The soil-bentonite(SB)cut-off wall has been widely considered a vertical barrier to effectively control the migration of pollutants in contaminated sites.Recently,active porous materials have been used as a promising ...The soil-bentonite(SB)cut-off wall has been widely considered a vertical barrier to effectively control the migration of pollutants in contaminated sites.Recently,active porous materials have been used as a promising candidate amendment for mitigating chemical degradation and improving the retardation capacity of the SB cut-off wall.In this study,the silty clay from a typical Cr(VI)contaminated site was selected as the body material of the SB cut-off wall,and zeolite and active carbon were used as the modifiers of the silty clay-bentonite backfills,respectively.The impact of the two modifiers on the engineering properties of the backfills was investigated through a series of slump tests,consolidation tests,hydraulic conductivity tests,and microstructure tests.The experimental results demonstrated that the slump curves closely exhibited a linear relationship between standard slump and moisture content.Meanwhile,bentonite could improve the optimum moisture content of the backfills,while the addition of the two modifiers yielded the opposite outcome.As the bentonite content increased,the compression index of the backfills significantly increased,while the hydraulic conductivity decreased.At a given bentonite content of 5%,the addition of zeolite or active carbon resulted in a reduction in the compression index and initial void ratio,while exhibiting minimal impact on the hydraulic conductivity.Scanning electron microscope(SEM)observations indicated that the silty clay-bentonite backfills became increasingly loose with increasing bentonite content,owing to the filling and expansion of dispersed bentonite layers.The amendment of zeolite or active carbon was able to decrease the backfill volume by promoting the agglomeration of layered bentonite.The findings of this study will be useful for the optimal selection of backfill materials and the performance evaluation of the cut-off wall.展开更多
Uneven lithium deposition leading to lithium dendrite growth severely hampers the application of lithium-metal batteries.Modifying the collector with lithiophilic materials helps improve lithium deposition.For lithoph...Uneven lithium deposition leading to lithium dendrite growth severely hampers the application of lithium-metal batteries.Modifying the collector with lithiophilic materials helps improve lithium deposition.For lithophilic materials to modify the collector,the choice of cut-off voltage is very important.While excessively high cut-off voltages may compromise the stability of the modified layer and consequently disrupt ordered lithium deposition,conventional approaches typically employ lower cut-off voltages(particularly 0.1 V)to maintain modification layer stability.However,the 0.1 V cut-off voltage results in incomplete lithium stripping from the lithiophilic material surface.This phenomenon significantly diminishes the lithiophilic properties of the modified layer and consequently leads to substantial nucleation overpotential.Here,we propose to use a moderate cut-voltage stimulation effect to slow down the interfacial shielding effect of residual lithium metal on lithiophilic materials.By optimizing the cut-off voltage for the Cu@Sb_(2)S_(3)collector,the stability of the modified layer can be preserved while enabling the complete stripping of lithium metal from the surface of the lithophilic material.The asymmetric cell received the highest Coulombic efficiency(CE)when the lithium stripping cut-off voltage was set at 0.5 V relative to 0.1 and 2.0 V.At a current density of 1 mA cm^(-2)and a deposition capacity of1 m A h cm^(-2),the CE remained 98.6% at a cut-off voltage of 0.5 V after 140 cycles in an ether electrolyte without lithium nitrate.展开更多
Because of actual requirement,shield machine always excavates with an inclined angle in longitudinal direction.Since many previous studies mainly focus on the face stability of the horizontal shield tunnel,the effects...Because of actual requirement,shield machine always excavates with an inclined angle in longitudinal direction.Since many previous studies mainly focus on the face stability of the horizontal shield tunnel,the effects of tensile strength cut-off and pore water pressure on the face stability of the longitudinally inclined shield tunnel are not well investigated.A failure mechanism of a longitudinally inclined shield tunnel face is constructed based on the spatial discretization technique and the tensile strength cut-off criterion is introduced to modify the constructed failure mechanism.The pore water pressure is introduced as an external force into the equation of virtual work and the objective function of the chamber pressure of the shield machine is obtained.Moreover,the critical chamber pressure of the longitudinally inclined shield tunnel is computed by optimal calculation.Parametric analysis indicates that both tensile strength cut-off and pore water pressure have a significant impact on the chamber pressure and the range of the collapse block.Finally,the theoretical results are compared with the numerical results calculated by FLAC3D software which proves that the proposed approach is effective.展开更多
