779 research outputs found

    Electronic, magnetic and transport properties of Fe intercalated 2H-TaS2_2 studied by means of the KKR-CPA method

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    The electronic, magnetic and transport properties of Fe intercalated 2H-TaS2_2 have been investigated by means of the Korringa-Kohn-Rostoker (KKR) method. The non-stoichiometry and disorder in the system has been accounted for using the Coherent Potential Approximation (CPA) alloy theory. A pronounced influence of disorder on the spin magnetic moment has been found for the ferro-magnetically ordered material. The same applies for the spin-orbit induced orbital magnetic moment and magneto-crystalline anisotropy energy. The temperature-dependence of the resistivity of disordered 2H-Fe0.28_{0.28}TaS2_2 investigated on the basis of the Kubo-St\v{r}eda formalism in combination with the alloy analogy model has been found in very satisfying agreement with experimental data. This also holds for the temperature dependent anomalous Hall resistivity ρxy(T) \rho_{\rm xy}(T) . The role of thermally induced lattice vibrations and spin fluctuations for the transport properties is discussed in detail

    Impact Evaluation of Improved Cooking Stoves in Burkina Faso. IOB Evaluation No. 388.

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    Mechanochemical Synthesis and Magnetic Characterization of Nanosized Cubic Spinel FeCr₂S₄ Particles

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    Nanosized samples of the cubic thiospinel FeCr2S4 were synthesized by ball milling of FeS and Cr2S3 precursors followed by a distinct temperature treatment between 500 and 800 °C. Depending on the applied temperature, volume weighted mean (Lvol) particle sizes of 56 nm (500 °C), 86 nm (600 °C), and 123 nm (800 °C) were obtained. All samples show a transition into the ferrimagnetic state at a Curie temperature TC of ∼ 167 K only slightly depending on the annealing temperature. Above TC, ferromagnetic spin clusters survive and Curie–Weiss behavior is observed only at T ≫ TC, with T depending on the heat treatments and the external magnetic field applied. Zero-field-cooled and field-cooled magnetic susceptibilities diverge significantly below TC in contrast to what is observed for conventionally solid-state-prepared polycrystalline samples. In the low-temperature region, all samples show a transition into the orbital ordered state at about 9 K, which is more pronounced for the samples heated to higher temperatures. This observation is a clear indication that the cation disorder is very low because a pronounced disorder would suppress this magnetic transition. The unusual magnetic properties of the samples at low temperatures and different external magnetic fields can be clearly related to different factors like structural microstrain and magnetocrystalline anisotropy

    The host of the Type I SLSN 2017egm: A young, sub-solar metallicity environment in a massive spiral galaxy

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    Here we present an integral-field study of the massive, high-metallicity spiral NGC 3191, the host of SN 2017egm, the closest SLSN Type I to date. We use data from PMAS/CAHA and the public MaNGA survey to shed light on the properties of the SLSN site and the origin of star-formation in this non-starburst spiral galaxy. We map the physical properties different \ion{H}{II} regions throughout the galaxy and characterize their stellar populations using the STARLIGHT fitting code. Kinematical information allows to study a possible interaction with its neighbouring galaxy as the origin of recent star formation activity which could have caused the SLSN. NGC 3191 shows intense star-formation in the western part with three large SF regions of low metallicity. The central regions of the host have a higher metallicity, lower specific star-formation rate and lower ionization. Modeling the stellar populations gives a different picture: The SLSN region has two dominant stellar populations with different ages, the youngest one with an age of 2-10 Myr and lower metallicity, likely the population from which the SN progenitor originated. Emission line kinematics of NGC 3191 show indications of interaction with its neighbour MCG+08-19-017 at \sim45 kpc, which might be responsible for the recent starburst. In fact, this galaxy pair has in total hosted 4 SNe, 1988B (Type Ia), SN 2003ds (Type Ic in MCG+08-19-017), PTF10bgl (SLSN-Type II) and 2017egm, underlying the enhanced SF in both galaxies due to interaction. Our study shows that one has to be careful interpreting global host and even gas properties without looking at the stellar population history of the region. SLSNe seem to still be consistent with massive stars (>> 20 M_\odot) requiring low (<0.6Z< 0.6Z_{\odot}) metallicity and those environments can also occur in massive, late-type galaxies but not necessarily starbursts.Comment: Accepted for publication in A&A, 13 pages, 11 figures, 7 tables. Abstract has been reduced to match arXiv form requirement

    The provision of solar energy to rural households through a fee-for-service system

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    This baseline report is part of an evaluation commissioned by the Policy and Operations Evaluation Department (IOB) of the Netherlands Ministry of Foreign Affairs. It belongs to a series of impact evaluations of renewable energy and development programmes supported by the Netherlands, with a focus on the medium and long term effects of these programmes on end-users or final beneficiaries. A characteristic of these studies is the use of mixed methods, being quantitative research techniques, in combination with qualitative techniques, to get insight in the magnitude of effects. The purpose of the impact evaluations is to account for assistance provided and to draw lessons from the findings for improvement of policy and policy implementation. The results of these impact evaluations will be input to a policy evaluation of the “Promoting Renewable Energy Programme” (PREP) to be concluded in 2014

    Ветро-дизельная система электроснабжения поселка

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    Работа направлена на решение проблемы электроснабжения отдаленных районов. Объектом исследования является гибридная ветро-дизельная система электроснабжения, находящаяся на юге Кемеровской области на высоте 1260 метров. В процессе исследования проводились анализ материалов в открытом доступе, запросы производителям, технико-экономическое сравнение. В результате исследования определен наиболее выгодный вариант. Область применения: энергодефицитные отдаленные районы, наиболее перспективные с точки зрения малой энергетики и обладающие потенциалом ВИЭ, в частности ветропотенциалом. Экономическая эффективность проекта заключается в снижении стоимости электроэнергии в шесть раз.Die Arbeit zielt auf die Losung der Energieversorgung von entlegenen Gebieten. Gegenstand der Studie ist ein Hybrid wind-Diesel-System der Elektrizitatsversorgung, das sich im Suden vom Gebiet Kemerowo auf einer Hohe von 1260 Meter. In der Studie wurden fur die Analyse von Materialien in der offentlichkeit, Anfragen von Herstellern, die technisch-wirtschaftlichen Vergleich. Die Studie ermittelt die Gunstigste Variante. Einsatzbereich: energiedefizite Randgebiete, die vielversprechendsten in Bezug auf niedrige Energie und mit dem Potential der erneuerbaren Energien, insbesondere Energiepotenzial. Die Wirtschaftseffektivitat des Projektes besteht in der Reduzierung der Kosten der Stromerzeugung in sechs mal
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