher gain, and thus with an improved signal to noise ratio. {copyright} {ital 1996 American Institute of Physics.}

  4. Australian SKA Pathfinder: A High-Dynamic Range Wide-Field of View Survey Telescope

    NASA Astrophysics Data System (ADS)

    DeBoer, D. R.; Gough, R. G.; Bunton, J. D.; Cornwell, T. J.; Beresford, R. J.; Johnston, S.; Feain, I. J.; Schinckel, A. E.; Jackson, C. A.; Kesteven, M. J.; Chippendale, A.; Hampson, G. A.; O'Sullivan, J. D.; Hay, S. G.; Jacka, C. E.; Sweetnam, T. W.; Storey, M. C.; Ball, L.; Boyle, B. J.

    2009-08-01

    The Australia SKA Pathfinder (ASKAP) is a new telescope under development as a world-class high-dynamic-range wide-field-of-view survey instrument. It will utilize focal plane phased array feeds on the 36 12-m antennas that will compose the array. The large amounts of data present a huge computing challenge, and ASKAP will store data products in an archive after near real-time pipeline processing. This powerful instrument will be deployed at a new radio-quiet observatory, the Murchison Radio-astronomy Observatory in the midwest region of Western Australia, to enable sensitive surveys of the entire sky to address some of the big questions in contemporary physics. As a pathfinder for the SKA, ASKAP will demonstrate field of view enhancement and computing/processing technology as well as the operation of a large-scale radio array in a remote and radio-quiet region of Australia.

  5. Synchronous digitization for high dynamic range lock-in amplification in beam-scanning microscopy

    SciTech Connect

    Muir, Ryan D.; Sullivan, Shane Z.; Oglesbee, Robert A.; Simpson, Garth J.

    2014-03-15

    Digital lock-in amplification (LIA) with synchronous digitization (SD) is shown to provide significant signal to noise (S/N) and linear dynamic range advantages in beam-scanning microscopy measurements using pulsed laser sources. Direct comparisons between SD-LIA and conventional LIA in homodyne second harmonic generation measurements resulted in S/N enhancements consistent with theoretical models. SD-LIA provided notably larger S/N enhancements in the limit of low light intensities, through the smooth transition between photon counting and signal averaging developed in previous work. Rapid beam scanning instrumentation with up to video rate acquisition speeds minimized photo-induced sample damage. The corresponding increased allowance for higher laser power without sample damage is advantageous for increasing the observed signal content.

  6. A Noise-Robust Continuous Speech Recognition System Using Block-Based Dynamic Range Adjustment

    NASA Astrophysics Data System (ADS)

    Sun, Yiming; Miyanaga, Yoshikazu

    A new approach to speech feature estimation under noise circumstances is proposed in this paper. It is used in noise-robust continuous speech recognition (CSR). As the noise robust techniques in isolated word speech recognition, the running spectrum analysis (RSA), the running spectrum filtering (RSF) and the dynamic range adjustment (DRA) methods have been developed. Among them, only RSA has been applied to a CSR system. This paper proposes an extended DRA for a noise-robust CSR system. In the stage of speech recognition, a continuous speech waveform is automatically assigned to a block defined by a short time length. The extended DRA is applied to these estimated blocks. The average recognition rate of the proposed method has been improved under several different noise conditions. As a result, the recognition rates are improved up to 15% in various noises with 10 dB SNR.

  7. Driver steering dynamics measured in car simulator under a range of visibility and roadmaking conditions

    NASA Technical Reports Server (NTRS)

    Allen, R. W.; Mcruer, D. T.

    1977-01-01

    A simulation experiment was conducted to determine the effect of reduced visibility on driver lateral (steering) control. The simulator included a real car cab and a single lane road image projected on a screen six feet in front of the driver. Simulated equations of motion controlled apparent car lane position in response to driver steering actions, wind gusts, and road curvature. Six drivers experienced a range of visibility conditions at various speeds with assorted roadmaking configurations (mark and gap lengths). Driver describing functions were measured and detailed parametric model fits were determined. A pursuit model employing a road curvature feedforward was very effective in explaining driver behavior in following randomly curving roads. Sampled-data concepts were also effective in explaining the combined effects of reduced visibility and intermittent road markings on the driver's dynamic time delay. The results indicate the relative importance of various perceptual variables as the visual input to the driver's steering control process is changed.

  8. Electrochemical Gold(III) Sensor with High Sensitivity and Tunable Dynamic Range.

    PubMed

    Wu, Yao; Lai, Rebecca Y

    2016-02-16

    We report the design and fabrication of a sensitive, specific, and selective electrochemical ion (E-ION) sensor for detection of Au(III). The signaling mechanism is based on the interactions between Au(III) and adenine; formation of these complexes rigidifies the methylene blue (MB)-modified oligoadenine probes, resulting in a concentration-dependent reduction in the MB signal. The dynamic range of the sensor can be tuned by simply changing the length of the DNA probe (six (A6) or 12 (A12) adenines). Independent of the probe length, both sensors have demonstrated to be sensitive, with a limits of detection of 50 and 20 nM for the A6 and A12 sensors, respectively. With further optimization, this sensing strategy may offer a promising approach for analyzing Au(III).

  9. High-dynamic-range cross-correlator for shot-to-shot measurement of temporal contrast

    NASA Astrophysics Data System (ADS)

    Kon, Akira; Nishiuchi, Mamiko; Kiriyama, Hiromitsu; Ogura, Koichi; Mori, Michiaki; Sakaki, Hironao; Kando, Masaki; Kondo, Kiminori

    2017-01-01

    The temporal contrast of an ultrahigh-intensity laser is a crucial parameter for laser plasma experiments. We have developed a multichannel cross-correlator (MCCC) for single-shot measurements of the temporal contrast in a high-power laser system. The MCCC is based on third-order cross-correlation, and has four channels and independent optical delay lines. We have experimentally demonstrated that the MCCC system achieves a high dynamic range of ˜1012 and a large temporal window of ˜1 ns. Moreover, we were able to measure the shot-to-shot fluctuations of a short-prepulse intensity at -26 ps and long-pulse (amplified spontaneous emission, ASE) intensities at -30, -450, and -950 ps before the arrival of the main pulse at the interaction point.

  10. Can ocean acidification affect population dynamics of the barnacle Semibalanus balanoides at its southern range edge?

    PubMed

    Findlay, Helen S; Burrows, Michael T; Kendall, Michael A; Spicer, John I; Widdicombe, Stephen

    2010-10-01

    The global ocean and atmosphere are warming. There is increasing evidence suggesting that, in addition to other environmental factors, climate change is affecting species distributions and local population dynamics. Additionally, as a consequence of the growing levels of atmospheric carbon dioxide (CO2), the oceans are taking up increasing amounts of this CO2, causing ocean pH to decrease (ocean acidification). The relative impacts of ocean acidification on population dynamics have yet to be investigated, despite many studies indicating that there will be at least a sublethal impact on many marine organisms, particularly key calcifying organisms. Using empirical data, we forced a barnacle (Semibalanus balanoides) population model to investigate the relative influence of sea surface temperature (SST) and ocean acidification on a population nearing the southern limit of its geographic distribution. Hindcast models were compared to observational data from Cellar Beach (southwestern United Kingdom). Results indicate that a declining pH trend (-0.0017 unit/yr), indicative of ocean acidification over the past 50 years, does not cause an observable impact on the population abundance relative to changes caused by fluctuations in temperature. Below the critical temperature (here T(crit) = 13.1 degrees C), pH has a more significant affect on population dynamics at this southern range edge. However, above this value, SST has the overriding influence. At lower SST, a decrease in pH (according to the National Bureau of Standards, pHNBs) from 8.2 to 7.8 can significantly decrease the population abundance. The lethal impacts of ocean acidification observed in experiments on early life stages reduce cumulative survival by approximately 25%, which again will significantly alter the population level at this southern limit. Furthermore, forecast predictions from this model suggest that combined acidification and warming cause this local population to die out 10 years earlier than

  11. Dynamic simulation of concentrated macromolecular solutions with screened long-range hydrodynamic interactions: Algorithm and limitations

    PubMed Central

    Ando, Tadashi; Chow, Edmond; Skolnick, Jeffrey

    2013-01-01

    Hydrodynamic interactions exert a critical effect on the dynamics of macromolecules. As the concentration of macromolecules increases, by analogy to the behavior of semidilute polymer solutions or the flow in porous media, one might expect hydrodynamic screening to occur. Hydrodynamic screening would have implications both for the understanding of macromolecular dynamics as well as practical implications for the simulation of concentrated macromolecular solutions, e.g., in cells. Stokesian dynamics (SD) is one of the most accurate methods for simulating the motions of N particles suspended in a viscous fluid at low Reynolds number, in that it considers both far-field and near-field hydrodynamic interactions. This algorithm traditionally involves an O(N3) operation to compute Brownian forces at each time step, although asymptotically faster but more complex SD methods are now available. Motivated by the idea of hydrodynamic screening, the far-field part of the hydrodynamic matrix in SD may be approximated by a diagonal matrix, which is equivalent to assuming that long range hydrodynamic interactions are completely screened. This approximation allows sparse matrix methods to be used, which can reduce the apparent computational scaling to O(N). Previously there were several simulation studies using this approximation for monodisperse suspensions. Here, we employ newly designed preconditioned iterative methods for both the computation of Brownian forces and the solution of linear systems, and consider the validity of this approximation in polydisperse suspensions. We evaluate the accuracy of the diagonal approximation method using an intracellular-like suspension. The diffusivities of particles obtained with this approximation are close to those with the original method. However, this approximation underestimates intermolecular correlated motions, which is a trade-off between accuracy and computing efficiency. The new method makes it possible to perform large-scale and

  12. Enhanced high dynamic range 3D shape measurement based on generalized phase-shifting algorithm

    NASA Astrophysics Data System (ADS)

    Wang, Minmin; Du, Guangliang; Zhou, Canlin; Zhang, Chaorui; Si, Shuchun; Li, Hui; Lei, Zhenkun; Li, YanJie

    2017-02-01

    Measuring objects with large reflectivity variations across their surface is one of the open challenges in phase measurement profilometry (PMP). Saturated or dark pixels in the deformed fringe patterns captured by the camera will lead to phase fluctuations and errors. Jiang et al. proposed a high dynamic range real-time three-dimensional (3D) shape measurement method (Jiang et al., 2016) [17] that does not require changing camera exposures. Three inverted phase-shifted fringe patterns are used to complement three regular phase-shifted fringe patterns for phase retrieval whenever any of the regular fringe patterns are saturated. Nonetheless, Jiang's method has some drawbacks: (1) the phases of saturated pixels are estimated by different formulas on a case by case basis; in other words, the method lacks a universal formula; (2) it cannot be extended to the four-step phase-shifting algorithm, because inverted fringe patterns are the repetition of regular fringe patterns; (3) for every pixel in the fringe patterns, only three unsaturated intensity values can be chosen for phase demodulation, leaving the other unsaturated ones idle. We propose a method to enhance high dynamic range 3D shape measurement based on a generalized phase-shifting algorithm, which combines the complementary techniques of inverted and regular fringe patterns with a generalized phase-shifting algorithm. Firstly, two sets of complementary phase-shifted fringe patterns, namely the regular and the inverted fringe patterns, are projected and collected. Then, all unsaturated intensity values at the same camera pixel from two sets of fringe patterns are selected and employed to retrieve the phase using a generalized phase-shifting algorithm. Finally, simulations and experiments are conducted to prove the validity of the proposed method. The results are analyzed and compared with those of Jiang's method, demonstrating that our method not only expands the scope of Jiang's method, but also improves

  13. A high dynamic range power sensor based on GaAs MMIC process and MEMS technology

    NASA Astrophysics Data System (ADS)

    Yi, Zhenxiang; Liao, Xiaoping

    2016-01-01

    This paper reports a high dynamic range power sensor based on GaAs process and MEMS technology. The proposed sensor consisted of the terminating-type sensor and the coupling-type sensor. The former measures low power while the latter is for high power detection. This device is designed and fabricated by GaAs MMIC process. In order to optimize microwave performance, impedance compensating technology by increasing the slot width of the CPW transmission line is developed. Related calculation and simulation are also presented in this paper. The microwave performance test reveals that the return loss is close to -28 dB@8 GHz, -27 dB@10 GHz and -26 dB@12 GHz, respectively. The microwave power response experiment is investigated from 1 mW to 150 mW. For the incident power less than 100 mW, the terminating-type sensor operates and the measured sensitivity is about 0.095 mV/mW@8 GHz, 0.088 mV/mW@10 GHz and 0.084 mV/mW@12 GHz, respectively. Related lumped equivalent circuit models of the loaded resistors are developed to explain the loss induced by the frequency of the signal. For the incident power with the improved dynamic range from 100 mW to 150 mW, the coupling-type sensor is adopted and the measured sensitivity is about 9.2 μV/mW@8 GHz, 8.6 μV/mW@8 GHz and 9.0 μV/mW@12 GHz, respectively.

  14. High-resolution full-field optical coherence tomography using high dynamic range image processing

    NASA Astrophysics Data System (ADS)

    Leong-Hoï, A.; Claveau, R.; Montgomery, P. C.; Serio, B.; Uhring, W.; Anstotz, F.; Flury, M.

    2016-04-01

    Full-field optical coherence tomography (FF-OCT) based on white-light interference microscopy, is an emerging noninvasive imaging technique for characterizing biological tissue or optical scattering media with micrometer resolution. Tomographic images can be obtained by analyzing a sequence of interferograms acquired with a camera. This is achieved by scanning an interferometric microscope objectives along the optical axis and performing appropriate signal processing for fringe envelope extraction, leading to three-dimensional imaging over depth. However, noise contained in the images can hide some important details or induce errors in the size of these details. To firstly reduce temporal and spatial noise from the camera, it is possible to apply basic image post processing methods such as image averaging, dark frame subtraction or flat field division. It has been demonstrate that this can improve the quality of microscopy images by enhancing the signal to noise ratio. In addition, the dynamic range of images can be enhanced to improve the contrast by combining images acquired with different exposure times or light intensity. This can be made possible by applying a hybrid high dynamic range (HDR) technique, which is proposed in this paper. High resolution tomographic analysis is thus performed using a combination of the above-mentioned image processing techniques. As a result, the lateral resolution of the system can be improved so as to approach the diffraction limit of the microscope as well as to increase the power of detection, thus enabling new sub-diffraction sized structures contained in a transparent layer, initially hidden by the noise, to be detected.

  15. An adaptive scheme for robot localization and mapping with dynamically configurable inter-beacon range measurements.

    PubMed

    Torres-González, Arturo; Martinez-de Dios, Jose Ramiro; Ollero, Anibal

    2014-04-25

    This work is motivated by robot-sensor network cooperation techniques where sensor nodes (beacons) are used as landmarks for range-only (RO) simultaneous localization and mapping (SLAM). This paper presents a RO-SLAM scheme that actuates over the measurement gathering process using mechanisms that dynamically modify the rate and variety of measurements that are integrated in the SLAM filter. It includes a measurement gathering module that can be configured to collect direct robot-beacon and inter-beacon measurements with different inter-beacon depth levels and at different rates. It also includes a supervision module that monitors the SLAM performance and dynamically selects the measurement gathering configuration balancing SLAM accuracy and resource consumption. The proposed scheme has been applied to an extended Kalman filter SLAM with auxiliary particle filters for beacon initialization (PF-EKF SLAM) and validated with experiments performed in the CONET Integrated Testbed. It achieved lower map and robot errors (34% and 14%, respectively) than traditional methods with a lower computational burden (16%) and similar beacon energy consumption.