The lack of soft magnetic composites with high power density in MHz frequency range has become an obstacle in the efficient operation of the electrical and electronic equipments.Here,a promising method to increase the...The lack of soft magnetic composites with high power density in MHz frequency range has become an obstacle in the efficient operation of the electrical and electronic equipments.Here,a promising method to increase the cut-off frequency of iron-based soft magnetic composites to hundreds of MHz is reported.The cut-off frequency is increased from 10 MHz to 1 GHz by modulating the height of the ring,the distribution of particles,and the particle size.The mechanism of cut-off frequency and permeability is the coherent rotation of domain modulated by inhomogeneous field due to the eddy current effect.An empirical formula for the cut-off frequency in a magnetic ring composed of iron-based particles is established from experimental data.This work provides an effective approach to fabricate soft magnetic composites with a cut-off frequency in hundreds of MHz.展开更多
BACKGROUND Glycated hemoglobin A1c(HbA1c)is considered the most suitable for diabetes mellitus diagnosis due to its accuracy and convenience.However,the effect of HbA1c on diabetic retinopathy(DR)in the Han and Korean...BACKGROUND Glycated hemoglobin A1c(HbA1c)is considered the most suitable for diabetes mellitus diagnosis due to its accuracy and convenience.However,the effect of HbA1c on diabetic retinopathy(DR)in the Han and Korean populations in Jilin,China,remains inconclusive.AIM To determine the best cut-off of HbA1c for diagnosing DR among the Chinese.METHODS This cross-sectional study included 1933 participants from the Yanbian area of Jilin Province,China.Trained investigators employed a questionnaire-based survey,physical examination,laboratory tests,and fundus photography for the investigation.The best cut-off value for HbA1c was established via the receiver operating characteristic curve.The factors associated with HbA1c-associated risk factors were determined via linear regression.RESULTS The analysis included 887 eligible Chinese Han and Korean participants,591 of whom were assigned randomly to the training set and 296 to the validation set.The prevalence of DR was 3.27% in the total population.HbA1c of 6.2% was the best cut-off value in the training set,while it was 5.9% in the validation set.In both Chinese Han and Korean populations,an HbA1c level of 6.2% was the best cut-off value.The optimal cut-off values of fasting blood glucose(FBG)≥7 mmol/L and<7 mmol/L were 8.1% and 6.2% respectively in Han populations,while those in Korean populations were 6.9%and 5.3%,respectively.Age,body mass index,and FBG were determined as the risk factors impacting HbA1c levels.CONCLUSION HbA1c may serve as a useful diagnostic indicator for DR.An HbA1c level of 6.2% may be an appropriate cut-off value for DR detection in the Chinese population.展开更多
The cut-off wall in a clay-core rockfill dam built on a thick overburden layer is subjected to a large compressive pressure under the action of the loads such as the dead weight of both the dam and the overburden laye...The cut-off wall in a clay-core rockfill dam built on a thick overburden layer is subjected to a large compressive pressure under the action of the loads such as the dead weight of both the dam and the overburden layer, the frictional force induced by the differential settlement between the cut-off wall and surrounding soils, and the water pressure. Thus, reduction of the stress of the cut-off wall has become one of the main problems for consideration in engineering design. In this paper, numerical analysis of a core rockfill dam built on a thick overburden layer was conducted and some factors influencing the stress-strain behaviors of the cut-off wall were investigated. The factors include the improvement of the overburden layer, the modeling approach for interfacial contact between the cut-off wall and surrounding soils, the modulus of the cut-off wall concrete, and the connected pattern between the cut-off wall and the clay core. The result shows that improving the overburden layer,selecting plastic concrete with a low modulus and high strength, and optimizing the connection between the cut-off wall and the clay core of the dam are effective measures of reducing the deformations and compressive stresses of the cut-off wall. In addition, both the Goodman element and the mud-layer element are suitable for simulating the interfacial contact between the cut-off wall and surrounding soils.展开更多
