Chromium(VI)(Cr(VI)),a toxic metal ion,is widely present in industrial wastewater.To reduce the contamination of Cr(VI),many technologies for the photocatalytic reduction of Cr(VI)to Cr(III)have been developed in the ...Chromium(VI)(Cr(VI)),a toxic metal ion,is widely present in industrial wastewater.To reduce the contamination of Cr(VI),many technologies for the photocatalytic reduction of Cr(VI)to Cr(III)have been developed in the past decades.However,the practical application of photocatalysts for the reduction of Cr(VI)inwastewater treatment is often hindered by the complicated photoreduction processes due to the sedimentation and stratification of catalyst particles that present during the treatment of the wastewater.Probing and understanding the influences of the sedimentation and stratification of the catalyst particles on the photoreduction processes are long-term challenges in the field.Herein,we demonstrate that this issue can be solved by using layer location integrated low-field time-domain nuclear magnetic resonance(LF-NMR)relaxometry.With paramagnetic Cr(III)cation as the molecular probe,we successfully monitored the Cr(VI)photoreduction processes by operando probing the 1 H T2 relaxation time of the photoreduction systems.The influences of catalyst sedimentation and the light wavelength on photocatalysis were studied and discussed.The results showed the great potential of LF-NMR relaxometry in the study of Cr(VI)photoreduction processes during industrial wastewater treatments.展开更多
NMR serves as an important technique for probing rock pore space,such as pore structure characterization,fluid identification,and petrophysical property testing,due to the reusability of cores,convenience in sample pr...NMR serves as an important technique for probing rock pore space,such as pore structure characterization,fluid identification,and petrophysical property testing,due to the reusability of cores,convenience in sample processing,and time efficiency in laboratory tests.In practice,NMR signal collection is normally achieved through polarized nuclei relaxation which releases crucial relaxation messages for result interpretation.The impetus of this work is to help engineers and researchers with petroleum background obtain new insights into NMR principals and extend existing methodologies for characterization of unconventional formations.This article first gives a brief description of the development history of relaxation theories and models for porous media.Then,the widely used NMR techniques for characterizing petrophysical properties and pore structures are presented.Meanwhile,limitations and deficiencies of them are summarized.Finally,future work on improving these insufficiencies and approaches of enhancement applicability for NMR technologies are discussed.展开更多
A series of (1-x)La0.6Dy0.1Sr0.3MnO3/0.5x(Sb2O3)(x=0.15) samples were prepared by the solid-state reaction method, and the influence of sintering temperature of the matrix on low-field magnetoresistance of (1-x)La0.6D...A series of (1-x)La0.6Dy0.1Sr0.3MnO3/0.5x(Sb2O3)(x=0.15) samples were prepared by the solid-state reaction method, and the influence of sintering temperature of the matrix on low-field magnetoresistance of (1-x)La0.6Dy0.1Sr0.3MnO3/0.5x (Sb2O3) was studied through the measurements of X-ray diffraction (XRD) patterns, scanning electron microscope (SEM) image, resistivity-temperature (ρ-T) curves, and magnetoresistance-temperature (MR-T) curves. The results indicate that for the samples with low sintering temperature of the matrix, lowfield magnetoresistance effect appears on the whole temperature range and can be explained by grain boundary effect; for the sample with high sintering temperature of the matrix, intrinsic magnetoresistance peak appears on the high-temperature range, low-field magnetore-sistance effect appears on low temperature range, and the magnetoresistance in the magnetic field of 0.2 T and on the comparatively large temperature range between 280 K and 225 K hardly changes with temperature and remains at 4.8%, which can be explained by the competition between the intrinsic magnetoresistance induced by double-exchange function inside grains and the tunneling magnetoresis-tance (TMR) induced by grain boundary effect. The temperature stability of magnetoresistance is beneficial to the practical applications of MR.展开更多
Low-field(nuclear magnetic resonance)NMR has been widely used in petroleum industry,such as well logging and laboratory rock core analysis.However,the signal-to-noise ratio is low due to the low magnetic field strengt...Low-field(nuclear magnetic resonance)NMR has been widely used in petroleum industry,such as well logging and laboratory rock core analysis.However,the signal-to-noise ratio is low due to the low magnetic field strength of NMR tools and the complex petrophysical properties of detected samples.Suppressing the noise and highlighting the available NMR signals is very important for subsequent data processing.Most denoising methods are normally based on fixed mathematical transformation or handdesign feature selectors to suppress noise characteristics,which may not perform well because of their non-adaptive performance to different noisy signals.In this paper,we proposed a“data processing framework”to improve the quality of low field NMR echo data based on dictionary learning.Dictionary learning is a machine learning method based on redundancy and sparse representation theory.Available information in noisy NMR echo data can be adaptively extracted and reconstructed by dictionary learning.The advantages and application effectiveness of the proposed method were verified with a number of numerical simulations,NMR core data analyses,and NMR logging data processing.The results show that dictionary learning can significantly improve the quality of NMR echo data with high noise level and effectively improve the accuracy and reliability of inversion results.展开更多
