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1

Lambert Absorption Coefficients of Water in the Infrared.  

National Technical Information Service (NTIS)

By use of a wedge-shaped cell providing an absorbing layer tapering in thickness from less than one wavelength of visible light at one end to approximately 20 micrometers at the other end, the Lambert absorption coefficient for water in the spectral regio...

C. W. Robertson D. Williams

1971-01-01

2

Determination of RW3-to-water mass-energy absorption coefficient ratio for absolute dosimetry.  

PubMed

The measurement of absorbed dose to water in a solid-phantom may require a conversion factor because it may not be radiologically equivalent to water. One phantom developed for the use of dosimetry is a solid water, RW3 white-polystyrene material by IBA. This has a lower mass-energy absorption coefficient than water due to high bremsstrahlung yield, which affects the accuracy of absolute dosimetry measurements. In this paper, we demonstrate the calculation of mass-energy absorption coefficient ratios, relative to water, from measurements in plastic water and RW3 with an Elekta Synergy linear accelerator (6 and 10 MV photon beams) as well as Monte Carlo modeling in BEAMnrc and DOSXYZnrc. From this, the solid-phantom-to-water correction factor was determined for plastic water and RW3. PMID:21960410

Seet, Katrina Y T; Hanlon, Peta M; Charles, Paul H

2011-12-01

3

Diffusion coefficients of water and leachables in methacrylate-based crosslinked polymers using absorption experiments.  

PubMed

The diffusion of water into dentin adhesive polymers and leaching of unpolymerized monomer from the adhesive are linked to their mechanical softening and hydrolytic degradation. Therefore, diffusion coefficient data are critical for the mechanical design of these polymeric adhesives. In this study, diffusion coefficients of water and leachables were obtained for sixteen methacrylate-based crosslinked polymers using absorption experiments. The experimental mass change data was interpreted using numerical solution of the two-dimensional diffusion equations. The calculated diffusion coefficients varied from 1.05 × 10(-8) cm(2)/sec (co-monomer TMTMA) to 3.15 × 10(-8) cm(2)/sec (co-monomer T4EGDMA). Correlation of the diffusion coefficients with crosslink density and hydrophilicity showed an inverse trend (R(2) = 0.41). The correlation of diffusion coefficient with crosslink density and hydrophilicity are closer for molecules differing by simple repeat units (R(2) = 0.95). These differences in the trends reveal mechanisms of interaction of the diffusing water with the polymer structure. PMID:22430592

Parthasarathy, Ranganathan; Misra, Anil; Park, Jonggu; Ye, Qiang; Spencer, Paulette

2012-05-01

4

Absorption and backscattering coefficients and their relations to water constituents of Poyang Lake, China.  

PubMed

The measurement and analysis of inherent optical properties (IOPs) of the main water constituents are necessary for remote-sensing-based water quality estimation and other ecological studies of lakes. This study aimed to measure and analyze the absorption and backscattering coefficients of the main water constituents and, further, to analyze their relations to the water constituent concentrations in Poyang Lake, China. The concentrations and the absorption and backscattering coefficients of the main water constituents at 47 sampling sites were measured and analyzed as follows. (1) The concentrations of chlorophyll a (C(CHL)), dissolved organic carbon (C(DOC)), suspended particulate matter (C(SPM)), including suspended particulate inorganic matter (C(SPIM)) and suspended particulate organic matter (C(SPOM)), and the absorption coefficients of total particulate (a(p)), phytoplankton (a(ph)), nonpigment particulate (a(d)), and colored/chromophoric dissolved organic matter (a(g)) were measured in the laboratory. (2) The total backscattering coefficients, including the contribution of pure water at six wavelengths of 420, 442, 470, 510, 590, and 700 nm, were measured in the field with a HydroScat-6 backscattering sensor. (3) The backscattering coefficients without the contribution of pure water (b(b)) were then derived by subtracting the backscattering coefficients of pure water from the total backscattering coefficients. (4) The C(CHL), C(SPM), C(SPIM), C(SPOM), and C(DOC) of the 41 remaining water samples were statistically described and their correlations were analyzed. (5) The a(ph), a(d), a(p), a(g), and b(b) were visualized and analyzed, and their relations to C(CHL), C(SPM), C(SPIM), C(SPOM), or C(DOC) were studied. Results showed the following. (1) Poyang Lake was a suspended particulate inorganic matter dominant lake with low phytoplankton concentration. (2) One salient a(ph) absorption peak was found at 678 nm, and it explained 72% of the variation of C(CHL). (3) The a(d) and a(p) exponentially decreased with increasing wavelength, and they explained 74% of the variation of C(SPIM) and 71% variation of C(SPM), respectively, at a wavelength of 440 nm. (4) The a(g) also exponentially decreased with increasing wavelength, and it had no significant correlation to C(DOC) at a significance level of 0.05. (5) The b(b) decreased with increasing wavelength, and it had strong and positive correlations to C(SPM), C(SPIM) and C(SPOM), a strong and negative correlation to C(CHL), and no correlation to C(DOC) at a significance level of 0.05. Such results will be helpful for the understanding of the IOPs of Poyang Lake. They, however, only represented the IOPs during the sampling time period, and more measurements and analyses in different seasons need to be carried out in the future to ensure a comprehensive understanding of the IOPs of Poyang Lake. PMID:22192987

Wu, Guofeng; Cui, Lijuan; Duan, Hongtao; Fei, Teng; Liu, Yaolin

2011-12-01

5

A simple two-band semi-analytical model for retrieval of specific absorption coefficients in coastal waters  

NASA Astrophysics Data System (ADS)

A non-linear iterative method is used to replace the traditional spectral slope technique in initializing the total absorption decomposition model. Based on comparison of absorption coefficient by QAA and two-band semi-analytical model (TSAA) models with field measurements collected from the West Florida Shelf waters and Bohai Sea, it is shown that both models are effective in estimating absorption coefficients from the West Florida Shelf waters, but the TSAA model is superior to the QAA model. Use of the TSAA model in estimating absorption coefficient in the West Florida Shelf and Bohai Sea decreases the uncertainty of estimation by 1.3–74.7% from the QAA model. The TSAA model's sensitivity to the input parameters was evaluated by varying one parameter and keeping the others fixed at their default values. Our results indicate that the TSAA model has quite a strong noise tolerance to addressing the field data of the total absorption coefficient.

Chen, Jun; Cui, Tingwei; Qiu, Zhongfeng; Lin, Changsong

2014-05-01

6

A comparison of methods for the measurement of the absorption coefficient in natural waters  

NASA Technical Reports Server (NTRS)

In the spring of 1992 an optical closure experiment was conducted at Lake Pend Orielle, Idaho. A primary objective of the experiment was to compare techniques for the measurement of the spectral absorption coefficent and other inherent optical properties of natural waters. Daily averages of absorption coefficents measured using six methods are compared at wavelengths of 456, 488, and 532 nm. Overall agreement was within 40% at 456 nm and improved with increasing wavelength to 25% at 532 nm. These absorption measurements were distributed over the final 9 days of the experiement, when bio-optical conditions in Lake Pend Oreille (as indexed by the beam attenuation coefficent c(sub p)(660) and chlorophyll a fluorescence profiles) were representative of those observed throughout the experiment. However, profiles of stimulated chlorophyll a fluorescence and beam transmission showed that bio-optical properties in the lake varied strongly on all time and space scales. Therefore environmental variabilty contributed significantly to deviations between daily mean absorption coefficients measured using the different techniques.

Pegau, W. Scott; Cleveland, Joan S.; Doss, W.; Kennedy, C. Dan; Maffione, Robert A.; Mueller, James L.; Stone, R.; Trees, Charles C.; Weidemann, Alan D.; Wells, Willard H.

1995-01-01

7

Photo-acoustic measurements of water vapor absorption coefficient in UV spectral region  

Microsoft Academic Search

Data on the absorption coefficient of H2O in binary mixture with N2 in UV region of spectra are presented. With the use of the high sensitivity photoacoustic spectrometer, the following values of the absorption coefficient were found: 2.3 × 10-9 cm-1 · Pa-1 (? = 255 nm), 0.9 × 10-9 cm-1 · Pa-1 (? = 271 nm), and 1.6 ×

B. A. Tikhomirov; V. O. Troitskii; V. A. Kapitanov; G. S. Evtushenko; Y. N. Ponomarev

1998-01-01

8

Photo-acoustic measurements of water vapor absorption coefficient in UV spectral region  

Microsoft Academic Search

Data on the absorption coefficient of H2O in binary mixture with N2 in UV region of spectra are presented. With the use of the high sensitivity photoacoustic spectrometer, the following values of the absorption coefficient were found: 2.3 × 10-9 cm-1 · Pa-1 (lambda = 255 nm), 0.9 × 10-9 cm-1 · Pa-1 (lambda = 271 nm), and 1.6 ×

B. A. Tikhomirov; V. O. Troitskii; V. A. Kapitanov; G. S. Evtushenko; Y. N. Ponomarev

1998-01-01

9

Specific absorption and backscattering coefficients of the main water constituents in Poyang Lake, China.  

PubMed

Obtaining and analyzing the specific inherent optical properties (SIOPs) of water bodies is necessary for bio-optical model development and remote sensing-based water quality retrievals and, further, for related ecological studies of aquatic ecosystems. This study aimed to measure and analyze the specific absorption and backscattering coefficients of the main water constituents in Poyang Lake, China. The specific absorption and/or backscattering coefficients of the main water constituents at 85 sampling sites (47 in 2010 and 38 in 2011) were measured and analyzed as follows: (1) the concentrations of chlorophyll a (C(CHL)), suspended particulate matter (C(SPM)) (including suspended particulate inorganic matter (C(SPIM)) and suspended particulate organic matter (C(SPOM))), and the absorption coefficients of total particulate (a(p)), phytoplankton (a(ph)), and non-pigment particulate (a(d)) were measured in the laboratory; (2) the total backscattering coefficients at six wavelengths of 420, 442, 470, 510, 590, and 700 nm, including the contribution of pure water, were measured in the field with a HydroScat-6 backscattering sensor, and the backscattering coefficients without the contribution of pure water (b(b)) were then derived by subtracting the backscattering coefficients of pure water from the total backscattering coefficients; (3) the specific absorption coefficients of total particulate (a*(p)), phytoplankton (a(ph)*), and non-pigment particulate (a*(d)) were calculated by dividing a(p), a(ph), and ad by C(SPM), C(CHL), and C(SPIM), respectively, while the specific backscattering coefficients of total suspended particulate matter (b*(b)) were calculated by dividing b(b) by CSPM; and (4) the a(ph)*, a*(d), a*(p) and b*(b) of the remaining samples (46 in 2010 and 36 in 2011) were visualized and analyzed, and their relations to CCHL, CSPIM or CSPM were studied, respectively. The main results are summarized as follows: (1) the a(ph)* values at 440 nm were 0.0367-0.7203 m(2) mg(-1) with a mean of 0.1623 ± 0.1426 m(2) mg(-1) in 2010 and 0.0319-0.7735 m(2) mg(-1) with a mean of 0.3145 ± 0.1961 m(2) mg(-1) in 2011; there existed significant, negative, and moderate correlations between a(ph)* and C(CHL) at 400-700 nm in 2010 and 2011 (p<0.05); (2) The a*(d) values at 440 nm were 0.0672-0.2043 m(2) g(-1) with a mean of 0.1022 ± 0.0326 m(2) g-1) in 2010 and 0.0559-0.1347 m(2) g(-1) with a mean of 0.0953 ± 0.0196 m(2) g(-1) in 2011; there existed negative correlations between a*(d) and C(SPIM), while the correlations showed overall decreasing and increasing trends before and after around 575 nm with increasing wavelengths, respectively; (3) The a*(p) values at 440 nm were 0.0690-0.1929 m(2) g(-1) with a mean of 0.1036 ± 0.0298 m(2) g(-1) in 2010 and 0.0571-0.1321 m(2) g(-1) with a mean of 0.1014 ± 0.0191 m(2) g(-1) in 2011, and the negative correlations between a*(p) and C(SPM) were found in both years; (4) The b*(b) at the six wavelengths generally decreased with increasing wavelengths, while the b*(b) values at 420 nm were lower than those at 442 nm for some samples; the correlation between b*(b) and C(SPM) increased with increasing wavelength. Such results can only represent the SIOPs during the sampling time periods, and more measurements and analyses considering different seasons need to be carried out in the future to comprehensively understand the SIOPs of Poyang Lake. PMID:22976118

Wu, Guofeng; Cui, Lijuan; Duan, Hongtao; Fei, Teng; Liu, Yaolin

2013-05-01

10

Heat transfer coefficients in two phase flow for the water\\/lithium bromide mixture used in solar absorption refrigeration systems  

Microsoft Academic Search

This paper describes the experimental results obtained from the heat transfer in saturated nucleate boiling for the water\\/lithium bromide mixture flowing upward in a uniformly heated vertical tube, which is the generator of a solar absorption refrigeration system. The concentration range for the mixture was from 48 to 56wt.% Plots of local and average heat transfer coefficients are shown against

W. Rivera; A. Xicale

2001-01-01

11

Absorption coefficients of marine waters: expanding multiband information to hyperspectral data  

Microsoft Academic Search

For many oceanographic studies and applications, it is desirable to know the spectrum of the attenuation coefficient. For water of the vast ocean, an effective way to get information about this property is through satellite measurements of ocean color. Past and present satellite sensors designed for ocean-color measurements, however, can only provide data in a few spectral bands. A tool

Zhong Ping Lee; W. Joseph Rhea; Robert Arnone; Wesley Goode

2005-01-01

12

Some comments on Sabine absorption coefficient (L)  

Microsoft Academic Search

The case of a nonzero reverberation time when all absorptive surfaces in a room have values of Sabine absorption coefficient of one, the existence of values of the coefficient that are larger than one, and the difference of the coefficient from the statistical absorption coefficient, are well known. So far, the reasons for these phenomena are still unclear. This letter

K. S. Sum

2005-01-01

13

Experimental boiling heat transfer coefficients in the high temperature generator of a double effect absorption machine for the lithium bromide\\/water mixture  

Microsoft Academic Search

The aim of this work is to determine the boiling heat transfer coefficients in the high temperature desorber (HTD) of an air-cooled double effect lithium bromide\\/water absorption prototype. The HTD is a plate heat exchanger (PHE) with thermal oil on one side, and a lithium bromide solution on the other side. Several experiments were performed with this PHE while the

J. D. Marcos; M. Izquierdo; R. Lizarte; E. Palacios; C. A. Infante Ferreira

2009-01-01

14

Mineral Specific IR Molar Absorption Coefficients for Routine Water Determination in Olivine, SiO2 polymorphs and Garnet  

NASA Astrophysics Data System (ADS)

Conventionally applied Infrared (IR) calibrations [1, 2] for quantitative water analyses in solids are established on hydrous minerals and glasses with several wt% water. These calibrations are based on a negative correlation between the IR molar absorption coefficient (?) for water and the mean wavenumber of the corresponding OH pattern. The correlation reflects the dependence of the OH band position on the appropriate O- H...O distances and thereby the magnitude of the dipole momentum which is proportional to the band intensity. However, it has been observed that these calibrations can not be adopted to nominally anhydrous minerals (NAMs) [3].To study the potential dependence of ? on structure and chemistry in NAMs we synthesized olivine and SiO2 polymorphs with specific isolated hydroxyl point defects, e.g. quartz, coesite and stishovite with B3++H+=Si4+ and/or Al3++H+=Si4+ substitutions. Experiments were performed with water in excess in piston cylinder and multi-anvil presses. Single crystal IR spectra demonstrate that we successfully managed to seperate generally complex OH patterns as e.g. observed in natural quartz and synthetic coesite. We quantified sample water contents of both natural samples and our run products by applying proton-proton-scattering [4], confocal microRaman spectroscopy [5] and Secondary Ion mass spectrometry. Resulting water concentrations were used to calculate new mineral specific ?s. For olivine with the mean wavenumber of 3517 cm-1 we determined an ? value of 41,000±5,000 lmol-1H2Ocm-2. Quantification of olivine with the mean wavenumber of 3550 cm-1 in contrast resulted in an ? value of 47,000±1,000 lmol-1H2Ocm-2. Taking into account previous studies [6, 7] there is evidence to suggest a linear wavenumber dependent correlation for olivine, where ? increases with decreasing wavenumber. In case of the SiO2 system it turns out that the magnitude of ? within one structure type is independent of the liable OH point defect and therewith the wavenumber of the observed band position. Consequently, one single mean ? of 68,000±5,000 lmol-1H2Ocm-2 could be determined for a suite of quartz samples with varying OH point defects. In contrast, ? varies with the structure itself. For polymorphic coesite we calculated a different ? of 214,000±8,000 lmol-1H2O}cm-2, that is in good agreement with earlier established data [8]. Quantification data of stishovite resulted in an even higher value of ?=867,000±29,000 lmol-1H2Ocm-2, similar to that determined by [9]. First data on natural garnet give an ? value of 40,000±2,000 lmol-1H2Ocm-2, that confirms prior suggested values [10]. Our results demonstrate that not using mineral specific calibrations for quantitative water analyses in NAMs leads to overestimation of sample water concentrations, that are required for modelling the earth's deep water cycle. [1]Paterson, M. S. (1982), Bull. Min., 105, 20-29. [2]Libowitzky, E., Rossman, G. R. (1997), Am. Min., 82, 1111- 1115. [3]Rossman, G. R. (2006), Rev. Mineral., 62, 1-28. [4]Reichart et al. (2004), Science, 306, 1537-1540. [5]Thomas et al. (2006), Am. Min., 91, 467-470. [6]Bell et al. (2003), JGR, 108, (B2), 2105-2113. [7]Koch-Mueller et al. (2006), PCM, 33, 276-287. [8]Koch-Mueller et al. (2001), PCM, 28, 693-705. [9]Pawley et al. (1993), Science, 261, 1024-1026. [10]Maldener et al. (2003), PCM, 30, 337-344.

Thomas, S.; Koch-Mueller, M.; Reichart, P.; Rhede, D.; Thomas, R.

2007-12-01

15

CO2 absorption coefficient 1655 - 1825 Å  

Microsoft Academic Search

The COultraviolet absorption coefficients were measured in the wavelength region from 1655 to 1825 A. This region overlaps earlier work and extends into most of the previously unmeasured region between the data of Inn et al. (!953) and the data of Thompson et al. (1963). These absorption coefficients are of present interest in the theoretical development of the photochemistry for

J. Heimerl

1970-01-01

16

Possible applications of surface electromagnetic waves to measure absorption coefficients  

Microsoft Academic Search

We show that surface electromagnetic waves can probably be used to measure the absorption coefficients of materials overlaying metals. The proposed experimental method is illustrated in the infrared frequency range using water, Teflon, and polyethylene as sample materials.

R. W. Alexander; R. J. Bell; C. A. Ward; J. H. Weaver; I. L. Tyler; B. Fischer

1973-01-01

17

Percutaneous Absorption of Hair Dyes: Correlation with Partition Coefficients  

Microsoft Academic Search

A homologous series of hair dyes was selected for percutaneous absorption studies with excised human skin. The permeability constants obtained for the dyes were compared with octanol\\/water and skin membrane\\/ water partition coefficients. The compounds examined were: p-phenylenediamine, o-phenylenediamine, 2-ni- tro-p-phenylenediamine, 2-amino-4-nitrophenol, 4- chloro-m-phenylenediamine, and 4-amino-2-nitro- phenol. Skin absorption of the dyes was observed when they were applied in an

Robert L. Bronaugh; Elaine R. Congdon

1984-01-01

18

A Multi-Band Analytical Algorithm for Deriving Absorption and Backscattering Coefficients from Remote-Sensing Reflectance of Optically Deep Waters  

NASA Technical Reports Server (NTRS)

A multi-band analytical (MBA) algorithm is developed to retrieve absorption and backscattering coefficients for optically deep waters, which can be applied to data from past and current satellite sensors, as well as data from hyperspectral sensors. This MBA algorithm applies a remote-sensing reflectance model derived from the Radiative Transfer Equation, and values of absorption and backscattering coefficients are analytically calculated from values of remote-sensing reflectance. There are only limited empirical relationships involved in the algorithm, which implies that this MBA algorithm could be applied to a wide dynamic range of waters. Applying the algorithm to a simulated non-"Case 1" data set, which has no relation to the development of the algorithm, the percentage error for the total absorption coefficient at 440 nm a (sub 440) is approximately 12% for a range of 0.012 - 2.1 per meter (approximately 6% for a (sub 440) less than approximately 0.3 per meter), while a traditional band-ratio approach returns a percentage error of approximately 30%. Applying it to a field data set ranging from 0.025 to 2.0 per meter, the result for a (sub 440) is very close to that using a full spectrum optimization technique (9.6% difference). Compared to the optimization approach, the MBA algorithm cuts the computation time dramatically with only a small sacrifice in accuracy, making it suitable for processing large data sets such as satellite images. Significant improvements over empirical algorithms have also been achieved in retrieving the optical properties of optically deep waters.

Lee, Zhong-Ping; Carder, Kendall L.

2001-01-01

19

Prediction of absorption coefficients by pulsed laser induced photoacoustic measurements  

NASA Astrophysics Data System (ADS)

In the current study, a pulsed laser induced photoacoustic spectroscopy setup was designed and developed, aiming its application in clinical diagnostics. The setup was optimized with carbon black samples in water and with various tryptophan concentrations at 281 nm excitations. The sensitivity of the setup was estimated by determining minimum detectable concentration of tryptophan in water at the same excitation, and was found to be 0.035 mM. The photoacoustic experiments were also performed with various tryptophan concentrations at 281 nm excitation for predicting optical absorption coefficients in them and for comparing the outcomes with the spectrophotometrically-determined absorption coefficients for the same samples. Absorption coefficients for a few serum samples, obtained from some healthy female volunteers, were also determined through photoacoustic and spectrophotometric measurements at the same excitations, which showed good agreement between them, indicating its clinical implications.

Priya, Mallika; Satish Rao, B. S.; Ray, Satadru; Mahato, K. K.

2014-06-01

20

Water absorption lines, 931-961 nm - Selected intensities, N2-collision-broadening coefficients, self-broadening coefficients, and pressure shifts in air  

NASA Technical Reports Server (NTRS)

Intensities were measured for 97 lines of H2O vapor between 932 and 961 nm. The lines were selected for their potential usefulness for remote laser measurements of H2O vapor in the earth's atmosphere. The spectra were obtained with several different H2O vapor abundances and N2 broadening gas pressures; the spectral resolution was 0.046/cm FWHM. Measured H2O line intensities range from 7 x 10 to the -25th to 7 x 10 to the -22nd/cm per (molecules/sq cm). H2O self-broadening coefficients were measured for 13 of these strongest lines; the mean value was 0.5/cm per atm. N2-collision-broadening coefficients were measured for 73 lines, and the average was 0.11 cm per atm HWHM. Pressure shifts in air were determined for a sample of six lines between 948 and 950 nm; these lines shift to lower frequency by an amount comparable to 0.1 of the collision-broadened widths measured in air or N2. The measured intensities of many lines of 300-000 band are much larger than expected from prior computations, in some cases by over an order of magnitude. Coriolis interactions with the stronger 201-000 band appear to be the primary cause of the enhancement of these line intensities.

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

1982-01-01

21

Aerosol Angstrom Absorption Coefficient Comparisons during MILAGRO.  

NASA Astrophysics Data System (ADS)

Measurements of aerosol absorption were obtained as part of the MAX-Mex component of the MILAGRO field campaign at site T0 (Instituto Mexicano de Petroleo in Mexico City) by using a 7-channel aethalometer (Thermo- Anderson) during the month of March, 2006. The absorption measurements obtained in the field at 370, 470, 520, 590, 660, 880, and 950 nm were used to determine the aerosol Angstrom absorption exponents by linear regression. Since, unlike other absorbing aerosol species (e.g. humic like substances, nitrated PAHs), black carbon absorption is relatively constant from the ultraviolet to the infrared with an Angstrom absorption exponent of -1 (1), a comparison of the Angstrom exponents can indicate the presence of aerosol components with an enhanced UV absorption over that expected from BC content alone. The Angstrom exponents determined from the aerosol absorption measurements obtained in the field varied from - 0.7 to - 1.3 during the study and was generally lower in the afternoon than the morning hours, indicating an increase in secondary aerosol formation and photochemically generated UV absorbing species in the afternoon. Twelve-hour integrated samples of fine atmospheric aerosols (<0.1micron) were also collected at site T0 and T1 (Universidad Technologica de Tecamac, State of Mexico) from 5 am to 5 pm (day) and from 5 pm to 5 am (night) during the month of March 2006. Samples were collected on quartz fiber filters with high volume impactor samplers. Continuous absorption spectra of these aerosol samples have been obtained in the laboratory from 280 to 900nm with the use of an integrating sphere coupled to a UV spectrometer (Beckman DU with a Labsphere accessory). The integrating sphere allows the detector to collect and spatially integrate the total radiant flux reflected from the sample and therefore allows for the measurement of absorption on highly reflective or diffusely scattering samples. These continuous spectra have also been used to obtain the aerosol Angstrom absorption exponents by linear regression over the entire UV-visible spectral range. These results are compared to results obtained from the absorbance measurements obtained in the field. The differences in calculated Angstrom absorption exponents between the field and laboratory measurements are attributed partly to the differences in time resolution of the sample collection resulting in heavier particle pileup on the filter surface of the 12-hour samples. Some differences in calculated results can also be attributed to the presence of narrow band absorbers below 400 nm that do not fall in the wavelengths covered by the 7 wavelengths of the aethalometer. 1. Marley, N.A., J.S. Gaffney, J.C. Baird, C.A. Blazer, P.J. Drayton, and J.E. Frederick, "The determination of scattering and absorption coefficients of size-fractionated aerosols for radiative transfer calculations." Aerosol Sci. Technol., 34, 535-549, (2001). This work was conducted as part of the Department of Energy's Atmospheric Science Program as part of the Megacity Aerosol Experiment - Mexico City during MILAGRO. This research was supported by the Office of Science (BER), U.S. Department of Energy Grant No. DE-FG02-07ER64329. We also wish to thank Mexican Scientists and students for their assistance from the Instituto Mexicano de Petroleo (IMP) and CENICA.

Marley, N. A.; Marchany-Rivera, A.; Kelley, K. L.; Mangu, A.; Gaffney, J. S.

2007-12-01

22

The spectral absorption coefficient at 254nm as a real-time early warning proxy for detecting faecal pollution events at alpine karst water resources  

PubMed Central

Because spring water quality from alpine karst aquifers can change very rapidly during event situations, water abstraction management has to be performed in near real-time. Four summer events (2005-2008) at alpine karst springs were investigated in detail in order to evaluate the spectral absorption coefficient at 254nm (SAC254) as a real-time early warning proxy for faecal pollution. For the investigation Low-Earth-Orbit (LEO) Satellite-based data communication between portable hydrometeorological measuring stations and an automated microbiological sampling device was used. The method for event triggered microbial sampling and analyzing was already established and described in a previous paper (Stadler et al., Wat. Sci. Technol. 58(4): 899-909, 2008). Data analysis including on-line event characterisation (i.e. precipitation, discharge, turbidity, SAC254) and comprehensive E. coli determination (n > 800) indicated that SAC254 is a useful early warning proxy. Irrespective of the studied event situations SAC254 always increased 3 to 6 hours earlier than the onset of faecal pollution, featuring different correlation phases. Furthermore, it seems also possible to use SAC254 as a real-time proxy parameter for estimating the extent of faecal pollution after establishing specific spring and event-type calibrations that take into consideration the variability of the occurrence and the transferability of faecal material It should be highlighted that diffuse faecal pollution from wildlife and live stock sources was responsible for spring water contamination at the investigated catchments. In this respect, the SAC254 can also provide useful information to support microbial source tracking efforts where different situations of infiltration have to be investigated.

Stadler, H.; Klock, E.; Skritek, P.; Mach, R.L.; Zerobin, W.; Farnleitner, A.H.

2011-01-01

23

Spectral absorption coefficients of living phytoplankton and nonalgal biogenous matter: A comparison between the Peru upwelling areaand the Sargasso Sea  

Microsoft Academic Search

Absorption coefficients of total particulate (biogenous) matter were determined in the meso- trophic waters of the Peruvian upwelling and the oligotrophic waters of the Sargasso Sea. A method based on spectral criteria was used to partition these coefficients into absorption by living algal cells and by nonalgal (mainly detrital) material. This method was tested by independently measuring absorption by nonalgal

ANNICK BRICAUD; DARIUSZ STRAMSKI

1990-01-01

24

Spectral absorption coefficients measured with an integrating cavity absorption meter  

NASA Astrophysics Data System (ADS)

Absorption spectra (400 to 700 nm) measured with a new instrument, the integrating cavity absorption meter, were compared to those measured with standard techniques for particles (collected on glass fiber filters) or solutions (in long pathlength cuvettes) . The integrating cavity absorption meter has two advantages over previously used methods: 1) low absorption signals can easily be measured due to the long effective pathlength created by the highly reflective walls of the cavity, and 2) scattering averages to zero because of the isotropic light source. For particulate absorption, the locations of absorption peaks were offset up to 5 nm in the integrating cavity spectra due to the use of interference filters for determining wavelength. The filter wheel has bands centered every 10 nm, while the spectrophotometer has a monochromator with 1 nm spectral resolution. Modifications of the integrating cavity, presently in progress, will include replacement of the filter wheel with a monochromator. Particulate absorption measured with the integrating cavity was similar to that measured with the glass fiber filters through a portion (500 to 700 nm) of the visible spectrum. However, from 400 to 500 nm, absorption measured in the integrating cavity was less than that measured on glass fiber filters. For example, at 400 nm, cavity values were only 45 to 83% of the glass fiber filter values. Possible causes of this difference are discussed. Absorption spectra for dissolved materials measured in the integrating cavity were similar to those measured in the spectrophotometer.

Cleveland, Joan S.; Pope, Robin M.; Fry, Edward S.

1990-09-01

25

Determination of optical absorption coefficient with focusing photoacoustic imaging  

NASA Astrophysics Data System (ADS)

Absorption coefficient of biological tissue is an important factor for photothermal therapy and photoacoustic imaging. However, its determination remains a challenge. In this paper, we propose a method using focusing photoacoustic imaging technique to quantify the target optical absorption coefficient. It utilizes the ratio of the amplitude of the peak signal from the top boundary of the target to that from the bottom boundary based on wavelet transform. This method is self-calibrating. Factors, such as absolute optical fluence, ultrasound parameters, and Grüneisen parameter, can be canceled by dividing the amplitudes of the two peaks. To demonstrate this method, we quantified the optical absorption coefficient of a target with various concentrations of an absorbing dye. This method is particularly useful to provide accurate absorption coefficient for predicting the outcomes of photothermal interaction for cancer treatment with absorption enhancement.

Li, Zhifang; Li, Hui; Zeng, Zhiping; Xie, Wenming; Chen, Wei R.

2012-06-01

26

Determination of optical absorption coefficient with focusing photoacoustic imaging.  

PubMed

Absorption coefficient of biological tissue is an important factor for photothermal therapy and photoacoustic imaging. However, its determination remains a challenge. In this paper, we propose a method using focusing photoacoustic imaging technique to quantify the target optical absorption coefficient. It utilizes the ratio of the amplitude of the peak signal from the top boundary of the target to that from the bottom boundary based on wavelet transform. This method is self-calibrating. Factors, such as absolute optical fluence, ultrasound parameters, and Gru?neisen parameter, can be canceled by dividing the amplitudes of the two peaks. To demonstrate this method, we quantified the optical absorption coefficient of a target with various concentrations of an absorbing dye. This method is particularly useful to provide accurate absorption coefficient for predicting the outcomes of photothermal interaction for cancer treatment with absorption enhancement. PMID:22734746

Li, Zhifang; Li, Hui; Zeng, Zhiping; Xie, Wenming; Chen, Wei R

2012-06-01

27

Calculation procedure to determine average mass transfer coefficients in packed columns from experimental data for ammonia–water absorption refrigeration systems  

Microsoft Academic Search

The ammonia purification process is critical in ammonia–water absorption refrigeration systems. In this paper, a detailed\\u000a and a simplified analytical model are presented to characterize the performance of the ammonia rectification process in packed\\u000a columns. The detailed model is based on mass and energy balances and simultaneous heat and mass transfer equations. The simplified\\u000a model is derived and compared with

Jaime Sieres; José Fernández-Seara

2008-01-01

28

Bandgap dependence in the multiphoton absorption coefficient of semiconductors  

NASA Astrophysics Data System (ADS)

Reports of two and three photon absorption coefficients in common semiconductors show a remarkably large lack of agreement and lack of scaling, indicating the need for more controlled experiments. We report nonlinear photon absorption in single-crystal Si, GaAs, and Ge carried out under identical conditions using an ultrafast high-power mid-IR laser. Wavelength- and bandgap-dependent multiphoton absorption coefficients were extracted and compared to current literature values, as well as the simpler scaling predictions for different bandgap materials. Our experimental data support the theoretical scaling law for the bandgap-dependent multiphoton absorption coefficients. Importantly, our coefficients are approximately 2 orders of magnitude smaller than current literature values.

Seo, Dongmin; Gregory, Justin; Feldman, Leonard; Tolk, Norman; Cohen, Philip

2010-03-01

29

Determination of Planck Mean Absorption Coefficients for Hydrocarbon Fuels  

Microsoft Academic Search

Infrared transmission of propane, n-heptane and propylene samples was measured using Fourier transform infrared spectroscopy (FTIR) for temperatures ?1000 K to facilitate calculation of absorption coefficients of fuel molecules at temperatures representative of non-premixed flame interiors. Spectrally resolved fits of the absorption coefficient data using a semi-empirical quantum-based expression provide a basis for calculating infrared spectra at any temperature. Experimentally-derived Planck

Kaoru Wakatsuki; Gregory S. Jackson; Jungho Kim; Anthony Hamins; Marc R. Nyden; Stephen P. Fuss

2008-01-01

30

Continuum Absorption Coefficient of Atoms and Ions  

NASA Technical Reports Server (NTRS)

The rate of heat transfer to the heat shield of a Jupiter probe has been estimated to be one order of magnitude higher than any previously experienced in an outer space exploration program. More than one-third of this heat load is due to an emission of continuum radiation from atoms and ions. The existing computer code for calculating the continuum contribution to the total load utilizes a modified version of Biberman's approximate method. The continuum radiation absorption cross sections of a C - H - O - N ablation system were examined in detail. The present computer code was evaluated and updated by being compared with available exact and approximate calculations and correlations of experimental data. A detailed calculation procedure, which can be applied to other atomic species, is presented. The approximate correlations can be made to agree with the available exact and experimental data.

Armaly, B. F.

1979-01-01

31

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

32

Comparison between different spectral models of the diffuse attenuation and absorption coefficients of seawater  

NASA Astrophysics Data System (ADS)

The goal of this work is to verify different spectral models of the diffuse attenuation and absorption coefficients of sea water and to work out a recommendation for their use. It is shown that the spectral models of the diffuse attenuation coefficient Kd((lambda) ) developed by Austin, Petzold, 1984 and by Volynsky, Sud'bin, 1992 correspond with each other, as well the models of Ivanov, Shemshura, 1973 and of Kopelevich, Shemshura, 1988 for calculation of the spectral absorption coefficient a((lambda) ) on the values of Kd((lambda) ). Theoretical foundation of the relation between a((lambda) ) and Kd((lambda) ) is given. The up-to-date physical model of the sea water light absorption is considered and checked by means of comparison with measured values of the attenuation coefficient at the ultraviolet and visible spectral ranges.

Kopelevich, Oleg V.; Filippov, Yuri V.

1994-10-01

33

Absorption coefficients of a hydrogen plasma for laser radiation  

NASA Technical Reports Server (NTRS)

The formalism for the calculation of the absorption of radiation by a hydrogen plasma at common laboratory conditions is summarized. The hydrogen plasma absorption coefficient for laser radiation has been computed for a wide range of electron densities and temperatures (10,000-40,000 K). The results of this computation are presented in a graphical form that permits a determination of the absorption coefficient for the following laser wavelengths: 0.176, 0.325, 0.337, 0.442, 0.488, 0.515, 0.633, 0.694, 1.06, 1.15, 2.36, 3.39, 5.40 and 10.6 microns. The application of these results and laser radiation absorption measurements to plasma diagnostics is discussed briefly.

Stallcop, J. R.

1974-01-01

34

Two-photon absorption coefficients of optical fibers with 240-nm absorption band  

Microsoft Academic Search

Summary form only given. Photosensitivity in germanosilicate fibers has been known to relate to 240-nm absorption band of Ge-related oxygen-deficiency defects. In the blue-green region, Hill-grating formation and second-harmonic generation are attained by two-photon (multiphoton) absorption. However, the spectral dependence of two-photon absorption (TPA) coefficients has not been made clear. The 240-nm absorption and the photosensitivity have been attributed mainly

T. Mizunami; M. Hashimoto; S. Gupta; Y. Uchida; T. Shimomura

1996-01-01

35

The reliability of H(-) free-free absorption coefficients  

NASA Astrophysics Data System (ADS)

A quantitative assessment is made of the reliability of current estimates of free-free absorption coefficients of the negative hydrogen ion. Results by sophisticated versions of the close coupling, polarised orbital and variational methods are shown to have converged. Analytic approximations for the evaluation of matrix elements are investigated and coefficients corrected by an empirical procedure shown to fit numerical results to a standard deviation of 1% for wavelengths greater than 0.5 microns.

John, T. L.

1994-02-01

36

Effect of Acoustic Absorption by Hydrophone and Cable on A Reverberation Technique for Measuring Sound Absorption Coefficient of Particulate Suspensions  

Microsoft Academic Search

A technique has been developed to measure the sound absorption coefficient of particulate suspensions using a reverberation time technique. This technique measures the change in the reverberation time of the test volume of water when small particles are added. It is described in detail in other publications, which are referenced. When measuring a reverberant sound field, it is good practice

T. G. Leighton; N. R. Brown; S. D. Richards

2002-01-01

37

Measurement of Acoustic Attenuation and Absorption Coefficients using Thermometry  

Microsoft Academic Search

Accurate knowledge of both the attenuation and the absorption coefficient of tissue are required when planning an optimal high intensity focused ultrasound treatment. A novel technique for simple measurement of this parameters has been developed in which a thin-film thermocouple (TFT) is placed between two layers of tissue of different thicknesses. The sample can be rotated about an axis through

Hugh Morris; Ian Rivens; Adam Shaw; Gail Ter Haar

2007-01-01

38

Calculation of Absorption Coefficient Using Average Temperature and Pressure.  

National Technical Information Service (NTIS)

This note describes the investigation of an expression to be used in bottom bounce propagation models presently in use at NUWC Code D556. Recently an expression was developed to predict the acoustic absorption coefficient of seawater from the frequency, t...

L. P. Berger H. R. Hall

1968-01-01

39

MEASUREMENT OF ABSORPTION COEFFICIENTS USING A SCANNING LASER DOPPLER VIBROMETER  

Microsoft Academic Search

Different well accepted standardized test methods exist to estimate absorption coefficients of acoustical materials from experiments. The most widespread technique uses the so-called Kundt's tube. This method clearly has its limitations since both the upper and lower frequencies are limited by the diameter and length of the used tube. Another standardised method uses the comparison of the reverberation times measured

Cedric Vuye; Steve Vanlanduit; Joris Vanherzeele; Patrick Guillaume

40

The Total Absorption Coefficient of the Negative Hydrogen Ion.  

National Technical Information Service (NTIS)

The free-free absorption coefficient of the negative hydrogen ion is calculated in both the length and velocity formulations using the method of polarized orbitals to describe the free electron. The bound-free cross section of Bell and Kingston(1967) is c...

K. L. Bell A. E. Kingston W. A. McIlveen

1974-01-01

41

Vapor-Phase Infrared Absorptivity Coefficient of HN1.  

National Technical Information Service (NTIS)

We report the vapor-phase IR absorptivity coefficient of the vesicant chemical agent, HN1. The data are provided at a spectral resolution of 0.25 cm 1 (data spacing of 0.125 cm 1). We describe the methods used to generate the spectra, process the raw data...

A. C. Samuels B. R. Williams J. R. Miles M. S. Hulet

2013-01-01

42

Satellite retrieval of the absorption coefficient of phytoplankton phycoerythrin pigment: theory and feasibility status.  

PubMed

Oceanic radiance model inversion methods are used to develop a comprehensive algorithm for retrieval of the absorption coefficients of phycourobilin (PUB) pigment, type I phycoerythrobilin (PEB) pigment rich in PUB, and type II PEB deficient in PUB pigment (together with the usual "big three" inherent optical properties: the total backscattering coefficient and the absorption coefficients of chromophoric dissolved organic matter (CDOM)-detritus and phytoplankton). This fully modeled inversion algorithm is then simplified to yield a hybrid modeled-unmodeled inversion algorithm in which the phycoerythrin (PE) absorption coefficient is retrieved as unmodeled 488-nm absorption (which exceeds the modeled phytoplankton and the CDOM-detritus absorption coefficients). Each algorithm was applied to water-leaving radiances, but only hybrid modeled-unmodeled inversions yielded viable retrievals of the PE absorption coefficient. Validation of the PE absorption coefficient retrieval was achieved by relative comparison with airborne laser-induced PEB fluorescence. The modeled-unmodeled retrieval of four inherent optical properties by direct matrix inversion is rapid and well conditioned, but the accuracy is strongly limited by the accuracy of the three principal inherent optical property models across all four spectral bands. Several research areas are identified to enhance the radiance-model-based retrievals: (a) improved PEB and PUB absorption coefficient models, (b) PE spectral shifts induced by PUB chromophore substitution at chromophore binding sites, (c) specific absorption-sensitive phytoplankton absorption modeling, (d) total constituent backscattering modeling, (e) unmodeled carotinoid and phycocyanin absorption that are not now accounted for in the chlorophyll-dominated phytoplankton absorption coefficient model, and (f) iterative inversion techniques to solve for six constituents with only five radiances. Although considerable progress has been made toward the satellite recovery of PE absorption, the maturity of the retrieval is presently insufficient for routine global application. Instead it must currently be used on a regional basis where localized ship and aircraft validation can be made available. The algorithm was developed for the MODIS (Moderate-Resolution Imaging Spectroradiometer) sensor but is applicable to any sensor having comparable band locations. PMID:18324297

Hoge, F E; Wright, C W; Lyon, P E; Swift, R N; Yungel, J K

1999-12-20

43

A method for measuring oblique incidence absorption coefficient of absorptive panels by stretched pulse technique  

Microsoft Academic Search

This paper proposes a pulse method for estimating the acoustical performance of absorptive panels to reduce noise reflections when applied to road structures such as parallel walls and ceilings of double deck viaducts. The acoustical performance is specified on the basis of oblique incidence absorption coefficient. It is determined from the ratio of the reflected sound energy from the surface

Kazunori Kimura; Kohei Yamamoto

2001-01-01

44

Impact of inhomogeneous optical scattering coefficient distribution on recovery of optical absorption coefficient maps using tomographic photoacoustic data.  

PubMed

We present a study through extensive simulation that considers the impact of inhomogeneous optical scattering coefficient distribution on recovery of optical absorption coefficient maps using tomographic photoacoustic data collected from media mimicking breast tissue. We found that while the impact of scattering heterogeneities/targets is modest on photoacoustic recovery of optical absorption coefficients, the impact of scattering contrast caused by adipose tissue, a layer of normal tissue along the boundary of the breast, is dramatic on reconstruction of optical absorption coefficients using photoacoustic data-up to 25.8% relative error in recovering the absorption coefficient is estimated in such cases. To overcome this problem, we propose a new method to enhance photoacoustic recovery of the optical absorption coefficient in heterogeneous media by considering inhomogeneous scattering coefficient distribution provided by diffuse optical tomography (DOT). Results from extensive simulations show that photoacoustic recovery of absorption coefficient maps can be improved considerably with a priori scattering information from DOT. PMID:23339968

Li, Xiaoqi; Jiang, Huabei

2013-02-21

45

Impact of inhomogeneous optical scattering coefficient distribution on recovery of optical absorption coefficient maps using tomographic photoacoustic data  

NASA Astrophysics Data System (ADS)

We present a study through extensive simulation that considers the impact of inhomogeneous optical scattering coefficient distribution on recovery of optical absorption coefficient maps using tomographic photoacoustic data collected from media mimicking breast tissue. We found that while the impact of scattering heterogeneities/targets is modest on photoacoustic recovery of optical absorption coefficients, the impact of scattering contrast caused by adipose tissue, a layer of normal tissue along the boundary of the breast, is dramatic on reconstruction of optical absorption coefficients using photoacoustic data—up to 25.8% relative error in recovering the absorption coefficient is estimated in such cases. To overcome this problem, we propose a new method to enhance photoacoustic recovery of the optical absorption coefficient in heterogeneous media by considering inhomogeneous scattering coefficient distribution provided by diffuse optical tomography (DOT). Results from extensive simulations show that photoacoustic recovery of absorption coefficient maps can be improved considerably with a priori scattering information from DOT.

Li, Xiaoqi; Jiang, Huabei

2013-02-01

46

Sound absorption coefficient measurements by phase-conjugate ultrasonic waves  

NASA Astrophysics Data System (ADS)

Measurements of the sound absorption coefficient in test objects containing solid microparticles randomly distributed over the object volumes are carried out. Two methods are used for this purpose: the standard echo-pulse insert-substitution method and a modified method using phase conjugation of ultrasound. The test objects are made from gelatin, and the size of the particles introduced in it is chosen to allow measurements in both the long- and medium-wavelength scattering modes of the probing beam. It is shown that, in the first scattering mode, in which the presence of particles causes additional viscous and temperature losses, the two aforementioned methods give identical results. In the second scattering mode, in which the dominant mechanism of additional loss is elastic scattering, the use of phase conjugation allows an almost complete reconstruction of the scattered field and, hence, a more reliable upper estimate for the coefficient of ultrasonic absorption in the test objects.

Smagin, N. V.; Krutyansky, L. M.; Brysev, A. P.

2013-03-01

47

A high absorption coefficient DL-MPP imitating owl skin  

NASA Astrophysics Data System (ADS)

This paper proposes a high absorption coefficient micro-perforated panel (MPP) imitating owl skin structure for acoustic noise reduction. Compared to the traditional micro-perforated panel, this device has two unique characteristics-simulating the owl skin structure, its radius of perforated apertures even can be as small as 55?, and its material is silicon and fabricated by micro-electrical mechanical system (MEMS) technology; So that its absorption coefficients of acoustic noise for normal incidence sound wave whose frequencies arrange from 1.5 kHz to 6.0 kHz are all above 0.8 which is the owl's hunts sensitivity frequency band. Double leaf MPP fabricated by MEMS technology is an absolutely bionic success in functional-imitation.

Guo, Lijun; Zhao, Zhan; Kong, Deyi; Wu, Shaohua; Du, Lidong; Fang, Zhen

2012-11-01

48

Field testing of sound absorption coefficients in a classroom  

Microsoft Academic Search

Formal procedures for determining the sound absorption coefficients of materials installed in the field do not exist. However, the U.S. Air Force requested such tests to prove that the sound-absorbing material used in classrooms at Beale AFB in Marysville, CA, met the specified NRC of 0.80. They permitted the use of two layers of 0.5-in. fiberboard or 1-in.-thick fiberglass panels

Steve Pettyjohn

2005-01-01

49

A parameterization scheme for the x-ray linear attenuation coefficient and energy absorption coefficient.  

