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Associate factors for endoscopic submucosal dissection operation time and postoperative delayed hemorrhage of early gastric cancer 被引量:6
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作者 Ren-Song Cai Wei-Zhong Yang Guang-Rui Cui 《World Journal of Gastrointestinal Surgery》 SCIE 2023年第1期94-104,共11页
BACKGROUND Endoscopic submucosal dissection(ESD)is a treatment for early gastric cancer with the advantages of small invasion,fewer complications,and a low local recurrence rate.However,there is a high risk of complic... BACKGROUND Endoscopic submucosal dissection(ESD)is a treatment for early gastric cancer with the advantages of small invasion,fewer complications,and a low local recurrence rate.However,there is a high risk of complications such as bleeding and perforation,and the operation time is also longer.ESD operation time is closely related to bleeding and perforation.AIM To investigate the influencing factors associated with ESD operation time and postoperative delayed hemorrhage to provide a reference for early planning,early identification,and prevention of complications.METHODS We conducted a retrospective study based on the clinical data of 520 patients with early gastric cancer in the Second Affiliated Hospital of Hainan Medical University from January 2019 to December 2021.The baseline data,clinical features,and endoscopic and pathological characteristics of patients were collected.The multivariate linear regression model was used to investigate the influencing factors of ESD operation time.Logistic regression analysis was carried out to evaluate the influencing factors of postoperative delayed hemorrhage.RESULTS The multivariate analysis of ESD operation time showed that the maximum lesion diameter could affect 8.815%of ESD operation time when other influencing factors remained unchanged.The operation time increased by 3.766%or 10.247%if the lesion was mixed or concave.The operation time increased by 4.417%if combined with an ulcer or scar.The operation time increased by 3.692%if combined with perforation.If infiltrated into the submucosa,it increased by 2.536%.Multivariate analysis of delayed hemorrhage after ESD showed that the maximum diameter of the lesion,lesion morphology,and ESD operation time were independent influencing factors for delayed hemorrhage after ESD.Patients with lesion≥3.0 cm(OR=3.785,95%CI:1.165-4.277),lesion morphology-concave(OR=10.985,95%CI:2.133-35.381),and ESD operation time≥60 min(OR=2.958,95%CI:1.117-3.526)were prone to delayed hemorrhage after ESD.CONCLUSION If the maximum diameter of the lesion in patients with early gastric cancer is≥3.0 cm,and the shape of the lesion is concave,or accompanied by an ulcer or scar,combined with perforation,and infiltrates into the submucosa,the ESD operation will take a longer time.When the maximum diameter of the lesion is≥3.0 cm,the shape of the lesion is concave in patients and the operation time of ESD takes longer time,the risk of delayed hemorrhage after ESD is higher. 展开更多
关键词 early gastric cancer Endoscopic submucosal dissection Operation time Delayed hemorrhage
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Early-season crop type mapping using 30-m reference time series 被引量:3
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作者 HAO Peng-yu TANG Hua-jun +2 位作者 CHEN Zhong-xin MENG Qing-yan KANG Yu-peng 《Journal of Integrative Agriculture》 SCIE CAS CSCD 2020年第7期1897-1911,共15页
