Wave shapes that induce velocity skewness and acceleration asymmetry are usually responsible for onshore sediment transport, whereas undertow and bottom slope effect normally contribute to offshore sediment transport....Wave shapes that induce velocity skewness and acceleration asymmetry are usually responsible for onshore sediment transport, whereas undertow and bottom slope effect normally contribute to offshore sediment transport. By incorporating these counteracting driving forces in a phase-averaged manner, the theoretically-based quasi-steady formula of Wang （2007） is modified to predict the magnitude and direction of net cross-shore total load transport under the coaction of wave and current. The predictions show an excellent agreement with the measurement data on medium and fine sand collected by Dohmen-Janssen and Hanes （2002） and Schretlen （2012） in a full-scale wave flume at the Coastal Research Centre in Hannover, Germany. The modified formula can predict the net onshore transport of fine sand in sheet flows. In particular, it can predict the net offshore transport of medium sand in rippled beds through enlarged bed roughness, as well as the net offshore transport of fine-to-coarse sand in sheet flows with the aid of a new criterion to judge the occurrence of net offshore transport.展开更多
To remove the scalar ambiguity in conventional blind channel estimation algorithms, totally blind channel estimation （TBCE） is proposed by using multiple constellations. To estimate the unknown scalar, its phase is ...To remove the scalar ambiguity in conventional blind channel estimation algorithms, totally blind channel estimation （TBCE） is proposed by using multiple constellations. To estimate the unknown scalar, its phase is decomposed into a fractional phase and an integer phase. However, the maximum-likelihood （ML） algorithm for the fractional phase does not have closed-form solutions and suffers from high computational complexity. By ex- ploring the structures of widely used constellations, this paper proposes a low-complexity fractional phase estimation algorithm which requires no exhaustive search. Analytical expressions of the asymptotic mean squared error （MSE） are also derived. The theo- retical analysis and simulation results indicate that the proposed fractional phase estimation algorithm exhibits almost the same performance as the ML algorithm but with significantly reduced computational burden.展开更多
针对高密度聚乙烯(High Density Polyethylene,HDPE)管热熔接头相控阵超声检测时存在的图谱判读效率低、人员经验要求高等问题,文章提出一种基于改进YoloX算法的热熔接头全聚焦(Total Focusing Method,TFM)相控阵超声图谱缺陷(以孔洞为...针对高密度聚乙烯(High Density Polyethylene,HDPE)管热熔接头相控阵超声检测时存在的图谱判读效率低、人员经验要求高等问题,文章提出一种基于改进YoloX算法的热熔接头全聚焦(Total Focusing Method,TFM)相控阵超声图谱缺陷(以孔洞为例)智能识别方法。在YoloX的加强特征提取网络中引入卷积注意力机制模块,提高模型对缺陷信息的关注度,使用CIoU损失函数计算回归损失,以提升模型的定位精度,降低漏检率。通过TFM相控阵超声检测实验,采集原始缺陷图谱,并在完成图像增强后创建数据集。采用迁移学习策略进行训练,加快模型收敛速度。结果表明:该方法对缺陷的识别精度达98.18%,检测平均速度达23.92帧·s^(-1),检测精度相较于原YoloX模型提升了2.57个百分点且对小目标缺陷有更好的检测效果。文中方法可以识别出TFM相控阵超声图谱中的缺陷,为热熔接头的精确检测提供技术支撑。展开更多
试验旨在探究酶解-超声辅助双水相法提取泡桐花总黄酮的最佳工艺参数,评价其体外抗氧化活性。采用单因素试验和响应面法优化泡桐花总黄酮的提取工艺,并对比几种不同的提取方法,测定总黄酮对DPPH自由基、OH自由基和ABTS自由基的清除率。...试验旨在探究酶解-超声辅助双水相法提取泡桐花总黄酮的最佳工艺参数,评价其体外抗氧化活性。采用单因素试验和响应面法优化泡桐花总黄酮的提取工艺,并对比几种不同的提取方法,测定总黄酮对DPPH自由基、OH自由基和ABTS自由基的清除率。结果表明:最优提取工艺条件:(NH4)2SO4质量分数20%、乙醇质量分数33%、超声温度60℃、液料比23∶1 m L/g,总黄酮的实际提取率为7.62%,与理论值7.59%的相对偏差为0.40%。不同提取方法比对,酶解-超声法提取率最高。泡桐花黄酮能够有效清除DPPH自由基、OH自由基和ABTS自由基,最高清除率分别为78.1%、86.2%和83.3%,可为其开发为天然饲料添加剂应用在动物生产领域提供科学参考。展开更多
A novel method for the preparation of single-phase ammonium dimolybdate with industrial ammonium molybdate was studied. Various in- fluential factors were evaluated in the paper, including reaction temperature, reacti...A novel method for the preparation of single-phase ammonium dimolybdate with industrial ammonium molybdate was studied. Various in- fluential factors were evaluated in the paper, including reaction temperature, reaction time, initial molybdenum concentration, initial NH_3 /Mo molar ratio, and stirring speed. Under the optimum experimental conditions, the crystallization rate of product is 85.23%. The X-ray diffraction (XRD) analysis and chemical analysis show that the product is single-phase ammonium dimolybdate, and no impurity phases exist. The scanning electronic microscope (SEM) image reveals uniform particle size, good particle dispersion, and no agglomeration between particles. Meanwhile, the final pH value of acidification was investigated. The total molybdenum recovery can reach up to 99.40%, and the main phases of acidification product are the same as those of raw material with the final pH value of 1.5. This determines that the acidification product can be used as a raw material to produce single-phase ammonium dimolybdate.展开更多
