Elastic-Plastic Contact Damage in a Lead Lanthanum Zirconate Titanate

Spherical indenters were used to produce elastic-plastic contact damage in a lead lanthanum zirconate titanate (PLZT) under conditions of quasi-static and impact loading. The extent of radial cracking produced under both loading conditions showed good correlation with the response predicted by an earlier fracture mechanics analysis for quasi-static conditions. Calculated radial crack lengths corresponding to conditions of impact loading exhibited excellent agreement with experimentally measured values. The dynamic hardness of the PLZT was determined to be ∼ 1.5 times the quasi-static hardness. Differences in the radial crack lengths produced under the two loading conditions were attributed primarily to this difference in hardness response.     

Inertia and Change in the Early Years: Employment Relations in Young, High Technology Firms

This paper considers processes of organizational imprintingin a sample of 100 young, high technology companies. It examinesthe effects of a pair of initial conditions: the founders' modelsof the employment relation and their business strategies. Ouranalyses indicate that these two features were well alignedwhen the firms were founded. However, the alignment has deterioratedover time, due to changes in the distribution of employmentmodels. In particular, the ‘star’ model and ‘commitment’model are less stable than the ‘engineering’ modeland the ‘factory’ model. Despite their instability,these two blueprints for the employment relation have strongeffects in shaping the early evolution of these firms. In particular,firms that embark with these models have significantly higherrates of replacing the founder chief executive with a non-founderas well as higher rates of completing an initial public stockoffering. Some implications of these findings for future studiesof imprinting and inertia in organizations are discussed.     

Electronic Sensing of Aromatic Volatiles for Quality Sorting of Blueberries

An electronic sniffer using semi-conductor gas sensors that nondestructively measured aromatic volatile gas emissions from fruit was developed to assess blueberry quality. The sniffer detected soft and damaged fruit in packaged containers at a 5% level of damage and distinguished four of five fruit ripeness classes: (1) mature-green and green-pink; (2) blue-pink; (3) blue; and (4) ripe fruit. Sniffer response increased as fruit ripened, as did total concentration of aromatic volatiles. Sniffer response correlated with berry firmness, pH, titratable acidity, and color, and detected differences among 10 cultivars, as did impact response analysis. The electronic sniffer is rapid, nondestructive and may be used to sort and quality check for presence of unripe or damaged fruit in closed packs of fresh berries.     

CHALLENGE STUDIES WITH CLOSTRIDIUM BOTULINUM TYPE E IN A VALUE-ADDED SURIMI PRODUCT STORED UNDER A MODIFIED ATMOSPHERE

Challenge studies were carried out on raw, cooked, and sterilized surimi nuggets, inoculated with 10⁴ spores/g of C. botulinum type E spores. All products were packaged in air and air with an Ageless SS oxygen absorbent and stored at 4, 12 and 25C. Toxin was not detected in any raw product throughout storage (28 days). The absence of toxigenesis was attributed to the low pH (4.1–4.3) due mainly to the growth of lactic acid bacteria (10⁷CFU/g). Toxin was also not detected in any cooked product after 28 days. Product pH did not decrease as previously (due to the absence of LAB), but counts of C. botulinum still decreased throughout storage.
In sterile nuggets , C. botulinum counts increased to 10⁶ cfu/g at both 12 and 25C, respectively, by 28 days. Lactic acid bacteria and Bacillus spp. were not detected throughout the 28 days storage period. Toxin was detected by days 28 and 14 at 12 and 25C, respectively, and toxigenesis preceded spoilage. The absence of toxin in cooked nuggets was attributed to the anti-botulinal role by Bacillus species, the predominant spoilage bacteria in cooked nuggets.     

Demonstration of the Performance of an Inclined Anaerobic Digester in Wine Stillage and Pea Blancher Wastewater Treatment

Disposal of high strength wastes has been a problem in the fruit and vegetable processing industries. We have designed and tested an inclined continuous anaerobic digester for the rapid treatment of unmodified wine stillage (21,000–25,000 mg COD per liter) and waste water from a pea blancher (20,000 mg COD per liter). The digester was successfully operated for periods up to 9 months using feed rates as high as 10.7g COD per liter per day (hydraulic detention time of 2.4 days). COD removal efficiency ranged from 95.9% to 99.5%, and effluent suspended solids were less than 800 mg per liter.     

Physical, Chemical and Sensory Changes in Irradiated Fresh Pork Packaged in Modified Atmosphere

The effects of irradiation dose (0, 0.5 and 1.0 kGy), headspace oxygen (0, 10 and 20% O₂, balance nitrogen) and storage temperature (5, 15 and 25°C) on the physical, chemical and sensory changes in fresh pork were studied using factorial design experiments. Irradiation in the absence of oxygen extended the sensory shelf life of pork from 9 to 26 days at 5°C and from & lt; 2 to 2 days at 25°C. Oxygen in the package headspace combined with irradiation adversely affected physical, chemical and sensory characteristics of the end product.     

RHEOLOGICAL TECHNIQUES TO EVALUATE THE SHELF-STABILITY OF STARCH-THICKENED,STRAINED APRICOTS2

The rheological behavior of strained apricots thickened with modified tapioca starch was investigated using mixer viscometry techniques. Initially, the sample showed irreversible thixotropy which was quantified by evaluating time-dependent torque decay. Mechanically degraded samples had time-independent properties and were evaluated as power-law fluids. Rheological techniques developed were successfully used to evaluate the textural shelf-life of strained apricots thickened with different types of modified tapioca starch.     

Equilibrium Cation Distribution in NiAl2O4, CuAl2O4, and ZnAl2O4 Spinels

Stoichiometric NiAl₂O₄, CuAl₂O₄, and ZnAl₂O₄ spinels were prepared and equilibrated at temperatures from 600° to 1400°C. The parameters u and x , denoting the oxygen position and fraction of divalent cations on tetrahedral sites, respectively, were determined from a detailed X-ray diffraction analysis. In NiAl₂O₄, x increased from 0.07 at 595° to 0.26 at 1391°C; in CuAl₂O₄, x decreased from 0.68 at 613° to 0.64 at 1195°C; and in ZnAl₂O₄, x decreased from 0.96 at 905° to 0.94 at 1197°C. The form of the temperature dependence of x could not be described using theoretically based equations advanced in the literature. A more general equation which allows for a non-distributional contribution to the configurational entropy was derived and observed to properly describe the temperature dependence; the results indicate that short-range order is of definite significance in these intermediate aluminate spinels.     

Robust Stabilization of Nonlinear Systems via Normalized Coprime Factor Representations

A reasonably complete theory for the synthesis of robust controllers for a broad class of nonlinear systems is now available. We use this theory to generalize the linear theory of normalized coprime factor robustness optimization to the case of affine input nonlinear systems. In particular, we show that the equilibrium controller may be characterized in terms of the stabilizing and destabilizing solutions of the Hamilton–Jacobi equation used to calculate the normalized (right) coprime factors of the plant. We also show that the optimal robustness margin of

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