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| 1 | 基于HHT和CSSD的多域融合自适应脑电特征提取方法显示文摘为改善运动想象脑电信号特征提取的自适应性和实时性,提出一种基于希尔伯特-黄变换(HHT)与共空域子空间分解算法(CSSD)的特征提取方法(HCSSD).在对脑电信号进行预处理的基础上,定义一种相对距离准则优选脑电极组合;计算脑电的Hilbert瞬时能量谱和边际能量谱,以获取脑电的时-频特征,并基于CSSD提取其空域特征,采用串行特征融合策略得到脑电的时-频-空特征;设计学习矢量量化神经网络分类器,实现脑电数据分类.在训练集与测试集间隔一周且减少导联数量的情况下,基于HCSSD对左手小指和舌头的运动想象ECoG脑电数据的平均识别率为92%.实验结果表明:HCSSD在增强特征提取方法的自适应性、改善实时性的同时,提高了脑电信号识别率,为便携式BCI系统在康复领域的应用创造了条件. | 李明爱 崔燕 杨金福 郝冬梅 | 2013 | 电子学报2013，41，12： | 36 |
| 2 | 工频交流电晕放电下SF_6气体分解物形成的影响因素显示文摘六氟化硫(SF6)作为一种理想的绝缘和灭弧气体广泛应用于气体绝缘电力设备。以往的研究和运行经验表明SF6气体分解物与电力设备的绝缘状态有密切的关联。因此,分析SF6气体分解物是监测气体绝缘电力设备绝缘状态的有效手段之一。本文用针-板电极模型模拟SF6气体中的工频交流电晕放电,以色谱-质谱法作为检测手段,研究不同影响因素下工频交流电晕放电中SF6气体分解组分的形成规律,如持续施加电压、放电时间、气体压力、电极间距等,分析影响因素对SF6气体分解物形成的作用规律。 | 林涛 韩冬 钟海峰 靳骁 张国强 | 2014 | 电工技术学报2014，29，2： | 35 |
| 3 | On Decomposition Theorem of normalized biholomorphic convex mappings in Reinhardt domains显示文摘The construction of normalized biholomorphic convex mappings in the Reinhardt domain Dp{(z1,z2,....zn):z1 p1+z1 p2+....+zn pn <1},(pj>2,j=1,2,.....n,) of n is discussed.The authors set up a Decomposition Theorem for such mappings. As a special case, it is proved that, for each suchthis derives the Decomposition Theorem of normalized biholo morphic convex mappings in the polydisc whichwas gotten by T.J. Suffridge in 1970. | 张文俊 刘太顺 | 2003 | Science China Mathematics2003，46，1： | 29 |
| 4 | Retrieval of global terrestrial solar-induced chlorophyll fluorescence from TanSat satellite显示文摘The first Chinese Carbon Dioxide Observation Satellite Mission(TanSat), which was launched on December 21, 2016, is intended to measure atmospheric CO_2 concentration.The high spectral resolution(0.044 nm) and high SNR(360 at 15.2 mW m^(-1) sr^(-1) nm^(-1)) measurements in the region of the O_2-A band of the Atmospheric Carbon dioxide Grating Spectroradiometer(AGCS) module onboard TanSat make it possible to retrieve solar-induced chlorophyll fluorescence(SIF) from TanSat observations at the global scale.This paper aims to explore the potential of the TanSat data for global SIF retrieval.A singular vector decomposition(SVD) statistical method was employed to retrieve SIF using radiance over a micro spectral window(~2 nm) around the Fe Fraunhofer lines(centered at 758.8 nm).The global SIF at 758.8 nm was successfully retrieved with a low residual error of 0.03 mW m^(-1) sr^(-1) nm^(-1).The results show that the spatial and temporal patterns of the retrieved SIF agree well with the global terrestrial vegetation pattern.The monthly SIF products retrieved from the TanSat data were compared with other remote sensing datasets, including OCO-2 SIF, MODIS NDVI, EVI and GPP.The overall consistency between TanSat and OCO-2 SIF products(R^2= 0.86) and the consistency of the spatial patterns and temporal variations between the TanSat SIF and MODIS vegetation indices and GPP enhance our confidence in the potential and feasibility of TanSat data for SIF retrieval.TanSat, therefore, provides a new opportunity for global sampling of SIF at fine spatial resolution(2 km × 2 km), thus improving photosynthesis observations from space. | Shanshan Du Liangyun Liu Xinjie Liu Xiao Zhang Xingying Zhang Yanmeng Bi Lianchong Zhang | 2018 | Science Bulletin2018，63，22： | 29 |
| 5 | Finite difference scheme based on proper orthogonal decomposition for the nonstationary Navier-Stokes equations显示文摘The proper orthogonal decomposition(POD)and the singular value decomposition(SVD) are used to study the finite difference scheme(FDS)for the nonstationary Navier-Stokes equations. Ensembles of data are compiled from the transient solutions computed from the discrete equation system derived from the FDS for the nonstationary Navier-Stokes equations.The optimal orthogonal bases are reconstructed by the elements of the ensemble with POD and SVD.Combining the above procedures with a Galerkin projection approach yields a new optimizing FDS model with lower dimensions and a high accuracy for the nonstationary Navier-Stokes equations.The errors between POD approximate solutions and FDS solutions are analyzed.It is shown by considering the results obtained for numerical simulations of cavity flows that the error between POD approximate solution and FDS solution is consistent with theoretical results.Moreover,it is also shown that this validates the feasibility and efficiency of POD method. | Zhen-dong LUO Rui-wen WANG Jiang ZHU | 2007 | Science China Mathematics2007，50，8： | 20 |
