The development of a core collection could enhance the utilization of germplasm collections in crop improvement programs and simplify their management. Selection of an appropriate sampling strategy is an important pre...The development of a core collection could enhance the utilization of germplasm collections in crop improvement programs and simplify their management. Selection of an appropriate sampling strategy is an important prerequisite to construct a core collection with appropriate size in order to adequately represent the genetic spectrum and maximally capture the genetic diversity in available crop collections. The present study was initiated to construct nested core collections to determine the appropriate sample size to represent the genetic diversity of rice landrace collection based on 15 quantitative traits and 34 qualitative traits of 2 262 rice accessions. The results showed that 50-225 nested core collections, whose sampling rate was 2.2%-9.9%, were sufficient to maintain the maximum genetic diversity of the initial collections. Of these, 150 accessions （6.6%） could capture the maximal genetic diversity of the initial collection. Three data types, i.e. qualitative traits （QT1）, quantitative traits （QT2） and integrated qualitative and quantitative traits （QTT）, were compared for their efficiency in constructing core collections based on the weighted pair-group average method combined with stepwise clustering and preferred sampling on adjusted Euclidean distances. Every combining scheme constructed eight rice core collections （225, 200, 175, 150, 125, 100, 75 and 50）. The results showed that the QTT data was the best in constructing a core collection as indicated by the genetic diversity of core collections. A core collection constructed only on the information of QT1 could not represent the initial collection effectively. QTT should be used together to construct a productive core collection.展开更多
Nutrient release from the dredged and undredged sediments in Lake Kasumigaura were simulated under the laboratory control conditions with large-size core samples. It was found that phosphate and ammonia release fluxes...Nutrient release from the dredged and undredged sediments in Lake Kasumigaura were simulated under the laboratory control conditions with large-size core samples. It was found that phosphate and ammonia release fluxes are less in aerobic than those in anaerobic. In different simulated dredged depth, the phosphate release showed large divergence in the anaerobic than in the aerobic. There was a larger accumulated release of phosphate and ammonia at actual dredged (St. B) than the undredged (St. A) in anaerobic condition. This showed that the sludge-dredging was effective of controlling phosphorus and nitrogen release. A preliminary assessment is drawn from the experiments that the sludge-dredging work in Tsuchiura Bay of Lake Kasumigaura can reduce about 15. 9% of phospbate and 56. 2% of anunonia release from the sediments respectively.展开更多
A novel statistical approach to evaluate the manufacturing quality of press coated tablets in terms of the centering of their core is presented. We also provide a formula to determine the necessary sample size. This a...A novel statistical approach to evaluate the manufacturing quality of press coated tablets in terms of the centering of their core is presented. We also provide a formula to determine the necessary sample size. This approach is applied to real data.展开更多
Dust phenomenon is one of the biggest environmental problems in arid and semiarid regions. In these areas, lakes and wetlands are natural dust traps and core sampling method can be an appropriate way to assess the phe...Dust phenomenon is one of the biggest environmental problems in arid and semiarid regions. In these areas, lakes and wetlands are natural dust traps and core sampling method can be an appropriate way to assess the phenomenon of the dust. Therefore, the purpose of this study is the study of frequency and characteristics of dust sediments in core samples from Hashilan wetlands, Kermanshah. Four intact core samples were taken from different parts of the Hashilan wetland in Kermanshah. Physical, chemical and micromorphological