期刊文献+
共找到190篇文章
< 1 2 10 >
每页显示 20 50 100
Bone alterations in inflammatory bowel diseases 被引量:11
1
作者 Dolores Sgambato Francesca Gimigliano +8 位作者 Cristiana De Musis Antimo Moretti Giuseppe Toro Emanuele Ferrante Agnese Miranda Domenico De Mauro Lorenzo Romano Giovanni Iolascon Marco Romano 《World Journal of Clinical Cases》 SCIE 2019年第15期1908-1925,共18页
Inflammatory bowel diseases(IBDs)are characterized by a multifactorial partially unknown etiology that involves genetic,immunological and environmental factors.Up to 50%of IBD patients experience at least one extraint... Inflammatory bowel diseases(IBDs)are characterized by a multifactorial partially unknown etiology that involves genetic,immunological and environmental factors.Up to 50%of IBD patients experience at least one extraintestinal manifestation;among them is the involvement of bone density which is referred to as metabolic bone disease(MBD),including osteopenia and osteoporosis.Bone alterations in IBDs population appear to have a multifactorial etiology:Decreased physical activity,inflammation-related bone resorption,multiple intestinal resections,dietary malabsorption of minerals and vitamin D deficiency,genetic factors,gut-bone immune signaling interaction,steroid treatment,microbiota and pathogenic micro-organisms interaction,and dietary malabsorption of minerals,that,all together or individually,may contribute to the alteration of bone mineral density.This review aims to summarize the prevalence and pathophysiology of metabolic bone alterations in IBD subjects outlining the main risk factors of bone fragility.We also want to underline the role of the screening and prophylaxis of bone alterations in Crohn’s disease and ulcerative colitis patients and the importance of treating appropriately MBD. 展开更多
关键词 Inflammatory BOWEL diseases BONE alterations BONE mineral density OsTEOPOROsIs OsTEOPENIA ULCERATIVE COLITIs Crohn’s disease
下载PDF
Endoscopic treatment of biliopancreatic pathology in patients with Whipple's pancreaticoduodenectomy surgical variants: Lessons learned from single-balloon enteroscopy-assisted ERCP
2
作者 Rodrigo Garcés-Durán Laurent Monino +2 位作者 Pierre H Deprez Hubert Piessevaux Tom G Moreels 《Hepatobiliary & Pancreatic Diseases International》 SCIE CAS CSCD 2024年第5期509-514,共6页
Background: Endoscopic treatment of biliopancreatic pathology is challenging due to surgically altered anatomy after Whipple's pancreaticoduodenectomy. This study aimed to evaluate the feasibility and safety of si... Background: Endoscopic treatment of biliopancreatic pathology is challenging due to surgically altered anatomy after Whipple's pancreaticoduodenectomy. This study aimed to evaluate the feasibility and safety of single-balloon enteroscopy-assisted endoscopic retrograde cholangiopancreatography(SBE-ERCP) to treat biliopancreatic pathology in patients with Whipple's pancreaticoduodenectomy surgical variants. Methods: We retrospectively analyzed 106 SBE-ERCP procedures in 46 patients with Whipple's variants. Technical and clinical success rates and adverse events were evaluated. Results: Biliary SBE-ERCP was performed in 34 patients and pancreatic SBE-ERCP in 17, including 5 with both indications. From a total of 106 SBE-ERCP procedures, 76 were biliary indication with technical success rate of 68/76(90%) procedures and clinical success rate of 30/34(88%) patients. Mild adverse event rate was 8/76(11%), without serious adverse events. From a total of 106 SBE-ERCP procedures, 30 were pancreatic indication with technical success rate of 24/30(80%) procedures( P = 0.194 vs. biliary SBEERCP) and clinical success rate of 11/17(65%) patients( P = 0.016 vs. biliary SBE-ERCP). Mild adverse event rate was 6/30(20%)( P = 0.194 vs. biliary SBE-ERCP), without serious adverse events. After SBE-ERCP failure, endoscopic ultrasound-guided drainage, percutaneous drainage and redo surgery were alternative therapeutic options. Conclusions: Biliopancreatic pathology after Whipple's pancreaticoduodenectomy variants can be treated using SBE-ERCP without serious adverse events. Technical and clinical success rates are high for biliary indications, whereas clinical success rate of pancreatic indications is significantly lower. SBE-ERCP can be considered as first-line treatment option in this patient group with surgically altered anatomy. 展开更多
