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  • Influence of raindrop impact load on dynamic response of transmission tower line system in different wind fields

    Subjects: Mechanics >> Other Disciplines of Mechanics submitted time 2024-04-19 Cooperative journals: 《应用力学学报》

    Abstract:
    The damage of transmission and transformation tower system under wind-rain coupling often attributes to wind load, ignoring the amplification effect of rain load coupling excitation. Based on the tensioning tower system model of a transmission line, the time-history loads of wind and rain in a normal weather field and a wet downburst field are simulated. The dynamic response analysis of the tower-line system is carried out. The results show that the rainfall has a significant impact on the response of the transmission tower-line system. With the increase of rainfall intensity, the response of the tower-line system increases obviously. Under the condition of extreme rainfall, the displacement of tower top in wet downburst field increased by 31.30% in X direction and 33.93% in Y direction, respectively. The displacement and acceleration power spectral density of the tower top increased significantly in both wind and rain fields,and the resonance response of the system was enhanced. The stress of the main material at the key position of the tower increased by 11.64% and 37.07%,respectively. In different wind fields, the increasing incentive effect of raindrop impact on tower-line system during heavy rainfall cannot be ignored.

  • 融媒体时代,电视新闻记者的提问技巧

    Subjects: Digital Publishing >> New Media submitted time 2023-10-08 Cooperative journals: 《中国传媒科技》

    Abstract:融媒体时代,新闻的传播方式和效率发生了很大的变化。网络的普及对电视新闻的发展带来很大的影响和冲击,信息传播呈现多样化的趋势。电视新闻的采访活动有着电视新闻采访的方式和特点。新闻现场采访过程中,记者的提问技巧对新闻采访的效果有着直接的影响。本文阐释了媒体深度融合与记者的使命和责任,探讨新闻采访现场记者如何进行提问、记者提问技巧以及提高新闻质量的途径,并就融媒体对电视传播的影响进行了分析,以期对新闻记者的采访活动有所帮助。

  • 儿童手势及其与学习的关系

    Subjects: Psychology >> Social Psychology submitted time 2023-03-28 Cooperative journals: 《心理科学进展》

    Abstract: Gestures are hand movements which are generated during communication or cognitive process and don’t act on the object directly. It has the mixed characteristics of concreteness and abstractness. On a continuum from action to abstraction, gestures are more abstract than action but still less abstract than verbal language. Gestures have the power not only to reflect the individual’s cognitive level, but also to change the individual’s cognitive level, and as a result, thus facilitating the learning of new knowledge. The classification of gestures is mainly divided from the perspectives of the source of gestures, the content of gestures, the intention of gestures, the matching between gestures and speech. According to the source of gestures, gestures can be divided into producing gestures and observing gestures. In terms of the content of gestures, the classic classification is McNeill’s (1992) elaboration on gesture’s classification, which divides gestures into four types: iconic gestures, deictic gestures, beat gestures and metaphoric gestures. The previous researches on children’s gestures mainly employ two experimental paradigms: laboratory experimental method and scenario experimental method. Between them, most of the studies use the laboratory experimental method, while a small number of studies use scenario experimental method, which is mostly used for the study of infant’s gestures development. In the aspect of the development of gestures, deictic gestures, iconic gestures, beat gestures and metaphoric gestures spontaneously occur at different time points in the process of children’s growth. Deictic gestures appear earliest and usually appear at around 12 months old, while metaphoric gestures appear the latest and usually appear after the children enter primary school. The developmental trends of different types of gestures are also distinguish. It is important to note that the advantage effect of gestures may occur earlier than the children’s spontaneous occurrence of gestures. Therefore, encouraging young children to use gestures may promote the development of gestures’ spontaneous occurrence. What’s more, encouraging particular types of gestures can even introduce new ideas into children’s repertoire. Both producing gestures and observing gestures can facilitate children’s vocabulary learning, speech expression, mathematical problem-solving, spatial learning and memory. That is to say, the self-producing gestures group perform better on the task than the non-producing gestures group, and the observing other people’s gestures group perform better on the task than the non-observing gestures group. However, the influence of gestures on speech comprehension has not reached a consistent conclusion, mainly because speech comprehension is affected by many factors, it needs to be considered in consideration of factors such as the type of gestures, difficulty level of tasks, and children’s age. In the process of children’s cognitive development, adults should pay attention to the phenomenon of “gesture-speech mismatches” which can give teachers and parents insight into the children’s cutting-edge thoughts, and actively guide the “implicit thoughts” expressed by gestures, so as to facilitate positive results of children’s learning and acquisition of new knowledge. Future research should continue to explore the following aspects. Firstly, factors such as culture and socio-economic status can be considered to investigate whether the occurrence time and developmental trends of gestures could be affected by these factors. The second is to compare the advantage effect of producing gestures and observing gestures in various learning fields. The third is to pay attention to the use of gestures among special children. The last is to focus on the advantage effect of gestures in the classroom teaching and family education.