analysis were done. Also clay mineralogy was performed using X-ray analysis (XRD) and shape of particles was photographed by scanning electron microscope (SEM). Considering that four samples had been taken from different parts of the wetland, the quantitative differences in dust amount are likely due to the location of the samples. The results of XRD and thin sections show that the dominant mineralogical composition of dust particles was clay minerals, quartz and calcite. SEM results for core sample 1 revealed that most particles had the size between 2 to 50 mm which ranged from fine silt to coarse silt. Considering the similarities between SEM images for core sample 1 and those from Kermanshah dust measurement station, it could be said that fine rounded particles detected at top 30 cm of core samples had Aeolian origin. These findings were in accordance with the results from dust measurement and weather station of Kermanshah about increased dust activities in the study area over past 10 years.展开更多
The widespread contamination of soils and aquifers by non-aqueous phase liquids （NAPL）, such as crude oil, poses serious environmental and health hazards globally. Understanding the infiltration characteristics of N...The widespread contamination of soils and aquifers by non-aqueous phase liquids （NAPL）, such as crude oil, poses serious environmental and health hazards globally. Understanding the infiltration characteristics of NAPL in soil is crucial in mitigating or remediating soil contamination. The infiltration characteristics of crude and diesel oils into undisturbed loessal soil cores, collected in polymethyl methacrylate cylindrical columns, were investigated under a constant fluid head （3 era） of either crude oil or diesel oil. The infiltration rate of both crude and diesel oils decreased exponentially as wetting depth increased with time. Soil core size and bulk density both had significant effects on NAPL infiltration through the undisturbed soil cores; a smaller core size or a greater bulk density could reduce oil penetration to depth. Compacting soil in areas susceptible to oil spills may be an effective stratage to reduce contamination. The infiltration of NAPL into soil cores was spatially anisotropic and heterogeneous, thus recording the data at four points on the soil core is a good stratage to improve the accuracy of experimental results. Our results revealed that crude and diesel oils, rather than their components, have a practical value for remediation of contaminated loessal soils.展开更多
The method for constructing core collection ofMalus sieversii based on molecular marker data was proposed. According to 128 SSR allele of 109 M. sieversii, an allele preferred sampling strategy was used to construct M...The method for constructing core collection ofMalus sieversii based on molecular marker data was proposed. According to 128 SSR allele of 109 M. sieversii, an allele preferred sampling strategy was used to construct M. sieversii core collection, using the UPGMA （unweighted pair-group average method） cluster method according to Nei ＆ Li, SM, and Jaccard genetic distances, by stepwise clustering, and compared with the random sampling strategy. The number of lost allele and t-test of Nei＇s gene diversity and Shannon＇s information index were used to evaluate the representative core collections. The results showed that compared with the random sampling strategy, allele preferred sampling strategy could construct more representative core collections. SM, difference for construction of M. sieversii core collection. Jaccard, and Nei ＆ Li genetic distances had no significant SRAP （sequence-related amplified polymorphism） data and morphological data showed that allele preferred sampling strategy was a good sampling strategy for constructing core collection of M. sieversii. Allele preferred sampling strategy combined with SM, Jaccard, and Nei ＆ Li genetic distances using stepwise clustering was the suitable method for constructing M. sieversii core collection.展开更多
