Generation of quasi-monoenergetic protons from thin multi-ion foils by a combination of laser radiation pressure acceleration and shielded Coulomb repulsion

We study theoretically and numerically the acceleration of protons by a combination of laser radiation pressure acceleration and Coulomb repulsion of carbon ions in a multi-ion thin foil made of carbon and hydrogen. The carbon layer helps to delay the proton layer from disruption due to the Rayleigh–Taylor instability, to maintain the quasi-monoenergetic proton layer and to accelerate it by the electron-shielded Coulomb repulsion for much longer duration than the acceleration time using single-ion hydrogen foils. Particle-in-cell simulations with a normalized peak laser amplitude of a_0 = 5 show a resulting quasi-monoenergetic proton energy of about 70 MeV with the foil made of 90% carbon and 10% hydrogen, in contrast to 10 MeV using a single-ion hydrogen foil. An analytical model is presented to explain quantitatively the proton energy evolution; this model is in agreement with the simulation results. The energy dependence of the quasi-monoenergetic proton beam on the concentration of carbon and hydrogen is also studied

Two-phase Framework for Automatic Kidney and Kidney Tumor Segmentation

Precise segmentation of kidney and kidney tumor is essential for computer aided diagnosis. Considering the diverse shape, low contrast with surrounding tissues and small tumor volumes, it’s still challenging to segment kidney and kidney tumor accurately. To solve this problem, we proposed a two-phase framework for automatic segmentation of kidney and kidney tumor. In the first phase, the approximate localization of kidney and kidney tumor is predicted by a coarse segmentation network to overcome GPU memory limitation. Taking the coarse prediction from first phase as input, the region of kidney and tumor is cropped and trained in an enhanced two-stage network to achieve a fine-grained segmentation result in the second phase. Besides, our network prediction flows into multiple post-processing steps to remove false positive such as cyst by taking medical prior knowledge into consideration. Data argumentation through registration and ensemble models are used to further enhance performance

Study on the Dynamic Mechanical Properties of Viscoelastic Materials Based on Asymmetrical Sandwich Beams

A modified estimation method for the dynamic mechanical properties of viscoelastic materials via asymmetrical sandwich specimens is presented. In contrast to the traditional vibrating cantilever beam test method (VCBTM), the proposed method allows asymmetrical base beams in sandwich specimens. Based on the complex stiffness method, complex parameters are introduced for general sandwich configurations. Calculation formulas for loss factor and shear modulus of the core material are presented. The effectiveness of this approach is validated numerically and experimentally by analysis of one symmetrical sandwich beam specimen and two specimens with asymmetrical thicknesses and materials. It is shown that dynamic mechanical parameters of the core material can be obtained regardless of sandwiches’ symmetry. The proposed method breaks the symmetrical criteria for sandwich specimens and may provide a wider application to measure viscoelastic materials’ dynamic properties

Application of system concept in vibration and noise reduction

Although certain vibration and noise control technologies are maturing, such as vibration absorption, vibration isolation, sound absorption and sound insulation, and new methods for specific frequency bands or special environments have been proposed unceasingly, there is still no guarantee that practical effective vibration and noise reduction can be obtained. An important constraint for vibration and noise reduction is the lack of a system concept, and the integrity and relevance of such practical systems as ship structure have not obtained enough attention. We have tried to use the system engineering theory in guiding vibration and noise reduction, and have already achieved certain effects. Based on the system concept, the noise control of a petroleum pipeline production workshop has been completed satisfactorily, and the abnormal noise source identification of an airplane has been accomplished successfully. We want to share our experience and suggestions to promote the popularization of the system engineering theory in vibration and noise control

An Enhanced Empirical Wavelet Transform for Features Extraction from Wind Turbine Condition Monitoring Signals

Feature extraction from nonlinear and non-stationary (NNS) wind turbine (WT) condition monitoring (CM) signals is challenging. Previously, much effort has been spent to develop advanced signal processing techniques for dealing with CM signals of this kind. The Empirical Wavelet Transform (EWT) is one of the achievements attributed to these efforts. The EWT takes advantage of Empirical Mode Decomposition (EMD) in dealing with NNS signals but is superior to the EMD in mode decomposition and robustness against noise. However, the conventional EWT meets difficulty in properly segmenting the frequency spectrum of the signal, especially when lacking pre-knowledge of the signal. The inappropriate segmentation of the signal spectrum will inevitably lower the accuracy of the EWT result and thus raise the difficulty of WT CM. To address this issue, an enhanced EWT is proposed in this paper by developing a feasible and efficient spectrum segmentation method. The effectiveness of the proposed method has been verified by using the bearing and gearbox CM data that are open to the public for the purpose of research. The experiment has shown that, after adopting the proposed method, it becomes much easier and more reliable to segment the frequency spectrum of the signal. Moreover, benefitting from the correct segmentation of the signal spectrum, the fault-related features of the CM signals are presented more explicitly in the time-frequency map of the enhanced EWT, despite the considerable noise contained in the signal and the shortage of pre-knowledge about the machine being investigated

New Construction of PVPKE Scheme and Its Application in Information Systems and Mobile Communication

In SCN12, Nieto et al. discussed an interesting property of public key encryption with chosen ciphertext security, that is, ciphertexts with public verifiability. Independently, we introduced a new cryptographic primitive, CCA-secure publicly verifiable public key encryption without pairings in the standard model (PVPKE), and discussed its application in proxy reencryption (PRE) and threshold public key encryption (TPKE). In Crypto’09, Hofheiz and Kiltz introduced the group of signed quadratic residues and discussed its application; the most interesting feature of this group is its “gap” property, while the computational problem is as hard as factoring, and the corresponding decisional problem is easy. In this paper, we give new constructions of PVPKE scheme based on signed quadratic residues and analyze their security. We also discuss PVPKE’s important application in modern information systems, such as achieving ciphertext checkable in the cloud setting for the mobile laptop, reducing workload by the gateway between the open internet and the trusted private network, and dropping invalid ciphertext by the routers for helping the network to preserve its communication bandwidth