In response to the problems of unclear distribution of deep-water pre-salt carbonate reservoirs and formation conditions of large oil fields in the Santos passive continental margin basin,based on comprehensive utiliz...In response to the problems of unclear distribution of deep-water pre-salt carbonate reservoirs and formation conditions of large oil fields in the Santos passive continental margin basin,based on comprehensive utilization of geological,seismic,and core data,and reconstruction of Early Cretaceous prototype basin and lithofacies paleogeography,it is proposed for the first time that the construction of pre-salt carbonate build-ups was controlled by two types of isolated platforms:inter-depression fault-uplift and intra-depression fault-high.The inter-depression fault-uplift isolated platforms are distributed on the present-day pre-salt uplifted zones between depressions,and are built on half-and fault-horst blocks that were inherited and developed in the early intra-continental and inter-continental rift stages.The late intra-continental rift coquinas of the ITP Formation and the early inter-continental rift microbial limestones of the BVE Formation are continuously constructed;intra-depression fault-high isolated platforms are distributed in the current pre-salt depression zones,built on the uplifted zones formed by volcanic rock build-ups in the early prototype stage of intra-continental rifts,and only the BVE microbial limestones are developed.Both types of limestones formed into mound-shoal bodies,that have the characteristics of large reservoir thickness and good physical properties.Based on the dissection of large pre-salt oil fields discovered in the Santos Basin,it has been found that both types of platforms could form large-scale combined structural-stratigraphic traps,surrounded by high-quality lacustrine and lagoon source rocks at the periphery,and efficiently sealed by thick high-quality evaporite rocks above,forming the optimal combination of source,reservoir and cap in the form of“lower generation,middle storage,and upper cap”,with a high degree of oil and gas enrichment.It has been found that the large oil fields are all bottom water massive oil fields with a unified pressure system,and they are all filled to the spill-point.The future exploration is recommended to focus on the inter-depression fault-uplift isolated platforms in the western uplift zone and the southern section of eastern uplift zones,as well as intra-depression fault-high isolated platforms in the central depression zone.The result not only provides an important basis for the advanced selection of potential play fairways,bidding of new blocks,and deployment of awarded exploration blocks in the Santos Basin,but also provides a reference for the global selection of deep-water exploration blocks in passive continental margin basins.展开更多
Surface subsidence is a typical ground movement due to longwall mining, which causes a series of environmental problems and hazards. In China, intensive coal extractions are commonly operated under dense-populated coa...Surface subsidence is a typical ground movement due to longwall mining, which causes a series of environmental problems and hazards. In China, intensive coal extractions are commonly operated under dense-populated coalfields, which exacerbates the negative subsequences resulted from surface settlement. Therefore, effective approaches to control the ground subsidence are in urgent need for the Chinese coal mining industry. This paper presents a newly developed subsidence control technology: isolated overburden grout injection, including the theory, technique and applications. Relevant procedures such as injection system design, grouting material selection, borehole layout, grout take estimation and injection process design are proposed. The applicability of this technology has been demonstrated through physical modelling, field measurements, and case studies. Since 2009, the technology has been successfully applied to 14 longwall areas in 9 Chinese coal mines. The ultimate surface subsidence factors vary from 0.10 to 0.15. This method has a great potential to be popularized and performed where longwall mining are implemented under villages and ground infrastructures.展开更多
Reducing the dimensions of metallic nanoparticles to isolated,single atom has attracted considerable attention in heterogeneous catalysis,because it significantly improves atomic utilization and often leads to distinc...Reducing the dimensions of metallic nanoparticles to isolated,single atom has attracted considerable attention in heterogeneous catalysis,because it significantly improves atomic utilization and often leads to distinct catalytic performance.Through extensive research,it has been recognized that the local coordination environment of single atoms has an important influence on their electronic structures and catalytic behaviors.In this review,we summarize a series of representative systems of single-atom catalysts,discussing their preparation,characterization,and structure-property relationship,with an emphasis on the correlation between the coordination spheres of isolated reactive centers and their intrinsic catalytic activities.We also share our perspectives on the current challenges and future research promises in the development of single-atom catalysis.With this article,we aim to highlight the possibility of finely tuning the catalytic performances by engineering the coordination spheres of single-atom sites and provide new insights into the further development for this emerging research field.展开更多
Isolated pillars in underground mines are subjected to uniaxial stress,and the load bearing cross-section of pillars is commonly rectangularly shaped.In addition,the uniaxial compression test(UCT)is widely used for de...Isolated pillars in underground mines are subjected to uniaxial stress,and the load bearing cross-section of pillars is commonly rectangularly shaped.In addition,the uniaxial compression test(UCT)is widely used for determining the basic mechanical properties of rocks and revealing the mechanism of isolated pillar disasters under unidimensional stress.The shape effects of rock mechanical properties under uniaxial compression are mainly quantitatively reflected in the specific shape ratios of rocks.Therefore,it is necessary to study the detailed shape ratio effects on the mechanical properties of rectangular prism rock specimens and isolated pillars under uniaxial compressive stress.In this study,granite,marble and sandstone rectangular prism specimens with various height to width ratios(r)and width to thickness ratios(u)were prepared and tested.The study results show that r and u have a great influence on the bearing ability of rocks,and thin or high rocks have lower uniaxial compressive strength.Reducing the level of r can enhance the u effect on the strength of rocks,and increasing the level of u can enhance the r effect on the strength of rocks.The lateral strain on the thickness side of the rock specimen is larger than that on the width side,which implies that crack growth occurs easily on the thickness side.Considering r and u,a novel strength prediction model of isolated pillars was proposed based on the testing results,and the prediction model was used for the safety assessment of 179 isolated pillars in the Xianglu Mountain Tungsten Mine.展开更多
