The start-up process of Stokes＇ second problem of a viscoelastic material with fractional element is studied. The fluid above an infinite flat plane is set in motion by a sudden acceleration of the plate to steady os...The start-up process of Stokes＇ second problem of a viscoelastic material with fractional element is studied. The fluid above an infinite flat plane is set in motion by a sudden acceleration of the plate to steady oscillation. Exact solutions are obtained by using Laplace transform and Fourier transform. It is found that the relationship between the first peak value and the one of equal-amplitude oscillations depends on the distance from the plate. The amplitude decreases for increasing frequency and increasing distance.展开更多
Four phenoxysilicon networks for nonlinear optical (NLO) applications were designed and prepared by an extended sol-gel process without additional H2O and catalyst. All poled polymer network films possess high second-...Four phenoxysilicon networks for nonlinear optical (NLO) applications were designed and prepared by an extended sol-gel process without additional H2O and catalyst. All poled polymer network films possess high second-order nonlinear optical coefficients (d(33)) Of 10(-7)similar to 10(-8) esu. The investigation of NLO temporal stability at room temperature and elevated temperature (120 degreesC) indicated that these films exhibit high d(33) stability because the orientation of the chromophores are locked in the phenoxysilicon organic/inorganic networks.展开更多
This paper studies the type-I phase-matched second harmonic generation using 25-fs input laser pulses in a thick BBO crystal. The harmonic signal exhibits a narrow spectrum bandwidth, even though the input pulse has a...This paper studies the type-I phase-matched second harmonic generation using 25-fs input laser pulses in a thick BBO crystal. The harmonic signal exhibits a narrow spectrum bandwidth, even though the input pulse has a broad bandwidth. The energy transfer efficiency and modulation of the fundamental spectrum are investigated.展开更多
In this article, we consider the long time behavior of the solutions to stochastic wave equations driven by a non-Gaussian Lévy process. We shall prove that under some appropriate conditions, the exponential stab...In this article, we consider the long time behavior of the solutions to stochastic wave equations driven by a non-Gaussian Lévy process. We shall prove that under some appropriate conditions, the exponential stability of the solutions holds. Finally, we give two examples to illustrate our results.展开更多
Nonlinear cascaded femtosecond third harmonic generation was experimentally investigated pumped by 100 fs pulses at optical communication band 1550 nm using a multi-grating 5 mol. % MgO-doped periodically poled lithiu...Nonlinear cascaded femtosecond third harmonic generation was experimentally investigated pumped by 100 fs pulses at optical communication band 1550 nm using a multi-grating 5 mol. % MgO-doped periodically poled lithium niobate crystal. The optimized efficiency of 10.8% was achieved with the simultaneous phase-matching of the second harmonic and sum frequency process. And the third harmonic spectrum reached as broad as 8.7 nm because of the choosing of a small group velocity mismatching between the fundamental and second harmonic pulses. Nonlinear cascaded method will provide a reference for the efficient frequency conversion in the high intensity range.展开更多
