期刊文献+
共找到763篇文章
< 1 2 39 >
每页显示 20 50 100
Conversion Carbon Capture and Storage Factors in Temperate Human Controlled Wetland
1
作者 Doimi Mauro Minetto Giorgio 《Journal of Environmental Science and Engineering(B)》 2023年第5期211-219,共9页
This paper provides guidance for the quantification and reporting of blue carbon removals in the temperate coastal ecosystems,“Italian valli da pesca”or H.C.W.(Human Controlled Wetland,Lat.45°Lon.12°),wher... This paper provides guidance for the quantification and reporting of blue carbon removals in the temperate coastal ecosystems,“Italian valli da pesca”or H.C.W.(Human Controlled Wetland,Lat.45°Lon.12°),where some pools as seagrasses,and salt marshes,are highly efficient at capturing and storing carbon dioxide(CO_(2))from the atmosphere.Halophyte salt marsh plants were found to have a%C on Dry Weight(D.W.)of 32.26±3.91(mean±standard deviation),macrophytes 33.65±7.99,seagrasses 29.23±2.23,tamarisk 48.42±2.80,while the first 5 centimetres of wetland mud,on average,had a%C of 8.56±0.94.Like the ISO(International Organization for Standardization)14064 guideline to quantify the GHG(Greenhouse Gas)emission,we have studied the different conversion factors to be used as a practical tool for measurement the CO_(2)sink activity.These factors are essential to calculate the overall carbon reduction in a project located in temperate wetland using a method as the ISO 14064.2,UNI-BNeutral,VCS VERRA or other that will come. 展开更多
关键词 Blue carbon carbon conversion factor Carbon Capture and Storage CO_(2) UNI BNeutral VERRA VCS WETLAND
下载PDF
Transcription factor-based gene therapy to treat glioblastoma through direct neuronal conversion 被引量:2
2
作者 Xin Wang Zifei Pei +2 位作者 Aasma Hossain Yuting Bai Gong Chen 《Cancer Biology & Medicine》 SCIE CAS CSCD 2021年第3期860-874,共15页
Objective:Glioblastoma(GBM)is the most prevalent and aggressive adult primary cancer in the central nervous system.Therapeutic approaches for GBM treatment are under intense investigation,including the use of emerging... Objective:Glioblastoma(GBM)is the most prevalent and aggressive adult primary cancer in the central nervous system.Therapeutic approaches for GBM treatment are under intense investigation,including the use of emerging immunotherapies.Here,we propose an alternative approach to treat GBM through reprogramming proliferative GBM cells into non-proliferative neurons.Methods:Retroviruses were used to target highly proliferative human GBM cells through overexpression of neural transcription factors.Immunostaining,electrophysiological recording,and bulk RNA-seq were performed to investigate the mechanisms underlying the neuronal conversion of human GBM cells.An in vivo intracranial xenograft mouse model was used to examine the neuronal conversion of human GBM cells.Results:We report efficient neuronal conversion from human GBM cells by overexpressing single neural transcription factor Neurogenic differentiation 1(Neuro D1),Neurogenin-2(Neurog2),or Achaete-scute homolog 1(Ascl1).Subtype characterization showed that the majority of Neurog2-and Neuro D1-converted neurons were glutamatergic,while Ascl1 favored GABAergic neuron generation.The GBM cell-converted neurons not only showed pan-neuronal markers but also exhibited neuron-specific electrophysiological activities.Transcriptome analyses revealed that neuronal genes were activated in glioma cells after overexpression of neural transcription factors,and different signaling pathways were activated by different neural transcription factors.Importantly,the neuronal conversion of GBM cells was accompanied by significant inhibition of GBM cell proliferation in both in vitro and in vivo models.Conclusions:These results suggest that GBM cells can be reprogrammed into different subtypes of neurons,leading to a potential alternative approach to treat brain tumors using in vivo cell conversion technology. 展开更多
