Larger Root Mean Square Research Articles

A comparison study of RAMS simulations with aircraft, wind profiler, lidar, tethered balloon and RASS data over Philadelphia during a 1999 summer episode

Abstract This study presents comparisons of Colorado State University's prognostic mesoscale Regional Atmospheric Modeling System (RAMS 4.3) results with observational data obtained from aircraft, wind profiler, lidar, tethered balloon and RASS during the Northeast Oxidant and Particle Study (NE-OPS) field program at Philadelphia, PA during a summer episode in 1999. Model simulations were performed for the 15–20 July 1999 period. The comparison of model-predicted temperatures with aircraft and tethered balloon data revealed that the mean relative error exhibited the same general trend in time for temperature noted by earlier investigators. The comparisons of model relative humidity with aircraft and tethered balloon indicate that the mean relative error varied from −13% to −21%. The mean relative error for water vapor mixing ratio with respect to lidar data exhibited a negative bias consistent with humidity bias corresponding to aircraft and tethered balloon. The largest root mean square (rms) errors obtained from 36 km resolution RAMS results and the regular upper air rawinsonde stations are associated with the relative humidity values. The smallest rms errors for any variable are all associated with the lower atmosphere while the largest rms errors are associated with the upper/mid-tropospheric region. The difficulty in correctly predicting upper level humidity is due to lack of consistency in the upper level moisture observations while the lower rms errors of relative humidity close to surface are due to increased availability of moisture data at surface. The results of the present study, by utilizing a variety of diverse observational platforms, broadly confirm the general traits of RAMS performance noted by earlier investigators.

Non-invasive laser Doppler perfusion measurements of large tissue volumes and human skeletal muscle blood RMS velocity

This study proposes the implementation of an algorithm allowing one to derive absolute blood root-mean-square (RMS) velocity values from laser Doppler perfusion meter (LDP) data. The algorithm is based on the quasi-elastic light scattering theory and holds for multiple scattering. While standard LDP measurements are normally applicable to a small region of interest (∼1 mm2), the present method allows the analysis of both small and large tissue volumes with small and large interoptode spacings (e.g., 1.5 cm). The applicability and the limits of the method are demonstrated with measurements on human skeletal muscle using a custom-built near-infrared LDP meter. Human brachioradialis muscle RMS velocity values of 9.99 ± 0.01 and 5.58 ± 0.03 mm s−1 at 1.5 cm and of 5.18 ± 0.01 and 2.54 ± 0.09 mm s−1 at 2 cm were found when the arm was (a) at rest and (b) occluded, respectively. At very large optode spacings or very high moving particle densities, the theory developed here would need to be amended to take into account second-order effects.

Calculation of electron inelastic mean free paths (IMFPs) VII. Reliability of the TPP‐2M IMFP predictive equation

AbstractWe report comparisons of electron inelastic mean free paths (IMFPs) determined from our predictive IMFP equation TPP‐2M and reference IMFPs calculated from optical data. These comparisons were made for values of the parameter Nv (the number of valence electrons per atom or molecule) that we have recommended and those that were recommended in a recent paper by Seah et al. (Surf. Interface Anal. 2001; 31: 778). The comparisons were made for eight elemental solids (K, Y, Gd, Tb, Dy, Hf, Ta and Bi) and two compounds (KBr and Y2O3) for which there were appreciable differences in the recommended Nv values from the two sources and for which optical data were available for the IMFP calculations. The average of the root‐mean‐square (RMS) deviations for the ten materials between IMFPs from the TPP‐2M equation with our Nv values and the reference IMFPs was 11.0%, whereas the corresponding average with the Seah et al. Nv values was 20.2%. The larger average in the latter comparison was mainly due to large (>20%) RMS deviations for four materials (K, Hf, Ta and KBr). For the other six materials, the RMS deviations with the Seah et al. values of Nv were similar to those with our values of Nv. Based on the comparisons for these ten materials, we believe that it is preferable to use our values of Nv in the TPP‐2M equation. Copyright © 2003 John Wiley & Sons, Ltd.