In this study, the main factors influencing the measurements by means of the off-line low-field 1H NMR in the lab were discussed base on a robust calibration model established by the PLS algorithm using 255 crude oil ...In this study, the main factors influencing the measurements by means of the off-line low-field 1H NMR in the lab were discussed base on a robust calibration model established by the PLS algorithm using 255 crude oil samples. The preheating temperature had a great influence on the viscosity of oil samples and the resolution of spectral analysis. The repeatability of spectral measurements was impacted by the metal and wax content of the oil samples. For the case of high wax content oils, the wax species began to crystallize in the course of determination that could affect the repeatability of spectral measurements. These factors have evidenced why the preheating devices and filter unit are necessary when low field NMR system is used in the online analysis process. The investigation is very important for the on-line application of the low field NMR.展开更多
In this paper,we proposed a novel method for low-field nuclear magnetic resonance(NMR)inversion based on low-rank and sparsity restraint(LRSR)of relaxation spectra,with which high quality construction is made possible...In this paper,we proposed a novel method for low-field nuclear magnetic resonance(NMR)inversion based on low-rank and sparsity restraint(LRSR)of relaxation spectra,with which high quality construction is made possible for one-and two-dimensional low-field and low signal to noise ratio NMR data.In this method,the low-rank and sparsity restraints are introduced into the objective function instead of the smoothing term.The low-rank features in relaxation spectra are extracted to ensure the local characteristics and morphology of spectra.The sparsity and residual term are contributed to the resolution and precision of spectra,with the elimination of the redundant relaxation components.Optimization process of the objective function is designed with alternating direction method of multiples,in which the objective function is decomposed into three subproblems to be independently solved.The optimum solution can be obtained by alternating iteration and updating process.At first,numerical simulations are conducted on synthetic echo data with different signal-to-noise ratios,to optimize the desirable regularization parameters and verify the feasibility and effectiveness of proposed method.Then,NMR experiments on solutions and artificial sandstone samples are conducted and analyzed,which validates the robustness and reliability of the proposed method.The results from simulations and experiments have demonstrated that the suggested method has unique advantages for improving the resolution of relaxation spectra and enhancing the ability of fluid quantitative identification.展开更多
Development of microstructure of early cement paste （0-6 h） was investigated with 1H low- field NMR. It was found that T2 （transverse relaxation time） distributions of fresh cement paste were bimodal and two peaks...Development of microstructure of early cement paste （0-6 h） was investigated with 1H low- field NMR. It was found that T2 （transverse relaxation time） distributions of fresh cement paste were bimodal and two peaks were ＇long component＇ and ＇short component＇. Separation degree of two peaks was a sign of exchange of water within flocculation and outside flocculation. Factors such as water cement ratio, specific surface area and dosage of superplasticizer had influences on the separation degree： the separation degree increased with the water cement ratio; the separation degree of cement paste prepared with cement with a high specific surface area was zero; dosage of superplasticizer will decrease separation degree. Results also suggested that T2 distribution gradually moved to the left and T2 of long component and initial fluidity were linearly correlated.展开更多
