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1

Integrating sphere effective optical path length calibration by gas absorption spectroscopy  

NASA Astrophysics Data System (ADS)

A method of integrating sphere effective optical path length (EOPL) evaluation using tunable diode laser absorption spectroscopy for gas detection was demonstrated. Oxygen was used as a sample gas for an 8.38 cm diameter integrating sphere calibration; 393.7 ± 1.3 cm EOPL was obtained from the wavelength modulation spectroscopy with second harmonic calibration by measuring oxygen P11 line at 764 nm, which is in agreement with that of 393 cm by using direct absorption spectroscopy calibration. The EOPL calibration accuracy of this method can reach 0.33 %. It has been justified that the EOPL of an integrating sphere is independent of the incident light intensity.

Gao, Qiang; Zhang, Yungang; Yu, Jia; Zhang, Zhiguo; Wu, Shaohua; Guo, Wei

2014-03-01

2

Path length errors of VLBI antennas  

NASA Astrophysics Data System (ADS)

The performance of single dish radio antennas or telescopes is depending on the surface accuracy of the reflectors in the beam path and the focus/pointing errors induced by deviations/misalignment of the reflectors from a desired direction. For multiple dish VLBI arrays an additional mechanical effect, the path length stability, is a further source of performance degradation. For application at higher frequencies environmental influences as wind and temperature have to be considered additionally to the usually required manufacturing and alignment accuracies. Active measurement ("metrology") of the antenna deformations and their compensation by "active optics" (AO) respectively "flexible body compensation" (FBC) are established methods. For the path length errors AO or FBC are up to now not established methods. The paper describes how to handle the path length errors and the related metrology analogues to the established methods used for surface and focus/pointing error corrections.

Kaercher, Hans J.; Sust, Eberhard; Emde, Peter; Kühn, Jürgen

2010-07-01

3

Optical path-length matrix method for estimating skin spectrum  

NASA Astrophysics Data System (ADS)

In this article, we propose a new method—the optical path-length matrix method (OPLM)—as a faster alternative to the Monte Carlo for multi-layered media (MCML), which is often used to simulate the skin spectrum. Theoretically, peripheral oxygen saturation can be estimated by iterating MCML, but it is not a realistic strategy because it requires huge computation time. The optical path-length matrix is obtained as the probabilistic density histograms of the optical path length in skin using MCML, and once the matrix is obtained, skin spectral reflectance can be calculated by accumulating all combinations of elements in the matrix and by setting an absorption coefficient based on the Beer-Lambert law. The computational time of OPLM was approximately 26,000 times faster than that of MCML.

Yamamoto, Satoshi; Fujiwara, Izumi; Yamauchi, Midori; Tsumura, Norimichi; Ogawa-Ochiai, Keiko

2012-11-01

4

Free Path Lengths in Quasi Crystals  

NASA Astrophysics Data System (ADS)

The Lorentz gas is a model for a cloud of point particles (electrons) in a distribution of scatterers in space. The scatterers are often assumed to be spherical with a fixed diameter d, and the point particles move with constant velocity between the scatterers, and are specularly reflected when hitting a scatterer. There is no interaction between point particles. An interesting question concerns the distribution of free path lengths, i.e. the distance a point particle moves between the scattering events, and how this distribution scales with scatterer diameter, scatterer density and the distribution of the scatterers. It is by now well known that in the so-called Boltzmann-Grad limit, a Poisson distribution of scatterers leads to an exponential distribution of free path lengths, whereas if the scatterer distribution is periodic, the free path length distribution asymptotically behaves as a power law. This paper considers the case when the scatters are distributed on a quasi crystal, i.e. non periodically, but with a long range order. Simulations of a one-dimensional model are presented, showing that the quasi crystal behaves very much like a periodic crystal, and in particular, the distribution of free path lengths is not exponential.

Wennberg, Bernt

2012-06-01

5

Average path length for Sierpinski pentagon  

E-print Network

In this paper,we investigate diameter and average path length(APL) of Sierpinski pentagon based on its recursive construction and self-similar structure.We find that the diameter of Sierpinski pentagon is just the shortest path lengths between two nodes of generation 0. Deriving and solving the linear homogenous recurrence relation the diameter satisfies, we obtain rigorous solution for the diameter. We also obtain approximate solution for APL of Sierpinski pentagon, both diameter and APL grow approximately as a power-law function of network order $N(t)$, with the exponent equals $\\frac{\\ln(1+\\sqrt{3})}{\\ln(5)}$. Although the solution for APL is approximate,it is trusted because we have calculated all items of APL accurately except for the compensation($\\Delta_{t}$) of total distances between non-adjacent branches($\\Lambda_t^{1,3}$), which is obtained approximately by least-squares curve fitting. The compensation($\\Delta_{t}$) is only a small part of total distances between non-adjacent branches($\\Lambda_t^{1,3}$) and has little effect on APL. Further more,using the data obtained by iteration to test the fitting results, we find the relative error for $\\Delta_{t}$ is less than $10^{-7}$, hence the approximate solution for average path length is almost accurate.

Junhao Peng; Guoai Xu

2011-12-21

6

Average path length for Sierpinski pentagon  

E-print Network

In this paper,we investigate diameter and average path length(APL) of Sierpinski pentagon based on its recursive construction and self-similar structure.We find that the diameter of Sierpinski pentagon is just the shortest path lengths between two nodes of generation 0. Deriving and solving the linear homogenous recurrence relation the diameter satisfies, we obtain rigorous solution for the diameter. We also obtain approximate solution for APL of Sierpinski pentagon, both diameter and APL grow approximately as a power-law function of network order $N(t)$, with the exponent equals $\\frac{\\ln(1+\\sqrt{3})}{\\ln(5)}$. Although the solution for APL is approximate,it is trusted because we have calculated all items of APL accurately except for the compensation($\\Delta_{t}$) of total distances between non-adjacent branches($\\Lambda_t^{1,3}$), which is obtained approximately by least-squares curve fitting. The compensation($\\Delta_{t}$) is only a small part of total distances between non-adjacent branches($\\Lambda_t^{1...

Peng, Junhao

2011-01-01

7

UV laser long-path absorption spectroscopy  

NASA Technical Reports Server (NTRS)

Long path Differential Optical Absorption Spectroscopy (DOAS) using a picosecond UV laser as a light source was developed in our institute. Tropospheric OH radicals are measured by their rotational absorption lines around 308 nm. The spectra are obtained using a high resolution spectrograph. The detection system has been improved over the formerly used optomechanical scanning device by application of a photodiode array which increased the observed spectral range by a factor of 6 and which utilizes the light much more effectively leading to a considerable reduction of the measurement time. This technique provides direct measurements of OH because the signal is given by the product of the absorption coefficient and the OH concentration along the light path according to Lambert-Beers law. No calibration is needed. Since the integrated absorption coefficient is well known the accuracy of the measurement essentially depends on the extent to which the OH absorption pattern can be detected in the spectra. No interference by self generated OH radicals in the detection lightpath has been observed. The large bandwidth (greater than 0.15 nm) and the high spectral resolution (1.5 pm) allows absolute determination of interferences by other trace gas absorptions. The measurement error is directly accessible from the absorption-signal to baseline-noise ratio in the spectra. The applicability of the method strongly depends on visibility. Elevated concentrations of aerosols lead to considerable attenuation of the laser light which reduces the S/N-ratio. In the moderately polluted air of Julich, where we performed a number of OH measurement spectra. In addition absorption features of unidentified species were frequently detected. A quantitative deconvolution even of the known species is not easy to achieve and can leave residual structures in the spectra. Thus interferences usually increase the noise and deteriorate the OH detection sensitivity. Using diode arrays for sensitive absorption measurements some specific problems of those detectors have to be solved experimentally (i.e. fixed pattern noise, dark signal noise, nonuniform efficiency of individual elements, spatial sensitivity variations). In order to improve the low spatial resolution we performed laboratory studies using a multiple reflection cell to convert the long path technique to a real in situ point measurement. Under the conditions of field experiments in Julich residual absorbance signals at present are about 1.5x10(exp -4) corresponding to an OH detection sensitivity of 2x10(exp 6) OH/cm(exp 3) using a light path of 5.8 km. Total integration times for one measurement point vary between a few minutes and an hour.

Dorn, Hans-Peter; Brauers, Theo; Neuroth, Rudolf

1994-01-01

8

FREE PATH LENGTHS IN QUASICRYSTALS JENS MARKLOF AND ANDREAS STROMBERGSSON  

E-print Network

FREE PATH LENGTHS IN QUASICRYSTALS JENS MARKLOF AND ANDREAS STR¨OMBERGSSON Abstract. Previous proves the existence of a limit distribution of the free path length, which answers a question loss of generality that v(t) = 1. The "phase space" is then the unit tangent bundle T1 (K) where K Rd

Marklof, Jens

9

Absorption Lengths in the Holographic Plasma  

E-print Network

We consider the effect of a periodic perturbation with frequency $\\omega$ on the holographic N=4 plasma represented by the planar AdS black hole. The response of the system is given by exponentially decaying waves. The corresponding complex wave numbers can be found by solving wave equations in the AdS black hole background with infalling boundary conditions on the horizon in an analogous way as in the calculation of quasinormal modes. The complex momentum eigenvalues have an interpretation as poles of the retarded Green's functions, where the inverse of the imaginary part gives an absorption length $\\lambda$. At zero frequency we obtain the screening length for a static field. These are directly related to the glueball masses in the dimensionally reduced theory. We also point out that the longest screening length corresponds to an operator with non-vanishing R-charge and thus does not have an interpretation as a QCD3 glueball.

Irene Amado; Carlos Hoyos; Karl Landsteiner; Sergio Montero

2007-06-19

10

Interferometric sensors based on sinusoidal optical path length modulation  

NASA Astrophysics Data System (ADS)

Sinusoidal optical path length modulation of the reference or the measurement arm of an interferometer is a technique which is a fast alternative to white light or phase shifting interferometry. In this paper three different sensors using this periodical modulation are presented. In addition, signal processing algorithms based on Discrete Fourier Transform, Hilbert Transform and parameter estimation are analyzed. These algorithms are used to obtain measurement results which demonstrate the capabilities of the presented interferometric sensors.

Knell, Holger; Schake, Markus; Schulz, Markus; Lehmann, Peter

2014-05-01

11

In-situ Measurements of Tropospheric Hydroxyl Radicals by Folded Long-Path Laser Absorption During the Field Campaign POPCORN  

Microsoft Academic Search

Absolutely calibrated in-situ measurements of tropospheric hydroxyl radicals, formaldehyde, sulfur dioxide, and naphthalene (C10H8) were performed by long-path laser absorption spectroscopy during the field campaign POPCORN. The absorption light path was folded into an open optical multiple reflection cell with a mirror separation of 38.5 m. Using a light path length of 1848 m and an integration time of 200

Uwe Brandenburger; Theo Brauers; Hans-Peter Dorn; Martin Hausmann; Dieter H. Ehhalt

1998-01-01

12

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

13

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

14

Temperature variable long path cell for absorption measurements  

NASA Technical Reports Server (NTRS)

The design and construction of a long path cell for absorption measurements at temperatures ranging from 215-470 K and at pressures from vacuum to 10 atm are described. The cell consists of three concentric stainless-steel tubes; the innermost tube is 6.5-in. in internal diameter, has a volume of about 47 l, and contains White-type optics, six thermocouples, and a gas input tube; and the outermost tube provides a vacuum Dewar around the inner assembly. The optical design and temperature control system for the long path temperature variable cell are examined. The long path cell is applicable for analyzing temperature and pressure dependence of spectra and reaction rates of gases, and the cell has flow and photolysis capabilities for studying transient species and photochemically initiated reactions. A diagram of the cell is provided.

Shetter, R. E.; Davidson, J. A.; Cantrell, C. A.; Calvert, J. G.

1987-01-01

15

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

16

Joint statistics of photon path length and cloud optical depth: Case studies  

Microsoft Academic Search

We show the joint statistics of photon path length and cloud optical depth for cloudy sky cases observed at the Atmospheric Radiation Measurement (ARM) Southern Great Plains (SGP) site between September and December 1997. The photon path lengths are retrieved from moderate resolution oxygen A-band observations taken by a rotating shadow band spectroradiometer (RSS). For high optical depth cloud cases,

Qilong Min; Lee C. Harrison; Eugene E. Clothiaux

2001-01-01

17

FREE PATH LENGTHS IN QUASICRYSTALS JENS MARKLOF AND ANDREAS STR OMBERGSSON  

E-print Network

FREE PATH LENGTHS IN QUASICRYSTALS JENS MARKLOF AND ANDREAS STR ¨OMBERGSSON Abstract. Previous proves the existence of a limit distribution for the free path length, which answers a question loss of generality that v(t) = 1. The "phase space" is then the unit tangent bundle T1 (K) where K Rd

Strömbergsson, Andreas

18

[Influence of optical path length on NIR analysis results for trace metal determination in Chinese rice wine].  

PubMed

The prediction performance of near infrared (NIR) spectra with different optical path-length for trace metal (potassium, calcium, magnesium, zincum, and iron) determination was investigated. NIR transmission spectra of Chinese rice wine were collected in rectangular quartz cuvette with different optical path lengths (1, 2, 5 and 10 mm) using Fourier transform near infrared (FT-NIR) spectrometer in the wavelength range of 800-2 500 nm with air as the reference. The reference data for potassium, calcium, magnesium, zinc, and iron were determined by atomic absorption spectroscopy (AAS). Calibration models were developed by partial least squares (PLS) regression. The PLS models of NIR spectra group with 5 mm path length gave the best calibration result. The determination coefficients (r2) for potassium, calcium, magnesium, zincum, and iron were 0.93, 0.85, 0.93, 0.72, and 0.66, respectively, and the root mean square error of cross validation (RMSECV) for the five elements were 26.5, 35.6, 4.63, 0.26, and 0.64 mg x L-(-1), respectively, whereas the models established by NIR spectra group of 10 mm path-length was the worst. And the r2 values for potassium, calcium, magnesium, zincum, and iron were 0.61, 0.65, 0.63, 0.09, and 0.25, respectively. The results indicated that the optical path length has an influence on the NIR analysis results for trace metal determination in Chinese rice wine, and that the appropriate path length for the NIR analysis should be determined by comparison analysis. PMID:17763771

Yu, Hai-Yan; Ying, Yi-Bin; Xie, Li-Juan; Fu, Xia-Ping

2007-06-01

19

In vivo quantification of chromophore concentration using fluorescence differential path length spectroscopy  

NASA Astrophysics Data System (ADS)

We present an optical method based on fluorescence spectroscopy for measuring chromophore concentrations in vivo. Fluorescence differential path length spectroscopy (FPDS) determines chromophore concentration based on the fluorescence intensity corrected for absorption. The concentration of the photosensitizer m-THPC (Foscan®) was studied in vivo in normal rat liver, which is highly vascularized and therefore highly absorbing. Concentration estimates of m-THPC measured by FDPS on the liver are compared with chemical extraction. Twenty-five rats were injected with 0.3 mg/kg m-THPC. In vivo optical concentration measurements were performed on tissue 3, 24, 48, and 96 h after m-THPC administration to yield a 10-fold variation in tissue concentration. After the optical measurements, the liver was harvested for chemical extraction. FDPS showed good correlation with chemical extraction. FDPS also showed a correlation between m-THPC fluorescence and blood volume fraction at the two shortest drug-light intervals. This suggests different compartmental localization of m-THPC for different drug-light intervals that can be resolved using fluorescence spectroscopy. Differences in measured m-THPC concentration between FDPS and chemical extraction are related to the interrogation volume of each technique; ~0.2 mm3 and ~102 mm3, respectively. This indicates intra-animal variation in m-THPC distribution in the liver on the scale of the FDPS sampling volume.

Kruijt, Bastiaan; Kascakova, Slavka; de Bruijn, Henriette S.; van der Ploeg-van den Heuvel, Angelique; Sterenborg, Henricus J. C. M.; Robinson, Dominic J.; Amelink, Arjen

2009-05-01

20

Students' Development of Length Concepts in a Logo-Based Unit on Geometric Paths  

Microsoft Academic Search

We investigated the development of linear measure concepts within an instructional unit on paths and lengths of paths, part of a large-scale curriculum development project funded by the National Science Foundation (NSF). We also studied the role of noncomputer and computer interactions in that development. Data from paper-and-pencil assessments, interviews, and case studies were collected within the context of a

Douglas H. Clements; Michael T. Battista; Sudha Swaminathan; Sue McMillen

1997-01-01

21

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

22

Qualms Regarding the Optimality of Cumulative Path Length Control in CSA\\/CMA-Evolution Strategies  

Microsoft Academic Search

The cumulative step-size adaptation (CSA) based on path length control is regarded as a robust alternative to the standard mutative self-adaptation technique in evolution strategies (ES), guaranteeing an almost optimal control of the mutation operator. In this short paper it is shown that the underlying basic assumption in CSA - the per- pendicularity of expected consecutive steps - does not

Hans-georg Beyer; Dirk V. Arnold

2003-01-01

23

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

24

Depth capabilities of neutron and synchrotron diffraction strain measurement instruments. I. The maximum feasible path length  

Microsoft Academic Search

In this paper an algorithm is presented for estimating the maximum feasible penetration path length for neutron and synchrotron X-ray strain measurement instruments. This reflects the attenuation and scattering capability of the material under examination, the incident flux and detector arrangement, the likely background signal, the required strain measurement accuracy, the sampling volume and the diffracting geometry. Its validity and

Philip John Withers

2004-01-01

25

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

E-print Network

Acoustic method for measuring the sound speed of gases over small path lengths J. S. Olfert,a M. D, Canada Received 9 February 2007; accepted 8 April 2007; published online 9 May 2007 Acoustic "phase shift this method the discrete acoustic wave and phase detection DAWPD method. Experimental results show

26

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

27

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

28

Optical path-length modulation for three-dimensional particle measurement in mirror-embedded microchannels.  

PubMed

Simple and low-cost implementation of three-dimensional (3D) particle measurement is vital for designing and characterizing microfluidic devices that show spatiotemporally varying characteristics in three dimensions. However, the conventional 3D particle image velocimetry or particle streak velocimetry has proven difficult to address the needs, requiring complex and expensive equipment, precise alignment between optical components, and specialized image-processing algorithms. Here, we report mirror-embedded microchannels and a method of optical path-length (OPL) modulation for 3D particle measurement in the channels. The mirror, ideally at 45 degrees, reflects the side view of the channels and enables 3D positional information to be obtained easily from two different orthogonal-axis images with different optical paths. To offset the optical path difference between two image views, we utilized a cover glass as a medium of high refractive index and placed it in the light path through which the side-view image propagates, thereby prolonging the OPL of the side view and simultaneously shifting its depth of field (DOF) range. This modulation ensures imaging of in-focus side view as well as top view. This 3D imaging principle was verified by observing 3D positions of 6 mum-sized beads in the linear and grooved microchannels. The mirror-embedded scheme can be readily fabricated with existing microfluidic designs, and offer easy and simple implementation of 3D particle measurement. PMID:20091005

Choi, Sungyoung; Kim, Seung-Hoon; Park, Je-Kyun

2010-02-01

29

Exact evaluation of the cutting path length in a percolation model on a hierarchical network.  

PubMed

This work presents an approach to evaluate the exact value of the fractal dimension of the cutting path d(f)(CP) on hierarchical structures with finite order of ramification. Our approach is based on a renormalization group treatment of the universality class of watersheds. By making use of the self-similar property, we show that d(f)(CP) depends only on the average cutting path (CP) of the first generation of the structure. For the simplest Wheastone hierarchical lattice (WHL), we present a mathematical proof. For a larger WHL structure, the exact value of d(f)(CP) is derived based on a computer algorithm that identifies the length of all possible CP's of the first generation. PMID:23679379

Andrade, R F S; Herrmann, H J

2013-04-01

30

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

31

LHC Predictions from an extended theory with Elastic, Inelastic, and Path Length Fluctuating Energy Loss  

E-print Network

We present the LHC predictions for the WHDG model of radiative, elastic, and path length fluctuating energy loss. We find the pT dependence of RAA is qualitatively very different from AWS-based energy loss extrapolations to the LHC; the large pT reach of the year one data at the LHC should suffice to distinguish between the two. We also discuss the importance of requiring a first elastic scatter before any medium-induced elastic or radiative loss occurs, a necessary physical effect not considered in any previous models.

William A. Horowitz

2007-02-27

32

Wave lengths of some new absorption bands of sulfur dioxide vapor  

E-print Network

WavE LENGTHS OF SOME NEW ABSORPTION BANDS OF SUIFUR DIOXIDE VAPOR A Thesis BOBBY L. LANDRUM Approved as to style and content by: Chairman of Committee Head of Department / August 195$ LIBRARY A &III CCLLEGE OF TEXAS WAVE LENGTHS OF SOME... NEW ABSORPTION BANDS OF SULFUR DIOXIDE VAPOR Bobby L. Landrum A Thesis Submitted to the Graduate School of the Agricultural and Mechanical College of Texas in Partial fulfillment of the requirements for the degree of MASTER OF SCIENCE IN PHYSICS...

Landrum, Bobby Lee

2012-06-07

33

Investigating brain community structure abnormalities in bipolar disorder using path length associated community estimation.  

PubMed

In this article, we present path length associated community estimation (PLACE), a comprehensive framework for studying node-level community structure. Instead of the well-known Q modularity metric, PLACE utilizes a novel metric, ?(PL), which measures the difference between intercommunity versus intracommunity path lengths. We compared community structures in human healthy brain networks generated using these two metrics and argued that ?(PL) may have theoretical advantages. PLACE consists of the following: (1) extracting community structure using top-down hierarchical binary trees, where a branch at each bifurcation denotes a collection of nodes that form a community at that level, (2) constructing and assessing mean group community structure, and (3) detecting node-level changes in community between groups. We applied PLACE and investigated the structural brain networks obtained from a sample of 25 euthymic bipolar I subjects versus 25 gender- and age-matched healthy controls. Results showed community structural differences in posterior default mode network regions, with the bipolar group exhibiting left-right decoupling. PMID:23798337

Gadelkarim, Johnson J; Ajilore, Olusola; Schonfeld, Dan; Zhan, Liang; Thompson, Paul M; Feusner, Jamie D; Kumar, Anand; Altshuler, Lori L; Leow, Alex D

2014-05-01

34

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

35

arXiv:physics/0511072v2[physics.optics]14Apr2006 Optical fibers with interferometric path length stability by controlled heating for  

E-print Network

path length of an optical fiber to an accuracy of about 1/100 of the laser wavelength. We study the dynamic response of the path length to modulation of an electrically conductive heater layer of the fiber. The path length is measured against the laser wavelength by use of the Pound-Drever-Hall method; negative

Peters, Achim

36

In-situ detection of tropospheric OH radicals by folded long-path laser absorption. Results from the POPCORN Field Campaign in August 1994  

NASA Astrophysics Data System (ADS)

Ground based in-situ measurements of tropospheric hydroxyl radicals were conducted by folded long-path laser absorption as part of the field campaign POPCORN in August 1994. The OH instrument used an open optical multiple-reflection cell of 38.5 m base length through which the laser beam was passed up to 80 times. The broadband emission of a short-pulse UV laser together with a multichannel detection system allowed the simultaneous observation of six OH absorption lines in a spectral interval of ???0.24 nm at 308.1nm (A²?+,?? = 0? X²?,?? = 0 transition). Along with the OH radicals, the trace gases SO2, HCHO, and naphthalene were measured by this technique. The large spectral detection range covered a multitude of rotational absorption lines of these trace gases which were all used for multicomponent analysis, thus allowing a specific and sensitive detection of tropospheric OH radicals. An average 2? detection limit of 1.5 × 106 OH/cm³ for an integration time of 200 seconds and an absorption light path length of 1848 m was determined from the field measurements. In total, 392 OH data were obtained by long-path absorption during 16 days of field measurements. The observed OH concentrations reached peak values of 13 × 106 cm-3 at noon.

Dorn, H.-P.; Brandenburger, U.; Brauers, T.; Hausmann, M.; Ehhalt, D. H.

37

Multispectral reflectance imaging of brain activation in rodents: methodological study of the differential path length estimations and first in vivo recordings in the rat olfactory bulb.  

PubMed

Dynamic maps of relative changes in blood volume and oxygenation following brain activation are obtained using multispectral reflectance imaging. The technique relies on optical absorption modifications linked to hemodynamic changes. The relative variation of hemodynamic parameters can be quantified using the modified Beer-Lambert Law if changes in reflected light intensities are recorded at two wavelengths or more and the differential path length (DP) is known. The DP is the mean path length in tissues of backscattered photons and varies with wavelength. It is usually estimated using Monte Carlo simulations in simplified semi-infinite homogeneous geometries. Here we consider the use of multilayered models of the somatosensory cortex (SsC) and olfactory bulb (OB), which are common physiological models of brain activation. Simulations demonstrate that specific DP estimation is required for SsC and OB, specifically for wavelengths above 600 nm. They validate the hypothesis of a constant path length during activation and show the need for specific DP if imaging is performed in a thinned-skull preparation. The first multispectral reflectance imaging data recorded in vivo during OB activation are presented, and the influence of DP on the hemodynamic parameters and the pattern of oxymetric changes in the activated OB are discussed. PMID:22352662

Renaud, Rémi; Martin, Claire; Gurden, Hirac; Pain, Frédéric

2012-01-01

38

Multispectral reflectance imaging of brain activation in rodents: methodological study of the differential path length estimations and first in vivo recordings in the rat olfactory bulb  

NASA Astrophysics Data System (ADS)

Dynamic maps of relative changes in blood volume and oxygenation following brain activation are obtained using multispectral reflectance imaging. The technique relies on optical absorption modifications linked to hemodynamic changes. The relative variation of hemodynamic parameters can be quantified using the modified Beer-Lambert Law if changes in reflected light intensities are recorded at two wavelengths or more and the differential path length (DP) is known. The DP is the mean path length in tissues of backscattered photons and varies with wavelength. It is usually estimated using Monte Carlo simulations in simplified semi-infinite homogeneous geometries. Here we consider the use of multilayered models of the somatosensory cortex (SsC) and olfactory bulb (OB), which are common physiological models of brain activation. Simulations demonstrate that specific DP estimation is required for SsC and OB, specifically for wavelengths above 600 nm. They validate the hypothesis of a constant path length during activation and show the need for specific DP if imaging is performed in a thinned-skull preparation. The first multispectral reflectance imaging data recorded in vivo during OB activation are presented, and the influence of DP on the hemodynamic parameters and the pattern of oxymetric changes in the activated OB are discussed.

Renaud, Rémi; Martin, Claire; Gurden, Hirac; Pain, Frédéric

2012-01-01

39

In situ detection of tropospheric OH radicals by folded long-path laser absorption. Results from the POPCORN field campaign in August 1994  

Microsoft Academic Search

Ground based in situ measurements of tropospheric hydroxyl radicals were conducted by folded long-path laser absorption as part of the field campaign POPCORN in August 1994. The OH instrument used an open optical multiple-reflection cell of 38.5 m base length through which the laser beam was passed up to 80 times. The broadband emission of a short-pulse UV laser together

H.-P. Dorn; U. Brandenburger; T. Brauers; M. Hausmann; D. H. Ehhalt

1996-01-01

40

Nearly arc-length tool path generation and tool radius compensation algorithm research in FTS turning  

NASA Astrophysics Data System (ADS)

In the non-rotational symmetrical microstrcture surfaces generation using turning method with Fast Tool Servo(FTS), non-uniform distribution of the interpolation data points will lead to long processing cycle and poor surface quality. To improve this situation, nearly arc-length tool path generation algorithm is proposed, which generates tool tip trajectory points in nearly arc-length instead of the traditional interpolation rule of equal angle and adds tool radius compensation. All the interpolation points are equidistant in radial distribution because of the constant feeding speed in X slider, the high frequency tool radius compensation components are in both X direction and Z direction, which makes X slider difficult to follow the input orders due to its large mass. Newton iterative method is used to calculate the neighboring contour tangent point coordinate value with the interpolation point X position as initial value, in this way, the new Z coordinate value is gotten, and the high frequency motion components in X direction is decomposed into Z direction. Taking a typical microstructure with 4?m PV value for test, which is mixed with two 70?m wave length sine-waves, the max profile error at the angle of fifteen is less than 0.01?m turning by a diamond tool with big radius of 80?m. The sinusoidal grid is machined on a ultra-precision lathe succesfully, the wavelength is 70.2278?m the Ra value is 22.81nm evaluated by data points generated by filtering out the first five harmonics.

Zhao, Minghui; Zhao, Xuesen; Li, Zengqiang; Sun, Tao

2014-08-01

41

Long-path absorption measurement of CO(2) with a Raman-shifted tunable dye laser.  

PubMed

A laser long-path absorption system was developed with a hydrogen Raman shifter pumped by a tunable dye laser. The absorption spectrum of CO(2) in the 2-µm region was measured in the open air with a retroreflector or a hard target. The concentration of CO(2) was determined from the spectrum by the least-squares method. Noise in the system was analyzed, and the propagation of error to the obtained concentration was investigated. The statistical error in the concentration was estimated at approximately 1% for a single spectrum measurement. Comparison with the simultaneous measurements with a nondispersive infrared gas analyzer showed good agreement. PMID:20856536

Sugimoto, N; Minato, A

1993-11-20

42

Error Reduction Methods for Integrated-path Differential-absorption Lidar Measurements  

NASA Technical Reports Server (NTRS)

We report new modeling and error reduction methods for differential-absorption optical-depth (DAOD) measurements of atmospheric constituents using direct-detection integrated-path differential-absorption lidars. Errors from laser frequency noise are quantified in terms of the line center fluctuation and spectral line shape of the laser pulses, revealing relationships verified experimentally. A significant DAOD bias is removed by introducing a correction factor. Errors from surface height and reflectance variations can be reduced to tolerable levels by incorporating altimetry knowledge and "log after averaging", or by pointing the laser and receiver to a fixed surface spot during each wavelength cycle to shorten the time of "averaging before log".

Chen, Jeffrey R.; Numata, Kenji; Wu, Stewart T.

2012-01-01

43

Alleviating the effects of light scattering in multivariate calibration of near-infrared spectra by path length distribution correction.  

PubMed

Near-infrared (NIR) spectroscopy has been used for noninvasive measurements of solid and liquid samples, through highly scattering media such as colloids, food, and tissue. It has seen many applications in agriculture, medicine, and petroleum industries, mainly due to the minimal sample preparation that is required. This minimal sample preparation does come at a cost to the analyst, since the high signal-to-noise ratio of a typical NIR instrument can be riddled with effects stemming from heterogeneity and the scattering of light. This work proposes a novel preprocessing method, the path length distribution correction (PDC) method, to correct spectral nonlinearities in samples of highly scattering media. These nonlinearities stem from the distribution of path lengths of the incident light, which are a result of the scattering of light in the sample. Recent developments in time-of-flight (TOF) spectroscopy have allowed for the acquisition of the distribution of times that photons travel within a sample simultaneous with the collection of the NIR spectrum. The TOF distribution is used to estimate a path length distribution within a sample, which is then used to fix the measurement spectra, giving each spectrum an apparent path length of unity. The PDC-corrected spectra can then be used with traditional multivariate calibration methods such as principal component regression (PCR) and partial least squares (PLS). Another discussion looks at the viability of using a lognormal distribution as a simple approximation of the TOF distribution. This would be very useful in circumstances in which experimental TOF distributions are not collected. PDC is shown to significantly improve prediction errors in experimental data sets, while diagnostic plots indicate that the corrected spectra do appear to have a path length of unity, thus alleviating effects of the distribution of path lengths. PMID:20223057

Leger, Marc N

2010-03-01

44

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

45

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

46

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

47

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

48

Discrete Mathematics and Theoretical Computer Science DMTCS vol. 9, 2007, 16 Note on the weighted internal path length of  

E-print Network

Discrete Mathematics and Theoretical Computer Science DMTCS vol. 9, 2007, 1­6 Note on the weighted of a class of edge-weighted random trees. This is a class of trees growing in continuous time which includes Introduction In this paper we derive a limit theorem for the internal path length of edge-weighted b-ary random

Paris-Sud XI, Université de

49

Influence of neglecting the curved path of the Achilles tendon on Achilles tendon length change at various ranges of motion.  

PubMed

Achilles tendon length has been measured using a straight-line model. However, this model is associated with a greater measurement error compared with a curved-line model. Therefore, we examined the influence of neglecting the curved path of the Achilles tendon on its length change at various ranges of motion. Ten male subjects participated in this study. First, the location of the Achilles tendon was confirmed by using ultrasonography, and markers were attached on the skin over the Achilles tendon path. Then, the three-dimensional coordinates of each marker at dorsiflexion (DF) 15°, plantarflexion (PF) 0°, PF15°, and PF30° were obtained. Achilles tendon length in the curved-line model was calculated as the sum of the distances among each marker. On the other hand, Achilles tendon length in the straight-line model was calculated as the straight distance between the two most proximal and distal markers projected onto the sagittal plane. The difference of the Achilles tendon length change between curved-line and straight-line models was calculated by subtracting the Achilles tendon length change obtained in curved-line model from that obtained in straight-line model with three different ranges of motion (i.e., PF0°, PF15°, and PF30° from DF15°, respectively). As a result, the difference in Achilles tendon length change between the two models increased significantly as the range of motion increased. In conclusion, neglecting the curved path of the Achilles tendon induces substantial overestimation of its length change when the extent of ankle joint angle change is large. PMID:25303951

Fukutani, Atsuki; Hashizume, Satoru; Kusumoto, Kazuki; Kurihara, Toshiyuki

2014-10-01

50

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

51

Measurement of distance changes using a fibre-coupled common-path interferometer with mechanical path length modulation  

NASA Astrophysics Data System (ADS)

We present a novel type of fibre-coupled interferometric sensor. A micro-optical probe acts as a common-path interferometer and focuses the measuring light emitted by a laser diode onto the surface under investigation. The probe is mounted on a bending beam and deflected periodically by a piezoelectric actuator. This generates a phase-modulated interference signal, which is transformed to an electrical signal by a photo diode. The measurement principle is based on the fact that a distance change between the probe and the measurement object leads to a characteristic phase-shift of the measured signal. The photo diode signal is analysed in different ways in order to enable both high accuracy in the nanometre range and high measurement speeds, where the data rate of the sensor is finally limited by the conversion rate of the used analogue-to-digital converter. In order to extend the range of unambiguity of the sensor and to improve the robustness of measurement, we apply a dual-wavelength technique using two laser diodes emitting at different wavelengths simultaneously. Repeatability measurements, responses to distance changes and, finally, the measurement of calibration specimens with well-defined surface profiles demonstrate the performance of the system.

Schulz, M.; Lehmann, P.

2013-06-01

52

[Open-path online monitoring of ambient atmospheric CO2 based on laser absorption spectrum].  

PubMed

With the conjunction of tunable diode laser absorption spectroscopy technology (TDLAS) and the open long optical path technology, the system designing scheme of CO2 on-line monitoring based on near infrared tunable diode laser absorption spectroscopy technology was discussed in detail, and the instrument for large-range measurement was set up. By choosing the infrared absorption line of CO2 at 1.57 microm whose line strength is strong and suitable for measurement, the ambient atmospheric CO2 was measured continuously with a 30 s temporal resolution at an suburb site in the autumn of 2007. The diurnal atmospheric variations of CO2 and continuous monitoring results were presented. The results show that the variation in CO2 concentration has an obvious diurnal periodicity in suburb where the air is free of interference and contamination. The general characteristic of diurnal variation is that the concentration is low in the daytime and high at night, so it matches the photosynthesis trend. The instrument can detect gas concentration online with high resolution, high sensitivity, high precision, short response time and many other advantages, the monitoring requires no gas sampling, the calibration is easy, and the detection limit is about 4.2 x 10(-7). It has been proved that the system and measurement project are feasible, so it is an effective method for gas flux continuous online monitoring of large range in ecosystem based on TDLAS technology. PMID:19385195

He, Ying; Zhang, Yu-Jun; Kan, Rui-Feng; Xia, Hui; Geng, Hui; Ruan, Jun; Wang, Min; Cui, Xiao-Juan; Liu, Wen-Qing

2009-01-01

53

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

54

Spectroscopic measurements of a CO2 absorption line in an open vertical path using an airborne lidar  

NASA Astrophysics Data System (ADS)

We used an airborne pulsed integrated path differential absorption lidar to make spectroscopic measurements of the pressure-induced line broadening and line center shift of atmospheric carbon dioxide at the 1572.335 nm absorption line. We scanned the lidar wavelength over 13 GHz (110 pm) and measured the absorption lineshape at 30 discrete wavelengths in the vertical column between the aircraft and ground. A comparison of our measured absorption lineshape to calculations based on HIgh-resolution TRANsmission molecular absorption database shows excellent agreement with the peak optical depth accurate to within 0.3%. Additionally, we measure changes in the line center position to within 5.2 MHz of calculations and the absorption linewidth to within 0.6% of calculations. These measurements highlight the high precision of our technique, which can be applied to suitable absorption lines of any atmospheric gas.

