Spectral Scale Research Articles

Spectral optical properties and thermodynamic performance of reflective coatings in a mild climate zone

Abstract The article deals with optical properties and thermodynamic performance of reflective coatings applied on the vertical non-transparent external building surfaces. The starting point of this study comes from the fact, that there are various modifications of coatings, that their guaranteed properties can reduce heating and cooling loads with their application on external building surfaces. The paper presents the results of a comparative nature investigating the optical properties and thermodynamic performance of coatings containing hollow microspheres, as regards their impact upon the thermal properties of buildings envelope walls. The spectral laboratory and full scale outdoor testing methods were used and finally confronted in an experimental study. The tested samples were monitored by dynamic outdoor testing especially under clear sky in daytime and nocturnal conditions. Hollow microspheres coating and standard facing coating of acrylic base as a reference were analyzed primarily and confronted with materials of low-emissivity functions. As a result, the measured data demonstrate no differences in thermodynamic performance of the studied coating due to reducing heating loads especially for nocturnal conditions as well as their thermal emissivity parameters in comparison with the standard facade coating. On the other hand, coatings of hollow microspheres can contribute to the thermodynamic performance up to 5% in daytime conditions of predominantly insolated and weakly isolated walls due to reducing cooling loads in comparison with the standard facade coatings of an identical color shade.

Novel detectors for traceable THz power measurements

Several novel types of detectors for the measurement of electromagnetic radiation in the THz spectral range are described. Firstly, detectors based on pyroelectric foil coated with different absorbers have been developed focusing on the following features: high accuracy due to well-characterized absorption, high sensitivity, large area absorbers and frequency and polarization independence. A three-dimensional design with five absorptions gave an overall absorption of more than 98 %. Secondly, detectors based on pyroelectric foils with thin metal layers were realized. An absorption of 50 % can be obtained if the thickness of the layers is carefully adjusted. According to electromagnetic theory this degree of absorption is independent of the polarization and frequency of the radiation in a wide range from at least 20 GHz to 5 THz. The third type of detector is based on a new type of volume absorber with a polished front surface and a gold-coated back side. It is the absorber of choice of the standard power detector for disseminating the spectral power responsivity scale. This standard detector allows the application of a physical model to calculate its spectral responsivity in the range from 1 THz to 5 THz if the detector has been calibrated at one single frequency. Finally, a THz detector calibration facility was set up and is now in operation at PTB to calibrate detectors from customers with an uncertainty as low as 1.7 %.

Retrieval of aerosol optical depth over Bohai rim region by exploiting multifunctional transport satellite and MODIS data

Atmospheric aerosol particles have a significant impact on global climate change. For the purpose of estimating the effect of aerosols on climate, information on the spatial and temporal distribution of the aerosols is necessary. In this study, we developed an algorithm to retrieve hourly aerosol optical depth (AOD) by using the Moderate Resolution Imaging Spectroradiometer (MODIS) and the data from the multifunctional transport satellite (MTSAT) visible channel over Bohai rim region. First, the MODIS data was used to identify aerosol module, and then the MTSAT data was used to calculate hourly AOD. The results show that the AOD derived from AERONET observations agrees well with the MTSAT-AOD products with spatio-temporal scale, as well as spectral scale. Therefore, the algorithm developed in this study has potential for monitoring AOD hourly.

Frequency-domain simulation of logging-while-drilling borehole sonic waveforms

Numerical simulation of sonic logging-while-drilling (LWD) borehole measurements is challenging because of significant wave propagation effects due to the massive drilling collar occupying a large portion of the borehole. In addition, the internal structure of the LWD tool can have a significant impact on the measured dispersions of Stoneley and quadrupole modes. The collar is typically constructed with a set of inner periodic grooves, which act as a mechanical filter to attenuate undesirable collar modes. Reliable numerical simulation and interpretation of LWD sonic waveforms requires that all features and dimensions of the drilling collar be included in the simulation model. Furthermore, the presence of the drilling collar can prompt numerical instabilities due to backward propagating modes in the perfectly matched layer (PML) commonly used to truncate the computational domain. This problem can be circumvented with the implementation of artificial viscoelastic attenuation in the collar whenever the simulations are intended to reproduce only wave propagation within the surrounding rock formations. In addition, reliable modeling of borehole wave propagation in the presence of high contrasts in material properties and the internal structure of the LWD collar requires a numerical method capable of accurately and stably resolving all spectral scales present in the model. We implemented an automatic [Formula: see text]-adaptive finite-element method in the frequency domain combined with a PML technique to simulate LWD sonic logging measurements. Examples of the application verified the accuracy and reliability of the simulated borehole and formation propagation modes in the presence of casing and internal structures in the LWD collar. The presence of steel casing and quality of casing/formation bond significantly influence the propagation modes excited in a borehole. However, it is still possible to estimate the formation shear slowness using monopole and quadrupole sources regardless of the quality of cement bond in fast formations. Assessment of the formation compressional slowness was significantly impeded by the strong pipe mode. Estimation of formation shear slowness in slow formations is practically impossible due to the presence of casing and a strong annulus mode when the quality of casing bond is poor.

