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The reductive catalytic fractionation (RCF) of lignocellulose, considering lignin valorization at design time, has demonstrated the entire utilization of all lignocellulose components; however, such processes always require catalysts based on precious metals or high‐loaded nonprecious metals. Herein, the study develops an ultra‐low loaded, atomically dispersed cobalt catalyst, which displays an exceptional performance in the RCF of lignocellulose. An approximately theoretical maximum yield of phenolic monomers (48.3 wt.%) from lignin is realized, rivaling precious metal catalysts. High selectivity toward 4‐propyl‐substituted guaiacol/syringol facilitates their purification and follows syntheses of highly adhesive polyesters. Lignin nanoparticles (LNPs) are generated by simple treatment of the obtained phenolic dimers and oligomers. RCF‐resulted carbohydrate pulp are more obedient to enzymatic hydrolysis. Experimental studies on lignin model compounds reveal the concerted cleavage of Cα–O and Cβ–O pathway for the rupture of β‐O‐4 structure. Overall, the approach involves valorizing products derived from lignin biopolymer, providing the opportunity for the comprehensive utilization of all components within lignocellulose. [ABSTRACT FROM AUTHOR]

Purpose: According to the Government Response tracker (oxCGRT) index, the overall government response, stringency, economic support, containment and health policies to COVID-19 from January 2020 to December 2022. The main objective of this paper is to explore how stock market performance is affected by these polices, respectively. Design/methodology/approach: The authors employ EGARCH and autoregressive distributional lag (ARDL) models to test the impact of epidemic prevention policy implementation on stock market returns, volatility and liquidity and make cross-country comparisons for six important world economies. Findings: Firstly, the implementation of various preventive policies hurts stock market returns and increases volatility, but there are a few indicators that have no effect or have an easing effect in some countries. Secondly, health policies exacerbate market volatility and have a stronger effect than other policy indicators. Thirdly, In China and the USA, anti-epidemic policies have been shown to worsen liquidity, while in Japan they have been shown to improve liquidity. Originality/value: First, enrich the growing body of COVID-19 research by comprehensively examining whether and how government prevention policies affect stock market returns, volatility and liquidity. Second, explore the impact of different types of intervention policies on stock market performance, separately. [ABSTRACT FROM AUTHOR]

Lignin represents the most abundant renewable aromatic resource, monophenolics, from which would serve as promising monomers for the synthesis of aromatic polymers in a sustainable manner. Hererin, we report that hydroxycinnamic derivatives, i.e., ethyl coumarate/ferulate (pCA-Et and FA-Et), with a conjugate and rigid structure can be selectively fragmented from herbaceous plant lignin over a ZnMoO4/MCM-41 catalyst, which upon a one-pot fluorosulfonation, carboxylation, and esterification, give aromatic diesters in high yields. Copolymerizing lignin-derived dicarboxylic species with holocellulose-derived butanediol and adipic acid results in a new family of aliphatic–aromatic polyesters, which display controllable mechanical, optical, and thermal performance, especially depending on the methoxyl group in lignin-derived units. The as-prepared copolyesters can be fully converted into monomers via ethanolysis at 80 °C, demonstrating excellent chemical recyclability. Overall, we provide a novel upstream and downstream route to transform sustainable biomass into functional polymers. [ABSTRACT FROM AUTHOR]

Femtosecond filament-induced breakdown spectroscopy (FIBS) is an efficient approach in remote and in situ detection of a variety of trace elements, but it was recently discovered that the FIBS of water is strongly dependent on the large-bandgap semiconductor property of water, making the FIBS signals sensitive to laser ionization mechanisms. Here, we show that the sensitivity of the FIBS technique in monitoring metal elements in water can be efficiently improved by using chirped femtosecond laser pulses, but an asymmetric enhancement of the FIBS intensity is observed for the negatively and positively chirped pulses. We attribute the asymmetric enhancement to their different ionization rates of water, in which the energy of the photons participating in the ionization process in the front part of the negatively chirped pulse is higher than that in the positively chirped pulse. By optimizing the pulse chirp, we show that the limit of detection of the FIBS technique for metal elements in water, e.g., aluminum, can reach to the sub-ppm level, which is about one order of magnitude better than that by the transform-limited pulse. We further examine the FIBS spectra of several representative water samples including commercial mineral water, tap water, and lake water taken from two different environmental zones, i.e., a national park and a downtown business district (Changchun, China), from which remarkably different concentrations of Ca, Na, and K elements of these samples are obtained. Our results provide a possibility of using FIBS for direct and fast metal elemental analysis of water in different field environments. [ABSTRACT FROM AUTHOR]

