Carbonylation reactions,crucial for carbonyl group incorporation,struggle with the inherent complexity of achieving selective mono-or double-carbonylation on single substrates,often due to competing reaction pathways....Carbonylation reactions,crucial for carbonyl group incorporation,struggle with the inherent complexity of achieving selective mono-or double-carbonylation on single substrates,often due to competing reaction pathways.Herein,our study introduces a strategy employing palladium amides,harnessing their unique reactivity control,to direct the selective carbonylation of amines for the targeted synthesis of urea and oxamide derivatives.The palladium amide structure was elucidated using single-crystal X-ray diffraction.Controlled experiments and cyclic voltammetry studies further elucidate that the oxidation of palladium amide or its insertion into a carbonyl group diverges into distinct pathways.By employing sodium percarbonate as an eco-friendly oxidant and base,we have successfully constructed a switchable carbonylation system co-catalyzed by palladium and iodide under room temperature.The utilizing strategy in this study not only facilitates effective control over reaction selectivity but also mitigates the risk of explosions,a critical safety concern in traditional carbonylation methods.展开更多
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...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.展开更多
In our previous work, the reactive dividing wall column(RDWC) was proposed and proved to be effective for selective hydrogenation and separation of C3 stream. In the present paper, the dynamics and control of the prop...In our previous work, the reactive dividing wall column(RDWC) was proposed and proved to be effective for selective hydrogenation and separation of C3 stream. In the present paper, the dynamics and control of the proposed RDWC are investigated. Four control structures including composition and temperature controls are proposed. The feed forward controllers are employed in the four control strategies to shorten the dynamic response time, reduce the maximum deviations and offer an immediate adjustment. The control structures are compared by applying them into the RDWC system with 20% disturbances in both the feed flow rate and the feed compositions, and the results are discussed.展开更多
Longwall mining continues to remain the most efficient method for underground coal recovery. A key aspect in achieving safe and productive longwall mining is to ensure that the shearer is always correctly positioned w...Longwall mining continues to remain the most efficient method for underground coal recovery. A key aspect in achieving safe and productive longwall mining is to ensure that the shearer is always correctly positioned within the coal seam. At present, this machine positioning task is the role of longwall personnel who must simultaneously monitor the longwall coal face and the shearer's cutting drum position to infer the geological trends of the coal seam. This is a labour intensive task which has negative impacts on the consistency and quality of coal production. As a solution to this problem, this paper presents a sensing method to automatically track geological coal seam features on the longwall face, known as marker bands, using thermal infrared imaging. These non-visible marker bands are geological features that link strongly to the horizontal trends present in layered coal seams. Tracking these line-like features allows the generation of a vertical datum that can be used to maintain the shearer in a position for optimal coal extraction. Details on the theory of thermal infrared imaging are given, as well as practical aspects associated with machine-based implementation underground. The feature detection and tracking tasks are given with real measurements to demonstrate the efficacy of the approach. The outcome is important as it represents a new selective mining capability to help address a long-standing limitation in longwall mining operations.展开更多
The importance of selective synthesis of high-value-added chemicals from renewable resources is paramount but remains a crucial challenge in organic synthesis and chemical reformation.Herein,we report the selective ph...The importance of selective synthesis of high-value-added chemicals from renewable resources is paramount but remains a crucial challenge in organic synthesis and chemical reformation.Herein,we report the selective photosynthesis of C-C coupling products and carbonyl compounds from biomass-derived alcohols.The key to ensuring high end-to-end selectivity is the modulation of the reactivity of ketyl radical(*RCHOH)intermediates by employing different metal co-catalysts(Au,Pt,Pd,Ru)supported on Cd0.6Zn0.4S solid solution(CZS)photocatalysts.In particular,the C-C coupling product,hydrobenzion,and fully oxidized benzaldehyde were obtained from benzyl alcohol with high selectivity(>98%)over Au-CZS and Ru-CZS,respectively.Combined experimental and theoretical analyses demonstrated that the affinity of*RCHOH for the surface of metals governs their subsequent transformations,in which weak and strong radical adsorption on Au and Ru results in C-C coupling products and carbonyl compounds,respectively.展开更多
Based on the practice of Baosteel＇ s 60000 m3/h air separation unit （ASU） ,which is the first domestically- integrated unit of such a scale, this paper studies the principles of type selection of the distribution c...Based on the practice of Baosteel＇ s 60000 m3/h air separation unit （ASU） ,which is the first domestically- integrated unit of such a scale, this paper studies the principles of type selection of the distribution control system （DCS）. It discusses the design of the unit＇s control system,which involves a compressor system,a purification system （molecular sieving）, a turbo expansion system and an air separation system. The final part of the paper discusses the maintenance and future development of the ASU control system at Baosteel.展开更多
