[en] The drop critical safety at the launch phase is the key point and difficult point in the design of space fast reactor. One of the general methods to ensure drop critical safety is using spectral shift absorption material as the structure material. The Mo-Re alloy is usually used as spectral shift absorption material and the structure material with its excellent spectral shift performance and high temperature performance. The study was focused on Prometheus basic core scheme, using MCNP code, calculated and analyzed the effect of Mo-Re alloy on drop critical safety and its mechanism in the different drop conditions. The results suggest that the drop condition has different effects on the critical safety with the different contents of Re. The strengthened resonance absorption caused by softenspectrum and the increase of Re content are the main factors of the change of the worst drop condition. (authors)

[en] This study uses bottom-up modeling framework in order to quantify potential energy savings and emission reduction impacts from the implementation of energy efficiency programs in the building sector in China. Policies considered include (1) accelerated building codes in residential and commercial buildings, (2) increased penetration of district heat metering and controls, (3) district heating efficiency improvement, (4) building energy efficiency labeling programs and (5) retrofits of existing commercial buildings. Among these programs, we found that the implementation of building codes provide by far the largest savings opportunity, leading to an overall 17% reduction in overall space heating and cooling demand relative to the baseline. Second are energy efficiency labels with 6%, followed by reductions of losses associated with district heating representing 4% reduction and finally, retrofits representing only about a 1% savings. - Highlights: • We use a bottom-up modeling approach to quantify emission reduction from efficiency programs. • Heating and cooling are the main focus of this study. • We find that building codes lead to 17% reduction compare to the baseline. • Other programs analyzed concern district heat, building labeling and retrofits of buildings.

[en] We report here a method for the preparation of amphiphilic dendrimer-like copolymers with dendritic polystyrene (PS) core and protonated poly(2-vinyl pyridine) (P2VP) or poly(methacrylic acid) (PMAA) shell. The method employed the efficient coupling reaction of anionic living polymer chains and chlorosilane. The synthesis started from a functionalized 3^rd generation dendritic polystyrene, G3PS-g-SiCl, used as the precursor. The dendrimer-like copolymer of styrene and 2-vinyl pyridine, G3PS-g-P2VP, was synthesized by direct coupling of living P2VPLi to the precursor. The dendrimer-like copolymer of styrene and tert-butyl methacrylate, G3PS-g-PtBMA, was synthesized by an indirect procedure in which a living polymer containing mainly PtBMA segment was attached to the precursor. Both methods resulted in the formation of dendrimer-like copolymers with the high molecular weights (up to 8.5 × 10⁶ Da), large molecular sizes (diameter up to 73 nm), and dense shells (number of arms up to 1300). These products, G3PS-g-P2VP and G3PS-g-PtBMA, were protonated with trifluoroacetic acid and acidic hydrolyzed, respectively. After transformation, amphiphilic dendrimer-like copolymers, G3PS-g-P2VPH⁺ and G3PS-g-PMAA, were obtained. Preliminary results on the solution properties of the amphiphilic products were presented.

[en] Ta coatings on the 3Y-TZP ceramic substrate were successfully fabricated by plasma alloying technique, and its effect on the tetragonal-to-monoclinic phase transformation was investigated. The results indicate that the surface morphology and grain size of Ta coatings were influenced by the deposition temperature. Results of the surface roughness and static contact angle provide further supports. Scratch tests of Ta coatings deposited at 800 °C (S2 specimen) show the good adhesion. The Ta coating has a thickness of ∼590 nm in S2 specimen. Moreover, the friction properties of these Ta coatings in phosphate buffered saline solution exhibit the low friction coefficient. The Ta coating of S2 specimen exhibits an effectively protection for the phase transformation of the 3Y-TZP ceramic tested by hydrothermal aging.

[en] Development of effective and stable catalysts for CO${}_2$ hydrogenation into ethanol remains a challenge. Herein, we report that Rh${}_1$/CeTiO${}_x$ single-atom catalyst constructed by embedding monoatomic Rh onto Ti-doped CeO${}_2$ support has shown a super high ethanol selectivity (≈99.1 %), record-breaking turnover frequency (493.1 h${}^{-<!--\; ???\; -->1}$), and outstanding stability. Synergistic effects of Ti-doption and monoatomic Rh contribute to this excellent catalytic performance by firstly facilitating oxygen vacancies formation to generate oxygen-vacancy-Rh Lewis-acid-base pairs, which favor CO${}_2$ adsorption and activation, cleavage of C-O bonds in CH${}_x$OH* and COOH* into CH${}_x$* and CO* species, subsequent C-C coupling and hydrogenation into ethanol, and secondly generating strong Rh-O bond by Ti-doping-induced crystal reconstruction, which contributes to striking stability. This work highlights the importance of support elaborating regulation for single-atom catalyst design to substantially improve the catalytic performance. (© 2022 Wiley‐VCH GmbH)