PubMed

A novel parameterization of x-ray interaction cross-sections is developed, and employed to describe the x-ray linear attenuation coefficient and mass energy absorption coefficient for both elements and mixtures. The new parameterization scheme addresses the Z-dependence of elemental cross-sections (per electron) using a simple function of atomic number, Z. This obviates the need for a complicated mathematical formalism. Energy dependent coefficients describe the Z-direction curvature of the cross-sections. The composition dependent quantities are the electron density and statistical moments describing the elemental distribution. We show that it is possible to describe elemental cross-sections for the entire periodic table and at energies above the K-edge (from 6 keV to 125 MeV), with an accuracy of better than 2% using a parameterization containing not more than five coefficients. For the biologically important elements 1 < or = Z < or = 20, and the energy range 30-150 keV, the parameterization utilizes four coefficients. At higher energies, the parameterization uses fewer coefficients with only two coefficients needed at megavoltage energies. PMID:15083673

Midgley, S M

2004-01-21

50

High temperature measurement of water vapor absorption  

NASA Technical Reports Server (NTRS)

An investigation was undertaken to measure the absorption coefficient, at a wavelength of 10.6 microns, for mixtures of water vapor and a diluent gas at high temperature and pressure. The experimental concept was to create the desired conditions of temperature and pressure in a laser absorption wave, similar to that which would be created in a laser propulsion system. A simplified numerical model was developed to predict the characteristics of the absorption wave and to estimate the laser intensity threshold for initiation. A non-intrusive method for temperature measurement utilizing optical laser-beam deflection (OLD) and optical spark breakdown produced by an excimer laser, was thoroughly investigated and found suitable for the non-equilibrium conditions expected in the wave. Experiments were performed to verify the temperature measurement technique, to screen possible materials for surface initiation of the laser absorption wave and to attempt to initiate an absorption wave using the 1.5 kW carbon dioxide laser. The OLD technique was proven for air and for argon, but spark breakdown could not be produced in helium. It was not possible to initiate a laser absorption wave in mixtures of water and helium or water and argon using the 1.5 kW laser, a result which was consistent with the model prediction.

Keefer, Dennis; Lewis, J. W. L.; Eskridge, Richard

1985-01-01

51

Optimization of the acoustic absorption coefficients of certain functional absorbents  

NASA Technical Reports Server (NTRS)

The sound absorption coefficients of some functional absorbents (mineral wool plates) are determined by the reverberation chamber method. The influence of the angle of inclination of the sound absorbing material with respect to the surface to be treated is analyzed as well as the influence of the covering index, defined as the ratio of the designed area of a plate and the area of the treated surface belonging to another plate. As compared with the conventional method of applying sound-absorbing plates, the analyzed structures have a higher technological and economical efficiency. The optimum structure corresponds to an angle of inclination of 15 deg and a covering index of 0.8.

Pocsa, V.; Biborosch, L.; Veres, A.; Halpert, E.; Lorian, R.; Botos, T.

1974-01-01

52

A method for monitoring nuclear absorption coefficients of aviation fuels  

NASA Technical Reports Server (NTRS)

A technique for monitoring variability in the nuclear absorption characteristics of aviation fuels has been developed. It is based on a highly collimated low energy gamma radiation source and a sodium iodide counter. The source and the counter assembly are separated by a geometrically well-defined test fuel cell. A computer program for determining the mass attenuation coefficient of the test fuel sample, based on the data acquired for a preset counting period, has been developed and tested on several types of aviation fuel.

Sprinkle, Danny R.; Shen, Chih-Ping

1989-01-01

53

Numerical analysis of falling film absorption with ammonia–water in magnetic field  

Microsoft Academic Search

Absorption strengthen is an effective way to improve the coefficient of performance (COP) of ammonia–water absorption refrigeration system. A mathematical absorption model for ammonia–water falling film absorption in magnetic field was built in this paper to study the influence of magnetic field on the absorption process. Macroscopic magnetic field force was introduced to the mathematical model. Changes in physical properties

Niu Xiaofeng; Du Kai; Du Shunxiang

2007-01-01

54

Absorption and Emission Coefficient Determination by a Zonal Ring Technique in a Circular Cylindrical Plasma Column.  

National Technical Information Service (NTIS)

An automated data acquisition and reduction system is described for obtaining absorption and emission coefficients in a circular cylindrical plasma column. The data reduction is based on a zonal ring method with the absorption coefficient accounted for in...

J. P. Oss

1966-01-01

55

Measurement of the absorption coefficient of acoustical materials using the sound intensity method  

Microsoft Academic Search

In this study the possibility of using the two-microphone sound intensity technique to measure the normal incidence and the random incidence sound absorption coefficient was investigated. The normal incidence absorption coefficient was determined by measuring the intensity incidence on the sample and the intensity reflected by the sample placed in an anechoic chamber. The random incidence absorption coefficient was determined

Mahabir S. Atwal; Malcolm J. Crocker

1987-01-01

56

DETERMINATION OF OCTANOL/WATER DISTRIBUTION COEFFICIENTS, WATER SOLUBILITIES, AND SEDIMENT/WATER PARTITION COEFFICIENTS FOR HYDROPHOBIC ORGANIC POLLUTANTS  

EPA Science Inventory

Octanol/water distribution coefficients, water solubilities, and sediment/water partition coefficients are basic to any assessment of transport or dispersion of organic pollutants. In addition, these determinations are prerequisites for many chemical or biological process studies...

57

Absorption of water and lubricating oils into porous nylon  

NASA Technical Reports Server (NTRS)

Oil and water absorption from air into sintered porous nylon can be described by infiltration into the pores of the material. This process can be modeled by a diffusion-like mechanism. For water absorption, we find a formal diffusion coefficient of 1.5 x 10(exp -4)sq cm/min when the nylon is initially dry. The diffusion coefficient is 4 x 10(exp -6)sq cm/min when the nylon is oil-impregnated prior to air exposure. In a 52% RH atmosphere, dry nylon absorbs 3% w/w water, and oil-impregnated nylon absorbs 0.6% w/w water. For oil absorption there are three steps: (1) surface absorption and infiltration into (2) larger and (3) smaller pores. Surface absorption is too fast to be measured in these experiments. The diffusion coefficient for the second step is 6 x 10(exp -4)sq cm/min for SRG-60 oil into dry nylon and 4 x 10(exp -4)sq cm/min for air-equilibrated nylon. The diffusion coefficient for the third step is about 1 x 10(exp -6)sq cm/min for both cases. The total amount of oil absorbed is 31% w/w. The interaction between water and nylon is not as strong as that between water and cotton-phenolic: oil can replace water, and only a small amount of water can enter previously oil-impregnated nylon.

Bertrand, P. A.

1995-01-01

58

Prediction of octanol?water partition coefficients, Henry coefficients and water solubilities using UNIFAC  

Microsoft Academic Search

Octanol\\/water partition coefficients, Henry coefficients and water solubilities can serve as basic physicochemical parameters for estimating the effects to the environment which can arise from potentially hazardous substances. We discuss the application of the UNIFAC method, which allows the prediction of these values on the basis of molecular structure. The UNIFAC method has the advantage over other models that the

G. Wienke; J. Gmehling

1998-01-01

59

Measurement and calculation of the sound absorption coefficient of pine wood charcoal  

NASA Astrophysics Data System (ADS)

Although charcoal has been widely utilized for physical therapy and as a deodorant, water purifier, etc. due to its porous features, research on its role as a sound-absorbing material is rarely found. Thus, the sound absorption coefficients of pine wood charcoal were measured using an impedance tube and were compared with the theoretical predictions in the frequency range of 500˜ 5000 Hz. The theory developed in the current study only considers the lowest possible mode propagating along the air channels of the charcoal and shows good agreements with the measurements. As the frequency is increased, the sound absorption coefficients of pine wood charcoals also increase, but are lower than those of other commonly-used sound-absorbing materials.

Suh, Jae Gap; Baik, Kyung min; Kim, Yong Tae; Jung, Sung Soo

2013-10-01

60

Mean mass energy absorption coefficient ratios for megavoltage x-ray beams.  

PubMed

Mean mass energy absorption coefficient ratios of acrylic, polystyrene, and water to air, were calculated using Monte Carlo generated energy spectra. The energy spectra were calculated for 4- to 50-MV x-ray beams, from machines using flattening filters and scanning beams. The validity of these spectra was verified by comparing the measured ionization ratios with the calculated values. The agreement was found to be within 1.9%. For beams of energy below 6 MV, our estimates of the mean mass energy absorption coefficient ratios agree well with those recommended by the TG-21 protocol. For higher energy beams, the discrepancy increases to about 3%. It was found that the discrepancy is attributable to the different spectra used in these calculations. PMID:7643787

Furhang, E E; Chui, C S; Lovelock, M

1995-05-01

61

Microwave Resonator Measurements of Atmospheric Absorption Coefficients: A Preliminary Design Study  

NASA Technical Reports Server (NTRS)

A preliminary design study examined the feasibility of using microwave resonator measurements to improve the accuracy of atmospheric absorption coefficients and refractivity between 18 and 35 GHz. Increased accuracies would improve the capability of water vapor radiometers to correct for radio signal delays caused by Earth's atmosphere. Calibration of delays incurred by radio signals traversing the atmosphere has applications to both deep space tracking and planetary radio science experiments. Currently, the Cassini gravity wave search requires 0.8-1.0% absorption coefficient accuracy. This study examined current atmospheric absorption models and estimated that current model accuracy ranges from 5% to 7%. The refractivity of water vapor is known to 1% accuracy, while the refractivity of many dry gases (oxygen, nitrogen, etc.) are known to better than 0.1%. Improvements to the current generation of models will require that both the functional form and absolute absorption of the water vapor spectrum be calibrated and validated. Several laboratory techniques for measuring atmospheric absorption and refractivity were investigated, including absorption cells, single and multimode rectangular cavity resonators, and Fabry-Perot resonators. Semi-confocal Fabry-Perot resonators were shown to provide the most cost-effective and accurate method of measuring atmospheric gas refractivity. The need for accurate environmental measurement and control was also addressed. A preliminary design for the environmental control and measurement system was developed to aid in identifying significant design issues. The analysis indicated that overall measurement accuracy will be limited by measurement errors and imprecise control of the gas sample's thermodynamic state, thermal expansion and vibration- induced deformation of the resonator structure, and electronic measurement error. The central problem is to identify systematic errors because random errors can be reduced by averaging. Calibrating the resonator measurements by checking the refractivity of dry gases which are known to better than 0.1% provides a method of controlling the systematic errors to 0.1%. The primary source of error in absorptivity and refractivity measurements is thus the ability to measure the concentration of water vapor in the resonator path. Over the whole thermodynamic range of interest the accuracy of water vapor measurement is 1.5%. However, over the range responsible for most of the radio delay (i.e. conditions in the bottom two kilometers of the atmosphere) the accuracy of water vapor measurements ranges from 0.5% to 1.0%. Therefore the precision of the resonator measurements could be held to 0.3% and the overall absolute accuracy of resonator-based absorption and refractivity measurements will range from 0.6% to 1.

Walter, Steven J.; Spilker, Thomas R.

1995-01-01

62

Oxygen absorption into moving water and tenside solutions  

Microsoft Academic Search

Oxygen absorption into water and waste water is an important process taking place with both natural and technical means, and a tool for a theoretical determination of the oxygen transfer coefficient, KL, is desirable.The objective of this investigation was to study the environment at and near the liquid side of a gas–liquid interface in order to present a model for

Tom Pedersen

2000-01-01

63

Absorption Coefficient Measurements of Strongly Scattering Media Using Time-Resolved Transmittance of a Short Pulse in Near-Infrared (NIR) Wavelength Range  

Microsoft Academic Search

Absorption coefficient measurements of strongly scattering and weakly absorbing media have been performed using time resolved transmittance of a 100 fs pulse through a 30 mm slab containing latex spheres suspended in water and absorbing ink solutions. The scattering and absorption coefficients were selected so that the optical properties of the media were similar to those of biological tissues. Measured

Sergei G. Proskurin; Yukio Yamada; Yukari Takahashi

1995-01-01

64

Measurement of sound absorption coefficients of flat surfaces in a workshop  

Microsoft Academic Search

To improve the acoustic treatment of facings and provide appropriate solutions for noise control at workplace, it is necessary to develop methods of acoustic characterization of the walls in industrial halls. Sound absorption coefficient measurement in industrial rooms is however quite a difficult task because of the partially reverberant conditions. This work describes the measurement of the sound absorption coefficient

J. Ducourneau; V. Planeau; J. Chatillon; A. Nejade

2009-01-01

65

Effects of circumferential air gaps on the measurement of the absorption coefficient of poroelastic materials  

Microsoft Academic Search

The influence of mounting conditions on the measurement of the absorption coefficient is investigated. More specifically, the effects of circumferential air gaps on poroelastic materials inside the standing wave tube are studied. The objective is to identify the materials, in terms of a ratio based on their physical properties, for which it is possible to measure the theoretical absorption coefficient

Dominic Pilon; Raymond Panneton

2002-01-01

66

Osmotic coefficients of trialkyl phosphates in water  

SciTech Connect

Osmotic and activity coefficients are reported at several temperatures for triethyl phosphate (TEP) and tripropyl phosphate (TPP) at low concentrations in water. TEP forms solutions that do not depart from ideality as much as do those formed from TPP. At 15 /sup 0/C the total excess Gibbs energies were -11 and -32 J.kg/sup -1/ at 0.05 mol.kg/sup -1/ for TEP and TPP, respectively. For TEP, the nonidealities resulted from a balance between entropic and enthalpic effects. 7 references, 2 figures, 1 table.

Sagert, N.H.

1984-01-01

67

Measurement of the absorption coefficient using the sound-intensity technique  

NASA Technical Reports Server (NTRS)

The possibility of using the sound intensity technique to measure the absorption coefficient of a material is investigated. This technique measures the absorption coefficient by measuring the intensity incident on the sample and the net intensity reflected by the sample. Results obtained by this technique are compared with the standard techniques of measuring the change in the reverberation time and the standing wave ratio in a tube, thereby, calculating the random incident and the normal incident adsorption coefficient.

Atwal, M.; Bernhard, R.

1984-01-01

68

A theoretical framework for quantitatively characterizing sound field diffusion based on scattering coefficient and absorption coefficient of walls.  

PubMed

This paper describes the development of a theoretical framework for quantitatively characterizing sound field diffusion based on scattering coefficient and absorption coefficient of walls. The concepts of equivalent scattering area, equivalent scatter reflection area, average scattering coefficient and average scatter reflection coefficient are introduced in order to express all walls' capability of scatter in a room. Using these concepts and the mean free path, scatter-to-absorption ratio, mean scatter time and diffusion time are defined in order to evaluate degree of diffusion of a space. Furthermore the effect of spatial scattering objects to sound field diffusion is formulated. In addition the time variation of specular and scattered components in a room impulse response is formulated. The verification of these characterization methods was performed with computer simulations based on the sound ray tracing method. The results supported that the ideas presented are basically valid. PMID:20815450

Hanyu, Toshiki

2010-09-01

69

Photoacoustic Methods for Measuring Surface and Bulk Absorption Coefficients in Highly Transparent Materials: Theory of a Gas Cell.  

National Technical Information Service (NTIS)

Researchers seek improved ways to measure the surface absorption and the bulk absorption coefficients of highly transparent materials. Procedures are presented here by which one may determine separately the surface absorption and the bulk absorption coeff...

H. S. Bennett R. A. Forman

1976-01-01

70

Measurement of diffusion coefficients important in modeling the absorption rate of carbon dioxide into aqueous N-methyldiethanolamine  

SciTech Connect

Natural gas processors use amine treating processes to remove the acid gases H{sub 2}S and CO{sub 2} from gas streams. Absorption rates of gaseous CO{sub 2} into aqueous N-methyldiethanolamine (MDEA) solutions were measured in a quiescent, inverted-tube diffusiometer by monitoring the rate of pressure drop. The absorption rate was found to be insensitive to the diffusion coefficient of CO{sub 2} in solution but very sensitive to the diffusion rate of bicarbonate and protonated MDEA ions. Evidence also suggested that chemical reaction equilibrium is rapid relative to diffusion. A numerical model was developed on the basis of these observations. The model was used to regress diffusion coefficients of bicarbonate and protonated amine, which must be equivalent by electroneutrality arguments, from measured absorption rates. Complete modeling of the absorption process also required data for the diffusion coefficient of MDEA in water. These were measured using a Taylor dispersion apparatus. CO{sub 2} absorption rates and diffusion coefficients of bicarbonate and protonated MDEA were obtained at 298.2 K and 318.2 K in solutions containing 20, 35, and 50 mass % MDEA in water.

Rowley, R.L.; Adams, M.E.; Marshall, T.L.; Oscarson, J.L.; Wilding, W.V.; Anderson, D.J. [Brigham Young Univ., Provo, UT (United States). Dept. of Chemical Engineering] [Brigham Young Univ., Provo, UT (United States). Dept. of Chemical Engineering

1997-03-01

71

Octanol-Water Partition Coefficients by Capillary Electrophoresis.  

National Technical Information Service (NTIS)

We have investigated the use of capillary electrophoresis (CE) for the modeling of octanol-water partition coefficients. Reversed-phase liquid chromatography (RPLC) is likely the most used method for estimation of octanol-water partition coefficients, wit...

J. G. Dorsey

1996-01-01

72

Mass-energy absorption coefficient and backscatter factor ratios for kilovoltage x-ray beams  

NASA Astrophysics Data System (ADS)

For low-energy (up to 150 kV) x-rays, the ratio of mass-energy absorption coefficients for water to air, , and the backscatter factor B are used in the conversion of air kerma, measured free-in-air, to water kerma on the surface of a water phantom. For clinical radiotherapy, similar conversion factors are needed for the determination of the absorbed dose to biological tissues on (or near) the surface of a human body. We have computed the ratios and B factor ratios for different biological tissues including muscle, soft tissue, lung, skin and bone relative to water. The ratios were obtained by integrating the respective mass-energy absorption coefficients over the in-air primary photon spectra. We have also calculated the ratios at different depths in a water phantom in order to convert the measured in-phantom water kerma to the absorbed dose to various biological tissues. The EGS4/DOSIMETER Monte Carlo code system has been used for the simulation of the energy fluence at different depths in a water phantom irradiated by a kilovoltage x-ray beam of variable beam quality (HVL: 0.1 mm Al-5 mm Cu), field size and source-surface distance (SSD). The same code was also used in the calculation of the B factor ratios, soft tissue to water and bone to water. The results show that the B factor for bone differs from the B factor for water by up to 20% for a 100 kV beam (HVL: 2.65 mm Al) with a 100 field. On the other hand, the difference in the B factor between water and soft tissue is insignificant (well within 1% generally). This means that the B factors for water may be directly used to convert the `in-air' water kerma to surface kerma for human soft tissues.

Ma, C.-M.; Seuntjens, J. P.

1999-01-01

73

Mass-energy absorption coefficient and backscatter factor ratios for kilovoltage x-ray beams.  

PubMed

For low-energy (up to 150 kV) x-rays, the ratio of mass-energy absorption coefficients for water to air, (mu(en)/rho)w.air, and the backscatter factor B are used in the conversion of air kerma, measured free-in-air, to water kerma on the surface of a water phantom. For clinical radiotherapy, similar conversion factors are needed for the determination of the absorbed dose to biological tissues on (or near) the surface of a human body. We have computed the mu(en)/rho ratios and B factor ratios for different biological tissues including muscle, soft tissue, lung, skin and bone relative to water. The mu(en)/rho ratios were obtained by integrating the respective mass-energy absorption coefficients over the in-air primary photon spectra. We have also calculated the mu(en)/rho ratios at different depths in a water phantom in order to convert the measured in-phantom water kerma to the absorbed dose to various biological tissues. The EGS4/DOSIMETER Monte Carlo code system has been used for the simulation of the energy fluence at different depths in a water phantom irradiated by a kilovoltage x-ray beam of variable beam quality (HVL: 0.1 mm Al-5 mm Cu), field size and source-surface distance (SSD). The same code was also used in the calculation of the B factor ratios, soft tissue to water and bone to water. The results show that the B factor for bone differs from the B factor for water by up to 20% for a 100 kV beam (HVL: 2.65 mm Al) with a 100 cm2 field. On the other hand, the difference in the B factor between water and soft tissue is insignificant (well within 1% generally). This means that the B factors for water may be directly used to convert the 'in-air' water kerma to surface kerma for human soft tissues. PMID:10071880

Ma, C M; Seuntjens, J P

1999-01-01

74

Absorption of laser radiation in a H-He plasma. I - Theoretical calculation of the absorption coefficient  

NASA Technical Reports Server (NTRS)

The theory for calculating the absorption of laser radiation by hydrogen is outlined for the temperatures and pressures of common laboratory plasmas. Nonhydrogenic corrections for determining the absorption by helium are also included. The coefficients for the absorption of He-Ne laser radiation at the wavelengths of 0.633, 1.15, and 3.39 microns in a H plasma is presented for temperatures in the range from 10,000 to 40,000 K and electron number densities in the range from 10 to the 15th power to 10 to the 18th power per cu cm. The total absorption of a H-He plasma calculated from this theory is compared with the measured absorption. The theoretical composition of the H-He absorption is analyzed with respect to the significant absorption processes, inverse bremsstrahlung, photoionization, resonance excitation, and photodetachment.

Stallcop, J. R.

1974-01-01

75

Synoptic water clarity assessment in the Florida Keys using diffuse attenuation coefficient estimated from Landsat imagery  

Microsoft Academic Search

The diffuse attenuation coefficient, K (m–1), is a measure of the effective attenuation of light in the water column. It characterizes water clarity and is used as a\\u000a proxy for water quality. Mapping of shallow water benthic habitats using optical means, including daytime visible satellite\\u000a imagery, requires knowledge of K to correct for water column effects such as light absorption

D. Palandro; C. Hu; S. Andréfouët; F. E. Muller-Karger

76

Particle scattering, backscattering, and absorption coefficients: An in situ closure and sensitivity study  

NASA Astrophysics Data System (ADS)

Comparisons between measured and calculated aerosol scattering, backscattering, and absorption coefficients were made based on in situ, ground-based measurements during the Melpitz INTensive (MINT) and Lindenberg Aerosol Characterization Experiment 1998 (LACE 98) field studies. Furthermore, airborne measurements made with the same type of instruments are reviewed and compared with the ground-based measurements. Agreement between measured and calculated values is on the order of ±20% for scattering and backscattering coefficients. A sensitivity analysis showed a large influence on the calculated particle scattering and backscattering coefficients resulting from sizing uncertainties in the measured number size distributions. Measured absorption coefficients were significantly smaller than the corresponding calculated values. The largest uncertainty for the calculated absorption coefficients resulted from the size-dependent fraction of elemental carbon (EC) of the aerosol. A correction for the measured fractions of EC could significantly improve the agreement between measured and calculated absorption coefficients. The overall uncertainty of the calculated values was investigated with a Monte Carlo method by simultaneously and randomly varying the input parameters of the calculations, where the variation of each parameter was bounded by its uncertainty. The measurements were mostly found to be within the range of uncertainties of the calculations, with uncertainties for the calculated scattering and backscattering coefficients of about ±20% and for the absorption coefficients of about ±30%. Thus, to increase the accuracy of calculated scattering, backscattering, and absorption coefficients, it is crucial to further reduce the error in particle number size distribution measurement techniques. In addition, further improvement of the techniques for measuring absorption coefficients and further investigation of the measurement of the fraction of EC of the aerosol is necessary.

Wex, Heike; Neusüß, Christian; Wendisch, Manfred; Stratmann, Frank; Koziar, Christian; Keil, Andreas; Wiedensohler, Alfred; Ebert, Martin

2002-11-01

77

[Simulation of backscattering coefficients of inland waters].  

PubMed

When we simulated backscattering coefficients (b(bp)) using quasi-analytical algorithm and optical closure theory, it was found that the position of reference wavelength (lambda(0)) had great impact on final results. In order to identify influence factors of the optimum lambda(0), datasets of Lake Taihu, Lake Chaohu and Lake Dianchi were used. After simulating of b(bp), the relationship between optimum lambda(0) and associated water quality parameters were analyzed. Meanwhile, power functions were utilized to model b(bp) spectra, and spectral slope parameters of Lake Taihu, Lake Chaohu and Lake Dianchi were 2.643 +/- 0.317, 2.719 +/- 0.242, 1.638 +/- 0.534, respectively. The results indicate that: (1) When the whole lakes are taken as objects of study, the lambda(0) should be changed to longer wavelength with the increasing of total suspended particle matter concentration (c(SPM)), suspended organic particle matter concentration (c(SPOM)) and chlorophyll a concentration (c(CHL)), the optimum location of lambda(0) of Lake Taihu is 695 nm, Lake Chaohu is 720 nm and Lake Dianchi is 730 nm; (2) When the samples in lakes are taken as objects of study, the influence factors are different due to the complexity of optical properties of inland waters. But it is to be noted that, c(SPM) is a key factor in common. Besides, the regularity mentioned above should be weakened with high c(CHL). (3) The relationship between b(bp) and c(SPM) is much stronger in the waters with suspended particles dominated by inorganic particles, in Lake Taihu, for example, relationship between these two variables is strong with R2 = 0.852. PMID:22165215

Zhang, Hong; Li, Yun-Mei; Huang, Jia-Zhu; Liu, Zhong-Hua; Xu, Yi-Fan; Xu, Xin; Guo, Yu-Long; Tan, Jing

2011-09-01

78

An Efficient Computational Approximation to the Lorentz Line Molecular Absorption Coefficient.  

National Technical Information Service (NTIS)

A rapid and accurate approximation to the Lorentz line molecular absorption coefficient has been developed which significantly reduces the time of line-by-line transmittance calculations. By separating computations required for each spectral line, atmosph...

M. T. Potter

1977-01-01

79

Optical Properties of Slags: Data for Refractive Indices and Absorption Coefficients.  

National Technical Information Service (NTIS)

The refractive indices and absorption coefficients of slags and glasses are important in the calculation of the radiation conductivity contribution to heat transfer in slags. Values of these properties have been collated and evaluated. (Copyright (c) Crow...

M. Susa K. C. Mills

1992-01-01

80

Absorption of laser radiation in a H-He plasma. II - Experimental measurement of the absorption coefficient  

NASA Technical Reports Server (NTRS)

The absorption coefficients of 0.633-, 1.15-, and 3.39-micron laser radiation for a homogeneous H-He plasma have been measured in the temperature range from 12.2 to 21.7 (x 1000 K) and in the electron number density range 0.45 to 6.5 (x 10 to the 17th power per cu cm). Good agreement is found between the experimentally determined total absorption for each of the wavelengths and that calculated from theory. Furthermore, because the 3.39-micron absorption is dominated by inverse bremsstrahlung, while the 0.633-micron absorption is dominated by photoionization and resonance absorption, the experiment indicates a correct assessment by the theory of these individual absorption mechanisms.

Billman, K. W.; Rowley, P. D.; Stallcop, J. R.; Presley, L.

1974-01-01

81

Spectral absorption coefficient of photosynthetically active pigments in the equatorial Pacific Ocean (165°11 150°W)  

NASA Astrophysics Data System (ADS)

Spectral absorption coefficients of total particulate material and detritus were measured throughout the euphotic zone along the equator between 165°E and 150°W and during time-series for each of these two longitudes in October 1994 (JGOFS-FLUPAC cruise). The sum of pigments obtained by spectrofluorometry (tChla=DV-chla+Chla) was used for normalization (and was also compared to fluorometric and HPLC measurements as an intercalibration study). In order to assess the specific absorption coefficient of photosynthetically active pigments (aps) from the pigment-specific absorption coefficient for phytoplankton ( aph*), we made a multiple regression analysis of measured phytoplankton absorption spectra onto published in vivo spectra of pure pigments. This made it possible to calculate the concentrations of photoprotective carotenoids (tPPC) when HPLC measurements were not available and thus to subtract their contribution to absorption from the total phytoplanktonic absorption coefficient ( aph). Methodological uncertainties in both coefficients used for calculating absorption coefficients and in pigment measurements are discussed. Pigments and absorption measurements made during the cruise enabled us to describe two typical trophic regimes in the equatorial Pacific ocean: oligotrophic waters of the "warm pool" west of 170°W and high-nutrient, low-chlorophyll waters (HNLC) of the upwelling east of 170°W. The vertical decreasing gradient of aph* from the surface to the deep chlorophyll maximum (DCM) was due to a high tPPC/tChla ratio at the surface and was higher in the oligotrophic (0.14-0.065 m 2 mg (tChl a) -1 biomass dominated by Prochlorococcus, rich in zeaxanthin) than in the mesotrophic area (0.07-0.06 m2 mg (tChl a)-' biomass dominated by picoeucaryotes). Below the DCM, aph* reached a similar minimum value in both oligotrophic and mesotrophic areas. a*ps varied less than a*ph from the surface layer to the DCM in both oligotrophic and mesotrophic areas. The difference in a*ph and a*ps from west to east of the transect could be interpreted as a shift in the phytoplankton composition, with a dominance of procaryotes in the west and a dominance of eucaryotes in the upwelling area. Higher aps in well-lit typical oligotrophic waters indicated that phytoplankton communities dominated by Proclorococcus might be more efficient for capturing light usable for photosynthesis than those present in the HNLC situation.

Dupouy, C.; Neveux, J.; An´, J. M.

82

Determination of the ultrasonic absorption coefficient in liquids by the thermal method  

Microsoft Academic Search

Summary  In liquids with a high ultrasonic absorption coefficient as, f.i. benzol, has been observed that an augmentation of the power\\u000a of the piezoelectric quartz might be a cause of energy dissipation to be ascribed to cavitation and acoustic flow which whould\\u000a be the origin of the high absorption coefficient. Measures are reported from which it appears that the augmentation of

E. Grossetti

1956-01-01

83

The Free-Free Absorption Coefficients of the Negative Helium Ion  

NASA Astrophysics Data System (ADS)

Free-free absorption coefficients of the negative helium ion are calculated by a phaseshift approximation, using continuum data that accurately account for electron-atom correlation and polarization. The approximation is considered to yield results within a few per cent of numerical values for wavelengths greater than 1 m, over the temperature range 1400-10080 K. These coefficients are expected to give the best current estimates of He - continuous absorption. Key words: atomic data - atomic processes - stars: atmospheres - infrared: general.

John, T. L.

1994-08-01

84

Molar extinction coefficients of IR absorption bands of Cu(II) dipivaloylmethanate  

Microsoft Academic Search

IR absorption spectra of an intracomplex chelate compound of Cu(II) bis-dipivaloylmethanate in the spectral range 4000–300\\u000a cm?1 are investigated. A comparison is made between the spectra of the complex in different aggregative states: as a solution\\u000a in heptane and as condensed films. The molar extinction coefficients of absorption bands are calculated. The extinction coefficients\\u000a found are used to evaluate the

L. F. Bakhturova; V. V. Bakovets; T. M. Levashova; I. P. Dolgovesova; V. O. Borisov

2000-01-01

85

A model comparison of the absorption coefficient of a Microperforated Insertion Unit in the frequency and time domains  

Microsoft Academic Search

The absorption coefficient of acoustic materials can be measured either in the frequency or the time domain. At normal incidence, a sample of the material is fitted within an impedance tube and the absorption coefficient is calculated in the frequency domain from the measurement of the transfer function between two microphones [ISO 10534-2. Acoustics – determination of sound absorption coefficient

Pedro Cobo

2008-01-01

86

Attenuation coefficients for water quality trading.  

PubMed

Water quality trading has been proposed as a cost-effective approach for reducing nutrient loads through credit generation from agricultural or point source reductions sold to buyers facing costly options. We present a systematic approach to determine attenuation coefficients and their uncertainty. Using a process-based model, we determine attenuation with safety margins at many watersheds for total nitrogen (TN) and total phosphorus (TP) loads as they transport from point of load reduction to the credit buyer. TN and TP in-stream attenuation generally increases with decreasing mean river flow; smaller rivers in the modeled region of the Ohio River Basin had TN attenuation factors per km, including safety margins, of 0.19-1.6%, medium rivers of 0.14-1.2%, large rivers of 0.13-1.1%, and very large rivers of 0.04-0.42%. Attenuation in ditches transporting nutrients from farms to receiving rivers is 0.4%/km for TN, while for TP attenuation in ditches can be up to 2%/km. A 95 percentile safety margin of 30-40% for TN and 6-10% for TP, applied to the attenuation per km factors, was determined from the in-stream sensitivity of load reductions to watershed model parameters. For perspective, over 50 km a 1% per km factor would result in 50% attenuation = 2:1 trading ratio. PMID:24866482

Keller, Arturo A; Chen, Xiaoli; Fox, Jessica; Fulda, Matt; Dorsey, Rebecca; Seapy, Briana; Glenday, Julia; Bray, Erin

2014-06-17

87

Estimating the sound absorption coefficients of perforated wooden panels by using artificial neural networks  

Microsoft Academic Search

Developing efficient sound absorption materials is a relevant topic for large scale structures such as gymnasiums, shopping malls, airports and stations. This study employs artificial neural network (ANN) algorithm to estimate the sound absorption coefficients of different perforated wooden panels with various setting combinations including perforation percentage, backing material and thickness. The training data sets are built by carrying out

Min-Der Lin; Kang-Ting Tsai; Bo-Sheng Su

2009-01-01

88

Experiment to Determine the Absorption Coefficient of Gamma Rays as a Function of Energy.  

ERIC Educational Resources Information Center

Simpler than x-ray diffractometer experiments, the experiment described illustrates certain concepts regarding the interaction of electromagnetic rays with matter such as the exponential decrease in the intensity with absorber thickness, variation of the coefficient of absorption with energy, and the effect of the K-absorption edge on the…

Ouseph, P. J.; And Others

1982-01-01

89

Absorption and Scattering Coefficients: A Biophysical-Chemistry Experiment Using Reflectance Spectroscopy  

ERIC Educational Resources Information Center

A biophysical-chemistry experiment, based on the reflectance spectroscopy for calculating the absorption and scattering coefficients of leaves is described. The results show that different plants species exhibit different values for both the coefficients because of their different pigment composition.

Cordon, Gabriela B.; Lagorio, M. Gabriela

2007-01-01

90

The average absorption coefficient for enclosed spaces with non uniformly distributed absorption  

Microsoft Academic Search

This study concerns the determination of an equivalent acoustic absorption model of the flat heterogeneous walls present in industrial rooms. Numerous measurements of the reverberation time in reverberant room were carried out for several facings with different distributed spatial absorption. Experimental results were compared to classical reverberation time models. The measurements showed that the change in average acoustic absorption depends

J. Ducourneau; V. Planeau

2003-01-01

91

Correlation analysis of optical absorption cross section and rate coefficient measurements in reacting systems  

SciTech Connect

A technique was developed for determining relative importance and correlation between reactions making up a complex kinetic system. This technique was used to investigate measurements of optical absorption cross sections and the correlation between cross sections and measured rate coefficients. It is concluded that (1) species, initial conditions, and temporal regions may be identified where cross sections may be measured without interference from the kinetic behavior of the observed species and (2) experiments designed to measure rate coefficients will always be correlated with the absorption cross section of the observed species. This correlation may reduce the accuracy of rate coefficient measurements.

Hessler, J.P. [Argonne National Lab., IL (United States); Ogren, P.J. [Earlham College, Richmond, IN (United States). Dept. of Chemistry

1992-08-31

92

On the Molar Extinction Coefficient and Integrated Molar Absorptivity of the Infrared Absorption Spectra of C60 and C70 Fullerenes  

Microsoft Academic Search

The molar extinction coefficients, known also as molar absorptivity ?, of C60 and C70 fullerenes infrared absorption spectra were determined at room temperature on samples embedded in KBr pellets. Furthermore, the integrated molar absorptivity ? of each absorption infrared band either of C60 and of C70 was measured and reported together with the relative intensity of the infrared absorption bands.

Franco Cataldo; Susana Iglesias-Groth; Arturo Manchado

2012-01-01

93

[Extracting THz absorption coefficient spectrum based on accurate determination of sample thickness].  

PubMed

Extracting absorption spectrum in THz band is one of the important aspects in THz applications. Sample's absorption coefficient has a complex nonlinear relationship with its thickness. However, as it is not convenient to measure the thickness directly, absorption spectrum is usually determined incorrectly. Based on the method proposed by Duvillaret which was used to precisely determine the thickness of LiNbO3, the approach to measuring the absorption coefficient spectra of glutamine and histidine in frequency range from 0.3 to 2.6 THz(1 THz = 10(12) Hz) was improved in this paper. In order to validate the correctness of this absorption spectrum, we designed a series of experiments to compare the linearity of absorption coefficient belonging to one kind amino acid in different concentrations. The results indicate that as agreed by Lambert-Beer's Law, absorption coefficient spectrum of amino acid from the improved algorithm performs better linearity with its concentration than that from the common algorithm, which can be the basis of quantitative analysis in further researches. PMID:22715781

Li, Zhi; Zhang, Zhao-hui; Zhao, Xiao-yan; Su, Hai-xia; Yan, Fang

2012-04-01

94

Si quantum dots with a high absorption coefficient: Analysis based on both intensive and extensive variables  

NASA Astrophysics Data System (ADS)

Silicon quantum dots (Si-QDs) were produced by pulsed laser ablation in liquid. By measuring the absorption spectra and the concentration of the Si-QD solution, two extinction coefficients were obtained from UV to near IR region: the atomic molar extinction coefficient and the quantum dot molar extinction coefficient. The magnitude of the atomic molar extinction coefficient of the Si-QDs was found to be up to 30 and 270 times those of crystalline and amorphous Si, respectively, and up to 740 times that of previously fabricated Si-QDs. The Si-QDs remained stably dispersed in hydrocarbon and alcohol solvents for over 10 months.

Kitasako, Takumi; Saitow, Ken-ichi

2013-10-01

95

Neural network approach to separate the non-algal absorption coefficient into dissolved and particulate  

NASA Astrophysics Data System (ADS)

We present a method for the separation of the non-algal absorption coefficient into its independent components of dissolved species and non-algal particulate absorptions from remote sensing reflectance (Rrs) measurements in the visible part of the spectrum. This separation is problematic due to the similar absorption spectra of these substances. Due to this complication, we approach the problem by constructing a neural network which relates the remote sensing reflectance at the available MODIS visible wavelengths (412, 443, 488, 531, 547 and 667nm) with the ratio of the absorption coefficient of non-algal particulates to the absorption coefficient of dissolved species, thereby permitting analytical separation of the total non-algal absorption into particulate and dissolved components. The resulting synthetically trained algorithm is tested on simulated data as well as independently on the NASA Bio-Optical Marine Algorithm Data set (NOMAD). Very good agreement is obtained, with R2 values of 87% and 78% for the non-algal particulate and dissolved absorption components, respectively for the NOMAD. Finally, we apply the algorithm to MODIS data and present global distributions for these parameters.

Ioannou, Ioannis; Foster, Robert; Gilerson, Alex; Ahmed, Sam

2013-08-01

96

Multi-wavelength measurements of aerosol optical absorption coefficients using a photoacoustic spectrometer  

NASA Astrophysics Data System (ADS)

The atmospheric aerosol absorption capacity is a critical parameter determining its direct and indirect effects on climate. Accurate measurement is highly desired for the study of the radiative budget of the Earth. A multi-wavelength (405 nm, 532 nm, 780 nm) aerosol absorption meter based on photoacoustic spectroscopy (PAS) invovling a single cylindrical acoustic resonator is developed for measuring the aerosol optical absorption coefficients (OACs). A sensitivity of 1.3 Mm?1 (at 532 nm) is demonstrated. The aerosol absorption meter is successfully tested through measuring the OACs of atmospheric nigrosin and ambient aerosols in the suburbs of Hefei city. The absorption cross section and absorption Ångström exponent (AAE) for ambient aerosol are determined for characterizing the component of the ambient aerosol.

Liu, Qiang; Huang, Hong-Hua; Wang, Yao; Wang, Gui-Shi; Cao, Zhen-Song; Liu, Kun; Chen, Wei-Dong; Gao, Xiao-Ming

2014-06-01

97

Birefringence and absorption coefficients of alpha barium borate in terahertz range  

NASA Astrophysics Data System (ADS)

In this paper we experimentally investigated the birefringence and absorption coefficients of alpha barium borate (?-BBO) crystal in the range of 0.3-10 THz by using a broadband air photonic terahertz time-domain spectrometer in both transmission and reflection modes. Several phonon modes were observed for o and e beams. The highest phonon mode at 6.8 THz has absorption coefficient of 1000 cm-1. The comparison between the optical properties of the ?-BBO and beta barium borate crystals showed that their phonon frequencies are different and ?-BBO crystal has smaller refractive index, birefringence, and absorption coefficients in low frequency region. The blueshift behavior of the lowest phonon of the ?-BBO crystal over the temperature range of 10-293 K has also been characterized.

Liu, Jingle; Zhang, X. C.

2009-07-01

98

Minority carrier diffusion lengths and absorption coefficients in silicon sheet material  

NASA Technical Reports Server (NTRS)

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

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

1980-01-01

99

A note on the prediction method of reverberation absorption coefficient of double layer micro-perforated membrane  

Microsoft Academic Search

The absorption performance of micro-perforated absorber (MPA) has been usually estimated by equivalent circuit (EC), however, it has been noted that the predicted absorption coefficient by EC does not agree completely with the experiment in some frequency range. Hence impedance transfer method (ITM) is adopted to predict the reverberation absorption coefficient of a double layer micro-perforated membrane (MPM) structure. Experimental

Jian Zou; Yong Shen; Jianbin Yang; Xiaojun Qiu

2006-01-01

100

A numerical study of a method for measuring the effective in situ sound absorption coefficient.  

PubMed

The accuracy of a method [Wijnant et al., Proc. of ISMA 31, Leuven, Belgium (2010), Vol. 31] for measurement of the effective area-averaged in situ sound absorption coefficient is investigated. Based on a local plane wave assumption, this method can be applied to sound fields for which a model is not available. Investigations were carried out by means of finite element simulations for a typical case. The results show that the method is a promising method for determining the effective area-averaged in situ sound absorption coefficient in complex sound fields. PMID:22979838

Kuipers, Erwin R; Wijnant, Ysbrand H; de Boer, André

2012-09-01

101

Measurement of the absorption coefficient of sound absorbing materials under a synthesized diffuse acoustic field.  

PubMed

This letter proposes an experimental method to estimate the absorption coefficient of sound absorbing materials under a synthesized diffuse acoustic field in free-field conditions. Comparisons are made between experiments conducted with this approach, the standard reverberant room method, and numerical simulations using the transfer matrix method. With a simple experimental setup and smaller samples than those required by standards, the results obtained with the proposed approach do not exhibit non-physical trends of the reverberant room method and provide absorption coefficients in good agreement with those obtained by simulations for a laterally infinite material. PMID:24993232

Robin, Olivier; Berry, Alain; Doutres, Olivier; Atalla, Noureddine

2014-07-01

102

Minority carrier diffusion lengths and absorption coefficients in silicon sheet material  

SciTech Connect

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

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

1980-01-01

103

The determination of absorption coefficients from the photo-response of silicon Schottky barriers  

NASA Astrophysics Data System (ADS)

A novel approach to the measurement of the absorption coefficient was made through the use of differential photo-currents of Schottky barriers in order to eliminate the influence of unknown surface conditions. By varying the reverse bias on Schottky barriers created by semitransparent Au on Si wafers, the depth of the barrier layer was varied and the resulting photocurrents were used to evaluate the absorption coefficient of the substrate at room temperature. The results are in good agreement with values published in the recent literature.

Mil'shtein, S.; Brada, Y.

1983-04-01

104

Infrared absorption coefficient of molten LiF and Li2S  

NASA Astrophysics Data System (ADS)

A method based on the 'submerged mirror' technique to measure absorption coefficients of liquids at elevated temperatures is presented. Modulated radiation reflected off the sample was collected by a HgCdTe infrared detector and the subsequent signals were processed by an FTIR spectrometer. Apparent reflectivities of two samples of different thicknesses and the first surface reflectivity were measured, and the absorption coefficients were calculated. Absorption coefficients in the range 0.5-11/cm were measured using samples of thicknesses 1-2 mm. The absorption coefficients of molten LiF, Li2S, and the (6LiF + Li2S) eutectic mixture were measured for wavelengths between 1.5 micron and their infrared absorption edge. Measurements were carried out for a range of temperatures between the respective melting points and 1400 C. The measured data for LiF at 900 C are in good agreement with published data. An uncertainty analysis shows the error associated with these measurements to be within 20 percent.

Gupta, Sreenath B.; Modest, Michael F.

1993-07-01

105

Expression of optical diffusion coefficient in high-absorption turbid media  

NASA Astrophysics Data System (ADS)

The optical diffusion coefficient in a homogeneous turbid medium with high absorption was determined by steady-state measurements of the light transmission under the infinite-boundary condition. The intensity of the transmission was well described by the solution of the optical diffusion equation. Moreover, the optical diffusion coefficient D was given by a constant, , where is the reduced scattering coefficient, up to the absorption coefficient of about . These results mean that attenuation by absorption only contributes to exponential attenuation along the optical path defined by the scattering coefficient and geometry of the system even in high-absorption turbid media such as the pathological living tissues of bleeding or haematoma.

Nakai, T.; Nishimura, G.; Yamamoto, K.; Tamura, M.

1997-12-01

106

Specific absorption coefficient of phytoplankton off the Southwest coast of the Iberian Peninsula: A contribution to algorithm development for ocean colour remote sensing  

NASA Astrophysics Data System (ADS)

The variability in coefficients of absorption for phytoplankton was assessed for an area off the Southwest coast of Portugal. This area included three sites at 2, 10 and 18 km perpendicular to the coast, sampled at surface, mid-Secchi and Secchi depths at each site. Phytoplankton absorption coefficients were transformed into specific coefficients (a*ph(?)) by normalizing them with respect to chlorophyll a (Chla) concentrations determined by High Performance Liquid Chromatography. The influence on the variability of the absorption coefficient of phytoplankton was assessed for physico-chemical and biological parameters such as nutrients or Chla levels, as well as size structure and abundance of the phytoplankton community. The results showed that the phytoplankton absorption coefficients decreased from inshore to offshore, but were relatively constant within the water column, revealing a well-mixed column. The a*ph(?) varied inversely with Chla content, with minima in Autumn and Spring, matching phytoplankton blooms. The effects of the size structure of the community and pigment composition on the variability of phytoplankton absorption coefficient were studied and results showed that size structure had a greater influence on the variability of the phytoplankton absorption, although the pigment contribution was also important.

Costa Goela, Priscila; Icely, John; Cristina, Sónia; Newton, Alice; Moore, Gerald; Cordeiro, Clara

2013-01-01

107

Frequency dependence of photoacoustic spectroscopy: Surface and bulk-absorption coefficients  

Microsoft Academic Search

Researchers seek improved ways to measure separately the surface- and bulk-absorption coefficients of highly transparent materials. The case in which a laser beam modulated at angular frequency ? passes through the weakly absorbing windows of a gas cell which contains a nonabsorbing gas is investigated in this paper. In particular, the frequency dependences of the acoustic stresses in the gas

Herbert S. Bennett; Richard A. Forman

1977-01-01

108

Microphone-free measurement of acoustic absorption coefficient of materials using a standing wave tube  

Microsoft Academic Search

This paper reports a method for measuring the specific acoustic impedance or absorption coefficient of acoustic material using a standing wave tube without a microphone. The method was validated by tests conducted in a normal standing wave or impedance tube—a straight solid-wall tube with a speaker and a material specimen perpendicularly mounted at each end, respectively. Assuming that sound waves

Dewei Peng; Shih-Fu Ling

2005-01-01

109

Determination of the optical absorption coefficient via analysis of laser-generated plate waves  

Microsoft Academic Search

A technique has been demonstrated which measures the optical absorption coefficient in weakly to moderately absorbing homogeneous isotropic elastic plates. This technique involves generating plate waves with a pulsed Nd:YAG laser and then detecting the disturbances in the acoustic far field where the majority of the acoustic energy has been coupled into the first symmetric, so, and antisymmetric, a o,

David H. Hurley; James B. Spicer; R. Jay Conant; Ken L. Telschow

1997-01-01

110

Use of statistical energy analysis for the prediction of Sabine absorption coefficient of modally reactive panels  

Microsoft Academic Search

Statistical energy analysis (SEA) is used to establish a relationship between the Sabine absorption coefficient of a modally reactive panel and the coupling of the panel with the sound field in a room. The acoustic-structural coupling is described by the coupling loss factors between the panel and the room. The application of the consistency relationship in SEA, which is based

K. S. Sum

2004-01-01

111

An optoacoustic technique for measuring the optical absorption coefficient in solids  

Microsoft Academic Search

An investigation was made of an optoacoustic technique for determining the optical absorption coefficients in solids. A train of laser pulses was passed through the solid, and the amplitude of the acoustic wave generated by the absorbed radiation was measured by a piezoelectric transducer attached directly to the sample. It was shown theoretically and experimentally that the output voltage from

A. Hordvik; H. Schlossberg; H. Miller; C. Gallagher

1976-01-01

112

Frequency dependence of photoacoustic spectroscopy: Surface and bulk-absorption coefficients  

Microsoft Academic Search

Researchers seek improved ways to measure separately the surface- and bulk-absorption coefficients of highly transparent materials. The case in which a laser beam modulated at angular frequency omega passes through the weakly absorbing windows of a gas cell which contains a nonabsorbing gas is investigated in this paper. In particular, the frequency dependences of the acoustic stresses in the gas

Herbert S. Bennett; Richard A. Forman

1977-01-01

113

MEASUREMENT OF NORMAL AND OBLIQUE INCIDENCE ABSORPTION COEFFICIENTS USING A SCANNING LASER DOPPLER VIBROMETER  

Microsoft Academic Search

Different well accepted standardized test methods exist to estimate absorption coefficients of acoustical materials from experiments. The most widespread technique uses the so-called Kundt's tube. This method clearly has its limitations since both the upper and lower frequencies are limited by the diameter and length of the used tube. Another standardised method uses the comparison of the reverberation times measured

Cedric Vuye; Steve Vanlanduit; Joris Vanherzeele; Patrick Guillaume; Hogeschool Antwerpen

114

The Free-Free Absorption Coefficient of the Negative Ion of Molecular Hydrogen.  

