Surface Diffuse Reflectance Research Articles

Modelization of combined radiative and conductive heat transfer in three‐dimensional complex enclosures

PurposeTo provide a finite volume code, based on Cartesian coordinates, for studying combined conductive and radiative heat transfer in three‐dimensional irregular geometries.Design/methodology/approachIn the present study, a three‐dimensional blocked‐off‐region procedure was presented and implemented in a numerical code based on the finite volume method to model combined conductive and radiative heat transfer in complex geometries. This formulation was developed and tested in three‐dimensional complex enclosures with diffuse reflective surfaces and containing gray absorbing‐emitting and isotropically scattering medium. This approach was applied to analyze the effect of the main of thermoradiative parameters on the temperature and flux values for three‐dimensional L‐shaped enclosure.FindingsThe proposed isotropic model leads to satisfactory solutions with comparison to reference data, which entitles us to extend it to anisotropic diffusion cases or to non‐gray media. The blocked‐off‐region procedure traits both straight and curvilinear boundaries. For curved or inclined boundaries, a fine or a non‐uniform grid is needed.Originality/valueThis paper offers a simple Cartesian practical technique to study the combined conductive and radiative heat transfer in three‐dimensional complex enclosures with both straight and curvilinear boundaries.

Improved algorithms and methods for room sound-field prediction by acoustical radiosity in arbitrary polyhedral rooms.

This paper explores acoustical (or time-dependent) radiosity--a geometrical-acoustics sound-field prediction method that assumes diffuse surface reflection. The literature of acoustical radiosity is briefly reviewed and the advantages and disadvantages of the method are discussed. A discrete form of the integral equation that results from meshing the enclosure boundaries into patches is presented and used in a discrete-time algorithm. Furthermore, an averaging technique is used to reduce computational requirements. To generalize to nonrectangular rooms, a spherical-triangle method is proposed as a means of evaluating the integrals over solid angles that appear in the discrete form of the integral equation. The evaluation of form factors, which also appear in the numerical solution, is discussed for rectangular and nonrectangular rooms. This algorithm and associated methods are validated by comparison of the steady-state predictions for a spherical enclosure to analytical solutions.

Electroless plating of nickel–phosphorous on surface-modified poly(ethylene terephthalate) films

Chemical surface preparation for Ni–P electroless metallization of poly(ethylene terephthalate) (PET) films without using Chromium-based chemicals, was studied. The applicability of this method was verified by a subsequent metallization process. Thermal analysis was conducted to observe the main thermal transitions and stability of the polymer and metallized films. Contact angle analysis was performed to assess the surface hydrophilicity so as to optimize the substrate preparation process. X-ray diffraction, EDAX and SEM analysis were used to understand the composition and morphology of the polymeric substrate and Ni–P coat growing process. Adherence strength, contact sheet resistivity and optical diffuse reflection were measured on the metallized films. The time of chemical etching affects the polymer surface hydrophilicity, polymer/metal adherence strength, surface resistance and optical diffuse reflection, while Ni coating morphology is controlled by the pH of the electroless bath. High wettability of the polymer surface, adherence strength of 800 N cm −2, high optical diffuse reflection and low surface resistivity of the Ni coating, were found for films etched for 60 min. Metallizations performed at pH 7.5 produce Ni–P coatings with 12.0 wt.% phosphorous content, which were amorphous and flexible. The contact sheet resistivity of the plated films is sensitive to roughness variations of the substrate. The method proposed in this work allows the production of metallized films appropriate for the fabrication of flexible circuits.

The preparation and characterization of nanoparticle TiO 2/Ti films and their photocatalytic activity

