Solids transport models comparison and fine‐tuning for horizontal,low concentration flow in single‐phase carrier fluid

We determined and fine‐tuned the solids transport models appropriate for predicting the single‐phase carrier fluid velocity to transport solid particles in conduits for horizontal, low concentration flow. A database with 538 experimental data points was compiled. A literature review was performed to determine the data ranges, forces, and mechanisms used to develop 44 models, and their velocity predictions were compared against the database using statistics. Using the dimensionless forms of the models and the data, the model parameters were adjusted to improve their accuracy and identify the dominant forces. At low concentrations: for liquid/solid flow from a bed of solids and gas/solid flow from the bottom of pipelines, the particle weight, and inertial and viscous forces dominate; for gas/solid flow from a bed of solids, the particle weight, and inertial, viscous, and adhesive forces play a role; and gaps exist in the data for large‐diameter pipes and high‐density gases. © 2013 American Institute of Chemical Engineers AIChE J, 60: 76–122, 2014     

Accelerated convergence for a normal state layered superconductor’s transverse resistance expression,measured with strip contacts

The expression of the transverse resistance for an ohmic parallelepipedic layered conductor, measured with strip contacts, extended along its width, is a slowly convergent series. This series is reworked and transformed to the sum of an analytical part and an exponentially convergent series, which reduces considerably the number of terms needed for the numerical evaluation. In addition, an asymptotic formula is obtained, valid for Γ < 2, Γ is the effective anisotropy. This formula is used to determine the room temperature resistivity anisotropy of two small Γ layered superconductors, which are 2H–NbSe₂ and 2H–TaSe₂.     

Pressure study of structural properties and phonons in YBa2Cu3 O7

The pressure dependence of crystal structure and vibrational properties of YBa ₂ Cu ₃ O ₇ is investigated by first-principles calculations based on density functional theory. We have determined the optimized geometry for different unit cell volumes by relaxing the atoms to their force-free positions. The tendency of altered bond strength with pressure is consistent with experimental investigations and previous c-axis strain calculations. The pressure effect on the three A _1g phonon frequencies dominated by oxygen vibrations is in very good agreement with experimental investigations showing constant linear pressure coefficients d/dp over a wide range of pressure values.     

Analyse des fonctions des protocoles ipsec et leur intégration dans un réseau privé virtuel

Many approaches may lead to integrate security functions in the intranet/internet services. These functions may be placed at the application layer or at lower OSI layers. IPsec suite protocols were specified by IETF in order to integrate security functionality at network layer. This paper describes the features of IPESC protocols and identifies the aspects which are not standardized. The network translation address (nat) functionality used by routers and firewalls is not always compatible with IPESC. We describe and discuss some solutions for the compatibility of ipsec and nat. The last part of this paper describes a typical architecture for ip vpn based on IPSec technology.     

Quality control in the optical industry: From a work analysis of lens inspection to a training programme, an experimental case study

A cognitive work analysis of quality inspection in the optical industry has been carried out in order to devise a training programme. The task concerned the inspection of high quality human eyeglass lenses. We conducted an experimental investigation of defect detection and acceptability decision-making tasks in 18 experts and novice inspectors. Detection and decision-making were investigated together and separately in two experimental sessions. We showed the effect of expertise on reaction times and errors, and we described the cognitive processes of novice inspectors. On the basis of the processing differences between the two groups, a training programme for new inspectors was devised and described. Finally, training effects were tested.     

Impact of Ethanol on Benzene Plume Lengths: Microbial and Modeling Studies

Recent legislation in several states has called for the removal of methyl tert-butyl ether (MTBE) from gasoline. In order to comply with Federal Clean Air Act requirements for carbon monoxide and ozone attainment, ethanol is being considered as a replacement for MTBE. The objective of this study is to evaluate the potential impact of ethanol on benzene plume lengths in subsurface environments following accidental spills of ethanol-blended gasoline. Two types of studies were conducted here. First, laboratory studies were performed using a pure culture indigenous to a gasoline-contaminated aquifer to evaluate the effect of ethanol on the rate of benzene biodegradation under aerobic conditions. Results from microbial studies showed that the biodegradation of 25 mg/L benzene was severely inhibited in the presence of 25 mg/L ethanol. While the enzymes responsible for benzene biodegradation by the culture were inducible, ethanol degradation appeared to be constitutive. Second, a two-dimensional model was developed to quantify the impact of ethanol on benzene plume lengths using weighted-average aerobic and anaerobic biodegradation rates for benzene in the presence and absence of ethanol. Model simulations indicated that benzene plume lengths are likely to increase by 16–34% in the presence of ethanol.     

Physiological and behavioral responses of Orchestia gammarellus (Amphipoda,Talitridae) towards trace elements contamination soil

Effects of trace elements on the hepatopancreas ultrastructure and on the locomotor activity rhythm were investigated in the amphipod talitrid Orchestia gammarellus collected from Bizerte lagoon banks situated in the north of Tunisia. Animals were exposed to a series of contaminated soil with different concentrations of cadmium and zinc. The locomotor activity rhythm was studied under constant darkness. Histopathological analysis showed that the trace elements, especially the Cd, induced significant changes in the morphology and in the ultrastructural organization of hepatopancreatic cells. The significant alterations obtained were dose dependent. Concerning the behavioral response, results revealed the presence of two components whatever the experimental conditions. In addition, a great inter-individual variability of the locomotor rhythm was observed. Patterns were in majority bimodal for the control individuals and became unimodal and multimodal when exposed under Cd and Zn, respectively. Furthermore, ultradian and circadian periods were determined. The circadian period lengthened after Zn exposure. In addition, the locomotor activity rhythm was more stable for control individuals. However, those exposed to Cd were less active.     

Improving packet filters management through automatic and dynamic schemes

The development of complex access control architectures raises the problem of their management. In this article, we describe an architecture providing packet filters automatic configuration in Internet based networks. Our architecture improves existing proposals in three different fields. It suppresses the security officer interactions with the management architecture when topology changes occur thus preventing temporary security holes. Moreover our architecture proposes three optimisations to provide the access control processes with efficient configurations. Simulations show that the complexity of these configurations is close to the complexity found in configurations created by hand. Finally we describe how the notion of access control integrity can be incorporated in our management architecture at a reasonable cost.