Electroclinic measurement of the coefficients of Landau expansion of some ferroelectric liquid crystals

The electroclinic effect in the smectic A phase of ferroelectric liquid crystals is a sensitive probe for measuring the soft mode response near the A-C* transition point. It is possible to evaluate several coefficients of the Landau theory describing the A-C* transition by simultaneously measuring the frequency dependence of both the optical signal and the current through the sample. We have made such measurements on a couple of homologous series [2S,3S]-4′-(2-chloro-3-methyl pentanoyloxy) phenyl-trans-4″-n alkoxy cinnamates synthesized in our labortory. The results show that the Landau meanfield theory is adequate to describe the A-C* phase transition in these compounds. Presented at the 15th International Liquid Crystal Conference, Budapest, 3–8 July 1994.     

Enhancement Effects in the Percutaneous Absorption of Alprazolam Through Human Skin in vitro

The enhancement effects of some chemicals on the percutaneous absorption of alprazolam through human skin was investigated in vitro. Linoleic acid, oleic acid, Comperlan F® (linoleic acid diethanolamide), Comperlan KD® (coconut fatty acid diethanolamide) and Ethomeen C12® (bis-(2-hydroxyethyl)cocamine) were evaluated for their enhancing effect either as neat solvents or combined with propylene glycol. The effects of skin pretreatment with the enhancers on the percutaneous absorption of alprazolam from a drug suspension in an aqueous gel were also investigated: skin pretreatment with some enhancers has shown potentially interesting aspects. The determination of alprazolam partitioning into untreated and pretreated horny layer supported the idea that, with oleic and linoleic acid, a contribution to the modification of the diffusional resistance of the skin was given by an increase of the drug solubility in the stratum coraeum.     

A partitioning technique for the finite element solution ofelectromagnetic scattering from electrically large dielectric cylinders

A finite element partitioning scheme has been developed to reduce the computational costs of modeling electrically large geometries. In the partitioning scheme, the cylinder is divided into many sections. The finite element method is applied to each section independent of the other sections, and then the solutions in each section are coupled through the use of the tangential field continuity conditions between adjacent sections. Since the coupling matrix is significantly smaller than the original finite element matrix, it is expected that both the CPU time and memory costs can be significantly reduced. The partitioning scheme is coupled to the bymoment method to account for the boundary truncation. Numerical results are presented to demonstrate the efficiency and accuracy of the method     

Experiments on hot electron noise in semiconductor materials forhigh-speed devices

Experimental results on noise temperature and spectral density of current fluctuations (electron diffusion) at high electric fields in silicon, gallium arsenide, and indium phosphide are presented. The dominant noise sources are discussed in their relation to electron scattering mechanisms. Physical backgrounds of high speed-low noise performance (noise-speed tradeoff) are considered. Suppression in short samples of the fluctuations having long correlation time constant and (or) high threshold energy is discussed     

Call control and traffic transport for connection-oriented highspeed wireless personal communications over metropolitan area networks

A distributed circuit-switched approach for supporting the deployment of high speed wireless personal communication services in urban areas through the interconnection of base stations via metropolitan area networks (MANs) is proposed. Broadband MANs minimize traffic congestion by dynamic sharing of link capacity and by serving as distributed switches for partitioning call control functions. While the DQDB protocol readily supports distributed packet-switching over the IEEE 802.6 MAN, isochronous traffic such as voice and video is best supported by circuit-switched connections. The authors present an enhanced bi-state pre-arbitrated (PA) transport mechanism, and associated call control and handoff management techniques, which enable distributed circuit-switching over the MAN. These capabilities are not currently addressed in the 802.6 standards. The bi-state PA transport mechanism facilitates statistical multiplexing of variable rate isochronous traffic sources. The network capacity is constrained by the call setup delay performance, and is analyzed by simulations. Alternative signaling architectures, involving different placements of call control network elements, are evaluated. The effects of erasure nodes, and close bus versus open bus architectures, are considered. The overlap inter-MAN call setup procedure is proposed to reduce delays. Different call handoff procedures are formulated according to the type of handoff and the resulting change in call connectivity. Most handoffs are intra-MAN, requiring simple procedures with short delays     

The impact of SONET digital cross-connect system architecture ondistributed restoration

The viability of distributed control restoration using digital cross-connect systems (DCS) depends on its capability for restoring services within specified time requirements, and its economics for providing restoration compared to other alternatives. The authors report a Bellcore study for the impact of the DCS architecture on distributed restoration. This study concludes that currently proposed distributed control DCS self-healing schemes may not meet the 2 second restoration objective for large metropolitan local exchange carrier's networks, regardless of the distributed algorithm used, if the present DCS system architecture which uses serial message processing and serial path cross-connection remains unchanged. They also discuss several DCS architecture enhancement options, including a parallel processing/cross-connect DCS architecture, which may improve the service restoration time     

Error monitoring issues for common channel signaling

Motivated by field data which showed a large number of link changeovers and incidences of link oscillations between in-service and out-of-service states in common channel signalling (CCS) networks, a number of analyses of the link error monitoring procedures in the SS7 protocol were performed by the authors. This paper summarizes the results obtained thus far and include the following: (a) results of an exact analysis of the performance of the error monitoring procedures under both random and bursty errors; (b) a demonstration that there exists a range of error rates within which the error monitoring procedures of SS7 may induce frequent changeovers and changebacks; (c) an analysis of the performance of the SS7 level-2 transmission protocol to determine the tolerable error rates within which the delay requirements can be met; (d) a demonstration that the tolerable error rate depends strongly on various link and traffic characteristics, thereby implying that a single set of error monitor parameters will not work well in all situations; and (e) some recommendations on a customizable/adaptable scheme of error monitoring with a discussion on their implementability. These issues may be particularly relevant in the presence of anticipated increases in SS7 traffic due to widespread deployment of advanced intelligent network (AIN) and personal communications service (PCS) as well as for developing procedures for high-speed SS7 links currently under consideration by standards bodies     

Simultaneous over- and underconfidence: The role of error in judgment processes.

Two empirical judgment phenomena appear to contradict each other. In the revision-of-opinion literature, subjective probability (SP) judgments have been analyzed as a function of objective probability (OP) and generally have been found to be conservative, that is, to represent underconfidence. In the calibration literature, analyses of OP (operationalized as relative frequency correct) as a function of SP have led to the opposite conclusion, that judgment is generally overconfident. Reanalysis of 3 studies shows that both results can be obtained from the same set of data, depending on the method of analysis. The simultaneous effects are then generated and factors influencing them are explored by means of a model that instantiates a very general theory of how SP estimates arise from true judgments perturbed by random error. Theoretical and practical implications of the work are discussed. (PsycINFO Database Record (c) 2010 APA, all rights reserved)