Nanoparticle TiO 2/Ti films were prepared by a sol–gel process using Ti(OBu) 4 as raw material, the as-prepared film samples were also characterized by TG-DTA, XRD, TEM, SEM, XPS, DRS, PL, SPS and EFISPS testing techniques. TiO 2 nanoparticles experienced two processes of phase transition, i.e. amorphous to anatase and anatase to rutile at the calcining temperature range from 450 to 700 °C. TiO 2 nanoparticles calcined at 600 °C had similar composition, structure, morphology and particle size with the internationally commercial P-25 TiO 2 particles. Thus, the conclusion that 600 °C might be the most appropriate calcining temperature during the preparation process of nanoparticle TiO 2/Ti film photocatalysts could be made by considering the main factors such as the properties of TiO 2 nanoparticles, the adhesion of nanoparticle TiO 2 film to Ti substrate, the effects of calcining temperature on Ti substrate and the surface characteristics and morphology of nanoparticle TiO 2/Ti film for the practice view. The Ti element mainly existed on the nanoparticle TiO 2/Ti(3) film calcined at 600 °C as the chemical state of Ti 4+, while O element mainly existed as three kinds of chemical states, i.e. crystal lattice oxygen, hydroxyl oxygen and adsorbed oxygen with increasing band energy. Its photoluminescence (PL) spectra with a peak at about 380 nm could be observed using 260 nm excitation, possibly resulting from the electron transition from the bottom of conduction band to the top of valence band. The PL peak position was nearly the same as the onset of its diffuse reflection spectra (DRS) and surface photovoltage spectroscopy (SPS), demonstrating that the effects of the quantum size on optical property were greater than that of the Coulomb and surface polarization. The PL spectra with two peaks related to the anatase and rutile, respectively, could be observed using the excited wavelength of 310 nm. Weak PL spectra could be observed using the excited wavelength of 450 nm, resulting from surface states. In addition, during the experimental process of the photocatalytic degradation phenol, the photocatalytic activity of nanoparticle TiO 2/Ti film with three layers calcined at 600 °C was the highest.

Polarized directional reflectance from laurel and mullein leaves

The ability to perform polarimetric imaging throughout the vis- ible and infrared (IR) wavebands has improved considerably in the past decade. Systems now exist that enable measurements to be made of all four Stokes parameters arising from each pixel in the image. The ques- tion of whether polarimetric imaging offers an advantage over conven- tional imaging methods for discrimination of plant type in scenes of natu- ral vegetation remains to be answered. Although the size of a leaf may be below the spatial resolution of an imaging system, the polarimetric properties of individual leaves may affect the data observed from a tree or forest canopy. We report the results of measurements of the polarized hemispherical directional reflectance (HDR), which is related to the di- rectional emissivity, and bidirectional reflectance distribution function (BRDF) from two examples of leaves. To completely characterize the polarimetric properties of a leaf, and ultimately a leaf canopy, an exten- sive measurement of the polarized BRDF and HDR of individual leaves is required. This is necessary because of the large range of possible relative orientations of the illumination, leaf and observer, and the range of polarization states of incident radiation. We report a limited set of laboratory measurements designed to investigate whether any gross po- larimetric difference exist between two dissimilar types of plant leaves in the visible, near IR (NIR), and IR spectral wavebands. Laurel (prunus laurecatious) has a wax surface creating a gloss or glabrous appearance to the leaf. The surface of mullein (verbascum thapsus) is highly pubes- cent with a dense layer of hair over the adaxial surface, creating a highly diffuse surface reflectance. Significant differences are found between the two species of leaf in the measured polarized directional reflectance and emissivity. © 2002 Society of Photo-Optical Instrumentation Engineers.

Preparation, characterization and physical properties of mixed Sb 1− xBi x TeI

We have synthesized Sb 1− x Bi x TeI (where x = 0.1, 0.4 and 0.9.). The structural variation, electrical resistivity, diffuse reflectance spectroscopy and surface morphology of Sb 1− x Bi x TeI have been studied. The compounds crystallize with the triclinic symmetry. The temperature dependence of electrical resistivity exhibits semiconducting behaviour. The activation energy and band gap of pure SbTeI are found to be 0.37 and 0.73 eV, respectively.

On measures to increase sound-field diffuseness and the applicability of diffuse-field theory

This letter discusses the definition of a diffuse sound field, two measures (diffuse surface reflection and volume scatterers) proposed to increase sound field diffuseness, and the applicability of diffuse-field theory. It is shown that the two proposed measures increase diffuseness, and the applicability of diffuse-field theory, with respect to sound decay/reverberation time. However, they decrease diffuseness, and the applicability of diffuse-field theory, with respect to steady-state sound-pressure level. The implications of these results for the definition of a diffuse sound field are discussed.