The highly selective catalytic hydrogenation of halogenated nitroaromatics was achieved by employing Pd‑based catalysts that were co‑modified with organic and inorganic ligands.It was demonstrated that the catalysts c...The highly selective catalytic hydrogenation of halogenated nitroaromatics was achieved by employing Pd‑based catalysts that were co‑modified with organic and inorganic ligands.It was demonstrated that the catalysts contained Pd species in mixed valence states,with high valence Pd at the metal‑support interface and zero valence Pd at the metal surface.While the strong coordination of triphenylphosphine(PPh3)to Pd0 on the Pd surface prevents the adsorption of halogenated nitroaromatics and thus dehalogenation,the coordination of sodium metavanadate(NaVO3)to high‑valence Pd sites at the interface helps to activate H2 in a heterolytic pathway for the selective hydrogenation of nitro‑groups.The excellent catalytic performance of the interfacial active sites enables the selective hydrogenation of a wide range of halogenated nitroaromatics.展开更多
CO_(2) hydrogenation into valuable chemical products has attracted intensive research interest in recent years,with product selectivity control remaining an important topic that requires fine tuning of the catalytic s...CO_(2) hydrogenation into valuable chemical products has attracted intensive research interest in recent years,with product selectivity control remaining an important topic that requires fine tuning of the catalytic structure and mechanistic understanding.Herein we report our study of anionic phosphorus-regulated indium oxide In_(2)O_(3)(P-In_(2)O_(3))nanocatalyst materials for CO_(2) hydrogenation and achieve nearly fullrange selectivity control between methanol and CO products by means of tuning the P content.In situ DRIFTS experiments and XPS characterization reveal the importance of P anion regulation in controlling the CO_(2) hydrogenation pathways,with an increase in the P content resulting in a decrease in the reducibility of In_(2)O_(3) that alters CO_(2) adsorption configuration by blocking and weakening oxygen vacancy(OV)sites for methanol generation and in the meantime creates new sites predominantly active for CO generation.This study demonstrates excellent control of the product selectivity property by regulating the catalyst composition with P anions and provides mechanistic discussions,which offers a new,effective strategy in CO_(2) hydrogenation catalyst research.展开更多
Selectivity-control has long been a central pursuit in organic chemistry.Most recent advances have focused on achieving individual forms of selectivity,such as chemo-,regio-,E/Z-,diastereo-,or enantioselectivity.Tradi...Selectivity-control has long been a central pursuit in organic chemistry.Most recent advances have focused on achieving individual forms of selectivity,such as chemo-,regio-,E/Z-,diastereo-,or enantioselectivity.Traditionally,multi-selectivities have been realized through one-dimensional linear synthetic routes,in which distinct sites are modified sequentially across multiple reaction steps.展开更多
Titanyl phthalocyanine(TiOPc)single crystals have received significant attention due to the remarkable mobility of charge carriers with excellent air stability and phase-dependent electrical properties.One of the bigg...Titanyl phthalocyanine(TiOPc)single crystals have received significant attention due to the remarkable mobility of charge carriers with excellent air stability and phase-dependent electrical properties.One of the biggest obstacles is their polymorphism behavior during crystal growth,which hinders the formation of desired crystals.Herein,we have attempted the selective polymorphism control of titanyl phthalocyanine(TiOPc)single crystals using the physical vapor transport(PVT)technique.Subsequently,the selective growth of the α-,β-,C-phase of TiOPc crystals can be successfully achieved depending on different types of substrates.The polymorphism control of the TiOPc crystals was found to be affected by interfacial energy variation through molecule–substrate interactions so that the unique molecular packing of TiOPc crystals is determined by the kind of substrate.Notably,it is reported for the first time that the C-phase of the TiOPc crystal has a rectangular tube-shaped morphology.Interestingly,it exhibits no PL emission as compared to that of the α-or β-phase crystals,indicating the dominant non-radiative relaxation of excitons.Accordingly,it shows much higher photoconductivity as compared to those of the α-and β-phases.These results provide an in-depth understanding of the crystal growth of phthalocyanines,particularly in view of polymorph control,and open up other possibilities for their practical applications in photoelectronic devices.展开更多
Carbon nanotube （CNT）-supported Ru nanoparticles with mean sizes ranging from 2.3 to 9.2 nm were prepared by different post-treatments and studied for Fischer-Tropsch （FT） synthesis. The effects of Ru particle siz...Carbon nanotube （CNT）-supported Ru nanoparticles with mean sizes ranging from 2.3 to 9.2 nm were prepared by different post-treatments and studied for Fischer-Tropsch （FT） synthesis. The effects of Ru particle size on catalytic behaviors were investigated at both shorter and longer contact times. At shorter contact time, where the secondary reactions were insignificant, the turnover frequency （TOF） for CO conversion was dependent on the mean size of Ru particles; TOF increased with the mean size of Ru particles from 2.3 to 6.3 nm and then decreased slightly. At the same time, the selectivities to C5＋ hydrocarbons increased gradually with the mean size of Ru particles up to 6.3 nm and then kept almost unchanged with a further increase in Ru particle size. At longer contact time, C10-C20 selectivity increased significantly at the expense of C21＋ selectivity, suggesting the occurrence of the selective hydrocracking of C21＋ to C10-C20 hydrocarbons.展开更多
