Accurate harmonic source identification using S-transform

This paper introduces the accurate identification of harmonic sources in the power distribution system using time-frequency distribution (TFD) analysis, which is S-transform. The S-transform is a very applicable method to represent signals parameters in time-frequency representation (TFR) such as TFR impedance (ZTFR) and the main advantages of S-transform it can provide better frequency resolution for low frequency components and also offers better time resolution for high-frequency components. The identification of multiple harmonic sources are based on the significant relationship of spectral impedances (ZS) that extracted from the ZTFR, consist of the fundamental impedance (Z1) and harmonic impedance (Zh). To verify the accuracy of the proposed method, MATLAB simulations carried out several unique cases on IEEE 4-bus test feeder cases. It is proven that the proposed method is superior, with 100% correct identification of harmonic source location. It is proven that the method is accurate, fast and cost-efficient to localize harmonic sources in the power distribution system

Muon and neutrino results from KGF experiment at a depth of 7000 hg/square cm

The KGF nucleon decay experiment at a depth of 7000 hg/sq cm has provided valuable data on muons and neutrinos. The detector comprised of 34 crossed layers of proportional counters (cross section 10 x 10 sq cm; lengths 4m and 6m) sandwiched between 1.2 cm thick iron plates can record tracks of charged particles to an accuracy of 1 deg from tracks that traverse the whole of the detector. A special two-fold coincidence system enables the detector to record charged particles that enter at very large zenith angles. In a live time of 3.6 years about 2600 events have been recorded. These events include atmospheric muons, neutrino induced muons from rock, stopping muons, showers and events which have their production vertex inside the detectors. The results on atmospheric muons and neutrino events are presented

Preparation and evaluation of properties of cast metallic foams with regular inner structure

Lately we encounter still more new applications of metallic foams, as well as possible methods of their manufacture. These metallic materials have specific properties, such as large rigidity at low density, in some cases high thermal conductivity, capability to absorb energy, etc. The work is focused on the preparation of these materials using conventional casting technology, which ensures rapid and economically feasible method for production of shaped components. In the experimental part we studied conditions of casting of metallic foams with a regular structure made of ferrous and non-ferrous alloys. For thus obtained castings we evaluated the achieved microstructure and mechanical properties, which determine the possible use of these materials. The samples were subjected to compression tests, by which we investigated deformation behaviour of selected materials and determined the value of energy absorption.Web of Science6231646164

Izdelava poroznih kovinskih ulitkov

The article deals with the foundry methods of manufacturing porous metal; it is focused on the materials with a regular arrangement of internal cells. Currently. there are many fields dealing with the problem of porous metals by either optimizing the already known technologies, developing new ones or using porous metals. The production of a porous metal with a regular structure of cells and the possibility of its functional usage are the main subjects of this article. Due to their shapes, sizes and distribution of internal pores, cast porous metals exhibit various properties including reduced weight, sufficient strength, an ability to absorb impact energy, a possibility to conduct heat, etc., that allow a wide range of applications in the areas such as construction. transport or power engineering.Članek opisuje livarske metode izdelave poroznih kovin. Osredotoča se na materiale s pravilno urejenostjo notranjih celic. Trenutno se na mnogih področjih ukvarjajo s problemi poroznih kovin, bodisi z optimizacijo že znanih tehnologij, razvojem novih, ali njihovo uporabo. Glavni predmet članka je izdelava poroznih kovin s pravilno strukturo celic in možnostjo njihove uporabe. Porozni ulitki imajo zaradi svoje značilne oblike, velikosti in porazdelitve por različne specifične lastnosti, vključno z manjšo maso, zadovoljivo trdnostjo, sposobnostjo absorpcije udarne energije, prevajanja toplote itd. Vse to omogoča njihovo uporabo na različnih področjih, kot so konstrukcije, transport, inženiring prenosa energije in moči.Web of Science53114113

Comparative study of analytical formulae for the fire resistance of steel beam-columns

peer reviewedThis paper investigates the difference between the buckling formulae published in the Eurocode 3 part 1.2 and the recommendations made in the final report of the Buckling Curves in Case of Fire (BCCF) research project. This study compares the critical temperatures obtained with both formulations to assess the impact on the fire endurance of steel columns subjected to axial compression and bending. An extensive comparison of the ultimate temperatures obtained with both formulations has been performed (382 profiles, buckling about the strong and weak axis, 12 column lengths, 6 M/N ratios and uniform and triangular bending moment distributions). Failure temperatures between 400°C and 860°C have been considered. The formulations are also compared with Finite Elements (F.E.) calculations performed for a S235 HEA 200 at 600ºC. This analysis shows that for buckling about the strong axis the BCCF method is better than the EC3 but for buckling about the weak axis the EC3 predicts failure temperatures closer to the F.E. model than the BCCF formulation. Finally, the ultimate temperatures predicted by the two formulations have also been compared with experimental results from the database SCOFIDAT. This comparison shows that there is no major difference between the two formulations for small and large bending moments. This study concludes that the EC3 and BCCF formulations are generally equivalent and that either formulation can be used