关键词 ENTEROsCOPY Endoscopic retrograde CHOLANGIOPANCREATOGRAPHY PANCREATICODUODENECTOMY surgically altered anatomy Whipple’s procedure
下载PDF
Casson hybrid nanofluid flow over a Riga plate for drug deliveryapplications with double diffusion
3
作者 Abeer S.Alnahdi Taza Gul 《Chinese Physics B》 SCIE EI CAS CSCD 2024年第10期311-320,共10页
Casson fluid-mediated hybrid nanofluids are more effective at transferring heat than traditional heat transfer fluids in terms of thermal conductivity.Heat exchangers,cooling systems and other thermal management syste... Casson fluid-mediated hybrid nanofluids are more effective at transferring heat than traditional heat transfer fluids in terms of thermal conductivity.Heat exchangers,cooling systems and other thermal management systems are ideal for use with Casson fluids.Precise control of the flow and release of medication is necessary when using Casson fluids in drug delivery systems because of their unique rheological properties.Nanotechnology involves the creation of nanoparticles that are loaded with drugs and distributed in Casson fluid-based carriers for targeted delivery.In this study,to create a hybrid nanofluid,both single-walled carbon nanotubes(SWCNTs)and multi-walled carbon nanotubes(MWCNTs)are dispersed in a Casson fluid with Fourier’s and Fick’s laws assumptions.The Casson fluid is suitable for various engineering and medical applications due to the enhancement of heat transfer and thermal conductivity by the carbon nanotubes.Our objective is to understand how SWCNTs and MWCNTs impact the flow field by studying the flow behavior of the Casson hybrid nanofluid when it is stretched against a Riga plate.The Darcy-Forchheimer model is also used to account for the impact of the porous medium near the stretching plate.Both linear and quadratic drag terms are taken into account in this model to accurately predict the flow behavior of the nanofluid.In addition,the homotopy analysis method is utilized to address the model problem.The outcomes are discussed and deliberated based on drug delivery applications.These findings shed valuable light on the flow characteristics of a Casson hybrid nanofluid comprising SWCNTs and MWCNTs.It is observed that the incorporation of carbon nanotubes makes the nanofluid a promising candidate for medical applications due to its improved heat transfer properties. 展开更多
关键词 carbon nanotubes(CNTs) Riga plate Casson fluid with fouriers and Fick’s laws analytical solutions
下载PDF
A holographic optical communication system based on RSA algorithm and quaternion function
4
作者 YANG Peng HAN Jianning 《Journal of Measurement Science and Instrumentation》 CAS CSCD 2024年第3期338-343,共6页
A facile encryption way was successfully applied to the holographic optical encryption system with high speed,multidimensionality,and high capacity,which provided a better security solution for underwater communicatio... A facile encryption way was successfully applied to the holographic optical encryption system with high speed,multidimensionality,and high capacity,which provided a better security solution for underwater communication.The reconstructed optical security system for information transmission was based on wavelengthλand focal length f that were keys to encryption and decryption.To finish the secure data transmission(λ,f)between sender and receiver,an extended Rivest-Shamir-Adleman(ERSA)algorithm for the encryption was achieved based on three-dimension quaternion function.Therein,the Pollard’s rho method was used for the evaluation and comparison of RSA and ERSA algorithms.The results demonstrate that the message encrypted by the ERSA algorithm has better security than that by RSA algorithm in the face of unpredictability and complexity of information transmission on the unsecure acoustic channel. 展开更多
关键词 HOLOGRAPHY QUATERNION fourier lens extended Rivest-shamir-Adleman(ERsA) Pollard’s rho method
