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The purpose of this study was to experimentally estimate the solid fraction at which the cessation of the flow of a molten Al–7%Si–0.3%Mg alloy and Cu–8%Sn alloy occurs in casting. The flow cessation mechanism of two alloys is known as the “mushy” formation type, which means that the flow ceases when the solid fraction at the molten metal tip reaches a certain critical value. Therefore, the flow velocity at the molten metal tip is assumed to decrease gradually. Thus, a new method for calculating the solid fraction at flow cessation based on computer simulations was examined using experimental measurements of the flow velocity and flow length. The result of the experiment shows the experimental flow length is consistent with the simulation results, the calculated solid fraction at flow cessation. The flow velocity gradually decreased from the initial stage, but there was a region where the velocity was almost constant after the initial stage. The molten metal temperature became lower from the root side to the tip side, and the solid fraction at the time of flow cessation was calculated from the measurement results, for the Al–7%Si–0.3%Mg alloy it was 0.35–0.4 near the tip, and for the Cu–8%Sn alloy it was 0.25. Computer simulations were performed by tuning the heat transfer coefficient so that the flow length and flow velocity would match the experimental results. Computer simulations were performed by tuning the heat transfer coefficients so that the flow length and flow velocity would match the experimental results and could simulate the changes in flow velocity obtained from the experiments. The solid fraction at the tip of the molten metal was almost the same as the experimental results. These results show that it is possible to estimate the solid fraction at the flow cessation from the flow velocity at the tip.

We perform magnetic susceptibility and magnetic torque measurements on the organic $\kappa$-(BEDT-TTF)$_2$Hg(SCN)$_2$Br, which is recently suggested to host an exotic quantum dipole-liquid in its low-temperature insulating phase. Below the metal-insulator transition temperature, the magnetic susceptibility follows a Curie-Weiss law with a positive Curie-Weiss temperature, and a particular $M\propto \sqrt{H}$ curve is observed. The emergent ferromagnetically interacting spins amount to about 1/6 of the full spin moment of localized charges. Taking account of the possible inhomogeneous quasi-charge-order that forms a dipole-liquid, we construct a model of antiferromagnetically interacting spin chains in two adjacent charge-ordered domains, which are coupled via fluctuating charges on a Mott-dimer at the boundary. We find that the charge fluctuations can draw a weak ferromagnetic moment out of the spin singlet domains., Comment: 9 pages, 5 figures, Supplementary Material attached

The aim of this study is to show the effect of the strain-rate on the forming limit strain of an aluminum alloy A5052 sheet and a mild steel sheet SPCC. Biaxial stretching test was carried out. The prescribed strain path was linear path or that with directional change in straining. The sheet was pre-strained by uniaxial tension in the latter path. The deformation speed was set to be quasi-static or high speed whose strain-rate was about 300 /s using the dedicated high speed stretching device. The forming limit strain of the A5052 sheet for the linear strain path was larger in the high speed stretching than that under the quasi-static condition. For the case with strain path change the forming limit strain was further large. This may be due to the softening phenomenon which occurs by aging treatment, because the stretching experiment was conducted about two weeks after the pre-straining operation. On the other hand, the forming limit strain of the SPCC under the high speed condition was smaller than that under the quasi-static condition in the linear strain path. This is attributed to the decreased strain hardening exponent when the strain-rate increases. Further, in the equi-biaxial stretching of the pre-strained specimen, large difference of the forming limit strain between the deformation speeds was found. It is concluded that A5052 aluminum alloy sheet has a good adaptability to high speed forming, on the other hand, attention should be paid in increasing the forming speed of SPCC.

This study investigated a method for accurately predicting the residual stress in die castings manufactured using aluminum alloy. To account for the mechanical properties caused by the material composition differences that occur in the thickness direction of the die castings, a model split in the thickness direction was used in the simulation model. Norton’s law was applied to the constitutive equation of the material, and the stress relaxation phenomenon was examined. The composition of Al-Si-Cu alloy (JIS-ADC12) die castings in the thickness direction were analyzed using scanning electron microscopy and energy dispersive X-ray spectroscopy (SEM-EDS), and differences in composition were confirmed. As a result of calculating the residual stress using the simulation, it was possible to calculate the residual stress that could not be reproduced by the simulation model of uniform composition. This suggested that the difference in mechanical properties of die castings in the micro-region influences the residual stress.