  16. An Adaptive Scheme for Robot Localization and Mapping with Dynamically Configurable Inter-Beacon Range Measurements

    PubMed Central

    Torres-González, Arturo; Martinez-de Dios, Jose Ramiro; Ollero, Anibal

    2014-01-01

    This work is motivated by robot-sensor network cooperation techniques where sensor nodes (beacons) are used as landmarks for range-only (RO) simultaneous localization and mapping (SLAM). This paper presents a RO-SLAM scheme that actuates over the measurement gathering process using mechanisms that dynamically modify the rate and variety of measurements that are integrated in the SLAM filter. It includes a measurement gathering module that can be configured to collect direct robot-beacon and inter-beacon measurements with different inter-beacon depth levels and at different rates. It also includes a supervision module that monitors the SLAM performance and dynamically selects the measurement gathering configuration balancing SLAM accuracy and resource consumption. The proposed scheme has been applied to an extended Kalman filter SLAM with auxiliary particle filters for beacon initialization (PF-EKF SLAM) and validated with experiments performed in the CONET Integrated Testbed. It achieved lower map and robot errors (34% and 14%, respectively) than traditional methods with a lower computational burden (16%) and similar beacon energy consumption. PMID:24776938

  17. Multichannel emission spectrometer for high dynamic range optical pyrometry of shock-driven materials

    NASA Astrophysics Data System (ADS)

    Bassett, Will P.; Dlott, Dana D.

    2016-10-01

    An emission spectrometer (450-850 nm) using a high-throughput, high numerical aperture (N.A. = 0.3) prism spectrograph with stepped fiberoptic coupling, 32 fast photomultipliers and thirty-two 1.25 GHz digitizers is described. The spectrometer can capture single-shot events with a high dynamic range in amplitude and time (nanoseconds to milliseconds or longer). Methods to calibrate the spectrometer and verify its performance and accuracy are described. When a reference thermal source is used for calibration, the spectrometer can function as a fast optical pyrometer. Applications of the spectrometer are illustrated by using it to capture single-shot emission transients from energetic materials or reactive materials initiated by kmṡs-1 impacts with laser-driven flyer plates. A log (time) data analysis method is used to visualize multiple kinetic processes resulting from impact initiation of HMX (octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine) or a Zr/CuO nanolaminate thermite. Using a gray body algorithm to interpret the spectral radiance from shocked HMX, a time history of temperature and emissivity was obtained, which could be used to investigate HMX hot spot dynamics. Finally, two examples are presented showing how the spectrometer can avoid temperature determination errors in systems where thermal emission is accompanied by atomic or molecular emission lines.

  18. Encounter success of free-ranging marine predator movements across a dynamic prey landscape.

    PubMed

    Sims, David W; Witt, Matthew J; Richardson, Anthony J; Southall, Emily J; Metcalfe, Julian D

    2006-05-22

    Movements of wide-ranging top predators can now be studied effectively using satellite and archival telemetry. However, the motivations underlying movements remain difficult to determine because trajectories are seldom related to key biological gradients, such as changing prey distributions. Here, we use a dynamic prey landscape of zooplankton biomass in the north-east Atlantic Ocean to examine active habitat selection in the plankton-feeding basking shark Cetorhinus maximus. The relative success of shark searches across this landscape was examined by comparing prey biomass encountered by sharks with encounters by random-walk simulations of 'model' sharks. Movements of transmitter-tagged sharks monitored for 964 days (16754 km estimated minimum distance) were concentrated on the European continental shelf in areas characterized by high seasonal productivity and complex prey distributions. We show movements by adult and sub-adult sharks yielded consistently higher prey encounter rates than 90% of random-walk simulations. Behavioural patterns were consistent with basking sharks using search tactics structured across multiple scales to exploit the richest prey areas available in preferred habitats. Simple behavioural rules based on learned responses to previously encountered prey distributions may explain the high performances. This study highlights how dynamic prey landscapes enable active habitat selection in large predators to be investigated from a trophic perspective, an approach that may inform conservation by identifying critical habitat of vulnerable species.

  19. Multiple conformational states of the hammerhead ribozyme, broad time range of relaxation and topology of dynamics

    PubMed Central

    Menger, Marcus; Eckstein, Fritz; Porschke, Dietmar

    2000-01-01

    The dynamics of a hammerhead ribozyme was analyzed by measurements of fluorescence-detected temperature jump relaxation. The ribozyme was substituted at different positions by 2-aminopurine (2-AP) as fluorescence indicator; these substitutions do not inhibit catalysis. The general shape of relaxation curves reported from different positions of the ribozyme is very similar: a fast decrease of fluorescence, mainly due to physical quenching, is followed by a slower increase of fluorescence due to conformational relaxation. In most cases at least three relaxation time constants in the time range from a few microseconds to ~200 ms are required for fitting. Although the relaxation at different positions of the ribozyme is similar in general, suggesting a global type of ribozyme dynamics, a close examination reveals differences, indicating an individual local response. For example, 2-AP in a tetraloop reports mainly the local loop dynamics known from isolated loops, whereas 2-AP located at the core, e.g. at the cleavage site or its vicinity, also reports relatively large amplitudes of slower components of the ribozyme dynamics. A variant with an A→G substitution in domain II, resulting in an inactive form, leads to the appearance of a particularly slow relaxation process (τ ≈200 ms). Addition of Mg2+ ions induces a reduction of amplitudes and in most cases a general increase of time constants. Differences between the hammerhead variants are clearly demonstrated by subtraction of relaxation curves recorded under corresponding conditions. The changes induced in the relaxation response by Mg2+ are very similar to those induced by Ca2+. The relaxation data do not provide any evidence for formation of Mg2+-inner sphere complexes in hammerhead ribozymes, because a Mg2+-specific relaxation effect was not visible. However, a Mg2+-specific effect was found for a dodeca-riboadenylate substituted with 2-AP, showing that the fluorescence of 2-AP is able to indicate inner sphere

  20. Multiple conformational states of the hammerhead ribozyme, broad time range of relaxation and topology of dynamics.

    PubMed

    Menger, M; Eckstein, F; Porschke, D

    2000-11-15

    The dynamics of a hammerhead ribozyme was analyzed by measurements of fluorescence-detected temperature jump relaxation. The ribozyme was substituted at different positions by 2-aminopurine (2-AP) as fluorescence indicator; these substitutions do not inhibit catalysis. The general shape of relaxation curves reported from different positions of the ribozyme is very similar: a fast decrease of fluorescence, mainly due to physical quenching, is followed by a slower increase of fluorescence due to conformational relaxation. In most cases at least three relaxation time constants in the time range from a few microseconds to approximately 200 ms are required for fitting. Although the relaxation at different positions of the ribozyme is similar in general, suggesting a global type of ribozyme dynamics, a close examination reveals differences, indicating an individual local response. For example, 2-AP in a tetraloop reports mainly the local loop dynamics known from isolated loops, whereas 2-AP located at the core, e.g. at the cleavage site or its vicinity, also reports relatively large amplitudes of slower components of the ribozyme dynamics. A variant with an A-->G substitution in domain II, resulting in an inactive form, leads to the appearance of a particularly slow relaxation process (tau approximately 200 ms). Addition of Mg(2+) ions induces a reduction of amplitudes and in most cases a general increase of time constants. Differences between the hammerhead variants are clearly demonstrated by subtraction of relaxation curves recorded under corresponding conditions. The changes induced in the relaxation response by Mg(2+) are very similar to those induced by Ca(2+). The relaxation data do not provide any evidence for formation of Mg(2+)-inner sphere complexes in hammerhead ribozymes, because a Mg(2+)-specific relaxation effect was not visible. However, a Mg(2+)-specific effect was found for a dodeca-riboadenylate substituted with 2-AP, showing that the fluorescence of 2

  1. Nonlinear analysis and dynamic compensation of stylus scanning measurement with wide range

    NASA Astrophysics Data System (ADS)

    Hui, Heiyang; Liu, Xiaojun; Lu, Wenlong

    2011-12-01

    Surface topography is an important geometrical feature of a workpiece that influences its quality and functions such as friction, wearing, lubrication and sealing. Precision measurement of surface topography is fundamental for product quality characterizing and assurance. Stylus scanning technique is a widely used method for surface topography measurement, and it is also regarded as the international standard method for 2-D surface characterizing. Usually surface topography, including primary profile, waviness and roughness, can be measured precisely and efficiently by this method. However, by stylus scanning method to measure curved surface topography, the nonlinear error is unavoidable because of the difference of horizontal position of the actual measured point from given sampling point and the nonlinear transformation process from vertical displacement of the stylus tip to angle displacement of the stylus arm, and the error increases with the increasing of measuring range. In this paper, a wide range stylus scanning measurement system based on cylindrical grating interference principle is constructed, the originations of the nonlinear error are analyzed, the error model is established and a solution to decrease the nonlinear error is proposed, through which the error of the collected data is dynamically compensated.

  2. Nonlinear mapping of the luminance in dual-layer high dynamic range displays

    NASA Astrophysics Data System (ADS)

    Guarnieri, Gabriele; Ramponi, Giovanni; Bonfiglio, Silvio; Albani, Luigi

    2009-02-01

    It has long been known that the human visual system (HVS) has a nonlinear response to luminance. This nonlinearity can be quantified using the concept of just noticeable difference (JND), which represents the minimum amplitude of a specified test pattern an average observer can discern from a uniform background. The JND depends on the background luminance following a threshold versus intensity (TVI) function. It is possible to define a curve which maps physical luminances into a perceptually linearized domain. This mapping can be used to optimize a digital encoding, by minimizing the visibility of quantization noise. It is also commonly used in medical applications to display images adapting to the characteristics of the display device. High dynamic range (HDR) displays, which are beginning to appear on the market, can display luminance levels outside the range in which most standard mapping curves are defined. In particular, dual-layer LCD displays are able to extend the gamut of luminance offered by conventional liquid crystals towards the black region; in such areas suitable and HVS-compliant luminance transformations need to be determined. In this paper we propose a method, which is primarily targeted to the extension of the DICOM curve used in medical imaging, but also has a more general application. The method can be modified in order to compensate for the ambient light, which can be significantly greater than the black level of an HDR display and consequently reduce the visibility of the details in dark areas.

  3. Adaptive reshaper for high dynamic range and wide color gamut video compression

    NASA Astrophysics Data System (ADS)

    Lu, Taoran; Pu, Fangjun; Yin, Peng; Pytlarz, Jaclyn; Chen, Tao; Husak, Walt

    2016-09-01

    High Dynamic Range (HDR) and Wider Color Gamut (WCG) content represents a greater range of luminance levels and a more complete reproduction of colors found in real-world scenes. The characteristics of HDR/WCG content are very different from the SDR content. It poses a challenge to the compression system which is originally designed for SDR content. Recently in MPEG/VCEG, two directions have been taken to improve compression performances for HDR/WCG video using HEVC Main10 codec. The first direction is to improve HDR-10 using encoder optimization. The second direction is to modify the video signal in pre/post processing to better fit compression system. The process therefore is out of coding loop and does not involve changes to the HEVC specification. Among many proposals in the second direction, reshaper is identified to be the key component. In this paper, a novel luma reshaper is presented which re-allocates the codewords to help codec improve subjective quality. In addition, encoder optimization can be performed jointly with reshaping. Experiments are conducted with ICtCp color difference signal. Simulation results show that if both joint optimization of reshaper and encoder are carried out, there is evidence that improvement over the HDR-10 anchor can be achieved.

  4. Wide dynamic range enrichment method of semiconducting single-walled carbon nanotubes with weak field centrifugation

    PubMed Central

    Reis, Wieland G.; Tomović, Željko; Weitz, R. Thomas; Krupke, Ralph; Mikhael, Jules

    2017-01-01

    The potential of single–walled carbon nanotubes (SWCNTs) to outperform silicon in electronic application was finally enabled through selective separation of semiconducting nanotubes from the as-synthesized statistical mix with polymeric dispersants. Such separation methods provide typically high semiconducting purity samples with narrow diameter distribution, i.e. almost single chiralities. But for a wide range of applications high purity mixtures of small and large diameters are sufficient or even required. Here we proof that weak field centrifugation is a diameter independent method for enrichment of semiconducting nanotubes. We show that the non-selective and strong adsorption of polyarylether dispersants on nanostructured carbon surfaces enables simple separation of diverse raw materials with different SWCNT diameter. In addition and for the first time, we demonstrate that increased temperature enables higher purity separation. Furthermore we show that the mode of action behind this electronic enrichment is strongly connected to both colloidal stability and protonation. By giving simple access to electronically sorted SWCNTs of any diameter, the wide dynamic range of weak field centrifugation can provide economical relevance to SWCNTs. PMID:28317942

  5. Wide dynamic range enrichment method of semiconducting single-walled carbon nanotubes with weak field centrifugation

    NASA Astrophysics Data System (ADS)

    Reis, Wieland G.; Tomović, Željko; Weitz, R. Thomas; Krupke, Ralph; Mikhael, Jules

    2017-03-01

    The potential of single–walled carbon nanotubes (SWCNTs) to outperform silicon in electronic application was finally enabled through selective separation of semiconducting nanotubes from the as-synthesized statistical mix with polymeric dispersants. Such separation methods provide typically high semiconducting purity samples with narrow diameter distribution, i.e. almost single chiralities. But for a wide range of applications high purity mixtures of small and large diameters are sufficient or even required. Here we proof that weak field centrifugation is a diameter independent method for enrichment of semiconducting nanotubes. We show that the non-selective and strong adsorption of polyarylether dispersants on nanostructured carbon surfaces enables simple separation of diverse raw materials with different SWCNT diameter. In addition and for the first time, we demonstrate that increased temperature enables higher purity separation. Furthermore we show that the mode of action behind this electronic enrichment is strongly connected to both colloidal stability and protonation. By giving simple access to electronically sorted SWCNTs of any diameter, the wide dynamic range of weak field centrifugation can provide economical relevance to SWCNTs.

  6. Exploring the dynamics of phase separation in colloid-polymer mixtures with long range attraction.

    PubMed

    Sabin, Juan; Bailey, Arthur E; Frisken, Barbara J

    2016-06-28

    We have studied the kinetics of phase separation and gel formation in a low-dispersity colloid - non-adsorbing polymer system with long range attraction using small-angle light scattering. This system exhibits two-phase and three-phase coexistence of gas, liquid and crystal phases when the strength of attraction is between 2 and 4kBT and gel phases when the strength of attraction is increased. For those samples that undergo macroscopic phase separation, whether to gas-crystal, gas-liquid or gas-liquid-crystal coexistence, we observe dynamic scaling of the structure factor and growth of a characteristic length scale that behaves as expected for phase separation in fluids. In samples that gel, the power law associated with the growth of the dominant length scale is not equal to 1/3, but appears to depend mainly on the strength of attraction, decreasing from 1/3 for samples near the coexistence region to 1/27 at 8kBT, over a wide range of colloid and polymer concentrations.

  7. a Step Towards Dynamic Scene Analysis with Active Multi-View Range Imaging Systems

    NASA Astrophysics Data System (ADS)

    Weinmann, M.; Jutzi, B.

