Science.gov

Sample records for geiger mode operation

  1. A Low Noise Planar-Type Avalanche Photodiode using a Single-Diffusion Process in Geiger-Mode Operation

    NASA Astrophysics Data System (ADS)

    Lee, Kiwon; Lee, Byoungwook; Yoon, Sunwoong; Hong, Jung-ho; Yang, Kyounghoon

    2013-07-01

    We report the performances of a planar-type Geiger-mode InGaAs/InP avalanche photodiode (APD) using a single-diffusion process based on a single wet recess-etching technique at a wavelength of 1.55 µm. The recess-etched window region is found to have a smoothly etched sidewall with a large slope width of 0.9 µm. The Geiger-mode characteristics have been measured at 240-280 K for a 20 µm diameter device. The fabricated Geiger-mode APD shows a low dark count probability (DCP) per gate pulse of 2.8×10-3, a high photon detection efficiency (PDE) of 17.4%, and a low noise equivalent power (NEP) of 1.74×10-16 W/Hz1/2 at 240 K. The results are the first demonstration of a planar-type single-diffused Geiger-mode APD using a single wet recess-etching.

  2. Medium altitude airborne Geiger-mode mapping LIDAR system

    NASA Astrophysics Data System (ADS)

    Clifton, William E.; Steele, Bradley; Nelson, Graham; Truscott, Antony; Itzler, Mark; Entwistle, Mark

    2015-05-01

    Over the past 15 years the Massachusetts Institute of Technology, Lincoln Laboratory (MIT/LL), Defense Advanced Research Projects Agency (DARPA) and private industry have been developing airborne LiDAR systems based on arrays of Geiger-mode Avalanche Photodiode (GmAPD) detectors capable of detecting a single photon. The extreme sensitivity of GmAPD detectors allows operation of LiDAR sensors at unprecedented altitudes and area collection rates in excess of 1,000 km2/hr. Up until now the primary emphasis of this technology has been limited to defense applications despite the significant benefits of applying this technology to non-military uses such as mapping, monitoring critical infrastructure and disaster relief. This paper briefly describes the operation of GmAPDs, design and operation of a Geiger-mode LiDAR, a comparison of Geiger-mode and traditional linear mode LiDARs, and a description of the first commercial Geiger-mode LiDAR system, the IntelliEarth™ Geospatial Solutions Geiger-mode LiDAR sensor.

  3. Characterization of Geiger mode avalanche photodiodes for fluorescence decay measurements

    NASA Astrophysics Data System (ADS)

    Jackson, John C.; Phelan, Don; Morrison, Alan P.; Redfern, R. Michael; Mathewson, Alan

    2002-05-01

    Geiger mode avalanche photodiodes (APD) can be biased above the breakdown voltage to allow detection of single photons. Because of the increase in quantum efficiency, magnetic field immunity, robustness, longer operating lifetime and reduction in costs, solid-state detectors capable of operating at non-cryogenic temperatures and providing single photon detection capabilities provide attractive alternatives to the photomultiplier tube (PMT). Shallow junction Geiger mode APD detectors provide the ability to manufacture photon detectors and detector arrays with CMOS compatible processing steps and allows the use of novel Silicon-on-Insulator(SoI) technology to provide future integrated sensing solutions. Previous work on Geiger mode APD detectors has focused on increasing the active area of the detector to make it more PMT like, easing the integration of discrete reaction, detection and signal processing into laboratory experimental systems. This discrete model for single photon detection works well for laboratory sized test and measurement equipment, however the move towards microfluidics and systems on a chip requires integrated sensing solutions. As we move towards providing integrated functionality of increasingly nanoscopic sized emissions, small area detectors and detector arrays that can be easily integrated into marketable systems, with sensitive small area single photon counting detectors will be needed. This paper will demonstrate the 2-dimensional and 3-dimensional simulation of optical coupling that occurs in Geiger mode APDs. Fabricated Geiger mode APD detectors optimized for fluorescence decay measurements were characterized and preliminary results show excellent results for their integration into fluorescence decay measurement systems.

  4. A discrete model of the development and relaxation of a local microbreakdown in silicon avalanche photodiodes operating in the Geiger mode

    SciTech Connect

    Vanyushin, I. V. Gergel, V. A.; Gontar', V. M.; Zimoglyad, V. A.; Tishin, Yu. I.; Kholodnov, V. A. Shcheleva, I. M.

    2007-06-15

    A new discrete theoretical model of the development and relaxation of a local microbreakdown in silicon avalanche photodiodes operating in the Geiger mode is developed. It is shown that the spreading resistance in the substrate profoundly affects both the amplitude of a single-photon electrical pulse and the possibility of attaining the steady-state form of the avalanche breakdown excluding the Geiger mode of the photodiode's operation. The model is employed to interpret the experimental data obtained using test single-photon cells of avalanche photodiodes fabricated on the basis of the 0.25-{mu}m silicon technology with the use of deep implantation to form the region of avalanche multiplication for the charge carriers. Excellent functional properties of the studied type of the single-photon (Geiger) cell are noted. A typical amplitude characteristic of the cell for optical radiation with the wavelength {lambda} = 0.56 {mu}m in the irradiance range of 10{sup -3}-10{sup 2} lx is presented; this characteristic indicates that the quantum efficiency of photoconversion is extremely high.

  5. Foliage penetration optimization for Geiger-mode avalanche photodiode lidar

    NASA Astrophysics Data System (ADS)

    Johnson, Steven E.

    2013-05-01

    Geiger-mode avalanche photodiode (GMAPD) Lidar systems can be used to image targets that are partially concealed by foliage. This application of GMAPD Lidar is challenging because most APDs operating in Geiger- mode report only one range measurement per transmitted laser pulse. If a GMAPD makes a foliage range measurement, it cannot make a range measurement to a target concealed by the foliage. When too much laser energy is received, the vast majority of range measurements are from the foliage and only a small percentage are from the target. Some GMAPD Lidar systems can report their average detection probability during operation. The average detection probability, which is often called "P-det", is calculated over an array of GMAPDs, over multiple laser pulses, or over both. However, the detection probability does not distinguish between target range measurements, foliage range measurements, and noise events. In this paper, it is shown that when certain collection parameters are known, that the probability of detecting a target obscured by foliage can be maximized by selecting the appropriate "P-det". It is also shown that for a typical foliage penetration scenario where most of the reflected laser energy is from the foliage that operating with a "P-det" between 65% and 80% produces a near-maximum target detection probability.

  6. Three-dimensional imaging with arrays of Geiger-mode avalanche photodiodes

    NASA Astrophysics Data System (ADS)

    Aull, Brian F.; Loomis, Andrew H.; Young, Douglas J.; Stern, Alvin; Felton, Bradley J.; Daniels, Peter J.; Landers, Debbie J.; Retherford, Larry; Rathman, Dennis D.; Heinrichs, Richard M.; Marino, Richard M.; Fouche, Daniel G.; Albota, Marius A.; Hatch, Robert E.; Rowe, Gregory S.; Kocher, David G.; Mooney, James G.; O'Brien, Michael E.; Player, Brian E.; Willard, Berton C.; Liau, Zong-Long; Zayhowski, John J.

    2004-06-01

    Lincoln Laboratory has developed 32 x 32-pixel ladar focal planes comprising silicon geiger-mode avalanche photodiodes and high-speed all-digital CMOS timing circuitry in each pixel. In Geiger mode operation, the APD can detect as little as a single photon, producing a digital CMOS-compatible voltage pulse. This pulse is used to stop a high-speed counter in the pixel circuit, thus digitizing the time of arrival of the optical pulse. This "photon-to-digital conversion" simultaneously achieves single-photon sensitivity and 0.5-ns timing. We discuss the development of these focal planes and present imagery from ladar systems that use them.

  7. Geiger-mode avalanche photodiodes, history, properties and problems

    NASA Astrophysics Data System (ADS)

    Renker, D.

    2006-11-01

    Geiger-mode avalanche photodiodes (G-APDs) have been developed during recent years and promise to be an alternative to photomultiplier tubes. They have many advantages like single photon response, high detection efficiency, high gain at low bias voltage and very good timing properties but some of their properties, the dark count rate for example, can be a problem. Several types of G-APDs are on the market and should be selected carefully for a given application.

  8. Limitations of Geiger-mode arrays for Flash LADAR applications

    NASA Astrophysics Data System (ADS)

    Williams, George M., Jr.

    2010-04-01

    It is shown through physics-based Monte Carlo simulations of avalanche photodiode (APD) LADAR receivers that under typical operating scenarios, Geiger-mode APD (GmAPD) flash LADAR receivers may often be ineffective. These results are corroborated by analysis of the signal photon detection efficiency and signal-to-noise ratio metrics. Due to their ability to detect only one pulse per laser shot, the target detection efficiency of GmAPD receivers, as measured by target signal events detected compared to those present at the receiver's optical aperture, is shown to be highly particular and respond nonlinearly to the specific LADAR conditions including range, laser power, detector efficiency, and target occlusion, which causes the GmAPD target detection capabilities to vary unpredictably over standard mission conditions. In the detection of partially occluded targets, GmAPD LADAR receivers perform optimally within only a narrow operating window of range, detector efficiency, and laser power; outside this window performance degrades sharply. Operating at both short and long standoff ranges, GmAPD receivers most often cannot detect partially occluded targets, and with an increased number of detector dark noise events, e.g. resulting from exposure to ionizing radiation, the probability that a GmAPD device is armed and able to detect target signal returns approaches zero. Even when multiple pulses are accumulated or contrived operational scenarios are employed, and even in weak-signal scenarios, GmAPDs most often perform inefficiently in their detection of target signal events at the aperture. It is concluded that the inability of the GmAPD to detect target signal present at the receiver's aperture may lead to a loss of operational capability, may have undesired implications for the equivalent optical aperture, laser power, and/or system complexity, and may incur other costs deleterious to operational efficacy.

  9. Redundancy analysis of raw Geiger-mode laser radar data

    NASA Astrophysics Data System (ADS)

    Lopez, Norman A.; Kamerman, Gary W.

    2010-04-01

    In the past decade arrays of Geiger-mode Avalanche Photodiode (GmAPD) detectors have increased in size from 4×4 to 128×32, resulting in significant increases in data rates. If not handled appropriately, data collected with larger arrays and higher laser pulse repetition frequencies could potentially stress existing data dissemination and storage infrastructures. Data compression techniques that reduce storage requirements by taking advantage of data redundancies could be used to mitigate this problem. In this paper we present an analysis of the coding redundancy that exists in raw data captured with three dimensional imaging laser radar systems that employ arrays of Geiger-mode Avalanche Photodiode (GmAPD) detectors. The data we analyzed was collected in three different scanning modes, namely: mapping-mode, target-mode and stare-mode. We found that there is a significant amount of coding redundancy in raw GmAPD data which can be used to minimize storage sizes. We demonstrate that a trivial and simple approach reduces data for some scan patterns. This work represents a first step towards developing robust compression algorithms for raw GmAPD data. We present considerations for future work.

  10. Geiger-mode Avalanche Photodiodes for High Time Resolution Astrophysics

    NASA Astrophysics Data System (ADS)

    Phelan, Don; Morrison, Alan P.

    Geiger-mode Avalanche Photodiodes (GM-APDs) are establishing themselves as potential candidates for the broad temporal range covered in high time resolution astrophysics (HTRA). These detectors have already been employed in astronomical instrumentation and significant results have been obtained to date. Their high time resolution and quantum efficiency make these single photon event counting detectors ideal for observations of stochastic phenomena, and ultimately for extreme HTRA observations. In this chapter, we review the technology and to illustrate their potential we briefly touch on specific science goals and astronomical applications. We then focus on the fabrication and characterisation of GM-APDs, and discuss the development and challenges posed in designing array devices.

  11. Geiger mode calorimeter for PEP-4 - The PEP-4 TPC collaboration

    SciTech Connect

    Aihara, H.; Alston-Garnjost, M.; Badtke, D.H.; Bakken, J.A.; Barbaro-Galtieri, A.; Barnes, A.V.; Barnett, B.A.; Blumenfeld, B.

    1983-02-01

    The PEP-4 hexagonal barrel calorimeter, with lead-laminate layers and 5x10mm/sup 2/ Geiger-mode discharge cells, has demonstrated excellent stability and uniformity in operation. The use of projective geometry in half degree-wide cathode strips at + or - 60 degrees to the sense wire channels provides excellent spatial resolution and reconstruction capability. The electronic noise-to-signal ratio without preamplification is sufficiently low that individual 50 pC Geiger discharges are accurately measured and used for energy calibration. Measurements made at 14.5 GeV e + or - beam energy have provided preliminary spectra of Bhabhas and of photon-photon invariant mass. The latter show that ..pi.. /SUP o/ 's can be reconstructed.

  12. Development of Fuses for Protection of Geiger-Mode Avalanche Photodiode Arrays

    NASA Astrophysics Data System (ADS)

    Grzesik, Michael; Bailey, Robert; Mahan, Joe; Ampe, Jim

    2015-11-01

    Current-limiting fuses composed of Ti/Al/Ni were developed for use in Geiger-mode avalanche photodiode arrays for each individual pixel in the array. The fuses were designed to burn out at ˜4.5 × 10-3 A and maintain post-burnout leakage currents less than 10-7 A at 70 V sustained for several minutes. Experimental fuse data are presented and successful incorporation of the fuses into a 256 × 64 pixel InP-based Geiger-mode avalanche photodiode array is reported.

  13. Multipixel geiger-mode photon detectors for ultra-weak light sources

    NASA Astrophysics Data System (ADS)

    Campisi, A.; Cosentino, L.; Finocchiaro, P.; Pappalardo, A.; Musumeci, F.; Privitera, S.; Scordino, A.; Tudisco, S.; Fallica, G.; Sanfilippo, D.; Mazzillo, M.; Condorelli, G.; Piazza, A.; Valvo, G.; Lombardo, S.; Sciacca, E.; Bonanno, G.; Belluso, M.

    2007-02-01

    Arrays of Single Photon Avalanche Detectors (SPAD) are considered today as a possible alternative to PMTs and other semiconductor devices in several applications, like physics research, bioluminescence, Positron Emission Tomography (PET) systems, etc. We have developed and characterized a first prototype array produced by STMicroelectronics in silicon planar technology and working at low voltage (30-40 V) in Geiger mode operation. The single cell structure (size down to 20 μm) and the geometrical arrangement give rise to appealing intrinsic characteristics of the device, such as photon detection efficiency, dark count map, cross-talk effects, timing and energy resolution. New prototypes are under construction with a higher number of pixels that have a common output signal to obtain a so-called SiPM (Silicon PhotoMultiplier) configuration.

  14. Geiger-mode avalanche photodiode focal plane arrays for three-dimensional imaging LADAR

    NASA Astrophysics Data System (ADS)

    Itzler, Mark A.; Entwistle, Mark; Owens, Mark; Patel, Ketan; Jiang, Xudong; Slomkowski, Krystyna; Rangwala, Sabbir; Zalud, Peter F.; Senko, Tom; Tower, John; Ferraro, Joseph

    2010-09-01

    We report on the development of focal plane arrays (FPAs) employing two-dimensional arrays of InGaAsP-based Geiger-mode avalanche photodiodes (GmAPDs). These FPAs incorporate InP/InGaAs(P) Geiger-mode avalanche photodiodes (GmAPDs) to create pixels that detect single photons at shortwave infrared wavelengths with high efficiency and low dark count rates. GmAPD arrays are hybridized to CMOS read-out integrated circuits (ROICs) that enable independent laser radar (LADAR) time-of-flight measurements for each pixel, providing three-dimensional image data at frame rates approaching 200 kHz. Microlens arrays are used to maintain high fill factor of greater than 70%. We present full-array performance maps for two different types of sensors optimized for operation at 1.06 μm and 1.55 μm, respectively. For the 1.06 μm FPAs, overall photon detection efficiency of >40% is achieved at <20 kHz dark count rates with modest cooling to ~250 K using integrated thermoelectric coolers. We also describe the first evalution of these FPAs when multi-photon pulses are incident on single pixels. The effective detection efficiency for multi-photon pulses shows excellent agreement with predictions based on Poisson statistics. We also characterize the crosstalk as a function of pulse mean photon number. Relative to the intrinsic crosstalk contribution from hot carrier luminescence that occurs during avalanche current flows resulting from single incident photons, we find a modest rise in crosstalk for multi-photon incident pulses that can be accurately explained by direct optical scattering.

  15. The blocking probability of Geiger-mode avalanche photo-diodes

    NASA Technical Reports Server (NTRS)

    Moision, Bruce; Srinivasan, Meera; Hamkins, Jon

    2005-01-01

    When a photo is detected by a Geiger-mode avalanche photo-diode (GMAPD), the detector is rendered inactive, or blocked, for a certain period of time. In this paper we derive the blocking probability for a GMAPD whose input is either an unmodulated, Benoulli modulated or pulse-position-modulated Poisson process.

  16. Photoionization of Trapped Carriers in Avalanche Photodiodes to Reduce Afterpulsing During Geiger-Mode Photon Counting

    NASA Technical Reports Server (NTRS)

    Krainak, Michael A.

    2005-01-01

    We reduced the afterpulsing probability by a factor of five in a Geiger-mode photon-counting InGaAs avalanche photodiode by using sub-band-gap (lambda = 1.95 micron) laser diode illumination, which we believe photoionizes the trapped carriers.

  17. Geiger-Mode Avalanche Photodiode Arrays Integrated to All-Digital CMOS Circuits.

    PubMed

    Aull, Brian

    2016-01-01

    This article reviews MIT Lincoln Laboratory's work over the past 20 years to develop photon-sensitive image sensors based on arrays of silicon Geiger-mode avalanche photodiodes. Integration of these detectors to all-digital CMOS readout circuits enable exquisitely sensitive solid-state imagers for lidar, wavefront sensing, and passive imaging. PMID:27070609

  18. Geiger-Mode Avalanche Photodiode Arrays Integrated to All-Digital CMOS Circuits

    PubMed Central

    Aull, Brian

    2016-01-01

    This article reviews MIT Lincoln Laboratory's work over the past 20 years to develop photon-sensitive image sensors based on arrays of silicon Geiger-mode avalanche photodiodes. Integration of these detectors to all-digital CMOS readout circuits enable exquisitely sensitive solid-state imagers for lidar, wavefront sensing, and passive imaging. PMID:27070609

  19. Linear LIDAR versus Geiger-mode LIDAR: impact on data properties and data quality

    NASA Astrophysics Data System (ADS)

    Ullrich, A.; Pfennigbauer, M.

    2016-05-01

    LIDAR has become the inevitable technology to provide accurate 3D data fast and reliably even in adverse measurement situations and harsh environments. It provides highly accurate point clouds with a significant number of additional valuable attributes per point. LIDAR systems based on Geiger-mode avalanche photo diode arrays, also called single photon avalanche photo diode arrays, earlier employed for military applications, now seek to enter the commercial market of 3D data acquisition, advertising higher point acquisition speeds from longer ranges compared to conventional techniques. Publications pointing out the advantages of these new systems refer to the other category of LIDAR as "linear LIDAR", as the prime receiver element for detecting the laser echo pulses - avalanche photo diodes - are used in a linear mode of operation. We analyze the differences between the two LIDAR technologies and the fundamental differences in the data they provide. The limitations imposed by physics on both approaches to LIDAR are also addressed and advantages of linear LIDAR over the photon counting approach are discussed.

  20. Non-Geiger mode single photon detector with multiple amplification and gain control mechanisms

    SciTech Connect

    Nawar Rahman, Samia Hall, David; Lo, Yu-Hwa

    2014-05-07

    A new type of single photon detector, Multiple Amplification Gain with Internal Control (MAGIC), is proposed and analyzed using Monte Carlo simulations based on a physical model of the device. The MAGIC detector has two coupled amplification mechanisms, avalanche multiplication and bipolar gain, and the net gain is regulated by a built-in feedback mechanism. Compared to conventional Geiger mode single photon avalanche detectors (SPADs), the MAGIC detector produces a much greater single photon detection efficiency of nearly 100%, low bit-error-ratio for single photon signals, and a large dynamic range. All these properties are highly desirable for applications that require single photon sensitivity and are absent for conventional Geiger-mode SPADs.

  1. SWIR Geiger-mode APD detectors and cameras for 3D imaging

    NASA Astrophysics Data System (ADS)

    Itzler, Mark A.; Entwistle, Mark; Krishnamachari, Uppili; Owens, Mark; Jiang, Xudong; Slomkowski, Krystyna; Rangwala, Sabbir

    2014-06-01

    The operation of avalanche photodiodes in Geiger mode by arming these detectors above their breakdown voltage provides high-performance single photon detection in a robust solid-state device platform. Moreover, these devices are ideally suited for integration into large format focal plane arrays enabling single photon imaging. We describe the design and performance of short-wave infrared 3D imaging cameras with focal plane arrays (FPAs) based on Geigermode avalanche photodiodes (GmAPDs) with single photon sensitivity for laser radar imaging applications. The FPA pixels incorporate InP/InGaAs(P) GmAPDs for the detection of single photons with high efficiency and low dark count rates. We present results and attributes of fully integrated camera sub-systems with 32 × 32 and 128 × 32 formats, which have 100 μm pitch and 50 μm pitch, respectively. We also address the sensitivity of the fundamental GmAPD detectors to radiation exposure, including recent results that correlate detector active region volume to sustainable radiation tolerance levels.

  2. Geiger-mode APD camera system for single-photon 3D LADAR imaging

    NASA Astrophysics Data System (ADS)

    Entwistle, Mark; Itzler, Mark A.; Chen, Jim; Owens, Mark; Patel, Ketan; Jiang, Xudong; Slomkowski, Krystyna; Rangwala, Sabbir

    2012-06-01

    The unparalleled sensitivity of 3D LADAR imaging sensors based on single photon detection provides substantial benefits for imaging at long stand-off distances and minimizing laser pulse energy requirements. To obtain 3D LADAR images with single photon sensitivity, we have demonstrated focal plane arrays (FPAs) based on InGaAsP Geiger-mode avalanche photodiodes (GmAPDs) optimized for use at either 1.06 μm or 1.55 μm. These state-of-the-art FPAs exhibit excellent pixel-level performance and the capability for 100% pixel yield on a 32 x 32 format. To realize the full potential of these FPAs, we have recently developed an integrated camera system providing turnkey operation based on FPGA control. This system implementation enables the extremely high frame-rate capability of the GmAPD FPA, and frame rates in excess of 250 kHz (for 0.4 μs range gates) can be accommodated using an industry-standard CameraLink interface in full configuration. Real-time data streaming for continuous acquisition of 2 μs range gate point cloud data with 13-bit time-stamp resolution at 186 kHz frame rates has been established using multiple solid-state storage drives. Range gate durations spanning 4 ns to 10 μs provide broad operational flexibility. The camera also provides real-time signal processing in the form of multi-frame gray-scale contrast images and single-frame time-stamp histograms, and automated bias control has been implemented to maintain a constant photon detection efficiency in the presence of ambient temperature changes. A comprehensive graphical user interface has been developed to provide complete camera control using a simple serial command set, and this command set supports highly flexible end-user customization.

  3. Measurements of the photon detection efficiency done for Geiger-mode avalanche photodiodes (G-APD)

    NASA Astrophysics Data System (ADS)

    Gentile, S.; Meddi, F.; Kuznetsova, E.

    2010-04-01

    Estimation of the Photon Detect Efficiency (PDE) of multi-pixel Geiger-mode avalanche photodiodes (G-APD) based on measurements of the G-APD response to low-intensity light is presented. The fit of the light-response spectra takes into account after-pulsing and cross-talk effects and yields the value of initial photons. Using a calibrated photo-detector as a reference, the value of the PDE can be calculated. The sources of systematic error of the obtained PDE is discussed as well as possibility for its minimization.

  4. Single-photon quantum efficiency of Geiger-mode InGaAs/InP avalanche photodiodes

    NASA Astrophysics Data System (ADS)

    Forsyth, Keith W.; Dries, J. C.

    2004-06-01

    The single-photon detection efficiency of various commercial InGaAs/InP avalanche photodiodes (APDs) operated in the Geiger mode has been reported previously. These studies showed substantial photon detection efficiency variation between individual devices, but did not indicate what device parameters might be responsible for this variation. We present data on the external single-photon detection efficiency of APDs operated as near-infrared single photon counters, and show how detection efficiency is related to both device design and operating conditions. We have fabricated APDs with near-infrared single-photon detection efficiency exceeding 50% at 10% excess bias, demonstrating that InGaAs/InP APDs of the proper design are well suited to many practical applications of photon counting in the 1.0 to 1.7 micron wavelength band.

  5. Demonstration of lasercom and spatial tracking with a silicon Geiger-mode APD array

    NASA Astrophysics Data System (ADS)

    Yarnall, Timothy M.; Horkley, Benjamin W.; Garg, Ajay S.; Hamilton, Scott A.

    2016-03-01

    We present a demonstration of a high-rate photon counting receiver with the potential to act as a spatial tracker based on a silicon Geiger-mode avalanche photodiode array (GM-APD). This array enables sensitive high-rate optical communication in the visible and near infrared regions of the spectrum. The array contains 1024 elements arranged in a 32x32 pixel square. This large number of elements supports high data rates through the mitigation of blocking losses and associated data rate limitations created by the reset time of an individual Geiger-mode detector. Measurement of bit error rates demonstrate that receiver sensitivities of 2.55 dB (detected) photons-per-bit for 78.8 Mb/s on-off-keying and -0.46 dB (detected) photons-per-bit for 19.4 Mb/s 16-ary pulse-position modulation are accessible with strong forward error correction. Additionally, the array can record the spatial coordinates of each detection event. By computing the centroid of the distribution of spatial detections it is possible to determine the angle-of-arrival of the detected photons. These levels of performance imply that Si GM-APD arrays are excellent candidates for a variety of free space lasercom applications ranging from atmospheric communication in the 1 micron or 780 nm spectral windows to underwater communication in the 480 nm to 520 nm spectral window

  6. Simulation of a Geiger-Mode Imaging LADAR System for Performance Assessment

    PubMed Central

    Kim, Seongjoon; Lee, Impyeong; Kwon, Yong Joon

    2013-01-01

    As LADAR systems applications gradually become more diverse, new types of systems are being developed. When developing new systems, simulation studies are an essential prerequisite. A simulator enables performance predictions and optimal system parameters at the design level, as well as providing sample data for developing and validating application algorithms. The purpose of the study is to propose a method for simulating a Geiger-mode imaging LADAR system. We develop simulation software to assess system performance and generate sample data for the applications. The simulation is based on three aspects of modeling—the geometry, radiometry and detection. The geometric model computes the ranges to the reflection points of the laser pulses. The radiometric model generates the return signals, including the noises. The detection model determines the flight times of the laser pulses based on the nature of the Geiger-mode detector. We generated sample data using the simulator with the system parameters and analyzed the detection performance by comparing the simulated points to the reference points. The proportion of the outliers in the simulated points reached 25.53%, indicating the need for efficient outlier elimination algorithms. In addition, the false alarm rate and dropout rate of the designed system were computed as 1.76% and 1.06%, respectively. PMID:23823970

  7. Evaluation of single photon and Geiger mode Lidar for the 3D Elevation Program

    USGS Publications Warehouse

    Stoker, Jason M.; Abdullah, Qassim; Nayegandhi, Amar; Winehouse, Jayna

    2016-01-01

    Data acquired by Harris Corporation’s (Melbourne, FL, USA) Geiger-mode IntelliEarth™ sensor and Sigma Space Corporation’s (Lanham-Seabrook, MD, USA) Single Photon HRQLS sensor were evaluated and compared to accepted 3D Elevation Program (3DEP) data and survey ground control to assess the suitability of these new technologies for the 3DEP. While not able to collect data currently to meet USGS lidar base specification, this is partially due to the fact that the specification was written for linear-mode systems specifically. With little effort on part of the manufacturers of the new lidar systems and the USGS Lidar specifications team, data from these systems could soon serve the 3DEP program and its users. Many of the shortcomings noted in this study have been reported to have been corrected or improved upon in the next generation sensors.

  8. Analysis and modeling of optical crosstalk in InP-based Geiger-mode avalanche photodiode FPAs

    NASA Astrophysics Data System (ADS)

    Chau, Quan; Jiang, Xudong; Itzler, Mark A.; Entwistle, Mark; Piccione, Brian; Owens, Mark; Slomkowski, Krystyna

    2015-05-01

    Optical crosstalk is a major factor limiting the performance of Geiger-mode avalanche photodiode (GmAPD) focal plane arrays (FPAs). This is especially true for arrays with increased pixel density and broader spectral operation. We have performed extensive experimental and theoretical investigations on the crosstalk effects in InP-based GmAPD FPAs for both 1.06-μm and 1.55-μm applications. Mechanisms responsible for intrinsic dark counts are Poisson processes, and their inter-arrival time distribution is an exponential function. In FPAs, intrinsic dark counts and cross talk events coexist, and the inter-arrival time distribution deviates from purely exponential behavior. From both experimental data and computer simulations, we show the dependence of this deviation on the crosstalk probability. The spatial characteristics of crosstalk are also demonstrated. From the temporal and spatial distribution of crosstalk, an efficient algorithm to identify and quantify crosstalk is introduced.

  9. Single ion implantation for single donor devices using Geiger mode detectors

    NASA Astrophysics Data System (ADS)

    Bielejec, E.; Seamons, J. A.; Carroll, M. S.

    2010-02-01

    Electronic devices that are designed to use the properties of single atoms such as donors or defects have become a reality with recent demonstrations of donor spectroscopy, single photon emission sources, and magnetic imaging using defect centers in diamond. Ion implantation, an industry standard for atom placement in materials, requires augmentation for single ion capability including a method for detecting a single ion arrival. Integrating single ion detection techniques with the single donor device construction region allows single ion arrival to be assured. Improving detector sensitivity is linked to improving control over the straggle of the ion as well as providing more flexibility in lay-out integration with the active region of the single donor device construction zone by allowing ion sensing at potentially greater distances. Using a remotely located passively gated single ion Geiger mode avalanche diode (SIGMA) detector we have demonstrated 100% detection efficiency at a distance of >75 µm from the center of the collecting junction. This detection efficiency is achieved with sensitivity to ~600 or fewer electron-hole pairs produced by the implanted ion. Ion detectors with this sensitivity and integrated with a thin dielectric, for example a 5 nm gate oxide, using low energy Sb implantation would have an end of range straggle of <2.5 nm. Significant reduction in false count probability is, furthermore, achieved by modifying the ion beam set-up to allow for cryogenic operation of the SIGMA detector. Using a detection window of 230 ns at 1 Hz, the probability of a false count was measured as ~10-1 and 10-4 for operation temperatures of ~300 K and ~77 K, respectively. Low temperature operation and reduced false, 'dark', counts are critical to achieving high confidence in single ion arrival. For the device performance in this work, the confidence is calculated as a probability of >98% for counting one and only one ion for a false count probability of 10-4 at

  10. Hybridization process for back-illuminated silicon Geiger-mode avalanche photodiode arrays

    NASA Astrophysics Data System (ADS)

    Schuette, Daniel R.; Westhoff, Richard C.; Loomis, Andrew H.; Young, Douglas J.; Ciampi, Joseph S.; Aull, Brian F.; Reich, Robert K.

    2010-04-01

    We present a unique hybridization process that permits high-performance back-illuminated silicon Geiger-mode avalanche photodiodes (GM-APDs) to be bonded to custom CMOS readout integrated circuits (ROICs) - a hybridization approach that enables independent optimization of the GM-APD arrays and the ROICs. The process includes oxide bonding of silicon GM-APD arrays to a transparent support substrate followed by indium bump bonding of this layer to a signal-processing ROIC. This hybrid detector approach can be used to fabricate imagers with high-fill-factor pixels and enhanced quantum efficiency in the near infrared as well as large-pixel-count, small-pixel-pitch arrays with pixel-level signal processing. In addition, the oxide bonding is compatible with high-temperature processing steps that can be used to lower dark current and improve optical response in the ultraviolet.

  11. The blocking probability of Geiger-mode avalanche photo-diodes

    NASA Astrophysics Data System (ADS)

    Moision, Bruce; Srinivasan, Meera; Hamkins, Jon

    2005-08-01

    When a photon is detected by a Geiger-mode avalanche photo-diode (GMAPD), the detector is rendered inactive, or blocked, for a certain period of time. In this paper we derive the blocking probability for a GMAPD whose input is either an unmodulated, Bernoulli modulated or pulse-position-modulated (PPM) Poisson process. We demonstrate how the PPM and Bernoulli cases differ, illustrating that the PPM blocking probability is larger than the Bernoulli. The blocking rates may be decreased by focusing the incident light on an array of detectors. We show that the binomial output statistics of an array of GMAPDs may be modeled as Poisson and measure the error in this approximation via the relative entropies of the two distributions.

  12. Cramer-Rao lower bound on range error for LADARs with Geiger-mode avalanche photodiodes.

    PubMed

    Johnson, Steven E

    2010-08-20

    The Cramer-Rao lower bound (CRLB) on range error is calculated for laser detection and ranging (LADAR) systems using Geiger-mode avalanche photodiodes (GMAPDs) to detect reflected laser pulses. For the cases considered, the GMAPD range error CRLB is greater than the CRLB for a photon-counting device. It is also shown that the GMAPD range error CRLB is minimized when the mean energy in the received laser pulse is finite. Given typical LADAR system parameters, a Gaussian-envelope received pulse, and a noise detection rate of less than 4 MHz, the GMAPD range error CRLB is minimized when the quantum efficiency times the mean number of received laser pulse photons is between 2.2 and 2.3. PMID:20733630

  13. Foliage penetration obscuration probability density function analysis from overhead canopy photos for gimbaled linear-mode and Geiger-mode airborne lidar

    NASA Astrophysics Data System (ADS)

    Burton, Robin R.

    2010-04-01

    Three-dimensional (3D) Light Detection And Ranging (LIDAR) systems designed for foliage penetration can produce good bare-earth products in medium to medium-heavy obscuration environments, but product creation becomes increasingly more difficult as the obscuration level increases. A prior knowledge of the obscuration environment over large areas is hard to obtain. The competing factors of area coverage rate and product quality are difficult to balance. Ground-based estimates of obscuration levels are labor intensive and only capture a small portion of the area of interest. Estimates of obscuration levels derived from airborne data require that the area of interest has been collected previously. Recently, there has been a focus on lacunarity (scale dependent measure of translational invariance) to quantify the gap structure of canopies. While this approach is useful, it needs to be evaluated relative to the size of the instantaneous field-of-view (IFOV) of the system under consideration. In this paper, the author reports on initial results to generate not just average obscuration values from overhead canopy photographs, but to generate obscuration probability density functions (PDFs) for both gimbaled linear-mode and geiger-mode airborne LIDAR. In general, gimbaled linear-mode (LM) LIDAR collects data with higher signal-to-noise (SNR), but is limited to smaller areas and cannot collect at higher altitudes. Conversely, geiger-mode (GM) LIDAR has a much lower SNR, but is capable of higher area rates and collecting data at higher altitudes. To date, geiger-mode LIDAR obscurant penetration theory has relied on a single obscuration value, but recent work has extended it to use PDFs1. Whether or not the inclusion of PDFs significantly changes predicted results and more closely matches actual results awaits the generation of PDFs over specific ground truth targets and comparison to actual collections of those ground truth targets. Ideally, examination of individual PDFs

  14. First detection of Cherenkov light from cosmic-particle-induced air showers by Geiger-mode avalanche photodiodes

    NASA Astrophysics Data System (ADS)

    Biland, A.; Britvitch, I.; Lorenz, E.; Otte, N.; Pauss, F.; Renker, D.; Ritt, S.; Roeser, U.; Schneebeli, M.

    2007-10-01

    We report on first tests of Geiger-mode APDs (G-APD) to detect Cherenkov light from cosmic particle induced air showers. The motivation for this study stems from the requirement to improve the sensitivity of large imaging atmospheric Cherenkov telescopes (IACT) by replacing the photomultipliers (PMT) by high detection efficiency G-APDs. Three tests have been carried out, confirming sufficiently high light sensitivity of blue-sensitive G-APDs as future replacement of PMTs in IACTs.

  15. Statistical analysis of dark count rate in Geiger-mode APD FPAs

    NASA Astrophysics Data System (ADS)

    Itzler, Mark A.; Krishnamachari, Uppili; Chau, Quan; Jiang, Xudong; Entwistle, Mark; Owens, Mark; Slomkowski, Krystyna

    2014-10-01

    We present a temporal statistical analysis of the array-level dark count behavior of Geiger-mode avalanche photodiode (GmAPD) focal plane arrays that distinguishes between Poissonian intrinsic dark count rate and non-Poissonian crosstalk counts by considering "inter-arrival" times between successive counts from the entire array. For 32 x 32 format sensors with 100 μm pixel pitch, we show the reduction of crosstalk for smaller active area sizes within the pixel. We also compare the inter-arrival time behavior for arrays with narrow band (900 - 1100 nm) and broad band (900 - 1600 nm) spectral response. We then consider a similar analysis of larger format 128 x 32 arrays. As a complement to the temporal analysis, we describe the results of a spatial analysis of crosstalk events. Finally, we propose a simple model for the impact of crosstalk events on the Poissonian statistics of intrinsic dark counts that provides a qualitative explanation for the results of the inter-arrival time analysis for arrays with varying degrees of crosstalk.

  16. Characterization and Monte Carlo simulation of single ion Geiger mode avalanche diodes integrated with a quantum dot nanostructure

    NASA Astrophysics Data System (ADS)

    Sharma, Peter; Abraham, J. B. S.; Ten Eyck, G.; Childs, K. D.; Bielejec, E.; Carroll, M. S.

    Detection of single ion implantation within a nanostructure is necessary for the high yield fabrication of implanted donor-based quantum computing architectures. Single ion Geiger mode avalanche (SIGMA) diodes with a laterally integrated nanostructure capable of forming a quantum dot were fabricated and characterized using photon pulses. The detection efficiency of this design was measured as a function of wavelength, lateral position, and for varying delay times between the photon pulse and the overbias detection window. Monte Carlo simulations based only on the random diffusion of photo-generated carriers and the geometrical placement of the avalanche region agrees qualitatively with device characterization. Based on these results, SIGMA detection efficiency appears to be determined solely by the diffusion of photo-generated electron-hole pairs into a buried avalanche region. Device performance is then highly dependent on the uniformity of the underlying silicon substrate and the proximity of photo-generated carriers to the silicon-silicon dioxide interface, which are the most important limiting factors for reaching the single ion detection limit with SIGMA detectors. Sandia National Laboratories is a multi-program laboratory managed and operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Corporation, for the U.S. Department of Energy's National Nuclear Security Administration under Contract DE-AC04-94AL85000.

  17. A novel camera type for very high energy gamma-ray astronomy based on Geiger-mode avalanche photodiodes

    NASA Astrophysics Data System (ADS)

    Anderhub, H.; Backes, M.; Biland, A.; Boller, A.; Braun, I.; Bretz, T.; Commichau, S.; Commichau, V.; Dorner, D.; Gendotti, A.; Grimm, O.; von Gunten, H.; Hildebrand, D.; Horisberger, U.; Krähenbühl, T.; Kranich, D.; Lorenz, E.; Lustermann, W.; Mannheim, K.; Neise, D.; Pauss, F.; Renker, D.; Rhode, W.; Rissi, M.; Röser, U.; Rollke, S.; Stark, L. S.; Stucki, J.-P.; Viertel, G.; Vogler, P.; Weitzel, Q.

    2009-10-01

    Geiger-mode avalanche photodiodes (G-APD) are promising new sensors for light detection in atmospheric Cherenkov telescopes. In this paper, the design and commissioning of a 36-pixel G-APD prototype camera is presented. The data acquisition is based on the Domino Ring Sampling (DRS2) chip. A sub-nanosecond time resolution has been achieved. Cosmic-ray induced air showers have been recorded using an imaging mirror setup, in a self-triggered mode. This is the first time that such measurements have been carried out with a complete G-APD camera.

  18. Spatial modeling of optical crosstalk in InGaAsP Geiger-mode APD focal plane arrays.

    PubMed

    Piccione, Brian; Jiang, Xudong; Itzler, Mark A

    2016-05-16

    We report a spatial model of optical crosstalk in InGaAsP Geiger-mode APD focal plane arrays created via non-sequential ray tracing. Using twenty-four equivalent experimental data sets as a baseline, we show that experimental results can be reproduced to a high degree of accuracy by incorporating secondary crosstalk effects, with reasonable assumptions of material and emission source properties. We use this model to categorize crosstalk according to source and path, showing that the majority of crosstalk in the immediate neighborhood of avalanching pixels in the present devices can be attributed to direct line-of-sight emissions. PMID:27409885

  19. Conception d'un circuit d'etouffement pour photodiodes a avalanche en mode geiger pour integration heterogene 3d

    NASA Astrophysics Data System (ADS)

    Boisvert, Alexandre

    Le Groupe de Recherche en Appareillage Medical de Sherbrooke (GRAMS) travaille actuellement sur un programme de recherche portant sur des photodiodes a avalanche mono-photoniques (PAMP) operees en mode Geiger en vue d'une application a la tomographie d'emission par positrons (TEP). Pour operer dans ce mode; la PAMP, ou SPAD selon l'acronyme anglais (Single Photon Avalanche Diode), requiert un circuit d'etouffement (CE) pour, d'une part, arreter l'avalanche pouvant causer sa destruction et, d'autre part. la reinitialiser en mode d'attente d'un nouveau photon. Le role de ce CE comprend egalement une electronique de communication vers les etages de traitement avance de signaux. La performance temporelle optimale du CE est realisee lorsqu'il est juxtapose a la PAMP. Cependant, cela entraine une reduction de la surface photosensible ; un element crucial en imagerie. L'integration 3D, a base d'interconnexions verticales, offre une solution elegante et performante a cette problematique par l'empilement de circuits integres possedant differentes fonctions (PAMP, CE et traitement avance de signaux). Dans l'approche proposee, des circuits d'etouffement de 50 pm x 50 pm realises sur une technologie CMOS 130 mn 3D Tezzaron, contenant chacun 112 transistors, sont matrices afin de correspondre a une matrice de PAMP localisee sur une couche electronique superieure. Chaque circuit d'etouffement possede une gigue temporelle de 7,47 ps RMS selon des simulations faites avec le logiciel Cadence. Le CE a la flexibilite d'ajuster les temps d'etouffement et de recharge pour la PAMP tout en presentant une faible consommation de puissance (~ 0,33 mW a 33 Mcps). La conception du PAMP necessite de supporter des tensions superieures aux 3,3 V de la technologie. Pour repondre a ce probleme, des transistors a drain etendu (DEMOS) ont ete realises. En raison de retards de production par Ies fabricants, les circuits n'ont pu etre testes physiquement par des mesures. Les resultats de ce memoire

  20. Operating a Geiger-Muller Tube Using a PC Sound Card

    ERIC Educational Resources Information Center

    Azooz, A. A.

    2009-01-01

    In this paper, a simple MATLAB-based PC program that enables the computer to function as a replacement for the electronic scalar-counter system associated with a Geiger-Muller (GM) tube is described. The program utilizes the ability of MATLAB to acquire data directly from the computer sound card. The signal from the GM tube is applied to the…

  1. Active quench and reset integrated circuit with novel hold-off time control logic for Geiger-mode avalanche photodiodes.

    PubMed

    Deng, Shijie; Morrison, Alan P

    2012-09-15

    This Letter presents an active quench-and-reset circuit for Geiger-mode avalanche photodiodes (GM-APDs). The integrated circuit was fabricated using a conventional 0.35 μm complementary metal oxide semiconductor process. Experimental results show that the circuit is capable of linearly setting the hold-off time from several nanoseconds to microseconds with a resolution of 6.5 ns. This allows the selection of the optimal afterpulse-free hold-off time for the GM-APD via external digital inputs or additional signal processing circuitry. Moreover, this circuit resets the APD automatically following the end of the hold-off period, thus simplifying the control for the end user. Results also show that a minimum dead time of 28.4 ns is achieved, demonstrating a saturated photon-counting rate of 35.2 Mcounts/s.

  2. Measured Temperature Dependence of Scintillation Camera Signals Read Out by Geiger-Müller Mode Avalanche Photodiodes.

    PubMed

    Hunter, William C J; Miyaoka, Robert S; Macdonald, L R; Lewellen, Thomas K

    2009-10-24

    We are developing a prototype monolithic scintillation camera with optical sensors on the entrance surface (SES) for use with statistically-estimated depth-of-interaction in a continuous scintillator. We opt to use Geiger-Müller mode avalanche photodiodes (GM-APDs) for the SES camera since they possess many desirable properties; for the intended application (SES and PET/MR imaging), they offer a thin attenuation profile and an operational insensitivity to large magnetic fields. However, one issue that must be addressed in using GM-APDs in an RF environment (as in MR scanners) is the thermal dissipation that can occur in this semiconductor material.Signals of GM-APDs are strongly dependent on junction temperature. Consequently, we are developing a temperature-controlled GM-APD-based PET camera whose monitored temperature can be used to dynamically account for the temperature dependence of the output signals. Presently, we aim to characterize the output-signal dependence on temperature and bias for a GM-APD-based scintillation camera.We've examined two GM-APDs, a Zecotek prototype MAPD-3N, and a SensL commercial SPMArray2. The dominant effect of temperature on gain that we observe results from a linear dependence of breakdown voltage on temperature (0.071 V/°C and 0.024 V/°C, respectively); at 2.3 V excess bias (voltage above breakdown) the resulting change in gain with temperature (without adjusting bias voltage) is -8.5% per °C for the MAPD-3N and -1.5 % per °C for the SPMArray2. For fixed excess bias, change in dark current with temperature varied widely, decreasing by 25% to 40% as temperature was changed from 20 °C to 10 °C and again by 20% to 35% going from 10 °C to 0 °C. Finally, using two MAPD-3N to read out a pair of 3.5-by-3.5-by-20 mm(3) Zecotek LFS-3 scintillators in coincidence, we observe a decrease from 1.7 nsec to 1.5 nsec in coincidence-time resolution as we lowered temperature from 23 °C to 10 °C.

  3. Dynamics of local micro-breakdown in the Geiger mode of avalanche photodiodes

    SciTech Connect

    Verhovtseva, A. V. Gergel, V. A.

    2009-07-15

    Mathematical modeling methods were used to study the dynamics of micro-breakdown development in structures of silicon avalanche photodiodes. The constructed model considers the locality of the avalanchexs multiplication region appearing during single photon absorption and the delay of the avalanchexs current spreading over the rear electrode of the diode. The calculations showed two different phases of transient process of the formation of the electrical signal, i.e., the rapid and slow ones due to current spreading and ordinary RC recharge, respectively. The load resistances required to implement the pulsed mode of operation of the structures of the avalanche photodiode were calculated for a series of actual diode capacitances and spreading resistances of the rear electrode.

  4. Detection of the Light Produced in Scintillating Tiles by Means of a Wls Fiber and AN Avalanche Photodiode Working in the Geiger Mode

    NASA Astrophysics Data System (ADS)

    Akindinov, A.; Mal'Kevich, D.; Martemiyanov, A.; Smirnitsky, A.; Voloshin, K.; Grigoriev, E.; Golovin, V.; Bondarenko, G.

    2004-07-01

    Plates of an organic scintillator BC408, 50 × 50 × 5 mm3, with a wavelength-shifting (WLS) fiber Kuraray Y11, embedded in circular grooves inside the plastic, were used in combination with 1 mm2 avalanche photodiodes working in the Geiger mode (APDg or MRS-APD). Beam tests with minimum ionizing particles (MIP), performed at the ITEP synchrotron, have shown high detection efficiencies (about 13 photo-electrons).

  5. Feasibility study to determine correct focus by analyzing photon distributions on Geiger-mode avalanche photodiode focal plane array

    NASA Astrophysics Data System (ADS)

    Kim, Tae Hoon; Kong, Hong Jin; Jo, Sung Eun; Oh, Min Seok

    2011-06-01

    A method to determine correct focus in direct detection laser radar system using Geiger-mode avalanche photodiode focal plane array (GmAPD-FPA) is proposed. It is implemented by laser pulses with controlled beam diameter and energy on a distant target. And the time-of-flight (TOF) of laser pulses are obtained for each pixel in GmAPD-FPA. With multiple laser pulses, time correlated single photon counting (TCSPC) is carried out to obtain target detection probability. Using target detection probabilities of each pixel, the photon distribution on GmAPD-FPA is acquired. The condition to determine correct focus is the minimum photon distribution in GmAPD-FPA. In theory part, the range of laser pulse energy is decided. The experiments are carried out with commercial 1x8 pixel GmAPD-FPA. The experimental results show that the focus position is founded using this method and a spatial resolution of a laser radar system is improved where the 1x8 pixel GmAPD-FPA is located in focus position.

  6. Comparison of 32 x 128 and 32 x 32 Geiger-mode APD FPAs for single photon 3D LADAR imaging

    NASA Astrophysics Data System (ADS)

    Itzler, Mark A.; Entwistle, Mark; Owens, Mark; Patel, Ketan; Jiang, Xudong; Slomkowski, Krystyna; Rangwala, Sabbir; Zalud, Peter F.; Senko, Tom; Tower, John; Ferraro, Joseph

    2011-05-01

    We present results obtained from 3D imaging focal plane arrays (FPAs) employing planar-geometry InGaAsP/InP Geiger-mode avalanche photodiodes (GmAPDs) with high-efficiency single photon sensitivity at 1.06 μm. We report results obtained for new 32 x 128 format FPAs with 50 μm pitch and compare these results to those obtained for 32 x 32 format FPAs with 100 μm pitch. We show excellent pixel-level yield-including 100% pixel operability-for both formats. The dark count rate (DCR) and photon detection efficiency (PDE) performance is found to be similar for both types of arrays, including the fundamental DCR vs. PDE tradeoff. The optical crosstalk due to photon emission induced by pixel-level avalanche detection events is found to be qualitatively similar for both formats, with some crosstalk metrics for the 32 x 128 format found to be moderately elevated relative to the 32 x 32 FPA results. Timing jitter measurements are also reported for the 32 x 128 FPAs.

  7. InP-based Geiger-mode avalanche photodiode arrays for three-dimensional imaging at 1.06 μm

    NASA Astrophysics Data System (ADS)

    Itzler, Mark A.; Entwistle, Mark; Owens, Mark; Jiang, Xudong; Patel, Ketan; Slomkowski, Krystyna; Koch, Tim; Rangwala, Sabbir; Zalud, Peter F.; Yu, Young; Tower, John; Ferraro, Joseph

    2009-05-01

    We report on the development of 32 x 32 focal plane arrays (FPAs) based on InGaAsP/InP Geiger-mode avalanche photodiodes (GmAPDs) designed for use in three-dimensional (3-D) laser radar imaging systems at 1064 nm. To our knowledge, this is the first realization of FPAs for 3-D imaging that employ a planar-passivated buried-junction InP-based GmAPD device platform. This development also included the design and fabrication of custom readout integrate circuits (ROICs) to perform avalanche detection and time-of-flight measurements on a per-pixel basis. We demonstrate photodiode arrays (PDAs) with a very narrow breakdown voltage distribution width of 0.34 V, corresponding to a breakdown voltage total variation of less than +/- 0.2%. At an excess bias voltage of 3.3 V, which provides 40% pixel-level single photon detection efficiency, we achieve average dark count rates of 2 kHz at an operating temperature of 248 K. We present the characterization of optical crosstalk induced by hot carrier luminescence during avalanche events, where we show that the worst-case crosstalk probability per pixel, which occurs for nearest neighbors, has a value of less than 1.6% and exhibits anisotropy due to isolation trench etch geometry. To demonstrate the FPA response to optical density variations, we show a simple image of a broadened optical beam.

  8. Model of turn-on characteristics of InP-based Geiger-mode avalanche photodiodes suitable for circuit simulations

    NASA Astrophysics Data System (ADS)

    Jordy, George; Donnelly, Joseph

    2015-05-01

    A model for the turn-on characteristics of separate-absorber-multiplier InP-based Geiger-mode Avalanche Photodiodes (APDs) has been developed. Verilog-A was used to implement the model in a manner that can be incorporated into circuit simulations. Rather than using SPICE elements to mimic the voltage and current characteristics of the APD, Verilog-A can represent the first order nonlinear differential equations that govern the avalanche current of the APD. This continuous time representation is fundamentally different than the piecewise linear characteristics of other models. The model is based on a driving term for the differential current, which is given by the voltage overbias minus the voltage drop across the device's space-charge resistance RSC. This drop is primarily due to electrons transiting the separate absorber. RSC starts off high and decreases with time as the initial breakdown filament spreads laterally to fill the APD. With constant bias voltage, the initial current grows exponentially until space charge effects reduce the driving function. With increasing current the driving term eventually goes to zero and the APD current saturates. On the other hand, if the APD is biased with a capacitor, the driving term becomes negative as the capacitor discharges, reducing the current and driving the voltage below breakdown. The model parameters depend on device design and are obtained from fitting the model to Monte-Carlo turn-on simulations that include lateral spreading of the carriers of the relevant structure. The Monte-Carlo simulations also provide information on the probability of avalanche, and jitter due to where the photon is absorbed in the APD.

  9. Optimization of a guard ring structure in Geiger-mode avalanche photodiodes fabricated at National NanoFab Center

    NASA Astrophysics Data System (ADS)

    Lim, K. T.; Kim, H.; Cho, M.; Kim, Y.; Kim, C.; Kim, M.; Lee, D.; Kang, D.; Yoo, H.; Park, K.; Sul, W. S.; Cho, G.

    2016-01-01

    A typical Geiger-mode avalanche photodiode (G-APD) contains a guard ring that protects the structure from having an edge breakdown due to the lowering of electric fields at junction curvatures. In this contribution, G-APDs with a virtual guard ring (vGR) merged with n-type diffused guard ring (nGR) in various sizes were studied to find the optimal design for G-APDs fabricated at National NanoFab Center (NNFC) . The sensors were fabricated via a customized CMOS process with a micro-cell size of 65× 65 μm2 on a 200 mm p-type epitaxial layer wafer. I-V characteristic curves for proposed structures were measured on a wafer-level with an auto probing system and plotted together to compare their performance. A vGR width of 1.5 μm and a nGR width of 1.5 μm with an overlapping between vGR and nGR of 1.5 μm showed the lowest leakage current before the breakdown voltage while suppressing the edge breakdown. Furthermore, the current level of the lowest-leakage-current structure was as low as that of only vGR with a width of 2.0 μm, indicating that the structure is also area efficient. Based on these results, the design with vGR, nGR, and OL with width of 1.5 μm is determined to be the optimal structure for G-APDs fabricated at NNFC.

  10. Non-Geiger-Mode Single-Photon Avalanche Detector with Low Excess Noise

    NASA Technical Reports Server (NTRS)

    Zhao, Kai; Lo, YuHwa; Farr, William

    2010-01-01

    This design constitutes a self-resetting (gain quenching), room-temperature operational semiconductor single-photon-sensitive detector that is sensitive to telecommunications optical wavelengths and is scalable to large areas (millimeter diameter) with high bandwidth and efficiencies. The device can detect single photons at a 1,550-nm wavelength at a gain of 1 x 10(exp 6). Unlike conventional single photon avalanche detectors (SPADs), where gain is an extremely sensitive function to the bias voltage, the multiplication gain of this device is stable at 1 x 10(exp 6) over a wide range of bias from 30.2 to 30.9 V. Here, the multiplication gain is defined as the total number of charge carriers contained in one output pulse that is triggered by the absorption of a single photon. The statistics of magnitude of output signals also shows that the device has a very narrow pulse height distribution, which demonstrates a greatly suppressed gain fluctuation. From the histograms of both pulse height and pulse charge, the equivalent gain variance (excess noise) is between 1.001 and 1.007 at a gain of 1 x 10(exp 6). With these advantages, the device holds promise to function as a PMT-like photon counter at a 1,550- nm wavelength. The epitaxial layer structure of the device allows photons to be absorbed in the InGaAs layer, generating electron/hole (e-h) pairs. Driven by an electrical field in InGaAs, electrons are collected at the anode while holes reach the multiplication region (InAlAs p-i-n structure) and trigger the avalanche process. As a result, a large number of e-h pairs are created, and the holes move toward the cathode. Holes created by the avalanche process gain large kinetic energy through the electric field, and are considered hot. These hot holes are cooled as they travel across a p -InAlAs low field region, and are eventually blocked by energy barriers formed by the InGaAsP/ InAlAs heterojunctions. The composition of the InGaAsP alloy was chosen to have an 80 me

  11. Restraint of range walk error in a Geiger-mode avalanche photodiode lidar to acquire high-precision depth and intensity information.

    PubMed

    Xu, Lu; Zhang, Yu; Zhang, Yong; Yang, Chenghua; Yang, Xu; Zhao, Yuan

    2016-03-01

    There exists a range walk error in a Geiger-mode avalanche photodiode (Gm-APD) lidar because of the fluctuation in the number of signal photoelectrons. To restrain this range walk error, we propose a new returning-wave signal processing technique based on the Poisson probability response model and the Gaussian functions fitting method. High-precision depth and intensity information of the target at the distance of 5 m is obtained by a Gm-APD lidar using a 6 ns wide pulsed laser. The experiment results show that the range and intensity precisions are 1.2 cm and 0.015 photoelectrons, respectively. PMID:26974630

  12. Autofocus technique for three-dimensional imaging, direct-detection laser radar using Geiger-mode avalanche photodiode focal-plane array.

    PubMed

    Oh, Min Seok; Kong, Hong Jin; Kim, Tae Hoon; Jo, Sung Eun

    2010-12-15

    An autofocus technique is proposed for a three-dimensional imaging, direct-detection laser radar system that uses a Geiger-mode avalanche photodiode focal plane array (GmAPD-FPA). This technique is implemented by pointing laser pulses on a target of interest and observing its scattered photon distribution on a GmAPD-FPA. Measuring the standard deviation of the photon distribution on a GmAPD-FPA enables the best focus condition to be found. The feasibility of this technique is demonstrated experimentally by employing a 1 × 8 pixel GmAPD-FPA. It is shown that the spatial resolution improves when the GmAPD-FPA is located in the best focus position found by the autofocus technique. PMID:21165141

  13. Performance assessment of simulated 3D laser images using Geiger-mode avalanche photo-diode: tests on simple synthetic scenarios

    NASA Astrophysics Data System (ADS)

    Coyac, Antoine; Hespel, Laurent; Riviere, Nicolas; Briottet, Xavier

    2015-10-01

    In the past few decades, laser imaging has demonstrated its potential in delivering accurate range images of objects or scenes, even at long range or under bad weather conditions (rain, fog, day and night vision). We note great improvements in the conception and development of single and multi infrared sensors, concerning embedability, circuitry reading capacity, or pixel resolution and sensitivity, allowing a wide diversity of applications (i.e. enhanced vision, long distance target detection and reconnaissance, 3D DSM generation). Unfortunately, it is often difficult to dispose of all the instruments to compare their performance for a given application. Laser imaging simulation has shown to be an interesting alternative to acquire real data, offering a higher flexibility to perform this sensors comparison, plus being time and cost efficient. In this paper, we present a 3D laser imaging end-to-end simulator using a focal plane array with Geiger mode detection, named LANGDOC. This work aims to highlight the interest and capability of this new generation of photo-diodes arrays, especially for airborne mapping and surveillance of high risk areas.

  14. Derivation of the sensitivity of a Geiger mode avalanche photodiode detector from a given efficiency for quantum key distribution experiments

    NASA Astrophysics Data System (ADS)

    Hammura, Kiyotaka; Williams, David

    2009-05-01

    The detection sensitivity (DS) of a commercial single-photon receiver based on an InGaAs gate-mode avalanche photodiode is estimated. The installation of a digital-blanking system (DBS) to reduce dark current differentiates between the DS, which is the efficiency of the detector during its open-gate/active state, and the total/overall detection efficiency (DE). Using numerical simulations it is found that the average number of light-pulses blanked by DBS following a registered pulse is 0.333. The DS is estimated at 0.216, which can be used for estimating the DE for an arbitrary photon arrival rate and gating frequency of the receiver.

  15. Derivation of Sensitivity of a Geiger Mode Apds Detector from a Given Efficiency to Estimate Total Photon Counts

    NASA Astrophysics Data System (ADS)

    Hammura, Kiyotaka; Williams, David Arfon

    2009-06-01

    The detection sensitivity (DS) of the commercial single-photon-receiver based on InGaAs gatemode avalanche photodiode is estimated. Instalment of a digital-blanking-system (DBS) to reduce dark current makes the difference between DS and the detection efficiency (DE). By numerical simulations, it is found that the blanked number of light-pulses by DBS is as many as a quarter of all incident pulses for a specific operation condition. DS is estimated at 0.27, which is 35% larger than a given DE.

  16. FLEXIBLE GEIGER COUNTER

    DOEpatents

    Richter, H.G.; Gillespie, A.S. Jr.

    1963-11-12

    A flexible Geiger counter constructed from materials composed of vinyl chloride polymerized with plasticizers or co-polymers is presented. The counter can be made either by attaching short segments of corrugated plastic sleeving together, or by starting with a length of vacuum cleaner hose composed of the above materials. The anode is maintained substantially axial Within the sleeving or hose during tube flexing by means of polystyrene spacer disks or an easily assembled polyethylene flexible cage assembly. The cathode is a wire spiraled on the outside of the counter. The sleeving or hose is fitted with glass end-pieces or any other good insulator to maintain the anode wire taut and to admit a counting gas mixture into the counter. Having the cathode wire on the outside of the counter substantially eliminates the objectional sheath effect of prior counters and permits counting rates up to 300,000 counts per minute. (AEC)

  17. Recent Enhancements to the National Transonic Facility (Mixed Mode Operations)

    NASA Technical Reports Server (NTRS)

    Kilgore, W. Allen; Chan, David; Balakrishna, S.; Wahls, Richard A.

    2006-01-01

    The U.S. National Transonic Facility continues to make enhancements to provide quality data in a safe, efficient and cost effective method for aerodynamic ground testing. Recent enhancements discussed in this paper include the development of a Mixed-mode of operations that combine Air-mode operations with Nitrogen-mode operations. This implementation and operational results of this new Mixed-mode expands the ambient temperature transonic region of testing beyond the Air-mode limitations at a significantly reduced cost over Nitrogen Mode operation.

  18. Extracting Operating Modes from Building Electrical Load Data: Preprint

    SciTech Connect

    Frank, S.; Polese, L. G.; Rader, E.; Sheppy, M.; Smith, J.

    2012-01-01

    Empirical techniques for characterizing electrical energy use now play a key role in reducing electricity consumption, particularly miscellaneous electrical loads, in buildings. Identifying device operating modes (mode extraction) creates a better understanding of both device and system behaviors. Using clustering to extract operating modes from electrical load data can provide valuable insights into device behavior and identify opportunities for energy savings. We present a fast and effective heuristic clustering method to identify and extract operating modes in electrical load data.

  19. Dual-Mode Scramjet Flameholding Operability Measurements

    NASA Technical Reports Server (NTRS)

    Donohue, James M.

    2012-01-01

    Flameholding measurements were made in two different direct connect combustor facilities that were designed to simulate a cavity flameholder in the flowfield of a hydrocarbon fueled dual-mode scramjet combustor. The presence of a shocktrain upstream of the flameholder has a significant impact on the inlet flow to the combustor and on the flameholding limits. A throttle was installed in the downstream end of the test rigs to provide the needed back-pressurization and decouple the operation of the flameholder from the backpressure formed by heat release and thermal choking, as in a flight engine. Measurements were made primarily with ethylene fuel but a limited number of tests were also performed with heated gaseous JP-7 fuel injection. The flameholding limits were measured by ramping inlet air temperature down until blowout was observed. The tests performed in the United Technologies Research Center (UTRC) facility used a hydrogen fueled vitiated air heater, Mach 2.2 and 3.3 inlet nozzles, a scramjet combustor rig with a 1.666 by 6 inch inlet and a 0.65 inch deep cavity. Mean blowout temperature measured at the baseline condition with ethylene fuel, the Mach 2.2 inlet and a cavity pressure of 21 psia was 1502 oR. Flameholding sensitivity to a variety of parameters was assessed. Blowout temperature was found to be most sensitive to fuel injection location and fuel flowrates and surprisingly insensitive to operating pressure (by varying both back-pressurization and inlet flowrate) and inlet Mach number. Video imaging through both the bottom and side wall windows was collected simultaneously and showed that the flame structure was quite unsteady with significant lateral movements as well as movement upstream of the flameholder. Experiments in the University of Virginia (UVa) test facility used a Mach 2 inlet nozzle with a 1 inch by 1.5 inch exit cross section, an aspect ratio of 1.5 versus 3.6 in the UTRC facility. The UVa facility tests were designed to measure the

  20. ASIC Readout Circuit Architecture for Large Geiger Photodiode Arrays

    NASA Technical Reports Server (NTRS)

    Vasile, Stefan; Lipson, Jerold

    2012-01-01

    The objective of this work was to develop a new class of readout integrated circuit (ROIC) arrays to be operated with Geiger avalanche photodiode (GPD) arrays, by integrating multiple functions at the pixel level (smart-pixel or active pixel technology) in 250-nm CMOS (complementary metal oxide semiconductor) processes. In order to pack a maximum of functions within a minimum pixel size, the ROIC array is a full, custom application-specific integrated circuit (ASIC) design using a mixed-signal CMOS process with compact primitive layout cells. The ROIC array was processed to allow assembly in bump-bonding technology with photon-counting infrared detector arrays into 3-D imaging cameras (LADAR). The ROIC architecture was designed to work with either common- anode Si GPD arrays or common-cathode InGaAs GPD arrays. The current ROIC pixel design is hardwired prior to processing one of the two GPD array configurations, and it has the provision to allow soft reconfiguration to either array (to be implemented into the next ROIC array generation). The ROIC pixel architecture implements the Geiger avalanche quenching, bias, reset, and time to digital conversion (TDC) functions in full-digital design, and uses time domain over-sampling (vernier) to allow high temporal resolution at low clock rates, increased data yield, and improved utilization of the laser beam.

  1. Mode coupling in hybrid square-rectangular lasers for single mode operation

    NASA Astrophysics Data System (ADS)

    Ma, Xiu-Wen; Huang, Yong-Zhen; Yang, Yue-De; Xiao, Jin-Long; Weng, Hai-Zhong; Xiao, Zhi-Xiong

    2016-08-01

    Mode coupling between a square microcavity and a Fabry-Pérot (FP) cavity is proposed and demonstrated for realizing single mode lasers. The modulations of the mode Q factor as simulation results are observed and single mode operation is obtained with a side mode suppression ratio of 46 dB and a single mode fiber coupling loss of 3.2 dB for an AlGaInAs/InP hybrid laser as a 300-μm-length and 1.5-μm-wide FP cavity connected to a vertex of a 10-μm-side square microcavity. Furthermore, tunable single mode operation is demonstrated with a continuous wavelength tuning range over 10 nm. The simple hybrid structure may shed light on practical applications of whispering-gallery mode microcavities in large-scale photonic integrated circuits and optical communication and interconnection.

  2. Harmonic gyrotrons operating in high-order symmetric modes

    SciTech Connect

    Nusinovich, Gregory S.; Kashyn, Dmytro G.; Antonsen, T. M.

