126 Matching Results

Search Results

Advanced search parameters have been applied.

On the speed of gravity and the nu/c corrections to the Shapirotime delay

Description: I compute the v/c correction to the gravitational time delayfor light passing by a massive object moving with speed v, and I finddisagreement with previously published results. It is also argued thatthe speed of gravity formula that was recently used in the conjunction ofJupiter and quasar J0842+1845 is frame dependent.
Date: March 26, 2003
Creator: Samuel, Stuart
Partner: UNT Libraries Government Documents Department

Channel Modeling and Time Delay Estimation for Clock Synchronization Among Seaweb Nodes

Description: From simulations, tracking of the impulse response is feasible. Potential to benefit other functions such as ranging between two nodes. Potential to combine the features of different protocols to create a new and more realistic clock-synchronization protocol.
Date: July 8, 2012
Creator: Gagnon, P; Rice, J & Clark, G A
Partner: UNT Libraries Government Documents Department

Time Delays, Bends, Acceleration and Array Reconfigurations

Description: This note was originally one of the parts of the work on a 50 MeV and 500 MeV Rb{sup +} driver and part of work on delay lines for a 60 GeV U{sup +12} driver. It is slightly expanded here to make it more generally applicable. The emphasis is on beam manipulations such as joining and separating beams at the two ends of a driver and providing various time delays between beams as required by the target.
Date: June 24, 2011
Creator: Faltens, A.
Partner: UNT Libraries Government Documents Department

Tomographic Imaging of Upper Mantle P- and S-wave Velocity Heterogeneity Beneath the Arabian Peninsula

Description: We report the estimates of three-dimensional P- and S-wave velocity structure beneath the Arabian Peninsula estimated from travel time delay tomography. We have completed travel time measurements and inversion of a partial data set provided by King Abdulaziz City for Science and Technology (KACST). This study builds on previous work by Benoit et al. (2003) following the methods of VanDecar and Crosson (1990) and VanDecar (1991). Data were collected from the Saudi Arabian National Digital Seismic Network (SANDSN) operated by KACST. The network consists of 38 stations (27 broadband and 11 short-period). We augmented the KACST data with delay times measured from permanent Incorporated Research Institutions for Seismology (IRIS) stations in the region (RAYN, EIL and MRNI) and the 1996 Saudi Arabian PASSCAL Experiment. This study shows the inverted P- and S-wave models computed with the combined data with all three different seismic networks (KASCST, IRIS, and the 1996 Saudi Arabian PASSCAL experiment) with best coverage beneath the Arabian Shield. Tomographic images reveal low velocity features in the upper mantle along a north-south line from the southern Asir region to the northeastern portion of the Arabian Shield.
Date: August 30, 2005
Creator: Park, Y; Nyblade, A; Rodgers, A & Al-Amri, A
Partner: UNT Libraries Government Documents Department

Two-electron time-delay interference in atomic double ionization by attosecond pulses

Description: A two-color two-photon atomic double ionization experiment using subfemtosecond UV pulses can be designed such that the sequential two-color process dominates and one electron is ejected by each pulse. Nonetheless, ab initio calculations show that, for sufficiently short pulses, a prominent interference pattern in the joint energy distribution of the sequentially ejected electrons can be observed that is due to their indistinguishability and the exchange symmetry of the wave function.
Date: October 4, 2009
Creator: Rescigno, Thomas N
Partner: UNT Libraries Government Documents Department

Timing Calibration in PET Using a Time Alignment Probe

Description: We evaluate the Scanwell Time Alignment Probe for performing the timing calibration for the LBNL Prostate-Specific PET Camera. We calibrate the time delay correction factors for each detector module in the camera using two methods--using the Time Alignment Probe (which measures the time difference between the probe and each detector module) and using the conventional method (which measures the timing difference between all module-module combinations in the camera). These correction factors, which are quantized in 2 ns steps, are compared on a module-by-module basis. The values are in excellent agreement--of the 80 correction factors, 62 agree exactly, 17 differ by 1 step, and 1 differs by 2 steps. We also measure on-time and off-time counting rates when the two sets of calibration factors are loaded into the camera and find that they agree within statistical error. We conclude that the performance using the Time Alignment Probe and conventional methods are equivalent.
Date: May 5, 2006
Creator: Moses, William W. & Thompson, Christopher J.
Partner: UNT Libraries Government Documents Department