    2012-07-01

    Obtaining an appropriate 3D description of the local environment remains a challenging task in photogrammetric research. As terrestrial laser scanners (TLSs) perform a highly accurate, but time-dependent spatial scanning of the local environment, they are only suited for capturing static scenes. In contrast, new types of active sensors provide the possibility of simultaneously capturing range and intensity information by images with a single measurement, and the high frame rate also allows for capturing dynamic scenes. However, due to the limited field of view, one observation is not sufficient to obtain a full scene coverage and therefore, typically, multiple observations are collected from different locations. This can be achieved by either placing several fixed sensors at different known locations or by using a moving sensor. In the latter case, the relation between different observations has to be estimated by using information extracted from the captured data and then, a limited field of view may lead to problems if there are too many moving objects within it. Hence, a moving sensor platform with multiple and coupled sensor devices offers the advantages of an extended field of view which results in a stabilized pose estimation, an improved registration of the recorded point clouds and an improved reconstruction of the scene. In this paper, a new experimental setup for investigating the potentials of such multi-view range imaging systems is presented which consists of a moving cable car equipped with two synchronized range imaging devices. The presented setup allows for monitoring in low altitudes and it is suitable for getting dynamic observations which might arise from moving cars or from moving pedestrians. Relying on both 3D geometry and 2D imagery, a reliable and fully automatic approach for co-registration of captured point cloud data is presented which is essential for a high quality of all subsequent tasks. The approach involves using sparse point

  8. Hydrogen detector

    DOEpatents

    Kanegae, Naomichi; Ikemoto, Ichiro

    1980-01-01

    A hydrogen detector of the type in which the interior of the detector is partitioned by a metal membrane into a fluid section and a vacuum section. Two units of the metal membrane are provided and vacuum pipes are provided independently in connection to the respective units of the metal membrane. One of the vacuum pipes is connected to a vacuum gauge for static equilibrium operation while the other vacuum pipe is connected to an ion pump or a set of an ion pump and a vacuum gauge both designed for dynamic equilibrium operation.

  9. Unattended real-time re-establishment of visibility in high dynamic range video and stills

    NASA Astrophysics Data System (ADS)

    Abidi, B.

    2014-05-01

    We describe a portable unattended persistent surveillance system that corrects for harsh illumination conditions, where bright sun light creates mixed contrast effects, i.e., heavy shadows and washouts. These effects result in high dynamic range scenes, where illuminance can vary from few luxes to a 6 figure value. When using regular monitors and cameras, such wide span of illuminations can only be visualized if the actual range of values is compressed, leading to the creation of saturated and/or dark noisy areas and a loss of information in these areas. Images containing extreme mixed contrast cannot be fully enhanced from a single exposure, simply because all information is not present in the original data. The active intervention in the acquisition process is required. A software package, capable of integrating multiple types of COTS and custom cameras, ranging from Unmanned Aerial Systems (UAS) data links to digital single-lens reflex cameras (DSLR), is described. Hardware and software are integrated via a novel smart data acquisition algorithm, which communicates to the camera the parameters that would maximize information content in the final processed scene. A fusion mechanism is then applied to the smartly acquired data, resulting in an enhanced scene where information in both dark and bright areas is revealed. Multi-threading and parallel processing are exploited to produce automatic real time full motion corrected video. A novel enhancement algorithm was also devised to process data from legacy and non-controllable cameras. The software accepts and processes pre-recorded sequences and stills, enhances visible, night vision, and Infrared data, and successfully applies to night time and dark scenes. Various user options are available, integrating custom functionalities of the application into intuitive and easy to use graphical interfaces. The ensuing increase in visibility in surveillance video and intelligence imagery will expand the performance and

  10. Maternal effects and range expansion: a key factor in a dynamic process?

    PubMed Central

    Duckworth, Renée A.

    2009-01-01

    generated in newly colonized populations. More generally, these results suggest that, as a key source of variation in colonizing phenotypes, maternal effects are of crucial importance for understanding the dynamics of range expansion. PMID:19324612

  11. Color signal encoding for high dynamic range and wide color gamut based on human perception

    NASA Astrophysics Data System (ADS)

    Nezamabadi, Mahdi; Miller, Scott; Daly, Scott; Atkins, Robin

    2014-01-01

    A new EOTF based on human perception, called PQ (Perceptual Quantizer), was proposed in a previous work (SMPTE Mot. Imag. J 2013, 122:52-59) and its performance was evaluated for a wide range of luminance levels and encoding bitdepth values. This paper is an extension of that previous work to include the color aspects of the PQ signal encoding. The efficiency of the PQ encoding and bit-depth requirements were evaluated and compared for standard color gamuts of Rec 709 (SRGB), and the wide color gamuts of Rec 2020, P3, and ACES for a variety of signal representations as RGB, YCbCr, and XYZ. In a selected color space for any potential local gray level 26 color samples were simulated by deviating one quantization step from the original color in each signal dimension. The quantization step sizes were simulated based on the PQ and gamma curves for different bit-depth values and luminance ranges for each of the color gamut spaces and signal representations. Color differences between the gray field and the simulated color samples were computed using CIE DE2000 color difference equation. The maximum color difference values (quantization error) were used as a metric to evaluate the performance of the corresponding EOTF curve. Extended color gamuts were found to require more bits to maintain low quantization error. Extended dynamic range required fewer additional bits in to maintain quantization error. Regarding the visual detection thresholds, the minimum bit-depth required by the PQ and gamma encodings are evaluated and compared through visual experiments.

  12. Chaotic dynamics and thermodynamics of periodic systems with long-range forces

    NASA Astrophysics Data System (ADS)

    Kumar, Pankaj

    Gravitational and electromagnetic interactions form the backbone of our theoretical understanding of the universe. While, in general, such interactions are analytically inexpressible for three-dimensional infinite systems, one-dimensional modeling allows one to treat the long-range forces exactly. Not only are one-dimensional systems of profound intrinsic interest, physicists often rely on one-dimensional models as a starting point in the analysis of their more complicated higher-dimensional counterparts. In the analysis of large systems considered in cosmology and plasma physics, periodic boundary conditions are a natural choice and have been utilized in the study of one dimensional Coulombic and gravitational systems. Such studies often employ numerical simulations to validate the theoretical predictions, and in cases where theoretical relations have not been mathematically formulated, numerical simulations serve as a powerful method in characterizing the system's physical properties. In this dissertation, analytic techniques are formulated to express the exact phase-space dynamics of spatially-periodic one-dimensional Coulombic and gravitational systems. Closed-form versions of the Hamiltonian and the electric field are derived for single-component and two-component Coulombic systems, placing the two on the same footing as the gravitational counterpart. Furthermore, it is demonstrated that a three-body variant of the spatially-periodic Coulombic or gravitational system may be reduced isomorphically to a periodic system of a single particle in a two-dimensional rhombic potential. The analytic results are utilized for developing and implementing efficient computational tools to study the dynamical and the thermodynamic properties of the systems without resorting to numerical approximations. Event-driven algorithms are devised to obtain Lyapunov spectra, radial distribution function, pressure, caloric curve, and Poincare surface of section through an N

  13. Spiral silicon drift detectors

    SciTech Connect

    Rehak, P.; Gatti, E.; Longoni, A.; Sampietro, M.; Holl, P.; Lutz, G.; Kemmer, J.; Prechtel, U.; Ziemann, T.

    1988-01-01

    An advanced large area silicon photodiode (and x-ray detector), called Spiral Drift Detector, was designed, produced and tested. The Spiral Detector belongs to the family of silicon drift detectors and is an improvement of the well known Cylindrical Drift Detector. In both detectors, signal electrons created in silicon by fast charged particles or photons are drifting toward a practically point-like collection anode. The capacitance of the anode is therefore kept at the minimum (0.1pF). The concentric rings of the cylindrical detector are replaced by a continuous spiral in the new detector. The spiral geometry detector design leads to a decrease of the detector leakage current. In the spiral detector all electrons generated at the silicon-silicon oxide interface are collected on a guard sink rather than contributing to the detector leakage current. The decrease of the leakage current reduces the parallel noise of the detector. This decrease of the leakage current and the very small capacities of the detector anode with a capacitively matched preamplifier may improve the energy resolution of Spiral Drift Detectors operating at room temperature down to about 50 electrons rms. This resolution is in the range attainable at present only by cooled semiconductor detectors. 5 refs., 10 figs.

  14. Pyroelectric detectors

    NASA Technical Reports Server (NTRS)

    Haller, Eugene E.; Beeman, Jeffrey; Hansen, William L.; Hubbard, G. Scott; Mcmurray, Robert E., Jr.

    1990-01-01

    The multi-agency, long-term Global Change programs, and specifically NASA's Earth Observing system, will require some new and advanced photon detector technology which must be specifically tailored for long-term stability, broad spectral range, cooling constraints, and other parameters. Whereas MCT and GaAs alloy based photovoltaic detectors and detector arrays reach most impressive results to wavelengths as long as 12 microns when cooled to below 70 K, other materials, such as ferroelectrics and pyroelectrics, appear to offer special opportunities beyond 12 microns and above 70 K. These materials have found very broad use in a wide variety of room temperature applications. Little is known about these classes of materials at sub-room temperatures and no photon detector results have been reported. From the limited information available, researchers conclude that the room temperature values of D asterisk greater than or equal to 10(exp 9) cm Hz(exp 1/2)/W may be improved by one to two orders of magnitude upon cooling to temperatures around 70 K. Improvements of up to one order of magnitude appear feasible for temperatures achievable by passive cooling. The flat detector response over a wavelength range reaching from the visible to beyond 50 microns, which is an intrinsic advantage of bolometric devices, makes for easy calibration. The fact that these materials have been developed for reduced temperature applications makes ferro- and pyroelectric materials most attractive candidates for serious exploration.

  15. General solution for high dynamic range three-dimensional shape measurement using the fringe projection technique

    NASA Astrophysics Data System (ADS)

    Feng, Shijie; Zhang, Yuzhen; Chen, Qian; Zuo, Chao; Li, Rubin; Shen, Guochen

    2014-08-01

    This paper presents a general solution for realizing high dynamic range three-dimensional (3-D) shape measurement based on fringe projection. Three concrete techniques are involved in the solution for measuring object with large range of reflectivity (LRR) or one with shiny specular surface. For the first technique, the measured surface reflectivities are sub-divided into several groups based on its histogram distribution, then the optimal exposure time for each group can be predicted adaptively so that the bright as well as dark areas on the measured surface are able to be handled without any compromise. Phase-shifted images are then captured at the calculated exposure times and a composite phase-shifted image is generated by extracting the optimally exposed pixels in the raw fringes images. For the second technique, it is proposed by introducing two orthogonal polarizers which are placed separately in front of the camera and projector into the first technique and the third one is developed by combining the second technique with the strategy of properly altering the angle between the transmission axes of the two polarizers. Experimental results show that the first technique can effectively improve the measurement accuracy of diffuse objects with LRR, the second one is capable of measuring object with weak specular reflection (WSR: e.g. shiny plastic surface) and the third can inspect surface with strong specular reflection (SSR: e.g. highlight on aluminum alloy) precisely. Further, more complex scene, such as the one with LRR and WSR, or even the one simultaneously involving LRR, WSR and SSR, can be measured accurately by the proposed solution.

  16. Orthostatic stress is necessary to maintain the dynamic range of cardiovascular control in space

    NASA Technical Reports Server (NTRS)

    Baisch, J. F.; Wolfram, G.; Beck, L.; Drummer, C.; Stormer, I.; Buckey, J.; Blomqvist, G.

    2000-01-01

    In the upright position, gravity fills the low-pressure systems of human circulation with blood and interstitial fluid in the sections below the diaphragm. Without gravity one pressure component in the vessels disappears and the relationship between hydrostatic pressure and oncotic pressure, which regulates fluid passage across the capillary endothelium in the terminal vascular bed, shifts constantly. The visible consequences of this are a puffy face and "bird" legs. The plasma volume shrinks in space and the range of cardiovascular control is reduced. When they stand up for the first time after landing, 30-50% of astronauts suffer from orthostatic intolerance. It remains unclear whether microgravity impairs cardiovascular reflexes, or whether it is the altered volume status that causes the cardiovascular instability following space flight. Lower body negative pressure was used in several space missions to stimulate the cardiovascular reflexes before, during and after a space flight. The results show that cardiovascular reflexes are maintained in microgravity. However, the astronauts' volume status changed in space, towards a volume-retracted state, as measurements of fluid-regulating hormones have shown. It can be hypothesized that the control of circulation and body fluid homeostasis in humans is adapted to their upright posture in the Earth's gravitational field. Autonomic control regulates fluid distribution to maintain the blood pressure in that posture, which most of us have to cope with for two-thirds of the day. A determined amount of interstitial volume is necessary to maintain the dynamic range of cardiovascular control in the upright posture; otherwise orthostatic intolerance may occur more often.

  17. Myosin-Va and dynamic actin oppose microtubules to drive long-range organelle transport.

    PubMed

    Evans, Richard D; Robinson, Christopher; Briggs, Deborah A; Tooth, David J; Ramalho, Jose S; Cantero, Marta; Montoliu, Lluis; Patel, Shyamal; Sviderskaya, Elena V; Hume, Alistair N

    2014-08-04

    In animal cells, microtubule and actin tracks and their associated motors (dynein, kinesin, and myosin) are thought to regulate long- and short-range transport, respectively. Consistent with this, microtubules extend from the perinuclear centrosome to the plasma membrane and allow bidirectional cargo transport over long distances (>1 μm). In contrast, actin often comprises a complex network of short randomly oriented filaments, suggesting that myosin motors move cargo short distances. These observations underpin the "highways and local roads" model for transport along microtubule and actin tracks. The "cooperative capture" model exemplifies this view and suggests that melanosome distribution in melanocyte dendrites is maintained by long-range transport on microtubules followed by actin/myosin-Va-dependent tethering. In this study, we used cell normalization technology to quantitatively examine the contribution of microtubules and actin/myosin-Va to organelle distribution in melanocytes. Surprisingly, our results indicate that microtubules are essential for centripetal, but not centrifugal, transport. Instead, we find that microtubules retard a centrifugal transport process that is dependent on myosin-Va and a population of dynamic F-actin. Functional analysis of mutant proteins indicates that myosin-Va works as a transporter dispersing melanosomes along actin tracks whose +/barbed ends are oriented toward the plasma membrane. Overall, our data highlight the role of myosin-Va and actin in transport, and not tethering, and suggest a new model in which organelle distribution is determined by the balance between microtubule-dependent centripetal and myosin-Va/actin-dependent centrifugal transport. These observations appear to be consistent with evidence coming from other systems showing that actin/myosin networks can drive long-distance organelle transport and positioning.

  18. Signal enhancement in optical projection tomography via virtual high dynamic range imaging of single exposure

    NASA Astrophysics Data System (ADS)

    Yang, Yujie; Dong, Di; Shi, Liangliang; Wang, Jun; Yang, Xin; Tian, Jie

    2015-03-01

    Optical projection tomography (OPT) is a mesoscopic scale optical imaging technique for specimens between 1mm and 10mm. OPT has been proven to be immensely useful in a wide variety of biological applications, such as developmental biology and pathology, but its shortcomings in imaging specimens containing widely differing contrast elements are obvious. The longer exposure for high intensity tissues may lead to over saturation of other areas, whereas a relatively short exposure may cause similarity with surrounding background. In this paper, we propose an approach to make a trade-off between capturing weak signals and revealing more details for OPT imaging. This approach consists of three steps. Firstly, the specimens are merely scanned in 360 degrees above a normal exposure but non-overexposure to acquire the projection data. This reduces the photo bleaching and pre-registration computation compared with multiple different exposures in conventional high dynamic range (HDR) imaging method. Secondly, three virtual channels are produced for each projection image based on the histogram distribution to simulate the low, normal and high exposure images used in the traditional HDR technology in photography. Finally, each virtual channel is normalized to the full gray scale range and three channels are recombined into one image using weighting coefficients optimized by a standard eigen-decomposition method. After applying our approach on the projection data, filtered back projection (FBP) algorithm is carried out for 3-dimentional reconstruction. The neonatal wild-type mouse paw has been scanned to verify this approach. Results demonstrated the effectiveness of the proposed approach.