This study examines a Kuroshio main path(KMP) cut-off event east of Taiwan Island occurred in fall-winter2013–2014 and its impacts on the South China Sea(SCS) by analyzing satellite altimetry and mooring observations...This study examines a Kuroshio main path(KMP) cut-off event east of Taiwan Island occurred in fall-winter2013–2014 and its impacts on the South China Sea(SCS) by analyzing satellite altimetry and mooring observations. Satellite altimeter sea level anomaly(SLA) images reveal a complete process that a huge cyclonic eddy(CE) from the Pacific collided with the Kuroshio and the western boundary from 15 October 2013 to 15 January 2014. Mooring observations evidenced that the Kuroshio upper ocean volume transport was cut off more than 82% from 17×106 m^3/s in September to 3×106 m^3/s in November 2013. The KMP cut-off event caused the Kuroshio branching and intruding into the SCS and strengthened the eddy kinetic energy in the northern SCS west of the Luzon Strait. Using the total momentum as a dynamic criterion to determine the role of eddy collision with the Kuroshio reasonably explains the KMP cut-off event.展开更多
The aim of this study was to evaluate the effects of low-dose tibolone therapy on ovarian area, uterine volume and endometrial thickness, and define the cut-off value of endometrial thickness for curettage during uter...The aim of this study was to evaluate the effects of low-dose tibolone therapy on ovarian area, uterine volume and endometrial thickness, and define the cut-off value of endometrial thickness for curettage during uterine bleeding. We followed 619 postmenopausal women, aged 40-60 years, for two years. There were 301 subjects in the low-dose tibolone treatment group and 318 subjects in the control group. The ovarian area, uterine volume and endometrial thickness in all participants were measured by transvaginal ultrasound prior to, one and two years post enrollment, respectively. Endometrial specimens were collected from all subjects with abnormal uterine bleeding during the follow-up period. We found that the uterine volume in the treatment group was greater than that in the control group, and the difference was significant （P〈0.05）, but there were no significant differences in ovarian area and endometrial thickness between the two groups （P〉0.05）. When the cut-off value for endometrial thickness was 7.35 ram, the sensitivity and specificity were 100% and 79.07%, respectively, and 85.71% and 93.02% when 7.55 mm was set as the cut-offduring tibolone therapy. The results indicate that low-dose tibolone therapy may postpone uterine atrophy and the cut-off value of endometrial thickness may be appropriately adjusted for curettage.展开更多
In situ measurements of the vertical structure of ozone were made in Changchun （43.53°N, 125.13°E）, China, by the Institute of Atmosphere Physics, in the summers of 2010-13. Analysis of the 89 validated oz...In situ measurements of the vertical structure of ozone were made in Changchun （43.53°N, 125.13°E）, China, by the Institute of Atmosphere Physics, in the summers of 2010-13. Analysis of the 89 validated ozone profiles shows the vari- ation of ozone concentration in the upper troposphere and lower stratosphere （UTLS） caused by cut-off lows （COLs） over Changchun. During the COL events, an increase of the ozone concentration and a lower height of the tropopause are observed. Backward simulations with a trajectory model show that the ozone-rich airmass brought by the COL is from Siberia. A case study proves that stratosphere-troposphere exchange （STE） occurs in the COL. The ozone-rich air mass transported from the stratosphere to the troposphere first becomes unstable, then loses its high ozone concentration. This process usually happens during the decay stage of COLs. In order to understand the influence of COLs on the ozone in the UTLS, statistical analysis of the ozone profiles within COLs, and other profiles, are employed. The results indicate that the ozone concentrations of the in-COL profiles are significantly higher than those of the other profiles between ±4 km around the tropopause. The COLs induce an increase in UTLS column ozone by 32% on average. Meanwhile, the COLs depress the lapse-rate tropopause （LRT）/dynamical tropopause height by 1.4/1.7 km and cause the atmosphere above the tropopause to be less stable. The influence of COLs is durable because the increased ozone concentration lasts at least one day after the COL has passed over Changchun. Furthermore, the relative coefficient between LRT height and lower stratosphere （LS） column ozone is -0.62, which implies a positive correlation between COL strength and LS ozone concentration.展开更多
Northeast Asian cut-off lows are crucial cyclonic systems that can bring temperature and precipitation extremes over large areas.Skillful subseasonal forecasting of Northeast Asian cut-off lows is of great importance....Northeast Asian cut-off lows are crucial cyclonic systems that can bring temperature and precipitation extremes over large areas.Skillful subseasonal forecasting of Northeast Asian cut-off lows is of great importance.Using two dynamical forecasting systems,one from the Beijing Climate Center(BCC-CSM2-HR)and the other from the Met Office(GloSea5),this study assesses simulation ability and subseasonal prediction skill for early-summer Northeast Asian cut-off lows.Both models are shown to have good ability in representing the spatial structure of cut-off lows,but they underestimate the intensity.The skillful prediction time scales for cut-off low intensity are about 10.2 days for BCC-CSM2-HR and 11.4 days for GloSea5 in advance.Further examination shows that both models can essentially capture the initial Rossby wave train,rapid growth and decay processes responsible for the evolution of cut-off lows,but the models show weaker amplitudes for the three-stage processes.The underestimated simulated strength of both the Eurasian midlatitude and East Asian subtropical jets may lead to the weaker local eddy-mean flow interaction responsible for the cut-off low evolution.展开更多
