期刊文献+
共找到35篇文章
< 1 2 >
每页显示 20 50 100
近57年营口市农耕期界限温度变化特征分析 被引量:4
1
作者 曲岩 金巍 +1 位作者 郝宏伟 吕一杰 《安徽农业科学》 CAS 北大核心 2009年第5期2086-2087,2138,共3页
对1951~2007年营口市稳定通过0℃、10℃积温和积温日数及其变率的分析表明:(1)近57年来营口市稳定通过0℃和10℃积温及积温日数呈递增趋势,其中稳定通过10℃积温、积温日数比通过0℃的递增趋势要强。(2)各阶段稳定通过O℃和10℃... 对1951~2007年营口市稳定通过0℃、10℃积温和积温日数及其变率的分析表明:(1)近57年来营口市稳定通过0℃和10℃积温及积温日数呈递增趋势,其中稳定通过10℃积温、积温日数比通过0℃的递增趋势要强。(2)各阶段稳定通过O℃和10℃积温变化趋势不同,第1个和第2个30年呈现递增趋势较弱、第3个30年和最近30年呈强递增趋势。(3)近57年营口市稳定通过0℃和10℃积温日数递增变化中,后期递增趋势较前期更为显著:最近30年营口市稳定通过0℃和10℃积温递增趋势显著加强趋势与全球变暖的大背景进一步加强趋势相一致。 展开更多
关键词 积温 积温日数 变率分析 营口市
下载PDF
阿勒泰地区10℃界限温度和积温变化分析 被引量:6
2
作者 潘冬梅 潘雪梅 徐永 《陕西气象》 2016年第2期23-25,共3页
利用1961—2010年新疆阿勒泰地区7个地面气象观测站的逐日平均气温资料,运用线性趋势、Manna-Kendall突变检验法,对阿勒泰地区近50a日平均气温稳定≥10℃初日、终日、持续日数和活动积温的时空变化特征进行分析。结果表明:≥10℃初日在... 利用1961—2010年新疆阿勒泰地区7个地面气象观测站的逐日平均气温资料,运用线性趋势、Manna-Kendall突变检验法,对阿勒泰地区近50a日平均气温稳定≥10℃初日、终日、持续日数和活动积温的时空变化特征进行分析。结果表明:≥10℃初日在空间分布上呈中部平原早,西部、东部山区晚的格局,≥10℃终日的空间分布与≥10℃初日的大体相反,≥10℃的持续日数和积温在空间分布上表现为由中部向外递减的特征。≥10℃的初日趋势略提前,≥10℃终日呈推后趋势,≥10℃的持续日数和积温分别以1.5d/(10a)和59.3℃/(10a)的倾向率呈增加趋势。突变分析表明,积温在1976年发生了一次增加的突变。在50a里,1993—2010年是热量和持续日数增幅最大的时期。 展开更多
关键词 界限温度 积温 时空分布 变率分析 突变分析
下载PDF
1850-2008年中国及世界主要国家的碳排放--碳排放与社会发展Ⅰ 被引量:33
3
作者 朱江玲 岳超 +1 位作者 王少鹏 方精云 《北京大学学报(自然科学版)》 EI CAS CSCD 北大核心 2010年第4期497-504,共8页
人类活动排放CO2包括3个重要时期,即1850年第二次工业革命至今,1950年战后世界经济迅速发展期至今,以及以1990年签署《联合国气候变化框架公约》为标志的人类关注碳排放时期至今。作者利用1850—2008年世界化石燃料CO2排放量和人口数据... 人类活动排放CO2包括3个重要时期,即1850年第二次工业革命至今,1950年战后世界经济迅速发展期至今,以及以1990年签署《联合国气候变化框架公约》为标志的人类关注碳排放时期至今。作者利用1850—2008年世界化石燃料CO2排放量和人口数据,得到3个时期全球主要国家及我国的累计碳排放量与人均累计碳排放量。结果表明:过去近160年全球历史累计碳排放量为345PgC(1PgC=10亿tC);发达国家历史累计排放量与人均累计排放量均远远高于发展中国家,1850—2008年,前者是后者的2.9倍(250和87PgC)和11.2倍(257和23tC);1950—2008年,分别是2.3倍(193和85PgC)和7.7倍(169和22tC);1990—2008年,分别为1.9倍(75和54PgC)和5.3倍(58和11tC)。尽管发展中国家与发达国家历史排放量的差距有缩小趋势,但发达国家的排放量一直远高于发展中国家,是大气CO2浓度升高的主要贡献者。对1850年以来中国的碳排放分析表明,3个时期历史累计排放量和人均累计排放量分别为31PgC与29tC,31PgC与28tC,21PgC与16tC。1980—2008年我国碳排放总量和人均排放量均呈快速增加趋势,平均年增量分别为0.05PgC和0.04tC。这表明,我国正在失去历史碳排放量较低的优势,节能减排是我国实现可持续发展战略的必由之路。 展开更多
关键词 累计碳排放 人均累计排放 减排 变率分析
下载PDF
上海市全社会月用电量预测模型 被引量:11
4
作者 穆海振 孙兰东 侯依玲 《中国电力》 CSCD 北大核心 2016年第6期146-150,共5页
较为准确的中短期用电量预测是制定科学合理电网运行计划的前提。利用2004—2014年上海市各月全社会用电量、气温、历年GDP、人口和单位GDP能耗等数据,采用年际同比变率分析方法,分析了影响月用电量的主要因子,建立了上海市逐月用电量... 较为准确的中短期用电量预测是制定科学合理电网运行计划的前提。利用2004—2014年上海市各月全社会用电量、气温、历年GDP、人口和单位GDP能耗等数据,采用年际同比变率分析方法,分析了影响月用电量的主要因子,建立了上海市逐月用电量预测模型。结果表明:采用年际同比变率分析方法能有效剔除气温、用电量等年际变化趋势对相关关系分析结果的影响,所得结论物理意义更为清晰;上海市月用电量呈现冬季和夏季双峰型特征,受经济总量增加等因素的影响,各月用电量都呈现出增加趋势;冬季和夏季的月用电量同比变化率与气温变化相关最为密切,春季和秋季的用电量同比变化率主要与经济总量增长和产业结构调整相关;综合考虑各影响因子建立的预测模型能够实现对各月用电量较精确的预测,也可用来研判经济走势。 展开更多
关键词 上海 月用电量 预测模型 同比变率分析
下载PDF
Modal macro-strain identification from operational macro-strain shape under changing loading conditions 被引量:1
5
作者 李舒 徐赵东 +1 位作者 王少杰 吴智深 《Journal of Southeast University(English Edition)》 EI CAS 2016年第2期219-225,共7页
To develop modal macro-strain ( MMS ) identification techniques and improve their applicability in a continuous health monitoring system for civil infrastructures, the concept of operational macro-strain shape (OMS... To develop modal macro-strain ( MMS ) identification techniques and improve their applicability in a continuous health monitoring system for civil infrastructures, the concept of operational macro-strain shape (OMSS) and the corresponding identification method are proposed under unknown ever-changing loading conditions, and the MMS is then obtained. The core of the proposed technique is mainly based on the specific property that the