Two Methods for a First Order Hardware Gradiometer Using Two HTS SQUID's

Description: Two different systems for noise cancellation (first order gradiometers) have been developed using two similar high temperature superconducting (HTS) SQUIDs. ''Analog'' gradiometry is accomplished in hardware by either (1) subtracting the signals from the sensor and background SQUIDs at a summing amplifier (parallel technique) or (2) converting the inverted background SQUID signal to a magnetic field at the sensor SQUID (series technique). Balance levels achieved are 2000 and 1000 at 20 Hz for the parallel and series methods respectively. The balance level as a function of frequency is also presented. The effect which time delays in the two sets of SQUID electronics have on this balance level is presented and discussed.
Date: September 15, 1998
Creator: Espy, M.A.; Flynn, E.R.; Kraus, R.H., Jr. & Matlachov, A.
Partner: UNT Libraries Government Documents Department

Delayed Light Emission in Green Plant Meterials:Temperature-Dependence and Quantum Yield

Description: The discovery of the delayed light emission of plant materials by Strahler and Arnold in 1951 has stimulated a good deal of interest in this rather remarkable property. The emitted light has been shown to be due to an electronic transition between the first excited singlet state of chlorophyll and the ground state. At room temperature, a luminescence is observable from about 0.01 seconds to several minutes after excitation. Thus, the electronic transition cannot be rate-determining and the process represents neither normal fluorescence nor normal phosphorescence. Indeed, there is some evidence that the decay curve of the luminescence is the resultant of more than one rate-limiting process. Strahler and co-workers have been able to demonstrate the existence of many relationships between delayed light emission and photosynthesis and thus have been led to interpret the luminescence phenomena as a consequence of the reversibility of some of the enzymatic photosynthetic reactions. Moreover, Tollin and Calvin have shown that the faster decaying components of the delayed light are present to as low a temperature as -100 C, suggesting that the early processes following light-absorption are non-enzymatic in nature. These latter observations, in conjunction with several other types of experimental and theoretical information, have suggested an interpretation of the physical processes leading to delayed light emission, and, by analogy, to photosynthesis, in terms of semiconductor theory. The earlier investigations in this laboratory have been limited to the study of the light emitted approximately 0.1 seconds after excitation by a flash discharge. The recent reports of luminescences at still shorter times after excitation have prompted the construction of a device capable of continuously observing the light emission of a sample of plant material from 0.0015 seconds to about 30 seconds after the onset of flash excitation. The present work describes a series of experiments carried ...
Date: July 1, 1958
Creator: Tollin, G.; Fujimori, E. & Calvin, M.
Partner: UNT Libraries Government Documents Department

Dynamic PID loop control

Description: The Horizontal Test Stand (HTS) SRF Cavity and Cryomodule 1 (CM1) of eight 9-cell, 1.3GHz SRF cavities are operating at Fermilab. For the cryogenic control system, how to hold liquid level constant in the cryostat by regulation of its Joule-Thompson JT-valve is very important after cryostat cool down to 2.0 K. The 72-cell cryostat liquid level response generally takes a long time delay after regulating its JT-valve; therefore, typical PID control loop should result in some cryostat parameter oscillations. This paper presents a type of PID parameter self-optimal and Time-Delay control method used to reduce cryogenic system parameters oscillation.
Date: June 1, 2011
Creator: Pei, L.; Klebaner, A.; Theilacker, J.; Soyars, W.; Martinez, A.; Bossert, R. et al.
Partner: UNT Libraries Government Documents Department

Micropulse Lidar (MPL) Handbook

Description: The micropulse lidar (MPL) is a ground-based optical remote sensing system designed primarily to determine the altitude of clouds overhead. The physical principle is the same as for radar. Pulses of energy are transmitted into the atmosphere; the energy scattered back to the transceiver is collected and measured as a time-resolved signal. From the time delay between each outgoing transmitted pulse and the backscattered signal, the distance to the scatterer is infered. Besides real-time detection of clouds, post-processing of the lidar return can also characterize the extent and properties of aerosol or other particle-laden regions.
Date: May 1, 2006
Creator: Mendoza, A & Flynn, C
Partner: UNT Libraries Government Documents Department

Innovative technology summary report.