Photocatalytic hydrogenation of furfural offers an ideal method for selective biomass upgrading into value-added chemicals or fuel additives under mild conditions. However, it is still challenging to control the produ...Photocatalytic hydrogenation of furfural offers an ideal method for selective biomass upgrading into value-added chemicals or fuel additives under mild conditions. However, it is still challenging to control the product selectivity due to side reactions of functional groups and reactive radical intermediates.Herein, photocatalytic transfer hydrogenation of furfural was studied using the TiO_(2)-based photocatalysts with alcohols as both the solvent and hydrogen donor. Ultralow loading metal supported on TiO_(2),together with adding a small amount of water in the system, were demonstrated to greatly increase the selectivity of furfuryl alcohol product. Electron paramagnetic resonance(EPR), ultraviolet-visible spectroscopy(UV-Vis) and photoluminescence(PL) measurements gave evidence that ultralow loading Pt or Pd on TiO_(2)increase the oxygen vacancy concentration and the photogenerated charge separation efficiency, which accelerates the photocatalytic reduction of furfural. In situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS) and mechanistic studies confirmed that photogenerated holes and electrons are active species, with dissociatively adsorbed methanol being directly oxidized by holes,furfural hydrogenated by protons and electrons and H_(2)O modifying the intermediate diffusion which contributes to high selectivity of furfuryl alcohol. This work demonstrates a simple approach to design photocatalysts and tune product selectivity in biomass valorization.展开更多
The chemical transformation of natural oils provides alternatives to limited fossil fuels and produces compounds with added value for the chemical industries.The selective deoxygenation of natural oils to diesel-range...The chemical transformation of natural oils provides alternatives to limited fossil fuels and produces compounds with added value for the chemical industries.The selective deoxygenation of natural oils to diesel-ranged hydrocarbons,bio-jet fuels,or fatty alcohols with controllable selectivity is especially attractive in natural oil feedstock biorefineries.This review presents recent progress in catalytic deoxygenation of natural oils or related model compounds(e.g.,fatty acids)to renewable liquid fuels(green diesel and bio-jet fuels)and valuable fatty alcohols(unsaturated and saturated fatty alcohols).Besides,it discusses and compares the existing and potential strategies to control the product selectivity over heterogeneous catalysts.Most research conducted and reviewed has only addressed the production of one category;therefore,a new integrative vision exploring how to direct the process toward fuel and/or chemicals is urgently needed.Thus,work conducted to date addressing the development of new catalysts and studying the influence of the reaction parameters(e.g.,temperature,time and hydrogen pressure)is summarized and critically discussed from a green and sustainable perspective using efficiency indicators(e.g.,yields,selectivity,turnover frequencies and catalysts lifetime).Special attention has been given to the chemical transformations occurring to identify key descriptors to tune the selectivity toward target products by manipulating the reaction conditions and the structures of the catalysts.Finally,the challenges and future research goals to develop novel and holistic natural oil biorefineries are proposed.As a result,this critical review provides the readership with appropriate information to selectively control the transformation of natural oils into either biofuels and/or value-added chemicals.This new flexible vision can help pave the wave to suit the present and future market needs.展开更多
In software-defined networking,the separation of control plane from forwarding plane introduces new challenges to network reliability.This paper proposes a fault-tolerant routing mechanism to improve survivability by ...In software-defined networking,the separation of control plane from forwarding plane introduces new challenges to network reliability.This paper proposes a fault-tolerant routing mechanism to improve survivability by converting the survivability problem into two sub-problems:constructing an elastic-aware routing tree and controller selection.Based on the shortest path tree,this scheme continuously attempts to prune the routing tree to enhance network survivability.After a certain number of iterations,elastic-aware routing continues to improve network resiliency by increasing the number of edges in this tree.Simulation results demonstrate this fault-tolerant mechanism performs better than the traditional method in terms of the number of protected nodes and network fragility indicator.展开更多
Air traffic complexity is an objective metric for evaluating the operational condition of the airspace. It has several applications, such as airspace design and traffic flow management.Therefore, identifying a reliabl...Air traffic complexity is an objective metric for evaluating the operational condition of the airspace. It has several applications, such as airspace design and traffic flow management.Therefore, identifying a reliable method to accurately measure traffic complexity is important. Considering that many factors correlate with traffic complexity in complicated nonlinear ways,researchers have proposed several complexity evaluation methods based on machine learning models which were trained with large samples. However, the high cost of sample collection usually results in limited training set. In this paper, an ensemble learning model is proposed for measuring air traffic complexity within a sector based on small samples. To exploit the classification information within each factor, multiple diverse factor subsets（FSSs） are generated under guidance from factor noise and independence analysis. Then, a base complexity evaluator is built corresponding to each FSS. The final complexity evaluation result is obtained by integrating all results from the base evaluators. Experimental studies using real-world air traffic operation data demonstrate the advantages of our model for small-sample-based traffic complexity evaluation over other stateof-the-art methods.展开更多
As an efficient and sustainable alternative to traditional thermocatalytic hydrogenation in both petrochemical and fine chemical processes,electrochemical hydrogenation powered by renewable energy has attracted consid...As an efficient and sustainable alternative to traditional thermocatalytic hydrogenation in both petrochemical and fine chemical processes,electrochemical hydrogenation powered by renewable energy has attracted considerable attention[1].Electrocatalytic CO_(2)reduction reaction(CO_(2)RR)offers an appealing route for CO_(2)resource utilization to produce high value-added chemicals or fuels.展开更多