In this work, attempts were made to estimate the total oil content (TOC) in single peanut kernels, using the CI meter (Chari’s Impedance meter, described below). Mature peanut kernels of selected varieties with a ran...In this work, attempts were made to estimate the total oil content (TOC) in single peanut kernels, using the CI meter (Chari’s Impedance meter, described below). Mature peanut kernels of selected varieties with a range of oil contents from 47% to 61% were placed one at a time, between the parallel-plate electrodes of the CI meter, and the impedance (Z) and phase angle (q) of the system were measured, and capacitance, C was computed at 1, 5 and 9 MHz. After the measurements, the TOC of each kernel was determined by Soxhlet method. Using the known TOC values, and the corresponding C, Z and q values, initially on a calibration group of kernels, calibration equations were developed. Using the model coefficients from the calibration, the TOCs of kernel samples of 31 diverse peanut genotypes grown in different environments in Australia were determined. The method predicted the TOC values of peanut kernels of 31 peanut genotypes, within 2% of the Soxhlet values, with an R2 of 0.87 (P 0.001).展开更多
To represent well the characteristics of temporal and spatial distributions, chart of 3-dekad moving total precipitation is proposed in this paper first. Then this kind of chart is expanded in terms of Chebyshev polyn...To represent well the characteristics of temporal and spatial distributions, chart of 3-dekad moving total precipitation is proposed in this paper first. Then this kind of chart is expanded in terms of Chebyshev polynomial at irregular grids, and the quantitative representation of precipitation is got. Finally the Chebyshev coefficients are forecasted by using the forecasting method of vector similarity in phase space proposed by Zhou (1992). Using above mentioned procedures temporal and spatial distributions of precipitation over the Huanghe-- Huaihe-- H aihe Plain in China are forecasted.展开更多
基金supported by the National Natural Science Foundation of China(Grant No.51179211)
文摘Wave shapes that induce velocity skewness and acceleration asymmetry are usually responsible for onshore sediment transport, whereas undertow and bottom slope effect normally contribute to offshore sediment transport. By incorporating these counteracting driving forces in a phase-averaged manner, the theoretically-based quasi-steady formula of Wang （2007） is modified to predict the magnitude and direction of net cross-shore total load transport under the coaction of wave and current. The predictions show an excellent agreement with the measurement data on medium and fine sand collected by Dohmen-Janssen and Hanes （2002） and Schretlen （2012） in a full-scale wave flume at the Coastal Research Centre in Hannover, Germany. The modified formula can predict the net onshore transport of fine sand in sheet flows. In particular, it can predict the net offshore transport of medium sand in rippled beds through enlarged bed roughness, as well as the net offshore transport of fine-to-coarse sand in sheet flows with the aid of a new criterion to judge the occurrence of net offshore transport.
基金supported by the National Science and Technology Major Project of China(2013ZX03003006-003)
文摘To remove the scalar ambiguity in conventional blind channel estimation algorithms, totally blind channel estimation （TBCE） is proposed by using multiple constellations. To estimate the unknown scalar, its phase is decomposed into a fractional phase and an integer phase. However, the maximum-likelihood （ML） algorithm for the fractional phase does not have closed-form solutions and suffers from high computational complexity. By ex- ploring the structures of widely used constellations, this paper proposes a low-complexity fractional phase estimation algorithm which requires no exhaustive search. Analytical expressions of the asymptotic mean squared error （MSE） are also derived. The theo- retical analysis and simulation results indicate that the proposed fractional phase estimation algorithm exhibits almost the same performance as the ML algorithm but with significantly reduced computational burden.
