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Theoretical Analysis of Cooperative Driving at Idealized Unsignalized Intersections

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Tsinghua Science and Technology 2024年第1期29卷 257-270页

作者： Shen li jiawei zhang Zhenwu Chen li li Department of Civil Engineering Tsinghua UniversityBeijing 100084China Department of Automation Tsinghua UniversityBeijing 100084China Shenzhen Urban Transport Planning Center Co. Ltd.Shenzhen 518000China

Cooperative driving is widely viewed as a promising method to better utilize limited road resources and alleviate traffic *** recent years,several cooperative driving approaches for idealized traffic scenarios(i.e.,uniform vehicle arrivals,lengths,and speeds)have been ***,theoretical analyses and comparisons of these approaches are *** this study,we propose a unified group-by-group zipper-style movement model to describe different approaches synthetically and evaluate their *** derive the maximum throughput for cooperative driving plans of idealized unsignalized intersections and discuss how to minimize the delay of *** obtained conclusions shed light on future cooperative driving studies.

关键词： cooperative driving connected and automated vehicles unsignalized intersection

Effects of mid-passage gap with a variable surface angle on a turbine vane endwall’s aerothermal and film cooling performances

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Chinese journal of Aeronautics 2024年第6期37卷 20-37页

作者： Zhiyu li Kaiyuan zhang Zhigang li jun li Institute of Turbomachinery Xi’an Jiaotong UniversityXi’an 710049China

The mid-passage gap is an inevitable structure in a vane passage due to turbine vanes being manufactured *** coolant from this gap is able to prevent hot mainstream ingression and provide cooling protection for the endwall.A novel idea of enlarging the endwall’s coverage area and reducing the endwall’s thermal load by applying the mid-passage gap with variable surface angles is carried out in this *** endwall’s aerothermal and film cooling performances under four mid-passage gap modes at three typical mass flow ratio conditions are numerically *** indicate that under the traditional mid-passage mode,the coolant flows into the mainstream with a perpendicular incidence angle and can’t stick to the ***,cooling failure occurs,and the endwall’s thermal load is badly *** film cooling level at the suction-side endwall is improved when applying the mid-passage gap of a 45surface angle due to the secondary vortex being *** addition,when applying the mid-passage gap of a 135surface angle,the horseshoe vortex is pushed away,and the coverage area at the pressure-side endwall is enlarged *** best film cooling performance is achieved when the upstream surface angle is 135and the downstream surface angle is 45due to the adiabatic film cooling effectiveness being increased at both the pressure-and suction-side *** the mass flow ratio is 1.5%,the coverage area is enlarged by 43%,and the area-averaged adiabatic film cooling effectiveness is increased by 37%,when compared with those under the traditional mid-passage mode.

关键词： Film cooling Heat transfer Surface angle Mid-passagegap Turbinevane endwall

False Negative Sample Detection for graph Contrastive Learning

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Tsinghua Science and Technology 2024年第2期29卷 529-542页

作者： Binbin zhang li Wang College of Data Science Taiyuan University of TechnologyJinzhong 030600China

Recently,self-supervised learning has shown great potential in graph Neural Networks (gNNs) through contrastive learning,which aims to learn discriminative features for each node without label information. The key to graph contrastive learning is data augmentation. The anchor node regards its augmented samples as positive samples,and the rest of the samples are regarded as negative samples,some of which may be positive samples. We call these mislabeled samples as “false negative” samples,which will seriously affect the final learning effect. Since such semantically similar samples are ubiquitous in the graph,the problem of false negative samples is very significant. To address this issue,the paper proposes a novel model,False negative sample Detection for graph Contrastive Learning (FD4gCL),which uses attribute and structure-aware to detect false negative samples. Experimental results on seven datasets show that FD4gCL outperforms the state-of-the-art baselines and even exceeds several supervised methods.

关键词： graph representation learning contrastive learning false negative sample detection

Nanoscale Zero-Valent Iron(nZVI)for Heavy Metal Wastewater Treatment:A Perspective

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Engineering 2024年第5期36卷 16-20页

作者： Shaolin li Lei li Weixian zhang State Key Laboratory for Pollution Control and Resource Reuse College of Environmental Science and EngineeringTongji UniversityShanghai 200092China Shanghai Institute of Pollution Control and Ecological Security Shanghai 200092China

Industries such as non-ferrous metal smelting discharge billions of gallons of highly toxic heavy metal wastewater(HMW)worldwide annually,posing a severe challenge to conventional wastewater treatment plants and harming the *** is traditionally treated via chemical precipitation using lime,caustic,or sulfide,but the effluents do not meet the increasingly stringent discharge *** issue has spurred an increase in research and the development of innovative treatment technologies,among which those using nanoparticles receive particular *** such initiatives,treatment using nanoscale zero-valent iron(nZVI)is one of the best *** nZVI is already well known for its site-remediation use,this perspective highlights its application in HMW treatment with metal *** demonstrate several advantages of nZVI in this wastewater application,including its multifunctionality in sequestrating a wide array of metal(loid)s(>30 species);its capability to capture and enrich metal(loid)s at low concentrations(with a removal capacity reaching 500 mg·g^(-1)nZVI);and its operational convenience due to its unique *** these advantages are attributable to nZVI’s diminutive nanoparticle size and/or its unique iron *** also present the first engineering practice of this application,which has treated millions of cubic meters of HMW and recovered tons of valuable metals(e.g.,Cu and Au).It is concluded that nZVI is a potent reagent for treating HMW and that nZVI technology provides an eco-solution to this toxic waste.

