High Temperature Time Research Articles

Fragile ground state and rigid field-induced structures in the zigzag ladder compound BaDy2O4

We report on a sequence of field-induced transitions in the zigzag ladder compound BaDy2O4 studied with powder neutron diffraction and magnetisation measurements. In agreement with the previously published results, the low temperature zero-field structure is characterised by two half-integer propagation vectors, k1=[1/2 0 1/2] and k2= 1/2 1/2 1/2]. However, on application of an external magnetic field, the Bragg peaks corresponding to the zero-field structure lose their intensity rather rapidly and disappear completely in a field of 2.5 kOe. In the intermediate fields, 2.5 to 22.5 kOe, new peaks are observed characterised by the propagation vector k0=[0 0 1/3] corresponding to an up-up-down (uud) structure as well k=0 ferromagnetic peaks. This regime of fields corresponds to a pronounced plateau in the magnetisation curve. Remarkably, the uud structure survives heating to at least 1.4 K, three times higher temperature than the TN of 0.48 K for the zero-field structure. Above 22.5 kOe, the k0 peaks disappear while the k = 0 peaks gain significant intensity indicating an increase in the polarisation of the system. The analysis of the intensities of the field-induced reflections allows for a clear identification of the magnetic structures in both the intermediate and high field regimes.

Evaluation on the Bond Capacity of the Fire-Protected FRP Bonded to Concrete Under High Temperature

To figure out the change in the reinforcing effect of FRP system used for the retrofit of RC beam when it is exposed to high temperature, it is required to evaluate not only the behavior of the entire beam, but also the bond performance at anchorage zone through a bond test according to the increase of external temperature. Moreover, the study to find various fire-protection methods is necessary to prevent the epoxy from reaching the critical temperature during an exposure to high temperature. In this manner, the fire-resistance performances of externally bonded (EB) FRP and near-surface-mounted (NSM) FRP to concrete block were evaluated by high-temperature exposure tests after performing a fire-protection on the surface in this paper. Board-type insulation with mortar was considered for the fire-protection of FRP system. After the fire-protection of the FRPs bonded to concrete blocks, an increasing exposure temperature was applied to the specimens with keeping a constant shear bond stress between concrete and the FRP. Based on the result, the temperature when the bond strength of the FRP disappears was evaluated. In addition, a finite element analysis was performed to find a proper method for predicting the temperature variation of the epoxy which is fire-protected with board-type insulation during the increase of external temperature. As a result of the test, despite the same fire-protection, NSM specimens were able to resist 1.54–2.08 times higher temperature than EB specimens. In the design of fire-protection of FRP system with the board-type insulation, it is necessary to consider the transfer from sides as well as the face with FRP. If there is no insulation of FP boards on the sides, the epoxy easily reaches its critical temperature by the heat penetrated to the sides, and increasing the thickness of the FP board alone for the face with FRP does not increase the fire-resistance capacity. As a result of the FE analysis, the temperature variation at epoxy can be predicted using the analytical approach with the proper thermal properties of FP mortar and board.

Global Mean Sea Level Nexus Climate Change: A Dynamic Cointegration and Causality Analyses

Nowadays, the impact of climate change on the global mean sea level variations is becoming an important issue to the researchers and policy makers as a general concern about environmental degradation is making their way into global policy agenda. That is why, in this paper the principal purpose has been made to investigate the dynamic cointegration and causality relationships between global mean sea level (GMSL) and its determinants. Also another purpose has been made to examine empirically the short-run and long-run effects of climate change, carbon dioxide emissions, energy consumption, trade openness and urbanization on global mean sea level based on the time series data from 1970-2019. From the Augmented Dickey-Fuller (ADF), Phillips-Perron (PP) and Kwiatkowski-Phillips-Schmidt-Shin (KPSS) tests results it is found that all the variables are integrated of order one i.e. I(1). From the bounds test approach, it is found that there exits only one cointegration relationship when GMSL is the dependent variable. From the Granger causality test results of VEC model, it is found that the short-run unidirectional causalities are running from carbon dioxide emissions and energy consumption to global mean sea level, from energy consumption and trade openness to carbon dioxide emissions and from trade openness to energy consumption. It has also been found that the error correction term is statistically significant at any significance level when global mean sea level is treated as endogenous variable indicating that there exists a long-run relationship among the variables in the form of Equation (1). It has also been found that in the short-run the variables temperature, carbon dioxide emissions, and urbanization have significant positive effects while energy consumption and trade openness have significant negative effects on global mean sea level at any significance level. The coefficient of ECM (-1) is statistically significant at any significance level, indicates that speed of adjustment for short-run to research in the long-run equilibrium is statistically significant and within the first year, when global mean sea level is above or below its equilibrium level, it adjusts 66.52%. It has also been found that in the long-run the variables temperature, carbon dioxide emissions, and urbanization have significant positive effects on global mean sea level at any significance level but the variable energy consumption has significant negative effects at 5% significance level. It is also found that over time higher temperature, and carbon dioxide emissions will increase global mean sea level rapidly. The CUSUM and CUSUMSQ tests results support that the VEC model is stable and can be applied for policy formulation and decision making purposes.

