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991.
We present a novel neural controller for a stepper motor. This controller is developed as follows. Modifying published results for nonlinear identification using dynamic neural networks (NNs), an NN identifier of triangular form is implemented. Then, based on this mode, a control law using sliding modes is derived. This neural identifier and the proposed control law allow trajectory tracking for stepping motors. Applicability of the approach is tested via simulations  相似文献   
992.
We report on the effect of implantation angle on contact resistance of non-alloyed ohmic contacts to selectively implanted source/drain regions in AlGaN/GaN high electron mobility transistor (HEMT) heterostructures. Three different components of contact resistance are observed for such contacts: (i) contact resistance between the metal and the semiconductor, (ii) resistance of the implanted region and (iii) an additional resistance attributed to a transition region between implanted and non-implanted region. This third component varies strongly with implantation angle. The variation with implantation angle shows that the ratio of lateral implantation damage to penetration depth is critical for implantation of AlGaN/GaN HEMT source/drain contact regions. Our results also show that increasing the implantation angle in combination with reducing the implantation width can reduce contact resistance.  相似文献   
993.
Fluoroscopic overlay images rendered from preoperative volumetric data can provide additional anatomical details to guide physicians during catheter ablation procedures for treatment of atrial fibrillation (AFib). As these overlay images are often compromised by cardiac and respiratory motion, motion compensation methods are needed to keep the overlay images in sync with the fluoroscopic images. So far, these approaches have either required simultaneous biplane imaging for 3-D motion compensation, or in case of monoplane X-ray imaging, provided only a limited 2-D functionality. To overcome the downsides of the previously suggested methods, we propose an approach that facilitates a full 3-D motion compensation even if only monoplane X-ray images are available. To this end, we use a training phase that employs a biplane sequence to establish a patient specific motion model. Afterwards, a constrained model-based 2-D/3-D registration method is used to track a circumferential mapping catheter. This device is commonly used for AFib catheter ablation procedures. Based on the experiments on real patient data, we found that our constrained monoplane 2-D/3-D registration outperformed the unconstrained counterpart and yielded an average 2-D tracking error of 0.6 mm and an average 3-D tracking error of 1.6 mm. The unconstrained 2-D/3-D registration technique yielded a similar 2-D performance, but the 3-D tracking error increased to 3.2 mm mostly due to wrongly estimated 3-D motion components in X-ray view direction. Compared to the conventional 2-D monoplane method, the proposed method provides a more seamless workflow by removing the need for catheter model re-initialization otherwise required when the C-arm view orientation changes. In addition, the proposed method can be straightforwardly combined with the previously introduced biplane motion compensation technique to obtain a good trade-off between accuracy and radiation dose reduction.  相似文献   
994.
The antiferromagnetic order in heterostructures of NiO/Pt thin films can be modified by optical pulses. After the irradiation with laser light, the optically induced creation of antiferromagnetic domains can be observed by imaging the created domain structure utilizing the X-ray magnetic linear dichroism effect. The effect of different laser polarizations on the domain formation can be studied and used to identify a polarization-independent creation of 180° domain walls and domains with 180° different Néel vector orientation. By varying the irradiation parameters, the switching mechanism can be determined to be thermally induced. This study demonstrates experimentally the possibility to optically create antiferromagnetic domains, an important step towards future functionalization of all optical switching mechanisms in antiferromagnets.  相似文献   
995.
Multidimensional, mapping-based complex wavelet transforms.   总被引:4,自引:0,他引:4  
Although the discrete wavelet transform (DWT) is a powerful tool for signal and image processing, it has three serious disadvantages: shift sensitivity, poor directionality, and lack of phase information. To overcome these disadvantages, we introduce multidimensional, mapping-based, complex wavelet transforms that consist of a mapping onto a complex function space followed by a DWT of the complex mapping. Unlike other popular transforms that also mitigate DWT shortcomings, the decoupled implementation of our transforms has two important advantages. First, the controllable redundancy of the mapping stage offers a balance between degree of shift sensitivity and transform redundancy. This allows us to create a directional, nonredundant, complex wavelet transform with potential benefits for image coding systems. To the best of our knowledge, no other complex wavelet transform is simultaneously directional and nonredundant. The second advantage of our approach is the flexibility to use any DWT in the transform implementation. As an example, we exploit this flexibility to create the complex double-density DWT: a shift-insensitive, directional, complex wavelet transform with a low redundancy of (3M - 1)/(2M - 1) in M dimensions. No other transform achieves all these properties at a lower redundancy, to the best of our knowledge. By exploiting the advantages of our multidimensional, mapping-based complex wavelet transforms in seismic signal-processing applications, we have demonstrated state-of-the-art results.  相似文献   
996.
The time‐of‐flight method has been used to study the effect of P3HT molecular weight (Mn = 13–121 kDa) on charge mobility in pristine and PCBM blend films using highly regioregular P3HT. Hole mobility was observed to remain constant at 10?4 cm2V?1s?1 as molecular weight was increased from 13–18 kDa, but then decreased by one order of magnitude as molecular weight was further increased from 34–121 kDa. The decrease in charge mobility observed in blend films is accompanied by a change in surface morphology, and leads to a decrease in the performance of photovoltaic devices made from these blend films.  相似文献   
997.
We present a both‐sides‐contacted thin‐film crystalline silicon (c‐Si) solar cell with a confirmed AM1.5 efficiency of 19.1% using the porous silicon layer transfer process. The aperture area of the cell is 3.98 cm2. This is the highest efficiency ever reported for transferred Si cells. The efficiency improvement over the prior state of the art (16.9%) is achieved by implementing recent developments for Si wafer cells such as surface passivation with aluminum oxide and laser ablation for contacting. The cell has a short‐circuit current density of 37.8 mA cm−2, an open‐circuit voltage of 650 mV, and a fill factor of 77.6%. Copyright © 2011 John Wiley & Sons, Ltd.  相似文献   
998.
Supporting Fair Exchange in Mobile Environments   总被引:1,自引:0,他引:1  
Mobile commerce over the Internet always includes the exchange of electronic goods. Fair exchange protocols establish fairness and ensure that both participants can engage in the exchange without the risk of suffering a disadvantage (e.g., losing their money without receiving anything for it). In general, fair exchange protocols require the continuous availability of an external trusted third party (TTP), a dedicated site which is trusted by both participants. Implementations of TTPs for fair exchange have been proposed to be based on carefully secured Internet hosts in order to establish trust. In this paper we present solutions to the fair exchange problem in mobile environments, where customers frequently disconnect from the network and thus continuous availability of the external TTP is not given. Our approach utilizes tamper-poof hardware on the customer's side partly taking over the duties of the TTP. Besides supporting disconnected operations our approach also allows the proper handling of time-sensitive items (i.e., items which lose value over time), a feature which previous protocols lack.  相似文献   
999.
The effects of background millimeter radiations (BMR) in patients with coronary artery disease (CAD), hypertension and in subjects with Inherited real risk of CAD, were investigated through invariant statistic measures, typical of nonlinear dynamics analysis of biological systems. The experimental evidences show that BMR ameliorate the nonlinear complexity in biosystems, recognized sign of physiological behavior, by increasing both the rate of unpredictability of heart rate variability (HRV) in patients with metabolic syndrome and the fractal dimension of coronary microvessel oscillations in subjects with pre-metabolic syndrome, healing their genetic alteration and CAD Inherited real risk.  相似文献   
1000.
A prototype expert system for generating image processing programs using the subroutine package SPIDER is described in this paper.Based on an interactive dialog,the system can generate a complete application program using SPIDER routines.  相似文献   
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