Liquid-phase acrylic acid hydration over solid-phase catalysts is a key reaction for the industrial productionof 3-hydroxypropionic acid. However, the relevant literature primarily focuses on the experimental aspects ...Liquid-phase acrylic acid hydration over solid-phase catalysts is a key reaction for the industrial productionof 3-hydroxypropionic acid. However, the relevant literature primarily focuses on the experimental aspects of catalystscreening and exploring reaction conditions, with few accurate descriptions of the reaction kinetics and determination ofthe reaction mechanism. Here, we combined kinetics experiments and theoretical calculations to elucidate the kinetics andmechanism of acrylic acid hydration on a resin catalyst. The pseudo-homogeneous model, and Langmuir-Hinshelwood-Haugen-Watson and Elie-Riedel (ER) heterogeneous models were used to explain the experimental kinetics data. TheER model can explain the experimental data very well, suggesting strong adsorption of acrylic acid on the surface of theresin catalyst. Furthermore, density functional theory calculations show that the hydration follows a stepwise, rather than aconcerted, reaction pathway. The present study provides theoretical insights into the reaction mechanism and kinetics, fillingthe gap in our understanding of the reaction on a fundamental level.展开更多
卓越工程师培养的质量保障和控制是一项复杂的系统工程,需要科学和规范的方法提供指导和决策支持。深入分析卓越工程师培养的通用标准和质量保障要求,构建基于动态质量功能展开(DQFD,Dynamic Quality Function Deployment)的卓越工程师...卓越工程师培养的质量保障和控制是一项复杂的系统工程,需要科学和规范的方法提供指导和决策支持。深入分析卓越工程师培养的通用标准和质量保障要求,构建基于动态质量功能展开(DQFD,Dynamic Quality Function Deployment)的卓越工程师培养质量保障控制模型,将质量需求以及来自社会、学生和各种监控活动的反馈信息逐层内化到质量规划和设计、保障要素规划和设计的各个环节中,实现卓越工程师培养质量的持续改进。展开更多
To achieve the confidentiality and retrievability of outsourced data simultaneously,a dynamic multi-keyword fuzzy ranked search scheme(DMFRS)with leakage resilience over encrypted cloud data based on two-level index s...To achieve the confidentiality and retrievability of outsourced data simultaneously,a dynamic multi-keyword fuzzy ranked search scheme(DMFRS)with leakage resilience over encrypted cloud data based on two-level index structure was proposed.The first level index adopts inverted index and orthogonal list,combined with 2-gram and location-sensitive Hashing(LSH)to realize a fuzzy match.The second level index achieves user search permission decision and search result ranking by combining coordinate matching with term frequency-inverse document frequency(TF-IDF).A verification token is generated within the results to verify the search results,which prevents the potential malicious tampering by cloud service providers(CSP).The semantic security of DMFRS is proved by the defined leakage function,and the performance is evaluated based on simulation experiments.The analysis results demonstrate that DMFRS gains certain advantages in security and performance against similar schemes,and it meets the needs of storage and privacy-preserving for outsourcing sensitive data.展开更多
浙江宁绍平原是研究河姆渡文化与自然环境发展关系的热点区域。选取田螺山遗址附近的TLS1402钻孔上部16.16 m的沉积物进行AMS 14C测定、孢粉和微炭屑分析，旨在研究宁绍平原中全新世植被历史、环境变化和人类活动的变化规律。结果表明：...浙江宁绍平原是研究河姆渡文化与自然环境发展关系的热点区域。选取田螺山遗址附近的TLS1402钻孔上部16.16 m的沉积物进行AMS 14C测定、孢粉和微炭屑分析，旨在研究宁绍平原中全新世植被历史、环境变化和人类活动的变化规律。结果表明：1）约8460~7700 a B.P.，植被类型以落叶阔叶林为主，含有常绿成分和针叶成分，揭示了气候温凉偏干的特点；7700~6300 a B.P.期间，乔灌木整体有所下降，波动显著，植被类型为亚热带常绿落叶阔叶混交林，气候暖湿，在7600~7500 a B.P.、7300~7200 a B.P.和6700~6300 a B.P.，粒径〉38 μm的禾本科明显增加，可能显示了人类的3个农业发展阶段。另外，微炭屑增加对应栽培作物花粉的增加，暗示植被变化可能与人类活动有关；6300 a B.P.至今，木本花粉含量总体大幅度下降，草本花粉含量升高，气候稍温凉偏干，植被类型仍以亚热带常绿落叶阔叶混交林为主，但植被变化可能受人类干扰。2）淡水藻类和沟鞭藻类含量表明，TLS1402钻孔所在地8460~7700 a B.P.可能为浅海湾环境，但也受到淡水注入影响。7700~7200 a B.P.为过渡时期；7200 a B.P.后环境发生较大变化，海平面上升速率大幅度降低，陆地逐渐生长，7000~6900 a B.P.河姆渡文化逐步开始发育，水稻农业发展，但之后受到海水影响，在7200~6700 a B.P.、6600~6500 a B.P.都出现农业发展低谷，分析认为和海水入侵有关。展开更多
