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1

Light absorption cell combining variable path and length pump  

DOEpatents

A device for use in making spectrophotometric measurements of fluid samples. In particular, the device is a measurement cell containing a movable and a fixed lens with a sample of the fluid therebetween and through which light shines. The cell is connected to a source of light and a spectrophotometer via optic fibers. Movement of the lens varies the path length and also pumps the fluid into and out of the cell. Unidirectional inlet and exit valves cooperate with the movable lens to assure a one-way flow of fluid through the cell. A linear stepper motor controls the movement of the lens and cycles it from a first position closer to the fixed lens and a second position farther from the fixed lens, preferably at least 10 times per minute for a nearly continuous stream of absorption spectrum data.

Prather, William S. (2419 Dickey Rd., Augusta, GA 30906)

1993-01-01

2

Light absorption cell combining variable path and length pump  

DOEpatents

A device is described for use in making spectrophotometric measurements of fluid samples. In particular, the device is a measurement cell containing a movable and a fixed lens with a sample of the fluid there between and through which light shines. The cell is connected to a source of light and a spectrophotometer via optic fibers. Movement of the lens varies the path length and also pumps the fluid into and out of the cell. Unidirectional inlet and exit valves cooperate with the movable lens to assure a one-way flow of fluid through the cell. A linear stepper motor controls the movement of the lens and cycles it from a first position closer to the fixed lens and a second position farther from the fixed lens, preferably at least 10 times per minute for a nearly continuous stream of absorption spectrum data. 2 figures.

Prather, W.S.

1993-12-07

3

Using integrating spheres as absorption cells: path-length distribution and application of Beer's law  

Microsoft Academic Search

We have modeled the path-length distribution in an integrating sphere used as a multipass optical cell for absorption measurements. The measured radiant flux as a function of analyte concentration is nonlinear as a result, deviating from that expected for a single path length. We have developed a full numerical model and introduce a new analytical relationship that describes this behavior

Jane Hodgkinson; Dackson Masiyano; Ralph P. Tatam

2009-01-01

4

Effective optical path length investigation for cubic diffuse cavity as gas absorption cell  

NASA Astrophysics Data System (ADS)

A simple cubic-shaped cavity with a high-diffuse-reflectivity inner coating as a novel gas detection cell was developed. The effective optical path length (EOPL) was evaluated by comparing the oxygen absorption signal in the cavity and in air based on tunable diode laser absorption spectroscopy. The law for a spherical cavity was applied and modified to a cubic cavity as a function of reflectivity ?, port fraction f, and the side length. Single-pass average path length of the cubic cavity was 0.723(7) times the side length. EOPL can be modified conveniently by adjusting the parameters of the cavity.

Yu, Jia; Zheng, Fu; Gao, Qiang; Li, Yinjie; Zhang, Yungang; Zhang, Zhiguo; Wu, Shaohua

2014-07-01

5

Cesium oscillator strengths measured with a multiple-path-length absorption cell  

NASA Technical Reports Server (NTRS)

Absorption-oscillator-strength measurements for the principal series in cesium were measured using a multiple-path-length cell. The optical arrangement included a movable transverse path for checking the uniformity of the alkali density along the length of the cell and which also allowed strength measurements to be made simultaneously on both strong and weak lines. The strengths measured on the first 10 doublets indicate an increasing trend in the doublet ratio. The individual line strengths are in close agreement with the high resolution measurements of Pichler (1974) and with the calculations of Norcross (1973).

Exton, R. J.

1976-01-01

6

Multiple-Path-Length Optical Absorbance Cell  

NASA Technical Reports Server (NTRS)

An optical absorbance cell that offers a selection of multiple optical path lengths has been developed as part of a portable spectrometric instrument that measures absorption spectra of small samples of water and that costs less than does a conventional, non-portable laboratory spectrometer. The instrument is intended, more specifically, for use in studying colored dissolved organic matter (CDOM) in seawater, especially in coastal regions. Accurate characterization of CDOM is necessary for building bio-optical mathematical models of seawater. The multiple path lengths of the absorption cell afford a wide range of sensitivity needed for measuring the optical absorbances associated with the wide range of concentrations of CDOM observed in nature. The instrument operates in the wavelength range of 370 to 725 nm. The major subsystems of the instrument (see figure) include a color-balanced light source; the absorption cell; a peristaltic pump; a high-precision, low-noise fiber optic spectrometer; and a laptop or other personal computer. A fiber-optic cable transmits light from the source to the absorption cell. Other optical fibers transmit light from the absorption cell to the spectrometer,

2001-01-01

7

Free Path Lengths in Quasicrystals  

NASA Astrophysics Data System (ADS)

Previous studies of kinetic transport in the Lorentz gas have been limited to cases where the scatterers are distributed at random (e.g., at the points of a spatial Poisson process) or at the vertices of a Euclidean lattice. In the present paper we investigate quasicrystalline scatterer configurations, which are non-periodic, yet strongly correlated. A famous example is the vertex set of a Penrose tiling. Our main result proves the existence of a limit distribution for the free path length, which answers a question of Wennberg. The limit distribution is characterised by a certain random variable on the space of higher dimensional lattices, and is distinctly different from the exponential distribution observed for random scatterer configurations. The key ingredients in the proofs are equidistribution theorems on homogeneous spaces, which follow from Ratner's measure classification.

Marklof, Jens; Strömbergsson, Andreas

2014-03-01

8

Variable path length spectrophotometric probe  

DOEpatents

A compact, variable pathlength, fiber optic probe for spectrophotometric measurements of fluids in situ. The probe comprises a probe body with a shaft having a polished end penetrating one side of the probe, a pair of optic fibers, parallel and coterminous, entering the probe opposite the reflecting shaft, and a collimating lens to direct light from one of the fibers to the reflecting surface of the shaft and to direct the reflected light to the second optic fiber. The probe body has an inlet and an outlet port to allow the liquid to enter the probe body and pass between the lens and the reflecting surface of the shaft. A linear stepper motor is connected to the shaft to cause the shaft to advance toward or away from the lens in increments so that absorption measurements can be made at each of the incremental steps. The shaft is sealed to the probe body by a bellows seal to allow freedom of movement of the shaft and yet avoid leakage from the interior of the probe.

O'Rourke, Patrick E. (157 Greenwood Dr., Martiney, GA 30907); McCarty, Jerry E. (104 Recreation Dr., Aiken, SC 29803); Haggard, Ricky A. (1144 Thornwood Drive, North Augusta, SC 29891)

1992-01-01

9

47 CFR 101.143 - Minimum path length requirements.  

Code of Federal Regulations, 2010 CFR

... Frequency band (MHz) Minimum path length (km) Below 1,850 N...Above 17,700 N/A (b) For paths shorter than those specified in the table...Section 101.113(a). A = Minimum path length from the Table above for...

2009-10-01

10

47 CFR 101.143 - Minimum path length requirements.  

Code of Federal Regulations, 2013 CFR

... Frequency band (MHz) Minimum path length (km) Below 1,850 N...Above 17,700 N/A (b) For paths shorter than those specified in the table...Section 101.113(a). A = Minimum path length from the Table above for...

2013-10-01

11

47 CFR 101.143 - Minimum path length requirements.  

Code of Federal Regulations, 2010 CFR

... Frequency band (MHz) Minimum path length (km) Below 1,850 N...Above 17,700 N/A (b) For paths shorter than those specified in the table...Section 101.113(a). A = Minimum path length from the Table above for...

2010-10-01

12

Diagnosis of multilayer clouds using photon path length distributions  

NASA Astrophysics Data System (ADS)

Photon path length distribution is sensitive to 3-D cloud structures. A detection method for multilayer clouds has been developed, by utilizing the information of photon path length distribution. The photon path length method estimates photon path length information from the low level, single-layer cloud structure that can be accurately observed by a millimeter-wave cloud radar (MMCR) combined with a micropulse lidar (MPL). As multiple scattering within the cloud layers and between layers would substantially enhance the photon path length, the multilayer clouds can be diagnosed by evaluating the estimated photon path information against observed photon path length information from a co-located rotating shadowband spectrometer (RSS). The measurements of MMCR-MPL and RSS at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site have been processed for the year 2000. Cases studies illustrate the consistency between MMCR-MPL detection and the photon path length method under most conditions. However, the photon path length method detected some multilayer clouds that were classified by the MMCR-MPL as single-layer clouds. From 1 year statistics at the ARM SGP site, about 27.7% of single-layer clouds detected by the MMCR-MPL with solar zenith angle less than 70° and optical depth greater than 10 could be multilayer clouds. It suggests that a substantial portion of single-layer clouds detected by the MMCR-MPL could also be influenced by some "missed" clouds or by the 3-D effects of clouds.

Li, Siwei; Min, Qilong

2010-10-01

13

Streamlining traceroute by estimating path lengths  

Microsoft Academic Search

Traditional traceroute determines the path through a network by sending probe packets with progressively increasing TTL\\/hop count values so that routers that are progressively further from the inquirer send ICMP time exceeded messages and so reveal their identity. This process can be slow (because traceroute must wait for a timeout or response to one probe before sending the next) and

Tim Moors

2004-01-01

14

All-optical, thermo-optical path length modulation based on the vanadium-doped fibers.  

PubMed

This paper presents an all-fiber, fully-optically controlled, optical-path length modulator based on highly absorbing optical fiber. The modulator utilizes a high-power 980 nm pump diode and a short section of vanadium-co-doped single mode fiber that is heated through absorption and a non-radiative relaxation process. The achievable path length modulation range primarily depends on the pump's power and the convective heat-transfer coefficient of the surrounding gas, while the time response primarily depends on the heated fiber's diameter. An absolute optical length change in excess of 500 µm and a time-constant as short as 11 ms, were demonstrated experimentally. The all-fiber design allows for an electrically-passive and remote operation of the modulator. The presented modulator could find use within various fiber-optics systems that require optical (remote) path length control or modulation. PMID:23736401

Matjasec, Ziga; Campelj, Stanislav; Donlagic, Denis

2013-05-20

15

Broadband ATR-sensor with variable path lengths  

NASA Astrophysics Data System (ADS)

A spectral Attenuated Total Reflection (ATR-) sensor with variable path lengths is proposed. Based on a new polymer cladding material, the numerical aperture and the related maximum propagation angle in Polymer Clad Silica Fiber (PCSF) have been increased significantly. The penetration depth of the evanescent field into the cladding of step-index fibers depends strongly on the propagation angle. We found that when removing its cladding, the effective path length in the interaction section can be adjusted, using meridional rays/modes of different propagation angles. Because the fiber length is short, the mode conversion in the light-transporting section of the PCSF is negligible. After measuring the optical properties of the PCSF, the ATR with selected liquids surrounding the light-guiding core is determined in dependence of wavelength and excitation-angle. Especially, the possibilities to change from low to high propagation angles including the excitation and detection system will be discussed.

Klein, Karl-Friedrich; Pandey, Subash; Dahal, Pasma; Klein, Moritz; Belz, Mathias; Hillrichs, Georg

2012-02-01

16

Path Length Fluctuations Derived from Site Testing Interferometer Data  

NASA Technical Reports Server (NTRS)

To evaluate possible sites for NASA's proposed Ka-band antenna array, the NASA Glenn Research Center has constructed atmospheric phase monitors (APM) which directly measure the tropospheric phase stability. These instruments observe an unmodulated 20.2 GHz beacon signal broadcast from a geostationary satellite (Anik F2) and measure the phase difference between the signals received by the two antennas. Two APM's have been deployed, one at the NASA Deep Space Network (DSN) Tracking Complex in Goldstone, California, and the other at the NASA White Sands Complex, in Las Cruces, New Mexico. Two station-years of atmospheric phase fluctuation data have been collected at Goldstone since operations commenced in May 2007 and 0.5 station-years of data have been collected at White Sands since operations began February 2009. With identical instruments operating simultaneously, we can directly compare the phase stability at the two sites. Phase stability is analyzed statistically in terms of the root-mean-square (rms) of the tropospheric path length fluctuations over 10 min blocks. Correlation between surface wind speed and relative humidity with interferometer phase are discussed. For 2 years, the path length fluctuations at the DSN site in Goldstone, California, have been better than 757 micrometer (with reference to a 300 m baseline and to Zenith) for 90 percent of the time. For the 6 months of data collected at White Sands, New Mexico, the path length fluctuations have been better than 830 micrometers (with reference to a 300 m baseline and to Zenith) for 90 percent of the time. This type of data analysis, as well as many other site quality characteristics (e.g., rain attenuation, infrastructure, etc.), will be used to determine the suitability of both sites for NASA s future communication services at Ka-band using an array of antennas.

Acosta, Roberto J.; Nessel, James A.; Morse, Jacquelynne R.

2010-01-01

17

Phylogenetic dating with confidence intervals using mean path lengths.  

PubMed

The mean path length (MPL) method, a simple method for dating nodes in a phylogenetic tree, is presented. For small trees the age estimates and corresponding confidence intervals, calibrated with fossil data, can be calculated by hand, and for larger trees a computer program gives the results instantaneously (a Pascal program is available upon request). Necessary input data are a rooted phylogenetic tree with edge lengths (internode lengths) approximately corresponding to the number of substitutions between the nodes. Given this, the MPL method produces relative age estimates with confidence intervals for all nodes of the tree. With the age of one or several nodes of the tree being known from reference fossils, the relative age estimates induce absolute age estimates and confidence intervals of the nodes of the tree. The MPL method relies on the assumptions that substitutions occur randomly and independently in different sites in the DNA sequence and that the substitution rates are approximately constant in time, i.e., assuming a molecular clock. A method is presented for identification of the nodes in the tree at which significant deviations from the clock assumption occur, such that dating may be done using different rates in different parts of the tree. The MPL method is illustrated with the Liliales, a group of monocot flowering plants. PMID:12128028

Britton, Tom; Oxelman, Bengt; Vinnersten, Annika; Bremer, Kåre

2002-07-01

18

Path length entropy analysis of diastolic heart sounds.  

PubMed

Early detection of coronary artery disease (CAD) using the acoustic approach, a noninvasive and cost-effective method, would greatly improve the outcome of CAD patients. To detect CAD, we analyze diastolic sounds for possible CAD murmurs. We observed diastolic sounds to exhibit 1/f structure and developed a new method, path length entropy (PLE) and a scaled version (SPLE), to characterize this structure to improve CAD detection. We compare SPLE results to Hurst exponent, Sample entropy and Multiscale entropy for distinguishing between normal and CAD patients. SPLE achieved a sensitivity-specificity of 80%-81%, the best of the tested methods. However, PLE and SPLE are not sufficient to prove nonlinearity, and evaluation using surrogate data suggests that our cardiovascular sound recordings do not contain significant nonlinear properties. PMID:23930808

Griffel, Benjamin; Zia, Mohammad K; Fridman, Vladamir; Saponieri, Cesare; Semmlow, John L

2013-09-01

19

47 CFR 78.108 - Minimum path lengths for fixed links.  

Code of Federal Regulations, 2010 CFR

... Frequency band (MHz) Minimum path length (km) 12,200 to 13...Above 17,700 N/A (b) For paths shorter than those specified in the Table...636 of this part. A = Minimum path length from the Table above...

2009-10-01

20

47 CFR 78.108 - Minimum path lengths for fixed links.  

Code of Federal Regulations, 2010 CFR

... Frequency band (MHz) Minimum path length (km) 12,200 to 13...Above 17,700 N/A (b) For paths shorter than those specified in the Table...636 of this part. A = Minimum path length from the Table above...

2010-10-01

21

47 CFR 74.644 - Minimum path lengths for fixed links.  

Code of Federal Regulations, 2010 CFR

... Frequency band(MHz) Minimum path length(km) Below 1,990 n...Above 17,700 n/a (b) For paths shorter than those specified in the Table...636 of this part. A = Minimum path length from the Table above...

2009-10-01

22

47 CFR 78.108 - Minimum path lengths for fixed links.  

Code of Federal Regulations, 2013 CFR

... Frequency band (MHz) Minimum path length (km) 12,200 to 13...Above 17,700 N/A (b) For paths shorter than those specified in the Table...636 of this part. A = Minimum path length from the Table above...

2013-10-01

23

47 CFR 74.644 - Minimum path lengths for fixed links.  

Code of Federal Regulations, 2010 CFR

... Frequency band(MHz) Minimum path length(km) Below 1,990 n...Above 17,700 n/a (b) For paths shorter than those specified in the Table...636 of this part. A = Minimum path length from the Table above...

2010-10-01

24

47 CFR 74.644 - Minimum path lengths for fixed links.  

Code of Federal Regulations, 2013 CFR

... Frequency band(MHz) Minimum path length(km) Below 1,990 n...Above 17,700 n/a (b) For paths shorter than those specified in the Table...636 of this part. A = Minimum path length from the Table above...

2013-10-01

25

Simulation of experimental investigations of X-ray spectral path lengths on Iskra-5 laser facility  

NASA Astrophysics Data System (ADS)

We describe an improved Slater average-ion model employed in the numerical-theoretical analysis of experimental data, which were obtained in the investigation of X-ray spectral path lengths performed on the Iskra-5 laser facility at the All-Russian Scientific Research Institute of Experimental Physics (VNIIEF). The proposed model permits determining the spectral characteristics of the X-ray radiation with an accuracy of a few electronvolts. We outline the results of simulations of experiments with X-ray radiation-heated aluminium and germanium specimens of initial thickness of ~0.1 mm, in which absorption lines arising from 1s—2p transitions in Al and the absorption band arising from 2p—3d transitions in Ge were recorded.

Bel'kov, S. A.; Sharov, O. O.

2011-10-01

26

Simulation of experimental investigations of X-ray spectral path lengths on Iskra-5 laser facility  

SciTech Connect

We describe an improved Slater average-ion model employed in the numerical-theoretical analysis of experimental data, which were obtained in the investigation of X-ray spectral path lengths performed on the Iskra-5 laser facility at the All-Russian Scientific Research Institute of Experimental Physics (VNIIEF). The proposed model permits determining the spectral characteristics of the X-ray radiation with an accuracy of a few electronvolts. We outline the results of simulations of experiments with X-ray radiation-heated aluminium and germanium specimens of initial thickness of {approx}0.1 mm, in which absorption lines arising from 1s-2p transitions in Al and the absorption band arising from 2p-3d transitions in Ge were recorded.

Bel'kov, S A; Sharov, O O [Russian Federal Nuclear Center 'All-Russian Research Institute of Experimental Physics', Sarov, Nizhnii Novgorod region (Russian Federation)

2011-10-31

27

On the Relationship of Tornado Path Length and Width to Intensity  

Microsoft Academic Search

Reported path lengths and widths of tornadoes have been modeled using Weibull distributions for different Fujita (F) scale values. The fits are good over a wide range of lengths and widths. Path length and width tend to increase with increasing F scale, although the temporal nonstationarity of the data for some parts of the data (such as width of F3

Harold E. Brooks

2004-01-01

28

Laser Metrology for an Optical-Path-Length Modulator  

NASA Technical Reports Server (NTRS)

Laser gauges have been developed to satisfy requirements specific to monitoring the amplitude of the motion of an optical-path-length modulator that is part of an astronomical interferometer. The modulator includes a corner-cube retroreflector driven by an electromagnetic actuator. During operation of the astronomical interferometer, the electromagnet is excited to produce linear reciprocating motion of the corner-cube retroreflector at an amplitude of 2 to 4 mm at a frequency of 250, 750, or 1,250 Hz. Attached to the corner-cube retroreflector is a small pick-off mirror. To suppress vibrations, a counterweight having a mass equal to that of the corner-cube retroreflector and pick-off mirror is mounted on another electromagnetic actuator that is excited in opposite phase. Each gauge is required to measure the amplitude of the motion of the pick-off mirror, assuming that the motions of the pick-off mirror and the corner-cube retroreflector are identical, so as to measure the amplitude of motion of the corner- cube retroreflector to within an error of the order of picometers at each excitation frequency. Each gauge is a polarization-insensitive heterodyne interferometer that includes matched collimators, beam separators, and photodiodes (see figure). The light needed for operation of the gauge comprises two pairs of laser beams, the beams in each pair being separated by a beat frequency of 80 kHz. The laser beams are generated by an apparatus, denoted the heterodyne plate, that includes stabilized helium-neon lasers, acousto-optical modulators, and associated optical and electronic subsystems. The laser beams are coupled from the heterodyne plate to the collimators via optical fibers.

Gursel, Yekta

2005-01-01

29

Optical Path Switching Based Differential Absorption Radiometry for Substance Detection  

NASA Technical Reports Server (NTRS)

A system and method are provided for detecting one or more substances. An optical path switch divides sample path radiation into a time series of alternating first polarized components and second polarized components. The first polarized components are transmitted along a first optical path and the second polarized components along a second optical path. A first gasless optical filter train filters the first polarized components to isolate at least a first wavelength band thereby generating first filtered radiation. A second gasless optical filter train filters the second polarized components to isolate at least a second wavelength band thereby generating second filtered radiation. The first wavelength band and second wavelength band are unique. Further, spectral absorption of a substance of interest is different at the first wavelength band as compared to the second wavelength band. A beam combiner combines the first and second filtered radiation to form a combined beam of radiation. A detector is disposed to monitor magnitude of at least a portion of the combined beam alternately at the first wavelength band and the second wavelength band as an indication of the concentration of the substance in the sample path.

Sachse, Glen W. (Inventor)

2000-01-01

30

Frequency path-length scaling of severe tornadoes during individual tornado outbreaks  

NASA Astrophysics Data System (ADS)

In this study we consider severe tornadoes, which we define as tornadoes with path lengths L > 10 km, in the continental USA (USA Storm Prediction Center Severe Weather Database). We find that for the period 1982-2011, for individual severe tornadoes (L > 10 km): (i) There is a strong linear scaling between the number of severe tornadoes in a year and their total path length in that year. (ii) The cumulative frequency path length data suggests that, not taking into account any changing trends over time, we would expect in a given year (on average) one severe tornado with a path length L > 115 km and in a decade (on average) one severe tornado with a path length L > 215 km. (iii) The noncumulative frequency-length statistics of severe tornado touchdown path lengths, 20 < L <200 km, is well approximated by an inverse power-law relationship with exponent near 3. We then consider the frequency path-length scaling of severe tornadoes (L > 10 km) during two tornado outbreaks, 27 April 2011 (67 severe tornadoes) and 25 May 2011 (16 severe tornadoes), and find similar statistical distributions with robust scaling. We believe that our robust scaling results provide evidence that touchdown path lengths can be used as quantitative measures of the systematic properties of severe tornadoes and severe tornado outbreaks.

Malamud, Bruce D.; Turcotte, Donald L.

2013-04-01

31

Common cavity resonators for passive laser beam combining: effects of path length errors  

Microsoft Academic Search

The sensitivity of coupled laser cavities to path length errors for coherent laser combining is analyzed, and new methods are described for reducing this sensitivity. We show that certain resonator structures are able to tolerate path length errors better than others, and present experimental measurements of this tolerance.

J. R. Leger; M. Khajavikhan; C. Wan

2010-01-01

32

Two dynamic reconfiguration approaches for optimizing the restoration path length in p-cycle protection network  

NASA Astrophysics Data System (ADS)

p-cycle is one of the most promising technique of span protection in optical transport networks with mesh-like efficiency and ring-like speed. Longer p-cycle provides better efficiency in term of spare capacity, but longer restored path increases end-to-end propagation delay, which reduces the reliability of the restored network. Hence, minimization of restoration path is a critical issue in p-cycle based protection network. In this paper, two new dynamic reconfiguration approaches namely inter-cycles switching (ICS) and local restoration paths (LRP) are discussed to reduce the length of restored paths in existing optimal spare capacity design of p-cycle. Both proposed approaches are meant to utilize the idle p-cycles thus significantly reducing the path length. This reduction in restored path length also releases the redundant spare capacity.

Yadav, Raghav; Yadav, Rama Shankar

2010-07-01

33

Gas spectroscopy and optical path-length assessment in scattering media using a frequency-modulated continuous-wave diode laser  

NASA Astrophysics Data System (ADS)

Simultaneous assessment of the spectroscopic absorption signal of gas enclosed in a scattering medium and the corresponding optical path length of the probing light is demonstrated using a single setup. Sensitive gas absorption measurements are performed by a tunable diode laser using wavelength-modulation spectroscopy, while the path length is evaluated by the frequency-modulated cw technique commonly used in the field of telecommunication. Proof-of-principle measurements are demonstrated with water vapor as the absorbing gas and using polystyrene foam as an inhomogeneously scattering medium. The combination of these techniques opens up new possibilities for straightforward evaluation of gas presence and exchange in scattering media.

Mei, Liang; Jayaweera, Hiran; Lundin, Patrik; Svanberg, Sune; Somesfalean, Gabriel

2011-08-01

34

Gas spectroscopy and optical path-length assessment in scattering media using a frequency-modulated continuous-wave diode laser.  

PubMed

Simultaneous assessment of the spectroscopic absorption signal of gas enclosed in a scattering medium and the corresponding optical path length of the probing light is demonstrated using a single setup. Sensitive gas absorption measurements are performed by a tunable diode laser using wavelength-modulation spectroscopy, while the path length is evaluated by the frequency-modulated cw technique commonly used in the field of telecommunication. Proof-of-principle measurements are demonstrated with water vapor as the absorbing gas and using polystyrene foam as an inhomogeneously scattering medium. The combination of these techniques opens up new possibilities for straightforward evaluation of gas presence and exchange in scattering media. PMID:21847151

Mei, Liang; Jayaweera, Hiran; Lundin, Patrik; Svanberg, Sune; Somesfalean, Gabriel

2011-08-15

35

All Pairs Shortest Paths for Graphs with Small Integer Length Edges  

Microsoft Academic Search

The authors have solved the all pairs shortest distances (APSD) problem for graphs with integer edge lengths. Our algorithm is subcubic for edge lengths of small (?M) absolute value. In this paper we show how to transform these algorithms to solve the all pairs shortest paths (APSP), in the same time complexity, up to a polylogarithmic factor. Forn=|V| the number

Zvi Galil; Oded Margalit

1997-01-01

36

An improved photon path length probability density function–based radiative transfer model for space-based observation of greenhouse gases  

Microsoft Academic Search

We present an improved model to describe the photon path length probability density function (PPDF) that effectively accounts for both aerosol and thin cloud effects for rapid retrieval of greenhouse gas data from space-based high spectral resolution measurements. The reasonably simple PPDF and effective transmittance parameterization permit vertical inhomogeneity of gas absorption and three plane-parallel arbitrarily located layers to account

Sergey Oshchepkov; Andrey Bril; Tatsuya Yokota

2009-01-01

37

Cloud Screening Using Proxy Photon Path Length Distributions Derived from High Resolution Spectra in the Near Infra-red  

NASA Astrophysics Data System (ADS)

Measurement of column amounts of trace gases from space using high resolution spectra of reflected sunlight in the near infra-red requires almost clear sky, and therefore reliable cloud screening. In a clear sky, photons will follow the direct path from sun to surface to satellite, because Rayleigh scattering is negligible in the near infra-red, so the distribution of photon path lengths will be a delta-function. A proxy for the photon path length distribution under any sky condition is recovered from high resolution spectra by representing the distribution as a weighted sum of delta-functions. Scenes are classified as clear or cloudy according to how closely the distribution approximates the ideal single delta-function for the direct path. An algorithm using the strong CO2 absorption band at 2 micrometers is described, and the efficiency and accuracy of the algorithm are characterized for observations over sun-glint using simulated spectra generated for multiple orbits of the Orbiting Carbon Observatory.

Obrien, D.; Polonsky, I. N.

2009-12-01

38

Visual target distance, but not visual cursor path length produces shifts in motor behavior  

PubMed Central

When using tools effects in body space and distant space often do not correspond. Findings so far demonstrated that in this case visual feedback has more impact on action control than proprioceptive feedback. The present study varies the dimensional overlap between visual and proprioceptive action effects and investigates its impact on aftereffects in motor responses. In two experiments participants perform linear hand movements on a covered digitizer tablet to produce ?-shaped cursor trajectories on the display. The shape of hand motion and cursor motion (linear vs. curved) is dissimilar and therefore does not overlap. In one condition the length of hand amplitude and visual target distance is similar and constant while the length of the cursor path is dissimilar and varies. In another condition the length of the hand amplitude varies while the lengths of visual target distance (similar or dissimilar) and cursor path (dissimilar) are constant. First, we found that aftereffects depended on the relation between hand path length and visual target distance, and not on the relation between hand and cursor path length. Second, increasing contextual interference did not reveal larger aftereffects. Finally, data exploration demonstrated a considerable benefit from gain repetitions across trials when compared to gain switches. In conclusion, dimensional overlap between visual and proprioceptive action effects modulates human information processing in visually controlled actions. However, adjustment of the internal model seems to occur very fast for this kind of simple linear transformation, so that the impact of prior visual feedback is fleeting.

Wendker, Nike; Sack, Oliver S.; Sutter, Christine

2014-01-01

39

Power-Law Distributions for the Free Path Length in Lorentz Gases  

NASA Astrophysics Data System (ADS)

It is well known that, in the Boltzmann-Grad limit, the distribution of the free path length in the Lorentz gas with disordered scatterer configuration has an exponential density. If, on the other hand, the scatterers are located at the vertices of a Euclidean lattice, the density has a power-law tail proportional to . In the present paper we construct scatterer configurations whose free path lengths have a distribution with tail for any positive integer . We also discuss the properties of the random flight process that describes the Lorentz gas in the Boltzmann-Grad limit. The convergence of the distribution of the free path length follows from equidistribution of large spheres in products of certain homogeneous spaces, which in turn is a consequence of Ratner's measure classification theorem.

Marklof, Jens; Strömbergsson, Andreas

2014-06-01

40

Power-Law Distributions for the Free Path Length in Lorentz Gases  

NASA Astrophysics Data System (ADS)

It is well known that, in the Boltzmann-Grad limit, the distribution of the free path length in the Lorentz gas with disordered scatterer configuration has an exponential density. If, on the other hand, the scatterers are located at the vertices of a Euclidean lattice, the density has a power-law tail proportional to ? ^{-3} . In the present paper we construct scatterer configurations whose free path lengths have a distribution with tail ? ^{-N-2} for any positive integer N . We also discuss the properties of the random flight process that describes the Lorentz gas in the Boltzmann-Grad limit. The convergence of the distribution of the free path length follows from equidistribution of large spheres in products of certain homogeneous spaces, which in turn is a consequence of Ratner's measure classification theorem.

Marklof, Jens; Strömbergsson, Andreas

2014-02-01

41

Temperature effects on the optical path length of infrared liquid transmission cells.  

PubMed

Infrared (IR) spectroscopy is widely used for studies of temperature-dependent properties of liquids and solutions, such as thermal denaturation of proteins and other molecules of biological interest. The variation of the spectroscopic signals with temperature can be affected by the changes in the optical path length due to the thermal expansion of the components of the sample cell. In this report we investigate the temperature dependence of the optical path length for a liquid IR sample cell of a design typical for aqueous solution experiments. The path lengths were measured from the interference fringes, both in dry cells and with cells partially filled with water. We found that the optical path length variations are significant, on the order of several percent within the temperature range used (0-87 °C). Several commercially available spacers (Teflon, mylar, and lead) and gaskets (Teflon, lead, silicone rubber, Viton, and neoprene) were tested to find materials with either the smallest or most reproducible effect. Teflon, due to its phase transition (known as the "knee point") near room temperature, leads to abrupt changes in path length when used as either spacer or gasket component. On the other hand, Teflon is preferred for its inertness, while several of the other tested materials, most notably lead, are not practically usable due to adhesion to the cell windows upon heating and contact with the aqueous sample. The combination that yielded the most reproducible results, with minimal complications due to adhesion, was Teflon spacer with neoprene gaskets. The implications of the optical path length changes for the temperature-dependent IR experiments and their possible corrections are discussed. PMID:22054091

Amunson, Krista E; Anderson, Benjamin A; Kubelka, Jan

2011-11-01

42

Analysis of light propagation in highly scattering media by path-length-assigned Monte Carlo simulations  

NASA Astrophysics Data System (ADS)

Numerical analysis of optical propagation in highly scattering media is investigated when light is normally incident to the surface and re-emerges backward from the same point. This situation corresponds to practical light scattering setups, such as in optical coherence tomography. The simulation uses the path-length-assigned Monte Carlo method based on an ellipsoidal algorithm. The spatial distribution of the scattered light is determined and the dependence of its width and penetration depth on the path-length is found. The backscattered light is classified into three types, in which ballistic, snake, and diffuse photons are dominant.

Ishii, Katsuhiro; Nishidate, Izumi; Iwai, Toshiaki

2014-05-01

43

Selection of optimum frequencies for atmospheric electric path length measurement by satellite-borne microwave radiometers  

NASA Technical Reports Server (NTRS)

Numerical experiments using regressions by leaps and bounds have been performed to determine the optimum frequencies for satellite-borne microwave radiometers to estimate atmospheric electrical path length over the sea. The frequency range 5-40 GHz was searched. The effect of surface wind speed, sea surface temperature, and clouds was considered in the optimum frequency selection. The analysis indicates that approximately 0.6-cm rms accuracy is possible for one-way path length measurement using a proper pair of frequencies. The best two-channel subset selected by the leaps and bounds techniques is (16.0, 21.0) GHz.

Pandey, P. C.; Kakar, R. K.

1983-01-01

44

Path Length Control in a Nulling Coronagraph with a MEMS Deformable Mirror and a Calibration Interferometer  

NASA Technical Reports Server (NTRS)

We report progress on a nulling coronagraph intended for direct imaging of extrasolar planets. White light is suppressed in an interferometer, and phase errors are measured by a second interferometer. A 1020-pixel MEMS deformable mirror in the first interferometer adjusts the path length across the pupil. A feedback control system reduces deflections of the deformable mirror to order of 1 nm rms.

Rao, Shanti R.; Wallacea, J. Kent; Samuele, Rocco; Chakrabarti, Supriya; Cook, Timothy; Hicks, Brian; Jung, Paul; Lane, Benjamin; Levine, B. Martin; Mendillo, Chris; Schmidtlin, Edouard; Shao, Mike; Stewart, Jason B.

2008-01-01

45

Topology and Shortest Path Length Evolution of The Internet Autonomous Systems Interconnectivity  

Microsoft Academic Search

Connection networks are observed in many areas of human knowledge. The characterization and topological studies of these networks may be performed through distribution of connectivity degrees, rank properties, shortest path length between nodes, adjacency matrix etc. This paper characterizes the Internet con- nections evolution over the last 10 years at the Autonomous Systems (AS) level analyzing the complete BGP data

N. ALVES Jr.; M. P. de ALBUQUERQUE; Xavier Sigaud; J. T. de ASSIS

46

On the determination of atmospheric path length by passive microwave radiometer  

NASA Technical Reports Server (NTRS)

Microwave radiometer techniques were evaluated for use in atmospheric path length correction of Pacific Plate Motion Experiment interferometer measurements. It is shown that passive microwave radiometry allows precise measurement of the brightness temperature of the sky. It is also noted that the technological requirements of radiometers are very different from the requirements of radio astronomy. The technology was used in the construction of radiometers which are sufficient for use in the path length correction problem. A simulation study shows that, when combined with surface meteorology data, passive microwave radiometer data would allow a determination of the path length correction to better than 2 cm at the zenith. By a careful choice of frequencies, a dual frequency system would allow a measurement of the path length correction to better than 4 cm at zenith angles as great as 60 deg. Because of the wide range of weather conditions to be expected for the PPME sites (which include Alaska, Hawaii and Massachusetts), it will probably be necessary to use a separate correction algorithm for each site.

Webster, W. J., Jr.

1975-01-01

47

Measurement of Optical Path Length for Cerebral Near-Infrared Spectroscopy in Newborn Infants  

Microsoft Academic Search

The time taken for an extremely short pulse of near-infrared laser light to traverse the heads of 6 preterm infants was measured after death. The values obtained were used to calculate a differential path length factor (DPF), defined as the mean distance travelled by the photons divided by the distance between the points where light entered and left the head.

J. S. Wyatt; M. Cope; D. T. Delpy; P. van der Zee; S. R. Arridge; A. D. Edwards; E. O. R. Reynolds

1990-01-01

48

Modal Analysis of Path Length Sensitivity in Superposition Architectures for Coherent Laser Beam Combining  

Microsoft Academic Search

An analytical model is developed to describe the modal behavior of a class of coherent beam combining resonators based on laser beam superposition. This model is used to explore the interplay between modal discrimination and tolerance to gain element path length changes. Under certain conditions, the sensitivity to the random phase fluctuations of the individual gain elements can be substantially

Mercedeh Khajavikhan; James R. Leger

2009-01-01

49

Acoustic method for measuring the sound speed of gases over small path lengths  

Microsoft Academic Search

Acoustic ``phase shift'' methods have been used in the past to accurately measure the sound speed of gases. In this work, a phase shift method for measuring the sound speed of gases over small path lengths is presented. We have called this method the discrete acoustic wave and phase detection (DAWPD) method. Experimental results show that the DAWPD method gives

J. S. Olfert; M. D. Checkel; C. R. Koch

2007-01-01

50

Optical path switching based differential absorption radiometry for substance detection  

NASA Technical Reports Server (NTRS)

An optical path switch divides sample path radiation into a time series of alternating first polarized components and second polarized components. The first polarized components are transmitted along a first optical path and the second polarized components along a second optical path. A first gasless optical filter train filters the first polarized components to isolate at least a first wavelength band thereby generating first filtered radiation. A second gasless optical filter train filters the second polarized components to isolate at least a second wavelength band thereby generating second filtered radiation. A beam combiner combines the first and second filtered radiation to form a combined beam of radiation. A detector is disposed to monitor magnitude of at least a portion of the combined beam alternately at the first wavelength band and the second wavelength band as an indication of the concentration of the substance in the sample path.

Sachse, Glen W. (Inventor)

2005-01-01

51

Optical path switching based differential absorption radiometry for substance detection  

NASA Technical Reports Server (NTRS)

An optical path switch divides sample path radiation into a time series of alternating first polarized components and second polarized components. The first polarized components are transmitted along a first optical path and the second polarized components along a second optical path. A first gasless optical filter train filters the first polarized components to isolate at least a first wavelength band thereby generating first filtered radiation. A second gasless optical filter train filters the second polarized components to isolate at least a second wavelength band thereby generating second filtered radiation. A beam combiner combines the first and second filtered radiation to form a combined beam of radiation. A detector is disposed to monitor magnitude of at least a portion of the combined beam alternately at the first wavelength band and the second wavelength band as an indication of the concentration of the substance in the sample path.

Sachse, Glen W. (Inventor)

2003-01-01

52

Water absorption length measurement with the ANTARES optical beacon system  

NASA Astrophysics Data System (ADS)

ANTARES is a neutrino telescope located in the Mediterranean Sea with the aim of detecting high energy neutrinos of extra-terrestrial origin. It consists of a three dimensional array on 12 detection lines of photomultiplier tubes (PMTs) able to detect the Cherenkov light induced by muons produced in the interaction of neutrinos with the surrounding water and seabed. To reach the best angular resolution, good time and positioning calibrations are required. The propagation of Cherenkov photons strongly depends on the optical properties of the sea water, which has an impact on the reconstruction efficiency. The determination of the optical parameters, as the absorption and scattering lengths, is crucial to calculate properly the effective area and the angular resolution of the detector. The ANTARES optical beacon system consists of pulsed and fast, well controlled light sources distributed throughout the detector to carry out in situ the relative time calibration of the detector components. In this contribution we show some results on the sea water optical properties and their stability measured with the optical beacon system.

Yepes-Ramirez, Harold; ANTARES Collaboration

2011-01-01

53

Carotid-Femoral Pulse Wave Velocity: Impact of Different Arterial Path Length Measurements  

PubMed Central

Background Carotid-femoral pulse wave velocity (PWV) is the most established index of arterial stiffness. Yet there is no consensus on the methodology in regard to the arterial path length measurements conducted on the body surface. Currently, it is not known to what extent the differences in the arterial path length measurements affect absolute PWV values. Methods Two hundred fifty apparently healthy adults (127 men and 123 women, 19-79 years) were studied. Carotid-femoral PWV was calculated using (1) the straight distance between carotid and femoral sites (PWVcar–fem), (2) the straight distance between suprasternal notch and femoral site minus carotid arterial length (PWV(ssn–fem)-(ssn–car)), (3) the straight distance between carotid and femoral sites minus carotid arterial length (PWV(car–fem)-(ssn–car)), and (4) the combined distance from carotid site to the umbilicus and from the umbilicus to femoral site minus carotid arterial length (PWV(ssn–umb–fem)-(ssn–car)). Results All the calculated PWV were significantly correlated with each other (r=0.966-0.995). PWV accounting for carotid arterial length were 16-31% lower than PWVcar–fem. PWVcar–fem value of 12 m/sec corresponded to 8.3 m/sec for PWV(ssn–fem)-(ssn–car), 10.0 m/sec for PWV(car–fem)-(ssn–car), and 8.9 m/sec for PWV(ssn–umb–fem)-(ssn–car). Conclusion Different body surface measurements used to estimate arterial path length would produce substantial variations in absolute PWV values.

Sugawara, Jun; Hayashi, Koichiro; Yokoi, Takashi; Tanaka, Hirofumi

2009-01-01

54

Volcanic Segmentation, Nb Depletion, Reactive Flow Path Length and Volcano Size are Linked in Central America  

NASA Astrophysics Data System (ADS)

Central America is unusual among the global set of arcs because the volcanic front is segmented by abrupt right steps of up to 40 km. Nb depletion (Zr/Nb) jumps at these steps (Bolge, 2005). Nb depletion is greater (Zr/Nb higher) at the volcano closer to the trench. Between steps, Nb depletion decreases to the SE, creating a saw- tooth pattern. Given the smooth Benioff zone revealed by seismicity and the slight anticlockwise rotation of the linear volcanic segments relative to the isobaths to the seismic zone, the variation in Nb depletion correlates with depth to the seismic zone. Thus, short paths have maximum Nb depletion and long paths have minimum depletion. This suggests a melt/fluid generation with a Nb retaining phase in the residue to create the initial depletion. A reactive flow through the mantle wedge then progressively reduces the initial depletion. The full set of incompatible elements is consistent with simple AFC models of this process. Furthermore, the uneven distribution of volcanic output along the volcanic front appears related to the variation in path length. A short path generates maximum Nb depletion and a small volcano. An intermediate length path generates a large volcano and moderate Nb depletion. A long path generates minimum Nb depletion and, again, a small volcano. This suggests that the magma generating region has an optimal depth or distance from the trench for magma productivity. Finally, although the origin of the volcanic lines is not explained, it must be a facet of upper plate tectonics, rather than a segmented slab.

Carr, M. J.; Bolge, L. L.

2007-12-01

55

A Graduated Cylinder Colorimeter: An Investigation of Path Length and the Beer-Lambert Law  

Microsoft Academic Search

A 10-mL graduated cylinder was used to construct a colorimeter to investigate the relationship between absorbance and path length found in the Beer-Lambert law. Light-emitting diodes (LEDs) were used as the light sources and filter monochromators. The experiments were conducted on intensely colored permanganate and tetraamminecopper(II) solutions. The device also was useful for demonstrating the relationship between absorbance and concentration.

James Gordon; Stephanie Harman

2002-01-01

56

Path length modulation technique for scatter noise immunity in squeezing measurements.  

PubMed

We present a technique for frequency shifting scattering induced noise on squeezed light beams, providing immunity from scattered light while preserving the squeezed states. Using a 500 Hz pre and postsqueezing apparatus path length modulation, we show up to a 20 dB reduction in scattering induced noise while recovering squeezing measurement below the shot noise level. Such a technique offers immunity to spurious scattering sources without the need for optically lossy isolation optics. PMID:23811897

Wade, Andrew R; Chua, Sheon S Y; Stefszky, Michael S; Shaddock, Daniel A; McClelland, David E

2013-07-01

57

Photon path length distributions in Oxygen A-band and water vapor band  

Microsoft Academic Search

A prototype high-resolution oxygen A-band and water vapor band spectrometer (HAWS) has been developed and demonstrated to study the applicability of photon path length statistics in the remote sensing of clouds, aerosols, and water vapor. The HAWS successfully achieves an out-of-band rejection of better than 10-5, a resolution of better than 0.5 cm-1, and high signal to noise ratio, which

Q. Min; L. C. Harrison; P. Kiedron; J. Berndt; E. E. Clothiaux; E. Joseph

2004-01-01

58

Fiber-optic liquid level sensor based on coupling optical path length variation.  

PubMed

The concept for a new and simple fiber-optic liquid level sensor is presented and experimental results are shown to demonstrate the principle. The sensing principle is based on light intensity modulation when rising and falling mode of liquid level causes coupling optical path distance variation between two optical fibers. Near continuous mode of liquid level variation could be monitored with resolution as low as 1 mm can be measured in the length scale of 25 cm. PMID:22667647

Nath, Pabitra; Singh, Hidam Kumarjit; Tiwari, Dhananjay; Basumatry, Tenisen

2012-05-01

59

Path-length dependence of energy loss within in-medium showers  

NASA Astrophysics Data System (ADS)

The study of the path-length dependence of high-transverse-momentum (PT) hadron suppression in heavy-ion collisions by measuring the dependence of hard-hadron production on the angle ? with the reaction plane in noncentral collisions has so far been one of the most successful tools in constraining the microscopic picture of leading-parton energy loss. With the imminent start of the Large Hadron Collider heavy-ion program and the possibility of full jet reconstruction, the focus has shifted to models that are capable of simulating full in-medium parton showers rather than tracing the leading parton only. Yet, on the level of single-inclusive hadron observables, such shower models need to reproduce the findings of leading-parton energy-loss models; in particular, they need to reproduce the correct reaction-plane-angle dependence of hadron suppression. The aim of this work is to illustrate, using the example of the Monte Carlo in-medium shower code, yajem (Yet another Jet Energy-loss Model), how path-length dependence arises in a Monte Carlo shower formulation, how it relates to path-length dependence of leading-parton energy loss, and how model results compare with data on the reaction-plane dependence of the nuclear suppression factor RAA(?).

Renk, Thorsten

2011-02-01

60

Visibility oscillation in a multimode laser interferometer signal and its use in optimizing path lengths.  