LyMAS: PREDICTING LARGE-SCALE Lyα FOREST STATISTICS FROM THE DARK MATTER DENSITY FIELD

[abridged] We describe LyMAS (Ly-alpha Mass Association Scheme), a method of predicting clustering statistics in the Ly-alpha forest on large scales from moderate resolution simulations of the dark matter distribution, with calibration from high-resolution hydrodynamic simulations of smaller volumes. We use the "Horizon MareNostrum" simulation, a 50 Mpc/h comoving volume evolved with the adaptive mesh hydrodynamic code RAMSES, to compute the conditional probability distribution P(F_s|delta_s) of the transmitted flux F_s, smoothed (1-dimensionally) over the spectral resolution scale, on the dark matter density contrast delta_s, smoothed (3-dimensionally) over a similar scale. In this study we adopt the spectral resolution of the SDSS-III BOSS at z=2.5, and we find optimal results for a dark matter smoothing length sigma=0.3 Mpc/h (comoving). In extended form, LyMAS exactly reproduces both the 1-dimensional power spectrum and 1-point flux distribution of the hydro simulation spectra. Applied to the MareNostrum dark matter field, LyMAS accurately predicts the 2-point conditional flux distribution and flux correlation function of the full hydro simulation for transverse sightline separations as small as 1 Mpc/h, including redshift-space distortion effects. It is substantially more accurate than a deterministic density-flux mapping ("Fluctuating Gunn-Peterson Approximation"), often used for large volume simulations of the forest. With the MareNostrum calibration, we apply LyMAS to 1024^3 N-body simulations of a 300 Mpc/h and 1.0 Gpc/h cube to produce large, publicly available catalogs of mock BOSS spectra that probe a large comoving volume. LyMAS will be a powerful tool for interpreting 3-d Ly-alpha forest data, thereby transforming measurements from BOSS and other massive quasar absorption surveys into constraints on dark energy, dark matter, space geometry, and IGM physics.

Coherence attribute at different spectral scales

In general, we wish to interpret the most broadband data possible. However, broadband data do not always provide the best insight for seismic attribute analysis. Obviously, spectral bands contaminated by noise should be eliminated. However, tuning gives rise to spectral bands with higher signal-to-noise ratios. To quantify geologic discontinuities in different scales, we combined spectral decomposition and coherence. Using spectral decomposition, the spectral amplitudes corresponding to a given scale geologic discontinuity, as well as some subtle features, which would otherwise be buried within the broadband seismic response, can be extracted. We applied this workflow to a 3D land data volume acquired over the Tarim Basin, Northwest China, where karst forms the principle reservoirs. We found that channels are better illuminated around 18 Hz, while subtle discontinuities were better delineated around 25 Hz.

Verification of spectral burn-up codes on 2D fuel assemblies of the GFR demonstrator ALLEGRO reactor

The gas-cooled fast reactor, which is one of the six GEN IV reactor concepts, is characterized by high operational temperatures and a hard neutron spectrum. The utilization of commonly used spectral codes, developed mainly for LWR reactors operated in the thermal/epithermal neutron spectrum, may be connected with systematic deviations since the main development effort of these codes has been focused on the thermal part of the neutron spectrum. To be able to carry out proper calculations for fast systems the used codes have to account for neutron resonances including the self-shielding effect. The presented study aims at verifying the spectral HELIOS, MCNPX and SCALE codes on the basis of depletion calculations of 2D MOX and ceramic fuel assemblies of the ALLEGRO gas-cooled fast reactor demonstrator in infinite lattice.

High-accuracy measurement of linearity of optical detectors based on flux addition of LEDs in an integrating sphere

We present an instrumental realization of linearity measurement of optical detectors based on flux addition of two light-emitting diodes (LEDs) in an integrating sphere. The instrument measures the linearity ratios at pre-defined photocurrent levels according to the algorithm which eliminates the drift effect of LED flux (Shin D J et al 2005 Metrologia 42 154). As a result, the non-linearity correction factors for detector responsivity are determined with their relative standard uncertainties ranging from 2 × 10−5 to 6 × 10−5 (k = 1) for photocurrent ranges from 10−8 A to 10−3 A. By changing the type of LEDs, the wavelength dependence of non-linearity can also be measured, which is demonstrated at 390 nm, 670 nm and 750 nm for a Si photodiode used as a transfer standard for spectral responsivity scale comparisons.

