POSTER SESSION I
ACCURATE SEGMENTATION OF COMPLEX SATELLITE
SCENES
James J. Simpson
Digital Image Analysis Laboratory
Scripps Institute of Oceanography
University California San Diego
La Jolla, CA 920930237, U.S.A.
Accurate cloud detection in Advanced Very High Resolution Radiometer
(AVHRR) data over land is a difficult task complicated by spatially
and temporally varying land surface reflectances and emissivities.
The AVHRR SplitandMerge Clustering (ASMC) algorithm for cloud
detection in AVHRR scenes over land provides a computationally
efficient, scene specific, objective way to circumvent these difficulties.
The algorithm consists of two steps: 1) a splitandmerge clustering
of the input data (calibrated channel 2 reflectance, calibrated
channel 4 temperature, and a channel 3  channel4 temperature
difference) which segments the scene into its natural groupings;
and 2) a cluster labeling procedure which uses scene specific
joint threedimensional adaptive thresholds (as opposed to constant
static thresholds) to label the clusters as either cloud, cloudfree
land, or uncertain. The uncertain class is used for those pixels
whose signature is not clearly cloudfree land or clouds (e.g.,
pixels at cloud boundaries which often contain subpixel cloud
and land information which has been averaged together by the integrating
aperture function of the AVHRR instrument). Results show that
the ASCM algorithm is neither regionally nor temporally specific
and can be used over a large range of solar altitudes. Sensitivity
of the segmentation and labeling steps to the choice of input
variables also was studied. Results obtained with the ASMC algorithm
also compare favorably with those obtained from a wide range of
currently used algorithms to detect cloud over land in AVHRR data.
Moreover, the ASMC algorithm can be adopted for use with data
to be taken by the Moderate Resolution Imaging SpectrometerNadir
(MODISN).
The accurate segmentation of sea ice from cloud and from cloudfree
ocean in polar AVHRR imagery is important for many for many scientific
applications (e.g., sea ice  albedo feedback mechanisms, heat
exchange between ocean and atmosphere in polar regions; studies
of the stability of surface water in polar regions). Unfortunately,
it is a difficult task complicated by the common visible reflectance
characteristics of sea ice and cloud. Moreover, AVHRR channel
3 data historically have been contaminated by their use in the
classification of polar scenes. Likewise, polar scenes often contain
pixels with mixed classes (e.g., sea ice and cloud). This paper
uses a combination of fuzzy logic classification methods, noise
reduction in AVHRR channel 3 data using Wiener filtering methods
(Simpson and Yhann, 1994), and a physically motivated rule base
which makes effective use of the Wiener filtered channel 3 data
to more accurately segment polar imagery. The new method's improved
classification skill compared to more traditional methods, as
well as its regional independence, is demonstrated. The algorithm
is computationally efficient and hence is suitable for analyzing
the large volumes of polar imagery needed in many global change
studies.
SIMULATION OF THE EXTINCTION OF A LASER BEAM
USING THE MONTE CARLO METHOD
C.A. Papavavlou, J.G. Marakis, E. Kakaras
Laboratory of Steam Boilers and Thermal Plants, Thermal Engineering Section,
National Technical University Of Athens, 28 Octobriu Str., 10682 Athens
Extinction of light in participating media has been extensively
used in applications such as laser diagnostics and inverse radiation
problems. The accuracy of these techniques is always judged upon
the adequacy of the underlying modeling. In that sense, the rigorous
modeling of the radiative phenomena is expected to improve substantially
the accuracy of the applied techniques. In the present paper a
direct statistical Monte Carlo method is adopted, together with
detailed treatment of the radiative properties of particles calculated
using the Mie theory. The method is firstly applied for the experiment
of Boothroyd et al. (Boothroyd, S.A., Jones, A.R., Nicholson,
K.W., and, Wood, R., Combust Flame 69, 235241, 1987) concerning
extinction of an expanded laser beam by fine streams of flyash
particles. This experiment is depicted in Fig. 1. For sampling
of the directions followed by the bundles after a scattering event
the exact, according to Mie theory, phase function is used. The
effects of polarization is not taken into account, since the laser
beam is appropriately prepared to simulate unpolarized light.
