Functional relationships between the conventional steady-state error characteristics and the weighting matrices in the quadratic performance index†

The requirements for achieving a desired value of steady-state error for an optimal control system utilizing the quadratic performance index with a linear plant arc derived for step, ramp and parabolic inputs. These requirements result in a number of the elements of the Riccati matrix being specified in terms of known parameters. It is shown that for an all-pole plant the control system cannot follow a parabolic input. For the stop input the q ₁₁ element of the Q matrix is specified as one for an all-pole plant or in terms of the fixed plant parameters for a pole-zero plant. Depending on the number of requirements and the order of the system it may be necessary to assume values for the remaining elements of the Q matrix in order to solve the reduced Riccati equation.     

Optimization of Processing Parameters for the Preparation of Flounder Frame Protein Product

Flounder frame was used as a raw material for the preparation of protein product. Processing parameters were evaluated using both fresh and frozen ground frames. The results indicate the following optima: (1) pH of extraction medium, ii; (2) extraction time, 60 min; (3) volume to weight ratio, 10: 1; (4) extraction temperature, 23°C. Isoelectric precipitation was conducted at pH 5 using KCI or H₃PO₄. Results indicate that NaOH was more effective than Ca(OH)₂ in solubilizing frame protein at pH 11. Ground frozen flounder frames gave a 10% decrease in protein extractability when compared to fresh frames using NaOH as the extractant and a 22% decrease when Ca(OH)₂ was employed as the extractant. Approximately 70% of the protein is recovered using the NaOH-HCI system.     

Multiple Forms of Phenoloxidase

SUMMARY— The phenoloxidase system in the tissues of mushrooms, potatoes, and apples was investigated using a polyacrylamide electrophoretic technique. The enzyme system was shown to exhibit the phenomenon of multiple forms. The multiple form pattern obtained was highly characteristic for each individual species and variety studied, and substrate specificity was evident. The mushroom phenoloxidase system ( Agaricus campestris ) was shown to consist of at least nine distinct dl-dopa-reactive multiple forms, and at least three forms reacting with I-tyrosine. Potatoes (var. Rural Russet) showed at least 11 bands of dl-dopa activity, while apples (var. Golden Delicious) had at least three multiple forms of dl-dopa activity. By introducing the "multiphase" gel electrophoretic technique a better resolution of the multiple forms was obtained. A group of closely related dl-dopa multiple forms in mushrooms had the unique ability to withstand the temperature of 70°C for one hour. Sulfite, ethylenediamine-tetraacetic acid (EDTA) and other treatments affected the multiple forms differently. Each multiple form behaved as an individual entity upon repeated elutions and electrophoreses.     

Isolation, Purification and Physicochemical Characterization of Polyphenoloxidases (PPO) from a Dwarf Variety of Banana (Musa cavendishii, L)

A procedure for isolating and purifying polyphenoloxidase from banana pulp is described. Maximum activity was obtained from the inner portion of the pulp by extraction with 0.2M sodium phosphate buffer, pH 7.0, containing 1% insoluble PVP and 0.25% Triton X-100. The enzyme was purified 38.8-fold after acetone precipitation, re-extraction of the precipitate with phosphate buffer containing Triton X-100, storage in the freezer for 7 days (-40°C), chromatography on Sephadex G-100 and electrophoresis on polyacrylamide gel. The purified enzyme (four isozymes) gave a poly-peptide molecular weight (SDS-gel) of 31,000 ± 1,000 and molecular weight on sucrose gradient ultracentrifugation of 62,000 ± 2,000. The isoelectric point, determined by isoelectric focusing on polyacrylamide gel, was 5.2. The enzyme was stable at 55°C for 30 min; it lost mole than 90% of the activity after 5 min at 85°C and was completely inactivated at 95°C for the same time. The absorption spectrum of the purified enzyme showed a maximum at 278 nm and a shoulder at 340-350 nm. This preparation, when submitted to paper chromatography revealed the presence of a fluorescent compound with R_f= 0.57, which was identical with chlorogenic acid.     

Stability of a feedback controlled distributed system by modal representation

In this work a linear distributed parameter system controlled by a finite number of lumped linear feedback loops is considered. The spatial portion of the system is decomposed using generalized Fourier expansions, and a complex frequency domain transcendental characteristic determinant results.

The theory developed is then applied to the automatic regulation of water flow in a ‘ reach ’ of an open irrigation canal. The dynamics of water flow in the transient state are described by a set of two first-order non-linear partial differential equations. The boundary conditions, governed by the water-flow dynamics under the gate, are also non-linear equations. For this particular system the feedback controller signal originates at the downstream boundary and controls the gates at the ‘ head ’ of the canal.

The stability analysis of the complete closed-loop system is based on perturbation about some steady-state flow conditions which allows for the linearization of the system's non-linear partial differential equations and boundary conditions. Subsequent application of the Nyquist criterion to a modal representation of the distributed parameter portion of the control loop in cascade with the lumped parameter controller yields the stability conditions.     

PREPARATION AND CHARACTERIZATION OF α-AMYLASE IMMOBILIZED ON COLLAGEN MEMBRANES

Crystalline pancreatic α-amylase was codispersed with hide collagen at pH 4.0 and tanned to form a membrane which degraded starch. The optimum pH for the codispersed membrane preparation was at pH 7.0 in contrast to the soluble enzyme which was as active at pH 8.0 as at pH 7.0. The immobilized enzyme responded maximally to 0.22M chloride whereas 0.02M chloride gave optimum rates for the soluble enzyme. The immobilized enzyme resisted thermal inactivation better than the soluble α-amylase. Raising the temperatures from 30 ° to 50 °C produced a 500% increase in rate for the bound enzyme. It was also demonstrated that membranes retained greater activity when stored in starch solution than in water. The effect of glutaraldehyde concentration on membrane activity was also studied.     

Preservation of Grayfish (Squalus acanthias) by Salting

Grayfish (Squalus acanthias) fillets were preserved by an improved salting technique with pre-brining procedure along with ascorbic acid treatment in order to retard rancidity. The protein loss during salting was 2.4% and more than 2/3 fatty acid content of salted fillets decreased over 8 wk of storage at 20°C. The added ascorbic acid had an antioxidative effect for 2 wk of storage, after which the TBA values rose sharply. The organoleptic evaluation indicated no significant decrease in flavor until after 4 wk of storage. Statistical T-test showed no significant differences for appearance, odor, and texture among salted grayfish and salted cod fillets.     

Chemical Composition and Protein Quality of Some Southern New England Marine Species

Chemical composition, nutritional quality of protein and mineral content of cod, whiting, scup, squid and monkfish were determined. With a protein content ranging between 15 and 18%, the amino acid composition, in vitro enzymatic digestibility and PER evaluation indicated variation among two species. Protein quality of scup was significantly superior and that of squid was significantly inferior (p < 0.05) when compared to other species. The ratio of essential to nonessential amino acids ranged between a high of 0.72 for whiting and a low of 0.62 for squid. The cholesterol values for all the species, except squid (80.65 mg/100g tissue), were between 18.58 and 37.69 mg/100g tissue. The elemental analysis indicated scup and squid values deviating from the other species for major essential trace elements.