| 6 | Changes in soil microbial biomass and community structure with addition of contrasting types of plant litter in a semiarid grassland ecosystem显示文摘Aims Elevated atmospheric CO_(2)has the potential to enhance the net primary productivity of terrestrial ecosystems.However,the role of soil microorganisms on soil C cycling following this increased available C remains ambiguous.This study was conducted to determine how quality and quantity of plant litter inputs would affect soil microorganisms and consequently C turnover.Methods Soil microbial biomass and community structure,bacterial community-level physiological profile,and CO_(2)emission caused by different substrate C decomposition were investigated using techniques of biological measurements,chemical and stable C isotope analysis,and BIOLOG-ECO microplates in a semiarid grassland ecosystem of northern China in 2006 and 2007 by mixing three contrasting types of plant materials,C_(3)shoot litter(SC_(3)),C_(3)root litter(RC_(3)),and C4 shoot litter(SC4),into the 10-to 20-cm soil layer at rates equivalent to 0(C0),60(C60),120(C120)and 240 g C m2(C240).Important Findings Litter addition significantly enriched soil microbial biomass C and N and resulted in changes in microbial structure.Principal component analysis of microbial structure clearly differentiated among zero addition,C_(3)-plant-derived litter,and C4-plant-derived litter and among shoot-and root-derived litter of C_(3)plants;soilmicroorganismsmainly utilized carbohydrates without litter addition,carboxylic acids with C_(3)-plant-derived litter addition and amino acidswith C4-plant-derived litter addition.We also detected stimulated decomposition of older substratewith C4-plant-derived litter inputs.Our results showthat both quality and quantity of belowground litter are involved in affecting soil microbial community structure in semiarid grassland ecosystem. | Hongmei Jin Osbert Jianxin Sun Jianfeng Liu | 2010 | Journal of Plant Ecology2010，3，3： | 18 |
| 7 | Finite element formulation based on proper orthogonal decomposition for parabolic equations显示文摘A proper orthogonal decomposition (POD) method is applied to a usual finite element (FE) formulation for parabolic equations so that it is reduced into a POD FE formulation with lower dimensions and enough high accuracy. The errors between the reduced POD FE solution and the usual FE solution are analyzed. It is shown by numerical examples that the results of numerical computations are consistent with theoretical conclusions. Moreover, it is also shown that this validates the feasibility and efficiency of POD method. | LUO ZhenDong CHEN Jing SUN Ping YANG XiaoZhong | 2009 | Science China Mathematics2009，52，3： | 16 |
| 8 | Assessment of bearing performance degradation via extension and EEMD combined approach显示文摘As a key component in rotating machinery, the operating reliability of bearing influences the performance and service life of the equipment directly. In order to describe bearing performance degradation(BPD) process effectively, an assessment approach combining extension and ensemble empirical mode decomposition(EEMD) was proposed. First, the extension was utilized to construct the matter-element of bearing operating state, and the energy moment of intrinsic mode functions(IMFs) was used as characteristic parameter of the matter-element. Then, to determine classical domains of characteristic parameters, the mathematical statistics method was adopted. Finally, the BPD was analyzed qualitatively and quantitatively according to the comprehensive correlation degree of bearing current operating state related to its healthy state. The analytic results of bearing test-rig show that the proposed method indicates the incipient fault approximately occurring in the 81 st hour, and the method also quantitatively presents the degree of BPD. By contrast, the BPD assessment based on time-domain features extraction method could not achieve the above two results effectively. | 刘玉梅 赵聪聪 熊明烨 赵颖慧 乔宁国 田广东 | 2017 | Journal of Central South University2017，24，5： | 16 |