下载PDF
Dynamic Uncertainty:Exploring the Spatial Order of Future Digital Architecture
5
作者 Yuxin Zhao 《Journal of Civil Engineering and Architecture》 2024年第10期475-484,共10页
The spatial order of architecture has been significantly impacted by digital architectural design and production,creating a dynamic uncertainty.This study aims to explore digital architecture from the perspective of s... The spatial order of architecture has been significantly impacted by digital architectural design and production,creating a dynamic uncertainty.This study aims to explore digital architecture from the perspective of spatial order,discussing the antidote/poison effect caused by digital technologies in architectural practice and the cultural digital changes in digital architectures.The study selected four digital architecture cases,including the(W)rapper at Los Angeles by Eric Owen Moss,Beijing Daxing International Airport by Zaha Hadid,3D Print Niaokan Bridge by Xu Weiguo,and World Internet Conference Center by Yuan Feng.This study is hypothesising that the future special order of digital architectures will be a dynamic and balanced new spatial order.This new order includes the symbiosis of a human-machine and virtual-real hierarchy;the interactive co-existence between nature,humanity and technology;and the creative multi-immersive sharing of parametric information,built-environment resources and cultural artistic information.The evolution of spatial order of future digital architecture will be discussed in connection with the idea of the metaverse.The value of this work is its ability to inspire a broader examination of the new order of digital architectural space. 展开更多
关键词 spatial superimposition digital technology’s antidote&poison effect the spatial order of digital architectures alteration of spatial order
下载PDF
基于AD9361星载USB测控接收设备设计
6
作者 何林飞 李晓飞 韩俊博 《电讯技术》 北大核心 2024年第5期778-784,共7页
针对星载统一S频段(Unified S-band,USB)测控应答机遥控接收高动态问题,提出了一种USB接收设备的设计方法。该方法基于AD9361+现场可编程逻辑门阵列(Field Programmable Gate Array,FPGA)硬件平台,采用并行+串行快速傅里叶变换(Fast Fou... 针对星载统一S频段(Unified S-band,USB)测控应答机遥控接收高动态问题,提出了一种USB接收设备的设计方法。该方法基于AD9361+现场可编程逻辑门阵列(Field Programmable Gate Array,FPGA)硬件平台,采用并行+串行快速傅里叶变换(Fast Fourier Transform,FFT)实现信号载波频率捕获,载波环路使用2阶锁频环(Frequency Lock Loop,FLL)辅助3阶锁相环(Phase Lock Loop,PLL)环路进行跟踪,遥控副载波环路采用2阶PLL环进行跟踪。对方法的可行性进行了理论推导,使用Matlab进行仿真,结果表明该方法可以满足多普勒动态不小于32 kHz/s下遥控数据解调要求。 展开更多
关键词 统一s频段测控应答机 高动态信号 快速傅里叶变换
下载PDF
Enhanced Wideband Frequency Estimation via FFT: Leveraging Polynomial Interpolation and Array Indexing
7
作者 Kiran Jayarama Chien-In Henry Chen 《Journal of Computer and Communications》 2024年第1期35-48,共14页
Accurate frequency estimation in a wideband digital receiver using the FFT algorithm encounters challenges, such as spectral leakage resulting from the FFT’s assumption of signal periodicity. High-resolution FFTs pos... Accurate frequency estimation in a wideband digital receiver using the FFT algorithm encounters challenges, such as spectral leakage resulting from the FFT’s assumption of signal periodicity. High-resolution FFTs pose computational demands, and estimating non-integer multiples of frequency resolution proves exceptionally challenging. This paper introduces two novel methods for enhanced frequency precision: polynomial interpolation and array indexing, comparing their results with super-resolution and scalloping loss. Simulation results demonstrate the effectiveness of the proposed methods in contemporary radar systems, with array indexing providing the best frequency estimation despite utilizing maximum hardware resources. The paper demonstrates a trade-off between accurate frequency estimation and hardware resources when comparing polynomial interpolation and array indexing. 展开更多
关键词 scalloping Loss Goertzel’s Algorithm sUPER-REsOLUTION Fast fourier Transform (FFT) Decimation in Frequency (DIF) Decimation in Time (DIT) spectral Leakage Frequency Estimation
下载PDF
欧式期权的Black-Scholes定价公式的Fourier推导
8
作者 唐耀宗 周伟萍 《喀什师范学院学报》 2009年第3期23-25,共3页
采用Fourier变换,对经典的Black-Scholes微分方程进行了推导,最后得到了欧式期权的解析定价公式,即B-S公式.
