The Isothermal Melting Kinetics of Ultra-High Molecular Weight Polyethylene Crystals.

The isothermal melting behaviors of ultra-high molecular weight polyethylene (UHMWPE) with different entangled states (i.e., nascent and melt-crystallized samples) are studied. For two kinds of UHMWPE samples, the result shows that the relative content of survived crystals (Xs) exponentially decreases with time and reaches a constant value. It is suggested that such a melting behavior is related to the observed nonlinear growth of crystals induced by the kinetically rejected entanglements accumulated at the growth front. Additionally, the exponential decay of Xs with time provides a characteristic melting time (τ) for the melting process. Compared to the melt-crystallized UHMWPE, the τ value of nascent UHMWPE is generally longer even in a higher temperature range, which is mainly because the former has a larger entanglement density difference. Furthermore, these observations demonstrate that UHMWPEs with different entangled states have an analogous melting mechanism since they exhibit a similar melting activation energy (≈1300 kJ mol-1).

EdgeMap: An Optimized Mapping Toolchain for Spiking Neural Network in Edge Computing.

Spiking neural networks (SNNs) have attracted considerable attention as third-generation artificial neural networks, known for their powerful, intelligent features and energy-efficiency advantages. These characteristics render them ideally suited for edge computing scenarios. Nevertheless, the current mapping schemes for deploying SNNs onto neuromorphic hardware face limitations such as extended execution times, low throughput, and insufficient consideration of energy consumption and connectivity, which undermine their suitability for edge computing applications. To address these challenges, we introduce EdgeMap, an optimized mapping toolchain specifically designed for deploying SNNs onto edge devices without compromising performance. EdgeMap consists of two main stages. The first stage involves partitioning the SNN graph into small neuron clusters based on the streaming graph partition algorithm, with the sizes of neuron clusters limited by the physical neuron cores. In the subsequent mapping stage, we adopt a multi-objective optimization algorithm specifically geared towards mitigating energy costs and communication costs for efficient deployment. EdgeMap-evaluated across four typical SNN applications-substantially outperforms other state-of-the-art mapping schemes. The performance improvements include a reduction in average latency by up to 19.8%, energy consumption by 57%, and communication cost by 58%. Moreover, EdgeMap exhibits an impressive enhancement in execution time by a factor of 1225.44×, alongside a throughput increase of up to 4.02×. These results highlight EdgeMap's efficiency and effectiveness, emphasizing its utility for deploying SNN applications in edge computing scenarios.

Detection and closed-loop control of piston errors for a Fizeau imaging interferometer.

In the Fizeau imaging interferometer testbed we recently built, the optical path difference (OPD; i.e., piston error) among three sub-telescopes should be corrected for phased imaging to enhance the spatial resolution. This study presents the detection of the OPD via a dispersed fringe sensor (DFS) method and its closed-loop control. The retrieval of the OPD from a dispersed fringe map is a fast-Fourier-transform-based DFS method, which indicates in theory that the OPD has a linear relationship with the displacement of the secondary peaks in the Fourier spectrum of the dispersed fringe map. Then the design and alignment of the OPD detection module are presented, as well as the OPD compensation module with a two-level motion stage. A unique benefit of the fast-Fourier-transform-based DFS is high time efficiency for closed-loop control; for a window of $32 \times 128 \;{\rm pixels}$32×128pixels, a 932 Hz computation rate was achieved by dedicated electrical hardware, which is significant for the distributed satellite formation-flying platform. The experiments validated (1) that the detection range of the DFS is more than $\pm {160}\;\unicode{x00B5}{\rm m}$±160µm, (2) that the OPD has a fine-line relationship with the secondary peak displacement, (3) the feasibility of the DFS method used for closed-loop control, and (4) that an OPD control precision of 0.0593 µm RMS is achieved.

Space-qualified fast steering mirror for an image stabilization system of space astronomical telescopes.

