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Efficient removal of Cr(VI) by polydopamine-modified lignin from aqueous solution: Batch and XAFS studies

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Water Science and Engineering 2024年第1期17卷 51-61页

作者： xiao-jie Guo Wei-kang Fu Jing-yuan ma bo-jun xi Chen Wang Meng-yao Guan College of materials and Environmental Engineering Hangzhou Dianzi UniversityHangzhou 310018China College of Textile and Garment Shaoxing UniversityShaoxing 312000China Shanghai Synchrotron Radiation Facility Shanghai Advanced Research InstituteChinese Academy of SciencesShanghai 201204China

Lignocellulose has the potential to become a bio-based adsorbent due to its biodegradability and renewability.In this study,a novel polydopamine functionalized-lignin(lignin@PDA),prepared via self-polymerization of dopamine(PDA)on lignin,was used as a bio-based adsorbent for rapid scavenging of hexavalent chromium(Cr(VI)).The morphology,functional groups,crystalline structure,and chemical composition of lignin@PDA were characterized with a scanning electron microscope-energy dispersive spectrometer,Fourier transform infrared spectroscopy,X-ray diffraction,and X-ray photoelectron spectroscopy.The Cr(VI)adsorption process of lignin@PDA was studied using batch experiments as a function of pH,ionic strength,adsorbent dose,and contact time at room temperature.The adsorption rate of lignin@PDA was five times greater than that of the unmodified lignin,with a maximum adsorption capacity of 102.6 mg/g in an acidic medium.The adsorption of Cr(VI)on lignin@PDA fit the pseudo-secondorder equation and the Freundlich model,indicating that the adsorption process was mainly dominated by chemisorption and surface complexation.The thermodynamic parameters showed that adsorption of Cr(VI)on lignin@PDA was an endothermic and spontaneous process.The X-ray absorption fine structure results showed that sorption and reduction of Cr(VI)into Cr(II)occurred simultaneously on lignin.Moreover,PDA coating not only improved the reactivity of lignin but also promoted the complete reduction of Cr(VI)by lignin.According to these results,polydopamine functionalized-lignin is a promising bio-based adsorbent for immobilization of Cr(VI)from wastewater.

关键词： Lignin Polydopamine Hexavalent chromium EXAFS Adsorption mechanism

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On Depolymerization

CCS Chemistry 2024年第2期6卷 297-312页

作者： bo Qin xi Zhang College of Chemistry and Chemical Engineering Hunan UniversityChangsha 410082 Department of Chemistry Tsinghua UniversityBeijing 100084

Polymers have become an essential part of modern life and the global economy on account of their costeffectiveness and versatile properties.However,most postconsumer polymer wastes are unrecycled,leading to environmental pollution and resource wastage.Depolymerization,as an efficient chemical recycling approach,holds great promise in establishing a circular polymer economy.In this review,we attempt to highlight recent and significant advancements in depolymerization methodologies.Two key research topics are discussed:(1)depolymerization of commodity polymers to produce reusable monomers and high-value chemicals;(2)depolymerization of intrinsically depolymerizable polymers.It is anticipated that this review will reflect the present status and future trends of this rapidly evolving realm of depolymerization.

关键词： depolymerization chemical recycling sustainable polymers circular polymer economy catalysis dynamic covalent chemistry

Access to High-Molecular-Weight Polyethylenes through High Temperature Ethylene Polymerization Catalysed by Ethylene-Bridged ansa-(3-R-Cyclopentadienyl)(Fluorenyl) Zirconocene Complexes

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Chinese Journal of Polymer Science 2024年第1期42卷 42-51,I0007页

作者： bo Li Haiyan ma Jiling Huang Shanghai Key Laboratory of Functional materials Chemistry and Laboratory of Organometallic Chemistry School of Chemistry and Molecular EngineeringEast China University of Science and TechnologyShanghai 200237China

A series of C1-symmetric ethylene-bridged ansa-(3-R-cyclopentadienyl)(fluorenyl) metallocene complexes(Zr: 1-5;Hf: 6) have been synthesized, characterized and investigated as catalyst precursors for the high temperature ethylene polymerization. Using methylaluminoxane(maO) as the cocatalyst, zirconium complexes 1-5 bearing a bulky substituent on the 3-position of the cyclopendienyl ring showed high catalytic activities up to 1.48×10^(7) g PE·mol_(Zr)^(-1)·h^(-1) toward the polymerization of ethylene and afforded polyethylenes with high molecular weights(1.49×10^(5)-6.31×10^(5) g/mol), meanwhile exhibting great thermal stability at high temperatures up to 120 ℃ together with a long catalytic life time up to 2 h. By adopting low Al/Zr ratios, such as 125, polyethylenes with ultra high molecular weights up to 2.86×106 g/mol were obtained. It is worthy of noting that zirconium complexes 1-4 bearing a substituent with an aryl pendant showed temperature-dependent activities, which increased rapidly with the increase of polymerization temperature, thus weak interaction of the pendent aryl group with the cationic active center is proposed to account for the very low activities displayed at low temperatures. In contrast to zirconocene complexes 1-5, hafnocene complex 6 only displayed very low catalytic activities toward the polymerization of ethylene and afforded polyethylenes with molecular weights ten times smaller than those obtained by zirconocene complexes 1-5. Zirconocene complexes 1-5 were also able to catalyse the polymerization of propylene at high temperatures, but only afforded waxes with low molecular weights.

