Input parallel–output parallel connected modular nonisolated DC-DC converters with current self-sharing capability operating in discontinuous conduction mode

This paper covers the self-sharing analysis of dc-dc nonisolated converters with input parallel–output parallel (IPOP) configuration and operating in discontinuous conduction mode (DCM). The main contribution of the proposed system is its capability of providing self-sharing of the currents on both sides of each individual converter, without average current sharing control, even in the face of parametric variations. This self-balance only occurs for DCM. When the addressed converters operate in continuous conduction mode (CCM), the self-sharing does not occur naturally under parametric differences among them, requiring the use of additional control loops. The use of self-sharing converters in nonisolated converters simplifies the control system, it makes the modular solution being attractive for many applications, and it increases the power range that the DCM converters may be applied. This paper brings the theoretical study of self-sharing of the current mechanism to six basic nonisolated converters operating in DCM. The self-sharing is verified by experimental results, which are obtained from three modules of dc-dc SEPIC converters. Both converters were designed to operate with 200-V input voltage, 125-V output voltage, 1500-W rated power (500 W each module), and switching frequency at 30 kHz.     

Tools and strategies for debugging distributed stream processing applications

Distributed data stream processing applications are often characterized by data flow graphs consisting of a large number of built‐in and user‐defined operators connected via streams. These flow graphs are typically deployed on a large set of nodes. The data processing is carried out on‐the‐fly, as tuples arrive at possibly very high rates, with minimum latency. It is well known that developing and debugging distributed, multi‐threaded, and asynchronous applications, such as stream processing applications, can be challenging. Thus, without domain‐specific debugging support, developers struggle when debugging distributed applications. In this paper, we describe tools and language support to support debugging distributed stream processing applications. Our key insight is to view debugging of stream processing applications from four different, but related, perspectives. First, debugging the semantics of the application involves verifying the operator‐level composition and inspecting the flows at the logical level. Second, debugging the user‐defined operators involves traditional source‐code debugging, but strongly tied to the stream‐level interactions. Third, debugging the deployment details of the application require understanding the runtime physical layout and configuration of the application. Fourth, debugging the performance of the application requires inspecting various performance metrics (such as communication rates, CPU utilization, etc.) associated with streams, operators, and nodes in the system. In light of this characterization, we developed several tools such as a debugger‐aware compiler and an associated stream debugger, composition and deployment visualizers, and performance visualizers, as well as language support, such as configuration knobs for logging and tracing, deployment configurations such as operator‐to‐process and process‐to‐node mappings, monitoring directives to inspect streams, and special sink adapters to intercept and dump streaming data to files and sockets, to name a few. We describe these tools in the context of Spade —a language for creating distributed stream processing applications, and System S —a distributed stream processing middleware under development at the IBM Watson Research Center. Published in 2009 by John Wiley & Sons, Ltd.     

Polydiacetylene as a Biosensor: Fundamentals and Applications in the Food Industry

Biosensors offer the potential for real-time pathogen detection. Polydiacetylene (PDA) is an ideal choice for use as a sensor due to its unique optical properties. PDA molecules can form thin films or vesicles that change color from deep blue to red in response to different stimuli, like temperature, pH, and the presence of biological molecules. PDA films and vesicles have been proven to be promising devices for the detection of bacteria and bacterial toxins. Langmuir troughs (for films) and microcalorimetry (for vesicles) are among the many techniques used to characterize PDA films and vesicles. In order to enable more applications of PDA films, it is imperative to elucidate and gain a deeper understanding of the molecular interactions associated with their color change. In addition, it is necessary to transfer the PDA film onto a solid support like plastic in order to incorporate PDA biosensors into an intelligent packaging system. Through the use of such a system, consumers can monitor food quality, thereby preventing foodborne outbreaks. In this review, we discuss the formation of PDA films and vesicles, their characteristics, and their potential applications as biosensors. The possibility to incorporate PDA biosensors into an intelligent packaging system to be used in the food industry is also explored.     

Quantification of bone mass gain in response to the application of biphasic bioceramics and platelet concentrate in critical-size bone defects

Biphasic bioceramics have been widely indicated for bone reconstruction; however, the real gain in bone mass due to the presence of such biomaterials has not been established yet nor the advantages of its association with platelet concentrate. This study aims at quantifying the volume of bone matrix, osteoblasts, osteocytes, blood vessels and adipose tissue after the application of a biphasic bioceramics composed of 65% hydroxyapatite and 35% β-tricalcium phosphate. Critical-size bone defects were produced in rabbit femora and reconstructed with bioceramics only, with bioceramics combined with platelet concentrate, with platelet concentrate alone, and with no treatment (blood clot). The quantitative evaluation was performed on histological sections using histomorphometry. Our data provide original evidence that consolidates the indication of bioceramics for clinical bone loss reconstruction. The application of biphasic bioceramics alone led to major bone mass gain and was followed by its association with platelet concentrate. On the other hand, platelet concentrate can contribute to the augmentation and maintenance of the adipose tissue, representing a new field for future applications in plastic surgery.     

Fabrication and characterization of nanostructured conducting polymer films containing magnetic nanoparticles

In this study, the layer-by-layer technique is used to deposit nanostructured films exhibiting electrical conductivity and magnetic behavior, from poly(o-ethoxyaniline) (POEA), sulfonated polystyrene (PSS) and positively-charged maghemite nanoparticles. In order to incorporate the nanoparticles into the films, maghemite nanoparticles, in the form of magnetic fluid, were added to POEA solutions, and the resulting suspensions were used for film deposition. UV-Vis spectroscopy and atomic force microscopy images reveal that POEA remains doped in the films, even in the presence of the maghemite nanoparticles, and its typical globular morphology is also present. Electrical measurements show that a POEA/PSS film prepared from POEA solution containing 800 µL of the magnetic fluid exhibits a similar conductivity to that of the control film and, additionally, magnetic measurements indicated that nanosized maghemite phase was incorporated within the polymeric film.     