macro-strain transmissibility tends to be independent of external excitations at the poles of the system and converges to a unique value. The proposed method is verified using the experimental data from a three-span continuous beam excited by an impact hammer at different locations. The identified results are also compared with the commonly used methods, such as the peak- picking (PP) method, the stochastic subspace identification (SSI) method, and numerical results, in the case of unknown input forces. Results show that the proposed technique has unique merits in accuracy and robustness due to its combining multiple tests under changing loading conditions, which also reveal the promising application of the distributed strain sensing system in identifying MMS of operational structures, as well as in the structural health monitoring (SHM) field. 展开更多
关键词 macro-stain/distributed strain fiber Bragggrating FBG operational modal analysis OMA operational deflection shape (ODS) TRANSMISSIBILITY
下载PDF
Available parking space occupancy change characteristics and short-term forecasting model 被引量:5
6
作者 季彦婕 王炜 邓卫 《Journal of Southeast University(English Edition)》 EI CAS 2007年第4期604-608,共5页
Based on an available parking space occupancy (APSO) survey conducted in Nanjing, China, an APSO forecasting model is proposed. The APSO survey results indicate that the time series of APSO with different time-secti... Based on an available parking space occupancy (APSO) survey conducted in Nanjing, China, an APSO forecasting model is proposed. The APSO survey results indicate that the time series of APSO with different time-sections are periodical and self-similar, and the fluctuation of the APSO increases with the decrease in time-sections. Taking the short-time change behavior into account, an APSO forecasting model combined wavelet analysis and a weighted Markov chain is presented. In this model, an original APSO time series is first decomposed by wavelet analysis, and the results include low frequency signals representing the basic trends of APSO and several high frequency signals representing disturbances of the APSO. Then different Markov models are used to forecast the changes of low and high frequency signals, respectively. Finally, integrating the predicted results induces the final forecasted APSO. A case study verifies the applicability of the proposed model. The comparisons between measured and forecasted results show that the model is a competent model and its accuracy relies on real-time update of the APSO database. 展开更多
关键词 available parking space occupancy change characteristics short-term forecasting wavelet analysis weighted Markov chain
下载PDF
Carbon Productivity Analysis to Address Global Climate Change 被引量:5
7
作者 He Jiankun Su Mingshan 《Chinese Journal of Population,Resources and Environment》 2011年第1期9-15,共7页
Developing low-carbon economy and enhancing carbon productivity are basic approaches to coordinating economic development and protecting global environment, which are also the major ways to address climate change unde... Developing low-carbon economy and enhancing carbon productivity are basic approaches to coordinating economic development and protecting global environment, which are also the major ways to address climate change under the framework of sustainable development. In this paper, the authors analyze the annual rate of carbon productivity growth, the differences of carbon productivity of different countries, and the factors for enhancing carbon productivity. Consequently, the authors clarify their viewpoint that the annual rate of carbon productivity growth can be used to weigh the efforts that a country takes to address climate change, and propose policies and suggestions on promoting carbon production. 展开更多
