PID-controller with predictor and auto-tuning algorithm: study of efficiency for thermal plants

The problem of efficiency estimation of an automatic control system (ACS) with a Smith predictor and PID-algorithm for thermal plants is considered. In order to use the predictor, it is proposed to include an auto-tuning module (ATC) into the controller; the module calculates parameters for a second-order plant module with a time delay. The study was conducted using programmable logical controllers (PLC), one of which performed control, ATC, and predictor functions. A simulation model was used as a control plant, and there were two variants of the model: one of them was built on the basis of a separate PLC, and the other was a physical model of a thermal plant in the form of an electrical heater. Analysis of the efficiency of the ACS with the predictor was carried out for several variants of the second order plant model with time delay, and the analysis was performed on the basis of the comparison of transient processes in the system when the set point was changed and when a disturbance influenced the control plant. The recommendations are given on correction of the PID-algorithm parameters when the predictor is used by means of using the correcting coefficient k for the PID parameters. It is shown that, when the set point is changed, the use of the predictor is effective taking into account the parameters correction with k = 2. When the disturbances influence the plant, the use of the predictor is doubtful, because the transient process is too long. The reason for this is that, in the neighborhood of the zero frequency, the amplitude-frequency characteristic (AFC) of the system with the predictor has an ascent in comparison with the AFC of the system without the predictor.     

Development of the First Oral Bioprecursors of Bis‐alkylguanidine Antimalarial Drugs

Plasmodium falciparum is responsible of the most severe form of malaria, and new targets and novel chemotherapeutic scaffolds are needed to fight emerging multidrug‐resistant strains of this parasite. Bis‐alkylguanidines have been designed to mimic choline, resulting in the inhibition of plasmodial de novo phosphatidylcholine biosynthesis. Despite potent in vitro antiplasmodial and in vivo antimalarial activities, a major drawback of these compounds for further clinical development is their low oral bioavailability. To solve this issue, various modulations were performed on bis‐alkylguanidines. The introduction of N‐disubstituents on the guanidino motif improved both in vitro and in vivo activities. On the other hand, in vivo pharmacological evaluation in a mouse model showed that the N‐hydroxylated derivatives constitute the first oral bioprecursors in bis‐alkylguanidine series. This study paves the way for bis‐alkylguanidine‐based oral antimalarial agents targeting plasmodial phospholipid metabolism.     

Novel portable electrical detection system for DNA SENSOR application

A novel, portable, electrical detection system was constructed for DNA sensor application to detect DNA hybridisation. The read-out circuit consists of an analogue circuit and a digital circuit. The analogue circuit with an IC MAX038 generates a sine wave with a constant frequency (10?kHz), which serves as the input for the DNA sensor. The DNA sensor consists of active and reference sensors. DNA hybridisation between the DNA probe and the target sequences causes changes in the conductance of the conductive membrane (DNA/MWCNTs) on the sensor surface, which lead to changes in the amplitude of the sine wave from the sensor output compared with that of the reference signal output (input sine wave). We used a digital circuit with a microprocessor (PIC33FJ256MC710) to determine the change in the amplitude of the sine wave signal of the sensor. From these digital data, the difference in the amplitudes of the active and reference sensors was calculated and displayed on the liquid crystal display. Measurement results show that the portable electrical detection system can detect DNA target concentrations as low as 0.16?µM. The detection of the amplified polymerase chain reaction sample and the reproducibility of the DNA sensor results were also determined using the designed readout circuit. The proposed electrical detection system is suitable for DNA sensor application.     

Microwave-assisted synthesis and characterization of Ti1 − xVxO2 (x = 0.0–0.10) nanopowders

Ti_1 ? xV_xO₂ (x = 0.0–0.10) nanopowders were successfully synthesized by a microwave-assisted sol–gel technique and their crystal structure and electronic structure were investigated. The products were characterized using X-ray diffraction (XRD), scanning electron microscopy (SEM), Raman and UV–Vis spectroscopy. The results revealed that TiO₂ powders maintained the anatase phase for calcination temperature below 600 °C, but gradually changed to the rutile phase above 800 °C. The formation of the rutile phase was completed at 1000 °C. For Ti_1 ? xV_xO₂ (x = 0.05) powders, the phase transformation appeared at 600 °C. The absorption edge of Ti_1 ? xV_xO₂ (x > 0) powders broadened to the visible region with increasing V concentration and a strong visible light absorption was obtained with 10% V doping. V doping and subsequent coexistence of both anatase and rutile phases in our Ti_1 ? xV_xO₂ nanoparticles are considered to be responsible for the enhanced absorption of visible light up to 800 nm.     

