38 Matching Results

Search Results

Advanced search parameters have been applied.

in creator/contributor: "Zardecki, A."

open access

Multiple-scattering corrections to the Beer-Lambert law

The effect of multiple scattering on the validity of the Beer-Lambert law is discussed for a wide range of particle-size parameters and optical depths. To predict the amount of received radiant power, appropriate correction terms are introduced. For particles larger than or comparable to the wavelength of radiation, the small-angle approximation is adequate; whereas for small densely packed particles, the diffusion theory is advantageously employed. These two approaches are used in the context … more

Date: January 1, 1983

Creator: Zardecki, A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Hydrodynamic effects in evaporating droplets

The vaporization of a spherically symmetric liquid droplet homogeneously heated by a high-intensity laser pulse is investigated on the basis of a hydrodynamic description of the system composed of the vapor and ambient gas. In the limit of convective vaporization, the boundary conditions at the fluid-gas interface are formulated by using the notion of a Knudsen layer across which translational equilibrium is established. Numerical solutions to the hydrodynamic equations exhibit the existence of… more

Date: September 25, 1986

Creator: Armstrong, R.L. & Zardecki, A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Energy balance in laser-irradiated vaporizing droplets

We analyze the interactions of atmospheric aerosols with a high-energy laser beam. The energy balance equation allows us to compute the conversion of the pulse energy into temperature increase, vaporization, conduction, and convection. We also include the shrinkage term whose significance has recently been discussed by Davies and Brock.

Date: September 8, 1987

Creator: Zardecki, A. & Armstrong, R.L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Propagation of high-energy laser beams through metallic aerosols

By combining the results of the hydrodynamic code CON1D and the beam propagation code LASER, we investigate the propagation of high-energy laser beams through vaporizing metallic aerosols in the regime for which the plasma generation becomes important. An effective plasma absorption coefficient allows us to set up a coupled system of equations describing the system consisting of the beam and vapor. 14 refs., 5 figs.

Date: August 1, 1988

Creator: Zardecki, A. & Armstrong, R.L.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Calculations of increased solar UV fluxes and DUV doses due to stratospheric-ozone depletions

Accurate radiative transfer calculations are performed in the middle ultraviolet spectral region for aerosol-loaded atmospheres with the goal of determining the solar irradiance at the ground and quantifying the irradiance perturbations due to the presence of aerosols and various ozone depletions. The extent of the increase of UV-B radiation as a function of wave-length and solar zenith angle is calculated for five model atmospheres. In addition, the damaging ultraviolet dose rates and radiatio… more

Date: February 1, 1982

Creator: Zardecki, A. & Gerstl, S.A.W.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Off-axis scattering of laser beams using single and multi-Gaussian phase function approximation

Within the small-angle approximation, a multi-Gaussian phase function model provides a new description of the multiple scattering process and leads to improved agreement with experiment data. Future work will be concerned with the combination of small-angle and diffusion approximations in the radiative transfer. This should lead to an improved predictive model of the performance of electroopitcal systems in aerosol-loaded atmospheres. 10 refs., 3 figs.

Date: September 1, 1986

Creator: Zardecki, A. & Gerstl, S.A.W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Reduction of photosynthetically active radiation under extreme stratospheric-aerosol loads

The recently published hypothesis that the Cretaceous-Tertiary extinctions might be caused by an obstruction of sunlight is tested by model calculations. First we compute the total mass of stratospheric aerosols under normal atmospheric conditions for four different (measured) aerosol size distributions and vertical profiles. For comparison, the stratospheric dust masses after four volcanic eruptions are also evaluated. Detailed solar radiative transfer calculations are then performed for artif… more

Date: January 1, 1981

Creator: Gerstl, S.A.W. & Zardecki, A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

