共查询到20条相似文献，搜索用时 265 毫秒
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做了基于矢量有限元法的谐振腔通用计算模拟器的模拟设计。该模拟器包括前处理、有限元求解和后处理三部分。首先在前处理中进行三维实体建模和网格划分,然后运用有限元方法生成矩阵并求解该矩阵,在后处理中计算谐振腔的任意本征频率,本征值及电磁场分布。通过分别对几种不同介质加载下的谐振腔进行仿真求解,并将计算结果与商业仿真软件HFS... 相似文献
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采用FLUENT软件,应用标准k-湍流模型和混合网格,采用分离隐式求解器,对某离心风机三维流场进行了CFD数值计算分析。计算表明:虽风机内部流场速度分布比较均匀,无明显的漩涡、二次流等出现,但风机内部流场顺畅性不佳,有待改进。 相似文献
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利用UG软件建立轴流泵叶片的三维模型,采用ANSYS CFX软件计算得到叶片上下表面的水压力分布,通过ANSYS Workbench软件强大的耦合分析功能将水压力加载到叶片有限元模型上,最后利用ANSYS软件进行求解计算,得到应力分布结果,根据第三强度理论做应力评定. 相似文献
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本文以主梁为结构内力计算为例,应用结构力学求解器(SM Solver)对工程结构进行内力计算分析,将其结果与系数表人工求解方法所得结果的主要数据进行对比分析,表明采用SM Solver计算的结果满足工程计算精度要求。将SM Solver计算结果导入数学分析软件MATLAB绘制出弯矩内力包络图,很好地解决了系数表人工求解方法中无法得到主梁跨中各控制截面最不利内力的问题。将SM Solver和MATLAB结合起来,提供了一种简便易行的结构内力计算和内力包络图绘制方法。 相似文献
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在最优控制中,控制率的求解往往最终化为一个两点边值问题(TPBVP)的求解。由于两点边值问题具有强耦合、非线性的特点,通常采用计算机迭代的方法来求取其数值解。但是几种常用方法均存在初始点不易选取和求解时间较长的缺点。本文结合神经网络及其误差反向传播的思想,在梯度下降法的基础上提出了一种求解两点边值问题的网络新型收敛算法。大量仿真结果表明该方法可有效改善迭代计算,提高了计算性能。 相似文献
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高压注水引起套管内压的变化,增加套损井数。采用三维有限元方法,建立了高压注水的三维有限元力学模型,对模型进行求解,得到了套管管体与射孔段应力强度、水泥环强度与注水压力变化的回归方程,分析了套管和水泥环应力的变化规律,加深了高压注水过程中套损机理的认识。 相似文献
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随着计算机迅速发展,利用计算机来进行仿真分析时可以求解一些无法利用理论分析解答的问题,待分析的实际问题多为三维图形,但利用分析软件对三维模型进行分析时,所需的计算量非常大,大多数情况下是将形状规则的三维模型简化为二维模型,但简化是有一定条件的,以电容器为例,利用ANSYS分析软件分析了阴极有圆锥型突起时的电场分布,与二维简化的模型进行了计算对比,从而得出简化模型的局限性。 相似文献
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提出一种离散化的光学层析成像方法用于提取检测物的纵向深度信息和光谱特性。利用液相的ZnSe量子点为光源,设计了分立的元件组成光学层析装置,提取了多层媒质的信息。在理论上分析了模型的有效性;在实验上,利用五层媒质验证了该方法的可行性。基于此方法的研究可以广泛地应用于光学成像、生物芯片等许多领域。 相似文献
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电离层层析成像技术的研究进展 总被引：2，自引：0，他引：2
作为日地空间环境的重要组成部分,电离层对无线电通讯、卫星导航与定位以及人类的空间活动有着重要的影响。电离层层析成像技术的出现,为探测电离层的时空结构开辟了广阔的前景。目前,层析成像(Computerized Tomography,简称为CT)技术在电离层探测上的应用还很薄弱,很多具体工作还没有开展。为了对CT技术在电离层探测上的应用有个全面、系统的了解,本文对近年来CT技术在电离层领域的研究及进展进行综述,并对电离层CT技术中存在的问题进行了分析,同时对未来待开展的工作进行了展望。 相似文献
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Xiang Ling Zhaokui Jin Qi Jiang Xiaotao Wang Bin Wei Zhongchang Wang Yangsen Xu Tianye Cao Jonathan W Engle Weibo Cai Chenliang Su Qianjun He 《国家科学评论(英文版)》2021,8(6)
Photothermal nanotheranostics, especially in the near infrared II (NIR-II) region, exhibits a great potential in precision and personalized medicine, owing to high tissue penetration of NIR-II light. NIR-II-photothermal nanoplatforms with high biocompatibility as well as high photothermal effect are urgently needed but rarely reported so far. Te nanomaterials possess high absorbance to NIR-II light but also exhibit high cytotoxicity, impeding their biomedical applications. In this work, the controllable incorporation of biocompatible Se into the lattice of Te nanostructures is proposed to intrinsically tune their inherent cytotoxicity and enhance their biocompatibility, developing TeSex nano-alloys as a new kind of theranostic nanoplatform. We have uncovered that the cytotoxicity of Te nanomaterials primarily derives from irreversible oxidation stress and intracellular imbalance of organization and energy, and can be eliminated by incorporating a moderate proportion of Se (x = 0.43). We have also discovered that the as-prepared TeSex nano-alloys have extraordinarily high NIR-II-photothermal conversion efficiency (77.2%), 64Cu coordination and computed tomography contrast capabilities, enabling high-efficacy multimodal photothermal/photoacoustic/positron emission tomography/computed tomography imaging-guided NIR-II-photothermal therapy of cancer. The proposed nano-alloying strategy provides a new route to improve the biocompatibility of biomedical nanoplatforms and endow them with versatile theranostic functions. 相似文献
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Q值结构对了解地壳的非弹性性质、地壳内部构造、热活动状态、地壳介质非均匀性以及断层分布有着重要的意义.编写了基于吸收特征时间t*的三维Q值层析成像人机交互软件,可以方便快捷地计算地震体波（P波和S波）的振幅谱并通过拟合振幅谱得到反映地震波衰减的吸收特征时间t*,并利用t*资料通过三维Q值层析成像方法得到三维Q值结构.实际观测资料处理结果表明,文中给出的方法和软件是有效且可行的. 相似文献
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Natalie Baddour 《Journal of The Franklin Institute》2008,345(7):792-818
Photo-acoustic signal generation has shown potential for medical tomography. This paper aims to present a consistent and unified approach to the mathematical modelling of the photo-acoustic problem, using a transfer function approach. A generalized version of the Fourier slice theorem is presented and proved. Reconstruction algorithms can be developed based on specific cases of this general theorem. Closed-form solutions to special cases are given in Cartesian, cylindrical and spherical polar coordinates. These can be used to simulate the forward problem and as test cases for any reconstruction algorithms. 相似文献