Determining the hydrometallurgical cut-off grades specifies the destination of low grade materials and this is subjected to more benefits in mining. Copper production rate is considered as one of the fundamental issue...Determining the hydrometallurgical cut-off grades specifies the destination of low grade materials and this is subjected to more benefits in mining. Copper production rate is considered as one of the fundamental issues in hydrometallurgical cut-off grades determination. Slags are remarked as one of the main sources of copper. It is not only regarded as a waste but also identified as another resource extracting base metals. Slags are characterized by copper high grade. Thus, slag copper recovery can be led to different cut-off grades and net present value(NPV). The current research scrutinizes the effect of slag recovery by both flotation and hydrometallurgical methods on the hydrometallurgical cut-off grades. For this purpose, the optimum cut-off grade algorithms of hydrometallurgical methods are developed by considering associated environmental parameters, incomes and also the costs. Then, their optimum amounts are calculated with NPV maximization as an objective function. The results indicate that considering slag copper recovery in the hydrometallurgical cut-off grade algorithms reduces the environmental costs caused by slag dumping and leads to more NPV by 9%.展开更多
The transverse relaxation time (T_(2)) cut-off value plays a crucial role in nuclear magnetic resonance for identifying movable and immovable boundaries, evaluating permeability, and determining fluid saturation in pe...The transverse relaxation time (T_(2)) cut-off value plays a crucial role in nuclear magnetic resonance for identifying movable and immovable boundaries, evaluating permeability, and determining fluid saturation in petrophysical characterization of petroleum reservoirs. This study focuses on the systematic analysis of T_(2) spectra and T_(2) cut-off values in low-permeability reservoir rocks. Analysis of 36 low-permeability cores revealed a wide distribution of T_(2) cut-off values, ranging from 7 to 50 ms. Additionally, the T_(2) spectra exhibited multimodal characteristics, predominantly displaying unimodal and bimodal morphologies, with a few trimodal morphologies, which are inherently influenced by different pore types. Fractal characteristics of pore structure in fully water-saturated cores were captured through the T_(2) spectra, which were calculated using generalized fractal and multifractal theories. To augment the limited dataset of 36 cores, the synthetic minority oversampling technique was employed. Models for evaluating the T_(2) cut-off value were separately developed based on the classified T_(2) spectra, considering the number of peaks, and utilizing generalized fractal dimensions at the weight <0 and the singular intensity range. The underlying mechanism is that the singular intensity and generalized fractal dimensions at the weight <0 can detect the T_(2) spectral shift. However, the T_(2) spectral shift has negligible effects on multifractal spectrum function difference and generalized fractal dimensions at the weight >0. The primary objective of this work is to gain insights into the relationship between the kurtosis of the T_(2) spectrum and pore types, as well as to predict the T_(2) cut-off value of low-permeability rocks using machine learning and data augmentation techniques.展开更多
As is well known, there exists a tradeoff between the breakdown voltage BVcEO and the cut-off frequency fT for a standard heterojunction bipolar transistor （HBT）. In this paper, this tradeoff is alleviated by collec...As is well known, there exists a tradeoff between the breakdown voltage BVcEO and the cut-off frequency fT for a standard heterojunction bipolar transistor （HBT）. In this paper, this tradeoff is alleviated by collector doping engineering in the SiGe HBT by utilizing a novel composite of P＋ and N- doping layers inside the collector-base （CB） space-charge region （SCR）. Compared with the single N-type collector, the introduction of the thin P＋ layers provides a reverse electric field weakening the electric field near the CB metallurgical junction without changing the field direction, and the thin N layer further effectively lowers the electric field near the CB metallurgical junction. As a result, the electron temperature near the CB metallurgical junction is lowered, consequently suppressing the impact ionization, thus BVcEO is improved with a slight degradation in fT. The results show that the product of fTXBVcEo is improved from 309.51 GHz.V to 326.35 GHz.V.展开更多
基金the National Natural Science Foundation of China (Grant Nos.42072318 and 42207227)Central South University Innovation-Driven Research Program (Grant No.2023CXQD044).