With the development of data age,data quality has become one of the problems that people pay much attention to.As a field of data mining,outlier detection is related to the quality of data.The isolated forest algorith...With the development of data age,data quality has become one of the problems that people pay much attention to.As a field of data mining,outlier detection is related to the quality of data.The isolated forest algorithm is one of the more prominent numerical data outlier detection algorithms in recent years.In the process of constructing the isolation tree by the isolated forest algorithm,as the isolation tree is continuously generated,the difference of isolation trees will gradually decrease or even no difference,which will result in the waste of memory and reduced efficiency of outlier detection.And in the constructed isolation trees,some isolation trees cannot detect outlier.In this paper,an improved iForest-based method GA-iForest is proposed.This method optimizes the isolated forest by selecting some better isolation trees according to the detection accuracy and the difference of isolation trees,thereby reducing some duplicate,similar and poor detection isolation trees and improving the accuracy and stability of outlier detection.In the experiment,Ubuntu system and Spark platform are used to build the experiment environment.The outlier datasets provided by ODDS are used as test.According to indicators such as the accuracy,recall rate,ROC curves,AUC and execution time,the performance of the proposed method is evaluated.Experimental results show that the proposed method can not only improve the accuracy and stability of outlier detection,but also reduce the number of isolation trees by 20%-40%compared with the original iForest method.展开更多
This paper theoretically investigates the high-order harmonic generation cutoff extension using intense few-cycle linearly chirped laser pulses. It shows that the cutoff of the harmonic can be extended remarkably by o...This paper theoretically investigates the high-order harmonic generation cutoff extension using intense few-cycle linearly chirped laser pulses. It shows that the cutoff of the harmonic can be extended remarkably by optimising the chirping parameters. The time-frequency characteristics of high-order harmonics with different chirping parameters are analysed by means of wavelet transform of the dipole acceleration. It also gives out the classical three-step model pictures of electron. By superposing a properly selected range of the harmonic spectrum, it obtains an isolated 65as pulse.展开更多
Adopting a soft site model built on soft interlayer soil foundation,a shaking table test for soft interlayer soil-isolated structure interaction is conducted to investigate the seismic response of isolated structure o...Adopting a soft site model built on soft interlayer soil foundation,a shaking table test for soft interlayer soil-isolated structure interaction is conducted to investigate the seismic response of isolated structure on soft site,and analyze its isolation effect.Test results show that the test can reflect the earthquake response characteristics of isolated structure on soft site.It is on soft site that the dynamic characteristics of isolated structure,acceleration magnification factor(AMF)of isolated structure and isolation efficiency of the isolation layer differ from those on rigid foundation with an soil-structure interaction(SSI)effect,represented by the reduction in fundamental vibration frequency of isolated structure and the increase of damping ratio with changes of the SSI effect.SSI can either increase or decrease AMF of isolated structure on soft site,depending on the characteristics of earthquake motion input.Furthermore,the isolation efficiency of isolation layer on soft site is decreased with the SSI effect,which is related to the peak ground acceleration(PGA)and the characteristics of earthquake motion input.展开更多
Objectives To reveal etiologies of persistent isolated hematuria （PIH） through ultrastructural pathological examination, to disclose clinicopathological correlation in cases with PIH, and to summarize appropriate ma...Objectives To reveal etiologies of persistent isolated hematuria （PIH） through ultrastructural pathological examination, to disclose clinicopathological correlation in cases with PIH, and to summarize appropriate management of patients with PIH. Methods we retrospectively studied 155 P1H patients receiving renal biopsy between January, 2003 and December, 2008 in Peking Union Medical College Hospital. All the clinical data and follow-up result were analyzed. Results All subjects included 38 children and 117 adults, with mean age of 11.38±3.25 years for children and 35.17±8.44 years for adults. Thin basement membrane nephropathy （TBMN） was the most common pathology （55.3% of children and 49.6% of adults）, followed by IgA nephropathy （18.4% of children and 32.5% of adults, mainly grade 2-3） and mesangial proliferative glomerulonephritis （MsPGN） without IgA deposition （13.2% of children and 12.8% of adults）. Besides, A1port syndrome （2.6% of children） and membrane nephropathy （2.6% of children and 0.9% of adults） were demonstrated as other causes of PIH. Elevated mean arteral pressure or protein excretion rate, as well as episodic macrohematuria, indicated higher risk for MsPGN rather than TBMN. On the other hand, severity of microhematuria was irrelevant to pathological types of PIH. Totally, 86 patients were followed up and 37 cases therein stayed on track for long term （mean duration 41.11±28.92 months, range 8-113 months）. Most cases had benign clinical course except 3 cases with TBMN, 5 cases with IgA nephropathy, 1 case with MsPGN （without IgA deposition）, and 1 case with Alport syndrome, who developed hypertension or proteinuria. All of them were administered timely intervention. Conclusions Close follow-up should be required as the primary management for PIH. Equally important is careful monitoring for early identification of undesirable predictors; while renal biopsy and other timely intervention are warranted if there is hypertension, significant proteinuria or renal impairment.展开更多
