A new framework for two loop disturbance rejection control

In this paper, a new framework of a two loop disturbance rejection control and its design methodology are proposed. The framework consists of a robust internal-loop compensator (RIC) to eliminate disturbances and an external-loop controller to achieve nominal control performance. As the main contribution of this paper, we define the design problem of the RIC as a regulation control problem, then show that this new definition with the RIC structure provides more design flexibility and less implementation constraints, which allows us to design the RIC aggressively against a specific disturbance. This is verified through a comparative structural analysis with a disturbance observer (DOB) and an adaptive robust control (ARC). Two design examples of the RIC are given, along with practical issues that should be considered in the design procedure. The proposed framework is demonstrated by simulations and experiments.     

Preparation of anhydrous magnesium chloride from ammonium magnesium chloride hexahydrate

Magnesium chloride hydrate can be dehydrated to some extent by heating. However, it is not possible to fully dehydrate magnesium chloride by heating in air because of hydrolytic decomposition. Accordingly, the dehydration should be carried out in hydrogen chloride gas atmosphere. However, this process causes many problems, including HCl gas storage and corrosive nature, consuming a large amount of HCl gas. Consequently, many alternative approaches have been tried for the production of anhydrous magnesium chloride. In this work, we proposed a process to prepare anhydrous magnesium chloride using ammonium magnesium chloride hexahydrate (NH₄MgCl₃·6H₂O). From this work, it was confirmed that anhydrous magnesium chloride can be produced by the dehydration of magnesium chloride hydrate in HCl gas atmosphere, and found that anhydrous magnesium chloride can be prepared from ammonium magnesium chloride hexahydrate at the reaction temperature range 50–400 °C and a reaction time of 30 min even in air atmosphere.     

Electromagnetic penetration into 2-D multiple slotted rectangularcavity: TM-wave

Electromagnetic wave penetration into the two-dimensional (2-D) rectangular cavity with multiple slots in an infinite conducting plane with a finite thickness is investigated. The Fourier transform and the mode-matching technique are used to obtain simultaneous equations, which are solved to represent the scattered and the penetrated fields in series forms that are suitable for numerical computations     

A Re-Examination of Radar Terrain Backscattering at Nadir

The theoretical behavior of nadir specular and diffuse radar backscattering from rough terrain is re-examined. Terrain is modeled as a random rough surface in the Kirchhoff approximation. The relative significance of specular (coherent) and diffuse (noncoherent) radar backscatter is compared in terms of the antenna system parameters (beamwidth, height, and frequency) and rough surface statistics. It has been found that in case of a high-altitude (space or airborne) radar, the ratio between coherent and noncoherent terrain backscatter is independent of its altitude of the radar platform. A possible explanation is suggested for the anomalous radar backscatter observed in the Skylab S-193 altimeter experiment.     

Chemical-looping combustion of syngas by means of spray-dried NiO oxygen carrier

Chemical-looping combustion (CLC) of syngas has a potential to generate power economically with achieving the inherent carbon dioxide capture. An oxygen carrier with high reactivity and excellent physical properties would make CLC technology more competitive. In this work, oxygen carrier with 70 wt% NiO was prepared by spray drying technique. The prepared oxygen carrier had excellent physical properties for fluidized-bed application of CLC process. The reactivity of the oxygen carrier in repeated reduction-oxidation was measured by thermogravimetric analyzer with simulated syngas. Oxygen carrier calcined at 1,100 °C showed high oxygen transfer capacity of 14.7 wt%, utilizing 98% of the transferable oxygen. Oxygen transfer capacity and oxygen transfer rate was increased with the increase of reaction temperature, and the highest oxygen transfer rate was observed when about half of the transferable oxygen reacted with syngas. The reduction rate of the syngas (mixture of H₂ and CO) appeared to be approximately the sum of the reaction rate of each fuel gas. The experimental results indicated that the spray-dried NiO oxygen carrier prepared in this work could be a good quality oxygen carrier for the CLC of syngas.     

Brain abscess in solid organ transplant recipients receiving cyclosporine-based immunosuppression

There is currently a stark therapeutic void in the treatment of evolving stroke. Although P-selectin is rapidly expressed by hypoxic endothelial cells in vitro, the functional significance of P-selectin expression in stroke remains unexplored. In order to identify the pathophysiological consequences of P-selectin expression and to identify P-selectin blockade as a potential new approach for the treatment of stroke, experiments were performed using a murine model of focal cerebral ischemia and reperfusion. Early P-selectin expression in the postischemic cerebral cortex was demonstrated by the specific accumulation of radiolabeled anti-murine P-selectin IgG, with the increased P-selectin expression localized to the ipsilateral cerebral microvascular endothelial cells by immunohistochemistry. In experiments designed to test the functional significance of increased P-selectin expression in stroke, neutrophil accumulation in the ischemic cortex of mice expressing the P-selectin gene (PS +/+) was demonstrated to be significantly greater than that in homozygous P-selectin-null mice (PS -/-). Reduced neutrophil influx was accompanied by greater postischemic cerebral reflow (measured by laser Doppler) in the PS -/- mice. In addition, PS -/- mice demonstrated smaller infarct volumes (5-fold reduction, P<.05) and improved survival compared with PS +/+ mice (88% versus 44%, P<.05). Functional blockade of P-selectin in PS +/+ mice using a monoclonal antibody directed against murine P-selectin also improved early reflow and stroke outcome compared with control mice, with reduced cerebral infarction volumes noted even when the blocking antibody was administered after occlusion of the middle cerebral artery. These data are the first to demonstrate a pathophysiological role for P-selectin in stroke and suggest that P-selectin blockade may represent a new therapeutic target in the treatment of stroke.     

Scattering from a Layered Medium Connected with Rough Interfaces: Matrx Doubling Method

A theoretical scattering model is developed that computes the scattered and transmitted intensities from an inhomogeneous layered medium above the half-space. A matrix doubling method technique is extended to handle multilayer scattering problems of which each scattering layer of spherical particles has rough boundary interfaces. Incoherent scattering is assumed in the formulation so that the Stokes vector representations are used to calculate the polarimetric multiple scattering effects. The scattering coefficients are computed for a two-layered Rayleigh scattering medium with a rough boundary. The developed scattering model of a radiative transfer approach is useful for scattering computations dealing with a random medium often encountered in active and passive microwave remote-sensing problems.     

EMG pattern classification using SOFMs for hand signal recognition

 We propose a method of pattern classification of electromyographic (EMG) signals using a set of self- organizing feature maps (SOFMs). The proposed method is simple to apply in that the EMG signals are directly input to the SOFMs without preprocessing. Experimental results are presented that show the effectiveness of the SOFM based classifier for the recognition of the hand signal version of the Korean alphabet from EMG signal patterns.