Chang’e-5 explorer successfully acquired lunar regolith core samples from depths of greater than 1 m of lunar surface.This study analyzed the lunar core drilling process based on the telemetry data,image information,...Chang’e-5 explorer successfully acquired lunar regolith core samples from depths of greater than 1 m of lunar surface.This study analyzed the lunar core drilling process based on the telemetry data,image information,and returned samples to optimize the sampling device design and enhance the understanding of the lunar regolith.In particular,a prediction method for the projected drilling path and local terrain fitting of drilling dip angle was proposed based on the flight events recorded during the core drilling process and the image information acquired before,during,and after sampling.The results revealed that the drilling dip angle of Chang’e-5 was approximately2.3.,and the deviation of the drilling length and depth was less than 2 mm.For continuous drilling,a fusion method based on telemetry data and image information was applied to determine the demarcation point of drilling with and without the lunar soil.The position of the demarcation point implied that the drilling point remained at approximately 6 mm loose soil,thereby lagging the action of the force response.Additionally,a characteristic parameter comparison method was proposed for the lunar and ground drilling to analyze the status of the lunar soil.Furthermore,the analysis results revealed that the majority of the Chang’e-5 drilling samples were derived from 0–73.8 cm below the lunar surface and few samples were extracted below 73.8 cm,as the drilling encountered several rocky regions.Moreover,the drilling point exhibited two prominent stratification variations at~28.7 cm and~70 cm below the lunar surface.Ultimately,the preliminary relationship between sample dissected position in soft tube and drilling displacement was analyzed.The segmented estimation results can support research on subsurface lunar soil.展开更多
One hundred and sixty-eight genotypes of cotton from the same growing region were used as a germplasm group to study the validity of different genetic distances in constructing cotton core subset. Mixed linear model a...One hundred and sixty-eight genotypes of cotton from the same growing region were used as a germplasm group to study the validity of different genetic distances in constructing cotton core subset. Mixed linear model approach was employed to unbiasedly predict genotypic values of 20 traits for eliminating the environmental effect. Six commonly used genetic distances(Euclidean,standardized Euclidean,Mahalanobis,city block,cosine and correlation distances) combining four commonly used hierarchical cluster methods(single distance,complete distance,unweighted pair-group average and Ward's methods) were used in the least distance stepwise sampling(LDSS) method for constructing different core subsets. The analyses of variance(ANOVA) of different evaluating parameters showed that the validities of cosine and correlation distances were inferior to those of Euclidean,standardized Euclidean,Mahalanobis and city block distances. Standardized Euclidean distance was slightly more effective than Euclidean,Mahalanobis and city block distances. The principal analysis validated standardized Euclidean distance in the course of constructing practical core subsets. The covariance matrix of accessions might be ill-conditioned when Mahalanobis distance was used to calculate genetic distance at low sampling percentages,which led to bias in small-sized core subset construction. The standardized Euclidean distance is recommended in core subset construction with LDSS method.展开更多
The deep cement mixing(DCM)is used to improve the capacity and reduce the settlement of the soft ground by forming cemented clay columns.The investigation on the mechanical behaviour of the DCM samples is limited to e...The deep cement mixing(DCM)is used to improve the capacity and reduce the settlement of the soft ground by forming cemented clay columns.The investigation on the mechanical behaviour of the DCM samples is limited to either laboratory-prepared samples or in-situ samples under unconfined compression.In this study,a series of drained and undrained triaxial shearing tests was performed on the in-situ cored DCM samples with high cement content to assess their mechanical behaviours.It is found