3D Graphene‐Infused Polyimide with Enhanced Electrothermal Performance for Long‐Term Flexible Space Applications

Polyimides (PIs) have been praised for their high thermal stability, high modulus of elasticity and tensile strength, ease of fabrication, and moldability. They are currently the standard choice for both substrates for flexible electronics and space shielding, as they render high temperature and UV stability and toughness. However, their poor thermal conductivity and completely electrically insulating characteristics have caused other limitations, such as thermal management challenges for flexible high‐power electronics and spacecraft electrostatic charging. In order to target these issues, a hybrid of PI with 3D‐graphene (3D‐C), 3D‐C/PI, is developed here. This composite renders extraordinary enhancements of thermal conductivity (one order of magnitude) and electrical conductivity (10 orders of magnitude). It withstands and keeps a stable performance throughout various bending and thermal cycles, as well as the oxidative and aggressive environment of ground‐based, simulated space environments. This makes this new hybrid film a suitable material for flexible space applications.     

Hydrogen production by catalysed pyrolysis of polymer blends

Differently composed mixtures of HDPE and PMMA were pyrolysed at 700 °C and 815 °C in pyrolysis reactor. It was directly coupled with gas chromatography/mass spectrometry (GC/MS). On line pyrolysis GC/MS was applied in analysis of hydrogen, methane and carbon monoxide yielding in polymer blends pyrolyzate with/without metal (Ni,Co) coated particles, tested as a methane to hydrogen conversion catalysts supporting additives. They were prepared by electrochemical deposition of Ni and Co on the small iron particles surface. Maximum hydrogen production was confirmed at the highest pyrolysis temperature (815 °C), and the highest HDPE contents in the blends mixture. Higher content of the PMMA in the mixture led to higher production of CO and lower hydrogen contents in pyrolyzate. Nickel and cobalt containing additives affected production of hydrogen and other components at both 700 °C and 815 °C pyrolysis temperatures. An effect of different heat distribution between metal particles and polyblends occurred and affected hydrogen production. Application of pyrolysis gas chromatography in hydrogen production from polyblends represents an important tool to model future technological outputs as well simultaneous hydrogen production and CO, CO₂ elimination. Moreover, catalysis assisted conversion of methane to hydrogen can improve final hydrogen content in pyrolyzate. Effectivity of pyrolysis hydrogen production was determined by its quantification based on analytical calibration.     

A linear time randomizing algorithm for searching ranked functions

Consider a setF ofn functions defined on a common intervalU. A ranked function overF is defined from the functions ofF by using order information such as thek largest function, the sum ofk largest functions, etc. We give a linear time randomizing algorithmic paradigm for finding local roots, optima, intersection points, etc., of ranked functions. The algorithm is generalized to the Cost Effective Resource Allocation Problem and to various variants of the Parametric Knapsack Problem.Part of this work was done when the author was visiting Tel Aviv University.Supported, in part, by NSF Grant ECS-812141, and by the Mia Fischer David Foundation through the Israel Institute of Business Research, Tel Aviv University. IIBR working papers are intended for preliminary circulation of tentative research results. Comments are welcome and should be addressed directly to the author.     

Decision-Analytic Methodology for Cost-Benefit Evaluation of Diagnostic Testers

A modular influence diagram model is proposed as a decision-analytic framework for reasoning about diagnostic testing in the manufacture of mechanical products. The influence diagram ties product design, manufacturing, and testing decisions to field quality, costs and risks. The decision-analytic theory of “expected value of information” is used to evaluate the cost-benefit of alternate testing systems. The structure of the model highlights research directions for engineering economics in evaluating cost-benefit tradeoffs in the product cycle from design, to manufacturing, marketing and field service. An implementation in the IDES (Influence Diagram Based Expert System) illustrates the potential of applying such a planning model to real-time diagnostic decisions in the manufacture of mechanical components for high-speed printers.     

(Semi)alternating stack automata

New results concerning the space complexity of languages accepted by stack automata, alternating stack automata, and alternating pushdown automata are derived. Some of the results generalize previously known results.Work supported by NSF Grant MCS79-09967.Work supported by NSF Grant MCS78-01736.     

A linear time randomizing algorithm for searching ranked functions

Consider a setF ofn functions defined on a common intervalU. A ranked function overF is defined from the functions ofF by using order information such as thek largest function, the sum ofk largest functions, etc. We give a linear time randomizing algorithmic paradigm for finding local roots, optima, intersection points, etc., of ranked functions. The algorithm is generalized to the Cost Effective Resource Allocation Problem and to various variants of the Parametric Knapsack Problem.     

A note on finite-valued and finitely ambiguous transducers

We look at some decision problems concerning nondeterministic finite transducers. The problems concern finite-valuedness, finite ambiguity, equivalence, etc. For a fixedk, we give a polynomial time algorithm for deciding whether or not a transducer isk-valued. The result holds when “valued” is replaced by “ambiguous”. In fact, the following problems are decidable: 1) Given a transducer, is itk-ambiguous for somek? 2) Given two finitely ambiguous transducers, are they equivalent? For unambiguous transducers, equivalence is decidable in polynomial time.     

Detection of gaseous plumes in IR hyperspectral images using hierarchical clustering

The emergence of IR hyperspectral sensors in recent years enables their use in remote environmental monitoring of gaseous plumes. IR hyperspectral imaging combines the unique advantages of traditional remote sensing methods such as multispectral imagery and nonimaging Fourier transform infrared spectroscopy, while eliminating their drawbacks. The most significant improvement introduced by hyperspectral technology is the capability of standoff detection and discrimination of effluent gaseous plumes without need for a clear reference background or any other temporal information. We introduce a novel approach for detection and discrimination of gaseous plumes in IR hyperspectral imagery using a divisive hierarchical clustering algorithm. The utility of the suggested detection algorithm is demonstrated on IR hyperspectral images of the release of two atmospheric tracers. The application of the proposed detection method on the experimental data has yielded a correct identification of all the releases without any false alarms. These encouraging results show that the presented approach can be used as a basis for a complete identification algorithm for gaseous pollutants in IR hyperspectral imagery without the need for a clear background.