The nano-iron nitride soft magnetic material has excellent magnetic properties and is expected to be a brilliant electromagnetic wave absorber.However,how to fully exploit its wave-absorbing potential re-mains a thoug...The nano-iron nitride soft magnetic material has excellent magnetic properties and is expected to be a brilliant electromagnetic wave absorber.However,how to fully exploit its wave-absorbing potential re-mains a thought-provoking question.Here,we have synthesized Fe/Fe_(4)N@SiO_(2)nanomagnetic core-shell materials with different Fe/Fe_(4)N ratios by performing nitridation reactions at different temperatures.Then,the flower-like core-shell Fe/Fe_(4)N@SiO_(2)structure was obtained by the etching method.Finally,with the synergy of the excellent magnetic and dielectric losses,an outstanding absorption performance could be achieved with a minimum refection loss(RL min)of−71.31 dB at the matching thickness of 1.4 mm,and the widest effective absorption bandwidth(EAB max)of 6.1 GHz less than−10 dB was realized at 1.16 mm.Moreover,this material also shows a preeminent advance in corrosion resistance to adapt to harsh environments.Hence,this iron nitride flower-like core-shell structure exhibits great potential in microwave absorption in harsh conditions.展开更多
For long-distance water conveyance shield tunnels in operation,the high internal water pressure may cause excessive deformation of composite linings,affecting their structural integrity and serviceability.However,the ...For long-distance water conveyance shield tunnels in operation,the high internal water pressure may cause excessive deformation of composite linings,affecting their structural integrity and serviceability.However,the deformation and failure characteristics of lining structures under internal water pressure are not well investigated in the literature,particularly for three-layer composite linings.This study presents an in situ experimental investigation on the response of two types of composite linings(i.e.separated and combined lining structures)subjected to internal pressures,in which a fiber optic nerve system(FONS)equipped with distributed strain and displacement sensing nerves was employed to monitor the performance of the two composite linings during testing.The experimental results clearly show that the damage of the tunnel lining under different internal pressures was mainly located in the self-compaction concrete layer.The separated lining structure responded more aggressively to the variations in internal pressures than the combined one.Moreover,two evaluation indices,i.e.radial displacement and effective stiffness coefficient,are proposed for describing the changes in the structural bearing performance.The effective stiffness coefficients of the two types of lining structures were reduced by 39.4%and 29.5%,respectively.Considering the convenience of field monitoring,it is suggested that the average strains at different layers can be used as characteristic parameters for estimating the health conditions of lining structures in service.The analysis results provide a practical reference for the design and health evaluation of water conveyance shield tunnels with composite linings.展开更多
The aquatic grass Zizania latifolia grows symbiotically with the fungus Ustilago esculenta producing swollen structures called Jiaobai,widely cultivated in China.A new disease of Z.latifolia was found in Zhejiang Prov...The aquatic grass Zizania latifolia grows symbiotically with the fungus Ustilago esculenta producing swollen structures called Jiaobai,widely cultivated in China.A new disease of Z.latifolia was found in Zhejiang Province,China.Initial lesions appeared on the leaf sheaths or sometimes on the leaves near the leaf sheaths.The lesions extended along the axis of the leaf shoots and formed long brown to dark brown streaks from the leaf sheath to the leaf,causing sheath rot and death of entire leaves on young plants.The