National Technical Information Service (NTIS)

The free-free absorption coefficient of the negative ion of molecular hydrogen is calculated in the dipole length formulation using wavefunctions which take account of exchange and polarization effects on the free electron. The results are found to be app...

K. L. Bell A. E. Kingston W. A. McIlveen

1974-01-01

115

Absorption Coefficients for the Wings of the First Two Resonance Doublets of Cesium Broadened by Argon  

Microsoft Academic Search

Measurements are reported of the absolute absorption coefficients in the wings of the 8944-, 8521-, 4593-, and 4555-Å resonance lines of cesium in the presence of argon at densities between about 6 × 1018 and 2 × 1019 atom cm-3. The data extend from about 0.7 Å to as much as 600 Å from the line center and were obtained

C. L. Chen; A. V. Phelps

1973-01-01

116

Equivalent absorption coefficient: A parameter for room sound pressure level prediction  

NASA Astrophysics Data System (ADS)

The development of an equivalent absorption coefficient is described. Its use facilitates the calculation of A-weighted sound pressure levels in rooms. Thus for the modelling of the acoustic field only one set of calculations need to be performed rather than a separate one for each octave band and eventual A-weighted summation.

Hundal, M. S.

1984-07-01

117

Vapor-Phase Absorptivity Coefficient of Ethyl N,N- Dimethylphosphoramidocyanidate.  

National Technical Information Service (NTIS)

We measured the vapor-phase absorptivity coefficient of the chemical warfare agent ethyl N,N-dimethylphosphoramidocyanidate (GA) in the mid-infrared (4000-550 cm'') at a spectral resolution of 0.125 cm''. The GA used in the feedstock was purified by fract...

A. C. Samuels B. R. William J. R. Miles M. S. Hulet

2010-01-01

118

Measurement of Aerosol Absorption Coefficient from Teflon Filters Using Integrating Plate and Integrating Sphere Techniques  

Microsoft Academic Search

Optical transmission of aerosol samples collected on Teflon filters measured by the integrating plate method (IPM) has been used as a means of determining the aerosol absorption coefficient, b , by the Air Quality Group at Crocker Nuclear Lab for over 9 years. The results of an intensive quality assurance program, using an integrating sphere photometer configured for measurement of

Dave Campbell; Scott Copeland; Thomas Cahill

1995-01-01

119

The use of the Milne-Eddington absorption coefficient for radiative heat transfer in combustion systems  

Microsoft Academic Search

The applicability of the Milne-Eddington absorption coefficient approximation is discussed in relation to the calculation of radiative transport involving the two distinct types of species produced in combustion systems - gases and soot particles. The approximation is found to apply well to hydrocarbon soot particles and as a result analytical closed-form solutions are derived for the radiative heat transfer inside

J. D. Felske; C. L. Tien

1977-01-01

120

Laboratory Measurements of the Ozone Absorption Coefficient in the Wavelength Region 339 to 362 nm at Different Temperatures.  

National Technical Information Service (NTIS)

Instrumentation for the absolute measurement of the ozone absorption coefficient in the Huggins bands at different temperatures was set up. Ozone is produced with an electrical discharge and stored cryogenically; differential absorption measurements are c...

M. Cacciani A. Disarra G. Fiocco

1987-01-01

121

Quantitative photoacoustic microscopy of optical absorption coefficients from acoustic spectra in the optical diffusive regime  

NASA Astrophysics Data System (ADS)

Photoacoustic (PA) microscopy (PAM) can image optical absorption contrast with ultrasonic spatial resolution in the optical diffusive regime. Conventionally, accurate quantification in PAM requires knowledge of the optical fluence attenuation, acoustic pressure attenuation, and detection bandwidth. We circumvent this requirement by quantifying the optical absorption coefficients from the acoustic spectra of PA signals acquired at multiple optical wavelengths. With the acoustic spectral method, the absorption coefficients of an oxygenated bovine blood phantom at 560, 565, 570, and 575 nm were quantified with errors of <3%. We also quantified the total hemoglobin concentration and hemoglobin oxygen saturation in a live mouse. Compared with the conventional amplitude method, the acoustic spectral method provides greater quantification accuracy in the optical diffusive regime. The limitations of the acoustic spectral method was also discussed.

Guo, Zijian; Favazza, Christopher; Garcia-Uribe, Alejandro; Wang, Lihong V.

2012-06-01

122

[Development of a photoacoustic spectroscopy system for the measurement of absorption coefficient of atmospheric aerosols].  

PubMed

In the present paper, the authors focus on the effect of the resonance frequency shift due to the changes in temperature and humidity on the PA signal, present several methods to control the noise derived form gas flow and vibration from the sampling pump. Based on the efforts mentioned above, a detection limit of 1.4 x 10(-8) W x cm(-1) x Hz(-1/2) was achieved for the measurement of atmospheric aerosols absorption coefficient. During the experiments, the PA cell was calibrated with the absorption of standard NO2 gas at 532 nm and the atmospheric aerosols were measured continuously. The measurement results show that the PAS is suitable for the real-time measurement of the absorption coefficient of atmospheric aerosols in their natural suspended state. PMID:24059163

Liu, Qiang; Niu, Ming-Sheng; Wang, Gui-Shi; Cao, Zhen-Song; Liu, Kun; Chen, Wei-Dong; Gao, Xiao-Ming

2013-07-01

123

Hitherto Unidentified Absorption Bands of Water Vapour  

Microsoft Academic Search

IN 1912-13, F. E. Fowle1 made studies of the absorption of infra-red radiation by water-vapour at 0.93mu, 1.13mu and 1.47mu, in order to determine spectroscopically the total water-vapour content of the atmosphere. The first two wave-lengths are at the centres of the rho and varphi bands; the last is about 450 cm.-1 from the Psi-band centre.

T. G. Cowling

1943-01-01

124

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

NASA Technical Reports Server (NTRS)

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

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

1979-01-01

125

[Influence of petroleum concentration in water on spectral backscattering coefficient].  

PubMed

The petroleum pollutants mixing proportion experiment and in-situ experiment were carried out in the estuary of Panjin, Liaoning province in May 2008 and August 2009. The optical properties and biochemical properties were measured to get the effect of petroleum concentration in water on backscattering coefficients spectrum. The results show that the power-law index of backscattering coefficient decreases as TSM concentration increases and the relationship of these variables follows logarithm mode. Specific backscattering coefficient's value of 440 to 856 nm is between 0.006 and 0.035 m2 x g(-1) and decreases as wavelength increases. The petroleum mass-specific backscattering coefficients (backscattering coefficients of unit petroleum concentration) decreases with the wavelength increasing and follows power law for petroleum concentration. Petroleum concentration has little effect on the power-law index of backscattering coefficient. PMID:21105413

Song, Qing-jun; Huang, Miao-fen; Tang, Jun-wu; Wang, Xiao-mei

2010-09-01

126

The ultraviolet absorption coefficient of melanosomes decreases with increasing pheomelanin content.  

PubMed

Uveal melanosomes from the iridal stroma contain both eumelanin and pheomelanin, the ratio of which varies with iris color. Herein, we report the absorption coefficient at lambda = 244 nm for individual human iridal stroma melanosomes from dark brown and blue-green irides. The melanosomes are nearly identical in size, but differ in the relative concentration composition, ranging from a eumelanin/pheomelanin ratio of 14.8:1 (dark brown) to 1.3:1 (blue-green or hazel). The absorption coefficient of the melanosome decreases as its pheomelanin content increases. The origin of this decrease is attributed to a corresponding decrease in the number of UV-absorbing chromophores, reflecting the different molecular volumes of the monomeric building blocks of the two pigments. In agreement with reported data on synthetic pigments, the absorption coefficient of pheomelanin is found to be slightly larger than that for eumelanin at lambda = 244 nm (by a factor of 1.2). On the basis of the reported optical properties of synthetic models, this result suggests that the absorption of pheomelanin is less than eumelanin at wavelengths of biological relevance ( approximately 315-400 nm). PMID:20614877

Peles, Dana N; Simon, John D

2010-07-29

127

Traffic-related differences in indoor and personal absorption coefficient measurements in Amsterdam, the Netherlands  

NASA Astrophysics Data System (ADS)

Population studies indicate that study participants living near major roads are more prone to chronic respiratory symptoms, lung function decrements and hospital admissions for asthma. The majority of the studies used proxy measures, such as distance to major roads or traffic intensity in the surroundings of the home. Few studies have communicated findings of concurrently performed measurements of outdoor, indoor and personal air pollution in urban streets with high- and low-traffic density. Measuring light absorption or reflectance of particulate matter (PM) collected on filters is an alternative method to determine elemental carbon, a marker for particles produced by incomplete combustion, compared to expensive and destructive analytical methods. This study sets out to test the null hypothesis that there is no difference in personal and indoor filter absorption coefficients for participants living along busy and quiet roads in Amsterdam. In one study we measured personal and indoor absorption coefficients in a sample of adults (50-70 years) and, in another study, the indoor levels in a population of adults (50-70 years) and school children (10-12 years). In the first study, the ratios of personal and indoor absorption coefficients in homes along busy roads compared with homes on quiet streets were significantly higher by 29% for personal measurements ( n=16 days, p<0.001), and by 19% for indoor measurements ( n=20, p<0.001), while in the second study, the ratio for the indoor measurements was higher by 26% ( n=25 days, p<0.05). Exposure differences between homes along busy compared to homes along quiet streets remained and significant after adjustment for potential indoor sources (such as cooking and use of unvented heating appliances). This study therefore provides tentative support for the use of the type of road as proxy measure for indoor and personal absorption coefficient measurements in epidemiological studies due to the limitations of the study.

Wichmann, Janine; Janssen, Nicole A. H.; van der Zee, Saskia; Brunekreef, Bert

128

Water and tissue equivalency of some gel dosimeters for photon energy absorption.  

PubMed

The mass energy absorption coefficients,, effective atomic numbers for photon energy absorption, ZPEAeff, and effective electron numbers for photon-energy absorption, NPEAeff, is calculated for 14 polymer gel dosimeter, five gel dosimeter, soft tissue and water, in the energy range from 1 keV to 20 MeV. The ZPEAeff(Gel)/ZPEAeff(Tissue) and NPEAeff(Gel)/NPEAeff (Tissue) are used to evaluate the tissue equivalency. PMID:24080343

Un, Adem

2013-12-01

129

Energy analysis of an ammonia-water absorption refrigeration system  

SciTech Connect

Absorption refrigeration systems (ARSs) are run on heat-operated cycles. In these systems a secondary fluid (i.e., absorbent) is used to absorb the primary fluid (i.e., refrigerant) vaporized in the evaporator. ARSs for industrial and domestic applications have been attracting increasing interest throughout the world. A simple energy analysis technique for ammonia-water refrigeration systems is presented and verified with actual experimental data taken from the literature. Comparison was made in terms of the coefficient of performance, and very good agreement was found.

Dincer, I.; Dost, S. [Univ. of Victoria, British Columbia (Canada). Dept. of Mechanical Engineering

1996-09-01

130

Correlation between oral drug absorption in humans and apparent drug permeability coefficients in human intestinal epithelial (Caco-2) cells  

Microsoft Academic Search

Monolayers of a well differentiated human intestinal epithelial cell line, Caco-2, were used as a model to study passive drug absorption across the intestinal epithelium. Absorption rate constants (expressed as apparent permeability coefficients) were determined for 20 drugs and peptides with different structural properties. The permeability coefficients ranged from approximately 5 x 10{sup - 8} to 5 x 10{sup -

P. Artursson; J. Karlsson

1991-01-01

131

AN INTERCOMPARISON CF THE INTEGRATING PLATE AND THE LASER TRANSMISSION METHODS FOR DETERMINATION OF AEROSOL ABSORPTION COEFFICIENTS  

SciTech Connect

The absorption coefficients determined by the integrating plate method and the laser transmission method are found to be comparable and highly correlated. Furthermore, a high correlation is found between these absorption coefficients and the carbon content of the aerosol in urbanized regions.

Sadler, M.; Charlson, R.J.; Rosen, H.; Novakov, T.

1980-07-01

132

Vacuum Ultraviolet Absorption of Supercritical Water  

NASA Astrophysics Data System (ADS)

The first continuum X&˜circ;->A&˜circ; peak in the gas phase absorption spectrum of H2O (maximum at 7.4 eV) , is ascribed to promotion of a nonbonding valence electron to a dissociative excited state which is an admixture of antibonding sigma and 3s Rydberg orbitals. Due to the large spatial extent of this orbital theX&˜circ;->A&˜circ; transition is strongly perturbed by the local environment. In liquid water, this peak is notably broadened and shifted to the blue, with an absorption maximum of 8.3 eV at room temperature. An obvious question is how this transition changes as a function of the water density in the supercritical regime as the system transitions from liquid to gas. As density decreases, most water molecules will be located at an interface between large clusters and voids. We will describe an experiment to measure the VUV absorption of the X&˜circ;->A&˜circ; transition in supercritical water (T>374 C, P>220 bar ) where the density can be tuned continuously. Experimentally this requires over six orders of magnitude detector dynamic range in the vacuum UV and a short path (ca. 1 micron) high temperature/pressure cell with sapphire windows. This has not been accomplished in any previous experiment. Results will be discussed in the light of recent ab initio calculations of the spectrum in large and small clusters.

Bartels, David; Janik, Ireneusz; Marin, Timothy

2009-03-01

133

Water absorption in horizontal corrugated boards under water sprays  

Microsoft Academic Search

Experiments were performed to determine the water absorption propensity of four different corrugated boards oriented horizontally and exposed to vertical water sprays from above. The corrugated samples used in the experiments were taken from cartons and partition boards from the FM Global Standard Plastic Commodity and from the inner and outer cartons of the FM Global Class II Commodity. These

T. M. Jayaweera; H.-Z. Yu

2006-01-01

134

Photoacoustic recovery of an absolute optical absorption coefficient with an exact solution of a wave equation.  

PubMed

We describe a new approach to recover an absolute optical absorption coefficient from measured photoacoustic signals based on an exact solution of the wave equation. We present a numerical model to describe the detection of photoacoustic waves by introducing a point spread function of a photoacoustic measuring system. This model is employed in an iterative fitting procedure in order to recover an absolute optical absorption coefficient. In addition, the fitting procedure utilizes the ratios of the amplitudes of the characteristic peaks of photoacoustic signals as the input, as opposed to using the total measured photoacoustic data. Such an arrangement increases computational speed and reduces the influence of signals from neighboring objects. The proposed method is then verified both numerically and experimentally on the gel samples, from which the accuracy is found to be in the range -5.2% to 4.8%. PMID:18854608

Wang, Yi; Wang, Ruikang

2008-11-01

135

Measurement of acoustic absorption coefficient with phase-conjugate ultrasonic waves  

Microsoft Academic Search

Experimental results on measurements of the acoustic absorption coefficient in test objects that were obtained with two methods, i.e., a standard insert-substitution method and a modification thereof using phase-conjugate waves, are given. Samples of gelatin and biological tissue in vitro (porcine muscle fibers) were used as test objects. Gelatin objects were manufactured that were both homogeneous and with inhomogeneities in

N. V. Smagin; L. M. Krutyansky; A. P. Brysev; F. V. Bunkin

2011-01-01

136

A new method for the determination of the acoustic absorption coefficient in liquids  

Microsoft Academic Search

Summary  A new way to obtain the acoustic absorption coefficient in liquids by an optical method, making use of standing ultrasonic\\u000a waves. Some results are given, in good agreement with the experimental results of other authors who worked with different\\u000a methods at the same frequency and temperature. A noteworthy exception is the case of Benzol, for which we obtained a value

A. Carrelli; F. S. Gaeta

1957-01-01

137

Measurement of acoustic absorption coefficient with phase-conjugate ultrasonic waves  

Microsoft Academic Search

Experimental results on measurements of the acoustic absorption coefficient in test objects that were obtained with two methods,\\u000a i.e., a standard insert-substitution method and a modification thereof using phase-conjugate waves, are given. Samples of\\u000a gelatin and biological tissue in vitro (porcine muscle fibers) were used as test objects. Gelatin objects were manufactured\\u000a that were both homogeneous and with inhomogeneities in

N. V. Smagin; L. M. Krutyansky; A. P. Brysev; F. V. Bunkin

2011-01-01

138

Quantitative reconstruction of absorption and scattering coefficients in ultrasound-modulated optical tomography  

NASA Astrophysics Data System (ADS)

The simultaneous and/or quantitative recovery of optical absorption and scattering coefficients in ultrasound modulated optical tomography requires the use of a model-based inversion procedure. In this work we employ a linearised forward model as part of a non-linear image reconstruction process, recovering parameters with an error of less than +/-3% from simulated measurements with 1% Gaussian noise and initial conditions differing by 10% from the actual background.

Powell, Samuel; Leung, Terence S.

2014-03-01

139

Higher-order virial coefficients of water models.  

PubMed

We use the Mayer sampling method, with both direct and overlap sampling, to calculate and compare classical virial coefficients up to B6 for various water models (SPC, SPC/E, MSPC/E, TIP3P, and TIP4P). The precision of the computed values ranges from 0.1% for B2 to an average of 25% for B6. When expressed in a form scaled by the critical properties, the values of the coefficients for SPC water are observed to greatly exceed the magnitude of corresponding coefficients for the simple Lennard-Jones model. We examine the coefficients in the context of the equation of state and the Joule-Thomson coefficient. Comparisons of these properties are made both to established molecular simulation data for each respective model and to real water. For all models, the virial series up to B5 describes the equation of state along the saturated vapor line better than the series that includes B6. At supercritical temperatures, however, the sixth-order series often describes pressure-volume-temperature behavior better than the fifth-order series. For example, the sixth-order virial equation of state for SPC/E water predicts the 673 K isotherm within 8% of published molecular simulation values up to a density of 9 mol/L (roughly half the critical density of SPC/E water). PMID:17850128

Benjamin, Kenneth M; Singh, Jayant K; Schultz, Andrew J; Kofke, David A

2007-10-01

140

Heat transfer coefficients in two-phase flow for mixtures used in solar absorption refrigeration systems  

Microsoft Academic Search

This paper describes the experimental results obtained on the heat transfer in saturated nucleate boiling of refrigerant mixtures used in solar absorption refrigeration systems flowing upward in a uniformly heated vertical tube. The mixtures analysed were water\\/ammonia, ammonia\\/lithium nitrate and water\\/lithium bromide. The concentration range for the water\\/ammonia was from 38 to 48wt%, for the ammonia\\/lithium nitrate was from 38

W Rivera; V Vélez; A Xicale

2000-01-01

141

Measurements of SO2 absorption coefficients using a tunable dye laser  

NASA Technical Reports Server (NTRS)

High-resolution measurements of SO2 absorption coefficients in the UV are presented in the wavelength interval between 2962 and 3011 A using a frequency-doubled dye laser as the radiation source. These measurements have application to pollution monitoring of SO2 using the differential absorption scattering (DAS) technique. The spectral resolution of the measurements was 0.2 A (determined by the linewidth of the dye laser) and the generated spectra exhibited considerable rotational structure on the (000) double prime to (060) prime, (070) prime, and (080) prime electronic-vibrational transitions. The latter transitions correspond to center wavelengths of 3001.8, 2981.0, and 2962 A, respectively. The laser measurements were obtained with a signal-processing technique which eliminated calibration procedures associated with conventional optical-absorption measurements. Using this technique, the statistical uncertainty associated with measured absorption coefficients has been reduced to less than plus or minus 2% with a wavelength uncertainty of the laser source of plus or minus 0.1 A.

Thompson, R. T., Jr.; Hoell, J. M., Jr.; Wade, W. R.

1975-01-01

142

Backscatter factors and mass energy-absorption coefficient ratios for diagnostic radiology dosimetry  

NASA Astrophysics Data System (ADS)

Backscatter factors, B, and mass energy-absorption coefficient ratios, (?en/?)w, air, for the determination of the surface dose in diagnostic radiology were calculated using Monte Carlo simulations. The main purpose was to extend the range of available data to qualities used in modern x-ray techniques, particularly for interventional radiology. A comprehensive database for mono-energetic photons between 4 and 150 keV and different field sizes was created for a 15 cm thick water phantom. Backscattered spectra were calculated with the PENELOPE Monte Carlo system, scoring track-length fluence differential in energy with negligible statistical uncertainty; using the Monte Carlo computed spectra, B factors and (?en/?)w, air were then calculated numerically for each energy. Weighted averaging procedures were subsequently used to convolve incident clinical spectra with mono-energetic data. The method was benchmarked against full Monte Carlo calculations of incident clinical spectra obtaining differences within 0.3-0.6%. The technique used enables the calculation of B and (?en/?)w, air for any incident spectrum without further time-consuming Monte Carlo simulations. The adequacy of the extended dosimetry data to a broader range of clinical qualities than those currently available, while keeping consistency with existing data, was confirmed through detailed comparisons. Mono-energetic and spectra-averaged values were compared with published data, including those in ICRU Report 74 and IAEA TRS-457, finding average differences of 0.6%. Results are provided in comprehensive tables appropriated for clinical use. Additional qualities can easily be calculated using a designed GUI interface in conjunction with software to generate incident photon spectra.

Benmakhlouf, Hamza; Bouchard, Hugo; Fransson, Annette; Andreo, Pedro

2011-11-01

143

Backscatter factors and mass energy-absorption coefficient ratios for diagnostic radiology dosimetry.  

PubMed

Backscatter factors, B, and mass energy-absorption coefficient ratios, (?(en)/?)(w, air), for the determination of the surface dose in diagnostic radiology were calculated using Monte Carlo simulations. The main purpose was to extend the range of available data to qualities used in modern x-ray techniques, particularly for interventional radiology. A comprehensive database for mono-energetic photons between 4 and 150 keV and different field sizes was created for a 15 cm thick water phantom. Backscattered spectra were calculated with the PENELOPE Monte Carlo system, scoring track-length fluence differential in energy with negligible statistical uncertainty; using the Monte Carlo computed spectra, B factors and (?(en)/?)(w, air) were then calculated numerically for each energy. Weighted averaging procedures were subsequently used to convolve incident clinical spectra with mono-energetic data. The method was benchmarked against full Monte Carlo calculations of incident clinical spectra obtaining differences within 0.3-0.6%. The technique used enables the calculation of B and (?(en)/?)(w, air) for any incident spectrum without further time-consuming Monte Carlo simulations. The adequacy of the extended dosimetry data to a broader range of clinical qualities than those currently available, while keeping consistency with existing data, was confirmed through detailed comparisons. Mono-energetic and spectra-averaged values were compared with published data, including those in ICRU Report 74 and IAEA TRS-457, finding average differences of 0.6%. Results are provided in comprehensive tables appropriated for clinical use. Additional qualities can easily be calculated using a designed GUI interface in conjunction with software to generate incident photon spectra. PMID:22024474

Benmakhlouf, Hamza; Bouchard, Hugo; Fransson, Annette; Andreo, Pedro

2011-11-21

144

On the uncertainties of photon mass energy-absorption coefficients and their ratios for radiation dosimetry.  

PubMed

A systematic analysis of the available data has been carried out for mass energy-absorption coefficients and their ratios for air, graphite and water for photon energies between 1 keV and 2 MeV, using representative kilovoltage x-ray spectra for mammography and diagnostic radiology below 100 kV, and for ¹?²Ir and ??Co gamma-ray spectra. The aim of this work was to establish 'an envelope of uncertainty' based on the spread of the available data. Type A uncertainties were determined from the results of Monte Carlo (MC) calculations with the PENELOPE and EGSnrc systems, yielding mean values for µ(en)/? with a given statistical standard uncertainty. Type B estimates were based on two groupings. The first grouping consisted of MC calculations based on a similar implementation but using different data and/or approximations. The second grouping was formed by various datasets, obtained by different authors or methods using the same or different basic data, and with different implementations (analytical, MC-based, or a combination of the two); these datasets were the compilations of NIST, Hubbell, Johns-Cunningham, Attix and Higgins, plus MC calculations with PENELOPE and EGSnrc. The combined standard uncertainty, u(c), for the µ(en)/? values for the mammography x-ray spectra is 2.5%, decreasing gradually to 1.6% for kilovoltage x-ray spectra up to 100 kV. For ??Co and ¹?²Ir, u(c) is approximately 0.1%. The Type B uncertainty analysis for the ratios of µ(en)/? values includes four methods of analysis and concludes that for the present data the assumption that the data interval represents 95% confidence limits is a good compromise. For the mammography x-ray spectra, the combined standard uncertainties of (µ(en)/?)(graphite,air) and (µ(en)/?)(graphite,water) are 1.5%, and 0.5% for (µ(en)/?)(water,air), decreasing gradually down to u(c) = 0.1% for the three µ(en)/? ratios for the gamma-ray spectra. The present estimates are shown to coincide well with those of Hubbell (1977 Rad. Res. 70 58-81), except for the lowest energy range (radiodiagnostic) where it is concluded that current databases and their systematic analysis represent an improvement over the older Hubbell estimations. The results for (µ(en)/?)(graphite,air) for the gamma-ray dosimetry range are moderately higher than those of Seltzer and Bergstrom (2005 private communication). PMID:22451262

Andreo, Pedro; Burns, David T; Salvat, Francesc

2012-04-21

145

On the uncertainties of photon mass energy-absorption coefficients and their ratios for radiation dosimetry  

NASA Astrophysics Data System (ADS)

A systematic analysis of the available data has been carried out for mass energy-absorption coefficients and their ratios for air, graphite and water for photon energies between 1 keV and 2 MeV, using representative kilovoltage x-ray spectra for mammography and diagnostic radiology below 100 kV, and for 192Ir and 60Co gamma-ray spectra. The aim of this work was to establish ‘an envelope of uncertainty’ based on the spread of the available data. Type A uncertainties were determined from the results of Monte Carlo (MC) calculations with the PENELOPE and EGSnrc systems, yielding mean values for µen/? with a given statistical standard uncertainty. Type B estimates were based on two groupings. The first grouping consisted of MC calculations based on a similar implementation but using different data and/or approximations. The second grouping was formed by various datasets, obtained by different authors or methods using the same or different basic data, and with different implementations (analytical, MC-based, or a combination of the two); these datasets were the compilations of NIST, Hubbell, Johns-Cunningham, Attix and Higgins, plus MC calculations with PENELOPE and EGSnrc. The combined standard uncertainty, uc, for the µen/? values for the mammography x-ray spectra is 2.5%, decreasing gradually to 1.6% for kilovoltage x-ray spectra up to 100 kV. For 60Co and 192Ir, uc is approximately 0.1%. The Type B uncertainty analysis for the ratios of µen/? values includes four methods of analysis and concludes that for the present data the assumption that the data interval represents 95% confidence limits is a good compromise. For the mammography x-ray spectra, the combined standard uncertainties of (µen/?)graphite,air and (µen/?)graphite,water are 1.5%, and 0.5% for (µen/?)water,air, decreasing gradually down to uc = 0.1% for the three µen/? ratios for the gamma-ray spectra. The present estimates are shown to coincide well with those of Hubbell (1977 Rad. Res. 70 58-81), except for the lowest energy range (radiodiagnostic) where it is concluded that current databases and their systematic analysis represent an improvement over the older Hubbell estimations. The results for (µen/?)graphite,air for the gamma-ray dosimetry range are moderately higher than those of Seltzer and Bergstrom (2005 private communication).

Andreo, Pedro; Burns, David T.; Salvat, Francesc

2012-04-01

146

Estimation of octanol/water partition coefficients using LSER parameters  

USGS Publications Warehouse

The logarithms of octanol/water partition coefficients, logKow, were regressed against the linear solvation energy relationship (LSER) parameters for a training set of 981 diverse organic chemicals. The standard deviation for logKow was 0.49. The regression equation was then used to estimate logKow for a test of 146 chemicals which included pesticides and other diverse polyfunctional compounds. Thus the octanol/water partition coefficient may be estimated by LSER parameters without elaborate software but only moderate accuracy should be expected.

Luehrs, Dean C.; Hickey, James P.; Godbole, Kalpana A.; Rogers, Tony N.

1998-01-01

147

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

148

Effects of the absorption coefficient on resonant infrared laser ablation of poly(ethylene glycol)  

SciTech Connect

We describe experiments on resonant infrared laser ablation of poly(ethylene glycol) (PEG) at two different resonant excitation wavelengths and for different molecular weights of PEG. The two resonant wavelengths correspond to different stretching vibrations of the polymer and have absorption coefficients that differ by roughly an order of magnitude. Ablation via excitation of the O-H terminal group stretching mode at 2.94 {mu}m, the weaker of the two absorptions, is delayed in time by several microseconds with respect to ablation at 3.47 {mu}m, the more strongly absorbing C-H stretching mode of the polymer. Time-resolved plume shadowgraphs along with ablation rate measurements for the two modes reveal that the absorption coefficient strongly affects the physical characteristics of the ejecta and plume, as well as the time scale for material removal. Temperature-rise calculations demonstrate that phase explosion is likely the operative mechanism in ablation at the C-H mode, while normal boiling may play a role in material removal at the O-H mode.

Johnson, S. L.; Schriver, K. E.; Haglund, R. F. Jr. [Department of Physics and Astronomy, Vanderbilt University, Nashville, Tennessee 37235 (United States); Bubb, D. M. [Department of Physics, Rutgers University-Camden, Camden, New Jersey 08102 (United States)

2009-01-15

149

PARTITION COEFFICIENTS FOR METALS IN SURFACE WATER, SOIL, AND WASTE  

EPA Science Inventory

This report presents metal partition coefficients for the surface water pathway and for the source model used in the Multimedia, Multi-pathway, Multi-receptor Exposure and Risk Assessment (3MRA) technology under development by the U.S. Environmental Protection Agency. Partition ...

150

Third Virial Coefficient for Air-Water Vapor Mixtures.  

National Technical Information Service (NTIS)

The third interaction virial coefficient Caww for air-water vapor mixtures is estimated in the temperature range 0 to 100C, by means of an approximate method based on molecular association. The results are believed accurate to within a factor of two. The ...

R. W. Hyland E. A. Mason

1967-01-01

151

A consecutive reconstruction strategy for estimating absorption and scattering coefficient distribution in multiple-illumination photoacoustic tomography (MIPAT)  

NASA Astrophysics Data System (ADS)

Quantitative photoacoustic microscopy (qPAT) is challenging. We present an algorithm which consecutively reconstructs absorption and scattering coefficient distributions with an iterative scheme in multiple-illumination photoacoustic tomography (MIPAT). In each iteration, the absorption distribution is estimated with the least-squares fixed-point iteration method. Then the diffusion coefficient is estimated with an updated version of optical fluence based on the previously modified absorption information. This procedure is repeated till an acceptable results is achieved. Simulation examples demonstrate the capability of this method in faithfully recovering the absorption and diffusion coeffient distributions, and fast convergence.

Shao, Peng; Harrison, Tyler J.; Zemp, Roger J.

2014-03-01

152

Polaron effects on the linear and nonlinear intersubband optical absorption coefficients in quantum wells with asymmetrical semi-exponential potential  

NASA Astrophysics Data System (ADS)

Linear and nonlinear intersubband optical absorption coefficients in quantum wells with asymmetrical semi-exponential potential are studied theoretically. We obtain unperturbed eigenfunctions and the energy eigenvalues by means of solving Schrödinger equation within the framework of effective mass approximation. The wave functions and energies with consideration of polaron are acquired through perturbation method. Besides, the analytic expressions of optical absorption coefficients are obtained using compact-density-matrix approach and iterative method. The results of calculation show that optical absorption is enhanced when effects of polaron are considered. Additionally, the parameters of confinement potential have great influences on optical absorption.

Mou, Sen; Guo, Kangxian; Xiao, Bo

2014-08-01

153

Non-uniform sound intensity distributions when measuring absorption coefficients in reverberation chambers using a phased beam tracing.  

PubMed

Measured absorption coefficients in reverberation chambers often differ from theoretical random incidence absorption coefficients, because ideal assumptions for the theoretical random incidence absorption coefficient are not fulfilled during measurements in actual reverberation chambers. Therefore sound intensity distributions on absorber under measurement conditions have been simulated using a phased beam tracing, and used as correction functions for reducing discrepancies between the measured and theoretical absorption coefficients. Two reverberation rooms were investigated by assuming that a test specimen was attached to a vertical surface and the floor. The frequency-dependent sound intensity distributions on absorbers were found to be affected by the reverberation chamber geometry and dimensions, the absorption capability of the specimen, and the placement of the specimen. High frequency intensity distributions above 1 kHz were similar for all studied cases, but some variations in low frequency intensity distributions were observed. If the non-uniform intensity distribution and a finite size effect are taken into account for correcting the theoretical absorption coefficients, a good agreement is found between corrected and measured statistical absorption coefficients. The non-uniform sound intensity can account for the discrepancy at high frequencies. PMID:20550256

Jeong, Cheol-Ho

2010-06-01

154

Statistical Estimation of the Atmospheric Aerosol Absorption Coefficient Based on the Data of Optical Measurements  

SciTech Connect

The problem of the choice of the aerosol optical constants and, in particular, imaginary part of the refractive index of particles in visible and infrared (IR) wavelength ranges is very important for calculation of the global albedo of the atmosphere in climatic models. The available models of the aerosol optical constants obtained for the prescribed chemical composition of particles (see, for example, Ivlev et al. 1973; Ivlev 1982; Volz 1972), often are far from real aerosol. It is shown in (Krekov et al. 1982) that model estimates of the optical characteristics of the atmosphere depending on the correctness of real and imaginary parts of the aerosol complex refractive index can differ by some hundreds percent. It is known that the aerosol extinction coefficient {alpha}({lambda}) obtained from measurements on a long horizontal path can be represented as {alpha}({lambda})={sigma}({lambda})+{beta}({lambda}), where {sigma} is the directed light scattering coefficient, and {beta} is the aerosol absorption coefficient. The coefficient {sigma}({lambda}) is measured by means of a nephelometer. Seemingly, if measure the values {alpha}({lambda}) and {sigma}({lambda}), it is easy to determine the value {beta}({lambda}). However, in practice it is almost impossible for a number of reasons. Firstly, the real values {alpha}({lambda}) and {sigma}({lambda}) are very close to each other, and the estimate of the parameter {beta}({lambda}) is concealed by the errors of measurements. Secondly, the aerosol optical characteristics on the long path and in the local volume of nephelometer can be different, that also leads to the errors in estimating {beta}({lambda}). Besides, there are serious difficulties in performing spectral measurements of {sigma}({lambda}) in infrared wavelength range. Taking into account these circumstances, in this paper we consider the statistical technique, which makes it possible to estimate the absorption coefficient of real aerosol on the basis of analysis of simultaneous measurements of the spectral aerosol extinction coefficients {alpha}({lambda}), the directed scattering coefficient of dry aerosol {sigma}{sub 0}(0.55) and the mass concentration of aerosol containing BC (black carbon) Ms.

Uzhegov, V.N.; Kozlov, V.S.; Panchenko, M.V.; Pkhalagov, Yu.A.; Pol'kin, V.V.; Terpugova, S.A.; Shmargunov, V.P.; Yausheva, E.P.

2005-03-18

155

Spectral absorption coefficients for the fundamental and first overtone vibration-rotation bands of CN  

NASA Technical Reports Server (NTRS)

A previous measurement of the transition moment of the fundamental vibration-rotation band of CN is combined with theoretical calculations of relative vibrational transition probabilities in order to compute absorption coefficients for the CN fundamental and first-overtone bands. Line strengths for 121 lines in each branch of all fundamental and first-overtone bands with upper-transition states not greater than 6 are calculated for temperatures of 2000, 3000, and 4000 K; these line strengths are presented as averaged over 8-kayser intervals. The relative vibrational transition moments are placed on an absolute scale, and the wavenumbers of the band origins and heads are given

Bailey, W. L.

1977-01-01

156

Nonlinear refractive index and three-photon absorption coefficient of poly(9,9-dioctylfluorence)  

Microsoft Academic Search

We investigate the optical Kerr effect and third harmonic generation (THG) arising from chi(3) of poly(9,9-dioctylfluorence), which is an emerging organic pi-conjugated polymer from the perspective of diverse optoelectronic applications. The measured nonlinear refractive index, obtained with closed-aperture Z-scan, is n2=(2.04+\\/-0.10)×10-12 esu at lambda=1540 nm. Open-aperture Z-scan yields the three-photon absorption coefficient of gamma=(1.88+\\/-0.26)×10-3 cm3\\/GW2 at lambda=1064 nm, arising from

J. I. Jang; S. Mani; J. B. Ketterson; P. Lovera; G. Redmond

2009-01-01

157

Diffusion Coefficients of SO2 in Water and Partition Coefficients of SO2 in Water-Air Interface at Different Temperature and pH Values  

Microsoft Academic Search

Reversed flow gas chromatography was applied to measure the diffusion coefficient of SO2 in water, the partition coefficient of SO2 in air–water interface, and the rate constant, kR, for chemical reaction between SO2 and water at various temperature and pH values. A linear increment of the diffusion coefficients of SO2 in water with temperature is drawn while the partition coefficients

A. Koliadima; J. Kapolos; L. Farmakis

2009-01-01

158

The use of X-ray CT to measure diffusion coefficients of heavy ions in water-saturated porous media  

Microsoft Academic Search

X-ray computerized tomography (CT) was applied for the first time to the measurement of diffusion coefficients of heavy ions in water-saturated clay and rock. The mass absorption coefficient of X-rays is high for heavy elements. Thus the migration of heavy ions in the porous samples was measured by the spatio-temporal change in intensity of X-ray CT images. The measurements of

Yoshito Nakashima

2000-01-01

159

Spectral variation of the infrared absorption coefficient in pulsed photothermal profiling of biological samples  

NASA Astrophysics Data System (ADS)

Pulsed photothermal radiometry can be used for non-invasive depth profiling of optically scattering samples, including biological tissues such as human skin. Computational reconstruction of the laser-induced temperature profile from recorded radiometric signals is sensitive to the value of the tissue absorption coefficient in the infrared detection band (?IR). While assumed constant in reported reconstruction algorithms, ?IR of human skin varies by two orders of magnitude in the commonly used 3-5 ?m detection band. We analyse the problem of selecting the effective absorption coefficient value to be used with such algorithms. In a numerical simulation of photothermal profiling we demonstrate that results can be markedly impaired, unless the reconstruction algorithm is augmented by accounting for spectral variation ?IR(?). Alternatively, narrowing the detection band to 4.5-5 ?m reduces the spectral variation ?IR(?) to a level that permits the use of the simpler, un-augmented algorithm. Implementation of the latter approach for depth profiling of port wine stain birthmarks in vivo is presented and discussed.

Majaron, Boris; Verkruysse, Wim; Tanenbaum, B. Samuel; Milner, Thomas E.; Nelson, J. Stuart

2002-06-01

160

A comparison study of linear reconstruction techniques for diffuse optical tomographic imaging of absorption coefficient  

NASA Astrophysics Data System (ADS)

We compare, through simulations, the performance of four linear algorithms for diffuse optical tomographic reconstruction of the three-dimensional distribution of absorption coefficient within a highly scattering medium using the diffuse photon density wave approximation. The simulation geometry consisted of a coplanar array of sources and detectors at the boundary of a half-space medium. The forward solution matrix is both underdetermined, because we estimate many more absorption coefficient voxels than we have measurements, and ill-conditioned, due to the ill-posedness of the inverse problem. We compare two algebraic techniques, ART and SIRT, and two subspace techniques, the truncated SVD and CG algorithms. We compare three-dimensional reconstructions with two-dimensional reconstructions which assume all inhomogeneities are confined to a known horizontal slab, and we consider two `object-based' error metrics in addition to mean square reconstruction error. We include a comparison using simulated data generated using a different FDFD method with the same inversion algorithms to indicate how our conclusions are affected in a somewhat more realistic scenario. Our results show that the subspace techniques are superior to the algebraic techniques in localization of inhomogeneities and estimation of their amplitude, that two-dimensional reconstructions are sensitive to underestimation of the object depth, and that an error measure based on a location parameter can be a useful complement to mean squared error.

Gaudette, Richard J.; Brooks, Dana H.; Di Marzio, Charles A.; Kilmer, Misha E.; Miller, Eric L.; Gaudette, Thomas; Boas, David A.

2000-04-01

161

Calculation of photon mass energy-transfer and mass energy-absorption coefficients.  

PubMed

Calculations of mass energy-transfer and mass energy-absorption coefficients for photon energies from 1 keV to 100 MeV have been developed, based on a re-examination of the processes involved after the initial photon interaction. The probabilities for the initial interaction are from the current photon interaction cross-section database at the National Institute of Standards and Technology. The calculations then take into account (1) electron binding effects on the Compton-scattered photon distribution; (2) the complete cascade of fluorescence emission after ionization events in any atomic subshell, including those associated with incoherent scattering and triplet production; and (3) the radiative energy losses of the secondary electrons and positrons slowing down in the medium, including the emission of bremsstrahlung, characteristic X rays from impact ionization, and positron in-flight as well as at-rest annihilation quanta. Consideration of the processes in (3) goes beyond the continuous-slowing-down approximation and includes the effects of energy-loss straggling. Results for the mass energy-absorption coefficient are compared with those from recent tabulations. PMID:8248472

Seltzer, S M

1993-11-01

162

Acoustical absorption coefficient in a diffuse field of a plane, rectangular material of finite dimensions placed on an infinite perfectly reflecting surface  

Microsoft Academic Search

This study deals with the evaluation of the acoustic absorption coefficient of a rectangular surface of known impedance, placed on an otherwise perfectly reflecting area. The incident acoustic field is supposed diffuse. This problem corresponds to the measurement of the absorption coefficient in a reverberation room. An analytic expression (approximation) is given for the evaluation of the absorption coefficient. From

J. F. Hamet

1985-01-01

163

Diurnal Variations in the Specific Absorption Coefficient: Recent Results from Mexico City  

NASA Astrophysics Data System (ADS)

The specific absorption coefficient, ?a, defined as the absorbance of light per unit path length and per unit of mass concentration, is an important, radiative property of the atmosphere and is also used as a conversion factor when estimating the mass of light absorbing material, usually black carbon, from measurements of the absorption coefficient. The magnitude of ?a varies over a wide range of values, 2 to 25 m 2g-1, due to the composition and structure of the light absorbing material. The value of this parameter is usually determined by measuring the absorption coefficient, Babs with a Particle Soot Absorption Photometer (PSAP) or an Aethalometer and the black carbon (BC) with one of several types of thermal optical techniques. There are two disadvantages to this approach, both associated with the thermo-optical derivations of BC. The first disadvantage is that significant sample times are needed to accumulate sufficient aerosol mass to derive the BC value. Secondly, there is a large uncertainty associated with the BC mass derived from the thermo-optical method. The recent development of the Single Particle Soot Photometer (SP-2) has allowed high resolution estimates of ?a . The SP2 measures directly the mass of single, light absorbing particles using laser induced incandescence. This mass, when combined with Babs derived from measurements of light attenuation, leads to an accurate, fast response estimate of ?a . This technique has been recently applied during a field campaign in Mexico City in April, 2005. An SP-2, PSAP, Nephelometer, and other particle counters measured the physical and optical properties of particles in the southwest sector of Mexico City. Measurements were made 24 hours a day so that the diurnal variations could be monitored. The value of ?a, derived every five minutes from the measurements of the SP-2 and PSAP, showed clear diurnal variations that reflect the changes in the age of the BC that is emitted by local sources. In the morning the BC is fresh as a result of the peak in traffic and ages with time as the boundary layer develop and photochemical processes presumably alter the characteristics of the BC.

Baumgardner, D.; Kok, G.; Raga, G. B.

2005-12-01

164

A reduced-scale railway noise barrier's insertion loss and absorption coefficients: comparison of field measurements and predictions  

Microsoft Academic Search

In situ testing determined the insertion loss (IL) and absorption coefficients of a candidate absorptive noise barrier (soundwall) to abate railway noise for residents of Anaheim, CA. A 4000m barrier is proposed south of the tracks, but residential areas to the north have expressed concerns that barrier reflections will increase their noise exposure. To address these concerns, a 3.66m high

T. A. Busch; R. E. Nugent

2003-01-01

165

Accurate Evaluation of Nonlinear Absorption Coefficients in InAs, InSb and HbCdTe Alloys (Postprint).  

National Technical Information Service (NTIS)

We present a full band structure calculation of temperature- and wavelength-dependent two-photon absorption (TPA) coefficients and free carrier absorption (FCA) cross sections in InAs, InSb, and Hg1&8722;xCdxTe alloys. Although the wavelength dependence o...

L. P. Gonzales S. Guha S. Krishnamurthy Z. G. Yu

2007-01-01

166

The Optical Absorption Coefficient of Bean Seeds Investigated Using Photoacoustic Spectroscopy  

NASA Astrophysics Data System (ADS)

A knowledge about seed optical parameters is of great relevance in seed technology practice. Such parameters provide information about its absorption and reflectance, which could be useful for biostimulation processes, by light sources, in early stages of seed germination. In the present research photoacoustic spectroscopy (PAS) and the Rosencwaig and Gersho model were used to determine the optical absorption coefficient (? ) of five varieties of bean seeds (Phaseolus vulgaris L.), of different productive cycles; the seeds were biostimulated by laser treatment to evaluate the effects of biostimulation pre-sowing. It was found that the bean varieties V1, V2, V4, and V5 were optically opaque in the visible spectrum; in the case of the V3 variety, this sample was optically transparent from 680 nm. The varieties of the studied bean seeds showed significant statistical differences in sizes and also in their optical absorption spectra. The biostimulation effects showed that the seed samples with a higher optical penetration length had a positive biostimulation, in the percentage of germination, obtaining an enhancement of 47 % compared to the control sample. The utility of PAS for the optical characterization of seeds has been demonstrated in this study of the laser biostimulation process of this kind of samples.

Sanchez-Hernandez, G.; Hernandez-Aguilar, C.; Dominguez-Pacheco, A.; Cruz-Orea, A.; Perez-Reyes, M. C. J.; Martinez, E. Moreno

2014-05-01

167

Octanol\\/water partition coefficients for environmentally important organic compounds  

Microsoft Academic Search

Partition coefficients PO,w\\u000a (i) describing the distribution of a solute i onto coexisting phases of 1-octanol and water are needed in a large variety of\\u000a applications. They can be measured directly by HPLC as long as log PO,w\\u000a (i)? 3.5. For more hydrophobic substances, several experimental procedures have been proposed in the literature. The reliability\\u000a of those methods is questionable.

Sylke Ritter; Werner H. Hauthal; Gerd Maurer

1995-01-01

168

Separation methods for estimating octanol-water partition coefficients.  

