Optimal Embedding of Functions for In-Network Computation: Complexity Analysis and Algorithms

We consider optimal distributed computation of a given function of distributed data. The input (data) nodes and the sink node that receives the function form a connected network that is described by an undirected weighted network graph. The algorithm to compute the given function is described by a weighted directed acyclic graph and is called the computation graph. An embedding defines the computation communication sequence that obtains the function at the sink. Two kinds of optimal embeddings are sought, the embedding that---(1)~minimizes delay in obtaining function at sink, and (2)~minimizes cost of one instance of computation of function. This abstraction is motivated by three applications---in-network computation over sensor networks, operator placement in distributed databases, and module placement in distributed computing. We first show that obtaining minimum-delay and minimum-cost embeddings are both NP-complete problems and that cost minimization is actually MAX SNP-hard. Next, we consider specific forms of the computation graph for which polynomial time solutions are possible. When the computation graph is a tree, a polynomial time algorithm to obtain the minimum delay embedding is described. Next, for the case when the function is described by a layered graph we describe an algorithm that obtains the minimum cost embedding in polynomial time. This algorithm can also be used to obtain an approximation for delay minimization. We then consider bounded treewidth computation graphs and give an algorithm to obtain the minimum cost embedding in polynomial time

Fabrication and characterization of organic light emitting diodes for display applications

Organic Light Emitting Diodes (OLEDs) based on the principle of electroluminescence, constitute a new and exciting emissive display technology for flat panel displays. In order to attain high quantum efficiency for electroluminescence, it is necessary to achieve three attributes: efficient charge injection from the electrodes at low drive voltage, good charge balance, and confinement of the injected charge carriers within the emitting layers. The purpose of this research work was to fabricate, measure and analyze OLEDs based on these fundamental principles using different cathode materials, injection layers and buffer layers in order to determine the best possible configuration. Starting from a simple bi-layered device, multilayered heterojunction OLEDs were built by employing energy band engineering. Since it was the first time that these imaging devices were being built in our Laboratory, developing tools and techniques to get reproducible OLEDs was a prerequisite to the realization of this goal. Thus, through this process, the Lab\u27s capability was realized from the fabrication and characterization perspective, and fundamental knowledge regarding the operation of OLEDs was gained. The OLEDs fabricated were of high efficiency and brightness, and their properties match well with the published literature

Investigation of Hydration Induced Structural Rearrangements of Poly(lactic Acid)

A comprehensive analysis of microstructural changes associated with hydration of Poly(lactic acid) (PLA) and their effect on the macroscopic properties has been provided. Although water absorbed in PLA is extremely small (~0.5% by weight or 1 water molecule per 30 PLA monomer units), we found significant increase in the kinetics of physical aging and crystallization in the presence of water. The fact that water has such a strong effect on PLA structure is attributed to the polar nature of water, strong intermolecular interactions present in PLA and their changes in the hydrated state. Using vibrational spectroscopy, features associated with bound water or free water were found for PLA with different hydration levels. The structural rearrangements were correlated to the presence of free liquid water disrupting the intermolecular interactions in PLA. The effect of these structural rearrangements on the mechanical behavior of PLA in different environments such as wet and submerged state was determined. The elastic modulus surprisingly increased by as much as 10% upon hydration at 37 oC as compared to the dry ones. However, based on DSC and X-ray diffraction data, no increase in the degree of crystallinity was found. Instead the increase in modulus was attributed to the extremely fast aging process that occurred when PLA was hydrated. This densification process resulted in a higher cohesive energy that can be characterized by a rise in Tg (~5 degrees Celsius) and a ~30% decrease in the intensity of the sub-Tg β transition peak. Time resolved FTIR spectroscopy in the near-IR frequency region showed different populations of water molecules having specific interactions with the carbonyl group of PLA. It was concluded that water forming intermolecular bridges between the PLA chains also contributed to the increase in elastic modulus. Interestingly, water had an opposite effect on the mechanical properties of semicrystalline PLA where the elastic modulus decreased by ~10% upon hydration. In semicrystalline PLA, in addition to the perturbing effects being limited by the constraints introduced by the crystalline domains, absorbed water exhibited bulk water like features, leading to decrease in the modulus

Tissue material process for forming bioprosthesis

A biomaterial useful for bioprostheses such as bioprosthetic heart valves is provided in which the fixed tissue has improved elastic properties. The high elastin-containing biomaterial is further characterized by having anisotropic properties wherein the biological material has a greater stiffness in one direction and a greater elasticity in a cross direction. For instance, the biological material has an elastin content of about 30% by weight. In one embodiment, the biological material is vena cava tissue

Multi-step connective tissue stabilization method and stabilized tissue formed thereby

A multi-step stabilization method for connective tissue is described. Stabilized tissues can exhibit increased resistance to degradation due to enzyme activity, fatigue and storage. The multi-step method includes a first step during which the tissue can be incubated with a glycosaminoglycanase inhibitor such as a sulfated oligosaccharide, one example of which being neomycin, a second step during which the tissue can be incubated with a crosslink activator such as a carbodiimide crosslink activator and/or a crosslinking agent such as a heterobifunctional crosslinking agent and/or a phenolic compound such as a tannin, examples of which include tannic acid and pentagalloylglucose, and a third step during which the tissue can be incubated with a second crosslink activator that can be the same or different as the first crosslink activator

Anthropometric and Strength Data of Indian Agricultural Workers for Equipment Design: A Review

Anthropometric and strength data of agricultural workers is very essential for the safe, user-friendliness and efficient design of farm equipments. This paper presents the review on the studies carried out so far to generate the anthropometric and strength data of agricultural workers for equipment design and ergonomics evaluation of farm equipments. Review shows that much of the studies are focused on anthropometric data and very few have considered strength parameters. For very few regions in India, anthropometric and strength data is available and it is essential to generate exhaustive region specific data (which was found varying region to region) for rest of the regions to suite the population in the particular region. Also there is necessity of ergonomic evaluation and optimization of farm equipments to reduce musculoskeletal disorders and prevent injuries in farm workers