Early-season crop type mapping could provide important information for crop growth monitoring and yield prediction,but the lack of ground-surveyed training samples is the main challenge for crop type identification.Al... Early-season crop type mapping could provide important information for crop growth monitoring and yield prediction,but the lack of ground-surveyed training samples is the main challenge for crop type identification.Although reference time series based method(RBM)has been proposed to identify crop types without the use of ground-surveyed training samples,the methods are not suitable for study regions with small field size because the reference time series are mainly generated using data set with low spatial resolution.As the combination of Landsat data and Sentinel-2 data could increase the temporal resolution of 30-m image time series,we improved the RBM by generating reference normalized difference vegetation index(NDVI)/enhanced vegetation index(EVI)time series at 30-m resolution(30-m RBM)using both Landsat and Sentinel-2 data,then tried to estimate the potential of the reference NDVI/EVI time series for crop identification at early season.As a test case,we tried to use the 30-m RBM to identify major crop types in Hengshui,China at early season of 2018,the results showed that when the time series of the entire growing season were used for classification,overall classification accuracies of the 30-m RBM were higher than 95%,which were similar to the accuracies acquired using the ground-surveyed training samples.In addition,cotton,spring maize and summer maize distribution could be accurately generated 8,6 and 8 weeks before their harvest using the 30-m RBM;but winter wheat can only be accurately identified around the harvest time phase.Finally,NDVI outperformed EVI for crop type classification as NDVI had better separability for distinguishing crops at the green-up time phases.Comparing with the previous RBM,advantage of 30-m RBM is that the method could use the samples of the small fields to generate reference time series and process image time series with missing value for early-season crop casification;while,samples collected from multiple years should be futher used so that the reference time series could contain more crop growth conditions. 展开更多
关键词 early season LANDSAT Sentinel-2 reference time series crop classification Hengshui
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A dynamic programming algorithm for scheduling problems on earliness award and tardiness penalty with time-dependent processing time 被引量:1
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作者 余英 孙世杰 何龙敏 《Journal of Shanghai University(English Edition)》 CAS 2008年第3期204-209,共6页
In this paper, a single-machine scheduling model with a given common due date is considered. Job processing time is a linear decreasing function of its starting time. The objective function is to minimize the total we... In this paper, a single-machine scheduling model with a given common due date is considered. Job processing time is a linear decreasing function of its starting time. The objective function is to minimize the total weighted earliness award and tardiness penalty. Our aim is to find an optimal schedule so as to minimize the objective function. As the problem is NP-hard, some properties and polynomial time solvable cases of this problem are given. A dynamic programming algorithm for the general case of the problem is provided. 展开更多
关键词 scheduling SINGLE-MACHINE linear decreasing processing time EARLINESS TARDINESS
