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The Optimization Research on College English Classroom Teaching Under the Network Environment—Based on the Feedback Report of College English Stratified Teaching in SASU 被引量:1
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作者 DENG Fei 《Sino-US English Teaching》 2020年第10期297-300,共4页
According to the requirements of College English Teaching Guide,together with the freshmen’s majors and the actual English level in SASU(Sichuan University of Arts and Science),College English stratified teaching has... According to the requirements of College English Teaching Guide,together with the freshmen’s majors and the actual English level in SASU(Sichuan University of Arts and Science),College English stratified teaching has been implemented in SASU since 2016.In order to completely master the teaching effect of the stratified teaching in the past four years,a questionnaire survey on College English learners has been carried out.On the basis of the feedback report and the teaching principles of College English under the network environment,this paper puts forward the optimization strategies and rectification suggestions. 展开更多
关键词 stratified teaching feedback report teaching principles optimization strategies
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Health behavior outcomes in stroke survivors prescribed wearables for atrial fibrillation detection stratified by age
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作者 Joanne Mathew Jordy Mehawej +11 位作者 Ziyue Wang Taylor Orwig Eric Ding Andreas Filippaios Syed Naeem Edith Mensah Otabil Alex Hamel Kamran Noorishirazi IrinaRadu Jane Saczynski David D.McManus Khanh-Van Tran 《Journal of Geriatric Cardiology》 SCIE CAS CSCD 2024年第3期323-330,共8页
BACKGROUND Smartwatches have become readily accessible tools for detecting atrial fibrillation(AF).There remains limited data on how they affect psychosocial outcomes and engagement in older adults.We examine the heal... BACKGROUND Smartwatches have become readily accessible tools for detecting atrial fibrillation(AF).There remains limited data on how they affect psychosocial outcomes and engagement in older adults.We examine the health behavior outcomes of stroke survivors prescribed smartwatches for AF detection stratified by age.METHODS We analyzed data from the Pulsewatch study,a randomized controlled trial that enrolled patients(≥50 years)with a history of stroke or transient ischemic attack and CHA2DS2-VASc≥2.Intervention participants were equipped with a cardiac patch monitor and a smartwatch-app dyad,while control participants wore the cardiac patch monitor for up to 44 days.We evaluated health behavior parameters using standardized tools,including the Consumer Health Activation Index,the Generalized Anxiety Disorder questionnaire,the 12-Item Short Form Health Survey,and wear time of participants categorized into three age groups:Group 1(ages 50-60),Group 2(ages 61-69),and Group 3(ages 70-87).We performed statistical analysis using a mixedeffects repeated measures linear regression model to examine differences amongst age groups.RESULTS Comparative analysis between Groups 1,2 and 3 revealed no significant differences in anxiety,patient activation,perception of physical health and wear time.The use of smartwatch technology was associated with a decrease in perception of mental health for Group 2 compared to Group 1(β=-3.29,P=0.046).CONCLUSION Stroke survivors demonstrated a willingness to use smartwatches for AF monitoring.Importantly,among these study participants,the majority did not experience negative health behavior outcomes or decreased engagement as age increased. 展开更多
关键词 PRESCRIBED stratified WEAR
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Application Effect of Stratified Nursing Intervention for ICU Mechanically Ventilated Patients in the Context of Aspiration Risk Assessment
