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Selective control of secondary alcohols upgrading using Ir-catalyzed cross-coupling strategy

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Science China Chemistry 2024年第3期67卷 914-921页

作者： Siqi yang Zeye Lu Jiale Ji qingshu Zheng Tao Tu Shanghai Key Laboratory of Molecular Catalysis and Innovative Materials Department of ChemistryFudan UniversityShanghai 200438China Frontiers Science Center for Transformative Molecules School of Chemistry and Chemical EngineeringShanghai Jiao Tong UniversityShanghai 200240China State Key Laboratory of Organometallic Chemistry Shanghai Institute of Organic ChemistryChinese Academy of SciencesShanghai 200032China

The selective coupling of alcohols is a fascinating yet challenging approach for upgrading alcohols. Herein, we accomplished the controlled production of β-disubstituted ketones or upgraded secondary alcohols via the Ir-catalyzed cross-coupling of secondary alcohols in excellent yields with broad substrate scopes. This selective control was achieved by using an in-situ generated monoNHC-Ir or a tris-NHC-Ir complex as the catalysts, respectively. Mechanistic studies revealed that the delicate balance between dehydrogenation and hydrogenation abilities of these bifunctional catalysts is crucial for achieving different selectivity. The tris-NHC-Ir complex effectively facilitated dehydrogenation of alcohols and hydrogenation of intermediates, leading to the desired upgraded secondary alcohols. Conversely, the high dehydrogenation ability of the mono-NHC-Ir complex promoted the conversion of formed secondary alcohols back to ketones.

关键词： cross-coupling hydrogen-borrowing NHC-Ir complexes selectivity control upgrading of alcohols

Impacts of the large amount of sand mining on riverbed morphology and tidal dynamics in lower reaches and delta of the Dongjiang River

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Journal of Geographical Sciences 2007年第2期17卷 197-211页

作者： JIA Liangwen LUO Zhangren yang qingshu OU Shuying LEI Yaping Coastal Ocean Research Center Sun Yat-sen University Guangzhou 510275 China Institute of Estuarine and Coastal Research Sun Yat-sen University Guangzhou 510275 China

The sand dredging and its impacts on riverbed evolution and tidal dynamic change in the lower reaches and delta of the Dongjiang River are examined in this paper. The large amount of sand, totally 3.32 billion m^3 from 1980 to 2002, was mined from the riverbeds of the lower reaches and delta of the Dongjiang River. Increasing of the channel capacity, lowering of the average riverbed elevation, deepening of the water depth and decreasing of the longitudinal riverbed gradient are the main effects on the riverbed evolution brought by the large amount of sand dredging. Under the strong sand dredging and associated significant riverbed deformation, the notable changes of the tidal dynamic in the lower reaches and delta of the Dongjiang River occurred, including：（1）in the upper reaches of the Dongjiang River delta and lower reaches of the Dongjiang River, tidal level dropped apparently, tidal range widened, flood tidal duration became longer, amplitudes for major tidal components became bigger and tidal dynamics intensified; （2） tidal wave spread faster; and （3） the limits of the tidal level, tidal current and salt water moved upstream.

关键词： Dongjiang River sand mining tide

The influence of runoff and wind on the dispersion patterns of suspended sediment in the Zhujiang(Pearl) River Estuary based on MODIS data

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Acta Oceanologica Sinica 2019年第3期38卷 26-35页

作者： Suying Ou qingshu yang Xiangxin Luo Fan Zhu Kaiwen Luo Hao yang Institute of Estuarine and Coastal Research School of Marine Sciences Sun Yat-sen University State-province Joint Engineering Laboratory of Estuarine Hydraulic Technology

Cloud-free moderate-resolution imaging spectroradiometer(MODIS) images of the Zhujiang(Pearl) River Estuary(ZRE) taken between 2002 and 2012 are retrieved and used to study the spatial and temporal patterns of suspended sediment concentrations(SSCs) across the estuary under runoff, wind, and tropical storm *** typical dispersal patterns of suspended sediments in the estuary are defined: Case I shows generally low SSCs under low dynamics; Case Ⅱ shows a river-dominant dispersal pattern of suspended sediments from the outlets,particularly from Modaomen, Jiaomen, Hengmen, and others; Case Ⅲ shows wind-dominant dispersal of high SSCs derived from the west shoal and southwesterly transport under a strong NE wind; Case IV is the combination of relatively large runoff and wind; and Case V is caused by a strong tropical storm with high river discharge and wind, which is characterized by the high SSCs across the entire estuary that are transported eastward by winddriven and buoyancy currents outside the estuary. Runoff is a dominant factor that controls seasonal and annual SSC variations in the ZRE, with the area of high SSCs being largest in the summer and smallest in the spring. The correlation coefficients between the monthly averaged river-suspended sediment discharge and the area of the high SSCs are approximately 0.6. The wind power over the west shoal increases with a wind speed, which induces more sediment resuspension and shows a close relationship between the wind speed and high SSC area.

