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51.
The design of a novel band-pass filter with narrow-band features based on an electromagnetic resonator at 6.4 GHz is presented. A prototype is manufactured and characterized in terms of transmission and reflection coefficient. The selective passband and suppression of the second harmonic make the filter suitable to be used in a C band frequency range for radar systems and satellite/terrestrial applications. To avoid substantial interference for this kind of applications, passive components with narrow band features and small dimensions are required. Between 3.6 GHz and 4.2 GHz the band-pass filter with harmonic suppression should have an attenuation of at least 35 dB, whereas for a passband, less than 10% is sufficient. 相似文献
52.
《Radiography》2017,23(4):e99-e102
IntroductionThe aim of this research was to study the effect of exposure factors on image quality for digital screening mammography units in Kuwait which use Tungsten (W) targets with Rhodium (Rh) and Silver (Ag) as filters.MethodsMammography Accreditation Phantom Model 015 was imaged using a Hologic Selenia Digital mammography unit with W targets and Rh and Ag filters. Four images, each at 26, 28, 30, and 32 kVp, were obtained using each target-filter combination (W/Rh and W/Ag). The images were evaluated by five senior technologists for the number of specks, fibers and masses visible on each image. Statistical analysis was carried out using non-parametric tests at p = 0.05 level.ResultsThere were significant changes in the visibility of fibers and specks between different kVp values with W/Rh (p < 0.001). However, with W/Ag combination, significant differences were observed in the fibers only (p < 0.001). Among the kVp values used, 28 kV emerged as the optimal value. Comparison of images obtained with the two filter materials, led to significant differences in the visibility of fibers and specks (p < 0.008). At 32 kVp, there were significant differences in the visibility of specks only (p < 0.008).ConclusionA W/Rh target-filter combination provides better image quality than that provided by W/Ag. In particular, 30 and 32 kVp X-ray beams produce higher quality images than the lower kV values. 相似文献
53.
《Ultrastructural pathology》2013,37(2):175-181
A simple membrane filter technique permits the collection of cells from cerebrospinal fluid for electron microscopy. The method is universally applicable for the concentration of small number of cells from free-floating cell suspensions and has several advantages: (1) Only a small fluid sample (1 ml) is needed. (2) Excellent cell preservation is obtainable. (3) High cell recovery rates are achieved. (4) Quantitative classification of cell types is possible. 相似文献
54.
Basil M. Al‐Hadithi Agustín Jiménez Fernando Matía 《Optimal control applications & methods.》2012,33(5):552-575
This paper describes new approaches to improve the local and global approximation (matching) and modeling capability of Takagi–Sugeno (T‐S) fuzzy model. The main aim is obtaining high function approximation accuracy and fast convergence. The main problem encountered is that T‐S identification method cannot be applied when the membership functions are overlapped by pairs. This restricts the application of the T‐S method because this type of membership function has been widely used during the last 2 decades in the stability, controller design of fuzzy systems and is popular in industrial control applications. The approach developed here can be considered as a generalized version of T‐S identification method with optimized performance in approximating nonlinear functions. We propose a noniterative method through weighting of parameters approach and an iterative algorithm by applying the extended Kalman filter, based on the same idea of parameters’ weighting. We show that the Kalman filter is an effective tool in the identification of T‐S fuzzy model. A fuzzy controller based linear quadratic regulator is proposed in order to show the effectiveness of the estimation method developed here in control applications. An illustrative example of an inverted pendulum is chosen to evaluate the robustness and remarkable performance of the proposed method locally and globally in comparison with the original T‐S model. Simulation results indicate the potential, simplicity, and generality of the algorithm. An illustrative example is chosen to evaluate the robustness. In this paper, we prove that these algorithms converge very fast, thereby making them very practical to use. Copyright © 2011 John Wiley & Sons, Ltd. 相似文献
55.
56.