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作者 Caisu Qin Yong Gao +1 位作者 Yanchi Zheng Wenjuan Wang 《Journal of Clinical and Nursing Research》 2024年第6期226-231,共6页
Objective:To explore the application effect of stratified nursing intervention based on the background of misinspiration risk assessment in mechanically ventilated patients in intensive care unit(ICU).Methods:100 case... Objective:To explore the application effect of stratified nursing intervention based on the background of misinspiration risk assessment in mechanically ventilated patients in intensive care unit(ICU).Methods:100 cases of mechanically ventilated patients who were admitted to the ICU of our hospital from March 2022 to March 2023 were selected and divided into an observation group and a control group according to the random number table method,with 50 cases in each of the two groups.The control group was given routine care in ICU,and the observation group was given stratified nursing interventions based on the background of the risk of aspiration assessment on the basis of the control group,and both groups were cared for until they were transferred out of the ICU,and the mechanical ventilation time,ICU stay time,muscle strength score,complication rate,adherence,and satisfaction were observed and compared between the two groups.Results:The mechanical ventilation time and ICU stay time of the observation group were shorter than that of the control group after the intervention;the muscle strength score,compliance and satisfaction of the observation group were higher than that of the control group after the intervention;and the complication rate of the observation group was lower than that of the control group after the intervention,all of which were P<0.05.Conclusion:The application of stratified nursing intervention based on the background of misaspiration risk assessment in ICU mechanically ventilated patients can improve the patient's muscle strength,shorten the time of mechanical ventilation,promote the patient's recovery,reduce the occurrence of complications,and improve the patient's compliance and satisfaction. 展开更多
关键词 Mechanical ventilation Aspiration risk assessment stratified care Muscle strength COMPLICATION
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On The Necessity of Stratified English Teaching in Higher Vocational Colleges
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作者 张天华 《海外英语》 2013年第16期53-54,共2页
The practice of stratified English teaching is determined by the features of vocational education. In addition, it is an inexorable trend of current higher education reform, and also a fundamental demand of higher voc... The practice of stratified English teaching is determined by the features of vocational education. In addition, it is an inexorable trend of current higher education reform, and also a fundamental demand of higher vocational education and quality-oriented education. This thesis argues for the need of stratified English teaching in high vocational colleges. 展开更多
关键词 Higher VOCATIONAL COLLEGES stratified English TEAC
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Radial Non-uniformity Index Research on High-density,High-flux CFB Riser with Stratified Injection 被引量:3
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作者 Geng Qiang Wang Lu +3 位作者 Li Zhichao Li Chunyi Liu Yibin You Xinghua 《China Petroleum Processing & Petrochemical Technology》 SCIE CAS 2012年第4期64-72,共9页