文摘The soil-bentonite(SB)cut-off wall has been widely considered a vertical barrier to effectively control the migration of pollutants in contaminated sites.Recently,active porous materials have been used as a promising candidate amendment for mitigating chemical degradation and improving the retardation capacity of the SB cut-off wall.In this study,the silty clay from a typical Cr(VI)contaminated site was selected as the body material of the SB cut-off wall,and zeolite and active carbon were used as the modifiers of the silty clay-bentonite backfills,respectively.The impact of the two modifiers on the engineering properties of the backfills was investigated through a series of slump tests,consolidation tests,hydraulic conductivity tests,and microstructure tests.The experimental results demonstrated that the slump curves closely exhibited a linear relationship between standard slump and moisture content.Meanwhile,bentonite could improve the optimum moisture content of the backfills,while the addition of the two modifiers yielded the opposite outcome.As the bentonite content increased,the compression index of the backfills significantly increased,while the hydraulic conductivity decreased.At a given bentonite content of 5%,the addition of zeolite or active carbon resulted in a reduction in the compression index and initial void ratio,while exhibiting minimal impact on the hydraulic conductivity.Scanning electron microscope(SEM)observations indicated that the silty clay-bentonite backfills became increasingly loose with increasing bentonite content,owing to the filling and expansion of dispersed bentonite layers.The amendment of zeolite or active carbon was able to decrease the backfill volume by promoting the agglomeration of layered bentonite.The findings of this study will be useful for the optimal selection of backfill materials and the performance evaluation of the cut-off wall.
基金support from the National Natural Science Foundation of China(22179006)the National Key Research and Development Program of China(2024YFF0505900)+1 种基金the Key Research and Development Program of Henan province,China(231111242500)the SINOPEC project(223128)。
文摘Uneven lithium deposition leading to lithium dendrite growth severely hampers the application of lithium-metal batteries.Modifying the collector with lithiophilic materials helps improve lithium deposition.For lithophilic materials to modify the collector,the choice of cut-off voltage is very important.While excessively high cut-off voltages may compromise the stability of the modified layer and consequently disrupt ordered lithium deposition,conventional approaches typically employ lower cut-off voltages(particularly 0.1 V)to maintain modification layer stability.However,the 0.1 V cut-off voltage results in incomplete lithium stripping from the lithiophilic material surface.This phenomenon significantly diminishes the lithiophilic properties of the modified layer and consequently leads to substantial nucleation overpotential.Here,we propose to use a moderate cut-voltage stimulation effect to slow down the interfacial shielding effect of residual lithium metal on lithiophilic materials.By optimizing the cut-off voltage for the Cu@Sb_(2)S_(3)collector,the stability of the modified layer can be preserved while enabling the complete stripping of lithium metal from the surface of the lithophilic material.The asymmetric cell received the highest Coulombic efficiency(CE)when the lithium stripping cut-off voltage was set at 0.5 V relative to 0.1 and 2.0 V.At a current density of 1 mA cm^(-2)and a deposition capacity of1 m A h cm^(-2),the CE remained 98.6% at a cut-off voltage of 0.5 V after 140 cycles in an ether electrolyte without lithium nitrate.
基金Projects(52278395,52208409) supported by the National Natural Science Foundation of ChinaProject(2022JJ40531) supported by the Natural Science Foundation of Hunan Province,China。
文摘Because of actual requirement,shield machine always excavates with an inclined angle in longitudinal direction.Since many previous studies mainly focus on the face stability of the horizontal shield tunnel,the effects of tensile strength cut-off and pore water pressure on the face stability of the longitudinally inclined shield tunnel are not well investigated.A failure mechanism of a longitudinally inclined shield tunnel face is constructed based on the spatial discretization technique and the tensile strength cut-off criterion is introduced to modify the constructed failure mechanism.The pore water pressure is introduced as an external force into the equation of virtual work and the objective function of the chamber pressure of the shield machine is obtained.Moreover,the critical chamber pressure of the longitudinally inclined shield tunnel is computed by optimal calculation.Parametric analysis indicates that both tensile strength cut-off and pore water pressure have a significant impact on the chamber pressure and the range of the collapse block.Finally,the theoretical results are compared with the numerical results calculated by FLAC3D software which proves that the proposed approach is effective.