Comparisons are made between the measured and calculated angular
distribution of the intensity and satisfactory agreement is found
(Fig. 2). The value of the flyash refractive index is initially
taken as suggested by the authors (n+ik=1.5+i0.012).
Due to the uncertainties concerned to the dependence of the refractive
index from the chemical composition of the ash, as well as the
sensitivity of Mie calculations on this index, lower values of
its imaginary part are considered, as measured by Goodwin and
Mitchner (Goodwin, D.G., and Mitchner, M.; Int. J. Heat Mass Transfer,
32, 627638, 1989). This consideration reveals significant discrepancies
of the calculated angular intensities (Fig. 3). For the specific
wavelength of the HeNe laser, a backward lobe is apparent for
all the diameters of the examined psd. The most drastic change
is concerned with the alteration of the scattering behavior. The
calculated scattering albedo was found in the order of 0.99. Thus,
ashes characterized by imaginary part of the refractive index
as low as measured by Goodwin, are almost conservative scatterers.
The concentration of the ash particles in the previously examined
experiment is found to be dilute enough to practically avoid multiple
scatterings. In order to gain a better insight on this phenomenon,
a numerical experiment is performed concerning the extinction
of the same laser beam by a suspension of particles with considerably
higher optical depth. At elevated concentrations, bundles undergo
multiple scatterings before reaching the photomultiplier. This
procedure is quantified by calculating the ratio of the bundles
reaching the photomultiplier after multiple scattering over the
total number of the received bundles. The angular distribution
of this ratio is presented in Fig. 4. From this figure it is evident
that for a wide angular interval the received scattered intensity
originates mostly from multiple scatterings. From the same figure,
angular positions where this ratio is minimized are easily identifiable.
Furthermore, the comparison between the angular distributions
of the singly scattered bundles and totally received ones imply
that a medium tends to be sensed as an increasingly isotropic
scatterer as the proportion of the multiple scatterings also increases.
DEPENDENCE OF RADIATIVE TRANSFER CHARACTERISTICS FROM GEOMETRY
OF AN ABSORBING, EMITTING AND SCATTERING MEDIUM
M.L. German, E.F. Nogotov
Heat & mass Transfer Institute, Belarus Academy of Sciences,
15, P.Brovka, Minsk, Belarus, 220728
For power production systems, it is necessary to know the values
of the incident and net radiant fluxes and their distributions
along the boundary surfaces. However, the analysis of literature
shows that these problems are not enough investigated yet. In
present work the theoretical investigation of the influence of
geometric form of an absorbing, emitting and scattering medium
on the incident radiant flux and its distribution along the boundary
surface is proposed. The problem is solved for a closed twodimensional
domain.
The presented investigation is based on the numerical solution
of the wellknown integrodifferential equation of radiative transfer
with the boundary conditions which are including the radiation
and reflection processes on the heatabsorbing surfaces. Resolution
algorithm of the mentioned above equation is a combination of
the finite element method, discreteordinate method and method
of iterations. The idea of this method is following: a) according
to the discrete ordinate method, few directions for calculation
are selected and the mentioned above equation is written for every
selected direction; b) obtained equations are solved by wellknown
method of finite elements; c) so as the radiative transfer equation
is nonlinear an iteration process is organized for calculation
the values of the radiation intensity at the nodes of the considering
domain.
On the base of proposed method the dependence of radiative characteristics
(density of incident and net radiative fluxes, structure of radiation
field, etc.) from geometrical form of an absorbing, emitting and
scattering medium is researched for domains with various geometry.
The results of investigations show possibility of discontinue
the radiant flux density at the corner point of domain. It is
shown that the discontinue take place on the condition when the
bisector of corresponding corner is not the symmetry axis of the
domain or the optical properties of medium. The influence of the
optical and geometrical properties of medium on the values of
discontinue is considered. The behavior of falling radiant flux
distribution along the boundary for various optical, heatphysical
and geometrical characteristics of medium is investigated. It
is shown that inhomogeneity of this distribution is increased
with the increasing relative difference between the boundary radiation
and the own medium radiation. The carried out investigation shows
that the form of domain filled with an absorbing, emitting and
scattering medium essentially effects the radiant flux distribution
along its boundary surfaces.