Description: Traditional site characterization methods rely on preplanned sampling programs and off-site analysis of samples to determine the extent and level of hazardous waste contamination. This process is costly and time-consuming. Static work plans specify the numbers and locations of samples to be collected, as well as the analyses to be performed on collected samples. Sampling crews are mobilized, samples are collected, and the crews are demobilized before final results become available. Additional sampling programs are often required to resolve uncertainties raised by the initial sampling and analysis results. The drawbacks of a traditional approach to sampling program design and execution are high costs per sample, pressure to over sample while at the site, and inevitable surprises in the analytical results that require additional sampling to resolve. A key step in the characterization of hazardous wastes at U.S. Department of Energy (DOE) sites is determination of the extent of contamination. The proper number and placement of sampling locations is required to both minimize characterization costs and guarantee that contamination extent can be estimated with reasonable confidence. Because ''soft'' information (i.e., historical records, computer modeling results, past experience, etc.) for a site are usually just as important as ''hard'' laboratory results, the approach taken must include a quantitative way of accounting for both hard and soft site data. An alternative to traditional sampling programs is Adaptive Sampling and Analysis Programs (ASAPs). ASAPs rely on field analytical methods to generate sample results quickly enough to have an impact on the course of the sampling program. Rather than a static work plan, ASAPs are based on dynamic work plans that specify the logic for how sampling numbers, locations, and analyses will be determined as the program proceeds. To ensure that the sampling stays on track, ASAPs also rely on rapid, field-level decision making. ASAPs ...
Date: May 9, 2006
Partner: UNT Libraries Government Documents Department

LX-17 and ufTATB Data for Corner-Turning, Failure and Detonation

Description: Data is presented for the size (diameter) effect for ambient and cold confined LX-17, unconfined ambient LX-17, and confined ambient ultrafine TATB. Ambient, cold and hot double cylinder corner-turning data for LX-17, PBX 9502 and ufTATB is presented. Transverse air gap crossing in ambient LX-17 is studied with time delays given for detonations that cross.
Date: February 3, 2010
Creator: Souers, P C; Lauderbach, L; Garza, R; Vitello, P & Hare, D E
Partner: UNT Libraries Government Documents Department

Development of Pulse Position Modulation/Optical CDMA (PPM/O-CDMA) for Gb/s Fiber Optic Networking

Description: Pulse position modulation (PPM) in lasercom systems is known to provide potential advantages over other modulation schemes. [1]. In PPM, a periodic time frame is established and data is transmitted by placing a pulse in any one of several subintervals (or ''slots'') within each frame. In PPM/O-CDMA all users use the same frame structure and each transmits its unique address code in place of the PPM pulse. The advantage of PPM as a pulsed signal format is that (1) a single pulse can transmit multiple bits during each frame; (2) decoding (determining which subinterval contains the pulse) is by comparison rather than threshold tests (as in on-off-keying); (3) each user transmits in only a small fraction of the frame, hence the multi-access interference (MAI) of any user statistically spreads over the entire frame time, reducing the chance of overlap with any other user; and (4) under an average power constraint, increasing frame time increases the peak pulse power (i.e., PPM trades average power for peak power). The most straightforward approach to implementing PPM/O-CDMA data modulator inserts the PPM pulse modulation first, then imposes the O-CDMA coding. A pulsed PPM modulator converts bits (words) into pulse positions. In the case of wavelength/time (W/T) matrix codes, multi-wavelength pulses are generated at the beginning of each frame, at the frame rate. For M-ary PPM, a block of k bits represents M = 2{sup k} unique interval positions in the frame corresponding to M-l specific time delays (the zero delay is also a position). PPM modulation is achieved by shifting the initial pulse into an interval position with delay D(i) (i=0,1,2,..,M-1). The location of a pulse position (selection of a delay) therefore identifies a unique k-bit word in the frame. At the receiver, determining which delay occurs relative to the frame start time decodes ...
Date: May 25, 2006
Creator: Mendez, A J; Hernandez, V J; Gagliardi, R M; Bennett, C V & Lennon, W J
Partner: UNT Libraries Government Documents Department


Description: We have found that selected Motorola transistors of the MM-486, MM-487, and MM-488 type are quite useful for avalanche-mode operation. Figure 1 shows a circuit used in conjunction with a traveling-wave oscilloscope for selecting avalanche units. The output of the line-type pulse generator is 40 to 60 volts (either polarity of output pulse is available), and the rise time is less than 0.5 nsec. Figure Z shows a plot of the static V-I characteristics of the collector-to-emitter junction for various units, avalanching and nonavalanching. A transistor that avalanches will do 80 over the entire flat portion of the V-I characteristic. One can expect that 10 to 30% of the transistors will avalanche. There is some indication that the low-beta type (MM-486) give the best yield. There is a time delay of a few nanoseconds between application of a trigger pulse and the rise of the main avalanche current. Figures 3 and 4 shows this delay, measured between the 50% point of the trigger-voltage waveform and the 50% point of the avalanche output waveform, as a function of trigger-voltage amplitude (Fig. 3) and static-collector current (Fig. 4). The negative-resistance region (such as that in Fig. 2) should be avoided if time and amplitude jitter of the output pulse are to be minimized. A temperature change from 70 to 150 F has negligible effect on time delay, but raises the breakdown knee (Fig. 2) to higher current (e. g., from 2 x 10{sup -3} to 8 x 10{sup -3} {micro}a).
Date: March 1, 1962
Creator: Miller, Harold W. & Kerns, Quentin A.
Partner: UNT Libraries Government Documents Department