Joint versus separate estimation of state and change in category frequencies from repeat stratified two-phase sampling with a fallible classifier.

Joint maximum likelihood estimates (JML) of category frequencies and change from repeat stratified two-phase sampling surveys with a fallible classifier are often seriously biased and have large root mean square errors when they are obtained for small populations (<5,000) with three or more categories and a moderate to small phase II sample size (<1,000). JML estimates of state also depend on antecedent or posterior data, a recipe for inconsistency. In these situations, a separate maximum likelihood estimation (SML) of category frequencies at each survey date appears preferable. SML estimates of net change are obtained as the difference in states. SML standard errors of change are obtained via an estimate of the temporal correlation and variances of state. A bivariate binary logistic model of change provided the estimate of temporal correlation. SML generally outperformed JML significantly in terms of bias and root mean square errors in eight case studies.

Estimation of the Cumulative Sensible Heat Flux over a Bare Soil and its Daily Mean Soil Temperature without Wind Speed Data.

The exchange speed (CHU) for sensible heat flux is one of the most important parameters for estimating sensible and latent heat fluxes by the bulk transfer method. CHU is also important for estimating soil temperature by using the heat balance model combined with the bulk transfer method. CHU is usually treated as a function of wind speed; however, if wind speed data is not available, it is not easy to estimate an accurate and representative value using measured wind speed from another location due to the effect of the surrounding environment. In this study, we investigated the accuracy of estimating the sensible heat flux over a bare soil surface and its daily mean soil temperature by the bulk transfer method using daily mean meteorological data without wind speed. This means that CHU is treated as a constant value. We also investigated a method of parameterization of CHU on a bare soil without observed flux data. The estimation of the daily mean sensible heat flux without wind speed data has a large root mean square error (RMSE). RMSE without wind speed was 18.3 W m-2, whereas that with wind speed was 10.5 W m-2. However, the accuracy of the estimation of cumulative monthly sensible heat flux without wind speed data was almost equal to that with wind speed data. The two values of RMSE of monthly estimations with and without wind speed data were about 5 W m-2. The estimated cumulative sensible heat flux without using wind speed data, over a period of more than several days, agreed with observed sensible heat flux values. With theoretical analysis and the parameterization of CHU on a bare soil without using observed flux data, the results indicate that cumulative sensible heat flux can be estimated from routine meteorological data without wind speed. The daily mean soil temperature was estimated by the method of Hirota et al. (1995) with and without wind speed data. The accuracy of the estimation of the daily mean soil temperature without wind speed data was almost equal to that with wind speed data. The result indicates that even if wind speed data is not used, the model provides a good estimation of the daily mean soil temperature.

On the Truncation of Long-Range Electrostatic Interactions in DNA

Long-range interactions are known to play an important role in highly polar biomolecules like DNA. In molecular dynamics simulations of nucleic acids and proteins, an accurate treatment of the long-range interactions are crucial for achieving stable nanosecond trajectories. In this report, we evaluate the structural and dynamic effects on a highly charged oligonucleotide in aqueous solution from different long-range truncation methods. Two group-based truncation methods, one with a switching function and one with a force-switching function were found to fail to give accurate stable trajectories close to the crystal structure. For these group-based truncation methods, large root mean square (rms) deviations from the initial structure were obtained and severe distortions of the oligonucleotide were observed. Another group-based truncation scheme, which used an abrupt truncation at 8.0 Å or at 12.0 Å was also investigated. For the short cutoff distance, the conformations deviated far away from the initial structure and were significantly distorted. However, for the longer cutoff, where all necessary electrostatic interactions were included, the trajectory was quite stable. For the particle mesh Ewald (PME) truncation method, a stable DNA simulation with a heavy atom rms deviation of 1.5 Å was obtained. The atom-based truncation methods also resulted in stable trajectories, according to the rms deviation from the initial B-DNA structure, of between 1.5 and 1.7 Å for the heavy atoms. In these stable simulations, the heavy atom rms deviations were ∼0.6–1.0 Å lower for the bases than for the backbone. An increase of the cutoff radius from 8 to 12 Å decreased the rms deviation by ∼0.2 Å for the atom-based truncation method with a force-shifting function, but increased the computational time by a factor of 2. Increasing the cutoff from 12 to 18 Å for the atom-based truncation method with a force-shifting function requires 2–3 times more computational time, but did not significantly change the rms deviation. Similar rms deviations from the initial structure were found for the atom-based method with a force-shifting function and for the PME method. The computational cost was longer for the PME method with a cutoff of 12.0 Å for the direct space nonbonded calculations than for the atom-based truncation method with a force-shifting function and a cutoff of 12.0 Å. If a nonperiodic boundary, e.g., a spherical boundary, was used, a considerable speedup could be achieved . From the rms fluctuations, the terminal nucleotides and especially the cytidines were found to be more flexible than the nonterminal nucleotides. The B-DNA form of the oligonucleotide was maintained throughout the simulations and is judged to depend on the parameters of the energy function and not on the truncation method used to handle the long-range electrostatic interactions. To perform accurate and stable simulations of highly charged biological macromolecules, we recommend that the atom-based force-shift method or the PME method should be used for the long-range electrostatics interactions.

