Eddy current and total power loss separation in the iron–phosphate–polyepoxy soft magnetic composites

This work investigates the magnetic properties of iron–phosphate–polyepoxy soft magnetic composite materials. FTIR spectra, EDX analysis, distribution maps, X-ray diffraction pattern and density measurements show that the particles surface layer contains a thin layer of nanocrystalline/amorphous phosphate with high coverage of powders surface. In this paper, a formula for calculating the eddy current loss and total loss components by loss separation method is presented and finally the different parts of power losses are calculated. The results show that, the contribution of eddy current in the bulk material for single coating layer (k_b = 0.18) is higher in comparison with double coating layer (k_b = 0.09). Moreover, iron–phosphate–polyepoxy composites (P = 0.000004f²) have lower power loss in comparison with iron–phosphate composites (P = 0.00002f²).     

Use of a microcalorimeter of the calvé type for determining the kinetic characteristics of thermal effects in chemically reacting materials

The construction of a dynamic microcalorimeter designed for measuring the kinetic characteristics of thermal effects in solid and powdered polymer materials which react chemically on heating is considered.Translated from Inzhenerno-Fizicheskii Zhumal, Vol. 29, No. 6, pp. 1080–1083, December, 1975.     

High-temperature thermoelectric properties of the sintered Bi2Sr2Ca1 − xYxCu2Oy (x = 0 – 1)

Electrical conductivity and Seebeck coefficient were measured in a temperature range of 320–1073 K for sintered samples of Bi₂Sr₂Ca_{1 – x} Y _x Cu₂O _y (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0). It has been found that the conduction behavior changes from n-type metallic to p-type semiconducting with increasing yttrium concentration. The power factors were in a range of 1.7–3.0 × 10^–5 Wm^–1 K^–2 for the sample with x = 0.8, being maximized by the optimization of the yttrium concentration. The thermal conductivity for the sample with x = 0.8 was 0.73 Wm^–1 K^–1 at 310 K, and decreased with increasing temperature. The values of thermoelectric figure of merit were estimated to be in a range of 3.4–4.8 × 10^–5 K^–1 at temperatures of 320–673 K for the sample with x = 0.8.     

Semiconducting properties of nonstoichiometric manganese silicides

Electrical resistivity, Hall coefficient and thermoelectric power were measured on manganese silicides of composition MnSi_2–x withx ranging from 0.25 to 0.28 in the temperature range from 80 to 1100K. At higher temperatures a forbidden energy gap estimated from the resistivity data was about 0.40 eV. It was confirmed that MnSi_2–x was a degenerated semiconductor and that the hole concentrations in the degenerated state varied from 1.8 to 2.3×10²¹ cm^–3. The ratio of electron to hole mobility was less than unity. The intrinsic resistivity and the hole mobility varied with temperature as 3.6×10^–4 exp(2320/T) and 1.2×10⁴ T ^–3/2 respectively. The value of Hall coefficient calculated by using a mobility ratio of 0.02 was in good agreement with that observed in the intrinsic region. From the relationship between hole concentration and thermoelectric power for MnSi_1.73 near room temperature, the hole effective mass was estimated to be twelve times as large as the free electron mass. The calculation of the thermoelectric power was carried out based on the assumptions that the scattering of carriers is dominated by acoustic lattice scattering and that the carriers obey Fermi-Dirac statistics. The calculated results were in reasonable agreement with the observed thermoelectric powers in the temperature range from 150 to 1100K.     

Rate-dependent fracture toughness of pure polycrystalline ice

A series of three-point bend tests using single edge notched testpieces of pure polycrystalline ice have been performed at three different temperatures (–20°C, –30°C and –40°C). The displacement rate was varied from 1 mm/min to 100 mm/min, producing the crack tip strain rates from about 10^–3 to 10^–1 s^–1. The results show that (a) the fracture toughness of pure polycrystalline ice given by the critical stress intensity factor (K _IC) is much lower than that measured from the J—integral under identical conditions; (b) from the determination of K _IC, the fracture toughness of pure polycrystalline ice decreases with increasing strain rate and there is good power law relationship between them; (c) from the measurement of the J—integral, a different tendency was appeared: when the crack tip strain rate exceeds a critical value of 6 × 10^–3 s^–1, the fracture toughness is almost constant but when the crack tip strain rate is less than this value, the fracture toughness increases with decreasing crack tip strain rate. Re-examination of the mechanisms of rate-dependent fracture toughness of pure polycrystalline ice shows that the effect of strain rate is related not only to the blunting of crack tips due to plasticity, creep and stress relaxation but also to the nucleation and growth of microcracks in the specimen.     