Formation of the core-shell structures from bimetallic Janus-like nanoclusters under low-energy Ar and Ar13 impacts: A molecular dynamics study

Using the molecular dynamics method, 100 and 500 ps evolutions of 390-atom Cu-Au and Cu-Bi free clusters under 0.05–1.4 keV Ar1 and Ar13 projectiles’ bombardment are simulated. Initial clusters have the Janus-like metastable construction of two mono-component parts with their insignificant overlap. Excluding low energy impacts, Ar13 projectiles induce a few times higher temperatures in the clusters and an order of the magnitude larger sputtering yields with a contribution of the thermal mechanism than Ar particles do. In both clusters, Cu atoms show the resultant trend of displacements into the cluster depth, while Au and Bi atoms tend to increase their near-surface concentrations that lead to various distributions of the components depending on external conditions. In particular, at 300 eV Ar13 impacts, an explicit core-shell structure with a mainly copper core coated by a bismuth-enriched near-surface layer in the Cu-Bi cluster is revealed. Along with that, an approximately homogeneous mixture with weak spatially fuzzy segregation of quantitatively dominating Cu atoms inside the Cu-Au cluster and Au atoms in the outer region is formed. At Ar1 impacts, transfer of atoms is less intense and leads to eccentric arrangements of the copper-enriched core in the Cu-Bi cluster and an inhomogeneous mixture in Cu-Au cluster with still higher inner gold concentration despite the relocation trends.

Nonlocal heat flux effects on temperature evolution of the solar atmosphere

Context. Heat flux is one of the main energy transport mechanisms in the weakly collisional plasma of the solar corona. There, rare binary collisions let hot electrons travel over long distances and influence other regions along magnetic field lines. Thus, the fully collisional heat flux models might not describe transport well enough since they consider only the local contribution of electrons. The heat flux in weakly collisional plasmas at high temperatures with large mean free paths has to consider the nonlocality of the energy transport in the frame of nonlocal models in order to treat energy balance in the solar atmosphere properly. Aims. We investigate the impact of nonlocal heat flux on the thermal evolution and dynamics of the solar atmosphere by implementing a nonlocal heat flux model in a 3D magnetohydrodynamic simulation of the solar corona. Methods. We simulate the evolution of solar coronal plasma and magnetic fields considering both a local collision dominated and a nonlocal heat flux model. The initial magnetic field is obtained by a potential extrapolation of the observed line-of-sight magnetic field of AR11226. The system is perturbed by moving the plasma at the photosphere. We compared the simulated evolution of the solar atmosphere in its dependence on the heat flux model. Results. The main differences for the average temperature profiles were found in the upper chromosphere/transition region. In the nonlocal heat transport model case, thermal energy is transported more efficiently to the upper chromosphere and lower transition region and leads to an earlier heating of the lower atmosphere. As a consequence, the structure of the solar atmosphere is affected with the nonlocal simulations producing on average a smoother temperature profile and the transition region placed about 500 km higher. Using a nonlocal heat flux also leads to two times higher temperatures in some of the regions in the lower corona. Conclusions. The results of our 3D MHD simulations considering nonlocal heat transport supports the previous results of simpler 1D two-fluid simulations. They demonstrated that it is important to consider a nonlocal formulation for the heat flux when there is a strong energy deposit, like the one observed during flares, in the solar corona.

One-dimensional dispersive magnon excitation in the frustrated spin-2 chain system Ca3Co2O6

Using inelastic neutron scattering, we have observed a quasi-one-dimensional dispersive magnetic excitation in the frustrated triangular-lattice spin-2 chain oxide Ca${}_{3}$Co${}_{2}$O${}_{6}$. At the lowest temperature ($T=1.5$ K), this magnon is characterized by a large zone-center spin gap of $\ensuremath{\sim}$27 meV, which we attribute to the large single-ion anisotropy, and disperses along the chain direction with a bandwidth of $\ensuremath{\sim}$3.5 meV. In the directions orthogonal to the chains, no measurable dispersion was found. With increasing temperature, the magnon dispersion shifts towards lower energies, yet persists up to at least 150 K, indicating that the ferromagnetic intrachain correlations survive up to six times higher temperatures than the long-range interchain antiferromagnetic order. The magnon dispersion can be well described within the predictions of linear spin-wave theory for a system of weakly coupled ferromagnetic chains with large single-ion anisotropy, enabling the direct quantitative determination of the magnetic exchange and anisotropy parameters.