| 9 | Gearbox Fault Diagnosis using Adaptive Zero Phase Time-varying Filter Based on Multi-scale Chirplet Sparse Signal Decomposition显示文摘When used for separating multi-component non-stationary signals, the adaptive time-varying filter(ATF) based on multi-scale chirplet sparse signal decomposition(MCSSD) generates phase shift and signal distortion. To overcome this drawback, the zero phase filter is introduced to the mentioned filter, and a fault diagnosis method for speed-changing gearbox is proposed. Firstly, the gear meshing frequency of each gearbox is estimated by chirplet path pursuit. Then, according to the estimated gear meshing frequencies, an adaptive zero phase time-varying filter(AZPTF) is designed to filter the original signal. Finally, the basis for fault diagnosis is acquired by the envelope order analysis to the filtered signal. The signal consisting of two time-varying amplitude modulation and frequency modulation(AM-FM) signals is respectively analyzed by ATF and AZPTF based on MCSSD. The simulation results show the variances between the original signals and the filtered signals yielded by AZPTF based on MCSSD are 13.67 and 41.14, which are far less than variances (323.45 and 482.86) between the original signals and the filtered signals obtained by ATF based on MCSSD. The experiment results on the vibration signals of gearboxes indicate that the vibration signals of the two speed-changing gearboxes installed on one foundation bed can be separated by AZPTF effectively. Based on the demodulation information of the vibration signal of each gearbox, the fault diagnosis can be implemented. Both simulation and experiment examples prove that the proposed filter can extract a mono-component time-varying AM-FM signal from the multi-component time-varying AM-FM signal without distortion. | WU Chunyan LIU Jian PENG Fuqiang YU Dejie LI Rong | 2013 | Chinese Journal of Mechanical Engineering2013，26，4： | 16 |
| 10 | Influence of environment and substrate quality on the decomposition of wetland plant root in the Sanjiang Plain,Northeast China显示文摘The litterbag method was used to study the decomposition of wetland plant root in three wetlands along a water level gradient in the Sanjiang Plain,Northeast China.These wetlands are Calamagrostis angustifolia(C.aa),Carex meyeriana(C.ma)and Carex lasiocarpa (C.la).The objective of our study is to evaluate the influence of environment and substrate quality on decomposition rates in the three wetlands.Calico material was used as a standard substrate to evaluate environmental influences.Roots native to each wetland were used to evaluate decomposition dynamics and substrate quality influences.Calico mass loss was statistically different among the three wetlands in the upper soil profile(0–10 cm)and in the lower depth range(10–20 cm).Hydrology,temperature and pH all influence calico decomposition rates in different ways at different depths of the soil profiles.The decomposition rates of native roots declined differentially with the increase of depth in the soil profiles.The mass loss of native roots showed a statistical decrease among the three wetlands in the upper soil profile(0–10 cm)and in the lower depth range(10–20 cm)as C.ma wetland>C.aa wetland>C.la wetland. Both the C:P ratio and N:P ratio were positively interrelated with decomposition rates.Decomposition rates were negatively related to initial P concentration in all three wetlands,indicating that P concentration seems to be an important factor controlling the litter loss. | GUO, Xuelian LU, Xianguo TONG, Shouzheng DAI, Guohua | 2008 | Journal of Environmental Sciences2008，20，12： | 14 |