Ramanathan, Anand; Mao, Jianping; Allan, Graham R.; Riris, Haris; Weaver, Clark J.; Hasselbrack, William E.; Browell, Edward V.; Abshire, James B.

2013-11-01

55

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

2011-03-01

56

Optical fibers with interferometric path length stability by controlled heating for transmission of optical signals and as components in frequency standards  

E-print Network

We present a simple method to stabilize the optical path length of an optical fiber to an accuracy of about 1/100 of the laser wavelength. We study the dynamic response of the path length to modulation of an electrically conductive heater layer of the fiber. The path length is measured against the laser wavelength by use of the Pound-Drever-Hall method; negative feedback is applied via the heater. We apply the method in the context of a cryogenic resonator frequency standard.

Müller, H; Peters, A; Braxmaier, Claus; Mueller, Holger; Peters, Achim

2006-01-01

57

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

58

Simulating the Effect of Modulated Tool-Path Chip Breaking On Surface Texture and Chip Length  

SciTech Connect

One method for creating broken chips in turning processes involves oscillating the cutting tool in the feed direction utilizing the CNC machine axes. The University of North Carolina at Charlotte and the Y-12 National Security Complex have developed and are refining a method to reliably control surface finish and chip length based on a particular machine's dynamic performance. Using computer simulations it is possible to combine the motion of the machine axes with the geometry of the cutting tool to predict the surface characteristics and map the surface texture for a wide range of oscillation parameters. These data allow the selection of oscillation parameters to simultaneously ensure broken chips and acceptable surface characteristics. This paper describes the machine dynamic testing and characterization activities as well as the computational method used for evaluating and predicting chip length and surface texture.

Smith, K.S.; McFarland, J.T.; Tursky, D. A.; Assaid, T. S.; Barkman, W. E.; Babelay, Jr., E. F.

2010-04-30

59

Calibration stability of hot cathode ionization gauges: A discussion of the importance of electron path length and gauge constant  

NASA Astrophysics Data System (ADS)

The ion current, i+, in an ionization gauge is given by the equation i+=Ki-P where K is a gas dependent gauge constant, i- is the electron current, and P is the pressure. Values of K for nitrogen for gauges designed for use at ultrahigh vacuum and extreme high vacuum range from 10/Torr to 106/Torr. It is important to know whether calibration stability is sacrificed when K, and the electron path length are large. Using a simple model, the electron path length is estimated as a function of the probability, beta, that an electron will make another pass through the ionizing region. An equation is obtained for K as a function of beta. The fractional change in K, DeltaK/K, is zero for those gauges where the electrons make a single pass, but is increasingly larger for higher sensitivity gauges with greater probabilities of multiple passes. As an example, assume that the probability of the next pass changes by 1%, then the change in sensitivity is 1.5% for a B-A with K=25/Torr, and 9% for a gauge with K=102/Torr. copyright 2002 American Vacuum Society.

Peacock, R. N.

2002-07-01

60

Temperature-dependent ballistic transport in a channel with length below the scattering-limited mean free path  

NASA Astrophysics Data System (ADS)

The temperature-dependent ballistic transport, using nonequilibrium Arora distribution function (NEADF), is shown to result in mobility degradation with reduction in channel length, in direct contrast to expectation of a collision-free transport. The ballistic mean free path (mfp) is much higher than the scattering-limited long-channel mfp, yet the mobility is amazingly lower. High-field effects, converting stochastic velocity vectors to streamlined ones, are found to be negligible when the applied voltage is less than the critical voltage appropriate for a ballistic mfp, especially at cryogenic temperatures. Excellent agreement with the experimental data on a metal-oxide-semiconductor field-effect transistor is obtained. The applications of NEADF are shown to cover a wide spectrum, covering regimes from the scattering-limited to ballistic, from nondegenerate to degenerate, from nanowire to bulk, from low- to high-temperature, and from a low electric field to an extremely high electric field.

Arora, Vijay K.; Zainal Abidin, Mastura Shafinaz; Tan, Michael L. P.; Riyadi, Munawar A.

2012-03-01

61

Ground-based integrated path coherent differential absorption lidar measurement of CO2: foothill target return  

NASA Astrophysics Data System (ADS)

The National Institute of Information and Communications Technology (NICT) has made a great deal of effort to develop a coherent 2 ?m differential absorption and wind lidar (Co2DiaWiL) for measuring CO2 and wind speed. First, coherent Integrated Path Differential Absorption (IPDA) lidar experiments were conducted using the Co2DiaWiL and a foothill target (tree and ground surface) located about 7.12 km south of NICT on 11, 27, and 28 December 2010. The detection sensitivity of a 2 ?m IPDA lidar was examined in detail using the CO2 concentration measured by the foothill reflection. The precisions of CO2 measurements for the foothill target and 900, 4500 and 27 000 shot pairs were 6.5, 2.8, and 1.2%, respectively. The results indicated that a coherent IPDA lidar with a laser operating at a high pulse repetition frequency of a few tens of KHz is necessary for XCO2 (column-averaged dry air mixing ratio of CO2) measurement with a precision of 1-2 ppm in order to observe temporal and spatial variations in the CO2. Statistical comparisons indicated that, although a small amount of in situ data and the fact that they were not co-located with the foothill target made comparison difficult, the CO2 volume mixing ratio obtained by the Co2DiaWiL measurements for the foothill target and atmospheric returns was about -5 ppm lower than the 5 min running averages of the in situ sensor. Not only actual difference of sensing volume or the natural variability of CO2 but also the fluctuations of temperature could cause this difference. The statistical results indicated that there were no biases between the foothill target and atmospheric return measurements. The 2 ?m coherent IPDA lidar can detect the CO2 volume mixing ratio change of 3% in the 5 min signal integration. In order to detect the position of the foothill target, to measure a range with a high SNR (signal-to-noise ratio), and to reduce uncertainty due to the presence of aerosols and clouds, it is important to make a precise range measurement with a Q-switched laser and a range-gated receiver.

Ishii, S.; Koyama, M.; Baron, P.; Iwai, H.; Mizutani, K.; Itabe, T.; Sato, A.; Asai, K.

2013-05-01

62

New method of estimating wavelength-dependent optical path length ratios for oxy- and deoxyhemoglobin measurement using near-infrared spectroscopy.  

PubMed

In near-infrared spectroscopy (NIRS), concentration changes in oxy- and deoxyhemoglobin are calculated using an attenuation change of the measurement light and by solving a linear equation based on the modified Lambert-Beer law. While solving this equation, we need to know the wavelength-dependent mean optical path lengths of the measurement lights. However, it is very difficult to know these values by a continuous-wave-type (CW-type) system. We propose a new method of estimating wavelength-dependent optical path length ratios of the measurement lights based on the data obtained by a triple wavelength CW-type NIRS instrument. The proposed method does not give a path length itself, but it gives a path length ratio. Thus, it is possible to obtain the accurate hemoglobin concentration changes without cross talk, although the method cannot contribute to the quantification of the absolute magnitude of hemoglobin changes. The method is based on the principle that two possible estimations of hemoglobin concentration changes calculated using a triple-wavelength measurement system should be identical. The method was applied to the experimental data of human subjects' foreheads. The estimated path length ratios were very similar to literature values obtained by using picosecond laser pulses and a streak camera detector [M. Essenpreis et al., Appl. Opt. 32(4), 418-425 (1993)]. PMID:19895139

Umeyama, Shinji; Yamada, Toru

2009-01-01

63

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

64

Investigation of atmospheric {{O}}2{{X}}{^{ 3}}{ sum_{{g}}^{ - }} {{to}} {{b}}{^{ 1}}{ sum_{{g}}^{ + }} using open-path tunable diode laser absorption spectroscopy  

NASA Astrophysics Data System (ADS)

A tunable diode laser absorption spectroscopy (TDLAS) device fiber coupled to a pair of 12.5 in. telescopes was used to study atmospheric propagation for open path lengths of 100-1,000 meters. More than 50 rotational lines in the molecular oxygen A-band O2 {{X}}{^{ 3}}{ sum_{{g}}^{ - }} {{to}} {{b}}{^{ 1}}{ sum_{{g}}^{ + }} transition near 760 nm were observed. Temperatures were determined from the Boltzmann rotational distribution to within 1.3 % (less than ±2 K). Oxygen concentration was obtained from the integrated spectral area of the absorption features to within 1.6 % (less than ±0.04 × 1018 molecules/cm3). Pressure was determined independently from the pressure-broadened Voigt lineshapes to within 10 %. A fourier transform interferometer (FTIR) was also used to observe the absorption spectra at 1 cm-1 resolution. The TDLAS approach achieves a minimum observable absorbance of 0.2 %, whereas the FTIR instrument is almost 20 times less sensitive. Applications include atmospheric characterization for high energy laser propagation and validation of monocular passive raging.

Rice, Christopher A.; Gross, Kevin C.; Perram, Glen P.

2013-05-01

65

Acyl chain length, saturation, and hydrophobicity modulate the efficiency of dietary fatty acid absorption in adult humans  

PubMed Central

Intestinal fat absorption is known to be, overall, a highly efficient process, but much less is known about the efficiency with which individual dietary fatty acids (FA) are absorbed by the adult small intestine. We therefore measured the absorption efficiency of the major dietary FA using sucrose polybehenate (SPB) as a nonabsorbable marker and analyzed how it is modulated by acyl chain physicochemical properties and polymorphisms of proteins involved in chylomicron assembly. Dietary FA absorption efficiency was measured in 44 healthy subjects fed a standard diet containing 35% fat and 5% SPB. FA and behenic acid (BA) were measured in homogenized diets and stool samples by gas chromatography-mass spectroscopy, and coefficients of absorption for each FA were calculated as 1 ? [(FA/BA)feces/(FA/BA)diet]. Absorption coefficients for saturated FA decreased with increasing chain length and hydrophobicity (mean ± SE) and ranged from 0.95 ± 0.02 for myristate (14:0), 0.80 ± 0.03 for stearate (18:0), to 0.26 ± 0.02 for arachidate (20:0). Absorption coefficients for unsaturated FA increased with increasing desaturation from 0.79 ± 0.03 for elaidic acid (18:1t), 0.96 ± 0.01 for linoleate (18:2), to near complete absorption for eicosapentaenoic (20:5) and docosahexaenoic (22:6) acids. Of several common genetic polymorphisms in key proteins involved in the chylomicron assembly pathway, only the intestinal fatty acid-binding protein-2 A54T allele (rs1799883) had any impact on FA absorption. We conclude that acyl chain length, saturation, and hydrophobicity are the major determinants of the efficiency with which dietary FA are absorbed by the adult small intestine. PMID:24008359

McKimmie, Ryan L.; Easter, Linda

2013-01-01

66

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

67

Phase locking in a fiber laser array with varying path lengths Liping Liu, Yi Zhou, Fanting Kong, and Y. C. Chena)  

E-print Network

demonstrated in fiber lasers coupled to a common resonator containing a spatial filter. The phase-locked modePhase locking in a fiber laser array with varying path lengths Liping Liu, Yi Zhou, Fanting Kong of which can be met in fiber laser arrays. © 2004 American Institute of Physics. [DOI: 10

68

The Noninvasive Measurement of Absolute Cerebral Deoxyhemoglobin Concentration and Mean Optical Path Length in the Neonatal Brain by Second Derivative Near Infrared Spectroscopy (Regular Articles)  

Microsoft Academic Search

We have used second differential near infrared spectroscopy of water to determine the mean optical path length of the neonatal brain. By obtaining the ratio of the second differential features of deoxyhemoglobin to those of water, the absolute cerebral concentration of deoxyhemoglobin can be monitored continuously and noninvasively. Nineteen neonates were studied; the gestational age at birth varied from 23

S. J. MATCHER; Chris Cooper; Hamamatsu Photonics

69

Monitoring complex trace-gas mixtures by long-path laser absorption spectrometry. [in long duration manned mission closed environments  

NASA Technical Reports Server (NTRS)

Laser-based spectrophotometric methods, which have been proposed for the detection of trace concentrations of gaseous contaminants, include Raman and passive radiometry. The paper discusses a simple long-path laser absorption method which is capable of resolving complex mixtures of closely related trace contaminants at ppm levels. A number of species were selected which are most likely to accumulate in closed environments, such as submarines or long-duration manned space flights. Absorption coefficients at CO2 laser wavelengths were measured, accurate to + 3 per cent or better, for each of these species. This data base was then used to determine the presence and concentration of the contaminants in prepared mixtures of 12 to 15 gases. Computer programs have been developed which will permit a real-time analysis of the monitored atmosphere. Minimum detectable concentrations for individual species are generally in the ppm range, and are not seriously degraded by interferences even in complex mixtures. Estimates of the dynamic range of this monitoring technique for various system configurations and comparison with other methods of analysis are discussed

Green, B. D.; Steinfeld, J. I.

1976-01-01

70

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

71

Analysing the structure of the optical path length of a supersonic mixing layer by using wavelet methods  

Microsoft Academic Search

The nano-particle-based planar laser scattering (NPLS) technique is used to measure the density distribution in the supersonic mixing layer of the convective Mach number 0.12, and the optical path difference (OPL), which is quite crucial for the study of aero-optics, is obtained by post processing. Based on the high spatiotemporal resolutions of the NPLS, the structure of the OPL is

Gao Qiong; Yi Shi-He; Jiang Zong-Fu; Zhao Yu-Xin; Xie Wen-Ke

2012-01-01

72

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

73

Analysing the structure of the optical path length of a supersonic mixing layer by using wavelet methods  

NASA Astrophysics Data System (ADS)

The nano-particle-based planar laser scattering (NPLS) technique is used to measure the density distribution in the supersonic mixing layer of the convective Mach number 0.12, and the optical path difference (OPL), which is quite crucial for the study of aero-optics, is obtained by post processing. Based on the high spatiotemporal resolutions of the NPLS, the structure of the OPL is analysed using wavelet methods. The coherent structures of the OPL are extracted using three methods, including the methods of thresholding the coefficients of the orthogonal wavelet transform and the wavelet packet transform, and preserving a number of wavelet packet coefficients with the largest amplitudes determined by the entropy dimension. Their performances are compared, and the method using the wavelet packet is the best. Based on the viewpoint of multifractals, we study the OPL by the wavelet transform maxima method (WTMM), and the result indicates that its scaling behaviour is evident.

Gao, Qiong; Yi, Shi-He; Jiang, Zong-Fu; Zhao, Yu-Xin; Xie, Wen-Ke

2012-06-01

74

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

75

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

76

Stopping powers of Ti for protons from 0.2 to 13.5 MeV: Correction for the actual path length due to multiple scattering  

NASA Astrophysics Data System (ADS)

Stopping powers of Ti were measured for protons from 0.2 to 13.5 MeV. The uncertainty of the present results was estimated to be ±0.40%. Although the present results agreed well with our previous result measured at 6.5 MeV, they were 1-2% smaller than those measured by Andersen et al. and 0.5-4% smaller than compilation values of ICRU Report 49. Analyzing the present results with the Bethe-Bloch formula with corrections, we could obtain the information on the lowest energy; beyond that we could not apply the formula to describe stopping powers. In order to obtain precise experimental values at low energies, we paid special attention to the effect of the enlargement of an actual path length over a target thickness. We measured angular distributions due to multiple scattering for 26 kinds of target thickness and incident energy combinations. In these cases energy losses of protons ranged from 1.3 to 62% of their initial energies. We found that angular distributions were excellently reproduced by both Molière's theory and the theory of Sigmund and Winterbon. Therefore, we could conclude that these theories gave a reliable evaluation of the correction for the actual path length.

Sakamoto, N.; Ogawa, H.; Tsuchida, H.

2000-04-01

77

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.

78

Global observations of atmospheric CH4 by Integrated Path Differential-Absorption Lidar: the French-German Climate Monitoring Initiative  

NASA Astrophysics Data System (ADS)

Atmospheric methane (CH4) is a powerful greenhouse gas, which has a Greenhouse Warming Potential (GWP) of 25 relative to CO2 on a time scale of 100 years. Despite the fact that the imbalance between the sources and sinks has decreased in the early 1990's to an insignificant value, a significant renewal of the CH4 growth is reported in recent years. Questions arise whether an increase of atmospheric CH4 might be fostered through melting of permafrost soil in the Arctic region or arise from changes of the tropical wetlands which comprise the biggest natural methane source. Another reason could be the change in the agro-industrial era of predominant human influence or the very large deposits of CH4 as gas hydrates on ocean shelves that are vulnerable to ocean warming. The French-German Climate Monitoring Initiative, which has recently been selected to undergo Phase0/A studies in a joint project by the space agencies CNES (France)and DLR (Germany), targets on satellite observations of atmospheric CH4 for the improvement of our knowledge on regional to synoptic scale CH4 sources on a global basis. As a novel feature, the observational instrument of this mission will be an Integrated Path Differential-Absorption (IPDA) Lidar system embarked on board of the French Myriade platform for the measurement of the column-weighted dry-air mixing ratio of CH4 in a nadir viewing configuration. This data will be provided by the lidar technique with no bias due to particles scattering in the light path and can directly be used as input for flux inversion models. In our presentation we will discuss the observational principle and the sampling strategy of the envisaged mission in connection to the needs for CH4 flux inversion experiments. In addition, we report on supporting campaign activities on airborne measurements of Lidar reflectivity data in the respective spectral region. The airborne data is of prime interest for the generation of pseudo CH4 data examples using the satellite instrument in order to address questions how to optimally aggregate the satellite measurements for maximum information content and minimum error. The field campaign was funded by the European Space Agency (ESA) in the framework of the A-SCOPE mission evaluation activity on active remote sensing of CO2 from space-borne platform.

Ehret, Gerhard; Flamant, Pierre; Ciais, Philippe; Fabien, Gibert; Amediek, Axel; Kiemle, Christoph; Fix, Andreas; Quatrevalet, Mathieu; Wirth, Martin

79

Intercomparison of OH Radical Measurements by Long-Path Absorption and Laser Induced Fluorescence in the Atmosphere Simulation Chamber SAPHIR  

NASA Astrophysics Data System (ADS)

A striking advantage of the SAPHIR chamber is the availability of two spectroscopic detection instruments for OH radicals: Laser-Induced Fluorescence Spectroscopy (LIF) and Long-Path Differential Optical Laser Absorption Spectroscopy (DOAS). Both instruments have already been compared in 1994 during the field measurement campaign POPCORN. They agreed well with a correlation coefficient of r=0.90 and a weighted linear fit with a slope of 1.09 +- 0.12. However, OH measurements in the simulation chamber differ significantly from measurements in ambient air. While DOAS measures OH as an integral value along the central longitudinal axis of SAPHIR, LIF samples the air locally and close (2 cm) to the floor of the chamber. Thus, the LIF measurements might be possibly affected by local concentration gradients caused by insufficient mixing of the chamber air or by deposition to the wall. On the other hand, if turbulent mixing of the chamber air is weak and high concentrations of ozone are used in experiments, the DOAS instrument might be subject to artificial formation of OH radicals in the air volume which is illuminated by the detection laser. This interference results from laser induced photolysis of ozone and the subsequent reaction of water vapor with the excited oxygen atoms formed. Thus it is of decisive importance to compare OH measurements from both instruments in order to investigate potential disturbing effects due to the specific sampling properties of both instruments within SAPHIR. We report on OH measurements accomplished simultaneously with both instruments using different trace gas compositions and experimental conditions.

Dorn, H.-P.; Brauers, T.; Greif, J.; Häseler, R.; Hofzumahaus, A.; Holland, F.; Rupp, L.

2003-04-01

80

Earth-satellite-Earth laser long-path absorption experiment using the Retroreflector in Space (RIS) on the Advanced Earth Observing Satellite (ADEOS)  

Microsoft Academic Search

This paper reports the results of the laser long-path absorption experiments carried out with the Retroreflector in Space (RIS) on the Advanced Earth Observing Satellite (ADEOS). The RIS is a 0.5 m diameter single-element hollow retroreflector with a unique optical design which uses a curved mirror surface to correct velocity aberrations caused by the satellite movement. In the RIS experiments

Nobuo Sugimoto; Nobuhiko Koga; Ichiro Matsui; Yasuhiro Sasano; Atsushi Minato; Kenichi Ozawa; Yasunori Saito; Akio Nomura; Tetsuo Aoki; Toshikazu Itabe; Hiroo Kunimori; Isao Murata; Hiroshi Fukunishi

1999-01-01

81

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

82

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

83

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

84

The influence of species and growing conditions on the 18-O enrichment of leaf water and its impact on 'effective path length'.  

PubMed

The stable oxygen isotope ratio (delta(18)O) of plant material has been shown to contain essential information on water and carbon fluxes at the plant and ecosystem scales. However, the effective path length (L(m)), a parameter introduced to leaf-water models still requires a comprehensive biological characterization to allow interpretation of delta(18)O values in plant material with confidence. Here, we tested the variability of L(m) across and within three species that developed leaves in environments with different relative humidity. We also tested whether the L(m) of fully developed leaves is affected by short-term fluctuations in relative humidity. We determined that significant differences in L(m) exist among Phaseolus vulgaris, Rizinus communis and Helianthus annuus. Within a given species, however, L(m) values did not differ significantly among individuals. These findings indicate that L(m) is species specific and a relatively constant parameter and that L(m) will not obscure the interpretation of delta(18)O values in plant material of a given species. We urge caution, however, because values for L(m) are derived from fitting leaf-water models to measured values of delta(18)O, so care must be taken in assigning a 'cause' to values of L(m) as they likely capture a combination of different biological leaf properties. PMID:19761496

Kahmen, Ansgar; Simonin, Kevin; Tu, Kevin; Goldsmith, Gregory R; Dawson, Todd E

2009-11-01

85

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

86

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

87

Probing grain boundary sink strength at the nanoscale: Energetics and length scales of vacancy and interstitial absorption by grain boundaries in ?-Fe  

SciTech Connect

The energetics and length scales associated with the interaction between point defects (vacancies and self-interstitial atoms) and grain boundaries in bcc Fe was explored. Molecular statics simulations were used to generate a grain boundary structure database that contained {approx}170 grain boundaries with varying tilt and twist character. Then, vacancy and self-interstitial atom formation energies were calculated at all potential grain boundary sites within 15 {angstrom} of the boundary. The present results provide detailed information about the interaction energies of vacancies and self-interstitial atoms with symmetric tilt grain boundaries in iron and the length scales involved with absorption of these point defects by grain boundaries. Both low- and high-angle grain boundaries were effective sinks for point defects, with a few low-{Sigma} grain boundaries (e.g., the {Sigma}3{l_brace}112{r_brace} twin boundary) that have properties different from the rest. The formation energies depend on both the local atomic structure and the distance from the boundary center. Additionally, the effect of grain boundary energy, disorientation angle, and {Sigma} designation on the boundary sink strength was explored; the strongest correlation occurred between the grain boundary energy and the mean point defect formation energies. Based on point defect binding energies, interstitials have {approx}80% more grain boundary sites per area and {approx}300% greater site strength than vacancies. Last, the absorption length scale of point defects by grain boundaries is over a full lattice unit larger for interstitials than for vacancies (mean of 6-7 {angstrom} versus 10-11 {angstrom} for vacancies and interstitials, respectively).

Tschopp, Mark A.; Solanki, K. N.; Gao, Fei; Sun, Xin; Khaleel, Mohammad A.; Horstemeyer, Mark

2012-02-10

88

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

89

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

90

Absorption and Emission Effects on Radiation Thermometry Measurements in Reformer Furnaces  

NASA Astrophysics Data System (ADS)

A simple model of the effects of atmospheric absorption and emission on radiation thermometer readings is described, and methods of correcting for these effects are given. These methods are applied to measurements made in a large reformer furnace using a commercially available radiation thermometer operating near 1 ?m, whose spectral responsivity partially overlaps some of the water vapor absorption bands. An effective absorption coefficient for the thermometer and the flue gas temperature are calculated and used to correct the thermometer readings. For relatively long measurement path lengths the corrections are almost as significant as reflection errors, and the uncertainties in the corrections increase very rapidly with path length.

Saunders, Peter

2003-09-01

91

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

92

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

93

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

94

SIGNIFICANCES OF THE VARIABILITY OF AIRWAY PATHS AND THEIR AIR FLOW RATES TO DOSIMETRY MODEL PREDICTIONS OF THE ABSORPTION OF GASES  

EPA Science Inventory

The ozone dosimetry model developed at EPA was developed to be used in conjunction with species lung models that summarize the structure of a lung as a lung of many equivalent paths. The paper reports the results of a preliminary study into the question of whether or not more rea...

95

Lengths of Ladybugs  

NSDL National Science Digital Library

This lesson plan for teachers of kindergarten students involves activities that introduce the concepts of using a non-standard unit to measure length and associating a measurement with a number. After introducing the lesson with a literature connection, students cut out their own measuring cards and use them to compare lengths, and measure distance along a path using a line of ladybug beans and a non-standard tape. Materials, handouts, and suggestions for extensions and parental involvement are included.

Lessonplans, Utah

2006-06-24

96

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

97

Convenient pulse length measurement of sub-20-fs pulses down to the deep UV via two-photon absorption in bulk material  

NASA Astrophysics Data System (ADS)

The beam attenuation by two-photon absorption in thin crystals and glass plates is utilized for directly measuring the intensity autocorrelation of UV femtosecond pulses without the need for an auxiliary pulse. We give a full description of the newly developed setup for operation from the blue down to the deep UV. The conditions that must be met to achieve reliable measurements are investigated. The choice of the two-photon-absorbing material governs the attainable wavelength range, the material thickness determines the shortest pulse that can be reliably characterized and high intensities influence the derived pulse duration due to saturation effects. The performance of the UV autocorrelator is demonstrated for pulses with durations below 20 fs, with energies of 3 nJ and with central wavelengths from the visible down to 195 nm. 2-Hz update rates are achieved at the 1-kHz repetition rate of the laser. The wavelength dependence of the two-photon-absorption coefficient of BBO is determined by z-scan measurements and we find that it decreases much faster at longer wavelengths than is expected from the linear absorption spectrum.

Homann, C.; Krebs, N.; Riedle, E.

2011-09-01

98

GR Proper Length Program  

NSDL National Science Digital Library

The GR Proper Length program simulates the distance between points using the Schwarzschild metric. It displays the proper length between two points and the light-travel path. It is distributed as a ready-to-run (compiled) Java archive. Double clicking the gr_properlength.jar file will run the program if Java is installed. GR Proper Length is part of a suite of Open Source Physics programs that model aspects of General Relativity. Other programs provide additional visualizations. They can be found by searching ComPADRE for Open Source Physics, OSP, or General Relativity.

Christian, Wolfgang; Belloni, Mario; Cox, Anne

2008-05-14

99

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

100

Photonic crystal slot waveguide for high sensitivity on-chip near-infrared optical absorption spectroscopy of xylene in water  

NASA Astrophysics Data System (ADS)

We experimentally demonstrate a 300?m long silicon photonic crystal slot waveguide for on-chip near-infrared absorption spectroscopy. Based on the Beer-Lambert absorption law, our device combines slow light in photonic crystal waveguide with high electric field intensity in low-index 75nm wide slot, which effectively increases the optical absorption path length of the analyte. We demonstrate near-infrared absorption spectroscopy of xylene in water, independent of near-infrared absorption signatures of water, with a hydrophobic PDMS sensing phase that extracts xylene from water. Xylene concentrations up to 100ppb (parts per billion) (86?g/L) in water were measured.

Chakravarty, Swapnajit; Lai, Wei-Cheng; Wang, Xiaolong; Lin, Che-Yun; Chen, Ray T.

2011-06-01

101

Measurements on Gaseous-Fuel Pool Fires with a Fiber-optic Absorption Probe  

Microsoft Academic Search

A new version of a watercooled and nitrogen-purged fiber-optic absorption probe is described. The probe measures absorption of infrared diode radiation at 0.96 ?m by double-pass over a path length of 60 mm. The new design was successful in suppressing thermal expansion effects on optical alignment present in an earlier design.Vertical centerline traverses have been performed with propylene pool fires

G. H. MARKSTEIN

1984-01-01

102

Design parameters for enhanced photon absorption in vertically aligned silicon nanowire arrays  

NASA Astrophysics Data System (ADS)

Superior photon absorption in ordered nanowire arrays has been demonstrated recently. However, systematic studies are still missing to explore the limits of their implementation as functional photonic devices. With emphasis on silicon nanowires, we investigated the effects of nanowire diameter, length, morphology, and pitch on the photon absorption within the visible solar spectrum based on simulations. Our results reveal that these parameters are crucial but disclose a path to improve the absorbance drastically.

Jäger, Stefan T.; Strehle, Steffen

2014-09-01

103

Dynamical Jahn-Teller effects in the near ultraviolet vapor phase absorption spectra of perrhenyl chloride, ReO3Cl, and pertechnyl chloride, TcO3Cl  

Microsoft Academic Search

The near ultraviolet vapor phase absorption spectra of perrhenyl chloride and pertechnyl chloride have been observed over a range of vapor pressures and path lengths. There are several similarities in the overall features of the spectra for the two molecules. Each spectrum shows evidence of two electronic transitions at wavelengths greater than 2000 Å the longer wave-length band system of

Alan Guest; Helen Elaine Howard-Lock; Colin James Lyne Lock

1978-01-01

104

Path Sensitization in Critical Path Problem  

Microsoft Academic Search

Since the delay of a circuit is determined by the delay of its longest sensitizable paths (such paths are called critical paths), the problem of estimating the delay of a circuit is called critical path problem. One important aspect of the critical path problem is to decide whether a path is sensitizable. A framework which allows various previously proposed path

Hsi-chuan Chen; David Hung-chang Du

1991-01-01

105

Noise estimation technique to reduce the effects of 1/f noise in Open Path Tunable Diode Laser Absorption Spectrometry (OP-TDLAS)  

NASA Astrophysics Data System (ADS)

Many techniques using high frequency modulation have been proposed to reduce the effects of 1/f noise in tunable diode-laser absorption spectroscopy (TDLAS). The instruments and devices used by these techniques are not suitable for space applications that require small, low mass and low power instrumentation. A new noise estimation technique has already been proposed and validated for two lasers to reduce the effect of 1/f noise at lower frequencies. This paper extends the noise estimation technique and applies it using one distribution feedback (DFB) laser diode. In this method a DFB laser diode is excited at two slightly different frequencies, giving two different harmonics that can be used to estimate the total noise in the measurement. Simulations and experimental results on ammonia gas validate that the 1/f noise is effectively reduced by the noise estimation technique using one laser. Outdoor experimental results indicate that the effect of 1/f noise is reduced to more than 1/4 its normal value.

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

2014-06-01

106

Functional Equivalence and Spatial Path Memory  

Microsoft Academic Search

Loomis, Klatzky, Avraamides, Lippa & Golledge (2007) suggest that, when it comes to spatial information, verbal description and perceptual experience are nearly functionally equivalent with respect to the cognitive representations they produce. We tested this idea for the case of spatial memory for complex paths. Paths consisted entirely of unit-length segments followed by 90-degree turns, thus assuring that a path

Don R. Lyon; Glenn M. Gunzelmann

2011-01-01

107

Standard Length versus Total Length  

Microsoft Academic Search

In an effort to determine the length measurement most representative of the bulk of the fish, the standard length and the total length were each compared with the weight of the fish. This comparison was made for four species of game fish, yellow perch (Perca flavescens), wall-eyed pike (Stizostedion v. vitreum), rock bass (Ambloplites rupestris), and lake trout (Cristivomer n.

William F. Royce

1942-01-01

108

Path Pascal  

NASA Technical Reports Server (NTRS)

Path Pascal is high-level experimental programming language based on PASCAL, which incorporates extensions for systems and real-time programming. Pascal is extended to treat real-time concurrent systems.

Campbell, R. H.; Kolstad, R. B.; Holle, D. F.; Miller, T. J.; Krause, P.; Horton, K.; Macke, T.

1983-01-01

109

Spreading paths in partially observed social networks.  

PubMed

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 static, structurally realistic social networks as platforms 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. PMID:22587148

Onnela, Jukka-Pekka; Christakis, Nicholas A

2012-03-01

110

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. PMID:22587148

Onnela, Jukka-Pekka; Christakis, Nicholas A.

2012-01-01

111

Spreading paths in partially observed social networks  

NASA Astrophysics Data System (ADS)

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 static, structurally realistic social networks as platforms 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.

2012-03-01

112

Completely automated open-path FT-IR spectrometry.  

PubMed

Atmospheric analysis by open-path Fourier-transform infrared (OP/FT-IR) spectrometry has been possible for over two decades but has not been widely used because of the limitations of the software of commercial instruments. In this paper, we describe the current state-of-the-art of the hardware and software that constitutes a contemporary OP/FT-IR spectrometer. We then describe advances that have been made in our laboratory that have enabled many of the limitations of this type of instrument to be overcome. These include not having to acquire a single-beam background spectrum that compensates for absorption features in the spectra of atmospheric water vapor and carbon dioxide. Instead, an easily measured "short path-length" background spectrum is used for calculation of each absorbance spectrum that is measured over a long path-length. To accomplish this goal, the algorithm used to calculate the concentrations of trace atmospheric molecules was changed from classical least-squares regression (CLS) to partial least-squares regression (PLS). For calibration, OP/FT-IR spectra are measured in pristine air over a wide variety of path-lengths, temperatures, and humidities, ratioed against a short-path background, and converted to absorbance; the reference spectrum of each analyte is then multiplied by randomly selected coefficients and added to these background spectra. Automatic baseline correction for small molecules with resolved rotational fine structure, such as ammonia and methane, is effected using wavelet transforms. A novel method of correcting for the effect of the nonlinear response of mercury cadmium telluride detectors is also incorporated. Finally, target factor analysis may be used to detect the onset of a given pollutant when its concentration exceeds a certain threshold. In this way, the concentration of atmospheric species has been obtained from OP/FT-IR spectra measured at intervals of 1 min over a period of many hours with no operator intervention. PMID:18946664

Griffiths, Peter R; Shao, Limin; Leytem, April B

2009-01-01

113

On-chip methane sensing by near-IR absorption signatures in a photonic crystal slot waveguide.  

PubMed

We demonstrate a 300??m long silicon photonic crystal (PC) slot waveguide device for on-chip near-infrared absorption spectroscopy, based on the Beer-Lambert law for the detection of methane gas. The device combines slow light in a PC waveguide with high electric field intensity in a low-index 90?nm wide slot, which effectively increases the optical absorption path length. A methane concentration of 100?ppm (parts per million) in nitrogen was measured. PMID:21403750

Lai, Wei-Cheng; Chakravarty, Swapnajit; Wang, Xiaolong; Lin, Cheyun; Chen, Ray T

2011-03-15

114

Intracavity absorption with a continuous wave dye laser - Quantification for a narrowband absorber  

NASA Technical Reports Server (NTRS)

An experimental investigation of the dependence of intracavity absorption on factors including transition strength, concentration, absorber path length, and pump power is presented for a CW dye laser with a narrow-band absorber (NO2). A Beer-Lambert type relationship is found over a small but useful range of these parameters. Quantitative measurement of intracavity absorption from the dye laser spectral profiles showed enhancements up to 12,000 (for pump powers near lasing threshold) when compared to extracavity measurements. The definition of an intracavity absorption coefficient allowed the determination of accurate transition strength ratios, demonstrating the reliability of the method.

