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Real-time porosity reduction during metal directed energy deposition using a pulse laser

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Journal of Materials Science & Technology 2022年第21期116卷 214-223页

作者： Hoon Sohn peipei liu Hansol Yoon Kiyoon Yi liu Yang Sangjun Kim Department of Civil and Environmental Engineering Korea Advanced Institute of Science and Technology(KAIST)Daejeon 34141Republic of Korea Center for 3D Printing Nondestructive Testing Korea Advanced Institute of Science and Technology(KAIST)Daejeon 34141Republic of Korea Global R&D Center SQ EngineeringSeoul 05818Republic of Korea Department of Civil and Environmental Engineering The Hong Kong University of Science and TechnologyClear Water BayKowloonHong KongChina

Porosity is a challenging issue in additive manufacturing and is detrimental to the quality of the additively manufactured products.In this study,a real-time porosity reduction technique was developed by incorporating a pulse laser into a laser metal powder directed energy deposition(DED)system.The incorporated pulse laser can accelerate fluid flow within the melt pool and facilitate the escape of pores before complete solidification.It achieves this real-time porosity reduction by inducing accelerated and turbulent Marangoni flow,ultrasonic waves,and shock waves into the melt pool.The uniqueness and advantages of the proposed technique include the following:(1)For a laser metal powder DED process,this study proposed a noncontact,nondestructive,and real-time porosity reduction technique at the melt pool level.(2)It was experimentally and numerically validated that the developed technique did not alter the geometry and the grain structure of the manufactured Ti-6Al-4V samples.(3)Because the porosity reduction is accomplished at the melt pool level,its application is not limited by the size,shape,or complexity of the printing target.(4)The developed technique can be readily incorporated into the existing DED systems without any modification of the original tool-path design.The experimental results showed that the pore volume fraction decreased from 0.132%to 0.005%,no pores larger than 6×10^(4)μm^(3) were observed,and a 91%reduction in the total pore number was achieved when the pulse laser energy reached 11.5 mJ.

关键词： Real-time porosity reduction Pulse laser Melt pool Directed energy deposition Ti-6Al-4V

Early embryonic transcriptomes of Zeugodacus tau provide insight into sex determination and differentiation genes

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Insect Science 2022年第3期29卷 915-931页

作者： peipei liu Wenping Zheng Jiao Qiao Ziniu Li Zhurong Deng Yimin Yuan Hongyu Zhang Key Laboratory of Horticultural Plant Biology(MOE) Hubei Hongshan LaboratoryChina-Australia Joint Research Center for Horticultural and Urban PestsInstitute of Urban and Horticultural EntomologyCollege of Plant Science and TechnologyHuazhong Agricultural UniversityWuhanChina College of Environmental Design Wuhan Institute of Design and SciencesWuhanChina

Zeugodacus tau(Walker)is an invasive pest.The sterile insect technique is an environment-friendly method for pest control.Understanding the mechanism of sex determination will contribute to improving efficiency of this technique.In this study,we identified the transformer(tra)gene in Z.tau.One female-specific and two male-specific isoforms of tra were found in Z.tau,and the male-specific splicing pattern of tra was found to occur 5 h after egg laying.We performed transcriptome sequencing at 1 h(E1),5 h(E5),and 9 h(E9)after egg laying and obtained high-quality transcriptome libraries of early embryo development.We identified 13297 and 11713 differentially expressed genes(DEGs)from E5 versus E1 and E9 versus E1 comparisons,respectively.To explore the potential functions of the DEGs during embryonic development,Gene Ontology,Clusters of Orthologous Groups of proteins,and Kyoto Encyclopedia of Genes and Genomes analyses were performed.Twenty-six genes potentially involved in sex determination or differentiation,including Maleness-on-the-Y(MoY),were identified in Z.tau.To verify the transcriptome results,15 genes were selected for quantitative real-time PCR validation.The results were consistent with the transcriptome sequencing results.Moreover,U2 small nuclear riboprotein auxiliary factor(U2AF-50),female lethal d(fl(2)d),and virilizer(vir)were highly expressed at E5,indicating that they may be related to the sex-specific splicing of tra.Further functional analysis is needed to confirm this speculation.Our data provide an insight into the mechanism underlying sex determination and differentiation in tephritid species.

