湿地景观格局研究是近十余年来新兴的热点领域,对进一步开展湿地演化和发展的基础研究及可持续化管理具有重要意义.基于知识图谱,通过文献发表情况、关键词共现、聚类和突现检测手段,对CNKI和Web of Science平台的文献进行计量分析,识...湿地景观格局研究是近十余年来新兴的热点领域,对进一步开展湿地演化和发展的基础研究及可持续化管理具有重要意义.基于知识图谱,通过文献发表情况、关键词共现、聚类和突现检测手段,对CNKI和Web of Science平台的文献进行计量分析,识别该领域的主题演变路径和前沿热点,透视其发展趋势.结果表明:①国外研究起步较早,国内较晚,都经历了“形成期—发展期—繁荣期”3个阶段,表现出理论研究转向实例验证的共性特征;②国内外的研究热点集中于景观格局量化评估、动态模型、驱动机制、研究尺度和保护修复5个方向,其演变进程与政策规划具有强耦合性;③国内外研究热点的差异主要表现为国外对湿地的生物地球化学循环过程和生物多样性更为关注,与生态水文学的交叉融合更紧密.最后提出展望:①加强湿地景观格局与碳储量的变化规律研究,助力“双碳”目标;②构建驱动机制模型,定量表征驱动因素对景观格局演变的影响程度;③探讨湿地与周边环境相互作用的生物地球化学循环过程,推进陆海统筹发展;④通过多学科交叉融合,研究景观格局与生态过程的耦合作用机制仍是景观生态学的核心主题.展开更多
In view of the importance of gas-liquid two-phase spiral flow and the few research reports at home and abroad,the gas-liquid two-phase spiral flow patterns have been researched in a horizontal pipe with different para...In view of the importance of gas-liquid two-phase spiral flow and the few research reports at home and abroad,the gas-liquid two-phase spiral flow patterns have been researched in a horizontal pipe with different parameters investigated by means of observation and a high-speed camera.Since the appearance of spiral flow makes the distribution of twophase flow more complicated,the flow patterns appearing in the experiments were divided into the Spiral Wavy Stratified Flow(SWS),the Spiral Bubble Flow(SB),the Spiral Slug Flow(SS),the Spiral Linear Flow(SL),the Spiral Axial Flow(SA),and the Spiral Dispersed Flow(SD) by the observations and with reference to the predecessors' research achievements.A flow pattern map has been drawn up.The influence of velocity,vane angle and vane area on flow pattern conversion boundary and pressure drop has been studied,with a solid foundation laid for the future research work.展开更多
Gas–liquid two-phase flow abounds in industrial processes and facilities. Identification of its flow pattern plays an essential role in the field of multiphase flow measurement. A bluff body was introduced in this s...Gas–liquid two-phase flow abounds in industrial processes and facilities. Identification of its flow pattern plays an essential role in the field of multiphase flow measurement. A bluff body was introduced in this study to recognize gas–liquid flow patterns by inducing fluid oscillation that enlarged differences between each flow pattern. Experiments with air–water mixtures were carried out in horizontal pipelines at ambient temperature and atmospheric pressure. Differential pressure signals from the bluff-body wake were obtained in bubble, bubble/plug transitional, plug, slug, and annular flows. Utilizing the adaptive ensemble empirical mode decomposition method and the Hilbert transform, the time–frequency entropy S of the differential pressure signals was obtained. By combining S and other flow parameters, such as the volumetric void fraction β, the dryness x, the ratio of density φ and the modified fluid coefficient ψ, a new flow pattern map was constructed which adopted S（1–x）φ and （1–β）ψ as the vertical and horizontal coordinates, respectively. The overall rate of classification of the map was verified to be 92.9% by the experimental data. It provides an effective and simple solution to the gas–liquid flow pattern identification problems.展开更多
文摘湿地景观格局研究是近十余年来新兴的热点领域,对进一步开展湿地演化和发展的基础研究及可持续化管理具有重要意义.基于知识图谱,通过文献发表情况、关键词共现、聚类和突现检测手段,对CNKI和Web of Science平台的文献进行计量分析,识别该领域的主题演变路径和前沿热点,透视其发展趋势.结果表明:①国外研究起步较早,国内较晚,都经历了“形成期—发展期—繁荣期”3个阶段,表现出理论研究转向实例验证的共性特征;②国内外的研究热点集中于景观格局量化评估、动态模型、驱动机制、研究尺度和保护修复5个方向,其演变进程与政策规划具有强耦合性;③国内外研究热点的差异主要表现为国外对湿地的生物地球化学循环过程和生物多样性更为关注,与生态水文学的交叉融合更紧密.最后提出展望:①加强湿地景观格局与碳储量的变化规律研究,助力“双碳”目标;②构建驱动机制模型,定量表征驱动因素对景观格局演变的影响程度;③探讨湿地与周边环境相互作用的生物地球化学循环过程,推进陆海统筹发展;④通过多学科交叉融合,研究景观格局与生态过程的耦合作用机制仍是景观生态学的核心主题.