Fluxes of nitrous oxide from soil under different crop rotations and tillage systems in the South of Brazil

The zero tillage (ZT) system is used in a large area (>24 Mha) of crop production in Brazil. This management system can contribute to soil C sequestration, but many studies in other countries have registered greater nitrous oxide emissions under ZT compared to conventional tillage (CT), which may reduce greenhouse gas mitigation benefits. The aim of this study was to estimate the emission of N₂O from cropping systems under conventional and zero tillage in an 18-year-old experiment conducted on a Rhodic Ferralsol in the South of Brazil. Fluxes of N₂O were measured over two years using static-closed chambers in the two tillage systems with three crop rotations. Soil water filled pore space (%WFPS) and soil mineral N were monitored along with rainfall and air temperature. Estimates of N₂O emissions were obtained by integrating the fluxes with time and also by applying the IPCC direct emission factor (EF1 = 1%) to the amounts of N added as fertilisers and returned as crop residues. Fluxes of N₂O were relatively low, apart from a short period at the beginning of measurements. No relationship between N₂O fluxes and %WFPS or mineral N were observed. Nitrous oxide emissions were not influenced either by tillage system or crop rotation. For the crop rotation receiving high rates of N fertiliser in the second year, field-measured N₂O emissions were significantly underestimated by the IPCC emission factor 1 (EF1). For the other treatments measured N₂O emissions fell within the EF1 uncertainty range, but always considerably lower than the EF1 estimate, which suggests IPCC EF1 overestimates true N₂O emissions for the Ferralsol under evaluation.     

3D Modeling and Section Properties of Ancient Irregular Timber Structures by Means of Digital Photogrammetry

Abstract:   This article deals with the application of low-cost Close Range Digital Photogrammetry to obtain an accurate three-dimensional (3D) re-construction of irregular geometry structures in the field of building construction, with special attention to the evaluation of old structures. Photogrammetry can be used as a non-destructive tool to give precise 3D information about the size and shape of some elements of a structure, quickly and with no risk to the surveyors. The geometric data achieved can be used by engineers and architects to obtain the section properties, and also to estimate the influence of geometric variations in the distribution of stress. This allows us to compare areas subject to higher stress, and could be of special interest regarding some historic and cultural heritage constructions—such as the timber roof structure included as a case study in this work—from two points of view: On the one hand, Photogrammetry makes it possible to obtain precise 3D models of highly irregular elements, as old timber purlines and trusses in the case of ancient constructions; on the other, Photogrammetry is a non-contact method that minimizes the measurement time and allows us to obtain the section properties, which can be used together with some material testing characterization to evaluate the structural safety of the construction.     

Increasing the throughput of HomePNA

In this paper we propose a new medium access mechanism for HomePNAv2 and HomePNAv3 standards. This mechanism uses a priority aggregation mechanism to avoid collisions, increasing these protocols throughput. Furthermore, this mechanism does not require modifying standards, since it can be implemented over their actual MAC sublayers. Simulation results show that the proposed mechanism is able to increase the throughput up to 44% for HomePNAv2 and 36% for HomePNAv3. Moreover, we also show how this mechanism affects network delay, analyzing average delay and jitter for all protocols presented. Copyright © 2008 John Wiley & Sons, Ltd.     

Leak detection in petroleum pipelines using a fuzzy system

A methodology for pipeline leakage detection using a combination of clustering and classification tools for fault detection is presented here. A fuzzy system is used to classify the running mode and identify the operational and process transients. The relationship between these transients and the mass balance deviation are discussed. This strategy allows for better identification of the leakage because the thresholds are adjusted by the fuzzy system as a function of the running mode and the classified transient level. The fuzzy system is initially off-line trained with a modified data set including simulated leakages. The methodology is applied to a small-scale LPG pipeline monitoring case where portability, robustness and reliability are amongst the most important criteria for the detection system. The results are very encouraging with relatively low levels of false alarms, obtaining increased leakage detection with low computational costs.     

Immobilization of zirconocene within silica–tungsten by entrapment: Tuning electronic effects of the support on the supported complex

The immobilization of Cp₂ZrCl₂ was performed by entrapment within the binary oxide SiO₂–WO₃ using a non-hydrolytic sol–gel route. The catalyst and oxide matrix were characterized by complementary techniques (Rutherford backscattering spectrometry, ultraviolet–visible diffuse reflectance and infrared transmission spectroscopy, differential pulse voltammetry, adsorption–desorption of N₂, and X-ray diffraction). The catalyst performance in terms of catalytic activity and polymer properties was evaluated by ethylene polymerization. Catalyst characterization suggested that the entrapped complex exhibited lower Zr electronic density than the corresponding unsupported metallocene. The polymerization results also revealed that this low Zr electronic density is optimized in terms of complex activation with low MAO concentration (low [Al/Zr] ratio) and reactivity. This fine tuning results in a catalyst system that is active with a low [Al/Zr] ratio and that achieves high catalytic activity. The results demonstrate that the entrapping method allows the generation of a catalyst system in which part of the activation process is attributed to the support. In this sense, the support may partially play MAO functions by stabilizing the active catalytic species.