  • Peri-perative nursing of a case of special abdominal aortic aneurysm treated by artery bypass graft surgery

    Subjects: Nursing >> Nursing submitted time 2022-11-06

    Abstract: This paper summarized the peri-operative nursing of a case of special abdominal aortic aneurysm treated by artery bypass graft surgery. Key issues of peri-perative nursing included pre-operative preparation, intra-operative cooperation, prevention of post-operative complications, psychological care, pain management and health guidance. Target nursing interventions should be carried out to ensure the success of artery bypass graft surgery and improve the post-operative recovery of the patient.

  • 中国社会智库的运营创新探析

    Subjects: Library Science,Information Science >> Information Science submitted time 2017-07-13 Cooperative journals: 《智库理论与实践》

    Abstract:[目的/意义]由于中外政治、经济和社会环境的不同,中国社会智库运营面临比发达国家智库更多的问题和挑战。如何在国内环境创新运营模式,是中国特色新型智库建设十分重要的一个方面。[方法/过程]本文通过对中外智库发展环境的对比,分析了中国社会智库创新运营模式的必要性和障碍,主要以中国典型社会智库——中国与全球化智库为例,探讨了中国社会智库在运营的创新策略。[结果/结论]本文总结出社会智库运营创新的五个方面,建议社会智库塑造研究核心竞争力,探索建立多元的收入机制,集聚国际化人才,重视社会传播和加强国际交流与合作。

  • 科技人才政策助推世界科技强国建设——以国际科技人才引进政策突破为例

    Subjects: Other Disciplines >> Synthetic discipline submitted time 2017-06-01 Cooperative journals: 《中国科学院院刊》

    Abstract:2016年5月,习近平总书记发出了“为建设世界科技强国而奋斗”的号召,并在“科技三会”上明确了“我国要建设世界科技强国,关键是要建设一支规模宏大、结构合理、素质优良的创新人才队伍”。近年来,我国相继出台各项政策以构建科技人才队伍。在引进全球科技人才方面,公安部在上海、北京、广东等地,依托对人才、企业、产业具有高度聚集效应和政策先行优势的中国(上海)自由贸易试验区、中关村国家自主创新示范区等园区推出了一系列政策,在聚集科技人才方面发挥了重要的作用。文章对科技人才、科技人才政策及其对世界科技强国的作用做了简单阐述,分析了我国国际科技人才出入境政策突破现状、国内外最新发展形势,提出了放宽外国留学生在华实习就业限制、吸引优秀留学人员回国创新创业、实施华裔卡制度吸引海外科技专业人士贡献力量、推动科技人才职业资格国际认证、进一步推动创新资源向国际开放、强化知识产权保护和服务等政策建议,以期助推我国世界科技强国建设。

  • The role of tumescent technique in stabilizing hemodynamics in early operation of massively burned patients

