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pH Induced Self-assembly of AIE Fluorescent Probe for Tumor Imaging

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Chinese Journal of Polymer Science 2024年第1期42卷 7-13,I0005页

作者： Jing-Yuan Xiang Wen-Long Zhang He-Ting Li Ya-Ning He department of chemical engineering Key Laboratory of Advanced Materials(MOE)Tsinghua UniversityBejing 100084China

This work reported an AIE fluorescent probe for tumor imaging based on the p H induced self-assembly strategy. The fluorescent probe was composed of an acid-responsive soluble copolymer PEG-b-PAMA-DMMA with a maleic acid amide group and an anionic soluble aggregation-induced emission fluorogen(AIEgen) TPE-2SO_(3)^(-). The polymer could be transformed into a protonated amine-containing polymer after the hydrolysis of maleic acid amide in acidic tumor microenvironment, which would be further self-assembled with TPE-2SO_(3)^(-)to form aggregated nanoparticles. The transition of TPE-2SO_(3)^(-)from dispersed state to aggregated state led to an obvious increase in fluorescence intensity due to its AIE characteristics.

关键词： p H-responsive Self-assembly Fluorescent probe AIE Tumor imaging

Effect of Interface Form on Creep Failure and Life of Dissimilar Metal Welds Involving Nickel-Based Weld Metal and Ferritic Base Metal

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Chinese Journal of Mechanical engineering 2024年第1期37卷 265-285页

作者： Xiaogang Li Junfeng Nie Xin Wang Kejian Li Haiquan Zhang Institute of Nuclear and New Energy Technology Key Laboratory of Advanced Reactor Engineering and Safety of Ministry of EducationTsinghua UniversityBeijing 100084China department of Mechanical engineering Tsinghua UniversityBeijing 100084China

For dissimilar metal welds(DMWs)involving nickel-based weld metal(WM)and ferritic heat resistant steel base metal(BM)in power plants,there must be an interface between WM and BM,and this interface suffers mechanical and microstructure mismatches and is often the rupture location of premature *** this study,a new form of WM/BM interface form,namely double Y-type interface was designed for the *** behaviors and life of DMWs containing double Y-type interface and conventional I-type interface were compared by finite element analysis and creep tests,and creep failure mechanisms were investigated by stress-strain analysis and microstructure *** applying double Y-type interface instead of conventional I-type interface,failure location of DMW could be shifted from the WM/ferritic heat-affected zone(HAZ)interface into the ferritic HAZ or even the ferritic BM,and the failure mode change improved the creep life of *** interface premature failure of I-type interface DMW was related to the coupling effect of microstructure degradation,stress and strain concentrations,and oxide notch on the WM/HAZ *** creep failure of double Y-type interface DMW was the result of Type IV fracture due to the creep voids and micro-cracks on fine-grain boundaries in HAZ,which was a result of the matrix softening of HAZ and lack of precipitate pinning at fine-grain *** double Y-type interface form separated the stress and strain concentrations in DMW from the WM/HAZ interface,preventing the trigger effect of oxide notch on interface failure and inhibiting the interfacial microstructure *** is a novel scheme to prolong creep life and enhance reliability of DMW,by means of optimizing the interface form,decoupling the damage factors from WM/HAZ interface,and then changing the failure mechanism and shifting the failure location.

关键词： Dissimilar metal weld Nickel-based weld metal Ferritic heat resistant steel Interface Creep strain Microstructure Failure mechanism Creep life

Failure Analysis of Dissimilar Metal Welds between Ferritic Heat Resistant Steels and Austenitic Stainless Steels in Power Plant

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Chinese Journal of Mechanical engineering 2024年第4期37卷 306-326页