Experimental investigation on the effect of natural gas composition on performance of autothermal reforming

This paper presents experimental study on catalytic autothermal reforming (ATR) of natural gas (NG) for hydrogen (_H2${\mathrm{H}}_2$) production over sulfide nickel catalyst supported on gamma alumina. The experiments are conducted on a cylindrical reactor of 30 mm in diameter and 200 mm in length with “simulated” NG of different composition under thermal-neutral conditions and fed with different molar air to fuel ratio (A/F$A/F$) and molar water to fuel ratio (W/F)$(W/F)$. The results showed that reforming performance is significantly dependent on A/F$A/F$, W/F$W/F$ and concentration of _C2+${\mathrm{C}}_{2+}$ hydrocarbons in inlet fuel. Fuels containing higher _C2+${\mathrm{C}}_{2+}$ hydrocarbons concentration have optimum performance in terms of more _H2${\mathrm{H}}_2$ at higher A/F$A/F$ and W/F$W/F$ but lower conversion efficiency. Good performance for ATR of fuel containing 15%–20% _C2H6${\mathrm{C}}_2{\mathrm{H}}_6$ can be achieved at A/F=5–7$A/F=5–7$ and W/F=4–6$W/F=4–6$, much higher than that for optimum performance of ATR of methane (A/F=3,W/F=2–2.5$A/F=3,W/F=2–2.5$). _CO2${\mathrm{CO}}_2$ in the inlet fuel does not have significant effect on the reversed water–gas shift reaction. Its effect on reforming performance is mainly due to the dilution of inlet fuel and products.     

Determination of a unique configuration of free-form tensegrity structures

A numerical method is presented for form-finding of free-form tensegrity structures. The topology and an initial randomly generated force density vector are the required information in the present form-finding process. An approach of defining a unique configuration of free-form tensegrity structures by specifying an independent set of nodal coordinates is rigorously provided, which means that the geometrical and mechanical properties of the structure can be at least partly controlled by the proposed method. Several numerical examples are presented to demonstrate the efficiency and robustness in searching new self-equilibrium stable free-form configurations of tensegrity structures.     

Form-finding of tensegrity structures with multiple states of self-stress

A numerical method is presented for form-finding of tensegrity structures with multiple states of self-stress. At the first stage, the range of feasible sets of the nodal coordinates and the force densities are iteratively calculated by the only known information of the topology and the types of members until the required rank deficiencies of the force density and equilibrium matrices are satisfied, respectively. The linear constraints on the force densities which are derived from the obtained configuration??s symmetry properties and/or directly assigned by designers are then utilized to define a single integral feasible force density vector in the second stage. An explanation on the null space of the force density matrix that generates the configurations of the tensegrities is rigorously given. Several numerical examples are presented to demonstrate the efficiency and robustness in searching new self-equilibrium stable configurations of tensegrity structures with multiple states of self-stress.     

Ultrasensitive guided-mode resonance biosensors superimposed with vertical-sidewall roughness

In this paper, we present our investigations of the effects of vertical-sidewall roughness (VSR) on guided-mode resonance (GMR) filters made of subwavelength grating for applications to ultrasensitive biosensors operated under IR illumination. We designed the spectral FWHM of the grating filter to be as narrow as possible in order to emphasize the sensitivity and VSR effects. Three types of VSR morphologies on the grating-in terms of the correlation length ξ and the rms of the maximum roughness deviation σ-were considered and evaluated. Rigorous coupled-wave analysis was then implemented to quantify the shifts in the reflective resonance peak wavelength value (PWV) of the grating filter. Our simulations show that for specific ξ values, the PWVs remain constant even if σ becomes as large as 10?nm; this indicates dramatic bandgaplike stripes, which are similar to the bandgaps observed in the band diagrams of photonic crystals in the ξ-σ diagram that we have proposed in this study. In other words, the effects of VSR on the GMR biosensor performance are insignificant when ξ is located at certain bands; therefore, this type of roughness is highly tolerable even if the linewidth of the filter is decreased to only a few tens of nanometers.     

Robust FIPP p-cycles against dual link failures

We propose a new generic flow formulation for Failure-Independent Path-Protecting (FIPP) p-cycles subject to multiple failures. While our new model resembles the decomposition model formulation proposed by Orlowski and Pioro (Networks, 2011) in the case of classical shared path protection, its originality lies in its adaptation to FIPP p-cycles. When adapted to that last pre-configured pre-cross connected protection scheme, the bandwidth sharing constraints must be handled in a different way in order to take care of the sharing along the FIPP p-cycles. It follows that, instead of a polynomial-time solvable pricing problem as in the model of Orlowski and Pioro (Networks, 2011), we end up with a much more complex pricing problem, which has an exponential number of constraints due to some subtour elimination constraints. Consequently, in order to efficiently solve the pricing problem, we consider: (i) a hierarchical decomposition of the original pricing problem; (ii) heuristics in order to go around the large number of constraints in the pricing problem. Performance evaluation is made in the case of FIPP p-cycles subject to dual failures. For small to medium size networks, the proposed model remains fairly scalable for increasing percentages of dual failures, and requires much less bandwidth than p-cycle protection schemes (ratio varies from 2 to 4). For larger networks, heuristics are required in order to keep computing times reasonable. In the particular case of single link failures, it compares very favorably (5 to 10 % of bandwidth saving) to the previously proposed column generation ILP model of Rocha, Jaumard and Stidsen (Telecommun. Syst., 2012).