关键词 carbon productivity annual rate of carbon productivity growth global climate change greenhouse gas reduction
下载PDF
Strain rate effects on sand and its quantitative analysis 被引量:1
8
作者 李福林 彭芳乐 +1 位作者 李建中 KONGKITKUL W 《Journal of Central South University》 SCIE EI CAS 2009年第4期658-662,共5页
Strain rate effects on the stress-strain behavior of sand were investigated by performing special plane strain and triaxial compression tests on saturated and air-dried sand specimens. In these tests, the loading stra... Strain rate effects on the stress-strain behavior of sand were investigated by performing special plane strain and triaxial compression tests on saturated and air-dried sand specimens. In these tests, the loading strain rate was changed many times by a factor of up to 1 000 during otherwise monotonous loading at a constant axial strain rate. Test results show that the stress jump upon a stepwise change in the strain rate decays with an increase in the irreversible strain when monotonous loading continues at the changed strain rate and the amount of stress jump is essentially proportional to the instantaneous stress. Based on the amount of these stress jumps, a parameter fl called the rate-sensitivity coefficient is introduced to represent the quantity of the observed viscous properties of sand, which equals 0.021 3 and 0.024 2 respectively for Hostun and Toyoura sands. Further analyses on the results indicate that the effect of the presence of pore water is deemed to be negligible with sand and the fl value is rather independent of loading method, wet condition and confining pressure. 展开更多
关键词 SAND strain rate viscous properties stress-strain relation
下载PDF
Lifting transform via Savitsky-Golay filter predictor and application of denoising 被引量:3
9
作者 周广柱 杨锋杰 王翠珍 《Journal of Coal Science & Engineering(China)》 2006年第2期66-69,共4页
The Savitsky-Golay filter isa smoothing filter based on polynomial regression.Itemploys the regression fitting capacity to improve the smoothing results.But Savit-sky-Golay filter uses a fix sized window.It has the sa... The Savitsky-Golay filter isa smoothing filter based on polynomial regression.Itemploys the regression fitting capacity to improve the smoothing results.But Savit-sky-Golay filter uses a fix sized window.It has the same shortage of Window FourierTransform.Wavelet mutiresolution analysis may deal with this problem.In this paper,tak-ing advantage of Savitsky-Golay filter's fitting ability and the wavelet transform's multiscaleanalysis ability,we developed a new lifting transform via Savitsky-Golay smoothing filteras the lifting predictor,and then processed the signals comparing with the ordinary Savit-sky-Golay Smoothing method.We useed the new lifting in noisy heavy sine denoising.Thenew transform obviously has better denoise ability than ordinary Savitsky-Golay smooth-ing method.At the same time singular points are perfectly retained in the denoised signal.Singularity analysis,multiscale interpolation,estimation,chemical data smoothing andother potential signal processing utility of this new lifting transform are in prospect. 展开更多