    Subjects: Medicine, Pharmacy >> Pharmacology submitted time 2023-11-12

    Abstract: Objective: To explore the clinical effect of tumescent technique in early operation of massively burned patients. Methods: A retrospective cohort study was conducted on 27 patients with large area burns accorded with the inclusive criteria and admitted from June 2019 to November 2022. Among them, 14 patients admitted from June 2021 to November 2022 were treated with intraoperative injection of tumescent fluid for hemostasis and were rolled in tumescent group, or observation group; 13 patients admitted from January 2019 to November 2021 were treated with tourniquet for hemostasis were rolled in tourniquet group, or control group. The operation time, blood loss, blood preparation, blood transfusion, preoperative and postoperative hemoglobin, intraoperative and postoperative blood pressure, heart rate, postoperative skin graft survival rate and other related indicators were compared between the two groups, and the clinical effects were observed. Results: There was no statistical difference in preoperative blood volume between the two groups (p > 0.05). The actual amount of blood transfusion in the observation group was less than that in the control group, and the difference was statistically significant (p < 0.05). The intraoperative blood loss and operation time in the observation group were significantly less than those in the control group, and the difference was statistically significant (P < 0.05). There was no statistical difference in preoperative and postoperative hemoglobin between the two groups (p > 0.05). The survival rate of skin grafting in the observation group were slightly higher than those in the control group, and the difference was statistically significant (P < 0.05). The vital signs of patients in the observation group were more stable than those in the control group, and the difference was statistically significant (P < 0.05). Conclusion: Tumescent technique can reduce the amount of intraoperative blood loss, shorten the operation time, improve the survival rate of postoperative skin grafting, and ensure the stability of intraoperative hemodynamics in early operation of massively burned patients.

  • An Analysison Provincial Medical Science Basic Research Competitiveness Based on the National Natural Science Foundation of China

    Subjects: Library Science,Information Science >> Library Science submitted time 2023-10-08 Cooperative journals: 《知识管理论坛》

    Abstract: [Purpose/significance] The National Natural Science Foundation of China (NSFC) is one of the most important channels to support basic research in China. Competition for funding by the NSFC has been a very important indicator to measure the basic research level of various province and scientific research institutions. [Method/process] By combing and analyzing the status quo of NSFC in medical science, it is helpful to narrow the provincial gap and improve the basic research of medical science in China. Based on the project information of NSFC and previous scholars’ research, the paper update the index of basic research competitiveness, and analyzes project number and project funding of medical science during 2006-2016. At the same time, the competitiveness of medical science basic research and its changing trend in 31 provinces of China are analyzed. [Result/conclusion] The result shows that, in recent years, China’s basic scientific research has greatly improved, but there is a large gap between the provinces.

  • 辩证领导行为及其对企业创新能力和绩效的影响: 一项基于中国传统文化的领导行为探究

    Subjects: Psychology >> Social Psychology submitted time 2023-03-27 Cooperative journals: 《心理学报》

    Abstract: Although the continuous spread of the pandemic and the rapid development of technology has brought challenges for top managers in China, the environmental uncertainty also offers an opportunity for them to practice and develop leadership skills. To answer what leadership behaviors will help top managers improve organizations’ adaptability and performance in a rapidly changing and complex environment, we developed a new leadership construct, namely, dialectical leadership behavior based on dialectical thinking rooted in the Chinese culture.Dialectical leadership behavior is characterized as a strategic leadership behavior including timely adapting organizational strategy and managerial practices to environmental changes, understanding and balancing between management contradictions, and holistically coordinating different departments and resources in organizations. According to upper echelon theory (Hambrick & Mason, 1984), CEOs’ leadership styles have a profound impact on the strategic choice and performance of the organization. We thus expect CEO dialectical leadership behavior to contribute to firm innovative capability and performance through strategic flexibility in a complex and uncertain business environment.To better understand dialectical leadership, we first developed and validated a scale. We found that dialectical leadership behavior was composed of six dimensions: timely adjusting, individualized mentoring, weighing contradictions, balancing kindness and strictness, promoting coordination, and holistically managing. We further distinguished dialectical leadership behavior from other related leadership constructs with theoretical and empirical efforts. Besides, as top managers of Chinese firms displayed a significantly higher dialectical leadership behavior than those of U.S. companies, the cultural uniqueness of dialectical leadership behavior was justified. Finally, we revealed that CEO dialectical leadership behavior in Chinese companies positively affected firm strategic flexibility and ultimately improved firm innovative capability and performance. We make several contributions. First, scholars constantly explore leadership constructs and practice based on the Western culture. However, the cultural difference between the East and the West matters when it comes to the effectiveness of leadership behaviors. Dialectical leadership behavior provides a new perspective for future exploration of indigenous leadership behaviors and influences by incorporating traditional wisdom of Eastern culture and the reality faced by Chinese enterprises. Second, by developing the measurement of dialectical leadership behavior, we contribute to the future investigation of dialectical leadership behavior and its correlations. Additionally, as we found that CEO dialectical leadership behavior is positively related to firm innovative capability and performance, which are critical for enterprises to survive and thrive during the crisis, we lend confidence in applying wisdom from the Chinese traditional culture to current management practice. Finally, by uncovering the role of firm strategic flexibility in mediating the influence of dialectical leadership behavior on firm innovative capability and performance, we extend understandings about the mechanism through which dialectical leadership behavior matters. We also provide the discussion on the limitation of the study and future research directions.

