Function Approximation Technique Based Adaptive Control for Chaos Synchronization between Different Systems with Unknown Dynamics

This paper presents a function approximation technique based immersion and invariance adaptive controller for chaos synchronization between nonidentical systems with unknown dynamics. In the proposed control scheme, the control system is reconstructed as the combination of a controllable linear system and a variation term from the original system. The variation term is treated as time-varying uncertainty and approximated by a group of weighted chosen basis functions. The immersion and invariance methodology is employed to design the adaptive control law such that both the synchronization error and uncertainty estimation error converge to zero. Two typical chaos synchronization problems are used in numerical simulations to verify the effectiveness and superiority of the proposed controller.

     

Hydrogen effect on the molecular weight distribution of polymers obtained by polymerization of ethylene and α-olefins over supported titanium-magnesium catalysts

Comparative data on the molecular weight distribution of polymers obtained by polymerization of ethylene, propylene and 1-hexene, and copolymerization of ethylene with α-olefins over the titanium-magnesium catalysts (TMC) in the absence and presence of hydrogen are presented. In contrast to the ethylene polymerization, in the cases of propylene and 1-hexene polymerization and copolymerization of ethylene with α-olefins, the hydrogen addition is characterized by noticeable narrowing of the molecular weight distribution (MWD) due to lower contribution of the MWD component with high molecular weight. This result is an evidence of the increased reactivity of TMC active sites producing high molecular weight poly-α-olefins and copolymers of ethylene with α-olefins in the chain transfer reaction with hydrogen. It is suggested that the increased reactivity of these sites in the transfer reaction with hydrogen appears after the 2,1-addition of α-olefin to the growing polymer chain.     

Monitoring the curing processes of epoxy oligomers with partially substituted polyethoxymetallosiloxanes by IR spectroscopy and thermomechanical analysis

In this work, the curing of «ED-20» epoxy resin with partially siloxy-substituted aluminum, iron, and zirconium siloxanes that we obtained previously was studied. The initial content of a metallosiloxane in the compositions was 5–50 wt% with respect to the resin. In all the cases, thermal curing was used to obtain a series of samples in the form of solid homogeneous materials. The fact of the epoxy ring opening in the resin was confirmed by IR spectroscopy. The catalytic properties of the metal atom in a metallosiloxane were found to affect the curing process. The samples demonstrate rather a high resistance to thermooxidative destruction, and in most cases, their glass transition temperatures are lower than those obtained upon standard curing of «ED-20» resin with triethylenetetramine. Partially siloxy-substituted metalloalkoxysiloxanes can be efficient agents for curing and formation of a hybrid material based on epoxy resins.     

A tree-covering problem arising in integrity of tree-structured data

We introduce and solve a problem motivated by integrity verification in third-party data distribution: Given an undirected tree, find a minimum-cardinality set of simple paths that cover all the tree edges and, secondarily, have smallest total path lengths. We give a linear time algorithm for this problem.     

Internet addiction: Meta-synthesis of qualitative research for the decade 1996–2006

Internet addiction is “an individual’s inability to control their Internet use, which in turn leads to feelings of distress and functional impairment of daily activities” [Shapira, N., Lessig, M., Goldsmith, T., Szabo, S., Lazoritz, M., Gold, M. et al. (2003). Problematic Internet use: Proposed classification and diagnostic criteria. Depression and Anxiety, 17(4), 207–216]. Previous research in this field has offered inconclusive data on whether Internet addiction can be classified as a disorder. This study provides an in-depth and comprehensive analysis of internet addiction through a meta-synthesis of qualitative studies on excessive Internet use published during the period of 1996–2006. Several constructs pertaining to the domain of Internet addiction have been identified and a theoretical model of Internet addiction has been proposed.     

