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971.
Stock market forecasting has been a challenging financial research topic for decades. In the literature, there are numerous
results based on point methods. However, poor forecasting quality has been a continuous problem. Motivated by the fact that
financial data varies within intervals, we apply interval methods on a well known stock pricing model [3] to predict stock
market variability as intervals. Empirical results obtained with a few different approaches in this paper consistently suggest
that interval forecasts have better overall quality than traditional point forecasts. 相似文献
972.
G. Heiberg Ch -A. Gandin H. Goerner L. Arnberg 《Metallurgical and Materials Transactions A》2004,35(9):2981-2991
Hypoeutectic aluminum silicon alloys without and with additions of magnesium, copper, iron, and strontium have been cast in
a mold, giving directional solidification from a chill. Detailed temperature measurements have been carried out. Solidification
modeling based on front tracking of the microstructure growth fronts allowed identification of the time and temperature at
which the dendrite tips and the first eutectic pass the thermocouples. The undercooling, growth rate, and thermal gradients
at the dendritic and eutectic growth fronts were derived. The effect of varying thermal parameters and alloy compositions
on the microstructure was investigated. Compared to the binary alloy, a coarser eutectic was observed in the alloys with magnesium,
iron, and/or copper. The coarsening is explained as a result of the transition from a eutectic forming at one specific temperature,
to a eutectic forming over a temperature range. The former is likely to grow as a plane front, whereas the latter is likely
to form an interdendritic eutectic mushy zone. 相似文献
973.
Summary Well-defined water-soluble poly(styrenesulfonate)-b-poly(ethylene glycol)-b- poly(styrenesulfonate) (PSS-b-PEG-b-PSS) triblock
copolymers with narrow molecular weight distribution (1.29 < Mw/Mn < 1.36) were synthesized in aqueous solution at 70 oC via reversible addition-fragmentation chain transfer (RAFT) polymerization. The complex formed by the PSS-b-PEG-b-PSS triblock
copolymer coordinated with aluminum ion was investigated with turbidimetry, dynamic light scattering (DSL), zeta-potential,
and transmission electron microscopy (TEM). The aggregation formation was based on the neutralization of the SO3- groups in the PSS blocks with Al3+ ions. The appearance, size and stability of the PSS-b-PEG-b-PSS/Al3+ aggregates were controlled by varying the PSS block length and degree of neutralization (DN). At DN = 0.33, where the PSS-b-PEG-b-PSS
copolymer was completely neutralized with Al3+, the aggregate size increased with increasing PSS block length. The transition from the shrinking coil of small size to the
interchain aggregates of large size was found at DN of about 0.33. 相似文献
974.
Youdong Lin Joshua A. Enszer Mark A. Stadtherr 《Computers & Chemical Engineering》2008,32(8):1714-1725
The two-point boundary value problem (TPBVP) occurs in a wide variety of problems in engineering and science, including the modeling of chemical reactions, heat transfer, and diffusion, and the solution of optimal control problems. A TPBVP may have no solution, a single solution, or multiple solutions. A new strategy is presented for reliably locating all solutions of a TPBVP. The method determines narrow enclosures of all solutions that occur within a specified search interval. Key features of the method are the use of a new solver for parametric ODEs, which is used to produce guaranteed bounds on the solutions of nonlinear dynamic systems with interval-valued parameters and initial states, and the use of a constraint propagation strategy on the Taylor models used to represent the solutions of the dynamic system. Numerical experiments demonstrate the use and computational efficiency of the method. 相似文献
975.
Modellierung in der Lehre an Hochschulen: Thesen und Erfahrungen 总被引:1,自引:1,他引:0
Martin Glinz 《Informatik-Spektrum》2008,31(5):425-434
Zusammenfassung Nicht erst seit Modellierung zum Modewort geworden ist, ist Modellierung ein wichtiges Thema in der Informatikausbildung.
Dieser Beitrag beleuchtet in zw?lf Thesen das Warum, Was, Wie viel, Wo, Wann und Wie von Modellierung in der Lehre im Rahmen
informatikbezogener Studieng?nge. Die Thesen basieren auf der Erfahrung des Verfassers mit einer seit über zehn Jahren gehaltenen
Modellierungsvorlesung an der Universit?t Zürich sowie dem Gedankenaustausch mit anderen Hochschullehrerinnen und -lehrern
im Rahmen der GI-Workshopreihe ,,Modellierung“. Zus?tzlich liefert eine Befragung von Absolventinnen und Absolventen an der
Universit?t Zürich empirische Evidenz für eine Reihe der Thesen. 相似文献
976.
977.
This paper will describe the solid oxide membrane (SOM) process as it applies to the energy-efficient and environmentally
sound production of magnesium from magnesium oxide. Also, it will describe the challenges encountered while using this process
for the production of transition metals like titanium from its higher oxides. Finally, a novel magnesiothermic SOM process
will be proposed that can enable production of transition metals from its higher oxides. 相似文献
978.
Do Hoon Kim Umme Farva Woo Sik Jung Eui Jung Kim Chinho Park 《Korean Journal of Chemical Engineering》2008,25(5):1184-1189
This paper reports an alternative method for the growth of GaN epitaxial layer on (0001) Al2O3 substrate by hot-wall vapor phase epitaxy technique. Tris (N,N-dimethyldithiocarbamato)-gallium (III), Ga(mDTC)3 was introduced as a precursor material for the seed layer formation in the growth of GaN. Optimal growth conditions with
seed layers formed by the Ga(mDTC)3 concentration of 0.047 mol/L were identified: Growth temperature was found to be 850 °C, and optimal distance between the
reactant outlet and substrate was determined to be 12.5 cm. Characterization results showed that this growth method produce
high-crystallinity GaN epitaxial layers at a relatively lower growth temperature compared to the existing growth techniques
and simplify the growth process. 相似文献
979.
The rate of filtration and the water content of cake are influenced by the existence of a dense skin in a highly compressible
cake. The phenomenon of the dense skin has been rarely studied, and its existence has not been verified experimentally. In
this study, the porosity variation in a very compressible cake is measured by using a new experimental apparatus, and with
this the existence of dense skin has been established experimentally. ‘Unified theory on solid-liquid separation’, a recently
developed theory, is utilized for calculating the porosity variation in a very compressible cake. 相似文献
980.