A novel controller for nonlinear uncertain systems using a combination of SDRE and function approximation technique: Regulation and tracking of flexible-joint manipulators

This paper presents a novel combined State Dependent Riccati Equation (SDRE) / Function Approximation Technique (FAT)-based control design for nonlinear uncertain systems. The SDRE is employed to construct an optimal controller and the function approximation technique is utilized to estimate time-varying disturbances and uncertainties. Moreover, a robust term in the proposed control law compensates for the truncation error. The closed-loop stability and boundedness of the tracking error and FAT weights approximation error are proved in the sense of Lyapunov, with consideration of truncation error. Due to the great importance of the adequate performance of transient response from practical point of view, performance evaluation has been accomplished. The proposed scheme is computationally simple due to utilizing the FAT to represent uncertainties and disturbances as a function of time. Compared with the SDRE based SMC, the proposed controller is superior in terms of capability to track a fast and highly complicated trajectory and no need to determine time-varying disturbances and uncertainties bounds. The case study is a Selective Compliant Articulated Robot for Assembly (SCARA) flexible joint manipulator as a representative of highly nonlinear, coupled, large robotic systems. Simulation results easily verify the effectiveness and superiority of the proposed controller.     

Doubly-terminated two-variable lossless ladder networks

In this paper necessary and sufficient conditions are derived for a two-variable positive real function to be the driving-point impedance of certain classes of doubly-terminated lossless ladder networks. Specifically, two classes of networks are studied: (a) the class of networks in which the lossless structure is a cascade of p₁- and p₂-variable two-ports, each two-port having its transmission zeros at the origin and/or at infinity; (b) the class of networks in which the lossless structure is a lowpass or highpass ladder network with series arms having p₁- and p₂-type elements in series and shunt arms having the p₁- and p₂-type elements in parallel. It is indicated that via suitable transformations of the variables, conditions for many other types of ladder structures can be derived.     

Is there an increased familial prevalence of psychopathology in children with nonverbal learning disorders?

The cognitive and behavioral symptoms of nonverbal learning disabilities (NLD) have been described by previous investigators. Nevertheless, we know far less about the potential genetic contributions that may predispose a child to have NLD. An endophenotype model was investigated in 5 samples of children ages 9 to 15 years: NLD (n = 32); reading disorders (RD; n = 59); participants with a psychiatric diagnosis but without a learning disability (n = 55); typically developing controls (n = 31); and children with velocardiofacial syndrome (VCFS), a chromosomal deletion syndrome that has been proposed as being an exemplar of NLD (VCFS + NLD; n = 20). Based on a family genetic interview, the authors' data suggest that children with NLD, RD, or a psychiatric diagnosis have a higher prevalence rate of attention-deficit/hyperactivity disorder (ADHD) and substance abuse/dependence. Psychiatric controls and children with NLD--but not children with RD-- showed higher prevalence rates of familial bipolar disorder.     

Comprehensive screening and selection of okra (Abelmoschus esculentus) germplasm for salinity tolerance at the seedling stage and during plant ontogeny

The okra germplasm was screened for salinity tolerance at the seedling stage and during plant ontogeny. Substantial variation existed in okra for salinity tolerance at the seedling stage. An 80 mmol/L NaCl concentration was suitable for discriminating tolerant and non-tolerant okra genotypes. The pooled ranking of the genotypes, based on individual rankings for each trait (root and shoot length, germination percentage, and relative Na⁺ and K⁺) in individual NaCl concentrations, was effective for selecting tolerant genotypes. Genotypes selected at the seedling stage maintained their tolerance to NaCl during plant ontogeny, suggesting that screening of the germplasm entries and advanced breeding materials for salt tolerance at the seedling stage is effective. Among 39 okra genotypes, five were identified as the most tolerant genotypes and showed potential for use in breeding programs that focus on the development of salt-tolerant, high-yield okra cultivars.     

Novel extension of the UTAUT model to understand continued usage intention of learning management systems: the role of learning tradition

Education and Information Technologies - The key objective of this study was to reveal the key factors that impact university students’ continued usage intentions with respect to Learning...