Evolution of heuristics by human operators in control systems.
Decision making mathematical model for control system operation modes, generating human operators heuristics evolution
Thomas, R. E.↗
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Space shuttle separation mechanisms
The development of space shuttle separation devices is reviewed to illustrate the mechanisms involved in separating the Orbiter from the Boeing 747 carrier aircraft and from the externally mounted propellant tank. Other aspects of the separation device development discussed include design evolution, operational experience during the orbiter approach and landing tests, and the work required to produce an operational system.
Rogers, W. F.↗
Space Shuttle separation mechanisms
The development of space shuttle separation devices is reviewed to illustrate the mechanisms involved in separating the orbiter from the Boeing 747 carrier aircraft and from the externally mounted propellant tank. Other aspects of the separation device development discussed include design evolution, operational experience during the orbiter approach and landing tests, and the work to be accomplished before an operational system becomes a reality.
Rogers, W. F.↗
Stochastic control of infinite dimensional systems in Hilbert space: A factorization perspective
A factorization perspective on problems of optimal causal estimation and optimal causal control of linear stochastic systems defined on an infinite-dimensional Hilbert space is presented. A separation principle is derived for the case in which the system input/output map is generated by an abstract evolution operator. The factorization formalism allows for an essentially algebraic approach to these problems.
Milman, Mark M.↗
Parameter identification for an abstract Cauchy problem by quasilinearization
A parameter identification problem is considered in the context of a linear abstract Cauchy problem with a parameter-dependent evolution operator. Conditions are investigated under which the gradient of the state with respect to a parameter possesses smoothness properties which lead to local convergence of an estimation algorithm based on quasi-linearization. Numerical results are presented concerning estimation of unknown parameters in delay-differential equations.
Brewer, Dennis W.↗
Implicit solvers for unstructured meshes
Implicit methods were developed and tested for unstructured mesh computations. The approximate system which arises from the Newton linearization of the nonlinear evolution operator is solved by using the preconditioned GMRES (Generalized Minimum Residual) technique. Three different preconditioners were studied, namely, the incomplete LU factorization (ILU), block diagonal factorization, and the symmetric successive over relaxation (SSOR). The preconditioners were optimized to have good vectorization properties. SSOR and ILU were also studied as iterative schemes. The various methods are compared over a wide range of problems. Ordering of the unknowns, which affects the convergence of these sparse matrix iterative methods, is also studied. Results are presented for inviscid and turbulent viscous calculations on single and multielement airfoil configurations using globally and adaptively generated meshes.
Venkatakrishnan, V.↗
Implicit solvers for unstructured meshes
Implicit methods for unstructured mesh computations are developed and tested. The approximate system which arises from the Newton-linearization of the nonlinear evolution operator is solved by using the preconditioned generalized minimum residual technique. These different preconditioners are investigated: the incomplete LU factorization (ILU), block diagonal factorization, and the symmetric successive over-relaxation (SSOR). The preconditioners have been optimized to have good vectorization properties. The various methods are compared over a wide range of problems. Ordering of the unknowns, which affects the convergence of these sparse matrix iterative methods, is also investigated. Results are presented for inviscid and turbulent viscous calculations on single and multielement airfoil configurations using globally and adaptively generated meshes.
Venkatakrishnan, V.↗
Parameter identification for an abstract Cauchy problem by quasilinearization
A parameter identification problem is considered in the context of a linear abstract Cauchy problem with a parameter-dependent evolution operator. Conditions are investigated under which the gradient of the state with respect to a parameter possesses smoothness properties which lead to local convergence of an estimation algorithm based on quasi-linearization. Numerical results are presented concerning estimation of unknown parameters in delay-differential equations.
Brewer, Dennis W.↗
Molecular vibrational states during a collision
Alternative algebraic techniques to approximate a given Hamiltonian by a harmonic oscillator are described both for time-independent and time-dependent systems. We apply them to the description of a one dimensional atom-diatom collision. From the resulting evolution operator, we evaluate vibrational transition probabilities as well as other time-dependent properties. As expected, the ground vibrational state becomes a squeezed state during the collision.
Recamier, Jose A.↗
Vibrational Schroedinger Cats
The optical Schroedinger cat states are simple realizations of quantum states having nonclassical features. It is shown that vibrational analogues of such states can be realized in an experiment of double pulse excitation of vibrionic transitions. To track the evolution of the vibrational wave packet we derive a non-unitary time evolution operator so that calculations are made in a quasi Heisenberg picture.