Brobst, William D.; Allen, John E., Jr.

1987-01-01

115

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

116

Snell's law and light traveling along the shortest path  

Microsoft Academic Search

the problem to be analyzed follows: Given a starting point s, an ending point t and a set of n Weighted Faces (or regions) in a 2-dimensional space, find the best path from s to t, where the length of the path is defined as the weighted sum of the Euclidean length of the sub paths inside each region. Let

Carlos Lara

2006-01-01

117

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.

BEGIN:VCARD VERSION:2.1 FN:Cynthia Ann Radle N:Ann Radle;Cynthia ORG:McCullough High School REV:2005-04-13 END:VCARD

1995-06-30

118

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

119

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

120

On the All-Pairs Euclidean Short Path Problem  

Microsoft Academic Search

Given a set of polygonal obstacles of n vertices in the plane', the problem of processing the all-pairs Euclidean short path queries is that of reporting an obstacle-avoiding path P (or its length) between two arbitrary query points p and q in the plane, such that the length of P is within a small factor of the length of a

Danny Z. Chent

121

On the all-pairs Euclidean short path problem  

Microsoft Academic Search

Given a set of polygonal obstacles of n vertices in the plane’, the problem of processing the all-pairs Euclidean short path queries is that of reporting an obstacle-avoiding path P (or its length) between two arbitrary query points p and q in the plane, such that the length of P is within a small factor of the length of a

Danny Z. Chent

1995-01-01

122

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

123

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

124

Extremal paths on a random Cayley tree  

Microsoft Academic Search

We investigate the statistics of extremal path(s) (both the shortest and the longest) from the root to the bottom of a Cayley tree. The lengths of the edges are assumed to be independent identically distributed random variables drawn from a distribution rho(l). Besides, the number of branches from any node is also random. Exact results are derived for arbitrary distribution

Satya N. Majumdar; P. L. Krapivsky

2000-01-01

125

Ray Paths  

NSDL National Science Digital Library

For the next two exercises, we will break up into groups of four. Each member of the group will represent one of four waves leaving the source: direct wave, ground roll, reflected wave, and head wave. All four "waves" will leave the source at the same time and travel at a particular speed and path as directed by the instructor. ALL students will record the arrival time of each "wave" at each geophone until all 12 geophones have been used. Plot arrival time versus distance for each "wave". Do any of the time versus distance curves fit a straight line? Do any of them not fit a straight line? Explain why they do or don't fit a straight line. Uses online and/or real-time data Has minimal/no quantitative component

126

Short paths in expander graphs  

SciTech Connect

Graph expansion has proved to be a powerful general tool for analyzing the behavior of routing algorithms and the interconnection networks on which they run. We develop new routing algorithms and structural results for bounded-degree expander graphs. Our results are unified by the fact that they are all based upon, and extend, a body of work asserting that expanders are rich in short, disjoint paths. In particular, our work has consequences for the disjoint paths problem, multicommodify flow, and graph minor containment. We show: (i) A greedy algorithm for approximating the maximum disjoint paths problem achieves a polylogarithmic approximation ratio in bounded-degree expanders. Although our algorithm is both deterministic and on-line, its performance guarantee is an improvement over previous bounds in expanders. (ii) For a multicommodily flow problem with arbitrary demands on a bounded-degree expander, there is a (1 + {epsilon})-optimal solution using only flow paths of polylogarithmic length. It follows that the multicommodity flow algorithm of Awerbuch and Leighton runs in nearly linear time per commodity in expanders. Our analysis is based on establishing the following: given edge weights on an expander G, one can increase some of the weights very slightly so the resulting shortest-path metric is smooth - the min-weight path between any pair of nodes uses a polylogarithmic number of edges. (iii) Every bounded-degree expander on n nodes contains every graph with O(n/log{sup O(1)} n) nodes and edges as a minor.

Kleinberg, J. [MIT, Cambridge, MA (United States); Rubinfeld, R. [Cornell Univ., Ithaca, NY (United States)

1996-12-31

127

Design parameters for enhanced photon absorption in vertically aligned silicon nanowire arrays  

PubMed Central

Superior photon absorption in ordered nanowire arrays has been demonstrated recently. However, systematic studies are still missing to explore the limits of their implementation as functional photonic devices. With emphasis on silicon nanowires, we investigated the effects of nanowire diameter, length, morphology, and pitch on the photon absorption within the visible solar spectrum based on simulations. Our results reveal that these parameters are crucial but disclose a path to improve the absorbance drastically. PACS 78.40.Fy; 78.67.Uh; 78.67.-n PMID:25276106

2014-01-01

128

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

129

Portable open-path chemical sensor using a quantum cascade laser  

NASA Astrophysics Data System (ADS)

Remote sensing of enemy installations or their movements by trace gas detection is a critical but challenging military objective. Open path measurements over ranges of a few meters to many kilometers with sensitivity in the parts per million or billion regime are crucial in anticipating the presence of a threat. Previous approaches to detect ground level chemical plumes, explosive constituents, or combustion have relied on low-resolution, short range Fourier transform infrared spectrometer (FTIR), or low-sensitivity near-infrared differential optical absorption spectroscopy (DOAS). As mid-infrared quantum cascade laser (QCL) sources have improved in cost and performance, systems based on QCL's that can be tailored to monitor multiple chemical species in real time are becoming a viable alternative. We present the design of a portable, high-resolution, multi-kilometer open path trace gas sensor based on QCL technology. Using a tunable (1045-1047cm-1) QCL, a modeled atmosphere and link-budget analysis with commercial component specifications, we show that with this approach, accuracy in parts per billion ozone or ammonia can be obtained in seconds at path lengths up to 10 km. We have assembled an open-path QCL sensor based on this theoretical approach at City College of New York, and we present preliminary results demonstrating the potential of QCLs in open-path sensing applications.

Corrigan, Paul; Lwin, Maung; Huntley, Reuven; Chhabra, Amandeep; Moshary, Fred; Gross, Barry; Ahmed, Samir

2009-05-01

130

Temperature- and pressure-dependent absorption coefficients for CO2 and O2 at 193 nm  

NASA Astrophysics Data System (ADS)

Absorption of laser radiation at 193 nm by CO2 and O2 was studied at a series of different temperatures up to 1273 K and pressures up to 1 bar. The spectrum for CO2 was found to be broadband, so that absorption could be fitted to a Beer-Lambert law. On the other hand, the corresponding O2 spectrum is strongly structured and parameterisation requires a more complex relation, depending on both temperature and the product (pressure × absorption path length). In this context, the influence of spectral structure on the resulting spectrally integrated absorption coefficients is discussed. Using the fitting parameters obtained, effective transmissions at 193 nm can be calculated for a wide range of experimental conditions. As an illustration of the practical application of these data, the calculation of effective transmission for a typical industrial flue gas is described.

Hartinger, K. T.; Nord, S.; Monkhouse, P. B.

131

Intracavity absorption with a continuous wave dye laser: quantification for a narowband absorber  

SciTech Connect

Although it is recognized as a very sensitive detection technique, the general application of intracavity absorption to areas such as chemical kinetics and photochemistry has been somewhat limited. Concerns are frequently expressed about the nonlinear nature, experimental difficulty, and reliability of the technique. To allay some of these objections, the dependence of intracavity absorption on factors such as transition strength, concentration, absorber path length, and pump power has been investigated experimentally for a cw dye laser with a narrowband absorber (NO/sub 2/). For this case a Beer-Lambert type relationship has been confirmed over a useful range of these parameters. The extent of intracavity absorption was quantitatively measured directly from the dye laser spectral profiles and, when compared to extracavity measurements, indicated enhancements as high as 12,000 for pump powers near lasing threshold. By defining an intracavity absorption coefficient, it was possible to demonstrate the reliability of the method by obtaining accurate transition strength ratios.

Brobst, W.D.; Allen J.E. Jr.

1987-09-01

132

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

133

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

134

Extremal paths on a random Cayley tree  

Microsoft Academic Search

We investigate the statistics of extremal path(s) (both the shortest and the\\u000alongest) from the root to the bottom of a Cayley tree. The lengths of the edges\\u000aare assumed to be independent identically distributed random variables drawn\\u000afrom a distribution \\\\rho(l). Besides, the number of branches from any node is\\u000aalso random. Exact results are derived for arbitrary distribution

Satya N. Majumdar; P. L. Krapivsky

2000-01-01

135

Precision and accuracy of miniature tunable diode laser absorption spectrometers  

NASA Astrophysics Data System (ADS)

Tunable Diode Laser Absorption Spectroscopy (TDLAS) is finding ever increasing utility for industrial process measurement and control. The technique's sensitivity and selectivity benefit continuous concentration measurement of selected analytes in complex gas mixtures. Tradeoff options among optical path length, absorption linestrength, linewidth, cross-interferences, and sampling methodology enable sensor designers to optimize detection for specific applications. This paper describes TDLAS measurement precision and accuracy limitations in emerging applications that demand increasing volumes of distributed miniaturized sensors at diminishing costs. In these situations, the TDLAS specificity is a key attribute, while high sensitivity enables novel sampling package designs with short optical pathlengths. Under these circumstances, the traditional approaches to optimizing accuracy and precision may fail if analyzer control features are sacrificed to reduce cost. We describe here a relatively simple TDLAS sensor designed to meet the needs for acceptable cost, and discuss its theory of operation along with the implications on measurement accuracy and precision.

Frish, M. B.; Wainner, R. T.; Laderer, M. C.; Parameswaran, K. R.; Sonnenfroh, D. M.; Druy, M. A.

2011-06-01

136

[Measurement on gas temperature distribution by tunable diode laser absorption spectroscopy].  

PubMed

The technique of tunable diode laser absorption spectroscopy (TDLAS) can be used for gas temperature distribution measurement by scanning multiple gas absorption lines with a tunable diode laser. The fundamental of gas temperature distribution measurement by TDLAS is introduced in the present paper, and the discretization strategy of equation for gas absorption is also given here. Using constrained linear least-square fitting method, the gas temperature distribution can be calculated with the help of physical constraints under the condition of uniform gas concentration and pressure. Based on the spectral parameters of four CO absorption lines near 6330 cm(-1) from HITRAN database, the model of two-temperature distribution at 300 and 600 K with each path length of 55 cm was set up. The effects of relative measurement error and different path length constraints of temperature bins on the gas temperature distribution measurement results were simulated by constrained linear least-square fitting. The results show that the temperature distribution calculation error increases as the relative measurement error rises. A measurement error of 5% could lead to a maximum relative error of 11%, and an average relative error of 2.2% for calculation result. And the weak physical constraints of path length for temperature bins could increase the calculation result error during the process of constrained linear least-square fitting. By setting up the model of two-temperature distribution with gas cells at room temperature as the cold section and in tube furnace as the hot section, the experiment of gas temperature distribution measurement in lab was carried out. Using four absorption lines of CO near 6330 cm(-1) scanned by VCSEL diode laser, and fitting the background laser intensity without absorption by the cubic polynomial to get the baseline signal, the integrals of spectral absorbance for gas temperature distribution measurement can be calculated. The relative calculation errors of path length for temperature bins are about 7.3%, 6.5%, 4.7% and 2.7% in the four cases. PMID:18975785

Li, Ning; Yan, Jian-hua; Wang, Fei; Chi, Yong; Cen, Ke-fa

2008-08-01

137

[Off-axis cavity enhanced absorption spectroscopy detection techniques for the measurement of carbon dioxide].  

PubMed

The spectrum of carbon monoxide was obtained around 1. 573 microm using a tunable distributed feedback semiconductor laser with a high-finesse cavity at room temperature via off-axis cavity enhanced absorption (CEA) spectroscopic technique. The absorption line of carbon monoxide at 6 357. 311 6 cm(-1) was chosen for trace detection. Meanwhile, in order to get more accurate measurements, absorption path length of the cavity calibration methods was studied, and a simple and practical calibration method was given. The results show that, the equivalent absorption path length of high-precision optical resonator was -1 195.73 m. At last, we got the concentration of carbon monoxide in the real atmosphere to be -388.346 ppm (S/N = 22), and the detection limit of carbon monoxide was 17.65 ppm. By combination of wavelength modulation technology and OA-CEAS technology, a minimum detectable concentration of 0.36 ppm (S/N = 1 064) was achieved eventually. PMID:22497123

Zhao, Hui; Wang, Gui-shi; Cai, Ting-dong; Gao, Xiao-ming

2012-01-01

138

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

139

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

140

Path and Trajectory Diversity: Theory and Algorithms Michael S. Branicky Ross A. Knepper James J. Kuffner  

E-print Network

Path and Trajectory Diversity: Theory and Algorithms Michael S. Branicky Ross A. Knepper James J sets of candidate paths or trajectories down to smaller subsets that maintain desirable characteristics in terms of overall reachability and path length. Consider the example of a set of candidate paths

Branicky, Michael S.

141

Graph Theory Worksheet Math 105, Fall 2010 Page 1 Paths and Circuits  

E-print Network

Graph Theory Worksheet Math 105, Fall 2010 Page 1 Paths and Circuits Path: a sequence of adjacent them all. A F B E C D For example, one path is ABCD, as shown: A F B E C D #12;Graph Theory Worksheet edges, where the edges used are used only once. Length: the number of edges in the path. Connected

Anderson, Douglas R.

142

Atmospheric absorption of high frequency noise and application to fractional-octave bands  

NASA Technical Reports Server (NTRS)

Pure tone sound absorption coefficients were measured at 1/12 octave intervals from 4 to 100 KHz at 5.5K temperature intervals between 255.4 and 310.9 K and at 10 percent relative humidity increments between 0 percent and saturation in a large cylindrical tube (i.d., 25.4 cm; length, 4.8 m). Special solid-dielectric capacitance transducers, one to generate bursts of sound waves and one to terminate the sound path and detect the tone bursts, were constructed to fit inside the tube. The absorption was measured by varying the transmitter receiver separation from 1 to 4 m and observing the decay of multiple reflections or change in amplitude of the first received burst. The resulting absorption was compared with that from a proposed procedure for computing sound absorption in still air. Absorption of bands of noise was numerically computed by using the pure tone results. The results depended on spectrum shape, on filter type, and nonlinearly on propagation distance. For some of the cases considered, comparison with the extrapolation of ARP-866A showed a difference as large as a factor of 2. However, for many cases, the absorption for a finite band was nearly equal to the pure tone absorption at the center frequency of the band. A recommended prediction procedure is described for 1/3 octave band absorption coefficients.

Shields, F. D.; Bass, H. E.

1977-01-01

143

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

144

Finding a Hamiltonian Path in a Cube with Specified Turns is Hard  

E-print Network

We prove the NP-completeness of finding a Hamiltonian path in an N × N × N cube graph with turns exactly at specified lengths along the path. This result establishes NP-completeness of Snake Cube puzzles: folding a chain ...

Abel, Zachary Ryan

145

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

E-print Network

Hard paths, soft paths or no paths? Cross-cultural perceptions of water solutions Drew Blasco1 to the availability of clean, safe water. In this study we examined cross cultural preferences for soft path vs. hard conceptualize water solutions (hard paths, soft paths, no paths) cross-culturally? 2) What role does development

Hall, Sharon J.

146

Walden's Paths - Ensemble Edition  

NSDL National Science Digital Library

WaldenÂs Paths enables users of digital document collections (e.g. the Web) to exploit these documents by reusing them for previously unintended audiences in an academic setting. Authors of paths (usually educators) overlay a linear, directed meta-structure over the Web documents and recontextualize these by adding explanatory text to achieve their curricular goals. Paths do not modifythe structure or content of the Web resources that they include. The creation of a path over pre-organized content (e.g. books, Web pages) to reorganize and associate related information serves to facilitate easy retrieval and communication. WaldenÂs Paths displays the information that the path points to in conjunction with the textual annotations added by the author of the path.

2011-01-04

147

Thermal Conductivity Spectroscopy Technique to Measure Phonon Mean Free Paths  

E-print Network

Size effects in heat conduction, which occur when phonon mean free paths (MFPs) are comparable to characteristic lengths, are being extensively explored in many nanoscale systems for energy applications. Knowledge of MFPs ...

Schmidt, A. J.

148

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

149

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

150

Multi-Vehicle Path Planning in Dynamically Changing Environments  

E-print Network

Multi-Vehicle Path Planning in Dynamically Changing Environments Ali Ahmadzadeh1, Nader Motee2, Ali such as rendezvous and area coverage. I. INTRODUCTION The problem of path planning for a vehicle in a dynam- ically multi-vehicle system in presence of moving obstacles. The objective is to find multiple fixed length

Pappas, George J.

151

Pivoted document length normalization  

Microsoft Academic Search

Automatic information retrieval systems have to deal with documents of varying lengths in a text collection. Document length normalization is used to fairly retrieve documents of all lengths. In this study, we ohserve that a normalization scheme that retrieves documents of all lengths with similar chances as their likelihood of relevance will outperform another scheme which retrieves documents with chances

Amit Singhal; Chris Buckley; Manclar Mitra

1996-01-01

152

Path Integrals and Hamiltonians  

NASA Astrophysics Data System (ADS)

1. Synopsis; Part I. Fundamental Principles: 2. The mathematical structure of quantum mechanics; 3. Operators; 4. The Feynman path integral; 5. Hamiltonian mechanics; 6. Path integral quantization; Part II. Stochastic Processes: 7. Stochastic systems; Part III. Discrete Degrees of Freedom: 8. Ising model; 9. Ising model: magnetic field; 10. Fermions; Part IV. Quadratic Path Integrals: 11. Simple harmonic oscillators; 12. Gaussian path integrals; Part V. Action with Acceleration: 13. Acceleration Lagrangian; 14. Pseudo-Hermitian Euclidean Hamiltonian; 15. Non-Hermitian Hamiltonian: Jordan blocks; 16. The quartic potential: instantons; 17. Compact degrees of freedom; Index.

Baaquie, Belal E.

2014-03-01

153

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

154

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

155

Bootlegging and path dependency  

Microsoft Academic Search

This paper confirms the importance of path dependency in the accumulation of firm-specific technological competencies. It shows that firms are guided by the selective logic of path dependency in their innovation processes, even if management has no part in decisions to invest in a new business idea. The research focuses on the output of bootlegging, defined as research in which

Peter Augsdorfer

2005-01-01

156

The SunPath  

NSDL National Science Digital Library

This site features an interactive applet that models the Sun's path from a geocentric view. It calculates and visualizes the position of the Sun based on latitude and time, and allows students to simulate the Sun's position and path for an hour, a day, a month or a year.

University, Australian N.

157

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.

158

Minimal entropy probability paths between genome families.  

PubMed

We develop a metric for probability distributions with applications to biological sequence analysis. Our distance metric is obtained by minimizing a functional defined on the class of paths over probability measures on N categories. The underlying mathematical theory is connected to a constrained problem in the calculus of variations. The solution presented is a numerical solution, which approximates the true solution in a set of cases called rich paths where none of the components of the path is zero. The functional to be minimized is motivated by entropy considerations, reflecting the idea that nature might efficiently carry out mutations of genome sequences in such a way that the increase in entropy involved in transformation is as small as possible. We characterize sequences by frequency profiles or probability vectors, in the case of DNA where N is 4 and the components of the probability vector are the frequency of occurrence of each of the bases A, C, G and T. Given two probability vectors a and b, we define a distance function based as the infimum of path integrals of the entropy function H( p) over all admissible paths p(t), 0 < or = t< or =1, with p(t) a probability vector such that p(0)=a and p(1)=b. If the probability paths p(t) are parameterized as y(s) in terms of arc length s and the optimal path is smooth with arc length L, then smooth and "rich" optimal probability paths may be numerically estimated by a hybrid method of iterating Newton's method on solutions of a two point boundary value problem, with unknown distance L between the abscissas, for the Euler-Lagrange equations resulting from a multiplier rule for the constrained optimization problem together with linear regression to improve the arc length estimate L. Matlab code for these numerical methods is provided which works only for "rich" optimal probability vectors. These methods motivate a definition of an elementary distance function which is easier and faster to calculate, works on non-rich vectors, does not involve variational theory and does not involve differential equations, but is a better approximation of the minimal entropy path distance than the distance //b-a//(2). We compute minimal entropy distance matrices for examples of DNA myostatin genes and amino-acid sequences across several species. Output tree dendograms for our minimal entropy metric are compared with dendograms based on BLAST and BLAST identity scores. PMID:15133624

Ahlbrandt, Calvin; Benson, Gary; Casey, William

2004-05-01

159

Frequency chirped differential absorption LIDAR  

NASA Astrophysics Data System (ADS)

We present a novel concept design of a differential absorption LIDAR for open path trace gas sensing in the atmosphere. To perform a range-resolved gas sensing we propose to arrange a set of retroreflectors in the laser beam path to measure a differential absorption in adjacent sections. In validation experiments we used a pulsed DFB quantum cascade laser fabricated by Alpes Lasers. The laser was excited with 200-ns current pulses with a repetition rate of 10 kHz. The frequency chirp rate was found to increase from 7.7 to 1.0 cm -1/?s as peak injection current was increased from 7.1, to 7.8 A. We utilized the frequency chirp at laser substrate temperature of 24.0 °C to scan the 967.0 - 968.5 cm -1 spectral interval containing the absorption lines of CO II and NH3. We detected ~ 0.25 ppmv of NH 3 in nitrogen at atmospheric pressure using a double-pass gas cell with an effective absorption path of 2.4 m. Digital filtering of the spectra was shown to be effective in eliminating a high-frequency noise. To demonstrate range-resolved capabilities of the sensor we used two retroreflectors inserted into the laser beam. A differential absorption of CO II at 967.7 cm -1 was measured with the gas cell placed in one of the sections. Our experiments indicate that the frequency chirped LIDAR can be used for open path spectroscopy of NH 3 over the ranges up to ~ 1 km with a spatial resolution of ~ 30 m and detection limit of ~ 20 ppbv per a 30-m section.

Lytkine, A.; Jäger, W.; Tulip, J.

2006-09-01

160

Extremal paths on a random cayley tree  

PubMed

We investigate the statistics of extremal path(s) (both the shortest and the longest) from the root to the bottom of a Cayley tree. The lengths of the edges are assumed to be independent identically distributed random variables drawn from a distribution rho(l). Besides, the number of branches from any node is also random. Exact results are derived for arbitrary distribution rho(l). In particular, for the binary 0,1 distribution rho(l)=pdelta(l,1)+(1-p)delta(l, 0), we show that as p increases, the minimal length undergoes an unbinding transition from a "localized" phase to a "moving" phase at the critical value, p=p(c)=1-b(-1), where b is the average branch number of the tree. As the height n of the tree increases, the minimal length saturates to a finite constant in the localized phase (pp(c)) where the velocity v(min)(p) is determined via a front selection mechanism. At p=p(c), the minimal length grows with n in an extremely slow double-logarithmic fashion. The length of the maximal path, on the other hand, increases linearly as v(max)(p)n for all p. The maximal and minimal velocities satisfy a general duality relation, v(min)(p)+v(max)(1-p)=1, which is also valid for directed paths on finite-dimensional lattices. PMID:11138046

Majumdar; Krapivsky

2000-12-01

161

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

162

Arc Length Gone Global  

ERIC Educational Resources Information Center

Everyone with a thorough knowledge of single variable calculus knows that integration can be used to find the length of a curve on a given interval, called its arc length. Fortunately, if one endeavors to pose and solve more interesting problems than simply computing lengths of various curves, there are techniques available that do not require an…

Boudreaux, Gregory M.; Wells, M. Scott

2007-01-01

163

Characterization of soil organic matter composition at intact preferential flow path surfaces  

NASA Astrophysics Data System (ADS)

In structured soils, the interaction of percolating water and reactive solutes with the soil matrix is mostly restricted to surfaces of preferential flow paths. Surfaces of flow paths that are formed by cracks, decayed root channels or worm burrows are often covered by clay-organic coatings (i.e., cutanes), in which the outermost layer is mainly organic matter (OM). The composition of OM finally controls wettability, sorption, and transfer properties. However, the in-situ local distribution of OM properties along such surfaces is largely unknown to date because experimental techniques to study the relatively thin and vulnerable coatings at intact structure surfaces were not available. The objective of this study was to analyze the local mm-scale distribution and composition of SOM at preferential flow paths. The Fourier transformed infrared spectroscopy in diffuse reflectance mode (DRIFT) was used to determine spectral information of the intact structural surfaces (cracks and biopores). With the DRIFT-mapping technique, potential flow path types, such as earthworm burrows, root channels, and cracks of structured subsoil horizons were analyzed in 1 mm steps along transects of 15 up to 65 mm length. The distribution of OM composition was characterized by evaluating the ratios of the absorption band intensities of the alkyl- (C-H-) and carbonyl (C=O-) functional groups (CH/CO), which represent a measure of the potential wettability of the OM of the surface. Samples of different soil types (Luvisol, Regosol, Stagnosol, Cambisol), of different geological provenance (till, loess, mudstone, limestone), and of different land use (arable, forest) were analyzed. The CH/CO-ratio was generally higher for earthworm burrows and root channels as compared to crack surfaces and the soil matrix. Differences between flow path types could be observed with respect to soil type, parent material, and land use. The local distribution of the OM properties may affect sorption and mass transfer during preferential flow in structured soils.

Leue, M.; Gerke, H. H.; Ellerbrock, R. H.

2012-04-01

164

Neutron scattering lengths and cross sections  

Microsoft Academic Search

The application of thermal neutron scattering to the study of the structure and dynamics of condensed matter requires a knowledge of the scattering lengths and the corresponding scattering and absorption cross sections of the elements. Ln some cases, values for the individual isotopes are needed as well. This information is required to obtain an absolute normalization ofthe scatteredneutron distributions, tocalculate

Varley F. Sears

1992-01-01

165

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

166

Improved particle swarm optimization approach to path planning of amphibious mouse robot  

Microsoft Academic Search

A new path planning approach based on improved particle swarm optimization (PSO) for an amphibious mouse robot is presented. In conventional path planning methods, the length of the path is the principal factor, but with the amphibious mouse robot side, other factors (especially the influence of liquid) must be taken into consideration. In this paper, an improved PSO is proposed,

Maopeng Ran; Haibin Duan; Xinge Gao; Zhili Mao

2011-01-01

167

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

168

The reweighted path ensemble.  

PubMed

We introduce a reweighting scheme for the path ensembles in the transition interface sampling framework. The reweighting allows for the analysis of free energy landscapes and committor projections in any collective variable space. We illustrate the reweighting scheme on a two dimensional potential with a nonlinear reaction coordinate and on a more realistic simulation of the Trp-cage folding process. We suggest that the reweighted path ensemble can be used to optimize possible nonlinear reaction coordinates. PMID:21054008

Rogal, Jutta; Lechner, Wolfgang; Juraszek, Jarek; Ensing, Bernd; Bolhuis, Peter G

2010-11-01

169

Path integration in tactile perception of shapes.  

PubMed

Whenever we move the hand across a surface, tactile signals provide information about the relative velocity between the skin and the surface. If the system were able to integrate the tactile velocity information over time, cutaneous touch may provide an estimate of the relative displacement between the hand and the surface. Here, we asked whether humans are able to form a reliable representation of the motion path from tactile cues only, integrating motion information over time. In order to address this issue, we conducted three experiments using tactile motion and asked participants (1) to estimate the length of a simulated triangle, (2) to reproduce the shape of a simulated triangular path, and (3) to estimate the angle between two-line segments. Participants were able to accurately indicate the length of the path, whereas the perceived direction was affected by a direction bias (inward bias). The response pattern was thus qualitatively similar to the ones reported in classical path integration studies involving locomotion. However, we explain the directional biases as the result of a tactile motion aftereffect. PMID:25151621

Moscatelli, Alessandro; Naceri, Abdeldjallil; Ernst, Marc O

2014-11-01

170

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

171

Study Tracks Path of Indian Ocean Tsunami  

NSDL National Science Digital Library

Since the Indian Ocean tsunami of December 26, 2004, scientists have tried to retrace the path of the giant waves to learn how and why the water moved in unexpected directions, even turning corners and producing simultaneous wavefronts coming from different directions. This radio broadcast describes efforts to measure the strength, distance traveled inland, and height of the tsunami, as well as mapping its route. The clip is 4 minutes in length.

172

Document Length Normalization  

Microsoft Academic Search

In the TREC collection—a large full-text experimental text collection with widely varying document lengths—we observe that the likelihood of a document being judged relevant by a user increases with the document length. We show that a retrieval strategy, such as the vector-space cosine match, that retrieves documents of different lengths with roughly equal chances, will not optimally retrieve useful documents

Amit Singhal; Gerard Salton; Mandar Mitra; Chris Buckley

1996-01-01

173

Sampling diffusive transition paths  

SciTech Connect

We 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 sampling infinitesimal Brownian increments of the path, as well as a different type of stiffness associated with sampling the coarse features of long paths. The fine-features sampling stiffness is eliminated with the use of the fast sampling algorithm (FSA), 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. We use the algorithm to sample the transition path ensemble for the structural interconversion of the 38-atom Lennard-Jones cluster at low temperature.

F. Miller III, Thomas; Predescu, Cristian

2006-10-12

174

Laser absorption spectroscopy of oxygen confined in highly porous hollow sphere xerogel.  

PubMed

An Al2O3 xerogel with a distinctive microstructure is studied for the application of laser absorption spectroscopy of oxygen. The xerogel has an exceptionally high porosity (up to 88%) and a large pore size (up to 3.6 µm). Using the method of gas-in-scattering media absorption spectroscopy (GASMAS), a long optical path length (about 3.5m) and high enhancement factor (over 300 times) are achieved as the result of extremely strong multiple-scattering when the light is transmitted through the air-filled, hollow-sphere alumina xerogel. We investigate how the micro-physical feature influences the optical property. As part of the optical sensing system, the material's gas exchange dynamics are also experimentally studied. PMID:24663551

Yang, Lin; Somesfalean, Gabriel; He, Sailing

2014-02-10

175

Neandertal clavicle length  

PubMed Central

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.

2014-01-01

176

Multi-path quenchers: efficient quenching of common fluorophores.  

PubMed

Fluorescence quenching groups are widely employed in biological detection, sensing, and imaging. To date, a relatively small number of such groups are in common use. Perhaps the most commonly used quencher, dabcyl, has limited efficiency with a broad range of fluorophores. Here, we describe a molecular approach to improve the efficiency of quenchers by increasing their electronic complexity. Multi-Path Quenchers (MPQ) are designed to have multiple donor or acceptor groups in their structure, allowing for a multiplicity of conjugation pathways of varied length. This has the effect of broadening the absorption spectrum, which in turn can increase quenching efficiency and versatility. Six such MPQ derivatives are synthesized and tested for quenching efficiency in a DNA hybridization context. Duplexes placing quenchers and fluorophores within contact distance or beyond this distance are used to measure quenching via contact or FRET mechanisms. Results show that several of the quenchers are considerably more efficient than dabcyl at quenching a wider range of common fluorophores, and two quench fluorescein and TAMRA as well as or better than a Black Hole Quencher. PMID:22034828

Crisalli, Pete; Kool, Eric T

2011-11-16

177

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

178

Differential optical absorption spectroscopy technique in emission monitoring: temperature and nonlinearity effects  

NASA Astrophysics Data System (ADS)

When applying the differential optical absorption spectroscopy (DOAS) technique for in-situ monitoring of flue-gas emissions, two main problems may occur in comparison to the atmospheric monitoring DOAS application. The first problem is due to the high and variable temperatures of flue gases, which significantly affects the magnitude of the differential absorption cross-sections. The second problem is caused by the limited choice of optical path- lengths, causing non-linearity effects due to large gas absorption. Measurements of the differential absorption cross-sections for NO, NO2, and SO2 have therefore been performed in a pyrex-glass cell contained in a heat-pipe, at temperatures between 20 and 400 degree(s)C, in the wavelength range of 205 to 440 nm. We also have performed measurements of the linear regions of the technique for measurements of SO2, NO2, and NO. The linear regions were shown to be 1 - 3200 mgm-2 for NO2, 0 - 2000 mgm-2 for SO2, and 0 - 120 mgm-2 for NO, in the spectral resolution range between 0.2 to 0.95 nm. The differential absorption cross-sections of NO2 and SO2 are strongly temperature dependent causing considerable errors in evaluated concentrations when using the DOAS technique. The relative errors due to temperature were of the order of 70% for SO2 and NO2 and of the order of 15% for NO at 400 degree(s)C.

Mellqvist, Johan M.; Axelsson, Hakan; Rosen, Arne

1993-03-01

179

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

NASA Astrophysics Data System (ADS)

Two measuring methods of the wide absorption spectrum by distributed feedback laser diodes (DFB-LDs) are presented in detecting the water vapor absorption line. One is the subsection scanning method, and it takes advantage of the wide spectrum tuning range by the 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 correspond to the specific temperature of DFB-LD, scanning every section by current modulation for hundreds times, and averaging the data to raise the signal to noise ratio (SNR), then 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 the absorption line-shape function; the absorption line can be described by fitting with partial measured data. The fitting absorption line was fitted well with the measured data, and the square of correlation coefficient (R-square) was 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.

2014-09-01

180

Gas Path Seal.  

National Technical Information Service (NTIS)

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 backi...

R. C. Bill, R. D. Johnson

1979-01-01

181

DNA Computing Hamiltonian path  

E-print Network

2014 DNA DNA #12;DNA Computing · Feynman · Adleman · DNASIMD · ... · · · · · DNADNA #12;DNA · DNA · · · · DNA · · #12;2000 2005 2010 1995 Hamiltonian path DNA tweezers DNA tile DNA origami DNA box Sierpinski DNA tile self assembly DNA logic gates Whiplash PCR DNA automaton DNA spider MAYA

Hagiya, Masami

182

World nuclear energy paths  

Microsoft Academic Search

In examing the world nuclear energy paths, the following assumptions were adopted: the world economy will grow somewhat more slowly than in the past, leading to reductions in electricity demand growth rates; national and international political impediments to the deployment of nuclear power will gradually disappear over the next few years; further development of nuclear power will proceed steadily, without

T. J. Connolly; U. Hansen; W. Jaek; K. H. Beckurts

1979-01-01

183

Off the Beaten Path.  

ERIC Educational Resources Information Center

Describes "Off the Beaten Path", a program that takes at-risk students out of the traditional classroom and puts them into a camping atmosphere in order to increase academic achievement, improve self-esteem, and promote better social skills. (WRM)

Grimm, Karen

1999-01-01

184

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

185

Myofilament length dependent activation  

SciTech Connect

The Frank-Starling law of the heart describes the interrelationship between end-diastolic volume and cardiac ejection volume, a regulatory system that operates on a beat-to-beat basis. The main cellular mechanism that underlies this phenomenon is an increase in the responsiveness of cardiac myofilaments to activating Ca{sup 2+} ions at a longer sarcomere length, commonly referred to as myofilament length-dependent activation. This review focuses on what molecular mechanisms may underlie myofilament length dependency. Specifically, the roles of inter-filament spacing, thick and thin filament based regulation, as well as sarcomeric regulatory proteins are discussed. Although the 'Frank-Starling law of the heart' constitutes a fundamental cardiac property that has been appreciated for well over a century, it is still not known in muscle how the contractile apparatus transduces the information concerning sarcomere length to modulate ventricular pressure development.

de Tombe, Pieter P.; Mateja, Ryan D.; Tachampa, Kittipong; Mou, Younss Ait; Farman, Gerrie P.; Irving, Thomas C. (IIT); (Loyola)

2010-05-25

186

Myofilament Length Dependent Activation  

PubMed Central

The Frank-Starling law of the heart describes the interrelationship between end-diastolic volume and cardiac ejection volume, a regulatory system that operates on a beat-to-beat basis. The main cellular mechanism that underlies this phenomenon is an increase in the responsiveness of cardiac myofilaments to activating Ca2+ ions at a longer sarcomere length, commonly referred to as myofilament length dependent activation. This review focuses on what molecular mechanisms may underlie myofilament length dependency. Specifically, the roles of inter-filament spacing, thick and thin filament based regulation, as well as sarcomeric regulatory proteins are discussed. Although the “Frank-Starling law of the heart” constitutes a fundamental cardiac property that has been appreciated for well over a century, it is still not known in muscle how the contractile apparatus transduces the information concerning sarcomere length to modulate ventricular pressure development. PMID:20053351

de Tombe, Pieter P.; Mateja, Ryan D.; Kittipong-Tachampa; Mou, Younss Ait; Farman, Gerrie P.; Irving, Thomas C.