Spatial information measurements for investigating specular and diffuse sound fields in enclosures

Attempts to predict the sound quality in large rooms can be made at the design stage using scale or computer simulation models but they are usually based on the assumption that the sound field is diffuse. Quality is said to be measured in existing rooms by known room-acoustic indicators but most of them have been developed without regard to direction sensing. Measurements in existing halls show that the sound field is far from diffuse. Specular and diffuse surface reflections not only vary from one room to another but also from seat to seat in the same room. To quantify this phenomena, both spatial and temporal diffuseness has to be investigated. Measuring the directional characteristics of sound in existing halls provides the prospect of quantifying such distribution. This work describes the development of a PC-based system to measure the spatial information of sound fields in large rooms. The system utilizes sound intensity measurement from three microphone pairs arranged in Cartesian coordinates or one pair in three successive orientations to calculate intensity vectors. The sound field can then be visualized on an energy directional basis versus arrival time and hence analyzed in greater detail than hitherto possible. The potential for quantifying spatial specular and diffuse sound fields will be discussed and example results presented. Such results may lead to new acoustic indices with respect to direction dictated quality. [Work supported by NSERC, Canada, Individual Operating Grant OGPIN 013.]

Scaling relationships for theories of anisotropic random walks applied to tissue optics

Monte Carlo simulations are used to discern scaling relationships for photon migration occurring within homogeneous, anisotropic scattering media of semi-infinite extent. Special attention is given to events associated with short path lengths. Empirical scaling relationships for path lengths and surface intensities are shown to agree with a consistency equation derived in an earlier study of anisotropic random walks. They are augmented here by a procedure that accounts for concomitant scaling of optical absorption coefficients. Results then are used to transform expressions that were obtained previously by analytical random-walk theory developed for an isotropic scattering model of photon migration. Quantities that are studied include the diffuse surface reflectance, the depth distribution of the fluence, and the time-resolved intensity of backreflected photons.

Evidence of diffuse surface reflections in rooms

In a recent publication [M. Hodgson, J. Acoust. Soc. Am. 84, 253–261 (1988)], predictions were compared with measurements made in an empty scale-model room and in various nominally empty factories and gymnasia. Consistent deviations between prediction and experiment were found. In order to explain these deviations, it was hypothesized that diffuse surface reflections were occurring in the test rooms. To test this hypothesis, further predictions have now been made using a ray-tracing model that takes diffuse surface reflection into account. It was found that excellent agreement between prediction and experiment is obtained as follows: (a) in the scale model, if all surfaces are 10%–40% diffusely reflecting; (b) in nominally empty factories, if the ceiling and walls are 60%–90% diffusely reflecting. This result represents strong evidence that typical untreated room surfaces are strongly diffusely reflecting.

Evidence of diffuse surface reflection in rooms

In a recent publication [M. Hodgson, J. Acoust. Soc. Am. 84, 253–261 (1988)], predictions were compared with measurements made in an empty scale‐model room and in various nominally empty factories and gymnasia. Consistent deviations between prediction and experiment were found. In order to explain these deviations, it was hypothesized that diffuse surface reflections were occurring in the test rooms. To test this hypothesis, further predictions have now been made using a ray‐tracing model that takes diffuse surface reflection into account. It was found that excellent agreement between prediction and experiment is obtained as follows: (a) in the scale model, if all surfaces are 10%–40% diffusely reflecting; (b) in nominally empty factories, if the ceiling and walls are 60%–90% diffusely reflecting. This result represents strong evidence that typical untreated room surfaces are strongly diffusely reflecting.

The reduction process of copper-zinc oxide-(alumina) methanol catalysts

CuO-ZnO-Al 2O 3 catalysts at different copper and zinc contents were obtained by thermal decomposition of hydroxycarbonate precursors at 350°C in air. They were characterized by using X-ray diffraction, diffuse reflectance spectroscopy and surface area determination. We find disticnt CuO and ZnO phases whose particle sizes, determined by XRD line broadening, are in the range 65–90 Å for CuO and around 100 Å for ZnO in the binary CuO/ZnO systems. For pure CuO the particle dimensions are higher (D~140 A ̊ ) . For the three component oxide, CuO|ZnO|Al 2O 3=60|30|10, the particle sizes of both CuO and ZnO phases are around 60 Å. The BET surface areas are around 70 m 2/g for the two components oxides, ~40 for pure CuO and for the three component systems. The reduction of the copper oxide (CuO) has been studied by in situ XRD. The reduction to metallic copper proceeds through the formation of intermediate Cu 2O which is present together with metallic copper even at relatively high extents of reduction. It has also been observed that the reduction process is much slower in the three component system than for pure CuO or the two component, CuO-ZnO, system. The presence of alumina in intimate contact with CuO and ZnO (due to the preparation conditions of the precursors) thus seems to hinder the reduction of the Cu 2+ species (to Cu + or Cu o) and to prevent the nucleation of both cuprous oxide and metallic copper partcles.

