A post-growth processing methodology to achieve barium strontium titanate thin films with low dielectric loss and high tunability for reconfigurable tunable devices

Ba_0.60Sr_0.40TiO₃ (BST) thin films, grown via RF-sputtering and the metalorganic solution deposition (MOSD) techniques, were post-growth annealed via conventional thermal annealing (CTA) and UV-photon irradiation annealing. With respect to the conventional thermal annealed films the UV-photon irradiation annealed films possessed improved structural properties and dielectric response. The optimization of the UV-photon irradiation annealing process parameters (using RF-sputtered BST films) was achieved via a detailed set of iso-thermal/chronal annealing experiments. The optimized UV-process parameters, applied to MOSD synthesized BST films revealed further enhanced dielectric response, i.e., 23% reduction in tan δ with sustained tunability of 42%. The improvements in the material properties of the UV-photon irradiation annealed BST thin films are attributed to stoichiometry and structural changes enabled through the UV-photon irradiation annealing process.     

QoS assurances through class selection and proportional differentiation in wireless networks

Quality-of-service (QoS) in wireless ad hoc networks is adversely affected by node mobility, changing network topologies, and uncontrolled medium contention. The paper addresses the challenges in concurrently providing a wide range of end-to-end throughput and delay assurances in such networks. The proposed solution is based on the neighborhood proportional delay differentiation (NPDD) service model. With NPDD, applications achieve their desired end-to-end QoS using dynamic class selection (DCS) algorithms. With simulations in various distinct mobile network scenarios, we demonstrate the significantly better QoS assurances achieved with the proposed mechanism as compared with best effort and strict priority approaches. With game theoretic concepts, we model DCS applications in an NPDD network as selfish players in a noncooperative game. For such games, we prove for single-hop and multihop NPDD networks the existence of an equilibrium, the feasibility of an equilibrium, and the guaranteed convergence to a feasible equilibrium when one exists.     

Schottky barrier diodes for millimeter wave detection in a foundry CMOS process

CoSi/sub 2/-Si Schottky barrier diodes on an n-well and on a p-well/substrate are fabricated without a guard ring in a 130-nm foundry CMOS process. The nand p-type diodes with an area of 16/spl times/0.32/spl times/0.32 /spl mu/m/sup 2/ achieve cutoff frequencies of /spl sim/1.5 and /spl sim/1.2 THz at 0-V bias, respectively. These are the highest cutoff frequencies for Schottky diodes fabricated in foundry silicon processes. The leakage currents at 1.0-V reverse bias vary between 0.4 to 10 nA for the n-type diodes. The break down voltage for these diodes is around 15 V. It should be possible to use these in millimeter wave and far infrared detection.     

Detecting vascular access dysfunction

Access flow (QACC) is a major determinant of patency. Access recirculation (AR > 2%), normalized venous intra-access pressure (vPIA/MAP), and QACC are used to detect access dysfunction. We compared these three measures of access function (ultrasound dilution to measure AR and QACC). A total of 779 measurements were performed on 58 arteriovenous fistulas (AVFs) and 114 polytetrafluoroethylene (PTFE) grafts (1-8/access) over 13 months, and the access parameters at the beginning of each period were related to access events within that period. Pump blood flow averaged > 420 ml/min. AR occurred uncommonly (3.8%), and in half the cases, resulted from technical error by staff. In accesses that thrombosed or underwent intervention for stenosis, AR was present in only 3 of 11 AVFs and 8 of 57 PTFE accesses. When AR was present in grafts, QACC averaged 270 +/- 23, and access thrombosis followed unless intervention occurred. In grafts, vPIA/MAP averaged 0.34 +/- 0.01 in those remaining patent, 0.52 +/- 0.08 in those that had undergone intervention, and 0.54 +/- 0.04 in those that had thrombosed. QACC averaged 1,121 +/- 26, 605 +/- 45, and 550 +/- 65 ml/min, respectively, in the three groups. By contrast, QACC differed significantly in patent AVFs (1,053 +/- 35) compared with failing AVFs (363 +/- 48), but vPIA/MAP did not. AR is thus a late manifestation of access failure. QACC is the best diagnostic test of access dysfunction in AVFs. Interpretation of vPIA/MAP in grafts is enhanced by periodic QACC measurements.     