Objective To investigate plasma N-terminal pro-brain natriuretic peptide (NT-BNP) levels and to assess their clinical significance in elderly patients with isolated diastolic dysfunction. Methods Plasma NT-BNP level w...Objective To investigate plasma N-terminal pro-brain natriuretic peptide (NT-BNP) levels and to assess their clinical significance in elderly patients with isolated diastolic dysfunction. Methods Plasma NT-BNP level were measured by electrochemiluminescence immunoassay in 34 symptomatic patients (Group 1), 34 asymptomatic patients (Group 2) with isolated diastolic dysfunction, and in 16 elderly healthy subjects (control group, Group 3), serving controls. Colored Doppler echocardiography was performed to evaluate the patients' cardiac structures and functions. Results The plasma NT-BNP level in Group 1 was significantly higher than those in Group 2 and Group 3 and increased with the severity of heart failure. There was no significant difference of plasma NT-BNP levels between Group 2 and Group 3 (p>0.05). A NT-BNP value of 102.75 pg/mL showed a sensitivity of 88.2%, a specificity of 87.5%, and an accuracy of 88.1% for diagnosing diastolic dysfunction. Patients with restrictive filling pattern on echocardiography had higher NT-BNP levels than those of impaired relaxation pattern (1961.2±304.9 versus 460.1±92.7pg/mL, p<0.001). Conclusion The elevation of plasma NT-BNP level in elderly patients with isolated diastolic dysfunction correlates with the severity of their diastolic abnormalities. The level of plasma NT-BNP has an important clinical value in the diagnosis of elderly patients with isolated diastolic dysfunction.展开更多
Isolation technique of ground structure is a hot topic in the field of earthquake engineering and structure dynamics.Since soil-isolated structure dynamic interaction study is of great significance to enhance seismic ...Isolation technique of ground structure is a hot topic in the field of earthquake engineering and structure dynamics.Since soil-isolated structure dynamic interaction study is of great significance to enhance seismic performance of isolated structures and revision of relevant isolation specifications,research on dynamic interaction of soil-isolated structure has attracted more and more attention.Based on the basic theory of soil-structure dynamic interaction,we summarize and analyze the research status quo of soil-isolated structure dynamic interaction by means of theoretical analysis,numerical simulation,model test,prototype observation and seismic performance.After reviewing the results of previous research,we reveal that some key issues,which can be used to uncover dynamic interaction mechanism and seismic response characteristics of soil-isolated structures interaction system,should not be neglected.Based on the concept of seismic performance design and the latest research of soil-isolated structure dynamic interaction,we predict the future development of soil-isolated structure dynamic interaction by elastoplastic time history analysis method,seismic performance level and practical analysis method based on energy.展开更多
Clinically, pulmonary embolism （PE） mostly comes from the lower extremity deep vein system, but if such pa- tients have no evidence of deep venous thrombosis （DVT）, other sources of emboli should be considered. It...Clinically, pulmonary embolism （PE） mostly comes from the lower extremity deep vein system, but if such pa- tients have no evidence of deep venous thrombosis （DVT）, other sources of emboli should be considered. It is very rare that embolus comes from the right heart system （in situ thrombosis）, Isolated fight ventricular noncompaction （iRVNC） can cause PE, but it has not been reported so far. Ventricular noncompaction （VNC） is an unusual cause of cardiomyopathy.展开更多
We theoretically study the selection of the quantum path in high-order harmonics（HHG） and isolated attosecond pulse generation from a one-dimensional（1D） model of a H_2~＋ molecule in few-cycle inhomogeneous laser...We theoretically study the selection of the quantum path in high-order harmonics（HHG） and isolated attosecond pulse generation from a one-dimensional（1D） model of a H_2~＋ molecule in few-cycle inhomogeneous laser fields.We show that the inhomogeneity of the laser fields play an important role in the HHG process.The cutoff of the harmonics can be extended remarkably,and the harmonic spectrum becomes smooth and has fewer modulations.We investigate the time-frequency profile of the time-dependent dipole,which shows that the short quantum path is enhanced and the long quantum path disappears in spatially inhomogeneous fields.The semi-classical three-step model is also applied to illustrate the physical mechanism of HHG.The influence of driving field carrier-envelop phase（CEP） on HHG is also discussed.By superposing a series of properly selected harmonics,an isolated attosecond pulse（IAP） with duration 53 as can be obtained by a 15-fs,1600-nm laser pulse with the parameter ε = 0.0013（e is the parameter that determines the order of inhomogeneity of the laser field）.展开更多
We theoretically investigate high-order harmonic generation（HHG） from a helium ion model in a two-color laser field,which is synthesized by a fundamental pulse and its second harmonic pulse.It is shown that a superc...We theoretically investigate high-order harmonic generation（HHG） from a helium ion model in a two-color laser field,which is synthesized by a fundamental pulse and its second harmonic pulse.It is shown that a supercontinuum spectrum can be generated in the two-color field.However,the spectral intensity is very low,limiting the application of the generated attosecond（as） pulse.By adding a static electric field to the synthesized two-color field,not only is the ionization yield of electrons contributing to the harmonic emission remarkably increased,but also the quantum paths of the HHG can be significantly modulated.As a result,the extension and enhancement of the supercontinuum spectrum are achieved,producing an intense isolated 26-as pulse with a bandwidth of about 170.5 eV.In particular,we also analyse the influence of the laser parameters on the ultrabroad supercontinuum spectrum and isolated sub-30-as pulse generation.展开更多
For very sparse tree land individual tree was the basic element of interaction between atmosphere and the surface. Drag of isolated tree was preliminary aerodynamic index for analyzing the atmospheric boundary layer o...For very sparse tree land individual tree was the basic element of interaction between atmosphere and the surface. Drag of isolated tree was preliminary aerodynamic index for analyzing the atmospheric boundary layer of this kind of surface. A simple pendulum method was designed and carried out in wind tunnel to measure drag of isolated tree models according to balance law of moment of force. The method was easy to conduct and with small error The results showed that the drag and drag coefficient of isolated tree increased with decreasing of its permeability or porosity. Relationship between drag coefficient and permeability of isolated tree empirically was expressed by quadric curve.展开更多
As a crucial parameter for a few-cycle laser pulse, the carrier envelope phase(CEP) substantially determines the laser waveform. We propose a method to directly describe the CEP of an isolated attosecond pulse(IAP) by...As a crucial parameter for a few-cycle laser pulse, the carrier envelope phase(CEP) substantially determines the laser waveform. We propose a method to directly describe the CEP of an isolated attosecond pulse(IAP) by the vortex-shaped momentum pattern, which is generated from the tunneling ionization of a hydrogen atom by a pair of time-delayed, oppositely and circularly polarized IAP-IR pulses. Superior to the angular streaking method that characterizes the CEP in terms of only one streak, our method describes the CEP of an IAP by the features of multiple streaks in the vortex pattern. The proposed method may open the possibility of capturing sub-cycle extreme ultraviolet dynamics.展开更多
