Valence Charge Fluctuations and Tc Retention in Tl1−xPbxSr1+xLa1−xCuO5−y (0.0 ≤ x ≤0.5) System

Structural and x-ray photoelectron spectroscopy (XPS) studies of the Tl_1?xPb_xSr_1+xLa_1?xCuO_5?y (0.0≤x≤0.5) system have been carried out. The unit cell parameters increase with x. Irrespective of x the T_c is retained in this series and the optimum hole concentration (n_h) is maintained for x≤ 0.5. An increase in Tl 4f and O ls binding energy with x suggests a reduction in their oxidation state. Origin of holes is discussed in terms of charge transfer between Tl, Pb and CuO₂ layers.     

Sharing Memory Optimally

Efficient design of service facilities, such as data or computer networks that meet random demands, often leads to the sharing of resources among users. Contention for the use of a resource results in queueing. The waiting room is a part of any such service facility. The number of accepted service requests per unit of time (throughput), or the fraction of the time the servers are busy (utilization), are often used as performance measures to compare designs. Most common models in queueing theory consider the design of the waiting rooms with the assumption that, although individual requests may differ from one another, they are statistically indistinguishable. However, there are several instances where available information allows us to classify the requests for service into different types. In such cases the design of the service facility not only involves the determination of an optimum size for the waiting room but also the rules of sharing it among the different types. Even with a fixed set of resources, the rules of sharing them can influence performance. In data networks (or computer networks) the "waiting room" consists of memory of one kind or another. Messages (jobs) destined for different locations (processors) sharing common storage is an important example of shared use of memory. Recently, Kleinrock and Kamoun have modeled such use of memory and computed the performance of various policies for managing the allocation of memory to several types of users. Decisions to accept or reject a demand for service were based on the number of waiting requests of each type. However, the optimal policy was not determined even in the case where there were only two types of users. We determine the structure of optimal policies for the model considered with three types of users. The optimal policy consists of limiting the number of waiting requests of each type, and reserving a part of the memory to each type.     

Airbridged high-speed AlGaAs-GaAs ridge waveguide lasers

The design of a high modulation response multiple-quantum-well ridge waveguide laser in AlGaAs-GaAs, with low parasitics is discussed. The device was fabricated on a semi-insulating substrate with a wide top contact, and airbridges have been used to connect the ridge top contact to the bonding pads on the semi-insulating substrate. The 3-dB frequency response of the laser has been measured to be 21 GHz, which is a record for unstrained quantum-well AlGaAs-GaAs lasers.     

Efficient management of time-evolving databases

Efficiently managing the history of a time-evolving system is one of the central problems in many database environments, like database systems that incorporate versioning, or object-oriented databases that implicitly or explicitly maintain the history of persistent objects. In this paper we propose algorithms that reconstruct past states of an evolving system for two general cases, i.e., when the system's state is represented by a set or by a hierarchy (a forest of trees). Sets are widely used as a canonical form of representing information in databases or program states. For more complex applications, like schema evolution in object-oriented databases, it becomes necessary to manage the history of data structures that have the form of forests or even graphs. The proposed algorithms use minimal space (proportional to the number of changes occurring in the evolution) and have the advantage of being on-line (in the amortized sense). Any past system state s(t) is reconstructed in time O(|s(t)|+log log T), where |s(t)| is the size of the answer and T is the maximal evolution time. For all practical cases the log log T factor is a constant, therefore our algorithms provide almost random access to any past system state. Moreover, we show that the presented algorithms are optimal among all algorithms that use space linear in the number of changes in the system's evolution     

Self‐assembled honeycomb polyurethane nanofibers

Electrospinning uses a high voltage electric field to produce fine fibers. A new phenomenon of self‐assembly in the electrospinning of polyurethane nanofibers is observed. This report is the first known self‐assembling phenomenon in polyurethane electrospun nanofibers. Electrospun polyurethane nanofibers self‐assemble into unique honeycomb patterns on the collector surface. This novel observation opens up new and interesting opportunities for electrospun fibers in the areas of drug delivery devices, protective clothing, filters, and tissue scaffolds. © 2006 Wiley Periodicals, Inc. J Appl Polym Sci 101: 3121–3124, 2006     

A “Weighted Aggregate” Approach to R & D Project Selection

This article describes a general model for setting priorities on proposed R & D projects. It reports on research that evaluates methods for implementing the model. Specifically investigated were techniques for establishing criteria weights, assigning quantitative scales to qualitative criteria and modifying the model to improve its performance. Methods for solving the problem of criteria independence and for estimating probability of project success are proposed, but not tested.     

A probabilistic framework based on hidden markov model for fiducial identification in image-guided radiation treatments

Fiducial tracking is a common target tracking method widely used in image-guided procedures such as radiotherapy and radiosurgery. In this paper, we present a multifiducial identification method that incorporates context information in the process. We first convert the problem into a state sequence problem by establishing a probabilistic framework based on a hidden Markov model (HMM), where prior probability represents an individual candidate's resemblance to a fiducial; transition probability quantifies the similarity of a candidate set to the fiducials' geometrical configuration; and the Viterbi algorithm provides an efficient solution. We then discuss the problem of identifying fiducials using stereo projections, and propose a special, higher order HMM, which consists of two parallel HMMs, connected by an association measure that captures the inherent correlation between the two projections. A novel algorithm, the concurrent viterbi with association (CVA) algorithm, is introduced to efficiently identify fiducials in the two projections simultaneously. This probabilistic framework is highly flexible and provides a buffer to accommodate deformations. A simple implementation of the CVA algorithm is presented to evaluate the efficacy of the framework. Experiments were carried out using clinical images acquired during patient treatments, and several examples are presented to illustrate a variety of clinical situations. In the experiments, the algorithm demonstrated a large tracking range, computational efficiency, ease of use, and robustness that meet the requirements for clinical use.      

Distributed non-negative matrix factorization with determination of the number of latent features

The Journal of Supercomputing - The holistic analysis and understanding of the latent (that is, not directly observable) variables and patterns buried in large datasets is crucial for data-driven...     

Sensitive pH detection on gold interdigitated electrodes as an electrochemical sensor

Microsystem Technologies - Miniaturized in-house high-performance sensors are mandatory for implementing the current needs efficiently. With the microsystems, electrode material is crucial to...