  19. Myosin-Va and Dynamic Actin Oppose Microtubules to Drive Long-Range Organelle Transport

    PubMed Central

    Evans, Richard D.; Robinson, Christopher; Briggs, Deborah A.; Tooth, David J.; Ramalho, Jose S.; Cantero, Marta; Montoliu, Lluis; Patel, Shyamal; Sviderskaya, Elena V.; Hume, Alistair N.

    2014-01-01

    Summary In animal cells, microtubule and actin tracks and their associated motors (dynein, kinesin, and myosin) are thought to regulate long- and short-range transport, respectively [1–8]. Consistent with this, microtubules extend from the perinuclear centrosome to the plasma membrane and allow bidirectional cargo transport over long distances (>1 μm). In contrast, actin often comprises a complex network of short randomly oriented filaments, suggesting that myosin motors move cargo short distances. These observations underpin the “highways and local roads” model for transport along microtubule and actin tracks [2]. The “cooperative capture” model exemplifies this view and suggests that melanosome distribution in melanocyte dendrites is maintained by long-range transport on microtubules followed by actin/myosin-Va-dependent tethering [5, 9]. In this study, we used cell normalization technology to quantitatively examine the contribution of microtubules and actin/myosin-Va to organelle distribution in melanocytes. Surprisingly, our results indicate that microtubules are essential for centripetal, but not centrifugal, transport. Instead, we find that microtubules retard a centrifugal transport process that is dependent on myosin-Va and a population of dynamic F-actin. Functional analysis of mutant proteins indicates that myosin-Va works as a transporter dispersing melanosomes along actin tracks whose +/barbed ends are oriented toward the plasma membrane. Overall, our data highlight the role of myosin-Va and actin in transport, and not tethering, and suggest a new model in which organelle distribution is determined by the balance between microtubule-dependent centripetal and myosin-Va/actin-dependent centrifugal transport. These observations appear to be consistent with evidence coming from other systems showing that actin/myosin networks can drive long-distance organelle transport and positioning [10, 11]. PMID:25065759

  20. Integrated Dual Imaging Detector

    NASA Technical Reports Server (NTRS)

    Rust, David M.

    1999-01-01

    A new type of image detector was designed to simultaneously analyze the polarization of light at all picture elements in a scene. The integrated Dual Imaging detector (IDID) consists of a lenslet array and a polarizing beamsplitter bonded to a commercial charge coupled device (CCD). The IDID simplifies the design and operation of solar vector magnetographs and the imaging polarimeters and spectroscopic imagers used, for example, in atmosphere and solar research. When used in a solar telescope, the vector magnetic fields on the solar surface. Other applications include environmental monitoring, robot vision, and medical diagnoses (through the eye). Innovations in the IDID include (1) two interleaved imaging arrays (one for each polarization plane); (2) large dynamic range (well depth of 10(exp 5) electrons per pixel); (3) simultaneous readout and display of both images; and (4) laptop computer signal processing to produce polarization maps in field situations.

  1. 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.

  2. Using high-dynamic-range digital repeat photography to measure plant phenology in a subarctic mire.

    NASA Astrophysics Data System (ADS)

    Garnello, A.; Dye, D. G.; Bogle, R.; Vogel, J.; Saleska, S. R.; Crill, P. M.

    2015-12-01

    A novel Visual Imaging System (VIS) was designed and deployed in a subarctic mire (68° 20' N, 19° 03'E) aimed at cataloging plant biological changes (phenology) and analyzing seasonal color shifts in relation to micrometeorological data along the summer growing season: June-November, 2015. The VIS is designed as a tower-based, solar-powered, automated phenology camera (Phenocam) that collects red, green, blue (RGB) and near-infrared (NIR) landscape images in High Dynamic Range (HDR) with fully programmable temporal resolution. HDR composite images are made through combining a series of rapid-capture photos with incremental increases of exposure times and a fixed focus, minimizing the spatial and visual data lost from shadows or from the over-saturation of light. This visual record of ecosystem phenology stages (Phenophases) is being used to (1) investigate vegetation-dependent spectral indices; (2) establish a cross-year comparison record of Phenophase seasonality; (3) investigate meteorological-dependent vegetation Phenophases; (4) provide ground-truthing measurements that enhance broader spatial-scale remote sensing analyses of subarctic wetlands.

  3. High Dynamic Range Image rendering of color in chameleons' camouflage using optical thin films

    NASA Astrophysics Data System (ADS)

    Prusten, Mark

    2008-08-01

    High Dynamic Range Image (HDRI) rendering and animation of color in the camouflage of chameleons is developed utilizing thin film optics. Chameleons are a lizard species, and have the ability to change their skin color. This change in color is an expression of the physical and physiological conditions of the lizard, and plays a part in communication. The different colors that can be produced depending on the species include pink, blue, red, orange, green, black, brown and yellow. The modeling, simulation, and rendering of the color, which their skin incorporates, thin film optical stacks. The skin of a chameleon has four layers, which together produce various colors. The outside transparent layer has chromatophores cells, of two kinds of color, yellow and red. Next there are two more layers that reflect light: one blue and the other white. The innermost layer contains dark pigment granules or melanophore cells that influences the amount of reflected light. All of these pigment cells can rapidly relocate their pigments, thereby influencing the color of the chameleon. Techniques like subsurface scattering, the simulation of volumetric scattering of light underneath the objects surface, and final gathering are defined in custom shaders and material phenomena for the renderer. The workflow developed to model the chameleon's skin is also applied to simulation and rendering of hair and fur camouflage, which does not exist in nature.

  4. Utilizing multiple state variables to improve the dynamic range of analog switching in a memristor

    SciTech Connect

    Jeong, YeonJoo; Kim, Sungho; Lu, Wei D.

    2015-10-26

    Memristors and memristive systems have been extensively studied for data storage and computing applications such as neuromorphic systems. To act as synapses in neuromorphic systems, the memristor needs to exhibit analog resistive switching (RS) behavior with incremental conductance change. In this study, we show that the dynamic range of the analog RS behavior can be significantly enhanced in a tantalum-oxide-based memristor. By controlling different state variables enabled by different physical effects during the RS process, the gradual filament expansion stage can be selectively enhanced without strongly affecting the abrupt filament length growth stage. Detailed physics-based modeling further verified the observed experimental effects and revealed the roles of oxygen vacancy drift and diffusion processes, and how the diffusion process can be selectively enhanced during the filament expansion stage. These findings lead to more desirable and reliable memristor behaviors for analog computing applications. Additionally, the ability to selectively control different internal physical processes demonstrated in the current study provides guidance for continued device optimization of memristor devices in general.

  5. Dynamic magnetic susceptibility of systems with long-range magnetic order

    SciTech Connect

    Vannette, Matthew Dano

    2009-01-01

    The utility of the TDR as an instrument in the study of magnetically ordered materials has been expanded beyond the simple demonstration purposes. Results of static applied magnetic field dependent measurements of the dynamic magnetic susceptibility, χ, of various ferromagnetic (FM) and antiferromagnetic (AFM) materials showing a range of transition temperatures (1-800 K) are presented. Data was collected primarily with a tunnel diode resonator (TDR) at different radio-frequencies (~10-30 MHz). In the vicinity of TC local moment ferromagnets show a very sharp, narrow peak in χ which is suppressed in amplitude and shifted to higher temperatures as the static bias field is increased. Unexpectedly, critical scaling analysis fails for these data. It is seen that these data are frequency dependent, however there is no simple method whereby measurement frequency can be changed in a controllable fashion. In contrast, itinerant ferromagnets show a broad maximum in χ well below TC which is suppressed and shifts to lower temperatures as the dc bias field is increased. The data on itinerant ferromagnets is fitted to a semi-phenomenological model that suggests the sample response is dominated by the uncompensated minority spins in the conduction band. Concluding remarks suggest possible scenarios to achieve frequency resolved data using the TDR as well as other fields in which the apparatus may be exploited.

  6. The relation of signal transduction to the sensitivity and dynamic range of bacterial chemotaxis.

    PubMed

    Namba, Toshinori; Nishikawa, Masatoshi; Shibata, Tatsuo

    2012-09-19

    Complex networks of interacting molecular components of living cells are responsible for many important processes, such as signal processing and transduction. An important challenge is to understand how the individual properties of these molecular interactions and biochemical transformations determine the system-level properties of biological functions. Here, we address the issue of the accuracy of signal transduction performed by a bacterial chemotaxis system. The chemotaxis sensitivity of bacteria to a chemoattractant gradient has been measured experimentally from bacterial aggregation in a chemoattractant-containing capillary. The observed precision of the chemotaxis depended on environmental conditions such as the concentration and molecular makeup of the chemoattractant. In a quantitative model, we derived the chemotactic response function, which is essential to describing the signal transduction process involved in bacterial chemotaxis. In the presence of a gradient, an analytical solution is derived that reveals connections between the chemotaxis sensitivity and the characteristics of the signaling system, such as reaction rates. These biochemical parameters are integrated into two system-level parameters: one characterizes the efficiency of gradient sensing, and the other is related to the dynamic range of chemotaxis. Thus, our approach explains how a particular signal transduction property affects the system-level performance of bacterial chemotaxis. We further show that the two parameters can be derived from published experimental data from a capillary assay, which successfully characterizes the performance of bacterial chemotaxis.

  7. Hardware-based smart camera for recovering high dynamic range video from multiple exposures

    NASA Astrophysics Data System (ADS)

    Lapray, Pierre-Jean; Heyrman, Barthélémy; Ginhac, Dominique

    2014-10-01

    In many applications such as video surveillance or defect detection, the perception of information related to a scene is limited in areas with strong contrasts. The high dynamic range (HDR) capture technique can deal with these limitations. The proposed method has the advantage of automatically selecting multiple exposure times to make outputs more visible than fixed exposure ones. A real-time hardware implementation of the HDR technique that shows more details both in dark and bright areas of a scene is an important line of research. For this purpose, we built a dedicated smart camera that performs both capturing and HDR video processing from three exposures. What is new in our work is shown through the following points: HDR video capture through multiple exposure control, HDR memory management, HDR frame generation, and representation under a hardware context. Our camera achieves a real-time HDR video output at 60 fps at 1.3 megapixels and demonstrates the efficiency of our technique through an experimental result. Applications of this HDR smart camera include the movie industry, the mass-consumer market, military, automotive industry, and surveillance.

  8. Extending the dynamic range of transcription factor action by translational regulation

    NASA Astrophysics Data System (ADS)

    Sokolowski, Thomas R.; Walczak, Aleksandra M.; Bialek, William; Tkačik, Gašper

    2016-02-01

    A crucial step in the regulation of gene expression is binding of transcription factor (TF) proteins to regulatory sites along the DNA. But transcription factors act at nanomolar concentrations, and noise due to random arrival of these molecules at their binding sites can severely limit the precision of regulation. Recent work on the optimization of information flow through regulatory networks indicates that the lower end of the dynamic range of concentrations is simply inaccessible, overwhelmed by the impact of this noise. Motivated by the behavior of homeodomain proteins, such as the maternal morphogen Bicoid in the fruit fly embryo, we suggest a scheme in which transcription factors also act as indirect translational regulators, binding to the mRNA of other regulatory proteins. Intuitively, each mRNA molecule acts as an independent sensor of the input concentration, and averaging over these multiple sensors reduces the noise. We analyze information flow through this scheme and identify conditions under which it outperforms direct transcriptional regulation. Our results suggest that the dual role of homeodomain proteins is not just a historical accident, but a solution to a crucial physics problem in the regulation of gene expression.

  9. Non-equilibrium entropy and dynamics in a system with long-range interactions

    NASA Astrophysics Data System (ADS)

    Rocha Filho, T. M.

    2016-05-01

    We extend the core-halo approach of Levin et al (2014 Phys. Rep. 535, 1) for the violent relaxation of long-range interacting system with a waterbag initial condition, in the case of a widely studied Hamiltonian mean field model. The Gibbs entropy maximization principle is considered with the constraints of energy conservation and of coarse-grained Casimir invariants of the Vlasov equation. The core-halo distribution function depends only on the one-particle mean-field energy, as is expected from the Jeans theorem, and depends on a set of parameters which in our approach is completely determined without having to solve an envelope equation for the contour of the initial state, as required in the original approach. We also show that a different ansatz can be used for the core-halo distribution with similar results. This work also reveals a link between a parametric resonance causing the non-equilibrium phase transition in the model, a dynamical property, and a discontinuity of the (non-equilibrium) entropy of the system.

  10. A Hybrid Shared-Memory Parallel Max-Tree Algorithm for Extreme Dynamic-Range Images.

    PubMed

    Moschini, Ugo; Meijster, Arnold; Wilkinson, Michael

    2017-03-30

    Max-trees, or component trees, are graph structures that represent the connected components of an image in a hierarchical way. Nowadays, many application fields rely on images with high-dynamic range or floating point values. Efficient sequential algorithms exist to build trees and compute attributes for images of any bit depth. However, we show that the current parallel algorithms perform poorly already with integers at bit depths higher than 16 bits per pixel. We propose a parallel method combining the two worlds of flooding and merging max-tree algorithms. First, a pilot max-tree of a quantized version of the image is built in parallel using a flooding method. Later, this structure is used in a parallel leaf-to-root approach to compute efficiently the final max-tree and to drive the merging of the sub-trees computed by the threads. We present an analysis of the performance both on simulated and actual 2D images and 3D volumes. Execution times are about 20 better than the fastest sequential algorithm and speed-up goes up to 30 40 on 64 threads.

  11. On the range of validity of the fluctuation theorem for stochastic Markovian dynamics

    NASA Astrophysics Data System (ADS)

    Rákos, A.; Harris, R. J.

    2008-05-01

    We consider the fluctuations of generalized currents in stochastic Markovian dynamics. The large deviations of current fluctuations are shown to obey a Gallavotti-Cohen (GC) type symmetry in systems with a finite state space. However, this symmetry is not guaranteed to hold in systems with an infinite state space. A simple example of such a case is the zero-range process (ZRP). Here we discuss in more detail the already reported (Harris et al 2006 Europhys. Lett. 75 227) breakdown of the GC symmetry in the context of the ZRP with open boundaries and we give a physical interpretation of the phases that appear. Furthermore, the earlier analytical results for the single-site case are extended to cover multiple-site systems. We also use our exact results to test an efficient numerical algorithm of Giardinà et al (2006 Phys. Rev. Lett. 96 120603), which was developed to measure the current large deviation function directly. We find that this method breaks down in some phases which we associate with the gapless spectrum of an effective Hamiltonian.

