为应对基于游戏的学习平台在知识追踪应用方面的不足,本研究利用Field Day Lab提供的教育游戏用户日志进行深入分析。采用方差法和Null Importance方法对数据集进行降维处理,并结合K折交叉验证与LightGBM算法,建立了一个高效的预测模型...为应对基于游戏的学习平台在知识追踪应用方面的不足,本研究利用Field Day Lab提供的教育游戏用户日志进行深入分析。采用方差法和Null Importance方法对数据集进行降维处理,并结合K折交叉验证与LightGBM算法,建立了一个高效的预测模型。此外,通过集成Logistic模型,构建起Stacking模型。研究表明,该模型在验证集上的Macro-F1值显著提升至0.699,同时也在测试集上显示出优异的泛化能力。本研究为教育游戏领域的知识追踪提供了创新方法,并为游戏开发与教育实践提供了宝贵参考,支持教育游戏的开发者为学生创造更有效的学习体验。展开更多
The acceleration of electrons near three-dimensional(3D)magnetic nulls is crucial to the energy conversion mechanism in the 3D magnetic reconnection process.To explore electron acceleration in a 3D magnetic null topol...The acceleration of electrons near three-dimensional(3D)magnetic nulls is crucial to the energy conversion mechanism in the 3D magnetic reconnection process.To explore electron acceleration in a 3D magnetic null topology,we constructed a pair of 3D magnetic nulls in the PKU Plasma Test(PPT)device and observed acceleration of electrons near magnetic nulls.This study measured the plasma floating potential and ion density profiles around the 3D magnetic null.The potential wells near nulls may be related to the energy variations of electrons,so we measured the electron distribution functions(EDFs)at different spatial positions.The axial variation of EDF shows that the electrons deviate from the Maxwell distribution near magnetic nulls.With scanning probes that can directionally measure and theoretically analyze based on curve fitting,the variations of EDFs are linked to the changes of plasma potential under 3D magnetic null topology.The kinetic energy of electrons accelerated by the electric field is 6 eV(v_(e)~7v_(Alfvén-e))and the scale of the region where accelerating electrons exist is in the order of serval electron skin depths.展开更多
Simultaneously manipulating multiple physical fields plays an important role in the increasingly complex integrated systems,aerospace equipment,biochemical productions,etc.For on-chip systems with high integration lev...Simultaneously manipulating multiple physical fields plays an important role in the increasingly complex integrated systems,aerospace equipment,biochemical productions,etc.For on-chip systems with high integration level,the precise and efficient control of the propagation of electromagnetic waves and heat fluxes simultaneously is particularly important.In this study,we propose a graphical designing method(i.e.,thermal-electromagnetic surface transformation)based on thermal-electromagnetic null medium to simultaneously control the propagation of electromagnetic waves and thermal fields according to the pre-designed paths.A thermal-electromagnetic cloak,which can create a cloaking effect on both electromagnetic waves and thermal fields simultaneously,is designed by thermal-electromagnetic surface transformation and verified by both numerical simulations and experimental measurements.The thermal-electromagnetic surface transformation proposed in this study provides a new methodology for simultaneous controlling on electromagnetic and temperature fields,and may have significant applications in improving thermal-electromagnetic compatibility problem,protecting of thermal-electromagnetic sensitive components,and improving efficiency of energy usage for complex onchip systems.展开更多
Using the Raychaudhuri equation, we associate quantum probability amplitudes (propagators) to equatorial principal ingoing and outgoing null geodesic congruences in the Kerr metric. The expansion scalars diverge at th...Using the Raychaudhuri equation, we associate quantum probability amplitudes (propagators) to equatorial principal ingoing and outgoing null geodesic congruences in the Kerr metric. The expansion scalars diverge at the ring singularity;however, the propagators remain finite, which is an indication that at the quantum level singularities might disappear or, at least, become softened.展开更多
