Stabilization Control of the Differential Mobile Robot Using Lyapunov Function and Extended Kalman Filter

This paper presents the design of a control model to navigate the differential mobile robot to reach the desired destination from an arbitrary initial pose. The designed model is divided into two stages: the state estimation and the stabilization control. In the state estimation, an extended Kalman filter is employed to optimally combine the information from the system dynamics and measurements. Two Lyapunov functions are constructed that allow a hybrid feedback control law to execute the robot movements. The asymptotical stability and robustness of the closed loop system are assured. Simulations and experiments are carried out to validate the effectiveness and applicability of the proposed approach.Comment: arXiv admin note: text overlap with arXiv:1611.07112, arXiv:1611.0711

Opportunistic secure transmission for wireless relay networks with modify-and-forward protocol

This paper investigates the security at the physical layer in cooperative wireless networks (CWNs) where the data transmission between nodes can be realised via either direct transmission (DT) or relaying transmission (RT) schemes. Inspired by the concept of physical-layer network coding (PNC), a secure PNC-based modify-and-forward (SPMF) is developed to cope with the imperfect shared knowledge of the message modification between relay and destination in the conventional modify-and-forward (MF). In this paper, we first derive the secrecy outage probability (SOP) of the SPMF scheme, which is shown to be a general expression for deriving the SOP of any MF schemes. By comparing the SOPs of various schemes, the usage of the relay is shown to be not always necessary and even causes a poorer performance depending on target secrecy rate and quality of channel links. To this extent, we then propose an opportunistic secure transmission protocol to minimise the SOP of the CWNs. In particular, an optimisation problem is developed in which secrecy rate thresholds (SRTs) are determined to find an optimal scheme among various DT and RT schemes for achieving the lowest SOP. Furthermore, the conditions for the existence of SRTs are derived with respect to various channel conditions to determine if the relay could be relied on in practice

Deficit Irrigation of Kentucky Bluegrass for Intermountain West Urban Landscapes

Due to end users irrigating with excess water, water conservation of turfgrass can make a large impact in urban water conservation by reducing water applied while still maintaining visual appearance. This study was conducted to determine if Kentucky bluegrass (Poapratensis L.) can be deficit irrigated to maintain minimum acceptable appearance while conserving water. The study investigated water stress in terms of stomatal conductance, chlorophyll index, leaf temperature and predawn leaf water potential at the point of water stress, or where visual quality no longer meets expectations during dry down conditions. Water use was measured over well established Kentucky bluegrass with an eddy covariance system that was validated with soil water measurements. Turfgrass was irrigated at 80% of reference evapotranspiration based on allowable depletion of 12 mm of soil water during growing season that was considered to be well-watered. Two dry downs were conducted over a two-year period (early and late summer). Turfgrass was allowed to dry down without irrigation until visual quality reached the minimum acceptable points (score ≤ 6). During drying periods, visual rating, chlorophyll index, predawn leaf water potential, and leaf temperature with stomatal conductance rapidly decreased once stomatal conductance fell to approximately half of well-watered levels. Both soil water content and evapotranspiration had weak correlation with stomatal conductance; however, stomatal conductance tended to have higher correlation with the change in soil moisture than with the change in crop evapotranspiration. Soil water use and eddy covariance data in terms of crop evapotranspiration had high correlation. The plant water use factor ranged from around 0.8 to 1.1 under well-watered condition corresponding to visual rating from 7 to 9. At the minimum acceptable point of visual rating, which is 5.5 to 6, the plant factor ranged from 0.65 to 0.87. This value of plant factor is quite high at this point. Even when Kentucky bluegrass went below acceptable visual quality, the grass still used significant amounts of water with the plant factor value ranging from 0.6 to 0.8. The data suggested that deficit irrigation cannot be applied with Kentucky bluegrass in the Intermountain West area

An Analysis of Fluvial Geomorphology Parameters Affecting Meander Migration and Dynamic Equilibrium of the White River in Arkansas

An analysis of a multitude of fluvial and morphological parameters was conducted to assess the current stability conditions of various White River reaches and to accentuate the contributions imparted by these parameters to the internal processes that governed the dynamic equilibrium within these reaches. The initial step involved the extractions and computations of pertinent fluvial and morphological parameters from the HEC-RAS Model and ArcGIS.Channel stability assessment emphasized three methodologies, namely stability assessment through parametric correlations between fluvial and morphological parameters; stability evaluation with the Rosgen Stream Classification System; and stability estimation through sediment analyses and sediment related parametric correlations. Morphological assessment implementing the Rosgen Stream Classification (RSC) system consisted of four inventory levels of classification. Sediment analyses conducted by implementing several sediment transport functions utilized the dominant bed materials attained from sieve analyses of approximately seven hundred soil samples collected from the channels of various ‘reference’ reaches

Mechanism investigation of pseudouridine synthases TruB and RluA with RNA containing 5-fluorouridine and 4-thiouridine.

Pseudouridine synthases (Ψ synthases) are the enzymes that catalyze the isomerization of uridine (U) to pseudouridine (Ψ), which is the most prevalent post-transcriptional modification of RNA. The Ψ synthases fall into six different families that share no significant global sequence similarity; however, they all involve a conserved aspartic acid residue which is absolutely essential for activity. Tyrosine is a conserved residue in the active site in five of the six families of Ψ synthases (phenylalanine in the TruD family) and was hypothesized as the general base for the isomerization reaction. To confirm the function of Tyr-96, Y96F RluA was assayed with both ASL and [F5U]ASL. U is converted to Ψ and F5U to F5U products. These results argue against the role of Tyr serving as general base. However, the slow rates of reactions and higher concentration of Y96F RluA needed for any reaction indicates that Tyr-96 does facilitates at least one step of the reaction. The major product of F5U from the action of Ψ synthases is a ribo isomer whereas the minor product is arabino, and its generation requires epimerization at C2′. The deprotonation at C2′ can be achieved by the conserved Asp or O2. To test if O2 is the general base, the isomerized U was replaced by 4-thiouridine (s4U). As an essential first step, RNA containing s4U needs to be verified as a good substrate for Ψ synthases, so RluA and TruB were incubated with [s4U]RNA. Intact [s4U]RNA shifted to later and shorter retention times after incubation with RluA and TruB, respectively. Traces of the digestion products of [s4U]RNA after incubation with the two enzymes also showed the new peaks that absorbed more strongly at 330 nm than 260 nm. These results indicate that [s4U]RNA can be handled as a substrate