    2015-01-05

    It is shown that gyrotrons operating at cyclotron harmonics can be designed for operation in symmetric TE{sub 0,p}-modes. Such operation in fundamental harmonic gyrotrons is possible only at small radial indices (p≤3) because of the severe mode competition with TE{sub 2,p}-modes, which are equally coupled to annular beams as the symmetric modes. At cyclotron harmonics, however, this “degeneracy” of coupling is absent, and there is a region in the parameter space where harmonic gyrotrons can steadily operate in symmetric modes. This fact is especially important for sub-THz and THz-range gyrotrons where ohmic losses limit the power achievable in continuous-wave and high duty cycle regimes.

  3. Detection of Cherenkov light from air showers with Geiger-APDs

    NASA Astrophysics Data System (ADS)

    Otte, A.N. Britvich, I.; Biland, A.; Goebel, F.; Lorenz, E.; Pauss, F.; Renker, D.; Röser, U.; Schweizer, T.

    We have detected Cherenkov light from air showers with Geiger-mode APDs (G-APDs). G-APDs are novel semiconductor photon-detectors which offer several advantages compared to conventional photomultiplier tubes in the field of air shower detection. Folded with the Cherenkov spectrum the response of G-APDs is up to a factor of three higher if compared with classical photomultipliers. Moreover they offer high gain (~105-106) at low operation voltages (<100 V). Under operation they can withstand excessive and prolonged exposure to bright light and are also mechanical robust. Dark count rates of some G-APDs are below the level of light coming from the night sky. Furthermore G-APDs can be mass-produced which allows to considerably reduce the costs of these sensors. According to the present state of the development of G-APD they promise to be a major progress for gamma-ray astronomy. Here we report on the detection of Cherenkov light from air showers with G-APD. We discuss first test results and the advantages and problems of G-APDs in Cherenkov telescopes.

  4. Charging system with galvanic isolation and multiple operating modes

    DOEpatents

    Kajouke, Lateef A.; Perisic, Milun; Ransom, Ray M.

    2013-01-08

    Systems and methods are provided for operating a charging system with galvanic isolation adapted for multiple operating modes. A vehicle charging system comprises a DC interface, an AC interface, a first conversion module coupled to the DC interface, and a second conversion module coupled to the AC interface. An isolation module is coupled between the first conversion module and the second conversion module. The isolation module comprises a transformer and a switching element coupled between the transformer and the second conversion module. The transformer and the switching element are cooperatively configured for a plurality of operating modes, wherein each operating mode of the plurality of operating modes corresponds to a respective turns ratio of the transformer.

  5. Hermitian Operators Conjugate to Two-Mode Number-Difference Operator Studied in Entangled State Representation

    NASA Astrophysics Data System (ADS)

    Xu, Xue-Fen

    2008-10-01

    In similar to the derivation of phase angle operator conjugate to the number operator by Arroyo Carrasco-Moya Cessay we deduce the Hermitian phase operators that are conjugate to the two-mode number-difference operator and the three-mode number combination operator. It is shown that these operators are on the same footing in the entangled state representation as the one of Turski in the coherent state representation.

  6. Composed planar Hall effect sensors with dual-mode operation

    NASA Astrophysics Data System (ADS)

    Mor, Vladislav; Roy, Debangsu; Schultz, Moty; Klein, Lior

    2016-02-01

    We present a composed planar Hall effect sensor with two modes of operation: (a) an ON mode where the composed sensor responds to magnetic field excitations similarly to the response of a regular planar Hall effect sensor, and (b) an OFF mode where the response is negligible. The composed planar Hall effect sensor switches from the OFF mode to the ON mode when it is exposed to a magnetic field which exceeds a certain threshold determined by the sensor design. The features of this sensor make it useful as a switch triggered by magnetic field and as a sensing device with memory, as its mode of operation indicates exposure to a magnetic field larger than a certain threshold without the need to be activated during the exposure itself.

  7. Proving Chaotic Behavior of CBC Mode of Operation

    NASA Astrophysics Data System (ADS)

    Abidi, Abdessalem; Wang, Qianxue; Bouallegue, Belgacem; Machhout, Mohsen; Guyeux, Christophe

    2016-06-01

    The cipher block chaining (CBC) mode of operation was invented by IBM (International Business Machine) in 1976. It presents a very popular way of encrypting that is used in various applications. In this paper, we have mathematically proven that, under some conditions, the CBC mode of operation can admit a chaotic behavior according to Devaney. Some cases will be properly studied in order to provide evidence for this idea.

  8. Complex Calorimeter with AC- and Relaxation-Mode Operation

    NASA Astrophysics Data System (ADS)

    Ema, Kenji; Uematsu, Takashi; Sugata, Atsushi; Yao, Haruhiko

    1993-04-01

    A complex calorimeter has been developed. This calorimeter, which can be operated both in the ac mode and the relaxation mode using the same sample cell and the same apparatus settings, uses only a small amount (30-50 mg) of sample. An application to measurements in the vicinity of the antiferroelectric phase transitions in the liquid crystal MHPOBC(4-(1-methylheptyloxycarbonyl)-phenyl 4'-octyloxybiphenyl-4-carboxylate) is demonstrated. It is shown that the present calorimeter, when operated in the relaxation mode, enables detection of the latent heat with a resolution of 0.002 J/g.

  9. Identifying a "default" visual search mode with operant conditioning.

    PubMed

    Kawahara, Jun-ichiro

    2010-09-01

    The presence of a singleton in a task-irrelevant domain can impair visual search. This impairment, known as the attentional capture depends on the set of participants. When narrowly searching for a specific feature (the feature search mode), only matching stimuli capture attention. When searching broadly (the singleton detection mode), any oddball captures attention. The present study examined which strategy represents the "default" mode using an operant conditioning approach in which participants were trained, in the absence of explicit instructions, to search for a target in an ambiguous context in which one of two modes was available. The results revealed that participants behaviorally adopted the singleton detection as the default mode but reported using the feature search mode. Conscious strategies did not eliminate capture. These results challenge the view that a conscious set always modulates capture, suggesting that the visual system tends to rely on stimulus salience to deploy attention.

  10. 47 CFR 73.1560 - Operating power and mode tolerances.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Operating power and mode tolerances. 73.1560 Section 73.1560 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Rules Applicable to All Broadcast Stations § 73.1560 Operating power and...

  11. 47 CFR 73.840 - Operating power and mode tolerances.

    Code of Federal Regulations, 2010 CFR

    2010-10-01

    ... 47 Telecommunication 4 2010-10-01 2010-10-01 false Operating power and mode tolerances. 73.840 Section 73.840 Telecommunication FEDERAL COMMUNICATIONS COMMISSION (CONTINUED) BROADCAST RADIO SERVICES RADIO BROADCAST SERVICES Low Power FM Broadcast Stations (LPFM) § 73.840 Operating power and...

  12. Perspective gyrotron with mode converter for co- and counter-rotation operating modes

    SciTech Connect

    Chirkov, A. V.; Kuftin, A. N.; Denisov, G. G.

    2015-06-29

    A gyrotron oscillator operating efficiently at modes of both rotations was developed and tested. The gyrotron operation can be switched between two modes: co- and counter rotating ones with respect to electron rotation in a resonance magnetic field. A synthesized mode converter provides output of both waves in the form of two different paraxial wave beams corresponding to direction of the mode rotation. Measured gyrotron power (up to 2 MW), interaction efficiency (34%), and diffraction losses in the mode converter (≈2%) agree well with the design values. The proposed gyrotron scheme alloys principal enhancement in the device parameters—possibility of electronic switching of output wave beam direction and possibility to arrange an effective scheme to provide frequency/phase locking of a gyrotron-oscillator.

  13. Perspective gyrotron with mode converter for co- and counter-rotation operating modes

    NASA Astrophysics Data System (ADS)

    Chirkov, A. V.; Denisov, G. G.; Kuftin, A. N.

    2015-06-01

    A gyrotron oscillator operating efficiently at modes of both rotations was developed and tested. The gyrotron operation can be switched between two modes: co- and counter rotating ones with respect to electron rotation in a resonance magnetic field. A synthesized mode converter provides output of both waves in the form of two different paraxial wave beams corresponding to direction of the mode rotation. Measured gyrotron power (up to 2 MW), interaction efficiency (34%), and diffraction losses in the mode converter (≈2%) agree well with the design values. The proposed gyrotron scheme alloys principal enhancement in the device parameters—possibility of electronic switching of output wave beam direction and possibility to arrange an effective scheme to provide frequency/phase locking of a gyrotron-oscillator.

  14. Operator performance with alternative manual control modes in teleoperation

    NASA Technical Reports Server (NTRS)

    Das, H.; Zak, H.; Kim, W. S.; Bejczy, A. K.; Schenker, P. S.

    1992-01-01

    Recent experiments conducted at the JPL comparing alternative manual control modes using the JPL Advanced Teleoperator system are described. Of particular interest were control modes that provide force reflection to the operator. The task selected for the experiment is a portion of the Solar Maximum Satellite Repair procedure we developed to demonstrate the repair of the Solar Maximum Satellite with teleoperators. The seven manual control modes evaluated in the experiment are combinations of manual position or resolved motion rate control with alternative control schemes for force reflection and remote manipulator compliance. Performance measures used were task completion times, average force and torque exerted during the execution of the task, and cumulative force and torque exerted. The results were statistically analyzed and they show that, in general, force reflection significantly improves operator performance and indicate that a specific force-reflecting scheme may yield the best performance among the control modes we tested. Also, our experiment showed that, for the selected task, the position control modes were preferable to the rate control modes and slave manipulator compliance reduced task interaction forces and torques.

  15. Surface wave and linear operating mode of a plasma antenna

    SciTech Connect

    Bogachev, N. N. Bogdankevich, I. L.; Gusein-zade, N. G.; Rukhadze, A. A.

    2015-10-15

    The relation between the propagation conditions of a surface electromagnetic wave along a finiteradius plasma cylinder and the linear operating mode of a plasma antenna is investigated. The solution to the dispersion relation for a surface wave propagating along a finite-radius plasma cylinder is analyzed for weakly and strongly collisional plasmas. Computer simulations of an asymmetrical plasma dipole antenna are performed using the KARAT code, wherein the dielectric properties of plasma are described in terms of the Drude model. The plasma parameters corresponding to the linear operating mode of a plasma antenna are determined. It is demonstrated that the characteristics of the plasma antenna in this mode are close to those of an analogous metal antenna.

  16. Large-mode-area fibers operating near single-mode regime.

    PubMed

    Kong, Fanting; Dunn, Christopher; Parsons, Joshua; Kalichevsky-Dong, Monica T; Hawkins, Thomas W; Jones, Maxwell; Dong, Liang

    2016-05-16

    Lower NA in large-mode-area fibers enables better single-mode operation and larger core diameters. Fiber NA has traditionally been limited to 0.06, mostly due to the control tolerance in the fabrication process. It has been recognized recently that transverse mode instability is a major limit to average power scaling in fiber lasers. One effective method to mitigate this limit is to operate nearer to the single-mode regime. Lower fiber NA is critical in this since it allows relatively larger core diameters which is the key to mitigate the limits imposed by nonlinear effects. We have developed a fabrication process of ytterbium-doped silica glass which is capable of highly accurate refractive index control and sufficient uniformity for LMA fibers. This process is also capable of large-volume production. It is based on a significant amount of post-processing once the fiber preforms are made. We have demonstrated 30/400 and 40/400 LMA fibers with a NA of ~0.028 operating very close to the single-mode regime. The second-order mode cuts off at ~1.2μm and ~1.55µm respectively. We have also studied issues related to bend losses due to the low NA and further optimization of LMA fibers. PMID:27409854

  17. Characterization of Al0.8Ga0.2As geiger photodiode

    NASA Astrophysics Data System (ADS)

    Chen, X. J.; Ren, Min; Chen, Yaojia; Johnson, E. B.; Campbell, Joe C.; Christian, James F.

    2015-08-01

    Solid-state photomultipliers (SSPM) are high gain photodetectors composed of Geiger photodiodes (GPD) operating above device breakdown voltage. In scintillation based radiation detection applications, SSPMs fabricated using silicon (SiPMs, MPPCs, etc) provide a compact, low cost alternative to photomultiplier tubes (PMTs), however, the high dark count rate due to its low band-gap (1.1eV) limits the signal-to-noise performance as the silicon SSPM is scaled to large areas. SSPMs fabricated in materials with a larger band-gap have the potential to surmount the performance limitations experienced by silicon. AlGaAs is a material that provides a bandgap from 1.55eV to 2.13 eV, depending on Al concentration. Using high Al concentration AlGaAs to engineer a wideband- gap (>2eV) SSPM is very desirable in terms of reducing dark noise, which promises better signal-to-noise performances when large detector areas is needed. This work describes the development of Geiger photodiodes (GPDs), the individual elements of a SSPM, fabricated in AlGaAs with 80% Al concentration. We present the design of the GPDs, the fabrication process, along with characterization data of fabricated GPD samples. To the best of our knowledge, we have demonstrated for the first time, a passively quenched Geiger photodiode in Al0.8Ga0.2As.

  18. Implementation of Enhanced Propulsion Control Modes for Emergency Flight Operation

    NASA Technical Reports Server (NTRS)

    Csank, Jeffrey T.; Chin, Jeffrey C.; May, Ryan D.; Litt, Jonathan S.; Guo, Ten-Huei

    2011-01-01

    Aircraft engines can be effective actuators to help pilots avert or recover from emergency situations. Emergency control modes are being developed to enhance the engines performance to increase the probability of recovery under these circumstances. This paper discusses a proposed implementation of an architecture that requests emergency propulsion control modes, allowing the engines to deliver additional performance in emergency situations while still ensuring a specified safety level. In order to determine the appropriate level of engine performance enhancement, information regarding the current emergency scenario (including severity) and current engine health must be known. This enables the engine to operate beyond its nominal range while minimizing overall risk to the aircraft. In this architecture, the flight controller is responsible for determining the severity of the event and the level of engine risk that is acceptable, while the engine controller is responsible for delivering the desired performance within the specified risk range. A control mode selector specifies an appropriate situation-specific enhanced mode, which the engine controller then implements. The enhanced control modes described in this paper provide additional engine thrust or response capabilities through the modification of gains, limits, and the control algorithm, but increase the risk of engine failure. The modifications made to the engine controller to enable the use of the enhanced control modes are described, as are the interaction between the various subsystems and importantly, the interaction between the flight controller/pilot and the propulsion control system. Simulation results demonstrate how the system responds to requests for enhanced operation and the corresponding increase in performance.

  19. Continuous-mode operation of a noiseless linear amplifier

    NASA Astrophysics Data System (ADS)

    Li, Yi; Carvalho, André R. R.; James, Matthew R.

    2016-05-01

    We develop a dynamical model to describe the operation of the nondeterministic noiseless linear amplifier (NLA) in the regime of continuous-mode inputs. We analyze the dynamics conditioned on the detection of photons and show that the amplification gain depends on detection times and on the temporal profile of the input state and the auxiliary single-photon state required by the NLA. We also show that the output amplified state inherits the pulse shape of the ancilla photon.

  20. Efficient potassium diode pumped alkali laser operating in pulsed mode.

    PubMed

    Zhdanov, Boris V; Rotondaro, Matthew D; Shaffer, Michael K; Knize, Randall J

    2014-07-14

    This paper presents the results of our experiments on the development of an efficient hydrocarbon free diode pumped alkali laser based on potassium vapor buffered by He gas at 600 Torr. A slope efficiency of more than 50% was demonstrated with a total optical conversion efficiency of 30%. This result was achieved by using a narrowband diode laser stack as the pump source. The stack was operated in pulsed mode to avoid limiting thermal effects and ionization.

  1. Contacting mode operation of work function energy harvester

    NASA Astrophysics Data System (ADS)

    Varpula, A.; Laakso, S. J.; Havia, T.; Kyynäräinen, J.; Prunnila, M.

    2014-11-01

    The work function energy harvester (WFEH) is a variable capacitance vibration energy harvester where the charging of the capacitor electrodes is driven by the work function difference of the electrode materials. In this work, we investigate operation modes of the WFEH by utilizing a macroscopic parallel plate capacitor with Cu and Al electrodes and varying plate distance. We show that by charging the electrodes of the WFEH by letting the electrode plates touch during the operation a significant output power enhancement can be achieved in comparison to the case where the electrodes are charged and discharged only through a load resistor.

  2. Seismic transmission operator reciprocity - II: impedance-operator symmetry via elastic lateral modes

    NASA Astrophysics Data System (ADS)

    Thomson, C. J.

    2015-08-01

    The properties of the overburden transmission response are of particular interest for the analysis of reflectivity illumination or blurring in seismic depth imaging. The first step to showing a transmission-operator reciprocity property is to identify the symmetry of the so-called displacement-to-traction operators. The latter are analogous to Dirichlet-to-Neumann operators and they may also be called impedance operators. Their symmetry is deduced here after development of a formal spectral or modal theory of lateral wavefunctions in a laterally heterogeneous generally anisotropic elastic medium. The elastic lateral modes are displacement-traction 6-vectors and they are built from two auxiliary 3-vector lateral-mode bases. These auxiliary modes arise from Hermitian and anti-Hermitian operators, so they have familiar properties such as orthogonality. There is no assumption of down/up symmetry of the elasticity tensor, but basic assumptions are made about the existence and completeness of the elastic modes. A point-symmetry property appears and plays a central role. The 6-vector elastic modes have a symplectic orthogonality property, which facilitates the development of modal expansions for 6-vector functions of the lateral coordinates when completeness is assumed. While the elastic modal theory is consistent with the laterally homogeneous case, numerical work would provide confidence that it is correct in general. An appendix contains an introductory overview of acoustic lateral modes that were studied by other authors, given from the perspective of this new work. A distinction is drawn between unit normalization of scalar auxiliary modes and a separate energy-flux normalization of 2-vector acoustic modes. Neither is crucial to the form of acoustic pressure-to-velocity or impedance operators. This statement carries over to the elastic case for the 3-vector auxiliary- and 6-vector elastic-mode normalizations. The modal theory is used to construct the kernel of the

  3. Mid-infrared fibers: variants for mode filtration for the single-mode operation

    NASA Astrophysics Data System (ADS)

    Tulaikova, Tamara V.; Kravtsov, Konstantin

    2004-11-01

    In presented paper the analytical method of the complex analysis for PIR fiber-optic depending on number of optical modes was applied with numeral estimations. In this paper the consideration of polycrystalline-fiber materials (ArBrCl) for the wavelengths 4-20mm were performed with real appropriate numeral estimations. The physical nature of imaginary part of refractive indexes was assumed as the total sum of material scattering with material absorption. The simple equations were received and used for calculations of the imaginary parts of these main functions as well as for the set of mode's attenuations (am) from the imaginary parts of propagation constants. Using designed in given paper algorithm, the analysis of the operation of surrounding water was organized for effective desirable absorption of the set of optical cladding's modes.

  4. Operation of a tokamak reactor in the radiative improved mode

    NASA Astrophysics Data System (ADS)

    Morozov, D. Kh.; Mavrin, A. A.

    2016-03-01

    The operation of a nuclear fusion reactor has been simulated within a model based on experimental results obtained at the TEXTOR-94 tokamak and other facilities in which quasistationary regimes were achieved with long confinement times, high densities, and absence of the edge-localized mode. The radiative improved mode of confinement studied in detail at the TEXTOR-94 tokamak is the most interesting such regime. One of the most important problems of modern tokamaks is the problem of a very high thermal load on a divertor (or a limiter). This problem is quite easily solved in the radiative improved mode. Since a significant fraction of the thermal energy is reemitted by an impurity, the thermal loading is significantly reduced. As the energy confinement time τ E at high densities in the indicated mode is significantly larger than the time predicted by the scaling of ITERH-98P(y, 2), ignition can be achieved in a facility much smaller than the ITER facility at plasma temperatures below 20 keV. The revealed decrease in the degradation of the confinement time τ E with an increase in the introduced power has been analyzed.

  5. Operation of Ferroelectric Plasma Sources in a Gas Discharge Mode

    SciTech Connect

    A. Dunaevsky; N.J. Fisch

    2004-03-08

    Ferroelectric plasma sources in vacuum are known as sources of ablative plasma, formed due to surface discharge. In this paper, observations of a gas discharge mode of operation of the ferroelectric plasma sources (FPS) are reported. The gas discharge appears at pressures between approximately 20 and approximately 80 Torr. At pressures of 1-20 Torr, there is a transition from vacuum surface discharge to the gas discharge, when both modes coexist and the surface discharges sustain the gas discharge. At pressures between 20 and 80 Torr, the surface discharges are suppressed, and FPS operate in pure gas discharge mode, with the formation of almost uniform plasma along the entire surface of the ceramics between strips. The density of the expanding plasma is estimated to be about 1013 cm-3 at a distance of 5.5 mm from the surface. The power consumption of the discharge is comparatively low, making it useful for various applications. This paper also presents direct measurements of the yield of secondary electron emission from ferroelectric ceramics, which, at low energies of primary electrons, is high and dependent on the polarization of the ferroelectric material

  6. Operating Modes of a Teeter-Rotor Wind Turbine

    SciTech Connect

    Bir, G. S.; Stol, K.

    1999-02-25

    We examine the operating modes of a two-bladed teetered wind turbine. Because of the gyroscopic asymmetry of its rotor, this turbine's dynamics can be quite distinct from those of a turbine with three or more blades. This asymmetry leads to system equations with periodic coefficients that are solved using the Floquet approach to extract the correct modal parameters. The system equations are derived using a simple analytical model with four degrees of freedom: cacelle yaw, rotor teeter, and flapping associated with each blade. Results confirm that the turbine modes become more dominated by the centrifugal and gyroscopic effects as the rotor speed increases. They gyroscopic effect may also cause dynamic instability. Under certain design conditions, yaw and teeter modal frequencies may coalesce.

  7. Mevva ion source operated in purely gaseous mode

    SciTech Connect

    Yushkov, G.Y.; MacGill, R.A.; Brown, I. G.

    2003-03-27

    We have operated a vacuum arc ion source in such a way as to form beams of purely gaseous ions. The vacuum arc configuration that is conventionally used to produce intense beams of metal ions was altered so as to form gaseous ion beams, with only minimal changes to the external circuitry and no changes at all internally to the ion source. In our experiments we formed beams from oxygen (O{sup +} and O{sub 2}{sup +}), nitrogen (N{sup +} and N{sub 2}{sup +}), argon (Ar{sup +}) and carbon dioxide (C{sup +}, CO{sub 2}{sup +}, O{sup +} and O{sub 2}{sup +}) at extraction voltage of 2 to 50 kV. We used a pulsed mode of operation, with beam pulses approximately 50 milliseconds long and repetition rate 10 pulses per second, for a duty cycle of about 50%. Downstream ion beam current as measured by a 5 cm diameter Faraday cup was typically 0.5 mA pulse or about 250 {micro}A time averaged. This time averaged beam current is very similar to that obtained for metal ions when the source is operated in the usual vacuum arc mode. Here we describe the modifications made to the source and the results of our investigations.

  8. Superconducting sextupole correction coil operating in persistent mode

    SciTech Connect

    Gilbert, W.; Borden, A.; Hassenzahl, W.; Mortiz, G.; Taylor, C.

    1984-09-01

    Error fields in a dipole due to superconductor magnetization and conductor misplacements add unwanted multipole, mainly sextupole and decapole, terms to the desired dipole field. Two persistent mode sextupole correction coils inside the bore of model SSC dipoles have been built and tested. A shorted superconducting sextupole coil has a current induced in it by the error sextupole field such that no sextupole field can penetrate into the proton beam region. The correction sextupole coils are one layer thick and are wound from a single length of insulated composite Nb-Ti and copper wire 0.60 mm in diameter. Each of the six poles has ten turns and is mounted on a 1.75 cm radius stainless steel bore tube. Details of testing and trimming of the correction coils are described. Test results of the measured magnetic field within the model SSC dipoles with the correction coils in and out of persistent mode operation are presented. An electrical heater is used to drive the coil out of the persistent mode. Measurements of joint resistance and coil decay time constants are also given.

  9. Mode Tracker for Mode-Hop-Free Operation of a Laser

    NASA Technical Reports Server (NTRS)

    Wysocki, Gerard; Tittel, Frank K.; Curl, Robert F.

    2010-01-01

    A mode-tracking system that includes a mode-controlling subsystem has been incorporated into an external-cavity (EC) quantum cascade laser that operates in a mid-infrared wavelength range. The mode-tracking system makes it possible to perform mode-hop-free wavelength scans, as needed for high-resolution spectroscopy and detection of trace gases. The laser includes a gain chip, a beam-collimating lens, and a diffraction grating. The grating is mounted on a platform, the position of which can be varied to effect independent control of the EC length and the grating angle. The position actuators include a piezoelectric stage for translation control and a motorized stage for coarse rotation control equipped with a piezoelectric actuator for fine rotation control. Together, these actuators enable control of the EC length over a range of about 90 m with a resolution of 0.9 nm, and control of the grating angle over a coarse-tuning range of +/-6.3deg and a fine-tuning range of +/-520 microrad with a resolution of 10 nrad. A mirror mounted on the platform with the grating assures always the same direction of the output laser beam.

  10. Single-mode operation of a coiled multimode fiber amplifier

    SciTech Connect

    Jeffrey P. Koplow; Dahv A. V. Kliner; Lew Goldberg

    2000-01-19

    The authors report a new approach to obtain single-transverse-mode operation of a multimode fiber amplifier, in which the gain fiber is coiled to induce significant bend loss for all but the lowest-order mode. They have demonstrated this method by constructing a coiled amplifier using Yb-doped, double-clad fiber with a core diameter of 25 {micro}m and NA of {minus}0.1 (V {approx} 7.4). When operated as an ASE source, the output beam had an M{sup 2} value of 1.09 {+-} 0.09; when seeded at 1,064 nm, the slope efficiency was similar to that of an uncoiled amplifier. This technique does not require exotic fiber designs or increase system complexity and is inexpensive to implement. It will allow scaling of pulsed fiber lasers and amplifiers to significantly higher pulse energies and peak powers and cw fiber sources to higher average powers while maintaining excellent beam quality.

  11. An experimental study of a VVER reactor's steam generator model operating in the condensing mode

    NASA Astrophysics Data System (ADS)

    Morozov, A. V.; Remizov, O. V.

    2012-05-01

    Results obtained from an experimental study of a VVER reactor's steam generator model operating in the condensing mode are presented. The obtained empirical dependence for calculating the power of heat exchangers operating in the steam condensation mode is presented.

  12. Single-mode operation of mushroom structure surface emitting lasers

    SciTech Connect

    Wang, Y.J.; Dziura, T.G.; Wang, S.C. ); Du, G.; Wang, S. )

    1991-01-01

    Mushroom structure vertical cavity surface emitting lasers with a 0.6 {mu}m GaAs active layer sandwiched by two Al{sub 0.6{sup {minus}}}Ga{sub 0.4}As-Al{sub 0.08}Ga{sub 0.92}As multilayers as top and bottom mirrors exhibit 15 mA pulsed threshold current at 880 nm. Single longitudinal and single transverse mode operation was achieved on lasers with a 5 {mu}m diameter active region at current levels near 2 {times} I{sub th}. The light output above threshold current was linearly polarized with a polarization ratio of 25:1.

  13. Study of potassium DPAL operation in pulsed and CW mode

    NASA Astrophysics Data System (ADS)

    Zhdanov, Boris V.; Rotondaro, Matthew D.; Schaffer, Michael K.; Knize, Randall J.

    2014-10-01

    This paper presents the results of our experiments on development of the efficient hydrocarbon free Diode Pumped Alkali Laser based on potassium vapor buffered by He gas at 600 Torr. We studied the performance of this laser operating in pulsed mode with pulses up to 5 ms long at different pulse energies and cell temperatures. A slope efficiency of more than 50% was demonstrated with total optical efficiency about 30% for the pump pulses with duration about 30 μs. For the longer pump pulses the DPAL efficiency degraded in time with a characteristic time in the range from 0.5 ms to 4.5 ms depending on the pump pulse energy and cell temperature. The recorded spectrum of the side fluorescence indicates that multi-photon excitation, energy pooling collisions and ionization may be strong candidates for explaining the observed performance degradation.

  14. Three operation modes of the vitamin-D-biodosimeter

    NASA Astrophysics Data System (ADS)

    Terenetskaya, Irina P.

    2016-04-01

    The original UV biodosimeter for an in situ monitoring of the vitamin-D-synthetic capacity of sunlight and/or artificial UV sources is based on the same photoreaction in vitro by which vitamin D is synthesized in human skin from initial provitamin D via photo- and thermo-induced monomolecular isomerizations. Therefore, targets for UV photons in the biodosimeter are the provitamin D molecules embedded in specially designed UV transparent and stable matrix. The dosimeter response to UV radiation is photoinduced conversion of provitamin D into previtamin D which is immediate precursor of vitamin D. Thus, biological `antirachitic' UV dose is determined by the amount of accumulated previtamin D. To follow the photoreaction course in real time three operation modes of varying complexity have been developed.

  15. Classification of US hydropower dams by their modes of operation

    DOE PAGESBeta

    McManamay, Ryan A.; Oigbokie, II, Clement O.; Kao, Shih -Chieh; Bevelhimer, Mark S.

    2016-02-19

    A key challenge to understanding ecohydrologic responses to dam regulation is the absence of a universally transferable classification framework for how dams operate. In the present paper, we develop a classification system to organize the modes of operation (MOPs) for U.S. hydropower dams and powerplants. To determine the full diversity of MOPs, we mined federal documents, open-access data repositories, and internet sources. W then used CART classification trees to predict MOPs based on physical characteristics, regulation, and project generation. Finally, we evaluated how much variation MOPs explained in sub-daily discharge patterns for stream gages downstream of hydropower dams. After reviewingmore » information for 721 dams and 597 power plants, we developed a 2-tier hierarchical classification based on 1) the storage and control of flows to powerplants, and 2) the presence of a diversion around the natural stream bed. This resulted in nine tier-1 MOPs representing a continuum of operations from strictly peaking, to reregulating, to run-of-river, and two tier-2 MOPs, representing diversion and integral dam-powerhouse configurations. Although MOPs differed in physical characteristics and energy production, classification trees had low accuracies (<62%), which suggested accurate evaluations of MOPs may require individual attention. MOPs and dam storage explained 20% of the variation in downstream subdaily flow characteristics and showed consistent alterations in subdaily flow patterns from reference streams. Lastly, this standardized classification scheme is important for future research including estimating reservoir operations for large-scale hydrologic models and evaluating project economics, environmental impacts, and mitigation.« less

  16. Asymmetric large-mode-area photonic crystal fiber structure with effective single-mode operation: design and analysis.

    PubMed

    Saini, Than Singh; Kumar, Ajeet; Sinha, Ravindra Kumar

    2016-03-20

    The asymmetrical structure of photonic crystal fiber has been reported for a large mode area with the single-mode operation. The design works on the principle of bend-induced mode filtering. The proposed structure can be designed (i) by introducing down-doped material rods in place of nine air holes of the inner ring near the core of the structure and (ii) by increasing the diameter of the rest of the three air holes of the same ring in the direction of bending. These three air holes together with nine down-doped material rods control the mode field inside the core region and hence the bending losses of the modes. The single-mode operation is ensured by introducing high bend loss for the first higher order mode and very low bend loss for the fundamental mode. The finite-element-method-based anisotropic perfectly matched layer boundary condition has been applied for accurate analysis of bend loss of the structure. Numerical results show that effective single-mode operation can be ensured with a mode area as large as 1530  μm2 at bend state with a bend radius of 30 cm. The proposed photonic crystal optical fiber with such a large mode area can have potential applications in compact high-power delivery devices such as high-power fiber lasers and amplifiers. PMID:27140567

  17. Operational mode analysis of the maps NTP system

    SciTech Connect

    Linet, F.L.; Bernard, S.; Carruge, D.; Poitevin, Y.; Raepsaet, X.

    1996-03-01

    Within the framework of the french NTP program MAPS, the analysis of the (start-up/shut-down) transient sequences whose negative impact on the specific impulsion Isp is important, requires the evaluation of the hydrogen system performance and consequently the development of a simulation computer program. This work induces a preliminary evaluation of the hydrogen system performance under nominal operating conditions. A first approach of the transient operating mode has been simultaneously performed; more specifically the evolution of the core during a shut-down sequence has been studied in order to improve the residual power evacuation and optimize necessary hydrogen amounts for cooling. Furthermore the {open_quote}{open_quote}SIMAPS{close_quote}{close_quote} computer program based on the 3D thermohydraulic code {open_quote}{open_quote}FLICA 4{close_quote}{close_quote} is being developed to analyze transient process and its benchmarking under nominal conditions is under way. Its summary presentation is given in conclusion. {copyright} {ital 1996 American Institute of Physics.}

  18. Dual-mode operation of dual-frequency liquid crystal cell by horizontal switching

    NASA Astrophysics Data System (ADS)

    Chen, Chao Ping; Preman, Smarty P.; Yoon, Tae-Hoon; Kim, Jae Chang

    2008-03-01

    A dual-mode operation featuring a dual-frequency liquid crystal (LC) cell has been proposed in this paper. This dual-mode operation conducted by the horizontal switching allows the device to work as either dynamic or memory mode, named in terms of the monostability and bistability, respectively, of which, the dynamic mode is responsible for the gray-scale generation by modulating the birefringence of LC, while the memory mode is responsible for the power saving by the long retention time of two stable states. We have revealed the switching mechanism for both operation modes, besides, the electro-optical effects will be demonstrated by the experimental results.

  19. Autophase operating mode of an O-type traveling wave tube

    NASA Astrophysics Data System (ADS)

    Kuraev, A. A.; Sinitsyn, A. K.

    1989-06-01

    The synchronous electron technique is used to analyze the autophase operating mode of an O-type TWT. It is shown that the electron efficiency in this mode reaches 85 percent in the absence of strong retarded and backstreaming electrons.

  20. Coupled-cavity terahertz quantum cascade lasers for single mode operation

    NASA Astrophysics Data System (ADS)

    Li, H.; Manceau, J. M.; Andronico, A.; Jagtap, V.; Sirtori, C.; Li, L. H.; Linfield, E. H.; Davies, A. G.; Barbieri, S.

    2014-06-01

    We demonstrate the operation of coupled-cavity terahertz frequency quantum-cascade lasers composed of two sub-cavities separated by an air gap realized by optical lithography and dry etching. This geometry allows stable, single mode operation with typical side mode suppression ratios in the 30-40 dB range. We employ a transfer matrix method to model the mode selection mechanism. The obtained results are in good agreement with the measurements and allow prediction of the operating frequency.

  1. Gain Filtering for Single-Spatial-Mode Operation of Large-Mode-Area Fiber Amplifiers

    SciTech Connect

    Marciante, J.R.

    2009-02-06

    Gain filtering of higher order modes in large-mode-area fibers is an extremely robust method for providing diffraction-limited performance regardless of core diameter or input beam quality. Analytic calculations demonstrate that reducing the diameter of the gain dopants compared to the waveguide diameter produces differential gain that is higher for the fundamental mode than all other fiber modes at all saturation levels. Matching the gain dopant to the mode profile is not as beneficial as a simple step profile since the primarymechanism of gain filtering is to deny gain toward the edge of the waveguide where most of the higher order mode power is contained. Numerical simulations of multikilowatt fiber amplifiers with up to 100-μm-diameter cores show that gain filtering is extremely robust, providing 99% of the output power in the fundamental mode output with only 90% of the seed power in the fundamental mode. Even with poor seed launch with 50% of the power in the fundamental mode, gain filtering can provide up to 90% of the output power in the fundamental mode.

  2. Suppression and nonlinear excitation of parasitic modes in second harmonic gyrotrons operating in a very high order mode

    SciTech Connect

    Nusinovich, Gregory S.; Pu, Ruifeng; Granatstein, Victor L.

    2015-07-06

    In recent years, there was an active development of high-power, sub-terahertz (sub-THz) gyrotrons for numerous applications. For example, a 0.67 THz gyrotron delivering more than 200 kW with about 20% efficiency was developed. This record high efficiency was achieved because the gyrotron operated in a high-order TE{sub 31,8}-mode with the power of ohmic losses less than 10% of the power of outgoing radiation. That gyrotron operated at the fundamental cyclotron resonance, and a high magnetic field of about 27 T was created by a pulse solenoid. For numerous applications, it is beneficial to use gyrotrons at cyclotron harmonics which can operate in available cryomagnets with fields not exceeding 15 T. However, typically, the gyrotron operation at harmonics faces severe competition from parasitic modes at the fundamental resonance. In the present paper, we consider a similar 0.67 THz gyrotron designed for operation in the same TE{sub 31,8}-mode, but at the second harmonic. We focus on two nonlinear effects typical for interaction between the fundamental and second harmonic modes, viz., the mode suppression and the nonlinear excitation of the mode at the fundamental harmonic by the second harmonic oscillations. Our study includes both the analytical theory and numerical simulations performed with the self-consistent code MAGY. The simulations show that stable second harmonic operation in the TE{sub 31,8} mode is possible with only modest sacrifice of efficiency and power.

  3. 47 CFR 73.840 - Operating power and mode tolerances.

    Code of Federal Regulations, 2012 CFR

    2012-10-01

    ... ten watts must be maintained as near as practicable to its authorized TPO and may not be less than 90... authorized TPO of ten watts or less may operate with less than the authorized power, but not more than...

  4. 47 CFR 73.840 - Operating power and mode tolerances.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... ten watts must be maintained as near as practicable to its authorized TPO and may not be less than 90... authorized TPO of ten watts or less may operate with less than the authorized power, but not more than...

  5. Investigation of the piezoelectric thimble tactile device operating modes.

    PubMed

    Bansevicius, Ramutis; Dragasius, Egidijus; Grigas, Vytautas; Jurenas, Vytautas; Mazeika, Darius; Zvironas, Arunas

    2014-01-01

    A multifunctional device to transfer graphical or text information for blind or visually impaired is presented. The prototype using tactile perception has been designed where information displayed on the screen of electronic device (mobile phone, PC) is transferred by oscillating needle, touching the fingertip. Having the aim to define optimal parameters of the fingertip excitation by needle, the computational analysis of different excitation modes has been carried out. A 3D solid computational finite element model of the skin segment, comprising four main fingertip skin layers (stratum corneum, epidermis, dermis and hypodermis) was built by using ANSYS Workbench FEA software. Harmonic analysis of its stress-strain state under excitation with different frequency (up to 10000 Hz) and harmonic force (0.01 N), acting outer stratum corneum layer in normal direction at one, two or three points has been performed. The influence of the mode of dynamic loading of skin was evaluated (in terms of the tactile signal level) on the basis of the normal and shear elastic strain in dermis, where mechanoreceptors are placed. It is shown that the tactile perception of information, delivered by three vibrating pins, may be influenced by configuration of excitation points (their number and phase of loading) and the frequency of excitation.

  6. Coupled-cavity terahertz quantum cascade lasers for single mode operation

    SciTech Connect

    Li, H. Manceau, J. M.; Andronico, A.; Jagtap, V.; Sirtori, C.; Barbieri, S.; Li, L. H.; Linfield, E. H.; Davies, A. G.

    2014-06-16

    We demonstrate the operation of coupled-cavity terahertz frequency quantum-cascade lasers composed of two sub-cavities separated by an air gap realized by optical lithography and dry etching. This geometry allows stable, single mode operation with typical side mode suppression ratios in the 30–40 dB range. We employ a transfer matrix method to model the mode selection mechanism. The obtained results are in good agreement with the measurements and allow prediction of the operating frequency.

  7. A method of suppressing mode competition in a coaxial localized-defect Bragg resonator operating in a higher-order mode

    SciTech Connect

    Lai Yingxin; Yang Lei; Zhang Shichang

    2011-06-15

    A coaxial localized-defect Bragg resonator has potential applications in high-power CARM oscillators. When it operates at sub-terahertz and terahertz frequencies, a higher-order mode is always required so as to get enough large geometry size. Analysis shows that higher-order mode operation may cause undesired mode competition due to the localized defect coupling the operating mode with its neighboring modes. A simple but efficient method is presented to solve the mode competition problem, where Hamming windowing-function distribution is separately applied to both sides of the localized defect.

  8. FDNS CFD Code Benchmark for RBCC Ejector Mode Operation

    NASA Technical Reports Server (NTRS)

    Holt, James B.; Ruf, Joe

    1999-01-01

    Computational Fluid Dynamics (CFD) analysis results are compared with benchmark quality test data from the Propulsion Engineering Research Center's (PERC) Rocket Based Combined Cycle (RBCC) experiments to verify fluid dynamic code and application procedures. RBCC engine flowpath development will rely on CFD applications to capture the multi-dimensional fluid dynamic interactions and to quantify their effect on the RBCC system performance. Therefore, the accuracy of these CFD codes must be determined through detailed comparisons with test data. The PERC experiments build upon the well-known 1968 rocket-ejector experiments of Odegaard and Stroup by employing advanced optical and laser based diagnostics to evaluate mixing and secondary combustion. The Finite Difference Navier Stokes (FDNS) code was used to model the fluid dynamics of the PERC RBCC ejector mode configuration. Analyses were performed for both Diffusion and Afterburning (DAB) and Simultaneous Mixing and Combustion (SMC) test conditions. Results from both the 2D and the 3D models are presented.

  9. Noiseless Optical Amplifier Operating on Hundreds of Spatial Modes

    NASA Astrophysics Data System (ADS)

    Corzo, N. V.; Marino, A. M.; Jones, K. M.; Lett, P. D.

    2012-07-01

    We implement a noiseless optical amplifier using a phase-sensitive four-wave mixing process in rubidium vapor. We observe performance near the quantum limit for this type of amplifier over a range of experimental parameters and show that the noise figure is always better than would be obtained with a phase-insensitive amplifier with the same gain. Additionally, we observe that the amplifier supports hundreds of spatial modes, making it possible to amplify complex two-dimensional spatial patterns with less than a 10% degradation of the input signal-to-noise ratio for gains up to 4.6. To confirm the multimode character of the amplifier, we study the noise figure as a function of spatially-varying losses. Additionally, we investigate the spatial resolution of the amplifier and show that it supports a range of spatial frequencies from 1.3 to more than 35 line pairs per millimeter.

  10. Multi-mode spectrographs for small telescopes: design, operation, performances and results

    NASA Astrophysics Data System (ADS)

    Munari, U.; Valisa, P.

    2014-03-01

    We present three generations (Mark.I, II and III) of spectrographs we put into operation with ANS Collaboration 0.61m, 0.70m and 0.84m telescopes. These spectrographs are of the Multi-Mode type, allowing for rapid interchange between Echelle high dispersion and two separate single dispersion modes (low and medium resolution). All three modes are long-slit, rotate to any angle (including parallactic compensation for atmospheric dispersion), allow to select among different comparison lamps, and are auto-guided by TV imaging the slit, which is continuously adjustable in width and by a step decker in height. The latest Mark.III model adds many new features including remote operation, spatial splitting of order overlap in single dispersion modes, interchange between prism and grating cross-dispersion in the Echelle mode, spectropolarimetry, a coronagraphic mode and direct filtered imaging without removing the spectrograph from the Cassegrain focus.

  11. Characterization of photomultiplier tubes in a novel operation mode for Secondary Emission Ionization Calorimetry

    NASA Astrophysics Data System (ADS)

    Tiras, E.; Dilsiz, K.; Ogul, H.; Southwick, D.; Bilki, B.; Wetzel, J.; Nachtman, J.; Onel, Y.; Winn, D.

    2016-10-01

    Hamamatsu single anode R7761 and multi-anode R5900-00-M16 Photomultiplier Tubes have been characterized for use in a Secondary Emission (SE) Ionization Calorimetry study. SE Ionization Calorimetry is a novel technique to measure electromagnetic shower particles in extreme radiation environments. The different operation modes used in these tests were developed by modifying the conventional PMT bias circuit. These modifications were simple changes to the arrangement of the voltage dividers of the baseboard circuits. The PMTs with modified bases, referred to as operating in SE mode, are used as an SE detector module in an SE calorimeter prototype, and placed between absorber materials (Fe, Cu, Pb, W, etc.). Here, the technical design of different operation modes, as well as the characterization measurements of both SE modes and the conventional PMT mode are reported.

  12. APET methodology for Defense Waste Processing Facility: Mode C operation

    SciTech Connect

    Taylor, R.P. Jr.; Massey, W.M.

    1995-04-01

    Safe operation of SRS facilities continues to be the highest priority of the Savannah River Site (SRS). One of these facilities, the Defense Waste Processing Facility or DWPF, is currently undergoing cold chemical runs to verify the design and construction preparatory to hot startup in 1995. The DWPFF is a facility designed to convert the waste currently stored in tanks at the 200-Area tank farm into a form that is suitable for long term storage in engineered surface facilities and, ultimately, geologic isolation. As a part of the program to ensure safe operation of the DWPF, a probabilistic Safety Assessment of the DWPF has been completed. The results of this analysis are incorporated into the Safety Analysis Report (SAR) for DWPF. The usual practice in preparation of Safety Analysis Reports is to include only a conservative analysis of certain design basis accidents. A major part of a Probabilistic Safety Assessment is the development and quantification of an Accident Progression Event Tree or APET. The APET provides a probabilistic representation of potential sequences along which an accident may progress. The methodology used to determine the risk of operation of the DWPF borrows heavily from methods applied to the Probabilistic Safety Assessment of SRS reactors and to some commercial reactors. This report describes the Accident Progression Event Tree developed for the Probabilistic Safety Assessment of the DWPF.

  13. Modeling operation mode of pellet boilers for residential heating

    NASA Astrophysics Data System (ADS)

    Petrocelli, D.; Lezzi, A. M.

    2014-11-01

    In recent years the consumption of wood pellets as energy source for residential heating lias increased, not only as fuel for stoves, but also for small-scale residential boilers that, produce hot water used for both space heating and domestic hot water. Reduction of fuel consumption and pollutant emissions (CO, dust., HC) is an obvious target of wood pellet boiler manufacturers, however they are also quite interested in producing low- maintenance appliances. The need of frequent maintenance turns in higher operating costs and inconvenience for the user, and in lower boiler efficiency and higher emissions also. The aim of this paper is to present a theoretical model able to simulate the dynamic behavior of a pellet boiler. The model takes into account many features of real pellet boilers. Furthermore, with this model, it is possible to pay more attention to the influence of the boiler control strategy. Control strategy evaluation is based not only on pellet consumption and on total emissions, but also on critical operating conditions such as start-up and stop or prolonged operation at substantially reduced power level. Results are obtained for a residential heating system based on a wood pellet boiler coupled with a thermal energy storage. Results obtained so far show a weak dependence of performance in terms of fuel consumption and total emissions on control strategy, however some control strategies present some critical issues regarding maintenance frequency.

  14. Versatile mode-locked fiber laser with switchable operation states of bound solitons.

    PubMed

    Zou, Xin; Qiu, Jifang; Wang, Xiaodong; Ye, Zi; Shi, Jindan; Wu, Jian

    2016-06-01

    Bound states of two solitons are among the typical forms of bound states and can be observed in various operation states of mode-locked fiber lasers. We experimentally investigated bound solitons (BSs) in a passively mode-locked erbium-doped fiber laser based on a semiconductor saturable absorber mirror, whose operation states can be switched among multiple pulses, passively harmonic mode-locking, and "giant pulses" by simply adjusting the in-line polarization controller with the pump power fixed. Up to four pulses, fourth-order harmonic mode-locking (HML), and a "giant pulse" with four BSs were obtained with increasing pump power. Experimental results showed a correlative relationship among those operation states (N pulses/Nth-order HML/"giant pulses" of N bound solitons) at different pump power levels. The birefringence induced by the erbium-doped fiber inside the laser cavity played a vital role in the transitions of those operation states. PMID:27411182

  15. Surveillance system and method having parameter estimation and operating mode partitioning

    NASA Technical Reports Server (NTRS)

    Bickford, Randall L. (Inventor)

    2005-01-01

    A system and method for monitoring an apparatus or process asset including creating a process model comprised of a plurality of process submodels each correlative to at least one training data subset partitioned from an unpartitioned training data set and each having an operating mode associated thereto; acquiring a set of observed signal data values from the asset; determining an operating mode of the asset for the set of observed signal data values; selecting a process submodel from the process model as a function of the determined operating mode of the asset; calculating a set of estimated signal data values from the selected process submodel for the determined operating mode; and determining asset status as a function of the calculated set of estimated signal data values for providing asset surveillance and/or control.

  16. Surveillance system and method having parameter estimation and operating mode partitioning

    NASA Technical Reports Server (NTRS)

    Bickford, Randall L. (Inventor)

    2003-01-01

    A system and method for monitoring an apparatus or process asset including partitioning an unpartitioned training data set into a plurality of training data subsets each having an operating mode associated thereto; creating a process model comprised of a plurality of process submodels each trained as a function of at least one of the training data subsets; acquiring a current set of observed signal data values from the asset; determining an operating mode of the asset for the current set of observed signal data values; selecting a process submodel from the process model as a function of the determined operating mode of the asset; calculating a current set of estimated signal data values from the selected process submodel for the determined operating mode; and outputting the calculated current set of estimated signal data values for providing asset surveillance and/or control.

  17. Versatile mode-locked fiber laser with switchable operation states of bound solitons.

    PubMed

    Zou, Xin; Qiu, Jifang; Wang, Xiaodong; Ye, Zi; Shi, Jindan; Wu, Jian

    2016-06-01

    Bound states of two solitons are among the typical forms of bound states and can be observed in various operation states of mode-locked fiber lasers. We experimentally investigated bound solitons (BSs) in a passively mode-locked erbium-doped fiber laser based on a semiconductor saturable absorber mirror, whose operation states can be switched among multiple pulses, passively harmonic mode-locking, and "giant pulses" by simply adjusting the in-line polarization controller with the pump power fixed. Up to four pulses, fourth-order harmonic mode-locking (HML), and a "giant pulse" with four BSs were obtained with increasing pump power. Experimental results showed a correlative relationship among those operation states (N pulses/Nth-order HML/"giant pulses" of N bound solitons) at different pump power levels. The birefringence induced by the erbium-doped fiber inside the laser cavity played a vital role in the transitions of those operation states.

  18. Active pixel image sensor with a winner-take-all mode of operation

    NASA Technical Reports Server (NTRS)

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

    2003-01-01

    An integrated CMOS semiconductor imaging device having two modes of operation that can be performed simultaneously to produce an output image and provide information of a brightest or darkest pixel in the image.

  19. Ship operation and failure mode analysis using a maneuver simulator

    NASA Astrophysics Data System (ADS)

    Cabrerizo-Morales, Miguel Angel; Molina, Rafael; de los Santos, Francisco; Camarero, Alberto

    2013-04-01

    In a ship or floating structure operation the agents that contribute to the systems behaviour are not only those derived from fluid-structure interaction, but also the ones linked to mooring-control line set-up evolution and human interaction. Therefore, the analysis of such systems is affected by boundary conditions that change during a complete operation. Frequently, monitoring techniques in laboratory (model) and field (prototype) are based in different instrumental techniques adding difficulty to data comparison and, in some cases, inducing precision and repeatability errors. For this reason, the main aim of this study is to develop the methods and tools to achieve a deep knowledge of those floating systems and obtain capabilities to optimize their operationally thresholds. This abstract presents a methodology and an instrumental system applicable both in field and laboratory: SRECMOCOS Project (Small scale REal-time Caisson MOnitoring and COntrol System). SRECMOCOS compiles three modules. For the monitoring and control of the structure it has been developed a synchronized open and modular microcontroller-based electronic system that comprises sensors, to monitor agents and reactions, and actuators to perform pertinent actions after processing the sensors' data. A secondary objective has been to design and implement a global scaled simulator (1:22), at the 3D basin of The Harbour Research Lab at Technical University of Madrid, in which climatic agents and those derived from the rig/maneuvering setup and the structural design were included. The particular case of Campamento's drydock, in Algeciras Bay (Spain), has been used to apply and validate the methodology. SRECMOCOS Project conjugates control, monitoring and wireless communication systems in a real time basis, offering the possibility to register and simulate all the parameters involved in port operations. This approach offers a step forward into a monitoring strategy to be included in monitoring

  20. Regimes of operation states in passively mode-locked fiber soliton ring laser

    NASA Astrophysics Data System (ADS)

    Gong, Y. D.; Shum, P.; Tang, D. Y.; Lu, C.; Guo, X.; Paulose, V.; Man, W. S.; Tam, H. Y.

    2004-06-01

    The principal of passively mode-locked fiber soliton ring lasers is summarized, including its three output operation states: normal soliton, bound-solitons and noise-like pulse. The experimental results of the passively mode-locked fiber soliton ring lasers developed by us are given. Bound-solitons with different discrete separations and three-bound-solitons state have been observed in our fiber laser for the first time. The relationship among three operation states in fiber soliton laser is analyzed.

  1. A multi-mode operation control strategy for flexible microgrid based on sliding-mode direct voltage and hierarchical controls.

    PubMed

    Zhang, Qinjin; Liu, Yancheng; Zhao, Youtao; Wang, Ning

    2016-03-01

    Multi-mode operation and transient stability are two problems that significantly affect flexible microgrid (MG). This paper proposes a multi-mode operation control strategy for flexible MG based on a three-layer hierarchical structure. The proposed structure is composed of autonomous, cooperative, and scheduling controllers. Autonomous controller is utilized to control the performance of the single micro-source inverter. An adaptive sliding-mode direct voltage loop and an improved droop power loop based on virtual negative impedance are presented respectively to enhance the system disturbance-rejection performance and the power sharing accuracy. Cooperative controller, which is composed of secondary voltage/frequency control and phase synchronization control, is designed to eliminate the voltage/frequency deviations produced by the autonomous controller and prepare for grid connection. Scheduling controller manages the power flow between the MG and the grid. The MG with the improved hierarchical control scheme can achieve seamless transitions from islanded to grid-connected mode and have a good transient performance. In addition the presented work can also optimize the power quality issues and improve the load power sharing accuracy between parallel VSIs. Finally, the transient performance and effectiveness of the proposed control scheme are evaluated by theoretical analysis and simulation results. PMID:26686458

  2. A multi-mode operation control strategy for flexible microgrid based on sliding-mode direct voltage and hierarchical controls.

    PubMed

    Zhang, Qinjin; Liu, Yancheng; Zhao, Youtao; Wang, Ning

    2016-03-01

    Multi-mode operation and transient stability are two problems that significantly affect flexible microgrid (MG). This paper proposes a multi-mode operation control strategy for flexible MG based on a three-layer hierarchical structure. The proposed structure is composed of autonomous, cooperative, and scheduling controllers. Autonomous controller is utilized to control the performance of the single micro-source inverter. An adaptive sliding-mode direct voltage loop and an improved droop power loop based on virtual negative impedance are presented respectively to enhance the system disturbance-rejection performance and the power sharing accuracy. Cooperative controller, which is composed of secondary voltage/frequency control and phase synchronization control, is designed to eliminate the voltage/frequency deviations produced by the autonomous controller and prepare for grid connection. Scheduling controller manages the power flow between the MG and the grid. The MG with the improved hierarchical control scheme can achieve seamless transitions from islanded to grid-connected mode and have a good transient performance. In addition the presented work can also optimize the power quality issues and improve the load power sharing accuracy between parallel VSIs. Finally, the transient performance and effectiveness of the proposed control scheme are evaluated by theoretical analysis and simulation results.

  3. Two stage activated sludge plants--influence of different operational modes on sludge bulking and nitrification.

    PubMed

    Wandl, G; Müller-Rechberger, H; Matsché, N; Svardal, K; Winkler, S

    2002-01-01

    Conventional two stage activated sludge plants often lack sufficient nutrient removal performance due to substrate limitation for denitrification in the second stage. For the extension of the Vienna Main WWTP a two stage concept has been developed and tested by means of a pilot plant (scale 1:10.000). The new concept enables the operation of two different modes: In BYPASS-mode a portion of the primary clarifier effluent is fed directly to the second stage; the HYBRID-mode includes the exchange of mixed liquor between the two stages; over the course of the pilot plant investigations it turned out that nutrient removal is strongly increased in comparison to conventional two stage mode, but the two modes of operation lead to different results with regard to the sludge quality and the nitrification performance. BYPASS mode yields a higher SVI in both stages and a lower nitrification performance in comparison to HYBRID mode. This is caused by the negative influence of the primary effluent on the biocoenosis of the second stage. Additionally, the reduced sludge loading of the first stage in this mode results in a higher sludge age which favours the growth of filaments (Microthrix and Nocardia). In HYBRID-mode the higher load of the first stage results in a lower sludge age, fatty components are metabolized and incorporated in the sludge, thus, the growth of filaments is significantly reduced. Additionally, nitrification inhibiting substances are degraded in the first stage, which results in a higher nitrification performance in the second stage.

  4. Application of shuttle EVA systems to payloads. Volume 1: EVA systems and operational modes description

    NASA Technical Reports Server (NTRS)

    1976-01-01

    Descriptions of the EVA system baselined for the space shuttle program were provided, as well as a compendium of data on available EVA operational modes for payload and orbiter servicing. Operational concepts and techniques to accomplish representative EVA payload tasks are proposed. Some of the subjects discussed include: extravehicular mobility unit, remote manipulator system, airlock, EVA translation aids, restraints, workstations, tools and support equipment.

  5. The Operation Modes of Kharkov X-Ray Generator Based on Compton Scattering NESTOR

    SciTech Connect

    Bulyak, E.V.; Gladkikh, P.; Karnaukhov, I.M.; Mytsykov, A.; Shcherbakov, A.A.; Zelinsky, A.Y.; Tatchyn, R.; /SLAC, SSRL

    2005-05-09

    The results of theoretical and numerical considerations of linear Compton scattering are used to evaluate characteristics of X-rays produced by collision between a low emittance electron beam and intensive laser light in an X-ray generator NESTOR of NSC KIPT. Two main generation modes have been under consideration at preliminary NESTOR design. There are the operation mode for medicine 33.4 keV X-rays production using 43 Mev electron beam and Nd:YAG laser beam and higher energy X-rays production mode providing X-rays with energy up to 900 keV with 225 MeV electron beam and Nd:YAG laser beam. It was supposed to use an optical cavity for laser beam accumulation of about 2.6 m long and an interaction angle of about 3{sup o} in both operation modes. A few more operation modes provide possibility to expand operation range of NESTOR. Using interaction angle 10{sup o} and 150{sup o} along with optical resonator of 42 cm long and the second mode of laser light it is possible to produce X-rays in energy range from a few keV till 1.5 MeV. The intensity and spectral brightness of the X-rays is expected to be {approx} 10{sup 13} phot/s and {approx}10{sup 13} phot/s/mm{sup 2}/mrad{sup 2}/0.1%BW respectively.

  6. Assessment of body mapping sportswear using a manikin operated in constant temperature mode and thermoregulatory model control mode

    NASA Astrophysics Data System (ADS)

    Wang, Faming; Del Ferraro, Simona; Molinaro, Vincenzo; Morrissey, Matthew; Rossi, René

    2014-09-01

    Regional sweating patterns and body surface temperature differences exist between genders. Traditional sportswear made from one material and/or one fabric structure has a limited ability to provide athletes sufficient local wear comfort. Body mapping sportswear consists of one piece of multiple knit structure fabric or of different fabric pieces that may provide athletes better wear comfort. In this study, the `modular' body mapping sportswear was designed and subsequently assessed on a `Newton' type sweating manikin that operated in both constant temperature mode and thermophysiological model control mode. The performance of the modular body mapping sportswear kit and commercial products were also compared. The results demonstrated that such a modular body mapping sportswear kit can meet multiple wear/thermal comfort requirements in various environmental conditions. All body mapping clothing (BMC) presented limited global thermophysiological benefits for the wearers. Nevertheless, BMC showed evident improvements in adjusting local body heat exchanges and local thermal sensations.

  7. Bioreaction engineering. Vol. 1: Fundamentals, thermodynamics, formal kinetics, idealized reactor types and operation modes

    SciTech Connect

    Schugeri, K.

    1987-01-01

    This volume, provides view of the current state of bioreaction engineering, the science of the reaction engineering of cells and microorganisms. Topics covered include the modus operandi of bioreactors, basic types, reactors circuits, formal kinetics of cell growth and product formation, growth in idealized reactors, substrate-limited growth, operation modes in stirred reactors, discontinuous (batch) operation, continuous operation, dynamic behavior of open and closed loop reactors, and more.

  8. Guidance system operations plan for manned CM earth orbital missions using program SKYLARK 1. Section 4: Operational modes

    NASA Technical Reports Server (NTRS)

    Dunbar, J. C.

    1972-01-01

    The operational modes for the guidance system operations plan for Program SKYLARK 1 are presented. The procedures control the guidance and navigation system interfaces with the flight crew and the mission control center. The guidance operational concept is designed to comprise a set of manually initiated programs and functions which may be arranged by the flight crew to implement a large class of flight plans. This concept will permit both a late flight plan definition and a capability for real time flight plan changes.

  9. Influence of air abrasion tips and operation modes on enamel-cutting characteristics

    PubMed Central

    Peruchi, Cláudia; Santos-Pinto, Ary; Dias, Tereza Cristina; Oliveira, Ana Carolina Mascarenhas; Santos-Pinto, Lourdes

    2013-01-01

    Objective: To assess the influence of air abrasion tips and system operation modes on enamel cutting. Methods: Forty bovine teeth were abraded with the air abrasion system Mach 4.1 for 10 and 15 seconds, employing conventional and sonic tips of 0.45-mm inner diameter and a 90° angle, and 27.5-μm aluminum oxide at 5.51 bar air pressure in continuous and pulsed modes. The width and depth of the resulting cuts were measured in SEM. Results: The multivariate analysis of variances revealed that, compared to the sonic tip, the conventional tip produced shallower cuts independent of the operation mode and the application period. Conclusions: The cutting patterns observed in this study suggest that the pulsed mode produced deeper cuts when both the conventional and sonic tips were used, and that the sonic tip cut more dental tissue than the conventional one. PMID:23408157

  10. Performance Analysis of Sleep Mode Operation in IEEE 802.16m Mobile WiMAX

    NASA Astrophysics Data System (ADS)

    Baek, Sangkyu; Son, Jung Je; Choi, Bong Dae

    We mathematically analyze the sleep mode operation of IEEE 802.16m. The sleep mode operation for downlink traffic is modeled as a 3-dimensional discrete time Markov chain. We obtain the average power consumption of a mobile station and the average delay of a message. Numerical results match simulations very well. Numerical results show that there is a tradeoff between power consumption and message delay. We find the optimal lengths of sleep cycle and close-down time that minimize the power consumption while satisfying the quality of service (QoS) constraint on message delay. The power consumption of the sleep mode in IEEE 802.16m is better than that of sleep modes in legacy IEEE 802.16e standard under the same delay bound.

  11. Energy-efficient operation of a booster RF system for Taiwan light source operated in top-up mode

    NASA Astrophysics Data System (ADS)

    Yeh, Meng-Shu; Wang, Chaoen; Chang, Lung-Hai; Chung, Fu-Tsai; Yu, Tsung-Chi; Lin, Ming-Chyuan; Chen, Ling-Jhen; Yang, Tz-Te; Chang, Mei-Hsia; Lin, Yu-Han; Tsai, Ming-Hsun; Lo, Chih-Hung; Liu, Zong-Kai

    2015-03-01

    Contemporary light sources operate in a top-up mode to maintain their photon intensity quasi-constant so as to improve significantly the thermal stability of the photon beam and to maximize ultimately the average photon flux at a designed maximum operational beam current. Operating in a top-up mode requires frequent beam injection from the synchrotron booster to the storage ring of the light source, but the injection intervals occupy only a tiny portion of the operational time of the integrated machine. To maintain a high operational reliability, the booster RF system practically operates necessarily under injection conditions around the clock and consumes full electric power whether during top-up injection or not. How to decrease the power consumption of the booster RF system during its stand-by time but not to sacrifice the reliability and availability of the RF system is obviously of fundamental interest for routine operation of the light source in a top-up mode. Here, an energy-efficient operation of a booster RF system adaptive to top-up operation of a light source is proposed that has been developed, realized and integrated into the booster RF system of the Taiwan Light Source (TLS), and routinely operated since the end of year 2008. The klystron cathode current and RF gap voltage of the booster's accelerating RF cavity are both periodically modulated to adapt the injection rhythm during top-up operation, which results in decreased consumption of electric power of the booster RF system by more than 78%. The impact on the reliability and availability of the booster RF system has been carefully monitored during the past five operational years, delivering more than 5000 h scheduled user beam time per year. The booster RF system retains its excellent reliability and availability as previously. Neither a decrease of the service time nor an induced reliability issue from the klystron or any high-power high-voltage component of the transmitter has been experienced

  12. Stable single-mode operation of surface-emitting terahertz lasers with graded photonic heterostructure resonators

    NASA Astrophysics Data System (ADS)

    Xu, Gangyi; Halioua, Yacine; Moumdji, Souad; Colombelli, Raffaele; Beere, Harvey E.; Ritchie, David A.

    2013-06-01

    Graded photonic heterostructures (GPH) can be regarded as energy wells for photons. We show that judicious engineering of such photonic wells, obtained by tailoring the grading and the slit width of the GPH resonator, allows one to ensure spectrally single-mode emission on the fundamental symmetric mode in the whole lasing dynamical range of terahertz quantum cascade lasers. Furthermore, the radiative character of the symmetric mode leads to single-mode emission with mW output power in continuous-wave operation, as well as to single-lobed far-field beam patterns. A careful combination of theoretical analysis and experimental observations reveals that the results stem from interplay between mode competition and spatial hole burning effects.

  13. Totem-Pole Power-Factor-Correction Converter under Critical-Conduction-Mode Interleaved Operation

    NASA Astrophysics Data System (ADS)

    Firmansyah, Eka; Tomioka, Satoshi; Abe, Seiya; Shoyama, Masahito; Ninomiya, Tamotsu

    This paper proposes a new power-factor-correction (PFC) topology, and explains its operation principle, its control mechanism, related application problems followed by experimental results. In this proposed topology, critical-conduction-mode (CRM) interleaved technique is applied to a bridgeless PFC in order to achieve high efficiency by combining benefits of each topology. This application is targeted toward low to middle power applications that normally employs continuous-conduction-mode boost converter.

  14. Communication: Effects of thermionic-gun parameters on operating modes in ultrafast electron microscopy.

    PubMed

    Kieft, Erik; Schliep, Karl B; Suri, Pranav K; Flannigan, David J

    2015-09-01

    Ultrafast electron microscopes with thermionic guns and LaB6 sources can be operated in both the nanosecond, single-shot and femtosecond, single-electron modes. This has been demonstrated with conventional Wehnelt electrodes and absent any applied bias. Here, by conducting simulations using the General Particle Tracer code, we define the electron-gun parameter space within which various modes may be optimized. The properties of interest include electron collection efficiency, temporal and energy spreads, and effects of laser-pulse duration incident on the LaB6 source. We find that collection efficiencies can reach 100% for all modes, despite there being no bias applied to the electrode.