  12. Extending the Dynamic Range of the Ion Trap by Differential Mobility Filtration

    NASA Astrophysics Data System (ADS)

    Hall, Adam B.; Coy, Stephen L.; Kafle, Amol; Glick, James; Nazarov, Erkinjon; Vouros, Paul

    2013-09-01

    A miniature, planar, differential ion mobility spectrometer (DMS) was interfaced to an LCQ classic ion trap to conduct selective ion filtration prior to mass analysis in order to extend the dynamic range of the trap. Space charge effects are known to limit the functional ion storage capacity of ion trap mass analyzers and this, in turn, can affect the quality of the mass spectral data generated. This problem is further exacerbated in the analysis of mixtures where the indiscriminate introduction of matrix ions results in premature trap saturation with non-targeted species, thereby reducing the number of parent ions that may be used to conduct MS/MS experiments for quantitation or other diagnostic studies. We show that conducting differential mobility-based separations prior to mass analysis allows the isolation of targeted analytes from electrosprayed mixtures preventing the indiscriminate introduction of matrix ions and premature trap saturation with analytically unrelated species. Coupling these two analytical techniques is shown to enhance the detection of a targeted drug metabolite from a biological matrix. In its capacity as a selective ion filter, the DMS can improve the analytical performance of analyzers such as quadrupole (3D or linear) and ion cyclotron resonance (FT-ICR) ion traps that depend on ion accumulation.

  13. Acoustical correlates of performance on a dynamic range compression discrimination task.

    PubMed

    Sabin, Andrew T; Gallun, Frederick J; Souza, Pamela E

    2013-09-01

    Dynamic range compression is widely used to reduce the difference between the most and least intense portions of a signal. Such compression distorts the shape of the amplitude envelope of a signal, but it is unclear to what extent such distortions are actually perceivable by listeners. Here, the ability to distinguish between compressed and uncompressed versions of a noise vocoded sentence was initially measured in listeners with normal hearing while varying the threshold, ratio, attack, and release parameters. This narrow condition was selected in order to characterize perception under the most favorable listening conditions. The average behavioral sensitivity to compression was highly correlated to several acoustical indices of modulation depth. In particular, performance was highly correlated to the Euclidean distance between the modulation spectra of the uncompressed and compressed signals. Suggesting that this relationship is not restricted to the initial test conditions, the correlation remained largely unchanged both (1) when listeners with normal hearing were tested using a time-compressed version of the original signal, and (2) when listeners with impaired hearing were tested using the original signal. If this relationship generalizes to more ecologically valid conditions, it will provide a straightforward method for predicting the detectability of compression-induced distortions.

  14. Spontaneous activity in the piriform cortex extends the dynamic range of cortical odor coding.

    PubMed

    Tantirigama, Malinda L S; Huang, Helena H-Y; Bekkers, John M

    2017-02-28

    Neurons in the neocortex exhibit spontaneous spiking activity in the absence of external stimuli, but the origin and functions of this activity remain uncertain. Here, we show that spontaneous spiking is also prominent in a sensory paleocortex, the primary olfactory (piriform) cortex of mice. In the absence of applied odors, piriform neurons exhibit spontaneous firing at mean rates that vary systematically among neuronal classes. This activity requires the participation of NMDA receptors and is entirely driven by bottom-up spontaneous input from the olfactory bulb. Odor stimulation produces two types of spatially dispersed, odor-distinctive patterns of responses in piriform cortex layer 2 principal cells: Approximately 15% of cells are excited by odor, and another approximately 15% have their spontaneous activity suppressed. Our results show that, by allowing odor-evoked suppression as well as excitation, the responsiveness of piriform neurons is at least twofold less sparse than currently believed. Hence, by enabling bidirectional changes in spiking around an elevated baseline, spontaneous activity in the piriform cortex extends the dynamic range of odor representation and enriches the coding space for the representation of complex olfactory stimuli.

  15. Extending the dynamic range of the ion trap by differential mobility filtration.

    PubMed

    Hall, Adam B; Coy, Stephen L; Kafle, Amol; Glick, James; Nazarov, Erkinjon; Vouros, Paul

    2013-09-01

    A miniature, planar, differential ion mobility spectrometer (DMS) was interfaced to an LCQ classic ion trap to conduct selective ion filtration prior to mass analysis in order to extend the dynamic range of the trap. Space charge effects are known to limit the functional ion storage capacity of ion trap mass analyzers and this, in turn, can affect the quality of the mass spectral data generated. This problem is further exacerbated in the analysis of mixtures where the indiscriminate introduction of matrix ions results in premature trap saturation with non-targeted species, thereby reducing the number of parent ions that may be used to conduct MS/MS experiments for quantitation or other diagnostic studies. We show that conducting differential mobility-based separations prior to mass analysis allows the isolation of targeted analytes from electrosprayed mixtures preventing the indiscriminate introduction of matrix ions and premature trap saturation with analytically unrelated species. Coupling these two analytical techniques is shown to enhance the detection of a targeted drug metabolite from a biological matrix. In its capacity as a selective ion filter, the DMS can improve the analytical performance of analyzers such as quadrupole (3D or linear) and ion cyclotron resonance (FT-ICR) ion traps that depend on ion accumulation.

  16. High-dynamic-range 4-Mpixel CMOS image sensor for scientific applications

    NASA Astrophysics Data System (ADS)

    Vu, Paul; Fowler, Boyd; Liu, Chiao; Mims, Steve; Bartkovjak, Peter; Do, Hung; Li, Wang; Appelbaum, Jeff; Lopez, Angel

    2012-03-01

    As bio-technology transitions from research and development to high volume production, dramatic improvements in image sensor performance will be required to support the throughput and cost requirements of this market. This includes higher resolution, higher frame rates, higher quantum efficiencies, increased system integration, lower read-noise, and lower device costs. We present the performance of a recently developed low noise 2048(H) x 2048(V) CMOS image sensor optimized for scientific applications such as life science imaging, microscopy, as well as industrial inspection applications. The sensor architecture consists of two identical halves which can be operated independently and the imaging array consists of 4T pixels with pinned photodiodes on a 6.5μm pitch with integrated micro-lens. The operation of the sensor is programmable through a SPI interface. The measured peak quantum efficiency of the sensor is 73% at 600nm, and the read noise is about 1.1e- RMS at 100 fps data rate. The sensor features dual gain column parallel ouput amplifiers with 11-bit single slope ADCs. The full well capacity is greater than 36ke-, the dark current is less than 7pA/cm2 at 20°C. The sensor achieves an intra-scene linear dynamic range of greater than 91dB (36000:1) at room temperature.

  17. Carbon nanotube vacuum gauges with wide-dynamic range and processes thereof

    NASA Technical Reports Server (NTRS)

    Manohara, Harish (Inventor); Kaul, Anupama B. (Inventor)

    2013-01-01

    A miniature thermal conductivity gauge employs a carbon single-walled-nanotube. The gauge operates on the principle of thermal exchange between the voltage-biased nanotube and the surrounding gas at low levels of power and low temperatures to measure vacuum across a wide dynamic range. The gauge includes two terminals, a source of constant voltage to the terminals, a single-walled carbon nanotube between the terminals, a calibration of measured conductance of the nanotube to magnitudes of surrounding vacuum and a current meter in electrical communication with the source of constant voltage. Employment of the nanotube for measuring vacuum includes calibrating the electrical conductance of the nanotube to magnitudes of vacuum, exposing the nanotube to a vacuum, applying a constant voltage across the nanotube, measuring the electrical conductance of the nanotube in the vacuum with the constant voltage applied and converting the measured electrical conductance to the corresponding calibrated magnitude of vacuum using the calibration. The nanotube may be suspended to minimize heat dissipation through the substrate, increasing sensitivity at even tower pressures.

  18. Comparison of performance between rescaled range analysis and rescaled variance analysis in detecting abrupt dynamic change

    NASA Astrophysics Data System (ADS)

    He, Wen-Ping; Liu, Qun-Qun; Jiang, Yun-Di; Lu, Ying

    2015-04-01

    In the present paper, a comparison of the performance between moving cutting data-rescaled range analysis (MC-R/S) and moving cutting data-rescaled variance analysis (MC-V/S) is made. The results clearly indicate that the operating efficiency of the MC-R/S algorithm is higher than that of the MC-V/S algorithm. In our numerical test, the computer time consumed by MC-V/S is approximately 25 times that by MC-R/S for an identical window size in artificial data. Except for the difference in operating efficiency, there are no significant differences in performance between MC-R/S and MC-V/S for the abrupt dynamic change detection. MC-R/S and MC-V/S both display some degree of anti-noise ability. However, it is important to consider the influences of strong noise on the detection results of MC-R/S and MC-V/S in practical application processes. Project supported by the National Basic Research Program of China (Grant No. 2012CB955902) and the National Natural Science Foundation of China (Grant Nos. 41275074, 41475073, and 41175084).

  19. Low-complexity, high-speed, and high-dynamic range time-to-impact algorithm

    NASA Astrophysics Data System (ADS)

    Åström, Anders; Forchheimer, Robert

    2012-10-01

    We present a method suitable for a time-to-impact sensor. Inspired by the seemingly "low" complexity of small insects, we propose a new approach to optical flow estimation that is the key component in time-to-impact estimation. The approach is based on measuring time instead of the apparent motion of points in the image plane. The specific properties of the motion field in the time-to-impact application are used, such as measuring only along a one-dimensional (1-D) line and using simple feature points, which are tracked from frame to frame. The method lends itself readily to be implemented in a parallel processor with an analog front-end. Such a processing concept [near-sensor image processing (NSIP)] was described for the first time in 1983. In this device, an optical sensor array and a low-level processing unit are tightly integrated into a hybrid analog-digital device. The high dynamic range, which is a key feature of NSIP, is used to extract the feature points. The output from the device consists of a few parameters, which will give the time-to-impact as well as possible transversal speed for off-centered viewing. Performance and complexity aspects of the implementation are discussed, indicating that time-to-impact data can be achieved at a rate of 10 kHz with today's technology.

  20. Extending the Dynamic Range of the Ion Trap by Differential Mobility Filtration

    PubMed Central

    Hall, Adam B.; Coy, Stephen L.; Kafle, Amol; Glick, James; Nazarov, Erkinjon

    2013-01-01

    A miniature, planar, differential ion mobility spectrometer (DMS) was interfaced to an LCQ classic ion trap to conduct selective ion filtration prior to mass analysis in order to extend the dynamic range of the trap. Space charge effects are known to limit the functional ion storage capacity of ion trap mass analyzers and this, in turn, can affect the quality of the mass spectral data generated. This problem is further exacerbated in the analysis of mixtures where the indiscriminate introduction of matrix ions results in premature trap saturation with non-targeted species, thereby reducing the number of parent ions that may be used to conduct MS/MS experiments for quantitation or other diagnostic studies. We show that conducting differential mobility-based separations prior to mass analysis allows the isolation of targeted analytes from electrosprayed mixtures preventing the indiscriminate introduction of matrix ions and premature trap saturation with analytically unrelated species. Coupling these two analytical techniques is shown to enhance the detection of a targeted drug metabolite from a biological matrix. In its capacity as a selective ion filter, the DMS can improve the analytical performance of analyzers such as quadrupole (3-D or linear) and ion cyclotron resonance (FT-ICR) ion traps that depend on ion accumulation. PMID:23797861

  1. Ultrananocrystalline Diamond Cantilever Wide Dynamic Range Acceleration/Vibration /Pressure Sensor

    DOEpatents

    Krauss, Alan R.; Gruen, Dieter M.; Pellin, Michael J.; Auciello, Orlando

    2003-09-02

    An ultrananocrystalline diamond (UNCD) element formed in a cantilever configuration is used in a highly sensitive, ultra-small sensor for measuring acceleration, shock, vibration and static pressure over a wide dynamic range. The cantilever UNCD element may be used in combination with a single anode, with measurements made either optically or by capacitance. In another embodiment, the cantilever UNCD element is disposed between two anodes, with DC voltages applied to the two anodes. With a small AC modulated voltage applied to the UNCD cantilever element and because of the symmetry of the applied voltage and the anode-cathode gap distance in the Fowler-Nordheim equation, any change in the anode voltage ratio V1/V2 required to maintain a specified current ratio precisely matches any displacement of the UNCD cantilever element from equilibrium. By measuring changes in the anode voltage ratio required to maintain a specified current ratio, the deflection of the UNCD cantilever can be precisely determined. By appropriately modulating the voltages applied between the UNCD cantilever and the two anodes, or limit electrodes, precise independent measurements of pressure, uniaxial acceleration, vibration and shock can be made. This invention also contemplates a method for fabricating the cantilever UNCD structure for the sensor.

  2. Ultrananocrystalline diamond cantilever wide dynamic range acceleration/vibration/pressure sensor

    DOEpatents

    Krauss, Alan R.; Gruen, Dieter M.; Pellin, Michael J.; Auciello, Orlando

    2002-07-23

    An ultrananocrystalline diamond (UNCD) element formed in a cantilever configuration is used in a highly sensitive, ultra-small sensor for measuring acceleration, shock, vibration and static pressure over a wide dynamic range. The cantilever UNCD element may be used in combination with a single anode, with measurements made either optically or by capacitance. In another embodiment, the cantilever UNCD element is disposed between two anodes, with DC voltages applied to the two anodes. With a small AC modulated voltage applied to the UNCD cantilever element and because of the symmetry of the applied voltage and the anode-cathode gap distance in the Fowler-Nordheim equation, any change in the anode voltage ratio V1/N2 required to maintain a specified current ratio precisely matches any displacement of the UNCD cantilever element from equilibrium. By measuring changes in the anode voltage ratio required to maintain a specified current ratio, the deflection of the UNCD cantilever can be precisely determined. By appropriately modulating the voltages applied between the UNCD cantilever and the two anodes, or limit electrodes, precise independent measurements of pressure, uniaxial acceleration, vibration and shock can be made. This invention also contemplates a method for fabricating the cantilever UNCD structure for the sensor.

  3. Cooperative motion in liquids: On librational dynamics of chloroform throughout its normal liquid-phase range

    NASA Astrophysics Data System (ADS)

    Rothschild, Walter G.; Cavagnat, Raymond M.

    1994-03-01

    We have extended the Raman spectral accumulations of the ν3 mode (A1, 367 cm-1) of liquid CHCl3-Cl-35 and its simulation in terms of an orientational equilibrium renewal process [W. G. Rothschild, R. M. Cavagnat, and P. Maraval, J. Chem. Phys. 99, 8922 (1993)] to a temperature of 338 K, about the normal boiling point of the system (335 K). The values of the best-fit parameters predict that the orientational motion of liquid chloroform, even at such a relatively high kinetic energy, is described predominantly by libratory states; their lifetime (˜1 ps) is four times longer than that of the free-rotational steps. The character of the orientational motion of the system, when traversing the range of 213 to 338 K from just above its melting to near its boiling point at about atmospheric pressure, reflects the softening of the liquid-cage structure in terms of an increasing dispersion and/or a decreasing value of the mean libration frequency, a lowering of the depth of its potential well, but near-invariance of its lifetime. Simultaneously, there is an approximately twofold increase in the lifetime of the much shorter stages of free-rotational motion. In essence, the system dynamics remain that of an assembly of librators.

  4. Dynamic magnetic susceptibility of systems with long-range magnetic order

    NASA Astrophysics Data System (ADS)

    Vannette, Matthew Dano

    The utility of the TDR as an instrument in the study of magnetically ordered materials has been expanded beyond the simple demonstration purposes. Results of static applied magnetic field dependent measurements of the dynamic magnetic susceptibility, chi, of various ferromagnetic (FM) and antiferromagnetic (AFM) materials showing a range of transition temperatures (1-800 K) are presented. Data was collected primarily with a tunnel diode resonator (TDR) at different radio-frequencies (~10-30 MHz). In the vicinity of TC local moment ferromagnets show a very sharp, narrow peak in chi which is suppressed in amplitude and shifted to higher temperatures as the static bias field is increased. Unexpectedly, critical scaling analysis fails for these data. It is seen that these data are frequency dependent, however there is no simple method whereby measurement frequency can be changed in a controllable fashion. In contrast, itinerant ferromagnets show a broad maximum in chi well below TC which is suppressed and shifts to lower temperatures as the dc bias field is increased. The data on itinerant ferromagnets is fitted to a semi-phenomenological model that suggests the sample response is dominated by the uncompensated minority spins in the conduction band. Concluding remarks suggest possible scenarios to achieve frequency resolved data using the TDR as well as other fields in which the apparatus may be exploited.