This study analysed the failure of dissimilar metal welds(DMWs)between ferritic heat resistant steels and austenitic stainless steels and investigated its influencing factors by means of numerical simulation,microstructure characterization and mechanical property *** the long-term high-temperature service condition in practical power plant,the DMW failure mode was along the interface between nickel-based weld metal(WM)and ferritic heat resistant steel,and the failure mechanism was stress/strain concentration,microstructure degradation and oxidation coupling acting on the *** numerical simulation results show that interface stress/strain concentration was due to the differences in coefficient of thermal expansion and creep strength,and the degree of stress/strain concentration was related to service *** ferrite band formed at the WM/ferritic steel interface was prone to cracking,attracting the fracture along the *** interface crack allowed oxidation to develop along the WM/ferritic steel *** long-term service,the interface stress/strain concentration,microstructure and oxidation all evolved,which synergistically promoted interface failure of ***,only under the long-term service of low stress conditions could trigger the interface failure of ***,long-term service would reduce the mechanical strength and plasticity of DMW.

关键词： Dissimilar metal weld Failure Interface Stress/strain concentration Microstructure Oxidation

Lift system optimization for hover-capable flapping wing micro air vehicle

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Frontiers of Mechanical engineering 2024年第3期19卷 61-75页

作者： Shengjie XIAO Yongqi SHI Zemin WANG Zhe NI Yuhang ZHENG Huichao DENG Xilun DING department of Mechanical engineering and Automation Beihang UniversityBeijing 100191China department of Mechanical engineering Tsinghua UniversityBeijing 100084China Shenzhen International Graduate School Tsinghua UniversityShenzhen 518055China

A key challenge is using bionic mechanisms to enhance aerodynamic performance of hover-capable flapping wing micro air vehicle(FWMAV).This paper presented a new lift system with high lift and aerodynamic efficiency,which use a hummingbird as a bionic *** new lift system is able to effectively utilize the high lift mechanism of hummingbirds,and this study innovatively utilizes elastic energy storage elements and installs them at the wing root to help improve aerodynamic performance.A flapping angle of 154°is achieved through the optimization of the flapping mechanism *** optimized wing shape and parameters are obtained through experimental studies on the ***,the max net lift generated is 17.6%of the flapping wing vehicle’s ***,energy is stored and released periodically during the flapping cycle,by imitating the musculoskeletal system at the wing roots of hummingbirds,thereby improving the energy utilization rate of the FWMAV and reducing power consumption by 4.5%under the same ***,strength verification and modal analyses are conducted on the flapping mechanism,and the weight of the flapping mechanism is reduced through the analysis and testing of different *** results show that the lift system can generate a stable lift of 31.98 g with a wingspan of 175 mm,while the lift system weighs only 10.5 g,providing aerodynamic conditions suitable for high maneuverability flight of FWMAVs.

关键词： lift optimization flapping wing elastic energy hovering flapping mechanism

Numerical analysis on seismic response and failure mechanism of articulated pile−structure system in a liquefiable site from shaking-table experiments

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Frontiers of Structural and Civil engineering 2024年第7期18卷 1117-1133页

作者： Pengfei DOU Hao LIU Chengshun XU Jinting WANG Yilong SUN Xiuli DU department of Hydraulic engineering Tsinghua UniversityBeijing 100084China Key Laboratory of Urban Security and Disaster engineering of the Ministry of Education Beijing University of TechnologyBeijing 100124China

This study investigates the seismic response and failure mode of a pile-structure system in a liquefiable site by employing a numerical simulation model combined with the shaking-table results of a soil-pile-structure dynamic *** pile and soil responses obtained from the numerical simulations agreed well with the experimental *** slopes of the dynamic shear-stress-shear-strain hysteretic curves at different positions also exhibited a decreasing trend,indicating that the shear strength of the soil in all parts of the foundation *** peak acceleration of the soil and pile was not clearly amplified in the saturated sand layer but appeared to be amplified in the top *** maximum bending moments appeared in the middle and lower parts of the pile shaft;however,the shear forces at the corresponding positions were not *** can be observed from the deformation mode of the pile-group foundation that a typical bending failure is caused by an excessive bending moment in the middle of the pile shaft if the link between the pile top and cap is articulated,and sufficient attention should be paid to the bending failure in the middle of the pile shaft.