The streak camera is an ultra-fast diagnostic instrument with high sensitivity, and a high temporal and spatial resolution. It is primarily employed in various scientific research, such as inertial confinement fusion(...The streak camera is an ultra-fast diagnostic instrument with high sensitivity, and a high temporal and spatial resolution. It is primarily employed in various scientific research, such as inertial confinement fusion(ICF),synchrotron light sources, and electron–positron colliders.An automatic control system for an X-ray streak camera is presented in this paper. The output terminal of an analogto-digital converter was isolated from its input terminal, to reduce interference from high-voltage electrodes. Compared with traditional methods, this scheme also improved the internal electromagnetic interface immunity. Therefore,the system stability was enhanced. With this optimized control system, some characterizations of the streak camera were measured. Static and dynamic spatial resolutions of 25 and 20 lp/mm(CTF = 20%), respectively, were obtained. In addition, a dynamic range of 552:1 and a temporal resolution of 7.3 ps were achieved. The results confirmed that these characterizations are sufficient for the specifications derived from the diagnostic requirements of ICF.展开更多
We briefly introduce the quantum Jarzynski and Bochkov-Kuzovlev equalities .in isolated quantum Hamiltonian sys- tems, including their origin, their derivations using a quantum Feynman-Kac formula, the quantum Crooks ...We briefly introduce the quantum Jarzynski and Bochkov-Kuzovlev equalities .in isolated quantum Hamiltonian sys- tems, including their origin, their derivations using a quantum Feynman-Kac formula, the quantum Crooks equality, the evolution equations governing the characteristic functions of the probability density functions for the quantum work, and recent experimental verifications. Some resultsare given here for the first time. We particularly emphasize the formally structural consistence between these quantum equalities and their classical counterparts, which are useful for understanding the existing equalities and pursuing new fluctuation relations in other complex quantum systems.展开更多
Based on regional geology,2D seismic and ocean drilling data,the formation of the Eratosthenes Seamount(ESM)and its surrounding isolated platforms,types of organic reefs and hydrocarbon accumulation conditions in the ...Based on regional geology,2D seismic and ocean drilling data,the formation of the Eratosthenes Seamount(ESM)and its surrounding isolated platforms,types of organic reefs and hydrocarbon accumulation conditions in the eastern Mediterranean were analyzed through fine tectonic interpretation and seismic facies study,and the future exploration targets were pointed out.The formation and evolution of the ESM and its peripheral isolated platforms are highly related to the open and close of the Neotethyan ocean.The precursors of the ESM and its peripheral isolated platforms are both horst-type fault blocks formed in the Middle Triassic-Early Jurassic intracontinental rift stage.The ESM and its peripheral isolated platforms underwent continued and inherited carbonate build-ups during the Middle Jurassic intercontinental rift stage,the Late Jurassic-Late Cretaceous Turonian passive drift stage,and Late Cretaceous Senonian-Miocene subduction stage,as well as medium-slight inversion transformation beginning in the Late Miocene Messinian caused by the closure of the Neotethyan ocean.Three types of isolated platforms formed controlled by variant paleo-tectonic settings:the first type is composed of a single patch-like reef controlled by a small-scale and narrow horst-type fault block,the second type consists of a single atoll controlled by a middle-scale and wide horst-type fault block,and the third type is comprised of multiple reef-beach complexes controlled by a large-scale and broad paleo-high.The first two types universally developed in the highs of the alternate sag-uplift structural zones on the south and west of Eratosthenes,and the third type only developed in the ESM.As a result of fluctuation of sea level,two sequences of reef build-ups,i.e.the Middle Jurassic Bajocian-Upper Cretaceous Turonian and the Miocene,developed in the ESM as well as the highs in the alternate sag-uplift structural zones on the south and west of Eratosthenes.Drillings have confirmed that the first two types of isolated platforms with a single patch-like reef and a single circle-like reef have good conditions for natural gas accumulations.The isolated platform of reef-beach complexes in the ESM also has accumulation potentials of natural gas and is worth prospecting.展开更多
This paper presents a method of tuning governor control parameters of an isolated hydropower generator considering the primary frequency performance and small-signal stability. First, generators that can be operated i...This paper presents a method of tuning governor control parameters of an isolated hydropower generator considering the primary frequency performance and small-signal stability. First, generators that can be operated in isolated state are identified. Second, different schemes are proposed for generator mode switching from on-grid to off-grid state through comparison and mechanism analysis. Third, the time domain model and frequency domain model of the isolated generator governor are constructed to respectively estimate the primary frequency performance and small signal stability. Parameter sets that satisfy the primary frequency performance and small signal stability are acquired as optimal values of governor control parameters. Finally, the measurement-based parameters of the governor are identified and validated using simulations to demonstrate the feasibility and effectiveness of the method.展开更多
Most of the schemes for generating isolated attosecond pulses（IAP） are sensitive to the carrier-envelope phase（CEP）of the driving lasers. We propose a scheme for generating IAP using two-color counter-rotating cir...Most of the schemes for generating isolated attosecond pulses（IAP） are sensitive to the carrier-envelope phase（CEP）of the driving lasers. We propose a scheme for generating IAP using two-color counter-rotating circularly polarized（TCCRCP） laser pulses. The results demonstrate that the dependence of the IAP generation on CEP stability is largely reduced in this scheme. IAP can be generated at most of CEPs. Therefore, the experiment requirements become lower.展开更多
基金Supported by the National Science and Technology Major Project(2016ZX05029001)CNPC Science and Technology Project(2019D-4310)。