New routes towards even shorter attosecond soft X‐ray pulses

New routes towards even shorter attosecond soft X‐ray pulses

Remote Sensing Image Matching using Sift And Affine Transformation

paper presents remote sensing image matching using sift algorithm and affine transformation. The novelty in our approach is to find the features in the reference image and then match the input image with that of reference image using Affine Transformation. Both synthetic and real data have been considered in this work for the evaluation of the proposed methodology. After registering the image, the outliers are removed. A speeded up affine invariant detector is proposed in this paper for local feature extraction. The experimental results show that the proposed algorithm decreases the redundancy of key points and speeds up the implementation. It is able to account for differences in spectral content, rotation, scale, translation, different viewpoint, and change in illumination. The proposed technique improves the computational efficiency and decrease the storage requirement.

Fundamental Limits of Cooperation

Cooperation is viewed as a key ingredient for interference management in wireless networks. This paper shows that cooperation has fundamental limitations. First, it is established that in systems that rely on pilot-assisted channel estimation, the spectral efficiency is upper-bounded by a quantity that does not depend on the transmit powers; in this framework, cooperation is possible only within clusters of limited size, which are subject to out-of-cluster interference whose power scales with that of the in-cluster signals. Second, an upper bound is also shown to exist if the cooperation extends to an entire (large) system operating as a single cluster; here, pilot-assisted transmission is necessarily transcended. Altogether, it is concluded that cooperation cannot in general change an interference-limited network to a noise-limited one. Consequently, the existing literature that routinely assumes that the high-power spectral efficiency scales with the log-scale transmit power provides only a partial characterization. The complete characterization proposed in this paper subdivides the high-power regime into a degree-of-freedom regime, where the scaling with the log-scale transmit power holds approximately, and a saturation regime, where the spectral efficiency hits a ceiling that is independent of the power. Using a cellular system as an example, it is demonstrated that the spectral efficiency saturates at power levels of operational relevance.

Avaliação dos processamentos de crosstalk e de correção atmosférica em dados ASTER para identificação da relação mineralógica caulinita/(caulinita + gibbsita) em solos no município de São João d'Aliança (GO)

The aim of this study was to analyze the influence of atmospheric correction and crosstalk in the spatial relationship of kaolinite/(kaolinite + gibbsite) in tropical soils through the application of the spectral index RCGb scale, in ASTER-SWIR L1A and L1B images, and in products on-demand AST_07 and AST_07XT, acquired on October 24, 2001. Atmospheric correction routines FLAASH and QUAC and the CRSTK30 software were used to correct for the crosstalk effect. The results were analyzed according to four approaches: comparing the behavior of RCGb scale and RCGbATG transects, analysis of the RCGb scale image of sliced values and analysis of the RCGb scale image and statistical analysis of the similarity between the values of the RCGb scale and RCGbATG transects through the Mann-Whitney statistical test. The routines FLAASH and QUAC hampered the identification of environments and mineralogical relationship. The combination CRSTK30-FLAASH impaired the identification of environments, as well as the relationship mineralogical and the behavior of the RCGb scale transect. The combination CRSTK30-QUAC provided better results in terms of the statistical similarity in relation to the results of the processing without corrections. The results indicated that the products on-demand AST_07 and images L1B converted to reflectance with crosstalk correction and atmospheric correction (QUAC) are the most appropriate, in this order.

Statistics of the Electrosensory Input in the Freely Swimming Weakly Electric FishApteronotus leptorhynchus

The neural computations underlying sensory-guided behaviors can best be understood in view of the sensory stimuli to be processed under natural conditions. This input is often actively shaped by the movements of the animal and its sensory receptors. Little is known about natural sensory scene statistics taking into account the concomitant movement of sensory receptors in freely moving animals. South American weakly electric fish use a self-generated quasi-sinusoidal electric field for electrolocation and electrocommunication. Thousands of cutaneous electroreceptors detect changes in the transdermal potential (TDP) as the fish interact with conspecifics and the environment. Despite substantial knowledge about the circuitry and physiology of the electrosensory system, the statistical properties of the electrosensory input evoked by natural swimming movements have never been measured directly. Using underwater wireless telemetry, we recorded the TDP of Apteronotus leptorhynchus as they swam freely by themselves and during interaction with a conspecific. Swimming movements caused low-frequency TDP amplitude modulations (AMs). Interacting with a conspecific caused additional AMs around the difference frequency of their electric fields, with the amplitude of the AMs (envelope) varying at low frequencies due to mutual movements. Both AMs and envelopes showed a power-law relationship with frequency, indicating spectral scale invariance. Combining a computational model of the electric field with video tracking of movements, we show that specific swimming patterns cause characteristic spatiotemporal sensory input correlations that contain information that may be used by the brain to guide behavior.