PubMed

The interference signal visibility V (difference to sum ratio of intensities at maximum and minimum interference) of an interferometer that uses a multimode laser is here derived for a given laser gain profile and spectral mode separation as a function of the difference Z(S) between the probe and reference beam optical path lengths and the spectral separation k(S) between the center of the laser gain profile and the nearest laser mode of higher frequency. k(S) has a significant effect on V for a given Z(S). This parameter, in lasers where it sweeps freely across the gain profile, and other effects, such as various misalignments and optical coupling inefficiencies, render V alone an unreliable parameter for quantifying Z(S) (for the purpose of reducing it, say). However, the difference to sum ratio of the maximum and minimum V due to variations in k(S) for a given Z(S) is an intrinsic property of the laser insensitive to configurational details. Parameter W so defined, therefore, proves very useful for balancing path lengths. This is of particular importance for systems where probe and/or reference beams are transmitted via long single mode optical fibers, so this application is detailed. Optical path lengths within such fibers often cannot be measured to sufficient accuracy by spatial path length measurements due to fiber nonuniformity resulting in variations in the mode's group velocity (needed to convert to optical path length). Two examples are provided using different makes and models of 0.633 ?m HeNe lasers with similar specifications. In the first case, the function W(Z(S)) is calculated directly from the laser's published gain profile and mode separation. In the second case, W is determined empirically for a range of Z(S)values for a laser with an unknown gain profile in a (heterodyned) interferometer whose interference signal oscillates between maximum and minimum intensity at 80 MHz due to the reference beam's optical frequency being acousto-optically upshifted by that amount, while k(S) spontaneously varies on an acoustic time scale. A single high-bandwidth waveform record for each Z(S), therefore, provides all the information needed to determine W. Despite the second laser's gain profile apparently differing in detail, qualitative agreement is achieved between the two methods sufficient to validate the technique. PMID:24182097

Ruden, E L; Camacho, J F; Lynn, A G

2013-10-01

61

Optical biopsy of breast tissue using differential path-length spectroscopy  

NASA Astrophysics Data System (ADS)

Differential path-length spectroscopy (DPS) was used to determine the local optical properties of breast tissue in vivo. DPS measurements were made on healthy and malignant breast tissue using a fibre-optic needle probe, and were correlated to the histological outcome of core-needle biopsies taken from the same location as the measurements. DPS yields information on the local tissue blood content, the local blood oxygenation, the average micro-vessel diameter, the ?-carotene concentration and the scatter slope. Our data show that malignant breast tissue is characterized by a significant decrease in tissue oxygenation and a higher blood content compared to normal breast tissue.

van Veen, Robert L. P.; Amelink, Arjen; Menke-Pluymers, Marian; van der Pol, Carmen; Sterenborg, Henricus J. C. M.

2005-06-01

62

Optical path length calculation of the auxiliary telescopes of the Very Large Telescope project  

NASA Astrophysics Data System (ADS)

The Optical Path Length (OPL) requirement for the Auxiliary Telescopes (AT's) is the variation of the OPL from the star to the output of M11 during short time windows corresponding to the exposure time of the interferometric instrument. The OPL variations considered in this design are those generated during the telescope tracking by the vibrations of all the mirrors. These vibrations include all telescope dependent effects and in particular: dynamic wind load on the AT, all internal vibration sources: bearings, cable wraps, normal micro seismic activities. The article presents the philosophy followed by AMOS for the optimisation of the design of the telescope to fulfill the OPL requirements.

Delrez, Christophe; Schumacher, Jean-Marc; Flebus, Carlo; Gloesener, Pierre; Koehler, Bertrand

63

A FORTRAN program for constrained sequence-slotting based on minimum combined path length  

NASA Astrophysics Data System (ADS)

This paper describes a program for combining or "slotting" together two ordered sequences of observations into a single combined sequence with the minimum possible "combined path length" while preserving the stratigraphic ordering within each original sequence. A dynamic programming approach is used to minimize the total length or distance through the combined sequence, taking as input user-defined distances or dissimilarities between each pair of observations. This optimization criterion in some situations may be more appropriate than other criteria. The program enables the user to specify, using simple mnemonic codes, any number of additional order constraints of 12 different types. The program is illustrated on a set of data comprising gamma, sonic, and induction logs from two wells. Detailed input instructions and a listing of the program are given.

Clark, R. M.

64

A volumetric approach to path-length measurements is essential when treating radiotherapy with modulated beams.  

PubMed

The established dosimetric benefits of intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy have lead to their increased use in prostate radiotherapy. Complimenting these techniques, volumetric image guidance has supported increased positional accuracy. In addition, 3-dimensional image guidance has also allowed for assessment of potential dosimetric variation that can be attributed to a deformation of either internal or external structures, such as rectal distension or body contour. Compounding these issues is the variation of tissue density through which the new field position passes and also the variation of dose across a modulated beam. Despite the growing level of interest in this area, there are only a limited number of articles that examine the effect of a variation in beam path length, particularly across a modulated field. IMRT and volumetric-modulated radiation therapy (VMAT) fields are dynamic in nature, and the dose gradient within these fields is variable. Assessment of variation of path length away from the beam?s central axis and across the entire field is vital where there is considerable variation of dose within the field, such as IMRT and VMAT. In these cases, reliance on the traditional central axis to focus skin distances is no longer appropriate. This article discusses these more subtle challenges that may have a significant clinical effect if left unrecognized and undervalued. PMID:24630910

Forde, Elizabeth; Booth, Jeremy; Leech, Michelle

2014-01-01

65

Comparison between solar electron and ion path lengths traveled during the Ground-Level Enhancement events in solar cycle 23  

NASA Astrophysics Data System (ADS)

The inconsistency of electron and ion path lengths during Solar Energetic Particle (SEP) events remains an open issue. In order to investigate the difference between the electron and ion path lengths during the Ground-Level Enhancement (GLE) events in solar cycle 23, electron and ion data from the WIND/3DP/SST and WIND/EPACT/LEMT instruments respectively have been used. The electron path lengths were determined for the GLEs in solar cycle 23 assuming that the solar release time of non-relativistic electrons is well represented by the onset time of metric type II or decametre-hectometric (DH) type III radio bursts. The values estimated for low-energy electrons (~ 27 keV) were compared to the ion path lengths deduced by Reames for the GLEs in solar cycle 23 based on the onset-time analysis and consistency within an error range of 10% was found. In addition, the electron path lengths were found to increase with increasing electron energies, with the increasing rate of path lengths corresponding to broader position angle distribution (PAD) of electrons, which suggests that electron path length enhancement is due to interplanetary scattering experienced by first-arriving electrons. Furthermore, the solar longitude distribution and IMF topology of the GLE events examined support that the non-relativistic electrons observed have been accelerated in shocks driven by CMEs. Finally, it should be stressed that the observed path length consistency leads to stability of magnetic flux tubes along which particles travel, with a maximum stability time of ~ 4.8 hours, which could be very important for forecasting since, based on the observed onset time of the electron event, it is possible to observe the arrival and duration of the proton event.

Malandraki, Olga; Tan, Lun; Reames, Donald; Ng, Chee; Wang, Linghua; Patsou, Ioanna; Papaioannou, Athanasios

2014-05-01

66

Temperature-Shifted White-Light Interferometry for Equalization of a Fiber Coupler to Near-Zero Path Length Difference  

Microsoft Academic Search

A method for equalizing the path lengths of two arms of an optical fiber coupler is presented as a critical step towards construction of a high-resolution 3-D interferometric imaging system. Based on white-light interferometry (WLI), the technique combines absolute measurement capability with the ability to accurately measure near-zero path length differences. A controlled temperature increase in one arm of the

Evan Lally; Tyler Shillig; Yunmiao Wang; Anbo Wang

2009-01-01

67

Analytic Expressions for the Statistics of the Primitive-Path Length in Entangled Polymers  

NASA Astrophysics Data System (ADS)

An analytic expression is proposed for the primitive-path length of entangled polymer chains. The expression is derived from statistical mechanics of a chain that is a random walk with randomly scattered entanglements. The only parameters are the number of Kuhn steps in the chain and a dimensionless parameter ? that contains information about the entanglement density and Kuhn step size. The expression is found to compare very favorably with numerical results recently found from examining topological constraints in microscopic simulations. The comparison also predicts well the plateau modulus of polyethylene, suggesting that the slip-link model is a viable intermediate in the search for true ab initio rheology predictions. Since the expression is analytic, it can be used to make predictions where the simulations cannot reach, and hence is applicable for coarse graining.

Khaliullin, Renat N.; Schieber, Jay D.

2008-05-01

68

The extension of the concept of the cosmic-ray path-length distribution to nonrelativistic energies  

NASA Technical Reports Server (NTRS)

The concept of the cosmic-ray path-length distribution is examined. The corresponding cosmic-ray propagation calculational procedure has been justified theoretically at relativistic energies (Ginzburg and Syrovatskii, 1964) where the effects of ionization energy loss are negligible. The present paper extends the use of the path-length distribution concept in cosmic-ray propagation calculations to nonrelativistic energies. Sufficient constraints to effect this extension are presented. The solution of the cosmic-ray propagation equations in terms of a Green's function approach is also investigated and is used to provide a formulation of the path-length distribution at nonrelativistic as well as relativistic energies in terms of the cosmic-ray source distribution and the propagation characteristics of the interstellar medium. The leaky-box model of cosmic-ray propagation is also examined.

Lezniak, J. A.

1979-01-01

69

A 2-Micron Pulsed Integrated Path Differential Absorption Lidar Development For Atmospheric CO2 Concentration Measurements  

NASA Technical Reports Server (NTRS)

A 2-micron pulsed, Integrated Path Differential Absorption (IPDA) lidar instrument for ground and airborne atmospheric CO2 concentration measurements via direct detection method is being developed at NASA Langley Research Center. This instrument will provide an alternate approach to measure atmospheric CO2 concentrations with significant advantages. A high energy pulsed approach provides high-precision measurement capability by having high signal-to-noise level and unambiguously eliminates the contamination from aerosols and clouds that can bias the IPDA measurement.

Yu, Jirong; Petros, Mulugeta; Reithmaier, Karl; Bai, Yingxin; Trieu, Bo C.; Refaat, Tamer F.; Kavaya, Michael J.; Singh, Upendra N.

2012-01-01

70

An open path, fast response infrared absorption gas analyzer for H2O and CO2  

Microsoft Academic Search

An open path infrared absorption based instrument for fast response measurements of H2O and CO2 fluctuations is described. This instrument performed reliably in several field experiments in both terrestrial and marine environments, on both fixed (tower) and mobile (boat, plane) flux platforms. Noise levels for H2O and CO2 concentrations were less than 10 mg\\/m3 and 300 ?g\\/m3, respectively for frequencies

David L. Auble; Tilden P. Meyers

1992-01-01

71

Optimizing the multiphoton absorption properties of maximally path-entangled number states  

SciTech Connect

In this paper we examine the N-photon absorption properties of maximally path-entangled number states (N00N states). We consider two cases. The first involves the N-photon absorption properties of the ideal N00N state, one that does not include spectral information. We study how the N-photon absorption probability of this state scales with N, confirming results presented by others in a previous paper by a different method. We compare this to the absorption probability of various other states. The second case is that of two-photon absorption for an N=2 N00N state generated from a type-II spontaneous down-conversion event. In this situation we find that the absorption probability is both better than analogous coherent light (due to frequency entanglement) and highly dependent on the optical setup. We show that the poor production rates of quantum states of light may be partially mitigated by adjusting the spectral parameters to improve their two-photon absorption rates. This work has application to quantum imaging, particularly quantum lithography, where the N-photon absorbing process in the lithographic resist must be optimized for practical applications.

Plick, William N.; Wildfeuer, Christoph F.; Anisimov, Petr M.; Dowling, Jonathan P. [Hearne Institute for Theoretical Physics, Department of Physics and Astronomy, Louisiana State University, Baton Rouge, Louisiana 70803 (United States)

2009-12-15

72

Water equivalent path length measurement in proton radiotherapy using time resolved diode dosimetry  

SciTech Connect

Purpose: To verify water equivalent path length (WEPL) before treatment in proton radiotherapy using time resolved in vivo diode dosimetry. Methods: Using a passively scattered range modulated proton beam, the output of a diode driving a fast current-to-voltage amplifier is recorded at a number of depths in a water tank. At each depth, a burst of overlapping single proton pulses is observed. The rms duration of the burst is computed and the resulting data set is fitted with a cubic polynomial. Results: When the diode is subsequently set to an arbitrary depth and the polynomial is used as a calibration curve, the ''unknown'' depth is determined within 0.3 mm rms. Conclusions: A diode or a diode array, placed (for instance) in the rectum in conjunction with a rectal balloon, can potentially determine the WEPL at that point, just prior to treatment, with submillimeter accuracy, allowing the beam energy to be adjusted. The associated unwanted dose is about 0.2% of a typical single fraction treatment dose.

Gottschalk, B.; Tang, S.; Bentefour, E. H.; Cascio, E. W.; Prieels, D.; Lu, H.-M. [Laboratory for Particle Physics and Cosmology, Harvard University, 18 Hammond Street, Cambridge, Massachusetts 02138 (United States); Francis H. Burr Proton Therapy Center, Boston, Massachusetts 02114 (United States); Ion Beam Applications S.A., Louvain-la-Neuve 1348 (Belgium); Francis H. Burr Proton Therapy Center, Boston, Massachusetts 02114 (United States); Ion Beam Applications S.A., Louvain-la-Neuve 1348 (Belgium); Francis H. Burr Proton Therapy Center, Boston, Massachusetts 02114 (United States)

2011-04-15

73

Continuous correction of differential path length factor in near-infrared spectroscopy  

NASA Astrophysics Data System (ADS)

In continuous-wave near-infrared spectroscopy (CW-NIRS), changes in the concentration of oxyhemoglobin and deoxyhemoglobin can be calculated by solving a set of linear equations from the modified Beer-Lambert Law. Cross-talk error in the calculated hemodynamics can arise from inaccurate knowledge of the wavelength-dependent differential path length factor (DPF). We apply the extended Kalman filter (EKF) with a dynamical systems model to calculate relative concentration changes in oxy- and deoxyhemoglobin while simultaneously estimating relative changes in DPF. Results from simulated and experimental CW-NIRS data are compared with results from a weighted least squares (WLSQ) method. The EKF method was found to effectively correct for artificially introduced errors in DPF and to reduce the cross-talk error in simulation. With experimental CW-NIRS data, the hemodynamic estimates from EKF differ significantly from the WLSQ (p<0.001). The cross-correlations among residuals at different wavelengths were found to be significantly reduced by the EKF method compared to WLSQ in three physiologically relevant spectral bands 0.04 to 0.15 Hz, 0.15 to 0.4 Hz and 0.4 to 2.0 Hz (p<0.001). This observed reduction in residual cross-correlation is consistent with reduced cross-talk error in the hemodynamic estimates from the proposed EKF method.

Talukdar, Tanveer; Moore, Jason H.; Diamond, Solomon G.

2013-05-01

74

Continuous correction of differential path length factor in near-infrared spectroscopy.  

PubMed

In continuous-wave near-infrared spectroscopy (CW-NIRS), changes in the concentration of oxyhemoglobin and deoxyhemoglobin can be calculated by solving a set of linear equations from the modified Beer-Lambert Law. Cross-talk error in the calculated hemodynamics can arise from inaccurate knowledge of the wavelength-dependent differential path length factor (DPF). We apply the extended Kalman filter (EKF) with a dynamical systems model to calculate relative concentration changes in oxy- and deoxyhemoglobin while simultaneously estimating relative changes in DPF. Results from simulated and experimental CW-NIRS data are compared with results from a weighted least squares (WLSQ) method. The EKF method was found to effectively correct for artificially introduced errors in DPF and to reduce the cross-talk error in simulation. With experimental CW-NIRS data, the hemodynamic estimates from EKF differ significantly from the WLSQ (p < 0.001). The cross-correlations among residuals at different wavelengths were found to be significantly reduced by the EKF method compared to WLSQ in three physiologically relevant spectral bands 0.04 to 0.15 Hz, 0.15 to 0.4 Hz and 0.4 to 2.0 Hz (p < 0.001). This observed reduction in residual cross-correlation is consistent with reduced cross-talk error in the hemodynamic estimates from the proposed EKF method. PMID:23640027

Talukdar, Tanveer; Moore, Jason H; Diamond, Solomon G

2013-05-01

75

Continuous correction of differential path length factor in near-infrared spectroscopy  

PubMed Central

Abstract. In continuous-wave near-infrared spectroscopy (CW-NIRS), changes in the concentration of oxyhemoglobin and deoxyhemoglobin can be calculated by solving a set of linear equations from the modified Beer-Lambert Law. Cross-talk error in the calculated hemodynamics can arise from inaccurate knowledge of the wavelength-dependent differential path length factor (DPF). We apply the extended Kalman filter (EKF) with a dynamical systems model to calculate relative concentration changes in oxy- and deoxyhemoglobin while simultaneously estimating relative changes in DPF. Results from simulated and experimental CW-NIRS data are compared with results from a weighted least squares (WLSQ) method. The EKF method was found to effectively correct for artificially introduced errors in DPF and to reduce the cross-talk error in simulation. With experimental CW-NIRS data, the hemodynamic estimates from EKF differ significantly from the WLSQ (p<0.001). The cross-correlations among residuals at different wavelengths were found to be significantly reduced by the EKF method compared to WLSQ in three physiologically relevant spectral bands 0.04 to 0.15 Hz, 0.15 to 0.4 Hz and 0.4 to 2.0 Hz (p<0.001). This observed reduction in residual cross-correlation is consistent with reduced cross-talk error in the hemodynamic estimates from the proposed EKF method.

Talukdar, Tanveer; Moore, Jason H.; Diamond, Solomon G.

2013-01-01

76

Changes in diffusion path length with old age in diffuse optical tomography  

NASA Astrophysics Data System (ADS)

Diffuse, optical near infrared imaging is increasingly being used in various neurocognitive contexts where changes in optical signals are interpreted through activation maps. Statistical population comparison of different age or clinical groups rely on the relative homogeneous distribution of measurements across subjects in order to infer changes in brain function. In the context of an increasing use of diffuse optical imaging with older adult populations, changes in tissue properties and anatomy with age adds additional confounds. Few studies investigated these changes with age. Duncan et al. measured the so-called diffusion path length factor (DPF) in a large population but did not explore beyond the age of 51 after which physiological and anatomical changes are expected to occur [Pediatr. Res. 39(5), 889-894 (1996)]. With increasing interest in studying the geriatric population with optical imaging, we studied changes in tissue properties in young and old subjects using both magnetic resonance imaging (MRI)-guided Monte-Carlo simulations and time-domain diffuse optical imaging. Our results, measured in the frontal cortex, show changes in DPF that are smaller than previously measured by Duncan et al. in a younger population. The origin of these changes are studied using simulations and experimental measures.

Bonnéry, Clément; Leclerc, Paul-Olivier; Desjardins, Michèle; Hoge, Rick; Bherer, Louis; Pouliot, Philippe; Lesage, Frédéric

2012-05-01

77

Minority carrier diffusion lengths and absorption coefficients in silicon sheet material  

SciTech Connect

One of the indicators which determine a material's potential for use as a solar cell is the minority carrier diffusion length (L/sub D/) of the material. To determine L/sub D/ a surface photovoltage (SPV) technique is used. This method is dependent upon an accurate knowledge of the optical absorption coefficient as function of wavelength. The results for the absorption coefficients for various types of silicon sheet material are compared to those previously used in the two models. The resultant effect upon the diffusion length is also discussed in detail. 7 refs.

Dumas, K.A.; Swimm, R.T.

1980-01-01

78

Photon path length distributions inferred from rotating shadowband spectrometer measurements at the Atmospheric Radiation Measurements Program Southern Great Plains site  

Microsoft Academic Search

An algorithm for retrieving the first two moments of the photon path length probability density function for both the oxygen A-band and the 0.820 mum water vapor band from measurements of the second generation Rotating Shadowband Spectrometer (RSS) is developed and applied to data from the Atmospheric Radiation Measurements (ARM) Program Southern Great Plains (SGP) site. In the algorithm, solar

Qilong Min; Eugene E. Clothiaux

2003-01-01

79

Photon path length distributions inferred from rotating shadowband spectrometer measurements at the Atmospheric Radiation Measurements Program Southern Great Plains site  

Microsoft Academic Search

An algorithm for retrieving the first two moments of the photon path length probability density function for both the oxygen A-band and the 0.820 ?m water vapor band from measurements of the second generation Rotating Shadowband Spectrometer (RSS) is developed and applied to data from the Atmospheric Radiation Measurements (ARM) Program Southern Great Plains (SGP) site. In the algorithm, solar

Qilong Min; Eugene E. Clothiaux

2003-01-01

80

Addressing the Path-Length-Dependency Confound in White Matter Tract Segmentation  

PubMed Central

We derive the Iterative Confidence Enhancement of Tractography (ICE-T) framework to address the problem of path-length dependency (PLD), the streamline dispersivity confound inherent to probabilistic tractography methods. We show that PLD can arise as a non-linear effect, compounded by tissue complexity, and therefore cannot be handled using linear correction methods. ICE-T is an easy-to-implement framework that acts as a wrapper around most probabilistic streamline tractography methods, iteratively growing the tractography seed regions. Tract networks segmented with ICE-T can subsequently be delineated with a global threshold, even from a single-voxel seed. We investigated ICE-T performance using ex vivo pig-brain datasets where true positives were known via in vivo tracers, and applied the derived ICE-T parameters to a human in vivo dataset. We examined the parameter space of ICE-T: the number of streamlines emitted per voxel, and a threshold applied at each iteration. As few as 20 streamlines per seed-voxel, and a robust range of ICE-T thresholds, were shown to sufficiently segment the desired tract network. Outside this range, the tract network either approximated the complete white-matter compartment (too low threshold) or failed to propagate through complex regions (too high threshold). The parameters were shown to be generalizable across seed regions. With ICE-T, the degree of both near-seed flare due to false positives, and of distal false negatives, are decreased when compared with thresholded probabilistic tractography without ICE-T. Since ICE-T only addresses PLD, the degree of remaining false-positives and false-negatives will consequently be mainly attributable to the particular tractography method employed. Given the benefits offered by ICE-T, we would suggest that future studies consider this or a similar approach when using tractography to provide tract segmentations for tract based analysis, or for brain network analysis.

Liptrot, Matthew G.; Sidaros, Karam; Dyrby, Tim B.

2014-01-01

81

Estimation of Path Length Reduction Factor by Using One Year Rain Attenuation Statistics over a Line of Sight Link Operating at 28.75 GHz in Amritsar (INDIA)  

NASA Astrophysics Data System (ADS)

The effect of environmental factors in general and rain droplets in particular, on microwave propagation is a very well known fact now. If the rain droplets are present in an inhomogeneous way across the path length of the microwave communication system then, a new concept of path length reduction factor is introduced which accounts for the inhomogeneous nature of the rain droplets along the path length of the microwave signal. The present paper presents results of path length reduction factor using data on attenuation levels obtained on a LOS link operating at 28.75 GHz in Amritsar region and its comparison with Crane's and ITU-R's model.

Sharma, Parshotam; Hudiara, Inderjit Singh; Singh, Maninder Lal

2011-02-01

82

Airborne measurements of atmospheric methane column abundance using a pulsed integrated-path differential absorption lidar.  

PubMed

We report airborne measurements of the column abundance of atmospheric methane made over an altitude range of 3-11 km using a direct detection integrated-path differential-absorption lidar with a pulsed laser emitting at 1651 nm. The laser transmitter was a tunable, seeded optical parametric amplifier pumped by a Nd:YAG laser, and the receiver used a photomultiplier detector and photon-counting electronics. The results follow the expected changes with aircraft altitude, and the measured line shapes and optical depths show good agreement with theoretical calculations. PMID:23207402

Riris, Haris; Numata, Kenji; Li, Steve; Wu, Stewart; Ramanathan, Anand; Dawsey, Martha; Mao, Jianping; Kawa, Randolph; Abshire, James B

2012-12-01

83

Topological versus rheological entanglement length in primitive-path analysis protocols, tube models, and slip-link models  

NASA Astrophysics Data System (ADS)

We show that the front factor appearing in the shear modulus of a phantom network, Gph=(1-2/f)(?kBT)/Ns, also controls the ratio of the strand length, Ns, and the number of monomers per Kuhn length of the primitive paths, NphPPKuhn, characterizing the average network conformation. In particular, NphPPKuhn=Ns/(1-2/f) and Gph=(?kBT)/NphPPKuhn. Neglecting the difference between cross-links and slip-links, these results can be transferred to entangled systems and the interpretation of primitive path analysis data. In agreement with the tube model, the analogy to phantom networks suggest that the rheological entanglement length, Nerheo=(?kBT)/Ge, should equal NePPKuhn. Assuming binary entanglements with f=4 functional junctions, we expect that Nerheo should be twice as large as the topological entanglement length, Netopo. These results are in good agreement with reported primitive path analysis results for model systems and a wide range of polymeric materials. Implications for tube and slip-link models are discussed.

Everaers, Ralf

2012-08-01

84

Algorithms for finding the weight-constrained k longest paths in a tree and the length-constrained k maximum-sum segments of a sequence  

Microsoft Academic Search

In this work, we obtain the following new results: - Given a tree T = (V;E) with a length function ' : E ! R and a weight function w : E !R, a positive integer k, and an interval (L;U), the Weight-Constrained k Longest Paths problem is to find the k longest paths among all paths in T with

Hsiao-fei Liu; Kun-mao Chao

2008-01-01

85

Design of a Simple Detection Cell with Extended Optical Path Length for Capillary Electrophoresis: Application to Multiresidue Pesticide Analysis  

Microsoft Academic Search

Absorbance detection in capillary electrophoresis (CE), offers an excellent mass sensitivity, but poor concentration detection limits owing to very small injection volumes (normally 1 to 10 nL). This aspect can be a limiting factor in the applicability of CE\\/UV to detect species at trace levels, particularly pesticide residues. In the present work, the optical path length of an “on?column” detection cell

Mário S. Galhiane; Sandra R. Rissato; Bernhard M. Apon

2005-01-01

86

Minority carrier diffusion lengths and absorption coefficients in silicon sheet material  

NASA Technical Reports Server (NTRS)

Most of the methods which have been developed for the measurement of the minority carrier diffusion length of silicon wafers require that the material have either a Schottky or an ohmic contact. The surface photovoltage (SPV) technique is an exception. The SPV technique could, therefore, become a valuable diagnostic tool in connection with current efforts to develop low-cost processes for the production of solar cells. The technique depends on a knowledge of the optical absorption coefficient. The considered investigation is concerned with a reevaluation of the absorption coefficient as a function of silicon processing. A comparison of absorption coefficient values showed these values to be relatively consistent from sample to sample, and independent of the sample growth method.

Dumas, K. A.; Swimm, R. T.

1980-01-01

87

PATH  

NSDL National Science Digital Library

Started in the 1970s as an agency to assist men and women in gaining access to a variety of birth control methods, PATH has since expanded its focus to provide "sustainable, culturally relevant [health] solutions, enabling communities worldwide to break longstanding cycles of poor health." The PATH website has more than a dozen videos and slideshows available to visitors at the "Our Multimedia" link near the bottom right hand corner of the homepage. A three-minute video entitled "Better Nutrition For Life" educates visitors about an innovative rice product that could bring greater nutrition to millions of malnourished people where rice is a staple food. The product is Ultra Rice, and is actually fortified pasta that looks, cooks, and tastes like rice, but is fortified with nutrients. The "rice" can be fortified with the needed nutrients the particular population being served is lacking. A slideshow about TB in the Ukraine, explains to visitors why there has been a resurgence of TB in Eastern Europe, and how PATH and its partners set out to help control it throughout the region.

88

A laser ranging method dedicated to path lengths equalization in diluted telescopes  

NASA Astrophysics Data System (ADS)

When implementing a diluted telescope with large dimensions, one has to reach the equal path condition to the different segments of the primary mirror. In this work we suggest a way to implement a fast laser ranging method able to provide the error signal, using phase detection of the microwave modulation of a laser beam.

Lintz, M.; Courde, C.

2014-04-01

89

Complex Experimental Evaluation of the Characteristics of Propagation of HF Signals Along Midlatitude Paths of Different Length and Orientation  

NASA Astrophysics Data System (ADS)

We outline a complex approach for measuring distance-frequency, angular, spectral, and statistical characteristics of HF signals and present the results of experimental studies of the turbidity coefficient, frequency-spread bandwidth, variations in the Doppler frequency shift, bearing, and elevation angle in a wide frequency range for the Khabarovsk-Rostov-on-Don, Moscow-Rostov-on-Don, and Cyprus-Rostov-on-Don sounding paths under various geophysical conditions. It is shown that the most probable values of the turbidity coefficient for one-hop paths in the afternoon range from 2 to 4. The turbidity coefficient decreases to about 0.6 in the twilight hours. The turbidity coefficient tends to decrease with the path length. The average frequency-spread bandwidth at the 95% level of the received signal power is found to be minimal for illuminated path and does not exceed a value from 0.1 to 0.3 Hz. The frequency-spread bandwidth increases in the sunset hours or under nonuniform illumination, but does not exceed 4 Hz. We estimated the range of Doppler frequency shift variations which are due mainly to the influence of medium-scale traveling ionospheric disturbances and do not exceed 2 Hz in the experiments. The method of one-position location of a radiation source is tested by the results of angular measurements on the basis of the IRI-2001 ionospheric model.

Vertogradov, G. G.; Myatezhnikov, Yu. P.; Uryadov, V. P.; Rozanov, S. V.

2004-01-01

90

Open-path tunable diode laser absorption for eddy correlation flux measurements of atmospheric trace gases  

NASA Technical Reports Server (NTRS)

Biogenic emissions from and dry deposition to terrestrial surfaces are important processes determining the trace gas composition of the atmosphere. An instrument has been developed for flux measurements of gases such as CH4, N2O, and O3 based on the eddy correlation technique which combines trace gas fluctuation measurements with simultaneous windfield measurements. The instrument combines a tunable diode laser infrared light source with an open-path multipass absorption cell in order to provide the fast time response and short base pathlength required for the eddy correlation method. Initial field tests using the instrument to measure methane emissions from a local wetland demonstrate the capability for high precision eddy correlation flux measurements.

Anderson, Stuart M.; Zahniser, Mark S.

1991-01-01

91

Development of a Pulsed 2-Micron Integrated Path Differential Absorption Lidar for CO2 Measurement  

NASA Technical Reports Server (NTRS)

Atmospheric carbon dioxide (CO2) is an important greenhouse gas that significantly contributes to the carbon cycle and global radiation budget on Earth. Active remote sensing of CO2 is important to address several limitations that contend with passive sensors. A 2-micron double-pulsed, Integrated Path Differential Absorption (IPDA) lidar instrument for ground and airborne atmospheric CO2 concentration measurements via direct detection method is being developed at NASA Langley Research Center. This active remote sensing instrument will provide an alternate approach of measuring atmospheric CO2 concentrations with significant advantages. A high energy pulsed approach provides high-precision measurement capability by having high signal-to-noise ratio level and unambiguously eliminates the contamination from aerosols and clouds that can bias the IPDA measurement. Commercial, on the shelf, components are implemented for the detection system. Instrument integration will be presented in this paper as well as a background for CO2 measurement at NASA Langley research Center

Singh, Upendra N.; Yu, Jirong; Petros, Mulugeta; Refaat, Tamer; Refaat, Tamer

2013-01-01

92

A tunable diode laser absorption system for long path atmospheric transmission and high energy laser applications  

NASA Astrophysics Data System (ADS)

An open-path Tunable Diode Laser Absorption Spectroscopy (TDLAS) system composed of narrow band (~300 kHz) diodes fiber coupled to a 12" Ritchey-Chrétien transmit telescope has been developed to study atmospheric transmission of key High Energy Laser wavelengths. The ruggedized system has been field deployed and tested for propagation distances of greater than 1 km. Initial experiments were performed in the vicinity of molecular oxygen X3?-g to b1?+gelectronic transition lines near 760 nm. The potassium version of the Diode Pumped Alkali Laser (DPAL) operates in between two of the sharp oxygen rotational features in the PP and the PQ branches. By scanning across many laser free spectral ranges and monitoring the laser frequency with a very precise wavemeter, the full structure of the oxygen molecular feature is observed. The device can also be used to observe rotational temperatures, oxygen concentrations, and total atmospheric pressure.

Rice, Christopher A.; Perram, Glen

2011-02-01

93

Effect of conjugation path length on quadratic nonlinear optical properties of monomer and aggregates of zwitterionic merocyanine dyes.  

PubMed

We present a quantum-chemical analysis of the conjugation path length effect on first hyperpolarizabilities of a series of zwitterionic merocyanine dyes whose synthesis has been reported earlier (J. Am. Chem. Soc.2002, 124, 9431, J. Am. Chem. Soc. 1997, 119, 3144). The effect of the conjugation path lengths is evaluated to demonstrate the engineering guidelines for enhancing molecular optical nonlinearity. The first hyperpolarizabilities are calculated for extended conjugated monomer and H and J type aggregates of merocyanine dyes, to provide insight into the intermolecular interactions and the relationship between structural and collective nonlinear optical properties. The molecular geometries for monomers are obtained via B3LYP/6-31G(d,p) level optimization including the SCRF/PCM approach, and the dynamic nonlinear optical (NLO) properties for monomer and aggregates are calculated with the ZINDO/CV method, including solvent effects. It is found that the chain length dependence of the first nonlinearity peaks at n = 6 and then it starts changing slowly for monomer and aggregates of zwitterionic merocyanine dyes. It is concluded that an excellent NLO response in solution might vanish when the active chromophore forms higher H aggregates. The importance of our results on the design of electrooptic materials has been discussed. PMID:16836460

Ray, Paresh C; Bonifassi, P; Leszczynski, J

2006-07-20

94

Investigation of an implantable dosimeter for single-point water equivalent path length verification in proton therapy  

SciTech Connect

Purpose: In vivo range verification in proton therapy is highly desirable. A recent study suggested that it was feasible to use point dose measurement for in vivo beam range verification in proton therapy, provided that the spread-out Bragg peak dose distribution is delivered in a different and rather unconventional manner. In this work, the authors investigate the possibility of using a commercial implantable dosimeter with wireless reading for this particular application. Methods: The traditional proton treatment technique delivers all the Bragg peaks required for a SOBP field in a single sequence, producing a constant dose plateau across the target volume. As a result, a point dose measurement anywhere in the target volume will produce the same value, thus providing no information regarding the water equivalent path length to the point of measurement. However, the same constant dose distribution can be achieved by splitting the field into a complementary pair of subfields, producing two oppositely ''sloped'' depth-dose distributions, respectively. The ratio between the two distributions can be a sensitive function of depth and measuring this ratio at a point inside the target volume can provide the water equivalent path length to the dosimeter location. Two types of field splits were used in the experiment, one achieved by the technique of beam current modulation and the other by manipulating the location and width of the beam pulse relative to the range modulator track. Eight MOSFET-based implantable dosimeters at four different depths in a water tank were used to measure the dose ratios for these field pairs. A method was developed to correct the effect of the well-known LET dependence of the MOSFET detectors on the depth-dose distributions using the columnar recombination model. The LET-corrected dose ratios were used to derive the water equivalent path lengths to the dosimeter locations to be compared to physical measurements. Results: The implantable dosimeters measured the dose ratios with a reasonable relative uncertainty of 1%-3% at all depths, except when the ratio itself becomes very small. In total, 55% of the individual measurements reproduced the water equivalent path lengths to the dosimeters within 1 mm. For three dosimeters, the difference was consistently less than 1 mm. Half of the standard deviations over the repeated measurements were equal or less than 1 mm. Conclusions: With a single fitting parameter, the LET-correction method worked remarkably well for the MOSFET detectors. The overall results were very encouraging for a potential method of in vivo beam range verification with millimeter accuracy. This is sufficient accuracy to expand range of clinical applications in which the authors could use the distal fall off of the proton depth dose for tight margins.

Lu, Hsiao-Ming; Mann, Greg; Cascio, Ethan [Francis H. Burr Proton Therapy Center, Massachusetts General Hospital, Boston, Massachusetts 02114 (United States); Sicel Technologies, Inc., Morrisville, North Carolina 27560 (United States); Francis H. Burr Proton Therapy Center, Massachusetts General Hospital, Boston, Massachusetts 02114 (United States)

2010-11-15

95

Phrase Length Matters: The Interplay between Implicit Prosody and Syntax in Korean "Garden Path" Sentences  

ERIC Educational Resources Information Center

In spoken language comprehension, syntactic parsing decisions interact with prosodic phrasing, which is directly affected by phrase length. Here we used ERPs to examine whether a similar effect holds for the on-line processing of written sentences during silent reading, as suggested by theories of "implicit prosody." Ambiguous Korean sentence…

Hwang, Hyekyung; Steinhauer, Karsten

2011-01-01

96

Differences Between Length of Stay and Healthcare Costs When Compared with Traditional and Clinical Path Management.  

National Technical Information Service (NTIS)

The purpose of this study is to describe the relationship of clinical pathways to length of stay (LOS) and healthcare costs in an Air Force Medical Center when compared to traditional care. This study compared clinical pathway client management with tradi...

V. J. Hagan

1997-01-01

97

Measurement of Urban Air Quality by an Open-Path Quantum Cascade Laser Absorption Spectrometer in Beijing During Summer 2008  

NASA Astrophysics Data System (ADS)

The 2008 Olympic Games focused attention on the air quality of Beijing, China and served as an important test-bed for developing, deploying, and testing new technologies for analysis of air quality and regional climate in urban environments. Poor air quality in urban locations has a significant detrimental effect on the health of residents while also impacting both regional and global climate change. As a result, there exists a great need for highly sensitive trace gas sensors for studying the atmosphere of the urban environment. Open-path remote sensors are of particular interest as they can obtain data on spatial scales similar to those used in regional climate models. Quantum cascade lasers (QCLs) can be designed for operation in the mid-infrared (mid-IR) with a central wavelength anywhere between 3 to 24 ?m and made tunable over a wavelength interval of over 0.1 ?m. The Quantum Cascade Laser Open-Path System (QCLOPS) is a mid-infrared laser absorption spectrometer that uses a tunable, thermoelectrically cooled, pulsed Daylight Solutions Inc. QCL for measurement of trace gases. The system is aimed at applications with path lengths ranging from approximately 0.1 to 1.0 km. The system is designed to continuously monitor multiple trace gases [water vapor (H2O), ozone (O3), ammonia (NH3), and carbon dioxide (CO2)] in the lower atmosphere. A field campaign from July to September 2008 in Beijing used QCLOPS to study trace gas concentrations before, during, and after the Olympic Games in an effort to capture changes induced by emissions reduction methods. QCLOPS was deployed at the Institute of Atmospheric Physics - Chinese Academy of Sciences on the roof of a two-story building, at an approximate distance of 2 miles from the Olympic National Stadium ("The Bird's Nest.") QCLOPS operated with an open-path round trip distance of approximately 75 m. The system ran with minimal human interference, twenty-four hours per day for the full campaign period. In order to collect data over numerous absorption peaks belonging to the target gases of H2O, NH3, O3, and CO2, measurements were made at 317 different wavelengths within the full tuning range of the laser (1020 - 1070 cm-1). We present the design of this novel sensor which was successfully built, deployed, and operated with minimal operator intervention for the three month field campaign period. Furthermore, we present the results of the field campaign and the capabilities of the QCLOPS system to measure fluctuations of the trace gases at parts-per-billion levels. The time series data illustrate the changing levels of the trace gases over the campaign period. In addition, data from commercial sensors simultaneously deployed at the field site are presented as a validation of the capabilities of the QCLOPS system. This work was supported by MIRTHE (NSF-ERC #EEC-0540832).

Michel, A. P.; Liu, P. Q.; Yeung, J. K.; Zhang, Y.; Baeck, M. L.; Pan, X.; Dong, H.; Wang, Z.; Smith, J. A.; Gmachl, C. F.

2009-05-01

98

Gold nanorod length controls dispersion, local ordering, and optical absorption in polymer nanocomposite films.  

PubMed

The dispersion, local orientation and optical absorption of polystyrene (PS, degree of polymerization P) nanocomposites containing PS-grafted gold nanorods (Au NRs, PS degree of polymerization N), with aspect ratios (? = length/diameter) ranging from 2.5 to 6.3, are studied using quantitative scanning electron microscopy (SEM) and optical spectroscopy. The experimentally observed nanorod assemblies and optical absorptions are compared with predictions from self-consistent field theory (SCFT) and finite difference time domain (FDTD) calculations, respectively. A pair correlation function for Au NRs is calculated from SEM images, and contains no correlation peaks for P/N = 0.9, indicating nanorods are dispersed within the nanocomposite. Large correlation peaks are observed for P/N = 7.6, representative of interparticle separation distances within nanorod aggregates, which do not vary with ?. On the basis of SCFT calculations, aggregation is attributed to significant depletion-attraction forces in the composite for P/N > 1. When Au NRs disperse, the longitudinal surface plasmon resonance (LSPR) peak red shifts from the visible into the near-IR as ? increases. No shift in the dispersed LSPR position is observed for v = 2.5 and 3.3 upon aggregation because the ratio of the interparticle distance to the nanorod length is too large for surface plasmon coupling. However, for v = 6.3, significant coupling between surface plasmons leads to a blue shift of the LSPR by approximately 140 nm, in agreement with FDTD calculations. PMID:24643463

Wang, Dongliang; Hore, Michael J A; Ye, Xingchen; Zheng, Chen; Murray, Christopher B; Composto, Russell J

2014-05-21

99

The azimuthal path of myosin V and its dependence on lever-arm length  

PubMed Central

Myosin V (myoV) is a two-headed myosin capable of taking many successive steps along actin per diffusional encounter, enabling it to transport vesicular and ribonucleoprotein cargos in the dense and complex environment within cells. To better understand how myoV navigates along actin, we used polarized total internal reflection fluorescence microscopy to examine angular changes of bifunctional rhodamine probes on the lever arms of single myoV molecules in vitro. With a newly developed analysis technique, the rotational motions of the lever arm and the local orientation of each probe relative to the lever arm were estimated from the probe’s measured orientation. This type of analysis could be applied to similar studies on other motor proteins, as well as other proteins with domains that undergo significant rotational motions. The experiments were performed on recombinant constructs of myoV that had either the native-length (six IQ motifs and calmodulins [CaMs]) or truncated (four IQ motifs and CaMs) lever arms. Native-length myoV-6IQ mainly took straight steps along actin, with occasional small azimuthal tilts around the actin filament. Truncated myoV-4IQ showed an increased frequency of azimuthal steps, but the magnitudes of these steps were nearly identical to those of myoV-6IQ. The results show that the azimuthal deflections of myoV on actin are more common for the truncated lever arm, but the range of these deflections is relatively independent of its lever-arm length.

Lewis, John H.; Beausang, John F.; Sweeney, H. Lee

2012-01-01

100

Directionality of real world networks as predicted by path length in directed and undirected graphs  

NASA Astrophysics Data System (ADS)

Many real world networks either support ordered processes, or are actually representations of such processes. However, the same networks contain large strong connectivity components and long circles, which hide a possible inherent order, since each vertex can be reached from each vertex in a directed path. Thus, the presence of an inherent directionality in networks may be hidden. We here discuss a possible definition of such a directionality and propose a method to detect it. Several common algorithms, such as the betweenness centrality or the degree, measure various aspects of centrality in networks. However, they do not address directly the issue of inherent directionality. The goal of the algorithm discussed here is the detection of global directionality in directed networks. Such an algorithm is essential to detangle complex networks into ordered process. We show that indeed the vast majority of measured real world networks have a clear directionality. Moreover, this directionality can be used to classify vertices in these networks from sources to sinks. Such an algorithm can be highly useful in order to extract a meaning from large interaction networks assembled in many domains.

Rosen, Yonatan; Louzoun, Yoram

2014-05-01

101

Tibiofemoral centroid velocity correlates more consistently with cartilage damage than does contact path length in two ovine models of stifle injury.  

PubMed

Anterior cruciate ligament (ACL) rupture and/or meniscal injury are known risk factors for post-traumatic osteoarthritis. We tested the hypothesis that increasingly abnormal tibiofemoral centroid path lengths and velocities would correlate with the severity of cartilage damage in injured sheep. Six sheep underwent combined ACL/medial collateral ligament transection (ACL/MCLx), five complete lateral meniscectomy (Mx), and four sham arthrotomy (Sham). Weighted centroids were used to estimate in vivo tibiofemoral cartilage contact path length during stance and the velocity of relative motion. Cartilage morphology was graded at dissection. Ligament transection significantly elongated plateau centroid path lengths and velocities, whereas condyle paths and velocities were reduced. Differences between plateau and femoral velocities (relative centroid velocity) were increased up to 10-fold over baseline values in the medial compartment. Reductions in Mx lateral compartment paths were significantly different from ACL/MCLx paths, but not relative to baseline or Sham values. Importantly, only centroid velocities consistently correlated with cartilage damage in either injury model, suggesting that while path length is valuable in detecting changes in the envelope of joint motion, it may average out meaningful peaks in the rate of relative motion that more closely relate to the mechanisms that might be damaging articular cartilage in these models. PMID:23832294

Beveridge, Jillian E; Heard, Bryan J; Shrive, Nigel G; Frank, Cyril B

2013-11-01

102

The cosmic-ray path length (age) distribution in the Galaxy - Experimental limits on the deviation from an exponential  

NASA Technical Reports Server (NTRS)

A systematic examination is presented of the observational effects that can provide information on the departure of the cosmic-ray path length distribution (PLD) for propagation in the Galaxy from a simple exponential distribution. The possible physical causes for this departure are examined in order to set realistic limits on how well a simple exponential PLD actually describes the distribution of sources and propagation of cosmic rays in the galaxy. From the findings, it is argued that the cosmic ray source distribution must be quite uniform, probably on a scale of about 50 pc or less near the sun. Extending this uniformity to the Galaxy as a whole would imply more than 100,000 active sources. The cosmic-ray propagation can be described quite well by a leaky box model which is equivalent to observing the particles through a dense fog.

Webber, W. R.

1993-01-01

103

Leaf morphological effects predict effective path length and enrichment of 18O in leaf water of different Eucalyptus species  

NASA Astrophysics Data System (ADS)

Stable isotopes have been a valuable tool to study water or carbon fluxes of plants and ecosystems. In particular oxygen isotopes (?18O) in leaf water or plant organic material are now beginning to be established as a simple and integrative measure for plant - water relations. Current ?18O models, however, are still limited in their application to a broad range of different species and ecosystems. It remains for example unclear, if species-specific effects such as different leaf morphologies need to be included in the models for a precise understanding and prediction of ?18O signals. In a common garden experiment (Currency Creek Arboretum, South Australia), where over 900 different Eucalyptus species are cultivated in four replicates, we tested effects of leaf morphology and anatomy on ?18O signals in leaf water of 25 different species. In particular, we determined for all species enrichment in 18O of mean lamina leaf water above source water (?18O) as related to leaf physiology as well as leaf thickness, leaf area, specific leaf area and weight and selected anatomical properties. Our data revealed that diurnal ?18O in leaf water at steady state was significantly different among the investigated species and with differences up to 10% at midday. Fitting factors (effective path length) of leaf water ?18O models were also significantly different among the investigated species and were highly affected by species-specific morphological parameters. For example, leaf area explained a high percentage of the differences in effective path length observed among the investigated species. Our data suggest that leaf water ?18O can act as powerful tool to estimate plant - water relations in comparative studies but that additional leaf morphological parameters need to be considered in existing ?18O models for a better interpretation of the observed ?18O signals.

Kahmen, A.; Merchant, A.; Callister, A.; Dawson, T. E.; Arndt, S. K.