关键词： RNA-Seq sex determination sex differentiation transformer Zeugodacus tau

An adjusted ELISpot-based immunoassay for evaluation of SARS-CoV-2-specific T-cell responses

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Biosafety and Health 2022年第3期4卷 179-185页

作者： Hao Lin Jie Zhang Shaobo Dong Yaning liu peipei liu George F.Gao William J.liu Guizhen Wu National Health Commission Key Laboratory of Biosafety Research Units of Adaptive Evolution and Control of Emerging VirusesChinese Academy of Medical SciencesNational Institute for Viral Disease Control and PreventionChinese Center for Disease Control and Prevention(China CDC)Beijing 102206China Macheng Center for Disease Control and Prevention Huanggang 438300China Center for Biosafety Mega-Science Chinese Academy of SciencesWuhan 430071China

Like antibody evaluation,using an effective antigen‐specific T‐cell immunity assessment method in coronavirus disease 2019(COVID‐19)patients,survivors and vaccinees is crucial for understanding the immune persistence,prognosis assessment,and vaccine development for COVID‐19.This study evaluated an empirically adjusted enzyme‐linked immunospot assay for detecting severe acute respiratory syndrome coronavirus 2(SARS‐CoV‐2)‐specific T‐cell immunity in 175 peripheral blood samples from COVID‐19 convalescents and healthy individuals.Results of viral nucleic acid were used as the gold standard of infection confirmation.The SARS‐CoV‐2M peptide pool had higher sensitivity of 85%and specificity of 71%for the single peptide pool.For combined peptide pools,the parallel evaluation(at least one of the peptide pools is positive)of total peptide pools(S1&S2&M&N)had higher sensitivity(up to 93%),and the serial evaluation(all peptide pools are positive)of total peptide pools had higher specificity(up to 100%).The result of the serial evaluation was better than that of the parallel evaluation as a whole.The detection efficiency of M and N peptide pool serial evaluation appeared the highest,with a sensitivity of 80%and specificity of 93%.This T‐cell immunity detection assay introduced in this report can achieve high operability and applicability.Therefore,it can be an effective SARS‐CoV‐2‐specific cellular immune function evaluation method.

关键词： SARS‐CoV‐2 COVID‐19 T‐cell response ELISpot assay Sensitivity Specificity

The genomic characteristics and pathogenicity of a mammalian orthoreovirus within a new lineage from wild pika in plateau

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Virologica Sinica 2023年第6期38卷 877-888页

作者： Kexin Zong Yuanyuan Guo Jingdong Song Maoshun liu Junfeng Hao Jie Zhang Xin Li Shiyan Zhu Shuting Huo Ziqian Xu peipei liu Yingze Zhao Yuhai Bi Jiapeng Qu George F.Gao Jun liu School of Laboratory Medicine and Life Sciences Wenzhou Medical UniversityWenzhou325035China NHC Key Laboratory of Biosafety National Institute for Viral Disease Control and PreventionChinese Center for Disease Control and Prevention(China CDC)Beijing102206China Laboratory Animal Center Institute of BiophysicsChinese Academy of SciencesBeijing100101China CAS Key Laboratory of Pathogen Microbiology and Immunology Institute of MicrobiologyChinese Academy of SciencesBeijing100101China Northwest Institute of Plateau Biology Chinese Academy of SciencesXining810001China Research Unit of Adaptive Evolution and Control of Emerging Viruses(2018RU009) Chinese Academy of Medical SciencesBeijing100021China