基金the National Natural Science Foun-dation of China(Grant Nos.91963201 and 12174163)the 111 Project(Grant No.B20063).
文摘The lack of soft magnetic composites with high power density in MHz frequency range has become an obstacle in the efficient operation of the electrical and electronic equipments.Here,a promising method to increase the cut-off frequency of iron-based soft magnetic composites to hundreds of MHz is reported.The cut-off frequency is increased from 10 MHz to 1 GHz by modulating the height of the ring,the distribution of particles,and the particle size.The mechanism of cut-off frequency and permeability is the coherent rotation of domain modulated by inhomogeneous field due to the eddy current effect.An empirical formula for the cut-off frequency in a magnetic ring composed of iron-based particles is established from experimental data.This work provides an effective approach to fabricate soft magnetic composites with a cut-off frequency in hundreds of MHz.
基金Supported by National Key R&D Program of China,No.2016YFC1305700.
文摘BACKGROUND Glycated hemoglobin A1c(HbA1c)is considered the most suitable for diabetes mellitus diagnosis due to its accuracy and convenience.However,the effect of HbA1c on diabetic retinopathy(DR)in the Han and Korean populations in Jilin,China,remains inconclusive.AIM To determine the best cut-off of HbA1c for diagnosing DR among the Chinese.METHODS This cross-sectional study included 1933 participants from the Yanbian area of Jilin Province,China.Trained investigators employed a questionnaire-based survey,physical examination,laboratory tests,and fundus photography for the investigation.The best cut-off value for HbA1c was established via the receiver operating characteristic curve.The factors associated with HbA1c-associated risk factors were determined via linear regression.RESULTS The analysis included 887 eligible Chinese Han and Korean participants,591 of whom were assigned randomly to the training set and 296 to the validation set.The prevalence of DR was 3.27% in the total population.HbA1c of 6.2% was the best cut-off value in the training set,while it was 5.9% in the validation set.In both Chinese Han and Korean populations,an HbA1c level of 6.2% was the best cut-off value.The optimal cut-off values of fasting blood glucose(FBG)≥7 mmol/L and<7 mmol/L were 8.1% and 6.2% respectively in Han populations,while those in Korean populations were 6.9%and 5.3%,respectively.Age,body mass index,and FBG were determined as the risk factors impacting HbA1c levels.CONCLUSION HbA1c may serve as a useful diagnostic indicator for DR.An HbA1c level of 6.2% may be an appropriate cut-off value for DR detection in the Chinese population.
基金the National Natural Science Foundation of China (Grant No.51379066)the Fundamental Research Funds for the Central Universities (Grant No.2016B03514)+1 种基金the National Key Technology Support Program (Grant No.2015BAB07B05)the Key Laboratory of Earth-Rock Dam Failure Mechanism and Safety Control Techniques (Grant No.YK913007).
文摘The cut-off wall in a clay-core rockfill dam built on a thick overburden layer is subjected to a large compressive pressure under the action of the loads such as the dead weight of both the dam and the overburden layer, the frictional force induced by the differential settlement between the cut-off wall and surrounding soils, and the water pressure. Thus, reduction of the stress of the cut-off wall has become one of the main problems for consideration in engineering design. In this paper, numerical analysis of a core rockfill dam built on a thick overburden layer was conducted and some factors influencing the stress-strain behaviors of the cut-off wall were investigated. The factors include the improvement of the overburden layer, the modeling approach for interfacial contact between the cut-off wall and surrounding soils, the modulus of the cut-off wall concrete, and the connected pattern between the cut-off wall and the clay core. The result shows that improving the overburden layer,selecting plastic concrete with a low modulus and high strength, and optimizing the connection between the cut-off wall and the clay core of the dam are effective measures of reducing the deformations and compressive stresses of the cut-off wall. In addition, both the Goodman element and the mud-layer element are suitable for simulating the interfacial contact between the cut-off wall and surrounding soils.
