Polynomial-based key management for secure intra-group and inter-group communication

Secure group communication has become an important issue in many applications. Both intra-group and inter-group multicast traffic must be protected by shared secret keys. In order to communicate securely in the same group and among different groups, we employed a polynomial $P$ to achieve efficient intra-group key refreshment and generated a polynomial $H\left(x\right)$ to create an inter-group key. Proposed polynomial-based key management schemes have the following advantages: (1) Group members and the group controller can share the intra-group key without any encryption/decryption. (2) When the members of the group get changed, the group controller needs to update and distribute the renewed group keys. The proposed mechanism can reduce the number of re-keying messages. (3) The proposed mechanism lessens the storage overhead of group members and the group controller by adopting a polynomial-based key management scheme. (4) As compared with previous approaches, the group controller does not need to broadcast heavy messages which are necessary for creating an inter-group key. Hence, it introduces only a small amount of broadcast traffic to the group members. The analysis of the proposed mechanism is conducted to demonstrate the improvements.     

Effect of stress levels applied to pre‐stressing strands on post‐tensioned beam‐to‐column connections

This article presents an experiment study on precast beam‐to‐column connections with 15.24 mm diameter pre‐stressing strands. Stress levels of 40%, 50% and 60% tensile stress were applied to the pre‐stressing strands. Following the experiments, precast specimens were compared with those of the reference specimen. The load capacity of the precast specimen stressed at the level of 60% tensile stress reached 98% of the load capacity of the reference specimen, and the amount of energy dissipated by the same specimen reached 48% of that dissipated by the reference specimen. The stiffness of the same precast specimen at 1.5% drift was observed to be 71% of the reference specimen at the same drift. In the experimental studies, it was seen that the maximum stress determined in this specimen, which pre‐stressing strands provide connection, reached approximately 75% of the tensile strength of the pre‐stressing strands. It could not be said that topping concrete in experiment specimens increased strength. Copyright © 2010 John Wiley & Sons, Ltd.     

Modification of Pipeline Equations and Simulation of Transients in Compressible Fluid Flow in Pipes

Abstract

A slow transient was simulated using Godunov numerical scheme to solve the model equations. The results proved that including the inertia term in the momentum equation makes the model more realistic and that the Godunov numerical scheme is a better numerical method compared to the previously used total variation diminishing numerical scheme. Modification was made to steady-state equations to account for change in diameter. The results showed that energy has been spent by the flowing fluid to overcome the effect of the change in diameter and that energy spent increases as the change in diameter increases.     

Advanced oxidation of a reactive dyebath effluent: comparison of O3, H2O2/UV-C and TiO2/UV-A processes

In the present study the treatment efficiency of different AOPs (O3/OH- H2O2/UV-C and TiO2/UV-A) were compared for the oxidation of simulated reactive dyebath effluent containing a mixture of monochlorotriazine type reactive dyes and various dye auxiliary chemicals at typical concentrations encountered in exhausted reactive dyebath liquors. A525 (color), UV280 (aromaticity) and TOC removal rates were assessed to screen the most appropriate oxidative process in terms of reactive dyebath effluent treatment. Special emphasis was laid on the effect of reaction pH and applied oxidant (O3, H2O2) dose on the observed reaction kinetics. It was established that the investigated AOPs were negatively affected by the Na2CO3 content (= 867 mg/L) which is always present at high concentrations in dychouse effluents since it is applied as a pH buffer and dye fixation agent during the reactive dyeing process. The ozonation reaction exhibited almost instantaneous decolorization kinetics and a reasonable TOC reduction rate. It appeared to be stable under the investigated advanced oxidation conditions and outranked the other studied AOPs based on the above mentioned criteria. Besides, the electrical energy requirements based on the EE/O parameter (the electrical energy required per order of pollutant removal in 1 m3 wastewater) was calculated for the homogenous AOPs in terms of decolorization kinetics. In view of the electrical energy efficiency, ozonation and H2O2/UV-C oxidation at the selected treatment conditions appear to be promising candidates for full-scale dyehouse effluent decolorization.     

