The Fe-A1-Ti system

An extensive experimental investigation of the Fe-Al-Ti system by metallography, microprobe analysis, and XRD on quenched specimens and on diffusion couples is presented. Two isothermal sections at 800 and 1000 °C were established; they differ substantially from the existing (800 °C) or partly determined (1000 °C) diagrams. From these results, existence of the τ₁ phase (Fe₂AlTi) can be ruled out. Existence of the ternary compounds, τ₂ (Al₂FeTi) and τ₃ (Al₂₂Fe₃Ti₈), is confirmed. The composition limits of both phases were determined; they differ considerably from those given in earlier reports. The τ₂ phase apparently exists in a cubic and a tetragonal polymorph, depending on composition. The cubic form exists at high titanium contents. At 1000 °C, the two polymorphs are separated by a miscibility gap. At compositions where the “X phase” (Al₆₉Fe₂₅Ti₆) was previously reported, single-phase samples were obtained at both temperatures. From the present results, there is no evidence to assume that this is a new ternary phase rather than the ternary homogeneity range of the Al₃Fe phase. In addition, extensions of the binary intermetallic phases into the ternary system were determined.     

Esters of hydroxystearic acids as primary low-temperature plasticizers for a vinyl chloride—Vinyl acetate copolymer

Summary Thirty-one acyloxy or aryloxy esters prepared from hydroxystearic acids have been evaluated as plasticizers for a vinyl chloride-vinyl acetate copolymer (95∶5). Many of them were found to be primary plasticizers, having outstanding low-temperature performance when employed at the 35% level. Formulations with these compounds compared quite favorably in tensile properties with those containing the di-2-ethylhexyl esters of phthalic, sebacic, azelaic, and adipic acids. Volatility losses were similar to those of the four di-2-ethylhexyl esters. The loss of plasticizer through migration was equal to or less than that from compositions containing the esters of sebacic, azelaic, and adipic acids but was greater than that of the phthalate ester. A mechanistic scheme of plasticizer-polymer interaction has been presented, proposing that the rate of diffusion of plasticizer through the polymer mass is a controlling factor in both good low-temperature performance and the resulting high migration losses. Methyl esters, some aromatic esters, and esters containing three or more polar centers have improved permanence but show a more rapid change in torsional modulus as the temperature is lowered during the determination of the Clash-Berg stiffening temperature. Eastern Utilization Research and Development Division, Agricultural Research Service, U. S. Department of Agriculture.     

Stereoisomere Aromastoffe

Zusammenfassung Die Synthese von acht verschiedenen 2-Alkoxy-5-alkyl-tetrahydrofuranen und ihren Stereoisomeren wird vorgestellt, sieben von ihnen sind als Aromastoffe der Wassermelone bekannt. Alle Stereoisomeren werden, ausgehend von optisch reinen-Nonalacton-Enantiomeren, synthetisiert und mit Diisobutylaluminiumhydrid selektiv zu den entsprechenden Lactolen reduziert. Die Lactole werden mit den gewünschten Alkoholen in schwach saurer Lösung zucis/trans-Diastereomeren umgesetzt und durch Flüssigchromatographie in optisch reine Stereoisomere getrennt. Die sensorische Charakteristik aller Stereoisomeren der sieben Verbindungen wird aufgezeigt. Die Trennung dercis/trans-Diastereomeren an DB-210 wird vorgestellt und die chirospezifische Differenzierung der acht Verbindungen diskutiert.

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Stereoisomeric flavour compounds L. Optically pure 2-alkoxy-5-alkyl-tetrahydrofurans — structures and properties

Summary The synthesis of eight different 2-alkoxy-5-alkyltetrahydrofurans and their stereoisomers is presented, seven of which are known to be flavour compounds of water melons. All stereoisomers were synthesized from optically pure-lactone enantiomers, which were selectively reduced by diisobutylaluminium hydride to the corresponding lactols. The lactols were treated with the desired alcohol component in weakly acidic media to yield thecis/trans diastereoisomers, which were separated into optically pure stereoisomers by liquid chromatography. The sensory characteristics of all four stereoisomers of the seven compounds are given. The Stereodifferentiation of thesecis/trans diastereoisomers on DB-210 is demonstrated and the direct chirospecific differentiation of all eight compounds discussed.

