Dynamic adaptation policies to improve quality of service of real-time multimedia applications in IEEE 802.11e WLAN Networks

With the increased popularity of wireless broadband networks and the growing demand for multimedia applications, such as streaming video and teleconferencing, there is a need to support diverse multimedia services over the wireless medium. In order to efficiently address these diverse needs, efforts have been pursued to provide Quality of Service (QoS) mechanisms for medium access, resulting in a standard called IEEE 802.11e. One of the enhancements proposed in IEEE 802.11e is a polling-based access mechanism, which is targeted for real-time multimedia flows. In this polling-based scheme, scheduling and time allocation are based on flow reservations. Hence, the effectiveness of the mechanism is heavily dependent on the accuracy of the flow requirements in the reservation. Flow requirements, however, can vary over time and an allocation based on fixed reservations cannot address this variability. This limitation, which is present in the reference scheduler of IEEE 802.11e, leads to degraded multimedia quality for flows with variable requirements, even when channel resources are available. In order to address the above limitation, we present an adaptation framework that dynamically adjusts the polling-based access mechanism and associates flows to different modes of access (polling-based/contention-based), according to the current needs of the application, as opposed to solely relying on the reservation parameters. We demonstrate that with our adaptation, the achieved QoS for real-time multimedia streams, in terms of delay and throughput metrics, can be significantly improved compared to other known mechanisms. Additionally, we show the benefits of our adaptation framework on overall multimedia quality and system capacity. This research is supported by the University of California Discovery Grant (com02-10123) and the Center for Wireless Communications (CWC), University of California, San Diego.     

TBFN: Trust Based Friend Network Design by Analyzing User’s Voice Call and SMS Pattern

Due to rapid development of Web 2.0 Technology social networking have gained explosive growth. This paper proposes a comparatively new approach to build a trust based social network named Trust Based Friend Net (TBFN) for smartphone users. In TBFN, call log and sms log extracted from user’s smartphone are outsourced into the corresponding social network cloud. Analyzing those real datasets the cloud service provider determines trust values of different direct and indirect friends of smartphone users. Global analysis of everyone’s data results in forming a trusted global social network that is free from fake profiles and that minimizes unscrupulous activities.     

Formation of high aspect ratio GaAs nanostructures with metal-assisted chemical etching

Periodic high aspect ratio GaAs nanopillars with widths in the range of 500-1000 nm are produced by metal-assisted chemical etching (MacEtch) using n-type (100) GaAs substrates and Au catalyst films patterned with soft lithography. Depending on the etchant concentration and etching temperature, GaAs nanowires with either vertical or undulating sidewalls are formed with an etch rate of 1-2 μm/min. The realization of high aspect ratio III-V nanostructure arrays by wet etching can potentially transform the fabrication of a variety of optoelectronic device structures including distributed Bragg reflector (DBR) and distributed feedback (DFB) semiconductor lasers, where the surface grating is currently fabricated by dry etching.     

A Sensor Network to Monitor Process Parameters of Fermentation and Drying in Black Tea Production

Fermentation and drying process in tea production are two important processes which play a crucial role in producing good quality tea. Tea colour and flavour are formed in the fermentation and enzyme reactions are terminated and moisture contents are reduced from the leaf particles in the drying process. Ambient temperature and relative humidity (RH) are two major factors for the fermentation process. Firing temperature of dryer is also responsible for the final quality of tea. This paper presents an instrument comprising of sensor network to monitor temperature and RH for the fermentation process and firing temperature of the dryer. For dryer temperature monitoring a thermocouple based measuring system is developed. For fermentation an RH to voltage converter and temperature to voltage converter type sensor is used to develop the RH and temperature monitoring sensor node. The sensor nodes for different stages are connected in RS 485 network. Data are logged into the hard drive of a personal computer using the developed data acquisition software. The instrument will be helpful for recording these parameters and so that their influence can be determined and final quality can be improved.     

Froth flotation as primary treatment of flowback water: Removal of total organic carbon and prediction of kinetics

Petroleum and exploration industries employ a hydrofracking process where a large volume of water (fracturing fluid) is injected and a fraction (known as flowback water) is returned to the surface. Froth flotation is a typical process employed for the primary treatment of water. In the present work, froth flotation has been used as a pretreatment method for real flowback water sourced from the petroleum and shale gas exploration industry. In the present work, a first-principle based convective mass transfer model has been developed to describe the froth flotation performance. The resultant equation was solved analytically and compared with the numerical solution, and a parametric sensitivity analysis of the process performance was also undertaken. In addition, a correlation to estimate the flotation rate constant was proposed, thereby circumventing the need to obtain a large number of cumbersome parameters experimentally. Overall, this study proposes froth flotation as an efficient primary treatment method towards the separation of dispersed oil droplets from the flowback water and the corresponding prediction of kinetics using a first-principle based transport model.