关键词 fourier变换 Black-scholes微分方程 B-s公式
下载PDF
H^p(S)中函数的Fourier系数 被引量:1
9
作者 肖建波 曹广福 《应用泛函分析学报》 CSCD 2001年第2期164-172,共9页
本文得到几个关于多变量 Hp空间中函数 Fourier系数的不等式.与单变量相应情形相比,我们的证明方法有较大的变化.
关键词 H^p (s)空间 fourier系数 Hausdorff-Yong不等式 HILBERT空间 Passeval公式 复空间 HARDY空间 范数
下载PDF
On the Fourier approximation method for steady water waves 被引量:2
10
作者 ZHAO Hongjun SONG Zhiyao +1 位作者 LI Ling KONG Jun 《Acta Oceanologica Sinica》 SCIE CAS CSCD 2014年第5期37-47,共11页
A computational method for steady water waves is presented on the basis of potential theory in the physical plane with spatial variables as independent quantities. The finite Fourier series are applied to approximatin... A computational method for steady water waves is presented on the basis of potential theory in the physical plane with spatial variables as independent quantities. The finite Fourier series are applied to approximating the free surface and potential function. A set of nonlinear algebraic equations for the Fourier coefficients are derived from the free surface kinetic and dynamic boundary conditions. These algebraic equations are numerically solved through Newton's iterative method, and the iterative stability is further improved by a relaxation technology. The integral properties of steady water waves are numerically analyzed, showing that (1) the set-up and the set-down are both non-monotonic quantities with the wave steepness, and (2) the Fourier spectrum of the free surface is broader than that of the potential function. The latter further leads us to explore a modification for the present method by approximating the free surface and potential function through different Fourier series, with the truncation of the former higher than that of the latter. Numerical tests show that this modification is effective, and can notably reduce the errors of the free surface boundary conditions. 展开更多
关键词 steady water waves fourier series Newton's method relaxation technology wave properties
下载PDF
Realization of -bit semiclassical quantum Fourier transform on IBM's quantum cloud computer 被引量:1
11
作者 Xiang-Qun Fu Wan-Su Bao +5 位作者 He-Liang Huang Tan Li Jian-Hong Shi Xiang Wang Shuo Zhang Feng-Guang Li 《Chinese Physics B》 SCIE EI CAS CSCD 2019年第2期117-122,共6页
To overcome the difficulty of realizing large-scale quantum Fourier transform(QFT) within existing technology, this paper implements a resource-saving method(named t-bit semiclassical QFT over Z_(2~n)), which could re... To overcome the difficulty of realizing large-scale quantum Fourier transform(QFT) within existing technology, this paper implements a resource-saving method(named t-bit semiclassical QFT over Z_(2~n)), which could realize large-scale QFT using an arbitrary-scale quantum register. By developing a feasible method to realize the control quantum gate Rk, we experimentally realize the 2-bit semiclassical QFT over Z_(2~3) on IBM's quantum cloud computer, which shows the feasibility of the method. Then, we compare the actual performance of 2-bit semiclassical QFT with standard QFT in the experiments.The squared statistical overlap experimental data shows that the fidelity of 2-bit semiclassical QFT is higher than that of standard QFT, which is mainly due to fewer two-qubit gates in the semiclassical QFT. Furthermore, based on the proposed method, N = 15 is successfully factorized by implementing Shor's algorithm. 展开更多
关键词 QUANTUM CLOUD computation QUANTUM fourier TRANsFORM sEMICLAssICAL QUANTUM fourier TRANsFORM shor’s algorithm
下载PDF
The Fourier Notation of the Geomagnetic Signals Informative Parameters 被引量:1
12
作者 Osvaldo Faggioni 《Journal of Signal and Information Processing》 2018年第3期153-166,共14页