The aim of this study is to experimentally determine the solid fraction at the cessation of the flow of a molten Al-Si-Mg alloy (JIS-AC4CH) ceases. In this study, an experimental apparatus to measure the melt temperature during flow was developed and was used to perform highly accurate temperature measurements. An immersion-type optical-fiber radiation thermometer without emissivity correction was used for the temperature measurement device in this apparatus. The solid fraction was calculated from the area of primary crystals when the molten metal at any temperature was quenched. The melt temperature at flow cessation was higher than the eutectic reaction temperature, and the solid fraction in the melt front was approximately 0.2. However, the maximum solid fraction was found at a position slightly away from the melt front toward the pouring gate, and was approximately 0.3. It was inferred for this Al-Si-Mg alloy, that the flow cessation mechanism was a mixture of skin formation and mushy formation types.

Metal-organic frameworks (MOFs), which are self-assemblies of metal ions and organic ligands, provide a tunable platform to search a new state of matter. A two-dimensional (2D) perfect kagome lattice, whose geometrical frustration is a key to realizing quantum spin liquids, has been formed in the ${\pi}$-${d}$ conjugated 2D MOF [Cu$_{3}$(C$_{6}$S$_{6}$)]$_{n}$ (Cu-BHT). The recent discovery of its superconductivity with a critical temperature $T_{\rm c}$ of 0.25\,kelvin raises fundamental questions about the nature of electron pairing. Here, we show that Cu-BHT is a strongly correlated unconventional superconductor with extremely low superfluid density. A nonexponential temperature dependence of superfluid density is observed, indicating the possible presence of superconducting gap nodes. The magnitude of superfluid density is much smaller than those in conventional superconductors, and follows the Uemura's relation of strongly correlated superconductors. These results imply that the unconventional superconductivity in Cu-BHT originates from electron correlations related to spin fluctuations of kagome lattice., Comment: 4 figures

Triangular lattice quasi-two-dimensional Mott insulators based on BEDT-TTF molecule and its analogies present a possibility to produce exotic phases by coupling charge and spin degrees of freedom. In this work we discuss magnetic properties of one of such materials, $\kappa$-(BEDT-TTF)$_2$Hg(SCN)$_2$Cl, which is found at the border of the phase transition between a Mott insulator into a charge ordered state. Our magnetic susceptibility and cantilever magnetisation measurements demonstrate how the charge degree of freedom defines magnetic properties for few different charge phases observed in this material as a function of temperature. Between $T_{CO}=30~K$ and $T_S=24~K$ we observe charge and spin separation due to one-dimensional charge stripes formed in this material below $T_{CO}=30~K$. Below $T_S=24~K$ charge and spin degrees of freedom demonstrate coupling. Spin singlet correlations develop below 24~K, however melting of charge order below 15~K prevents the spin singlet state formation, leaving the system in the inhomogeneous state with charge ordered spin singlet domains and charge and spin fluctuating ones.

Topological transports of fermions are governed by the Chern numbers of the energy bands lying below the Fermi energy. For bosons, e.g. phonons and magnons in a crystal, topological transport is dominated by the Chern number of the lowest energy band when the band gap is comparable to the thermal energy. Here, we demonstrate the presence of topological transport by bosonic magnons in a lattice of magnetic skyrmions - topological defects formed by a vortex-like texture of spins. We find a distinct thermal Hall signal in the magnetic skyrmion phase of an insulating polar magnet GaV4Se8, identified as the topological thermal Hall effect of magnons governed by the Chern number of the lowest energy band of the magnons in a triangular lattice of magnetic skyrmions. Our findings lay a foundation for studying topological phenomena of other bosonic excitations through thermal Hall probe., Comment: 24 pages, 5 figures, 1 Table and Supplementary Materials. To appear in Phys. Rev. Research