Description: Short over-all time delay, low time jitter, and excellent long-term reliability are among the desirable features designed into a pulse generator that produces a 2-MW output pulse 30 nsec after the application of a 1-V signal at its 50-ohm input connector. The 10-kV output pulse can be used to trigger simultaneously several spark gaps of the type used in spark-chamber pulse modulators. The 10{sup 8} power gain of the spark-gap-trigger amplifier is achieved by four stages of amplification packaged in a 5-1/4 inch rack-mount chassis that operates directly from a 117-V line. The individual stages, each selected to give minimum time delay for a given power gain at their respective power levels are: avalanche transistors, planar triode, grounded-grid planar triode, and a triggered-spark gap. The techniques used for the last stage, a spark gap triggered by a corona light, are of particular interest since the same techniques are applicable to obtaining short time delays and long-term reliability from the larger spark gaps that the amplifier was designed to trigger. During 10 months of operation, there have been no failures and no adjustments necessary in any of the seven spark-gap trigger amplifiers used in various spark-chamber experiments at the Lawrence Radiation Laboratory of the University of California (UCLRL) in Berkeley.
Date: October 20, 1964
Creator: Kerns, Q.A. & Miller, H.W.
Partner: UNT Libraries Government Documents Department

State International Fuel Tax Agreement (IFTA) Data Reporting Procedures

Description: This report documents a review of State practices of reporting International Fuel Tax Agreement (IFTA) data to the U.S. Federal Highway Administration (FHWA). The purpose of the review is described in a notice published in the Federal Register (Vol. 65, No. 160, August 17, 2000, 50269-50272). The purpose is ''to increase the understanding of States on the importance of reporting adjusted IFTA data to the FHWA'', and ''to develop additional guidance on IFTA reporting''. The purpose is not to critique IFTA or any State. The review includes a survey of the forty eight IFTA member States, which was conducted January-April 2002. The States' responses to the survey are discussed in this report. The organization of the report follows further discussion in the Federal Register notice. Section 2 of the report is a general overview of IFTA. Section 3 describes in more detail how each State collects IFTA revenues. Section 4 is about how States separate out revenues not related to gallons of motor-fuel and direct motor-fuel gallon taxes. Section 5 describes how States calculate net IFTA gallons and the time delay in the processing. Section 6 is about difficulties in processing and reporting IFTA data. Timeliness is discussed further in Section 7, and alternatives for IFTA calculations if complete IFTA data are not available are discussed in Section 8. The IFTA survey questionnaire and instructions are in Appendices A and B. The survey responses of the States and the review of the IFTA system suggest that IFTA collections and data reporting are for the most part working well. Possible exceptions include (1) using off-road fuel use in IFTA mileage-per-gallon (mpg) estimates, (2) inconsistencies among States in definitions of taxable mileage or taxable fuel and consequential reporting differences, and (3) possible misinterpretations of ''net taxable gallons''.
Date: April 8, 2003
Creator: Schmoyer, R.L.
Partner: UNT Libraries Government Documents Department

Z-Beamlet (ZBL) Multi-Frame Back-lighter (MFB) System for ICF/Plasma Diagnostics

Description: Z-Beamlet [1] is a single-beam high-energy Nd:glass laser used for backlighting high energy density (HED) plasma physics experiments at Sandia's Z-accelerator facility. The system currently generates a single backlit image per experiment, and has been employed on approximately 50% of Z-accelerator system shots in recent years. We have designed and are currently building a system that uses Z-Beamlet to generate two distinct backlit images with adjustable time delay ranging from 2 to 20 ns between frames. The new system will double the rate of data collection and allow the temporal evolution of high energy density phenomena to be recorded on a single shot.
Date: September 8, 2005
Creator: Caird, J A; Erlandson, A C; Molander, W A; Murray, J E; Robertson, G K; Smith, I C et al.
Partner: UNT Libraries Government Documents Department

Ultrafast dynamics in helium nanodroplets probed by femtosecond time-resolved EUV photoelectron imaging