A rapid and accurate method for calculation of stratospheric photolysis rates with molecular scattering

A method is presented for rapid and accurate calculations of photodissociation rates needed for photochemical modeling of the stratosphere, which include the effects of molecular scattering. Under the assumption of isotropic scattering and diffuse surface reflection, the linearity of the radiative transfer equation is used to decompose the total diffuse radiance field into two subfields that are referred to as the atmospheric and surface components. The atmospheric component accounts for the portion of the diffuse field that arises from scattering of the direct solar beam, while the surface component accounts for the portion of the diffuse field associated with radiation (direct plus diffuse) reflected by the surface that is subsequently scattered. Furthermore, the surface component has been normalized with respect to the total reflected radiation, so that it represents a relative field that is independent of solar angle and surface radiation properties that are contained in a surface scaling parameter. This independence can be effectively utilized when calculating photolysis rates for a series of sun angles, since the surface field need only be computed once. When the atmospheric and surface components are appropriately normalized, the wavelength variation of the resultant fields is sufficiently smooth that by using nine nodal points between 300 and 730 nm and cubic spline interpolation, accurate values of these fields at intermediate wavelengths are rapidly obtained. Further reductions in computational time are achieved by applying Sokolov's iterative procedure of averaging functional corrections to calculate approximate solutions for the atmospheric and surface fields at the nodal points. For wavelengths greater than 340 nm, a single iteration is sufficient to give results that agree with the exact values to better than 10% at altitudes above 15 km. Three iterations are used at shorter wavelengths due to increases in optical depth. The accuracy of the method for calculating photodissociation rates of 27 photolysis processes at 40 altitude levels between 0 and 53 km is typically better than 5% for altitudes above 10 km and all zenith angles.

Zenith angle effects in multichannel infrared sea surface remote sensing

Several approaches to infrared multichannel sea surface temperature retrievals propose using a universal set of constants. It is shown that the single-channel multiangle technique (i.e., GOES and NOAA) and the multichannel single-angle technique (NOAA-n) are similar concepts with a common derivation from radiative transfer theory. It is also shown that the linear correlation factor between surface temperature minus satellite temperature in one channel versus the difference in satellite temperatures in two channels is not independent of the difference in satellite sensed equivalent blackbody temperature. The 3.7-μm, 11-μm, and 12-μm channels on the NOAA-n AVHRR can be used in combination to compute atmospheric transmissivity and average atmospheric temperature, but a better combination would be substituting three 0.5-μm-wide channels centered on 11.25 μm, 11.75 μm, and 12.25 μm. A triple window multispectral scanner in the 11–12.5 μm region allows determination of diffuse surface reflectance which can bias sea surface temperatures −0.4 K±0.3 K.

Radiation Heat Transfer Between Specularly and Diffusely Reflecting Surfaces

Abstract Radiation heat transfer between specularly and diffusely reflecting plane surfaces is exactly analyzed based on radiation intensity without employing the image method. With this analysis, specular reflection can be treated easier than with the image method, leading to possible formulation of the basic equation in defiance of the number of specular reflections. The basic equation is applied to the simple two-dimensional radiation transfer system, from which approximate expressions are made for the surfaces nearly perfectly reflecting diffusely and for those nearly perfectly reflecting specularly. Numerical solutions are obtained of both exact and approximate expressions for systems of parallel plates and adjoint plates. It is confirmed that the approximations are quite acceptable, except for the case with very low emittance. The mean heat fluxes over the plate obtained by approximate solutions agree well with those by exact expressions.

