共查询到20条相似文献,搜索用时 15 毫秒
1.
BACKGROUND: This study was performed to assess chemical shift magnetic resonance imaging (CSMRI) for characterizing adrenal masses in patients with lung cancer, and to compare charges associated with two algorithms for assessing adrenal masses in these patients. METHODS: Forty-two patients with lung cancer underwent both CSMRI (using in-phase and opposed-phase gradient echo images) and computed tomography-guided percutaneous biopsy of adrenal masses. Adrenal-to-spleen signal intensity ratios on the opposed-phase images were correlated with histopathologic results. The normalized charges for two algorithms were compared. In algorithm A, computed tomography-guided biopsy is used first to evaluate an adrenal mass; in algorithm B, CSMRI is used first, followed by computed tomography-guided biopsy only if CSMRI findings are not diagnostic of adenoma. RESULTS: Biopsy showed 24 (57%) adrenal adenomas and 18 (43%) metastases. Chemical shift magnetic resonance imaging was 96% sensitive for adenoma and 100% specific. The average normalized charges associated with algorithm A were $1,905 per patient versus $1,890 with algorithm B. CONCLUSIONS: Initial use of CSMRI in evaluating an adrenal mass in lung cancer patients can obviate biopsy in 55% of patients, and its charges are similar to those for performing computed tomography-guided biopsy in all patients. 相似文献
2.
Reconstructing damage geometry with computationally efficient and effective algorithms is of primary importance in establishing a robust structural health monitoring (SHM) system. In this paper, Born imaging algorithm is proposed for three-dimensional (3D) damage imaging of reinforced concrete structures using electromagnetic waves. This algorithm is derived in time domain for inhomogeneous isotropic and lossy structures. In order to reduce the computational cost of the algorithm, different imaging conditions are introduced. Numerical simulations in a 2D transverse magnetic case for a reinforced concrete slab with multiple damages are performed to test the effectiveness of the algorithm. In this simulated study, sensor data, incident field, and back-propagated field are computed via a finite difference time-domain method. It is concluded that the proposed imaging algorithm is capable of efficiently identifying the damages’ geometries and may be employed in a SHM system. 相似文献
3.
ME Nichita?lo VE Medvedev AN Litvinenko BA Tarasiuk PV Ogorodnik 《Canadian Metallurgical Quarterly》1994,(11):25-28
Results of 194 patients observation with cancer of corpus et cauda pancreatis are adduced. Clinical forms of the disease are distinguished. Rational algorithm for the examination of patients with probable cancer of corpus et cauda pancreatis diagnosis was elaborated grounded on the efficacy analysis of various methods of examination (ultrasonic investigation, computed tomography, endoscopic retrograde cholangiopancreatography, selective, angiography and so on). The algorithm application permitted to improve significantly the diagnosis of disease. 相似文献
4.
This paper describes the development of an efficient numerical integration algorithm for an orthotropic viscoelastic-mechanosorptive-plastic material model for wood, which was presented in Part I of this serial. This development utilizes both a semianalytical algorithm for the viscoelastic parts, and the return-mapping algorithm known from plasticity for the mechanosorptive-plastic part of the model. This yields an easily computed, closed form expression for the consistent tangent operator, and, as a consequence, a quadratic rate of asymptotic convergence on the global level of the incremental-iterative analysis by means of the FEM. To prove the practical applicability of the presented formulation, a numerical study of the so-called case-hardening phenomenon as observed on fast dried pine wood was performed. Selected results are presented and discussed. 相似文献
5.
Longitudinal cracks are common defects of continuous casting slabs and may lead to serious quality accidents. Image capturing and recognition of hot slabs is an effective way for on-line detection of cracks, and recognition of cracks is essential because the surface of hot slabs is very complicated. In order to detect the surface longitudinal cracks of the slabs, a new feature extraction method based on Curvelet transform and kernel locality preserving projections (KLPP) is proposed. First, sample images are decomposed into three levels by Curvelet transform. Second, Fourier transform is applied to all sub-band images and the Fourier amplitude spectrum of each sub-band is computed to get features with translational invariance. Third, five kinds of statistical features of the Fourier amplitude spectrum are computed and combined in different forms. Then, KLPP is employed for dimensionality reduction of the obtained 62 types of high-dimensional combined features. Finally, a support vector machine (SVM) is used for sample set classification. Experiments with samples from a real production line of continuous casting slabs show that the algorithm is effective to detect longitudinal cracks, and the classification rate is 91. 89%. 相似文献
6.