Organic synthesis driven by heterogeneous catalysis is a central research theme to both fundamental research and industrial production of fine chemicals.However,the employment of stoichiometric strong oxidizing or red...Organic synthesis driven by heterogeneous catalysis is a central research theme to both fundamental research and industrial production of fine chemicals.However,the employment of stoichiometric strong oxidizing or reducing reagents(e.g.,K_(2)Cr_(2)O_(7) and LiAlH_(4))and harsh reaction conditions(e.g.,high temperature and pressure)always leads to the products of overreaction and other by-product residues(e.g.,salt and acid waste).Thus the poor control of product selectivity and tremendous energy consumption result in the urgent demand to develop novel technologies for heterogeneous catalysis.Given the current global theme of development in CO_(2) reduction and sustainable energy utilization,one promising protocol is heterogeneous photocatalysis.It enables sustainable solar-to-chemical energy conversion under mild conditions(e.g.,room temperature,ambient pressure,and air as the oxidant)and offers unique reaction pathways for improved selectivity control.To accurately tailor the selectivity of desired products,the electronic structure(e.g.,positions of valence-band maximum and conduction-band minimum),geometric structure(e.g.,nanorod,nanosheet,and porous morphology),and surface chemical micro-environment(e.g.,vacancy sites and co-catalysts)of heterogeneous photocatalysts require rational design and construction.In this review,we will briefly analyze some effective photocatalytic systems with the excellent regulation ability of product selectivity in organic transformations(mainly oxidation and reduction types)under visible light irradiation,and put forward opinions on the optimal fabrication of nanostructured photocatalysts to realize selective organic synthesis.展开更多
Uncertain friction is a key factor that influences the accuracy of servo system in CNC machine.In this paper,based on the principle of Active Disturbance Rejection Control(ADRC),a control method is proposed,where both...Uncertain friction is a key factor that influences the accuracy of servo system in CNC machine.In this paper,based on the principle of Active Disturbance Rejection Control(ADRC),a control method is proposed,where both the extended state observer(ESO) and the reduced order extended state observer(RESO) are used to estimate and compensate for the disturbance.The authors prove that both approaches ensure high accuracy in theory,and give the criterion for parameters selection.The authors also prove that ADRC with RESO performs better than that with ESO both in disturbance estimation and tracking error.The simulation results on CNC machine show the effectiveness and feasibility of our control approaches.展开更多
Luminescence concentration quenching and thermal quenching are closely related to the energy transfer(ET)process between optically active ions.Herein,we utilize the structural confinement effect in Sr_(9)Ga(PO_(4))(7)...Luminescence concentration quenching and thermal quenching are closely related to the energy transfer(ET)process between optically active ions.Herein,we utilize the structural confinement effect in Sr_(9)Ga(PO_(4))(7)(SGP)to selectively control ET pathways so as to suppress luminescence concentration and thermal quenching.In the Fe^(3+)-doped SGP compound,the relatively large Fe^(3+)-Fe^(3+)distances can inhibit the ET between Fe^(3+)ions,leading to weak concentration quenching.The Sr_(9)Ga_(0.8)(PO_(4))_(7):0.2Fe^(3+)(SGP:0.2Fe^(3+))phosphor exhibits the highest near-infrared(NIR)luminescence intensity,and the emission intensity for 50%and 100%Fe^(3+)-doped SGP phosphors is 73.46%and 18.25%of that for the optimal sample SGP:0.2Fe^(3+),respectively.Upon co-doping Yb^(3+)into SGP:0.2Fe^(3+),Fe^(3+)-Yb^(3+)distances are much shorter than those of Fe^(3+)-Fe^(3+),causing energy to quickly migrate from the quenching center Fe^(3+)to the thermally stable center Yb^(3+).The thermal stability of SGP:0.2Fe^(3+),0.07Yb^(3+)is greatly enhanced compared to SGP:0.2Fe^(3+).This study provides a strategy for enhancing NIR luminescence through utilizing structural confinement to control ET pathways toward suppressing concentration and thermal quenching.Finally,we demonstrate the potential applications of SGP:0.2Fe^(3+)and SGP:0.2Fe^(3+),0.07Yb^(3+)phosphors in night vision and optical thermometry fields.展开更多
Electrocatalytic ammonia oxidation reaction(AOR)represents a sustainable synthesis approach for valuable nitrogen‑containing compounds like nitrites and nitrates.However,the numerous AOR intermediates often complicate...Electrocatalytic ammonia oxidation reaction(AOR)represents a sustainable synthesis approach for valuable nitrogen‑containing compounds like nitrites and nitrates.However,the numerous AOR intermediates often complicate the precise regulation of target intermediate adsorption,hindering the efficient and selective nitrate/nitrite production.We herein present a NiCu‑BDC MOF with tunable AOR product selectivity,which undergoes a controllable in situ reconstruction into Cu‑β‑NiOOH at 1.7 V vs.RHE,enabling the shift of the reaction pathway from NH_(4)^(+)‑to‑NO_(2)^(−)to NH_(4)^(+)‑to‑NO_(3)^(−).The unique restructuring behavior of this material,combined with its dense active sites,enables highly selective production of nitrites and nitrates(94.9%NO_(2)^(−)selectivity at 1.60 V vs.RHE and 92.6%NO_(3)^(−)selectivity at 1.95 V vs.RHE).Theoretical simulations reveal that the Cu incorporation in NiCu‑BDC modulates the electronic configuration of Ni sites,facilitating moderate adsorption of key NO and NOOH intermediates,thus promoting efficient nitrite generation at low potentials.At higher potentials,NiCu‑BDC undergoes reconstruction to Cu‑β‑NiOOH,stabilizing the conversion of NO_(2)to NO_(2)OH,making nitrate formation thermodynamically favorable and a rapid selectivity shift.This potential‑driven selectivity control not only provides a new strategy for efficient nitrites/nitrates synthesis by simply adjusting applied potentials but also provides fundamental insights into regulating selectivity in multi‑product electrochemical reactions.展开更多
基金The National Key Research and Development Program of Ministry of Science and Technology(No.2022YFA1504602)Natural Science Foundation of Jiangsu Province(No.BK20211094)National Natural Science Foundation of China(No.22302214,21972152,U22B20137).