The Fine-Kinney model is a quantitative and effective method to identify and evaluate potential risks. The Fine-Kinney method has been widely used in practice, while the traditional Fine-Kinney method is difficult to access risk parameters precisely in practice. Besides, the current Fine-Kinney method fails to take into account the fact that decision makers are interrelated in practice. Further, the detailed relationships among the potential hazards cannot be reflected in the conventional Fine-Kinney method during the risk priority process, especially in the case of uncertain information. To compensate these deficiencies, this paper proposes an extended Fine-Kinney framework by integrating ORESTE (organísation, rangement et Syn-thèse de données relarionnelles) (in French), Choquet integral, and Probabilistic Linguistic Term Sets (PLTSs). Firstly, the PLTSs are utilized to express the decision makers' complex risk preference information. Then, the Choquet integral is used to integrate risk evaluation information, which can simulate the potential interaction relationships among individual risk evaluation of decision-makers. Next, an extended ORESTE based on the PLTSs method is used to obtain the priorities of potential hazards, in which distance measure of PLTSs is applied to replace Besson's ranks. Moreover, the PIR (preference, indifference, and incomparability) structure is constructed to describe the detailed relationships between potential hazards. Finally, an illustrative example is described to illustrate the proposed risk evaluation method. After that, the rationality and efficiency of the proposed method are tested through the comparison with other similar methods. [ABSTRACT FROM AUTHOR]

We present an upper bound of cumulative return in financial trading time series to formulate the most possible profit of many trades. The bound can be used to formally analyze the cumulative return varied by the number of trades, the mean return, and transaction cost rate. We also prove and show the validation of the upper bound, and verify the trend of cumulative return is consistent with that of the proposed bound via simulation experiments. Introducing a set of stochastic assessment methodology based on bootstrap into the organization of experimental data, we illustrate the influence on cumulative return from the relationship between the mean of return and transaction cost rate, technical trading rules, and stock indexes. To the best of our knowledge, this is the first to present and prove a bound of cumulative return of a stock trading series in theory. Both theoretical analyses and simulation experiments show the presented bound is a good mathematical tool to evaluate the trading risks and chances using given trading rules in stock trading markets. [ABSTRACT FROM AUTHOR]

In order to reduce the damage of blasting to rock mass and improve the half-hole rate of presplitting blasting, the dynamic finite element analysis software ANSYS/LS-DYNA is used to simulate and analyze the action process of sequential controlled blasting. The effects of the detonation delay time of the postblasting hole and the hole spacing of the postblasting hole on the crack formation of the sequential controlled presplitting blasting are studied. The results show that when the blast hole with a diameter of 42 mm is used for sequential controlled presplitting blasting and the first blast hole pitch is 60 cm, the reasonable detonation delay time is 80∼120 μs. When the detonation delay time is 80 μs, the reasonable postblast hole spacing is 60 cm. Field tests show that when reasonable optimized blasting parameters are used, presplit blasting with sequential control can reduce drilling workload and explosive consumption. The sequential controlled presplitting blasting not only increases the hole spacing but also plays a better role in protecting the surrounding rock. [ABSTRACT FROM AUTHOR]

In electric vehicles and hybrid electric vehicles, insulated-gate bipolar transistor (IGBT) power module trends to dissipate higher heat flux due to increased power rating and reduced package size. An inefficient cooling method will result in stringent thermal reliability problems. Therefore, there is a strong need for innovative and efficient cooling technologies in order to tackle these issues. In this article, a localized direct phase-change cooling strategy is applied and integrated with direct bonded copper in IGBT power module. Vapor chamber with light weight, high thermal conductivity, and even temperature uniformity replaces original copper baseplate. Layers of thermal grease and original cooling plate are removed, leading to a further reduction in thermal resistance. In order to evaluate the new module, a thermal model and an experiment were built to analyze temperature distribution in layers, junction temperature, temperature uniformity, and thermal resistance. Results indicate the integrated thermal management system outperforms traditional cooling solutions on the cooling capacity. Improvements on junction temperature, temperature uniformity, and total thermal resistance are 34.6%, 76.6%, and 41.6%, respectively. The results illustrate the potential of phase-change cooling by vapor chamber. It provides a new perspective in the compact and efficient design of power electric modules. [ABSTRACT FROM AUTHOR]

Reductive catalytic fractionation (RCF) of lignocellulosic biomass, that is depolymerization of the native lignin component into well-defined monomeric phenols in the first step, offers an opportunity to utilize entire biomass components. Herein, we report that Ni@ZIF-8 can serve as a chemodivergent catalyst in RCF of eucalyptus sawdust, thus selectively producing phenolic compounds having either a propyl or propanol end-chain under different reaction conditions. In both cases, high yields of lignin monomers and a high degree of delignification were achieved, next to well-preserved carbohydrate pulp suitable for further processing. A mechanistic study using model compounds indicated that the dehydroxylation at the γ-position of the β-O-4 structure may be involved in the selectivity-controlling step. [ABSTRACT FROM AUTHOR]

