Reversible Fragmentation and Self‐Assembling of Nematic Liquid Crystal Droplets on Functionalized Pyroelectric Substrates

Investigation on the behavior of nematic liquid crystals on functionalized polar dielectric crystal substrates is accomplished. Very interesting effects can be observed in maneuvering liquid crystal droplets on the substrate surface, driven by electric fields generated by pyroelectric effect. Reversible drops fragmentation and self‐assembling in different configurations can be achieved. The dynamics of the observed phenomena is studied and the repeatability of the process is full assessed.     

QoS online routing and MPLS multilevel protection: a survey

A survey of MPLS protection methods and their utilization in combination with online routing methods is presented in this article. Usually, fault management methods pre-establish backup paths to recover traffic after a failure. In addition, MPLS allows the creation of different backup types, and hence MPLS is a suitable method to support traffic-engineered networks. In this article, an introduction of several label switch path backup types and their pros and cons are pointed out. The creation of an LSP involves a routing phase, which should include QoS aspects. In a similar way, to achieve a reliable network the LSP backups must also be routed by a QoS routing method. When LSP creation requests arrive one by one (a dynamic network scenario), online routing methods are applied. The relationship between MPLS fault management and QoS online routing methods is unavoidable, in particular during the creation of LSP backups. Both aspects are discussed in this article. Several ideas on how these actual technologies could be applied together are presented and compared.     

A decentralized kinematic control architecture for collaborative and cooperative multi-arm systems

In this paper a two-layer decentralized framework for kinematic control of cooperative and collaborative multi-robot systems is developed. The motion of the system is specified at the workpiece level, by adopting a task-oriented formulation for cooperative tasks. The first layer computes the motion of the single arms in the system. In detail, the control unit of each robot computes the end-effector motion references in a decentralized fashion on the basis of the knowledge of the assigned cooperative task and the motion references computed by its neighbors. Then, in the second layer, each control unit computes the reference joint motion of the corresponding manipulator from the end-effector reference motion. The approach is, then, tested in simulation on a work-cell composed by several manipulators, and experimentally on a dual-arm kinematically redundant work-cell composed by industrial manipulators.     

Order allocation in purchasing management: a review of state-of-the-art studies from a supply chain perspective

Supplier selection (SS) and order allocation (OA) are strategic decisions that have a substantial effect on a company’s performance. However, order allocation is often neglected, since it results from supplier selection and is considered supplementary: little attention has been paid to its specific nature and complexity. Consequently, the authors conducted a systematic literature review specifically regarding order allocation methods. The research aimed to evaluate how often and when the issue has been dignified with an individual focus, independently of the supplier selection problem. This study conducted a comprehensive examination of the order allocation models and solutions, criteria for order quantity allocation, features of suppliers, items, planning periods, and demand most commonly considered in the literature. Finally, it aimed to discover whether supply chain configurations and trends have been considered in efforts to find a solution to the problem. The scientific contribution of this study is threefold: (i) to expand the review of scientific literature regarding order allocation models, (ii) to identify research gaps and highlight research opportunities, and (iii) to suggest a research agenda for the development of order allocation models according to the requirements of current trends in supply chain management.     

Gastric ulcers: a rare manifestation of secondary syphilis

Gastric lesions in the progression of syphilis are very rare and they have several forms of presentation resembling lesions of different nature. We describe a case of secondary syphilis in an heterosexual patient, with persistent gastric ulcers and hepatic affection, in which the evolution and the observations with laparotomy suggested neoplasia. In the gastric biopsy, an infiltration of plasmatic and neutrophil cells was observed and in the hepatic biopsy, necrotic nodules and granulomas. The spirochaeta-specific tinction, although not indispensable, confirms the diagnosis of gastric syphilis. The previous presence of a syphilitic chancre and typical cutaneous lesions are of great help in suspecting a luetic process.     

Improved all-optical switching in a three-slab nonlineardirectional coupler with gain

We propose and study numerically with a split-step finite-element method, an all-optical switching device made of three nonlinear active optical planar waveguides. Solving directly the nonlinear partial differential equations for the transverse electric polarised fields, the method can analyze real slab structures, where the gain is introduced by doping the guiding region with high erbium concentration. The effect of different amount of gain and loss on the switching performance is investigated. The introduction of suitable gain overcomes the problem of performance degradation due to losses, decreases the switching power and allows the input power to be successfully switched, by a simple power control, among all the three output ports     

A new procedure for nonlinear statistical model extraction of GaAs FET‐integrated circuits

A new statistical nonlinear model of GaAs FET MMICs which allows the representation of distance‐dependent technological parameter variations by means of equivalent circuit parameters, and an automatic extraction procedure, are presented. The capability to reproduce statistical distribution has been successfully checked on S parameters at different distances in the 1–50 GHz frequency range. © 2003 Wiley Periodicals, Inc. Int J RF and Microwave CAE 13, 348–356, 2003.     

Performance limits in amplified dense WDM networks in the presenceof four-wave mixing and gain peaking

The performance of amplified dense wavelength division multiplexed systems is theoretically analysed to evaluate the limitations owing to four-wave mixing and gain peaking effects. Optimisation of dispersion management and wavelength allocation result in the possible transmission of 88 channels (0.25 nm spacing) over 500 km