that the drainage condition affects significantly the stiffness,peak and residual strengths of the DCM samples,which is mainly due to the state of excess pore water pressure at different strain levels,i.e.being positive before the peak deviatoric stress and negative after the peak deviatoric stress,in the undrained tests.The slope of the failure envelope changes obviously with the confining pressures,being steeper at lower stress levels and flatter at higher stress levels.The strength parameters,effective cohesion and friction angle obtained from lower stress levels(c′0 andφ′0)are 400 kPa and 58°,respectively,which are deemed to be true for design in most DCM applications where the in-situ stress levels are normally at lower values of 50-200 kPa.Additionally,the computed tomography(CT)scanning system was adopted to visualize the internal structures of DCM samples.It is found that the clay pockets existing inside the DCM samples due to uneven mixing affect markedly their stress-strain behaviour,which is one of the main reasons for the high variability of the DCM samples.展开更多
为重建晚更新世以来鲍威尔海盆的古海洋环境演变历史,本文对南极半岛鲍威尔海盆D3-5柱样的硅藻进行了分析,D3-5柱样的156个样品中共鉴定出硅藻54个种和变种,以海水种和冷水种为主。通过硅藻分析,将晚更新世以来鲍威尔海盆的海洋环境变...为重建晚更新世以来鲍威尔海盆的古海洋环境演变历史,本文对南极半岛鲍威尔海盆D3-5柱样的硅藻进行了分析,D3-5柱样的156个样品中共鉴定出硅藻54个种和变种,以海水种和冷水种为主。通过硅藻分析,将晚更新世以来鲍威尔海盆的海洋环境变化划分如下:58.6~72.5 ka BP期间,硅藻以冷水种和海冰种为主,并出现沿岸种,推测因南极冰盖增长,鲍威尔海盆受极地冷水团控制,气候出现明显冷-暖交替,而且海平面较低,站位水深较浅;40.7~58.6 ka BP期间,出现明显气候冷-暖转变,海洋环境受气候变化影响较大,变得不稳定,由于海冰融化、温盐循环加强和冰筏碎屑事件的频发导致硅藻种类、丰度骤减;26.2~40.7 ka BP期间,硅藻种类明显增加,出现海冰种,冷水种增加,推测处于末次冰盛期的冰盖增长前期,中纬度暖水团在南极海区的影响范围向南扩大,冷、暖水团强烈混合,驱动温盐循环;26.2 ka BP至今,硅藻丰度增加,极地冷、暖水团混合的指示种Fragilariopsis oceanica指示研究区的表层与底层水体混合增强,海冰覆盖面积持续增大,威德尔环流势力增强,中纬度暖水势力减弱。总体来说,自晚更新世以来鲍威尔海盆经历了冷期(南极冰盖发育)-暖期-冷期(末次冰盛期)的阶段转变,而在深海氧同位素3阶段(marine isotope stages 3,MIS 3)中存在一段较长时间的冰筏碎屑事件时期。展开更多
以鄂尔多斯盆地某区块的砂泥夹层岩心为研究对象,使用基于小波变换的去噪神经网络(denoising neural network based on wavelet transformation,DWTNet)对于岩心的图像进行去噪研究。该方法的评断结果采用峰值信噪比(peak signal to noi...以鄂尔多斯盆地某区块的砂泥夹层岩心为研究对象,使用基于小波变换的去噪神经网络(denoising neural network based on wavelet transformation,DWTNet)对于岩心的图像进行去噪研究。该方法的评断结果采用峰值信噪比(peak signal to noise ratio,PSNR)和去噪后的图像结果进行了对比。研究表明,利用DWTNet在测试集YX1、YX2测试所提出的算法,并与EGDNet等去噪算法进行对比,PSNR在噪声为25、50、75 dB时,高于EGDNet算法0.527、0.418、1.1 dB。所提的算法在峰值信噪比等指标均高于其他算法;并在视觉效果上其处理得到的图像也更加清晰。方法的提出对于孔隙度、平均体积比表面积、平均曲率计算等都有着非常重要的意义。展开更多
基金supported by the National Natural Science Foundation of China (Grant No. 30700494)the Principal Fund of South China Agricultural University, China (Grant No. 2003K053)
文摘The development of a core collection could enhance the utilization of germplasm collections in crop improvement programs and simplify their management. Selection of an appropriate sampling strategy is an important prerequisite to construct a core collection with appropriate size in order to adequately represent the genetic spectrum and maximally capture the genetic diversity in available crop collections. The present study was initiated to construct nested core collections to determine the appropriate sample size to represent the genetic diversity of rice landrace collection based on 15 quantitative traits and 34 qualitative traits of 2 262 rice accessions. The results showed that 50-225 nested core collections, whose sampling rate was 2.2%-9.9%, were sufficient to maintain the maximum genetic diversity of the initial collections. Of these, 150 accessions （6.6%） could capture the maximal genetic diversity of the initial collection. Three data types, i.e. qualitative traits （QT1）, quantitative traits （QT2） and integrated qualitative and quantitative traits （QTT）, were compared for their efficiency in constructing core collections based on the weighted pair-group average method combined with stepwise clustering and preferred sampling on adjusted Euclidean distances. Every combining scheme constructed eight rice core collections （225, 200, 175, 150, 125, 100, 75 and 50）. The results showed that the QTT data was the best in constructing a core collection as indicated by the genetic diversity of core collections. A core collection constructed only on the information of QT1 could not represent the initial collection effectively. QTT should be used together to construct a productive core collection.
