Highly dispersed NiMo@rGO nanocomposite catalysts fabricated by a two-step hydrothermal method for hydrogen evolution

Exploring and designing a high-performance non-noble metal catalyst for hydrogen evolution reaction(HER)are crucial for the large-scale application of H2 by water electrolysis.Here,novel catalysts with NiMo nanoparticles decorated on reduced graphene oxide(NiMo@r GO)synthesized by a two-step hydrothermal method were reported.Physical characterization results showed that the prepared NiMo@r GO-1 had an irregular lamellar structure,and the NiMo nanoparticles were uniformly dispersed on the rGO.NiMo@rGO-1 exhibited outstanding HER performance in an alkaline environment and required only 93 and 180 mV overpotential for HER in 1.0 M KOH solution to obtain current densities of-10 and-50 mA·cm^(-2),respectively.Stability tests showed that NiMo@rGO-1 had a certain operating stability for32 h.Under the same condition,the performance of NiMo@rGO-1 can be comparable with that of commercial Pt/C catalysts at high current density.The synergistic effect between NiMo particles and lamellate graphene can remarkably promote charge transfer in electrocatalytic reactions.As a result,NiMo@rGO-1 presented the advantages of high intrinsic activity,large specific surface area,and small electrical impedance.The lamellar graphene played a role in dispersion to prevent the aggregation of nanoparticles.The prepared NiMo@rGO-1 can be used in anion exchange membrane water electrolysis to produce hydrogen.This study provides a simple preparation method for efficient and low-cost water electrolysis to produce hydrogen in the future.

Finite-time H_(∞) filtering for Markov jump systems with uniform quantization

This paper is concerned with finite-time H_(∞) filtering for Markov jump systems with uniform quantization. The objective is to design quantized mode-dependent filters to ensure that the filtering error system is not only mean-square finite-time bounded but also has a prescribed finite-time H_(∞) performance. First, the case where the switching modes of the filter align with those of the MJS is considered. A numerically tractable filter design approach is proposed utilizing a mode-dependent Lyapunov function, Schur’s complement, and Dynkin’s formula. Then, the study is extended to a scenario where the switching modes of the filter can differ from those of the MJS. To address this situation, a mode-mismatched filter design approach is developed by leveraging a hidden Markov model to describe the asynchronous mode switching and the double expectation formula. Finally, a spring system model subject to a Markov chain is employed to validate the effectiveness of the quantized filter design approaches.

真核生物mRNA翻译起始机制研究进展

在真核生物中,m RNA翻译是一个复杂的多步骤过程,包括起始、延伸和终止3个阶段。其中,起始阶段的调控是影响m RNA翻译的关键。目前已经发现,m RNA翻译起始方式有多种,以最早发现的m7G帽依赖性扫描机制最为经典,但当细胞处于逆境,经典起始机制受到抑制时,其他类型的起始机制会将其替代以保证翻译的顺利进行。本文对目前已发现的真核生物m RNA不同翻译起始机制特别是经典起始机制的替代机制进行了综述,旨在为深入认识真核生物基因在翻译水平上的表达调控提供参考。

Effects of pyrite on the spontaneous combustion of coal

Abstract Pyrite has a significant effect on the spontaneous combustion of coal. The presence of pyrite can change the propensity of coal towards spontaneous combustion. The influences of various pyrite contents on the parameters of spontaneous combustion, such as index gases, temperature and released heat etc., were investigated in this study, Coal samples with different pyrite contents （0 %, 3 %, 5 %, 7 % and 9 %） were made by mixing coal and pyrite. The oxidation experiments under temperature-programmed condition were carried out to test the release rate of gaseous oxidation products at different temperatures. Differential scanning calorimeter （DSC） was employed to measure the intensity of heat release during coal oxidation for various pyrite contents. The results indicate that pyrite can nonlinearly accelerate the process of spontaneous combustion. The coal sample with a pyrite content of 5 % has the largest CO release rate and oxygen adsorption as well. However, the coal sample with a pyrite content of ？ % has the largest rate of heat flow according to the results from the DSC tests. Pyrite contents of 5 %-7 % in coal has the most significant effects on spontaneous combustion within the range of this study. The conclusions are conducive to the evaluation and control for the spontaneous combustion of coal.

Signal recovery method based on co-prime array

A signal waveform recovery method based on the co-prime array is investigated to extract the waveform of the desired signal from spatial interferences in narrowband scenarios. The direction of arrivals (DOAs) of the desired signal and interference signals are estimated with the compressive sensing approach based on angle grids, and the signal power together with the noise power are estimated. Thereafter, a modified steepest descent (SD) method is derived to recover the waveform of the desired signal and interferences utilizing the estimated power and directions. The recovered waveform of the desired signal is the output of the proposed method. The situation in which the signals are not on the predefined angle grids is also considered. The DOAs estimated via the predefined angle grids are corrected based on the maximum likelihood (ML) angle estimation. Compared to the existing beamforming methods on co-prime array, the proposed method can obtain the waveform of the desired signal. Simulation results demonstrate that the proposed method can achieve good performance in signal waveform recovery and output signal to noise ratio. © 2017 Beijing Institute of Aerospace Information.