关键词： Nanoscale zero-valent iron Wastewater Heavy metal Resource recovery

Interface Engineering of Titanium Nitride Nanotube Composites for Excellent Microwave Absorption at Elevated Temperature

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Nano-Micro Letters 2024年第9期16卷 147-160页

作者： Cuiping li Dan li Shuai zhang Long Ma Lei zhang jingwei zhang Chunhong gong College of Chemistry and Molecular Sciences Henan UniversityKaifeng 475004People’s Republic of China National and Local joint Engineering Research Center for Applied Technology of Hybrid Nanomaterials Henan UniversityKaifeng 475004People’s Republic of China

Currently,the microwave absorbers usually suffer dreadful electromagnetic wave absorption(EMWA)performance damping at elevated temperature due to impedance mismatching induced by increased conduction ***,the development of high-performance EMWA materials with good impedance matching and strong loss ability in wide temperature spectrum has emerged as a top ***,due to the high melting point,good electrical conductivity,excellent environmental stability,EM coupling effect,and abundant interfaces of titanium nitride(TiN)nanotubes,they were designed based on the controlling kinetic diffusion procedure and Ostwald ripening *** from boosted heterogeneous interfaces between TiN nanotubes and polydimethylsiloxane(PDMS),enhanced polarization loss relaxations were created,which could not only improve the depletion efficiency of EMWA,but also contribute to the optimized impedance matching at elevated ***,the TiN nanotubes/PDMS composite showed excellent EMWA performances at varied temperature(298-573 K),while achieved an effective absorption bandwidth(EAB)value of 3.23 gHz and a minimum reflection loss(RLmin)value of−44.15 dB at 423 *** study not only clarifies the relationship between dielectric loss capacity(conduction loss and polarization loss)and temperature,but also breaks new ground for EM absorbers in wide temperature spectrum based on interface engineering.

关键词： TiN nanotubes Interface engineering Polarization loss Impedance matching Electromagnetic wave absorption performance

Heterogeneous Catalysis with Metal-Containing Crystalline Porous Materials:Element-and Site-Specific Insights

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CCS Chemistry 2024年第5期6卷 1110-1129页

作者： Yan li Andrew g.Walsh Peng zhang Tianjun zhang State Key Laboratory of New Pharmaceutical Preparations and Excipients College of Chemistry and Materials ScienceHebei UniversityBaoding 071002 Department of Chemistry Dalhousie UniversityHalifaxNova Scotia B3H 4R2

Metal-containing crystalline porous materials(CPMs)are gaining popularity in heterogeneous catalysis because of their highly crystalline and porous systems,and their excellent chemical *** of the metal species and framework structure permits them to have greater activity,selectivity,and stability over other *** in-depth understanding of the complex nature of metal active sites in CPMs is essential for revealing the structure-performance relationships and directing the rational design of such *** to conventional characterization techniques,the rapid development of X-ray absorption spectroscopy(XAS)has provided element-and site-specific deep insights into the electronic and structural information of metal species in *** such,this review begins by summarizing novel XAS techniques and analysis methods in accurately obtaining such ***,the combination of XAS with other high-level characterization methods into disclosing the configuration of active sites in metalcontaining CPMs is ***,the utilization of theory-assisted XAS data analysis in examining complex metal-containing CPM catalysts is ***,advanced in-situ/operando XAS studies into revealing the working sites in metal-containing CPMs under catalytic conditions are *** conclude by outlining the future challenges and prospects of XAS measurements,data analyses,and in-situ/operando setups in advancing the study of metal-in-CPM catalysts.

关键词： X-ray absorption spectroscopy in-situ metal species crystalline porous materials heterogeneous catalysis

Effects of ignition voltage and electrode structure on electric ignition and combustion characteristics of Ammonium Dinitramide(ADN)-based liquid propellants in electric ignition mode in inert gas environment

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Chinese journal of Aeronautics 2024年第4期37卷 229-242页

作者： Lei li guoxiu li Hongmeng li Zhaopu YAO Tao zhang jinze WU Shuo zhang School of Mechanical Electronic and Control EngineeringBeijing Jiaotong UniversityBeijing 100044China Beijing Institute of Control Engineering Beijing 100190China