2006-12-01

104

Halogen oxide measurements at Masaya Volcano, Nicaragua using active long path differential optical absorption spectroscopy  

NASA Astrophysics Data System (ADS)

Active Long Path Differential Optical Absorption Spectroscopy (LP-DOAS) measurements of halogen oxides were conducted at Masaya Volcano, in Nicaragua from April 14 to 26, 2007. The active LP-DOAS system allowed night-time halogen measurements and reduced the ClO detection limit by an order of magnitude when compared to previous passive DOAS measurements, as wavelengths below 300 nm could be used for the DOAS retrievals. BrO was detected with an average BrO/SO2 molecular ratio of approximately 3 × 10-5 during the day. However, BrO values were below the detection limit of the instrument for all night-time measurements, a strong indication that BrO is not directly emitted, but rather the result of photochemical formation in the plume itself according to the autocatalytic “bromine explosion” mechanism. Despite the increased sensitivity, both ClO and OClO could not be detected. The achieved upper limits for the X/SO2 ratios were 5 × 10-3 and 7 × 10-6, respectively. A rough calculation suggests that ClO and OClO should be present at similar abundances in volcanic plumes. Since the DOAS technique is orders of magnitude more sensitive for OClO than for ClO, this indicates that OClO should always be detectable in plumes in which ClO is found. However, further LP-DOAS studies are needed to conclusively clarify the role of chlorine oxides in volcanic plumes.

Kern, Christoph; Sihler, Holger; Vogel, Leif; Rivera, Claudia; Herrera, Martha; Platt, Ulrich

2009-08-01

105

Retrieval of atmospheric carbon dioxide and methane from GOSAT data with the photon path length probability density function method  

NASA Astrophysics Data System (ADS)

The Greenhouse Gases Observing Satellite "IBUKI" (GOSAT) is the world's first spacecraft to measure the concentrations of carbon dioxide (CO2) and methane (CH4). The satellite has been operating properly from January 23, 2009. This paper presents retrievals of CO2 and CH4 from GOSAT data with the photon pathlength probability density function (PPDF) method that has been developed at the National Institute of Environmental Studies. This paper focus on a validation of the retrievals using satellite data during 38 months of GOSAT operation from June 2009 and ground-based Fourier Transform Spectrometer measurements from the Total Carbon Column Observing Network (TCCON) as the reference data for the column-averaged dry air mole fractions of the atmospheric gases. The TCCON-GOSAT coincidence criteria for validating the satellite-based retrievals included GOSAT single scan data over land within a 5° radius latitude/ longitude circle centered at each of 12 TCCON stations. The ground-based TCCON data were mean values measured within plus/minus 1 hour of the GOSAT overpass time. We use the latest version of PPDF-based method that retrieves simultaneously gas abundance and light path modification through the atmosphere. The radiance spectra from all three GOSAT SWIR bands (0.76 ?m; 1.6 ?m and 2.0 ?m) were used to retrieve CO2 and basic PPDF parameters that described light path shortening and light path lengthening. The retrieval state vector also included vertical profile of CO2 mixing ratio; scaling factor of prior water vapor profile; and stretch factor for adjusting the position of the wave-number grids. Temperature and surface pressure data were prescribed and provided by Japan Meteorological Agency. For the methane retrievals we processed radiance spectra in 1.67-?m absorption band using PPDF parameters derived from simultaneous CO2 and PPDF retrievals. In particular, a statistical pairwise comparison between GOSAT and TCCON coincident measurements of CO2 column abundance (over 3500 GOSAT single scans) performed with the weighed least squares fit showed a correlation coefficient 0.8; a standard deviation of 1.9 ppm, negative bias of 0.4 ppm; and slope of 1.04 for the slope-intercept form of the linear regression. After a posteriori bias correction these characteristics were 0.9; 1.65 ppm; 0.01 ppm; and 0.99, respectively.

Oshchepkov, Sergey; Bril, Andrey; Yokota, Tatsuya; Yoshida, Yukio

2014-05-01

106

Shortest-path and minimum-delay algorithms in networks with time-dependent edge-length  

Microsoft Academic Search

In this paper the shortest-path problem in networks in which the delay (or weight) of the edges changes with time according to arbitrary functions is considered. Algorithms for finding the shortest path and minimum delay under various waiting constraints are presented and the properties of the derived path are investigated. It is shown that if departure time from the source

Ariel Orda; Raphael Rom

1990-01-01

107

Review and analysis of VHF/UHF field strength measurements: Measurements at VHF over path lengths greater than 100 km  

NASA Astrophysics Data System (ADS)

In 1983 CCIRIWP 5/5 put forward a number of proposals for improvements to the field strength prediction methods of CCIR Recommendation 370 and associated Report 239, as used for international planning negotiations in the VHF and UHF Broadcast Bands. Described are the results of studies carried out by the BBC, in conjunction with other propagation investigations, to assess the validity of those proposals of IWP 5/5 which relate to propagation over path lengths in excess of about 100 km in the VHF Bands. It is concluded that these proposals can be supported with only one exception, relating to an addition of 7 dB to beyond-horizon oversea curves. Subsequently, the VHF proposals (excepting the one relating to the 7 dB correction) have been endorsed by CCIR Study Group 5 and adopted by the Plenar Meeting in 1986 for inclusion as modifications to Recommendation 370. Even so, limitations in the exsiting methods are identified and further work is proposed.

Sandell, R. S.; Bell, C. P.; Taplin, D. W.

1986-12-01

108

In vivo quantification of photosensitizer concentration using fluorescence differential path-length spectroscopy: influence of photosensitizer formulation and tissue location  

NASA Astrophysics Data System (ADS)

In vivo measurement of photosensitizer concentrations may optimize clinical photodynamic therapy (PDT). Fluorescence differential path-length spectroscopy (FDPS) is a non-invasive optical technique that has been shown to accurately quantify the concentration of Foscan® in rat liver. As a next step towards clinical translation, the effect of two liposomal formulations of mTHPC, Fospeg® and Foslip®, on FDPS response was investigated. Furthermore, FDPS was evaluated in target organs for head-and-neck PDT. Fifty-four healthy rats were intravenously injected with one of the three formulations of mTHPC at 0.15 mg kg-1. FDPS was performed on liver, tongue, and lip. The mTHPC concentrations estimated using FDPS were correlated with the results of the subsequent harvested and chemically extracted organs. An excellent goodness of fit (R2) between FDPS and extraction was found for all formulations in the liver (R2=0.79). A much lower R2 between FDPS and extraction was found in lip (R2=0.46) and tongue (R2=0.10). The lower performance in lip and in particular tongue was mainly attributed to the more layered anatomical structure, which influences scattering properties and photosensitizer distribution.

de Visscher, Sebastiaan A. H. J.; Witjes, Max J. H.; Kaš?áková, Slávka; Sterenborg, Henricus J. C. M.; Robinson, Dominic J.; Roodenburg, Jan L. N.; Amelink, Arjen

2012-06-01

109

The effect of cross-head velocity and length of tube on energy absorption of aluminium tube  

Microsoft Academic Search

The objective of this study is to investigate the effect of variation of the tube length and the crosshead velocity on the amount of energy absorption of aluminium tubes (Al 6061) towards the inversion collapsed mode. The tests were performed on the Aluminium tubes using compression test apparatus according to ASTM E8 standard procedures. Two parameters that are included in

Mohd Suhairil Meon; Hazran Husain; Muhamad Fauzi Othman; Muhammad Fairuz Remeli; Mohd Syahar Mohd Syawal

2011-01-01

110

Cavity enhanced absorption spectroscopy using room temperature quantum cascade lasers  

Microsoft Academic Search

Achieving the high sensitivity necessary for trace gas detection generally requires long absorption path lengths. An alternative approach to conventional linear absorption spectroscopy employing multiple pass cells is to use a high finesse cavity. With the help of such cavities the effective path length of the laser beam in the absorbing medium can essentially be increased to more than the

S. Welzel; P. B. Davies; R. Engeln; J. Röpcke

2009-01-01

111

Effect of water vapor absorption on integrating sphere output radiance and consequences for instrument calibration  

Microsoft Academic Search

Multiple photon scatterings inside an integrating sphere can result in significant path lengths compared with line-of- sight sources. In strong water vapor absorption channels, such as those on MODIS and the MODIS airborne simulator, these internal path lengths can result in a significant reduction in sphere output radiance. Path length probability distributions for photons exiting a sphere are determined using

Steven E. Platnick; Peter Abel; Michael D. King

1996-01-01

112

High-efficiency high-power diode laser beam shaping and focusing with constant optical-path length equalization  

NASA Astrophysics Data System (ADS)

In this work we report on a novel optical design for beam shaping and focalization of high-power diode laser bars. The goals of our study are: the increase the optical throughput of the beam shaping device with respect to standard solutions and either to enhance the irradiance on a target or to inject the laser beam into a smaller fibre than with respect to beam shaping system based on plane surfaces. The high power diode laser bars pose serious difficulties in their optical handling due to their strong difference between the two transverse axes, which induce a strong astigmatic and asymmetric output radiation. As is well known, the beam quality is very different in the two axes called slow axis and fast axis, and in particular the slow axis is composed by the superposition of several multimodal sources. The beam quality in this axis is very low (its etendue may exceed 2000 mm mrad). On the other hand, the fast axis has a very high beam quality, near diffraction limited, although with very high divergence (30°-50°). The common solution for the application of the laser radiation is a fast axis aspheric micro lens in front of the emitters, in order to achieve its collimation. Typical values of the fast axis collimated beam are 0.7mm and less than 6mrad. However, the so obtained collimated beam is poorly focusable with a standard lens, and a few methods were proposed to overcome the problem. The more relevant solutions include: the stepped mirror technique, the plane parallel mirrors pair, micro prisms array and confocal micro lens array. Each of these techniques is based on the equalization of the beam parameter product by the subdivision of the beam in the slow axis and its reshaping. For all these techniques the efficiency spans from 50% to 70%. The best focalization results allow the coupling in a fibre of 400?m diameter, with NA-0.22. The aim of this work is the design and the realization of a new device, that is considered as target the following aspects: 1) the maximum optical efficiency in the beam shaping process, 2) the optimal equalization of the beam parameter product for the two axes, 3) the use of few optical elements and 4) a very compact size. These goals are addressed by a scheme that splits the collimated beam from the laser diode into different portions while the length of the optical paths of each sub element is kept constant, and by the subsequent use of short focal length aspheric lenses for the focalization of the transformed beam. Each sub-beam is deflected by a couple of plane parallel mirrors, whose normal is directed to equalize the BPP without any mutual shadowing. An optimal solution can be easily envisaged for a laser source of common size of 0.7 x 10 mm. The condition on equal optical path length has the noticeable property of placing the virtual position of the individual portions into which the original beam is split at the same distance with respect to target. Thanks to this, their subsequent focusing is unaffected by the axial displacement of the common solution by the stepped mirrors. In fact, to correct this effect, this latter technique requires the use of a prism pair, involving complexity, size enlargement and higher costs. In this work both an extensive ray tracing and optical analysis is presented as well as the experimental characterization of an experimental model. Moreover, we also report on the technique for the realization of th tilted-face plane mirrors of which is composed our beam shaping device. The scheme of beam shaping here reported can be extended to higher power beam by means of the technique of the beam combination by polarization coupling or that of the optical beam compression. Examples of theses developments are discussed in the paper, and experimental results presented. The most direct applications of the class of optical devices here reported are the high power diode laser direct application in material processing or manufacturing, the coupling into multimode optical fiber of the diode laser radiation as well as the fiber laser end pumping.

Bonora, Stefano; Villoresi, Paolo

2006-04-01

113

Optical absorption coefficient and minority carrier diffusion length measurements in low-cost silicon solar cell material  

SciTech Connect

The optical absorption coefficient of silicon solar cell material grown by three low-cost growth methods was measured in the wavelength interval 0.8< or =lambda< or =1.0 ..mu..m, the wavelength region of interest in surface photovoltage measurements of the minority carrier diffusion length. The square root of the absorption coefficient was found to vary linearly with photon energy over the wavelengths studied, and the measured data agree with a linear empirical fit to within 0.5% RMS. The absorption coefficients obtained are slightly lower than those reported by Runyan, with the greatest disagreement at long wavelengths. Minority carrier diffusion lengths computed using the present absorption coefficients are approximately 16% greater than those calculated using Runyan's data. Excellent sample-to-sample agreement within and between lots indicates that for two of the growth methods studied, material quality as judged by optical properties has not been sacrificed by the use of low-cost growth methods. Samples grown by the third growth method studied showed measurably poorer optical quality.

Swimm, R.T.; Dumas, K.A.

1982-11-01

114

LONG PATH DIFFERENTIAL OPTICAL ABSORPTION SPECTROMETER AND EPA-APPROVED FIXED POINT METHODS INTERCOMPARISON  

EPA Science Inventory

Differential optical absorption spectrometry (DOAS) has been used by a number of investigators over the past 10 years to measure a wide range of gaseous air pollutants. ecently OPSIS AB, Lund, Sweden, has developed and made commercially available DOAS instrument that has a number...

115

Numerical study of random variations of span lengths and span path-average dispersions on dispersion-managed soliton system performance  

Microsoft Academic Search

We have studied the performance of dispersion-managed (DM) soliton systems with random variations of span lengths and span path-average dispersions by numerical simulation. We show that while DM solitons still exist in systems with nonperiodic dispersion maps, those nonperiodic maps tend to degrade system performance. We investigate the performance degradation of both on-off keyed and differential phase-shift keyed DM-soliton systems

Chongjin Xie; Linn F. Mollenauer; Nadejda Mamysheva

2003-01-01

116

AFM-based measurement of the mechanical properties of thin polymer films and determination of the optical path length of nearly index-matched cavities  

NASA Astrophysics Data System (ADS)

Two technologies, immersion and imprint lithography, represent important stepping stones for the development of the next generation of lithography tools. However, although the two approaches offer important advantages, both pose many significant technological challenges that must be overcome before they can be successfully implemented. For imprint lithography, special care must be taken when choosing an etch barrier because studies have indicated that some physical material properties may be size dependent. Additionally, regarding immersion lithography, proper image focus requires that the optical path length between the lens and substrate be maintained during the entire writing process. The work described in this document was undertaken to address the two challenges described above. A new mathematical model was developed and used in conjunction with AFM nano-indentation techniques to measure the elastic modulus of adhesive, thin polymer films as a function of the film thickness. It was found that the elastic modulus of the polymer tested did not change appreciably from the value determined using bulk measurement techniques in the thickness range probed. Additionally, a method for monitoring and controlling the optical path length within the gap of a nearly index-matching cavity based on coherent broadband interference was developed. In this method, the spectrum reflected for a cavity illuminated with a modelocked Ti:Sapphire laser was collected and analyzed using Fourier techniques. It was found that this method could determine the optical path length of the cavity, quickly and accurately enough to control a servo-based feedback system to correct deviations in the optical path length in real time when coupled with special computation techniques that minimized unnecessary operations.

Wieland, Christopher F.

117

Uptake, transport and peroral absorption of fatty glyceride grafted chitosan copolymer-enoxaparin nanocomplexes: Influence of glyceride chain length.  

PubMed

The objective of this paper is to elucidate the influence of fatty glyceride chain length in chitosan copolymers on the peroral absorption of enoxaparin. First of all, a series of chitosan copolymers with glyceryl monocaprylate (GM8), glyceryl monolaurate (GM12) and glyceryl monostearate (GM18) as the hydrophobic part were synthesized. The structure of the copolymers was characterized using proton nuclear magnetic resonance. 3-(4,5-Dimethylthiazol-2-yl)-2,5-diphenyltetrazolium bromide assay demonstrated that all the copolymers were non-toxic. Enoxaparin nanocomplexes were prepared by self-assembly. Mucoadhesion of the nanocomplexes was characterized using the mucin particle method. Nanocomplex uptake and transport were quantified in Caco-2 cells and cellular localization was visualized by confocal laser scanning microscopy. Enoxaparin uptake was enhanced by nanocomplex formation, and was dependent on incubation time, concentration, temperature and glyceride chain length. The GM8 grafted chitosan-enoxaparin nanocomplex exhibited the strongest bioadhesion and the best uptake and transport in both cell culture and in vivo absorption in rats. The uptake mechanism was assumed to be adsorptive endocytosis via clathrin- and caveolae-mediated processes. In conclusion, oral absorption of enoxaparin can be further enhanced by using GM8 grafted chitosan copolymer as the carrier to form nanocomplexes. PMID:24814881

Wang, Linlin; Sun, Yujiao; Shi, Chenjun; Li, Liang; Guan, Jian; Zhang, Xin; Ni, Rui; Duan, Xiaopin; Li, Yaping; Mao, Shirui

2014-08-01

118

Determination of the absorption length of CO 2 and high power diode laser radiation for a high volume alumina-based refractory material  

NASA Astrophysics Data System (ADS)

The laser beam absorption lengths of CO 2 (10.6 ?m wavelength) and a high power diode laser (HPDL) (810 nm wavelength) radiation for an Al 2O 3/SiO 2-based refractory have been determined through the application of Beer-Lambert's law. The findings revealed marked differences in the absorption lengths despite the material having similar beam absorption coefficients for both lasers. The absorption lengths for the Al 2O 3/SiO 2-based refractory of CO 2 and a HPDL radiation were calculated as being 345±22 and 198±15 ?m, respectively. Moreover, this method of laser beam absorption length determination, which has hitherto been used predominantly with lasers operated in the pulsed mode, is shown to be valid for use with lasers operated in the continuous wave (CW) mode, depending upon the material being treated.

Lawrence, J.; Li, L.

2000-12-01

119

Determination of the absorption length of CO 2, Nd:YAG and high power diode laser radiation for a selected grouting material  

NASA Astrophysics Data System (ADS)

The laser beam absorption lengths of CO 2, Nd:YAG and a high power diode laser (HPDL) radiation for a newly developed SiO 2/Al 2O 3-based tile grout have been determined through the application of Beer-Lambert's law. The findings revealed marked differences in the absorption lengths despite the material having similar beam absorption coefficients for the lasers. The absorption lengths for the SiO 2/Al 2O 3-based tile grout for CO 2, Nd:YAG and HPDL radiation were calculated as being 232±11, 193±4 and 183±8 ?m, respectively. Moreover, this method of laser beam absorption length determination, which has hitherto been used predominantly with lasers operated in the pulsed mode, is shown to be valid for use with lasers operated in the continuous wave (CW) mode, depending upon the material being treated.

Lawrence, J.; Minami, K.; Li, L.; Edwards, R. E.; Gale, A. W.

2002-01-01

120

Integrated Path Differential Absorption Lidar Optimizations Based on Pre-Analyzed Atmospheric Data for ASCENDS Mission Applications  

NASA Technical Reports Server (NTRS)

In this paper a modeling method based on data reductions is investigated which includes pre analyzed MERRA atmospheric fields for quantitative estimates of uncertainties introduced in the integrated path differential absorption methods for the sensing of various molecules including CO2. This approach represents the extension of our existing lidar modeling framework previously developed and allows effective on- and offline wavelength optimizations and weighting function analysis to minimize the interference effects such as those due to temperature sensitivity and water vapor absorption. The new simulation methodology is different from the previous implementation in that it allows analysis of atmospheric effects over annual spans and the entire Earth coverage which was achieved due to the data reduction methods employed. The effectiveness of the proposed simulation approach is demonstrated with application to the mixing ratio retrievals for the future ASCENDS mission. Independent analysis of multiple accuracy limiting factors including the temperature, water vapor interferences, and selected system parameters is further used to identify favorable spectral regions as well as wavelength combinations facilitating the reduction in total errors in the retrieved XCO2 values.

Pliutau, Denis; Prasad, Narasimha S.

2012-01-01

121

Comparison of path integral molecular dynamics methods for the infrared absorption spectrum of liquid water.  

PubMed

The ring polymer molecular dynamics (RPMD) and partially adiabatic centroid molecular dynamics (PA-CMD) methods are compared and contrasted in an application to the infrared absorption spectrum of a recently parametrized flexible, polarizable, Thole-type potential energy model for liquid water. Both methods predict very similar spectra in the low-frequency librational and intramolecular bending region at wavenumbers below 2500 cm(-1). However, the RPMD spectrum is contaminated in the high-frequency O-H stretching region by contributions from the internal vibrational modes of the ring polymer. This problem is avoided in the PA-CMD method, which adjusts the elements of the Parrinello-Rahman mass matrix so as to shift the frequencies of these vibrational modes beyond the spectral range of interest. PA-CMD does not require any more computational effort than RPMD and it is clearly the better of the two methods for simulating vibrational spectra. PMID:19044777

Habershon, Scott; Fanourgakis, George S; Manolopoulos, David E

2008-08-21

122

Comparison of path integral molecular dynamics methods for the infrared absorption spectrum of liquid water  

NASA Astrophysics Data System (ADS)

The ring polymer molecular dynamics (RPMD) and partially adiabatic centroid molecular dynamics (PA-CMD) methods are compared and contrasted in an application to the infrared absorption spectrum of a recently parametrized flexible, polarizable, Thole-type potential energy model for liquid water. Both methods predict very similar spectra in the low-frequency librational and intramolecular bending region at wavenumbers below 2500 cm-1. However, the RPMD spectrum is contaminated in the high-frequency O-H stretching region by contributions from the internal vibrational modes of the ring polymer. This problem is avoided in the PA-CMD method, which adjusts the elements of the Parrinello-Rahman mass matrix so as to shift the frequencies of these vibrational modes beyond the spectral range of interest. PA-CMD does not require any more computational effort than RPMD and it is clearly the better of the two methods for simulating vibrational spectra.

Habershon, Scott; Fanourgakis, George S.; Manolopoulos, David E.

2008-08-01

123

Tornado Paths  

NSDL National Science Digital Library

This website catalogs all the tornado paths in the United States since 1950. The tornado path data is overlaid onto a Google Maps base for easy browsing and manipulation of the map view. Clicking on individual tornados provides the user with information such as its Fujita rating, the amount of damage caused by the tornado, the size of the path that the tornado made, and the length of time the tornado was on the ground.

Samson, Perry; Michigan, University O.

124

CHARM-F: An airborne integral path differential absorption lidar for simultaneous measurements of carbon dioxide and methane columns  

NASA Astrophysics Data System (ADS)

CHARM-F (CO2 and CH4 Atmospheric Remote Monitoring - Flugzeug) is DLR's airborne Integral Path Differential Absorption (IPDA) lidar for simultaneous measurements of the column-weighted average dry-air mixing ratios of atmospheric carbon dioxide and methane, designed to be flown on DLR's new High-Altitude, LOng-range research aircraft, HALO. It is meant to serve as a demonstrator of the use of spaceborne active optical instruments in inferring atmospheric CO2 and CH4 surface fluxes from total column measurements by inverse modeling. As it will be shown, this is enabled by HALO's high flight altitude and its range of 8000 km, which will make it possible to produce real-world data at truly regional scales with a viewing geometry and vertical weighting function similar to those enabled by a space platform. In addition, CHARM-F has the potential to be used as a validation tool not only for active but also passive spaceborne instruments utilizing scattered solar radiation for remote sensing of greenhouse gases. Building on the expertise from CHARM, a helicopter-borne methane IPDA lidar for pipeline monitoring developed in collaboration with E.ON, and WALES, DLR's water vapour differential absorption lidar, CHARM-F relies on a double-pulse transmitter architecture producing nanosecond pulses which allows for a precise ranging and a clean separation of atmospheric influences from the ground returns leading to an unambiguously defined column. One pulse is tuned to an absorption line of the trace gas under consideration, the other to a nearby wavelength with much less absorption. The close temporal separation of 250 ?s within each pulse pair ensures that nearly the same spot on ground is illuminated. The ratio of both return signals is then a direct function of the column-weighted average dry-air mixing ratio. The two laser systems, one for each trace gas, use highly efficient and robust Nd:YAG lasers to pump an optical parametric oscillator (OPO) level which converts the pump radiation to the desired wavelengths. Because typical surface CO2 and CH4 sources and sinks alter the total column only by a few percent, the required precision and accuracy are very stringent. This puts particularly challenging requirements on the spectral properties of the emitted pulses. To achieve single mode operation with very high spectral purity, both pumps and OPOs are injection seeded. Absolute stability of the emitted wavelengths is achieved by locking the seed lasers to the same absorption lines as those used in the atmosphere by means of a single absorption cell filled with a mixture of CO2 and CH4, and monitoring the wavelength deviations between each outgoing laser pulse and the corresponding seed laser to detect and correct for possible mode pulling effects. Another key requirement is the monitoring of the relative outgoing pulse energies with high accuracy, which is based on a specifically designed optical architecture. Assembly and laboratory tests of the instrument are on-going, the first ground tests are planned for summer 2012.

Amediek, A.; Büdenbender, H.-C.; Ehret, G.; Fix, A.; Kiemle, C.; Quatrevalet, M.; Wirth, M.; Hoffmann, D.; Löhring, J.; Klein, V.

2012-04-01

125

Mapping of methane spatial distribution around biogas plant with an open-path tunable diode absorption spectroscopy scanning system  

NASA Astrophysics Data System (ADS)

An open-path tunable diode laser absorption spectroscopy (OP-TDLAS) detector was applied to detect the methane emission from a biogas plant in a dairy farm. Two OP-TDLAS scanning systems were built according to maximum likelihood with expectation minimization (MLEM) and smooth basis function minimization (SBFM) algorithms to reconstruct the two-dimensional (2-D) distribution maps. Six reconstruction maps with the resolution of 30×80 were obtained by the MLEM algorithm with "grid translation method" and three reconstruction maps were obtained by the SBFM algorithm with 2-D Gaussian model. The maximum mixing ratio in the first result was between 0.85 and 1.30 ppm, while it was between 1.14 and 1.30 ppm in the second result. The average mixing ratio in the first result was between 0.54 and 0.49 ppm, and between 0.56 and 0.65 ppm in the second result. The reconstruction results validated that the two algorithms could effectively reflect the methane mixing ratio distribution within the target area. However, with the more simple optical rays and less equipment requirements, the OP-TDLAS scanning system based on SBFM algorithm provides a useful monitoring tool of methane emissions in agricultural production.

Zhang, Shirui; Wang, Jihua; Dong, Daming; Zheng, Wengang; Zhao, Xiande

2013-02-01

126

Analysis of sensitivity and optical path-length in non-invasive measurement of glucose with near infrared spectroscopy  

NASA Astrophysics Data System (ADS)

Non-invasive glucose monitoring with optical methods has obtained increasing interest, in that the methods have shown great benefit for diabetes. Nevertheless, low sensitivity and signal to noise ratio (ratio of effective photons) are two major difficulties in non-invasively NIR spectral monitoring of blood glucose concentration. Designing the optical probe properly is one of the effective ways to improve measuring sensitivity and ratio of effective photons. In this paper, definition about ratio of effective photons in measurement of glucose is introduced. And then effect of glucose on optical properties of human skin is analyzed, based on this, two kind of sensitivities for diffuse reflectance, namely sensitivity to absorption and that to scattering, is derived. To investigate the ratio of effective photons and sensitivities, Monte Carlo simulations have been performed on a three-layered media with optical parameters similar to those of human skin. The results have shown that (1) high ratio of effective photons, even as high as 60%, can be obtained by choosing proper the separation between source and detector; (2) sensitivity of diffuse reflectance to absorption and scattering has different dependence on source-detector separation, which enables one can have different options by making use of different effect from glucose level changing. In the end, some suggestions have been put forward to improve precision of measurement of blood glucose.

Luo, Yunhan; Liu, Rong; Chen, Wenliang; Cui, Houxin; Xu, Kexin

2005-03-01

127

The absorption spectrum of the solvated electron in fluid helium by maximum entropy inversion of imaginary time correlation functions from path integral Monte Carlo simulations  

Microsoft Academic Search

The dipole absorption spectrum of an electron in fluid helium is calculated by the maximum entropy method (MEM) numerical inversion of quantum Monte Carlo data obtained from a path integral Monte Carlo (PIMC) simulation at 309 K at the reduced densities &rgr;*=0.1, 0.3, 0.5, 0.7, and 0.9. Our results agree with the RISM-polaron theory results of Nichols and Chandler [A.

E. Gallicchio; B. J. Berne

1994-01-01

128

Absorption  

NSDL National Science Digital Library

The process of absorption is a cellular process (microscopic). Absorption cells line the stomach and intestine walls and allow small nutrients (broken down from the food we eat) to pass through and into our blood. The process of absorption is much like a leaking balloon filled with water. The balloon is the stomach or intestine, the tiny holes are the absorption cells, and the water is nutrients leaving.

Katie Hale (CSUF;)

2002-09-26

129

Extended x-ray-absorption fine-structure study of hydrogenated amorphous silicon-germanium alloys. II. Dependence of bond length and coordination on composition  

Microsoft Academic Search

The local structure of hydrogenated amorphous Si-Ge alloys has been determined using the extended x-ray-absorption fine-structure (EXAFS) technique. Numerical computations and comparison with experimental Ge K-edge EXAFS have shown that Ge-Ge and Ge-Si bond lengths are constant throughout the entire compositional range studied and equal to 2.46 and 2.41 Å, respectively. The Ge-Si bond length is found to be close

Yoichi Nishino; Shin-Ichi Muramatsu; Yukio Takano; Hiroshi Kajiyama

1988-01-01

130

Analyzing Water's Optical Absorption  

NASA Technical Reports Server (NTRS)

A cooperative agreement between World Precision Instruments (WPI), Inc., and Stennis Space Center has led the UltraPath(TM) device, which provides a more efficient method for analyzing the optical absorption of water samples at sea. UltraPath is a unique, high-performance absorbance spectrophotometer with user-selectable light path lengths. It is an ideal tool for any study requiring precise and highly sensitive spectroscopic determination of analytes, either in the laboratory or the field. As a low-cost, rugged, and portable system capable of high- sensitivity measurements in widely divergent waters, UltraPath will help scientists examine the role that coastal ocean environments play in the global carbon cycle. UltraPath(TM) is a trademark of World Precision Instruments, Inc. LWCC(TM) is a trademark of World Precision Instruments, Inc.

2002-01-01

131

Path Relaxation: Path Planning for a Mobile Robot  

Microsoft Academic Search

Path Relaxation is a method of planning safe paths around obstacles for mobile robots. It works in two steps: a global grid starch that finds a rough path, followed by a local relaxation step that adjusts each node on the path to lower the overall path cost. The representation used by Path Relaxation allows an explicit tradeoff among length of

Charles E. Thorpe; L. Matthies

1984-01-01

132

Classification of Leptospires of the Pyrogenes Serogroup Isolated from Cattle in Zimbabwe by Cross-Agglutinin Absorption and Restriction Fragment Length Polymorphism Analysis  

Microsoft Academic Search

Five strains of the genus Leptuspiru belonging to serogroup Pyrogenes were isolated from cattle slaughtered in Zimbabwe and subjected to cross-agglutinin absorption and restriction fragment length polymorphism analysis. One strain, SBF 2, represents a new genetic strain of serovar kwule, while another strain, SBF 49, is a new genetic strain closely related to serovar nigeriu. Three strains belong to a

SARA B. FERESU; CAROLE A. BOLIN; HANS KORVER; WIEPKO J. TERPSTRA

133

Determination of Lead Associated with Airborne Particulate Matter by Flame Atomic Absorption and Wave-Length Dispersive X-Ray Fluorescence Spectrometry  

Microsoft Academic Search

The lead content of airborne particulate matter was determined by flame atomic absorption spectrometry (FAAS) following digestion with a mixture of nitric acid and hydrogen peroxide and also by wave-length dispersive x-ray fluorescence (WDXRF). The extraction procedure was checked by analyzing a standard reference material of airborne particulate matter (NIST, SRM — 1648). It was concluded that lead can quantitatively

S. M. Talebi

1998-01-01

134

Adjusting the tasseled cap brightness and greenness factors for atmospheric path radiance and absorption on a pixel by pixel basis  

NASA Technical Reports Server (NTRS)

A radiative transfer model was used to convert ground measured reflectances into the radiance at the top of the atmosphere, for several levels of atmospheric path radiance. The radiance in MSS7 (0.8 to 1.1 m) was multiplied by the transmission fraction for atmospheres having different levels of precipitable water. The radiance values were converted to simulated LANDSAT digital counts for four path radiance levels and four levels of precipitable water. These values were used to calculate the Kauth-Thomas brightness, greenness, yellowness, and nonsuch factors. Brightness was affected by surface conditions and path radiance. Greenness was affected by surface conditions, path radiance, and precipitable water. Yellowness was affected by path radiance and nonsuch by precipitable water, and both factors changed only slightly with surface conditions. Yellowness and nonsuch were used to adjust brightness and greenness to produce factors that were affected only by surface conditions such as soils and vegetation, and not by path radiance and precipitable water.

Jackson, R. D.; Slater, P. N.; Pinter, P. J. (principal investigators)

1982-01-01

135

Inhibition of Ileal Water Absorption by Intraluminal Fatty Acids INFLUENCE OF CHAIN LENGTH, HYDROXYLATION, AND CONJUGATION OF FATTY ACIDS  

PubMed Central

The influence of fatty acids on ileal absorption of water, electrolytes, glucose, and taurocholate was examined in Thirty-Vella fistulas in five mongrel dogs. Fatty acid absorption also was measured. Segments of terminal ileum were perfused at steady state with isotonic electrolyte solutions containing 11.2 mM glucose, 4.5 mM taurocholate, and 0.1-5.0 mM fatty acid. Three C18 fatty acids, oleic acid, 10(9)-hydroxystearic acid, and ricinoleic acid, completely inhibited water absorption at 5 mM. Sodium, chloride, and potassium absorptions were inhibited in parallel with absorption of water. Differences between the potencies of C18 fatty acids were apparent when lesser concentrations were perfused. Dodecanoic and decanoic acids were as effective as C18 fatty acids at 5 mM but octanoic and hexanoic acids were ineffective. The polar group of C18 fatty acids was modified by conjugating oleic and ricinoleic acids with taurine. When these compounds and a substituted C18 fatty acid, p-n-decylbenzenesulfonate, were perfused, water absorption was also inhibited. Short-chain fatty acids (C3 and C4) and their hydroxylated derivatives were ineffective at 5 mM. When water absorption was inhibited, absorption of glucose and taurocholate was decreased. We speculate that the phenomenon of inhibition of water and electrolyte absorption by fatty acids may be relevant to steatorrhea and diarrhea in man. Images

Ammon, Helmut V.; Phillips, Sidney F.

1974-01-01

136

Adjusting the Tasseled Cap Brightness and Greenness Factors for Atmospheric Path Radiance and Absorption on a Pixel by Pixel Basis.  

National Technical Information Service (NTIS)

A radiative transfer model was used to convert ground measured reflectances into the radiance at the top of the atmosphere, for several levels of atmospheric path radiance. The radiance in MSS7 (0.8 to 1.1 m) was multiplied by the transmission fraction fo...

R. D. Jackson P. N. Slater P. J. Pinter

1982-01-01

137

Correlation of Electron Path Lengths Observed in the Highly Wound Outer Region of Magnetic Clouds with the Slab Fraction of Magnetic Turbulence in the Dissipation Range  

NASA Astrophysics Data System (ADS)

Three magnetic cloud events, in which solar impulsive electron events occurred in their outer region, are employed to investigate the difference of path lengths L 0eIII traveled by non-relativistic electrons from their release site near the Sun to the observer at 1 AU, where L 0eIII = v l × (t l – t III), v l and t l being the velocity and arrival time of electrons in the lowest energy channel (~27 keV) of the Wind/3DP/SST sensor, respectively, and t III being the onset time of type III radio bursts. The deduced L 0eIII value ranges from 1.3 to 3.3 AU. Since a negligible interplanetary scattering level can be seen in both L 0eIII > 3 AU and ~1.2 AU events, the difference in L 0eIII could be linked to the turbulence geometry (slab or two-dimensional) in the solar wind. By using the Wind/MFI magnetic field data with a time resolution of 92 ms, we examine the turbulence geometry in the dissipation range. In our examination, ~6 minutes of sampled subintervals are used in order to improve time resolution. We have found that, in the transverse turbulence, the observed slab fraction is increased with an increasing L 0eIII value, reaching ~100% in the L 0eIII > 3 AU event. Our observation implies that when only the slab spectral component exists, magnetic flux tubes (magnetic surfaces) are closed and regular for a very long distance along the transport route of particles.

Tan, Lun C.; Reames, Donald V.; Ng, Chee K.; Shao, Xi; Wang, Linghua

2014-05-01

138

Absorption  

NSDL National Science Digital Library

This activity can be used to allow students to explore the concept of absorption using a variety of materials. Extensions include exploring how Native Americans used absorbtion in a number of ways. This inquiry activity was developed by a K-12 science teacher in the American Physiological SocietyÃÂs 1998 Frontiers in Physiology Program. The NSES Standards addressed by this activity are current as of the year of development. For more information on the Frontiers in Physiology Program, please visit www.frontiersinphys.org.

Katherine M Knudson (Polson Middle School)

1998-04-01

139

Path planning for UAVs  

Microsoft Academic Search

In this paper, a two step path-planning algorithm for UAVs is proposed. The algorithm generates a stealthy path through a set of enemy radar sites of known location, and provides an intuitive way to trade-off stealth versus path length. In the first step, a suboptimal rough-cut path is generated through the radar sites by constructing and searching a graph based

S. A. Bortoff; E. Hartford

2000-01-01

140

The influence of a probe on the optical path of atomic absorption spectrometer with a graphite tube atomizer  

NASA Astrophysics Data System (ADS)

We have studied the influence on the atomic absorption signal of the obscuring of the transmission beam by a probe for the two-stage atomization in a graphite tube atomizer. The following parameters were varied: the thickness of the probe (0.5-1.0 mm), its displacement from the optical axis of the spectrometer (up to 2 mm), the diameter of the transmission beam (1.3-4.0 mm), the slit width of the monochromator, and the shape of the intensity distribution over the cross section of the beam emitted either by a hollow cathode lamp, or a deuterium lamp, or an electrodeless lamp. We have shown that, using a probe with a thickness that is optimal for the two-stage atomization (1 mm), it is possible to register analytical absorption signals from 28 chemical elements out of 56 (except Hg), which can be determined in graphite atomizers, with a maximal sensitivity and with no optical interference. The remaining elements can be determined with a lower sensitivity because of the necessity to lower the temperature of the secondary atomization.

Zakharov, Yu. A.; Kokorina, O. B.; Okunev, R. V.

2014-04-01

141

Theoretical study of photochromic compounds. 1. Bond length alternation and absorption spectra for the open and closed forms of 29 diarylethene derivatives.  

PubMed

We apply several exchange-correlation functionals in combination with time-dependent density functional theory to predict the maximum wavelengths in the absorption spectra for 29 diarylethene derivatives in both open and closed isomeric forms. Solvent effects and accurate molecular geometries are found to be important to obtain good agreement with experimental absorption wavelengths. In order to evaluate the quality of geometry optimization, we compare predicted bond length alternation parameters with experimental ones. We find the TD-M05/6-31G*/PCM//M05-2x/6-31G*/PCM theory level to give the best predictions for the structural and spectral parameters of the diarylethene derivatives. Applications of the photochromic diarylethene compounds as materials for optical switching and data storage based on their photocyclization properties are also discussed. PMID:19569671

Patel, Pansy D; Masunov, Artëm E

2009-07-23

142

Effect of hydrocarbon chain length in 1,2-alkanediols on percutaneous absorption of metronidazole: toward development of a general vehicle for controlled release.  

PubMed

The objective of the present study is to investigate the effect of hydrocarbon chain length in 1,2-alkanediols on percutaneous absorption of metronidazole (MTZ). Twelve formulations (1,2-propanediol, 1,2-butanediol, 1,2-pentanediol, 1,2-hexanediol in 4% concentration, 1,2-hexanediol, and 1,2-heptanediol in 1% concentration, in the absence and presence of 1,4-cyclohexanediol, respectively) were studied in an in vitro hairless mouse skin model using Franz diffusion cell. Based on the flux values and retardation ratios (RR), a penetration retardation effect on percutaneous absorption of MTZ was observed for the formulations containing 1,2-diols having six- to seven-carbon chain in the presence of 1,4-cyclohexanediol (1,2-hexanediol with chain length of six hydrocarbons, RRs are 0.69 and 0.76 in the concentration of 4% and 1%, respectively; 1,2-heptanediol with chain length of seven hydrocarbons, RR is 0.78 in the concentration of 1%). On the other hand, no retardation effect was observed in formulations containing short alkyl chains (RRs of 1,2-propanediol, 1,2-butanediol, and 1,2-pentanediol are 0.99, 1.61, and 0.96, respectively). Instead, a penetration enhancement effect was observed for 1,2-diols having four and five carbons. In other words, effect of 1,2-alkanediols on percutaneous absorption of MTZ can be systematically modulated by simply varying number of -CH2 groups in the hydrocarbon chain-from being a penetration enhancer to retardant. These observations shed light on mechanism of the penetration enhancement and retardation effect and provide insight into rational design of penetration enhancers and retardants. Furthermore, the combination of 1,2-alkanediols and 1,4-cyclohexanediol could become a general vehicle for controlled release of pharmaceutical and cosmetic active ingredients. PMID:24395400

Li, Nan; Jia, Weibu; Zhang, Yan; Zhang, Michelle C; Tan, Fengping; Zhang, Jerry

2014-04-01

143

Toward stand-off open-path measurements of NO and NO(2) in the sub-parts per million meter range using quantum cascade lasers (QCLs) in the intra-pulse absorption mode.  

PubMed

Two thermoelectrically cooled mid-infrared distributed feedback quantum cascade lasers operated in pulsed mode have been used for the quasi-simultaneous determination of NO and NO2 in the sub-parts per million meter (sub-ppm-m) range. Using a beam splitter, the beams of the two lasers were combined and sent to a retro-reflector. The returned light was recorded with a thermoelectrically cooled mercury cadmium telluride detector with a rise time of 4 ns. Alternate operation of the lasers with pulse lengths of 300 ns and a repetition rate of 66 kHz allowed quasi-simultaneous measurements. During each pulse the laser temperature increased, causing a thermal chirp of the laser line of up to 1.3 cm(-1). These laser chirps were sufficient to scan rotational bands of NO centered at 1902 cm(-1) and NO2 located at 1632 cm(-1). In that way an absorption spectrum could be recorded from a single laser pulse. Currently achieved limits of detection are 600 parts per billion meter (ppb-m) for NO and 260 ppb-m for NO2 using signal averaging over 1 min. This work presents the first steps toward a portable stand-off, open-path instrument that uses thermoelectrically cooled detector and lasers. PMID:24359649

Reidl-Leuthner, Christoph; Lendl, Bernhard

2013-12-01

144

Space-borne remote sensing of CO2, CH4, and N2O by integrated path differential absorption lidar: a sensitivity analysis  

NASA Astrophysics Data System (ADS)

CO2, CH4, and N2O are recognised as the most important greenhouse gases, the concentrations of which increase rapidly through human activities. Space-borne integrated path differential absorption lidar allows global observations at day and night over land and water surfaces in all climates. In this study we investigate potential sources of measurement errors and compare them with the scientific requirements. Our simulations reveal that moderate-size instruments in terms of telescope aperture (0.5 1.5 m) and laser average power (0.4 4 W) potentially have a low random error of the greenhouse gas column which is 0.2% for CO2 and 0.4% for CH4 for soundings at 1.6 ?m, 0.4% for CO2 at 2.1 ?m, 0.6% for CH4 at 2.3 ?m, and 0.3% for N2O at 3.9 ?m. Coherent detection instruments are generally limited by speckle noise, while direct detection instruments suffer from high detector noise using current technology. The wavelength selection in the vicinity of the absorption line is critical as it controls the height region of highest sensitivity, the temperature cross-sensitivity, and the demands on frequency stability. For CO2, an error budget of 0.08% is derived from our analysis of the sources of systematic errors. Among them, the frequency stability of ± 0.3 MHz for the laser transmitter and spectral purity of 99.9% in conjunction with a narrow-band spectral filter of 1 GHz (FWHM) are identified to be challenging instrument requirements for a direct detection CO2 system operating at 1.6 ?m.

Ehret, G.; Kiemle, C.; Wirth, M.; Amediek, A.; Fix, A.; Houweling, S.

2008-03-01

145

Comparing different light-emitting diodes as light sources for long path differential optical absorption spectroscopy NO2 and SO2 measurements  

NASA Astrophysics Data System (ADS)

In this paper, we present a comparison of different light-emitting diodes (LEDs) as the light source for long path differential optical absorption spectroscopy (LP-DOAS) atmospheric trace gas measurements. In our study, we use a fiberoptic design, where high power LEDs used as the light source are coupled into the telescope using a Y shape fiber bundle. Two blue and one ultraviolet (UV) LEDs with different emission wavelength ranges are tested for NO2 and SO2 measurements. The detailed description of the instrumental setup, the NO2 and SO2 retrieval procedure, the error analysis, and the preliminary results from the measurements carried out in Science Island, Hefei, Anhui, China are presented. Our first measurement results show that atmospheric NO2 and SO2 have strong temporal variations in that area and that the measurement accuracy is strongly dependent on the visibility conditions. The measured NO2 and SO2 data are compared to the Ozone Monitoring Instrument (OMI) satellite observations. The results show that the OMI NO2 product underestimates the ground level NO2 by 45%, while the OMI SO2 data are highly influenced by clouds and aerosols, which can lead to large biases in the ground level concentrations. During the experiment, the mixing ratios of the atmospheric NO2 and SO2 vary from 8 ppbv to 36 ppbv and from 3 ppbv to 18 ppbv, respectively.

Chan, Ka-Lok; Ling, Liu-Yi; Andreas, Hartl; Zheng, Ni-Na; Gerrit, Kuhlmann; Qin, Min; Sun, You-Wen; Xie, Pin-Hua; Liu, Wen-Qing; Mark, Wenig

2012-11-01

146

The effects of forage particle length and exogenous phytase inclusion on phosphorus digestion and absorption in lactating cows.  

PubMed

Accurate estimates of phosphorus (P) availability from feed are needed to allow P requirements to be met with reduced P intake, thus reducing P excretion by livestock. Exogenous phytase supplementation in poultry and swine diets improves bioavailability of P, and limited research suggests that this strategy may have some application in dairy cattle rations. The effects of exogenous phytase and forage particle length on site and extent of P digestion were evaluated with 5 ruminally and ileally cannulated lactating cows (188 ± 35 d in milk). Cows were assigned in a 2 × 2 factorial arrangement of treatments in 2 incomplete Latin squares with four 21-d periods. Diets contained P slightly in excess of National Research Council requirements with all P from feed sources. During the last 4d of each period, total mixed ration, refusals, omasal, ileal, and fecal samples were collected and analyzed for total P, inorganic P (Pi), and phytate (Pp). Total P intake was not influenced by dietary treatments but Pp intake decreased and Pi intake increased with supplemental phytase, suggesting rapid action of the enzyme in the total mixed ration after mixing. Omasal flow of Pi decreased with phytase supplementation, but we observed no effect of diet in ileal flow or small intestinal digestibility of any P fraction. Fecal excretion of total P was slightly higher and Pp excretion was lower for cows receiving diets supplemented with phytase. Milk yield and composition were unaffected by diets. When phytase was added to the mixed ration, dietary Pp was rapidly degraded before intake and total-tract Pp digestion was increased. The lack of effect of phytase supplementation on dietary P utilization was probably because these late-lactation cows had a low P requirement and were fed P-adequate diets. PMID:24210479

Jarrett, J P; Wilson, J W; Ray, P P; Knowlton, K F

2014-01-01

147

A two-laser beam technique for improving the sensitivity of low frequency open path tunable diode laser absorption spectrometer (OP-TDLAS) measurements  

NASA Astrophysics Data System (ADS)

Open path tunable diode-laser absorption spectroscopy (OP-TDLAS) is a promising technique to detect low concentrations of possible biogenic gases on Mars. This technique finds the concentration of a gas by measuring the amount of laser light absorbed by gaseous molecules at a specific wavelength. One of the major factors limiting sensitivity in the TDLAS systems operating at low modulation frequencies is 1/f noise. 1/f noise is minimized in many spectroscopy systems by the use of high frequency modulation techniques. However, these techniques require complex instruments that include reference cells and other devices for calibration, making them relatively large and bulky. We are developing a spectroscopy system for space applications that requires small, low mass and low power instrumentation, making the high frequency techniques unsuitable. This paper explores a new technique using two-laser beam to reduce the affect of 1/f noise and increase the signal strength for measurements made at lower frequencies. The two lasers are excited at slightly different frequencies. An algorithm is used to estimate the noise in the second harmonic from the combined spectra of both lasers. This noise is subtracted from the signal to give a more accurate measurement of gas concentration. The error in estimation of 1/f noise is negligible as it corresponds to noise level made at much higher frequencies. Simulation results using ammonia gas and two lasers operating at 500 and 510 Hz respectively shows that this technique is able to decrease the error in estimation of gas concentration to 1/6 its normal value.