关键词： Zhujiang(Pearl) River Estuary suspended sediment concentration(SSC) moderate-resolution imaging spectroradiometer wind runoff tides

Impacts of human interventions on the seasonal and nodal dynamics of the M_(2)and K_(1)tidal constituents in Lingdingyang Bay of the Zhujiang River Delta,China

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Acta Oceanologica Sinica 2021年第10期40卷 49-64页

作者： Ping Zhang qingshu yang Haidong Pan Heng Wang Meifang Xie Huayang Cai Nanyang Chu Liangwen Jia Institute of Estuarine and Coastal Research School of Marine Engineering and TechnologySun Yat-sen UniversityZhuhai 519082China Guangdong Provincial Engineering Research Center of Coasts Islands and ReefsZhuhai 519082China Southern Marine Science and Engineering Guangdong Laboratory(Zhuhai) Zhuhai 519080China Key Laboratory of Physical Oceanography Ministry of EducationQingdao 266100China School of Marine Science Sun Yat-sen UniversityZhuhai 519082China

Natural and human-induced changes may exert considerable impacts on the seasonal and nodal dynamics of M2 and K1 tidal ***,quantifying the influences of these factors on tidal regime changes is essential for sustainable water resources management in coastal *** this study,the enhanced harmonic analysis was applied to extract the seasonal variability of the M2 and K1 tidal amplitudes and phases at three gauging stations along Lingdingyang Bay of the Zhujiang River *** seasonal dynamics in terms of tidal wave celerity and amplification/damping rate were used to quantify the impacts of human-induced estuarine morphological alterations on M2 and K1 tidal hydrodynamics in inner and outer Lingdingyang *** results show that both tidal amplification/damping rate and wave celerity were considerably increased from the pre-anthropogenic activity period(Pre-AAP)to the post-anthropogenic activity period(Post-AAP)excepting the tidal amplification/damping rate in outer Lingdingyang Bay,and the variations in outer Lingdingyang Bay was larger than those in inner Lingdingyang *** alterations in these two parameters were more significant in flood season than in dry season in both inner and outer Lingdingyang *** seasonal variability of M2 and K1 tidal amplitudes were further quantified using a regression model accounting for the 18.61-year lunar nodal modulation,where this study observes a considerable alteration in M2 constituent owing to human *** the Post-AAP,the M2 amplitudes at the downstream station were larger than those that would have occurred in the absence of strong human interventions,whereas the opposite was true for the upstream station,leading to a substantial decrease in tidal amplification in outer Lingdingyang ***,it is opposite in inner Lingdingyang *** underlying mechanism can be primarily attributed to channel deepening and narrowing caused by human interventions,that resulted in substan

关键词： tidal dynamics S_(T)IDE model nodal modulation channel deepening tidal wave celerity

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美国图书馆员的供需关系与职业声望分析

图书馆杂志 2015年第8期34卷 93-97页

作者：杨庆书海南政法职业学院图书馆

图书馆员的收入水平、社会地位和职业声望都会受到其在劳动力市场中供需关系的影响。在美国,图书馆员职业在劳动力市场中越来越受到欢迎,职业的稳定性和不断提高的收入水平使其更具吸引力,图书馆员的多样性也受到重视。随着美国图书馆... 详细信息

图书馆员的收入水平、社会地位和职业声望都会受到其在劳动力市场中供需关系的影响。在美国,图书馆员职业在劳动力市场中越来越受到欢迎,职业的稳定性和不断提高的收入水平使其更具吸引力,图书馆员的多样性也受到重视。随着美国图书馆员社会地位的提高和社会声望的增强,图书馆员已成为重要的就业选择之一。通过分析美国图书馆员的供需关系及职业声望,发现美国图书馆员职业的需求会不断增长,职业声望也有所提升,但职业收入仍有待提高。

关键词：图书馆员职业供需关系职业声望美国

Fresh-Keeping Decision and Coordination of Fresh Agricultural Product Supply Chain Considering Carbon Cap-and-Trade under Different Dominance

