139La-NMR study of spin-flop and spin structure in La2−x Sr x CuO4(x∼1/8)

The external field dependence of the hyperfine field at La-site has been studied on La _2–x Sr _x CuO ₄ (x=0.115) and La _2–x Ba _x CuO ₄ (x=0.125), where the magnetic ordering in Cu-3d spins exists at low temperature. In La _1.885 Sr _0.115 CuO ₄, a significant decrease in the resonance line width was observed above a field of H _c 7.5T, which is the direct evidence of the spin-flop in the canted-spin system with Dzyaloshinski-Moriya interaction. The spin-flop field H _c of 7.5T is slightly lower than that in La ₂ CuO ₄ (H _c 10T), reflecting the decrease of the tilting angle of the CuO ₆ octahedra by the substitution of Sr ²⁺ ion for La-site.     

Morphology of sputter deposited Al alloy films

Morphology of Al–2.0at%Ta and Al–2.0 at.% Nd alloy films before and after annealing was investigated for applications of interconnections for liquid crystal displays. It was found that the morphology and the microstructure of Al–2.0 at.% Nd alloy films changed markedly by annealing at the temperature region from 200°C to 300°C, while the morphology of Al–2.0 at.% Ta alloy films did not change by annealing up to 400°C. For the case of Al–2.0 at.% Nd alloy films, the incline of the <111> fiber texture to the substrate normal was observed during annealing. Structural characteristics of the Al films were investigated by TEM, SAD and XRD to determine the influence of alloying elements on the morphology and the fiber texture. From these results, it was concluded that the microstructures strongly influence the morphology and the grain orientation of Al alloy films.     

Temperature dependence of tensile strength and hardness for nodular cast iron and their mutual correlation

Nodular cast iron has mechanical properties which make it superior to relatively brittle pig cast iron. As a matter of fact, by using appropriate heat treatment processes, the tensile strength of nodular cast iron can be improved to such a degree that its hardness corresponds to that of carbon steels. The main aims in this study are to find the most preferable heat treatment conditions which will yield high strength levels, and to clarify the temperature dependence of mechanical properties for nodular cast iron. The estimation of tensile strength from hardness is also discussed, since tensile tests at elevated temperatures are usually more expensive and time consuming than the hardness tests. Nodular cast irons, having four different microstructures were first prepared by performing the following heat treatments: (1) as-cast, (2) annealed, (3) normalized and (4) bainitized. Tensile property and hardness were then measured for the respective cast irons under elevated temperatures. The temperature dependence of the tensile strength as well as hardness was investigated. It was found that the dependence was well represented by an expression of =₀exp(–BT). Thus results were discussed from a view-point of the reaction rate process. The correlation between tensile strength and hardness was also examined and a significant linearity was found between them. Based on this strict correlation, an estimation procedure of the tensile strength was finally proposed.     

Adsorptive removal of fluoride from aqueous solution using orange waste loaded with multi-valent metal ions

Adsorption gels for fluoride ion were prepared from orange waste by saponification followed by metal loading. The pectin compounds contained in orange waste creates ligand exchange sites once it is loaded with multi-valent metal ions such as Al³⁺, La³⁺, Ce³⁺, Ti⁴⁺, Sn⁴⁺, and V⁴⁺ to be used for fluoride removal from aqueous solution. The optimum pH for fluoride removal depends on the type of loaded metal ions. The isotherm experiments showed the Langmuir type monolayer adsorption. Among all kinds of metal loaded gels tested, Al loaded gel appeared to exhibit the most favorable adsorption behavior. The adsorption kinetics of fluoride on loaded gel demonstrated fast adsorption process. The presence of NO₃⁻, Cl⁻ and Na⁺ ions has negligible effect on fluoride removal whereas SO₄²⁻ and HCO₃⁻ retarded the fluoride removal capacity in some extent. Fluoride removal at different adsorbent doses showed that fluoride concentration can be successfully lowered down to the acceptable level of environmental standard. The fluoride adsorption mechanism was interpreted in terms of ligand exchange mechanism. The complete elution of adsorbed fluoride from the gel was successfully achieved using NaOH solution.     

Reappraisal of Size Effect of Bearing Capacity from Plastic Solution

A simplified method for estimating the ultimate bearing capacity of surface footings on sand is described with special attention to the dependency of the angle of internal friction of sand on confining stress. An extended slip line method is developed, in which the dependency of the angle of internal friction on the confining stress is formulated from results of conventional triaxial compression tests for various sands. Based on results from a comprehensive series of calculations employing the extended slip line method, the writers reappraise size effects on bearing capacity and investigate the relationship between strength parameters of sand and size effects on bearing capacity. A modified formula and several diagrams that provide a simple estimation method are proposed to consider size effects on bearing capacity. A comparison between estimations using the formula and ultimate bearing capacities measured from several series of centrifuge tests demonstrates the practicability of the proposed method for both strip and circular footings.     