Emerging and re-emerging viruses from wild animals have seriously threatened the health of humans and domesticated animals in recent years.Herein,we isolated a new mammalian orthoreovirus(MRV),Pika/MRV/GCCDC7/2019(PMRV-GCCDC7),in the Qinghai-Tibet Plateau wild pika(Ochotona curzoniae).Though the PMRVGCCDC7 shows features of a typical reovirus with ten gene segments arranged in 3:3:4 in length,the virus belongs to an independent evolutionary branch compared to other MRVs based on phylogenetic tree analysis.The results of cellular susceptibility,species tropism,and replication kinetics of PMRV-GCCDC7 indicated the virus could infect four human cell lines(A549,Huh7,HCT,and LoVo)and six non-human cell lines,including Vero-E6,LLCMK2,BHK-21,N2a,MDCK,and RfKT cell,derived from diverse mammals,i.***.monkey,mice,canine and bat,which revealed the potential of PMRV-GCCDC7 to infect a variety of hosts.Infection of BALB/c mice with PMRVGCCDC7 via intranasal inoculation led to relative weight loss,lung tissue damage and inflammation with the increase of virus titer,but no serious respiratory symptoms and death occurred.The characterization of the new reovirus from a plateau-based wild animal has expanded our knowledge of the host range of MRV and provided insight into its risk of trans-species transmission and zoonotic diseases.

关键词： Plateau pika Mammalian orthoreovirus(MRV) Emerging viruses Genomic characteristics Cellular tropism and pathogenicity

DNA cytosine methylation dynamics and functional roles in horticultural crops

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Horticulture Research 2023年第10期10卷 273-283页

作者： peipei liu Ruie liu Yaping Xu Caixi Zhang Qingfeng Niu Zhaobo Lang National Engineering Laboratory of Crop Stress Resistance Breeding School of Life SciencesAnhui Agricultural UniversityHefei230036China School of Agriculture and Biology Shanghai Jiao Tong UniversityShanghai 200240China Shanghai Center for Plant Stress Biology National Key Laboratory of Plant Molecular GeneticsCenter for Excellence in Molecular Plant SciencesChinese Academy of SciencesShanghai 201602China Institute of Advanced Biotechnology School of Life SciencesSouthern University of Science and TechnologyShenzhen 518055China

Methylation of cytosine is a conserved epigenetic modification that maintains the dynamic balance of methylation in plants under the regulation of methyltransferases and demethylases.In recent years,the study of DNA methylation in regulating the growth and development of plants and animals has become a key area of research.This review describes the regulatory mechanisms of DNA cytosine methylation in plants.It summarizes studies on epigenetic modifications of DNA methylation in fruit ripening,development,senescence,plant height,organ size,and under biotic and abiotic stresses in horticultural crops.The review provides a theoretical basis for understanding the mechanisms of DNA methylation and their relevance to breeding,genetic improvement,research,innovation,and exploitation of new cultivars of horticultural crops.

关键词： crops maintain breeding

Research Article Core/hybrid-shell structures boost thermoelectric performance of flexible inorganic/organic nanowire films

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Nano Research 2023年第4期16卷 5702-5708页

作者： Changcun Li Xiaoqi Lan peipei liu Jingkun Xu Qinglin Jiang Congcong liu Cheng liu Fengxing Jiang Jiangxi Key Laboratory of Flexible Electronics Jiangxi Science and Technology Normal UniversityNanchang 330013China School of Optoelectronic Science and Engineering University of Electronic Science and Technology of ChinaChengdu 610054China Institute of Polymer Optoelectronic Materials and Devices State Key Laboratory of Luminescent Materials and DevicesSouth China University of TechnologyGuangzhou 510640China

Interface control in inorganic/organic composites has always been regarded as one of the effective means to optimize their thermoelectric(TE)performance,and the past few years have witnessed its development,including carrier-energy filtering and phonon scattering.However,the energy barrier created by the band alignment at the composite interface depends on the Fermi level difference between the organic and inorganic components,which is difficult to be controlled by the common means.Herein,a core/hybrid-shell strategy aiming for efficient interface control is proposed to tune the energy barrier of the inorganic/organic core/shell nanowire interface.The Fermi level of hybrid-shell can be effectively controlled by separating the charge carriers compared to the single-shell composites.The energy barrier of the core/hybrid-shell interface is tuned to an appropriate position,and the energy filtering effect is utilized,resulting in a substantial improvement in power factor and reduction in thermal conductivity for the prepared core/hybrid-shell composites with good air-stability and flexibility.Moreover,both the flexible p type and p-n type TE devices based on the prepared core/hybrid-shell films yield excellent output properties with the maximum power densities of 41 and 45μW·cm^(−2)at a temperature difference of ca.30 K,respectively.This study provides a novel strategy to improve the TE performance of the inorganic/organic composites,displaying great potential for low-power wearable electronics.