Neural network retrieval of wind velocity profiles from satellite data

AbstractA method has been developed for retrieval of wind velocity profiles from satellite sounder radiances using a neural network technique. Each wind velocity represents a mean value for a layer approximately centred at that standard height or pressure level. The neural network input vector includes sounder radiances from the Geostationary Operational Environmental Satellite (GOES), plus ancillary information such as latitude and longitude. A set of ‘co‐incident’ rawinsonde soundings provide the ‘truth’ data set. In the initial results root mean square errors for the standard levels from 850 to 300 hPa have about the same magnitude as those for current methods such as tracking of moisture features in GOES imagery. As with more traditional methods, the largest root mean square error occurs near the tropopause. Although the results to date appear highly promising, considerable further work is needed before we have an operationally capable technique. Copyright © 2000 Royal Meteorological Society

Atomic force microscopy imaging of polycrystalline CuInSe2 thin films

In this study, atomic force microscopy (AFM) imaging has been used to study the structural properties of polycrystalline CuInSe2 films, which are widely used as absorber materials in thin film solar cell devices. This technique demonstrated an excellent capability for the reproducible imaging of these rough polycrystalline materials. AFM imaging in combination with statistical analysis revealed distinct differences in the structural properties (i.e. grain width and height distributions, root-mean-square (RMS) and peak to valley (R(p-v)) roughness values) as a function of the specific growth technique used and the bulk composition of the films. In the case of Cu-rich films, prepared by the H2Se/Ar treatment of Cu/In/Cu alloys, rough surface structures were in general observed. Statistical analysis revealed two distinct distribution of grains in these samples (1.0-2.5 &mgr;m and 3-5.5 &mgr;m) with large RMS and R(p-v) roughness values of 380 nm and 2.6 &mgr;m, respectively. In-rich films were characterized by the presence of much smaller, roughly circular clusters with a significant reduction in both the width and height distributions as well as RMS and R(p-v) roughness values. The most successful growth techniques, in terms of producing homogeneous and dense films, were in the cases of H2Se/Ar treated metallic InSe/Cu/InSe alloys and the coevaporation of all materials to form CuInSe2. Both these techniques produced absorber films with very narrow grain width and height distributions as well as small roughness values. It was possible to establish that high efficiency devices are associated with the use of absorber films with narrow width distributions between 0.5 and 2 &mgr;m and small RMS (> 300 nm) roughness values. These values are used as a figure of merit in our laboratories to evaluate the structural properties of our CuInSe2 thin films.

