Nanomorphology influence on the light conversion mechanisms in highly efficient diketopyrrolopyrrole based organic solar cells

In this work, diketopyrrolopyrrole-based polymer bulk heterojunction solar cells with inverted and regular architecture have been investigated. The influence of the polymer:fullerene ratio on the photoactive film nanomorphology has been studied in detail. Transmission Electron Microscopy and Atomic Force Microscopy reveal that the resulting film morphology strongly depends on the fullerene ratio. This fact determines the photocurrent generation and governs the transport of free charge carriers. Slight variations on the PCBM ratio respect to the polymer show great differences on the electrical behavior of the solar cell. Once the polymer:fullerene ratio is accurately adjusted, power conversion efficiencies of 4.7% and 4.9% are obtained for inverted and regular architectures respectively. Furthermore, by correlating the optical and morphological characterization of the polymer:fullerene films and the electrical behavior of solar cells, an ad hoc interpretation is proposed to explain the photovoltaic performance as a function of this polymer:blend composition.     

Business-to-business e-commerce adoption: An empirical investigation of business factors

We develop an overarching model to explain the adoption of business-to-business e-commerce using five business factors: external environment, organizational context, decision-maker’s characteristics, technology context, and organizational learning. Data collected from IS executives was analyzed using logistic regression. Our model has a good fit with over 77 % variance explained. Findings indicate that the existence of informal interest groups, and the tolerant attitude of decision makers towards negative information about business-to-business e-commerce have significant influence on the adoption decision. In addition, our results indicate that price intensity and perceived barriers negatively affect the adoption decision.     

High-gain InGaAlAs/InGaAs heterojunction bipolar transistors andphototransistors

The characteristics of InGaAlAs/InGaAs heterojunction bipolar transistors (HBTs) grown by molecular beam epitaxy are described. A current gain of 15600 at a current density of ~10⁴ A/cm² and an emitter-base heterojunction ideality factor of 1.02 were measured. Appropriately designed InGaAlAs/InGaAs HBTs, when operated as phototransistors, also had high gains. A current gain of 1000 for a collector current of only 10 μA was obtained for phototransistors. Such high gains are due to low recombination currents as a consequence of the good crystalline quality of the InGaAlAs bulk and InGaAlAs/InGaAs interface     

A comparative study of mathematical models for gas-solid non-catalytic reactions

Experimental data on desulphurisation of a simulated coal gas mixture containing 200 ppm H₂S, using CuO/ZnO mixed oxide sorbent in a fluidised bed reactor, are used to evaluate four representative structural models for gas-solid non-catalytic reactions. The four models chosen for evaluation are the spherical changing-grain-size model of Georgakis and co-workers, the rectangular grains version of the general formulation of Szekely and co-workers, the single-pore model of Ramachandran and Smith and the random pore model of Bhatia and Perlmutter. All the model parameters except the reaction rate constant are calculated from experimental measurements or from literature correlations. The rate constant alone is adjusted so as to obtain good agreement between the model and the experiment. It is shown that at any given temperature all the models describe the data well. However, the random pore model predicts conversions lower than experiment at large times while the rectangular grains model predicts conversions higher than experiment for small times. The rate constants decrease as temperature increases indicating an inadequacy of all the models in this regard. The models also predict much smaller variations in conversion with change in particle size than those observed experimentally.     

Taylor kernel fuzzy C-means clustering algorithm for trust and energy-aware cluster head selection in wireless sensor networks

Wireless Networks - Wireless sensor networks depend on the effective functioning of the nodes in the network, which is concerned regarding the energy that is essential for the extended network...     

Influence of rare earth content on electrode kinetics in Misch metal-based AB5 MH alloys – Cyclic voltammetric investigations

The influence of lanthanum/cerium ratio (0.42–14.14) in Misch metal (Mm)-based AB₅-type hydrogen storage alloys has been investigated. The samples were subjected to X-ray florescence (XRF) and cyclic voltammetry (CV) studies. The metal hydride electrodes were assembled, and their discharge capacity was determined. These alloys delivered discharge capacity between 118 and 266 mAh/g. CV investigations threw light on charge-transfer reactions at the electrode/electrolyte interface and hydrogen surface coverage capacity. The CV parameters in general indicate that the battery activity increases with lanthanum/cerium ratio. At low lanthanum/cerium values, the discharge reactions proceed at potentials that are more negative. Furthermore, electrochemical reversibility of the hydrogen absorption–desorption on the alloy surface is enhanced at optimum lanthanum/cerium ratio as revealed by decreasing values of peak separation. The slopes of graphical plots of I_peak (anodic) vs. ν^1/2 for the fully charged samples reverse direction at very high lanthanum/cerium values. The results suggest that the discharge plateau is optimum at lanthanum/cerium ratio around 12.     

