Coalescence and evaporation dynamics of multiple droplet impingement over a heated surface

The present work aims at unveiling the spread and heat transfer characteristics associated with droplet interactions over a heated wall. This information can be used to understand the overall process of spray cooling used for electronic cooling applications. Experimental investigation using high-speed photography and infrared thermography and numerical simulations implemented in the open-source CFD toolbox OpenFOAM are carried out to realise the underlying physics of the process

Generational Garbage Collection of C++ Targeted to SPARC Architectures

Dynamic memory management plays a crucial role in the development of large software systems. Traditional techniques for managing dynamic memory require the programmer to free an allocated object when it is no longer required. In addition to posing an intellectual burden on the programmer, this approach has often proved error-prone. Many bugs in existing software systems are known to be caused by dynamic memory management errors. Garbage collectors free the programmer from this intellectual burden by automatically reclaiming allocated objects that are no longer in use. In systems with garbage collection, the programmer need not concern himself with releasing objects no longer in use. Most traditional garbage collectors suspend the application program during the collection process. Generational garbage collectors are known to achieve short pause times as they rely on the observation that most objects die young. They concentrate most of their efforts in reclaiming recently allocated objects, occasionally performing a complete collection. In this project, we have implemented a generational garbage collector for C++ targeted to SPARC architectures. Our technique imposes only minor restrictions on the usage of dynamic memory in C++ and runs on stock hardware. * Portions of this paper were excerpted from Code Generation to Support Efficient Accurate Garbage Collection of C++ on Stock Hardware , a paper currently being prepared for publication by Kelvin Nilsen, Ravichandran Ganesan, Satish Guggilla, Satish Kumar, and Kannan Narasimhan

Examining Thermal Management Strategies for a Microcombustion Power Device

Microcombustion attracts interest with its promise of energy dense power generation for electronics. Yet, challenges remain to develop this technology further. Thermal management of heat losses is a known hurdle. Simultaneously, non-uniformities in heat release within the reaction regions also affect the device performance. Therefore a combination of thermal management strategies are necessary for further performance enhancements. Here, a bench top platinum nanoparticle based microcombustion reactor, coupled with thermoelectric generators is used. Methanol-air mixtures achieve room temperature ignition within a catalytic cartridge. In the current study, the reactor design is modified to incorporate two traditional thermal management strategies. By limiting enthalpic losses through the exhaust and reactor sides, using multi-pass preheating channels and heat recirculation, expected improvements are achieved. The combined strategies doubled the power output to 1.01 W when compared to the previous design. Furthermore, a preliminary study of catalyst distribution is presented to mitigate non-uniform catalytic activity within the substrate. To do this, tailored distribution of catalyst particles was investigated. This investigation shows a proof-of-concept to achieve localized control, thus management, over heat generation within substrates. By optimizing heat generation, a highly refined combustion-based portable power devices can be envisioned

A Perspective on the Recent Progress in Solution-processed Methods for Highly Efficient Perovskite Solar Cells

Perovskite solar cells (PSCs) were developed in 2009 and have led to a number of significant improvements in clean energy technology. The power conversion efficiency (PCE) of PSCs has increased exponentially and currently stands at 22%. PSCs are transforming photovoltaic (PV) technology, outpacing many established PV technologies through their versatility and roll-to-roll manufacturing compatibility. The viability of low-temperature and solution-processed manufacturing has further improved their viability. This article provides a brief overview of the stoichiometry of perovskite materials, the engineering behind various modes of manufacturing by solution processing methods, and recommendations for future research to achieve large-scale manufacturing of high efficienc

A Versatile Technique for the Fabrication of PEDOT: PSS Films for Organic Solar Cells

Organic solar cells hold the potential of low-cost production as compared to inorganic solar cells, as well as the increase in efficiency. To realize these possibilities, the key is to fabricate most of the functional films in requisite structures via ambient solution-processed techniques. The PEDOT: PSS films, which are commonly used as an anode layer in organic electronic devices, were deposited on large-area ITO glass substrates under optimized conditions. The spin, spray, brush and brush+spray-coating techniques were utilized to examine their suitability in the fabrication of organic solar cells (OSCs). The films were characterized for their morphology, molecular structure, optical and electrical properties and results are compared with the existing data. A smooth and thin films of PEDOT: PSS were obtained by “Spray+Brush” coating method with attractive sheet-conductivity having  potential in fabricating OSCs with different architectures.Key words: Organic solar cells; PEDOT: PSS films; Solution-processed technique

Study on the Drying Characteristics of Green Gram, Cowpea and Soybean

The study reveals the drying characteristics of Green gram, Cowpea and Soybean when exposed to two different drying mechanisms namely convective (i.e., Tray Drying) and a innovative method (i.e., microwave drying). The objective of the study is to come out with a most appropriate drying technique which gives the product a better keeping quality. In this study the drying characteristics i.e the amount of moisture removed for every 10min is calculated at different temperatures for the respective samples. The sample was dried in tray dryer and microwave at two temperatures

Impact of similarity measures on causal relation based feature selection method for clustering maritime accident reports

Abstract: Unsupervised document clustering is an automated process in which documents are analyzed based on their similarity. In this paper, we propose a new feature selection method based on causal relations to classify maritime accident reports in unsupervised manner. We also compare the impact of different similarity measures on proposed feature selection method. Based on the analysis, we conclude that the proposed feature selection method has better performance over the conventional method due to the effect of dimensionality curse. The impact of similarity measures improves with the proposed feature selection method. In the analysis, we have compared Correlation, Cosine, Spearman, Bray-Curtis, Euclidean, City-block, Squared-Euclidean, Standardized Euclidean, and, Chebychev similarity measures. The first two produced the best results, followed by the next two. The rest did not produce good results with the maritime accident reports used in our analysis. Interestingly Chi-Square gave good results with proposed method in our analysis