A space-qualified fast steering mirror (SQ-FSM) was designed, built, and tested at the National Astronomical Observatories of the Chinese Academy of Sciences for an image stabilization system of space astronomical telescopes, which is used for the tip-tilt correction of small jitter of the satellite platform; this achieved image stability in a closed-loop manner. Its design primarily faces four challenges involving (1) sustaining the specified sine and random vibration without launch lock, as well as shock response spectrum experiments; (2) surface form error of a clear aperture of ϕ120 mm less than 1/50λ root mean square (RMS, λ=632.8 nm) with a relatively rigid mirror support; (3) resonance frequency of at least 800 Hz and as high as possible; (4) minimum reaction force and torque in order to decrease its unfavorable influence on the satellite platform. To achieve these goals, the global optimizations and compromises have to be made throughout the design process. The study reviews the detailed design of the SQ-FSM with respect to the four challenges, mainly by keeping the mirror and its support lightweight, mirror bonding and solidification, actuator and its stiffness, flexure support of the mirror and its holder, material optimization for weight, stiffness, and coefficient of thermal expansion, as well as finite element analysis on statics and dynamics. The performances are also measured and expatiated, including the surface form, resonant frequency, tip-tilt stroke, vibration and shock response spectrum experiments, etc., which validate the performances of the SQ-FSM.

Design and experimental demonstration of pointing correction module for a Fizeau imaging interferometer.

To increase the spatial resolution while circumventing the problems of increased mass and volume of monolithic telescopes, a Fizeau imaging interferometer testbed (FIIT) with three individual subtelescopes was designed and constructed for high resolution astronomical observation. FIIT is intended to be mounted on a distributed small-satellite constellation with a formation fly configuration; thus the extremely stable pointing of the subtelescopes is the prerequisite for phased imaging, which is because the satellite suffers from some extent of detrimental jitters and drifts needs to be corrected by FIIT itself. FIIT makes use of a shared tip/tilt detection module with a cross-correlation algorithm, three fast-steering mirrors, and closed-loop control technology for pointing correction of three subtelescopes, which can make sure the images are coaligned for a long period of time used to image some faint astronomical objects. This study gives a detailed description of the detection algorithm of image shifts, the hardware design, and data processing flow, followed by closed-loop experiments of a wide-band white light point source. The results of residual errors on the detection camera and the beam-combining camera demonstrate the performance of the pointing correction function, which is a significant milestone for FIIT.

Wide-band white light sparse-aperture Fizeau imaging interferometer testbed for a distributed small-satellites constellation.

Under the background of astronomical observation by a distributed small-satellites constellation, a Fizeau imaging interferometer testbed (FIIT) was designed and constructed at National Astronomical Observatories of the Chinese Academy of Sciences in the past four years that achieved wide-band white light (400-700 nm) phased imaging at laboratory with a field of view (FOV) ∼2 arcmin. This study presents the design of FIIT, which is mainly composed of a light source module for simulating infinite objects, three sub-telescopes in a Golay-3 distribution (i.e., equilateral triangle), three tip/tilt correction modules and optical path delay modules, as well as three detecting telescopes and one beam-combining telescope for phased imaging. The three detecting telescopes could determine the piston and tip/tilt errors, which could be compensated for by optical path delay modules and fast steering mirrors in a close-loop mode. The performance of FIIT is also derived analytically and simulated by a ray-tracing model. The tolerance analysis of the pupil geometry and magnification matching are also performed for achieving a better FOV. The optical test of each module could efficiently validate them to achieve diffraction limit imaging. The preliminary experimental results for both point source and extend scene could sufficiently demonstrate the phased mode imaging of FIIT, thus validating the good prospects of this technique in the future.

Effect of various g-C3N4 precursors on the catalytic performance of alkylorganotin-based catalysts in acetylene hydrochlorination.

A series of alkylorganotin-based catalysts (Sn-g-C3N4 /AC) was prepared by wet impregnation in ethanol using different g-C3N4 precursors and alkylorganotin compounds. The structure, texture, surface composition, and adsorption properties of the as-prepared catalysts were extensively characterized. Then, the obtained samples were evaluated for their catalytic performance in hydrochlorination of acetylene. The results provided by the X-ray photoelectron spectroscopy, acetylene temperature-programmed desorption, and HCl adsorption confirmed the nature of the active sites (i.e. Sn-Nx) involved in the reactant adsorption, and hence in the improved catalytic performance. These active sites were also related to the improved lifetime of alkylorganotin-based catalysts in the hydrochlorination of acetylene. At a constant reaction temperature of 200 °C with an acetylene gas hourly space velocity (C2H2 -GHSV) of 30 h-1 , Sn-g1 -C3N4 /AC-550 exhibited the highest acetylene conversion (~98.0%) and selectivity toward the vinyl chloride monomer (>98.0%). From the catalytic test results, it was reasonably concluded that the hexamethylenetetramine is the most suitable N precursor, as compared to the dicyandiamide and urea, to prepare high-performance catalysts. From the BET specific surface area of fresh and used catalysts, it was suggested that, in contrast to dicyandiamide and urea, hexamethylenetetramine could delay the deposition of coke on alkylorganotin-based catalysts, which is reflected by the extended lifetime.