The aluminum shielded room has been an important part of ultra-low-field magnetic resonance imaging （ULF MRI） based on the superconducting quantum interference device （SQUID）. The shielded room is effective to att...The aluminum shielded room has been an important part of ultra-low-field magnetic resonance imaging （ULF MRI） based on the superconducting quantum interference device （SQUID）. The shielded room is effective to attenuate the external radio-frequency field and keep the extremely sensitive detector, SQUID, working properly. A high-performance shielded room can increase the signal-to-noise ratio （SNR） and improve image quality. In this study, a circular coil with a diameter of 50 cm and a square coil with a side length of 2.0 m was used to simulate the magnetic fields from the nearby electric apparatuses and the distant environmental noise sources. The shielding effectivenesses （SE） of the shielded room with different thicknesses of aluminum sheets were calculated and simulated. A room using 6-mm-thick aluminum plates with a dimension of 1.5 m x 1.5 m x 2.0 m was then constructed. The SE was experimentally measured by using three-axis SQUID magnetometers, with tranisent magnetic field induced in the aluminum plates by the strong pre-polarization pulses. The results of the measured SE agreed with that from the simulation. In addition, the introduction of a 0.5-mm gap caused the obvious reduction of SE indicating the importance of door design. The nuclear magnetic resonance （NMR） signals of water at 5.9 kHz were measured in free space and in a shielded room, and the SNR was improved from 3 to 15. The simulation and experimental results will help us design an aluminum shielded room which satisfies the requirements for future ULF human brain imaging. Finally, the cancellation technique of the transient eddy current was tried, the simulation of the cancellation technique will lead us to finding an appropriate way to suppress the eddy current fields.展开更多
Development of microstructure of early cement paste (0–6 h) was investigated with 1H low-field NMR. It was found that T 2 (transverse relaxation time) distributions of fresh cement paste were bimodal and two peaks we...Development of microstructure of early cement paste (0–6 h) was investigated with 1H low-field NMR. It was found that T 2 (transverse relaxation time) distributions of fresh cement paste were bimodal and two peaks were ‘long component’ and ‘short component’. Separation degree of two peaks was a sign of exchange of water within flocculation and outside flocculation. Factors such as water cement ratio, specific surface area and dosage of superplasticizer had influences on the separation degree: the separation degree increased with the water cement ratio; the separation degree of cement paste prepared with cement with a high specific surface area was zero; dosage of superplasticizer will decrease separation degree. Results also suggested that T 2 distribution gradually moved to the left and T 2 of long component and initial fluidity were linearly correlated.展开更多
Low field NMR technique was applied to investigate the hydration of cement pastes with different water to cement ratios or addition of superplasticizer. As a nondestructive method, this technique can be used to monito...Low field NMR technique was applied to investigate the hydration of cement pastes with different water to cement ratios or addition of superplasticizer. As a nondestructive method, this technique can be used to monitor the hydration kinetics process by following the changes of longitudinal relaxation time （T1） of water constrained in the pastes. The experimental results indicate that the T1 distributions of water in the fresh paste normally exhibite bimodal distribution, where the large peak is corresponding to the free water while the small one is contributed by the water stored in the flocculations. Time dependence of the weighted average T1 has a good agreement with the hydration process and could be divided into four stages, i e, initial period, dormant period, accelerated period and steady period. The hydration mechanism of each stage was described based on the theory of cement chemistry. In addition, the total signal intensity, which is proportional to the content of the physically bound water in the samples, decrease successively during the hydration reflecting the consumption of physically bound water by hydration reactions.展开更多
CO_(2)geological storage and utilization(CGSU)is considered a far-reaching technique to meet the demand of increasing energy supply and decreasing CO_(2)emissions.For CGSUs related to shale gas reservoirs,experimental...CO_(2)geological storage and utilization(CGSU)is considered a far-reaching technique to meet the demand of increasing energy supply and decreasing CO_(2)emissions.For CGSUs related to shale gas reservoirs,experimental investigations have attracted variable methodologies,among which low-field NMR(LF-NMR)is a promising method and is playing an increasingly key role in reservoir characterization.Herein,the application of this nondestructive,sensitive,and quick LF-NMR technique in characterizing CGSU behavior in shale gas reservoirs is reviewed.First,the basic principle of LF-NMR for 1H-fluid detection is introduced,which is the theoretical foundation of the reviewed achievements in this paper.Then,the reviewed works are related to the LF-NMR-based measurements of CH_(4)adsorption capacity and the CO_(2)-CH_(4)interaction in shale,as well as the performance on CO_(2)sequestration and simultaneous enhanced gas recovery from shale.Basically,the reviewed achievements have exhibited a large potential for LF-NMR application in CGSUs related to shale gas reservoirs,although some limitations and deficiencies still need to be improved.Accordingly,some suggestions are proposed for a more responsible development of the LF-NMR technique.Hopefully,this review is helpful in promoting the expanding application of the LF-NMR technique in CGSU implementation in shale gas reservoirs.展开更多
