Comparison between unipolar and bipolar single phase grid-connected inverters for PV applications

An inverter is essential for the interfacing of photovoltaic panels with the AC network. There are many possible inverter topologies and inverter switching schemes and each one will have its own relative advantages and disadvantages. Efficiency and output current distortion are two important factors governing the choice of inverter system. In this paper, it is argued that current controlled inverters offer significant advantages from the point of view of minimisation of current distortion. Two inverter switching strategies are explored in detail. These are the unipolar current controlled inverter and the bipolar current controlled inverter. With respect to low frequency distortion, previously published works provide theoretical arguments in favour of bipolar switching. On the other hand it has also been argued that the unipolar switched inverter offers reduced switching losses and generates less EMI. On efficiency grounds, it appears that the unipolar switched inverter has an advantage. However, experimental results presented in this paper show that the level of low frequency current distortion in the unipolar switched inverter is such that it can only comply with Australian Standard 4777.2 above a minimum output current. On the other hand it is shown that at the same current levels bipolar switching results in reduced low frequency harmonics

3D IC optimal layout design. A parallel and distributed topological approach

The task of 3D ICs layout design involves the assembly of millions of components taking into account many different requirements and constraints such as topological, wiring or manufacturability ones. It is a NP-hard problem that requires new non-deterministic and heuristic algorithms. Considering the time complexity, the commonly applied Fiduccia-Mattheyses partitioning algorithm is superior to any other local search method. Nevertheless, it can often miss to reach a quasi-optimal solution in 3D spaces. The presented approach uses an original 3D layout graph partitioning heuristics implemented with use of the extremal optimization method. The goal is to minimize the total wire-length in the chip. In order to improve the time complexity a parallel and distributed Java implementation is applied. Inside one Java Virtual Machine separate optimization algorithms are executed by independent threads. The work may also be shared among different machines by means of The Java Remote Method Invocation system.Comment: 26 pages, 9 figure

Demonstrating the antinociceptive action of renin-angiotensin system modulators in mice

Research done in the present study belongs to a wider area of experimental determinations on nociception models, when using laboratory animals. Their aim is to determine the ED50 value (Efficient dose 50) in conditions of inflammatory (chemical stimulus) and non-inflammatory (thermic stimulus) antinociception of some renin-angiotensin system modulators: captopril, ramipril, candesartan. The experimental determinations were realized accordingly to bioethical regulations concerning laboratory animals. The study has used Swiss mice, weighing between 20-30g, being held in constant temperature (21°C ± 2°C) and a dark / light cycle of 12 hours (7.00 AM / 7.00 PM). The researched substances are administered as CMC-Na 0.1% suspensions in geometrical progression doses. The following nociception models have been used: abdominal constrictive response test, hot plate test, formalin test. The abdominal constrictive response test has been evaluated as quantal, the hot plate test and the formalin test have been interpreted as gradual. The regression line, the correlation coefficient and the interval of trust for each substance and studied model have been analyzed. The obtained ED50 values are compared to each other to evaluate the potency of the substances for each nociception model. The obtained data is used for realizing fixed-ratio antinociceptive combinations

Enforcing Multifunctionality: A Pressure-Induced Spin-Crossover Photomagnet

Photomagnetic compounds are usually achieved by assembling preorganized individual molecules into rationally designed molecular architectures via the bottom-up approach. Here we show that a magnetic response to light can also be enforced in a nonphotomagnetic compound by applying mechanical stress. The nonphotomagnetic cyano-bridged Fe^II–Nb^IV coordination polymer {[Fe^II(pyrazole)₄]₂[Nb^IV(CN)₈]·4H₂O}_<i>n</i> (<b>FeNb</b>) has been subjected to high-pressure structural, magnetic and photomagnetic studies at low temperature, which revealed a wide spectrum of pressure-related functionalities including the light-induced magnetization. The multifunctionality of <b>FeNb</b> is compared with a simple structural and magnetic pressure response of its analog {[Mn^II(pyrazole)₄]₂[Nb^IV(CN)₈]·4H₂O}_<i>n</i> (<b>MnNb</b>). The <b>FeNb</b> coordination polymer is the first pressure-induced spin-crossover photomagnet

STUDY REGARDING THE ATTRACTIVENESS OF TRACK AND FIELD THEMED LESSONS

During 1989-2012, the Physical Education activity in Romania has registered a visible downfall, recording both a drop in the time given to exercise, and Physical Education having a less than optimal number of lessons in the curriculum. Thus, every person involved in Physical Education in schools are currently forced to find concrete solutions to re-launch it. In this context, the Physical Education teacher, together with the decision-makers, have the duty to find and implement those methods and means of teaching that would meet the quality demands of a modern, European education, in compliance with the "White Book" and the recommendations of the Council of Europe. The Physical Education lessons with track and field themes represent a small portion of the Physical Education in schools, but we think this theme of research is very current, considering the previously mentioned aspects. The study, conducted over the academic year of 2011-2012, in 10 Bacau County schools, has highlighted a series of negative aspects in the teaching process, caused, on one side, by a faulty communication between pupil - teacher - parent - principal, and on the other side, by the application of a schematic and unattractive methodology of conducting the track and field themed lessons, doubled by a lack of interest of the teachers to continuously perfect themselves, a disinterest caused by the marginalization of this activity by the state governmental structures, or even by some school principals by not giving the maximum number of hours foreseen in the curriculum, or by not introducing Physical Education on the optional classes list, in favor of other disciplines

Arduino to the Rescue: Swaying Undecided Freshmen Engineering Students to Electrical and Computer Engineering

We describe the implementation and outcomes of the Arduino based electrical engineering and computer engineering (EECE) module, which is integrated within the Engineering Discovery 1 course taken by all computer, electrical and mechanical engineering freshmen at Marquette University. Because a significant number of students enrolled in this course have not yet chosen a specific engineering major, one of the goals of the EECE module is to provide experiential learning activities designed to be engaging and fun while presenting important electrical and computer engineering concepts to attract and motivate undecided students to select electrical or computer engineering as their major. In addition, these activities are intended to retain those students who have already declared an electrical or computer engineering major as well as to give them a taste what\u27s to come. Data and student feedback indicate that the new EECE module was received very positively as it stirred increased interest into EECE and motivated students to be proactive. In the future, we plan to double the duration of the module and thus expand it to cover an even larger spectrum of EECE topics

M.C. Gibb and his wife, New South Wales, ca. 1930s, 1 [picture].

Title devised from accompanying information where available.; Part of the: Fairfax archive of glass plate negatives.; Fairfax number: 4566.; Possibly Reverend M.C. Gibb of Broken Hill; Also available online at: http://nla.gov.au/nla.pic-vn6247614; Acquired from Fairfax Media, 2012