In Magnetic Resonance Imaging (MRI), the success of deep learning-based under-sampled MR image reconstruction depends on: (i) size of the training dataset, (ii) generalization capabilities of the trained neural network. Whenever there is a mismatch between the training and testing data, there is a need to retrain the neural network from scratch with thousands of MR images obtained using the same protocol. This may not be possible in MRI as it is costly and time consuming to acquire data. In this research, a transfer learning approach i.e. end-to-end fine tuning is proposed for U-Net to address the data scarcity and generalization problems of deep learning-based MR image reconstruction. First the generalization capabilities of a pre-trained U-Net (initially trained on the human brain images of 1.5 T scanner) are assessed for: (a) MR images acquired from MRI scanners of different magnetic field strengths, (b) MR images of different anatomies and (c) MR images under-sampled by different acceleration factors. Later, end-to-end fine tuning of the pre-trained U-Net is proposed for the reconstruction of the above-mentioned MR images (i.e. (a), (b) and (c)). The results show successful reconstructions obtained from the proposed method as reflected by the Structural SIMilarity index, Root Mean Square Error, Peak Signal-to-Noise Ratio and central line profile of the reconstructed images. 相似文献
The no-touch bipolar radiofrequency ablation (RFA) for cancer treatment is advantageous primarily because of its capability to prevent tumour track seeding (TTS). In this technique, the RF probes are placed at a distance (no-touch gap) away from the tumour boundary. Ideally, the RF probes should be placed sufficiently far from the tumour in order to avoid TTS. However, having a gap that is too large can lead to ineffective ablation. This paper investigates how the selection of the no-touch gap can affect the tissue electrical and thermal responses during the no-touch bipolar RFA treatment. Simulations were carried out on a two compartment model using the finite element method. Results obtained indicated that a gap that is too large may lead to incomplete ablation and failure to achieve significant ablation margin. However, keeping the gap to be too small may not be clinically practical. It was suggested that the incomplete ablation and the insufficient ablation margin observed in some of the cases may require the placement of additional probes around the tumour. The present study stresses on the importance of identifying the optimal no-touch gap that can avoid TTS without compromising the treatment outcome. 相似文献
The objective of this work is to present sufficient conditions for having positive topological entropy for continuous self-maps defined on a closed surface by using the action of this map on the homological groups of the closed surface. 相似文献
To establish a new method of testing and evaluating the quality of refined montan wax (RMW), digital color and GC fingerprint technology were introduced and applied. CIE Lab color mode was used to digitize the exterior colors of RMW, and the score obtained through a fitting function was also used to reflect its quality. It is shown that they were in complete accord with the human visual perception trend. The GC fingerprint was used to characterize the internal chemical information of RMW, and the composition of its internal features was reflected through the relative retention time (RRT) and relative peak area (RPA) values. It is shown that there was a high degree of similarity between the fingerprints, while certain differences also existed. This can be used to implement effective application of RMW to aspects such as quality control, adulteration identification, and origin attributions.
The eight-band κ·p model is used to establish the energy band structure model of the type-II InAs/GaSb superlattice detectors with a cut-off wavelength of 10.5μm,and the best composition of M-structure in this type of device is calculated theoretically.In addition,we have also experimented on the devices designed with the best performance to investigate the effect of the active region p-type doping temperature on the quantum efficiency of the device.The results show that the modest active region doping temperature(Be:760℃)can improve the quantum efficiency of the device with the best performance,while excessive doping(Be:>760℃)is not conducive to improving the photo response.With the best designed structure and an appropriate doping concentration,a maximum quantum efficiency of 45% is achieved with a resistance-area product of 688?·cm^2,corresponding to a maximum detectivity of 7.35×10^11cm·Hz^1/2/W. 相似文献
Nanobubble is a rising research field, which attracts more and more attentions due to its potential applications in medical science, catalysis, electrochemistry and etc. To better implement these applications, it is urgent to understand one of the most important mechanisms of nanobubbles, the evolution. However, few attentions have been paid in this aspect because of the methodology difficulties. Here we successfully used dark-field microscopy to study the evolution process of single nanobubbles generated from formic acid dehydrogenation on single Pd-Ag nanoplates. We found some of the nanobubbles in this system can exhibit three distinct states representing different sizes, which can transform among each other. These transitions are not direct but through some intermediate states. Further kinetic analysis reveals complicated mechanisms behind the evolution of single nanobubbles. The results acquired from this study can be applicable to nanobubble systems in general and provide insights into the understanding of mechanisms affecting the stability of nanobubbles and their applications. 相似文献
In this study, parenchyma cellulose, which was extracted from maize stalk pith as an abundant source of agricultural residues, was applied for preparing cellulose nanoparticles (CNPs) via an ultrasound-assisted etherification and a subsequent sonication process. The ultrasonic-assisted treatment greatly improved the modification of the pith cellulose with glycidyltrimethylammonium chloride, leading to a partial increase in the dissolubility of the as-obtained product and thus disintegration of sheet-like cellulose into nanoparticles. While the formation of CNPs by ultrasonication was largely dependent on the cellulose consistency in the cationic-modified system. Under the condition of 25% cellulose consistency, the longer sono-treated duration yielded a more stable and dispersible suspension of CNP due to its higher zeta potential. Degree of substitution and FT-IR analyses indicated that quaternary ammonium salts were grafted onto hydroxyl groups of cellulose chain. SEM and TEM images exhibited the CNP to have spherical morphology with an average dimeter from 15 to 55 nm. XRD investigation revealed that CNPs consisted mainly of a crystalline cellulose Ι structure, and they had a lower crystallinity than the starting cellulose. Moreover, thermogravimetric results illustrated the thermal resistance of the CNPs was lower than the pith cellulose. The optimal CNP with highly cationic charges, good stability and acceptable thermostability might be considered as one of the alternatively renewable reinforcement additives for nanocomposite production. 相似文献
A new process of leaching zinc oxide dust by ozone oxidation in a sulfuric acid system was studied. The main factors affecting the leaching rate, such as ozone time, leaching temperature, initial acidity, leaching time, and liquid/solid mass ratio, were comprehensively investigated. The results show that leaching efficiency depends on all the above factors. The optimum conditions for leaching Zn and Ge from zinc oxide dust are as follows: ozone time 10 min, leaching temperature 90 ℃, initial acidity 160 g/L, leaching time 60 min, and liquid/solid mass ratio 7:1. Under the optimum conditions, the leaching rates of Zn and Ge are 95.79% and 93.65%, respectively. The leaching rates of zinc and germanium in the ozone leaching are 4.05% and 10.49% higher than those of the atmospheric leaching, respectively. Therefore, it is determined that ozone in solution plays a key role in rapidly oxidizing sulfide and releasing encapsulated germanium. Sulfuric acid-ozone media can efficiently extract Zn and Ge from zinc oxide dust. 相似文献
FeOx, TiO2, and Fe–Ti–Ox catalysts were synthesized and used in the catalytic hydrolysis of hydrogen cyanide (HCN). Nearly 100% HCN conversion was achieved at 250 °C over the Fe–Ti–Ox catalyst. TiO2 rutile was detected over TiO2, but not over Fe–Ti–Ox, which suggested that the interaction between Fe and Ti species could inhibit the TiO2 phase transition. Furthermore, the interaction between Fe and Ti species over Fe–Ti–Ox could promote the selectivity of NH3 and CO. The mechanism of hydrolysis of HCN over FeOx, TiO2, and Fe–Ti–Ox can be given as follows: HCN + H2O → methanamide → ammonium formate → formic acid → H2O + CO. 相似文献