Mohammad, Israa L.; Anderson, Gary T.; Chen, Youhua

2013-09-01

148

Planning multiple paths with evolutionary speciation  

Microsoft Academic Search

This paper demonstrates a new approach to multidimensional path planning that is based on multiresolution path representation, where explicit configuration space computation is not required, and incorporates an evolutionary algorithm for solving the multimodal optimization problem, generating multiple alternative paths simultaneously. The multiresolution path representation reduces the expected search length for the path-planning problem and accordingly reduces the overall computational

Cem Hocaoglu; Arthur C. Sanderson

2001-01-01

149

Cross-Validation of Open-Path and Closed-Path Eddy-Covariance Techniques for Observing Methane Fluxes  

NASA Astrophysics Data System (ADS)

Methane () fluxes observed with the eddy-covariance technique using an open-path analyzer and a closed-path analyzer in a rice paddy field were evaluated with an emphasis on the flux correction methodology. A comparison of the fluxes obtained by the analyzers revealed that both the open-path and closed-path techniques were reliable, provided that appropriate corrections were applied. For the open-path approach, the influence of fluctuations in air density and the line shape variation in laser absorption spectroscopy (hereafter, spectroscopic effect) was significant, and the relative importance of these corrections would increase when observing small fluxes. A new procedure proposed by Li-Cor Inc. enabled us to accurately adjust for these effects. The high-frequency loss of the open-path analyzer was relatively large (11 % of the uncorrected covariance) at an observation height of 2.5 m above the canopy owing to its longer physical path length, and this correction should be carefully applied before correcting for the influence of fluctuations in air density and the spectroscopic effect. Uncorrected fluxes observed with the closed-path analyzer were substantially underestimated (37 %) due to high-frequency loss because an undersized pump was used in the observation. Both the bandpass and transfer function approaches successfully corrected this flux loss. Careful determination of the bandpass frequency range or the transfer function and the cospectral model is required for the accurate calculation of fluxes with the closed-path technique.

Iwata, Hiroki; Kosugi, Yoshiko; Ono, Keisuke; Mano, Masayoshi; Sakabe, Ayaka; Miyata, Akira; Takahashi, Kenshi

2014-04-01

150

Shortest Paths for Line Segments  

Microsoft Academic Search

Abstract We study the problem of shortest paths for a line segment in the plane. As a measure of the distance traversed by a path, we take the average curve length of the orbits of prescribed points on the line segment. This problem is nontrivial even in free space (i.e., in the absence of obstacles). We characterize all shortest paths

Christian Icking; Giinter Rote; Emo Welzl; Chee-keng Yap

1993-01-01

151

Azimuthal Anisotropy of ?0 Production in Au+Au Collisions at sNN=200GeV: Path-Length Dependence of Jet Quenching and the Role of Initial Geometry  

NASA Astrophysics Data System (ADS)

We have measured the azimuthal anisotropy of ?0 production for 1path-length dependence steeper than what is implied by current PQCD energy-loss models show reasonable agreement with the data.

Adare, A.; Afanasiev, S.; Aidala, C.; Ajitanand, N. N.; Akiba, Y.; Al-Bataineh, H.; Alexander, J.; Aoki, K.; Aramaki, Y.; Atomssa, E. T.; Averbeck, R.; Awes, T. C.; Azmoun, B.; Babintsev, V.; Bai, M.; Baksay, G.; Baksay, L.; Barish, K. N.; Bassalleck, B.; Basye, A. T.; Bathe, S.; Baublis, V.; Baumann, C.; Bazilevsky, A.; Belikov, S.; Belmont, R.; Bennett, R.; Berdnikov, A.; Berdnikov, Y.; Bickley, A. A.; Bok, J. S.; Boyle, K.; Brooks, M. L.; Buesching, H.; Bumazhnov, V.; Bunce, G.; Butsyk, S.; Camacho, C. M.; Campbell, S.; Chen, C.-H.; Chi, C. Y.; Chiu, M.; Choi, I. J.; Choudhury, R. K.; Christiansen, P.; Chujo, T.; Chung, P.; Chvala, O.; Cianciolo, V.; Citron, Z.; Cole, B. A.; Connors, M.; Constantin, P.; Csanád, M.; Csörg?, T.; Dahms, T.; Dairaku, S.; Danchev, I.; Das, K.; Datta, A.; David, G.; Denisov, A.; Deshpande, A.; Desmond, E. J.; Dietzsch, O.; Dion, A.; Donadelli, M.; Drapier, O.; Drees, A.; Drees, K. A.; Durham, J. M.; Durum, A.; Dutta, D.; Edwards, S.; Efremenko, Y. V.; Ellinghaus, F.; Engelmore, T.; Enokizono, A.; En'Yo, H.; Esumi, S.; Fadem, B.; Fields, D. E.; Finger, M., Jr.; Finger, M.; Fleuret, F.; Fokin, S. L.; Fraenkel, Z.; Frantz, J. E.; Franz, A.; Frawley, A. D.; Fujiwara, K.; Fukao, Y.; Fusayasu, T.; Garishvili, I.; Glenn, A.; Gong, H.; Gonin, M.; Goto, Y.; Granier de Cassagnac, R.; Grau, N.; Greene, S. V.; Grosse Perdekamp, M.; Gunji, T.; Gustafsson, H.-Å.; Haggerty, J. S.; Hahn, K. I.; Hamagaki, H.; Hamblen, J.; Hanks, J.; Han, R.; Hartouni, E. P.; Haslum, E.; Hayano, R.; Heffner, M.; Hegyi, S.; Hemmick, T. K.; Hester, T.; He, X.; Hill, J. C.; Hohlmann, M.; Holzmann, W.; Homma, K.; Hong, B.; Horaguchi, T.; Hornback, D.; Huang, S.; Ichihara, T.; Ichimiya, R.; Ide, J.; Ikeda, Y.; Imai, K.; Inaba, M.; Isenhower, D.; Ishihara, M.; Isobe, T.; Issah, M.; Isupov, A.; Ivanischev, D.; Jacak, B. V.; Jia, J.; Jin, J.; Johnson, B. M.; Joo, K. S.; Jouan, D.; Jumper, D. S.; Kajihara, F.; Kametani, S.; Kamihara, N.; Kamin, J.; Kang, J. H.; Kapustinsky, J.; Karatsu, K.; Kawall, D.; Kawashima, M.; Kazantsev, A. V.; Kempel, T.; Khanzadeev, A.; Kijima, K. M.; Kim, B. I.; Kim, D. H.; Kim, D. J.; Kim, E. J.; Kim, E.; Kim, S. H.; Kim, Y. J.; Kinney, E.; Kiriluk, K.; Kiss, Á.; Kistenev, E.; Kochenda, L.; Komkov, B.; Konno, M.; Koster, J.; Kotchetkov, D.; Kozlov, A.; Král, A.; Kravitz, A.; Kunde, G. J.; Kurita, K.; Kurosawa, M.; Kwon, Y.; Kyle, G. S.; Lacey, R.; Lai, Y. S.; Lajoie, J. G.; Lebedev, A.; Lee, D. M.; Lee, J.; Lee, K. B.; Lee, K.; Lee, K. S.; Leitch, M. J.; Leite, M. A. L.; Leitner, E.; Lenzi, B.; Liebing, P.; Linden Levy, L. A.; Liška, T.; Litvinenko, A.; Liu, H.; Liu, M. X.; Li, X.; Love, B.; Luechtenborg, R.; Lynch, D.; Maguire, C. F.; Makdisi, Y. I.; Malakhov, A.; Malik, M. D.; Manko, V. I.; Mannel, E.; Mao, Y.; Masui, H.; Matathias, F.; McCumber, M.; McGaughey, P. L.; Means, N.; Meredith, B.; Miake, Y.; Mignerey, A. C.; Mikeš, P.; Miki, K.; Milov, A.; Mishra, M.; Mitchell, J. T.; Mohanty, A. K.; Morino, Y.; Morreale, A.; Morrison, D. P.; Moukhanova, T. V.; Murata, J.; Nagamiya, S.; Nagle, J. L.; Naglis, M.; Nagy, M. I.; Nakagawa, I.; Nakamiya, Y.; Nakamura, T.; Nakano, K.; Newby, J.; Nguyen, M.; Nouicer, R.; Nyanin, A. S.; O'Brien, E.; Oda, S. X.; Ogilvie, C. A.; Okada, K.; Oka, M.; Onuki, Y.; Oskarsson, A.; Ouchida, M.; Ozawa, K.; Pak, R.; Pantuev, V.; Papavassiliou, V.; Park, I. H.; Park, J.; Park, S. K.; Park, W. J.; Pate, S. F.; Pei, H.; Peng, J.-C.; Pereira, H.; Peresedov, V.; Peressounko, D. Yu.; Pinkenburg, C.; Pisani, R. P.; Proissl, M.; Purschke, M. L.; Purwar, A. K.; Qu, H.; Rak, J.; Rakotozafindrabe, A.; Ravinovich, I.; Read, K. F.; Reygers, K.; Riabov, V.; Riabov, Y.; Richardson, E.; Roach, D.; Roche, G.; Rolnick, S. D.; Rosati, M.; Rosen, C. A.; Rosendahl, S. S. E.; Rosnet, P.; Rukoyatkin, P.; Ruži?ka, P.; Sahlmueller, B.; Saito, N.; Sakaguchi, T.; Sakashita, K.; Samsonov, V.; Sano, S.; Sato, T.; Sawada, S.; Sedgwick, K.; Seele, J.; Seidl, R.; Semenov, A. Yu.; Seto, R.; Sharma, D.; Shein, I.; Shibata, T.-A.; Shigaki, K.; Shimomura, M.; Shoji, K.; Shukla, P.; Sickles, A.; Silva, C. L.; Silvermyr, D.; Silvestre, C.; Sim, K. S.; Singh, B. K.; Singh, C. P.; Singh, V.; Slune?ka, M.; Soltz, R. A.; Sondheim, W. E.; Sorensen, S. P.; Sourikova, I. V.; Sparks, N. A.; Stankus, P. W.; Stenlund, E.; Stoll, S. P.; Sugitate, T.; Sukhanov, A.; Sziklai, J.; Takagui, E. M.; Taketani, A.; Tanabe, R.; Tanaka, Y.; Tanida, K.; Tannenbaum, M. J.; Tarafdar, S.; Taranenko, A.; Tarján, P.; Themann, H.; Thomas, T. L.; Togawa, M.; Toia, A.; Tomášek, L.; Torii, H.; Towell, R. S.; Tserruya, I.; Tsuchimoto, Y.; Vale, C.; Valle, H.; van Hecke, H. W.; Vazquez-Zambrano, E.; Veicht, A.; Velkovska, J.; Vértesi, R.; Vinogradov, A. A.; Virius, M.; Vrba, V.; Vznuzdaev, E.; Wang, X. R.; Watanabe, D.; Watanabe, K.

2010-10-01

152

Method and apparatus for background signal reduction in opto-acoustic absorption measurement  

NASA Technical Reports Server (NTRS)

The sensitivity of an opto-acoustic absorption detector is increased to make it possible to measure trace amounts of constituent gases. A second beam radiation path is created through the sample cell identical to a first path except as to length, alternating the beam through the two paths and minimizing the detected pressure difference for the two paths while the beam wavelength is tuned away from the absorption lines of the sample. Then with the beam wavelength tuned to the absorption line of any constituent of interest, the pressure difference is a measure of trace amounts of the constituent. The same improved detector may also be used for measuring the absorption coefficient of known concentrations of absorbing gases.

Rosengren, L. G. (inventor)

1976-01-01

153

Shortest Paths.  

ERIC Educational Resources Information Center

There are many uses for the shortest path algorithm presented which are limited only by our ability to recognize when a problem may be converted into the shortest path in a graph representation. (Author/TG)

Shore, M. L.

1980-01-01

154

Non-reciprocity observed by the VLF reception of NWC (19.8 kHz) over trans-equatorial east-west paths to India with reception over a non-equatorial west-east path of similar length to Dunedin, New Zealand  

NASA Astrophysics Data System (ADS)

VLF diurnal phase and amplitude variations from NWC (19.8kHz) received over trans-equatorial east-west VLF paths at a number of sites in India are compared with the diurnal variations of NWC received in Dunedin, New Zealand over a non-equatorial west-east path of similar length. Transequatorial non-reciprocity is evident at the Indian sites as a marked and erratic reduction in night amplitude below the daytime value and changes in the sunrise modal interference minima relative to those in New Zealand. Night amplitudes in New Zealand were relatively steady and uniformly higher than day values. In contrast, the diurnal phase shifts at all sites were consistent with middle latitude values and the slight non-reciprocity known to be present there. The diurnal phase measurements confirm measurements made by Meara (1973) that east-west transequatorial propagation does not affect the phase velocity of the dominant night mode at frequencies at and above 18.6 kHz. This result contrasts with east-west transequatorial VLF measurements at Omega frequencies below 14 kHz which show an apparent increase in average phase velocity at night. Co-authors: James Brundell, Sandip K. Chakrabarti, Sushanta Kumar Mondal, Rajesh Singh, B. Veenadhari, Morris B Cohen, C.T. More

Lynn, Kenneth; Singh, Rajesh; Chakrabarti, Sandip Kumar; Veenadhari, Bhasakara; More, Chandrakant; Brundell, James

2012-07-01

155

Clustering Techniques for Minimizing External Path Length  

Microsoft Academic Search

There are a variety of main-memory access structures, such as segment trees, and quad trees, whose properties, such as good worst- case behaviour, make them attractive for database applicdions. Unfortunately, the structures are typically 'long and skinny', whereas disk data structuies must be 'short- and-fat (that is, have a high fanout and low height) in order to minimize I\\/O. We

Ajit A. Diwan; Sanjeeva Rane; S. Seshadri; S. Sudarshan

1996-01-01

156

EXPERIMENTAL STUDY OF THE ABSORPTION IN DISTILLED WATER, ARTIFICIAL SEA WATER, AND HEAVY WATER IN THE VISIBLE REGION OF THE SPECTRUM  

Microsoft Academic Search

The absorption of light in distilled water, artificial sea water, and ; heavy water was measured in the visible region. A Nielsen spectrometer with ; glass optics was used with a tungsten source and photomultiplier detector. Path ; lengths were 60.0 and 132.0 cm. The absorption in distilled and artificiai sea ; water differs little; maxima below 745 m mu

SERAPHIN A. SULLIVAN

1963-01-01

157

Path discrepancies between great circle and rhumb line  

NASA Technical Reports Server (NTRS)

A simulation of a mathematical model to compute path discrepancies between great circle and rhumb line flight paths is presented. The model illustrates that the path errors depend on the latitude, the bearing, and the trip length of the flight.

Kaul, Rajan

1987-01-01

158

Shortest Paths Without a Map  

Microsoft Academic Search

Papadimitriou, C.H. and M. Yannakakis, Shortest paths without a map, Theoretical Computer Science 84 (1991) 127-150. We study several versions of the shortest-path problem when the map is not known in advance, but is specified dynamically. We are seeking dynamic decision rules that optimize the worst-case ratio of the distance covered to the length of the (statically) optimal path. We

Christos H. Papadimitriou; Mihalis Yannakakis

1989-01-01

159

Geometry of optimal path hierarchies  

NASA Astrophysics Data System (ADS)

We investigate the hierarchy of optimal paths in a disordered landscape, based on the best path, the second best path and so on in terms of an energy. By plotting each path at a height according to its energy above some zero level, a landscape appears. This landscape is self-affine and controlled by two Hurst exponents: the one controlling the height fluctuations is 1/3 and the one controlling the fluctuations of the equipotential lines in the landscape is 2/3. These two exponents correspond to the exponents controlling energy and shape fluctations in the directed polymer problem. We furthermore find that the density of spanning optimal paths scale as the length of the paths to -2/3 and the histogram of energy differences between consecutive paths scale as a power law in the difference size with exponent -2.5.

Talon, Laurent; Auradou, Harold; Pessel, Marc; Hansen, Alex

2013-08-01

160

In situ Gas Temperature Measurements by UV-Absorption Spectroscopy  

NASA Astrophysics Data System (ADS)

The absorption spectrum of the NO A2?+ ? X2??-system can be used for in situ evaluation of gas temperature. Experiments were performed with a newly developed atmospheric-pressure high-temperature flow gas cell at highly uniform and stable gas temperatures over a 0.533 m path in the range from 23 °C to 1,500 °C. The gas temperature was evaluated (1) from the analysis of the structure of selected NO high-resolution ?-absorption bands and (2) from the analysis of vibrational distribution in the NO ?-absorption system in the (211-238) nm spectral range. The accuracy of both methods is discussed. Validation of the classical Lambert-Beer law has been demonstrated at NO concentrations up to 500 ppm and gas temperatures up to 1,500 °C over an optical absorption path length of 0.533 m.

Fateev, A.; Clausen, S.

2009-02-01

161

Asymptotic Optimality of Shortest Path Routing.  

National Technical Information Service (NTIS)

Many communication networks use adaptive shortest path routing. By this the authors mean that each network link is periodically assigned a length that depends on its congestion level during the preceding period, and all traffic generated between length up...

E. M. Gafni D. P. Pertsekas

1983-01-01

162

Global sampling of the photochemical reaction paths of bromoform by ultrafast deep-UV through near-IR transient absorption and ab initio multiconfigurational calculations  

NASA Astrophysics Data System (ADS)

Ultrafast deep-ultraviolet through near infrared (210-950 nm) transient absorption spectroscopy complemented by ab initio multiconfigurational calculations offers a global description of the photochemical reaction pathways of bromoform following 255-nm excitation in methylcyclohexane and acetonitrile solutions. Photoexcitation of CHBr3 leads to the ground-state iso-CHBr3 product in a large quantum yield (~35%), formed through two different mechanisms: concerted excited-state isomerization and cage-induced isomerization through the recombination of the nascent radical pair. These two processes take place on different time scales of tens of femtoseconds and several picoseconds, respectively. The novel ultrafast direct isomerization pathway proposed herein is consistent with the occurrence of a conical intersection between the first excited singlet state of CHBr3 and the ground electronic state of iso-CHBr3. Complete active space self-consistent field calculations characterize this singularity in the vicinity of a second order saddle point on the ground state which connects the two isomer forms. For cage-induced isomerization, both the formation of the nascent radical pair and its subsequent collapse into ground-state iso-CHBr3 are directly monitored through the deep-ultraviolet absorption signatures of the radical species. In both mechanisms, the optically active (i.e., those with largest Franck-Condon factors) C-Br-Br bending and Br-Br stretching modes of ground-state iso-CHBr3 have the largest projection on the reaction coordinate, enabling us to trace the structural changes accompanying vibrational relaxation of the non-equilibrated isomers through transient absorption dynamics. The iso-CHBr3 photoproduct is stable in methylcyclohexane, but undergoes either facile thermal isomerization to the parent CHBr3 structure through a cyclic transition state stabilized by the polar acetonitrile medium (~300-ps lifetime), and hydrolysis in the presence of water.

Pal, S. K.; Mereshchenko, A. S.; Butaeva, E. V.; El-Khoury, P. Z.; Tarnovsky, A. N.

2013-03-01

163

Refractive index and absorption length of YAP: Ce scintillation crystal and reflectance of the coating used in YAP : Ce single-crystal matrix  

Microsoft Academic Search

Recent works show growing interest in optically isolated YAP : Ce single-crystal matrices as high spatial resolution detectors for imaging applications in Nuclear Medicine. Such matrices are manufactured by Preciosa Crytur (Czech Republic) by means of a special sticking procedure of YAP : Ce pillars about 10 mm in length and with cross section ranging between 0.6 mm × 0.6

S. Baccaro; A. Cecilia; M. Montecchi; T. Malatesta; F. de Notaristefani; S. Torrioli; F. Vittori

1998-01-01

164

Investigation of Diode Pumped Alkali Laser Atmospheric Transmission Using Tunable Diode Laser Absorption Spectroscopy.  

National Technical Information Service (NTIS)

A field deployable ruggedized tunable diode laser absorption spectroscopy (TDLAS) device fiber coupled to a pair of 12.5' Ritchey-Chretien telescopes was used to study atmospheric propagation for open path lengths of 100 to 1,000 meters to estimate atmosp...

C. A. Rice

2012-01-01

165

Measuring Length  

NSDL National Science Digital Library

This article focuses on young students encountering the measurement of length. The article cites examples of key concepts in recognizing length as an attribute and in proper and improper ways to measure length. Conservation and additivity of length, standard and non-standard units, iteration, and the zero point are among the topics presented.

2009-08-01

166

Differential optical absorption spectroscopy measurement of CO2 using a nanosecond white light continuum.  

PubMed

We built a differential optical absorption spectroscopy system to measure near-surface CO2 absorption in the atmosphere using a nanosecond white light continuum. The white light laser can cover wavelengths ranging from 420 to 2400 nm, where the CO2 and H2O absorption lines are located. At an optical path length of 568 m, it was possible to evaluate atmospheric CO2 concentration from absorption bands of CO2 and H2O in the vicinity of 2000 nm detected by broadband white light simultaneously. PMID:22179882

Somekawa, Toshihiro; Manago, Naohiro; Kuze, Hiroaki; Fujita, Masayuki

2011-12-15

167

Beneficial roles of Al back reflectors in optical absorption of Si nanowire array solar cells  

NASA Astrophysics Data System (ADS)

We investigate the influence of Al back reflectors on the optical absorption spectra of Si nanowire (NW) arrays by using the finite-difference time-domain simulation method. A flat Al layer enhances the absorption in the NW array due to not only the reflection-induced optical path length enlargement but also reflection of light between NWs and localized surface plasmon induced optical field confinement. An Al underlayer with a grating structure allows grating-coupled surface plasmon polariton excitation and raise the optical absorption in the Si NWs. Interplay among all these factors on the optical absorption and expected solar cell performance of the NW arrays is discussed.

Lee, Eunsongyi; Zhou, Keya; Gwon, Minji; Jung, Jin-Young; Lee, Jung-Ho; Kim, Dong-Wook

2013-09-01

168

Measurement of light absorption by aquatic particles: improvement of the quantitative filter technique by use of an integrating sphere approach.  

PubMed

Determination of particulate absorption in natural waters is often made by measuring the transmittance of samples on glass-fiber filters with the so-called quantitative filter technique (QFT). The accuracy of this technique is limited due to variations in the optical properties of the sample/filter composite, and due to uncertainties in the path-length amplification induced by multiple scattering inside the filter. Some variations in the optical properties of the sample/filter composite can be compensated by additional measurements of the filter's reflectance (transmittance-reflectance method [T-R] [S. Tassan and G. M. Ferrari, Limnol. Oceanogr. 40, 1358 (1995)]). We propose a different, rarely used approach, namely to measure the filter's absorptance in the center of a large integrating sphere, to avoid problems with light losses due to scattering. A comparison with other QFTs includes a sensitivity study for different error sources and determination of path-length amplification factors for each measurement technique. Measurements with a point-source integrating-cavity absorption meter were therefore used to determine the true absorption. Filter to filter variability induced a much lower error in absorptance compared to a measured transmittance. This reduced error permits more accurate determination of the usually low absorption coefficient in the near IR spectral region. The error of the T-R method was lower than that of the transmittance measurement but slightly higher than that of an absorptance measurement. The mean path-length amplification was much higher for the absorptance measurement compared to the T-R method (4.50 versus 2.45) but was found to be largely independent of wavelength and optical density. With natural samples the path-length amplification was less variable for the absorptance measurement, reducing the overall error for absorption to less than ±14%, compared to ±25% for the T-R method. PMID:22441480

Röttgers, Rüdiger; Gehnke, Steffen

2012-03-20

169

Spreading paths in partially observed social networks  

PubMed Central

Understanding how and how far information, behaviors, or pathogens spread in social networks is an important problem, having implications for both predicting the size of epidemics, as well as for planning effective interventions. There are, however, two main challenges for inferring spreading paths in real-world networks. One is the practical difficulty of observing a dynamic process on a network, and the other is the typical constraint of only partially observing a network. Using a static, structurally realistic social network as a platform for simulations, we juxtapose three distinct paths: (1) the stochastic path taken by a simulated spreading process from source to target; (2) the topologically shortest path in the fully observed network, and hence the single most likely stochastic path, between the two nodes; and (3) the topologically shortest path in a partially observed network. In a sampled network, how closely does the partially observed shortest path (3) emulate the unobserved spreading path (1)? Although partial observation inflates the length of the shortest path, the stochastic nature of the spreading process also frequently derails the dynamic path from the shortest path. We find that the partially observed shortest path does not necessarily give an inflated estimate of the length of the process path; in fact, partial observation may, counterintuitively, make the path seem shorter than it actually is.

Onnela, Jukka-Pekka; Christakis, Nicholas A.

2012-01-01

170

Output-Sensitive Reporting of Disjoint Paths  

Microsoft Academic Search

A k-path query on a graph consists of computing k vertex-disjoint paths between two givenvertices of the graph, whenever they exist. In this paper, we study the problem of performingk-path queries, with k 3, in a graph G with n vertices. We denote with ` the total length ofthe paths reported. For k 3, we present an optimal data structure

Giuseppe Di Battista; Roberto Tamassia; Luca Vismara

1999-01-01

171

Path Finder  

NSDL National Science Digital Library

Finding certain files on a computer can be an onerous chore from time to time, and Path Finder is a good solution for anyone who's been bedeviled by such a task. The application includes a dual pane browser, cut and paste support, and a website that includes an interactive tour through its other features. This version of Path Finder is compatible with systems running Mac OS X 10.5 and newer. Also, this is a 30-day free trial version, and a full paid license is required after that point.

172

Thermal Diffusivity and Conductivity Measurements: Effect of Sample Length and Radiation  

NASA Astrophysics Data System (ADS)

Measurements of thermal diffusivity D and conductivity ? commonly show an upturn as a function of temperature. The upturn is very apparent in semi-transparent materials such as upper mantle minerals at absolute temperatures T of the order of 600-700 K. Although the effect is readily attributed to a radiative component, it shows a temperature dependence that is more characteristic of a black body (e.g., T3) than that expected from actual optical absorption spectra at high temperature for very large dimensions. When radiative conductivity ?r is obtained from optical methods, it tends begin at lower temperatures and to level off as absorption increases with T. Part of the discrepancy can be assigned to the fact that photon mean free path mfp( T) is usually comparable with sample dimensions. However, the problem is worsened in portions of the spectra by spectral path lengths (reciprocal absorption coefficients) substantially longer than sample lengths, an effect manifested in length-dependent radiative diffusion. For olivine (Mg0.91,Fe0.09)2SiO4 we have used a model of 1-dimensional spectral absorption and emission between volume elements to demonstrate that as sample length increases, ?r approaches that expected from spectral methods.

Shankland, T. J.; Schilling, F. R.; Gibert, B.; Gratz, K.

2005-12-01

173

Mid-infrared absorption cross sections for acetone (propanone)  

Microsoft Academic Search

Infrared absorption cross sections for acetone (propanone) have been determined in the 830–1950cm?1 spectral region from spectra recorded using a high-resolution FTIR spectrometer (Bruker IFS 125HR) and a multipass cell with a maximum optical path length of 19.3m. The spectra of mixtures of acetone with dry synthetic air were recorded at 0.015cm?1 resolution (calculated as 0.9\\/MOPD using the Bruker definition

Jeremy J. Harrison; Neil Humpage; Nicholas D. C. Allen; Alison M. Waterfall; Peter F. Bernath; John J. Remedios

2011-01-01

174

Term Paths  

NSDL National Science Digital Library

Students follow several pathways using anatomical directions on a simulated "body" produced from a copy of a school building's fire evacuation plan. The main hallways are designated as major blood vessels and the various areas of the school, the head, chest, abdomen, etc. Students complete several pathways using anatomical terms as directions. For example, one of my paths begins, "Ex- ot-, ad- superior, ecto- derm-, peri-frontal, circum- rhino-, " which loosely means, exit the ear, go to the superior region, outside the skin, around the frontal region, around the nose. At the end of each path I leave a clue that lets me know the students actually made it. The combined clues form a sentence.

Cynthia Ann Radle (McCullough High School REV)

1995-06-30

175

Inbound traffic engineering for multihomed ASs using AS path prepending  

Microsoft Academic Search

This article considers the AS path prepending approach to engineer inbound traffic for multihomed ASs. The AS path prepending approach artificially inflates the length of the AS path attribute on one of the links in hopes of diverting some of the traffic to other links. Unlike the current practice that determines the prepending length in a trial-and-error way, we propose

Rocky K. C. Chang; M. Lo

2005-01-01

176

Path Clearance  

Microsoft Academic Search

In military scenarios, agents (i.e., troops of soldiers, convoys, and unmanned vehicles) may often have to traverse environments with only a limited intelligence about the locations of adversaries. We study a particular instance of this problem that we refer to as path clearance problem.This article presents a survey of our work on scalable and suitable for real-time use approaches to

Maxim Likhachev; Anthony Stentz

2009-01-01

177

Optical Path, Phase, and Interference  

NASA Astrophysics Data System (ADS)

A powerful tool in wave optics is the concept of optical path length, a notion usually introduced with Fermat's principle.1-3 The analysis of Fermat's principle requires the application of the calculus of variations and the concept of an extremum, ideas too advanced for beginning students. However, the concept has proven its usefulness in the analysis4 of interference experiments such as those of Michelson and Fabry-Perot. In this paper we shall show how optical path length can aid in the analysis of a modified two-slit Young experiment.

Newburgh, Ronald

2005-11-01

178

A comprehensive study on energy absorption and exposure buildup factors for some essential amino acids, fatty acids and carbohydrates in the energy range 0.015-15 MeV up to 40 mean free path  

NASA Astrophysics Data System (ADS)

The gamma ray energy absorption ( EABF) and exposure buildup factors ( EBF) have been calculated for some essential amino acids, fatty acids and carbohydrates in the energy region 0.015-15 MeV up to a penetration depth of 40 mfp (mean free path). The five parameter geometric progression (G-P) fitting approximation has been used to calculate both EABF and EBF. Variations of EABF and EBF with incident photon energy, penetration depth and weight fraction of elements have been studied. While the significant variations in EABF and EBF for amino acids and fatty acids have been observed at the intermediate energy region where Compton scattering is the main photon interaction process, the values of EABF and EBF appear to be almost the same for all carbohydrates in the continuous energy region. It has been observed that the fatty acids have the largest EABF and EBF at 0.08 and 0.1 MeV, respectively, whereas the maximum values of EABF and EBF have been observed for aminoacids and carbohydrates at 0.1 MeV. At the fixed energy of 1.5 MeV, the variation of EABF with penetration depth appears to be independent of the variations in chemical composition of the amino acids, fatty acids and carbohydrates. Significant variations were also observed between EABF and EBF which may be due to the variations in chemical composition of the given materials.

Kurudirek, Murat; Özdemir, Yüksel

2011-01-01

179

k-Link Shortest Paths in Weighted Subdivisions  

Microsoft Academic Search

We study the shortest path problem in weighted polygonal subdivisions of the plane, with the additional constraint of an upper bound, k, on the number of links (segments) in the path. We prove structural properties of optimal paths and utilize these results to ob- tain approximation algorithms that yield a path having O(k) links and weighted length at most (1

Ovidiu Daescu; Joseph S. B. Mitchell; Simeon C. Ntafos; James D. Palmer; Chee-keng Yap

2005-01-01

180

Approximation Algorithms for Shortest Path Motion Planning (Extended Abstract)  

Microsoft Academic Search

This paper gives approximation algorithms for solvingthe following motion planning problem: Given aset of polyhedral obstacles and points s and t, find ashortest path from s to t that avoids the obstacles.The paths found by the algorithms are piecewise linear,and the length of a path is the sum of the lengthsof the line segments making up the path. Approximationalgorithms will

Kenneth L. Clarkson

1987-01-01

181

Off-axis paths in spherical mirror interferometers  

Microsoft Academic Search

vO = 24r, and g being integers, the rays retrace their paths. These ray paths give rise to additional resonances which were observed. Pictures of the points of reflection are reproduced. The theory is in good agreement with the experi- mental observations. In laser amplifiers these ray paths enable one to obtain long effective path lengths in the active medium

D. Herriott; H. Kogelnik; R. Kompfner

1964-01-01

182

HPGe detector photopeak efficiency calculation including self-absorption and coincidence corrections for Marinelli beaker sources using compact analytical expressions  

Microsoft Academic Search

Direct mathematical methods to calculate total and full-energy peak (photopeak) efficiencies, coincidence correction factors and the source self-absorption of a closed end coaxial HPGe detector for Marinelli beaker sources have been derived. The source self-absorption is determined by calculating the photon path length in the source volume. The attenuation of photons by the Marinelli beaker and the detector cap materials

Mahmoud I. Abbas

2001-01-01

183

First geometrical path length probability density function derivation of the skylight from high-resolution oxygen A-band spectroscopy 2. Derivation of the Lévy index for the skylight transmitted by midlatitude clouds  

Microsoft Academic Search

For the first time Lévy indices (gamma) of the solar light transmitted by cloudy skies at mid latitude (50°N, 8.2°E) are reported. The Lévy index describes the dependence of the mean geometrical paths () of photons transmitted from cloudy skies as a function of the vertical cloud extension (Hc) expressed by the scaling law ~Hcgamma. For a set of 33

K. Pfeilsticker

1999-01-01

184

Significance of self-absorption for emission spectral lines  

NASA Astrophysics Data System (ADS)

Accurate optical measuring techniques of spectral lines are needed for low pressure plasma semiconductor manufacturing diagnostics. One spectral line broadening problem which has been widely overlooked and its importance neglected is self-absorption. Self-absorption is an effect when a photon emitted by an atom may be absorbed by a different atom before it escapes from the source. In this study the method used to quantify the self-absorption involves changing the optical path length of the measured OES plasma spectral emission. This is achieved by taking OES measurements from two different viewports on the reactive ion etch (RIE) plasma chamber, one directly on top of the plasma chamber and the other on the side of the chamber, both differ in optical length. If the increase in signal intensity changes corresponding to optical length, there is no self-absorption. The experiments are performed in an RIE chamber, 13.56 MHz with maximum RF power of 600 W, Ar - O2 mixture. Almost all the measured spectral lines have been affected by self-absorption e.g. the Argon 750 nm spectral line has its intensity affected by up to 40%. In the case of Actinometry calculation, taking into account Ar and O2 emission, correction of self-absorption could change the final result up to 20%.

Gudimenko, Evgueni; Milosavljevic, Vladimir; Daniels, Stephen

2012-10-01

185

Path Planning Control.  

National Technical Information Service (NTIS)

Viewgraphs on path planning control are presented. Topics covered include: model based path planning; sensor based path planning; hybrid path planning; proximity sensor array; and applications for fuzzy logic.

M. Mcroberts

1990-01-01

186

Path planning control  

NASA Technical Reports Server (NTRS)

Viewgraphs on path planning control are presented. Topics covered include: model based path planning; sensor based path planning; hybrid path planning; proximity sensor array; and applications for fuzzy logic.

Mcroberts, Malcolm

1990-01-01

187

TDLAS-based open-path laser hygrometer using simple reflective foils as scattering targets  

NASA Astrophysics Data System (ADS)

We present a new, very simple to use and very easy to align, inexpensive, robust, mono-static optical hygrometer based on tunable diode laser absorption spectroscopy (TDLAS) that makes use of very inexpensive reflective foils as scattering targets at the distant side of the absorption path. Various alternative foils as scattering targets were examined concerning their reflective behaviour and their suitability for TDLAS applications. Using a micro prismatic reflection tape as the optimum scattering target we determined absolute water vapour concentrations employing open path TDLAS. With the reflection tape being in a distance of 75 cm to 1 m (i.e., absorption path lengths between 1.5 and 2 m) we detected ambient H2O concentrations of up to 12,300 ppmv with detectivities of 1 ppm which corresponds to length and bandwidth normalized H2O detection limits of up to 0.9 ppmv m/ sqrt {{Hz}} , which is only a factor of 2 worse than our previous bi-static TDLAS setups (Hunsmann, Appl. Phys. B 92:393-401, 1). This small sensitivity disadvantage is well compensated for by the simplicity of the spectrometer setup and particularly by its extreme tolerance towards misalignment of the scattering target.

Seidel, A.; Wagner, S.; Ebert, V.

2012-11-01

188

A Random Walk on a Circular Path  

ERIC Educational Resources Information Center

This short note introduces an interesting random walk on a circular path with cards of numbers. By using high school probability theory, it is proved that under some assumptions on the number of cards, the probability that a walker will return to a fixed position will tend to one as the length of the circular path tends to infinity.

Ching, W.-K.; Lee, M. S.

2005-01-01

189

Online preconcentration for the determination of lead, cadmium and copper by slotted tube atom trap (STAT)-flame atomic absorption spectrometry  

Microsoft Academic Search

An online sensitivity enhancement by using atom trapping in flame atomic absorption spectrophotometry was examined for increasing the residence time of the analyte atoms in the light path. For this purpose, various parameters of quartz tubes of the slotted tube atom trap were tested. The studied parameters include the internal diameter, the length of the upper slot and the wall

Gokce Kaya; Mehmet Yaman

2008-01-01

190

Fiber laser intracavity absorption spectroscopy for in situ multicomponent gas analysis in the atmosphere and combustion environments  

NASA Astrophysics Data System (ADS)

Intracavity absorption spectroscopy with a broadband Er3+-doped fiber laser is applied for the measurements of several molecular species revealing quantitative information about the gas concentration, temperature and chemical reactions in flames. The spectral range of measurements extends from 6200 cm-1 to 6550 cm-1 with the proper choice of the fiber length and by moving an intracavity lens. With a pulsed laser applied in this experiment, the sensitivity to absorption corresponds to an effective absorption path length of 3 km assuming the cavity is completely filled with the sample. For a cw laser, the effective absorption path length is estimated to be 50 km. Absorption spectra of various molecules such as CO2, CO, H2O, H2S, C2H2 and OH were recorded separately in the cell and/or in low-pressure methane and propane flames. The presented measurements demonstrate simultaneous in situ detection of three molecular products of chemical reactions at different flame locations. Variation of the relative strengths of OH absorption lines with the temperature enables the estimation of the local flame temperature. The sensitivity of this laser does not depend on the broadband cavity losses and it can be used for in situ measurements of absorption spectra in hostile environments such as contaminated samples, flames or combustion engines. The presented technique can be applied for various diagnostic purposes, such as in environmental, combustion and plasma research, in medicine and in the determination of stable isotope ratios.

Löhden, B.; Kuznetsova, S.; Sengstock, K.; Baev, V. M.; Goldman, A.; Cheskis, S.; Pálsdóttir, B.

2011-02-01

191

Finger Length  

NSDL National Science Digital Library

Although life experience plays a huge role in shaping who we are, the foundations of our personality begin in the womb. This Science Update describes a recent study that looks to finger length for signs of a man's pre-natal exposure to testosterone.

Science Update;

2005-03-28

192

Exciton coherence length fluctuations in chromophore aggregates probed by multidimensional optical spectroscopy  

PubMed Central

The coherent third order optical response of molecular aggregates with fluctuating frequencies, couplings, and transition dipole moments is studied. We derived stochastic nonlinear exciton equations (SNEEs) by combining the quasiparticle picture of excitons with the path integral over stochastic bath paths described by the stochastic Liouville equations. Coherent two-dimensional (2D) spectra are calculated for a tetramer model system whose transition dipole orientations undergo two-state stochastic jumps on an arbitrary timescale. Correspondence between domains of ordered dipoles, which determine the exciton coherence length and the absorption peaks, is established. Signatures of domain coherence length fluctuations are observed in the cross peak dynamics of the 2D spectra in specific pulse polarization configurations.

Sanda, Frantisek; Perlik, Vaclav; Mukamel, Shaul

2010-01-01

193

Infrared spectra of methylidynes formed in reactions of re atoms with methane, methyl halides, methylene halides, and ethane: methylidyne C-H stretching absorptions, bond lengths, and s character.  

PubMed

Rhenium carbyne complexes (HC identical with ReH 3, HC identical with ReH 2X, HC identical with ReHX 2, [X = F, Cl, and Br] and CH 3C identical with ReH 3) are produced by reactions of laser-ablated Re atoms with methane, methyl halides, methylene halides, and ethane via oxidative C-H(X) insertion and alpha-hydrogen migration in favor of the carbon-metal triple bond. The stabilities of the carbyne complexes relative to other possible products are predicted by DFT calculations. The diagnostic methylidyne C-H stretching absorptions of HC identical with ReH 3 and its mono- and dihalo derivatives are observed on the blue sides of the precursor C-H stretching bands, and the frequency decreases and the bond length increases in the order of H, F, Cl, and Br, following the decreasing s character in hybridization for the C-H bond. The dihalo methylidynes have higher C-H stretching frequencies and s characters than the monohalo species. The rhenium methylidynes have C s structures, and as a result the HC identical with ReH 3 and CH 3C identical with ReH 3 complexes have two equivalent shorter and one longer Re-H bonds, as compared to the tungsten methylidyne HC identical with WH 3 with three equivalent W-H bonds. PMID:18257553

Cho, Han-Gook; Andrews, Lester

2008-03-01

194

Finger Length  

NSDL National Science Digital Library

This Science Update explores male agression patterns and their correlation to pre-natal testosterone exposure. Although life experience plays a huge role in shaping who we are, the foundations of our personality begin in the womb. One recent study looks to finger length for signs of a man's pre-natal exposure to testosterone.n women, the index and ring finger are roughly equal in length. But in most men, the ring finger is longer. That's a result of fetal exposure to testosterone. Psychologists Alison Bailey and Pete Hurd, of the University of Alberta in Canada, studied these finger ratios in male college students. And they found that men with more dramatic differences tended to be more aggressive. Additional links to resources are given for further inquiry.

American Association for the Advancement of Science (;)

2005-03-28

195

Planning Paths of Complete Coverage of an Unstructured Environment by a Mobile Robot  

Microsoft Academic Search

Much of the focus of the research effort in path planning for mobile robots has centred on the problem of finding a path from a start location to a goal location, while minimising one or more parameters such as length of path, energy consumption or journey time. A path of complete coverage is a planned path in which a robot

A. Zelinsky; R. A. Jarvis; J. C. Byrne; S. Yuta

1993-01-01

196

Intelligent Recommender System Using Shopper's Path and Purchase Analysis  

Microsoft Academic Search

Shoppers having a predefined shopping list usually follow the shortest path through a supermarket or store in order to make their purchases. This paper aims to study customer behaviour of such shoppers with respect to two aspects: (1) the path followed through the store to make those purchases. (2) the average path length to make those purchases. The paper also

Anala A Pandit; Jyot Talreja; M. Agrawal; Deepak Prasad; Swati Baheti; G. Khalsa

2010-01-01

197

PG 1411 + 442 - The nearest broad absorption line quasar  

NASA Technical Reports Server (NTRS)

IUE observations reveal strong, moderately broad absorption troughs in the blue wings of the C IV and N V emission lines of the quasar PG 1411 + 442. No absorption from weakly ionized gas is detected. The emission-line strengths and overall shape of the ultraviolet/optical/near-infrared/far-infrared continuum of the new broad absorption line quasar are within the range normally measured in quasars. Its redshift is low enough to allow the morphology of the host galaxy to be studied in deep broad-band and intermediate-band CCD images. The galaxy appears to be a large spiral with a very long arm or tail. The inclination angle is 57 deg, which rules out the possibility that the line of sight to the nucleus intersects a large path length in a galactic disk.

Malkan, Matthew A.; Green, Richard F.; Hutchings, John B.

1987-01-01

198

Development of Multireflection Absorption Spectroscopy Device using Ultraviolet LED  

NASA Astrophysics Data System (ADS)

An ultraviolet absorption spectroscopy device using light-emitting diodes (LEDs) as the light source was constructed. The measurement cell, light source, transmitting and receiving optics were installed on a breadboard of 30 cm × 30 cm. A measurement optical path length of 1 m was made possible by multireflection optics. The device can mount two LEDs in tandem, and the transmitted light is coupled to an optical fiber, which is connected to a compact spectrometer. Here, two LEDs of center wavelengths 280 nm and 295 nm were used to provide an emission spectrum which covered the peak region of the absorption spectrum of SO2. Experiments confirmed the linearity of the absorption coefficient measured by the device for SO2 concentrations in the range 16-800 ppm.

Fukuchi, Tetsuo; Shiina, Tatsuo

199

Opportunity's Path  

NASA Technical Reports Server (NTRS)

This Long Term Planning graphic was created from a mosaic of navigation camera images overlain by a polar coordinate grid with the center point as Opportunity's original landing site. The blue dots represent the rover position at various locations.

The red dots represent the center points of the target areas for the instruments on the rover mast (the panoramic camera and miniature thermal emission spectrometer). Opportunity visited Stone Mountain on Feb. 5. Stone Mountain was named after the southernmost point of the Appalachian Mountains outside of Atlanta, Ga. On Earth, Stone Mountain is the last big mountain before the Piedmont flatlands, and on Mars, Stone Mountain is at one end of Opportunity Ledge. El Capitan is a target of interest on Mars named after the second highest peak in Texas in Guadaloupe National Park, which is one of the most visited outcrops in the United States by geologists. It has been a training ground for students and professional geologists to understand what the layering means in relation to the formation of Earth, and scientists will study this prominent point of Opportunity Ledge to understand what the layering means on Mars.

The yellow lines show the midpoint where the panoramic camera has swept and will sweep a 120-degree area from the three waypoints on the tour of the outcrop. Imagine a fan-shaped wedge from left to right of the yellow line.

The white contour lines are one meter apart, and each drive has been roughly about 2-3 meters in length over the last few sols. The large white blocks are dropouts in the navigation camera data.

Opportunity is driving along and taking a photographic panorama of the entire outcrop. Scientists will stitch together these images and use the new mosaic as a 'base map' to decide on geology targets of interest for a more detailed study of the outcrop using the instruments on the robotic arm. Once scientists choose their targets of interest, they plan to study the outcrop for roughly five to fifteen sols. This will include El Capitan and probably one to two other areas.