  • <p>Nursing experience of an elderly conscious patient with severe pneumonia and ARDS undergoing prone position ventilation</p>

    Subjects: Nursing >> Nursing submitted time 2023-08-28

    Abstract: Summarize the nursing experience of an elderly conscious patient with severe pneumonia and ARDS undergoing prone position ventilation. Severe pneumonia is a relatively serious respiratory system disease, and patients often suffer from acute respiratory distress syndrome (ARDS), which involves other organ systems and is prone to various complications. By summarizing the nursing experience of a patient with severe pneumonia and ARDS undergoing prone position ventilation, the aim is to explore its therapeutic effect and practical precautions. The patient recovered and was discharged after being hospitalized for 19 days. During a 3-month regular follow-up, the patient recovered well.

  • 基于T_NAG模型的攻击路径预测方法研究

    Subjects: Computer Science >> Integration Theory of Computer Science submitted time 2020-09-28 Cooperative journals: 《计算机应用研究》

    Abstract: In order to depict the attacker's attack trajectory better, this paper proposed a path prediction method based on T_NAG(time attribute network attack graph) model. First of all, proposed a new attack graph model T_NAG to distinguish the attacker's ability according to the real-time behavior trace. Secondly, according to the characteristics of the attacker's different capabilities, proposed the concept of attack intention, considered the operation risk and attack profit as a whole and introduced the time decay parameter into the intention calculation, and designed a vulnerability utilization quantification method based on the attacker's capabilities. Finally, further integrated attack intention and vulnerability utilization into the consideration of path reachability probability, and given the IntenAbi-PathPre algorithm to predict the attack path. The experimental results show that this method can effectively remove the redundancy in the attack graph and improve the accuracy of attack path prediction.

  • 环氧树脂复合泡沫塑料的制备及其拉压性能

    Subjects: Materials Science >> Materials Science (General) submitted time 2017-03-31 Cooperative journals: 《材料研究学报》

    Abstract:使用万能试验机对粉煤灰微珠/环氧树脂复合泡沫塑料进行拉伸和压缩实验,并用扫描电镜(SEM)观察 其断面形貌,研究了微珠含量、微珠粒径以及级配比例对复合泡沫塑料拉伸和压缩性能的影响。结果表明,随 着微珠含量的增加复合泡沫塑料的拉伸和压缩强度都表现出先升高后下降的趋势,且在填充量为 15phr 时达 到最大,其拉伸强度和压缩强度比纯环氧树脂分别提高了 9.15%和 6.86%。在填充量相同的条件下,微珠的粒 径越小复合泡沫塑料的拉伸和压缩强度越高。填充小粒径微珠(20 μm)比填充大粒径微珠(250 μm)复合泡沫 塑料的拉伸强度和压缩强度分别高 158.41%和 19.96%,拉伸模量和压缩模量分别高 32.77%和 73.59%。不同粒 径微珠级配填充环氧树脂复合泡沫塑料的拉伸和压缩性能主要受小粒径微珠含量的影响,小粒径微珠含量越 高其拉伸和压缩强度越高。

