A series of discrete-time models of a continuous-time system based on fluency signal approximation

A discrete-time system model based on the discretization of a continuous-time system has been called a sampled-data system. But, in such discretization of the continuous-time system, it has been assumed that input signal u(t) is a staircase signal, that is, u(τ) has a constant value of u(kh) = u_k over the integration interval. The present paper derives a series of discrete-time models of a continuous-time system based on m-order fluency signal approximation. It is revealed that the series of models includes and generalizes the conventional system model based on the assumption of staircase signal input (m = 1). Furthermore, the adaptive discretization is obtained by selecting the appropriate order m according to the characteristic (continuous differentiability) of the input signal of the continuous-time system we are dealing with. Thus, this concept provides a better family of the relationship between the discrete-time system model and the continuous-time system     

Calcium Fortification of Soy Milk with Calcium-Lecithin Liposome System

Calcium ion was enveloped with a membrane system before addition to soy protein to prevent soy protein from being coagulated and precipitated by calcium ion. Soy lecithin was first sonicated in calcium salt solution to envelop the calcium ion with a liposomal structure composed of lecithin. Then, the calcium-lecithin liposomes were added to soy protein solution. Precipitation and coagulation were not observed in this soy protein-lecithin liposome system containing 60 mM Ca²⁺. By this method, it was possible to prepare calcium fortified soy milk containing more calcium (120 mg/100g) than in cow's milk. These results suggest that this calcium-lecithin liposome system is useful for calcium fortification of soy milk.     

Proteinaceous Surfactants Produced from Gelatin by Enzymatic Modification: Evaluation for Their Functionality

Proteinaceous surfactants were prepared by applying the “one-step process” which permitted covalent incorporation of amino acid esters directly into proteins during treatment with papain. Gelatin was used as a hydrophile and n-alkyl esters of L-leucine as lipophiles. Each of the hydrophile-lipophile mixtures was incubated with papain under the following conditions: medium, 1M carbonate (pH 9) or a 20:80 mixture of acetone-1M carbonate (pH 9) containing 2 mM 2-mercaptoethanol; concentration of gelatin in the medium, 33% (w/w); L-leucine ester vs gelatin ratio, 0.1 mole/100g; papain vs gelatin, 1% (w/w); incubation period, 15 min; and temperature, 37°C. The enzymatic reaction was stopped by adding 1N HCl and the product purified by dialysis followed by washing with hot acetone or dichloromethane to remove low-molecular species. Each product was found to be a mixture of peptides having a wide range of molecular weight, with an average at approximately 7,500 daltons. The amounts of the alkyl moieties covalently incorporated were in a range 1.1–1.2 moles per 7,500g of the products. Their surfactancy varied depending particularly on the carbon number of the alkyl moiety; the products resulting from the incorporation of C₄–C₆ alkyl esters of leucine showed greater whippability, whereas the incorporation of the C₁₀–C₁₂ alkyl esters gave products having a higher ability to stabilize an o/w type emulsions.     

Preparation of Cerium-Activated Silica Glasses: Phosphorus and Aluminum Codoping Effects on Absorption and Fluorescence Properties

Cerium-activated silica (SiO₂) glasses were prepared by plasma torch chemical vapor deposition (CVD). In Ce-doped SiO₂ glasses, most Ce exists as Ce⁴⁺ ions; the remaining small amount of Ce³⁺ ions exhibits a broad fluorescence spectrum with a large Stokes shift, ∼9600 cm^-1, from the excitation spectrum peak of 324 nm. Aluminum and phosphorus codoping considerably increases the Ce³⁺ ratio and shifts the peaks of both spectra to shorter wavelengths. P codoping is the more effective way to achieve this result and in some cases produces an absorption spectrum similar to that of a Ce-doped phosphate glass. These findings are consistent with the solvatiorn shell model for codoping, as previously proposed. To codope P, a soot remelting method was devised to deal with the highly volatile P₂O₅.     

Fabrication of YSZ electrolyte for intermediate temperature solid oxide fuel cell using electrostatic spray deposition: II – Cell performance

Electrostatic spray deposition (ESD) was applied to fabricate a thin-layer of yttria-stabilized zirconia (YSZ) electrolyte on a solid oxide fuel cell (SOFC) anode substrate consisting of nickel-YSZ cermet. A colloidal solution of 8 mol% YSZ in ethanol was sprayed onto the substrate anode surface at 250–300 °C by ESD. After sintering the deposited layer at 1250–1400 °C for 1–2 h depending on temperature, the cathode layer, consisting of lanthanum strontium manganate (LSM), was sprayed or brush coated onto the electrolyte layer. Performance tests and AC impedance measurements of the complete cell were carried out at 800 °C to evaluate the density and conductance of the electrolyte layer formed by ESD. With a 97% H₂/3% H₂O mixture and air as fuel and oxidant gas, respectively, the open-circuit voltage (OCV) was close to theoretical and electrolyte impedance was about 0.23Ω cm². A power density of 0.45 W cm⁻² at 0.62 V was obtained. No abnormal degradation was observed after 170 h operation. The electrolyte sintering temperature and time did not significantly affect the electrolyte impedance. on leave from     

