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Atmospheric processes determining the late-time evolution of near-surface dust concentrations from nuclear bursts are examined, with the objective of providing model representations for late-time dispersion codes. Turbulent transfer in the atmospheric boundary layer is an important phenomenon for small particles, since turbulent eddy velocities are on the order of 1ms-1 and extend from the surface up to altitudes of 1 km or higher. Simplified estimates for turbulence structure and diffusion rates are given. The effect of absorption of solar radiation by the dust is also considered, and a radiative transfer mode is described. Turbulent deposition of particles to various surface types, including open terrain or vegetative canopies, is considered and simple parameterization schemes are recommended. An extensive study of boundary layer flow over complex terrain has been conducted, using Large-Eddy Simulation to represent the energy-containing turbulent motions. A generalized scheme for estimating the average surface drag over complex terrain is derived. The effect of terrain on atmospheric turbulence levels and dispersion characteristics is studied, and simple estimation schemes for use in late-time models are suggested.

Based on examples from several projects this paper reflects MBB's experience with applicability, limitations, acceptance, and effectiveness of helicopter simulation. Some of the key points are the objective and subjective validation of a simulator and the various factors, which influence the acceptance by pilots. In this context it is very important to make a trade-off between simulator sophistication (i.e. cost) and required result i.e. design input in the actual phase of development. Other aspects of simulation effectiveness include evaluation and training of critical flight conditions prior to flight tests as well as involving the customer from early concept studies up to full mission simulations, which gives him more influence on the design and leads to better identification with the product., This article is from 'Piloted Simulation Effectiveness Held in Brussels, Belgium on 14-17 October 1991 (L'Efficacite de la Simulation Pilotee),' AD-A253 007, p6-1 thru 6-11.

A modern integrated helmet (IH) consists out of two Image Intensifier Tubes (IIT) and two Cathode Ray Tubes (CRT) with an optical system including combiners to present the images binocular. Additional symbology can be superimposed to the CRT- or IIT-image. An IH is a further development of a Helmet Mounted Display (HMD). A Helmet-Mounted-Sight (HMS) can steer a sensor platform with a thermal camera or an air-to-air missile system. The main helicopter (HC) requirements of such a system are: (1) human factors (2) optimized day, twilight and night optical modules (3) large exit pupil, good transmission of the optical path and a large adjustment range (4) fit of helmet including optimized centre of gravity(CG) and weight (5) good geometrical resolution / Modulation Transfer Function (MTF) with a large Field of View (FOV) (6) high focussing range of the IIT and a good S/N ratio below 1 mLux (7) CRT automatic brightness and contrast control (8) flight symbology presentation for one or two eyes (9) good static and dynamic HMS-accuracy with a large Head Motion Box (HMB) (10) NBC and Laser protection compatibility MBB and the Army Corps have made in this year ground and flight trails with an Integrated Helmet and a HMS on a PAH 1 respectively a BK 11 7 helicopter. The paper will present IH requirements for HC application and some test results., This article is from Conference Proceedings on Helmet Mounted Displays and Night Vision Goggles (Visuels Montes sur le Casque et Equipements de Vision Nocturne) Held in Pensacola, FL on May 2, 1991, AD-A246 925, p3-1 thru 3-17.

The purpose of this report is to document the final results and conclusions of work on the behavior of aluminum titanate materials in a diesel engine environment. The work was conducted in three phases. Phase 1 covered investigation of material properties and microstructures of aluminum titanate materials from three different manufacturers. Phase 2 consisted of testing and evaluation of the material properties and microstructure, of each of the materials, after environmental exposures. Phase 3 work involved investigation of casting procedures to produce a cast-in-place exhaust port. Temperature profiles were recorded and different external compliant layers and core sand compositions were examined. The aluminum titanate material from the three different manufacturers showed significant differences in strength, stability and thermophysical properties. One material was low density with low strength, modulus and conductivity. The second material exhibited degradation to alpha- Al2O3 after aging at temperatures greater than 1000 C. The third material had very high strength as-received but showed a strength loss of up to 40% after aging. However, the strength for this material after aging remained greater than the as-received strength of the other two materials. The casting studies showed that cast-in-place ports can be produced. The most promising results were seen when the core sand composition was 50% SiC/50% Fe.