This paper presents a global damage detection and assessment algorithm based on a parameter estimation method using a finite-element model and the measured modal response of a structure. Damage is characterized as a reduction of the member constitutive parameter from a known baseline value. An optimization scheme is proposed to localize damaged parts of the structure. The algorithm accounts for the possibility of multiple solutions to the parameter estimation problem that arises from using spatially sparse measurements. Errors in parameter estimates caused by sensitivity to measurement noise are reduced by selecting a near-optimal measurement set from the data at each stage of the localization algorithm. Damage probability functions are computed upon completion of the localization process for candidate elements. Monte Carlo methods are used to compute the required probabilities based on the statistical distributions of the parameters for the damaged and the associated baseline structure. The algorithm is tested in a numerical simulation environment using a planar bridge truss as a model problem. 相似文献
7.
J Shemesh A Tenenbaum KK Kopecky S Apter J Rozenman Y Itzchak M Motro 《Canadian Metallurgical Quarterly》1997,32(9):503-506
RATIONALE AND OBJECTIVES: Coronary calcium (CC) measured by fast computed tomography (CT) was proposed recently as a noninvasive method of monitoring the coronary atherosclerotic process. Assessment of the reproducibility of CC measurements (mainly interstudy variability) is essential for consistent interpretation of serial studies. METHODS: The authors scanned 74 patients (50 men and 24 women) twice on the same day to determine the interstudy variability of a new scoring algorithm, using the average instead of conventional peak CT density values. RESULTS: Nineteen patients had no calcium on either scan. In the remaining 55 patients, interstudy variability was decreased by 31% using the average algorithm (32%-23%; P < 0.001). CONCLUSIONS: Using the average instead of conventional peak density score provides better reproducible measurements of calcium by double helical CT. 相似文献
8.
本文把物理学中的万有引力定律引入推荐系统,提出一种个性化推荐算法,即基于万有引力的个性化推荐算法.算法把用户使用的标签看作用户喜欢物体的组成颗粒,标注项目的标签被看作项目物体的组成颗粒,社会标签的类型就是颗粒的类型,由此构建了用户喜好物体模型和项目物体模型.喜好物体和项目物体间存在着万有引力,并且引力大小遵循万有引力定律.计算喜好物体和项目物体间的万有引力,并把该引力大小作为二者的相似度度量,引力越大,二者的相似度就越高,对应的项目物体就越有可能被用户喜欢.实验结果证明本文提出的算法可以获得好的推荐性能. 相似文献
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10.
The filtered-x LMS algorithm and its modified versions have been successfully applied in suppressing acoustic noise such as single and multiple tones and broadband random noise. This paper presents an adaptive algorithm based on the filtered-x LMS algorithm which may be applied in attenuating tonal acoustic noise. In the proposed method, the weights of the adaptive filter and estimation of the phase shift due to the acoustic path from a loudspeaker to a microphone are computed simultaneously for optimal control. The algorithm possesses advantages over other filtered-x LMS approaches in three aspects: (1) each frequency component is processed separately using an adaptive filter with two coefficients, (2) the convergence parameter for each sinusoid can be selected independently, and (3) the computational load can be reduced by eliminating the convolution process required to obtain the filtered reference signal. Simulation results for a single-input/single-output (SISO) environment demonstrate that the proposed method is robust to the changes of the acoustic path between the actuator and the microphone and outperforms the filtered-x LMS algorithm in simplicity and convergence speed. 相似文献
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12.