Selection of timed token protocol parameters to guarantee messagedeadlines

Networks that use the timed token protocol (such as the 100 Mbit/s FDDI network) are well suited for real-time applications because they guarantee, to each node, an average bandwidth and a bounded access time to the communication network. This guarantee is necessary but not sufficient for the timely delivery of deadline-constrained messages; protocol parameters must be carefully selected to ensure that these messages meet their deadlines. This paper addresses the issue of selecting the protocol parameters TTRT (target token rotation time) and the synchronous capacities assigned to each node. The objective is to guarantee that each synchronous message is transmitted before its deadline. An upper bound is derived on the worst case achievable utilization (WCAU) of any parameter selection scheme. The WCAU of a scheme is defined as the maximum utilization U such that the scheme guarantees all synchronous messages as long as their utilization is less than U. An algorithm for selecting the above parameters is proposed, The algorithm is shown to have a WCAU that is very close to the upper bound     

Fault-tolerant clock synchronization in distributed systems

Existing fault-tolerant clock synchronization algorithms are compared and contrasted. These include the following: software synchronization algorithms, such as convergence-averaging, convergence-nonaveraging, and consistency algorithms, as well as probabilistic synchronization; hardware synchronization algorithms; and hybrid synchronization. The worst-case clock skews guaranteed by representative algorithms are compared, along with other important aspects such as time, message, and cost overhead imposed by the algorithms. More recent developments such as hardware-assisted software synchronization and algorithms for synchronizing large, partially connected distributed systems are especially emphasized     

Silver Stars: Silver–Polymer Composite Stars: Synthesis and Applications (Adv. Funct. Mater. 9/2011)

Colloidal “silver stars” were synthesized upon poly(lactic‐co‐glycolic) acid nanosphere templates via a facile two‐step silver reduction method. Myriad dendrimer‐like Ag star morphologies were synthesized by varying the amount of poly(vinyl alcohol) and trisodium citrate used during silver reduction. Scanning electron microscopy studies revealed that star‐shaped silver–polymer composites possessing nanoscopic, fractal morphologies with diameters ranging from 500 nm to 7 μm were produced. These composites have broad applications from antibacterial agents to catalysis; two such applications were tested here. Surface‐enhanced Raman spectroscopy (SERS) studies showed multiple hot spots of SERS activity within a single star. Electrochemical catalysis experiments demonstrated the feasibility of using the silver stars instead of platinum for the oxygen reduction reaction in alkaline fuel cells.     

Data envelopment analysis for weight derivation and aggregation in the analytic hierarchy process

Data envelopment analysis (DEA) is proposed in this paper to generate local weights of alternatives from pair-wise comparison judgment matrices used in the analytic hierarchy process (AHP). The underlying assumption behind the approach is explained, and some salient features are explored. It is proved that DEA correctly estimates the true weights when applied to a consistent matrix formed using a known set of weights. DEA is further proposed to aggregate the local weights of alternatives in terms of different criteria to compute final weights. It is proved further that the proposed approach, called DEAHP in this paper, does not suffer from rank reversal when an irrelevant alternative(s) is added or removed.     

Communication architectures and algorithms for media mixing inmultimedia conferences

The problem of media mixing that arises in teleconferencing applications such as teleorchestra is addressed. The mixing algorithm presented minimizes the difference between generation times of the media packets that are being mixed together in the absence of globally synchronized clocks, but in the presence of jitter in communication delays on packet switched networks. In order to support applications, such as teleorchestra, that involve a large number of participants, hierarchical mixing architectures are proposed, and it is shown that they are an order of magnitude more scalable than purely centralized or distributed architectures. Furthermore, mechanisms for minimizing the delays incurred by mixing in various communication architectures are presented. The mixing algorithms are implemented on a network of workstations connected by Ethernets, and the performance of various mixing architectures is experimentally evaluated. The results reveal the maximum number of participants that can be supported in a conference