pathogen was isolated and identified as the bacterium Pantoea ananatis,based on 16 S ribosomal RNA(r RNA)gene sequencing,multilocus sequence analysis(atp D(β-subunit of ATP synthase F1),gyr B(DNA gyrase subunit B),inf B(translation initiation factor 2),and rpo B(β-subunit of RNA polymerase)genes),and pathogenicity tests.Ultrastructural observations using scanning electron microscopy revealed that the bacterial cells colonized the vascular tissues in leaf sheaths,forming biofilms on the inner surface of vessel walls,and extended between vessel elements via the perforated plates.To achieve efficient detection and diagnosis of P.ananatis,species-specific primer pairs were designed and validated by testing closely related and unrelated species and diseased tissues of Z.latifolia.This is the first report of bacterial sheath rot disease of Z.latifolia caused by P.ananatis in China.展开更多
Sm_2 Fe_(17) prepared by reduction-diffusion method needs to be washed with water to remove calcium oxide. Electrochemical corrosion occurs when Sm_2 Fe_(17) powder is in contact with liquid water. Corrosion mechanism...Sm_2 Fe_(17) prepared by reduction-diffusion method needs to be washed with water to remove calcium oxide. Electrochemical corrosion occurs when Sm_2 Fe_(17) powder is in contact with liquid water. Corrosion mechanism of H_2 O on Sm_2 Fe_(17) powder and nitrogenation process of corroded Sm_2 Fe_(17) were studied by analyzing the structure and morphology. It is indicated that the metallic hydroxide forms and deposits on the Sm_2 Fe_(17) powder surfaces during water corrosion. At the same time, oxygen and hydrogen enter the unit cell of Sm2 Fe_(17), causing a slight increase in Curie temperature. In the subsequent nitriding process,the hydroxide is dehydrated and hydrogen is desorbed. The resulting oxide reacts with Sm_2 Fe_(17)N_x to form a-Fe and Sm_2 O_3. Thermodynamic calculations using the HSC Chemistry 6.0 software indicate that the reaction can occur spontaneously. The effect of water corrosion on the magnetic properties of the nitride can be eliminated by hydrogen reduction prior to nitriding.展开更多
Replacement of samarium(Sm) with abundant yttrium(Y) can help solve the potential shortage of Sm in the preparation of promising Sm2 Fe17 Nx magnets.In this article,phase composition,microstructure and magnetic proper...Replacement of samarium(Sm) with abundant yttrium(Y) can help solve the potential shortage of Sm in the preparation of promising Sm2 Fe17 Nx magnets.In this article,phase composition,microstructure and magnetic properties of(Sm1-yYy)2 Fe17Nx(y=0,0.2,0.4,0.6,0.8,1.0) were investigated.Maximum energy product(BH)max is improved when less than 40 at% Y is doped in(Sm1-yYy)2 Fe17Nx powder.In particular,when 20 at% Y replaces Sm,(BH)max of(Sm1-yYy)2 Fe17Nx powder increases by 15.1% from 131.7 to151.6 kJ/m3.The effect of annealing temperature on the structural properties of high Y doping(Sm0.6Y0.4)2 Fe17 and the magnetic properties of the corresponding nitrides were subsequently investigated.In the RE2 Fe17 phase grain combination process,the interlaced structure of the rhombohedral Th2 Zn17-type structural phase and the hexagonal Th2 Ni17-type structural phase is formed.Due to shortrange exchange coupling,the nitride with the highest content of two interlaced RE2 Fe17 phases has the highest magnetic properties:Br=1.23 T,HcJ=443.9 kA/m and(BH)max=197.6 kJ/m3.展开更多