For the anti-interference/denoise purpose,it usually requires minimizing the sidelobe level(SLL)of a wide-beam pattern with a desired low nulling level(NL)in the nulling region.To realize such an objective,the shaped-...For the anti-interference/denoise purpose,it usually requires minimizing the sidelobe level(SLL)of a wide-beam pattern with a desired low nulling level(NL)in the nulling region.To realize such an objective,the shaped-beam pattern synthesis(SBPS)is the most commonly used approach.However,since the SBPS problem focuses on synthesizing a predetermined beam shape,the minimum SLL via this approach cannot ensure to obtain the maximum power gain.Conversely,it cannot obtain the lowest SLL with a certain power gain requirement.Based on such consideration,this paper tries to further minimize SLL of a wide-beam pattern with a desired low NL nulling region,by solving the power gain pattern synthesis(PGPS)problem.The PGPS problem selects the array excitation by directly optimizing the power gain.Hence,it has the potential to reduce SLL,when achieving the equal mainlobe power gain constraint via SBPS.An iterative algorithm which converts the primal optimization problem into convex sub-problems is proposed,resulting in an effective problem-solving scheme.Numerical simulations demonstrate the proposed algorithm can obtain about 10-dB lower SLL than the existing algorithms.展开更多
The timing of flowering is an important driver of species distribution and community assembly patterns.However,we still have much to learn about the factors that shape flowering diversity(i.e.,number of species flower...The timing of flowering is an important driver of species distribution and community assembly patterns.However,we still have much to learn about the factors that shape flowering diversity(i.e.,number of species flowering per period) in plant communities.One potential explanation of flowering diversity is the mid-domain effect,which states that geometric constraints on species ranges within a bounded domain(space or time) will yield a mid-domain peak in diversity regardless of ecological factors.Here,we determine whether the mid-domain effect explains peak flowering time(i.e.,when most species of communities are flowering) across China.We used phenological data of 16,267 herbaceous and woody species from the provincial Flora in China and species distribution data from the Chinese Vascular Plant Distribution Database to determine relationships between the observed number of species flowering and the number of species flowering as predicted by the mid-domain effect model,as well as between three climatic variables(mean minimum monthly temperature,mean monthly precipitation,and mean monthly sunshine duration).We found that the mid-domain effect explained a significant proportion of the temporal variation in flowering diversity across all species in China.Further,the mid-domain effect explained a greater proportion of variance in flowering diversity at higher latitudes than at lower latitudes.The patterns of flowering diversity for both herbaceous and woody species were related to both the mid-domain effect and environmental variables.Our findings indicate that including geometric constraints in conjunction with abiotic and biotic predictors will improve predictions of flowering diversity patterns.展开更多
This paper considers the rational expectations model with multiplicative noise and input delay,where the system dynamics rely on the conditional expectations of future states.The main contribution is to obtain a suffi...This paper considers the rational expectations model with multiplicative noise and input delay,where the system dynamics rely on the conditional expectations of future states.The main contribution is to obtain a sufficient condition for the exact controllability of the rational expectations model.In particular,we derive a sufficient Gramian matrix condition and a rank condition for the delay-free case.The key is the solvability of the backward stochastic difference equations with input delay which is derived from the forward and backward stochastic system.展开更多
The concept of finite null subtractivity of fuzzy measure is introduced. The relations among the several kinds of convergences for sequence of measurable function are discussed by using the new structural characteris...The concept of finite null subtractivity of fuzzy measure is introduced. The relations among the several kinds of convergences for sequence of measurable function are discussed by using the new structural characteristic of fuzzy measure. Egoroff's theorem is further generalized on fuzzy measure space.展开更多