This letter addresses the transient current distribution in the multichip half-bridge power modules, where two types of paralleling connections with different current commutation mechanisms are considered: paralleling dies and paralleling half-bridges. It reveals that with paralleling dies, both the high-side and low-side paralleled devices experience a similar transient current imbalance due to the mismatched stray inductance. However, with paralleling half-bridges and with the same mismatched stray inductances, the high-side paralleled devices have much smaller transient current imbalance, the cause of which is found be to the current commutation process. Theoretical analysis based on the circuit modeling and current commutation process elaborates the findings, which are then confirmed by experimental results. [ABSTRACT FROM AUTHOR]

Abstract: Lignin is the largest renewable resource of bioaromatics, and the catalytic fragmentation of lignin into phenolic monomers is increasingly recognized as an important starting point for lignin valorization. Herein, we report that ZnMoO4 supported on MCM‐41 can catalyze the fragmentation of biorefinery technical lignin, enzymatic mild acidolysis lignin, and native lignin derived from corncob to yield lignin oily products that contain 15–37.8 wt % phenolic monomers, in which the high selectivities towards methyl coumarate (1) and methyl ferulate (2) were obtained (up to 78 %). The effects of some key parameters such as the influence of the solvent, reaction temperature, time, H2 pressure, and catalyst dosage were examined in view of activity and selectivity. The loss of Zn from the catalyst is discussed as the primary cause of deactivation, and the catalytic activity and selectivity can be well preserved in at least six runs by thermal calcination. The high selectivity to 1 and 2 leads to their easy separation and purification from lignin oily product to provide sustainable monomers for the preparation of functional polyether esters and polyesters. [ABSTRACT FROM AUTHOR]

Abstract: The search for efficient routes for the production of fructose from biomass‐derived glucose is of great interest and importance, as fructose is a highly attractive substrate in the conversion of cellulosic biomass into biofuels and chemicals. In this study, a one‐pot, multistep procedure involving enzyme‐catalyzed oxidation of glucose at C2 and Ni/C‐catalyzed hydrogenation of d‐glucosone at C1 selectively gives fructose in 77 % yield. Starting from upstream substrates such as α‐cellulose and starch, fructose was also generated with similar efficiency and selectivity by the combination of enzymatic and heterogeneous catalysis. This method constitutes a new means of preparing fructose from biomass‐derived substrates in an efficient fashion. [ABSTRACT FROM AUTHOR]

Silicon carbide (SiC) and gallium nitride metal–oxide–semiconductor field-effect transistors (MOSFETs) are capable of processing high power at high switching frequencies with less switching losses and conduction losses. The gate driver circuit power consumption is directly proportional to the switching frequency. The power taken from the gate supply is dissipated in the gate resistance of the conventional gate driver (CGD) circuit. Instead of dissipating all the gate driver energy, some energy can be recovered or recycled by utilizing the principle of resonance. This reduces the net power being taken from the gate supply. This paper presents a new resonant gate driver (RGD) circuit which consumes less power compared to the CGD circuit at high switching frequencies. The proposed gate driver is designed for SiC MOSFETs. It can be modified appropriately to suit for insulated-gate bipolar transistors and other MOSFETs also. The performance of the proposed circuit is simulated in LTSpice environment, and an experimental prototype of the proposed circuit is developed to validate its performance. The proposed RGD circuit has achieved nearly 50% reduction in gate driver power consumption compared to the CGD circuit. [ABSTRACT FROM PUBLISHER]

This paper addresses the influences of device and circuit mismatches on paralleling the silicon carbide (SiC) MOSFETs. Comprehensive theoretical analysis and experimental validation from paralleled discrete devices to paralleled dies in multichip power modules are first presented. Then, the influence of circuit mismatch on paralleling SiC MOSFETs is investigated and experimentally evaluated for the first time. It is found that the mismatch of the switching loop stray inductance can also lead to on-state current unbalance with inductive output current, in addition to the on-state resistance of the device. It further reveals that circuit mismatches and a current coupling among the paralleled dies exist in a SiC MOSFET multichip power module, which is critical for the transient current distribution in the power module. Thus, a power module layout with an auxiliary source connection is developed to reduce such a coupling effect. Finally, simulations and experimental tests are carried out to validate the analysis and effectiveness of the developed layout. [ABSTRACT FROM AUTHOR]