Improvement of bitumen and bituminous mixtures performances by triethylene glycol based synthetic polyboron

This study investigates the modification of bitumen with triethylene glycol based polyboron (TEGPB). TEGPB is a new additive material which was chemically synthesized at laboratory conditions. Four different TEGPB concentrations were used to modify 50/70 penetration grade bitumen: 1%(w/w), 2%(w/w), 3%(w/w) and 5%(w/w). The effects of TEGPB modification on the bitumen and bituminous mixture properties were determined by means of softening point, Marshall stability, Nicholson stripping, rotational viscosity (RV), Dynamic Shear Rheometer (DSR) and Bending Beam Rheometer (BBR) tests. Amount of TEGPB to be used within the bitumen has been chosen as 2%(w/w) according to RV test results. BBR and Nicholson stripping test results have showed that creep properties and stripping resistance of the modified bitumen was not adversely affected. It was also found out that softening point and rutting resistance of the bitumen as well as Marshall stability of the bituminous mixtures were increased by TEGPB modification.     

Modeling fire growth in a combustible corner

A fire growth model was developed to predict the flame spread and total heat release rate of a fire in a corner configuration with a combustible lining. Input data for the combustible lining were developed using small-scale test data from the ASTM E1354 cone calorimeter and ASTM E1321 LIFT. The fire growth model includes a flame spread model linked with a two zone compartment fire model, CFAST Version 3.1.2. At a user selected time interval, the flame spread model uses the gas temperature from CFAST to predict the heat release rate of the fire at that time interval, and then provides CFAST with a new heat release rate to predict conditions during the next time step. The flame spread model is an improved version of the flat wall flame spread model previously developed for the US Navy. The model is capable of predicting flame spread in a variety of configurations including a flat wall, a corner with a ceiling, flat wall with a ceiling, unconfined ceiling, and parallel walls. The model has been validated against ISO 9705 test data and was used in this study to simulate conditions that develop in three open corner tests each with a different lining material. The model was able to predict the heat release rate of the fire and provide a reasonable estimate of the flame fronts and flame lengths during the growing fire.     

Galvanic corrosion of titanium-based dental implant materials

This paper describes an investigation of the corrosion behavior of Ti-based dental materials with Au, CrNi and CoCr in Ringer solution by the use of Tafel plots, Evans diagrams and EIS Nyguist diagrams. The galvanic potentials and currents obtained for various implant couples are as follows: For, Ti6Al4V/CrNi couple −0.030 V (Ag/AgCl (3 M NaCl)) and 7.94 μA cm⁻²; for Ti6Al4V/CoCr couple −0.020 V (Ag/AgCl (3 M NaCl)) and 7.08 μA cm⁻²; for Ti6Al4V/Au couple −0.020 V (Ag/AgCl (3 M NaCl)) and 5.62 μA cm⁻². The Ti6Al4V/Au couple was found to be the most suitable one against galvanic corrosion according to both the Tafel method and mixed potential theory. The corrosion behaviors of Ti6Al4V/CoCr and Ti6Al4V/CrNi couples were found to be similar.     

Analytic Models for When and How to Expedite in Make-to-Order Systems

Expediting is defined as using overtime or subcontracting to supplement regular production. This is usually done when the number of backorders has grown to be unacceptably large. In this paper, we consider analytic models for deciding when and how to expedite in a single-product make-to-order environment. We derive the structure of the optimal expediting policy in both continuous- and discrete-time cases. The continuous-time model corresponds best to subcontracting and the discrete-time model corresponds to either overtime or subcontracting. Models for performance analysis of the continuous-time case are also given.     

Cochannel interference suppression with successive cancellation innarrow-band systems

Successive cancellation of cochannel signals is described in the context of TDMA mobile radio systems employing coherent receivers. Both symbol aligned and mis-aligned cochannel signals are studied. Signal separability, a major problem in successive cancellation of cochannel signals, is obtained using the relative timing delay between cochannel signals. Both hard and soft subtractions are examined. Soft subtraction, along with initial signal separation, leads to significant C/I gains