文摘In response to the problems of unclear distribution of deep-water pre-salt carbonate reservoirs and formation conditions of large oil fields in the Santos passive continental margin basin,based on comprehensive utilization of geological,seismic,and core data,and reconstruction of Early Cretaceous prototype basin and lithofacies paleogeography,it is proposed for the first time that the construction of pre-salt carbonate build-ups was controlled by two types of isolated platforms:inter-depression fault-uplift and intra-depression fault-high.The inter-depression fault-uplift isolated platforms are distributed on the present-day pre-salt uplifted zones between depressions,and are built on half-and fault-horst blocks that were inherited and developed in the early intra-continental and inter-continental rift stages.The late intra-continental rift coquinas of the ITP Formation and the early inter-continental rift microbial limestones of the BVE Formation are continuously constructed;intra-depression fault-high isolated platforms are distributed in the current pre-salt depression zones,built on the uplifted zones formed by volcanic rock build-ups in the early prototype stage of intra-continental rifts,and only the BVE microbial limestones are developed.Both types of limestones formed into mound-shoal bodies,that have the characteristics of large reservoir thickness and good physical properties.Based on the dissection of large pre-salt oil fields discovered in the Santos Basin,it has been found that both types of platforms could form large-scale combined structural-stratigraphic traps,surrounded by high-quality lacustrine and lagoon source rocks at the periphery,and efficiently sealed by thick high-quality evaporite rocks above,forming the optimal combination of source,reservoir and cap in the form of“lower generation,middle storage,and upper cap”,with a high degree of oil and gas enrichment.It has been found that the large oil fields are all bottom water massive oil fields with a unified pressure system,and they are all filled to the spill-point.The future exploration is recommended to focus on the inter-depression fault-uplift isolated platforms in the western uplift zone and the southern section of eastern uplift zones,as well as intra-depression fault-high isolated platforms in the central depression zone.The result not only provides an important basis for the advanced selection of potential play fairways,bidding of new blocks,and deployment of awarded exploration blocks in the Santos Basin,but also provides a reference for the global selection of deep-water exploration blocks in passive continental margin basins.
基金financial support provided by the National Natural Science Foundation of China(51604258)is greatly appreciated
文摘Surface subsidence is a typical ground movement due to longwall mining, which causes a series of environmental problems and hazards. In China, intensive coal extractions are commonly operated under dense-populated coalfields, which exacerbates the negative subsequences resulted from surface settlement. Therefore, effective approaches to control the ground subsidence are in urgent need for the Chinese coal mining industry. This paper presents a newly developed subsidence control technology: isolated overburden grout injection, including the theory, technique and applications. Relevant procedures such as injection system design, grouting material selection, borehole layout, grout take estimation and injection process design are proposed. The applicability of this technology has been demonstrated through physical modelling, field measurements, and case studies. Since 2009, the technology has been successfully applied to 14 longwall areas in 9 Chinese coal mines. The ultimate surface subsidence factors vary from 0.10 to 0.15. This method has a great potential to be popularized and performed where longwall mining are implemented under villages and ground infrastructures.
基金This work is supported by NSFC(21773242,21935010)the Strategic Priority Research Program of the Chinese Academy of Sciences(XDB20000000)+1 种基金National Key Research and Development Program of China(2018YFA0208600)King Abdullah University of Science and Technology.J.Dong acknowledges financial support from Youth Innovation Promotion Association of Chinese Academy of Sciences(2018017).
文摘Reducing the dimensions of metallic nanoparticles to isolated,single atom has attracted considerable attention in heterogeneous catalysis,because it significantly improves atomic utilization and often leads to distinct catalytic performance.Through extensive research,it has been recognized that the local coordination environment of single atoms has an important influence on their electronic structures and catalytic behaviors.In this review,we summarize a series of representative systems of single-atom catalysts,discussing their preparation,characterization,and structure-property relationship,with an emphasis on the correlation between the coordination spheres of isolated reactive centers and their intrinsic catalytic activities.We also share our perspectives on the current challenges and future research promises in the development of single-atom catalysis.With this article,we aim to highlight the possibility of finely tuning the catalytic performances by engineering the coordination spheres of single-atom sites and provide new insights into the further development for this emerging research field.
基金funded by the National Natural Science Foundation of China(Nos.51774326,42177164,41807259,and41702350)Hunan Young Talent(No.2021RC3007)+2 种基金the open fund of Mining Disaster Prevention and Control Ministry Key Laboratory at Shandong University of Science and Technology(No.MDPC201917)the Fundamental Research Funds for the Central Universities of Central South University(No.2019zzts668)the Innovation-Driven Project of Central South University(No.2020CX040)。
文摘Isolated pillars in underground mines are subjected to uniaxial stress,and the load bearing cross-section of pillars is commonly rectangularly shaped.In addition,the uniaxial compression test(UCT)is widely used for determining the basic mechanical properties of rocks and revealing the mechanism of isolated pillar disasters under unidimensional stress.The shape effects of rock mechanical properties under uniaxial compression are mainly quantitatively reflected in the specific shape ratios of rocks.Therefore,it is necessary to study the detailed shape ratio effects on the mechanical properties of rectangular prism rock specimens and isolated pillars under uniaxial compressive stress.In this study,granite,marble and sandstone rectangular prism specimens with various height to width ratios(r)and width to thickness ratios(u)were prepared and tested.The study results show that r and u have a great influence on the bearing ability of rocks,and thin or high rocks have lower uniaxial compressive strength.Reducing the level of r can enhance the u effect on the strength of rocks,and increasing the level of u can enhance the r effect on the strength of rocks.The lateral strain on the thickness side of the rock specimen is larger than that on the width side,which implies that crack growth occurs easily on the thickness side.Considering r and u,a novel strength prediction model of isolated pillars was proposed based on the testing results,and the prediction model was used for the safety assessment of 179 isolated pillars in the Xianglu Mountain Tungsten Mine.