  15. Performance Assessment of Single Electrode-Supported Solid Oxide Cells Operating in the Steam Electrolysis Mode

    SciTech Connect

    X. Zhang; J. E. O'Brien; R. C. O'Brien; N. Petigny

    2011-11-01

    An experimental study is under way to assess the performance of electrode-supported solid-oxide cells operating in the steam electrolysis mode for hydrogen production. Results presented in this paper were obtained from single cells, with an active area of 16 cm{sup 2} per cell. The electrolysis cells are electrode-supported, with yttria-stabilized zirconia (YSZ) electrolytes ({approx}10 {mu}m thick), nickel-YSZ steam/hydrogen electrodes ({approx}1400 {mu}m thick), and modified LSM or LSCF air-side electrodes ({approx}90 {mu}m thick). The purpose of the present study is to document and compare the performance and degradation rates of these cells in the fuel cell mode and in the electrolysis mode under various operating conditions. Initial performance was documented through a series of voltage-current (VI) sweeps and AC impedance spectroscopy measurements. Degradation was determined through long-term testing, first in the fuel cell mode, then in the electrolysis mode. Results generally indicate accelerated degradation rates in the electrolysis mode compared to the fuel cell mode, possibly due to electrode delamination. The paper also includes details of an improved single-cell test apparatus developed specifically for these experiments.

  16. Thermodynamic Analysis of Dual-Mode Scramjet Engine Operation and Performance

    NASA Technical Reports Server (NTRS)

    Riggins, David; Tacket, Regan; Taylor, Trent; Auslender, Aaron

    2006-01-01

    Recent analytical advances in understanding the performance continuum (the thermodynamic spectrum) for air-breathing engines based on fundamental second-law considerations have clarified scramjet and ramjet operation, performance, and characteristics. Second-law based analysis is extended specifically in this work to clarify and describe the performance characteristics for dual-mode scramjet operation in the mid-speed range of flight Mach 4 to 7. This is done by a fundamental investigation of the complex but predictable interplay between heat release and irreversibilities in such an engine; results demonstrate the flow and performance character of the dual mode regime and of dual mode transition behavior. Both analytical and computational (multi-dimensional CFD) studies of sample dual-mode flow-fields are performed in order to demonstrate the second-law capability and performance and operability issues. The impact of the dual-mode regime is found to be characterized by decreasing overall irreversibility with increasing heat release, within the operability limits of the system.

  17. Open-phase operating modes of power flow control topologies in a Smart Grid Distribution Network

    NASA Astrophysics Data System (ADS)

    Astashev, M. G.; Novikov, M. A.; Panfilov, D. I.; Rashitov, P. A.; Remizevich, T. V.; Fedorova, M. I.

    2015-12-01

    The power flow regulating circuit node in an alternating current system is reviewed. The circuit node is accomplished based on a thyristor controlled phase angle regulator (TCPAR) with controlled thyristor switch. Research results of the individual phase control of the output voltage for the TCPAR are presented. Analytical expressions for the overvoltage factor calculation in the thyristor switch circuit for open-phase operating modes are received. Based on evaluation of overvoltage in operational and emergency modes, the implementability conditions of the individual phase control of the output voltage are determined. Under these conditions, maximal performance and complete controllability are provided.

  18. Unified operator approach for deriving Hermite-Gaussian and Laguerre-Gaussian laser modes.

    PubMed

    Enderlein, Jörg; Pampaloni, Francesco

    2004-08-01

    A unified operator approach is described for deriving Hermite-Gaussian and Laguerre-Gaussian laser beams by using as a starting point a plane-wave-spectrum representation of the electromagnetic field. We show that by using the plane-wave representation of the fundamental Gaussian mode as a seed function, all higher-order beam modes can be derived by acting with differential operators on this fundamental solution. The approach presented can be easily generalized to nonparaxial situations and to include vector effects of the electromagnetic field.

  19. Unified operator approach for deriving Hermite-Gaussian and Laguerre-Gaussian laser modes

    NASA Astrophysics Data System (ADS)

    Enderlein, Jörg; Pampaloni, Francesco

    2004-08-01

    A unified operator approach is described for deriving Hermite-Gaussian and Laguerre-Gaussian laser beams by using as a starting point a plane-wave-spectrum representation of the electromagnetic field. We show that by using the plane-wave representation of the fundamental Gaussian mode as a seed function, all higher-order beam modes can be derived by acting with differential operators on this fundamental solution. The approach presented can be easily generalized to nonparaxial situations and to include vector effects of the electromagnetic field.

  20. Stability in single longitudinal mode operation in GaInAsP/InP phase-adjusted DFB lasers

    SciTech Connect

    Soda, H.; Kotaki, Y.; Sudo, H.; Ishikawa, H.; Yamakoshi, S.; Imai, H.

    1987-06-01

    A single longitudinal mode (SLM) operating condition for phase-adjusted (PA) DFB lasers has been made clear both experimentally and theoretically. As expected, the authors got a high SLM operation yield of 80 percent in a moderate coupled case up to a light output power of 10 mW. However, in the strongly coupled cases, the two-mode operation with the TEO mode and the TE + 1 mode occurred frequently. To explain the two-mode operation and to optimize the PA-DFB laser structure, they have developed a theory.

  1. High-power, surface-emitting quantum cascade laser operating in a symmetric grating mode

    NASA Astrophysics Data System (ADS)

    Boyle, C.; Sigler, C.; Kirch, J. D.; Lindberg, D. F.; Earles, T.; Botez, D.; Mawst, L. J.

    2016-03-01

    Grating-coupled surface-emitting (GCSE) lasers generally operate with a double-lobed far-field beam pattern along the cavity-length direction, which is a result of lasing being favored in the antisymmetric grating mode. We experimentally demonstrate a GCSE quantum-cascade laser design allowing high-power, nearly single-lobed surface emission parallel to the longitudinal cavity. A 2nd-order Au-semiconductor distributed-feedback (DFB)/distributed-Bragg-reflector (DBR) grating is used for feedback and out-coupling. The DFB and DBR grating regions are 2.55 mm- and 1.28 mm-long, respectively, for a total grating length of 5.1 mm. The lasers are designed to operate in a symmetric (longitudinal) grating mode by causing resonant coupling of the guided optical mode to the antisymmetric surface-plasmon modes of the 2nd-order metal/semiconductor grating. Then, the antisymmetric modes are strongly absorbed by the metal in the grating, causing the symmetric mode to be favored to lase, which, in turn, produces a single-lobed beam over a range of grating duty-cycle values of 36%-41%. Simulations indicate that the symmetric mode is always favored to lase, independent of the random phase of reflections from the device's cleaved ends. Peak pulsed output powers of ˜0.4 W were measured with nearly single-lobe beam-pattern (in the longitudinal direction), single-spatial-mode operation near 4.75 μm wavelength. Far-field measurements confirm a diffraction-limited beam pattern, in agreement with simulations, for a source-to-detector separation of 2 m.

  2. Controlling the mode of operation of organic transistors through side-chain engineering

    PubMed Central

    Giovannitti, Alexander; Sbircea, Dan-Tiberiu; Inal, Sahika; Nielsen, Christian B.; Bandiello, Enrico; Hanifi, David A.; Sessolo, Michele; Malliaras, George G.; McCulloch, Iain; Rivnay, Jonathan

    2016-01-01

    Electrolyte-gated organic transistors offer low bias operation facilitated by direct contact of the transistor channel with an electrolyte. Their operation mode is generally defined by the dimensionality of charge transport, where a field-effect transistor allows for electrostatic charge accumulation at the electrolyte/semiconductor interface, whereas an organic electrochemical transistor (OECT) facilitates penetration of ions into the bulk of the channel, considered a slow process, leading to volumetric doping and electronic transport. Conducting polymer OECTs allow for fast switching and high currents through incorporation of excess, hygroscopic ionic phases, but operate in depletion mode. Here, we show that the use of glycolated side chains on a thiophene backbone can result in accumulation mode OECTs with high currents, transconductance, and sharp subthreshold switching, while maintaining fast switching speeds. Compared with alkylated analogs of the same backbone, the triethylene glycol side chains shift the mode of operation of aqueous electrolyte-gated transistors from interfacial to bulk doping/transport and show complete and reversible electrochromism and high volumetric capacitance at low operating biases. We propose that the glycol side chains facilitate hydration and ion penetration, without compromising electronic mobility, and suggest that this synthetic approach can be used to guide the design of organic mixed conductors. PMID:27790983

  3. Operating modes of field emission assisted microplasmas in the microwave regime

    NASA Astrophysics Data System (ADS)

    Alamatsaz, Arghavan; Venkattraman, Ayyaswamy

    2016-09-01

    The operating modes of microwave microplasma devices integrated with field emitting cathodes are studied using one-dimensional particle-in-cell with Monte Carlo collision (PIC-MCC) simulations. The PIC-MCC simulations predict operation in two modes—an α-mode characterized by a positive differential resistance with negligible influence of boundary processes and a γ-mode with significant field-induced electron emission. PIC-MCC results are presented for two representative 0.5 GHz argon microplasmas operating in the α and γ modes. The field emission-induced transition to γ-mode modifies the electron number density profiles in the sheath apart from leading to a higher contribution of conduction current in the sheath. The interpretation of electrical characteristics using time history of voltage and current demonstrates that the microplasma device impedance decreases as a result of the thinner sheath. It is also shown that the presence of field emitting cathodes leads to lower power requirements (about 64% of the case presented without field emission) to achieve a given plasma density.

  4. THz quantum cascade lasers operating on the radiative modes of a 2D photonic crystal.

    PubMed

    Halioua, Y; Xu, G; Moumdji, S; Li, L H; Davies, A G; Linfield, E H; Colombelli, R

    2014-07-01

    Photonic-crystal lasers operating on Γ-point band-edge states of a photonic structure naturally exploit the so-called "nonradiative" modes. As the surface output coupling efficiency of these modes is low, they have relatively high Q factors, which favor lasing. We propose a new 2D photonic-crystal design that is capable of reversing this mode competition and achieving lasing on the radiative modes instead. Previously, this has only been shown in 1D structures, where the central idea is to introduce anisotropy into the system, both at unit-cell and resonator scales. By applying this concept to 2D photonic-crystal patterned terahertz frequency quantum cascade lasers, surface-emitting devices with diffraction-limited beams are demonstrated, with 17 mW peak output power.

  5. Flight Simulator Evaluation of Enhanced Propulsion Control Modes for Emergency Operation

    NASA Technical Reports Server (NTRS)

    Litt, Jonathan, S; Sowers, T.; Owen, A., Karl; Fulton, Christopher, E.; Chicatelli, Amy, K.

    2012-01-01

    This paper describes piloted evaluation of enhanced propulsion control modes for emergency operation of aircraft. Fast Response and Overthrust modes were implemented to assess their ability to help avoid or mitigate potentially catastrophic situations, both on the ground and in flight. Tests were conducted to determine the reduction in takeoff distance achievable using the Overthrust mode. Also, improvements in Dutch roll damping, enabled by using yaw rate feedback to the engines to replace the function of a stuck rudder, were investigated. Finally, pilot workload and ability to handle the impaired aircraft on approach and landing were studied. The results showed that improvement in all aspects is possible with these enhanced propulsion control modes, but the way in which they are initiated and incorporated is important for pilot comfort and perceived benefit.

  6. Effect of water vapor on the performance of glass RPCs in avalanche mode operation

    NASA Astrophysics Data System (ADS)

    Raveendrababu, K.; Behera, P. K.; Satyanarayana, B.; Mukhopadhayay, S.; Majumdar, N.

    2016-08-01

    We studied the effect of water vapor on the performance of glass Resistive Plate Chambers (RPCs) in the avalanche mode operation. Controlled amount of water vapor was added to the RPC gas mixture that has C2H2F4 as the major component. The deterioration in the performance of RPC was observed while operating with the wet gas and recovered after switching to the standard gas.

  7. Development of calorimeters using thin chambers operating in a high gain mode

    NASA Astrophysics Data System (ADS)

    Bella, G.; Cohen, J.; Czyrkowski, H.; Fink, P.; Horwitz, N.; Kalo, J.; Lupu, N.; Majewski, S.; Mikenberg, G.; Mir, R.; Nowak, R.; Revel, D.; Walczak, R.; Walker, J.

    1986-12-01

    A new type of thin multiwire proportional chamber detector operating in a high gain mode has been developed. Its characteristics have been optimized for calorimetric use. Two setups consisting of ten such detectors (electromagnetic calorimeter) interlaced with lead plates of 6 mm thickness and with iron plates of 8 cm thickness (hadron calorimeter) were tested. The characteristics of these detectors operating in calorimetric environments have been investigated and compared with theoretical expectations.

  8. Linear Analysis of a Cyclotron Autoresonance Maser (CARM) Operating in a Transverse Magnetic Mode

    NASA Astrophysics Data System (ADS)

    Yang, Na; Zhang, Shi-Chang

    2009-04-01

    In the fast-wave devices like gyrotron, gyro-peniotron and cyclotron autoresonance maser (CARM) that generate millimeter and sub-millimeter waves, the transverse dimensions of the resonator and the output cylindrical waveguide become small. In order to prevent loss of electrons and thermal loading of the rf structure, the electron beam must be kept relatively far from the walls. The latter requirement demands smaller transverse dimensions of the helical electron beam as well. In this paper linear formulation of a CARM operating in a general transverse-magnetic (TM) mode is derived, and a detailed analysis of the influences of the parameters is presented for the TM1,1 mode CARM. It is found that, compared to the TE1,1 mode which is often employed in gyrotron traveling wave tube (gyro-TWT) and CARM experiments, the TM1,1 mode has a greater eigen value and consequently leads to a greater waveguide radius for a given cutoff wave number, and also, allows the electron beam to be settled close to the waveguide axis to have a small transverse dimension. Results show that a TM-mode CARM can reach high power and ultrahigh gain, just as a TE-mode CARM or a TE-mode gyro-TWT does.

  9. Impact of various operating modes on performance and emission parameters of small heat source

    NASA Astrophysics Data System (ADS)

    Vician, Peter; Holubčík, Michal; Palacka, Matej; Jandačka, Jozef

    2016-06-01

    Thesis deals with the measurement of performance and emission parameters of small heat source for combustion of biomass in each of its operating modes. As the heat source was used pellet boiler with an output of 18 kW. The work includes design of experimental device for measuring the impact of changes in air supply and method for controlling the power and emission parameters of heat sources for combustion of woody biomass. The work describes the main factors that affect the combustion process and analyze the measurements of emissions at the heat source. The results of experiment demonstrate the values of performance and emissions parameters for the different operating modes of the boiler, which serve as a decisive factor in choosing the appropriate mode.

  10. The Hubble Space Telescope fine guidance system operating in the coarse track pointing control mode

    NASA Technical Reports Server (NTRS)

    Whittlesey, Richard

    1993-01-01

    The Hubble Space Telescope (HST) Fine Guidance System has set new standards in pointing control capability for earth orbiting spacecraft. Two precision pointing control modes are implemented in the Fine Guidance System; one being a Coarse Track Mode which employs a pseudo-quadrature detector approach and the second being a Fine Mode which uses a two axis interferometer implementation. The Coarse Track Mode was designed to maintain FGS pointing error to within 20 milli-arc seconds (rms) when guiding on a 14.5 Mv star. The Fine Mode was designed to maintain FGS pointing error to less than 3 milli-arc seconds (rms). This paper addresses the HST FGS operating in the Coarse Track Mode. An overview of the implementation, the operation, and both the predicted and observed on orbit performance is presented. The discussion includes a review of the Fine Guidance System hardware which uses two beam steering Star Selector servos, four photon counting photomultiplier tube detectors, as well as a 24 bit microprocessor, which executes the control system firmware. Unanticipated spacecraft operational characteristics are discussed as they impact pointing performance. These include the influence of spherically aberrated star images as well as the mechanical shocks induced in the spacecraft during and following orbital day/night terminator crossings. Computer modeling of the Coarse Track Mode verifies the observed on orbit performance trends in the presence of these optical and mechanical disturbances. It is concluded that the coarse track pointing control function is performing as designed and is providing a robust pointing control capability for the Hubble Space Telescope.

  11. Surveillance system and method having an operating mode partitioned fault classification model

    NASA Technical Reports Server (NTRS)

    Bickford, Randall L. (Inventor)

    2005-01-01

    A system and method which partitions a parameter estimation model, a fault detection model, and a fault classification model for a process surveillance scheme into two or more coordinated submodels together providing improved diagnostic decision making for at least one determined operating mode of an asset.

  12. Operability test report for rotary mode core sampling system number 3

    SciTech Connect

    Corbett, J.E.

    1996-03-01

    This report documents the successful completion of operability testing for the Rotary Mode Core Sampling (RMCS) system {number_sign}3. The Report includes the test procedure (WHC-SD-WM-OTP-174), exception resolutions, data sheets, and a test report summary.

  13. A Typology of Actional-Operational Modes in Earth Science and Implications for Science Literacy Instruction

    ERIC Educational Resources Information Center

    Wilson, Amy Alexandra

    2013-01-01

    Framed in theories of social semiotics, this multiple case study describes and categorizes the actional-operational modes used by three middle school earth science teachers throughout the course of one school year. Data included fieldnotes, photographs, and video recordings of classroom instructions as well as periodic interviews with the…

  14. Eddy current inspection tool which is selectively operable in a discontinuity detection mode and a discontinuity magnitude mode

    DOEpatents

    Petrini, R.R.; Van Lue, D.F.

    1983-10-25

    A miniaturized inspection tool, for testing and inspection of metal objects in locations with difficult accessibility, which comprises eddy current sensing equipment with a probe coil, and associated coaxial coil cable, coil energizing means, and circuit means responsive to impedance changes in the coil as effected by induced eddy currents in a test object to produce a data output signal proportional to such changes. The coil and cable are slideably received in the utility channel of the flexible insertion tube of fiberoptic scope. The scope is provided with light transmitting and receiving fiberoptics for viewing through the flexible tube, and articulation means for articulating the distal end of the tube and permitting close control of coil placement relative to a test object. The eddy current sensing equipment includes a tone generator 30 for generating audibly signals responsive to the data output signal. In one selected mode of operation, the tone generator responsive to the output signal above a selected level generates a constant single frequency tone for signaling detection of a discontinuity and, in a second selected mode, generates a tone whose frequency is proportional to the difference between the output signal and a predetermined selected threshold level. 5 figs.

  15. Eddy current inspection tool which is selectively operable in a discontinuity detection mode and a discontinuity magnitude mode

    DOEpatents

    Petrini, Richard R.; Van Lue, Dorin F.

    1983-01-01

    A miniaturized inspection tool, for testing and inspection of metal objects in locations with difficult accessibility, which comprises eddy current sensing equipment (12) with a probe coil (11), and associated coaxial coil cable (13), coil energizing means (21), and circuit means (21, 12) responsive to impedance changes in the coil as effected by induced eddy currents in a test object to produce a data output signal proportional to such changes. The coil and cable are slideably received in the utility channel of the flexible insertion tube 17 of fiberoptic scope 10. The scope 10 is provided with light transmitting and receiving fiberoptics for viewing through the flexible tube, and articulation means (19, 20) for articulating the distal end of the tube and permitting close control of coil placement relative to a test object. The eddy current sensing equipment includes a tone generator 30 for generating audibly signals responsive to the data output signal. In one selected mode of operation, the tone generator responsive to the output signal above a selected level generates a constant single frequency tone for signalling detection of a discontinuity and, in a second selected mode, generates a tone whose frequency is proportional to the difference between the output signal and a predetermined selected threshold level.

  16. Techniques for setting modes of thermal and deformation effect at combined hardening and finishing operations

    NASA Astrophysics Data System (ADS)

    Rakhimyanov, Kh M.; Rakhimyanov, K. Kh; Rakhimyanov, A. Kh; Kutyshkin, A. V.

    2016-04-01

    This paper considers the issues of setting the modes of thermal and deformation effects in the basic schemes at combined hardening and finishing operations. On the basis of solving the thermal physical problem of material high rate heating, the parameters of a thermohardened layer were determined within the range of the investigated modes. An algorithm for setting the mode parameters of high rate heating responsible for the hardening effect at the combined processing was proposed. The analysis of the mathematical model for forming a surface microrelief at ultrasonic deformation showed that the sizes, the form of fragments and the density of a microrelief were determined by the processing kinematic parameters. An algorithm for setting the rotation speed and feeding at ultrasonic deformation according to microrelief characteristics was developed. The conditions to form a completely regular microrelief on the processed surface that represent the ratio between a single imprint diameter at the ultrasonic deformation and the processing kinematic parameters were determined. The complex of the algorithms suggested for setting the mode parameters of high rate heating and ultrasonic deformation constitutes the techniques for setting the modes of combined hardening and finishing operations.

  17. Anode-biofilm electron transfer behavior and wastewater treatment under different operational modes of bioelectrochemical system.

    PubMed

    Wu, Baoguo; Feng, Chunhua; Huang, Liqiao; Lv, Zhisheng; Xie, Daohai; Wei, Chaohai

    2014-04-01

    Anode-biofilm electron transfer behavior was investigated during the advanced wastewater treatment process by three bioelectrochemical systems (BESs): microbial fuel cell (MFC), MFC operated under short circuit condition (MSC), and microbial electrolysis cell (MEC). Under different operational modes, current produced by the anode biofilm varied from 0.92, 4.15 to 8.21mA in the sequence of MFC, MSC and MEC, respectively. The cyclic voltammetry test on the anode biofilm suggested that the current generation was achieved via various bioelectroactive species with formal potentials at -0.473, -0.402 and -0.345V (vs. SCE). Gibbs free energy and charge transfer resistance data demonstrated that different amounts of available bioelectroactive species functioned in different BESs. The comparative investigation among MFC, MSC and MEC suggested that MEC was the only feasible operational mode for advanced wastewater treatment, because of its superior current generation capability.

  18. Improving Reliability of High Power Quasi-CW Laser Diode Arrays Operating in Long Pulse Mode

    NASA Technical Reports Server (NTRS)

    Amzajerdian, Farzin; Meadows, Byron L.; Barnes, Bruce W.; Lockard, George E.; Singh, Upendra N.; Kavaya, Michael J.; Baker, Nathaniel R.

    2006-01-01

    Operating high power laser diode arrays in long pulse regime of about 1 msec, which is required for pumping 2-micron thulium and holmium-based lasers, greatly limits their useful lifetime. This paper describes performance of laser diode arrays operating in long pulse mode and presents experimental data of the active region temperature and pulse-to-pulse thermal cycling that are the primary cause of their premature failure and rapid degradation. This paper will then offer a viable approach for determining the optimum design and operational parameters leading to the maximum attainable lifetime.

  19. Status and new operation modes of the versatile VLT/NaCo

    NASA Astrophysics Data System (ADS)

    Girard, Julien H. V.; Kasper, Markus; Quanz, Sascha P.; Kenworthy, Matthew A.; Rengaswamy, Sridharan; Schödel, Rainer; Gallenne, Alexandre; Gillessen, Stefan; Huerta, Nicolas; Kervella, Pierre; Kornweibel, Nick; Lenzen, Rainer; Mérand, Antoine; Montagnier, Guillaume; O'Neal, Jared; Zins, Gérard

    2010-07-01

    This paper aims at giving an update on the most versatile Adaptive Optics fed instrument to date, the well known and successful NACO*. Although NACO is only scheduled for about two more years† at the Very Large Telescope (VLT), it keeps on evolving with additional operation modes bringing original astronomical results. The high contrast imaging community uses it creatively as a test-bench for SPHERE‡ and other second generation planet imagers. A new visible wavefront sensor (WFS) optimized for Laser Guide Star (LGS) operations has been installed and tested, the cube mode is more and more required for frame selection on bright sources, a seeing enhancer mode (no tip/tilt correction) is now offered to provide full sky coverage and welcome all kind of extragalactic applications, etc. The Instrument Operations Team (IOT) and Paranal engineers are currently working hard at maintaining the instrument overall performances but also at improving them and offering new capabilities, providing the community with a well tuned and original instrument for the remaining time it is being used. The present contribution delivers a non-exhaustive overview of the new modes and experiments that have been carried out in the past months.

  20. Relationship Between Absorber Layer Properties and Device Operation Modes For High Efficiency Thin Film Solar Cells

    NASA Astrophysics Data System (ADS)

    Ravichandran, Ram; Kokenyesi, Robert; Wager, John; Keszler, Douglas; CenterInverse Design Team

    2014-03-01

    A thin film solar cell (TFSC) can be differentiated into two distinct operation modes based on the transport mechanism. Current TFSCs predominantly exploit diffusion to extract photogenerated minority carriers. For efficient extraction, the absorber layer requires high carrier mobilities and long minority carrier lifetimes. Materials exhibiting a strong optical absorption onset near the fundamental band gap allows reduction of the absorber layer thickness to significantly less than 1 μm. In such a TFSC, a strong intrinsic electric field drives minority carrier extraction, resulting in drift-based transport. The basic device configuration utilized in this simulation study is a heterojunction TFSC with a p-type absorber layer. The diffusion/drift device operation modes are simulated by varying the thickness and carrier concentration of the absorber layer, and device performance between the two modes is compared. In addition, the relationship between device operation mode and transport properties, including carrier mobility and minority carrier lifetime are explored. Finally, candidate absorber materials that enable the advantages of a drift-based TFSC developed within the Center for Inverse Design are presented. School of Electrical Engineering and Computer Science.

  1. Operability test procedure for rotary mode core sampling system {number_sign}3

    SciTech Connect

    Farris, T.R.; Jarecki, T.D.

    1995-04-26

    This document gives instructions for the Operability Testing of the Rotary Mode Core Sampling (RMCS) System No. 3. This document is based on the Operability Test Procedure for RMCS system No. 2 because the basic design is the same for all three systems. Modifications have been made from the original design only when exact duplication was not feasible or design improvements could be incorporated without affecting the operation of the system. Operability testing of the Rotary Mode Core Sampling System No. 3, will verify that functional and operational requirements have been met. Testing will be completed in two phases. The first phase of testing (section 7) will involve operating the truck equipment to demonstrate its capabilities. The second phase of testing (section 8) will take repeated samples in a simulated operation environment. These tests will be conducted at the ``Rock Slinger`` test site located just south of U-Plant in the 200 West Area. Tests will be done in a simulated tank farm environment. All testing will be non-radioactive and stand-in materials shall be used to simulate waste tank conditions. Systems will be assembled and arranged in a manner similar to that expected in the field.

  2. Operability test procedure for rotary mode core sampling system {number_sign}4

    SciTech Connect

    Farris, T.R.; Jarecki, T.D.

    1995-04-26

    This document gives instructions for the Operability Testing of the Rotary Mode Core Sampling (RMCS) System No. 4. This document is based on the Operability Test Procedure for RMCS system No. 2 because the basic design is the same for all three systems. Modifications have been made from the original design only when exact duplication was not feasible or design improvements could be incorporated without affecting the operation of the system. Operability testing of the Rotary Mode Core Sampling System No. 4 will verify that functional and operational requirements have been met. Testing will be completed in two phases. The first phase of testing (section 7) will involve operating the truck equipment to demonstrate its capabilities. The second phase of testing (section 8) will take repeated samples in a simulated operation environment. These tests will be conducted at the ``Rock Slinger`` test site located just south of U-Plant in the 200 West Area. Tests will be done in a simulated tank farm environment. All testing will be non-radioactive and stand-in materials shall be used to simulate waste tank conditions. Systems will be assembled and arranged in a manner similar to that expected in the field.

  3. Collision effects on high-n ballooning modes with a full Lorentz collision operator

    NASA Astrophysics Data System (ADS)

    Liu, Jianxun; Chen, Shaoyong; Tang, Changjian

    2012-02-01

    The dispersion relation for high-n ballooning modes is obtained from the customary drift gyro-kinetic equation employing the energy-dependent Lorenz collision operator. There are significant differences between our results and those with the Krook collision operator. The present results show that collision seems to have much weaker stabilizing effects, if any, on the high-n ballooning modes than those with the Krook collision operator when the collisionality, υ*e, is smaller than a critical value. However, contrary to the phenomenon, the collision shows strong stabilizing effects on the ballooning mode once the collisionality exceeds a critical value. These differences are supposed to arise from boundary layer behaviour which refers to the electron perturbation at the boundary between trapped and passing electrons in velocity space, but the physical process cannot be described by non-conserving Krook collision operators. This destabilizing mechanism of boundary layer behaviour is discussed in this paper. In addition, the critical value shows a considerably strong dependence on ηe (ηe ≡ d ln Te/d ln Ne).

  4. Investigation of pulsed mode operation with the frequency tuned CAPRICE ECRIS

    NASA Astrophysics Data System (ADS)

    Maimone, F.; Tinschert, K.; Endermann, M.; Hollinger, R.; Kondrashev, S.; Lang, R.; Mäder, J.; Patchakui, P. T.; Spädtke, P.

    2016-02-01

    In order to increase the intensity of the highly charged ions produced by the Electron Cyclotron Resonance Ion Sources (ECRISs), techniques like the frequency tuning and the afterglow mode have been developed and in this paper the effect on the ion production is shown for the first time when combining both techniques. Recent experimental results proved that the tuning of the operating frequency of the ECRIS is a promising technique to achieve higher ion currents of higher charge states. On the other hand, it is well known that the afterglow mode of the ECRIS operation can provide more intense pulsed ion beams in comparison with the continuous wave (cw) operation. These two techniques can be combined by pulsing the variable frequency signal driving the traveling wave tube amplifier which provides the high microwave power to the ECRIS. In order to analyze the effect of these two combined techniques on the ion source performance, several experiments were carried out on the pulsed frequency tuned CAPRICE (Compacte source A Plusiers Résonances Ionisantes Cyclotron Electroniques)-type ECRIS. Different waveforms and pulse lengths have been investigated under different settings of the ion source. The results of the pulsed mode have been compared with those of cw operation.

  5. Development of a modular virus clearance package for anion exchange chromatography operated in weak partitioning mode.

    PubMed

    Iskra, Timothy; Sacramo, Ashley; Gallo, Chris; Godavarti, Ranga; Chen, Shuang; Lute, Scott; Brorson, Kurt

    2015-01-01

    Anion exchange chromatography (AEX) operated under weak partitioning mode has been proven to be a powerful polishing step as well as a robust viral clearance step in Pfizer's monoclonal antibody (mAb) platform purification process. A multivariate design of experiment (DoE) study was conducted to understand the impact of operating parameters and feedstream impurity levels on viral clearance by weak partitioning mode AEX. Bacteriophage was used initially as a surrogate for neutral and acidic isoelectric point mammalian viruses (e.g., retrovirus and parvovirus). Five different mAbs were used in the evaluation of process parameters such as load challenge (both product and impurities), load pH, load conductivity, and contact time (bed height and flow-rate). The operating ranges obtained from phage clearance studies and Pfizer's historical data were used to define an appropriate operating range for a subsequent clearance study with model retrovirus and parvovirus. Both phage and virus clearance evaluations included feedstreams containing different levels of impurities such as high molecular mass species (HMMS), host cell proteins (HCPs), and host cell DNA. For all the conditions tested, over 5 log10 of clearance for both retrovirus and parvovirus was achieved. The results demonstrated that weak partitioning mode AEX chromatography is a robust step for viral clearance and has the potential to be included as part of the modular viral clearance approach.

  6. A square-plate ultrasonic linear motor operating in two orthogonal first bending modes.

    PubMed

    Chen, Zhijiang; Li, Xiaotian; Chen, Jianguo; Dong, Shuxiang

    2013-01-01

    A novel square-plate piezoelectric ultrasonic linear motor operated in two orthogonal first bending vibration modes (B₁) is proposed. The piezoelectric vibrator of the linear motor is simply made of a single PZT ceramic plate (sizes: 15 x 15 x 2 mm) and poled in its thickness direction. The top surface electrode of the square ceramic plate was divided into four active areas along its two diagonal lines for exciting two orthogonal B₁ modes. The achieved driving force and speed from the linear motor are 1.8 N and 230 mm/s, respectively, under one pair orthogonal voltage drive of 150 V(p-p) at the resonance frequency of 92 kHz. The proposed linear motor has advantages over conventional ultrasonic linear motors, such as relatively larger driving force, very simple working mode and structure, and low fabrication cost.

  7. Communication: Effects of thermionic-gun parameters on operating modes in ultrafast electron microscopy

    PubMed Central

    Kieft, Erik; Schliep, Karl B.; Suri, Pranav K.; Flannigan, David J.

    2015-01-01

    Ultrafast electron microscopes with thermionic guns and LaB6 sources can be operated in both the nanosecond, single-shot and femtosecond, single-electron modes. This has been demonstrated with conventional Wehnelt electrodes and absent any applied bias. Here, by conducting simulations using the General Particle Tracer code, we define the electron-gun parameter space within which various modes may be optimized. The properties of interest include electron collection efficiency, temporal and energy spreads, and effects of laser-pulse duration incident on the LaB6 source. We find that collection efficiencies can reach 100% for all modes, despite there being no bias applied to the electrode. PMID:26798820

  8. The DELPHI Hadron Calorimeter module characteristics in the saturated proportional mode of its detector operation

    NASA Astrophysics Data System (ADS)

    Filatova, N. A.; Gotra, Yu. N.; Kadyrov, R. B.; Pozdnyakov, V. N.; Ryzhov, V. N.; Sadovsky, A. B.; Spassov, Tz.; Timofeev, V. G.; Tsyganov, E. N.; Tyapkin, I. A.; Vodopianov, A. S.; Zimin, N. I.; Zinchenko, A. I.

    1989-07-01

    A preamplifier allowing an increase in the sensitivity of the already produced DELPHI Hadron Calorimeter front-end electronics up to 0.1 pC is described. The presented preamplifier permits a considerable reduction of the gas gain and transition to the saturated avalanche mode region. The HC barrel module characteristics in the proportional mode of its detector operation are explored. The possibility of selecting muon tracks in the HC and using them for detector triggering has been investigated. It is shown that the transition to the proportional mode does not worsen the main characteristics of the HC and the reliability of its detectors will be considerably increased. The investigation has been performed at the Laboratory of High Energies, JINR.

  9. Improvement in the statistical operation of a Blumlein pulse forming line in bipolar pulse mode

    SciTech Connect

    Pushkarev, A. I. Isakova, Y. I.; Khaylov, I. P.

    2014-07-15

    The paper presents the results of studies on shot-to-shot performance of a water Blumlein pulse forming line of 1–1.2 kJ of stored energy. The experiments were carried using the TEMP-4M pulsed ion beam accelerator during its operation in both unipolar pulse mode (150 ns, 250–300 kV) and bipolar-pulse mode with the first negative (300–600 ns, 100–150 kV) followed by a second positive (120 ns, 250–300 kV) pulse. The analysis was carried out for two cases when the Blumlein was terminated with a resistive load and with a self-magnetically insulated ion diode. It was found that in bipolar pulse mode the shot-to-shot variation in breakdown voltage of a preliminary spark gap is small, the standard deviation (1σ) does not exceed 2%. At the same time, the shot-to-shot variation in the breakdown voltage of the main spark gap in both bipolar-pulse and unipolar pulse mode is 3–4 times higher than that for the preliminary spark gap. To improve the statistical performance of the main spark gap we changed the regime of its operation from a self-triggered mode to an externally triggered mode. In the new arrangement the first voltage pulse at the output of Blumlein was used to trigger the main spark gap. The new trigatron-type regime of the main spark gap operation showed a good stability of breakdown voltage and thus allowed to stabilize the duration of the first pulse. The standard deviation of the breakdown voltage and duration of the first pulse did not exceed 2% for a set of 50 pulses. The externally triggered mode of the main gap operation also allowed for a decrease in the charging voltage of the Blumlein to a 0.9–0.95 of self-breakdown voltage of the main spark gap while the energy stored in Marx generator was decreased from 4 kJ to 2.5 kJ. At the same time the energy stored in Blumlein remained the same.

  10. Sodium calcium exchanger operates in the reverse mode in metastatic human melanoma cells.

    PubMed

    Sennoune, S R; Santos, J M; Hussain, F; Martínez-Zaguilán, R

    2015-01-01

    Cytosolic Ca2+ ([Ca2+]cyt) is important in the regulation of several cellular functions involved in metastasis. We hypothesize that distinct [Ca2+]cyt regulation explains the acquisition of a more metastatic phenotype. To test this hypothesis, we used highly and lowly metastatic human melanoma cells and [Ca2+]cyt was monitored using Fura—2AM and fluorescence spectroscopy. Stimulation with ATP elicited a sustained increase in [Ca2+]cyt in highly metastatic cells, but a transient increase in lowly metastatic cells. Na+ substitution revealed Na+/Ca2+ exchanger (NCX) activity in reverse mode in highly, but not in lowly metastatic cells. In highly metastatic cells, addition of Na+ in the plateau phase of [Ca2+]cyt increase elicited with ATP, in the absence of Na+, resulted in a rapid return to basal, indicating that NCX can operate in both reverse and forward modes. Inhibition and knockdown of NCX, using KB—R7943 and siRNA NCX—1 respectively, supported the significance of NCX in [Ca2+]cyt regulation in highly metastatic cells. Stimulation with UTP triggered a rapid increase in highly metastatic cells [Ca2+]cyt, but not in lowly metastatic cells suggesting that highly and lowly metastatic cells exhibit distinct purinergic receptors. These data indicate that following agonist—stimulation, NCX operates preferentially in the reverse mode to enable a sustained [Ca2+]cyt increase in highly metastatic cells. The forward mode of NCX operation to extrude Ca2+ is preferred in lowly metastatic cells. The acquisition of a more metastatic phenotype involves a switch in NCX activity from forward to reverse mode that is favorable to maintain elevated [Ca2+]cyt in response to agonist stimulation.

  11. A standing wave linear ultrasonic motor operating in face-diagonal-bending mode

    NASA Astrophysics Data System (ADS)

    Ci, Penghong; Liu, Guoxi; Chen, Zhijiang; Dong, Shuxiang

    2013-09-01

    We report a piezoelectric standing wave linear ultrasonic motor with double driving tips for generating precision motion. The motor's piezoelectric actuator was made of a simple Pb(Zr,Ti)O3 square-plate (15 × 15 × 2 mm3) operating in a single face-diagonal-bending standing wave mode to produce symmetric, bi-directional linear motion. The motor generated a driving force of 3.0 N and a moving speed of up to 165 mm/s under a relatively low applied electric field of 75 Vpp/mm at a resonance frequency of 141.5 kHz. This motor is superior to those previously reported because of the double friction-tip standing wave driving mechanism and the operating mode.

  12. Performance of an ion-cyclotron-wave plasma apparatus operated in the radiofrequency sustained mode

    NASA Technical Reports Server (NTRS)

    Swett, C. C.; Woollett, R. R.

    1973-01-01

    An experimental study has been made of an ion-cyclotron-wave apparatus operated in the RF-sustained mode, that is, a mode in which the Stix RF coil both propagates the waves and maintains the plasma. Problems associated with this method of operation are presented. Some factors that are important to the coupling of RF power are noted. In general, the wave propagation and wave damping data agree with theory. Some irregularities in wave fields are observed. Maximum ion temperature is 870 eV at a density of five times 10 to the 12th power cu cm and RF power of 90 kW. Coupling efficiency is 70 percent.

  13. Simplified analytical model for open-phase operating mode of thyristor-controlled phase angle regulator

    NASA Astrophysics Data System (ADS)

    Astashev, M. G.; Novikov, M. A.; Panfilov, D. I.; Rashitov, P. A.; Fedorova, M. I.

    2015-12-01

    In this paper, an approach to the development of a simplified analytical model for the analysis of electromagnetic processes of a thyristor-controlled phase angle regulator with an individual phase-controlled thyristor switch is considered. The analytical expressions for the calculation of electrical parameters in symmetrical and open-phase operating mode are obtained. With a concrete example, the verification of the developed analytical model is carried out. It is accomplished by means of comparison between current and voltage calculation results when the thyristor-controlled phase angle regulator is in an open-phase operating mode with the simulation results in the MatLab software environment. Adequacy check of the obtained analytical model is carried out by comparison between the analytical calculation and experimental data received from the actual physical model.

  14. Reactor issues for tandem mirrors operating in the negative-potential mode

    SciTech Connect

    Perkins, L.J.; Campbell, R.B.

    1985-12-02

    During 1985, interest has been revived at LLNL in tandem mirrors operating in the negative-potential mode. The negative tandem is formed by combining ECRH-sustained hot electron end cell plasmas with pumping mechanisms to remove trapped ions from the end cells. No sloshing ions are required. The resulting negative potential in the end cells confines the central cell electrons. The requirement of charge neutrality causes the ambipolar potential of the central cell to become negative relative to the end wall (hence, the name ''negative' tandem mirror), thereby providing central cell ion confinement. This potential distribution is the exact inverse of the axial distribution for the conventional (positive) tandem mirror without thermal barriers. In the negative tandem mirror, central cell electrons are confined electrostatically, end cell electrons are confined magnetically, and ions are confined electrostatically everywhere. In this report, we briefly assess the reactor issues pertinent to the operation of the tandem mirror in the negative mode. 7 refs., 5 figs.

  15. Operational modes for a wave injection facility aboard spacelab and a sub-satellite

    NASA Technical Reports Server (NTRS)

    Dyson, P. L.

    1978-01-01

    Various modes of operation are described for an orbiting wave injection facility planned to measure the properties of waves propagating in space plasma. Such a facility would cover a wide frequency range including MF and HF. Phase shift and Doppler shift measurements will yield more accurate measurements of echo time delay and the angle of arrival. Because Spacelab will involve some sub-satellites, some consideration is given to propagation between two vehicles both at HF and VHF.

  16. Retrieval of original signals for superconducting quantum interference device operating in flux locked mode

    NASA Astrophysics Data System (ADS)

    Liu, Dang-Ting; Tian, Ye; Zhao, Shi-Ping; Ren, Yu-Feng; Chen, Geng-Hua

    2015-04-01

    We discuss a simple relation between the input and output signals of a superconducting quantum interference device magnetometer operating in flux locked mode in a cosine curve approximation. According to this relation, an original fast input signal can be easily retrieved from its distorted output response. This technique can be used in some areas such as sensitive and fast detection of magnetic or metallic grains in medicine and food security checking.

  17. Kinetic instabilities in pulsed operation mode of a 14 GHz electron cyclotron resonance ion source.

    PubMed

    Tarvainen, O; Kalvas, T; Koivisto, H; Komppula, J; Kronholm, R; Laulainen, J; Izotov, I; Mansfeld, D; Skalyga, V

    2016-02-01

    The occurrence of kinetic plasma instabilities is studied in pulsed operation mode of a 14 GHz A-electron cyclotron resonance type electron cyclotron resonance ion source. It is shown that the temporal delay between the plasma breakdown and the appearance of the instabilities is on the order of 10-100 ms. The most important parameters affecting the delay are magnetic field strength and neutral gas pressure. It is demonstrated that kinetic instabilities limit the high charge state ion beam production in the unstable operating regime. PMID:26931919

  18. Operational condition of direct single-mode-fiber coupled FSO terminal under strong atmospheric turbulence

    NASA Astrophysics Data System (ADS)

    Arimoto, Yoshinori

    2011-03-01

    This paper discusses the operational condition for direct single-mode-fiber-coupling FSO terminals under the various adverse weather conditions, such as strong atmospheric turbulences and rain falls. A good correlation between the scintillation index of the intensities of beacon receiving power and the signal fading depth has been observed, which allows us to predict the signal link quality based on the beacon scintillation index provided by the classical scintillation theory and concludes that the scintillation index for the beacon beam should be less than 0.1. This paper also reports the effect of performance enhancements provided by the new adaptive controller for the stable and robust terminal operation.

  19. Selection of stirling engine parameter and modes of joint operation with the Topaz II

    SciTech Connect

    Kirillov, E.Y.; Ogloblin, B.G.; Shalaev, A.I.

    1996-03-01

    In addition to a high-temperature thermionic conversion cycle, application of a low-temperature machine cycle, such as the Stirling engine, is being considered. To select the optimum mode for joint operation of the Topaz II system and Stirling engine, output electric parameters are obtained as a function of thermal power released in the TFE fuel cores. The hydraulic diagram used for joint operation of the Topaz II and the Stirling engine is considered. Requirements to hydraulic characteristics of the Stirling engine heat exchanges are formulated. Scope of necessary modifications to mount the Stirling Engine on the Topaz II is estimated. {copyright} {ital 1996 American Institute of Physics.}

  20. Modified Adaptive Control for Region 3 Operation in the Presence of Wind Turbine Structural Modes

    NASA Technical Reports Server (NTRS)

    Frost, Susan Alane; Balas, Mark J.; Wright, Alan D.

    2010-01-01

    Many challenges exist for the operation of wind turbines in an efficient manner that is reliable and avoids component fatigue and failure. Turbines operate in highly turbulent environments resulting in aerodynamic loads that can easily excite turbine structural modes, possibly causing component fatigue and failure. Wind turbine manufacturers are highly motivated to reduce component fatigue and failure that can lead to loss of revenue due to turbine down time and maintenance costs. The trend in wind turbine design is toward larger, more flexible turbines that are ideally suited to adaptive control methods due to the complexity and expense required to create accurate models of their dynamic characteristics. In this paper, we design an adaptive collective pitch controller for a high-fidelity simulation of a utility-scale, variable-speed horizontal axis wind turbine operating in Region 3. The objective of the adaptive pitch controller is to regulate generator speed, accommodate wind gusts, and reduce the excitation of structural modes in the wind turbine. The control objective is accomplished by collectively pitching the turbine blades. The adaptive collective pitch controller for Region 3 was compared in simulations with a baseline classical Proportional Integrator (PI) collective pitch controller. The adaptive controller will demonstrate the ability to regulate generator speed in Region 3, while accommodating gusts, and reducing the excitation of certain structural modes in the wind turbine.

  1. Dual-mode operation of 2D material-base hot electron transistors

    PubMed Central

    Lan, Yann-Wen; Torres, Jr., Carlos M.; Zhu, Xiaodan; Qasem, Hussam; Adleman, James R.; Lerner, Mitchell B.; Tsai, Shin-Hung; Shi, Yumeng; Li, Lain-Jong; Yeh, Wen-Kuan; Wang, Kang L.

    2016-01-01

    Vertical hot electron transistors incorporating atomically-thin 2D materials, such as graphene or MoS2, in the base region have been proposed and demonstrated in the development of electronic and optoelectronic applications. To the best of our knowledge, all previous 2D material-base hot electron transistors only considered applying a positive collector-base potential (VCB > 0) as is necessary for the typical unipolar hot-electron transistor behavior. Here we demonstrate a novel functionality, specifically a dual-mode operation, in our 2D material-base hot electron transistors (e.g. with either graphene or MoS2 in the base region) with the application of a negative collector-base potential (VCB < 0). That is, our 2D material-base hot electron transistors can operate in either a hot-electron or a reverse-current dominating mode depending upon the particular polarity of VCB. Furthermore, these devices operate at room temperature and their current gains can be dynamically tuned by varying VCB. We anticipate our multi-functional dual-mode transistors will pave the way towards the realization of novel flexible 2D material-based high-density and low-energy hot-carrier electronic applications. PMID:27581550

  2. Failure mode and effects analysis using intuitionistic fuzzy hybrid weighted Euclidean distance operator

    NASA Astrophysics Data System (ADS)

    Liu, Hu-Chen; Liu, Long; Li, Ping

    2014-10-01

    Failure mode and effects analysis (FMEA) has shown its effectiveness in examining potential failures in products, process, designs or services and has been extensively used for safety and reliability analysis in a wide range of industries. However, its approach to prioritise failure modes through a crisp risk priority number (RPN) has been criticised as having several shortcomings. The aim of this paper is to develop an efficient and comprehensive risk assessment methodology using intuitionistic fuzzy hybrid weighted Euclidean distance (IFHWED) operator to overcome the limitations and improve the effectiveness of the traditional FMEA. The diversified and uncertain assessments given by FMEA team members are treated as linguistic terms expressed in intuitionistic fuzzy numbers (IFNs). Intuitionistic fuzzy weighted averaging (IFWA) operator is used to aggregate the FMEA team members' individual assessments into a group assessment. IFHWED operator is applied thereafter to the prioritisation and selection of failure modes. Particularly, both subjective and objective weights of risk factors are considered during the risk evaluation process. A numerical example for risk assessment is given to illustrate the proposed method finally.

  3. Dual-mode operation of 2D material-base hot electron transistors

    NASA Astrophysics Data System (ADS)

    Lan, Yann-Wen; Torres, Carlos M., Jr.; Zhu, Xiaodan; Qasem, Hussam; Adleman, James R.; Lerner, Mitchell B.; Tsai, Shin-Hung; Shi, Yumeng; Li, Lain-Jong; Yeh, Wen-Kuan; Wang, Kang L.

    2016-09-01

    Vertical hot electron transistors incorporating atomically-thin 2D materials, such as graphene or MoS2, in the base region have been proposed and demonstrated in the development of electronic and optoelectronic applications. To the best of our knowledge, all previous 2D material-base hot electron transistors only considered applying a positive collector-base potential (VCB > 0) as is necessary for the typical unipolar hot-electron transistor behavior. Here we demonstrate a novel functionality, specifically a dual-mode operation, in our 2D material-base hot electron transistors (e.g. with either graphene or MoS2 in the base region) with the application of a negative collector-base potential (VCB < 0). That is, our 2D material-base hot electron transistors can operate in either a hot-electron or a reverse-current dominating mode depending upon the particular polarity of VCB. Furthermore, these devices operate at room temperature and their current gains can be dynamically tuned by varying VCB. We anticipate our multi-functional dual-mode transistors will pave the way towards the realization of novel flexible 2D material-based high-density and low-energy hot-carrier electronic applications.

  4. Dual-mode operation of 2D material-base hot electron transistors.

    PubMed

    Lan, Yann-Wen; Torres, Carlos M; Zhu, Xiaodan; Qasem, Hussam; Adleman, James R; Lerner, Mitchell B; Tsai, Shin-Hung; Shi, Yumeng; Li, Lain-Jong; Yeh, Wen-Kuan; Wang, Kang L

    2016-01-01

    Vertical hot electron transistors incorporating atomically-thin 2D materials, such as graphene or MoS2, in the base region have been proposed and demonstrated in the development of electronic and optoelectronic applications. To the best of our knowledge, all previous 2D material-base hot electron transistors only considered applying a positive collector-base potential (VCB > 0) as is necessary for the typical unipolar hot-electron transistor behavior. Here we demonstrate a novel functionality, specifically a dual-mode operation, in our 2D material-base hot electron transistors (e.g. with either graphene or MoS2 in the base region) with the application of a negative collector-base potential (VCB < 0). That is, our 2D material-base hot electron transistors can operate in either a hot-electron or a reverse-current dominating mode depending upon the particular polarity of VCB. Furthermore, these devices operate at room temperature and their current gains can be dynamically tuned by varying VCB. We anticipate our multi-functional dual-mode transistors will pave the way towards the realization of novel flexible 2D material-based high-density and low-energy hot-carrier electronic applications. PMID:27581550

  5. Dual-mode operation of 2D material-base hot electron transistors.

    PubMed

    Lan, Yann-Wen; Torres, Carlos M; Zhu, Xiaodan; Qasem, Hussam; Adleman, James R; Lerner, Mitchell B; Tsai, Shin-Hung; Shi, Yumeng; Li, Lain-Jong; Yeh, Wen-Kuan; Wang, Kang L

    2016-09-01

    Vertical hot electron transistors incorporating atomically-thin 2D materials, such as graphene or MoS2, in the base region have been proposed and demonstrated in the development of electronic and optoelectronic applications. To the best of our knowledge, all previous 2D material-base hot electron transistors only considered applying a positive collector-base potential (VCB > 0) as is necessary for the typical unipolar hot-electron transistor behavior. Here we demonstrate a novel functionality, specifically a dual-mode operation, in our 2D material-base hot electron transistors (e.g. with either graphene or MoS2 in the base region) with the application of a negative collector-base potential (VCB < 0). That is, our 2D material-base hot electron transistors can operate in either a hot-electron or a reverse-current dominating mode depending upon the particular polarity of VCB. Furthermore, these devices operate at room temperature and their current gains can be dynamically tuned by varying VCB. We anticipate our multi-functional dual-mode transistors will pave the way towards the realization of novel flexible 2D material-based high-density and low-energy hot-carrier electronic applications.

  6. Treatment of dairy manure using the microwave enhanced advanced oxidation process under a continuous mode operation.

    PubMed

    Yu, Yang; Lo, Ing W; Liao, Ping H; Lo, Kwang V

    2010-11-01

    The microwave enhanced advanced oxidation process (MW/H(2)O(2)-AOP) was used to treat dairy manure for solubilization of nutrients and organic matters. This study investigated the effectiveness of the MW/H(2)O(2)-AOP under a continuous mode of operation, and compared the results to those of batch operations. The main factors affecting solubilization by the MW/H(2)O(2)-AOP were heating temperature and hydrogen peroxide dosage. Soluble chemical oxygen demand (SCOD) and volatile fatty acids (VFA) increased with an increase of microwave (MW) heating temperature; very high concentrations were obtained at 90°C. Insignificant amounts of ammonia and reducing sugars were released in all runs. An acidic pH condition was required for phosphorus solubilisation from dairy manure. The best yield was obtained at 90°C with an acid dosage of 1.0 %; about 92 % of total phosphorus and 90 % of total chemical oxygen demand were in the soluble forms. The MW/H(2)O(2)-AOP operated in a continuous operation mode showed pronounced synergistic effects between hydrogen peroxide and microwave irradiation when compared to a batch system under similar operating conditions, resulting in much better yields.

  7. Fifteen Years of Service Mode Operations: Closing the Loop with the Community

    NASA Astrophysics Data System (ADS)

    Primas, F.; Tacconi-Garman, L.; Marteau, S.; Mainieri, V.; Rejkuba, M.; Mysore, S.; Dumas, C.; Kaufer, A.; Patat, F.; Sterzik, M.

    2014-12-01

    The first Service Mode (SM) observations with the VLT were made by ISAAC in April 1999. Since then new instruments have become operational and first generation ones replaced, filling the 12 VLT foci and feeding the VLT Interferometer and its four Auxiliary Telescopes. Efficiently operating such a broad range of instruments, installed and available every night of each year, on four 8-metre telescopes offers many challenges. Although it may appear that little has changed since 1999, the underlying VLT operational model has evolved in order to accommodate different requirements from the user community and features of new instruments. As ESO and its Member States approach routine operations with ALMA, and at the same time prepare for the next challenge, the construction of the E-ELT, it seems timely to take a closer look at what SM has brought to the scientific arena, both in terms of science data and support. Did it fulfil its original goal, if so, how well, and what are the lessons learned? A careful analysis of statistics and trends in Phase 1 and Phase 2 are now being conducted in the DOME (Dashboard for Operational Metrics at ESO) project. We summarise the main findings, concentrating on the handling of Service Mode.

  8. Energy balance affected by electrolyte recirculation and operating modes in microbial fuel cells.

    PubMed

    Jacobson, Kyle S; Kelly, Patrick T; He, Zhen

    2015-03-01

    Energy recovery and consumption in a microbial fuel cell (MFC) can be significantly affected by the operating conditions. This study investigated the effects of electrolyte recirculation and operation mode (continuous vs sequence batch reactor) on the energy balance in a tubular MFC. It was found that decreasing the anolyte recirculation also decreased the energy recovery. Because of the open environment of the cathode electrode, the catholyte recirculation consumed 10 to 50 times more energy than the anolyte recirculation, and resulted in negative energy balances despite the reduction of the anolyte recirculation. Reducing the catholyte recirculation to 20% led to a positive energy balance of 0.0288 kWh m(-3). The MFC operated as a sequence batch reactor generated less energy and had a lower energy balance than the one with continuous operation. Those results encourage the further development of MFC technology to achieve neutral or even positive energy output.

  9. An Educational Study of the Barometric Effect of Cosmic Rays with a Geiger Counter

    ERIC Educational Resources Information Center

    Famoso, Barbara; La Rocca, Paola; Riggi, Francesco

    2005-01-01

    An educational study of the barometric effect of cosmic rays was carried out using an inexpensive experimental set-up that allowed for long-term monitoring of atmospheric pressure and cosmic ray flux as measured in a Geiger counter. The investigation was intended as a pilot study in view of ongoing involvements of high-school teams operating…

  10. Timing the Random and Anomalous Arrival of Particles in a Geiger Counter with GPS Devices

    ERIC Educational Resources Information Center

    Blanco, F.; La Rocca, P.; Riggi, F.; Riggi, S.

    2008-01-01

    The properties of the arrival time distribution of particles in a detector have been studied by the use of a small Geiger counter, with a GPS device to tag the event time. The experiment is intended to check the basic properties of the random arrival time distribution between successive events and to simulate the investigations carried out by…

  11. Cosmic Rays with Portable Geiger Counters: From Sea Level to Airplane Cruise Altitudes

    ERIC Educational Resources Information Center

    Blanco, Francesco; La Rocca, Paola; Riggi, Francesco

    2009-01-01

    Cosmic ray count rates with a set of portable Geiger counters were measured at different altitudes on the way to a mountain top and aboard an aircraft, between sea level and cruise altitude. Basic measurements may constitute an educational activity even with high school teams. For the understanding of the results obtained, simulations of extensive…

  12. Educational Studies of Cosmic Rays with a Telescope of Geiger-Muller Counters

    ERIC Educational Resources Information Center

    Wibig, T.; Kolodziejczak, K.; Pierzynski, R.; Sobczak, R.

    2006-01-01

    A group of high school students (XII Liceum) in the framework of the Roland Maze Project has built a compact telescope of three Geiger-Muller counters. The connection between the telescope and a PC computer was also created and programmed by students involved in the Project. This has allowed students to use their equipment to perform serious…

  13. Science Fair Report: Detection of Solar X-Ray Flares with a Geiger Counter.

    ERIC Educational Resources Information Center

    Mims, Vicki Rae

    1991-01-01

    Described is a science fair project in which M- and X-class x-ray flares on the surface of the earth were detected using a Geiger counter. Background information, the problem, hypothesis, a list of needed materials, the procedure, observations, conclusions, and a critique are included. (KR)

  14. Neutron production from a mobile linear accelerator operating in electron mode for intraoperative radiation therapy

    NASA Astrophysics Data System (ADS)

    Loi, G.; Dominietto, M.; Cannillo, B.; Ciocca, M.; Krengli, M.; Mones, E.; Negri, E.; Brambilla, M.

    2006-02-01

    Intraoperative electron beam radiotherapy is increasingly performed using mobile linac delivering therapeutic radiation doses in unshielded operating rooms. While no special neutron-shielding problem should arise for operation at 10 MeV or less, it is not clear whether this holds true for operation at higher energies. This paper reports the measured neutron production from a Mobetron mobile electron linac, operated at 12 MeV, and compares the results with those from a conventional linac, also operated at 12 MeV in electron mode. Neutron leakage measurements were performed by means of passive bubble detectors in the scattering foil, patient and floor planes. Neutron dose equivalent rates per unit of electron dose delivered by the Mobetron at its normal treatment distance (50 cm SSD) were 0.33 µSv Gy-1 at the accelerator head, 0.18 µSv Gy-1 in the patient plane at 15 cm from the beam axis and 0.31 µSv Gy-1 at the floor plane, on the beam axis and under the beam stopper. For a weekly workload of 250 Gy, the weekly neutron dose equivalents at 12 MeV for the Mobetron at a distance of 300 cm from the scattering foil were 14.3 and 1.7 µSv/week for floor below and adjoining areas on the same floor, respectively. Neutron dose equivalent rates generated from Mobetron are at least one order of magnitude lower than ones produced by a conventional linac operated at the same energy in electron mode. Mobetron can be used at 12 MeV in an unshielded operating room for a weekly workload of up to 250 Gy if the bremsstrahlung x-rays are shielded to negligible levels.

  15. Ultrafiltration of wastewater: effects of particles, mode of operation, and backwash effectiveness.

    PubMed

    Bourgeous, K N; Darby, J L; Tchobanoglous, G

    2001-01-01

    The effects that wastewater quality and mode of operation have on the performance of an asymmetric, hollow fiber, polysulfone, ultrafiltration (UF) membrane with a molecular weight cutoff of 100,000 Daltons were investigated. Performance was assessed through monitoring membrane flux, transmembrane pressure, effluent biochemical oxygen demand, and operational cost of the experimental system while treating filtered secondary, secondary, and filtered primary effluents. Fluxes achieved for filtered secondary (129-173 l/m2 h), secondary (101-158 l/m2 h), and filtered primary (20-41 l/m2 h) effluents were compared to those obtained at three other locations where similar UF systems were operated. A conceptual model of the impact of an insufficient backwash and of operating the UF system at constant flux on membrane performance is presented to explain the differences in fluxes. Employing pre-membrane granular filtration to remove a portion of the problematic particles in secondary effluent prior to UF led to optimal operational conditions. The costs associated with the operation of pre-membrane granular filtration were offset by the increase in production achieved. Although the use of recirculation could increase maintainable flux when treating a concentrated feed (e.g., filtered primary effluent), the associated costs were high. Improved UF performance was found to result from allowing flux to decline naturally, rather than using a constant flux mode of operation. The effluents produced when filtered secondary and secondary effluents were the feeds would be equivalent to an oxidized, coagulated, clarified, and filtered wastewater as per Title 22 California Wastewater Reclamation Criteria. PMID:11257896

  16. Using the Virtual Heart Model to validate the mode-switch pacemaker operation.

    PubMed

    Jiang, Zhihao; Connolly, Allison; Mangharam, Rahul

    2010-01-01

    Artificial pacemakers are one of the most widely-used implantable devices today, with millions implanted worldwide. The main purpose of an artificial pacemaker is to treat bradycardia, or slow heart beats, by pacing the atrium and ventricles at a faster rate. While the basic functionality of the device is fairly simple, there are many documented cases of death and injury due to device malfunctions. The frequency of malfunctions due to firmware problems will only increase as the pacemaker operations become more complex in an attempt to expand the use of the device. One reason these malfunctions arise is that there is currently no methodology for formal validation and verification of medical device software, as there are in the safety-critical domains of avionics and industrial control automation. We have developed a timed-automata based Virtual Heart Model (VHM) to act as platform for medical device software validation and verification. Through a case study involving multiple arrhythmias, this investigation shows how the VHM can be used with closed-loop operation of a pacemaker to validate the necessity and functionality of the complex mode-switch pacemaker operation. We demonstrate the correct pacemaker operation, to switch from one rhythm management mode to another, in patients with supraventricular tachycardias. (1).

  17. Operation Mode on Pulse Modulation in Atmospheric Radio Frequency Glow Discharges

    NASA Astrophysics Data System (ADS)

    Zhang, Jie; Guo, Ying; Huang, Xiaojiang; Zhang, Jing; Shi, Jianjun

    2016-10-01

    The discharge operation regime of pulse modulated atmospheric radio frequency (RF) glow discharge in helium is investigated on the duty cycle and frequency of modulation pulses. The characteristics of radio frequency discharge burst in terms of breakdown voltage, alpha(α)-gamma(γ) mode transition voltage and current are demonstrated by the discharge current voltage characteristics. The minimum breakdown voltage of RF discharge burst was obtained at the duty cycle of 20% and frequency of 400 kHz, respectively. The α-γ mode transition of RF discharge burst occurs at higher voltage and current by reducing the duty cycle and elevating the modulation frequency before the RF discharge burst evolving into the ignition phase, in which the RF discharge burst can operate stably in the γ mode. It proposes that the intensity and stability of RF discharge burst can be improved by manipulating the duty cycle and modulation frequency in pulse modulated atmospheric RF glow discharge. supported by National Natural Science Foundation of China (Nos. 11475043 and 11375042)

  18. Circuit breaker operation and potential failure modes during an earthquake: a preliminary investigation

    SciTech Connect

    Lambert, H.E.

    1984-04-09

    This study addresses the effect of a strong-motion earthquake on circuit breaker operation. It focuses on the loss of offsite power (LOSP) transient caused by a strong-motion earthquake at the Zion Nuclear Power Plant. This report also describes the operator action necessary to prevent core melt if the above circuit breaker failure modes occur simultaneously on three 4.16 KV buses. Numerous circuit breakers important to plant safety, such as circuit breakers to diesel generators and engineered safety systems, (ESS), must open and/or close during this transient while strong motion is occurring. Nearly 500 electrical drawings were examined to address the effects of earthquakes on circuit breaker operation. Due to the complexity of the problem, this study is not intended to be definitive but serves as a focusing tool for further work. 5 references, 9 figures, 3 tables.

  19. A Graphite Absorbed-Dose Calorimeter in the Quasi-Isothermal Mode of Operation

    NASA Astrophysics Data System (ADS)

    Witzani, J.; Duftschmid, K. E.; Strachotinsky, Ch; Leitner, A.

    1984-01-01

    A quasi-isothermal method of operating an absorbed-dose graphite calorimeter is described in theory and practice. In contrast with the well-known quasi-adiabatic operation, which entails temperature increases during measurements, in the quasi-isothermal mode the temperatures of the different graphite bodies remain constant except for small temperature drifts throughout the measurement. This implies that the temperature dependence of the specific heat of the absorber and of the sensitivity of the temperature sensor influence the absorbed-dose determination significantly less. The method is characterized by a power-compensating measuring principle which is illustrated with a 3-body graphite calorimeter. Comparisons of the quasi-isothermal with the quasi-adiabatic method of operation showed good agreement.

  20. Current distribution measurements inside an electromagnetic plasma gun operated in a gas-puff mode.

    PubMed

    Poehlmann, Flavio R; Cappelli, Mark A; Rieker, Gregory B

    2010-12-01

    Measurements are presented of the time-dependent current distribution inside a coaxial electromagnetic plasma gun. The measurements are carried out using an array of six axially distributed dual-Rogowski coils in a balanced circuit configuration. The radial current distributions indicate that operation in the gas-puff mode, i.e., the mode in which the electrode voltage is applied before injection of the gas, results in a stationary ionization front consistent with the presence of a plasma deflagration. The effects of varying the bank capacitance, transmission line inductance, and applied electrode voltage were studied over the range from 14 to 112 μF, 50 to 200 nH, and 1 to 3 kV, respectively.

  1. Current distribution measurements inside an electromagnetic plasma gun operated in a gas-puff mode

    PubMed Central

    Poehlmann, Flavio R.; Cappelli, Mark A.; Rieker, Gregory B.

    2010-01-01

    Measurements are presented of the time-dependent current distribution inside a coaxial electromagnetic plasma gun. The measurements are carried out using an array of six axially distributed dual-Rogowski coils in a balanced circuit configuration. The radial current distributions indicate that operation in the gas-puff mode, i.e., the mode in which the electrode voltage is applied before injection of the gas, results in a stationary ionization front consistent with the presence of a plasma deflagration. The effects of varying the bank capacitance, transmission line inductance, and applied electrode voltage were studied over the range from 14 to 112 μF, 50 to 200 nH, and 1 to 3 kV, respectively. PMID:21267082

  2. Current distribution measurements inside an electromagnetic plasma gun operated in a gas-puff mode

    NASA Astrophysics Data System (ADS)

    Poehlmann, Flavio R.; Cappelli, Mark A.; Rieker, Gregory B.

    2010-12-01

    Measurements are presented of the time-dependent current distribution inside a coaxial electromagnetic plasma gun. The measurements are carried out using an array of six axially distributed dual-Rogowski coils in a balanced circuit configuration. The radial current distributions indicate that operation in the gas-puff mode, i.e., the mode in which the electrode voltage is applied before injection of the gas, results in a stationary ionization front consistent with the presence of a plasma deflagration. The effects of varying the bank capacitance, transmission line inductance, and applied electrode voltage were studied over the range from 14 to 112 μF, 50 to 200 nH, and 1 to 3 kV, respectively.