Molecular Dynamics Simulations on Parallel and Antiparallel C.G*G Triplexes

Molecular dynamics (MD) studies have been carried out on the Hoogsteen hydrogen bonded parallel and the reverse Hoogsteen hydrogen bonded antiparallel C.G*G triplexes. Earlier, the molecular mechanics studies had shown that the parallel structure was energetically more favourable than the antiparallel structure. To characterize the structural stability of the two triplexes and to investigate whether the antiparallel structure can transit to an energetically more favourable structure, due to the local fluctuations in the structure during the MD simulation, the two structures were subjected to 200ps of constant temperature vacuum MD simulations at 300K. Initially no constraints were applied to the structures and it was observed that for the antiparallel triplex, the structure showed a large root mean square deviation from the starting structure within the first 12ps and the N4-H41—06 hydrogen bond in the WC duplex got distorted due to a high propeller twist and a moderate increase in the opening angle in the basepairs. Starting from an initial value of 30°, helical twist of the average structure from this simulation had a value of 36°, while the parallel structure stabilized at a twist of 33°. In spite of the hydrogen bond distortions in the antiparallel triplex, it was energetically comparable to the parallel triplex. To examine the structural characteristics of an undistorted structure, another MD simulation was performed on the antiparallel triplex by constraining all the hydrogen bonds. This structure stabilized at an average twist of 33°. In the course of the dynamics though the energy of the molecule—;compared to the initial structure—;improved, it did not become comparable to the parallel structure. Energy minimization studies performed in the presence of explicit water and counterions also showed the two structures to be equally favourable energetically. Together these results indicate that the parallel C.G*G triplex with Hoogsteen hydrogen bonds also represents a stereochemically and energetically favourable structure for this class of triplexes.

Spin contamination in quantum Monte Carlo wave functions

The wave function usually employed in quantum Monte Carlo (QMC) electronic structure calculations is the product of a Jastrow factor and a sum of products of up-spin and down-spin determinants. Typically, a different Jastrow factor is used for parallel- and antiparallel-spin electrons in order to satisfy the cusp conditions and thereby ensure that the local energy at electron–electron coincidence points is finite. However, when the Jastrow factor is not completely symmetric under interchange of the spatial coordinates of the electrons, the resulting wave function may not be an eigenstate of the spin operator Ŝ2. For the Li and Be atoms, we evaluate the spin contamination in a variety of wave functions with progressively higher body-order correlations in the Jastrow factor. The spin contamination is found to be small for all the wave functions (10−3–10−5), the smaller values being obtained for the more accurate wave functions. On the other hand, if we eliminate the spin contamination by employing a symmetric Jastrow (and sacrificing the parallel-spin cusp condition), the resulting wave functions typically have about 20%–40% larger root mean square fluctuations in the local energy. A wave function which both satisfies the cusp conditions and has definite spin can be constructed, but for systems with many electrons, its computational cost is higher than for the commonly used QMC wave functions.

Variability of Laboratory Measured Soil Lines of Soils from Southeastern Brazil

Linear relationships (soil lines) between the conventional red (R) and near-infrared (NIR), and between unconventional NIR reflectance bands were investigated for the effects of spectral positioning and widths of approximately simulated bands of some broad- and narrow-band sensors, and for the influence of the chemical constituents and moisture in the samples. The investigation was based on laboratory spectra of air-dried samples from soil profiles from southeastern Brazil, an experiment for the chemical removal of organic matter, and on a wetting process of the soil samples. The relationships were evaluated for a general soil line and for the individual lines of some soil types, under air-dried condition, through the determination of the line parameters, dispersion statistics, and principal components analysis (PCA). Soil lines obtained with broad or narrow NIR bands positioned at shorter wavelengths, and consequently at smaller distance differences between the pair of bands, presented better fitted lines than the ones obtained with NIR bands located at longer wavelengths and at larger distances. Compared with the broad bands, spectrally better positioned narrow NIR/R bands produced closely similar results because of the propitious effect of the larger bandwidth. However, unconventional NIR/NIR bands presented better fitted lines than the R/NIR bands. The inherent interplay between organic matter and iron oxides is accountable for the variability in the linear parameters of the individual lines. The general line for the samples considered is composed of nonparallel segments of the different soil types, with a tendency for an increased obliquity in the low albedo soils. Soil types with very low albedo present line slope values below 1, poor correlations, but small root mean square (RMS) values, whereas soil types with moderate and high albedo present line slope values above 1, strong correlations, and large RMS values. The former is rich in organic matter and iron oxides whereas the latter has more transparent components, such as quartz, or less opaque substances. However, in soil types with a lesser content of organic matter, the iron spectral features are enhanced and variations in the shape of the spectra are produced because of the larger reflectance increase in the R band than in the NIR interval. The maximum spectral contrast resulting from this compositional interplay is assessed when the NIR band is positioned at longer wavelengths. Similarly, soil wetting introduces nonlinear spectral changes that also affect the characteristics of the soil lines. The analysis of field measured reflectance spectra derived from an experiment designed to monitor the growth of a bean crop indicates that the shift of the NIR band towards shorter wavelengths produces not only better fitted soil lines but also stronger vegetation signals. The enhancement of the vegetation signal obtained with the displacement of the NIR band results from the steeper descending slope towards longer wavelengths of the NIR plateau observed in the vegetation spectra. The results place constraints on an unsupported choice of bands to derive vegetation indices, especially those of the advanced hyperspectral imaging sensors. The most recommended pair of NIR-R bands for crop vegetation indices is the one from LANDSAT-TM, closely followed by JERS-OPS and SPOT-HRV, or from narrow NIR-R bands positioned within these ranges at spectral intervals not affected by atmospheric attenuation.