A high-density, high-flux circulating fluidized bed (CFB) riser (100 mm in ID and 10.614 m in height) was applied in a wide range of operating conditions (with solid fluxes up to 400 kg/m2s and superficial gas velocit... A high-density, high-flux circulating fluidized bed (CFB) riser (100 mm in ID and 10.614 m in height) was applied in a wide range of operating conditions (with solid fluxes up to 400 kg/m2s and superficial gas velocities up to 12 m/s) to examine its radial non-uniformity dynamics. The solids holdup was determined through the use of a fiber-optic probe at 11 axial levels. The results indicated that under all operating conditions, the high superficial gas velocity and low solid fluxes maintained a low radial non-uniformity index (RNI). The high-density/flux CFB riser had several unique characteristics, so that the peak of the radial solids holdup profile occurred at a position with r/R=0.8. The RNI and solids holdup at the cross-sectional position had a good logarithmic relationship at the low-density condition (with a mean solids holdup of <0.2), and the RNI decreased when the mean solids holdup exceeded 0.2. Investigation of the dynamics of stratified injection revealed that the feed ratio had an important effect on Gs and on solids holdup distribution. A novel "<" shaped axial solids holdup profile was found. Gs decreased sharply when the up-flow feed ratio exceeded 0.5, and RNI was lowest when the up-flow feed ratio was 1. 展开更多
关键词 气固循环流化床 高密度 高通量 均匀性指标 径向 颗粒浓度分布 固体通量 喷射
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Discussion on the Application of Stratified Evaluation in Middle School Football Teaching and Training
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作者 Wang Haiting 《教育研究前沿(中英文版)》 2019年第3期80-84,共5页
The evaluation of education in the training process is important for students, and its importance is at the level of students and thecorresponding level of evaluation. Understanding the guidance and training of the mi... The evaluation of education in the training process is important for students, and its importance is at the level of students and thecorresponding level of evaluation. Understanding the guidance and training of the middle school football team is an important partof rapidly improving the level of Chinese football. It is necessary to adapt to the development characteristics of middle schoolstudents and conduct reasonable guidance training. Plans must be strengthened to implement training programs. On the trainingschedule, we must balance learning and training, and must fully consider the growth of students. As part of a layered education,stratified evaluation has the unique advantages of basic education and secondary education. The evaluation of the students whofocus on various levels of learning. Football coaching and training requires a full display of the student's personality. The teacher'sstratified evaluation method is very important for improving students' confidence in learning, enhancing students' enthusiasm forfootball training, and promoting students' continuous improvement. This study takes the application of stratified evaluation in theteaching and training of middle school football as the research direction, and puts forward reasonable suggestions by analyzing thetraining cases of the layered evaluation. 展开更多
关键词 Middle School Sports Football teaching Training Method stratified Evaluation TRAINING
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Combined effect of subsurface dam and layered heterogeneity on groundwater flow and salinity distribution in stratified coastal aquifers
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作者 Chao Gao Jun Kong +2 位作者 Jun Wang Tong Zhou Yuncheng Wen 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2023年第8期49-60,共12页
In this paper,for the first time,we investigated the combined effect of subsurface dams and a typical stratified aquifer(two high-permeability layers with a low-permeability layer between them)on groundwater flow and ... In this paper,for the first time,we investigated the combined effect of subsurface dams and a typical stratified aquifer(two high-permeability layers with a low-permeability layer between them)on groundwater flow and salinity distribution in a tidally influenced coastal unconfined aquifer.Subsurface dams can inhibit the invasion of saltwater,and the low-permeability layer(LPL)and tide action can increase the effect of subsurface