Blue Dot Dates Sol 7 / Jan 31 = Egress & first soil data collected by instruments on the arm Sol 9 / Feb 2 = Second Soil Target Sol 12 / Feb 5 = First Rock Target Sol 16 / Feb 9 = Alpha Waypoint Sol 17 / Feb 10 = Bravo Waypoint Sol 19 or 20 / Feb 12 or 13 = Charlie Waypoint

2004-01-01

200

Algebraic Properties of the Path Ideal of a Tree  

Microsoft Academic Search

The path ideal (of length t ? 2) of a directed graph ? is the monomial ideal, denoted It(?), whose generators correspond to the directed paths of length t in ?. We study some of the algebraic properties of It(?) when ? is a tree. We first show that It(?) is the facet ideal of a simplicial tree. As a consequence, the

Jing He; Adam Van Tuyl

2010-01-01

201

Output-Sensitive Reporting of Disjoint Paths (Extended Abstract)  

Microsoft Academic Search

A k-path query on a graph consists of computing k vertex-disjoint paths between two given vertices of the graph, whenever they exist. In this paper, we study the problem of performing k-path queries, with k 3, in a graph G with n vertices. We denote with l the total length of the paths reported. For k 3, we present an

Giuseppe Di Battista; Roberto Tamassia; Luca Vismara

1996-01-01

202

Automatic Control Of Length Of Welding Arc  

NASA Technical Reports Server (NTRS)

Nonlinear relationships among current, voltage, and length stored in electronic memory. Conceptual microprocessor-based control subsystem maintains constant length of welding arc in gas/tungsten arc-welding system, even when welding current varied. Uses feedback of current and voltage from welding arc. Directs motor to set position of torch according to previously measured relationships among current, voltage, and length of arc. Signal paths marked "calibration" or "welding" used during those processes only. Other signal paths used during both processes. Control subsystem added to existing manual or automatic welding system equipped with automatic voltage control.

Iceland, William F.

1991-01-01

203

Development of an open-path incoherent broadband cavity-enhanced spectroscopy based instrument for simultaneous measurement of HONO and NO2 in ambient air  

NASA Astrophysics Data System (ADS)

We report on the development of an optical instrument based on incoherent broadband cavity-enhanced absorption spectroscopy (IBBCEAS) for simultaneous open-path measurements of nitrous acid (HONO) and nitrogen dioxide (NO2) in ambient air using a UV light emitting diode operating at ˜366 nm. Detection limits of ˜430 pptv for HONO and ˜1 ppbv for NO2 were achieved with an optimum acquisition time of 90 s, determined by an Allan variance analysis. Based on a 1.85 m long high optical finesse open-path cavity, the effective optical path length of 2.8 km was realized in aerosol-free samples or in an urban environment at modest aerosol levels. Such a kilometer long optical absorption is comparable to that achieved in the well established differential optical absorption spectroscopy (DOAS) technology while keeping the instrument very compact. Open-path detection configuration allows one to avoid absorption cell wall losses and sampling induced artifacts. The demonstrated sensitivity and specificity shows high potential of this cost-effective and compact infrastructure for future field applications with high spatial resolution.

Wu, T.; Chen, W.; Fertein, E.; Cazier, F.; Dewaele, D.; Gao, X.

2012-02-01

204

Crack-path effect on material toughness  

NASA Technical Reports Server (NTRS)

The main features of a toughening mechanism associated with a curvilinear crack path are examined using a model consisting of a macrocrack in a brittle solid with a curvilinear segment at the crack tip. A numerical procedure for finite and semiinfinite cracks is formulated and evaluated using an example which has an exact solution (a finite crack in the form of a circular arc in a uniform stress field). It is shown that, for a relatively small amplitude of crack path oscillations, the toughening ratio can be taken equal to the ratio of the corresponding crack path lengths.

Rubinstein, Asher A.

1990-01-01

205

The weighted region problem: finding shortest paths through a weighted planar subdivision  

Microsoft Academic Search

The problem of determining shortest paths through a weighted planar polygonal subdivision with n vertices is considered. Distances are measured according to a weighted Euclidean metric: The length of a path is defined to be the weighted sum of (Euclidean) lengths of the subpaths within each region. An algorithm that constructs a (restricted) “shortest path map” with respect to a

Joseph S. B. Mitchell; Christos H. Papadimitriou

1991-01-01

206

Spatial variations in the chlorophyll-specific absorption coefficients of phytoplankton and photosynthetically active pigments in the equatorial Pacific  

Microsoft Academic Search

Chlorophyll-specific absorption coefficients of particles, ap*(lambda), and of phytoplankton, aph*(lambda), were determined using the glass-fiber filter technique along 150°W in the equatorial Pacific (13°S-1°N). A site-specific algorithm for correcting the path length amplification effect was derived from field measurements. Then a decomposition technique using the high-performance liquid chromatography pigment information and taking into account the package effect was used to

Karima Allali; Annick Bricaud; Hervé Claustre

1997-01-01

207

DISCUSS: Critical Path Analysis  

NSDL National Science Digital Library

This module, by Barrie Baker and Neville Hunt of Coventry University, introduces critical path analysis and addresses the following topics: Networks, Critical paths, Floats, Activity-on-node (AON) networks. Excel spreadsheets are used to provide examples and exercises.

Baker, Barrie; Hunt, Neville

2009-04-23

208

Long Path Problems  

Microsoft Academic Search

We demonstrate the interesting, counter-intuitive result that simple paths to the global optimum can be so long that climbing the path is intractable. This means that a unimodal search space, which consists of a single hill and in which each point in the space is on a simple path to the global optimum, can be difficult for a hillclimber to

Jeffrey Horn; David E. Goldberg; Kalyanmoy Deb

1994-01-01

209

Thinnest Path Problem.  

National Technical Information Service (NTIS)

We consider the thinnest path problem for secure communication in wireless ad hoc networks. For a given source and a destination, the thinnest path problem asks for a path from the source to the destination that results in the minimum number of nodes hear...

A. Swami J. Gao Q. Zhao

2013-01-01

210

Propagation path length variations due to bending of optical fibers  

NASA Technical Reports Server (NTRS)

The geometric effect and material stress effects are included. Calculations are shown that put an upper limit on the expected phase shift in single mode fibers. The fractional change in propagation constant is presented. Moding effects in multimode fibers cause extraneous phase shifts of unusually high magnitude. This does not occur in single mode fibers, rendering them very insensitive to bending with a theoretical limit given by the above relation.

Lau, K. Y.

1981-01-01

211

Continuously variable focal length lens  

DOEpatents

A material preferably in crystal form having a low atomic number such as beryllium (Z=4) provides for the focusing of x-rays in a continuously variable manner. The material is provided with plural spaced curvilinear, optically matched slots and/or recesses through which an x-ray beam is directed. The focal length of the material may be decreased or increased by increasing or decreasing, respectively, the number of slots (or recesses) through which the x-ray beam is directed, while fine tuning of the focal length is accomplished by rotation of the material so as to change the path length of the x-ray beam through the aligned cylindrical slows. X-ray analysis of a fixed point in a solid material may be performed by scanning the energy of the x-ray beam while rotating the material to maintain the beam's focal point at a fixed point in the specimen undergoing analysis.

Adams, Bernhard W; Chollet, Matthieu C

2013-12-17

212

Optimization of A 2-Micron Laser Frequency Stabilization System for a Double-Pulse CO2 Differential Absorption Lidar  

NASA Technical Reports Server (NTRS)

A carbon dioxide (CO2) Differential Absorption Lidar (DIAL) for accurate CO2 concentration measurement requires a frequency locking system to achieve high frequency locking precision and stability. We describe the frequency locking system utilizing Frequency Modulation (FM), Phase Sensitive Detection (PSD), and Proportional Integration Derivative (PID) feedback servo loop, and report the optimization of the sensitivity of the system for the feed back loop based on the characteristics of a variable path-length CO2 gas cell. The CO2 gas cell is characterized with HITRAN database (2004). The method can be applied for any other frequency locking systems referring to gas absorption line.

Chen, Songsheng; Yu, Jirong; Bai, Yingsin; Koch, Grady; Petros, Mulugeta; Trieu, Bo; Petzar, Paul; Singh, Upendra N.; Kavaya, Michael J.; Beyon, Jeffrey

2010-01-01

213

A cryogenic circulating advective multi-pass absorption cell  

SciTech Connect

A novel absorption cell has been developed to enable a spectroscopic survey of a broad range of polycyclic aromatic hydrocarbons (PAH) under astrophysically relevant conditions and utilizing a synchrotron radiation continuum to test the still controversial hypothesis that these molecules or their ions could be carriers of the diffuse interstellar bands. The cryogenic circulating advective multi-pass absorption cell resembles a wind tunnel; molecules evaporated from a crucible or injected using a custom gas feedthrough are entrained in a laminar flow of cryogenically cooled buffer gas and advected into the path of the synchrotron beam. This system includes a multi-pass optical White cell enabling absorption path lengths of hundreds of meters and a detection sensitivity to molecular densities on the order of 10{sup 7} cm{sup -3}. A capacitively coupled radio frequency dielectric barrier discharge provides ionized and metastable buffer gas atoms for ionizing the candidate molecules via charge exchange and the Penning effect. Stronger than expected clustering of PAH molecules has slowed efforts to record gas phase PAH spectra at cryogenic temperatures, though such clusters may play a role in other interstellar phenomena.

Stockett, M. H.; Lawler, J. E. [Department of Physics, University of Wisconsin, 1150 University Avenue, Madison, Wisconsin 53706 (United States)

2012-03-15

214

A cryogenic circulating advective multi-pass absorption cell.  

PubMed

A novel absorption cell has been developed to enable a spectroscopic survey of a broad range of polycyclic aromatic hydrocarbons (PAH) under astrophysically relevant conditions and utilizing a synchrotron radiation continuum to test the still controversial hypothesis that these molecules or their ions could be carriers of the diffuse interstellar bands. The cryogenic circulating advective multi-pass absorption cell resembles a wind tunnel; molecules evaporated from a crucible or injected using a custom gas feedthrough are entrained in a laminar flow of cryogenically cooled buffer gas and advected into the path of the synchrotron beam. This system includes a multi-pass optical White cell enabling absorption path lengths of hundreds of meters and a detection sensitivity to molecular densities on the order of 10(7) cm(-3). A capacitively coupled radio frequency dielectric barrier discharge provides ionized and metastable buffer gas atoms for ionizing the candidate molecules via charge exchange and the Penning effect. Stronger than expected clustering of PAH molecules has slowed efforts to record gas phase PAH spectra at cryogenic temperatures, though such clusters may play a role in other interstellar phenomena. PMID:22462957

Stockett, M H; Lawler, J E

2012-03-01

215

Limited path percolation in complex networks.  

PubMed

We study the stability of network communication after removal of a fraction q=1-p of links under the assumption that communication is effective only if the shortest path between nodes i and j after removal is shorter than al(ij)(a> or =1) where l(ij) is the shortest path before removal. For a large class of networks, we find analytically and numerically a new percolation transition at p(c)=(kappa(0)-1)((1-a)/a), where kappa(0) [triple bond] / and k is the node degree. Above p(c), order N nodes can communicate within the limited path length al(ij), while below p(c), N(delta) (delta<1) nodes can communicate. We expect our results to influence network design, routing algorithms, and immunization strategies, where short paths are most relevant. PMID:17995444

López, Eduardo; Parshani, Roni; Cohen, Reuven; Carmi, Shai; Havlin, Shlomo

2007-11-01

216

Robot path planning using a genetic algorithm  

NASA Technical Reports Server (NTRS)

Robot path planning can refer either to a mobile vehicle such as a Mars Rover, or to an end effector on an arm moving through a cluttered workspace. In both instances there may exist many solutions, some of which are better than others, either in terms of distance traversed, energy expended, or joint angle or reach capabilities. A path planning program has been developed based upon a genetic algorithm. This program assumes global knowledge of the terrain or workspace, and provides a family of good paths between the initial and final points. Initially, a set of valid random paths are constructed. Successive generations of valid paths are obtained using one of several possible reproduction strategies similar to those found in biological communities. A fitness function is defined to describe the goodness of the path, in this case including length, slope, and obstacle avoidance considerations. It was found that with some reproduction strategies, the average value of the fitness function improved for successive generations, and that by saving the best paths of each generation, one could quite rapidly obtain a collection of good candidate solutions.

Cleghorn, Timothy F.; Baffes, Paul T.; Wang, Liu

1988-01-01

217

Beamsplitter path equalization for white-light interferometry  

Microsoft Academic Search

In a two-beam, white-light, or polychromatic-light interferometer, any path-length difference in the beamsplitter introduces wavelength-dependent path delay because of the glass dispersion. A technique to align balanced path is described. The method is based on two- or three-wavelength simultaneous interferometry. Difference in intensity of fringes placed symmetrically around the zero interference order (ZIO) is used to measure and equalize the

Marek Dobosz; Hirokazu Matsumoto; Shigeo Iwasaki

1995-01-01

218

TATP stand-off detection with open path: FTIR techniques  

NASA Astrophysics Data System (ADS)

TATP is a very easy to synthesize [9], sensitive, high explosive [10] and high volatile explosive [1, 3, 7] with great absorption in the IR Spectra [4, 5, 6]. In this project we detect TATP gas traces with open path FTIR - techniques. The first project phase was to construct and build a heatable multi-reflection cell with adjustable optical path length and a heatable intake to evaporate solid TATP samples. In this cell reference TATP - spectra were collected under controlled conditions with a Bruker FTIR system (Typ OPAG 33). The next step was to find out how the TATP gas will be diluted in the ambient air and validate some physical properties which are described inconsistently in literature e.g. evaporation rates. We constructed a special double - T shaped chamber with stabile air conditions. In this chamber the dispersion kinetics of the TATP vapour could be tested. It turned out that the TATP vapours has the tendency to drop down. Therefore the highest TATP - concentrations were measured below the TATP sample. During the investigation for this study it turned out, that some materials scrub the TATP- vapour out of the air, e.g. Metals, fabric, leather. In the second phase of the project successful open path FTIR- measurements were taken in ambient air and will be continued with different system configurations of the OPAG 33 to lower the detection limits. Also successful measurements were taken in indoor ambient air with a Hyper spectral camera (passive FTIR with array sensor) to detect TATP in solid and gaseous phase. This technique allows detecting TATP and identifying the TATP source. The poster shows some selected results of the continued research.

Fischer, C.; Pohl, T.; Weber, K.; Vogel, A.; van Haren, G.; Schweikert, W.

2012-10-01

219

Characterizing high-altitude horizontal path optical propagation  

Microsoft Academic Search

The high-energy airborne laser system must be able to effectively propagate a short- wavelength (near IR) laser beam over long path lengths at high altitude to be effective in the Theater Missile Defense mission. High-altitude atmospheric turbulence along these very long paths can have a potentially serious degrading effect on laser propagation. Adaptive optical systems design to compensate for the

Darrell E. Spreen; Charles B. Hogge

1994-01-01

220

A distributed, loop-free, shortest-path routing algorithm  

Microsoft Academic Search

A new distributed algorithm for the dynamic computation of the shortest paths in a computer network is presented, validated, and analyzed. According to this algorithm, each node maintains the lengths of the shortest path to each network destination and a feasibility vector. Update messages from a node are sent only to its neighbors; each such message contains one or more

1988-01-01

221

Optimal shortest path queries in a simple polygon  

Microsoft Academic Search

Let P be a simple polygon with n sides. This paper shows how to preprocess the polygon so that, given two query points p and q inside P, the length of the shortest path inside the polygon from p to q can be found in time &Ogr;(log n). The path itself must be polygonal and can be extracted in additional

Leonidas J. Guibas; John Hershberger

1987-01-01

222

Multi-vehicle path planning in dynamically changing environments  

Microsoft Academic Search

In this paper, we propose a path planning method for nonholonomic multi-vehicle system in presence of moving obstacles. The objective is to find multiple fixed length paths for multiple vehicles with the following properties: (i) bounded curvature (ii) obstacle avoidant (iii) collision free. Our approach is based on polygonal approximation of a continuous curve. Using this idea, we formulate an

Ali Ahmadzadeh; Nader Motee; Ali Jadbabaie; George J. Pappas

2009-01-01

223

Multilayer Active Control For Structural Damping And Optical-Path Regulation  

NASA Technical Reports Server (NTRS)

Two active-control concepts incorporated into system for suppression of vibrations in truss structure and regulation of length of optical path on structure to nanometer level. Optical-path-length-control subsystem contains two feedback control loops to obtain active damping in wide amplitude-and-frequency range. Concept described in more detail in number of previous articles, including "Stabilizing Optical-Path Length on a Vibrating Structure" (NPO-19040), "Controllable Optical Delay Line for Stellar Interferometry" (NPO-18686), "Test Bed for Control of Optical-Path Lengths" (NPO-18487).

Rahman, Zahidul H.; Spanos, John T.; Fanson, James L.

1995-01-01

224

Optimization of hollow waveguides as absorption cells for spectroscopic gas sensing.  

PubMed

Flexible and low-loss hollow waveguide has many advantages as an absorption cell for spectroscopic gas sensing. The characteristics of the sensing system are dependent on the parameters of the hollow waveguide cell. In this paper, a mathematical model was proposed to analyze the waveguide cell by considering waveguide loss, effective optical path length, and signal-to-noise ratio of the system. Simulation results show that the gas absorption intensity and system sensitivity are dependent not only on the waveguide length but also on the bore-diameter, signal-to-noise ratio, and the concentration of the target gases. The results provide optimizing methods for the sensing system and algorithms for error compensation. Preliminary experiments on concentration detection of methane gas were carried out and measured data showed good agreements with the simulation results. PMID:23452494

Zhou, Jia-Qi; Lu, Wei-Jia; Yao, Zhang-Rui; Wei, Yu-Qing; Shi, Yi-Wei

2013-03-01

225

Intensities and N2 collision-broadening coefficients measured for selected H2O absorption lines between 715 and 732 nm  

NASA Technical Reports Server (NTRS)

Intensities and N2 collision-broadening coefficients are measured for 62 water vapor absorption lines between 715 and 732 nm potentially applicable to laser remote sensing of atmospheric water vapor. Absolute line strengths and widths were determined from spectra corrected for instrument resolution, air-path absorption and Lorentz and Doppler broadening for pure water vapor and water vapor-nitrogen mixtures in a multipass absorption cell with a base path length of 25 m (White cell). Line strengths are observed to range from 4 x 10 to the -25th to 4 x 10 to the -23rd kayser/molecule per sq cm, and collision broadening coefficients are found to be approximately equal to 0.1 kayser/atm.

Wilkerson, T. D.; Schwemmer, G.; Gentry, B.; Giver, L. P.

1979-01-01

226

Shortest path algorithms  

Microsoft Academic Search

Theshortest path problem is considered from a computational point of view. Eight algorithms which solve theshortest path tree problem on directed graphs are presented, together with the results of wide-ranging experimentation designed to compare their relative performances on different graph topologies. The focus of this paper is on the implementation of the different data structures used in the algorithms. A

Giorgio Gallo; Stefano Pallottino

1988-01-01

227

Path Following Robot.  

National Technical Information Service (NTIS)

Given a desired path to be followed by a Robot, a set of commands must be given to the Robot joint servos so that the Robot Tip, or Endpoint, can follow that path. These commands must be synchronized in time and scaled so as to maintain accuracy in the pr...

S. G. Goodway

1987-01-01

228

Advanced Physics: Path Integral  

NSDL National Science Digital Library

A cursor is shown in an x-y graph. The cursor can be dragged around the graph and its path is marked as it is moved. The data are sent to a DataTable which shows x, y, and the value of the path integral, F.dl.

Christian, Wolfgang; Belloni, Mario

2006-01-19

229

Operational transfer path analysis  

NASA Astrophysics Data System (ADS)

One of the tools used to study the NVH behaviour of a system is the transfer path analysis. It aims to identify the operational forces and the propagation paths of the vibrations and is especially interesting in the case when the system is composed of different subsystems. The classical techniques identify the transfer paths when the system is disassembled. This way one eliminates flanking transfer paths. Yet it is very time-consuming and the boundary conditions are not correct anymore. The presented method makes it possible to identify the transfer paths without disassembling the system. The advantages are that the overall testing time is reduced and that the real boundary conditions are present. In this article the theory will be reviewed and it will be validated using data generated by finite element simulations.

De Sitter, Gert; Devriendt, Christof; Guillaume, Patrick; Pruyt, Erik

2010-02-01

230

Fracturing the optimal paths.  

PubMed

Optimal paths play a fundamental role in numerous physical applications ranging from random polymers to brittle fracture, from the flow through porous media to information propagation. Here for the first time we explore the path that is activated once this optimal path fails and what happens when this new path also fails and so on, until the system is completely disconnected. In fact many applications can also be found for this novel fracture problem. In the limit of strong disorder, our results show that all the cracks are located on a single self-similar connected line of fractal dimension D(b) approximately = 1.22. For weak disorder, the number of cracks spreads all over the entire network before global connectivity is lost. Strikingly, the disconnecting path (backbone) is, however, completely independent on the disorder. PMID:20366106

Andrade, J S; Oliveira, E A; Moreira, A A; Herrmann, H J

2009-11-27

231

Path Relaxation: Path Planning for a Mobile Robot.  

National Technical Information Service (NTIS)

Path Relaxation is a method of planning safe paths around obstacles for mobile robots. It works in two steps: a global grid search that finds a rough path, followed by a local relaxation step that adjusts each node on the path to lower the overall path co...

C. E. Thorpe

1984-01-01

232

Critical-Path-whitepaper  

Cancer.gov

NEGOTIATING THE CRITICAL PATH..................................................................................................7 SCIENTIFIC AND TECHNICAL DIMENSIONS ALONG THE CRITICAL PATH...................................9 A BETTER PRODUCT DEVELOPMENT TOOLKIT IS URGENTLY NEEDED ..................................11 TOOLS FOR ASSESSING SAFETY......................................................................................................16 Towards a Better Safety Toolkit................................................................................................17 Getting to the Right Safety Standards......................................................................................20 TOOLS FOR DEMONSTRATING MEDICAL UTILITY .......................................................................20 Towards a Better Effectiveness Toolkit ...................................................................................21 Getting to the Right Effectiveness Standards .........................................................................25 TOOLS FOR CHARACTERIZATION AND MANUFACTURING .........................................................25 Towards a Better Manufacturing Toolkit.................................................................................27 Getting to the Right Manufacturing Standards .......................................................................28 A PATH FORWARD .............................................................................................................................29 The Orphan Products Grant Program.

233

Earth's Atmospheric CO2 Saturated IR Absorption  

NASA Astrophysics Data System (ADS)

Using the on-line SpectraCalc IR absorption simulator, the amount of IR absorption by the 15 ? line of the current atmospheric CO2 was obtained and compared with that of twice the amount of CO2. The simulation required a fixed density equivalent for the atmospheric path length. This was obtained by numerically integrating the NOAA Standard Atmospheric model. While the current line is saturated, doubling the CO2 will cause a slight width increase. Using this and the blackbody radiation curve plus considering the effects of water vapor, the temperature rise of the Earth will be less than 2.5 deg. C. Integrating a NASA Martian atmospheric model, we find that the Martian atmosphere has 45 times more CO2 to penetrate than Earth, and yet, the Martian diurnal temperature swings exceed those of the Sahara desert. I.e., large amounts of CO2 alone do not necessarily cause planetary warming. As the oceans warm from any cause, more CO2 is boiled out, but if they cool, they will absorb more CO2 just as a carbonated drink does, so that temperature and CO2 density will correlate. It is to be noted that the Earth's known petroleum reserves contain only enough CO2 to increase the atmospheric CO2 by some 15%.

Wall, Ernst

2008-10-01

234

High-precision direct measurements of (13)CH(4)/(12)CH(4) and (12)CH(3)D/(12)CH(4) ratios in atmospheric methane sources by means of a long-path tunable diode laser absorption spectrometer.  

PubMed

Measurements of (13)CH(4)/(12)CH(4) and (12)CH(3)D/(12)CH(4) ratios in atmospheric methane (CH(4)) sources provide important information about the global CH(4) budget as well as about CH(4) production and consumption processes occurring within the various sources. As an alternative to the conventional mass spectrometer (MS) technique, which requires conversion of CH(4) to CO(2) and H(2), we have developed a tunable diode laser absorption spectrometer (TDLAS), which permits rapid direct measurements of the (13)CH(4)/(12)CH(4) and (12)CH(3)D/(12)CH(4) ratios. An intercomparison between TDLAS and MS techniques for samples from natural wetlands, landfills, and natural gas sources resulted in a mean deviation of ??(13)C = 0.44‰ and ??D = 5.1‰. In the present system the minimum mixing ratios required are 50 parts in 10(6) by volume (ppmv) CH(4) (sample size 2 µmol CH(4)) for direct ?(13)C measurements and 2000 ppmv (sample size 80 µmol CH(4)) for direct ?D measurements. These mixing-ratio limits are adequate for most CH(4) source characterization studies without requiring sample preconcentration. PMID:20962979

Bergamaschi, P; Schupp, M; Harris, G W

1994-11-20

235

Critical Path Method Reports.  

National Technical Information Service (NTIS)

The computer system for the Critical Path Method Reports consists of three programs. The programs are CPM Calculation, CPM Calendar Dating and CPM Time-Sequence Plot. The CPM Calculations Program is used for doing the arithmetic calculations associated wi...

R. C. Tennent

1964-01-01

236

Air Vehicle Path Planning.  

National Technical Information Service (NTIS)

This dissertation explores optimal path planning for air vehicles. An air vehicle exposed to illumination by a tracking radar is considered and the problem of determining an optimal planar trajectory connecting two prespecified points is addressed. An ana...

J. M. Hebert

2001-01-01

237

Tortuous path chemical preconcentrator  

DOEpatents

A non-planar, tortuous path chemical preconcentrator has a high internal surface area having a heatable sorptive coating that can be used to selectively collect and concentrate one or more chemical species of interest from a fluid stream that can be rapidly released as a concentrated plug into an analytical or microanalytical chain for separation and detection. The non-planar chemical preconcentrator comprises a sorptive support structure having a tortuous flow path. The tortuosity provides repeated twists, turns, and bends to the flow, thereby increasing the interfacial contact between sample fluid stream and the sorptive material. The tortuous path also provides more opportunities for desorption and readsorption of volatile species. Further, the thermal efficiency of the tortuous path chemical preconcentrator is comparable or superior to the prior non-planar chemical preconcentrator. Finally, the tortuosity can be varied in different directions to optimize flow rates during the adsorption and desorption phases of operation of the preconcentrator.

Manginell, Ronald P. (Albuquerque, NM); Lewis, Patrick R. (Albuquerque, NM); Adkins, Douglas R. (Albuquerque, NM); Wheeler, David R. (Albuquerque, NM); Simonson, Robert J. (Cedar Crest, NM)

2010-09-21

238

A Path to Discovery  

ERIC Educational Resources Information Center

The path taken and the turns made as a turtle traces a polygon are examined to discover an important theorem in geometry. A unique tool, the Angle Adder, is implemented in the investigation. (Contains 9 figures.)

Stegemoller, William; Stegemoller, Rebecca

2004-01-01

239

Follow the Paths  

NSDL National Science Digital Library

In this lesson, younger students will be introduced to the various orbital paths that are used for satellites. Using a globe and a satellite model or a large picture of Earth, the teacher will introduce three types of orbital paths (polar, elliptical, and geosynchronous). The students should be able to define 'satellite', define the three types of orbits, describe how satellites orbit the Earth, and understand how they are slowed down by drag from the atmosphere.

240

Detection of optical path in spectroscopic space-based observations of greenhouse gases: Application to GOSAT data processing  

NASA Astrophysics Data System (ADS)

We present a method to detect optical path modification due to atmospheric light scattering in space-based greenhouse gas spectroscopic sounding. This method, which was applied to the analysis of radiance spectra measured by the Greenhouse Gases Observing Satellite (GOSAT), is based on the path length probability density function (PPDF) and on retrieval of PPDF parameters from radiance spectra in the oxygen A-band of absorption at 0.76 ?m. We show that these parameters can be effectively used to characterize the impact of atmospheric light scattering on carbon dioxide retrieval in the atmospheric carbon dioxide (CO2) absorption bands at 1.6 ?m and 2.0 ?m. The threshold for PPDF parameters is set so that the optical-path modification is negligible, and these settings are recommended as a basic guideline for selecting the clearest atmospheric scenarios. An example of data processing for six global GOSAT repeat cycles in April and July 2009 shows that PPDF-based selection efficiently removes CO2 retrieval biases associated with subvisible cirrus and sandstorm activities.

Oshchepkov, Sergey; Bril, Andrey; Maksyutov, Shamil; Yokota, Tatsuya

2011-07-01

241

Geodesy by radio interferometry: Effects of atmospheric modeling errors on estimates of baseline length  

Microsoft Academic Search

Analysis of very long baseline interferometry data indicates that systematic errors in prior estimates of baseline length, of order 5 cm for  8000-km baselines, were due primarily to mismodeling of the electrical path length of the troposphere and mesosphere (\\

J. L. Davis; T. A. Herrinch; I. I. Shapiro; A. E. E. Rollers; G. Elgered

1985-01-01

242

Cane Technique: Modifying the Touch Technique for Full Path Coverage  

ERIC Educational Resources Information Center

Measurements of height of cane hand, cane length, step size, and forearm length of 17 cane using blind (14-21 years old) Ss were taken for the purpose of testing the hypothesis that the touch technique does not provide 100 percent path coverage. (Author)

Uslan, Mark M.

1978-01-01

243

Multiline absorption spectroscopy for methane gas detection  

Microsoft Academic Search

A multiline absorption spectroscopy technique was investigated based on the single-line absorption spectroscopy technique. An open-path methane-detecting system was designed. An LED was used as a broadband source, and a Fabry-Perot interferometer whose transmission peaks matched the methane R-branch absorption lines was used to enhance the detectable sensitivity. We demonstrate a minimum-detectable concentration of 7600 ± 10% ppm (parts per

Yi Qu; Zhi-Hui Kang; Yun Jiang; Jin-Yue Gao

2006-01-01

244

Investigation of Diode Pumped Alkali Laser atmospheric transmission using tunable diode laser absorption spectroscopy  

NASA Astrophysics Data System (ADS)

A field deployable ruggedized tunable diode laser absorption spectroscopy (TDLAS) device fiber coupled to a pair of 12.5" Ritchey-Chretien telescopes was used to study atmospheric propagation for open path lengths of 100 to 1,000 meters to estimate atmospheric transmission at key High Energy Laser (HEL) wavelengths. The potassium (K) version of the Diode Pumped Alkali Laser (DPAL) operates in between two of the sharp oxygen rotational features in the PP and the PQ branches. The device can be used to observe rotational temperature, concentrations, and atmospheric pressure. Molecular oxygen absorption lines near the potassium, and water vapor absorption lines near the rubidium and cesium DPALs at wavelengths near 770 nm, 795 nm, and 895 nm, respectively, were investigated using the Line-by-Line Radiative Transfer Model (LBLRTM) with the High Energy Laser End-to-End Simulation (HELEEOS). A tunable diode laser absorption spectroscopy (TDLAS) device was used to anchor simulations to actual outdoor atmospheric open-path collections. The implications of different laser gain cell configurations in DPAL systems are discussed, including spectral lineshape and atmospheric transmittance and are compared to existing high power laser systems.

Rice, Christopher A.

245

On the Shortest Path to Solve the Problem Based on Vague Sets  

Microsoft Academic Search

The shortest path problem (SPP) is currently being greatly studied in fuzzy sets and systems area. Previously published algorithms and methods for the fuzzy shortest path problem based on discrete or continuous types fuzzy sets of fuzzy arc lengths. However, to present an arc real length in vague set is more reasonable than in fuzzy set. Moreover,carrying on various kinds

Yaling Dou; Hongxing Guo; Jingli Zhou

2008-01-01

246

Two-photon absorption and first nonlinear optical properties of ionic octupolar molecules: structure-function relationships and solvent effects.  

PubMed

We present a quantum-chemical analysis of the two-photon absorption properties and first hyperpolarizabilities of a series of ionic octupolar molecules and a comparison of their characteristics with corresponding neutral molecules. The molecular geometries are obtained via BL3YP/6-31G (d,p) level optimization including the SCRF/PCM approach, while the dynamic NLO and two-photon absorption properties are calculated with the ZINDO/CV method including solvent effects. The effects of donor or acceptor substitution and elongation of the conjugation path length are established to demonstrate the engineering guidelines for enhancing two-photon absorption cross section and molecular optical nonlinearities. It is found that the chain length dependence of the two-photon absorption and the first nonlinearity follow the same trend, displaying a saturation limit at n = 5. The solvent induced effect on the two-photon absorption and NLO properties are studied using the ZINDO/CV/SCRF method. It has been observed that two-photon absorption and the first nonlinearity peaks at epsilon approximately = 20 and then decreases slightly, approaching saturation. We also compare our theoretical findings with the experimental results wherever available in the literature. PMID:16834021

Ray, Paresh Chandra; Leszczynski, Jerzy

2005-08-01

247

Sampling diffusive transition paths.  

PubMed

The authors address the problem of sampling double-ended diffusive paths. The ensemble of paths is expressed using a symmetric version of the Onsager-Machlup formula, which only requires evaluation of the force field and which, upon direct time discretization, gives rise to a symmetric integrator that is accurate to second order. Efficiently sampling this ensemble requires avoiding the well-known stiffness problem associated with the sampling of infinitesimal Brownian increments of the path, as well as a different type of stiffness associated with the sampling of the coarse features of long paths. The fine-feature sampling stiffness is eliminated with the use of the fast sampling algorithm, and the coarse-feature sampling stiffness is avoided by introducing the sliding and sampling (S&S) algorithm. A key feature of the S&S algorithm is that it enables massively parallel computers to sample diffusive trajectories that are long in time. The authors use the algorithm to sample the transition path ensemble for the structural interconversion of the 38-atom Lennard-Jones cluster at low temperature. PMID:17444696

Miller, Thomas F; Predescu, Cristian

2007-04-14

248

Oscillatory fracture paths in thin elastic sheets  

NASA Astrophysics Data System (ADS)

We report results on a novel mode of quasi-static oscillatory crack propagation in thin elastic sheets [1]. A cutting tip of width w is perpendicularly driven through a thin brittle polymer film, held along its lateral boundaries, that progressively cuts the material as it advances [2]. For thin enough cutting tips (w < wc with w_c=0.2mm) the fracture path is straight. However, for w > w_c, the crack follows a well defined and highly reproducible oscillatory path. The amplitude and wavelength of the oscillatory crack paths scale linearly with the width of the cutting tip over a wide range of length scales but are independent of both of the cutting speed and the width of the sheet. We develop a model for this phenomena, based on the coupling between crack propagation and out-of-plane deformations of the film, which exhibits behaviour in remarkably good agreement with the experimental crack paths. [1] B. Roman, P.M. Reis, B. Audoly , S. DeVilliers, V. Viguié, D. Vallet, Oscillatory fracture paths in thin elastic sheets C.R. de Mecanique, vol 331, no 12, p. 811--816 (2003). [2] http://www.lmm.jussieu.fr/platefracture/

Reis, Pedro Miguel; Audoly, Basile; Roman, Benoit

2004-03-01

249

Absorption of planar waves in a draining bathtub  

SciTech Connect

We present an analysis of the absorption of acoustic waves by a black hole analogue in (2+1) dimensions generated by a fluid flow in a draining bathtub. We show that the low-frequency absorption length is equal to the acoustic hole circumference and that the high-frequency absorption length is 4 times the ergoregion radius. For intermediate values of the wave frequency, we compute the absorption length numerically and show that our results are in excellent agreement with the low- and high-frequency limits. We analyze the occurrence of superradiance, manifested as negative partial absorption lengths for corotating modes at low frequencies.

Oliveira, Ednilton S.; Dolan, Sam R.; Crispino, Luis C. B. [Instituto de Fisica, Universidade de Sao Paulo, CP 66318, 05315-970, Sao Paulo, SP (Brazil) and Faculdade de Fisica, Universidade Federal do Para, 66075-110, Belem, Para (Brazil); School of Mathematics, University of Southampton, Highfield, Southampton SO17 1BJ (United Kingdom); Faculdade de Fisica, Universidade Federal do Para, 66075-110, Belem, Para (Brazil)

2010-06-15

250

Mobile transporter path planning  

NASA Technical Reports Server (NTRS)

The use of a genetic algorithm (GA) for solving the mobile transporter path planning problem is investigated. The mobile transporter is a traveling robotic vehicle proposed for the space station which must be able to reach any point of the structure autonomously. Elements of the genetic algorithm are explored in both a theoretical and experimental sense. Specifically, double crossover, greedy crossover, and tournament selection techniques are examined. Additionally, the use of local optimization techniques working in concert with the GA are also explored. Recent developments in genetic algorithm theory are shown to be particularly effective in a path planning problem domain, though problem areas can be cited which require more research.

Baffes, Paul; Wang, Lui

1990-01-01

251

Self Absorption Effects on the Detection of Hg and Cd in an Atmospheric Microwave Sustained Plasma  

NASA Astrophysics Data System (ADS)

The detection limits for cadmium and mercury at the 228.8 nm and 253.65 nm transitions, respectively, in an atmospheric 1.5 kW, 2.45 GHz microwave sustained plasma has been found to depend on the path length between the plasma and the detection system. Atomic emission spectroscopy of such microwave plasma is under development as a real-time monitor of EPA regulated hazardous metals in smokestacks. Measurements of the detection limits for axial and radial side views of the discharge show a clear increase of the axial detection limit. Self absorption by unexcited cadmium and mercury along the longer turbulent axial propagation path is shown to be responsible for the increase of the detection limits.

Hadidi, Kamal; Woskov, Paul; Flores, Guadalupe; Green, Karen; Thomas, Paul

1999-10-01

252

Absorption Optics of Aqueous Foams  

NASA Astrophysics Data System (ADS)

Aqueous foams are composed of gas bubbles packed together in a small volume of soapy water. The large number of gas-liquid interfaces in foams results in very strong scattering of light, which explains the opaque nature of conventional aqueous foams such as shaving foams and mousse. For dry foams, the interfaces can take the following three forms: the soap films where two bubbles meet, the triangular plateau borders where three soap films meet and the vertices where four plateau borders meet. Previous experiments have shown that most of the scattering occurs from the plateau borders 2,3 and the transport mean free path of light (l*), the bubble radius (R) and the liquid fraction of foam (epsilon) is related through the relation l*=R/(epsilon0.5). To understand the reflection and scattering of light at the gas-bubble interfaces, we study the absorption of photons in the liquid network as a function of the foam absorptivity. We do this to confirm if the time spent by the photons in the liquid phase is proportional to the liquid fraction of the foam. Our results indicate that for a specific range of liquid fractions (0.05 is less than e is less than 0.1), the photons seem to get trapped in the liquid network. This result is independent of the absorptivity of the foam and leads us to conclude that under appropriate conditions, an aqueous foam behaves very much like an optical fiber network. Aqueous foam is generated in the lab by the method of turbulent mixing of N2 gas with a jet of alpha-olefin-sulfonate (AOS) solution. The foam has been made absorbing by dissolving small quantities of rhodamine dye (R = 0.005 g/l, R = 0.01 g/l and R = 0.0124 g/l) in the AOS solution. The transmission of photons through the foams of liquid fractions 0.0297 is less than e is less than 0.35 has been studied using Diffuse Transmission Spectroscopy (DTS). For each liquid fraction, the transport mean free path l* (the length over which the photon travels before it gets completely randomized) has been estimated from DTS experiments on foams with R = 0.0 g/l. In the liquid fraction range 0.05 is less than epsilon is less than 0.1, the ratio is found to be lower than the theoretical prediction. The deviation of the experimental estimates of (la)foam/(la)soln from the solid line leads us to conclude that at 0.05 is less than e is less than 0.1, the foam behaves like an optical fiber network with the photons getting trapped in and then channeled through the plateau borders. We believe that our results may be explained quantitatively by relating the reflectance of light at liquid-gas and gas-liquid interfaces to the average angles of incidence at these interfaces. Additional information is included in the original extended abstract.

Bandyopadhyay, Ranjini; Gittings, Alex; Durian, D. J.

2002-11-01

253

Concentration Measurement of Gas Embedded in Scattering Media by Employing Absorption and Time-Resolved Laser Spectroscopy  

NASA Astrophysics Data System (ADS)

Diode-laser-based absorption spectroscopy for the evaluation of embedded gas concentrations in porous materials is demonstrated in measurements of molecular oxygen dispersed throughout scattering polystyrene foam, used here as a generic test material. The mean path length of light scattered in the material is determined with the temporal characteristics of the radiation transmitted through the sample. This combined with sensitive gas-absorption measurements employing wavelength-modulation spectroscopy yields an oxygen concentration in polystyrene foam of 20.4% corresponding to a foam porosity of 98%, which is consistent with manufacturing specifications. This feasibility study opens many possibilities for quantitative measurements by using the method of gas-in-scattering-media absorption spectroscopy.

Somesfalean, Gabriel; Sjöholm, Mikael; Alnis, Janis; Klinteberg, Claes Af; Andersson-Engels, Stefan; Svanberg, Sune

2002-06-01

254

Concentration measurement of gas embedded in scattering media by employing absorption and time-resolved laser spectroscopy.  

PubMed

Diode-laser-based absorption spectroscopy for the evaluation of embedded gas concentrations in porous materials is demonstrated in measurements of molecular oxygen dispersed throughout scattering polystyrene foam, used here as a generic test material. The mean path length of light scattered in the material is determined with the temporal characteristics of the radiation transmitted through the sample. This combined with sensitive gas-absorption measurements employing wavelength-modulation spectroscopy yields an oxygen concentration in polystyrene foam of 20.4% corresponding to a foam porosity of 98%, which is consistent with manufacturing specifications. This feasibility study opens many possibilities for quantitative measurements by using the method of gas-in-scattering-media absorption spectroscopy. PMID:12078678

Somesfalean, Gabriel; Sjöholm, Mikael; Alnis, Janis; af Klinteberg, Claes; Andersson-Engels, Stefan; Svanberg, Sune

2002-06-20

255

Measuring Thermodynamic Length  

NASA Astrophysics Data System (ADS)

Thermodynamic length is a metric distance between equilibrium thermodynamic states. Among other interesting properties, this metric asymptotically bounds the dissipation induced by a finite time transformation of a thermodynamic system. It is also connected to the Jensen-Shannon divergence, Fisher information, and Rao’s entropy differential metric. Therefore, thermodynamic length is of central interest in understanding matter out of equilibrium. In this Letter, we will consider how to define thermodynamic length for a small system described by equilibrium statistical mechanics and how to measure thermodynamic length within a computer simulation. Surprisingly, Bennett’s classic acceptance ratio method for measuring free energy differences also measures thermodynamic length.

Crooks, Gavin E.

2007-09-01

256

Measuring Thermodynamic Length  

SciTech Connect

Thermodynamic length is a metric distance between equilibrium thermodynamic states. Among other interesting properties, this metric asymptotically bounds the dissipation induced by a finite time transformation of a thermodynamic system. It is also connected to the Jensen-Shannon divergence, Fisher information, and Rao's entropy differential metric. Therefore, thermodynamic length is of central interestin understanding matter out of equilibrium. In this Letter, we will consider how to denethermodynamic length for a small system described by equilibrium statistical mechanics and how to measure thermodynamic length within a computer simulation. Surprisingly, Bennett's classic acceptance ratio method for measuring free energy differences also measures thermodynamic length.

Crooks, Gavin E

2007-09-07

257

Following the Path  

ERIC Educational Resources Information Center

This article profiles Diane Stanley, an author and illustrator of children's books. Although she was studying to be a medical illustrator in graduate school, Stanley's path changed when she got married and had children. As she was raising her children, she became increasingly enamored of the colorful children's books she would check out of the…

Rodia, Becky

2004-01-01

258

Path to the Profession  

ERIC Educational Resources Information Center

A growing number of institutions are being more deliberate about bringing in fundraisers who fit the culture of the development department and about assessing skills and providing training that fill specific needs. Development shops are paying more attention to cultivating their staffs, staying attuned to employees' needs and creating career paths

Coleman, Toni

2012-01-01

259

Gas path seal  

NASA Technical Reports Server (NTRS)

A gas path seal suitable for use with a turbine engine or compressor is described. A shroud wearable or abradable by the abrasion of the rotor blades of the turbine or compressor shrouds the rotor bades. A compliant backing surrounds the shroud. The backing is a yieldingly deformable porous material covered with a thin ductile layer. A mounting fixture surrounds the backing.

Bill, R. C.; Johnson, R. D. (inventors)

1979-01-01

260

An Unplanned Path  

ERIC Educational Resources Information Center

The authors elucidate what they saw as three important challenges to overcome along the path to becoming elementary school mathematics teacher leaders: marginal interest in math, low self-confidence, and teaching in isolation. To illustrate how these challenges were mitigated, they focus on the stories of two elementary school teachers--Laura and…

McGarvey, Lynn M.; Sterenberg, Gladys Y.; Long, Julie S.

2013-01-01

261

CareerPath  

NSDL National Science Digital Library

CareerPath offers a searchable index of employment ads from six major newspapers: The Boston Globe, Chicago Tribune, Los Angeles Times, The New York Times, The San Jose Mercury News, and The Washington Post. The total ads available on October 21 was 21,442. The site is attractive and easy to use.

262

Ship-based liquid water path estimates in marine stratocumulus  

Microsoft Academic Search

We examine liquid water paths (LWPs) derived from ship-based microwave radiometer brightness temperature (Tb) measurements collected within southeastern Pacific stratocumulus at 20°S, 85°W in October 2001. The boundary layer was typically well mixed and overcast. Three gaseous absorption models and two liquid dielectric models are evaluated. Total differences in retrieved LWP attributable to microwave absorption model differences are 10–25 g

Paquita Zuidema; Edgeworth R. Westwater; Chris Fairall; Duane Hazen

2005-01-01

263

Ship-based liquid water path estimates in marine stratocumulus  

Microsoft Academic Search

We examine liquid water paths (LWPs) derived from ship-based microwave radiometer brightness temperature (Tb) measurements collected within southeastern Pacific stratocumulus at 20°S, 85°W in October 2001. The boundary layer was typically well mixed and overcast. Three gaseous absorption models and two liquid dielectric models are evaluated. Total differences in retrieved LWP attributable to microwave absorption model differences are 10-25 g

Paquita Zuidema; Edgeworth R. Westwater; Chris Fairall; Duane Hazen

2005-01-01

264

Apparatus and method for quantitative measurement of small differences in optical absorptivity between two samples using differential interferometry and the thermooptic effect  

DOEpatents

An apparatus and method for the measurement of small differences in optical absorptivity of weakly absorbing solutions using differential interferometry and the thermooptic effect have been developed. Two sample cells are placed in each arm of an interferometer and are traversed by colinear probe and heating laser beams. The interrogation probe beams are recombined forming a fringe pattern, the intensity of which can be related to changes in optical path length of these laser beams through the cells. This in turn can be related to small differences in optical absorptivity which results in different amounts of sample heating when the heating laser beams are turned on, by the fact that the index of refraction of a liquid is temperature dependent. A critical feature of this invention is the stabilization of the optical path of the probe beams against drift. Background (solvent) absorption can then be suppressed by a factor of approximately 400. Solute absorptivities of about 10[sup [minus]5] cm[sup [minus]1] can then be determined in the presence of background absorptions in excess of 10[sup [minus]3] cm[sup [minus]1]. In addition, the smallest absorption measured with the instant apparatus and method is about 5 [times] 10[sup [minus]6] cm[sup [minus]1]. 6 figs.