  3. Current distribution measurements inside an electromagnetic plasma gun operated in a gas-puff mode.

    PubMed

    Poehlmann, Flavio R; Cappelli, Mark A; Rieker, Gregory B

    2010-12-01

    Measurements are presented of the time-dependent current distribution inside a coaxial electromagnetic plasma gun. The measurements are carried out using an array of six axially distributed dual-Rogowski coils in a balanced circuit configuration. The radial current distributions indicate that operation in the gas-puff mode, i.e., the mode in which the electrode voltage is applied before injection of the gas, results in a stationary ionization front consistent with the presence of a plasma deflagration. The effects of varying the bank capacitance, transmission line inductance, and applied electrode voltage were studied over the range from 14 to 112 μF, 50 to 200 nH, and 1 to 3 kV, respectively. PMID:21267082

  4. Experimental researches of fiber Bragg gratings operating in a few-mode regime

    NASA Astrophysics Data System (ADS)

    Kafarova, Anastasia M.; Faskhutdinov, Lenar M.; Kuznetzov, Artem A.; Minaeva, Alina Y.; Sevruk, Nikita L.; Nureev, Ilnur I.; Vasilets, Alexander A.; Bourdine, Anton V.; Morozov, Oleg G.; Burdin, Vladimir A.

    2016-03-01

    This work presents results of experimental researches of fiber Bragg gratings (FBG) operating in a few-mode regime. We tested FBGs written on silica graded-index multimode fibers 50/125 Cat. OM2+/OM3 with Bragg wavelength 1550 nm by using them in a set of developed experimental schemes based on excitation of multimode fibers by corresponding laser sources. The researches were focused on analysis of both spectral and pulse responses under changing of selected mode mixing and power diffusion processes due to tension and/or stress local and distributed action to FBG or sensor fiber. Results of spectral and pulse response measurements at the output of schemes with installed described FBGs are represented.

  5. Current distribution measurements inside an electromagnetic plasma gun operated in a gas-puff mode

    SciTech Connect

    Poehlmann, Flavio R.; Cappelli, Mark A.; Rieker, Gregory B.

    2010-12-15

    Measurements are presented of the time-dependent current distribution inside a coaxial electromagnetic plasma gun. The measurements are carried out using an array of six axially distributed dual-Rogowski coils in a balanced circuit configuration. The radial current distributions indicate that operation in the gas-puff mode, i.e., the mode in which the electrode voltage is applied before injection of the gas, results in a stationary ionization front consistent with the presence of a plasma deflagration. The effects of varying the bank capacitance, transmission line inductance, and applied electrode voltage were studied over the range from 14 to 112 {mu}F, 50 to 200 nH, and 1 to 3 kV, respectively.

  6. A standing wave linear ultrasonic motor operating in in-plane expanding and bending modes.

    PubMed

    Chen, Zhijiang; Li, Xiaotian; Ci, Penghong; Liu, Guoxi; Dong, Shuxiang

    2015-03-01

    A novel standing wave linear ultrasonic motor operating in in-plane expanding and bending modes was proposed in this study. The stator (or actuator) of the linear motor was made of a simple single Lead Zirconate Titanate (PZT) ceramic square plate (15 × 15 × 2 mm(3)) with a circular hole (D = 6.7 mm) in the center. The geometric parameters of the stator were computed with the finite element analysis to produce in-plane bi-mode standing wave vibration. The calculated results predicted that a driving tip attached at midpoint of one edge of the stator can produce two orthogonal, approximate straight-line trajectories, which can be used to move a slider in linear motion via frictional forces in forward or reverse direction. The investigations showed that the proposed linear motor can produce a six times higher power density than that of a previously reported square plate motor.

  7. A standing wave linear ultrasonic motor operating in in-plane expanding and bending modes

    NASA Astrophysics Data System (ADS)

    Chen, Zhijiang; Li, Xiaotian; Ci, Penghong; Liu, Guoxi; Dong, Shuxiang

    2015-03-01

    A novel standing wave linear ultrasonic motor operating in in-plane expanding and bending modes was proposed in this study. The stator (or actuator) of the linear motor was made of a simple single Lead Zirconate Titanate (PZT) ceramic square plate (15 × 15 × 2 mm3) with a circular hole (D = 6.7 mm) in the center. The geometric parameters of the stator were computed with the finite element analysis to produce in-plane bi-mode standing wave vibration. The calculated results predicted that a driving tip attached at midpoint of one edge of the stator can produce two orthogonal, approximate straight-line trajectories, which can be used to move a slider in linear motion via frictional forces in forward or reverse direction. The investigations showed that the proposed linear motor can produce a six times higher power density than that of a previously reported square plate motor.

  8. Operation modes of a hydro-generator as a part of the inverter micro hydropower plant

    NASA Astrophysics Data System (ADS)

    Lukutin, B. V.; Shandarova, E. B.; Matukhin, D. L.; Makarova, A. F.; Fuks, I. L.

    2016-04-01

    The paper dwells on the selection problem of power equipment for a stand-alone inverter micro hydropower plant, in particular a hydro-generator, and evaluation of its operation modes. Numerical experiments included the modes calculation of hydroelectric units of the same type with various nominal power, supplied to the consumer according to the unchanged electric load curve. The studies developed requirements for a hydro-turbine and a synchronous generator in terms of a speed range and installed capacity, depending on the load curve. The possibility of using general industrial hydroelectric units with nominal power equal to half-maximum capacity of a typical daily load curve in rural areas was shown.

  9. Trickle-Charge: a New Operational Mode for PEP-II

    SciTech Connect

    Kozanecki, W.; Colocho, W.S.; Decker, F.-J.; Ecklund, S.; Fisher, A.S.; Iverson, R.H.; O'Grady, C.; Seeman, J.; Sullivan, M.K.; Turner, J.L.; Weaver, M.; Wienands, U.; /SLAC

    2005-05-09

    In regular top-up-and-coast operation, PEP-II average luminosity is about 70-75% of the peak luminosity due to detector ramp-down and ramp-up times plus the time it takes to top-up both beams. We recently commissioned a new operational mode where the Low Energy Ring is injected continuously without ramping down the detector. The benefits--increased luminosity lifetime and roughly half the number of top-ups per shift--were expected to give an increase in delivered luminosity of about 15% at the same peak luminosity; this was confirmed in test runs. In routine trickle operation, however, it appears that the increase in delivered luminosity is more than twice that due to an increase in availability credited to the more stable operating conditions during trickle operation. Further gains were made when continuous injection was extended to the high energy ring as well. In this paper we will present our operational experience as well as some of the diagnostics we use to monitor and maintain tuning of the machine in order to control injection background and protect the detector.

  10. First operation of an FEL in same-cell energy recovery mode

    SciTech Connect

    G.R. Neil; S. Benson; G. Biallas; C.L. Bohn; D. Douglas; H.F. Dylla; R. Evans; J. Fugitt; J. Gubeli; R. Hill; K. Jordan; G. Krafft; R. Li; L. Merminga; D. Oepts; P. Piot; J. Preble; Michelle D. Shinn; T. Siggins; R. Walker; B. Yunn

    1999-09-01

    The driver for Jefferson Lab's kW-level infrared free-electron laser (FEL) is a superconducting, recirculating accelerator that recovers 75% of the electron-beam power and converts it to radio frequency power. As reported in FEL'98, the accelerator operated ''straight-ahead'' to deliver 38 MeV, 1.1 mA cw current for lasing at wavelengths in the vicinity of 5 microns. The waste beam was sent directly to a dump, bypassing the recirculation loop. Stable operation at up to 311 W cw was achieved in this mode. The machine has now recirculated cw average current up to 4.6 mA and has lased cw with energy recovery up to 1,720 W output at 3.1 microns. This is the first FEL to ever operate in the ''same-cell'' energy recovery mode. Energy recovery offers several advantages (reduced RF power and dramatically reduced radio-nuclide production at the dump) and several challenges will be described. The authors have observed heating effects in the mirrors which will be described. They will also report on the additional performance measurements of the FEL that have been performed and connect those measurements to standard models.

  11. New constant-temperature operating mode for graphite calorimeter at LNE-LNHB

    NASA Astrophysics Data System (ADS)

    Daures, J.; Ostrowsky, A.

    2005-09-01

    The realization of the unit of absorbed dose at LNE-LNHB is based on calorimetry with the present GR8 graphite calorimeter. For this reason the calorimetric technique must be maintained, developed and improved in the laboratory. The usual quasi-adiabatic operating mode at LNHB is based on the thermal feedback between the core (sensitive element) and the jacket (adjacent body). When a core-jacket temperature difference is detected, a commercially available analogue PID (Proportional, Integral, Derivative) controller sends to the jacket an amount of electrical power to reduce this difference. Nevertheless, the core and jacket temperatures increase with irradiations and electrical calibrations whereas the surrounding is maintained at a fixed temperature to shield against the room temperature variations. At radiotherapy dose rates, fewer than ten measurements, or electrical calibrations, per day can be performed. This paper describes the new constant-temperature operating mode which has been implemented recently to improve flexibility in use and, to some extent, accuracy. The core and the jacket temperatures are maintained at fixed temperatures. A steady state is achieved without irradiation. Then, under irradiation, the electrical power needed to maintain the assigned temperature in the core is reduced by the amount of heat generated by ionizing radiation. The difference between these electrical powers, without and with irradiation, gives the mean absorbed dose rate to the core. The quality of this electrical power substitution measurement is strongly dependent upon the quality of the core and jacket thermal control. The core temperature is maintained at the set value using a digital PID regulator developed at the laboratory with LabView software on PC for this purpose. This regulator is versatile and particularly well suited for calorimetry purposes. Measurements in a cobalt-60 beam have shown no significant difference (<0.09%) between the two operating modes, with

  12. The formation of liquid bridge in different operating modes of AFM

    NASA Astrophysics Data System (ADS)

    Wei, Zheng; Sun, Yan; Ding, WenXuan; Wang, ZaiRan

    2016-09-01

    The liquid bridge is one of the principal factors that cause artifacts in ambient-pressure atomic force microscope (AFM) images. Additionally, it is the main component of the adhesion force in ambient conditions. To understand the AFM imaging mechanism and the sample characteristics, it is essential to study the liquid bridge. This study interprets the physical mechanism involved in liquid bridge formation, which is composed of three different physical processes: the squeezing process, capillary condensation, and liquid film flow. We discuss the contributions of these three mechanisms to the volume and the capillary force of the liquid bridge in different AFM operation modes.

  13. Equilibration of a Graphite Absorbed-Dose Calorimeter and the Quasi-Isothermal Mode of Operation

    NASA Astrophysics Data System (ADS)

    Janssens, A.; Cottens, E.; Paulsen, A.; Poffijn, A.

    1986-01-01

    From a mathematical model of a three-body absorbed-dose calorimeter a procedure for achieving thermal equilibrium is developed which uses calculational methods to determine the exact amount and timing of electrical energy to be dissipated in the calorimetric bodies. This procedure is applied to the quasi-isothermal mode of operation in which a radiation beam and equivalent electrical heating are alternately used to keep the calorimetric bodies at temperatures as constant as possible. Measurements of the dose rate of a 60Co beam in graphite using this technique are reported.

  14. High-power pulsed-current-mode operation of an overdriven tapered amplifier.

    PubMed

    Takase, Ken; Stockton, John K; Kasevich, Mark A

    2007-09-01

    We experimentally investigate the performance of a commercial tapered amplifier diode operating in a pulsed-current mode with a peak current that is significantly higher than the specified maximum continuous current. For a tapered amplifier rated at 500 mW of continuous power, we demonstrate 2.6 W of peak optical output power with 15 mW of injection light for 200 micros, 7 A current pulses. Different failure mechanisms for the tapered amplifier, including thermal and optical damage, are identified under these conditions. PMID:17767324

  15. A dual-mode operation overmoded coaxial millimeter-wave generator with high power capacity and pure transverse electric and magnetic mode output

    NASA Astrophysics Data System (ADS)

    Bai, Zhen; Zhang, Jun; Zhong, Huihuang

    2016-04-01

    An overmoded coaxial millimeter-wave generator with high power capacity and pure transverse electric and magnetic (TEM) mode output is designed and presented, by using a kind of coaxial slow wave structure (SWS) with large transversal dimension and small distance between inner and outer conductors. The generator works in dual-mode operation mechanism. The electron beam synchronously interacts with 7π/8 mode of quasi-TEM, at the meanwhile exchanges energy with 3π/8 mode of TM01. The existence of TM01 mode, which is traveling wave, not only increases the beam-wave interaction efficiency but also improves the extraction efficiency. The large transversal dimension of coaxial SWS makes its power capacity higher than that of other reported millimeter-wave devices and the small distance between inner and outer conductors allows only two azimuthally symmetric modes to coexist. The converter after the SWS guarantees the mode purity of output power. Particle-in-cell simulation shows that when the diode voltage is 400 kV and beam current is 3.8 kA, the generation of microwave at 32.26 GHz with an output power of 611 MW and a conversion efficiency of 40% is obtained. The power percentage carried by TEM mode reaches 99.7% in the output power.

  16. Shape effect of torsional resonance mode AFM cantilevers operated in fluids

    NASA Astrophysics Data System (ADS)

    Haochih Liu, Bernard; Chuang, Sheng-Kai; Lowai Huang, Allison

    2014-09-01

    Nanoscale resolution, high scanning rate, and non-destructive measurement are highly desirable attributes for imagining living cells in fluids. Torsional resonance (TR) mode is a promising approach that can satisfy these requirements. In this study, we have fabricated scanning probes with suitable cantilever designs for use in TR mode in fluids, using computer simulation as an aid in the design and fabrication iterations. Several geometrical parameters of cantilevers were considered and simulated for mechanical properties and dynamic characteristics, and selected designs were fabricated for performance evaluation. The influences of design parameters on scan performance were investigated by statistical analysis. Based on this approach, we designed and fabricated optimal cantilevers that can be operated in TR mode in water with high quality (Q) factor (˜60), high resonance frequency (˜240 kHz), and low spring constant (˜0.14 N m-1). Overall, O-shape cantilevers have demonstrated superior Q factors to typical rectangular shape, A-shape and V-shape designs.

  17. Geometric characterization of separability and entanglement in pure Gaussian states by single-mode unitary operations

    SciTech Connect

    Adesso, Gerardo; Giampaolo, Salvatore M.; Illuminati, Fabrizio

    2007-10-15

    We present a geometric approach to the characterization of separability and entanglement in pure Gaussian states of an arbitrary number of modes. The analysis is performed adapting to continuous variables a formalism based on single subsystem unitary transformations that has been recently introduced to characterize separability and entanglement in pure states of qubits and qutrits [S. M. Giampaolo and F. Illuminati, Phys. Rev. A 76, 042301 (2007)]. In analogy with the finite-dimensional case, we demonstrate that the 1xM bipartite entanglement of a multimode pure Gaussian state can be quantified by the minimum squared Euclidean distance between the state itself and the set of states obtained by transforming it via suitable local symplectic (unitary) operations. This minimum distance, corresponding to a, uniquely determined, extremal local operation, defines an entanglement monotone equivalent to the entropy of entanglement, and amenable to direct experimental measurement with linear optical schemes.

  18. Geometric characterization of separability and entanglement in pure Gaussian states by single-mode unitary operations

    NASA Astrophysics Data System (ADS)

    Adesso, Gerardo; Giampaolo, Salvatore M.; Illuminati, Fabrizio

    2007-10-01

    We present a geometric approach to the characterization of separability and entanglement in pure Gaussian states of an arbitrary number of modes. The analysis is performed adapting to continuous variables a formalism based on single subsystem unitary transformations that has been recently introduced to characterize separability and entanglement in pure states of qubits and qutrits [S. M. Giampaolo and F. Illuminati, Phys. Rev. A 76, 042301 (2007)]. In analogy with the finite-dimensional case, we demonstrate that the 1×M bipartite entanglement of a multimode pure Gaussian state can be quantified by the minimum squared Euclidean distance between the state itself and the set of states obtained by transforming it via suitable local symplectic (unitary) operations. This minimum distance, corresponding to a , uniquely determined, extremal local operation, defines an entanglement monotone equivalent to the entropy of entanglement, and amenable to direct experimental measurement with linear optical schemes.

  19. TMX-Upgrade (TMX-U) operation in the sloshing-ion mode

    SciTech Connect

    Simonen, T.C.; Allen, S.L.; Casper, T.A.

    1982-09-24

    This report summarizes initial results from TMX-U carried out from June through August 1982. In these successful experiments we operated TMX-U in the sloshing-ion mode. We generated sloshing ions, measured improved energy confinement, and observed improved microstability compared to TMX. The experiments operated about as we expected and we are pleased with the results. During this period many additional achievements were also recorded. The magnetically confined sloshing ions constitute one of the two ingredients needed to build a thermal barrier. The second ingredient consists of magnetically confined electrons, which will be studied in the next series of TMX-U experiments using microwave heating of the electrons. Later, the hot ions and electrons will be combined to form thermal barriers.

  20. Enhanced performance of bio-cathode microbial fuel cells with the applying of transient-state operation modes.

    PubMed

    Liang, Peng; Yuan, Lulu; Wu, Wenlong; Yang, Xufei; Huang, Xia

    2013-11-01

    To enhance the MFC's denitrification performance, this study investigated three different external circuits/operation modes of the MFC: alternative charging and discharging (ACD), intermittent charging (IC) and constant external resistance (R). Results showed that the ACD and IC modes offered larger output currents as well as higher nitrate and COD removal rates than the steady R mode. The best performance was achieved with the ACD mode. At the initial [COD]=~1200 mg/L and [NO3(-)]=~140 mg/L, the ACD mode delivered an average power density of 0.91 W/m(3), an average nitrate removal rate of 15.5mg/(Ld) and an average COD removal rate of 137 mg/(Ld), 268%, 207% and 168% respectively greater than those by the R mode. The enhancement by the ACD and IC modes was more pronounced at lower nitrate and COD concentrations and/or with the lack of stirring of electrolyte solutions.

  1. The energy spread of a LaB6 cathode operated in the virtual source mode

    NASA Astrophysics Data System (ADS)

    Wells, T.; El-Gomati, M.

    2014-06-01

    The LaB6 cathode has been the brightest thermionic source used in microprobe applications requiring longer lifetime [1-2]. It is x100 lower in brightness than thermal field emitters (TFE) ca Zr/W (100) [3]. There are attractive similarities between these cathodes in terms of work function and operating temperature that are worth considering. Major differences include their respective source sizes (>10μm vs 30nm) and energy spread of 1-2 eV vs 0.6-0.7eV for the LaB6 and TFE, respectively [4,3]. We report here on the experimental measurement of the energy spread of a LaB6 cathode operated in the virtual source mode. The cathode used has an end-form measuring 15μm. Total energy spread values obtained using a dedicated electron energy analyser shows values of 0.4eV-0.7eV, significantly lower than typical values in the thermionic mode of 1-2eV.

  2. Fluid modeling of operating modes in a field emission driven alternating current (FEDAC) microdischarge

    NASA Astrophysics Data System (ADS)

    Venkattraman, Ayyaswamy; Alamatsaz, Arghavan; Shivaprasad, Therazhundur Ramesh

    2014-10-01

    The recent interest in electrostatic microscale devices has lead to a great emphasis on electrical breakdown of gases in microgaps. The breakdown process has been shown to be significantly different from its counterpart in macrogaps with field emission of electrons from the cathode playing a major role. This work aims to build on prior work dealing with pre-breakdown and post-breakdown operating modes in direct current field emission driven (FED) microdischarges. Specifically, charged particle dynamics in microscale gaps that are driven by time-varying fields are studied using an in-house two-fluid code with appropriate cathode boundary conditions including field emission. The model includes continuity and energy equations for both electrons and ions to account for the significant non-equilibrium and is augmented by the Poisson's equation for electrostatic potential. The frequency dependence of breakdown behavior as well as pre-breakdown and post-breakdown current-voltage characteristics is determined for a wide range of frequencies from low radio frequency (RF) to microwave and contrasted with existing results for direct current FED microdischarges. The results are also used to explain trends recently observed in an evanescent-mode cavity resonator operating in the microwave regime.

  3. Burst-mode-operated, sub-nanosecond fiber MOPA system incorporating direct seed-packet shaping.

    PubMed

    Chen, Tao; Liu, Hao; Kong, Wei; Shu, Rong

    2016-09-01

    We report a novel burst-mode-operated sub-nanosecond fiber Master Oscillator, Power Amplifier (MOPA) system incorporating direct seed-packet shaping without external modulators. A fast digital-to-analog converter with 1 Gsps sampling rate and 16 bit resolution was developed to control the pulse amplitudes and sequences of a distributed feedback semiconductor seed laser to realize packet-shaped burst mode operation. Optical pulses with durations as short as 700 ps and peak power as high as 1 W can be generated from the seed by applying proper reverse voltages after positive electrical pulses to the laser driver to cancel the residual charges at its gate electrode. The average power of the laser can be amplified to nearly 40 W with FWHM spectral linewidth of ~0.12 nm after three stages of polarization maintaining fiber amplifiers. Different packet shapes including ramp-off, Gaussian, square and double rectangle can be produced from the fiber MOPA by finely pre-shaping the seed pulse bursts. It is believed that such a laser has provided a cost-effective solution to the generation of pulse bursts with arbitrary packet shapes for different practical applications including material micromachining and nonlinear frequency conversion. PMID:27607699

  4. Collection efficiency of ultrafine particles by an electrostatic precipitator under DC and pulse operating modes

    SciTech Connect

    Zukeran, Akinori; Looy, P.C.; Chakrabarti, A.; Berezin, A.A.; Jayaram, S.; Cross, J.D.; Ito, Tairo; Chang, J.S.

    1999-10-01

    High particle collection efficiency in terms of particle weight/volume mg/m{sup 3} is well achieved by a conventional electrostatic precipitator (ESP). However, the collection efficiencies in terms of number density for the ultrafine (particle size between 0.01--0.1 {micro}m) or submicrometer particles by a conventional ESP are still relatively low. Therefore, it is necessary to improve the collection efficiency for ultrafine particles. In this paper, attempts have been made to improve the ultrafine particle collection efficiency by controlling dust loading, as well as using the short pulse energizations. The present version of the ESP consists of three sets of wire-plate-type electrodes. For the ESP under dc operation modes, experimental results show that the collection efficiency for dc applied voltage decreases with increasing dust loading when particle density is larger than 2.5 x 10{sup 10} particles/m{sup 3} due to inefficient collections of ultrafine particles. However, under pulse operating modes without dc bias, high particle collection efficiency for ultrafine particles was obtained, which is thought to be due to the enhancement of particle charging by electrons.

  5. Reduced group delay dispersion in quantum dot passively mode-locked lasers operating at elevated temperature

    NASA Astrophysics Data System (ADS)

    Mee, J. K.; Raghunathan, R.; Murrell, D.; Braga, A.; Li, Y.; Lester, L. F.

    2014-09-01

    A detailed study of the pulse characteristics emitted from a monolithic Quantum Dot (QD) passively Mode-Locked Laser (MLL) has been performed using a state-of-the-art Frequency Resolved Optical Gating (FROG) pulse measurement system. While traditionally the time-domain pulse characteristics of semiconductor MLLs have been studied using digital sampling oscilloscope or intensity autocorrelation techniques, the FROG measurements allow for simultaneous characterization of time and frequency, which has been shown to be necessary and sufficient for true determination of mode-locked stability. In this paper, FROG pulse measurements are presented on a two-section QD MLL operating over wide temperature excursions. The FROG measurement allows for extraction of the temporal and spectral intensity and phase profiles from which the Group Delay Dispersion (GDD) can be determined. The magnitude of the GDD is found to decrease from 16.1 to 3.5 ps/nm when the temperature is increased from 20 to 50 oC, mirroring the trend of pulse width reduction at elevated temperature, which has been shown to correlate strongly with reduced unsaturated absorption. The possibility to further optimize pulse generation via intra-cavity dispersion compensation in a novel three-section MLL design is also examined, and shows strong potential toward providing valuable insight into the optimal cavity designs and operating parameters for QD MLLs.

  6. Cosmic rays with portable Geiger counters: from sea level to airplane cruise altitudes

    NASA Astrophysics Data System (ADS)

    Blanco, Francesco; La Rocca, Paola; Riggi, Francesco

    2009-07-01

    Cosmic ray count rates with a set of portable Geiger counters were measured at different altitudes on the way to a mountain top and aboard an aircraft, between sea level and cruise altitude. Basic measurements may constitute an educational activity even with high school teams. For the understanding of the results obtained, simulations of extensive air showers induced by high-energy primary protons in the atmosphere were also carried out, involving undergraduate and graduate teaching levels.

  7. Tunable S-band erbium-doped triple-ring laser with single-longitudinal-mode operation

    NASA Astrophysics Data System (ADS)

    Yeh, C.-H.; Huang, T. T.; Chien, H.-C.; Ko, C.-H.; Chi, S.

    2007-01-01

    We propose and demonstrate a tunable and stable single-longitudinal-mode (SLM) erbium fiber laser with a passive triple-ring cavity structure in S-band operation. The proposed laser is fundamentally structured by using three different lengths of ring cavities, which serve as the mode filters. When a mode-restricting intracavity fiber Fabry-Perot tunable filter (FFP-TF) is combined, the proposed resonator can guarantee a tunable and stable SLM laser oscillation. Moreover, the performances of the output power, wavelength stability, tuning range, and side-mode suppression ratio (SMSR) are studied.

  8. Pulsed-mode operation and performance of a ferromagnetic shape memory alloy actuator

    NASA Astrophysics Data System (ADS)

    Asua, E.; García-Arribas, A.; Etxebarria, V.; Feuchtwanger, J.

    2014-02-01

    The actuation capabilities and positioning performance of a single crystal ferromagnetic shape memory alloy (FSMA) operated in pulsed mode are evaluated in a prototype device. It consists of two orthogonal coil pairs that produce the magnetic fields necessary for the non-contact deformation of the material. The position of the top of the crystal after actuation is measured by a capacitive sensor. A specifically designed power module drives the discharge of a set of capacitors through the coils, producing fast current pulses of large amplitudes (about 250 A), the coil pairs are driven independently to control the direction of actuation. Open-loop experiments demonstrate that successive pulses of increasing magnitude successfully produced the desired expansion and contraction of the crystal, depending on the pair of coils that is activated. The deformation achieved is maintained after the pulses, highlighting the advantageous set-and-forget operation of the device. Closed-loop experiments are performed using a double proportional-integral-derivative controller, designed to take advantage of the energy-saving quality of the set-and-forget operation. Despite the nonlinear response and hysteric response of FSMA materials, a reference position can be reached and maintained with a maximum error of 0.5 μm.

  9. New Operational Modes to Increase Energy Efficiency in Capacitive Deionization Systems.

    PubMed

    García-Quismondo, Enrique; Santos, Cleis; Soria, Jorge; Palma, Jesús; Anderson, Marc A

    2016-06-01

    In order for capacitive deionization (CDI) as a water treatment technology to achieve commercial success, substantial improvements in the operational aspects of the system should be improved in order to efficiently recover the energy stored during the deionization step. In the present work, to increase the energy efficiency of the adsorption-desorption processes, we propose a new operational procedure that utilizes a concentrated brine stream as a washing solution during regeneration. Using this approach, we demonstrate that by replacing the electrolyte during regeneration for a solution with higher conductivity, it is possible to substantially increase round-trip energy efficiency. This procedure was experimentally verified in a flow cell reactor using a pair of carbon electrodes (10(2) cm geometric area) and NaCl solutions having concentrations between 50 and 350 mmol·L(-1). According to experimental data, this new operational mode allows for a better utilization of the three-dimensional structure of the porous material. This increases the energetic efficiency of the global CDI process to above 80% when deionization/regeneration currents ratio are optimized for brackish water treatment.

  10. Energetic electron avalanches and mode transitions in planar inductively coupled radio-frequency driven plasmas operated in oxygen

    SciTech Connect

    Zaka-ul-Islam, M.; Niemi, K.; Gans, T.; O'Connell, D.

    2011-07-25

    Space and phase resolved optical emission spectroscopic measurements reveal that in certain parameter regimes, inductively coupled radio-frequency driven plasmas exhibit three distinct operation modes. At low powers, the plasma operates as an alpha-mode capacitively coupled plasma driven through the dynamics of the plasma boundary sheath potential in front of the antenna. At high powers, the plasma operates in inductive mode sustained through induced electric fields due to the time varying currents and associated magnetic fields from the antenna. At intermediate powers, close to the often observed capacitive to inductive (E-H) transition regime, energetic electron avalanches are identified to play a significant role in plasma sustainment, similar to gamma-mode capacitively coupled plasmas. These energetic electrons traverse the whole plasma gap, potentially influencing plasma surface interactions as exploited in technological applications.

  11. Argon gas-puff radius optimiaztion for Saturn operating in the long-pulse mode.

    SciTech Connect

    Apruzese, John P.; Jackson, S. L.; Commisso, Robert J.; Weber, Bruce V.; Mosher, Daniel A.

    2010-06-01

    Argon gas puff experiments using the long pulse mode of Saturn (230-ns rise time) have promise to increase the coupled energy and simplify operations because the voltage is reduced in vacuum and the forward-going energy is higher for the same Marx charge. The issue addressed in this work is to determine if the 12-cm-diameter triple nozzle used in Saturn long-pulse-mode experiments to date provides maximum K-shell yield, or if a different-radius nozzle provides additional radiation. Long-pulse implosions are modeled by starting with measured density distributions from the existing 12-cm-diameter nozzle, and then varying the outer radius in an implosion-energy-conserving self-similar manner to predict the gas-puff diameter that results in the maximum K-shell yield. The snowplow-implosions and multi-zone radiation transport models used in the analysis are benchmarked against detailed measurements from the 12-cm-diameter experiments. These calculations indicate that the maximum K-shell emission is produced with very nearly the existing nozzle radius.

  12. Nanostethoscopy: A new mode of operation of the atomic force microscope

    SciTech Connect

    Keaton, A.; Holzrichter, J.F.; Balhorn, R.; Siekaus, W.J.

    1994-02-01

    The authors introduce a new mode of operation of the atomic force microscope (AFM). This detection scheme, a {open_quotes}Nano-Stethoscope{close_quotes}. Involves using the atomic force microscope in a novel acoustic mode not generally recognized. The Nano-Stethoscope uses the conventional scanning feature to locate a desired site, positions the AFM microscope tip over the site, holds the cantilever stationary (in x and v) and records the tip`s z-motion as a function of time. The tip/cantilever system thus functions as a micro-motion detector to respond to characteristic {open_quotes}pulsations{close_quotes}, nano-configurational chances, or any other event that influences the position of the tip as a function of time. The authors have demonstrated the feasibility of using the tip of an AFM in this manner in a biological system with a measurement of the vibrations of an emerging shrimp egg nauplius ({approximately}3 {mu}m. -10 Hz) and on the Angstrom scale in a non-biological system i.e.. the thermal expansion of metal interconnect lines on a microelectronic circuit.

  13. Speech enhancement using empirical mode decomposition and the Teager-Kaiser energy operator.

    PubMed

    Khaldi, Kais; Boudraa, Abdel-Ouahab; Komaty, Ali

    2014-01-01

    In this paper a speech denoising strategy based on time adaptive thresholding of intrinsic modes functions (IMFs) of the signal, extracted by empirical mode decomposition (EMD), is introduced. The denoised signal is reconstructed by the superposition of its adaptive thresholded IMFs. Adaptive thresholds are estimated using the Teager-Kaiser energy operator (TKEO) of signal IMFs. More precisely, TKEO identifies the type of frame by expanding differences between speech and non-speech frames in each IMF. Based on the EMD, the proposed speech denoising scheme is a fully data-driven approach. The method is tested on speech signals with different noise levels and the results are compared to EMD-shrinkage and wavelet transform (WT) coupled with TKEO. Speech enhancement performance is evaluated using output signal to noise ratio (SNR) and perceptual evaluation of speech quality (PESQ) measure. Based on the analyzed speech signals, the proposed enhancement scheme performs better than WT-TKEO and EMD-shrinkage approaches in terms of output SNR and PESQ. The noise is greatly reduced using time-adaptive thresholding than universal thresholding. The study is limited to signals corrupted by additive white Gaussian noise. PMID:24437785

  14. Numerical Examination of Silicon Avalanche Photodiodes Operated in Charge Storage Mode

    NASA Technical Reports Server (NTRS)

    Parks, Joseph W., Jr.; Brennan, Kevin F.

    1998-01-01

    The behavior of silicon-based avalanche photodiodes (APD's) operated in the charge storage mode is examined. In the charge storage mode, the diodes are periodically biased to a sub-breakdown voltage and then open-circuited. During this integration period, photo-excited and thermally generated carriers are accumulated within the structure. The dynamics of this accumulation and its effects upon the avalanching of the diode warrants a detailed, fully numerical analysis. The salient features of this investigation include device sensitivity to the input photo-current including the self-quenching effect of the diode and its limitations in sensing low light levels, the dependence of the response on the bulk lifetime and hence on the generation current within the device, the initial gain, transient response, dependence of the device uniformity upon performance, and the quantity of storable charge within the device. To achieve these tasks our device simulator, STEBS-2D, was utilized. A modified current-controlled boundary condition is employed which allows for the simulation of the isolated diode after the initial reset bias has been applied. With this boundary condition, it is possible to establish a steady-state voltage on the ohmic contact and then effectively remove the device from the external circuit while still including effects from surface recombination, trapped surface charge, and leakage current from the read-out electronics.

  15. Output Feedback Fractional-Order Nonsingular Terminal Sliding Mode Control of Underwater Remotely Operated Vehicles

    PubMed Central

    Chen, Jiawang; Gu, Linyi

    2014-01-01

    For the 4-DOF (degrees of freedom) trajectory tracking control problem of underwater remotely operated vehicles (ROVs) in the presence of model uncertainties and external disturbances, a novel output feedback fractional-order nonsingular terminal sliding mode control (FO-NTSMC) technique is introduced in light of the equivalent output injection sliding mode observer (SMO) and TSMC principle and fractional calculus technology. The equivalent output injection SMO is applied to reconstruct the full states in finite time. Meanwhile, the FO-NTSMC algorithm, based on a new proposed fractional-order switching manifold, is designed to stabilize the tracking error to equilibrium points in finite time. The corresponding stability analysis of the closed-loop system is presented using the fractional-order version of the Lyapunov stability theory. Comparative numerical simulation results are presented and analyzed to demonstrate the effectiveness of the proposed method. Finally, it is noteworthy that the proposed output feedback FO-NTSMC technique can be used to control a broad range of nonlinear second-order dynamical systems in finite time. PMID:24983004

  16. Output feedback fractional-order nonsingular terminal sliding mode control of underwater remotely operated vehicles.

    PubMed

    Wang, Yaoyao; Chen, Jiawang; Gu, Linyi

    2014-01-01

    For the 4-DOF (degrees of freedom) trajectory tracking control problem of underwater remotely operated vehicles (ROVs) in the presence of model uncertainties and external disturbances, a novel output feedback fractional-order nonsingular terminal sliding mode control (FO-NTSMC) technique is introduced in light of the equivalent output injection sliding mode observer (SMO) and TSMC principle and fractional calculus technology. The equivalent output injection SMO is applied to reconstruct the full states in finite time. Meanwhile, the FO-NTSMC algorithm, based on a new proposed fractional-order switching manifold, is designed to stabilize the tracking error to equilibrium points in finite time. The corresponding stability analysis of the closed-loop system is presented using the fractional-order version of the Lyapunov stability theory. Comparative numerical simulation results are presented and analyzed to demonstrate the effectiveness of the proposed method. Finally, it is noteworthy that the proposed output feedback FO-NTSMC technique can be used to control a broad range of nonlinear second-order dynamical systems in finite time.

  17. Does the ocean-atmosphere system have more than one stable mode of operation?

    NASA Technical Reports Server (NTRS)

    Broecker, W. S.; Peteet, D. M.; Rind, D.

    1985-01-01

    The climate record obtained from two long Greenland ice cores reveals several brief climate oscillations during glacial time. The most recent of these oscillations, also found in continental pollen records, has greatest impact in the area under the meteorological influence of the northern Atlantic, but none in the United States. This suggests that these oscillations are caused by fluctuations in the formation rate of deep water in the northern Atlantic. As the present production of deep water in this area is driven by an excess of evaporation over precipitation and continental runoff, atmospheric water transport may be an important element in climate change. Changes in the production rate of deep water in this sector of the ocean may push the climate system from one quasi-stable mode of operation to another.

  18. Memristive operation mode of a site-controlled quantum dot floating gate transistor

    SciTech Connect

    Maier, P. Hartmann, F.; Mauder, T.; Emmerling, M.; Schneider, C.; Kamp, M.; Worschech, L.; Höfling, S.

    2015-05-18

    We have realized a floating gate transistor based on a GaAs/AlGaAs heterostructure with site-controlled InAs quantum dots. By short-circuiting the source contact with the lateral gates and performing closed voltage sweep cycles, we observe a memristive operation mode with pinched hysteresis loops and two clearly distinguishable conductive states. The conductance depends on the quantum dot charge which can be altered in a controllable manner by the voltage value and time interval spent in the charging region. The quantum dot memristor has the potential to realize artificial synapses in a state-of-the-art opto-electronic semiconductor platform by charge localization and Coulomb coupling.

  19. Dielectric Huygens' Metasurface for High-Efficiency Hologram Operating in Transmission Mode.

    PubMed

    Zhao, Wenyu; Jiang, Huan; Liu, Bingyi; Song, Jie; Jiang, Yongyuan; Tang, Chengchun; Li, Junjie

    2016-01-01

    Conventional metasurface holograms relying on metal antennas for phase manipulation suffer from strong Ohmic loss and incomplete polarization conversion. The efficiency is limited to rather small values when operating in transmission mode. Here, we implement a high-efficiency transmissive metasurface hologram by leveraging the recently developed Huygens' metasurface to construct an electric and magnetic sheet with a transmission efficiency up to 86% and optical efficiency of 23.6%. The high-efficiency originates from the simultaneous excitations of the Mie-type electric and magnetic dipole resonances in the meta-atoms composed of silicon nanodisks. Our hologram shows high fidelity over a wide spectral range and promises to be an outstanding alternative for display applications. PMID:27457708

  20. On the zero modes of the Faddeev-Popov operator in the Landau gauge

    SciTech Connect

    Landim, R. R.; Vilar, L. C. Q. Lemes, V. E. R.; Ventura, O. S.

    2014-02-15

    Following Henyey procedure [Phys. Rev. D 20, 1460 (1979)], we construct examples of zero modes of the Faddeev-Popov operator in the Landau gauge in Euclidean space in D dimensions, for both SU(2) and SU(3) groups. We obtain gauge field configurations A{sub μ}{sup a} which give rise to a field strength, F{sub μν}{sup a}=∂{sub μ}A{sub ν}{sup a}−∂{sub ν}A{sub μ}{sup a}+f{sup abc}A{sub μ}{sup b}A{sub ν}{sup c}, whose nonlinear term, f{sup abc}A{sub μ}{sup b}A{sub ν}{sup c}, turns out to be non-vanishing. To our knowledge, this is the first time where such a non-abelian configuration is explicitly obtained in the case of SU(3) in 4D.

  1. Dielectric Huygens’ Metasurface for High-Efficiency Hologram Operating in Transmission Mode

    NASA Astrophysics Data System (ADS)

    Zhao, Wenyu; Jiang, Huan; Liu, Bingyi; Song, Jie; Jiang, Yongyuan; Tang, Chengchun; Li, Junjie

    2016-07-01

    Conventional metasurface holograms relying on metal antennas for phase manipulation suffer from strong Ohmic loss and incomplete polarization conversion. The efficiency is limited to rather small values when operating in transmission mode. Here, we implement a high-efficiency transmissive metasurface hologram by leveraging the recently developed Huygens’ metasurface to construct an electric and magnetic sheet with a transmission efficiency up to 86% and optical efficiency of 23.6%. The high-efficiency originates from the simultaneous excitations of the Mie-type electric and magnetic dipole resonances in the meta-atoms composed of silicon nanodisks. Our hologram shows high fidelity over a wide spectral range and promises to be an outstanding alternative for display applications.

  2. FDNS CFD Code Benchmark for RBCC Ejector Mode Operation: Continuing Toward Dual Rocket Effects

    NASA Technical Reports Server (NTRS)

    West, Jeff; Ruf, Joseph H.; Turner, James E. (Technical Monitor)

    2000-01-01

    Computational Fluid Dynamics (CFD) analysis results are compared with benchmark quality test data from the Propulsion Engineering Research Center's (PERC) Rocket Based Combined Cycle (RBCC) experiments to verify fluid dynamic code and application procedures. RBCC engine flowpath development will rely on CFD applications to capture the multi -dimensional fluid dynamic interactions and to quantify their effect on the RBCC system performance. Therefore, the accuracy of these CFD codes must be determined through detailed comparisons with test data. The PERC experiments build upon the well-known 1968 rocket-ejector experiments of Odegaard and Stroup by employing advanced optical and laser based diagnostics to evaluate mixing and secondary combustion. The Finite Difference Navier Stokes (FDNS) code [2] was used to model the fluid dynamics of the PERC RBCC ejector mode configuration. Analyses were performed for the Diffusion and Afterburning (DAB) test conditions at the 200-psia thruster operation point, Results with and without downstream fuel injection are presented.

  3. Dielectric Huygens’ Metasurface for High-Efficiency Hologram Operating in Transmission Mode

    PubMed Central

    Zhao, Wenyu; Jiang, Huan; Liu, Bingyi; Song, Jie; Jiang, Yongyuan; Tang, Chengchun; Li, Junjie

    2016-01-01

    Conventional metasurface holograms relying on metal antennas for phase manipulation suffer from strong Ohmic loss and incomplete polarization conversion. The efficiency is limited to rather small values when operating in transmission mode. Here, we implement a high-efficiency transmissive metasurface hologram by leveraging the recently developed Huygens’ metasurface to construct an electric and magnetic sheet with a transmission efficiency up to 86% and optical efficiency of 23.6%. The high-efficiency originates from the simultaneous excitations of the Mie-type electric and magnetic dipole resonances in the meta-atoms composed of silicon nanodisks. Our hologram shows high fidelity over a wide spectral range and promises to be an outstanding alternative for display applications. PMID:27457708

  4. Dielectric Huygens' Metasurface for High-Efficiency Hologram Operating in Transmission Mode.

    PubMed

    Zhao, Wenyu; Jiang, Huan; Liu, Bingyi; Song, Jie; Jiang, Yongyuan; Tang, Chengchun; Li, Junjie

    2016-07-26

    Conventional metasurface holograms relying on metal antennas for phase manipulation suffer from strong Ohmic loss and incomplete polarization conversion. The efficiency is limited to rather small values when operating in transmission mode. Here, we implement a high-efficiency transmissive metasurface hologram by leveraging the recently developed Huygens' metasurface to construct an electric and magnetic sheet with a transmission efficiency up to 86% and optical efficiency of 23.6%. The high-efficiency originates from the simultaneous excitations of the Mie-type electric and magnetic dipole resonances in the meta-atoms composed of silicon nanodisks. Our hologram shows high fidelity over a wide spectral range and promises to be an outstanding alternative for display applications.

  5. Integrated Mode Choice, Small Aircraft Demand, and Airport Operations Model User's Guide

    NASA Technical Reports Server (NTRS)

    Yackovetsky, Robert E. (Technical Monitor); Dollyhigh, Samuel M.

    2004-01-01

    A mode choice model that generates on-demand air travel forecasts at a set of GA airports based on changes in economic characteristics, vehicle performance characteristics such as speed and cost, and demographic trends has been integrated with a model to generate itinerate aircraft operations by airplane category at a set of 3227 airports. Numerous intermediate outputs can be generated, such as the number of additional trips diverted from automobiles and schedule air by the improved performance and cost of on-demand air vehicles. The total number of transported passenger miles that are diverted is also available. From these results the number of new aircraft to service the increased demand can be calculated. Output from the models discussed is in the format to generate the origin and destination traffic flow between the 3227 airports based on solutions to a gravity model.

  6. Thermal Spray Using a High-Frequency Pulse Detonation Combustor Operated in the Liquid-Purge Mode

    NASA Astrophysics Data System (ADS)

    Endo, T.; Obayashi, R.; Tajiri, T.; Kimura, K.; Morohashi, Y.; Johzaki, T.; Matsuoka, K.; Hanafusa, T.; Mizunari, S.

    2016-02-01

    Experiments on thermal spray by pulsed detonations at 150 Hz were conducted. Two types of pulse detonation combustors were used, one operated in the inert gas purge (GAP) mode and the other in the liquid-purge (LIP) mode. In both modes, all gases were supplied in the valveless mode. The GAP mode is free of moving components, although the explosive mixture is unavoidably diluted with the inert gas used for the purge of the hot burned gas. In the LIP mode, pure fuel-oxygen combustion can be realized, although a liquid-droplet injector must be actuated cyclically. The objective of this work was to demonstrate a higher spraying temperature in the LIP mode. First, the temperature of CoNiCrAlY particles heated by pulsed detonations was measured. As a result, the spraying temperature in the LIP mode was higher than that in the GAP mode by about 1000 K. Second, the temperature of yttria-stabilized zirconia (YSZ) particles, whose melting point was almost 2800 °C, heated by pulsed detonations in the LIP mode was measured. As a result, the YSZ particles were heated up to about 2500 °C. Finally, a thermal spray experiment using YSZ particles was conducted, and a coating with low porosity was successfully deposited.

  7. Analytical model for tilting proprotor aircraft dynamics, including blade torsion and coupled bending modes, and conversion mode operation

    NASA Technical Reports Server (NTRS)

    Johnson, W.

    1974-01-01

    An analytical model is developed for proprotor aircraft dynamics. The rotor model includes coupled flap-lag bending modes, and blade torsion degrees of freedom. The rotor aerodynamic model is generally valid for high and low inflow, and for axial and nonaxial flight. For the rotor support, a cantilever wing is considered; incorporation of a more general support with this rotor model will be a straight-forward matter.

  8. STOMP Sparse Vegetation Evapotranspiration Model for the Water-Air-Energy Operational Mode

    SciTech Connect

    Ward, Anderson L.; White, Mark D.; Freeman, Eugene J.; Zhang, Z. F.

    2005-09-15

    The Water-Air-Energy (WAE) Operational Mode of the Subsurface Transport Over Multiple Phases (STOMP) numerical simulator solves the coupled conservation equations for water mass, air mass, and thermal energy in multiple dimensions. This addendum describes the theory, input file formatting, and application of a soil-vegetation-atmosphere transfer (SVAT) scheme for STOMP that is based on a sparse vegetation evapotranspiration model. The SVAT scheme is implemented as a boundary condition on the upper surface of the computational domain and has capabilities for simulating evaporation from bare surfaces as well as evapotranspiration from sparsely vegetated surfaces populated with single or multiple plant species in response to meteorological forcings. With this extension, the model calculates water mass, air mass and thermal energy across a boundary surface in addition to root-water transport between the subsurface and atmosphere. This mode represents the barrier extension of the WAE mode and is designated as STOMP-WAE-B. Input for STOMP-WAE-B is specified via three input cards and include: atmospheric conditions through the Atmospheric Conditions Card; time-invariant plant species data through the Plant Properties Card; and time varying plant species data through the Boundary Conditions Card. Two optional cards, the Observed Data and UCODE Control Cards allow use of STOMP-WAE with UCODE in an inverse mode to estimate model parameters. STOMP-WAE was validated by solving a number of test problems from the literature that included experimental observations as well as analytical or numerical solutions. Several of the UNSAT-H verification problems are included along with a benchmark simulation derived from a recently published intercode comparison for barrier design tools. Results show that STOMP is able to meet, and in most cases, exceed performance of other commonly used simulation codes without having to resort to may of their simplifying assumptions. Use of the fully

  9. Testing to expand the rotary mode core sampling system operating envelope

    SciTech Connect

    Witwer, K.S.

    1998-01-21

    Rotary sampling using the Rotary Mode Core Sampling System (RMCSS) is constrained by what is referred to as the ``Operating Envelope``. The Operating Envelop defines the maximum downward force, maximum rotational speed and minimum purge gas flow allowed during operation of the RMCSS. The original values of 1170 lb. down force, 55 RPM rotational speed, and 30 SCFM nitrogen purge gas were determined during original envelope testing. This envelope was determined by observing the temperature rise on the bitface while drilling into waste simulants. The maximum temperature in single-shell tanks (SSTS) is considered to be approximately 9O C and the critical drill bit temperature, which is the temperature at which an exothermic reaction could be initiated in the tank waste, was previously determined to be 150 C. Thus, the drill bit temperature increase was limited to 60 C. Thermal properties of these simulants approximated typical properties of waste tank saltcake. Later, more detailed envelope testing which used a pumice block simulant, showed a notably higher temperature rise while drilling. This pumice material, which simulated a ``worst case`` foreign object embedded in the waste, has lower thermal conductivity and lower thermal diffusivity than earlier simulants. These properties caused a slower heat transfer in the pumice than in the previous simulants and consequently a higher temperature rise. The maximum downward force was subsequently reduced to 750 lb (at a maximum 55 RPM and minimum 30 SCFM purge gas flow) which was the maximum value at which the drill bit could be operated and still remain below the 60 C temperature rise.

  10. Message Mode Operations for Spacecraft: A Proposal for Operating Spacecraft During Cruise and Mitigating the Network Loading Crunch

    NASA Technical Reports Server (NTRS)

    Greenberg, Ed; MacMedan, Marv; Kazz, Greg; Kallemeyn, Pieter

    2000-01-01

    The NASA Deep Space Network (DSN) is a world-class spacecraft tracking facility with stations located in Spain, Australia and USA, servicing Deep Space Missions of many space agencies. The current system of scheduling spacecraft during cruise for multiple 8 hour tracking sessions per week currently leads to an overcommitted DSN. Studies indicate that future projected mission demands upon the Network will only make the loading problem worse. Therefore, a more efficient scheduling of DSN resources is necessary in order to support the additional network loading envisioned in the next few years: The number of missions is projected to increase from 25 in 1998 to 34 by 2001. In fact given the challenge of the NASA administrator, Dan Goldin, of launching 12 spacecraft per year, the DSN would be tracking approximately 90 spacecraft by 2010. Currently a large amount of antenna time and network resources are subscribed by a project in order to have their mission supported during the cruise phase. The recently completed Mars Pathfinder mission was tracked 3 times a week (8 hours/day) during the majority of its cruise to Mars. This paper proposes an innovative approach called Message Mode Operations (MMO) for mitigating the Network loading problem while continuing to meet the tracking, reporting, time management, and scheduling requirements of these missions during Cruise while occupying very short tracking times. MMO satisfies these requirements by providing the following services: Spacecraft Health and Welfare Monitoring Service Command Delivery Service Adaptive Spacecraft Scheduling Service Orbit Determination Service Time Calibration Service Utilizing more efficient engineering telemetry summarization and filtering techniques on-board the spacecraft and collapsing the navigation requirements for Doppler and Range into shorter tracks, we believe spacecraft can be adequately serviced using short 10 to 30 minute tracking sessions. This claim assumes that certain changes would

  11. Comparison of biogas recovery from MSW using different aerobic-anaerobic operation modes.

    PubMed

    Xu, Qiyong; Tian, Ying; Kim, Hwidong; Ko, Jae Hac

    2016-10-01

    Aeration pretreatment was demonstrated as an efficient technology to promote methane recovery from a bioreactor landfill with high food waste content. In this study, a short-term experiment was conducted to investigate the effects of aerobic-anaerobic operation modes on biogas recovery. Three landfill-simulated columns (anaerobic control (A1), a constant aeration (C1) and a gradually reduced aeration (C2)) were constructed and operated for 130days. The aeration frequency was adjusted by oxygen consumption in an aerated MSW landfill. After aerobic pretreatment was halted, the methanogenic phase was rapidly developed in both the C1 and C2 columns, reducing the volatile fatty acid (VFA) concentrations and increasing pH. The methane volumes per dry MSW produced from the C1 and C2 columns were approximately 62L/kg VS and 75L/kg VS, respectively, while methane produced from the A1 column was almost negligible. The result clearly showed that aerobic pretreatment with gradual reduction of aeration rates could not only improve methane recovery from waste decomposition, but also enhance leachate COD and VFA removal. PMID:27426021

  12. Operational modes and control philosophy of the SSCL Magnet Test Lab. (MTL) cryogenic system

    SciTech Connect

    Ganni, V.; Than, R.; Thirumaleshwar, M.

    1993-05-01

    The MTL`s function is to test prototype and industrially manufactured magnets for the Superconducting Super Collider Laboratory (SSCL). The cryogenic system of the MTL has a main refrigeration system consisting of a two-stage compression system, a refrigerator/liquefier coldbox, a liquid helium dewar, warm gas storage, and a regeneration skid. The MTL cryogenic system also includes the following auxiliary equipment: two cleaning, cooling, warmup and purification (CCWP) coldbox modules with a regeneration skid for the charcoal beds, two CCWP compressors, a dehydration skid with its own regeneration system, a pump box, a refrigeration recovery unit, and five distribution boxes. At any given time, the refrigeration system has the capacity to simultaneously test at least six magnets under normally required testing conditions. Every magnet will undergo cleaning, cooldown, and filling prior to general testing, conditioning, quench testing, and other experiments. At the completion of general testing, etc., the magnet must be emptied prior to warming it up to ambient temperature. Furthermore, conditioning, training, and testing of the magnets can be carried out at different temperatures between 4.5 K and 2.5 K. The cryogenic system is designed to test multiple magnets, not all of which are necessarily in the same preparational or operational stage. This paper describes the different operational modes and the behavior and control of the total cryogenic system during multiple magnet tests.

  13. Gravitationally induced zero modes of the Faddeev-Popov operator in the Coulomb gauge for Abelian gauge theories

    SciTech Connect

    Canfora, Fabrizio; Giacomini, Alex; Oliva, Julio

    2010-08-15

    It is shown that on curved backgrounds, the Coulomb gauge Faddeev-Popov operator can have zero modes even in the Abelian case. These zero modes cannot be eliminated by restricting the path integral over a certain region in the space of gauge potentials. The conditions for the existence of these zero modes are studied for static spherically symmetric spacetimes in arbitrary dimensions. For this class of metrics, the general analytic expression of the metric components in terms of the zero modes is constructed. Such expression allows one to find the asymptotic behavior of background metrics, which induce zero modes in the Coulomb gauge, an interesting example being the three-dimensional anti-de Sitter spacetime. Some of the implications for quantum field theory on curved spacetimes are discussed.

  14. Helium ELMy H-modes in Alcator C-Mod in Support of ITER Helium Operating Phases

    NASA Astrophysics Data System (ADS)

    Kessel, C. E.; Wolfe, S. M.; Chilenski, M. A.; Hughes, J. W.; Lin, Y.; Reinke, M. L.; Wukitch, S. J.; C-Mod Team

    2015-11-01

    ITER will operate helium majority plasmas in its earlier phases to shakedown the facility and provide plasmas in both L-mode and H-mode for commissioning and preparation for DT burning plasma operation. Part of this activity is to produce ELMy H-modes to test ELM mitigation schemes and observe the ELM impacts on the plasma facing components. It is of interest to characterize helium ELMy H-modes on present experiments to provide some basis to project to ITER and anticipate the plasma performance and ability to obtain H-modes with sufficient performance. ELMy H-mode is accessed in C-Mod by using LSN with an elongation of about 1.55, and with high lower triangularity and low upper triangularity. These regimes were produced with 1.5-4.0 MW of ICRF heating, and with H-mode line average densities of 2.0-3.2x1020 /m3, producing higher frequency repetitive to large infrequent ELMs, respectively. The infrequent ELM regime showed a cross between EDA and ELMy H-mode, with the EDA signature of a quasi-coherent mode at about 200 kHz. Tungsten laser blow-off was done. The pedestal features, energy confinement, ELM character, L-H threshold (1.7-2.5 MW) and W confinement will be discussed. Comparisons with deuterium ELMy H-modes will be made. Work supported by DOE DE-AC02-09CH11466 and DE-FC02-99ER54512.

  15. A millimeter wave relativistic backward wave oscillator operating in TM{sub 03} mode with low guiding magnetic field

    SciTech Connect

    Ye, Hu; Wu, Ping; Teng, Yan; Chen, Changhua; Ning, Hui; Song, Zhimin; Cao, Yibing

    2015-06-15

    A V-band overmoded relativistic backward wave oscillator (RBWO) guided by low magnetic field and operating on a TM{sub 03} mode is presented to increase both the power handling capacity and the wave-beam interaction conversion efficiency. Trapezoidal slow wave structures (SWSs) with shallow corrugations and long periods are adopted to make the group velocity of TM{sub 03} mode at the intersection point close to zero. The coupling impedance and diffraction Q-factor of the RBWO increase, while the starting current decreases owing to the reduction of the group velocity of TM{sub 03} mode. In addition, the TM{sub 03} mode dominates over the other modes in the startup of the oscillation. Via numerical simulation, the generation of the microwave pulse with an output power of 425 MW and a conversion efficiency of 32% are achieved at 60.5 GHz with an external magnetic field of 1.25 T. This RBWO can provide greater power handling capacity when operating on the TM{sub 03} mode than on the TM{sub 01} mode.

  16. 50 mW stable single longitudinal mode operation of a 780 nm GaAlAs DFB laser

    SciTech Connect

    Takigawa, S.; Kume, M.; Hamada, K.; Yoshikawa, N.; Shimizu, H.; Gano, G.; Uno, T.

    1989-06-01

    Stable single longitudinal mode (SLM) operation has been attained with powers as high as 50 mW in a 780 nm GaAlAs distributed feedback laser. This excellent operation is due to the use of the buried twin-ridge substrate structure which allows the stable fundamental spatial mode operation even at high-power levels. The coupling strength designed is 0.5 from the viewpoint of obtaining a low operation current at 50 mW. The SLM operation in this laser was maintained for powers up to 50 mW at room temperature and in the temperature range from -17 to 37/sup 0/C at 50 mW. The maximum power attained was 62 mW.

  17. Compatible operation of the power system for steady state and pulse modes in a magnetic torus KT-5D

    NASA Astrophysics Data System (ADS)

    Yu, Yi; Wang, Zhi-jiang; Xu, Min; Zhu, Zhen-hua; Lu, Rong-hua; Wen, Yi-zhi; Yu, Chang-xuan; Wan, Shu-de; Liu, Wan-dong; Wang, Jun; Xu, Xiao-yuan; Hu, Ling-ying

    2006-12-01

    Compatible operation of steady state mode and pulse mode is realized in the KT-5D device. New power supplies with the operation control systems for the steady state toroidal magnetic field as well as for the vertical field are added, and the rf wave injection systems for sustaining steady state plasmas are upgraded. After the modification, the device now can work not only as a tokomak with pulsed plasma currents as it was but also as a simple magnetized torus with steady state plasma discharges. It allows more flexible and efficient experimental researches on the magnetically confined plasmas to be carried on in the same device.

  18. Compatible operation of the power system for steady state and pulse modes in a magnetic torus KT-5D

    SciTech Connect

    Yu Yi; Wang Zhijiang; Xu Min; Zhu Zhenhua; Lu Ronghua; Wen Yizhi; Yu Changxuan; Wan Shude; Liu Wandong; Wang Jun; Xu Xiaoyuan; Hu Lingying

    2006-12-15

    Compatible operation of steady state mode and pulse mode is realized in the KT-5D device. New power supplies with the operation control systems for the steady state toroidal magnetic field as well as for the vertical field are added, and the rf wave injection systems for sustaining steady state plasmas are upgraded. After the modification, the device now can work not only as a tokomak with pulsed plasma currents as it was but also as a simple magnetized torus with steady state plasma discharges. It allows more flexible and efficient experimental researches on the magnetically confined plasmas to be carried on in the same device.

  19. Performance of Single Electrode-Supported Cells Operating in the Electrolysis Mode

    SciTech Connect

    J. E. O'Brien; G. K. Housley; D. G. Milobar

    2009-11-01

    An experimental study is under way to assess the performance of electrode-supported solid-oxide cells operating in the steam electrolysis mode for hydrogen production over a temperature range of 800 to 900ºC. Results presented in this paper were obtained from single cells, with an active area of 16 cm2 per cell. The electrolysis cells are electrode-supported, with yttria-stabilized zirconia (YSZ) electrolytes (~10 µm thick), nickel-YSZ steam/hydrogen electrodes (~1400 µm thick), and manganite (LSM) air-side electrodes. The experiments were performed over a range of steam inlet mole fractions (0.1 – 0.6), gas flow rates, and current densities (0 to 0.6 A/cm2). Steam consumption rates associated with electrolysis were measured directly using inlet and outlet dewpoint instrumentation. On a molar basis, the steam consumption rate is equal to the hydrogen production rate. Cell performance was evaluated by performing DC potential sweeps at 800, 850, and 900°C. The voltage-current characteristics are presented, along with values of area-specific resistance as a function of current density. Long-term cell performance is also assessed to evaluate cell degradation. Details of the custom single-cell test apparatus developed for these experiments are also presented.

  20. Highly sensitive and selective WO3 nanoparticle gas sensor operating in thermally modulated dynamic mode

    NASA Astrophysics Data System (ADS)

    Ionescu, Radu; Hoel, Anders; Granqvist, Claes-Goran; Llobet, Eduard; Heszler, Peter

    2004-05-01

    Nanoparticle films of crystalline WO3, designed for gas sensing applications, were deposited on alumina substrates by reactive gas deposition. H2S, ethanol vapour, and binary mixtures of ethanol/H2S, ethanol/NO2 and H2S/NO2 were used in different concentrations for testing the performance of the sensor device. The sensor was operated in dynamic mode by modulating its temperature between 150 and 250 °C. Coefficients were extracted by applying Fast Fourier Transform (FFT) and Discrete Wavelet Transform (DWT) methods to the dynamic resistance response of the sensor. These coefficients were then used as inputs for pattern recognition methods to extract both quantitative (concentration) and qualitative (chemical selectivity) information about the test gases. After sensor calibration, it was possible to detect as little as 200 ppb of ethanol and 20 ppb of H2S with good accuracy. Furthermore, ethanol and H2S could be detected with good sensitivity and selectivity in the presence of both reducing and oxidising gases.

  1. Dual-mode Operation of a Rocket-Ramjet Combined Cycle Engine

    NASA Astrophysics Data System (ADS)

    Tomioka, Sadatake; Tani, Koichiro; Masumoto, Ryo; Ueda, Shuuichi

    One-dimensional evaluation of Ramjet-mode operation was carried out on a rocket-ramjet combined cycle engine model. For simplicity, instantaneous mixing between the airflow and rocket exhaust, instantaneous heat release, and pressure recovery by a normal-shock wave were assumed. Shock wave location was so decided that the heat release at the injection (heat addition) location was to thermally-choke the combustion gas flow. By changing the injection location, it was shown that a further downstream injection resulted in a further thrust production and a further fuel flow rate requirement for choking, and a lesser specific impulse. Balancing the thrust production and the specific impulse in terms of the launch vehicle acceleration performance should be pursued. The total pressure loss within the engine model was dominated by the shock wave location, not depended on injection location and fuel flow rate, so that having shock wave penetration to further upstream location was beneficial both for thrust production in the engine and at the external nozzle.

  2. Design Considerations of ISTAR Hydrocarbon Fueled Combustor Operating in Air Augmented Rocket, Ramjet and Scramjet Modes

    NASA Technical Reports Server (NTRS)

    Andreadis, Dean; Drake, Alan; Garrett, Joseph L.; Gettinger, Christopher D.; Hoxie, Stephen S.

    2003-01-01

    The development and ground test of a rocket-based combined cycle (RBCC) propulsion system is being conducted as part of the NASA Marshall Space Flight Center (MSFC) Integrated System Test of an Airbreathing Rocket (ISTAR) program. The eventual flight vehicle (X-43B) is designed to support an air-launched self-powered Mach 0.7 to 7.0 demonstration of an RBCC engine through all of its airbreathing propulsion modes - air augmented rocket (AAR), ramjet (RJ), and scramjet (SJ). Through the use of analytical tools, numerical simulations, and experimental tests the ISTAR program is developing and validating a hydrocarbon-fueled RBCC combustor design methodology. This methodology will then be used to design an integrated RBCC propulsion system that produces robust ignition and combustion stability characteristics while maximizing combustion efficiency and minimizing drag losses. First order analytical and numerical methods used to design hydrocarbon-fueled combustors are discussed with emphasis on the methods and determination of requirements necessary to establish engine operability and performance characteristics.

  3. Design Considerations of Istar Hydrocarbon Fueled Combustor Operating in Air Augmented Rocket, Ramjet and Scramjet Modes

    NASA Technical Reports Server (NTRS)

    Andreadis, Dean; Drake, Alan; Garrett, Joseph L.; Gettinger, Christopher D.; Hoxie, Stephen S.

    2002-01-01

    The development and ground test of a rocket-based combined cycle (RBCC) propulsion system is being conducted as part of the NASA Marshall Space Flight Center (MSFC) Integrated System Test of an Airbreathing Rocket (ISTAR) program. The eventual flight vehicle (X-43B) is designed to support an air-launched self-powered Mach 0.7 to 7.0 demonstration of an RBCC engine through all of its airbreathing propulsion modes - air augmented rocket (AAR), ramjet (RJ), and scramjet (SJ). Through the use of analytical tools, numerical simulations, and experimental tests the ISTAR program is developing and validating a hydrocarbon-fueled RBCC combustor design methodology. This methodology will then be used to design an integrated RBCC propulsion system thai: produces robust ignition and combustion stability characteristics while maximizing combustion efficiency and minimizing drag losses. First order analytical and numerical methods used to design hydrocarbon-fueled combustors are discussed with emphasis on the methods and determination of requirements necessary to establish engine operability and performance characteristics.

  4. Development of a numerical tool to study the mixing phenomenon occurring during mode one operation of a multi-mode ejector-augmented pulsed detonation rocket engine

    NASA Astrophysics Data System (ADS)

    Dawson, Joshua

    A novel multi-mode implementation of a pulsed detonation engine, put forth by Wilson et al., consists of four modes; each specifically designed to capitalize on flow features unique to the various flow regimes. This design enables the propulsion system to generate thrust through the entire flow regime. The Multi-Mode Ejector-Augmented Pulsed Detonation Rocket Engine operates in mode one during take-off conditions through the acceleration to supersonic speeds. Once the mixing chamber internal flow exceeds supersonic speed, the propulsion system transitions to mode two. While operating in mode two, supersonic air is compressed in the mixing chamber by an upstream propagating detonation wave and then exhausted through the convergent-divergent nozzle. Once the velocity of the air flow within the mixing chamber exceeds the Chapman-Jouguet Mach number, the upstream propagating detonation wave no longer has sufficient energy to propagate upstream and consequently the propulsive system shifts to mode three. As a result of the inability of the detonation wave to propagate upstream, a steady oblique shock system is established just upstream of the convergent-divergent nozzle to initiate combustion. And finally, the propulsion system progresses on to mode four operation, consisting purely of a pulsed detonation rocket for high Mach number flight and use in the upper atmosphere as is needed for orbital insertion. Modes three and four appear to be a fairly significant challenge to implement, while the challenge of implementing modes one and two may prove to be a more practical goal in the near future. A vast number of potential applications exist for a propulsion system that would utilize modes one and two, namely a high Mach number hypersonic cruise vehicle. There is particular interest in the dynamics of mode one operation, which is the subject of this research paper. Several advantages can be obtained by use of this technology. Geometrically the propulsion system is fairly

  5. Integrator or Coincidence Detector: A Novel Measure Based on the Discrete Reverse Correlation to Determine a Neuron's Operational Mode.