[Objectives]The infection symptoms of cyst nematodes were found in Yuexi, Sichuan. In order to identify the pathogen, the isolated nematodes were identified by morphology and molecular biology. [Methods] The potato ro...[Objectives]The infection symptoms of cyst nematodes were found in Yuexi, Sichuan. In order to identify the pathogen, the isolated nematodes were identified by morphology and molecular biology. [Methods] The potato roots and soil around the roots were collected, the nematodes in the roots were stained and observed, and the cysts were separated by the simple floating method. The second-stage juveniles(J2 s), females and cysts were found, and they were photographed and morphologically measured. The DNA of cysts and J2 s were extracted and identified by species-specific PCR. The DNA sequences of 18 S gene, 28 S D2-D3 region and ITS region in ribosomal DNA were obtained. Sequences of some cyst nematode species were downloaded from GenBank for sequence alignment, and MrBayes 3.2.3 software was used to construct a Bayesian phylogenetic tree. [Results] The nematodes could invade hosts’ root system. The basal knobs of J2 s was nearly round and inclined backward;the average length of the stylet was shorter than 23 μm;the Granek ratio of cysts was greater than or equal to 3, which is highly consistent with that of Globodera rostochiensis. The DNA templates of three cysts and four J2 s were amplified by species-specific PCR, and a band of about 430 bp was obtained. After further sequencing, the length was 434 bp, which is consistent with G. rostochiensis. The evolutionary analysis of rDNA 18 S and 28 S showed that the cyst nematode population was a Globodera species, and further evolutionary analysis of ITS gene confirmed that the population was G. rostochiensis. [Conclusions] The nematodes are G. rostochiensis, which is a quarantine species of great concern to both domestic and import quarantine. Once introduced and colonized, it is hard to eradicate. It is necessary to establish a monitoring system as soon as possible, strengthen the quarantine, supervision and management, increase investment in G. rostochiensis research and development, and develop detection and control technologies, so as to escort the healthy and su展开更多
为缓解基站的视频流量过载,本文针对时延敏感的实时视频业务,设计一种D2D协作视频多播传输方案。该方案采用可伸缩视频编码(Scalable Video Coding, SVC)对视频流进行编码处理,利用SVC流的分层结构特征来应对多播信道间的差异性。在SVC...为缓解基站的视频流量过载,本文针对时延敏感的实时视频业务,设计一种D2D协作视频多播传输方案。该方案采用可伸缩视频编码(Scalable Video Coding, SVC)对视频流进行编码处理,利用SVC流的分层结构特征来应对多播信道间的差异性。在SVC编码的基础上,为了改善用户观看体验及提升用户所接收的视频质量,所提出的协作式视频传输方案引入有效吞吐量这一概念,在一定时延约束下,根据信道反馈信息灵活地对不同信道上的不同SVC视频层进行码率调整。仿真结果表明,所提出的方案能够有效地减小端到端时延,有效丢失率,提高有效吞吐量。展开更多
基金supported by the National Natural Science Foun-dation of China(Nos.52071294 and U1809215)Natural Science Foundation of Zhejiang Province(Grant LY20E020015)National Key Research and Development Program(No.2019YFE012862).
文摘The nano-iron nitride soft magnetic material has excellent magnetic properties and is expected to be a brilliant electromagnetic wave absorber.However,how to fully exploit its wave-absorbing potential re-mains a thought-provoking question.Here,we have synthesized Fe/Fe_(4)N@SiO_(2)nanomagnetic core-shell materials with different Fe/Fe_(4)N ratios by performing nitridation reactions at different temperatures.Then,the flower-like core-shell Fe/Fe_(4)N@SiO_(2)structure was obtained by the etching method.Finally,with the synergy of the excellent magnetic and dielectric losses,an outstanding absorption performance could be achieved with a minimum refection loss(RL min)of−71.31 dB at the matching thickness of 1.4 mm,and the widest effective absorption bandwidth(EAB max)of 6.1 GHz less than−10 dB was realized at 1.16 mm.Moreover,this material also shows a preeminent advance in corrosion resistance to adapt to harsh environments.Hence,this iron nitride flower-like core-shell structure exhibits great potential in microwave absorption in harsh conditions.
基金This work was financially supported by the National Natural Science Foundation of China(Grant Nos.42225702 and 42077235)the Postgraduate Research&Practice Innovation Program of Jiangsu Province,China(Grant No.KYCX22_0162)the scientific research project of Guangdong Yue Hai Pearl River Delta Water Supply Co.,Ltd.The authors thank Guangqing Wei,Lixiang Jia,and Zhen Zhang,all of Suzhou Nanzee Sensing Co.,Ltd.,for their assistance in the tests.The valuable suggestions provided by Professor Baojun Wang,Nanjing University,are also gratefully acknowledged.
