Exponential Stability of Interval Dynamical Systems with Quadratic Nonlinearity

This article proposes an approach for investigating the exponential stability of a nonlinear interval dynamical system with the nonlinearity of a quadratic type on the basis of the Lyapunov’s direct method. It also constructs an inner estimate of the attraction domain to the origin for the system under consideration.     

An Application of Interval Methods to Stock Market Forecasting

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.     

Synthesis and aggregate formation of poly(styrenesulfonate)-b-poly(ethylene glycol)-b-poly(styrenesulfonate) triblock copolymers in aqueous solution induced by binding with aluminum ions

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 < M_w/M_n < 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.     

Modellierung in der Lehre an Hochschulen: Thesen und Erfahrungen

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.     

A lower carbon footprint process for production of metals from their oxide sources

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.     

Epitaxial growth of GaN on (0001) Al<Subscript>2</Subscript>O<Subscript>3</Subscript> via solution-cast seed layer formation process using Ga(mDTC)<Subscript>3</Subscript>

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.     

Porosity distribution in highly compressible cake: Experimental and theoretical verification of the dense skin

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.     

Use of external conduit impairs liver function in patients with biliary atresia

An external conduit (stoma) for patients with biliary atresia has been used to prevent postoperative cholangitis. Thirty-two patients with biliary atresia who had hepatic portoenterostomies with external conduits were studied retrospectively with respect to frequency and severity of postoperative cholangitis or stoma bleeding. Changes in their liver enzyme levels, and total bilirubin (TB) levels were measured before and after closure of the stoma. Cholangitis was observed in 20 patients (62.5%), and major hemorrhage from the stoma site was seen in 14 patients (43.8%) prior to closure. Levels of liver enzymes such as glutamic oxaloacetic transaminase (SGOT), glutamic pyruvic transaminase (SGPT), gamma-glutamyl transpeptidase (gamma-GTP), and alkaline phosphatase (ALP) improved significantly within 1 month after closure of the stoma, and remained low thereafter. The TB concentration was the only liver function that did not change significantly following closure. In summary, the authors do not recommend an external conduit in patients with biliary atresia because it is not an effective way of reducing the incidence of postoperative cholangitis, and it may be deleterious to liver function.