The microenvironment of a nerve cell is essential to its function and the characterization of this domain is a major issue in contemporary neurobiology. The behavior of neurons is strictly related to their physiological activity, which is itself dependent on the chemical composition of the encompassing environment. Beyond this crucial role, the interstitial space of the brain serves as a conduit for the transmission of information. The microenvironment does not function in isolation, however, because two major components are intimately involved with it; these are the glial cells of the brain and the blood-brain barrier. Progress in these areas has been made through several approaches: the use of ion-selective electrodes, charaterization of glial membrane physiology, the application of concepts and recent advances in transport physiology, and the development of new techniques for studying the blood-brain barrier. This book brings together three groups of investigators working on the biophysics of the microenvironment, the blood-brain barrier, and membrane properties of glial cells. The aim was to begin a dialogue and exchange of concepts between the groups that could eventually lead to unified concepts that encompass the three components.

Sponsored in part by Grant NSF-MCS79-05774.

A convenient method for proving weak convergence of a sequence of non-Markovian processes x(epsilon) (.) to a jump-diffusion process is proved. Basically, it is shown that the limit solves the martingale problem of Strook and Varadhan. The proofs are relatively simple, and the conditions apparently weaker than required by other current methods (in particular, for limit theorems for a sequence of ordinary differential equations with random right hand sides). In order to illustrate the relative ease of applicability in many cases, a simpler proof of a known result on averaging is given. (Author), Sponsored in part by Grant NSF-ENG73-03846

At the start, three and a half years ago, the finite fluid element method (Section 1) was the only one under consideration. Things went badly with that method, and progress with its implementation went far more slowly than we ever anticipated. As a result, by the end of the first year, a second method, which originally was developed for a check on results of the first, had become by far the more promising of the two. Most of this report (Sections 3-6) describes progress we have made with the application of biased differences (Section 2) to a variety of fairly difficult problems of numerical fluid mechanics. Finally, in the last six months of the period covered by this report, the major difficulties with finite fluid elements were overcome, so it became possible to begin a comparison of the two methods (Section 6). Preliminary indications are that both methods are reliable, and both are considerably more efficient than a third method with which they have been compared. Section 7 is a report of progress with a boundary integral method that is not closely related to the others except by being numerical, and Section 8 is a description of the kinds of graphical software we had to develop for interpretation of our numerical computations.

In this project work, means were considered to achieve high-speed (GHz) switching and modulation in integrated optical circuits, suitable for fiber optics applications. In particular, design and performance criteria were calculated for a planar coupled optical channel device, electro-optically switched by synchronous electrical signals propagating along an asymmetric coplanar waveguide stripline. Design was also executed for several of the components in the laboratory although full integration was not completed within the project period. (Author)

The objective of this investigation is to give sufficient conditions on f and g such that local semigroups can be associated with the equation (1). This will imply representation formulas for the solutions of (1), and secondly to discuss various notions of solutions which have arisen in the study of (1). Although only the autonomous equation is considered here, many of the results remain true if f and g depend on t. (Author)

A concept of controllability for systems Ax + Bx = Cu(t) in which A may be singular is introduced. When det(As+B) not equal 0, s epsilon ir, this is shown to be equivalent to the condition that c superscript T/(As+B)C = 0 implies c = 0., Prepared in cooperation with Southern Illinois Univ., Carbondale. Dept. of Mathematics.

In this paper, the authors are concerned with the existence of optimal controls for problems. The method depends on introducing another stochastic control problem which is called a 'separated' problem. For several years the question of proving a general theorem about existence of optimal controls in the strict sense has been open. The authors do not obtain such a result here. However, they obtain an existence theorem in which a somewhat wider class of control processes is admitted.

Prepared in cooperation with Chicago Univ., IL, and Bell Telephone Labs., Murray Hill, NJ. Sponsored in part by Grant NSF-DMR77-09931.