Hydrazine is toxic and carcinogenic, which greatly increases the difficulty of application and no longer meets the needs of green aerospace. As a green propellant, the Ammonium Dinitramide(ADN)-based liquid propellant has the advantages of higher specific impulse, being non-toxic,pollution-free, and easy storage. However, an ADN-based space engine in orbit has exposed the problems of high-temperature deactivation of catalysts and cold-start failure. An active ignition technology—electric ignition technology was explored in this paper to break through the technical bottleneck of catalyst deactivation and the inability to a cold start. An experimental system of a constant-volume combustor for the ADN-based liquid propellant based on the electric ignition method was established. The electric ignition and combustion characteristics of the ADN-based liquid propellant in a volume combustor with an electric ignition method were studied. The influencing mechanisms of the ignition voltage and the electrode structure on the electric ignition characteristics of the ADN-based liquid propellant were investigated. An elevation of the ignition voltage could facilitate the ignition process of the ADN-based liquid propellant, curtail electric energy input and heating effect, while exerting an adverse impact on the combustion process of the *** increase in the ignition voltage enhanced the ignition process of the propellant while simultaneously suppressing its combustion process when utilizing mesh electrodes. Compared to the strip electrodes, the mesh electrodes increased the contact area between the electrodes and the propellant,increased the electric energy input power in the electric ignition process, and reduced the ignition delay time. The mesh electrodes could promote the combustion process of the propellant to a certain extent.

关键词： ADN-based liquid propellant Resistive ignition Electrical ignition characteristic Combustion Inert gas

Enhanced charge separation by incomplete calcination modified co-doped TiO_(2)nanoparticle for isothiazolinone photocatalytic degradation

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Nano Research 2024年第6期17卷 4834-4843页

作者： Zhiren guo Xiao zhang Xinyuan li Chang Cui Zilei zhang Hansheng li Dongxiang zhang jinying li Xiyan Xu jiatao zhang School of Chemistry and Chemical Engineering Beijing Institute of TechnologyBeijing 102488China Department of Chemistry MSU-BIT UniversityShenzhen 517182Chin

Photocatalytic oxidation techniques are promising for degradation of the highly ecotoxic and refractory isothiazolinone bactericides in relevant industrial ***,low charge separation and directional transport efficiency under solar light radiation restrain their practical ***,we report a nanostructured photocatalyst doped with gd and B in TiO_(2)with carbon incorporation and defect formation through incomplete *** specific surface area,grain size,and hydrophilicity of TiO_(2)are improved,which is beneficial for the interfacial reaction between the photocatalyst and *** reduction of the bandgap,the broadening of the photo-absorption range,and the retarded electron-hole recombination promote the photocatalytic performance due to the improved oxygen vacancies based on the electron distribution *** difference in partial density of states(ΔPDOS)between the current catalyst and raw TiO_(2)indicates that the co-doping of gd and B with incomplete calcination changes the electronic hybridization of conduction band and valence band near the Fermi level,and affects the band gap *** improved charge separation and directional transport efficiency and benefited the formation of main active species,including•OH and O_(2)•−,for the pollutant *** rate of photocatalytic removal of benzisothiazolinone(BIT)by the current photocatalyst reaches 1.25 h^(−1),being 4.31 times that of TiO_(2).The current work offers a constructive approach to the design and synthesis of nanostructured photocatalysts for the photocatalytic degradation of refractory organic pollutants.

关键词： TiO_(2)nanoparticle charge separation oxygen vacancies electron distribution modification photocatalytic degradation

Flexible regulation engineering of titanium nitride nanofibrous membranes for efficient electromagnetic microwave absorption in wide temperature spectrum

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Nano Research 2024年第3期17卷 1666-1675页

作者： Cuiping li Lu zhang Shuai zhang Qiqi Yu Dan li Lei zhang Chunhong gong jingwei zhang Institute of Functional Polymer Composites College of Chemistry and Molecular SciencesHenan UniversityKaifeng 475004China National&Local joint Engineering Research Center for Applied Technology of Hybrid Nanomaterials Henan UniversityKaifeng 475004China

Simultaneous development of well impedance matching and strong loss capability has become a mainstream method for achieving outstanding electromagnetic microwave absorption(EMWA)performances over wide temperature ***,it is difficult to pursue both due to the mutual restraint of relationship between impedance matching and loss capability about ***,we propose a flexible regulation engineering of titanium nitride(TiN)nanofibrous membranes(NMs,TNMs),which could be distributed uniformly in the polydimethylsiloxane(PDMS)matrix and contributed to the formation of abundant local conductive networks,generating the local conductive loss and enhancing the loss ability of ***,when the TNMs are used as functional units and dispersed in the matrix,the corresponding composites exhibit an outstanding anti-reflection effect on *** hoped,under the precondition of good impedance matching,local conductive loss and polarization loss together improve the loss capacity at room temperature,and polarization loss can compensate the local conductive loss to acquire effective dielectric response at elevated *** from the reasonably synergistic loss ability caused by flexible regulation engineering,the corresponding composites exhibit the perfect EMWA performances in a wide temperature range from 298 to 573 *** work not only elaborates the ponderable insights of independent membrane in the composition-structure-function connection,but also provides a feasible tactic for resolving coexistence of well impedance matching and strong loss capability issues in wide temperature spectrum.

关键词： flexible titanium nitride nanofibrous membranes local conductive loss dielectric loss electromagnetic microwave absorption wide temperature spectrum