Antiferromagnetism in the semiconducting lanthanide cuprates Ln2CuO4

The semiconducting lanthanide cuprates Pr₂CuO₄, Nd₂CuO₄, and Gd₂CuO₄ have been investigated using X-ray diffraction, magnetic susceptibility, and electron paramagnetic resonance techniques. The susceptibility and resonance studies indicate that the Cu²⁺ ions are ordered antiferromagnetically and that the exchange interactions involving the Ln³⁺ ions are relatively weak. The deviations from the Curie-Weiss law in Pr₂CuO₄ and Nd₂CuO₄ are in qualitative agreement with the predicted behavior for isolated Ln³⁺ ions under the influence of a crystal field. Hence these compounds provide interesting examples of planar Cu²⁺-ion antiferromagnets.     

Existence and uniqueness of minimal realizations of nonlinear systems

In the theory of finite dimensional linear systems, it is well known that every input-output map that can be realized by one such system can also be realized by a system which is minimal, i.e. both controllable and observable. Moreover, the minimal realization of a given map is unique up to isomorphism. It is shown here that similar results hold for the class of all systems whose state space is a real analytic manifold, whose dynamics is given by a family of complete real analytic vector fields, and whose output is an arbitrary real analytic function on the state space.Research partially supported by NSF Grant GP-37488.     

Analyzing an inventory system with multiple reorder points and periodic replenishment

This paper investigates multiple reorder point, periodic replenishment systems similar to those utilized on board some U.S. naval vessels for Selected Item Management (SIM). This inventory system is of interest since it involves both regular and priority replenishment, three reorder points, and cyclical restocking of regular orders. A simulation model is developed to study the impact of demand distribution, cycle time, priority order leadtime, and the quantity of units ordered on the performance of the system. It is found that the frequency of service and days without shortages performance measures can be maximized by setting the reorder points at equal intervals between the zero level and the high level. Also, a power approximation model is presented that estimates the high level that will lead to a desired percent days without shortage percentage.     

A Parallel Implementation of Multiple Secret Image Sharing Based on Cellular Automata

Recently, a multisecret sharing scheme for secret color images among a set of users was proposed, which allows that each participant to share secret color images with the rest of participants in such way that all of them can recover all secret color images only if all participants pool their shares. In this work a parallel implementation of the cellular automata-based multisecret sharing scheme is proposed, in which the technology of CUDA （Compute Unified Device Architecture） is used in parallelization, taking advantage that each cell of cellular automata can be processed independently. The processing time of the proposed scheme is analyzed and it is proved that the proposed parallel algorithm using the CUDA structure is more than 12 times faster than the conventional sequential algorithm. This reduction of temporal complexity allows the practical use of the secret sharing scheme in many information security fields.     

The TSIMMIS Approach to Mediation: Data Models and Languages

TSIMMIS—The Stanford-IBM Manager of Multiple InformationSources—is a system for integrating information. It offers a datamodel and a common query language that are designed to support thecombining of information from many different sources. It also offerstools for generating automatically the components that are needed tobuild systems for integrating information. In this paper we shalldiscuss the principal architectural features and their rationale.