Cold sintering of diatomaceous earth

Diatomite, a natural silicate-based sedimentary rock, was densified by cold sintering at room temperature and 150°C under various pressures (100, 200, and 300 MPa) and using different NaOH water solutions (0–3 M). The relative density of cold sintered diatomite can be as high as 90%, a condition that can be achieved by conventional firing only at 1200–1300°C. The cold sintered materials maintain the same mineralogical composition of the starting powder (quartz, glass, and illite) and are constituted by well-deformed and flattened grains oriented orthogonally to the applied pressure. Conversely, an evident phase evolution takes place upon conventional firing with the formation of cristobalite and mullite. The bending strength of cold sintered artifacts can exceed 40 MPa and increases to ≈80 MPa after post-annealing at 800°C, such mechanical strength is much larger than that of conventionally pressed samples sintered at 800°C, which is only ≈1 MPa.     

Void reactivity coefficient benchmark results for a 10 × 10 BWR assembly in the full 0–100% void fraction range

A boiling water reactor SVEA-96+ fresh fuel lattice has been used as the basis for a benchmark study of the void reactivity coefficient at assembly level in the full voidage range. Results have been obtained using the deterministic codes CASMO-4, HELIOS, PHOENIX, BOXER and the probabilistic code MCNP4C, combined for almost all cases with different cross section libraries. A statistical analysis of the results obtained showed that the void reactivity coefficient tends to become less negative beyond 80% void and that the discrepancies between codes tend to increase from less than 15% at voidages lower than 40% to more than 25% at voidages higher than 70%. The void reactivity coefficient results and the corresponding differences between codes were isotopically decomposed to interpret discrepancies. The isotopic decomposition shows that the minimum observed in the void reactivity coefficient between 80% and 90% void is largely due to the decrease in the relative importance of the ¹⁵⁷Gd(n, γ) rate with increasing voidage, and that the fundamental discrepancies between codes or libraries are mainly governed by the different predictions of the ²³⁸U(n, γ) variation with voidage.     

High-performance laser-processed polysilicon thin-film transistors

We present electrical results from hydrogenated laser-processed polysilicon thin-film transistors (TFT's) fabricated using a simple four-mask self-aligned aluminum top-gate process. Transistor field-effect mobilities of 280-450 cm²/Vs and on/off current ratios of more than 10⁸ are measured in these devices. Except for the amorphous-silicon deposition step, the highest processing temperature that the substrate was subjected to was 350°C. Such good performance is attributed to an optimized laser-crystallization process combined with hydrogenation     

选择适合目标应用的正确时钟芯片

本文对时钟芯片划分为若干基本大类,供设计者做出更加明智的时钟选择.     

In-situ diagnostic of femtosecond laser probe pulses for high resolution ultrafast imaging

Ultrafast imaging is essential in physics and chemistry to investigate the femtosecond dynamics of nonuniform samples or of phenomena with strong spatial variat...     

Laser Recrystallization of Polycrystalline Silicon in Recessed Structures

The pulsed-laser recrystallization of polysilicon in recessed structures, consisting of a silicon film deposited on a patterned oxide layer on a heat sink, is investigated for the first time. The different thermal environments created by the recess area, when compared to those outside this area, causes the recessed silicon to cool first. The different cooling rates in the continuous silicon film creates lateral temperature gradients, producing large elongated grains. Additionally, the recessed structure can lead to different film microstructures within the recessed area compared to outside this area. This structure is therefore capable of grain engineering different microstructures for polysilicon.     

Formation of reconfigurable singlemode channel waveguides in LiNbO/sub 3/ using spatial solitons

The formation of reconfigurable singlemode channel waveguides using photovoltaic dark spatial solitons is demonstrated in a titanium-diffused slab LiNbO/sub 3/ waveguide. The generated mode profile is shown to be influenced by the presence of titanium.     

Experimental validation of radial reconstructed pin-power distributions in full-scale BWR fuel assemblies with and without control blade

Total fission rate measurements have been performed on full-size BWR fuel assemblies of type SVEA-96+ in the zero power reactor PROTEUS at the Paul Scherrer Institute. This paper presents comparisons of reconstructed 2D pin fission rates from nodal diffusion calculations to the experimental results in two configurations: one “regular” (I-1A) and the other “controlled” (I-2A). Both configurations consist of an array of 3 × 3 SVEA-96+ fuel assemblies moderated with light water at 20 °C. In configuration I-2A, an L-shaped hafnium control blade (half of a real cruciform blade) is inserted adjacent to the north-west corner of the central fuel assembly. To minimise the impact of the surroundings, all measurements were done in fuel pins belonging to the central assembly. The 3 × 3 experimental configuration (test zone) was modelled using the core monitoring and design tools that are applied at the Leibstadt Nuclear Power Plant (KKL). These are the 2D transport code HELIOS, used for the cross-section generation, and the 3D, 2-group nodal diffusion code PRESTO-2. The exterior is represented, in the axial and radial directions, by 2-group partial current ratios (PCRs) calculated at the test zone boundary using a 3D Monte Carlo (MCNPX) model of the whole PROTEUS reactor. Sensitivity cases are analysed to show the impact of changes in the 2D lattice modelling on the calculated fission rate distribution and reactivity. Further, the effects of variations in the test zone boundary PCRs and their behaviour in energy are investigated.     

Hyperbolic representation of light propagation in a multilayer medium

By analogy with the representation of the polarization of light on the Poincaré sphere, we describe the propagation and the reflection/transmission of light in a multilayer on a hyperbolic surface. We show that the propagation of light corresponds to a classical rotation on this surface and that its reflection/transmission corresponds to a hyperbolic rotation.     

Performance improvement obtained for thin-film transistorsfabricated in prepatterned laser-recrystallized polysilicon

Thin-film transistors (TFT's) are fabricated in polysilicon films that are laser recrystallized either before or after active-area definition. We find the the performance of TPT's fabricated in active areas that are prepatterned before laser recrystallization is dramatically improved. For example, the field-effect mobility is increased by a factor of three, the threshold voltage is reduced from 5.32 V to 0.07 V, and the subthreshold slope is cut in half for W/L = 10 μm/10 μm TFT's. All TFT's discussed utilize gas-immersion laser-doped source and drain junctions and are unhydrogenated