Method of Shortening Settling Time Using Final State Control for High‐Precision Stage with Decouplable Structure of Fine and Coarse Parts

High‐precision stages require high‐speed and high‐precision control to improve their production throughput and quality. However, their motion speed and accuracy are expected to reach a limit in the near future if the conventional high‐precision stage structure is used. Therefore, the authors designed and fabricated a “catapult stage,” which has a structure that can be decoupled into a fine stage and coarse stage. The catapult stage is different from conventional dual stages in which the fine stage is disturbed by the coarse stage because they contact each other. This paper proposes a novel control system design for the catapult stage and a control method that shortens the settling time by using final state control (FSC). So far, FSC has mainly been used for applications such as hard disk drives, for which the initial states are zero. However, it is important to consider the initial states for the catapult stage because the initial position, velocity, and acceleration of the catapult stage are not equal to zero. Simulations and experiments were performed to demonstrate the effectiveness of the proposed methods.     

Robust control for a constantly rising temperature system (Hm control approach)

Thermoluminescence dating has attracted the attention of geology and archaeology researchers as a new method. This method requires a heating device to raise the temperature of the specimens at an exact rate. This paper describes the design method of a control system that can achieve this goal. This control system lends to be unstable because of the existence of the parameter perturbation and dead time. In this paper, the perturbation and dead time are treated as perturbations of a nominal plant regarded as a first-order lag time system. Improvement of tracking characteristics in the low-frequency domain and robust stability in the high-frequency domain of the control system are achieved by using the solution of the mixed-sensitivity problem that is a kind of H^∞ control theory. Experiments verify the effectiveness of this method.     

GERT analysis of a single conveyor system†

Graphical Evaluation and Review Technique (GERT) has been applied to the analysis of the discrete conveyor model for service time distributions which are general but bounded and where there is no storage at work stations and no recirculation. The model is described by states with the Markovian property. The GERT analysis gives a visual representation of the conveyor system and useful information in the conveyor system design.     

EFFECT OF DIFFERENT DRYERS AND DRYING CONDITIONS ON ACCEPTABILITY AND PHYSICO-CHEMICAL CHARACTERISTICS OF DURIAN LEATHER

Optimization study on drying condition ofdurian leather was carried out using Response Surface Methodology (RSM). The optimization was conducted for two different dryers, oven dryer and forced-air cabinet dryer, with temperature and time of drying as independent variables. It was shown that both variables significantly affected most of the sensory properties. For both dryers, the optimum points for 5 sensory attributes evaluated including taste, aroma, texture, appearance and overall acceptability, were at temperatures ranged from 47–55 C for 10–14 h. Based on the overall acceptability, the optimum condition for oven-dried leather was achieved at temperature 50C for 12.6 h, while for cabinet-dried leather at 52.5C for 10 h. Results showed that panelist preferred product dried with low temperature-long time compared with high temperature-short time. Except for Hunter color b value of cabinet-dried product, results also indicated that drying condition was significantly influencing the physico-chemical properties such as moisture, A_w, nonenzymatic browning, texture, vitamin C and color of durian leather.     

PURIFICATION OF AMINOPEPTIDASE FROM THE JAPANESE CLASSIFIED BARLEY FLOUR

In a search for biologically active materials from the classified barley flour produced in Japan an aminopeptidase activity was identified. In this paper, the purification of aminopeptidase is described. The activity of the enzyme was monitored using L-leucine-p-nitroanilide as the substrate. After extraction using 20 mM sodium acetate buffer, pH 5.5, from the 95–75% classification flour, ammonium sulfate fractionation was performed between 30 and 50% saturation. The aminopeptidase was then purified about 160-fold to homogeneity as assessed by HPLC using the following sequential chromatography steps: hydrophobic interaction chromatography, Sephacryl S-200HR gel chromatography, DEAM-ion exchange chromatography, hydroxylapatite chromatography, Sephacryl S-100HR gel chromatography. The molecular weight of this enzyme was estimated as 62 kDα by size exclusion HPLC. The enzyme had a K_m value of 0.22 mM and α pH optimum of 7.0.