Internet telephony signaling

The term “multimedia session” refers to the integration of data coming from various sources, such as sound, video and text, within a computer application. Telephony over the Internet is among the more exciting current developments. The signaling of a telephone call consists of the set of messages and procedures used to establish a connection, to request changes in communication bandwidth, to obtain the message status for the end points participating in the conversation, and to close the link. At present there exist two competing signaling protocols for Internet telephony, viz., the H.323 protocol sponsored by the ITU and the Session Invitation Protocol (SIP) sponsored by the IETF. Each of them supplies its own signaling mechanisms.

In this paper, these two protocols in terms of their main functionalities are compared. Based on the results of this comparison, a Client/Server architecture for the development of an application that supports a basic SIP implementation, as well as the formulation of requests allowing the establishment and the disconnection of communications between a number of users in a multimedia session are then defined.     

Deformation of NiTiCu shape memory single crystals in compression

Single-crystal orientations of NiTi10Cu alloys were studied under incremental, cyclic compression conditions to establish the pseudoelastic and shape memory response of this class of alloys. This material exhibits a two-step transformation involving cubic to orthorhombic martensite (B2 → B19) followed by orthorhombic to monoclinic martensite (B19 → B19′). The transformation parameters (shear magnitudes and directions for habit and twin planes) were determined associated with the B2 → B19 transformation. The growth of monoclinic martensite correspondent variant pairs (CVPs) emanating from the orthorhombic structure was also analyzed. The transformation strain for the B2 → B19 case was orientation dependent and lower than the B19 → B19′ transformation in compression for all orientations except those near the [001] pole. The experimental results show that the critical transformation stress is orientation dependent and is in the range 30 to 58 MPa. Orientations that exhibit lower transformation stress (or high resolved shear stress factors, [100] and [012]) produce higher recoverable strains (as high as 4 pct), while other orientations ([011], [111], and [123]) with lower resolved shear stress factors result in recoverable strains less than 3 pct. At higher strains, inelastic deformation develops, limiting recoverability. The recoverable strains are lower than the theoretical values for two main reasons: the transformation is curtailed first by austenite slip and subsequently by martensite slip, and the orthorhombic structure does not fully transform to the monoclinic martensite.     

Phosphorus removal by an 'active' slag filter-a decade of full scale experience

Active filters, which facilitate phosphorus (P) removal via precipitation and/or adsorption, offer a promising 'appropriate technology' for upgrading small wastewater treatment systems. Research on active filters for P removal using steel slag material has been conducted in laboratories across the world, however, field experiments have been limited and long-term data is practically non-existent. This paper presents a decade of experience on P removal by active slag filters at a full-scale treatment plant. During 1993-1994 the filter removed 77% of the total phosphorus (TP), and over the first 5 years of the filter's operation it reduced the mean effluent TP concentration to 2.3 mgl(-1). However during the sixth year of operation P removal was significantly reduced. Over the 11 years of monitoring, 22.4 tonnes of TP was removed by the filter, 19.7 tonnes of this in the first 5-year period. It was determined that the slag material maintained its maximum removal potential until reaching a P-retention ratio of 1.23 kg TP per tonne of slag. This paper provides the first long-term field data for slag filters, and shows that they can provide P removal for a half a decade before filter replacement/rejuvenation is required.     

Hybrids for finishing cotton fabric with durable handle performance

New poly(acrylic acid/epichlorohydrin) hybrids were prepared under different polymerization conditions and the proper hybrid was used as a stiffening agent or what may be called hand builder. The latter was incorporated in dimethyloldihydroxy ethylene urea (DMDHEU) finishing formulation and the onset of this on fabric performance as monitored by nitrogen content, wrinkle recovery angle, tensile strength, stiffness, dyeability, and oily stain release was studied. Durability of the new finish was also examined. Results disclose substantial improvement in fabric performance and imply that the hybrid in question acts as a durable hand builder through fixation via its hydroxyl groups within the DMDHEU finish which, in turn, is chemically bonded to cotton cellulose. Scanning electron microscopy of finished fabric revealed that this chemical bonding resulted in hybrid encapsulation, deposition and/or coating of fabric fibers.     