The paper discusses the quantitative definition of the s/n (signal to noise ratio) by means of new computational parameters derived (and computed) by the Fourier analysis. The theme is of great relevance when the geom... The paper discusses the quantitative definition of the s/n (signal to noise ratio) by means of new computational parameters derived (and computed) by the Fourier analysis. The theme is of great relevance when the geomagnetic observed field has high transient noise and high energy content (i.e.geomagnetic signal interfered by human activity magnetic band) and when the signal analysis action is oriented to the detection of magnetic sources characterized by quasi-punctiform size, low energy level and kinetic mechanical status (i.e.uw armed terrorist). The paper shows the results obtained introducing two new informative spectral parameters: the informative capability “C” and the enhanced informative capability “eC”. These parameters are depending on the comparison of the energy of the target signal with total field energy and they are characteristics of each elementary signal. C classifies the energy of the spectrum in two metrological bands: elementary signal informative energy EI (band or single signal) and passive energy EP. This metrological classification of the energy overtakes the concept of noise: each signal is part of the noise band when it is not under observation and becomes out of the band when it is under observation (numerical observation→computation). C (and eC) allows to compute the value of the “visibility” of the informative signals in a high energy geomagnetic field (or spectrum). C is a fundamental parameter for the evaluation of the effectiveness of singularity magnetic metrology in the passive detection of small magnetic sources in high noised magnetic field. 展开更多
关键词 Geomatic INFORMATIVE signal ANALYsIs fourier ANALYsIs GEOMAGNETIsM Metrology of singularity Frequency Domain Observations s/N Manipulation
下载PDF
Quantum-Classical Algorithm for an Instantaneous Spectral Analysis of Signals:A Complement to Fourier Theory 被引量:2
13
作者 Mario Mastriani 《Journal of Quantum Information Science》 2018年第2期52-77,共26页
A quantum time-dependent spectrum analysis, or simply, quantum spectral analysis (QSA) is presented in this work, and it’s based on Schr&#246;dinger’s equation. In the classical world, it is named frequency in t... A quantum time-dependent spectrum analysis, or simply, quantum spectral analysis (QSA) is presented in this work, and it’s based on Schr&#246;dinger’s equation. In the classical world, it is named frequency in time (FIT), which is used here as a complement of the traditional frequency-dependent spectral analysis based on Fourier theory. Besides, FIT is a metric which assesses the impact of the flanks of a signal on its frequency spectrum, not taken into account by Fourier theory and lets alone in real time. Even more, and unlike all derived tools from Fourier Theory (i.e., continuous, discrete, fast, short-time, fractional and quantum Fourier Transform, as well as, Gabor) FIT has the following advantages, among others: 1) compact support with excellent energy output treatment, 2) low computational cost, O(N) for signals and O(N2) for images, 3) it does not have phase uncertainties (i.e., indeterminate phase for a magnitude = 0) as in the case of Discrete and Fast Fourier Transform (DFT, FFT, respectively). Finally, we can apply QSA to a quantum signal, that is, to a qubit stream in order to analyze it spectrally. 展开更多
关键词 fourier Theory Heisenberg’s Uncertainty Principle Quantum fourier Transform Quantum Information Processing Quantum signal Processing schrodinger’s Equation spectral Analysis
下载PDF
Uncertainty Principles for the Generalized Fourier Transform Associated with Spherical Mean Operator
14
作者 Hatem Mejjaoli Youssef Othmani 《Analysis in Theory and Applications》 2013年第4期309-332,共24页
The aim of this paper is to establish an extension of qualitative and quantitative uncertainty principles for the Fourier transform connected with the spherical mean operator.