The East China coastal plain is one of the most important Neolithic culture areas in China, where rich archaeological sites including those producing the earliest domesticated rice are observed. It is also a place whe...The East China coastal plain is one of the most important Neolithic culture areas in China, where rich archaeological sites including those producing the earliest domesticated rice are observed. It is also a place where landscape has experienced dramatic evolution during the Holocene when both sea level and climate changed, such that it is an ideal place for studying human-environment interaction. This study investigated over 2000 sites of pre-history and Shang and Zhou Dynasties, with 655 of which being Neolithic ages, by using DEM and GIS methods. The results suggest that the spatial and temporal distribution of Neolithic sites has largely been controlled by landscape evolution(particularly changes in coastal line), which ultimately governed by sea level changes. During early Holocene, Neolithic sites sparsely distributed in the intermountain basins of east Zhejiang Province, far from the influence of ocean. Over the period of 9–7 ka, the coastal plain(including the shelf) was largely submerged,only the feet of low hills to the south and southwest of the study area, and islands protruding the estuary, cradled limited number of settlements with characteristic "maritime components". At about 7 ka, sea level rise decelerated prominently, while sediments supply in the drainage remained high value, the combination of which led to land formation and propagation. Vast space during this period facilitated the growth of settlements in both size and number. In the mean time, however, the coastal plain was vulnerable to extreme environmental events such as storms and flooding owning to its geomorphic nature, which exerted great influence on the rise and fall of Neolithic culture.展开更多
文摘Liquid-phase acrylic acid hydration over solid-phase catalysts is a key reaction for the industrial productionof 3-hydroxypropionic acid. However, the relevant literature primarily focuses on the experimental aspects of catalystscreening and exploring reaction conditions, with few accurate descriptions of the reaction kinetics and determination ofthe reaction mechanism. Here, we combined kinetics experiments and theoretical calculations to elucidate the kinetics andmechanism of acrylic acid hydration on a resin catalyst. The pseudo-homogeneous model, and Langmuir-Hinshelwood-Haugen-Watson and Elie-Riedel (ER) heterogeneous models were used to explain the experimental kinetics data. TheER model can explain the experimental data very well, suggesting strong adsorption of acrylic acid on the surface of theresin catalyst. Furthermore, density functional theory calculations show that the hydration follows a stepwise, rather than aconcerted, reaction pathway. The present study provides theoretical insights into the reaction mechanism and kinetics, fillingthe gap in our understanding of the reaction on a fundamental level.