dams and the removal rate of residual saltwater.Through sensitivity analysis,it was discovered that shifting the dam location towards the inland resulted in a reduction in the effective heights of the dam.The upper saline plume contracted with increasing dam height,and the upper boundary of LPL was moved to shallower regions.And the natural removal time increased significantly with increasing dam height and the bottom boundary of LPL was moved to deeper regions.In addition,if the dam location was close to the sea boundary and the bottom boundary of LPL was moved to deeper regions,we could increase the subsurface dam height to reduce the risks of control of saltwater intrusion.This study provides us a comprehensive understanding of the complex hydrodynamics of saltwater intrusion and provides guides for the design of subsurface dams aimed at saltwater intrusion control in stratified coastal aquifers. 展开更多
关键词 stratified subsurface dams saltwater intrusion residual saltwater natural removal
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Wax deposition modeling in oil-water stratified pipe flow
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作者 Hui-Shu Liu Ji-Miao Duan +5 位作者 Jiang Li Jian Wang Hao Yan Ke-Yu Lin Ke-Cheng Gu Chang-Jun Li 《Petroleum Science》 SCIE EI CAS CSCD 2023年第1期526-539,共14页
Wax deposition in oil-water stratified flow is commonly encountered onshore and offshore oil production pipe systems,and typically reduces transportation capacity of oil.The accurate predicted model of wax deposition ... Wax deposition in oil-water stratified flow is commonly encountered onshore and offshore oil production pipe systems,and typically reduces transportation capacity of oil.The accurate predicted model of wax deposition has becomes an indispensable approach to design effective remediation strategies.However,a reliable mechanistic model for wax deposition prediction in oil-water two-phase stratified pipe flow is lacking to validate the deposition process.In this work,a three-dimensional(axial,radial,and angular)robust wax deposit model for oil-water stratified circular pipe flow was developed.The model of formation of a gel deposit based on the first principles of rheology was developed,associated with the results obtained from hydrodynamics and heat/mass transfer simulations.The predictions for wax deposition are found to compare satisfactorily with experimental data with two different oils for single phase and four different water cuts for oil-water stratified pipe flow.It can be seen from the wax gelation mechanism that an increase in water cut can help to reduce the wall/oil-deposit interface shear stress,thereby leading to an increase in the degree of gelation as well as the deposit rate.Furthermore,a local deposit analysis in the circumferential direction was conducted,for water cut 75%and total flow rate 5 m3/h,which provided insights to understand that the thickness on pipe wall was roughly uniformly distributed locates near the top of the pipe and the nearer the position gets close to two points,where the oil-water interface contacts the inner wall,the deposition thickness quickly dropped to 0.It was attributed to the fact that a roughly uniformly thickness far away from the oil-water interface contact the inner wall resulted in the slowly changes temperature along the circumferential pipe wall wetted by oil. 展开更多
关键词 Wax deposition Oil-water flow stratified flow Heat and mass transfer
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Non-symmetric distributions of solids deposition for solid-water stratified flow in deviated tubing strings
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作者 Xin-Fu Liu Chun-Hua Liu +7 位作者 Zhong-Xian Hao Ying Zheng Kai Zhang Jian-Feng Wang Song-Bo Wei Ai-Gang Hao Jun-Ling Tao Hui Cheng 《Petroleum Science》 SCIE EI CSCD 2023年第5期3048-3061,共14页