Magnetic Properties and Temperature Stability of Nanocrystalline Fe-Based Soft Magnetic Alloys

The effect of the nanocrystallization conditions on the structure, magnetic characteristics and temperature stability of the Fe73.5Cu1Nb3Si13.5B9, Fe73.5Cu1Nb1.5Мo1.5Si13.5B9, Fe69Cu1Nb1.5Мo1.5Si13.5B9Co4.5, and (Fe0.6Co0.4)86Hf7B6Cu1 nanocrystalline soft magnetic alloys has been analyzed. The samples were nanocrystallized in the absence of a field, in a dc or ac magnetic field. It has been shown that the Fe73.5Cu1Nb1.5Мo1.5Si13.5B9 alloy has unique magnetic properties and a high temperature-time stability. It has been found that nanocrystallization of the (Fe0.6Co0.4)86Hf7B6Cu1 amorphous alloy in an ac magnetic field considerably improves its static and dynamic magnetic properties.

Properties of Gallium Implanted Furnace and Rapidly Annealed Polycrystalline Silicon

ABSTRACTPolycrystalline silicon films have been amorphized by implantation with 100keV Ga ions of doses 0.3 and 6×1015cm−2. These films were subsequently recrystallized using either a furnace for longer times lower temperature (∼30 mins, 600° C) or rapid thermal processing (RTP) for shorter times higher temperatures ( ≤ 30 sec, 800° C, 900° C) in an endeavour to suppress any long range movement of the Ga during the anneal phase. It is found that for both the furnace and RTP for temperatures ≤ 800°C no significant movement is observed and that the lower temperature anneal for the highest dose produces the highest electrical conductivity. By contrast however, annealing at 900° C, even though the initial conductivity is higher than for any other anneal we observe a significant reduction with time and extremely rapid movement of the dopant species throughout the original poly layer. An initial rationale for this behaviour is proposed in terms of a liquid phase transformation during annealing.

Responses of summer flounder, Paralichthys dentatus, embryos to thermal shock

Summer flounder eggs, fertilized artificially, were exposed to time series of abrupt thermal shocks and examined for lethal and sublethal effects. The temperature increments (ΔTs) ranged from 8° to 20°C above the holding temperature, the periods of exposure to the ΔTs were for 2, 4, 8 and 16 minutes. Eggs were exposed at early embryo and late embryo stages of development. The eggs were found highly resistant to thermal shock, early embryo stage eggs survived the highest temperature-time exposure used, at ΔT 20°C for 16 minutes; late embryo stage eggs showed significantly increased mortalities in the region of ΔT 16° C for 16 minutes and ΔT 18° C for 2 minutes and at all higher temperature exposures. Larvae hatching from the late embryo stage eggs after thermal shock were examined for anomalous anatomical development. A pattern of increasing incidence of developmental anomalies appeared at ΔT 14°C after exposures of between 4 and 8 minutes. Such sublethal effects probably lead quickly to larval death from starvation, predation, etc., and must be taken into consideration in assessing effects of thermal shock.

Alpha-methyl-p-tyrosine shifts circadian temperature rhythms.

alpha-Methyl-p-tyrosine shifts the acrophase (time of highest temperature) of the circadian temperature rhythm of the rat to earlier or later times of day depending on the phase of the circadian cycle at which the drug is administered. When alpha-methyl-p-tyrosine methyl ester HCl is injected intraperitoneally at a dose of 100 mg/kg late in the projected 8-h light phase, the acrophase of the intraperitoneal temperature rhythm is delayed by up to 3 h. However, when the same dose of drug is given 9-10 h into the projected 16-h dark phase of the daily cycle, the acrophase of the temperature rhythm occurs about 2 h earlier than expected. The times of alpha-methyl-p-tyrosine administration leading to maximal phase delays or advances are correlated with the times of minimal and maximal turnover of norepinephrine in the hypothalamus. These results suggest that changing rates of norepinephrine turnover in the hypothalamus may regulate the circadian temperature rhythm in rats. The results also emphasize the fact that the effects of drugs may vary as a function of the time of administration. This fact must be taken into account in pharmacologic testing.

METAMORPHIC FACIES IN THE WISSAHICKON SCHIST NEAR PHILADELPHIA, PENNSYLVANIA

The mica schists and mica gneisses of the Wissahickon formation in the Philadelphia region are described in terms of metamorphic facies. Representatives of the amphibolite facies (sillimanite-almandine and staurolite-kyanite subfacies) predominate, but show incipient alteration to minerals characteristic of the epidote-albite amphibolite facies. The status of rocks containing the assemblages kyanite-orthoclase, sillimanite-muscovite, and kyanite-almandine is also discussed. Metamorphism of the highest grade is found in the southwestern end of the schist belt; but evidence is presented to show that the most intense metamorphism took place, not at the time of highest temperatures, but during a succeeding period of declining temperatures, when mineral changes were facilitated by copious hydrothermal solutions and strong regional deformation. The decipherable history is therefore largely one of retrograde metamorphism; many of the higher grade rocks have been converted by granitization to microcline gneiss (“granodiorite”), especially in the southern part of the schist belt, while farther to the north and west, incipient chloritization has been favored by late crushing. The period of metamorphism is tentatively dated as Paleozoic.