High-energy laser-assisted imaging through vaporizing aerosols

The degradation of image quality due to multiple scattering in a turbid medium is analyzed various conditions of illumination. The emphasis is on the forward-peaked multiple scattering effects, which can adequately be described by the small-angle approximation. In the case of incoherent illumination, the modulation transfer function (MTF) can be given explicity both in the low- and high-frequency limits. For scattering with smaller degree of anisotropy, the MTF should be imputed numerically by … more

Date: February 1, 1988

Creator: Zardecki, A. & Gerstl, S.A.W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Reduction of photosynthetically active radiation under extreme stratospheric aerosol loads

Date: August 1, 1981

Creator: Gerstl, S.A.W. & Zardecki, A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Fuzzy risk analysis for nuclear safeguards

Analysis of a safeguards system, based on the notion of fuzzy sets and linguistic variables, concerns such as complexity and inherent imprecision in estimating the possibility of loss or compromise. The automated risk analysis allows the risk to be determined for an entire system based on estimates for lowest level components and the component proportion. In addition, for each component (asset) the most effective combination of protection mechanisms against a given set of threats is determined.… more

Date: January 1, 1993

Creator: Zardecki, A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Vaporization and recondensation in propagation and imaging of laser beams

To study the response of a medium to a localized disturbance, the coupled aerosol-beam equations---in which the dominant interactions are diffusive mass transport and conductive energy transport---are solved numerically, thus giving the spatio-temporal behavior of the propagating beam and the irradiated aerosols. In the context of the cloud clearing problem, a deleterious effect of recondensation is assessed. We examine the effect of turbulence on the distribution of droplet sizes during the re… more

Date: February 1, 1989

Creator: Zardecki, A. & Gerstl, S.A.W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Fuzzy Risk Analysis for Nuclear Safeguards

Date: May 1, 1993

Creator: Zardecki, A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Analysis of inventory difference using fuzzy controllers

The principal objectives of an accounting system for safeguarding nuclear materials are as follows: (a) to provide assurance that all material quantities are present in the correct amount; (b) to provide timely detection of material loss; and (c) to estimate the amount of any loss and its location. In fuzzy control, expert knowledge is encoded in the form of fuzzy rules, which describe recommended actions for different classes of situations represented by fuzzy sets. The concept of a fuzzy cont… more

Date: August 1, 1994

Creator: Zardecki, A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Fuzzy controllers in nuclear material accounting

Fuzzy controllers are applied to predicting and modeling a time series, with particular emphasis on anomaly detection in nuclear material inventory differences. As compared to neural networks, the fuzzy controllers can operate in real time; their learning process does not require many iterations to converge. For this reason fuzzy controllers are potentially useful in time series forecasting, where the authors want to detect and identify trends in real time. They describe an object-oriented impl… more

Date: October 1, 1994

Creator: Zardecki, A.

Item Type: Report

Partner: UNT Libraries Government Documents Department

open access

Continued fractions: Yet another tool to overcome the curse of dimensionality

The authors provide a rapid prediction method, in which a larger number of antecedents than currently considered is accounted for. To this end, they encode the successive (possibly rescaled) values of a time series, as the partial quotients of a continued fraction, resulting in a number from the unit interval. The accuracy of a ruled-based system utilizing this coding is investigated to some extent. Qualitative criteria for the applicability of the algorithm are formulated.

Date: December 31, 1998

Creator: Zardecki, A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Effect of noise on chaotic fuzzy mappings

Chaotic mappings in the space of fuzzy sets induced by mappings of the underlying reference set are investigated. Different fuzzification schemes are considered and their impact on the resultant iterated fuzzy set, under a quadratic mapping, is studied numerically. The fuzzy set mapping is described in terms of the mapping of level cuts, resulting from the resolution theorem for fuzzy sets. In the two-dimensional case, a generalized notion, given as a fuzzy set, of the Hausdorff dimension is fo… more

Date: March 1, 1996

Creator: Zardecki, A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

ILUM code: solar and lunar flux calculations for multi-cloud layered atmospheres

The computer code ILUM computes solar/lunar illumination received at the ground as a function of geographical location, date, standard time, and meteorological conditions. Both the computational method and program logic are described.