2010-01-01

187

Measurements of the Vertical Coherence Length in Neutron Interferometry  

SciTech Connect

The study and use of macroscopic quantum coherence requires long coherence lengths. Here we describe an approach to measuring the vertical coherence length in neutron interferometry, along with improvements to the NIST interferometer that led to a measured coherence length of 790 A. The measurement is based on introducing a path separation and measuring the loss in contrast as this separation is increased. The measured coherence length is consistent with the momentum distribution of the neutron beam. Finally, we demonstrate that the loss in contrast with beam displacement in one leg of the interferometer can be recovered by introducing a corresponding displacement in the second leg.

Pushin, D. A.; Cory, D. G. [Department of Nuclear Science and Engineering, Massachusetts Institute of Technology, Cambridge, Massachusetts (United States); Arif, M. [National Institute of Standards and Technology, Gaithersburg, Maryland (United States); Huber, M. G. [Department of Physics, Tulane University, New Orleans, Louisiana (United States)

2008-06-27

188

Editorial: Redefining Length  

SciTech Connect

Technological changes have moved publishing to electronic-first publication where the print version has been relegated to simply another display mode. Distribution in HTML and EPUB formats, for example, changes the reading environment and reduces the need for strict pagination. Therefore, in an effort to streamline the calculation of length, the APS journals will no longer use the printed page as the determining factor for length. Instead the journals will now use word counts (or word equivalents for tables, figures, and equations) to establish length; for details please see http://publish.aps.org/authors/length-guide. The title, byline, abstract, acknowledgment, and references will not be included in these counts allowing authors the freedom to appropriately credit coworkers, funding sources, and the previous literature, bringing all relevant references to the attention of readers. This new method for determining length will be easier for authors to calculate in advance, and lead to fewer length-associated revisions in proof, yet still retain the quality of concise communication that is a virtue of short papers.

Sprouse, Gene D. [American Physical Society (United States)

2011-07-15

189

Absorption of white light in photoreceptors  

Microsoft Academic Search

The fraction F of incident light absorbed by a photoreceptor of length l has traditionally been given by F =1 -e?kl, where k is the absorption coefficient of the photoreceptor. Unfortunately, this widely-used expression is incorrect for absorption of the type of light most common in natural scenes—broad spectrum “white” light—and significantly over-estimates absorption. This is because the measured values

Eric J. Warrant; Dan-E. Nilsson

1998-01-01

190

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

191

Stabilizing Intelligent Route Control: Randomized Path Monitoring, Randomized Path  

E-print Network

Stabilizing Intelligent Route Control: Randomized Path Monitoring, Randomized Path Switching or History-aware Path Switching? Alexandre Fonte1,2 , Jos´e Martins1 , Marilia Curado1 , and Edmundo Monteiro, Castelo Branco, Portugal Abstract. Multihoming Intelligent Route Control (IRC) plays a signif- icant role

Monteiro, Edmundo

192

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

193

PATHS groundwater hydrologic model  

SciTech Connect

A preliminary evaluation capability for two-dimensional groundwater pollution problems was developed as part of the Transport Modeling Task for the Waste Isolation Safety Assessment Program (WISAP). Our approach was to use the data limitations as a guide in setting the level of modeling detail. PATHS Groundwater Hydrologic Model is the first level (simplest) idealized hybrid analytical/numerical model for two-dimensional, saturated groundwater flow and single component transport; homogeneous geology. This document consists of the description of the PATHS groundwater hydrologic model. The preliminary evaluation capability prepared for WISAP, including the enhancements that were made because of the authors' experience using the earlier capability is described. Appendixes A through D supplement the report as follows: complete derivations of the background equations are provided in Appendix A. Appendix B is a comprehensive set of instructions for users of PATHS. It is written for users who have little or no experience with computers. Appendix C is for the programmer. It contains information on how input parameters are passed between programs in the system. It also contains program listings and test case listing. Appendix D is a definition of terms.

Nelson, R.W.; Schur, J.A.

1980-04-01

194

Upper Extremity Length Equalization  

PubMed Central

Significant upper extremity length inequality is uncommon but can cause major functional problems. The ability to position and use the hand may be impaired by shortness of any of the long bones of the upper extremity. In many respects upper and lower extremity length problems are similar. They most commonly occur after injury to a growing bone and the treatment modalities utilized in the lower extremity may be applied to the upper extremity. These treatment options include epiphysiodesis, shortening osteotomy, angulatory correction osteotomy and lengthening. This report reviews the literature relative to upper extremity length inequality and equalization and presents an algorithm for evaluation and planning appropriate treatment for patients with this condition. This algorithm is illustrated by two clinical cases of posttraumatic shortness of the radius which were effectively treated. ImagesFigure 1Figure 2Figure 3

DeCoster, Thomas A.; Ritterbusch, John; Crawford, Mark

1992-01-01

195

AIR QUALITY MONITORING IN ATLANTA WITH THE DIFFERENTIAL OPTICAL ABSORPTION SPECTROMETER  

EPA Science Inventory

During July and August of 1990, a differential optical absorption spectrometer (DOAS) made by OPSIS Inc. was used to measure gaseous air pollutants over three separate open paths in Atlanta, GA. ver path 1 (1099 m) and path 2 (1824 m), ozone (O3), sulfur dioxide (SO2), nitrogen d...

196

MINIMUM WEIGHT PATHS TIMEDEPENDENT NETWORKS  

E-print Network

MINIMUM WEIGHT PATHS in TIME­DEPENDENT NETWORKS Ariel Orda Raphael Rom Department of Electrical) ABSTRACT We investigate the minimum weight path problem in networks whose link weights and link delays weight problem always has a solution. We also characterize the structure of an infinite optimal path

Orda, Ariel

197

A new calibration system for lightweight, compact and mobile Cavity-Enhanced Differential Optical Absorption Spectroscopy instruments  

NASA Astrophysics Data System (ADS)

Absorption Spectroscopy has been employed for several decades now to study the earth's atmosphere. While the focus has been on remote sensing for a long time, lately there has been a renewed interest in in-situ methods, as point measurements allow an easier interpretation for highly inhomogeneous distributions of gases of interest compared to the integration approach of most remote sensing methods. One comparatively new method offering both advantages of in-situ measurements as well as being contactless is open-path Cavity-Enhanced Differential Optical Absorption Spectroscopy (CE-DOAS). Broadband open-path CE-DOAS instruments have been used for ten years now, and in the meantime allow the measurement of numerous atmospheric trace gases (e.g. NO2, NO3, IO, CHOCHO, HCHO). While those instruments were bulky and not very mobile at first, recent developments resulted in relatively lightweight (< 30 kg) instruments with a relatively low power consumption allowing mobile open-path measurements at remote field locations. An important operational issue has been the path length calibration in the field, necessary for the determination of the concentration of measured gases. Until now, often calibration gases were used with different scattering properties than air or known concentrations. However this methods has several major shortcomings, being rather inconvenient and cumbersome in the field with the need for compressed gas cylinders, as well as time consuming, preventing a quick check of the state of the instrument in the field after changing measurement locations. Here we present a new wavelength-resolved method for broadband CE-DOAS path length calibration. A small, custom made ring-down system is employed with a pulsed LED as light source. The wavelength is then resolved by tilting a narrow band interference filter. The system not only allows quick, automated path length calibrations without physical interaction on the instrument, but also saves weight, space and the necessity to transport compressed gas cylinders, which is a great advantage e.g. for measurements in remote coastal areas or polar regions. The technical implementation is presented and compared to other CE-DOAS calibration methods.

Zielcke, Johannes; Horbanski, Martin; Pöhler, Denis; Frieß, Udo; Platt, Ulrich

2013-04-01

198

Mappability and read length  

PubMed Central

Power-law distributions are the main functional form for the distribution of repeat size and repeat copy number in the human genome. When the genome is broken into fragments for sequencing, the limited size of fragments and reads may prevent an unique alignment of repeat sequences to the reference sequence. Repeats in the human genome can be as long as 104 bases, or 105 ? 106 bases when allowing for mismatches between repeat units. Sequence reads from these regions are therefore unmappable when the read length is in the range of 103 bases. With a read length of 1000 bases, slightly more than 1% of the assembled genome, and slightly less than 1% of the 1 kb reads, are unmappable, excluding the unassembled portion of the human genome (8% in GRCh37/hg19). The slow decay (long tail) of the power-law function implies a diminishing return in converting unmappable regions/reads to become mappable with the increase of the read length, with the understanding that increasing read length will always move toward the direction of 100% mappability.

Li, Wentian; Freudenberg, Jan

2014-01-01

199

Absorptance of infrared radiation by methane at elevated temperatures  

SciTech Connect

In large-scale fires and flames, radiative transport can be an important factor determining the rate of fuel volatilization and flame spread in condensed fuels, and in general can affect the amount of soot that is produced by the flame. The radiant flux can be significantly attenuated by core hydrocarbon gases that have absorption features in the infrared. The spectral absorptance of the {upsilon}{sub 3} (centered at approximately 3020 cm{sup -1}) and {upsilon}{sub 4} (centered at approximately 1306 cm{sup -1}) fundamental bands of methane were measured at elevated temperatures. The measurements were made using a FTIR spectrometer coupled to a gas cell that was maintained at a constant temperature in a furnace. The partial pressure of the methane was varied between 5 and 95 percent, yielding pressure path lengths between 1.14 and 21.74 atm-cm. The total pressure was maintained at 1 atm. Measurements were made at temperatures between 296 and 900 K. The effect of spectral resolution on the measurements and derived parameters was examined. Spectral resolutions between 4 and 32 cm{sup -1} were used. The spectral mean parameters of line strength and line shape were determined for the Elsasser narrow band radiation model using the data taken at a resolution of 4 cm{sup -1}. The band model parameters were incorporated into RADCAL, a narrow band model used to predict spectral intensity and transmittance. 13 refs., 10 figs., 1 tab.

Fuss, S.P.; Ezekoye, O.A.; Hall, M.J. [Univ. of Texas, Austin, TX (United States)

1996-11-01

200

Light trapping and near-unity solar absorption in a three-dimensional photonic-crystal.  

PubMed

We report what is to our knowledge the first observation of the effect of parallel-to-interface-refraction (PIR) in a three-dimensional, simple-cubic photonic-crystal. PIR is an acutely negative refraction of light inside a photonic-crystal, leading to light-bending by nearly 90 deg over broad wavelengths (?). The consequence is a longer path length of light in the medium and an improved light absorption beyond the Lambertian limit. As an illustration of the effect, we show near-unity total absorption (?98%) in ?=520-620 nm and an average absorption of ~94% over ?=400-700 nm for our ?-Si:H photonic-crystal sample of an equivalent bulk thickness of t˜=450 nm. Furthermore, we have achieved an ultra-wide angular acceptance of light over ?=0°-80°. This demonstration opens up a new door for light trapping and near-unity solar absorption over broad ?s and wide angles. PMID:24321959

Kuang, Ping; Deinega, Alexei; Hsieh, Mei-Li; John, Sajeev; Lin, Shawn-Yu

2013-10-15

201

Tracking hurricane paths  

NASA Technical Reports Server (NTRS)

The South East coastal region experiences hurricane threat for almost six months in every year. To improve the accuracy of hurricane forecasts, meteorologists would need the storm paths of both the present and the past. A hurricane path can be established if we could identify the correct position of the storm at different times right from its birth to the end. We propose a method based on both spatial and temporal image correlations to locate the position of a storm from satellite images. During the hurricane season, the satellite images of the Atlantic ocean near the equator are examined for the hurricane presence. This is accomplished in two steps. In the first step, only segments with more than a particular value of cloud cover are selected for analysis. Next, we apply image processing algorithms to test the presence of a hurricane eye in the segment. If the eye is found, the coordinate of the eye is recorded along with the time stamp of the segment. If the eye is not found, we examine adjacent segments for the existence of hurricane eye. It is probable that more than one hurricane eye could be found from different segments of the same period. Hence, the above process is repeated till the entire potential area for hurricane birth is exhausted. The subsequent/previous position of each hurricane eye will be searched in the appropriate adjacent segments of the next/previous period to mark the hurricane path. The temporal coherence and spatial coherence of the images are taken into account by our scheme in determining the segments and the associated periods required for analysis.

Prabhakaran, Nagarajan; Rishe, Naphtali; Athauda, Rukshan

1997-01-01

202

Horizontal path propagation measurements over the sea  

NASA Astrophysics Data System (ADS)

We report on the current status of a horizontal path length laser propagation campaign that is being performed over the sea, just off the coast of Puerto Rico. The effects of atmospheric turbulence in a tranquil marine environment have been measured with a video rate Shack--Hartmann wavefront sensor. The small perturbations in the wavefront phase and the degree of scintillation are presently being determined in a single pass from source to receiver, over a trial distance of 110 meters. Additional sites have been identified which allow for single pass measurements up to approximately 1 kilometer. Over 70 hours of data have been sampled to date, between December 2003 and April 2004.

Chang, Mark P.; Santiago, Freddie; Font, Carlos O.; Luna, Yaitza; Roura, Erick; Restaino, Sergio R.

2004-10-01

203

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

204

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

205

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

206

Open-Path High Sensitivity Atmospheric Ammonia Sensing with a Quantum Cascade Laser Instrument  

NASA Astrophysics Data System (ADS)

Atmospheric trace-gas sensing with quantum cascade laser (QCL) spectroscopy offers the potential for high sensitivity, fast, selective mid-infrared absorption measurements of atmospheric species such as ammonia (NH3). As the third most abundant nitrogen species and most gaseous base in the atmosphere, ammonia plays important roles in neutralizing acidic species and as a gas-phase precursor to ammoniated fine particulate matter. High precision gas phase measurements are necessary to constrain highly uncertain emission sources and sinks with implications for understanding how chemical components of fine particulate matter affect air quality and climate as well as nitrogen deposition to ecosystems. Conventional ammonia sensors employing chemical ionization, denuder or filter techniques are labor-intensive, not gas-selective and exhibit low time resolution. As an advantageous alternative to conventional measurement techniques, we develop an open-path quantum cascade laser-based ammonia sensor operating at 9.06 ?m for ground-based measurements. A continuous wave, thermoelectrically cooled quantum cascade laser is used to perform wavelength modulation absorption spectroscopy (WMS). Room-temperature, unattended operation with minimal surface adsorption effects due to the open-path configuration represent significant improvements over cryogenically cooled, closed path systems. The feasibility of a cylindrical mirror multi-pass optical cell for achieving long path lengths near 50 m in a compact design is also assessed. Meaningful ammonia measurements require fast sub-ppbv detection limits due to ammonia’s large dynamic range and temporal and spatial atmospheric variability. When fully developed, our instrument will achieve high time resolution (up to 10 Hz) measurements with ammonia detection limits in the 100 pptv range. Initial results include ambient laboratory ammonia detection at 58 ppbv relative to a 0.4% ammonia reference cell based on the WMS signal integrated area. We estimate a limit of detection based on our signal to noise ratio of ~400 pptv NH3. Non-cryogenic, unattended operation of this compact sensor offers the potential for applications in particulate matter gas-phase precursor monitoring networks. Future sensor measurements can also be utilized for evaluations of and data assimilation into air quality and aerosol forecast models of particular importance for regions where ammonia plays a critical role in fine particulate matter formation.

Miller, D. J.; Dirisu, A.; Rafferty, K.; Parkes, B.; Zondlo, M. A.

2009-12-01

207

Planck-Length Phenomenology  

E-print Network

This author's recent proposal of interferometric tests of Planck-scale-related properties of space-time is here revisited from a strictly phenomenological viewpoint. The results announced previously are rederived using elementary dimensional considerations. The dimensional analysis is then extended to the other two classes of experiments (observations of neutral kaons at particle accelerators and observations of the gamma rays we detect from distant astrophysical sources) which have been recently considered as opportunities to explore "foamy" properties of space-time. The emerging picture suggests that there is an objective and intuitive way to connect the sensitivities of these three experiments with the Planck length. While in previous studies the emphasis was always on some quantum-gravity scenario and the analysis was always primarily aimed at showing that the chosen scenario would leave a trace in a certain class of doable experiments, the analysis here reported takes as starting point the experiments and, by relating in a direct quantitative way the sensitivities to the Planck length, provides a model-independent description of the status of Planck-length phenomenology.

Giovanni Amelino-Camelia

2000-08-04

208

Hausdorff dimension of a particle path in a quantum manifold  

SciTech Connect

After recalling the concept of the Hausdorff dimension, we study the fractal properties of a quantum particle path. As a novelty we consider the possibility for the space where the particle propagates to be endowed with a quantum-gravity-induced minimal length. We show that the Hausdorff dimension accounts for both the quantum mechanics uncertainty and manifold fluctuations. In addition the presence of a minimal length breaks the self-similarity property of the erratic path of the quantum particle. Finally we establish a universal property of the Hausdorff dimension as well as the spectral dimension: They both depend on the amount of resolution loss which affects both the path and the manifold when quantum gravity fluctuations occur.

Nicolini, Piero; Niedner, Benjamin [Frankfurt Institute for Advanced Studies (FIAS), Institut fuer Theoretische Physik, Johann Wolfgang Goethe-Universitaet, Ruth-Moufang-Strasse 1, 60438 Frankfurt am Main (Germany)

2011-01-15

209

Grazing exit versus grazing incidence geometry for x-ray absorption near edge structure analysis of arsenic traces  

SciTech Connect

In the presented study the grazing exit x-ray fluorescence was tested for its applicability to x-ray absorption near edge structure analysis of arsenic in droplet samples. The experimental results have been compared to the findings of former analyses of the same samples using a grazing incidence (GI) setup to compare the performance of both geometries. Furthermore, the investigations were accomplished to gain a better understanding of the so called self-absorption effect, which was observed and investigated in previous studies using a GI geometry. It was suggested that a normal incidence-grazing-exit geometry would not suffer from self-absorption effects in x-ray absorption fine structure (XAFS) analysis due to the minimized path length of the incident beam through the sample. The results proved this assumption and in turn confirmed the occurrence of the self-absorption effect for GI geometry. Due to its lower sensitivity it is difficult to apply the GE geometry to XAFS analysis of trace amounts (few nanograms) of samples but the technique is well suited for the analysis of small amounts of concentrated samples.

Meirer, F.; Streli, C.; Wobrauschek, P.; Zoeger, N. [Atominstitut, Vienna University of Technology, 1020 Wien (Austria); Pepponi, G. [Fondazione Bruno Kessler, via Sommarive 18, 38050 Povo, Trento (Italy)

2009-04-01

210

Greenhouse gas measurements over a 144 km open path in the Canary Islands  

NASA Astrophysics Data System (ADS)

A new technique for the satellite remote sensing of greenhouse gases in the atmosphere via the absorption of short-wave infrared laser signals transmitted between counter-rotating satellites in low Earth orbit has recently been proposed; this would enable the acquisition of a long-term, stable, global set of altitude-resolved concentration measurements. We present the first ground-based experimental demonstration of this new infrared-laser occultation method, in which the atmospheric absorption of CO2 near 2.1 ?m was measured over a ~144 km path length between two peaks in the Canary Islands (at an altitude of ~2.4 km), using relatively low power diode lasers (~4 to 10 mW). The retrieved CO2 volume mixing ratio of 400 ppm (±15 ppm) is consistent within experimental uncertainty with simultaneously recorded in situ validation measurements. We conclude that the new method has a sound basis for monitoring CO2 in the free atmosphere; other greenhouse gases such as methane, nitrous oxide and water vapour can be monitored in the same way.

Brooke, J. S. A.; Bernath, P. F.; Kirchengast, G.; Thomas, C. B.; Wang, J.-G.; Tereszchuk, K. A.; González Abad, G.; Hargreaves, R. J.; Beale, C. A.; Harrison, J. J.; Schweitzer, S.; Proschek, V.; Martin, P. A.; Kasyutich, V. L.; Gerbig, C.; Kolle, O.; Loescher, A.

2012-09-01

211

"Minimax Length Links" of a Dissimilarity Matrix and Minimum Spanning Trees.  

ERIC Educational Resources Information Center

A theorem is proved stating that the set of all "minimax links," defined as links minimizing, over paths, the maximum length of links in any path connecting a pair of objects comprising nodes in an undirected weighted graph, comprises the union of all minimum spanning trees of that graph. (Author/SLD)

Carroll, J. Douglas

1995-01-01

212

Steepest entropy ascent paths towards the Max-Ent distribution  

E-print Network

With reference to two general probabilistic description frameworks, Information Theory and Classical Statistical Mechanics, we discuss the geometrical reasoning and mathematical formalism leading to the differential equation that defines in probability space the smooth path of Steepest Entropy Ascent (SEA) connecting an arbitrary initial probability distribution to the unique Maximum Entropy (MaxEnt) distribution with the same mean values of a set of constraints. The SEA path is relative to a metric chosen to measure distances in square-root probability distribution space. Along the resulting SAE path, the metric turns out to be proportional to the concept of Onsager resistivity generalized to the far non-equilibrium domain. The length of the SEA path to MaxEnt provides a novel global measure of degree of disequilibrium (DoD) of the initial probability distribution, whereas a local measure of DoD is given by the norm of a novel generalized concept of non-equilibrium affinity.

Gian Paolo Beretta

2013-12-18

213

An upper limit for water dimer absorption in the 750 nm spectral region and a revised water line list  

NASA Astrophysics Data System (ADS)

Absorption of solar radiation by water dimer molecules in the Earth's atmosphere has the potential to act as a positive feedback effect for climate change. There seems little doubt from the results of previous laboratory and theoretical studies that significant concentrations of the water dimer should be present in the atmosphere, yet attempts to detect water dimer absorption signatures in atmospheric field studies have so far yielded inconclusive results. Here we report spectral measurements in the near-infrared around 750 nm in the expected region of the | 0⟨f | 4⟩b|0 ⟩ overtone of the water dimer's hydrogen-bonded OH stretching vibration. The results were obtained using broadband cavity ringdown spectroscopy (BBCRDS), a methodology that allows absorption measurements to be made under controlled laboratory conditions but over absorption path lengths representative of atmospheric conditions. In order to account correctly and completely for the overlapping absorption of monomer molecules in the same spectral region, we have also constructed a new list of spectral data (UCL08) for the water monomer in the 750-20 000 cm-1 (13 ?m-500 nm) range. Our results show that the additional lines included in the UCL08 spectral database provide an improved representation of the measured water monomer absorption in the 750 nm region. No absorption features other than those attributable to the water monomer were detected in BBCRDS experiments performed on water vapour samples containing dimer concentrations up to an order of magnitude greater than expected in the ambient atmosphere. The absence of detectable water dimer features leads us to conclude that, in the absence of significant errors in calculated dimer oscillator strengths or monomer/dimer equilibrium constants, the widths of any water dimer absorption features present around 750 nm are of the order of 100 cm-1 HWHM, and certainly greater than the 25-30 cm-1 HWHM reported in the literature for lower energy water dimer transitions up to 8000 cm-1.

Shillings, A. J. L.; Ball, S. M.; Barber, M. J.; Tennyson, J.; Jones, R. L.

2011-05-01

214

Efficient optical path folding by using multiple total internal reflections in a microcavity  

E-print Network

We propose using an asymmetric resonant microcavity for the efficient generation of an optical path that is much longer than the diameter of the cavity. The path is formed along a star polygonal periodic orbit within the cavity, which is stable and confined by total internal reflection. We fabricated a semiconductor device based on this idea with an average diameter of 0.3 mm, and achieved a path length of 2.79 mm experimentally.

Shinohara, Susumu; Fukushima, Takehiro; Harayama, Takahisa; Arai, Kenichi; Yoshimura, Kazuyuki

2014-01-01

215

a Study of Basic Properties and Applications of Extended X-Ray Absorption Fine Structure  

NASA Astrophysics Data System (ADS)

One of the advantages of Extended X-ray Absorption Fine Structure (EXAFS) is the capability of probing the local structure around different kinds of atoms separately. This aspect of the EXAFS has been used to determine the local structure of solid solutions of Ga(,1-x)In(,x)As and Ga(,1 -x)In(,x)Sb. The structure of Ga(,1-x)In(,x)As has been studied by Mikkelsen et al and the results have been published('1). The results of this work agree with theirs. EXAFS study shows that the nearest neighbor bond lengths change linearly with x and the changes are smaller than the values suggested by the virtual crystal approximation (VCA). Next nearest neighbor environments show that the As atoms around the Ga and In atoms form a slightly distorted tetrahedron. The distribution of Ga and In atoms is consistent with a model with no correlation among Ga and In atoms. Though EXAFS is successful in probing the local structures, there are several aspects where the experimental results do not agree with theoretical calculations. Many body effects, which are neglected in the independent particle approximation, is one example. The inelastic scattering of the photoelectron and the decay of the core hole state reduces the EXAFS amplitudes from further back- scattering atoms. Their effects have been included by a single mean free path term in the EXAFS equation so far. EXAFS amplitudes of GaAs and InAs were analyzed to study the mean free path in the systems and the mean free path in InAs was obtained by two different methods. They do not agree with each other, indicating that some of the assumptions used in deriving the mean free path are wrong. No single factor can explain the difference. The comparison of the first shell amplitudes of GaAs and InAs shows that the core radius in InAs is about the same as in GaAs, giving a significant mean free path effect on the first shell amplitude. Finally, the mean free paths in different materials were compared. The results seem to indicate that the mean free path in the small k region depends on the band gap energy and the large k region depends on the kind of intervening atoms. This still does not explain the difference in the mean free path in InAs, indicating some of the other assumptions are wrong. An. important factor to be considered is the interference between the lifetime of the core hole state and the photoelectron state. ('1)J. C. Mikkelsen, Jr. and J. B. Boyce, Phys. Rev. B29, 7130 (1983).

Kim, Kyungha

216

Load Balanced Short Path Routing in Wireless Networks Jie Gao, IEEE member, Li Zhang  

E-print Network

1 Load Balanced Short Path Routing in Wireless Networks Jie Gao, IEEE member, Li Zhang Abstract, and achieve good load balance, for balancing the energy use. We consider the special case when all the nodes that of the most load-balanced algorithm without path length constraint. In addition, our routing algo- rithms make

Gao, Jie

217

757 Path Loss Measurements  

NASA Technical Reports Server (NTRS)

Path Loss Measurements were obtained on three (3) GPS equipped 757 aircraft. Systems measured were Marker Beacon, LOC, VOR, VHF (3), Glide Slope, ATC (2), DME (2), TCAS, and GPS. This data will provide the basis for assessing the EMI (Electromagnetic Interference) safety margins of comm/nav (communication and navigation) systems to portable electronic device emissions. These Portable Electronic Devices (PEDs) include all devices operated in or around the aircraft by crews, passengers, servicing personnel, as well as the general public in the airport terminals. EMI assessment capability is an important step in determining if one system-wide PED EMI policy is appropriate. This data may also be used comparatively with theoretical analysis and computer modeling data sponsored by NASA Langley Research Center and others.

Horton, Kent; Huffman, Mitch; Eppic, Brian; White, Harrison

2005-01-01

218

Flight Paths of Orbiting Satellites  

NSDL National Science Digital Library

This is an activity to help students visualize the relationship of motion, time and space as it relates to objects orbiting the earth. They will be able to track the path of an orbiting object on a globe, plot the path of an orbiting object on a flat world map, and explain that an object orbiting earth on a plane will produce a flight path which appears as wavy lines on the earths surface.

219

Path Layout in ATM Networks  

Microsoft Academic Search

This paper surveys recent results in the area of virtual path layout in ATM networks. We focus on the one-to-all (or broadcast) and the all-to-all problems. We present a model for theoretical studies of these layouts, which amounts to covering the network with simple paths, under various constraints. The constraints are the hop count (the number of paths traversed between

Shmuel Zaks

1997-01-01

220

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

221

Path and path deviation equations for p-branes  

NASA Astrophysics Data System (ADS)

Path and path deviation equations for neutral, charged, spinning and spinning charged test particles, using a modified Bazanski Lagrangian, are derived. We extend this approach to strings and branes. We show how the Bazanski Lagrangian for charged point particles and charged branes arises à la Kaluza-Klein from the Bazanski Lagrangian in 5-dimensions.

Pavši?, Matej; Kahil, Magd E.

2012-04-01

222

Indeterminate-length quantum coding  

E-print Network

The quantum analogues of classical variable-length codes are indeterminate-length quantum codes, in which codewords may exist in superpositions of different lengths. This paper explores some of their properties. The length observable for such codes is governed by a quantum version of the Kraft-McMillan inequality. Indeterminate-length quantum codes also provide an alternate approach to quantum data compression.

Benjamin Schumacher; Michael D. Westmoreland

2000-11-02

223

Moments of Directed Paths in a Wedge  

NASA Astrophysics Data System (ADS)

A directed path from the origin in the square lattice, and confined to a wedge, exerts a net entropic force on the wedge. If the wedge is formed by the Y -axis and the line Y = rX, then the moment of the force on the line Y = rX about the origin is given by {\\cal M}_\\alpha = \\frac{-\\log \\cot\\alpha}{(1+\\cot\\alpha)^2} \\qquad \\if 0 \\leq \\alpha\\leq \\pi/4 where ? is the vertex angle of the wedge formed by the lines X = 0 and Y = rX in the square lattice. If ? in [ ?/4, ?/2), then the moment about the origin is zero. This model is closely related to a model of a descending directed path crossing a wedge from the point (0, N) to the point (pM, qM) on the line Y = (q/p)X. If lengths in this model are rescaled by pM, while N = lfloor?qMrfloor and (q/p) ? r, where r is an irrational number, then a limiting model of a path crossing the wedge from the point (0, ?) to the point (1, r) on the line Y = rX is obtained. The limiting path exerts a force on the line Y = rX, and the moment of this force about the origin is {\\cal M}_\\alpha = \\frac{-(\\beta-1)\\log((\\beta-1)\\cot\\alpha) }{(1+(\\beta-1)\\cot\\alpha)^2} if ? > 1 and where ? ? [0, ?/2] is the vertex angle of the wedge.

Janse van Rensburg, E. J.

2006-06-01

224

Stabilizing Intelligent Route Control: Randomized Path Monitoring, Randomized Path Switching or History-Aware Path Switching?  

Microsoft Academic Search

Multihoming Intelligent Route Control (IRC) plays a significant role in improving the performance of Internet accesses. However,\\u000a in a competitive environment, IRC systems may introduce persistent route oscillations, causing significant performance degradation.\\u000a In this study, three design alternatives to cope with this issue are investigated: Randomized Path Monitoring, Randomized\\u000a Path Switching and History-aware Path Switching. The simulation results show that

Alexandre Fonte; José Martins; Marilia Curado; Edmundo Monteiro

2008-01-01

225

Shock wave response of materials at different length scales  

SciTech Connect

After a brief introduction to shock wave propagation in solids, recent experimental developments to understand the real time response of shocked materials at various length scales are outlined. Results from two representative studies are summarized: x-ray diffraction to examine elastic-plastic deformation in shocked LiF crystals; and picosecond optical absorption to examine structural transformation in shocked CdS crystals. Issues related to examining material processes at different length scales in shock wave experiments are discussed briefly.

Gupta, Y.M.

1999-07-01

226

Infinite characteristic length on small-world systems  

Microsoft Academic Search

It was recently claimed that on d-dimensional small-world networks with a\\u000adensity p of shortcuts, the typical separation s(p) ~ p^{-1\\/d} between\\u000ashortcut-ends is a characteristic length for shortest-paths{cond-mat\\/9904419}.\\u000aThis contradicts an earlier argument suggesting that no finite characteristic\\u000alength can be defined for bilocal observables on these systems\\u000a{cont-mat\\/9903426}. We show analytically, and confirm by numerical simulation,\\u000athat shortest-path

Cristian F. Moukarzel; Marcio Argollo de Menezes

1999-01-01

227

On shortest paths and sorting  

Microsoft Academic Search

In finding shortest paths, the operation of finding, successively, a minimum from a list of numbers may require more work than the remainder of the algorithm. It is shown how algorithms from sorting literature can be used to accomplish this part of the shortest path algorithm. Bounds on the largest possible amount of work are established, and results of a

Ellis L. Johnson

1972-01-01

228

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

229

Path Jacobians: Theory and Applications  

Microsoft Academic Search

In accordance with Fermat's Variation Principle, a ray path connecting two arbitrary points in a scene via multiple reflectors is given by a non-linear system. If we fix one of the two points and let the other change, the system can be considered as a function relating the reflection points along the path to the varying point. In this paper,

Min Chen; James Arvo

1998-01-01

230

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

231

Arc-Length-Based Axial Deformation and Length Preserving Deformation  

Microsoft Academic Search

This paper presents an arc-length preserving axial deformation along a B-spline curve based on arc-length parameterization of the axial curve. Space spanned by arc length and rotation minimizing frame on the axis is taken as the embedded space. As in real life, the length of an object's skeleton usually remains constant when it is axially deformed such as a swimming

Qunsheng Peng; Xiaogang Jin; Jieqing Feng

232

[On using tunable diode laser absorption spectroscopy to determine gas fluxes over cropland].  

PubMed

Tunable diode laser absorption spectroscopy (TDLAS) is a compact, automated, high precision technique and fit for in-situ or field measurements. Two spectroscopy measurement systems, TDLAS and NDIR (non-dispersive infrared spectroscopy), were used to monitor trace gas emission over cropland at Fengqiu Agricultural Ecology Experimental Station for one month. The fluxes of carbon dioxide were estimated by flux-gradient and eddy covariance method, respectively. A footprint model was developed during experiment. Based on this model, the source areas of TDLAS and NDIR were investigated. The effects of different factors on the flux measurement were also analyzed. The authors concluded that the source areas for the two techniques are discrepant in most of the cases. The source areas increase with path length and detecting height. This result will help the installation of instruments. PMID:22715787

Tian, Yong-zhi; Liu, Jian-guo; Zhang, Yu-jun; Lu, Yi-huai; He, Ying

2012-04-01

233

Improved algorithms of differential optical absorption spectroscopy for monitoring SO2, NO2 from flue gas  

NASA Astrophysics Data System (ADS)

Valuable achievements in differential optical absorption spectroscopy (DOAS) for monitoring atmospheric trace gas have been made in the past decades. However, in flue gas monitoring, it is difficult to monitor the pollutant gases at low optical density. In this paper, two improved inversion algorithms based on the genetic algorithm and Kalman filter, respectively, were developed to accurately calculate the concentrations of SO2 and NO2 from flue gas. Experimental results show that the improved algorithms have the detection limit of 10 ppm and have a zero drift of 1 ppm at a light path length of 0.5 m. Additionally, the improved algorithms of DOAS combined with the traditional DOAS algorithm can broaden the measurement range of pollutant gases by appropriately setting critical values for the maximum value of the differential optical density.

Guanghua, Tang; Chuanlong, Xu; Litang, Shao; Bin, Zhou; Daoye, Yang; Qi, Pan; Shimin, Wang

2009-01-01

234

Effective utilization of quantum-cascade distributed-feedback lasers in absorption spectroscopy  

NASA Technical Reports Server (NTRS)

A variable duty cycle quasi-cw frequency scanning technique was applied to reduce thermal effects resulting from the high heat dissipation of type I quantum-cascade lasers. This technique was combined with a 100-m path-length multipass cell and a zero-air background-subtraction technique to enhance detection sensitivity to a parts-in-10(9) (ppb) concentration level for spectroscopic trace-gas detection of CH4, N2O, H2O, and C2H5OH in ambient air at 7.9 micrometers. A new technique for analysis of dense high resolution absorption spectra was applied to detection of ethanol in ambient air, yielding a 125-ppb detection limit.

Kosterev, A. A.; Curl, R. F.; Tittel, F. K.; Gmachl, C.; Capasso, F.; Sivco, D. L.; Baillargeon, J. N.; Hutchinson, A. L.; Cho, A. Y.

