德州仪器

In this paper, we investigate the degradation of the thermal conductivity of diamond due to the presence of the isotope C-13. We employ a full-band Monte Carlo simulation in which phonons are modeled as semiclassical particles, and the full nonlinear phonon Boltzmann transport equation is solved. The thermal conductivity of diamond with C-13 concentrations of 0.005% (isotopically ultrapure), 0.1% (isotopically enriched), and 1.07% (naturally occurring) is computed for a temperature range of 80-500 K, showing good agreement with experimental data. The degradation of thermal conductivity with increasing isotope concentration is observed across the entire temperature range and is significant at low temperatures. At 80 K, the thermal conductivity of the naturally occurring sample is about four times lower than that of the isotopically enriched sample and eleven times lower than that of the isotopically ultrapure one. We further investigate the isotope effect on individual phonon modes and compute their individual contribution to the thermal conductivity. We also calculate the expected value of the mean free path and relaxation time of all phonon modes' population. Acoustic phonons are the principal contributors to thermal conductivity across all isotope concentrations. The optical phonon modes present relaxation times and mean free paths that are affected by the isotope concentration but are fairly constant over the entire temperature range. The acoustic phonon mean free paths decrease with increasing isotope concentration and are temperature-dependent, ranging from 2 mm to 0.5 mu m.

This paper presents an ultra-miniaturized and high-quality factor embedded loaded coaxial substrate integrated waveguide (ELCSIW) filter. Integrating a substrate-integrated coaxial resonator with a capacitively loaded air cavity achieves a 99% reduction in size compared to a conventional SIW cavity. Incorporating an air gap in the capacitive loading structure significantly enhances the resonator's quality factor. A comprehensive analysis of the miniaturization factor and quality factor in relation to cavity structure dimensions is performed. Guidelines for fabricating the highly loaded cavity are presented. To demonstrate the benefits of this technique, a two-pole band-pass filter with a 6.3% bandwidth at 1.1 GHz is designed, fabricated, and measured. The overall footprint of the filter is 10.5 mm & times; 20.5 mm, which is comparable to 0.07 lambda g & times; 0.14 lambda g. The measured insertion loss is 0.54 dB, and the upper band is spurious-free up to 7 times the resonant frequency. The exceptional performance and compactness of the loaded coaxial substrate integrated waveguide cavities highlight their immense potential for compact advanced wireless systems.

Reinforcement learning has become central to improving large reasoning models, but its success still relies heavily on verifiable rewards or labeled supervision. This limits its applicability to open ended domains where correctness is ambiguous and cannot be verified. Moreover, reasoning trajectories remain largely unconstrained, and optimization towards final answer can favor early exploitation over generalization. In this work, we ask whether general reasoning ability can be improved by teaching models how to think (the structure of reasoning) rather than what to produce (the outcome of reasoning) and extend traditional RLVR to open ended settings. We introduce structure aware reinforcement learning (SARL), a label free framework that constructs a per response Reasoning Map from intermediate thinking steps and rewards its small world topology, inspired by complex networks and the functional organization of the human brain. SARL encourages reasoning trajectories that are both locally coherent and globally efficient, shifting supervision from destination to path. Our experiments on Qwen3-4B show SARL surpasses ground truth based RL and prior label free RL baselines, achieving the best average gain of 9.1

In this paper, we report a novel ohmic contact formation scheme for extreme bandgap AlxGa1-xN (x > 0.6) channel high electron mobility transistors with undoped barrier layers. Our approach consists of using a new low-temperature pulsed metal-organic chemical vapor deposition doping scheme for the n(++)-GaN regrown contacts and an AlxGa1-xN digital alloy (DA) channel layer comprising short-period superlattices of AlN and GaN. Pulsed growth and doping yield a sheet resistivity that is a factor of 3-5 lower than that of conventional doped n(++)-GaN layers grown under identical conditions. Moreover, the regrown n(++)-GaN layer has no hetero-barrier with the GaN layers of the DA channel, which leads to linear ohmic contacts and a record low contact resistance R-c similar to 6.5 Omega-mm to the Al0.62Ga0.38N DA channel layer of a HEMT with an AlN barrier layer.

We report an extreme-bandgap (EBG) AlGaN HEMT employing an undoped AlN barrier over a digital-alloy (DA) channel formed by AlN/GaN short-period superlattice (SPSL) and metalorganic chemical vapor deposition (MOCVD) regrown n(++)-GaN contacts on sapphire. The coupling of carrier wave functions through thin AlN barriers in DA leads to the formation of minibands in the transverse direction, due to which the DA channel acts as an Al (0.62) Ga (0.38) N layer. In lateral direction, regrown n++-GaN is in direct contact with GaN layers of DA, thus removing severe interface barriers existing in most known EBG HEMTs, showing a low contact resistance of R (C)=6.5 Omega & sdot; mm. With a peak drain current of 333 mA/mm, the DA-channel HEMT achieved an on-resistance R (ON)=28 Omega & sdot; mm at 6 mu m source-drain spacing, a subthreshold swing (SS) of 77 mV/dec, an ON/OFF ratio >10(7) , negligible gate hysteresis, and a critical breakdown field E (C)approximate to 2.3 MV/cm without field-plating. These results establish DA-channel as a promising new design for EBG HEMT with insulating AlN barriers for high-power and high-voltage electronics.