Influence of Grain Growth on Dielectric Properties of Nb-Doped BaTiO3

Effects of grain size and grain growth in Nb-doped BaTiO₃ on temperature and frequency dependencies of the dielectric constant were investigated. When 0.65 μm powder is sintered to an average grain size of 1 μm, two dielectric constant peaks indicate the presence of Nb-free BaTiO₃ and of Nb-containing material. Single peaks are observed above room temperature after additional grain growth or when 0.07 μm powder is sintered to an average grain size of 1 μm. The Curie point of pure BaTiO₃ with 1 μm grains is 4 to 6°C lower than that of material with grains >10 μm. Thermodynamically, this behavior is accounted for by a phase inversion stress ∼ the room-temperature stress.     

Optical and Magnetic Properties of Some Transition Metal Ions in Barium Phosphate Glass

In barium phosphate glass containing first-row transition metal ions, the ions appear to possess normal oxidation states: Cr³⁺, Mn³⁺, Fe^2+,3+, Co²⁺, Ni²⁺, and Cu²⁺. Room temperature and 77°K spectra for Cr³⁺-, Mn³⁺-, Fe^2+,3+-, Ni²⁺-, and Cu²⁺-containing glasses can be interpreted, on the, basis of octahedrally coordinated metal ions, whereas the spectrum of the Co²⁺ glass correlates with a tetrahedrally coordinated metal ion. Magnetic moments for the glasses are similar to those for the spin-only values of the various metal ions.     

Effects of Grain Growth on the Distribution of Nb in BaTiO3 Ceramics

Measurements of Nb diffusion into large- and small-grained BaTiO₃ disks show a high ratio of grain boundary to bulk diffusivity. Well defined X-ray diffraction lines are found in Nb-doped BaTiO₃ only when significant grain growth occurs during sintering. When grain growth of a 0.65 μm grain size powder is limited at ∼1 μm, excess line broadening results. This is attributed to the simultaneous presence of Nb-free and Nb-rich regions. Because of its low bulk diffusivity little Nb penetrates into the original BaTiO₃ grain cores, and a solid solution forms only in the regions of recrystallization. When grain growth is limited, the "sintering reaction" results in a non-homogeneous system; when appreciable grain growth occurs, most of the original grain cores are eliminated and an essentially uniform system is obtained.     

THE VALUTON: AN AUTOMATION MODEL OF A SOCIOLOGICAL THEORY OF VALUE GENESIS

Abstract

Theories of value are legion, few axe satisfactory, however. Scarcity as source of value is too relativistic and also unable to explain negative evaluation of scarce objects. Labor as a basis of value cannot take account of observed variations of the value of goods. The present approach is an attempt to see value as the result of two sociological processes: proliferation and status association. The first process determines the value of a commodity by its information content, the other by a perceptional process, the halo-effect. The value of a commodity is hence the result of its history, a string of inputs. They lend themselves to be represented in form of an automaton. A prototype of such an automaton is presented, the valuton. A critical assessment concludes the article.     

Preparation of Small-Grained and Large-Grained Ceramics from Nb-Doped BaTiO3

Barium titanate powders with average grain sizes of 0.07 and 0.65 μm were coated with an organic Nb ester, using a liquid-solid mixing process. Small-grained (1 to 3 μm) ceramic dielectrics from both powders and large-grained (>50 μm) dielectrics from the 0.65 μm powder were fired using 0 to 2 at.% Nb. Microstructures, densities, and electrical resistivities were investigated.     

Effect of Using Frozen Concentrated Direct-to-the-Vat Culture on the Yield and Quality of Cheddar Cheese

Approximately 53,000 liters (14,000 gal) pasteurized whole milk was used to make 16 batches of cheese, eight control batches using conventional bulk starter and eight batches using a frozen concentrated direct-to-the-vat culture. The calculated yields were based on both the weight of milk and cheese, and on the weight of milk solids and cheese solids. The yields averaged, respectively, 9.517% and 48.608% with the bulk starter and 9.707% and 49.191% with the frozen concentrated culture. These differences, slightly favoring the frozen concentrated direct-to-the-vat culture, can be of economic and commercial significance. The compositions of the cheeses made with the two starter cultures were very similar. Sensory evaluation did not reveal significant differences in flavor and texture of the two types of cheese when examined at 3, 6, 9 and 12 months.     

Singlet Oxygen as an Intermediate in the Catalytic Fading of Dye Mixtures

The catalytic fading of some yellow azo dyes in the presence of blue, violet or red anthraquinonoid dyes has been investigated. It can be shown that this phenomenon occurs only in the presence of oxygen and is suppressed by adding typical singlet oxygen quenchers. On substituting singlet oxygen producers like methylene blue for the anthraquinonoid dyes, the catalytic fading still takes place, indicating that a photo-oxygenation reaction according to the type II mechanism is responsible. By carrying out competitive photooxidation experiments in ethylcellulose films, relative rate constants for the reaction with singlet oxygen in a rigid material were determined.     

Material requirements planning in hierarchical production planning systems

Material requirements planning (MRP) is a way to develop the time phased material and other resource requirements to satisfy the needs of a master production schedule. Hierarchical production planning (HPP) is a framework for analysis and decision making in complex production environments. They are complementary approaches to the decision support system needs of multi-stage production systems. The hierarchical approach provides for efficient management review of proposed plans at corporate, plant, and shop levels while MRP provides a sound and detailed basis for understanding the implications of proposed plans and for executing the selected plan. The relationships between these two approaches are illustrated with an example application.