文摘卓越工程师培养的质量保障和控制是一项复杂的系统工程,需要科学和规范的方法提供指导和决策支持。深入分析卓越工程师培养的通用标准和质量保障要求,构建基于动态质量功能展开(DQFD,Dynamic Quality Function Deployment)的卓越工程师培养质量保障控制模型,将质量需求以及来自社会、学生和各种监控活动的反馈信息逐层内化到质量规划和设计、保障要素规划和设计的各个环节中,实现卓越工程师培养质量的持续改进。
基金supported by the National Natural Science Foundation of China(62272076)the Chongqing Natural Science Foundation of China(cstc2020jcyj-msxm X0343,cstc2020jcyj-msxm X1021)+1 种基金the Science and Technology Research Program of Chongqing Municipal Education Commission(KJZD-K20200602)the Sichuan Science and technology Foundation of China(22ZDYF3568)。
文摘To achieve the confidentiality and retrievability of outsourced data simultaneously,a dynamic multi-keyword fuzzy ranked search scheme(DMFRS)with leakage resilience over encrypted cloud data based on two-level index structure was proposed.The first level index adopts inverted index and orthogonal list,combined with 2-gram and location-sensitive Hashing(LSH)to realize a fuzzy match.The second level index achieves user search permission decision and search result ranking by combining coordinate matching with term frequency-inverse document frequency(TF-IDF).A verification token is generated within the results to verify the search results,which prevents the potential malicious tampering by cloud service providers(CSP).The semantic security of DMFRS is proved by the defined leakage function,and the performance is evaluated based on simulation experiments.The analysis results demonstrate that DMFRS gains certain advantages in security and performance against similar schemes,and it meets the needs of storage and privacy-preserving for outsourcing sensitive data.
文摘浙江宁绍平原是研究河姆渡文化与自然环境发展关系的热点区域。选取田螺山遗址附近的TLS1402钻孔上部16.16 m的沉积物进行AMS 14C测定、孢粉和微炭屑分析，旨在研究宁绍平原中全新世植被历史、环境变化和人类活动的变化规律。结果表明：1）约8460~7700 a B.P.，植被类型以落叶阔叶林为主，含有常绿成分和针叶成分，揭示了气候温凉偏干的特点；7700~6300 a B.P.期间，乔灌木整体有所下降，波动显著，植被类型为亚热带常绿落叶阔叶混交林，气候暖湿，在7600~7500 a B.P.、7300~7200 a B.P.和6700~6300 a B.P.，粒径〉38 μm的禾本科明显增加，可能显示了人类的3个农业发展阶段。另外，微炭屑增加对应栽培作物花粉的增加，暗示植被变化可能与人类活动有关；6300 a B.P.至今，木本花粉含量总体大幅度下降，草本花粉含量升高，气候稍温凉偏干，植被类型仍以亚热带常绿落叶阔叶混交林为主，但植被变化可能受人类干扰。2）淡水藻类和沟鞭藻类含量表明，TLS1402钻孔所在地8460~7700 a B.P.可能为浅海湾环境，但也受到淡水注入影响。7700~7200 a B.P.为过渡时期；7200 a B.P.后环境发生较大变化，海平面上升速率大幅度降低，陆地逐渐生长，7000~6900 a B.P.河姆渡文化逐步开始发育，水稻农业发展，但之后受到海水影响，在7200~6700 a B.P.、6600~6500 a B.P.都出现农业发展低谷，分析认为和海水入侵有关。
基金supported by the National Basic Research Program of China (Grant No. 2015CB953803)the National Natural Science Foundation of China (Grant No. 41672344)the CAS Strategic Priority Research Program (Grant No. XDB03020301)
文摘The East China coastal plain is one of the most important Neolithic culture areas in China, where rich archaeological sites including those producing the earliest domesticated rice are observed. It is also a place where landscape has experienced dramatic evolution during the Holocene when both sea level and climate changed, such that it is an ideal place for studying human-environment interaction. This study investigated over 2000 sites of pre-history and Shang and Zhou Dynasties, with 655 of which being Neolithic ages, by using DEM and GIS methods. The results suggest that the spatial and temporal distribution of Neolithic sites has largely been controlled by landscape evolution(particularly changes in coastal line), which ultimately governed by sea level changes. During early Holocene, Neolithic sites sparsely distributed in the intermountain basins of east Zhejiang Province, far from the influence of ocean. Over the period of 9–7 ka, the coastal plain(including the shelf) was largely submerged,only the feet of low hills to the south and southwest of the study area, and islands protruding the estuary, cradled limited number of settlements with characteristic "maritime components". At about 7 ka, sea level rise decelerated prominently, while sediments supply in the drainage remained high value, the combination of which led to land formation and propagation. Vast space during this period facilitated the growth of settlements in both size and number. In the mean time, however, the coastal plain was vulnerable to extreme environmental events such as storms and flooding owning to its geomorphic nature, which exerted great influence on the rise and fall of Neolithic culture.