关键词 lifting wavelet Savitsky-Golay filter PREDICTOR DENOISE
下载PDF
Hydraulic bulging process with axial feedings and strain field of U-shaped metal bellows 被引量:1
10
作者 HAO Zeng-liang XI Chen-yang +2 位作者 HUANG Zhi-heng ZHANG Chun-xiang LUO Jun-ting 《Journal of Central South University》 SCIE EI CAS CSCD 2018年第11期2712-2721,共10页
Based on the traditional hydraulic bulging process,an improved hydraulic bulging process with axial feeding in the bulging process was proposed.The finite element simulation and experiment of bellows formed by the tra... Based on the traditional hydraulic bulging process,an improved hydraulic bulging process with axial feeding in the bulging process was proposed.The finite element simulation and experiment of bellows formed by the traditional and improved hydraulic bulging processes were conducted.The grid strain measurement system analysis results of strain and wall thickness distribution of the metal bellows,obtained from simulation and experiment,show that the maximum thinning rates of the wall thickness under the traditional and improved processes were 15%and 10%,respectively.And the wall thickness distribution of the metal bellows formed with improved process was more uniform.The strain values from the root to crown of the waveform increased gradually.However,the strain values were smaller than those of traditional process due to the axial feeding of the improved process in bulging process. 展开更多
关键词 hydraulic bulging process finite element simulation thinning rate of wall thickness grid strain measurement system
下载PDF
Power Spectral Analysis of Heart Rate Variability of Driver Fatigue 被引量:2
11
作者 焦昆 李增勇 +1 位作者 陈铭 王成焘 《Journal of Donghua University(English Edition)》 EI CAS 2005年第1期11-15,共5页
This investigation was to evaluate the driving fatigue based on power spectral analysis of heart rate variability (HRV) under vertical vibration. Forty healthy male subjects (29.7±3.5 years) were randomly divided... This investigation was to evaluate the driving fatigue based on power spectral analysis of heart rate variability (HRV) under vertical vibration. Forty healthy male subjects (29.7±3.5 years) were randomly divided into two groups, Group A (28.8±4.3 years) and Group B (30.6±2.7 years). Group A (experiment group) was required to perform the simulated driving and Group B (control group) kept calm for 90 min. The frequency domain indices of HRV such as low frequency (0.04 0.15 Hz, LF), high frequency (0.150.4 Hz, HF), LF/HF together with the indices of hemodynamics such as blood pressure (BP) and heart rate (HR) of the subjects between both groups were calculated and analyzed after the simulated driving. There were significances of the former indices between both groups (P<0.05). All the data collected after experiment of Group A was observed the remarkable linear correlation (P<0.05) and parameters and errors of their linear regression equation were stated (α=0.05, P<0.001) in this paper, respectively. The present study investigated that sympathetic activity of the subjects enhanced after the simulated driving while parasympathetic activities decreased. The sympathovagal balance was also improved. As autonomic function indictors of HRV reflected fatigue level, quantitative evaluation of driving mental fatigue from physiological reaction could be possible. 展开更多
关键词 driving fatigue heart rate variability blood pressure heart rate VIBRATION correlation.