文摘Carbonylation reactions,crucial for carbonyl group incorporation,struggle with the inherent complexity of achieving selective mono-or double-carbonylation on single substrates,often due to competing reaction pathways.Herein,our study introduces a strategy employing palladium amides,harnessing their unique reactivity control,to direct the selective carbonylation of amines for the targeted synthesis of urea and oxamide derivatives.The palladium amide structure was elucidated using single-crystal X-ray diffraction.Controlled experiments and cyclic voltammetry studies further elucidate that the oxidation of palladium amide or its insertion into a carbonyl group diverges into distinct pathways.By employing sodium percarbonate as an eco-friendly oxidant and base,we have successfully constructed a switchable carbonylation system co-catalyzed by palladium and iodide under room temperature.The utilizing strategy in this study not only facilitates effective control over reaction selectivity but also mitigates the risk of explosions,a critical safety concern in traditional carbonylation methods.
基金supported by the National Natural Science Foundation of China(22271060)the Department of Chemistry at Fudan University。
文摘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.
基金Supported by the National Basic Research Program of China(2012CB720500)the National Supporting Research Program of China(2013BAA03B01)+1 种基金the National Natural Science Foundation of China(21176178)China Scholarship Council(CSC[2015]3022)
文摘In our previous work, the reactive dividing wall column(RDWC) was proposed and proved to be effective for selective hydrogenation and separation of C3 stream. In the present paper, the dynamics and control of the proposed RDWC are investigated. Four control structures including composition and temperature controls are proposed. The feed forward controllers are employed in the four control strategies to shorten the dynamic response time, reduce the maximum deviations and offer an immediate adjustment. The control structures are compared by applying them into the RDWC system with 20% disturbances in both the feed flow rate and the feed compositions, and the results are discussed.
基金the Australian Coal Association Research Program(ACARP)for their invaluable support that enabled new research and development into longwall shearer automation
文摘Longwall mining continues to remain the most efficient method for underground coal recovery. A key aspect in achieving safe and productive longwall mining is to ensure that the shearer is always correctly positioned within the coal seam. At present, this machine positioning task is the role of longwall personnel who must simultaneously monitor the longwall coal face and the shearer's cutting drum position to infer the geological trends of the coal seam. This is a labour intensive task which has negative impacts on the consistency and quality of coal production. As a solution to this problem, this paper presents a sensing method to automatically track geological coal seam features on the longwall face, known as marker bands, using thermal infrared imaging. These non-visible marker bands are geological features that link strongly to the horizontal trends present in layered coal seams. Tracking these line-like features allows the generation of a vertical datum that can be used to maintain the shearer in a position for optimal coal extraction. Details on the theory of thermal infrared imaging are given, as well as practical aspects associated with machine-based implementation underground. The feature detection and tracking tasks are given with real measurements to demonstrate the efficacy of the approach. The outcome is important as it represents a new selective mining capability to help address a long-standing limitation in longwall mining operations.
文摘The importance of selective synthesis of high-value-added chemicals from renewable resources is paramount but remains a crucial challenge in organic synthesis and chemical reformation.Herein,we report the selective photosynthesis of C-C coupling products and carbonyl compounds from biomass-derived alcohols.The key to ensuring high end-to-end selectivity is the modulation of the reactivity of ketyl radical(*RCHOH)intermediates by employing different metal co-catalysts(Au,Pt,Pd,Ru)supported on Cd0.6Zn0.4S solid solution(CZS)photocatalysts.In particular,the C-C coupling product,hydrobenzion,and fully oxidized benzaldehyde were obtained from benzyl alcohol with high selectivity(>98%)over Au-CZS and Ru-CZS,respectively.Combined experimental and theoretical analyses demonstrated that the affinity of*RCHOH for the surface of metals governs their subsequent transformations,in which weak and strong radical adsorption on Au and Ru results in C-C coupling products and carbonyl compounds,respectively.
文摘Based on the practice of Baosteel＇ s 60000 m3/h air separation unit （ASU） ,which is the first domestically- integrated unit of such a scale, this paper studies the principles of type selection of the distribution control system （DCS）. It discusses the design of the unit＇s control system,which involves a compressor system,a purification system （molecular sieving）, a turbo expansion system and an air separation system. The final part of the paper discusses the maintenance and future development of the ASU control system at Baosteel.
文摘The highly selective catalytic hydrogenation of halogenated nitroaromatics was achieved by employing Pd‑based catalysts that were co‑modified with organic and inorganic ligands.It was demonstrated that the catalysts contained Pd species in mixed valence states,with high valence Pd at the metal‑support interface and zero valence Pd at the metal surface.While the strong coordination of triphenylphosphine(PPh3)to Pd0 on the Pd surface prevents the adsorption of halogenated nitroaromatics and thus dehalogenation,the coordination of sodium metavanadate(NaVO3)to high‑valence Pd sites at the interface helps to activate H2 in a heterolytic pathway for the selective hydrogenation of nitro‑groups.The excellent catalytic performance of the interfacial active sites enables the selective hydrogenation of a wide range of halogenated nitroaromatics.
基金the Ohio Development Services Agency(R-16-04)for the financial support of this study.
文摘CO_(2) hydrogenation into valuable chemical products has attracted intensive research interest in recent years,with product selectivity control remaining an important topic that requires fine tuning of the catalytic structure and mechanistic understanding.Herein we report our study of anionic phosphorus-regulated indium oxide In_(2)O_(3)(P-In_(2)O_(3))nanocatalyst materials for CO_(2) hydrogenation and achieve nearly fullrange selectivity control between methanol and CO products by means of tuning the P content.In situ DRIFTS experiments and XPS characterization reveal the importance of P anion regulation in controlling the CO_(2) hydrogenation pathways,with an increase in the P content resulting in a decrease in the reducibility of In_(2)O_(3) that alters CO_(2) adsorption configuration by blocking and weakening oxygen vacancy(OV)sites for methanol generation and in the meantime creates new sites predominantly active for CO generation.This study demonstrates excellent control of the product selectivity property by regulating the catalyst composition with P anions and provides mechanistic discussions,which offers a new,effective strategy in CO_(2) hydrogenation catalyst research.
