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[en] Moessbauer spectroscopy of cobalt-silicides proved the existence of three stoichiometric phases: CoSi2, CoSi and Co2Si. The values of the hyperfine parameters indicated covalent bonds between Co and Si in all phases and could be understood on the basis of their crystallographic structure and of theoretical predictions for the electronic structure. For CoSi2, anomalous spectra were obtained, the origin of which was not clear. The different spectra of the cobalt-silicides permit the prospective use of Moessbauer spectroscopy for the study of formation and structure of Co/silicide/silicon interfaces. (orig.)
[en] This article concerns the investigation of the magnetic behavior of the surface impedance tensor cflx var-sigma in CoSiB amorphous wires having a residual torsion stress and a helical anisotropy. The full tensor cflx var-sigma involving three different components is found by measuring the S21 parameter at a required excitation with a Hewlett-Packard network/spectrum analyzer at MHz frequencies. In general, the impedance plots versus axial magnetic field Hex exhibit a hysteresis related to that for the case of static magnetization. The diagonal components of cflx var-sigma (longitudinal var-sigmazz and circular var-sigmavar-phivar-phi) show a sharp peak in a narrow field interval where the domain walls form and contribute to the ac magnetization dynamics. This peak is not seen for the off-diagonal component var-sigmazvar-phi (var-sigmavar-phiz) since the existence of the domain structure suppresses it. Applying a dc bias current results in a gradual transition to a nonhysteretic asymmetrical behavior with an enhanced sensitivity. The portions of the experimental plots associated with the rotational dynamic process are in qualitative agreement with the theory based on a single-domain model. [copyright] 2001 American Institute of Physics
[en] Crsytal structure of phosphides: Ti2Co12P7, Zr2Co12P7, Zr2Ni12P7, Nb2Co12P7, Nb2Co4P3 is studied by the roentgenographic analysis method. Compound roentgenograms, lattice parameters are presented. It is stated, that Ti2Co12P7, Zr2Co12P7, Zr2Ni12P7, Nb2Co12P7 have the structure of Zr2Fe12P7 type, and Nb2Co4P3 the structure of Hf2Co4P3 type
[en] Highlights: • The performance of an R410A air-conditioner adopting a DEEC. • The effects of operating parameters on the COP and CSPF. • Optimized mixing section diameter of the ejector. • The maximum limit of the entrainment ratio (ER). - Abstract: Even though a dual evaporator ejector cycle (DEEC) offers several advantages over a standard two-phase ejector cycle, few experimental investigations of the performance of the DEEC are available in the literature. This study presents the performance characteristics of an R410A air-conditioner adopted with a DEEC under various operating conditions and ejector geometries. The COP of the DEEC decreased with an increase in entrainment ratio (ER) due to the decrease in pressure lifting ratio. For the optimum ER, the effectiveness of the DEEC increased with an increase in compressor speed with a larger total mass flow rate. The optimum mixing section diameter was determined to be 5 mm based on the cooling seasonal performance factor (CSPF) and CSPFbin of the DEEC. The maximum allowable limit for the ER was also suggested to be 0.3. In addition, the CSPF of the DEEC was 6.3% higher than that of the baseline cycle at an ER of 0.1.
