PHASE AND MORPHOLOGY OF PbNb2O6 OBTAINED BY MOLTEN SALT SYNTHESIS

ABSTRACT

The morphologic development of lead metanlobate powder particles in KC1 is examined with special emphases on the heating- conditions and starting compositions. Potassium ions are substituted in the Pb-x K_2xNb₂0₆(PKN) With the Sthorhoobic modifications.The.morophology of particles changed during PKN formation and particle growth. During the formation process of PKN, equiaxed and rod-shaped particles were obtained both above and below the melting temperature of KC1. The rod-shaped particles have a columnar structure but decrease in number with Increasing potassium content in the starting mixtures. During the growth process, equiaxed particles grew to simple rod-shaped particles without a columnar structure. Potassium in the starting oxide was found to promote the formation of simple rod-shaped particles. PKN powder composed of only simple rod-shaped particles is obtainable.     

Comparison Study of (001)-/(100)-Oriented Epitaxial and Fiber-Textured Pb(Zr,Ti)O3 Thick Films Prepared by MOCVD

(001)-/(100)-oriented epitaxial PZT films and fiber-textured PZT films with a thickness of 2 μ m were deposited on (100) _c SrRuO₃//(100)SrTiO₃ and (111)Pt/TiO₂/SiO₂/(100)Si substrates, respectively, by metalorganic chemical vapor deposition (MOCVD). Crystal structure and the electrical properties were compared for epitaxial PZT films with those of fiber-textured ones, which had the same out-of-plane orientation but different in-plane orientation. The constituent phase change from the single phase of tetragonal PZT, mixture phases of tetragonal and rhombohedral ones and the single phase of rhombohedral one for both films when the Zr/(Zr + Ti) ratio increased. The out-of-plane lattice parameter of (001)- and (100)-axes of PZT films were almost the same value for both films. This indicates the residual strain in the PZT films was almost the same. Dielectric constant (? _r) took the maximum value around the MPB composition for (001)-/(100)-oriented fiber-textured films but was almost independent of the Zr/(Zr + Ti) ratio for epitaxial ones. Moreover, there was no significantly dependence of remanent polarization (P _r) value on the Zr/(Zr + Ti) ratio for (001)-/(100)-oriented fiber-textured films, while it took minimum value near the morphotropic phase boundary (MPB) for epitaxial ones.     

KINETICS OF ABSORPTION OF OXYGEN IN ALKALINE SOLUTIONS CONTAINING A QUINONE-TYPE COMPOUND

The rates of absorption of pure oxygen in alkaline aqueous solutions containing sodium salt of 1,4-naphthoquinone 2-sulfonic acid (NQS) as a catalyzer for the Takahax desulfurization process were measured at 25°C using a liquid jet column.

The kinetics of the absorption was examined based on the theory for gas absorption accompanied by an irreversible second order chemical reaction. The pH of the solution, that is, the concentration of hydroxyl ion plays an important role in a reaction of first order with respect to oxygen and to NQS. The reaction rate constant is directly proportional to pH in the range 9.8-11.5, for more alkaline solutions being found to be 4.5 × l0⁶L/mole ? s.     

REMOVAL OF TOXIC Pb2+ IONS BY SYNTHETIC HYDROXYAPATITES

The removal behavior of toxic Pb²⁺ ions from aqueous and nonaqueous solutions by two synthetic hydroxyapatites (S-1 and S-2) has been investigated by using both batch and column methods.

It was found that Pb²⁺ ions in the both solutions were easily removed to the apatite samples mainly by cation-exchange reactions between the Pb²⁺ ions in the solutions and Ca²⁺ ions of the samples at room temperature. Further, in the system of aqueous PbF₂ solutions, anion-exchange reactions between F^? ions in the solutions and OH ^? ions of the samples occurred simultaneously and the liberated OH ^? and Ca²⁺ ions influenced removal behavior of Pb²⁺ and F^? ions. The maximum removal amount of Pb²⁺ ions from the aqueous solutions was 400?mg per g of S-1. Pb^? ions in the waste water from lead plating factories were completely removed to the apatite samples. In this manner, it was found that the apatites, especially S-1 can be employed as a new removal agent for the treatment of poisonous Pb²⁺ ions in waste water.     