The measurement and use of registered reflectance and range data in scene analysis

The theory and use of a laser sensor designed to provide arrays of registered intensity and range data for three-dimensional scene analysis are described in this paper. Equations are derived to relate the mean and variance of both the intensity and the range data to the physical properties of the target and the parameters of the sensor. Experimental results that verify these equations are given. Adaptive data smoothing and normalization procedures are presented. These procedures reduce photon noise and correct the intensity data for inverse square-law effects. The resulting intensity data give the product of the diffuse surface reflectance and the cosine of the angle of incidence for each picture element in the scene. Simple procedures are given for finding outlines of occluding objects, obtaining normal views of obliquely sensed planar surfaces, and extracting the images of horizontal surface regions from a scene. These procedures demonstrate the advantages of having registered reflectance and range data for scene analysis.

ChemInform Abstract: BIVALENT METAL COMPLEXES OF N,N‐BIS(2‐HYDROXYETHYL)GLYCINE

AbstractAnhand von IR‐ und Elektronenspektren sowie magnetischer Suszeptibilität und thermischer Analyse wird die Komplexbildung zweiwertiger Metalle mit dem Titelliganden untersucht, wobei diskutiert wird, inwieweit die Hydroxylgruppen die Koordination mit dem Metall beeinflussen.

Bivalent Metal Complexes of N,N-Bis(2-hydroxyethyl)glycine

Abstract Complexes of N,N-bis(2-hydroxyethyl)glycine(BHEG) with a bivalent cation (Cu(II), Ni(II), Co(II), Zn(II), Fe(II), Cd(II), and Pb(II)) have been prepared and investigated by means of infrared absorption spectra, powder surface diffuse reflection spectra, electronic spectra, magnetic susceptibility, and thermal analysis. They can be classified into two types: (A) ML2·nH2O and (B) ML·X·nH2O, (M: metal, L: BHEG−, X: Cl− or NO3−). Ni(II), Co(II), Zn(II), and Fe(II) complexes are of type A, and those of Cd(II) and Pb(II) of type B. In the case of Cu(II) complexes, a blue A type complex (Cu(II)-A) has been prepared from a basic solution and a green B type one (Cu(II)-B) from an acidic solution. From detailed assignments of IR spectra, BHEG is found to have a zwitter ion structure. From magnetic moment data and reflection spectra, we presume that the A type complexes have a trans octahedral structure and the B type complexes a tetrahedral structure.

Diffuse surface reflection in free-molecular flow at a speed of 10 km/sec

An experimental investigation has been made of a diffuse-reflection scheme for conditions where the velocity of the particles bombarding a surface is 10 km/sec, and the surface is covered with an adsorbing layer. It is shown that the use of diffuse reflection is valid over a range of incident angles from θ=0 to θ≲40‡. For θ>40‡ the diffuse reflection is a crude approximation, since it does not take into account the contribution of scattered particles which are reflected in a quasispecular manner and have speed approximately equal to the incident speed.

The Solid State Photochemical Decomposition of Potassium Ethylenediaminetetraacetatomanganate (III)

The photochemical effect on the decomposition of solid potassium ethy enediaminetetraacetatomanganate (III)was examined by irradiating it with a mercury lamp(Toshiba SHL-100UV) at a distance of 15 cm. The principal mercury line spectra occurred between 250 and 600nm, below 300 nm the intensity was weak and it showed maximum at 546 nm.Infrared spectra of K[MnEDTA]e2(1/2) H20 and the reaction products were L e4amined by the NujoFrtiull method. The spectrum of the chelate before irradiation indicated the pres. ence of'eoorainated carboxylic acid group band at 1680 cm i. However, the intensity of this bapd decreased markedly a ter irradiation, and a new band appeared at ab6ut 1610 cmi, due to the reductio: n-of the manga: nese(III)chelate to the manganese(II)1 According to Sievers and B-aMii-a r, b D, (Coo) chanW wh6h the ratio of metal ion charge to its radius is 3.6thg sqrpe was true for the change of manganese(III)to manganese(II)and the above mentioned shift of band was thus well explained. The 2349 cm th band shownl in the Fig.1 was due to the CO2 gas produced in the decompositon process.The. ch-ange of the powder surface diffuse reflectance spectra of the chelate by irradiation is given in Fig.2. The spectrum of the initial chelate had peak maxima, one at 5PO nm and 6ther in the region lower than 330 nm. Aftet irradiation, both maxima dis-appeareq.Tha process oV the photochemical decomposition may be shown by the following fashion.