文摘Nutrient release from the dredged and undredged sediments in Lake Kasumigaura were simulated under the laboratory control conditions with large-size core samples. It was found that phosphate and ammonia release fluxes are less in aerobic than those in anaerobic. In different simulated dredged depth, the phosphate release showed large divergence in the anaerobic than in the aerobic. There was a larger accumulated release of phosphate and ammonia at actual dredged (St. B) than the undredged (St. A) in anaerobic condition. This showed that the sludge-dredging was effective of controlling phosphorus and nitrogen release. A preliminary assessment is drawn from the experiments that the sludge-dredging work in Tsuchiura Bay of Lake Kasumigaura can reduce about 15. 9% of phospbate and 56. 2% of anunonia release from the sediments respectively.
文摘A novel statistical approach to evaluate the manufacturing quality of press coated tablets in terms of the centering of their core is presented. We also provide a formula to determine the necessary sample size. This approach is applied to real data.
文摘Dust phenomenon is one of the biggest environmental problems in arid and semiarid regions. In these areas, lakes and wetlands are natural dust traps and core sampling method can be an appropriate way to assess the phenomenon of the dust. Therefore, the purpose of this study is the study of frequency and characteristics of dust sediments in core samples from Hashilan wetlands, Kermanshah. Four intact core samples were taken from different parts of the Hashilan wetland in Kermanshah. Physical, chemical and micromorphological analysis were done. Also clay mineralogy was performed using X-ray analysis (XRD) and shape of particles was photographed by scanning electron microscope (SEM). Considering that four samples had been taken from different parts of the wetland, the quantitative differences in dust amount are likely due to the location of the samples. The results of XRD and thin sections show that the dominant mineralogical composition of dust particles was clay minerals, quartz and calcite. SEM results for core sample 1 revealed that most particles had the size between 2 to 50 mm which ranged from fine silt to coarse silt. Considering the similarities between SEM images for core sample 1 and those from Kermanshah dust measurement station, it could be said that fine rounded particles detected at top 30 cm of core samples had Aeolian origin. These findings were in accordance with the results from dust measurement and weather station of Kermanshah about increased dust activities in the study area over past 10 years.
基金supported by the Innovation Team Pro-gram of Chinese Academy of Sciencesthe Program for Innovative Research Team in University (No IRT0749)
文摘The widespread contamination of soils and aquifers by non-aqueous phase liquids （NAPL）, such as crude oil, poses serious environmental and health hazards globally. Understanding the infiltration characteristics of NAPL in soil is crucial in mitigating or remediating soil contamination. The infiltration characteristics of crude and diesel oils into undisturbed loessal soil cores, collected in polymethyl methacrylate cylindrical columns, were investigated under a constant fluid head （3 era） of either crude oil or diesel oil. The infiltration rate of both crude and diesel oils decreased exponentially as wetting depth increased with time. Soil core size and bulk density both had significant effects on NAPL infiltration through the undisturbed soil cores; a smaller core size or a greater bulk density could reduce oil penetration to depth. Compacting soil in areas susceptible to oil spills may be an effective stratage to reduce contamination. The infiltration of NAPL into soil cores was spatially anisotropic and heterogeneous, thus recording the data at four points on the soil core is a good stratage to improve the accuracy of experimental results. Our results revealed that crude and diesel oils, rather than their components, have a practical value for remediation of contaminated loessal soils.
基金financially supported by the National Natural Science Foundation of China (30871679)National 863 Program of China (2006AA100108)Agricultural Improved Variety Project of Shandong Province, China.