  • 模拟压水堆一回路条件添加Pt技术研究

    Subjects: Materials Science >> Materials Science (General) submitted time 2016-11-11 Cooperative journals: 《中国腐蚀与防护学报》

    Abstract:采用扫描电镜(SEM)、X射线光电子谱(XPS)、X射线衍射(XRD)和电感耦合等离子体原子发射光谱(ICP-AES)法并结合线性极化曲线方法研究了模拟压水堆一回路加氢水化学条件下预氧化的316LN不锈钢表面沉积贵金属Pt的方法及其对材料电化学行为的影响。预氧化膜实验和高温电化学实验条件为模拟反应堆一回路条件,贵金属沉积实验为模拟反应堆热停堆条件。结果表明,预氧化实验中,材料表面形成了双层氧化膜,外层为富Ni层,内层为富Cr层,与反应堆实际运行中材料表面产生的氧化膜结构和成分相似;在模拟热停堆实验条件下,用Na2Pt(OH)6配制含Pt量为0ppb,10ppb,50ppb,100ppb的溶液能够在316LN材料表面沉积达到目标要求的Pt;电化学实验表明Pt沉积量越多,材料的腐蚀电流密度变化很小,腐蚀电位急剧降低,说明材料抗腐蚀性能提高。

  • 304L在模拟压水堆一回路条件下长期均匀腐蚀性能研究

    Subjects: Materials Science >> Materials Science (General) submitted time 2016-11-09 Cooperative journals: 《中国腐蚀与防护学报》

    Abstract:摘要:在模拟压水堆一回路水条件下,用静态高压釜对304L不锈钢进行了1680h的腐蚀考验,对氧化膜进行了宏观和微观分析,对均匀腐蚀和均匀腐蚀速率进行了定量评估。结果表明:304L不锈钢在很短的时间内(14天)就形成了氧化物层。氧化物分为两层,最靠近基体的氧化物颗粒直径为50-100纳米,在细小致密的氧化物颗粒表面均匀分布着0.5-1.6微米的多边形大颗粒。经过70天高温高压腐蚀试验,最靠近基体的氧化物颗粒直径增大为80-250纳米,致密细小氧化物颗粒表面分布的多边形颗粒直径增大为0.8至2.5微米。致密细小氧化物膜具有极强的耐蚀性,腐蚀增重速率先是大幅降低,然后逐渐平缓。经过1680h后,其均匀腐蚀速率降为仅2.85×10-3mg/dm2?h。

  • Optimization of Charge Measurement for LHAASO Muon Detector

    Subjects: Astronomy >> Astrophysical processes submitted time 2023-10-18 Cooperative journals: 《天文研究与技术》

    Abstract: The Large High Altitude Air Shower Observatory (LHAASO) is mainly used for exploring the origin of high-energy cosmic rays, the evolution of high-energy celestial bodies and the research of new frontiers of physics. The large area Muon Detector (MD) array has high identification ability of primary gamma rays and can detect ultra-high energy gamma rays with high sensitivity. MD achieves a large dynamic range detection of 1-10 000 muons through the common readout of the anode and the seventh dynode. In order to reduce the error of directly converting the anode signal into the dynode signal in the saturated area, an optimization scheme of charge measurement was proposed by combining the anode (the unsaturated part of the anode) and the dynode (the saturated part of the anode) signals. The connection mode between the anode and the dynode is obtained by numerical simulation, and the relationship between the anode and dynode calibrated in the laboratory could be used for connection. Numerical simulation results show that the proposed scheme can effectively reduce the measurement error in the large dynamic range of 1-10 000 muons, the error is less than 1%, and the muons spectrum structure is obviously improved. The results of data analysis with full waveform signal are in good agreement with the simulation results, which verifies the effectiveness of the scheme.
     