    PubMed

    Kanev, Jacob; Koutsou, Achilleas; Christodoulou, Chris; Obermayer, Klaus

    2016-10-01

    In this letter, we propose a definition of the operational mode of a neuron, that is, whether a neuron integrates over its input or detects coincidences. We complete the range of possible operational modes by a new mode we call gap detection, which means that a neuron responds to gaps in its stimulus. We propose a measure consisting of two scalar values, both ranging from -1 to +1: the neural drive, which indicates whether its stimulus excites the neuron, serves as background noise, or inhibits it; the neural mode, which indicates whether the neuron's response is the result of integration over its input, of coincidence detection, or of gap detection; with all three modes possible for all neural drive values. This is a pure spike-based measure and can be applied to measure the influence of either all or subset of a neuron's stimulus. We derive the measure by decomposing the reverse correlation, test it in several artificial and biological settings, and compare it to other measures, finding little or no correlation between them. We relate the results of the measure to neural parameters and investigate the effect of time delay during spike generation. Our results suggest that a neuron can use several different modes simultaneously on different subsets of its stimulus to enable it to respond to its stimulus in a complex manner. PMID:27557103

  6. Report on Testing to Expand the Rotary Mode Core Sampling Operating Envelope

    SciTech Connect

    BOGER, R.M.

    1999-12-13

    The Tank Waste Remediation System (TWRS) Characterization Equipment Group requested that the Numatec Hanford Corporation--Engineering Testing Laboratory (ETL) perform Rotary Mode Core Sampling (RMCS) Operating Envelope (OE) testing. This testing was based upon Witwer 1998a and was performed at different time periods between May and September 1998. The purpose of this testing was to raise the maximum down force limit for rotary mode core sampling as outlined in the current OE. If testing could show that a higher down force could be used while drilling into a concrete/pumice block simulant while still remaining below the 60 C limitation, then the current OE could be revised to include the new, higher, down force limit. Although the Test Plan discussed varying the purge flow rate and rotation rate to find ''optimal'' drilling conditions, the number of drill bits that could be destructively tested was limited. Testing was subsequently limited in scope such that only the down force would be varied while the purge flow rate and rotation rate were kept constant at 30 scfm and 55 rpm respectively. A second objective, which was not part of the original test plan, was added prior to testing. The Bit Improvement testing, mentioned previously, revealed that the drill bits tested in the OE testing were made of a slightly different metal matrix than the ones currently used. The older bits, a Longyear part number 100IVD/5 (/5 bit), had tungsten carbide mixed into the metal matrix that forms the cutting teeth. The currently used bits, Longyear part number 100IVD/8 (/8 bit), instead have tungsten metal in the matrix and no tungsten carbide. Rockwell C hardness testing showed that the /5 bit was significantly harder than the /8 bit, with values of /8 vs. 8, respectively. The change from the /5 bit to the /8 bit was made immediately after the previous OE testing in 1996 because of sparking concerns with the tungsten carbide in the /5 bit. This difference in hardness between the two

  7. Persistent Operational Synchrony within Brain Default-Mode Network and Self-Processing Operations in Healthy Subjects

    ERIC Educational Resources Information Center

    Fingelkurts, Andrew A.; Fingelkurts, Alexander A.

    2011-01-01

    Based on the theoretical analysis of self-consciousness concepts, we hypothesized that the spatio-temporal pattern of functional connectivity within the default-mode network (DMN) should persist unchanged across a variety of different cognitive tasks or acts, thus being task-unrelated. This supposition is in contrast with current understanding…

  8. Tunable single-longitudinal-mode operation of an injection-locked TEA CO2 laser. [ozone absorption spectroscopy

    NASA Technical Reports Server (NTRS)

    Megie, G.; Menzies, R. T.

    1979-01-01

    The tunable single-longitudinal-mode operation of a TEA CO2 laser by an injection technique using a CW waveguide laser as the master oscillator is reported. With the experimental arrangement described, in which the waveguide laser frequency is tuned to correspond to one of the oscillating longitudinal modes of the TEA laser, single-longitudinal-mode operation was achieved with no apparent reduction in the TEA output energy, on various CO2 lines with frequency offsets from the line center as large as 300 MHz. The capability of this technique for high-resolution spectroscopy or atmospheric lidar studies is demonstrated by the recording of the absorption spectrum of a strong ozone line.

  9. Why solid oxide cells can be reversibly operated in solid oxide electrolysis cell and fuel cell modes?

    PubMed

    Chen, Kongfa; Liu, Shu-Sheng; Ai, Na; Koyama, Michihisa; Jiang, San Ping

    2015-12-14

    High temperature solid oxide cells (SOCs) are attractive for storage and regeneration of renewable energy by operating reversibly in solid oxide electrolysis cell (SOEC) and solid oxide fuel cell (SOFC) modes. However, the stability of SOCs, particularly the deterioration of the performance of oxygen electrodes in the SOEC operation mode, is the most critical issue in the development of high performance and durable SOCs. In this study, we investigate in detail the electrochemical activity and stability of La0.8Sr0.2MnO3 (LSM) oxygen electrodes in cyclic SOEC and SOFC modes. The results show that the deterioration of LSM oxygen electrodes caused by anodic polarization can be partially or completely recovered by subsequent cathodic polarization. Using in situ assembled LSM electrodes without pre-sintering, we demonstrate that the deteriorated LSM/YSZ interface can be repaired and regenerated by operating the cells under cathodic polarization conditions. This study for the first time establishes the foundation for the development of truly reversible and stable SOCs for hydrogen fuel production and electricity generation in cyclic SOEC and SOFC operation modes. PMID:26548929

  10. Why solid oxide cells can be reversibly operated in solid oxide electrolysis cell and fuel cell modes?

    PubMed

    Chen, Kongfa; Liu, Shu-Sheng; Ai, Na; Koyama, Michihisa; Jiang, San Ping

    2015-12-14

    High temperature solid oxide cells (SOCs) are attractive for storage and regeneration of renewable energy by operating reversibly in solid oxide electrolysis cell (SOEC) and solid oxide fuel cell (SOFC) modes. However, the stability of SOCs, particularly the deterioration of the performance of oxygen electrodes in the SOEC operation mode, is the most critical issue in the development of high performance and durable SOCs. In this study, we investigate in detail the electrochemical activity and stability of La0.8Sr0.2MnO3 (LSM) oxygen electrodes in cyclic SOEC and SOFC modes. The results show that the deterioration of LSM oxygen electrodes caused by anodic polarization can be partially or completely recovered by subsequent cathodic polarization. Using in situ assembled LSM electrodes without pre-sintering, we demonstrate that the deteriorated LSM/YSZ interface can be repaired and regenerated by operating the cells under cathodic polarization conditions. This study for the first time establishes the foundation for the development of truly reversible and stable SOCs for hydrogen fuel production and electricity generation in cyclic SOEC and SOFC operation modes.

  11. Theory and analysis of operating modes in microplasmas assisted by field emitting cathodes

    SciTech Connect

    Venkattraman, Ayyaswamy

    2015-05-15

    Motivated by the recent interest in the development of novel diamond-based cathodes, we study microplasmas assisted by field emitting cathodes with large field enhancement factors using a simplified model and comparisons with particle-in-cell with Monte Carlo collision (PIC-MCC) simulations and experiments. The model used to determine current-voltage characteristics assumes a linearly varying electric field in the sheath and predicts transition from an abnormal glow to arc mode at moderate current densities in a 1 mm argon gap. The influence of an external circuit is also considered to show the dependence of current as a function of the applied voltage, including potential drop across external resistors. PIC-MCC simulations confirm the validity of the model and also show the significant non-equilibrium nature of these low-temperature microplasmas with electron temperatures ∼1 eV and ion temperatures ∼0.07 eV in the quasi-neutral region. The model is also used to explain experimental data reported for a 1 mm argon gap at a pressure of 2 Torr using three different diamond-based cathodes with superior field emitting properties. The comparison shows that operating conditions in the experiments may not result in significant field emission and the differences observed in current-voltage characteristics can be attributed to small differences in the secondary electron emission coefficient of the three cathodes. However, the model and simulations clearly indicate that field emission using novel cathodes with high field enhancement factors can be used to enhance microplasmas by significantly decreasing the power requirements to achieve a given plasma number density even in gaps at which field emission is traditionally not considered to be a dominant mechanism.

  12. Simultaneous dual mode combustion engine operating on spark ignition and homogenous charge compression ignition

    DOEpatents

    Fiveland, Scott B.; Wiggers, Timothy E.

    2004-06-22

    An engine particularly suited to single speed operation environments, such as stationary power generators. The engine includes a plurality of combustion cylinders operable under homogenous charge compression ignition, and at least one combustion cylinder operable on spark ignition concepts. The cylinder operable on spark ignition concepts can be convertible to operate under homogenous charge compression ignition. The engine is started using the cylinders operable under spark ignition concepts.

  13. Design and operation of FACT - the first G-APD Cherenkov telescope

    NASA Astrophysics Data System (ADS)

    Anderhub, H.; Backes, M.; Biland, A.; Boccone, V.; Braun, I.; Bretz, T.; Buß, J.; Cadoux, F.; Commichau, V.; Djambazov, L.; Dorner, D.; Einecke, S.; Eisenacher, D.; Gendotti, A.; Grimm, O.; von Gunten, H.; Haller, C.; Hildebrand, D.; Horisberger, U.; Huber, B.; Kim, K.-S.; Knoetig, M. L.; Köhne, J.-H.; Krähenbühl, T.; Krumm, B.; Lee, M.; Lorenz, E.; Lustermann, W.; Lyard, E.; Mannheim, K.; Meharga, M.; Meier, K.; Montaruli, T.; Neise, D.; Nessi-Tedaldi, F.; Overkemping, A.-K.; Paravac, A.; Pauss, F.; Renker, D.; Rhode, W.; Ribordy, M.; Röser, U.; Stucki, J.-P.; Schneider, J.; Steinbring, T.; Temme, F.; Thaele, J.; Tobler, S.; Viertel, G.; Vogler, P.; Walter, R.; Warda, K.; Weitzel, Q.; Zänglein, M.

    2013-06-01

    The First G-APD Cherenkov Telescope (FACT) is designed to detect cosmic gamma-rays with energies from several hundred GeV up to about 10 TeV using the Imaging Atmospheric Cherenkov Technique. In contrast to former or existing telescopes, the camera of the FACT telescope is comprised of solid-state Geiger-mode Avalanche Photodiodes (G-APD) instead of photomultiplier tubes for photo detection. It is the first full-scale device of its kind employing this new technology. The telescope is operated at the Observatorio del Roque de los Muchachos (La Palma, Canary Islands, Spain) since fall 2011. This paper describes in detail the design, construction and operation of the system, including hardware and software aspects. Technical experiences gained after one year of operation are discussed and conclusions with regard to future projects are drawn.

  14. Design and control of a prosthetic leg for above-knee amputees operated in semi-active and active modes

    NASA Astrophysics Data System (ADS)

    Park, Jinhyuk; Yoon, Gun-Ha; Kang, Je-Won; Choi, Seung-Bok

    2016-08-01

    This paper proposes a new prosthesis operated in two different modes; the semi-active and active modes. The semi-active mode is achieved from a flow mode magneto-rheological (MR) damper, while the active mode is obtained from an electronically commutated (EC) motor. The knee joint part of the above knee prosthesis is equipped with the MR damper and EC motor. The MR damper generates reaction force by controlling the field-dependent yield stress of the MR fluid, while the EC motor actively controls the knee joint angle during gait cycle. In this work, the MR damper is designed as a two-end type flow mode mechanism without air chamber for compact size. On other hand, in order to predict desired knee joint angle to be controlled by EC motor, a polynomial prediction function using a statistical method is used. A nonlinear proportional-derivative controller integrated with the computed torque method is then designed and applied to both MR damper and EC motor to control the knee joint angle. It is demonstrated that the desired knee joint angle is well achieved in different walking velocities on the ground ground.

  15. Operation of the TFTR Pellet Charge Exchange Diagnostic in the Pulse Counting Mode during H+ RF-minority Heating

    SciTech Connect

    Medley, S.S., PPPL

    1998-05-01

    The Pellet Charge Exchange technique on TFTR has been used primarily to obtain active charge exchange measurements using a high energy (0.5 - 4.0 MeV) neutral particle analyzer (NPA) in conjunction with impurity pellet injection (Li and B) with the scintillator-photomultiplier detector system operated in the current mode. While passive measurements using pulse counting were also obtained using this instrumentation, operation in this mode was very restrictive with pulse counting rates limited to less than {approximately}10 kHz in the absence of any significant neutron and gamma induced background signal. An upgrade to a specialized pulse counting capability which was developed by the Ioffe Institute was implemented which consisted of CsI(Tl) scintillators having features designed to minimize signals induced by background neutron and gamma rays and 16-channel pulse height analysis electronics on each of the eight NPA energy channels. Passive measurements of RF-driven energetic hydrogen minority ions which served to verify operation of the pulse counting mode are reported. It is shown that in the passive mode the main donors for the neutralization of H+ ions in this energy range are C5+ ions. The measured effective H+ tail temperatures range from 0.15 MeV at an RF power of 2 MW to 0.35 MeV at 6 MW.

  16. Novel ultrafast sources on chip: filter driven four wave mixing lasers, from high repetition rate to burst mode operation

    NASA Astrophysics Data System (ADS)

    Pasquazi, Alessia; Peccianti, Marco; Chu, Sai T.; Moss, Dave J.; Morandotti, Roberto

    2016-03-01

    Passive fiber mode-locked lasers enable the excitation of multiple pulses per round trip representing a potential solutions for the increasing demand of practical optical sources with repetition rates of hundreds of GHz or higher. The control of such high repetition rate regimes is however a challenge. To this purpose, linear filters have been used in an "intracavity" configuration to force the repetition rate of the laser. This design is known as dissipative four wave mixing (DFWM) but it is usually unstable and hence marginally suitable for practical applications. We explore the use of nonlinear intracavity filters, such as integrated micro-ring resonators, capable of "driving" the FWM interaction in the laser. We term this approach as Filter-Driven FWM. With a proper choice of the filter properties in terms of free spectral range (FSR) and Q factor, we could observe stable regimes over a wide range of operating conditions, from high repetition rate oscillation at a 200GHz to the formation of two stable spectral comb replicas separated by the FSR of the main cavity (65MHz). High order filters, moreover, allow achieving nonlinear operation over large passbands. With an 11th order filter we achieve low-frequency mode-locking between the main cavity modes that oscillate within each resonance of the filter, producing burst pulsed operation. A stable mode-locked pulse train at 655GHz with an envelope of 42ps at 6.45MHz is achieved.

  17. Tunable single-longitudinal-mode operation of a sandwich-type YAG/Ho:YAG/YAG ceramic laser

    NASA Astrophysics Data System (ADS)

    Wu, Jing; Ju, Lin; Yao, Baoquan; Li, Jiang; Ge, Lin; Zhang, Zhenguo; Zhang, Ye; Xu, Liwei; Dai, Tongyu; Ju, Youlun

    2016-09-01

    We present a 2.09 μm single-longitudinal-mode sandwich-type YAG/Ho:YAG/YAG ceramic laser pumped by a Tm-doped fiber laser for the first time. A pair of F-P etalons was used to achieve tunable single-longitudinal-mode operation. The maximum single-longitudinal-mode output power of 530 mW at 2091.4 nm was obtained with an absorbed pump power of 8.06 W, corresponding to an optical conversion efficiency of 6.6% and a slope efficiency of 12.7%. Wavelength tunable was achieved by tuning the angle of etalons and the wavelength could be tuned from 2091.1 nm to 2092.1 nm, corresponding to a tuning frequency of 68 GHz. The M2 factor was measured to be 1.23.

  18. Theoretical analysis of the operating regime of a passively-mode-locked fiber laser through nonlinear polarization rotation

    SciTech Connect

    Komarov, Andrey; Leblond, Herve; Sanchez, Francois

    2005-12-15

    The dynamics of a fiber laser passively mode-locked through nonlinear polarization rotation is theoretically investigated. The model is based on an iterative equation for the nonlinear polarization rotation and the phase plates and on a scalar differential equation for the gain, the Kerr nonlinearity, and the dispersion. It is demonstrated that depending on the orientation of the phase plates, the laser can be continuous, mode-locked, or Q-switched. In the latter case, an additional equation for the gain dynamics must be taken into account. Hysteresis dependence of the operating regime versus the orientation angles of the phase plates is shown. A large bistability domain between the Q-switch and the continuous regimes is demonstrated. This model allows us to obtain the main features observed in passively-mode-locked fiber lasers.

  19. 240 GHz pedestal-free colliding-pulse mode-locked laser with a wide operation range

    NASA Astrophysics Data System (ADS)

    Hou, L.; Haji, M.; Marsh, J. H.

    2014-11-01

    A 240 GHz, sixth-harmonic monolithic ~1.55 μm colliding-pulse mode-locked laser is reported using a three-quantum-well active layer design and a passive far-field reduction layer. The device emits 0.88 ps pulses with a peak power of 65 mW and intermediate longitudinal modes suppressed by >30 dB. The device demonstrates a wide operation range compared to the conventional five-quantum-well design as well as having a low divergence angle (12.7° × 26.3°), granting a twofold improvement in butt-coupling efficiency into a flat cleaved single-mode fibre.

  20. Wear modes active in angular contact ball bearings operating in liquid oxygen environment of the Space Shuttle turbopumps

    NASA Astrophysics Data System (ADS)

    Chase, Thaddeus J.

    1993-04-01

    Extensive experimental investigation has been carried out on used flight bearings of the high pressure oxidizer turbopumps (HPOTP) of the space shuttle main engine (SSME) in order to determine the dominant wear modes, their extent, and causes. The paper presents the methodology, various surface analysis techniques used, results, and discussion. The mode largely responsible for premature bearing wear has been identified as adhesive/shear peeling of the upper layers of bearing balls and rings. This mode relies upon the mechanisms of scale formation, breakdown, and removal, all of which are greatly enhanced by the heavy oxidation environment of the HPOTP. Major causes of the high wear rates appear to be lubrication and cooling, both inadequate for the imposed conditions of operation. Numerous illustrations and evidence are provided.

  1. Empirical Mode Decomposition Technique with Conditional Mutual Information for Denoising Operational Sensor Data

    SciTech Connect

    Omitaomu, Olufemi A; Protopopescu, Vladimir A; Ganguly, Auroop R

    2011-01-01

    A new approach is developed for denoising signals using the Empirical Mode Decomposition (EMD) technique and the Information-theoretic method. The EMD technique is applied to decompose a noisy sensor signal into the so-called intrinsic mode functions (IMFs). These functions are of the same length and in the same time domain as the original signal. Therefore, the EMD technique preserves varying frequency in time. Assuming the given signal is corrupted by high-frequency Gaussian noise implies that most of the noise should be captured by the first few modes. Therefore, our proposition is to separate the modes into high-frequency and low-frequency groups. We applied an information-theoretic method, namely mutual information, to determine the cut-off for separating the modes. A denoising procedure is applied only to the high-frequency group using a shrinkage approach. Upon denoising, this group is combined with the original low-frequency group to obtain the overall denoised signal. We illustrate our approach with simulated and real-world data sets. The results are compared to two popular denoising techniques in the literature, namely discrete Fourier transform (DFT) and discrete wavelet transform (DWT). We found that our approach performs better than DWT and DFT in most cases, and comparatively to DWT in some cases in terms of: (i) mean square error, (ii) recomputed signal-to-noise ratio, and (iii) visual quality of the denoised signals.

  2. H-mode pedestal and threshold studies over an expanded operating space on Alcator C-Moda)

    NASA Astrophysics Data System (ADS)

    Hubbard, A. E.; Hughes, J. W.; Bespamyatnov, I. O.; Biewer, T.; Cziegler, I.; LaBombard, B.; Lin, Y.; McDermott, R.; Rice, J. E.; Rowan, W. L.; Snipes, J. A.; Terry, J. L.; Wolfe, S. M.; Wukitch, S.

    2007-05-01

    This paper reports on studies of the edge transport barrier and transition threshold of the high confinement (H) mode of operation on the Alcator C-Mod tokamak [I. H. Hutchinson et al., Phys. Plasmas 1, 1511 (1994)], over a wide range of toroidal field (2.6-7.86T) and plasma current (0.4-1.7MA). The H-mode power threshold and edge temperature at the transition increase with field. Barrier widths, pressure limits, and confinement are nearly independent of field at constant current, but the operational space at high B shifts toward higher temperature and lower density and collisionality. Experiments with reversed field and current show that scrape-off-layer flows in the high-field side depend primarily on configuration. In configurations with the B ×∇B drift away from the active X-point, these flows lead to more countercurrent core rotation, which apparently contributes to higher H-mode thresholds. In the unfavorable case, edge temperature thresholds are higher, and slow evolution of profiles indicates a reduction in thermal transport prior to the transition in particle confinement. Pedestal temperatures in this case are also higher than in the favorable configuration. Both high-field and reversed-field results suggest that parameters at the L-H transition are influencing the evolution and parameters of the H-mode pedestal.

  3. An investigation of dual-mode operation of a nuclear-thermal rocket engine

    SciTech Connect

    Kirk, W.L.; Hedstrom, J.C.; Moore, S.W.; McFarland, R.D.; Merrigan, M.A.; Buksa, J.J.; Cappiello, M.W.; Hanson, D.L.; Woloshun, K.A.

    1991-06-01

    A preliminary assessment of the technical feasibility and mass competitiveness of a dual-mode nuclear propulsion and power system based on Rover-type reactors has been completed. Earlier studies have indicated that dual-mode systems appear attractive for electrical power levels of a few kilowatts. However, at the megawatt electrical power level considered in this study, it appears that extensive modifications to the nuclear-thermal engines would be required, the feasibility of which is unclear. Mass competitiveness at high electrical power levels is also uncertain. Further study of reactor and shield design in conjuction with mission and vehicle studies is necessary in order to determine a useful dual-mode power range. 9 refs., 20 figs., 4 tabs.

  4. Increased wavelength options in the visible and ultraviolet for Raman lasers operating on dual Raman modes.

    PubMed

    Mildren, R P; Piper, J A

    2008-03-01

    We report increased wavelength options from Raman lasers for Raman media having two Raman modes of similar gain coefficient. For an external-cavity potassium gadolinium tungstate Raman laser pumped at 532 nm, we show that two sets of Stokes orders are generated simultaneously by appropriate orientation of the Raman crystal, and also wavelengths that correspond to sums of the two Raman modes. Up to 14 visible Stokes lines were observed in the wavelength range 555-675 nm. The increase in Stokes wavelengths also enables a much greater selection of wavelengths to be accessed via intracavity nonlinear sum frequency and difference frequency mixing. For example, we demonstrate 30 output wavelength options for a wavelength-selectable 271-321 nm Raman laser with intracavity sum frequency mixing in BBO. We also present a theoretical analysis that enables prediction of wavelength options for dual Raman mode systems.

  5. Graphene oxide mode-locked Yb:GAGG bulk laser operating in the femtosecond regime

    NASA Astrophysics Data System (ADS)

    Cui, Liang; Lou, Fei; Li, Yan-bin; Hou, Jia; He, Jing-Liang; Jia, Zhi-Tai; Liu, Jing-Quan; Zhang, Bai-Tao; Yang, Ke-Jian; Wang, Zhao-Wei; Tao, Xu-Tang

    2015-04-01

    High-quality graphene oxide saturable absorber (SA) is successfully fabricated with 1-2 layer graphene oxide. By employing this SA, we have demonstrated femtosecond pulse generation from a graphene oxide passively mode locked bulk laser for the first time to our best knowledge. With two Gires-Tournois interferometer mirrors for dispersion compensation, pulses as short as 493 fs with an average power of 500 mW are obtained at the central wavelength of 1035.5 nm. These results presented here indicate the great potential of GO for generating femtosecond mode-locked pulses in the bulk laser.

  6. Test assessment of RC structures in marine environment: the Geiger Key Bridge

    NASA Astrophysics Data System (ADS)

    Loreto, G.; Di Benedetti, M.; Nanni, A.

    2012-04-01

    Reinforced concrete marine structures are highly vulnerable to corrosion due to chloride ion attack; the severity of the attack being dependent on, among other factors, the prevailing climatic condition. The aggressiveness of the warm marine environment of Florida has led to the premature deterioration of numerous bridges and building along the coastline. This paper describes a methodology for structural assessment of concrete bridges while incorporating analysis uncertainty. The procedure includes the use of visual, electrochemical and non-destructive methods in order to define the cause and the level of concrete deterioration. A probabilistic mechanistic model is used to generate the distribution of the time to corrosion initiation based on statistical models of the governing parameters obtained from field data. The proposed methodology is applied to predict the time to corrosion initiation and predict the residual service life of the reinforcing steel in the concrete girders of the Geiger Bridge in Key West, FL.

  7. [Basic research for development of pinhole camera using a Geiger Mueller counter].

    PubMed

    Takegami, Kazuki; Hayashi, Hiroaki; Fukuda, Ikuma; Konishi, Yuki; Hanamitsu, Hiroki; Hashizume, Takuya; Murakami, Jun; Mitani, Satoshi

    2013-09-01

    To visualize the scattered X-ray distribution in the diagnosis domain, we examined whether a Geiger Mueller (GM) counter could be applied to a pinhole camera as an X-ray detector. The GM counter detects radiation at certain detection points. To obtain two-dimensional images using the GM counter, the detector needs to be moved two-dimensionally. We constructed an apparatus using industrial actuators to move the detector. To investigate the usability of the developed apparatus, the scattered X-rays from the phantom were measured using the GM counter. The images obtained were then compared with those measured using the phosphor plate. Our results demonstrated that the GM counter can detect low count-rate radiation, but further research will be needed to obtain clear two-dimensional images. In this paper, we propose that the GM counter can be used as a complementary detector to a phosphor plate.

  8. Efficient TEM(00)-mode operation of a laser-diode side-pumped Nd:YAG laser

    NASA Technical Reports Server (NTRS)

    Welford, D.; Rines, D. M.; Dinerman, B. J.

    1991-01-01

    The operation of a laser-diode side-pumped Nd:YAG laser with a novel pumping geometry that ensures efficient conversion of pump energy into the TEM(00) mode is reported. Of the 1064-nm output, 11.8 microJ of energy was obtained in a 200-microsec pulse with 64 microJ of pump energy at 808 nm. The overall conversion and slope efficiencies were 18 and 23 percent, respectively.

  9. Discovery of multiple, ionization-created CS{sub 2} anions and a new mode of operation for drift chambers

    SciTech Connect

    Snowden-Ifft, Daniel P.

    2014-01-15

    This paper focuses on the surprising discovery of multiple species of ionization-created CS{sub 2} anions in gas mixtures containing electronegative CS{sub 2} and O{sub 2}, identified by their slightly different drift velocities. Data are presented to understand the formation mechanism and identity of these new anions. Regardless of the micro-physics, however, this discovery offers a new, trigger-less mode of operation for the drift chambers. A demonstration of trigger-less operation is presented.

  10. Dynamic control of the operation regimes of a mode-locked fiber laser based on intracavity polarizing fibers: experimental and theoretical validation.

    PubMed

    Villanueva, Guillermo E; Pérez-Millán, Pere

    2012-06-01

    An intracavity polarizing fiber is proposed to control the emission regime of a passively mode-locked fiber laser. Stable operation in self-starting high and low dispersion soliton mode-locking and 100 GHz multiwavelength regimes is demonstrated through numerical simulations and experimental validation. Mode-locking stability is ensured by a saturable absorber in the ring cavity. The effective selection of operation regime is dynamically carried out by controlling the intracavity polarization state.

  11. Operation of RF driven negative ion source in a pure-hydrogen mode

    SciTech Connect

    Abdrashitov, G.; Belchenko, Yu. Gusev, I.; Senkov, D.; Sanin, A.; Shikhovtsev, I.; Kondakov, A.; Ivanov, A. A.; Sotnikov, O.

    2015-04-08

    The production of negative hydrogen ions in the radio-frequency driven long-pulsed source with external antenna is studied. RF drivers with various geometry of external antenna, Faraday shield and magnets at the rear flange were examined. H- beam extraction through the single emission aperture was performed in the source pure-hydrogen mode with no external seed of alkali additives. H- beam with ion emission current density up to 5 mA/cm{sup 2} and energy up to 75 keV was regularly obtained in the 1 s pulses of the pure-hydrogen mode. The regular temporal increase of H- ion production due to deposition of impurities on the plasma grid surface was recorded. The H- emission current density increased up to 9 mA/cm{sup 2} in this case.

  12. Investigation of the autophase mode of operation in a relativistic orotron

    NASA Astrophysics Data System (ADS)

    Kuraev, N. A.; Sinitsyn, A. K.

    1987-11-01

    Numerical calculations show that a relativistic orotron is an efficient oscillator with a theoretically attainable efficiency exceeding 80 percent. The energy-exchange mechanism is investigated, and a simple one-dimensional model is used to determine the optimal device parameters. It is found that the minimum length of the orotron in the autophase mode for voltages ranging from 127 to 676 kV amounts to 30-150 cm at wavelengths of 0.2-1.5 cm.

  13. Dynamic viscous behavior of magneto-rheological fluid in coupled mode operation

    NASA Astrophysics Data System (ADS)

    Kaluvan, Suresh; Park, JinHyuk; Choi, Seung-Hyun; Kim, Pyunghwa; Choi, Seung-Bok

    2015-11-01

    A new method of measuring the coupled mode viscosity behavior of magneto-rheological (MR) fluid using the resonance concept is proposed. The coupled mode viscosity measurement device is designed as a resonant system using a cantilever beam probing with the rotating shaft mechanism. The ‘C’ shaped iron core of an electromagnetic coil, mounted in a resonating cantilever beam is used as a probing tip. The MR fluid between the probing tip and the rotating shaft mechanism experiences both squeeze and shear force. The vibration induced by the resonating cantilever beam creates only squeeze force on the MR fluid when the shaft is stationary. When the cantilever beam is vibrating at resonance and the shaft is rotating, the MR fluid experiences coupled (shear and squeeze) force. The cantilever beam is vibrated at its resonant frequency using the piezoelectric actuation technique and the resonance is maintained using simple closed loop resonator electronics. The input current to the probing coil is varied to produce a variable magnetic field which causes the viscosity change of the MR fluid. The viscosity change of the MR fluid produces a coupled force, which induces an additional stiffness on the resonating cantilever beam and alters its initial resonant frequency. The shift in resonant frequency due to the change in viscosity of the MR fluid is measured with the help of a resonator electronics circuit and its viscosity is related to the field dependent coupled mode yield stress of the MR fluid. The proposed measurement device is analytically derived and experimentally evaluated.

  14. Multimode Raman light-atom interface in warm atomic ensemble as multiple three-mode quantum operations

    NASA Astrophysics Data System (ADS)

    Parniak, Michał; Pęcak, Daniel; Wasilewski, Wojciech

    2016-11-01

    We analyse the properties of a Raman quantum light-atom interface in long atomic ensemble and its applications as a quantum memory or two-mode squeezed state generator. We consider the weak-coupling regime and include both Stokes and anti-Stokes scattering and the effects of Doppler broadening in buffer gas assuming frequent velocity-averaging collisions. We find the Green functions describing multimode transformation from input to output fields of photons and atomic excitations. Proper mode basis is found via singular value decomposition for short interaction times. It reveals that triples of modes are coupled by a transformation equivalent to a combination of two beamsplitters and a two-mode squeezing operation. We analyse the possible transformations on an example of warm rubidium-87 vapour. The model we present bridges the gap between the Stokes only and anti-Stokes only interactions providing simple, universal description in a temporally and longitudinally multimode situation. Our results also provide an easy way to find an evolution of the states in a Schrödinger picture thus facilitating understanding and design.

  15. Task Analytic Models to Guide Analysis and Design: Use of the Operator Function Model to Represent Pilot-Autoflight System Mode Problems

    NASA Technical Reports Server (NTRS)

    Degani, Asaf; Mitchell, Christine M.; Chappell, Alan R.; Shafto, Mike (Technical Monitor)

    1995-01-01

    Task-analytic models structure essential information about operator interaction with complex systems, in this case pilot interaction with the autoflight system. Such models serve two purposes: (1) they allow researchers and practitioners to understand pilots' actions; and (2) they provide a compact, computational representation needed to design 'intelligent' aids, e.g., displays, assistants, and training systems. This paper demonstrates the use of the operator function model to trace the process of mode engagements while a pilot is controlling an aircraft via the, autoflight system. The operator function model is a normative and nondeterministic model of how a well-trained, well-motivated operator manages multiple concurrent activities for effective real-time control. For each function, the model links the pilot's actions with the required information. Using the operator function model, this paper describes several mode engagement scenarios. These scenarios were observed and documented during a field study that focused on mode engagements and mode transitions during normal line operations. Data including time, ATC clearances, altitude, system states, and active modes and sub-modes, engagement of modes, were recorded during sixty-six flights. Using these data, seven prototypical mode engagement scenarios were extracted. One scenario details the decision of the crew to disengage a fully automatic mode in favor of a semi-automatic mode, and the consequences of this action. Another describes a mode error involving updating aircraft speed following the engagement of a speed submode. Other scenarios detail mode confusion at various phases of the flight. This analysis uses the operator function model to identify three aspects of mode engagement: (1) the progress of pilot-aircraft-autoflight system interaction; (2) control/display information required to perform mode management activities; and (3) the potential cause(s) of mode confusion. The goal of this paper is twofold

  16. Numerical analysis of flow features and operation characteristics of a rocket-based combined-cycle inlet in ejector mode

    NASA Astrophysics Data System (ADS)

    Shi, Lei; Liu, Xiaowei; He, Guoqiang; Qin, Fei; Wei, Xianggeng; Yang, Bin; Liu, Jie

    2016-10-01

    A ready-made central strut-based rocket-based combined-cycle (RBCC) engine was numerically investigated in the ejector mode. The flow features in the RBCC inlet and the matching characteristics between the inlet and the embedded rocket during different flight regimes were examined in detail. It was necessary to perform integrated numerical simulations in the ejector mode within considerable pressure far fields around the inlet/exhaust system. The observed flow features and operation characteristics in the RBCC inlet were strongly correlated with the flight conditions, inlet configuration, and operation of the embedded rocket. It was further found that the integrated function status of multiple factors significantly influenced the performance of the RBCC engine in the ejector mode. The two parameters that macroscopically affected the performance most were the air entrainment mass and the drag of the RBCC inlet. To improve these parameters, it is vital to employ an appropriate design of the RBCC inlet and establish the optimal flight trajectory of the flight vehicle.

  17. Efficient single-mode operation of a cladding-pumped ytterbium-doped helical-core fiber laser.

    PubMed

    Wang, P; Cooper, L J; Sahu, J K; Clarkson, W A

    2006-01-15

    A novel approach to achieving robust single-spatial-mode operation of cladding-pumped fiber lasers with multimode cores is reported. The approach is based on the use of a fiber geometry in which the core has a helical trajectory within the inner cladding to suppress laser oscillation on higher-order modes. In a preliminary proof-of-principle study, efficient single-mode operation of a cladding-pumped ytterbium-doped helical-core fiber laser with a 30 microm diameter core and a numerical aperture of 0.087 has been demonstrated. The laser yielded 60.4 W of output at 1043 nm in a beam with M2 < 1.4 for 92.6 W launched pump power from a diode stack at 976 nm. The slope efficiency at pump powers well above threshold was approximately 84%, which compares favorably with the slope efficiencies achievable with conventional straight-core Yb-doped double-clad fiber lasers.

  18. LONG-TERM PERFORMANCE OF SOLID OXIDE STACKS WITH ELECTRODE-SUPPORTED CELLS OPERATING IN THE STEAM ELECTROLYSIS MODE

    SciTech Connect

    J. E. O'Brien; R. C. O'Brien; X. Zhang; G. Tao; B. J. Butler

    2011-11-01

    Performance characterization and durability testing have been completed on two five-cell high-temperature electrolysis stacks constructed with advanced cell and stack technologies. The solid oxide cells incorporate a negative-electrode-supported multi-layer design with nickel-zirconia cermet negative electrodes, thin-film yttria-stabilized zirconia electrolytes, and multi-layer lanthanum ferrite-based positive electrodes. The per-cell active area is 100 cm2. The stack is internally manifolded with compliant mica-glass seals. Treated metallic interconnects with integral flow channels separate the cells. Stack compression is accomplished by means of a custom spring-loaded test fixture. Initial stack performance characterization was determined through a series of DC potential sweeps in both fuel cell and electrolysis modes of operation. Results of these sweeps indicated very good initial performance, with area-specific resistance values less than 0.5 ?.cm2. Long-term durability testing was performed with A test duration of 1000 hours. Overall performance degradation was less than 10% over the 1000-hour period. Final stack performance characterization was again determined by a series of DC potential sweeps at the same flow conditions as the initial sweeps in both electrolysis and fuel cell modes of operation. A final sweep in the fuel cell mode indicated a power density of 0.356 W/cm2, with average per-cell voltage of 0.71 V at a current of 50 A.

  19. Comparison of different operational modes of a two-stage activated sludge pilot plant for the extension of the Vienna STP.

    PubMed

    Müller-Rechberger, H; Wandl, G; Winkler, S; Svardal, K; Matsché, N

    2001-01-01

    A pilot plant has been operated over a period of two years in order to investigate the performance and the operating characteristics of the plant concept developed for the extension of the main Vienna STP and to develop a simulation model which will be applied for operation support of the full stage plant. The pilot plant is a two stage activated sludge plant, each stage comprising of four aeration tanks and a clarifier tank. The pilot plant layout allows three different operational modes, each of which has been operated for several periods. The performance of the pilot plant during these periods is described and the different operational modes are compared to each other.

  20. Reliability of High Power Laser Diode Arrays Operating in Long Pulse Mode

    NASA Technical Reports Server (NTRS)

    Amzajerdian, Farzin; Meadows, Byron L.; Barnes, Bruce W.; Lockard, George E.; Singh, Upendra N.; Kavaya, Michael J.; Baker, Nathaniel R.

    2006-01-01

    Reliability and lifetime of quasi-CW laser diode arrays are greatly influenced by their thermal characteristics. This paper examines the thermal properties of laser diode arrays operating in long pulse duration regime.

  1. Single-longitudinal-mode Er:GGG microchip laser operating at 2.7  μm.

    PubMed

    You, Zhenyu; Wang, Yan; Xu, Jinlong; Zhu, Zhaojie; Li, Jianfu; Wang, Hongyan; Tu, Chaoyang

    2015-08-15

    We reported on a diode-end-pumped single-longitudinal-mode microchip laser using a 600-μm-thick Er:GGG crystal at ∼2.7  μm, generating a maximum output power of 50.8 mW and the maximum pulsed energy of 0.306 mJ, with repetition rates of pumping light of 300, 200, and 100 Hz, respectively. The maximum slope efficiency of the laser was 20.1%. The laser was operated in a single-longitudinal mode centered at about 2704 nm with a FWHM of 0.42 nm. The laser had a fundamental beam profile and the beam quality parameter M(2) was measured as 1.46. These results indicate that the Er:GGG microchip laser is a potential compact mid-infrared laser source. PMID:26274675

  2. HgCdTe APD-based linear-mode photon counting components and ladar receivers

    NASA Astrophysics Data System (ADS)

    Jack, Michael; Wehner, Justin; Edwards, John; Chapman, George; Hall, Donald N. B.; Jacobson, Shane M.

    2011-05-01

    Linear mode photon counting (LMPC) provides significant advantages in comparison with Geiger Mode (GM) Photon Counting including absence of after-pulsing, nanosecond pulse to pulse temporal resolution and robust operation in the present of high density obscurants or variable reflectivity objects. For this reason Raytheon has developed and previously reported on unique linear mode photon counting components and modules based on combining advanced APDs and advanced high gain circuits. By using HgCdTe APDs we enable Poisson number preserving photon counting. A metric of photon counting technology is dark count rate and detection probability. In this paper we report on a performance breakthrough resulting from improvement in design, process and readout operation enabling >10x reduction in dark counts rate to ~10,000 cps and >104x reduction in surface dark current enabling long 10 ms integration times. Our analysis of key dark current contributors suggest that substantial further reduction in DCR to ~ 1/sec or less can be achieved by optimizing wavelength, operating voltage and temperature.

  3. Desert Rats 2011 Mission Simulation: Effects of Microgravity Operational Modes on Fields Geology Capabilities

    NASA Technical Reports Server (NTRS)

    Bleacher, Jacob E.; Hurtado, J. M., Jr.; Meyer, J. A.

    2012-01-01

    Desert Research and Technology Studies (DRATS) is a multi-year series of NASA tests that deploy planetary surface hardware and exercise mission and science operations in difficult conditions to advance human and robotic exploration capabilities. DRATS 2011 (Aug. 30-Sept. 9, 2011) tested strategies for human exploration of microgravity targets such as near-Earth asteroids (NEAs). Here we report the crew perspective on the impact of simulated microgravity operations on our capability to conduct field geology.

  4. 322 W single-mode Yb-doped all-fiber laser operated at 1120 nm

    NASA Astrophysics Data System (ADS)

    Zhang, Hanwei; Xiao, Hu; Zhou, Pu; Zhang, Kun; Wang, Xiaolin; Xu, Xiaojun

    2014-05-01

    An all-fiber, high-power, spectrally clean, single-mode Yb-doped fiber oscillator at 1120 nm wavelength is demonstrated. By optimizing the reflectivity of the output coupler and the length of the gain fiber, an output power of 322 W and an optical efficiency of 71% have been achieved. The output power, spectra, and bandwidth broadening are presented and briefly discussed. The power scaling capability of the cavity is analyzed on the basis of the thermal effect, and a maximal thermal-damage-free output power of 450 W could be expected.

  5. Monolithically integrated mid-infrared sensor using narrow mode operation and temperature feedback

    SciTech Connect

    Ristanic, Daniela; Schwarz, Benedikt Reininger, Peter; Detz, Hermann; Zederbauer, Tobias; Andrews, Aaron Maxwell; Schrenk, Werner; Strasser, Gottfried

    2015-01-26

    A method to improve the sensitivity and selectivity of a monolithically integrated mid-infrared sensor using a distributed feedback laser (DFB) is presented in this paper. The sensor is based on a quantum cascade laser/detector system built from the same epitaxial structure and with the same fabrication approach. The devices are connected via a dielectric-loaded surface plasmon polariton waveguide with a twofold function: it provides high light coupling efficiency and a strong interaction of the light with the environment (e.g., a surrounding fluid). The weakly coupled DFB quantum cascade laser emits narrow mode light with a FWHM of 2 cm{sup −1} at 1586 cm{sup −1}. The room temperature laser threshold current density is 3 kA∕cm{sup 2} and a pulsed output power of around 200 mW was measured. With the superior laser noise performance, due to narrow mode emission and the compensation of thermal fluctuations, the lower limit of detection was expanded by one order of magnitude to the 10 ppm range.

  6. Monolithically integrated mid-infrared sensor using narrow mode operation and temperature feedback

    NASA Astrophysics Data System (ADS)

    Ristanic, Daniela; Schwarz, Benedikt; Reininger, Peter; Detz, Hermann; Zederbauer, Tobias; Andrews, Aaron Maxwell; Schrenk, Werner; Strasser, Gottfried

    2015-01-01

    A method to improve the sensitivity and selectivity of a monolithically integrated mid-infrared sensor using a distributed feedback laser (DFB) is presented in this paper. The sensor is based on a quantum cascade laser/detector system built from the same epitaxial structure and with the same fabrication approach. The devices are connected via a dielectric-loaded surface plasmon polariton waveguide with a twofold function: it provides high light coupling efficiency and a strong interaction of the light with the environment (e.g., a surrounding fluid). The weakly coupled DFB quantum cascade laser emits narrow mode light with a FWHM of 2 cm-1 at 1586 cm-1. The room temperature laser threshold current density is 3 kA/cm2 and a pulsed output power of around 200 mW was measured. With the superior laser noise performance, due to narrow mode emission and the compensation of thermal fluctuations, the lower limit of detection was expanded by one order of magnitude to the 10 ppm range.

  7. L-H transition studies on DIII-D to determine H-mode access for operational scenarios in ITER

    SciTech Connect

    Gohil, P.; Evans, T.E.; Fenstermacher, M; Ferron, J.R.; Osborne, T.H.; Schmitz, O.; Scoville, J. T.

    2011-01-01

    A comprehensive set of L-H transition experiments has been performed on DIII-D to determine the requirements for access to H-mode plasmas in ITER's first (non-nuclear) operational phase with H and He plasmas and the second (activated) operational phase with D plasmas. The H-mode power threshold, P(TH), was evaluated for different operational configurations and auxiliary heating methods for the different main ion species. Helium plasmas have significantly higher P(TH) than deuterium plasmas at low densities for all heating schemes, but similar P(TH) as deuterium plasmas at high densities except for H-neutral beam injection-heated discharges, which are still higher. Changes in P(TH) are observed when helium concentration levels in deuterium plasmas exceed 40%. There is a strong dependence of P(TH) on the magnetic geometry in the vicinity of the divertor. The trend of decreasing P(TH) with decreasing X-point height is observed for all of the main ion species irrespective of the heating method, which appears to indicate that there is a common physics process behind this effect for all of the ion species. Helium and deuterium plasmas exhibit a significant increase in P(TH) for strong resonant magnetic perturbations. The application of a local magnetic ripple of 3% from test blanket module mock-up coils did not change P(TH) in deuterium plasmas.

  8. Köppen-Geiger Climate Classification for Europe Recaptured via the Hölder Regularity of Air Temperature Data

    NASA Astrophysics Data System (ADS)

    Deliège, Adrien; Nicolay, Samuel

    2016-08-01

    In this paper, we make use of the monoHölder nature of surface air temperature data to recapture the Köppen-Geiger climate classification in Europe. Using data from the European Climate Assessment and Dataset (ECA&D), we first show that the Hölder exponents of surface air temperature data are statistically related to pressure anomalies. Then, we establish a climate classification based on these Hölder exponents in such a way that it allows to recover the Köppen-Geiger climate classification. We show that the two classifications match for a vast majority of stations, and we corroborate these observations with a confirmation test. We compare these results with those obtained with another dataset (NCEP-NCAR Reanalysis Project) to show that the new classification is still well-adapted, before eventually discussing these findings.

  9. The effect of different operations modes on science capabilities during the 2010 Desert RATS test: Insights from the geologist crewmembers

    NASA Astrophysics Data System (ADS)

    Bleacher, Jacob E.; Hurtado, José M.; Young, Kelsey E.; Rice, James W.; Garry, W. Brent

    2013-10-01

    The 2010 Desert RATS field test utilized two Space Exploration Vehicles (prototype planetary rovers) and four crewmembers (2 per rover) to conduct a geologic traverse across northern Arizona while testing continuous and twice-per-day communications paired with operation modes of separating and exploring individually (Divide & Conquer) and exploring together (Lead & Follow), respectively. This report provides qualitative conclusions from the geologist crewmembers involved in this test as to how these modes of communications and operations affected our ability to conduct field geology. Each mode of communication and operation provided beneficial capabilities that might be further explored for future Human Spaceflight Missions to other solar system objects. We find that more frequent interactions between crews and an Apollo-style Science Team on the Earth best enables scientific progress during human exploration. However, during multiple vehicle missions, this communication with an Earth-based team of scientists, who represent "more minds on the problem", should not come at the exclusion of (or significantly decrease) communication between the crewmembers in different vehicles who have the "eyes on the ground". Inter-crew communications improved when discussions with a backroom were infrequent. Both aspects are critical and cannot be mutually exclusive. Increased vehicle separation distances best enable encounters with multiple geologic units. However, seemingly redundant visits by multiple vehicles to the same feature can be utilized to provide improved process-related observations about the development and modification of the local terrain. We consider the value of data management, transfer, and accessibility to be the most important lesson learned. Crews and backrooms should have access to all data and related interpretations within the mission in as close to real-time conditions as possible. This ensures that while on another planetary surface, crewmembers are as

  10. Wilsonville SRC-I pilot plant: I. Fractionation area corrosion studies; II. Hot vs. normal separation mode of operation

    SciTech Connect

    Lee, J.M.

    1981-04-01

    Extensive corrosion studies in solvent recovery columns have been done with different coals (mainly Kentucky number 9 Lafayette, Dotiki and Fies). Sodium carbonate (0.1 to 1.1% of coal) was added as neutralizer to control corrosion rate. Chloride balance runs were made for isolation of corrosive streams with high chlorine content. A caustic wash program of inlet streams has been developed for selective treatment of corrosive streams as an alternative means for possible replacement of sodium carbonate addition. High chlorine content coals such as Kentucky number 9 Lafayette and Dotiki (0.2 to 0.3%) were very corrosive, compared to low chlorine content coal, Kentucky number 9 Fies (< 0.1%). Sodium carbonate addition (0.6 to 0.7% of coal) reduced corrosion rate from 500 MPY to an insignificant level of less than 5 MPY. Caustic wash of solvents could reduce corrosion rate by 50%, removing most corrosive compounds present in the 440 to 480/sup 0/F boiling fraction. Extensive studies for the hot separator mode of operation have been done as a means of saving substantial energy by elimination of dissolver slurry cooling (0.3 MM Btu/hr) and reheating for solvent recovery (1 MM Btu/h). Impacts of the hot separator mode on plant operability, product quality and Kerr-McGee CSD Unit recovery have been studied. The hot separator mode of operation was carried out by controlling the V103 temperature to 740/sup 0/F. It was observed that preasphaltene contents increased in the SRC products such as V110 L/F SRC and CSD feed; CSD unit recovery was not affected significantly; solvent quality was not affected significantly.

  11. Dual-wavelength operation of continuous-wave and mode-locked erbium-doped fiber lasers

    NASA Astrophysics Data System (ADS)

    Pottiez, O.; Martinez-Rios, A.; Monzon-Hernandez, D.; Ibarra-Escamilla, B.; Kuzin, E. A.; Hernandez-Garcia, J. C.

    2012-06-01

    We study numerically and experimentally multiple-wavelength operation of an erbium-doped figure-eight fiber laser including a multiple-bandpass optical filter formed by two concatenated fiber tapers. Both continuous-wave and pulsed operations are considered. In the continuous-wave regime, stable long-term operation at multiple closely spaced wavelengths is only obtained if fine adjustments of the cavity losses are performed. Under these conditions, simultaneous lasing at up to four wavelengths separated by 1.5 nm was observed experimentally. Tunable single-wavelength operation over more than 20 nm is also observed in the continuous-wave regime. In the passive mode locking regime, numerical simulations indicate that mechanisms involving the filter losses and the nonlinear transmission characteristic of the NOLM contribute in principle to stabilize dual-wavelength operation, allowing less demanding cavity loss adjustments. In this regime, the problem of synchronization between the pulse trains generated at each wavelength adds an additional dimension to the problem. In presence of cavity dispersion, the pulses at each wavelength tend to be asynchronous if the wavelength separation is large, however they can be synchronous in the case of closely spaced wavelengths, if cross-phase modulation is able to compensate for the dispersion-induced walkoff. Experimentally, fundamental and 2nd-order harmonic mode locking was observed, characterized by the generation of noise-like pulses. Finally, a regime of multi-wavelength passive Q-switching was also observed. We believe that this work will be helpful to guide the design of multiple-wavelength fiber laser sources, which are attractive for a wide range of applications including Wavelength Division Multiplexing transmissions, signal processing and sensing.

  12. Enabling cost-effective high-current burst-mode operation in superconducting accelerators

    SciTech Connect

    Sheffield, Richard L.

    2015-06-01

    Superconducting (SC) accelerators are very efficient for CW or long-pulse operation, and normal conducting (NC) accelerators are cost effective for short-pulse operation. The addition of a short NC linac section to a SC linac can correct for the energy droop that occurs when pulsed high-current operation is required that exceeds the capability of the klystrons to replenish the cavity RF fields due to the long field fill-times of SC structures, or a requirement to support a broad range of beam currents results in variable beam loading. This paper describes the implementation of this technique to enable microseconds of high beam-current, 90 mA or more, in a 12 GeV SC long-pulse accelerator designed for the MaRIE 42-keV XFEL proposed for Los Alamos National Laboratory.

  13. Enabling cost-effective high-current burst-mode operation in superconducting accelerators

    DOE PAGESBeta

    Sheffield, Richard L.

    2015-06-01

    Superconducting (SC) accelerators are very efficient for CW or long-pulse operation, and normal conducting (NC) accelerators are cost effective for short-pulse operation. The addition of a short NC linac section to a SC linac can correct for the energy droop that occurs when pulsed high-current operation is required that exceeds the capability of the klystrons to replenish the cavity RF fields due to the long field fill-times of SC structures, or a requirement to support a broad range of beam currents results in variable beam loading. This paper describes the implementation of this technique to enable microseconds of high beam-current,more » 90 mA or more, in a 12 GeV SC long-pulse accelerator designed for the MaRIE 42-keV XFEL proposed for Los Alamos National Laboratory.« less

  14. MFTF: a computer program for calculating the MARS mode operating parameters for the axicell MFTF-B

    SciTech Connect

    Jong, R.A.

    1983-01-13

    We describe the models used to calculate the equilibrium operating point for the MARS mode of the axicell MFTF-B, and present the model equations necessary to calculate the plasma and potential parameters in the central-cell, axicell, and anchor regions. In addition, we calculate the neutral beam, rf power, and gas inputs required to sustain the plasma and maintain the ion and electron-particle energy balance. After a brief description of the MFTF code, we present the results of a sample calculation using MFTF.

  15. Development of energy compensated Geiger Muller detector based on the T2416A Canberra Co. GM detector

    NASA Astrophysics Data System (ADS)

    Mohamed Noor, Omar

    Geiger Muller counters have been a fundamental device in radiation detection for decades due to their simplicity and low cost. Canberra Company has been designing and manufacturing Geiger Muller detectors in various designs for radiation monitoring and field characterization. However, these devices have a draw back when it comes to radiation activity measurements due to the over response of the detector in low energy range i.e., 20 -- 250 keV. One of the widely used Geiger Muller counter in the industrial sector is the T2416A. This device is used not only as a survey meter in high intensity gamma radiation fields, but also as a detection device employed in different survey meters for calibration purposes. Among such instruments one can cite the Inspector 1000 and the RadiaGem system. The T2416A GM detector has an over response in the low energy region of about a factor of 6 to 40 relative to 137Cs energy (i.e. 662 keV). In an attempt to flatten this response, in this study, the counter has been redesigned to be an energy compensated Geiger Muller counter. To achieve this goal, a special filtering material has been designed with a composition of different materials and in different thicknesses. The work has been carried out by adopting an approach of simulating the response of the detector with different materials as well as measurements at different photon energies up to 250 keV with and without filtering materials. A series of experimental and simulation data has been analyzed and compared against each other.

  16. Development of photodetection system based on multipixel avalanche Geiger photodiodes with WLS for LXe low-background detectors

    NASA Astrophysics Data System (ADS)

    Akimov, D. Yu.; Akindinov, A. V.; Alexandrov, I. S.; Burenkov, A. A.; Danilov, M. V.; Kovalenko, A. G.; Stekhanov, V. N.

    2010-04-01

    A multipixel avalanche Geiger photodiode with a p-terphenyl wavelength shifter in front of it has been tested in the liquid xenon to detect the 175-nm scintillation light. The global detection efficiency of the VUV photons of ~10% is obtained. A photodetection system with sensitivity to sub-keV ionization and few-mm coordinate accuracy is proposed for LXe low-background experiments.

  17. Optimal operating regime of saturable absorbers in mode-locked lasers

    SciTech Connect

    Narovlyanskaya, N.M.; Tikhonov, E.A.

    1982-01-01

    An investigation was made of ultrashort pulse generation by passive mode locking in a rhodamine 6G jet laser with pulsed laser pumping of up to 300 nsec duration. In order to obtain single ultrashort pulses per axial period in these systems, it was essential to reduce their time of formation to several loop passes. It was shown experimentally that the rate of formation of ultrashort pulses is influenced appreciably by the nonlinear absorber dye and, for a given intracavity intensity, the best dyes are those having a purely electronic transition near the lasing frequency. In this case, the critical bleaching intensity and relaxation time are minimized as a result of the increased role of stimulated resonance transitions in the dye modulator. Optimal types of polymethine dyes are suggested for nonlinear absorbers of tunable ultrashort-pulse rhodamine 6G lasers.

  18. Multi-echo processing by a bottlenose dolphin operating in "packet" transmission mode at long range.

    PubMed

    Finneran, James J; Schroth-Miller, Maddie; Borror, Nancy; Tormey, Megan; Brewer, Arial; Black, Amy; Bakhtiari, Kimberly; Goya, Gavin

    2014-11-01

    Bottlenose dolphins performing echolocation tasks at long ranges may utilize a transmission mode where bursts, or "packets," of echolocation clicks are emitted rather than single clicks. The clicks within each packet are separated by time intervals well below the two-way travel time, while the packets themselves are emitted at intervals greater than the two-way travel time. Packet use has been shown to increase with range; however, the exact function of packets and the advantages gained by their utilization remain unknown. In this study, the capability for dolphins to utilize multi-echo processing within packets of echoes was investigated by manipulating the number of available echoes within each packet as a dolphin performed a long-range echolocation task. The results showed an improvement in detectability with an increase in the number of echoes in each packet and suggest that packet use is an adaptation to allow multi-echo processing at long ranges without introducing range ambiguity.

  19. Risk contribution from low power, shutdown, and other operational modes beyond full power

    SciTech Connect

    Whitehead, D.W.; Brown, T.D.; Chu, T.L.

    1995-04-01

    During 1989 the Nuclear Regulatory Commission (NRC) initiated an extensive program to carefully examine the potential risks during low power and shutdown operations. Two plants, Surry (a pressurized water reactor) and Grand Gulf (a boiling water reactor), were selected for study by Brookhaven National Laboratory and Sandia National Laboratories, respectively. The program objectives included assessing the risks of severe accidents initiated during plant operational states other than full power and comparing estimated core damage frequencies, important accident sequences, and other qualitative and quantitative results with full power accidents as assessed in NUREG-1150. The scope included a Level 3 probabilistic risk assessment (PRA) for traditional internal events and a Level 1 PRA on fire, flooding, and seismically induced core damage sequences. A phased approach was used in Level 1. In Phase 1 the concept of plant operational states (POSs) was developed to provide a better representation of the plant as it transitions from power to nonpower operation. This included a coarse screening analysis of all POSs to identify vulnerable plant configurations, to characterize (on a high, medium, or low basis) potential frequencies of core damage accidents, and to provide a foundation for a detailed Phase 2 analysis. In Phase 2, selected POSs from both Grand Gulf and Surry were chosen for detailed analysis. For Grand Gulf, POS 5 (approximately cold shutdown as defined by Grand Gulf Technical Specifications) during a refueling outage was selected. For Surry, three POSs representing the time the plant spends in midloop operation were chosen for analysis. These included POS 6 and POS 10 of a refueling outage and POS 6 of a drained maintenance outage. Level 1 and Level 2/3 results from both the Surry and Grand Gulf analyses are presented.

  20. Evaluation of waste temperatures in AWF tanks for bypass mode operation of the 702-AZ ventilation system, Project W-030

    SciTech Connect

    Sathyanarayana, K.

    1997-09-10

    This report describes the results of thermal hydraulic analysis performed to provide data in support of Project W-030 to startup new 702-AZ Primary Ventilation System. During the startup of W-030 system, the ventilation system will be operating in bypass mode. In bypass made of operation, the system is capable of supplying 1000 cfm total flow for all four AWF doubleshell tanks. The design of the W-030 system is based on the assumption that both the recirculation loop of the primary ventilation system and the secondary ventilation which provides cooling would be operating. However, during the startup neither the recirculation system nor the secondary ventilation system will be operating. A minimum flow of 100 cfm is required to prevent any flammable gas associated risk. The remaining 600 cfm flow can be divided among the four tanks as necessary to keep the peak sludge temperatures below the operating temperature limit. For the purpose of determining the minimum flow required for cooling each tank, the thermal hydraulic analysis is performed to predict the peak sludge temperatures in AY/AZ tanks under different ventilation flows. The heat load for AZ farm tanks is taken from characterization reports and for the AY farm tanks, the heat load was estimated by thermal analysis using the measured waste temperatures and the waste liquid evaporation rates. The tank 241-AZ-101 and the tank 241-AZ-102 have heat loads of 241,600 and 199,500 Btu/hr respectively. The tank 241-AY-101 and tank 241-AY-102 have heat loads of 41,000 and 33,000 Btu/hr respectively. Using the ambient meteorological conditions of temperature and relative humidity for the air and tank, some soil surface and the sludge levels reported in recent documents, the peak sludge and supernatant temperatures were predicted for various primary ventilation flows ranging from 100 to 400 cfm for AZ tanks and 100 and 150 cfm for AY tanks. The results of these thermal hydraulic analyses are presented. Based on the

  1. Visualization of the operational space of edge-localized modes through low-dimensional embedding of probability distributions

    SciTech Connect

    Shabbir, A. Noterdaeme, J. M.; Verdoolaege, G.; Kardaun, O. J. W. F.; Collaboration: JET-EFDA Team

    2014-11-15

    Information visualization aimed at facilitating human perception is an important tool for the interpretation of experiments on the basis of complex multidimensional data characterizing the operational space of fusion devices. This work describes a method for visualizing the operational space on a two-dimensional map and applies it to the discrimination of type I and type III edge-localized modes (ELMs) from a series of carbon-wall ELMy discharges at JET. The approach accounts for stochastic uncertainties that play an important role in fusion data sets, by modeling measurements with probability distributions in a metric space. The method is aimed at contributing to physical understanding of ELMs as well as their control. Furthermore, it is a general method that can be applied to the modeling of various other plasma phenomena as well.

  2. Pixel detector Timepix operated in pile-up mode for pulsed imaging with ultra-soft X-rays

    NASA Astrophysics Data System (ADS)

    Krejci, F.; Jakubek, J.; Kroupa, M.; Bruza, P.; Panek, D.

    2012-12-01

    The hybrid semiconductor pixel detector Timepix operated in the Time-over-Threshold mode (ToT) enables direct energy measurement in each pixel. The advantage of noiseless position sensitive detection combined with per pixel spectroscopic capability opens the way to numerous new applications, which were till now, however, restricted to detection of radiation which is basically above the detector energy threshold (typically 3-4 keV). This limitation excludes application of the hybrid pixel technology to highly interesting fields such as plasma diagnostics or X-ray microscopy. In this contribution we demonstrate how the Timepix detector working in ToT mode can be operated as a detector for particles which are in principle below the detector threshold, namely for soft X-ray photons with energy typically 0.5 keV. The approach is based on the detection of a larger number of photons incoming in the pixel signal processing chain in a time significantly shorter than the shaping time of the pixel electronics, i.e. forming signal pile-up. The proposed approach enables a CCD-like integrating operation with the many advantages of the hybrid counting technology (direct conversion, high sensitivity, dark-current free, room temperature operation, fully digital output and possibility to utilize various read-out architectures). Using the proposed approach we performed single-shot X-ray radiography with a laser-induced plasma source in the spectral region of water window. The same technique was used for the characterization of the source itself.

  3. Evaluation of persistent-mode operation in a superconducting MgB2 coil in solid nitrogen

    NASA Astrophysics Data System (ADS)

    Patel, Dipak; Hossain, Md Shahriar Al; See, Khay Wai; Qiu, Wenbin; Kobayashi, Hiroki; Ma, Zongqing; Kim, Seong Jun; Hong, Jonggi; Park, Jin Yong; Choi, Seyong; Maeda, Minoru; Shahabuddin, Mohammed; Rindfleisch, Matt; Tomsic, Mike; Xue Dou, Shi; Kim, Jung Ho

    2016-04-01

    We report the fabrication of a magnesium diboride (MgB2) coil and evaluate its persistent-mode operation in a system cooled by a cryocooler with solid nitrogen (SN2) as a cooling medium. The main purpose of SN2 was to increase enthalpy of the cold mass. For this work, an in situ processed carbon-doped MgB2 wire was used. The coil was wound on a stainless steel former in a single layer (22 turns), with an inner diameter of 109 mm and height of 20 mm without any insulation. The two ends of the coil were then joined to make a persistent-current switch to obtain the persistent-current mode. After a heat treatment, the whole coil was installed in the SN2 chamber. During operation, the resultant total circuit resistance was estimated to be <7.4 × 10-14 Ω at 19.5 K ± 1.5 K, which meets the technical requirement for magnetic resonance imaging application.

  4. Microbial community composition of polyhydroxyalkanoate-accumulating organisms in full-scale wastewater treatment plants operated in fully aerobic mode.

    PubMed

    Oshiki, Mamoru; Onuki, Motoharu; Satoh, Hiroyasu; Mino, Takashi

    2013-01-01

    The removal of biodegradable organic matter is one of the most important objectives in biological wastewater treatments. Polyhydroxyalkanoate (PHA)-accumulating organisms (PHAAOs) significantly contribute to the removal of biodegradable organic matter; however, their microbial community composition is mostly unknown. In the present study, the microbial community composition of PHAAOs was investigated at 8 full-scale wastewater treatment plants (WWTPs), operated in fully aerobic mode, by fluorescence in situ hybridization (FISH) analysis and post-FISH Nile blue A (NBA) staining techniques. Our results demonstrated that 1) PHAAOs were in the range of 11-18% in the total number of cells, and 2) the microbial community composition of PHAAOs was similar at the bacterial domain/phylum/class/order level among the 8 full-scale WWTPs, and dominant PHAAOs were members of the class Alphaproteobacteria and Betaproteobacteria. The microbial community composition of α- and β-proteobacterial PHAAOs was examined by 16S rRNA gene clone library analysis and further by applying a set of newly designed oligonucleotide probes targeting 16S rRNA gene sequences of α- or β-proteobacterial PHAAOs. The results demonstrated that the microbial community composition of PHAAOs differed in the class Alphaproteobacteria and Betaproteobacteria, which possibly resulted in a different PHA accumulation capacity among the WWTPs (8.5-38.2 mg-C g-VSS(-1) h(-1)). The present study extended the knowledge of the microbial diversity of PHAAOs in full-scale WWTPs operated in fully aerobic mode. PMID:23257912

  5. Concept and realization of unmanned aerial system with different modes of operation

    SciTech Connect

    Czyba, Roman; Szafrański, Grzegorz; Janusz, Wojciech; Niezabitowski, Michał; Czornik, Adam; Błachuta, Marian

    2014-12-10

    In this paper we describe the development process of unmanned aerial system, its mechanical components, electronics and software solutions. During the stage of design, we have formulated some necessary requirements for the multirotor vehicle and ground control station in order to build an optimal system which can be used for the reconnaissance missions. Platform is controlled by use of the ground control station (GCS) and has possibility of accomplishing video based observation tasks. In order to fulfill this requirement the on-board payload consists of mechanically stabilized camera augmented with machine vision algorithms to enable object tracking tasks. Novelty of the system are four modes of flight, which give full functionality of the developed UAV system. Designed ground control station is consisted not only of the application itself, but also a built-in dedicated components located inside the chassis, which together creates an advanced UAV system supporting the control and management of the flight. Mechanical part of quadrotor is designed to ensure its robustness while meeting objectives of minimizing weight of the platform. Finally the designed electronics allows for implementation of control and estimation algorithms without the needs for their excessive computational optimization.