A recurrent neural network for a fed-batch fermentation with recombinant Escherichia coli subject to inflow disturbances

A fed-batch fermentation for β-galactosidase production by a recombinant Escherichia coli strain has been simulated with interruptions in the inflow rates of a concentrated substrate and a diluent. Data covering a 12 h fermentation period were simulated by a 6-12-4 Elman neural network with two extra- and two intracellular variables as outputs. Three types of inflow failure were considered: either of the two feed streams separately or both together. Despite the fermentation performance being quite different for each type of failure, a network trained with data pertaining to one kind of failure was able to mimic the performance adequately for the other two data sets. The largest error and root mean square error were 14 and 10%, respectively, among the plasmid DNA and the intracellular protein concentrations, and 9 and 6% for the concentrations and mass fractions of recombinant cells. The accuracy is better than that reported for back-propagation networks.

Small-Sample Bias in GMM Estimation of Covariance Structures

We examine the small sample properties of the GMM estimator for models of covariance structures, where the technique is often referred to as the optimal minimum distance (OMD) estimator. We present a variety of Monte Carlo experiments based on simulated data and on the data used by Abowd and Card (1987, 1990) in an examination of the covariance structure of hours and earnings changes. Our main finding is that OMD is seriously biased in small samples for many distributions and in relatively large samples for poorly behaved distributions. The bias is almost always downward in absolute value. It arises because sampling errors in the second moments are correlated with sampling errors in the weighting matrix used by OMD. Furthermore, OMD usually has a larger root mean square error and median absolute error than equally weighted minimum distance (EWMD). We also propose and investigate an alternative estimator, which we call independently weighted optimal minimum distance (IWOMD). IWOMD is a split sample estimator using separate groups of observations to estimate the moments and the weights. IWOMD has identical large sample properties to the OMD estimator but is unbiased regardless of sample size. However, the Monte Carlo evidence indicates that IWOMD is usually dominated by EWMD.

Adaptive DFE for GMSK in indoor radio channels

We simulate the performance of an equalized Gaussian minimum shift keying (GMSK) signal in an indoor radio environment with fading, noise, imperfect carrier recovery, cochannel interference (CCI), and intersymbol interference (ISI). We show that data rates of 20 Mb/s at bit error rates (BER) /spl les/10/sup -4/ are possible with root mean square (RMS) delay spreads up to 25 ns using a simple limiter-discriminator-integrator (LDI) receiver and a (6, 4) decision feedback equalizer (DFE). In environments with larger RMS delay spreads, coherent detection is required for the same performance. We show that using a decision-directed second-order digital carrier synchronizer with time varying loop filters, frequency offsets up to 200 kHz can be corrected with negligible performance degradation. This paper utilizes a DFE structure which compensates for both modulator and channel ISI, and yet requires no power-intensive multiplication operations in the feedback section. A DFE (8, 8) with two-level switched (selection) diversity is shown to allow 20 Mb/s data transfer at a BER/spl les/10/sup -4/ for RMS delay spreads under 150 ns, with CCI. A light BCH (26, 31) code allows error-free reception of over 90% of packets with RMS delay spreads under 150 ns, and up to 70% of packets with RMS delays of 150 ns.

