期刊文献+
共找到112,586篇文章
< 1 2 250 >
每页显示 20 50 100
钒和钨负载量对V_2O_5-WO_3/TiO_2表面形态及催化性能的影响 被引量:24
1
作者 陈建军 李俊华 +2 位作者 柯锐 康守方 郝吉明 《环境科学》 EI CAS CSCD 北大核心 2007年第9期1949-1953,共5页
采用浸渍法制备了一系列不同钒和钨负载量的V2O5-WO3/TiO2催化剂样品,对样品NH3选择性催化还原NO性能进行了评价,并用BET、XRD、XPS等手段对催化剂样品的表面形态进行了表征.研究发现,钒的负载量对催化剂的比表面积和催化活性有显著影响... 采用浸渍法制备了一系列不同钒和钨负载量的V2O5-WO3/TiO2催化剂样品,对样品NH3选择性催化还原NO性能进行了评价,并用BET、XRD、XPS等手段对催化剂样品的表面形态进行了表征.研究发现,钒的负载量对催化剂的比表面积和催化活性有显著影响,当钒负载量从1%升高到8%时,催化剂比表面积下降了16 m2/g,最高活性温度降低了约100℃.钨起到稳定剂和助剂的双重作用,当钒负载量为1%时,钨负载量从0升高到6%,催化剂比表面积仅下降了3 m2/g,而活性温度窗口向高温和低温各拓宽了约50℃.研究表明钒和钨负载量都能影响催化剂表面的VOx物种,但对催化剂的表面晶型没有明显影响. 展开更多
关键词 V2O5-WO3/TIO2催化剂 负载量 表面形态 选择性催化还原
下载PDF
边坡支护结构荷载取值问题研究 被引量:22
2
作者 方玉树 《工程地质学报》 CSCD 2008年第2期190-195,共6页
边坡支护结构上的荷载一般采用传统的土(岩)压力理论计算,本文对这种荷载取值方法存在的问题进行了分析,提出了以稳定性为基础确定边坡支挡结构上荷载的方法,该方法能弥补现行荷载取值方法的不足。
关键词 边坡 支护结构 荷载取值 土压力 稳定性
下载PDF
基于电子鼻技术的小麦种子活力鉴别 被引量:13
3
作者 张婷婷 赵宾 +2 位作者 杨丽明 王建华 孙群 《中国农业大学学报》 CAS CSCD 北大核心 2018年第9期123-130,共8页
为探究准确高效鉴别种子活力的新技术,利用电子鼻系统对未老化(CK)、58℃热水浴老化(Hot water aging method,HW)和50%甲醇老化(Methanol solution aging method,MS)后的山农27小麦种子进行检测,采用主成分分析(Principal component ana... 为探究准确高效鉴别种子活力的新技术,利用电子鼻系统对未老化(CK)、58℃热水浴老化(Hot water aging method,HW)和50%甲醇老化(Methanol solution aging method,MS)后的山农27小麦种子进行检测,采用主成分分析(Principal component analysis,PCA)、线性判别分析(Linear discriminant analysis,LDA)及载荷分析(Loadings)对老化处理后不同活力水平的小麦种子进行鉴别研究。试验结果:1)老化处理后不同活力水平的小麦种子在电子鼻传感器上有不同的特征性响应图谱;2)PCA分析无法区分热水浴老化后活力接近的小麦种子;3)LDA分析对热水浴老化和甲醇老化不同活力水平的小麦种子均具有较好的区分效果;4)载荷分析确定了热水浴老化各活力水平小麦种子的差异气味主要来自于无机硫化物(W1W)、小分子氮氧化合物(W5S)和有机硫化物(W2W),短链烷烃(W1S)、醇醚醛酮类气体(W2S)和氢气类(W6S)。甲醇老化各活力水平小麦种子的差异气味主要来自于有机硫化物(W2W)、小分子氮氧化合物(W5S)、短链烷烃(W1S)、醇醚醛酮类气体(W2S)和无机硫化物(W1W)。本研究结果揭示以电子鼻技术作为检测手段,通过对小麦种子挥发性成分的检测结合LDA分析,可以实现对不同活力小麦种子进行快速准确高效地鉴别,再结合Loading分析,可以进一步分析相关的差异性气体成分。 展开更多
关键词 电子鼻 小麦种子 活力 主成分分析 线性判别分析 载荷分析
原文传递
Ground-borne vibrations due to dynamic loadings from moving trains in subway tunnels 被引量:12
4
作者 Xue-cheng BIAN Wan-feng JIN Hong-guang JIANG 《Journal of Zhejiang University-Science A(Applied Physics & Engineering)》 SCIE EI CAS CSCD 2012年第11期870-876,共7页
In this study,ground vibrations due to dynamic loadings from trains moving in subway tunnels were investigated using a 2.5D finite element model of an underground tunnel and surrounding soil interactions.In our model,... In this study,ground vibrations due to dynamic loadings from trains moving in subway tunnels were investigated using a 2.5D finite element model of an underground tunnel and surrounding soil interactions.In our model,wave propagation in the infinitely extended ground is dealt with using a simple,yet efficient gradually damped artificial boundary.Based on the assumption of invariant geometry and material distribution in the tunnel's direction,the Fourier transform of the spatial dimension in this direction is applied to represent the waves in terms of the wave-number.Finite element discretization is employed in the cross-section perpendicular to the tunnel direction and the governing equations are solved for every discrete wave-number.The 3D ground responses are calculated from the wave-number expansion by employing the inverse Fourier transform.The accuracy of the proposed analysis method is verified by a semi-analytical solution of a rectangular load moving inside a soil stratum.A case study of subway train induced ground vibration is presented and the dependency of wave attenuation at the ground surface on the vibration frequency of the moving load is discussed. 展开更多