Heat transfer in conductive microcalorimeters

The process of heat transfer in Calvet-type conductive microcalorimeter has been analysed. The method of reconstructing the true curve of heat liberation from the shape of the thermograms has been presented.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 27, No. 2, pp. 270–276, August, 1974.     

The Middle Product Algorithm I

We present new algorithms for the inverse, division, and square root of power series. The key trick is a new algorithm – MiddleProduct or, for short, MP – computing the n middle coefficients of a (2n–1)×n full product in the same number of multiplications as a full n×n product. This improves previous work of Brent, Mulders, Karp and Markstein, Burnikel and Ziegler. These results apply both to series and polynomials.Received: 20 July 2000     

Laminar Heat Transfer in a Rotating Disk under Conditions of Forced Air Impingement Cooling: Approximate Analytical Solution

The laminar heat transfer of a rotating disk under conditions of forced impingement cooling with a uniform velocity profile at infinity is investigated. The integral method is used to obtain an approximate analytical solution whose constants are found by adjustment to the exact numerical solution of the problem for different values of the Prandtl number Pr = 0.1–1 and the exponent in the power radial distribution of the disk temperature n* = –2–4. Boundaries of different modes of heat transfer are determined. The results of simulation are in good agreement with experiments in the stagnation region for impinging jets flowing coaxially against the disk.     

Enhanced performance of organic light-emitting diodes by inserting wide-energy-gap interlayer between hole-transport layer and light-emitting layer

We demonstrated that driving voltages, external quantum efficiencies, and power conversion efficiencies of organic light-emitting diodes (OLEDs) are improved by inserting a wide-energy-gap interlayer of (4,4′-N,N′-dicarbazole)biphenyl (CBP) between a hole-transport layer of N,N-di(naphthalen-1-yl)-N,N′-diphenyl-benzidine (α-NPD) and a light-emitting layer of tris(8-hydroxyquinoline)aluminum. By optimization of CBP thicknesses, the device with a 3-nm-thick CBP layer had the lowest driving voltage and the highest power conversion efficiency among the OLEDs. We attributed these improvements to enhancement of a carrier recombination efficiency and suppression of exciton–polaron annihilation. Moreover, we found that the degradation of the OLEDs is caused by decomposition of CBP molecules and excited-state α-NPD molecules.     

Similarity solutions for nonlinear diffusion — further exact solutions

Although the nonlinear diffusion equation has been extensively studied and there exists substantial literature in many diverse areas of science and technology, the number of exact concentration profiles is nevertheless limited. In a recent article in this journal (Hill [1]) a brief review of known exact results is given, as well as an elementary integration procedure which appears to be a general device for obtaining integrals associated with similarity solutions. This paper extends the results given in [1] and for particular power law diffusivitiesc ^m (such asm = –/12, –1, –/32 and –2) presents a number of new exact solutions obtained by fully integrating the ordinary differential equations derived in [1]. In addition new results are found for a general nonlinear diffusion equation which includes one-dimensional diffusion with an inhomogenouus and nonlinear diffusivityc ^mx^mas well as symmetric nonlinear diffusion in cylinders and spheres. Moreover by a separate and ad-hoc procedure a new solution is obtained of the travelling wave type but with a variable wave speed. Some of the new exact solutions obtained for one-dimensional nonlinear diffusion with power law diffusivitiesc ^mare illustrated graphically.     

The effect of two-frequency low-cycle loading on the fatigue life of steels and welded joints

Some parts of nuclear power equipment (NPE) are subjected mostly to two-frequency loading during their service. Oscillations with a lower stress amplitude are superimposed on the basic slow loading with high stress (or strain) amplitude. The damage cumulation law, which is valid relatively well for random loading, seems to be less suitable for two-frequency loading. According to the design specifications [1] the service life of parts at two-frequency loading may be 10 to 20 times lower than that at single-frequency loading. The decrease in life depends on both the ratio of loading frequencies and amplitudes, and the material characteristics.Published inProblemy Prochnosti, Nos. 1–2, pp. 118–125, January–February, 1995.     