关键词： ansa-Metallocene Ethylene Propylene Polymerization High temperature

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CToMP: a cycle-task-oriented memory protection scheme for unmanned systems

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Science China(Information Sciences) 2024年第6期67卷 399-417页

作者： Chengyan ma Ning xi Di LU Yebo FENG Jianfeng ma School of Cyber Engineering Xidian University School of Computer Science and Technology Xidian University Department of Computer and Information Science University of Oregon

Memory corruption attacks(MCAs) refer to malicious behaviors of system intruders that modify the contents of a memory location to disrupt the normal operation of computing systems, causing leakage of sensitive data or perturbations to ongoing processes. Unlike general-purpose systems, unmanned systems cannot deploy complete security protection schemes, due to their limitations in size, cost and performance.MCAs in unmanned systems are particularly difficult to defend against. Furthermore, MCAs have diverse and unpredictable attack interfaces in unmanned systems, severely impacting digital and physical sectors. In this paper, we first generalize, model and taxonomize MCAs found in unmanned systems currently, laying the foundation for designing a portable and general defense approach. According to different attack mechanisms,we found that MCAs are mainly categorized into two types — return2libc and return2shellcode. To tackle return2libc attacks, we model the erratic operation of unmanned systems with cycles and then propose a cycle-task-oriented memory protection(CToMP) approach to protect control flows from tampering. To defend against return2shellcode attacks, we introduce a secure process stack with a randomized memory address by leveraging the memory pool to prevent Shellcode from being executed. Moreover, we discuss the mechanism by which CTo MP resists the return-oriented programming(ROP) attack, a novel variant of return2libc attacks. Finally, we implement CTo MP on CUAV V5+ with Ardupilot and Crazyflie. The evaluation and security analysis results demonstrate that the proposed approach CTo MP is resilient to various MCAs in unmanned systems with low footprints and system overhead.

关键词： unmanned system memory corruption attack memory protection system security randomized memory address

Corporate Credit Ratings Based on Hierarchical Heterogeneous Graph Neural Networks

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machine Intelligence Research 2024年第2期21卷 257-271页

作者： bo-Jing Feng xi Cheng Hao-Nan Xu Wen-Fang Xue Center for Research on Intelligent Perception and Computing National Laboratory of Pattern RecognitionInstitute of AutomationChinese Academy of SciencesBeijing 100190China

order to help investors understand the credit status of target corporations and reduce investment risks,the corporate credit rating model has become an important evaluation tool in the financial market.These models are based on statistical learning,machine learning and deep learning especially graph neural networks(GNNs).However,we found that only few models take the hierarchy,heterogeneity or unlabeled data into account in the actual corporate credit rating process.Therefore,we propose a novel framework named hierarchical heterogeneous graph neural networks(HHGNN),which can fully model the hierarchy of corporate features and the heterogeneity of relationships between corporations.In addition,we design an adversarial learning block to make full use of the rich unlabeled samples in the financial data.Extensive experiments conducted on the public-listed corporate rating dataset prove that HHGNN achieves SOTA compared to the baseline methods.

关键词： Corporate credit rating hierarchical relation heterogeneous graph neural networks adversarial learning

Corrosion evaluation and resistance study of alloys in chloride salts for concentrating solar power plants

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Rare Metals 2024年第3期43卷 1222-1233页

作者： Dong-Mei Han Yong Shuai Bachirou Guene Lougou bo-xi Geng xi-bo He Tian-Tian Yan Jia-Meng Song School of Energy Science and Engineering Harbin Institute of TechnologyHarbin150001China

Thermal energy storage(TES)systems based on molten salt are widely used in concentrating solar power(CSP)plants.The investigation of the corrosion behavior of alloy materials in molten salt is crucial for the correct selection of alloy materials and the design of TES systems.In this study,the corrosion behavior of 304,310S,316,and In625 alloys in molten chloride salts(27 mol%NaCl-22 mol%KCl-51 mol%MgCl,)was investigated.The evolution of mass loss of the alloy samples with corrosion time and temperature and the analysis of the experimental results by scanning electron microscopy(SEM),energy dispersive spectrometer(EDS),and X-ray diffraction(XRD)revealed the corrosion mechanism of the alloy samples in molten chloride salts.The main factors affecting the corrosion of the alloy samples were further analyzed.It was found that the loose multi-layer corrosion was formed on the surface of the corroded alloy samples with the increase in corrosion degree.Moreover,the experimental results.showed that Mo played a positive role in improving the corrosion resistance of the alloy samples because the presence of Mo could inhibit the outward diffusion of alloying element Cr.This work enriches the molten salt corrosion database and provides a reference for the selection of alloy materials for TES systems with potential application in CSP plants.