An adaptive multiscale inverse scattering approach to photothermal depth profilometry

Photothermal depth profilometry is formulated as a nonlinear inverse scattering problem. Starting with the one-dimensional heat diffusion equation, we derive a mathematical model relating arbitrary variation in the depth-dependent thermal conductivity to observed thermal wavefields at the surface of a material sample. The form of the model is particularly convenient for incorporation into a nonlinear optimization framework for is particularly convenient for incorporation into a nonlinear optimization framework for recovering the conductivity based on thermal wave data obtained at multiple frequencies. We develop an adaptive, multiscale algorithm for solving this highly ill-posed inverse problem. The algorithm is designed to produce an accurate, low-order representation of the thermal conductivity by automatically controlling the level of detail in the reconstruction. This control is designed to reflect both (1) the nature of the underlying physics, which says that scale should decrease with depth, and (2) the particular structure of the conductivity profile, which may require a sparse collection of fine-scale components to adequately represent significant features such as a layering structure. The approach is demonstrated in a variety of synthetic examples representative of nondestructive evaluation problems seen in the steel industry.The work of authors E. L. Miller and I. Yavuz was supported by a CAREER Award from the National Science Foundation MIP-9623721, an ODDR&E MURI under Air Force Office of Scientific Research contract F49620-96-1-0028, and the Army Research Office Demining MURI under grant DAAG55-97-1-0013. The work of authors L. Nicolaides and A. Mandelis was supported by a research contract from Material and Manufacturing Ontario (MMO).     

Grid-Tied PV-BES system based on modified bat algorithm-FLC MPPT technique under uniform conditions

Neural Computing and Applications - Grid-connected photovoltaic (PV) systems play an important role in reducing emissions resulting from conventional fossil-fuel-based power plants. However, in...     

Microbial Fuel Cell Membrane Bioreactor in Wastewater Treatment,Electricity Generation and Fouling Mitigation

Membrane bioreactors (MBR) have gained much attention due to their ability to achieve higher treatment efficiency. However, high external energy consumption in aeration for membrane fouling mitigation has been limiting their application. Microbial fuel cells (MFC) can ideally extract energy from wastewater in the form of electricity and reduce membrane fouling. Thus, the use of MFC-MBR is rapidly expanding. However, the MFC-MBR design and operation is not fully mature and further research is needed to optimize the process efficiency and enhance the applicability. This review gives an overview of recent studies on the performances of MFC-MBR systems, regarding the design and configuration of the integrated system, irrespective of whether optimization was done or not in the operating system.     

Parametric investigation on hydrogen driven homogeneous charge compression ignition mode with advanced diesel injection using chemical kinetics based numerical model

In the present study, a numerical model based on chemical kinetics was developed to investigate the effect of different parameters on characteristics of hydrogen diesel homogeneous charge compression ignition (HDHCCI) mode. The results showed that the combustion process was retarded with diminished cool flame as increasing hydrogen energy share (HES) due to reduction of H₂O₂, H₂O and OH radicals with hydrogen addition. Thus, it increased the indicated thermal efficiency (ITE) and decreased the indicated specific energy consumption (ISEC). The levels of NO_x and soot emissions were reduced by 22% and 63% at maximum HES. A spray angle of 10° decreased the total fuel impingement compared with a spray angle of 74° because of improvement in air-fuel mixing phenomena. Incomplete combustion was recovered at HES of 25% when increasing the charge temperature or adapting the twin-pulse in HDHCCI mode, consequently the ITE was improved with a decrease in ISEC.     

Tracklet clustering for robust multiple object tracking using distance dependent Chinese restaurant processes

To contrive an accurate and efficient strategy for object detection–object track assignment problem, we present a tracklet clustering approach using distance dependent Chinese restaurant processes (ddCRPs), which employ a two-level robust object tracker. The first level is an ordinary tracklet generator that obtains short yet reliable tracklets. In the second level, we cluster the tracklets over time based on color, spatial and temporal attributes, where the nonparametric process of clustering with ddCRPs allows us to maintain an unknown number of objects. Unlike the previously proposed Chinese restaurant processes and Dirichlet process mixture models, our ddCRPs method does not require prescribed complex cluster models to be initialized and updated, and thus, we can cluster complex tracklets by only computing similarities between them. Our comparative evaluations on tracking different object types demonstrate the generality of our approach.