关键词： hybrid-shell nanowires surface modification thermoelectric materials flexible electronics

Social engineering in cybersecurity:a domain ontology and knowledge graph application examples

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Cybersecurity 2021年第1期4卷 480-500页

作者： Zuoguang Wang Hongsong Zhu peipei liu Limin Sun School of Cyber Security University of Chinese Academy of SciencesBeijing 100049China Beijing Key Laboratory of IoT Information Security Technology Institute of Information EngineeringChinese Academy of Sciences(CAS)Beijing 100093China

Social engineering has posed a serious threat to cyberspace security.To protect against social engineering attacks,a fundamental work is to know what constitutes social engineering.This paper first develops a domain ontology of social engineering in cybersecurity and conducts ontology evaluation by its knowledge graph application.The domain ontology defines 11 concepts of core entities that significantly constitute or affect social engineering domain,together with 22 kinds of relations describing how these entities related to each other.It provides a formal and explicit knowledge schema to understand,analyze,reuse and share domain knowledge of social engineering.Furthermore,this paper builds a knowledge graph based on 15 social engineering attack incidents and scenarios.7 knowledge graph application examples(in 6 analysis patterns)demonstrate that the ontology together with knowledge graph is useful to 1)understand and analyze social engineering attack scenario and incident,2)find the top ranked social engineering threat elements(e.***.the most exploited human vulnerabilities and most used attack mediums),3)find potential social engineering threats to victims,4)find potential targets for social engineering attackers,5)find potential attack paths from specific attacker to specific target,and 6)analyze the same origin attacks.

关键词： Social engineering attack Cyber security Ontology Knowledge graph Attack scenarios Threat analysis Attack path Attack model Taxonomy Composition and structure

Partition region-based suppressed fuzzy C-means algorithm

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Journal of Systems Engineering and Electronics 2017年第5期28卷 996-1008页

作者： Kun Zhang Weiren Kong peipei liu Jiao Shi Yu Lei Jie Zou Min liu School of Electronics and Information Northwestern Polytechnical University Science and Technology on Electro-Optic Control Laboratory

Aimed at the problem that the traditional suppressed fuzzy C-means clustering algorithms ignore the real needs of different objects, applying the same suppressed parameter for modifying membership degrees of all the objects, a novel partition region-based suppressed fuzzy C-means clustering algorithm with better capacity of adaptability and robustness is proposed in this paper. The model based on the real needs of different objects is built, making it clear to decide whether to proceed with further determination; in addition, the external user-defined suppressed parameter is automatically selected according to the intrinsic structural characteristic of each dataset, making the proposed method become robust to the fluctuations in the incoming dataset and initial conditions. Experimental results show that the proposed method is more robust than its counterparts and overcomes the weakness of the original suppressed clustering algorithm in most cases.

关键词： shadowed set suppressed fuzzy C-means clustering automatically parameter selection soft computing techniques

Mammalian mitochondrial RNAs are degraded in the mitochondrial intermembrane space by RNASET2

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Protein & Cell 2017年第10期8卷 735-749页

作者： peipei liu Jinliang Huang Qian Zheng Leiming Xie Xinping Lu Jie Jin Geng Wang MOE Key laboratory of Bioinformatics Cell Biology and Development Center School of Life Sciences Tsinghua University Beijing 100084 China

Mammalian mitochondrial genome encodes a small set of tRNAs, rRNAs, and mRNAs. The RNA synthesis process has been well characterized. How the RNAs are degraded, however, is poorly understood. It was long assumed that the degradation happens in the matrix where transcription and translation machineries reside. Here we show that contrary to the assumption, mammalian mitochondrial RNA degradation occurs in the mitochondrial intermembrane space （IMS） and the IMS- localized RNASET2 is the enzyme that degrades the RNAs. This provides a new paradigm for understanding mitochondrial RNA metabolism and transport.

关键词： mitochondria intermembrane space ribonuclease mtRNA RNA degradation decay RNASET2 RNase T2 inner membrane transport RNA trafficking