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31.
Kernel density estimators (KDE) used for many medical image applications only consider the intensity information of each pixel or its neighbors without the ability of expressing the structure and shape of tissues and organs, and they suffer from boundary bias problem. In this paper, we propose a new first-order kernel density estimation (FOKDE) method for 1D intensity information and 2D spatial information of medical image in two steps. First, the FOKDE of intensity information is estimated and applied to medical image segmentation with the multi-thresholding algorithm. Second, we estimate the FOKDE of spatial information on the initial segmentation, which can express the structure and shape of organs and tissues. In order to evaluate the FOKDE and KDE of the 2D spatial information, we apply them to medical image segmentation with the hill-climbing strategy. Density estimation experiments and segmentation application results on the simulated dataset and real abdomen CT images show us that the FOKDE has smaller boundary bias than the KDE, and that it can estimate the structure and shape of tissues and organs with spatial information effectively. 相似文献
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《Communications in Nonlinear Science & Numerical Simulation》2014,19(6):1822-1835
An analysis is presented for the steady boundary layer flow and heat transfer of a viscous and incompressible fluid in the stagnation point towards a non-linearly moving flat plate in a parallel free stream with a partial slip velocity. The governing partial differential equations are converted into nonlinear ordinary differential equations by a similarity transformation, which are then solved numerically using the function bvp4c from Matlab for different values of the governing parameters. Dual (upper and lower branch) solutions are found to exist for certain parameters. Particular attention is given to deriving numerical results for the critical/turning points which determine the range of existence of the dual solutions. A stability analysis has been also performed to show that the upper branch solutions are stable and physically realizable, while the lower branch solutions are not stable and, therefore, not physically possible. 相似文献
35.
《Communications in Nonlinear Science & Numerical Simulation》2014,19(6):1926-1934
Some dynamical and statistical properties of a time-dependent rotating oval billiard are studied. We considered cases with (i) positive and (ii) negative curvature for the boundary. For (i) we show the system does not present unlimited energy growth. For case (ii) however the average velocity for an ensemble of noninteracting particles grows as a power law with acceleration exponent well defined. Finally, we show for both cases that after introducing time-dependent perturbation, the mixed structure of the phase space observed for static case is recovered by making a suitable transformation in the angular position of the particle. 相似文献
36.
Yusong Li Guangqiang Sun Yuehua Zhang Cunwang Ge Ning Bao Yihong Wang 《Mikrochimica acta》2014,181(7-8):751-757
Single-walled bismuth nanotubes (sw-BiNTs) were self-assembled with octa(3-aminopropyl) silsesquioxane as a framework and to govern morphology. Deposited on a glassy carbon electrode (GCE), the sw-BiNTs were used for the simultaneous analysis of Pb(II) and Cd(II) by square wave stripping voltammetry. The sw-BiNTs were prepared by (a) coordination interaction between the amino groups of the silsesquioxane and the Bi(III) ions, and by (b) reduction with sodium borohydride. Transmission electron microscopy images revealed single-walled tubular structures with diameters of ~4–6 nm, and with lengths of several hundreds nanometers. GCEs modified with such sw-BiNTs perform much better than bare GCEs in stripping analysis of Pb(II) and Cd(II). The effects of adsorption quantity of sw-BiNTs, solution pH, pulse amplitude, and pulse width were optimized. The modified electrode was then used for the analysis of Pb(II) and Cd(II) in a linear response range from 0.4 to 6 μM with a sensitivity of 4.692 μA μM?1 and 3.835 μA μM?1, and detection limits of 1 nM and 5 nM, respectively. The method was successfully applied to the analysis of Pb(II) and Cd(II) in toy leachates, and the results were in good agreement with those obtained with atomic absorption spectrometry. Sensitivity and detection limits were compared with other voltammetric methods, and the sw-BiNTs are deemed to be an attractive alternative for practical applications. Other features of the electrode include low costs, a well reproducible nanostructure, and ease of scale-up of the fabrication process. Figure
Single-walled bismuth nanotubes (BiNTs) were self-assemblied with octa(3-aminopropyl) silsesquioxane as framework and morphology control agent for the simultaneous detection of trace Pb(II) and Cd(II) by square wave stripping voltammetry. The proposal preparation avoids time-consuming pre-treatment and experienced operation. The sensitivity and detection limit of the method was comparable to reported voltammetric methods, and BiNTs might be an alternative candidate for practical applications of electrochemical detection. 相似文献
37.
