Laser-Based Printing: From Liquids to Microstructures

Assembly of materials into microstructures under laser guidance is attracting wide attention. The ability to pattern various materials and form 2D and 3D structures with micron/sub-micron resolution and less energy and material waste compared with standard top-down methods make laser-based printing promising for many applications, for example medical devices, sensors, and microelectronics. Assembly from liquids provides a smaller feature size than powders and has advantages over other states of matter in terms of relatively simple setup, easy handling, and recycling. However, the simplicity of the setup conceals a variety of underlying mechanisms, which cannot be identified simply according to the starting or resulting materials. This progress report surveys the various mechanisms according to the source of the material—preformed or locally synthesized. Within each category, methods are defined according to the driving force of material deposition. The advantages and limitations of each method are critically discussed, and the methods are compared, shedding light on future directions and developments required to advance this field.     

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.     

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.     

(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.     

Effects of Magnetic Field on Conductance and Electroluminescence in Organic Devices

In this contribution we review recent advances of the organic magnetic field effects, namely magneto-conductance and magneto-electroluminescence, in both experiment and theory. We describe a number of processes, including the polaron-pair and triplet-triplet pair mechanisms that are responsible for the magnetic field effects in organic semiconductor systems. For the polaron pair mechanism, we review in detail the effect of the hyperfine interaction, both isotropic and anisotropic; different g-factors of the two polarons composing the pair; and the spin orbit interaction. The effect of the triplet-triplet annihilation process is also analyzed. Experimental examples for each case treated theoretically are given.