下载PDF
THE RELATIONSHIP BETWEEN GLOBAL WARMING AND THE VARIATION IN TROPICAL CYCLONE FREQUENCY OVER THE WESTERN NORTH PACIFIC 被引量:8
12
作者 马丽萍 陈联寿 《Journal of Tropical Meteorology》 SCIE 2009年第1期38-44,共7页
The relationship between global warming and the variation in tropical cyclone (TC) genesis frequency is analyzed using the data of the Tropical Cyclone Year Book by the China Meteorological Administration and the Nati... The relationship between global warming and the variation in tropical cyclone (TC) genesis frequency is analyzed using the data of the Tropical Cyclone Year Book by the China Meteorological Administration and the National Centers for Environmental Prediction (NCEP) reanalysis data from 1949 to 2007. The observational results indicate that the average sea surface temperature (SST) in the Intertropical Convergence Zone (ITCZ) region (10°N– 20°N, 100°E– 140°E) increases by 0.6°C against the background of global warming, while the frequency of tropical cyclone geneses in this region decreases significantly. Generally, the rise of SSTs is favorable for the genesis of tropical cyclones, but it is now shown to be contrary to the normal effect. Most of the tropical cyclones in the western North Pacific (WNP) are generated in the ITCZ. This is quite different from the case in the Atlantic basin in which the tropical cyclones are mostly generated from the easterly wave. Our research results demonstrate that the ITCZ has a weakening trend in strength, and it has moved much more equatorward in the past 40 years; both are disadvantageous to the formation of tropical cyclones. Furthermore, our study also found that the ridge of the subtropical high tends to shift slightly equatorward, which is another adverse mechanism for the formation of tropical cyclones. 展开更多
关键词 CLIMATOLOGY tropical cyclone frequency long-term variation ITCZ
下载PDF
Dynamic probabilistic analysis of stress and deformation for bladed disk assemblies of aeroengine 被引量:3
13
作者 白斌 白广忱 《Journal of Central South University》 SCIE EI CAS 2014年第10期3722-3735,共14页
In order to describe and control the stress distribution and total deformation of bladed disk assemblies used in the aeroengine, a highly efficient and precise method of probabilistic analysis which is called extremum... In order to describe and control the stress distribution and total deformation of bladed disk assemblies used in the aeroengine, a highly efficient and precise method of probabilistic analysis which is called extremum response surface method(ERSM) is produced based on the previous deterministic analysis results with the finite element model(FEM). In this work, many key nonlinear factors, such as the dynamic feature of the temperature load, the centrifugal force and the boundary conditions, are taken into consideration for the model. The changing patterns with time of bladed disk assemblies about stress distribution and total deformation are obtained during the deterministic analysis, and at the same time, the largest deformation and stress nodes of bladed disk assemblies are found and taken as input target of probabilistic analysis in a scientific and reasonable way. Not only their reliability, historical sample, extreme response surface(ERS) and the cumulative probability distribution function but also their sensitivity and effect probability are obtained. Main factors affecting stress distribution and total deformation of bladed disk assemblies are investigated through the sensitivity analysis of the model. Finally, compared with the response surface method(RSM) and the Monte Carlo simulation(MCS), the results show that this new approach is effective. 展开更多
关键词 bladed disk assemblies probabilistic analysis finite element model extremum response surface method sensitivity analysis transient dynamic analysis
下载PDF
Estimation of Ground Deformation Caused by the Earthquake (M7.2) in Japan,2008,from the Geomorphic Image Analysis of High Resolution LiDAR DEMs 被引量:2
14
作者 MUKOYAMA Sakae 《Journal of Mountain Science》 SCIE CSCD 2011年第2期239-245,共7页
In this study, a new method for quantitative and efficient measurement for the ground surface movement was developed. The feature of this technique is to identify geomorphic characteristics by image matching analysis,... In this study, a new method for quantitative and efficient measurement for the ground surface movement was developed. The feature of this technique is to identify geomorphic characteristics by image matching analysis, using the intelligent images made from high resolution DEM(Digital Elevation Model). This method is useful to extract the small ground displacement where the surface shape was not intensely deformed. 展开更多
关键词 Ground deformation Ground surface movement Digital Elevation Model(DEM) Geomorphic image analysis JAPAN
下载PDF
Weekend and nighttime effect on the prognosis of peptic ulcer bleeding 被引量:6
15
作者 Young Hoon Youn Yong Jin Park +3 位作者 Jae Hak Kim Tae Joo Jeon Jae Hee Cho Hyojin Park 《World Journal of Gastroenterology》 SCIE CAS CSCD 2012年第27期3578-3584,共7页