文摘Selectivity-control has long been a central pursuit in organic chemistry.Most recent advances have focused on achieving individual forms of selectivity,such as chemo-,regio-,E/Z-,diastereo-,or enantioselectivity.Traditionally,multi-selectivities have been realized through one-dimensional linear synthetic routes,in which distinct sites are modified sequentially across multiple reaction steps.
基金supported by the National Research Foundation of Korea(NRF)grant funded by the Korea government(MSIT)(No.2019R1C1C1002290)funding from the Veteran Researcher Grant(No.2019R1A2C2004259)managed by the NRF and Samsung Electronics.
文摘Titanyl phthalocyanine(TiOPc)single crystals have received significant attention due to the remarkable mobility of charge carriers with excellent air stability and phase-dependent electrical properties.One of the biggest obstacles is their polymorphism behavior during crystal growth,which hinders the formation of desired crystals.Herein,we have attempted the selective polymorphism control of titanyl phthalocyanine(TiOPc)single crystals using the physical vapor transport(PVT)technique.Subsequently,the selective growth of the α-,β-,C-phase of TiOPc crystals can be successfully achieved depending on different types of substrates.The polymorphism control of the TiOPc crystals was found to be affected by interfacial energy variation through molecule–substrate interactions so that the unique molecular packing of TiOPc crystals is determined by the kind of substrate.Notably,it is reported for the first time that the C-phase of the TiOPc crystal has a rectangular tube-shaped morphology.Interestingly,it exhibits no PL emission as compared to that of the α-or β-phase crystals,indicating the dominant non-radiative relaxation of excitons.Accordingly,it shows much higher photoconductivity as compared to those of the α-and β-phases.These results provide an in-depth understanding of the crystal growth of phthalocyanines,particularly in view of polymorph control,and open up other possibilities for their practical applications in photoelectronic devices.
基金supported by the National Basic Research Program of China (No. 2013CB933100)the National Natural Science Foundation of China (21173174, 21161130522, 21033006 and 20923004)+1 种基金the Program for Changjiang Scholars and Innovative Research Team in University (No. IRT1036)the Research Fund for the Doctoral Program of Higher Education (No. 20090121110007)
文摘Carbon nanotube （CNT）-supported Ru nanoparticles with mean sizes ranging from 2.3 to 9.2 nm were prepared by different post-treatments and studied for Fischer-Tropsch （FT） synthesis. The effects of Ru particle size on catalytic behaviors were investigated at both shorter and longer contact times. At shorter contact time, where the secondary reactions were insignificant, the turnover frequency （TOF） for CO conversion was dependent on the mean size of Ru particles; TOF increased with the mean size of Ru particles from 2.3 to 6.3 nm and then decreased slightly. At the same time, the selectivities to C5＋ hydrocarbons increased gradually with the mean size of Ru particles up to 6.3 nm and then kept almost unchanged with a further increase in Ru particle size. At longer contact time, C10-C20 selectivity increased significantly at the expense of C21＋ selectivity, suggesting the occurrence of the selective hydrocracking of C21＋ to C10-C20 hydrocarbons.
基金supported by the Ministry of Science and Technology of the People’s Republic of China, China (2018YFE0118100)the National Natural Science Foundation of China, China (21905275, 22025206, 21721004, 21991090)+5 种基金the Liaoning Revitalization Talents Program, China (XLYC2002012)the Joint Fund of the Yulin University and the Dalian National Laboratory for Clean Energy, China (Grant. YLU-DNL Fund 2021019)the CAS-NSTDA Joint Research Project, China (GJHZ2075)Dalian Institute of Chemical Physics, CAS, China (Grant: DICP I202131)the Science and Technology Commission of Shanghai Municipality, China (19DZ2271100)support of the Liaoning Key Laboratory of Biomass Conversion for Energy and Material。
文摘Photocatalytic hydrogenation of furfural offers an ideal method for selective biomass upgrading into value-added chemicals or fuel additives under mild conditions. However, it is still challenging to control the product selectivity due to side reactions of functional groups and reactive radical intermediates.Herein, photocatalytic transfer hydrogenation of furfural was studied using the TiO_(2)-based photocatalysts with alcohols as both the solvent and hydrogen donor. Ultralow loading metal supported on TiO_(2),together with adding a small amount of water in the system, were demonstrated to greatly increase the selectivity of furfuryl alcohol product. Electron paramagnetic resonance(EPR), ultraviolet-visible spectroscopy(UV-Vis) and photoluminescence(PL) measurements gave evidence that ultralow loading Pt or Pd on TiO_(2)increase the oxygen vacancy concentration and the photogenerated charge separation efficiency, which accelerates the photocatalytic reduction of furfural. In situ diffuse reflectance infrared Fourier transform spectroscopy(DRIFTS) and mechanistic studies confirmed that photogenerated holes and electrons are active species, with dissociatively adsorbed methanol being directly oxidized by holes,furfural hydrogenated by protons and electrons and H_(2)O modifying the intermediate diffusion which contributes to high selectivity of furfuryl alcohol. This work demonstrates a simple approach to design photocatalysts and tune product selectivity in biomass valorization.
