Towards a Dual-Tip STM Application in Mesoscopic Electron Transport

A new design for a dual-tip scanning tunneling microscope (STM) is presented. The design is a variation on the mechanically controllable break-junction with two electron beam-induced deposition nano-tips. The new design enables one to scan surfaces simultaneously with two probes having a nano-gap separation. By collecting the lateral current flowing between the tips, the transconductance map can then be compared with the STM images for local characterizations of the electron transport. Since the lateral beam carries the property of the density of states of the surface at momentum space, the dispersion of the electronic structure should give an orientation and position dependence of the local transconductance current. In addition, the reduced terminal separation, on the order of the characteristic mesoscopic length scales, is likely to be sensitive to a variety of typically observed interactions and interference effects.     

Hydrogels based on graft copolymers of collagen synthesis

Graft copolymerization of 2-hydroxyethyl methacrylate in combination with hydrophobic monomers onto soluble collagen was employed in the synthesis of hydrogels. The hydrogels were formed by simultaneous graft copolymerization and crosslinking. In order to study the effect of various crosslinking agents on the water retention character of the hydrogels, three different crosslinking agents, namely, N,N′-methylene bis acrylamide, 1,4-butanediol dimethacrylate, and hexamethylene urethanediacrylate were used. Hexamethylene urethanediacrylate crosslinked systems require a minimum amount of crosslinking agent to attain maximum water content in comparison to the other systems.     

A robust estimation approach for uncertain systems with perturbed measurements

This paper deals with state estimation problem for uncertain continuous‐time systems. A numerical treatment is proposed for designing interval observers that ensures guaranteed upper and lower bounds on the estimated states. In order to take into account possible perturbations on the system and its outputs, a new type of interval observers is introduced. Such interval observers consist of two coupled general Luenberger‐type observers that involve dilatation functions. In addition, we provide an optimality criterion in order to find optimal interval observers that lead to tight interval error estimation. The proposed existence and optimality conditions are expressed in terms of linear programming. Also, some illustrative examples are given. Copyright © 2015 John Wiley & Sons, Ltd.     

Preference-based content replacement using recency-latency tradeoff

This work introduces and establishes a new model for cache management, where clients suggest preferences regarding their expectations for the time they are willing to wait, and the level of obsolescence they are willing to tolerate. The cache uses these preferences to decide upon entrance and exit of objects to and from its storage, and select the best copy of requested object among all available copies (fresh, cached, remote). We introduce three replacement policies, each evicts objects based on ongoing scores, considering users’ preferences combined with other objects’ properties such as size, obsolescence rate and popularity. Each replacement algorithm follows a different strategy: (a) an optimal solution that use dynamic programming approach to find the best objects to be kept (b) another optimal solution that use branch and bound approach to find the worst objects to be thrown out (c) an algorithm that use heuristic approach to efficiently select the objects to be evicted. Using these replacement algorithms the cache is able to keep the objects that are best suited for users preferences and dump the other objects. We compare our proposed algorithms to the Least-Recently-Used algorithm, and provide evidence to the advantages of our algorithms providing better service to cache’s users with less burden on network resources and reduced workloads on origin servers.     

Energy efficient redundant configurations for real-time parallel reliable servers

Modular redundancy and temporal redundancy are traditional techniques to increase system reliability. In addition to being used as temporal redundancy, with technology advancements, slack time in a system can also be used by energy management schemes to save energy. In this paper, we consider the combination of modular and temporal redundancy to achieve energy efficient reliable real-time service provided by multiple servers. We first propose an efficient adaptive parallel recovery scheme that appropriately processes service requests in parallel to increase the number of faults that can be tolerated and thus system reliability. Then we explore schemes to determine the optimal redundant configurations of the parallel servers to minimize system energy consumption for a given reliability goal or to maximize system reliability for a given energy budget. Our analysis results show that small requests, optimistic approaches, and parallel recovery favor lower levels of modular redundancy, while large requests, pessimistic approaches and restricted serial recovery favor higher levels of modular redundancy.

LMI-Based Approach for Output-Feedback Stabilization for Discrete-Time Takagi--Sugeno Systems

Static output-feedback stabilizing controllers for nonlinear systems represented by discrete-time Takagi--Sugeno fuzzy models are studied. The main result concerns the stabilization based on the parallel distributed compensation (PDC) approach. Sufficient conditions are provided for quadratic and nonquadratic stability. To design static output-feedback stabilizing controllers, a numerical procedure based on the cone complementarity algorithm is given. It is shown that the relaxed conditions proposed in the nonquadratic case outperform those for the quadratic case. Two numerical examples are given to illustrate the efficiency of the proposed approach.      

Parallel Gauss-Jordan elimination for the solution of dense linear systems

Any factorization/back substitution scheme for the solution of linear systems consists of two phases which are different in nature, and hence may be inefficient for parallel implementation on a single computational network. The Gauss-Jordan elimination scheme unifies the nature of the two phases of the solution process and thus seems to be more suitable for parallel architectures, especially if reconfiguration of the communication pattern is not permitted. In this communication, a computational network for the Gauss-Jordan algorithm is presented. This network compares favorably with optimal implementations of the Gauss elimination/back substitution algorithm.