AIM:To evaluate whether weekend or nighttime admission affects prognosis of peptic ulcer bleeding despite early endoscopy.METHODS:Retrospective data collection from four referral centers,all of which had a formal out-... AIM:To evaluate whether weekend or nighttime admission affects prognosis of peptic ulcer bleeding despite early endoscopy.METHODS:Retrospective data collection from four referral centers,all of which had a formal out-of-hours emergency endoscopy service,even at weekends.A total of 388 patients with bleeding peptic ulcers who were admitted via the emergency room between January 2007 and December 2009 were enrolled.Analyzed parameters included time from patients' arrival until endoscopy,mortality,rebleeding,need for surgery and length of hospital stay.RESULTS:The weekday and weekend admission groups comprised 326 and 62 patients,respectively.There were no significant differences in baseline characteristics between the two groups,except for younger age in the weekend group.Most patients (97%) had undergone early endoscopy,which resulted in a low mortality rate regardless of point of presentation (1.8% overall vs 1.6% on the weekend).The only outcome that was worse in the weekend group was a higher rate of rebleeding (12% vs 21%,P = 0.030).However,multivariate analysis revealed nighttime admission and a high Rockall score (≥ 6) as significant independent risk factors for rebleeding,rather than weekend admission.CONCLUSION:Early endoscopy for peptic ulcer bleeding can prevent the weekend effect,and nighttime admission was identified as a novel risk factor for rebleeding,namely the nighttime effect. 展开更多
关键词 Early endoscopy Nighttime effect Pepticulcer bleeding REBLEEDING Weekend effect
下载PDF
Effect of confining pressure on deformation and failure of rock at higher strain rate 被引量:1
16
作者 王学滨 潘一山 《Journal of Coal Science & Engineering(China)》 2005年第2期32-36,共5页
Influence of confining pressure from 0 to 28 MPa, which acts on the two lateral edges of rock specimen in plane strain compression, on the shear failure processes and patterns as well as on the macroscopically mechani... Influence of confining pressure from 0 to 28 MPa, which acts on the two lateral edges of rock specimen in plane strain compression, on the shear failure processes and patterns as well as on the macroscopically mechanical responses were numerically modeled by use of FLAC. A material imperfection with lower strength in comparison with the intact rock, which is close to the lower-left corner of the specimen, was prescribed. In elastic stage, the adopted constitutive relation of rock was linear elastic; in strain-softening stage, a composite Mohr-Coulomb criterion with tension cut-off and a post-peak linear constitutive relation were adopted. The numerical results show that with an increase of confining pressure the peak strength of axial stress-axial strain curve and the corresponding axial strain linearly increase; the residual strength and the stress drop from the peak strength to the residual strength increase; the failure modes of rock transform form the multiple shear bands close to the loading end of the specimen (confining pressure=0-0.1 MPa), to the conjugate shear bands (0.5-2.0 MPa), and then to the single shear band (4-28 MPa). Once the tip of the band reaches the loading end of the specimen, the direction of the band changes so that the reflection of the band occurs. At higher confining pressure, the new-formed shear band does not intersect the imperfection, bringing extreme difficulties in prediction of the failure of rock structure, such as rock burst. The present results enhance the understanding of the shear failure processes and patterns of rock specimen in higher confining pressure and higher loading strain rate. 展开更多
关键词 confining pressure shear failure shear strain localization strength stress-strain curve rock burst
下载PDF
Analysis of the Motion and Deformation Characteristics along the Zhangjiakou-Bohai Fault 被引量:1
17
作者 Chen Changyun 《Earthquake Research in China》 CSCD 2017年第1期66-78,共13页
We have collected GPS data in the period of 1999-2007 from the Crustal Motion Observation Network of China along the Zhangjiakou-Bohai fault and its adjacent regions to study the characteristics of present-day crustal... We have collected GPS data in the period of 1999-2007 from the Crustal Motion Observation Network of China along the Zhangjiakou-Bohai fault and its adjacent regions to study the characteristics of present-day crustal horizontal motion velocities in the research zone.Strain rate components are computed in the spheric coordinate system by the least square collocation method.According to the spatial distribution of the principal strain rate,dilation rate and maximum shear strain rate derived from GPS measurements,this paper analyses the deformation of the subordinary faults of the Zhangjiakou-Bohai fault.The principal compression strain rates are apparently greater than the principal extension strain rates.The larger shear strain rate is mainly in and around the Xianghe,Wenan and Tangshan areas in Hebei Province.According to the profiles across different segments of the Zhangjiakou-Bohai fault,the three segments glong the Zhangjiakou-Bohai fault show an obviously left-lateal strike-slip and compression characteristics.By analysis of the motion characteristics of the blocks,e.g.the Yanshan block,North China Plain block,Ordos block,and Ludong-Huanghai block in and around the North China region,this paper speculates that the dynamics of the motion styles of Zhangjiakou-Bohai fault may directly come from the relative movement between the Yanshan block and the North China plain block,and the ultimate dynamics may be the results of the collison between Indian plate and Eurasian plate,and the persistent northeastward extrusion of the Indian plate. 展开更多