文摘For long-distance water conveyance shield tunnels in operation,the high internal water pressure may cause excessive deformation of composite linings,affecting their structural integrity and serviceability.However,the deformation and failure characteristics of lining structures under internal water pressure are not well investigated in the literature,particularly for three-layer composite linings.This study presents an in situ experimental investigation on the response of two types of composite linings(i.e.separated and combined lining structures)subjected to internal pressures,in which a fiber optic nerve system(FONS)equipped with distributed strain and displacement sensing nerves was employed to monitor the performance of the two composite linings during testing.The experimental results clearly show that the damage of the tunnel lining under different internal pressures was mainly located in the self-compaction concrete layer.The separated lining structure responded more aggressively to the variations in internal pressures than the combined one.Moreover,two evaluation indices,i.e.radial displacement and effective stiffness coefficient,are proposed for describing the changes in the structural bearing performance.The effective stiffness coefficients of the two types of lining structures were reduced by 39.4%and 29.5%,respectively.Considering the convenience of field monitoring,it is suggested that the average strains at different layers can be used as characteristic parameters for estimating the health conditions of lining structures in service.The analysis results provide a practical reference for the design and health evaluation of water conveyance shield tunnels with composite linings.
基金supported by the Key Project of National Natural Science Foundation of China(NSFC)Regional Innovation and Development Joint Foundation(No.U20A2043)the NSFC(No.31501342)。
文摘The aquatic grass Zizania latifolia grows symbiotically with the fungus Ustilago esculenta producing swollen structures called Jiaobai,widely cultivated in China.A new disease of Z.latifolia was found in Zhejiang Province,China.Initial lesions appeared on the leaf sheaths or sometimes on the leaves near the leaf sheaths.The lesions extended along the axis of the leaf shoots and formed long brown to dark brown streaks from the leaf sheath to the leaf,causing sheath rot and death of entire leaves on young plants.The pathogen was isolated and identified as the bacterium Pantoea ananatis,based on 16 S ribosomal RNA(r RNA)gene sequencing,multilocus sequence analysis(atp D(β-subunit of ATP synthase F1),gyr B(DNA gyrase subunit B),inf B(translation initiation factor 2),and rpo B(β-subunit of RNA polymerase)genes),and pathogenicity tests.Ultrastructural observations using scanning electron microscopy revealed that the bacterial cells colonized the vascular tissues in leaf sheaths,forming biofilms on the inner surface of vessel walls,and extended between vessel elements via the perforated plates.To achieve efficient detection and diagnosis of P.ananatis,species-specific primer pairs were designed and validated by testing closely related and unrelated species and diseased tissues of Z.latifolia.This is the first report of bacterial sheath rot disease of Z.latifolia caused by P.ananatis in China.
基金Project supported by Natural Science Foundation of Ningbo,China(2017A610079)Technology Innovation&Achievement Industrialization Project of Ningbo China(2014B11010)
文摘Sm_2 Fe_(17) prepared by reduction-diffusion method needs to be washed with water to remove calcium oxide. Electrochemical corrosion occurs when Sm_2 Fe_(17) powder is in contact with liquid water. Corrosion mechanism of H_2 O on Sm_2 Fe_(17) powder and nitrogenation process of corroded Sm_2 Fe_(17) were studied by analyzing the structure and morphology. It is indicated that the metallic hydroxide forms and deposits on the Sm_2 Fe_(17) powder surfaces during water corrosion. At the same time, oxygen and hydrogen enter the unit cell of Sm2 Fe_(17), causing a slight increase in Curie temperature. In the subsequent nitriding process,the hydroxide is dehydrated and hydrogen is desorbed. The resulting oxide reacts with Sm_2 Fe_(17)N_x to form a-Fe and Sm_2 O_3. Thermodynamic calculations using the HSC Chemistry 6.0 software indicate that the reaction can occur spontaneously. The effect of water corrosion on the magnetic properties of the nitride can be eliminated by hydrogen reduction prior to nitriding.