Dynamic performance on solids flow with water in deviated tubing is essential for the reliability of pump and normal operation of horizontal and directional wells.Compared with coal-water flow in vertical tubing and s... Dynamic performance on solids flow with water in deviated tubing is essential for the reliability of pump and normal operation of horizontal and directional wells.Compared with coal-water flow in vertical tubing and sand-oil flow with high production in deviated tubing,solids deposition with water shows obvious non-symmetric distributions in deviated tubing from simulations and experiments.The mathematical model of two phase flow was developed under coupling conditions of deviated tubing,low flow rate and viscosity based on the kinetic theory of granular flow and first-order discrete scheme.The results show that solid-water stratified flow in deviated tubing can be divided into two zones of suspension bed and the moving bed throughout the flow field.The solid flowing velocity with water is negative and particles slide down at the bottom of moving bed zone.The process of solids flow with water in deviated tubing will produce pressure loss and consume the kinetic energy.The thickness of deposited layer and the flowing velocity of solids flow downward with water at the moving bed zone enhance with the decreased inlet flow rate and the increased particle size,tubing inside diameter(ID)and inclination angle.Solids are easier into suspension from the upper part of moving bed zone to suspension bed zone and more solid particles flow with water towards the tubing outlet with the increase of inlet flowing velocity.The decision is made to reduce the screen width,tubing ID and inclination angle to maintain to be greater than critical deposition velocity in order to prevent solids settling.And it provides the theoretical basis and technical reserves for solid control and offers an effective approach to enhance tubing cleaning in deviated strings. 展开更多
关键词 Deviated tubing stratified flow Solid deposition Critical velocity Prevent solids settling
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Linear logistic regression with weight thresholding for flow regime classification of a stratified wake
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作者 Xinyi L.D.Huang Robert F.Kunz Xiang I.A.Yang 《Theoretical & Applied Mechanics Letters》 CAS CSCD 2023年第2期120-127,共8页
A stratified wake has multiple flow regimes,and exhibits different behaviors in these regimes due to the competing physical effects of momentum and buoyancy.This work aims at automated classification of the weakly and... A stratified wake has multiple flow regimes,and exhibits different behaviors in these regimes due to the competing physical effects of momentum and buoyancy.This work aims at automated classification of the weakly and the strongly stratified turbulence regimes based on information available in a full Reynolds stress model.First,we generate a direct numerical simulation database with Reynolds numbers from 10,000 to 50,000 and Froude numbers from 2 to 50.Order(100)independent realizations of temporally evolving wakes are computed to get converged statistics.Second,we train a linear logistic regression classifier with weight thresholding for automated flow regime classification.The classifier is designed to identify the physics critical to classification.Trained against data at one flow condition,the classifier is found to generalize well to other Reynolds and Froude numbers.The results show that the physics governing wake evolution is universal,and that the classifier captures that physics. 展开更多
关键词 stratified wake CLASSIFICATION Supervised learning Full Reynolds stress modelling
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Heat and Mass Transfers in a Two-Phase Stratified Turbulent Fluid Flow in a Geothermal Pipe with Chemical Reaction
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作者 Eric M. Nyariki Mathew N. Kinyanjui Jeconia O. Abonyo 《Journal of Applied Mathematics and Physics》 2023年第2期484-513,共30页
