•Growth of TbCr3(BO3)4.•Melt-solution based on Bi2Mo3O12 and Li2WO4.•Crystal structure.•Magnetic properties.
The phase formation of terbium chromoborate TbCr3(BO3)4 in the bismuth trimolybdate and ...lithium tungstate melt–solutions has been studied. The absence of the terbium chromoborate trigonal phase in the bismuth trimolybdate-based system at all component ratios has been shown. The component ratio in the lithium tungstate-based system has been found at which the TbCr3(BO3)4 trigonal crystals are formed at temperatures above 1100 °C; below this temperature, the monoclinic phase dominates. The structural and magnetic properties of the grown crystals have been studied. It has been established that the trigonal and monoclinic TbCr3(BO3)4 crystals synthesized from the lithium tungstate-based solvent exhibit identical magnetic properties. At the same time, a significant difference of the magnetic properties of the single crystals synthesized from the bismuth molybdate melt–solution has been observed. This difference has been attributed to the effect of Bi3+ ions that partially replace Tb3+ ions.
We studied the dechanneling length of 150 GeV/cπ− interacting with a short bent silicon crystal. Dechanneling length measures the rate and the strength of incoherent interactions of channeled ...particles in a crystal. The mechanism of dechanneling of negatively charged particles has been elucidated through simulation and experiment. It was found that the dechanneling length for negative particles is comparable to the nuclear dechanneling length for positive charges. Indeed, dechanneling of negative particles occurs as a result of incoherent interactions with the nuclei because the trajectories of such particles always intersect atomic planes, explaining the lower channeling efficiency for such particles. Obtained results can be useful for the design of crystals for manipulating high-energy negative particle beams through channeling.
•Due to competition between magnetic anisotropies of Fe3+ and Mn3+ spontaneous orientational transition occurs at Tc = 22 K.•Below Tc, antiferromagnetic vector rotates in rhombic bc plane under ...increasing temperature tending to c axis at T = Tc.•Its rotation to the c axis occurs also at fixed temperature T < Tc with increasing magnetic field.•For H||c orientation one more inclined phase is formed with antiferromagnetic vector rotates toward the rhombic a axis.
Single crystals of the Pb2Fe2−xMnxGe2O9 (x = 0.16) antiferromagnet have been grown. Using the specific heat measurements, a Néel temperature of TN = (42.0 ± 0.5) K for the synthesized crystals has been found. It has been shown using the magnetic measurements that, due to the competition between the magnetoanisotropic contributions of the iron and manganese subsystems in the crystals, near a temperature of Tc = 22 K, a spontaneous spin-reorientation transition occurs, the temperature of which in an applied magnetic field changes with the field value and orientation relative to the rhombic axes of the crystal. Based on the analysis of the temperature and field dependences of the magnetization obtained at different orientations of the magnetic field, it has been established that, below Tc, an inclined magnetic structure is formed in the crystal. The antiferromagnetic vector of the inclined structure rotates smoothly in the rhombic bc plane with increasing temperature from a direction close to the b axis at T = 4.2 K and tends to the rhombic c axis at T = Tc. The rotation of the antiferromagnetic vector occurs also at fixed temperatures T < Tc with increasing magnetic field. In the temperature range of Tc < T < TN, the antiferromagnetic vector is oriented along the rhombic c axis.
Magnetic phase diagrams of states have been built for different magnetic field orientations relative to the rhombic axes of the crystal. The richest phase diagram is shown to correspond to the orientation H||c and contains, along with the above-listed states, one more inclined phase, in which the antiferromagnetic vector rotates toward the rhombic a axis direction with a change in temperature or magnetic field.
Channeling efficiency in a target-crystal assembly Scandale, W.; Cerutti, F.; Esposito, L.S. ...
Nuclear instruments & methods in physics research. Section B, Beam interactions with materials and atoms,
03/2020, Letnik:
467
Journal Article
Recenzirano
In view of possible future fixed target experiments requiring precisely steered charged particle beams, the UA9 Collaboration has undertaken experimental studies of the use of bent silicon crystals ...for this purpose. The channeling efficiency of positively charged particles inside the crystalline lattice has been investigated in detail for a setup with a tungsten target installed in front of the crystal. Due to multiple Coulomb scattering inside the target, the channeling efficiency was observed to be reduced by a factor of about 6.1 for a 180 GeV/c quasi-parallel hadron beam. The yield of nuclear interaction secondaries as an estimation of the additional machine background is also discussed.