Probing Red Blood Cell Morphology Using High-Frequency Photoacoustics

A method that can rapidly quantify variations in the morphology of single red blood cells (RBCs) using light and sound is presented. When irradiated with a laser pulse, an RBC absorbs the optical energy and emits an ultrasonic pressure wave called a photoacoustic wave. The power spectrum of the resulting photoacoustic wave contains distinctive features that can be used to identify the RBC size and morphology. When particles 5–10 μm in diameter (such as RBCs) are probed with high-frequency photoacoustics, unique periodically varying minima and maxima occur throughout the photoacoustic signal power spectrum at frequencies >100 MHz. The location and distance between spectral minima scale with the size and morphology of the RBC; these shifts can be used to quantify small changes in the morphology of RBCs. Morphological deviations from the normal biconcave RBC shape are commonly associated with disease or infection. Using a single wide-bandwidth transducer sensitive to frequencies between 100 and 500 MHz, we were able to differentiate healthy RBCs from irregularly shaped RBCs (such as echinocytes, spherocytes, and swollen RBCs) with high confidence using a sample size of just 21 RBCs. As each measurement takes only seconds, these methods could eventually be translated to an automated device for rapid characterization of RBC morphology and deployed in a clinical setting to help diagnose RBC pathology.

Monitoring and assessing of landscape heterogeneity at different scales

In numerous studies, spatial and spectral aggregations of pixel information using average values from imaging spectrometer data are suggested to derive spectral indices and the subsequent vegetation parameters that are derived from these. Currently, there are very few empirical studies that use hyperspectral data, to support the hypothesis for deriving land surface variables from different spectral and spatial scales. In the study at hand, for the first time ever, investigations were carried out on fundamental scaling issues using specific experimental test flights with a hyperspectral sensor to investigate how vegetation patterns change as an effect of (1) different spatial resolutions, (2) different spectral resolutions, (3) different spatial and spectral resolutions as well as (4) different spatial and spectral resolutions of originally recorded hyperspectral image data compared to spatial and spectral up- and downscaled image data. For these experiments, the hyperspectral sensor AISA-EAGLE/HAWK (DUAL) was mounted on an aircraft to collect spectral signatures over a very short time sequence of a particular day. In the first experiment, reflectance measurements were collected at three different spatial resolutions ranging from 1 to 3 m over a 2-h period in 1 day. In the second experiment, different spectral image data and different additional spatial data were collected over a 1-h period on a particular day from the same test area. The differently recorded hyperspectral data were then spatially and spectrally rescaled to synthesize different up- and down-rescaled images. The normalised difference vegetation index (NDVI) was determined from all image data. The NDVI heterogeneity of all images was compared based on methods of variography. The results showed that (a) the spatial NDVI patterns of up- and downscaled data do not correspond with the un-scaled image data, (b) only small differences were found between NDVI patterns determined from data recorded and resampled at different spectral resolutions and (c) the overall conclusion from the tests carried out is that the spatial resolution is more important in determining heterogeneity by means of NDVI than the depth of the spectral data. The implications behind these findings are that we need to exercise caution when interpreting and combining spatial structures and spectral indices derived from satellite images with differently recorded geometric resolutions.

Numerical simulation of a dispersion-managed active harmonically mode-locked fiber laser using a spectral double-grid technique

A comprehensive lumped model approach has been presented in this paper for the simulation of a dispersion-managed active mode-locked fiber laser. A key aspect of our model is that it operates simultaneously at two different spectral scales, corresponding to the gain bandwidth of the erbium-doped fiber and the frequency content of the mode-locked laser (MLL) pulse. The lumped model consists of a detailed amplifier model that is evolved using a predictor–corrector-based adaptive approach. Convergence analysis of this algorithm is also presented in this paper, highlighting the step size reduction achieved when the amplifier migrates from linear to saturation regime. A simple adaptive frequency domain approach is followed to control the fine grid spectral points and the coarse grid wavelengths. Such an approach has been used to simulate a harmonic MLL cavity in two widely different dispersion regimes facilitated by a pair of chirped fiber Bragg gratings. We validate our model by comparing such simulated results with carefully planned experiments.