该文对不同发酵阶段的黄酒样品进行低场核磁共振(low-field nuclear magnetic resonance,LF-NMR)检测,比较了陈酿时间、酒精度和品牌对黄酒低场核磁弛豫特性的影响,最后对9个品牌黄酒的LF-NMR弛豫信息进行了主成分分析。结果表明,发酵...该文对不同发酵阶段的黄酒样品进行低场核磁共振(low-field nuclear magnetic resonance,LF-NMR)检测,比较了陈酿时间、酒精度和品牌对黄酒低场核磁弛豫特性的影响,最后对9个品牌黄酒的LF-NMR弛豫信息进行了主成分分析。结果表明,发酵后样品的单组分弛豫时间(T_(2W))显著缩短,而陈酿后黄酒的T_(2W)又相对延长。多组分弛豫图谱(T_(2))表明,对照组和浸米样品均只有1个峰。发酵后样品的T_(2)图谱均出现2个峰。从第一次发酵到煎酒期间,T_(21)和T_(22)不断缩短,而陈酿期间T_(21)和T_(22)相对延长。同一品牌及陈酿时间的黄酒,酒精度越大,体系的T_(2W),T_(21)和T_(22)越短;同一品牌及酒精度下,陈酿时间仅对T_(21)有一定影响。不同品牌黄酒因酿造工艺的区别而使弛豫分布有一定特点。主成分分析表明,不同酒精度、陈酿时间、品牌及种类的黄酒的弛豫特性的PCA分布及间距不同。说明应用LF-NMR技术可实现对不同工艺生产的黄酒的快速辨别。展开更多
大豆含油率的高低直接影响榨油与育种结果。为探究大豆含油率的最佳检测方法与构建含油率高低判别模型,该研究基于不同维度低场核磁共振(low field nuclear magnetic resonance,LF-NMR)技术,以国标法为对照,利用LF-NMR波谱和LF-NMR含油...大豆含油率的高低直接影响榨油与育种结果。为探究大豆含油率的最佳检测方法与构建含油率高低判别模型,该研究基于不同维度低场核磁共振(low field nuclear magnetic resonance,LF-NMR)技术,以国标法为对照,利用LF-NMR波谱和LF-NMR含油含水率软件检测大豆含油率;核磁共振成像(magnetic resonance imaging,MRI)结合深度学习,建立大豆含油率高低判别模型。引入低场二维核磁共振(low field two-dimensional nuclear magnetic resonance,LF-2D-NMR)技术,定性分析一维波谱中信号重叠无法区分组分的问题。试验结果表明,LF-NMR含油含水率软件能快速准确检测大豆含油率,T1-T2二维核磁图谱成功解决了自由水和油信号重叠问题。利用U-net++深度学习模型对MRI成像的矢状面、冠状面、横截面以及三面混合数据集进行训练,其中横截面评价指标与其他数据集相比更优,语义分割部分中平均交并比(mean intersection over union,mIoU)约0.9058,全局准确率0.9980,训练后的模型能够将MRI图像识别并分割,快速判别大豆含油率高低。试验证明,LF-NMR及MRI能够快速无损掌握大豆含油率信息,为大豆的高油育种提供了新思路和技术支持。展开更多
文冠果的含水、含油率的高低影响其育种及加工储藏结果。为探求一种无损、快速、准确的文冠果含水含油率检测方法,该研究分别采用干取样法结合低场核磁共振技术(low field nuclear magnetic resonance,LF-NMR)、低场二维核磁共振技术(lo...文冠果的含水、含油率的高低影响其育种及加工储藏结果。为探求一种无损、快速、准确的文冠果含水含油率检测方法,该研究分别采用干取样法结合低场核磁共振技术(low field nuclear magnetic resonance,LF-NMR)、低场二维核磁共振技术(low field two-dimensional nuclear magnetic resonance,LF-2D-NMR)两种试验方式进行数据采集。通过系列试验确定两种技术在检测文冠果含水含油率的可行性。结果表明:与国标法测试结果相比,LF-NMR结合干取样法采集获取的数据异常,并且由于LF-NMR无法区分重叠峰信号,无法解释产生异常变化的原因,故该方法不适用于文冠果含油含水率的检测;LF-2D-NMR能够定性分析一维波谱中信号重叠无法区分组分的问题,成功解释了干取样法结合LF-NMR数据异常的原因。同时,LF-2D-NMR测得的文冠果T_(1)-T_(2)谱峰面积与烘箱干燥法及索氏提取法获取的水油含量之间存在显著的线性相关性,经与真值验证过后的决定系数R_2分别为0.920 9和0.942 4,可以用于文冠果含水含油率的定量分析。该研究拓展了低场核磁共振技术的理论认知深度,提高检测精度及在实际生产中的指导价值。展开更多
This paper reports a multifunctional magnetic-photoelectric laminate device based on the integration of spintronic material(La_(0.7)Sr_(0.3)MnO_(3))and multiferroic(Ni-doped BiFeO_(3)),in which the repeatable modulati...This paper reports a multifunctional magnetic-photoelectric laminate device based on the integration of spintronic material(La_(0.7)Sr_(0.3)MnO_(3))and multiferroic(Ni-doped BiFeO_(3)),in which the repeatable modulation effect on the photoelectric properties were achieved by applying external magnetic fields.More obviously,photocurrent density(J)of the laminate was largely enhanced,the change rate of J up to 287.6%is obtained.This sensing function effect should be attributed to the low-field magnetoresistance effect in perovskite manganite and the scattering of spin photoelectron in multiferroic material.The laminate perfectly combines the functions of sensor and controller,which can not only reflect the intensity of environmental magnetic field,but also modulate the photoelectric conversion performance.This work provides an alternative and facile way to realize multi-degree-of-freedom control for photoelectric conversion performances and lastly miniaturize multifunction device.展开更多
Here,we aimed to study the changes in proteome of golden pompano fillets during post-mortem storage.Tandem mass tags(TMT)-labeled quantitative proteomic strategy was applied to investigate the relationships between pr...Here,we aimed to study the changes in proteome of golden pompano fillets during post-mortem storage.Tandem mass tags(TMT)-labeled quantitative proteomic strategy was applied to investigate the relationships between protein changes and quality characteristics of modified atmosphere packaging(MAP)fillets during superchilling(-3°C)storage.Scanning electron microscopy was used to show that the muscle histology microstructure of fillets was damaged to varying degrees,and low-field nuclear magnetic resonance was used to find that the immobilized water and free water in the muscle of fillets changed significantly.Total sulfhydryl content,TCA-soluble peptides and Ca2+-ATPase activity also showed that the fillet protein had a deterioration by oxidation and denaturation.The Fresh(FS),MAP,and air packaging(AP)groups were set.Total of 150 proteins were identified as differential abundant proteins(DAPs)in MAP/FS,while 209 DAPs were in AP/FS group.The KEGG pathway analysis indicated that most DAPs were involved in binding proteins and protein turnover.Correlation analysis found that 52 DAPs were correlated with quality traits.Among them,8 highly correlated DAPs are expected to be used as potential quality markers for protein oxidation and water-holding capacity.These results provide a further understanding of the muscle deterioration mechanism of packaging golden pompano fillets during superchilling.展开更多
基金supported by the National Natural Science Foundation of China(grant nos.22072045,21603073,and 21574043)the Ministry of Science and Technology of the People's Republic of China(grant no.2018YFC1602800)Xing-FuZhi-Hua Foundation of ECNU and Microscale Magnetic Resonance Platform of ECNU and the Microscale Magnetic Resonance Platform of ECNU.
