Kagome materials are a class of material with a lattice structure composed of corner-sharing triangles that produce various exotic electronic phenomena,such as Dirac fermions,van Hove singularities,and flat bands.Howe...Kagome materials are a class of material with a lattice structure composed of corner-sharing triangles that produce various exotic electronic phenomena,such as Dirac fermions,van Hove singularities,and flat bands.However,most of the known kagome materials have a flat band detached from the Fermi energy,which limits the investigation of the emergent flat band physics.In this work,by combining soft x-ray angle-resolved photoemission spectroscopy(ARPES)and the first-principles calculations,the electronic structure is investigated of a novel kagome metal CeNi_(5) with a clear dispersion along the kz direction and a Fermi level flat band in theΓ–K–M–Γplane.Besides,resonant ARPES experimental results indicate that the valence state of Ce ions is close to 4^(+),which is consistent with the transport measurement result.Our results demonstrate the unique electronic properties of CeNi_(5) as a new kagome metal and provide an ideal platform for exploring the flat band physics and the interactions between different types of flat bands by tuning the valence state of Ce ions.展开更多
The In segregation and its suppression in InGaAs/AlGaAs quantum well are investigated by using high-resolution x-ray diffraction(XRD)and photoluminescence(PL),combined with the state-of-the-art aberration corrected sc...The In segregation and its suppression in InGaAs/AlGaAs quantum well are investigated by using high-resolution x-ray diffraction(XRD)and photoluminescence(PL),combined with the state-of-the-art aberration corrected scanning transmission electron microscopy(Cs-STEM)techniques.To facility our study,we grow two multiple quantum wells(MQWs)samples,which are almost identical except that in sample B a thin GaAs layer is inserted in each of the InGaAs well and AlGaAs barrier layer comparing to pristine InGaAs/AlGaAs MQWs(sample A).Our study indeed shows the direct evidences that In segregation occurs in the InGaAs/AlGaAs interface,and the effect of the Ga As insertion layer on suppressing the segregation of In atoms is also demonstrated on the atomic-scale.Therefore,the atomic-scale insights are provided to understand the segregation behavior of In atoms and to unravel the underlying mechanism of the effect of GaAs insertion layer on the improvement of crystallinity,interface roughness,and further an enhanced optical performance of InGaAs/AlGaAs QWs.展开更多
Post-processing correction is an effective way to improve the model forecasting result. Especially, the machine learning methods have played increasingly important roles in recent years. Taking the meteorological obse...Post-processing correction is an effective way to improve the model forecasting result. Especially, the machine learning methods have played increasingly important roles in recent years. Taking the meteorological observational data in a period of two years as the reference, the maximum and minimum temperature predictions of Shenyang station from the European Center for Medium-Range Weather Forecasts (ECMWF) and national intelligent grid forecasts are objectively corrected by using wavelet analysis, sliding training and other technologies. The evaluation results show that the sliding training time window of the maximum temperature is smaller than that of the minimum temperature, and their difference is the largest in August, with a difference of 2.6 days. The objective correction product of maximum temperature shows a good performance in spring, while that of minimum temperature performs well throughout the whole year, with an accuracy improvement of 97% to 186%. The correction effect in the central plains is better than in the regions with complex terrain. As for the national intelligent grid forecasts, the objective correction products have shown positive skills in predicting the maximum temperatures in spring (the skill-score reaches 0.59) and in predicting the minimum temperature at most times of the year (the skill-score reaches 0.68).展开更多
Two-dimensional honeycomb lattices show great potential in the realization of Dirac nodal line fermions(DNLFs).Here,we successfully synthesized a gold telluride(AuTe)monolayer by direct tellurizing an Au(111)substrate...Two-dimensional honeycomb lattices show great potential in the realization of Dirac nodal line fermions(DNLFs).Here,we successfully synthesized a gold telluride(AuTe)monolayer by direct tellurizing an Au(111)substrate.Low energy electron diffraction measurements reveal that it is(2×2)AuTe layer stacked onto(3×3)Au(111)substrate.Moreover,scanning tunneling microscopy images show that the AuTe layer has a honeycomb structure.Scanning transmission electron microscopy reveals that it is a single-atom layer.In addition,first-principles calculations demonstrate that the honeycomb AuTe monolayer exhibits Dirac nodal line features protected by mirror symmetry,which is validated by angle-resolved photoemission spectra.Our results establish that monolayer AuTe can be a good candidate to investigate 2D DNLFs and provides opportunities to realize high-speed low-dissipation devices.展开更多