Cremers, D.A.; Keller, R.A.

1984-05-08

265

Fast orthogonal transforms and generation of Brownian paths  

PubMed Central

We present a number of fast constructions of discrete Brownian paths that can be used as alternatives to principal component analysis and Brownian bridge for stratified Monte Carlo and quasi-Monte Carlo. By fast we mean that a path of length n can be generated in O(nlog(n)) floating point operations. We highlight some of the connections between the different constructions and we provide some numerical examples.

Leobacher, Gunther

2012-01-01

266

A Complete Approximation Algorithm for Shortest Bounded-Curvature Paths  

Microsoft Academic Search

We address the problem of finding a polynomial-time approximation scheme for shortest bounded-curvature paths in the presence\\u000a of obstacles. Given an arbitrary environment E\\\\mathcal{E} consisting of polygonal obstacles, two feasible configurations, a length ?, and an approximation factor ?, our algorithm either (i) verifies that every feasible bounded-curvature path joining the two configurations is longer than\\u000a ? or (ii) constructs

Jonathan Backer; David Kirkpatrick

2008-01-01

267

Geodesics Between 3D Closed Curves Using Path-Straightening  

Microsoft Academic Search

In order to analyze shapes of continuous curves in R3, we parameterize them by arc-length and represent them as curves on a unit two-sphere. We identify the subset denoting the closed curves, and study its difierential geometry. To compute geodesics between any two such curves, we connect them with an arbitrary path, and then iteratively straighten this path using the

Eric Klassen; Anuj Srivastava

2006-01-01

268

Effect of radiometric errors on accuracy of temperature-profile measurement by spectral scanning using absorption-emission pyrometry  

NASA Technical Reports Server (NTRS)

The spectral-scanning method may be used to determine the temperature profile of a jet- or rocket-engine exhaust stream by measurements of gas radiation and transmittance, at two or more wavelengths. A single, fixed line of sight is used, using immobile radiators outside of the gas stream, and there is no interference with the flow. At least two sets of measurements are made, each set consisting of the conventional three radiometric measurements of absorption-emission pyrometry, but each set is taken over a different spectral interval that gives different weight to the radiation from a different portion of the optical path. Thereby, discrimination is obtained with respect to location along the path. A given radiometric error causes an error in computed temperatures. The ratio between temperature error and radiometric error depends on profile shape, path length, temperature level, and strength of line absorption, and the absorption coefficient and its temperature dependency. These influence the choice of wavelengths, for any given gas. Conditions for minimum temperature error are derived. Numerical results are presented for a two-wavelength measurement on a family of profiles that may be expected in a practical case of hydrogen-oxygen combustion. Under favorable conditions, the fractional error in temperature approximates the fractional error in radiant-flux measurement.

Buchele, D. R.

1972-01-01

269

A fuzzy shortest path with the highest reliability  

NASA Astrophysics Data System (ADS)

This paper concentrates on a shortest path problem on a network where arc lengths (costs) are not deterministic numbers, but imprecise ones. Here, costs of the shortest path problem are fuzzy intervals with increasing membership functions, whereas the membership function of the total cost of the shortest path is a fuzzy interval with a decreasing linear membership function. By the max-min criterion suggested in [R.E. Bellman, L.A. Zade, Decision-making in a fuzzy environment, Management Science 17B (1970) 141-164], the fuzzy shortest path problem can be treated as a mixed integer nonlinear programming problem. We show that this problem can be simplified into a bi-level programming problem that is very solvable. Here, we propose an efficient algorithm, based on the parametric shortest path problem for solving the bi-level programming problem. An illustrative example is given to demonstrate our proposed algorithm.

Keshavarz, Esmaile; Khorram, Esmaile

2009-08-01

270

Stratospheric measurements of continuous absorption near 2400 per cm  

NASA Astrophysics Data System (ADS)

Measurements of continuous absorption near 2400 per cm by N2 and CO2 over long path lengths in the lower stratosphere are presented. The continua were measured in a stratospheric solar spectrum obtained during sunset with a balloon-borne Michelson interferometer in the 2380-2500 per cm region, and transmittances were calculated by ratioing the amplitudes to those of a high-sun spectrum in order to eliminate the wavelength dependence of the measured flux. Comparison of the measured transmittances with those calculated for a multilayered atmospheric model using laboratory absorption measurements results in a fair agreement, and reveals the primary component of the absorption throughout most of the range to be N2, with the CO2 contribution equal to that of N2 only at the CO2 band head. In this region, the shape of the continuum is very sensitive to the sub-Lorentzian line shape assumed in the calculations, and so, if the shape of the N2 continuum at low temperatures can be determined through laboratory measurements, may be used to infer air-broadened far-wing CO2 line shape.

Rinsland, C. P.; Smith, M. A. H.; Russell, J. M., III; Park, J. H.; Farmer, C. B.

1981-12-01

271

Non uniform random generation of generalized Motzkin paths  

Microsoft Academic Search

We consider in this paper the class M\\u000a \\u000a k\\u000a \\u000a \\u000a n\\u000a of generalized Motzkin paths of length n, that is, lattice paths using steps (1,1), (1,?1), (k,0), where k is a fixed positive integer, starting at the origin (0,0), running above the x-axis, and ending at (n,0). The area is the region bounded by the path and the x-axis. We first

Srecko Brlek; Elisa Pergola; Olivier Roques

2006-01-01

272

Optimal Path and Minimal Spanning Trees in Random Weighted Networks  

NASA Astrophysics Data System (ADS)

We review results on the scaling of the optimal path length in random networks with weighted links or nodes. In strong disorder we find that the length of the optimal path increases dramatically compared to the known small world result for the minimum distance. For Erd\\H{o}s-R\\'enyi (ER) and scale free networks (SF), with parameter $\\lambda$ ($\\lambda >3$), we find that the small-world nature is destroyed. We also find numerically that for weak disorder the length of the optimal path scales logaritmically with the size of the networks studied. We also review the transition between the strong and weak disorder regimes in the scaling properties of the length of the optimal path for ER and SF networks and for a general distribution of weights, and suggest that for any distribution of weigths, the distribution of optimal path lengths has a universal form which is controlled by the scaling parameter $Z=\\ell_{\\infty}/A$ where $A$ plays the role of the disorder strength, and $\\ell_{\\infty}$ is the length of the optimal path in strong disorder. The relation for $A$ is derived analytically and supported by numerical simulations. We then study the minimum spanning tree (MST) and show that it is composed of percolation clusters, which we regard as "super-nodes", connected by a scale-free tree. We furthermore show that the MST can be partitioned into two distinct components. One component the {\\it superhighways}, for which the nodes with high centrality dominate, corresponds to the largest cluster at the percolation threshold which is a subset of the MST. In the other component, {\\it roads}, low centrality nodes dominate. We demonstrate the significance identifying the superhighways by showing that one can improve significantly the global transport by improving a very small fraction of the network.

Braunstein, Lidia A.; Wu, Zhenhua; Chen, Yiping; Buldyrev, Sergey V.; Kalisky, Tomer; Sreenivasan, Sameet; Cohen, Reuven; López, Eduardo; Havlin, Shlomo; Stanley, H. Eugene

273

Circumference and Arc Length  

NSDL National Science Digital Library

This unit will introduce you to circumference of a circle, and how to find the measurement of the edge of a piece of pizza! (Arc length!) Ok. Let's make sure you remember circumference of a circle, you know, the distance around a circle? Click on the following link and take notes! Circle Circumference Now we can use that to find the arc length, or the length of the crust part of the edge of a pizza! Take notes: Arcs in Circles Now, let's ...

Neubert, Mrs.

2011-03-24

274

Tunable path centrality: Quantifying the importance of paths in networks  

NASA Astrophysics Data System (ADS)

Centrality is a fundamental measure in network analysis. Specifically, centrality of a path describes the importance of the path with respect to the remaining part of the network. In this paper, we propose a tunable path centrality (TPC) measure, which quantifies the centrality of a path by integrating the path degree (PD) (number of neighbors of the path) and the path bridge (PB) (number of bridges in the path) with a control parameter ?. Considering the complexity of large-scale and dynamical topologies of many real-world networks, both PD and PB are computed with only the local topological structure of a path. We demonstrate the distribution of the three path centralities (TPC, PD and PB) in computer-generated networks and real-world networks. Furthermore, we apply the three path centralities to the network fragility problem, and exploit the distribution of the optimal control parameter ? through simulation and analysis. Finally, the simulation results show that generally TPC is more efficient than PD and PB in the network fragility problem. These path centralities are also applicable in many other network problems including spread, control, prediction and so on.

Pu, Cun-Lai; Cui, Wei; Yang, Jian

2014-07-01

275

Note: Cavity enhanced self-absorption spectroscopy: A new diagnostic tool for light emitting matter  

NASA Astrophysics Data System (ADS)

We introduce the concept of Cavity Enhanced Self-Absorption Spectroscopy (CESAS), a new sensitive diagnostic tool for analyzing light-emitting samples. The technique works without an additional light source and its implementation is straight forward. In CESAS, a sample (plasma, flame, or combustion source) is located in an optically stable cavity consisting of two high reflectivity mirrors, and here it acts both as light source and absorbing medium. A modest portion of the emitted light is trapped inside the cavity, making 104-105 cavity round trips while crossing the sample and an artificial augmentation of the path length of the absorbing medium occurs as the light transverses the cavity. Light leaking out of the cavity simultaneously provides emission and absorption features. The performance is illustrated by CESAS results on supersonically expanding pulsed hydrocarbon plasma. We expect CESAS to become a generally applicable analytical tool for real time and in situ diagnostics.

Walsh, Anton J.; Zhao, Dongfeng; Linnartz, Harold

2013-02-01

276

Spatially resolved absorption spectroscopy of bio - assemblies on a micron scale  

NASA Astrophysics Data System (ADS)

We have developed a novel approach to measure optical absorption spectra with spatial resolution at the micron scale. The setup employs a confocal microscope with a broadband white light excitation beam in transmission geometry. An aperture controls the amount of illuminating light and localizes the area of excitation. The setup is employed to measure the absorption spectrum of single red blood cells (˜ 7 microns diameter) under solution conditions. The spatial resolution in the lateral direction is found to be better than three microns. Through measurements of the transmitted intensity in met- myoglobin and calcein dye nanoliter solutions at fixed path lengths, we establish that the absorbance varies linearly with concentration over the range from 0.1 to 2 mM. Our instrument enables measurements of spatial variations in the optical density of small samples and may find application in monitoring biological assemblies at the single cell level.

Arora, Silki; Mauser, Jennifer; Chakrabarti, Debopam; Schulte, Alfons

2011-03-01

277

Lander flight path analysis  

NASA Technical Reports Server (NTRS)

The primary functions of the Lander Flight Path Analysis Team (LFPAT) were to (1) design the Viking Lander (VL) descent trajectory and compute the descent guidance parameters for command transmission to the Viking Lander and Viking Orbiter (VO), (2) reconstruct the VL trajectory from separation to touchdown using data transmitted from the VL to Earth via the VO during descent, and (3) predict the VL/VO relay link system performance during descent and post touchdown. The preflight VL capability, the history of proposed descent trajectory designs as the site selection process evolved, and the final trajectory design and guidance parameters for each vehicle are addressed along with the trajectory reconstruction process, including the overall reconstructed VL flight path summary and a detailed discussion of the entry trajectory and atmosphere reconstruction results. The postland relay link prediction function is discussed.

Euler, E. A.; Adams, G. L.; Hopper, F. W.

1979-01-01

278

Leg Length Inequality  

PubMed Central

Leg length inequality, a common abnormality, can cause musculoskeletal pain, scoliosis, and osteoarthritis of the hip. Seven percent of the asymptomatic population has a leg length inequality greater than 12 mm; the incidence is considerably higher (13%-22%) in individuals complaining of low back pain. Correction can usually be accomplished by shoe modification, and can result in dramatic relief of pain. Leg length inequality of more than half an inch is considered clinically significant. Leg length measurement should be routine in all patients complaining of low back pain, hip pain, and atypical flank and lower quadrant pain. Correction might prove very cost-effective.

Sharpe, Colin R.

1983-01-01

279

The effects of random path fluctuations on the accuracy of laser ranging systems. [statistical analysis of atmospheric turbulence effects on optical paths  

NASA Technical Reports Server (NTRS)

The precision of satellite ranging systems, limited in part by atmospheric refraction and scattering, is examined. The effects of atmospheric turbulence on the accuracy of single color and multicolor ranging systems is discussed. The statistical characteristics of the random path length fluctuations induced by turbulence are examined. Correlation and structure functions are derived using several proposed models for the variations of the optical path length. For single color systems it is shown that the random path length fluctuations can limit the accuracy of a range measurement to a few centimeters. Two color systems can partially correct for the random path fluctuations so that in most cases their accuracy is limited to a few millimeters. However, at low elevation angles and over long horizontal paths two color systems can also have errors approaching a few centimeters.

Gardner, C. S.; Rao, N. N.

1975-01-01

280

OPEN PATH AMBIENT MEASUREMENTS OF POLLUTANTS WITH A DOAS SYSTEM  

EPA Science Inventory

A differential optical absorption spectrometer (DOAS) has been in operation since August 1991 at the U.S. EPA in RTP, NC. he analyzer unit is located in an environmentally-controlled shelter in the EPA parking lot. our separate open optical paths have been established, ranging fr...

281

Laser absorption in microdroplet plasmas  

NASA Astrophysics Data System (ADS)

We present experimental measurements of the absorption of ultrashort laser pulses by 15 ?m diameter methanol microdroplets. The droplet absorbs upto 70% of the incidence laser energy in the presence of a prepulse at intensities of about 1.5×1016 W cm-2. In the absence of a prepulse, the absorption is only about 20%. Simultaneous measurements of X-ray yield (12 keV to 350 keV) and the absorption in the droplet plasma, shows that our earlier measurements of efficient generation (Anand M. et al. Appl. Phys. Lett., 88 (2006) 181111) of hard X-rays from the droplet plasma is due to the increased absorption in the droplets in the presence of optimum prepulse. 1-D PIC simulations, mimicing the mass-limited droplet density profile, demonstrate the effectiveness of the large scale-length droplet plasma in providing optimal conditions for resonant laser absorption energy and generation of hot electrons.

Anand, M.; Gibbon, P.; Krishnamurthy, M.

2007-10-01

282

Finding the k Shortest Paths  

Microsoft Academic Search

We describe algorithms for finding the k shortest paths connectinga given pair of vertices in a digraph (allowing cycles). Our algorithmsoutput an implicit representation of the paths as an unordered setin time O(m + n log n + k). The paths can be output in order bylength in total time O(m + n log n + k log k). We

David Eppstein

1994-01-01

283

Neandertal clavicle length.  

PubMed

The Late Pleistocene archaic humans from western Eurasia (the Neandertals) have been described for a century as exhibiting absolutely and relatively long clavicles. This aspect of their body proportions has been used to distinguish them from modern humans, invoked to account for other aspects of their anatomy and genetics, used in assessments of their phylogenetic polarities, and used as evidence for Late Pleistocene population relationships. However, it has been unclear whether the usual scaling of Neandertal clavicular lengths to their associated humeral lengths reflects long clavicles, short humeri, or both. Neandertal clavicle lengths, along with those of early modern humans and latitudinally diverse recent humans, were compared with both humeral lengths and estimated body masses (based on femoral head diameters). The Neandertal do have long clavicles relative their humeri, even though they fall within the ranges of variation of early and recent humans. However, when scaled to body masses, their humeral lengths are relatively short, and their clavicular lengths are indistinguishable from those of Late Pleistocene and recent modern humans. The few sufficiently complete Early Pleistocene Homo clavicles seem to have relative lengths also well within recent human variation. Therefore, appropriately scaled clavicular length seems to have varied little through the genus Homo, and it should not be used to account for other aspects of Neandertal biology or their phylogenetic status. PMID:24616525

Trinkaus, Erik; Holliday, Trenton W; Auerbach, Benjamin M

2014-03-25

284

Simulation run length planning  

Microsoft Academic Search

To design a stochastic simulation experiment, it is helpful to have an estimate of the simulation run lengths required to achieve desired statistical precision. Preliminary estimates of required run lengths can be obtained by approximating the stochastic model of interest by a more elementary Markov model that can be analyzed analytically. When steady-state quantities are to be estimated by sample

Ward Whitt

1989-01-01

285

Wide absorption spectrum measuring methods by DFB-LDs in water vapor detection system  

NASA Astrophysics Data System (ADS)

Two measuring methods of wide absorption spectrum by DFB-LDs are presented in detecting water vapor absorption line. One is subsection scanning method, it takes advantage of wide spectrum tuning range by temperature modulation and fast spectrum tuning speed by current modulation, specifically, this method is realized by dividing a target spectral region into several sections which corresponding to specific temperature of DFB-LD, and scanning every section by current modulation for hundreds times and average the data to raise SNR, combining all sections to get the whole spectrum. An accuracy of 10 ppmv had been obtained in the measurement of water vapor with a 10-cm path length by this method. Another is data fitting method, based on absorption line-shape function, the absorption line can be described by fitting with partial measured data. The fitting absorption line is fitted well with the measured data, and the square of correlation coefficient (R-square) is no less than 0.99.

Liu, Y. N.; Chang, J.; Lian, J.; Wang, Q.; Lv, G. P.; Wang, W. J.; Liu, Z.; Liu, X. Z.; Zhang, S. S.; Wang, Z. L.; Jiang, S.; Zhu, C. G.; Wei, W.; Sun, B. N.

2013-09-01

286

Near-IR diode laser absorption for measurement of tropospheric HO2  

NASA Technical Reports Server (NTRS)

The possibility of using tunable lead salt diode lasers in the infrared for measurement of tropospheric HO2 has been frequently considered. Although the sensitivity of diode laser absorption has been improved through the use of high frequency detection techniques, nature has been unkind in that the HO2 absorption cross sections are weak. Even using the most optimistic assumptions about attainable path length and detectable absorbance, measurement of tropospheric HO2 by diode laser absorption in the mid-IR appears marginal. A possible alternative method for measuring HO2 is by absorption at near-infrared wavelengths. Several absorption bands of HO2 occur in the wavelength region between 1.2 and 1.6 micron due to electronic transitions and overtones of the fundamental vibrational modes. InGaAsP diode lasers operate in this wavelength region and can be used for high resolution spectroscopy in a manner analogous to the lead salt lasers. A diode laser system in the near-IR offers some advantages.

Stanton, Alan C.

1994-01-01

287

APPLYING OPEN-PATH OPTICAL SPECTROSCOPY TO HEAVY-DUTY DIESEL EMISSIONS  

EPA Science Inventory

Non-dispersive infrared absorption has been used to measure gaseous emissions for both stationary and mobile sources. Fourier transform infrared spectroscopy has been used for stationary sources as both extractive and open-path methods. We have applied the open-path method for bo...

288

The path planning of UAV based on orthogonal particle swarm optimization  

NASA Astrophysics Data System (ADS)

To ensure the attack mission success rate, a trajectory with high survivability and accepted path length and multiple paths with different attack angles must be planned. This paper proposes a novel path planning algorithm based on orthogonal particle swarm optimization, which divides population individual and speed vector into independent orthogonal parts, velocity and individual part update independently, this improvement advances optimization effect of traditional particle swarm optimization in the field of path planning, multiple paths are produced by setting different attacking angles, this method is simulated on electronic chart, the simulation result shows the effect of this method.

Liu, Xin; Wei, Haiguang; Zhou, Chengping; Li, Shujing

2013-10-01

289

Pick-a-Path  

NSDL National Science Digital Library

This mobile app (available for both iOS and Android devices) was developed by the National Council of Teachers of Mathematics with funding from Verizon Foundation. The app is based on the Decimal Maze from the popular lesson "Too Big or Too Small". The goal is to help Okta reach the target (maximum, minimum, or a specific value) by choosing a path from the top of the maze to the bottom â adding, subtracting, multiplying and dividing as the player goes. Seven levels with seven puzzles in each level test the player's skills with operation with powers of ten, negative numbers, fractions, decimals, and exponents.

2012-01-01

290

Byrds Flight Path  

NSDL National Science Digital Library

The Ohio State Universitys Library web site notes As a navigational aviator, Byrd pioneered in the technology that would be the foundation for modern polar exploration and investigation. As a decorated and much celebrated hero, Byrd drew popular attention to areas of the world that became focal points of scientific investigation in numerous disciplines. More information about Admiral Richard E. Byrd can be found at (http:--www.lib.ohio-state.edu-arvweb-polar-byrd-byrd.htm). The next animation, #1001, shows Byrds plane as it follows the flight path presented in this animation.

Biddlecome, Tom; Snodgrass, Stuart; Newcombe, Marte; Jezek, Ken

1999-11-08

291

Portage and Path Dependence*  

PubMed Central

We examine portage sites in the U.S. South, Mid-Atlantic, and Midwest, including those on the fall line, a geomorphological feature in the southeastern U.S. marking the final rapids on rivers before the ocean. Historically, waterborne transport of goods required portage around the falls at these points, while some falls provided water power during early industrialization. These factors attracted commerce and manufacturing. Although these original advantages have long since been made obsolete, we document the continuing importance of these portage sites over time. We interpret these results as path dependence and contrast explanations based on sunk costs interacting with decreasing versus increasing returns to scale.

Bleakley, Hoyt; Lin, Jeffrey

2012-01-01

292

JAVA PathFinder  

NASA Technical Reports Server (NTRS)

JPF is an explicit state software model checker for Java bytecode. Today, JPF is a swiss army knife for all sort of runtime based verification purposes. This basically means JPF is a Java virtual machine that executes your program not just once (like a normal VM), but theoretically in all possible ways, checking for property violations like deadlocks or unhandled exceptions along all potential execution paths. If it finds an error, JPF reports the whole execution that leads to it. Unlike a normal debugger, JPF keeps track of every step how it got to the defect.

Mehhtz, Peter

2005-01-01

293

Absorption Spectroscopy  

Microsoft Academic Search

Absorption spectroscopy is one of the most widely used techniques employed for determining the concentrations of absorbing species (chromophores) in solutions. It is a nondestructive technique which biologists and biochemists and now systems biologists use to quantify the cellular components and characteristic parameters of functional molecules. This quantification is most relevant in the context of systems biology. For creating a

Sanjay M. Nilapwar; Maria Nardelli; Hans V. Westerhoff; Malkhey Verma

2011-01-01

294

Length Paradox in Relativity  

ERIC Educational Resources Information Center

Describes a thought experiment using a general analysis approach with Lorentz transformations to show that the apparent self-contradictions of special relativity concerning the length-paradox are really non-existant. (GA)

Martins, Roberto de A.

1978-01-01

295

Length and Elongation Sensor.  

National Technical Information Service (NTIS)

A length and elongation sensor includes an elastomeric optical wave guide and a time domain reflectometer. The elastomeric optical wave guide consists of a urethane outer cladding and an optical gel core. A transparent window is hermetically sealed to the...

L. E. Sansone

1996-01-01

296

Coefficients of Effective Length.  

ERIC Educational Resources Information Center

Under certain conditions, a validity Coefficient of Effective Length (CEL) can produce highly misleading results. A modified coefficent is suggested for use when empirical studies indicate that underlying assumptions have been violated. (Author/BW)

Edwards, Roger H.

1981-01-01

297

Photodeactivation paths in norbornadiene.  

PubMed

The first high level ab initio quantum-chemical calculations of potential energy surfaces (PESs) for low-lying singlet excited states of norbornadiene in the gas phase are presented. The optimization of the stationary points (minima and conical intersections) and the recalculation of the energies were performed using the multireference configuration interaction with singles (MR-CIS) and the multiconfigurational second-order perturbation (CASPT2) methods, respectively. It was shown that the crossing between valence V2 and Rydberg R1 states close to the Franck-Condon (FC) point permits an easy population switch between these states. Also, a new deactivation path in which the doubly excited state with (?3)(2) configuration (DE) has a prominent role in photodeactivation from the R1 state due to the R1/DE and the DE/V1 conical intersections very close to the R1 and DE minima, respectively, was proposed. Subsequent deactivation from the V1 to the ground state goes through an Olivucci-Robb-type conical intersection that adopts a rhombic distorted geometry. The deactivation path has negligible barriers, thereby making ultrafast radiationless decay to the ground state possible. PMID:23553256

Antol, Ivana

2013-06-30

298

Phoenix's Path to Mars  

NASA Technical Reports Server (NTRS)

[figure removed for brevity, see original site] Click on the image for movie of Phoenix's Path to Mars

This artist's animation shows the route NASA's Phoenix Mars Lander took to get from Earth to Mars. The spacecraft's path is shown in yellow, and the orbits of Mars and Earth are shown in red and blue, respectively.

Phoenix was launched from Cape Canaveral Air Force Station, Fla., on Aug. 4, 2007, when Earth and Mars were 195 million kilometers (121 million miles) apart. It will have traveled a total of 679 million kilometers (422 million miles) when it is scheduled to reach Mars on May 25, 2008. At that time, Earth and Mars will be farther apart, at 276 million kilometers (171 million miles).

The Phoenix Mission is led by the University of Arizona, Tucson, on behalf of NASA. Project management of the mission is by NASA's Jet Propulsion Laboratory, Pasadena, Calif. Spacecraft development is by Lockheed Martin Space Systems, Denver

2008-01-01

299

Path ensembles and path sampling in nonequilibrium stochastic systems.  

PubMed

Markovian models based on the stochastic master equation are often encountered in single molecule dynamics, reaction networks, and nonequilibrium problems in chemistry, physics, and biology. An efficient and convenient method to simulate these systems is the kinetic Monte Carlo algorithm which generates continuous-time stochastic trajectories. We discuss an alternative simulation method based on sampling of stochastic paths. Utilizing known probabilities of stochastic paths, it is possible to apply Metropolis Monte Carlo in path space to generate a desired ensemble of stochastic paths. The method is a generalization of the path sampling idea to stochastic dynamics, and is especially suited for the analysis of rare paths which are not often produced in the standard kinetic Monte Carlo procedure. Two generic examples are presented to illustrate the methodology. PMID:17867733

Harland, Ben; Sun, Sean X

2007-09-14

300

pathChirp: Efficient Available Bandwidth Estimation for Network Paths  

Microsoft Academic Search

This paper presents pathChirp, a new active probing tool for estimating the available bandwidth on a communication network path. Based on the concept of ''self-induced congestion,'' pathChirp features an exponential flight pattern of probes we call a chirp. Packet chips offer several significant advantages over current probing schemes based on packet pairs or packet trains. By rapidly increasing the probing

Les

2003-01-01

301

Atmospheric Refraction Path Integrals of Ground-Based Interferometry  

Microsoft Academic Search

One basic effect of the Earth's atmospheric refraction on telescope operation is the reduction of the true zenith angle to the apparent zenith angle, associated with prismatic aberrations due to the dispersion in air. Coherent superposition of star images in ground-based interferometry depends in addition on the optical path length associated with the refracted rays. In a precolumbian model of

Richard J. Mathar

2005-01-01

302

Faster Shortest-Path Algorithms for Planar Graphs  

Microsoft Academic Search

Abstract: We give a linear-time algorithm for single-source shortest paths in planar graphs with nonnegativeedge-lengths. Our algorithm also yields a linear-time algorithm for maximum flow in a planar graphwith the source and sink on the same face.

Monika Rauch Henzinger; Philip N. Klein; Satish Rao; Sairam Subramanian

1997-01-01

303

Finding the K Shortest Loopless Paths in a Network  

Microsoft Academic Search

This paper presents an algorithm for finding the K loopless paths that have the shortest lengths from one node to another node in a network. The significance of the new algorithm is that its computational upper bound increases only linearly with the value of K. Consequently, in general, the new algorithm is extremely efficient as compared with the algorithms proposed

Jin Y. Yen

1971-01-01

304

Finding Shortest Paths on Surfaces Using Level Sets Propagation  

Microsoft Academic Search

We present a new algorithm for determining minimal length paths between two regions on a three dimensional surface. The numerical implementation is based on finding equal geodesic distance contours from a given area. These contours are calculated as zero sets of a bivariate function designed to evolve so as to track the equal distance curves on the given surface. The

Ron Kimmel; Arnon Amir; Alfred M. Bruckstein

1995-01-01

305

Dynamic path planning in sensor-based terrain acquisition  

Microsoft Academic Search

The terrain acquisition problem is formulated as that of continuous motion planning, and no constraints are imposed on obstacle geometry. Two algorithms are described for acquiring planar terrains with obstacles of arbitrary shape. Estimates of the algorithm performance are derived as upper bounds on the lengths of generated paths

V. J. Lumelsky; S. Mukhopadhyay; K. Sun

1990-01-01

306

Recognition of Sensitized Longest Paths in Transition Delay Test  

Microsoft Academic Search

The progress of design and fabrication technologies has led to an increase in small delay failures in systems-on-a-chip. To evaluate the delay testing quality accurately, the authors have already proposed a statistical approach that calculates actual sensitized path lengths that detect small delay defects in the transition delay test. However, the calculation requires a huge amount of CPU time. This

Shuji Hamada; Toshiyuki Maeda; Atsuo Takatori; Yasuyuki Noduyama; Yasuo Sato

2006-01-01

307

Correlations between bond lengths, Tc, and O vibration frequencies: Raman-scattering and infrared-absorption study of the 1:2:1:2 structure (Ca1-yYy)Sr2(Tl0.5Pb0.5)Cu2O7 as a function of doping  

NASA Astrophysics Data System (ADS)

Raman-scattering and infrared-absorption measurements on optical phonons are used to investigate the doping-induced changes in the electronic structure of (Ca1-yYy)Sr2(Tl0.5Pb0.5)Cu2O7 (Tl/Pb-1:2:1:2). In contrast to YBa2Cu3O7-? (YBCO), the doping of the CuO2 planes is achieved by direct substitution of Ca2+ for Y3+ in between the CuO2 planes, enabling the effects of the dynamic out-of-plane charge transfer and doping to be separated. In spite of large changes in Cu to apical-O bond lengths as measured by neutron scattering, we observe no corresponding apical O(2) vibration frequency shifts with doping of the type found in YBCO. Instead, the frequencies of the A1g Raman-active apical O(2) phonon and an A2u IR-active out-of-plane phonon are correlated with the Tc curve.

Mertelj, T.; Mihailovi?, D.; Matacotta, F. C.; Liu, R. S.; Cooper, J. R.; Gameson, I.; Edwards, P. P.

1993-05-01

308

Absorption spectroscopy.  

PubMed

Absorption spectroscopy is one of the most widely used techniques employed for determining the concentrations of absorbing species (chromophores) in solutions. It is a nondestructive technique which biologists and biochemists and now systems biologists use to quantify the cellular components and characteristic parameters of functional molecules. This quantification is most relevant in the context of systems biology. For creating a quantitative depiction of a metabolic pathway, a number of parameters and variables are important and these need to be determined experimentally. This chapter describes the UV-visible absorption spectroscopy used to produce experimental data for bottom-up modeling approaches of systems biology which uses concentrations and kinetic parameters (K(m) and V(max)) of enzymes of metabolic/signaling pathways, intracellular concentrations of metabolites and fluxes. It also briefly describes the application of this technique for quantification of biomolecules and investigating biomolecular interactions. PMID:21943892

Nilapwar, Sanjay M; Nardelli, Maria; Westerhoff, Hans V; Verma, Malkhey

2011-01-01

309

Interactive cutting path analysis programs  

NASA Technical Reports Server (NTRS)

The operation of numerically controlled machine tools is interactively simulated. Four programs were developed to graphically display the cutting paths for a Monarch lathe, Cintimatic mill, Strippit sheet metal punch, and the wiring path for a Standard wire wrap machine. These programs are run on a IMLAC PDS-ID graphic display system under the DOS-3 disk operating system. The cutting path analysis programs accept input via both paper tape and disk file.

Weiner, J. M.; Williams, D. S.; Colley, S. R.

1975-01-01

310

Path planning for virtual bronchoscopy.  

PubMed

We have developed an automated path planning method, which enables virtual bronchoscopic 3D multidetector computed tomography (MDCT) image analysis and follow on image-guided bronchoscopy. The method fundamentals are novel combination of distance transformation and snake-based models. The computation time of our algorithm is faster than similar works and there were no missing or false branches in the final path of airways. The planned path is suitable for quantitative airway analysis and smooth virtual navigation. PMID:17946384

Negahdar, Mohamadreza; Ahmadian, Alireza; Navab, Nassir; Firouznia, Kavous

2006-01-01

311

Method for Veterbi decoding of large constraint length convolutional codes  

NASA Technical Reports Server (NTRS)

A new method of Viterbi decoding of convolutional codes lends itself to a pipline VLSI architecture using a single sequential processor to compute the path metrics in the Viterbi trellis. An array method is used to store the path information for NK intervals where N is a number, and K is constraint length. The selected path at the end of each NK interval is then selected from the last entry in the array. A trace-back method is used for returning to the beginning of the selected path back, i.e., to the first time unit of the interval NK to read out the stored branch metrics of the selected path which correspond to the message bits. The decoding decision made in this way is no longer maximum likelihood, but can be almost as good, provided that constraint length K in not too small. The advantage is that for a long message, it is not necessary to provide a large memory to store the trellis derived information until the end of the message to select the path that is to be decoded; the selection is made at the end of every NK time unit, thus decoding a long message in successive blocks.

Hsu, In-Shek (inventor); Truong, Trieu-Kie (inventor); Reed, Irving S. (inventor); Jing, Sun (inventor)

1988-01-01

312

Handbook of Feynman Path Integrals  

NASA Astrophysics Data System (ADS)

The Handbook of Feynman Path Integrals appears just fifty years after Richard Feynman published his pioneering paper in 1948 entitled "Space-Time Approach to Non-Relativistic Quantum Mechanics", in which he introduced his new formulation of quantum mechanics in terms of path integrals. The book presents for the first time a comprehensive table of Feynman path integrals together with an extensive list of references; it will serve the reader as a thorough introduction to the theory of path integrals. As a reference book, it is unique in its scope and will be essential for many physicists, chemists and mathematicians working in different areas of research.

Grosche, Christian, Steiner, Frank

313

On internodal length.  

PubMed Central

A study has been made of changes in internodal lengths in rat tibial nerves and human sural nerves with age. Myelinated fibre counts on these nerves showed that maximum numbers were reached at an early stage of development. The slope of regression lines relating internodal length to fibre diameter was relatively flat at this stage, but became steeper with increasing age. Maximum internodal length in rat tibial nerve was closely related to growth of the limb bones. Whilst this study confirms that the largest fibres are subjected to hind limb growth for the greatest period, and therefore have the longest internodes, it does not support the generally accepted view that short internodes are the consequence of the later myelination of small fibres, and hence shorter period of extension due to growth. Images Figs. 2-3

Jacobs, J M

1988-01-01

314

Electromagnetic wave absorption properties of composites with ultrafine hollow magnetic fibers  

NASA Astrophysics Data System (ADS)

Ultrafine hollow magnetic fibers were prepared by electroless plating using hydrolyzed polyester fiber as a sacrificial substrate. These hollow fibers can be served for lightweight and efficient electromagnetic (EM) absorbing materials. As observed from SEM and EDS analysis, hollow structures consisting of Ni inner layer and Fe or Fe-Co outer layer were obtained. By introducing Co onto Fe, oxidation of the Fe layer was successfully prevented making it possible to enhance the complex permeability compared to a case in which only Fe was used. Polymeric composites containing the hollow fibers with different weight fractions and fiber lengths were prepared by a simple mixing process. The electromagnetic wave properties of the composites were measured by a vector network analyzer and it was found that the hollow magnetic fibers show a clear resonance peak of the complex permittivity around the X-band range (8-12 GHz) and the resonance frequency strongly depends on the fiber concentration and length. A possible explanation for the unique resonance is that the hollow fibers possess relatively low electrical conductivity and a long mean free path due to their oxidized phase and hollow structure. The calculated EM wave absorption with the measured EM wave properties showed that the composite containing 30 wt% hollow Ni/Fe-Co (7:3) fibers in length of 180 ?m exhibited multiple absorbance peaks resulting in a broad absorption bandwidth of 4.2 GHz. It is obvious that this multiple absorbance is attributed to the resonance characteristic of the composite.

Yi, Jin Woo; Lee, Sang Bok; Kim, Jin Bong; Lee, Sang Kwan; Park, O. Ok

2014-06-01

315

Variable focal length microlenses  

NASA Astrophysics Data System (ADS)

Refractive surface relief microlenses (150 ?m diameter) are immersed in nematic liquid crystal in a cell. Application of a variable voltage across the cell effectively varies the refractive index of the liquid crystal and results in a change of the focal length by the lensmakers formula (E. Hecht, Optics, 2nd edn., Addison-Wesley, Reading, Massachusetts, 1987, p. 138). We describe the cell design and construction and demonstrate a range of focal lengths from +490 to +1000 ?m for 2 to 12 V applied. A diverging lens results when the voltage is lower. Theoretical models are developed to account for some of the observed aberrations.

Commander, L. G.; Day, S. E.; Selviah, D. R.

2000-04-01

316

Kinetic paths, time scale, and underlying landscapes: A path integral framework to study global natures of nonequilibrium systems and networks  

NASA Astrophysics Data System (ADS)

We developed a general framework to quantify three key ingredients for dynamics of nonequilibrium systems through path integrals in length space. First, we identify dominant kinetic paths as the ones with optimal weights, leading to effective reduction of dimensionality or degrees of freedom from exponential to polynomial so large systems can be treated. Second, we uncover the underlying nonequilibrium potential landscapes from the explorations of the state space through kinetic paths. We apply our framework to a specific example of nonequilibrium network system: lambda phage genetic switch. Two distinct basins of attractions emerge. The dominant kinetic paths from one basin to another are irreversible and do not follow the usual steepest descent or gradient path along the landscape. It reflects the fact that the dynamics of nonequilibrium systems is not just determined by potential gradient but also the residual curl flux force, suggesting experiments to test theoretical predictions. Third, we have calculated dynamic transition time scales from one basin to another critical for stability of the system through instantons. Theoretical predictions are in good agreements with wild type and mutant experiments. We further uncover the correlations between the kinetic transition time scales and the underlying landscape topography: the barrier heights along the dominant paths. We found that both the dominant paths and the landscape are relatively robust against the influences of external environmental perturbations and the system tends to dissipate less with less fluctuations. Our general framework can be applied to other nonequilibrium systems.

Wang, Jin; Zhang, Kun; Wang, Erkwang

2010-09-01

317

Anomalous paths in quantum mechanical path-integrals  

NASA Astrophysics Data System (ADS)

We investigate modifications of the discrete-time lattice action, for a quantum mechanical particle in one spatial dimension, that vanish in the naïve continuum limit but which, nevertheless, induce non-trivial effects due to quantum fluctuations. These effects are seen to modify the geometry of the paths contributing to the path-integral describing the time evolution of the particle, which we investigate through numerical simulations. In particular, we demonstrate the existence of a modified lattice action resulting in paths with any fractal dimension, df, between one and two. We argue that df=2 is a critical value, and we exhibit a type of lattice modification where the fluctuations in the position of the particle becomes independent of the time step, in which case the paths are interpreted as superdiffusive Lévy flights. We also consider the jaggedness of the paths, and show that this gives an independent classification of lattice theories.

Grimsmo, Arne L.; Klauder, John R.; Skagerstam, Bo-Sture K.

2013-11-01

318

A path decomposition approach for computing blocking probabilities in wavelength-routing networks  

Microsoft Academic Search

We study a class of circuit-switched wave- length-routing networks with fixed or alternate routing and with random wavelength allocation. We present an iterative path decomposition algorithm to evaluate accurately and efficiently the blocking performance of such networks with and without wave- length converters. Our iterative algorithm analyzes the original network by decomposing it into single-path subsystems. These subsystems are analyzed

Yuhong Zhu; George N. Rouskas; Harry G. Perros

2000-01-01

319

Lengths of Ladybugs  

NSDL National Science Digital Library

In this math lesson, learners explore the concept of using units to measure length. Learners first read "Ladybug on the Move" by Richard Fowler and measure the distance the ladybug travels on each page using yarn. Next, learners make their own "Go Ladybug Go!" books and use lima beans and a ladybug ruler to make and record measurements.

Lessonplans, Utah

2012-09-18

320

Extended Fuel Cycle Length.  

National Technical Information Service (NTIS)

Extended fuel cycle length and burnup are currently offered by Framatome and Fragema in order to satisfy the needs of the utilities in terms of fuel cycle cost and of overall systems cost optimization. We intend to point out the consequences of an increas...

M. Bruyere A. Vallee C. Collette

1986-01-01

321

Optimizing light absorption in a thin-film p-i-n solar cell using a quasi-periodic grating  

NASA Astrophysics Data System (ADS)

A p-i-n solar cell is best suited for strong absorbers with poor collection capabilities. However, the absorption naturally decreases at photon energies close to the electronic bandgap of the semiconductor. We hypothesized that a quasi-periodic surface textures in the role of diffraction gratings at the back contact can efficiently scatter light increasing the optical path length inside the absorber layer. The effect of quasi-periodic corrugated backing metallic contact of various types was studied theoretically. To help optimizing the design of the quasi periodic grating the corresponding canonical problem was considered. The absorption of light was calculated using the rigorous coupled-wave approach. The n- and i-layers consist of isotropic nonhomogeneous multilayered semiconductor.

Atalla, Mahmoud R. M.

2014-03-01

322

Path Analysis: A Brief Introduction.  

ERIC Educational Resources Information Center

Path analysis is presented as a technique that can be used to test on a priori model based on a theoretical conceptualization involving a network of selected variables. This being an introductory source, no previous knowledge of path analysis is assumed, although some understanding of the fundamentals of multiple regression analysis might be…

Carducci, Bernardo J.

323

Data Generation for Path Testing  

Microsoft Academic Search

We present two stochastic search algorithms for generating test cases that execute specified paths in a program. The two algorithms are: a simulated annealing algorithm (SA), and a genetic algorithm (GA). These algorithms are based on an optimization formulation of the path testing problem which include both integer- and real-value test cases. We empirically compare the SA and GA algorithms

Nashat Mansour; Miran Salame

2004-01-01

324

Analysis of Crossing Path Crashes.  

National Technical Information Service (NTIS)

This report defines the problem of crossing path crashes in the United States. This crash type involves one moving vehicle that cuts across the path of another when their initial approach comes from either lateral or opposite directions and they typically...

W. G. Najm J. D. Smith D. L. Smith

2001-01-01

325

British Pathe Newsreels Online  

NSDL National Science Digital Library

British Pathe, one of the oldest media companies in the world, recently made available its entire 3500-hour film archive, covering "news, sport, social history and entertainment from 1896 to 1970." At the Web site, users can search by keyword or try out advanced search, if details such as reel numbers or exact titles are known. Casual users may prefer the "Lucky Dip" search, which provides a random selection of films to see. After a search returns a hit list of films, choices include "Preview Film: a page of stills, with a textual description of the clip;" "Download Now: a free, low resolution clip;" or "Add to basket, to purchase higher resolutions of the film." (A rate card giving prices for low and high resolution clips is provided.) One hint for first-time users, though: if files do not seem to download properly, check your email, because you will be sent the URL to retrieve your film. After just a bit of finagling on our first visit, we watched the Beatles at a water-skiing show, Charlie Chaplin, and Sir Ernest Shackleton and his sled dogs photographed in 1916 on returning from their Antarctic expedition.

2002-01-01

326

Reconfigurable data path processor  

NASA Technical Reports Server (NTRS)

A reconfigurable data path processor comprises a plurality of independent processing elements. Each of the processing elements advantageously comprising an identical architecture. Each processing element comprises a plurality of data processing means for generating a potential output. Each processor is also capable of through-putting an input as a potential output with little or no processing. Each processing element comprises a conditional multiplexer having a first conditional multiplexer input, a second conditional multiplexer input and a conditional multiplexer output. A first potential output value is transmitted to the first conditional multiplexer input, and a second potential output value is transmitted to the second conditional multiplexer output. The conditional multiplexer couples either the first conditional multiplexer input or the second conditional multiplexer input to the conditional multiplexer output, according to an output control command. The output control command is generated by processing a set of arithmetic status-bits through a logical mask. The conditional multiplexer output is coupled to a first processing element output. A first set of arithmetic bits are generated according to the processing of the first processable value. A second set of arithmetic bits may be generated from a second processing operation. The selection of the arithmetic status-bits is performed by an arithmetic-status bit multiplexer selects the desired set of arithmetic status bits from among the first and second set of arithmetic status bits. The conditional multiplexer evaluates the select arithmetic status bits according to logical mask defining an algorithm for evaluating the arithmetic status bits.

Donohoe, Gregory (Inventor)

2005-01-01

327

MACROMOLECULAR ABSORPTION  

PubMed Central

The immature small intestine of neonatal mammals is permeable to gamma globulins as a source of passive immunity. Allegedly, macromolecular absorption ceases when the epithelial cell membrane matures. However, some evidence exists that adult animals retain a limited capacity to transport antigenic and biologically active quantities of large molecules. In this study, the mechanism of absorption of the tracer protein, horseradish peroxidase (HRP), was tested in neonatal and adult rat gut sacs. Transport into serosal fluid was quantitated by enzymatic assay and monitored morphologically by histochemical techniques. A greater transport of HRP was noted in the adult jejunum compared to adult ileum and neonatal intestine. Morphologically, the uptake mechanism in adult intestine was similar to the endocytosis previously reported in neonatal animals Like other endocytotic processes, HRP uptake in adult rats is an energy-dependent process as determined by metabolic inhibitors and temperature-controlled studies. An understanding of the mechanism whereby macromolecules are bound to intestinal membranes and engulfed by them is necessary before the action of physiologic macromolecules such as enterotoxins can be appreciated.

Walker, W. A.; Cornell, R.; Davenport, L. M.; Isselbacher, K. J.

1972-01-01

328

Hard paths, soft paths or no paths? Cross-cultural perceptions of water solutions  

NASA Astrophysics Data System (ADS)

In this study, we examine how development status and water scarcity shape people's perceptions of "hard path" and "soft path" water solutions. Based on ethnographic research conducted in four semi-rural/peri-urban sites (in Bolivia, Fiji, New Zealand, and the US), we use content analysis to conduct statistical and thematic comparisons of interview data. Our results indicate clear differences associated with development status and, to a lesser extent, water scarcity. People in the two less developed sites were more likely to suggest hard path solutions, less likely to suggest soft path solutions, and more likely to see no path to solutions than people in the more developed sites. Thematically, people in the two less developed sites envisioned solutions that involve small-scale water infrastructure and decentralized, community-based solutions, while people in the more developed sites envisioned solutions that involve large-scale infrastructure and centralized, regulatory water solutions. People in the two water-scarce sites were less likely to suggest soft path solutions and more likely to see no path to solutions (but no more likely to suggest hard path solutions) than people in the water-rich sites. Thematically, people in the two water-rich sites seemed to perceive a wider array of unrealized potential soft path solutions than those in the water-scarce sites. On balance, our findings are encouraging in that they indicate that people are receptive to soft path solutions in a range of sites, even those with limited financial or water resources. Our research points to the need for more studies that investigate the social feasibility of soft path water solutions, particularly in sites with significant financial and natural resource constraints.

Wutich, A.; White, A. C.; White, D. D.; Larson, K. L.; Brewis, A.; Roberts, C.