关键词 Generalized fourier transform Hardy's type theorem Cowling-Price's theorem Beurling's theorem Miyachi's theorem Donoho-stark's uncertainty principle.
下载PDF
Authentication and Secret Message Transmission Technique Using Discrete Fourier Transformation
15
作者 Debnath BHATTACHARYYA Jhuma DUTTA +2 位作者 Poulami DAS Samir Kumar BANDYOPADHYAY Tai-hoon KIM 《International Journal of Communications, Network and System Sciences》 2009年第5期363-370,共8页
In this paper a novel technique, Authentication and Secret Message Transmission using Discrete Fourier Transformation (ASMTDFT) has been proposed to authenticate an image and also some secret message or image can be t... In this paper a novel technique, Authentication and Secret Message Transmission using Discrete Fourier Transformation (ASMTDFT) has been proposed to authenticate an image and also some secret message or image can be transmitted over the network. Instead of direct embedding a message or image within the source image, choosing a window of size 2 x 2 of the source image in sliding window manner and then con-vert it from spatial domain to frequency domain using Discrete Fourier Transform (DFT). The bits of the authenticating message or image are then embedded at LSB within the real part of the transformed image. Inverse DFT is performed for the transformation from frequency domain to spatial domain as final step of encoding. Decoding is done through the reverse procedure. The experimental results have been discussed and compared with the existing steganography algorithm S-Tools. Histogram analysis and Chi-Square test of source image with embedded image shows the better results in comparison with the S-Tools. 展开更多
关键词 Data Hiding AUTHENTICATION Frequency Domain DIsCRETE fourier Transformation (DFT) INVERsE DIsCRETE fourier TRANsFORM (IDFT) s-Tools
下载PDF
Realizing the potential of exploiting human IPSCs and their derivatives in research of Down syndrome
16
作者 YAFEI WANG JIELEI NI +5 位作者 YUHAN LIU DINGYING LIAO QIANWEN ZHOU XIAOYANG JI GANG NIU YANXIANG NI 《BIOCELL》 SCIE 2023年第12期2567-2578,共12页