基金financially supported by the National Natural Science Foundation of China (No.21536007)the 111 Project (B17030)+1 种基金support from China Scholarship Council (CSC No.202006240156)the Spanish Ministry of Science,Innovation and Universities for the Juan de la Cierva (JdC)fellowships (Grant Numbers FJCI-2016-30847 and IJC2018-037110-I)awarded.
文摘The chemical transformation of natural oils provides alternatives to limited fossil fuels and produces compounds with added value for the chemical industries.The selective deoxygenation of natural oils to diesel-ranged hydrocarbons,bio-jet fuels,or fatty alcohols with controllable selectivity is especially attractive in natural oil feedstock biorefineries.This review presents recent progress in catalytic deoxygenation of natural oils or related model compounds(e.g.,fatty acids)to renewable liquid fuels(green diesel and bio-jet fuels)and valuable fatty alcohols(unsaturated and saturated fatty alcohols).Besides,it discusses and compares the existing and potential strategies to control the product selectivity over heterogeneous catalysts.Most research conducted and reviewed has only addressed the production of one category;therefore,a new integrative vision exploring how to direct the process toward fuel and/or chemicals is urgently needed.Thus,work conducted to date addressing the development of new catalysts and studying the influence of the reaction parameters(e.g.,temperature,time and hydrogen pressure)is summarized and critically discussed from a green and sustainable perspective using efficiency indicators(e.g.,yields,selectivity,turnover frequencies and catalysts lifetime).Special attention has been given to the chemical transformations occurring to identify key descriptors to tune the selectivity toward target products by manipulating the reaction conditions and the structures of the catalysts.Finally,the challenges and future research goals to develop novel and holistic natural oil biorefineries are proposed.As a result,this critical review provides the readership with appropriate information to selectively control the transformation of natural oils into either biofuels and/or value-added chemicals.This new flexible vision can help pave the wave to suit the present and future market needs.
基金supported by the Key Laboratory of Universal Wireless Communications(Beijing University of Posts and Telecommunications)Ministry of Education,P.R.China(KFKT-2013104)+6 种基金the National Natural Science Foundation of China(61501105,61471109,61302071)the China Postdoctoral Science Foundation(2013M541243)the Doctoral Scientific Research Foundation of Liaoning Province(20141014)the Fundamental Research Funds for the Central Universities(N150404018,N130304001,N150401002,N150404015)the National 973 Advance Research Program(2014CB360509)the Postdoctoral Science Foundation of Northeast University(20140319)Ministry of Education-China Mobile Research Foundation(MCM20130131)
文摘In software-defined networking,the separation of control plane from forwarding plane introduces new challenges to network reliability.This paper proposes a fault-tolerant routing mechanism to improve survivability by converting the survivability problem into two sub-problems:constructing an elastic-aware routing tree and controller selection.Based on the shortest path tree,this scheme continuously attempts to prune the routing tree to enhance network survivability.After a certain number of iterations,elastic-aware routing continues to improve network resiliency by increasing the number of edges in this tree.Simulation results demonstrate this fault-tolerant mechanism performs better than the traditional method in terms of the number of protected nodes and network fragility indicator.
基金co-supported by the State Key Program of National Natural Science Foundation of China (No. 91538204)the National Science Fund for Distinguished Young Scholars (No. 61425014)the National Key Technologies R&D Program of China (No. 2015BAG15B01)
文摘Air traffic complexity is an objective metric for evaluating the operational condition of the airspace. It has several applications, such as airspace design and traffic flow management.Therefore, identifying a reliable method to accurately measure traffic complexity is important. Considering that many factors correlate with traffic complexity in complicated nonlinear ways,researchers have proposed several complexity evaluation methods based on machine learning models which were trained with large samples. However, the high cost of sample collection usually results in limited training set. In this paper, an ensemble learning model is proposed for measuring air traffic complexity within a sector based on small samples. To exploit the classification information within each factor, multiple diverse factor subsets（FSSs） are generated under guidance from factor noise and independence analysis. Then, a base complexity evaluator is built corresponding to each FSS. The final complexity evaluation result is obtained by integrating all results from the base evaluators. Experimental studies using real-world air traffic operation data demonstrate the advantages of our model for small-sample-based traffic complexity evaluation over other stateof-the-art methods.
基金supported by the National Natural Science Foundation of China(No.92477134)Provincial Natural Science Foundation of Shandong(No.ZR2023ME014).
文摘As an efficient and sustainable alternative to traditional thermocatalytic hydrogenation in both petrochemical and fine chemical processes,electrochemical hydrogenation powered by renewable energy has attracted considerable attention[1].Electrocatalytic CO_(2)reduction reaction(CO_(2)RR)offers an appealing route for CO_(2)resource utilization to produce high value-added chemicals or fuels.
基金This work was supported by the National Key R&D Program of China(No.2020YFA0406103)the National Natural Science Foundation of China(NSFC)(Nos.21725102 and 91961106)+1 种基金the Dalian National Laboratory for Clean Energy(DNL)Cooperation Fund,Chinese Academy of Sciences(CAS)(No.DNL201922)the startup grant from University of Science and Technology of China(USTC)(No.KY2260080010).