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Classification of Short Time Series in Early Parkinson’s Disease With Deep Learning of Fuzzy Recurrence Plots 被引量:9
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作者 Tuan D.Pham Karin Wardell +1 位作者 Anders Eklund Goran Salerud 《IEEE/CAA Journal of Automatica Sinica》 EI CSCD 2019年第6期1306-1317,共12页
There are many techniques using sensors and wearable devices for detecting and monitoring patients with Parkinson’s disease(PD).A recent development is the utilization of human interaction with computer keyboards for... There are many techniques using sensors and wearable devices for detecting and monitoring patients with Parkinson’s disease(PD).A recent development is the utilization of human interaction with computer keyboards for analyzing and identifying motor signs in the early stages of the disease.Current designs for classification of time series of computer-key hold durations recorded from healthy control and PD subjects require the time series of length to be considerably long.With an attempt to avoid discomfort to participants in performing long physical tasks for data recording,this paper introduces the use of fuzzy recurrence plots of very short time series as input data for the machine training and classification with long short-term memory(LSTM)neural networks.Being an original approach that is able to both significantly increase the feature dimensions and provides the property of deterministic dynamical systems of very short time series for information processing carried out by an LSTM layer architecture,fuzzy recurrence plots provide promising results and outperform the direct input of the time series for the classification of healthy control and early PD subjects. 展开更多
关键词 Deep learning early Parkinson’s disease(PD) fuzzy recurrence plots long short-term memory(LSTM) neural networks pattern classification short time series
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Probabilistic earthquake early warning times in Fujian Province 被引量:1
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作者 Hongcai Zhang Xing Jin 《Earthquake Science》 2013年第1期33-41,共9页
Earthquake early warning (EEW) systems are a new and effective way to mitigate the damage associated with earthquakes. A prototype EEW system is currently being constructed in the Fujian Province, a region along the... Earthquake early warning (EEW) systems are a new and effective way to mitigate the damage associated with earthquakes. A prototype EEW system is currently being constructed in the Fujian Province, a region along the Southeast coast of China. It is anticipated that the system will be completed in time to be tested at the end of this year (2013). In order to evaluate how much advanced warning the EEW system will be able to provide different cities in Fujian, we established an EEW information release scheme based on the seismic monitoring stations distributed in the region. Based on this scheme, we selected 71 historical earthquakes. We then obtained the delineation of the region's potential seismic source data in order to estimate the highest potential seismic intensities for each city as well as the EEW system warning times. For most of the Fujian Province, EEW alarms would sound several seconds prior to the arrival of the destructive wave. This window of time gives city inhabitants the opportunity to take protective measures before the full intensity of the earthquake strikes. 展开更多
关键词 Earthquake early warning systems Lead time Fujian region