  6. Concept and realization of unmanned aerial system with different modes of operation

    NASA Astrophysics Data System (ADS)

    Czyba, Roman; Szafrański, Grzegorz; Janusz, Wojciech; Niezabitowski, Michał; Czornik, Adam; Błachuta, Marian

    2014-12-01

    In this paper we describe the development process of unmanned aerial system, its mechanical components, electronics and software solutions. During the stage of design, we have formulated some necessary requirements for the multirotor vehicle and ground control station in order to build an optimal system which can be used for the reconnaissance missions. Platform is controlled by use of the ground control station (GCS) and has possibility of accomplishing video based observation tasks. In order to fulfill this requirement the on-board payload consists of mechanically stabilized camera augmented with machine vision algorithms to enable object tracking tasks. Novelty of the system are four modes of flight, which give full functionality of the developed UAV system. Designed ground control station is consisted not only of the application itself, but also a built-in dedicated components located inside the chassis, which together creates an advanced UAV system supporting the control and management of the flight. Mechanical part of quadrotor is designed to ensure its robustness while meeting objectives of minimizing weight of the platform. Finally the designed electronics allows for implementation of control and estimation algorithms without the needs for their excessive computational optimization.

  7. Operating modes of a hydrogen ion source based on a hollow-cathode pulsed Penning discharge.

    PubMed

    Oks, E M; Shandrikov, M V; Vizir, A V

    2016-02-01

    An ion source based on a hollow-cathode Penning discharge was switched to a high-current pulsed mode (tens of amperes and tens of microseconds) to produce an intense hydrogen ion beam. With molecular hydrogen (H2), the ion beam contained three species: H(+), H2(+), and H3(+). For all experimental conditions, the fraction of H2 (+) ions in the beam was about 10 ÷ 15% of the total ion beam current and varied little with ion source parameters. At the same time, the ratio of H(+) and H3(+) depended strongly on the discharge current, particularly on its distribution in the gap between the hollow and planar cathodes. Increasing the discharge current increased the H(+) fraction in ion beam. The maximum fraction of H(+) reached 80% of the total ion beam current. Forced redistribution of the discharge current in the cathode gap for increasing the hollow cathode current could greatly increase the H3(+) fraction in the beam. At optimum parameters, the fraction of H3(+) ions reached 60% of the total ion beam current.

  8. Analytical expressions for chatter analysis in milling operations with one dominant mode

    NASA Astrophysics Data System (ADS)

    Iglesias, A.; Munoa, J.; Ciurana, J.; Dombovari, Z.; Stepan, G.

    2016-08-01

    In milling, an accurate prediction of chatter is still one of the most complex problems in the field. The presence of these self-excited vibrations can spoil the surface of the part and can also cause a large reduction in tool life. The stability diagrams provide a practical selection of the optimum cutting conditions determined either by time domain or frequency domain based methods. Applying these methods parametric or parameter traced representations of the linear stability limits can be achieved by solving the corresponding eigenvalue problems. In this work, new analytical formulae are proposed related to the parameter domains of both Hopf and period doubling type stability boundaries emerging in the regenerative mechanical model of time periodical milling processes. These formulae are useful to enrich and speed up the currently used numerical methods. Also, the destabilization mechanism of double period chatter is explained, creating an analogy with the chatter related to the Hopf bifurcation, considering one dominant mode and using concepts established by the Pioneers of chatter research.

  9. Operating modes of a hydrogen ion source based on a hollow-cathode pulsed Penning discharge

    NASA Astrophysics Data System (ADS)

    Oks, E. M.; Shandrikov, M. V.; Vizir, A. V.

    2016-02-01

    An ion source based on a hollow-cathode Penning discharge was switched to a high-current pulsed mode (tens of amperes and tens of microseconds) to produce an intense hydrogen ion beam. With molecular hydrogen (H2), the ion beam contained three species: H+, H2+, and H3+. For all experimental conditions, the fraction of H2+ ions in the beam was about 10 ÷ 15% of the total ion beam current and varied little with ion source parameters. At the same time, the ratio of H+ and H3+ depended strongly on the discharge current, particularly on its distribution in the gap between the hollow and planar cathodes. Increasing the discharge current increased the H+ fraction in ion beam. The maximum fraction of H+ reached 80% of the total ion beam current. Forced redistribution of the discharge current in the cathode gap for increasing the hollow cathode current could greatly increase the H3+ fraction in the beam. At optimum parameters, the fraction of H3+ ions reached 60% of the total ion beam current.

  10. Elastomeric Microchip Electrospray Emitter for Stable Cone-Jet Mode Operation in the Nanoflow Regime.

    SciTech Connect

    Kelly, Ryan T.; Tang, Keqi; Irimia, Daniel; Toner, Mehmet; Smith, Richard D.

    2008-05-15

    Despite widespread interest in applying lab-on-a-chip technologies to mass spectrometry (MS)-based analyses, the coupling of microfluidics to electrospray ionization (ESI)-MS remains challenging. We report a robust, integrated poly(dimethylsiloxane) microchip interface for ESI-MS using simple and widely accessible microfabrication procedures. The interface uses an auxiliary channel to provide electrical contact in the Taylor cone of the electrospray without sample loss or dilution. The electric field at the channel terminus is enhanced by two vertical cuts that cause the interface to taper to a line rather than to a point, and the formation of small Taylor cones at the channel exit ensures sub-nL post-column dead volumes. While comparable ESI-MS sensitivities were achieved using both microchip and conventional fused silica capillary emitters, stable cone-jet mode electrospray could be established over a far broader range of flow rates (from 50–1000 nL/min) and applied potentials using the microchip emitters. This special feature of the microchip emitter should minimize the fine tuning required for electrospray optimization and make the stable electrospray more resistant to external perturbations.

  11. Amplitude and timing properties of a Geiger discharge in a SiPM cell

    NASA Astrophysics Data System (ADS)

    Popova, E.; Buzhan, P.; Pleshko, A.; Vinogradov, S.; Stifutkin, A.; Ilyin, A.; Besson, D.; Mirzoyan, R.

    2015-07-01

    The amplitude and timing properties of a Geiger discharge in a stand-alone SiPM cell have been investigated in detail. Use of a single stand-alone SiPM cell allows us to perform measurements with better accuracy than the multicell structure of conventional SiPMs. We have studied the dependence of the output charge and amplitude from an SiPM cell illuminated by focused light vs the number of primary photoelectrons. We propose a SPICE model which explains the amplitude over saturation (when the SiPM's amplitude is greater than the sum over all cells) characteristics of SiPM signals for more than one initial photoelectrons. The time resolutions of a SiPM cell have been measured for the case of single (SPTR) and multiphoton light pulses. The Full Width Half Max (FWHM) for SPTR has been found to be at the level of 30 ps for focused and 40 ps for unfocused light (100 μm cell size).

  12. Educational studies of cosmic rays with a telescope of Geiger Müller counters

    NASA Astrophysics Data System (ADS)

    Wibig, T.; Kolodziejczak, K.; Pierzynski, R.; Sobczak, R.

    2006-11-01

    A group of high school students (XII Liceum) in the framework of the Roland Maze Project has built a compact telescope of three Geiger Müller counters. The connection between the telescope and a PC computer was also created and programmed by students involved in the Project. This has allowed students to use their equipment to perform serious scientific measurements concerning the single cosmic ray muon flux at ground level and below. These measurements were then analysed with the programs on the basis of current knowledge on statistics. An overview of the apparatus, methods and results have been presented at several student conferences and recently won the first prize in a national competition for high school students' scientific work. The telescope itself, in spite of its 'scientific' purposes, is built in such a way that it can be hung on a wall in a school physics lab and count muons continuously. This can help to raise in interest in studying physics among others. At present a few (three) groups of young participants of the Roland Maze Project have already built their own telescopes for their schools and some others are working on it. This work is a perfect example of what can be done by young people when respective opportunities are created by more experienced researchers and a little help and advice is given.

  13. Geiger avalanche photodiodes as tentative light detectors for VHE gamma ray astronomy

    NASA Astrophysics Data System (ADS)

    Pellion, D.; Jradi, K.; Le Padellec, A.; Rennane, A.; Moutier, F.; Borrel, V.; Esteve, D.; Magenc, C.; Bazer-Bachi, A. R.

    2010-03-01

    Due to its sensitivity and speed, the detector still widely used in Cerenkov astrophysics experiments remains the PhotoMultiplier Tube (PMT). For instance, recent pathbreaking experiments in Very High Energy astrophysics (VHE), such as MAGIC and HESS, have used mainstream PMT technology [Aharonian, F. et al Astron. Astrophys. 492(1):L25-L28 (2008)]. Moreover the Cerenkov Telescope Array (CTA) which is now in its design phase, is also planed to be based on PMT’s. However, there are some disadvantages to the PMT technology: the rather poor quantum efficiency, the use of high voltages, the high cost when used in large number in a matrix arrangement and the large weight. Hence, we have investigated the possibility to design future Cerenkov telescopes based on solid state technology, specifically Geiger avalanche photodiodes. In a preliminary development test, we placed HAMAMATSU avalanche photodiodes at the focal plane of a 60 cm diameter telescope at the Pic du Midi in the French Pyrénées, in order to record incident cosmic rays. In this paper, we describe not only the experimental setup but we also put special emphasis to the reduction of the semi-conductor noise. We also show first data that were recorded during two runs in the fall of 2006, and conclude by the presentation of the design of an “integrated, low-cost solid state photodiode arrangement” which might be an alternative to PMT’s for future VHE telescopes.

  14. New mode of operating a magnetized coaxial plasma gun for injecting magnetic helicity into a spheromak.

    PubMed

    Woodruff, S; Hill, D N; Stallard, B W; Bulmer, R; Cohen, B; Holcomb, C T; Hooper, E B; McLean, H S; Moller, J; Wood, R D

    2003-03-01

    By operating a magnetized coaxial plasma gun continuously with just sufficient current to enable plasma ejection, large gun-voltage spikes (approximately 1 kV) are produced, giving the highest sustained voltage approximately 500 V and highest sustained helicity injection rate observed in the Sustained Spheromak Physics Experiment. The spheromak magnetic field increases monotonically with time, exhibiting the lowest fluctuation levels observed during formation of any spheromak (B/B>/=2%). The results suggest an important mechanism for field generation by helicity injection, namely, the merging of helicity-carrying filaments.

  15. Impact of MSWI bottom ash codisposed with MSW on landfill stabilization with different operational modes.

    PubMed

    Li, Wen-Bing; Yao, Jun; Malik, Zaffar; Zhou, Gen-Di; Dong, Ming; Shen, Dong-Sheng

    2014-01-01

    The aim of the study was to investigate the impact of municipal solid waste incinerator (MSWI) bottom ash (BA) codisposed with municipal solid waste (MSW) on landfill stabilization according to the leachate quality in terms of organic matter and nitrogen contents. Six simulated landfills, that is, three conventional and three recirculated, were employed with different ratios of MSWI BA to MSW. The results depicted that, after 275-day operation, the ratio of MSWI BA to fresh refuse of 1 : 10 (V : V) in the landfill was still not enough to provide sufficient acid-neutralizing capacity for a high organic matter composition of MSW over 45.5% (w/w), while the ratio of MSWI BA to fresh refuse of 1 : 5 (V : V) could act on it. Among the six experimental landfills, leachate quality only was improved in the landfill operated with the BA addition (the ratio of MSWI BA to fresh refuse of 1 : 5 (V : V)) and leachate recirculation. PMID:24779006

  16. Impact of MSWI Bottom Ash Codisposed with MSW on Landfill Stabilization with Different Operational Modes

    PubMed Central

    Li, Wen-Bing; Yao, Jun; Zhou, Gen-Di; Dong, Ming; Shen, Dong-Sheng

    2014-01-01

    The aim of the study was to investigate the impact of municipal solid waste incinerator (MSWI) bottom ash (BA) codisposed with municipal solid waste (MSW) on landfill stabilization according to the leachate quality in terms of organic matter and nitrogen contents. Six simulated landfills, that is, three conventional and three recirculated, were employed with different ratios of MSWI BA to MSW. The results depicted that, after 275-day operation, the ratio of MSWI BA to fresh refuse of 1 : 10 (V : V) in the landfill was still not enough to provide sufficient acid-neutralizing capacity for a high organic matter composition of MSW over 45.5% (w/w), while the ratio of MSWI BA to fresh refuse of 1 : 5 (V : V) could act on it. Among the six experimental landfills, leachate quality only was improved in the landfill operated with the BA addition (the ratio of MSWI BA to fresh refuse of 1 : 5 (V : V)) and leachate recirculation. PMID:24779006

  17. Fundamental limits of MWIR HgCdTe barrier detectors operating under non-equilibrium mode

    NASA Astrophysics Data System (ADS)

    Kopytko, M.; Jóźwikowski, K.; Rogalski, A.

    2014-10-01

    The paper presents numerical considerations of temperature-dependent performance of different mid-wave infrared HgCdTe detectors (with p- and n-type active layer) for non-equilibrium operation. Current-voltage characteristics of double heterostructure PpN photodiode, pBppN barrier photodiode, nBnn and nBnnN barrier detectors are compared to find an optimal architecture for high-operating temperature conditions. Using our model, the calculated characteristics of the devices are fitted to the experimental results for HgCdTe photodiode grown on GaAs substrate by metal organic chemical vapour deposition. The performance of photodiodes with p-type absorber are limited by the generation current associated with the Shockley-Read-Hall process, while nBnn type devices (with the n-type absorber) indicate a diffusion limited dark currents associated with Auger processes. At high values of the reverse bias (over 1 V), the trap states located at dislocations lead to strong band-to-band and trap-assisted tunnelling due to high electric field within the depletion layer.

  18. Design considerations in achieving 1 MW CW operation with a whispering-gallery-mode gyrotron

    SciTech Connect

    Felch, K.; Feinstein, J.; Hess, C.; Huey, H.; Jongewaard, E.; Jory, H.; Neilson, J.; Pendleton, R.; Pirkle, D.; Zitelli, L. )

    1989-09-01

    Varian is developing high-power, CW gyrotrons at frequencies in the range 100 GHz to 150 GHz, for use in electron cyclotron heating applications. Early test vehicles have utilized a TE{sub 15,2,1} interaction cavity, have achieved short-pulse power levels of 820 kW and average power levels of 80 kW at 140 GHz. Present tests are aimed at reaching 400 kW under CW operating conditions and up to 1 MW for short pulse durations. Work is also underway on modifications to the present design that will enable power levels of up to 1 MW CW to be achieved. 7 refs., 2 figs.

  19. Discovering operating modes in telemetry data from the Shuttle Reaction Control System

    NASA Technical Reports Server (NTRS)

    Manganaris, Stefanos; Fisher, Doug; Kulkarni, Deepak

    1994-01-01

    This paper addresses the problem of detecting and diagnosing faults in physical systems, for which suitable system models are not available. An architecture is proposed that integrates the on-line acquisition and exploitation of monitoring and diagnostic knowledge. The focus is on the component of the architecture that discovers classes of behaviors with similar characteristics by observing a system in operation. A characterization of behaviors based on best fitting approximation models is investigated. An experimental prototype has been implemented to test it. Preliminary results in diagnosing faults of the reaction control system of the space shuttle are presented. The merits and limitations of the approach are identified and directions for future work are set.

  20. Operator-based triple-mode Floquet theory in solid-state NMR.

    PubMed

    Scholz, Ingo; Meier, Beat H; Ernst, Matthias

    2007-11-28

    Many solid-state NMR experiments exploit interference effects between time dependencies in the system Hamiltonian to design an effective time-independent Hamiltonian with the desired properties. Effective Hamiltonians can be designed such that they contain only selected parts of the full system Hamiltonian while all other parts are averaged to zero. A general theoretical description of such experiments has to accommodate several time-dependent perturbations with incommensurate frequencies. We describe an extension of the analytical operator-based Floquet description of NMR experiments to situations with three incommensurate frequencies. Experiments with three time dependencies are quite common in solid-state NMR. Examples include experiments which combine magic-angle spinning and radio-frequency irradiation on two nuclei or asynchronous multiple-pulse sequences on a single spin species. The Floquet description is general in the sense that the resulting effective Hamiltonians can be calculated without a detailed knowledge of the spin-system Hamiltonian and can be expressed fully as a function of the Fourier components of the time-dependent Hamiltonian. As a prototype experiment we treat the application of two continuous-wave (cw) radio-frequency fields under magic-angle spinning. Experiments that are included in such a description are Hartmann-Hahn cross polarization or rotary-resonance recoupling experiments with simultaneous cw decoupling. PMID:18052439

  1. Frequency-modulated atomic force microscopy operation by imaging at the frequency shift minimum: The dip-df mode

    NASA Astrophysics Data System (ADS)

    Rode, Sebastian; Schreiber, Martin; Kühnle, Angelika; Rahe, Philipp

    2014-04-01

    In frequency modulated non-contact atomic force microscopy, the change of the cantilever frequency (Δf) is used as the input signal for the topography feedback loop. Around the Δf(z) minimum, however, stable feedback operation is challenging using a standard proportional-integral-derivative (PID) feedback design due to the change of sign in the slope. When operated under liquid conditions, it is furthermore difficult to address the attractive interaction regime due to its often moderate peakedness. Additionally, the Δf signal level changes severely with time in this environment due to drift of the cantilever frequency f0 and, thus, requires constant adjustment. Here, we present an approach overcoming these obstacles by using the derivative of Δf with respect to z as the input signal for the topography feedback loop. Rather than regulating the absolute value to a preset setpoint, the slope of the Δf with respect to z is regulated to zero. This new measurement mode not only makes the minimum of the Δf(z) curve directly accessible, but it also benefits from greatly increased operation stability due to its immunity against f0 drift. We present isosurfaces of the Δf minimum acquired on the calcite CaCO3(10overline{1}4) surface in liquid environment, demonstrating the capability of our method to image in the attractive tip-sample interaction regime.

  2. Frequency-modulated atomic force microscopy operation by imaging at the frequency shift minimum: The dip-df mode

    SciTech Connect

    Rode, Sebastian; Schreiber, Martin; Kühnle, Angelika; Rahe, Philipp

    2014-04-15

    In frequency modulated non-contact atomic force microscopy, the change of the cantilever frequency (Δf) is used as the input signal for the topography feedback loop. Around the Δf(z) minimum, however, stable feedback operation is challenging using a standard proportional-integral-derivative (PID) feedback design due to the change of sign in the slope. When operated under liquid conditions, it is furthermore difficult to address the attractive interaction regime due to its often moderate peakedness. Additionally, the Δf signal level changes severely with time in this environment due to drift of the cantilever frequency f{sub 0} and, thus, requires constant adjustment. Here, we present an approach overcoming these obstacles by using the derivative of Δf with respect to z as the input signal for the topography feedback loop. Rather than regulating the absolute value to a preset setpoint, the slope of the Δf with respect to z is regulated to zero. This new measurement mode not only makes the minimum of the Δf(z) curve directly accessible, but it also benefits from greatly increased operation stability due to its immunity against f{sub 0} drift. We present isosurfaces of the Δf minimum acquired on the calcite CaCO{sub 3}(101{sup ¯}4) surface in liquid environment, demonstrating the capability of our method to image in the attractive tip-sample interaction regime.

  3. Multistage depressed collector with efficiency of 90 to 94 percent for operation of a dual-mode traveling wave tube in the linear region

    NASA Technical Reports Server (NTRS)

    Ramins, P.; Fox, T. A.

    1980-01-01

    An axisymmetric, multistage, depressed collector of fixed geometric design was evaluated in conjunction with an octave bandwidth, dual mode traveling wave tube (TWT). The TWT was operated over a wide range of conditions to simulate different applications. The collector performance was optimized (within the constraint of fixed geometric design) over the range of TWT operating conditions covered. For operation of the TWT in the linear, low distortion range, 90 percent and greater collector efficiencies were obtained leading to TWT overall efficiencies of 20 to 35 percent, as compared with 2 to 5 percent with an undepressed collector. With collectors of this efficiency and minimized beam interception losses, it becomes practical to design dual mode TWT's such that the low mode can represent operation well below saturation. Consequently, the required pulse up in beam current can be reduced or eliminated, and this mitigates beam control and dual mode TWT circuit design problems. For operation of the dual mode TWT at saturation, average collector efficiencies in excess of 85 percent were obtained for both the low and high modes across an octave bandwidth, leading to a three to fourfold increase in the TWT overall efficiency.

  4. Bidirectional operation of 100 fs bound solitons in an ultra-compact mode-locked fiber laser.

    PubMed

    Li, Lei; Ruan, Qiujun; Yang, Runhua; Zhao, Luming; Luo, Zhengqian

    2016-09-01

    We report on the experimental observation of bidirectional 100-fs bound solitons from a nanotube-mode-locked dispersion-managed Er-fiber laser with an ultra-simple linear cavity. Two mode-locked pulse trains in opposite directions are delivered simultaneously from the linear cavity. Under the pump power of <74 mW, both the bidirectional outputs of the laser work at the single-soliton state with pulse duration of 173 fs and 182 fs, respectively. Once the pump power is more than 74 mW, both the bidirectional outputs evolve into the two-soliton bound states with soliton separation of 1.53 ps. Interestingly, the bidirectional operations can show the different bound states, i.e. the forward bound solitons with phase difference of + π/2, and the backward ones with phase difference of -π/2. This is, to the best of our knowledge, the first demonstration of such compact bidirectional soliton fiber laser with the sub-200 fs pulses. PMID:27607705

  5. Pulse oximeter using a gain-modulated avalanche photodiode operated in a pseudo lock-in light detection mode

    NASA Astrophysics Data System (ADS)

    Miyata, Tsuyoshi; Iwata, Tetsuo; Araki, Tsutomu

    2006-01-01

    We propose a reflection-type pulse oximeter, which employs two pairs of a light-emitting diode (LED) and a gated avalanche photodiode (APD). One LED is a red one with an emission wavelength λ = 635 nm and the other is a near-infrared one with that λ = 945 nm, which are both driven with a pulse mode at a frequency f (=10 kHz). Superposition of a transistor-transistor-logic (TTL) gate pulse on a direct-current (dc) bias, which is set so as not exceeding the breakdown voltage of each APD, makes the APD work in a gain-enhanced operation mode. Each APD is gated at a frequency 2f (=20 kHz) and its output signal is fed into a laboratory-made lock-in amplifier that works in synchronous with the pulse modulation signal of each LED at a frequency f (=10 kHz). A combination of the gated APD and the lock-in like signal detection scheme is useful for the reflection-type pulse oximeter thanks to the capability of detecting a weak signal against a large background (BG) light.

  6. Segmentation of a Vibro-Shock Cantilever-Type Piezoelectric Energy Harvester Operating in Higher Transverse Vibration Modes

    PubMed Central

    Zizys, Darius; Gaidys, Rimvydas; Dauksevicius, Rolanas; Ostasevicius, Vytautas; Daniulaitis, Vytautas

    2015-01-01

    The piezoelectric transduction mechanism is a common vibration-to-electric energy harvesting approach. Piezoelectric energy harvesters are typically mounted on a vibrating host structure, whereby alternating voltage output is generated by a dynamic strain field. A design target in this case is to match the natural frequency of the harvester to the ambient excitation frequency for the device to operate in resonance mode, thus significantly increasing vibration amplitudes and, as a result, energy output. Other fundamental vibration modes have strain nodes, where the dynamic strain field changes sign in the direction of the cantilever length. The paper reports on a dimensionless numerical transient analysis of a cantilever of a constant cross-section and an optimally-shaped cantilever with the objective to accurately predict the position of a strain node. Total effective strain produced by both cantilevers segmented at the strain node is calculated via transient analysis and compared to the strain output produced by the cantilevers segmented at strain nodes obtained from modal analysis, demonstrating a 7% increase in energy output. Theoretical results were experimentally verified by using open-circuit voltage values measured for the cantilevers segmented at optimal and suboptimal segmentation lines. PMID:26703623

  7. Bidirectional operation of 100 fs bound solitons in an ultra-compact mode-locked fiber laser.

    PubMed

    Li, Lei; Ruan, Qiujun; Yang, Runhua; Zhao, Luming; Luo, Zhengqian

    2016-09-01

    We report on the experimental observation of bidirectional 100-fs bound solitons from a nanotube-mode-locked dispersion-managed Er-fiber laser with an ultra-simple linear cavity. Two mode-locked pulse trains in opposite directions are delivered simultaneously from the linear cavity. Under the pump power of <74 mW, both the bidirectional outputs of the laser work at the single-soliton state with pulse duration of 173 fs and 182 fs, respectively. Once the pump power is more than 74 mW, both the bidirectional outputs evolve into the two-soliton bound states with soliton separation of 1.53 ps. Interestingly, the bidirectional operations can show the different bound states, i.e. the forward bound solitons with phase difference of + π/2, and the backward ones with phase difference of -π/2. This is, to the best of our knowledge, the first demonstration of such compact bidirectional soliton fiber laser with the sub-200 fs pulses.

  8. Segmentation of a Vibro-Shock Cantilever-Type Piezoelectric Energy Harvester Operating in Higher Transverse Vibration Modes.

    PubMed

    Zizys, Darius; Gaidys, Rimvydas; Dauksevicius, Rolanas; Ostasevicius, Vytautas; Daniulaitis, Vytautas

    2015-01-01

    The piezoelectric transduction mechanism is a common vibration-to-electric energy harvesting approach. Piezoelectric energy harvesters are typically mounted on a vibrating host structure, whereby alternating voltage output is generated by a dynamic strain field. A design target in this case is to match the natural frequency of the harvester to the ambient excitation frequency for the device to operate in resonance mode, thus significantly increasing vibration amplitudes and, as a result, energy output. Other fundamental vibration modes have strain nodes, where the dynamic strain field changes sign in the direction of the cantilever length. The paper reports on a dimensionless numerical transient analysis of a cantilever of a constant cross-section and an optimally-shaped cantilever with the objective to accurately predict the position of a strain node. Total effective strain produced by both cantilevers segmented at the strain node is calculated via transient analysis and compared to the strain output produced by the cantilevers segmented at strain nodes obtained from modal analysis, demonstrating a 7% increase in energy output. Theoretical results were experimentally verified by using open-circuit voltage values measured for the cantilevers segmented at optimal and suboptimal segmentation lines. PMID:26703623

  9. Segmentation of a Vibro-Shock Cantilever-Type Piezoelectric Energy Harvester Operating in Higher Transverse Vibration Modes.

    PubMed

    Zizys, Darius; Gaidys, Rimvydas; Dauksevicius, Rolanas; Ostasevicius, Vytautas; Daniulaitis, Vytautas

    2015-12-23

    The piezoelectric transduction mechanism is a common vibration-to-electric energy harvesting approach. Piezoelectric energy harvesters are typically mounted on a vibrating host structure, whereby alternating voltage output is generated by a dynamic strain field. A design target in this case is to match the natural frequency of the harvester to the ambient excitation frequency for the device to operate in resonance mode, thus significantly increasing vibration amplitudes and, as a result, energy output. Other fundamental vibration modes have strain nodes, where the dynamic strain field changes sign in the direction of the cantilever length. The paper reports on a dimensionless numerical transient analysis of a cantilever of a constant cross-section and an optimally-shaped cantilever with the objective to accurately predict the position of a strain node. Total effective strain produced by both cantilevers segmented at the strain node is calculated via transient analysis and compared to the strain output produced by the cantilevers segmented at strain nodes obtained from modal analysis, demonstrating a 7% increase in energy output. Theoretical results were experimentally verified by using open-circuit voltage values measured for the cantilevers segmented at optimal and suboptimal segmentation lines.

  10. HIGH POWER TEST OF A 3.9 GHZ 5-CELL DEFLECTING-MODE CAVITY IN A CRYOGENIC OPERATION

    SciTech Connect

    Shin, Young-Min; Church, Michael

    2013-11-24

    A 3.9 GHz deflecting mode (S, TM110) cavity has been long used for six-dimensional phase-space beam manipulation tests [1-5] at the A0 Photo-Injector Lab (16 MeV) in Fermilab and their extended applications with vacuum cryomodules are currently planned at the Advanced Superconducting Test Accelerator (ASTA) user facility (> 50 MeV). Despite the successful test results, the cavity, however, demonstrated limited RF performance during liquid nitrogen (LN2) ambient operation that was inferior to theoretical prediction. We have been performing full analysis of the designed cavity by analytic calculation and comprehensive system simulation analysis to solve complex thermodynamics and mechanical stresses. The re-assembled cryomodule is currently under the test with a 50 kW klystron at the Fermilab A0 beamline, which will benchmark the modeling analysis. The test result will be used to design vacuum cryomodules for the 3.9 GHz deflecting mode cavity that will be employed at the ASTA facility for beam diagnostics and phase-space control.

  11. Development and Operation of Dual-Mode Analyzers for Wireless Power Consortium/Power Matters Alliance Wireless Power Systems.

    PubMed

    Um, Keehong

    2016-05-01

    We have designed a protocol analyzer to be used in wireless power systems and analyzed the operation of wireless chargers defined by standards of Qi of Wireless Power Consortium (WPC) and Power Matters Alliance (PMA) protocols. The integrated circuit (IC, or microchip) developed so far for wireless power transmission is not easily adopted by chargers for specific purposes. A device for measuring the performance of test equipment currently available is required to transform and expand the types of protocol. Since a protocol analyzer with these functions is required, we have developed a device that can analyze the two protocols of WPC and PMA at the same time. As a result of our research, we present a dual-mode system that can analyze the protocols of both WPC and PMA.

  12. Development and Operation of Dual-Mode Analyzers for Wireless Power Consortium/Power Matters Alliance Wireless Power Systems.

    PubMed

    Um, Keehong

    2016-05-01

    We have designed a protocol analyzer to be used in wireless power systems and analyzed the operation of wireless chargers defined by standards of Qi of Wireless Power Consortium (WPC) and Power Matters Alliance (PMA) protocols. The integrated circuit (IC, or microchip) developed so far for wireless power transmission is not easily adopted by chargers for specific purposes. A device for measuring the performance of test equipment currently available is required to transform and expand the types of protocol. Since a protocol analyzer with these functions is required, we have developed a device that can analyze the two protocols of WPC and PMA at the same time. As a result of our research, we present a dual-mode system that can analyze the protocols of both WPC and PMA. PMID:27483911

  13. Single Spatial-Mode Room-Temperature-Operated 3.0 to 3.4 micrometer Diode Lasers

    NASA Technical Reports Server (NTRS)

    Frez, Clifford F.; Soibel, Alexander; Belenky, Gregory; Shterengas, Leon; Kipshidze, Gela

    2010-01-01

    Compact, highly efficient, 3.0 to 3.4 m light emitters are in demand for spectroscopic analysis and identification of chemical substances (including methane and formaldehyde), infrared countermeasures technologies, and development of advanced infrared scene projectors. The need for these light emitters can be currently addressed either by bulky solid-state light emitters with limited power conversion efficiency, or cooled Interband Cascade (IC) semiconductor lasers. Researchers here have developed a breakthrough approach to fabrication of diode mid-IR lasers that have several advantages over IC lasers used for the Mars 2009 mission. This breakthrough is due to a novel design utilizing the strain-engineered quantum-well (QW) active region and quinternary barriers, and due to optimization of device material composition and growth conditions (growth temperatures and rates). However, in their present form, these GaSb-based laser diodes cannot be directly used as a part of sensor systems. The device spectrum is too broad to perform spectroscopic analysis of gas species, and operating currents and voltages are too high. In the current work, the emitters were fabricated as narrow-ridge waveguide index-guided lasers rather than broad stripe-gain guided multimode Fabry-Perot (FP) lasers as was done previously. These narrow-ridge waveguide mid-IR lasers exhibit much lower power consumptions, and can operate in a single spatial mode that is necessary for demonstration of single-mode distributed feedback (DBF) devices for spectroscopic applications. These lasers will enable a new generation of compact, tunable diode laser spectrometers with lower power consumption, reduced complexity, and significantly reduced development costs. These lasers can be used for the detection of HCN, C2H2, methane, and ethane.

  14. Microbial Community Composition of Polyhydroxyalkanoate-Accumulating Organisms in Full-Scale Wastewater Treatment Plants Operated in Fully Aerobic Mode

    PubMed Central

    Oshiki, Mamoru; Onuki, Motoharu; Satoh, Hiroyasu; Mino, Takashi

    2013-01-01

    The removal of biodegradable organic matter is one of the most important objectives in biological wastewater treatments. Polyhydroxyalkanoate (PHA)-accumulating organisms (PHAAOs) significantly contribute to the removal of biodegradable organic matter; however, their microbial community composition is mostly unknown. In the present study, the microbial community composition of PHAAOs was investigated at 8 full-scale wastewater treatment plants (WWTPs), operated in fully aerobic mode, by fluorescence in situ hybridization (FISH) analysis and post-FISH Nile blue A (NBA) staining techniques. Our results demonstrated that 1) PHAAOs were in the range of 11–18% in the total number of cells, and 2) the microbial community composition of PHAAOs was similar at the bacterial domain/phylum/class/order level among the 8 full-scale WWTPs, and dominant PHAAOs were members of the class Alphaproteobacteria and Betaproteobacteria. The microbial community composition of α- and β-proteobacterial PHAAOs was examined by 16S rRNA gene clone library analysis and further by applying a set of newly designed oligonucleotide probes targeting 16S rRNA gene sequences of α- or β-proteobacterial PHAAOs. The results demonstrated that the microbial community composition of PHAAOs differed in the class Alphaproteobacteria and Betaproteobacteria, which possibly resulted in a different PHA accumulation capacity among the WWTPs (8.5–38.2 mg-C g-VSS−1 h−1). The present study extended the knowledge of the microbial diversity of PHAAOs in full-scale WWTPs operated in fully aerobic mode. PMID:23257912

  15. Design of large-bandwidth single-mode operation waveguides in silicon three-dimensional photonic crystals using two guided modes.

    PubMed

    Fu, Jiapeng; Tandaechanurat, Aniwat; Iwamoto, Satoshi; Arakawa, Yasuhiko

    2013-05-20

    We report on the design of silicon three-dimensional (3D) photonic crystal (PC) waveguides with a combination of acceptor-type and donor-type line defects. Tuning the width of the acceptor-type line defect allows the waveguide to support two guided modes, which enable single-mode propagation over 98.7% of the complete photonic bandgap (cPBG). In addition, we demonstrate that the frequency ranges for single-mode propagation can be extended to the entire range of the cPBG by further tuning the thickness of the layers in which the donor-type line defects are located. The wide ranges of available frequencies for single mode propagation enable flexible design of 3D PC components and will provide a route towards future 3D photonic circuits. PMID:23736463

  16. Operating Modes and Cooling Capabilities of the Flight ADR for the SXS Instrument on Astro-H

    NASA Technical Reports Server (NTRS)

    Shirron, Peter; Kimball, Mark; DiPirro, Michael

    2015-01-01

    The microcalorimeter array on the Soft X-ray Spectrometer instrument on Astro-H requires cooling to 50 mK, which will be accomplished by a 3-stage adiabatic demagnetization refrigerator (ADR). The ADR is surrounded by a cryogenic system consisting of a superfluid helium tank, a 4.5 K Joule-Thomson (JT) cryocooler, and additional 2-stage Stirling cryocoolers that pre-cool the JT cooler and radiation shields within the cryostat. The unique ADR design allows the instrument to meet all of its science requirements using either the stored cryogen or the JT cryocooler as its heat sink, giving the instrument an unusual degree of tolerance for component failures or degradation in the cryogenic system. The flight detector assembly, ADR and dewar were integrated in early 2014, and have since been extensively characterized and calibrated. At present, the four instruments are being integrated with the spacecraft in preparation for an early 2016 launch. This presentation summarizes the operation and performance of the ADR in all of its operating modes.

  17. Operating Characteristics in DIII-D ELM-Suppressed RMP H-modes with ITER Similar Shapes

    SciTech Connect

    Evans, T E; Fenstermacher, M E; Jakubowski, M; Moyer, R A; Osborne, T H; Schaffer, M J; Schmitz, O; Watkins, J G; Zeng, L; Baylor, L R; Boedo, J A; Burrell, K H; deGrassie, J S; Gohil, P; Joseph, I; Lasnier, C J; Leonard, A W; Mordijck, S; Petty, C C; Pinsker, R I; Rhodes, T L; Rost, J C; Snyder, P B; Unterberg, E; West, W P

    2008-10-13

    Fast energy transients, incident on the DIII-D divertors due to Type-I edge localized modes (ELMs), are eliminated using small dc currents in a simple set of non-axisymmetric coils that produce edge resonant magnetic perturbations (RMP). In ITER similar shaped (ISS) plasmas, with electron pedestal collisionalities matched to those expected in ITER a sharp resonant window in the safety factor at the 95 percent normalized poloidal flux surface is observed for ELM suppression at q{sub 95}=3.57 with a minimum width {delta}q{sub 95} of {+-}0.05. The size of this resonant window has been increased by a factor of 4 in ISS plasmas by increasing the magnitude of the current in an n=3 coil set along with the current in a separate n=1 coil set. The resonant ELM-suppression window is highly reproducible for a given plasma shape, coil configuration and coil current but can vary with other operating conditions such as {beta}{sub N}. Isolated resonant windows have also been found at other q95 values when using different RMP coil configurations. For example, when the I-coil is operated in an n=3 up-down asymmetric configuration rather than an up-down symmetric configuration a resonant window is found near q{sub 95}=7.4. A Fourier analysis of the applied vacuum magnetic field demonstrates a statistical correlation between the Chirikov island overlap parameter and ELM suppression. These results have been used as a guide for RMP coil design studies in various ITER operating scenarios.

  18. Pedestal and Transport Properties of Steady-state I-mode Plasmas over Expanded Operational Space in Alcator C-Mod

    NASA Astrophysics Data System (ADS)

    Marmar, Earl

    2011-10-01

    I-mode operation on Alcator C-Mod combines a strong edge thermal transport barrier with L-mode levels of particle and impurity transport, allowing access to very high performance discharges with low pedestal collisionality and central temperatures up to 8 keV, and without large ELMs or other intermittent edge instabilities. In recent campaigns, C-Mod I-modes have been extended to quasi-steady-state, with access in both favorable and unfavorable ion drift directions and typical normalized energy confinement quality factor H98 ~ 1.0 to 1.2. Adding ICRF mode-conversion flow-drive enhances toroidal flow shear near the plasma edge and confinement is further enhanced. I-mode has been maintained with input power up to nearly 2x the I-mode threshold power, with the largest accessible range in closed divertor geometry at modest triangularity. Simple extrapolations at fixed field imply that ITER in unfavorable drift could access I-mode with available power, and stay in I-mode with alpha-dominant heating. Detailed pedestal fluctuation measurements reveal changes in the turbulence, with decreases in the power at some frequencies and size scales, and growth of a weakly coherent mode (WCM) (kθ ~ 1.5 cm-1, δf/f ~.3) which propagates in the electron diamagnetic direction in the plasma frame. The WCM, which has density, temperature and magnetic signatures, appears to play a key role in pedestal density and impurity regulation, and detailed experimental results and associated modeling are presented. The distribution of divertor exhaust power depends on ion drift direction; new measurements of I-mode heat flux footprints on the outer divertor are compared with those in H-mode. Pedestal stability analyses will be shown for I-modes, including some which exhibited small ELMs. Supported by USDOE Award DE-FC02-99-ER54512.

  19. Semi-guiding high-aspect-ratio core (SHARC) fiber providing single-mode operation and an ultra-large core area in a compact coilable package.

    PubMed

    Rockwell, David A; Shkunov, Vladimir V; Marciante, John R

    2011-07-18

    A new class of optical fiber is presented that departs from the circular-core symmetry common to conventional fibers. By using a high-aspect-ratio (~30:1) rectangular core, the mode area can be significantly expanded well beyond 10,000 μm2. Moreover, by also specifying a very small refractive-index step at the narrow core edges, the core becomes "semi-guiding," i.e. it guides in the narrow dimension and is effectively un-guiding in the wide mm-scale dimension. The mode dependence of the resulting Fresnel leakage loss in the wide dimension strongly favors the fundamental mode, promoting single-mode operation. Since the modal loss ratios are independent of mode area, this core structure offers nearly unlimited scalability. The implications of using such a fiber in fiber laser and amplifier systems are also discussed. PMID:21934837

  20. A Large Signal Model for CMUT Arrays with Arbitrary Membrane Geometries Operating in Non-Collapsed Mode

    PubMed Central

    Satir, Sarp; Zahorian, Jaime; Degertekin, F. Levent

    2014-01-01

    A large signal, transient model has been developed to predict the output characteristics of a CMUT array operated in the non-collapse mode. The model is based on separation of the nonlinear electrostatic voltage-to-force relation and the linear acoustic array response. For linear acoustic radiation and crosstalk effects, the boundary element method is used. The stiffness matrix in the vibroacoustics calculations is obtained using static finite element analysis of a single membrane which can have arbitrary geometry and boundary conditions. A lumped modeling approach is used to reduce the order of the system for modeling the transient nonlinear electrostatic actuation. To accurately capture the dynamics of the non-uniform electrostatic force distribution over the CMUT electrode during large deflections, the membrane electrode is divided into patches shaped to match higher order membrane modes, each introducing a variable to the system model. This reduced order nonlinear lumped model is solved in the time domain using Simulink. The model has two linear blocks to calculate the displacement profile of the electrode patches and the output pressure for a given force distribution over the array, respectively. The force to array displacement block uses the linear acoustic model, and the Rayleigh integral is evaluated to calculate the pressure at any field point. Using the model, the transient transmitted pressure can be simulated for different large signal drive signal configurations. The acoustic model is verified by comparison to harmonic FEA in vacuum and fluid for high and low aspect ratio membranes as well as mass-loaded membranes. The overall Simulink model is verified by comparison to transient 3D FEA and experimental results for different large drive signals; and an example for a phased array simulation is given. PMID:24158297

  1. Comparison of emissions from on-road sources using a mobile laboratory under various driving and operational sampling modes

    NASA Astrophysics Data System (ADS)

    Zavala, M.; Herndon, S. C.; Wood, E. C.; Jayne, J. T.; Nelson, D. D.; Trimborn, A. M.; Dunlea, E.; Knighton, W. B.; Mendoza, A.; Allen, D. T.; Kolb, C. E.; Molina, M. J.; Molina, L. T.

    2009-01-01

    Mobile sources produce a significant fraction of the total anthropogenic emissions burden in large cities and have harmful effects on air quality at multiple spatial scales. Mobile emissions are intrinsically difficult to estimate due to the large number of parameters affecting the emissions variability within and across vehicles types. The MCMA-2003 Campaign in Mexico City has showed the utility of using a mobile laboratory to sample and characterize specific classes of motor vehicles to better quantify their emissions characteristics as a function of their driving cycles. The technique clearly identifies "high emitter" vehicles via individual exhaust plumes, and also provides fleet average emission rates. We have applied this technique to Mexicali during the Border Ozone Reduction and Air Quality Improvement Program (BORAQIP) for the Mexicali-Imperial Valley in 2005. We analyze the variability of measured emission ratios for emitted NOx, CO, specific VOCs, NH3, and some primary fine particle components and properties by deploying a mobile laboratory in roadside stationary sampling, chase and fleet average operational sampling modes. The measurements reflect various driving modes characteristic of the urban fleets. The observed variability for all measured gases and particle emission ratios is greater for the chase and roadside stationary sampling than for fleet average measurements. The fleet average sampling mode captured the effects of traffic conditions on the measured on-road emission ratios, allowing the use of fuel-based emission ratios to assess the validity of traditional "bottom-up" emissions inventories. Using the measured on-road emission ratios, we estimate CO and NOx mobile emissions of 175±62 and 10.4±1.3 metric tons/day, respectively, for the gasoline vehicle fleet in Mexicali. Comparisons with similar on-road emissions data from Mexico City indicated that fleet average NO emission ratios were around 20% higher in Mexicali than in Mexico City

  2. Comparison of emission ratios from on-road sources using a mobile laboratory under various driving and operational sampling modes

    NASA Astrophysics Data System (ADS)

    Zavala, M.; Herndon, S. C.; Wood, E. C.

    2008-04-01

    Mobile sources produce a significant fraction of the total anthropogenic emissions burden in large cities and have harmful effects on air quality at multiple spatial scales. Mobile emissions are intrinsically difficult to estimate due to the large number of parameters affecting the emissions variability within and across vehicles types. The MCMA-2003 Campaign in Mexico City has showed the utility of using a mobile laboratory to sample and characterize specific classes of motor vehicles to better quantify their emissions characteristics as a function of their driving cycles. The technique clearly identifies "high emitter" vehicles via individual exhaust plumes, and also provides fleet average emission rates. We have applied this technique to Mexicali during the Border Ozone Reduction and Air Quality Improvement Program for the Mexicali-Imperial Valley in 2005. In this paper we analyze the variability of measured emission ratios for emitted NOx, CO, specific VOCs, NH3, and some primary fine particle components and properties obtained during the Border Ozone Reduction and Air Quality Improvement Program for the Mexicali-Imperial Valley in 2005 by deploying a mobile laboratory in roadside stationary sampling, chase and fleet average operational sampling modes. The measurements reflect various driving modes characteristic of the urban fleets. The observed variability for all measured gases and particle emission ratios is greater for the chase and roadside stationary sampling than for fleet average measurements. The fleet average sampling mode captured the effects of traffic conditions on the measured on-road emission ratios, allowing the use of fuel-based emission ratios to assess the validity of traditional "bottom-up" emissions inventories. Using the measured on-road emission ratios, we estimate CO and NOx mobile emissions of 175±62 and 10.4±1.3 metric tons/day, respectively, for the gasoline vehicle fleet in Mexicali. Comparisons with similar on-road emissions data

  3. Performance of computer-designed small-sized four-stage depressed collector for operation of dual-mode traveling wave tube

    NASA Technical Reports Server (NTRS)

    Ramins, P.; Fox, T. A.

    1981-01-01

    A computer-designed axisymmetric 2.4-cm-diameter four-stage depressed collectors was evaluated in conjunction with an octave bandwidth, dual-mode traveling wave tube (TWT). The TWT was operated over a wide range of conditions to simulate different applications. The collector performance was optimized (within the constraint of fixed collector geometry which was designed for operation of the TWT at saturation) over the range of TWT operating conditons covered. For operation of the dual-mode TWT at saturation, average collector efficiencies of 81 1/2 and 82 percent for the high and low modes, respectively, were obtained across an octave bandwidth, leading to a three-fold increase in the TWT overall efficiency. For operation of the TWT in the linear, low distortion range, collector efficiencies of 87 to 92 percent were obtained, leading to TWT overall efficiencies as high as 35 percent. For operation of the dual-mode TWT over a 10 to 1 range in output power, overall efficiencies of 14 to 41 percent were obtained.

  4. Comparative analysis between overlapping and non-overlapping operation modes for the PWM buck converter using the three-state switching cell

    NASA Astrophysics Data System (ADS)

    Robles Balestero, Juan Paulo; Lessa Tofoli, Fernando; Mendes de Seixas, Claudiner; Torrico Bascopé, Grover Victor; José Mendes de Seixas, Falcondes

    2014-04-01

    This article presents a comparative study involving a buck converter derived from the three-state switching cell in both operation modes, i.e. non-overlapping and overlapping modes, since it is well known in literature that several advantages can be addressed to topologies based on this approach. In the case of the mentioned converter, only part of the load delivered to the load flows through the controlled switches, so that operation at high-current high-power levels is possible. Besides, the design of reactive elements such as very autotransformer and filter inductor is performed for twice the switching frequency, with consequent reduction of size, weight and volume. Another clear advantage is that the area for which the converter operates in continuous conduction mode is wider than that for the discontinuous conduction mode in comparison with the so-called classical non-isolated buck converter. The operation of the converter, which was previously proposed in literature, is analysed considering the aforementioned modes in terms of the efficiency, and similar approaches for the non-isolated dc-dc conversion are also investigated.

  5. Advanced LSI-based amperometric sensor array with light-shielding structure for effective removal of photocurrent and mode selectable function for individual operation of 400 electrodes.

    PubMed

    Inoue, Kumi Y; Matsudaira, Masahki; Nakano, Masanori; Ino, Kosuke; Sakamoto, Chika; Kanno, Yusuke; Kubo, Reyushi; Kunikata, Ryota; Kira, Atsushi; Suda, Atsushi; Tsurumi, Ryota; Shioya, Toshihito; Yoshida, Shinya; Muroyama, Masanori; Ishikawa, Tomohiro; Shiku, Hitoshi; Satoh, Shiro; Esashi, Masayoshi; Matsue, Tomokazu

    2015-02-01

    We have developed a large-scale integrated (LSI) complementary metal-oxide semiconductor (CMOS)-based amperometric sensor array system called "Bio-LSI" as a platform for electrochemical bio-imaging and multi-point biosensing with 400 measurement points. In this study, we newly developed a Bio-LSI chip with a light-shield structure and a mode-selectable function with the aim of extending the application range of Bio-LSI. The light shield created by the top metal layer of the LSI chip significantly reduces the noise generated by the photocurrent, whose value is less than 1% of the previous Bio-LSI without the light shield. The mode-selectable function enables the individual operation of 400 electrodes in off, electrometer, V1, and V2 mode. The off-mode cuts the electrode from the electric circuit. The electrometer-mode reads out the electrode potential. The V1-mode and the V2-mode set the selected sensor electrode at two different independent voltages and read out the current. We demonstrated the usefulness of the mode-selectable function. First, we displayed a dot picture based on the redox reactions of 2.0 mM ferrocenemethanol at 400 electrodes by applying two different independent voltages using the V1 and V2 modes. Second, we carried out a simultaneous detection of O2 and H2O2 using the V1 and V2 modes. Third, we used the off and V1 modes for the modification of the osmium-polyvinylpyridine gel polymer containing horseradish peroxidase (Os-HRP) at the selected electrodes, which act as sensors for H2O2. These results confirm that the advanced version of Bio-LSI is a promising tool that can be applied to a wide range of analytical fields.

  6. Dimensionless Model of a Thermoelectric Cooling Device Operating at Real Heat Transfer Conditions: Maximum Cooling Capacity Mode

    NASA Astrophysics Data System (ADS)

    Melnikov, A. A.; Kostishin, V. G.; Alenkov, V. V.

    2016-09-01

    Real operating conditions of a thermoelectric cooling device are in the presence of thermal resistances between thermoelectric material and a heat medium or cooling object. They limit performance of a device and should be considered when modeling. Here we propose a dimensionless mathematical steady state model, which takes them into account. Analytical equations for dimensionless cooling capacity, voltage, and coefficient of performance (COP) depending on dimensionless current are given. For improved accuracy a device can be modeled with use of numerical or combined analytical-numerical methods. The results of modeling are in acceptable accordance with experimental results. The case of zero temperature difference between hot and cold heat mediums at which the maximum cooling capacity mode appears is considered in detail. Optimal device parameters for maximal cooling capacity, such as fraction of thermal conductance on the cold side y, fraction of current relative to maximal j' are estimated in range of 0.38-0.44 and 0.48-0.95, respectively, for dimensionless conductance K' = 5-100. Also, a method for determination of thermal resistances of a thermoelectric cooling system is proposed.

  7. Liquid Microjunction Surface Sampling Probe Fluid Dynamics: Characterization and Application of an Analyte Plug Formation Operational Mode

    SciTech Connect

    ElNaggar, Mariam S; Van Berkel, Gary J

    2011-01-01

    The recently discovered sample plug formation and injection operational mode of a continuous flow, coaxial tube geometry, liquid microjunction surface sampling probe (LMJ-SSP) (J. Am. Soc. Mass Spectrom, 2011) was further characterized and applied for concentration and mixing of analyte extracted from multiple areas on a surface and for nanoliter-scale chemical reactions of sampled material. A transparent LMJ-SSP was constructed and colored analytes were used so that the surface sampling process, plug formation, and the chemical reactions could be visually monitored at the sampling end of the probe before being analyzed by mass spectrometry of the injected sample plug. Injection plug peak widths were consistent for plug hold times as long as the 8 minute maximum attempted (RSD below 1.5%). Furthermore, integrated injection peak signals were not significantly different for the range of hold times investigated. The ability to extract and completely mix individual samples within a fixed volume at the sampling end of the probe was demonstrated and a linear mass spectral response to the number of equivalent analyte spots sampled was observed. Using the color and mass changing chemical reduction of the redox dye 2,6-dichlorophenol-indophenol with ascorbic acid, the ability to sample, concentrate, and efficiently run reactions within the same plug volume within the probe was demonstrated.

  8. Liquid Microjunction Surface Sampling Probe Fluid Dynamics: Characterization and Application of an Analyte Plug Formation Operational Mode

    NASA Astrophysics Data System (ADS)

    Elnaggar, Mariam S.; van Berkel, Gary J.

    2011-10-01

    The recently discovered sample plug formation and injection operational mode of a continuous flow, coaxial tube geometry, liquid microjunction surface sampling probe (LMJ-SSP) was further characterized and applied for concentration and mixing of analyte extracted from multiple areas on a surface and for nanoliter-scale chemical reactions of sampled material. A transparent LMJ-SSP was constructed and colored analytes were used so that the surface sampling process, plug formation, and the chemical reactions could be visually monitored at the sampling end of the probe before being analyzed by mass spectrometry of the injected sample plug. Injection plug peak widths were consistent for plug hold times as long as the 8 min maximum attempted (RSD below 1.5%). Furthermore, integrated injection peak signals were not significantly different for the range of hold times investigated. The ability to extract and completely mix individual samples within a fixed volume at the sampling end of the probe was demonstrated and a linear mass spectral response to the number of equivalent analyte spots sampled was observed. Using the color and mass changing chemical reduction of the redox dye 2,6-dichlorophenol-indophenol with ascorbic acid, the ability to sample, concentrate, and efficiently run reactions within the same plug volume within the probe was demonstrated.

  9. Detectors for alpha particles and X-rays operating in ambient air in pulse counting mode or/and with gas amplification

    NASA Astrophysics Data System (ADS)

    Charpak, G.; Benaben, P.; Breuil, P.; Peskov, V.

    2008-02-01

    Ionization chambers working in ambient air in current detection mode are attractive due to their simplicity and low cost and are widely used in several applications such as smoke detection, dosimetry, therapeutic beam monitoring and so on. The aim of this work was to investigate if gaseous detectors can operate in ambient air in pulse counting mode as well as with gas amplification which potentially offers the highest possible sensitivity in applications like alpha particle detection or high energy X-ray photon or electron detection. To investigate the feasibility of this method two types of open- end gaseous detectors were build and successfully tested. The first one was a single wire or multiwire cylindrical geometry detector operating in pulse mode at a gas gain of one (pulse ionization chamber). This detector was readout by a custom made wide -band charge sensitive amplifier able to deal with slow induced signals generated by slow motion of negative and positive ions. The multiwire detector was able to detect alpha particles with an efficiency close to 22%. The second type of an alpha detector was an innovative GEM-like detector with resistive electrodes operating in air in avalanche mode at high gas gains (up to 104). This detector can also operate in a cascaded mode or being combined with other detectors, for example with MICROMEGAS. This detector was readout by a conventional charge -sensitive amplifier and was able to detect alpha particles with 100% efficiency. This detector could also detect X-ray photons or fast electrons. A detailed comparison between these two detectors is given as well as a comparison with commercially available alpha detectors. The main advantages of gaseous detectors operating in air in a pulse detection mode are their simplicity, low cost and high sensitivity. One of the possible applications of these new detectors is alpha particle background monitors which, due to their low cost can find wide application not only in houses, but

  10. Direct ion speciation analysis with ion-selective membranes operated in a sequential potentiometric/time resolved chronopotentiometric sensing mode.

    PubMed

    Ghahraman Afshar, Majid; Crespo, Gastón A; Bakker, Eric

    2012-10-16

    Ion-selective membranes based on porous polypropylene membranes doped with an ionophore and a lipophilic cation-exchanger are used here in a new tandem measurement mode that combines dynamic electrochemistry and zero current potentiometry into a single protocol. Open circuit potential measurements yield near-nernstian response slopes in complete analogy to established ion-selective electrode methodology. Such measurements are well established to give direct information on the so-called free ion concentration (strictly, activity) in the sample. The same membrane is here also operated in a constant current mode, in which the localized ion depletion at a transition time is visualized by chronopotentiometry. This dynamic electrochemistry methodology gives information on the labile ion concentration in the sample. The sequential protocol is established on potassium and calcium ion-selective membranes. An increase of the ionophore concentration in the membrane to 180 mM makes it possible to determine calcium concentrations as high as 3 mM by chronopotentiometry, thereby making it possible to directly detect total calcium in undiluted blood samples. Recovery times after current perturbation depend on the current amplitude but can be kept to below 1 min for the polypropylene based ion-selective membranes studied here. Plasticized PVC as membrane material is less suited for this protocol, especially when the measurement at elevated concentrations is desired. An analysis of current amplitudes, transition times, and concentrations shows that the data are described by the Sand equation and that migration effects are insignificant. A numerical model describes the experimental findings with good agreement and gives guidance on the required selectivity in order to observe a well-resolved transition time and on the expected errors due to insufficient selectivity. The simulations suggest that the methodology compares well to that of open circuit potentiometry, despite giving

  11. Dual-wavelength synchronous operation of a mode-locked 2-μm Tm:CaYAlO4 laser.

    PubMed

    Kong, L C; Qin, Z P; Xie, G Q; Xu, X D; Xu, J; Yuan, P; Qian, L J

    2015-02-01

    We experimentally demonstrated dual-wavelength synchronous operation of a high-power passively mode-locked 2-μm Tm:CaYAlO4 (Tm:CYA) disordered crystal laser with semiconductor saturable absorber mirror (SESAM) as mode locker. The mode-locked laser emitted an average output power as high as 830 mW with pulse duration of 35.3 ps and repetition rate of 145.4 MHz. The mode-locking dual wavelengths were centered at 1958.9 nm and 1960.6 nm, respectively. Autocorrelation trace clearly shows beating pulses with pulse width of 3.5 ps and repetition rate of 0.13 THz. PMID:25680046

  12. Formal operational reasoning modes: Predictors of critical thinking abilities and grades assigned by teachers in science and mathematics for students in grades nine through twelve

    NASA Astrophysics Data System (ADS)

    Bitner, Betty L.

    To test the hypothesis that formal operational reasoning modes are predictors of critical thinking abilities and grades assigned by teachers in science and mathematics, in September 1986 the Group Assessment of Logical Thinking (GALT) and in December 1986 the Watson-Glaser Critical Thinking Appraisal (WGCTA) were administered to 101 rural students in Grades 9 through 12. The grades assigned by teachers were collected in May 1987. Construct and criterion-related validities and internal-consistency reliability using Cronbach's alpha method were established on the GALT. On the WGCTA, content and construct validities and internal consistency reliability using the split-half procedure, coefficient of stability, and coefficient of equivalence were established. The five formal operational reasoning modes in the GALT were found to be significant predictors of critical thinking abilities and grades assigned by teachers in science and mathematics. The variance in the five critical thinking abilities attributable to the five formal operational reasoning modes ranged between 28% and 70%. The five formal operational reasoning modes explained 29% of the variance in mathematics achievement and 62% of the variance in science achievement.

  13. Linear Mode Photon Counting LADAR Camera Development for the Ultra-Sensitive Detector Program

    NASA Astrophysics Data System (ADS)

    Jack, M.; Bailey, S.; Edwards, J.; Burkholder, R.; Liu, K.; Asbrock, J.; Randall, V.; Chapman, G.; Riker, J.

    Advanced LADAR receivers enable high accuracy identification of targets at ranges beyond standard EOIR sensors. Increased sensitivity of these receivers will enable reductions in laser power, hence more affordable, smaller sensors as well as much longer range of detection. Raytheon has made a recent breakthrough in LADAR architecture by combining very low noise ~ 30 electron front end amplifiers with moderate gain >60 Avalanche Photodiodes. The combination of these enables detection of laser pulse returns containing as few as one photon up to 1000s of photons. Because a lower APD gain is utilized the sensor operation differs dramatically from traditional "geiger mode APD" LADARs. Linear mode photon counting LADAR offers advantages including: determination of intensity as well as time of arrival, nanosecond recovery times and discrimination between radiation events and signals. In our talk we will review the basic amplifier and APD component performance, the front end architecture, the demonstration of single photon detection using a simple 4 x 4 SCA and the design of a fully integrated photon counting camera under development in support of the Ultra-Sensitive Detector (USD) program sponsored by the Air Force Research Laboratory at Kirtland AFB, NM. Work Supported in Part by AFRL - Contract # FA8632-05-C-2454 Dr. Jim Riker Program Manager.

  14. The Middeck 0-gravity Dynamics Experiment (MODE)

    NASA Technical Reports Server (NTRS)

    Crawley, Edward F.; Deluis, Javier

    1992-01-01

    Viewgraphs on the middeck 0-gravity dynamics experiment (MODE) are presented. Topics covered include: MODE flight hardware elements; MODE science objectives; MODE team; flight operations; and summary.

  15. Thermally accelerated life testing of single mode, double-heterostructure, AlGaAs laser diodes operated pulsed at 50 mW peak power

    SciTech Connect

    Barry, J.D.; Archambeault, W.J.; Dye, R.A.; Einhorn, A.J.; Mecherle, G.S.; Nelson, P.

    1985-04-01

    Single spatial mode, double-heterostructure, channel-substrate-planar AlGaAs laser diodes have been life tested under thermally accelerated conditions to characterize the reliability of the diodes in a digital, optical communication system intended for space application. The diodes were operated pulsed under constant drive current conditions at 50 mW peak power, 25 ns pulse width, and 1 percent duty cycle in a dry, inert environment at ambient test temperatures at 40, 55, and 70/sup 0/C. Diode performance parameters as related to the space application, such as pulsewidth, peak power, wavelength spectrum, spatial mode, and threshold current, were periodically monitored. Tests have continued for over 14 000 h. The test results for all diodes with failure defined by power degradation alone is compared to the test results for single mode diodes with failure defined by power degradation, wavelength shift and spatial mode changes. It is found that the life test results are substantially equivalent but differ from earlier published reports for laser diodes operated CW. An activation energy of about 0.39 eV is deduced with a predicted median life of about 5 X 10/sup 4/ h at 20/sup 0/C. These values are somewhat lower than those found for diodes operated CW and are attributed to the use of single mode laser diodes here. It is concluded that thermally accelerated life testing for single spatial mode laser diodes must incorporate a means to separate bulk material, current, and optical density induced degradation effects. A test scheme is proposed.

  16. An analysis of the binding of repressor protein ModE to modABCD (molybdate transport) operator/promoter DNA of Escherichia coli.

    PubMed

    Grunden, A M; Self, W T; Villain, M; Blalock, J E; Shanmugam, K T

    1999-08-20

    Expression of the modABCD operon in Escherichia coli, which codes for a molybdate-specific transporter, is repressed by ModE in vivo in a molybdate-dependent fashion. In vitro DNase I-footprinting experiments identified three distinct regions of protection by ModE-molybdate on the modA operator/promoter DNA, GTTATATT (-15 to -8; region 1), GCCTACAT (-4 to +4; region 2), and GTTACAT (+8 to +14; region 3). Within the three regions of the protected DNA, a pentamer sequence, TAYAT (Y = C or T), can be identified. DNA-electrophoretic mobility experiments showed that the protected regions 1 and 2 are essential for binding of ModE-molybdate to DNA, whereas the protected region 3 increases the affinity of the DNA to the repressor. The stoichiometry of this interaction was found to be two ModE-molybdate per modA operator DNA. ModE-molybdate at 5 nM completely protected the modABCD operator/promoter DNA from DNase I-catalyzed hydrolysis, whereas ModE alone failed to protect the DNA even at 100 nM. The apparent K(d) for the interaction between the modA operator DNA and ModE-molybdate was 0.3 nM, and the K(d) increased to 8 nM in the absence of molybdate. Among the various oxyanions tested, only tungstate replaced molybdate in the repression of modA by ModE, but the affinity of ModE-tungstate for modABCD operator DNA was 6 times lower than with ModE-molybdate. A mutant ModE(T125I) protein, which repressed modA-lac even in the absence of molybdate, protected the same region of modA operator DNA in the absence of molybdate. The apparent K(d) for the interaction between modA operator DNA and ModE(T125I) was 3 nM in the presence of molybdate and 4 nM without molybdate. The binding of molybdate to ModE resulted in a decrease in fluorescence emission, indicating a conformational change of the protein upon molybdate binding. The fluorescence emission spectra of mutant ModE proteins, ModE(T125I) and ModE(Q216*), were unaffected by molybdate. The molybdate-independent mutant ModE

  17. High speed flux feedback for tuning a universal field oriented controller capable of operating in direct and indirect field orientation modes

    DOEpatents

    De Doncker, Rik W. A. A.

    1992-01-01

    The direct (d) and quadrature (q) components of flux, as sensed by flux sensors or determined from voltage and current measurements in a direct field orientation scheme, are processed rapidly and accurately to provide flux amplitude and angular position values for use by the vector rotator of a universal field-oriented (UFO) controller. Flux amplitude (linear or squared) is provided as feedback to tune the UFO controller for operation in direct and indirect field orientation modes and enables smooth transitions from one mode to the other.

  18. High speed flux feedback for tuning a universal field oriented controller capable of operating in direct and indirect field orientation modes

    DOEpatents

    De Doncker, R.W.A.A.

    1992-09-01

    The direct (d) and quadrature (q) components of flux, as sensed by flux sensors or determined from voltage and current measurements in a direct field orientation scheme, are processed rapidly and accurately to provide flux amplitude and angular position values for use by the vector rotator of a universal field-oriented (UFO) controller. Flux amplitude (linear or squared) is provided as feedback to tune the UFO controller for operation in direct and indirect field orientation modes and enables smooth transitions from one mode to the other. 3 figs.

  19. Broadband wavelength tunable mode-locked thulium-doped fiber laser operating in the 2 μm region by using a graphene saturable absorber on microfiber

    NASA Astrophysics Data System (ADS)

    Yang, Guang; Liu, Yan-ge; Wang, Zhi; Lou, Jiachang; Wang, Zhenhong; Liu, Zhibo

    2016-06-01

    A broadband wavelength tunable mode-locked Tm3+-doped fiber laser operating in the 2 μm region based on a graphene saturable absorber is experimentally investigated. A section of graphene film is transferred on a microfiber, which allows light-graphene interaction via evanescent field. The microfiber based graphene not only acts as an excellent saturable absorber for mode-locking, but also induces a polarizing effect to form an artificial birefringent filter for wavelength selection. By tuning the polarization states in the laser cavity, the laser exhibits tunable wavelength mode-locked pulses over a wide range from 1880 to 1940 nm. Such a system provides a compact, user friendly and low cost wavelength tunable ultrashort pulse source in the 2 μm region.

  20. Towards low timing phase noise operation in fiber lasers mode locked by graphene oxide and carbon nanotubes at 1.5 µm.