We have investigated the thermal-transport properties of the kagome antiferromagnet Cd-kapellasite (Cd-K). We find that a field suppression effect on the longitudinal thermal conductivity k_xx sets in below ~25 K, suggesting a large spin contribution k_xx^sp in k_xx. We also find clear thermal Hall signals in the spin liquid phase in all Cd-K samples. The magnitude of the thermal Hall conductivity k_xy shows a significant dependence on the sample's scattering time. On the other hand, the temperature dependence of k_xy is similar in all Cd-K samples; k_xy shows a peak at almost the same temperature of the peak of the phonon thermal conductivity k_xy^ph which is estimated by k_xx at 15 T. These results indicate the presence of a dominant phonon thermal Hall k_xy^ph at 15 T. In addition to k_xy^ph, we find that the field dependence of k_xy at low fields turns out to be non-linear at low temperatures, concomitantly with the appearance of the field suppression of k_xx, indicating the presence of a spin thermal Hall k_xy^sp at low fields. Remarkably, by assembling the k_xx dependene of k_xy^sp data of other kagome antiferromagnets, we find that, whereas k_xy^sp stays a constant in the low-k_xx region, k_xy^sp starts to increase as k_xx does in the high-k_xx region. This k_xx dependence of k_xy^sp indicates the presence of both intrinsic and extrinsic mechanisms in the spin thermal Hall effect in kagome antiferromagnets. Furthermore, both k_xy^ph and k_xy^sp disappear in the antiferromagnetic ordered phase at low fields, showing that phonons alone do not exhibit the thermal Hall effect. A high field above ~7 T induces k_xy^ph, concomitantly with a field-induced increase of k_xx and the specific heat, suggesting a coupling of the phonons to the field-induced spin excitations as the origin of k_xy^ph., Comment: 33 pages, 16 figures; analyses and figures for the heat capacity and the spin thermal Hall effect were added

A method for the estimation of the die release force of die castings of JIS-ADC12 aluminum alloy manufactured through high-pressure die casting was examined. The die release force was evaluated by the strain in the axial direction of the extrusion pin when releasing the die castings. In this research, it was assumed that the factors that influenced the die release force were the thermal deformation of the die and die castings and the reaction layer of Al and Fe generated during the solidification process in the die. These factors in the resistance of the die release were evaluated by the friction coefficient. The die and die castings temperature in the die release process were simulated, and calculation results were mapped onto an FE model, and a coupled analysis of the thermal structure was performed. The calculated value of the mold release force was approximately the same as the actual value, and the friction coefficient was estimated to be approximately 0.5.

In this study, the machinability of the machining method for controlling chip thickness during the cutting operation was evaluated using simulation based on NC data. A comparative three-dimensional cutting test with a ball end mill was performed using both original and modified NC data. The modified NC data was created for the purpose of controlling the chip thickness generated when cutting with a constant rotation value and changing the feed rate of the original NC data. The results indicated that the actual chip thickness exceeded that of the calculated value although the thickness fluctuation was suppressed. The results revealed that the maximum cutting force and the fluctuation range of cutting force were low, and tool wear after cutting was suppressed using the modified NC data. The application of the method to the cutting of complicated shapes with high removing volume led to reductions in the cutting time by 31 %.

Three point bending test of aluminum tubular structure with hat cross-section was carried out under impact condition. The structures which were strengthened with carbon fiber reinforced thermoplastic sheet attached to hat-top or hat-side were also tested. When the structure made with only aluminum was bent, one-lobe deformation mode arose in most cases, where the buckling lobe was formed at center exhibiting very low deformation resistance. This mode was found to be attributed to the low friction at central anvil by conducting the numerical simulation. The energy absorption performance was evaluated for a variety of structures. When the sheet attachment was applied for the structure with one-lobe deformation mode, the absorbed energy was improved drastically.