Qian Wang Peter Molenaar Saurabh Harsh Kenneth Freeman Jinyu Xie Carol Gold Mike Rovine Jan Ulbrecht 《Journal of diabetes science and technology》2014,8(2):331-345
An essential component of any artificial pancreas is on the prediction of blood glucose levels as a function of exogenous and endogenous perturbations such as insulin dose, meal intake, and physical activity and emotional tone under natural living conditions. In this article, we present a new data-driven state-space dynamic model with time-varying coefficients that are used to explicitly quantify the time-varying patient-specific effects of insulin dose and meal intake on blood glucose fluctuations. Using the 3-variate time series of glucose level, insulin dose, and meal intake of an individual type 1 diabetic subject, we apply an extended Kalman filter (EKF) to estimate time-varying coefficients of the patient-specific state-space model. We evaluate our empirical modeling using (1) the FDA-approved UVa/Padova simulator with 30 virtual patients and (2) clinical data of 5 type 1 diabetic patients under natural living conditions. Compared to a forgetting-factor-based recursive ARX model of the same order, the EKF model predictions have higher fit, and significantly better temporal gain and J index and thus are superior in early detection of upward and downward trends in glucose. The EKF based state-space model developed in this article is particularly suitable for model-based state-feedback control designs since the Kalman filter estimates the state variable of the glucose dynamics based on the measured glucose time series. In addition, since the model parameters are estimated in real time, this model is also suitable for adaptive control. 相似文献
57.
背景:同态滤波与直方图均衡化都能单独对图像进行增强处理,但各自还有许多不足之处。
目的:观察将同态滤波与直方图均衡化结合使用对增强图像的效果,减少单独使用这两种方法产生的缺点。
方法:在频域内,首先对超声图像分别进行高通同态滤波和低通同态滤波的分频处理;再将得到的两幅滤波图像线性组合;最后再对该组合图像进行全局的直方图均衡化得到最终的增强超声图像。
结果与结论:实验结果表明,超声图像经过上述方法的处理,边界十分突出明显,且整体视觉效果更明亮清晰。通过分析对比得到的均方根误差和信噪比数据,也证实了实验所用的超声图像增强法是十分切实有效的。 相似文献
58.
电加热炉系统是一个较为复杂的被控对象,一般认为它是一个大惯性、纯滞后的系统.文章首先利用MATLAB工具箱中提供的函数对电加热炉的阶跃响应曲线进行滤波,在此基础上对电加热炉的系统参数进行辨识,仿真结果表明,这种辨识方法编程较简单,且辨识的参数精度较高. 相似文献
59.
Objective
In a contaminated environment, respiratory protection for ventilator dependent patients can be achieved by attaching a chemical, biological, radiological, or nuclear (CBRN) filter to the air intake port of a portable ventilator. We evaluated the effect of the filter on battery performance of four portable ventilators in a laboratory setting.Methods
Each ventilator was attached to a test lung. Ventilator settings were: assist control (AC) mode, respiratory rate 35 bpm, tidal volume 450 ml, positive end-expiratory pressure (PEEP) 10 cm H2O, inspiratory time 0.8 s, and FIO2 0.21. Ventilators were operated until the battery was fully discharged. We also evaluated the ventilators’ ability to deliver all the gas through the CBRN filter and analyzed the pressures required to breathe through the anti-asphyxiation valve of a failed device.Results
The range of battery life varied widely across different ventilator models (99.8-562.6 min). There was no significant difference in battery life (p < 0.01) when operating with or without the CBRN filter attached. Only the Impact 731 routed all inspired gases through the CBRN filter. The pressure required to breathe though the failed device was −4 cm H2O to −9 cm H2O.Conclusions
Duration of operation from the internal battery was not altered by attachment of the CBRN filter. The use of a CBRN filter is necessary for protection of ventilator dependent patients when environmental contamination is present, although conditions exist where all gas does not pass through the filter with some ventilators under normal operating conditions. 相似文献60.
Negi N Yoshikawa T Ohno Y Somiya Y Sekitani T Sugihara N Koyama H Kanda T Kanata N Murakami T Kawamitsu H Sugimura K 《European journal of radiology》2012,81(11):3048-3054