关键词 Subway tunnel Moving train loadings Ground-borne vibration 2.5D finite element Gradually damped artificial boundary
原文传递
Growth and nutrient accumulation of Phragmites australis in relation to water level variation and nutrient loadings in a shallow lake 被引量:9
5
作者 Ying Zhao Xinghui Xia Zhifeng Yang 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2013年第1期16-25,共10页
Shallow lake eutrophication is a global environmental issue. This study investigated the effects of water level variation and nutrient loadings on the growth and nutrient accumulation of Phragmites australis (reed) ... Shallow lake eutrophication is a global environmental issue. This study investigated the effects of water level variation and nutrient loadings on the growth and nutrient accumulation of Phragmites australis (reed) by field samplings in Baiyangdian Lake, the largest shallow lake of northern China. The field samplings were conducted in two sites of different nutrient loadings during the whole growth period of reeds, and three types of zones with different water depths were chosen for each site, including the terrestrial zone with water level below the ground, the ecotone zone with the water level varying from belowground to aboveground, and the submerged zone with water level above the ground. The result showed that reed growth was more limited by water level variation than nutrient loadings. The average stem lengths and diameters in terrestrial zones were about 26.3%-27.5% and 7.2%-12.0% higher than those in submerged zones, respectively. Similarly, the terrestrial status increased the aboveground biomass of reeds by 36.6%-51.8% compared with the submerged status. Both the nutrient concentrations and storages in the aboveground reeds were mainly influenced by the nutrient loadings in surface water and sediment rather than the water level variation of the reed growth environment, and the nutrient storages reached their maxima in late August or early September. It was observed that the maximum nitrogen storage occurred in the terrestrial zone with higher nutrient loadings, with the value of 74.5 g/m2. This study suggested that water level variation and nutrient loadings should be considered when using reeds to control and remediate eutrophication of shallow lakes. 展开更多
关键词 water level variation nutrient loadings Phragmites australis reed growth nutrient accumulation
原文传递
PHB监测A^2/O工艺除磷及负荷率耦合关系的研究 被引量:7
6
作者 高尚 戴兴春 +5 位作者 陈曦 高岩 朱勇 黄燕 黄民生 王国华 《环境科学》 EI CAS CSCD 北大核心 2008年第11期3093-3097,共5页
以上海市白龙港城市污水厂初沉池污水为进水,培养驯化污泥并构建A2/O试验系统,监测PHB消耗、生成的动态变化,并分析其与除磷和BOD5负荷率的耦合关系.结果显示,曝气池中PHB的消耗与除磷呈现良好的正相关关系(p<0.05),平均消耗约140 m... 以上海市白龙港城市污水厂初沉池污水为进水,培养驯化污泥并构建A2/O试验系统,监测PHB消耗、生成的动态变化,并分析其与除磷和BOD5负荷率的耦合关系.结果显示,曝气池中PHB的消耗与除磷呈现良好的正相关关系(p<0.05),平均消耗约140 mg左右的PHB可去除1 mg P;厌氧池中PHB的生成与释磷存在着极显著的正相关关系(p<0.01),平均释放1.17mg的磷可生成约100 mg的PHB;厌氧池中PHB的含量与系统F/M的正相关性显著(p<0.05),负荷为0.176 g/(g.d)较负荷0.413 g/(g.d)下PHB的生成量平均减少约4 mg/g(以MLSS计);PHB的合成与厌氧池中BOD5的去除量的相关性较差(p>0.05),但与温度呈极为显著的正相关关系(p<0.01),温度的升高有助于微生物合成PHB,最高温度(33.2℃)比最低温度(17.1℃)活性污泥中PHB含量约增加5 mg/g(以MLSS计),占总量的20%左右. 展开更多