| 11 | An overview on properties,thermal decomposition,and combustion behavior of ADN and ADN based solid propellants显示文摘Ammonium dinitramide [NH4 N(NO_2)2, ADN] is considered as a possible replacement for ammonium perchlorate(AP) in nearly all kind of solid rocket propulsions in the coming future. The reason to use ADN instead of AP in solid rocket propulsion is because of its harmless combustion products, along with its capacity to generate high specific impulse(Isp). ADN is fairly a new member in the solid oxidizer community and is considered under green energetic material(GEM). Application and feasible utilization of ADN as an oxidizer for composite solid propellants(CSP's) requires complete knowledge of its thermal decomposition processes along with its combustion behavior. A detailed overview on the physical and chemical properties, thermal decomposition, and combustion behavior of ADN and ADN based propellants has been discussed in this paper. Catalytic effect on thermal decomposition, combustion wave structure, and burning rate of ADN is also discussed. | Pratim Kumar Alliance | 2018 | Defence Technology(防务技术)2018，14，6： | 14 |
| 12 | 行(或列)对称矩阵的满秩分解及其算法显示文摘1 引言矩阵满秩分解是线性代数的基本分解方法之一,在广义逆矩阵的求解过程中起着重要的作用.矩阵A的满秩分解及A的Moore-Penrose逆不仅有着广泛的现实应用,而且也有理论研究意义,尤其是在数理统计,系统理论,优化计算和控制论等许多领域应用十分广泛.如用计算机对具有对称性质的图像进行采样。 | 王震 蔺小林 蒋耀林 | 2005 | 高等学校计算数学学报2005，27，S1： | 13 |
| 13 | 基于双树复小波和奇异差分谱的齿轮故障诊断研究显示文摘针对齿轮故障振动信号的非平稳特性和包含强烈噪声,很难提取故障特征频率的情况,提出了基于双树复小波和奇异差分谱的故障诊断方法。首先将非平稳的故障振动信号通过双树复小波分解为几个不同频段的分量;由于噪声的影响,从各个分量的频谱中难以准确地得到故障频率。然后对包含故障特征的分量构建Hankel矩阵并进行奇异值分解,求奇异值差分谱曲线,确定奇异值个数进行SVD重构降噪,由此实现对故障特征信息的提取。最后再求希尔伯特包络谱,便能准确地得到故障频率。实验结果和工程应用表明,该方法可以有效地提取齿轮的故障特征信息,验证了方法的可行性和有效性。 | 胥永刚 孟志鹏 陆明 付胜 | 2014 | 振动与冲击2014，33，1： | 13 |
| 14 | Partial Regularity for Two Dimensional Landau-Lifshitz Equations | Chen Yunmei Ding Shijin Guo Doling Department of Mathematics, University of Florida, Gainesville, FL32611, U.S.A. Institute of Applied Physics and Computational Mathematics, P. O. Box 8009, Beijing, 100088, China | 1998 | Acta Mathematica Sinica,English Series1998，14，3： | 12 |
| 15 | An explicit four-dimensional variational data assimilation method显示文摘A new data assimilation method called the explicit four-dimensional variational (4DVAR) method is proposed. In this method, the singular value decomposition (SVD) is used to construct the orthogonal basis vectors from a forecast ensemble in a 4D space. The basis vectors represent not only the spatial structure of the analysis variables but also the temporal evolution. After the analysis variables are ex-pressed by a truncated expansion of the basis vectors in the 4D space, the control variables in the cost function appear explicitly, so that the adjoint model, which is used to derive the gradient of cost func-tion with respect to the control variables, is no longer needed. The new technique significantly simpli-fies the data assimilation process. The advantage of the proposed method is demonstrated by several experiments using a shallow water numerical model and the results are compared with those of the conventional 4DVAR. It is shown that when the observation points are very dense, the conventional 4DVAR is better than the proposed method. However, when the observation points are sparse, the proposed method performs better. The sensitivity of the proposed method with respect to errors in the observations and the numerical model is lower than that of the conventional method. | QIU ChongJian ZHANG Lei SHAO AiMei | 2007 | Science China Earth Sciences2007，50，8： | 11 |
| 16 | Phase transformation refinement of coarse primary carbides in M2 high speed steel | Fu-sheng PAN Wei-qing WANG Ai-tao TANG Li-zhi WU Ting-ting LIU Ren-ju CHENG | 2011 | Progress in Natural Science:Materials International2011，21，2： | 10 |