文摘The method for constructing core collection ofMalus sieversii based on molecular marker data was proposed. According to 128 SSR allele of 109 M. sieversii, an allele preferred sampling strategy was used to construct M. sieversii core collection, using the UPGMA （unweighted pair-group average method） cluster method according to Nei ＆ Li, SM, and Jaccard genetic distances, by stepwise clustering, and compared with the random sampling strategy. The number of lost allele and t-test of Nei＇s gene diversity and Shannon＇s information index were used to evaluate the representative core collections. The results showed that compared with the random sampling strategy, allele preferred sampling strategy could construct more representative core collections. SM, difference for construction of M. sieversii core collection. Jaccard, and Nei ＆ Li genetic distances had no significant SRAP （sequence-related amplified polymorphism） data and morphological data showed that allele preferred sampling strategy was a good sampling strategy for constructing core collection of M. sieversii. Allele preferred sampling strategy combined with SM, Jaccard, and Nei ＆ Li genetic distances using stepwise clustering was the suitable method for constructing M. sieversii core collection.
基金supported by the National Medium and Longterm Science and Technology Major Special Project of ChinaYoung Top Talents Foundation of China Aerospace Science and Technology Corporation+1 种基金Pre-research project on Civil Aerospace Technologies by CNSA under Grant D020201the National Natural Science Foundation of China(Research on Supporting Management Strategy of Scientific Research Activities in Lunar Exploration under Grant 42142033)。
文摘Chang’e-5 explorer successfully acquired lunar regolith core samples from depths of greater than 1 m of lunar surface.This study analyzed the lunar core drilling process based on the telemetry data,image information,and returned samples to optimize the sampling device design and enhance the understanding of the lunar regolith.In particular,a prediction method for the projected drilling path and local terrain fitting of drilling dip angle was proposed based on the flight events recorded during the core drilling process and the image information acquired before,during,and after sampling.The results revealed that the drilling dip angle of Chang’e-5 was approximately2.3.,and the deviation of the drilling length and depth was less than 2 mm.For continuous drilling,a fusion method based on telemetry data and image information was applied to determine the demarcation point of drilling with and without the lunar soil.The position of the demarcation point implied that the drilling point remained at approximately 6 mm loose soil,thereby lagging the action of the force response.Additionally,a characteristic parameter comparison method was proposed for the lunar and ground drilling to analyze the status of the lunar soil.Furthermore,the analysis results revealed that the majority of the Chang’e-5 drilling samples were derived from 0–73.8 cm below the lunar surface and few samples were extracted below 73.8 cm,as the drilling encountered several rocky regions.Moreover,the drilling point exhibited two prominent stratification variations at~28.7 cm and~70 cm below the lunar surface.Ultimately,the preliminary relationship between sample dissected position in soft tube and drilling displacement was analyzed.The segmented estimation results can support research on subsurface lunar soil.
基金Project supported by the National Natural Science Foundation of China (No. 30270759)the Cooperation Project in Science and Technology between China and Poland Governments (No. 32-38)the Scientific Research Foundation for Doctors in Shandong Academy of Agricultural Sciences (No. [2007]20), China
文摘One hundred and sixty-eight genotypes of cotton from the same growing region were used as a germplasm group to study the validity of different genetic distances in constructing cotton core subset. Mixed linear model approach was employed to unbiasedly predict genotypic values of 20 traits for eliminating the environmental effect. Six commonly used genetic distances(Euclidean,standardized Euclidean,Mahalanobis,city block,cosine and correlation distances) combining four commonly used hierarchical cluster methods(single distance,complete distance,unweighted pair-group average and Ward's methods) were used in the least distance stepwise sampling(LDSS) method for constructing different core subsets. The analyses of variance(ANOVA) of different evaluating parameters showed that the validities of cosine and correlation distances were inferior to those of Euclidean,standardized Euclidean,Mahalanobis and city block distances. Standardized Euclidean distance was slightly more effective than Euclidean,Mahalanobis and city block distances. The principal analysis validated standardized Euclidean distance in the course of constructing practical core subsets. The covariance matrix of accessions might be ill-conditioned when Mahalanobis distance was used to calculate genetic distance at low sampling percentages,which led to bias in small-sized core subset construction. The standardized Euclidean distance is recommended in core subset construction with LDSS method.