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Journal of Systems Science and Systems Engineering 2024年第1期33卷 30-51页

作者： yang yang Guanxin Yao China Institute for Agricultural Equipment Industrial Development Jiangsu UniversityZhenjiang212013China Jiangsu Modern Logistics Research Base Yangzhou UniversityYangzhou225009China

In the context of low carbon,this paper discussed the impact of the carbon cap-and-trade policy on the fresh-keeping decision-making of two-echelon fresh agricultural product supply chains under different dominance,and designed cost-sharing contracts to coordinate the supply chain of fresh agricultural products dominated by suppliers and retailers *** results showed that:dominance has no effect on the fresh-keeping decision and total revenue of fresh agricultural product supply chain,but it affects the internal income distribution,and dominance does not always bring more benefits;the implementation of carbon cap-and-trade reduces the fresh-keeping decision-making of fresh agricultural products supply chain and reduces the free-rider income of followers;the role of higher carbon trading price is twofold,which not only brings about the speculation of leading enterprises,but also promotes the application of low-carbon technologies;consumers’high preference for freshness,low-cost and high-efficiency low-carbon technology are all conducive to improving the fresh-keeping efforts and benefits of the supply chain;cost-sharing contracts can coordinate the supply chain of fresh agricultural products.

关键词： Dominant power carbon cap-and-trade policy fresh agricultural product supply chain fresh-keeping decision-making

Overview of radar detection methods for low altitude targets in marine environments

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Journal of Systems Engineering and Electronics 2024年第1期35卷 1-13页

作者： yang Yong yang Boyu School of Electronic Science National University of Defense TechnologyChangsha 410073China

In this paper,a comprehensive overview of radar detection methods for low-altitude targets in maritime environments is presented,focusing on the challenges posed by sea clutter and multipath *** performance of the radar detection methods under sea clutter,multipath,and combined conditions is categorized and summarized,and future research directions are outlined to enhance radar detection performance for low-altitude targets in maritime environments.

关键词： radar sea clutter multipath scattering detection low altitude target

Selective nano-buckling improves the performance of graphene logic transistors

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National Science Review 2024年第2期11卷 95-96页

作者： Tong yang Ming yang Department of Applied Physics The Hong Kong Polytechnic University Research Centre for Nanoscience and Nanotechnology The Hong Kong Polytechnic University

The massive integration of silicon-based transistors into modern electronic devices greatly increases power consumption and heat generation/dissipation[1]. In this concern, transistors based on atomically-thin graphene that exhibit high electric and thermoelectric conductivities with negligible contact resistance,

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Design Optimization and Operating Performance of S-CO_(2) Brayton Cycle under Fluctuating Ambient Temperature and Diverse Power Demand Scenarios

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Journal of Thermal Science 2024年第1期33卷 190-206页

作者： yang Jingze yang Zhen DUAN Yuanyuan Key Laboratory for Thermal Science and Power Engineering of MOE Beijing Key Laboratory for CO_(2) Utilization and Reduction TechnologyTsinghua UniversityBeijing 100084China

The supercritical CO_(2)(S-CO_(2)) Brayton cycle is expected to replace steam cycle in the application of solar power tower system due to the attractive potential to improve efficiency and reduce *** the concentrated solar power plant with thermal energy storage is usually located in drought area and used to provide a dispatchable power output,the S-CO_(2) Brayton cycle has to operate under fluctuating ambient temperature and diverse power demand *** addition,the cycle design condition will directly affect the off-design *** this work,the combined effects of design condition,and distributions of ambient temperature and power demand on the cycle operating performance are analyzed,and the off-design performance maps are proposed for the first time.A cycle design method with feedback mechanism of operating performance under varied ambient temperature and power demand is introduced *** show that the low design value of compressor inlet temperature is not conductive to efficient operation under low loads and sufficient output under high ambient *** average yearly efficiency is most affected by the average power demand,while the load cover factor is significantly influenced by the average ambient *** multi-objective optimization,the optimal solution of designed compressor inlet temperature is close to the minimum value of35℃ in Delingha with low ambient temperature,while reaches 44.15℃ in Daggett under the scenario of high ambient temperature,low average power demand,long duration and large value of peak load during the peak temperature *** the cycle designed with compressor inlet temperature of 35℃ instead of 44.15℃ in Daggett under light industry power demand,the reduction of load cover factor will reach 0.027,but the average yearly efficiency can barely be improved.

关键词： supercritical CO_(2)Brayton cycle ambient temperature fluctuating power demand scenarios design optimization off-design performance