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Evaluation of reference genes for quantitative real-time PCR analysis of gene expression during early development processes of the tongue sole(Cynoglossus semilaevis) 被引量:3
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作者 MA Qian ZHUANG Zhimeng +2 位作者 FENG Wenrong LIU Shufang TANG Qisheng 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2015年第10期90-97,共8页
Differential expression of genes is crucial to growth and development of fish. To select the appropriate genes for gene normalization during Cynoglossus semilaevis early developmental process, eight candidate referenc... Differential expression of genes is crucial to growth and development of fish. To select the appropriate genes for gene normalization during Cynoglossus semilaevis early developmental process, eight candidate reference genes (ACTB, B2M, EF1A, GADPH, RPL7, TUBA, UBCE and 18S) were tested for their adequacy by using quantitative real-time PCR. The results showed that the expression of all the examined genes exhibited tissue dependent variations in the mature C. semilaevis. EFIA was listed as the most stable reference among the 14 tissues by RefFinder. Furthermore, the recommended comprehensive ranking of the stability determined by RefFinder showed that 18S was the most stable gene during the early developmental stages (from oosphere to 90 days old) in this study. However, when divided the Ct value data of the above mentioned early developmental stages into two separate periods (embryo and post-hatching periods), TUBA and 18S represented the most stable references of these two developmental periods, respectively. Consequently, the reference gene should be carefully and accurately chosen even for studies of the same species at various developmental processes. The relevant data may help in selecting appropriate reference genes for mRNA expression analysis, and is of great value in the studies of fish growth and development. 展开更多
关键词 quantitative real-time PCR reference gene early development Cynoglossus semilaevis
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A Study on the Early Warning Time of Strong Earthquakes in Taiwan
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作者 Chen Huifang Kang Lanchi +2 位作者 Jin Xing Shao Pingrong Cao Yi 《Earthquake Research in China》 CSCD 2017年第1期125-135,共11页
The paper collects the records by the Fujian Digital Seismic Network of 40 shallow earthquakes in Taiwan with M_S≥5.0 from 1999 to 2013,analyzes the seismic phase(Pn,Sn phase)characteristics and travel-time rules,det... The paper collects the records by the Fujian Digital Seismic Network of 40 shallow earthquakes in Taiwan with M_S≥5.0 from 1999 to 2013,analyzes the seismic phase(Pn,Sn phase)characteristics and travel-time rules,determines travel-time models and develops a seismic phase travel-time equation based on the two-step fitting algorithm.With the deduction of processing time and network delay time,this method can provide an accurate estimation of early warning time of Taiwan earthquakes for the Fujian region,and has been officially employed in the earthquake early warning system of Fujian Province. 展开更多
关键词 Strong earthquakes of Taiwan Characteristics of seismic phases Traveltime rule early warning time
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DETECTION OF EARLY RUB-IMPACT IN ROTORS VIA HIGHER-ORDER TIME-FREQUENCY ENTROPY 被引量:1