[en] TiAl-based alloys have received extensive attention recently due to their excellent properties. However, the weak oxidation resistance at temperatures higher than 800 °C can limit their further high-temperature structural applications. To improve the oxidation resistance of a high-Nb-content γ-TiAl alloy (Ti-45Al-8.5Nb, in units of at.%), a chromium (Cr) coating is prepared by using the plasma surface alloying technique, separately, at 800 °C and 1000 °C. The x-ray diffraction (XRD) patterns reveal that an oxide surface layer consisting of Cr₂O₃, Al₂O₃, and TiO₂ is produced on the Cr-coated Nb containing γ-TiAl substrates during the initial oxidation. However, the Cr₂O₃ is dominated in the oxide surface layer after being isothermally oxidized for 300 h. The oxidation kinetic curves are composed of a parabolic law stage (≤ 90 h) and a biquadratic law stage (≥ 90 h), fit by weight–gain curves. Due to diffusion in the fabrication process and oxidation process, the Cr-coated specimens have an adhesion force after being isothermally oxidized, specifically 69 N for a specimen after oxidation for 300 h. These results demonstrate that the Cr coating enhances the oxidation resistance and adhesion of a Ti-45Al-8.5Nb alloy, which may provide a new feasible scheme for designing oxidation protection layers. (paper)

[en] This paper deduces the expression of the Schottky contact capacitance of AlGaN/AlN/GaN high electron mobility transistors (HEMTs), which will help to understand the electron depleting process. Some material parameters related with capacitance-voltage profiling are given in the expression. Detailed analysis of the forward-biased capacitance has been carried on. The gate capacitance of undoped AlGaN/AlN/GaN HEMT will fall under forward bias. If a rising profile is obviously observed, the donor-like impurity or trap is possibly introduced in the barrier. (condensed matter: electronic structure, electrical, magnetic, and optical properties)

[en] 63 mm diameter polycrystalline diamond (PCD) films were synthesized via a microwave plasma chemical vapor deposition (MPCVD) reactor in 99% H₂–1% CH₄ atmosphere. Two different conditions, i.e. the typical condition (input power of 5 kW and gas pressure of 13 kPa) and the high power density condition (input power of 10 kW and gas pressure of 18 kPa), were employed for diamond depositions. The color changes of the plasma under the two proposed conditions with and without methane were observed by photographs. Likewise, the concentrations of hydrogen atoms and carbon active chemical species in plasma were analyzed by optical emission spectroscopy (OES). The morphologies and purity of the PCD films were investigated by scanning electron microscopy (SEM) and Raman spectroscopy, respectively. Finally, the transmission spectrum of the polished PCD plates was characterized by a UV–Vis–NIR spectrometer. Experimental results showed that both the concentrations of hydrogen atoms and carbon radicals increased obviously, with the boost input power and higher pressure. The films synthesized under the high power density condition displayed higher purity and more uniform thickness. The growth rates in 10 kW and 18 kPa reached ∼7.7 µ m h⁻¹, approximately 6.5 times as much as that occurred in the typical process. Moreover, the polished plates synthesized under the high power density condition possessed a relatively high optical transmittance (∼69%), approaching the theoretical values of approximately 71.4% in IR. These results indicate that the purity and growth rate of big-area PCD films could be simultaneously increased with power density. (paper)

[en] Electromagnetic compatibility (EMC) is very important for intelligent instruments, and it is an important guarantee for its reliable operation. The complexity of EMC is mainly reflected in how to quickly and accurately locate the disturbance source, effectively suppress the disturbance source, and correctly judge the disturbance coupling path. Intelligent instruments have similar hardware characteristics. In this paper, the characteristics of common hardware characteristics of disturbance source and coupling path are analyzed, the equivalent antenna model of disturbance is analyzed, and the disturbance suppression method is given. Finally, the correctness of the method is verified by experiments. (paper)

[en] Although China became the world's largest CO₂ emitter in 2007, the country has also taken serious actions to reduce its energy and carbon intensity. This study uses the bottom-up LBNL China End-Use Energy Model to assess the role of energy efficiency policies in transitioning China to a lower emission trajectory and meeting its 2020 intensity reduction goals. Two scenarios – Continued Improvement and Accelerated Improvement – were developed to assess the impact of actions already taken by the Chinese government as well as planned and potential actions, and to evaluate the potential for China to reduce energy demand and emissions. This scenario analysis presents an important modeling approach based in the diffusion of end-use technologies and physical drivers of energy demand and thereby help illuminate China's complex and dynamic drivers of energy consumption and implications of energy efficiency policies. The findings suggest that China's CO₂ emissions will not likely continue growing throughout this century because of saturation effects in appliances, residential and commercial floor area, roadways, fertilizer use; and population peak around 2030 with slowing urban population growth. The scenarios also underscore the significant role that policy-driven efficiency improvements will play in meeting 2020 carbon mitigation goals along with a decarbonized power supply. - Highlights: ► Bottom-up model of China's energy and CO₂ reductions through sectoral policies. ► 2 scenarios evaluate impact of actions already taken/planned and future potential. ► China's CO₂ will not likely continue growing through 2050 due to saturation effects. ► Results emphasize both policy-driven efficiency and decarbonized power supply.