关键词 聚羟基丁酸(PHB) A2/O系统 城市污水 除磷 负荷 耦合关系 试验研究
下载PDF
Earth slope reliability analysis under seismic loadings using neural network 被引量:8
7
作者 彭怀生 邓建 古德生 《Journal of Central South University of Technology》 EI 2005年第5期606-610,共5页
A new method was proposed to cope with the earth slope reliability problem under seismic loadings. The algorithm integrates the concepts of artificial neural network, the first order second moment reliability method a... A new method was proposed to cope with the earth slope reliability problem under seismic loadings. The algorithm integrates the concepts of artificial neural network, the first order second moment reliability method and the deterministic stability analysis method of earth slope. The performance function and its derivatives in slope stability analysis under seismic loadings were approximated by a trained multi-layer feed-forward neural network with differentiable transfer functions. The statistical moments calculated from the performance function values and the corresponding gradients using neural network were then used in the first order second moment method for the calculation of the reliability index in slope safety analysis. Two earth slope examples were presented for illustrating the applicability of the proposed approach. The new method is effective in slope reliability analysis. And it has potential application to other reliability problems of complicated engineering structure with a considerably large number of random variables. 展开更多
关键词 slope reliability analysis neural network seismic loadings
下载PDF
钢铁材料的泛环境负荷及其环境经济损益分析 被引量:7
8
作者 刘江龙 钱小蓉 +2 位作者 丁培道 孙阳 顾恒岳 《环境科学进展》 CSCD 1998年第4期64-69,共6页
本文研究了钢铁材料生产过程中的生态环境问题,包括资源、能源、废弃物。定义了材料的泛环境函数及泛环境负荷。由此可以定量描述和度量钢铁材料对生态环境的影响程度。作为一个探索,研究了碳素钢的具体泛环境负荷及其与强度和塑性的... 本文研究了钢铁材料生产过程中的生态环境问题,包括资源、能源、废弃物。定义了材料的泛环境函数及泛环境负荷。由此可以定量描述和度量钢铁材料对生态环境的影响程度。作为一个探索,研究了碳素钢的具体泛环境负荷及其与强度和塑性的关系。 展开更多
关键词 钢铁材料 生产过程 环境经济损益 生态环境影响
原文传递
Electrochemically Grown Ultrathin Platinum Nanosheet Electrodes with Ultralow Loadings for Energy-Saving and Industrial-Level Hydrogen Evolution 被引量:4
9
作者 Lei Ding Zhiqiang Xie +8 位作者 Shule Yu Weitian Wang Alexander Y.Terekhov Brian K.Canfield Christopher B.Capuano Alex Keane Kathy Ayers David A.Cullen Feng-Yuan Zhang 《Nano-Micro Letters》 SCIE EI CAS CSCD 2023年第9期257-274,共18页
Nanostructured catalyst-integrated electrodes with remarkably reduced catalyst loadings,high catalyst utilization and facile fabrication are urgently needed to enable cost-effective,green hydrogen production via proto... Nanostructured catalyst-integrated electrodes with remarkably reduced catalyst loadings,high catalyst utilization and facile fabrication are urgently needed to enable cost-effective,green hydrogen production via proton exchange membrane electrolyzer cells(PEMECs).Herein,benefitting from a thin seeding layer,bottom-up grown ultrathin Pt nanosheets(Pt-NSs)were first deposited on thin Ti substrates for PEMECs via a fast,template-and surfactant-free electrochemical growth