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21.
The recently developed methods of explicit (multi-parametric) model predictive control (e-MPC) for hybrid systems provide an interesting opportunity for solving a class of nonlinear control problems. With this approach, the nonlinear process is approximated by a piecewise affine (PWA) hybrid model containing a set of local linear dynamics. Compared to linear-model-based MPC, a performance improvement is expected with the reduction of the plant-to-model mismatch; however at a cost of controller computation complexity. In order to reduce the computational load, so that desired horizon lengths may be used, we present an efficient sub-optimal solution. The feasibility of the approach for the application was evaluated in an experimental case study, where an output feedback, offset-free-tracking hybrid e-MPC controller was considered as a replacement for a PID-controller-based scheme for the control of the pressure in a wire-annealing machine. 相似文献
22.
Buckwheat has a strong characteristic aroma, but its phytochemical background has not yet been fully elucidated. The aims of this study were identification and quantification of individual compounds responsible for the buckwheat aroma. Volatiles from a freshly ground buckwheat flour were extracted by different methods: direct extraction with petroleum ether, pentane or methanol, distillation with Clevenger apparatus and a headspace solid-phase microextraction method. The extracts were analysed by GC–MS with electron ionisation. Compounds were identified by MS and by comparison of retention times with reference compounds. Direct extraction with methanol and distillation proved to be very efficient. In these extracts twenty-five and thirty-five compounds were identified, respectively. The first extract contained more hydrophilic compounds and the latter more volatile compounds. Most of the compounds were quantified and their odour activity value (OAV) calculated. Only two compounds (salicylaldehyde and phenylacetaldehyde) were found in both extracts. The compounds with the highest contribution to the buckwheat aroma were: 2,5-dimethyl-4-hydroxy-3(2H)-furanone, (E,E)-2,4-decadienal, phenylacetaldehyde, 2-methoxy-4-vinylphenol, (E)-2-nonenal, decanal, hexanal and salicylaldehyde (2-hydroxybenzaldehyde). 相似文献
23.
Distribution of selenium and phenolics in buckwheat plants grown from seeds soaked in Se solution and under different levels of UV-B radiation 总被引:1,自引:0,他引:1
Ljerka Obolt Samo Kreft Ivan Kreft Mateja Germ Vekoslava Stibilj 《Food chemistry》2008,110(3):691-696
Seeds of common buckwheat (Fagopyrum esculentum) were soaked in water, sodium selenate (5, 10 or 20 mg SeVI/L), or sodium selenite (10 or 20 mg SeIV/L) solutions. Plants grown from soaked seeds were exposed to reduced UV-B radiation, ambient, or enhanced UV-B. The mass fraction of selenium in leaves was much higher in plants obtained from seeds soaked with selenate (up to 185 ng/g) in comparison to selenite (up to 103 ng/g). In plants obtained from seeds soaked in water, regardless of UV-B levels, the highest concentration of selenium was found in leaves, where the values were between 45 and 66 ng Se/g. In buckwheat leaves 44.5–63.6 mg/100 g d.m. of fagopyrin was found, and in stems 14.3–26.4 mg/100 g d.m.; here no influence of seed soaking solution or UV-B exposure was found. The content of total flavonoids in leaves was 7.8–15.9% and in stems 1.4–4.1%. 相似文献
24.
Sašo Blažič Igor Škrjanc Samo Gerkšič Gregor Dolanc Stanko Strmčnik Mincho B. Hadjiski Anna Stathaki 《Engineering Applications of Artificial Intelligence》2009,22(4-5):628-638
The paper presents the identification issues of the self-tuning nonlinear controller ASPECT (Advanced control algorithmS for ProgrammablE logiC conTrollers). The controller is implemented on a simple PLC platform with an extra mathematical coprocessor, but is intended for the advanced control of complex processes. The model of the controlled plant is obtained by means of experimental modelling. A special batch-wise algorithm that is based on the Takagi–Sugeno model and uses “fuzzy instrumental variables” technique is described in the paper. Many robustness problems of the classical adaptive approaches can be circumvented to some extent by the proposed batch-wise approach combined with a supervisory mechanism. The paper also includes some experimental results on the hydraulic pilot plant and some simulation case studies. 相似文献
25.
