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Frontiers of Environmental Science & Engineering 2024年第5期18卷 127-136页

作者： Hao zhang Huinan Li pengyi zhang Tingxia Hu Xianjie Wang State Key Joint Laboratory of Environment Simulation and Pollution Control School of EnvironmentTsinghua UniversityBeijing100084China Beijing Key Laboratory for Indoor Air Quality Evaluation and Control Beijing100084China Midea Corporate Research Center Foshan528311China

Copper intercalated birnessite MnO2(δ-MnO2)with weak crystallinity and high specific surface area(421 m2/g)was synthesized by a one-pot redox method and investigated for low-temperature CO oxidation.The molar ratio of Cu/Mn was as high as 0.37,which greatly weakened the Mn-O bond and created a lot of low-temperature active oxygen species.In situ DRIFTS revealed strong bonding of copper ions with CO.As-synthesized MnO2-150Cu achieved 100%conversion of 250 ppm CO in normal air(3.1 ppm H2O)even at−10°C under the weight-hourly space velocity(WHSV)of 150 L/(g·h).In addition,it showed high oxygen storage capacity to oxidize CO in inert atmosphere.Though the concurrent moisture in air significantly inhibited CO adsorption and its conversion at ambient temperature,MnO2-150Cu could stably convert CO in 1.3%moisture air at 70°C owing to its great low-temperature activity and reduced competitive adsorption of water with increased temperature.This study discovers the excellent low-temperature activity of weakly crystallizedδ-MnO2 induced by high content intercalated copper ions.

关键词： CO oxidation Birnessite Interlayer copper Low-temperature Oxygen storage capacity

Research advances on blockchain-as-a-service:architectures,applications and challenges

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Digital Communications and Networks 2022年第4期8卷 466-475页

作者： Jie Song pengyi zhang Mohammed Alkubati Yubin Bao Ge Yu Software College Northeastern University Shenyang110819China School of Computer Science and Engineering Northeastern UniversityShenyang110819China

Due to the complexity of blockchain technology,it usually costs too much effort to build,maintain and monitor a blockchain system that supports a targeted application.To this end,the emerging“Blockchain as a Service”(BaaS)makes the blockchain and distributed ledgers more accessible,particularly for businesses,by reducing costs and overheads.BaaS combines the high computing power of cloud computing,the pervasiveness of IoT and the decentralization of blockchain,allowing people to build their own applications while ensuring the transparency and openness of the system.This paper surveys the research outputs of both academia and industry.First,it introduces the representative architectures of BaaS systems and then summarizes the research contributions of BaaS from the technologies for service provision,roles,container and virtualization,interfaces,customization and evaluation.The typical applications of BaaS in both academic and practical domains are also introduced.At present,the research on the blockchain is abundant,but research on BaaS is still in its infancy.Six challenges of BaaS are concluded in this paper for further study directions.

关键词： Blockchain as a service Blockchain Service Internet of things Cloud computing

Fabrication of MnO2 coating on aluminum honeycomb for fast catalytic decomposition of ozone at room temperature

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Journal of Environmental Sciences 2023年第12期134卷 34-43页

作者： Yunjuan He pengyi zhang Jie Yang Shan Wang Jinge Li State Key Joint Laboratory of Environment Simulation and Pollution Control School of EnvironmentTsinghua UniversityBeijing 100084China Beijing Key Laboratory for Indoor Air Quality Evaluation and Control Beijing 100084China