Phase-only pattern synthesis based on gradient-descent optimization

By applying phase-only technique in array antenna pattern synthesis, antenna arrays can form desired patterns with the use of phase shifters only. A novel phase-only pattern synthesis algorithm is proposed for the passive phased array seeker. This algorithm synthesizes the main beam of the antenna pattern through least-squares approximation, thus minimizing the errors between the actual and the desired main beams. The synthesis problem can be solved by applying gradient-descent optimization. The item for suppressing side lobes is added to the above synthesis problem. To obtain a side lobe level as low as possible, the algorithm assigns different weights to different directions in the side lobe region. The algorithm is run repeatedly and the weights are adjusted adaptively according to the normalized power in the side lobe directions. Detailed examples are presented to demonstrate the accuracy and effectiveness of the proposed approach.

Review on heat-to-power conversion technologies for hypersonic vehicles

Hypersonic vehicles have enormous military and economic value,while their power and thermal protection demands will increase substantially with the rise in Mach number and duration.Converting the tremendous high-quality heat on the vehicle surface and engine wall into electrical energy through heat-to-power technologies will not only play a role in thermal protection,but also supply power for the vehicle.This paper provides a comprehensive review of heat-to-power conversion technologies on hypersonic vehicles,including the indirect conversion of Brayton and Rankine cycles,direct conversion of thermoelectric materials,and combined conversion.For the open Brayton cycle with hydrocarbon fuel as the working fluid,the Power-to-Weight Ratio(PWR)can achieve the highest,at around 1.8,due to the high PWR of the hydrocarbon fuel turbine and the few components of the system.However,its work capacity is limited by the flow rate of the supplied fuel.The closed Brayton cycle can maintain a relatively high PWR,ranging from 0.2 to 0.8,while achieving relatively high output power and conversion efficiency.The Rankine cycle has a higher PWR,its range is close to that of the closed Brayton cycle,peaking at about 0.88.The thermoelectric materials technology has a small power generation level,making it more suitable for scenarios with low power demand.This review provides a basis for selecting and developing heat-to-power conversion technologies on hypersonic vehicles.

基于原位形成的氮杂邻亚甲基苯醌和卤代萘酚的分子间[4+1]螺环化/去芳香化反应

报道了一种碱促进的卤代萘酚与N-(邻氯甲基)芳基酰胺[4+1]螺环化/去芳构化策略,以此来直接有效地合成氮杂螺环化合物.在温和条件下以中等至优秀的收率、高非对映选择性地合成了一系列氮杂螺环化合物.该反应可以兼容各种官能团,如醛基、游离羟基和不同的N保护基,如Bz和Ts等.对产物进行了转化,并提出了可能的反应机理.

Modelling medium-and long-term purchasing plans for environment-orientated container trucks:a case study of Yangtze River port

The transportation sector is the most significant contributor to anthropogenic greenhouse gas(GHG)emissions.Particularly,maritime transportation,which is predominantly powered by fossil-fuel engines,accounts for more than 90%of world freight movement and emits 3%of global carbon dioxide(CO_(2))emissions.China is the world’s largest emitter of CO_(2 )and plays a key role in mitigating global climate change.In order to tackle this pressing concern,this study analyses the port’s throughput,the current number of trucks and their emissions during the container truck purchasing process.Previous studies about container truck purchasing plans mostly focused on the trucks’price and port needs.The objective of this study is to minimize the total cost of a port’s inland transportation using optimization technique such as the interval uncertainty planning model to convert container truck emissions into social costs.The study considers the port of Yangtze as a case study.The study has designed two scenarios.(i)The base scenario(business-asusual,BAU)is used to quantify the relationship between pollutant emissions and system cost.In the base scenario,no environmental control facilities are used during the planning period,and there is no need to purchase new energy container trucks.(ii)The expected scenario(Scenario A)is for three planning periods.In Scenario A,the emissions levels are required to remain at the same level as the first planning period during the whole planning period.By solving the above model,the number of all truck types,system cost,container throughput and truck emissions in the port area were analysed.The results showed that if no emission reduction control measures are implemented in the next 9 years,the growth rate of pollutants in the port area could reach 20%.In addition,the findings showed clearly that truck emissions are reduced by purchasing new energy trucks and restricting the number of fossil-fuel(diesel)trucks.This study could also help to minimize system costs associated with port planning and management.

An Efficient and Simple Method for Stereoselective Synthesis of N-Substituted Iminosugars from D-Xylose Derivative

A series of new N-substituted iminosugars were successfully synthesized through a general synthetic route from D-xylose derivative.This approach provided a convenient access to the synthesis of N-alkylated iminosugars as po-tential glucosidase inhibitors,which included a reaction of reductive amination.Various N-alkylated iminosugars were prepared in good yields with high stereoselectivity.