Investigation of high quality GaAs:In layers grown by liquid phase epitaxy

Indium-doped GaAs layers are investigated by low-field Hall effect, photoluminescence, and double crystal x-ray diffraction in order to study the influence of the In concentration on the electrical, optical, and crystallographic properties. The layers were grown by liquid phase epitaxy from solution with In concentrations in the range 0–10 at.%. It was found that epitaxial growth from the melt with 7 at.% In content produces the highest quality epitaxial layers.     

Hydrogel-magnetic nanoparticles with immobilized l-asparaginase for biomedical applications

The association of magnetic nanoparticles, which could be controlled by a magnetic field and have dimensions which facilitate their penetration in cells/tissues, with hydrogel type biopolymeric shells confer them compatibility and the capacity to retain and deliver bioactive substances. The main objective of this work is the development of a new system based on a biocompatible polymer with organic–inorganic structure capable of vectoring support for biologic active agents (l-asparaginase, e.g.). Characterization of size and morphology of the hydrogel-magnetic nanoparticles with entrapped l-asparaginase was made using Dynamic Light Scattering method, Transmission Electron Microscopy and Confocal Microscopy. The structure of magnetic nanoparticles coated with hydrogel was characterized by Fourier Transformed Infrared Spectroscopy. The cytotoxicity of nanoparticles was evaluated and also the interactions with microorganisms. We obtained hydrogel-magnetic nanoparticles with l-asparaginase entrapped, with sizes below 30 nm in dried stage, capable to penetrate the cells and tissues.     

Progress towards marketable earth-abundant chalcogenide solar cells

Kesterite-related photovoltaic materials are considered a promising alternative to CdTe and Cu(In,Ga)(S,Se)₂ absorbers, primarily because they are not reliant on scarce elements such as indium and tellurium or the heavy metal cadmium. Recently, we reported a performance breakthrough for this materials class, reaching by a simple hydrazine-based deposition technique 9.6% power conversion efficiency for Cu₂ZnSn(S,Se)₄ devices (40% improvement over vacuum-based methods). Here, more detailed characterization for a hydrazine-prepared device shows the potential of this technology for further efficiency improvement. We also present initial device results for Cu₂ZnSn(S,Se)₄ films deposited using a mixed water-hydrazine-based solvent, yielding devices with 8.1% efficiency.     

Solution‐processed Cu(In,Ga)(S,Se)2 absorber yielding a 15.2% efficient solar cell

The remarkable potential for inexpensive upscale of solution processing technologies is expected to enable chalcogenide‐based photovoltaic systems to become more widely adopted to meet worldwide energy needs. Here, we report a thin‐film solar cell with solution‐processed Cu(In,Ga)(S,Se)₂ (CIGS) absorber. The power conversion efficiency of 15.2% is the highest published value for a pure solution deposition technique for any photovoltaic absorber material and is on par with the best nonvacuum‐processed CIGS devices. We compare the performance of our cell with a world champion vacuum‐deposited CIGS cell and perform detailed characterization, such as biased quantum efficiency, temperature‐dependent electrical measurement, time‐resolved photoluminescence, and capacitance spectroscopy. Copyright © 2012 John Wiley & Sons, Ltd.     

The Theory of Planned Behavior and Information Security Policy Compliance

ABSTRACT

Much of the research on security policy compliance has tested the relationships posited by the theory of planned behavior. This theory explains far from all of the measurable variance in policy compliance intentions. However, it is associated with something called the sufficiency assumption, which essentially states that no variable is missing from the theory. This paper addresses this assumption in the context of information security policy compliance. A meta-analysis of published tests on information security behavior and a review of the literature in related fields are used to identify variables that have the potential to improve the theory’s predictions. These results are tested using a random sample of 645 white-collar workers. The results suggest that the variables anticipated regret and habit improve the predictions. The variables increase the explained variance by 3.4 and 2.6 percentage points, respectively, when they are added individually, and by 5.4 percentage points when both are added.     

Using graph coloring in an algebraic compiler

An algebraic compiler allows incremental development of the source program and builds its target image by composing the target images of the program components. In this paper we describe the general structure of an algebraic compiler focusing on compositional code generation. We show that the mathematical model for register management by an algebraic compiler is a graph coloring problem in which an optimally colored graph is obtained by composing optimally colored subgraphs. More precisely, we define the clique-composition of graphs and as the graph obtained by joining all the vertices in a clique in with all the vertices in a clique in and show that optimal register management by an algebraic compiler is achieved by performing clique-composition operations. Thus, an algebraic compiler provides automatically adequate clique separation of the global register management graph. We present a linear-time algorithm that takes as input optimally colored graphs and and constructs an optimal coloring of any clique-composition of and . Motivated by the operation of clique-composition, we define the class of clique-composable graphs as those graphs that can be iteratively built from single vertices using the clique-composition operation. We show that the class of clique-composable graphs coincides with the well-known class of chordal graphs. Received: 11 May 1995 / 30 November 1995     