Selective adsorption of precious metals from hydrochloric acid solutions using porous carbon prepared from barley straw and rice husk

Porous carbon was prepared by carbonization from agro-waste such as rice husk and barley straw to evaluate the adsorption of precious and base metals from metal solutions. The effects of hydrochloric acid concentration, metal ion concentration, and contact time on adsorption were examined. Rice husk carbon was found to be highly selective for Au(III) and inert to Pt(IV), Pd(II) and other base metals. Barley straw carbon adsorbed these three precious metal ions, but was inert to base metal ions such as Cu(II), Fe(III) and Ni(II). The maximum adsorption capacity of rice husk carbon for Au(III) was 0.76 mol/kg and the maximum adsorption capacity of barley straw carbon for Au(III), Pt(IV) and Pd(II) was 1.47, 0.39 and 0.64 mol/kg, respectively. The effectiveness of recovery of precious metals from industrial solution was also tested and barley straw carbon was found to be highly efficient and selective for the targeted metal ions in the presence of excess of other metal ions. Rice husk and barley straw carbon are thus potential alternatives to commercially available activated carbon as they have high selectivity and are efficient with low production costs.     

Polymeric chiral crown ethers

Summary Copolymerizations of (S)-3,3-dimethyl-2,2-bis[2-(2-vinyloxyethoxy)ethoxy]-1, 1-binaphthyl (S-MVN) or 1,3:4,6-di-O-benzylidene-2,5-bis-O-[2-(2-vinyloxyethoxy)ethyl]-d-mannitol (D-BVM) with isobutyl vinyl ether (IBVE) were carried out with BF₃·OEt₂ in CH₂Cl₂ at 0 °C. The copolymers obtained were soluble in CHCl₃ and THF, and consited of (S)-binaphtho-21-crown-6 or d-manno-21-crown-6 units and IBVE, i.e., poly(S-DVN-co-IBVE) and poly(D-BVM-co-IBVE). These host copolymers dominantly formed complexes with l-phenylglycine methyl ester, whose properties were similar to those for homopolymers of S-MVN and D-BVM.Part 8: H. Hashimoto, T. Kakuchi, O. Haba, K. Yokota: Macromolecules 25 1828 (1992)     

Proposal of Asynchronous Time Division Multiple Access Radio Highway Using Chirp Multiplexing Transform

Asynchronous TDMA bus-link systems using chirp multiplexing transform(CMT) are proposed for radio highway networks to provide the flexibleconstruction of fiber-optic radio access networks and thepossibility of the universal use of these networks among future diverseradio services. The CMT equipped at the radio base station performs twofunctions. One is the conversion of FDM multiple radio services intosignals with a TDMA format and the other is the time compression ofthe generated signal in order to allow asynchronous access. As aresult, the proposed systems can realize the unified transmission ofmultiple radio services and the switching of them in the optical stage(photonic routing) in the networks according to the type of radioservice. The realization of such photonic routing of the radio servicewould greatly benefit the goal of a seamless and universalnetwork available to different types of radio service. Therelationship between the pulse-loss probability performance and thecall-blocking probability performance is theoretically analyzed. Theeffect on the performance of traffic partiality in the coveredarea and the way the performance can be improved are theoreticallyinvestigated. Finally, one of the ways to determine the network sizecovered by a bus link and the number of connected radio base stationsis introduced.     

Oxygen pressure measurements of silica saturated Fe-O-SiO2 melts by the EMF method using zirconia solid electrolyte

The thermodynamic properties of silica-saturated iron silicate slags have been studied from oxygen partial pressure measurements using a solid electrolyte galvanic cell. The oxygen activity in molten silver bath equilibrated with iron silicate slags was determined by the following cell type, Pt, NiNiOJO= /slag-Ag(O), LaCrO₃, Pt at temperatures between 1473 and 1573 K for the slags ranging in compositions from iron saturation to magnetite saturation. The oxygen partial pressures obtained in this investigation were in good agreement with those given by the previous study using the CO-CO₂ gas equilibrium method. The data showed that the Fe^{+ ++}/Fe⁺⁺ ratio is proportional to . Formerly Graduate Students, Kyoto University     

Effective Zone Structure by Use of MLCR Method forRadio ATM Entrance Network

The aim of this paper is to effectivelyconstruct zones in a radio ATM entrance network. A QoSindex is newly proposed in order to consider both celltransfer delay and cell loss rate. The QoS index shows the optimal number of access points coveringeach zone and also shows the allowable user trafficintensity. It is clarified that the modulation levelcontrolled radio method can reduce the number of APs and accommodate more user traffic intensitycomparing with QPSK method.