Description: The dynamics of electronically excited helium nanodroplets are studied by femtosecond time-resolved photoelectron imaging. EUV excitation into a broad absorption band centered around 23.8 eV leads to an indirect photoemission process that generates ultraslow photoelectrons. A 1.58 eV probe pulse transiently depletes the indirect photoemission signal for pump-probe time delays <200 fs and enhances the signal beyond this delay. The depletion is due to suppression of the indirect ionization process by the probe photon, which generates a broad, isotropically emitted photoelectron band. Similar time scales in the decay of the high energy photoelectron signal and the enhancement of the indirect photoemission signal suggest an internal relaxation process that populates states in the range of a lower energy droplet absorption band located just below the droplet ionization potential (IP {approx} 23.0 eV). A nearly 70% enhancement of the ultraslow photoelectron signal indicates that interband relaxation plays a more dominant role for the droplet de-excitation mechanism than photoemission.
Date: July 9, 2010
Creator: Kornilov, Oleg; Wang, Chia C.; Buenermann, Oliver; Healy, Andrew T.; Leonard, Mathew; Peng, Chunte et al.
Partner: UNT Libraries Government Documents Department

Design of Microwave Band Pass Filters for the Debuncher Stochastic Cooling System

Description: The FIR filters designed for the debuncher stochastic cooling system needed improvement. Its bandwidth was too wide, its magnitude was not flat, its phase ripple was too great, and it was difficult to control the characteristics of the filter. A simple microwave technique was employed to have a short time delay, simple robust layout, and small board size. A significant savings was seen over the FIR technique and these filters were installed in the Antiproton Source Debuncher while the FIR filters were removed from the debuncher stochastic cooling entirely.
Date: January 1, 2001
Creator: Deibele, C.
Partner: UNT Libraries Government Documents Department

Ionization efficiency and effusive delay time characterization of high temperature target-ion sources for RIB generation

Description: Ion sources for radioactive ion beam (RIB) generation must efficiently ionize short-lived-radioactive nuclei released from on-line targets with minimal delay times. Delay times attributable to interactions between chemically active species and surfaces of the vapor transport system which are long compared to the half-life of the desired radioactive atom and/or low ionization efficiency of the target/ion source (TIS) will result in a severe reduction of the RM intensity available for research. We have developed complementary off-line techniques for directly measuring both effusive delay times and ionization efficiencies for chemically active species in high temperature TISs using only the stable complements of the radioactive element of interest. Equipment, designed and developed for these measurements, include: a high-temperature Ta valve; a differentially cooled injection nozzle; and a gaseous flow measurement and control system. These techniques are employed in a systematic investigation of fluorine transport and ionization in an electron-beam-plasma target/ion source (EBPTIS) designed for initial use at the Holifield Radioactive Ion Beam Facility (HRIBF).
Date: December 1, 1996
Creator: Welton, R.F.; Alton, G.D.; Murray, S.N. & Cui, B.
Partner: UNT Libraries Government Documents Department

On routing algorithms with end-to-end delay guarantees

Description: The authors consider the transmission of a message of size r from a source to a destination with guarantees on the end-to-end delay over a computer network with n nodes and m links. There are three sources of delays: (a) propagation delays along the links, (b) delays due to bandwidth availability on the links, and (c) queuing delays at the intermediate nodes. First, the authors consider that delays on various links and nodes are given as functions of the message size. If the delay in (b) is a non-increasing function of the bandwidth, they propose O(m{sup 2} + mn log n) time algorithm to compute a path with the minimum end-to-end delay for any given message size r. They then consider that the queuing delay in (c) is a random variable correlated with the message size according to an unknown distribution. At each node, the measurements of queuing delays and message sizes are available. They propose two algorithms to compute paths whose delays are close to optimal delays with a high probability, irrespective of the distribution of the delays, and based entirely on the measurements of sufficient size.
Date: November 1, 1998
Creator: Rao, N.S.V. & Batsell, S.G.
Partner: UNT Libraries Government Documents Department

Method and Apparatus for Monitoring the Integrity of a Geomembrane Liner using time Domain Reflectometry

Description: Leaks are detected in a multi-layered geomembrane liner by a two-dimensional time domain reflectometry (TDR) technique. The TDR geomembrane liner is constructed with an electrically conductive detection layer positioned between two electrically non-conductive dielectric layers, which are each positioned between the detection layer and an electrically conductive reference layer. The integrity of the TDR geomembrane liner is determined by generating electrical pulses within the detection layer and measuring the time delay for any reflected electrical energy caused by absorption of moisture by a dielectric layer.
Date: November 9, 1998
Creator: Morris, John L.
Partner: UNT Libraries Government Documents Department