Portugal's contribution to navigation and discovery of the New World

Even before the birth of Prince Henry the Navigator (1394) Portugal had displayed a maritime calling due to its 500-mile shore line and numerous natural bays. Inspired by the riches of India he saw during the Portuguese exploration along the coast of West Africa, Prince Henry set out methodically to collect information by bringing together Jews and Moors with geographical knowledge to found his School of Navigation. From 1415 until his death in 1460 he attracted to his school the foremost contemporary scholars in mathematics, astronomy, and cartography along with experts in knowledge of the compass, astrolabe, water currents, and the winds. This concentration of talent yielded the invention of the caravel, the most important navigational advancement of the time, crucial for long voyages across the high seas. Although the rest of Europe busied itself in political and religious wars, for 70 years (1415-1492) Portugal alone pursued the discovery of the Atlantic. "No nation in the 15th century exhibited so great a spirit of maritime enterprise as the Portuguese."     

Histology, histochemistry and stereology of the adipose fin of Prochilodus lineatus

The adipose fin is small, nonpared, and usually located medially between the dorsal and caudal fin. Its taxonomic occurrence is very restrict; thus, it represents an important trace for taxon distinction. As it does not play a known vital physiological roll and it is easily removed, it is commonly used in marking and recapture studies. The present study characterizes the adipose fin of Prochilodus lineatus, as it is poorly explored by the literature. The adipose fin consists basically of a loose connective core, covered by a stratified epithelium supported by collagen fibers. At the epithelium, pigmented cells and alarm substance cells are found. Despite the name, adipocytes or lipid droplets are not observed on the structure of the fin.     

Influence of photoperiod on carbon dioxide and methane emissions from two pilot-scale stabilization ponds

Greenhouse gas (GHG) emissions (CO(2), CH(4)) from pilot-scale algal and duckweed-based ponds (ABP and DBP) were measured using the static chamber methodology. Daylight and nocturnal variations of GHG and wastewater characteristics (e.g. chemical oxygen demand (COD), pH) were determined via sampling campaigns during midday (12:30-15:30) and midnight (00:30-03:30) periods. The results showed that under daylight conditions in ABP median emissions were -232 mg CO(2) m(-2) d(-1) and 9.9 mg CH(4) m(-2) d(-1), and in DBP median emissions were -1,654.5 mg CO(2) m(-2) d(-1) and 71.4 mg CH(4) m(-2) d(-1), respectively. During nocturnal conditions ABP median emissions were 3,949.9 mg CO(2) m(-2) d(-1), 12.7 mg CH(4) m(-2) d(-1), and DBP median emissions were 5,116 mg CO(2) m(-2) d(-1), 195.2 mg CH(4) m(-2) d(-1), respectively. Once data measured during daylight were averaged together with nocturnal data the median emissions for ABP were 1,566.8 mg CO(2) m(-2) d(-1) and 72.1 mg CH(4) m(-2) d(-1), whilst for DBP they were 3,016.9 mg CO(2) m(-2) d(-) and 178.9 mg CH(4) m(-2) d(-1), respectively. These figures suggest that there were significant differences between CO(2) emissions measured during daylight and nocturnal periods (p < 0.05). This shows a sink-like behaviour for both ABP and DBP in the presence of solar light, which indicates the influence of photosynthesis in CO(2) emissions. On the other hand, the fluxes of CH(4) indicated that DBP and ABP behave as net sources of CH(4) during day and night, although higher emissions were observed from DBP. Overall, according to the compound average (daylight and nocturnal emissions) both ABP and DBP systems might be considered as net sources of GHG.     