为进一步提高温度业务预报水平,本文采用美国国家环境预报中心环境模式中心(National Centers for Environmental Prediction-Environmental Modeling Center,NCEP-EMC)研发的基于递归贝叶斯模型过程(recursive Bayesian model process,...为进一步提高温度业务预报水平,本文采用美国国家环境预报中心环境模式中心(National Centers for Environmental Prediction-Environmental Modeling Center,NCEP-EMC)研发的基于递归贝叶斯模型过程(recursive Bayesian model process,RBMP)的多模式集合技术,开展了华东2 m温度预报试验。利用2016—2017年欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF)、NCEP和加拿大气象中心(Canadian Meteorological Centre,CMC)3个具有代表性的全球集合预报系统产品,在对各模式进行偏差订正的基础上,开展了RBMP算法应用试验和评估,建立了华东地区应用方案,再利用2019年9月—2020年5月ECMWF、NCEP集合预报资料开展试运行,初步讨论了RBMP方法在冬春季节预报失败案例中的适用性。结果表明:RBMP方法能够提供更加可靠的概率预报分布并有效提高短期时效的预报技巧。其中,冬季改进最明显,集合平均的均方根误差比ECMWF订正预报和等权重多模式集合分别降低3.0%~10.5%和2.0%~5.0%,且对高温和低温事件均具有更优的分辨能力。此外,RBMP方法还能够提高大部分预报失败案例的预报准确率,为难报案例提供了有价值的不确定信息。总体而言,RBMP技术不仅保留了BMA(Bayesian model averaging)方法的优势,且能满足业务应用对资料存储和计算效率的需求,通过二阶矩调整可以有效校正集合离散度,为进一步提高短期温度预报技巧提供了一种思路。展开更多
为探究废食用油(waste cooking oil,WCO)两段式工艺(先生成脂肪酸甲酯后生成烷烃)在中国落地建厂的可行性,该研究基于中国本土数据天工数据库v0.2.0,通过生命周期评价软件openLCA 2.4.0进行工艺的环境评估研究。通过WCO收集与运输、预酯...为探究废食用油(waste cooking oil,WCO)两段式工艺(先生成脂肪酸甲酯后生成烷烃)在中国落地建厂的可行性,该研究基于中国本土数据天工数据库v0.2.0,通过生命周期评价软件openLCA 2.4.0进行工艺的环境评估研究。通过WCO收集与运输、预酯化/酯交换、加氢脱氧/临氢异构3个阶段模拟WCO基第二代生物柴油生产的整个生命周期。研究结果表明:WCO基第二代生物柴油生产工艺的全球变暖(CO_(2)排放量)、细颗粒物形成(PM2.5排放量)和陆地酸化(SO_(2)排放量)3个中间点指标分别为506.78 kg/t(10.93 kg/GJ)、0.04 kg/t(8.63×10^(-4) kg/GJ)和0.14 kg/t(3.02×10^(-3) kg/GJ),加氢脱氧/临氢异构阶段分别占整个工艺相应总值的55.73%、56.69%和58.00%。1 t WCO基第二代生物柴油生产工艺对人类健康(伤残调整生命年(disability-adjusted life year,DALY))、生态系统(物种年损失值(loss of species in a year,species.yr))和资源(CNY)的终点指标数值分别为4.97×10^(-4)、-1.75×10^(-5)和-12.39。与化石柴油相比,该工艺生产的第二代生物柴油具有很好的环境优势。后续工艺的改良措施需要关注降低整个工艺中涉及到的含氯和溴的气体排放,以及温室气体的排放。展开更多
文摘The start-up process of Stokes＇ second problem of a viscoelastic material with fractional element is studied. The fluid above an infinite flat plane is set in motion by a sudden acceleration of the plate to steady oscillation. Exact solutions are obtained by using Laplace transform and Fourier transform. It is found that the relationship between the first peak value and the one of equal-amplitude oscillations depends on the distance from the plate. The amplitude decreases for increasing frequency and increasing distance.
文摘Four phenoxysilicon networks for nonlinear optical (NLO) applications were designed and prepared by an extended sol-gel process without additional H2O and catalyst. All poled polymer network films possess high second-order nonlinear optical coefficients (d(33)) Of 10(-7)similar to 10(-8) esu. The investigation of NLO temporal stability at room temperature and elevated temperature (120 degreesC) indicated that these films exhibit high d(33) stability because the orientation of the chromophores are locked in the phenoxysilicon organic/inorganic networks.
基金Project supported by the National Basic Research Program of China (Grant No. 2006CB806007)the National Natural Science Foundation of China (Grant Nos. 10574006,10634020 and 10821062)
文摘This paper studies the type-I phase-matched second harmonic generation using 25-fs input laser pulses in a thick BBO crystal. The harmonic signal exhibits a narrow spectrum bandwidth, even though the input pulse has a broad bandwidth. The energy transfer efficiency and modulation of the fundamental spectrum are investigated.