  • Research Progress and Outlook of Livestock Feeding Robot

    Subjects: Agriculture, Forestry,Livestock & Aquatic Products Science >> Other Disciplines of Agriculture, Forestry,Livestock & Aquatic Products Science submitted time 2023-02-17 Cooperative journals: 《智慧农业(中英文)》

    Abstract: The production mode of livestock breeding has changed from extensive to intensive, and the production level is improved. However, low labor productivity and labor shortage have seriously restricted the rapid development of China's livestock breeding industry. As a new intelligent agricultural machinery equipment, agricultural robot integrates advanced technologies, such as intelligent monitoring, automatic control, image recognition technology, environmental modeling algorithm, sensors, flexible execution, etc. Using modern information and artificial intelligence technology, developing livestock feeding and pushing robots, realizing digital and intelligent livestock breeding, improving livestock breeding productivity are the main ways to solve the above contradiction. In order to deeply analyze the research status of robot technology in livestock breeding, products and literature were collected worldwide. This paper mainly introduced the research progress of livestock feeding robot from three aspects: Rail feeding robot, self-propelled feeding robot and pushing robot, and analyzed the technical characteristics and practical application of feeding robot.The rail feeding robot runs automatically along the fixed track, identifies the target animal, positions itself, and accurately completes feed delivery through preset programs to achieve accurate feeding of livestock. The self-propelled feeding robot can walk freely in the farm and has automatic navigation and positioning functions. The system takes single chip microcomputer as the control core and realizes automatic walking by sensor and communication module. Compared with the rail feeding robot, the feeding process is more flexible, convenient and technical, which is more conducive to the promotion and application of livestock farms. The pushing robot will automatically push the feed to the feeding area, promote the increase of feed intake of livestock, and effectively reduce the labor demand of the farm. By comparing the feeding robots of developed countries and China from two aspects of technology and application, it is found that China has achieved some innovation in technology, while developted countries do better in product application. The development of livestock robot was prospected. In terms of strategic planning, it is necessary to keep up with the international situation and the trend of technological development, and formulate the agricultural robot development strategic planning in line with China's national conditions. In terms of the development of core technologies, more attention should be paid to the integration of information perception, intelligent sensors and deep learning algorithms to realize human-computer interaction. In terms of future development trends, it is urgent to strengthen innovation, improve the friendliness and intelligence of the robot, and improve the learning ability of the robot. To sum up, intelligent livestock feeding and pushing machine operation has become a cutting-edge technology in the field of intelligent agriculture, which will surely lead to a new round of agricultural production technology reform, promote the transformation and upgrading of China's livestock industry. .

  • LHAASO—MD光电倍增管的性能测试

    Subjects: Astronomy >> Astrophysical processes submitted time 2019-11-13 Cooperative journals: 《天文研究与技术》

    Abstract: 高海拔宇宙线观测站(LHAASO)的核心科学目标是探索高能宇宙线起源以及相关的宇宙演化、高能天体运动和新物理前沿的研究。通过大面积铺设μ子探测器(MD)极大的压低宇宙射线背景,从而提高高能伽马射线探测的灵敏度。作为MD的核心部件之一的光电倍增管(PMT)负责接收水中的切伦科夫光子并将其转换成电信号输出,因此PMT的性能好坏直接影响MD的性能。稻城实验室2%抽样测试结果表明PMT的各性能达到MD的指标要求,与批量测试结果的相对偏差小于2%。

  • 国际数据期刊出版的案例分析及其特征

    Subjects: Library Science,Information Science >> Library Science submitted time 2016-06-14

    Abstract:【目的】通过梳理国际代表性数据期刊特点!更好地了解数据期刊发展的趋势和特征。 【方法】 选择15种数据期刊进行调研,对其发展现状、学科分布、出版方式、收录内容、引用机制、版权协议以及出版费用等方面进行了分析%。【结果】基于 Scientific Data、F1000 Reaseach、GigaScience 等代表性期刊的分析,成功的数据期刊特点包括科研人员的认知度、学术社群的认可度、知识产权保护以及管理透明化。【结论】中国数据期刊出版界在搭建数据知识库和数据期刊出版平台后,还需关注如何提升国际认知度和认可度,图书馆员除了为科研人员推荐这些开放获取的数据资源外,更重要的是协助他们鉴别良好的数据期刊,以保护他们的知识产权权益。