关键词 GLIOBLASTOMA neuronal conversion transcription factors Neuro D1 neurogenin-2 Ascl1
下载PDF
The conversion factor of K_(eff) to K_(3.7) in thermoluminescence dating 被引量:3
3
作者 Wang Wei-Da Zhou Zhi-Xin +1 位作者 Xia Jun-Ding (Research Laborotory for Conservation and Archaeology, Shanghai Museum, Shanghai 200951)Leung P L Stokes M J(Department of Physics and Materials Science, City University of Hong Kong) 《Nuclear Science and Techniques》 SCIE CAS CSCD 1998年第4期227-230,共4页
In the fine-grain TL dating the full o dose must be converted into the equivalent P dose. The conversion is finished by Keff-value, which is an effective or effectiveness. But the Keff can not be measured directly for... In the fine-grain TL dating the full o dose must be converted into the equivalent P dose. The conversion is finished by Keff-value, which is an effective or effectiveness. But the Keff can not be measured directly for each sample and only the external radiative efficiency K3.7 can be measured. In order to obtain the Keff a special study for the conversion factor of Keff to K3.t has been made using the ultrathin TLD. The results show that the conversion factor of tile TLD for archaeological samples is 0.847, which is in agreement with calculated value 0.85. 展开更多
关键词 考古学 热致发光断定年代 Keff-K3.7 变换因子
下载PDF
Variability in the empirical leucine-to-carbon conversion factors along an environmental gradient
4
作者 LI Xiangfu XU Jie +2 位作者 SHI Zhen LI Qian LI Ruihuan 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2018年第4期77-82,共6页
Bacterial production is one of the key parameters to evaluate bacterial role in ocean carbon fluxes.Estimation of bacterial production requires the leucine-to-carbon conversion factors that change widely across enviro... Bacterial production is one of the key parameters to evaluate bacterial role in ocean carbon fluxes.Estimation of bacterial production requires the leucine-to-carbon conversion factors that change widely across environments.However,empirical leucine-to-carbon conversion factors(e CFs) are seldom determined in situ because of time consuming and little is known on regulating factors for the e CFs.During May 2015 to January 2016,fourteen dilution experiments were conducted,from the Zhujiang(Pearl River) Estuary to the coast of the northern South China Sea,to determine spatiotemporal variability in the e CFs and its potential controlling factors along an environmental gradient.The e CFs showed clear spatial variations with the highest(1.27–1.69(kg C)/(mol Leu)) in low salinity waters(salinity〈15),intermediate(1.03–1.25(kg C)/(mol Leu)) in moderate salinity(salinity of 15–25),and the lowest(0.48–0.85(kg C)/(mol Leu)) in high salinity waters(salinity〉25).Substrate availability was responsible for spatial variability in the e CFs.In the pristine coastal waters,low e CFs was related to substrate limitation and leucine incorporated was respired to maximize the survival rather than bacterial production.Hence,the e CFs measurement was needed for estimating bacterial production accurately in various marine environments. 展开更多
关键词 BACTERIA leucine incorporation conversion factors Zhujiang (Pearl River) Estuary
下载PDF
Form and Interconversion Factor of Selenium in Soil
5