    PubMed

    Wu, Kan; Li, Xiaohui; Wang, Yonggang; Wang, Qi Jie; Shum, Perry Ping; Chen, Jianping

    2015-01-12

    We investigate the timing phase noise of fiber lasers mode locked by graphene oxide (GO) and carbon nanotubes (CNTs), respectively, integrated in a linear cavity fiber laser in the reflecting operation. Due to the shorter decay time of the GO and CNTs, weaker slow saturable absorber effects are expected and mode-locked lasers based on these two saturable absorbers exhibit low excess timing phase noise coupled from the laser intensity noise. Compared with a reference laser mode locked by semiconductor saturable absorber mirror (SESAM), GO based laser obtains a timing phase noise reduction of 7 dB at 1 kHz and a timing jitter reduction of 45% experimentally whereas CNTs based laser obtains a timing phase noise reduction of 3 dB and a timing jitter reduction of 29%. This finding suggests that saturable absorbers with short decay time have the potential for achieving mode locking operation with low timing phase noise, which is important for applications including frequency metrology, high-precision optical sampling, clock distribution and optical sensing.

  1. All-fiber passively mode-locked Tm-doped NOLM-based oscillator operating at 2-μm in both soliton and noisy-pulse regimes.

    PubMed

    Li, Jianfeng; Zhang, Zuxing; Sun, Zhongyuan; Luo, Hongyu; Liu, Yong; Yan, Zhijun; Mou, Chengbo; Zhang, Lin; Turitsyn, Sergei K

    2014-04-01

    A self-starting all-fiber passively mode-locked Tm(3+)-doped fiber laser based on nonlinear loop mirror (NOLM) is demonstrated. Stable soliton pulses centered at 2017.33 nm with 1.56 nm FWHM were produced at a repetition rate of 1.514 MHz with pulse duration of 2.8 ps and pulse energy of 83.8 pJ. As increased pump power, the oscillator can also operate at noise-like (NL) regime. Stable NL pulses with coherence spike width of 341 fs and pulse energy of up to 249.32 nJ was achieved at a center wavelength of 2017.24 nm with 21.33 nm FWHM. To the best of our knowledge, this is the first 2 µm region NOLM-based mode-locked fiber laser operating at two regimes with the highest single pulse energy for NL pulses. PMID:24718163

  2. Thermal instability explanation of similar density limits in gas fueled, DIII-D H-mode shots with different operating conditions

    NASA Astrophysics Data System (ADS)

    Stacey, W. M.; Petrie, T. W.; Leonard, A. W.

    2002-03-01

    Recent experiments on DIII-D [J. L. Luxon, F. Batty, C. Baxi et al., Plasma Physics and Controlled Nuclear Fusion Research 1986 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159] examined the effect of different operating conditions ("open" and "closed" divertor geometry, active pumping, fueling location) on the maximum achievable density in gas fueled H-mode (high confinement mode) discharges. Several phenomena observed at these higher densities (≈0.8 the Greenwald density)—degradation in energy confinement, detachment of the core plasma from the divertor plate, multifaceted asymmetric radiation from edge formation—are found to be correlated with the predicted onset of various thermal instabilities in the plasma edge or divertor regions. The similarity of the maximum achievable densities under the different operating conditions can be related to a similarity of edge thermal instability characteristics.

  3. On-chip waveguide isolator based on bismuth iron garnet operating via nonreciprocal single-mode cutoff.

    PubMed

    Drezdzon, Samuel M; Yoshie, Tomoyuki

    2009-05-25

    We analyze an on-chip optical isolator based on direction dependent single-mode cutoff, which is described in 1D and 2D momentum space. Isolation is shown using 3D finite difference time domain (FDTD) where the magnetization is represented by imaginary off-diagonal permittivity tensor elements. The isolator designs are optimized using perturbation theory, which successfully predicts increased isolation for rib waveguides and structures with non-magnetic dielectric layers. Our isolators are based on bismuth iron garnet and its compatible substrates; an isolation ratio of 10.7 dB/mm is achieved for TM modes.

  4. Design of energy-storage reactors for single-winding constant-frequency dc-to-dc converters operating in the discontinuous-reactor-current mode

    NASA Technical Reports Server (NTRS)

    Chen, D. Y.; Owen, H. A., Jr.; Wilson, T. G.

    1980-01-01

    This paper presents an algorithm and equations for designing the energy-storage reactor for dc-to-dc converters which are constrained to operate in the discontinuous-reactor-current mode. This design procedure applied to the three widely used single-winding configurations: the voltage step-up, the current step-up, and the voltage-or-current step-up converters. A numerical design example is given to illustrate the use of the design algorithm and design equations.

  5. Kraus Operator-Sum Solution to the Master Equation Describing the Single-Mode Cavity Driven by an Oscillating External Field in the Heat Reservoir

    NASA Astrophysics Data System (ADS)

    Meng, Xiang-Guo; Wang, Ji-Suo; Gao, Hua-Chao

    2016-08-01

    Exploiting the thermo entangled state approach, we successfully solve the master equation for describing the single-mode cavity driven by an oscillating external field in the heat reservoir and then get the analytical time-evolution rule for the density operator in the infinitive Kraus operator-sum representation. It is worth noting that the Kraus operator M l, m is proved to be a trace-preserving quantum operation. As an application, the time-evolution for an initial coherent state ρ | β> = | β>< β| in such an environment is investigated, which shows that the initial coherent state decays to a new mixed state as a result of thermal noise, however the coherence can still be reserved for amplitude damping.

  6. Many small consumers, one growing problem: Achieving energy savings for electronic equipment operating in low power modes

    SciTech Connect

    Payne, Christopher T.; Meier, Alan K.

    2004-08-24

    An increasing amount of electricity is used by equipment that is neither fully ''on'' nor fully ''off.'' We call these equipment states low power modes, or ''lopomos.'' ''Standby'' and ''sleep'' are the most familiar lopomos, but some new products already have many modes. Lopomos are becoming common in household appliances, safety equipment, and miscellaneous products. Ross and Meier (2000) reports that several international studies have found standby power to be as much as 10 percent of residential energy consumption. Lopomo energy consumption is likely to continue growing rapidly as products with lopomos that use significant amounts of energy penetrate the market. Other sectors such as commercial buildings and industry also have lopomo energy use, perhaps totaling more in aggregate than that of households, but no comprehensive measurements have been made. In this paper, we propose a research agenda for study of lopomo energy consumption. This agenda has been developed with input from over 200 interested parties. Overall, there is consensus that lopomo energy consumption is an important area for research. Many see this as a critical time for addressing lopomo issues. As equipment designs move from the binary ''on/off'' paradigm to one that encompasses multiple power modes, there is a unique opportunity to address the issue of low power mode energy consumption while technology development paths are still flexible.

  7. Potential of chiral anion-exchangers operated in various subcritical fluid chromatography modes for resolution of chiral acids.

    PubMed

    Pell, Reinhard; Lindner, Wolfgang

    2012-07-01

    Anion-exchange-type chiral stationary phases (CSPs) derived from quinine or quinidine were applied in subcritical fluid chromatography (SFC) for the direct separation of chiral acidic compounds. Employing subcritical (sc) mobile phase modes (CO₂ + methanol as co-solvent and acids and bases as additives) first the influence of type and amount of acidic and basic additives on separation performance was investigated. Secondly, water was tested as a neutral additive and the influence of temperature variation on enantioselectivity was studied. Thirdly, we could chromatographically confirm that the often verbalized "inherent acidity" of sc CO₂ + methanol is manifested by the in situ formation of methylcarbonic acids in the sc mobile phase and thus functioning as acidic additive. Accordingly the dissociated methylcarbonic acid, acting as a counterion, enables an anion exchange mechanism between the cationic CSP and the corresponding acidic analyte. In the absence of a dissociable acid in the mobile phase such an ion exchange mode would not work following a stoichiometric displacement model. This finding is further corroborated by the use of ammonia in methanol as co-solvent thus generating in situ the ammonium salt of methylcarbonic acid. In summary, we report on ion-exchange mediated chromatographic separations in SFC modes by merely using (i) sc CO₂ and MeOH, (ii) sc CO₂ and ammonia in MeOH, and (iii) sc CO₂ and MeOH plus acids and bases as additives. Comparisons to HPLC mode have been undertaken to evaluate merits and limitations. This mode exhibits high potential for preparative chromatography of chiral acids combining pronounced enantioselectivity with high column loadability and avoiding possibly troublesome mobile phase additives, as the in situ formed methylcarbonic acid disintegrates to CO₂ and methanol upon pressure release.

  8. Dynamic operation of optical fibres beyond the single-mode regime facilitates the orientation of biological cells

    PubMed Central

    Kreysing, Moritz; Ott, Dino; Schmidberger, Michael J.; Otto, Oliver; Schürmann, Mirjam; Martín-Badosa, Estela; Whyte, Graeme; Guck, Jochen

    2014-01-01

    The classical purpose of optical fibres is delivery of either optical power, as for welding, or temporal information, as for telecommunication. Maximum performance in both cases is provided by the use of single-mode optical fibres. However, transmitting spatial information, which necessitates higher-order modes, is difficult because their dispersion relation leads to dephasing and a deterioration of the intensity distribution with propagation distance. Here we consciously exploit the fundamental cause of the beam deterioration—the dispersion relation of the underlying vectorial electromagnetic modes—by their selective excitation using adaptive optics. This allows us to produce output beams of high modal purity, which are well defined in three dimensions. The output beam distribution is even robust against significant bending of the fibre. The utility of this approach is exemplified by the controlled rotational manipulation of live cells in a dual-beam fibre-optical trap integrated into a modular lab-on-chip system. PMID:25410595

  9. Synchronized two-color operation of a passively mode-locked erbium-doped fiber laser by dual injection locking

    SciTech Connect

    Margalit, M.; Orenstein, M.; Eisenstein, G.

    1996-10-01

    The recently introduced harmonic injection locking is a method for generating pulse trains at high repetition rates from passively mode-locked lasers. We report the simultaneous injection locking of two spectral bands in an erbium-doped fiber laser by injection of two spectrally distinct and temporally synchronized pulse trains. The injection-locked laser simultaneously produced pulses at wavelengths of 1.53 and 1.55{mu}m, each at a 7.5-GHz repetition rate and with a pulse width of 10ps. We compared the experimental results with those of a previous model [G. Agrawal, {ital Nonlinear} {ital Fiber} {ital Optics} (Academic, San Diego, Calif., 1989)], using a recently introduced method for passively mode-locked laser simulation. {copyright} {ital 1996 Optical Society of America.}

  10. Shifts in Köppen-Geiger climate zones over southern Africa in relation to key global temperature goals

    NASA Astrophysics Data System (ADS)

    Engelbrecht, Christien J.; Engelbrecht, Francois A.

    2016-01-01

    Potential changes in Köppen-Geiger climate zones over southern Africa (Africa south of 22 °S) under future climate change are investigated using an ensemble of high-resolution projections of a regional climate model. The projections are performed under the A2 scenario of the Special Report on Emission Scenarios (SRES), and changes are presented for those times in the future when the increase in global average surface temperature reaches thresholds of 1, 2, and 3 °C, relative to the present-day baseline climatology. Widespread shifts in climate regimes are projected, of which the southern and eastern expansion of the hot desert and hot steppe zones is the most prominent. From occupying 33.1 and 19.4 % of southern Africa under present-day climate, these regions are projected to occupy between 47.3 and 59.7 % (hot desert zone) and 24.9 and 29.9 % (hot steppe zone) of the region in a future world where the global temperature has increased by 3 °C. The cold desert and cold steppe zones are projected to decrease correspondingly. The temperate regions of eastern South Africa, the Cape south coast, and winter rainfall region of the southwestern Cape are also projected to contract. An expansion of the hot steppe zone into the cold steppe and temperate zones may favor the intrusion of trees (and therefore the savanna biome) into the most pristine grasslands of southern Africa. However, the correlative climate-vegetation approach of using projected changes in Köppen-Geiger zones to infer future vegetation patterns is of limited value in the savanna complex of southern Africa, where complex feedbacks occur between carbon dioxide (CO2) concentrations, trees, C4 grasses, fire, and climate. The present-day temperate Cape Fynbos regime may come under increasing pressure as the encompassing temperate zone is invaded mainly from the east by the hot steppe climate regime under climate change, with the incidence of Fynbos fires also becoming more likely in a generally warmer and

  11. Mode-locking operation of quasi-continuous diode pumped TGT-grown Nd,Y-codoped:SrF2 crystal

    NASA Astrophysics Data System (ADS)

    Jelínek, Michal; Kubeček, Václav; Su, Liangbi; Jiang, Dapeng; Ma, Fengkai; Zhang, Qian; Cao, Yuexin; Xu, Jun

    2015-01-01

    Fluoride-type crystals (CaF2, SrF2) doped with neodymium Nd3+ present interesting alternative as a laser active media for the diode-pumped mode-locked laser systems mainly because of their broad emission spectra as well as longer fluorescence lifetime in comparison with well-known materials as Nd:YAG or Nd:YVO4. In comparison with Nd:glass active material, SrF2 and CaF2 have better thermal conductivity. In spite of the thermal conductivity decreases with doping concentration, these crystal might be interesting alternative for the Nd:glass mode-locked laser systems. In this contribution we present the first results of the Nd,Y:SrF2 mode-locked laser diode-pumped at 796nm. Mode-locking operation using SESAM was successfully achieved in the pulsed pumping regime (pulse-duration 1.5 ms, frequency 10 Hz) with the overall average output power of 2.3 mW (corresponding to the power amplitude of 153 mW) in one output beam at the wavelength of ~1055 nm. The actual pulse-duration was 87 ps.

  12. Measuring atmospheric dispersion with WLRS in multiple wavelength mode

    NASA Technical Reports Server (NTRS)

    Schreiber, Ulrich; Haufe, K. H.; Dassing, Reiner

    1993-01-01

    The WLRS (Wettzell Laser Ranging System) allows the simultaneous tracking of satellites on two different wavelengths. These are the fundamental frequency of Nd:YAG at 1.064 microns and the second harmonic at 532 nm. Range measurements to the satellite LAGEOS were carried out with different experimental set-ups, after developing a detector unit based on a silicon avalanche photodiode in Geiger mode, which is sufficiently sensitive in the infrared domain. An approach towards a quantitative interpretation of the data is suggested and discussed briefly.

  13. Power-gated 32 bit microprocessor with a power controller circuit activated by deep-sleep-mode instruction achieving ultra-low power operation

    NASA Astrophysics Data System (ADS)

    Koike, Hiroki; Ohsawa, Takashi; Miura, Sadahiko; Honjo, Hiroaki; Ikeda, Shoji; Hanyu, Takahiro; Ohno, Hideo; Endoh, Tetsuo

    2015-04-01

    A spintronic-based power-gated micro-processing unit (MPU) is proposed. It includes a power control circuit activated by the newly supported power-off instruction for the deep-sleep mode. These means enable the power-off procedure for the MPU to be executed appropriately. A test chip was designed and fabricated using 90 nm CMOS and an additional 100 nm MTJ process; it was successfully operated. The guideline of the energy reduction effects for this MPU was presented, using the estimation based on the measurement results of the test chip. The result shows that a large operation energy reduction of 1/28 can be achieved when the operation duty is 10%, under the condition of a sufficient number of idle clock cycles.

  14. Near-Diffraction-Limited Operation of Step-Index Large-Mode-Area Fiber Lasers Via Gain Filtering

    SciTech Connect

    Marciante, J.R.; Roides, R.G.; Shkunov, V.V.; Rockwell, D.A.

    2010-06-04

    We present, for the first time to our knowledge, an explicit experimental comparison of beam quality in conventional and confined-gain multimode fiber lasers. In the conventional fiber laser, beam quality degrades with increasing output power. In the confined-gain fiber laser, the beam quality is good and does not degrade with output power. Gain filtering of higher-order modes in 28 μm diameter core fiber lasers is demonstrated with a beam quality of M^2 = 1.3 at all pumping levels. Theoretical modeling is shown to agree well with experimentally observed trends.

  15. Selectivity Enhancement for Chloride Ion by In(III)-Porphyrin-Based Polymeric Membrane Electrode Operated in Pulsed Chronopotentiometric Mode

    PubMed Central

    Gemene, Kebede L.; Meyerhoff, Mark E.

    2013-01-01

    A robust selectivity enhancement of an In(III)-porphyrin ionophore-based chloride-selective electrode under pulsed chronopotentiometric measurement mode that enables the detection of chloride ions in the presence of a normally interfering concentration of salicylate ions is described. This enhancement is achieved by the rapid depletion of the surface concentration of the more dilute lipophilic anion during an initial anodic current pulse period due to extraction of this preferred anion into the membrane phase. Measurement of chloride with a detection limit of 8 mM and near Nernstian response slope in the presence of 1 mM salicylate is possible using the pulstrode method. PMID:23355767

  16. List mode multichannel analyzer

    SciTech Connect

    Archer, Daniel E.; Luke, S. John; Mauger, G. Joseph; Riot, Vincent J.; Knapp, David A.

    2007-08-07

    A digital list mode multichannel analyzer (MCA) built around a programmable FPGA device for onboard data analysis and on-the-fly modification of system detection/operating parameters, and capable of collecting and processing data in very small time bins (<1 millisecond) when used in histogramming mode, or in list mode as a list mode MCA.

  17. Spatial distribution and dose-response relationship for different operation modes in a reaction-diffusion model of the MAPK cascade

    NASA Astrophysics Data System (ADS)

    Zhao, Qi; Yi, Ming; Liu, Yan

    2011-10-01

    The mitogen-activated protein kinase (MAPK) cascade plays a critical role in the control of cell growth. Deregulation of this pathway contributes to the development of many cancers. To better understand its signal transduction, we constructed a reaction-diffusion model for the MAPK pathway. We modeled the three layers of phosphorylation-dephosphorylation reactions and diffusion processes from the cell membrane to the nucleus. Based on different types of feedback in the MAPK cascade, four operation modes are introduced. For each of the four modes, spatial distributions and dose-response curves of active kinases (i.e. ppMAPK) are explored by numerical simulation. The effects of propagation length, diffusion coefficient and feedback strength on the pathway dynamics are investigated. We found that intrinsic bistability in the MAPK cascade can generate a traveling wave of ppMAPK with constant amplitude when the propagation length is short. ppMAPK in this mode of intrinsic bistability decays more slowly than it does in all other modes as the propagation length increases. Moreover, we examined the global and local responses to Ras-GTP of these four modes, and demonstrated how the shapes of these dose-response curves change as the propagation length increases. Also, we found that larger diffusion constant gives a higher response level on the zero-order regime and makes the ppMAPK profiles flatter under strong Ras-GTP stimulus. Furthermore, we observed that spatial responses of ppMAPK are more sensitive to negative feedback than to positive feedback in the broader signal range. Finally, we showed how oscillatory signals pass through the kinase cascade, and found that high frequency signals are damped faster than low frequency ones.

  18. The Effect of Different Operations Modes on Science Capabilities During the 2010 Desert-RATS Test: Insights from the Geologist Crewmembers

    NASA Technical Reports Server (NTRS)

    Bleacher, Jacob E.; Hurtado, Jose M., Jr.; Young, Kelsey E.; Rice, James W., Jr.; Garry, W. Brent

    2011-01-01

    The 2010 Desert RATS field test utilized two Space Exploration Vehicles (prototype planetary rovers) and four crewmembers (2 per rover) to conduct a geologic traverse across northern Arizona while testing continuous and twice-per-day communications paired with operation modes of separating and exploring individually (Divide & Conquer) and exploring together (Lead & Follow), respectively. This report provides qualitative conclusions from the geologist crewmembers involved in this test as to how these modes of communications and operations affected our ability to conduct field geology. Each mode of communication and operation provided beneficial capabilities that might be further explored for future Human Spaceflight Missions to other solar system objects. We find that more frequent interactions between crews and an Apollo-style Science Team on the Earth best enables scientific progress during human exploration. However, during multiple vehicle missions, this communication with an Earth-based team of scientists, who represent "more minds on the problem", should not come at the exclusion of (or significantly decrease) communication between the crewmembers in different vehicles who have the "eyes on the ground". Inter-crew communications improved when discussions with a backroom were infrequent. Both aspects are critical and cannot be mutually exclusive. Increased vehicle separation distances best enable encounters with multiple geologic units. However, seemingly redundant visits by multiple vehicles to the same feature can be utilized to provide improved process-related observations about the development and modification of the local terrain. We consider the value of data management, transfer, and accessibility to be the most important lesson learned. Crews and backrooms should have access to all data and related interpretations within the mission in as close to real-time conditions as possible. This ensures that while on another planetary surface, crewmembers are as

  19. Two-gigawatt burst-mode operation of the intense microwave prototype (IMP) free-electron laser (FEL) for the microwave tokamak experiment (MTX)

    SciTech Connect

    Felker, B.; Allen, S.; Bell, H.

    1993-10-06

    The MTX explored the plasma heating effects of 140 GHz microwaves from both Gyrotrons and from the IMP FEL wiggler. The Gyrotron was long pulse length (0.5 seconds maximum) and the FEL produced short-pulse length, high-peak power, single and burst modes of 140 GHZ microwaves. Full-power operations of the IMP FEL wiggler were commenced in April of 1992 and continued into October of 1992. The Experimental Test Accelerator H (ETA-II) provided a 50-nanosecond, 6-MeV, 2--3 kAmp electron beam that was introduced co-linear into the IMP FEL with a 140 GHz Gyrotron master oscillator (MO). The FEL was able to amplify the MO signal from approximately 7 kW to peaks consistently in the range of 1--2 GW. This microwave pulse was transmitted into the MTX and allowed the exploration of the linear and non-linear effects of short pulse, intense power in the MTX plasma. Single pulses were used to explore and gain operating experience in the parameter space of the IMP FEL, and finally evaluate transmission and absorption in the MTX. Single-pulse operations were repeatable. After the MTX was shut down burst-mode operations were successful at 2 kHz. This paper will describe the IMP FEL, Microwave Transmission System to MTX, the diagnostics used for calorimetric measurements, and the operations of the entire Microwave system. A discussion of correlated and uncorrelated errors that affect FEL performance will be made Linear and non-linear absorption data of the microwaves in the MTX plasma will be presented.

  20. Normal mode analysis of a rotating group of lashed turbine blades by substructures. [calculations for blades at rest and at operating speed

    NASA Technical Reports Server (NTRS)

    Filstrup, A. W.

    1973-01-01

    A group of 5 lashed identical stream turbine blades is studied through the use of single level substructuring using NASTRAN level 15.1. An altered version, similar to DMAP Program Number 3 of the NASTRAN Newsletter, of Rigid Format 13.0 was used. Steady-state displacements and stresses due to centrifugal loads are obtained both without and with consideration of differential stiffness. The normal mode calculations were performed for blades at rest and at operating speed. Substructuring lowered the computation costs of the analysis by a factor of four.

  1. Texas Instruments' virtual phase charge-coupled device (CCD) imager operated in the frontside electron-bombarded mode

    NASA Technical Reports Server (NTRS)

    Everett, P.; Hynecek, J.; Zucchino, P.; Lowrance, J.

    1982-01-01

    The present investigation is concerned with the suitability of the virtual phase CCD imager for frontside detection of electrons up to 25 keV. The investigation has the objective to determine if the imager can be used in the frontside mode with a photocathode to detect very low light levels in astronomical applications, the ultimate goal being individual photon detection. It is found that the standard virtual phase imager will function properly over an extended period at low levels of 20 kV electron irradiation consistent with photon counting applications. The imager can detect individual primary electrons with nearly 100 percent efficiency. However, further studies are needed to determine the mechanisms for the flat band shifts so that the imager design may be modified to eliminate or at least reduce them.

  2. Recrystallization of bulk and plasma-coated tungsten with accumulated thermal energy relevant to Type-I ELM in ITER H-mode operation

    NASA Astrophysics Data System (ADS)

    Kim, Hyun-Su; Lim, Sun-Taek; Jin, Younggil; Lee, Jin Young; Song, Jae-Min; Kim, Gon-Ho

    2015-08-01

    The recrystallization of bulk tungsten is investigated under various thermal loads that are relevant to the accumulation energy during Type-I ELM in ITER H-mode operation. A thermal plasma torch is used to examine only the thermal load effect on the material; therefore, the charge and atomic effects are ignored. In this condition, recrystallization is observed in bulk W with a surface temperature above 1700 °C. The effect becomes severe with a finite recrystallization thickness near the surface, which introduces vertical cracking along grain boundaries with increasing thermal load. However, plasma-sprayed tungsten (PS-W) is not crystallized because neighboring lamellas merge, destroying their interlayer and producing no vertical cracks. This is attributed to an annealing effect in PS-W. Therefore, these results suggest that a multilayer W structure is advantageous in the fabrication of W, especially for long pulse operation in a future fusion reactor.

  3. Dry anaerobic digestion in batch mode: design and operation of a laboratory-scale, completely mixed reactor.

    PubMed

    Guendouz, J; Buffière, P; Cacho, J; Carrère, M; Delgenes, J-P

    2010-10-01

    A laboratory-scale (40 l) reactor was designed to investigate dry anaerobic digestion. The reactor is equipped with an intermittent paddle mixer, enabling complete mixing in the reactor. Three consecutive batch dry digestion tests of municipal solid waste were performed under mesophilic conditions and compared to operation results obtained on a pilot-scale (21 m(3)) with the same feedstock. Biogas and methane production at the end of the tests were similar (around 200 m(3) CH(4)STP/tVS), and the dynamics of methane production and VFA accumulation concurred. However, the maximal levels of VFA transitory accumulation varied between reactors and between runs in a same reactor. Ammonia levels were similar in both reactors. These results show that the new reactor accurately imitates the conditions found in larger ones. Adaptation of micro-organisms to the waste and operating conditions was also pointed out along the consecutive batches.

  4. Variability of heavy duty vehicle operating mode frequencies for prediction of mobile emissions. Report for March 1995--March 1996

    SciTech Connect

    Grant, C.D.; Guensler, R.; Meyer, M.D.

    1996-01-01

    The paper discusses a new geographic information system (GIS)-based modal emissions model being developed with EPA and Georgia Tech to account for vehicle load conditions that will significantly improve the spatial resolution of emissions estimates. The GIS-based modal research model employs detailed subfleet engine and emissions characteristics and the speed/acceleration profiles for vehicle activity along links in the transportation system. Composition of the vehicle subfleet affects the amount of emissions produced under various operating conditions, dependent upon the load induced by the vehicle and driver, and the physical constraints of the vehicle. The aggregate modal frequencies are compared across vehicle classes to show differences in how heavy duty vehicles are operated.

  5. Large mode radius resonators

    NASA Technical Reports Server (NTRS)

    Harris, Michael R.

    1987-01-01

    Resonator configurations permitting operation with large mode radius while maintaining good transverse mode discrimination are considered. Stable resonators incorporating an intracavity telescope and unstable resonator geometries utilizing an output coupler with a Gaussian reflectivity profile are shown to enable large radius single mode laser operation. Results of heterodyne studies of pulsed CO2 lasers with large (11mm e sup-2 radius) fundamental mode sizes are presented demonstrating minimal frequency sweeping in accordance with the theory of laser-induced medium perturbations.

  6. Stable, tunable, and single-mode operation of an erbium-doped fibre laser system using a saturable absorber for gas spectroscopy applications

    NASA Astrophysics Data System (ADS)

    Arsad, Norhana; Stewart, George

    2009-02-01

    We present an erbium doped fibre ring laser system to realize single frequency lasing by incorporating a reflector with ~2m of un-pumped polarization-maintaining erbium-doped fibre to act as a saturable absorber. Depending on the particular requirements, the fibre reflector may be a fibre Bragg grating (FBG), loop mirror (LM) or a reflective coating on the fibre end. In this way, a transient grating is formed in the saturable absorber which acts as a narrow-band optical filter, reducing the number of modes over which the laser can operate and hence suppressing mode hopping in the cavity. Polarization-maintaining (PM) components are used throughout the system, except for the EDFA, and a polarization controller is used for enhancing stability and to ensure that the state of polarization is properly aligned. With this system we have observed a long period of stable, narrow line-width and single mode operation, tuneable over 30nm. The intended application is for gas spectroscopy using wavelength scanning and pump modulation. A Sagnac loop filter (SLF) can be used to scan the centre wavelength over a gas absorption line while the pump modulation produces an amplitude modulated signal on the output, suitable for detection by a lock-in (phase-sensitive) amplifier. The method is useful for the recovery of absorption line-shapes in the near-IR where the overtone absorption lines are weak. Compared with the use of a traditional DFB laser source, the fibre laser offers the advantages of a much broader tuning range and recovery of distortion-free line-shapes since wavelength and amplitude modulation may be performed independently.

  7. Modeling the Effects of (lambda)-gun on SSPX Operation: Mode Spectra, Internal Magnetic Field Structure, and Energy Confinement

    SciTech Connect

    Hooper, E

    2005-08-23

    The Sustained Spheromak Physics Experiment (SSPX) shows considerable sensitivity to the value of the injected (''gun'') current, I{sub gun}, parameterized by the relative values of {lambda}{sub gun} = {mu}{sub 0}I{sub gun}/{Psi}{sub gun} (with {Psi}{sub gun} the bias poloidal magnetic flux) to the lowest eigenvalue of {del} x B = {lambda}{sub FC}B in the flux conserver geometry. This report discusses modeling calculations using the NIMROD resistive-MHD code in the SSPX geometry. The behavior is found to be very sensitive to the profile of the safety factor, q, with the excitation of interior MHD modes at low-order resonant surfaces significantly affecting the evolution. Their evolution affects the fieldline topology (closed flux, islands, stochastic fieldlines confined by KAM surfaces, and open fieldlines), and thus electron temperature and other parameters. Because of this sensitivity, a major effect is the modification of the q-profile by the current on the open fieldlines in the flux core along the geometric axis. The time-history of a discharge can thus vary considerably for relatively small changes in I{sub gun}. The possibility of using this sensitivity for feedback control of the discharge evolution is discussed, but modeling of the process is left for future work.

  8. Single mode operation with mid-IR hollow fibers in the range 5.1-10.5 µm.

    PubMed

    Sampaolo, Angelo; Patimisco, Pietro; Kriesel, Jason M; Tittel, Frank K; Scamarcio, Gaetano; Spagnolo, Vincenzo

    2015-01-12

    Single mode beam delivery in the mid-infrared spectral range 5.1-10.5 μm employing flexible hollow glass waveguides of 15 cm and 50 cm lengths, with metallic/dielectric internal layers and a bore diameter of 200 μm were demonstrated. Three quantum cascade lasers were coupled with the hollow core fibers. For a fiber length of 15 cm, we measured losses down to 1.55 dB at 5.4 μm and 0.9 dB at 10.5 μm. The influence of the launch conditions in the fiber on the propagation losses and on the beam profile at the waveguide exit was analyzed. At 10.5 µm laser wavelength we found near perfect agreement between measured and theoretical losses, while at ~5 µm and ~6 µm wavelengths the losses were higher than expected. This discrepancy can be explained considering an additional scattering loss effect, which scales as 1/λ(2) and is due to surface roughness of the metallic layer used to form the high-reflective internal layer structure of the hollow core waveguide. PMID:25835666

  9. Enhanced efficiency in the excitation of higher modes for atomic force microscopy and mechanical sensors operated in liquids

    SciTech Connect

    Penedo, M. Hormeño, S.; Fernández-Martínez, I.; Luna, M.; Briones, F.; Raman, A.

    2014-10-27

    Recent developments in dynamic Atomic Force Microscopy where several eigenmodes are simultaneously excited in liquid media are proving to be an excellent tool in biological studies. Despite its relevance, the search for a reliable, efficient, and strong cantilever excitation method is still in progress. Herein, we present a theoretical modeling and experimental results of different actuation methods compatible with the operation of Atomic Force Microscopy in liquid environments: ideal acoustic, homogeneously distributed force, distributed applied torque (MAC Mode™), photothermal and magnetostrictive excitation. From the analysis of the results, it can be concluded that magnetostriction is the strongest and most efficient technique for higher eigenmode excitation when using soft cantilevers in liquid media.

  10. Method of operating a two-stroke-cycle engine with variable valve timing in a four-stroke-cycle mode

    SciTech Connect

    Richeson, W.E.

    1992-07-21

    This patent describes a method of operating an internal combustion engine of the type comprising a piston reciprocable in a cylinder, intake port means for admitting air into the cylinder, an exhaust valve that is opened and closed by valve actuator means independent of crankshaft position, spark ignition means, and fuel injection means. It comprises a first stroke wherein the piston moves from BDC to TDC, a second stroke wherein the piston moves from TDC to BDC, a third stroke wherein the piston moves from BDC to TDC, a fourth stroke wherein the piston moves from TDC to BDC.

  11. Induction of anoxic microenvironment in multi-phase metabolic shift strategy during periodic discontinuous batch mode operation enhances treatment of azo dye wastewater.

    PubMed

    Nagendranatha Reddy, C; Naresh Kumar, A; Annie Modestra, J; Venkata Mohan, S

    2014-08-01

    Variation in anoxic microenvironment (multi-phase (MP) metabolic shift strategy) during cycle operation of periodic discontinuous batch/sequencing batch (PDBR/SBR) mode operation showed enhanced degradation of recalcitrant azo dye (C.I. Acid Black 10B) at higher dye load (1250mg/l). The process performance was evaluated by varying anoxic phasing period during cycle operation. Before multiphase (BMP) operation with 2.1% of anoxic period showed color/COD removal efficiency of 41.9%/46.3%. Increment in anoxic period responded favorable in enhancing treatment efficiency [AMPI (16.2%), 49.4%/52.4%; AMPII (26.6%), 54.7%/57.2%; AMPIII (34.9%), 58.4%/61.5%]. Relatively higher bio-electrochemical activity, persistent reductive behavior (redox catalytic currents, 0.26/-0.72μA), prevalence of redox shuttlers (Fe-S proteins, cytochromes, quinones) facilitating enhanced electron transfer by minimization of associated losses and higher enzyme activities were observed with induction of anoxic phase. Anoxic condition shifts system microenvironment between oxidation and reduction assisting reduction of dye to its intermediates followed by their mineralization.

  12. Optimization of the GOSAT global observation from space with region-by-region target-mode operations

    NASA Astrophysics Data System (ADS)

    kuze, A.; Suto, H.; Shiomi, K.; Kawakami, S.; Nakajima, M.

    2013-12-01

    Since its launch in 2009, the Thermal And Near infrared Sensor for carbon Observation Fourier-Transform Spectrometer (TANSO-FTS) onboard the Greenhouse gases Observing SATellite (GOSAT) has continued its grid observation and acquired about 20,000 samples per day. Now that more than 10 programs are planned or proposed to monitor greenhouse gases from space. TANSO-FTS is the only instrument that uses a Fourier transfer spectrometer. It is not an imaging spectrometer but has a symmetrical instrument line shape function (ILSF) that can be expressed to high precision for all wavelengths with a simple analytical function and can reduce fitting errors for atmosphere remote sensing. Therefore, other future instruments can cross-calibrate their data with accurate and precise GOSAT spectra. Since August 2010, TANSO-FTS has selected 3-point cross-track scan mode, which has the current best pointing stability and observes a single point three times in 14 sec. Column-averaged dry air mole fractions of CO2 (XCO2) and CH4 (XCH4) have been well validated at the TCCON sites, where surface albedo is not high and aerosol optical thickness is small. Long term GOSAT data show seasonal and latitudinal variation and annual increase accurately and precisely. JAXA has been processing and providing all the Level 1B spectra data that were acquired on-orbit. Thus the distribution of the Level 1B is spatially equal. The Level 2 users are retrieving XCO2 and XCH4 from the Level 1 by filtering cloud contaminated, aerosol thick, and low signal-to-noise ratio scenes. As a result, the yield rate at cloudy area such as Amazon, south-east Asia, and Central America, low surface albedo area such as snow and ice, bay and channels is very low. Aerosol thick area such as Sahara also has larger errors. Now that GOSAT demonstrated accurate XCO2 and XCH4 remote sensing, demand for emission source measurements of mega cities, power plants, gas fields, and volcanos has increased. In addition to grid

  13. The Membrane-anchoring Domain of Epidermal Growth Factor Receptor Ligands Dictates Their Ability to Operate in Juxtacrine Mode

    SciTech Connect

    Dong, Jianying; Opresko, Lee; Chrisler, William B.; Orr, Galya; Quesenberry, Ryan D.; Lauffenburger, Douglas A.; Wiley, H S.

    2005-06-01

    All ligands of the epidermal growth factor receptor (EGFR) are synthesized as membrane-anchored precursors. Previous work has suggested that some ligands, such as EGF, must be proteolytically released to be active, whereas others, such as heparin binding EGF-like growth factor (HB-EGF) can function while still anchored to the membrane (i.e., juxtacrine signaling). To explore the structural basis for these differences in ligand activity, we engineered a series of membrane-anchored ligands in which the core, receptor-binding domain of EGF was combined with different domains of both EGF and HB-EGF. We found that ligands having the N-terminal extension of EGF could not bind to the EGFR, even when released from the membrane. Ligands lacking an N-terminal extension, but possessing the membrane-anchoring domain of EGF still required proteolytic release for activity, whereas ligands with the membrane anchoring domain of HB-EGF could elicit full biological activity while still membrane anchored. Ligands containing the HB-EGF membrane anchor, but lacking an N-terminal extension, activated EGFR during their transit through the Golgi apparatus . However, cell-mixing experiments and fluorescence resonance energy transfer (FRET) studies showed that juxtacrine signaling typically occurred in trans at the cell surface, at points of cell-cell contact. Our data suggest that the membrane-anchoring domain of ligands selectively controls their ability to participate in juxtacrine signaling and thus, only a subclass of EGFR ligands can act in a juxtacrine mode.

  14. Operation of a quantum dot in the finite-state machine mode: Single-electron dynamic memory

    NASA Astrophysics Data System (ADS)

    Klymenko, M. V.; Klein, M.; Levine, R. D.; Remacle, F.

    2016-07-01

    A single electron dynamic memory is designed based on the non-equilibrium dynamics of charge states in electrostatically defined metallic quantum dots. Using the orthodox theory for computing the transfer rates and a master equation, we model the dynamical response of devices consisting of a charge sensor coupled to either a single and or a double quantum dot subjected to a pulsed gate voltage. We show that transition rates between charge states in metallic quantum dots are characterized by an asymmetry that can be controlled by the gate voltage. This effect is more pronounced when the switching between charge states corresponds to a Markovian process involving electron transport through a chain of several quantum dots. By simulating the dynamics of electron transport we demonstrate that the quantum box operates as a finite-state machine that can be addressed by choosing suitable shapes and switching rates of the gate pulses. We further show that writing times in the ns range and retention memory times six orders of magnitude longer, in the ms range, can be achieved on the double quantum dot system using experimentally feasible parameters, thereby demonstrating that the device can operate as a dynamic single electron memory.

  15. Dynamic MTF improvement scheme and its validation for CCD operating in TDI mode for Earth imaging applications

    NASA Astrophysics Data System (ADS)

    Dubey, Neeraj; Banerjee, Arup

    2016-05-01

    The paper presents the scheme for improving the image contrast in the remote sensing images and highlights the novelty in hardware & software design in the test system developed for measuring image contrast function. Modulation transfer function (MTF) is the most critical quality element of the high-resolution imaging payloads for earth observation consisting of TDI-CCD (Time Delayed Integration Charge Coupled Device) image. From the mathematical model for MTF Smear MTF of 65% (35% degradation) is observed. Then a operating method for TDI-CCD is developed, using which 96% of Motion Smear MTF will occur within the imaging operation. As a major part of the validation, indigenously designed and developed a test system for measuring the dynamic MTF of TDI Sensors which consists of the optical scanning system, TDI-CCD camera drive & video processing electronics, thermal control system and telecentric uniform illumination system. The experimental results confirm that image quality improvement can be achieved by this method. This method is now implemented in the flight model hardware of the remote sensing payload.

  16. Evaluation of Mixed-Mode Data-Link Communications for NextGen 4DT and Equivalent Visual Surface Operations

    NASA Technical Reports Server (NTRS)

    Prinzel, Lawrence J., III; Shelton, Kevin J.; Jones, Denise R.; Allamandola, Angela S.; Arthur, Jarvis, J., III; Bailey, Randall E.

    2010-01-01

    By 2025, U.S. air traffic is predicted to increase 3-fold and may strain the current air traffic management system, which may not be able to accommodate this growth. In response to this challenge, a revolutionary new concept has been proposed for U.S. aviation operations, termed the Next Generation Air Transportation System or NextGen. Many key capabilities are being identified to enable NextGen, including the use of data-link communications. Because NextGen represents a radically different approach to air traffic management and requires a dramatic shift in the tasks, roles, and responsibilities for the flight deck, there are numerous research issues and challenges that must be overcome to ensure a safe, sustainable air transportation system. Flight deck display and crew-vehicle interaction concepts are being developed that proactively investigate and overcome potential technology and safety barriers that might otherwise constrain the full realization of NextGen. The paper describes simulation research examining data-link communications during 4DT and equivalent visual surface operations.

  17. Implementation of human thermal comfort information in Köppen-Geiger climate classification—the example of China

    NASA Astrophysics Data System (ADS)

    Yang, Shi-Qi; Matzarakis, Andreas

    2016-03-01

    Köppen-Geiger climate classification (KGC) is accepted and applied worldwide. The climatic parameters utilised in KGC, however, cannot indicate human thermal comfort (HTC) conditions or air humidity (AH) conditions directly, because they are originally based on climatic effects on vegetation, instead of that on human body directly. In addition, HTC is driven by meteorological parameters together. Thus, the objective of this study is to preliminarily implement the HTC information and the AH information in KGC. Physiologically equivalent temperature (PET) has been chosen as the HTC index, and vapour pressure (VP) is for the quantification of AH conditions. In this preliminary study, 12 Chinese cities in total have been taken into account as the assumed representatives of 11 climate types. Basic meteorological data of each city with 3-h resolution in 2000-2012 has been analysed. RayMan model has been applied to calculate PET within the same time period. Each climate type has been described by frequencies of PET and frequencies of VP. For example, the Aw (Sanya) has the most frequent occurrence of thermally stressful conditions compared to other climate types: PET in 22 % points in time of the year was above 35 °C. The driest AH conditions existed in Dwc (Lhasa) and Dfb (Urumqi) with VP rarely above 18 hPa in the wettest month. Implementation of the HTC information and the additional AH information in each climate type of KGC can be helpful for the topics of human health, energy consumption, tourism, as well as urban planning.

  18. Effects of electrokinetic operation mode on removal of polycyclic aromatic hydrocarbons (PAHs), and the indigenous fungal community in PAH-contaminated soil.

    PubMed

    Wang, Jian; Li, Fengmei; Li, Xu; Wang, Xiujuan; Li, Xinyu; Su, Zhencheng; Zhang, Huiwen; Guo, Shuhai

    2013-01-01

    Electrokinetic remediation is an emerging physical remediation technology for the removal of heavy metals and organic chemicals from contaminated soil. We set up a soil chamber (24 × 12 × 8 cm) with two stainless steel electrodes (12 × 0.5 cm), and a constant voltage gradient of 1.0 v cm(-1) or 2.0 v cm(-1) was applied to study the effects of unidirectional and altered directional electric field operation modes on the moisture content and pH, the removal rate of PAHs, and the abundance and diversity of indigenous fungi in a PAH-contaminated soil at the Benxi Iron and Steel Group Corporation (N41°17'24.4″, E123°43'05.8″), Liaoning Province, Northeast China. Electrokinetic remediation increased the PAH removal rate, but had less effect on soil moisture content and pH, in comparison with the control. In the 1 v cm(-1) altered directional operation, in particular, the PAH removal rate by the end of the experiment (on day 23) had increased from 5.2% of the control to 13.84% and 13.69% at distances of 4 and 20 cm from the anode, respectively, and to 18.97% in the middle region of the soil chamber. On day 23, the indigenous fungal 18S rRNA gene copy numbers and community diversity were significantly higher in a voltage gradient of 1 v cm(-1) than in a voltage gradient 2 v cm(-1). An altered directional operation was more conducive to the fungal community's uniform distribution than was a unidirectional operation of the electric field. We found the major PAH-degrading fungi Fusarium oxysporum and Rhizophlyctis rosea to be present under EK remediation. We suggest that a 1 v cm(-1) altered directional operation could be an appropriate electrokinetic operation mode for PAH removal, and the maintenance of abundance and diversity of the indigenous fungal community.

  19. Effects of electrokinetic operation mode on removal of polycyclic aromatic hydrocarbons (PAHs), and the indigenous fungal community in PAH-contaminated soil.

    PubMed

    Wang, Jian; Li, Fengmei; Li, Xu; Wang, Xiujuan; Li, Xinyu; Su, Zhencheng; Zhang, Huiwen; Guo, Shuhai

    2013-01-01

    Electrokinetic remediation is an emerging physical remediation technology for the removal of heavy metals and organic chemicals from contaminated soil. We set up a soil chamber (24 × 12 × 8 cm) with two stainless steel electrodes (12 × 0.5 cm), and a constant voltage gradient of 1.0 v cm(-1) or 2.0 v cm(-1) was applied to study the effects of unidirectional and altered directional electric field operation modes on the moisture content and pH, the removal rate of PAHs, and the abundance and diversity of indigenous fungi in a PAH-contaminated soil at the Benxi Iron and Steel Group Corporation (N41°17'24.4″, E123°43'05.8″), Liaoning Province, Northeast China. Electrokinetic remediation increased the PAH removal rate, but had less effect on soil moisture content and pH, in comparison with the control. In the 1 v cm(-1) altered directional operation, in particular, the PAH removal rate by the end of the experiment (on day 23) had increased from 5.2% of the control to 13.84% and 13.69% at distances of 4 and 20 cm from the anode, respectively, and to 18.97% in the middle region of the soil chamber. On day 23, the indigenous fungal 18S rRNA gene copy numbers and community diversity were significantly higher in a voltage gradient of 1 v cm(-1) than in a voltage gradient 2 v cm(-1). An altered directional operation was more conducive to the fungal community's uniform distribution than was a unidirectional operation of the electric field. We found the major PAH-degrading fungi Fusarium oxysporum and Rhizophlyctis rosea to be present under EK remediation. We suggest that a 1 v cm(-1) altered directional operation could be an appropriate electrokinetic operation mode for PAH removal, and the maintenance of abundance and diversity of the indigenous fungal community. PMID:23947706

  20. TMRBAR: a code to calculate plasma parameters for tandem-mirror reactors operating in the MARS mode

    SciTech Connect

    Campbell, R.B.

    1983-08-30

    The purpose of this report is to document the plasma power balance model currently used by LLNL to calculate steady state operating points for tandem mirror reactors. The code developed from this model, TMRBAR, has been used to predict the performance and define supplementary heating requirements for drivers used in the Mirror Advanced Reactor Study (MARS) and for the Fusion Power Demonstration (FPD) study. The equations solved included particle and energy balance for central cell and end cell species, quasineutrality at several cardinal points in the end cell region, as well as calculations of volumes, densities and average energies based on given constraints of beta profiles and fusion power output. Alpha particle ash is treated self-consistently, but no other impurity species is treated.

  1. Effect of fed-batch vs. continuous mode of operation on microbial fuel cell performance treating biorefinery wastewater

    DOE PAGESBeta

    Pannell, Tyler C.; Goud, R. Kannaiah; Schell, Daniel J.; Borole, Abhijeet P.

    2016-05-01

    Bioelectrochemical systems have been shown to treat low-value biorefinery streams while recovering energy, however, low current densities and anode conversion efficiencies (ACE) limit their application. A bioanode was developed via enrichment of electroactive biofilm under fed-batch and continuous feeding conditions using corn stover-derived waste stream. The continuously-fed MFC exhibited a current density of 5.8±0.06 A/m2 and an ACE of 39%±4. The fed-batch MFC achieved a similar current density and an ACE of 19.2%, however, its performance dropped after 36 days of operation to 1.1 A/m2 and 0.5%, respectively. In comparison, the ACE of the continuously-fed MFC remained stable achieving anmore » ACE of 30% ± 3 after 48 days of operation. An MFC treating a biorefinery stream post fuel separation achieved a current density of 10.7±0.1 A/m2 and an ACE of 57% ± 9 at an organic loading of 12.5 g COD/L-day. Characterization of the microbial communities indicate higher abundance of Firmicutes and Proteobacteria and lower abundance of Bacteriodetes and a higher level of Geobacter spp. (1.4% vs. 0.2%) in continuously-fed MFC vs. fed-batch MFC. Finally, the results demonstrate that limiting substrate to the equivalent maximum current that the anode can generate, maintains MFC performance over a long term for high strength wastewaters, such as those generated in the biorefinery.« less

  2. Impact of ultrasonic pretreatment under different operational conditions on the mesophilic anaerobic digestion of sunflower oil cake in batch mode.

    PubMed

    Fernández-Cegrí, V; de la Rubia, M A; Raposo, F; Borja, R

    2012-09-01

    In this study ultrasonic (US) pretreatment was investigated with the aim of improving the anaerobic digestion of sunflower oil cake (SuOC), the solid waste derived from the extraction process of sunflower oil. Five ultrasonic pretreatment assays were conducted at specific energy (SE) and sonication times in a range from 24,000 kJ/kg TS and 16.6 min (assay 1: US1) to 597,600 kJ/kg TS and 331.2 min (assay 5: US5), respectively, all operating at a constant sonication frequency (20 kHz) and ultrasonic power (120 W). As regards ultrasonic pretreatment, the working conditions of the first assay (US1) using samples of SuOC at 2% (w/v) showed to be the most appropriate in terms of both lignin and hemicellulose degradation (57.7% and 66.7%, respectively) and cellulose increase (54% increase with respect to its initial concentration). The percentage of COD solubilization increased from only 14% to 21% when SE was 25 times higher. Results obtained in batch anaerobic digestion experiments (biochemical methane potential - BMP - tests) conducted at 35°C of the solid and liquid fractions released from the different ultrasonic conditions tested, indicated that for the first experiment (US1) the average ultimate methane yield obtained was 53.8% higher than that achieved for untreated SuOC. Finally, the kinetic constants of the anaerobic digestion of the solid and liquid fractions released after the ultrasonic pretreatment were virtually independent of the operation conditions assayed. PMID:22366228

  3. Discovery of stationary operation of quiescent H-mode plasmas with net-zero neutral beam injection torque and high energy confinement on DIII-D

    NASA Astrophysics Data System (ADS)

    Burrell, K. H.; Barada, K.; Chen, X.; Garofalo, A. M.; Groebner, R. J.; Muscatello, C. M.; Osborne, T. H.; Petty, C. C.; Rhodes, T. L.; Snyder, P. B.; Solomon, W. M.; Yan, Z.; Zeng, L.

    2016-05-01

    Recent experiments in DIII-D [J. L. Luxon et al., in Plasma Physics and Controlled Nuclear Fusion Research 1996 (International Atomic Energy Agency, Vienna, 1987), Vol. I, p. 159] have led to the discovery of a means of modifying edge turbulence to achieve stationary, high confinement operation without Edge Localized Mode (ELM) instabilities and with no net external torque input. Eliminating the ELM-induced heat bursts and controlling plasma stability at low rotation represent two of the great challenges for fusion energy. By exploiting edge turbulence in a novel manner, we achieved excellent tokamak performance, well above the H98y2 international tokamak energy confinement scaling (H98y2 = 1.25), thus meeting an additional confinement challenge that is usually difficult at low torque. The new regime is triggered in double null plasmas by ramping the injected torque to zero and then maintaining it there. This lowers E × B rotation shear in the plasma edge, allowing low-k, broadband, electromagnetic turbulence to increase. In the H-mode edge, a narrow transport barrier usually grows until MHD instability (a peeling ballooning mode) leads to the ELM heat burst. However, the increased turbulence reduces the pressure gradient, allowing the development of a broader and thus higher transport barrier. A 60% increase in pedestal pressure and 40% increase in energy confinement result. An increase in the E × B shearing rate inside of the edge pedestal is a key factor in the confinement increase. Strong double-null plasma shaping raises the threshold for the ELM instability, allowing the plasma to reach a transport-limited state near but below the explosive ELM stability boundary. The resulting plasmas have burning-plasma-relevant βN = 1.6-1.8 and run without the need for extra torque from 3D magnetic fields. To date, stationary conditions have been produced for 2 s or 12 energy confinement times, limited only by external hardware constraints. Stationary operation with

  4. Operation of a New Half-Bridge Gate Driver for Enhancement - Mode GaN FETs, Type LM5113, Over a Wide Temperature Range

    NASA Technical Reports Server (NTRS)

    Patterson, Richard; Hammoud, Ahmad

    2011-01-01

    A new commercial-off-the-shelf (COTS) gate driver designed to drive both the high-side and the low-side enhancement-mode GaN FETs, National Semiconductor's type LM5113, was evaluated for operation at temperatures beyond its recommended specified limits of -40 C to +125 C. The effects of limited thermal cycling under the extended test temperature, which ranged from -194 C to +150 C, on the operation of this chip as well as restart capability at the extreme cryogenic and hot temperatures were also investigated. The driver circuit was able to maintain good operation throughout the entire test regime between -194 C and +150 C without undergoing any major changes in its outputs signals and characteristics. The limited thermal cycling performed on the device also had no effect on its performance, and the driver chip was able to successfully restart at each of the extreme temperatures of -194 C and +150 C. The plastic packaging of this device was also not affected by either the short extreme temperature exposure or the limited thermal cycling. These preliminary results indicate that this new commercial-off-the-shelf (COTS) halfbridge eGaN FET driver integrated circuit has the potential for use in space exploration missions under extreme temperature environments. Further testing is planned under long-term cycling to assess the reliability of these parts and to determine their suitability for extended use in the harsh environments of space.

  5. Multi-mode radio frequency device

    DOEpatents

    Gilbert, Ronald W.; Carrender, Curtis Lee; Anderson, Gordon A.; Steele, Kerry D.

    2007-02-13

    A transponder device having multiple modes of operation, such as an active mode and a passive mode, wherein the modes of operation are selected in response to the strength of a received radio frequency signal. A communication system is also provided having a transceiver configured to transmit a radio frequency signal and to receive a responsive signal, and a transponder configured to operate in a plurality of modes and to activate modes of operation in response to the radio frequency signal. Ideally, each mode of operation is activated and deactivated independent of the other modes, although two or more modes may be concurrently operational.

  6. Current crowding impact at spatially and temporarily resolved thermal characters of large-area AlGaInP light emitting diodes operating in dimming/flashing modes

    NASA Astrophysics Data System (ADS)

    Malyutenko, V. K.; Podoltsev, A. D.; Malyutenko, O. Yu.

    2015-10-01

    By exploring spatially (μm-scale) and temporarily (ms-scale) resolved light and 8-12 μm thermal imaging analyses, we demonstrate how current crowding alternates the thermal parameters of light emitting diodes (LEDs) operating in dimming/flashing mode. For example, in AlGaInP/GaAs high-current (I ≥ 1 A) large-area (≥1 mm2) LEDs, we measured the thermal time constant (2.5 ms), heat diffusion length (110 μm), current crowding length (≤75 μm), thermal diffusivity (0.08 cm2/s) of GaAs substrate, and current-dependent thermal patterns taken from the front and sidewall facet of chips. We discovered that even at I = 100 mA emitting ships are already divided by two regions with different temperatures, small area high-temperature central regions (effective volumes) with high current density and larger area lower-temperature peripheral regions with much lower current density. The experiments evidence that the simplified computer simulations of dimming mode based on mean chip temperature, mean thermal resistance, and average current density, as well as temperature-independent ABC-modeling must be regarded with skepticism.

  7. Improved semi-conductor laser device, operating, at room temperature, with an array of three lasers in the spatially coherent, free running mode

    NASA Technical Reports Server (NTRS)

    Rutz, E. M.

    1975-01-01

    The peak pulse power was increased by operating an array of three homostructure Ga As lasers in the laser device. A spatial filter in the laser device selects the spatially coherent, free running, mode. The optical peak power is 5 watts, which is three times the peak power of a single laser in the array. The far-field distribution of the three laser array is a single Gaussian beam of spatial coherence without sidelobes or grating lobes. The length of the optical pulses of spatial coherence was increased to 200 ns by improved heat transfer from the p-n junctions of the lasers to the metal housing of the pulse transformer, and by doubling the core area and increasing the turns of the primary windings of the pulse transformer. The mechanical stability of the laser device was improved and the transition from mechanical alignment to electro-mechanical alignment control, was facilitated.

  8. Sub-100  fs passively mode-locked holmium-doped fiber oscillator operating at 2.06  μm.

    PubMed

    Li, Peng; Ruehl, Axel; Grosse-Wortmann, Uwe; Hartl, Ingmar

    2014-12-15

    We demonstrate a simple and compact Holmium-doped fiber femtosecond oscillator, in-band pumped by a commercial Tm-doped fiber laser. The oscillator operates in the dispersion managed soliton regime at net zero intracavity dispersion and delivers >1  nJ pulse energy at 35 MHz repetition rate. The pulse duration directly at the oscillator output is 160 fs FWHM, close to the Fourier-limit of 145 fs FWHM. Using an additional nonlinear compressor stage, sub-100 fs FWHM pulse durations could be achieved. The nonlinear fiber compressor is implemented by a solid core highly nonlinear fiber for spectral broadening and a single mode fiber for pulse compression.

  9. Measurements of clothing insulation with a thermal manikin operating under the thermal comfort regulation mode: comparative analysis of the calculation methods.

    PubMed

    Oliveira, A Virgílio M; Gaspar, Adélio R; Quintela, Divo A

    2008-11-01

    The present work is dedicated to a comparative analysis of calculation methods about clothing insulation with a thermal manikin operating under the thermal comfort regulation mode. The serial, global, and parallel calculation methods are considered and the thermal insulation results for garments (30) and ensembles (9) are discussed. The serial and parallel methods presents the higher and lower values, respectively, and the differences were sometimes significant. Considering the results for the effective thermal insulation, the mean values of the relative differences between the serial and global methods were 25.7% for the daily wear garments, 45.2% for the cold protective garments and 38.5% for the ensembles. The corresponding mean values for the global and parallel methods were 8.7, 15.8, and 10.5%, respectively. Since any uneven clothing insulation is to be expected as a source of error, particular care must be required when the calculation methods deal with cold protective clothing.

  10. Grating array systems having a plurality of gratings operative in a coherently additive mode and methods for making such grating array systems

    DOEpatents

    Kessler, Terrance J.; Bunkenburg, Joachim; Huang, Hu

    2007-02-13

    A plurality of gratings (G1, G2) are arranged together with a wavefront sensor, actuators, and feedback system to align the gratings in such a manner, that they operate like a single, large, monolithic grating. Sub-wavelength-scale movements in the mechanical mounting, due to environmental influences, are monitored by an interferometer (28), and compensated by precision actuators (16, 18, 20) that maintain the coherently additive mode. The actuators define the grating plane, and are positioned in response to the wavefronts from the gratings and a reference flat, thus producing the interferogram that contains the alignment information. Movement of the actuators is also in response to a diffraction-limited spot on the CCD (36) to which light diffracted from the gratings is focused. The actuator geometry is implemented to take advantage of the compensating nature of the degrees of freedom between gratings, reducing the number of necessary control variables.

  11. Analytical prediction and experimental verification of performance at various operating conditions of a dual-mode traveling wave tube with multistage depressed collectors

    NASA Technical Reports Server (NTRS)

    Dayton, J. A., Jr.; Kosmahl, H. G.; Ramins, P.; Stankiewicz, N.

    1981-01-01

    A comparison of analytical and experimental results is presented for a high performance dual-mode traveling wave tube (TWT) operated over a wide range conditions. The computations are carried out with advanced multidimensional computer programs. These programs model the electron beam as a series of disks or rings of charge and follow their trajectories from the rf input of the TWT through the slow-wave structure refocusing system to their points of impacts in the depressed collector. TWT performance, collector efficiency, and collector current distribution are computed and compared with measurements. Very good agreement was obtained between computed and measured TWT performance and collector efficiencies, and the computer design of a highly efficient collector was demonstrated.

  12. Operating modes and cooling capabilities of the 3-stage ADR developed for the Soft-X-ray Spectrometer instrument on Astro-H

    NASA Astrophysics Data System (ADS)

    Shirron, Peter J.; Kimball, Mark O.; James, Bryan L.; Muench, Theodore; DiPirro, Michael J.; Letmate, Richard V.; Sampson, Michael A.; Bialas, Tom G.; Sneiderman, Gary A.; Porter, Frederick S.; Kelley, Richard L.

    2016-03-01

    A 3-stage adiabatic demagnetization refrigerator (ADR) (Shirron et al., 2012) is used on the Soft X-ray Spectrometer instrument (Mitsuda et al., 2010) on Astro-H (Takahashi et al., 2010) [3] to cool a 6 × 6 array of X-ray microcalorimeters to 50 mK. The ADR is supported by a cryogenic system (Fujimoto et al., 2010) consisting of a superfluid helium tank, a 4.5 K Joule-Thomson (JT) cryocooler, and additional 2-stage Stirling cryocoolers that pre-cool the JT cooler and cool radiation shields within the cryostat. The ADR is configured so that it can use either the liquid helium or the JT cryocooler as its heat sink, giving the instrument an unusual degree of tolerance for component failures or degradation in the cryogenic system. The flight detector assembly, ADR and dewar were integrated into the flight dewar in early 2014, and have since been extensively characterized and calibrated. This paper summarizes the operation and performance of the ADR in all of its operating modes.

  13. Dark current studies on a normal-conducting high-brightness very-high-frequency electron gun operating in continuous wave mode

    NASA Astrophysics Data System (ADS)

    Huang, R.; Filippetto, D.; Papadopoulos, C. F.; Qian, H.; Sannibale, F.; Zolotorev, M.

    2015-01-01

    We report on measurements and analysis of a field-emitted electron current in the very-high-frequency (VHF) gun, a room temperature rf gun operating at high field and continuous wave (CW) mode at the Lawrence Berkeley National Laboratory (LBNL). The VHF gun is the core of the Advanced Photo-injector Experiment (APEX) at LBNL, geared toward the development of an injector for driving the next generation of high average power x-ray free electron lasers. High accelerating fields at the cathode are necessary for the high-brightness performance of an electron gun. When coupled with CW operation, such fields can generate a significant amount of field-emitted electrons that can be transported downstream the accelerator forming the so-called "dark current." Elevated levels of a dark current can cause radiation damage, increase the heat load in the downstream cryogenic systems, and ultimately limit the overall performance and reliability of the facility. We performed systematic measurements that allowed us to characterize the field emission from the VHF gun, determine the location of the main emitters, and define an effective strategy to reduce and control the level of dark current at APEX. Furthermore, the energy spectra of isolated sources have been measured. A simple model for energy data analysis was developed that allows one to extract information on the emitter from a single energy distribution measurement.

  14. Two-stage coal liquefaction process materials from the Wilsonville Facility operated in the nonintegrated and integrated modes: chemical analyses and biological testing

    SciTech Connect

    Later, D.W.

    1985-01-01

    This document reports the results from chemical analyses and biological testing of process materials sampled during operation of the Wilsonville Advanced Coal Liquefaction Research and Development Facility (Wilsonville, Alabama) in both the noncoupled or nonintegrated (NTSL Run 241) and coupled or integrated (ITSL Run 242) two-stage liquefaction operating modes. Mutagenicity and carcinogenicity assays were conducted in conjunction with chromatographic and mass spectrometric analyses to provide detailed, comparative chemical and biological assessments of several NTSL and ITSL process materials. In general, the NTSL process materials were biologically more active and chemically more refractory than analogous ITSL process materials. To provide perspective, the NTSL and ITSL results are compared with those from similar testing and analyses of other direct coal liquefaction materials from the solvent refined coal (SRC) I, SRC II and EDS processes. Comparisons are also made between two-stage coal liquefaction materials from the Wilsonville pilot plant and the C.E. Lummus PDU-ITSL Facility in an effort to assess scale-up effects in these two similar processes. 36 references, 26 figures, 37 tables.

  15. A tandem laboratory scale protein purification process using Protein A affinity and anion exchange chromatography operated in a weak partitioning mode.

    PubMed

    Shamashkin, Michael; Godavarti, Ranga; Iskra, Timothy; Coffman, Jon

    2013-10-01

    A significant consequence of scaling up production of high titer monoclonal antibody (mAb) processes in existing facilities is the generation of in-process pools that exceed the capacity of storage vessels. A semi-continuous downstream process where columns and filters are linked and operated in tandem would eliminate the need for intermediate holding tanks. This study is a bench-scale demonstration of the feasibility of a tandem process for the purification of mAbs employing an affinity Protein A capture step, followed by a flow-through anion-exchange (AEX) step with the possibility of adding an in-line virus filtration step (VF). All three steps were linked sequentially and operated as one continuous process using an ÄKTA FPLC equipped with two pumps and a system of valves and bypasses that allowed the components to be engaged at different stages of the process. The AEX column was operated in a weak partitioning (WP) mode enabled by a precise in-line titration of Protein A effluent. In order to avoid complex control schemes and facilitate validation, quality and robustness were built into the system through selection of buffers based on thermodynamic and empirical models. The tandem system utilized the simplest possible combination of valves, pumps, controls, and automation, so that it could easily be implemented in a clinical or commercial production facility. Linking the purification steps in a tandem process is expected to generate savings in time and production costs and also reduce the size of quality systems due to reduced documentation requirements, microbial sampling, and elimination of hold time validation. PMID:23633385

  16. A Thomson-type mass and energy spectrometer for characterizing ion energy distributions in a coaxial plasma gun operating in a gas-puff mode

    NASA Astrophysics Data System (ADS)

    Rieker, G. B.; Poehlmann, F. R.; Cappelli, M. A.

    2013-07-01

    Measurements of ion energy distribution are performed in the accelerated plasma of a coaxial electromagnetic plasma gun operating in a gas-puff mode at relatively low discharge energy (900 J) and discharge potential (4 kV). The measurements are made using a Thomson-type mass and energy spectrometer with a gated microchannel plate and phosphor screen as the ion sensor. The parabolic ion trajectories are captured from the sensor screen with an intensified charge-coupled detector camera. The spectrometer was designed and calibrated using the Geant4 toolkit, accounting for the effects on the ion trajectories of spatial non-uniformities in the spectrometer magnetic and electric fields. Results for hydrogen gas puffs indicate the existence of a class of accelerated protons with energies well above the coaxial discharge potential (up to 24 keV). The Thomson analyzer confirms the presence of impurities of copper and iron, also of relatively high energies, which are likely erosion or sputter products from plasma-electrode interactions.

  17. A Thomson-type mass and energy spectrometer for characterizing ion energy distributions in a coaxial plasma gun operating in a gas-puff mode

    PubMed Central

    Rieker, G. B.; Poehlmann, F. R.; Cappelli, M. A.

    2013-01-01

    Measurements of ion energy distribution are performed in the accelerated plasma of a coaxial electromagnetic plasma gun operating in a gas-puff mode at relatively low discharge energy (900 J) and discharge potential (4 kV). The measurements are made using a Thomson-type mass and energy spectrometer with a gated microchannel plate and phosphor screen as the ion sensor. The parabolic ion trajectories are captured from the sensor screen with an intensified charge-coupled detector camera. The spectrometer was designed and calibrated using the Geant4 toolkit, accounting for the effects on the ion trajectories of spatial non-uniformities in the spectrometer magnetic and electric fields. Results for hydrogen gas puffs indicate the existence of a class of accelerated protons with energies well above the coaxial discharge potential (up to 24 keV). The Thomson analyzer confirms the presence of impurities of copper and iron, also of relatively high energies, which are likely erosion or sputter products from plasma-electrode interactions. PMID:23983449

  18. A Thomson-type mass and energy spectrometer for characterizing ion energy distributions in a coaxial plasma gun operating in a gas-puff mode.