2000-01-01

235

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

236

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

237

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

238

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

239

Path of the Sun at Different Latitudes  

NSDL National Science Digital Library

There is a lot of information packed into this Flash animation. Find the path of the sun above the horizon (on the celestial sphere) for four locations (both poles, equator, and 41 degrees north) during equinox and solstices. An important point that can be extrapolated from this animation is that although each pole has perpetual day during its respective summer solstice, the sun never exceeds around 24 degrees above the horizon. Given the sun�s oblique rays, there is enhanced atmospheric scattering and absorption resulting in lower temperatures. In addition, ice shelves and glaciers promote high albedos, further lowering temperatures. Thus, it�s a refrigerator even during perpetual day. The animation can easily be rewound or paused to stress important points.

Burrows, Charles; District, East R.

240

[The development of acetylene on-line monitoring technology based on laser absorption spectrum].  

PubMed

As one of the materials in organic chemical industry, acetylene has been used in many aspects of chemical industry. But acetylene is a very dangerous inflammable and explosive gas, so it needs in-situ monitoring during industrial storage and production. Tunable diode laser absorption spectroscopy (TDLAS) technology has been widely used in atmospheric trace gases detection, because it has a lot of advantageous characteristics, such as high sensitivity, good selectivity, and rapid time response. The distribution characteristics of absorption lines of acetylene in near infrared band were studied, and then the system designing scheme of acetylene on-line monitoring based on near infrared tunable diode laser absorption spectroscopy technology was discussed in detail. Moreover, the system of experiment measurement was set up and the method of signal detection and the algorithm of concentration inversion were studied. In addition, the sample cell with a path length of 10 cm, and the acetylene of different known concentrations were measured. As a result, the detection limit obtained reached 1.46 cm3 x m(-3). Finally the dynamic detection experiment was carried out, and the measurement result is stable and reliable, so the design of the system is practicable through experiment analysis. On-line acetylene leakage monitoring system was developed based on the experiment, and it is suitable for giving a leakage alarm of acetylene during its storage, transportation and use. PMID:19123378

He, Ying; Zhang, Yu-jun; Kan, Rui-feng; Xia, Hui; Wang, Min; Cui, Xiao-juan; Chen, Jiu-ying; Chen, Dong; Liu, Wen-qing; Liu, Jian-guo

2008-10-01

241

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

242

221A Lecture Notes Path Integral  

E-print Network

221A Lecture Notes Path Integral 1 Feynman's Path Integral Formulation Feynman's formulation with a weight factor given by the classical action for each path. Hence the name path integral. This is it. Note of quantum mechanics using the so-called path inte- gral is arguably the most elegant. It can be stated

Murayama, Hitoshi

243

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

244

Path Planning with obstacle avoidance  

NASA Technical Reports Server (NTRS)

The research report here summarizes a solution for two dimensional Path Planning with obstacle avoidance in a workspace with stationary obstacles. The solution finds the shortest path for the end effector of a manipulator arm. The program uses an overhead image of the robot work space and the starting and ending positions of the manipulator arm end effector to generate a search graph which is used to find the shortest path through the work area. The solution was originally implemented in VAX Pascal, but was later converted to VAX C.

Krause, Donald M.

1987-01-01

245

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.

246

Structural Testing: An Introduction Flow Graphs Path Testing Conclusions Path Testing  

E-print Network

Structural Testing: An Introduction Flow Graphs Path Testing Conclusions Path Testing Mohammad Mousavi Eindhoven University of Technology, The Netherlands Software Testing, 2012 Mousavi: Path Testing #12;Structural Testing: An Introduction Flow Graphs Path Testing Conclusions Outline Structural

Mousavi, Mohammad

247

Structural Testing: An Introduction Flow Graphs Path Testing Conclusions Path Testing  

E-print Network

Structural Testing: An Introduction Flow Graphs Path Testing Conclusions Path Testing Mohammad Mousavi Eindhoven University of Technology, The Netherlands Software Testing, 2013 Mousavi: Path Testing #12;Structural Testing: An Introduction Flow Graphs Path Testing Conclusions Outline Structural

Mousavi, Mohammad

248

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

249

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

250

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

251

Learning for informative path planning  

E-print Network

Through the combined use of regression techniques, we will learn models of the uncertainty propagation efficiently and accurately to replace computationally intensive Monte- Carlo simulations in informative path planning. ...

Park, Sooho, S.M. Massachusetts Institute of Technology

2008-01-01

252

Collaborative Authoring of Walden's Paths  

E-print Network

The World Wide Web contains rich collections of digital materials that can be used in education and learning settings. The collaborative authoring prototype of Walden's Paths targets two groups of users: educators and learners. From the perspective...

Li, Yuanling

2012-10-19

253

Morse theory in path space  

E-print Network

We consider the path space of a curved manifold on which a point particle is introduced in a conservative physical system with constant total energy to formulate its action functional and geodesic equation together with breaks on the path. The second variation of the action functional is exploited to yield the geodesic deviation equation and to discuss the Jacobi fields on the curved manifold. We investigate the topology of the path space using the action functional on it and its physical meaning by defining the gradient of the action functional, the space of bounded flow energy solutions and the moduli space associated with the critical points of the action functional. We also consider the particle motion on the $n$-sphere $S^{n}$ in the conservative physical system to discuss explicitly the moduli space of the path space and the corresponding homology groups.

Yong Seung Cho; Soon-Tae Hong

2007-06-01

254

Torsional and cyclic fatigue resistances of glide path preparation instruments: G-file and PathFile.  

PubMed

This study aimed to compare cyclic fatigue and torsional resistances of glide path creating instruments with different tapers and tip sizes. Two sizes (G1 and G2) from G-File system and three sizes (PathFile #1, #2, and #3) from PathFile system were used for torsional resistance and cyclic fatigue resistance tests (n?=?10). The torsional resistance was evaluated at 2-, 3-, 4-, 5-, and 6-mm from the file tip by plotting the torsional load changes until fracture by rotational loading of 2?rpm. The cyclic fatigue resistance was compared by measuring the number of cycles to failure. Data were analyzed statistically using one-way ANOVA and Duncan's post-hoc comparison. The length of the fractured file fragment was also measured. All fractured fragments were observed under a scanning electron microscope (SEM). Although G-2 file showed a lower torsional strength than PathFile #3 at 2- and 3-mm levels (p??0.05). The smaller files of each brand had a significantly higher cyclic fatigue resistance than the bigger ones (p?PathFile #1 and #2 had higher fatigue resistances than G-files (p?PathFile #3, G-2 showed the lowest and PathFile #1 showed the highest resistances among the tested groups (p?path with minimal risk of fracture. SCANNING 36:500-506, 2014. © 2014 Wiley Periodicals, Inc. PMID:24737525

Sung, Sang Yup; Ha, Jung-Hong; Kwak, Sang-Won; Abed, Rashid El; Byeon, Kyeongmin; Kim, Hyeon-Cheol

2014-09-01

255

Formal language constrained path problems  

SciTech Connect

In many path finding problems arising in practice, certain patterns of edge/vertex labels in the labeled graph being traversed are allowed/preferred, while others are disallowed. Motivated by such applications as intermodal transportation planning, the authors investigate the complexity of finding feasible paths in a labeled network, where the mode choice for each traveler is specified by a formal language. The main contributions of this paper include the following: (1) the authors show that the problem of finding a shortest path between a source and destination for a traveler whose mode choice is specified as a context free language is solvable efficiently in polynomial time, when the mode choice is specified as a regular language they provide algorithms with improved space and time bounds; (2) in contrast, they show that the problem of finding simple paths between a source and a given destination is NP-hard, even when restricted to very simple regular expressions and/or very simple graphs; (3) for the class of treewidth bounded graphs, they show that (i) the problem of finding a regular language constrained simple path between source and a destination is solvable in polynomial time and (ii) the extension to finding context free language constrained simple paths is NP-complete. Several extensions of these results are presented in the context of finding shortest paths with additional constraints. These results significantly extend the results in [MW95]. As a corollary of the results, they obtain a polynomial time algorithm for the BEST k-SIMILAR PATH problem studied in [SJB97]. The previous best algorithm was given by [SJB97] and takes exponential time in the worst case.

Barrett, C.; Jacob, R.; Marathe, M.

1997-07-08

256

Path matched vibration insensitive Fizeau interferometer  

NASA Astrophysics Data System (ADS)

An on-axis, vibration insensitive, polarization Fizeau interferometer is realized through the use of a novel pixelated mask spatial carrier phase shifting technique in conjunction with a low coherence source and a polarization path matching mechanism. In this arrangement, coherence is used to effectively separate out the orthogonally polarized test and reference beam components for interference. With both the test and the reference beams on-axis, the common path cancellation advantages of the Fizeau interferometer are maintained. Microwave modulation of a high powered red laser diode is used to create a 15 mW laser source having a coherence length of 250 um with minimal sidelobe ringing. With a 15 mW source, the maximum camera shutter speed, used when measuring a 4% reflector, was 150 usec, resulting in very robust vibration insensitivity. Additionally, stray light interference is substantially reduced due to the source's short coherence, allowing the measurement of thin transparent optics. Experimental results show the performance of this new interferometer to be within the specifications of commercial phase shifting interferometers. This work starts with a basic review of interferometry, phase shifting, and polarization as a lead in to a description of the theory and operation of the pixelated mask spatial carrier phase shifting technique. An analysis of the standard Fizeau Interferometer is then given. This is followed by detailed theoretical discussion of the path matched vibration insensitive (PMVI) Fizeau, which includes a theoretical model of the effects of multiple beam return from the test surface when measuring high value reflectors. The coherence properties of laser diodes are then discussed, a theoretical model for the effects of high frequency drive current is derived, and experimental results are given. Finally, the performance of the PMVI Fizeau is experimentally analyzed, potential error sources discussed, and suggestions for improvements provided.

Kimbrough, Bradley Trent

257

Partnership for Advancing Technologies in Housing (PATH)  

NSF Publications Database

... Technology Systems Interactions and Whole House Approaches PATH?s mission is to advance technology ... technology arena. Far reaching exploratory research that can lead to breakthrough technologies and ...

258

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

259

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

260

A novel approach to the prediction of musculotendon paths.  

PubMed

One of the most important aspects of the modelling of musculoskeletal systems is the determination of muscle moment arms which are dependent upon the paths of the muscles. These paths are often required to wrap around passive structures that can be modelled as simple geometric shapes. A novel technique for the prediction of the paths of muscles modelled as strings when wrapping around smooth analytical surfaces is presented. The theory of geodesics is used to calculate the shortest path of the string on the surface and a smoothness constraint is used to determine the correct solutions for the string path between insertions. The application of the technique to tapered cylinders and ellipsoids is presented as an extension of previous work on right-circular cylinders and spheres. The technique is assessed with reference to a particular biomechanical scenario; string lengths and moment arms are calculated and compared with alternative approximate methods. This illustrates the potential of the technique to provide more accurate muscle moment arm predictions. PMID:18335718

Marsden, S P; Swailes, D C

2008-01-01

261

Measuring the scattering mean free path of Rayleigh waves on a volcano from spatial phase decoherence  

NASA Astrophysics Data System (ADS)

We analyse the statistics of phase fluctuations of seismic signals obtained from a temporary small aperture array deployed on a volcano in the French Auvergne. We demonstrate that the phase field satisfies Circular Gaussian statistics. We then determine the scattering mean free path of Rayleigh waves from the spatial phase decoherence. This phenomenon, observed for diffuse wavefields, is found to yield a good approximation of the scattering mean free path. Contrary to the amplitude, spatial phase decoherence is free from absorption effects and provides direct access to the scattering mean free path.

Obermann, Anne; Larose, Eric; Margerin, Ludovic; Rossetto, Vincent

2014-04-01

262

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

263

Gas-path seal technology  

NASA Technical Reports Server (NTRS)

Improved gas-path seals are needed for better fuel economy, longer performance retention, and lower maintenance, particularly in advanced, high-performance gas turbine engines. Problems encountered in gas-path sealing are described, as well as new blade-tip sealing approaches for high-pressure compressors and turbines. These include a lubricant coating for conventional, porous-metal, rub-strip materials used in compressors. An improved hot-press metal alloy shows promise to increase the operating surface temperatures of high-pressure-turbine, blade-tip seals to 1450 K (2150 F). Three ceramic seal materials are also described that have the potential to allow much higher gas-path surface operating temperatures than are possible with metal systems.

Zuk, J.

1976-01-01

264

Path Abstraction for Combined Navigation and Animation  

NASA Astrophysics Data System (ADS)

Natural motion of virtual characters is crucial in games and simulations. The quality of such motion strongly depends on the path the character walks and the animation of the character locomotion. Therefore, much work has been done on path planning and character animation. However, the combination of both fields has received less attention. Combining path planning and motion synthesis introduces several problems. A path generated by a path planner is often a simplification of the character movement. This raises the question which (body) part of the character should follow the path generated by the path planner and to what extent it should closely follow the path. We will show that enforcing the pelvis to follow the path will lead to unnatural animations and that our proposed solution, using path abstractions, generates significantly better animations.

van Basten, Ben J. H.; Egges, Arjan

265

Crack Path Selection Fatigue crack path imaged via SEM  

E-print Network

phases fail in a brittle manner Fatigue Crack Growth ABSTRACT Advanced aerospace materials continue Crack path selects secondary phases and interface Conclusions ·Nb-Si Alloys tested exhibited toughness at high temperatures. An important property of any high temperature aerospace engineering material is its

Rollins, Andrew M.

266

Multiple paths in complex tasks  

NASA Technical Reports Server (NTRS)

The relationship between utility judgments of subtask paths and the utility of the task as a whole was examined. The convergent validation procedure is based on the assumption that measurements of the same quantity done with different methods should covary. The utility measures of the subtasks were obtained during the performance of an aircraft flight controller navigation task. Analyses helped decide among various models of subtask utility combination, whether the utility ratings of subtask paths predict the whole tasks utility rating, and indirectly, whether judgmental models need to include the equivalent of cognitive noise.

Galanter, Eugene; Wiegand, Thomas; Mark, Gloria

1987-01-01

267

Multi-channel absolute distance measurement system with sub ppm-accuracy and 20 m range using frequency scanning interferometry and gas absorption cells.  

PubMed

We present an implementation of an absolute distance measurement system which uses frequency scanning interferometry (FSI). The technique, referred to as dynamic FSI, uses two frequency scanning lasers, a gas absorption cell and a reference interferometer to determine the unknown optical path length difference (OPD) of one or many measurement interferometers. The gas absorption cell is the length reference for the measurement system and is traceable to international standards through knowledge of the frequencies of its absorption features. The OPD of the measurement interferometers can vary during the measurement and the variation is measured at the sampling rate of the system (2.77 MHz in the system described here). The system is shown to measure distances from 0.2 m to 20 m with a combined relative uncertainty of 0.41 × 10-6 at the two sigma level (k = 2). It will be shown that within a scan the change in OPD of the measurement interferometer can be determined to a resolution of 40 nm. PMID:25322060

Dale, John; Hughes, Ben; Lancaster, Andrew J; Lewis, Andrew J; Reichold, Armin J H; Warden, Matthew S

2014-10-01

268

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

269

The Routing Continuum from Shortest-path to All-path: A Unifying Theory  

E-print Network

The Routing Continuum from Shortest-path to All-path: A Unifying Theory Yanhua Li, Zhi-Li Zhang of data and sensor networks, routing strategies such as shortest-path, multi-path and potential-based ("all-path") routing have been developed. Based on the connection between routing and flow optimization

Boley, Daniel

270

COMPUTER SCIENCE: MISCONCEPTIONS, CAREER PATHS  

E-print Network

Undergraduate Student) #12;Computer Science Misconceptions Intro to Computer Science - Florida International much can I make out of college? Data from the Bureau of Labor Statistics #12;Computer ScienceCOMPUTER SCIENCE: MISCONCEPTIONS, CAREER PATHS AND RESEARCH CHALLENGES School of Computing

Hristidis, Vagelis

271

The Path of Human Evolution  

Microsoft Academic Search

A complex series of evolutionary steps, contingent upon a dynamic environmental context and a long biological heritage, have led to the ascent of Homo sapiens as a dominant component of the modern biosphere. In a field where missing links still abound and new discoveries regularly overturn theoretical paradigms, our understanding of the path of human evolution has made tremendous advances

C. S. Feibel

2004-01-01

272

Advances in steam path technology  

Microsoft Academic Search

For many years, GE has been conducting research to understand better the loss mechanisms that degrade the aerodynamic performance of steam turbine stages, and to develop new computational fluid dynamics (CFD) computer programs to predict these losses accurately. This paper describes a number of new steam path design features that have been introduced in the GE steam turbine product line

John I. Cofer; J. I. IV

1996-01-01

273

Commercializing Biorefineries The Path Forward  

E-print Network

Commercializing Biorefineries The Path Forward Bioenergy ExCo 59 Workshop Golden, CO Lawrence J/R&DFocus Timeframe for R&D Successes & Commercialization 2006 200920082007 20112010 2012: R&D on bench and pilot for commercial demonstration projects 2006: Announced loan guarantee program for projects employing new energy

274

On the Shortest Path Game  

E-print Network

Sep 19, 2014 ... tree, whose child nodes are all leaves, the associated player can reach a decision by simply ... moved to its parent node. In this way, we can ... towards t, since the cost of the path from s to v does not influence the decision in v.

2014-09-19

275

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...

276

Immigration: Rubio's path to presidency?  

E-print Network

Immigration: Rubio's path to presidency? In media blitz retorting conservative critics, he aims Writer Of the four Democratic and four Republican senators who wrote the immigration reform proposal now, both in Congress and nationwide, need more convincing on immigration reform than Democrats. And Rubio

Fernandez, Eduardo

277

Career Paths of Academic Deans.  

ERIC Educational Resources Information Center

This paper examines various career paths leading to deanship and considers the implications of the findings for women and minorities who aspire to this position. The paper is part of a larger study of academic deanship conducted by the Center for Academic Leadership at Washington State University between October 1996 and January 1997. Data for the…

Wolverton, Mimi; Gonzales, Mary Jo

278

A triangular path inverting interferometer  

Microsoft Academic Search

A triangular path inverting interferometer is described with application to the study of thermal 'schlieren'. This is practically free of any vibration and coherence troubles, and possesses the unique feature that either differential or total shear may be obtained only with proper positioning of the object; once aligned, the optical components need not be disturbed further. This simple and stable

D. Chakrabarti; S. P. Basu; M. De

1977-01-01

279

NPRE at Illinois Three Paths  

E-print Network

production; Nuclear power operations and control � Plasma sciences; Applied plasma physics; Nuclear fusionNPRE at Illinois Three Paths Students choose from three concentrations: � Plasma and Fusion � Power and interactions of radiation with matter � Applications of nuclear processes � Nuclear fission for electric power

Gilbert, Matthew

280

Soft tissue absorption tomography with correction for scattering aberrations.  

PubMed

Among the many factors involved in ultrasound attenuation phenomena, scattering effects play a major role, even in the unexpected case of soft tissues. It is proposed in this study to quantitatively evaluate the scattering affecting the measurements before reconstructing the absorption parameter alone. The reconstruction procedure involves three steps: (1) Estimating the sound speed map using a transmission tomography algorithm. This estimation procedure provides a numerical phantom of the organ probed, cleared of all dissipative components. This absorption free phantom mimics the (viscoacoustic) tissues imaged except for the density and absorption characteristics: the density a priori equals 1000 kg/m3 and the absorption is not taken into account. The impedance fluctuations in the object are therefore approximated on the basis of the sound speed contrast. (2) Synthesing the field scattered by the absorption free phantom; the attenuation observed here results solely from the scattering phenomenon. The synthesis is carried out using a finite-element time domain code simulating the ultrasonic propagation through the phantom. It provides the scattering distortion reference introduced into the log spectral absorption estimator. (3) Reducing the scattering distortions affecting the integrated absorption measured along the ray paths using a log spectral procedure. The corrected integrated absorption is then processed using a tomographic reconstruction procedure that provides an estimate of the absorption distribution. Simple numerical simulations show the improvement obtained in the absorption estimates with this approach. PMID:16761784

Franceschini, Emilie; Pauzin, Marie-Christine; Mensah, Serge; Groby, Jean-Philippe

2005-10-01

281

Depletion lengths in semiconductor nanostructures  

NASA Astrophysics Data System (ADS)

We calculate the depletion length, W( R), at the surface of a cylindrical nanostructure of radius R and show that W( R) satisfies the inequality Wp? W( R)? Rc, where W p= 2? ?/(e 2N d) is the depletion length at a planar interface ( ? is the surface potential energy barrier, ? is the dielectric constant and Nd is the doping density), and R c= 2W p is, as we show, a critical radius below which, for R? Rc, the structure is fully depleted. The standard result Wp therefore underestimates the depletion length in a finite structure. The discrepancy between W( R) and Wp becomes significant when the dimensions of the structure becomes comparable to the depletion length, as can occur in nanostructure devices.

Luscombe, J. H.; Frenzen, C. L.

2002-06-01

282

Measurements on CO Concentration and gas temperature at 1.58 um with Tunable Diode Laser Absorption Spectroscopy  

NASA Astrophysics Data System (ADS)

The technique based on tunable diode laser absorption Spectroscopy (TDLAS) has been developed to realize the real-time and dynamic measurement of the combustion-generated pollutants. In this paper the fundamental of concentration and temperature measurement with TDLAS is presented. To validate the method, an experimental system of TDLAS is set up. A simple VCSEL diode without temperature controller is used for direct absorption and WMS setup. Restricted by modulation voltage and noise from diode laser and detector, concentration of 0.2% for 1 m path length can be detected. Temperature measurement in tube furnace is also carried out by CO2 absorption lines near 1.58um, and below 800K the difference between calculation by TDLAS and temperature signal by K-thermocouple is less than 60K. The method to eliminate the effects of the particles is also discussed here. By using three-order polynomial program, the measurement can be not affected by particles and power fluctuation.

Wang, Fei; Li, Ning; Huang, Qunxing; Yan, Jianhua; Cen, Kefa

2007-06-01

283

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 -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 , 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 -periodic configuration of—possibly intersecting—convex bodies with 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

2014-10-01

284

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. PMID:22409812

Stojmirovi?, Aleksandar

2012-01-01

285

A genetic analysis of path length and pupation height in a natural population of Drosophila melanogaster  

E-print Network

population of Drosophila melanogaster. Can. J. Genet. Cytol. 27: 334-340. Behaviour-genetic studies using from a natural population of Drosophila melanogaster. These strains showed a second-chromosome based in a natural population of Drosophila melanogaster. Can. J. Genet. Cytol. 27: 334-340. Les ktudes de

Sokolowski, Marla

286

Radial bunch compression: Path-length compensation in an rf photoinjector with a curved cathode  

E-print Network

or free-electron lasers (FELs) and for direct use in applications such as pulsed radiolysis [1] and time such as the free-electron laser by making them more compact and with shorter pulse duration, and could provide photoinjector is an ideal electron source for driving coherent spontaneous or superradiant free-electron lasers

Boyer, Edmond

287

Information flow in interaction networks II: channels, path lengths, and potentials.  

PubMed

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. PMID:22409812

Stojmirovi?, Aleksandar; Yu, Yi-Kuo

2012-04-01

288

Phase and Amplitude Control Ability using Spatial Light Modulators and Zero Path Length Difference Michelson Interferometer  

NASA Astrophysics Data System (ADS)

A new method is presented for amplitude and phase control using two liquid crystal spatial light modulators in conjunction with a white light Michelson interferometer. Preliminary proof-of-concept measurements are given showing the prospect of using this method for correction of amplitude errors in telescopes.

Littman, Michael G.; Carr, Michael; Leighton, Jim; Burke, Ezekiel; Spergel, David N.; Kasdin, N. J.

2003-02-01

289

Path-length-resolved diffusive particle dynamics in spectral-domain optical coherence tomography.  

PubMed

We describe a new method to measure the decorrelation rate of the optical coherence tomography (OCT) magnitude simultaneously in space and time. We measure the decorrelation rate of the OCT magnitude in a Fourier-domain OCT system for a large range of translational diffusion coefficients by varying the sphere diameter. The described method uses the sensitivity advantage of Fourier-domain OCT over time-domain OCT to increase the particle diffusion imaging speed by a factor of 200. By coherent gating, we reduce the contribution of multiple scattering to the detected signal, allowing a quantitative study of diffusive particle dynamics in high concentration samples. We demonstrate that this technique is well suited to image diffusive particle dynamics in samples with a complex geometry as we measure the morphology and diffusive particle dynamics simultaneously with both high spatial and high temporal resolution. PMID:21231201

Kalkman, J; Sprik, R; van Leeuwen, T G

2010-11-01

290

A New Path Length Measure Based on GO for Gene Similarity with Evaluation Using SGD Pathways  

E-print Network

of the leading measures (Resnik [11] and Wang et al. [15]). Our method showed impressive accuracy with results in the general English domain. For example, Resnik [11], Jiang and Conrath [5] and Lin [6] proposed information

Al-Mubaid, Hisham

291

Mean free-path length theory of predator–prey interactions: Application to juvenile salmon migration  

Microsoft Academic Search

Ecological theory traditionally describes predator–prey interactions in terms of a law of mass action in which the prey mortality rate depends on the density of predators and prey. This simplifying assumption makes population-based models more tractable but ignores potentially important behaviors that characterize predator–prey dynamics. Here, we expand traditional predator–prey models by incorporating directed and random movements of both predators

James J. Anderson; Eliezer Gurarie; Richard W. Zabel

2005-01-01

292

[Monitoring the flux of carbon dioxide gas with tunable diode laser absorption spectroscopy].  

PubMed

The greenhouse effect exacerbated by the increase of Carbon-containing gases is the more important causes of the climate change, It is very meaningful to the large-scale flux of carbon dioxide detection for the estimate the contributions of the main greenhouse gases in the atmosphere of various errestrial eco-systems. Tunable diode laser absorption spectroscopy (TDLAS) is a highly sensitive, highly selective and fast time response trace gas detection technique. In the present paper, the authors used a DFB laser was used as the light source, and by employing wavelength modulation method, and measuring the second harmonic signal of one absorption line near 1.573 microm of carbon dioxide molecule, the authors built a system for online monitoring of carbon dioxide concentration within the optical path of more than 700 meters at different heights. Combined with Alonzo Mourning -Obukhov length and characteristic velocity detected by large aperture scintillometer, the flux of carbon dioxide gas within one day calculated by the formula is within--1.5-2.5, breaking through the phenomenon of only providing the flux of trace gases near the ground at present, makking the measurement of trace gas fluxes within a large area possible. PMID:21428084

Song, Xue-Mei; Liu, Jian-Guo; Zhang, Yu-Jun; Zeng, Zong-Yong; He, Ying; Cui, Yi-Ben; Chen, Yin; Tian, Yong-Zhi; Zhang, Liang

2011-01-01

293

UV differential optical absorption method for measuring sulfur content in coal  

NASA Astrophysics Data System (ADS)

Determining the sulfur content in coal rapidly and accurately can provide a technical basis for the enterprises and the environmental administration departments. A novel method for measuring the sulfur content in coal based on UV differential optical absorption is presented in this paper. However, compared with the applications in atmosphere monitoring, the UV differential optical absorption spectroscopy (DOAS) for the sulfur content measurement in coal has the problems that the concentration range of SO2 in the flue gas is wider and the optical path-length of the gas cell is shorter. To solve these problems, an improved DOAS algorithm based on a finite impulse response (FIR) filter and a nonlinear compensation technique is proposed. An experimental measurement system based on the modified DOAS is designed and established. The standard SO2 gas and five kinds of standard coals are experimentally tested. Theoretical and experimental results show that the lower detection limit of the system is better than 0.014%, and the repeatability of the measurement system fairly meets the national standard of China. The system has advantages of low maintenance and shorter measurement duration (4 min).

Song, Feihu; Xu, Chuanlong; Wang, Shimin

2012-02-01

294

Minimum-fuel, three-dimensional flight paths for jet transports  

NASA Technical Reports Server (NTRS)

A number of studies dealing with fuel minimization are concerned with three-dimensional flight. However, only Neuman and Kreindler (1982) consider cases involving commercial jet transports. In the latter study, only the climb-out and descent portions of complete long-range flight paths below 10,000 ft altitude have been investigated. The present investigation is concerned with the computation of minimum-fuel nonturning and turning flight paths for climb-outs from 2000 to 10,000 ft for long-range flights (greater than 50 n mi), and for complete flight paths of lengths between 5 and 50 n mi.

Neuman, F.; Kreindler, E.

1985-01-01

295

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

296

LASER-BASED, LONG PATH MONITORING OF AMBIENT GASES, ANALYSIS OF TWO SYSTEMS  

EPA Science Inventory

New long path absorption techniques for measurement of ambient O3 and CO have recently been demonstrated using a CO2 laser and a semiconductor diode laser, respectively. For the CO2 laser system the use of closely spaced wavelengths minimizes system drift and simplifies the deter...

297

Walking on inclines: how do desert ants monitor slope and step length  

PubMed Central

Background During long-distance foraging in almost featureless habitats desert ants of the genus Cataglyphis employ path-integrating mechanisms (vector navigation). This navigational strategy requires an egocentric monitoring of the foraging path by incrementally integrating direction, distance, and inclination of the path. Monitoring the latter two parameters involves idiothetic cues and hence is tightly coupled to the ant's locomotor behavior. Results In a kinematic study of desert ant locomotion performed on differently inclined surfaces we aimed at pinpointing the relevant mechanisms of estimating step length and inclination. In a behavioral experiment with ants foraging on slippery surfaces we broke the otherwise tightly coupled relationship between stepping frequency and step length and examined the animals' ability to monitor distances covered even under those adverse conditions. We show that the ants' locomotor system is not influenced by inclined paths. After removing the effect of speed, slope had only marginal influence on kinematic parameters. Conclusion From the obtained data we infer that the previously proposed monitoring of angles of the thorax-coxa joint is not involved in inclinometry. Due to the tiny variations in cycle period, we also argue that an efference copy of the central pattern generator coding the step length in its output frequency will most likely not suffice for estimating step length and complementing the pedometer. Finally we propose that sensing forces acting on the ant's legs could provide the desired neuronal correlate employed in monitoring inclination and step length. PMID:18518946

Seidl, Tobias; Wehner, Rudiger

2008-01-01

298

Folded path LWIR system for SWAP constrained platforms  

NASA Astrophysics Data System (ADS)

Folded path reflection and catadioptric optics are of growing interest, especially in the long wave infrared (LWIR), due to continuing demands for reductions in imaging system size, weight and power (SWAP). We present the optical design and laboratory data for a 50 mm focal length low f/# folded-path compact LWIR imaging system. The optical design uses 4 concentric aspheric mirrors, each of which is described by annular aspheric functions well suited to the folded path design space. The 4 mirrors are diamond turned onto two thin air-spaced aluminum plates which can be manually focused onto the uncooled LWIR microbolometer array detector. Stray light analysis will be presented to show how specialized internal baffling can be used to reduce stray light propagation through the folded path optical train. The system achieves near diffraction limited performance across the FOV with a 15 mm long optical train and a 5 mm back focal distance. The completed system is small enough to reside within a 3 inch diameter ball gimbal.

Fleet, Erin F.; Wilson, Michael L.; Linne von Berg, Dale; Giallorenzi, Thomas; Mathieu, Barry

2014-06-01

299

Calcium absorption and achlorhydria  

Microsoft Academic Search

Defective absorption of calcium has been thought to exist in patients with achlorhydria. The author compared absorption of calcium in its carbonate form with that in a pH-adjusted citrate form in a group of 11 fasting patients with achlorhydria and in 9 fasting normal subjects. Fractional calcium absorption was measured by a modified double-isotope procedure with 0.25 g of calcium

Robert R. Recker

1985-01-01

300

Shortest Paths for Disc Obstacles  

Microsoft Academic Search

\\u000a Given a number of obstacles in a plane, the problem of computing a geodesic (or the shortest path) between two points has\\u000a been studied extensively. However, the case where the obstacles are circular discs has not been explored as much as it deserves.\\u000a In this paper, we present an algorithm to compute a geodesic among a set of mutually disjoint

Deok-soo Kim; Kwangseok Yu; Youngsong Cho; Donguk Kim; Chee-keng Yap

2004-01-01

301

Path integral on star graph  

NASA Astrophysics Data System (ADS)

In this paper we study path integral for a single spinless particle on a star graph with N edges, whose vertex is known to be described by U(N) family of boundary conditions. After carefully studying the free particle case, both at the critical and off-critical levels, we propose a new path integral formulation that correctly captures all the scale-invariant subfamily of boundary conditions realized at fixed points of boundary renormalization group flow. Our proposal is based on the folding trick, which maps a scalar-valued wave function on star graph to an N-component vector-valued wave function on half-line. All the parameters of scale-invariant subfamily of boundary conditions are encoded into the momentum independent weight factors, which appear to be associated with the two distinct path classes on half-line that form the cyclic group Z2. We show that, when bulk interactions are edge-independent, these weight factors are generally given by an N-dimensional unitary representation of Z2. Generalization to momentum dependent weight factors and applications to worldline formalism are briefly discussed.

Ohya, Satoshi

2012-06-01

302

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

303

Electron Inelastic-Mean-Free-Path Database  

National Institute of Standards and Technology Data Gateway

SRD 71 NIST Electron Inelastic-Mean-Free-Path Database (PC database, no charge)   This database provides values of electron inelastic mean free paths (IMFPs) for use in quantitative surface analyses by AES and XPS.

304

Path-Based, Randomized, Oblivious, Minimal Routing  

E-print Network

Path-based, Randomized, Oblivious, Minimal routing (PROM) is a family of oblivious, minimal, path-diverse routing algorithms especially suitable for Network-on-Chip applications with n x n mesh geometry. Rather than choosing ...

Cho, Myong Hyon

2009-01-01

305

Screening length in plasma winds  

E-print Network

We study the screening length L_s of a heavy quark-antiquark pair in strongly coupled gauge theory plasmas flowing at velocity v. Using the AdS/CFT correspondence we investigate, analytically, the screening length in the ultra-relativistic limit. We develop a procedure that allows us to find the scaling exponent for a large class of backgrounds. We find that for conformal theories the screening length is (boosted energy density)^{-1/d}. As examples of conformal backgrounds we study R-charged black holes and Schwarzschild-anti-deSitter black holes in (d+1)-dimensions. For non-conformal theories, we find that the exponent deviates from -1/d and as examples we study the non-extremal Klebanov-Tseytlin and Dp-brane geometries. We find an interesting relation between the deviation of the scaling exponent from the conformal value and the speed of sound.

Elena Caceres; Makoto Natsuume; Takashi Okamura

2006-07-28

306

Data-path layout design inside SOC  

Microsoft Academic Search

As more data-path stacks are integrated into system-on-a-chip (SOC), data-path is becoming a critical part of the whole giga-scale integrated circuits (GSI) design. The traditional layout design methodology can not satisfy the data-path performance requirements because it has no knowledge of the data-path bit-sliced structure and the strict performance (such as timing, coupling, and crosstalk) constraints. In this paper, we

Tong Jing; Xian-Long Hong; Yi-Ci Cai; Jing-Yu Xu; Chang-Qi Yang; Yi-Qian Zhang; Qiang Zhou; Weimin Wu

2002-01-01

307

Multiple Paths to Encephalization and Technical Civilizations  

NASA Astrophysics Data System (ADS)

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.

Schwartzman, David; Middendorf, George

2011-12-01

308

Module theory over Leavitt path algebras and $K$-theory.  

E-print Network

Let $k$ be a field and let $E$ be a finite quiver. We study the structure of the finitely presented modules of finite length over the Leavitt path algebra $L_k (E)$ and show its close relationship with the finite-dimensional representations of the inverse quiver $\\overline{E}$ of $E$, as well as with the class of finitely generated $P_k(E)$-modules $M$ such that ${\\rm Tor}_q^{P_k (E)}(k^{|E^0|},M)=0$ for all $q$, where $P_k(E)$ is the usual path algebra of $E$. By using these results we compute the higher $K$-theory of the von Neumann regular algebra $Q_k (E)=L_k (E)\\Sigma^{-1}$, where $\\Sigma $ is the set of all square matrices over $P_k (E)$ which are sent to invertible matrices by the augmentation map $\\epsilon \\colon P_k (E)\\to k^{|E^0|}$.

