415 research outputs found

    Multi-Renewable Energy Agent Based Control for Economic Dispatch and Frequency Regulation of Autonomous Renewable Grid

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    This paper addresses frequency regulation and the economic dispatch problem of an Autonomous Renewable Grid (ARG) primarily composed of Multi Renewable Energy Agents (MRAs), interfaced through DC/AC inverters. A large number of MRAs that have an inherent fluctuating nature and frequent disturbances in inter-connected systems require fast and robust control to stabilize the frequency and to maintain cost-effective operation of an ARG. To address the above control challenges, Distributed Averaging Integrator (DAI) based control schemes were proposed in various research works. The main flaws of such schemes were slow convergence, sluggish response, poor transient performance and a difficult selection of an appropriate damping-factor. The proposed approach introduces a Distributed Sliding Mode Control (DSMC) based solution for fast convergence and improved transient response. The DSMC control is based on a distributed sliding surface, designed using a combination of local information and information from neighbouring MRAs. The control is implemented locally at each MRA and achieves the asymptotic global consensus. Finally, the convergence of the proposed control scheme is proved mathematically, and performance is validated using the MRA system which has been implemented using MATLAB/Simulink. The results of the proposed control technique are compared with conventional DAI control, which shows that the proposed scheme outperforms the conventional scheme in terms of fast convergence, considering renewable resources as distributed generation

    Environmental and Economically Conscious Magnesium Production: Solar Thermal Electrolytic Production of Mg from MgO

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    One method to improve the fuel efficiency of American made vehicles is to reduce vehicle weight by substituting steel components with lighter magnesium (Mg) components. Unfortunately, U.S. produced Mg currently costs approximately 3.31perkg,overseventimesthepriceofsteel.Furthermore,Mgproductionhasastaggeringenergyandenvironmentalimpact,consumingupto102kWhr/kgMgofenergyandproducing36kgofCO2/kgMg.ToreducetheoverwhelmingeconomicandenvironmentalimpactofMg,anewsolarthermalelectrolyticprocesshasbeendevelopedfortheproductionofMgfromMgO.Throughthisprocess,liquidMgisproducedinasolarreactorutilizingboththermalandelectricalenergy.Atelevatedtemperatures,thethermalenergyfromconcentratedsunlightreducestherequiredelectricalworkbelowthatofcurrentprocesses.Thereactorabsorbstheconcentratedsolarenergy,heatingamoltensaltMgOmixtureinanelectrolyticcell.Electricityisthensuppliedtothecell,producingliquidMgandCO.ItisestimatedthatthisnewprocesswillproduceMgat3.31 per kg, over seven times the price of steel. Furthermore, Mg production has a staggering energy and environmental impact, consuming up to 102 kW-hr/kg-Mg of energy and producing 36 kg of CO2/kg-Mg. To reduce the overwhelming economic and environmental impact of Mg, a new solar thermal electrolytic process has been developed for the production of Mg from MgO. Through this process, liquid Mg is produced in a solar reactor utilizing both thermal and electrical energy. At elevated temperatures, the thermal energy from concentrated sunlight reduces the required electrical work below that of current processes. The reactor absorbs the concentrated solar energy, heating a molten salt-MgO mixture in an electrolytic cell. Electricity is then supplied to the cell, producing liquid Mg and CO. It is estimated that this new process will produce Mg at 2.50 per kg, with costs decreasing as the technology is further developed. This process requires approximately 8.3 kW-hr/kg-Mg of energy and produces only 3.44 kg of CO2/kg-Mg, large reductions compared to current processes

    Electronic detection of charged particle effects in a Penning trap

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    We present a thorough analysis of the electronic detection of charged particles, confined in a Penning trap, via image charges induced in the trap electrodes. Trapping of charged particles in an electrode structure leads to frequency shifts, which are due to image charge and space charge effects. These effects are of importance for Penning trap experiments which involve high charge densities or require high precision in the motional frequencies. Our analysis of image charges shows that only (higher order) odd powers of the particle displacement lead to induced charge differences, giving rise to a signal. This implies that, besides the centre-of-mass frequency of a trapped particle cloud, also higher order individual particle frequencies induce a signal, which can be picked up by an electronic detection circuit attached to the trap electrodes. We also derive analytic expressions for the image charge and space charge induced frequency shifts and perform simulations of space charge effects. In relation to this, we discuss the consequences of the shifted particle frequencies for resistive cooling of the particle motion.Comment: 16 pages, 4 figure

    European integration assessed in the light of the 'rules vs. standards debate'

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    The interplay of various legal systems in the European Union (EU) has long triggered a debate on the tension between uniformity and diversity of Member States' (MS) laws. This debate takes place among European legal scholars and is also paralleled by economic scholars, e.g. in the ambit of the 'theory of federalism'. This paper takes an innovative perspective on the discrepancy between 'centralized' and 'decentralized' law-making in the EU by assessing it with the help of the rules versus standards debate. When should the EU legislator grant the national legislator leeway in the formulation of new laws and when should all be fixed ex ante at European level? The literature on the 'optimal shape of legal norms' shall be revisited in the light of law-making in the EU, centrally dealing with the question how much discretion shall be given to the national legislator; and under which circumstances. This paper enhances the established decisive factors for the choice of a rule or a standard in a national setting (complexity, volatility, judges' specialization and frequency of application) by two new crucial factors (switching costs and the benefit of uniformity in terms of information costs) in order to assess law-making policies at EU level

    Genetic risk variants associated with in situ breast cancer

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    INTRODUCTION: Breast cancer in situ (BCIS) diagnoses, a precursor lesion for invasive breast cancer, comprise about 20 % of all breast cancers (BC) in countries with screening programs. Family history of BC is considered one of the strongest risk factors for BCIS. METHODS: To evaluate the association of BC susceptibility loci with BCIS risk, we genotyped 39 single nucleotide polymorphisms (SNPs), associated with risk of invasive BC, in 1317 BCIS cases, 10,645 invasive BC cases, and 14,006 healthy controls in the National Cancer Institute's Breast and Prostate Cancer Cohort Consortium (BPC3). Using unconditional logistic regression models adjusted for age and study, we estimated the association of SNPs with BCIS using two different comparison groups: healthy controls and invasive BC subjects to investigate whether BCIS and BC share a common genetic profile. RESULTS: We found that five SNPs (CDKN2BAS-rs1011970, FGFR2-rs3750817, FGFR2-rs2981582, TNRC9-rs3803662, 5p12-rs10941679) were significantly associated with BCIS risk (P value adjusted for multiple comparisons <0.0016). Comparing invasive BC and BCIS, the largest difference was for CDKN2BAS-rs1011970, which showed a positive association with BCIS (OR = 1.24, 95 % CI: 1.11-1.38, P = 1.27 x 10(-4)) and no association with invasive BC (OR = 1.03, 95 % CI: 0.99-1.07, P = 0.06), with a P value for case-case comparison of 0.006. Subgroup analyses investigating associations with ductal carcinoma in situ (DCIS) found similar associations, albeit less significant (OR = 1.25, 95 % CI: 1.09-1.42, P = 1.07 x 10(-3)). Additional risk analyses showed significant associations with invasive disease at the 0.05 level for 28 of the alleles and the OR estimates were consistent with those reported by other studies. CONCLUSIONS: Our study adds to the knowledge that several of the known BC susceptibility loci are risk factors for both BCIS and invasive BC, with the possible exception of rs1011970, a putatively functional SNP situated in the CDKN2BAS gene that may be a specific BCIS susceptibility locus
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