Progress is described on a method for stabilizing linear differential systems by state variable feedback in which the gain matrix stems from the finite pure integration of the controllability Gramian and the resulting system tolerates a large class of nonlinearities in the loop without destroying stability. Research results are summarized for the thoeretical investigation of minimum energy controls for a class of commutative bilinear systems which relate to a two-dimensional intercept control problem. Progress and research results are also described for a new equation error formulation for the least squares parameter estimation problem for nonlinear system identification and signal reconstruction. (Author)

An analysis is presented of the long-term dormant storage test data experimentally accumlated on two microelectronic devices. All relevant information on the experimental test program was reviewed very carefully. The existence of error sources, anomalous data, and data acquisition discontinuities was identified. The unanticipated final result of the analysis was that the data collected was of an insufficient quality to enable the identification of any aging behavior as a function of time, temperature, or operational stress. (Author)

Results are summarized for the feedback stabilization of linear time varying differential and discrete-time linear systems, as well as a class of differential-delay systems. Extensions are described for a control law which tolerates a large class of nonlinearities in the loop without destroying stability. Research results are also described for the control of a class of intercept systems including its interpretation as a commutative bilinear system and a feedback control law which incorporates least squares estimation of the target speed and turning rate. Results are described for parameter identification of a class of nonlinear systems with particular attention given to the identification of parameters for a helicopter system in longitudinal motion using input-output data on a finite time interval. Extensions to a signal estimation problem are indicated. (Author)

The purpose of this paper is to study the existence of a smooth Hopf bifurcation for functional equations. The bifurcation parameters may include the delays. Results will be described for a special case of equations considered. (Author), Sponsored in part by NSF-MCS76-07246. Prepared in cooperation with Sao Paulo Univ (Brazil). Instituto de Matematica e Estatistica.

A robust computable approximation to the nonlinear filtering problem for a diffusion model is treated, where the system and data models are given by dx = f(x)dt + sigma(x)dz, dy = g(x)dt + dw. The approximation (with approximation parameter h) is robust in the sense that it is locally Lipschitz continuous in the data y(dot) (sup norm) uniformly in h and, as h approaches 0, it converges to the optimal filter for the diffusion. (Author), Sponsored in part by NSF-MCS76-07247.

A new SAW time inversion system is described. It requires fewer chirp filter elements than those required with the common method of cascading two Fourier or Fresnel transformations. This new method is based on the fact that the Fourier transform of a linear F.M. signal whose envelope is modulated by a given time function has (approximately) the time inverted function as its amplitude. Theoretical discussion and some experimental results are included., Prepared in cooperation with Tel-Aviv Univ. (Israel) and Ministry of Defense Armament Development Authority, Haifa (Israel).

Results are presented of a series of experiments performed with two steels to investigate the dependence of flow stress on strain rate and its history. For this purpose quasi-static, dynamic and incremental strain rate tests were conducted on SAE 1020 hot-rolled steel and SAE 1018 cold-rolled steel at room temperature. It is shown that while the flow stress of both steels exhibits a significant strain rate sensitivity, the effect of strain rate history is relatively small in comparison with that generally found in fcc and hcp metals. A comparison is made with results of the work of other investigators. (Author)

We derive an equation for invariant curves in the motion of a vortex blotch. Kirchhoff's elliptical vortex is shown to satisfy the equation exactly. We also find that perturbations to a circular vortex are invariant configurations to the (third) order of approximation calculated.

We consider a head-on collision between two solitary waves on the surface of an inviscid, homogeneous fluid. A perturbation method which in principle can generate an asymptotic series of all orders, is used to calculate the effects of the collision. We find that the waves emerging from (i.e. long after) the collision preserve their original identities to the third order of accuracy we have calculated. However a collision does leave imprints on the colliding waves with phase shifts and shedding of secondary waves. The latter propagate with diminishing amplitudes in the direction opposite to that of the main waves. We have also calculated the maximum run-up amplitude of two colliding waves. The result checks with existing experiments. (Author)

The work on the rate equation descriptions of pulse propagation in homogeneous media is complete and is being prepared for publication. The Pulse duration limit was chosen as long compared to the coherence time so that true coherence effects such as self-induced transparency is absent. However, the system of rate equations are velocity dependent so droppler broaden mechanisms are included. Attempts have continued to determine if it is possible to utilize a plasma break down in air to deduce velocity. Thus far, it has been determined that the magnitude of the scattered signal provides ample signal for short ranges. This technique will prove useful where conventional doppler velocimetry is not possible due to the absence of naturally occurring scattering centers. The density matrix equations for three energy level gases have been formulated. For situations were the pulse or pumping time is longer than a dephasing time, the rate equations explicity contain contributions that are nonlinear. (Author)