Rill hydraulics on a semiarid hillslope, southern Arizona

Seventy field experiments were conducted in seven rills located on a semiarid rangeland hillslope underlain by gravelly soils at Walnut Gulch, Arizona. The rills, which are characterized by wide, shallow cross-sections and gravel-covered beds, have mean at-a-station hydraulic geometry exponents of b = 0·33, f = 0·34 and m = 0·33. Although the differences between these values and typical values of b = 0·30, f = 0·40 and m = 0·30 for cropland rills are not statistically significant, they are thought to be real, as cropland rills often have more rectangular cross-sections and steeper sides than the rangeland rills under study. For rills formed in silty loamy soils, Govers developed an empirical relation between mean flow velocity and discharge. Emphasizing the generality of this relation, he suggested that it may be used as a simple means of routing runoff through rills. He also noted that this relation appeared to be unaffected by either slope or soil materials. The present data represent rills underlain by coarser and somewhat more varied gravel-rich soils. These data do not conform to Govers' relation, and a multiple regression analysis reveals that slope and soil materials, either directly or indirectly through bed roughness, exert almost as much influence on flow velocity as does discharge. Three alternative methods are developed for predicting flow velocity in the rills under study. All three methods give good results with the largest root mean square deviation being 3·115 cm s−1.

Identifying the mechanism of protein loop closure: a molecular dynamics simulation of the Bacillus stearothermophilus LDH loop in solution.

The 'loop' involving residues 98-110 in Bacillus stearothermophilus lactate dehydrogenase (BSLDH) is of great interest as substrate-induced 'loop' closure is thought to be rate-limiting and essential in catalyzing the reaction and in determining substrate specificity. Consequently, we have explored the mechanism underlying 'loop' opening in BSLDH through a molecular dynamics simulation at high temperature (1000 K) in the presence of explicit solvent, starting from the X-ray structure of BSLDH complexed with the co-enzyme NAD+ and oxamate at 2.5 A. During the simulation, a significant conformational change occurred, as evidenced by sharp dihedral angle transitions, hydrogen bond breaking and formation and large root mean square deviations from the starting structure; these changes define the criteria for 'loop' opening. The mechanical elements responsible for 'loop' opening, i.e. 'loop' hinges and flap, are defined through a combination of order parameters, dihedral angle changes and their correlations and the dynamical cross-correlation map of atomic displacements for the 'loop' residues. The results indicate that the 'loop' consists of two flexible hinge regions on either side of a relatively rigid three-residue segment that undergoes a significant spatial displacement during 'loop' opening. 'Loop' opening is made possible through an array of correlated dihedral angle changes and intra-'loop' rearrangements of hydrogen-bond interactions. The present findings are compared to previous work related to 'loop' opening and site-directed mutagenesis experiments.

X-band SAR and scatterometer data inversion based on geometrical optics model and Kalman filter approach

This paper describes the activity performed in the framework of the 1990 AVIOSAR 580 SAR and scatterometer Italian campaign over the Matera test site. The experiment has been carried out to ascertain the reliability of surface scattering models in order to tackle with the data inversion problem. To achieve this goal, physical and geometrical features of 38 homogeneous bare soil fields are considered as a result of ground truth data collection. X band - VV polarization σ° values from the HUTSCAT scatterometer at 45° and from the CCRS airborne SAR sensor at the incidence angles between 50° and 62° are compared with those obtained from modeled data. The SAR data have been calibrated using both corner reflectors and extended natural targets. The backscatter variability due to surface roughness has been analyzed. Due to the characteristics of the analyzed data set, i.e., high incidence angle and surfaces with large root mean square slope profile m, the SPM and PO models were not suitable for many fields in the scene; on the other hand, a good agreement between theoretical predictions and experimental data is found when the Geometrical Optics (GO) model is used. A threshold value for m as function of the incidence angle is found and a physical interpretation of this behavior is also proposed. After the assessment of the GO model results, the problem of retrieving the real part of the soil relative dielectric constant Re(∈r) and m value is addressed as well, considering the extended Kalman filter approach. The comparison between the obtained values and the experimental data shows the reliability of the inversion approach, thus encouraging the use of more sophisticated backscattering models.

