Adaptive MAC Protocol for Solar Energy Harvesting Based Wireless Sensor Networks in Agriculture

The wireless sensor network is one of the promising technologies in the agriculture field. Its actual usage in real agriculture fields is limited by its dependence on the small batteries which cannot make the network survive for long. Various protocols are being designed at the network and MAC layer to increase the lifetime of the nodes, but up to a certain extent only. Hence the energy harvesting to power up the WSN nodes is a promising technology to fulfill this ever energy demand, but the protocols need to be redesigned for this scenario. Solar energy harvesting based MAC protocol which is adaptive to the changing weather conditions is designed in this paper for the smart agriculture applications. It is based on the multilayer and receiver-initiated process to improve network quality. It has shown the remarkable performance over the other energy harvesting based protocols in terms of ENO ratio, energy consumption and collision rate.

     

Taste masking technologies in oral pharmaceuticals: recent developments and approaches

Taste is one of the most important parameters governing patient compliance. Undesirable taste is one of several important formulation problems that are encountered with certain drugs. Oral administration of bitter drugs with an acceptable degree of palatability is a key issue for health care providers, especially for pediatric patients. Several oral pharmaceuticals, numerous food and beverage products, and bulking agents have unpleasant, bitter-tasting components. So, any pharmaceutical formulation with a pleasing taste would definitely be preferred over a competitor's product and would translate into better compliance and therapeutic value for the patient and more business and profits for the company. The desire of improved palatability in these products has prompted the development of numerous formulations with improved performance and acceptability. This article reviews the earlier applications and methodologies of taste masking and discusses the most recent developments and approaches of bitterness reduction and inhibition for oral pharmaceuticals.     

Nework topology for maximizing the terminal reliability in a Computer Communication Network

In the design of a Computer Communication Network (CCN), the reliability between any pair of nodes and the maximum permissible installation cost are of great importance. These characteristics are largely dependant upon the topological layout of the links, their costs and reliabilities. Having the knowledge of the topological layout of the various computer centres (nodes) and maximum permissible cost of installing the various links at their pre-assigned positions; in this paper an algorithm for obtaining an optimal network topology which gives the maximum s?t reliability is presented. The developed method is general and is computerized. The proposed method has an additional advantage that the system is not to be redesigned, if at a later stage the permissible cost is enhanced by budgetary provisions. An example illustrates the algorithm.     

A stable energy efficient clustering protocol for wireless sensor networks

Sensor networks comprise of sensor nodes with limited battery power that are deployed at different geographical locations to monitor physical events. Information gathering is a typical but an important operation in many applications of wireless sensor networks (WSNs). It is necessary to operate the sensor network for longer period of time in an energy efficient manner for gathering information. One of the popular WSN protocol, named low energy adaptive clustering hierarchy (LEACH) and its variants, aim to prolong the network lifetime using energy efficient clustering approach. These protocols increase the network lifetime at the expense of reduced stability period (the time span before the first node dies). The reduction in stability period is because of the high energy variance of nodes. Stability period is an essential aspect to preserve coverage properties of the network. Higher is the stability period, more reliable is the network. Higher energy variance of nodes leads to load unbalancing among nodes and therefore lowers the stability period. Hence, it is perpetually attractive to design clustering algorithms that provides higher stability, lower energy variance and are energy efficient. In this paper to overcome the shortcomings of existing clustering protocols, a protocol named stable energy efficient clustering protocol is proposed. It balances the load among nodes using energy-aware heuristics and hence ensures higher stability period. The results demonstrate that the proposed protocol significantly outperforms LEACH and its variants in terms of energy variance and stability period.     

Soft Magnetic Properties and Electrochemical Behavior of Nanocrystalline CoFeCu Thin Films Electrodeposited from Citrate-Added Baths