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作者 ChenZhongsheng YangYongmin HuZheng ShenGuoji 《Chinese Journal of Mechanical Engineering》 SCIE EI CAS CSCD 2004年第4期614-617,共4页
Due to the calculation problem of classical methods (such as Lyapunovexponent) for chaotic behavior, a new method of identifying nonlinear dynamics with higher-ordertime-frequency entropy (HOTFE) based on time-frequen... Due to the calculation problem of classical methods (such as Lyapunovexponent) for chaotic behavior, a new method of identifying nonlinear dynamics with higher-ordertime-frequency entropy (HOTFE) based on time-frequency analysis and information theorem is proposed.Firstly, the meaning of HOTFE is defined, and then its validity is testified by numericalsimulation. In the end vibration data from rotors are analyzed by HOTFE. The results demonstratethat it can indeed identify the early rub-impact chaotic behavior in rotors and also is simpler tocalculate than previous methods. 展开更多
关键词 Higher-order time-frequeney entropy(HOTFE) Chaotic behavior early faults RUB-IMPACT
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Early Estimation of Strong Aftershock Duration Time
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作者 Zhou Cuiying,Wang Hongwei,Wang Mei,and Zhang YuxiaSeismological Bureau of Shandong Province,Jinan 250014,China Center for Analysis and Prediction,SSB,Beijing 100036,China 《Earthquake Research in China》 1997年第4期35-44,共10页
In order to solve the problem of early estimation of moderately strong aftershock duration time in an earthquake sequence,this study has been conducted.First,the definition of the strong aftershock has been given.It i... In order to solve the problem of early estimation of moderately strong aftershock duration time in an earthquake sequence,this study has been conducted.First,the definition of the strong aftershock has been given.It is pointed out that there is a difference in the strong aftershock duration time between the main shock type sequence and the strong earthquake swarm sequence.After dividing the three cases,i.e.,a strong aftershock duration time larger than 1 day,smaller than 1 day,and no strong aftershock occurred in a main shock type sequence by using the pattern recognition method,we gave the rough correlation relation between strong aftershock duration time and first large shock magnitude for two types of sequences.Finally,the judgment index and method of estimating strong aftershock duration times for different sequence types have been given. 展开更多
关键词 STRONG AFTERSHOCK DURATION time PATTERN recognition early estimation.
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On the Feminist Comparative Study of Views on Marriage Between the Early Nineteenth Century and Modern Times—Taking Pride and Prejudice for Example
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作者 张平 《海外英语》 2016年第9期176-178,共3页
Marriage is a theme influenced by cultural progress. Economic factor is one of the main elements that people of the early nineteenth century considered when deciding a marriage. The pursuit of economic interest result... Marriage is a theme influenced by cultural progress. Economic factor is one of the main elements that people of the early nineteenth century considered when deciding a marriage. The pursuit of economic interest results in the advent of some tragic marriages while now it is a side reason. However, women today have made great advancement in education background, employment situation and social status. Women gradually have their economic ability, autonomy and social status. Hence, they