process at room temperature,showing highly uniform Pt surface coverage with ultralow loadings and vertically well-aligned nanosheet morphologies.Combined with an anode-only Nafion 117 catalyst-coated membrane(CCM),the Pt-NS electrode with an ultralow loading of 0.015 mgPt cm−2 demonstrates superior cell performance to the commercial CCM(3.0 mgPt cm^(−2)),achieving 99.5%catalyst savings and more than 237-fold higher catalyst utilization.The remarkable performance with high catalyst utilization is mainly due to the vertically well-aligned ultrathin nanosheets with good surface coverage exposing abundant active sites for the electrochemical reaction.Overall,this study not only paves a new way for optimizing the catalyst uniformity and surface coverage with ultralow loadings but also provides new insights into nanostructured electrode design and facile fabrication for highly efficient and low-cost PEMECs and other energy storage/conversion devices. 展开更多
关键词 Seeding layer Electrochemically grown Pt nanosheet Ultralow loadings High catalyst utilization Hydrogen evolution
下载PDF
DECAGONAL QU ASICRYSTALLINE ELLIPTICAL INCLUSIONS UNDER THERMOMECHANICAL LOADING 被引量:6
10
作者 Xu Wang Peter Schiavone 《Acta Mechanica Solida Sinica》 SCIE EI CSCD 2014年第5期518-530,共13页
In this work, an elegant method is proposed to derive the thermoelastic field in- duced by thermomechanical loadings in a decagonal quasicrystalline composite composed of an infinite matrix reinforced by an elliptical... In this work, an elegant method is proposed to derive the thermoelastic field in- duced by thermomechanical loadings in a decagonal quasicrystalline composite composed of an infinite matrix reinforced by an elliptical inclusion. The thermomechanical loadings include a uniform temperature change, remote uniform in-plane heat fluxes and remote uniform in-plane stresses. The corresponding boundary value problem is ultimately reduced to the solution of two independent sets of four coupled linear algebraic equations, each of which involves four complex constants characterizing the internal stress field. The solution demonstrates that a uniform tem- perature change and remote uniform stresses will induce an internal uniform stress field, and that uniform heat fluxes will result in a linearly distributed internal stress field within the elliptical inclusion. The induced uniform rigid body rotation within the inclusion is given explicitly. 展开更多
关键词 elliptical inclusion thermomechanical loadings decagonal quasicrystal complexvariable method
原文传递
Probabilistic analysis of tunnel face seismic stability in layered rock masses using Polynomial Chaos Kriging metamodel 被引量:1
11
作者 Jianhong Man Tingting Zhang +1 位作者 Hongwei Huang Daniel Dias 《Journal of Rock Mechanics and Geotechnical Engineering》 SCIE CSCD 2024年第7期2678-2693,共16页