2014-01-01

329

Hard paths, soft paths or no paths? Cross-cultural perceptions of water solutions  

NASA Astrophysics Data System (ADS)

In this study, we examine how development status and water scarcity shape people's perceptions of "hard path" and "soft path" water solutions. Based on ethnographic research conducted in four semi-rural/peri-urban sites (in Bolivia, Fiji, New Zealand, and the US), we use content analysis to conduct statistical and thematic comparisons of interview data. Our results indicate clear differences based on development status and, to a lesser extent, water scarcity. People in less developed sites were more likely to suggest hard path solutions, less likely to suggest soft path solutions, and more likely to see no path to solutions than people in more developed sites. Thematically, people in less developed sites envisioned solutions that involve small-scale water infrastructure and decentralized, community based solutions, while people in more developed sites envisioned solutions that involve large-scale infrastructure and centralized, regulatory water solutions. People in water-scarce sites were less likely to suggest soft path solutions and more likely to see no path to solutions (but no more likely to suggest hard path solutions) than people in water-rich sites. Thematically, people in water-rich sites seemed to perceive a wider array of unrealized potential soft path solutions than those in water-scarce sites. On balance, our findings are encouraging in that they indicate that people are receptive to soft path solutions in a range of sites, even those with limited financial or water resources. Our research points to the need for more studies that investigate the social feasibility of soft path water solutions, particularly in sites with significant financial and natural resource constraints.

Wutich, A.; White, A. C.; Roberts, C. M.; White, D. D.; Larson, K. L.; Brewis, A.

2013-06-01

330

Laser Intracavity Absorption.  

National Technical Information Service (NTIS)

The fractional absorption which can be obtained using a single-mode laser with an internal absorption cell is compared to the fractional absorption obtainable with the more conventional system of a laser with an external absorption cell.

H. K. Holt

1976-01-01

331

A predictive model of backscattering at subdiffusion length scales  

PubMed Central

We provide a methodology for accurately predicting elastic backscattering radial distributions from random media with two simple empirical models. We apply these models to predict the backscattering based on two classes of scattering phase functions: the Henyey-Greenstein phase function and a generalized two parameter phase function that is derived from the Whittle-Matérn correlation function. We demonstrate that the model has excellent agreement over all length scales and has less than 1% error for backscattering at subdiffusion length scales for tissue-relevant optical properties. The presented model is the first available approach for accurately predicting backscattering at length scales significantly smaller than the transport mean free path.

Turzhitsky, Vladimir; Radosevich, Andrew; Rogers, Jeremy D.; Taflove, Allen; Backman, Vadim

2010-01-01

332

An advanced open-path atmospheric monitor design  

SciTech Connect

The conceptual design of an open-path atmospheric monitor combines an acousto-optic tunable filter for emission spectroscopy (3-14 {mu}m) with a mid-IR (4.6-5.4 {mu}m) for absorption spectroscopy. It utilizes mostly commercially available components, covers a large area ({approximately}4 km radius), measures the distance to any reflecting object, can take measurements along any line-of-sight, and is eye safe. Of twenty test pollutants it is to detect, the concentrations of all twenty will be measurable via emission spectroscopy and ten by the more sensitive absorption spectroscopy.

Taylor, L.; Suhre, D. [Westinghouse Electric Corp., Pittsburgh, PA (United States); Mech, S. [Westinghouse Hanford Co., Richland, WA (United States)

1996-05-01

333

Resonant absorption and not-so-resonant absorption in short, intense laser irradiated plasma  

SciTech Connect

An analytical model for laser-plasma interaction during the oblique incidence by an ultrashort ultraintense p-polarized laser on a solid-density plasma is proposed. Both the resonant absorption and not-so-resonant absorption are self-consistently included. Different from the previous theoretical works, the physics of resonant absorption is found to be valid in more general conditions as the steepening of the electron density profile is considered. Even for a relativistic intensity laser, resonant absorption can still exist under certain plasma scale length. For shorter plasma scale length or higher laser intensity, the not-so-resonant absorption tends to be dominant, since the electron density is steepened to a critical level by the ponderomotive force. The laser energy absorption rates for both mechanisms are discussed in detail, and the difference and transition between these two mechanisms are presented.

Ge, Z. Y.; Zhuo, H. B.; Ma, Y. Y.; Yang, X. H.; Yu, T. P.; Zou, D. B.; Yin, Y.; Shao, F. Q. [College of Science, National University of Defense Technology, Changsha 410073 (China)] [College of Science, National University of Defense Technology, Changsha 410073 (China); Yu, W.; Luan, S. X. [Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China)] [Shanghai Institute of Optics and Fine Mechanics, Chinese Academy of Sciences, Shanghai 201800 (China); Zhou, C. T. [College of Science, National University of Defense Technology, Changsha 410073 (China) [College of Science, National University of Defense Technology, Changsha 410073 (China); Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China); Peng, X. J. [Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China)] [Institute of Applied Physics and Computational Mathematics, Beijing 100088 (China)

2013-07-15

334

Optimal Shortest Path Queries in a Simple Polygon  

Microsoft Academic Search

Abstract Let P be a simple polygon with n sides. This paper shows how to preprocess,the polygon so that, given two query points p and q inside P, the length of the shortest,path,inside the polygon($#$to q can be found,in time,O(Iogn). The path,itself must,be polygonal and can be extracted,in additional,time proportional,to the number,of turns,it makes.,The preprocessing consists of triangulation,plus a linear

Leonidas J. Guibas; John Hershberger

1989-01-01

335

Path planning and execution monitoring for a planetary rover  

NASA Technical Reports Server (NTRS)

A path planner and an execution monitoring planner that will enable the rover to navigate to its various destinations safely and correctly while detecting and avoiding hazards are described. An overview of the complete architecture is given. Implementation and testbeds are described. The robot can detect unforseen obstacles and take appropriate action. This includes having the rover back away from the hazard and mark the area as untraversable in the in the rover's internal map. The experiments have consisted of paths roughly 20 m in length. The architecture works with a large variety of rover configurations with different kinematic constraints.

Gat, Erann; Slack, Marc G.; Miller, David P.; Firby, R. James

1990-01-01

336

A flight investigation with a STOL airplane flying curved, descending instrument approach paths  

NASA Technical Reports Server (NTRS)

A flight investigation using a De Havilland Twin Otter airplane was conducted to determine the configurations of curved, 6 deg descending approach paths which would provide minimum airspace usage within the requirements for acceptable commercial STOL airplane operations. Path configurations with turns of 90 deg, 135 deg, and 180 deg were studied; the approach airspeed was 75 knots. The length of the segment prior to turn, the turn radius, and the length of the final approach segment were varied. The relationship of the acceptable path configurations to the proposed microwave landing system azimuth coverage requirements was examined.

Benner, M. S.; Mclaughlin, M. D.; Sawyer, R. H.; Vangunst, R.; Ryan, J. L.

1974-01-01

337

Multiresolution path planning for mobile robots  

Microsoft Academic Search

The problem of automatic collision-free path planning is central to mobile robot applications. An approach to automatic path planning based on a quadtree representation is presented. Hierarchical path-searching methods are introduced, which make use of this multiresolution representation, to speed up the path planning process considerably. The applicability of this approach to mobile robot path planning is discussed.

S. Kambhampati; L. S. Davis

1986-01-01

338

A subterranean mammal uses the magnetic compass for path integration  

PubMed Central

Path integration allows animals to navigate without landmarks by continuously processing signals generated through locomotion. Insects such as bees and ants have evolved an accurate path integration system, assessing and coding rotations with the help of a general directional reference, the sun azimuth. In mammals, by contrast, this process can take place through purely idiothetic (mainly proprioceptive and vestibular) signals. However, without any stable external reference for measuring direction, path integration is highly affected by cumulative errors and thus has been considered so far as valid only for short-distance navigation. Here we show through two path integration experiments (homing and shortcut finding) that the blind mole rat assesses direction both through internal signals and by estimating its heading in relation to the earth's magnetic field. Further, it is shown that the greater the circumvolution and length of the traveled path, the more the animal relies on the geomagnetic field. This path integration system strongly reduces the accumulation of errors due to inaccuracies in the estimation of rotations and thus allows the mole rat to navigate efficiently in darkness, without the help of any landmark, over both short and long distances.

Kimchi, Tali; Etienne, Ariane S.; Terkel, Joseph

2004-01-01

339

Finding reaction paths using the potential energy as reaction coordinate  

NASA Astrophysics Data System (ADS)

The intrinsic reaction coordinate curve (IRC), normally proposed as a representation of a reaction path, is parametrized as a function of the potential energy rather than the arc-length. This change in the parametrization of the curve implies that the values of the energy of the potential energy surface points, where the IRC curve is located, play the role of reaction coordinate. We use Carathéodory's relation to derive in a rigorous manner the proposed parametrization of the IRC path. Since this Carathéodory's relation is the basis of the theory of calculus of variations, then this fact permits to reformulate the IRC model from this mathematical theory. In this mathematical theory, the character of the variational solution (either maximum or minimum) is given through the Weierstrass E-function. As proposed by Crehuet and Bofill [J. Chem. Phys. 122, 234105 (2005)], we use the minimization of the Weierstrass E-function, as a function of the potential energy, to locate an IRC path between two minima from an arbitrary curve on the potential energy surface, and then join these two minima. We also prove, from the analysis of the Weierstrass E-function, the mathematical bases for the algorithms proposed to locate the IRC path. The proposed algorithm is applied to a set of examples. Finally, the algorithm is used to locate a discontinuous, or broken, IRC path, namely, when the path connects two first order saddle points through a valley-ridged inflection point.

Aguilar-Mogas, Antoni; Giménez, Xavier; Bofill, Josep Maria

2008-03-01

340

Finding reaction paths using the potential energy as reaction coordinate.  

PubMed

The intrinsic reaction coordinate curve (IRC), normally proposed as a representation of a reaction path, is parametrized as a function of the potential energy rather than the arc-length. This change in the parametrization of the curve implies that the values of the energy of the potential energy surface points, where the IRC curve is located, play the role of reaction coordinate. We use Caratheodory's relation to derive in a rigorous manner the proposed parametrization of the IRC path. Since this Caratheodory's relation is the basis of the theory of calculus of variations, then this fact permits to reformulate the IRC model from this mathematical theory. In this mathematical theory, the character of the variational solution (either maximum or minimum) is given through the Weierstrass E-function. As proposed by Crehuet and Bofill [J. Chem. Phys. 122, 234105 (2005)], we use the minimization of the Weierstrass E-function, as a function of the potential energy, to locate an IRC path between two minima from an arbitrary curve on the potential energy surface, and then join these two minima. We also prove, from the analysis of the Weierstrass E-function, the mathematical bases for the algorithms proposed to locate the IRC path. The proposed algorithm is applied to a set of examples. Finally, the algorithm is used to locate a discontinuous, or broken, IRC path, namely, when the path connects two first order saddle points through a valley-ridged inflection point. PMID:18345872

Aguilar-Mogas, Antoni; Giménez, Xavier; Bofill, Josep Maria

2008-03-14

341

Overcoming path dependency: path generation in open systems  

Microsoft Academic Search

Studies on societal path dependencies tend to focus on mechanisms that anchor and stabilize national trajectories while paying\\u000a less attention to transnational interactions and multilevel governance. This paper explores processes of path transformation\\u000a in societies that are presumed to have the characteristics of open systems. Two pairs of case studies are presented and compared.\\u000a The first illustrates institutional change through

Marie-Laure Djelic; Sigrid Quack

2007-01-01

342

Lengthy Relationships: Foot Length, Stride, Leg Length, Height  

NSDL National Science Digital Library

Paleontologists occasionally find ancient tracks and footprints preserved in the rocks. This lesson opens the door to analysing those footprints, and gleaning information about body size and activities of the extinct animals that made the tracks. Students will learn that patterns can reveal much about the past, in light of the present; and that bipedalism has appeared several times. Relationships will be found between foot length and leg length; foot length and height; leg length and height; stride length and leg length; and stride length and speed.

Johnson, Jennifer

343

Length of Time's Arrow  

NASA Astrophysics Data System (ADS)

An unresolved problem in physics is how the thermodynamic arrow of time arises from an underlying time reversible dynamics. We contribute to this issue by developing a measure of time-symmetry breaking, and by using the work fluctuation relations, we determine the time asymmetry of recent single molecule RNA unfolding experiments. We define time asymmetry as the Jensen-Shannon divergence between trajectory probability distributions of an experiment and its time-reversed conjugate. Among other interesting properties, the length of time’s arrow bounds the average dissipation and determines the difficulty of accurately estimating free energy differences in nonequilibrium experiments.

Feng, Edward H.; Crooks, Gavin E.

2008-08-01

344

Length of the Day  

NSDL National Science Digital Library

In this activity, students measure the length of the day using the rotation of the Earth, and discover that the Sun is not exactly in the same place at the same clock time every day, understand that the changes are due to motions of the Earth, and lead to differences in solar, star, and sidereal time. This resource is from PUMAS - Practical Uses of Math and Science - a collection of brief examples created by scientists and engineers showing how math and science topics taught in K-12 classes have real world applications.

345

Electrostatic persistence length.  

PubMed

The persistence length is calculated for polyelectrolyte chains with fixed bond lengths and bond angles (pi-theta), and a potential energy consisting of the screened Coulomb interaction between beads, potential wells alpha phi(i)2 for the dihedral angles phi(i), and coupling terms beta phi(i) phi(i+/-1). This model defines a librating chain that reduces in appropriate limits to the freely rotating or wormlike chains, it can accommodate local crumpling or extreme stiffness, and it is easy to simulate. A planar-quadratic (pq), analytic approximation is based on an expansion of the electrostatic energy in eigenfunctions of the quadratic form that describes the backbone energy, and on the assumption that the quadratic form not only is positive but also adequately confines the chain in an infinite phase space of dihedral angles to the physically unique part with all |phi(i)| < pi. The pq approximation is available under these weak constraints, but the simulations confirm its quantitative accuracy only under the expected condition that alpha is large, that is, for very stiff chains. Stiff chains can also be simulated with small alpha and small theta and compared to an OSF approximation suitably generalized to chains with finite rather than vanishing theta, and increasing agreement with OSF is found the smaller is theta. The two approximations, one becoming exact as alpha --> infinity with fixed theta, the other as theta --> 0 with fixed alpha, are quantitatively similar in behavior, both giving a persistence length P = P0 + aD2 for stiff chains, where D is the Debye length. However, the coefficient apq is about twice the value of aOSF. Under other conditions the simulations show that P may or not be linear in D2 at small or moderate D, depending on the magnitudes of alpha, beta, theta, and the charge density but always becomes linear at large D. Even at a moderately low charge density, corresponding to fewer than 20% of the beads being charged, and with strong crumpling induced by large beta, increasing D dissolves blobs and recovers a linear dependence of P on D2, although a lower power of D gives an adequate fit at moderate D. For the class of models considered, it is concluded that the only universal feature is the asymptotic linearity of P in D2, regardless of flexibility or stiffness. PMID:20148527

Fixman, Marshall

2010-03-11

346

The application of differential optical absorption spectroscopy (DOAS) from space  

NASA Astrophysics Data System (ADS)

Trace gas measurements by absorptions spectroscopy make use of the attenuation of radiation by molecules. The central idea of Differential Optical Absorption Spectroscopy (DOAS) is to analyse strongly structured (fingerprint) absorptions of visible, UV, or near IR radiation by atmospheric trace gases. In contrast to traditional spectroscopic methods relying on measuring the attenuation of the radiation intensity at a few, selected wavelengths (typically pairs of `on line' and `off line' wavelengths) only, DOAS typically uses intensity measurements at hundreds or even thousands of wavelengths. The strength of DOAS lies in the excellent specificity, inherent calibration, the potential for real time measurements, and its remote sensing capabilities. Since its introduction in the late 1970's by Platt and Perner significant advances have been made in the DOAS technique, including the development of reliable evaluation techniques based and new methods allowing a realistic estimate of the resulting errors, also techniques to compensate for instrumental effects, like residual spectra, were developed. Most importantly the range of application of DOAS was greatly enhanced to include observations using scattered sunlight, multi axis observ ation (MAX-DOAS), vertical trace gas -concentration profiles, and measurements from satellites (e.g. the GOME, SCIAMACHY, GOME-2, and OMI instruments). At the same time the palette of species measurable by DOAS was expanded from the original SO2, NO2, CH2O, and O3 to include many free radicals (e.g. OH, NO3, IO, OIO, BrO, ClO, OClO), nitrous acid (HONO), and a large set of aromatic compounds (e.g. benzene, toluene, xylenes, phenols, benzaldehyde). In addition it is now possible to determine the photon path-length distribution in clouds by ground based observation of O2 and O4 bands. Here the new approaches, specific requirements and sample applications for space- borne DOAS instruments are described. Recent advances and directions of future development are dis c u s s e d .

Platt, U.

347

Path Generation of Regular Polygon Using a Geared-Parallelogram Mechanism  

NASA Astrophysics Data System (ADS)

The paper proposes a geared-parallelogram mechanism (GPM) for path generation of regular polygon. The model presents the structural features of the mechanism as shown in Fig. 1 which forms the basis for the guiding features of its path and also for the guiding function in its kinematic parameters and dimensions. It is shown from the analysis results that length l2 has an effect on the size of the path, the initial phase ? on path direction and transmission ratio k on number of polygon sides. More important is that length ratio ? plays a crucial role in path curvature and defines indirectly the straightness for the regular polygon of path generation. In order to generate the path of regular polygon, some available value ranges of each parameter have been suggested. An example to solve path generation task with such mechanism using the method presented in this paper is given, through which a practical procedure to develop a synthesis tool for generating a regular polygon path will be provided. Fig. 1 Structural diagram of GPM

Lin, S.; Fan, Y.; Ren, Z.; Hanke, U.

348

Path Characterization Algorithms for FASCODE.  

National Technical Information Service (NTIS)

This report has described the results of a study undertaken at AER to identify and implement a state of the art nonlinear retrieval approach to characterize line of sight variability of atmospheric thermal and constituent environments. This path character...

B. L. Linder J. L. Moncet R. G. Isaacs S. A. Clough S. D. Worsham

1990-01-01

349

Length of stain dosimeter  

NASA Technical Reports Server (NTRS)

Payload customers for the Space Shuttle have recently expressed concerns about the possibility of their payloads at an adjacent pad being contaminated by plume effluents from a shuttle at an active pad as they await launch on an inactive pad. As part of a study to satisfy such concerns a ring of inexpensive dosimeters was deployed around the active pad at the inter-pad distance. However, following a launch, dosimeters cannot be read for several hours after the exposure. As a consequence factors such as different substrates, solvent systems, and possible volatilization of HCl from the badges were studied. This observation led to the length of stain (LOS) dosimeters of this invention. Commercial passive LOS dosimeters are sensitive only to the extent of being capable of sensing 2 ppm to 20 ppm if the exposure is 8 hours. To map and quantitate the HCl generated by Shuttle launches, and in the atmosphere within a radius of 1.5 miles from the active pad, a sensitivity of 2 ppm HCl in the atmospheric gases on an exposure of 5 minutes is required. A passive length of stain dosimeter has been developed having a sensitivity rendering it capable of detecting a gas in a concentration as low as 2 ppm on an exposure of five minutes.

Lueck, Dale E. (inventor)

1994-01-01

350

Shortest paths on a polyhedron  

Microsoft Academic Search

We present an algorithm for determining the shortest path between a source point and any destination point along the surface of a polyhedron (need not be convex). Our algorithm uses a new approach which deviates from the conventional “continuous Dijkstra” technique. It takes &Ogr;(n2) time and ⊖(n) space to determine the shortest path and to compute the inward layout which

Jindong Chen; Yijie Han

1990-01-01

351

Shortest Paths in Euclidean Graphs  

Microsoft Academic Search

We analyze a simple method for finding shortest paths inEuclidean graphs (where vertices are points in a Euclidean space and edge weights are Euclidean distances between points). For many graph\\u000a models, the average running time of the algorithm to find the shortest path between a specified pair of vertices in a graph\\u000a withV vertices andE edges is shown to beO(V)

Robert Sedgewick; Jeffrey Scott Vitter

1986-01-01

352

Path integration on Darboux spaces  

Microsoft Academic Search

In this paper, the Feynman path integral technique is applied to two-dimensional spaces of nonconstant curvature: these spaces\\u000a are called Darboux spaces D\\u000a I-D\\u000a IV. We start each consideration in terms of the metric and then analyze the quantum theory in the separable coordinate systems.\\u000a The path integral in each case is formulated and then solved in the majority of

Christian Grosche; Theoretische Physik

2006-01-01

353

Backup Path Classification Based on Failure Risks for Efficient Backup Path Computation  

Microsoft Academic Search

Abstract. We propose a new approach exploiting the failure risk (node, link or Shared Risk Link Group) structures to enhance the backup path computation. Upon failure, our approach classifies the backup paths into two categories: operative backup paths and inoperative backup,paths. An operative backup path is an active backup path which really receives traffic of some affected communications while an

Mohand Yazid Saidi; Bernard Cousin; Jean-louis Le Roux

2009-01-01

354

Path selection process utilizing rapid estimation scheme. [for Martian rover  

NASA Technical Reports Server (NTRS)

The paper describes the use of a rapid estimation scheme for path selection by a roving vehicle. Essentially, the evaluation procedure simulates movement of the rover over each of several corridors lying radially outward from the scanning position. Two levels of corridors are used, and the path selection scheme selects the optimal primary corridor according to a dynamic programming algorithm. In the present version, the length of the corridors is variable. The rapid estimation scheme provides information to define corridor dimensions. This corridor structure, which varies as a function of the terrain, eliminates the need for backtracking, except in certain extreme cases. Computer results are promising in that obstacles were avoided while corridor lengths were kept to a maximum where safety permitted.

Ring, H.; Shen, C. N.

1978-01-01

355

NOAA Aeronomy Laboratory long-path OH experiment, Fritz Peak Observatory, Colorado  

NASA Technical Reports Server (NTRS)

Long path absorption of laser light over a 20.6 km path at Fritz Peak Observatory 17 km west of Boulder is described: elevation 2800 m, average beam height above terrain approximately 250 m, and operational since March 1991. System runs at maximum signal to noise with integration times longer than 64 seconds. Most of the data obtained to date are 15-minute averages due to the lengthy data analysis required.

Mount, George H.

1994-01-01

356

Feynman path integrals in the young double-slit experiment  

Microsoft Academic Search

An estimate for the value of the nonlinear interference term in the Young double-slit experiment is found using the Feynman path-integral method. In our time-dependent calculation the usual interference term becomes multiplied by 1+e withe proportional to cos(2m? L\\/ hT), where ? is the distance between the two slits (holes) andL is the length of the shortest trajectory of electrons

H. Yabuki

1986-01-01

357

Feynman Path Integrals in the Young Double-Slit Experiment  

NASA Astrophysics Data System (ADS)

An estimate for the value of the nonlinear interference term in the Young double-slit experiment is found using the Feynman path-integral method. In our time-dependent calculation the usual interference term becomes multiplied by 1+ e with e proportional to cos(2 m? L/ ? T), where ? is the distance between the two slits (holes) and L is the length of the shortest trajectory of electrons between the source and the observation point.

Yabuki, H.

1986-02-01

358

Logarithmic Sobolev Inequalities on Path Spaces Over Riemannian Manifolds  

NASA Astrophysics Data System (ADS)

Let Wo(M) be the space of paths of unit time length on a connected, complete Riemannian manifold M such that ?(0) =o, a fixed point on M, and ? the Wiener measure on Wo(M) (the law of Brownian motion on M starting at o).If the Ricci curvature is bounded by c, then the following logarithmic Sobolev inequality holds:

Hsu, Elton P.

359

Atmospheric Refraction Path Integrals in Ground-Based Interferometry  

Microsoft Academic Search

The basic effect of the earth's atmospheric refraction on telescope operation\\u000ais the reduction of the true zenith angle to the apparent zenith angle,\\u000aassociated with prismatic aberrations due to the dispersion in air. If one\\u000aattempts coherent superposition of star images in ground-based interferometry,\\u000aone is in addition interested in the optical path length associated with the\\u000arefracted rays.

Richard J. Mathar; Sterrewacht Leiden

2004-01-01

360

Faster shortest-path algorithms for planar graphs  

Microsoft Academic Search

We give a linear-time algorithm for single-sourceshortest paths in planar graphs with nonnegative edgelengths.Our algorithm also yields a linear-time algorithmfor maximum flow in a planar graph with thesource and sink on the same face. The previous best algorithmsfor these problemsrequired\\\\Omega\\\\Gammanplog n) timewhere n is the number of nodes in the input graph.For the case where negative edge-lengths are allowed,we give

Philip N. Klein; Satish Rao; Monika Raucht; Sairam Subramanian

1994-01-01

361

Feynman path integrals in the young double-slit experiment  

SciTech Connect

An estimate for the value of the nonlinear interference term in the Young double-slit experiment is found using the Feynman path-integral method. In our time-dependent calculation the usual interference term becomes multiplied by 1 + e with e proportional to cos(2mlambdaL//eta/T), where lambda is the distance between the two slits (holes) and L is the length of the shortest trajectory of electrons between the source and the observation point.

Yabuki, H.

1986-02-01

362

Vehicle path-planning in three dimensions using optics analogs for optimizing visibility and energy cost  

NASA Technical Reports Server (NTRS)

Path planning is an important issue for space robotics. Finding safe and energy-efficient paths in the presence of obstacles and other constraints can be complex although important. High-level (large-scale) path planning for robotic vehicles was investigated in three-dimensional space with obstacles, accounting for: (1) energy costs proportional to path length; (2) turn costs where paths change trajectory abruptly; and (3) safety costs for the danger associated with traversing a particular path due to visibility or invisibility from a fixed set of observers. Paths optimal with respect to these cost factors are found. Autonomous or semi-autonomous vehicles were considered operating either in a space environment around satellites and space platforms, or aircraft, spacecraft, or smart missiles operating just above lunar and planetary surfaces. One class of applications concerns minimizing detection, as for example determining the best way to make complex modifications to a satellite without being observed by hostile sensors; another example is verifying there are no paths (holes) through a space defense system. Another class of applications concerns maximizing detection, as finding a good trajectory between mountain ranges of a planet while staying reasonably close to the surface, or finding paths for a flight between two locations that maximize the average number of triangulation points available at any time along the path.

Rowe, Neil C.; Lewis, David H.

1989-01-01

363

Design of a simple cryogenic system for ultraviolet-visible absorption spectroscopy with a back-reflectance fiber optic probe.  

PubMed

We report a convenient and inexpensive technique for the rapid acquisition of absorption spectra from small samples at cryogenic temperatures using a home built cryostat with novel collection optics. A cylindrical copper block was constructed with a coaxial bore to hold a 4.00 mm diameter electron paramagnetic resonance (EPR) tube and mounted on a copper feed in thermal contact with liquid nitrogen. A 6.35 mm diameter hole was bored into the side of the cylinder so a fiber optic cable bundle could be positioned orthogonally to the EPR tube. The light passing through the sample is reflected off of the opposing surfaces of the EPR tube and surrounding copper, back through the sample. The emergent light is then collected using the fiber optic bundle and analyzed using a dispersive spectrometer. Absorption spectra for KMnO4 were measured between 400 and 700 nm. Absorption intensity at 506, 525, 545, and 567 nm was found to be proportional to concentration, displaying Beer's law-like behavior. The EPR tube had an internal diameter of 3.2 mm; the double pass of the probe beam through the sample affords a central path length of about 6.4 mm. Comparing these measurements with those recorded on a conventional tabletop spectrometer using a cuvette with a 10.00 mm path length, we consistently found a ratio between intensities of 0.58 rather than the anticipated 0.64. These 6% smaller values we attribute to the curvature of the EPR tube and transmission/reflection losses. This system is particularly well-suited to studying the kinetics and dynamics of chemical reactions at cryogenic temperatures. The rapid response (100 ms) and multiplex advantage provided the opportunity of recording simultaneous time courses at several wavelengths following initiation of a chemical reaction with a pulsed laser source. PMID:24405962

Vinyard, Andrew; Hansen, Kaj A; Byrd, Ross; Stuart, Douglas A; Hansen, John E

2014-01-01

364

Collisionless absorption in sharp-edged plasmas  

NASA Astrophysics Data System (ADS)

The absorption of subpicosecond, obliquely incident laser light is studied using a 11/2D particle-in-cell code. Density scale lengths from L/?=0.01 to 2 and laser irradiances between I?2=1014 and 1018 W cm-2 ?m2 are considered. ``Vacuum heating'' [F. Brunel, Phys. Rev. Lett. 59, 52 (1987)] dominates over resonance absorption for scale lengths L/?<0.1, and is most efficient when vosc/c~=3.1(L/?)2. Absorbed energy is carried mainly by a ``superhot'' electron population with Uhot~(I?2)1/3-1/2.

Gibbon, Paul; Bell, A. R.

1992-03-01

365

New Sufficient Conditions for Hamiltonian Paths  

PubMed Central

A Hamiltonian path in a graph is a path involving all the vertices of the graph. In this paper, we revisit the famous Hamiltonian path problem and present new sufficient conditions for the existence of a Hamiltonian path in a graph.

Kaykobad, M.

2014-01-01

366

An Appraisal of Some Shortest Path Algorithms.  

National Technical Information Service (NTIS)

A critical review of the literature of shortest paths in networks that examines methods for determining (1) the shortest path between two specified nodes; (2) the shortest path between all pairs of nodes; (3) the second, third, etc., shortest path; (4) th...

S. E. Dreyfus

1967-01-01

367

Open-path atmospheric transmission for a diode-pumped cesium laser.  

PubMed

A tunable diode laser absorption spectroscopy device was developed to study atmospheric propagation for emerging high-energy laser weapons. The cesium diode-pumped alkali laser operates near 895 nm in the vicinity of several water-vapor absorption lines. Temperature, pressure, and water vapor concentration were determined for 150 m and 1 km open paths with statistical errors of ?0.2%. Comparison with meteorological instruments yields agreement for the 1 km path to within 0.6% for temperature, 3.7% for pressure, and 2.4% for concentration. PMID:23207380

Rice, Christopher A; Lott, Gordon E; Perram, Glen P

2012-12-01

368

Signatures of Absorption Mechanisms for J{psi} and {psi}` Production in High Energy Heavy-Ion Collisions  

SciTech Connect

J/psi and psi` produced in high-energy heavy-ion collisions are absorbed by their collisions with nucleons and produced soft particles, leading to two distinct absorption mechanisms. The signature of absorption by produced soft particles, as revealed by psi` production data, consists of a gap and a change of the slope in going from the pA line to the nucleus-nucleus line when we make a semi-log plot of the survival probability as a function of the path length. Using this signature, we find from the J/psi production data in pA, O-Cu, O-U, and S-U collisions that the degree of J/psi absorption by produced soft particles is small and cannot account for the J/psi data in Pb-Pb collisions. The anomalous suppression of J/psi production in Pb-Pb collisions can be explained as due to the occurrence of a new phase of strong J/psi absorption, which sets in when the local energy density exceeds about 3.4 GeV/fm3. To probe the chemical content of the new phase, we propose to study the abundance of open-charm mesons and charm hyperons which depends sensitively on the quark chemical potential.

Wong, Cheuk-Yin

1997-06-01

369

Sensor for headspace pressure and H2O concentration measurements in closed vials by tunable diode laser absorption spectroscopy  

NASA Astrophysics Data System (ADS)

The concentration of H2O and the pressure in the headspace of vials are simultaneously measured by a tunable diode laser sensor based on absorption spectroscopy techniques. The 7168.437 cm?1 spectral line of H2O is chosen as the sensing transition for its strong absorption strength and being reasonably far away from its neighboring molecular transitions. In order to prevent interference absorption by ambient water vapor in the room air, a difference between the measured signal and the referenced signal is used to calculate the pressure and H2O concentration in the headspace of vials, eliminating the need for inert gas purges and calibration with known gas. The validation of the sensor is conducted in a static vial, yielding an accuracy of 1.23% for pressure and 3.81% for H2O concentration. The sensitivity of the sensor is estimated to be about 2.5 Torr for pressure and 400 ppm for H2O concentration over a 3 cm absorption path length respectively. Accurate measurements for commercial freeze-dried products demonstrate the in-line applications of the sensor for the pharmaceutical industry.

Cai, Tingdong; Wang, Guishi; Cao, Zhensong; Zhang, Weijun; Gao, Xiaoming

2014-07-01

370

CW DFB RT diode laser based sensor for trace-gas detection of ethane using novel compact multipass gas absorption cell  

NASA Astrophysics Data System (ADS)

The development of a continuous wave (CW), thermoelectrically cooled (TEC), distributed feedback (DFB) laser diode based spectroscopic trace-gas sensor for ultra sensitive and selective ethane (C2H6) concentration measurements is reported. The sensor platform used tunable laser diode absorption spectroscopy (TDLAS) and wavelength modulation spectroscopy (WMS) as the detection technique. TDLAS was performed with an ultra-compact 57.6 m effective optical path length innovative spherical multipass cell capable of 459 passes between two mirrors separated by 12.5 cm. For an interference free C2H6 absorption line located at 2976.8 cm-1 a 1? minimum detection limit of 130 pptv with a 1 second lock-in amplifier time constant was achieved.

Jahjah, Mohammad; Lewicki, Rafal; Tittel, Frank K.; Krzempek, Karol; Stefanski, Przemyslaw; So, Stephen; Thomazy, David

2013-01-01

371

CW DFB RT diode laser-based sensor for trace-gas detection of ethane using a novel compact multipass gas absorption cell  

NASA Astrophysics Data System (ADS)

The development of a continuous wave, thermoelectrically cooled (TEC), distributed feedback diode laser-based spectroscopic trace-gas sensor for ultra-sensitive and selective ethane (C2H6) concentration measurements is reported. The sensor platform used tunable diode laser absorption spectroscopy (TDLAS) and wavelength modulation spectroscopy as the detection technique. TDLAS was performed using an ultra-compact 57.6 m effective optical path length innovative spherical multipass cell capable of 459 passes between two mirrors separated by 12.5 cm and optimized for the 2.5-4 ?m range TEC mercury-cadmium-telluride detector. For an interference-free C2H6 absorption line located at 2,976.8 cm-1, a 1 ? minimum detection limit of 740 pptv with a 1 s lock-in amplifier time constant was achieved.

Krzempek, Karol; Jahjah, Mohammad; Lewicki, Rafa?; Stefa?ski, Przemys?aw; So, Stephen; Thomazy, David; Tittel, Frank K.

2013-09-01

372

Optically generated small electron and hole polarons in nominally undoped and Fe-doped KNbO3 investigated by transient absorption spectroscopy  

NASA Astrophysics Data System (ADS)

Transient light-induced absorption in nominally undoped and Fe-doped KNbO3 crystals is observed in the visible and infrared spectral ranges after single pulse illumination with ?=532nm . For nominally undoped KNbO3 the decay of the light-induced absorption in a single step can be explained by incoherent hopping transport of optically generated small bound O- hole and small free Nb4+ electron polarons and their mutual recombination. Iron doping causes an additional slow decay component and, remarkably, accelerates the initial decay process. A consistent model for the formation, hopping, and recombination paths of hole and electron polarons is deduced from the experimental data set for both nominally undoped and Fe-doped KNbO3 . The decrease in the polaron hopping-transport length in Fe-doped samples is attributed to the increased number densities of optically generated hole polarons by additional one-quantum excitations.

Torbrügge, S.; Imlau, M.; Schoke, B.; Merschjann, C.; Schirmer, O. F.; Vernay, S.; Gross, A.; Wesemann, V.; Rytz, D.

2008-09-01

373

Stochastic method for determining the coherence length of a TEA CO2 laser  

NASA Astrophysics Data System (ADS)

In this work the results of the measurement of the coherence length of a TEA CO2 laser developed in DEILAP are presented. A Michelson interferometer of about 5 m of optical path length difference was built for this purpose. A motorized translation optical mount was placed in one arm in order to enable the variation of the optical path length in many wavelengths. The length of the other arm was varied manually in steps of several tens of centimeters. Spatial filtering forced the laser to oscillate in a single transverse mode, TEM00. An innovative stochastic technique for data analysis allowed determining the amount of longitudinal modes, the amplitude and the individual average coherence length of each mode as well as the global coherence length of the laser. This technique was later compared with a method based on the analysis of the Fourier transform of the time series obtained at the interferometer input.

Codnia, J.; Gómez, N. D.; Azcárate, M. L.

2013-12-01

374

Writhe and mutual entanglement combine to give the entanglement length  

NASA Astrophysics Data System (ADS)

We propose a method to estimate Ne, the entanglement length, that incorporates both local and global topological characteristics of chains in a melt under equilibrium conditions. This estimate uses the writhe of the chains, the writhe of the primitive paths, and the number of kinks in the chains in a melt. An advantage of this method is that it works for both linear and ring chains, works under all periodic boundary conditions, does not require knowing the contour length of the primitive paths, and does not rely on a smooth set of data. We apply this method to linear finitely extendable nonlinear elastic chains and we observe that our estimates are consistent with those from other studies.

Panagiotou, E.; Kröger, M.; Millett, K. C.

2013-12-01

375

Calculating Least Risk Paths in 3d Indoor Space  

NASA Astrophysics Data System (ADS)

Over the last couple of years, research on indoor environments has gained a fresh impetus; more specifically applications that support navigation and wayfinding have become one of the booming industries. Indoor navigation research currently covers the technological aspect of indoor positioning and the modelling of indoor space. The algorithmic development to support navigation has so far been left mostly untouched, as most applications mainly rely on adapting Dijkstra's shortest path algorithm to an indoor network. However, alternative algorithms for outdoor navigation have been proposed adding a more cognitive notion to the calculated paths and as such adhering to the natural wayfinding behaviour (e.g. simplest paths, least risk paths). These algorithms are currently restricted to outdoor applications. The need for indoor cognitive algorithms is highlighted by a more challenged navigation and orientation due to the specific indoor structure (e.g. fragmentation, less visibility, confined areas…). As such, the clarity and easiness of route instructions is of paramount importance when distributing indoor routes. A shortest or fastest path indoors not necessarily aligns with the cognitive mapping of the building. Therefore, the aim of this research is to extend those richer cognitive algorithms to three-dimensional indoor environments. More specifically for this paper, we will focus on the application of the least risk path algorithm of Grum (2005) to an indoor space. The algorithm as proposed by Grum (2005) is duplicated and tested in a complex multi-storey building. The results of several least risk path calculations are compared to the shortest paths in indoor environments in terms of total length, improvement in route description complexity and number of turns. Several scenarios are tested in this comparison: paths covering a single floor, paths crossing several building wings and/or floors. Adjustments to the algorithm are proposed to be more aligned to the specific structure of indoor environments (e.g. no turn restrictions, restricted usage of rooms, vertical movement) and common wayfinding strategies indoors. In a later stage, other cognitive algorithms will be implemented and tested in both an indoor and combined indoor-outdoor setting, in an effort to improve the overall user experience during navigation in indoor environments.

Vanclooster, A.; De Maeyer, Ph.; Fack, V.; Van de Weghe, N.

2013-08-01

376

Fine-wire thermometer to correct CO 2 fluxes by open-path analyzers for artificial density fluctuations  

Microsoft Academic Search

A fine-wire thermometer was applied to measure high-frequency air temperature fluctuations averaged over the length of the optical path of an LI-7500 open-path gas analyzer that was used for CO2 flux measurements over a forest clear-cut in Sweden. Heat fluxes derived by the fine-wire temperature data were used to correct the CO2 fluxes for density fluctuations within the optical path.

Achim Grelle; George Burba

2007-01-01

377

FILAMENT LENGTHS IN STRIATED MUSCLE  

Microsoft Academic Search

Filament lengths in resting and excited frog muscles have been measured in the electron microscope, and investigations made of the changes in length that are found under different conditions, to distinguish between those changes which arise during preparation and the actual differences in the living muscles. It is concluded that all the measured differences in filament length are caused by

SALLY G. PAGE; H. E. HUXLEY

1963-01-01

378

The temperature dependence of the absorption edge in bismuth vanadate crystals (BiVO4)  

Microsoft Academic Search

The temperature dependence of the absorption edge in bismuth vanadate single crystal was measured, and it has turned out that the absorption edge shifts towards the longer wave-length side with increasing temperature

Yoshihiro Ishibashi; Takashi Fujii; Akikatsu Sawada

1982-01-01

379

Measurement of Debye length in laser-produced plasma.  

NASA Technical Reports Server (NTRS)

The Debye length of an expanded plasma created by placing an evacuated chamber with an entrance slit in the path of a freely expanding laser produced plasma was measured, using the slab geometry. An independent measurement of electron density together with the observed value for the Debye length also provided a means for evaluating the plasma electron temperature. This temperature has applications in ascertaining plasma conductivity and magnetic field necessary for confinement of the laser produced plasma. Also, the temperature obtained would be useful in analyzing electron-ion recombination rates in the expanded plasma and the dynamics of the cooling process of the plasma expansion.

Ehler, W.

1973-01-01

380

Polyelectrolyte persistence length: Attractive effect of counterion correlations and fluctuations  

NASA Astrophysics Data System (ADS)

The persistence length of a single, strongly charged, stiff polyelectrolyte chain is investigated theoretically. Path integral formulation is used to obtain the effective electrostatic interaction between the monomers. We find significant deviations from the classical Odijk, Skolnick and Fixman (OSF) result. An induced attraction between monomers is due to thermal fluctuations and correlations between bound counterions. The electrostatic persistence length is found to be smaller than the OSF value and indicates a possible mechanical instability (collapse) for highly charged polyelectrolytes with multivalent counterions. In addition, we calculate the amount of condensed counterions on a slightly bent polyelectrolyte. More counterions are found to be adsorbed as compared to the Manning condensation on a cylinder.

Ariel, G.; Andelman, D.

2003-01-01

381

Long Path Quantum Cascade Laser Based Sensor for Environment Sensing/Ambient Detection of CH4 and N2O  

NASA Astrophysics Data System (ADS)

Methane (CH4) and Nitrous Oxide (N2O) are long-lived greenhouse gases in the atmosphere with significant global warming effects. These gases also are known to be produced in a number of anthropogenic settings such as manure management systems, which releases substantial GHGs and is mandated by the EPA to provide continuous monitoring. In addition, natural gas leaks in urban areas is another source of strong spatially inhomogeneous methane emissions Most open path methods for quantitative detection of trace gases utilize either Fourier Transform Spectrometer (FTIR) or near-IR differential optical absorption spectroscopy (DOAS). Although, FTIR is suitable for ambient air monitoring measurement of more abundant gases such as CO2 and H20 etc., the lack of spectral resolution makes the retrieval of weaker absorbing features such as N20 more difficult. On the other hand, conventional DOAS systems can be large and impractical. As an alternative, we illustrate a robust portable quantum cascade laser (QCL) approach for simultaneous detection of CH4 and N2O. In particular, gas spectra were recorded by ultrafast pulse intensity (thermal) chirp tuning over the 1299 - 1300cm-1 spectral window. Etalon measurements insure stable tuning was obtained. To deal with multiple species, a LSQ spectral fitting approach was used which accounted for both the overlapping trace gases , background water vapor as well as detector drift and calibration. In summary, ambient concentrations of CH4 with and N2O with accuracy < 1% was obtained on the order of 5ms using optical paths of 500 m path length. In addition, unattended long term operation was demonstrated and validations using other sensors when possible were shown to be consistent. The system accuracy is limited by systemic errors, which are still being explored.

Castillo, P. C.; Sydoryk, I.; Gross, B.; Moshary, F.

2013-12-01

382

Coaxial atomizer liquid intact lengths  

NASA Technical Reports Server (NTRS)

Average intact lengths of round liquid jets generated by airblast coaxial atomizer were measured from over 1500 photographs. The intact lengths were studied over a jet Reynolds number range of 18,000 and Weber number range of 260. Results are presented for two different nozzle geometries. The intact lengths were found to be strongly dependent on Re and We numbers. An empirical equation was derived as a function of these parameters. A comparison of the intact lengths for round jets and flat sheets shows that round jets generate shorter intact lengths.

Eroglu, Hasan; Chigier, Norman; Farago, Zoltan

1991-01-01

383

Infrared absorption of carbon dioxide at high densitites with application to the atmosphere of Venus. Ph.D. Thesis - Columbia Univ.  

NASA Technical Reports Server (NTRS)

Several new infrared absorptions were found in carbon dioxide. All are normally forbidden, and were collision-induced in an absorbing cell whose combination of pressure and path length has a unique sensitivity for induced absorptions. The new absorptions in the 2.3 micron region are attributed to transitions from ground to the 3(1)1 Fermi pair at 4248 and 4391/cm. Other absorptions are attributed to simultaneous CO2-N2 transitions and to the 00(0)0-00(0)2 transition in CO2 polarizability derivatives and regular progressions in strength versus increasing quantum number. The spectra were used to predict the radiative transfer in a dry CO2 model of the lower Venus atmosphere. The results indicate that the radiation balance in the lower atmosphere is adequately explained by a dry massive atmosphere of CO2 with a layer of infrared-opaque clouds. The absorptions in the 2.3 micron region are significant in accounting for the opacity to sustain Venus' 768 K surface temperature.

Moore, J. F.

1971-01-01

384

Path Analysis with Composite Variables.  

ERIC Educational Resources Information Center

Six methods for fitting path models with weighted composites of variables replacing latent variables (of which five are easily implemented with conventional computer software) are introduced and related to "soft" modeling by Partial Least Squares. Criteria for comparing their performance are devised, and some evaluative remarks are offered.…

McDonald, Roderick P.

1996-01-01

385

Randomized distributed shortest paths algorithms  

Microsoft Academic Search

This paper is concerned with distributed algorithm for finding shortest paths in an asynchronous communication network. For the problem of Breadth First Search, the best previously known algorithms required either &THgr;(V) time, or &THgr; (E + V · D) communication. We present new algorithm, which requires O(D1+?) time, and O(E1+?) messages, for any ? > 0. (Here, V is number

B. Awerbuch

1989-01-01

386

Perceived Shrinkage of Motion Paths  

ERIC Educational Resources Information Center

We show that human observers strongly underestimate a linear or circular trajectory that a luminous spot follows in the dark. At slow speeds, observers are relatively accurate, but, as the speed increases, the size of the path is progressively underestimated, by up to 35%. The underestimation imposes little memory load and does not require…

Sinico, Michele; Parovel, Giulia; Casco, Clara; Anstis, Stuart

2009-01-01

387

Moldovan employment relations: “path dependency”?  

Microsoft Academic Search

Purpose – The paper aims to examine the theory that trade unions' functions in a transitional economy are characterised by “path dependency”. Design\\/methodology\\/approach – The research is based on case studies of employment relations in enterprises operating in Moldova. The approach is realist (critical materialism). An ethnographic approach is taken to analysing social relations in three locally and foreign-owned companies

Claudio Morrison; Richard Croucher

2010-01-01

388

Thinking on the Write Path  

ERIC Educational Resources Information Center

The present paper underscores the importance of the cognitive orientation of English as a Foreign Language (EFL) students in their success in writing courses. A few suggestions are made as to how EFL teachers can put their students on the right cognitive path in their writings.