This research focused on the study of heat and mass transfers in a two-phase stratified turbulent fluid flow in a geothermal pipe with chemical reaction. The derived non-linear partial differential equations governing... This research focused on the study of heat and mass transfers in a two-phase stratified turbulent fluid flow in a geothermal pipe with chemical reaction. The derived non-linear partial differential equations governing the flow were solved using the Finite Difference Method. The effects of various physical parameters on the concentration, skin friction, heat, and mass transfers have been determined. Analysis of the results obtained indicated that the coefficient of skin friction decreased with an increase in Reynolds number and solutal Grasholf number, the rate of heat transfer increased with an increase in Eckert number, Prandtl number, and angle of inclination, and the rate of mass transfer increased with increase in Reynolds number, Chemical reaction parameter and angle of inclination. The findings would be useful to engineers in designing and maintaining geothermal pipelines more effectively. 展开更多
关键词 TWO-PHASE Turbulence Non-Newtonian INCLINATION Heat Transfer Mass Transfer stratified
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Predicting disease progression in cirrhotic patients after transjugular intrahepatic portosystemic shunt implantation:A sexstratified analysis
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作者 Qian Zhang Li Long +4 位作者 Hong-Lin Zhu Hong Peng Xin-Hua Luo Kang-Shun Zhu Rong-Pin Wang 《World Journal of Gastroenterology》 SCIE CAS 2023年第42期5768-5780,共13页
BACKGROUND Transjugular intrahepatic portosystemic shunt(TIPS)has been extensively used to treat portal hypertension-associated complications,including cirrhosis.The prediction of post-TIPS prognosis is important for ... BACKGROUND Transjugular intrahepatic portosystemic shunt(TIPS)has been extensively used to treat portal hypertension-associated complications,including cirrhosis.The prediction of post-TIPS prognosis is important for cirrhotic patients,as more aggressive liver transplantation is needed when the post-TIPS prognosis is poor.AIM To construct a nutrition-based model that could predict the disease progression of cirrhotic patients after TIPS implantation in a sex-dependent manner.METHODS This study retrospectively recruited cirrhotic patients undergoing TIPS implantation for analysis.Muscle quality was assessed by measuring the skeletal muscle index(SMI)by computed tomography.Multivariate Cox proportional hazard models were utilized to determine the association between SMI and disease progression in cirrhotic patients after TIPS implantation.RESULTS This study eventually included 186 cirrhotic patients receiving TIPS who were followed up for 30.5±18.8 mo.For male patients,the 30-mo survival rate was significantly lower and the probability of progressive events was higher(3.257-fold)in the low-level SMI group than in the high-level SMI group.According to the multivariate Cox analysis of male patients,SMI<32.8 was an independent risk factor for long-term adverse outcomes after TIPS implantation.A model was constructed,which involved creatinine,plasma ammonia,SMI,and acute-on-chronic liver failure and hepatic encephalopathy occurring within half a year after surgery.This model had an area under the receiver operating characteristic curve of 0.852,sensitivity of 0.926,and specificity of 0.652.According to the results of the DeLong test,this model outperformed other models(Child-Turcotte-Pugh,Model for End-Stage Liver Disease,and Freiburg index of post-TIPS survival)(P<0.05).CONCLUSION SMI is strongly associated with poor long-term outcomes in male patients with cirrhosis who underwent TIPS implantation. 展开更多
关键词 Transjugular intrahepatic portosystemic shunt Skeletal muscle index NUTRITION CIRRHOSIS Sex stratified Prognosis