Bismuth(Bi)-doped near-infared(NIR)glass that can cover the entire optical communication window(850,1310,and1550 nm)has become the subject of extensive research for developing photonic devices,particularly,tunable fib...Bismuth(Bi)-doped near-infared(NIR)glass that can cover the entire optical communication window(850,1310,and1550 nm)has become the subject of extensive research for developing photonic devices,particularly,tunable fiber lasers and ultrabroadband optical amplifiers.However,the realization of highly efficient NIR luminescence from Bi-doped glass is still full of challenges.Notably,due to the co-existence of multiple Bi NIR centers in the glass,the origin of newly generated Bi NIR emission peaks at~930 and~1520 nm is still controversial.Here,we report a new Bi-doped nitridated germanate glass with tunable ultrabroadband NIR emission(850–1700 nm)and high external quantum efficiency(EQE)of~50%.A series of studies,including spectral analysis,nuclear magnetic resonance(NMR),and others,provide powerful evidence for the mechanism of luminescence enhancement and tunability,and make reasonable inferences about the origin of the new emission bands at~930 and~1520 nm.We believe that the results discussed above would enrich our understanding about multiple Bi NIR emission behaviors and contribute to the design and fabrication of highly efficient Bi-doped ultrabroadband wavelength-tunable optical glass fiber amplifiers and lasers in the future.展开更多
近年来,在医药卫生领域,利用真实世界数据生成真实世界证据的研究方法在药品研发、审批、适应证拓展等领域取得广泛的关注和认可,开展真实可信、高质量的真实世界研究证据(real world evidence,RWE),已成为循证医学的一个重要发展方向...近年来,在医药卫生领域,利用真实世界数据生成真实世界证据的研究方法在药品研发、审批、适应证拓展等领域取得广泛的关注和认可,开展真实可信、高质量的真实世界研究证据(real world evidence,RWE),已成为循证医学的一个重要发展方向。本文介绍了近年来国内外关于结直肠癌真实世界研究的现状,将真实世界研究(real world research/study,RWS)与相应的随机对照研究(randomized controlled trial,RCT)的meta分析结果进行对比和评价,以阐述RWS的特征、研究方法、相对于传统RCT研究的优势,并归纳其在肠癌领域的应用现状。在此基础上,对RWS在结直肠癌临床研究中的价值和前景进行总结,为后续研究提供新的思路。展开更多
Studies on the kinetics of gas-phase chemical reactions currently rely on calculations or simulations and lack simple,fast,and accurate direct measurement methods.We developed a tunable laser molecular absorption spec...Studies on the kinetics of gas-phase chemical reactions currently rely on calculations or simulations and lack simple,fast,and accurate direct measurement methods.We developed a tunable laser molecular absorption spectroscopy measurement system to achieve direct measurements of such reactions by using wavelength modulated spectroscopy and performed online measurements and diagnostics of molecular concentration,reaction temperature,and pressure change during the redox reaction of ozone with nitrogen oxides(NOx)with 0.1 s temporal resolution.This study provides a promising diagnostic tool for studying gas-phase chemical reaction kinetics.展开更多
The Goodgrant Foundation is a charitable organization that wants to improve education performance of undergraduates attending colleges and universities in the US. So the foundation plans to contribute a total of US 50...The Goodgrant Foundation is a charitable organization that wants to improve education performance of undergraduates attending colleges and universities in the US. So the foundation plans to contribute a total of US 50 million for a suitable team of schools per year under the condition of avoiding repeated other large grant organizations’ investment. The DEA (Data Estimate Analysis) model is developed to determine an optimal investment strategy for the Goodgrant Foundation. In this paper, two questions were solved: how to choose a suitable team of schools and how to allocate the investment. Before the establishment of the model, the EXCEL software is used to preprocess data. Then the DEA model which includes two models in the paper is developed. For the first question, the CCR model is established to rank schools which used efficiency from DEAP 2.1. For the second question, the resource allocation model is established to allocate investment amount by weights of allocation from MATLAB software. Accordingly, the optimal investment strategy is received for the Goodgrant Foundation. Through the analysis above, 23 from 293 schools are selected to invest. Then the schools are ranked and the investment of US 50 million for 23 schools is allocated.展开更多