began to lay emphasis on the equality and sense of happiness. This is why the views on marriage vary in different eras. This paper, based on the view of marriage from the nineteenth- century English novel Pride and Pejudice, is dedicated to elucidating the changes and improvements of view on marriage from feminist perspective via comparing and contrasting the similarities and the differences of people's view on marriage between the early 1800 s and modern times, and then draws a conclusion that the women's degree of receptive education can influence their social status and view on marriage. In modern times the view on marriage based on equality attribute to the sense of happiness of a family and the degree of satisfaction of marriage. 展开更多
关键词 the early 1800s modern times view on MARRIAGE FEMINIST perspective SIMILARITIES differences degree o
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Recognizing Early Warning Signs (EWS) in Patients Is Critically Important
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作者 Shamsa Samani Salma Amin Rattani 《Open Journal of Nursing》 2023年第1期53-64,共12页
Introduction: Monitoring vital signs is a basic indicator of a patient’s health status and allows prompt detection of delayed recovery or adverse effects and early intervention. Patients with adverse events during ho... Introduction: Monitoring vital signs is a basic indicator of a patient’s health status and allows prompt detection of delayed recovery or adverse effects and early intervention. Patients with adverse events during hospitalization often display clinical decline for several hours before the event is observed. Non-critical care Nurses’ inconsistent recognition and response to patient deterioration lead to an increase in the length of hospital stay, unexpected admissions to the ICU, and increased morbidity and mortality. Aim: The study aimed to assess the factors that facilitate or impede the detection of early warning signs among adult patients hospitalized in tertiary care settings. Training should be provided to improve nurses’ knowledge, practice and attitude toward early warning signs of deteriorating patients leading to enhanced clinical judgment, skills and decision-making in addressing alerts. Methodology: A literature search was carried out in various databases;these were Cumulative Index to Nursing and Allied Health Literature (CINHAL), Google Scholar, PubMed, Science Direct, and Sage. The search area was narrowed from 2017 to 2022. The keywords used were “prevalence” AND “unplanned ICU admission”, “the importance of early warning signs” “outcome failure in rescue” “patient deterioration, communication” “improvement in early detection” AND “patient outcome admission” AND “early warning signs” AND “Pakistan”. After the analysis process, around 33 articles that met the inclusion criteria and were most relevant to the scope and context of the current study were considered. Conclusion: Most of the studies had reviewed literature in a qualitative retrospective observational study, content analysis, mixed method, and quasi-experimental study. The literature review identified that long hours of shift, nurse staffing levels, missed vital signs, lack of nursing training and education, and communication impact nurses’ ability to recognize and respond to early warning signs. 展开更多
关键词 early Warning Signs Handover Communication Long Hours Rapid Response Team Just in time Training