Face stability is an essential issue in tunnel design and construction.Layered rock masses are typical and ubiquitous;uncertainties in rock properties always exist.In view of this,a comprehensive method,which combines... Face stability is an essential issue in tunnel design and construction.Layered rock masses are typical and ubiquitous;uncertainties in rock properties always exist.In view of this,a comprehensive method,which combines the Upper bound Limit analysis of Tunnel face stability,the Polynomial Chaos Kriging,the Monte-Carlo Simulation and Analysis of Covariance method(ULT-PCK-MA),is proposed to investigate the seismic stability of tunnel faces.A two-dimensional analytical model of ULT is developed to evaluate the virtual support force based on the upper bound limit analysis.An efficient probabilistic analysis method PCK-MA based on the adaptive Polynomial Chaos Kriging metamodel is then implemented to investigate the parameter uncertainty effects.Ten input parameters,including geological strength indices,uniaxial compressive strengths and constants for three rock formations,and the horizontal seismic coefficients,are treated as random variables.The effects of these parameter uncertainties on the failure probability and sensitivity indices are discussed.In addition,the effects of weak layer position,the middle layer thickness and quality,the tunnel diameter,the parameters correlation,and the seismic loadings are investigated,respectively.The results show that the layer distributions significantly influence the tunnel face probabilistic stability,particularly when the weak rock is present in the bottom layer.The efficiency of the proposed ULT-PCK-MA is validated,which is expected to facilitate the engineering design and construction. 展开更多
关键词 Tunnel face stability Layered rock masses Polynomial Chaos Kriging(PCK) Sensitivity index Seismic loadings
下载PDF
Dealing with Multicollinearity in Factor Analysis: The Problem, Detections, and Solutions
12
作者 Theodoros Kyriazos Mary Poga 《Open Journal of Statistics》 2023年第3期404-424,共21页
Multicollinearity in factor analysis has negative effects, including unreliable factor structure, inconsistent loadings, inflated standard errors, reduced discriminant validity, and difficulties in interpreting factor... Multicollinearity in factor analysis has negative effects, including unreliable factor structure, inconsistent loadings, inflated standard errors, reduced discriminant validity, and difficulties in interpreting factors. It also leads to reduced stability, hindered factor replication, misinterpretation of factor importance, increased parameter estimation instability, reduced power to detect the true factor structure, compromised model fit indices, and biased factor loadings. Multicollinearity introduces uncertainty, complexity, and limited generalizability, hampering factor analysis. To address multicollinearity, researchers can examine the correlation matrix to identify variables with high correlation coefficients. The Variance Inflation Factor (VIF) measures the inflation of regression coefficients due to multicollinearity. Tolerance, the reciprocal of VIF, indicates the proportion of variance in a predictor variable not shared with others. Eigenvalues help assess multicollinearity, with values greater than 1 suggesting the retention of factors. Principal Component Analysis (PCA) reduces dimensionality and identifies highly correlated variables. Other diagnostic measures include the condition number and Cook’s distance. Researchers can center or standardize data, perform variable filtering, use PCA instead of factor analysis, employ factor scores, merge correlated variables, or apply clustering techniques for the solution of the multicollinearity problem. Further research is needed to explore different types of multicollinearity, assess method effectiveness, and investigate the relationship with other factor analysis issues. 展开更多