PubMed

Separation methods for the indirect estimation of the octanol-water partition coefficient (logP) are reviewed with an emphasis on high throughput methods with a wide application range. The solvation parameter model is used to identify suitable separation systems for estimating logP in an efficient manner that negates the need for empirical trial and error experiments. With a few exceptions, systems based on reversed-phase chromatography employing chemically bonded phases are shown to be unsuitable for estimating logP for compounds of diverse structure. This is because the fundamental properties responsible for chromatographic retention tend to be different to those responsible for partition between octanol and water, especially the contribution from hydrogen bonding interactions. On the other hand, retention in several micellar and microemulsion electrokinetic chromatography systems is shown to be highly correlated with the octanol-water partition coefficient. These systems are suitable for the rapid, high throughput determination of logP for neutral, weakly acidic, and weakly basic compounds. For compounds with a permanent charge, electrophoretic migration and electrostatic interactions with the stationary phase results in inaccurate estimation of partition coefficients. The experimental determination of solute descriptors offers an alternative approach for estimating logP, and other biopartitioning properties. A distinct advantage of this approach is that once the solute descriptors are known, solute properties can be estimated for any distribution or transport system for which a solvation parameter model has been established. PMID:14630140

Poole, Salwa K; Poole, Colin F

2003-11-25

169

Tomographic imaging of absolute optical absorption coefficient in turbid media using combined photoacoustic and diffusing light measurements.  

PubMed

We present a new method that can provide high resolution images of absolute optical absorption coefficient in heterogeneous turbid media. In this method, acoustic measurements in conventional photoacoustic tomography are combined with diffusing light measurements to separate the product of absorption coefficient and optical fluence or photon density. We validate this method using a series of tissuelike phantom experiments. The experimental results show that targets as small as 0.5 mm in diameter with optical absorption contrasts as low as 1.5 relative to a 50 mm diameter scattering background medium can be clearly detected. PMID:17767303

Yin, Lu; Wang, Qiang; Zhang, Qizhi; Jiang, Huabei

2007-09-01

170

Effects of suspended sediment concentration on the absorption and scattering coefficients  

Microsoft Academic Search

The scattering coefficient (b) for the nearshore waters off the coast of North Carolina near Camp Lejeune is strongly influenced by suspended sediment concentration and total particulate cross-sectional area (xg). In-situ measurements of a and b were made using a WET Labs AC9 meter. Estimates of suspended sediment concentration and total particulate cross-sectional area were determined from laser particle size

Gregory E. Terrie; Sherwin Ladner; Richard A. Gould

1997-01-01

171

Performance analysis and evaluation of a commercial absorption–refrigeration water–ammonia (ARWA) system  

Microsoft Academic Search

The Robur absorption–refrigeration water–ammonia (ARWA) system is analyzed using Aspen Plus flowsheet simulator. The results are compared with experimental and some manufacturer data reported in the open literature. Among performance parameters analyzed are coefficient of performance (COP), heat duties of the evaporator, absorber, and the condenser, refrigerant concentration in the weak and strong solution, and flow rates of the weak

N. A. Darwish; S. H. Al-Hashimi; A. S. Al-Mansoori

2008-01-01

172

High resolution absorption coefficients for Freon-12. [by using tunable diode laser spectroscopy  

NASA Technical Reports Server (NTRS)

The ultra high resolution absorption coefficients of the Q-branch of Freon-12 obtained with tunable diode laser spectroscopy are presented. Continuous spectra are presented from 1155/cm to 1163/cm, and absolute wavelength calibration was obtained using SO2 spectra as a standard and a 5 cm Ge etalon for relative calibration between SO2 lines. The Freon-12 data obtained at a pressure of 0.05 torr showed a rich and highly structured spectra, but with the exception of three isolated features, collisional broadening reduces the spectra to a structureless continuum for nitrogen pressures greater than 20 torr. The spectra at 1161/cm continue to exhibit structure at atmospheric pressure.

Hoell, J. M.; Bair, C. H.; Williams, B.; Harward, C.

1979-01-01

173

Temperature imaging of water in a microchannel using thermal sensitivity of near-infrared absorption.  

PubMed

This paper presents a remote and preparation-free method of temperature imaging of aqueous solutions in microchannels of microfluidic chips. The principle of this method is based on the temperature dependency of the near-infrared (NIR) absorption band (?(2) + ?(3) band) of water. Temperature images were constructed from absorbances in a narrow wavelength range including 1908 nm, the most sensitive to temperature in the band, measured by using an NIR camera and an optical narrow-bandpass filter. Calculation and calibration results demonstrated a linear relationship between the absorption coefficient and temperature with a temperature coefficient of 1.5 × 10(-2) K(-1) mm(-1). Temperature images of 50 ?m thick water in a Y-shaped PDMS microchannel locally heated by a neighboring hot wire were obtained, in which thermal diffusion processes in the microchip were visualized. Temperature resolution was estimated to be approximately 0.2 K according to the temperature coefficient and noise level. PMID:21869986

Kakuta, Naoto; Fukuhara, Yuko; Kondo, Katsuya; Arimoto, Hidenobu; Yamada, Yukio

2011-10-21

174

Remote sensing of the absorption coefficients and chlorophyll a concentration in the United States southern Middle Atlantic Bight from SeaWiFS and MODIS-Aqua  

NASA Astrophysics Data System (ADS)

At present, satellite remote sensing of coastal water quality and constituent concentration is subject to large errors as compared to the capability of satellite sensors in oceanic waters. In this study, field measurements collected on a series of cruises within United States southern Middle Atlantic Bight (SMAB) were applied to improve retrievals of satellite ocean color products from the Sea-viewing Wide Field-of-view Sensor (SeaWiFS) and the Moderate Resolution Imaging Spectrometer (MODIS-Aqua) in order to examine the factors that regulate the bio-optical properties within the continental shelf waters of the SMAB. The first objective was to develop improvements in satellite retrievals of absorption coefficients of phytoplankton (aph), colored dissolved organic matter (CDOM) (ag), nonpigmented particles (ad), nonpigmented particles plus CDOM (adg), and chlorophyll a concentration ([Chl_a]). Several algorithms were compared to derive constituent absorption coefficients from remote sensing reflectance (Rrs) ratios. The validation match-ups showed that the mean absolute percent differences were typically <35%, although higher errors were found for ad retrievals. Seasonal and spatial variability of satellite-derived absorption coefficients and [Chl_a] was apparent and consistent with field data. CDOM is a major contributor to the bio-optical properties of the SMAB, accounting for 35-70% of total light absorption by particles plus CDOM at 443 nm, as compared to 30-45% for phytoplankton and 0-20% for nonpigmented particles. The overestimation of [Chl_a] from the operational satellite algorithms may be attributed to the strong CDOM absorption in this region. River discharge is important in controlling the bio-optical environment but cannot explain all of the regional and seasonal variability of biogeochemical constituents in the SMAB.

Pan, Xiaoju; Mannino, Antonio; Russ, Mary E.; Hooker, Stanford B.

2008-11-01

175

Remote Sensing of the Absorption Coefficients and Chlorophyll a Concentration in the U.S. Southern Middle Atlantic Bight from SeaWiFS and MODIS-Aqua  

NASA Technical Reports Server (NTRS)

At present, satellite remote sensing of coastal water quality and constituent concentration is subject to large errors as compared to the capability of satellite sensors in oceanic waters. In this study, field measurements collected on a series of cruises within U.S. southern Middle Atlantic Bight (SMAB) were applied to improve retrievals of satellite ocean color products in order to examine the factors that regulate the bio-optical properties within the continental shelf waters of the SMAB. The first objective was to develop improvements in satellite retrievals of absorption coefficients of phytoplankton (a(sub ph)), colored dissolved organic matter (CDOM) (a(sub g)), non-pigmented particles (a(sub d)), and non-pigmented particles plus CDOM (a(sub dg)), and chlorophyll a concentration ([Chl_a]). Several algorithms were compared to derive constituent absorption coefficients from remote sensing reflectance (R(sub rs)) ratios. The validation match-ups showed that the mean absolute percent differences (MAPD) were typically less than 35%, although higher errors were found for a(sub d) retrievals. Seasonal and spatial variability of satellite-derived absorption coefficients and [Chl_a] was apparent and consistent with field data. CDOM is a major contributor to the bio-optical properties of the SMAB, accounting for 35-70% of total light absorption by particles plus CDOM at 443 nm, as compared to 30-45% for phytoplankton and 0-20% for non-pigmented particles. The overestimation of [Chl_a] from the operational satellite algorithms may be attributed to the strong CDOM absorption in this region. River discharge is important in controlling the bio-optical environment, but cannot explain all of the regional and seasonal variability of biogeochemical constituents in the SMAB.

Pan, Xiaoju; Mannino, Antonio; Russ, Mary E.; Hooker, Stanford B.

2008-01-01

176

Water absorption of poly(methyl methacrylate) containing 4-methacryloxyethyl trimellitic anhydride.  

PubMed

The amount of water absorption of poly(methyl methacrylate) (PMMA) containing 0, 1, 3 and 5 wt% of an adhesive monomer, 4-methacryloxyethyl trimellitic anhydride (4-META), was measured at 7 degrees C, 37 degrees C and 60 degrees C. After the water uptake reached equilibrium in specimens, they were desorbed to obtain a constant value and the absorption process was repeated. Mass changes in the second desorption were recorded for the storage temperatures of 37 degrees C and 60 degrees C. Multiple regression analyses were conducted on three independent variables, 4-META concentration, storage temperature and absorption-desorption cycle. A statistically significant relationship was found between the maximum water uptake and 4-META concentration, while there was no relationship between the maximum water uptake and diffusion coefficient obtained using the Fick's law. The negative relationship in the latter did not support the free space theory. The significant and positive relationship between the maximum water uptake and 4-META concentration demonstrates that water molecules diffuse through the formation of a hydrogen bond at polar sites. The maximum water uptake was not influenced by temperature, while the diffusion coefficient increased with the rise in temperature. The activation energy was 41-47 and 50-53 kJ/mol in the first and second absorption tests, respectively. PMID:12527279

Unemori, Masako; Matsuya, Yoko; Matsuya, Shigeki; Akashi, Akane; Akamine, Akifumi

2003-04-01

177

OCTANOL/WATER PARTITION COEFFICIENTS AND WATER SOLUBILITIES OF PHTHALATE ESTERS  

EPA Science Inventory

Measurements of the octanol/water partition coefficients (K-ow) and water solubilities of di-n-octyl phthalate (DnOP) and di-n-decyl phthalate (DnDP) by the slow-stirring method are reported. The water solubility was also measured for di-n-hexyl phthalate (DnHP). The log K-ow val...

178

Relationships between macroscopic paper structure and water absorption behavior  

Microsoft Academic Search

Macroscopic structure of paper influences how paper behaves in many ways. In this research, the relationship between macroscopic paper structure and water absorption behavior was investigated. The structure of the handsheets made from commercial hardwood pulp was modified by varying basis weight, beating levels and wet press levels. The structural properties as well as the water absorption properties were measured.

Kuntinee Suvarnakich; Toshiharu Enomae; Akira Isogai

179

An empirical ocean color algorithm for estimating the contribution of chromophoric dissolved organic matter to total light absorption in optically complex waters  

Microsoft Academic Search

To estimate the depth-integrated rate of photochemical processes involving chromophoric dissolved organic matter (CDOM) in coastal waters, the contribution of CDOM to the total absorption coefficient must be known from UV to green. At 307 sites sampled in various coastal marine environments, the ratio between CDOM and the total absorption coefficient ([a CDOM \\/a t ]) at 412 nm was

Simon Bélanger; Marcel Babin; Pierre Larouche

2008-01-01

180

Sound conversion phenomena at the free surface of liquid helium. II. Experimental determination of acoustic coefficients and surface absorption coefficients  

Microsoft Academic Search

The acoustic coefficients of reflection, transmission, and transformation of first-, second-, and gas sound waves incident normally on the free surface of liquid helium have been determined. The experimental results are compared with the theory developed in Part I of this paper. It is shown that equilibrium theories of boundary conditions disagree with the experiments. Nonequilibrium theories, however, which take

H. Wiechert; F. I. Buchholz

1983-01-01

181

A correction of random incidence absorption coefficients for the angular distribution of acoustic energy under measurement conditions.  

PubMed

Most acoustic measurements are based on an assumption of ideal conditions. One such ideal condition is a diffuse and reverberant field. In practice, a perfectly diffuse sound field cannot be achieved in a reverberation chamber. Uneven incident energy density under measurement conditions can cause discrepancies between the measured value and the theoretical random incidence absorption coefficient. Therefore the angular distribution of the incident acoustic energy onto an absorber sample should be taken into account. The angular distribution of the incident energy density was simulated using the beam tracing method for various room shapes and source positions. The averaged angular distribution is found to be similar to a Gaussian distribution. As a result, an angle-weighted absorption coefficient was proposed by considering the angular energy distribution to improve the agreement between the theoretical absorption coefficient and the reverberation room measurement. The angle-weighted absorption coefficient, together with the size correction, agrees satisfactorily with the measured absorption data by the reverberation chamber method. At high frequencies and for large samples, the averaged weighting corresponds well with the measurement, whereas at low frequencies and for small panels, the relatively flat distribution agrees better. PMID:19354382

Jeong, Cheol-Ho

2009-04-01

182

The influence of the Ramsauer-Townsend effect on free-free absorption coefficients of the negative argon ion at far infrared wavelengths  

NASA Astrophysics Data System (ADS)

0953-4075/31/1/009/img1 free-free absorption coefficients in the far-IR are calculated using relativistic continuum wavefunctions from solutions of the Dirac equation. Absorption coefficients are shown to exhibit a Ramsauer-Townsend minimum near 1200 K. We compare these results with coefficients derived from non-relativistic and experimental atomic data.

John, T. L.

1998-01-01

183

Spectral absorption coefficient of molten aluminum oxide from 0.385 to 0.780 μm  

Microsoft Academic Search

The spectral extinction coefficient, k{sub λ}, and the absorption coefficient, α{sub λ}, of liquid aluminum oxide were determined from emission measurements on partially molten single-crystal sapphire filaments. Measurements were made at wavelengths from 0.385 to 0.780 μm in both argon and oxygen atmospheres and at 0.650 μm in a 10% Hâ-90% Nâ mixture. The values of α{sub λ} were found

J. K. Richard Weber; Shankar Krishnan; Collin D. Anderson; Paul C. Nordine

1995-01-01

184

Absorption Coefficients of the Methane-Nitrogen Binary Ice System: Implications for Pluto  

NASA Astrophysics Data System (ADS)

Near infrared spectroscopic measurements of Pluto display methane (CH4) ice absorption bands shifted toward shorter wavelengths compared to the central wavelengths of pure CH4 obtained in the laboratory. This shift, described by Schmitt and Quirico (1992), occurs when CH4 is dissolved at low concentrations in a matrix of solid N2, and the magnitude of the shift varies from one CH4 band to another. This is the main argument behind the modeling analysis of Pluto’s spectra available in literature, employing pure CH4 and CH4 diluted at low concentrations in N2. However, the nitrogen-methane binary phase diagram generated from X-ray diffraction studies by Prokhvatilov & Yantsevich (1983) indicates that at temperatures relevant to the surfaces of icy dwarf planets, like Pluto, two phases contribute to the absorptions: methane ice saturated with nitrogen and nitrogen ice saturated with methane. No optical constants are available so far for the latter component, limiting this way the knowledge of the methane-nitrogen mixing ratio across and into the surface of Pluto and other dwarf planets. New infrared absorption coefficient spectra of CH4-I diluted in ?-N2 and ?-N2 diluted in CH4-I were measured at temperatures between 40 and 90 K, in the wavelength range 0.8-2.5 ?m at different mixing ratios. The spectra were derived from transmission measurements of crystals grown from the liquid phase in closed cells. In particular, a systematic study of the changes in CH4:N2 mixtures spectral behavior with mixing ratio is presented for the first time, in order to understand whether the peak frequencies of the CH4-ice bands correlate with the amount of N2-ice. We report a linear trend of the blueshifts of the CH4-ice bands vs CH4 abundance. This trend varies from band to band, while it is fairly constant with temperature. These data are applied to interpret unpublished high dispersion H and K bands spectra of Pluto acquired with the NACO instrument at the ESO VLT on 27 June 2008. Acknowledgments: This work was supported in part by grant number NNX11AM53G from NASA's Outer Planets Research Program.

Protopapa, Silvia; Grundy, W.; Tegler, S.; Bergonio, J.; Boehnhardt, H.; Barrera, L.

2013-10-01

185

Void coefficient in a unit cell for UPu water breeder reactors  

Microsoft Academic Search

The possibility of breeding with the Pu-U fuel cycle in light or heavy water has been established. For such lattices the void coefficient in a unit cell was calculated. It was found that for light water lattices the void coefficient is negative whereas for heavy water lattices the void coefficient is positive. However, it was shown that by introducing a

Y. Ronen; M. Cojocaru; A. Radkowsky

1980-01-01

186

Optoelectronic properties of Mg{sub 2}Si semiconducting layers with high absorption coefficients  

SciTech Connect

In an attempt to develop a low-cost material for solar cell devices, polycrystalline magnesium silicide (poly-Mg{sub 2}Si) semiconducting layers have been prepared by applying rf magnetron sputtering using a Mg{sub 2}Si target. The optimum substrate temperature for the poly-Mg{sub 2}Si growth was found to be T{sub s} = 200 deg. C; the film deposition at higher temperatures leads to desorption of Mg atoms from the growing surface, while the amorphous phase formation occurs at room temperature. The poly-Mg{sub 2}Si layer deposited at T{sub s} = 200 deg. C shows the (111) preferential orientation with a uniform grain size of {approx}50 nm. The dielectric function of the poly-Mg{sub 2}Si layer has been determined accurately by spectroscopic ellipsometry. From the analysis, quite high absorption coefficients and an indirect gap of 0.77 eV in the poly-Mg{sub 2}Si layer have been confirmed. The above poly-Mg{sub 2}Si layer shows clear photoconductivity and can be applied as a narrow-gap bottom layer in multi-junction solar cell devices.

Kato, Takashi; Sago, Yuichiro; Fujiwara, Hiroyuki [Center of Innovative Photovoltaic Systems (CIPS), Gifu University, 1-1 Yanagido, Gifu 501-1193 (Japan)

2011-09-15

187

Accurate estimation of normal incidence absorption coefficients with confidence intervals using a scanning laser Doppler vibrometer  

NASA Astrophysics Data System (ADS)

When using optical measurements of the sound fields inside a glass tube, near the material under test, to estimate the reflection and absorption coefficients, not only these acoustical parameters but also confidence intervals can be determined. The sound fields are visualized using a scanning laser Doppler vibrometer (SLDV). In this paper the influence of different test signals on the quality of the results, obtained with this technique, is examined. The amount of data gathered during one measurement scan makes a thorough statistical analysis possible leading to the knowledge of confidence intervals. The use of a multi-sine, constructed on the resonance frequencies of the test tube, shows to be a very good alternative for the traditional periodic chirp. This signal offers the ability to obtain data for multiple frequencies in one measurement, without the danger of a low signal-to-noise ratio. The variability analysis in this paper clearly shows the advantages of the proposed multi-sine compared to the periodic chirp. The measurement procedure and the statistical analysis are validated by measuring the reflection ratio at a closed end and comparing the results with the theoretical value. Results of the testing of two building materials (an acoustic ceiling tile and linoleum) are presented and compared to supplier data.

Vuye, Cedric; Vanlanduit, Steve; Guillaume, Patrick

2009-06-01

188

Optoelectronic properties of Mg2Si semiconducting layers with high absorption coefficients  

NASA Astrophysics Data System (ADS)

In an attempt to develop a low-cost material for solar cell devices, polycrystalline magnesium silicide (poly-Mg2Si) semiconducting layers have been prepared by applying rf magnetron sputtering using a Mg2Si target. The optimum substrate temperature for the poly-Mg2Si growth was found to be Ts = 200 °C the film deposition at higher temperatures leads to desorption of Mg atoms from the growing surface, while the amorphous phase formation occurs at room temperature. The poly-Mg2Si layer deposited at Ts = 200 °C shows the (111) preferential orientation with a uniform grain size of ~50 nm. The dielectric function of the poly-Mg2Si layer has been determined accurately by spectroscopic ellipsometry. From the analysis, quite high absorption coefficients and an indirect gap of 0.77 eV in the poly-Mg2Si layer have been confirmed. The above poly-Mg2Si layer shows clear photoconductivity and can be applied as a narrow-gap bottom layer in multi-junction solar cell devices.

Kato, Takashi; Sago, Yuichiro; Fujiwara, Hiroyuki

2011-09-01

189

Absorption removal of sulfur dioxide by falling water droplets in the presence of inert solid particles  

NASA Astrophysics Data System (ADS)

An experimental analysis of the absorption removal of sulfur dioxide by the free falling water droplets containing the inert solid particles is presented. The wheat flour powder is introduced as the inert solid particles. Tests with and without the flour powder in the water droplets are examined. The mass fluxes and mass transfer coefficients of SO 2 for the cases with and without the flour powder are compared to elucidate the effects of the inert solid particles contained in the water droplets on the gas absorption. The results indicate aignificant difference between the two cases for the concentrations of the flour powder in the absorbent droplets ( Cs) within the ranges of the experimental conditions, namely 0.1 to 10 wt% flour powder in the absorbent droplets. In general, the inert solid particles of the flour powder as the impurities in the water droplets tend to decrease the SO 2 absorption rate for the experimental absorption system under investigation. Various values of Cs cause various levels of the interfacial resistance and affect the gas absorption rate. The interfacial resistance is recognized by introducing an interfacial mass transfer coefficient ks with its reciprocal being proportional to the magnitude of the interfacial resistance. The values of 1/ ks may be computed by the use of the equation 1/ ks=(1/ KOLs-1/ KOL), where KOLs and KOL are the overall liquid-phase mass transfer coefficients with and without the inert solid particles, respectively. The values of ks with Cs of 0.1 to 10 wt% are about 0.295-0.032 cms -1 for absorbing 1000-3000 ppmv SO 2 with the water droplets. This kind of information is useful for the SO 2 removal and the information of acid rain that the impurities of the inert solid particles contaminate the water droplets.

Liu, I.-Hung; Chang, Ching-Yuan; Liu, Su-Chin; Chang, I.-Cheng; Shih, Shin-Min

190

Some advantages of calculating octanol-water partition coefficients.  

PubMed

Reliable values for the octanol-water partition coefficients of small solutes used in enzyme binding/inhibition studies are desirable if a hydrophobic effect is being examined. Many investigators will grant that measuring each solute by shake-flask is the ideal, but reversed-phase HPLC data is becoming more commonplace since it is easier to obtain. This note examines one study where HPLC hydrophobicity, from an apparently valid procedure, obscured an obvious hydrophobic relationship. Another example is cited where probable errors in shake-flask measurement also lead to an erroneous conclusion. In both instances, values obtained from a simple method of calculation of log P(o/w) values could have provided a warning. PMID:3572757

Leo, A J

1987-02-01

191

Quantitative photoacoustic tomography from boundary pressure measurements: noniterative recovery of optical absorption coefficient from the reconstructed absorbed energy map.  

PubMed

We describe a noniterative method for recovering optical absorption coefficient distribution from the absorbed energy map reconstructed using simulated and noisy boundary pressure measurements. The source reconstruction problem is first solved for the absorbed energy map corresponding to single- and multiple-source illuminations from the side of the imaging plane. It is shown that the absorbed energy map and the absorption coefficient distribution, recovered from the single-source illumination with a large variation in photon flux distribution, have signal-to-noise ratios comparable to those of the reconstructed parameters from a more uniform photon density distribution corresponding to multiple-source illuminations. The absorbed energy map is input as absorption coefficient times photon flux in the time-independent diffusion equation (DE) governing photon transport to recover the photon flux in a single step. The recovered photon flux is used to compute the optical absorption coefficient distribution from the absorbed energy map. In the absence of experimental data, we obtain the boundary measurements through Monte Carlo simulations, and we attempt to address the possible limitations of the DE model in the overall reconstruction procedure. PMID:18758563

Banerjee, Biswanath; Bagchi, Srijeeta; Vasu, Ram Mohan; Roy, Debasish

2008-09-01

192

Acoustic-based measurements of material absorption coefficients: Relationship between laser pulse duration and stress confinement time  

Microsoft Academic Search

Ideally, to use photoacoustics to determine the absorption coefficient ?a of a medium, the laser pulse duration ?p is much shorter than the stress confinement time ?sr required for a laser-induced stress wave to propagate a distance equal to the light penetration depth ?. However, without prior knowledge of ? (equal to 1\\/?a), it is not clear whether a given

Bernard Choi; E. Duco Jansen; Ashley J. Welch

2003-01-01

193

DIFFUSE SOUND ABSORPTION COEFFICIENT DETERMINATION FROM IN SITU SPECIFIC BOUNDARY IMPEDANCE MEASUREMENTS BY THE SOUND INTENSITY TECHNIQUE  

Microsoft Academic Search

At present, the most part of errors on acoustic prediction and modelling of acoustic designs are as a result of the use of low precision sound absorption coefficients. To predict the acoustic performance of a material, within the infinity possible forms of assembly and constructive terminations, is mathematically complex. On the other hand, the most used method for the sound

Adrián Montoya; Ricardo Pesse

194

Analysis of the uncertainty budget for the reflection and absorption coefficient given by the two-microphone method  

Microsoft Academic Search

The method for measurement of the reflection and absorption coefficient at normal incidence consists of a sound source at one end of an impedance tube, where the plane waves propagated are reflected from a sample that is at the other end of the tube. Those plane waves are generated by a random signal, and the decomposition of the standing wave

Adolfo Esquivel D; Guillermo Silva P

2002-01-01

195

Acoustic-based measurements of material absorption coefficients: Relationship between laser pulse duration and stress confinement time  

Microsoft Academic Search

Ideally, to use photoacoustics to determine the absorption coefficient mua of a medium, the laser pulse duration taup is much shorter than the stress confinement time tausr required for a laser-induced stress wave to propagate a distance equal to the light penetration depth delta. However, without prior knowledge of delta (equal to 1\\/mua), it is not clear whether a given

Bernard Choi; E. Duco Jansen; Ashley J. Welch

2003-01-01

196

A Method for Deriving the Acoustic Absorption Coefficient of Gases from Measurement of the Decay-time of a Resonator  

Microsoft Academic Search

A unique result for the absorption coefficient is obtained from calculations based on measurement of the decay-time using longitudinal and radial modes of propagation. Expressions are given for the energy losses in the viscous and thermal boundary layers at the walls of the resonator. The method is applicable in the range of frequency divided by pressure of 1 to 45

P. D. Edmonds; J. Lamb

1958-01-01

197

The free-free absorption coefficients of the negative ion of molecular hydrogen in the far-IR. spectrum  

NASA Astrophysics Data System (ADS)

Accurate momentum transfer cross-sections from experimental and theoretical sources are used to calculate Hj free-free absorption coefficients at far-IR wavelengths. We include results from recent theoretical computations for vibrational motion of the molecular nuclei. Key words: molecular data - molecular processes - stars: atmospheres - infrared: general.

John, T. L.

1994-08-01

198

Effect of absorption parameters on calculation of the dose coefficient: example of classification of industrial uranium compounds.  

PubMed

In the Human Respiratory Tract Model (HRTM) described in ICRP Publication 66, time-dependent dissolution is described by three parameters: the fraction dissolved rapidly, fr, and the rapid and slow dissolution rates sr and ss. The effect of these parameters on the dose coefficient has been studied. A theoretical analysis was carried out to determine the sensitivity of the dose coefficient to variations in the values of these absorption parameters. Experimental values of the absorption parameters and the doses per unit intake (DPUI) were obtained from in vitro dissolution tests, or from in vivo experiments with rats, for five industrial uranium compounds UO2, U3O8, UO4, UF4 and a mixture of uranium oxides. These compounds were classified in terms of absorption types (F, M or S) according to ICRP. The overall result was that the factor which has the greatest influence on the dose coefficient was the slow dissolution rate ss. This was verified experimentally, with a variation of 20% to 55% for the DPUI according to the absorption type of the compound. In contrast, the rapid dissolution rate sr had little effect on the dose coefficient, excepted for Type F compounds. PMID:11487809

Chazel, V; Houpert, P; Paquet, F; Ansoborlo, E

2001-01-01

199

A new method to retrieve the aerosol layer absorption coefficient from airborne flux density and actinic radiation measurements  

Microsoft Academic Search

A new method is presented to derive the mean value of the spectral absorption coefficient of an aerosol layer from combined airborne measurements of spectral net irradiance and actinic flux density. While the method is based on a theoretical relationship of radiative transfer theory, it is applied to atmospheric radiation measurements for the first time. The data have been collected

Eike Bierwirth; Manfred Wendisch; Evelyn Jäkel; André Ehrlich; K. Sebastian Schmidt; Harald Stark; Peter Pilewskie; Michael Esselborn; Gian Paolo Gobbi; Richard Ferrare; Thomas Müller; Antony Clarke

2010-01-01

200

Measurement of the absorption coefficient of freely poured one-component metallic powders and its change during laser sintering  

Microsoft Academic Search

governing the physical processes that form the basis of the technology. One 3f the most important aspects of these types of studies is examination of features of the effect of laser radiation on the surface of the powders, in particular, the change in the absorption coefficient during laser treatment. The results obtained from such investigations should be considered in the

N. K. Tolochko; Yu. V. Khlopkov; S. E. Mozzharov; N. V. Sobolenko; I. A. Yadroitsev

1997-01-01

201

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

SciTech Connect

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

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

1982-11-01

202

ESTIMATION OF WATER SOLUBILITY AND OCTANOL/WATER PARTITION COEFFICIENT OF HYDROPHOBIC DYES - PART I. RELATIONSHIP BETWEEN SOLUBILITY AND PARTITION COEFFICIENT  

EPA Science Inventory

Three regression approaches are examined for use in estimating water solubilities and octanol/water partition coefficients, two fundamental equilibrium constants that are widely used predicting the fate of organic chemicals in aquatic systems. pproaches examined are regression of...

203

Estimation of Water Solubility and Octanol/Water Partition Coefficient of Hydrophobic Dyes. Part 1. Relationship between Solubility and Partition Coefficient.  

National Technical Information Service (NTIS)

Three regression approaches are examined for use in estimating water solubilities and octanol/water partition coefficients, two fundamental equilibrium constants that are widely used in predicting the fate of organic chemicals in aquatic systems. Approach...

G. L. Baughman E. J. Weber

1991-01-01

204

Effects of suspended sediment concentration on the absorption and scattering coefficients  

NASA Astrophysics Data System (ADS)

The scattering coefficient (b) for the nearshore waters off the coast of North Carolina near Camp Lejeune is strongly influenced by suspended sediment concentration and total particulate cross-sectional area (xg). In-situ measurements of a and b were made using a WET Labs AC9 meter. Estimates of suspended sediment concentration and total particulate cross-sectional area were determined from laser particle size analyses of surface water samples. The SeaWiFS bio-optical algorithm was modified for Case II waters and used to estimate a and bb from remote sensing reflectance (Rrs). After conversion from backscattering (bb) to total scattering (b), modeled a and b values from the modified SeaWiFS algorithm were compared to the measured values. The differences between the measured and estimated values appear to be directly related to increases in suspended sediment concentration and xg. Correlations of about 0.90 were obtained for b vs xg and bb vs xg.

Terrie, Gregory E.; Ladner, Sherwin; Gould, Richard A., Jr.

1997-02-01

205

Vertical profiles of aerosol absorption coefficient from micro-Aethalometer data and Mie calculation over Milan.  

PubMed

Vertical profiles of aerosol number-size distribution and black carbon (BC) concentration were measured between ground-level and 500m AGL over Milan. A tethered balloon was fitted with an instrumentation package consisting of the newly-developed micro-Aethalometer (microAeth® Model AE51, Magee Scientific, USA), an optical particle counter, and a portable meteorological station. At the same time, PM(2.5) samples were collected both at ground-level and at a high altitude sampling site, enabling particle chemical composition to be determined. Vertical profiles and PM(2.5) data were collected both within and above the mixing layer. Absorption coefficient (b(abs)) profiles were calculated from the Aethalometer data: in order to do so, an optical enhancement factor (C), accounting for multiple light-scattering within the filter of the new microAeth® Model AE51, was determined for the first time. The value of this parameter C (2.05±0.03 at ?=880nm) was calculated by comparing the Aethalometer attenuation coefficient and aerosol optical properties determined from OPC data along vertical profiles. Mie calculations were applied to the OPC number-size distribution data, and the aerosol refractive index was calculated using the effective medium approximation applied to aerosol chemical composition. The results compare well with AERONET data. The BC and b(abs) profiles showed a sharp decrease at the mixing height (MH), and fairly constant values of b(abs) and BC were found above the MH, representing 17±2% of those values measured within the mixing layer. The BC fraction of aerosol volume was found to be lower above the MH: 48±8% of the corresponding ground-level values. A statistical mean profile was calculated, both for BC and b(abs), to better describe their behaviour; the model enabled us to compute their average behaviour as a function of height, thus laying the foundations for valid parametrizations of vertical profile data which can be useful in both remote sensing and climatic studies. PMID:21546060

Ferrero, L; Mocnik, G; Ferrini, B S; Perrone, M G; Sangiorgi, G; Bolzacchini, E

2011-06-15

206

Osmotic second virial coefficient of methane in water.  

PubMed

A correlation-function-based scheme is proposed for calculating the osmotic second virial coefficient B for solutes that dissolve very little in a solvent. The short-distance contribution to B, a volume integral of the solute-solute pair correlation function h(r) from 0 to some finite distance rc, is evaluated with h(r) obtained by molecular simulation. The remaining contribution to B from rc to ? is calculated with an asymptotic form of h(r) (Evans, R.; et al. J. Chem. Phys. 1994, 100, 591). It is shown here that B for a model system of methane in water is obtained accurately in the temperature range between 238 and 373 K at 1 bar, with a result that B is a monotonically decreasing function of temperature, and the hydrophobic interaction between methane molecules measured by B is repulsive (B > 0) in supercooled water, virtually null (B ? 0) at around 0 °C, and attractive (B < 0) at higher temperatures. It is also remarked that a nearly linear relation holds between B and the first-peak height of the solute-solute radial distribution function. PMID:24050222

Koga, K

2013-10-17

207

Energy absorption probes control oily-water discharges  

Microsoft Academic Search

Energy absorption instrumentation is rapidly emerging as the preferred method of interface control for separation processes. This high-frequency electromagnetic measurement technique accurately senses volume percentages (not level) in phase separations such as water and oil. Instead of searching for or assuming a clean interface, the instruments monitor percentages of water at points in the system, and can measure either water

G. Agar; P. Clewis; C. Spencer

1993-01-01

208

Distillation column configurations in ammonia–water absorption refrigeration systems  

Microsoft Academic Search

In ammonia–water absorption refrigeration systems a purification process to reduce the water content in the vapour leaving the generator is required. During this process the water content in the vapour must be reduced to a minimum, otherwise it tends to accumulate in the evaporator and strongly deteriorates the efficiency of the system. The vapour purification can be carried out by

José Fernández-Seara; Jaime Sieres; Manuel Vázquez

2003-01-01

209

Specific absorption coefficient and phytoplankton biomass in the southern region of the California Current  

NASA Astrophysics Data System (ADS)

In recent years, experts of optical hydrology have shown great interest in the variability of the specific absorption coefficient of light by phytoplankton ( aph*). This parameter is important and necessary for comparing in situ bio-optical and satellite optical measurements. Such comparisons are needed for detecting primary productivity at a mesoscale level. At present, however, the parameters used in algorithms for predicting productivity are global averages. To avoid this bias, we measured the spatial-temporal variability of aph* as part of the Jan-01 Investigaciones Mexicanas de la Corriente de California cruise along the southern California Current. We observed median values of 0.041 m 2 (mg chlorophyll a (Chl a)) -1 at 440 nm and 0.015 at 674 nm, with significant differences between inshore and offshore stations. In general, the stations located in the area of Bahía Vizcaíno, with oceanographic conditions favorable for the growth of phytoplankton, showed lower values of the aph*. The nano-microphytoplankton (>5 ?m) community comprised of 26 diatom genera with mean abundance values of the 19.5×10 3 cells l -1. Nitzschia closterium, a pennate diatom, was almost uniform throughout the study region. Flow cytometry measurements indicated that the picoplankton (<5 ?m) community consisted of two prokaryotes, Prochlorococcus (mean 3.6×10 6 cells l -1) and Synechococcus (mean 10.4×10 6 cells l -1), and a mixture of picoeukaryotes (mean 6.5×10 6 cells l -1). Analyses of Chl and carotenoid pigments determined by high-performance liquid chromatographic confirmed the presence of the divinyl Chl a characteristic of Prochlorococcus. The nano-micro- and picoplankton were 82% and 18% of total phytoplankton biomass (?g C l -1), respectively. In general, we concluded that the phytoplankton community structure and biomass on this cruise showed conditions similar to oligotrophic systems.

Millán-Núñez, Eduardo; Sieracki, Michael E.; Millán-Núñez, Roberto; Lara-Lara, José Rubén; Gaxiola-Castro, Gilberto; Trees, Charles C.

2004-03-01

210

Condensation of water vapor: Experimental determination of mass and thermal accommodation coefficients  

NASA Astrophysics Data System (ADS)

Experimental determinations of mass and thermal accommodation coefficients ?m and ?t for condensation of water vapor in air have been conducted covering a temperature range from about 250 to 290 K. For the first time, both coefficients have been determined directly and simultaneously. To this end, growth of water droplets in air has been observed at different total gas pressures ranging from about 1000 down to 100 hPa. Monodispersed seed particles have been used as condensation nuclei. After addition of water vapor with well-defined partial vapor pressure, supersaturation was achieved by adiabatic expansion in an expansion chamber. Most experiments reported in the present paper were performed at vapor saturation ratios ranging from 1.30 to 1.50. Monodispersed Ag particles with a diameter of 9 nm have been used as condensation nuclei, and for humidification a diffusion humidifier was applied. One experiment was performed at the saturation ratio of 1.02, which resembles conditions observed in the Earth's lower atmosphere. In this experiment, monodispersed DEHS particles with a diameter of 80 nm were used as condensation nuclei, and water vapor was generated by quantitative evaporation of a liquid jet. Droplet growth was monitored using the CAMS method. For determination of the accommodation coefficients, experimental droplet growth curves were compared to corresponding theoretical curves. Quantitative comparison was performed by varying the respective accommodation coefficient and the starting time of droplet growth in a two-parameter best fit procedure. Considering the uncertainty with respect to the starting time of droplet growth and the uncertainties of the experimental water vapor supersaturation, corresponding maximum errors have been determined. From the results obtained it can be stated that ?t is larger than 0.85 over the whole considered temperature range. For 250-270 K, values of ?m below 0.8 are excluded, and for higher temperatures up to 290 K we can exclude values of ?m below 0.4. Both coefficients are likely to be unity for all studied conditions. The results of this study enable accurate predictions of the formation and growth of cloud droplets required to parameterize cloud light scattering/absorption and precipitation properties in climate models.

Winkler, P. M.; Vrtala, A.; Rudolf, R.; Wagner, P. E.; Riipinen, I.; Vesala, T.; Lehtinen, K. E. J.; Viisanen, Y.; Kulmala, M.

2006-10-01

211

IRON (III) MOLAR EXTINCTION COEFFICIENTS IN LIGHT AND HEAVY WATER SOLUTIONS  

Microsoft Academic Search

The iron(III) molar extinction coefficient in HâO-0.4 M HâSO\\/; sub 4\\/ solution at maximum absorption and 25 deg C, epsilon \\/sub s\\/, was ; determined to be 2220 plus or minus 20 liters mole⁻¹ cm⁻¹. The ; ratio of the iron(III) molar extinction coefficient in DâO-0.4 M HâSO\\/; sub 4\\/ solution at maximum absorption and 25 deg C to epsilon

J. W. Boyle; H. A. Mahlman

1962-01-01

212

Energy Analysis of an Ammonia-Water Absorption Refrigeration System  

Microsoft Academic Search

A simple energy analysis technique for ammonia-water refrigeration systems is presented and verified with actual experimental data taken from the literature. Comparison was made in terms of the coefficient of performance, and very good agreement was found.

IBRAHIM DINCER; SADIK DOST

1996-01-01

213

A reduced-scale railway noise barrier's insertion loss and absorption coefficients: comparison of field measurements and predictions  

NASA Astrophysics Data System (ADS)

In situ testing determined the insertion loss ( IL) and absorption coefficients of a candidate absorptive noise barrier (soundwall) to abate railway noise for residents of Anaheim, CA. A 4000 m barrier is proposed south of the tracks, but residential areas to the north have expressed concerns that barrier reflections will increase their noise exposure. To address these concerns, a 3.66 m high by 14.6 m long demonstration barrier was built in the parking lot of Edison Field, Anaheim, as part of a public open house, thereby allowing for acoustical measurements. Insertion loss ( IL) was measured in third-octave bands assuming 1/2-scale construction. The IL for three, scaled railway noise sub-sources (rail/wheel interface, locomotive, and train horn) was measured at six, scaled distances. The highest total, A-weighted IL, after corrections for finite-barrier and point-source speaker effects was 22 dB(A) for rail/wheel noise, 18 dB(A) for locomotive noise, and 20 dB(A) for train horn noise. These results can be compared favourably to IL predictions made using algorithms from the US Federal Rail Administration (FRA) noise assessment guidelines. For the actual barrier installation, shielded residential receivers located south of the project are expected to see their future noise exposures reduced from an unmitigated 78 CNEL to 65 CNEL. Absorption coefficients were measured using time delay spectrometry. At lower frequencies, measured absorption coefficients were notably less than the reverberation room results advertised in the manufacturer's literature, but generally conformed with impedance tube results. At higher frequencies the correspondence between measured absorption coefficients and reverberation room results was much improved. For the actual barrier installation, unshielded residential receivers to the north are expected to experience noise exposure increases of less than 1 dB(A). This factor of increase is consistent with a finding of no impact when assessed using FRA guidelines for allowable increases of noise exposure.

Busch, T. A.; Nugent, R. E.

2003-10-01

214

Absorption and Attenuation Coefficients Using the WET Labs ac-s in the Mid-Atlantic Bight: Field Measurements and Data Analysis  

NASA Technical Reports Server (NTRS)

Ocean color algorithms are based on the parameterization of apparent optical properties as a function of inherent optical properties. WET Labs underwater absorption and attenuation meters (ac-9 and ac-s) measure both the spectral beam attenuation [c (lambda)] and absorption coefficient [a (lambda)]. The ac-s reports in a continuous range of 390-750 nm with a band pass of 4 nm, totaling approximately 83 distinct wavelengths, while the ac-9 reports at 9 wavelengths. We performed the ac-s field measurements at nine stations in the Mid-Atlantic Bight from water calibrations to data analysis. Onboard the ship, the ac-s was calibrated daily using Milli Q-water. Corrections for the in situ temperature and salinity effects on optical properties of water were applied. Corrections for incomplete recovery of the scattered light in the ac-s absorption tube were performed. The fine scale of spectral and vertical distributions of c (lambda) and a (lambda) were described from the ac-s. The significant relationships between a (674) and that of spectrophotometric analysis and chlorophyll a concentration of discrete water samples were observed.

Ohi, Nobuaki; Makinen, Carla P.; Mitchell, Richard; Moisan, Tiffany A.

2008-01-01

215

Measurement of atmospheric precipitable water using a solar radiometer. [water vapor absorption effects  

NASA Technical Reports Server (NTRS)

A technique is described and tested that allows the determination of atmospheric precipitable water from two measurements of solar intensity: one in a water-vapor absorption band and another in a nearby spectral region unaffected by water vapor.

Pitts, D. E.; Dillinger, A. E.; Mcallum, W. E.

1974-01-01

216

Selection of stopping-power and mass energy-absorption coefficient ratios for high-energy x-ray dosimetry  

SciTech Connect

A method for the selection of average stopping-power (L-bar/rho)/sup med//sub air/ and energy-absorption coefficient ( mu-bar/sub en//rho)/sup med//sub air/ ratios has been developed. The quality of the x-ray beam is characterized by the ratio of ionization chamber readings at depths of 20 and 10 cm in water (TMR)/sup 20//sub 10/. For convenience, a relationship is established between experimental (TMR)/sup 20//sub 10/ and the nominal accelerating potential (MV) of the accelerator. Experimental (TMR)/sup 20//sub 10/ are related to (L-bar/rho)/sup med//sub air/ and ( mu-bar/sub en//rho)/sup med//sub air/ in a three-step process. First, using experimental and theoretical spectra in the range /sup 60/Co to 45 MV, (TMR)/sup 20//sub 10/ were calculated for primary and first-scatter photons, and a graph of experimental versus calculated (TMR)/sup 20//sub 10/ for these same spectra was constructed. Second, (L-bar/rho)/sup med//sub air/ and ( mu-bar/sub en//rho)/sup med//sub air/ were calculated for a large number of primary spectra (for most of which experimental (TMR)/sup 20//sub 10/ were not available) and a graph constructed that related these quantities and (TMR)/sup 20//sub 10/ calculated as above for this group of spectra. Third, using the graphs from the preceding steps, graphs relating the calculated (L-bar/rho)/sup med//sub air/ and ( mu-bar/sub en//rho)/sup med//sub air/ with experimental (TMR)/sup 20/3exclamation/sub 0/ were constructed. Data are presented for water, polystyrene, acrylic, graphite, A-150, C-552, Bakelite, and nylon for beams with nominal accelerating potentials in the range 2--45 MV.

Cunningham, J.R.; Schulz, R.J.

1984-09-01

217

Influence of the scattering and absorption coefficients on homogeneous room simulations that use a diffusion equation model.  

PubMed

The diffusion equation model was used for room acoustic simulations to predict the sound pressure level and the reverberation time. The technical literature states that the diffusion equation method accurately models the late portion of the room impulse response if the energy is sufficiently scattered. This work provides conclusions on the validity of the diffusion equation model for rooms with homogeneous dimensions in relation to the scattering coefficients of the boundaries. A systematic evaluation was conducted out to determine the ranges of the absorption and scattering coefficient values that result in low noticeable differences between the predictions from a geometrical acoustic model and those from the diffusion equation model. PMID:23463993

Navarro, Juan M; Escolano, José; Cobos, Maximo; López, José J

2013-03-01

218

Novel method to measure the refractive index and the absorption coefficient of organic nonlinear crystals in the ultra wideband THz region  

Microsoft Academic Search

A method for simultaneously measuring the refractive index and absorption coefficient of nonlinear optical crystals in the ultra-wideband terahertz (THz) region was developed. This method is based on the analysis of a collinear difference frequency generation (DFG) process using a tunable, dual-wavelength, optical parametric oscillator. The refractive index and the absorption coefficient in the organic nonlinear crystal DAS were experimentally

S. Ohno; K. Miyamoto; H. Minamide; H. Ito

2009-01-01

219

Bias in Dobson total ozone measurements at high latitudes due to approximations in calculations of ozone absorption coefficients and air mass  

Microsoft Academic Search

The Dobson spectrophotometer is the primary standard instrument for ground-based measurements of total column ozone. The accuracy of its data depends on the knowledge of ozone absorption coefficients used for data reduction. We document an error in the calculations that led to the set of absorption coefficients currently recommended by the World Meteorological Organisation (WMO). This error has little effect

G. Bernhard; R. D. Evans; G. J. Labow; S. J. Oltmans

2005-01-01

220

CO(2) Laser Absorption Coefficients for Determining Ambient Levels of O(3), NH(3), and C(2)H(4).  