Date: January 1, 1984

Creator: Duncan, L. D.; Shirkey, R. C. & Zardecki, A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Scattered radiation field of a laser beam propagating through turbid media

A combination of the small-angle approximation and the diffusion approximation is used to study the propagation of laser beams through dense scattering media. 8 refs., 3 figs.

Date: January 1, 1986

Creator: Gerstl, S.A.W.; Chitanvis, S.M. & Zardecki, A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Defense in depth and resource optimization for safeguards

The resource allocation problem for safeguards is solved by using dynamic programming. The existing program RAOPS (Resource Allocation Optimization Program for Safeguards) is extended to include both divergent and convergent configurations of activities. The new algorithm is applicable to any configuration that can be described in terms of a tree data structure. To treat the problem of defense in depth, a stochastic optimization -- in which the optimization applies to expected values -- is util… more

Date: January 1, 1991

Creator: Zardecki, A. & Markin, J.T.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Hydrodynamics of evaporating aerosols irradiated by intense laser beams

An analysis is presented describing the interactions of atmospheric aerosols with a high-intensity laser beam propagating along an atmospheric path. For the case of moderate beam irradiances, diffusive mass transport and conductive energy transport dominate the aerosol-beam interactions. In this regime, the coupled aerosol-beam equations are solved numerically to obtain the spatic-temporal behavior of the propagating beam, and of the irradiated aerosols. For higher beam irradiances, convective … more

Date: January 1, 1985

Creator: Armstrong, R.L.; Zardecki, A. & Gerstl, S.A.W.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Fuzzy resource optimization for safeguards

Authorization, enforcement, and verification -- three key functions of safeguards systems -- form the basis of a hierarchical description of the system risk. When formulated in terms of linguistic rather than numeric attributes, the risk can be computed through an algorithm based on the notion of fuzzy sets. Similarly, this formulation allows one to analyze the optimal resource allocation by maximizing the overall detection probability, regarded as a linguistic variable. After summarizing the n… more

Date: January 1, 1991

Creator: Zardecki, A. & Markin, J.T.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Smoke clearing by high energy laser beams

We describe the clearing phenomenon that occurs when a continuous wave (CW) high energy laser beam, incident upon a cloud of hygroscopic droplets, vaporizes these droplets. We consider the case when the incident wavelength is greater than the average droplet radius. Williams' model is used to describe the vaporization of a single droplet. The propagation of the laser beam is described by the radiative transfer equation in a slab geometry. The radiative transfer equation is solved using the meth… more

Date: April 10, 1987

Creator: Chitanvis, S.M.; Gerstl, S.A.W. & Zardecki, A.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

Imaging through a multiple scattering medium

The existing theory of imaging through an aerosol medium, based on the small-angle approximation to radiative transfer, is extended to the general case of multiple scattering with an arbitrary degree of anisotropy. By applying the discrete-ordinates, finite-element radiation transport code TWOTRAN, we compute the modulation transfer function for a medium characterized by optical depth, single scattering albedo, and a symmetry parameter. An extended version of this investigation will appear in a… more

Date: January 1, 1984

Creator: Zardecki, A.; Gerstl, S.A.W. & Embury, J.F.

Item Type: Article

Partner: UNT Libraries Government Documents Department

open access

RAOPS: Resource Allocation Optimization Program for Safegurards

RAOPS--Resource Allocation Optimization Program for Safeguards is extended to a multiobjective return function having the detection probability and expected detection time as criteria. The expected detection time is included as a constraint, based on the well-known Avenhaus model of the optimum number of inventory periods. Examples of computation are provided.

Date: March 1, 1994

Creator: Zardecki, A. & Markin, J. T.

Item Type: Article

Partner: UNT Libraries Government Documents Department