This paper considers the problem of stabilizing a first-order plant with dead time using a proportional-integral-derivative (PID) controller. Using a version of the Hermite-Biehler theorem that is ...applicable to quasi-polynomials, the complete set of stabilizing PID parameters is determined for both open-loop stable and unstable plants. The range of admissible proportional gains is first determined in closed form. For each proportional gain in this range, the stabilizing set in the space of the integral and derivative gains is shown to be either a trapezoid, a triangle or a quadrilateral. For the case of an open-loop unstable plant, a necessary and sufficient condition on the time delay is determined for the existence of stabilizing PID controllers.
This Letter proposes a stochastic model of the wearable sensor nodes of a wireless body area network (WBAN) based on Markov decision process (MDP). The proposed technique tackles the problem of ...maximising the likelihood of data transmission while minimising the computational cost and energy. Suitable transmission strategies subject to the energy level of the nodes and channel conditions are needed to be investigated to strike a balance between network lifetime and packet delivery ratio. MDP formulation of the problem is solved offline to find out the optimal transmission strategies for the representative input conditions. The results of this offline computation approach can directly map to optimal transmission policies for intra-WBAN communications. The experimental results demonstrate the robustness of the proposed scheme in handling both favourable and unfavourable operating conditions.
A fast Fourier transform (FFT) based computational approach integrating phase-field method (PFM) and crystal plasticity (CP) is proposed to model recrystallization of plastically deformed ...polycrystals in three dimensions (3-D). CP at the grain level is employed as the constitutive description to predict the inhomogeneous distribution of strain and stress fields after plastic deformation of a polycrystalline aggregate while the kinetics of recrystallization is obtained employing a PFM in the plastically deformed grain structure. The elasto-viscoplastic equilibrium is guaranteed during each step of temporal phase-field evolution. Static recrystallization involving plasticity during grain growth is employed as an example to demonstrate the proposed computational framework. The simulated recrystallization kinetics is compared using the classical Johnson–Mehl–Avrami–Kolmogorov (JMAK) theory. This study also gives us a new computational pathway to explore the plasticity-driven evolution of 3D microstructures.
Rationale
Stress is a risk factor for psychosis and treatments which mitigate its harmful effects are needed. Cannabidiol (CBD) has antipsychotic and anxiolytic effects.
Objectives
We investigated ...whether CBD would normalise the neuroendocrine and anxiety responses to stress in clinical high risk for psychosis (CHR) patients.
Methods
Thirty-two CHR patients and 26 healthy controls (HC) took part in the Trier Social Stress Test (TSST) and their serum cortisol, anxiety and stress associated with public speaking were estimated. Half of the CHR participants were on 600 mg/day of CBD (CHR-CBD) and half were on placebo (CHR-P) for 1 week.
Results
One-way analysis of variance (ANOVA) revealed a significant effect of group (HC, CHR-P, CHR-CBD (
p
= .005) on cortisol reactivity as well as a significant (
p
= .003) linear decrease. The change in cortisol associated with experimental stress exposure was greatest in HC controls and least in CHR-P patients, with CHR-CBD patients exhibiting an intermediate response. Planned contrasts revealed that the cortisol reactivity was significantly different in HC compared with CHR-P (
p
= .003), and in HC compared with CHR-CBD (
p
= .014), but was not different between CHR-P and CHR-CBD (
p
= .70). Across the participant groups (CHR-P, CHR-CBD and HC), changes in anxiety and experience of public speaking stress (all
p
’s < .02) were greatest in the CHR-P and least in the HC, with CHR-CBD participants demonstrating an intermediate level of change.
Conclusions
Our findings show that it is worthwhile to design further well powered studies which investigate whether CBD may be used to affect cortisol response in clinical high risk for psychosis patients and any effect this may have on symptoms.
