Content-based communication in disconnected mobile ad hoc networks

In content-based communication, information flows to-wards interested hosts rather than towards specifically set destinations. This new style of communication perfectly fits the needs of applications dedicated to information shar-ing, news distribution, service advertisement and discovery, etc. In this paper we address the problem of supporting content-based communication in partially or intermittently connected mobile ad hoc networks (MANETs). The protocol we designed leverages on the concepts of opportunistic net-working and delay-tolerant networking in order to account for the absence of end-to-end connectivity in disconnected MANETs. The paper provides an overview of the protocol, as well as simulation results that show how this protocol can perform in realistic conditions. 1

A Message Service for Opportunistic Computing in Disconnected MANETs

International audienceDisconnected mobile ad hoc networks (or D-MANETs) are partially or intermittently connected wireless networks in which instant end-to-end connectivity between any pair of mobile hosts is never guaranteed. Recent advances in delay/disruption-tolerant networking make it possible to support communication in such conditions, but designing and implementing distributed applications for D-MANETs is still a challenging task. Middleware systems such as the Java Message Service (JMS) have made application development easy and cost-effective in traditional wired networks. In this paper, we introduce JOMS (Java Opportunistic Message Service), a JMS provider specifically designed for D-MANETs, and with which pre-existing or new JMS-based applications can be easily deployed in such networks

An Innovative High Pressure Mixing Cell for Microcalorimetry: Application to Gas Hydrates.

High pressure differential scanning calorimetry (HP-DSC) is of importance in several fields involving “gas hydrates”, such as oil and gas production, flow assurance, carbon dioxide capture and storage, and refrigeration. Gas hydrates are icelike crystals that contain gas molecules in molecular cavities. To improve classical calorimetric cells used for gas hydrates characterization, we present here our last prototype: a calorimetric cell equipped with an in-situ mechanical agitation system, which allow performing experiments both under pressure and agitated conditions. The m-cell, called MICROMIXCELL®, was developed for micro-calorimetry analysis (experiments carried out using a mDSC7 evo from SETARAM Instrumentation). In this work, thermophysical properties of the cyclopentane hydrate − a “model” clathrate hydrate which forms at atmospheric pressure − were measured. Technical details of the system and results are given and commented. The use of such novel calorimetric mixing cells opens a wide range of possibilities for the analysis of complex fluids, which must be analyzed in both pressurized and agitated conditions

A novel stirred microcalorimetric cell for DSC measurements applied to the study of ice slurries and clathrate hydrates

A novel prototype of a microcalorimetric cell with in-situ stirring has been developed to per-form DSC measurements under atmospheric or pressure conditions. After a brief technical description of the apparatus, preliminary tests are presented which analyzed the influ-ence of the stirrer rotation on the heat-flow signal. Experiments were then performed with complex fluids such as ice slurries and clathrate hydrates formed with cyclopentane and with carbon dioxide. They took place in stirred and non-stirred conditions and the results obtained were then compared. It was proven that the rotation of the microstirrer in the measuring cell does not disrupt the heat-flow signal during the analysis. As regards the prac-tical applications tested, the in-situ stirrer efficiently reduces crystallization metastability, increases the water-to-hydrate conversion, and reduces the amount of time needed for anal-ysis. The dissociation enthalpy of cyclopentane (CP) hydrates was measured at atmospheric pressure; it is effectively very difficult to analyze this system with non-stirred calorimetry techniques because the two liquid phases are immiscible. The experimental results, in good agreement with other data found in the literature, showed complete water-to-CP hydrate conversion within a short period of time using a simple protocol. Experiments were also performed under pressure to demonstrate that CO2 hydrate phase equilibrium data could be obtained rapidly and easily. It is therefore our opinion that the potential of this novel technology has been thoroughly demonstrated

Mechanically agitated calorimetric cells working under pressure: technical aspects and results obtained at macro and micro scale

This study presents two prototypes of calorimetric cells equipped with an in-situ mechanical agitation system, which allow performing experiments under pressure. The first system presented, called MIXCEL®, was developed for macro-calorimetry analysis (experiments carried out with a BT 2.15 Calvet Calorimeter from Setaram Instrumentation) and already patented in 2012 1. Concerning the micro-calorimetric agitated cell (called MICROMIXCEL®), it is the first time that such a system will be presented. This novel prototype was developed for micro-DSC analysis (experiments carried out with a DSC VII from Setaram Instrumentation). Both technical aspects, and results obtained at macro and micro scale with polyphasic complex systems (gas hydrates or ice slurries), are presented and discussed. The use of such calorimetric cells opens a wide range of possibilities for systems which must be analyzed in both pressurized and agitated conditions