Pere Ara; Miquel Brustenga

309

Magnon thermal mean free path in yttrium iron garnet  

NASA Astrophysics Data System (ADS)

The magnetothermal properties of monocrystalline yttrium iron garnet (YIG) are reported. The magnon contribution to both the thermal conductivity and specific heat at low temperatures has been determined by measuring these properties under an applied magnetic field, which allows us to freeze the magnon modes and isolate the phonon contribution relative to the zero-field behavior. These results are interpreted within the framework of a simple kinetic gas model for magnon heat conduction that allows us to estimate the magnon thermal mean free path, i.e., the inelastic scattering length scale for thermally driven bulk magnons. We observe this parameter to reach as high as approximately 100 ?m at 2 K. It tracks the acoustic phonon thermal mean free path closely and decreases rapidly as the temperature is increased. This relatively short length scale suggests that magnon modes at thermal energies in YIG are not solely or directly responsible for coherent macroscale thermal spin transport (e.g., in the spin Seebeck effect) at high temperatures. Instead, these results support a growing consensus that subthermal magnons, i.e., those at energies below about 30 ± 10 K, are important for spin transport in YIG at all temperatures. These results also emphasize that magnon effects should be considered wavelength dependent, and that magnon-magnon interactions may be just as important for thermal spin transport as magnon-phonon scattering. This, in turn, has implications for understanding the characteristic temperature and length scales involved in spin caloritronic phenomena.

Boona, Stephen R.; Heremans, Joseph P.

2014-08-01

310

The Shortest Path Problem Under Partial Monitoring  

Microsoft Academic Search

Abstract. The on-line shortest path problem is considered under partial monitoring scenarios. At each round, a decision maker has to choose a path between two distinguished vertices of a weighted directed acyclic graph whose edge weights can change in an arbitrary (adversarial) way such that the loss of the chosen path (dened as the sum of the weights of its

András György; Tamás Linder; György Ottucsák

2006-01-01

311

Free Space Path Loss of UWB Communications  

Microsoft Academic Search

Although the Friis' formula is widely used to calculate the free space path loss of narrowband communications, it is considered only single frequency. Therefore, it should be extended to calculate the free space path loss of ultra wideband (UWB) communications by considering the frequency bandwidth. In this paper, the free space path loss of UWB communications is studies. The Friis'

Pichaya Supanakoon; Sathit Aroonpraparat; Sathaporn Promwong; Jun-ichi Takada

312

Path and Trajectory Diversity Theory and Algorithms  

E-print Network

Path and Trajectory Diversity Theory and Algorithms Ross A. Knepper International Conference and Kuffner, SIGGRAPH, 2006] Introduction ConclusionResultsAlgorithmsApproach Theory #12;R.A. Knepper PathResultsAlgorithmsApproach Theory #12;R.A. Knepper Path and Trajectory Diversity 4 Diversity Spectrum Easy to increase diversity

Branicky, Michael S.

313

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

314

Transition Path Theory E. Vanden-Eijnden  

E-print Network

Transition Path Theory E. Vanden-Eijnden Courant Institute of Mathematical Sciences, New York University New York, NY 10012 eve2cims.nyu.edu Eric Vanden-Eijnden E. Vanden-Eijnden: Transition Path Theory State Theory (TST) and Transition Path Sampling (TPS). . . . . . . . . . . . . . . . . . . . . . 455 6

Van Den Eijnden, Eric

315

Z-path SAW RFID tag.  

PubMed

Surface acoustic wave (SAW) radio-frequency identification (RFID) tags are soon expected to be produced in very high volumes. The size and cost of a SAW RFID tag will be key parameters for many applications. Therefore, it is of primary importance to reduce the chip size. In this work, we describe the design principles of a 2.4-GHz SAW RFID tag that is significantly smaller than earlier reported tags. We also present simulated and experimental results. The coded signal should arrive at the reader with a certain delay (typically about 1 micros), i.e., after the reception of environmental echoes. If the tag uses a bidirectional interdigital transducer (IDT), space for the initial delay is needed on both sides of the IDT. In this work, we replace the bidirectional IDT by a unidirectional one. This halves the space required by the initial delay because all the code reflectors must now be placed on the same side of the IDT. We reduce tag size even further by using a Z-path geometry in which the same space in x-direction is used for both the initial delay and the code reflectors. Chip length is thus determined only by the space required by the code reflectors. PMID:18334326

Härmä, Sanna; Plessky, Victor P; Hartmann, Clinton S; Steichen, William

2008-01-01

316

Effect of triglyceride structure on fat absorption.  

PubMed

Stereospecific distribution of fatty acids on triacylglycerol structures influences the technological behavior of fats as well as their absorption fate. Long-chain fatty acids in external (sn-1 and sn-3) positions may impair fat absorption and therefore the physiological response to dietary fats. Lower digestibility of bovine milk fat compared with that of human milk is related to the different position of palmitic acid in both fats. Stereospecific analysis of cocoa butter and fats containing stearic acid of the stearic-oleic-stearic acid (SOS) type showed that long-chain saturated fatty acids are almost exclusively present in sn-1 and sn-3 positions, which could explain their impaired absorption and therefore their neutral effect on serum lipid in humans despite their saturation and chain length. The true energy value of these fats therefore needs to be verified in mixed diets. PMID:7977140

Bracco, U

1994-12-01

317

What Determines Absorptive Capacity?  

Microsoft Academic Search

The paper analyses the effect of R&D activities, human resource and knowl- edge management, and the organisation of knowledge sharing within a firm on absorptive capacity of innovative firms empirically. Using data from the German innovation survey we investigate firms' ability to exploit knowledge from exter- nal partners for successful innovation activities. We distinguish between three types of absorptive capacity

Tobias Schmidt

318

Finite length Taylor Couette flow  

NASA Technical Reports Server (NTRS)

Axisymmetric numerical solutions of the unsteady Navier-Stokes equations for flow between concentric rotating cylinders of finite length are obtained by a spectral collocation method. These representative results pertain to two-cell/one-cell exchange process, and are compared with recent experiments.

Streett, C. L.; Hussaini, M. Y.

1987-01-01

319

Telomere Length Wildlife Aging Technique  

E-print Network

2/22/2009 1 Telomere Length as a Wildlife Aging Technique Forestry, Wildlife and Fisheries GraduateNon-invasive genetic sampling Telomeres: · Form · Function · Methods of measuring · Telomeres in wildlife aging #12;2/22/2009 4 Telomere Form: ·Short repeated sequences of DNA ·Found at the ends of linear eukaryotic

Gray, Matthew

320

Incubation length of dabbling ducks  

USGS Publications Warehouse

We collected unincubated eggs from wild Mallard (Anas platyrhynchos), Gadwall (A. strepera), Blue-winged Teal (A. discors), and Northern Shoveler (A. clypeata) nests and artificially incubated them at 37.5??C. Average incubation lengths of Mallard, Gadwall, and Northern Shoveler eggs did not differ from their wild-nesting counterparts, but artificially incubated Blue-winged Teal eggs required an additional 1.7 days to hatch, suggesting that wild-nesting teal incubated more effectively. A small sample of Mallard, Gadwall, and Northern Shoveler eggs artificially incubated at 38.3??C hatched 1 day sooner, indicating that incubation temperature affected incubation length. Mean incubation length of Blue-winged Teal declined by 1 day for each 11-day delay in nesting, but we found no such seasonal decline among Mallards, Gadwalls, or Northern Shovelers. There is no obvious explanation for the seasonal reduction in incubation length for Blue-winged Teal eggs incubated in a constant environment, and the phenomenon deserves further study. ?? The Cooper Ornithological Society 2005.

Wells-Berlin, A. M.; Prince, H.H.; Arnold, T.W.

2005-01-01

321

Petawatt laser absorption bounded  

NASA Astrophysics Data System (ADS)

The interaction of petawatt (1015?W) lasers with solid matter forms the basis for advanced scientific applications such as table-top particle accelerators, ultrafast imaging systems and laser fusion. Key metrics for these applications relate to absorption, yet conditions in this regime are so nonlinear that it is often impossible to know the fraction of absorbed light f, and even the range of f is unknown. Here using a relativistic Rankine-Hugoniot-like analysis, we show for the first time that f exhibits a theoretical maximum and minimum. These bounds constrain nonlinear absorption mechanisms across the petawatt regime, forbidding high absorption values at low laser power and low absorption values at high laser power. For applications needing to circumvent the absorption bounds, these results will accelerate a shift from solid targets, towards structured and multilayer targets, and lead the development of new materials.

Levy, Matthew C.; Wilks, Scott C.; Tabak, Max; Libby, Stephen B.; Baring, Matthew G.

2014-06-01

322

Petawatt laser absorption bounded  

E-print Network

The interaction of petawatt ($10^{15}\\ \\mathrm{W}$) lasers with solid matter forms the basis for advanced scientific applications such as table-top particle accelerators, ultrafast imaging systems and laser fusion. Key metrics for these applications relate to absorption, yet conditions in this regime are so nonlinear that it is often impossible to know the fraction of absorbed light $f$, and even the range of $f$ is unknown. Here using a relativistic Rankine-Hugoniot-like analysis, we show for the first time that $f$ exhibits a theoretical maximum and minimum. These bounds constrain nonlinear absorption mechanisms across the petawatt regime, forbidding high absorption values at low laser power and low absorption values at high laser power. For applications needing to circumvent the absorption bounds, these results will accelerate a shift from solid targets, towards structured and multilayer targets, and lead the development of new materials.

Levy, Matthew C; Tabak, Max; Libby, Stephen B; Baring, Matthew G

2014-01-01

323

Attention trees and semantic paths  

NASA Astrophysics Data System (ADS)

In the last few decades several techniques for image content extraction, often based on segmentation, have been proposed. It has been suggested that under the assumption of very general image content, segmentation becomes unstable and classification becomes unreliable. According to recent psychological theories, certain image regions attract the attention of human observers more than others and, generally, the image main meaning appears concentrated in those regions. Initially, regions attracting our attention are perceived as a whole and hypotheses on their content are formulated; successively the components of those regions are carefully analyzed and a more precise interpretation is reached. It is interesting to observe that an image decomposition process performed according to these psychological visual attention theories might present advantages with respect to a traditional segmentation approach. In this paper we propose an automatic procedure generating image decomposition based on the detection of visual attention regions. A new clustering algorithm taking advantage of the Delaunay- Voronoi diagrams for achieving the decomposition target is proposed. By applying that algorithm recursively, starting from the whole image, a transformation of the image into a tree of related meaningful regions is obtained (Attention Tree). Successively, a semantic interpretation of the leaf nodes is carried out by using a structure of Neural Networks (Neural Tree) assisted by a knowledge base (Ontology Net). Starting from leaf nodes, paths toward the root node across the Attention Tree are attempted. The task of the path consists in relating the semantics of each child-parent node pair and, consequently, in merging the corresponding image regions. The relationship detected in this way between two tree nodes generates, as a result, the extension of the interpreted image area through each step of the path. The construction of several Attention Trees has been performed and partial results will be shown.

Giusti, Christian; Pieroni, Goffredo G.; Pieroni, Laura

2007-02-01

324

Measurements of OH mole fraction and temperature up to 20 kHz by using a diode-laser-based UV absorption sensor  

NASA Astrophysics Data System (ADS)

Diode-laser-based sum-frequency generation of ultraviolet (UV) radiation at 313.5 nm was utilized for high-speed absorption measurements of OH mole fraction and temperature at rates up to 20 kHz. Sensor performance was characterized over a wide range of operating conditions in a 25.4 mm path-length, steady, C2H4 air diffusion flame through comparisons with coherent anti-Stokes Raman spectroscopy (CARS), planar laser-induced fluorescence (PLIF), and a two-dimensional numerical simulation with detailed chemical kinetics. Experimental uncertainties of 5% and 11% were achieved for measured temperatures and OH mole fractions, respectively, with standard deviations of <3% at 20 kHz and an OH detection limit of <1 part per million in a 1 m path length. After validation in a steady flame, high-speed diode-laser-based measurements of OH mole fraction and temperature were demonstrated for the first time in the unsteady exhaust of a liquid-fueled, swirl-stabilized combustor. Typical agreement of ˜5% was achieved with CARS temperature measurements at various fuel/air ratios, and sensor precision was sufficient to capture oscillations of temperature and OH mole fraction for potential use with multiparameter control strategies in combustors of practical interest.

Meyer, Terrence R.; Roy, Sukesh; Anderson, Thomas N.; Miller, Joseph D.; Katta, Viswanath R.; Lucht, Robert P.; Gord, James R.

2005-11-01

325

Ranking nodes according to their path-complexity  

E-print Network

Thermalization is one of the most important phenomena in statistical physics. Often, the transition probabilities between different states in the phase space is or can be approximated by constants. In this case, the system can be described by Markovian transition kernels, and when the phase space is discrete, by Markov chains. In this paper, we introduce a macroscopic entropy on the states of paths of length $k$ and, studying the recursion relation, obtain a fixed point entropy. This analysis leads to a centrality approach to Markov chains entropy.

Caravelli, Francesco

2014-01-01

326

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

327

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

328

Communication path for extreme environments  

NASA Technical Reports Server (NTRS)

Methods and systems for using one or more radio frequency identification devices (RFIDs), or other suitable signal transmitters and/or receivers, to provide a sensor information communication path, to provide location and/or spatial orientation information for an emergency service worker (ESW), to provide an ESW escape route, to indicate a direction from an ESW to an ES appliance, to provide updated information on a region or structure that presents an extreme environment (fire, hazardous fluid leak, underwater, nuclear, etc.) in which an ESW works, and to provide accumulated thermal load or thermal breakdown information on one or more locations in the region.

Jorgensen, Charles C. (Inventor); Betts, Bradley J. (Inventor)

2010-01-01

329

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

330

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

331

Quasar Absorption Studies  

NASA Technical Reports Server (NTRS)

The aim of the proposal is to investigate the absorption properties of a sample of inter-mediate redshift quasars. The main goals of the project are: Measure the redshift and the column density of the X-ray absorbers; test the correlation between absorption and redshift suggested by ROSAT and ASCA data; constrain the absorber ionization status and metallicity; constrain the absorber dust content and composition through the comparison between the amount of X-ray absorption and optical dust extinction. Unanticipated low energy cut-offs where discovered in ROSAT spectra of quasars and confirmed by ASCA, BeppoSAX and Chandra. In most cases it was not possible to constrain adequately the redshift of the absorber from the X-ray data alone. Two possibilities remain open: a) absorption at the quasar redshift; and b) intervening absorption. The evidences in favour of intrinsic absorption are all indirect. Sensitive XMM observations can discriminate between these different scenarios. If the absorption is at the quasar redshift we can study whether the quasar environment evolves with the Cosmic time.

Mushotzky, Richard (Technical Monitor); Elvis, Martin

2004-01-01

332

[Correlation and path analyses of phenotypic traits and body mass of transgenic carp with growth hormone gene of salmon].  

PubMed

Thirty 2-year old transgenic carp individuals with growth hormone gene of salmon were randomly selected to study the affecting degree of their phenotypic traits on their body mass by the methods of correlation and path analyses, with 30 individuals of non-transgenic carp as the control, aimed to ascertain the main phenotypic parameters affecting the body mass of the transgenic and non-transgenic carps. The test phenotypic traits were total length, body length, body height, least height of caudal peduncle, length of caudal peduncle, length of head, snout length, eyes horizontal diameter, inter-orbital distance, and body depth. Correlation analysis showed that for both of the transgenic and non-transgenic carps, most of the test phenotypic parameters were significantly correlated to body mass (P<0.01). Path analysis indicated that for transgenic carp, its body length and body height were the main predictable factors affecting body mass, with the path coefficient being 0.572 and 0.415, respectively, while for non-transgenic carp, its body depth and tail length were the main predictable factors affecting body mass, with the path coefficient being 0.610 and 0.377, respectively. PMID:22007470

Liu, Chun-lei; Chang, Yu-mei; Liang, Li-qun; Xu, Li-hua; Liu, Jin-liang; Chi, Bing-jie; Wu, Xue-gong

2011-07-01

333

[Concentration calibration method of ambient trace-gas monitoring with tunable diode laser absorption spectroscopy].  

PubMed

Tunable diode laser absorption spectroscopy (TDLAS) is a new method to detect trace-gas qualitatively or quantificationally based on the scan characteristic of the diode laser used to obtain the absorption spectroscopy in the characteristic absorption region It needs to be combined with a long absorption path in the ambient trace-gas measurements. TDLAS is a new trace gas detective method developed with the combination of a tunable diode laser source and a long absorption path; it has significant advantages not only in the sensitivity but also in rapidity of response. It has been widely used in many atmospheric trace-gases detection, ground trace-gas detection and, gas leakage detection. On-line calibrating is necessary to most trace gas monitor, and in the present paper the authors introduced a simple and accurate method, analyzed it in the theory, and proved it's feasibility in the experiment. PMID:16830737

Kan, Rui-feng; Liu, Wen-qing; Zhang, Yu-jun; Liu, Jian-guo; Wang, Min; Gao, Shan-hu; Chen, Jun

2006-03-01

334

k-Link Shortest Paths in Weighted Subdivisions Ovidiu Daescu1  

E-print Network

k-Link Shortest Paths in Weighted Subdivisions Ovidiu Daescu1 , Joseph S.B. Mitchell2 , Simeon nonnegative weight. The weighted length of a line segment, ab, joining two points a and b within the same by NSF grant CCF-0430366. J. Mitchell is partially supported by the U.S.-Israel Binational Science

Mitchell, Joseph S.B.

335

Efficient algorithms for the minimum shortest path Steiner arborescence problem with applications to VLSI physical design  

Microsoft Academic Search

Given an undirected graph G = (V; E) with positive edge weights (lengths) w : E ! <,, a set of termi-nals (sinks) N V, and a unique root node r 2 N, a shortest-path Steiner arborescence (simply called an arborescence in the following) is a Steiner tree rooted at r spanning all terminals in N such that every source-to-sink

Jason Cong; Andrew B. Kahng; Kwok-shing Leung

1998-01-01

336

A CO2 laser scintillometer for C(2) sub n measurements over a many kilometer path  

Microsoft Academic Search

A CO2 laser scintillometer for the measurement of refractive index over pathlengths from 100 m to 10 km is described. Electronic adjustment procedures, calibration, and the operation region of the instrument are outlined. The scintillometer performs well in tests over path lengths of 449, 5900, and 9700 m.

W. Kohsiek

1985-01-01

337

Universality of modulation length exponents  

NASA Astrophysics Data System (ADS)

We study systems (classical or quantum) with general pairwise interactions. Our prime interest is in frustrated spin systems. First, we focus on systems with a crossover temperature T^* across which the correlation function changes from exhibiting commensurate to incommensurate modulations. We report on a new exponent, ?L, characterizing the universal nature of this crossover. Near the crossover, the characteristic wave-vector k on the incommensurate side differs from that on the commensurate side, q by |k-q||T-T^*|^?L. We find, in general, that ?L=1/2, or in some special cases, other rational numbers. We discuss applications to the axial next nearest neighbor Ising model, Fermi systems (with application to the metal to band insulator transition) and Bose systems. Second, we obtain a universal form of the high temperature correlation function in general systems. From this, we show the existence of a diverging correlation length in the presence of long range interactions. Such a correlation length tends to the screening length in the presence of screening. We also find a way of obtaining the pairwise interaction potentials in the high temperature phase from the correlation functions.

Chakrabarty, Saurish; Seidel, Alexander; Nussinov, Zohar

2012-02-01

338

Spectral properties of microwave graphs with local absorption  

E-print Network

The influence of absorption on the spectra of microwave graphs has been studied experimentally. The microwave networks were made up of coaxial cables and T junctions. First, absorption was introduced by attaching a 50 Ohm load to an additional vertex for graphs with and without time-reversal symmetry. The resulting level-spacing distributions were compared with a generalization of the Wigner surmise in the presence of open channels proposed recently by Poli et al. [Phys. Rev. Lett. 108, 174101 (2012)]. Good agreement was found using an effective coupling parameter. Second, absorption was introduced along one individual bond via a variable microwave attenuator, and the influence of absorption on the length spectrum was studied. The peak heights in the length spectra corresponding to orbits avoiding the absorber were found to be independent of the attenuation, whereas, the heights of the peaks belonging to orbits passing the absorber once or twice showed the expected decrease with increasing attenuation.

M. Allgaier; S. Gehler; S. Barkhofen; H. -J. Stöckmann; U. Kuhl

2013-12-15

339

Determination of unsaturated flow paths in a randomly distributed fracture network  

SciTech Connect

We present a numerical investigation of steady flow paths in a two-dimensional, unsaturated discrete-fracture network. The fracture network is constructed using field measurement data including fracture density, trace lengths, and orientations from a particular site. The fracture network with a size of 100m x 150m contains more than 20,000 fractures. The steady state unsaturated flow in the fracture network is investigated for different boundary conditions. Simulation results indicate that the flow paths are generally vertical, and horizontal fractures mainly provide pathways between neighboring vertical paths. The simulation results support that the average spacing between flow paths in a layered system tends to increase or flow becomes more focused with depth as long as flow is gravity driven (Liu et al. 2002).

Zhang, Keni; Wu, Yu-Shu; Bodvarsson, G.S.; Liu, Hui-Hai

2003-02-17

340

Telomere length dynamics in aging mice.  

E-print Network

??Leukocyte telomere length (TL) shortens with age and is associated with age-related pathologies. However, inherited and acquired variation in telomere length in individuals complicates clinical… (more)

Comartin, Paul J

2012-01-01

341

Compounds affecting cholesterol absorption  

NASA Technical Reports Server (NTRS)

A class of novel compounds is described for use in affecting lymphatic absorption of cholesterol. Compounds of particular interest are defined by Formula I: ##STR1## or a pharmaceutically acceptable salt thereof.

Hua, Duy H. (Inventor); Koo, Sung I. (Inventor); Noh, Sang K. (Inventor)

2004-01-01

342

Absorption heat pump system  

DOEpatents

The efficiency of an absorption heat pump system is improved by conducting liquid from a second stage evaporator thereof to an auxiliary heat exchanger positioned downstream of a primary heat exchanger in the desorber of the system.

Grossman, G.

1982-06-16

343

Absorption heat pump system  

DOEpatents

The efficiency of an absorption heat pump system is improved by conducting liquid from a second stage evaporator thereof to an auxiliary heat exchanger positioned downstream of a primary heat exchanger in the desorber of the system.

Grossman, Gershon (Oak Ridge, TN)

1984-01-01

344

Optical absorption measurement system  

DOEpatents

The system of the present invention contemplates a non-intrusive method for measuring the temperature rise of optical elements under high laser power optical loading to determine the absorption coefficient. The method comprises irradiating the optical element with a high average power laser beam, viewing the optical element with an infrared camera to determine the temperature across the optical element and calculating the absorption of the optical element from the temperature.

Draggoo, Vaughn G. (Livermore, CA); Morton, Richard G. (San Diego, CA); Sawicki, Richard H. (Pleasanton, CA); Bissinger, Horst D. (Livermore, CA)

1989-01-01

345

Solar selective absorption coatings  

DOEpatents

A new class of solar selective absorption coatings are disclosed. These coatings comprise a structured metallic overlayer such that the overlayer has a sub-micron structure designed to efficiently absorb solar radiation, while retaining low thermal emissivity for infrared thermal radiation. A sol-gel layer protects the structured metallic overlayer from mechanical, thermal, and environmental degradation. Processes for producing such solar selective absorption coatings are also disclosed.

Mahoney, Alan R. (Albuquerque, NM); Reed, Scott T. (Albuquerque, NM); Ashley, Carol S. (Albuquerque, NM); Martinez, F. Edward (Horseheads, NY)

2004-08-31

346

Sequential Path Entanglement for Quantum Metrology  

PubMed Central

Path entanglement is a key resource for quantum metrology. Using path-entangled states, the standard quantum limit can be beaten, and the Heisenberg limit can be achieved. However, the preparation and detection of such states scales unfavourably with the number of photons. Here we introduce sequential path entanglement, in which photons are distributed across distinct time bins with arbitrary separation, as a resource for quantum metrology. We demonstrate a scheme for converting polarization Greenberger-Horne-Zeilinger entanglement into sequential path entanglement. We observe the same enhanced phase resolution expected for conventional path entanglement, independent of the delay between consecutive photons. Sequential path entanglement can be prepared comparably easily from polarization entanglement, can be detected without using photon-number-resolving detectors, and enables novel applications.

Jin, Xian-Min; Peng, Cheng-Zhi; Deng, Youjin; Barbieri, Marco; Nunn, Joshua; Walmsley, Ian A.

2013-01-01

347

Intricacies of quantum computational paths  

NASA Astrophysics Data System (ADS)

Graph search represents a cornerstone in computer science and is employed when the best algorithmic solution to a problem consists in performing an analysis of a search space representing computational possibilities. Typically, in such problems it is crucial to determine the sequence of transitions performed that led to certain states. In this work we discuss how to adapt generic quantum search procedures, namely quantum random walks and Grover's algorithm, in order to obtain computational paths. We then compare these approaches in the context of tree graphs. In addition we demonstrate that in a best-case scenario both approaches differ, performance-wise, by a constant factor speedup of two, whilst still providing a quadratic speedup relatively to their classical equivalents. We discuss the different scenarios that are better suited for each approach.

Tarrataca, Luís; Wichert, Andreas

2013-02-01

348

The Logic behind Feynman's Paths  

E-print Network

The classical notions of continuity and mechanical causality are left in order to refor- mulate the Quantum Theory starting from two principles: I) the intrinsic randomness of quantum process at microphysical level, II) the projective representations of sym- metries of the system. The second principle determines the geometry and then a new logic for describing the history of events (Feynman's paths) that modifies the rules of classical probabilistic calculus. The notion of classical trajectory is replaced by a history of spontaneous, random an discontinuous events. So the theory is reduced to determin- ing the probability distribution for such histories according with the symmetries of the system. The representation of the logic in terms of amplitudes leads to Feynman rules and, alternatively, its representation in terms of projectors results in the Schwinger trace formula.

Edgardo T. Garcia Alvarez

2010-11-22

349

Choosing Your Geosciences Career Path  

NASA Astrophysics Data System (ADS)

There are many possibilities for rewarding careers in the geosciences including positions in academia, government, industry, and other parts of the private sector. How do you choose the right path to meet your goals and needs and find the right career? What are the tradeoffs and strategic moves that you should make at different stages in your career? Some of the pros and cons between soft-money research, government research, and management and industry positions are discussed from a personal perspective. In addition this presentation will provide some perspective on different career choices as seen by program managers in funding agencies. The competing priorities between work life and private life are discussed with the some thoughts on compromising between "having it all" and finding what works for you.

Paluszkiewicz, T.

2002-12-01

350

Seven-effect absorption refrigeration  

DOEpatents

A seven-effect absorption refrigeration cycle is disclosed utilizing three absorption circuits. In addition, a heat exchanger is used for heating the generator of the low absorption circuit with heat rejected from the condenser and absorber of the medium absorption circuit. A heat exchanger is also provided for heating the generator of the medium absorption circuit with heat rejected from the condenser and absorber of the high absorption circuit. If desired, another heat exchanger can also be provided for heating the evaporator of the high absorption circuit with rejected heat from either the condenser or absorber of the low absorption circuit. 1 fig.

DeVault, R.C.; Biermann, W.J.

1989-05-09

351

Seven-effect absorption refrigeration  

DOEpatents

A seven-effect absorption refrigeration cycle is disclosed utilizing three absorption circuits. In addition, a heat exchanger is used for heating the generator of the low absorption circuit with heat rejected from the condenser and absorber of the medium absorption circuit. A heat exchanger is also provided for heating the generator of the medium absorption circuit with heat rejected from the condenser and absorber of the high absorption circuit. If desired, another heat exchanger can also be provided for heating the evaporator of the high absorption circuit with rejected heat from either the condenser or absorber of the low absorption circuit.

DeVault, Robert C. (Knoxville, TN); Biermann, Wendell J. (Fayetteville, NY)

1989-01-01

352

Farewell to the Voyagers: Measuring the Local ISM in the Immediate Path of the Two Voyager Spacecraft  

NASA Astrophysics Data System (ADS)

Astronomical observations of the interstellar medium often struggle to measure fundamental physical properties of the gas on small scales because most observations are averaged along the line of sight, leading to difficulties in evaluating pressure equilibrium, turbulence, magnetic field structure, and volume density. The local ISM has helped in this regard by providing relatively simple ISM absorption profiles over short path lengths, with low column densities only detectable with strong transitions in the UV . On August 25, 2012, the first human-made object, the Voyager 1 spacecraft, crossed the heliosphere, effectively leaving the solar system and entering the galactic interstellar environment. Voyager 2 is expected to do the same in the coming years, and over the next decade both spacecraft will continue to make daily measurements of fundamental physical properties. We propose to make the first observations of nearby stars along the same line of sight as the current locations of the Voyager spacecraft in order to measure the same interstellar material. The proposed observations are of the very closest stars in these directions and will provide measurements of the kinematic structure, electron density, temperature and turbulence, elemental abundances and small scale structure by comparing two closely spaced sight lines. With both HST and the Voyager spacecraft approaching the end of long and fruitful missions, we have the opportunity to acquire a unique dataset which synthesizes the independent and complimentary in situ observations with the shortest possible line-of-sight observations, to provide an unprecedented study of the galactic ISM surrounding the Sun.

Redfield, Seth

2014-10-01

353

Quantum Entanglement Molecular Absorption Spectrum Simulator  

NASA Technical Reports Server (NTRS)

Quantum Entanglement Molecular Absorption Spectrum Simulator (QE-MASS) is a computer program for simulating two photon molecular-absorption spectroscopy using quantum-entangled photons. More specifically, QE-MASS simulates the molecular absorption of two quantum-entangled photons generated by the spontaneous parametric down-conversion (SPDC) of a fixed-frequency photon from a laser. The two-photon absorption process is modeled via a combination of rovibrational and electronic single-photon transitions, using a wave-function formalism. A two-photon absorption cross section as a function of the entanglement delay time between the two photons is computed, then subjected to a fast Fourier transform to produce an energy spectrum. The program then detects peaks in the Fourier spectrum and displays the energy levels of very short-lived intermediate quantum states (or virtual states) of the molecule. Such virtual states were only previously accessible using ultra-fast (femtosecond) laser systems. However, with the use of a single-frequency continuous wave laser to produce SPDC photons, and QEMASS program, these short-lived molecular states can now be studied using much simpler laser systems. QE-MASS can also show the dependence of the Fourier spectrum on the tuning range of the entanglement time of any externally introduced optical-path delay time. QE-MASS can be extended to any molecule for which an appropriate spectroscopic database is available. It is a means of performing an a priori parametric analysis of entangled photon spectroscopy for development and implementation of emerging quantum-spectroscopic sensing techniques. QE-MASS is currently implemented using the Mathcad software package.

Nguyen, Quang-Viet; Kojima, Jun

2006-01-01

354

Haploinsufficiency and telomere length homeostasis.  

PubMed

In humans, autosomal dominant or X-linked disease can arise through a phenomenon termed haploinsufficiency, where one remaining wild-type allele is insufficient for function. In model organisms, the impact of heterozygosity can be tested directly with engineered mutant alleles or in a hemizygous state where the expression of one allele is abrogated completely. This review will focus on haploinsufficiency as it relates to telomerase and telomere length maintenance and, citing selected examples in various model organisms, it will discuss how the problem of gene dosage relates to telomere function in normal and diseased states. PMID:22100521

Harrington, Lea

2012-02-01

355

The Length of Time's Arrow  

SciTech Connect

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 divergencebetween 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.

2008-08-21

356

The Length of My Foot  

NSDL National Science Digital Library

In this math lesson, learners explore the concept of using units to measure length. Learners first read "How Big is a Foot" by Rolf Myller and learn about units. Then, learners visit four measurement centers. In each center, learners will measure items with various kinds of units. Learners use non-standard units to measure their shoes, the distance between beanbags and a bullâs-eye target, their body parts (arms, legs, etc.), and some everyday objects. This lesson guide includes instructions on how to set up a "Shoe Store" dramatic play area that can be used to introduce learners to measurement prior to this activity.

Lyman, Nichol

2012-09-26

357

The Feynman Path Integral: An Historical Slice  

E-print Network

Efforts to give an improved mathematical meaning to Feynman's path integral formulation of quantum mechanics started soon after its introduction and continue to this day. In the present paper, one common thread of development is followed over many years, with contributions made by various authors. The present version of this line of development involves a continuous-time regularization for a general phase space path integral and provides, in the author's opinion at least, perhaps the optimal formulation of the path integral.

John R. Klauder

2003-03-07

358

Maximum Flux Transition Paths of Conformational Change  

PubMed Central

Given two metastable states A and B of a biomolecular system, the problem is to calculate the likely paths of the transition from A to B. Such a calculation is more informative and more manageable if done for a reduced set of collective variables chosen so that paths cluster in collective variable space. The computational task becomes that of computing the “center” of such a cluster. A good way to define the center employs the concept of a committor, whose value at a point in collective variable space is the probability that a trajectory at that point will reach B before A. The committor “foliates” the transition region into a set of isocommittors. The maximum flux transition path is defined as a path that crosses each isocommittor at a point which (locally) has the highest crossing rate of distinct reactive trajectories. This path is based on the same principle as the minimum resistance path of Berkowitz et al (1983), but it has two advantages: (i) the path is invariant with respect to a change of coordinates in collective variable space and (ii) the differential equations that define the path are simpler. It is argued that such a path is nearer to an ideal path than others that have been proposed with the possible exception of the finite-temperature string method path. To make the calculation tractable, three approximations are introduced, yielding a path that is the solution of a nonsingular two-point boundary-value problem. For such a problem, one can construct a simple and robust algorithm. One such algorithm and its performance is discussed. PMID:20890401

Zhao, Ruijun; Shen, Juanfang; Skeel, Robert D.

2010-01-01

359

The path integral for dendritic trees  

Microsoft Academic Search

We construct the path integral for determining the potential on any dendritic tree described by a linear cable equation. This is done by generalizing Brownian motion from a line to a tree. We also construct the path integral for dendritic structures with spatially-varying and\\/or time-dependent membrane conductivities due, for example, to synaptic inputs. The path integral allows novel computational techniques

L. F. Abbott; Edward Farhi; Sam Gutmann

1991-01-01

360

FTIR-spectrometer-determined absorption coefficients of seven hydrazine fuel gases - Implications for laser remote sensing  

NASA Technical Reports Server (NTRS)

The absorption spectra of three hydrazines and four of their air-oxidation products were measured in the 9-12-micron spectral region with a Fourier transform infrared (FTIR) spectrometer with a 0.05-kayser resolution to determine absorption coefficients at CO2 and tunable diode laser wavelengths. The measurements agreed well with published CO2 laser determinations for many of the absorption coefficients, except where the published values are thought to be in error. The coefficients were then used to estimate the sensitivity for remote detection of these gases using CO2 and tunable diode lasers in long-path differential absorption measurements.

Molina, L. T.; Grant, W. B.

1984-01-01

361

Generalized path dependent representations for gauge theories  

SciTech Connect

A set of differential operators acting by continuous deformations on path dependent functionals of open and closed curves is introduced. Geometrically, these path operators are interpreted as infinitesimal generators of curves in the base manifold of the gauge theory. They furnish a representation with the action of the group of loops having a fundamental role. We show that the path derivative, which is covariant by construction, satisfies the Ricci and Bianchi identities. Also, we provide a geometrical derivation of covariant Taylor expansions based on particular deformations of open curves. The formalism includes, as special cases, other path dependent operators such as end point derivatives and area derivatives.

Reyes, Marat C. [Instituto de Ciencias Nucleares, Universidad Nacional Autonoma de Mexico, 04510 Mexico D.F. (Mexico) and Universidad Tecnica Federico Santa Maria, Campus Santiago, C.P. 766-0251, Santiago (Chile)

2007-05-15

362

Generalized Path Dependent Representations for Gauge Theories  

E-print Network

A set of differential operators acting by continuous deformations on path dependent functionals of open and closed curves is introduced. Geometrically, these path operators are interpreted as infinitesimal generators of curves in the base manifold of the gauge theory. They furnish a representation with the action of the group of loops having a fundamental role. We show that the path derivative, which is covariant by construction, satisfies the Ricci and Bianchi identities. Also, we provide a geometrical derivation of covariant Taylor expansions based on particular deformations of open curves. The formalism includes, as special cases, other path dependent operators such as end point derivatives and area derivatives.