Impact joining device was developed to achieve the joining at plate edge. The sheared faces obtained by high-speed shear are availed in the joining method. The temperature remarkably elevates and the material softens in the thin severely deformed layer. The cut faces are contacted each other with sliding motion immediately after shearing process. Slight overlap for the opposed cut faces is set. In the similar material combination of mild steel (SPC), the effect of overlap length on the average joining efficiency was not clear. The data spread became smaller for the shorter overlap length. Microscopic observation discovered that there is a narrow band where the grain flow was not visible due to the remarkable temperature rise. In the dissimilar material combination of titanium (TP340C) and SPC, generation of a certain metallic compound was implied by energy dispersive X-ray analysis.

High-speed biaxial stretching apparatus was developed, where the punch was driven by a drop weight. Effect of the strain-rate on the forming limit strain of thin aluminum A1050 and A5052 sheets was inspected for various strain ratios. Strain-rate was about 100 /s in the high-speed test. It was from 0.0003 to 0.1 /s in the low-speed test. Limit strain of A1050 was larger in high speed. The strain of A5052 in high speed was comparable with that in 0.1 /s, though there exists a slight difference under low-speed conditions. Multiple cracks were formed in high-speed stretching of A5052 attributed to the positive strain-rate sensitivity. Profile of the crack opening is rough in high speed. Growth of the ductile fracture dimple size and depth in microscopic view may play a role to increase the roughness. Sheet thickness at the crack becomes smaller in high-speed stretching, which accords with the tendency of the forming limit strain.

Strongly enhanced quantum fluctuations often lead to a rich variety of quantum-disordered states. Developing approaches to enhance quantum fluctuations may open paths to realize even more fascinating quantum states. Here, we demonstrate that a coupling of localized spins with the zero-point motion of hydrogen atoms, that is, proton fluctuations in a hydrogen-bonded organic Mott insulator provides a different class of quantum spin liquids (QSLs). We find that divergent dielectric behavior associated with the approach to hydrogen-bond order is suppressed by the quantum proton fluctuations, resulting in a quantum paraelectric (QPE) state. Furthermore, our thermal-transport measurements reveal that a QSL state with gapless spin excitations rapidly emerges upon entering the QPE state. These findings indicate that the quantum proton fluctuations give rise to a QSL—a quantum-disordered state of magnetic and electric dipoles—through the coupling between the electron and proton degrees of freedom., The organic material κ-H3(Cat-EDT-TTF)2 has been suggested to exhibit a quantum spin liquid phase in which quantum fluctuations prevent the formation of magnetic order. Here, the authors show that this may be a result of fluctuations of hydrogen atoms, rather than more conventional geometric frustration.

Hole making process of metal and composite sheets using impact hydraulic pressure is investigated. The sheet is mounted in contact with the die face that locates at the bottom end of the cylinder. The piston at the top end is impacted by a drop-hammer with 10 m/s velocity, by which very high pressure is put on the sheet face to induce shear force at die edge. The die hole is circular, square or rhombic. The test materials are pure aluminum and its alloy, pure titanium, stainless steel and carbon fiber reinforcement plastic (CFRP) sheets. The cut surface is rather rough and the shear drop is larger compared with that in conventional punching. Burr generation is successfully suppressed for the metallic materials. Interlaminar fracture of CFRP sheet occurs in the hole vicinity. Corner radius of the square and rhombic holes is rounded. Counter punch in the die cavity is useful for improving shape accuracy.

Advancements in 3D-Flash memory-layer-stacking technology has enabled density scaling that circumvents the lithography limitations which have prevented 2D-NAND Flash memory from scaling [1]. Bit densities as high as 5.95Gb/mm2 on a single die were recently reported [2], where a 512Gb NAND Flash was built on 96 layers of memory. As memory density increases, with memory layers increasing from 96 layers to 128 layers, higher bit density can be achieved by adopting larger capacity die; however, NAND performance per bit density is reducing with the 2-plane architecture. In this work, we propose a 512Gb 3b/cell 128WL-layer NAND Flash, with a bit density of 7.80Gb/mm2: a 31% improvement over the previously reported. Three key performance improving technologies have been implemented. (1) A 4-plane architecture with circuit under array (CUA) technology to improve performance per bit density. (2) A multi-die peak-power management (PPM) system to manage peak-power consumption in the system, via the ZQ pin. (3) A 4KB-page-read mode to reduce power consumption. Figure 13.5.1(a) summarized the key features and Fig. 13.5.1(b) shows the die photograph and the floorplan for this work. Figure 13.5.2 shows a table comparing this work to previous work.