关键词 MULTICOLLINEARITY Factor Analysis Biased Factor loadings Unreliable Factor Structure Reduced Stability Variance Inflation Factor
下载PDF
Robustness of anammox granular sludge treating low-strength sewage under various shock loadings:Microbial mechanism and little N2O emission 被引量:4
13
作者 Shanyun Wang Guibing Zhu +3 位作者 Yifei Li Xiaoxia Wang Jiemin Zhou Yongzhen Peng 《Journal of Environmental Sciences》 SCIE EI CAS CSCD 2019年第12期141-153,共13页
With the increasing application of anammox for the treatment of high-strength industrial wastewater,application of anammox in municipal sewage has been gaining more attention.Sludge granulation in particular enhances ... With the increasing application of anammox for the treatment of high-strength industrial wastewater,application of anammox in municipal sewage has been gaining more attention.Sludge granulation in particular enhances the enrichment and retention of anammox bacteria in municipal sewage treatment systems.However,the performance of granular sludge under continuous and varying hydraulic loading shock remains little understood.In this study,the robustness of anammox granular sludge in treating lowstrength municipal sewage under various shock loadings was investigated.Results showed that an upflow anaerobic sludge blanket(UASB)reactor with anammox granules performed well,with anammox specific activity up to 0.28 kg N/kg VSS/day and anti-loading shock capability up to 187.2 L/day during the 8-month testing period.The accumulation rate of N2O(<0.01 kg N/kg VSS/day)in the liquid phase was seven times higher than that of the gas phase,which could be mainly attributed to the incomplete denitrification and insufficient carbon source.However,only a small part of the produced N2O escaped into the atmosphere.High-throughput sequencing and molecular ecological network analyses also identified the bacterial diversity and community structure,indicating the potential resistance against loading shock.The composition and structural analyses showed that polysaccharides were an important functional component in the tightly bound extracellular polymeric substances(TB-EPS),which was the major EPS layer of anammox granules.Scanning electron microscopy(SEM)also showed that the gaps in between the anammoxclusters in the granules inhibit the flotation of the sludge and ensure efficient settling and retention of anammox granules. 展开更多
关键词 ANAMMOX Low-strength sewage Varying shock loadings Microbial mechanism N2O emission
原文传递
SPME-HS-GC-MS与电子鼻分析不同产地芦根饮片气味特征
14
作者 陈光宇 瞿昊宇 +3 位作者 谢梦洲 孙晶 范蓓 王凤忠 《中国食物与营养》 2023年第10期30-34,44,共6页