Estimating global solar radiation from common meteorological observations in western Canada

The interest in using crop growth simulation models for estimating large area yields in western Canada has led to a requirement for daily values of solar radiation on an historical and a real time basis. Because such data are usually not readily available, an equation was developed which relates solar transmissivity (ζ) (the ratio of incoming global solar radiation at the earth surface (Q) to solar radiation at the top of the atmosphere (Q0)) to daily observations of maximum and minimum air temperature and total precipitation (P):[Formula: see text]where a, b, c and d are empirical coefficients which vary with time of year and ΔT is the range in daily temperature extremes. During the late fall-winter period, correlation coefficients between observed and calculated transmissivities were less than 0.5 with relative large root mean square errors (RMSE). However, during the growing season when the equation would be of most use, correlation coefficients were 0.7 or higher with RMSEs of 0.12 or lower. The coefficients a, b, c and d were found not to be site-specific during the growing season. No significant differences were found between wheat yields estimated with observed solar radiation and those estimated with the calculated solar radiation from the equation. Key words: Solar radiation, transmissivity, crop growth modelling, wheat yield

An EXAFS study of Ag 3AsS 3 glass

The local structures of Ag 3AsS 3 glass at 80 and 300 K have been investigated by extended X-ray absorption fine structure analysis. By comparing the glass structure with that of Ag 3AsS 3 crystal (proustite), the possibility of ionic conduction by this glass is discussed. The local structure around an As atom in the glass is similar to that in the crystal. This fact suggest that, even in the glass structure, the As atoms from AsS 3 trigonal pyramids of shape similar to that in the crystal. The AgS distance (2.449 Å at 300 K) and the large root mean square displacement, σ, for the AgS atomic pairs in the glass, groups with a by the parameter fitting method, show that the Ag atoms are quite randomly distributed around the AsS 3 groups with a similar AgS distance to that in the crystal. Further, it is possible that the large thermal contribution to σ AgS 2 for the glass may indicate the involvement of the Ag atoms in ionic conduction.

Analysis of slit function errors in single-shot coherent anti-Stokes Raman spectroscopy (CARS) in practical combustors

The temperature determined by a single-shot coherent anti-Stokes Raman spectroscopy (CARS) system is directly related to the half width at half maximum of the instrument slit function. Therefore, an accurate knowledge of the instrument slit function is necessary to determine temperature with CARS. However, in turbulent systems, the input slits of the spectrometer may be removed in order to guarantee signal throughput and establish the necessary dynamic range. In this case, the physical input slits of the spectrometer are replaced with apparent slits created by focussing the input beams near the entrance plane of the spectrometer. The slit function will then depend on the physical relationship among all of the optical components, the probe volume, and the dispersive performance of the spectrometer and detector, as well as the optical path through density and temperature gradients which may not be invariant in a turbulent system. The presence of high temperatures and turbulence levels can effect the size of the CARS signal origin and the optical path, and as a result, the slit function is not invariant. Ignoring these changes can result in large root mean square temperatures (decreased precision) as well as mean temperature errors. The variability of the slit width can be accounted for on a shot-to-shot basis by using a two parameter (HWHM of the slit function and temperature) fitting routine. For temperatures greater than 1200 K there is convergence on a best curve implying both a temperature and a slit width. This method can be used alone or in concert with various weighting schemes to improve the precision. There are two major advantages gained by allowing the slit function to vary in a CARS system: (a) it allows an increase in the precision; (b) it allows temperatures to be calculated without the assumption that the slit function does not change with temperature or turbulence or position within the flame. In fact, it allows the temperature to be determined with almost no previous knowledge of the slit function except the general shape. These two advantages combine to significantly simplify the study of turbulent combusting systems with CARS and to improve the precision, both point-to-point and shot-to-shot, of CARS.