  5. Achieving large dynamic range control of gene expression with a compact RNA transcription-translation regulator.

    PubMed

    Westbrook, Alexandra M; Lucks, Julius B

    2017-04-06

    RNA transcriptional regulators are emerging as versatile components for genetic network construction. However, these regulators suffer from incomplete repression in their OFF state, making their dynamic range less than that of their protein counterparts. This incomplete repression causes expression leak, which impedes the construction of larger synthetic regulatory networks as leak propagation can interfere with desired network function. To address this, we demonstrate how naturally derived antisense RNA-mediated transcriptional regulators can be configured to regulate both transcription and translation in a single compact RNA mechanism that functions in Escherichia coli. Using in vivo gene expression assays, we show that a combination of transcriptional termination and ribosome binding site sequestration increases repression from 85% to 98%, or activation from 10-fold to over 900-fold, in response to cognate antisense RNAs. We also show that orthogonal repressive versions of this mechanism can be created through engineering minimal antisense RNAs. Finally, to demonstrate the utility of this mechanism, we use it to reduce network leak in an RNA-only cascade. We anticipate these regulators will find broad use as synthetic biology moves beyond parts engineering to the design and construction of more sophisticated regulatory networks.

  6. A parallel unbalanced digitization architecture to reduce the dynamic range of multiple signals

    NASA Astrophysics Data System (ADS)

    Vallérian, Mathieu; HuÅ£u, Florin; Villemaud, Guillaume; Miscopein, Benoît; Risset, Tanguy

    2016-05-01

    Technologies employed in urban sensor networks are permanently evolving, and thus the gateways employed to collect data in such kind of networks have to be very flexible in order to be compliant with the new communication standards. A convenient way to do that is to digitize all the received signals in one shot and then to digitally perform the signal processing, as it is done in software-defined radio (SDR). All signals can be emitted with very different features (bandwidth, modulation type, and power level) in order to respond to the various propagation conditions. Their difference in terms of power levels is a problem when digitizing them together, as no current commercial analog-to-digital converter (ADC) can provide a fine enough resolution to digitize this high dynamic range between the weakest possible signal in the presence of a stronger signal. This paper presents an RF front end receiver architecture capable of handling this problem by using two ADCs of lower resolutions. The architecture is validated through a set of simulations using Keysight's ADS software. The main validation criterion is the bit error rate comparison with a classical receiver.

  7. Lightness perception in high-dynamic range images: local and remote effects

    PubMed Central

    Allred, Sarah R; Radonjic, Ana; Gilchrist, Alan L; Brainard, David H

    2012-01-01

    We measured the perceived lightness of target patches embedded in high dynamic range checkerboards. We independently varied the luminance of checks immediately surrounding the test and those remote from it. The data establish context transfer functions (CTFs) that characterize perceptual matches across checkerboard contexts. Several features of the CTFs are broadly consistent with previous research: matched luminance decreases when overall context luminance decreases; matched luminance increases when overall context luminance increases; manipulating context locations near the target has a greater effect than manipulating locations far from the target patch. The measured CTFs are not well-described, however, by changes with context in multiplicative gain alone or by changes in both multiplicative and subtractive adaptation parameters. We were able to fit the data with a three-parameter model of adaptation. This allowed us to characterize the CTFs by specifying the luminances that appeared white, black, and gray (white point, black point, and gray point respectively). The white and black points depended additively on the local and remote contrasts, but accounting for the gray point required an interaction term. Analysis of this effect suggests that the target patch itself must be included in a description of the visual context. PMID:22323784

  8. Multidiagnostics analysis of ion dynamics in ultrafast laser ablation of metals over a large fluence range

    SciTech Connect

    Anoop, K. K.; Polek, M. P.; Bruzzese, R.; Amoruso, S.; Harilal, Sivanandan S.

    2015-02-28

    The ions dynamics in ultrafast laser ablation of metals is studied over a fluence range spanning from the ablation threshold up to ~75 J/cm2 by means of three established diagnostic techniques. Langmuir probe, Faraday cup and spectrally resolved ICCD imaging simultaneously monitor the laser-produced plasma ions produced during ultrafast laser ablation of a copper target. The fluence dependence of ion yield is analyzed observing the occurrence of three different regimes. Moreover, the specific ion yield shows a maximum at about 4-5 J/cm2, followed by a gradual reduction and a transition to a high-fluence regime above ~50 J/cm2. The fluence variation of the copper ions angular distribution is also analyzed, observing a gradual increase of forward peaking of Cu ions for fluences up to ~10 J/cm2. Then, a broader ion component is observed at larger angles for fluences larger than ~10 J/cm2. Finally, an experimental characterization of the ions angular distribution for several metallic targets (Mg, Al, Cr, Fe, Cu, and W) is carried out at a relatively high fluence of ~66 J/cm2. Interestingly, the ion emission from the volatile metals show a narrow forward peaked distribution and a high peak ion yield compared to the refractory metals. Moreover, the width of ion angular distributions presents a striking correlation with the peak ion yield.

  9. Extending the dynamic range of transcription factor action by translational regulation

    PubMed Central

    Sokolowski, Thomas R.; Walczak, Aleksandra M.; Bialek, William; Tkačik, Gašper

    2016-01-01

    A crucial step in the regulation of gene expression is binding of transcription factor (TF) proteins to regulatory sites along the DNA. But transcription factors act at nanomolar concentrations, and noise due to random arrival of these molecules at their binding sites can severely limit the precision of regulation. Recent work on the optimization of information flow through regulatory networks indicates that the lower end of the dynamic range of concentrations is simply inaccessible, overwhelmed by the impact of this noise. Motivated by the behavior of homeodomain proteins, such as the maternal morphogen Bicoid in the fruit fly embryo, we suggest a scheme in which transcription factors also act as indirect translational regulators, binding to the mRNA of other regulatory proteins. Intuitively, each mRNA molecule acts as an independent sensor of the input concentration, and averaging over these multiple sensors reduces the noise. We analyze information flow through this scheme and identify conditions under which it outperforms direct transcriptional regulation. Our results suggest that the dual role of homeodomain proteins is not just a historical accident, but a solution to a crucial physics problem in the regulation of gene expression. PMID:26986359

  10. Towards high dynamic range extensions of HEVC: subjective evaluation of potential coding technologies

    NASA Astrophysics Data System (ADS)

    Hanhart, Philippe; Řeřábek, Martin; Ebrahimi, Touradj

    2015-09-01

    This paper reports the details and results of the subjective evaluations conducted at EPFL to evaluate the responses to the Call for Evidence (CfE) for High Dynamic Range (HDR) and Wide Color Gamut (WCG) Video Coding issued by Moving Picture Experts Group (MPEG). The CfE on HDR/WCG Video Coding aims to explore whether the coding efficiency and/or the functionality of the current version of HEVC standard can be signi_cantly improved for HDR and WCG content. In total, nine submissions, five for Category 1 and four for Category 3a, were compared to the HEVC Main 10 Profile based Anchor. More particularly, five HDR video contents, compressed at four bit rates by each proponent responding to the CfE, were used in the subjective evaluations. Further, the side-by-side presentation methodology was used for the subjective experiment to discriminate small differences between the Anchor and proponents. Subjective results shows that the proposals provide evidence that the coding efficiency can be improved in a statistically noticeable way over MPEG CfE Anchors in terms of perceived quality within the investigated content. The paper further benchmarks the selected objective metrics based on their correlations with the subjective ratings. It is shown that PSNR-DE1000, HDRVDP- 2, and PSNR-Lx can reliably detect visible differences between the proposed encoding solutions and current HEVC standard.

  11. Extending the dynamic range of transcription factor action by translational regulation.

    PubMed

    Sokolowski, Thomas R; Walczak, Aleksandra M; Bialek, William; Tkačik, Gašper

    2016-02-01

    A crucial step in the regulation of gene expression is binding of transcription factor (TF) proteins to regulatory sites along the DNA. But transcription factors act at nanomolar concentrations, and noise due to random arrival of these molecules at their binding sites can severely limit the precision of regulation. Recent work on the optimization of information flow through regulatory networks indicates that the lower end of the dynamic range of concentrations is simply inaccessible, overwhelmed by the impact of this noise. Motivated by the behavior of homeodomain proteins, such as the maternal morphogen Bicoid in the fruit fly embryo, we suggest a scheme in which transcription factors also act as indirect translational regulators, binding to the mRNA of other regulatory proteins. Intuitively, each mRNA molecule acts as an independent sensor of the input concentration, and averaging over these multiple sensors reduces the noise. We analyze information flow through this scheme and identify conditions under which it outperforms direct transcriptional regulation. Our results suggest that the dual role of homeodomain proteins is not just a historical accident, but a solution to a crucial physics problem in the regulation of gene expression.

  12. Dynamic dose assessment by Large Eddy Simulation of the near-range atmospheric dispersion.

    PubMed

    Vervecken, Lieven; Camps, Johan; Meyers, Johan

    2015-03-01

    In order to improve the simulation of the near-range atmospheric dispersion of radionuclides, computational fluid dynamics is becoming increasingly popular. In the current study, Large-Eddy Simulation is used to examine the time-evolution of the turbulent dispersion of radioactive gases in the atmospheric boundary layer, and it is coupled to a gamma dose rate model that is based on the point-kernel method with buildup factors. In this way, the variability of radiological dose rate from cloud shine due to instantaneous turbulent mixing processes can be evaluated. The steady release in an open field of (41)Ar and (133)Xe for 4 different release heights is studied, thus covering radionuclides that decay with a high-energy gamma and a low-energy gamma, respectively. Based on these simulations, the variability of dose rates at ground level for different averaging times in the dose measurements is analyzed. It is observed that turbulent variability in the wind field can lead to dose estimates that are underestimated by up to a factor of four when conventional long-term measurements are used to estimate the dose from short-term exposures.

  13. Bi-directional flow sensor with a wide dynamic range for medical applications.

    PubMed

    Al-Salaymeh, A; Jovanović, J; Durst, F

    2004-10-01

    This paper describes a novel three-wire thermal flow sensor for medical applications. The present innovation for low-frequency measurements involves the use of a pulsed-wire anemometer with a comparatively large wire diameter (12.5 microm and larger) together with a novel signal processing approach. A small wire is heated using a sinusoidal alternating current, and two sensing wires, acting as resistance thermometers, are set parallel to, and at a small distance on either side of, the pulsed wire. The thermal wake of the pulsed wire is convected downstream to one of the two receiving wires which detect its delayed arrival. This arrangement allows the sensing of both the direction and the flow velocity component normal to the three probes. By appropriate signal processing, the present sensor can be operated such that the phase shift between the periodic current that drives the central wire and the detected signal by either the upstream or downstream wire takes into account a combination of convection, diffusion and the finite thermal response time of both the pulsed wire and the receiving wire. Because the time constants increase as the flow velocity decreases, the time lag due to thermal inertia supplements the time lag due to the true time of flight, thus yielding an effective operating range of 0.05 m/s dynamic range of 500:1. This wide velocity range is an order of magnitude larger than that for the traditional time-of-flight pulsed-wire anemometers. An important application of the bi-directional thermal flowmeter is the measurement of human respiration, e.g. for early diagnostics of asthmatic attacks. The main advantage of the present sensor is its low sensitivity to variations in temperature and also to the composition of the flowing gas. Also, a calibration will be not needed for each density and gas used in addition to that for velocity. The resultant design work aimed at developing a sensor that can be mass

  14. The Design and Realization of Linear Calibration System of a Large Dynamic Range Readout Unit for a BGO Calorimeter

    NASA Astrophysics Data System (ADS)

    Xie, M. G.; Guo, J. H.; Wu, J.; Chang, J.

    2014-03-01

    The DArk Matter Particle Explorer (DAMPE) is proposed by Purple Mountain Observatory, Chinese Academy of Sciences. This project expects to find the evidence of the existence of dark matter particle in the universe via the detection of high-energy electron and gamma-ray. A major component of the payload is a BGO (Bismuth Germanate Oxide) calorimeter, which is used to detect the particles in the energy range from 5 GeV to 10 TeV. According to a physical simulation, the dynamic range of each BGO detection unit is about 1.5×10^{5}. In order to test the linearity of BGO detection readout unit, we implement a simple linearity calibration system covering such a large dynamic range. The experimental result shows that the nonlinearity of the entire dynamic range is less than 2.7%.

  15. The Design and Realization of Linear Calibration System of a Large Dynamic Range Readout Unit for a BGO Calorimeter

    NASA Astrophysics Data System (ADS)

    Xie, Ming-Gang; Guo, Jian-Hua; Wu, Jian; Chang, Jin

    2015-01-01

    The DArk Matter Particle Explorer (DAMPE) is proposed by the Purple Mountain Observatory, Chinese Academy of Sciences. This project expects to find the evidence of the existence of dark matter particles in the universe via the detection of the high-energy electrons and gamma-ray particles produced possibly by the annihilation of dark matter particles. The major component of the satellite payload is a BGO (Bismuth Germanate Oxide) calorimeter, which is used to detect the particles in the energy range from 5 GeV to 10 TeV. According to a physical simulation, the dynamic range of each BGO detection unit is about 1.5×105. In order to test the readout linearity of the BGO detection unit, we have implemented a simple linear calibration system covering such a large dynamic range. The experimental result shows that the readout nonlinearity of the BGO detection unit in the entire dynamic range is less than 2.7%.

  16. [Pulmonary functional diagnostic imaging using a dynamic flat-panel detector: comparison with findings in pulmonary scintigraphy].

    PubMed

    Tanaka, Rie; Sanada, Shigeru; Fujimura, Masaki; Yasui, Masahide; Tsuji, Shiro; Hayashi, Norio; Nanbu, Yuko; Matsui, Osamu

    2009-06-20

    Pulmonary ventilation and circulation dynamics are reflected on dynamic chest radiographs as changes in X-ray translucency,i.e., pixel values. The present study was performed to develop a pulmonary functional evaluation method based on the changes in pixel value, and to investigate the clinical usefulness of our method. Sequential chest radiographs of 20 subjects (abnormal,n=12; normal,n=8) during respiration were obtained with a dynamic flat-panel detector (FPD) system. The average pixel value in each local area was measured tracking the same area. To facilitate visual evaluation, the results were mapped on the original image using a grayscale in which small changes were shown in black and large changes were shown in white. In our clinical evaluation in comparison with a pulmonary scintigraphy, pulmonary ventilation disorder was indicated as a reduction of changes in pixel values. In many patients, there was a correlation between our result and a pulmonary scintigraphy (0.7

  17. Observation of the dynamic behavior of liquid crystals using T-FDP (Transmission type four detectors polarimeter)

    NASA Astrophysics Data System (ADS)

    Kawabata, Shuichi; Arizi, Junichi; Shibuya, Takehisa; Wakaki, Moriaki

    2003-11-01

    We have constructed the four detectors polarimeter of transmission type (T-FDP) whose principle was originally invented by Azzam et. al. Some of the distinct features of our instrument are the liner optical axis and high speed data acquisition of msec order. It can determine the polarization state of the light that passed through the anisotropic materials such as liquid crystals in a very short time. We observed the dynamic change of the polarization state of the transmitted light through the liquid crystals (smectic and super twisted nematic) that are driven by alternating voltage. The behaviors of the both liquid crystals showed hysteresis. We also showed the trajectory of the polarization state observed through the super twisted nematic liquid crystal on the Poincare sphere.