文摘Chromium(VI)(Cr(VI)),a toxic metal ion,is widely present in industrial wastewater.To reduce the contamination of Cr(VI),many technologies for the photocatalytic reduction of Cr(VI)to Cr(III)have been developed in the past decades.However,the practical application of photocatalysts for the reduction of Cr(VI)inwastewater treatment is often hindered by the complicated photoreduction processes due to the sedimentation and stratification of catalyst particles that present during the treatment of the wastewater.Probing and understanding the influences of the sedimentation and stratification of the catalyst particles on the photoreduction processes are long-term challenges in the field.Herein,we demonstrate that this issue can be solved by using layer location integrated low-field time-domain nuclear magnetic resonance(LF-NMR)relaxometry.With paramagnetic Cr(III)cation as the molecular probe,we successfully monitored the Cr(VI)photoreduction processes by operando probing the 1 H T2 relaxation time of the photoreduction systems.The influences of catalyst sedimentation and the light wavelength on photocatalysis were studied and discussed.The results showed the great potential of LF-NMR relaxometry in the study of Cr(VI)photoreduction processes during industrial wastewater treatments.
基金financially supported by the National Science Foundation for Distinguished Young Scholars(51525404)the National Science and Technology Major Project(No.2016ZX05002002)the National Science and Technology Major Project(2016ZX05048-004-006)。
文摘NMR serves as an important technique for probing rock pore space,such as pore structure characterization,fluid identification,and petrophysical property testing,due to the reusability of cores,convenience in sample processing,and time efficiency in laboratory tests.In practice,NMR signal collection is normally achieved through polarized nuclei relaxation which releases crucial relaxation messages for result interpretation.The impetus of this work is to help engineers and researchers with petroleum background obtain new insights into NMR principals and extend existing methodologies for characterization of unconventional formations.This article first gives a brief description of the development history of relaxation theories and models for porous media.Then,the widely used NMR techniques for characterizing petrophysical properties and pore structures are presented.Meanwhile,limitations and deficiencies of them are summarized.Finally,future work on improving these insufficiencies and approaches of enhancement applicability for NMR technologies are discussed.
基金supported by the National Natural Foundation of China (No. 19934003) the Natural Science Research Key Program of Anhui Educational Committee (No. KJ2011A259)+3 种基金the Opening Program of Cultivating Base of Anhui Key Laboratory of Spintronics and Nanomaterials (Nos. 2010YKF04 2011YKF05)the Professors’and Doctors’Research Startup Foundation of Suzhou University (Nos. 2011jb01 2011jb02)
文摘A series of (1-x)La0.6Dy0.1Sr0.3MnO3/0.5x(Sb2O3)(x=0.15) samples were prepared by the solid-state reaction method, and the influence of sintering temperature of the matrix on low-field magnetoresistance of (1-x)La0.6Dy0.1Sr0.3MnO3/0.5x (Sb2O3) was studied through the measurements of X-ray diffraction (XRD) patterns, scanning electron microscope (SEM) image, resistivity-temperature (ρ-T) curves, and magnetoresistance-temperature (MR-T) curves. The results indicate that for the samples with low sintering temperature of the matrix, lowfield magnetoresistance effect appears on the whole temperature range and can be explained by grain boundary effect; for the sample with high sintering temperature of the matrix, intrinsic magnetoresistance peak appears on the high-temperature range, low-field magnetore-sistance effect appears on low temperature range, and the magnetoresistance in the magnetic field of 0.2 T and on the comparatively large temperature range between 280 K and 225 K hardly changes with temperature and remains at 4.8%, which can be explained by the competition between the intrinsic magnetoresistance induced by double-exchange function inside grains and the tunneling magnetoresis-tance (TMR) induced by grain boundary effect. The temperature stability of magnetoresistance is beneficial to the practical applications of MR.
基金supported by Science Foundation of China University of Petroleum,Beijing(Grant Number ZX20210024)Chinese Postdoctoral Science Foundation(Grant Number 2021M700172)+1 种基金The Strategic Cooperation Technology Projects of CNPC and CUP(Grant Number ZLZX2020-03)National Natural Science Foundation of China(Grant Number 42004105)
文摘Low-field(nuclear magnetic resonance)NMR has been widely used in petroleum industry,such as well logging and laboratory rock core analysis.However,the signal-to-noise ratio is low due to the low magnetic field strength of NMR tools and the complex petrophysical properties of detected samples.Suppressing the noise and highlighting the available NMR signals is very important for subsequent data processing.Most denoising methods are normally based on fixed mathematical transformation or handdesign feature selectors to suppress noise characteristics,which may not perform well because of their non-adaptive performance to different noisy signals.In this paper,we proposed a“data processing framework”to improve the quality of low field NMR echo data based on dictionary learning.Dictionary learning is a machine learning method based on redundancy and sparse representation theory.Available information in noisy NMR echo data can be adaptively extracted and reconstructed by dictionary learning.The advantages and application effectiveness of the proposed method were verified with a number of numerical simulations,NMR core data analyses,and NMR logging data processing.The results show that dictionary learning can significantly improve the quality of NMR echo data with high noise level and effectively improve the accuracy and reliability of inversion results.