Down syndrome(DS)is a genetic condition characterized by intellectual disability,delayed brain development,and early onset Alzheimer’s disease.The use of primary neural cells and tissues is important for understandin... Down syndrome(DS)is a genetic condition characterized by intellectual disability,delayed brain development,and early onset Alzheimer’s disease.The use of primary neural cells and tissues is important for understanding this disease,but there are ethical and practical issues,including availability from patients and experimental manipulability.Moreover,there are significant genetic and physiological differences between animal models and humans,which limits the translation of the findings in animal studies to humans.Advancements in induced pluripotent stem cells(iPSC)technology have revolutionized DS research by providing a valuable tool for studying the cellular and molecular pathologies associated with DS.Induced pluripotent stem cells derived from cells obtained from DS patients contain the patient’s entire genome including trisomy 21.Trisomic iPSCs as well as their derived cells or organoids can be useful for disease modeling,investigating the molecular mechanisms,and developing potential strategies for treating or alleviating DS.In this review,we focus on the use of iPSCs and their derivatives obtained from DS individuals and healthy humans for DS research.We summarize the findings from the past decade of DS studies using iPSCs and their derivatives.We also discuss studies using iPSC technology to investigate DS-associated genes(e.g.,APP,OLIG1,OLIG2,RUNX1,and DYRK1A)and abnormal phenotypes(e.g.,dysregulated mitochondria and leukemia risk).Lastly,we review the different strategies for mitigating the limitations of iPSCs and their derivatives,for alleviating the phenotypes,and for developing therapies. 展开更多
关键词 Down syndrome Induced pluripotent stem cell Trisomy 21 NEURODEVELOPMENT Genetic alterations Alzheimer’s disease
下载PDF
基于快速傅里叶变换和改进T-S模糊神经网络集成模型的逆变器开路故障诊断方法研究
17
作者 田广强 乔珊珊 +1 位作者 侯奥 王福忠 《电力科学与技术学报》 CAS CSCD 北大核心 2023年第6期76-86,共11页
针对受负载扰动和测量噪声影响,逆变器开路时的故障边界间、故障与特征间存在交叠和模糊性问题,在对逆变器功率管开路故障特征的分析基础上,提出基于快速傅里叶变换和改进T‑S(Takagi‑Sugeno)模糊神经网络集成模型的逆变器开路故障诊断... 针对受负载扰动和测量噪声影响,逆变器开路时的故障边界间、故障与特征间存在交叠和模糊性问题,在对逆变器功率管开路故障特征的分析基础上,提出基于快速傅里叶变换和改进T‑S(Takagi‑Sugeno)模糊神经网络集成模型的逆变器开路故障诊断模型。首先,依据快速傅里叶变换分析逆变器的三相输出电流波形,提取功率管发生不同类型开路故障时的故障特征;其次,采用规则自分裂技术和模糊C均值设计T‑S模糊神经网络的前件网络的隶属函数层;然后,依托自适应Levenberg‑Marquardt算法对T‑S网络参数进行训练;最后,利用训练后的T‑S网络实现逆变器功率管的多种故障类型与位置的诊断。实验结果表明,所提出模型的诊断准确率高达96%,能够显著改善逆变器功率管开路故障诊断时所存在的问题。 展开更多