The article presents a novel non-linear multivariate and multiscale statistical process monitoring and signal denoising method which combines the strengths of the Kernel Principal Component Analysis (KPCA) non-linear multivariate monitoring approach with the benefits of Ensemble Empirical Mode Decomposition (EEMD) to handle multiscale system dynamics. The proposed method which enables us to cope with complex even severe non-linear systems with a wide dynamic range was named the EEMD-based multiscale KPCA (EEMD-MSKPCA). The method is quite general in nature and could be used in different areas for various tasks even without any really deep understanding of the nature of the system under consideration. Its efficiency was first demonstrated by an illustrative example, after which the applicability for the task of bearing fault detection, diagnosis and signal denosing was tested on simulated as well as actual vibration and acoustic emission (AE) signals measured on purpose-built large-size low-speed bearing test stand. The positive results obtained indicate that the proposed EEMD-MSKPCA method provides a promising tool for tackling non-linear multiscale data which present a convolved picture of many events occupying different regions in the time-frequency plane. 相似文献
26.
Meta Kokalj Metka Rihtari?Samo Kreft 《Chemometrics and Intelligent Laboratory Systems》2011,108(2):154-161
The use of infrared spectroscopy has spread from single compound research to the investigation of complex biological samples. In infrared spectroscopy, spectral pre-treatment techniques have been assumed to be equally applicable and effective in the analysis of biological samples with complex chemical composition and structure. In this research, the most commonly used pre-treatment techniques were investigated based on the identification of species from whole leaf samples of pharmaceutically important Epilobium and Hypericum genera. Two spectral collection modes were used; whole leaf transmission and KBr-tablet transmission mode. The results of this study do not support the current standard in pre-treatment methods. After the frequency decomposition of a spectral signal by Fourier transform and wavelet decomposition, it was revealed that the important information of whole plant leaf as an example of biological samples was contained in the spectral details. Therefore, smoothing techniques were not appropriate because high frequency information is lost. A vast majority of published work used a Savitzky-Golay smoothing method on infrared spectra of complex biological samples. This method was shown to be less effective. In contrast, taking the derivative of the spectra showed significantly better results; with this pre-treatment method, the overlapping bands become more evident. 相似文献
27.
Darko Lovrec Mitja Kastrevc Samo Ulaga 《The International Journal of Advanced Manufacturing Technology》2009,41(11-12):1066-1075
High-power transmission capacity at low-energy losses, low noise emissions, high reliability, and ease of maintenance, as well as convenient cost-effectiveness, are required for industrial applications regarding variable electro-hydraulic supply systems. Only up-to-date principles regarding volumetrically controlled hydraulic energy using variable supply systems and appropriate control strategy have proven satisfactory for these requirements. The aim of the present work was to study the applicability of a low-priced drive concept using a speed-controlled induction motor in combination with a constant-displacement pump applied in a load-sensing control strategy. The suggested approach of the drive concept has been experimentally verified on a prototype of the drive. A hydraulic press-brake used for the machining of casting products in the automotive industry was taken into consideration. 相似文献
28.
29.
The effect of water-soluble sorbents on exocrine function of the liver was studied in chronic experiments on 2 dogs with a brought out bile duct. It is shown that choline and digitonin sorbents exhibit choleretic properties similar to those of cholestyramine. Choline sorbent causes a drop in the concentration of (2-4-fold) cholic acid in the bile unlike digitonin sorbent. No prolonging action was seen upon cholestyramine administration, while choline sorbent do demonstrate it. Cholesterol and bilirubin levels do not respond noticeably to the above sorbents. 相似文献