基金the financial support from the SINOPEC (ST 13028)
文摘In this study, the main factors influencing the measurements by means of the off-line low-field 1H NMR in the lab were discussed base on a robust calibration model established by the PLS algorithm using 255 crude oil samples. The preheating temperature had a great influence on the viscosity of oil samples and the resolution of spectral analysis. The repeatability of spectral measurements was impacted by the metal and wax content of the oil samples. For the case of high wax content oils, the wax species began to crystallize in the course of determination that could affect the repeatability of spectral measurements. These factors have evidenced why the preheating devices and filter unit are necessary when low field NMR system is used in the online analysis process. The investigation is very important for the on-line application of the low field NMR.
基金supported by “National Natural Science Foundation of China (Grant No. 42204106)”“China Postdoctoral Science Foundation (Grant No. 2021M700172)”+1 种基金“The Strategic Cooperation Technology Projects of CNPC and CUP (Grant No. ZLZX2020-03)”“Natural Science Foundation of the Jiangsu Higher Education Institutions of China (Grant No. 20KJD430002)”
文摘In this paper,we proposed a novel method for low-field nuclear magnetic resonance(NMR)inversion based on low-rank and sparsity restraint(LRSR)of relaxation spectra,with which high quality construction is made possible for one-and two-dimensional low-field and low signal to noise ratio NMR data.In this method,the low-rank and sparsity restraints are introduced into the objective function instead of the smoothing term.The low-rank features in relaxation spectra are extracted to ensure the local characteristics and morphology of spectra.The sparsity and residual term are contributed to the resolution and precision of spectra,with the elimination of the redundant relaxation components.Optimization process of the objective function is designed with alternating direction method of multiples,in which the objective function is decomposed into three subproblems to be independently solved.The optimum solution can be obtained by alternating iteration and updating process.At first,numerical simulations are conducted on synthetic echo data with different signal-to-noise ratios,to optimize the desirable regularization parameters and verify the feasibility and effectiveness of proposed method.Then,NMR experiments on solutions and artificial sandstone samples are conducted and analyzed,which validates the robustness and reliability of the proposed method.The results from simulations and experiments have demonstrated that the suggested method has unique advantages for improving the resolution of relaxation spectra and enhancing the ability of fluid quantitative identification.
基金Funded by the National Natural Science Foundation of China （No. 51178339）, and the National Basic Research Program （No. 2009CB623104-5）
文摘Development of microstructure of early cement paste （0-6 h） was investigated with 1H low- field NMR. It was found that T2 （transverse relaxation time） distributions of fresh cement paste were bimodal and two peaks were ＇long component＇ and ＇short component＇. Separation degree of two peaks was a sign of exchange of water within flocculation and outside flocculation. Factors such as water cement ratio, specific surface area and dosage of superplasticizer had influences on the separation degree： the separation degree increased with the water cement ratio; the separation degree of cement paste prepared with cement with a high specific surface area was zero; dosage of superplasticizer will decrease separation degree. Results also suggested that T2 distribution gradually moved to the left and T2 of long component and initial fluidity were linearly correlated.
基金Project supported in part by the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant No.XDB04020200)in part by the National Natural Science Foundation of China(Grant No.11204339)
文摘The aluminum shielded room has been an important part of ultra-low-field magnetic resonance imaging （ULF MRI） based on the superconducting quantum interference device （SQUID）. The shielded room is effective to attenuate the external radio-frequency field and keep the extremely sensitive detector, SQUID, working properly. A high-performance shielded room can increase the signal-to-noise ratio （SNR） and improve image quality. In this study, a circular coil with a diameter of 50 cm and a square coil with a side length of 2.0 m was used to simulate the magnetic fields from the nearby electric apparatuses and the distant environmental noise sources. The shielding effectivenesses （SE） of the shielded room with different thicknesses of aluminum sheets were calculated and simulated. A room using 6-mm-thick aluminum plates with a dimension of 1.5 m x 1.5 m x 2.0 m was then constructed. The SE was experimentally measured by using three-axis SQUID magnetometers, with tranisent magnetic field induced in the aluminum plates by the strong pre-polarization pulses. The results of the measured SE agreed with that from the simulation. In addition, the introduction of a 0.5-mm gap caused the obvious reduction of SE indicating the importance of door design. The nuclear magnetic resonance （NMR） signals of water at 5.9 kHz were measured in free space and in a shielded room, and the SNR was improved from 3 to 15. The simulation and experimental results will help us design an aluminum shielded room which satisfies the requirements for future ULF human brain imaging. Finally, the cancellation technique of the transient eddy current was tried, the simulation of the cancellation technique will lead us to finding an appropriate way to suppress the eddy current fields.