关键词 Zhangjiakou-Bohai fault zone Crustal deformation Velocity filed Strain rate filed Left-lateral strike-slip
下载PDF
Determination of potential management zones from soil electrical conductivity,yield and crop data
18
作者 Yan LI Zhou SHI +2 位作者 Ci-fang WU Hong-yi LI Feng LI 《Journal of Zhejiang University-Science B(Biomedicine & Biotechnology)》 SCIE CAS CSCD 2008年第1期68-76,共9页
One approach to apply precision agriculture to optimize crop production and environmental quality is identifying management zones. In this paper,the variables of soil electrical conductivity (EC) data,cotton yield dat... One approach to apply precision agriculture to optimize crop production and environmental quality is identifying management zones. In this paper,the variables of soil electrical conductivity (EC) data,cotton yield data and normalized differ-ence vegetation index (NDVI) data in an about 15 ha field in a coastal saline land were selected as data resources,and their spatial variabilities were firstly analyzed and spatial distribution maps constructed with geostatistics technique. Then fuzzy c-means clustering algorithm was used to define management zones,fuzzy performance index (FPI) and normalized classification entropy (NCE) were used to determine the optimal cluster numbers. Finally one-way variance analysis was performed on 224 georefer-enced soil and yield sampling points to assess how well the defined management zones reflected the soil properties and produc-tivity level. The results reveal that the optimal number of management zones for the present study area was 3 and the defined management zones provided a better description of soil properties and yield variation. Statistical analyses indicate significant differences between the chemical properties of soil samples and crop yield in each management zone,and management zone 3 presented the highest nutrient level and potential crop productivity,whereas management zone 1 the lowest. Based on these findings,we conclude that fuzzy c-means clustering approach can be used to delineate management zones by using the given three variables in the coastal saline soils,and the defined management zones form an objective basis for targeting soil samples for nutrient analysis and development of site-specific application strategies. 展开更多
关键词 Management zones Fuzzy clustering Spatial variability Saline land Precision agriculture
下载PDF
Fault Feature Extraction of Rotating Machinery Based on Wavelet Transformation and Multi-resolution Analysis
19
作者 公茂法 刘庆雪 +1 位作者 刘明 张晓丽 《Journal of Measurement Science and Instrumentation》 CAS 2010年第4期312-314,共3页
This paper expounded in detail the principle of energy spectrum analysis based on discrete wavelet transformation and multiresolution analysis. In the aspect of feature extraction method study, with investigating the ... This paper expounded in detail the principle of energy spectrum analysis based on discrete wavelet transformation and multiresolution analysis. In the aspect of feature extraction method study, with investigating the feature of impact factor in vibration signals and considering the non-placidity and non-linear of vibration diagnosis signals, the authors import wavelet analysis and fractal theory as the tools of faulty signal feature description. Experimental results proved the validity of this method. To some extent, this method provides a good approach of resolving the wholesome problem of fault feature symptom description. 展开更多
关键词 discrete wavelet transform (DWT) multi-resolution analysis fault diagnosis rotating madchinery feature extraction
下载PDF
Change of Nonlinear Heart Rate Variability Indices in Different Seasons
20
作者 Natalya Botoeva 《Journal of Earth Science and Engineering》 2012年第10期576-583,共8页
The study investigates the nonlinear heart rate variability indices in different seasons and their dependence on current meteorological factors. The study included 61 relatively healthy student volunteers, their age w... The study investigates the nonlinear heart rate variability indices in different seasons and their dependence on current meteorological factors. The study included 61 relatively healthy student volunteers, their age were 19-23 and they were examined repeatedly in different seasons. The HRV (heart rate variability) recording was performed with the use of the hardware-software complex "Varikard 2.51" Nonlinear HRV indices were calculated by means of the Kubios HRV 2.1. The following indicators: SD1, SD2, SD1/SD2, D2, DFA, SampEn and quantitative indicators of recurrence analysis (RQA )---Lmean, Lmax, REC, DET, ShanEn had been analyzed. Statistical analysis was performed using the Statistica 6.0. For the detection of between-group differences were used Repeated Measures ANOVA, and the dependence of nonlinear HRV indices on meteorological was analyzed with the use of multiple non-linear regression. The investigation showed a relative increase in SampEn and the reduction of al in winter and spring seasons, strengthening relationships SampEn correlation with other indicators in the winter season as well as the dependence SampEn on meteorological factors in summer. The detected changes can be considered as the realization of adaptive response of a healthy body. 展开更多
关键词 Nonlinear heart rate variability SEASONS weather factors.
下载PDF
上一页 1 2 下一页 到第
使用帮助 返回顶部