Kis, Z.↗
Theory of the lattice Boltzmann Method: Dispersion, Dissipation, Isotropy, Galilean Invariance, and Stability
The generalized hydrodynamics (the wave vector dependence of the transport coefficients) of a generalized lattice Boltzmann equation (LBE) is studied in detail. The generalized lattice Boltzmann equation is constructed in moment space rather than in discrete velocity space. The generalized hydrodynamics of the model is obtained by solving the dispersion equation of the linearized LBE either analytically by using perturbation technique or numerically. The proposed LBE model has a maximum number of adjustable parameters for the given set of discrete velocities. Generalized hydrodynamics characterizes dispersion, dissipation (hyper-viscosities), anisotropy, and lack of Galilean invariance of the model, and can be applied to select the values of the adjustable parameters which optimize the properties of the model. The proposed generalized hydrodynamic analysis also provides some insights into stability and proper initial conditions for LBE simulations. The stability properties of some 2D LBE models are analyzed and compared with each other in the parameter space of the mean streaming velocity and the viscous relaxation time. The procedure described in this work can be applied to analyze other LBE models. As examples, LBE models with various interpolation schemes are analyzed. Numerical results on shear flow with an initially discontinuous velocity profile (shock) with or without a constant streaming velocity are shown to demonstrate the dispersion effects in the LBE model; the results compare favorably with our theoretical analysis. We also show that whereas linear analysis of the LBE evolution operator is equivalent to Chapman-Enskog analysis in the long wave-length limit (wave vector k = 0), it can also provide results for large values of k. Such results are important for the stability and other hydrodynamic properties of the LBE method and cannot be obtained through Chapman-Enskog analysis.
Lallemand, Pierre↗
Stout Smearing on a Quantum Computer
Smearing of gauge-field configurations in lattice field theory improves the results of lattice simulations by suppressing high energy modes from correlation functions. In quantum simulations, high kinetic energy eigenstates are introduced when the time evolution operator is approximated such as Trotterization. While improved Trotter product formulae exist to reduce the errors, they have diminishing accuracy returns with respect to resource costs. Therefore having an algorithm that has fewer resources than an improved Trotter formula is desirable. In this work I develop a representation agnostic method for quantum smearing and show that it reduces the coupling to high energy modes in the discrete nonabelian gauge theory $D_4$
Gustafson, Erik J.↗
Topological terms with qubit regularization and relativistic quantum circuits
Qubit regularization provides a rich framework to explore quantum field theories. The freedom to choose how the important symmetries of the theory are embedded in the qubit regularization scheme allows us to construct new lattice models with rich phase diagrams. Some of the phases can contain topological terms which lead to critical phases. In this work we introduce and study the SU(3)-F qubit regularization scheme to embed the SO(3) spin-symmetry. We argue that qubit models in this regularization scheme contain several phases including a critical phase which describes the k = 1 Wess-Zumino-Witten (WZW) conformal field theory (CFT) at long distances, and two massive phases one of which is trvially gapped and the other which breaks the lattice translation symmetry. We construct a simple space-time Euclidean lattice model with a single coupling U and study it using the Monte Carlo method. We show the model has a critical phase at small U and a trivially massive phase at large U with a first order transition separating the two. Another feature of our model is that it is symmetric under space-time rotations, which means the temporal and spatial lattice spacing are connected to each other. The unitary time evolution operator obtained by a Wick rotation of the transfer matrix of our model can help us compute the physics of the k = 1 WZW CFT in real time without the need for tuning the temporal lattice spacing to zero. We use this idea to introduce the concept of a relativistic quantum circuit on a discrete space-time lattice.
Bhattacharya, Tanmoy↗
Achieving cost reductions in EOSDIS operations through technology evolution
The earth observing system (EOS) data information system (EOSDIS) mission includes the cost-effective management and distribution of large amounts of data to the earth science community. The effect of the introduction of new information system technologies on the evolution of EOSDIS is considered. One of the steps taken by NASA to enable the introduction of new information system technologies into the EOSDIS is the funding of technology development through prototyping. Recent and ongoing prototyping efforts and their potential impact on the performance and cost-effectiveness of the EOSDIS are discussed. The technology evolution process as it related to the effective operation of EOSDIS is described, and methods are identified for the support of the transfer of relevant technology to EOSDIS components.