In this paper, we deal with isommetric immersions of globally null warped product manifolds into Lorentzian manifolds with constant curvature c in codimension k≥3. Under the assumptions that the globally null warped ...In this paper, we deal with isommetric immersions of globally null warped product manifolds into Lorentzian manifolds with constant curvature c in codimension k≥3. Under the assumptions that the globally null warped product manifold has no points with the same constant sectional curvature c as the Lorentzian ambient, we show that such isometric immersion splits into warped product of isometric immersions.展开更多
AIM In order to study the association betweenthe null genotypes of GSTM1 and GSTT1 and thegenetic susceptibility to hepatocellularcarcinoma(HCC).METHODS The genotypes of GSTM1 and GSTT1of 63 cases of HCC and 88 contro...AIM In order to study the association betweenthe null genotypes of GSTM1 and GSTT1 and thegenetic susceptibility to hepatocellularcarcinoma(HCC).METHODS The genotypes of GSTM1 and GSTT1of 63 cases of HCC and 88 controls were detectedwith the multiple PCR technique.RESULTS The frequency of GSTM1 nullgenotype was 57.1% among the cases,and42.0% among the controls,the difference beingstatistically significant(χ~2=3.35,P=0.067),but χ~2 value approaching the significance level.The odds ratio was 1.84(95% Cl= 0.91-3.37).The frequency of GSTT1 non-null genotype was87.3% among the cases and 52.5% among thecontrols,the difference being statisticallysignificant(χ~2=11.42,P=0.0007274).The oddsratio was 4.13(95% Cl=1.64-10.70).According to the cross analysis,the GSTT1 non-null genotype was more closely associated withHCC than GSTM1 null genotype,and these twofactors play an approximate additive interactionin the occurrence of HCC.CONCLUSION The persons with GSTM1 nullgenotype and GSTT1 non-null genotype have theincreased risk to HCC.展开更多
Microsatellites were screened in a backcross family of the Pacific oyster, Crassostrea gigas. Fifteen microsatellite loci were distinguishable and polymorphic with 6 types of allele-combinations. Null alleles were det...Microsatellites were screened in a backcross family of the Pacific oyster, Crassostrea gigas. Fifteen microsatellite loci were distinguishable and polymorphic with 6 types of allele-combinations. Null alleles were detected in 46.7% of loci, accounting for 11.7% of the total alleles. Four loci did not segregate in Mendelian Ratios. Three linkage groups were identified among 7 of the 15 segregating loci. Fluorescence-based automated capillary electrophoresis (ABI 310 Genetic Analyzer) that used to detect the microsatellite loci, has been proved a fast, precise, and reliable method in microsatellite genotyping.展开更多
文摘为应对基于游戏的学习平台在知识追踪应用方面的不足,本研究利用Field Day Lab提供的教育游戏用户日志进行深入分析。采用方差法和Null Importance方法对数据集进行降维处理,并结合K折交叉验证与LightGBM算法,建立了一个高效的预测模型。此外,通过集成Logistic模型,构建起Stacking模型。研究表明,该模型在验证集上的Macro-F1值显著提升至0.699,同时也在测试集上显示出优异的泛化能力。本研究为教育游戏领域的知识追踪提供了创新方法,并为游戏开发与教育实践提供了宝贵参考,支持教育游戏的开发者为学生创造更有效的学习体验。
基金supported by National Natural Science Foundation of China(No.11975038)the National Key Research and Development Program of China(No.2022YFA1604600)。
文摘The acceleration of electrons near three-dimensional(3D)magnetic nulls is crucial to the energy conversion mechanism in the 3D magnetic reconnection process.To explore electron acceleration in a 3D magnetic null topology,we constructed a pair of 3D magnetic nulls in the PKU Plasma Test(PPT)device and observed acceleration of electrons near magnetic nulls.This study measured the plasma floating potential and ion density profiles around the 3D magnetic null.The potential wells near nulls may be related to the energy variations of electrons,so we measured the electron distribution functions(EDFs)at different spatial positions.The axial variation of EDF shows that the electrons deviate from the Maxwell distribution near magnetic nulls.With scanning probes that can directionally measure and theoretically analyze based on curve fitting,the variations of EDFs are linked to the changes of plasma potential under 3D magnetic null topology.The kinetic energy of electrons accelerated by the electric field is 6 eV(v_(e)~7v_(Alfvén-e))and the scale of the region where accelerating electrons exist is in the order of serval electron skin depths.