作者 Ying XING Yongxian LIU +4 位作者 Panxia LIANG Qing LIAO Liping PAN Taiqing HUANG Zepu JIANG 《Agricultural Biotechnology》 CAS 2019年第1期116-120,共5页
In recent years,production and processing of natural selenium-rich agricultural products has become a research hotspot. The main factor affecting the selenium content in plant is the content of effective selenium in s... In recent years,production and processing of natural selenium-rich agricultural products has become a research hotspot. The main factor affecting the selenium content in plant is the content of effective selenium in soil. So it is important to understand the form and conversion relationship of selenium in soil and find ways to improve selenium effectiveness. By summarizing the researches on selenium at home and abroad,we analyze the classification of soil selenium form,the transformation among different selenium forms and the improving factors of selenium effectiveness. We understand the relationship between chemical form and extraction form of selenium,analyze the driving factors of conversion among different forms,and discuss the ways to improve selenium effectiveness of soil in high selenium-rich area. By combining characteristics of soil and crop in different selenium-rich regions,different selenium activation methods are used,which could provide more scientific evidence for further selenium research. 展开更多
关键词 SOIL SELENIUM FORM conversion factor
下载PDF
Gross Chemical Profile and Calculation of Nitrogen-to-Protein Conversion Factors for Five Tropical Seaweeds 被引量:1
6
作者 Graciela S.Diniz Elisabete Barbarino +2 位作者 João Oiano-Neto Sidney Pacheco Sergio O.Lourenco 《American Journal of Plant Sciences》 2011年第3期287-296,共10页
Despite decades of research on marine algae, there are still significant gaps in basic knowledge about chemical composition of these organisms, especially in tropical environments. In this study, the amino acid compos... Despite decades of research on marine algae, there are still significant gaps in basic knowledge about chemical composition of these organisms, especially in tropical environments. In this study, the amino acid composition and contents of total nitrogen, phosphorus, lipid, carbohydrate and protein were determined in Asparagopsis taxiformis, Centroceras clavulatum, Chaetomorpha aerea, Sargassum filipendula and Spyridia hypnoides. The seaweeds showed low lipid contents (lower than 5.5% d.w. in all species) and were rich in carbohydrates (more than 16% d.w. in all seaweeds). The percentage of nitrogen, phosphorus and protein varied widely among species, which red algae showed the highest con-centrations. The amino acid composition was similar among the seaweeds, which glutamic acid, aspartic acid and leu-cine as the most abundant. All species are poor in histidine. An average of 24.2% of the total nitrogen is non-proteinaceous. From data of total amino acid and total nitrogen, specific nitrogen-to-protein conversion factors were calculated for each species. The nitrogen-to-protein conversion factors calculated ranged from 4.51 to 5.21, with an overall average of 4.86. These findings show that the traditional conversion factor of 6.25 should be avoided for seaweeds, since it overestimates the actual protein content. 展开更多
关键词 Nitrogen-to-Protein conversion factors PROTEIN Amino Acid Seaweeds Element Composition Tropical Environment
下载PDF
Analysis on the Influencing Factors and Control Measures of "Non-Grain Conversion" of Cultivated Land in Agricultural Land Transfer
7
作者 Lixian XIA Zisheng YANG 《Asian Agricultural Research》 2021年第10期5-11,共7页