Thermophysical properties of gas hydrates with stirred, high pressure calorimetric cells

High pressure differential scanning calorimetry (HP-DSC) is of importance in several fields involving gas hydrates, such as oil and gas production, flow assurance, carbon dioxide capture and storage, CO2 hydrates reversible formation/dissociation for refrigeration loops. However, the technique suffered for some limitations linked to the fact that the gas hydrate formation in the calorimetric cell occurs at the gas-liquids interface, leading to problems such as inefficient gas dissolution, formation of a hydrate crust covering the gas/liquid interface, low hydrate to water conversion, and difficulties to crystallize these compounds even at low temperature. It is for example rather difficult to determine accurately the heat capacities and the enthalpies of formation/dissociation of several systems involving gas hydrates. To overcome such limitations, we present two prototypes of calorimetric cells equipped with an in-situ mechanical agitation system, which allow performing experiments under pressure (150 bar max). The first one is called MIXCEL®, and was developed for macro-calorimetry analysis (experiments carried out with a BT 2.15 Calvet Calorimeter from SETARAM Instrumentation). The second one, called MICROMIXCEL®, was developed for micro-calorimetry analysis (experiments carried out using a microDSC7 evo from Setaram Instrumentation). In this study, technical details of the two cells and results obtained both at macro and micro scales will be presented, and compared to the case with no agitation. Thermophysical properties of the cyclopentane hydrate (phase change enthalpy, and specific heat) will be given and commented. The use of such novel calorimetric cells opens a wide range of possibilities for complex systems, such as gas hydrates, which must be analysed in both pressurized and agitated conditions

1,3 Dioxolane versus tetrahydrofuran as promoters for CO 2 -hydrate formation: Thermodynamics properties, and kinetics in presence of sodium dodecyl sulfate

This paper makes a comparison between tetrahydrofuran (THF) and 1,3 dioxolane (DIOX) in terms of their respective performances as promoters for the formation of clathrate hydrates with CO2. The aim is to find products that can be substituted for THF, which is known to be harmful and difficult to handle. Drawing on a review of the chemical and physical properties of these two organic compounds, experiments were performed using high-pressure differential scanning calorimetry (DSC) and a batch reactor. Details of the thermodynamic equilibria of mixed THF+CO2 and DIOX+CO2 hydrates obtained with various additive concentrations are provided, along with hydrate kinetics data relating to the hydrate formation. The effect of the presence of an anionic surfactant, SDS (sodium dodecyl sulfate), on hydrate formation kinetics was also evaluated, showing that a combination of THF or DIOX and SDS is a very advantageous solution for accelerating hydrate formation. THF has been found to outperform DIOX as a hydrate promoter from both a thermodynamic, and a kinetic standpoint in presence of SDS. However, DIOX remains an interesting practical solution, due to the benefits offered as the least toxic and aggressive of these two organic compounds

Mechanically agitated calorimetric cells working under pressure at macro and micro scale: application to gas hydrates

Originally applied to fields related to oil and gas production and flow assurance, high pressure differential scanning calorimetry (HP-DSC) has now been involved in several new studies such as carbon dioxide sequestration by CO2/CH4 exchange in naturally occurring gas hydrates or CO2 hydrate reversible formation/dissociation for refrigeration loops. However, the technique still has some limitations, which are linked to the fact that the gas hydrate formation occurs at the gas/liquid interface, and because the hydrate nucleation can be rather difficult in small volumes especially in quiescent conditions. It leads to several problems such as inefficient gas dissolution, long induction times, formation of a hydrate crust covering the gas/liquid interface, low hydrate to water conversion, etc. As a result, it is very difficult to determine accurately the heat capacities and the kinetics of formation/dissociation of several systems involving gas hydrates. This study presents two prototypes of calorimetric cells equipped with an in-situ mechanical agitation system, which allow performing experiments under pressure (150 bar maximum for the cells used in this work). The first system presented, called MIXCEL®, was developed for macro-calorimetry analysis (experiments carried out with a BT 2.15 Calvet Calorimeter from SETARAM Instrumentation). Very recently, we have developed a novel prototype of micro-calorimetric agitated cell (called MICROMIXCEL®) for microDSC analyses (experiments carried out using a microDSC7 evo from SETARAM Instrumentation). Both technical aspects, and results obtained at macro and micro scales with gas hydrate systems are presented and discussed