关键词： numerical simulation soil liquefaction pile foundation shaking-table experiment seismic responses failure model

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

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Chinese Journal of Aeronautics 2024年第5期37卷 148-179页

作者： Yinke QI Xiaofeng MA Peixue JIANG Yinhai ZHU Key Laboratory for Thermal Science and Power engineering of Ministry of Education Department of Energy and Power EngineeringTsinghua UniversityBeijing 100084China beijing Key Laboratory of CO_(2)Utilization and Reduction Technology Department of Energy and Power EngineeringTsinghua UniversityBeijing 100084China

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 *** 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 *** 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 *** 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 ***,its work capacity is limited by the flow rate of the supplied *** closed Brayton cycle can maintain a relatively high PWR,ranging from 0.2 to 0.8,while achieving relatively high output power and conversion *** Rankine cycle has a higher PWR,its range is close to that of the closed Brayton cycle,peaking at about *** thermoelectric materials technology has a small power generation level,making it more suitable for scenarios with low power *** review provides a basis for selecting and developing heat-to-power conversion technologies on hypersonic vehicles.

关键词： Hypersonic vehicles Heat-to-power conversion Brayton cycle Rankine cycle Thermoelectric materials

Seismic and vibration control of segmented isolation layer in underground structure-diaphragm wall system

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Underground Space 2024年第6期19卷 72-86页

作者： Zhidong Gao Mingbo Li Mi Zhao Xiuli Du Key Laboratory of Urban Security and Disaster engineering of Ministry of Education Beijing University of TechnologyBeijing 100124China department of Hydraulic engineering Tsinghua UniversityBeijing 100084China

In this paper,a seismic and vibration reduction measure of subway station is developed by setting a segmented isolation layer between the sidewall of structure and the diaphragm *** segmented isolation layer consists of a rigid layer and a flexible *** rigid layer is installed at the joint section between the structural sidewall and slab,and the flexible layer is installed at the remaining sections.A diaphragm wall-segmented isolation layer-subway station structure system is *** and vibration control performance of the diaphragm wall-segmented isolation layer-subway station structure system is evaluated by the detailed numerical ***,a three-dimensional nonlinear time-history analysis is carried out to study the seismic response of the station structure by considering the effect of different earthquake motions and stiffness of segmented isolation ***,the vibration response of site under training loading is also studied by considering the influence of different train velocities and stiffness of the segmented isolation *** results demonstrate that the diaphragm wall-segmented isolation layer-subway station structure system can not only effectively reduce the lateral deformation of station structure,but also reduce the tensile damage of the roof *** the other hand,the developed reduction measure can also significantly reduce the vertical peak displacements of site under training loading.

关键词： Subway station Diaphragm wall Segmented isolation layer Seismic response Train vibration

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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 ***,most postconsumer polymer wastes are unrecycled,leading to environmental pollution and resource ***,as an efficient chemical recycling approach,holds great promise in establishing a circular polymer *** this review,we attempt to highlight recent and significant advancements in depolymerization *** key research topics are discussed:(1)depolymerization of commodity polymers to produce reusable monomers and high-value chemicals;(2)depolymerization of intrinsically depolymerizable *** 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

Demixing microwave signals using system-on-chip photonic processor

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Light(Science & Applications) 2024年第3期13卷 399-401页

作者： Sheng Gao Chu Wu Xing Lin department of Electronic engineering Tsinghua University100084 BeijingChina beijing National Research Center for Information Science and Technology Tsinghua University100084 BeijingChina

The integrated photonic processor,co-packaged with electronic peripherals,is proposed for blind source separation of microwave signals,which separates signal-of-interest from dynamic interference with real-time adapta... 详细信息

关键词： processor microwave mixing