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文物古迹的保存和修复等安全问题一直以来备受各界人士的关注。如何针对性检测这些物质文化遗产内部缺陷和风化程度,确定最佳的修复措施是文物管理保护工作者所关心的主要问题之一。因此针对此类安全检测问题,充分利用地球物理无损探伤技术是经济实用的办法,其重点是观测系统的布置和探测精度等问题。目前通过超声波CT技术和雷达测试技术在文物微观测试中发挥着重要作用。笔者通过总结其探测特征及实例分析说明其可行性及适用性。同时可为我国相关微地球物理探测技术应用的开展提供参考。 相似文献
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Eugene M. Lavely Yan Zhang Edward H. Hill III Yi-san Lai Peter Weichman Angela Chapman 《Journal of The Franklin Institute》2008,345(6):592-617
We consider the problem of building structure estimation using microwave ray tomography. A Bayesian formulation is developed, and a Markov chain Monte Carlo (MCMC) procedure is used to sample the posterior distribution, which is based on a data likelihood defined in terms of a residual misfit between observed and predicted waveforms. To accelerate model optimization, a simulated annealing approach is combined with the MCMC, using specific model moves to explore each component of the model space. Our approach is applicable to data acquired in the frequency or time domain and for monostatic or bistatic acquisition modes. Experimental data for a multi-wall laboratory test structure were acquired using a horn antenna connected to a vector network analyzer and used to validate both the forward model and the inversion approach. Although, in true remote sensing problems for building structure, the model order is usually unknown, in this initial study, the actual inversion experiment is performed in a reduced-dimension model space for which a subset of the variables are taken as known or fixed. Generalization to the variable-dimension problem can be achieved by using reversible jump MCMC sampling procedures. 相似文献
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《Information processing & management》2022,59(5):103046
In computed tomography (CT)-based diagnoses of liver tumors, contrast-enhanced CT may cause renal toxicity and allergic reactions. Regular health examinations prefer plain CT, but subsequent diagnoses significantly depend on subjective experience. Radiomics provides a quantitative, objective, and noninvasive way for diagnosing liver tumors. This study aimed to use plain CT-based radiomics to diagnose hepatocellular (HCC, malignant) and hemangioma (HH, benign) liver tumors. Inspired by the knowledge that HCC and HH exhibit different histopathological characteristics, we developed a novel feature extraction technique (referred to as maximum wavelet-coefficient statistics, MWCS) to highlight the differences in histopathological characteristics by reorganizing and expressing the patterns of wavelet-coefficients that represent local changes. We attempted multiple feature selection algorithms and various machine learning approaches to train classification models and tested these models on an independent test cohort. Experimental results showed that the classification models based on the proposed MWCS-COM (using a statistical method of co-occurrence matrix in MWCS) feature set exhibited performance superior to those based on traditional feature sets. Furthermore, the linear support vector machine (SVM) model achieved state-of-the-art performance in the classification experiments with a test area under receiver operator characteristic curve (AUC) of 0.8734 (95% confidence interval, 0.8666–0.8802). This result indicated that the MWCS-COM features are highly advantageous to the differential diagnosis of HCC and HH from plain CT images. We also explored the potential associations between MWCS-COM features and histopathological characteristics and observed that the MWCS-COM features could potentially enhance radiologists’ diagnostic ability. 相似文献
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Meera S. Ghadge Purva P. Naik Bijaynath P. Tiwari Ruprekha M. Hegde Tanaji J. Matale 《Indian journal of clinical biochemistry : IJCB》2012,27(1):97-99
Breast cancer is one of the most frequent malignancies in the world. Available staging procedures to detect breast cancer
are bone scan, chest X-ray, liver ultrasonography, computerized tomography, estimation of tumor markers like carbohydrate
antigen (CA15-3) and carcino embryonic antigen. These procedures are expensive and may not be required in all cases. Out of
70 patients studied, 55 had normal CA15-3 and 15 had elevated levels of Ca15-3. Eight (14.5%) of the 55 patients with normal
CA15-3 had abnormal bone scan. Fifteen patients had CA15-3 levels above the normal range and among these 9 (60%) had abnormal
bone scan. While prime facie it would appear that a high level of CA15-3 correlate with abnormal bone scan, it is also true
that the numbers are small at present and conclusions about the validity of CA15-3 as marker of bone metastasis may be premature. 相似文献