    PubMed

    Rieker, G B; Poehlmann, F R; Cappelli, M A

    2013-07-01

    Measurements of ion energy distribution are performed in the accelerated plasma of a coaxial electromagnetic plasma gun operating in a gas-puff mode at relatively low discharge energy (900 J) and discharge potential (4 kV). The measurements are made using a Thomson-type mass and energy spectrometer with a gated microchannel plate and phosphor screen as the ion sensor. The parabolic ion trajectories are captured from the sensor screen with an intensified charge-coupled detector camera. The spectrometer was designed and calibrated using the Geant4 toolkit, accounting for the effects on the ion trajectories of spatial non-uniformities in the spectrometer magnetic and electric fields. Results for hydrogen gas puffs indicate the existence of a class of accelerated protons with energies well above the coaxial discharge potential (up to 24 keV). The Thomson analyzer confirms the presence of impurities of copper and iron, also of relatively high energies, which are likely erosion or sputter products from plasma-electrode interactions.

  19. Study on the Interrater Reliability of an OSPE (Objective Structured Practical Examination) – Subject to the Evaluation Mode in the Phantom Course of Operative Dentistry

    PubMed Central

    Schmitt, Laura; Möltner, Andreas; Rüttermann, Stefan; Gerhardt-Szép, Susanne

    2016-01-01

    Introduction: The aim of the study presented here was to evaluate the reliability of an OSPE end-of-semester exam in the phantom course for operative dentistry in Frankfurt am Main taking into consideration different modes of evaluation (examiner’s checklist versus instructor’s manual) and number of examiners (three versus four). Methods: In an historic, monocentric, comparative study, two different methods of evaluation were examined in a real end-of-semester setting held in OSPE form (Group I: exclusive use of an examiner’s checklist versus Group II: use of an examiner’s checklist including an instructor’s manual). For the analysis of interrater reliability, the generalisability theory was applied that contains a generalisation of the concept of internal consistency (Cronbach’s alpha). Results: The results show that the exclusive use of the examiner’s checklist led to higher interrater reliability values than the in-depth instructor’s manual used in addition to the list. Conclusion: In summary it can be said that the examiner’s checklists used in the present study, without the instructor’s manual, resulted in the highest interrater reliability in combination with three evaluators within the context of the completed OSPE. PMID:27579361

  20. Ultrafine-Particle Emission Factors as a Function of Vehicle Mode of Operation for LDVs Based on Near-Roadway Monitoring.

    PubMed

    Zhai, Wenjuan; Wen, Dongqi; Xiang, Sheng; Hu, Zhice; Noll, Kenneth E

    2016-01-19

    This paper presents ultrafine-particle (UFP) emission factors (EFs) as a function of vehicle mode of operation (free flow and congestion) using (1) concurrent 5 min measurements of UFPs and carbon monoxide (CO) concentration, wind speed and direction, traffic volume and speed near a roadway that is restricted to light-duty vehicles (LDVs) and (2) inverse dispersion model calculations. Short-term measurements are required to characterize the highly variable and rapidly changing UFP concentration generated by vehicles. Under congestion conditions, the UFP vehicle EFs increased from 0.5 × 10(13) to 2 × 10(13) (particles km(-1) vehicle(-1)) when vehicle flow increased from 5500 to 7500 vehicles/h. For free-flow conditions, the EF is constant at 1.5 × 10(13) (particles km(-1) vehicle(-1)). The analysis is based on the assumption that air-quality models adequately describe the dilution process due to both traffic and atmospheric turbulence. The approach used to verify this assumption was to use an emission factor model to determine EFs for CO and then estimate dilution factors using measured CO concentrations. This procedure eliminates the need to rely only on air quality models to generate dilution factors. The EFs are suitable for fleet emissions under real-world traffic conditions. PMID:26674658

  1. A Thomson-type mass and energy spectrometer for characterizing ion energy distributions in a coaxial plasma gun operating in a gas-puff mode

    SciTech Connect

    Rieker, G. B.; Poehlmann, F. R.; Cappelli, M. A.

    2013-07-15

    Measurements of ion energy distribution are performed in the accelerated plasma of a coaxial electromagnetic plasma gun operating in a gas-puff mode at relatively low discharge energy (900 J) and discharge potential (4 kV). The measurements are made using a Thomson-type mass and energy spectrometer with a gated microchannel plate and phosphor screen as the ion sensor. The parabolic ion trajectories are captured from the sensor screen with an intensified charge-coupled detector camera. The spectrometer was designed and calibrated using the Geant4 toolkit, accounting for the effects on the ion trajectories of spatial non-uniformities in the spectrometer magnetic and electric fields. Results for hydrogen gas puffs indicate the existence of a class of accelerated protons with energies well above the coaxial discharge potential (up to 24 keV). The Thomson analyzer confirms the presence of impurities of copper and iron, also of relatively high energies, which are likely erosion or sputter products from plasma-electrode interactions.

  2. Mapping Weathering and Alteration Minerals in the Comstock and Geiger Grade Areas using Visible to Thermal Infrared Airborne Remote Sensing Data

    NASA Technical Reports Server (NTRS)

    Vaughan, Greg R.; Calvin, Wendy M.

    2005-01-01

    To support research into both precious metal exploration and environmental site characterization a combination of high spatial/spectral resolution airborne visible, near infrared, short wave infrared (VNIR/SWIR) and thermal infrared (TIR) image data were acquired to remotely map hydrothermal alteration minerals around the Geiger Grade and Comstock alteration regions, and map the mineral by-products of weathered mine dumps in Virginia City. Remote sensing data from the Airborne Visible Infrared Imaging Spectrometer (AVIRIS), SpecTIR Corporation's airborne hyperspectral imager (HyperSpecTIR), the MODIS-ASTER airborne simulator (MASTER), and the Spatially Enhanced Broadband Array Spectrograph System (SEBASS) were acquired and processed into mineral maps based on the unique spectral signatures of image pixels. VNIR/SWIR and TIR field spectrometer data were collected for both calibration and validation of the remote data sets, and field sampling, laboratory spectral analyses and XRD analyses were made to corroborate the surface mineralogy identified by spectroscopy. The resulting mineral maps show the spatial distribution of several important alteration minerals around each study area including alunite, quartz, pyrophyllite, kaolinite, montmorillonite/muscovite, and chlorite. In the Comstock region the mineral maps show acid-sulfate alteration, widespread propylitic alteration and extensive faulting that offsets the acid-sulfate areas, in contrast to the larger, dominantly acid-sulfate alteration exposed along Geiger Grade. Also, different mineral zones within the intense acid-sulfate areas were mapped. In the Virginia City historic mining district the important weathering minerals mapped include hematite, goethite, jarosite and hydrous sulfate minerals (hexahydrite, alunogen and gypsum) located on mine dumps. Sulfate minerals indicate acidic water forming in the mine dump environment. While there is not an immediate threat to the community, there are clearly sources of

  3. Path planning during combustion mode switch

    SciTech Connect

    Jiang, Li; Ravi, Nikhil

    2015-12-29

    Systems and methods are provided for transitioning between a first combustion mode and a second combustion mode in an internal combustion engine. A current operating point of the engine is identified and a target operating point for the internal combustion engine in the second combustion mode is also determined. A predefined optimized transition operating point is selected from memory. While operating in the first combustion mode, one or more engine actuator settings are adjusted to cause the operating point of the internal combustion engine to approach the selected optimized transition operating point. When the engine is operating at the selected optimized transition operating point, the combustion mode is switched from the first combustion mode to the second combustion mode. While operating in the second combustion mode, one or more engine actuator settings are adjusted to cause the operating point of the internal combustion to approach the target operating point.

  4. Should Radial Modes Always Be Regarded as p-Modes?

    NASA Astrophysics Data System (ADS)

    Takata, M.

    2013-12-01

    As standard textbooks of stellar oscillations say, the only restoring force of radial modes in spherically symmetric stars is the pressure gradient, whereas the buoyancy force does not operate because no horizontal inhomogeneity is generated by radial oscillations. This is the physical reason why all radial modes should be classified as p-modes. In this presentation, however, we numerically demonstrate that unstable (adiabatic) radial modes should not be regraded as p-modes, because they are closely related to f-modes or g-modes of nonradial oscillations.

  5. Dual-Mode Combustor

    NASA Technical Reports Server (NTRS)

    Trefny, Charles J (Inventor); Dippold, Vance F (Inventor)

    2013-01-01

    A new dual-mode ramjet combustor used for operation over a wide flight Mach number range is described. Subsonic combustion mode is usable to lower flight Mach numbers than current dual-mode scramjets. High speed mode is characterized by supersonic combustion in a free-jet that traverses the subsonic combustion chamber to a variable nozzle throat. Although a variable combustor exit aperture is required, the need for fuel staging to accommodate the combustion process is eliminated. Local heating from shock-boundary-layer interactions on combustor walls is also eliminated.

  6. Orthogonally dual-polarization passively mode-locking operation of Nd:La0.25Gd0.75VO4 crystal

    NASA Astrophysics Data System (ADS)

    Xu, Honghao; Tang, Dingyuan; Yu, Haohai; Zhang, Huaijin; Wang, Jiyang

    2016-11-01

    We demonstrated in an a-cut Nd:La0.25Gd0.75VO4 mixed crystal the passively mode locking laser of two different wavelengths in orthogonal polarization states with a semiconductor saturable absorber mirror (SESAM). Due to the special anisotropic gain feature of the mixed crystal, through careful controlling on the cavity loss anisotropy, the simultaneous orthogonal polarization states laser were also achieved. In σ polarization states, the pulse width of 2.2 ps was close to the shortest pulse width obtained with Nd-doped vanadate crystal to my knowledge. What's more, dual-wavelength synchronized mode locking and bound-soliton-like pulse mode locking was also experimentally observed.

  7. Measurement of radon decay products and thoron decay products in air by beta counting using end-window Geiger-Muller counter.

    PubMed

    Papp, Z; Daróczy, S

    1997-04-01

    A new grab sampling method has been developed for the simultaneous measurement of radon decay products and thoron decay products in air. It is based on direct beta counting of filtered aerosol sample over successive time intervals by end-window Geiger-Muller counter. Defined solid angle absolute counting was used to evaluate the efficiencies for the decay products one by one. Absolute activity concentrations can be determined with less than 10% systematic error. Glass-fiber filter, high sampling flow rate, and long duration of sampling can be used, as a result of which the detection limits are about 0.1, 0.2, and 0.01 Bq m(-3) for 214Pb, 214Bi, and 212Pb, respectively. Indoor saturated activity concentrations were measured in 86 buildings in Ajka town, Hungary, where industrial wastes rich in uranium had been used as building materials. Elevated radon decay product levels were found in houses built before 1960. Radon gas concentration was also measured simultaneously in 26 cases and the minimum, maximum, and average values of the equilibrium factor were 0.17, 0.73, and 0.40, respectively.

  8. Stationary phase-related investigations of quinine-based zwitterionic chiral stationary phases operated in anion-, cation-, and zwitterion-exchange modes.

    PubMed

    Hoffmann, Christian V; Reischl, Roland; Maier, Norbert M; Lämmerhofer, Michael; Lindner, Wolfgang

    2009-02-13

    The concept of recently introduced Cinchona alkaloid-type zwitterionic chiral stationary phases (CSPs) is based on fusing key cation- and anion-exchange (CX, AX) moieties in one single low-molecular mass chiral selector (SO) with the resulting CSPs allowing enantiomer separations of a wide range of chiral ionizable analytes comprising acids, bases, and zwitterionic compounds. Herein, we report principal, systematic investigations of the ion-exchange-type retention mechanisms available with the novel zwitterionic CSPs in nonaqueous polar organic mode. Typical CX and AX processes, corresponding to the parent single ion exchangers, are confirmed also for zwitterionic CSPs. Also the mechanism leading to recognition and retention of zwitterions was found to be ion exchange mediated in a zwitterion-exchange (ZX) mode. In both AX and CX modes the additional ionizable group within the SO besides the site responsible for the respective ion-exchange process could be characterized as an intramolecular counterion (IMCI) that effectively participates in the ion-exchange equilibria and thus, contributes to solute elution. In the ZX mode both oppositely charged groups of the zwitterionic SO were found not only to be the sites for simultaneous ion pairing with the analyte but also functioned as IMCIs at the same time. The main practical consequences of the IMCI feature were significant reduction of the amounts and even elimination of acidic and basic additives required in the eluent systems to afford analyte elution while still providing faster analysis than the parent single ion-exchanger-type CSPs. The set of ten structurally different zwitterionic CSPs employed in this study facilitated the establishment of correlations between chromatographic behavior of the CSPs with particular SO elements, thereby supporting the understanding of the working principles of these novel packing materials on a molecular level.

  9. Electrocautery Devices With Feedback Mode and Teflon-Coated Blades Create Less Surgical Smoke for a Quality Improvement in the Operating Theater.

    PubMed

    Kisch, Tobias; Liodaki, Eirini; Kraemer, Robert; Mailaender, Peter; Brandenburger, Matthias; Hellwig, Veronika; Stang, Felix H

    2015-07-01

    Monopolar electrocautery is a fast and elegant cutting option. However, as it creates surgical smoke containing polycyclic aromatic hydrocarbons (PAHs), it may be hazardous to the health of the surgical team. Although new technologies, such as feedback mode (FM) and Teflon-coated blades (TBs), reduce tissue damage, their impact on surgical smoke creation has not yet been elucidated. Therefore, we analyzed the plume at its source.The aim of this study was to evaluate if electrocautery FM and TBs create less surgical smoke.Porcine tissue containing skin was cut in a standardized manner using sharp-edged Teflon-coated blades (SETBs), normal-shaped TBs, or stainless steel blades (SSBs). Experiments were performed using FM and pure-cut mode. Surgical smoke was sucked through filters or adsorption tubes. Subsequently, filters were scanned and analyzed using a spectrophotometer. A high-performance liquid chromatography (HPLC-UV) was performed to detect benzo[a]pyrene (BaP) and phenanthrene as 2 of the most critical PAHs. Temperature changes at the cutting site were measured by an infrared thermometer.In FM, more surgical smoke was created using SSB compared with TBs (P < 0.001). Furthermore, differences between FM and pure-cut mode were found for SSB and TB (P < 0.001), but not for SETB (P = 0.911). Photometric analysis revealed differences in the peak heights of the PAH spectrum. In HLPC-UV, the amount of BaP and phenanthrene detected was lower for TB compared with SSB. Tissue temperature variations increased when SSB was used in FM and pure-cut mode. Furthermore, different modes revealed higher temperature variations with the use of SETB (P = 0.004) and TB (P = 0.005) during cutting, but not SSB (P = 0.789).We found that the use of both TBs and FM was associated with reduced amounts of surgical smoke created during cutting. Thus, the surgical team may benefit from the adoption of such new technologies, which could contribute to the primary

  10. Electrocautery Devices With Feedback Mode and Teflon-Coated Blades Create Less Surgical Smoke for a Quality Improvement in the Operating Theater

    PubMed Central

    Kisch, Tobias; Liodaki, Eirini; Kraemer, Robert; Mailaender, Peter; Brandenburger, Matthias; Hellwig, Veronika; Stang, Felix H.

    2015-01-01

    Abstract Monopolar electrocautery is a fast and elegant cutting option. However, as it creates surgical smoke containing polycyclic aromatic hydrocarbons (PAHs), it may be hazardous to the health of the surgical team. Although new technologies, such as feedback mode (FM) and Teflon-coated blades (TBs), reduce tissue damage, their impact on surgical smoke creation has not yet been elucidated. Therefore, we analyzed the plume at its source. The aim of this study was to evaluate if electrocautery FM and TBs create less surgical smoke. Porcine tissue containing skin was cut in a standardized manner using sharp-edged Teflon-coated blades (SETBs), normal-shaped TBs, or stainless steel blades (SSBs). Experiments were performed using FM and pure-cut mode. Surgical smoke was sucked through filters or adsorption tubes. Subsequently, filters were scanned and analyzed using a spectrophotometer. A high-performance liquid chromatography (HPLC-UV) was performed to detect benzo[a]pyrene (BaP) and phenanthrene as 2 of the most critical PAHs. Temperature changes at the cutting site were measured by an infrared thermometer. In FM, more surgical smoke was created using SSB compared with TBs (P < 0.001). Furthermore, differences between FM and pure-cut mode were found for SSB and TB (P < 0.001), but not for SETB (P = 0.911). Photometric analysis revealed differences in the peak heights of the PAH spectrum. In HLPC-UV, the amount of BaP and phenanthrene detected was lower for TB compared with SSB. Tissue temperature variations increased when SSB was used in FM and pure-cut mode. Furthermore, different modes revealed higher temperature variations with the use of SETB (P = 0.004) and TB (P = 0.005) during cutting, but not SSB (P = 0.789). We found that the use of both TBs and FM was associated with reduced amounts of surgical smoke created during cutting. Thus, the surgical team may benefit from the adoption of such new technologies, which could contribute to the

  11. Dual-cavity mode converter for a fundamental mode output in an over-moded relativistic backward-wave oscillator

    NASA Astrophysics Data System (ADS)

    Li, Jiawei; Xiao, Renzhen; Bai, Xianchen; Zhang, Yuchuan; Zhang, Xiaowei; Zhu, Qi; Shao, Hao; Chen, Changhua; Huang, Wenhua

    2015-03-01

    A dual-cavity TM02-TM01 mode converter is designed for a dual-mode operation over-moded relativistic backward-wave oscillator. With the converter, the fundamental mode output is achieved. Particle-in-cell simulation shows that the efficiency of beam-wave conversion was over 46% and a pureTM01 mode output was obtained. Effects of end reflection provided by the mode converter were studied. Adequate TM01 mode feedback provided by the converter enhances conversion efficiency. The distance between the mode converter and extraction cavity critically affect the generation of microwaves depending on the reflection phase of TM01 mode feedback.

  12. Biosensing operations based on whispering-gallery-mode optical cavities in single 1.0-µm diameter hexagonal GaN microdisks grown by radio-frequency plasma-assisted molecular beam epitaxy

    NASA Astrophysics Data System (ADS)

    Kouno, Tetsuya; Sakai, Masaru; Kishino, Katsumi; Hara, Kazuhiko

    2016-05-01

    Biosensing operations based on a whispering-gallery-mode optical cavity in a single hexagonal GaN microdisk of approximately 1.0 µm diameter were demonstrated here. The sharp resonant peak in the photoluminescence spectrum obtained from the microdisk in aqueous sucrose solution redshifts with a change in sucrose concentration. The results indicate that an extremely small microdisk could be used as an optical transducer for sensing sugar, namely, as a biosensor. Furthermore, we investigate the relationship between the diameter of the microdisk and the sensitivity of the biosensor.

  13. 20 kHz sonoelectrochemical degradation of perchloroethylene in sodium sulfate aqueous media: influence of the operational variables in batch mode.

    PubMed

    Sáez, Verónica; Esclapez, María Deseada; Tudela, Ignacio; Bonete, Pedro; Louisnard, Olivier; González-García, José

    2010-11-15

    A preliminary study of the 20 kHz sonoelectrochemical degradation of perchloroethylene in aqueous sodium sulfate has been carried out using controlled current density degradation sonoelectrolyses in batch mode. An important improvement in the viability of the sonochemical process is achieved when the electrochemistry is implemented, but the improvement of the electrochemical treatment is lower when the 20 kHz ultrasound field is simultaneously used. A fractional conversion of 100% and degradation efficiency around 55% are obtained independently of the ultrasound power used. The current efficiency is also enhanced compared to the electrochemical treatment and a higher speciation is also detected; the main volatile compounds produced in the electrochemical and sonochemical treatment, trichloroethylene and dichloroethylene, are not only totally degraded, but also at shorter times than in the sonochemical or electrochemical treatments. PMID:20705391

  14. TESTING AND PERFORMANCE ANALYSIS OF NASA 5 CM BY 5 CM BI-SUPPORTED SOLID OXIDE ELECTROLYSIS CELLS OPERATED IN BOTH FUEL CELL AND STEAM ELECTROLYSIS MODES

    SciTech Connect

    R. C. O'Brien; J. E. O'Brien; C. M. Stoots; X. Zhang; S. C. Farmer; T. L. Cable; J. A. Setlock

    2011-11-01

    A series of 5 cm by 5 cm bi-supported Solid Oxide Electrolysis Cells (SOEC) were produced by NASA for the Idaho National Laboratory (INL) and tested under the INL High Temperature Steam Electrolysis program. The results from the experimental demonstration of cell operation for both hydrogen production and operation as fuel cells is presented. An overview of the cell technology, test apparatus and performance analysis is also provided. The INL High Temperature Steam Electrolysis laboratory has developed significant test infrastructure in support of single cell and stack performance analyses. An overview of the single cell test apparatus is presented. The test data presented in this paper is representative of a first batch of NASA's prototypic 5 cm by 5 cm SOEC single cells. Clearly a significant relationship between the operational current density and cell degradation rate is evident. While the performance of these cells was lower than anticipated, in-house testing at NASA Glenn has yielded significantly higher performance and lower degradation rates with subsequent production batches of cells. Current post-test microstructure analyses of the cells tested at INL will be published in a future paper. Modification to cell compositions and cell reduction techniques will be altered in the next series of cells to be delivered to INL with the aim to decrease the cell degradation rate while allowing for higher operational current densities to be sustained. Results from the testing of new batches of single cells will be presented in a future paper.

  15. Mode decomposition evolution equations

    PubMed Central

    Wang, Yang; Wei, Guo-Wei; Yang, Siyang

    2011-01-01

    Partial differential equation (PDE) based methods have become some of the most powerful tools for exploring the fundamental problems in signal processing, image processing, computer vision, machine vision and artificial intelligence in the past two decades. The advantages of PDE based approaches are that they can be made fully automatic, robust for the analysis of images, videos and high dimensional data. A fundamental question is whether one can use PDEs to perform all the basic tasks in the image processing. If one can devise PDEs to perform full-scale mode decomposition for signals and images, the modes thus generated would be very useful for secondary processing to meet the needs in various types of signal and image processing. Despite of great progress in PDE based image analysis in the past two decades, the basic roles of PDEs in image/signal analysis are only limited to PDE based low-pass filters, and their applications to noise removal, edge detection, segmentation, etc. At present, it is not clear how to construct PDE based methods for full-scale mode decomposition. The above-mentioned limitation of most current PDE based image/signal processing methods is addressed in the proposed work, in which we introduce a family of mode decomposition evolution equations (MoDEEs) for a vast variety of applications. The MoDEEs are constructed as an extension of a PDE based high-pass filter (Europhys. Lett., 59(6): 814, 2002) by using arbitrarily high order PDE based low-pass filters introduced by Wei (IEEE Signal Process. Lett., 6(7): 165, 1999). The use of arbitrarily high order PDEs is essential to the frequency localization in the mode decomposition. Similar to the wavelet transform, the present MoDEEs have a controllable time-frequency localization and allow a perfect reconstruction of the original function. Therefore, the MoDEE operation is also called a PDE transform. However, modes generated from the present approach are in the spatial or time domain and can be

  16. Dual mode laser velocimeter

    NASA Technical Reports Server (NTRS)

    Gunter, William D., Jr. (Inventor); Donaldson, Ralph W. (Inventor); Anderson, Alma G., Jr. (Inventor)

    1987-01-01

    Described is a laser Doppler velocimeter (LDV) which is capable of operating with a small focus diameter for analyzing fluid flows at low velocity with high spatial resolution, or with a larger focus diameter to measure fluid flows at higher velocities accurately. More particularly, this is an LDV in which a simple reversal of a lens pair will allow it to operate in the two focus diameter modes.

  17. RendezVous sensor for automatic guidance of transfer vehicles to ISS concept of the operational modes depending on actual optical and geometrical-dynamical conditions

    NASA Astrophysics Data System (ADS)

    Moebius, Bettina G.; Kolk, Karl-Hermann

    2000-10-01

    Based on an ATV RendezVous Predevelopment Program initiated by ESTEC, an automatically operating Rendez Vous Sensor has been developed. The sensor--a Scanning Tele-Goniometer--shall guide docking and retreat of the European Automatic Transfer Vehicle as well as berthing and retreat of the Japanese H-II Transfer Vehicle. The sensor performance will be strongly connected with the properties of cooperative targets, consisting of an arrangement of retro reflectors mounted on ISS each.

  18. Plasma Modes

    NASA Astrophysics Data System (ADS)

    Dubin, D. H. E.

    This chapter explores several aspects of the linear electrostatic normal modes of oscillation for a single-species non-neutral plasma in a Penning trap. Linearized fluid equations of motion are developed, assuming the plasma is cold but collisionless, which allow derivation of the cold plasma dielectric tensor and the electrostatic wave equation. Upper hybrid and magnetized plasma waves in an infinite uniform plasma are described. The effect of the plasma surface in a bounded plasma system is considered, and the properties of surface plasma waves are characterized. The normal modes of a cylindrical plasma column are discussed, and finally, modes of spheroidal plasmas, and finite temperature effects on the modes, are briefly described.

  19. Lipid production of microalga Chlorella sorokiniana CY1 is improved by light source arrangement, bioreactor operation mode and deep-sea water supplements.

    PubMed

    Chen, Chun-Yen; Chang, Hsin-Yueh

    2016-03-01

    Microalgae-based biodiesel has been recognized as a sustainable and promising alternative to fossil diesel. High lipid productivity of microalgae is required for economic production of biodiesel from microalgae. This study was undertaken to enhance the growth and oil accumulation of an indigenous microalga Chlorella sorokiniana CY1 by applying engineering strategies using deep-sea water as the medium. First, the microalga was cultivated using LED as the immersed light source, and the results showed that the immersed LED could effectively enhance the oil/lipid content and final microalgal biomass concentration to 53.8% and 2.5 g/l, respectively. Next, the semi-batch photobioreactor operation with deep-sea water was shown to improve lipid content and microalgal growth over those from using batch and continuous cultures under similar operating conditions. The optimal replacement ratio was 50%, resulting in an oil/lipid content and final biomass concentration of 61.5% and 2.8 g/l, respectively. A long-term semi-batch culture utilizing 50%-replaced medium was carried out for four runs. The final biomass concentration and lipid productivity were 2.5 g/L and 112.2 mg/L/d, respectively. The fatty acid composition of the microalgal lipids was predominant by palmitic acid, stearic acid, oleic acid and linoleic acid, and this lipid quality is suitable for biodiesel production. This demonstrates that optimizing light source arrangement, bioreactor operation and deep-sea water supplements could effectively promote the lipid production of C. sorokiniana CY1 for the applications in microalgae-based biodiesel industry. PMID:26632521

  20. The Chief Role of Frontal Operational Module of the Brain Default Mode Network in the Potential Recovery of Consciousness from the Vegetative State: A Preliminary Comparison of Three Case Reports

    PubMed Central

    Fingelkurts, Alexander A.; Fingelkurts, Andrew A.; Bagnato, Sergio; Boccagni, Cristina; Galardi, Giuseppe

    2016-01-01

    It has been argued that complex subjective sense of self is linked to the brain default-mode network (DMN). Recent discovery of heterogeneity between distinct subnets (or operational modules - OMs) of the DMN leads to a reconceptualization of its role for the experiential sense of self. Considering the recent proposition that the frontal DMN OM is responsible for the first-person perspective and the sense of agency, while the posterior DMN OMs are linked to the continuity of ‘I’ experience (including autobiographical memories) through embodiment and localization within bodily space, we have tested in this study the hypothesis that heterogeneity in the operational synchrony strength within the frontal DMN OM among patients who are in a vegetative state (VS) could inform about a stable self-consciousness recovery later in the course of disease (up to six years post-injury). Using EEG operational synchrony analysis we have demonstrated that among the three OMs of the DMN only the frontal OM showed important heterogeneity in VS patients as a function of later stable clinical outcome. We also found that the frontal DMN OM was characterized by the process of active uncoupling (stronger in persistent VS) of operations performed by the involved neuronal assemblies. PMID:27347264

  1. The Chief Role of Frontal Operational Module of the Brain Default Mode Network in the Potential Recovery of Consciousness from the Vegetative State: A Preliminary Comparison of Three Case Reports.

    PubMed

    Fingelkurts, Alexander A; Fingelkurts, Andrew A; Bagnato, Sergio; Boccagni, Cristina; Galardi, Giuseppe

    2016-01-01

    It has been argued that complex subjective sense of self is linked to the brain default-mode network (DMN). Recent discovery of heterogeneity between distinct subnets (or operational modules - OMs) of the DMN leads to a reconceptualization of its role for the experiential sense of self. Considering the recent proposition that the frontal DMN OM is responsible for the first-person perspective and the sense of agency, while the posterior DMN OMs are linked to the continuity of 'I' experience (including autobiographical memories) through embodiment and localization within bodily space, we have tested in this study the hypothesis that heterogeneity in the operational synchrony strength within the frontal DMN OM among patients who are in a vegetative state (VS) could inform about a stable self-consciousness recovery later in the course of disease (up to six years post-injury). Using EEG operational synchrony analysis we have demonstrated that among the three OMs of the DMN only the frontal OM showed important heterogeneity in VS patients as a function of later stable clinical outcome. We also found that the frontal DMN OM was characterized by the process of active uncoupling (stronger in persistent VS) of operations performed by the involved neuronal assemblies. PMID:27347264

  2. A dark-field microscope for background-free detection of resonance fluorescence from single semiconductor quantum dots operating in a set-and-forget mode.

    PubMed

    Kuhlmann, Andreas V; Houel, Julien; Brunner, Daniel; Ludwig, Arne; Reuter, Dirk; Wieck, Andreas D; Warburton, Richard J

    2013-07-01

    Optically active quantum dots, for instance self-assembled InGaAs quantum dots, are potentially excellent single photon sources. The fidelity of the single photons is much improved using resonant rather than non-resonant excitation. With resonant excitation, the challenge is to distinguish between resonance fluorescence and scattered laser light. We have met this challenge by creating a polarization-based dark-field microscope to measure the resonance fluorescence from a single quantum dot at low temperature. We achieve a suppression of the scattered laser exceeding a factor of 10(7) and background-free detection of resonance fluorescence. The same optical setup operates over the entire quantum dot emission range (920-980 nm) and also in high magnetic fields. The major development is the outstanding long-term stability: once the dark-field point has been established, the microscope operates for days without alignment. The mechanical and optical designs of the microscope are presented, as well as exemplary resonance fluorescence spectroscopy results on individual quantum dots to underline the microscope's excellent performance.

  3. A dark-field microscope for background-free detection of resonance fluorescence from single semiconductor quantum dots operating in a set-and-forget mode

    SciTech Connect

    Kuhlmann, Andreas V.; Houel, Julien; Warburton, Richard J.; Brunner, Daniel; Ludwig, Arne; Reuter, Dirk; Wieck, Andreas D.

    2013-07-15

    Optically active quantum dots, for instance self-assembled InGaAs quantum dots, are potentially excellent single photon sources. The fidelity of the single photons is much improved using resonant rather than non-resonant excitation. With resonant excitation, the challenge is to distinguish between resonance fluorescence and scattered laser light. We have met this challenge by creating a polarization-based dark-field microscope to measure the resonance fluorescence from a single quantum dot at low temperature. We achieve a suppression of the scattered laser exceeding a factor of 10{sup 7} and background-free detection of resonance fluorescence. The same optical setup operates over the entire quantum dot emission range (920–980 nm) and also in high magnetic fields. The major development is the outstanding long-term stability: once the dark-field point has been established, the microscope operates for days without alignment. The mechanical and optical designs of the microscope are presented, as well as exemplary resonance fluorescence spectroscopy results on individual quantum dots to underline the microscope's excellent performance.

  4. Manipulation of gold colloidal nanoparticles with atomic force microscopy in dynamic mode: influence of particle–substrate chemistry and morphology, and of operating conditions

    PubMed Central

    Darwich, Samer; Rao, Akshata; Gnecco, Enrico; Jayaraman, Shrisudersan; Haidara, Hamidou

    2011-01-01

    Summary One key component in the assembly of nanoparticles is their precise positioning to enable the creation of new complex nano-objects. Controlling the nanoscale interactions is crucial for the prediction and understanding of the behaviour of nanoparticles (NPs) during their assembly. In the present work, we have manipulated bare and functionalized gold nanoparticles on flat and patterned silicon and silicon coated substrates with dynamic atomic force microscopy (AFM). Under ambient conditions, the particles adhere to silicon until a critical drive amplitude is reached by oscillations of the probing tip. Beyond that threshold, the particles start to follow different directions, depending on their geometry, size and adhesion to the substrate. Higher and respectively, lower mobility was observed when the gold particles were coated with methyl (–CH3) and hydroxyl (–OH) terminated thiol groups. This major result suggests that the adhesion of the particles to the substrate is strongly reduced by the presence of hydrophobic interfaces. The influence of critical parameters on the manipulation was investigated and discussed viz. the shape, size and grafting of the NPs, as well as the surface chemistry and the patterning of the substrate, and finally the operating conditions (temperature, humidity and scan velocity). Whereas the operating conditions and substrate structure are shown to have a strong effect on the mobility of the particles, we did not find any differences when manipulating ordered vs random distributed particles. PMID:21977418

  5. Batch vs continuous-feeding operational mode for the removal of pesticides from agricultural run-off by microalgae systems: A laboratory scale study.

    PubMed

    Matamoros, Víctor; Rodríguez, Yolanda

    2016-05-15

    Microalgae-based water treatment technologies have been used in recent years to treat different water effluents, but their effectiveness for removing pesticides from agricultural run-off has not yet been addressed. This paper assesses the effect of microalgae in pesticide removal, as well as the influence of different operation strategies (continuous vs batch feeding). The following pesticides were studied: mecoprop, atrazine, simazine, diazinone, alachlor, chlorfenvinphos, lindane, malathion, pentachlorobenzene, chlorpyrifos, endosulfan and clofibric acid (tracer). 2L batch reactors and 5L continuous reactors were spiked to 10 μg L(-1) of each pesticide. Additionally, three different hydraulic retention times (HRTs) were assessed (2, 4 and 8 days) in the continuous feeding reactors. The batch-feeding experiments demonstrated that the presence of microalgae increased the efficiency of lindane, alachlor and chlorpyrifos by 50%. The continuous feeding reactors had higher removal efficiencies than the batch reactors for pentachlorobenzene, chlorpyrifos and lindane. Whilst longer HRTs increased the technology's effectiveness, a low HRT of 2 days was capable of removing malathion, pentachlorobenzene, chlorpyrifos, and endosulfan by up to 70%. This study suggests that microalgae-based treatment technologies can be an effective alternative for removing pesticides from agricultural run-off.

  6. Room temperature plasmonic lasing in a continuous wave operation mode from an InGaN/GaN single nanorod with a low threshold

    PubMed Central

    Hou, Y.; Renwick, P.; Liu, B.; Bai, J.; Wang, T.

    2014-01-01

    It is crucial to fabricate nano photonic devices such as nanolasers in order to meet the requirements for the integration of photonic and electronic circuits on the nanometre scale. The great difficulty is to break down a bottleneck as a result of the diffraction limit of light. Nanolasers on a subwavelength scale could potentially be fabricated based on the principle of surface plasmon amplification by stimulated emission of radiation (SPASER). However, a number of technological challenges will have to be overcome in order to achieve a SPASER with a low threshold, allowing for a continuous wave (cw) operation at room temperature. We report a nano-SPASER with a record low threshold at room temperature, optically pumped by using a cw diode laser. Our nano-SPASER consists of a single InGaN/GaN nanorod on a thin SiO2 spacer layer on a silver film. The nanorod containing InGaN/GaN multi-quantum-wells is fabricated by means of a cost-effective post-growth fabrication approach. The geometry of the nanorod/dielectric spacer/plasmonic metal composite allows us to have accurate control of the surface plasmon coupling, offering an opportunity to determine the optimal thickness of the dielectric spacer. This approach will open up a route for further fabrication of electrically injected plasmonic lasers. PMID:24852881

  7. INVESTIGATION OF A PLASMA MODE IN EBTS.

    SciTech Connect

    HERSHCOVITCH,A.

    2000-11-06

    A plasma related mode has been identified when EBTS operated with long trap length. The mode frequency scaling showed monotonic increased with confinement time. Initial scaling qualitatively suggested the mode to an electron beam driven ion cyclotron instability. However, a more quantitative evaluation is indicative of a drift mode. Nevertheless, the possibility of a structure mode, though unlikely, can not be completely excluded. The process of proper instability identification and stabilization is described.

  8. Detection performance improvement of chirped amplitude modulation ladar based on Gieger-mode avalanche photoelectric detector.

    PubMed

    Zhang, Zijing; Wu, Long; Zhang, Yu; Zhao, Yuan; Sun, Xiudong

    2011-12-10

    This paper presents an improved system structure of photon-counting chirped amplitude modulation (AM) ladar based on the Geiger-mode avalanche photoelectric detector (GmAPD). The error-pulse probability is investigated with statistical method. The research shows that most of the error pulses that are triggered by noise are distributed in the intensity troughs of the chirped AM waveform. The error-pulse probability is lowered with the sliding window and the threshold. With the average intensity of noise and signal being 0.3 count/sample and 1 count/sample, respectively, the probability of error pulses is reduced from 12% to 1.0%, and the SNR is improved by 2.2 dB in the improved system. PMID:22193131

  9. What is Local Mode (LM)? Global Mode (GM)? Calibration Mode?

    Atmospheric Science Data Center

    2014-12-08

    ... measurement in Global Mode (GM), Local Mode (LM), and Calibration. Global Mode is the normal acquisition with pole to pole coverage ... targets approximately 300 km in length Calibration Implemented bi-monthly Spectralon solar ...

  10. Methanol sensor operated in a passive mode

    DOEpatents

    Ren, Xiaoming; Gottesfeld, Shimshon

    2002-01-01

    A sensor outputs a signal related to a concentration of methanol in an aqueous solution adjacent the sensor. A membrane electrode assembly (MEA) is included with an anode side and a cathode side. An anode current collector supports the anode side of the MEA and has a flow channel therethrough for flowing a stream of the aqueous solution and forms a physical barrier to control access of the methanol to the anode side of the MEA. A cathode current collector supports the cathode side of the MEA and is configured for air access to the cathode side of the MEA. A current sensor is connected to measure the current in a short circuit across the sensor electrodes to provide an output signal functionally related to the concentration of methanol in the aqueous solution.

  11. Dual-cavity mode converter for a fundamental mode output in an over-moded relativistic backward-wave oscillator

    SciTech Connect

    Li, Jiawei; Huang, Wenhua; Xiao, Renzhen; Bai, Xianchen; Zhang, Yuchuan; Zhang, Xiaowei; Shao, Hao; Chen, Changhua; Zhu, Qi

    2015-03-16

    A dual-cavity TM{sub 02}–TM{sub 01} mode converter is designed for a dual-mode operation over-moded relativistic backward-wave oscillator. With the converter, the fundamental mode output is achieved. Particle-in-cell simulation shows that the efficiency of beam-wave conversion was over 46% and a pureTM{sub 01} mode output was obtained. Effects of end reflection provided by the mode converter were studied. Adequate TM{sub 01} mode feedback provided by the converter enhances conversion efficiency. The distance between the mode converter and extraction cavity critically affect the generation of microwaves depending on the reflection phase of TM{sub 01} mode feedback.

  12. CALIPSO Instrument Operational

    Atmospheric Science Data Center

    2014-03-05

    ... being briefly in data acquisition mode, the CALIPSO payload computer (PLC) was commanded OFF due to another solar event earlier this ... remain above the 10MeV threshold for laser operations. Science data is not acquired while the payload is in SAFE mode.   ...

  13. CALIPSO Instrument Operational

    Atmospheric Science Data Center

    2014-09-18

    CALIPSO Instrument Operational Thursday, September 11, 2014 The CALIPSO payload is back in data acquisition mode as of Wednesday, September 17, 2014.  CALIPSO data processing has returned to a nominal state, and...

  14. Landsat-5 bumper-mode geometric correction

    USGS Publications Warehouse

    Storey, J.C.; Choate, Michael J.

    2004-01-01

    The Landsat-5 Thematic Mapper (TM) scan mirror was switched from its primary operating mode to a backup mode in early 2002 in order to overcome internal synchronization problems arising from long-term wear of the scan mirror mechanism. The backup bumper mode of operation removes the constraints on scan start and stop angles enforced in the primary scan angle monitor operating mode, requiring additional geometric calibration effort to monitor the active scan angles. It also eliminates scan timing telemetry used to correct the TM scan geometry. These differences require changes to the geometric correction algorithms used to process TM data. A mathematical model of the scan mirror's behavior when operating in bumper mode was developed. This model includes a set of key timing parameters that characterize the time-varying behavior of the scan mirror bumpers. To simplify the implementation of the bumper-mode model, the bumper timing parameters were recast in terms of the calibration and telemetry data items used to process normal TM imagery. The resulting geometric performance, evaluated over 18 months of bumper-mode operations, though slightly reduced from that achievable in the primary operating mode, is still within the Landsat specifications when the data are processed with the most up-to-date calibration parameters.

  15. Experimental investigation on flow modes of electrospinning

    NASA Astrophysics Data System (ADS)

    Si, Ting; Li, Guang-Bin; Chen, Xing-Xing; Tian, Rui-Jun; Yin, Xie-Zhen

    2012-06-01

    Electrospinning experiments are performed by using a set of experimental apparatus, a stroboscopic system is adopted for capturing instantaneous images of the conejet configuration. The cone and the jet of aqueous solutions of polyethylene oxide (PEO) are formed from an orifice of a capillary tube under the electric field. The viscoelastic constitutive relationship of the PEO solution is measured and discussed. The phenomena owing to the jet instability are described, five flow modes and corresponding structures are obtained with variations of the fluid flow rate Q, the electric potential U and the distance h from the orifice of the capillary tube to the collector. The flow modes of the cone-jet configuration involves the steady bending mode, the rotating bending mode, the swinging rotating mode, the blurring bending mode and the branching mode. Regimes in the Q-U plane of the flow modes are also obtained. These results may provide the fundamentals to predict the operating conditions expected in practical applications.

  16. Photon Detection with Cooled Avalanche Photodiodes: Theory and Preliminary Experimental Results

    NASA Technical Reports Server (NTRS)

    Robinson, D. L.; Hays, D. A.

    1985-01-01

    Avalanche photodiodes (APDs) can be operated in a geiger-tube mode so that they can respond to single electron events and thus be used as photon counting detectors. Operational characteristics and theory of APDs while used in this mode are analyzed and assessed. Preliminary experimental investigation of several commercially available APDs has commenced, and initial results for dark count statistics are presented.

  17. SAMPEX Spin Stabilized Mode

    NASA Technical Reports Server (NTRS)

    Tsai, Dean C.; Markley, F. Landis; Watson, Todd P.

    2008-01-01

    The Solar, Anomalous, and Magnetospheric Particle Explorer (SAMPEX), the first of the Small Explorer series of spacecraft, was launched on July 3, 1992 into an 82' inclination orbit with an apogee of 670 km and a perigee of 520 km and a mission lifetime goal of 3 years. After more than 15 years of continuous operation, the reaction wheel began to fail on August 18,2007. With a set of three magnetic torquer bars being the only remaining attitude actuator, the SAMPEX recovery team decided to deviate from its original attitude control system design and put the spacecraft into a spin stabilized mode. The necessary operations had not been used for many years, which posed a challenge. However, on September 25, 2007, the spacecraft was successfully spun up to 1.0 rpm about its pitch axis, which points at the sun. This paper describes the diagnosis of the anomaly, the analysis of flight data, the simulation of the spacecraft dynamics, and the procedures used to recover the spacecraft to spin stabilized mode.

  18. Resonant Mode-hopping Micromixing.

    PubMed

    Jang, Ling-Sheng; Chao, Shih-Hui; Holl, Mark R; Meldrum, Deirdre R

    2007-07-20

    A common micromixer design strategy is to generate interleaved flow topologies to enhance diffusion. However, problems with these designs include complicated structures and dead volumes within the flow fields. We present an active micromixer using a resonating piezoceramic/silicon composite diaphragm to generate acoustic streaming flow topologies. Circulation patterns are observed experimentally and correlate to the resonant mode shapes of the diaphragm. The dead volumes in the flow field are eliminated by rapidly switching from one discrete resonant mode to another (i.e., resonant mode-hop). Mixer performance is characterized by mixing buffer with a fluorescence tracer containing fluorescein. Movies of the mixing process are analyzed by converting fluorescent images to two-dimensional fluorescein concentration distributions. The results demonstrate that mode-hopping operation rapidly homogenized chamber contents, circumventing diffusion-isolated zones. PMID:19551159

  19. Correspondence between Koopman mode decomposition, resolvent mode decomposition, and invariant solutions of the Navier-Stokes equations

    NASA Astrophysics Data System (ADS)

    Sharma, Ati S.; Mezić, Igor; McKeon, Beverley J.

    2016-07-01

    The relationship between Koopman mode decomposition, resolvent mode decomposition, and exact invariant solutions of the Navier-Stokes equations is clarified. The correspondence rests upon the invariance of the system operators under symmetry operations such as spatial translation. The usual interpretation of the Koopman operator is generalized to permit combinations of such operations, in addition to translation in time. This invariance is related to the spectrum of a spatiotemporal Koopman operator, which has a traveling-wave interpretation. The relationship leads to a generalization of dynamic mode decomposition, in which symmetry operations are applied to restrict the dynamic modes to span a subspace subject to those symmetries. The resolvent is interpreted as the mapping between the Koopman modes of the Reynolds stress divergence and the velocity field. It is shown that the singular vectors of the resolvent (the resolvent modes) are the optimal basis in which to express the velocity field Koopman modes where the latter are not a priori known.

  20. Semi-guiding high-aspect-ratio core (SHARC) fiber amplifiers with ultra-large core area for single-mode kW operation in a compact coilable package.

    PubMed

    Marciante, John R; Shkunov, Vladimir V; Rockwell, David A

    2012-08-27

    A new class of optical fiber, the SHARC fiber, is analyzed in a high-power fiber amplifier geometry using the gain-filtering properties of confined-gain dopants. The high-aspect-ratio (~30:1) rectangular core allows mode-area scaling well beyond 10,000 μm2, which is critical to high-pulse-energy or narrow-linewidth high-power fiber amplifiers. While SHARC fibers offer modally dependent edge loss at the wide "semi-guiding" edge of the waveguide, the inclusion of gain filtering adds further modal discrimination arising from the variation of the spatial overlap of the gain with the various modes. Both methods are geometric in form, such that the combination provides nearly unlimited scalability in mode area. Simulations show that for kW-class fiber amplifiers, only the fundamental mode experiences net gain (15 dB), resulting in outstanding beam quality. Further, misalignment of the seed beam due to offset, magnification, and tilt are shown to result in a small (few percent) efficiency penalty while maintaining kW-level output with 99% of the power in the fundamental mode for all cases.

  1. Dual-Mode Adhesive Pad

    NASA Technical Reports Server (NTRS)

    Hartz, Leslie

    1994-01-01

    Tool helps worker grip and move along large, smooth structure with no handgrips or footholds. Adheres to surface but easily released by actuating simple mechanism. Includes handle and segmented contact-adhesive pad. Bulk of pad made of soft plastic foam conforming to surface of structure. Each segment reinforced with rib. In sticking mode, ribs braced by side catches. In peeling mode, side catches retracted, and segmented adhesive pad loses its stiffness. Modified versions useful in inspecting hulls of ships and scaling walls in rescue operations.

  2. Dual-Mode Combustion

    NASA Technical Reports Server (NTRS)

    Goyne, Christopher P.; McDaniel, James C.

    2002-01-01

    The Department of Mechanical and Aerospace Engineering at the University of Virginia has conducted an investigation of the mixing and combustion processes in a hydrogen fueled dual-mode scramjet combustor. The experiment essentially consisted of the "direct connect" continuous operation of a Mach 2 rectangular combustor with a single unswept ramp fuel injector. The stagnation enthalpy of the test flow simulated a flight Mach number of 5. Measurements were obtained using conventional wall instrumentation and laser based diagnostics. These diagnostics included, pressure and wall temperature measurements, Fuel Plume Imaging (FPI) and Particle Image Velocimetry (PIV). A schematic of the combustor configuration and a summary of the measurements obtained are presented. The experimental work at UVa was parallel by Computational Fluid Dynamics (CFD) work at NASA Langley. The numerical and experiment results are compared in this document.

  3. Failure modes in surface micromachined microelectromechanical actuators

    SciTech Connect

    Miller, S.L.; Rodgers, M.S.; LaVigne, G.; Sniegowski, J.J.; Clews, P.; Tanner, D.M.; Peterson, K.A.

    1998-03-01

    In order for the rapidly emerging field of MicroElectroMechanical Systems (MEMS) to meet its extraordinary expectations regarding commercial impact, issues pertaining to how they fail must be understood. The authors identify failure modes common to a broad range of MEMS actuators, including adhesion (stiction) and friction induced failures caused by improper operational methods, mechanical instabilities, and electrical instabilities. Demonstrated methods to mitigate these failure modes include implementing optimized designs, model based operational methods, and chemical surface treatments.

  4. Mode Transitions in Hall Effect Thrusters

    NASA Technical Reports Server (NTRS)

    Sekerak, Michael J.; Longmier, Benjamin W.; Gallimore, Alec D.; Brown, Daniel L.; Hofer, Richard R.; Polk, James E.

    2013-01-01

    Mode transitions have been commonly observed in Hall Effect Thruster (HET) operation where a small change in a thruster operating parameter such as discharge voltage, magnetic field or mass flow rate causes the thruster discharge current mean value and oscillation amplitude to increase significantly. Mode transitions in a 6-kW-class HET called the H6 are induced by varying the magnetic field intensity while holding all other operating parameters constant and measurements are acquired with ion saturation probes and ultra-fast imaging. Global and local oscillation modes are identified. In the global mode, the entire discharge channel oscillates in unison and azimuthal perturbations (spokes) are either absent or negligible. Downstream azimuthally spaced probes show no signal delay between each other and are very well correlated to the discharge current signal. In the local mode, signals from the azimuthally spaced probes exhibit a clear delay indicating the passage of "spokes" and are not well correlated to the discharge current. These spokes are localized oscillations propagating in the ExB direction that are typically 10-20% of the mean value. In contrast, the oscillations in the global mode can be 100% of the mean value. The transition between global and local modes occurs at higher relative magnetic field strengths for higher mass flow rates or higher discharge voltages. The thrust is constant through mode transition but the thrust-to-power decreased by 25% due to increasing discharge current. The plume shows significant differences between modes with the global mode significantly brighter in the channel and the near-field plasma plume as well as exhibiting a luminous spike on thruster centerline. Mode transitions provide valuable insight to thruster operation and suggest improved methods for thruster performance characterization.

  5. Development and characterization of CMOS avalanche photodiode arrays

    NASA Astrophysics Data System (ADS)

    Lawrence, William G.; Christian, James F.; Augustine, Frank L.; Squillante, Michael R.; Entine, Gerald

    2005-04-01

    Avalanche photodiode (APD) arrays fabricated by using complementary metal-oxide-semiconductor (CMOS) fabrication technology offer the possibility of combining these high sensitivity detectors with cost effective, on-board, complementary circuitry. Using CMOS techniques, Radiation Monitoring Devices has developed prototype pixels with active diameters ranging from 5 to 60 microns and with measured quantum efficiencies of up to 65%. The prototype CMOS APD pixel designs support both proportional and Geiger modes of photo-detection. When operating in Geiger mode, these APD"s act as single-optical-photon-counting detectors that can be used for time-resolved measurements under signal-starved conditions. We have also designed and fabricated CMOS chips that contain not only the APD pixels, but also associated circuitry for both actively and passively quenching the self-propagating Geiger avalanche. This report presents the noise and timing performance for the prototype CMOS APD pixels in both the proportional and Geiger modes of operation. It compares the quantum efficiency and dark-count rate of different pixel designs as a function of the applied bias and presents a discussion of the maximum count rates that is obtained with each of the two types of quenching circuits for operating the pixel in Geiger mode. Preliminary data on the application of the APD pixels to laser ranging and fluorescent lifetime measurement is also presented.

  6. Quasi-interferometric scheme improved by fiber Bragg grating for detection of outer mechanical stress influence on distributed sensor being silica multimode optical fiber operating in a few-mode regime

    NASA Astrophysics Data System (ADS)

    Kafarova, Anastasia M.; Faskhutdinov, Lenar M.; Kuznetzov, Artem A.; Minaeva, Alina Y.; Sevruk, Nikita L.; Nureev, Ilnur I.; Vasilets, Alexander A.; Bourdine, Anton V.; Morozov, Oleg G.; Burdin, Vladimir A.

    2016-03-01

    This work presents results of experimental approbation of modified fiber optic stress sensor based on a few-mode effects occurring during laser-excited optical signal propagation over silica multimode optical fiber (MMF). Modification is concerned with adding of quasi-interferometric scheme realized by two multimode Y-couplers with equalized arm lengths improved by fiber Bragg grating (FBG) and special offset launching conditions providing laser-based excitation of higher-order modes. We tested FBGs written on graded-index MMFs 50/125 with Bragg wavelength 1550 nm connected to different parts of proposed scheme. Researches are focused on comparing analysis of both spectral and pulse responses under changing of selected mode mixing and power diffusion processes due to stress local and distributed action to sensor fiber depending on scheme configuration. Here we considered FBGs not only as particular wavelength reflector during spectral response measurement but also as local periodic microstructure defect strongly effecting few-mode signal components mixing process that provides pulse response variation. Some results of spectral and pulse response measurements produced for different scheme configuration and their comparison analysis are represented.

  7. Single-mode cylindrical graphene plasmon waveguide

    NASA Astrophysics Data System (ADS)

    Yang, Jianfeng; Yang, Jingjing; Huang, Ming

    2016-08-01

    A cylindrical graphene plasmon waveguide (CGPW) which consists of two rolled graphene ribbons, a dielectric core and a dielectric interlayer is proposed. An analytical model for the single-mode condition and cutoff frequency of high-order graphene surface plasmon (GSP) modes is presented and verified by finite element method (FEM) simulations. Single-mode operation region of CGPW is identified in the frequency-radius space. By varying the separation between two graphene sheets and the Fermi level of graphene, a large tunability of the mode behavior is also demonstrated. The proposed structure may provide a new freedom to manipulate GSPs, and would lead to novel applications in optics.

  8. Large bandwidth mode order converter by differential waveguides.

    PubMed

    Oner, B B; Üstün, K; Kurt, H; Okyay, A K; Turhan-Sayan, G

    2015-02-01

    In this article, we propose a large bandwidth mode-order converter design by dielectric waveguides with equal lengths but different cross-sectional areas. The efficient conversion between even and odd modes is verified by inducing required phase difference between the equal length waveguides of different widths. Y-junctions are composed of both tapered mode splitter and combiner to connect mono-mode waveguide to multi-mode waveguide. The converted mode profiles at the output port show that the device operates successfully at designed wavelengths with wide bandwidth. This study provides a novel technique to implement compact mode order converters and direction selective/sensitive photonic structures.

  9. Diagnostic for two-mode variable valve activation device

    SciTech Connect

    Fedewa, Andrew M

    2014-01-07

    A method is provided for diagnosing a multi-mode valve train device which selectively provides high lift and low lift to a combustion valve of an internal combustion engine having a camshaft phaser actuated by an electric motor. The method includes applying a variable electric current to the electric motor to achieve a desired camshaft phaser operational mode and commanding the multi-mode valve train device to a desired valve train device operational mode selected from a high lift mode and a low lift mode. The method also includes monitoring the variable electric current and calculating a first characteristic of the parameter. The method also includes comparing the calculated first characteristic against a predetermined value of the first characteristic measured when the multi-mode valve train device is known to be in the desired valve train device operational mode.

  10. Surface acoustic wave mode conversion resonator

    NASA Astrophysics Data System (ADS)

    Martin, S. J.; Gunshor, R. L.; Melloch, M. R.; Datta, S.; Pierret, R. F.

    1983-08-01

    The fact that a ZnO-on-Si structure supports two distinct surface waves, referred to as the Rayleigh and the Sezawa modes, if the ZnO layer is sufficiently thick is recalled. A description is given of a unique surface wave resonator that operates by efficiently converting between the two modes at the resonant frequency. Since input and output coupling is effected through different modes, the mode conversion resonator promises enhanced out-of-band signal rejection. A Rayleigh wave traversing the resonant cavity in one direction is reflected as a Sezawa wave. It is pointed out that the off-resonance rejection of the mode conversion resonator could be enhanced by designing the transducers to minimize the level of cross coupling between transducers and propagating modes.

  11. Controllable mode multistability in microring lasers.

    PubMed

    Yuan, Guohui; Wang, Zhuoran

    2013-04-22

    We investigate mode multistability, i.e. coexistence of direction bistability and wavelength bi/multistability in microring lasers (MRLs) theoretically and numerically. We derive the expressions for conditions required for mode multistable operation in microring lasers based on a nonlinear multimode model with nonlinear effects stemming from carrier density pulsation, carrier heating and spectral hole burning included. We find theoretically that lasing mode can be selected from the multistable modes by external optical injection through gain saturation, and removal of the external optical injection will not affect the stability of the established lasing mode. Numerical results on all-optical multistate flip-flop function demonstrate that switching between multistable modes can be induced by trigger signals with each states self-sustained after the removal of the trigger signals in a 50µm-radius microring laser.

  12. Few-mode erbium-doped fiber amplifier with photonic lantern for pump spatial mode control.

    PubMed

    Lopez-Galmiche, G; Sanjabi Eznaveh, Z; Antonio-Lopez, J E; Velazquez Benitez, A M; Rodriguez Asomoza, J; Sanchez Mondragon, J J; Gonnet, C; Sillard, P; Li, G; Schülzgen, A; Okonkwo, C M; Amezcua Correa, R

    2016-06-01

    We demonstrate a few-mode erbium-doped fiber amplifier employing a mode-selective photonic lantern for controlling the modal content of the pump light. Amplification of six spatial modes in a 5 m long erbium-doped fiber to ∼6.2  dBm average power is obtained while maintaining high modal fidelity. Through mode-selective forward pumping of the two degenerate LP21 modes operating at 976 nm, differential modal gains of <1  dB between all modes and signal gains of ∼16  dB at 1550 nm are achieved. In addition, low differential modal gain for near-full C-band operation is demonstrated. PMID:27244421

  13. Few-mode erbium-doped fiber amplifier with photonic lantern for pump spatial mode control.

    PubMed

    Lopez-Galmiche, G; Sanjabi Eznaveh, Z; Antonio-Lopez, J E; Velazquez Benitez, A M; Rodriguez Asomoza, J; Sanchez Mondragon, J J; Gonnet, C; Sillard, P; Li, G; Schülzgen, A; Okonkwo, C M; Amezcua Correa, R

    2016-06-01

    We demonstrate a few-mode erbium-doped fiber amplifier employing a mode-selective photonic lantern for controlling the modal content of the pump light. Amplification of six spatial modes in a 5 m long erbium-doped fiber to ∼6.2  dBm average power is obtained while maintaining high modal fidelity. Through mode-selective forward pumping of the two degenerate LP21 modes operating at 976 nm, differential modal gains of <1  dB between all modes and signal gains of ∼16  dB at 1550 nm are achieved. In addition, low differential modal gain for near-full C-band operation is demonstrated.

  14. Influencing factors on the mode transition in a dual-mode scramjet

    NASA Astrophysics Data System (ADS)

    Yan, Zhang; Bing, Chen; Gang, Liu; Baoxi, Wei; Xu, Xu

    2014-10-01

    An experimental investigation was performed to characterize the effects of fuel type, injector configuration, inflow total temperature and fuel injection distribution on the mode transition in a dual-mode scramjet combustor. High enthalpy vitiated air was heated to three total temperatures by the hydrogen-oxygen combustion, entering the isolator entrance at a Mach number of 2.0. Fuel was injected through a four-hole aero-ramp or transverse injector, and ignited by a gas-pilot flame. At an inflow stagnation condition of P0=0.85 MPa and T0=1200 K, three combustion modes, namely Pure Scram Mode, Dual-Mode Scram Mode and Dual-Mode Ram Mode, were classified through the wall pressure distributions, one-dimensional performance analysis, and optical visualization. Two critical fuel equivalence ratios were selected to divide three combustion modes. At the lower transition point, ERlc, the transition from Pure Scram Mode to Dual-Mode Scram Mode occurred corresponding to a normalized wall pressure at x/H=2.5 of 0.23; while at the upper transition point, ERuc, the transition from Dual-Mode Scram Mode to Dual-Mode Ram Mode occurred corresponding to a normalized wall pressure at x/H=2.5 of 0.34. The transition width, ERw, was defined as the difference of two transition points. In this limited range, the combustor was operating in the Dual-Mode Scram Mode. The ERuc was estimated based on the Rayleigh flow relation, and the applicability of the analytic equation was testified through a series of experiments with different boundary conditions. The experimental results showed that two transition points in the ethylene case were higher in ER than in the hydrogen case, and the measured ERuc of two fuels were all 2.5 times larger than the predicted values. However, two fuels had little difference on the transition width. Due to the angled injection, two transition points in the aero-ramp case were higher in ER than in the transverse injector case; while the influence of injector

  15. Airborne Measurements of Atmospheric Pressure made Using an IPDA Lidar Operating in the Oxygen A-Band

    NASA Technical Reports Server (NTRS)

    Riris, Haris; Abshire, James B.; Stephen, Mark; Rodriquez, Michael; Allan, Graham; Hasselbrack, William; Mao, Jianping

    2012-01-01

    We report airborne measurements of atmospheric pressure made using an integrated path differential absorption (IPDA) lidar that operates in the oxygen A-band near 765 nm. Remote measurements of atmospheric temperature and pressure are needed for NASA s Active Sensing of CO2 Emissions Over Nights, Days, and Seasons (ASCENDS) mission to measure atmospheric CO2. Accurate measurements of tropospheric CO2 on a global scale are very important in order to better understand its sources and sinks and to improve our predictions of climate change. The goal of ASCENDS is to determine the CO2 dry mixing ratio with lidar measurements from space at a level of 1 ppm. Analysis to date shows that with current weather models, measurements of both the CO2 column density and the column density of dry air are needed. Since O2 is a stable molecule that uniformly mixed in the atmosphere, measuring O2 absorption in the atmosphere can be used to infer the dry air density. We have developed an airborne (IPDA) lidar for Oxygen, with support from the NASA ESTO IIP program. Our lidar uses DFB-based seed laser diodes, a pulsed modulator, a fiber laser amplifier, and a non-linear crystal to generate wavelength tunable 765 nm laser pulses with a few uJ/pulse energy. The laser pulse rate is 10 KHz, and average transmitted laser power is 20 mW. Our lidar steps laser pulses across a selected line O2 doublet near 764.7 nm in the Oxygen A-band. The direct detection lidar receiver uses a 20 cm diameter telescope, a Si APD detector in Geiger mode, and a multi-channel scalar to detect and record the time resolved laser backscatter in 40 separate wavelength channels. Subsequent analysis is used to estimate the transmission line shape of the doublet for the laser pulses reflected from the ground. Ground based data analysis allows averaging from 1 to 60 seconds to increase SNR in the transmission line shape of the doublet. Our retrieval algorithm fits the expected O2 lineshapes against the measurements and

  16. IPS guidestar selection for stellar mode (ASTRO)

    NASA Technical Reports Server (NTRS)

    Mullins, Larry; Wooten, Lewis

    1988-01-01

    This report describes how guide stars are selected for the Optical Sensor Package (OSP) for the Instrument Pointing System (IPS) when it is operating in the stellar mode on the ASTRO missions. It also describes how the objective loads are written and how the various roll angles are related; i.e., the celestial roll or position angle, the objective load roll angles, and the IPS gimbal angles. There is a brief description of how the IPS operates and its various modes of operation; i.e., IDOP, IDIN, and OSPCAL.

  17. Integrated mode converter for mode division multiplexing

    NASA Astrophysics Data System (ADS)

    Perez-Galacho, Diego; Alonso-Ramos, Carlos Alberto; Marris-Morini, Delphine; Vakarin, Vladyslav; Le Roux, Xavier; Ortega-Moñux, Alejandro; Wangüemert-Perez, Juan Gonzalo; Vivien, Laurent

    2016-05-01

    The ever growing demands of bandwidth in optical communication systems are making traditional Wavelength Division Multiplexing (WDM) based systems to reach its limit. In order to cope with future bandwidth demand is necessary to use new levels of orthogonality, such as the waveguide mode or the polarization state. Mode Division Multiplexing (MDM) has recently attracted attention as a possible solution to increase aggregate bandwidth. In this work we discuss the proposition a of mode converter that can cover the whole C-Band of optical communications. The Mode Converter is based on two Multimode Interference (MMI) couplers and a phase shifter. Insertion loss (IL) below 0.2 dB and Extinction ratio (ER) higher than 20 dB in a broad bandwidth range of 1.5 μm to 1.6 μm have been estimated. The total length of the device is less than 30 μm.

  18. Few-mode fibers for mode division multiplexing transmission

    NASA Astrophysics Data System (ADS)

    Kubota, Hirokazu; Morioka, Toshio

    2012-01-01

    A study is presented of the fiber properties needed to achieve 10-mode multiplexing transmission. A combination of MIMO processing with optical LP mode separation is proposed to prevent the need for massive MIMO computation. The impact of mode crosstalk, differential mode delay, and the mode dependent loss of the few-mode fibers on mode multiplexing are discussed.

  19. Mode Orientation Control For Sapphire Dielectric Ring Resonator

    NASA Technical Reports Server (NTRS)

    Santiago, David G.; Dick, G. John; Prata, Aluizio

    1996-01-01

    Small sapphire tuning wedge used in technique for solving mode-purity problem associated with sapphire dielectric-ring resonator part of cryogenic microwave frequency discriminator. Breaks quasi-degeneracy of two modes and allows selective coupling to just one mode. Wedge mounted on axle entering resonator cavity and rotated while resonator cryogenically operating in vacuum. Furthermore, axle moved vertically to tune resonant frequency.

  20. Designing a VH-mode core/L-mode edge discharge

    SciTech Connect

    Staebler, G.M.; Hinton, F.L.; Wiley, J.C.

    1995-12-01

    An operating mode with a very high confinement core like the VH-mode but a very low power flow to the divertor plates and low edge particle confinement like an L-mode would be beneficial. For a large tokamak like the proposed ITER, the power density at the separatrix is not that far above the scaled H-mode power threshold so not much of the power can be radiated inside of the separatrix without causing a return to L-mode. The thicker scrape-off layer of an L-mode increases the radiating volume of the scrape-off layer and helps shield impurities from the core. This is especially important if the first wall is metallic. In this paper an H-mode transport model based on E x B velocity shear suppression of turbulence will be used to show that it is possible to have a strongly radiating mantle near the separatrix, which keeps the edge in L-mode, while having a VH-mode core with a broad region of suppressed turbulence. The existing results of enhanced L-mode confinement during impurity injection on a number of tokamaks will be surveyed. The operating conditions which will most likely result in the further improvement of the core confinement by control of the heating, fueling, and torque profiles will be identified.