目的:分析不同产地芦根饮片的气味特征,为产地判别、分析方法改进提供依据。方法:以10个产地的芦根饮片细粉为研究样品,采用固相微萃取-顶空进样-气质联用法(SPME-HS-GC-MS)分析芦根饮片指纹图谱,采用电子鼻智能感官评定技术分析芦根饮... 目的:分析不同产地芦根饮片的气味特征,为产地判别、分析方法改进提供依据。方法:以10个产地的芦根饮片细粉为研究样品,采用固相微萃取-顶空进样-气质联用法(SPME-HS-GC-MS)分析芦根饮片指纹图谱,采用电子鼻智能感官评定技术分析芦根饮片气味雷达图,采用主成分(PCA)、Loadings方法分析电子鼻信号响应结果,构建产地判别模型。结果:气质联用法结果共鉴别出38个挥发性成分,其中18个差异性挥发性成分可用于6个产地的区分。电子鼻结果表明,主成分判别分析能较好地区分不同产地芦根饮片,芦根饮片在气味上的差异主要体现在无机硫化物、有机硫化物、小分子氮氧化物、短链烷烃类、醇类、醛酮类等成分上。结论:不同产地芦根饮片的气味特征存在差异,可作为产地判别依据。电子鼻技术可为芦根饮片分析及质量标准提供简单、快速的新方法。 展开更多
关键词 芦根 气质联用 电子鼻 主成分 loadings
下载PDF
基于水质水量的城镇污水处理厂工艺运行稳定性研究 被引量:6
15
作者 杨敏 谷声文 +2 位作者 吴鹏 何京莲 李卫 《环境污染与防治》 CAS CSCD 北大核心 2015年第7期46-49,54,共5页
采用四川省2座位于不同排水服务区域的城镇污水处理厂的样本数据,统计分析了日处理水量,COD、TN、TP浓度及负荷和C/N、C/P等统计量的累积频率分布规律,并分析了各统计量的分布特征对工艺运行稳定性的影响。结果表明,污水处理厂A进水污... 采用四川省2座位于不同排水服务区域的城镇污水处理厂的样本数据,统计分析了日处理水量,COD、TN、TP浓度及负荷和C/N、C/P等统计量的累积频率分布规律,并分析了各统计量的分布特征对工艺运行稳定性的影响。结果表明,污水处理厂A进水污染物负荷的累积频率分布范围较大,其采用的周期循环活性污泥(CASS)工艺基本能适应进水水质的随机变化,但因存在碳源随机性不足情况,可能导致其脱氮稳定性降低;污水处理厂B进水污染物负荷的累积频率分布范围较小,虽然其采用的厌氧—缺氧—好氧(A2/O)工艺的调控能力较低,但也基本能适应其服务区域内进水水质的随机变化;2座污水处理厂的日处理水量累积频率分布与污染物浓度及负荷的累积频率分布之间均存在显著的差异,日处理水量的累积频率分布比较集中,而污染物浓度及负荷的累积频率分布的离散范围较大,这也潜在威胁到工艺运行的稳定性。总体来看,2座污水处理厂的处理工艺选择恰当,均能较好适应其服务区域的进水水质和水量的要求。 展开更多
关键词 统计量 负荷 样本 正态分布 稳定性
下载PDF
一种基于稀疏主成分的基因表达数据特征提取方法 被引量:6
16
作者 沈宁敏 李静 +1 位作者 周培云 庄毅 《计算机科学》 CSCD 北大核心 2015年第S1期453-458,共6页
聚类已成为基因表达数据的一种前沿分析方法,通过基因类别的划分可以较快速地发现病变细胞,以实现对疾病的诊断。然而,高维、小样本的数据特点使得原始采集的基因表达数据具有大量的冗余与干扰信息,直接聚类会使得算法运行时间长,分析... 聚类已成为基因表达数据的一种前沿分析方法,通过基因类别的划分可以较快速地发现病变细胞,以实现对疾病的诊断。然而,高维、小样本的数据特点使得原始采集的基因表达数据具有大量的冗余与干扰信息,直接聚类会使得算法运行时间长,分析结果精度低。主成分分析是一种经典的数据降维方法,在保持方差最大的情况下,将高维数据映射到低维空间。但负载因子的非零特性使得主成分不具有强解释能力。提出基于截断幂的稀疏主成分分析方法对基因表达数据进行特征提取,并结合K-means方法对稀疏提取的特征基因数据进行聚类分析。最后,利用3个公开的基因数据集进行实验分析,验证了所提出的特征提取方法可提高基因表达数据聚类的精确性与高效性。 展开更多
关键词 基因表达数据 负载因子 截断幂 稀疏主成分分析 特征提取
下载PDF
The Effect of Core Eccentricity on the Structural Behavior of Concrete Tall Buildings
17
作者 Tarek Anwar Taha Awida 《Journal of Civil Engineering and Architecture》 2024年第3期112-117,共6页
The main purpose of this paper is to investigate the effect of core eccentricity on the structural behavior of concrete tall buildings.Concrete buildings of 55 floors with plan dimensions 48.0×48.0 m2 were invest... The main purpose of this paper is to investigate the effect of core eccentricity on the structural behavior of concrete tall buildings.Concrete buildings of 55 floors with plan dimensions 48.0×48.0 m2 were investigated.Three cases of main core locations are studied:centric(A),eccentric by one sixth(B)and one third(C)of building width.The three-dimensional finite element method has been used in conducting structural analysis through ETABS software.Gravity and lateral(wind and seismic)loadings are applied to all building cases.It has been concluded that the core location is the prime parameter governing the structural behavior of tall buildings.Although the first two cases(A,B)have acceptable and similar structural behaviors conforming to code limits,in the third case(C),the building behavior came beyond code limits.The author introduced remedial action by adding two secondary cores in the opposite direction of the main core(C-R)to restore the building behavior to the code limits.The results of this action were satisfactory. 展开更多
关键词 Concrete tall buildings core eccentricity structural behavior GRAVITY WIND seismic loadings
下载PDF