基金The National Natural Science Foundation of China under contract No.41776034the Ministry of Science and Technology of Taiwan under contract Nos MOST 105-2611-M-019-001 and MOST 106-2611-M-019-015+1 种基金the GASI Project under contract Nos GASI-IPOVAI-01-02 and GASI-02-SCS-YGST2-02the Foundation of Guangdong Province for Outstanding Young Teachers in University under contract No.YQ201588
文摘This study examines a Kuroshio main path(KMP) cut-off event east of Taiwan Island occurred in fall-winter2013–2014 and its impacts on the South China Sea(SCS) by analyzing satellite altimetry and mooring observations. Satellite altimeter sea level anomaly(SLA) images reveal a complete process that a huge cyclonic eddy(CE) from the Pacific collided with the Kuroshio and the western boundary from 15 October 2013 to 15 January 2014. Mooring observations evidenced that the Kuroshio upper ocean volume transport was cut off more than 82% from 17×106 m^3/s in September to 3×106 m^3/s in November 2013. The KMP cut-off event caused the Kuroshio branching and intruding into the SCS and strengthened the eddy kinetic energy in the northern SCS west of the Luzon Strait. Using the total momentum as a dynamic criterion to determine the role of eddy collision with the Kuroshio reasonably explains the KMP cut-off event.
基金supported by the Sci-tech Research Development Program of Shaanxi Province (No.2015SF015)
文摘The aim of this study was to evaluate the effects of low-dose tibolone therapy on ovarian area, uterine volume and endometrial thickness, and define the cut-off value of endometrial thickness for curettage during uterine bleeding. We followed 619 postmenopausal women, aged 40-60 years, for two years. There were 301 subjects in the low-dose tibolone treatment group and 318 subjects in the control group. The ovarian area, uterine volume and endometrial thickness in all participants were measured by transvaginal ultrasound prior to, one and two years post enrollment, respectively. Endometrial specimens were collected from all subjects with abnormal uterine bleeding during the follow-up period. We found that the uterine volume in the treatment group was greater than that in the control group, and the difference was significant （P〈0.05）, but there were no significant differences in ovarian area and endometrial thickness between the two groups （P〉0.05）. When the cut-off value for endometrial thickness was 7.35 ram, the sensitivity and specificity were 100% and 79.07%, respectively, and 85.71% and 93.02% when 7.55 mm was set as the cut-offduring tibolone therapy. The results indicate that low-dose tibolone therapy may postpone uterine atrophy and the cut-off value of endometrial thickness may be appropriately adjusted for curettage.
基金jointly supported by the National Basic Research Program of China (Grant No.2010CB428602)the National Natural Science Foundation of China (Grant Nos.41275046 and 41025017)
文摘In situ measurements of the vertical structure of ozone were made in Changchun （43.53°N, 125.13°E）, China, by the Institute of Atmosphere Physics, in the summers of 2010-13. Analysis of the 89 validated ozone profiles shows the vari- ation of ozone concentration in the upper troposphere and lower stratosphere （UTLS） caused by cut-off lows （COLs） over Changchun. During the COL events, an increase of the ozone concentration and a lower height of the tropopause are observed. Backward simulations with a trajectory model show that the ozone-rich airmass brought by the COL is from Siberia. A case study proves that stratosphere-troposphere exchange （STE） occurs in the COL. The ozone-rich air mass transported from the stratosphere to the troposphere first becomes unstable, then loses its high ozone concentration. This process usually happens during the decay stage of COLs. In order to understand the influence of COLs on the ozone in the UTLS, statistical analysis of the ozone profiles within COLs, and other profiles, are employed. The results indicate that the ozone concentrations of the in-COL profiles are significantly higher than those of the other profiles between ±4 km around the tropopause. The COLs induce an increase in UTLS column ozone by 32% on average. Meanwhile, the COLs depress the lapse-rate tropopause （LRT）/dynamical tropopause height by 1.4/1.7 km and cause the atmosphere above the tropopause to be less stable. The influence of COLs is durable because the increased ozone concentration lasts at least one day after the COL has passed over Changchun. Furthermore, the relative coefficient between LRT height and lower stratosphere （LS） column ozone is -0.62, which implies a positive correlation between COL strength and LS ozone concentration.
基金supported by the National Key Research and Development Program of China(2021YFA0718000)NSF of China under Grant No.42175075the UK-China Research&Innovation Partnership Fund through the Met Office Climate Science for Service Partnership(CSSP)China as part of the Newton Fund.