Marat C. Reyes

2006-11-15

363

Path Deviation Equations in AP-Geometry  

NASA Astrophysics Data System (ADS)

Recently, it has been shown that Absolute Parallelism (AP) geometry admits paths that are naturally quantized. These paths have been used to describe the motion of spinning particles in a background gravitational field. In case of a weak static gravitational field limits, the paths are applied successfully to interpret the discrepancy in the motion of thermal neutrons in the Earth's gravitational field (COW-experiment). The aim of the present work is to explore the properties of the deviation equations corresponding to these paths. In the present work the deviation equations are derived and compared to the geodesic deviation equation of the Riemannian geometry.

Wanas, M. I.; Kahil, M. E.

2006-02-01

364

Initial investigation of the wavelength dependence of optical properties measured with a new multi-pass Aerosol Extinction Differential Optical Absorption Spectrometer (AE-DOAS)  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols directly affect climate by scattering and absorbing radiation. The magnitude of the impact is dependent upon the wavelength of light, but is often estimated near 550 nm. When light scattering and absorption by aerosols is approximated, the wavelength dependence of the refractive index for specific components is lost. As a result, climate models would have inherent uncertainties for aerosol contributions to radiative forcing when considering the entire solar spectrum. An aerosol extinction differential optical absorption spectrometer has been developed to directly measure aerosol extinction at mid-ultraviolet to near infrared wavelengths. The instrument consists of a spectrometer coupled to a closed White-type multi-pass gas cell with an adjustable path length of up to approximately 20 m. Laboratory measurements of various gases are compared with known absorption cross sections. Additionally, the extinction of monodisperse samples of polystyrene latex spheres are measured and compared to Mie theory generated with refractive index values from the literature to validate the new instrument. The polystyrene experiments also emphasize the ability of the new instrument to retrieve the wavelength dependent refractive index, especially in the ultraviolet wavelength regions where variability is expected. The spectrometer will be a significant advancement for determining wavelength dependent complex refractive indices in future laboratory studies as well as provide the ability to monitor ambient aerosol light extinction.

Chartier, R. T.; Greenslade, M. E.

2012-04-01

365

Cryogenic Absorption Cells Operating Inside a Bruker IFS-125HR: First Results for 13CH4 at 7 Micrometers  

NASA Technical Reports Server (NTRS)

New absorption cells designed specifically to achieve stable temperatures down to 66 K inside the sample compartment of an evacuated Bruker IFS-125HR Fourier transform spectrometer (FTS) were developed at Connecticut College and tested at the Jet Propulsion Laboratory (JPL). The temperature stabilized cryogenic cells with path lengths of 24.29 and 20.38 cm were constructed of oxygen free high conductivity (OFHC) copper and fitted with wedged ZnSe windows using vacuum tight indium seals. In operation, the temperature-controlled cooling by a closed-cycle helium refrigerator achieved stability of 0.01 K. The unwanted absorption features arising from cryodeposits on the cell windows at low temperatures were eliminated by building an internal vacuum shroud box around the cell which significantly minimized the growth of cryodeposits. The effects of vibrations from the closed-cycle helium refrigerator on the FTS spectra were characterized. Using this set up, several high-resolution spectra of methane isotopologues broadened with nitrogen were recorded in the 1200-1800 per centimeter spectral region at various sample temperatures between 79.5 and 296 K. Such data are needed to characterize the temperature dependence of spectral line shapes at low temperatures for remote sensing of outer planets and their moons. Initial analysis of a limited number of spectra in the region of the R(2) manifold of the v4 fundamental band of 13CH4 indicated that an empirical power law used for the temperature dependence of the N2-broadened line widths would fail to fit the observed data in the entire temperature range from 80 to 296 K; instead, it follows a temperature-dependence similar to that reported by Mondelain et al. [17,18]. The initial test was very successful proving that a high precision Fourier transform spectrometer with a completely evacuated optical path can be configured for spectroscopic studies at low temperatures relevant to the planetary atmospheres.

Sung, K.; Mantz, A. W.; Smith, M. A. H.; Brown, L. R.; Crawford, T. J.; Devi, V. M.; Benner, D. C.

2010-01-01

366

Physical and Water Absorption Characteristics of Some Improved Rice Varieties  

Microsoft Academic Search

The physical and water absorption characteristics of paddy and brown rice from some early maturing Oryza sativa varieties and newly developed interspecific (O. sativa × Oryza glaberrima) rice varieties were studied. The physical dimensions (length, breadth and width, length\\/width ratio, equivalent diameter),\\u000a grain surface area and volume, sphericity, 1,000-kernel weight, bulk and true densities as well as porosity were determined.

Taofik Akinyemi Shittu; M. B. Olaniyi; A. A. Oyekanmi; K. A. Okeleye

367

Absorption Spectroscopy of Pulsed Power Driven Metal Plasmas  

Microsoft Academic Search

We present here the use of the continuum radiation from X-pinch-produced point x-ray sources for absorption spectroscopy as a new diagnostic to investigate the properties of aluminum plasmas created by pulsed power machines at 500 kA and 1 MA. This technique is being developed to provide a path towards determining time and space resolved plasma parameters (charge state, temperature and

Patrick Knapp; Sergei Pikuz; Tania Shelkovenko; Adam Cahill; John Greenly; David Hammer

2010-01-01

368

Absolute Rovibrational Intensities of C-12O2-16 Absorption Bands in the 3090-3850/ CM Spectral Region  

NASA Technical Reports Server (NTRS)

A multispectrum nonlinear least-squares fitting technique has been used to determine the absolute intensities for approximately 1500 spectral lines in 36 vibration - rotation bands Of C-12O2-16 between 3090 and 3850/ cm. A total of six absorption spectra of a high- purity (99.995% minimum) natural sample of carbon dioxide were used in the analysis. The spectral data (0.01/cm resolution) were recorded at room temperature and low pressure (1 to 10 Torr) using the McMath-Pierce Fourier transform spectrometer of the National Solar Observatory (NSO) on Kitt Peak. The absorption path lengths for these spectra varied between 24.86 and 385.76 m. The first experimental determination of the intensity of the theoretically predicted 2(nu)(sub 2, sup 2) + nu(sub 3) "forbidden" band has been made. The measured line intensities obtained for each band have been analyzed to determine the vibrational band intensity, S(sub nu), in /cm/( molecule/sq cm) at 296 K, square of the rotationless transition dipole moment |R|(exp 2) in Debye, as well as the nonrigid rotor coefficients. The results are compared to the values listed in the 1996 HITRAN database which are obtained using the direct numerical diagonalization (DND) technique as well as to other published values where available.

Devi, V. Malathy; Benner, D. Chris; Rinsland, Curtis P.; Smith, Mary Ann H.

1998-01-01

369

Penetration distances and their applications to path planning  

NASA Astrophysics Data System (ADS)

The proximal relationship of two objects is of interest for many reasons, e.g., the interference detection problem in robot motion planning. When the mathematical representations of two objects are separated the natural measure of the proximal relationship is the shortest Euclidean distance. However, much less is known when the representations intersect. In this dissertation, one of the main foci is the characterization and computation of measures of the proximal relationship between two intersecting objects. We call these measures penetration distances. A formal exposition of penetration distances and their mathematical properties is given. A penetration distance is defined by the least 'movement' needed to separate the two objects. In general, 'movement' involves both rotation and translation. Several ways of measuring the degree of rotation and translation are introduced and each yields a different definition of penetration distance. In the special case of convex objects, it is shown that the various penetration distances are the same and are determined from translational motion alone. The above-mentioned penetration distances are difficult to compute. An important contribution of this thesis is the development of a new penetration distance based on ideas of 'growing' the mathematical representations of objects. It is called the growth distance and can be computed easily for a pair of convex objects. The mathematical properties and computational aspects of the growth distance are developed at length. For instance, its relationship to the other penetration distances is determined. When two objects are separated, the growth distance is also a measure of separation. An important application of the growth distance is to path finding for robotic systems in the presence of obstacles. Our approach is to convert the path finding problem into an optimization problem. path. &This novel approach involves searching among collision paths. Problems unique to this formulation are discussed. Our approach has several advantages over existing approaches and has performed well in several examples.

Ong, Chong Jin

370

Optical Scattering Lengths in Large Liquid-Scintillator Neutrino Detectors  

E-print Network

For liquid-scintillator neutrino detectors of kiloton scale, the transparency of the organic solvent is of central importance. The present paper reports on laboratory measurements of the optical scattering lengths of the organic solvents PXE, LAB, and Dodecane which are under discussion for next-generation experiments like SNO+, Hanohano, or LENA. Results comprise the wavelength range from 415 to 440nm. The contributions from Rayleigh and Mie scattering as well as from absorption/re-emission processes are discussed. Based on the present results, LAB seems to be the preferred solvent for a large-volume detector.

Michael Wurm; Franz von Feilitzsch; Marianne Goeger-Neff; Martin Hofmann; Tobias Lachenmaier; Timo Lewke; Teresa Marrodan Undagoitita; Quirin Meindl; Randoplh Moellenberg; Lothar Oberauer; Walter Potzel; Marc Tippmann; Sebastian Todor; Christoph Traunsteiner; Juergen Winter

2010-04-06

371

Design and performance of an optical path cross-connect system based on wavelength path concept  

Microsoft Academic Search

This paper describes the system design and performance of an optical path cross-connect (OPXC) system based on wavelength path concept. The (OPXC) is designed to offer 16 sets of input and output fiber ports with each fiber transporting eight multiwavelength signals for optical paths. Each optical path has a capacity of 2.5 Gb\\/s. Consequently, the total system throughput is 8×16×2.5=320

Masafumi Koga; Yoshiyuki Hamazumi; Atsushi Watanabe; Satoru Okamoto; Hitoshi Obara; Ken-Ichi Sato; Masayuki Okuno; Senichi Suzuki

1996-01-01

372

Path planning by optimal-path-map construction for homogeneous-cost two-dimensional regions  

Microsoft Academic Search

Algorithms to construct optimal-path maps for single isolated homogeneous-cost convex-polygonal regions are discussed. Assuming the ability to construct optimal paths for a certain set of key points, a complete analysis is given of one of the four possible single-region situations, showing how to partition the map into regions of similar path behavior. An algorithm is then proposed for constructing optimal-path

Robert S. Alexander; Neil C. Rowe

1990-01-01

373

On the Representability of Arbitrary Path Sets as Shortest Paths: Theory, Algorithms, and Complexity  

Microsoft Academic Search

\\u000a The question, whether an optional set of routes can be represented as shortest paths, and if yes, then how, has been a rather\\u000a scarcely investigated problem up until now. In turn, an algorithm that, given an arbitrary set of traffic engineered paths,\\u000a can efficiently compute OSPF link weights as to map the given paths to shortest paths may be of

Gábor Rétvári; Róbert Szabó; József Bíró

2004-01-01

374

Path and Path Deviation Equations in Kaluza-Klein Type Theories  

E-print Network

Path and path deviation equations for charged, spinning and spinning charged objects in different versions of Kaluza-Klein (KK) theory using a modified Bazanski Lagrangian have been derived. The significance of motion in five dimensions, especially for a charged spinning object, has been examined. We have also extended the modified Bazanski approach to derive the path and path deviation equations of a test particle in a version of non-symmetric KK theory.

M. E. Kahil

2005-11-07

375

Methodology for Augmenting Existing Paths with Additional Parallel Transects  

SciTech Connect

Visual Sample Plan (VSP) is sample planning software that is used, among other purposes, to plan transect sampling paths to detect areas that were potentially used for munition training. This module was developed for application on a large site where existing roads and trails were to be used as primary sampling paths. Gap areas between these primary paths needed to found and covered with parallel transect paths. These gap areas represent areas on the site that are more than a specified distance from a primary path. These added parallel paths needed to optionally be connected together into a single path—the shortest path possible. The paths also needed to optionally be attached to existing primary paths, again with the shortest possible path. Finally, the process must be repeatable and predictable so that the same inputs (primary paths, specified distance, and path options) will result in the same set of new paths every time. This methodology was developed to meet those specifications.

Wilson, John E.

2013-09-30

376

QSO absorption lines - Introduction  

NASA Astrophysics Data System (ADS)

A brief account is given of the physical properties of the heavy-element and Ly-alpha forest absorption redshift systems observed in QSO spectra. Theories for their origin are summarized. It is emphasized that the two types of absorption system have qualitatively different properties and that they are almost certainly not components of a single population as Tytler has recently claimed. Extensive new data on the heavy-element redshifts reveal clustering on velocity scales unlikely to have been produced by the motions of clouds within galaxies. Extensive absorption systems observed in the relatively wide QSO pair Q1037-2704 and Q1038-2712 and in the spectra of other QSOs in the surrounding field are described. Observations of this kind appear to represent a new way of studying the large-scale distribution of galaxies at earlier epochs in the expansion of the Universe.

Sargent, W. L. W.

377

Path planning and path tracking control of unmanned ground vehicles (UGVs)  

Microsoft Academic Search

Unmanned ground vehicles (UGVs) will be playing increasingly important role in the future battlefields. How to automatically guide and control UGVs under varying environment conditions represents a challenging issue. This paper presents a novel approach to achieving path planning and path tracking of UGVs under dynamic environments. We apply the topology theory to find the optimal path given any starting

Liguo Weng; D. Y. Song

2005-01-01

378

A Continuous-State Version of Discrete Randomized Shortest-Paths, with Application to Path Planning  

E-print Network

are of capital importance in a variety of problems, from robot path planning, to maze solving. Path planning [16] is a well-known problem in the robotics community, described by [26] as "checking the consequences. This distribution, though peaked around optimal paths, let the random walker take a random transition according

Del Moral , Pierre

379

Optical Path Cross-Connect System Scale Evaluation Using Path Accommodation Design for Restricted Wavelength Multiplexing  

Microsoft Academic Search

The optical path (OP) technology, which employs both wavelength-division multiplexing and wavelength routing, will be the key to enhanced network integrity and an ubiquitous broadband integrated services digital network (B-ISDN) in the future. To construct the OP network, path accommodation design that can solve simultaneously the problems of path routing and wavelength assignment must be established. Since optical wavelengths are

Naohide Nagatsu; Satoru Okamoto; Ken-ichi Sato

1996-01-01

380

MODELING DENDRITIC SHAPES Using Path Planning  

E-print Network

the humble to the spectacular: lichens, coral, river systems, and lightning are all examples of naturally of objects exhibiting dendritic shape include lichens, coral, trees, lightning, rivers, crystals least-cost paths through the lattice. Multiple paths from a single starting location (or gen- erator

Mould, David

381

Shortest Paths in Microseconds Rachit Agarwal  

E-print Network

to compute and store a partial shortest path tree (PSPT) for each node. The PSPTs have the property to be an extremely small frac- tion of the entire network; hence, PSPTs can be stored efficiently and each shortest path can be computed ex- tremely quickly. For a real network with 5 million nodes and 69 mil- lion

382

Katrina'sPath Lake Pontchartrain  

E-print Network

miles to the west · Eye-wall pushes into Pearl River floodplain Impacts · Spillway overtopped into canal #12;Hudson'sPath Future Scenario Hurricane Hudson · Same Katrina path · Intensity increased 3 · 15mph forward speed Jourdan River Basin Pearl River Basin Rolls Royce Test Complex Building 1100

383

Evaluation of Calcine Disposition Path Forward  

SciTech Connect

This document describes an evaluation of the baseline and two alternative disposition paths for the final disposition of the calcine wastes stored at the Idaho Nuclear Technology and Engineering Center at the Idaho National Engineering and Environmental Laboratory. The pathways are evaluated against a prescribed set of criteria and a recommendation is made for the path forward.

Birrer, S.A.; Heiser, M.B.

2003-02-26

384

Evaluation of Calcine Disposition - Path Forward  

SciTech Connect

This document describes an evaluation of the baseline and two alternative disposition paths for the final disposition of the calcine wastes stored at the Idaho Nuclear Technology and Engineering Center at the Idaho National Engineering and Environmental Laboratory. The pathways are evaluated against a prescribed set of criteria and a recommendation is made for the path forward.

Steve Birrer

2003-02-01

385

Bounding the error of path loss models  

Microsoft Academic Search

In this paper we analyze the efficacy of basic path loss models at predicting median path loss in urban environments. We attempt to bound the practical error of these models and look at how they may hinder practical wireless applications, and in particular dynamic spectrum access networks. This analysis is made using a large set of measurements from production networks

Caleb Phillips; Douglas Sicker; Dirk Grunwald

2011-01-01

386

Functional test generation for path delay faults  

Microsoft Academic Search

We present a novel test generation technique for path delay faults, based on the growth (G) and disappearance (D) faults of programmable logic arrays (PLA). The circuit is modeled as a PLA that is prime and irredundant with respect to every output. Certain tests for G faults, generated by using known efficient methods are transformed into tests for path delay

Mandyam-komar Srinivas; Vishwani D. Agrawal; Michael L. Bushnell

1995-01-01

387

Path-based control of smoke simulations  

Microsoft Academic Search

In this paper, we propose a novel path-based control method for generating realistic smoke animations. Our method allows an animator to specify a 3D curve for the smoke to follow. Path control is then achieved using a linear (closed) feedback loop to match the velocity field obtained from a 3D flow simulation with a target velocity field. The target velocity

Yootai Kim; Raghu Machiraju; David Thompson

2006-01-01

388

Protecting Location Privacy Through Path Confusion  

Microsoft Academic Search

We present a path perturbation algorithm which can maximize users? location privacy given a quality of service constraint. This work concentrates on a class of applications that continuously collect location samples from a large group of users, where just removing user identifiers from all samples is insufficient because an adversary could use trajectory information to track paths and follow users?

Baik Hoh; Marco Gruteser

2005-01-01

389

Next Generation Science Standards (NGSS) Path Finder  

NSDL National Science Digital Library

This interactive visual 'path finder' from the Concord Consortium allows users to explore the component pieces of the Next Generation Science Standards. After selecting the appropriate practices, core ideas, and crosscutting concepts, the path finder will suggest relevant resources from the Concord Consortium's collection.

Consortium, The C.

390

Control-path Oriented Workflow Intelligence Analyses  

Microsoft Academic Search

This paper proposes two kinds of control-path oriented workflow knowledge analy- sis approaches which will be applied to a workflow intelligence and quality improve- ment framework aiming at the high degree of the workflow traceability and rediscover- ability. The framework needs two kinds of algorithms ? One is for generating the total sequences of the control-paths from a workflow model,

Minjae Park; Kwanghoon Kim

2008-01-01

391

Cellular Absorption of Herbicides  

NSDL National Science Digital Library

Before a herbicide can kill a plant, it must be absorbed by the plant’s leaves or roots and enter a cell which possesses the metabolic pathway the herbicide targets.  This lesson follows the fate of the herbicide after it has entered the plant via leaf or root tissue, and explains the factors controlling transport of a herbicide into plant cells.  This lesson describes 1) the barriers to herbicide entry, such as the plant cell membrane, 2) the role that the herbicide’s chemical properties have on the rate of cellular absorption, and 3) experimental approaches to understanding herbicide absorption at the cellular level.

392

Absorption heat pump system  

DOEpatents

An improvement in an absorption heat pump cycle is obtained by adding adiabatic absorption and desorption steps to the absorber and desorber of the system. The adiabatic processes make it possible to obtain the highest temperature in the absorber before any heat is removed from it and the lowest temperature in the desorber before heat is added to it, allowing for efficient utilization of the thermodynamic availability of the heat supply stream. The improved system can operate with a larger difference between high and low working fluid concentrations, less circulation losses, and more efficient heat exchange than a conventional system.

Grossman, Gershon (Oak Ridge, TN); Perez-Blanco, Horacio (Knoxville, TN)

1984-01-01

393

Chaotic Systems with Absorption  

NASA Astrophysics Data System (ADS)

Motivated by applications in optics and acoustics we develop a dynamical-system approach to describe absorption in chaotic systems. We introduce an operator formalism from which we obtain (i) a general formula for the escape rate ? in terms of the natural conditionally invariant measure of the system, (ii) an increased multifractality when compared to the spectrum of dimensions Dq obtained without taking absorption and return times into account, and (iii) a generalization of the Kantz-Grassberger formula that expresses D1 in terms of ?, the positive Lyapunov exponent, the average return time, and a new quantity, the reflection rate. Simulations in the cardioid billiard confirm these results.

Altmann, Eduardo G.; Portela, Jefferson S. E.; Tél, Tamás

2013-10-01

394

Decision paths in complex tasks  

NASA Technical Reports Server (NTRS)

Complex real world action and its prediction and control has escaped analysis by the classical methods of psychological research. The reason is that psychologists have no procedures to parse complex tasks into their constituents. Where such a division can be made, based say on expert judgment, there is no natural scale to measure the positive or negative values of the components. Even if we could assign numbers to task parts, we lack rules i.e., a theory, to combine them into a total task representation. We compare here two plausible theories for the amalgamation of the value of task components. Both of these theories require a numerical representation of motivation, for motivation is the primary variable that guides choice and action in well-learned tasks. We address this problem of motivational quantification and performance prediction by developing psychophysical scales of the desireability or aversiveness of task components based on utility scaling methods (Galanter 1990). We modify methods used originally to scale sensory magnitudes (Stevens and Galanter 1957), and that have been applied recently to the measure of task 'workload' by Gopher and Braune (1984). Our modification uses utility comparison scaling techniques which avoid the unnecessary assumptions made by Gopher and Braune. Formula for the utility of complex tasks based on the theoretical models are used to predict decision and choice of alternate paths to the same goal.

Galanter, Eugene

1991-01-01

395

Path integral for inflationary perturbations  

SciTech Connect

The quantum theory of cosmological perturbations in single-field inflation is formulated in terms of a path integral. Starting from a canonical formulation, we show how the free propagators can be obtained from the well-known gauge-invariant quadratic action for scalar and tensor perturbations, and determine the interactions to arbitrary order. This approach does not require the explicit solution of the energy and momentum constraints, a novel feature which simplifies the determination of the interaction vertices. The constraints and the necessary imposition of gauge conditions is reflected in the appearance of various commuting and anticommuting auxiliary fields in the action. These auxiliary fields are not propagating physical degrees of freedom but need to be included in internal lines and loops in a diagrammatic expansion. To illustrate the formalism we discuss the tree-level three-point and four-point functions of the inflaton perturbations, reproducing the results already obtained by the methods used in the current literature. Loop calculations are left for future work.

Prokopec, Tomislav [Institute for Theoretical Physics and Spinoza Institute, Utrecht University, Leuvenlaan 4, 3584 CE Utrecht (Netherlands); Rigopoulos, Gerasimos [Helsinki Institute of Physics, P.O. Box 64, FIN-00014, University of Helsinki (Finland)

2010-07-15

396

Converging towards the optimal path to extinction  

PubMed Central

Extinction appears ubiquitously in many fields, including chemical reactions, population biology, evolution and epidemiology. Even though extinction as a random process is a rare event, its occurrence is observed in large finite populations. Extinction occurs when fluctuations owing to random transitions act as an effective force that drives one or more components or species to vanish. Although there are many random paths to an extinct state, there is an optimal path that maximizes the probability to extinction. In this paper, we show that the optimal path is associated with the dynamical systems idea of having maximum sensitive dependence to initial conditions. Using the equivalence between the sensitive dependence and the path to extinction, we show that the dynamical systems picture of extinction evolves naturally towards the optimal path in several stochastic models of epidemics. PMID:21571943

Schwartz, Ira B.; Forgoston, Eric; Bianco, Simone; Shaw, Leah B.

2011-01-01

397

A rapid method to derive horizontal distributions of trace gases and aerosols near the surface using multi-axis differential optical absorption spectroscopy  

NASA Astrophysics Data System (ADS)

We apply a novel experimental procedure for the rapid measurement of the average volume mixing ratios (VMRs) and horizontal distributions of trace gases such as NO2, SO2, and HCHO in the boundary layer, which was recently suggested by Sinreich et al. (2013). The method is based on two-dimensional scanning multi-axis differential optical absorption spectroscopy (MAX-DOAS). It makes use of two facts (Sinreich et al. 2013): First, the light path for observations at 1° elevation angle traverses mainly air masses located close to the ground (typically < 200 m). Second, the light path length can be calculated using the simultaneous measured absorption of the oxygen dimer O4. Thus, the average value of the trace gas VMR in the atmospheric layer between the surface and the altitude, for which this observation was sensitive, can be calculated. Compared to the originally proposed method, we introduce several important modifications and improvements: We apply the method only to measurements at 1° elevation angles, for which the uncertainties are especially small. Using only 1 elevation angle also allows an increased temporal resolution. We apply correction factors (and their uncertainties) as function of the simultaneously modelled O4 absorption. In this way the correction factors can be directly determined according to the measured O4 dAMF. Finally, the method is extended to trace gases analysed at other wavelengths and also to the retrieval of the aerosol extinction. Depending on the atmospheric visibility, the typical uncertainty of the results ranges from about 15 to 30%. We apply the rapid method to observations of a newly developed ground-based multifunctional passive differential optical absorption spectroscopy (GM-DOAS) instrument in the north-west outskirt near Hefei City in China. We report NO2, SO2, and HCHO VMRs and aerosol extinction for four azimuth angles and compare these results with those from simultaneous long-path DOAS observations. Good agreement is found (squares of the correlation coefficients for NO2, SO2, and HCHO were 0.92, 0.84, and 0.59, respectively), verifying the reliability of this novel method. Similar agreement is found for the comparison of the aerosol extinction with results from visibility meters. Future studies may conduct measurements using a larger number of azimuth angles to increase the spatial resolution.

Wang, Y.; Li, A.; Xie, P. H.; Wagner, T.; Chen, H.; Liu, W. Q.; Liu, J. G.

2013-09-01

398

Density dependence of electron mean-free paths from low to high energies  

SciTech Connect

The mean-free path of an electron scattering inelastically in a degenerate electron gas at zero temperature has been calculated, using the dielectric function/self-energy formalism of Ritchie (Phys. Rev. {bold 114}, 644 (1959)). The objective of this work is to model accurately the mean-free path as a function of photoelectron energy and density for use in the calculation of extended x-ray absorption fine structure (EXAFS) (Rev. Mod. Phys. {bold 53}, 1 (1981)) of fluids and plasmas whose structure can be described by a radial distribution function. Results are compared with proposed universal mean-free path formulas and it is found that a more generalized version of a power law provides an adequate fit. A table of the best-fit parameters of this law at a range of densities of interest for the EXAFS colliding shock experiments on foil targets is presented.

Gordon, F.I. (Department of Physics, Essex University, Colchester CO4 3SQ (United Kingdom)); Djaoui, A. (Rutherford Appleton Laboratory, Chilton, Didcot, Oxfordshire, OX11 0QX (United Kingdom))

1992-12-01

399

Path planning using a hybrid evolutionary algorithm based on tree structure encoding.  

PubMed

A hybrid evolutionary algorithm using scalable encoding method for path planning is proposed in this paper. The scalable representation is based on binary tree structure encoding. To solve the problem of hybrid genetic algorithm and particle swarm optimization, the "dummy node" is added into the binary trees to deal with the different lengths of representations. The experimental results show that the proposed hybrid method demonstrates using fewer turning points than traditional evolutionary algorithms to generate shorter collision-free paths for mobile robot navigation. PMID:24971389

Ju, Ming-Yi; Wang, Siao-En; Guo, Jian-Horn

2014-01-01

400

Infrared neural stimulation: beam path in the guinea pig cochlea  

PubMed Central

It has been demonstrated INS can be utilized to stimulate spiral ganglion cells in the cochlea. Although neural stimulation can be achieved without direct contact of the radiation source and the tissue, the presence of fluids or bone between the target structure and the radiation source may lead to absorption or scattering of the radiation, which may limit the efficacy of INS. The present study demonstrates the neural structures in the radiation beam path that can be stimulated. Histological reconstructions and microCT of guinea pig cochleae stimulated with an infrared laser suggest that the orientation of the beam from the optical fiber determined the site of stimulation in the cochlea. Best frequencies of the INS-evoked neural responses obtained from the central nucleus of the inferior colliculus matched the histological sites in the spiral ganglion. PMID:21763410

Moreno, Laura E; Rajguru, Suhrud M; Matic, Agnella Izzo; Yerram, Nitin; Robinson, Alan M; Hwang, Margaret; Stock, Stuart; Richter, Claus-Peter

2011-01-01

401

Gas Lamp Absorption  

NSDL National Science Digital Library

This resource, part of the Spectroscopy Lab Suite, simulates optical transitions in gasses. Absorption spectra from gas emission tubes illuminated by a white light are shown, along with a tool for students to create bound state energy levels and electronic transitions to match the observed spectra.

Group, Kansas S.; Zollman, Dean A.

2004-03-05

402

Absorptive capacity of the transplanted small bowel.  

PubMed Central

Small bowel transplantation (SBT) has been carried out in man in several cases without success, because immunologic problems were unsolved. In experimental SBT a 'two step' model was developed, which enables long term observation of immunologic phenomena. In this model the graft is in a heterotopic position to the recipient's own small bowel. After 35 days the recipient's own bowel is removed and replaced by the graft, now in orthotopic position and again in contact with luminal chymus. To investigate functional and morphological changes, which result from the procedure, the resorption of glucose and water was measured in syngeneic transplanted rats by an in vivo recirculation system and the mucosa was evaluated three dimensionally. The graft mucosa showed a significant reduction in villus height, crypt length and villus surface and a corresponding decrease in glucose and water absorption during heterotopic position. If the graft came into the orthotopic position, the mucosa did regenerate which was expressed by the significant longer crypts of the graft compared with those of the controls, although the graft's villus height and surface are still smaller. Glucose and water absorption increased and were higher in orthotopic transplanted animals, when absorption was expressed per unit intestinal length. The results indicate that in the 'two step' model of SBT the absorption of water and glucose is influenced to such an extent, that recovery is possible after three weeks, thus enabling orthotopic SBT. This almost complete recovery of the mucosa is further evidence of the regeneratory capacity of the small bowel, which enables clinical small bowel transplantation. PMID:3500897

Schroeder, P; Deltz, E; Seifert, J; Sandforth, F; Thiede, A

1987-01-01

403

Extendable nickel complex tapes that reach NIR absorptions.  

PubMed

Stepwise synthesis of linear nickel complex oligomer tapes with no need for solid-phase support has been achieved. The control of the length in flat arrays allows a fine-tuning of the absorption properties from the UV to the NIR region. PMID:25348258

Audi, Hassib; Chen, Zhongrui; Charaf-Eddin, Azzam; D'Aléo, Anthony; Canard, Gabriel; Jacquemin, Denis; Siri, Olivier

2014-11-01

404

Impact behavior and energy absorption of paper honeycomb sandwich panels  

Microsoft Academic Search

Dynamic cushioning tests were conducted by free drop and shock absorption principle. The effect of paper honeycomb structure factors on the impact behavior was analyzed. Results of many experiments show that the dynamic impact curve of paper honeycomb sandwich panel is concave and upward; the thickness and length of honeycomb cell-wall have a great effect on its cushioning properties; increasing

Dongmei Wang

2009-01-01

405

All-Optical Monitoring Path Computation Using Lower Bounds of Required Number of Paths  

NASA Astrophysics Data System (ADS)

To reduce the cost of fault management in all-optical networks, it is a promising approach to detect the degradation of optical signal quality solely at the terminal points of all-optical monitoring paths. The all-optical monitoring paths must be routed so that all single-link failures can be localized using route information of monitoring paths where signal quality degradation is detected. However, route computation for the all-optical monitoring paths that satisfy the above condition is time consuming. This paper proposes a procedure for deriving the lower bounds of the required number of monitoring paths to localize all single-link failures, and proposes an efficient monitoring path computation method based on the derived lower bounds. The proposed method repeats the route computation for the monitoring paths until feasible routes can be found, while the assumed number of monitoring paths increases, starting from the lower bounds. With the proposed method, the minimum number of monitoring paths with the overall shortest routes can be obtained quickly by solving several small-scale integer linear programming problems when the possible terminal nodes of monitoring paths are arbitrarily given. Thus, the proposed method can minimize the required number of monitors for detecting the degradation of signal quality and the total overhead traffic volume transferred through the monitoring paths.

Ogino, Nagao; Nakamura, Hajime

406

The Path of Human Evolution  

NASA Astrophysics Data System (ADS)

A complex series of evolutionary steps, contingent upon a dynamic environmental context and a long biological heritage, have led to the ascent of Homo sapiens as a dominant component of the modern biosphere. In a field where missing links still abound and new discoveries regularly overturn theoretical paradigms, our understanding of the path of human evolution has made tremendous advances in recent years. Two major trends characterize the development of the hominin clade subsequent to its origins with the advent of upright bipedalism in the Late Miocene of Africa. One is a diversification into two prominent morphological branches, each with a series of 'twigs' representing evolutionary experimentation at the species or subspecies level. The second important trend, which in its earliest manifestations cannot clearly be ascribed to one or the other branch, is the behavioral complexity of an increasing reliance on technology to expand upon limited inherent morphological specializations and to buffer the organism from its environment. This technological dependence is directly associated with the expansion of hominin range outside Africa by the genus Homo, and is accelerated in the sole extant form Homo sapiens through the last 100 Ka. There are interesting correlates between the evolutionary and behavioral patterns seen in the hominin clade and environmental dynamics of the Neogene. In particular, the tempo of morphological and behavioral innovation may be tracking major events in Neogene climatic development as well as reflecting intervals of variability or stability. Major improvements in analytical techniques, coupled with important new collections and a growing body of contextual data are now making possible the integration of global, regional and local environmental archives with an improved biological understanding of the hominin clade to address questions of coincidence and causality.

Feibel, C. S.

2004-12-01

407

An Analysis of Path-Vector Routing Protocol Convergence Algorithms  

Microsoft Academic Search

Today's Internet uses a path vector routing protocol, BGP, for global routing. After a connectivity change, a path vector protocol tends to explore a potentially large number of alternative paths before converging on new stable paths. Several techniques for improving path vector convergence have been proposed, however there has been no comparative analysis to judge the relative merit of each

Dan Pei; UCLA CSD; Beichuan Zhang; Dan Massey; Lixia Zhang

408

Broadband solar absorption enhancement via periodic nanostructuring of electrodes.  

PubMed

Solution processed colloidal quantum dot (CQD) solar cells have great potential for large area low-cost photovoltaics. However, light utilization remains low mainly due to the tradeoff between small carrier transport lengths and longer infrared photon absorption lengths. Here, we demonstrate a bottom-illuminated periodic nanostructured CQD solar cell that enhances broadband absorption without compromising charge extraction efficiency of the device. We use finite difference time domain (FDTD) simulations to study the nanostructure for implementation in a realistic device and then build proof-of-concept nanostructured solar cells, which exhibit a broadband absorption enhancement over the wavelength range of ? = 600 to 1,100 nm, leading to a 31% improvement in overall short-circuit current density compared to a planar device containing an approximately equal volume of active material. Remarkably, the improved current density is achieved using a light-absorber volume less than half that typically used in the best planar devices. PMID:24121519

Adachi, Michael M; Labelle, André J; Thon, Susanna M; Lan, Xinzheng; Hoogland, Sjoerd; Sargent, Edward H

2013-01-01

409

Nebular Hydrogen Absorption in the Ejecta of Eta Carinae  

NASA Technical Reports Server (NTRS)

Space Telescope Imaging Spectrograph (STIS) observations of Eta Carinae and immediate ejecta reveal narrow Balmer absorption lines in addition to the nebular-scattered broad P-Cygni absorptions. The narrow absorption correlates with apparent disk structure that separates the two Homunculus lobes. We trace these features about half way up the Northern lobe until the scattered stellar Balmer line doppler-shifts redward beyond the nebular absorption feature. Three-dimensional data cubes, made by mapping the Homunculus at Balmer alpha and Balmer beta with the 52 x 0.1 arcsecond aperture and about 5000 spectral resolving power, demonstrate that the absorption feature changes slowly in velocity with nebular position. We have monitored the stellar Balmer alpha line profile of the central source over the past four years. The equivalent width of the nebular absorption feature changes considerably between observations. The changes do not correlate with measured brightness of Eta Carinae. Likely clumps of neutral hydrogen with a scale size comparable to the stellar disk diameter are passing through the intervening light path on the timescales less than several months. The excitation mechanism involves Lyman alpha radiation (possibly the Lyman series plus Lyman continuum) and collisions leading to populating the 2S metastable state. Before the electron can jump to the ground state by two photon emission (lifetime about 1/8 second), a stellar Balmer photon is absorbed and the electron shifts to an NP level. We see the absorption feature in higher Balmer lines, and but not in Paschen lines. Indeed we see narrow nebular Paschen emission lines. At present, we do not completely understand the details of the absorption. Better understanding should lead to improved insight of the unique conditions around Eta Carinae that leads to these absorptions.