CoFeCu thin films were electrodeposited from baths with natural pH (instead of pH～2.8 used in conventional baths) and containing different sodium citrate dosages. ChemEQL V.3.0 software was employed to study speciation diagrams of citrate-added CoFeCu bath with natural pH. At low sodium citrate dosage, Co⁺⁺, Fe⁺⁺, and Cu⁺⁺ species were dominant in CoFeCu bath with natural pH (around 5.2). However, as dosage of sodium citrate in the bath increased, the concentration of complexed species (especially Co(C₆H₅O₇)^?, Fe(C₆H₅O₇)^?, and Cu(OHC₆H₅O₇)^2?) significantly raised. Cyclic voltammetry (CV) studies showed that the formation of complexed species in the bath shifted reduction potential of metals towards more negative potentials. Moreover, in order to deposit cobalt and iron simultaneously with copper, it was necessary to increase the reverse potential (E _λ ) value gradually with sodium citrate dosage, otherwise, only copper would have deposited from citrate-added CoFeCu bath. Scanning electron micrographs illustrated that using natural pH (about 5.2) remarkably decreased the number of microvoids in the deposited films compared with the film deposited from conventional baths with pH level of 2.8. EDS, XRD, and VSM were also used for characterization of the deposited films. All deposited films exhibited nanocrystalline structures, and increasing sodium citrate into the baths led to reduction in grain sizes (D) and coercivity (H _c) of the CoFeCu thin films. Plotting log(H _c) versus log(D ⁶) demonstrated that films coercivity followed the “D ⁶ law”. There were only two phase structures (FCC (Co) or BCC (Fe)) observed in the X-ray diffraction patterns of the films. In addition, films with double-phase structures (FCC+BCC) showed finer grain sizes and therefore exhibited lower coercivity in comparison with single-phase (FCC or BCC) films. CoFeCu thin films deposited at higher dosages of sodium citrate (>20 g/L) were poor in diamagnetic copper and consequently showed higher saturation magnetizations.     

Effect of friction stir processing on the corrosion behavior of pure Mg

As cast pure magnesium was friction stir processed (FSPed) by multiple passes. The treated materials were characterized by scanning electron microscope and X-ray diffraction methods. The corrosion behavior of the materials was also studied using electrochemical impedance spectroscopy. Results showed that FSP refined the structure dramatically to mean grain size value of about 1% of that of in as cast Mg. In addition, FSP dominated basal texture in the treated area of the Mg surface. The grain size was reduced and basal texture intensity increased further by repeating FSP. As a result, the corrosion resistance of the treated material improved considerably to more than 10 times of that of in as cast Mg.     

Liquid phase surface alloying of CP-titanium with aluminum in an atmosphere of argon and nitrogen

In the present work, surface alloying of CP-titanium with different mixtures of titanium and aluminum powders in a gas mixture of 20% argon and 80% nitrogen was carried out using tungsten inert gas (TIG) process. The microstructures of the alloyed layers were investigated by optical microscope (OM), scanning electron microscope (SEM), and the phases formed were studied by X-ray diffraction analysis. The hardness of these layers was also evaluated using a microhardness machine. The results showed that the surface hardness was significantly enhanced from 175 HV_0.1 for the untreated substrate to more than 1000 HV_0.1 for the alloyed layers, due to the formation of Ti₃Al₂N₂ as well as Ti₃Al and TiN in the modified layers. It was also noticed that the alloyed layers exhibited better wear resistance as compared with the untreated substrate.     

The use of intermediate memories for low-latency memory access in supercomputer scalar units

One of the prime considerations for high scalar performance in supercomputers is a low memory latency. With the increasing disparity between main memory and CPU clock speeds, the use of an intermediate memory in the hierarchy becomes necessary. In this paper, we present an intermediate memory structure called a programmable cache. A programmable cache exploits structural locality to decrease the average memory access time. We evaluate the concept of a programmable cache by using the vector registers in the CRAY X-MP and Y-MP supercomputers as a programmable cache. Our results indicate that a programmable cache can be used profitably to reduce the memory latency if the pattern of references to a data structure can be determined at compile time.The work of the first author was supported in part by NSF Grant CCR-8706722.     

Electrochemical studies of zinc–cobalt alloy coatings deposited from alkaline baths containing glycine as complexing agent

Co-deposition of Zn–Co alloy coatings that were electrodeposited from weakly alkaline glycine solutions has been studied by cyclic voltammetry. Scanning electron microscopy (SEM), energy depressive spectroscopy (EDS), and X-ray diffraction (XRD) analyses were used to study surface morphology, chemical composition, and phase structure of the coatings. Corrosion behavior of the coatings was also studied using potentiodynamic polarization tests in 3.5 wt% NaCl solution. Cyclic voltammetry results showed that in Zn–Co deposition from an alkaline bath in the presence of glycine, cobalt deposited at a potential near to that of zinc together with successful co-deposition of Co and Zn. It was also shown that reduction–oxidation (redox) reactions of Zn–Co alloy deposits were quasi-reversible and resulted in deviation of electrodeposited alloys from the equilibrium phase diagrams. The corrosion resistance of the deposits was also highly influenced by the composition and morphology of the coatings. Overall, Zn–Co deposit containing 0.89 wt% Co showed that the highest corrosion resistance among the coatings that was due to its single phase structure and fine morphology.