[en] This paper presents the basic concepts and fundamental equations of the Thermodynamics with Finite Speed (TFS) resulted by the systematically study of the thermal reciprocating machine in relation with the piston finite speed and thermal molecular speed measured in the considered thermodynamic system. These concepts are based on the idea that any propagation of the interaction in the thermodynamic systems of finite dimensions is achieved by finite speeds: (1) - piston speed, (2) - average speed of the gas molecules inside the cylinder. A specific approach (scheme of calculation) for non-equilibrium (irreversible) thermodynamic processes is developed within TFS in order to find the fundamental equations appropriate for Optimizing Efficiency or COP and Power of thermal reciprocating machines. Analytical equations for all 5 irreversible thermodynamic processes in gases (isometric, isothermal, isobaric, adiabatic, polytropic) are deduced by integration of the combined First and Second Laws equation for processes with Finite Speed . This paper is limited to Irreversible Processes with Finite Speed, without taking into account the Friction and Throttling effects. It also notes the main moments in the development of TFS that led to these concepts and fundamental equations . (paper)
[en] The ambulatory measurement of ground reaction force (GRF) and human motion under free-living conditions is convenient, inexpensive and never restricted to gait analysis in a laboratory environment and is therefore much desired by researchers and clinical doctors in biomedical applications. A wearable force plate system was developed by integrating small triaxial force sensors and three-dimensional (3D) inertial sensors for estimating dynamic triaxial GRF in biomechanical applications. The system, in comparison to existent systems, is characterized by being lightweight, thin and easy-to-wear. A six-axial force sensor (Nitta Co., Japan) was used as a verification measurement device to validate the static accuracy of the developed force plate. To evaluate the precision during dynamic gait measurements, we compared the measurements of the triaxial GRF and the center of pressure (CoP) by using the developed system with the reference measurements made using a stationary force plate and an optical motion analysis system. The root mean square (RMS) differences of the two transverse components (x- and y-axes) and the vertical component (z-axis) of the GRF were 4.3 ± 0.9 N, 6.0 ± 1.3 N and 12.1 ± 1.1 N, respectively, corresponding to 5.1 ± 1.1% and 6.5 ± 1% of the maximum of each transverse component and 1.3 ± 0.2% of the maximum vertical component of GRF. The RMS distance between the two systems' CoP traces was 3.2 ± 0.8 mm, corresponding to 1.2 ± 0.3% of the length of the shoe. Moreover, based on the results of the assessment of the influence of the system on natural gait, we found that gait was almost never affected. Therefore, the wearable system as an alternative device can be a potential solution for measuring CoP and triaxial GRF in non-laboratory environments
[en] We report on tailoring the perpendicular anisotropy, and out-of-plane exchange bias in (Co/Pd) multilayer exchange coupled to CoO, by patterning them into ordered arrays of antidots or 'holes'. The coercivity in the multilayers is enhanced due to strong domain wall pinning in the vicinity of the antidots. We also observed a smaller degree of asymmetry in the reversal of the exchange-biased antidots as compared to the continuous film. Moreover, a strong interplay between thermal activation and CoO domain size confinement results in the exchange bias for the antidots being either smaller or larger than the continuous film.
[en] The current status of the first generation eutectics, gamma/gamma transition - delta and NiTaC-13, is described in detail. Several second generation systems, such as gamma/gamma transition - alpha and NiTaC 3-116A, gamma - beta, and CoTaC 74 are also reviewed with particular emphasis on their critical physical and mechanical properties, future research directions, and potential applications. Results of recent cost-benefit analyses of eutectic turbine blades are discussed
[en] Highlights: • Experimental investigations of a commercial DAR refrigerator are carried out. • A detailed steady state simulation model of the DAR is developed using Aspen-Plus. • The refrigerator model is validated using the experimental measurements. - Abstract: Experimental investigations and numerical simulations of a low capacity commercial diffusion-absorption refrigerator (DAR) in stationary mode are carried out. The tests are performed under different heat input conditions. Optimal operation of the DAR refrigerator is reached with a power supply of 46 W at a generator temperature of 167 °C, corresponding to a coefficient of performance () of 0.159. Numerical simulations of the refrigerator using a model developed with the commercial flow-sheeting Aspen-Plus software are also perfomed. The computer model is validated by comparing its predictions with experimental data for three generator heat supply rates: 46 W, 56 W and 67 W. Deviations between model predictions and experimental measurements in terms of cooling capacity and coefficient of performance are less than 1%. The proposed model could be very useful to predict the functioning of the commercial diffusion-absorption refrigerator under steady state regime.