PubMed

A carbon dioxide laser source was used to determine absorption coefficients for dilute absorber-air mixtures at wavelengths corresponding to several vibration-rotation lines in each branch of the 00 degrees 1-02 degrees 0 band at 9.4 microm and the 00 degrees 1-10 degrees 0 band at 10.4 microm. For all samples the total pressure was 1 atm and the temperature was 300 K; the concentrations ranged from 10 ppm (parts per million by volume) to 357 ppm for NH(3) and C(2)H(4), and from 10 ppm to 80 ppm for O(3). The absorption coefficients are tabulated, and the use of selected laser lines in monitoring ambient concentrations is discussed. PMID:20134799

Patty, R R; Russwurm, G M; McClenny, W A; Morgan, D R

1974-12-01

221

Optimum hot water temperature for absorption solar cooling  

Microsoft Academic Search

The hot water temperature that maximizes the overall instantaneous efficiency of a solar cooling facility is determined. A modified characteristic equation model is used and applied to single-effect lithium bromide–water absorption chillers. This model is based on the characteristic temperature difference and serves to empirically calculate the performance of real chillers. This paper provides an explicit equation for the optimum

A. Lecuona; R. Ventas; M. Venegas; A. Zacarías; R. Salgado

2009-01-01

222

Gastrointestinal Absorption of Soluble Uranium from Drinking Water.  

National Technical Information Service (NTIS)

The manuscript describes results of an experiment to determine the gastrointestinal absorption of uranium from drinking water in 12 health adults. Most of the uranium ingested was excreted in feces in the first 2 days following ingestion of the water. The...

M. E. Wrenn N. P. Singh H. Ruth D. Burleigh

1988-01-01

223

A method for calculating the absorption coefficient of a multi-layer absorbent using the electro-acoustic analogy  

Microsoft Academic Search

A theoretical method for calculating the absorption coefficient of the multi-layer absorbers composed of perforated plates, airspaces and porous materials is proposed. Initially, for multi-layer absorbers composed either of perforated plates and airspaces or perforated plates and porous materials, the acoustic impedance is calculated using an electro-acoustic analogy. Then, for multi-layer absorbers composed of perforated plates, airspaces and porous materials,

Zhu Congyun; Huang Qibai

2005-01-01

224

Account of frequency dependence of the acoustic absorption coefficient in solving problems of acoustic-brightness thermometry  

Microsoft Academic Search

We perform a comparative analysis of the estimate bias in measuring the internal thermodynamic temperature and time of thermal\\u000a destruction of biological tissue using the acoustothermometry method based on the model of recording of thermoacoustic radiation\\u000a from a temperature-inhomogeneous medium with allowance for frequency dependence of the acoustic absorption coefficient. An\\u000a expression for acoustic-brightness temperature is obtained in the case

E. V. Krotov; A. M. Reyman; P. V. Subochev

2006-01-01

225

Opto-acoustic measurement of the absorption coefficients of IR window materials for a CO2 laser  

Microsoft Academic Search

A laser opto-acoustic technique has been used to measure the absorption coefficients of IR window materials (for example NaCl, KCl, AR-coated Ge, BaF2, CaF2 and ZnS) on the R(20) and the P(20) lines of a CO2 laser. In this paper the above materials under their working conditions have also been assessed.

C.-J. Ming; Z.-X. Li; L.-J. Wang; C.-W. Chen; Y.-T. Liu

1982-01-01

226

Comparison of the uncertainty budget between the one- and the two-microphone method for reflection and absorption coefficient  

Microsoft Academic Search

The impedance tube is mostly used to measure the reflection and absorption coefficient at normal incidence based on ISO 10534-2. It is possible to use the one-microphone or the two-microphone method, where either a pseudorandom or random signal is used to produce a standing wave pattern inside the impedance tube in order to measure the transfer function and obtain the

Adolfo Esquivel D; Lorenzo M. Muniz

2002-01-01

227

Comments on “measurement of the absorption coefficients for the He?Ne laser radiation in a pure hydrogen plasma”  

Microsoft Academic Search

In a recent publication in this journal, ke described an experiment designed to measure the total absorption coefficients\\u000a for 0.6328- and 1.15-?m He?Ne laser radiation in a hydrogen plasma. It is the purpose of the present note to indicate some\\u000a errors in the publication which invalidate the conclusions drawn by the author.

Kenneth W. Billman; James R. Stallcop; Gülay Öke

1976-01-01

228

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

Microsoft Academic Search

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

Karima Allali; Annick Bricaud; Hervé Claustre

1997-01-01

229

Dynamic viscoelastic properties, water absorption, and solubility of home reliners.  

PubMed

Scant rheological information is available regarding home reliners (liner type denture adhesives). We evaluated 6 different home reliners in regard to their viscoelastic properties, water absorption and solubility. Dynamic viscoelastic properties and changes over time were determined using a dynamic viscoelastometer, while weight changes, absorption, and solubility during immersion in water were also investigated. We found that the dynamic viscoelasticity of the tested home reliners was sensitive to changes in frequency, while the materials used had nearly no elasticity and exhibited viscous behaviors. They showed a dramatic change in viscoelastic properties and increase in weight after approximately 1 day of water immersion. A considerably high percentage of water absorption was also observed. From the viewpoint of dynamic viscoelastic properties and durability, our results indicate that the tested home reliners would not be suitable for improvement of ill-fitting dentures. PMID:20733263

Murata, Hiroshi; Hong, Guang; Yamakado, Chiaki; Kurogi, Tadafumi; Kano, Hiroshi; Hamada, Taizo

2010-10-01

230

Reconstruction of the optical absorption coefficient from photoacoustic signals measured by scanning coaxial probe with regularization methods  

NASA Astrophysics Data System (ADS)

Reconstruction of the absorption coefficient from photoacoustic signals is discussed. The photoacoustic (PA) signals were acquired by using a ring-shaped P(VDF-TrFE) acoustic sensor coaxially arranged with an optical fiber. The acoustic sensor scanned the measured object. The linearized image reconstruction method previously presented by the authors was modified for the measurement with the coaxial probe. The distribution of the absorption coefficient was reconstructed by solving the inverse problem based on the PA wave equation and the photon diffusion equation. The linearized forward model was formulated by solving the partial differential equations with finite element method. To eliminate the effect of the unknown background on the PA signal, the differences between the PA signals measured at different positions were used for the image reconstruction. The image reconstruction method was validated by numerical and phantom experiments. Moreover, the reconstructed images with the Tikhonov and lp sparsity regularization methods were compared from the standpoints of spatial resolution, robustness to noise and quantification of the absorption coefficient.

Okawa, Shinpei; Hirasawa, Takeshi; Kushibiki, Toshihiro; Ishihara, Miya

2014-03-01

231

Effects of temperature-dependent molecular absorption coefficients on the thermal infrared remote sensing of the earth surface  

NASA Technical Reports Server (NTRS)

The effect of temperature-dependent molecular absorption coefficients on thermal infrared spectral signatures measured from satellite sensors is investigated by comparing results from the atmospheric transmission and radiance codes LOWTRAN and MODTRAN and the accurate multiple scattering radiative transfer model ATRAD for different atmospheric profiles. The sensors considered include the operational NOAA AVHRR and two research instruments planned for NASA's Earth Observing System (EOS): MODIS-N (Moderate Resolution Imaging Spectrometer-Nadir-Mode) and ASTER (Advanced Spaceborne Thermal Emission and Reflection Radiometer). The difference in band transmittance is as large as 6 percent for some thermal bands within atmospheric windows and more than 30 percent near the edges of these atmospheric windows. The effect of temperature-dependent molecular absorption coefficients on satellite measurements of sea-surface temperature can exceed 0.6 K. Quantitative comparison and factor analysis indicate that more accurate measurements of molecular absorption coefficients and better radiative transfer simulation methods are needed to achieve SST accuracy of 0.3 K, as required for global numerical models of climate, and to develop land-surface temperature algorithms at the 1-K accuracy level.

Wan, Zhengming; Dozier, Jeff

1992-01-01

232

Thermodynamic modeling of an ammonia–water absorption chiller  

Microsoft Academic Search

This article develops a general thermodynamic framework for the modeling of an irreversible absorption chiller at the design point, with application to a single-stage ammonia–water absorption chiller. Component models of the chiller have been assembled so as to quantify the internal entropy production and thermal conductance (UA) in a thermodynamically rigorous formalism, which is in agreement with the simultaneous heat-and-mass

H. T. Chua; H. K. Toh; K. C. Ng

2002-01-01

233

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

234

Low-temperature FIR and submillimetre mass absorption coefficient of interstellar silicate dust analogues  

NASA Astrophysics Data System (ADS)

Context. Cold dust grains are responsible for the far-infrared and submillimetre (FIR/submm) emission observed by Herschel and Planck. Their thermal emission is usually expressed as a modified black body law in which the FIR/submm dust opacity, or mass absorption coefficient (MAC), is described by the MAC at a given wavelength ??0 and the temperature- and wavelength-independent emissivity spectral index ?. However, numerous data from previous space and balloon-borne missions and recently from Herschel and Planck show that the dust emission is not well understood, as revealed for example by the observed anti-correlation of ? with the grain temperature. Aims: The aim of this work is to measure the optical properties of interstellar dust analogues at low temperatures to give astronomers the necessary data for interpreting FIR/submm observations such as those from the Herschel and Planck satellites. Methods: We synthesised, via sol-gel methods, analogues of interstellar amorphous silicate grains, rich in Mg and Ca, and having stoichiometry of olivine and pyroxene. The samples are characterised by various techniques to determine their composition, size, amorphisation degree. All the amorphous samples are annealed at 1100 °C to study the crystallised materials for comparison. We measured the MAC of all the samples in the 2-25 ?m range at room temperature and in the 100-1000/1500 ?m range for grain temperatures varying from 300 to 10 K. Results: The experimental results show that, for all the amorphous samples, the grain MAC decreases when the grain temperature decreases and that the local spectral index, ?, defined as the slope of the MAC curve, is anti-correlated with the grain temperature. These variations, which are not observed in the crystallised samples, are related to the amorphous nature of the samples. In addition, the spectral shape of the MAC is complex and cannot be described by a single spectral index over the 100-1500 ?m range. At short wavelengths (? ? 500/700 ?m), ? is in the range 1.6-2.1 for all grain temperature and grain composition. However, at longer wavelengths (? ? 500/700 ?m), ? ? 2 for samples with a pyroxene stoichiometry and ? ? 2 for samples with an olivine stoichiometry. Conclusions: The dust properties in the FIR/submm domain and at low temperature are more complicated than expected. The simplifying asymptotic expression based on a single temperature- and wavelength-independent spectral index used by astronomers is not appropriate to describe the dust MAC, hence the dust emission, and may induce significant errors on the derived parameters, such as the dust mass and the dust physical and chemical properties. Instead, dust emission models should use the dust MAC as a function of wavelength and temperature.

Coupeaud, A.; Demyk, K.; Meny, C.; Nayral, C.; Delpech, F.; Leroux, H.; Depecker, C.; Creff, G.; Brubach, J.-B.; Roy, P.

2011-11-01

235

Diffusion coefficients significant in modeling the absorption rate of carbon dioxide into aqueous blends of N-methyldiethanolamine and diethanolamine and of hydrogen sulfide into aqueous N-methyldiethanolamine  

SciTech Connect

Absorption rates of gaseous CO{sub 2} into aqueous blends of N-methyldiethanolamine (MDEA) and diethanolamine (DEA) and of gaseous H{sub 2}S into aqueous MDEA were measured in a quiescent, inverted-tube diffusiometer by monitoring the rate of pressure drop. A numerical model for absorption, diffusion, and reaction of CO{sub 2} and H{sub 2}S in blends of MDEA, DEA, and water was developed. The model was used to regress diffusion coefficients of bicarbonate, carbamate, and MDEAH{sub 2}CO{sub 3} for the case of CO{sub 2} absorption and of bisulfide ion for the case of H{sub 2}S absorption from measured absorption rates. CO{sub 2} absorption rates and diffusion coefficients of bicarbonate, carbamate, and MDEAH{sub 2}CO{sub 3} were obtained at 298.2 K and 318.2 K in aqueous solutions containing 50 mass % total amine at DEA:MDEA mole ratios of 1:20, 1:4, 1L3, and 2:3. H{sub 2}S absorption rates and diffusion coefficients of bisulfide ion were obtained at 298.2 K and 318.2 K in aqueous solutions containing 20, 35, and 50 mass % MDEA.

Adams, M.E.; Marshall, T.L.; Rowley, R.L. [Brigham Young Univ., Provo, UT (United States). Dept. of Chemical Engineering] [Brigham Young Univ., Provo, UT (United States). Dept. of Chemical Engineering

1998-07-01

236

Light absorption and fluorescence properties of chromophoric dissolved organic matter (CDOM), in the St. Lawrence Estuary (Case 2 waters)  

Microsoft Academic Search

The absorption coefficient and the fluorescence emission of chromophoric (coloured) dissolved organic matter (CDOM) were determined along a 1200 km transect in the Estuary and Gulf of St. Lawrence. Fluorescence spectra were spectrally corrected against a reference standard and normalized to the water Raman signal to provide results in Raman units. Because CDOM originates mainly from freshwater river runoff in

B. Nieke; R. Reuter; R. Heuermann; H. Wang; M. Babin; J. C. Therriault

1997-01-01

237

Determination of fixed water in rocks by infrared absorption  

USGS Publications Warehouse

An infrared absorption technique has been developed for the quantitative determination of "fixed water" (H2O+) in rocks. Potassium bromide disks containing 2-mg samples are scanned in the 3-??m spectral region and absorption at 2.96 ??m is determined. Although the exact nature of this peak is not known, other than that it is caused by an interaction between the potassium bromide and hydroxyl groups and water, it can be used for quantitative analysis. Rock samples, other than those containing significant percentages of clay minerals, can be analyzed with a standard deviation of 0.26%.

Breger, I. A.; Chandler, J. C.

1969-01-01

238

The effect of an optical pump on the absorption coefficient of magnesium-doped near-stoichiometric lithium niobate in terahertz range  

NASA Astrophysics Data System (ADS)

The absorption coefficient of magnesium-doped near-stoichiometric lithium niobate crystal is measured by terahertz time-domain spectroscopy in a frequency range of 0.2 THz-0.9 THz at room temperature. The absorption coefficient is modulated by external optical pump fields. Experimental results show that the absorption coefficient of near-SLN:Mg crystal is approximately in a range of 22 cm-1-35 cm-1 in a frequency range of 0.2 THz-0.9 THz and tunable up to nearly 15%. Further theoretical analysis reveals that the variation of absorption coefficient is related to the number of light-induced carriers, domain reversal process, and OH- absorption in this crystal.

Zuo, Zhi-Gao; Ling, Fu-Ri; Ma, De-Cai; Wu, Liang; Liu, Jin-Song; Yao, Jian-Quan

2013-10-01

239

Backscattering and absorption coefficients for electrons: Solutions of invariant embedding transport equations using a method of convergence  

NASA Astrophysics Data System (ADS)

The backscattering coefficient is a magnitude whose measurement is fundamental for the characterization of materials with techniques that make use of particle beams and particularly when performing microanalysis. In this work, we report the results of an analytic method to calculate the backscattering and absorption coefficients of electrons in similar conditions to those of electron probe microanalysis. Starting on a five level states ladder model in 3D, we deduced a set of integro-differential coupled equations of the coefficients with a method know as invariant embedding. By means of a procedure proposed by authors, called method of convergence, two types of approximate solutions for the set of equations, namely complete and simple solutions, can be obtained. Although the simple solutions were initially proposed as auxiliary forms to solve higher rank equations, they turned out to be also useful for the estimation of the aforementioned coefficients. In previous reports, we have presented results obtained with the complete solutions. In this paper, we present results obtained with the simple solutions of the coefficients, which exhibit a good degree of fit with the experimental data. Both the model and the calculation method presented here can be generalized to other techniques that make use of different sorts of particle beams.

Figueroa, C.; Brizuela, H.; Heluani, S. P.

2014-05-01

240

Near-Infrared Studies of Glucose and Sucrose in Aqueous Solutions: Water Displacement Effect and Red Shift in Water Absorption from Water-Solute Interaction  

NASA Astrophysics Data System (ADS)

We use near infrared spectroscopy to obtain concentration dependent glucose absorption spectra in their aqueous solutions in the near-infrared range (3800 - 7500 cm^{-1}). We introduce a new method to obtain reliable glucose absorption bands from aqueous glucose solutions without measuring the water displacement coefficients of glucose separately. Additionally, we are able to extract the water displacement coefficients of glucose, and this may give a new general method using spectroscopy techniques applicable to other water soluble materials. We also observe red shifts in the absorption bands of water in the hydration shell around solute molecules, which comes from contribution of the interacting water molecules around the glucose molecules in solutions. The intensity of the red shift get larger as the concentration increases, which indicates that as the concentration increases more water molecules are involved in the interaction. However, the red shift in frequency does not seem to depend significantly on the concentration up to our highest concentration. We also performed the same measurements and analysis with sucrose instead of glucose as solute and compare.

Jung, Youngeui; Hwang, Jungseek

2013-02-01

241

Contribution a l'etude du coefficient de temperature des reacteurs a eau legere. (Contribution to the study of the temperature reactivity coefficient for light water reactors).  

National Technical Information Service (NTIS)

In this work, we looked for the error sources in the calculation of the isothermal temperature coefficient for light water lattices. We studied three fields implied: the nuclear data, the calculation methods, and the temperature coefficient measurement. A...

C. Mounier

1994-01-01

242

Critically evaluated data on optical and transport properties of solids (refractive index and absorption coefficient of selected optical materials)  

NASA Astrophysics Data System (ADS)

Under this contract a study was carried out of the optical properties of selected optical materials through data compilation, critical data evaluation and generation of recommended values based on available data from worldwide literature. The selected optical materials include alkali halides, alkaline earth halides, silicon and germanium, and III-V compounds. A major contribution of this work has been the exhaustive compilation of absorption coefficient and the formulation of an Urbach type equation for the multiphonon region near the infrared absorption edge of alkali halides and alkaline earth fluorides. This equation is used to calculate the intrinsic absorption coefficient as a function of both wavelength and temperature in the temperature region of practical interest with the calculated result in concordance with the best contemporary experimental measurements for the pure samples. Optical constants of silicon and germanium were studied in a similar manner as for the above mentioned materials. Refractive index data for silicon and germanium were exhaustively compiled and analyzed. Recommended values of refractive index for the transparent wavelength region were generated in the range 1.2 to 14 microns and 100-750 K for silicon, and 1.9 to 16 microns and 100-550 K for germanium.

Li, H. H.

1981-06-01

243

Light scattering and absorption caused by bacterial activity in water.  

PubMed

There is a growing class of elementary particle detectors, large-water ?erenkov detectors, that have a body of water (thousands of tons) as a sensitive medium. Particles are detected when they interact with the water and produce ?erenkov light, so detection efficiency relies on the transparency of the water. These detectors are active typically for many years, so biological activity (primarily bacterial growth) is one of the means by which the transparency of the water may be reduced. We present the results of a measurement of light scattering and absorption from a population of Escherichia coli in water, which is used as a model for bacteria in general. One can separate the scattering and absorption by varying the refractive index of the medium by using a solute of high molecular weight. We show that the results can be understood simply in terms of light scattering from small spheres (radius ? wavelength) with an effective refractive index, n(b), plus a small amount of absorption in the ultraviolet. We compare his scattering with Rayleigh scattering in pure water. PMID:20941320

Waltham, C; Boyle, J; Ramey, B; Smit, J

1994-11-01

244

Inherent optical properties of the ocean: Retrieval of the absorption coefficient of chromophoric dissolved organic matter from fluorescence measurements  

Microsoft Academic Search

The quantitative relationship between the absorption and fluorescence emission of chromophoric (col- ored) dissolved organic matter (CDOM) has been determined along five cruise tracks in the western North Atlantic Ocean, the Gulf of Mexico, and Monterey Bay, and includes Gulf Stream, Loop Current, slope, shelf, and coastal waters. We present a protocol for the determination of CDOM fluorescence that will

FRANK E. HOGE; ANTHONY VODACEK; NEIL V. BLOUGH

1993-01-01

245

Assessment of the relationships between dominant cell size in natural phytoplankton communities and the spectral shape of the absorption coefficient  

Microsoft Academic Search

Size-fractionated chlorophyll concentration and phytoplankton absorption spectra were compared for a wide variety of natural communities. We found that, in general, when phytoplankton abundance increases, larger size- classes are added incrementally to a background of smaller cells. Natural phytoplankton communities from surface waters were explicitly characterized according to their dominant cell size and taxonomic group, and the relationships between this

Aurea M. Ciotti; Marlon R. Lewis; John J. Cullen

2002-01-01

246

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

NASA Astrophysics Data System (ADS)

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

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

2013-09-01

247

Effect of electron collisions on transport coefficients induced by the inverse bremsstrahlung absorption in plasmas  

SciTech Connect

The transport coefficients of fully ionized plasmas under the influence of a high-frequency electric field are derived solving numerically the electron Fokker-Planck equation using a perturbation method, parametrized as a function of the electron mean-free-path {lambda}{sub ei} compared to the spatial scales L. The isotropic and anisotropic contributions of the inverse bremsstrahlung heating are considered. Electron-electron collision terms are kept in the analysis, which allows us to consider with sufficient accuracy to describe plasmas with arbitrary atomic number Z. Practical numerical fits of the transport coefficients are proposed as functions of Z and the collisionality parameter {lambda}{sub ei}/L.

Bendib, A.; Tahraoui, A.; Bendib, K.; Mohammed El Hadj, K.; Hueller, S. [Laboratoire d'Electronique Quantique, Faculte de Physique, USTHB, El Alia BP 32, Bab Ezzouar 16111, Algiers (Algeria); Centre de Physique Theorique, Ecole Polytechnique, F-91128 Palaiseau Cedex (France)

2005-03-01

248

Research on the reverberation absorption coefficient of material measured by underwater reverberation field method  

Microsoft Academic Search

In this article, an underwater reverberation time model of a rubber board is established. Then a theory formula of reverberation time T(rm,?m) is given according to the energy relation of sound field in the reverberation chamber. rm is the reflecting fraction and ?m is the absorption fraction, when sound wave is injected to a rubber board. rm and ?m can

Yang Song; Zhen-qi Zhao; Wei Zhang; Sheng-qi Yu

2011-01-01

249

Parametric study of the influence of compression on the acoustical absorption coefficient of automotive felts  

Microsoft Academic Search

The present note describes some work related to the modelization of acoustical absorption properties of compressed porous materials. An `equivalent fluid' model with five parameters is used. This prediction technique is validated with some industrial materials being 1-D compressed along their thickness, starting from a felt mat having a given basic weight. The obtained results tend to indicate that an

Bernard Castagnède; Julian Tizianel; Alexei Moussatov; Achour Aknine; Bruno Brouard

2001-01-01

250

Measurement of acoustic absorption coefficients by the tone-burst method in a noisy environment  

Microsoft Academic Search

The tone-burst method was proposed as a means of measuring the absorption of acoustical materials in the presence of environmental factors, for example a strong tangential flow of air which would result in a noisy test environment. Mathematical models were developed to determine the effects of the pulse parameters, duration and bandwidth, and of the properties of the material on

W. J. Webster

1975-01-01

251

Effect of absorption on the diffusion coefficient of classical waves in random media with microstructure resonances  

NASA Astrophysics Data System (ADS)

The effect of absorption on the diffusion constant of classical waves propagating in media with randomly positioned Mie scatterers is studied. Profound changes including a significant increase in the diffusion constant are found and attributed to the growth of the transport mean free path in the vicinity of Mie resonances. Copyright (c) 1995 Optical Society of America

Livdan, D.; Lisyansky, A. A.

1995-12-01

252

Influence of impact velocity on energy absorption characteristics and friction coefficient of expansion tube  

Microsoft Academic Search

Used as a crash element, the expansion tube dissipates crash energy through the internal deformation energy of the tube and frictional energy. In this paper, in order to study the effects of impact velocity on the energy absorption characteristics of an expansion tube, friction quasi-static and dynamic experiments were carried out and an inverse method using a finite element analysis

Won Mok Choi; Tae Su Kwon; Hyun Sung Jung; Jin Sung Kim

2012-01-01

253

A comparison between ammonia-water and water-lithium bromide solutions in vapor absorption refrigeration systems  

SciTech Connect

A Vapor Absorption Refrigeration (VAR) System is similar to a Vapor Compression Refrigeration (VCR) System. In both systems the required refrigeration is provided by refrigerants vaporizing in the evaporator. However, in the VAR System, a physico-chemical process replaces the mechanical process of the VCR system and heat rather than a mechanical and electrical energy is used. The advantages of this system lie in the possibility of utilizing of waste energy from industrial plants as well as of using solar energy. The study included an investigation to analyze the Vapor Absorption Refrigeration systems using ammonia-water and water-lithium bromide solutions. A fundamental VAR system is described and the operating sequence is explained. Since the most common VAR systems use ammonia-water solution with ammonia as the refrigerant and water-lithium bromide solution with water as the refrigerant, the comparison of the two is presented in respect of the coefficient of performance (COP), the cooling capacity and the maximum and minimum system pressures. It is concluded that the VAR system using water-lithium bromide solution provided better performance than the system using ammonia-water solution. However, there are some points to be considered such as: the danger of crystallization and impossibility of operating in very low temperatures because of the use of water as the refrigerant.

Horuz, I. [Univ. of Uludag, Bursa (Turkey)] [Univ. of Uludag, Bursa (Turkey)

1998-07-01

254

An empirical ocean color algorithm for estimating the contribution of chromophoric dissolved organic matter to total light absorption in optically complex waters  

Microsoft Academic Search

To estimate the depth-integrated rate of photochemical processes involving chromophoric dissolved organic matter (CDOM) in coastal waters, the contribution of CDOM to the total absorption coefficient must be known from UV to green. At 307 sites sampled in various coastal marine environments, the ratio between CDOM and the total absorption coefficient ([aCDOM\\/at]) at 412 nm was found to vary over

Simon Bélanger; Marcel Babin; Pierre Larouche

2008-01-01

255

Ammonia-Water Absorption-Heat-Pump Cycle.  

National Technical Information Service (NTIS)

The state-of-art in ammonia-water absorption cooling has been applied to an air-source heating-only heat-pump cycle which delivers its heat indoors via circulating liquid. The cycle is described, differences from the cooling application noted, and test re...

D. Kuhlenschmidt R. H. Merrick

1983-01-01

256

Investigation of a Ammonia-Water Absorption Chiller Performance  

Microsoft Academic Search

An experimental prototype of a single stage ammonia-water absorption chiller was designed, built and tested. The thermodynamic models of the components, based on the First and Second Laws, have been assembled so as to quantify the simultaneous heat and mass transfer processes occurring within the exchangers. Calculated results were compared with experimental data. The results show that the cooling effect

Dingfeng Kong; Jianhua Liu; Liang Zhang; Zhiyun Fang

2010-01-01

257

Water Absorption Tests for Measuring Permeability of Field Concrete.  

National Technical Information Service (NTIS)

The research results from CFIRE Project 04-06 were communicated to engineers and researchers in this project. Specifically, the water absorption of concrete samples (i.e., 2-in. thick, 4-in. diameter discs cut from concrete cylinders) was found strongly r...

H. Tabatabai J. Zhao

2013-01-01

258

Study of Second Harmonic Generation Coefficients and Ultraviolet Absorption Edge of Barium Borate Crystal.  

National Technical Information Service (NTIS)

Barium borate (beta-BaB2O4) is a new type of non-linear optical crystal. In this paper the authors report one-electron energies and wave functions of barium borate by use of EHMO theory. Both the calculated values of SHG coefficient and ultraviolet absorp...

J. K. Zhu B. Zhang S. H. Liu

1985-01-01

259

Parameterization of light absorption by components of seawater in optically complex coastal waters of the Crimea Peninsula (Black Sea).  

PubMed

The absorption of sunlight by oceanic constituents significantly contributes to the spectral distribution of the water-leaving radiance. Here it is shown that current parameterizations of absorption coefficients do not apply to the optically complex waters of the Crimea Peninsula. Based on in situ measurements, parameterizations of phytoplankton, nonalgal, and total particulate absorption coefficients are proposed. Their performance is evaluated using a log-log regression combined with a low-pass filter and the nonlinear least-square method. Statistical significance of the estimated parameters is verified using the bootstrap method. The parameterizations are relevant for chlorophyll a concentrations ranging from 0.45 up to 2 mg/m(3). PMID:19252624

Dmitriev, Egor V; Khomenko, Georges; Chami, Malik; Sokolov, Anton A; Churilova, Tatyana Y; Korotaev, Gennady K

2009-03-01

260

Enhancing the absorption coefficient of a backed rigid frame porous layer by embedding circular periodic inclusions.  

PubMed

The acoustic properties of a porous sheet of medium static air flow resistivity (around 10,000 N m s(-4)), in which a periodic set of circular inclusions is embedded and which is backed by a rigid plate, are investigated. The inclusions and porous skeleton are assumed motionless. Such a structure behaves like a multi-component diffraction grating. Numerical results show that this structure presents a quasi-total (close to unity) absorption peak below the quarter-wavelength resonance of the porous sheet in absence of inclusions. This result is explained by the excitation of a complex trapped mode. When more than one inclusion per spatial period is considered, additional quasi-total absorption peaks are observed. The numerical results, as calculated with the help of the mode-matching method described in this paper, agree with those calculated using a finite element method. PMID:22225034

Groby, J-P; Dazel, O; Duclos, A; Boeckx, L; Kelders, L

2011-12-01

261

Acoustical Absorption Coefficient in a Diffuse Field of a Plane, Rectangular Material of Finite Dimensions Placed on an Infinite Perfectly Reflecting Surface.  

National Technical Information Service (NTIS)

This study deals with the evaluation of the acoustic absorption coefficient of a rectangular surface of known impedance, placed on an otherwise perfectly reflecting area. The incident acoustic field is supposed diffuse. This problem corresponds to the mea...

J. F. Hamet

1985-01-01

262

Measuring the acoustic absorption coefficient in biological tissue specimens using ultrasonic phase conjugation  

NASA Astrophysics Data System (ADS)

Acoustic absorption has been measured in a series of biological tissue specimens—porcine muscle, renal and fat tissues—by the standard insert-substitution method, as well as by ultrasonic phase conjugation. Comparison of the experimental results and revealed differences confirm the promise of using phase conjugate waves to measure acoustic losses in biological objects. It is demonstrated that in inhomogeneous tissues, the phase conjugation method makes it possible to obtain a more reliable estimate of dissipative losses.

Smagin, N. V.; Krutyansky, L. M.; Zelenova, Z. V.; Brysev, A. P.

2014-03-01

263

Nonlinear refractive index and three-photon absorption coefficient of Poly(9,9-dioctylfluorence) (PFO)  

Microsoft Academic Search

We report on the nonlinear optical Kerr effect and third harmonic generation (THG) arising from &(3)circ; of Poly(9,9- dioctylfluorence) (PFO), which is an emerging organic pi- conjugated polymer from the perspective of diverse optoelectronic applications. The measured nonlinear refractive index, obtained with closed-aperture Z-scan, is n2= (2.04 ±0.10)x10-12 esu at lambda= 1540 nm. Open- aperture Z-scan yields the three-photon absorption

Shahin Mani; Joon Jang; John Ketterson; Pierre Lovera; Gareth Redmond

2010-01-01

264

Water Absorption by Atmospheric Organic Particles: Evidence, Causes and Simulations  

NASA Astrophysics Data System (ADS)

The optical and chemical properties of atmospheric fine particles and their ability to act as cloud condensation nuclei depend strongly upon their affinity for water. Laboratory experiments have shown that water-soluble sulfates and nitrates, which are major inorganic components of atmospheric fine particles, absorb water in an amount proportional to water vapor pressure. Analogous information about the interactions between water and organics is lacking. Moreover, the molecular composition of atmospheric particulate organics remains poorly characterized; information on the molecular composition of the water-soluble fraction is particularly sparse. Here we first analyze concurrent observations of particle chemical composition and water content from a continental nonurban (Grand Canyon) and an urban (Los Angeles) location to determine whether the water content of atmospheric particles is influenced by the presence of organics. We find that the aggregate hygroscopic properties of inorganic particles are altered substantially when organics are also present. For the nonurban location, organics enhance water absorption by inorganics. For the urban location, on the other hand, the net effect of organics is to diminish water absorption of the inorganics. Second, we identify specific compounds that are likely to contribute to the water-soluble fraction by juxtaposing published observations regarding the extraction characteristics and the molecular composition of atmospheric particulate organics with compound-specific solubility and condensibility for a wide variety of organics. We find that water-soluble organics, which constitute a substantial fraction of the total organic mass, include C2 to C7 multifunctional compounds (e.g. diacids, polyols, amino acids). Third, towards developing a simulation capability, we (1) synthesize published laboratory data to evaluate the water absorption behavior of multifunctional oxygenated organic compounds; and (2) test the reliability of the UNIFAC method for estimating water activities of aqueous organic solutions. Laboratory data show that multifunctional oxygenated compounds can absorb water over the entire range of relative humidities. For a wide variety of compounds (e.g., glycols, dicarboxylic acids, keto acids) and a wide range of solute concentrations (0 to over 90% by wt), we find that in most cases, water activities can be estimated within approximately 15% error.

Saxena, Pradeep

265

Comparison of three measurement techniques for the normal absorption coefficient of sound absorbing materials in the free field.  

PubMed

Three different techniques for evaluating the absorption coefficient of sound absorbing materials in free field conditions are discussed. One technique measures the acoustic impedance at one point nearby a specimen, the other two techniques evaluate the impedance from the transfer function of two sound pressures and two particle velocities at two points. These are called "PU-method," "PP-method," and "UU-method," respectively. An iterative algorithm to estimate the acoustic impedance of the locally reactive specimen in the spherical wave field is also applied. First, the effect of receiver positions, specimen areas, and source heights to the measured normal absorption coefficient is investigated by the boundary element method. According to these investigations, the PU-method is most stable against the effect of specimen area, and the UU-method is easily affected by that effect. Closer source to the specimen distance is advantageous for the signal to noise ratio of these measurement techniques, but correction for the effect of the spherical wave field has to be applied. As a finding, the iterative algorithm works for all of three techniques. Finally, the PU-method is applied experimentally with a pressure-velocity sensor and a loudspeaker in a hemi-anechoic room. As a result, the calculated results have been verified. PMID:20000915

Hirosawa, Kunikazu; Takashima, Kazuhiro; Nakagawa, Hiroshi; Kon, Makoto; Yamamoto, Aki; Lauriks, Walter

2009-12-01

266

Effect of pressure on mass absorption in an ammonia-water absorption system  

NASA Astrophysics Data System (ADS)

Absorption phenomenon of ammonia vapor into ammonia water solution has been investigated experimentally, by inserting superheated ammonia vapor into a test cell containing a stagnant pool of ammonia water solution. Before commencing the experiment, the pressure in the test cell corresponds to the equilibrium vapor of the ammonia-water system at room temperature. When the valve is opened, mechanical equilibrium is established quickly and the pressure in the test cell becomes equal to that of the ammonia vapor cylinder. The difference between the initial pressure in the vapor cylinder and the initial pressure in the test cell is found to have a major influence on the absorption rate. The main objective of this study is to investigate the effect of this initial pressure difference on the absorption rate of ammonia vapor. A correlation which gives the total absorbed mass of ammonia as a function of the initial concentration, the initial pressure difference and time is derived. In addition the absorbed mass at no pressure difference could be estimated from the absorbed mass at initial pressure difference.

Mustafa, Hatem; Monde, Masanori

2007-11-01

267

Systematic studies of fractal dimension parameters, absorption and scattering coefficients for cancerous and normal prostate tissues  

NASA Astrophysics Data System (ADS)

The optical coefficients (?s, ?a, ?'s and g)of human cancerous and normal prostate tissues were investigated and compared in the spectral range of 750nm - 860 nm. The fractal dimensional parameters including fractal dimension (Df), cutoff diameter (dmax) and the most efficient diameter (dm) between the cancerous and normal prostate tissues were determined based on the extinction and diffusion reflection intensity measurements and the determination of?s, ?a, ?'s and g. The results are in good agreement with prostate cancer evolution defined by Gleason Grades. The difference of fractal dimensional parameters and optic

Pu, Yang; Wang, Wubao; Alrubaiee, M.; Gayen, S. K.; Xu, Min

2012-02-01

268

Accurate Evaluation Nonlinear Absorption Coefficients for Light Propagation in InAs, InSb, and HgCdTe Alloys (Preprint).  

National Technical Information Service (NTIS)

We present a full-bandstructure calculation of temperature- and wavelength-dependent two-photon absorption (TPA) coefficients and free-carrier absorption (FCA) cross sections in InAs, InSb, Hg1-xCdxTe alloys. Although the wavelength dependence of the TPA ...

L. Gonzalez S. Guha S. Krishnamurthy Z. G. Yu

2007-01-01

269

An Exergy Analysis of LiBr-Water Absorption Refrigerators  

NASA Astrophysics Data System (ADS)

Absorption refrigerators are very efficient as a heat recovery unit in a co-generation system.In order to design an absorption refrigerator for an arbitrary heat source properly, it is important to consider not only quantity but also quality of heat flow. The evaluation of exergy loss in each component is also effective for the improvement of system. This paper deals with the exergy analysis on a LiBr-water absorption refrigerator consisted of a single-and a double-effect cycle driven by the exhaust gas of the micro gas turbine with the output power of about 30 kW. Moreover, exergy loss in absorption process was eva1uated. As a result, it was shown that 80% of the exergy loss in an absorber was caused in absorption process, and the exergy loss decreased with decreasing the change in solution concentration in absorber. In these calculated results,the maximum cooling load of 77.8 kW was obtained from the exhaust gas with the temperature of 2900°C by utilizing both a single-and a double-effect cycles in combination. The energy and exergy efficiency of the system was 88.0% and 25.6%, respectively.

Asano, Hitoshi; Fujii, Terushige; Wang, Xiao; Origane, Takafumi; Katayama, Masatoshi; Inoue, Umeo

270

Can the Lambert-Beer law be applied to the diffuse attenuation coefficient of ocean water?  

Microsoft Academic Search

Radiative transfer theory is combined with a bio-optical model of Case 1 waters and an optical model of the atmosphere to simulate the transport of radiation in the ocean-atmosphere system. The results are treated as experimental data to study the downwelling irradiance attenuation coefficient. It is shown that the downwelling irradiance attenuation coefficient just beneath the surface and the mean

HOWARD R. GORDON

1989-01-01

271

A time-resolved single-pass technique for measuring optical absorption coefficients of window materials under 100 GPa shock pressures  

NASA Astrophysics Data System (ADS)

An experimental method was developed to perform time-resolved, single-pass optical absorption measurements and to determine absorption coefficients of window materials under strong shock compression up to ~200 GPa. Experimental details are described of (i) a configuration to generate an in situ dynamic, bright, optical source and (ii) a sample assembly with a lithium fluoride plate to essentially eliminate heat transfer from the hot radiator into the specimen and to maintain a constant optical source within the duration of the experiment. Examples of measurements of optical absorption coefficients of several initially transparent single crystal materials at high shock pressures are presented.

Li, Jun; Zhou, Xianming; Li, Jiabo

2008-12-01

272

Diffuse attenuation coefficients Kd(PAR) at the estuarine North Sea-Baltic Sea transition: time-series, partitioning, absorption, and scattering  

NASA Astrophysics Data System (ADS)

The study is based on a 1 year record ( n=46) of the diffuse attenuation coefficient— Kd(PAR) (m -1)—in combination with CTD-casts at one position in Århus Bay, Kattegat, the North Sea-Baltic Sea estuarine transition. Water samples were collected occasionally for determination of suspended particulate matter (SPM) and chromomorphic dissolved organic matter (CDOM). The Kd(PAR) varied between 0.152 and 0.557 (m -1) with an average of 0.293 (m -1). The depth of the photic zone (1% light level) varied between 8.3 and 15.7 m at maximum and average Kd(PAR). Maximum Kd(PAR) values occurred in periods of high chl-a concentrations. The average CDOM absorption coefficient was 0.232 (m -1) whereas the average chl-a and inorganic SPM concentrations equalled 3.3 (mg m -3) and 4.5 (g m -3). Light attenuation partitioning in percent was: water (9), CDOM (17), SPM (42), and phytoplankton (32) at average conditions. Attenuation by phytoplankton reached up to 74% at high chl-a concentrations whereas SPM light attenuation reached 45% at high SPM concentrations. Results show that light attenuation in the bay is governed by phytoplankton and SPM concentrations whereas CDOM is of less significance. Light absorption in the PAR range— a(PAR)—ranged between 0.262 (m -1) at average conditions and 0.49 (m -1) at maximum phytoplankton concentrations. Scattering was governed by SPM at average conditions whereas phytoplankton scattering was higher than SPM scattering at chl-a concentrations >4.5 (mg m -3).

Lund-Hansen, Lars Chresten

2004-10-01

273

Determination of thermally induced change of the refractive index of cubic crystals and the measurement of their light-absorption coefficient  

NASA Astrophysics Data System (ADS)

An iterative method is used to calculate thermoelastic deformations in cubic crystals due to the absorption of laser radiation propagating along the fourth-order axis. The zeroth approximation, coinciding with the solution for transversely isotropic media, is sufficient to calculate the change in refractive index produced by thermoelastic stresses. Numerical values of this change are obtained for LiF, KCl, KBr, NaCl, and KI crystals. The obtained total temperature coefficient of the refractive index can be used to measure the light-absorption coefficients of cubic crystals. A thermooptic interference method was used to measure such coefficients for KI, KBr, NaCl, and KCl.

Zhilionis, A. A.; Maldutis, E. K.; Sakalauskas, S. V.

1982-05-01

274

Synoptic water clarity assessment in the Florida Keys using diffuse attenuation coefficient estimated from Landsat imagery  

Microsoft Academic Search

The diffuse attenuation coefficient, K (m? 1), is a measure of the effective attenuation of light in the water column. It characterizes water clarity and is used as a\\u000a proxy for water quality. Mapping of shallow water benthic habitats using optical means, including daytime visible satellite\\u000a imagery, requires knowledge of K to correct for water column effects such as light

D. Palandro; C. Hu; S. Andréfouët; F. E. Muller-Karger

2004-01-01

275

Neutron Radioscopic Measurement of Water Adsorption Coefficients in Aerogels  

Microsoft Academic Search

In this work, neutron radioscopy was utilized to investigate water vapor uptake by a hydrophilic silica aerogel. Aerogel is an unusual porous material, produced by a sol-gel process that results in a solid material with a unique microstructure composed of nanometer-size particles and pores. Aerogels have an extraordinarily large internal surface area which is accessible via open pores, making them

D. A. Bostain; J. S. Brenizer Jr; P. M. Norris

2002-01-01

276

Temperature and Water Vapor Pressure Effects on the Friction Coefficient of Hydrogenated Diamondlike Carbon Films.  

National Technical Information Service (NTIS)

Microtribological measurements of a hydrogenated diamondlike carbon film in controlled gaseous environments show that water vapor plays a significant role in the friction coefficient. These experiments reveal an initial high friction transient behavior th...

A. Erdemir N. Argibay O. L. Eryilmaz P. L. Dickrell W. G. Sawyer

2009-01-01

277

OVERALL MASS TRANSFER COEFFICIENT FOR POLLUTANT EMISSIONS FROM SMALL WATER POOLS UNDER SIMULATED INDOOR ENVIRONMENTAL CONDITIONS  

EPA Science Inventory

Small chamber tests were conducted to experimentally determine the overall mass transfer coefficient for pollutant emissions from still water under simulated indoor-residential or occupational-environmental conditions. Fourteen tests were conducted in small environmental chambers...

278

Neutron Radioscopic Measurement of Water Adsorption Coefficients in Aerogels  

Microsoft Academic Search

.    In this work, neutron radioscopy was utilized to investigate water vapor uptake by a hydrophilic silica aerogel. Aerogel\\u000a is an unusual porous material, produced by a sol-gel process that results in a solid material with a unique microstructure\\u000a composed of nanometer-size particles and pores. Aerogels have an extraordinarily large internal surface area which is accessible\\u000a via open pores,

D. A. Bostain; P. M. Norris

2002-01-01

279

Partition coefficients of organic compounds in lipid-water systems and correlations with fish bioconcentration factors  

USGS Publications Warehouse

Triolein-water partition coefficients (KtW) have been determined for 38 slightly water-soluble organic compounds, and their magnitudes have been compared with the corresponding octanol-water partition coefficients (KOW). In the absence of major solvent-solute interaction effects in the organic solvent phase, the conventional treatment (based on Raoult's law) predicts sharply lower partition coefficients for most of the solutes in triolein because of its considerably higher molecular weight, whereas the Flory-Huggins treatment predicts higher partition coefficients with triolein. The data are in much better agreement with the Flory-Huggins model. As expected from the similarity in the partition coefficients, the water solubility (which was previously found to be the major determinant of the KOW) is also the major determinant for the Ktw. When the published BCF values (bioconcentration factors) of organic compounds in fish are based on the lipid content rather than on total mass, they are approximately equal to the Ktw, which suggests at least near equilibrium for solute partitioning between water and fish lipid. The close correlation between Ktw and Kow suggests that Kow is also a good predictor for lipid-water partition coefficients and bioconcentration factors.

Chiou, C. T.

1985-01-01

280

Human intestinal water absorption: direct vs. indirect measurements.  

PubMed

Distilled water, a carbohydrate-electrolyte (CE; 4% sucrose, 2% glucose, 17.2 meq/l NaCl, and 2.8 meq/l KCl) solution, or a 10% glucose solution, all containing the nonabsorbed indicator polyethylene glycol (PEG) and deuterium oxide (D2O, 30 ppm), were infused (15 ml/min) into the duodenojejunum of seven men by using the triple lumen technique. Net water absorption was determined directly from the change in PEG concentration and was calculated from plasma D2O derived from D2O in the perfusion solutions. The protocol included a 45-min equilibration period followed by a 90-min test period. Intestinal samples were drawn at 10-min intervals from 15 to 45 min and at 15-min intervals thereafter. Blood was drawn at 45, 50, 55, 60, 75, 90, 105, 120, and 135 min. Intestinal samples were analyzed for D2O, Na+, K+, osmolality, PEG, and glucose; blood was analyzed for D2O. Results (+/- SE; positive values secretion, negative values absorption) showed net fluid absorption from distilled water (-9.40 +/- 1.28 ml.h-1.cm-1) and the CE (-13.30 +/- 1.22 ml.h-1.cm-1) solution, but net secretion (4.40 +/- 1.25 ml.h-1.cm-1) from the 10% glucose solution. All values were significantly (P less than 0.05) different from each other. Perfusing the CE solution caused net Na+ and K+ absorption, whereas perfusing the 10% dextrose solution caused net electrolyte secretion. Rates of D2O accumulation in the plasma were independent of the solutions perfused.(ABSTRACT TRUNCATED AT 250 WORDS) PMID:2305887

Gisolfi, C V; Summers, R W; Schedl, H P; Bleiler, T L; Oppliger, R A

1990-02-01

281

Variability in the light absorption coefficients of phytoplankton, non-algal particles, and colored dissolved organic matter in a subtropical bay (Brazil)  

NASA Astrophysics Data System (ADS)

This study characterized the variability in magnitudes and spectral shapes of the absorption coefficients of phytoplankton, detritus, and colored dissolved organic matter (CDOM) in a dynamic bay (Santos Bay) in southeastern Brazil in response to the contributions of the main estuarine channel and large tide variations, therefore in different time scales. Two strategies were adopted: (1) monthly year-round sampling in the estuarine channel and Santos Bay and (2) sampling in Santos Bay during spring/neap tides and cold/warm months. Chlorophyll-a concentration and CDOM absorption were higher during warm (wet) months, while the relative contribution of organic and inorganic particles was driven by neap/spring tide cycles. Salinity partially accounted for changes in optical variables, especially for CDOM absorption and total suspended matter (TSM) during cold months and neap tides, respectively. The spectral shapes of detritus and CDOM absorption showed relatively little variability for the entire dataset and were not considered feasible for monitoring purposes. The spectral shape of phytoplankton absorption (index of cell size) varied broadly, with no remarkable dependence on the sampling conditions. Comparison of absorption coefficients measured by the Quantitative Filter Technique (QFT) and Transmittance Reflectance (TR) method showed higher phytoplankton coefficients toward longer visible wavelengths (flatter spectra) and shallower slopes of detritus absorption yielded by the TR method. Our results also suggest that measurements at the near red spectral region result from not only scattering signals but also non-algal particle absorption.

