We revisit previously published dielectric and viscoelastic data of binary blends of linear cis-polyisoprene Watanabe, H.; Ishida, S.; Matsumiya, Y.; Inoue, T. Macromolecules 2004, 37, 6619 in order ...to test the validity of the dynamic tube dilution (DTD) picture and to determine the most appropriate value of the dilution exponent α. We conclude that the DTD picture with α = 1 is more appropriate at short times, while at longer time, a larger exponent of α = 4/3 gives a better description of the experiments. Furthermore, between these two time regions, a broad crossover zone is found, going from an effective α = 1 to an effective α = 4/3. On the basis of this result, we propose to consider a new relaxation process, which is combined with the classical DTD picture with α = 1 to give the experimentally observed effective α = 4/3 at long times. This extra relaxation process results from the tension equilibration along the long chains, which takes place thanks to the blinking feature of release/reformation of the long–short entanglements and leads to a partial disorientation of the primitive path itself within the dilated tube. We have formulated the relaxation function considering this tension equilibration and demonstrated its validity for description of the experiments in the entire range of time.
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IJS, KILJ, NUK, PNG, UL, UM
Oxynitride perovskites, having oxide and nitride anions together in a compound, are a new class of dielectric material. The shaping process in either bulk ceramics or thin films is an essential ...factor for investigating and utilizing the dielectric properties of these materials. In this perspective, recent studies on the shaping of dielectric oxynitride perovskites are reviewed with a consideration of the powder preparation and thermal stability for sintering, several sintering methods, ultra-high pressure compaction, and thin-film formation.
This perspective reviews recent studies on the fabrication of dielectric oxynitride perovskites for powders, ceramics, compacts and thin films.
The dynamics of chain entanglement/disentanglement in concentrated polymer solutions are matters of current debate. We report the results of step strain rate experiments in uniaxial extensional flow ...on a well-characterized polymer solution containing about 22 entanglements per chain which allows these dynamics to be probed. In these experiments the polymer solution is subjected to homogeneous stretching at a given strain rate up until a predetermined value of strain. After this strain is reached, the strain rate is changed to a new value, and stretching is continued until steady state is acquired in the extensional stress. The strain rates are increased in step-up experiments and decreased in step-down experiments. The strain rates are adjusted so that both the orientation and the stretching dynamics can be probed. Additionally, the predictions of two recent single-mode molecular models are evaluated against the experimental data. These models include the effects of entanglement dynamics in their predictions in an ad hoc manner. This leads to only a qualitative improvement in the predictive capacity of one of the models and reduces that of the other. Slip-link simulations using the primitive chain network model are also included for further insight into the underlying dynamics. The models are found to yield qualitative predictions of the experimental observations.
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Slight enhancement of saturation magnetization to 219Am2kg−1 was observed from 199Am2kg−1 for the original α-Fe on the intermediate nitrided mixture of “α′′-Fe16N2” with residual α-Fe among the low ...temperature ammonia nitridation products under 5T magnetic field at room temperature. The value changed not linearly against the yield as had been expected. Crystal structure refinement indicated that the phase similar to α′′-Fe16N2 had deviations on its lattice constants and positional parameters, compared to previously reported values for α′′-Fe16N2. Spin-polarized total energy calculations were performed using the projector-augmented wave method as implemented in the Vienna ab-initio simulation package (VASP) to calculate magnetic moment on the refined crystal structure of the intermediate “α′′-Fe16N2”. The calculations supported the observed magnetization enhancement in the intermediate nitridation product.
