联合式电路保护有助于防止损坏DVB网络设备

随着广播、电信和IT业的融合，未来的电话和数字电视都将成为互联网上的应用．这样就需要采用新型的客户端设备（CPE）和网络基础设施．以适应更高数据传输速率的要求．并满足新出现的DVB—T／SIC标准以及符合当前和提议中的通讯要求。     

Potable Water Tariffs in Mexico City: Towards a Policy Based on Demand Management?

This paper evaluates whether potable water tariffs in Mexico City 1 are directed towards the administration of demand management, or whether they are primarily a continuation of historical policies which have always put the main emphasis on supply management. The paper also reviews some technical aspects of tariff-related issues in Mexico City, as well as the situation at the national level.     

Structural recovery of self-irradiated natural and Pu-doped zircon in an acidic solution at 175 °C

We have investigated the aqueous stability of self-irradiated natural and synthetic ²³⁸Pu-doped zircon (4.7 wt% of ²³⁸Pu) in an acidic solution at 175 °C. Both zircon samples have suffered a similar degree of self-irradiation damage, as given by their degree of amorphization. X-ray diffraction measurements revealed that during the hydrothermal treatment only the disordered crystalline remnants recovered in the natural zircon, whereas in the ²³⁸Pu-doped zircon the amorphous phase strongly recrystallized. Such a different alteration behavior of natural and Pu-doped zircon is discussed in terms of two fundamentally different alteration mechanisms. Our results demonstrate that further experimental studies with Pu-doped zircon are required before any reliable prediction about the long-term aqueous stability of an actinide waste form based on zircon can be made.     

Hydrogen in fullerites

The peculiar kind of fullerene molecule structure is also reflected in the crystal structure of fullerites. The cubic lattices of metal fullerides and hydrofullerenes behave similarly to the cubic lattices of different metals and alloys. They form interstitial solid solutions when impurity elements are distributed in octahedral and tetrahedral interstitial sites. By replacement of C₆₀ and C₇₀ molecules in lattice sites they make up substitution solid solutions. Forming exo- and endohedral compounds, the fullerene molecules, located in sites of the crystal lattice, can modify greatly the crystal properties with no change of crystalline structure. Some peculiarities of fullerite crystalline structures will be discussed in the present paper.     

On cognitive processes in cognitive radio networks

In this article we model the cognitive processes and evaluate their impact on the performance of cognitive radio networks (CRN). Operation of the cognitive radio nodes, can be characterized by two types of processes: communication processes such as packets transmission, and cognitive processes such as estimation of the network state and decision-making for dynamic resource allocation. We propose a continuous time Markov chain model of CRN that couples these processes into unified queueing framework and analyze it by means of the matrix-geometric approach. From the obtained results, we derive the performance measures of CRN such as average delay and throughput, and establish their dependencies on the underlying cognitive processes. Additionally, we design an efficient policy for accessing the vacant channels and managing the transmission-sensing trade-off, which arises when transmissions and sensing are mutually exclusive. The policy search is carried out by the stochastic optimization method of cross-entropy. The optimized policy leads to significantly enhanced performance of CRN.     

Effect of various parameters on the conductivity of free standing electrosynthesized polypyrrole films

Electrical characteristics of polypyrrole films electrodeposited in different aqueous electrolyte solutions including p-toluenesulfonate, naphtalenesulfonate, nitrate, tetrafluoroborate, and perchlorate anions were investigated using the Van der Pauw procedure. The polymer films were synthesized by electrochemical oxidation at a fixed potential. Experimental parameters including the pyrrole concentration, electrolyte, applied potential and substrate were shown to affect the electrical conductivity σ of polypyrrole films. Since the substrate contributes significantly to the overall conductivity of polypyrrole-coated electrodes, the results obtained with free standing polymer films appeared more reliable. The results indicated that the p-toluenesulfonate doped PPy film showed the highest average conductivity (σ_293 K = 4.5 × 10⁵ S m^?1) whereas the perchlorate doped one produced the lowest of all the films prepared (σ_293 K = 2 × 10⁴ S m^?1).     

On the design and fabrication by two-photon polymerization of a readily assembled micro-valve

This paper reports on the conceptual design and fabrication of a complex shape, readily assembled micro check valve using the two-photon polymerization technique. The material used for the fabrication of the valve is a zirconium containing organic–inorganic hybrid photosensitive sol-gel known to exhibit negligible distortion during photopolymerization. A preliminary computational fluid dynamics study has been carried out in order to evaluate the flow performance of the valve under blood pressures exhibited in healthy human veins. The fabricated micro-valves exhibit good dimensional accuracy when compared to the CAD-created valve design and the capability of an internal moving component to perform its intended function.     

Effect of media size and mechanical properties on milling efficiency and media consumption

The effect of media size and properties on milling efficiency, media wear, and power consumption will be discussed. A predictive model has been developed and was verified by analyzing results of laboratory trials in a mineral grinding application. Recent developments in high density media capabilities for a range of feed types and particle sizes will be presented.     

Taking Advantage of Overhearing in Low Power Listening WSNs: A Performance Analysis of the LWT-MAC Protocol

LWT-MAC is a new Low Power Listening MAC protocol for WSNs designed to rapidly react to instantaneous increases of the network load. It takes advantage of overhearing by waking up all nodes at the end of a transmission to send or receive packets without needing to transmit the long preamble before. In this work, detailed analytical models of the LWT-MAC and B-MAC protocols, for both saturated and unsaturated conditions, are presented. Moreover, the key LWT-MAC parameters are optimized in order to minimize the energy consumption, constrained to obtain the same throughput as the IEEE 802.11 (CSMA/CA) MAC protocol. From the behavior of the optimal LWT-MAC parameters, a heuristic configuration is proposed. Finally, the LWT-MAC is compared to B-MAC, in both single and multi-hop scenarios, showing improvements in energy consumption, throughput and delay.