基于电子鼻的桑葚采后品质预测 被引量:5
18
作者 石国英 高思宇 +2 位作者 韦静静 房皓 黄晓杰 《食品与发酵工业》 CAS CSCD 北大核心 2016年第3期193-197,共5页
以桑葚为研究对象,以失重率、腐烂指数和感官评分为指标,结合电子鼻检测,探究20℃和4℃贮藏条件下桑葚果实品质变化规律。结果表明:失重率、腐烂指数均随着贮藏时间的延长而呈现不同程度的增加,而感官评分逐渐下降。桑葚果实挥发性气体... 以桑葚为研究对象,以失重率、腐烂指数和感官评分为指标,结合电子鼻检测,探究20℃和4℃贮藏条件下桑葚果实品质变化规律。结果表明:失重率、腐烂指数均随着贮藏时间的延长而呈现不同程度的增加,而感官评分逐渐下降。桑葚果实挥发性气体成分随着贮藏时间的延长也发生了明显的变化。利用PCA、LDA方法能有效区分桑葚果实的贮藏期,总体来看,电子鼻分析结果与感官分析的结果基本一致,即电子鼻可用于快速评价桑葚品质。 展开更多
关键词 温度 贮藏期 主成分分析 线性判别分析 负荷加载分析
下载PDF
Hydroarylation of terminal alkynes with arylboronic acids catalyzed by low loadings of palladium
19
作者 Lei Xu Shiyu Li +3 位作者 Qi Zhang Ning Deng Biao Zhang Huajian Xu 《Chinese Chemical Letters》 SCIE CAS CSCD 2023年第2期165-169,共5页
The hydroarylation reaction of terminal alkynes with arylboronic acids catalyzed by low(400 ppm) loadings of palladium has been developed. The reaction is broad in scope and high-yielding, even on multigram scale. It ... The hydroarylation reaction of terminal alkynes with arylboronic acids catalyzed by low(400 ppm) loadings of palladium has been developed. The reaction is broad in scope and high-yielding, even on multigram scale. It is suitable for the synthesis of alkenes labeled with deuterium, and for the late-stage modification of bioactive molecules. 展开更多
关键词 HYDROARYLATION Low loadings Terminal alkyne Deuterium-labeled PALLADIUM
原文传递
Applications of AnnAGNPS Model for Sediment and Nutrient Loadings for Funiu Mountain Area, China
20
作者 TIAN Yaowu LIU Yali +2 位作者 ZHANG Chulei ZHANG Zizheng LI Xiaolin 《Journal of Landscape Research》 2023年第5期85-88,共4页
The main goal of this study was to evaluate the performance of AnnAGNPS(Annualized AGricultural NonPoint Source)pollution model,in calculating runoff,sediment loading and nutrient loadings for Funiu Mountain area.Most... The main goal of this study was to evaluate the performance of AnnAGNPS(Annualized AGricultural NonPoint Source)pollution model,in calculating runoff,sediment loading and nutrient loadings for Funiu Mountain area.Most of the model input parameters were sourced from Luanchuan Forest Ecology Station(LFES)in Funiu Mountain area.The data on 23 storms in 2018 was used to calibrate the model and the data on 33 storms in 2019 for validation.The whole evaluation consisted of determining the coefficient of determination(R^(2)),Nash-Sutcliffe coefficient of efficiency(E),and the percentage volume error(VE).Results showed that the runoff volumes were underpredicted by 5.0%with R^(2) of 0.93(P<0.05)during calibration and underpredicted by 5.3%with R^(2) of 0.90(P<0.05)during validation.But sediment loading was able to produce a moderate result.The model underpredicted the daily sediment loading by 15.1%with R^(2) of 0.63(P<0.05)during calibration and 13.5%with R^(2) of 0.66(P<0.05)during validation.Nitrogen loading was overpredicted by 20.3%with R^(2)=0.68(P<0.05),and phosphorus loading performance was slightly poor with R^(2)=0.65(P<0.05)during validation.In general,the model performed well in simulating runoff compared to sediment loading and nutrient loadings. 展开更多
关键词 AnnAGNPS model RUNOFF Sediment loading Nutrient loadings Funiu Mountain area PERFORMANCE
下载PDF
上一页 1 2 250 下一页 到第
使用帮助 返回顶部