基金supported by the National Natural Science Foundation of China (Nos. 61971300, 12274317, 12374277, 61905208)Open Foundation of China-Belarus Belt and Road Joint Laboratory on Electromagnetic Environment Effect (No. ZBKF2022031202)+1 种基金Scientific and Technological Innovation Programs (STIP) of Higher Education Institutions in Shanxi (Nos. 2019L0159 and 2019L0146)2022 University Outstanding Youth Foundation of Taiyuan University of Technology
文摘Simultaneously manipulating multiple physical fields plays an important role in the increasingly complex integrated systems,aerospace equipment,biochemical productions,etc.For on-chip systems with high integration level,the precise and efficient control of the propagation of electromagnetic waves and heat fluxes simultaneously is particularly important.In this study,we propose a graphical designing method(i.e.,thermal-electromagnetic surface transformation)based on thermal-electromagnetic null medium to simultaneously control the propagation of electromagnetic waves and thermal fields according to the pre-designed paths.A thermal-electromagnetic cloak,which can create a cloaking effect on both electromagnetic waves and thermal fields simultaneously,is designed by thermal-electromagnetic surface transformation and verified by both numerical simulations and experimental measurements.The thermal-electromagnetic surface transformation proposed in this study provides a new methodology for simultaneous controlling on electromagnetic and temperature fields,and may have significant applications in improving thermal-electromagnetic compatibility problem,protecting of thermal-electromagnetic sensitive components,and improving efficiency of energy usage for complex onchip systems.
文摘Using the Raychaudhuri equation, we associate quantum probability amplitudes (propagators) to equatorial principal ingoing and outgoing null geodesic congruences in the Kerr metric. The expansion scalars diverge at the ring singularity;however, the propagators remain finite, which is an indication that at the quantum level singularities might disappear or, at least, become softened.
基金supported by the Natural Science Foundation of Sichuan Province under Grant No.2022NSFSC0564the National Natural Science Foundation of China under Grants No.U20B2043 and No.62001095.
文摘For the anti-interference/denoise purpose,it usually requires minimizing the sidelobe level(SLL)of a wide-beam pattern with a desired low nulling level(NL)in the nulling region.To realize such an objective,the shaped-beam pattern synthesis(SBPS)is the most commonly used approach.However,since the SBPS problem focuses on synthesizing a predetermined beam shape,the minimum SLL via this approach cannot ensure to obtain the maximum power gain.Conversely,it cannot obtain the lowest SLL with a certain power gain requirement.Based on such consideration,this paper tries to further minimize SLL of a wide-beam pattern with a desired low NL nulling region,by solving the power gain pattern synthesis(PGPS)problem.The PGPS problem selects the array excitation by directly optimizing the power gain.Hence,it has the potential to reduce SLL,when achieving the equal mainlobe power gain constraint via SBPS.An iterative algorithm which converts the primal optimization problem into convex sub-problems is proposed,resulting in an effective problem-solving scheme.Numerical simulations demonstrate the proposed algorithm can obtain about 10-dB lower SLL than the existing algorithms.
基金supported by the National Natural Science Foundation of China (Grant number 42261004)supported by the Jiangsu Social Development Project (BE2022792)。
文摘The timing of flowering is an important driver of species distribution and community assembly patterns.However,we still have much to learn about the factors that shape flowering diversity(i.e.,number of species flowering per period) in plant communities.One potential explanation of flowering diversity is the mid-domain effect,which states that geometric constraints on species ranges within a bounded domain(space or time) will yield a mid-domain peak in diversity regardless of ecological factors.Here,we determine whether the mid-domain effect explains peak flowering time(i.e.,when most species of communities are flowering) across China.We used phenological data of 16,267 herbaceous and woody species from the provincial Flora in China and species distribution data from the Chinese Vascular Plant Distribution Database to determine relationships between the observed number of species flowering and the number of species flowering as predicted by the mid-domain effect model,as well as between three climatic variables(mean minimum monthly temperature,mean monthly precipitation,and mean monthly sunshine duration).We found that the mid-domain effect explained a significant proportion of the temporal variation in flowering diversity across all species in China.Further,the mid-domain effect explained a greater proportion of variance in flowering diversity at higher latitudes than at lower latitudes.The patterns of flowering diversity for both herbaceous and woody species were related to both the mid-domain effect and environmental variables.Our findings indicate that including geometric constraints in conjunction with abiotic and biotic predictors will improve predictions of flowering diversity patterns.