Authors are thankful to the Belarus Foundation of Fundamental
Investigations for the financial support of this work.
DEPENDENCE OF RADIATIVE TRANSFER CHARACTERISTICS
FROM OPTICAL PROPERTIES OF AN ABSORBING, EMITTING AND SCATTERING
MEDIUM
M.L. German, E.F. Nogotov
Heat & Mass Transfer Institute, Belarus Academy of Sciences,
15, P.Brovka, Minsk, Belarus, 220728
Study of the mechanism of radiation propagation in twophase media
(gas and solid particles) has a significant number of applications
in applied physics and engineering. These include radiative and
combined heat transfer, direct and inverse problems in spectroscopy
of scattering medium, heat transfer enhancement in thermal and
nuclear engineering and metallurgy and so on. The development
of modern technology and enhancement due to the increasing capacity
of heat power plants have influenced a growing interest in radiative
heat transfer in new types of equipment. As a result, new, more
stringent requirements for analysis of radiative transfer and
correct and timely solutions of problems in this field are needed.
At present time many methods for resolution of transport equation
are known. But these methods do not estimate complex geometrical
form of real objects. That is why the authors propose a resolution
method for the integrodifferential equation of radiative transfer,
which is free from mentioned above demerit at least.
Numerical solution of the wellknown integrodifferential equation
of radiative transfer with the boundary conditions which are including
the radiation and reflection processes on the heatabsorbing surfaces.
Algorithm of resolution of the mentioned above equation is a combination
of the finite element method, discreteordinate method and method
of iterations. The idea of this method is following: a) according
to the discrete ordinate method, few directions for calculation
are selected and the mentioned above equation is written for every
selected direction; b) obtained equations are solved by wellknown
method of finite elements; c) so as the radiative transfer equation
is nonlinear an iteration process is organized for calculation
the values of the radiation intensity at the nodes of the considering
domain. In the report this method is described in full details.
On the basis of proposed method the dependence of radiative characteristics
(density of incident and net radiative fluxes, structure of radiation
field, etc.) from optical properties (optical density of medium,
Shuster's number, emissivity of boundary and so on) of an absorbing,
emitting and scattering medium is researched. In particularly
the results of investigation show that scattering processes may
increase or decrease the value of leaving radiant intensity in
dependence on the optical thickness of medium along the direction
of propagation. This result is important for the definition of
absorbing index of selective, absorbing, emitting and scattering
medium in the finite spectral range and for diagnosing of such
media.
Authors are thankful to the Belarus Foundation of Fundamental
Investigations for the financial support of this work.
COMPARISON OF NUMERICAL QUADRATURE SCHEMES
APPLIED IN THE METHOD OF DISCRETE TRANSFER
Flemming M.B.Andersen
Laboratory of Heating and Air Conditioning
Technical University of Denmark, Building 402
DK2800, Lyngby, Denmark
The quadrature scheme in the method of discrete transfer is considered.
Since the numerical solution of the radiation problem is very
time consuming, it is of the utmost importance that the most efficient
numerical quadrature schemes be applied in order to obtain a solution
with a prescribed accuracy with the minimum computation costs.
Little research has been performed in this area and only two schemes
have been put forward by Shah (1979) and Bressloff et al. (1995).
Shah (1979) suggested a scheme in which the peripherential angle
() and the angle
() from the
normal of the wall are divided into equal size angles. This type of
discretisation leads to solid angles which are highly unequal and the
scheme is a simple midpoint quadrature in the
,
space.