Herein, the coating of MnO2nanomaterials on the surface of aluminum honeycomb was carried out to meet the requirements of high air velocity, low pressure drop and high activity in ozone removal scenarios. A commercially readily available waterborne silica sol mixed with waterborne acrylate latex was creatively utilized as the binder. A series of coating samples were prepared by spray coating method and evaluated focusing on their adhesion strength and catalytic activity towards ozone decomposition in an air duct at room temperature, by varying MnO2/binder mass ratio and number of sprayings. It was found that the adhesion strength of the catalytic coatings on the aluminum honeycomb increased with the increase of binder mass ratio, but the increased binder made the catalyst particles closely packed,resulting in reduced exposure of active sites and decrease of ozone conversion. Accordingly,catalyst slurry with 81.8 wt.% MnO2in dry coating and spraying times of two were determined as the optimal process parameters. As-prepared aluminum honeycomb filter with MnO2layer of 50 μm thickness achieved ozone conversion of 29.3%±1.7% under conditions of air velocity 3.0 m/sec, relative humidity50%, room temperature(26°C) and initial ozone concentration of 200 ppbV. This filter can be well adaptable to indoor air purification equipment operating at high air velocity with low wind resistance.

关键词： Manganese dioxide Waterborne binder Coating Ozone conversion Catalyst

Effects of pH on photochemical decomposition of perfluorooctanoic acid in different atmospheres by 185 nm vacuum ultraviolet

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Journal of Environmental Sciences 2014年第11期26卷 2207-2214页

作者： Yuan Wang pengyi zhang State Key Joint Laboratory of Environmental Simulation and Pollution Control School of Environment Tsinghua University School of Chemistry and Chemical Engineering Guizhou University

Perfluorooctanoic acid （PFOA）, a persistent organic pollutant, receives increasing concerns due to its worldwide occurrence and resistance to most conventional treatment processes. The photochemical decomposition by 185 nm vacuum ultraviolet （VUV） is one of the efficient methods for PFOA decomposition. The effects of pH on PFOA decomposition in nitrogen atmosphere or oxygen atmosphere were investigated. At its original pH （4.5） of PFOA aqueous solution, PFOA decomposed efficiently both in nitrogen and in oxygen atmosphere. However, when the pH increased to 12.0, PFOA decomposition was greatly inhibited in oxygen atmosphere, while it was greatly accelerated in nitrogen atmosphere with a very short half-life time （9 rain）. Furthermore, fluorine atoms originally contained in PFOA molecules were almost completely transformed into fluoride ions. Two decomposi- tion pathways have been proposed to explain the PFOA decomposition under different conditions. In acidic and neutral solutions, PFOA predominantly decomposes via the direct photolysis in both atmospheres; while in the alkaline solution and in the absence of oxygen, the decomposition of PFOA is mainly induced by hydrated electrons.

关键词： Perfluorocarboxylic acids （PFCAs）185 nm vacuum ultraviolet Persistent organic pollutants Photochemical Perfluorinated compounds

Photochemical decomposition of 1H,1H,2H,2H-perfluorooctane sulfonate(6:2FTS)induced by ferric ions

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Journal of Environmental Sciences 2017年第1期29卷 120-127页

作者： Ling Jin Chuanjia Jiang pengyi zhang State Key Joint Laboratory of Environment Simulation and Pollution Control School of EnvironmentTsinghua UniuersityBeijing 100084China.

Perfluorooctane sulfonate（PFOS） had wide applications,such as in the electroplating industry,but its use was restricted in 2009 by the Stockholm Convention,due to its environmental persistence and potential hazards.As the most common PFOS alternative,lH,lH,2H,2H-perfluorooctane sulfonic acid（6：2FTS） and its salts have been increasingly used.However,little is known about its photochemical decomposition.This paper reports the ferric ion-induced efficient decomposition and defluorination of 6：2FTS under 254 nm ultraviolet（UV） irradiation;the underlying mechanisms were also investigated.In the presence of 100 ｜imol/L ferric ion and at pH 3.0,the first-order decomposition rate constant of 6：2FTS（10 mg/L） was 1.59/hr,which was 6 times higher than for direct UV photolysis.The effects of the ferric ion concentration and the solution pH on the 6：2FTS photodecomposition were investigated and the optimal reaction conditions were determined.In addition to fluoride and sulfate ions,shorter-chain PFCAs（C2-C7） were detected as major intermediates.The addition of hydrogen peroxide or oxalic acid accelerated the decomposition of 6：2FTS under UV irradiation,but not its defluorination,indicating that hydroxyl radicals can directly react with 6：2FTS but not with the shorter-chain PFCAs.Accordingly,a mechanism for 6：2FTS photochemical decomposition in the presence of ferric ion was proposed,which comprises two reaction pathways.First,hydroxyl radicals can directly attack 6：2FTS,leading to C- C bond cleavage.Alternatively,6：2FTS coordinates with ferric ion to form Fe（III）-6：2FTS complexes,which can undergo ligand-to-metal charge transfer under UV irradiation,causing C-S bond cleavage.