Analyzing the effects of particle size on remotely sensed spectra: a study on optical properties and spectral similarity scale of suspended particulate matters in water: errata

Analyzing the effects of particle size on remotely sensed spectra: a study on optical properties and spectral similarity scale of suspended particulate matters in water: errata

A non-standard auxiliary integrating sphere and correction method for the realization of diffuse reflectance

To realize spectral diffuse reflectance scale in 0/d geometric condition at National Institute of Metrology in China (NIM), a facility based on a non-standard auxiliary integrating sphere method with special structure has been built up and a correction method for the influence on the thickness of PTFE (polytetrafluoroethylene) coating at the port of auxiliary integrating sphere is mainly discussed. The uncertainty of spectral diffuse reflectance in NIM is approximately 0.25% (k=2) in 380–800nm. This facility has been used to establish China diffuse reflectance scales in the VIS–NIR part of the spectrum. This system and correction method presented in this paper can be easily implemented on most commercial spectrophotometers with a lower cost.

Ultrafast 2DIR probe of a host-guest inclusion complex: Structural and dynamical constraints of nanoconfinement

Two-dimensional infrared (2DIR) spectroscopy is used to study the influence of nanoconfinement on the spectral diffusion dynamics of cyclopentadienyl manganese tricarbonyl (CpMn(CO)3, CMT) free in solution and confined in the cavity of β-cyclodextrin. Contrary to the reorientation correlation function of the solvent molecules, determined through molecular dynamics simulations, measurements in three different solvents indicate that CMT confined in β-cyclodextrin undergoes spectral diffusion that is faster than free CMT. To account for this discrepancy, we propose that spectral diffusion time scales contain a dynamical contribution that is dependent on the effective size of the conformational space presented by the solvation environment. This solvation state space size is related to the number of participating solvent molecules, which in turn is proportional to the solvent accessible surface area (SASA). We test the role of the number of participating solvent molecules using a simple Gaussian-Markov simulation and find that an increase in the number of participating solvent molecules indeed slows the time required to search the available conformational space. Finally, we test this dependence by comparing the spectral diffusion of a previously studied manganese carbonyl, dimanganese decacarbonyl (Mn2(CO)10, DMDC), to CMT and find that DMDC, which has a larger SASA, exhibits slower spectral diffusion. The experimental observations and the supporting simplistic solvation model suggest that vibrational probe molecules, such as CMT, might be able to function as sensors of conformational entropy.

Effect of Solvent Polarity on the Vibrational Dephasing Dynamics of the Nitrosyl Stretch in an FeII Complex Revealed by 2D IR Spectroscopy

The vibrational dephasing dynamics of the nitrosyl stretching vibration (ν(NO)) in sodium nitroprusside (SNP, Na2[Fe(CN)5NO]·2H2O) are investigated using two-dimensional infrared (2D IR) spectroscopy. The ν(NO) in SNP acts as a model system for the nitrosyl ligand found in metalloproteins which play an important role in the transportation and detection of nitric oxide (NO) in biological systems. We perform a 2D IR line shape study of the ν(NO) in the following solvents: water, deuterium oxide, methanol, ethanol, ethylene glycol, formamide, and dimethyl sulfoxide. The frequency of the ν(NO) exhibits a large vibrational solvatochromic shift of 52 cm(-1), ranging from 1884 cm(-1) in dimethyl sulfoxide to 1936 cm(-1) in water. The vibrational anharmonicity of the ν(NO) varies from 21 to 28 cm(-1) in the solvents used in this study. The frequency-frequency correlation functions (FFCFs) of the ν(NO) in SNP in each of the seven solvents are obtained by fitting the experimentally obtained 2D IR spectra using nonlinear response theory. The fits to the 2D IR line shape reveal that the spectral diffusion time scale of the ν(NO) in SNP varies from 0.8 to 4 ps and is negatively correlated with the empirical solvent polarity scales. We compare our results with the experimentally determined FFCFs of other charged vibrational probes in polar solvents and in the active sites of heme proteins. Our results suggest that the vibrational dephasing dynamics of the ν(NO) in SNP reflect the fluctuations of the nonhomogeneous electric field created by the polar solvents around the nitrosyl and cyanide ligands. The solute solvent interactions occurring at the trans-CN ligand are sensed through the π-back-bonding network along the Fe-NO bond in SNP.