Low-power high-speed phase frequency detector based on carbon nano-tube field effect transistors

A phase frequency detector (PFD) with a very low dead zone is proposed which is based on a configuration adaptable to both CMOS or carbon nano-tube transistors (CNTFETs). In the first step the proposed configuration is designed using CMOS transistors, and then CNTFETs are substituted to improve the speed and reduce the propagation delay. The proposed PFD in addition to very low dead zone, has low power consumption and high frequency range of operation, which are achieved as a result of the elimination of the reset path. The simulation results based on 32 nm technology for CNTFET and 180 nm technology for CMOS, illustrate that CNTFET-based proposed circuit dissipates 2 µW and has frequency of operation up to 30 GHz, and the dead zone equal to 1 ps. Compared to the conventional PFD based on CMOS technology, its dead zone and power consumption are lower. In addition, the effects of blocks’ parameters including the phase detector, which affect the operation of the phase locked loop, or delay locked loop, are systematically analyzed.

     

Mobile Agent Connection Establishment and Management (CEMA)—Message Exchange for Pervasive Computing Environments

Pervasive computing is an emerging technology that offers new possibilities to distributed computing and computer networking; it employs a wide variety of smart, ubiquitous devices throughout an individual's working and living environment. Mobile agents are software entities that can migrate between servers (mobile agent environments) of the network accomplishing various tasks on the behalf of their owners. The objective of this paper is to describe a test and prototyping environment for experimenting with mobile agents in pervasive environments. A prototype environment for a novel, proactive infrastructure is described for mobile agent assisted pervasive computing. In addition, a new message passing algorithm is provided for mobile agent connection establishment and management (CEMA). Simulation results show the performance of the proposed approach.     

Eddy current detection of changes in stainless steel after cold reduction

An investigation was conducted to explore the applicability of eddy current technique to characterize austenitic variation during cold reduction in various stainless steels. A series of stainless steel samples were cold rolled for this purpose. It was observed that eddy current flow and its phase are affected due to the variation in volume percent of austenite. It is suggested that eddy current measurement technique is a useful tool for the characterization of austenite variation during the cold working of stainless steels.     

An approximate method for separated spectral analysis of connected buildings with added damping

The problem of determining maximum seismic responses, or spectral analysis, of connected adjacent structures is studied in this research. The goal of the study is twofold. First, determining when the dynamic coupling is important in such a problem and, second, establishing how to analyze each of the two structures separately when coupling is important. For tall buildings in many cases, the connecting link is intentionally accommodated with an added damping to suppress the lateral displacements. Therefore, effect of the localized damping is also accounted for in the analysis. Using essentials of modal analysis, a criterion is developed for estimation of the dynamic coupling of the two adjacent structures. Also, a procedure is developed for separated analysis of each structure incorporating the stiffness and inertial effects of the adjacent structures when coupling is important. The representative examples confirm good accuracy of the presented method.     

Heat treatment effects on the optical properties of Sol–gel Ta2O5 thin films

In this work optical properties of Ta₂O₅ thin films with respect to heat treatment temperature were investigated. Ta₂O₅ thin films were prepared by sol–gel process using dip-coated method with a constant speed of 107 mm/min. Optical properties have been calculated from optical transmission measurements as a function of heat treatment temperature. The refractive indices and absorption coefficients were affected by heat treatment. The refractive index at λ=550 nm increased from 1.84 to 2.04 and absorption coefficient increased from 241 to 5668 cm⁻¹ when heat treatment temperature increased from 100°C to 500°C. The thickness of the film decreased from 272 to 190 nm and their optical band gap decreased from 3.68±0.09 eV to 3.51±0.08 eV for the film heated from 100°C to 500°C.     

A new group contribution-based model for estimation of lower flammability limit of pure compounds

In the present study, a new method is presented for estimation of lower flammability limit (LFL) of pure compounds. This method is based on a combination of a group contribution method and neural networks. The parameters of the model are the occurrences of a new collection of 105 functional groups. Basing on these 105 functional groups, a feed forward neural network is presented to estimate the LFL of pure compounds. The average absolute deviation error obtained over 1057 pure compounds is 4.62%. Therefore, the model is an accurate model and can be used to predict the LFL of a wide range of pure compounds.     

Development of a general model for determination of thermal conductivity of liquid chemical compounds at atmospheric pressure

In this communication, a general model for representation/presentation of the liquid thermal conductivity of chemical compounds (mostly organic) at 1 atm pressure for temperatures below normal boiling point and at saturation pressure for temperatures above the normal boiling point is developed using the Gene Expression Programming algorithm. Approximately 19,000 liquid thermal conductivity data at different temperatures related to 1636 chemical compounds collected from the DIPPR 801 database are used to obtain the model as well as to assess its predictive capability. The parameters of the model comprise temperature, acentric factor, critical pressure, normal boiling temperature, and molecular weight. Nearly 80% of the data set (15,221 data) is randomly assigned to develop the model equation, 10% of the data set (1902 data) is used to validate the model, and the remaining data (1902 data) were implemented to evaluate its predictive power. The average absolute relative deviation of the model results from the DIPPR 801 data is less than 9%. In terms of simplicity and wide range of applicability, this empirical model shows acceptable accuracy. © 2012 American Institute of Chemical Engineers AIChE J, 59: 1702–1708, 2013     

Voltage imbalance analysis in residential low voltage distribution networks with rooftop PVs

The installation of domestic rooftop photovoltaic cells (PVs) are on the rise due to feed-in tariff and changes driven by environmental concerns. Even though the increase in the PV installation is gradual, their locations and ratings are often random. Therefore, such single-phase bi-directional power flow can have adverse effect on the voltage imbalance of a three-phase distribution network. In this paper, a voltage imbalance sensitivity analysis and stochastic evaluation based on the ratings and locations of single-phase grid-connected rooftop PVs in a residential low voltage distribution network are presented. The stochastic evaluation, based on Monte Carlo method, predicts a failure index of non-standard voltage imbalance in the network in presence of PVs. Some improvement methods are discussed and a new improvement method based on PV converter control is proposed.