文摘Organic synthesis driven by heterogeneous catalysis is a central research theme to both fundamental research and industrial production of fine chemicals.However,the employment of stoichiometric strong oxidizing or reducing reagents(e.g.,K_(2)Cr_(2)O_(7) and LiAlH_(4))and harsh reaction conditions(e.g.,high temperature and pressure)always leads to the products of overreaction and other by-product residues(e.g.,salt and acid waste).Thus the poor control of product selectivity and tremendous energy consumption result in the urgent demand to develop novel technologies for heterogeneous catalysis.Given the current global theme of development in CO_(2) reduction and sustainable energy utilization,one promising protocol is heterogeneous photocatalysis.It enables sustainable solar-to-chemical energy conversion under mild conditions(e.g.,room temperature,ambient pressure,and air as the oxidant)and offers unique reaction pathways for improved selectivity control.To accurately tailor the selectivity of desired products,the electronic structure(e.g.,positions of valence-band maximum and conduction-band minimum),geometric structure(e.g.,nanorod,nanosheet,and porous morphology),and surface chemical micro-environment(e.g.,vacancy sites and co-catalysts)of heterogeneous photocatalysts require rational design and construction.In this review,we will briefly analyze some effective photocatalytic systems with the excellent regulation ability of product selectivity in organic transformations(mainly oxidation and reduction types)under visible light irradiation,and put forward opinions on the optimal fabrication of nanostructured photocatalysts to realize selective organic synthesis.
基金partially supported by the National Key Basic Research Project of China under Grant No.2011CB302400the National Basic Research Program of China under Grant No.2014CB845303the National Center for Mathematics and Interdisciplinary Sciences,Chinese Academy of Sciences
文摘Uncertain friction is a key factor that influences the accuracy of servo system in CNC machine.In this paper,based on the principle of Active Disturbance Rejection Control(ADRC),a control method is proposed,where both the extended state observer(ESO) and the reduced order extended state observer(RESO) are used to estimate and compensate for the disturbance.The authors prove that both approaches ensure high accuracy in theory,and give the criterion for parameters selection.The authors also prove that ADRC with RESO performs better than that with ESO both in disturbance estimation and tracking error.The simulation results on CNC machine show the effectiveness and feasibility of our control approaches.
基金supported by the National Natural Science Foundation of China(no.12274023 and 51972020)We express our special thanks to Prof.Zhiguo Xia from South China University of Technology for the IQE/EQE measurements.
文摘Luminescence concentration quenching and thermal quenching are closely related to the energy transfer(ET)process between optically active ions.Herein,we utilize the structural confinement effect in Sr_(9)Ga(PO_(4))(7)(SGP)to selectively control ET pathways so as to suppress luminescence concentration and thermal quenching.In the Fe^(3+)-doped SGP compound,the relatively large Fe^(3+)-Fe^(3+)distances can inhibit the ET between Fe^(3+)ions,leading to weak concentration quenching.The Sr_(9)Ga_(0.8)(PO_(4))_(7):0.2Fe^(3+)(SGP:0.2Fe^(3+))phosphor exhibits the highest near-infrared(NIR)luminescence intensity,and the emission intensity for 50%and 100%Fe^(3+)-doped SGP phosphors is 73.46%and 18.25%of that for the optimal sample SGP:0.2Fe^(3+),respectively.Upon co-doping Yb^(3+)into SGP:0.2Fe^(3+),Fe^(3+)-Yb^(3+)distances are much shorter than those of Fe^(3+)-Fe^(3+),causing energy to quickly migrate from the quenching center Fe^(3+)to the thermally stable center Yb^(3+).The thermal stability of SGP:0.2Fe^(3+),0.07Yb^(3+)is greatly enhanced compared to SGP:0.2Fe^(3+).This study provides a strategy for enhancing NIR luminescence through utilizing structural confinement to control ET pathways toward suppressing concentration and thermal quenching.Finally,we demonstrate the potential applications of SGP:0.2Fe^(3+)and SGP:0.2Fe^(3+),0.07Yb^(3+)phosphors in night vision and optical thermometry fields.
基金National Natural Science Foundation of China(No.22379111,22179093,52473287)Key Research Project of Shenzhen(KCXFZ20240903094159005)+1 种基金Fund of the Department of Education of Guangdong Province for Higher Educational Institution(No.2022ZDZX4104,2024KCXTD064)Shenzhen General Project for Institutions of Higher Education(No.20231127113219001).
文摘Electrocatalytic ammonia oxidation reaction(AOR)represents a sustainable synthesis approach for valuable nitrogen‑containing compounds like nitrites and nitrates.However,the numerous AOR intermediates often complicate the precise regulation of target intermediate adsorption,hindering the efficient and selective nitrate/nitrite production.We herein present a NiCu‑BDC MOF with tunable AOR product selectivity,which undergoes a controllable in situ reconstruction into Cu‑β‑NiOOH at 1.7 V vs.RHE,enabling the shift of the reaction pathway from NH_(4)^(+)‑to‑NO_(2)^(−)to NH_(4)^(+)‑to‑NO_(3)^(−).The unique restructuring behavior of this material,combined with its dense active sites,enables highly selective production of nitrites and nitrates(94.9%NO_(2)^(−)selectivity at 1.60 V vs.RHE and 92.6%NO_(3)^(−)selectivity at 1.95 V vs.RHE).Theoretical simulations reveal that the Cu incorporation in NiCu‑BDC modulates the electronic configuration of Ni sites,facilitating moderate adsorption of key NO and NOOH intermediates,thus promoting efficient nitrite generation at low potentials.At higher potentials,NiCu‑BDC undergoes reconstruction to Cu‑β‑NiOOH,stabilizing the conversion of NO_(2)to NO_(2)OH,making nitrate formation thermodynamically favorable and a rapid selectivity shift.This potential‑driven selectivity control not only provides a new strategy for efficient nitrites/nitrates synthesis by simply adjusting applied potentials but also provides fundamental insights into regulating selectivity in multi‑product electrochemical reactions.