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Code synchronization based on lumped time-delay compensation scheme with a linearly chirped fiber Bragg grating in all-optical analog-to-digital conversion
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作者 王涛 康哲 +4 位作者 苑金辉 田野 颜玢玢 桑新柱 余重秀 《Chinese Physics B》 SCIE EI CAS CSCD 2014年第10期180-185,共6页
We propose a novel lumped time-delay compensation scheme for all-optical analog-to-digital conversion based on soliton self-frequency shift and optical interconnection techniques. A linearly chirped fiber Bragg gratin... We propose a novel lumped time-delay compensation scheme for all-optical analog-to-digital conversion based on soliton self-frequency shift and optical interconnection techniques. A linearly chirped fiber Bragg grating is optimally designed and used to compensate for the entire time-delays of the quantized pulses precisely. Simulation results show that the compensated coding pulses are well synchronized with a time difference less than 3.3 ps, which can support a maximum sampling rate of 151.52 GSa/s. The proposed scheme can efficiently reduce the structure complexity and cost of all-optical analog-to-digital conversion compared to the previous schemes with multiple optical time-delay lines. 展开更多
关键词 all-optical analog-to-digital lumped time-delay compensation soliton self-frequency shift lin-early chirped fiber Bragg grating
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基于LSTM网络的单台仪器地震烈度预测模型 被引量:2
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作者 李山有 王博睿 +4 位作者 卢建旗 王傲 张海峰 谢志南 陶冬旺 《地球物理学报》 SCIE EI CAS CSCD 北大核心 2024年第2期587-599,共13页
烈度是地震预警系统的关键产出.如何实现快速预测目标场址的地震烈度是地震预警方法技术研究中的核心问题.本文提出了一种基于长短时记忆神经网络(Long Short-Term Memory,LSTM)的单台仪器地震烈度的预测模型(LSTM-Ⅰ).该模型以一个台... 烈度是地震预警系统的关键产出.如何实现快速预测目标场址的地震烈度是地震预警方法技术研究中的核心问题.本文提出了一种基于长短时记忆神经网络(Long Short-Term Memory,LSTM)的单台仪器地震烈度的预测模型(LSTM-Ⅰ).该模型以一个台站观测到地震动参数的时间序列特征为输入,实现动态预测该台站可能遭受的最大烈度.选取了日本K-NET台网记录的102次地震的5103条强震加速度记录训练了神经网络,利用89次地震的3781条数据检验了模型的泛化能力.利用准确率、漏报率以及误报率三个评价指标评价了LSTM-Ⅰ模型的性能.结果表明,当采用P波触发后3 s的序列进行预测时,模型出现漏报的概率为46.78%,出现误报的概率为1.25%;当采用P波触发后10 s的序列进行预测时,模型出现漏报的概率大幅降低到17.6%,出现误报的概率降低到1.14%.结果表明LSTM-Ⅰ模型很好把握住了时间序列中蕴含的特征.进一步基于LSTM-Ⅰ模型评估了Ⅵ度下台站所能提供的预警时间.本文模型能够提供的预警时间与P-S波到时差接近,说明LSTM-Ⅰ模型具有较高的时效性. 展开更多
关键词 地震预警 时间序列特征 LSTM神经网络 仪器地震烈度 预测
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基于分形维数的高速铁路地震预警系统地震P波震相识别方法 被引量:1
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作者 杨长卫 张凯文 +3 位作者 吴东升 张志方 张良 瞿立明 《铁道学报》 EI CAS CSCD 北大核心 2024年第1期164-171,共8页
为更好保障高速铁路的运营安全,高速铁路地震预警系统的实施十分必要。5级以下的小震事件占据地震事件的95%以上,提高高速铁路预警系统在小震震相识别的速度与精度能有效保障高铁安全运营。提出一种基于分形维数的地震震相识别算法,优... 为更好保障高速铁路的运营安全,高速铁路地震预警系统的实施十分必要。5级以下的小震事件占据地震事件的95%以上,提高高速铁路预警系统在小震震相识别的速度与精度能有效保障高铁安全运营。提出一种基于分形维数的地震震相识别算法,优化传统分形维数的计算方法,提高分形维数的计算速度。引入分形斜率曲线并划分为4个阶段,分析临界点的分形斜率特征,通过识别分形斜率极值时刻判断地震波精准到达时刻。提出的算法平均误差达到0.006 3 s,标准差达到0.043 8 s,满足高速铁路地震预警系统的时效性和准确度要求。 展开更多
关键词 高速铁路 地震预警 P波识别 长时窗均值与短时窗均值之比 赤池信息法则
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早龄期机制砂混凝土抗压强度与弹性模量时效关系及本构模型试验研究
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作者 郭琦 张卓 +2 位作者 蒲广宁 刘斌 孙虎平 《公路工程》 2024年第2期138-144,共7页
为了研究早龄期机制砂混凝土在单轴受压状态下抗压强度与弹性模量的时效关系和本构模型,通过对8组不同龄期的C60机制砂混凝土试件进行立方体抗压强度试验、静力受压弹性模量试验和单轴受压应力-应变曲线试验,并参考多种已有研究模型,建... 为了研究早龄期机制砂混凝土在单轴受压状态下抗压强度与弹性模量的时效关系和本构模型,通过对8组不同龄期的C60机制砂混凝土试件进行立方体抗压强度试验、静力受压弹性模量试验和单轴受压应力-应变曲线试验,并参考多种已有研究模型,建立了早龄期机制砂混凝土在单轴受压状态下的抗压强度与弹性模量时效关系模型和分段式应力-应变本构模型。结果表明,采用的抗压强度与弹性模量时效关系模型和分段式应力-应变本构模型与试验数据吻合效果理想,能够较好地描述早龄期C60机制砂混凝土在单轴受压状态下的力学性能。 展开更多
关键词 早龄期 时效关系 分段式 本构模型
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考虑椭圆模型M_W≥5.5地震震源参数时域计算方法