Through the method of literature analysis,this paper analyzes the present situation of the"non-grain conversion"of cultivated land in the transfer of agricultural land in China,summarizes the influencing fac... Through the method of literature analysis,this paper analyzes the present situation of the"non-grain conversion"of cultivated land in the transfer of agricultural land in China,summarizes the influencing factors and consequences of the phenomenon of"non-grain conversion"of cultivated land in the transfer of agricultural land,and finally puts forward some measures.The study found that costs and benefits are the fundamental factors affecting the"non-grain conversion"of cultivated land in agricultural land transfer,and other main factors include government and policy guidance,industrial and commercial capital to the countryside,labor transfer and so on.The"non-grain conversion"of cultivated land in the transfer of agricultural land is a serious threat to China s food security,leading to the decline of the quality of agricultural land and the destruction of the ecological environment,as well as the risk of breach of contract in"industrial and commercial capital to the countryside".Based on the understanding of the influencing factors of non-grain conversion,this paper puts forward the following measures:strengthening the control of the use of cultivated land in agricultural land transfer;implementing accurate subsidies for grain cultivation and ensuring the benefit of grain growers;adopting grain planting incentive mechanism to increase grain enthusiasm;strengthening media publicity and education to enhance food security awareness.The improvement of the current situation of the"non-grain conversion"of cultivated land in the transfer of agricultural land will be of great significance to the protection of agricultural land and food security in China. 展开更多
关键词 Agricultural land transfer Non-grain conversion of cultivated land Food security Influencing factors Measures
下载PDF
Application of Single-to-Single Phase Matrix Conversion in Conventional Rectifier-Inverter 被引量:3
8
作者 YANG Xi jun, GONG You min School of Electromechanical Engineering and Automation, Shanghai University, Shanghai 200072, China 《Journal of Shanghai University(English Edition)》 CAS 2001年第3期211-216,共6页
The principle of single to single phase matrix electric power conversioin is further studied and the conversioin switch function is introduced into conventional rectifier inverter, thus a general character of the t... The principle of single to single phase matrix electric power conversioin is further studied and the conversioin switch function is introduced into conventional rectifier inverter, thus a general character of the two conversion techniques is discovered. It is characteristic of the switch functiion to follow mains voltage distortion and mains frequency drift. By utilizing the merit, unidirectional switch duty rations of the inverter follow the variation of DC link voltage automatically, thus the size of DC link electrolytic capacitor can be reduced considerably, bringing about improved mains side power factor. Corresponding topologies and theoretical and theoretical derivations are given, and so are the simulation results, based on which it is confirmed that the single to single phase matrix conversion technique is potentially useful in large scale production, and the introduction of switch function can yield good economic returns. 展开更多
关键词 sinele to sinele phase matrix electric power conversion introduction rectifier inverter DC link electrolytic capacitor mains side power factor
