Charge trapping and detrapping in polymeric materials

Space charge formation in polymeric materials can cause some serious concern for design engineers as the electric field may severely be distorted, leading to part of the material being overstressed. At the worst, this may result in material degradation and possibly premature failure. It is therefore important to understand charge generation, trapping, and detrapping processes in the material. In the present paper, the characteristics of charge trapping and detrapping in low density polyethylene under dc electric field have been investigated using the pulsed electroacoustic technique. It has been found that the charge decay shows very different characteristics for the sample with different periods of electric field application. To explain the results a simple trapping and detrapping model based on two trapping levels has been proposed. Qualitative analysis revealed the similar features to those observed experimentally

Spiking Neural P Systems with Addition/Subtraction Computing on Synapses

Spiking neural P systems (SN P systems, for short) are a class of distributed and parallel computing models inspired from biological spiking neurons. In this paper, we introduce a variant called SN P systems with addition/subtraction computing on synapses (CSSN P systems). CSSN P systems are inspired and motivated by the shunting inhibition of biological synapses, while incorporating ideas from dynamic graphs and networks. We consider addition and subtraction operations on synapses, and prove that CSSN P systems are computationally universal as number generators, under a normal form (i.e. a simplifying set of restrictions)

An equivalent condition of continuous metric selection

AbstractAn intrinsic characterization is given of those finite-dimensional subspaces whose metric projections admit continuous selections

Probing spin, charge and lattice coupling in manganites

Complex oxides such as the manganites exhibit an intimate coupling of the electron spin, charge and lattice degrees of freedom. The characteristic feature of these materials is the existence of a ground state topology with many closely lying minima. The system can be switched from one minimum to another by the application of external parameters such as strain, temperature, magnetic fields, or electrical fields. These materials thus exhibit large responses to these external parameters and can be used as novel sensors in data storage and other applications. Understanding the couplings will have an impact on the fundamental science of highly correlated materials as well as in applications to industry. This work focuses on applying pressure to probe the properties of Colossal Magnetoresistance Manganites, self-doped LaxMnO3 (X=0.85, 0.75) and chemically doped La0.67Ca0.33MnO3. For all of them, obvious pressure effects on electronic transport and structure have been investigated; especially, critical pressures were found between ~3.4 GPa to ~4.0GPa. Below P*, pressures increase the metal-insulator transition temperature and electrical conductivity while both of them decrease with increasing pressures above P~. In particular, the bandwidth increase drives the increase of TMI for pressures below The reduction of TMI at higher pressures is found to result from the Jahn-Teller distortions of the MnO6 octahedra and the localization of 3d electrons. The general trend is expected to be a characteristic feature of Colossal Magnetoresistance manganites

Distributed product development approaches and system for achieving optimal design.

The research in this dissertation attempts to provide theoretic approaches and design systems to support engineers who are located in different places and belong to different teams or companies to work collaboratively to perform product development.The second challenge is addressed by developing a collaborative design process modeling technique based on Petri-net. Petri-net is used to describe complex design processes and to construct different design process alternatives. These alternative Petri-net models are then analyzed to evaluate design process alternatives and to select the appropriate process.In this dissertation, three major challenges are identified in realization of a collaborative design paradigm: (i) development of design method that supports multidisciplinary xi design teams to collaboratively solve coupled design problems, (ii) development of process modeling techniques to support representation and improve complex collaborative design process, and (iii) implementation of a testbed system that demonstrates the feasibility of enhancing current design system to satisfy with the needs of organizing collaborative design process for collaborative decision making and associated design activities.New paradigms, along with accompanying approaches and software systems are necessary to support collaborative design work, in a distributed design environment, of multidisciplinary engineering teams who have different knowledge, experience, and skills. Current research generally focuses on the development of online collaborative tools, and software frameworks that integrate and coordinate these tools. However, a gap exists between the needs of a distributed collaborative design paradigm and current collaborative design tools. On one side, design methodologies facilitating engineering teams' decision making is not well developed. In a distributed collaborative design paradigm, each team holds its own perspective towards the product realization problem, and each team seeks design decisions that can maximize the design performance in its own discipline. Design methodologies that coordinate the separate design decisions are essential to achieve successful collaboration. On the other side, design of products is becoming more complex. Organizing a complex design process is a major obstacle in the application of a distributed collaborative design paradigm in practice. Therefore, the principal research goal in this dissertation is to develop a collaborative multidisciplinary decision making methodology and design process modeling technique that bridges the gap between a collaborative design paradigm and current collaborative design systems.To overcome the first challenge, decision templates are constructed to exchange design information among interacting disciplines. Three game protocols from game theory are utilized to categorize the collaboration in decision makings. Design formulations are used to capture the design freedom among coupled design activities.The third challenge, implementation of collaborative design testbed, is addressed by integration of existing Petri-net modeling tools into the design system. The testbed incorporates optimization software, collaborative design tools, and management software for product and process design to support group design activities.Two product realization examples are presented to demonstrate the applicability of the research and collaborative testbed. A simplified manipulator design example is used for explanation of collaborative decision making and design process organization. And a reverse engineering design example is introduced to verify the application of collaborative design paradigm with design support systems in practice