基金Funded by the National Natural Science Foundation of China(No.51178339)the National Basic Research Program(No.2009CB623104-5)
文摘Development of microstructure of early cement paste (0–6 h) was investigated with 1H low-field NMR. It was found that T 2 (transverse relaxation time) distributions of fresh cement paste were bimodal and two peaks were ‘long component’ and ‘short component’. Separation degree of two peaks was a sign of exchange of water within flocculation and outside flocculation. Factors such as water cement ratio, specific surface area and dosage of superplasticizer had influences on the separation degree: the separation degree increased with the water cement ratio; the separation degree of cement paste prepared with cement with a high specific surface area was zero; dosage of superplasticizer will decrease separation degree. Results also suggested that T 2 distribution gradually moved to the left and T 2 of long component and initial fluidity were linearly correlated.
基金Funded by the Major State Basic Research Development Program of China(‘973’ Program) (No. 2009CB623105)
文摘Low field NMR technique was applied to investigate the hydration of cement pastes with different water to cement ratios or addition of superplasticizer. As a nondestructive method, this technique can be used to monitor the hydration kinetics process by following the changes of longitudinal relaxation time （T1） of water constrained in the pastes. The experimental results indicate that the T1 distributions of water in the fresh paste normally exhibite bimodal distribution, where the large peak is corresponding to the free water while the small one is contributed by the water stored in the flocculations. Time dependence of the weighted average T1 has a good agreement with the hydration process and could be divided into four stages, i e, initial period, dormant period, accelerated period and steady period. The hydration mechanism of each stage was described based on the theory of cement chemistry. In addition, the total signal intensity, which is proportional to the content of the physically bound water in the samples, decrease successively during the hydration reflecting the consumption of physically bound water by hydration reactions.
基金the Science and Technology Department of Sichuan Province(Nos.2021YFH0048 and 2021YFH0118)the Fundamental Research Funds for the Central Universities(No.20826041E4199)+3 种基金the National Natural Science Foundation of China(Grant No.20740099)the Natural Science Foundation of Chongqing,China(No.CSTB2022NSCQ-BHX0721)the Chongqing Natural Science Foundation for Distinguished Young Scientists(No.cstc2021jcyj-jqX0007)the Key Laboratory of Shale Gas Exploration,Ministry of Natural Resources(No.KLSGE-202103).
文摘CO_(2)geological storage and utilization(CGSU)is considered a far-reaching technique to meet the demand of increasing energy supply and decreasing CO_(2)emissions.For CGSUs related to shale gas reservoirs,experimental investigations have attracted variable methodologies,among which low-field NMR(LF-NMR)is a promising method and is playing an increasingly key role in reservoir characterization.Herein,the application of this nondestructive,sensitive,and quick LF-NMR technique in characterizing CGSU behavior in shale gas reservoirs is reviewed.First,the basic principle of LF-NMR for 1H-fluid detection is introduced,which is the theoretical foundation of the reviewed achievements in this paper.Then,the reviewed works are related to the LF-NMR-based measurements of CH_(4)adsorption capacity and the CO_(2)-CH_(4)interaction in shale,as well as the performance on CO_(2)sequestration and simultaneous enhanced gas recovery from shale.Basically,the reviewed achievements have exhibited a large potential for LF-NMR application in CGSUs related to shale gas reservoirs,although some limitations and deficiencies still need to be improved.Accordingly,some suggestions are proposed for a more responsible development of the LF-NMR technique.Hopefully,this review is helpful in promoting the expanding application of the LF-NMR technique in CGSU implementation in shale gas reservoirs.