基金supported by the National Natural Science Foundation of China (Grant number 51776015)
文摘In view of the importance of gas-liquid two-phase spiral flow and the few research reports at home and abroad,the gas-liquid two-phase spiral flow patterns have been researched in a horizontal pipe with different parameters investigated by means of observation and a high-speed camera.Since the appearance of spiral flow makes the distribution of twophase flow more complicated,the flow patterns appearing in the experiments were divided into the Spiral Wavy Stratified Flow(SWS),the Spiral Bubble Flow(SB),the Spiral Slug Flow(SS),the Spiral Linear Flow(SL),the Spiral Axial Flow(SA),and the Spiral Dispersed Flow(SD) by the observations and with reference to the predecessors' research achievements.A flow pattern map has been drawn up.The influence of velocity,vane angle and vane area on flow pattern conversion boundary and pressure drop has been studied,with a solid foundation laid for the future research work.
基金Project(51576213)supported by the National Natural Science Foundation of ChinaProject(2015RS4015)supported by the Hunan Scientific Program,ChinaProject(2016zzts323)supported by the Innovation Project of Central South University,China
文摘Gas–liquid two-phase flow abounds in industrial processes and facilities. Identification of its flow pattern plays an essential role in the field of multiphase flow measurement. A bluff body was introduced in this study to recognize gas–liquid flow patterns by inducing fluid oscillation that enlarged differences between each flow pattern. Experiments with air–water mixtures were carried out in horizontal pipelines at ambient temperature and atmospheric pressure. Differential pressure signals from the bluff-body wake were obtained in bubble, bubble/plug transitional, plug, slug, and annular flows. Utilizing the adaptive ensemble empirical mode decomposition method and the Hilbert transform, the time–frequency entropy S of the differential pressure signals was obtained. By combining S and other flow parameters, such as the volumetric void fraction β, the dryness x, the ratio of density φ and the modified fluid coefficient ψ, a new flow pattern map was constructed which adopted S（1–x）φ and （1–β）ψ as the vertical and horizontal coordinates, respectively. The overall rate of classification of the map was verified to be 92.9% by the experimental data. It provides an effective and simple solution to the gas–liquid flow pattern identification problems.
文摘采用外周血淋巴细胞培养及G带染色体标本制作技术,研究和分析华南虎(Panthera tigris amoyensis)染色体的核型和带型。结果表明:华南虎二倍体染色体数为2n=38条,其中常染色体18对,性染色体1对。常染色体按相对长度从长到短依次编号为1~18。根据着丝粒指数可将华南虎染色体分为4组,即A组(m),包括2、5、13、18和X;B组(Sm),包括1、4、7、8、9、10、11、12、14、17和Y;C组(St),包括3、6;D组(t),包括15、16。核型公式为8(m)+20(Sm)+4(St)+4(t),XY(m,Sm)/XX(m,m)。本研究成功制备了华南虎染色体核型标本,初步建立了华南虎染色体G带核型模式图谱。经比对,发现华南虎与东北虎(P. t. altaica)染色体核型存在明显差异,可为虎亚种的分类研究提供依据,同时能为华南虎种群基因多样性及遗传学研究提供新的参考和开辟新的途径。