基金Project supported by State Key Laboratory of Rare Earth Permanent Magnetic Materials (SKLREPM17OF06)National Natural Science Foundation of China (U1802254+1 种基金51871201)Xinmiao Talent Planning of Zhejiang Province (2019R403055)。
文摘Replacement of samarium(Sm) with abundant yttrium(Y) can help solve the potential shortage of Sm in the preparation of promising Sm2 Fe17 Nx magnets.In this article,phase composition,microstructure and magnetic properties of(Sm1-yYy)2 Fe17Nx(y=0,0.2,0.4,0.6,0.8,1.0) were investigated.Maximum energy product(BH)max is improved when less than 40 at% Y is doped in(Sm1-yYy)2 Fe17Nx powder.In particular,when 20 at% Y replaces Sm,(BH)max of(Sm1-yYy)2 Fe17Nx powder increases by 15.1% from 131.7 to151.6 kJ/m3.The effect of annealing temperature on the structural properties of high Y doping(Sm0.6Y0.4)2 Fe17 and the magnetic properties of the corresponding nitrides were subsequently investigated.In the RE2 Fe17 phase grain combination process,the interlaced structure of the rhombohedral Th2 Zn17-type structural phase and the hexagonal Th2 Ni17-type structural phase is formed.Due to shortrange exchange coupling,the nitride with the highest content of two interlaced RE2 Fe17 phases has the highest magnetic properties:Br=1.23 T,HcJ=443.9 kA/m and(BH)max=197.6 kJ/m3.
基金Supported by Sichuan Science and Technology Program (2021YFN0009)Science and Technology Project of General Administration of Customs(2020HK161)+1 种基金Key Project of Ningbo Public Welfare Science and Technology Program (2021S024)Technology Development Project of Ningbo Joysun Product Testing Service Company (2020ZS003)。
文摘[Objectives]The infection symptoms of cyst nematodes were found in Yuexi, Sichuan. In order to identify the pathogen, the isolated nematodes were identified by morphology and molecular biology. [Methods] The potato roots and soil around the roots were collected, the nematodes in the roots were stained and observed, and the cysts were separated by the simple floating method. The second-stage juveniles(J2 s), females and cysts were found, and they were photographed and morphologically measured. The DNA of cysts and J2 s were extracted and identified by species-specific PCR. The DNA sequences of 18 S gene, 28 S D2-D3 region and ITS region in ribosomal DNA were obtained. Sequences of some cyst nematode species were downloaded from GenBank for sequence alignment, and MrBayes 3.2.3 software was used to construct a Bayesian phylogenetic tree. [Results] The nematodes could invade hosts’ root system. The basal knobs of J2 s was nearly round and inclined backward;the average length of the stylet was shorter than 23 μm;the Granek ratio of cysts was greater than or equal to 3, which is highly consistent with that of Globodera rostochiensis. The DNA templates of three cysts and four J2 s were amplified by species-specific PCR, and a band of about 430 bp was obtained. After further sequencing, the length was 434 bp, which is consistent with G. rostochiensis. The evolutionary analysis of rDNA 18 S and 28 S showed that the cyst nematode population was a Globodera species, and further evolutionary analysis of ITS gene confirmed that the population was G. rostochiensis. [Conclusions] The nematodes are G. rostochiensis, which is a quarantine species of great concern to both domestic and import quarantine. Once introduced and colonized, it is hard to eradicate. It is necessary to establish a monitoring system as soon as possible, strengthen the quarantine, supervision and management, increase investment in G. rostochiensis research and development, and develop detection and control technologies, so as to escort the healthy and su
文摘为缓解基站的视频流量过载,本文针对时延敏感的实时视频业务,设计一种D2D协作视频多播传输方案。该方案采用可伸缩视频编码(Scalable Video Coding, SVC)对视频流进行编码处理,利用SVC流的分层结构特征来应对多播信道间的差异性。在SVC编码的基础上,为了改善用户观看体验及提升用户所接收的视频质量,所提出的协作式视频传输方案引入有效吞吐量这一概念,在一定时延约束下,根据信道反馈信息灵活地对不同信道上的不同SVC视频层进行码率调整。仿真结果表明,所提出的方案能够有效地减小端到端时延,有效丢失率,提高有效吞吐量。
