Scopul nostru este sprijinirea şi promovarea cercetării ştiinţifice şi facilitarea comunicării între cercetătorii români din întreaga lume.
In this paper a gyrator implementation using a LM13700 operational transconductance amplifier is analyzed. It was first verified under PSpice simulation and experimentally the antireciprocity of this gyrator, i.e., its properties. This type of gyrator can be used for controlling the energy transfer from one port to the other by modifying the bias currents of the operational transconductance amplifier.
Read moreA multivariant martensitic Cu-Zn-Al-Fe Shape Memory Alloy has been analysed by means of tensile loading-unloading tests, X-ray diffraction and scanning electron microscopy. The tensile superelastic curve was correlated with the crystallographic reorientation of the martensite plate variants. The stress plateaus correspond to the reversible formation of (016) variant, up to 20 MPa, accompanied by the increase of the second and third order microstrains
Read moreThe paper reports the effects of 100 to 500 training cycles applied to lamellar specimens of a Cu-Zn-Al Shape Memory Alloy (SMA). The training procedure consisted in the bending, during the cooling to room temperature (RT) of martensitic specimens, by the load fastened at their free end and in load lifting by Shape Memory Effect (SME) during heating up to austenitic domain. During cooling, the concave surface of bent specimens was compressed and
Read moreFe-14 Mn-6 Si-9 Cr-5 Ni (mass. %) shape memory alloys (SMAs) were produced from raw powders employed both in initial commercial state and in a mixture state of equal fractions of commercial and mechanically alloyed (MA’d) particles. After blending, pressing and sintering, powder compacts were hot rolled (HR’d) and solution treated (ST’d) before being machined into plane-parallel lamellas. Specimens with special geometry were pre-strained on
Read moreReminding us of the failure of academia to predict the East European revolutions, and the challenges presented by the latter to the theories of revolution, the essay claims that in order to understand why the exit from communism comprised so many varied modes, one should take a 'path-dependence' diachronic and synchronic comparative perspective. Based on this dual approach and a set of variables, the essay advances a typology of East European revolutions
Read moreThe term bioindicator defines organisms that respond to a pollutant load with changes in vital functions or accumulate pollutants (Arndt et al. 1987). The use of bioindicator organisms may allow researchers to evaluate the effects of mixtures of pollutants on ecosystems in time and space, depending on the selected species and approach (Hellawell 1986). In contrast, simple instrumental analyses of pollutants can provide extremely precise data about
Read moreSome aspects of Kostant's geometric quantization for the symmetric free rigid body are given. The basic idea is to show that the spectrum of a symmetrical free rigid body can always determine via Kostant's geometric quantization in the correction 1/2 forms as well as geometric pre-quantization approach.
Read moreResistance spot welding (RSW) is one of the most used methods of joining sheet metals. The RSW process is based on Joule Lenz effect, of the electric current passing trough the (similar or dissimilar ) joining metal sheets positioned between the two contact electrodes. At welding process , some important changes occurs in metallurgical and mechanical properties of the welded areas and heat affected zones (HAZ) . The purpose of this work is to highlight
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