基金supported by National Natural Science Foundation of China(11571190)the Fundamental Research Funds for the Central Universities+3 种基金supported by the China Scholarship Council(201807315008)National Natural Science Foundation of China(11501565)the Youth Project of Humanities and Social Sciences of Ministry of Education(19YJCZH251)supported by National Natural Science Foundation of China(11701084 and 11671084)
文摘In this article, we consider the long time behavior of the solutions to stochastic wave equations driven by a non-Gaussian Lévy process. We shall prove that under some appropriate conditions, the exponential stability of the solutions holds. Finally, we give two examples to illustrate our results.
文摘Nonlinear cascaded femtosecond third harmonic generation was experimentally investigated pumped by 100 fs pulses at optical communication band 1550 nm using a multi-grating 5 mol. % MgO-doped periodically poled lithium niobate crystal. The optimized efficiency of 10.8% was achieved with the simultaneous phase-matching of the second harmonic and sum frequency process. And the third harmonic spectrum reached as broad as 8.7 nm because of the choosing of a small group velocity mismatching between the fundamental and second harmonic pulses. Nonlinear cascaded method will provide a reference for the efficient frequency conversion in the high intensity range.
文摘为进一步提高温度业务预报水平,本文采用美国国家环境预报中心环境模式中心(National Centers for Environmental Prediction-Environmental Modeling Center,NCEP-EMC)研发的基于递归贝叶斯模型过程(recursive Bayesian model process,RBMP)的多模式集合技术,开展了华东2 m温度预报试验。利用2016—2017年欧洲中期天气预报中心(European Centre for Medium-Range Weather Forecasts,ECMWF)、NCEP和加拿大气象中心(Canadian Meteorological Centre,CMC)3个具有代表性的全球集合预报系统产品,在对各模式进行偏差订正的基础上,开展了RBMP算法应用试验和评估,建立了华东地区应用方案,再利用2019年9月—2020年5月ECMWF、NCEP集合预报资料开展试运行,初步讨论了RBMP方法在冬春季节预报失败案例中的适用性。结果表明:RBMP方法能够提供更加可靠的概率预报分布并有效提高短期时效的预报技巧。其中,冬季改进最明显,集合平均的均方根误差比ECMWF订正预报和等权重多模式集合分别降低3.0%~10.5%和2.0%~5.0%,且对高温和低温事件均具有更优的分辨能力。此外,RBMP方法还能够提高大部分预报失败案例的预报准确率,为难报案例提供了有价值的不确定信息。总体而言,RBMP技术不仅保留了BMA(Bayesian model averaging)方法的优势,且能满足业务应用对资料存储和计算效率的需求,通过二阶矩调整可以有效校正集合离散度,为进一步提高短期温度预报技巧提供了一种思路。
文摘为探究废食用油(waste cooking oil,WCO)两段式工艺(先生成脂肪酸甲酯后生成烷烃)在中国落地建厂的可行性,该研究基于中国本土数据天工数据库v0.2.0,通过生命周期评价软件openLCA 2.4.0进行工艺的环境评估研究。通过WCO收集与运输、预酯化/酯交换、加氢脱氧/临氢异构3个阶段模拟WCO基第二代生物柴油生产的整个生命周期。研究结果表明:WCO基第二代生物柴油生产工艺的全球变暖(CO_(2)排放量)、细颗粒物形成(PM2.5排放量)和陆地酸化(SO_(2)排放量)3个中间点指标分别为506.78 kg/t(10.93 kg/GJ)、0.04 kg/t(8.63×10^(-4) kg/GJ)和0.14 kg/t(3.02×10^(-3) kg/GJ),加氢脱氧/临氢异构阶段分别占整个工艺相应总值的55.73%、56.69%和58.00%。1 t WCO基第二代生物柴油生产工艺对人类健康(伤残调整生命年(disability-adjusted life year,DALY))、生态系统(物种年损失值(loss of species in a year,species.yr))和资源(CNY)的终点指标数值分别为4.97×10^(-4)、-1.75×10^(-5)和-12.39。与化石柴油相比,该工艺生产的第二代生物柴油具有很好的环境优势。后续工艺的改良措施需要关注降低整个工艺中涉及到的含氯和溴的气体排放,以及温室气体的排放。
