A PROCEDURE FOR THE PRODUCTION OF ULTRA-PURE PRECURSORS FROM COAL FOR THE MANUFACTURE OF VALUE-ADDED CARBON PRODUCTS - TREATMENT OF THE RESIDUE

Solvent extraction of coal results in a coal-derived extract containing the solvent-soluble organic portion of coal free of almost all mineral matter. A residue is also produced and consists of most of the mineral matter. Although a procedure has been developed to manufacture ultra-pure coke precursors for value-added carbon products from coal-derived extracts, treatment/rc-usc of the residue is necessary to make the process economically attractive and environmentally friendly. In this study, a technique has been developed to beneficiate the residue by specific gravity fractionation. It is found that nearly 70 % of the residue can be separated into a fraction containing less than 3.5% ash for a typical WV bituminous coal using an organic liquid having a specific gravity of 1.5. This treatment enables the residue to serve as a low-ash boiler fuel or a suitable precursor for the manufacture of materials such as activated carbons. Consequently, the potential for coal-derived precursors leading to new and non-conventionai marketable carbon products can be realized easily.     

The VLISP verified PreScheme compiler

This paper describes a verified compiler for PreScheme, the implementation language for thevlisp run-time system. The compiler and proof were divided into three parts: A transformational front end that translates source text into a core language, a syntax-directed compiler that translates the core language into a combinator-based tree-manipulation language, and a linearizer that translates combinator code into code for an abstract stored-program machine with linear memory for both data and code. This factorization enabled different proof techniques to be used for the different phases of the compiler, and also allowed the generation of good code. Finally, the whole process was made possible by carefully defining the semantics ofvlisp PreScheme rather than just adopting Scheme's. We believe that the architecture of the compiler and its correctness proof can easily be applied to compilers for languages other than PreScheme.This work was supported by Rome Laboratory of the United States Air Force, contract No. F19628-89-C-0001, through the MITRE Corporation, and by NSF and DARPA under NSF grants CCR-9002253 and CCR-9014603. Author's current address: Department of Computer Science and Engineering, Oregon Graduate Institute, P.O. Box 91000, Portland, OR 97291-1000.The work reported here was supported by Rome Laboratory of the United States Air Force, contract No. F19628-89-C-0001. Preparation of this paper was generously supported by The MITRE Corporation.This work was supported by Rome Laboratory of the United States Air Force, contract No. F19628-89-C-0001, through the MITRE Corporation, and by NSF and DARPA under NSF grants CCR-9002253 and CCR-9014603.     

On formalism and stability of switched systems

In this paper,we formulate a uniform mathematical framework for studying switched systems with piecewise linear partitioned state space and state dependent switching.Based on known results from the the...     

Intrinsically patterned electrical systems: physical requirements and experimental demonstration

Microsystem Technologies - This paper introduces a method of replicating electrical circuits through a series of specific requirements as part of a design methodology referred to as Intrinsically...     

On finding optimal and near-optimal lineal spanning trees

The search for good lineal, or depth-first, spanning trees is an important aspect in the implementation of a wide assortment of graph algorithms. We consider the complexity of findingoptimal lineal spanning trees under various notions of optimality. In particular, we show that several natural problems, such as constructing a shortest or a tallest lineal tree, are NP-hard. We also address the issue of polynomial-time, near-optimization strategies for these difficult problems, showing that efficient absolute approximation algorithms cannot exist unlessP = NP.     

The expected complexity of analytic tableaux analyses in propositional calculus — II

The article continues a study of the complexity of an analytic tableaux algorithm for SAT. The main result is that the average number of branches in analytic tableaux of formulae of lengthn is((1.09988...) ⁿ ). The maximum number of branches is also studied. Both the average and worst case complexity measures are used to compare analytic tableaux and truth tables.For the average case result the precise number of consistent branches and the precise number of inconsistent branches (for formulae of lengthn) are each expressed as multiply indexed sums whose terms involve factorials and Stirling numbers of the second kind. The asymptotic behavior of these sums is determined by adapting a classical technique for determining the asymptotic behavior of singly indexed sums whose terms involve factorials.     

An analytical and numerical study of the two-dimensional Bratu equation

Bratu's problem, which is the nonlinear eigenvalue equationu+ exp(u)=0 withu=0 on the walls of the unit square and as the eigenvalue, is used to develop several themes on applications of Chebyshev pseudospectral methods. The first is the importance ofsymmetry: because of invariance under the C₄ rotation group and parity in bothx andy, one can slash the size of the basis set by a factor of eight and reduce the CPU time by three orders of magnitude. Second, the pseudospectral method is ananalytical as well as a numerical tool: the simple approximation3.2A exp(–0.64A), whereA is the maximum value ofu(x, y), is derived via collocation with but a single interpolation point, but is quantitatively accurate for small and moderateA. Third, the Newton-Kantorovich/Chebyshev pseudospectral algorithm is so efficient that it is possible to compute good numerical solutions—five decimal places—on amicrocomputer inbasic. Fourth, asymptotic estimates of the Chebyshev coefficients can be very misleading: the coefficients for moderately or strongly nonlinear solutions to Bratu's equations fall off exponentially rather than algebraically withv untilv is so large that one has already obtained several decimal places of accuracy. The corner singularities, which dominate the behavior of the Chebyshev coefficients in thelimit v, are so weak as to be irrelevant, and replacing Bratu's problem by a more complicated and realistic equation would merely exaggerate the unimportance of the corner branch points even more.     

An Active Feedback System for Stabilizing Visual Images

In normal vision, eye movements cause the image to move on the retina. Special apparatus can stabilize the image on the retina so it cannot move, and vision fades away. Previous methods for stabilizing the image were either optical systems or complex computer-controlled feedback systems. A simpler feedback system is presented which detects eye motion and rotates a mirror through which the target is viewed, to exactly compensate for eye motion. Unlike previous optical systems, this new system has no lenses in either the viewing or the image-forming path to limit the spatial resolution.     

The Future of High Energy Accelerators

This paper begins with a review of those high energy accelerators which are now in operation. Accelerators under construction are discussed and very high energy machines, still far in the future, are listed and described. Possible uses of cryogenic and superconducting magnets are mentioned. Colliding beam projects in operation and planned are presented. High energy physics has become very expensive. The total investment in Brookhaven's 33-GeV accelerator complex is now over $60 million and is still rising. Merely to operate the accelerator and its experimental areas requires the services of over 400 people. Our power bill is about $1 million per year. All of this is to produce new knowledge, very fundamental in nature but without evident immediate application. With the budget of the United States in a state of unbalance and with growing sentiment that money spent should show immediate results, is it wise or even sensible to think of new and more expensive steps along the route to the solution of the many mysteries of the nucleus and its components? I think that it is wise and that frontier fields like that of high energy physics must be pursued vigorously if we are to maintain our intellectual and technical position in the world. Sooner or later our experimental results will have important impacts on our life, probably in quite unforeseeable fashions. Nuclear physics began its history before the turn of the century; only in the last two decades has it resulted in a new power industry.     

Toughening by Metallic Lamina in Nickel/Alumina Composites

Tape casting and hot-pressing were used to produce metal/ alumina laminate composites. The mechanical behavior of these laminates was characterized. The strength and toughness of the laminates were greatly improved in comparison to that of monolithic alumina. Indentation strength values of the laminates remained approximately constant for indent loads between 10 and 100 N. Thus, this type of laminate appears to be a good candidate for damage-tolerant composite material design.