关键词： Thermal energy storage Molten chloride salt Alloy materials Corrosion mechanism Corrosion resistance

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Catalytic recycling of polyesters via a binuclear catalyst

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Science China Chemistry 2024年第2期67卷 426-427页

作者： bo Sun Ding ma Beijing National Laboratory for Molecular Science New Cornerstone Science LaboratoryCollege of Chemistry and Molecular EngineeringPeking UniversityBeijing100871China

Plastics play a crucial role in modern society life. While the increasing use of plastics and rapid accumulation of plastic waste in nature environment have caused severe environmental crisis and the waste of carbon resources. Catalytic upcycling is a promising approach to transform plastic waste into high value-added chemicals to achieve a sustainable circular economy.

关键词： Catalytic polyester catalyst

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Coordination of distinctive pesticide adjuvants and atomization nozzles on droplet spectrum evolution for spatial drift reduction

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Chinese Journal of Chemical Engineering 2024年第2期66卷 250-262页

作者： Shidong Xue Jingkun Han xi xi Zhong Lan Rongfu Wen Xuehu ma State Key Laboratory of Fine Chemicals Liaoning Key Laboratory of Clean Utilization of Chemical ResourcesInstitute of Chemical EngineeringSchool of Chemical EngineeringDalian University of TechnologyDalian 16024China School of Fashion and Textiles The Hong Kong Polytechnic UniversityHong Kong 999077China China Tianchen Engineering Corporation Tianjin 300400China School of Energy and Power Engineering Dalian University of TechnologyDalian 116024China

Pesticide adjuvants,as crop protection products,have been widely used to reduce drift loss and improve utilization efficiency by regulating droplet spectrum.However,the coordinated regulation mechanisms of adjuvants and nozzles on droplet spectrum remain unclear.Here,we established the relationship between droplet spectrum evolution and liquid atomization by investigating the typical characteristics of droplet diameter distribution near the nozzle.Based on this,the regulation mechanisms of distinctive pesticide adjuvants on droplet spectrum were clarified,and the corresponding drift reduction performances were quantitively evaluated by wind tunnel experiments.It shows that the droplet diameter firstly shifts to the smaller due to the liquid sheet breakup and then prefers to increase caused by droplet interactions.Reducing the surface tension of sprayed liquid facilitates the uniform liquid breakup and increasing the viscosity inhibits the liquid deformation,which prolong the atomization process and effectively improve the droplet spectrum.As a result,the drift losses of flat-fan and hollow cone nozzles are reduced by about 50%after adding organosilicon and vegetable oil adjuvants.By contrast,the air induction nozzle shows a superior anti-drift ability,regardless of distinctive adjuvants.Our findings provide insights into rational adjuvant design and nozzle selection in the field application.

关键词： Pesticide drift Spray droplets Particle size distribution Spray atomization Transport processes Adjuvants

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Ultra-high energy cosmic neutrinos from gamma-ray bursts

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Fundamental Research 2024年第1期4卷 51-56页

作者： Yanqi Huang bo-Qiang ma School of Physics Peking UniversityBeijing 100871China Center for High Energy Physics Peking UniversityBeijing 100871China Collaborative Innovation Center of Quantum matter Beijing 100871China

Based on the recent association of IceCube TeV and PeV neutrino events with gamma-ray bursts(GRBs)by considering the Lorentz violation of neutrinos,we provide a new estimate on the GRB neutrino flux with a more significant result compared to the previous constraint by the IceCube Collaboration.Among these 24 neutrino“shower”events above 60 TeV,12 events are associated with GRBs.Such a result is compatible with the prediction from GRB fireball models.Analysis of track events provides a consistent result with the shower events to associate high energy cosmic neutrinos with GRBs under the same Lorentz violation features of neutrinos.We also make a background estimation and reveal GRBs as a significant source for the ultra-high energy IceCube neutrino events.Our work supports the Lorentz violation and CPT-violation of neutrinos,indicating new physics beyond relativity.

关键词： Cosmic neutrino Gamma-ray burstLorentz invariance violation Neutrino and anti-neutrino asymmetry CPT-violation of neutrinos