Compact yet efficient hardware implementation of artificial neural networks with customized topology

There are several neural network implementations using either software, hardware-based or a hardware/software co-design. This work proposes a hardware architecture to implement an artificial neural network (ANN), whose topology is the multilayer perceptron (MLP). In this paper, we explore the parallelism of neural networks and allow on-the-fly changes of the number of inputs, number of layers and number of neurons per layer of the net. This reconfigurability characteristic permits that any application of ANNs may be implemented using the proposed hardware. In order to reduce the processing time that is spent in arithmetic computation, a real number is represented using a fraction of integers. In this way, the arithmetic is limited to integer operations, performed by fast combinational circuits. A simple state machine is required to control sums and products of fractions. Sigmoid is used as the activation function in the proposed implementation. It is approximated by polynomials, whose underlying computation requires only sums and products. A theorem is introduced and proven so as to cover the arithmetic strategy of the computation of the activation function. Thus, the arithmetic circuitry used to implement the neuron weighted sum is reused for computing the sigmoid. This resource sharing decreased drastically the total area of the system. After modeling and simulation for functionality validation, the proposed architecture synthesized using reconfigurable hardware. The results are promising.     

Preference-based multi-objective evolutionary algorithms for power-aware application mapping on NoC platforms

Network-on-chip (NoC) are considered the next generation of communication infrastructure in embedded systems. In the platform-based design methodology, an application is implemented by a set of collaborative intellectual property (IP) blocks. The selection of the most suited set of IPs as well as their physical mapping onto the NoC infrastructure to implement efficiently the application at hand are two hard combinatorial problems that occur during the synthesis process of Noc-based embedded system implementation. In this paper, we propose an innovative preference-based multi-objective evolutionary methodology to perform the assignment and mapping stages. We use one of the well-known and efficient multi-objective evolutionary algorithms NSGA-II and microGA as a kernel. The optimization processes of assignment and mapping are both driven by the minimization of the required silicon area and imposed execution time of the application, considering that the decision maker’s preference is a pre-specified value of the overall power consumption of the implementation.     

Porous methacrylate tissue engineering scaffolds: using carbon dioxide to control porosity and interconnectivity

Porous scaffold structures are used in tissue engineering to provide structural guidance for regenerating tissues. The use of carbon dioxide (CO₂) to create such scaffolds has received some attention in the past but many researchers believe that although CO₂ processing of polymers can lead to porous scaffolds there is limited interconnectivity between the pores. In this study, highly porous (greater than 85%) and well interconnected scaffolds were obtained in which the size, distribution and number of pores could be controlled. This control was achieved by altering the rate of venting from polymer discs saturated with CO₂ under modest temperature and pressure. The polymer used is a blend of poly (ethyl methacrylate) and tetrahydrofurfuryl methacrylate (PEMA/THFMA). This polymer system has shown promise for potential applications in cartilage repair.     

Effect of winding harmonics on the asynchronous torque of a single-phase line-start permanent-magnet motor

This paper presents an analytical method for calculating the effect of winding harmonics on the asynchronous torque of a single-phase line-start permanent-magnet motor. The method is an extension of earlier work, which combines symmetrical-component analysis with d-q-axes theory to model the various components of forward and backward rotating fields. The effect of individual winding harmonics is brought out both theoretically and experimentally by comparing the calculated and measured torque/speed characteristics for a series of six motors with different distributions of turns in both main and auxiliary windings.     

User interface modeling in UMLi

Although user interfaces represent an essential part of software systems, the Unified Modeling Language )UML) seems to have been developed with little specific attention given to user interface issues. Several researchers have investigated integrating interface modeling techniques with UML. In UML, one models tasks using extended activity diagrams rather than by incorporating a completely new notation into UML. UMLi also addresses the relationships between use cases, tasks, and views, and thoroughly addresses the relationship between tasks and the data on which they act. UMLi is probably the most technically mature proposal for interface development in UML.     

Parallel processing applied to the planning of hydrothermal systems

The objective of the long-term operating planning problem is to determine the optimum strategy for the generation of electricity, aiming toward the minimization of total operating cost over the planning period. In a competitive electricity market, with the participation of a significant number of hydroplants, such as in Brazil, precision modelling for operating planning is required so that a better use of hydraulic resources can be obtained. We present a long-term operating planning model based on an individual power plant representation. In order to support the high computational burden, a suitable parallel processing algorithm is proposed.     

AC motor drive systems with a reduced-switch-count converter

This paper presents two reduced-switch-count AC drive systems. One of the configurations was conceived to operate with a two-phase motor and the other one with a three-phase motor. The drive systems provide both bidirectional power flow and power factor control. Pulsewidth modulation techniques for the converter control are discussed. Experimental results are presented.