Matrix Transformation in Boron Containing High-Temperature Co–Re–Cr Alloys

An addition of boron largely increases the ductility in polycrystalline high-temperature Co–Re alloys. Therefore, the effect of boron on the alloy structural characteristics is of high importance for the stability of the matrix at operational temperatures. Volume fractions of ε (hexagonal close-packed—hcp), γ (face-centered cubic—fcc) and σ (Cr₂Re₃ type) phases were measured at ambient and high temperatures (up to 1500 °C) for a boron-containing Co–17Re–23Cr alloy using neutron diffraction. The matrix phase undergoes an allotropic transformation from ε to γ structure at high temperatures, similar to pure cobalt and to the previously investigated, more complex Co–17Re–23Cr–1.2Ta–2.6C alloy. It was determined in this study that the transformation temperature depends on the boron content (0–1000 wt. ppm). Nevertheless, the transformation temperature did not change monotonically with the increase in the boron content but reached a minimum at approximately 200 ppm of boron. A probable reason is the interplay between the amount of boron in the matrix and the amount of σ phase, which binds hcp-stabilizing elements (Cr and Re). Moreover, borides were identified in alloys with high boron content.     

Nonuniformity of phase structure in immiscible polymer blends

This article is focused on the phase structure development in immiscible polymer blends during melt mixing. Nonuniformity of the phase structure, i.e., the coexistence of areas containing particles with markedly different size distribution, was detected in quenched and compression molded samples of a number of various blends prepared by long and intensive mixing in the chamber of a Plasticorder. The same effect was found also for polystyrene/polyamide blends prepared in a twin‐screw extruder. It was shown that neglecting nonuniformity of the phase structure can lead to considerable error in evaluation of the effect of system parameters on the blend morphology. The reasons for the effect were discussed and it was found that inhomogeneous flow field in mixers is a plausible explanation of the nonuniform phase structure. POLYM. ENG. SCI., 2008. © 2008 Society of Plastics Engineers     

Convolutional solutions of partial difference equations

A significant part of the theory of one-dimensional linear shift-invariant systems is based on the concept of weighting function (or impulse response): the output is the convolution of the weighting function with the input. This paper introduces the concept of linear translation-invariant systems and uses this notion in studying impulse response, z-transforms, and transfer functions for multidimensional systems.     

Mapping field density distribution in radiators by microwave noise

In his earlier paper on Active Microwave Radiometry, the author indicated that microwave noise can be used to map field density distribution inside radiators and in antenna systems, without the need for anechoic chambers. The presented paper gives details and results of such experiment. The method is described, details of equipment are given and results are presented with a concluding commentary.     

Carcass traits and meat quality of male lambs fed monensin or lasalocid

Male lambs, crossbred Merino × Ille de France, were fed a diet supplemented with 31 mg monensin or 32 mg lasalocid per kg of feed dry matter from an initial body weight of 23·6–23·9 kg to the slaughter weight of approximately 40 kg.

Carcass traits and meat quality were evaluated after slaughter; the values obtained were compared with those of the control group fed the same diet without the ionophore supplement.

There were few significant differences among the individual groups in carcass value, sensoric and technological properties of meat and of its composition. However, the lasalocid-fed group seemed to be somewhat better in muscling and in the composition of meat.     

Observation of higher order NMR larmor lines by SQUID in solids at low magnetic field

We describe an apparatus allowing the observation of the NMR static longitudinal component of nuclear magnetizationM _z by a SQUID at low magnetic fields and atT=4.2 K in Plexiglas, Teflon, and CaF₂. The higher order NMR Larmor lines at 2f ₀, 3f ₀, and 4f ₀, wheref ₀ is the Larmor frequency of the allowed NMR line, were measured. These lines correspond to a flip of two, three, and four spins, respectively, by one photon. The amplitudes of 2f ₀ and 3f ₀ lines and their field dependences show that the common assertion that the forbidden lines at 2f ₀ and 3f ₀ appear in the same order of perturbation theory and that their intensity decreases with static magnetic fieldB ₀ asB ₀ ^–2 is wrong. In fact, the third Larmor line 3f ₀ appears at higher order than the second Larmor line 2f ₀ and its intensity decreases asB ₀ ^–4 . This is also shown by a theoretical calculation of its intensity. For the first time the NMR SQUID technique allowed the detection of the 4f ₀ line, corresponding to the simultaneous flip of four spins by one photon.