WJ Fokkens GJ Nolst Trenite M Virmond A KleinJan VL Andrade NG van Baar B Naafs 《Canadian Metallurgical Quarterly》1998,66(3):328-339
The alignment of single-particle images fails at low signal-to-noise ratios and small particle sizes, because noise produces false peaks in the cross-correlation function used for alignment. A maximum-likelihood approach to the two-dimensional alignment problem is described which allows the underlying structure to be estimated from large data sets of very noisy images. Instead of finding the optimum alignment for each image, the algorithm forms a weighted sum over all possible in-plane rotations and translations of the image. The weighting factors, which are the probabilities of the image transformations, are computed as the exponential of a cross-correlation function. Simulated data sets were constructed and processed by the algorithm. The results demonstrate a greatly reduced sensitivity to the choice of a starting reference, and the ability to recover structures from large data sets having very low signal-to-noise ratios. 相似文献
13.
A Schmermund KR Bailey JA Rumberger JE Reed PF Sheedy RS Schwartz 《Canadian Metallurgical Quarterly》1999,33(2):444-452
OBJECTIVES: We sought to model an algorithm for noninvasive identification of angiographically obstructive three-vessel and/or left main disease based on conventional cardiac risk assessment and site and extent of coronary calcium determined by electron-beam computed tomography (EBCT). BACKGROUND: Such an algorithm would greatly facilitate clinical triage in symptomatic patients with no previous diagnosis of coronary artery disease (CAD). METHODS: We examined 291 patients with suspected, but not previously diagnosed, CAD who underwent coronary angiography for clinical indications. Cardiac risk factors were determined as defined by the National Cholesterol Education Program. An EBCT scan was performed in all patients, and a coronary calcium score (Agatston method) was computed. Total per-patient calcium scores and separate scores for the major coronary arteries were generated. These scores were also analyzed for localization of coronary calcium in the more distal versus proximal tomographic sections. These parameters and the risk factors were considered for the model described in the following section. RESULTS: Sixty-eight patients (23%) had angiographic three-vessel and/or left main CAD. Multiple logistic regression analysis determined male sex, presence of diabetes and left anterior descending (LAD) and circumflex (LCx) coronary calcium scores, independent from more distal calcium localization, as independent predictors for identification of three-vessel and/or left main CAD. Based on this four variable model, a simple noninvasive index (NI) was constructed as the following: loge(LAD score) + log(e)(LCx score) + 2[if diabetic] + 3[if male]. Receiver operating characteristic curve analysis for this NI yielded an area under the curve of 0.88+/-0.03 (p < 0.0001) for separating patients with, versus without, angiographic three-vessel and/or left main CAD. Various NI cutpoints demonstrated sensitivities from 87-97% and specificities from 46-74%. The NI values >14 increased the probability of angiographic three-vessel and/or left main CAD from 23% (pretest) to 65-100% (posttest), and NI values <10 increased the probability of no three-vessel and/or left main CAD from 77% (pretest) to 95-100% (posttest). CONCLUSIONS: On the basis of a simple algorithm ("noninvasive index"), EBCT calcium scanning in conjunction with risk factor analysis can rule in or rule out angiographically severe disease, i.e., three-vessel and/or left main CAD, in symptomatic patients. 相似文献
14.
基于高性能的YOLOv3目标检测算法,提出一种分阶段高效火车号识别算法。整个识别过程分为两个阶段:第一阶段在低分辨率全局图像中检测出火车号区域位置;第二阶段在局部高分辨率图像中检测出组成火车号的字符,根据字符的空间位置关系搜索得到12位火车号,并利用每个字符的识别置信度及火车号编码规则进行校验得到最终火车号。另外,本文提出一种结合批一化因子和滤波器相关度的剪枝算法,通过对两个阶段检测模型的剪枝,在保证识别准确率不降(实验中略有提升)的条件下降低了存储空间占用率和计算复杂度。在现场采集的1072幅火车号图像上的实验结果表明,本文提出的火车号识别算法达到了96.92%的整车号识别正确率,平均识别时间仅为191 ms。 相似文献
15.
The transport phenomena based heat transfer and fluid flow calculations in weld pool require a number of input parameters.