基金funded by the Environment and Conservation Fund(Grant Nos.2020-170 and 2021-156)the National Natural Science Foundation of China(Grant No.42102327).
文摘The deep cement mixing(DCM)is used to improve the capacity and reduce the settlement of the soft ground by forming cemented clay columns.The investigation on the mechanical behaviour of the DCM samples is limited to either laboratory-prepared samples or in-situ samples under unconfined compression.In this study,a series of drained and undrained triaxial shearing tests was performed on the in-situ cored DCM samples with high cement content to assess their mechanical behaviours.It is found that the drainage condition affects significantly the stiffness,peak and residual strengths of the DCM samples,which is mainly due to the state of excess pore water pressure at different strain levels,i.e.being positive before the peak deviatoric stress and negative after the peak deviatoric stress,in the undrained tests.The slope of the failure envelope changes obviously with the confining pressures,being steeper at lower stress levels and flatter at higher stress levels.The strength parameters,effective cohesion and friction angle obtained from lower stress levels(c′0 andφ′0)are 400 kPa and 58°,respectively,which are deemed to be true for design in most DCM applications where the in-situ stress levels are normally at lower values of 50-200 kPa.Additionally,the computed tomography(CT)scanning system was adopted to visualize the internal structures of DCM samples.It is found that the clay pockets existing inside the DCM samples due to uneven mixing affect markedly their stress-strain behaviour,which is one of the main reasons for the high variability of the DCM samples.
文摘为重建晚更新世以来鲍威尔海盆的古海洋环境演变历史,本文对南极半岛鲍威尔海盆D3-5柱样的硅藻进行了分析,D3-5柱样的156个样品中共鉴定出硅藻54个种和变种,以海水种和冷水种为主。通过硅藻分析,将晚更新世以来鲍威尔海盆的海洋环境变化划分如下:58.6~72.5 ka BP期间,硅藻以冷水种和海冰种为主,并出现沿岸种,推测因南极冰盖增长,鲍威尔海盆受极地冷水团控制,气候出现明显冷-暖交替,而且海平面较低,站位水深较浅;40.7~58.6 ka BP期间,出现明显气候冷-暖转变,海洋环境受气候变化影响较大,变得不稳定,由于海冰融化、温盐循环加强和冰筏碎屑事件的频发导致硅藻种类、丰度骤减;26.2~40.7 ka BP期间,硅藻种类明显增加,出现海冰种,冷水种增加,推测处于末次冰盛期的冰盖增长前期,中纬度暖水团在南极海区的影响范围向南扩大,冷、暖水团强烈混合,驱动温盐循环;26.2 ka BP至今,硅藻丰度增加,极地冷、暖水团混合的指示种Fragilariopsis oceanica指示研究区的表层与底层水体混合增强,海冰覆盖面积持续增大,威德尔环流势力增强,中纬度暖水势力减弱。总体来说,自晚更新世以来鲍威尔海盆经历了冷期(南极冰盖发育)-暖期-冷期(末次冰盛期)的阶段转变,而在深海氧同位素3阶段(marine isotope stages 3,MIS 3)中存在一段较长时间的冰筏碎屑事件时期。
文摘以鄂尔多斯盆地某区块的砂泥夹层岩心为研究对象,使用基于小波变换的去噪神经网络(denoising neural network based on wavelet transformation,DWTNet)对于岩心的图像进行去噪研究。该方法的评断结果采用峰值信噪比(peak signal to noise ratio,PSNR)和去噪后的图像结果进行了对比。研究表明,利用DWTNet在测试集YX1、YX2测试所提出的算法,并与EGDNet等去噪算法进行对比,PSNR在噪声为25、50、75 dB时,高于EGDNet算法0.527、0.418、1.1 dB。所提的算法在峰值信噪比等指标均高于其他算法;并在视觉效果上其处理得到的图像也更加清晰。方法的提出对于孔隙度、平均体积比表面积、平均曲率计算等都有着非常重要的意义。