The paper examines the impact of interparticle interactions on the superparamagnetic relaxation of ultrasmall nanoparticle ensembles, using Fe
2
O
3
∙
n
H
2
O iron oxyhydroxide (ferrihydrite) ...nanoparticles as an example. Two samples were analyzed: ferrihydrite of biogenic origin (with an average particle size of
≈ 2.7 nm) with a natural organic shell, and a sample (with
≈ 3.5 nm) that underwent low-temperature annealing, during which the organic shell was partially removed. The
DC
and
AC
magnetic susceptibilities (χ′(
T
), χ′′(
T
)) in a small magnetic field in the superparamagnetic (SPM) blocking region of the nanoparticles were measured. The results show that an increase in interparticle interactions leads to an increase in the SPM blocking temperature from 28 to 52 K according to DC magnetization data. It is shown that below the SPM blocking temperature, magnetic interactions of nanoparticles lead to the formation of a collective state similar to spin glass in bulk materials. The scaling approach reveals that the dynamics of correlated magnetic moments on the particle surface slow down with increasing interparticle interactions. Simulation of χ′′(
T
) dependence has shown that the dissipation of magnetic energy occurs in two stages. The first stage is directly related to the blocking of the magnetic moment of nanoparticles, while the second stage reflects the spin-glass behavior of surface spins and strongly depends on the strength of interparticle interactions.
Background: The aim of the study was to develop a mobile program for choosing a method of surgical treatment and mathematical prediction of findings in patients with postoperative median abdominal ...hernias, sized small to large, using a complex of non-linear mathematical models to help a practicing surgeon. Methods and Results: There has been detected a non-linear dependence of the parameters of the degree of fatigue and the total electrical activity of the abdominal muscles six months after surgery, based on their preoperative values compared to SpO2 values on the preoperative day and on the postoperative Day 7, and compared to SpO2 values under physical simulation of hernia repair and the selected treatment option. Conclusion: A mobile program has been developed for smartphones that implements the recommended choice of hernioplasty technique and predicts typical features of the patient’s postoperative condition.
This paper presents the numerical and experimental results of hardening of an annular zone on the flat surface of an X20Cr13 steel specimen by friction stir processing (FSP) with a WC-Co hard alloy ...tool moving along circular and fan-shaped paths. A finite element model of the process is proposed for predicting the temperature distribution through the width and depth of the annular zone for the considered tool paths and for detecting the reverse tempering regions. The influence of the paths of a cylindrical friction stir tool with a flat end on microhardness distribution in the surface layer of the hardened zone was studied experimentally. It was shown that FSP along the fan-shaped path provides uniform hardening of the annular zone, while processing along the circular trajectory leads to softening of the material in the regions where the friction tracks overlap. The uniformity of surface hardness in the friction stir processed annular zone of X20Cr13 steel was evaluated by calculating the “covering uniformity” (CU) index proposed by Campana. The hardening behavior is in full agreement with the results of finite element simulation of the FSP process. Hardness measurements and microstructural studies showed that the fan-shaped tool path provides surface layer hardening to a depth of 400 μm with the CU index ranging from 0.78 to 1.00. In the case of the circular path, the CU index ranges from 0.48 to 0.72 at the same depth. The proposed research methods can be applied to evaluate the FSP efficiency when using other workpiece and tool materials.
Induction electric motors are widely used as drives of various mechanisms in power engineering and industry. Their failure can lead to costly repairs, to a reduction in power, or, for example, to a ...complete shutdown of a power plant unit. One of the reasons for the failure of high-voltage induction motors operating under severe starting conditions is damage to the squirrel-cage rotor winding. Existing methods for monitoring the breakage of the winding bars of such electric motors are ineffective due to the peculiarities of their operating modes. Therefore, monitoring the condition of the bars of high-voltage motors at startup and searching for diagnostic signs is an urgent task. Initially, the studies were carried out with a model of a high-voltage induction motor, developed in the ANSYS software package. To confirm the results obtained for a real motor, research has also been conducted on the developed experimental bench. The recorded signals were processed based on the method of short-time Fourier transform in the MatLab environment. In the course of the study, it was shown that, in the presence of bar breaks, the spectrum of an induction motor exhibits sharply increased amplitudes of harmonic components of the dummy rotor winding at the lower side frequencies of the first orders; this confirms the possibility of using external magnetic field signal at startup to detect the presence of bar breaks in the squirrel-cage rotor winding of high-voltage induction motors with heavy prolonged starts.
Questions on the joint application of various diagnostic methods in order to evaluate the technical state of the functional units of induction motors are examined. The possibility of using a set of ...methods of vibration monitoring and signature analysis of the stator current and external magnetic field in the start-up and steady-state modes of induction motors is assessed. The studies were conducted on an actual high-voltage induction motor of the induced-draft fan of one of the thermal power plants. During the study, a search was done for mechanical defects, dynamic eccentricity, and rotor winding faults. The results of the conducted studies were analyzed, and confirmation was done of the effectiveness and expediency of the methods of the joint application of vibration monitoring and signature analysis of the signals of the stator current and external magnetic field, in order to detect faults in the rotor winding and the mechanical components of the induction motors.
A special tool has been devised incorporating a closed loop system based on Peltier thermoelectric couples to cool replaceable hard alloy inserts. Experimental research has been done into dry turning ...of a X20Cr13 steel welded surface with a SECO cubic boron nitride circular plate at the cutting speed increasing from 100 to 300 m/min. It has been determined that Ra surface roughness decreases by 22% while Rz surface roughness goes down by 26%; in addition, the wear flat of tool tips diminishes by 17%.
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