Ferreira, Amabile; Ciotti, Áurea Maria; Coló Giannini, Maria Fernanda

2014-02-01

282

Photoelectric quantum efficiencies and filter window absorption coefficients from 20 eV to 10 KeV  

SciTech Connect

Photodiodes with x-ray sensitive photocathodes are commonly used as broadband x-ray detectors in fusion plasma diagnostics. We have measured the photocathode quantum efficiency between 1--500 A of common photocathode materials including aluminum, copper, nickel, gold, three forms of carbon, chromium, and cesium iodide. We have also studied the effects of the experimental environment and long-term cathode aging on the measured quantum efficiencies. In addition, we have measured the x-ray mass-absorption coefficients of x-ray filter windows of Kimfoil, aluminum, polypropylene, and Formvar in energy regions where data were previously unavailable. Measurements between 1--50 A were performed at the Los Alamos Scientific Laboratory's low-energy x-ray calibration facility, while the measurements between 50--500 A were performed at the National Bureau of Standard's synchrotron ultraviolet radiation facility.

Day, R.H.; Lee, P.; Saloman, E.B.; Nagel, D.J.

1981-11-01

283

Validation of phenol red versus gravimetric method for water reabsorption correction and study of gender differences in Doluisio's absorption technique.  

PubMed

The aim of the present study was to develop a method for water flux reabsorption measurement in Doluisio's Perfusion Technique based on the use of phenol red as a non-absorbable marker and to validate it by comparison with gravimetric procedure. The compounds selected for the study were metoprolol, atenolol, cimetidine and cefadroxil in order to include low, intermediate and high permeability drugs absorbed by passive diffusion and by carrier mediated mechanism. The intestinal permeabilities (Peff) of the drugs were obtained in male and female Wistar rats and calculated using both methods of water flux correction. The absorption rate coefficients of all the assayed compounds did not show statistically significant differences between male and female rats consequently all the individual values were combined to compare between reabsorption methods. The absorption rate coefficients and permeability values did not show statistically significant differences between the two strategies of concentration correction. The apparent zero order water absorption coefficients were also similar in both correction procedures. In conclusion gravimetric and phenol red method for water reabsorption correction are accurate and interchangeable for permeability estimation in closed loop perfusion method. PMID:24887261

Tu?cu-Demiröz, Fatmanur; Gonzalez-Alvarez, Isabel; Gonzalez-Alvarez, Marta; Bermejo, Marival

2014-10-01

284

Spectral absorption coefficient of molten aluminum oxide from 0.385 to 0.780 {mu}m  

SciTech Connect

The spectral extinction coefficient, k{sub {lambda}}, and the absorption coefficient, {alpha}{sub {lambda}}, of liquid aluminum oxide were determined from emission measurements on partially molten single-crystal sapphire filaments. Measurements were made at wavelengths from 0.385 to 0.780 {mu}m in both argon and oxygen atmospheres and at 0.650 {mu}m in a 10% H{sub 2}-90% N{sub 2} mixture. The values of {alpha}{sub {lambda}} were found to vary with the time for which the specimen had been molten and achieved different steady-state values in the three processing atmospheres. A decrease in {alpha}{sub {lambda}} with wavelength (Urbach tail) was observed from 0.385 {mu}m to about 0.420 {mu}m in argon and 0.490 {mu}m in oxygen, and approximately constant values were obtained at longer wavelengths. Steady-state values of {alpha}{sub {lambda}} at the optical pyrometer wavelength of 6.650 {mu}m were 9 {+-} 2 cm{sup {minus}1} in argon, 41 {+-} 8 cm{sup {minus}1} in oxygen, and 14 {+-} 2 cm{sup {minus}1} in the 10% hydrogen-90% nitrogen gas mixture.

Weber, J.K.R.; Krishnan, S.; Anderson, C.D.; Nordine, P.C. [Intersonics, Inc., Northbrook, IL (United States)

1995-03-01

285

A far wing line shape theory and its application to the foreign-broadened water continuum absorption. III  

NASA Technical Reports Server (NTRS)

The far wing line shape theory developed previously and applied to the calculation of the continuum absorption of pure water vapor is extended to foreign-broadened continua. Explicit results are presented for H2O-N2 and H2O-CO2 in the frequency range from 0 to 10,000/cm. For H2O-N2 the positive and negative resonant frequency average line shape functions and absorption coefficients are computed for a number of temperatures between 296 and 430 K for comparison with available laboratory data. In general the agreement is very good.

Ma, Q.; Tipping, R. H.

1992-01-01

286

Ground water contaminant source and transport parameter identification by correlation coefficient optimization  

Microsoft Academic Search

The initial step in a ground water contamination remediation process is to identify the extent of the plume. One way to optimize well deployment is to solve an inverse contaminant transport problem. Inverse procedures bas4ed on correlation coefficient optimization are developed to locate ground water contaminant sources and to identify transport parameters. For cases involving two-dimensional instantaneous and continuous sources,

P. Sidauruk; A. H. D. Cheng; D. Ouazar

1998-01-01

287

Some evaluations of drag and bulk transfer coefficients over water bodies of different sizes  

Microsoft Academic Search

Three recent experiments allow evaluation of the bulk transfer coefficients for momentum, water vapour and sensible heat over water bodies of different sizes. As part of a study of evaporation rates from a swamp, measurements of latent and sensible heat fluxes were made over Lake Wyangan in southern N.S.W., Australia. This lake is of several kilometers diameter. In a later

B. B. Hicks

1972-01-01

288

Temperature effects on diffusion coefficient for 6-gingerol and 6-shogaol in subcritical water extraction  

NASA Astrophysics Data System (ADS)

6-gingerol and 6-shogaol are the main constituents as anti-inflammatory or bioactive compounds from zingiber officinale Roscoe. These bioactive compounds have been proven for inflammatory disease, antioxidatives and anticancer. The effect of temperature on diffusion coefficient for 6-gingerol and 6-shogaol were studied in subcritical water extraction. The diffusion coefficient was determined by Fick's second law. By neglecting external mass transfer and solid particle in spherical form, a linear portion of Ln (1-(Ct/Co)) versus time was plotted in determining the diffusion coefficient. 6-gingerol obtained the higher yield at 130°C with diffusion coefficient of 8.582x10?11 m2/s whilst for 6-shogaol, the higher yield and diffusion coefficient at 170°C and 19.417 × 10?11 m2/s.

Ilia Anisa, Nor; Azian, Noor; Sharizan, Mohd; Iwai, Yoshio

2014-04-01

289

A method to obtain the absorption coefficient spectrum of single grain coal in the aliphatic C-h stretching region using infrared transflection microspectroscopy.  

PubMed

A method was developed to obtain the absorption coefficient spectrum of a grain of coal (as small as 10(-7)) in the region of aliphatic and aromatic C-H stretching bands (2700-3200 cm(-1)) using infrared transflection microspectroscopy. In this method, the complex refractive index n - ik was determined using an optimization algorithm with the Kramers-Kronig transform so that the calculated transflection spectrum from the Fresnel equation corresponded to the measured one. The obtained absorption coefficients were compared with the bulk values determined from the potassium bromide (KBr) pellet measurement method. PMID:25014839

Tonoue, Ryota; Katsura, Makoto; Hamamoto, Mai; Bessho, Hiroki; Nakashima, Satoru

2014-07-01

290

A nonisothermal emissivity and absorptivity formulation for water vapor  

NASA Technical Reports Server (NTRS)

An emissivity approach is taken to modeling fluxes and cooling rates in the atmosphere. The nonisothermal water vapor long wave radiation emissivity and absorptivity model that is developed satisfies the requirements of defining a monochromatic transfer equation for predicting water vapor emissions. Predictions made with the model compare favorably with fluxes predicted by a radiation model for narrow-band emissions in 5 kayser intervals. The spectral resolution assumed in narrow-band models is shown to be an arbitrary parameter and, if a far wing continuum-type opacity is included in the emissivity scheme presented, results can be obtained which are as accurate as predictions made with state of the art line-by-line (LBL) calculations.

Ramanathan, V.; Downey, P.

1986-01-01

291

Theoretical and Experimental Analysis of a Single Stage Ammonia-Water Absorption Chiller Performance  

Microsoft Academic Search

The ammonia-water absorption chillers are thermally driven devices producing a cooling effect. It can be operated without any use of electrical or mechanical energy. The advantage of absorption chillers is precisely that they can utilize low grade energy. An experimental prototype of a single stage ammonia-water absorption chiller with complete condensation was designed, built and tested. The thermodynamic models of

Kong Dingfeng; Liu Jianhua; Zhang Liang; Fang Zhiyun; Zheng Guangping

2009-01-01

292

On the selection of stopping-power and mass energy-absorption coefficient ratios for high-energy x-ray dosimetry.  

PubMed

A method for the selection of average stopping-power (L/rho)medair and energy-absorption coefficient (mu en/rho)medair ratios has been developed. The quality of the x-ray beam is characterized by the ratio of ionization chamber readings at depths of 20 and 10 cm in water (TMR)2010. For convenience, a relationship is established between experimental (TMR)2010 and the nominal accelerating potential (MV) of the accelerator. Experimental (TMR)2010 are related to (L/rho)medair and (mu en/rho)medair in a three-step process. First, using experimental and theoretical spectra in the range 60Co to 45 MV, (TMR)2010 were calculated for primary and first-scatter photons, and a graph of experimental versus calculated (TMR)2010 for these same spectra was constructed. Second, (L/rho)medair and (mu en/rho)medair were calculated for a large number of primary spectra [for most of which experimental (TMR)2010 were not available] and a graph constructed that related these quantities and (TMR)2010 calculated as above for this group of spectra. Third, using the graphs from the preceding steps, graphs relating the calculated (L/rho)medair and (mu en/rho)medair with experimental (TMR)2010 were constructed. Data are presented for water, polystyrene, acrylic, graphite, A-150, C-552, Bakelite, and nylon for beams with nominal accelerating potentials in the range 2-45 MV. PMID:6503876

Cunningham, J R; Schulz, R J

1984-01-01

293

IOP from reflectance measurements to obtain the Kd coefficient: application to the Gabon and Congo coastal waters  

NASA Astrophysics Data System (ADS)

During the "Optic-Congo" oceanographic survey which took place in 2005 on board the "Beautemp-Beaupré" SHOM vessel, different optical measurements of the surface water were acquired using a TRIOS radiance sensor fixed onboard a mini-catamaran. Hydrological measurements (CTD, fluorescence, attenuation, scattering) and water samples were simultaneously collected in order to measure SPM, Chlorophyll-a and CDOM concentrations. Four types of surface water colours (blue, green-yellow, dark and brown) were identified. The main characteristics of these waters were the very low Chlorophyll-a concentrations for this period of the year (March), and the very high CDOM concentrations along the Congo coast, and particularly in the turbid plume of the Congo River. The attenuation and scattering measurements highlighted the predominance of organic matter at the water surface. These observations were documented using a beam electron microscope and by microanalysis. This data set was used to classify the water bodies along the Gabon and Congo coasts. We propose here to use the remote sensing reflectance (Rrs) measurements to invert the IOP (absorption (a) and backscattering (bb)) using the WASI numerical bio-optical model. The model is iterative: the Rrs WASI simulations are computed given initial values of ocean constituents' concentrations and iteratively adjusted to the Rrs in-situ measurements. The IOP computations are satisfying when the correlations between simulated and measured Rrs are optimized. Then, the attenuation coefficients (Kd) are computed from the IOP coefficients. These results are compared with measurements of Ku carried out during the survey.

Schmeltz, M.; Froidefond, J.-M.; Jourdain, F.; Martiny, N.

2009-08-01

294

The partition coefficients of ethylene between hydrate and vapor for methane + ethylene + water and methane + ethylene + SDS + water systems  

Microsoft Academic Search

The hydrate formation of CH4+C2H4 mixture was studied experimentally in two different cases, with and without the presence of sodium dodecyl sulfate (SDS) in water. The results manifested that the presence of SDS could not only accelerate the hydrate formation process, but also increase the partition coefficient of ethylene between hydrate and vapor drastically. The partition coefficients of ethylene between

L.-W. Zhang; G.-J. Chen; C.-Y. Sun; S.-S. Fan; Y.-M. Ding; X.-L. Wang; L.-Y. Yang

2005-01-01

295

Terahertz absorption spectrum of para and ortho water vapors at different humidities at room temperature  

Microsoft Academic Search

Terahertz time-domain spectroscopy has been used to measure the absorption of water vapor in 0.2-2.4 THz range from low to high humidity at room temperature. The observed absorption lines are due to the water molecular rotations in the ground vibrational state. We find that the absorption strength of para transitions increases as humidity increases, while the absorption strength of ortho

X. Xin; H. Altan; A. Saint; D. Matten; R. R. Alfano

2006-01-01

296

Application of the ISO 13472-1 in situ technique for measuring the acoustic absorption coefficient of grass and artificial turf surfaces  

Microsoft Academic Search

This paper presents the applicability of an in situ technique based on ISO 13472-1 standard for measuring the acoustic absorption coefficient of grass and artificial turf surfaces for normal incidence from a sound source. The in situ method is based on acoustic impulse response measurement of the material surface. A maximum length sequence (MLS) signal is played through a loudspeaker

Niranjan Londhe; Mohan D. Rao; Jason R. Blough

2009-01-01

297

The Nonlinear Absorption Coefficient of a Strong Electromagnetic Wave by Confined Electrons in Quantum Wells Under the Influences of Confined Phonons  

Microsoft Academic Search

The nonlinear absorption coefficient (NAC) of a strong electromagnetic wave (EMW) by confined electrons in quantum wells under the influences of confined phonons is theoretically studied by using the quantum transport equation for electrons. In comparison with the case of unconfined phonons, the dependence of the NAC on the energy (??), the amplitude (Eo) of external strong EMW, the width

N. Q. Bau; L. T. Hung; N. D. Nam

2010-01-01

298

Scattering and absorption coefficients of aerosols in a semi-arid area in China: Diurnal cycle, seasonal variability and dust events  

NASA Astrophysics Data System (ADS)

The authors investigated variations of aerosol scattering and absorptive properties in a semi-arid climate Observatory in the Inner Mongolia of China and factors affecting the variation. They use integrated nephelometer and aethalometer observations collected in 2005 and 2006 at the Silinhot Observatory. The results are as follows. 1) in autumn and winter, the diurnal cycle of scattering coefficient exhibited a clear bi-modal variation, and the scattering coefficient was indicative of the type of sandy weather. 2) The concentration of black carbon (BC) aerosols was much higher in winter than in the other seasons with an evident bimodal diurnal variation. 3) When the wind speed was lower than 3.5 m s-1, the dilution effect of air evidently influenced the scattering coefficient and BC mass concentration; for the wind speed above 3.5 m s-1, there appeared to be little correlation between wind speed and scattering coefficient or BC mass concentration. 4) Atmospheric visibility calculated from the aerosol scattering and absorptive coefficients was in good agreement with the direct observation of visibility. 5) Absorption by aerosols accounted for 25% of the total extinction in December.

Niu, Sheng-Jie; Zhang, Qiu-Ying

2010-02-01

299

Slip flow coefficient analysis in water hydraulics gear pump for environmental friendly application  

NASA Astrophysics Data System (ADS)

Water hydraulics is the sustainable option in developing fluid power systems with environmental friendly approach. Therefore, an investigation on water-based external gear pump application is being conducted, as a low cost solution in the shifting effort of using water, instead of traditional oil hydraulics in fluid power application. As the gear pump is affected by fluid viscosity, an evaluation has been conducted on the slip flow coefficient, in order to understand to what extent the spur gear pump can be used with water-based hydraulic fluid. In this paper, the results of a simulated study of variable-speed fixed displacement gear pump are presented. The slip flow coefficient varies from rotational speed of 250 RPM to 3500 RPM, and provides volumetric efficiency ranges from 9 % to 97% accordingly.

Yusof, A. A.; Wasbari, F.; Zakaria, M. S.; Ibrahim, M. Q.

2013-12-01

300

Temperature and water vapor pressure effects on the friction coefficient of hydrogenated diamondlike carbon films.  

SciTech Connect

Microtribological measurements of a hydrogenated diamondlike carbon film in controlled gaseous environments show that water vapor plays a significant role in the friction coefficient. These experiments reveal an initial high friction transient behavior that does not reoccur even after extended periods of exposure to low partial pressures of H{sub 2}O and O{sub 2}. Experiments varying both water vapor pressure and sample temperature show trends of a decreasing friction coefficient as a function of both the decreasing water vapor pressure and the increasing substrate temperature. Theses trends are examined with regard to first order gas-surface interactions. Model fits give activation energies on the order of 40 kJ/mol, which is consistent with water vapor desorption.

Dickrell, P. L.; Sawyer, W. G.; Eryilmaz, O. L.; Erdemir, A.; Energy Technology; Univ. of Florida

2009-07-01

301

Water absorption length measurement with the ANTARES optical beacon system  

NASA Astrophysics Data System (ADS)

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

Yepes-Ramirez, Harold; ANTARES Collaboration

2011-01-01

302

New method to determine the refractive index and the absorption coefficient of organic nonlinear crystals in the ultra-wideband THz region.  

PubMed

A method for simultaneously measuring the refractive index and absorption coefficient of nonlinear optical crystals in the ultra-wideband terahertz (THz) region is described. This method is based on the analysis of a collinear difference frequency generation (DFG) process using a tunable, dual-wavelength, optical parametric oscillator. The refractive index and the absorption coefficient in the organic nonlinear crystal DAST were experimentally determined in the frequency range 2.5-26.2 THz by measuring the THz-wave output using DFG. The resultant refractive index in the x-direction was approximately 2.3, while the absorption spectrum was in good agreement with FT-IR measurements. The output of the DAST-DFG THz-wave source was optimized to the phase-matching condition using the measured refractive index spectrum in THz region, which resulted in an improvement in the output power of up to a factor of nine. PMID:20721118

Ohno, Seigo; Miyamoto, Katsuhiko; Minamide, Hiroaki; Ito, Hiromasa

2010-08-01

303

Inverse temperature dependence of Henry’s law coefficients for volatile organic compounds in supercooled water  

Microsoft Academic Search

Upon supercooling, water expels volatile organic compounds (VOC), and Henry’s law coefficients are increasing concomitant with decreasing temperature. This unexpected observation was found by measuring the VOC partitioning between supercooled water and gas phase in the temperature range from ?5°C to ?15°C for benzene, toluene, ethlybenzene, m-, p-, o-xylenes (BTEX), methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE). Aqueous

Karsten Sieg; Elena Starokozhev; Martin U. Schmidt; Wilhelm Püttmann

2009-01-01

304

ESTIMATION OF OCTANOL/WATER PARTITION COEFFICIENTS FOR ORGANIC POLLUTANTS USING REVERSE-PHASE HPLC  

EPA Science Inventory

Octanol/water partition coefficients (K(ow's)) of organic solutes are estimated with reasonable accuracy (standard deviation + or - 0.25 log K(ow)units) by elution from a C-18 column with 75:25 (v/v) MeOH-H20, based on results with 37 test compounds. Changes in solute activity co...

305

A neural network based prediction of octanol–water partition coefficients using atomic5 fragmental descriptors  

Microsoft Academic Search

An artificial neural network based approach using Atomic5 fragmental descriptors has been developed to predict the octanol–water partition coefficient (logP). We used a pre-selected set of organic molecules from PHYSPROP database as training and test sets for a feedforward neural network. Results demonstrate the superiority of our non-linear model over the traditional linear method.

László Molnár; György M. Keseru?; Ákos Papp; Zsolt Gulyás; Ferenc Darvas

2004-01-01

306

First CRDS-measurements of water vapour continuum in the 940 nm absorption band  

Microsoft Academic Search

Measurements of near-infrared water vapour continuum using continuous wave cavity ring down spectroscopy (cw-CRDS) have been performed at around 10611.6 and 10685.2cm-1. The continuum absorption coefficients for N2-broadening have been determined to be CF296K=(1.0±0.2)×10-24cm2mol-1atm-1 and CF278K=(1.8±0.4)×10-24cm2mol-1atm-1 at 10611.6cm-1, and CF296K=(1.6±0.5)×10-24cm2mol-1atm-1 and CF278K=(2.1±0.4)×10-24cm2mol-1atm-1 at 10685.2cm-1, respectively.These results represent the first near-IR continuum laboratory data determined within the complex spectral environment in

L. Reichert; M. D. Andrés Hernández; J. P. Burrows; A. B. Tikhomirov; K. M. Firsov; I. V. Ptashnik

2007-01-01

307

Comparison of activity coefficient models for atmospheric aerosols containing mixtures of electrolytes, organics, and water  

NASA Astrophysics Data System (ADS)

Atmospheric aerosols generally comprise a mixture of electrolytes, organic compounds, and water. Determining the gas-particle distribution of volatile compounds, including water, requires equilibrium or mass transfer calculations, at the heart of which are models for the activity coefficients of the particle-phase components. We evaluate here the performance of four recent activity coefficient models developed for electrolyte/organic/water mixtures typical of atmospheric aerosols. Two of the models, the CSB model [Clegg, S.L., Seinfeld, J.H., Brimblecombe, P., 2001. Thermodynamic modelling of aqueous aerosols containing electrolytes and dissolved organic compounds. Journal of Aerosol Science 32, 713-738] and the aerosol diameter dependent equilibrium model (ADDEM) [Topping, D.O., McFiggans, G.B., Coe, H., 2005. A curved multi-component aerosol hygroscopicity model framework: part 2—including organic compounds. Atmospheric Chemistry and Physics 5, 1223-1242] treat ion-water and organic-water interactions but do not include ion-organic interactions; these can be referred to as "decoupled" models. The other two models, reparameterized Ming and Russell model 2005 [Raatikainen, T., Laaksonen, A., 2005. Application of several activity coefficient models to water-organic-electrolyte aerosols of atmospheric interest. Atmospheric Chemistry and Physics 5, 2475-2495] and X-UNIFAC.3 [Erdakos, G.B., Change, E.I., Pandow, J.F., Seinfeld, J.H., 2006. Prediction of activity coefficients in liquid aerosol particles containing organic compounds, dissolved inorganic salts, and water—Part 3: Organic compounds, water, and ionic constituents by consideration of short-, mid-, and long-range effects using X-UNIFAC.3. Atmospheric Environment 40, 6437-6452], include ion-organic interactions; these are referred to as "coupled" models. We address the question—Does the inclusion of a treatment of ion-organic interactions substantially improve the performance of the coupled models over that of the decoupled models? Performance is judged by the extent to which each model is able to reproduce experimental water activity data for mixtures of organic acids (malonic, succinic, glutaric, citric, maleic, and malic acids) and inorganic electrolytes (NaCl and (NH 4) 2SO 4). It is found, based on the comparisons reported here, that the decoupled models perform as well as, and in some cases better than, the coupled models. Since such activity coefficient models are likely to continue to be developed in the future and because we consider here only a limited set of organic compounds, the current study should be viewed as an interim assessment. The scarcity of experimental data for mixtures of atmospheric relevance remains a limitation for testing activity coefficient models.

Tong, Chinghang; Clegg, Simon L.; Seinfeld, John H.

308

Broadband Measurement of Black Carbon Absorption and Scattering Coefficients using a Supercontinuum Integrated Photoacoustic and Nephelometer Instrument  

NASA Astrophysics Data System (ADS)

The study of light absorbing and scattering properties of atmospheric aerosols is necessary for predicting the effects of aerosols on the climate. Integrated photoacoustic-nephelometer spectrometers are commonly used for simultaneous measurement of light absorption and scattering from atmospheric aerosol particles. Commercially available photoacoustic-nephelometer instruments use one to three discrete operating wavelengths. The optical properties of some aerosol particles vary with the aerosol composition, and exhibit unique wavelength dependencies, especially for biomass burning and mineral dust aerosols. Additionally, atmospheric processes like mixing and aging change the aerosol optical properties. Therefore, there is a need to characterize the aerosol optical properties at more than a few discrete wavelengths. Using a light source which spans a wide and continuous wavelength range in combination with photoacoustic spectrometer and nephelometer techniques would facilitate the study of the optical behavior of aerosols over the solar spectrum. In the environmental optics laboratory at Michigan Technological University and in collaboration with the Desert Research Institute in Reno, Nevada, we are developing a new integrated photoacoustic-nephelometer spectrometer that uses a supercontinuum laser as light source. The emission of the supercontinuum laser continuously covers the entire visible spectrum and part of the infrared spectrum (i.e., from 400nm to 2200nm) and should therefore allow characterizing the aerosol optical properties over almost the entire solar spectrum. Currently, our focus is on studying the aerosol optical properties of combustion aerosol in the visible part of the spectrum (i.e., 400-700nm). The current prototype uses a filter wheel with bandpass optical filters of wavelength 417nm (bandwidth 60nm), 475nm (bandwidth 64nm), 542nm (bandwidth 50nm), 607nm (bandwidth 70nm) and 675nm (bandwidth 67nm). In July 2012 we performed a laboratory study at the Desert Research Institute, measuring absorption and scattering coefficients of kerosene soot and sodium chloride aerosols. As a reference system we used a commercial three-wavelength photoacoustic-nephelometer instrument (DMT Inc.). Here, we present the results of this laboratory intercomparison.

sharma, N.; Arnold, I. J.; Moosmuller, H.; Arnott, P.; Mazzoleni, C.

2012-12-01

309

Temperature dependence of diffusion coefficient of nitrogen gas in water: A molecular dynamics study  

NASA Astrophysics Data System (ADS)

We have carried out the molecular dynamics (MD) simulation to study the structural properties and to estimate the diffusivity of molecular nitrogen (N2) gas (solute) in extended simple point charge model (SPC/E) water (solvent) with N2 mole fraction of 0.018 at different temperatures. For the structural properties of the system, we have determined radial distribution function (RDF). The solute-solute, solute-solvent and solvent-solvent RDF have been evaluated. Self-diffusion coefficient of N2 was estimated by evaluating mean-squared displacement (MSD) and velocity autocorrelation function (VACF) separately. The diffusion coefficients obtained from the two methods agree within 3%. The results are in agreement with the experimentally determined values within 10%. The self-diffusion coefficient of water (H2O) was also estimated by evaluating MSD. Mutual diffusion coefficient of the system have also been estimated invoking Darken's relation. The temperature dependance of the diffusion coefficients were found to follow Arrhenius relation.

Sharma, Keshav; Adhikari, Narayan P.

2014-04-01

310

Micropulse water vapor differential absorption lidar: transmitter design and performance.  

PubMed

An all diode-laser-based micropulse differential absorption lidar (DIAL) laser transmitter for tropospheric water vapor and aerosol profiling is presented. The micropulse DIAL (MPD) transmitter utilizes two continuous wave (cw) external cavity diode lasers (ECDL) to seed an actively pulsed, overdriven tapered semiconductor optical amplifier (TSOA). The MPD laser produces up to 7 watts of peak power over a 1 µs pulse duration (7 µJ) and a 10 kHz pulse repetition frequency. Spectral switching between the online and offline seed lasers is achieved on a 1Hz basis using a fiber optic switch to allow for more accurate sampling of the atmospheric volume between the online and offline laser shots. The high laser spectral purity of greater than 0.9996 coupled with the broad tunability of the laser transmitter will allow for accurate measurements of tropospheric water vapor in a wide range of geographic locations under varying atmospheric conditions. This paper describes the design and performance characteristics of a third generation MPD laser transmitter with enhanced laser performance over the previous generation DIAL system. PMID:23187280

Nehrir, Amin R; Repasky, Kevin S; Carlsten, John L

2012-10-22

311

Intermolecular potential energy surface and second virial coefficients for the water-CO2 dimer.  

PubMed

A five-dimensional potential energy surface is calculated for the interaction of water and CO(2), using second-order Møller-Plesset perturbation theory and coupled-cluster theory with single, double, and perturbative triple excitations. The correlation energy component of the potential energy surface is corrected for basis set incompleteness. In agreement with previous studies, the most negative interaction energy is calculated for a structure with C(2v) symmetry, where the oxygen atom of water is close to the carbon atom of CO(2). Second virial coefficients for the water-CO(2) pair are calculated for a range of temperatures, and their uncertainties are estimated. The virial coefficients are shown to be in close agreement with the available experimental data. PMID:21476757

Wheatley, Richard J; Harvey, Allan H

2011-04-01

312

Ultrasonic measurements of the reflection coefficient at a water/polyurethane foam interface.  

PubMed

Measured ultrasonic reflection coefficients as a function of normal incidence angle are reported for several samples of polyurethane foam submerged in a water bath. Three reflection coefficient models are employed as needed in this analysis to approximate the measured data: (1) an infinite plane wave impinging on an elastic halfspace, (2) an infinite plane wave impinging on a single fluid layer overlying a fluid halfspace, and (3) a finite acoustic beam impinging on an elastic halfspace. The compressional wave speed in each sample is calculated by minimizing the sum of squared error (SSE) between the measured and modeled data. PMID:23968059

Sagers, Jason D; Haberman, Michael R; Wilson, Preston S

2013-09-01

313

Atmospheric absorption of near infrared and visible solar radiation by the hydrogen bonded water dimer  

Microsoft Academic Search

Summary Based on the physico-chemical properties of water dimers, we calculated their near infrared and visible absorption of solar radiation in the Earth's atmosphere. Our calculation has used equilibrium constants determined by statistical mechanics and a vibrational absorption spectrum determined by a coupled oscillator quantum mechanics model and ab-initio quantum chemistry. The resulting total atmospheric absorption was calculated using a

V. Vaida; J. S. Daniel; H. G. Kjaergaard; L. M. Goss; A. F. Tuck

2001-01-01

314

Determination of Self-, Air-, and Oxygen-Broadening Coefficients of Pure Rotational Absorption Lines of Ozone and of Their Temperature Dependencies  

NASA Astrophysics Data System (ADS)

Room temperature measurements of self-, air-, and oxygen-broadening coefficients are reported for 101 pure rotational absorption lines for 16O 3 covering a range of 7? J??34 and 3? K-1??11 in the spectral region 50 to 90 cm -. In addition, the temperature dependence of the coefficients has been determined for most of these lines. A total of 14 high-resolution Fourier transform far-IR spectra (0.004 cm - resolution) of ozone/air/dioxygen mixtures were recorded at various temperatures (212, 252, and 296 K). The broadening coefficients and corresponding temperature exponents were deduced by analyzing all of the 14 spectra simultaneously for each absorption line using a nonlinear least-squares fitting technique. Several sources of systematic errors were taken into account: the values of the partial pressures of the species involved, the value of the total optical path length, the sample temperature, thermal emission from sources other than the spectrometer source (e.g., sample emission), the effect of convolution with the instrument function, and intensity contributions from weak and neighbouring absorption lines. The variation of the determined broadening coefficients and temperature exponents with the rotational quantum numbers J? and K-1? has been examined. Furthermore the determined pressure-broadening parameters have been compared to the data reported in the 2000 edition of the HITRAN compilation.

Larsen, R. Wugt; Nicolaisen, F. M.; Sørensen, G. O.

2001-12-01

315

Temperature dependence of the evaporation coefficient of water in air and nitrogen under atmospheric pressure: study in water droplets.  

PubMed

The evaporation coefficients of water in air and nitrogen were found as a function of temperature by studying the evaporation of a pure water droplet. The droplet was levitated in an electrodynamic trap placed in a climatic chamber maintaining atmospheric pressure. Droplet radius evolution and evaporation dynamics were studied with high precision by analyzing the angle-resolved light scattering Mie interference patterns. A model of quasi-stationary droplet evolution accounting for the kinetic effects near the droplet surface was applied. In particular, the effect of thermal effusion (a short-range analogue of thermal diffusion) was discussed and accounted for. The evaporation coefficient alpha in air and in nitrogen were found to be equal. The alpha was found to decrease from approximately 0.18 to approximately 0.13 for the temperature range from 273.1 to 293.1 K and follow the trend given by the Arrhenius formula. The agreement with condensation coefficient values obtained with an essentially different method by Li et al. [Li, Y.; Davidovits, P.; Shi, Q.; Jayne, J.; Kolb, C.; Worsnop, D. J. Phys. Chem. A. 2001, 105, 10627] was found to be excellent. The comparison of experimental conditions used in both methods revealed no dependence of the evaporation/condensation coefficient on the droplet charge nor the ambient gas pressure within the experimental parameters range. The average value of the thermal accommodation coefficient over the same temperature range was found to be 1 +/- 0.05. PMID:18491849

Zientara, M; Jakubczyk, D; Kolwas, K; Kolwas, M

2008-06-12

316

Effects of laser energy density on impulse coupling coefficient of laser ablation of water for propulsion  

NASA Astrophysics Data System (ADS)

Time-resolved force sensing and intensified charge-coupled device (ICCD) imaging techniques were applied to the study of the effects of laser energy density on impulse coupling coefficient of laser ablation of water for propulsion. A Transversely Excited at Atmospheric pressure (TEA) CO2 laser operated at 10.6 ?m, 30 J pulse energy was used to ablate water contained in a quadrate quartz container. Net imparted impulse and coupling coefficients were derived from the force sensor data and relevant results were presented for various laser energy densities. ICCD imaging was used in conjunction with the dynamic force techniques to examine the dependencies on laser energy density. Results showed that the impulse coupling coefficient could reach a maximum value when laser energy density was about 105 J/m2, and it would increase before laser energy got to this point and would decrease after this point, and ICCD imaging supplied important phenomenon to explain this variation, which were water ablation before laser energy density got to 105 J/m2 and laser-induced air-breakdown with water as an induction when laser energy density was higher than 105 J/m2.

Cui, C. Y.; Hong, Y. J.; Ye, J. F.; Wen, M.; Li, N. L.

2011-04-01

317

Reduction of tetranitromethane by electronically excited aromatics in acetonitrile: Spectra and molar absorption coefficients of radical cations of anthracene, phenanthrene and pyrene  

NASA Astrophysics Data System (ADS)

Room temperature absorption spectra of the long-lived transient species produced by photolysing solutions containing tetranitromethane (TNM) or a TNM/arene mixture have been recorded with a multi-channel spectrophotometer, capable of ?s time resolution and covering a wide spectral range (200-1010 nm). The arene was anthracene ( A), naphthalene ( N), phenanthrene ( ?), or pyrene ( P). In methanol, Arad + , Nrad + and ?rad + disappear within the available time resolution, but all four cations live for tens or hundreds of ?s in acetonitrile; the molar absorption coefficients of Arad + , ?rad + and Prad + in the latter solvent match those of the respective anions in tetrahydrofuran.

Naqvi, K. Razi; Melø, Thor Bernt

2006-09-01

318

MEASUREMENT OF PARAMETRS OF LASER RADIATION: Opto-acoustic measurement of the local light absorption coefficient in turbid media: 1. Monte-Carlo simulation of laser fluence distribution at the beam axis beneath the surface of a turbid medium  

Microsoft Academic Search

A new method for measuring the local light absorption coefficient in turbid media, for example, biological tissues, is proposed. The method is based on the fact that the amplitude of the excited opto-acoustic (OA) signal is proportional to the absorbed laser power density (the product of the light absorption coefficient and the laser fluence) at the medium interface. In the

Ivan M. Pelivanov; M. I. Barskaya; N. B. Podymova; Tanya D. Khokhlova; Aleksander A. Karabutov

2009-01-01

319

Opto-acoustic measurement of the local light absorption coefficient in turbid media: 1. Monte-Carlo simulation of laser fluence distribution at the beam axis beneath the surface of a turbid medium  

Microsoft Academic Search

A new method for measuring the local light absorption coefficient in turbid media, for example, biological tissues, is proposed. The method is based on the fact that the amplitude of the excited opto-acoustic (OA) signal is proportional to the absorbed laser power density (the product of the light absorption coefficient and the laser fluence) at the medium interface. In the

Ivan M Pelivanov; M I Barskaya; N B Podymova; Tanya D Khokhlova; Aleksander A Karabutov

2009-01-01

320

An optical model for deriving the spectral particulate backscattering coefficients in oceanic waters  

NASA Astrophysics Data System (ADS)

An optical model is developed based on the diffuse attenuation coefficient (Kd) to estimate particulate backscattering coefficients bbp(?) in oceanic waters. A large in situ data set is used to establish robust relationships between bbp(530) and bbp(555) and Kd(490) using an efficient nonlinear least-square method which uses the trust region algorithm with Bisquare weights scheme to adjust the coefficients. These relationships are obtained with good correlation coefficients (R2 = 0.786 and 0.790), low root mean square error (RMSE = 0.00076 and 0.00072) and 95% confidence bounds. The new model is tested with three independent data sets: the NOMAD SeaWiFS Match ups, OOXIX IOP algorithm workshop evaluation data set (Version 2.0w APLHA), and IOCCG simulated data set. Results show that the new model makes good retrievals of bbp at all key wavelengths (from 412-683 nm), with statistically significant improvements over other inversion models. Thus, the new model has the potential to improve our present knowledge of particulate matter and their optical variability in oceanic waters.

Tiwari, S. P.; Shanmugam, P.

2013-11-01

321

Combination of COSMOmic and molecular dynamics simulations for the calculation of membrane-water partition coefficients.  

PubMed

The importance of membrane-water partition coefficients led to the recent extension of the conductor-like screening model for realistic solvation (COSMO-RS) to micelles and biomembranes termed COSMOmic. Compared to COSMO-RS, this new approach needs structural information to account for the anisotropy of colloidal systems. This information can be obtained from molecular dynamics (MD) simulations. In this work, we show that this combination of molecular methods can efficiently be used to predict partition coefficients with good agreement to experimental data and enables screening studies. However, there is a discrepancy between the amount of data generated by MD simulations and the structural information needed for COSMOmic. Therefore, a new scheme is presented to extract data from MD trajectories for COSMOmic calculations. In particular, we show how to calculate the system structure from MD, the influence of lipid conformers, the relation to the COSMOmic layer size, and the water/lipid ratio impact. For a 1,2-dimyristoyl-sn-glycero-3-phosphocholine (DMPC) bilayer, 66 partition coefficients for various solutes were calculated. Further, 52 partition coefficients for a 1-palmitoyl-2-oleoyl-sn-glycero-3-phosphocholine (POPC) bilayer system were calculated. All these calculations were compared to experimental data. PMID:23447371

Jakobtorweihen, Sven; Ingram, Thomas; Smirnova, Irina

2013-06-01

322

Modeling infinite dilution activity coefficients of environmental pollutants in water using conformal solution theory  

SciTech Connect

The fate of organic pollutants in the environment and in wastewater treatment processes is commonly modeled using a Henry`s law constant approach. By definition, Henry`s law constant is the product of a compound`s vapor pressure and infinite dilution activity coefficient. For many organic compounds in water solution, the infinite dilution activity coefficients are very large and are not adequately modeled by conventional methods such as UNIFAC. In this work, infinite dilution activity coefficients were determined for phenol, pyridine, aniline, p-toluidine, and o-toluidine in water by differential ebulliometry. An equation rigorously derived from conformal solution theory and van der Waals one-fluid mixing rules was used to model the temperature dependency of the infinite dilution activity coefficients. No corrections other than the introduction of two adjustable parameters were incorporated into the model to account for the strong interactions between molecules. Relationships derived from corresponding states theory were used to relate molecular parameters for size and energy interaction to the critical properties. Arithmetic mean combining rules and geometric mean combining rules were used to calculate size and interaction parameters, respectively.

Moore, R.C. [Univ. of Tennessee, Knoxville, TN (United States); Cochran, H.D.; Bienkowski, P.R. [Univ. of Tennessee, Knoxville, TN (United States)]|[Oak Ridge National Laboratory, Oak Ridge, TN (United States)

1995-04-01

323

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

324

Near-infrared diode laser absorption diagnostic for temperature and water vapor in a scramjet combustor  

Microsoft Academic Search

Tunable diode laser absorption measurements of gas temperature and water concentration were made at the exit of a model scramjet combustor fueled on JP-7. Multiplexed, fiber-coupled, near-infrared distributed feedback lasers were used to probe three water vapor absorption features in the 1.34 1.47 mum spectral region (2v1 and v1+v3 overtone bands). Ratio thermometry was performed using direct-absorption wavelength scans of

Jonathan T. C. Liu; Gregory B. Rieker; Jay B. Jeffries; Mark R. Gruber; Campbell D. Carter; Tarun Mathur; Ronald K. Hanson

2005-01-01

325

Near-infrared diode laser absorption diagnostic for temperature and water vapor in a scramjet combustor  

Microsoft Academic Search

Tunable diode laser absorption measurements of gas temperature and water concentration were made at the exit of a model scramjet combustor fueled on JP-7. Multiplexed, fiber-coupled, near-infrared distributed feedback lasers were used to probe three water vapor absorption features in the 1.34-1.47 μm spectral region (2v1and v1+ v3overtone bands). Ratio thermometry was performed using direct-absorption wavelength scans of isolated features

Tarun Mathur

2005-01-01

326

Dynamics of Water Absorption and Evaporation During Methanol Droplet Combustion in Microgravity.  

National Technical Information Service (NTIS)

The combustion of methanol droplets is profoundly influenced by the absorption and evaporation of water, generated in the gas phase as a part of the combustion products. Initially there is a water-absorption period of combustion during which the latent he...

D. L. Dietrich F. A. Williams M. C. Hicks V. Nayagam

2012-01-01

327

Modeling, simulation and optimization of a solar collector driven water heating and absorption cooling plant  

Microsoft Academic Search

A cogeneration system consisting of a solar collector, a gas burner, a thermal storage reservoir, a hot water heat exchanger, and an absorption refrigerator is devised to simultaneously produce heating (hot water heat exchanger) and cooling (absorption refrigerator system). A simplified mathematical model, which combines fundamental and empirical correlations, and principles of classical thermodynamics, mass and heat transfer, is developed.

J. V. C. Vargas; J. C. Ordonez; E. Dilay; J. A. R. Parise

2009-01-01

328

Water absorption by secondary organic aerosol and its effect on inorganic aerosol behavior  

Microsoft Academic Search

The hygroscopic nature of atmospheric aerosol has generally been associated with its inorganic fraction. In this study, a group contribution method is used to predict the water absorption of secondary organic aerosol (SOA). Compared against growth measurements of mixed inorganic-organic particles, this method appears to provide a first-order approximation in predicting SOA water absorption. The growth of common SOA species

Asif S. Ansari; Spyros N. Pandis

2000-01-01

329

Partition coefficients for alcohol tracers between nonaqueous-phase liquids and water from UNIFAC-solubility method  

Microsoft Academic Search

In this work, we have applied a group-contribution activity-coefficient model, UNIFAC, and the solubility of alcohols in water to estimate partition coefficients for alcohol tracers between water and nonaqueous-phase liquids (NAPLs). The effects of temperature and mutual solubility between NAPL and aqueous phases on the estimation of partition coefficients were also investigated. By comparing the estimated results with experimental partition

Peng Wang; Varadarajan Dwarakanath; Bruce A. Rouse; Gary A. Pope; Kamy Sepehrnoori

1998-01-01

330

Octanol-water partition coefficients of substituted alpha, N-diphenylnitrones and benzonitrile N-oxides  

SciTech Connect

Experimental octanol-water partition coefficients are reported for substituted alpha, N-diphenylnitrones and benzonitrile N-oxides. The results of these measurements are used to calculate the aromatic fragment constants pi HC = N(O)C6H5, pi C = N----O, fHC = N(O), and fC = N----O for the group contribution methods of Hansch and Leo.

Kirchner, J.J.; Acree, W.E. Jr.; Leo, A.J.; Gelli, G.

1985-10-01

331

The Reactivity Temperature Coefficient Analysis in Light Water Moderated UOâ and UOâ-PuOâ Lattices  

Microsoft Academic Search

The contributions of different physical phenomena to the reactivity temperature coefficient (RTC) in typical light water moderated lattices have been assessed. Using the APOLLO2 code with the CEA93 cross-section library based on JEF2.2 data, we have analyzed the main French experiments available on the RTC: the CREOLE and MISTRAL experiments. In these experiments performed in the EOLE critical facility located

L. Erradi; A. Santamarina; O. Litaize

2003-01-01

332

Ground water contaminant source and transport parameter identification by correlation coefficient optimization  

SciTech Connect

The initial step in a ground water contamination remediation process is to identify the extent of the plume. One way to optimize well deployment is to solve an inverse contaminant transport problem. Inverse procedures bas4ed on correlation coefficient optimization are developed to locate ground water contaminant sources and to identify transport parameters. For cases involving two-dimensional instantaneous and continuous sources, the inverse formulas are explicit. These procedures allow not only for the delineation of the sampled contaminant plume, but also the tracing and the projection of the plume history.

Sidauruk, P.; Cheng, A.H.D. [Univ. of Delaware, Newark, DE (United States). Dept. of Civil and Environmental Engineering; Ouazar, D. [Univ. Mohammed 5, Rabat (Morocco). Ecole Mohammadia d`Ingenieurs

1998-03-01

333

Exponential Sum Absorption Coefficients of Phosphine from 2750 to 3550/cm for Application to Radiative Transfer Analyses on Jupiter and Saturn  

NASA Technical Reports Server (NTRS)

PH3 exponential sum k coefficients were computed between 2750 and 3550/cm (2.82-3.64 (microns), in view of future application to radiative transfer analyses of Jupiter and Saturn in a phosphine absorption band near 3 microns. The temperature and pressure of this data set cover the ranges from 80 to 350 K and from 10 (exp -3)to 10(exp 1) bars, respectively. Transmission uncertainty incurred by the use of the k coefficients is smaller than a few percent as long as the radiation is confined above an altitude of a few bars in the giant planets. In spectral regions of weak absorption at high pressures close to 10 bars, contributions from far wings of strong absorption lines must be carefully taken into account. Our data set helps map the three-dimensional distribution of PH3 on the giant planets, revealing their global atmospheric dynamics extending down to the deep interior. The complete k coefficient data set of this work is available at the Web site of the NASA Planetary Data System Atmospheres Node.

Temma, T.; Baines, K. H.; Butler, R. A. H.; Brown, L. R.; Sagui, L.; Kleiner, I.

2006-01-01

334

Measurement of the mass energy-absorption coefficient of air for x-rays in the range from 3 to 60 keV  

NASA Astrophysics Data System (ADS)

For the first time the absolute photon mass energy-absorption coefficient of air in the energy range of 10 to 60 keV has been measured with relative standard uncertainties below 1%, considerably smaller than those of up to 2% assumed for calculated data. For monochromatized synchrotron radiation from the electron storage ring BESSY II both the radiant power and the fraction of power deposited in dry air were measured using a cryogenic electrical substitution radiometer and a free air ionization chamber, respectively. The measured absorption coefficients were compared with state-of-the art calculations and showed an average deviation of 2% from calculations by Seltzer. However, they agree within 1% with data calculated earlier by Hubbell. In the course of this work, an improvement of the data analysis of a previous experimental determination of the mass energy-absorption coefficient of air in the range of 3 to 10 keV was found to be possible and corrected values of this preceding study are given.

Buhr, H.; Büermann, L.; Gerlach, M.; Krumrey, M.; Rabus, H.

2012-12-01

335

Parameters and computer software for the evaluation of mass attenuation and mass energy-absorption coefficients for body tissues and substitutes  

PubMed Central

The mass attenuation and energy-absorption coefficients (radiation interaction data), which are widely used in the shielding and dosimetry of X-rays used for medical diagnostic and orthovoltage therapeutic procedures, are strongly dependent on the energy of photons, elements and percentage by weight of elements in body tissues and substitutes. Significant disparities exist in the values of percentage by weight of elements reported in literature for body tissues and substitutes for individuals of different ages, genders and states of health. Often, interested parties are in need of these radiation interaction data for body tissues or substitutes with percentage by weight of elements and intermediate energies that are not tabulated in literature. To provide for the use of more precise values of these radiation interaction data, parameters and computer programs, MUA_T and MUEN_T are presented for the computation of mass attenuation and energy-absorption coefficients for body tissues and substitutes of arbitrary percentage-by-weight elemental composition and photon energy ranging between 1 keV (or k-edge) and 400 keV. Results are presented, which show that the values of mass attenuation and energy-absorption coefficients obtained from computer programs are in good agreement with those reported in literature.

Okunade, Akintunde A.

2007-01-01

336

Parameters and computer software for the evaluation of mass attenuation and mass energy-absorption coefficients for body tissues and substitutes.  