关键词： 6：2 Fluorotelomer sulfonate（6：2FTS） Perfluorooctane sulfonate（PFOS） alternative Ferric ion Photodecomposition

Indoor carbonyl compounds in an academic building in Beijing, China： concentrations and influencing factors

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Frontiers of Environmental Science & Engineering 2012年第2期6卷 184-194页

作者： Chuanjia JIANG pengyi zhang State Key Joint Laboratory of Environmental Simulation and Pollution Control School of EnvironmentTsinghua UniversityBeijing 100084China

Carbonyl compounds in indoor air are of great concern for their adverse health effects. Between February and May, 2009, concentrations of 13 carbonyl compounds were measured in an academic building in Beijing, China. Total concentration of the detected carbonyls ranged from 20.7 to 189.1 μg·m , and among them acetone and formaldehyde were the most abundant, with mean concentrations of 26.4 and 22.6 μg·m , respectively. Average indoor concentrations of other carbonyls were below 10 μg·m . Principal component analysis identified a combined effect of common indoor carbonyl sources and ventilation on indoor carbonyl levels. Diurnal variations of the carbonyl compounds were investigated in one office room, and carbonyl concentrations tended to be lower in the daytime than at night, due to enhanced ventilation. Average concentrations of carbonyl compounds in the office room were generally higher in early May than in late February, indicating the influence of temperature. Carbonyl source emission rates from both the room and human occupants were estimated during two lectures, based on one-compartment mass balance model. The influence of human occupants on indoor carbonyl concentrations varies with environmental conditions, and may become significant in the case of a large human occupancy.

关键词： carbonyl compounds indoor air ventilation,human occupancy source emission rate （SER） principalcomponent analysis （PCA）

Catalytic decomposition of low level ozone with gold nanoparticles supported on activated carbon

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Frontiers of Environmental Science & Engineering 2009年第3期3卷 281-288页

作者： pengyi zhang Bo zhang Rui SHI Department of Environmental Science and Engineering Tsinghua UniversityBeijing 100084China

Highly dispersed gold nanoparticles were supported on coal-based activated carbon(AC)by a sol immobilization method and were used to investigate their catalytic activity for low-level ozone decomposition at ambient temperature.Nitrogen adsorption-desorption,scanning electron microscope(SEM),and X-ray photoelectron spectroscopy(XPS)were used to characterize the catalysts before and after ozone decomposition.The results showed that the supported gold nanoparticles prepared with microwave heating were much smaller and more uniformly dispersed on the activated carbon than those prepared with traditional conduction heating,exhibiting higher catalytic activity for ozone decomposition.The pH values of gold precursor solution significantly influenced the catalytic activity of supported gold for ozone decomposition,and the best pH value was 8.In the case of space velocity of 120000 h–1,inlet ozone concentration of 50 mg/m3,and relative humidity of 45%,the Au/AC catalyst maintained the ozone removal ratio at 90.7%after 2500 min.After being used for ozone decomposition,the surface carbon of the catalyst was partly oxidized and the oxygen content increased accordingly,while its specific surface area and pore volume only decreased a little.Ozone was mainly catalytically decomposed by the gold nanoparticles supported on the activated carbon.