Bressloff et al. (1995) suggested a quasiequal solid angle
discretisation of the hemisphere and obtained a better accuracy for
the same computational cost. In the present paper, the GaussLegendre
quadrature is applied for the integral of the irradiation written in
three ways: (i) as a function of ,
(ii) as a function of ,
(=cos), and (iii) as a function
of , 1/2^{2}. Furthermore,
(iv) the quadrature schemes are compared for simple geometries with an
isothermal absorbing, emitting gray gas with a prescribed constant
temperature regarding the accuracy and computational costs.
Keywords: Thermal Radiation, Discrete Transfer, Integration.
BOUNDARY CONDITION FOR RADIATION MODELLED
BY HIGH ORDER SPHERICAL HARMONICS
Flemming M.B. Andersen
Laboratory of Heating and Air Conditioning
Technical University of Denmark, Building 402
DK2800, Lyngby, Denmark
A recurrence formula is derived for coefficients in the Marshak
boundary condition which is used in connection with the method
of spherical harmonics when modelling radiation heat transfer
in absorbing, emitting and scattering material. The case considered
is a onedimensional layer of material with azimuthally symmetry
surrounded by opaque, diffusely and specularly reflecting and
diffusely emitting walls. The other coefficients in the Marshak
condition are related to the first mentioned coefficient by simple
expressions. This new method of calculating the coefficients by
recurrence is easier to apply than deriving the boundary condition
by tedious manual integrations. A recurrence formula for the cumulated
errors is derived and the analyses shows that acceptable low errors
occur when using the appropriate type of floating point numbers
in the computer program taking into account the approximation
order. The coefficients found by recurrence are compared to coefficients
found by numerical integration and in one case the analytical
solution and the agreement is excellent. The application of the
recurrence formulas is demonstrated using a computer program solving
the equations of the method of the spherical harmonics for arbitrary
approximation order. The intensity as function of the direction
cosine at the walls is analyzed for approximation orders up to
41. High order approximations are necessary for accurate modelling
of the intensity as function of the direction due to discontinuities
at the walls.
Keywords: Radiation, Spherical Harmonics, Marshak Condition.
RADIATION IN HYPERSONIC IONIZED TURBULENT
GAS JETS
K. B. Galitseisky
Moscow Aviation Institute, Moscow, Russia
The object of the work has been the development of a semiempiric
design model for radiationconvection heatmass exchange in reactive
chemically jet flows, including a technique of radio band radiation
design. The design technique for electromagnetic radiation of
ionized jets based on the solution of the equation of radiation
transfer in isotropic medium, taking into account electromagnetic
waves radiation, refraction and absorption. According to this
model a basic source of the electromagnetic radiation in the radio
band is bremsstrahlung, provided for interaction of electrons
and heavy neutral particles. In this case a kinetic model of plasma
may be described by Boltszmann equation for electrons in which
the collision integral is proportional to the frequency of electrons
and neutral particles. In order to simulate the hypersonic axialsymmetric
jet flow it has been proposed in this work the mathematics model
based on the solution of the stationary system of the equations
in partial derivatives of parabola type, including the parabolized
system of NavierStokes equations (in projection onto transverse
and longitudinal coordinate axes); the equations for kinetic energy
and velocity of turbulent pulsation dissipation (the K model
of turbulence), the energy equation, the diffusion equation for
components and mixture elements, as well the equations of chemical
kinetics and the radiation transfer equation. In order to attain
numeral count stability the equations of continuity with the artificial
viscosity have been used in this system of equations. The equation
of energy regarding to temperature has been applied, so it has
been allowed to reduce an iterative process of its determination
and to rise a count rate essentially. The presented technique
for chemical kinetics design allows to design both nonequilibrium
and equilibrium chemical processes. Newton's method has been used
for the solution of the system of the nonlinear algebraic equations,
determining an equilibrium composition of a mixture. It is a model
of low ionized plasma, that has been applied to determine a degree
of jet flow ionization. According to this model the basic chemical
reactions are isolated to be used for determination of a basic
chemical composition, pressure, density and temperature of a mixture.