基金supported by the State Grid Liaoning Electric Power Supply CO, LTDthe financial support for the “Key Technology and Application Research of the Self-Service Grid Big Data Governance (No.SGLNXT00YJJS1800110)”
文摘With the development of data age,data quality has become one of the problems that people pay much attention to.As a field of data mining,outlier detection is related to the quality of data.The isolated forest algorithm is one of the more prominent numerical data outlier detection algorithms in recent years.In the process of constructing the isolation tree by the isolated forest algorithm,as the isolation tree is continuously generated,the difference of isolation trees will gradually decrease or even no difference,which will result in the waste of memory and reduced efficiency of outlier detection.And in the constructed isolation trees,some isolation trees cannot detect outlier.In this paper,an improved iForest-based method GA-iForest is proposed.This method optimizes the isolated forest by selecting some better isolation trees according to the detection accuracy and the difference of isolation trees,thereby reducing some duplicate,similar and poor detection isolation trees and improving the accuracy and stability of outlier detection.In the experiment,Ubuntu system and Spark platform are used to build the experiment environment.The outlier datasets provided by ODDS are used as test.According to indicators such as the accuracy,recall rate,ROC curves,AUC and execution time,the performance of the proposed method is evaluated.Experimental results show that the proposed method can not only improve the accuracy and stability of outlier detection,but also reduce the number of isolation trees by 20%-40%compared with the original iForest method.
基金supported by the National Natural Science Foundation of China (Grant No.10974068)
文摘This paper theoretically investigates the high-order harmonic generation cutoff extension using intense few-cycle linearly chirped laser pulses. It shows that the cutoff of the harmonic can be extended remarkably by optimising the chirping parameters. The time-frequency characteristics of high-order harmonics with different chirping parameters are analysed by means of wavelet transform of the dipole acceleration. It also gives out the classical three-step model pictures of electron. By superposing a properly selected range of the harmonic spectrum, it obtains an isolated 65as pulse.
基金supported by the Jiangsu Natural Science Foundation of China(Grant No.BK2012477)the Science Research Foundation of Nanjing Institute of Technology(CKJA201505,JCYJ201618)
文摘Adopting a soft site model built on soft interlayer soil foundation,a shaking table test for soft interlayer soil-isolated structure interaction is conducted to investigate the seismic response of isolated structure on soft site,and analyze its isolation effect.Test results show that the test can reflect the earthquake response characteristics of isolated structure on soft site.It is on soft site that the dynamic characteristics of isolated structure,acceleration magnification factor(AMF)of isolated structure and isolation efficiency of the isolation layer differ from those on rigid foundation with an soil-structure interaction(SSI)effect,represented by the reduction in fundamental vibration frequency of isolated structure and the increase of damping ratio with changes of the SSI effect.SSI can either increase or decrease AMF of isolated structure on soft site,depending on the characteristics of earthquake motion input.Furthermore,the isolation efficiency of isolation layer on soft site is decreased with the SSI effect,which is related to the peak ground acceleration(PGA)and the characteristics of earthquake motion input.
文摘Objectives To reveal etiologies of persistent isolated hematuria （PIH） through ultrastructural pathological examination, to disclose clinicopathological correlation in cases with PIH, and to summarize appropriate management of patients with PIH. Methods we retrospectively studied 155 P1H patients receiving renal biopsy between January, 2003 and December, 2008 in Peking Union Medical College Hospital. All the clinical data and follow-up result were analyzed. Results All subjects included 38 children and 117 adults, with mean age of 11.38±3.25 years for children and 35.17±8.44 years for adults. Thin basement membrane nephropathy （TBMN） was the most common pathology （55.3% of children and 49.6% of adults）, followed by IgA nephropathy （18.4% of children and 32.5% of adults, mainly grade 2-3） and mesangial proliferative glomerulonephritis （MsPGN） without IgA deposition （13.2% of children and 12.8% of adults）. Besides, A1port syndrome （2.6% of children） and membrane nephropathy （2.6% of children and 0.9% of adults） were demonstrated as other causes of PIH. Elevated mean arteral pressure or protein excretion rate, as well as episodic macrohematuria, indicated higher risk for MsPGN rather than TBMN. On the other hand, severity of microhematuria was irrelevant to pathological types of PIH. Totally, 86 patients were followed up and 37 cases therein stayed on track for long term （mean duration 41.11±28.92 months, range 8-113 months）. Most cases had benign clinical course except 3 cases with TBMN, 5 cases with IgA nephropathy, 1 case with MsPGN （without IgA deposition）, and 1 case with Alport syndrome, who developed hypertension or proteinuria. All of them were administered timely intervention. Conclusions Close follow-up should be required as the primary management for PIH. Equally important is careful monitoring for early identification of undesirable predictors; while renal biopsy and other timely intervention are warranted if there is hypertension, significant proteinuria or renal impairment.