Adequacy of the methods used to approximate the volt-ampere characteristics of dc electric-arc plasma generators

The adequacy of power approximation of volt-ampere characteristics of a dc electric-arc generator is estimated. Using Fisher's ratio for the variances of the inadequacy and random error, it is shown that this approximation is acceptable. It is also shown that the power source has a slight effect on the characteristics of the arc.Notation A constant - G gas flow rate through the discharge channel of the plasma generator - I current - u voltage across the arc - F Fisher's ratio for variances Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 68, No. 5, pp. 815–819, September–October, 1995.     

Specific features of the interaction of alloys of the didymium-iron-boron system with hydrogen

We study the interaction of alloys of the Dd-Fe-B system [M-82, M-83, M-84, and M-85 alloys with a mass content of 33–40% didymium, up to 0.5% aluminum, and 1–1.25% boron (the rest is iron)] with hydrogen using volumetric, X-ray phase, and differential thermal analysis. If the initial hydrogen pressure is 1.0 MPa, hydrides with 0.4–0.6 mass % of hydrogen are formed. The saturation of these alloys with hydrogen is accompanied by an increase in the spacing a of an elementary cell by 1.2–1.4% and in c by 0.8–1.1% (the general increase in volume is 3.2–3.9%). If the initial pressure is 0.15–0.2 MPa, the time of complete saturation with hydrogen is 15–20 min for most alloys. At 973–1033 K, the alloys under study in hydrogen disproportionate into DdHx didymium hydride (a = 0.5449 – 0.5458 nm), -iron (a = 0.2864 – 0.2866 nm), and Fe2 B iron boride (a = 0.5112 – 0.5117 nm, c = 0.4228 nm). An increase in the initial hydrogen pressure from 0.1 to 5.0 MPa is accompanied by a decrease in the disproportionation temperature to 930 K.Translated from Fizyko-Khimichna Mekhanika Materialiv, Vol. 40, No. 2, pp. 105–112, March–April, 2004.     

Structural and Transport Properties of Sn-Doped Bi2Te3 – x Se x Single Crystals

The transport properties of Bi_{2 – y} Sn _y Te_{3 – x} Se _x solid solutions are studied. The results demonstrate that doping with Sn has a strong effect on the temperature dependences of the thermoelectric power and electrical conductivity of the crystals. This suggests that the valence band of the crystals contains Sn-related resonance states. The point defects and dislocation system in Bi₂Te₃ and Bi_{2 – y} Sn _y Te_{3 – x} Se _x solid solutions are studied by transmission electron microscopy. It is shown that the predominant defects in the crystals studied, grown by the Czochralski technique, are dislocations lying in the (0001) plane. The estimated dislocation density is 10⁸ to 10⁹ cm^–2, and the primary slip plane is (0001). Electron-microscopic examination indicates the presence of stacking faults and very small dislocation loops in both Bi₂Te₃ and Bi_{2 – y} Sn _y Te_{3 – x} Se _x single crystals. Since all of the crystals are highly degenerate semiconductors, it is reasonable to assume that structural defects have an insignificant effect on their electrical properties.     

Investigation of Microinhomogeneities in a-SiC r :H Films Using the Chemical Induction Model

Amorphous hydrogenated silicon–carbon (a-SiC _r :H) films grown by decomposing silane–methane mixtures in a low-frequency (55 kHz) glow discharge at different methane concentrations are studied by IR spectroscopy. The absorption band in the range 1850–2300 cm^–1 is decomposed into four Gaussian components, and the results are compared with calculations in the chemical induction model. It is found that the carbon atoms are nonuniformly distributed in the nearest neighbor environment of the SiH groups in the form of HSi–Si_{3 – n} C _n (n= 0–3) structures. The random bonding model is used to evaluate the probability of formation of each HSi–Si_{3 – n} C _n structure as a function of the C/Si ratio. Comparison with experimental data points to an inhomogeneous microstructure of the films.     

