Time-discretization of nonlinear systems with time delayed output via Taylor series

An output time delay always exists in practical systems. Analysis of the delay phenomenon in a continuous-time domain is sophisticated. It is appropriate to obtain its corresponding discrete-time model for implementation via a digital computer. A new method for the discretization of nonlinear systems using Taylor series expansion and the zero-order hold assumption is proposed in this paper. This method is applied to the sampled-data representation of a nonlinear system with a constant output time-delay. In particular, the effect of the time-discretization method on key properties of nonlinear control systems, such as equilibrium properties and asymptotic stability, is examined. In addition, ‘hybrid’ discretization schemes resulting from a combination of the ‘scaling and squaring’ technique with the Taylor method are also proposed, especially under conditions of very low sampling rates. A performance of the proposed method is evaluated using two nonlinear systems with time-delay output.     

Time-discretization of nonlinear systems with delayed multi-input using Taylor series

This study proposes a new scheme for the sampled-data representation of nonlinear systems with time-delayed multi-input. The proposed scheme is based on the Taylor-series expansion and zero-order hold assumption. The mathematical structure of a new discretization scheme is explored. On the basis of this structure, the sampled-data representation of nonlinear systems including time-delay is derived. The new scheme is applied to nonlinear systems with two inputs and then the delayed multi-input general equation is derived. The resulting time-discretization provides a finite-dimensional representation of nonlinear control systems with time-delay enabling existing controller design techniques to be applied to them. In order to evaluate the tracking performance of the proposed scheme, an algorithm is tested for some of the examples including maneuvering of an automobile and a 2-DOF mechanical system.     

Output feedback controller design for input time-delayed nonlinear system

The linearization of an input/output controller has been designed for an input time delay nonlinear time discretized nonlinear system. The time discretized nonlinear model has been obtained based on Taylor-Lie series expansion method and zero order hold assumption. The resulting control algorithm enables the time delay nonlinear system control, while the continuous time controller cannot handle a time delay nonlinear system due to its infinite dimensionality. The performance of the proposed controller is evaluated by using two different case studies: a Van Der Pol equation and a Continuous Stirred Tank Reactor (CSTR) system that all exhibit nonlinear behavior and input time delay. For all the case studies, the results validate the proposed methods.     

A real-time DSP-based imbalance analysis system for rotating machine with vibration signal

This paper describes a new digital signal processor (DSP) imbalance measurement system dedicated to real-time vibration analysis on rotating machine. To accomplish real-time analysis, the vibration signals are on-line acquired and processed to analyze the mass imbalance and phase position. This is achieved through the use of FFT and Lissajous diagram. The method followed to analyze the mass imbalance with the chosen hardware and software solutions are described in detail in this paper. Several experimental tests demonstrate the efficiency and accuracy in imbalance analysis performance of the DSP system.     

Preparation of PLLA/PBAT‐strengthened degradable expanded polystyrene

To enhance the flexural strength of degradable expanded polystyrene (DEPS) while maintaining degradability, during the manufacturing processes of DEPS, cerium(III) stearate (CeSt₃) and poly‐L‐lactide (PLLA)/poly(butylene adipate‐co‐terephthalate) (PBAT) are used as a nontoxic oxidizer and a co‐biodegradable polymer filler, respectively. The flexural strength of DEPS is decreased by the oxidizer and increased by the biodegradable polymers. Furthermore, by favorable interfacial interaction between PLLA and PBAT, the flexural strength is more enhanced when the two biodegradable polymers are used simultaneously than used separately. The photo‐, bio‐ and oxo‐degradation behaviors of DEPS were evaluated by UV irradiation, thermal treatments, landfill, and non‐landfill tests. Molecular weight of our DEPS is decreased to 90.26% after 2 weeks of UV irradiation and 74.4% after 3 months of thermal treatment test. 35.4 and 31.4% of weight of our DEPS is reduced after 3 months of landfill and non‐landfill test. It is confirmed that the decomposition period of DEPS could be adjusted by controlling the amount of the oxidizer and/or the biodegradable polymers. The FT‐IR study demonstrated that oligomers and nonylphenol which are known to cause the environmental hazards are not generated after the degradation of DEPS. POLYM. ENG. SCI., 57:883–890, 2017. © 2016 Society of Plastics Engineers     

Chemical immobilization of retinoic acid within poly(ε‐caprolactone) nanoparticles based on drug–polymer bioconjugates