PubMed

The mass attenuation and energy-absorption coefficients (radiation interaction data), which are widely used in the shielding and dosimetry of X-rays used for medical diagnostic and orthovoltage therapeutic procedures, are strongly dependent on the energy of photons, elements and percentage by weight of elements in body tissues and substitutes. Significant disparities exist in the values of percentage by weight of elements reported in literature for body tissues and substitutes for individuals of different ages, genders and states of health. Often, interested parties are in need of these radiation interaction data for body tissues or substitutes with percentage by weight of elements and intermediate energies that are not tabulated in literature. To provide for the use of more precise values of these radiation interaction data, parameters and computer programs, MUA_T and MUEN_T are presented for the computation of mass attenuation and energy-absorption coefficients for body tissues and substitutes of arbitrary percentage-by-weight elemental composition and photon energy ranging between 1 keV (or k-edge) and 400 keV. Results are presented, which show that the values of mass attenuation and energy-absorption coefficients obtained from computer programs are in good agreement with those reported in literature. PMID:21157532

Okunade, Akintunde A

2007-07-01

337

Moisture diffusivities evaluated at high moisture levels from a series of water absorption tests  

Microsoft Academic Search

This paper presents measured moisture diffusivities for sedimentary calcareous sandstone, lime silica bricks, bricks, and\\u000a autoclaved, aerated concrete. The moisture diffusivities were calculated from the relation between the water sorption coefficients\\u000a and the initial water content in the specimen before testing. The method used is based on Boltzmann transformation. The relation\\u000a between the water sorption coefficients and the initial water

M. Janz

2002-01-01

338

A Three-Wavelength Optical Extinction Cell for Measuring Aerosol Light Extinction and Its Application to Determining Light Absorption Coefficient  

Microsoft Academic Search

An optical extinction cell (OEC) was used to measure aerosol particle extinction coefficient ?EP at three wavelengths, 467, 530, and 660 nm. The details of the design and the results of its use in the Reno Aerosol Optics Study (RAOS) in June 2002 are presented. The OEC agreed well with the scattering coefficient ?SP measured using an integrating nephelometer for

Aki Virkkula; Norman C. Ahlquist; Patrick J. Sheridan; William P. Arnott; John A. Ogren

2005-01-01

339

Temperature Dependences of Mechanisms Responsible for the Water-Vapor Continuum Absorption  

NASA Technical Reports Server (NTRS)

The water-vapor continuum absorption plays an important role in the radiative balance in the Earth's atmosphere. It has been experimentally shown that for ambient atmospheric conditions, the continuum absorption scales quadratically with the H2O number density and has a strong, negative temperature dependence (T dependence). Over the years, there have been three different theoretical mechanisms postulated: far-wings of allowed transition lines, water dimers, and collision-induced absorption. The first mechanism proposed was the accumulation of absorptions from the far-wings of the strong allowed transition lines. Later, absorption by water dimers was proposed, and this mechanism provides a qualitative explanation for the continuum characters mentioned above. Despite the improvements in experimental data, at present there is no consensus on which mechanism is primarily responsible for the continuum absorption.

Ma, Qiancheng

2014-01-01

340

Quasi-random narrow-band model fits to near-infrared low-temperature laboratory methane spectra and derived exponential-sum absorption coefficients  

NASA Technical Reports Server (NTRS)

Near-infrared 10/cm resolution spectra of methane obtained at various temperatures, pressures, and abundances are fit to a quasi-random narrow-band model. Exponential-sum absorption coefficients for three temperatures (112, 188, and 295 K), and 20 pressures from 0.0001 to 5.6 bars, applicable to the cold environments of the major planets, are then derived from the band model for the 230 wavelengths measured from 1.6 to 2.5 microns. RMS deviations between the laboratory and the exponential-sum synthetic transmissions are reported for the best fitting 50 wavelengths. Deviations relevant to broadband, 1-percent spectral resolution observations are also presented. The validity of exponential-sum coefficients derived from broadband (10/cm) transmission data is demonstrated via direct comparison with line-by-line calculations. The complete atlas of coefficients is available from the Planetary Data System-Planetary Atmospheres Discipline Node.

Baines, Kevin H.; West, Robert A.; Giver, Lawrence P.; Moreno, Fernando

1993-01-01

341

Relation of sound absorption and shallow water modal attenuation to plane wave attenuation.  

PubMed

Prediction of attenuation of acoustic fields in weakly absorbing media often uses the substitution of (omega/c)-->(omega/c)+ialpha(pw) into the idealized equations for constant frequency, with alpha(pw) representing the local plane wave attenuation coefficient. This assumption is flawed whenever the local absorption of sound is proportional to the square of the gradient of the acoustic pressure, as is the case when the absorption is caused by fluid velocity relaxation. A realistic analysis yields an improved weighting function over depth for determination of guided mode attenuation coefficients. PMID:19894791

Pierce, Allan D

2009-11-01

342

Inverse temperature dependence of Henry's law coefficients for volatile organic compounds in supercooled water.  

PubMed

Upon supercooling, water expels volatile organic compounds (VOC), and Henry's law coefficients are increasing concomitant with decreasing temperature. This unexpected observation was found by measuring the VOC partitioning between supercooled water and gas phase in the temperature range from -5 degrees C to -15 degrees C for benzene, toluene, ethlybenzene, m-, p-, o-xylenes (BTEX), methyl tert-butyl ether (MTBE) and ethyl tert-butyl ether (ETBE). Aqueous standard solutions were analyzed using a static headspace method in combination with gas chromatography/mass spectrometry (GC/MS). Dimensionless Henry's law coefficients (K(AW)) were calculated from measurements of the concentration of the VOCs in the headspace above the standard solutions at temperatures between -25 degrees C and 25 degrees C. The results show that the well known temperature dependence of Henry's law coefficients at temperatures above 0 degrees C is inversed upon decreasing the temperature below 0 degrees C and formation of supercooled water while decreasing the temperature to -15 degrees C. Upon further decrease of the temperature to -25 degrees C freezing of the supercooled water occurs. K(AW) values increase from 0.092 (benzene), 0.099 (toluene), 0.098 (ethylbenzene), 0.117 (m/p-xylene), 0.076 (o-xylene), 0.012 (MTBE) and 0.014 (ETBE at 5 degrees C to 0.298 (benzene), 0.498 (toluene), 0.944 (ethylbenzene), 0.327 (m/p-xylene), 0.342 (o-xylene), 0.029 (MTBE) and 0.041 (ETBE) at -25 degrees C, respectively. Inversion of Henry coefficients upon cooling the aqueous solutions to temperatures below 0 degrees C is explained by the increasing formation of ice-like clusters in the water below 0 degrees C. The VOC are expelled from these clusters resulting in enhanced VOC concentrations in the gas phase upon supercooling. Formation of ice upon further cooling to -25 degrees C results in a further increase of the VOC concentrations in the gas phase above the ice. The findings have implications for the partitioning of VOC in clouds between the gas phase, supercooled water droplets, aerosol particles and ice. PMID:19604535

Sieg, Karsten; Starokozhev, Elena; Schmidt, Martin U; Püttmann, Wilhelm

2009-09-01

343

Terahertz absorption spectrum of para and ortho water vapors at different humidities at room temperature  

NASA Astrophysics Data System (ADS)

Terahertz time-domain spectroscopy has been used to measure the absorption of water vapor in 0.2-2.4 THz range from low to high humidity at room temperature. The observed absorption lines are due to the water molecular rotations in the ground vibrational state. We find that the absorption strength of para transitions increases as humidity increases, while the absorption strength of ortho transitions increases and then decreases in intensity with increasing humidity. We explain this difference based on the nuclear spin statistics based ratio of ortho to para water monomer populations at room temperature. The preferential adsorption on the solid surfaces of para water leads to an ortho dominated vapor cloud whose monomer rotational absorption intensity decreases due to the effects of dimerization, molecular collisions, clustering, and interactions with liquid droplets at high concentrations.

Xin, X.; Altan, H.; Saint, A.; Matten, D.; Alfano, R. R.

2006-11-01

344

A new term “Jzeff” derived from measured total attenuation coefficients of photons near the absorption edges of some compounds  

NASA Astrophysics Data System (ADS)

In order to determine the effect of XAFS (X-ray absorption fine structure) on Jzeff, we have measured ?/ ? values of compounds, which are determined by the mixture rule or the independent atomic model. Also, we want to obtain both XAFS effect and non-applicability or applicability of mixture rule. The most crucial finding in this study is that measurement of the effective atomic number is not appropriate near the absorption edge and the effective atomic number is affected by near the absorption edge. The results obtained have been compared with theoretical values. Also, the objective of this study is to show that there is a term " Jzeff" between effective atomic numbers and absorption jump factor.

Polat, Recep; ?çelli, Orhan

2010-09-01

345

Field observation and modeling of dissolved fraction sediment-water exchange coefficients for PCBs in the Hudson River.  

PubMed

Chemical fate and transport models that simulate sediment-water exchange of contaminants typically employ empirically determined sediment-water exchange coefficients for the dissolved fraction to describe the net effect of poorly understood mechanisms. This paper presents field-derived observations of the coefficient for 12 PCB congeners and two PCB mixtures in the Thompson Island Pool, Hudson River, and also presents an evaluation of a theoretical sediment-water exchange model. An extensive PCB data set was used to compute apparent coefficients for PCBs in the pool. Average exchange coefficients for the 12 congeners ranged from 2.6 to 18.8 cm/ day, and results showed a strong seasonal dependence. Peak coefficient values occurred in mid-May to early July, preceding peak water temperatures by 1 month and lagging the spring high-flow period. The coefficients increase with increasing partition coefficients, suggesting a dependence on congener properties. The large magnitude of the coefficients and the variation among the congeners is inconsistent with the pore-water molecular-diffusion transport process. A theory-based, mechanistic two-layer model reproduces the nonlinear relationship between the sediment-water exchange coefficients and partition coefficients. This model includes transfer through the mixed sediment layer by bioturbation and diffusion transfer through a water-side boundary layer governed by flow velocity. Results suggest that this algorithm can provide increased accuracyto future system-level fate and transport models for hydrophobic chemicals. The seasonal variation in the transfer coefficient appears to be a poorly understood interaction of physical and biological processes and merits further study. PMID:15707055

Erickson, Michael J; Turner, Carrie L; Thibodeaux, Louis J

2005-01-15

346

Diffusion coefficients of energetic water group ions near Comet Giacobini-Zinner  

NASA Astrophysics Data System (ADS)

Data from the ultralow-energy charge analyzer and energetic particle anisotropy spectrometer sensors, acquired when the ICE spacecraft flew past Comet Giacobini-Zinner on September 11, 1985, are combined, and a single, self-consistent analysis technique is applied to derive a single-particle spectrum from about 200 to 1600 km/s. This information, together with the deduced bulk flow speed of the ions, is used to calculate a parallel diffusion coefficient in the transition region downstream of the bow wave (2.3 +/- 0.5) x 10 exp 17 sq cm/s; the corresponding scattering mean free path is (6 +/- 1) x 10 exp 4 km. The parallel diffusion coefficient is found to depend on the collision frequency of water group ions with Alfven waves, which are assumed to be propagating parallel (antiparallel) to the magnetic field.

Tan, L. C.; Mason, G. M.; Richardson, I. G.; Ipavich, F. M.

1993-03-01

347

Worldwide data sets constrain the water vapor uptake coefficient in cloud formation.  

PubMed

Cloud droplet formation depends on the condensation of water vapor on ambient aerosols, the rate of which is strongly affected by the kinetics of water uptake as expressed by the condensation (or mass accommodation) coefficient, ?c. Estimates of ?c for droplet growth from activation of ambient particles vary considerably and represent a critical source of uncertainty in estimates of global cloud droplet distributions and the aerosol indirect forcing of climate. We present an analysis of 10 globally relevant data sets of cloud condensation nuclei to constrain the value of ?c for ambient aerosol. We find that rapid activation kinetics (?c > 0.1) is uniformly prevalent. This finding resolves a long-standing issue in cloud physics, as the uncertainty in water vapor accommodation on droplets is considerably less than previously thought. PMID:23431189

Raatikainen, Tomi; Nenes, Athanasios; Seinfeld, John H; Morales, Ricardo; Moore, Richard H; Lathem, Terry L; Lance, Sara; Padró, Luz T; Lin, Jack J; Cerully, Kate M; Bougiatioti, Aikaterini; Cozic, Julie; Ruehl, Christopher R; Chuang, Patrick Y; Anderson, Bruce E; Flagan, Richard C; Jonsson, Haflidi; Mihalopoulos, Nikos; Smith, James N

2013-03-01

348

MEASUREMENT OF THE ABSORPTION CHARACTERISTICS OF SUPERSATURATED WATER VAPOR  

Microsoft Academic Search

the atmosphere by as much as 40 Wm-2. This enhanced absorption, which was recognised by comparing model calculations with satellite-borne radiometric measurements, remains to be explained. Controversial explanations of this newly discovered fact have been offered and debated. A school of thought suggests that the enhanced absorption of the incoming short-wave solar radiation is due to erroneous depiction of the

Prasad Varanasi; B. Ranganayakamma; S. Mathur; T. Refaat; C. R. Prasad

349

Spectral absorption properties of dissolved and particulate matter in Lake Erie  

Microsoft Academic Search

Spectral absorption properties of particulate and dissolved matter were determined for Lake Erie waters in order to investigate the natural variability of the absorption coefficients required as inputs to optical models for converting satellite observations of water colour into water quality information. Particulate absorption measured using the quantitative filter technique yielded absorption spectra containing a fraction that could not be

Caren E. Binding; John H. Jerome; Robert P. Bukata; William G. Booty

2008-01-01

350

Absorption kinetics of ozone in water with ultrasonic radiation.  

PubMed

A mathematical model was proposed to depict classical unsteady state method that was used to determine volumetric mass transfer coefficient of ozone from gaseous phase to aqueous phase during sonolysis. The rate constant of ozone self-decomposition with ultrasonic radiation, which was one of the parameters in the model, was determined with separate experiments. The results showed that self-decomposition rate constants of ozone were enhanced by ultrasound. The self-decomposition rate constant of ozone is linearly dependent on ultrasonic power, but the increase of the decomposition rate could not enhance ozone mass transfer coefficient. The volumetric mass transfer coefficients of ozone were also enhanced by ultrasonic radiation, while ultrasonic power had little effect on volumetric mass transfer coefficient of ozone. The degassing effect of ozone due to ultrasonic radiation was insignificant in the sparged system when ozone was bubbled during sonolysis. PMID:17084654

Zhang, Hui; Duan, Lijie; Zhang, Daobin

2007-07-01

351

Opto-acoustic measurement of the local light absorption coefficient in turbid media: 2. On the possibility of light absorption coefficient measurement in a turbid medium from the amplitude of the opto-acoustic signal  

Microsoft Academic Search

The second part of this work describes the experimental technique of measuring the local light absorption in turbid media. The technique is based on the measurement of the amplitude of an opto-acoustic (OA) signal excited in a turbid medium under the condition of one-sided access to the object under study. An OA transducer is developed to perform the proposed measurement

Ivan M Pelivanov; M I Barskaya; N B Podymova; Tanya D Khokhlova; Aleksander A Karabutov

2009-01-01

352

Partition coefficients for alcohol tracers between nonaqueous-phase liquids and water from UNIFAC-solubility method  

NASA Astrophysics Data System (ADS)

In this work, we have applied a group-contribution activity-coefficient model, UNIFAC, and the solubility of alcohols in water to estimate partition coefficients for alcohol tracers between water and nonaqueous-phase liquids (NAPLs). The effects of temperature and mutual solubility between NAPL and aqueous phases on the estimation of partition coefficients were also investigated. By comparing the estimated results with experimental partition coefficients for 30 alcohol tracers between 10 NAPLs and water, we found that: i) the UNIFAC-solubility method, in which the UNIFAC model in its infinite-dilution form is applied to the NAPL phase and the solubility of tracers in water is used for estimation of the activity coefficient in the aqueous phase, works better than the UNIFAC model; ii) a linear relation between the logarithm of partition coefficients and the logarithm of tracer solubility in water is observed for those tracers having a similar chemical structure (i.e. the same number of branched methyl groups). This can serve as a useful tool for quick selection of the tracers that exhibit the desired partition coefficients; iii) the effect of mutual solubility between NAPL and aqueous phases can be neglected because such miscibility is very small, usually of the order of 10 -3 mole/mole unit; and iv) temperature variation between 15° and 25°C does not significantly affect partition coefficients.

Wang, Peng; Dwarakanath, Varadarajan; Rouse, Bruce A.; Pope, Gary A.; Sepehrnoori, Kamy

353

Absorption cold and warm water system utilizing solar heat  

SciTech Connect

An absorbtion cold and warm water system utilizing solar heat is disclosed. Heat source water is obtained by heating water by the solar heat and a main heating source. The system is selectively made to function as a warm water system, a first heat pump and a second heat pump in accordance with temperature conditions associated with the heat source water.

Hibino, Y.; Kamejima, K.; Nara, Y.

1985-02-12

354

Polyethylene-water partitioning coefficients for parent- and alkylated-polycyclic aromatic hydrocarbons and polychlorinated biphenyls.  

PubMed

We report polyethylene (PE)-water partitioning coefficients (K(PE)) for 17 parent-polycyclic aromatic hydrocarbons (PAHs), 22 alkylated-PAHs, 3 perdeuterated parent-PAHs, and 100 polychlorinated biphenyl (PCB) congeners or coeluting congener groups. The K(PE) values for compounds in the same homologue group are within 0.2 log units for alkylated-PAHs but span up to an order of magnitude for PCBs, due to the greater contribution of the position of the substituents (i.e., chlorines for PCBs and alkyl groups for alkylated-PAHs) to the molecular structure. The K(PE) values in deionized water for parent- and alkylated-PAHs show a good correlation with a regression model employing the number of aromatic carbons (C(AR)) and aliphatic carbons (C(AL)) in each compound: log K(PE) = -0.241 + 0.313 C(AR) + 0.461 C(AL). The regression model is useful for the assessment of freely dissolved aqueous concentrations of alkylated-PAHs, which comprise a significant fraction of the total in petroleum-derived PAHs and in some pyrogenic PAH mixtures. For PCBs, experimentally determined octanol-water partitioning coefficients are the best predictor of the K(PE) values among the molecular parameters studied. The effect of salinity up to 20 or 30 parts per thousand is found to be relatively insignificant on K(PE) values for PAHs or PCBs, respectively. PMID:23488618

Choi, Yongju; Cho, Yeo-Myoung; Luthy, Richard G

2013-07-01

355

Recent measurements of the spectral backward-scattering coefficient in coastal waters  

NASA Astrophysics Data System (ADS)

The backward scattering coefficient bb was measured in various coastal waters with fixed-angle backscattering sensors developed by the authors. Measurements were made at four discrete wavelengths covering the spectral range 440 to 675 nm. A power law spectral dependence of bb due to scattering by particles was investigated of the form bbp((lambda) ) equals bbp ((lambda) 0) ((lambda) 0/(lambda) )(gamma , where the superscript p denotes particle scattering and (lambda) is the wavelength. The exponent (gamma) depends on the particle size distribution and composition of particles. Extensive measurements in Monterey Bay, California, showed that 0.1 waters generally below 10 m. For the upper 10 m, 0.7 waters near Panama City, Florida, (gamma) for the upper 10 m was found to be in the range, 0.9 water, 0.9 waters of East Sound, Washington, 0 waters measured.

Maffione, Robert A.; Dana, David R.

1997-02-01

356

A parameterization for the absorption of solar radiation by water vapor in the earth's atmosphere  

NASA Technical Reports Server (NTRS)

A parameterization for the absorption of solar radiation as a function of the amount of water vapor in the earth's atmosphere is obtained. Absorption computations are based on the Goody band model and the near-infrared absorption band data of Ludwig et al. A two-parameter Curtis-Godson approximation is used to treat the inhomogeneous atmosphere. Heating rates based on a frequently used one-parameter pressure-scaling approximation are also discussed and compared with the present parameterization.

Wang, W.-C.

1976-01-01

357

Accumulation of lipophilic chemicals in plant cuticles: Prediction from octanol\\/water partition coefficients  

Microsoft Academic Search

Partition coefficients of lipophilic organic compounds have been determined for the system plant cuticle\\/water. The cuticles were isolated enzymatically from leaves of rubber plant (Ficus elastica) and bitter orange (Citrus aurantium) and from fruits of tomato (Lycopersicon esculentum) and green pepper (Capsicum annuum). The sorption in cuticles of 4-nitrophenol, (2,4-dichlo-rophenoxy) acetic acid (2,4-D), 6-chloro-N-ethyl-N-(1-methylethyl)-1,3,5-triazine-2,4-diamine (atrazine), (2,4,5-trichlorophenoxy)acetic acid (2,4,5-T), pentachlorophenol (PCP),

Franz Kerler; Jörg Schönherr

1988-01-01

358

Water/n-octanol partition coefficients of 1,2-dithiole-3-thiones.  

PubMed

Water/n-octanol partition coefficients (log P) for 33 1,2-dithiole-3-thiones and for 18 1,2-dithiol-3-ones were determined by RP-HPLC measurement of the concentration of the solute in aqueous solution after equilibrium. Depending on the nature of the substituents (alkyl or aryl) and their position(s) (4,5, or both) on the dithiole nucleus, some peculiar behaviors were revealed. Therefore, different fragmental constants containing the 1,2-dithiole-3-thione nucleus were inferred in order to calculate in a complementary work, a priori, the log P values of new dithiolethiones and dithiolones. PMID:8537890

Bona, M; Boudeville, P; Zekri, O; Christen, M O; Burgot, J L

1995-09-01

359

Measurements of absorbed heat flux and water-side heat transfer coefficient in water wall tubes  

NASA Astrophysics Data System (ADS)

The tubular type instrument (flux tube) was developed to identify boundary conditions in water wall tubes of steam boilers. The meter is constructed from a short length of eccentric tube containing four thermocouples on the fire side below the inner and outer surfaces of the tube. The fifth thermocouple is located at the rear of the tube on the casing side of the water-wall tube. The boundary conditions on the outer and inner surfaces of the water flux-tube are determined based on temperature measurements at the interior locations. Four K-type sheathed thermocouples of 1 mm in diameter, are inserted into holes, which are parallel to the tube axis. The non-linear least squares problem is solved numerically using the Levenberg-Marquardt method. The heat transfer conditions in adjacent boiler tubes have no impact on the temperature distribution in the flux tubes.

Taler, Jan; Taler, Dawid; Kowal, Andrzej

2011-04-01

360

Small effect of water on upper-mantle rheology based on silicon self-diffusion coefficients.  

PubMed

Water has been thought to affect the dynamical processes in the Earth's interior to a great extent. In particular, experimental deformation results suggest that even only a few tens of parts per million of water by weight enhances the creep rates in olivine by orders of magnitude. However, those deformation studies have limitations, such as considering only a limited range of water concentrations and very high stresses, which might affect the results. Rock deformation can also be understood as an effect of silicon self-diffusion, because the creep rates of minerals at temperatures as high as those in the Earth's interior are limited by self-diffusion of the slowest species. Here we experimentally determine the silicon self-diffusion coefficient DSi in forsterite at 8?GPa and 1,600?K to 1,800?K as a function of water content CH2O from less than 1 to about 800 parts per million of water by weight, yielding the relationship, DSi???(CH2O)(1/3). This exponent is strikingly lower than that obtained by deformation experiments (1.2; ref. 7). The high nominal creep rates in the deformation studies under wet conditions may be caused by excess grain boundary water. We conclude that the effect of water on upper-mantle rheology is very small. Hence, the smooth motion of the Earth's tectonic plates cannot be caused by mineral hydration in the asthenosphere. Also, water cannot cause the viscosity minimum zone in the upper mantle. And finally, the dominant mechanism responsible for hotspot immobility cannot be water content differences between their source and surrounding regions. PMID:23765497

Fei, Hongzhan; Wiedenbeck, Michael; Yamazaki, Daisuke; Katsura, Tomoo

2013-06-13

361

Investigation of stimulated Brillouin scattering media perfluoro-compound and perfluoropolyether with a low absorption coefficient and high power-load ability.  

PubMed

The correlations between stimulated Brillouin scattering (SBS) characteristics of perfluoro-compound (PFC) and perfluoropolyether (PFPE) and their chemical structure are analyzed in detail and a series of new PFC and PFPE are reported. In the Nd:YAG laser system, the absorption coefficient, optical breakdown threshold (OBT), SBS threshold, and Brillouin frequency shift of new media such as FC-87, FC-43, HT-55, and DET are measured. Parameters such as gain coefficient, Brillouin linewidth, and phonon lifetime are calculated. The results demonstrate their good SBS properties: the absorption coefficients are below 10(-3)cm(-1) and OBTs are above 100 GW/cm(2). These media also exhibit a series of unique physicochemical properties, i.e., high heat-resistance, high oxidation stability, good chemical inertness, and insulation properties. The discovery of new media not only diversifies SBS medium, but also improves the performance of the SBS system, thereby laying a good foundation for the application of a SBS phase conjugation mirror in a high-power laser system. PMID:18311273

Hasi, W L J; Lu, Z W; Gong, S; Liu, S J; Li, Q; He, W M

2008-03-01

362

Investigation of stimulated Brillouin scattering media perfluoro-compound and perfluoropolyether with a low absorption coefficient and high power-load ability  

NASA Astrophysics Data System (ADS)

The correlations between stimulated Brillouin scattering (SBS) characteristics of perfluoro-compound (PFC) and perfluoropolyether (PFPE) and their chemical structure are analyzed in detail and a series of new PFC and PFPE are reported. In the Nd:YAG laser system, the absorption coefficient, optical breakdown threshold (OBT), SBS threshold, and Brillouin frequency shift of new media such as FC-87, FC-43, HT-55, and DET are measured. Parameters such as gain coefficient, Brillouin linewidth, and phonon lifetime are calculated. The results demonstrate their good SBS properties: the absorption coefficients are below 10-3cm-1 and OBTs are above 100 GW/cm2. These media also exhibit a series of unique physicochemical properties, i.e., high heat-resistance, high oxidation stability, good chemical inertness, and insulation properties. The discovery of new media not only diversifies SBS medium, but also improves the performance of the SBS system, thereby laying a good foundation for the application of a SBS phase conjugation mirror in a high-power laser system.

Hasi, W. L. J.; Lu, Z. W.; Gong, S.; Liu, S. J.; Li, Q.; He, W. M.

2008-03-01

363

Absorption  

NSDL National Science Digital Library

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

Katherine M Knudson (Polson Middle School)

1998-04-01

364

The influence of water mixtures on the dermal absorption of glycol ethers  

Microsoft Academic Search

Glycol ethers are solvents widely used alone and as mixtures in industrial and household products. Some glycol ethers have been shown to have a range of toxic effects in humans following absorption and metabolism to their aldehyde and acid metabolites. This study assessed the influence of water mixtures on the dermal absorption of butoxyethanol and ethoxyethanol in vitro through human

Matthew J. Traynor; Simon C. Wilkinson; Faith M.. Williams

2007-01-01

365

Drinking Spring Water and Lithium Absorption: A Preliminary Study  

Microsoft Academic Search

Background: In Japan, there are several resorts with cold springs that have mineral water containing relatively high levels of lithium compared to tap water. Visitors to such cold-spring resorts traditionally drink 2 to 4 L of mineral water for several hours in the early morning in the belief that the water has properties which maintain physical health. The present study

Ippei Shiotsuki; Takeshi Terao; Hirochika Ogami; Nobuyoshi Ishii; Reiji Yoshimura; Jun Nakamura

366

The effect of water absorption on the dielectric properties of epoxy nanocomposites  

Microsoft Academic Search

In this research, the influence of water absorption on the dielectric properties of epoxy resin and epoxy micro-composites and nano-composites filled with silica has been studied. Nanocomposites were found to absorb significantly more water than unfilled epoxy. However, the microcomposite absorbed less water than unfilled epoxy: corresponding to the reduced proportion of the epoxy in this composite. The glass transition

Chen Zou; J. C. Fothergill; S. W. Rowe

2008-01-01

367

Characteristics of the membrane utilized in a compact absorber for lithium bromide–water absorption chillers  

Microsoft Academic Search

This study aims at investigating experimentally and analytically the characteristics and properties of a membrane utilized to design compact absorbers for lithium bromide–water absorption chillers. The main focus of this study are the factors that influence the water vapor transfer flux into a lithium bromide–water solution in confined narrow channels under vacuum conditions, as well as the properties limits for

Ahmed Hamza H. Ali; Peter Schwerdt

2009-01-01

368

Improved prediction of octanol-water partition coefficients from liquid-solute water solubilities and molar volumes  

USGS Publications Warehouse

A volume-fraction-based solvent-water partition model for dilute solutes, in which the partition coefficient shows a dependence on solute molar volume (V??), is adapted to predict the octanol-water partition coefficient (K ow) from the liquid or supercooled-liquid solute water solubility (Sw), or vice versa. The established correlation is tested for a wide range of industrial compounds and pesticides (e.g., halogenated aliphatic hydrocarbons, alkylbenzenes, halogenated benzenes, ethers, esters, PAHs, PCBs, organochlorines, organophosphates, carbamates, and amidesureas-triazines), which comprise a total of 215 test compounds spanning about 10 orders of magnitude in Sw and 8.5 orders of magnitude in Kow. Except for phenols and alcohols, which require special considerations of the Kow data, the correlation predicts the Kow within 0.1 log units for most compounds, much independent of the compound type or the magnitude in K ow. With reliable Sw and V data for compounds of interest, the correlation provides an effective means for either predicting the unavailable log Kow values or verifying the reliability of the reported log Kow data. ?? 2005 American Chemical Society.

Chiou, C. T.; Schmedding, D. W.; Manes, M.

2005-01-01

369

Effect of Heterogeneity of Absorbing Rod Position in a Core Formation of the Reactivity Temperature Coefficient in Uranium Water Assemblies.  

National Technical Information Service (NTIS)

Results of calculational and experimental investigations obtained when studying reactivity temperature coefficients (RTC) in uranium-water assemblies with rho/sub H//rho/sub 5/ approx 130 depending on the way of positing the gadolinium burnable poison rod...

V. S. Bykovskij M. N. Lantsov V. I. Lependin O. I. Makarov V. I. Matveenko

1986-01-01

370

Ammonia and ammonium hydroxide sensors for ammonia/water absorption machines: Literature review and data compilation.  

National Technical Information Service (NTIS)

This report describes an evaluation of various sensing techniques for determining the ammonia concentration in the working fluid of ammonia/water absorption cycle systems. The purpose of this work was to determine if any existing sensor technology or inst...

N. C. Anheier C. E. McDonald J. M. Cuta F. M. Cuta K. B. Olsen

1995-01-01

371

Optoacoustic measurements of water vapor absorption at selected CO laser wavelengths in the 5-micron region  

NASA Technical Reports Server (NTRS)

Measurements of water vapor absorption were taken with a resonant optoacoustical detector (cylindrical pyrex detector, two BaF2 windows fitted into end plates at slight tilt to suppress Fabry-Perot resonances), for lack of confidence in existing spectral tabular data for the 5-7 micron region, as line shapes in the wing regions of water vapor lines are difficult to characterize. The measurements are required for air pollution studies using a CO laser, to find the differential absorption at the wavelengths in question due to atmospheric constituents other than water vapor. The design and performance of the optoacoustical detector are presented. Effects of absorption by ambient NO are considered, and the fixed-frequency discretely tunable CO laser is found suitable for monitoring urban NO concentrations in a fairly dry climate, using the water vapor absorption data obtained in the study.

Menzies, R. T.; Shumate, M. S.

1976-01-01

372

Terahertz absorption spectrum of water vapor at different humidity at room temperature  

NASA Astrophysics Data System (ADS)

We measured the absorption spectrum of water vapor in 0.2-2.4THz range at different humidity from 17% to 98% at room temperature using Er: doped fiber laser (IMRA America Inc.) based terahertz time-domain spectroscopy. The experiments were performed in a nitrogen-purged cage at atmosphere environment to obtain the reference and water absorption information. The seventeen absorption lines were observed due to water molecular rotations in the ground vibration state. The first three absorption lines at low frequencies increase with humidity, following the Beer-Lambert Law, while some of high frequency lines were found to decrease with humidity. These effects will be discussed. The observed line broadening is due to collisions occurring among water and nitrogen molecules.

Xin, Xuying; Altan, Hakan; Matten, David; Saint, Angelamaria; Alfano, Robert

2006-03-01

373

EV-13 Helium Valve Discharge Coefficient Characterization by Continuous Water Flow Test  

NASA Astrophysics Data System (ADS)

In this project, the students of the Suborbital Center of Excellence characterized the discharge coefficient of a modified NASA scientific Balloon valve using a water channel that was designed and built by the students specifically to test this valve. This coefficient is used in the balloon flight models (SINBAD) to predict the helium discharge rates at various altitudes and appropriate helium vent durations. Previous phases of the project subjected the valve to both highly transient and steady air flows resulting in a relatively small range of possible discharge coeffi- cient values that compared well to previous tests of the EV-13 valve. In this test, water is to be used as the working fluid because there will be fewer variables in the equation. Fewer equation variables translate to an error rate smaller than some of the previous test phases. Additionally, the authors present a detailed error/uncertainty analysis, description of the test setup, experimental procedures, calculations, results from previous phases, and literature searches.

Walker, Seth

374

Remote sensing of the diffuse attenuation coefficient of ocean water. [coastal zone color scanner  

NASA Technical Reports Server (NTRS)

A technique was devised which uses remotely sensed spectral radiances from the sea to assess the optical diffuse attenuation coefficient, K (lambda) of near-surface ocean water. With spectral image data from a sensor such as the coastal zone color scanner (CZCS) carried on NIMBUS-7, it is possible to rapidly compute the K (lambda) fields for large ocean areas and obtain K "images" which show synoptic, spatial distribution of this attenuation coefficient. The technique utilizes a relationship that has been determined between the value of K and the ratio of the upwelling radiances leaving the sea surface at two wavelengths. The relationship was developed to provide an algorithm for inferring K from the radiance images obtained by the CZCS, thus the wavelengths were selected from those used by this sensor, viz., 443, 520, 550 and 670 nm. The majority of the radiance arriving at the spacecraft is the result of scattering in the atmospheric and is unrelated to the radiance signal generated by the water. A necessary step in the processing of the data received by the sensor is, therefore, the effective removal of these atmospheric path radiance signals before the K algorithm is applied. Examples of the efficacy of these removal techniques are given together with examples of the spatial distributions of K in several ocean areas.

Austin, R. W.

1981-01-01

375

Estimating phospholipid membrane-water partition coefficients using comprehensive two-dimensional gas chromatography.  

PubMed

Recent studies have shown that membrane-water partition coefficients of organic chemicals can be used to predict bioaccumulation and type I narcosis toxicity more accurately than the traditional K(OW)-based approach. In this paper, we demonstrate how comprehensive two-dimensional gas chromatography (GC × GC) can be used to estimate such membrane-water partition coefficients (K(PLW)s), focusing in particular on phosphatidyl choline based lipids. This method performed well for a set of 38 compounds, including polycyclic aromatic hydrocarbons, polychlorinated benzenes and biphenyls, and substituted benzenes including some phenols and anilines. The average difference between the estimated and the measured log K(PLW) values of 0.47 log units is smaller than in the case of a log K(OW) correlation approach but larger than seen using a polyparameter linear free energy relationship based approach. However, the GC × GC based method presents the advantage that it can be applied to mixtures of chemicals that are not completely identified, such as petroleum hydrocarbon mixtures. At the same time, our application of the GC × GC method suffered larger errors when applied to certain hydrogen bonding compounds due to the inability of the GC × GC capillary columns phases that we used to interact with analytes via hydrogen bond donation/electron acceptance. PMID:22397714

Tcaciuc, A Patricia; Nelson, Robert K; Reddy, Christopher M; Gschwend, Philip M

2012-03-20

376

Determination of the sticking coefficient and scattering dynamics of water on ice using molecular beam techniques  

NASA Astrophysics Data System (ADS)

The sticking coefficient for D2O impinging on crystalline D2O ice was determined for incident translational energies between 0.3 and 0.7 eV and for H2O on crystalline H2O ice at 0.3 eV. These experiments were done using directed molecular beams, allowing for precise control of the incident angle and energy. Experiments were also performed to measure the intensity and energy of the scattered molecules as a function of scattering angle. These results show that the sticking coefficient was near unity, slightly increasing with decreasing incident energy. However, even at the lowest incident energy, some D2O did not stick and was scattered from the ice surface. We observe under these conditions that the sticking probability asymptotically approaches but does not reach unity for water sticking on water ice. We also present evidence that the scattered fraction is consistent with a binary collision; the molecules are scattered promptly. These results are especially relevant for condensation processes occurring under nonequilibrium conditions, such as those found in astrophysical systems.

Gibson, K. D.; Killelea, Daniel R.; Yuan, Hanqiu; Becker, James S.; Sibener, S. J.

2011-01-01

377

Pressure-broadening and narrowing coefficients and temperature dependence measurements of CO2 at 2.68 ?m by laser diode absorption spectroscopy for atmospheric applications  

NASA Astrophysics Data System (ADS)

By using a tunable diode laser absorption spectrometer in conjunction with a cryogenically cooled multipath cell, we have revisited the air-induced pressure-broadening coefficients and the narrowing coefficients related to the Dicke effect, as well as the temperature dependences, for the R(18) and R(20) lines of the (1 0° 1)I ? (0 0° 0) vibrational band at 2.68 ?m of carbon dioxide. The selected transitions are used to probe in situ CO2 in the troposphere and the lower stratosphere by using balloon-borne laser sensors. The achieved measurements are thoroughly compared to existing former determinations. The impact of processing the in situ atmospheric CO2 spectra with this new set of molecular data is reported.

Ghysels, M.; Durry, G.; Amarouche, N.

2013-04-01

378

Determination of the absorption and scattering coefficients of highly scattering media from the experimentally established temporal distributions of laser pulse intensities  

SciTech Connect

The passage of laser radiation through a scattering medium is studied experimentally. A method of determining the optical characteristics of a scattering media is proposed. The method is based on the measurements of time distributions of the intensity of ultrashort laser pulses for two layer thicknesses of the medium to be studied. The measurements are carried out with the use of a single-photon counting system. The proposed method is used to determine the absorption and scattering coefficients of a model medium from the experimental data.

Danilov, A. A.; Tereshchenko, S. A., E-mail: tsa@miee.ru; P'yanov, I. V.; Gavrikov, A. I. [Moscow State Institute of Electronic Technology (Technical University) (Russian Federation)

2011-12-15

379

Absorption refrigeration method with alternative water-ammonia solution circulation system for microelectronics cooling  

Microsoft Academic Search

The study develops an analytical model of an optimized small scale absorption ammonia\\/water refrigeration system, designed to fit smaller scale power electronics, using a pump to circulate the binary ammonia-water solution cooling agent in the proposed miniaturized system. This continues the authors' previous study of a refrigeration absorption system, by replacing the thermo-siphon and gravitational based circulation of the compensatory

Victor Chiriac; Florea Chiriac

2010-01-01

380

RF Design, Power Handling, and Hot Switching of Waveguide Water-Based Absorptive Switches  

Microsoft Academic Search

This paper presents the first complete water-based waveguide absorptive switch from 25-40 GHz integrated with commercially available micropumps. The design exploits the absorptive properties of water in the microwave and millimeter-wave bands along with innovative techniques to achieve an optimized performance in both switching states. Besides its static RF performance, the hot-switching response is also experimentally characterized. Successful hot-switching measurements

Chung-Hao Chen; Dimitrios Peroulis

2009-01-01

381

Evaluation of the effects of water agitation by air injection and water recirculation on the heat transfer coefficients in immersion cooling  

Microsoft Academic Search

Most industrial food cooling is performed by air blast, water spraying and immersion cooling. Immersion cooling is simple, with low operational cost and leads to food quick cooling. The objective of this work was to investigate the influence of water agitation method (water injection, air injection and water injection coupled to a Venturi ejector) on the average heat transfer coefficient

J. B. Laurindo; B. A. M. Carciofi; R. R. Silva; C. E. Dannenhauer; H. Hense

2010-01-01

382

Linear and nonlinear optical absorption coefficients and refractive index changes of a spherical quantum dot placed at the center of a cylindrical nano-wire: Effects of hydrostatic pressure and temperature  

NASA Astrophysics Data System (ADS)

The combined effects of hydrostatic pressure and temperature on the optical absorption coefficients and refractive index changes of an InAs spherical quantum dot which is located at the center of a GaAs cylindrical nano-wire have been investigated. The wave functions and corresponding eigenvalues are calculated using finite element method in the framework of effective mass approximation. Analytical expressions for the linear and third order nonlinear optical absorption coefficients and refractive index changes are obtained by means of the compact-density matrix formalism. The linear and third order nonlinear absorption coefficient and refractive index changes are presented as a function of the photon energy, dot radius, pressure, temperature, incident photon intensity and relaxation time. It is found from our calculations that the linear and third order nonlinear optical absorption coefficients, refractive index changes and resonance energy are quite sensitive to the dot size, applied hydrostatic pressure and temperature.

Akbarnavaz Farkoush, B.; Safarpour, Gh.; Zamani, A.

2013-07-01

383

Water absorption by secondary organic aerosol and its effect on inorganic aerosol behavior  

SciTech Connect

The hygroscopic nature of atmospheric aerosol has generally been associated with its inorganic fraction. In this study, a group contribution method is used to predict the water absorption of secondary organic aerosol (SOA). Compared against growth measurements of mixed inorganic-organic particles, this method appears to provide a first-order approximation in predicting SOA water absorption. The growth of common SOA species is predicted to be significantly less than common atmospheric inorganic salts such as (NH{sub 4}){sub 2}SO{sub 4} and NaCl. Using this group contribution method as a tool in predicting SOA water absorption, an integrated modeling approach is developed combining available SOA and inorganic aerosol models to predict overall aerosol behavior. The effect of SOA on water absorption and nitrate partitioning between the gas and aerosol phases is determined. On average, it appears that SOA accounts for approximately 7% of total aerosol water and increases aerosol nitrate concentrations by approximately 10%. At high relative humidity and low SOA mass fractions, the role of SOA in nitrate partitioning and its contribution to total aerosol water is negligible. However, the water absorption of SOA appears to be less sensitive to changes in relative humidity than that of inorganic species, and thus at low relative humidity and high SOA mass fraction concentrations, SOA is predicted to account for approximately 20% of total aerosol water and a 50% increase in aerosol nitrate concentrations. These findings could improve the results of modeling studies where aerosol nitrate has often been underpredicted.

Ansari, A.S.; Pandis, S.N.

2000-01-01

384

A WATER VAPOR MONITOR USING DIFFERENTIAL INFRARED ABSORPTION  

EPA Science Inventory

A water vapor monitor has been developed with adequate sensitivity and versatility for a variety of applications. Two applications for which the instrument has been designed are the continuous monitoring of water in ambient air and the measuring of the mass of water desorbed from...

385

Activity of Water and Osmotic Coefficients of Histidine Derivatives in Aqueous Solutions at 310.15 K  

Microsoft Academic Search

From the data of vapor pressure osmometry the activity of water, osmotic coefficients, and the values of activity coefficients\\u000a of two derivatives of histidine: N-Boc-L-histidine (Boc-His-OH, m=0.005–0.14 mol?kg?1) and N-Boc-L-histidine-methyl ether (Boc-His-OMe, m=0.005–0.05 mol?kg?1) are obtained in aqueous solutions at 310.15 K. From the comparison of water activity and osmotic coefficient values it follows\\u000a that Boc-His-OMe shows a more pronounced deviation from

Elena N. Tsurko; Roland Neueder; Werner Kunz

2008-01-01

386

Determination of the water vapor continuum absorption by THz-TDS and Molecular Response Theory.  

PubMed

Determination of the water vapor continuum absorption from 0.35 to 1 THz is reported. The THz pulses propagate though a 137 m long humidity-controlled chamber and are measured by THz time-domain spectroscopy (THz-TDS). The average relative humidity along the entire THz path is precisely obtained by measuring the difference between transit times of the sample and reference THz pulses to an accuracy of 0.1 ps. Using the measured total absorption and the calculated resonance line absorption with the Molecular Response Theory lineshape, based on physical principles and measurements, an accurate continuum absorption is obtained within four THz absorption windows, that agrees well with the empirical theory. The absorption is significantly smaller than that obtained using the van Vleck-Weisskopf lineshape with a 750 GHz cut-off. PMID:24663762

Yang, Yihong; Mandehgar, Mahboubeh; Grischkowsky, D

2014-02-24

387

Rate coefficient of the O + H 2 = OH + H reaction determined via shock tube-laser absorption spectroscopy  

Microsoft Academic Search

The rate coefficient for the reaction O + H2 = OH + H was determined via OH profile measurements in a lean H2\\/O2\\/Ar mixture behind reflected shock waves. Over the temperature range 1424–2427 K our expression is k2 = (1.88 ± 0.07) × 1014 exp(?6897 ± 53 K\\/T) cm3 mol?1 s?1. We do not support strong curvature in the rate

Si-Ok Ryu; Soon Muk Hwang; Martin Jay Rabinowitz

1995-01-01

388

Donor impurity-related linear and nonlinear intraband optical absorption coefficients in quantum ring: effects of applied electric field and hydrostatic pressure  

PubMed Central

The linear and nonlinear intraband optical absorption coefficients in GaAs three-dimensional single quantum rings are investigated. Taking into account the combined effects of hydrostatic pressure and electric field, applied along the growth direction of the heterostructure, the energies of the ground and first excited states of a donor impurity have been found using the effective mass approximation and a variational method. The energies of these states are examined as functions of the dimensions of the structure, electric field, and hydrostatic pressure. We have also investigated the dependencies of the linear, nonlinear, and total optical absorption coefficients as a function of incident photon energy for several configurations of the system. It is found that the variation of distinct sizes of the structure leads to either a redshift and/or a blueshift of the resonant peaks of the intraband optical spectrum. In addition, we have found that the application of an electric field leads to a redshift, whereas the influence of hydrostatic pressure leads to a blueshift (in the case of on-ring-center donor impurity position) of the resonant peaks of the intraband optical spectrum.

2012-01-01

389

Measurement of the x-ray mass energy-absorption coefficient of air using 3 keV to 10 keV synchrotron radiation.  

PubMed

For the first time absolute photon mass energy-absorption coefficients of air in the energy range 3 keV to 10 keV have been measured with relative standard uncertainties less than 1%, significantly smaller than those of up to 5% assumed hitherto for calculated data. Monochromatized synchrotron radiation was used to measure both the total radiant energy by means of silicon photodiodes calibrated against a cryogenic radiometer and the fraction of radiant energy that is deposited in dry air by means of a free air ionization chamber. The measured ionization charge was converted into energy absorbed in air by calculated effective W values of photons as a function of their energy based on new measurements of the W values in dry air for electron kinetic energies between 1 keV and 7 keV, also presented in this work. The measured absorption coefficients were compared with state-of-the art calculations and found to agree within 0.7% with data calculated earlier by Hubbell at energies above 4 keV but were found to differ by values up to 2.1% at 10 keV from more recent calculations of Seltzer. PMID:17019029

Büermann, L; Grosswendt, B; Kramer, H-M; Selbach, H-J; Gerlach, M; Hoffmann, M; Krumrey, M

2006-10-21

390

Determination of the reaction rate coefficient of sulphide mine tailings deposited under water.  