CIVIC CULTURE AND CORPORATE REGIME IN LOUISVILLE

ABSTRACT: We examine the civic culture in Louisville focusing upon the community power structure, community value system, and public decision‐making system as described by knowledgeable persons. Interviewees were selected for their first‐hand knowledge of community decision making as participants and close observers and to represent different interests. Respondents described what resembles a corporate‐centered regime in economic development but which does not necessarily extend to education. The civic culture and attendant myths hold together a city that otherwise is greatly divided by race, class, and status apparent in the geographic segregation of the community into the East, West, and South Ends. The city's self identity and perception in some way may be at odds with its current situation and development strategies.     

WHY IS JAPAN NEOLIBERALIZING? RESCALING OF THE JAPANESE DEVELOPMENTAL STATE AND IDEOLOGY OF STATE–CAPITAL FIXING

ABSTRACT: This study examines Japan's state spatial restructuring to explore the reasons behind it. By doing so, it investigates the grounds on which Japan is adopting neoliberalism. Since the early 2000s, Japan's leaders have been pursuing a combination of state decentralization and selective urban revitalization. At the same time, leaders have abandoned Japan's long‐held goal of balanced spatial development. On the surface, this policy mix resembles the neoliberal state spatial restructuring observed in Western Europe. This study finds, however, that Japan's state spatial restructuring has less to do with scalar adjustment to capital's uneven spatial expansion and the supply‐side economy for economic development. Rather, it has more to do with the political goal of addressing Japan's collectivist culture and government failure. To reach this conclusion, the “locality as agent” approach to politics of scale proposed by Cox and Mair (1991) is applied to the historic analysis of the Japanese developmental state.     

Behavior of Pores in the Sintering of Acicular Fe2O3 Powder

The sintering of acicular Fe₂O₃ powder was studied by isothermal dilatometry, hysteresis Hg porosimetry, and SEM of powder compacts using a resin-impregnating technique, and compared with an ordinary equiaxed powder. It is shown that the pores in the acicular powder compacts remain connected until a later stage of sintering than those in the spherical powder, and that the observed rapid initial densification, along with preferential shrinkage in the parallel-to-pressing direction, can be interpreted in terms of particle rearrangement.     

Kinetic Studies on the Precipitation of Hematite from Iron-Rich Spinel Solid Solutions

The kinetics of hematite precipitation from iron-rich spinel solid solutions has been studied with special emphasis on the effect of divalent cations and iron-oxide concentration. The precipitation kinetics is expressed by the Avrami equation α= 1 – exp [– k ( t –t ₀) ⁿ ] with n = 1, where α, k , and t are fractional precipitation, proportionality constant, and time, respectively. The process is characterized by an activation energy of 30·0.5 kcal/mol, independent of iron-oxide concentration. Stabilization of spinel solid solutions by the cation is most pronounced for Ni followed by Mg and Zn in the order stated, and the effect of the cation is interpreted in terms of the cation distribution in the spinel lattice.     

On the design of optimal and sub-optimal control systems†

Though dynamic programming is an excellent and versatile algorithm, there are many cases in which we cannot apply this algorithm favourably to control system design because of the limited capacity of a digital computer and other difficulties.

Considering these facts, the successively optimizing method and the combined algorithm of dynamic programming and successively optimizing method are presented in this paper.

One of the objects of this paper is to present a practical method for obtaining the optimal solution of control systems with an integral form performance index by the use of dynamic programming.

The other is to present sub-optiinal solutions by the successively optimizing method and the combined algorithm.

These methods are very easy when compared with dynamic programming. Furthermore, these sub-optimal solutions can be made to converge to the optimum by using the recurrent equations repeatedly.