文摘该文对不同发酵阶段的黄酒样品进行低场核磁共振(low-field nuclear magnetic resonance,LF-NMR)检测,比较了陈酿时间、酒精度和品牌对黄酒低场核磁弛豫特性的影响,最后对9个品牌黄酒的LF-NMR弛豫信息进行了主成分分析。结果表明,发酵后样品的单组分弛豫时间(T_(2W))显著缩短,而陈酿后黄酒的T_(2W)又相对延长。多组分弛豫图谱(T_(2))表明,对照组和浸米样品均只有1个峰。发酵后样品的T_(2)图谱均出现2个峰。从第一次发酵到煎酒期间,T_(21)和T_(22)不断缩短,而陈酿期间T_(21)和T_(22)相对延长。同一品牌及陈酿时间的黄酒,酒精度越大,体系的T_(2W),T_(21)和T_(22)越短;同一品牌及酒精度下,陈酿时间仅对T_(21)有一定影响。不同品牌黄酒因酿造工艺的区别而使弛豫分布有一定特点。主成分分析表明,不同酒精度、陈酿时间、品牌及种类的黄酒的弛豫特性的PCA分布及间距不同。说明应用LF-NMR技术可实现对不同工艺生产的黄酒的快速辨别。
文摘大豆含油率的高低直接影响榨油与育种结果。为探究大豆含油率的最佳检测方法与构建含油率高低判别模型,该研究基于不同维度低场核磁共振(low field nuclear magnetic resonance,LF-NMR)技术,以国标法为对照,利用LF-NMR波谱和LF-NMR含油含水率软件检测大豆含油率;核磁共振成像(magnetic resonance imaging,MRI)结合深度学习,建立大豆含油率高低判别模型。引入低场二维核磁共振(low field two-dimensional nuclear magnetic resonance,LF-2D-NMR)技术,定性分析一维波谱中信号重叠无法区分组分的问题。试验结果表明,LF-NMR含油含水率软件能快速准确检测大豆含油率,T1-T2二维核磁图谱成功解决了自由水和油信号重叠问题。利用U-net++深度学习模型对MRI成像的矢状面、冠状面、横截面以及三面混合数据集进行训练,其中横截面评价指标与其他数据集相比更优,语义分割部分中平均交并比(mean intersection over union,mIoU)约0.9058,全局准确率0.9980,训练后的模型能够将MRI图像识别并分割,快速判别大豆含油率高低。试验证明,LF-NMR及MRI能够快速无损掌握大豆含油率信息,为大豆的高油育种提供了新思路和技术支持。
文摘文冠果的含水、含油率的高低影响其育种及加工储藏结果。为探求一种无损、快速、准确的文冠果含水含油率检测方法,该研究分别采用干取样法结合低场核磁共振技术(low field nuclear magnetic resonance,LF-NMR)、低场二维核磁共振技术(low field two-dimensional nuclear magnetic resonance,LF-2D-NMR)两种试验方式进行数据采集。通过系列试验确定两种技术在检测文冠果含水含油率的可行性。结果表明:与国标法测试结果相比,LF-NMR结合干取样法采集获取的数据异常,并且由于LF-NMR无法区分重叠峰信号,无法解释产生异常变化的原因,故该方法不适用于文冠果含油含水率的检测;LF-2D-NMR能够定性分析一维波谱中信号重叠无法区分组分的问题,成功解释了干取样法结合LF-NMR数据异常的原因。同时,LF-2D-NMR测得的文冠果T_(1)-T_(2)谱峰面积与烘箱干燥法及索氏提取法获取的水油含量之间存在显著的线性相关性,经与真值验证过后的决定系数R_2分别为0.920 9和0.942 4,可以用于文冠果含水含油率的定量分析。该研究拓展了低场核磁共振技术的理论认知深度,提高检测精度及在实际生产中的指导价值。
基金financially supported by National Natural Science Foundation of China(11074031)National Key R&D Program of China(2017YFE0301401)Natural Science Foundation of Fujian Province,China(2020J01192,2021J01191)
文摘This paper reports a multifunctional magnetic-photoelectric laminate device based on the integration of spintronic material(La_(0.7)Sr_(0.3)MnO_(3))and multiferroic(Ni-doped BiFeO_(3)),in which the repeatable modulation effect on the photoelectric properties were achieved by applying external magnetic fields.More obviously,photocurrent density(J)of the laminate was largely enhanced,the change rate of J up to 287.6%is obtained.This sensing function effect should be attributed to the low-field magnetoresistance effect in perovskite manganite and the scattering of spin photoelectron in multiferroic material.The laminate perfectly combines the functions of sensor and controller,which can not only reflect the intensity of environmental magnetic field,but also modulate the photoelectric conversion performance.This work provides an alternative and facile way to realize multi-degree-of-freedom control for photoelectric conversion performances and lastly miniaturize multifunction device.
基金supported by Central Public-Interest Scientific Institution Basal Research Fund,CAFS(2023TD74,2023TD78)the Earmarked Fund for CARS-47(CARS-47)+2 种基金Guangdong Provincial Science and Technology Plan Project(2023B0202010015)Central Public-Interest Scientific Institution Basal Research Fund,CAFS(Sanya Yazhou Bay Science and Technology City(SKJC-2020-02-013))Special Funds for Promoting Economic Development in Guangdong Province(For Modern Fishery)(YueNong 2019B14).
文摘Here,we aimed to study the changes in proteome of golden pompano fillets during post-mortem storage.Tandem mass tags(TMT)-labeled quantitative proteomic strategy was applied to investigate the relationships between protein changes and quality characteristics of modified atmosphere packaging(MAP)fillets during superchilling(-3°C)storage.Scanning electron microscopy was used to show that the muscle histology microstructure of fillets was damaged to varying degrees,and low-field nuclear magnetic resonance was used to find that the immobilized water and free water in the muscle of fillets changed significantly.Total sulfhydryl content,TCA-soluble peptides and Ca2+-ATPase activity also showed that the fillet protein had a deterioration by oxidation and denaturation.The Fresh(FS),MAP,and air packaging(AP)groups were set.Total of 150 proteins were identified as differential abundant proteins(DAPs)in MAP/FS,while 209 DAPs were in AP/FS group.The KEGG pathway analysis indicated that most DAPs were involved in binding proteins and protein turnover.Correlation analysis found that 52 DAPs were correlated with quality traits.Among them,8 highly correlated DAPs are expected to be used as potential quality markers for protein oxidation and water-holding capacity.These results provide a further understanding of the muscle deterioration mechanism of packaging golden pompano fillets during superchilling.