下载PDF
Factor Analysis on Oral English Conversational Competence of College Students
9
作者 LI La 《Journal of Literature and Art Studies》 2020年第3期209-215,共7页
Oral English is always a difficult part for Chinese students,some can speak several sentences while not clearly know others’saying;others can understand the speakers’words while not express their own meaning fluentl... Oral English is always a difficult part for Chinese students,some can speak several sentences while not clearly know others’saying;others can understand the speakers’words while not express their own meaning fluently.This paper will focus on what factors influences the college students’spoken English by the specific experiment and SPSS app,whose data shows four ones,namely Language Monitor,Meaning Negotiation,Turn Taking and Empathetic Exchange.Thus,the paper takes conclusions and poses some suggestions to oral English teaching according to the affecting causes.It is expecting to help improve the ability of the oral English Conversation for Chinese College students. 展开更多
关键词 ORAL English conversATIONAL ability factor analysis COLLEGE students
下载PDF
Optimum Efficiency of Photogalvanic Cell for Solar Energy Conversion: Lissamine Green B-Ascorbic Acid-NaLS System
10
作者 Kishna Ram Genwa Kewal Singh 《Smart Grid and Renewable Energy》 2013年第3期306-311,共6页
Photogalvanic cells are photoelectrochemical cells chargeable in light for solar energy conversion and storage. They may be energy source for the future, if their electrical performance is increased. In this study, a ... Photogalvanic cells are photoelectrochemical cells chargeable in light for solar energy conversion and storage. They may be energy source for the future, if their electrical performance is increased. In this study, a photosensitizer Lissamine green B, a reductant Ascorbic acid and a surfactant NaLS have been used in the photogalvanic cell. The generated photopotential and photocurrent are 850.0 mV and 375.0 μA respectively. The conversion efficiency of the cell, fill factor and the cell performance were observed 1.0257%, 0.2598% and 170.0 minutes in dark respectively. The effects of different parameters on the electrical output of the photogalvanic cell were observed. A mechanism was proposed for the photogeneration of electrical energy. 展开更多
关键词 Lissamine Green B Ascorbic Acid SODIUM Lauryl Sulphate (NaLS) Photopotential PHOTOCURRENT FILL factor conversion EFFICIENCY
下载PDF
建筑空间最优节能设计模型仿真研究 被引量:1
11
作者 周忠长 刘集成 《计算机仿真》 2024年第3期528-532,共5页
由于建筑结构主体较多,空间能耗难以合并控制,导致目前建筑空间能源耗用量较大。为此,构建基于等效转换法的建筑空间最优节能模型,并对其仿真研究。提出建筑总体能耗作为初始优化的“尺度”概念,该尺度为建筑空间的外墙、内墙、屋顶、... 由于建筑结构主体较多,空间能耗难以合并控制,导致目前建筑空间能源耗用量较大。为此,构建基于等效转换法的建筑空间最优节能模型,并对其仿真研究。提出建筑总体能耗作为初始优化的“尺度”概念,该尺度为建筑空间的外墙、内墙、屋顶、分户楼板以及门窗等参数,求解这些尺度的最佳标准值。采用等效转换法计算在节能条件下所能接受的最大能耗范围。在此基础上,以上述范围值为约束条件,建立控制函数。将上述提到标准尺度值和最大能耗范围设置为最优解,建立最优节能设计模型,设定温差调节因子,对每一次室内外温差实施有效调节控制,保证建筑体参数符合最佳能耗范围。仿真结果证明,所提方法对冬季采暖和夏季制冷的能耗控制效果均较佳,节能效果最优且算法收敛性高,鲁棒性较好。 展开更多
关键词 建筑空间 最优节能设计 等效转换 控制函数 调节因子
下载PDF
靶向药物甲磺酸伊马替尼的分子标志物BCR-ABL融合基因定量检测平台的质量评价方法的研究
12
作者 孙楠 李丽莉 +2 位作者 张文新 黄杰 曲守方 《中国药事》 CAS 2024年第1期58-65,共8页
目的:使用BCR-ABL定量标准品,评价BCR-ABL融合基因检测试剂盒(数字PCR法)的性能。方法:提取BCR-ABL定量标准品的RNA,测定其浓度和纯度。使用BCR-ABL融合基因定量检测试剂盒(数字PCR法)和数字PCR仪进行检测,得到标准品的BCR-ABL融合基因... 目的:使用BCR-ABL定量标准品,评价BCR-ABL融合基因检测试剂盒(数字PCR法)的性能。方法:提取BCR-ABL定量标准品的RNA,测定其浓度和纯度。使用BCR-ABL融合基因定量检测试剂盒(数字PCR法)和数字PCR仪进行检测,得到标准品的BCR-ABL融合基因的分子学反应。结果:用于准确度项目检测的标准品WS2和WS3的BCR-ABL融合基因的MR绝对偏差均不超过±0.5 log,用于检出限项目检测的标准品WS4能检出BCR-ABL融合基因突变阳性,用于重复性项目检测的标准品WS1和WS4的BCR-ABL融合基因的MR的变异系数(CV)均<3.0%。结论:BCR-ABL融合基因定量检测试剂盒(数字PCR法)的准确度、检出限和重复性的性能指标符合制定的《断裂点簇集区-艾贝尔逊白血病病毒(BCR-ABL)融合基因检测试剂盒》标准的相应要求,为标准的实施提供了技术支撑。 展开更多
