Model predictive control for multivariable unstable processes with constraints on manipulated variables

The original MPC(Model Predictive Control) algorithm cannot be applied to open loop unstable systems, because the step responses of the open loop unstable system never reach steadystates. So when we apply MPC to the open loop unstable systems, first we have to stabilize them by state feedback or output feedback. Then the stabilized systems can be controlled by MPC. But problems such as valve saturation may occur because the manipulated input is the summation of the state feedback output and the MPC output. Therefore, we propose Quadratic Dynamic Matrix Control(QDMC) combined with state feedback as a new method to handle the constraints on manipulated variables for multivariable unstable processes. We applied this control method to a single-input-single-output unstable nonlinear system and a multi-input-multi-output unstable system. The results show that this method is robust and can handle the input constraints explicitly and also its control performance is better than that of others such as well tuned PI control. Linear Quadratic Regulator (LQR) with integral action.     

Vocal fold scarring: current concepts and management

Scarring of the vocal folds can occur as the result of blunt laryngeal trauma or, more commonly, as the result of surgical, iatrogenic injury after excision or removal of vocal fold lesions. The scarring results in replacement of healthy tissue by fibrous tissue and can irrevocably alter vocal fold function and lead to a decreased or absent vocal fold mucosal wave. The assessment and treatment of persistent dysphonia in patients with vocal fold scarring presents both diagnostic and therapeutic challenges to the voice treatment team. The common causes of vocal fold scarring are described, and prevention of vocal fold injury during removal of vocal fold lesions is stressed. The anatomic and histologic basis for the subsequent alterations in voice production and contemporary modalities for clinical and objective assessment will be discussed. Treatment options will be reviewed, including nonsurgical treatment and voice therapy, collagen injection, fat augmentation, endoscopic laryngoplasty, and Silastic medialization.     

Interactions of rhodium carbonyl compounds supported on inorganic oxides with CO,H2 and propylene

RhCl(CO)(PPh₃)₂, RhH(CO)(PPh₃)₃, and [RhClfCO)₂]₂ were supported on silica gel, γ-alumina, titania.and magensia in 3 to 5 wt % to study the interactions of rhodium carbonyl with the surface of inorganic oxides When trans-RhCI(CO)(PPh₃)₂ was supported on the surface of silica gel, cis-RhCl(CO) (PPh₃)₂ species was detected via the splitting of the CO infra red stretching band of trans-RhCI (CO)(PPh₃)₂. With other supports, same phenomenon was observed but with the different pattern of intensities of the splitted CO stretching bands. RhH(CO)(PPh₃)₃ was easily decarbonylated, after interacting with the surface of silica gel, γ-alumina, and titania. However, [RhCl(CO)₂]₂ was decarbonylated on the surface of inorganic oxides mentioned above and most of supported [RhCl(CO)₂]₂ converted to a stable surface carbonyl species [M-OH-RhCI(CO)₂; M = Si, Al, Ti]. Diffuse reflectance infrared spectroscopy (DRS) was used to study the interactions of 5 wt % RhCl(CO)(PPh₃)₂ supported on silica gel with H₂, CO and/or propylene at various temperatures. The result indicated that the surface intermediates formed from the interaction of RhCl(CO)(PPh₃)₂ with CO, H₂ and C₃H₆ were not identical to the corresponding liquid-phase intermediates of RhCl(CO)(PPh₃)₂ in the presence of solvent.     

Acquisition and transfer of skilled performance: Are visual discrimination skills stimulus specific?

The authors examine how the difficulty of initial training influences the acquisition and transfer of both stimulus-specific knowledge and strategic knowledge not tied to specific stimuli. Participants were asked to discriminate between random polygon stimuli. The order of exposure to very similar and less similar discriminations was varied, in which difficulty of discriminations was defined by the similarity of the stimuli being discriminated. Participants were then transferred to making discriminations between a completely novel set of random polygons. Exposure to discriminations between highly similar stimuli led to eventually faster and more accurate discriminations and superior transfer performance on novel stimuli. The results are explained by a theory of skill acquisition that includes both stimulus-specific knowledge and strategic knowledge that is driven by exposure to specific stimuli, but is not stimulus specific. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Cyclic stress effects on the grain boundary cracking in Al-Mg solid solution

The difference in the grain boundary deformation between statically and cyclically crept specimens of Al-Mg solid solution has been investigated at the temperature of 580 K and for the peak stress level of 15 to 20 M Pa. In statically crept specimens, the grain boundaries deform irregularly and no crack is formed either at the triple point or along the serrated boundaries. However, in cyclically crept specimens, where the stress frequency, stress amplitude and the ratio of on-load to off-load time are 3 cycles per minute, 90% of maximum peak stress and less than 1, respectively, the grain boundaries remain smooth and wedge-type cracks are formed at the triple points, which results in intercrystalline fracture. On the basis of the experimental observations it is believed that cyclic stressing enhances grain boundary sliding through an accelerated recovery with the help of mechanically generated excess vacancies during cycling. However, due to the constraints of the grain alignment, boundary sliding becomes very difficult and creates an intercrystalline fracture at a triple point. On the other hand, under static stress, since the grain boundary is serrated to decrease the stress concentration at a triple point, a crack hardly forms at the triple point.     

Chronic fatigue syndrome in young persons

The prevalence of chronic fatigue syndrome (CFS) in teenagers is 10-20 per 100,000 inhabitants in the Netherlands. The natural course of the disorder is not favourable according to the literature. Proposed criteria for the diagnosis 'CFS' in adolescence are: absence of a physical explanation for the complaints, a disabling fatigue for at least six months and prolonged school absenteeism or severe motor and social disabilities. Exclusion criterion should be a psychiatric disorder. Factors that attribute to the persistence of fatigue are somatic attributions, illness enhancing cognitions and behaviour of parents as well as physical inactivity. The role of the physician and the role of parents can enhance the problems. The treatment should focus on decreasing the somatic attributions, on reinforcement by the parents of healthy adolescent behaviour, on the gradual increase of physical activity and on decreasing attention (including medical attention) for the somatic complaints.