Anisotropy of Young's modulus and tensile properties in cold rolled α′ martensite Ti–V–Sn alloys

Young's modulus and tensile properties of cold rolled Ti–8 mass% V and (Ti–8 mass% V)–4 mass% Sn alloy plates consisting of α′ martensite were investigated as a function of tensile axis orientation in this work. A single phase of α′ (hcp) martensite is obtained in Ti–8 mass% V and (Ti–8 mass% V)–4 mass% Sn alloys by quenching after solution treatment. By 86% cold rolling, acicular α′ martensite microstructures change into extremely refined dislocation cell-like structure with an average size of 60 nm, accompanied with the development of cold rolling texture in which the basal plane normal is tilted from the plate normal direction (ND) toward transverse direction (TD) at angles of ±49° for Ti–8% V alloy and ±46° for (Ti–8 mass% V)–4 mass% Sn alloy. No apparent anisotropy of Young's modulus (E) is observed for as-quenched Ti–8% V (E = 76–83 GPa) and (Ti–8% V)-4%Sn (E = 69–79 GPa). In contrast, Young's modulus increases with increasing angle from the rolling direction (RD) to TD for cold rolled Ti–8% V (E = 72–94 GPa) and (Ti–8% V)–4%Sn (E = 63–85 GPa). The observed anisotropy of Young's modulus can be reasonably explained in terms of the cold rolling α′ texture.0.2% proof stress and tensile strength are independent of tensile orientation for cold rolled Ti–8% V and (Ti–8% V)–4%Sn alloys. In contrast, larger elongation to fracture is obtained in specimens deviated by 30°, 45° and 60° from RD than by 0°, 75° and 90°. Scanning electron microscopy (SEM) fractographs reveal that quasi-cleavage-like fracture plane appears in 0° specimen of cold rolled Ti–8% V which shows brittle fracture and other specimens of cold rolled Ti–8% V and (Ti–8% V)–4%Sn alloys are fractured accompanied with necking and dimple formation. It is suggested from these results that brittle fracture is related to the activation of limited number of slip system and Sn addition leads to the activation of multiple slip systems.     

Composition and Properties of Layered Compounds in the GeTe–Sb2Te3System

The 620-K section of the Ge–Sb–Te phase diagram was mapped out using x-ray diffraction, microstructural analysis, and microhardness measurements. The transport properties of the layered tetradymite-like compounds nGeTe · mSb₂Te₃(n, m= 1–4) were studied in wide temperature ranges (Hall effect and electrical resistivity, from 77 to 800 K, and thermoelectric power, from 90 to 450 K). The results show that the nGeTe · mSb₂Te₃compounds are degeneratep-type semiconductors with a fairly high hole concentration due to the high density of intrinsic point defects. The temperature dependences of the Hall coefficient and resistivity exhibit anomalies related to solid-state phase transitions. The room-temperature lattice thermal conductivity ofnGeTe · mSb₂Te₃is fairly low, in the range 8–10 mW/(cm K).     

Electrical transport properties of Eu2Ti2O7 single crystal

The electrical conductivity, thermoelectric power and dielectric constant of Eu₂Ti₂O₇ single crystal have been studied in the temperature range 300–1000 K. Eu₂Ti₂O₇ is found to be a n-type semiconductor with energy band gap of 2.5 eV. The compound exhibits an extrinsic nature upto 700 K and intrinsic nature above 700 K. Thermoelectric power decreases with temperature in the region 300–700 K whereas it increases with temperature in the region 700–1000 K. Dielectric constant increases with temperature in the entire temperature range studied with a discontinuity atT 700 K.     

Strain rate dependence of iodine-induced stress corrosion cracking of Zircaloy-4 under internal pressurization tests

Pressurization tests were run on unirradiated Zircaloy-4 tubing in the pressure range of 400 to 550 MPa and temperature, 330 to 400 ° C. The effects of the mechanical factor on the susceptibility of Zircaloy to iodine-induced stress corrosion cracking (ISCC) were studied in terms of both time-to-failure and failure strain. The time-to-failure was related to thenth power of stress, and the failure strain was a parabolic function of the strain rate in the limited range of 10^–7 to 10^–4 sec^–1. The ISCC susceptibility was determined by the strain rate rather than the stress, and decreased with increasing test temperature. The results suggest that the film rupture step should be involved in the Zircaloy ISCC and that gas adsorption process is an important step in the overall ISCC.     

Phase transitions of <Emphasis Type="Italic">p</Emphasis>-type ZnAs<Subscript>2</Subscript> at very high pressures

The electrical resistance and thermoelectric power of p-ZnAs₂ are measured in the pressure range 15–50 GPa. The results attest to phase transitions at 7–10 and 25–30 GPa.Translated from Neorganicheskie Materialy, Vol. 41, No. 2, 2005, pp. 135–137Original Russian Text Copyright © 2005 by Mollaev, Arslanov, Saipulaeva, Babushkin, Tatur, Marenkin, Volfkovich.