| 17 | Wind power prediction based on variational mode decomposition multi-frequency combinations显示文摘Because of the uncertainty and randomness of wind speed, wind power has characteristics such as nonlinearity and multiple frequencies. Accurate prediction of wind power is one effective means of improving wind power integration. Because the traditional single model cannot fully characterize the fluctuating characteristics of wind power, scholars have attempted to build other prediction models based on empirical mode decomposition(EMD) or ensemble empirical mode decomposition(EEMD) to tackle this problem. However, the prediction accuracy of these models is affected by modal aliasing and illusive components. Aimed at these defects, this paper proposes a multi-frequency combination prediction model based on variational mode decomposition(VMD). We use a back propagation neural network(BPNN),autoregressive moving average(ARMA)model, and least square support vector machine(LS-SVM) to predict high, intermediate,and low frequency components,respectively. Based on the predicted values of each component, the BPNN is applied to combine them into a final wind power prediction value.Finally,the prediction performance of the single prediction models(ARMA,BPNN and LS-SVM)and the decomposition prediction models(EMD and EEMD) are used to compare with the proposed VMD model according to the evaluation indices such as average absolute error, mean square error,and root mean square error to validate its feasibility and accuracy. The results show that the prediction accuracy of the proposed VMD model is higher. | Gang ZHANG Hongchi LIU Jiangbin ZHANG Ye YAN Lei ZHANG Chen WU Xia HUA Yongqing WANG | 2019 | Journal of Modern Power Systems and Clean Energy2019，7，2： | 10 |
| 18 | Hydrothermal Synthesis and Thermal Decomposition Mechanism of Alkaline Earth Benzoates显示文摘0IntroductionAlkalineearthbenzoatesareakindofstablecompound.Thecoordinationcompoundsformedbyalkalineearthandcarboxylicacidsha... | Zhang, Keli Yuan, Jibing Yuan, Liangjie Sun, Jutang | 1999 | Wuhan University Journal of Natural Sciences1999，4，1： | 9 |
| 19 | Nitrogen forms and decomposition of organic carbon in the southern Bohai Sea core sediments显示文摘Study on form characteristics of nitrogen in marine sediments is the primary method to research its biogeochemical cycling and nitrogen form characteristics in core sediments can reflect the process and results of early diagenesis in a certain degree. In this paper, Sequential extraction process in natural grain size was used for studying the existent forms of nitrogen in five core sediments of the southern Bohai Sea for the first time. Nitrogen was divided into two parts - transferable and fixed based on whether it could be extracted by the reagent. Distributions and early diagenesis of transferable nitrogen forms in the southern Bohai Sea were researched integratedly. Results indicate that IEF- N and OSFN are predominant forms in transferable part in the studied core sediments. Contents of different nitrogen forms vary differently with depth, and have different diagenesis process. Decomposition constant of organic nitrogen (ON) and OC are about 15.51 × 10-3a-1and 4.79 × 10-3a-1 respectively, and the decomposition content of biogenic elements C, N, P, Si has the sequence N>P>C>Si. OC/TN (simplified as C/N in the following) ratio is much lower than OC/ON, which indicates that sediment preserves plenty of inorganic nitrogen (IN) and/or fixed nitrogen, and the decrease of OC/ON ratio with depth is due to ON reservation in sediments. Generally, transferable nitrogen accounts for more proportion of TN in the surface layer than in the deep layer of core sediments, whereas, some stable forms of nitrogen can activate and become transferable under appropriate environment, which induces the proportion of transferable nitrogen in TN in the deep layer to be almost the same as that in the surface layer. | 宋金明 马红波 吕晓霞 | 2002 | Acta Oceanologica Sinica2002，21，1： | 9 |
| 20 | Decompositions of the 3-uniform hypergraphs K_v^(3) into hypergraphs of a certain type显示文摘In this paper,we investigate a generalization of graph decomposition,called hypergraph decomposition.We show that a decomposition of a 3-uniform hypergraph Kv3into a special kind of hypergraph K43-e exists if and only if v≡0,1,2(mod 9)and v≥9. | Tao FENG Yan-xun CHANG Institute of Mathematics,Beijing Jiaotong University,Beijing 100044,China | 2007 | Science China Mathematics2007，50，7： | 8 |
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