This paper presents the experimental results of recycled aggregate concrete (RAC) beams prepared with different amount of recycled coarse aggregate (RCA) subjected to low velocity impact. The ...recycled coarse aggregates are obtained from a demolished RCC culvert. Four concrete mixes with 0%, 25%, 50% and 100% RCA respectively are prepared. With each mix three beam specimens of size 1.15
×
0.1
×
0.15
m are prepared and tested under drop weight impact load. The behavior of the RAC beams are studied in terms of acceleration, strains and support reaction histories under impact load in addition to the physical and mechanical characteristics of RCA and RAC. It is observed that 25% RCA does not influence the strength of concrete. In addition, it is found that for a given impact energy (the energy imparted by the hammer per blow) the reactions and strains of RAC with 50% and 100% RCA are significantly lower and higher respectively than those of normal concrete and RAC with 25% RCA.
Abstract
An embedded-domain phase-field formalism is used for studying phase transformation pathways in bimetallic nanoparticles (BNPs). Competition of bulk and surface-directed spinodal ...decomposition processes and their interplay with capillarity are identified as the main determinants of BNP morphology. Two dimensionless groups are found to reflect this competition and interaction: (a) the ratio of bulk to capillary driving forces (
Δ
f
˜
), and (b) ratio of difference in surface energies to the interfacial energy which relates to the three-phase contact angle (
θ
). The simulated morphologies, namely, core–shell, Janus and inverse core–shell, are found to cluster neatly into distinct regions of the
Δ
f
˜
-
θ
space. To connect phase-field simulations with specific BNP systems, the variation of
θ
with
Δ
f
˜
as a function of temperature is computed for Ag–Cu using a CALPHAD approach. The computed
Δ
f
˜
-
θ
trajectory for Ag–Cu, when superimposed on the morphology map derived from simulations, enabled the prediction of different morphological transitions as a function of temperature. Therefore, by providing an alternative and efficient approach to connect phase-field simulations with CALPAHD, the study demonstrates a unique computational framework that can assist in tailoring nanoparticle morphology through a variation of processing parameters.
The flow-field and solute transport through and around a porous cylinder is investigated numerically. The range of Reynolds number (based on the cylinder diameter and the uniform sinking rate of the ...cylinder) considered here is between 1 and 40 with Darcy number (
Da) in the range
10
-
6
⩽
Da
⩽
1.5
and porosity in the range
0.629
⩽
ε
⩽
0.999
. The motivation of the present study is the application of flow through porous cylinder extensively applied in nuclear biological chemical filters as well as reduction of carbon fines in filtered water. The influence of
Da on the drag coefficient, separation angle, recirculation length, streamline and vorticity pattern are investigated. The drag ratio, defined as the ratio of drag coefficient of porous cylinder to that of solid cylinder, is found to approach zero from unity as
Da is increased from
10
-
6
to
1.5
. The separation point shifts towards the rear stagnation point as
Da is increased. The time evolution of the solutal field at different Reynolds number and Darcy number is presented. A long slender concentration plume is found to evolve from the cylinder with decreasing concentration at the outer edge.
Phase pure Lithium orthosilicate (Li4SiO4) nanopowder was synthesized by solution combustion method using glycine as the fuel and silicic acid as a silica source. The effect of the fuel-to-oxidizer ...ratio (Φe) (0.6–1.0) in the combustion process and phase evolution was studied. We found that by controlling the fuel-to-oxidizer ratio of the starting solution phase purity can be achieved at 700 °C. Li4SiO4 powder was also prepared by solid state method and phase purity was achieved at 800 °C. The surface area, powder morphology, sintering behavior and CO2 capture properties of the Li4SiO4 were investigated. The powder synthesized by solution combustion route showed higher surface area, sinterability and CO2 absorption capacity compared to the solid state route powder. It could be attributed to the nanostructured morphology of the particles. The grain size in the sintered sample could be kept well below 5 μm. The current report provides a novel method to fabricate lithium orthosilicate, and shows promise for application as high temperature CO2 absorption as well as solid breeder in fusion reactor.
Display omitted
•Nanoscale Li4SiO4 powder prepared by glycine-nitrate solution combustion technique.•The effect of fuel-to-oxidizer ratio on combustion and phase evolution was studied.•Particle size, morphology, surface area was compared with solid-state route sample.•Combustion-derived powder shows improved CO2 absorption at high temperature.•Combustion route powder shows greater sinterability and smaller grain size (<5 μm).
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