关键词 断裂点簇集区-艾贝尔逊白血病病毒融合基因 国际标准化 转化系数 分子学反应 准确度 检出限 重复性 溯源
下载PDF
烟草CYP82E4基因启动子功能分析
13
作者 望锦 张幸子 +2 位作者 王雅琦 宋时洋 李凤霞 《中国烟草科学》 CSCD 北大核心 2024年第1期17-23,30,共8页
烟碱转化是指在烟叶成熟期,烟叶中的烟碱大量转化成降烟碱,烟叶品质发生显著变化的过程。前期研究表明烟碱转化由烟碱去甲基酶一步催化完成,其编码基因为CYP82E4(NtE4)。为解析NtE4启动子功能,探究其调控机制,本研究通过在线数据库分析N... 烟碱转化是指在烟叶成熟期,烟叶中的烟碱大量转化成降烟碱,烟叶品质发生显著变化的过程。前期研究表明烟碱转化由烟碱去甲基酶一步催化完成,其编码基因为CYP82E4(NtE4)。为解析NtE4启动子功能,探究其调控机制,本研究通过在线数据库分析NtE4启动子上的顺式作用元件,预测其上游靶向转录因子;通过5’端缺失构建启动子融合GUS基因的重组表达载体并瞬时转化本氏烟,确定启动子活性区域。结果表明,NtE4启动子包含2个脱落酸、11个乙烯响应元件,9个WRKY和7个NAC结合位点等;-500~-1000 bp是NtE4启动子核心区域,-500~-1967 bp存在较多增强启动子活性的元件;预测ERF、WRKY和NAC为NtE4基因上游靶向转录因子;荧光定量表达分析显示ERF5、WRKY50和NAC29在叶片衰老过程中具有和NtE4相似的表达趋势。本研究将为阐明烟叶衰老过程中NtE4介导的烟碱转化机制提供理论依据。 展开更多
关键词 烟碱转化 CYP82E4 启动子活性 转录因子
下载PDF
性别和疫苗接种次数对轻型Omicron感染患者症状和核酸转阴时间的影响
14
作者 李正汉 刘斌 +2 位作者 罗利萍 钮柏琳 肖骏 《现代医药卫生》 2024年第4期559-562,共4页
目的探讨不同性别和疫苗接种次数对奥密克戎(Omicron)感染轻症患者症状和核酸转阴时间的影响。方法收集2022年3-5月入住吉林省长春市双阳区奢岭方舱医院348例Omicron感染者的临床资料,分析不同性别、基础疾病、疫苗接种次数患者临床症... 目的探讨不同性别和疫苗接种次数对奥密克戎(Omicron)感染轻症患者症状和核酸转阴时间的影响。方法收集2022年3-5月入住吉林省长春市双阳区奢岭方舱医院348例Omicron感染者的临床资料,分析不同性别、基础疾病、疫苗接种次数患者临床症状和核酸转阴时间的特点。结果不同性别、基础疾病、疫苗接种次数患者感染Omicron后核酸转阴时间比较,差异无统计学意义(P>0.05);但与男性比较,女性感染Omicron后更容易出现多个轻型症状(≥3个),差异有统计学意义(P<0.05)。结论女性感染Omicron后更容易出现多个轻型症状;而性别和疫苗接种次数对Omicron感染者核酸转阴时间影响不显著。 展开更多
关键词 奥密克戎 疫苗 接种 性别因素 症状 核酸转阴时间
下载PDF
Understanding Surface Water-Groundwater Conversion Relationship and Associated Hydrogeochemistry Evolution in the Upper Reaches of Luan River Basin, North China
15
作者 Le Zhao Chunli Su +1 位作者 Wenbo Liu Xianjun Xie 《Journal of Earth Science》 SCIE CAS CSCD 2024年第3期1010-1023,共14页
Luan River is the main water source in Beijing-Tianjin-Hebei region,northern China,where the groundwater system is vulnerable and pollution issue is serious.It is significant for regional groundwater resources protect... Luan River is the main water source in Beijing-Tianjin-Hebei region,northern China,where the groundwater system is vulnerable and pollution issue is serious.It is significant for regional groundwater resources protection to identify the hydrogeochemistry evolution and affecting factors along flow direction occurred in the upper reaches,especially the surface water-groundwater(SWGW)conversion relationship.In this study,recharge,conversion and geochemistry evolution of SW and GW were elucidated based on physical-hydrochemical indicators and stable isotopes in 36 GW samples and 20 SW samples,which were collected in July 2019 and July 2020.The factor analysis was further utilized to determine the main factors responsible for regional hydrogeochemical evolution.Results indicate that GW recharged SW in plateau area,and SW and GW recharged each other in typical Alpine valley area.The hydrochemical types are HCO3-Ca·Mg and HCO3-Ca,and the hydrochemical evolution is dominated by weathering of silicate and carbonate minerals.The cation exchange adsorption has minor impact on groundwater hydrochemistry.The rise of SO42-and NO3-contents in groundwater is related to industrial and agricultural activities.The main controlling factors of SW hydrochemical components included recharge from groundwater,industrial and mining activities,explaining 90.04%of data variance.However,water-rock interaction,agricultural and domestic sewage are responsible for GW quality,accounting for 83.38%. 展开更多
关键词 GROUNDWATER water sources conversion relationship hydrogeochemical characteristics evolutional processes water-rock interaction factor analysis Luan River Basin.