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作者 王江 马强 +3 位作者 陶冬旺 章旭斌 解全才 林德昕 《地球物理学报》 SCIE EI CAS CSCD 北大核心 2024年第3期1093-1107,共15页
为提高时效性,地震预警系统对震源的处理一般采用“点源”假定,不考虑震源尺度、破裂方向和震源区应力降,对震源参数简化处理使得预测地震动参数分布过于粗略,特别是对破坏性大震.本文应用日本地震(M_W≥5.5)强震动数据,考虑椭圆震源模... 为提高时效性,地震预警系统对震源的处理一般采用“点源”假定,不考虑震源尺度、破裂方向和震源区应力降,对震源参数简化处理使得预测地震动参数分布过于粗略,特别是对破坏性大震.本文应用日本地震(M_W≥5.5)强震动数据,考虑椭圆震源模型,提出了一种适用于中、大地震矩震级、拐角频率和应力降等震源参数时域计算方法,并分析了场地效应、地震动传播衰减、震源效应和滤波频带等因素对时域方法的影响.结果表明,该方法能利用P波信息快速获取震源能量释放过程,量化随破裂传播震源谱拐角频率、应力降和破裂面积的演化过程,为地震动预测提供更多重要的震源参数. 展开更多
关键词 地震预警 时间域 矩震级 拐角频率 应力降 破裂面积
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我国经济风险的实时监测:结构性拐点判别与预警信息辨识
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作者 隋建利 吕文强 刘金全 《统计研究》 CSSCI 北大核心 2024年第10期32-48,共17页
实时监测经济风险、判别经济风险演化方向,对于促进高质量发展和高水平安全良性互动具有重要意义。本文运用马尔科夫区制转移偏正态分布模型甄别经济风险的结构变迁路径,并基于驱动结构分解、概率分布矩、概率密度函数以及尾部风险等多... 实时监测经济风险、判别经济风险演化方向,对于促进高质量发展和高水平安全良性互动具有重要意义。本文运用马尔科夫区制转移偏正态分布模型甄别经济风险的结构变迁路径,并基于驱动结构分解、概率分布矩、概率密度函数以及尾部风险等多维视阈,有效辨析经济和金融状况对于经济风险的预警功能。研究发现,首先,随着经济增长概率分布的风险区制由低到高,经济增长增速预期降低、波动区间扩张以及下行风险升高。其次,经济风险在2012年存在显著的结构性拐点,在突变点后,偏度系数由正转负,经济步入长期的下行风险通道。此外,经济风险在2019年以及2021年前后存在阶段性拐点,短期内经济上行概率较高。然后,经济风险的动态演化路径表现出显著的“事件驱动”特征,在极端事件冲击下,经济下行风险有所增加。最后,经济和金融状况对于经济风险的预警功能存在明显的异质性,其中经济状况无法提供经济风险的预警信息,而金融状况能够灵敏地识别与捕捉经济增长的风险信息,且在经济高风险时期,金融状况的预警功能更为显著。 展开更多
关键词 经济风险 实时监测 结构性拐点 预警信息 马尔科夫区制转移偏正态分布模型
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基于LSTM神经网络的现地烈度实时估算模型——以JMA烈度为例
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作者 李山有 肖莹 +3 位作者 卢建旗 谢志南 马强 陶冬旺 《世界地震工程》 北大核心 2024年第3期37-45,共9页
如何快速并且准确估计目标场点烈度是地震预警中的关键问题。常用基于衰减关系的场点烈度估计和基于P波信息的现地烈度估计往往存在大震烈度低估的问题。本文提出了一种基于长短时记忆神经网络(logn short-term memery,LSTM)的现地JMA... 如何快速并且准确估计目标场点烈度是地震预警中的关键问题。常用基于衰减关系的场点烈度估计和基于P波信息的现地烈度估计往往存在大震烈度低估的问题。本文提出了一种基于长短时记忆神经网络(logn short-term memery,LSTM)的现地JMA烈度持续估计模型。该模型以现地观测地震动的能量、能量增长率、地震动卓越周期和震源距作为输入,以该点的最大仪器地震烈度为预测目标。选取了日本K-NET台网记录101次地震数据作为训练集,94次地震数据作为测试集,训练了现地烈度估算LSTM神经网络模型。结果表明:在采用3 s时窗长度的序列进行预测时,高估的比例为1.51%,低估的比例为4.00%;并且,随着时窗长度的增加,高估和低估的比例也在不断降低。模型对高烈度(大于等于4.5度)样本的预测时效性随震源距的增加而增加,对大震远场高烈度区域能提供20 s以上的预警时间。 展开更多
关键词 地震预警 现地预警 长短时记忆神经网络 实时减灾 烈度估计
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基于Sentinel-2的青铜峡灌区春小麦和苜蓿早期识别
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作者 朱磊 张伟业 +5 位作者 潘自林 丁一民 雷晓萍 张宗和 孙伯颜 柴明堂 《灌溉排水学报》 CAS CSCD 2024年第5期86-94,共9页
【目的】基于决策树分类算法对青铜峡灌区春小麦和苜蓿进行早期识别。【方法】在实地调研的基础上,结合Sentinel-2遥感影像,构建能够不断融入遥感数据的决策树分类算法,对青铜峡灌区春小麦和苜蓿进行早期识别。【结果】4月上旬,由于春... 【目的】基于决策树分类算法对青铜峡灌区春小麦和苜蓿进行早期识别。【方法】在实地调研的基础上,结合Sentinel-2遥感影像,构建能够不断融入遥感数据的决策树分类算法,对青铜峡灌区春小麦和苜蓿进行早期识别。【结果】4月上旬,由于春小麦和苜蓿生长特征较为相似,春小麦和苜蓿的总体分类精度分别为69%和75%。此后,随着观测数据的不断融入,分类精度逐步提升,5月14日二者的分类精度即可达到90%以上。5月31日利用全部5期卫星影像数据时,春小麦的总体精度可达到94%,Kappa系数为0.75,苜蓿的总体精度可达到97%,Kappa为0.86。2023年青铜峡灌区春小麦种植面积为24 000 hm^(2),苜蓿种植面积为2 000 hm^(2)。其中,春小麦种植结构较为复杂,既存在集中连片的大规模种植,也存在大量面积较小的碎片化种植带。【结论】基于Sentinel-2遥感数据的决策树分类方法,可在4月上旬获取初步分类结果,在5月中旬苜蓿第1次收割之前对青铜峡灌区春小麦和苜蓿进行较为准确的识别。 展开更多
关键词 遥感 早期识别 决策树 时间序列 春小麦 苜蓿
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核爆炸早中期电磁脉冲产生的数值模拟方法
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作者 王建国 《电波科学学报》 CSCD 北大核心 2024年第5期787-796,共10页
由于核电磁脉冲(nuclear electromagnetic pulse,NEMP)电场与爆炸当量、爆高、方位角、大气参数和观测位置等密切相关,NEMP产生的数值模拟是非常复杂的问题。本文评述了核爆炸电磁脉冲产生过程的数值模拟方法,包括NEMP产生的物理模型、... 由于核电磁脉冲(nuclear electromagnetic pulse,NEMP)电场与爆炸当量、爆高、方位角、大气参数和观测位置等密切相关,NEMP产生的数值模拟是非常复杂的问题。本文评述了核爆炸电磁脉冲产生过程的数值模拟方法,包括NEMP产生的物理模型、γ射线和中子在大气中输运及康普顿电流源、大气电导率模型和电磁场求解方法;给出了NEMP的典型数值模拟结果,主要包括早期电磁脉冲和中期电磁脉冲联合模拟结果,并分析了早期电磁脉冲和中期电磁脉冲峰值、起止时间和频谱等特征参数。 展开更多
关键词 核电磁脉冲(NEMP) 中子次级γ射线 大气电导率 早期电磁脉冲 中期电磁脉冲
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