  18. Characterizing the Seasonal Dynamics of Plant Community Photosynthesis Across a Range of Vegetation Types

    SciTech Connect

    Gu, Lianhong; Post, Wilfred M; Baldocchi, Dennis; Black, Andy; Suyker, A.E.,; Verma, Shashi; Vesala, Timo; Wofsy, Steve

    2009-01-01

    The seasonal cycle of plant community photosynthesis is one of the most important biotic oscillations to mankind. This study built upon previous efforts to develop a comprehensive framework to studying this cycle systematically with eddy covariance flux measurements. We proposed a new function to represent the cycle and generalized a set of phenological indices to quantify its dynamic characteristics. We suggest that the seasonal variation of plant community photosynthesis generally consists of five distinctive phases in sequence each of which results from the interaction between the inherent biological and ecological processes and the progression of climatic conditions and reflects the unique functioning of plant community at different stages of the growing season. We applied the improved methodology to seven vegetation sites ranging from evergreen and deciduous forests to crop to grasslands and covering both cool-season (vegetation active during cool months, e.g. Mediterranean climate grasslands) and warm-season (vegetation active during warm months, e.g. temperate and boreal forests) vegetation types. Our application revealed interesting phenomena that had not been reported before and pointed to new research directions. We found that for the warm-season vegetation type, the recovery of plant community photosynthesis at the beginning of the growing season was faster than the senescence at the end of the growing season while for the coolseason vegetation type, the opposite was true. Furthermore, for the warm-season vegetation type, the recovery was closely correlated with the senescence such that a faster photosynthetic recovery implied a speedier photosynthetic senescence and vice versa. There was evidence that a similar close correlation could also exist for the cool-season vegetation type, and furthermore, the recovery-senescence relationship may be invariant between the warm-season and cool-season vegetation types up to an offset in the intercept. We also

  19. Enhancement tuning and control for high dynamic range images in multi-scale locally adaptive contrast enhancement algorithms

    NASA Astrophysics Data System (ADS)

    Cvetkovic, Sascha D.; Schirris, Johan; de With, Peter H. N.

    2009-01-01

    For real-time imaging in surveillance applications, visibility of details is of primary importance to ensure customer confidence. If we display High Dynamic-Range (HDR) scenes whose contrast spans four or more orders of magnitude on a conventional monitor without additional processing, results are unacceptable. Compression of the dynamic range is therefore a compulsory part of any high-end video processing chain because standard monitors are inherently Low- Dynamic Range (LDR) devices with maximally two orders of display dynamic range. In real-time camera processing, many complex scenes are improved with local contrast enhancements, bringing details to the best possible visibility. In this paper, we show how a multi-scale high-frequency enhancement scheme, in which gain is a non-linear function of the detail energy, can be used for the dynamic range compression of HDR real-time video camera signals. We also show the connection of our enhancement scheme to the processing way of the Human Visual System (HVS). Our algorithm simultaneously controls perceived sharpness, ringing ("halo") artifacts (contrast) and noise, resulting in a good balance between visibility of details and non-disturbance of artifacts. The overall quality enhancement, suitable for both HDR and LDR scenes, is based on a careful selection of the filter types for the multi-band decomposition and a detailed analysis of the signal per frequency band.

  20. Design improvement of the three-beam detector towards a precise long-range 6-degree of freedom motion sensor system

    SciTech Connect

    Kim, Young-Keun; Kim, Kyung-Soo Kim, Soohyun; Jang, In Gwun

    2014-01-15

    This paper presents performance enhancement of the three beam detector through design improvement based on the error analysis. The three-beam detector is a novel sensor system that measures six motions (i.e., 3 translations and 3 rotations) of a remote object with high accuracy by implementing three laser distance sensors and a vision sensor. In this paper, finite element analysis and parameter analysis are applied to the three-beam detector to analyze its structural frames and sensor configuration, respectively, in terms of sensing error. By virtue of such a systematic, quantitative error analysis, this research has successfully improved the performance of the three-beam detector and thoroughly validated through field tests that it can detect the 6-degree of freedom motions of a remote target at 30 m with an accuracy of 1.51 mm and 0.18° and precision of 0.38 mm and 0.13°.

  1. Measurements of the perceived dynamic range of a medical imaging workstation

    NASA Astrophysics Data System (ADS)

    Kenney, Robert S.; Channin, David S.; Prior, Fred W.

    1996-03-01

    Murch and Weiman have demonstrated that greater than 11 bits of contrast information are perceivable by a human observer. Digital display controllers with 10 or 12 bit digital to analog converters are becoming available. Before attempting to determine if these technologies improve the clinical effectiveness of medical imaging workstations it is first necessary to determine if measurable differences can be produced in the perceived dynamic range (PDR) of the displays. A set of experiments have been performed to determine a baseline PDR for an 8- bit per pixel display. This data will be used as the control for future measurements at 10 bits per pixel. The experimental design includes all psychovisual factors that affect an observer's perception of contrast. Stimulus display duration, physical size of the stimulus and training factors were all studied and controlled in the experiments. Simple images are used to avoid complicating the observer's task and display time is kept short to prevent adaptation and boredom effects. Data was collected using four non-radiologists and four radiologists. Each subject had at least normal corrected vision and wore his corrective lenses during each session. All experiments were conducted on a SUN SPARC workstation using an Image Systems (M21P-47SO1-2KHB) portrait monitor driven by a modified DOME Imaging Systems (Md2/SUN) 10-bit, grayscale, video board initially configured to run in 8-bit mode. Specially developed software was used to control the experiments and to gather and analyze the data. Pizer and Chan's methodology for computing PDR was adapted for the above hardware and software environment. A rating experiment was used to determine the just noticeable difference in contrast for a given reference intensity. Integration over the range of the monitor provides the PDR for that display for one observer. This data is then averaged with all other observations to determine a baseline PDR. These experiments allow for the determination

  2. Shock initiation of nano-Al/Teflon: High dynamic range pyrometry measurements

    NASA Astrophysics Data System (ADS)

    Wang, Jue; Bassett, Will P.; Dlott, Dana D.

    2017-02-01

    Laser-launched flyer plates (25 μm thick Cu) were used to impact-initiate reactive materials consisting of 40 nm Al particles embedded in TeflonAF polymer (Al/Teflon) on sapphire substrates at a stoichiometric concentration (2.3:1 Teflon:Al), as well as one-half and one-fourth that concentration. A high dynamic range emission spectrometer was used to time and spectrally resolve the emitted light and to determine graybody temperature histories with nanosecond time resolution. At 0.5 km s-1, first light emission was observed from Teflon, but at 0.6 km s-1, the emission from Al/Teflon became much more intense, so we assigned the impact threshold for Al/Teflon reactions to be 0.6 (±0.1) km s-1. The flyer plates produced a 7 ns duration steady shock drive. Emission from shocked Al/Teflon above threshold consisted of two bursts. At the higher impact velocities, the first burst started 15 ns after impact, peaked at 25 ns, and persisted for 75 ns. The second burst started at a few hundred nanoseconds and lasted until 2 μs. The 15 ns start time was exactly the time the flyer plate velocity dropped to zero after impact with sapphire. The first burst was associated with shock-triggered reactions and the second, occurring at ambient pressure, was associated with combustion of leftover material that did not react during shock. The emission spectrum was found to be a good fit to a graybody at all times, allowing temperature histories to be extracted. At 25 ns, the temperature at 0.7 km s-1 and the one-fourth Al load was 3800 K. Those temperatures increased significantly with impact velocity, up to 4600 K, but did not increase as much with Al load. A steady combustion process at 2800 (±100) K was observed in the microsecond range. The minimal dependence on Al loading indicates that these peak temperatures arise primarily from Al nanoparticles reacting almost independently, since the presence of nearby heat sources had little influence on the peak temperatures.

  3. Short- and medium-range structure of amorphous zircon from molecular dynamics simulations

    SciTech Connect

    Du, Jincheng; Devanathan, Ram; Corrales, Louis R.; Weber, William J.; Cormack, Alastair N.

    2006-12-18

    We have obtained new insights into the structure of amorphous zircon using classical molecular dynamics simulations with a partial charge model. We present detailed structural characterizations of the simulated high and low density amorphous zircon and compare our results with available neutron diffraction, EXAFS, NMR and other experimental results. The results show that amorphization leads to polymerization of the silicon-oxygen network and the formation of regions rich in zirconium. The average n value of Qn species is 1.6-1.8. A considerable percentage of the oxygen ions (around 20%) have only zirconium in the first coordination shell (free oxygen) in amorphous zircon. The Zr-O bond length (around 2.10?) is shorter and the oxygen coordination number around zirconium smaller (6-7) than those in crystalline zircon, in good agreement with the EXAFS results. The total structure factors of simulated amorphous zircon also agree well with neutron diffraction results. We have examined the effects of the simulation cell size and relative density on the amorphous structure. The general features such as polymerization of silicon-oxygen network and the formation of clustered zirconium rich regions appear to be independent of system size and volume expansion in the range of 11 to 18%. Based on the obtained amorphous zircon structure, experimentally observed lower chemical durability of amorphous zircon compared to its crystalline form can be explained by the existence of the silicon-oxygen networks and zirconium rich regions in amorphous zircon that provides diffusion channels and eases dissolution processes. Battelle operates PNNL for the USDOE

  4. High dynamic range optical scanning of sediments and rock samples: More than colour?

    NASA Astrophysics Data System (ADS)

    Klug, Martin; Fabian, Karl; Knies, Jochen

    2015-04-01

    An automated high dynamic range (HDR) scanning procedure for cores and single sediment samples has been developed based on the GeoTek core scanner equipped with a 3* 2048 pixel CCD array GeoScan colour line-scan camera and a Sigma AF 105mm F2.8 EX DG MACRO lens. Repeated colour line scans of the same core sequence using different illumination and exposure time settings, but equal aperture, can be combined into single HDR images. This yields improved colour definition especially if layers of highly variable brightness occur in the same sequence. Colour calibration is performed automatically during image processing based on synchronization of colour charts. Polarized light is used to minimize gloss on wet surfaces. Beyond improved colour detection, high resolution scans with pixel size down to 25 µm provide the possibility of quantifying fabric, texture, and colour contrast between mottle and matrix. We present examples from marine sediments, lake sediments, hard rock cores, and individual soil samples. Due to the high resolution in sediment sequences, the improved images provide important background information to interpret synchronous measurements of density, magnetic susceptibility, or X-ray fluorescence with respect to their respective measurement footprint. If for example an XRF measurement indicates a 2% increase in Fe at a location of a thin black layer of 1/10 of the XRF measurement footprint, within an otherwise homogenous sequence, it can be inferred that the real Fe abundance within the layer is probably 20% higher than in the surrounding sediment. HDR scanning can therefore help to provide high resolution informed interpolation and deconvolution of measurements with larger sensor footprints.

  5. Do High Dynamic Range threatments improve the results of Structure from Motion approaches in Geomorphology?

    NASA Astrophysics Data System (ADS)

    Gómez-Gutiérrez, Álvaro; Juan de Sanjosé-Blasco, José; Schnabel, Susanne; de Matías-Bejarano, Javier; Pulido-Fernández, Manuel; Berenguer-Sempere, Fernando

    2015-04-01

    In this work, the hypothesis of improving 3D models obtained with Structure from Motion (SfM) approaches using images pre-processed by High Dynamic Range (HDR) techniques is tested. Photographs of the Veleta Rock Glacier in Spain were captured with different exposure values (EV0, EV+1 and EV-1), two focal lengths (35 and 100 mm) and under different weather conditions for the years 2008, 2009, 2011, 2012 and 2014. HDR images were produced using the different EV steps within Fusion F.1 software. Point clouds were generated using commercial and free available SfM software: Agisoft Photoscan and 123D Catch. Models Obtained using pre-processed images and non-preprocessed images were compared in a 3D environment with a benchmark 3D model obtained by means of a Terrestrial Laser Scanner (TLS). A total of 40 point clouds were produced, georeferenced and compared. Results indicated that for Agisoft Photoscan software differences in the accuracy between models obtained with pre-processed and non-preprocessed images were not significant from a statistical viewpoint. However, in the case of the free available software 123D Catch, models obtained using images pre-processed by HDR techniques presented a higher point density and were more accurate. This tendency was observed along the 5 studied years and under different capture conditions. More work should be done in the near future to corroborate whether the results of similar software packages can be improved by HDR techniques (e.g. ARC3D, Bundler and PMVS2, CMP SfM, Photosynth and VisualSFM).

  6. Intruder Detector

    NASA Technical Reports Server (NTRS)

    1978-01-01

    The shadowy prowler is attempting a break-in, unaware that his presence has already been detected and reported by the device in the lower left corner of the photo. It is part of a three-element ntruder Detecti on System developed by NASA's Ames Research Center from technology acquired in the Apollo lunar exploration program. Apollo astronauts left behind on the moon small portable seismic (shock) detectors to record subsurface vibrations and transmit to Earth data on the moon's density and thickness. A similar seismic detector is the key component of the lntruder Detection System. Encased in a stainless steel tube, the detector is implanted in the ground outside the facility being protected-home, bank, industrial or other facilities. The vibration-sensing detector picks up the footstep of anyone within a preset range. The detector is connected by cable to the transmitter, which relays the warning to a portable radio receiver. The radio alerts plant guards or home occupants by emitting an audible tone burst for each footstep.

  7. Analysis of Light Gathering Abilities of Dynamically Solidified Micro-lenses, and Their Implementation to Improve Sensitivity of Fluorescent PCR Micro-detectors.

    PubMed

    Wu, Jian; Guo, Wei; Wang, Chunyan; Yu, Kuanxin; Chen, Tao; Li, Yinghui

    2015-06-01

    Fluorescent polymerase chain reaction (PCR) is becoming the preferred method of quantitative analysis due to its high specificity and sensitivity. We propose to use a new kind of micro-lens, dynamically solidified with optic glue, to improve the sensitivity of fluorescent PCR micro-detector. We developed light ray track equations for these lenses and used them to calculate relative light intensity distribution curve for stimulation lenses and illumination point probability distribution curve for detection lenses. We manufactured dynamically solidified micro-lenses using optic glue NOA61, and measured their light gathering ability. Lenses with radius/thickness (R/H) ratio of 4 reached light focusing ratio of 3.85 (stimulation lens) and photon collection efficiency of 0.86 (detection lens). We then used dynamically solidified lenses in PCR fluorescence micro-detector and analyzed their effect on the detector sensitivity. We showed that the use of dynamically solidified micro-lenses with R/H = 4 resulted in over 4.4-fold increased sensitivity of the detector.

  8. A new broadband square law detector. [microwave radiometers

    NASA Technical Reports Server (NTRS)

    Reid, M. S.; Gardner, R. A.; Stelzried, C. T.

    1975-01-01

    A broadband constant law detector was developed for precision power measurements, radio metric measurements, and other applications. It has a wide dynamic range and an accurate square law response. Other desirable characteristics, which are all included in a single compact unit, are: (1) high-level dc output with immunity to ground loop problems; (2) fast response times; (3) ability to insert known time constants; and (4) good thermal stability. The detector and its performance are described in detail. The detector can be operated in a programmable system with a ten-fold increase in accuracy. The use and performance of the detector in a noise-adding radiometer system is also discussed.

  9. Dynamics of formation of photoresponse in a detector structure made of gallium arsenide

    SciTech Connect

    Ayzenshtat, G. I. Lelekov, M. A.; Tolbanov, O. P.

