Increasing the Efficiency of Organic Dye‐Sensitized Solar Cells over 10.3% Using Locally Ordered Inverse Opal Nanostructures in the Photoelectrode

3D inverse opal (3D‐IO) oxides are very appealing nanostructures to be integrated into the photoelectrodes of dye‐sensitized solar cells (DSSCs). Due to their periodic interconnected pore network with a high pore volume fraction, they facilitate electrolyte infiltration and enhance light scattering. Nonetheless, preparing 3D‐IO structures directly on nonflat DSSC electrodes is challenging. Herein, 3D‐IO TiO₂ structures are prepared by templating with self‐assembled polymethyl methacrylate spheres on glass substrates, impregnation with a mixed TiO₂:SiO₂ precursor and calcination. The specific surface increases from 20.9 to 30.7 m² g^?1 after SiO₂ removal via etching, which leads to the formation of mesopores. The obtained nanostructures are scraped from the substrate, processed as a paste, and deposited on photoelectrodes containing a mesoporous TiO₂ layer. This procedure maintains locally the 3D‐IO order. When sensitized with the novel benzothiadiazole dye YKP‐88, DSSCs containing the modified photoelectrodes exhibit an efficiency of 10.35% versus 9.26% for the same devices with conventional photoelectrodes. Similarly, using the ruthenium dye N719 as sensitizer an efficiency increase from 5.31% to 6.23% is obtained. These improvements originate mainly from an increase in the photocurrent density, which is attributed to an enhanced dye loading obtained with the mesoporous 3D‐IO structures due to SiO₂ removal.     

MHEGAM-a multimedia messaging system

MHEGAM (MHEC-1 Advanced Mail) is a complete multimedia messaging system for the creation, exchange, and restitution of multimedia messages that express spatial and temporal synchronization among their components. MHEGAM can be based on the standard messaging systems X.420 or MIME. We present the multimedia extensions MHECAM-X.420 and MHEGAM-MIME and discuss the multimedia message format and architecture components for both systems     

Amorphous Zinc Stannate (Zn2SnO4) Nanofibers Networks as Photoelectrodes for Organic Dye‐Sensitized Solar Cells

A new strategy for developing dye‐sensitised solar cells (DSSCs) by combining thin porous zinc tin oxide (Zn₂SnO₄) fiber‐based photoelectrodes with purely organic sensitizers is presented. The preparation of highly porous Zn₂SnO₄ electrodes, which show high specific surface area up to 124 m²/g using electrospinning techniques, is reported. The synthesis of a new organic donor‐conjugate‐acceptor (D‐π‐A) structured orange organic dye with molar extinction coefficient of 44 600 M^?1 cm^?1 is also presented. This dye and two other reference dyes, one organic and a ruthenium complex, are employed for the fabrication of Zn₂SnO₄ fiber‐based DSSCs. Remarkably, organic dye‐sensitized DSSCs displayed significantly improved performance compared to the ruthenium complex sensitized DSSCs. The devices based on a 3 μm‐thick Zn₂SnO₄ electrode using the new sensitizer in conjunction with a liquid electrolyte show promising photovoltaic conversion up to 3.7% under standard AM 1.5G sunlight (100 mW cm^?2). This result ranks among the highest reported for devices using ternary metal oxide electrodes.     

Impact of memory contention on dynamic scheduling on NUMAmultiprocessors

Self-scheduling is a method for task scheduling in parallel programs, in which each processor acquires a new block of tasks for execution whenever it becomes idle. To get the best performance, the block size must be chosen to balance the scheduling overhead against the load imbalance. To determine the best block size, a better understanding of the role of load imbalance in self-scheduling performance is needed. In this paper we study the effect of memory contention on task duration distributions and, hence, load balancing in self-scheduling on a Nonuniform Memory Access (NUMA) machine. Experimental studies on a BBN TC2000 are used to reveal the strengths and weaknesses of analytical performance models to predict running time and optimal block size. The models are shown to be very accurate for small block sizes. However, the models fail when the block size is large due to a previously unrecognized source of load imbalance. We extend the analytical models to address this failure. The implications for the construction of compilers and runtime systems are discussed     

Synchronization Minimization in a SPMD Execution Model

This paper presents an algorithm for synchronization placement when using a SPMD execution model, where synchronizations are enforced only when there exists a cross-processor data dependence. In this paper, we investigate two scheduling techniques, loop-based and data-based, both of which use a SPMD model. Using scheduling information from previous stages in the compilation process, a new technique to determine potential cross-processor data dependences is presented. Given the minimum number of cross-processor data dependences that must be satisfied, a new optimization is used so as to minimize the number of synchronization points needed to satisfy them. This algorithm has been successfully implemented in an experimental compiler. Initial experimental data show this technique to be very effective, outperforming existing methods.