Atomic data from the Iron Project VII. Radiative dipole transition probabilities for Fe II

Relevant data is available at: http://www.astronomy.ohio-state.edu/~nahar/nahar_radiativeatomicdata/index.htmlOscillator strengths, line strengths and Einstein A-coefficients are obtained for a large number of dipole allowed (ΔS = 0) fine structure transitions in Fe II. Spectroscopic energies of the observed fine structure levels are employed in the transformation from LS coupled multiplet strengths to the individual fine structure lines. The transition probabilities are thus significantly improved in accuracy over those obtained with calculated energies. As part of the second phase of the Iron Project the present work is part of the effort to improve the accuracy and the utility of the Opacity Project data. The calculations correspond to a 83-state close coupling calculations for Fe II described by Nahar & Pradhan (1994). Comparison of present oscillator strengths and lifetimes is made with experimental values, and with those calculated by Kurucz; the present values show an overall better agreement with the experimental data. Radiative data is obtained for 21,589 dipole allowed fine structure transitions in Fe II.The work was supported by NASA (NAGW-3315) under the Long Term Space Astrophysics (LTSA) program and by a fellowship awarded by the College of Mathematical and Physical Sciences at the Ohio State University

An adaptation of the objective cyclone detection algorithm to a Medicane event

Póster elaborado para la European Conference on Severe Storms celebrada en Palma de Mallorca del 3 al 7 de octubre de 2011Trabajo parcialmente patrocinado por: MEDICANES/CGL200801271 projec

Study on Nano-Engineering of High-Capacity Anode Materials for High-Power Energy Storage System