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Laboratory investigation on damping characteristics of homogeneous and stratified soil-ash system
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作者 Amit Kumar Ram Supriya Mohanty 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2023年第10期2757-2777,共21页
In this study,the damping responses of uniform soil,equi-proportional fly ash,and local soil as a single unit were investigated.The large-strain cyclic triaxial tests were performed for the specimen compacted at the d... In this study,the damping responses of uniform soil,equi-proportional fly ash,and local soil as a single unit were investigated.The large-strain cyclic triaxial tests were performed for the specimen compacted at the desired density(95%e99%of maximum dry density).The compacted specimens were tested under the loading frequency of 0.3e1 Hz with medium confinement of 70e100 kPa.Also,the unsymmetrical behavior of the hysteresis loop was analyzed using three different damping estimation approaches,i.e.symmetric hysteresis loop(SHL),asymmetric hysteresis loop(ASHL),and the modified American Society for Testing and Materials(ASTM)method.The outcome of the study shows for fly ash,local soil,and layered soil-ash,the ASHL technique has the highest damping value,followed by ASTM and then the SHL approach.The specimens prepared under high density and subjected to high confinement show low damping values.However,the specimens tested at high frequency exhibits high damping behavior.Similarly,the damping value of fly ash determined using the SHL and ASHL methods has a similar profile and reaches a maximum at 1%shear strain value before decreasing.The composite stratified deposit exhibits more dependency on relative compaction,confining pressure,and less on loading frequency.Based on the results,it is highly recommended to use the ASHL approach,especially under large strain conditions irrespective of soil type.The maximum damping ratio of stratified deposits is always in between the damping ratio of local soil and fly ash.The damping ratio of stratified soil and local soil is slightly larger than that of the other soils,although the damping ratio of fly ash is equivalent to that of the sand and clayey soil.These results may be helpful in the accurate determination of the damping properties of the layered soil-ash system that is required in the seismic response analysis. 展开更多
关键词 Homogeneous soil stratified soil-ash system Damping behavior Cyclic triaxial test Asymmetric hysteresis loop Model fitting
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Stratified Teaching Method of English Picture Book Reading in Primary Schools
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作者 Yidan Xu 《Journal of Contemporary Educational Research》 2021年第9期103-108,共6页
With the advancement of the new curriculum reform,many schools have put forward the idea of combing English reading with stratified teaching.Enhancing the effectiveness of reading English picture books is an important... With the advancement of the new curriculum reform,many schools have put forward the idea of combing English reading with stratified teaching.Enhancing the effectiveness of reading English picture books is an important goal that most English teachers uphold when reforming the teaching of English reading.In order to achieve this goal,it is necessary to improve the teaching methods of reading.Reading picture books is an important way to improve students5 core competencies in English.However,at present,the method of teaching reading in primary school is simple;in addition,the teaching activities are not well organized.Therefore,in order to improve students5 core competencies in English,this article points out several issues in the teaching of English picture book reading and provides some pedagogical implications for the teaching in this aspect based on the stratified teaching method and classroom observation by including Class 1,Grade 2 students from a primary school in Leshan as the research subjects. 展开更多