文摘针对高密度聚乙烯(High Density Polyethylene,HDPE)管热熔接头相控阵超声检测时存在的图谱判读效率低、人员经验要求高等问题,文章提出一种基于改进YoloX算法的热熔接头全聚焦(Total Focusing Method,TFM)相控阵超声图谱缺陷(以孔洞为例)智能识别方法。在YoloX的加强特征提取网络中引入卷积注意力机制模块,提高模型对缺陷信息的关注度,使用CIoU损失函数计算回归损失,以提升模型的定位精度,降低漏检率。通过TFM相控阵超声检测实验,采集原始缺陷图谱,并在完成图像增强后创建数据集。采用迁移学习策略进行训练,加快模型收敛速度。结果表明:该方法对缺陷的识别精度达98.18%,检测平均速度达23.92帧·s^(-1),检测精度相较于原YoloX模型提升了2.57个百分点且对小目标缺陷有更好的检测效果。文中方法可以识别出TFM相控阵超声图谱中的缺陷,为热熔接头的精确检测提供技术支撑。
文摘试验旨在探究酶解-超声辅助双水相法提取泡桐花总黄酮的最佳工艺参数,评价其体外抗氧化活性。采用单因素试验和响应面法优化泡桐花总黄酮的提取工艺,并对比几种不同的提取方法,测定总黄酮对DPPH自由基、OH自由基和ABTS自由基的清除率。结果表明:最优提取工艺条件:(NH4)2SO4质量分数20%、乙醇质量分数33%、超声温度60℃、液料比23∶1 m L/g,总黄酮的实际提取率为7.62%,与理论值7.59%的相对偏差为0.40%。不同提取方法比对,酶解-超声法提取率最高。泡桐花黄酮能够有效清除DPPH自由基、OH自由基和ABTS自由基,最高清除率分别为78.1%、86.2%和83.3%,可为其开发为天然饲料添加剂应用在动物生产领域提供科学参考。
基金supported by the National Natural Science Foundation of China(No.51072233)
文摘A novel method for the preparation of single-phase ammonium dimolybdate with industrial ammonium molybdate was studied. Various in- fluential factors were evaluated in the paper, including reaction temperature, reaction time, initial molybdenum concentration, initial NH_3 /Mo molar ratio, and stirring speed. Under the optimum experimental conditions, the crystallization rate of product is 85.23%. The X-ray diffraction (XRD) analysis and chemical analysis show that the product is single-phase ammonium dimolybdate, and no impurity phases exist. The scanning electronic microscope (SEM) image reveals uniform particle size, good particle dispersion, and no agglomeration between particles. Meanwhile, the final pH value of acidification was investigated. The total molybdenum recovery can reach up to 99.40%, and the main phases of acidification product are the same as those of raw material with the final pH value of 1.5. This determines that the acidification product can be used as a raw material to produce single-phase ammonium dimolybdate.
文摘In this work, attempts were made to estimate the total oil content (TOC) in single peanut kernels, using the CI meter (Chari’s Impedance meter, described below). Mature peanut kernels of selected varieties with a range of oil contents from 47% to 61% were placed one at a time, between the parallel-plate electrodes of the CI meter, and the impedance (Z) and phase angle (q) of the system were measured, and capacitance, C was computed at 1, 5 and 9 MHz. After the measurements, the TOC of each kernel was determined by Soxhlet method. Using the known TOC values, and the corresponding C, Z and q values, initially on a calibration group of kernels, calibration equations were developed. Using the model coefficients from the calibration, the TOCs of kernel samples of 31 diverse peanut genotypes grown in different environments in Australia were determined. The method predicted the TOC values of peanut kernels of 31 peanut genotypes, within 2% of the Soxhlet values, with an R2 of 0.87 (P 0.001).
文摘To represent well the characteristics of temporal and spatial distributions, chart of 3-dekad moving total precipitation is proposed in this paper first. Then this kind of chart is expanded in terms of Chebyshev polynomial at irregular grids, and the quantitative representation of precipitation is got. Finally the Chebyshev coefficients are forecasted by using the forecasting method of vector similarity in phase space proposed by Zhou (1992). Using above mentioned procedures temporal and spatial distributions of precipitation over the Huanghe-- Huaihe-- H aihe Plain in China are forecasted.