基金supported by the National Natural Science Foundation of China under Grants 61821004,62250056,62350710214,U23A20325,62350055the Natural Science Foundation of Shandong Province,China(ZR2021ZD14,ZR2021JQ24)+2 种基金High-level Talent Team Project of Qingdao West Coast New Area,China(RCTD-JC-2019-05)Key Research and Development Program of Shandong Province,China(2020CXGC01208)Science and Technology Project of Qingdao West Coast New Area,China(2019-32,2020-20,2020-1-4).
文摘This paper considers the rational expectations model with multiplicative noise and input delay,where the system dynamics rely on the conditional expectations of future states.The main contribution is to obtain a sufficient condition for the exact controllability of the rational expectations model.In particular,we derive a sufficient Gramian matrix condition and a rank condition for the delay-free case.The key is the solvability of the backward stochastic difference equations with input delay which is derived from the forward and backward stochastic system.
文摘The concept of finite null subtractivity of fuzzy measure is introduced. The relations among the several kinds of convergences for sequence of measurable function are discussed by using the new structural characteristic of fuzzy measure. Egoroff's theorem is further generalized on fuzzy measure space.
文摘In this paper, we deal with isommetric immersions of globally null warped product manifolds into Lorentzian manifolds with constant curvature c in codimension k≥3. Under the assumptions that the globally null warped product manifold has no points with the same constant sectional curvature c as the Lorentzian ambient, we show that such isometric immersion splits into warped product of isometric immersions.
基金the National Natural Science Foundation of China,No.39470628the Scientific Foundation of Ministry of Health,China,No.96-1-189
文摘AIM In order to study the association betweenthe null genotypes of GSTM1 and GSTT1 and thegenetic susceptibility to hepatocellularcarcinoma(HCC).METHODS The genotypes of GSTM1 and GSTT1of 63 cases of HCC and 88 controls were detectedwith the multiple PCR technique.RESULTS The frequency of GSTM1 nullgenotype was 57.1% among the cases,and42.0% among the controls,the difference beingstatistically significant(χ~2=3.35,P=0.067),but χ~2 value approaching the significance level.The odds ratio was 1.84(95% Cl= 0.91-3.37).The frequency of GSTT1 non-null genotype was87.3% among the cases and 52.5% among thecontrols,the difference being statisticallysignificant(χ~2=11.42,P=0.0007274).The oddsratio was 4.13(95% Cl=1.64-10.70).According to the cross analysis,the GSTT1 non-null genotype was more closely associated withHCC than GSTM1 null genotype,and these twofactors play an approximate additive interactionin the occurrence of HCC.CONCLUSION The persons with GSTM1 nullgenotype and GSTT1 non-null genotype have theincreased risk to HCC.
基金Supported by the National Natural Science Foundation of China (NO.40730845, 39825121)
文摘Microsatellites were screened in a backcross family of the Pacific oyster, Crassostrea gigas. Fifteen microsatellite loci were distinguishable and polymorphic with 6 types of allele-combinations. Null alleles were detected in 46.7% of loci, accounting for 11.7% of the total alleles. Four loci did not segregate in Mendelian Ratios. Three linkage groups were identified among 7 of the 15 segregating loci. Fluorescence-based automated capillary electrophoresis (ABI 310 Genetic Analyzer) that used to detect the microsatellite loci, has been proved a fast, precise, and reliable method in microsatellite genotyping.