Gull, Theodore R.; Ishibashi, K.; Davidson, K.; Fisher, Richard R. (Technical Monitor)

2000-01-01

410

Infrared Absorption Spectroscopy Measurement of SOx using Tunable Infrared Laser  

NASA Astrophysics Data System (ADS)

The absorption characteristics of sulfur dioxide (SO2) and sulfur trioxide (SO3) in the infrared region were measured using a quantum cascade laser and an absorption cell of length 1 m heated to 150°C. The laser was scanned over the wavelength range 6.9-7.4 ?m, which included the absorption bands of SO2 and SO3. Measurement results showed that the absorption bands of SO2 and SO3 partially overlapped, with peaks at 7.28 ?m and 7.35 ?m for SO2 and 7.14 ?m and 7.25 ?m for SO3. These results showed the possbility of using infrared laser absorption spectroscopy for measurement of sulfur oxides (SOx) in flue gas. For SO3 measurement, infrared absorption spectroscopy was shown to be more suitable than ultraviolet absorption spectroscopy. The absorption characteristics of open air in the same wavelength region showed that the interference due to water vapor must be efficiently removed to perform SOx measurement in flue gas.

Fukuchi, Tetsuo

411

Atmospheric Precorrected Differential Absorption technique to retrieve columnar water vapor  

SciTech Connect

Differential absorption techniques are suitable to retrieve the total column water vapor contents from imaging spectroscopy data. A technique called Atmospheric Precorrected Differential Absorption (APDA) is derived directly from simplified radiative transfer equations. It combines a partial atmospheric correction with a differential absorption technique. The atmospheric path radiance term is iteratively corrected during the retrieval of water vapor. This improves the results especially over low background albedos. The error of the method for various ground reflectance spectra is below 7% for most of the spectra. The channel combinations for two test cases are then defined, using a quantitative procedure, which is based on MODTRAN simulations and the image itself. An error analysis indicates that the influence of aerosols and channel calibration is minimal. The APDA technique is then applied to two AVIRIS images acquired in 1991 and 1995. The accuracy of the measured water vapor columns is within a range of {+-}5% compared to ground truth radiosonde data.

Schlaepfer, D.; Itten, K.I. [Univ. of Zuerich (Switzerland). Dept. of Geography] [Univ. of Zuerich (Switzerland). Dept. of Geography; Borel, C.C. [Los Alamos National Lab., NM (United States)] [Los Alamos National Lab., NM (United States); Keller, J. [Paul Scherrer Inst., Villigen (Switzerland)] [Paul Scherrer Inst., Villigen (Switzerland)

1998-09-01

412

Dinosaur Skull and Body Length Predictions  

NSDL National Science Digital Library

In this activity (located on page 2 of PDF), learners will look for a relationship between skull size and body length among various dinosaurs. Starting from a list of dinosaur measurements, learners will compare dinosaur sizes to common objects and create a chart that plots body length against skull length to see if the data predicts other dinosaurs' length from skull size. Relates to the linked video, DragonflyTV GPS: Baby Dinosaurs.

Twin Cities Public Television, Inc.

2007-01-01

413

Broadband polarization-independent resonant light absorption using ultrathin plasmonic super absorbers.  

PubMed

Resonant plasmonic and metamaterial structures allow for control of fundamental optical processes such as absorption, emission and refraction at the nanoscale. Considerable recent research has focused on energy absorption processes, and plasmonic nanostructures have been shown to enhance the performance of photovoltaic and thermophotovoltaic cells. Although reducing metallic losses is a widely sought goal in nanophotonics, the design of nanostructured 'black' super absorbers from materials comprising only lossless dielectric materials and highly reflective noble metals represents a new research direction. Here we demonstrate an ultrathin (260 nm) plasmonic super absorber consisting of a metal-insulator-metal stack with a nanostructured top silver film composed of crossed trapezoidal arrays. Our super absorber yields broadband and polarization-independent resonant light absorption over the entire visible spectrum (400-700 nm) with an average measured absorption of 0.71 and simulated absorption of 0.85. Proposed nanostructured absorbers open a path to realize ultrathin black metamaterials based on resonant absorption. PMID:22044996

Aydin, Koray; Ferry, Vivian E; Briggs, Ryan M; Atwater, Harry A

2011-01-01

414

Computational investigation of carbon dioxide absorption in alkanolamine solutions.  

PubMed

We investigated CO2 absorption in aqueous alkanolamine solutions using density functional theory with dielectric continuum solvation models (SMD/IEF-PCM and COSMO-RS). We varied the alkyl chain length (m?=?2, 3, 4) and the alcohol chain length (n?=?2, 3, 4) in the alkanolamine structures, H(CH2) m NH(CH2) n OH. Using the SMD/IEF-PCM/B3LYP/6-311++G(d,p) and COSMO-RS/BP/TZVP levels of theory, our calculations predict that the product of CO2 absorption (carbamate or bicarbonate) is strongly affected by the alcohol length but does not differ significantly by varying the alkyl chain length. This prediction was confirmed experimentally by (13)C-NMR. The observed sensitivity to the alcohol chain length can be attributed to hydrogen bonding effects. The intramolecular hydrogen bonds of HN · · · HO, NH2 (+) · · · OH, and NCOO(-) · · · HO induce ring structure formation in neutral alkanolamines, protonated alkanolamines, and carbamate anions, respectively. The results from our studies demonstrate that intramolecular hydrogen bonds play a key role in CO2 absorption reactions in aqueous alkanolamine solutions. PMID:23306736

Yamada, Hidetaka; Matsuzaki, Yoichi; Chowdhury, Firoz; Higashii, Takayuki

2013-10-01

415

69. INTERIOR VIEW OF THE ABSORPTION TOWER BUILDING, ABSORPTION TOWER ...  

Library of Congress Historic Buildings Survey, Historic Engineering Record, Historic Landscapes Survey

69. INTERIOR VIEW OF THE ABSORPTION TOWER BUILDING, ABSORPTION TOWER UNDER CONSTRUCTION. (DATE UNKNOWN). - United States Nitrate Plant No. 2, Reservation Road, Muscle Shoals, Muscle Shoals, Colbert County, AL

416

Effect of defoliation upon root growth, phosphate absorption and respiration in nutrient-limited tundra graminoids  

Microsoft Academic Search

Moderate experimental defoliation stimulated root respiration and phosphate absorption in two tundra graminoids, Eriophorum vaginatum and Carex aquatilis, growing under nutrient-limited field conditions in northern Alaska. The increase in phosphate absorption rate following defoliation of Eriophorum was associated with a decrease in root phosphate and available carbohydrate contents per unit root length but a constant root nitrogen content. Only after

F. Stuart Chapin; Mari Slack

1979-01-01

417

The Water-Vapor Continuum Absorption in the Mid-Infrared Windows at Temperatures from 311 K to 363 K  

NASA Astrophysics Data System (ADS)

The water-vapor continuum absorption in the mid-infrared 10 ?m and 4 ?m atmospheric windows plays an important role in the radiative balance of the Earth. We have derived the continuum absorption coefficients from spectra recorded at NIST with a resolution of 0.1 wn over a wide range of pressures from 2.8 kPa (21 torr) to 15.1 kPa (113 torr) and temperatures from 311 K to 363 K with path lengths ranging from 74 to 116 m. These measurements were performed with a BOMEM DA3-002 FTIR spectrometer with a 2 m base multi-pass cell. The spectral range was from 800 to 3500 wn . We have published the results obtained in the 10 ?m region recently. At the conditions given above, the continuum absorption in the higher frequency atmospheric window is quite detectable reaching as high as 4%. In order to avoid mistakes caused by the non-linear behavior of a MCT detector we later recorded an additional set of spectra with a highly-linear InSb detector. Both sets of spectra provide absorption coefficients coinciding within error bars. Our results around 5 ?m are in good agreement with those obtained from the widely used MT-CKD continuum model. However, at shorter wave lengths, the values diverge dramatically increasing up to one order of magnitude at the center of the window. Despite the comparatively large uncertainties of our data, comparison with all other available results leads us to the conclusion that the MT-CKD model greatly underestimates the self-broadened continuum over the 4 ?m atmospheric window. We have also extended our measurements to lower frequencies with the use of KRS-5 cell windows. The current spectral range is down to 600 wn. Yu. I. Baranov, W. J. Lafferty, Q. Ma, R. H. Tipping, JQSRT 109, 2291, (2008) S. A. Clough, F. X. Kneizys, and R. W. Davies, Atmos. Res. 23, 229, (1989)

Baranov, Yu. I.; Lafferty, W. J.

2009-06-01

418

Oral Drug Absorption  

E-print Network

Stability 0 20 40 60 80 100 25 10 5 1 0.5 size? r 0 (?m) Fr action absor b ed in hum an (% ) Peff =5.0 Peff =3.0 Peff =1.0 Peff =0.5 Peff =0.1 Solubility? Cs = 1.0 (?g/ml) Effect of micronization on intestinal absorption of poorly soluble drugs Peff... ?? permeability to human intestine? (cm/sec x 10 -4 ) 8 Effect of Solubility on intestinal absorption of poorly soluble drugs Cs (?g/ml) 0 5 10 15 50 Fr action absor b ed in hum an (% ) 0 20 40 60 80 100 Peff =5.0 Peff =3.0 Peff =1.0 Peff =0.5 Peff =0.1 r 0 = 1...

Yamashita, Shinji

2006-10-26

419

Transports along paths in Fibre Bundles. I. General Theory  

E-print Network

Transports along path in fibre bundles are axiomatically introduced. Their general functional form and some their simple properties are investigated. The relationships of the transports along paths and lifting of paths are studied.

Bozhidar Z. Iliev

2005-03-01

420

Pathways of iron absorption.  

PubMed

Iron is vital for all living organisms but excess iron can be lethal because it facilitates free radical formation. Thus iron absorption is carefully regulated to maintain an equilibrium between absorption and body loss of iron. In countries where meat is a significant part of the diet, most body iron is derived from dietary heme because heme binds few of the dietary chelators that bind inorganic iron. Uptake of heme into enterocytes occurs as a metalloporphyrin in an endosomal process. Intracellular iron is released from heme by heme oxygenase to enter plasma as inorganic iron. Ferric iron is absorbed via a beta(3) integrin and mobilferrin pathway (IMP) which is unshared with other nutritional metals. Ferrous iron uptake is facilitated by a DMT-1 pathway which is shared with manganese. In the iron deficient gut, large quantities of both mobilferrin and DMT-1 are found in goblet cells and intraluminal mucins suggesting that they are secreted with mucin into the intestinal lumen to bind iron to facilitate uptake by the cells. In the cytoplasm, IMP and DMT associate in a large protein complex called paraferritin which serves as a ferrireductase. Paraferritin solublizes iron binding proteins and reduces iron to make iron available for production of iron containing proteins such as heme. Iron uptake by intestinal absorptive cells is regulated by the iron concentration within the cell. Except in hemochromatosis it remains in equilibrium with total body stores via transferrin receptors on the basolateral membrane of absorptive cells. Increased intracellular iron either up-regulates or satiates iron binding proteins on regulatory proteins to alter their location in the intestinal mucosa. PMID:12547224

Conrad, Marcel E; Umbreit, Jay N

2002-01-01

421

QSO Lyman limit absorption  

Microsoft Academic Search

The redshift distribution of QSO absorption systems which are optically thick in the Lyman continuum matches that of a nonevolving population of absorbers in a standard Friedmann cosmological model over the redshift range 0.4-3.5. The density of absorbers per unit velocity in the QSO rest frame is roughly constant for v\\/c between -0.001 to 0.2 and shows a rapid increase

David Tytler

1982-01-01

422

Realistic Human Walking Paths David C. Brogan  

E-print Network

development for entertainment applications and many classes of simulations. We present a novel behav- ioral- served paths in black on the floor. A library exit (a) and a university hallway (b). A realistic walking

Brogan, David

423

Riemann Curvature Tensor and Closed Geodesic Paths  

ERIC Educational Resources Information Center

Demonstrates erroneous results obtained if change in a vector under parallel transport about a closed path in Riemannian spacetime is made in a complete circuit rather than just half a circuit. (Author/SL)

Morganstern, Ralph E.

1977-01-01

424

Cooperative optimal path planning for herding problems  

E-print Network

destination following weighted time-optimal and effort-optimal control paths. Simulation of this herding problem is accomplished through dynamic programming by utilizing the SNOPT software in the MATLAB environment. The numerical solution gives us the optimal...

Lu, Zhenyu

2009-05-15

425

Path integration in relativistic quantum mechanics  

E-print Network

The simple physics of a free particle reveals important features of the path-integral formulation of relativistic quantum theories. The exact quantum-mechanical propagator is calculated here for a particle described by the simple relativistic action proportional to its proper time. This propagator is nonvanishing outside the light cone, implying that spacelike trajectories must be included in the path integral. The propagator matches the WKB approximation to the corresponding configuration-space path integral far from the light cone; outside the light cone that approximation consists of the contribution from a single spacelike geodesic. This propagator also has the unusual property that its short-time limit does not coincide with the WKB approximation, making the construction of a concrete skeletonized version of the path integral more complicated than in nonrelativistic theory.

Ian H. Redmount; Wai-Mo Suen

1992-10-28

426

How Do Paths Look From Different Perspectives?  

NSDL National Science Digital Library

Using both literature (a book featuring a path, such as Little Red Riding Hood) and satellite images, students will identify paths, observe and analyze them from different altitudes, and distinguish natural paths from those made by humans. Students will learn how images can inform the building, use and maintenance of paths. The URL opens to the investigation directory, with links to teacher and student materials, lesson extensions, resources, teaching tips, and assessment strategies. This is Investigation 2 of four found in the Grades K-4 Module 4 of Mission Geography. The Mission Geography curriculum integrates data and images from NASA missions with the National Geography Standards. Each of the four investigations in Module 4, while related, can be done independently. Please see Investigation 1 of this module for a two-page module overview and list of all standards addressed.

427

Predicting missing links via effective paths  

NASA Astrophysics Data System (ADS)

Recently, in complex network, link prediction has brought a surge of researches, among which similarity based link prediction outstandingly gains considerable success, especially similarity in terms of paths. In investigation of paths based similarity, we find that the effective influence of endpoints and strong connectivity make paths contribute more similarity between two unconnected endpoints, leading to a more accurate link prediction. Accordingly, we propose a so-called effective path index (EP) in this paper to leverage effective influence of endpoints and strong connectivity in similarity calculation. For demonstrating excellence of our index, the comparisons with six mainstream indices are performed on experiments in 15 real datasets and results show a great improvement of performance via our index.

Zhu, Xuzhen; Tian, Hui; Cai, Shimin

2014-11-01

428

An Alternate Path To Stoichiometric Problem Solving.  

ERIC Educational Resources Information Center

Discusses an alternate path to teaching introductory stoichiometry based on research findings. The recommendation is to use problems that can be solved easily by rapid mental calculation as well as by pure logic. (AIM)

Schmidt, Hans-Jurgen

1997-01-01

429

IRIS Optical Instrument and Light Paths  

NASA Video Gallery

The optical portion of the instrument and the light paths from the primary and secondary mirror of the telescope assembly into the spectrograph. The spectrograph then breaks the light into 2 Near U...

430

Identifying decohering paths in closed quantum systems  

NASA Technical Reports Server (NTRS)

A specific proposal is discussed for how to identify decohering paths in a wavefunction of the universe. The emphasis is on determining the correlations among subsystems and then considering how these correlations evolve. The proposal is similar to earlier ideas of Schroedinger and of Zeh, but in other ways it is closer to the decoherence functional of Griffiths, Omnes, and Gell-Mann and Hartle. There are interesting differences with each of these which are discussed. Once a given coarse-graining is chosen, the candidate paths are fixed in this scheme, and a single well defined number measures the degree of decoherence for each path. The normal probability sum rules are exactly obeyed (instantaneously) by these paths regardless of the level of decoherence. Also briefly discussed is how one might quantify some other aspects of classicality. The important role that concrete calculations play in testing this and other proposals is stressed.

Albrecht, Andreas

1990-01-01

431

Building a path in cell biology  

E-print Network

Setting up a new lab is an exciting but challenging prospect. We discuss our experiences in finding a path to tackle some of the key current questions in cell biology and the hurdles that we have encountered along the way.

Cheeseman, Iain McPherson

432

Non-classical paths in interference experiments  

E-print Network

In a double slit interference experiment, the wave function at the screen with both slits open is not exactly equal to the sum of the wave functions with the slits individually open one at a time. The three scenarios represent three different boundary conditions and as such, the superposition principle should not be applicable. However, most well known text books in quantum mechanics implicitly and/or explicitly use this assumption which is only approximately true. In our present study, we have used the Feynman path integral formalism to quantify contributions from non-classical paths in quantum interference experiments which provide a measurable deviation from a naive application of the superposition principle. A direct experimental demonstration for the existence of these non-classical paths is hard. We find that contributions from such paths can be significant and we propose simple three-slit interference experiments to directly confirm their existence.

Sawant, Rahul; Sinha, Aninda; Sinha, Supurna; Sinha, Urbasi

2014-01-01

433

Nonclassical paths in quantum interference experiments.  

PubMed

In a double slit interference experiment, the wave function at the screen with both slits open is not exactly equal to the sum of the wave functions with the slits individually open one at a time. The three scenarios represent three different boundary conditions and as such, the superposition principle should not be applicable. However, most well-known text books in quantum mechanics implicitly and/or explicitly use this assumption that is only approximately true. In our present study, we have used the Feynman path integral formalism to quantify contributions from nonclassical paths in quantum interference experiments that provide a measurable deviation from a naive application of the superposition principle. A direct experimental demonstration for the existence of these nonclassical paths is difficult to present. We find that contributions from such paths can be significant and we propose simple three-slit interference experiments to directly confirm their existence. PMID:25279612

Sawant, Rahul; Samuel, Joseph; Sinha, Aninda; Sinha, Supurna; Sinha, Urbasi

2014-09-19

434

A chemist building paths to cell biology.  

PubMed

Galileo is reported to have stated, "Measure what is measurable and make measurable what is not so." My group's trajectory in cell biology has closely followed this philosophy, although it took some searching to find this path. PMID:24174456

Weibel, Douglas B

2013-11-01

435

A chemist building paths to cell biology  

PubMed Central

Galileo is reported to have stated, “Measure what is measurable and make measurable what is not so.” My group's trajectory in cell biology has closely followed this philosophy, although it took some searching to find this path. PMID:24174456

Weibel, Douglas B.

2013-01-01

436

Nonclassical Paths in Quantum Interference Experiments  

NASA Astrophysics Data System (ADS)

In a double slit interference experiment, the wave function at the screen with both slits open is not exactly equal to the sum of the wave functions with the slits individually open one at a time. The three scenarios represent three different boundary conditions and as such, the superposition principle should not be applicable. However, most well-known text books in quantum mechanics implicitly and/or explicitly use this assumption that is only approximately true. In our present study, we have used the Feynman path integral formalism to quantify contributions from nonclassical paths in quantum interference experiments that provide a measurable deviation from a naive application of the superposition principle. A direct experimental demonstration for the existence of these nonclassical paths is difficult to present. We find that contributions from such paths can be significant and we propose simple three-slit interference experiments to directly confirm their existence.

Sawant, Rahul; Samuel, Joseph; Sinha, Aninda; Sinha, Supurna; Sinha, Urbasi

2014-09-01

437

Unified classical path theories of pressure broadening  

Microsoft Academic Search

A unified classical path theory of pressure broadening is derived using only elementary concepts. It is shown that the theory of Smith, Cooper and Vidal is only correct at all frequencies to first order in the number density of perturbers.

C. Bottcher

1971-01-01

438

Orbital Path of the International Space Station  

NASA Video Gallery

Astronauts Don Pettit, Andre Kuipers and Dan Burbank explain the orbital path of the International Space Station. Earth video credit: Image Science and Analysis Laboratory, NASA's Johnson Space Cen...

439

Animation: Path of 2010 Solar Eclipse  

NASA Video Gallery

On Sunday, 2010 July 11, a total eclipse of the Sun is visible from within a narrow corridor that traverses Earth's southern hemisphere. The path of the Moon's umbral shadow crosses the South Pacif...

440

Chromatin repeat length in somatic hybrids.  

PubMed Central

In order to study the mechanisms by which a characteristic repeat length is inherited in somatic cells, it was necessary to develop a method for determining repeat length with a precision of 1 to 2 base pairs. Hybrid clones between parental cell lines differing in repeat length by 6 base pairs were isolated. The four independent hybrid clones characterized had repeat lengths intermediate between those of the parental lines; however, it could be demonstrated that these repeat lengths are unique values and do not arise from a double distribution of the parental repeat lengths. It therefore is concluded that repeat length in somatic cells is determined by a common pool of diffusible substances. Images PMID:6930661

Sperling, L; Tardieu, A; Weiss, M C

1980-01-01

441

Multi-chord fiber-coupled interferometer with a long coherence length laser for the Plasma Liner Experiment  

E-print Network

This paper describes a 561 nm laser heterodyne interferometer that provides time-resolved measurements of line-integrated plasma electron density within the range of 10^15-10^18 cm^(-2). Such plasmas are produced by railguns on the Plasma Liner Experiment (PLX), which aims to produce $\\mu$s-, cm-, and Mbar-scale plasmas through the merging of thirty plasma jets in a spherically convergent geometry. A long coherence length, 320 mW laser allows for a strong, sub-fringe phase-shift signal without the need for closely-matched probe and reference path lengths. Thus only one reference path is required for all eight probe paths, and an individual probe chord can be altered without altering the reference or other probe path lengths. Fiber-optic decoupling of the probe chord optics on the vacuum chamber from the rest of the system allows the probe paths to be easily altered to focus on different spatial regions of the plasma. We demonstrate that sub-fringe resolution capability allows the interferometer to operate dow...

Merritt, Elizabeth C; Gilmore, Mark A; Hsu, Scott C

2011-01-01

442

Corrosion Problems in Absorption Chillers  

ERIC Educational Resources Information Center

Absorption chillers use a lithium bromide solution as the medium of absorption and water as the refrigerant. Discussed are corrosion and related problems, tests and remedies, and cleaning procedures. (Author/MLF)

Stetson, Bruce

1978-01-01

443

corotating interaction cosmic noise absorption  

E-print Network

Keywords corotating interaction regions cosmic noise absorption electron precipitation high speed absorption (CNA) as a proxy for the precipitation. The arrival of the co-rotating interaction region (CIR

Ulich, Thomas

444

Potential energy surface exploration with equilibrial paths. Part I: Theory  

Microsoft Academic Search

The equilibrial path concept is further developed. Special attention is spent the symmetry conservation along equilibrial paths and symmetry-breaking. Symmetry-breaking can occur only at singular points. The simple singular points of an equilibrial path are valley–ridge inflection points. In contrast to the intrinsic reaction paths and the gradient extremal paths, the equilibrial paths enable to describe the branching of reaction

Wolfgang Kliesch

2000-01-01

445

Highway Hierarchies Hasten Exact Shortest Path Queries  

Microsoft Academic Search

\\u000a We present a new speedup technique for route planning that exploits the hierarchy inherent in real world road networks. Our\\u000a algorithm preprocesses the eight digit number of nodes needed for maps of the USA or Western Europe in a few hours using linear\\u000a space. Shortest (i.e. fastest) path queries then take around eight milliseconds to produce exact shortest paths. This

Peter Sanders; Dominik Schultes

2005-01-01

446

Path Selection and Multipath Congestion Control  

Microsoft Academic Search

In this paper we investigate the potential benefits of coordinated congestion control for multipath data transfers, and contrast with uncoordinated control. For static random path selections, we show the worst-case throughput performance of uncoordinated control behaves as if each user had but a single path (scaling like log(log(N ))\\/ log(N ) where N is the system size, measured in number

Peter B. Key; Laurent Massoulié; Donald F. Towsley

2007-01-01

447

Path-integral formulation of ion heating  

SciTech Connect

A description of the generation and evolution of ionospheric oxygen-ion conic distributions by electromagnetic ion-cyclotron-resonance heating is formulated in terms of a path integral. All of the relevant physics is contained in this path integral, which may be used to calculate measurable properties of the conic distribution. Although the presentation is applied to this specific ionospheric context, the treatment may be generalized to treat other diffusion problems of interest.

Crew, G.B.; Chang, T.

1986-11-01

448

Steam Path Audits on Industrial Steam Turbines  

E-print Network

exhaust, fuel to heat the steam is not a direct cost to producing power in the steam turbine. Increasing turbine efficiency, therefore, benefits the Lyondell facility by increasing power output. DESCRIPTION OF THE STEAM PATH AUDIT The basic approach... National Industrial Energy Technology Conference, Houston, TX, April 22-23, 1992 ---------- ---------- steam path after the initial turbine inlet. The extraction valves cause a large pressure drop between the exhaust of stage 2 and the inlet to stage 3...

Mitchell, D. R.

449

Walden's Paths quiz: system design and implementation  

E-print Network

WAI. DEN'S PATHS QUIZ: SYSTEM DESIGN AND IMPLEMENTATION A Thesis by AVITAL JAYANT ARORA Submitted to the Offtce of Graduate Studies of Texas AJtM University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE... WAI. DEN'S PATHS QUIZ: SYSTEM DESIGN AND IMPLEMENTATION A Thesis by AVITAL JAYANT ARORA Submitted to the Offtce of Graduate Studies of Texas AJtM University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE...

Arora, Avital Jayant

2012-06-07

450

Path Loss For Short Range Telemetry  

Microsoft Academic Search

The popular Friis transmission formula is used to evaluate the amount of path loss in free space between the transmit and\\u000a receive antennas for the design of wireless transceivers. It is could be also used to estimate the path loss for the link\\u000a of the on-body network when there is no barrier and no body surface in between. Paying special

Yong Liu; Kairaz Contractor; Yunjuan Kang

451

Landmobile satellite excess path loss measurements  

Microsoft Academic Search

This paper describes an experiment conducted with the ATS-6 satellite to determine the additional path loss over free-space loss experienced by land-mobile communication links. This excess path loss is measured as a function of (1) local environment, (2) vehicle heading, (3) link frequency, (4) satellite elevation angle, and (5) street side. An excess loss model developed from the data shows

Garry C. Hess

1979-01-01

452

Landmobile satellite excess path loss measurements  

Microsoft Academic Search

An experiment conducted with the ATS-6 satellite to determine the additional path loss over free-space loss experienced by land-mobile communication links is described. This excess path loss is measured as a function of 1) local environment, 2) vehicle heading, 3) link frequency, 4) satellite elevation angle, and 5) street side. A statistical description of excess loss developed from the data

GARRY C. HESS

1980-01-01

453

A Path Algorithm for Constrained Estimation  

PubMed Central

Many least-square problems involve affine equality and inequality constraints. Although there are a variety of methods for solving such problems, most statisticians find constrained estimation challenging. The current article proposes a new path-following algorithm for quadratic programming that replaces hard constraints by what are called exact penalties. Similar penalties arise in l1 regularization in model selection. In the regularization setting, penalties encapsulate prior knowledge, and penalized parameter estimates represent a trade-off between the observed data and the prior knowledge. Classical penalty methods of optimization, such as the quadratic penalty method, solve a sequence of unconstrained problems that put greater and greater stress on meeting the constraints. In the limit as the penalty constant tends to ?, one recovers the constrained solution. In the exact penalty method, squared penalties!are replaced by absolute value penalties, and the solution is recovered for a finite value of the penalty constant. The exact path-following method starts at the unconstrained solution and follows the solution path as the penalty constant increases. In the process, the solution path hits, slides along, and exits from the various constraints. Path following in Lasso penalized regression, in contrast, starts with a large value of the penalty constant and works its way downward. In both settings, inspection of the entire solution path is revealing. Just as with the Lasso and generalized Lasso, it is possible to plot the effective degrees of freedom along the solution path. For a strictly convex quadratic program, the exact penalty algorithm can be framed entirely in terms of the sweep operator of regression analysis. A few well-chosen examples illustrate the mechanics and potential of path following. This article has supplementary materials available online. PMID:24039382

Zhou, Hua; Lange, Kenneth

2013-01-01

454

New England Forests: The Path to Sustainability  

E-print Network

New England Forests: The Path to Sustainability A R E P O R T B Y N E W E N G L A N D F O R E S T R Y F O U N D A T I O N #12;#12;New England Forests: The Path to Sustainability Forests define New tree in a town or state park? Forests are part of New Englanders' daily lives. Nearly all of us rely

Wolfe, Patrick J.

455

Affinity Paths and Information Diffusion in Social Networks  

E-print Network

Widespread interest in the diffusion of information through social networks has produced a large number of Social Dynamics models. A majority of them use theoretical hypothesis to explain their diffusion mechanisms while the few empirically based ones average out their measures over many messages of different content. Our empirical research tracking the step-by-step email propagation of an invariable viral marketing message delves into the content impact and has discovered new and striking features. The topology and dynamics of the propagation cascades display patterns not inherited from the email networks carrying the message. Their disconnected, low transitivity, tree-like cascades present positive correlation between their nodes probability to forward the message and the average number of neighbors they target and show increased participants' involvement as the propagation paths length grows. Such patterns not described before, nor replicated by any of the existing models of information diffusion, can be e...

Iribarren, José Luis; 10.1016/j.socnet.2010.11.003

2011-01-01

456

SNAPP: Stateless Network-Authenticated Path Pinning  

E-print Network

This paper examines a new building block for next-generation networks: SNAPP, or Stateless Network-Authenticated Path Pinning. SNAPP-enabled routers securely embed their routing decisions in the packet headers of a stream of traffic, effectively pinning a flow’s path between sender and receiver. A sender can use the pinned path (even if routes subsequently change) by including the path embedding in later packet headers. This architectural building block decouples routing from forwarding, which greatly enhances the availability of a path in the face of routing misconfigurations or malicious attacks. To demonstrate the extreme flexibility of SNAPP, we show how it can support a wide range of applications, including sender-controlled paths, expensive route lookups, sender anonymity, and sender accountability. Our analysis shows that SNAPP’s overhead is low, and the system is easily implemented in hardware. We believe that SNAPP is a worthy addition to the network architect’s toolbox, enabling a variety of new designs and trade-offs.

Bryan Parno; Adrian Perrig; Dave Andersen

2008-01-01

457

Quantum cosmology based on discrete Feynman paths  

SciTech Connect

Although the rules for interpreting local quantum theory imply discretization of process, Lorentz covariance is usually regarded as precluding time quantization. Nevertheless a time-discretized quantum representation of redshifting spatially-homogeneous universe may be based on discrete-step Feynman paths carrying causal Lorentz-invariant action--paths that not only propagate the wave function but provide a phenomenologically-promising elementary-particle Hilbert-space basis. In a model under development, local path steps are at Planck scale while, at a much larger ''wave-function scale'', global steps separate successive wave-functions. Wave-function spacetime is but a tiny fraction of path spacetime. Electromagnetic and gravitational actions are ''at a distance'' in Wheeler-Feynman sense while strong (color) and weak (isospin) actions, as well as action of particle motion, are ''local'' in a sense paralleling the action of local field theory. ''Nonmaterial'' path segments and ''trivial events'' collaborate to define energy and gravity. Photons coupled to conserved electric charge enjoy privileged model status among elementary fermions and vector bosons. Although real path parameters provide no immediate meaning for ''measurement'', the phase of the complex wave function allows significance for ''information'' accumulated through ''gentle'' electromagnetic events involving charged matter and ''soft'' photons. Through its soft-photon content the wave function is an ''information reservoir''.

Chew, Geoffrey F.

2002-10-10

458

The Near Infrared Absorption Spectrum of Water by CRDS Between 1.26-1.70 µm:Complete Empirical Line List and Continuum Absorption  

NASA Astrophysics Data System (ADS)

Due to the increasing performances of Airborne- and ground-based spectrometers, a more and more accurate characterization of the water vapor absorption is required. This is especially true in the transparency windows, corresponding to low absorption spectral regions widely used for probing the Earth's atmosphere. State-of-the-art experimental developments are required to fulfill the needs in terms of accuracy of the spectroscopic data. For that purpose, we are using high-sensitivity Continuous Wave Cavity Ring Down Spectroscopy (CW-CRDS) allowing reproducing in laboratory conditions comparable to the atmospheric ones in terms of absorption path length (tens of kilometers), temperature and pressure. From extensive analysis of our CRDS spectra, we have constructed an empirical line list for "natural" water vapor at 296 K in the 5850 7920 cm-1 region including 38 318 transitions of four major water isotopologues (H2 16O, H218O, H217O and HD16O) with an intensity cut-off of 1·10-29 cm/molecule. The list is made mostly complete over the whole spectral region by including a large number of unobserved weak lines with positions calculated using experimentally determined energy levels and intensities obtained from variational calculations. In addition, we provide HD18O and HD 17O lists in the same region for transitions with intensities larger than 1·10-29 cm/molecule. The HD18O and HD17O lists (1 972 lines in total) were obtained using empirical energy levels available in the literature and variational intensities. The global list (40 290 transitions) including the contribution of the six major isotopologues has been adopted for the new edition of the GEISA database in the region. The advantages and drawbacks of our list will be discussed in comparison with the list provided for the same region in the 2012 edition of the HITRAN database. Separate experiments were dedicated to the measurement of the water vapor self-continuum crosssections in the 1.6 µm window by CW-CRDS at different temperatures (from room temperature to 340 K). Due to the weakness of the broadband absorption signal to be measured, very few measurements of the water vapor continuum are available in the NIR windows especially for temperature conditions relevant for our atmosphere. This is in particular the case for the 1.6 µm window where the very few available measurements show a large disagreement. The absorption cross-sections, Cs(?, T), were retrieved for different selected wave numbers from a fit of the absorption coefficients measured in real time during pressure ramps, after subtraction of the contributions of the local water monomer lines and of water adsorbed on the CRDS mirrors. The values measured between 5875 and 6665 cm-1 range between 1.5·10-25 and 2·10-24 cm2 molec-1 atm-1 with a minimum around 6300 cm-1. Overall, our measurements are found in strong disagreement with recent FTS measurements and in a good agreement with the values predicted by the MT CKD2.5 model, except for the temperature dependence in the center of the window which is found significantly smaller than predicted.

Mondelain, Didier; Campargue, Alain; Kassi, Samir; Mikhailenko, Semen

2014-06-01

459

Evolutionary paths to mammalian cochleae.  

PubMed

Evolution of the cochlea and high-frequency hearing (>20 kHz; ultrasonic to humans) in mammals has been a subject of research for many years. Recent advances in paleontological techniques, especially the use of micro-CT scans, now provide important new insights that are here reviewed. True mammals arose more than 200 million years (Ma) ago. Of these, three lineages survived into recent geological times. These animals uniquely developed three middle ear ossicles, but these ossicles were not initially freely suspended as in modern mammals. The earliest mammalian cochleae were only about 2 mm long and contained a lagena macula. In the multituberculate and monotreme mammalian lineages, the cochlea remained relatively short and did not coil, even in modern representatives. In the lineage leading to modern therians (placental and marsupial mammals), cochlear coiling did develop, but only after a period of at least 60 Ma. Even Late Jurassic mammals show only a 270 ° cochlear coil and a cochlear canal length of merely 3 mm. Comparisons of modern organisms, mammalian ancestors, and the state of the middle ear strongly suggest that high-frequency hearing (>20 kHz) was not realized until the early Cretaceous (~125 Ma). At that