A Language for Multi-dimensional Updates

Dynamic Logic Programming (DLP) was introduced to deal with knowledge about changing worlds, by assigning semantics to sequences of generalized logic programs, each of which represents a state of the world. These states permit the representation, not only of time, but also of specificity, strength of updating instance, hierarchical position of the knowledge source, etc. Subsequently, the Language of Updates LUPS was introduced to allow for the association, with each state, of a set of transition rules. It thereby provides for an interleaving sequence of states and transition rules within an integrated declarative framework. DLP (and LUPS), because defined only for a linear sequence of states, cannot deal simultaneously with more than a single dimension (e.g. time, hierarchies,…). To overcome this limitation, Multi-dimensional Dynamic Logic Programming (MDLP) was therefore introduced, so as to make it possible to organize states into arbitrary acyclic digraphs (DAGs). In this paper we now extend LUPS, setting forth a Language for Multi-dimensional Updates (MLUPS). MLUPS admits the specification of flexible evolutions of such DAG organized logic programs, by allowing not just the specification of the logic programs representing each state, but to the evolution of the DAG topology itself as well.     

Nonlinear Control for the Dual Smart Drive Using Backstepping and a Time-Optimal Reference

The Dual Smart Drive is a specially designed nonlinear actuator intended for use in climbing and walking legged robots. It features a continuously changing transmission ratio and dual properties and is very suitable for situations where the same drive is required to perform two different types of start-stop motions of a mobile link. Then, the associated control problem to this nonlinear actuator is established and a backstepping design strategy adopted to develop Lyapunov-based nonlinear controllers that ensure asymptotic tracking of the desired laws of motion, which have been properly selected using time-optimal control. The approach is extended for bounded control inputs. Both simulation and experimental results are presented to show the effectiveness and feasibility of the proposed nonlinear control methods for the Dual Smart Drive. Supported by the Spanish Ministry of Education under Grant F.P.U. Supported by the National Science Foundation under Grant No. ECS-0242798 Supported by the Spanish Ministry of Science and Technology under Grant Ramón y Cajal, Project “Theory of optimal Dual Drives for Automation and Robotics” Roemi E. Fernández was born in Madrid, Spain, in 1977. She received the B.S. degree in Electronic Engineering from Santa Maria La Antigua University, Panamá, in 2000. She is currentlya PhD candidate at the Polytechnic University of Madrid, Spain and at the Industrial Automation Institute, which belongs to the Spanish Council for Scientific Research. Her research interests include nonlinear control theory, walking and climbing robots, resonance and quasi-resonance drives, and mechatronics. Joáo P. Hespanha was born in Coimbra, Portugal, in 1968. He received the Licenciatura and the M.S. degree in electrical and computer engineering from Instituto Superior Técnico, Lisbon, Portugal, in 1991 and 1993, respectively, and the M.S. and Ph.D. degrees in electrical engineering and applied science from Yale University, New Haven, Connecticut, in 1994 and 1998, respectively. For his PhD work, Dr. Hespanha received Yale University's Henry Prentiss Becton Graduate Prize for exceptional achievement in research in Engineering and Applied Science. Dr. Hespanha currently holds an Associate Professor position with the Department of Electrical and Computer Engineer at the University of California, Santa Barbara. From 1999 to 2001 he was an Assistant Professor at the University of Southern California, Los Angeles. His research interests include switching and hybrid systems; nonlinear control, both robust and adaptive; control of communication networks; the use of vision in feedback control; and stochastic games. Dr. Hespanha is the recipient of an NSF CAREER Award (2001) and the 2002–2004 Automatica Theory/Methodology best paper prize. Since 2003, he has been an Associate Editor of the IEEE Transactions on Automatic Control. Teodor Akinfiev received his M.S. degree from the Moscow State University and PhD degree from Mechanical Engineering Research Institute of the Academy of Sciences of Russia. From Year 1976 he was Researcher, Principal Researcher and Head of the Research Laboratory at the Mechanical Engineering Research Institute of the Academy of Sciences of Russia. From Year 1995 he holds Position at the Industrial Automation Institute, which belongs to the Spanish Council for Scientific Research. Teodor Akinfiev is the author over 200 publications (including more than 70 patents). His research interests include oscillation theory, mechanical engineering, control systems, robotics, intelligent drives, and mechatronics. In Year 2002 he was elected a Member of the Academy of Natural Sciences of Russia for his research cycle on resonance and quasi-resonance drives. Manuel A. Armada received his PhD in Physics from the University of Valladolid (Spain) in 1979. Since 1976 he has been involved in research activities related to Automatic Control and Robotics. He has been working in more than forty RTD projects (European ones: EUREKA, ESPRIT, BRITE/EURAM, GROWTH, with Latin America: CYTED). He is member of the Russian Academy of Natural Sciences. Dr. Armada owns several patents and has published over 200 papers. He is currently the Head of the Automatic Control Department at the Instituto de Automatica Industrial (IAI-CSIC), being his main research in walking and climbing robots.