原文传递
初始不可切除结直肠癌肝转移患者转化治疗结局的影响因素及风险预测模型构建
16
作者 陈明凯 李潇 +1 位作者 张宇 魏辰 《实用癌症杂志》 2024年第5期803-808,共6页
目的探讨初始不可切除结直肠癌肝转移患者转化治疗结局的影响因素,并构建风险预测模型。方法采用回顾性研究,选取转化治疗失败的50例初始不可切除结直肠癌肝转移患者作为转化失败组,另选取同期转化治疗成功的81例患者作为转化成功组。... 目的探讨初始不可切除结直肠癌肝转移患者转化治疗结局的影响因素,并构建风险预测模型。方法采用回顾性研究,选取转化治疗失败的50例初始不可切除结直肠癌肝转移患者作为转化失败组,另选取同期转化治疗成功的81例患者作为转化成功组。收集两组患者的基线资料及相关临床指标,采用Logistic回归性分析检验影响初始不可切除结直肠癌肝转移患者转化治疗结局的影响因素,依据回归结果构建风险预测模型,再绘制受试者工作曲线(ROC)分析风险预测模型效能。结果两组患者在肿瘤原发部位、肝转移灶数量、是否侵犯门静脉、血清白蛋白、是否贫血方面比较,差异有统计学意义(P<0.05)。经Logistic回归性分析显示肿瘤位于右半结肠,转移灶数量≥5个,侵犯门静脉,血清白蛋白<36 g/L,贫血是影响初始不可切除结直肠癌肝转移患者转化治疗结局的影响因素(P<0.05)。构建风险预测模型,ROC内部验证显示曲线下面积(AUC)为0.784,AUC的95%CI为:0.703~0.864、P<0.001、特异度:0.654,敏感度:0.880,约登指数:0.534。外部验证:AUC为0.793,AUC的95%CI为0.714~0.873、P<0.001、特异度:0.654,敏感度:0.880,约登指数:0.534。结论肿瘤原发部位、侵犯门静脉、血清白蛋白、贫血及肝转移灶数量是影响初始不可切除结直肠癌肝转移患者转化治疗结局的影响因素,基于上述因素构建的风险预测模型对转化治疗效果具有中等预测价值。 展开更多
关键词 初始不可切除结直肠癌肝转移 转化治疗 影响因素 风险预测模型
下载PDF
基于VMD自适应模态重组的光学下变频信号分离方法
17
作者 孙世腾 谢树果 +1 位作者 宋雨杭 濮晗春 《强激光与粒子束》 CAS CSCD 北大核心 2024年第4期145-152,共8页
光学下变频技术可将宽频带内全部电磁信号同时下变频到低频区间进行接收,是一种新型宽频带电磁环境快速接收技术。但是,获取的光学下变频信号中包含源个数未知、带宽不同的多种信号,现有信号分离方法需要获知源信号的个数,且无法同时分... 光学下变频技术可将宽频带内全部电磁信号同时下变频到低频区间进行接收,是一种新型宽频带电磁环境快速接收技术。但是,获取的光学下变频信号中包含源个数未知、带宽不同的多种信号,现有信号分离方法需要获知源信号的个数,且无法同时分离窄带信号和宽带信号。为实现对光学下变频信号的自动分离,提出了一种基于变分模态分解(VMD)自适应模态重组的光学下变频信号分离方法。通过频谱分割因子和频谱包络检测,对光学下变频信号的VMD过分解模态进行自动重组和信号重组模态提取,实现光学下变频信号分离。对于包含普通脉冲信号、宽带码分多址(WCDMA)信号和线性调频脉冲信号的光学下变频信号,可自动实现对三种信号的分离,且与原信号的相似系数均高于0.97。实验结果表明,所提及方法在分离光学下变频信号时无需获知源信号的个数,并能同时分离具有不同带宽的多种源信号。 展开更多
关键词 变分模态分解 光学下变频 单通道信号分离 频谱分割因子 频谱包络检测
下载PDF
船桥碰撞非线性数值仿真研究
18
作者 周阳 陈斌 罗宇 《湖南工业大学学报》 2024年第2期14-19,共6页