基金supported by the National Key R&D Program of China(2022YFA1403500,2018YFA0703700,2022YFA1405600,and 2021YFA1202900)the National Natural Science Foundation of China(52025023,12274456,51991342,52021006,92163206,11888101,T2188101,12104018,52250398,52203331,and 91964203)+2 种基金Guangdong Major Project of Basic and Applied Basic Research(2021B0301030002)the Strategic Priority Research Program of Chinese Academy of Sciences(XDB33000000)Beijing Municipal Science and Technology Project(Z221100005822003)。
基金Project support by the Science Fund from Shanghai Committee of Science and Technology,China (Grant No.23JC1403300)the Shanghai Municipal Science and Technology Major Project,China+3 种基金the TDLI Starting up Grant,the National Natural Science Foundation of China (Grant Nos.12374063,12204223,and 23Z990202580)the Fund from the Ministry of Science and Technology of China (Grant No.2023YFA1407400)the Shanghai Natural Science Fund for Original Exploration Program,China (Grant No.23ZR1479900)Shanghai Talent Program,China。
文摘Kagome materials are a class of material with a lattice structure composed of corner-sharing triangles that produce various exotic electronic phenomena,such as Dirac fermions,van Hove singularities,and flat bands.However,most of the known kagome materials have a flat band detached from the Fermi energy,which limits the investigation of the emergent flat band physics.In this work,by combining soft x-ray angle-resolved photoemission spectroscopy(ARPES)and the first-principles calculations,the electronic structure is investigated of a novel kagome metal CeNi_(5) with a clear dispersion along the kz direction and a Fermi level flat band in theΓ–K–M–Γplane.Besides,resonant ARPES experimental results indicate that the valence state of Ce ions is close to 4^(+),which is consistent with the transport measurement result.Our results demonstrate the unique electronic properties of CeNi_(5) as a new kagome metal and provide an ideal platform for exploring the flat band physics and the interactions between different types of flat bands by tuning the valence state of Ce ions.
基金X.H.gratefully acknowledges the financial support from the National Natural Science Foundation of China(Grant No.21902096)the Scientific Research Foundation of Shaanxi University of Science and Technology(Grant No.126061803)+1 种基金S.M.and B.X.thank the National Natural Science Foundation of China(Grant No.21972103)the Shanxi Provincial Key Innovative Research Team in Science and Technology(Grant No.201703D111026).
文摘The In segregation and its suppression in InGaAs/AlGaAs quantum well are investigated by using high-resolution x-ray diffraction(XRD)and photoluminescence(PL),combined with the state-of-the-art aberration corrected scanning transmission electron microscopy(Cs-STEM)techniques.To facility our study,we grow two multiple quantum wells(MQWs)samples,which are almost identical except that in sample B a thin GaAs layer is inserted in each of the InGaAs well and AlGaAs barrier layer comparing to pristine InGaAs/AlGaAs MQWs(sample A).Our study indeed shows the direct evidences that In segregation occurs in the InGaAs/AlGaAs interface,and the effect of the Ga As insertion layer on suppressing the segregation of In atoms is also demonstrated on the atomic-scale.Therefore,the atomic-scale insights are provided to understand the segregation behavior of In atoms and to unravel the underlying mechanism of the effect of GaAs insertion layer on the improvement of crystallinity,interface roughness,and further an enhanced optical performance of InGaAs/AlGaAs QWs.
文摘Post-processing correction is an effective way to improve the model forecasting result. Especially, the machine learning methods have played increasingly important roles in recent years. Taking the meteorological observational data in a period of two years as the reference, the maximum and minimum temperature predictions of Shenyang station from the European Center for Medium-Range Weather Forecasts (ECMWF) and national intelligent grid forecasts are objectively corrected by using wavelet analysis, sliding training and other technologies. The evaluation results show that the sliding training time window of the maximum temperature is smaller than that of the minimum temperature, and their difference is the largest in August, with a difference of 2.6 days. The objective correction product of maximum temperature shows a good performance in spring, while that of minimum temperature performs well throughout the whole year, with an accuracy improvement of 97% to 186%. The correction effect in the central plains is better than in the regions with complex terrain. As for the national intelligent grid forecasts, the objective correction products have shown positive skills in predicting the maximum temperatures in spring (the skill-score reaches 0.59) and in predicting the minimum temperature at most times of the year (the skill-score reaches 0.68).