Arc efficiency, effective thermal conductivity, and viscosity in weld pool are some of these parameters, values of which are
rarely known and difficult to assign a priori based on the scientific principles alone. The present work reports a bi-directional three-dimensional (3-D) heat transfer
and fluid flow model, which is integrated with a real number based genetic algorithm. The bi-directional feature of the integrated
model allows the identification of the values of a required set of uncertain model input parameters and, next, the design
of process parameters to achieve a target weld pool dimension. The computed values are validated with measured results in
linear gas-tungsten-arc (GTA) weld samples. Furthermore, a novel methodology to estimate the overall reliability of the computed
solutions is also presented. 相似文献
16.
Yiu-Chung Hon Kwok Fai Cheung Xian-Zhong Mao Edward J. Kansa 《Canadian Metallurgical Quarterly》1999,125(5):524-533
A computational algorithm based on the multiquadric, which is a continuously differentiable radial basis function, is devised to solve the shallow water equations. The numerical solutions are evaluated at scattered collocation points and the spatial partial derivatives are formed directly from partial derivatives of the radial basis function, not by any difference scheme. The method does not require the generation of a grid as in the finite-element method and allows easy editing and refinement of the numerical model. To increase confidence in the multiquadric solution, a sensitivity and convergence analysis is performed using numerical models of a rectangular channel. Applications of the algorithm are made to compute the sea surface elevations and currents in Tolo Harbour, Hong Kong, during a typhoon attack. The numerical solution is shown to be robust and stable. The computed results are compared with measured data and good agreement is indicated. 相似文献
17.
BP (Baek Propagation)算法和遗传算法相结合的混合训练方法步骤为:首先用遗传算法定位出一个较好的搜索空间,然后采用BP算法在这个小的解空间中搜索出最优解。分别用遗传算法和混合遗传算法训练100 t电弧炉终点温度神经网络预报模型。仿真结果表明:混合遗传算法有更快的收敛速度和更高的预报命中率。当目标温度的精度范围为±2℃、±4℃、±6℃和±8℃时,BP算法的温度命中率分别为75%、82%、86%和92%,混合遗传算法的温度命中率分别为80%、88%、90%和96%。 相似文献
18.
RA Levy 《Canadian Metallurgical Quarterly》1995,2(7):592-596
RATIONALE AND OBJECTIVES: I conducted a study designed to facilitate thresholding and reduce volume averaging in three-dimensional (3D) computed tomography (CT) craniofacial modeling. METHODS: Three-dimensional CT reconstructions of orbits from two cadavers and seven clinical cases were generated from paired axial and coronal data. A histogram-based algorithm that was based on preliminary phantom and craniofacial specimen trials was applied to orbital data to identify volume averaged regions of thin bone to be used in conjunction with standard bone thresholds. Region-of-interest measurement of the orbital floors on the original two-dimensional slice data assessed algorithm performance. RESULTS: In five of the nine cases (55%), configuration of the superimposed histograms predicted regions of volume averaging. In only one case did such a region localize to the orbital floor. In the remaining four cases, the air-mucosa interface deep to the orbital floor was identified by the histogram method. CONCLUSION: Operator-dependent editing remains superior to this histogram-based algorithm in reducing volume averaging in 3D craniofacial modeling. 相似文献
19.
Confidence intervals for the WAIS-R were computed for the Verbal, Performance, and Full Scale IQ scores. IQ intervals for the 85, 90, 95, and 99% levels of confidence are reported for each of the 9 standardization sample age groups and the entire sample. Differences between Verbal and Performance IQ scores required for 90 and 99% levels of significance are also reported. All values are computed on the basis of the standard errors of measurement reported in the WAIS-R manual for the standardization sample. (5 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved) 相似文献
20.
The fluid flow in a continuous casting tundish is computed for an optimum parameter setting such that the stresses produced at the walls get minimized. This optimization task is carried out using a Genetic Algorithms based procedure that worked in tandem with a 3‐D transient Navier‐Stokes equation solver. The fluid flow equations are iteratively solved by using a pressure‐based finite volume method, according to the SIMPLER algorithm. The k‐ε model is used for achieving the turbulence closure. The numerical simulations reveal how the Genetic Algorithm can be effectively used for optimizing the fluidic design of the tundish. 相似文献