PubMed

The efficiency of a water cover to limit dissolved oxygen (DO) availability to underlying acid-generating mine tailings can be assessed by calculating the DO flux at the tailings-water interface. Fick's equations, which are generally used to calculate this flux, require knowing the effective DO diffusion coefficient (Dw) and the reaction (consumption) rate coefficient (Kr) of the tailings, or the DO concentration profile. Whereas Dw can be accurately estimated, few studies have measured the parameter Kr for submerged sulphide tailings. The objective of this study was to determine Kr for underwater sulphide tailings in a laboratory experiment. Samples of sulphide mine tailings (an approximately 6 cm layer) were placed in a cell under a water cover (approximately 2 cm) maintained at constant DO concentration. Two tailings were studied: TA1 with high sulphide content (83% pyrite) and TA2 with low sulphide content (2.8% pyrite). DO concentration was measured with a microelectrode at various depths above and below the tailings-water interface at 1 mm intervals. Results indicate that steady-state condition was rapidly attained. As expected, a diffusive boundary layer (DBL) was observed in all cases. An iterative back-calculation process using the numerical code POLLUTEv6 and taking the DBL into account provided the Kr values used to match calculated and experimental concentration profiles. Kr obtained for tailings TA1 and TA2 was about 80 d(-1) and 6.5 d(-1), respectively. For comparison purposes, Kr obtained from cell tests on tailings TA1 was lower than Kr calculated from the sulphate production rate obtained from shake-flask tests. Steady-state DO flux at the water-tailings interface was then calculated with POLLUTEv6 using tailings characteristics Dw and Kr. For the tested conditions, DO flux ranged from 608 to 758 mg O2/m(2)/d for tailings TA1 and from 177 to 221 mg O2/m(2)/d for tailings TA2. The impact of placing a protective layer of inert material over the tailings was also investigated for tailings TA1 (with high sulphide content). A protective layer of only 5 cm reduced the DO flux into the tailings at about 5 mg/m(2)/d, compared to 608 mg O2/m(2)/d without a protective layer, or an approximately 99% reduction in flux. PMID:23906653

Awoh, Akué Sylvette; Mbonimpa, Mamert; Bussière, Bruno

2013-10-15

391

Interrelation between the crystallinity of polysaccharides and water absorption  

NASA Astrophysics Data System (ADS)

The maximum sorption of water and its vapors is calculated using experimental data from calorimetric and effusion studies of flax, wood, and cotton cellulose. X-day diffraction is used to determine the crystallinity of cellulose samples. The equations relating crystallinity ( X) with maximum sorption and the enthalpy of interaction between cellulose and water are presented. Experimental results and the literature data on water sorption by chitin, chitosan and other polysaccharides show that our equations for calculating crystallinity are correct.

Prusov, A. N.; Prusova, S. M.; Radugin, M. V.; Zakharov, A. G.

2014-05-01

392

Water absorption in polyethylene under external electric fields.  

PubMed

Monte Carlo simulations of the solubility and structure of water in polyethylene in thermodynamic equilibrium with liquid water were performed in external fields ranging from 2 x 10(5) to 4 x 10(9) V/m. For a given equilibrium temperature and pressure, the water solubility decreases at higher fields. This occurs since it is energetically favorable for water molecules to be in the pure water phase than in the polyethylene matrix at high field strengths, and results in an increased density in the water phase. However, fields relevant to high voltage conduction (in the absence of defects that can lead to large local field strengths) do not change the solubility. In addition, at large fields the number of water clusters decreases for all cluster sizes. The rate of decrease is highest for large clusters, and a larger fraction of water molecules exist as monomers in the polyethylene matrix at high fields. Large fields also cause alignment of the water molecules, which leads to more clusters with linear topologies and hence an increase in the cluster radius of gyration. PMID:17640146

Johansson, E; Bolton, K; Ahlström, P

2007-07-14

393

Predicting infinite dilution activity coefficients of organic compounds in water by quantum-connectivity descriptors.  

PubMed

Quantitative structure-property relationship (QSPR) models are developed to predict the logarithm of infinite dilution activity coefficient of hydrocarbons, oxygen containing organic compounds and halogenated hydrocarbons in water at 298.15 K. The description of the molecular structure in terms of quantum-connectivity descriptors allows to obtain more simple QSPR models because of the quantum-chemical and topological information coded in this type of descriptors. The models developed in this paper have fewer descriptors and better statistics than other models reported in literature. The current models allow a more transparent physical interpretation of the phenomenon in terms of intermolecular interactions which occur in solution and which explain the respective deviations from ideality. PMID:17051339

Estrada, Ernesto; Díaz, Gerardo A; Delgado, Eduardo J

2006-09-01

394

Methane-water cross second virial coefficient with quantum corrections from an ab initio potential  

NASA Astrophysics Data System (ADS)

We present our calculations of the cross second virial coefficient (B12) and of a related quantity, ?12=B12-TdB12/dT, for the methane-water system in the temperature range T=200-1000 K. These calculations were performed using one of the ab initio potentials developed in previous work [Akin-Ojo and Szalewicz, J. Chem. Phys. 123, 134311 (2005)]. Quantum corrections of order ?2 were added to the computed classical values. We have estimated the uncertainties in our computed B12 and ?12(T). This allowed evaluation of the quality of the experimental data to which we compare our results. We also provide an analytical expression for B12(T) as a function of the temperature T obtained by fitting the calculated values. This formula also predicts values of ?12(T) consistent with the directly calculated values.

Akin-Ojo, Omololu; Harvey, Allan H.; Szalewicz, Krzysztof

2006-07-01

395

PAMPA--a drug absorption in vitro model 8. Apparent filter porosity and the unstirred water layer.  

PubMed

In the parallel artificial membrane permeability assay (PAMPA), if more lipid is used than needed to fill all the pores of a microfilter, the excess lipid layer on both sides of the lipophilic filter increases the "apparent" porosity, epsilon(a), of the filter. The specific resistance of the artificial membrane barrier is lowered with increasing lipid excess. If this effect is not recognized, and the uncorrected value of filter porosity, epsilon, is used, then the calculated intrinsic permeability and the unstirred water layer (UWL) permeability coefficient of the permeating molecule can be significantly overestimated, resulting in underestimates of the thickness of the unstirred water layer. Unstirred water layer corrections are important in pharmaceutical research for in vitro-in vivo correlations aimed at predicting oral absorption and blood-brain barrier penetration characteristics of lead candidate compounds. The novel concept of the apparent porosity is introduced, described, and its utility demonstrated with the drugs diclofenac, desipramine, caffeine, and piroxicam. The PAMPA data of Wohnsland and Faller [J. Med. Chem. 44 (2001) 923] is taken as an example, where the reported extraordinarily efficient stirring is thought to be better explained in terms of normal stirring when apparent porosity is taken into account in the calculation of the effective permeability coefficient. PMID:15113581

Nielsen, Per E; Avdeef, Alex

2004-05-01

396

A new method for retrieval of the extinction coefficient of water clouds by using the tail of the CALIOP signal  

Microsoft Academic Search

A method is developed based on Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) level 1 attenuated backscatter profile data for deriving the mean extinction coefficient of water droplets close to cloud top. The method is applicable to low level (cloud top <2 km), opaque water clouds in which the lidar signal is completely attenuated beyond about 100 m of

J. Li; Y. Hu; J. Huang; K. Stamnes; Y. Yi; S. Stamnes

2011-01-01

397

A new method for retrieval of the extinction coefficient of water clouds by using the tail of the CALIOP signal  

Microsoft Academic Search

A method is developed based on Cloud-Aerosol Lidar and Infrared Pathfinder Satellite Observations (CALIPSO) level 1 attenuated backscatter profile data for deriving the mean extinction coefficient of water droplets close to cloud top. The method is applicable to low level (cloud top < 2 km), opaque water clouds in which the lidar signal is completely attenuated beyond about 100 m

J. Li; Y. Hu; J. Huang; K. Stamnes; Y. Yi

2010-01-01

398

Dynamics of Water Absorption and Evaporation During Methanol Droplet Combustion in Microgravity  

NASA Technical Reports Server (NTRS)

The combustion of methanol droplets is profoundly influenced by the absorption and evaporation of water, generated in the gas phase as a part of the combustion products. Initially there is a water-absorption period of combustion during which the latent heat of condensation of water vapor, released into the droplet, enhances its burning rate, whereas later there is a water-evaporation period, during which the water vapor reduces the flame temperature suffciently to extinguish the flame. Recent methanol droplet-combustion experiments in ambient environments diluted with carbon dioxide, conducted in the Combustion Integrated Rack on the International Space Station (ISS), as a part of the FLEX project, provided a method to delineate the water-absorption period from the water-evaporation period using video images of flame intensity. These were obtained using an ultra-violet camera that captures the OH* radical emission at 310 nm wavelength and a color camera that captures visible flame emission. These results are compared with results of ground-based tests in the Zero Gravity Facility at the NASA Glenn Research Center which employed smaller droplets in argon-diluted environments. A simplified theoretical model developed earlier correlates the transition time at which water absorption ends and evaporation starts. The model results are shown to agree reasonably well with experiment.

Hicks, Michael C.; Dietrich, Daniel L.; Nayagam, Vedha; Williams, Forman A.

2012-01-01

399

The importance of the ammonia purification process in ammonia–water absorption systems  

Microsoft Academic Search

Practical experience in working with ammonia–water absorption systems shows that the ammonia purification process is a crucial issue in order to obtain an efficient and reliable system. In this paper, the detrimental effects of the residual water content in the vapour refrigerant are described and quantified based on the system design variables that determine the effectiveness of the purification process.

José Fernández-Seara; Jaime Sieres

2006-01-01

400

Methods for analysis of selected metals in water by atomic absorption  

USGS Publications Warehouse

This manual describes atomic-absorption-spectroscopy methods for determining calcium, copper, lithium, magnesium, manganese, potassium, sodium, strontium and zinc in atmospheric precipitation, fresh waters, and brines. The procedures are intended to be used by water quality laboratories of the Water Resources Division of the U.S. Geological Survey. Detailed procedures, calculations, and methods for the preparation of reagents are given for each element along with data on accuracy, precision, and sensitivity. Other topics discussed briefly are the principle of atomic absorption, instrumentation used, and special analytical techniques.

Fishman, Marvin J.; Downs, Sanford C.

1966-01-01

401

Computer simulation and optimization of ammonia-water absorption refrigeration systems  

SciTech Connect

The ammonia-water absorption refrigeration system is attracting increasing research interests, since the system can be powered by waste thermal energy, thus avoiding using ozone-depletion refrigerants and reducing demand on electricity supply. In the article, a mathematical model coupled with detailed equations for thermodynamic properties of an ammonia-water mixture is described. A computer simulation software based on the model is developed. With the software, the performance characteristics of ammonia-water absorption refrigeration systems are analyzed, and detailed optimum operation maps for the systems are presented. These maps can be used as guides in choosing operating conditions for designing such systems or for existing systems.

Sun, D.W. [National Univ. of Ireland, Dublin (Ireland)

1997-08-01

402

Mouse organ coefficient and abnormal sperm rate analysis with exposure to tap water and source water in Nanjing reach of Yangtze River.  

PubMed

Organ coefficients (including kidney, testis, liver and spleen coefficient) and abnormal sperm rate were used in our study to reflect the exposure to the Yangzte River water. The concentrations of total dissolved metals and semi-volatile organic compounds in tap and source water were measured by ICP-OES and GC-MS, respectively. After mice were fed with purified water (CK), Nanjing tap water (NJT) and Nanjing source water (NJS) for 90 day, the individual and organs (including kidney, testis, liver and spleen) of each mouse were weighted. And abnormal sperm types (such as hook less, banana-like form, amorphous, folded and two tails) were determined by microscope. The results showed that significant differences of liver coefficient between experimental group (NJT, NJS) and control group (CK) were observed; furthermore liver coefficient is positive correlation with the concentrations of total dissolved metals. However, no significant differences of abnormal sperm rates between experimental group (NJT, NJS) and control group (CK) were noted. So liver coefficient might be more sensitive than other organ coefficients to reflect the exposure to tap water and source water, while abnormal sperm rate could not be used to reveal the exposure to them. PMID:24664459

Zhang, Rongfei; Zhang, Liujun; Jiang, Dongsheng; Zheng, Kai; Cui, Yibin; Li, Mei; Wu, Bing; Cheng, Shupei

2014-05-01

403

Intestinal absorption of water-soluble vitamins in health and disease  

PubMed Central

Our knowledge of the mechanisms and regulation of intestinal absorption of water-soluble vitamins under normal physiological conditions, and of the factors/conditions that affect and interfere with theses processes has been significantly expanded in recent years as a result of the availability of a host of valuable molecular/cellular tools. Although structurally and functionally unrelated, the water-soluble vitamins share the feature of being essential for normal cellular functions, growth and development, and that their deficiency leads to a variety of clinical abnormalities that range from anaemia to growth retardation and neurological disorders. Humans cannot synthesize water-soluble vitamins (with the exception of some endogenous synthesis of niacin) and must obtain these micronutrients from exogenous sources. Thus body homoeostasis of these micronutrients depends on their normal absorption in the intestine. Interference with absorption, which occurs in a variety of conditions (e.g. congenital defects in the digestive or absorptive system, intestinal disease/resection, drug interaction and chronic alcohol use), leads to the development of deficiency (and sub-optimal status) and results in clinical abnormalities. It is well established now that intestinal absorption of the water-soluble vitamins ascorbate, biotin, folate, niacin, pantothenic acid, pyridoxine, riboflavin and thiamin is via specific carrier-mediated processes. These processes are regulated by a variety of factors and conditions, and the regulation involves transcriptional and/or post-transcriptional mechanisms. Also well recognized now is the fact that the large intestine possesses specific and efficient uptake systems to absorb a number of water-soluble vitamins that are synthesized by the normal microflora. This source may contribute to total body vitamin nutrition, and especially towards the cellular nutrition and health of the local colonocytes. The present review aims to outline our current understanding of the mechanisms involved in intestinal absorption of water-soluble vitamins, their regulation, the cell biology of the carriers involved and the factors that negatively affect these absorptive events.

Said, Hamid M.

2014-01-01

404

Transfer Coefficients of Momentum, Heat and Water Vapour in the Atmospheric Surface Layer of a Large Freshwater Lake  

NASA Astrophysics Data System (ADS)

In studies of lake-atmosphere interactions, the fluxes of momentum, water vapour and sensible heat are often parametrized as being proportional to the differences in wind, humidity and air temperature between the water surface and a reference height above the surface. Here, the proportionality via transfer coefficients in these relationships was investigated with the eddy-covariance method at three sites within an eddy-covariance mesonet across Lake Taihu, China. The results indicate that the transfer coefficients decreased with increasing wind speed for weak winds and approached constant values for strong winds. The presence of submerged macrophytes reduced the momentum transfer (drag) coefficient significantly. At the two sites free of submerged macrophytes, the 10-m drag coefficients under neutral stability were 1.8 and at the wind speed of , which are 38 and 34 % greater than the prediction by the Garratt model for the marine environment.

Xiao, Wei; Liu, Shoudong; Wang, Wei; Yang, Dong; Xu, Jiaping; Cao, Chang; Li, Hanchao; Lee, Xuhui

2013-09-01

405

Assessment of an ammonia-water type absorption system as a heat pump  

Microsoft Academic Search

Traditionally, the application of an absorption system for use as a heat pump has been the adaptation of an existing cooling unit to function in the heating mode. The thermodynamic behavior of an ammonia-water type absorption system specifically designed to function as an air-to-air heater is discussed. The fluid flow pattern selected attempts to be consistent with actual machines. System

W. F. Rush; S. A. Weil

1976-01-01

406

Water vapour foreign-continuum absorption in near-infrared windows from laboratory measurements.  

PubMed

For a long time, it has been believed that atmospheric absorption of radiation within wavelength regions of relatively high infrared transmittance (so-called 'windows') was dominated by the water vapour self-continuum, that is, spectrally smooth absorption caused by H(2)O--H(2)O pair interaction. Absorption due to the foreign continuum (i.e. caused mostly by H(2)O--N(2) bimolecular absorption in the Earth's atmosphere) was considered to be negligible in the windows. We report new retrievals of the water vapour foreign continuum from high-resolution laboratory measurements at temperatures between 350 and 430?K in four near-infrared windows between 1.1 and 5??m (9000-2000?cm(-1)). Our results indicate that the foreign continuum in these windows has a very weak temperature dependence and is typically between one and two orders of magnitude stronger than that given in representations of the continuum currently used in many climate and weather prediction models. This indicates that absorption owing to the foreign continuum may be comparable to the self-continuum under atmospheric conditions in the investigated windows. The calculated global-average clear-sky atmospheric absorption of solar radiation is increased by approximately 0.46?W?m(-2) (or 0.6% of the total clear-sky absorption) by using these new measurements when compared with calculations applying the widely used MTCKD (Mlawer-Tobin-Clough-Kneizys-Davies) foreign-continuum model. PMID:22547232

Ptashnik, Igor V; McPheat, Robert A; Shine, Keith P; Smith, Kevin M; Williams, R Gary

2012-06-13

407

Water diffusion coefficients of horizontal soil columns from natural saline-alkaline wetlands in a semiarid area  

Microsoft Academic Search

Water diffusion coefficients of soils directly control the solute (such as nitrogen and phosphorous) movement in wetlands,\\u000a which greatly influences the water quality of rivers. The processes of water diffusion in natural saline-alkaline wetland\\u000a soils were simulated by using horizontal soil columns from the Erbaifangzi (EBFZ) wetland in the Xianghai National Natural\\u000a Reserve of China in 2001. The results showed

Junhong Bai; Wei Deng; Baoshan Cui; Hua Ouyang

2007-01-01

408

The distribution coefficients of phenol and substituted phenols in the ammonium sulfate-poly-N-vinylpyrrolidone-water system  

NASA Astrophysics Data System (ADS)

The extraction of phenols from water-salt solutions was performed using a water-soluble polymer (poly-N-vinylpyrrolidone). The distribution coefficients, the degree of extraction of 13 phenols, and interrelation between the extraction characteristics and structure of distributed compounds were determined. The conditions of the process were optimized to provide maximum extraction of phenols by poly-N-vinylpyrrolidone from water-salt solutions.

Churilina, E. V.; Sukhanov, P. T.; Korenman, Ya. I.; Il'in, A. N.; Shatalov, G. V.; Bolotov, V. M.

2011-04-01

409

Low-Dimensional Water on Ru(0001)Model System for X-ray Absorption Spectroscopy Studies of Liquid Water  

SciTech Connect

We present an x-ray absorption spectroscopy results for fully broken to a complete H-bond network of water molecules on Ru(0001) by varying the morphology from isolated water molecules via two-dimensional clusters to a fully covered monolayer as probed by scanning tunneling microscopy. The sensitivity of x-ray absorption to the symmetry of H-bonding is further elucidated for the amino (-NH{sub 2}) group in glycine adsorbed on Cu(110) where the E-vector is parallel either to the NH donating an H-bond or to the non-H-bonded NH. The results give further evidence for the interpretation of the various spectral features of liquid water and for the general applicability of x-ray absorption spectroscopy to analyze H-bonded systems.

Nordlund, D

2012-02-14

410

Development of an Integrating Cavity Absorption Meter to Measure Optical Absorption of Pure Waters and Suspended Particulates.  

National Technical Information Service (NTIS)

The Integrating Cavity Absorption Meter (ICAM) provides an instrument capable of measuring optical absorption independent of scattering effects. The measurement of optical absorption has always been complicated by scattering effects. The most common and p...

R. M. Pope

1990-01-01

411

Impact of MIE-Resonances on the Atmospheric Absorption of Water Clouds  

NASA Technical Reports Server (NTRS)

Clouds strongly modulate radiative transfer processes in the Earth's atmosphere. Studies, which simulate bulk properties of clouds, such as absorption, require methods that accurately account for multiple scattering among individual cloud particles. Multiple scattering processes are well described by MIE-theory, if interacting particles have a spherical shape. This is a good assumption for water droplets. Thus, simulations for water clouds (especially for interactions with solar radiation) usually apply readily available MIE-codes. The presence of different drop-sizes, however, necessitates repetitive calculations for many sizes. The usual representation by a few sizes is likely to miss contributions from densely distributed, sharp resonances. Despite their usually narrow width, integrated over the entire size-spectrum of a cloud droplet distribution, the impact of missed resonances could add up. The consideration of these resonances tends to increase cloud extinction and cloud absorption. This mechanism for a larger (than by MIE-methods predicted) solar absorption has the potential to explain observational evidence of larger than predicted cloud absorption at solar wavelengths. The presentation will address the absorption impact of added resonances for typical properties of water clouds (e.g. drop size distributions, drop concentrations and cloud geometry). Special attention will be given to scenarios with observational evidence of law than simulated solar absorption; particularly if simultaneous measurements of cloud micro- and macrophysical properties are available.

Wiscombe, W.; Kinne, S.; Nussenzveig, H.; Lau, William K. M. (Technical Monitor)

2002-01-01

412

Nonlinear absorption of femtosecond laser pulses (800 nm) by atmospheric air and water vapour  

SciTech Connect

Quantitative data on the nonlinear absorption cross sections of femtosecond Ti : Sapphire laser pulses in air and water vapour have been obtained. A photoacoustic spectrometer calibrated based on the calculated value of linear absorption of laser pulses with a wavelength of 800 nm and a spectral width of 17.7 nm is used to find the nonlinear absorption cross sections of water vapour and air: {sigma}{sub 2}{sup w} = (2.6{+-}0.4) Multiplication-Sign 10{sup -55} cm{sup 4} s and {sigma}{sub 2}{sup a} = (8.7{+-}1.0) Multiplication-Sign 10{sup -56} cm{sup 4} s, respectively. Based on measuring the absorption of femtosecond Ti : Sapphire laser pulses with a photoacoustic detector calibrated with the known linear absorption of ruby laser radiation by water vapour in air, the air nonlinear absorption cross section is found to be (8.2{+-}0.9) Multiplication-Sign 10{sup -56} cm{sup 4} s.

Kiselev, A M; Ponomarev, Yu N; Stepanov, A N; Tikhomirov, A B; Tikhomirov, B A

2011-11-30

413

Towards the reanalysis of void coefficients measurements at proteus for high conversion light water reactor lattices  

SciTech Connect

High Conversion Light Water Reactors (HCLWR) allows a better usage of fuel resources thanks to a higher breeding ratio than standard LWR. Their uses together with the current fleet of LWR constitute a fuel cycle thoroughly studied in Japan and the US today. However, one of the issues related to HCLWR is their void reactivity coefficient (VRC), which can be positive. Accurate predictions of void reactivity coefficient in HCLWR conditions and their comparisons with representative experiments are therefore required. In this paper an inter comparison of modern codes and cross-section libraries is performed for a former Benchmark on Void Reactivity Effect in PWRs conducted by the OECD/NEA. It shows an overview of the k-inf values and their associated VRC obtained for infinite lattice calculations with UO{sub 2} and highly enriched MOX fuel cells. The codes MCNPX2.5, TRIPOLI4.4 and CASMO-5 in conjunction with the libraries ENDF/B-VI.8, -VII.0, JEF-2.2 and JEFF-3.1 are used. A non-negligible spread of results for voided conditions is found for the high content MOX fuel. The spread of eigenvalues for the moderated and voided UO{sub 2} fuel are about 200 pcm and 700 pcm, respectively. The standard deviation for the VRCs for the UO{sub 2} fuel is about 0.7% while the one for the MOX fuel is about 13%. This work shows that an appropriate treatment of the unresolved resonance energy range is an important issue for the accurate determination of the void reactivity effect for HCLWR. A comparison to experimental results is needed to resolve the presented discrepancies. (authors)

Hursin, M.; Koeberl, O.; Perret, G. [Paul Scherrer Institut PSI, 5232 Villigen (Switzerland)

2012-07-01

414

Determination of cost coefficients of priority-based water allocation linear programming model - a network flow approach  

NASA Astrophysics Data System (ADS)

This paper presents a method to establish the objective function of a network flow programming model for simulating river/reservoir system operations and associated water allocation, with an emphasis on situations when the links other than demand or storage have to be assigned with nonzero cost coefficients. The method preserves the priorities defined by rule curves of reservoir, operational preferences for conveying water, allocation of storage among multiple reservoirs, and trans-basin water diversions. Path enumeration analysis transforms these water allocation rules into linear constraints that can be solved to determine link cost coefficients. An approach to prune the original system into a reduced network is proposed to establish the precise constraints of nonzero cost coefficients which can then be efficiently solved. The cost coefficients for the water allocation in the Feitsui and Shihmen Reservoirs joint operating system of northern Taiwan was adequately assigned by the proposed method. This case study demonstrates how practitioners can correctly utilize network-flow-based models to allocate water supply throughout complex systems that are subject to strict operating rules.

Chou, F. N.-F.; Wu, C.-W.

2013-12-01

415

Determination of cost coefficients of a priority-based water allocation linear programming model - a network flow approach  

NASA Astrophysics Data System (ADS)

This paper presents a method to establish the objective function of a network flow programming model for simulating river-reservoir system operations and associated water allocation, with an emphasis on situations when the links other than demand or storage have to be assigned with nonzero cost coefficients. The method preserves the priorities defined by rule curves of reservoir, operational preferences for conveying water, allocation of storage among multiple reservoirs, and transbasin water diversions. Path enumeration analysis transforms these water allocation rules into linear constraints that can be solved to determine link cost coefficients. An approach to prune the original system into a reduced network is proposed to establish the precise constraints of nonzero cost coefficients, which can then be efficiently solved. The cost coefficients for the water allocation in the Feitsui and Shihmen reservoirs' joint operating system of northern Taiwan was adequately assigned by the proposed method. This case study demonstrates how practitioners can correctly utilize network-flow-based models to allocate water supply throughout complex systems that are subject to strict operating rules.

Chou, F. N.-F.; Wu, C.-W.

2014-05-01

416

Linear and nonlinear optical absorption coefficients and refractive index changes in modulation-doped quantum wells: Effects of the magnetic field and hydrostatic pressure  

NASA Astrophysics Data System (ADS)

In this study, the linear, the third-order nonlinear and total optical absorption coefficients and refractive index changes of a modulation-doped GaAs/AlxGaAs quantum well are investigated numerically. In the effective-mass approximation, the electronic structure of modulation-doped quantum well is calculated by solving the Schrödinger and Poisson equations self-consistently. Optical properties are obtained using the compact density matrix approach. The effects of structure parameters, the applied magnetic field and the hydrostatic pressure on the optical properties of the modulation-doped quantum well are studied. Results show that the resonant peaks shift toward the higher (lower) energies with the increase in the magnetic field (pressure). The magnitude of the resonant peaks of the optical properties decreases with the increasing magnetic field or pressure.

Nazari, M.; Karimi, M. J.; Keshavarz, A.

2013-11-01

417

The Effect of Heat on Structural Characteristics and Water Absorption Behavior of Agave Fibers  

NASA Astrophysics Data System (ADS)

The structural characteristics and water absorptions behavior agave fibers were investigated over a range of temperature by using XRD, IR, TG and gravimetric methods. Three distinct thermal processes were observed during heating the fiber in the temperature range 310-760 K in air, oxygen and nitrogen invariably. The cellulose structures of the fibers were unaffected on heating up to 450 K. The samples showed thermal decomposition processes beyond 500 K. Fibers displayed a two-stage diffusion behavior. The structural parameters and kinetic of water absorption of the fibers at specific temperatures were analyzed.

Saikia, Dip

2008-04-01

418

Assessment of PDMS-water partition coefficients: implications for passive environmental sampling of hydrophobic organic compounds  

USGS Publications Warehouse

Solid-phase microextraction (SPME) has shown potential as an in situ passive-sampling technique in aquatic environments. The reliability of this method depends upon accurate determination of the partition coefficient between the fiber coating and water (Kf). For some hydrophobic organic compounds (HOCs), Kf values spanning 4 orders of magnitude have been reported for polydimethylsiloxane (PDMS) and water. However, 24% of the published data examined in this review did not pass the criterion for negligible depletion, resulting in questionable Kf values. The range in reported Kf is reduced to just over 2 orders of magnitude for some polychlorinated biphenyls (PCBs) when these questionable values are removed. Other factors that could account for the range in reported Kf, such as fiber-coating thickness and fiber manufacturer, were evaluated and found to be insignificant. In addition to accurate measurement of Kf, an understanding of the impact of environmental variables, such as temperature and ionic strength, on partitioning is essential for application of laboratory-measured Kf values to field samples. To date, few studies have measured Kf for HOCs at conditions other than at 20 degrees or 25 degrees C in distilled water. The available data indicate measurable variations in Kf at different temperatures and different ionic strengths. Therefore, if the appropriate environmental variables are not taken into account, significant error will be introduced into calculated aqueous concentrations using this passive sampling technique. A multiparameter linear solvation energy relationship (LSER) was developed to estimate log Kf in distilled water at 25 degrees C based on published physicochemical parameters. This method provided a good correlation (R2 = 0.94) between measured and predicted log Kf values for several compound classes. Thus, an LSER approach may offer a reliable means of predicting log Kf for HOCs whose experimental log Kf values are presently unavailable. Future research should focus on understanding the impact of environmental variables on Kf. Obtaining the data needed for an LSER approach to estimate Kf for all environmentally relevant HOCs would be beneficial to the application of SPME as a passive-sampling technique.

DiFilippo, Erica L.; Eganhouse, Robert P.

2010-01-01

419

Estimating the absorption coefficient of the bottom layer in four-layered turbid mediums based on the time-domain depth sensitivity of near-infrared light reflectance.  

PubMed

Expanding our previously proposed "time segment analysis" for a two-layered turbid medium, this study attempted to selectively determine the absorption coefficient (?a) of the bottom layer in a four-layered human head model with time-domain near-infrared measurements. The difference curve in the temporal profiles of the light attenuation between an object and a reference medium, which are obtained from Monte Carlo simulations, is divided into segments along the time axis, and a slope for each segment is calculated to obtain the depth-dependent ?a(?aseg). The reduced scattering coefficient (?s') of the reference is determined by curve fitting with the temporal point spread function derived from the analytical solution of the diffusion equation to the time-resolved reflectance of the object. The deviation of ?aseg from the actual ?a is expressed by a function of the ratio of ?aseg in an earlier time segment to that in a later segment for mediums with different optical properties and thicknesses of the upper layers. Using this function, it is possible to determine the ?a of the bottom layer in a four-layered epoxy resin-based phantom. These results suggest that the method reported here has potential for determining the ?a of the cerebral tissue in humans. PMID:24057194

Sato, Chie; Shimada, Miho; Tanikawa, Yukari; Hoshi, Yoko

2013-09-01

420

[Determination of distribution and effective distribution coefficient of Cr3+ in LiNbO3 single crystals using UV/Visible absorption spectra and ICP].  

PubMed

The LiNbO3 crystals doped with Cr3+ ion (Cr:LN) and co-doped with Cr3+ and Zn ions (Zn:Cr:LN) were grown by the Bridgman method. The absorption coefficient and concentration of Cr3+ in crystals were measured by UV/Visible spectra and inductively coupled plasma (ICP) spectrometry, respectively. The effective distribution coefficients (k) of Cr3+ in the crystals were calculated. The results indicated that the k for Cr:LN crystal decreased from 3.75 to 2.49 as the incorporating concentration of Cr3+ increased from 0.1 to 0.5 mol%; the introduction of ZnO in Cr:LN induced the reduction of k value effectively. However, the k value increased from 1.85 to 2.25 as the incorporating concentration of ZnO increased from 3 to 6 mol%. The variation of the k value was explained by the suppressing effect of ZnO on the incorporation of Cr3+ ions and the distribution of Cr3+ in LN. PMID:16201383

Xia, Hai-ping; Wang, Jin-hao; Zeng, Xian-lin; Zhang, Jian-li; Zhang, Xin-min; Nie, Qiu-hua

2005-06-01

421

Octanol/water partition coefficient of ortho-substituted aromatic solutes.  

PubMed

The partition coefficient (P) of some mono- and di-ortho-substituted aromatic compounds was measured in a 1-octanol/water system. For each series of compounds with the same functional group, the pi value (the difference in the log P value between the substituted and unsubstituted compound) was analyzed on the same basis as the values of meta- and para-substituted isomers by an extended Hammett-Taft procedure. In the procedure, we considered the intramolecular electronic and steric effects, operating between substituents and governing the relative hydrogen-bonding solvation with partitioning solvents for solutes in which internal hydrogen-bond formation can be ignored. The pi value for mono- and di-ortho-substituted derivatives was adequately included in the correlation equation for the values of the meta- and para-substituted derivatives in each series. The effect of di-ortho substituents on partition behaviors could be roughly expressed by the sum of the effects of the 2- and 6-position substituents. PMID:8377112

Sotomatsu, T; Shigemura, M; Murata, Y; Fujita, T

1993-08-01

422

Correlation of membrane/water partition coefficients of detergents with the critical micelle concentration.  

PubMed Central

The membrane/water partition coefficients, K, of 15 electrically neutral (non-charged or zwitterionic) detergents were measured with phospholipid vesicles by using isothermal titration calorimetry, and were compared to the corresponding critical micellar concentrations, cmc. The detergents measured were oligo(ethylene oxide) alkyl ethers (C(m)EO(n) with m = 10/n = 3, 7 and m = 12/n = 3.8); alkylglucosides (octyl, decyl); alkylmaltosides (octyl, decyl, dodecyl); diheptanoylphosphatidylcholine; Tritons (X-100, X-114) and CHAPS. A linear relation between the free energies of partitioning into the membrane and micelle formation was found such that K. CMC approximately 1. The identity K. CMC = 1 was used to classify detergents with respect to their membrane disruption potency. "Strong" detergents are characterized by K. CMC < 1 and solubilize lipid membranes at detergent-to-lipid ratios X(b) < 1 (alkylmaltosides, tritons, heptaethylene glycol alkyl ethers). "Weak" detergents are characterized by K. CMC > 1 and accumulate in the membrane- to detergent-to-lipid ratios X(b) > 1 before the bilayer disintegrates (alkylglucosides, pentaethylene glycol dodecyl ether).

Heerklotz, H; Seelig, J

2000-01-01

423

A NON-LINEAR STRUCTURE-PROPERTY MODEL FOR OCTANOL-WATER PARTITION COEFFICIENT  

PubMed Central

Octanol-water partition coefficient (Kow) is an important thermodynamic property used to characterize the partitioning of solutes between an aqueous and organic phase and has importance in such areas as pharmacology, pharmacokinetics, pharmacodynamics, chemical production and environmental toxicology. We present a non-linear quantitative structure-property relationship model for determining Kow values of new molecules in silico. A total of 823 descriptors were generated for 11,308 molecules whose Kow values are reported in the PhysProp dataset by Syracuse Research. Optimum network architecture and its associated inputs were identified using a wrapper-based feature selection algorithm that combines differential evolution and artificial neural networks. A network architecture of 50-33-35-1 resulted in the least root-mean squared error (RMSE) in the training set. Further, to improve on single-network predictions, a neural network ensemble was developed by combining five networks that have the same architecture and inputs but differ in layer weights. The ensemble predicted the Kow values with RMSE of 0.28 and 0.38 for the training set and internal validation set, respectively. The ensemble performed reasonably well on an external dataset when compared with other popular Kow models in the literature.

Yerramsetty, Krishna M.; Neely, Brian J.; Gasem, Khaled A. M.

2012-01-01

424

Ab initio calculation of the electronic absorption spectrum of liquid water  

NASA Astrophysics Data System (ADS)

The electronic absorption spectrum of liquid water was investigated by coupling a one-body energy decomposition scheme to configurations generated by classical and Born-Oppenheimer Molecular Dynamics (BOMD). A Frenkel exciton Hamiltonian formalism was adopted and the excitation energies in the liquid phase were calculated with the equation of motion coupled cluster with single and double excitations method. Molecular dynamics configurations were generated by different approaches. Classical MD were carried out with the TIP4P-Ew and AMOEBA force fields. The BLYP and BLYP-D3 exchange-correlation functionals were used in BOMD. Theoretical and experimental results for the electronic absorption spectrum of liquid water are in good agreement. Emphasis is placed on the relationship between the structure of liquid water predicted by the different models and the electronic absorption spectrum. The theoretical gas to liquid phase blue-shift of the peak positions of the electronic absorption spectrum is in good agreement with experiment. The overall shift is determined by a competition between the O-H stretching of the water monomer in liquid water that leads to a red-shift and polarization effects that induce a blue-shift. The results illustrate the importance of coupling many-body energy decomposition schemes to molecular dynamics configurations to carry out ab initio calculations of the electronic properties in liquid phase.

Martiniano, Hugo F. M. C.; Galamba, Nuno; Cabral, Benedito J. Costa

2014-04-01

425

Ab initio calculation of the electronic absorption spectrum of liquid water.  

PubMed

The electronic absorption spectrum of liquid water was investigated by coupling a one-body energy decomposition scheme to configurations generated by classical and Born-Oppenheimer Molecular Dynamics (BOMD). A Frenkel exciton Hamiltonian formalism was adopted and the excitation energies in the liquid phase were calculated with the equation of motion coupled cluster with single and double excitations method. Molecular dynamics configurations were generated by different approaches. Classical MD were carried out with the TIP4P-Ew and AMOEBA force fields. The BLYP and BLYP-D3 exchange-correlation functionals were used in BOMD. Theoretical and experimental results for the electronic absorption spectrum of liquid water are in good agreement. Emphasis is placed on the relationship between the structure of liquid water predicted by the different models and the electronic absorption spectrum. The theoretical gas to liquid phase blue-shift of the peak positions of the electronic absorption spectrum is in good agreement with experiment. The overall shift is determined by a competition between the O-H stretching of the water monomer in liquid water that leads to a red-shift and polarization effects that induce a blue-shift. The results illustrate the importance of coupling many-body energy decomposition schemes to molecular dynamics configurations to carry out ab initio calculations of the electronic properties in liquid phase. PMID:24784291

Martiniano, Hugo F M C; Galamba, Nuno; Cabral, Benedito J Costa

2014-04-28

426

Near-infrared diode laser absorption diagnostic for temperature and water vapor in a scramjet combustor  

NASA Astrophysics Data System (ADS)

Tunable diode laser absorption measurements of gas temperature and water concentration were made at the exit of a model scramjet combustor fueled on JP-7. Multiplexed, fiber-coupled, near-infrared distributed feedback lasers were used to probe three water vapor absorption features in the 1.34 1.47 ?m spectral region (2v1 and v1+v3 overtone bands). Ratio thermometry was performed using direct-absorption wavelength scans of isolated features at a 4-kHz repetition rate, as well as 2f wavelength modulation scans at a 2-kHz scan rate. Large signal-to-noise ratios demonstrate the ability of the optimally engineered optical hardware to reject beam steering and vibration noise. Successful measurements were made at full combustion conditions for a variety of fuel/air equivalence ratios and at eight vertical positions in the duct to investigate spatial uniformity. The use of three water vapor absorption features allowed for preliminary estimates of temperature distributions along the line of sight. The improved signal quality afforded by 2f measurements, in the case of weak absorption, demonstrates the utility of a scanned wavelength modulation strategy in such situations.

Liu, Jonathan T. C.; Rieker, Gregory B.; Jeffries, Jay B.; Gruber, Mark R.; Carter, Campbell D.; Mathur, Tarun; Hanson, Ronald K.

2005-11-01

427

Near-infrared diode laser absorption diagnostic for temperature and water vapor in a scramjet combustor.  

PubMed

Tunable diode laser absorption measurements of gas temperature and water concentration were made at the exit of a model scramjet combustor fueled on JP-7. Multiplexed, fiber-coupled, near-infrared distributed feedback lasers were used to probe three water vapor absorption features in the 1.34-1.47 microm spectral region (2v1 and vl + v3 overtone bands). Ratio thermometry was performed using direct-absorption wavelength scans of isolated features at a 4-kHz repetition rate, as well as 2f wavelength modulation scans at a 2-kHz scan rate. Large signal-to-noise ratios demonstrate the ability of the optimally engineered optical hardware to reject beam steering and vibration noise. Successful measurements were made at full combustion conditions for a variety of fuel/air equivalence ratios and at eight vertical positions in the duct to investigate spatial uniformity. The use of three water vapor absorption features allowed for preliminary estimates of temperature distributions along the line of sight. The improved signal quality afforded by 2f measurements, in the case of weak absorption, demonstrates the utility of a scanned wavelength modulation strategy in such situations. PMID:16270559

Liu, Jonathan T C; Rieker, Gregory B; Jeffries, Jay B; Gruber, Mark R; Carter, Campbell D; Mathur, Tarun; Hanson, Ronald K

2005-11-01

428

Near-infrared diode laser absorption diagnostic for temperature and water vapor in a scramjet combustor  

SciTech Connect

Tunable diode laser absorption measurements of gas temperature and water concentration were made at the exit of a model scramjet combustor fueled on JP-7. Multiplexed, fiber-coupled, near-infrared distributed feedback lasers were used to probe three water vapor absorption features in the 1.34-1.47 {mu}m spectral region (2v1and v1+ v3overtone bands). Ratio thermometry was performed using direct-absorption wavelength scans of isolated features at a 4-kHz repetition rate, as well as 2f wavelength modulation scans at a 2-kHz scan rate. Large signal-to-noise ratios demonstrate the ability of the optimally engineered optical hardware to reject beam steering and vibration noise. Successful measurements were made at full combustion conditions for a variety of fuel/air equivalence ratios and at eight vertical positions in the duct to investigate spatial uniformity. The use of three water vapor absorption features allowed for preliminary estimates of temperature distributions along the line of sight. The improved signal quality afforded by 2f measurements, in the case of weak absorption, demonstrates the utility of a scanned wavelength modulation strategy in such situations.

Liu, Jonathan T.C.; Rieker, Gregory B.; Jeffries, Jay B.; Gruber, Mark R.; Carter, Campbell D.; Mathur, Tarun; Hanson, Ronald K

2005-11-01

429

New in vitro dermal absorption database and the prediction of dermal absorption under finite conditions for risk assessment purposes  

Microsoft Academic Search

Most QSARs for dermal absorption predict the permeability coefficient, Kp, of a molecule, which is valid for infinite dose conditions. In practice, dermal exposure mostly occurs under finite dose conditions. Therefore, a simple model to predict finite dose dermal absorption from infinite dose data (Kp and lag time) and the stratum corneum\\/water partition coefficient (KSC,W) was developed. To test the

Harrie E. Buist; Johan A. van Burgsteden; Andreas P. Freidig; Wilfred J. M. Maas

2010-01-01

430

Liquid water absorption and scattering effects in DOAS retrievals over oceans  

NASA Astrophysics Data System (ADS)

It is well-known that spectral effects of liquid water are present in absorption (DOAS) measurements above the ocean and insufficiently removed liquid water structures may interfere with trace gas absorptions leading to wrong (sometimes even non-physical) results. Currently available literature cross-sections of liquid water absorption are provided in coarser resolution than hyperspectral DOAS applications require and Vibrational Raman Scattering (VRS) is mostly unconsidered or compensated for using simulated pseudo cross-sections from radiative transfer modelling. During the ship-based TransBrom campaign across the western Pacific in October 2009, MAX-DOAS measurements were performed into very clear natural waters achieving underwater light paths of up to 50 m. From these measurements, the retrieval of a residual (H2Ores) spectrum is presented compensating simultaneously for insufficiencies of the liquid water absorption cross-section and broad-banded VRS structures. Small-banded (Ring) structures caused by VRS were found to be very efficiently compensated for by the intensity offset (straylight) correction included in the DOAS fit. In the MAX-DOAS tropospheric NO2 retrieval, this method was able to compensate entirely for all liquid water effects that decrease the fit quality. This was not achieved using a liquid water cross-section in combination with a simulated VRS spectrum. Typical values of improvement depend on the measurement's contamination with liquid water structures and range from ? 30% for measurements slightly towards the water surface to several percent in small angles above the horizon. Furthermore, the H2Ores spectrum was found to prevent misfits of NO2 slant columns especially for very low NO2 scenarios and thus increase the reliability of the fit. In test fits on OMI satellite data, the H2Ores spectrum was found selectively above ocean surfaces where it leads to fit quality improvements of up to 6-18%.

Peters, E.; Wittrock, F.; Richter, A.; Alvarado, L. M. A.; Rozanov, V. V.; Burrows, J. P.

2014-05-01

431

Accuracy of the theoretical calculation of the Soret coefficient for water-ethanol mixtures in comparison with experimental data  

NASA Astrophysics Data System (ADS)

The Soret coefficient of water-ethanol mixtures at one atmosphere and temperatures ranging from 20°C to 40°C has been studied in detail. Comparisons between the experimental data and predictions of existing theoretical models showed satisfactory agreement only for certain conditions. In order to properly model the behavior of water in the mixture, the thermodynamic properties of water-ethanol mixtures were calculated using the Cubic Plus Association (CPA) equation of state. Compared to the theoretical models of Haase, Kempers, Dougherty and Drickamer, the Firoozabadi model was found to perform much better in predicting the thermal diusion phenomena for water-alcohol mixtures.

Jiang, Charles Guobing; Saghir, M. Ziad; Derawi, Samer; Kawaji, Masahiro

2005-11-01

432

Evaluation of distribution coefficients for the prediction of strontium and cesium migration in a natural sand at different water contents  

NASA Astrophysics Data System (ADS)

Contaminant distribution coefficient determined under saturated conditions are often used to model solute transport in the vadose zone. However, the water content of porous media may affect the transport behaviour of conservative and sorbing solutes. We performed column experiments using sand from Chernobyl area and we investigated the transport of tritiated water as conservative tracer, ^{85}Sr and ^{134}Cs as reactive solutes at different water saturation levels. The results indicate that when the Kd model is applicable, a decrease of the water content leads to a decrease of the Kd value.

Szenknect, S.; Gaudet, J. P.; Dewiere, L.

2003-05-01

433

Water and NaCl absorption by the intestine of the tilapia Sarotherodon mossambicus adapted to fresh water or seawater and the possible role of prolactin and cortisol  

Microsoft Academic Search

Rates of intestinal water, sodium and chloride absorption in tilapia, adapted to fresh water (FW) and seawater (SW), were measured in vitro, using noneverted sacs made from the anterior, middle and posterior intestinal regions. The anterior intestine from SW fish showed considerably less water, sodium and chloride absorption compared with that seen in FW fish. The middle intestine showed either

James R. Mainoya

1982-01-01

434

Application of Photothermal Techniques in the Determination of the Water-Vapor Diffusion Coefficient and Thermal Effusivity of Hydrogels  

NASA Astrophysics Data System (ADS)

The main objective of this work is to determine the effect of different sodium alginate concentrations in hydrogels on their water-vapor diffusion coefficient (WVDC) and thermal effusivity (. These physical parameters were measured by photoacoustic and pyroelectric techniques, respectively. The results indicate that the higher values for the WVDC are presented at a concentration of 2 % sodium alginate. At lower concentrations of sodium alginate, the sample thermal effusivity increases, with a value close to the water thermal effusivity.

Raymundo-Ortiz, A. I.; Ramos-Ramirez, E. G.; Cruz-Orea, A.; Salazar-Montoya, J. A.

2013-09-01

435

Grapevine water use and the crop coefficient are linear functions of the shaded area measured beneath the canopy  

Microsoft Academic Search

The relationships among water use and the crop coefficient of Vitis vinifera L. cv. Thompson Seedless with several measures of canopy development were determined with the aid of a weighing lysimeter in the San Joaquin Valley of California. At various times during two growing seasons, vine leaf area, calculated leaf area index (LAI) and the amount of shade cast on

L. E. Williams; J. E. Ayars

2005-01-01

436

Predicting inhomogeneous water absorption in an ionic diblock polymer membrane  

NASA Astrophysics Data System (ADS)

Fuel cells convert fuel directly into electrical power. Their performance depends on a permeable (yet strong) membrane to allow ion conduction (while preventing combustion). Anion-exchange membrane fuel-cells are especially economical to produce, but technological hurdles currently limit durability and OH^- conductivity of the membrane. One solution to these problems is a diblock morphology. Layers of stiff hydrophobic polymer provide structure, while interspersed layers of polyelectrolyte provide avenues for conduction. Previously, little was known about the structure within the conducting layer. We adapted Scheutjens-Fleer polymer-brush theory to a lamellar geometry. The calculation tells where the polyelectrolytes congregate within a lamella, and hence how conduction occurs. This talk focuses on a new diblock material, PMB-PVBTMA. We show how the features of the material determine the intra-lamellar structure. We conclude that at low humidity, the bulkiness of PVBTMA causes it to adopt a near-uniform distribution within the conducting block. At high humidity, however, a phase separation may induce abrupt water channels. Understanding the architecture within the conducting layer will help guide research into better anion-exchange membranes materials.

Herbst, Daniel; Witten, Thomas

2013-03-01

437