Throughput analysis in wireless networks with multiple users and multiple channels

We consider the problem of maximizing throughput in a multi-carrier wireless network that employs predictive link adaptation. We explicitly consider the time-penalty incurred due to link adaptation. The contributions of this paper are twofold. Firstly, several high performance algorithms (offline and online) are developed for efficient performance in multiple user and multiple channel environment under the practicable lookahead prediction of one time slot. Secondly, the presented algorithms and heuristics are shown to be competitive by deterministic and probabilistic analyses. Our results show that a modest consumption of resources for channel prediction and link adaptation may result in a significant throughput improvement.     

Electromagnetic acoustic transducer for in-plane and plane-normal velocity measurements

A new electromagnetic acoustic transducer (EMAT) is developed that measures velocities and absolute surface displacements in-plane and plane-normal to the direction of wave propagation. This transducer is flexible in shape and design to conform with irregular surfaces and has unique characteristics of nonresonant frequency response. Tests show that the sensitivity of this EMAT can be increased by increasing the applied magnetic field. Because this transducer is mode selective and nonresonent, its response can be related uniquely to the wave motion. This property is highly desirable for research purposes, though generally not wanted in field monitoring situations.     

Variability of Starch and Sugar Contents in Grains of Sorghum Forages and its Correlation with Tannin and Mineral Matter Content

Ninteen promising strains of fodder sorghum were selected for the present study. The starch content in the seed varied from 42.68 to 68.31%, total sugars from 3.13 to 7.81%, mineral matter from 1.12 to 4.09%. The amylose content was approximately in the range of 12 — 13% and amylose : amylopectin ratio was 1:4 to 1:10. The tannin content ranged from 0.23 to 3.73 mg/g of seed and it was high in non sweet varieties and low in sweet varieties. There was not much difference in the sugar content of sweet and non sweet varieties. The protein content of the seed varied from 8.31 to 14.41%. Starch content of seed was significantly negatively correlated with tannin and mineral matter content of the seed (−0.595 and −0.491) but tannin content was positively correlated with mineral matter content and was significant ( + 0.581). A genetic manipulation of breeding material can bring about high amylose and protein varieties.     

The effect of temperature on toluene sorption by granular activated carbon and its use in permeable reactive barriers in cold regions

Granular activated carbon (GAC) has been used as an adsorbent for hydrocarbons in a range of permeable reactive barriers. This work investigates the influence of temperature on adsorption performance. In particular, the influence of temperature in the range of 20 °C to 4 °C on the sorption equilibrium and kinetics of toluene on GAC surface were investigated. The results show that low temperature leads to decreased toluene sorption by GAC and slower reaction kinetics. Sorption kinetics studies show that diffusion coefficients are also lower at 4 °C (3.65 × 10⁻¹³ m² s⁻¹) than 20 °C (5.112 × 10⁻¹³ m² s⁻¹).     

Transparent magnesium aluminate spinel: a prospective biomaterial for esthetic orthodontic brackets

Adult orthodontics is recently gaining popularity due to its importance in esthetics, oral and general health. However, none of the currently available alumina or zirconia based ceramic orthodontic brackets meet the esthetic demands of adult patients. Inherent hexagonal lattice structure and associated birefringence limits the visible light transmission in polycrystalline alumina and make them appear white and non transparent. Hence focus of the present study was to assess the feasibility of using magnesium aluminate (MgAl₂O₄) spinel; a member of the transparent ceramic family for esthetic orthodontic brackets. Transparent spinel specimens were developed from commercially available white spinel powder through colloidal shaping followed by pressureless sintering and hot isostatic pressing at optimum conditions of temperature and pressure. Samples were characterized for chemical composition, phases, density, hardness, flexural strength, fracture toughness and optical transmission. Biocompatibility was evaluated with in-vitro cell line experiments for cytotoxicity, apoptosis and genotoxicity. Results showed that transparent spinel samples had requisite physico-chemical, mechanical, optical and excellent biocompatibility for fabricating orthodontic brackets. Transparent spinel developed through this method demonstrated its possibility as a prospective biomaterial for developing esthetic orthodontic brackets.     

The configuration space of duty-cycled CSMA-based wireless MACs

Wireless sensor network (WSN) applications vary widely in their traffic and node density patterns. Conventional wisdom says that a medium access control (MAC) protocol that performs well for one application can perform poorly for another. Perhaps as a result of this view, a large number of MAC protocols have been proposed, often with specific performance metrics in mind; many of the widely used ones have focused on the low duty cycle case. In this paper, we study how the choice of the MAC protocol as well as the configuration of its parameters impacts performance for diverse traffic rates and node densities. Specifically, we classify CSMA-based MAC protocols in terms of critical MAC-design factors and introduce a framework for performance modeling of each MAC class as a function of key protocol parameters. We use this framework to analyze various performance metrics comprehensively across the configuration space of the protocols; extensive experimentation corroborates our analysis. Our results serve not only as a basis for comparing protocols, they also yield insight into how to adapt MACs to changing traffics in a distributed way. Although the framework focuses on single-hop traffic patterns, potential for extending the framework to analyze richer application scenarios is also investigated and discussed. A surprising finding of our comparative evaluation is that one class of MAC protocols consistently achieves the best or close to the best performance for various metrics across much of the configuration space.