关键词 逆变器 开路故障诊断 快速傅里叶变换 改进T‑s模糊神经网络 自适应LM算法
下载PDF
六相永磁同步电机驱动系统直流环节电容器电流RMS值估计
18
作者 张志刚 常加冕 张鹏程 《控制与信息技术》 2023年第5期62-66,共5页
六相永磁同步电机(PMSM)驱动系统相比传统三相PMSM驱动系统具有低压大功率、转矩脉动小、控制灵活和容错率高等特点。直流环节电容器对驱动系统的稳定性起着决定性作用,但由于其结构特殊,需承受较高的纹波电流均方根(RMS)值。而直流电... 六相永磁同步电机(PMSM)驱动系统相比传统三相PMSM驱动系统具有低压大功率、转矩脉动小、控制灵活和容错率高等特点。直流环节电容器对驱动系统的稳定性起着决定性作用,但由于其结构特殊,需承受较高的纹波电流均方根(RMS)值。而直流电容器的电流RMS值是决定其使用成本、体积和寿命的重要参考指标。因此对直流电容器的电流RMS值进行估计显得尤为重要。针对采用传统双重傅里叶积分算法计算电容的电流RMS值时存在的过程繁琐、涉及许多未解积分等问题,文章提出了一种基于多项式插值求积法Cotes的直流电容器电流RMS值的计算方法。即在等距离步长中分布5个采样点,对推导出的函数积分生成近似解,采用Cotes法可以省去大量的积分计算过程,同时提高计算精度。该方法简化了传统算法的繁琐计算过程并且保证了较高的计算精度,可为直流环节电容器的优化选型和寿命监测控制器设计提供指导。最后,文章将所提方法与现有方法进行了对比分析,实验结果验证了所提方法的计算速度比传统双重傅里叶积分算法快50%左右,且计算精度较牛顿3/8法提高了约5%。 展开更多
关键词 六相永磁同步电机 直流电容 电流RMs 双重傅里叶积分
下载PDF
黄河水沙监测数据分析模型
19
作者 陈瑶 徐萌 +1 位作者 金成涛 王积建 《数学建模及其应用》 2024年第2期100-113,共14页
为研究黄河小浪底水库下游某水文站水沙通量的变化规律和“调水调沙”效果,以2016-2022年水位、水流量与含沙量的实际监测数据为依据,估算出年均径流量325亿立方米,年均排沙量2亿吨.分别使用双对数回归分析、M-K检验、小波分析、R/S分... 为研究黄河小浪底水库下游某水文站水沙通量的变化规律和“调水调沙”效果,以2016-2022年水位、水流量与含沙量的实际监测数据为依据,估算出年均径流量325亿立方米,年均排沙量2亿吨.分别使用双对数回归分析、M-K检验、小波分析、R/S分析对水沙通量的敏感性、突变性、周期性、趋势性进行了分析,得出结论:水位每增加1%,含沙量就增加37.63%,含沙量关于水位非常敏感;水沙通量均在2018年3月发生了突变;水沙通量均以18月为主周期振荡;水通量、沙通量在未来2年分别是增长趋势和下降趋势.使用傅里叶级数叠加线性函数预测未来2年的水沙通量,并建立了0-1规划模型对今后2年的监测方案进行了优化.通过比较“调水调沙”前后水沙通量、河底高程的变化,证明了“调水调沙”效果非常显著. 展开更多
关键词 双对数回归 M-K检验 小波分析 R/s分析 傅里叶级数 0-1规划
下载PDF
磺胺甲噁唑对绿藻的生长抑制作用及其潜在毒理学机制
20
作者 熊倩 田斐 +3 位作者 刘芳 张林宝 张喆 陈海刚 《生态毒理学报》 CAS CSCD 北大核心 2024年第3期342-352,共11页
磺胺甲噁唑(sulfamethoxazole,SMX)常用于动物和人类疾病治疗,导致其在多种环境介质中广泛检出。绿藻作为水生生态系统中的初级生产者,因其灵敏度较高而常用作毒性评估的模式生物。然而,目前关于SMX对绿藻的毒性研究普遍以传统毒性测试... 磺胺甲噁唑(sulfamethoxazole,SMX)常用于动物和人类疾病治疗,导致其在多种环境介质中广泛检出。绿藻作为水生生态系统中的初级生产者,因其灵敏度较高而常用作毒性评估的模式生物。然而,目前关于SMX对绿藻的毒性研究普遍以传统毒性测试为主,缺乏对其生物大分子水平毒性效应的深入认识。本研究结合藻类生长抑制实验和傅里叶变换红外光谱(Fourier transform infrared spectroscopy,FTIR)分析深入探究SMX对绿藻生物大分子水平的毒性作用机制。藻类生长抑制实验结果表明,SMX对3株绿藻的EC 50(置信度95%)依次为斜生栅藻(8.53 mg·L^(-1))<四尾栅藻(14.30 mg·L^(-1))<尖细栅藻(90.45 mg·L^(-1))。基于FTIR分析发现,SMX暴露引起绿藻生物大分子发生变化且存在明显的剂量效应关系。脂质水平上,脂质发生过氧化、改变脂肪酸烷基链长度,进而影响细胞膜的流动性和通透性。蛋白质水平上,酰胺Ⅰ和酰胺Ⅱ的变化揭示蛋白质二级结构发生变化。DNA水平上,DNA构型发生变化,由常见的B-DNA型转换为能抵御外界干扰A-DNA型。3株绿藻在生物大分子水平对SMX暴露的响应差异可能与其细胞壁结构组成差异有关。 展开更多
关键词 磺胺甲噁唑 微藻 毒理学机制 傅里叶变换红外光谱 生物大分子变化
下载PDF
上一页 1 2 10 下一页 到第
使用帮助 返回顶部