Cobaltosic Oxide Catalysts for Catalytically Removing Hydrogen from Tail Chlorine.

Cobaltosic oxide has been used as catalysts in dehydrogenation for tail chlorine due to the advantages of low price and security. The Co3O4/ZSM-5 was synthesized by the volume impregnation method. The catalytic dehydrogenation performance of Co3O4/ZSM-5 was investigated, the catalytic reaction of hydrogen with oxygen and chlorine was carried out in a fixed-bed, and the mixed reactant gases were prepared according to the composition and content of tail chlorine in industry: Cl2(65%-80%), N2(6-16%), O2(8%-10%) and H2(1.5%-4%). The catalytic efficiency and stability of Co3O4/ZSM-5 in dehydrogenation for tail chlorine were better than that of Co3O4. After the calcination on 300°C, the Co3O4/ZSM-5 with 1 %wt. Co3O4 shown excellent catalytic performance at 50°C, and the average conversion of hydrogen can reach up to 99.59%.

[Key enzymes in butanol fermentation by a facultative anaerobe Bacillus sp. TSH1].

Bacillus sp. TSH1 is a butanol-producing microorganism newly isolated in our laboratory; it can grow and ferment under facultative anaerobic conditions, while sharing similar fermentation pathways and products with Clostridium acetobutylicum. To illustrate the relationships between the products and the enzyme activities in Bacillus sp. TSH1, key butanol- and ethanol-forming enzymes were studied, including butyraldehyde dehydrogenase, butanol dehydrogenase and alcohol dehydrogenase. The activities of the three enzymes increased rapidly after the initiation of fermentation. Activities of three enzymes peaked before 21 h, and simultaneously, product concentrations also began to increase gradually. The maximum activity of alcohol dehydrogenase was 0.054 U/mg at 12 h, butyraldehyde dehydrogenase 0.035 U/mg at 21 h and butanol dehydrogenase 0.055 U/mg at 15 h. The enzyme activities then decreased, but remained constant at a low level after 24 h, while the concentrations of butanol, acetone, and ethanol continued increasing until the end of the fermentation. The results will attribute to the understanding of the butanol metabolic mechanism, and provide a reference for further study of a facultative Bacillus metabolic pathway.

[Optimization of ethylene production from ethanol dehydration using Zn-Mn-Co/HZSM-5 by response surface methodology].

The effects of reaction temperature, ethanol concentration and weight hourly space velocity (WHSV) on the ethylene production from ethanol dehydration using zinc, manganese and cobalt modified HZSM-5 catalyst were investigated by response surface methodology (RSM). The results showed that the most significant effect among factors was reaction temperature and the factors had interaction. The optimum conditions were found as 34.4% ethanol concentration, 261.3 0 degrees C of reaction temperature and 1.18 h(-1) of WHSV, under these conditions the yield of ethylene achieved 98.69%.

Statistical optimization of sulfite pretreatment of corncob residues for high concentration ethanol production.

In this study, a central composite design of response surface method was used to optimize sulfite pretreatment of corncob residues, in respect to sulfite charge (5-10%), treatment time (1-2h), liquid/solid (l/s) ratio (6:1-10:1) and temperature (150-180°C) for maximizing glucose production in enzymatic hydrolysis process. The relative optimum condition was obtained as follows: sulfite charge 7.1%, l/s ratio 7.6:1, temperature 156°C for 1.4h, corresponding to 79.3% total glucan converted to glucose+cellobiose. In the subsequent simultaneous saccharification and fermentation (SSF) experiments using 15% glucan substrates pretreated under this kind of conditions, 60.8 g ethanol l(-1) with 72.2% theoretical yield was obtained.