基金Project supported by the National Key R&D Program of China (Grant No.2018YFA0305800)the National Natural Science Foundation of China (Grant Nos.61925111,61888102,and 52102193)+2 种基金the Strategic Priority Research Program of Chinese Academy of Sciences (Grant Nos.XDB28000000 and XDB30000000)CAS Project for Young Scientists in Basic Research (Grant No.YSBR-003)the Fundamental Research Funds for the Central Universities。
文摘Two-dimensional honeycomb lattices show great potential in the realization of Dirac nodal line fermions(DNLFs).Here,we successfully synthesized a gold telluride(AuTe)monolayer by direct tellurizing an Au(111)substrate.Low energy electron diffraction measurements reveal that it is(2×2)AuTe layer stacked onto(3×3)Au(111)substrate.Moreover,scanning tunneling microscopy images show that the AuTe layer has a honeycomb structure.Scanning transmission electron microscopy reveals that it is a single-atom layer.In addition,first-principles calculations demonstrate that the honeycomb AuTe monolayer exhibits Dirac nodal line features protected by mirror symmetry,which is validated by angle-resolved photoemission spectra.Our results establish that monolayer AuTe can be a good candidate to investigate 2D DNLFs and provides opportunities to realize high-speed low-dissipation devices.
基金supported by the National Key R&D Program of China(No.2021YFB2800500)the Research Program of Zhejiang Lab(No.113014-AC2101)+1 种基金the National Natural Science Foundation of China(Nos.51872095,U20A20211,and 62105297)the Zhejiang Provincial Natural Science Foundation(Nos.LQ22A040011 and LZ23F050002)。
文摘Bismuth(Bi)-doped near-infared(NIR)glass that can cover the entire optical communication window(850,1310,and1550 nm)has become the subject of extensive research for developing photonic devices,particularly,tunable fiber lasers and ultrabroadband optical amplifiers.However,the realization of highly efficient NIR luminescence from Bi-doped glass is still full of challenges.Notably,due to the co-existence of multiple Bi NIR centers in the glass,the origin of newly generated Bi NIR emission peaks at~930 and~1520 nm is still controversial.Here,we report a new Bi-doped nitridated germanate glass with tunable ultrabroadband NIR emission(850–1700 nm)and high external quantum efficiency(EQE)of~50%.A series of studies,including spectral analysis,nuclear magnetic resonance(NMR),and others,provide powerful evidence for the mechanism of luminescence enhancement and tunability,and make reasonable inferences about the origin of the new emission bands at~930 and~1520 nm.We believe that the results discussed above would enrich our understanding about multiple Bi NIR emission behaviors and contribute to the design and fabrication of highly efficient Bi-doped ultrabroadband wavelength-tunable optical glass fiber amplifiers and lasers in the future.
文摘近年来,在医药卫生领域,利用真实世界数据生成真实世界证据的研究方法在药品研发、审批、适应证拓展等领域取得广泛的关注和认可,开展真实可信、高质量的真实世界研究证据(real world evidence,RWE),已成为循证医学的一个重要发展方向。本文介绍了近年来国内外关于结直肠癌真实世界研究的现状,将真实世界研究(real world research/study,RWS)与相应的随机对照研究(randomized controlled trial,RCT)的meta分析结果进行对比和评价,以阐述RWS的特征、研究方法、相对于传统RCT研究的优势,并归纳其在肠癌领域的应用现状。在此基础上,对RWS在结直肠癌临床研究中的价值和前景进行总结,为后续研究提供新的思路。
基金supported in part by the National Natural Science Foundation of China(No.52176064)Tianjin Natural Science Foundation(No.20JCYBJC00160).
文摘Studies on the kinetics of gas-phase chemical reactions currently rely on calculations or simulations and lack simple,fast,and accurate direct measurement methods.We developed a tunable laser molecular absorption spectroscopy measurement system to achieve direct measurements of such reactions by using wavelength modulated spectroscopy and performed online measurements and diagnostics of molecular concentration,reaction temperature,and pressure change during the redox reaction of ozone with nitrogen oxides(NOx)with 0.1 s temporal resolution.This study provides a promising diagnostic tool for studying gas-phase chemical reaction kinetics.
文摘The Goodgrant Foundation is a charitable organization that wants to improve education performance of undergraduates attending colleges and universities in the US. So the foundation plans to contribute a total of US 50 million for a suitable team of schools per year under the condition of avoiding repeated other large grant organizations’ investment. The DEA (Data Estimate Analysis) model is developed to determine an optimal investment strategy for the Goodgrant Foundation. In this paper, two questions were solved: how to choose a suitable team of schools and how to allocate the investment. Before the establishment of the model, the EXCEL software is used to preprocess data. Then the DEA model which includes two models in the paper is developed. For the first question, the CCR model is established to rank schools which used efficiency from DEAP 2.1. For the second question, the resource allocation model is established to allocate investment amount by weights of allocation from MATLAB software. Accordingly, the optimal investment strategy is received for the Goodgrant Foundation. Through the analysis above, 23 from 293 schools are selected to invest. Then the schools are ranked and the investment of US 50 million for 23 schools is allocated.