Electrochemiluminescence Sensor for Phosphate Ions Based on Europium(III)‐Modulated CdSe Quantum Dots 下载免费PDF全文
Phosphate anions are determined based on the electrochemiluminescence (ECL) of CdSe quantum dots (CdSe QDs) capped with 3‐mercaptopropionic acid. The ECL gets quenched with the introduction of Eu3+ ions, but it is restored on the further addition of phosphate anions. The sensing mechanism might be due to the strong and specific interaction between phosphate anions and the Eu3+ ions, leading to the releasing of CdSe QDs from aggregates. On the basis of the quenching/recovery ECL behaviors, the ECL sensor offer acceptable sensitivity, high selectivity, and a linear response from 0.1 to 120 µM with a detection limit of 0.03 µM (3δ) for phosphate anions. 相似文献
38.
以聚吡咯包覆聚苯乙烯核壳结构衍生的中空碳球(hollow carbon spheres,HCS)为载体,乙酰丙酮钛(TOAC)为钛源,通过湿化学法和可控热解法制备了HCS负载纳米二氧化钛(HCS@TiO2)复合材料。通过粉末X射线衍射、紫外可见光谱、X射线光电子能谱、热重分析、扫描电子显微镜、透射电子显微镜、光致发光光谱和Mott-Schottky曲线对HCS@TiO2的晶态结构、微观形貌、光学性能等进行表征,并通过调控TiO2的负载量和热解温度对HCS@TiO2复合材料进行了结构优化。在模拟太阳光照射条件下,以大肠杆菌(E. coli)和金黄色葡萄球菌(S. aureus)为实验对象,研究了不同TiO2负载量的HCS@TiO2复合材料及TiO2和HCS对照样品的光催化抗菌性能,以及光照时间对抗菌性能的影响。结果表明,当TOAC与HCS质量比为15∶1、热解温度为650℃时,最优化的HCS@TiO2-15复合材料... 相似文献
39.
Enhanced Anodic Electrochemiluminescence of Dissolved Oxygen with 2‐(Dibutylamino) ethanol at TiO2 Nanoparticles Modified Platinum Electrode for Dopamine Detection 下载免费PDF全文
The anodic electrochemiluminescence (ECL) of dissolved oxygen with 2‐(dibutylamino) ethanol (DBAE) on platinum electrode has been reported previously by our group. Interestingly, the ECL intensity can be greatly amplified at TiO2 nanoparticles modified platinum electrode (TiO2/Pt), which is due to the catalytic effect of TiO2 nanoparticles to electrochemical oxidation of DBAE. It is the first case to obtain the enhanced ECL from luminophor by electrochemical catalysis of co‐reactant. The enhanced anodic ECL intensity can be quenched by dopamine sensitively. And the ECL intensity versus the logarithm of concentration of dopamine was linear over the 4.0×10?12–1.8×10?8 M (R2=0.9957), with the limit of detection of 2.7×10?12 M (S/N=3). 相似文献
40.
本文利用基于复合网格系统的计算方法,对Re=50~1200的近壁插入圆柱流场进行数值模拟,研究过渡流状态下在壁面附近插入圆柱对下游壁面传热强化的影响。并基于低速循环水槽流动实验台,采用粒子成像测试法(PIV)对Re=100~500的近壁插入圆柱流场进行可视化实验研究,验证了数值模拟方法的可靠性。研究结果表明:近壁插入圆柱流场在Re=100时进入过渡流状态;Re直接影响圆柱尾流中周期性涡脱和壁面涡岛的发生位置及其洗刷效应的大小,随着Re的增大,洗刷效应明显增强,因而,过渡流范围内Re越大,圆柱下游壁面传热强化越大。 相似文献