关键词 stratified teaching English picture book reading Core competencies in English
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技术转移分层靶向机制构建研究 被引量:1
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作者 李娟 潘国轩 赵金梅 《科技进步与对策》 北大核心 2024年第7期31-39,共9页
技术成果“转出去”是发挥创新驱动效能与缓解技术转移困境的重要举措,其离不开技术需求管理的有效支撑。研究发现,缺乏对技术需求微观层次属性的关注是导致技术成果转不出去的重要原因。基于分层次管理理论,从技术需求微观层次视角出发... 技术成果“转出去”是发挥创新驱动效能与缓解技术转移困境的重要举措,其离不开技术需求管理的有效支撑。研究发现,缺乏对技术需求微观层次属性的关注是导致技术成果转不出去的重要原因。基于分层次管理理论,从技术需求微观层次视角出发,构建以技术需求精细化分层体系为核心,以精准识别、分层靶向、精准反馈、精准管理为关键要点的技术转移分层靶向机制。依托知识产权制度保障与大数据驱动的有效支撑,技术转移分层靶向机制可有效促进技术供需主体精准对接,引导技术创新要素分层次组合与配置,更有效地将技术成果“转出去”。 展开更多
关键词 技术转移 分层次管理理论 分层靶向 精准对接
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当量比分层压燃的火焰发展特性与控制机制
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作者 王洋 王安伟 +1 位作者 杨灿 朱宏武 《内燃机学报》 EI CAS CSCD 北大核心 2024年第3期209-215,共7页
针对柴油机当量比分层充量压缩着火的可控性问题,基于OpenFOAM平台构建了一维分层充量自燃及火焰发展的理论模型,在压力为6MPa、温度为850 K工况条件下,研究了当量比分层压缩燃烧过程的基本特征和控制机制,以及当量比分层策略对燃烧过... 针对柴油机当量比分层充量压缩着火的可控性问题,基于OpenFOAM平台构建了一维分层充量自燃及火焰发展的理论模型,在压力为6MPa、温度为850 K工况条件下,研究了当量比分层压缩燃烧过程的基本特征和控制机制,以及当量比分层策略对燃烧过程的调控作用.结果表明:当量比分层压燃早期的组分扩散对化学反应影响较大,中期主要受化学反应和压力波耦合后的共同控制,而后期化学反应和压力波解耦,主要受化学反应控制,压力波影响较小;小负荷工况(整体当量比为0.3)下通过组织合理的充量分层可以使50%放热对应的时间从1.312 ms缩短到0.685 ms,燃烧速度提高近1倍,而大负荷工况(整体当量比为0.7)下可以通过部分分层策略将50%放热对应的时间从0.357 ms延长到0.477 ms. 展开更多
关键词 可控低温 燃烧 当量比分层压燃
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联合比估计法在敏感性问题调查中的应用
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作者 刘媛媛 冀鹏浩 吴国荣 《统计与决策》 北大核心 2024年第8期41-45,共5页
文章基于定性特征敏感性随机化模型——分层抽样下的Warner模型,运用联合比估计法对敏感性问题调查比例的估计量及估计误差进行了理论推导。通过效率比较得出:当各层样本量较大、比估计有效时,联合比估计法的精度优于分层估计法的精度... 文章基于定性特征敏感性随机化模型——分层抽样下的Warner模型,运用联合比估计法对敏感性问题调查比例的估计量及估计误差进行了理论推导。通过效率比较得出:当各层样本量较大、比估计有效时,联合比估计法的精度优于分层估计法的精度。经调查实例验证,上述结论正确。 展开更多
关键词 分层随机抽样 WARNER模型 联合比估计法 敏感属性比例
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机械刻划层分结构铝膜刀具磨损研究
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作者 张宝庆 马群 +3 位作者 安阳杰 吉日嘎兰图 石广丰 吴铁华 《制造技术与机床》 北大核心 2024年第2期111-116,共6页
掌握机刻光栅刀具磨损机理是稳定制备大面积光栅的关键,由镀制工艺决定的具有层分结构铝膜是机刻光栅的首选膜坯。为获取光栅机械刻划过程中层分构铝膜对金刚石刻划刀具磨损影响规律,首次开展层分构铝膜力学性能测试与刀具刻划磨损规律... 掌握机刻光栅刀具磨损机理是稳定制备大面积光栅的关键,由镀制工艺决定的具有层分结构铝膜是机刻光栅的首选膜坯。为获取光栅机械刻划过程中层分构铝膜对金刚石刻划刀具磨损影响规律,首次开展层分构铝膜力学性能测试与刀具刻划磨损规律研究,采用纳米压痕实验测得层分构铝膜硬度与弹性模量分别为0.48 GPa与65.2 GPa,满足Hall-Petch强化理论。据此,首次运用Deform 3D有限元分析软件建立层分构铝膜模型,将刻深位置设置在铝膜层分界面位置,分别对刻深在2μm与4μm的单层与4层铝膜进行刻划仿真后发现,分层膜界面对于其应力传递影响作用明显,且刻深突破第一、二层铝膜界面时,该界面对于应力传递的阻碍作用消失;不同刻深刻划单层和4层铝膜时刀具磨损形式与磨损部位大体相同,但刻划4层铝膜时刀具磨损较小,与后续机刻试验结果相符。 展开更多
关键词 中阶梯光栅 机械刻划 层分结构 铝膜 刀具磨损
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编制价格指数的爬虫数据抽样方法研究
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作者 雷兵 梁凯凯 刘维 《统计与决策》 北大核心 2024年第12期24-28,共5页
文章针对全量爬虫数据编制价格指数成本高的问题,提出了一种抽样方法。该方法采用“大数据—小数据”思想,在基期通过网络爬虫技术全量抓取电商平台的商品交易数据,形成抽样框;在连续性调查中采用抽样技术,根据分层抽样思想,运用聚类算... 文章针对全量爬虫数据编制价格指数成本高的问题,提出了一种抽样方法。该方法采用“大数据—小数据”思想,在基期通过网络爬虫技术全量抓取电商平台的商品交易数据,形成抽样框;在连续性调查中采用抽样技术,根据分层抽样思想,运用聚类算法及其轮廓系数实现总体数据分层,并通过不等概率随机抽样获取各层代表性样本;考虑到连续性调查中入选样本存在无回答现象,提出正式和备选样本思路,针对每个正式样本,采用最近邻匹配法挑选若干个备选样本,当正式样本无回答时,以备选样本作为替补来完成价格指数编制。以天猫商城粮油品类为例进行验证,结果表明:在抓取的数据中,基期全量爬虫数据有18351条,第2—8期连续性调查的平均抽样比为10.18%,抽样的平均相对误差为0.59%,说明该方法是可行的。 展开更多
关键词 价格指数 爬虫数据 分层抽样 聚类算法 样本匹配
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分层一次爆破成井精确延时爆破参数研究
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作者 李祥龙 颜世骞 +2 位作者 王建国 姚永鑫 黄原明 《高压物理学报》 CAS CSCD 北大核心 2024年第2期173-185,共13页
为了研究精确延时微差起爆对一次成井分层爆破效果的影响,理论计算了层内孔间微差时间,利用LS-DYNA软件,采用JH-2岩石模型,模拟了大直径深孔一次成井爆破中的精确延时分层起爆,分析了井筒岩石的损伤演化过程,试验验证了延期时间参数。... 为了研究精确延时微差起爆对一次成井分层爆破效果的影响,理论计算了层内孔间微差时间,利用LS-DYNA软件,采用JH-2岩石模型,模拟了大直径深孔一次成井爆破中的精确延时分层起爆,分析了井筒岩石的损伤演化过程,试验验证了延期时间参数。结果表明,层间采用18 ms延期时间时,爆破效果最佳。结合理论分析和数值模拟结果确定了一次成井的延期时间方案。井筒的成形大致相似,其特征截面面积相似度在83.4%~96.6%之间。通过理论分析、数值模拟和现场试验获得了一次爆破成井工程的精确延时微差分层爆破方法,具有实际应用价值。 展开更多
关键词 一次成井 微差起爆 岩石损伤 分层爆破 精确延时
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