For the numeral solution of the parabolized system of the equations,
cited above and offered for heatmass transfer in reactive chemically
jet flows, an algorithm has been proposed in which an implicit
numeral scheme according to the "predictorcorrector"
method has been used. On the basis of numeral simulation the investigation
of heatmass exchange and radio frequency radiation of a hypersonic
under expanded jet, while its discharging into hypersonic air
flow, has been worked out. As a result of the numeral computations
been fulfilled the basic hydrodynamic and heat parameters distribution
have been determined, such as: velocity, pressure, temperature,
basic components concentration, including electrons concentration
and spectral intensity of radio radiation.
RADIATIVE TRANSFER IN SEMITRANSPARENT MEDIUMS
LIKE ISOLATING FOAM AND GLASS WOOL
D. Billerey and C. Martin
LEMTACNRS URA 875 INPL UNIVERSITE HENRI POINCARE
ENSEM  2 avenue de la Forêt de Haye  54516 VandoeuvrelesNancy
CedexFRANCE
There are several engineering applications of simultaneous radiation
and conduction in a participating medium. For example, in heat
transfer at room temperature through porous insulating materials
such as fibers and foams, thermal radiation is comparable to conduction.
In such situations a separate calculation of conductive and radiation
heat fluxes without any consideration of the interaction between
thermal radiation and conduction may introduce error in the heat
transfer results.
For the fibrous insulants an accurate modelization allows the
simulation of radiative transfer starting with the optical and
morphological characteristics of the medium. The absence of simplifying
hypothesis allows the study of parameters influencing the transfer.
This method is impossible for the foams because the optical and
morphological characteristics are complicated or unknown.
An experimental and a phenomenological approach are necessary.
Measurements of thermal conductivity, using a k meter guarded
hot plates apparatus, showed that the steady state thermal conductivity
depends of the specimen thickness.
We make use of this property and induce the extinction parameter
for the radiation transfer. The energy equation for simultaneous
conduction and radiation may be solved.
Particularly the phenomenological approach for the fibrous insulants
are analyzed and compared with the rigorous model showing a good
agreement.
NONSTEADY RADIANT HEATING OF A COMPOSITE
SLAB
T.W. Davies, F. Hashagen
School of Engineering, Exeter University, Exeter EX4 4QF, U.K.
This paper describes a method of predicting the thermal response
of a twodimensional composite slab which is subjected to nonlinear
thermal boundary conditions and which has temperaturedependent
physical properties. One of the exposed faces of the composite
slab is subjected to a timedependent radiative flux whilst the
other face is exposed to the ambient fluid and a radiation sink.
Thus the boundary conditions involve both counteracting and combined
radiative and natural convective heat transfer, which are both
nonlinear in temperature. The conduction equation itself becomes
nonlinear when the physical properties (such as conductivity)
are temperature dependent. Additional problems arise from the
presence of discontinuities in physical properties at the interfaces
of the slab components. The analysis was developed in order to
predict the temperature distribution in a composite plate rotating
backwards and forwards in a beam of thermal radiation.
This problem poses considerable challenges for the analyst; of
all the available methods of solution the heat balance integral
(HBI) technique is particularly well suited. Of central importance
to the accuracy of the HBI technique is the choice of approximation
for the timedependent temperature profile in a spreading thermal
disturbance and the main contribution of this paper is the presentation
of an integral solution to this complex transient conduction problem
which uses Hermite polynomials as the approximations for the temperature
profile.
ON THE HEAT TRANSFER PHENOMENON IN A BODY
WITH WAVELENGTHDEPENDENT PROPERTIES
R.M. Saldanha da Gama
Laboratório Nacional de Computaçao Científica
Rio de Janeiro, Brazil
In this work the coupled conduction/radiation heat transfer phenomenon
in an opaque convex body with radiation properties depending on
the wavelength is mathematically modelled. The considered heat
transfer process is described by a partial differential equation
subjected to a nonlinear boundary condition which involves the
Classical Planck's law. In order to provide a more adequate description,
it is constructed a modified version of Planck's law. It is presented
a minimum principle which is employed for proving existence and
uniqueness of the solution and which provides a way for simulating
the considered nonlinear energy transfer phenomenon.