Mathematical semantics is introduced as the study of mappings between configuration spaces and image algebras. An image algebra is synthesized using generators that are relations. This will serve as the semantic counterpart of a formal language. The image algebra is analyzed in terms of its similarity group, bond relations and connection type. The semantic map is studied in terms of the morphisms of a category, the term used in its algebraic sense. We present strategies for constructing semantic maps with special properties related to memory requirements. Some examples are given, showing how the semantic categories can be constructed. (Author)

The topic of convergence has seen much work, starting with the fundamental papers of Wong and Zakai, and followed by others, including Khazminskii, Papanicolaou and Kohler, etc. From a non-probabilistic point of view, it has been dealt with by McShane and Sussmann. In this paper, a rather general and efficient method of getting the correct limits is discussed. The idea exploits some general semigroup approximation results of Kurtz, and often not only gets better results than those obtained by preceding methods, but is also easier to use., Sponsored in part by Grant NSF-ENG77-12946.

A feedback control law is derived for a two dimensional missile intercept system which combines in a step-by-step manner the closed form solutions to a least squares estimation of the target turn rate, line speed and heading with a minimum control energy problem subject to a terminal intercept constraint. The major assumptions are that the pursuer possesses thrust modulation capabilities, in addition to thrust vectoring, and that continuous measurements of the range coordinates are available for estimation purposes. Simulation results are included which indicate that good terminal accuracy is achieved when the estimation errors are small and illustrate the limitations on accuracy when fluctuations occur in the target speed and turn rate. (Author)

This paper considers an optimal regulator problem which is different from the conventional linear quadratic cost problem but leads to a stable linear feedback control. The problem considers a double integral quadratic cost function and an integral constraint on state trajectories. The optimal open-loop control is transformed to a closed-loop control and subsequently a modified control is obtained based on a receding horizon notion. This modified control law is shown to be asymptotically stable and to result in a new method for stabilizing linear time-varying systems, as well as providing an easy means to stabilize time-invarient systems. Moreover, the gain matrix for the modified control is obtained from a Riccati-type equation over a finite time interval, and a large class of nonlinearities can be allowed in the closed-loop without destroying its stability.

With disturbances modeled by arbitrary solutions to a linear homogeneous differential equation, a deterministic theory is developed for parameter estimation using data over a limited time interval which has applications to signal estimation and system identification. Linear and certain classes of nonlinear and time varying systems can be treated for identification purposes. The approach circumvents the need to estimate unknown initial conditions through the use of a certain projection operator. (Author)

Applications are described of two estimation techniques to obtain final deflections and response times of plane rectangular frames subjected to impulsive loading on the transverse (beam) member. Deflections up to roughly one third the span (thirty thicknesses) are estimated by the mode approximation and deflection bounds techniques, treating the plastic rate dependence by means of homogeneous viscous constitutive equations. Comparisons are made with recent test results, and the degree of agreement is discussed in terms of the known error sources of the two techniques. (Author)

Tests are described on circular plates of mild steel and commercially pure titanium loaded impulsively by means of explosive sheet. Three loading geometries were used, with magnitudes such that final deflections in the range from one to about seven plate thicknesses were produced. Clamping against radial as well as transverse deflections at the edge was provided. Both materials exhibit strong plastic rate sensitivity. Parameters describing this behavior were obtained from stress-strain tests at low to intermediate rates together with published data for high strain rates. The measured final deflections and response times are compared with predictions of the mode approximation technique as extended to large deflections of viscoplastic structures. (Author)

The nonlinear equations of motion for an incompressible simple fluid, occupying a fixed bounded container, are formulated on the basis of the finite-linear viscoelastic theory for materials with fading memory; this formal boundary-initial value problem is then viewed as a nonlinear abstract evolution equation on a certain Hilbert space. It is shown that a linearized version of this evolution equation is associated with a linear dynamical system on this Hilbert space, and several stability and asymptotic behavior results for this linearized problem are proved through the use of Liapunov stability methods. On the assumption that the original nonlinear evolution equation also is associated with some dynamic system on the same space, it is shown that the rest condition of the fluid is stable and all motions are bounded. The Liapunov function employed for this purpose can be interpreted as a mechanical energy function for the fluid. (Author), Prepared in cooperation with Northwestern Univ., Evanston, IL. Dept. of Mechanical Engineering. Sponsored in part by Grants NSF-ENG76-81570, AFOSR-76-3063.