Newsome, Penny↗
Learning two-phase microstructure evolution using neural operators and autoencoder architectures
Abstract Phase-field modeling is an effective but computationally expensive method for capturing the mesoscale morphological and microstructure evolution in materials. Hence, fast and generalizable surrogate models are needed to alleviate the cost of computationally taxing processes such as in optimization and design of materials. The intrinsic discontinuous nature of the physical phenomena incurred by the presence of sharp phase boundaries makes the training of the surrogate model cumbersome. We develop a framework that integrates a convolutional autoencoder architecture with a deep neural operator (DeepONet) to learn the dynamic evolution of a two-phase mixture and accelerate time-to-solution in predicting the microstructure evolution. We utilize the convolutional autoencoder to provide a compact representation of the microstructure data in a low-dimensional latent space. After DeepONet is trained in the latent space, it can be used to replace the high-fidelity phase-field numerical solver in interpolation tasks or to accelerate the numerical solver in extrapolation tasks.
36 MATERIALS SCIENCE↗
Operando X-Ray Tomography Imaging of Solid-State Electrolyte Response to Li Evolution under Realistic Operating Conditions
Solid-state Li-ion conductors are a next-generation battery technology that are particularly promising for electric vehicles, offering the capacitive benefits of Li metal anodes with nonflammable electrolytes. Microstructural evolution in these solid-state batteries, especially the Li anode, requires deeper understanding of the conditions under which certain undesired behaviors are more likely to occur. This study utilizes operando X-ray computed tomography to visualize the behavior of lithium in response to device operation, considering variables that are relevant to a realistic battery: stack pressure, microscale defects such as pores, and temperature. This work demonstrates that experimental and operational conditions, especially temperature, affect the fundamental driving forces of realistic solid electrolyte systems and provides visual insight into possible mechanisms of Li migration. In particular, the effect of these variables on Li propagation from the anode through pre-existing defects and Li nucleation within the imperfectly electron-insulating electrolyte is highlighted.
battery↗
Space Shuttle Main Engine (SSME) Systems Operation Overview and Evolution
The Space Shuttle Main Engine (SSME) is a large thrust class, reusable, staged combustion cycle rocket engine employing liquid hydrogen and liquid oxygen propellants. A cluster of three SSMEs is used on every space shuttle mission to propel the space shuttle orbiter vehicle into low earth orbit. Development of the SSME began in the early 70's and the first flight of the space shuttle occurred in 1981. Today, the SSME has accrued over one million seconds of ground test and flight operational time, launching 129 space shuttle missions. The systems operation of the SSME was developed and evolved to support the specific requirements of the Space Shuttle Program (SSP). This paper provides a systems operation overview of the SSME, including: engine cycle, propellant flowpaths, and major components; control system; operations during pre-start, start, mainstage, and shutdown phases; launch commit criteria (LCCs) and operational redlines. Furthermore, this paper will discuss how changes to the SSME over its history have impacted systems operations.
Benefield, Philip A.↗
Quantum state preparation and nonunitary evolution with diagonal operators
Realizing nonunitary transformations on unitary-gate-based quantum devices is critically important for simulating a variety of physical problems, including open quantum systems and subnormalized quantum states. Here, we present a dilation-based algorithm to simulate nonunitary operations using probabilistic quantum computing with only one ancilla qubit. We utilize the singular-value decomposition (SVD) to decompose any general quantum operator into a product of two unitary operators and a diagonal nonunitary operator, which we show can be implemented by a diagonal unitary operator in a one-qubit dilated space. While dilation techniques increase the number of qubits in the calculation, and thus the gate complexity, our algorithm limits the operations required in the dilated space to a diagonal unitary operator, which has known circuit decompositions. We use this algorithm to prepare random subnormalized two-level states on a quantum device with high fidelity. Furthermore, we present the accurate nonunitary dynamics of two-level open quantum systems in a dephasing channel and an amplitude-damping channel computed on a quantum device. The algorithm presented will be most useful for implementing general nonunitary operations when the SVD can be readily computed, which is the case for most operators in the noisy intermediate-scale quantum computing era.
71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