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[en] The results of various conventional tests with this 1000kW experimental reactor (KSTR) are shown in diagrams. The comparatively high negative temperature coefficient of the reactivity was found to be a great advantage. Some inexplicable temperature differences and temperature changes in the reactor vessel were found. (J.S.)
[en] We consider the superconducting transition in fermionic quantum critical systems. Assuming the validity of Migdal theorem, the gap equation can be written in terms of the retarded pair susceptibility. Instead of the usual BCS form, the pair susceptibility is now subject to scale invariance. The gap and transition temperature is thus of the algebraic form, totally different from the exponential behavior in BCS theory. Consequently, with reasonably small glue strength, we can get very large gap and transition temperature comparable to those discovered in cuprates. The ratio of the gap to retardation gets boosted by increasing retardation. We also find the upper critical field has a different scaling with the critical temperature. With a non-Lorentzian dynamical exponent, the upper critical field is greatly enhanced when approaching the critical point, though the critical temperature only changes modestly, in agreement with recent experiments on heavy fermions.
[en] The extended thermodynamics of static charged AdS black holes in conformal gravity is analyzed. The P–V criticality of these black holes has some unusual features. There exists a single critical point with critical temperature T_c and critical pressure P_c. At fixed T>T_c (or at fixed P>P_c), there are two zeroth order phase transition points but no first order phase transition points. The systems favors large pressure states at constant T, or high temperature states at constant P
[en] The equation of state of fuel plays an important part in determining the consequences of super-prompt-critical excursions in fast reactors. It is often derived using the principle of corresponding states, which requires a knowledge of the critical constants of the material. In this paper the available methods and estimates of critical constants for uranium di-oxide are critically examined and found to be unacceptable either due to internal inconsistency or due to the use of methods, which, starting from acceptable data, lead to values with unacceptable divergence. A new method, which avoids the weaknesses of the available methods, is proposed and used to derive the critical constants for uranium di-oxide. The low temperature data predicted on the basis of the derived set of critical constants, are found to agree well with the available measured values. (Auth.)
[en] In multisublattice compounds consisting of a stable and magnetically unstable (metamagnetic) sublattices, the molecular field acting on the latter one, Bmol(met), decreases monotonously with increasing temperature. Hence temperature can be considered as an additional external parameter that can drive the magnetic state of the unstable sublattice. If the metamagnetic sublattice is in a high magnetic state at low temperatures, with increasing temperature at a certain critical value Tm the internal field Bmol(met)(Tm) becomes equal to the critical field of the metamagnetic transition Bm(Tm). Then, above Tm the metamagnetic sublattice will turn into a low magnetic state. This effect is named a temperature-induced itinerant-electron metamagnetism (TIMT). Recently TIMT has been found in the RCo3 series. In most of these intermetallics, due to a strong intersublattice R-Co molecular field, the Co sublattice is in a high magnetic state at low temperatures and can be changed with increasing temperature into a lower magnetic one at a critical temperature for which Bmol(RCo)(Tm)=Bm(Tm). The experimental results for some RCo3 compounds are presented and discussed
[en] It is reported that the repeated bending loads at room temperature for Nb3 Sn wires, which show the strain dependence of superconducting properties, cause the large enhancement of a critical current, an upper critical field and a critical temperature. Those phenomena are so called ''prebending effect''. It is considered that the enhancement effect is associated with the reduction of the residual strain state for Nb3 Sn wires. In order to apply the prebending treatment to a react-and-wind processed Nb3 Sn superconducting magnet, repeatedly bent Nb3 Sn wires with bending strains up to 1.0% were fabricated by using pulleys, and were confirmed to demonstrate the large enhancement of the critical current in spite of the bending strain of 0.5%. From these experimental results, we intended to fabricate the high strength Nb3 Sn strands applying the prebending effect for the cabling conductor. As a first step, we prepared triplet cables using prebent CuNb/Nb3 Sn and Cu/Nb3 Sn strands and evaluated critical currents and n-values of each strand. The prebent Nb3 Sn strands show the large enhancement of critical current Ic even after the cabling process. Hence, it is expected that the prebent high strength Nb3 Sn strands may be useful for the cabling conductors
[en] As a phonon-media superconductor, the superconducting properties of MgB2 are very sensitive to the lattice parameters. Lattice strain has significant effects on the superconducting properties in MgB2 superconductor. We have systematically studied the relationship between lattice strain and superconducting properties (such as critical temperature, Tc, the upper critical field, Hc2, the irreversibility field, Hirr, and hence the critical current density, Jc) in pure and different chemical doped MgB2 samples. In contrast to the common practice of improving the Jc and Hc2 of MgB2 through chemical substitution, by taking advantage of residual thermal strains we are able to design a composite, which shows only a small drop in Tc and little increase in resistivity, but a significant improvement over the Jc and Hc2 of MgB2.
[en] Highlights: • The effects of small-scale of the both nanoflow and nanostructure on the vibrational response of fluid flowing single-walled carbon nanotubes are investigated. • Critical flow velocity decreases as the wave number increases, employed. • Kn effect has considerable impact on the reduction of critical velocities especially for the air-flow flowing through the CNT. In this study, the effects of small-scale of the both nanoflow and nanostructure on the vibrational response of fluid flowing single-walled carbon nanotubes are investigated. To this purpose, two various flowing fluids, the air-nano-flow and the water nano-flow using Knudsen number, and two different continuum theories, the nonlocal theory and the strain-inertia gradient theory are studied. Nano-rod model is used to model the fluid-structure interaction, and Galerkin method of weighted residual is utilizing to solve and discretize the governing obtained equations. It is found that the critical flow velocity decreases as the wave number increases, excluding the first mode divergence that it has the least value among of the other instabilities if the strain-inertia gradient theory is employed. Moreover, it is observed that Kn effect has considerable impact on the reduction of critical velocities especially for the air-flow flowing through the CNT. In addition, by increasing a nonlocal parameter and Knudsen number the critical flow velocity decreases but it increases as the characteristic length related to the strain-inertia gradient theory increases.
[en] LaRu4As12 with the critical temperature = 10.4 K displays several features which point at a non-singlet superconducting order parameter, although the bcc crystal structure of the filled skutterudites does not favour the emergence of multiple energy gaps. LaRu4As12 displays an unexpected enhancement of the lower critical field deep in superconducting state which can be attributed to the existence of two superconducting gaps. At = 0.4 K, the local magnetization measurements were performed utilizing miniaturized Hall sensors.
[en] Highlights: • Double peak in the imaginary part of the ac susceptibility χ(T) of Nb3Sn. • Explanation of the effect assuming a universal relationship χ″(χ′). • Different creep exponents apply within and outside the peak-effect region. -- Abstract: We performed a systematic study of the ac magnetic-susceptibility on a Nb3Sn single crystal which displays a strong peak effect near the upper critical field Hc2. In external magnetic fields above μ0H ≈ 3 T, the peak effect manifests itself in a single, distinct peak in the real part χ′(T) of the ac susceptibility as a function of temperature T, the size of which continuously increases with increasing magnetic field H. In the imaginary part χ″(T) of the ac susceptibility, on the other hand, a single peak initially grows with increasing H up to a well-defined value, and then splits into two sharp peaks which separate when H is further increased. We explain this surprising behavior by a flux-creep model and taking into account the enhancement of the critical-current density in the peak-effect region near Tc in which Bean’s critical-state model seems to apply. Outside this region, the crystal is clearly in a flux-creep regime with finite creep exponent n