Reduced Order Observer for Linear Time-Invariant Multivariable Systems with Unknown Inputs

This paper presents the design of a new reduced order observer to estimate the state for a class of linear time-invariant multivariable systems with unknown inputs. The proposed design approach is a combination of the approaches proposed by Hou and Muller (IEEE Trans. Autom. Control 37:871–875, 1992) and Boubaker (Int. J. Autom. Control Syst. Eng. 5:45–51, 2005); matrix decompositions, state transformations, and substitutions based on coordinate changes are used. It is shown that the problem of reduced order observers for linear systems with unknown inputs can be reduced to a standard one (the unknown input vector will not interfere in the observer equations). The effectiveness of the suggested design algorithm is illustrated by a numerical example (aircraft lateral motion), and, for the same aircraft dynamics, we compare our new observer with other already existing observers from the existence conditions and dynamic characteristics point of view; the superiority of the new designed observer is demonstrated.     

Addressing the Risk of Surface Water Intrusion in Old Romanian Salt Mines

In Romania, surface waters near underground salt mines represent a significant risk to the stability of the mine workings. Such problems occur in many salt exploiting facilities, i.e. Slanic Prahova, Targu Ocna, Praid. In this paper, the authors present a method of dealing with this issue at the Praid salt mine with research targeted at avoiding the hazard presented by intrusion of surface waters into old mine workings. Monitoring activities are proposed to prevent damage due to the seepage of Corund Creek water into the subsurface salt body, which could compromise and even produce collapses in the salt mine sanatorium and old and new mines.     

Nanoparticles from a Gold Complex with Sulfite Ion as Ligand: Preparation and Characterization

Gold colloidal nanoparticles (GNPs) were prepared by reducing a complex of Au⁺. Na₃Au(SO₃)₂ with sodium citrate. The procedure provides control of the dimension of nanoparticles produced, which is a function of reaction time and concentration of reactants. The nanoparticles were separated by centrifugation and their characteristics and dimensions were studied using UV-Vis and IR spectroscopy and transmission electronic microscopy (TEM).     

Transient thermo-reflectance measurements of the thermal conductivity and interface resistance of metallized natural and isotopically-pure silicon

The transient thermoreflectance method has been used to measure the thermal conductivity of natural silicon and isotopically-pure silicon-28 layers that are epitaxially grown on natural silicon substrates. The measurements were performed at room temperature for both a low level (10¹⁶) and a higher level (2×10¹⁹) of Boron doping of the epitaxial layers. The results indicate a gain of approximately 55% in the thermal conductivity of Si²⁸ as compared to that of natural Si, at both low and higher levels of doping, and a loss of approximately 19% for both types of silicon due to the higher level of doping.     

Social Influence of an International Celebrity: Responses to the Death of Princess Diana

When Diana, Princess of Wales, was killed in 1997, a massive public outpouring of grief occurred. Six years after her death, the public and the tabloids still debate whether the paparazzi were to blame for her fatal car accident. Previous studies of celebrities suggest that psychological involvement with a celebrity will determine to what extent stories of the celebrity and their subsequent social influence will affect the general public. The same process was examined in this study of Princess Diana. To study this phenomenon, a survey administered immediately after her fatal car accident compared people's level of involvement with Princess Diana to their viewing of stories about her funeral and their attitudes toward the press. Results showed that gender and age similarities predicted involvement with Princess Diana. This involvement, in turn, predicted people's media use in response to her death and their attitudes toward the press. This finding reinforces previous studies that have shown involvement is an important variable that influences both media consumption and media effects. The authors consider implications of this research for investigating the growing international influence of celebrities through mass media.     

Hydrogen absorption in MgNiFe alloys

The hydrogenation properties of the alloys of overall formula Mg₂Ni_1?xFe_x (x ? 0.37) have been studied. In this range of composition multi-phase alloys were obtained containing Mg₂Ni, Mg and more or less finely dispersed Fe in different coordination as proved by the EXAFS technique and Mössbauer spectroscopy. There is no significant substitution of Ni by Fe atoms in the Mg₂Ni lattice. Two or three plateau-pressures are observed on the pressure-composition isotherms of the hydrides with the heats of formation in the range ?18.4 to 20.4 kcal/mol H₂ (?77 to ?85.4 kJ/mol H₂). The hydrides of the Fe containing alloys show higher desorption rates of hydrogen compared to the pure Mg₂Ni hydride.     

Polycondensation of tetrachlorobisphenol a with chloromethylphosphonic dichloride. 1H-NMR kinetic study

The temperature-programmed polycondensation of tetrachlorobisphenol A with chloromethylphosphonic dichloride is carried out in the sample tube of an NMR spectrometer. From the spectra during polycondensation, the instantaneous concentration of components can be determined. Phosphorus and chlorine-containing polymers with flame-retardant properties are obtained.     

Hydrogen absorption in beryllium substituted Mg2Ni

The alloys Mg₂Ni_1–xBe_x (x = 0.15 and 0.25) retain the Mg₂Ni structure showing a lattice dilation proportional to the beryllium content. The pressure-composition isotherms are reported for the dissociation of hydrided samples. The results suggest that there are two type of interstices able to absorb up to 4 H atoms per formula unit. The heats of formation obtained from the van't Hoff relationship show an increased stability for the hydrides of the beryllium substituted alloys compared to the pure Mg₂Ni. The results suggest that the electronic factors are more important for hydride stability than variations in the unit cell volume.     

The influence of aluminium on the properties of the Mg2Cu-H2 system

The addition of aluminium to a mixture of Mg-Cu (2:1 atomic ratio) leads by melting to the formation of increasing amounts of Mg(Cu,Al)₂ where aluminium substitutes for copper atoms in the MgCu₂ lattice, raising the lattice parameter. The hydrogen absorbed in this phase is strongly bounded, as proved by desorption isotherms and nuclear magnetic resonance data.