Department of Energy Engineering(Battery Science and Technology)Nano-engineering and nanotechnology issue in various industry fields such as semiconductor, chemistry, energy solution, material science, and medicine. A definition of nanotechnology includes quantum mechanics, molecular chemistry, biology, and atomic level behaviors. Also, nanostructured materials (e.g., nanoparticle, nanorod, nanotube, nanowire, hollow, and yolk-shell) improve properties of materials for performance enhancement of devices. These nanomaterials have been synthesized using bottom-up and top-down approaches. In the early 2000s, many researchers garnered information and experiences about the nanotechnology that led to innovation and progress in industry and academy of science. As a result, many electronic devices were developed for a convenience of our life. Especially, significant advances of devices lead to the development of another new device with more improved performances including faster processing ability, longer working time, light weight, and easy transportation. In this regard, gradual development of energy storage system must need to satisfy this demand for new electric device (e.g. electric vehicle (EV), energy storage system (ESS), even drone) As one of the powerful energy storage systems, lithium-ion batteries (LIBs) are critically important to operate portable electronic devices. However, they cannot meet requirements for more advanced applications, like electric vehicles and energy storage systems due to limitations of conventional cathode/anode materials in high power and high energy density. To overcome these limitations, several strategies have been developed, including nanostructured design of electrode materials, coating of active materials with electrically conductive layers, and control of electrode architectures. Herein, we study on a simple, cost effective and unique synthesis method of various shaped functional materials by nano-engineering process in an each chapter. Also, we conduct research about a mechanism of reaction, key for synthesizing good materials, change of chemical reaction in experiment. So, the developed materials appear outstanding properties such as structural stability, chemical stability in electrochemical test, and mainly used energy storage system like LIBs. In chapter III, we demonstrate a simple route for fabricating trench-type copper patterns by combining a photo-lithography with a wet etching process. Nanostructured CuO was grown on the patterned Cu current collectors via a simple solution immersion process. And silicon nanoparticles were filled into the patterned Cu current collectors. The strongly immobilized CuO on the patterned Cu exhibited high electrochemical performance, including a high reversible capacity and a high rate capability. In chapter IV, we demonstrate multi-scale patterned electrodes that provide surface-area enhancement and strong adhesion between electrode materials and current collector. The combination of multi-scale structured current collector and active materials (cathode and anode) enables us to make high-performance Li-ion batteries (LIBs). When LiFePO4 (LFP) cathode and Li4Ti5O12 (LTO) anode materials are combined with patterned current collectors, their electrochemical performances are significantly improved, including a high rate capability (LFP : 100 mAhg-1, LTO : 60 mAhg-1 at 100 C rate) and highly stable cycling. Moreover, we successfully fabricate full cell system consisting of patterned LFP cathode and patterned LTO anode, exhibiting high-power battery performances. We extend this idea to Si anode that exhibits a large volume change during lithiation/delithiation process. The patterned Si electrodes show significantly enhanced electrochemical performances, including a high specific capacity (825 mAhg-1) at high rate of 5 C and a stable cycling retention. In chapter V, Chemical reduction of micro-assembled CNT@TiO2@SiO2 leads to the formation of titanium silicide-containing Si nanotubular structures. The Si-based nanotube anodes exhibit a high capacity (>1850 mAh g-1) and an excellent cycling performance (capacity retention of >99% after 80 cycles). In chapter VI, we revisit the metallothermic reduction process to synthesize shape-preserving macro-/nano-porous Si particles via aluminothermic and subsequent magnesiotheric reaction of porous silica particles. This process enables us to control the specific capacity and volume expansion of shape-preserving porous Si-based anodes. Two step metallothermic reactions have several advantages including a successful synthesis of shape-preserving Si particles, tunable specific capacity of as-synthesized Si anode, accommodation of a large volume change of Si by porous nature and alumina layers, and a scalable synthesis (hundreds of gram per batch). An optimized macroporous Si/Al2O3 composite anode exhibits a reversible capacity of ~1500 mAh g-1 after 100 cycles at 0.2 C and a volume expansion of ~34% even after 100 cycles. In chapter VII, we report a redox-transmetalation reaction-based route for the large-scale synthesis of mesoporous germanium particles from germanium oxide at temperatures of 420 ~ 600 oC. We could confirm that a unique redox-transmetalation reaction occurs between Zn0 and Ge4+ at approximately 420 oC using temperature-dependent in situ X-ray absorption fine structure analysis. This reaction has several advantages, which include (i) the successful synthesis of germanium particles at a low temperature (∼450 oC), (ii) the accommodation of large volume changes, owing to the mesoporous structure of the germanium particles, and (iii) the ability to synthesize the particles in a cost-effective and scalable manner, as inexpensive metal oxides are used as the starting materials. The optimized mesoporous germanium anode exhibits a reversible capacity of∼1400 mA h g-1 after 300 cycles at a rate of 0.5 C (corresponding to the capacity retention of 99.5%), as well as stable cycling in a full cell containing a LiCoO2 cathode with a high energy density. In chapter VIII, we report a unique synthesis of redox-responsive assembled carbon-sheathed germanium coaxial nanowire heterostructures without a need of metal catalyst. In our approach, germanium nanowires are grown by reduction of germanium oxide particles and subsequent self-catalytic growth mechanism during thermal decomposition of natural gas, and simultaneously, carbon sheath layers are uniformly coated on the germanium nanowire surface. This process is a simple (one-step process), reproducible, easy size-controllable and cost-effective (mass production) process which total mass of metal oxides can be transformed into nanowires. Furthermore, the germanium nanowires exhibit outstanding electrochemical performance including capacity retention of ~96% after 1000 cycles at 1C rate as lithium-ion battery anode.ope

Exploiting graphic processing units parallelism to improve intelligent data acquisition system performance in JET's correlation reflectometer

The performance of intelligent data acquisition systems relies heavily on their processing capabilities and local bus bandwidth, especially in applications with high sample rates or high number of channels. This is the case of the self adaptive sampling rate data acquisition system installed as a pilot experiment in KG8B correlation reflectometer at JET. The system, which is based on the ITMS platform, continuously adapts the sample rate during the acquisition depending on the signal bandwidth. In order to do so it must transfer acquired data to a memory buffer in the host processor and run heavy computational algorithms for each data block. The processing capabilities of the host CPU and the bandwidth of the PXI bus limit the maximum sample rate that can be achieved, therefore limiting the maximum bandwidth of the phenomena that can be studied. Graphic processing units (GPU) are becoming an alternative for speeding up compute intensive kernels of scientific, imaging and simulation applications. However, integrating this technology into data acquisition systems is not a straight forward step, not to mention exploiting their parallelism efficiently. This paper discusses the use of GPUs with new high speed data bus interfaces to improve the performance of the self adaptive sampling rate data acquisition system installed on JET. Integration issues are discussed and performance evaluations are presente