Three point bending experiment of aluminium tubular structure with hat cross-section was carried out under quasi-static and impact conditions. The structure was strengthened with carbon fibre reinforced plastic (CFRP) sheet. The objective is to exhibit the effective strengthening method for such tubular structure. The anvil speed was 10 m/s in impact test. The anvil force commonly showed a rapid increase in the early deformation stage and it changed to the gradual increase after yielding. The force reached peak followed by the decrease with saturating manner. The absorbed energy was approximately 10% greater under impact condition comparing with that under quasi-static one. The thickness of CFRP sheet was less effective. The energy absorption performance was slightly improved when the CFRP sheet was attached to the hat bottom. When the sheet was attached to both the hat top and the hat bottom, the performance was improved about 40% in maximum. It was improved about 10% when the hat sides were stre...

The coexistence and competition between superconductivity and electronic orders, such as spin or charge density waves, have been a central issue in high transition-temperature (${T_{\rm c}}$) superconductors. Unlike other iron-based superconductors, FeSe exhibits nematic ordering without magnetism whose relationship with its superconductivity remains unclear. More importantly, a pressure-induced fourfold increase of ${T_{\rm c}}$ has been reported, which poses a profound mystery. Here we report high-pressure magnetotransport measurements in FeSe up to $\sim9$ GPa, which uncover a hidden magnetic dome superseding the nematic order. Above ${\sim6}$ GPa the sudden enhancement of superconductivity (${T_{\rm c}\le38.3}$ K) accompanies a suppression of magnetic order, demonstrating their competing nature with very similar energy scales. Above the magnetic dome we find anomalous transport properties suggesting a possible pseudogap formation, whereas linear-in-temperature resistivity is observed above the high-${T_{\rm c}}$ phase. The obtained phase diagram highlights unique features among iron-based superconductors, but bears some resemblance to that of high-${T_{\rm c}}$ cuprates., Comment: 15 pages, 4 figures

Shallow cup drawing of magnesium alloy AZ31-O sheet was performed under cold condition using the Maslennikov’s technique. A deformable rubber pad was used, instead of the “hard” punch, in this technique. A small die profile radius was adopted, which was twice or four-times the sheet thickness. A semisolid lubricant was used for lubrication of the blank-die interface. On the other hand, the rubber-blank interface was degreased to increase friction. A limiting drawing ratio of 1.31 was obtained in the circular cup drawing. A peculiar fracture mode appeared in which the material suddenly fractured with the crack evolution emanating from the flange periphery. In the square cup drawing, an adequate blank shape was found to be circular compared with the other ones. Numerical simulation was also conducted using dynamic explicit finite element method. Adequate setting including speed scaling enabled us to predict the accurate deformation pattern and the forming force.

We have succeeded in growing a new heavy fermion compound YbNi2Si3 (space group: I4/mmm, #139) by the flux method. The local inversion symmetry at the ytterbium site is broken in tetragonal YbNi2Si...

A clear thermal Hall signal ($\kappa_{xy}$) was observed in the spin liquid phase of the $S=1/2$ kagom\'e antiferromagnet Ca kapellasite (CaCu$_3$(OH)$_6$Cl$_2\cdot 0.6$H$_2$O). We found that $\kappa_{xy}$ is well reproduced, both qualitatively and quantitatively, using the Schwinger-boson mean-field theory with the Dzyaloshinskii--Moriya interaction of $D/J \sim 0.1$. In particular, $\kappa_{xy}$ values of Ca kapellasite and those of another kagom\'e antiferromagnet, volborthite, converge to one single curve in simulations modeled using Schwinger bosons, indicating a common temperature dependence of $\kappa_{xy}$ for the spins of a kagom\'e antiferromagnet., Comment: 5 pages, 4 figures + Supplemental Material(9 pages, 6 figures)