All‐trans‐retinoic acid (RA) was chemically conjugated to biodegradable poly(ε‐caprolactone) (PCL₁₀; number‐average M_w ≈ 1250) via an ester linkage. The conjugation was carried out using N,N‐dicyclohexylcarbodiimide and 4‐dimethyl aminopyridine as a coupling agent. The molar ratio of the drug to the polymer was 1.11 as determined by ¹H‐NMR analysis. DSC and WAXD results showed that the formation of crystalline structures of RA was effectively suppressed by conjugation with PCL. The RA–PCL conjugates were formulated into nanoparticles by a spontaneous phase‐inversion technique. Morphological characteristics of the resultant nanoparticles and drug‐loading efficiencies were compared with those of free RA‐loaded nanoparticles. The drug‐loading efficiency of RA–PCL conjugates was almost 100%, while that of free RA was only ～12%. The majority of unconjugated RA was found to form undesirable free‐drug crystals out of nanoparticles, as observed by TEM analysis. This study demonstrates that the conjugation approach of RA to PCL can be an effective means to immobilize and encapsulate RA within nanoparticles for pharmaceutical applications. © 2003 Wiley Periodicals, Inc. J Appl Polym Sci 89: 1631–1637, 2003     

Allelopathic effects ofChrysanthemum morifolium on germination and growth of several herbaceous plants

Aqueous extracts obtained from young green tops ofChrysanthemum morifolium inhibited the germination of six flowering plants, including chrysanthemum itself, provided for experiments. The same phenomenon was also clearly observed when powder made from young green tops and old leaves of chrysanthemum was used. Moreover, the growth of seedlings planted again in garden soil which was once used for the culture of chrysanthemum was greatly interrupted. Chrysanthemum cultured in used garden soil showed far less dry weight than that cultured in fresh garden soil. The weight of chrysanthemum cultured using its root exudates was also less than that cultured with water leachate of fresh garden soil, and therefore these results may be considered to indicate allelopathic effects. In order to find the allelochemicals related to this phenomenon, benzoic acid and phenolic acids such as salicylic,p-hydroxybenzoic, vanillic, gentisic, protocatechuic, syringic, gallic, ferulic, and caffeic acids were identified by gas chromatography.     

Reinforcement of mechanical properties of a poly(ethylene terephthalate) and polycarbonate blend by the addition of thermotropic liquid crystalline polymer

Mechanical properties of the ternary blends of poly(ethylene terephthalate) (PET), polycarbonate (PC), and thermotropic liquid crystalline (TCLP, Vectra A950) were investigated. The ternary blends were prepared by varying the amount TLCP but fixing the ration of PET and PC. The fiber fallen freely through the capillary die had the highest initial modulus (1.46 GPa)/tensile strength (73 MPa) when 10% of TLCP was added. Above this TLCP content, however initial modulus and tensile strength decreased. The scanning electron microscope (SEM) micrographs of the TLCP phase which was extracted by dissolving PET/PC matrix from the blend showed the fine fibrils formed at 5 and 10% of TLCP, while the aggregated TLCP phases at 20 and 30% of TLCP. It was suggested that the decrease of the mechanical properties of the resulting blend was caused by the aggregation of TLCP phase above 10% of TLCP. A high draw ratio gave a rise to the formation of highly oriented fibrils of TLCP phase in the PET/PC matrix and the improvement of mechanical properties of the ternary blend.     

Phytotoxic and antimicrobial activity of volatile constituents ofArtemisia princeps var.orientalis

The volatile constituents ofArtemisia princeps var.orientalis (wormwood) were investigated for phytotoxic and antimicrobial activities. The germination and radicle elongation of receptor plants were inhibited by volatile substances emitted from wormwood leaf and effects were concentration-dependent. Essential oil of the plant extracted by Karlsruker's apparatus suppressed seed germination and seedling elongation of the receptor plants at a threshold concentration of 4.8l/100 ml.Escherichia coli was not susceptible to the wormwood essential oil, but the growth ofBacillus subtilis, Aspergillus nidulans, Fusarium solani, andPleurotus ostreatus was inhibited severely.     

Estimation of the heating value of oily mill sludges from steel plant

Heating values of oily mill sludges were measured and calculated. The calculated values with conventional equations showed severe discrepancies with measured ones. Most of the oxygen was confirmed to be associated with iron rather than with combustibles by a series of experiments such as proximate analysis, ultimate analysis, thermal analysis and chemical analysis. The heating value of the sludge was predicted well by using a modified Dulong's equation which ignores the oxygen content in the sludge.