Определение интервалов квазистационарности экономических систем

В работе рассмотрен вопрос определения оптимального интервала адаптации алгоритма динамического управления капиталом для нестационарного случая методами расчета показателя Херста и построения автокорреляционной функции для анализа временных рядов. Проведен анализ влияния выбора интервала адаптации на эффективность алгоритма. Из анализа полученных результатов следует, что метод расчета показателя Херста позволяет более эффективно, чем метод построения автокорреляционной функции, определить интервал стационарности модели функционирования экономической системы.Робота присвячена питанню визначення оптимального інтервалу адаптації алгоритму динамічного керування капіталом для нестаціонарного випадку за допомогою методів розрахунку показника Херста і побудови автокореляційної функції задля аналізу часових рядів. Проведено аналіз впливу вибору інтервалу адаптації на ефективність алгоритму. Порівняння результатів проведеного аналізу дозволяє стверджувати, що метод розрахунку показника Херста дозволяє більш ефективно, ніж метод побудови автокореляційної функції, визначити інтервал стаціонарності моделі функціонування економічної системи

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Correction to “Elastic wave speeds and moduli in polycrystalline ice Ih, sI methane hydrate, and sII methane-ethane hydrate”

Author Posting. © American Geophysical Union, 2009. This article is posted here by permission of American Geophysical Union for personal use, not for redistribution. The definitive version was published in Journal of Geophysical Research 114 (2009): B04299, doi:10.1029/2009JB006451

Benchmarking a first-principles thermal neutron scattering law for water ice with a diffusion experiment

The neutron scattering properties of water ice are of interest to the nuclear criticality safety community for the transport and storage of nuclear materials in cold environments. The common hexagonal phase ice Ih has locally ordered, but globally disordered, H2O molecular orientations. A 96-molecule supercell is modeled using the VASP ab initio density functional theory code and PHONON lattice dynamics code to calculate the phonon vibrational spectra of H and O in ice Ih. These spectra are supplied to the LEAPR module of the NJOY2012 nuclear data processing code to generate thermal neutron scattering laws for H and O in ice Ih in the incoherent approximation. The predicted vibrational spectra are optimized to be representative of the globally averaged ice Ih structure by comparing theoretically calculated and experimentally measured total cross sections and inelastic neutron scattering spectra. The resulting scattering kernel is then supplied to the MC21 Monte Carlo transport code to calculate time eigenvalues for the fundamental mode decay in ice cylinders at various temperatures. Results are compared to experimental flux decay measurements for a pulsed-neutron die-away diffusion benchmark

Additive Pressures of Elevated Sea Surface Temperatures and Herbicides on Symbiont-Bearing Foraminifera

Elevated ocean temperatures and agrochemical pollution individually threaten inshore coral reefs, but these pressures are likely to occur simultaneously. Experiments were conducted to evaluate the combined effects of elevated temperature and the photosystem II (PSII) inhibiting herbicide diuron on several types of symbiotic algae (diatom, dinoflagellate or rhodophyte) of benthic foraminifera in hospite. Diuron was shown to evoke a direct effect on photosynthetic efficiency (reduced effective PSII quantum yield ΔF/F′m), while elevated temperatures (>30°C, only 2°C above current average summer temperatures) were observed to impact photosynthesis more indirectly by causing reductions in maximum PSII quantum yield (Fv/Fm), interpreted as photodamage. Additionally, elevated temperatures were shown to cause bleaching through loss of chlorophyll a in foraminifera hosting either diatoms or dinoflagellates. A significant linear correlation was found between reduced Fv/Fm and loss of chlorophyll a. In most cases, symbionts within foraminifera proved more sensitive to thermal stress in the presence of diuron (≥1 µg L−1). The mixture toxicity model of Independent Action (IA) described the combined effects of temperature and diuron on the photosystem of species hosting diatoms or dinoflagellates convincingly and in agreement with probabilistic statistics, so a response additive joint action can be assumed. We thus demonstrate that improving water quality can improve resilience of symbiotic phototrophs to projected increases in ocean temperatures. As IA described the observed combined effects from elevated temperature and diuron stress it may therefore be employed for prediction of untested mixtures and for assessing the efficacy of management measures

Wear Resistant Materials Containing Recycled TiC

High mechanical loads, corrosion and abrasion decreases the life time of many tooling materialsused in the modern economy. One way to increase the wear resistance of tooling materials can befound in the addition of hard particles for example titanium carbide.Titanium carbide (TiC) has a high hardness, good corrosion resistance and a low density.Because of the aforementioned characteristics, TiC is used in Metal Matrix Composites (MMCs) toincrease the wear resistance of the material. However, TiC is a cost-intensive material, therebyproviding a strong incentive for recycling of TiC from worn parts or machining chips. Due to a newrecycling process it is possible to recycle TiC from worn parts or machining chips.In this study, the recycled TiC (RecyTiC) is investigated with regard to the morphology, particle size,chemical composition and phase analyses. In addition, the results were compared to industrialproduced TiC. In the next step, the RecyTiC was reused for the production of MMCs. The MMCsreinforced with RecyTiC was also characterized with respect to the microstructure and wearbehavior

Wear mechanisms of coated steels during press hardening

In this work microstructure of Al-base coated press-hardening steel 22MnB5, austenitized at920°C, was analyzed with respect to the phase formation at the steel/coating interface. Thereby,iron diffusion into the Al-base coating led to the formation of intermetallic AlxFey phases. Theintermetallic phases transformed to more Fe-rich phases with increasing dwell time. The coatingwas characterized by a layered structure of phases Al5Fe2 and AlFe after a dwell time of tAus = 6min (conventional press-hardening parameters). Cracks were formed in the coating due to the lowfracture toughness of the formed intermetallic phases mainly of type Al13Fe4, Al5Fe2 and AlFe.Forming and quenching in the press-hardening tools took place at a temperature range of approx.800°C to room temperature (RT). We found that the high hardness (520-1130 HV) and low fracturetoughness of the intermetallic phases led to strong wear of the press-hardening hot-work tool steelX38CrMoV5-3. The hardness of the intermetallic phases decreased in the direction of a highertemperature, leading to less abrasive wear at higher forming temperatures, thus wear by adhesionis more pronounced. Phase AlFe was found to mainly induce adhesive wear, while phase Al5Fe2led to strong abrasive wear due to the delamination of coating particles

New wear-resistant materials for mining applications

Economic and political driving forces are leading to an ambitious search for substitutes for fusedtungsten carbide (FTC) in ultra-high wear-resistant metal matrix composites (MMC), which areused for mining applications. In the presented paper, possible substitutes such as alumina (Al2O3),zirconia (ZrO2) and silicon carbide (SiC) are discussed. To enhance the wettability of oxides (e. g.Al2O3, ZrO2) by Fe-base melts or to counteract strong dissolution of metastable covalent bondedhard-particles (e.g. SiC) it is proposed to coat the particles with a thin titanium nitride (TiN) layer bymeans of chemical vapor deposition (CVD). For this reason a CVD-apparatus for particle coatingwas constructed and is shown in this paper. In addition, it is demonstrated that such a TiN coatingon the oxide particles can increase the wettability and therefore improve the embedding behaviorof the particles into a Fe-base matrix. In addition, it is shown that TiN coatings on covalent bondedhard-particle SiC can be used as a diffusion barrier coating, thus counteracting a dissolution of thehard-particles during processing by sintering techniques. However, due to the difference in linearthermal expansion coefficients the coating tends to delaminate, partially