Results from two parametric nearfield experiments have been reported. The data, known to contain substantial receiving hydrophone intermodulation distortion, have been corrected to deducing the level of the distortion and coherently subtracting the distortion pressure from the measured data. A test of several nearfield theories has been made. Because of the condition of the experimental data, the test is not particularly discriminating. Also, there is not a great deal of spread among the theories considered.

Tests are described on plane frames of mild steel and titanium (commercial purity) in which high intensity short duration pressure pulses were applied transversely to the beam member either uniformly over this member or concentrated at its center. The objective was to examine applications of two estimation techniques (upper bounds on deflections and the mode approximation technique) for major response features of pulse loaded structures at large deflections, taking account of strong plastic strain rate sensitivity. Loads over a range such as to cause final deflections up to about a third of the span were applied by detonating explosive sheet. Agreement between estimated and measured final deflections was often very good (generally conservative) but the intrinsic error of the mode technique was not observed as expected. (Author)

Results are given for stabilizing time varying discrete linear systems by means of a feedback control stemming from a receding horizon concept and a minimum quadratic cost with a fixed terminal constraint. The results parallel those recently obtained from continuous time systems (8) and extend a well known method of Kleinman for stabilizing discrete fixed linear systems. (Author)

A minimum energy control problem is considered for commutative bilinear systems with and without terminal constraints. Optimal controls are shown to be constant vectors determined by the boundary conditions. Sufficient conditions are derived for uniqueness of the optimal control in the absence of a terminal constraint. A class of physical bilinear systems is discussed which posses the commutative property. (Author)

The application of the mode approximation technique to a fully clamped plate is here described. Mode solutions for finite deflections are obtained from a sequence of instantaneous modes. Master solutions for chosen initial velocity amplitudes are constructed in nondimensional form. These depend weakly on a parameter of viscoplastic material behavior and size of structure, and so can be applied to a variety of loadings and structures. Finding each instantaneous mode shape and acceleration constitutes an eigen-problem, solved by finite elements with iterations. Comparisons with recent tests on steel and titanium plates are discussed in some detail. (Author)

Sufficient conditions for global controllability of a class of bilinear and nonlinear systems have been derived. These results shed some light in applying fixed-point arguments to investigate the controllability of nonlinear systems which contain unbounded nonlinearities. An interesting problem is to link the closedness of the attainable set for commutative bilinear systems with the conditions obtained here so that an explicit input function can be derived or computed through iterative schemes. (Author)

This report considers a feedback control law for linear time-varying and time invariant discrete systems based on a receding horizon concept applied to a minimum energy problem with fixed terminal constraints. The control law is shown to be asymptotically stable and to result in a new method for stabilizing linear time-varying systems as well as extending some well known methods for stabilizing time invariant systems. In particular, the stabilizing gains of the feedback control law are obtained from the solution to a discrete Riccati equation over an arbitrary finite time interval, which is relatively easy to compute. The gain matrix reduces to a constant matrix for linear time invariant systems. Some stability results will turn out to be special cases of these results. The results parallel those for linear continuous time systems, although the technical details are tedious and more involved.

We have obtained the full modal spectrum of the lowest order modes (TE,n=0) for a simple model of the ferrite loaded stripline. Although quantitatively the results cannot be expected to be in good agreement with experimental results. Nevertheless, qualitatively the results should reflect accurately the behavior of such a waveguiding system. It has become clear that components purportedly using an edge-guided (i.e., quasi-surface) mode in fact employ the field displaced quasi-TEM waveguide (or dynamic) mode. This latter mode, for even moderately wide ferrite slabs (line widths) will assume a surface mode-like structure. Even from the limited simple calculations it appears that operation over two octaves may well become possible. However, further studies on a better model which also considers the effect of material and conductor losses must be completed before definitive conclusions can be reached. It appears currently that the greatest difficulty will lie in suppressing unwanted surface modes while higher order modes will be quite readily suppressed using lossy films on the appropriate ferrite-dielectric interface or guide edge.