文摘Northeast Asian cut-off lows are crucial cyclonic systems that can bring temperature and precipitation extremes over large areas.Skillful subseasonal forecasting of Northeast Asian cut-off lows is of great importance.Using two dynamical forecasting systems,one from the Beijing Climate Center(BCC-CSM2-HR)and the other from the Met Office(GloSea5),this study assesses simulation ability and subseasonal prediction skill for early-summer Northeast Asian cut-off lows.Both models are shown to have good ability in representing the spatial structure of cut-off lows,but they underestimate the intensity.The skillful prediction time scales for cut-off low intensity are about 10.2 days for BCC-CSM2-HR and 11.4 days for GloSea5 in advance.Further examination shows that both models can essentially capture the initial Rossby wave train,rapid growth and decay processes responsible for the evolution of cut-off lows,but the models show weaker amplitudes for the three-stage processes.The underestimated simulated strength of both the Eurasian midlatitude and East Asian subtropical jets may lead to the weaker local eddy-mean flow interaction responsible for the cut-off low evolution.
文摘Determining the hydrometallurgical cut-off grades specifies the destination of low grade materials and this is subjected to more benefits in mining. Copper production rate is considered as one of the fundamental issues in hydrometallurgical cut-off grades determination. Slags are remarked as one of the main sources of copper. It is not only regarded as a waste but also identified as another resource extracting base metals. Slags are characterized by copper high grade. Thus, slag copper recovery can be led to different cut-off grades and net present value(NPV). The current research scrutinizes the effect of slag recovery by both flotation and hydrometallurgical methods on the hydrometallurgical cut-off grades. For this purpose, the optimum cut-off grade algorithms of hydrometallurgical methods are developed by considering associated environmental parameters, incomes and also the costs. Then, their optimum amounts are calculated with NPV maximization as an objective function. The results indicate that considering slag copper recovery in the hydrometallurgical cut-off grade algorithms reduces the environmental costs caused by slag dumping and leads to more NPV by 9%.
基金supported by National Natural Science Foundation of China(Nos.42002171,42172159)China Postdoctoral Science Foundation(Nos.2020TQ0299,2020M682520)Postdoctoral Innovation Science Foundation of Hubei Province of China.
文摘The transverse relaxation time (T_(2)) cut-off value plays a crucial role in nuclear magnetic resonance for identifying movable and immovable boundaries, evaluating permeability, and determining fluid saturation in petrophysical characterization of petroleum reservoirs. This study focuses on the systematic analysis of T_(2) spectra and T_(2) cut-off values in low-permeability reservoir rocks. Analysis of 36 low-permeability cores revealed a wide distribution of T_(2) cut-off values, ranging from 7 to 50 ms. Additionally, the T_(2) spectra exhibited multimodal characteristics, predominantly displaying unimodal and bimodal morphologies, with a few trimodal morphologies, which are inherently influenced by different pore types. Fractal characteristics of pore structure in fully water-saturated cores were captured through the T_(2) spectra, which were calculated using generalized fractal and multifractal theories. To augment the limited dataset of 36 cores, the synthetic minority oversampling technique was employed. Models for evaluating the T_(2) cut-off value were separately developed based on the classified T_(2) spectra, considering the number of peaks, and utilizing generalized fractal dimensions at the weight <0 and the singular intensity range. The underlying mechanism is that the singular intensity and generalized fractal dimensions at the weight <0 can detect the T_(2) spectral shift. However, the T_(2) spectral shift has negligible effects on multifractal spectrum function difference and generalized fractal dimensions at the weight >0. The primary objective of this work is to gain insights into the relationship between the kurtosis of the T_(2) spectrum and pore types, as well as to predict the T_(2) cut-off value of low-permeability rocks using machine learning and data augmentation techniques.
基金supported by the National Natural Science Foundation of China(Grant Nos.60776051,61006059,and 61006044)the Beijing Municipal Natural Science Foundation,China(Grant Nos.4142007,4143059,4082007,and 4122014)the Beijing Municipal Education Committee,China(Grant Nos.KM200710005015 and KM200910005001)
文摘As is well known, there exists a tradeoff between the breakdown voltage BVcEO and the cut-off frequency fT for a standard heterojunction bipolar transistor （HBT）. In this paper, this tradeoff is alleviated by collector doping engineering in the SiGe HBT by utilizing a novel composite of P＋ and N- doping layers inside the collector-base （CB） space-charge region （SCR）. Compared with the single N-type collector, the introduction of the thin P＋ layers provides a reverse electric field weakening the electric field near the CB metallurgical junction without changing the field direction, and the thin N layer further effectively lowers the electric field near the CB metallurgical junction. As a result, the electron temperature near the CB metallurgical junction is lowered, consequently suppressing the impact ionization, thus BVcEO is improved with a slight degradation in fT. The results show that the product of fTXBVcEo is improved from 309.51 GHz.V to 326.35 GHz.V.