Crystal structural parameters slightly change in the intermediate nitrided “α′′-Fe16N2” from those in α′′-Fe16N2 to show the magnetization maxima in the mixture of “α′′-Fe16N2” and the residual α-F. Display omitted
► Larger magnetization was observed than the value of Fe16N2 on its intermediate nitrided mixture with residual α-Fe. ► The enhancement was related to the crystal structural deviation from Fe16N2 on the intermediate nitride. ► It was supported by spin-polarized total energy calculation using the deviated structure.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
Crystallization and magnetic property of Fe
2O
3 nanoparticle precipitated in SiO
2 matrix was investigated. Fe
2O
3/SiO
2 nanocomposite thin film was obtained by annealing of the amorphous Fe–Si–O ...thin film deposited by RF-magnetron sputtering of (α-Fe
2O
3)
1−
x
/(SiO
2)
x
composite targets. The Fe
2O
3 crystallite size increased with decreasing SiO
2 area ratio,
x of the target and increasing annealing temperature. ɛ-Fe
2O
3 with the crystallite size of 20–30
nm was obtained after annealing the film deposited in SiO
2 area ratio,
x
=
0.33–0.42 at 900
°C. Lower SiO
2 area ratio (
x) than 0.25 and higher annealing temperature resulted in precipitation of α-Fe
2O
3 with the larger crystallite size than 40
nm. In the case of SiO
2 area ratio,
x
≥
0.50, the annealed film was amorphous and showed higher magnetization and smaller coercivity due to the precipitation of very small crystalline γ-Fe
2O
3. The ɛ-Fe
2O
3/SiO
2 composite thin film showed ferromagnetic hysteresis with coercive force of 0.14
T.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
SrTaO2N prepared by a citrate route was capsule hot isostatic press sintered at 196MPa for 3h at 1200, 1400 and 1600°C. Densification over 80% was attained for all the sintered bodies with partial ...reduction, which was observed as a change of color from brown to dark gray. Exaggerated grain growth was observed with some amount of open pore for the product sintered at 1400°C. The sample was successfully returned to the brown insulator color after annealing in ammonia flow at 1000°C. The resultant SrTaO2N ceramics exhibited a considerably high relative dielectric permittivity of 7.8×103 at 102Hz.
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GEOZS, IJS, IMTLJ, KILJ, KISLJ, NUK, OILJ, PNG, SAZU, SBCE, SBJE, UL, UM, UPCLJ, UPUK
The superconducting transition temperature of niobium silicon oxynitride (Nb0.87Si0.09□0.04)(N0.87O0.13) exhibits a gradual reduction from 16.8K to around 11K under an increasing applied magnetic ...field of up to 14T. This relatively small Tc reduction under an applied magnetic field suggests a robustness of its superconducting behavior in comparison to that in the parent niobium oxynitride. It was similar to the flux pinning effect observed in the large magnetic hysteresis of the niobium-silicon oxynitrides in our previous study. Both Si K-edge XANES and 29Si MAS-NMR indicated that the local structure of pinning centers around the silicon atoms close to cationic vacancies was similar to that of Si in amorphous SiO2 in the rock-salt structure of niobium oxynitride.
Potential energy scan of the Si atom in the most stable Si3□O3N cube around the vacancy in our preliminary simulation on niobium silicon oxynitride (Nb0.87Si0.09□0.04)(N0.87O0.13). A possible distortion of the Si atom was suggested from its octahedral towards tetrahedral position forming the local structure similar to that in amorphous SiO2. Display omitted
•Critical current density was enhanced in superconducting niobium oxynitride.•The robustness was introduced by forming rock-salt type niobium silicon oxynitride.•The silicon atom had a local structure similar to that in amorphous SiO2 in the rock-salt type lattice.•The local structure was formed together with its neighboring cationic vacancy.•It contributed as the flux pinning center in the NbSiNO.
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Fine iron oxide powder is required for the preparation of ferromagnetic alpha"-Fe16N2 powders during low temperature nitridation. A magnetite and maghemite mixture was obtained by the reaction of ...iron acetylacetonate Fe(acac)3 in benzyl alcohol. It was reduced to alpha-Fe in hydrogen at 400 C. The particle size of alpha-Fe was 300 nm in the reduction of iron oxides obtained from 2 g of Fe(acac)3. It decreased to 100 nm during preparation using 8 g of Fe(acac)3. After successive nitridation under flowing ammonia at 160 C, the highest yield of alpha"-Fe16N2 of 66 wt% was observed for the nitrided product from the latter alpha-Fe, because of the smallest alpha-Fe particle size after the reduction. The yield and reproducibility of alpha"-Fe16N2 formation in low temperature nitridation was improved using the iron oxide prepared in non-aqueous benzyl alcohol compared with magnetite obtained from an aqueous solution.
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This paper reviews the design challenges that current and future processors must face, with stringent power limits, high-frequency targets, and the continuing system integration trends. This paper ...then describes the architecture, circuit design, and physical implementation of a first-generation Cell processor and the design techniques used to overcome the above challenges. A Cell processor consists of a 64-bit Power Architecture processor coupled with multiple synergistic processors, a flexible IO interface, and a memory interface controller that supports multiple operating systems including Linux. This multi-core SoC, implemented in 90-nm SOI technology, achieved a high clock rate by maximizing custom circuit design while maintaining reasonable complexity through design modularity and reuse.
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