Salmani-Nodoushan, Mohammad Ali

2007-01-01

389

Career Paths in Environmental Sciences  

EPA Science Inventory

Career paths, current and future, in the environmental sciences will be discussed, based on experiences and observations during the author's 40 + years in the field. An emphasis will be placed on the need for integrated, transdisciplinary systems thinking approaches toward achie...

390

Errors in spectroscopic measurements of SOâ due to nonexponential absorption of laser radiation, with application to the remote monitoring of atmospheric pollutants  

Microsoft Academic Search

Methods of measuring the concentration of atmospheric pollutants by laser absorption spectroscopy, such as differential absorption lidar (DIAL) and integrated long-path techniques, all rely on the validity of Beer's exponential absorption law. It is shown here that departures from this law occur if the probing laser has a bandwidth larger than the wavelength scale of structure in the absorption spectrum

D. J. Brassington; T. M. Moncrieff; R. C. Felton; B. W. Jolliffe; B. R. Marx; W. R. C. Rowley; P. T. Woods

1984-01-01

391

Centrifugal Length Separation of Carbon Nanotubes  

SciTech Connect

Separation of single-wall carbon nanotubes (SWCNTs) by length via centrifugation in a high density medium, and the characterization of both the separated fractions and the centrifugation process are presented. Significant quantities of the separated SWCNTs ranging in average length from < 50 nm to ?2 ?m were produced, with the distribution width being coupled to the rate of the separation. Less rapid separation is shown to produce narrower distributions; these length fractions, produced using sodium deoxycholate dispersed SWCNTs, were characterized by UV-visible-nearinfrared absorption and fluorescence spectroscopy, dynamic light scattering, Raman scattering, and atomic force microscopy. Several parameters of the separation were additionally explored: SWCNT concentration, added salt concentration, liquid density, rotor speed, surfactant concentration, and the processing temperature. The centrifugation technique is shown to support 10 mg per day scale processing and is applicable to all of the major SWCNT production methods. The cost per unit of the centrifugation-based separation is also demonstrated to be significantly less than size exclusion chromatography-based separations.

Fagan, Jeffrey A.; Becker, Matthew L.; Chun, Jaehun; Nie, Pingting; Bauer, Barry J.; Simpson, Jeffrey R.; Hight-Walker, Angela; Hobbie, Erik K.

2008-12-16

392

Estimation of microwave absorption in the Jupiter atmosphere  

NASA Technical Reports Server (NTRS)

A procedure for estimating the microwave absorption loss of the Jupiter atmosphere is presented. Estimation of microwave absorption by planetary atmospheres involves two different investigative disciplines (1) the determination of an acceptable model of the atmosphere itself and (2) the determination of the microwave attenuation rate applicable to each different volume sample of the atmosphere, and the integration of this loss over the varying radio propagation path for any given entry trajectory to obtain the total loss.

Coombs, W. C.

1971-01-01

393

PSTD Simulation of optical phase conjugation of light propagating long optical paths.  

PubMed

The phenomenon of Optical Phase Conjugation (OPC) can be rigorously simulated using the pseudospectral time-domain (PSTD) technique. However, with finite computational memory, it is infeasible to simulate light propagating long optical paths. We report a robust OPC simulation technique that can account for long optical path lengths by sequentially inverting the electromagnetic fields. Specifically, the ideal efficiency of OPC refocusing of light through scattering medium can be accurately determined. PMID:19333316

Tseng, Snow H

2009-03-30

394

Algorithms and Bounds for Shortest Paths and Diameter in Faulty Hypercubes  

Microsoft Academic Search

In an n-dimensional hypercube Qn, with the fault set |F|<2n-2, assuming S and D are not isolated, it is shown that there exists a path of length equal to at most their Hamming distance plus 4. An algorithm with complexity O (|F|logn) is given to find such a path. A bound for the diameter of the faulty hypercube Qn-F, when

Sing-ban Tien; C. S. Raghavendra

1993-01-01

395

Sarcomere length control in striated muscle.  

PubMed

A system that makes control of muscle length (ML), sarcomere length (SL), and force (F) possible in striated muscle preparations is described. SL was measured by light diffraction techniques and two diffractometers. Control was performed by influencing ML with a penmotor system with a frequency response of 190 Hz. SL or F could be controlled by interrupting the internal position (i.e., ML) feedback of the motor and by closing the respective loop. Velocity feedback of the motor through an internal velocity coil was maintained in all cases for optimal damping. Steady-state error of the system was minimized by an integrating loop filter. The feedback path was selected by means of potentiometers or analog switches. Electronic stops in the circuit protected the muscle against excessive stretch and load. A microprocessor-based average-response computer could be used for feedforward control to eliminate noise or to analyze longitudinal uniformity of the muscle. Responses of rat cardiac trabeculae during SL and F control are shown. Transient behavior of SL and F during control and measures to eliminate the transients are discussed. PMID:7065201

van Heuningen, R; Rijnsburger, W H; ter Keurs, H E

1982-03-01

396

Radar-based open-path chemical sensor created.  

SciTech Connect

Researchers at the U.S. Department of Energy's Argonne National Laboratory developed an interference-free, open-path, radar-based, millimeter-wave sensor to remotely detect trace levels of airborne chemicals. The new sensor works in remote positions, for environmental monitoring (continuous emission and fenceline), leak detection, and arms-control treaty verification. However, the transmitter/detector and a reflector have to sandwich the targeted chemical plume to get accurate measurements. Millimeter-wave absorption spectra of plume chemicals are determined by measuring the swept-frequency radar return signals, with and without the plume being in the beam's path. To determine actual chemical concentrations, users match measured spectra to a spectral library.

Gopalsami, N.; Raptis, A. C.; Energy Technology

1999-07-01

397

Intestinal Calcium Absorption: Mechanisms and Applications  

Microsoft Academic Search

Calcium absorption from the intestine in volves two sets of events. One, a saturable transcellular process is regulated by vitamin D via its molecular product, the calcium-binding protein (CaBP, MW = 8800). This transcellular movement is largely confined to the proximal portion of the intestine. The second process is nonsatur- able, occurs throughout the length of the intestine and is

FELIX BRONNER

398

Interstellar absorption toward HD 14633  

NASA Technical Reports Server (NTRS)

Observations are reported of optical interstellar absorption lines of Ti II, Ca II, and Na I in the spectrum of HD 14633, a probable runaway O star ejected from the Perseus spiral arm. Unusually high gas-phase abundances of the normally depleted elements Ca and Ti are found in three high-velocity interstellar line components; the light paths to only a few other stars are known to show a comparably strong Routly-Spitzer effect. The greatly reduced heavy-element depletions in these parcels of gas presumably reflect the disruption of interstellar grains in gas which may be located in the lower galactic halo at an absolute value of 2 of about 1 kpc.

Hobbs, L. M.

1983-01-01

399

Interstellar absorption toward HD 14633  

SciTech Connect

Observations are reported of optical interstellar absorption lines of Ti II. Ca II, and Na I in the spectrum of HD 14633, a probable runaway O star ejected from the Perseus spiral arm. Unusually high gas-phase abundances of the normally depleted elements Ca and Ti are found in three high-velocity interstellar line components; the light paths to only a few other stars are known to show a comparable strong Routly-Spitzer effect. The greatly reduced heavy-element depletions in these parcels of gas presumably reflect the disruption of interstellar grains in gas which may be located in the lower galactic halo at Vertical BarzVertical Barroughly-equal1 kpc.

Hobbs, L.M.

1983-02-15

400

Comments on Electrostatic Persistence Length  

NASA Astrophysics Data System (ADS)

I have shown that the quadratic dependence of the electrostatic persistence length on the Debye screening length obtained in the classical Odijk-Skolnick-Fixman (OSF) theory is a result of incorrect assumption made about the energetic penalty for chain deformation. By including chain elasticity the linear dependence of the electrostatic persistence length on the Debye screening length is obtained. This result is derived by applying simple scaling analysis of the angle fluctuations and Gaussian variational principle to the system of strongly and weakly charged polymer chains.

Dobrynin, Andrey

2005-03-01

401

Colloidal quantum dot photovoltaics: a path forward.  

PubMed

Colloidal quantum dots (CQDs) offer a path toward high-efficiency photovoltaics based on low-cost materials and processes. Spectral tunability via the quantum size effect facilitates absorption of specific wavelengths from across the sun's broad spectrum. CQD materials' ease of processing derives from their synthesis, storage, and processing in solution. Rapid advances have brought colloidal quantum dot photovoltaic solar power conversion efficiencies of 6% in the latest reports. These achievements represent important first steps toward commercially compelling performance. Here we review advances in device architecture and materials science. We diagnose the principal phenomenon-electronic states within the CQD film band gap that limit both current and voltage in devices-that must be cured for CQD PV devices to fulfill their promise. We close with a prescription, expressed as bounds on the density and energy of electronic states within the CQD film band gap, that should allow device efficiencies to rise to those required for the future of the solar energy field. PMID:21967723

Kramer, Illan J; Sargent, Edward H

2011-11-22

402

Path similarity skeleton graph matching.  

PubMed

This paper presents a novel framework to for shape recognition based on object silhouettes. The main idea is to match skeleton graphs by comparing the shortest paths between skeleton endpoints. In contrast to typical tree or graph matching methods, we completely ignore the topological graph structure. Our approach is motivated by the fact that visually similar skeleton graphs may have completely different topological structures. The proposed comparison of shortest paths between endpoints of skeleton graphs yields correct matching results in such cases. The skeletons are pruned by contour partitioning with Discrete Curve Evolution, which implies that the endpoints of skeleton branches correspond to visual parts of the objects. The experimental results demonstrate that our method is able to produce correct results in the presence of articulations, stretching, and occlusion. PMID:18550909

Bai, Xiang; Latecki, Longin Jan

2008-07-01

403

Spin Path Integrals and Generations  

Microsoft Academic Search

The spin of a free electron is stable but its position is not. Recent quantum information research by G. Svetlichny, J. Tolar,\\u000a and G. Chadzitaskos have shown that the Feynman position path integral can be mathematically defined as a product of incompatible states; that is, as a product of mutually unbiased\\u000a bases (MUBs). Since the more common use of MUBs

Carl Brannen

2010-01-01

404

Large margin shortest path routing  

Microsoft Academic Search

A new discriminative approach to routing inspired by the large margin criterion serving as a basis for support vector machines\\u000a is presented. The proposed formulation uses the benefit of the dualization convex program, and it is possible for standard\\u000a solvers to learn the weighting metrics of the shortest path routing. In order to demonstrate this and due to its simplicity,

Yadamsuren Lutbat; Rentsen Enkhbat; Won-Joo Hwang

405

Quasi-Randomized Path Planning  

Microsoft Academic Search

We propose the use of quasi-random sampling techniquesfor path planning in high-dimensional congurationspaces. Following similar trends from relatednumerical computation elds, we show several advantagesoered by these techniques in comparison to randomsampling. Our ideas are evaluated in the contextof the probabilistic roadmap (PRM) framework.Two quasi-random variants of PRM-based plannersare proposed: 1) a classical PRM with quasi-randomsampling, and 2) a quasi-random Lazy-PRM....

Micliael S. Branicky; Steven M. Lavalle; Kari Olson; Libo Yang

2001-01-01

406

Deterministic technique of path summation  

SciTech Connect

A numerical method, based on the Euclidean path integral formulation of quantum mechanics, to evaluate the ground state energy and wave function of a quantum system is discussed. The method is illustrated in one-dimensional cases, and then applied to a two-body system interacting through central and tensor potentials. A detailed discussion of the deuteron problem with a realistic nuclear potential is given.

Rosa-Clot, M.; Taddei, S. (Dipartimento di Fisica, Universita degli Studi di Firenze and Istituto Nazionale di Fisica Nucleare, Sezione di Firenze, Largo Enrico Fermi 2, I-50125, Firenze (Italy))

1994-08-01

407

Fourier transform infrared absorption spectroscopy characterization of gaseous atmospheric pressure plasmas with 2 mm spatial resolution  

SciTech Connect

This paper describes an optical setup built to record Fourier transform infrared (FTIR) absorption spectra in an atmospheric pressure plasma with a spatial resolution of 2 mm. The overall system consisted of three basic parts: (1) optical components located within the FTIR sample compartment, making it possible to define the size of the infrared beam (2 mm Multiplication-Sign 2 mm over a path length of 50 mm) imaged at the site of the plasma by (2) an optical interface positioned between the spectrometer and the plasma reactor. Once through the plasma region, (3) a retro-reflector module, located behind the plasma reactor, redirected the infrared beam coincident to the incident path up to a 45 Degree-Sign beamsplitter to reflect the beam toward a narrow-band mercury-cadmium-telluride detector. The antireflective plasma-coating experiments performed with ammonia and silane demonstrated that it was possible to quantify 42 and 2 ppm of these species in argon, respectively. In the case of ammonia, this was approximately three times less than this gas concentration typically used in plasma coating experiments while the silane limit of quantification was 35 times lower. Moreover, 70% of the incoming infrared radiation was focused within a 2 mm width at the site of the plasma, in reasonable agreement with the expected spatial resolution. The possibility of reaching this spatial resolution thus enabled us to measure the gaseous precursor consumption as a function of their residence time in the plasma.

Laroche, G. [Laboratoire d'Ingenierie de Surface, Centre de Recherche sur les Materiaux Avances, Departement de genie des mines, de la metallurgie et des materiaux, Universite Laval, 1065, avenue de la Medecine, Quebec G1V 0A6 (Canada); Centre de recherche du CHUQ, Hopital St Francois d'Assise, 10, rue de l'Espinay, local E0-165, Quebec G1L 3L5 (Canada); Vallade, J. [Laboratoire Procedes, Materiaux et Energie Solaire, PROMES, CNRS, Technosud, Rambla de la Thermodynamique, F-66100 Perpignan (France); Agence de l'environnement et de la Ma Latin-Small-Letter-Dotless-I -carettrise de l'Energie, 20, avenue du Gresille, BP 90406, F-49004 Angers Cedex 01 (France); Bazinette, R.; Hernandez, E.; Hernandez, G.; Massines, F. [Laboratoire Procedes, Materiaux et Energie Solaire, PROMES, CNRS, Technosud, Rambla de la Thermodynamique, F-66100 Perpignan (France); Nijnatten, P. van [OMT Solutions bv, High Tech Campus 9, 5656AE Eindhoven (Netherlands)

2012-10-15

408

Accelerating cleanup: Paths to closure  

SciTech Connect

This document was previously referred to as the Draft 2006 Plan. As part of the DOE`s national strategy, the Richland Operations Office`s Paths to Closure summarizes an integrated path forward for environmental cleanup at the Hanford Site. The Hanford Site underwent a concerted effort between 1994 and 1996 to accelerate the cleanup of the Site. These efforts are reflected in the current Site Baseline. This document describes the current Site Baseline and suggests strategies for further improvements in scope, schedule and cost. The Environmental Management program decided to change the name of the draft strategy and the document describing it in response to a series of stakeholder concerns, including the practicality of achieving widespread cleanup by 2006. Also, EM was concerned that calling the document a plan could be misconstrued to be a proposal by DOE or a decision-making document. The change in name, however, does not diminish the 2006 vision. To that end, Paths to Closure retains a focus on 2006, which serves as a point in time around which objectives and goals are established.

Edwards, C.

1998-06-30

409

Model for Delay Faults Based upon Paths  

Microsoft Academic Search

Delay testing of combinational logic in a clocked environment is analyzed. A model based upon paths is introduced for delay faults. Any path with a total delay exceeding the clock interval is called a \\

Gordon L. Smith

1985-01-01

410

Multiresolution Path Planning for Mobile Robots.  

National Technical Information Service (NTIS)

The problem of automatic collision-free path planning is central to mobile robot applications. This report presents an approach to automatic two dimensional path planning based on a quadtree representation. (A quadtree is a recursive decomposition of a 2-...

S. Kambhampati L. S. Davis

1985-01-01

411

Path Integral Methods for Inelastic Scattering.  

National Technical Information Service (NTIS)

Corrections to the primitive semi-classical amplitude for multiple inelastic scattering are obtained from a path integral formulation of scattering theory. The path integrals are calculated by making an expansion about a classical orbit describing elastic...

C. V. Sukumar D. M. Brink

1983-01-01

412

Surface Waves: Source and Path Properties.  

National Technical Information Service (NTIS)

Several characteristics of oceanic surface waves can be altered by low rigidity sediments along the propagation path. Specifically spectral shape of both Love and Rayleigh waves as well as path phase velocity can be affected. The theoretical Love wave spe...

D. J. Weidner

1975-01-01

413

PathExpress update: the enzyme neighbourhood method of associating gene-expression data with metabolic pathways  

PubMed Central

The post-genomic era presents us with the challenge of linking the vast amount of raw data obtained with transcriptomic and proteomic techniques to relevant biological pathways. We present an update of PathExpress, a web-based tool to interpret gene-expression data and explore the metabolic network without being restricted to predefined pathways. We define the Enzyme Neighbourhood (EN) as a sub-network of linked enzymes with a limited path length to identify the most relevant sub-networks affected in gene-expression experiments. PathExpress is freely available at: http://bioinfoserver.rsbs.anu.edu.au/utils/PathExpress/.

Goffard, Nicolas; Frickey, Tancred; Weiller, Georg

2009-01-01

414

Multiple paths to encephalization and technical civilizations.  

PubMed

We propose consideration of at least two possible evolutionary paths for the emergence of intelligent life with the potential for technical civilization. The first is the path via encephalization of homeothermic animals; the second is the path to swarm intelligence of so-called superorganisms, in particular the social insects. The path to each appears to be facilitated by environmental change: homeothermic animals by decreased climatic temperature and for swarm intelligence by increased oxygen levels. PMID:22139517

Schwartzman, David; Middendorf, George

2011-12-01

415

Folded-Light-Path Colloidal Quantum Dot Solar Cells  

PubMed Central

Colloidal quantum dot photovoltaics combine low-cost solution processing with quantum size-effect tuning to match absorption to the solar spectrum. Rapid advances have led to certified solar power conversion efficiencies of over 7%. Nevertheless, these devices remain held back by a compromise in the choice of quantum dot film thickness, balancing on the one hand the need to maximize photon absorption, mandating a thicker film, and, on the other, the need for efficient carrier extraction, a consideration that limits film thickness. Here we report an architecture that breaks this compromise by folding the path of light propagating in the colloidal quantum dot solid. Using this method, we achieve a substantial increase in short-circuit current, ultimately leading to improved power conversion efficiency.

Koleilat, Ghada I.; Kramer, Illan J.; Wong, Chris T. O.; Thon, Susanna M.; Labelle, Andre J.; Hoogland, Sjoerd; Sargent, Edward H.

2013-01-01

416

The Length of My Feet  

NSDL National Science Digital Library

This is Lesson 1 of a five lesson unit. "This lesson focuses students' attention on the attributes of length and develops their knowledge of and skill in using nonstandard units of measurement, their feet. It provides practice with and remediation of the measurable attributes of length." (from NCTM Illuminations)

Math, Illuminations N.

2009-01-28

417

Line Lengths and Starch Scores.  

ERIC Educational Resources Information Center

Investigates readability of different line lengths in advertising body copy, hypothesizing a normal curve with lower scores for shorter and longer lines, and scores above the mean for lines in the middle of the distribution. Finds support for lower scores for short lines and some evidence of two optimum line lengths rather than one. (SKC)

Moriarty, Sandra E.

1986-01-01

418

On the Distribution of Free Path Lengths for the Periodic Lorentz Gas III  

NASA Astrophysics Data System (ADS)

For r(0,1), let Zr={xR2|dist(x,Z2)>r/2} and define ?r(x,v)=inf{t>0|x+tv?Zr}. Let ?r(t) be the probability that ?r(x,v)>=t for x and v uniformly distributed in Zr and §1 respectively. We prove in this paper that as t-->+?. This result improves upon the bounds on ?r in Bourgain-Golse-Wennberg [Commun. Math. Phys. 190, 491-508 (1998)]. We also discuss the applications of this result in the context of kinetic theory.

Caglioti, Emanuele; Golse, François

419

Tail Asymptotics of Free Path Lengths for the Periodic Lorentz Process: On Dettmann's Geometric Conjectures  

NASA Astrophysics Data System (ADS)

In the simplest case, consider a {mathbb{Z}^d} -periodic (d ? 3) arrangement of balls of radii < 1/2, and select a random direction and point (outside the balls). According to Dettmann's first conjecture, the probability that the so determined free flight (until the first hitting of a ball) is larger than t > > 1 is {˜C/t} , where C is explicitly given by the geometry of the model. In its simplest form, Dettmann's second conjecture is related to the previous case with tangent balls (of radii 1/2). The conjectures are established in a more general setup: for {mathcal{L}} -periodic configuration of—possibly intersecting—convex bodies with {mathcal{L}} being a non-degenerate lattice. These questions are related to Pólya's visibility problem (Arch Math Phys Ser 2:135-142, 1918), to theories of Bourgain et al. (Commun Math Phys 190:491-508,1998), and of Marklof-Strömbergsson (Ann Math 172:1949-2033,2010). The results also provide the asymptotic covariance of the periodic Lorentz process assuming it has a limit in the super-diffusive scaling, a fact if d = 2 and the horizon is infinite.

Nándori, Péter; Szász, Domokos; Varjú, Tamás

2014-06-01

420

Experimental Demonstration of Reduced Path-length Sensitivity in Coherent Beam Combining Architectures  

Microsoft Academic Search

Proper exploitation of spatial supermodes in Michelsontype cavities reduces the sensitivity of coherent beam combining to pathleng th variations. The resulting radiance improvement is experimentally demonstrated in a commonpath generalized Michelson cavity formed by polarization multiplexing the two gain arms into a common space. ©2009 Optical Society of America OCIS codes: 140.3298, 140.3510 All configurations for coherent laser beam combining

M. Khajavikhan; J. R. Leger

421

Information Flow in Interaction Networks II: Channels, Path Lengths, and Potentials  

PubMed Central

Abstract In our previous publication, a framework for information flow in interaction networks based on random walks with damping was formulated with two fundamental modes: emitting and absorbing. While many other network analysis methods based on random walks or equivalent notions have been developed before and after our earlier work, one can show that they can all be mapped to one of the two modes. In addition to these two fundamental modes, a major strength of our earlier formalism was its accommodation of context-specific directed information flow that yielded plausible and meaningful biological interpretation of protein functions and pathways. However, the directed flow from origins to destinations was induced via a potential function that was heuristic. Here, with a theoretically sound approach called the channel mode, we extend our earlier work for directed information flow. This is achieved by constructing a potential function facilitating a purely probabilistic interpretation of the channel mode. For each network node, the channel mode combines the solutions of emitting and absorbing modes in the same context, producing what we call a channel tensor. The entries of the channel tensor at each node can be interpreted as the amount of flow passing through that node from an origin to a destination. Similarly to our earlier model, the channel mode encompasses damping as a free parameter that controls the locality of information flow. Through examples involving the yeast pheromone response pathway, we illustrate the versatility and stability of our new framework.

Stojmirovic, Aleksandar

2012-01-01

422

Pulsed Laval nozzle with a large optical path length of 50 cm  

Microsoft Academic Search

This note describes the design and performance of a pulsed valve developed as a gas source for a 500 mm long supersonic Laval nozzle with a 3 mm wide throat. The valve consists of a rotating drum with a slit, which allows an opening duration of approximately 14 ms. The duration of quasi-steady-state expansion is measured to be 10 ms

Yoshiki Okada; Shohei Isomura; Sakae Satooka; Kazuo Takeuchi

1994-01-01

423

Cam-driven pulsed Laval nozzle with a large optical path length of 50 cm  

Microsoft Academic Search

This article describes the design and performance of a pulsed valve developed as a gas source for a 500-nm-long supersonic Laval nozzle with a 3-mm-wide throat. The valve consists of a plate cam and a valve seat equipped with O-rings on both the upper and lower faces. The duration of quasi-steady-state expansion is measured to be 12 ms at the

Yoshiki Okada; Shohei Isomura; Sakae Satooka; Kazuo Takeuchi

1996-01-01

424

[Ultrasound determination of leg length].  

PubMed

A diagnostic method is presented for measuring the leg length and the difference in leg lengths with ultrasound. A special device for holding and moving the ultrasound transducer was constructed. The measuring points on the hip, knee, and upper ankle can be visualized with a 5- or 7.5-MHz linear scanner. The measuring device gives the distance of the points in centimeters so that the difference corresponds to the real length of the leg, femur, and tibia. Tests conducted on corpses and clinical examples show that ultrasound in combination with our special device is an ideal method for determining the exact length of the leg. Ultrasound measurement of the leg length offers a reliable, noninvasive, and easily performed method. Because ultrasound is not limited by radiation hazards, our technique can be used for clinical screening. PMID:12017860

Konermann, W; Gruber, G

2002-03-01

425

Wavelet formulation of path integral Monte Carlo  

Microsoft Academic Search

A wavelet formulation of path integral Monte Carlo (PIMC) is constructed. Comparison with Fourier path integral Monte Carlo is presented using simple one-dimensional examples. Wavelet path integral Monte Carlo exhibits a few advantages over previous methods for PIMC. The efficiency of the current method is at least comparable to other techniques.

Art E. Cho; J. D. Doll; David L. Freeman

2002-01-01

426

Removing False Paths from Combinational Modules 1  

Microsoft Academic Search

The existence of false paths complicates the task of accurate tim- ing analysis significantly. A technique to remove false paths from a combinational circuit without degrading its performance h as a prac- tical value since topological timing analysis is then good e nough to estimate the performance of false-path-free circuits accu rately. One can think of the KMS algorithm (1)

Yuji Kukimoto; Robert K. Brayton

427

Chip layout optimization using critical path weighting  

Microsoft Academic Search

A chip layout procedure for optimizing the performance of critical timing paths in a synchronous digital circuit is presented. The procedure uses the path analysis data produced by a static timing analysis program to generate weights for critical nets on clock and data paths. These weights are then used to bias automatic placement and routing in the layout program. This

A. E. Dunlop; V. D. Agrawal; D. N. Deutsch; M. F. Jukl; P. Kazak

1988-01-01

428

Fast Algorithms for Solving Path Problems  

Microsoft Academic Search

Let G = (V, E) be a directed graph with a distinguished source vertex s. The single-source path expression problem is to find, for each vertex v, a regular expression P(s, v) which represents the set of all paths in G from s to v A solution to this problem can be used to solve shortest path problems, solve sparse

Robert Endre Tarjan

1981-01-01

429

Global path planning using artificial potential fields  

Microsoft Academic Search

The author describes a path planning technique for robotic manipulators and mobile robots in the presence of stationary obstacles. The planning consists of applying potential fields around configuration-space obstacles and using these fields to select a safe path for the robot to follow. The advantage of using potential fields in path planning is that they offer a relatively fast and

Charles W. Warren

1989-01-01

430

Path diversity for enhanced media streaming  

Microsoft Academic Search

Media streaming over best effort packet networks such as the Internet is quite challenging because of the dynamic and unpredictable available bandwidth, loss rate, and delay. Recently, streaming over multiple paths to provide path diversity has emerged as an approach to help overcome these problems. This article provides an overview of the benefits and use of path diversity for media

John G. Apostolopoulos; Mitchell D. Trott

2004-01-01

431

SCTP Performance Issue on Path Delay Differential  

Microsoft Academic Search

This paper studies the effect of path delay on SCTP performance. It focuses on the SCTP fast retransmit algorithm and demonstrates that the performance in the current retransmission strategy will degrade acutely when the secondary path delay is less than the primary path delay at a certain level. The performance degradation is due to the disordered SACKs and constant congestion

Yuansong Qiao; Enda Fallon; Liam Murphy; John Murphy; Austin Hanley; Xiaosong Zhu; Adrian Matthews; Eoghan Conway; Gregory Hayes

2007-01-01

432

Path delay fault simulation of sequential circuits  

Microsoft Academic Search

To analyze path delay faults in synchronous sequential circuits, stimuli are simulated in a dual-vector mode. The signal states represent the logic and transition conditions for two consecutive vectors. After the simulation of each vector, only the activated paths are traced and the corresponding fault effect, if propagated to a flip-flop, is added to its fault list. A path numbering

Soumitra Bose; Prathima Agrawal; Vishwani D. Agrawal

1993-01-01

433

Path Integral Analyses of the Hydrogen Atom  

Microsoft Academic Search

The path integral analysis of the hydrogen atom problem are presented in this dissertation. The Green's function for the hydrogen atom is calculated exactly by path integration. The scattering phase shifts are also expressed in terms of path integrals and evaluated for the Coulomb potential with or without additional modifying potentials. First, the hydrogen atom in two dimensions is treated

Roger Chung Chor Ho

1982-01-01

434

Path integral analyses of the hydrogen atom  

Microsoft Academic Search

The path integral analysis of the hydrogen atom problem are presented in this dissertation. The Green's function for the hydrogen atom is calculated exactly by the path integration. The scattering phase shifts are also expressed in terms of path integrals and evaluated for the Coulomb potential with or without additional modifying potentials. First, the hydrogen atom in two dimensions is

1982-01-01

435

14 CFR 25.111 - Takeoff path.  

Code of Federal Regulations, 2010 CFR

...2009-01-01 2009-01-01 false Takeoff path. 25.111 Section 25.111 Aeronautics and...AIRPLANES Flight Performance § 25.111 Takeoff path. (a) The takeoff path extends from a standing start to a point...

2009-01-01

436

14 CFR 25.111 - Takeoff path.  

Code of Federal Regulations, 2010 CFR

...2010-01-01 2010-01-01 false Takeoff path. 25.111 Section 25.111 Aeronautics and...AIRPLANES Flight Performance § 25.111 Takeoff path. (a) The takeoff path extends from a standing start to a point...

2010-01-01

437

14 CFR 23.57 - Takeoff path.  

Code of Federal Regulations, 2010 CFR

...2009-01-01 2009-01-01 false Takeoff path. 23.57 Section 23.57 Aeronautics...Flight Performance § 23.57 Takeoff path. For each commuter category airplane, the takeoff path is as follows: (a) The...

2009-01-01

438

Randomized path coloring on binary trees  

Microsoft Academic Search

Motivated by the problem of WDM routing in all-optical networks, we study the following NP-hard problem. We are given a directed binary tree T and a set R of directed paths on T. We wish to assign colors to paths of R, in such way that no two paths that share a directed arc of T are assigned the same

Vincenzo Auletta; Ioannis Caragiannis; Christos Kaklamanis; Pino Persiano

2002-01-01

439

Evaluation of the Learning Path Specification  

ERIC Educational Resources Information Center

Flexible lifelong learning requires that learners can compare and select learning paths that best meet individual needs, not just in terms of learning goals, but also in terms of planning, costs etc. To this end a learning path specification was developed, which describes both the contents and the structure of any learning path, be it formal,…

Janssen, Jose; Berlanga, Adriana J.; Koper, Rob

2011-01-01

440

Quantifying the Causes of Path Inflation  

Microsoft Academic Search

Researchers have shown that the Internet exhibits path inflation - end-to-end paths can be significantly longer than necessary. We present a trace-driven study of 65 ISPs that characterizes the root causes of path inflation, namely topology and routing policy choices within an ISP, between pairs of ISPs, and across the global Inter- net. To do so, we develop and validate

Neil Spring; Ratul Mahajan; Thomas Anderson

2003-01-01

441

A Two Micron Coherent Differential Absorption Lidar Development  

NASA Technical Reports Server (NTRS)

A pulsed, 2-micron coherent Differential Absorption Lidar (DIAL)/Integrated Path Differential Absorption (IPDA) transceiver, developed under the Laser Risk Reduction Program (LRRP) at NASA, is integrated into a fully functional lidar instrument. This instrument measures atmospheric CO2 profiles (by DIAL) from a ground platform. It allows the investigators to pursue subsequent in science-driven deployments, and provides a unique tool for Active Sensing of CO2 Emissions over Night, Days, and Seasons (ASCENDS) validation that was strongly advocated in the recent ASCENDS Workshop. Keywords: Differential Absorption Lidar, Near Infrared Laser,

Yu, Jirong; Petros, Mulugeta; Chen, Songsheng; Bai, Yingxin; Petzar, Paul J.; Trieu, Bo C.; Koch, Grady J.; Beyon, Jeffrey Y.; VanValkenburg, Randal L.; Kavaya, Michael J.; Singh, Upendra N.

2010-01-01

442

Tunable Diode Laser Absorption Spectrometer Coal Mine Methane Detection System Based on DSP  

Microsoft Academic Search

Tunable diode laser absorption spectroscopy (TDLAS) technology is a new detective method developed with the combination of a tunable diode laser source and a long absorption path. It has the characteristic of high sensitivity, high precision and rapid response. Based on TDLAS and high performance microcontroller (DSP), the system is developed to monitor the coal mine methane. The second harmonic

Renbao Wang; Hongyan Feng

2010-01-01

443

Processor Would Find Best Paths On Map  

NASA Technical Reports Server (NTRS)

Proposed very-large-scale integrated (VLSI) circuit image-data processor finds path of least cost from specified origin to any destination on map. Cost of traversal assigned to each picture element of map. Path of least cost from originating picture element to every other picture element computed as path that preserves as much as possible of signal transmitted by originating picture element. Dedicated microprocessor at each picture element stores cost of traversal and performs its share of computations of paths of least cost. Least-cost-path problem occurs in research, military maneuvers, and in planning routes of vehicles.

Eberhardt, Silvio P.

1990-01-01

444

Switching mesh with broadcast path redundancy  

US Patent & Trademark Office Database

One embodiment disclosed relates to a method of broadcasting packets through a network of switches. A packet is received to be broadcast through the network of switches. A broadcast path is selected from a plurality of generated broadcast paths. A broadcast path tag associated with the selected broadcast path is created and inserted into the packet. A determination is made of the port(s) by which to forward the packet, and the packet is transmitted via the port(s) to next switch(es) in accordance with the selected broadcast path.

2008-11-04

445

Evaluation of guidewire path reproducibility.  

PubMed

The number of minimally invasive vascular interventions is increasing. In these interventions, a variety of devices are directed to and placed at the site of intervention. The device used in almost all of these interventions is the guidewire, acting as a monorail for all devices which are delivered to the intervention site. However, even with the guidewire in place, clinicians still experience difficulties during the interventions. As a first step toward understanding these difficulties and facilitating guidewire and device guidance, we have investigated the reproducibility of the final paths of the guidewire in vessel phantom models on different factors: user, materials and geometry. Three vessel phantoms (vessel diameters approximately 4 mm) were constructed having tortuousity similar to the internal carotid artery from silicon tubing and encased in Sylgard elastomer. Several trained users repeatedly passed two guidewires of different flexibility through the phantoms under pulsatile flow conditions. After the guidewire had been placed, rotational c-arm image sequences were acquired (9 in. II mode, 0.185 mm pixel size), and the phantom and guidewire were reconstructed (512(3), 0.288 mm voxel size). The reconstructed volumes were aligned. The centerlines of the guidewire and the phantom vessel were then determined using region-growing techniques. Guidewire paths appear similar across users but not across materials. The average root mean square difference of the repeated placement was 0.17 +/- 0.02 mm (plastic-coated guidewire), 0.73 +/- 0.55 mm (steel guidewire) and 1.15 +/- 0.65 mm (steel versus plastic-coated). For a given guidewire, these results indicate that the guidewire path is relatively reproducible in shape and position. PMID:18561663

Schafer, Sebastian; Hoffmann, Kenneth R; Noël, Peter B; Ionita, Ciprian N; Dmochowski, Jacek

2008-05-01

446

Multiple order common path spectrometer  

NASA Technical Reports Server (NTRS)

The present invention relates to a dispersive spectrometer. The spectrometer allows detection of multiple orders of light on a single focal plane array by splitting the orders spatially using a dichroic assembly. A conventional dispersion mechanism such as a defraction grating disperses the light spectrally. As a result, multiple wavelength orders can be imaged on a single focal plane array of limited spectral extent, doubling (or more) the number of spectral channels as compared to a conventional spectrometer. In addition, this is achieved in a common path device.

Newbury, Amy B. (Inventor)

2010-01-01

447

Intellimotion: California PATH's Quarterly Newsletter  

NSDL National Science Digital Library

The California Partners for Advanced Transit and Highways (PATH) researches methods for increasing highway safety, reducing congestion, and minimizing pollution and energy consumption. Intellimotion is one of its publications that highlights some of the current projects. Although it is labeled as a quarterly newsletter, Intellimotion is released on a very irregular basis. The 2002 issue covers several stories, including a project that makes vehicle navigation with the Global Positioning System extremely accurate. Another article looks at intelligent transportation systems and the issues regarding Bus Rapid Transit. Many past issues of Intellimotion are available on this Web site. This site is also reviewed in the October 25, 2002 Scout Report.

1998-01-01

448

A temporal ant colony optimization approach to the shortest path problem in dynamic scale-free networks  

NASA Astrophysics Data System (ADS)

A large number of networks in the real world have a scale-free structure, and the parameters of the networks change stochastically with time. Searching for the shortest paths in a scale-free dynamic and stochastic network is not only necessary for the estimation of the statistical characteristics such as the average shortest path length of the network, but also challenges the traditional concepts related to the “shortest path” of a network and the design of path searching strategies. In this paper, the concept of shortest path is defined on the basis of a scale-free dynamic and stochastic network model, and a temporal ant colony optimization (TACO) algorithm is proposed for searching for the shortest paths in the network. The convergence and the setup for some important parameters of the TACO algorithm are discussed through theoretical analysis and computer simulations, validating the effectiveness of the proposed algorithm.

Yu, Feng; Li, Yanjun; Wu, Tie-Jun

2010-02-01

449

Mechanics of the crack path formation  

NASA Technical Reports Server (NTRS)

A detailed analysis of experimentally obtained curvilinear crack path trajectories formed in a heterogeneous stress field is presented. Experimental crack path trajectories were used as data for numerical simulations, recreating the actual stress field governing the development of the crack path. Thus, the current theories of crack curving and kinking could be examined by comparing them with the actual stress field parameters as they develop along the experimentally observed crack path. The experimental curvilinear crack path trajectories were formed in the tensile specimens with a hole positioned in the vicinity of a potential crack path. The numerical simulation, based on the solution of equivalent boundary value problems with the possible perturbations of the crack path, is presented here.

Rubinstein, Asher A.

1989-01-01

450

Mechanics of the crack path formation  

NASA Technical Reports Server (NTRS)

A detailed analysis of experimentally obtained curvilinear crack path trajectories formed in a heterogeneous stress field is presented. Experimental crack path trajectories were used as data for the numerical simulations, recreating the actual stress field governing the development of the crack path. Thus, the current theories of crack curving and kinking could be examined by comparing them with the actual stress field parameters as they develop along the experimentally observed crack path. The experimental curvilinear crack path trajectories were formed in the tensile specimens with a hole positioned in the vicinity of a potential crack path. The numerical simulation, based on the solution of equivalent boundary value problems with the possible perturbations of the crack path, is presented.

Rubinstein, Asher A.

1991-01-01

451

Scale Length of Disk Galaxies  

NASA Astrophysics Data System (ADS)

As a part of a Euro-VO research initiative, we have undertaken a programme aimed at studying the scale length of 54909 Sa-Sd spiral galaxies from the SDSS DR6 catalogue. We have retrieved u, g, r, i, z-band images for all galaxies in order to derive the light profiles. We also calculate asymmetry parameters to select non-disturbed disks for which we will derive exponential disk scale lengths. As images in different bands probe different optical depths and stellar populations, it is likely that a derived scale length value should depend on waveband, and our goal is to use the scale length variations with band pass, inclination, galaxy type, redshift, and surface brightness, in order to better understand the nature of spiral galaxies.

Fathi, K.; Allen, M.; Gonzalez-Solares, E.; Hatziminaoglou, E.; Peletier, R.

2009-07-01

452

Optimal Patent Length and Breadth  

Microsoft Academic Search

In providing rewards to innovators, there is a tradeoff between patent length and breadth. This article provides conditions under which the optimal patent policy involves infinitely-lived patents, with patent breadth adjusting to provide the required reward for innovation.

Richard Gilbert; Carl Shapiro

1990-01-01

453

Design of periodic metal-insulator-metal waveguide back structures for the enhancement of light absorption in thin-film solar cells  

NASA Astrophysics Data System (ADS)

To increase the absorption in a thin layer of absorbing material (amorphous silicon, a-Si), a light trapping design is presented. The designed structure incorporates periodic metal-insulator-metal waveguides to enhance the optical path length of light within the solar cells. The new design can result in broadband optical absorption enhancement not only for transverse magnetic (TM)-polarized light, but also for transverse electric (TE)-polarized light. No plasmonic modes can be excited in TE-polarization, but because of the coupling into the a-Si planar waveguide guiding modes and the diffraction of light by the bottom periodic structures into higher diffraction orders, the total absorption in the active region is also increased. The results from rigorous coupled wave analysis show that the overall optical absorption in the active layer can be greatly enhanced by up to 40%. The designed structures presented in this paper can be integrated with back contact technology to potentially produce high-efficiency thin-film solar cell devices.

Zheng, Gai-Ge; Jiang, Jian-Li; Xian, Feng-Lin; Qiang, Hai-Xia; Wu, Hong; Li, Xiang-Yin

2011-09-01

454

Extreme light absorption in a necking-free monolayer of resonant-size nanoparticles for photoelectrochemical cells  

NASA Astrophysics Data System (ADS)

Semiconductor photoelectrodes for water oxidation that absorb visible light usually have poor electronic transport properties and small optical absorption coefficients near their absorption edge. Therefore, innovative designs that lead to significant optical absorption in relatively thin layers of these compounds are highly desirable. Here, using full-field electromagnetic optical simulations, we demonstrate that a monolayer of resonant-size {{BiV}}{{{{O}}}_{4}} spheres can provide enhancement up to a factor of two in solar light absorption relative to dense planar layers. In this monolayer, {{BiV}}{{{{O}}}_{4}} spheres do not need to be interconnected; therefore, such monolayers are flexible and their fabrication process does not require the complicated necking steps to establish electrical contact among the nanoparticles. These resonant-size spheres support Mie resonance modes that efficiently trap light and hence significantly increase effective optical path length. Under air mass 1.5 global (AM1.5G) irradiation, the maximum achievable photocurrent density (MAPD) in a monolayer of 250 nm diameter {{BiV}}{{{{O}}}_{4}} spheres reaches 4.9 mA.cm^{-2}. This is about twofold improvement over the MAPD for a 250 nm thick dense planar layer and well above the 3.8\\;{{mA}}.{{c}}{{{{m}}}^{-2}} MAPD for a 1 ?m thick dense planar layer. In addition, it is shown that lower-order resonance modes of the spheres are superior to higher-order modes for broadband optical absorption. The insight provided in this work can also be applied to nitride and oxynitride photoanode materials.

Dabirian, Ali

2014-07-01

455

Path correlation considered prioritized burst segmentation for quality of service support in optical burst switching networks  

NASA Astrophysics Data System (ADS)

Burst segmentation (BS) is a high-efficiency contention resolution scheme in bufferless optical burst switching (OBS) networks. A prioritized BS scheme for quality of service (QoS) support is developed. Unlike the existing work on the BS scheme, the proposed BS model considers path-correlated factors, such as path length, the adjoining paths carrying traffic on a given path, and the multipriority traffic coming from all paths. Byte loss probability for high-priority and low-priority bursts under the time-based assembly approach and the length-based assembly approach to estimate the performance of the proposed BS scheme by comparing the cumulative distribution function of a burst length in an OBS ingress node (source) with that in an egress node (destination) is introduced. A preemptive BS policy for different priority bursts is proposed to support the QoS of the OBS network. Finally, a simulation is given to validate the proposed analytical model in an existing OBS network with two priority bursts. It is shown that the proposed BS scheme can realize the service differentiation for multipriority traffic under the consideration of network topology-dependent parameters.

Hou, Rui; Changyue, Jiana; He, Tingting; Yu, Jianwei; Lei, Bo; Mao, Tengyue

2013-04-01

456

SSME propellant path leak detection  

NASA Technical Reports Server (NTRS)

The primary objective of this phase of the investigation is the experimental validation of techniques for detecting and analyzing propellant path external leaks which have a high probability of occurring on the SSME. The selection of candidate detection methods requires a good analytic model for leak plumes which would develop from external leaks and an understanding of radiation transfer through the leak plume. One advanced propellant path leak detection technique is obtained by using state-of-art technology of infrared (IR) thermal imaging systems combined with computer, digital image processing and expert systems for the engine protection. The feasibility of the IR leak plume detection will be evaluated on subscale simulated laboratory plumes to determine sensitivity, signal to noise, and general suitability for the application. The theoretical analysis was undertaken with the objective of developing and testing simple, easy-to-use models to predict the amount of radiation coming from a radiation source, background plate (BP), which can be absorbed, emitted and scattered by the gas leaks.

Crawford, Roger; Shohadaee, Ahmad Ali; Powers, W. T.

1995-01-01

457

Correlations between bond lengths, Tc, and O vibration frequencies: Raman-scattering and infrared-absorption study of the 1:2:1:2 structure (Ca1-yYy)Sr2(Tl0.5Pb0.5)Cu2O7 as a function of doping  

Microsoft Academic Search

Raman-scattering and infrared-absorption measurements on optical phonons are used to investigate the doping-induced changes in the electronic structure of (Ca1-yYy)Sr2(Tl0.5Pb0.5)Cu2O7 (Tl\\/Pb-1:2:1:2). In contrast to YBa2Cu3O7-delta (YBCO), the doping of the CuO2 planes is achieved by direct substitution of Ca2+ for Y3+ in between the CuO2 planes, enabling the effects of the dynamic out-of-plane charge transfer and doping to be separated.

T. Mertelj; D. Mihailovic; F. C. Matacotta; R. S. Liu; J. R. Cooper; I. Gameson; P. P. Edwards

1993-01-01

458

Orthorhombic phase of crystalline polyethylene: A constant pressure path-integral Monte Carlo study  

Microsoft Academic Search

In this paper we present a path-integral Monte Carlo (PIMC) simulation of the orthorhombic phase of crystalline polyethylene, using an explicit atom force field with unconstrained bond lengths and angles. This work represents a quantum extension of our recent classical simulation [R. Martonák et al., J. Chem. Phys. 106, 8918 (1997)]. It is aimed both at exploring the applicability of

R. Martonák; W. Paul; K. Binder

1998-01-01

459

Crack Path Selection in Adhesively-Bonded Joints: The Role of Material Properties  

Microsoft Academic Search

This paper investigates the role of material properties on crack path selection in adhesively bonded joints. First, a parametric study of directionally unstable crack propagation in adhesively-bonded double cantilever beam specimens (DCB) is presented. The results indicate that the characteristic length of directionally unstable cracks varies with the Dundurs' parameters characterizing the material mismatch. Second, the effect of interface properties

Buo Chen; David A. Dillard; John G. Dillard; Richard L. Clark Jr

2001-01-01

460

A genetic algorithm for shortest path routing problem and the sizing of populations  

Microsoft Academic Search

This paper presents a genetic algorithmic approach to the shortest path (SP) routing problem. Variable-length chromosomes (strings) and their genes (parameters) have been used for encoding the problem. The crossover operation exchanges partial chromosomes (partial routes) at positionally independent crossing sites and the mutation operation maintains the genetic diversity of the population. The proposed algorithm can cure all the infeasible

Chang Wook Ahn; Rudrapatna S. Ramakrishna

2002-01-01