A model of languages syntax acquisition is formulated as an inference problem: to guess the wiring diagram of an unreliable automaton. A constructive method is developed which solves the grammatical inference problem via an abductory inductive process applied to the sample strings generated by the stochastic automaton whose internal wiring diagram is unavailable for inspection. The right invariant equivalence classes which correspond to the states of the sought-for automaton are established by the training sequence and a teacher. The structural description of strings is found directly without a priori assumptions on the number of states (or lengths of strings).

The functional differential equation Q'(t) = AQ(t) + B((Q(tau - t)) to the T-th power), - infinity t infinity, where A,B are n x n constant matrices, tau or = 0, Q(t) is a differentiable n x n matrix and (Q(t)) to the T-th power is its transpose, is studied. Existence, uniqueness and an algebraic representation of its solutions is given. This equation, of considerable interest in its own right, naturally arises in the construction of Liapunov functionals of difference differential equations of the type dx(t)/dt = Cx(t) + Dx(t-tau), where C,D are constant n x n matrices. The role played by the matrix Q(t) is analogous to the one played by a positive definite matrix in the construction of Liapunov functions for ordinary differential equations. In this paper, we show that, in spite of the functional nature of this equation, the linear vector space of its solutions is n squared; moreover, ,we give a complete algebraic characterization of its solutions and indicate computationally simple methods for obtaining these solutions, which we illustrate through an example. Finally, we briefly indicate how to obtain solutions for the nonhomogeneous problem, through the usual variation of constants method.

The existence of organized structures in turbulent shear flow has been the subject of recent observational discoveries in both the laboratory and in the atmosphere and ocean. The resent work on modeling such structures in a temporally developing, horizontally homogeneous turbulent free shear layer has been extended to the spatially developing mixing layer, there being no available rational transformation between the two nonlinear problems. The basis for the consideration is the kinetic energy development of the mean flow, large-scale structure and fine-grained turbulence with a conditional average, supplementing the usual time average, to separate the nonrandom from the random part of the fluctuations. The integrated form of the energy equations and the accompanying shape assumptions, is used to derive amplitude equations for the mean flow, characterized by the shear layer thickness, the nonrandom and random components of flow which are characterized by their respective energy densities. In general, the large-scale structure augments the spreading of the shear layer and enhances the fine-grained turbulence by taking energy from the mean flow and transferring it to the turbulence as it amplifies and subsequently decays. The maximal amplitude of the large-scale structure is attained by the initially most amplified mode, however, the relative enhancement of the fine-grained turbulence is achieved by both the magnitude of the large-scale structure and its streamwise lifetime. Thus a greater enhancement of the turbulence is achievable by the lower frequency mdoes which have longer streamwise lifetimes. The large-scale structure can also be controlled by increasing the initial level of turbulence, which would render its decay more rapidly. (Author), Reprint from Proceedings of Symposium on Turbulent Shear Flows, 18-20 Apr 77, p11.1-11.11, Pennsylvania State Univ.

The paper discusses the significance and calculation of dynamic plastic mode form solutions for small deflections of structures of rigid-perfectly plastic materials subjected to load systems of fixed distribution and magnitude. These solutions have separated form, with velocity the product of a scalar function of time by a vector-valued function of space variables. The relation is shown on the one hand to mode form solutions for a structure of viscoplastic material and on the other hand to limit load solutions for those of perfectly plastic behavior. Numerical examples are given for circular plates of material obeying Tresca and Mises' Laws. (Author)

Briefly described, the problem attacked under these contracts can be summarized by the questions, 'Are cholesterol oxidation products present in dried foods known to contain cholesterol. Are these oxidation products potentially harmful. Will any of these cholesterol derivatives violate the 'Delaney Amendment' which prohibits the induction within, or addition to, natural foods of carcinogens during processing.

An annotated bibliography of all reports published under these contracts, with supplementary remarks. (Author)

The research aimed at finding and developing methods for estimating the main features of response of engineering structures subjected to severe dynamic loading of pulse type, with emphasis put on methods valid both for large deflections and for structures of materials exhibiting strong strain rate sensitivity in the plastic range. Problem types of practical importance include explosive loading, either external due to military attack or internal for example due to disruptive accident in a pressure vessel or containment structure; various types of vehicular impact; wave impact on ship or offshore structures; and high energy rate forming. Preliminary applications have been made of the methods under investigation in the program presently being reviewed in all but the last of the above areas.