Semantic indexing in structured peer-to-peer networks

The past few years have seen tremendous advances in distributed storage infrastructure. Unstructured and structured overlay networks have been successfully used in a variety of applications, ranging from file-sharing to scientific data repositories. While unstructured networks benefit from low maintenance overhead, the associated search costs are high. On the other hand, structured networks have higher maintenance overheads, but facilitate bounded time search of installed keywords. When dealing with typical data sets, though, it is infeasible to install every possible search term as a keyword into the structured overlay.     

Influence of helix twisted tape on heat transfer and friction factor in forced circulation V-trough solar water heater

The effect of helix twisted tape with several twist ratios (Y?=?3, 4, 5 and 6) in a V-trough solar water heater for enhancing heat transfer, thermal performance and the friction factor has been examined experimentally in forced circulation with the Reynolds number ranging from 3000 to 23,000. The experimental results of plain V-trough solar collector (PVT) fitted with the standard equations and the variation in the Nusselt number are ±7.23% and the variation in friction factor is about ±5.91%. The PVT has been compared with plain flat plate (PFP) collector. The obtained result shows that the average Nusselt number of PVT performs better than PFP by 8.4%. This is owing to the additional reflectors, reflection of the solar incident rays to the receiver plate, which tend to rise in the temperature gradient of water inlet and outlet of the system. The thermal performance has been increased further by inserting the helix twisted tape with several twist ratios and the results are also presented. The minimum twist ratio 3 provides a higher heat transfer rate and friction factor owing to the increase in the hydraulic length and swirl flow. The experimental Nusselt number and friction factor are correlated and the deficiency falls ±6.44% and ±11.91%, respectively.     

An assessment of inter-firm networks in a wood biomass industrial cluster: lessons for integrated policymaking

Effective use of biomass is emerging in various agro-industries, offering new avenues for sustainable regional development. A case analysis is done on a wood industrial cluster in Maniwa, Japan to analyze the drivers and barriers for community-based actions in improving environmental performance of small businesses operating in the cluster. Wood processing businesses in Maniwa generate wastes such as wood trimmings and shavings. Community-based actions of various businesses in the supply chain realized the commercial value in such waste products and explored options of wood such as biomass fuel, extraction of ethanol, wood-based concrete and organic strawberry farming. Various technologies enabled the process to be carried out, and knowledge/information was brought in by local research institutes. Taking leadership and participation by business in community-based social networks increased the availability of market information and lowered its cost. It also led them to reach collective decisions and implement actions together. Evidences from a strength, weakness, opportunities and potential analysis of the Maniwa wood cluster revealed that stimulating community-based actions, providing enabling technologies, creation of social capital and policy integration are the pillars for transforming local industrial clusters into eco-friendly industrial clusters. Technical facts, policy experiences and findings suggest that grouping of biomass-based industries and developing joint actions for sound material flow represent a promising strategy to promote sustainable production and consumption while providing a new model for environment friendly regional development.     

Concurrent programming constructs for parallel MPI applications

Concurrency and parallelism have long been viewed as important, but somewhat distinct concepts. While concurrency is extensively used to amortize latency (for example, in web- and database-servers, user interfaces, etc.), parallelism is traditionally used to enhance performance through execution on multiple functional units. Motivated by an evolving application mix and trends in hardware architecture, there has been a push toward integrating traditional programming models for concurrency and parallelism. Use of conventional threads APIs (POSIX, OpenMP) with messaging libraries (MPI), however, leads to significant programmability concerns, owing primarily to their disparate programming models. In this paper, we describe a novel API and associated runtime for concurrent programming, called MPI Threads (MPIT), which provides a portable and reliable abstraction of low-level threading facilities. We describe various design decisions in MPIT, their underlying motivation, and associated semantics. We provide performance measurements for our prototype implementation to quantify overheads associated with various operations. Finally, we discuss two real-world use cases: an asynchronous message queue and a parallel information retrieval system. We demonstrate that MPIT provides a versatile, low overhead programming model that can be leveraged to program large parallel ensembles.