文摘Objective To investigate plasma N-terminal pro-brain natriuretic peptide (NT-BNP) levels and to assess their clinical significance in elderly patients with isolated diastolic dysfunction. Methods Plasma NT-BNP level were measured by electrochemiluminescence immunoassay in 34 symptomatic patients (Group 1), 34 asymptomatic patients (Group 2) with isolated diastolic dysfunction, and in 16 elderly healthy subjects (control group, Group 3), serving controls. Colored Doppler echocardiography was performed to evaluate the patients' cardiac structures and functions. Results The plasma NT-BNP level in Group 1 was significantly higher than those in Group 2 and Group 3 and increased with the severity of heart failure. There was no significant difference of plasma NT-BNP levels between Group 2 and Group 3 (p>0.05). A NT-BNP value of 102.75 pg/mL showed a sensitivity of 88.2%, a specificity of 87.5%, and an accuracy of 88.1% for diagnosing diastolic dysfunction. Patients with restrictive filling pattern on echocardiography had higher NT-BNP levels than those of impaired relaxation pattern (1961.2±304.9 versus 460.1±92.7pg/mL, p<0.001). Conclusion The elevation of plasma NT-BNP level in elderly patients with isolated diastolic dysfunction correlates with the severity of their diastolic abnormalities. The level of plasma NT-BNP has an important clinical value in the diagnosis of elderly patients with isolated diastolic dysfunction.
基金This work was supported by the National Natural Science Foundation of China(No.51778282).
文摘Isolation technique of ground structure is a hot topic in the field of earthquake engineering and structure dynamics.Since soil-isolated structure dynamic interaction study is of great significance to enhance seismic performance of isolated structures and revision of relevant isolation specifications,research on dynamic interaction of soil-isolated structure has attracted more and more attention.Based on the basic theory of soil-structure dynamic interaction,we summarize and analyze the research status quo of soil-isolated structure dynamic interaction by means of theoretical analysis,numerical simulation,model test,prototype observation and seismic performance.After reviewing the results of previous research,we reveal that some key issues,which can be used to uncover dynamic interaction mechanism and seismic response characteristics of soil-isolated structures interaction system,should not be neglected.Based on the concept of seismic performance design and the latest research of soil-isolated structure dynamic interaction,we predict the future development of soil-isolated structure dynamic interaction by elastoplastic time history analysis method,seismic performance level and practical analysis method based on energy.
文摘Clinically, pulmonary embolism （PE） mostly comes from the lower extremity deep vein system, but if such pa- tients have no evidence of deep venous thrombosis （DVT）, other sources of emboli should be considered. It is very rare that embolus comes from the right heart system （in situ thrombosis）, Isolated fight ventricular noncompaction （iRVNC） can cause PE, but it has not been reported so far. Ventricular noncompaction （VNC） is an unusual cause of cardiomyopathy.
基金supported by the National Natural Science Foundation of China(Grant Nos.11174108,11104108,and 11271158)
文摘We theoretically study the selection of the quantum path in high-order harmonics（HHG） and isolated attosecond pulse generation from a one-dimensional（1D） model of a H_2~＋ molecule in few-cycle inhomogeneous laser fields.We show that the inhomogeneity of the laser fields play an important role in the HHG process.The cutoff of the harmonics can be extended remarkably,and the harmonic spectrum becomes smooth and has fewer modulations.We investigate the time-frequency profile of the time-dependent dipole,which shows that the short quantum path is enhanced and the long quantum path disappears in spatially inhomogeneous fields.The semi-classical three-step model is also applied to illustrate the physical mechanism of HHG.The influence of driving field carrier-envelop phase（CEP） on HHG is also discussed.By superposing a series of properly selected harmonics,an isolated attosecond pulse（IAP） with duration 53 as can be obtained by a 15-fs,1600-nm laser pulse with the parameter ε = 0.0013（e is the parameter that determines the order of inhomogeneity of the laser field）.
基金Project supported by the Science Foundation of Baoji University of Arts and Sciences,China (Grant Nos. ZK10122,ZK11061,ZK11135,ZK11060,and ZK1032)the Education Committee Natural Science Foundation of Shaanxi Province,China (GrantNo. 2010JK405)
文摘We theoretically investigate high-order harmonic generation（HHG） from a helium ion model in a two-color laser field,which is synthesized by a fundamental pulse and its second harmonic pulse.It is shown that a supercontinuum spectrum can be generated in the two-color field.However,the spectral intensity is very low,limiting the application of the generated attosecond（as） pulse.By adding a static electric field to the synthesized two-color field,not only is the ionization yield of electrons contributing to the harmonic emission remarkably increased,but also the quantum paths of the HHG can be significantly modulated.As a result,the extension and enhancement of the supercontinuum spectrum are achieved,producing an intense isolated 26-as pulse with a bandwidth of about 170.5 eV.In particular,we also analyse the influence of the laser parameters on the ultrabroad supercontinuum spectrum and isolated sub-30-as pulse generation.
文摘For very sparse tree land individual tree was the basic element of interaction between atmosphere and the surface. Drag of isolated tree was preliminary aerodynamic index for analyzing the atmospheric boundary layer of this kind of surface. A simple pendulum method was designed and carried out in wind tunnel to measure drag of isolated tree models according to balance law of moment of force. The method was easy to conduct and with small error The results showed that the drag and drag coefficient of isolated tree increased with decreasing of its permeability or porosity. Relationship between drag coefficient and permeability of isolated tree empirically was expressed by quadric curve.
基金Supported by the National Natural Science Foundation of China under Grant Nos 11674243 and 11674242
文摘As a crucial parameter for a few-cycle laser pulse, the carrier envelope phase(CEP) substantially determines the laser waveform. We propose a method to directly describe the CEP of an isolated attosecond pulse(IAP) by the vortex-shaped momentum pattern, which is generated from the tunneling ionization of a hydrogen atom by a pair of time-delayed, oppositely and circularly polarized IAP-IR pulses. Superior to the angular streaking method that characterizes the CEP in terms of only one streak, our method describes the CEP of an IAP by the features of multiple streaks in the vortex pattern. The proposed method may open the possibility of capturing sub-cycle extreme ultraviolet dynamics.