Microstructure,Phase Composition,and Thermal Stability of Two Zirconium Alloys Subjected to High‐Pressure Torsion at Different Temperatures

The structure, phase composition, and thermal stability of the industrial zirconium alloys, namely, E110 (Zr–1% Nb) and E635 (Zr–1% Nb–0.3% Fe–1.2% Sn), which are subjected to high‐pressure torsion (HPT) at room temperature (RT), 200, and 400 °С have been studied. HPT of Zr‐alloys at RT (10 revolutions) leads to the formation of grain–subgrain nano‐sized structure and to increase the microhardness by 2.1…2.8 times. The increase in the HPT temperature to 200–400 °С leads to the increase in the structural‐element average size. The structural‐element size in the complexly alloyed E635 alloy in all cases is lower compared with the E110 alloy. The hardening of the alloys after HPT at RT and 200 °С is close, and at 400 °С is much less. HPT initiates the α‐Zr → (ω‐Zr + β‐Zr) transformation, which is the main factor for alloys hardening. The α‐Zr → (ω‐Zr + β‐Zr) transformation in the E635 alloy occurs less quickly. The maximum amount (ω‐Zr + β‐Zr) phase in the structure of the alloys is observed after HPT at RT and 200 °C, and the minimum ? at 400 °C. During heating, the alloys undergo the reverse (ω‐Zr + β‐Zr) → α transformation which depends on both the alloy composition and HPT temperature.

     

Wet Chemical Treatment and Mg Doping of p-InP Surfaces for Ohmic Low-Resistive Metal Contacts

Manufacturing a low-resistive Ohmic metal contact on p-type InP crystals for various applications is a challenge because of the Fermi-level pinning via surface defects and the diffusion of p-type doping atoms in InP. Development of wet-chemistry treatments and nanoscale control of p-doping for InP surfaces is crucial for decreasing the device resistivity losses and durability problems. Herein, a proper combination of HCl-based solution immersion, which directly provides an unusual wet chemical-induced InP(100)c(2 × 2) atomic structure, and low-temperature Mg-surface doping of the cleaned InP before Ni-film deposition is demonstrated to decrease the contact resistivity of Ni/p-InP by the factor of 10 approximately as compared to the lowest reference value without Mg. Deposition of the Mg intermediate layer on p-InP and postheating of Mg/p-InP at 350 °C, both performed in ultrahigh-vacuum (UHV) chamber, lead to intermixing of Mg and InP elements according to X-ray photoelectron spectroscopy. Introducing a small oxygen gas background (O₂ ≈ 10⁻⁶ mbar) in UHV chamber during the postheating of Mg/p-InP enhances the indium outdiffusion and provides the lowest contact resistivity. Quantum mechanical simulations indicate that the presence of InP native oxide or/and metal indium alloy at the interface increases In diffusion.     

HLA-DRB1 genes and disease severity in rheumatoid arthritis. The MIRA Trial Group. Minocycline in Rheumatoid Arthritis

OBJECTIVE: To examine the effect of alleles encoding the "shared"/"rheumatoid" epitope on rheumatoid arthritis (RA) disease severity in patients who participated in the minocycline in RA (MIRA) trial. METHODS: Of 205 patients with a week-48 visit, blood was available for typing of HLA-DRB1 and HLA-DQB1 in 174 (85%) and successfully completed in 169 (82%). Baseline erosions were used to assess disease severity and new erosions at the last visit served as a proxy for progression. RESULTS: At baseline, there was no association between the presence of erosive disease or rheumatoid factor status and the dose of rheumatoid epitope (homozygous, heterozygous, none) or the specific alleles identified. At the final visit, a gradient was observed for the 3 allelic subgroups (and their gene doses) in the occurrence of new erosions among the Caucasian placebo-treated, but not the minocycline-treated, patients. A treatment group/HLA-DR4 epitope interaction was demonstrated in multivariate analyses. Approximately two-thirds of African-American patients did not have the rheumatoid epitope. CONCLUSION: HLA-DRB1 oligotyping may be useful in predicting the progression of disease in some Caucasian patients. Our study corroborates the infrequency of the epitope among African-American patients with RA.