  • 黄河流域城市间旅游经济联系格局及影响因素研究

    Subjects: Geosciences >> Geography submitted time 2023-09-19 Cooperative journals: 《干旱区地理》

    Abstract: Based on the time section data of 2010, 2015 and 2019, the modified gravitational model and socialnetwork method were used to analyze the temporal and spatial evolution characteristics of tourism economiclinks among 89 cities in the Yellow River Basin, and the influencing factors of tourism economic connectionchanges in the Yellow River Basin were analyzed by combining geographical detectors. The results show that: (1)The east-west multi-core network structure of the tourism economic network in the Yellow River Basin graduallyformed, and the characteristics of regional differentiation and inter-provincial barrier effect between cities are significant. (2) The tourism economic linkage network has gone through the initial stage of polarization and largebarriers, the transitional stage of organic connection and enhanced interaction, and the consolidation stage of balanced and cluster development. (3) A small number of core cities represented by Xi’an City and Zhengzhou Cityplay a strong intermediary role in the tourism economic connection network. (4) The level of industrial structure,tourism resource endowment and environmental quality are the main influencing factors of tourism economiclinkages, and the interaction between various factors can enhance the explanatory power of tourism economiclinkages. The research results can provide effective optimization suggestions for the high-quality development oftourism economy in the Yellow River Basin.

  • Porphyrin and Semiconducting Single Wall Carbon Nanotubes based Semiconductor Field Effect Gas Sensor for Determination of Phytophthora Strawberries

    Subjects: Agriculture, Forestry,Livestock & Aquatic Products Science >> Other Disciplines of Agriculture, Forestry,Livestock & Aquatic Products Science submitted time 2023-02-17 Cooperative journals: 《智慧农业(中英文)》

    Abstract: Phytophthora strawberries, as a kind of plant pathogenic fungi, can cause strawberry skin and crown rot without safe and effective treatment, which affect the economic benefits of planting strawberries. Therefore, it is urgent to use low-cost diagnostic methods to achieve early prevention. Strawberry plants infected with Phytophthora cactorum would release a unique organic volatile gas, 4-ethylphenol, with a concentration ranging from 1.12 to 22.56 mg/kg, which could be used as a marker gas for rapid diagnosis of the disease. In this study, semiconducting single-walled carbon nanotubes (SWNT) and field effect sensors (FET) were used to prepare semiconductor field effect gas sensors (SWNT/FET) without selectivity. And then the metal porphyrin MnOEP with high sensitivity and selectivity to 4-ethylphenol was immoblized on the SWNT's surface to obtain MnOEP-SWNT/FET. MnOEP-SWNT/FET has the advantages of low cost, low power consumption, small size, high sensitivity and easy integration, which can effectively overcome the shortcomings of gas chromatography-mass spectrometry, high-performance liquid chromatography and other analytical methods. By comparing the sensitivity and selectivity of different sensors, MnOEP-SWNT/FET is very suitable for real-time monitoring of 4-ethylphenol. The key reasons for the high sensitivity and selectivity are: MnOEP is a macromolecular heterocyclic compound formed by four pyrrole rings connected together by methylene and manganese ion(Mn), each pyrrole ring consists of four carbons and one nitrogen, and all nitrogen atoms inside the ring form a central cavity; the coordination metal ions of MnOEP are in an unsaturated state, gas molecules can interact with the central metal ions through van der Waals force and hydrogen bond at the axial position of MnOEP to change their own optical or electrical properties. MnOEP-SWNT/FET was studied by Raman spectrum, UV spectrum and voltammetry. The physical and chemical properties were analyzed and the detection conditions were optimized to improve the gas sensitivity of MnOEPSWNT/ FET to 4-ethylphenol. Under the optimal detection conditions, MnOEP-SWNT/FET has a good linear relationship with 0.25% ~100% saturated vapor of 4-ethylphenol (20 ℃) and the detection limit is 0.15% saturated vapor of 4-ethylphenol. The relative standard error of different concentrations was less than 10%. By measuring the actual samples, it has high detection accuracy for strawberry plants infected with Phytophthora, but it still exists false positive for healthy strawberry.