     

Deformation behaviour and oxidation resistance of single-phase and two-phase L21-ordered Fe–Al–Ti alloys

Single-phase Fe–Al–Ti alloys with the Heusler-type L2₁ structure and two-phase L2₁ Fe–Al–Ti alloys with MgZn₂-type Laves phase or Mn₂₃Th₆-type τ₂ phase precipitates were studied with respect to hardness at room temperature, compressive 0.2% yield stress at 20–1100 °C, brittle-to-ductile transition temperature (BDTT), creep resistance at 800 and 1000 °C and oxidation resistance at 20–1000 °C. At high temperatures the L2₁ Fe–Al–Ti alloys show considerable strength and creep resistance which are superior to other iron aluminide alloys. Alloys with not too high Ti and Al contents exhibit a yield stress anomaly with a maximum at temperatures as high as 750 °C. BDTT ranges between 675 and 900 °C. Oxidation at 900 °C is controlled by parabolic scale growth.     

New airborne scanning lidar system: applications for atmospheric remote sensing

A new scanning airborne-aerosol lidar system that has the potential to be a valuable atmospheric remote-sensing tool has been developed. The system has the ability to scan both parallel and perpendicular to an aircraft's flight path, and this ability permits both the three-dimensional rendering of the aerosol structure below the aircraft and the measurement of aerosol extinction and optical depth. The system has been integrated into a NASA P-3 aircraft and during a recent flight was used to acquire excellent data with both scanning modes. The system design, the application of the across-track scanning data to the study of the atmospheric boundary layer, and the computation of optical depth derived from along-track scan data are reported.     

Pseudo-T2 mapping for normalization of T2-weighted prostate MRI

Magnetic Resonance Materials in Physics, Biology and Medicine - Signal intensity normalization is necessary to reduce heterogeneity in T2-weighted (T2W) magnetic resonance imaging (MRI) for...     

A neural framework for adaptive robot control

This paper investigates how dynamics in recurrent neural networks can be used to solve some specific mobile robot problems such as motion control and behavior generation. We have designed an adaptive motion control approach based on a novel recurrent neural network, called Echo state networks. The advantage is that no knowledge about the dynamic model is required, and no synaptic weight changing is needed in presence of time varying parameters in the robot. To generate the robot behavior over time, we adopted a biologically inspired approach called neural fields. Due to its dynamical properties, a neural field produces only one localized peak that indicates the optimum movement direction, which navigates a mobile robot to its goal in an unknown environment without any collisions with static or moving obstacles.     

Propane heat pump with low refrigerant charge: design and laboratory tests

Independently of the choice of refrigerant, environmental and or safety issues can be minimised by reducing the amount of refrigerant charge per heat pump or refrigeration system. In the investigation reported here, a laboratory test rig was built, simulating a water-to-water heat pump with a heating capacity of 5 kW. The system was designed to minimize the charge of refrigerant mainly by use of mini-channel aluminium heat exchangers. It was shown that the system could be run with 200 g of propane at typical Swedish operating conditions without reduction of the COP compared to a traditional design. Additional charge reduction is possible by selecting proper compressor lubrication oils or by using a compressor with less lubrication oil.     

Discussion: Integrating SPC and APC

The problem of partitioning the blends (runs) of four mixture components into two orthogonal blocks when a quadratic model is fitted is considered. This is motivated by an industrial investigation of bread-making flours carried out at Spillers Milling Limited, a member of the Dalgety group of companies in the United Kingdom. The design solution proposed by John and described by Cornell is discussed and extended. Study of the characteristics of Latin squares of side 4 leads to reliable rules for quickly obtaining designs of specified kinds. One such design was selected for the experiment at Spillers Milling. Mixture-component values that cause singularity in the new designs are identified, and values that provide designs with highest D-criterion values are obtained for the class of designs discussed. Conveniently rounded, near-optimal mixture component values were chosen for the Spillers Milling experiment, and the analysis led to the prediction of an optimal flour mixture.