文摘The streak camera is an ultra-fast diagnostic instrument with high sensitivity, and a high temporal and spatial resolution. It is primarily employed in various scientific research, such as inertial confinement fusion(ICF),synchrotron light sources, and electron–positron colliders.An automatic control system for an X-ray streak camera is presented in this paper. The output terminal of an analogto-digital converter was isolated from its input terminal, to reduce interference from high-voltage electrodes. Compared with traditional methods, this scheme also improved the internal electromagnetic interface immunity. Therefore,the system stability was enhanced. With this optimized control system, some characterizations of the streak camera were measured. Static and dynamic spatial resolutions of 25 and 20 lp/mm(CTF = 20%), respectively, were obtained. In addition, a dynamic range of 552:1 and a temporal resolution of 7.3 ps were achieved. The results confirmed that these characterizations are sufficient for the specifications derived from the diagnostic requirements of ICF.
基金supported by the National Natural Science Foundation of China (Grant No. 11174025)
文摘We briefly introduce the quantum Jarzynski and Bochkov-Kuzovlev equalities .in isolated quantum Hamiltonian sys- tems, including their origin, their derivations using a quantum Feynman-Kac formula, the quantum Crooks equality, the evolution equations governing the characteristic functions of the probability density functions for the quantum work, and recent experimental verifications. Some resultsare given here for the first time. We particularly emphasize the formally structural consistence between these quantum equalities and their classical counterparts, which are useful for understanding the existing equalities and pursuing new fluctuation relations in other complex quantum systems.
基金Supported by the China National Science and Technology Major Project(2016ZX05029001)the CNPC Science and Technology Project(2019D-4310)。
文摘Based on regional geology,2D seismic and ocean drilling data,the formation of the Eratosthenes Seamount(ESM)and its surrounding isolated platforms,types of organic reefs and hydrocarbon accumulation conditions in the eastern Mediterranean were analyzed through fine tectonic interpretation and seismic facies study,and the future exploration targets were pointed out.The formation and evolution of the ESM and its peripheral isolated platforms are highly related to the open and close of the Neotethyan ocean.The precursors of the ESM and its peripheral isolated platforms are both horst-type fault blocks formed in the Middle Triassic-Early Jurassic intracontinental rift stage.The ESM and its peripheral isolated platforms underwent continued and inherited carbonate build-ups during the Middle Jurassic intercontinental rift stage,the Late Jurassic-Late Cretaceous Turonian passive drift stage,and Late Cretaceous Senonian-Miocene subduction stage,as well as medium-slight inversion transformation beginning in the Late Miocene Messinian caused by the closure of the Neotethyan ocean.Three types of isolated platforms formed controlled by variant paleo-tectonic settings:the first type is composed of a single patch-like reef controlled by a small-scale and narrow horst-type fault block,the second type consists of a single atoll controlled by a middle-scale and wide horst-type fault block,and the third type is comprised of multiple reef-beach complexes controlled by a large-scale and broad paleo-high.The first two types universally developed in the highs of the alternate sag-uplift structural zones on the south and west of Eratosthenes,and the third type only developed in the ESM.As a result of fluctuation of sea level,two sequences of reef build-ups,i.e.the Middle Jurassic Bajocian-Upper Cretaceous Turonian and the Miocene,developed in the ESM as well as the highs in the alternate sag-uplift structural zones on the south and west of Eratosthenes.Drillings have confirmed that the first two types of isolated platforms with a single patch-like reef and a single circle-like reef have good conditions for natural gas accumulations.The isolated platform of reef-beach complexes in the ESM also has accumulation potentials of natural gas and is worth prospecting.
基金supported by the Fujian Provincial Government Project (Title: Research on whole process evaluation of dynamic stability and control strategy in condition of grid connection of ultra-high voltage and large scale penetration of nuclear power.No.2015H0023)the State Grid Science & Technology Project (Title: Research on the improvement on stability of primary frequency of generator in account of the tolerance of equipment.No.52130417002P)the Key project of State Grid Fujian Electric Power Company,Ltd (research on key technologies of primary frequency power oscillation mechanism analysis and inhibition measures in large-scale unit in Fujian power grid.No.52130417000J)
文摘This paper presents a method of tuning governor control parameters of an isolated hydropower generator considering the primary frequency performance and small-signal stability. First, generators that can be operated in isolated state are identified. Second, different schemes are proposed for generator mode switching from on-grid to off-grid state through comparison and mechanism analysis. Third, the time domain model and frequency domain model of the isolated generator governor are constructed to respectively estimate the primary frequency performance and small signal stability. Parameter sets that satisfy the primary frequency performance and small signal stability are acquired as optimal values of governor control parameters. Finally, the measurement-based parameters of the governor are identified and validated using simulations to demonstrate the feasibility and effectiveness of the method.
基金Project supported by the National Natural Science Foundation of China(Grants Nos.61690223,11561121002,61521093,11227902,11404356,and 11574332)the Strategic Priority Research Program of the Chinese Academy of Sciences(Grant No.XDB16)
文摘Most of the schemes for generating isolated attosecond pulses（IAP） are sensitive to the carrier-envelope phase（CEP）of the driving lasers. We propose a scheme for generating IAP using two-color counter-rotating circularly polarized（TCCRCP） laser pulses. The results demonstrate that the dependence of the IAP generation on CEP stability is largely reduced in this scheme. IAP can be generated at most of CEPs. Therefore, the experiment requirements become lower.
