Causal simulation and sensor planning in predictive monitoring

Two issues are addressed which arise in the task of detecting anomalous behavior in complex systems with numerous sensor channels: how to adjust alarm thresholds dynamically, within the changing operating context of the system, and how to utilize sensors selectively, so that nominal operation can be verified reliably without processing a prohibitive amount of sensor data. The approach involves simulation of a causal model of the system, which provides information on expected sensor values, and on dependencies between predicted events, useful in assessing the relative importance of events so that sensor resources can be allocated effectively. The potential applicability of this work to the execution monitoring of robot task plans is briefly discussed

A model-based reasoning approach to sensor placement for monitorability

An approach is presented to evaluating sensor placements to maximize monitorability of the target system while minimizing the number of sensors. The approach uses a model of the monitored system to score potential sensor placements on the basis of four monitorability criteria. The scores can then be analyzed to produce a recommended sensor set. An example from our NASA application domain is used to illustrate our model-based approach to sensor placement

Structure of 2,9-dimethyl-1,10-phenanthroline hemihydrate

C14H12N2•½H2O, Mr = 217•27, tetragonal I41/a, a = 14•258 (3), c = 22•286 (4) Å, V = 4531 (3) Å3, Z = 16, Dx = 1•274 (1) g cm-3, Mo Kα radiation λ = 0•71073 Å, µ = 0•74 cm-1, F(000) = 1840, T = 297 K, R = 0•041 for 1196 unique observed reflections with I \u3e 2σ(I). Pairs of dimethylphenanthroline molecules related by a twofold axis are bridged by water molecules lying on the twofold axis and H bonded to one of the N atoms in each molecule. The H bonds are long and far from linear: O—H 1•06 (4), H•••N 154 (3)°. This is presumably a consequence of the approximately parallel arrangement of the two phenanthroline molecules in the (phen)2.H2O complex, which are tilted 4•7 (1)° with respect to each other; the atoms in one molecule are 3•50 to 3•81 Å from the plane of the other molecule. On the other side of the phenanthroline is another phenanthroline related by a center of symmetry with the atoms of one molecule 3•41 to 3•45 Å from the plane of the other molecule. The phenanthroline molecule has close to 2mm symmetry, but the individual C6 rings are tilted about 1° with respect to each other

Robust nonlinear control of vectored thrust aircraft

An interdisciplinary program in robust control for nonlinear systems with applications to a variety of engineering problems is outlined. Major emphasis will be placed on flight control, with both experimental and analytical studies. This program builds on recent new results in control theory for stability, stabilization, robust stability, robust performance, synthesis, and model reduction in a unified framework using Linear Fractional Transformations (LFT's), Linear Matrix Inequalities (LMI's), and the structured singular value micron. Most of these new advances have been accomplished by the Caltech controls group independently or in collaboration with researchers in other institutions. These recent results offer a new and remarkably unified framework for all aspects of robust control, but what is particularly important for this program is that they also have important implications for system identification and control of nonlinear systems. This combines well with Caltech's expertise in nonlinear control theory, both in geometric methods and methods for systems with constraints and saturations

Representing Change for Common-Sense Physical Reasoning

Change pervades every moment of our lives. Much of our success in dealing with a constantly changing world is based in common-sense physical reasoning about processes and physical systems. Processes are the way quantities interact over time. Physical systems can be described as a set of quantities and the processes that operate on them. Representations for causality, time, and quantity are needed to fully characterize change in this domain. Several ideas for these representations are examined and synthesized in this paper towards the goal of constructing a framework to support understanding of, reasoning about, and learning how things work.MIT Artificial Intelligence Laborator

The Rise and (Relative) Fall of Earmarks: Congress and Reform, 2006–2010

Congressional earmark reform efforts began in 2006. This paper reviews the literature on earmarks and documents the rise and relative fall in earmark spending using four databases. It identifies and critiques earmark reforms, including congressional rules and initiatives taken by the appropriations committees and congressional party organizations. Rules and committee-initiated reforms were the most effective, producing significant improvements in transparency and expediting availability of information. The number of earmarks and their dollar value first dropped noticeably in 2007 after an earmark moratorium, then stabilized as reforms were implemented. It is premature to conclude that reforms will alter the policy content of earmarks or their distribution

Aspects of the Rover Problem

The basic task of a rover is to move about automonously in an unknown environment. A working rover must have the following three subsystems which interact in various ways: 1) locomotion--the ability to move, 2) perception--the ability to determine the three-dimensional structure of the environment, and 3) navigation--the ability to negotiate the environment. This paper will elucidate the nature of the problem in these areas and survey approaches to solving them while paying attention to real-world issues.MIT Artificial Intelligence Laborator

The effects of properties, microstructure and phase transformation on the erosion of hard materials

BaBibliography: pages 88-92.A variety of ceramic and ultrahard materials have been subjected to both solid particle and cavitation erosion. The materials tested include three grain sizes of alumina, stabilised zirconias, sialon, cubic boron nitride and polycrystalline diamond, and these have a range of microstructural, physical and mechanical properties. The damage modes are described for the two types of erosion and the results are critically discussed. It has been shown that different properties and microstructural features control the respective types of erosion. Hardness is the critical property which controls material loss during solid particle erosion. Cavitation erosion in contrast is less sensitive to hardness, but is extremely defect sensitive and preferentially attacks weak or damaged regions on the target. Grain size and shape, and th.e properties of the grain boundary or intergranular phase exert a strong influence on both types of erosion. It has in addition been concluded, that a propensity for a stress induced phase transformation, such as that exhibited by stabilised zirconia, will benefit the resistance of a ceramic to erosion. Ultrahard materials generally outperform the structural ceramics that were tested. While it was not possible to ascertain the effects of grain size conclusively, a large extent of intergrowth between the crystallites during manufacture appears to be beneficial to erosion resistance