关键词： ozone decomposition activated carbon gold nanoparticles catalysis sodium citrate microwave

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融合用户数据的高校图书馆书目系统设计

图书馆建设 2024年第1期 121-130,145页

作者：王一博张鹏翼北京大学信息管理系北京大学图书馆

融合图书馆用户数据、Web图书数据的新型高校图书馆书目系统分为数据准备和数据清洗、数据规范和数据集成、数据分析和结果呈现三个模块;用户数据源来自北京大学图书馆数据资源服务中心的用户及其行为数据和馆藏资源及其使用数据,Web数... 详细信息

融合图书馆用户数据、Web图书数据的新型高校图书馆书目系统分为数据准备和数据清洗、数据规范和数据集成、数据分析和结果呈现三个模块;用户数据源来自北京大学图书馆数据资源服务中心的用户及其行为数据和馆藏资源及其使用数据,Web数据源包括豆瓣读书数据、当当图书数据、京东图书数据以及中国知网引文数据;数据处理方法包括数据清洗、数据规范和数据集成;系统实现的三个关键技术为融合用户数据及内容的图书推荐方法、豆瓣读书笔记的摘要和关键词生成方法以及情感分析方法。该书目系统聚焦于解决书目信息单一的问题,通过集成和分析图书馆用户数据和Web图书数据,丰富书目信息的内容,为下一代图书馆书目系统的设计与实现提供了参考。

关键词：高校图书馆图书馆书目系统用户数据网络数据图书推荐

基于VUCA背景下中小企业供应链韧性的管理研究

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全国流通经济 2024年第5期 96-99页

作者：张鹏艺天津理工大学管理学院天津300384

在VUCA的环境下,企业面临着日益复杂和变化多端的外部环境,给企业的日常经营常常会带来各种问题。而中小企业在经济体系中占比最大,是国家经济的重要支柱,因此,研究如何保障中小企业的持续运作,对稳定整体经济环境具有重要的意义。本文... 详细信息

在VUCA的环境下,企业面临着日益复杂和变化多端的外部环境,给企业的日常经营常常会带来各种问题。而中小企业在经济体系中占比最大,是国家经济的重要支柱,因此,研究如何保障中小企业的持续运作,对稳定整体经济环境具有重要的意义。本文聚焦于中小企业,对其在建立韧性中遇到的挑战与阻碍进行了分析,主要归为五类:中小企业融资困境、中小企业获取资源的局限性、中小企业管理存在问题、中小企业创新动力不足、中小企业数字化应用程度不高。并且,以打破融资困境为第一要义,提出管理能力、创新能力两手抓,并积极引进数字化为应对策略,以期能够提升中小企业供应链韧性,为企业应对外部不确定性环境保驾护航。

关键词：中小企业供应链韧性管理研究

Identification and Analysis of Multi-tasking Product Information Search Sessions with Query Logs

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Journal of Data and Information Science 2016年第3期1卷 79-94页

作者： Xiang Zhou pengyi zhang Jun Wang Department of Information Management Peking University

Purpose： This research aims to identify product search tasks in online shopplng ana analyze the characteristics of consumer multi-tasking search sessions. Design/methodology/approach： The experimental dataset contains 8,949 queries of 582 users from 3,483 search sessions. A sequential comparison of the Jaccard similarity coefficient between two adjacent search queries and hierarchical clustering of queries is used to identify search tasks. Findings：（1） Users issued a similar number of queries （1.43 to 1.47） with similar lengths （7.3-7.6 characters） per task in mono-tasking and multi-tasking sessions, and （2） Users spent more time on average in sessions with more tasks, but spent less time for each task when the number of tasks increased in a session. Research limitations： The task identification method that relies only on query terms does not completely reflect the complex nature of consumer shopping behavior.Practical implications： These results provide an exploratory understanding of the relationships among multiple shopping tasks, and can be useful for product recommendation and shopping task prediction. Originality/value： The originality of this research is its use of query clustering with online shopping task identification and analysis, and the analysis of product search session characteristics.

关键词： Product search Shopping task identification Shopping task analysis Multi-tasking session