    2008-04-15

    The influence of capture effects on the characteristics of detectors of the ionizing radiation based on semi-insulating gallium arsenide is considered. Generation of nonequilibrium electrons and holes along the entire thickness of the active region was performed under illumination with an infrared light-emitting diode with a wavelength of 0.9 {mu}m. In this case, the situation emerging in the device structure under the effect of X-ray radiation or a high-energy electron beam was simulated. It is shown that the variation in the shape of the output signal with time in this case is caused by variation in the electric field profile due to the capture of holes at deep centers in gallium arsenide. An absolutely different distribution of the electric field emerges in the structure under irradiation of a semitransparent cathode of the structure with a red light-emitting diode, emission of which penetrates into the active region for mere 1 {mu}m. In this case, the transformation of the electric field is caused by the capture of electrons. Under the prolonged effect of such radiation, a space-charge-limited current mode emerges in the device.

  10. Device localization and dynamic scan plane selection using a wireless MRI detector array

    PubMed Central

    Riffe, Matthew J.; Yutzy, Stephen R.; Jiang, Yun; Twieg, Michael D.; Blumenthal, Colin J.; Hsu, Daniel P.; Pan, Li; Gilson, Wesley D.; Sunshine, Jeffrey L.; Flask, Christopher A.; Duerk, Jeffrey L.; Nakamoto, Dean; Gulani, Vikas; Griswold, Mark A.

    2013-01-01

    Purpose A prototype wireless guidance device using single sideband amplitude modulation (SSB) is presented for a 1.5T MRI system. Methods The device contained three fiducial markers each mounted to an independent receiver coil equipped with wireless SSB technology. Acquiring orthogonal projections of these markers determined the position and orientation of the device, which was used to define the scan plane for a subsequent image acquisition. Device localization and scan plane update required approximately 30 ms, so it could be interleaved with high temporal resolution imaging. Since the wireless device is used for localization and doesn’t require full imaging capability, the design of the SSB wireless system was simplified by allowing an asynchronous clock between the transmitter and receiver. Results When coupled to a high readout bandwidth, the error caused by the lack of a shared frequency reference was quantified to be less than one pixel (0.78 mm) in the projection acquisitions. Image-guidance with the prototype was demonstrated with a phantom where a needle was successfully guided to a target and contrast was delivered. Conclusion The feasibility of active tracking with a wireless detector array is demonstrated. Wireless arrays could be incorporated into devices to assist in image-guided procedures. PMID:23900921

  11. Dynamic CFD Simulations of the Supersonic Inflatable Aerodynamic Decelerator (SIAD) Ballistic Range Tests

    NASA Technical Reports Server (NTRS)

    Brock, Joseph M; Stern, Eric

    2016-01-01

    Dynamic CFD simulations of the SIAD ballistic test model were performed using US3D flow solver. Motivation for performing these simulations is for the purpose of validation and verification of the US3D flow solver as a viable computational tool for predicting dynamic coefficients.

  12. Ultra-high-resolution large-dynamic-range optical fiber static strain sensor using Pound-Drever-Hall technique.

    PubMed

    Liu, Qingwen; Tokunaga, Tomochika; He, Zuyuan

    2011-10-15

    We report the realization of a fiber-optic static strain sensor with ultrahigh resolution and large dynamic range for the applications of geophysical research. The sensor consists of a pair of fiber-Bragg-grating-based Fabry-Perot interferometers as sensor heads for strain sensing and reference, respectively. The Pound-Drever-Hall technique is employed to interrogate the sensor heads, and a cross-correlation algorithm is used to figure out the strain information with high precision. Static strain resolution down to 5.8 nanostrains is demonstrated. The dynamic range can be extended up to hundreds of microstrains, and the measuring period is a few tens of seconds.

  13. Combination of current-integrating/photon-counting detector modules for spectral CT.

    PubMed

    Chu, Jiyang; Cong, Wenxiang; Li, Liang; Wang, Ge

    2013-10-07

    Inspired by compressive sensing theory and spectral detection technology, here we propose a novel design of a CT detector array that uses current-integrating/photon-counting modules in an interlacing fashion so that strengths of each detector type can be synergistically combined. For geometrical symmetry, an evenly alternating pattern is initially assumed for these detector modules to form a hybrid detector array. While grayscale detector modules acquire regular raw data in a large dynamic range cost-effectively, spectral detector modules simultaneously sense energy-discriminative data in multiple energy bins. A split Bregman iterative algorithm is developed for spectral CT reconstruction from projection data of an object collected with the hybrid detector array. With mathematical phantoms, an optimal ratio of the number of the spectral elements over the number of grayscale elements is determined based on classic image quality evaluation. This hybrid detector array is capable of delivering a performance comparable with that of a full spectral detector array.

  14. The range of dynamic recrystallization of quartz - An updated correlation between nature and experiment

    NASA Astrophysics Data System (ADS)

    Stipp, Michael

    2014-05-01

    Several microstructural correlations between natural and experimental conditions for dynamic recrystallization of quartz have been proposed (e.g., Hirth et al. 2001; Stipp et al. 2002), but an attempt to unify the different results and data sets is missing. Based on additional experiments and a statistical analysis of microstructural data (e.g., Stipp et al. 2006, 2010) four characteristic microstructural zones with corresponding recrystallized grain size (D) ranges can be identified. (I) D < 3 µm: Experimental dislocation creep regime 1 of Hirth and Tullis (1992). Microstructures are characterized by porphyroclasts with serrations, bulges and very small recrystallized grains along the grain boundaries. Electron backscatter diffraction data indicate that both local grain boundary migration and subgrain rotation contribute to recrystallization, and that grain boundary sliding may operate at high strain (Stipp and Kunze, 2008). Comparable microstructures have not been observed in natural shear zones; their formation is not possible at greenschist facies conditions, because the required differential stresses would be larger than the confining pressure and so in conflict with the Goetze criterion (Kohlstedt et al. 1995). (II) D ˜3-35 µm: Experimental dislocation creep regimes 2 and 3 (Hirth and Tullis 1992), corresponding to the natural BLG zone of Stipp et al. (2002). Microstructures are again characterized by porphyroclasts with grain boundary bulges and small recrystallized grains. Compared to zone I, less strain is required to produce a considerable amount of recrystallized grains, forming "core-mantle microstuctures". (III) D ˜35-120 µm: Upper experimental dislocation creep regime 3, and natural SGR zone (Stipp et al. 2006, 2010). Microstructures are characterized by porphyroclastic ribbon grains and recrystallized grains which are about the same size or slightly larger than optical subgrains. Subgrain formation and dynamic recrystallization are initiated at

  15. Development of functional chest imaging with a dynamic flat-panel detector (FPD).

    PubMed

    Tanaka, Rie; Sanada, Shigeru; Fujimura, Masaki; Yasui, Masahide; Nakayama, Kazuya; Matsui, Takeshi; Hayashi, Norio; Matsui, Osamu

    2008-07-01

    Dynamic FPD permits the acquisition of distortion-free radiographs with a large field of view and high image quality. In the present study, we investigated the feasibility of functional imaging for evaluating the pulmonary sequential blood distribution with an FPD, based on changes in pixel values during cardiac pumping. Dynamic chest radiographs of seven normal subjects were obtained in the expiratory phase by use of an FPD system. We measured the average pixel value in each region of interest that was located manually in the heart and lung areas. Subsequently, inter-frame differences and differences from a minimum-intensity projection image, which was created from one cardiac cycle, were calculated. These difference values were then superimposed on dynamic chest radiographs in the form of a color display, and sequential blood distribution images and a blood distribution map were created. The results were compared to typical data on normal cardiac physiology. The clinical effectiveness of our method was evaluated in a patient who had abnormal pulmonary blood flow. In normal cases, there was a strong correlation between the cardiac cycle and changes in pixel value. Sequential blood distribution images showed a normal pattern at determined by the physiology of pulmonary blood flow, with a symmetric distribution and no blood flow defects throughout the entire lung region. These findings indicated that pulmonary blood flow was reflected on dynamic chest radiographs. In an abnormal case, a defect in blood flow was shown as defective in color in a blood distribution map. The present method has the potential for evaluation of local blood flow as an optional application in general chest radiography.

  16. Dynamic range and sensitivity requirements of satellite ocean color sensors: learning from the past.

    PubMed

    Hu, Chuanmin; Feng, Lian; Lee, Zhongping; Davis, Curtiss O; Mannino, Antonio; McClain, Charles R; Franz, Bryan A

    2012-09-01

    Sensor design and mission planning for satellite ocean color measurements requires careful consideration of the signal dynamic range and sensitivity (specifically here signal-to-noise ratio or SNR) so that small changes of ocean properties (e.g., surface chlorophyll-a concentrations or Chl) can be quantified while most measurements are not saturated. Past and current sensors used different signal levels, formats, and conventions to specify these critical parameters, making it difficult to make cross-sensor comparisons or to establish standards for future sensor design. The goal of this study is to quantify these parameters under uniform conditions for widely used past and current sensors in order to provide a reference for the design of future ocean color radiometers. Using measurements from the Moderate Resolution Imaging Spectroradiometer onboard the Aqua satellite (MODISA) under various solar zenith angles (SZAs), typical (L(typical)) and maximum (L(max)) at-sensor radiances from the visible to the shortwave IR were determined. The L(typical) values at an SZA of 45° were used as constraints to calculate SNRs of 10 multiband sensors at the same L(typical) radiance input and 2 hyperspectral sensors at a similar radiance input. The calculations were based on clear-water scenes with an objective method of selecting pixels with minimal cross-pixel variations to assure target homogeneity. Among the widely used ocean color sensors that have routine global coverage, MODISA ocean bands (1 km) showed 2-4 times higher SNRs than the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) (1 km) and comparable SNRs to the Medium Resolution Imaging Spectrometer (MERIS)-RR (reduced resolution, 1.2 km), leading to different levels of precision in the retrieved Chl data product. MERIS-FR (full resolution, 300 m) showed SNRs lower than MODISA and MERIS-RR with the gain in spatial resolution. SNRs of all MODISA ocean bands and SeaWiFS bands (except the SeaWiFS near-IR bands) exceeded

  17. Dynamic Range and Sensitivity Requirements of Satellite Ocean Color Sensors: Learning from the Past

    NASA Technical Reports Server (NTRS)

    Hu, Chuanmin; Feng, Lian; Lee, Zhongping; Davis, Curtiss O.; Mannino, Antonio; McClain, Charles R.; Franz, Bryan A.

    2012-01-01

    Sensor design and mission planning for satellite ocean color measurements requires careful consideration of the signal dynamic range and sensitivity (specifically here signal-to-noise ratio or SNR) so that small changes of ocean properties (e.g., surface chlorophyll-a concentrations or Chl) can be quantified while most measurements are not saturated. Past and current sensors used different signal levels, formats, and conventions to specify these critical parameters, making it difficult to make cross-sensor comparisons or to establish standards for future sensor design. The goal of this study is to quantify these parameters under uniform conditions for widely used past and current sensors in order to provide a reference for the design of future ocean color radiometers. Using measurements from the Moderate Resolution Imaging Spectroradiometer onboard the Aqua satellite (MODISA) under various solar zenith angles (SZAs), typical (L(sub typical)) and maximum (L(sub max)) at-sensor radiances from the visible to the shortwave IR were determined. The Ltypical values at an SZA of 45 deg were used as constraints to calculate SNRs of 10 multiband sensors at the same L(sub typical) radiance input and 2 hyperspectral sensors at a similar radiance input. The calculations were based on clear-water scenes with an objective method of selecting pixels with minimal cross-pixel variations to assure target homogeneity. Among the widely used ocean color sensors that have routine global coverage, MODISA ocean bands (1 km) showed 2-4 times higher SNRs than the Sea-viewing Wide Field-of-view Sensor (Sea-WiFS) (1 km) and comparable SNRs to the Medium Resolution Imaging Spectrometer (MERIS)-RR (reduced resolution, 1.2 km), leading to different levels of precision in the retrieved Chl data product. MERIS-FR (full resolution, 300 m) showed SNRs lower than MODISA and MERIS-RR with the gain in spatial resolution. SNRs of all MODISA ocean bands and SeaWiFS bands (except the SeaWiFS near-IR bands

  18. High dynamic range adaptive real-time smart camera: an overview of the HDR-ARTiST project

    NASA Astrophysics Data System (ADS)

    Lapray, Pierre-Jean; Heyrman, Barthélémy; Ginhac, Dominique

    2015-04-01

    Standard cameras capture only a fraction of the information that is visible to the human visual system. This is specifically true for natural scenes including areas of low and high illumination due to transitions between sunlit and shaded areas. When capturing such a scene, many cameras are unable to store the full Dynamic Range (DR) resulting in low quality video where details are concealed in shadows or washed out by sunlight. The imaging technique that can overcome this problem is called HDR (High Dynamic Range) imaging. This paper describes a complete smart camera built around a standard off-the-shelf LDR (Low Dynamic Range) sensor and a Virtex-6 FPGA board. This smart camera called HDR-ARtiSt (High Dynamic Range Adaptive Real-time Smart camera) is able to produce a real-time HDR live video color stream by recording and combining multiple acquisitions of the same scene while varying the exposure time. This technique appears as one of the most appropriate and cheapest solution to enhance the dynamic range of real-life environments. HDR-ARtiSt embeds real-time multiple captures, HDR processing, data display and transfer of a HDR color video for a full sensor resolution (1280 1024 pixels) at 60 frames per second. The main contributions of this work are: (1) Multiple Exposure Control (MEC) dedicated to the smart image capture with alternating three exposure times that are dynamically evaluated from frame to frame, (2) Multi-streaming Memory Management Unit (MMMU) dedicated to the memory read/write operations of the three parallel video streams, corresponding to the different exposure times, (3) HRD creating by combining the video streams using a specific hardware version of the Devebecs technique, and (4) Global Tone Mapping (GTM) of the HDR scene for display on a standard LCD monitor.

  19. Passive Ranging of Dynamic Rocket Plumes Using Infrared and Visible Oxygen Attenuation

    DTIC Science & Technology

    2011-03-01

    405 m range and a full -scale solid rocket motor at 900 m range. The NIR O2 band provided range estimates accurate to within 3 % for both tests, while...and zenith angles. Data sets for passive ranging were taken of both a halogen lamp and a full scale stationary solid rocket motor at various ranges up...combustion was targeted as the emission source. Two static tests were conducted with a full scale solid rocket motor and a shoulder-launched model SAM

  20. Relaxation dynamics of glasses along a wide stability and temperature range

    PubMed Central

    Rodríguez-Tinoco, C.; Ràfols-Ribé, J.; González-Silveira, M.; Rodríguez-Viejo, J.

    2016-01-01

    While lots of measurements describe the relaxation dynamics of the liquid state, experimental data of the glass dynamics at high temperatures are much scarcer. We use ultrafast scanning calorimetry to expand the timescales of the glass to much shorter values than previously achieved. Our data show that the relaxation time of glasses follows a super-Arrhenius behaviour in the high-temperature regime above the conventional devitrification temperature heating at 10 K/min. The liquid and glass states can be described by a common VFT-like expression that solely depends on temperature and limiting fictive temperature. We apply this common description to nearly-isotropic glasses of indomethacin, toluene and to recent data on metallic glasses. We also show that the dynamics of indomethacin glasses obey density scaling laws originally derived for the liquid. This work provides a strong connection between the dynamics of the equilibrium supercooled liquid and non-equilibrium glassy states. PMID:27767071