为了研究湘江流域典型桥梁船桥碰撞时的撞击力和能量转换过程,为后续大桥的防船撞设计提供参考,以株洲建宁大桥为研究背景,按照实际尺寸建立货船和桥墩模型,并使用ABAQUS有限元软件对其进行非线性动力仿真分析,研究了船桥碰撞过程中,船... 为了研究湘江流域典型桥梁船桥碰撞时的撞击力和能量转换过程,为后续大桥的防船撞设计提供参考,以株洲建宁大桥为研究背景,按照实际尺寸建立货船和桥墩模型,并使用ABAQUS有限元软件对其进行非线性动力仿真分析,研究了船桥碰撞过程中,船的撞击速度、吨位和撞击角度对撞击力的影响,以及船的变形情况和船桥碰撞中的能量转化关系。研究结果表明:船撞力峰值和船速存在正相关关系;船舶的吨位越大,撞击力峰值越大并且撞击的时间越长;船的撞击角度与碰撞时间之间没有呈现出明显的规律;船的撞击速度、吨位和撞击角度3种影响因素对船桥碰撞的撞击力和船体变形均有影响,但主要因素还是船速和船的吨位;在碰撞过程中,船的撞击动能基本转化为塑性变形能,船体变形主要集中在船艏碰撞区域,远离碰撞区域的船身部位没有明显的变形。 展开更多
关键词 船桥碰撞 非线性动力学 撞击力 影响因素 变形和能量转化
下载PDF
亚热带森林转换对土壤无脊椎动物群落结构的影响
19
作者 温辉辉 张慧玲 +3 位作者 彭艳 彭清清 邱丹妮 吴福忠 《生态学报》 CAS CSCD 北大核心 2024年第10期4254-4262,共9页
受人类活动干扰的增加,亚热带森林频繁转换为次生林和人工林,可能显著影响土壤无脊椎动物群落结构及其生态功能,但当前的认识并不一致。因此,于2022年7月调查了亚热带天然常绿阔叶林转换为次生林、米槠人工林、杉木人工林后土壤无脊椎... 受人类活动干扰的增加,亚热带森林频繁转换为次生林和人工林,可能显著影响土壤无脊椎动物群落结构及其生态功能,但当前的认识并不一致。因此,于2022年7月调查了亚热带天然常绿阔叶林转换为次生林、米槠人工林、杉木人工林后土壤无脊椎动物群落结构特征。共捕获土壤无脊椎动物659只,丰度为26540只/m~2,隶属1门6纲13目59科,其中蚁科和球角虫兆科为优势类群。森林转换改变了土壤无脊椎动物群落组成和多样性。天然林向米槠人工林和杉木人工林转换后,土壤无脊椎动物丰度和类群均明显降低,其中大型土壤无脊椎动物丰度的响应更为敏感,在2种林型中分别显著降低了33.58%和36.53%。尽管林型转换对土壤无脊椎动物群落多样性指数无显著影响,但改变了土壤无脊椎动物群落组成,其中天然林与杉木人工林群落组成极不相似(J<0.25),等节虫兆科为杉木人工林优势类群,占比达到59.84%。冗余分析显示,土壤湿度、凋落物现存量和凋落物磷含量是影响土壤无脊椎动物群落的主要因子,对土壤无脊椎动物群落的解释率为69.30%。可见,林型转换可能通过改变土壤理化性质和凋落物质量,调控土壤无脊椎动物群落结构。 展开更多
关键词 森林转换 土壤无脊椎动物 群落特征 环境因子
下载PDF
海洋温差发电混合工质二次热回收循环系统理论和实验研究
20
作者 陈凤云 彭景平 +3 位作者 刘蕾 葛云征 王泉斌 刘伟民 《海洋科学进展》 CAS CSCD 北大核心 2024年第1期185-195,共11页
因海洋温差发电系统中可利用的温差较小,发电效率相对较低,寻求海洋温差发电系统高效热力循环方式一直是该领域的重要研究内容。本文构建了非共沸混合工质的海洋温差发电热力循环,增加了稀溶液支路的二次热回收装置,并进行理论分析与数... 因海洋温差发电系统中可利用的温差较小,发电效率相对较低,寻求海洋温差发电系统高效热力循环方式一直是该领域的重要研究内容。本文构建了非共沸混合工质的海洋温差发电热力循环,增加了稀溶液支路的二次热回收装置,并进行理论分析与数值计算,得到了循环效率与工质浓度、透平进口压力和抽气系数等参数之间的关系。结果表明:通过增加稀溶液支路的二次热回收装置,循环效率最高可达5.25%。研建了10 kW二次热回收海洋温差发电系统,得到了平稳运行工况下的系统性能,发电系统效率最高达3.8%,同时得到了蒸发器和冷凝器在该换热条件下的换热系数,为工程应用提供基础数据和技术支撑。 展开更多
关键词 海洋温差发电 热力循环 循环效率 工质浓度 抽气系数
下载PDF
上一页 1 2 39 下一页 到第
使用帮助 返回顶部