A model for failure in the contact system of a semiconductor device on temperature cycling

A physical model is proposed for the failure in a multilayer contact system for a semiconductor device on temperature cycling.     

The effect of the thermal decomposition reaction on the mechanical and magnetocaloric properties of La(Fe,Si,Co)13

We report on the influence of the Co content in the magnetocaloric system La(Fe,Si,Co)₁₃ on the thermal decomposition (TD) reaction, and subsequently on the magnetocaloric properties. In the course of the TD reaction, the magnetocaloric La(Fe,Si,Co)₁₃ phase reversibly decomposes into α-Fe(Co,Si) and the intermetallic LaFeSi phase, thus enhancing the mechanical properties and therefore the machinability of the compound. The addition of Co significantly speeds up the reaction kinetics. The optimum temperature range for the TD reaction was determined to be 973–1073 K, with the lower and upper limit at 873 K and 1173 K, respectively. With electron microscopy a lamellar microstructure has been found in the decomposed state, indicating a eutectoid-type phase reaction. The width of the lamellae is ～26 nm in LaFe₁₂Si and decreases with increasing Co content. Three-dimensional atom probe (3DAP) measurements show the enrichment of Co and Si in LaFeSi lamellae. We conclude that the addition of Co somehow decreases the lamellar spacing, which is the main reason for the enhanced TD kinetics. Finally, it is interesting to note that the highly ordered nano-scale mixture of strongly ferromagnetic α-Fe(Co) with the non-ferromagnetic phase induces a significant increase in coercivity, H_c. The shape anisotropy of the thin α-Fe(Co) lamellae yields a semi-hard permanent magnet with a coercivity of ～100 A cm^?1.     

Mechanism of Formation of a Fast Gas Jet

The formation of a fast gas jet from not too long, plane, Ushaped charges is studied by radiography. It is shown that a shockcompressed region is formed in the air cavity as a result of collision of explosion products. After detonation of the charge, a jet flows from this region with a velocity exceeding the detonation velocity. The jet exhibits a cumulative effect, which is maximal for a square air cavity.     

Application of a wedge-type Fabry-Perot etalon to the study of low-density air flows

A Fabry-Perot etalon with a wedge-shaped arrangement of the mirrors is applied to the study of low-density air flows. Interferograms of a gas flow past a cylinder at a pressure of 5 · 10^–2 torr are presented.     

Design and watertight effectiveness of the underground contour of the Sayano-Shushenskoe dam

Conclusions Seepage in the foundation of the SSh hydrostation has a nonuniform but regular character and substantially depends on the acting head and SSS. At an elevation of the UPL of less than 520 m, a change in the permeability of the rock mass is observed mainly on the upstream side of the grout curtain. The intensity of decompression of the rocks increases with increase of elevation of the UPL, especially above 534 m. At 540 m the zone of decompression of the contact part of the foundation in some places intersects the grout curtain and in individual cases intercepts the drainage; the discharge of the drain wells increases by 5–7 times in comparison with the discharge at an elevation of the UPL of 500 m. The width of the joints near the drainage (according to calculation) averages from 0.3–0.5 to 0.73 mm; here and there it can reach 1.5–2 mm. The average gradient of the head in the grout curtain is within 10–15; at individual places near the drainage it reaches 26, which is at the level of the allowable for a rock mass.A method of controlling seepage is mainly used in such cases — repeated grouting at low elevations of the UPL, including with the use of plastic grouts, which in individual cases accelerate setting of the additives.As measures for improving the seepage conditions and quality of monitoring, we can recommend plugging places of water shows through the grouting holes at an elevation of the UPL of 500–510 m, intensifying drainage in stretches of increased inflows and passages of the head beyond the drainage line, and broadening of geophysical and hydrogeological investigations for a detailed study of the character of change in permeability and seepage during fluctuations of the reservoir, especially at high elevations. During operation of the dam it is necessary not to exceed the attained rates and level of filling the reservoir (elevation 540.25 m), since at levels close to the NPL, the seepage discharge increases intensely.The underground contour of the Sayano-Shushenskoe dam is of high quality and operates effectively and reliably under conditions of a varying stress-strain state of the foundation during fluctuations of the reservoir level.Translated from Gidrotekhnicheskoe Stroitel'stvo, No. 1, pp. 17–24, January, 1992.     

Fluctuations with 1/<Emphasis Type="Italic">f</Emphasis> Spectrum under Conditions of Acoustic Cavitation of Water

The results are given of an experimental investigation of fluctuations under conditions of cavitation of water in an ultrasonic field. The laser photometry and resistive methods are employed. The fluctuations of the intensity of transmitted laser radiation and the fluctuations of electrical conductivity during the passage of electric current through a weak aqueous electrolyte under conditions of ultrasonic cavitation are measured in the experiments. A mode is found which is characterized by the 1/f-behavior of power spectra and by the bimodal function of local distribution of fluctuation amplitudes. The distribution function under conditions of scale roughening of realizations is investigated. It is found that an increase in the region being probed leads to scale-invariant Gaussian distributions; this agrees with the theoretical concepts of the generation of 1/f fluctuations in the case of nonequilibrium phase transitions.__________Translated from Teplofizika Vysokikh Temperatur, Vol. 43, No. 4, 2005, pp. 631–636.Original Russian Text Copyright © 2005 by V. P. Koverda, V. N. Skokov, A. V. Reshetnikov, and A. V. Vinogradov.     

Magnetocrystalline anisotropy of R2Fe17Hx (x=0, 3) single crystals

The magnetocrystalline anisotropy of R₂Fe₁₇ (R=Y, Gd, Tb, Ho and Er) and their hydrides are studied by analyzing the magnetization curves of single crystal samples in the temperature range 4.2–300 K in magnetic fields up to 140 kOe. There is no noticeable influence of hydrogenation on the magnetic anisotropy in the Y₂Fe₁₇ and Gd₂Fe₁₇ compounds. An easy-plane to easy-cone transition is detected for a Tb₂Fe₁₇H₃ single crystal after hydrogenation. A significant change of the magnetization process has been observed in the hydrides Ho₂Fe₁₇H₃ and Er₂Fe₁₇H₃. Hydrogenation induces a FOMP-type transition in the Ho₂Fe₁₇H₃ compound and, on the contrary, leads to the disappearance of the FOMP type transition in the Er₂Fe₁₇H₃ compound. The obtained results are discussed on the basis of a model based on the interaction of the quadrupolar moment and the magnetic moment of the 4f electron shell of the rare earth ion with the interstitial hydrogen. It is established that the orientation of the quadrupolar moment of the asymmetric 4f shell with respect to the direction of the resulting magnetic moment of 4f electrons plays an important role.