To improve the mechanical properties and wear resistance of QAl9-4 aluminum bronze alloy parts of high-speed rail brake calipers, the solid aluminum bronze alloy was treated with a pulsed magnetic ...field in which the magnetic induction intensity was 3T at room temperature. After that, a tensile test and a friction and wear test were carried out on the alloy. The results indicate that the magnetic field promotes the movement of low-angle grain boundaries less than 2° and splices to form subcrystals or fine crystals, which reduces the mean grain size of the alloy. The disordered dislocation changed into a locally ordered dislocation line, the dislocation distribution became uniform, and the dislocation density increased, which simultaneously improved the alloy’s tensile strength and elongation. The elongation increased by 10.2% compared with that without the magnetic field. The increase in strength can provide strong support for the wear-resistant hard phase, and the enhancement of plasticity can increase the alloy’s ability to absorb frictional vibration. Therefore, it was hard for cracks to form and extend, and the specimen’s average friction coefficient was reduced by 22.05%. The grinding crack width and depth decreased, the wear debris became more uniform and fine, and the alloy’s wear resistance increased.
Overload-induced fatigue crack growth behavior in DP780 steel.
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•The extent of crack retardation increased with overload ratio and crack length.•Crack branching was not significant ...effect for crack retardation under overload.•The factor (n−1)/(n+1) makes Irwin model and Wheeler model more accurate.
The purpose of this study was to analyze the effect of single tensile overload on fatigue crack growth (FCG) behavior in DP780 dual phase steel. The compact tension samples were tested under constant amplitude load and overload condition. The results showed that all the material conditions responded favorably to the single tensile overloads; the magnitude and extent of crack retardation was amplified due to an increase in overload ratio (OLR) and a longer crack length at overload application. The error between the overload affected crack growth increment and the magnitude of overload monotonic plastic zone size decreased about 30% after introducing the factor (n−1)/(n+1) into Irwin model. A plastic zone size factor was used to modify the Wheeler model to calculate the FCG rate during retardation period after an overload, the predicted results were in good agreement with the experimental data. During the application of an overload, a crescent moon shaped damage zone was formed ahead of the crack tip characterized by cleavage surfaces, tearing ridges, dimples and voids. The fracture morphology after crack front reformation was severely damaged due to the premature contact of the crack flanks. Crack branching was not significant interaction effect for the crack growth retardation under overload.
With the application of Internet of Things (IoT) technologies in smart city, intelligent medical terminals play a more and more significant role in our daily life. These terminals can monitor our ...physical conditions and get lots of medical data in time. For the sake of data security and practicality, the collected big data can be encrypted and then stored on a cloud server such that only authorized users, such as the data owner and the doctors, can access. However, smart terminals are usually limited in computing power and users' privacy issues remain. To tackle this challenging problem, an efficient medical data sharing scheme is presented in this paper. To solve the privacy issues in users' data sharing, we utilize attribute-based encryption to enable data sharing. In addition, we remove the attribute matching function and use the attribute bloom filter to hide all the attributes in the access control structure. In order to improve the efficiency of encryption, we introduce the online/offline encryption technology in the encryption phase. Before the message is known, a large amount of work that is needed at the encryption stage will be done. Then, once the message is known, the ciphertext can be generated quickly. Besides, the initialization stage of the system does not need to specify all attributes. When the overall attributes of the system users increase, the system does not need to be reinitialized, which will also improve the system efficiency. Security analysis and performance analysis show that the data sharing scheme is secure and can improve data processing ability in IoT based data sharing.
Aquaculture has grown rapidly in the field of food industry in recent years; however, it brought many environmental problems, such as water pollution and reclamations of lakes and coastal wetland ...areas. Thus, the evaluation and management of aquaculture industry are needed, in which accurate aquaculture mapping is an essential prerequisite. Due to the difference between inland and marine aquaculture areas and the difficulty in processing large amounts of remote sensing images, the accurate mapping of different aquaculture types is still challenging. In this study, a novel approach based on multi-source spectral and texture features was proposed to map simultaneously inland and marine aquaculture areas. Time series optical Sentinel-2 images were first employed to derive spectral indices for obtaining texture features. The backscattering and texture features derived from the synthetic aperture radar (SAR) images of Sentinel-1A were then used to distinguish aquaculture areas from other geographical entities. Finally, a supervised Random Forest classifier was applied for large scale aquaculture area mapping. To address the low efficiency in processing large amounts of remote sensing images, the proposed approach was implemented on the Google Earth Engine (GEE) platform. A case study in the Pearl River Basin (Guangdong Province) of China showed that the proposed approach obtained aquaculture map with an overall accuracy of 89.5%, and the implementation of proposed approach on GEE platform greatly improved the efficiency for large scale aquaculture area mapping. The derived aquaculture map may support decision-making services for the sustainable development of aquaculture areas and ecological protection in the study area, and the proposed approach holds great potential for mapping aquacultures on both national and global scales.
Drug development based on target proteins has been a successful approach in recent decades. However, the conventional structure-based drug design (SBDD) pipeline is a complex, human-engineered ...process with multiple independently optimized steps. Here, we propose a sequence-to-drug concept for computational drug design based on protein sequence information by end-to-end differentiable learning. We validate this concept in three stages. First, we design TransformerCPI2.0 as a core tool for the concept, which demonstrates generalization ability across proteins and compounds. Second, we interpret the binding knowledge that TransformerCPI2.0 learned. Finally, we use TransformerCPI2.0 to discover new hits for challenging drug targets, and identify new target for an existing drug based on an inverse application of the concept. Overall, this proof-of-concept study shows that the sequence-to-drug concept adds a perspective on drug design. It can serve as an alternative method to SBDD, particularly for proteins that do not yet have high-quality 3D structures available.
Industrial CFB risers usually handle polydisperse mixtures with broad size distribution, which significantly influenced the performance of the reactors. However, traditional Computational Fluid ...Dynamics (CFD) models usually assumed that the particle followed the mono-disperse distribution. In the present work, the method of computational particle fluid dynamic (CPFD) was applied for simulating the complex hydrodynamics in the CFB riser with various particle size distributions (PSDs). Two kinds of PSDs, namely Gaussian and Lognormal distribution with various PSD widths, were implemented into the CPFD scheme. With the CPFD method, the present work extensively studied the effects of PSD on the hydrodynamics and on the solids back-mixing. The CPFD results showed that the PSD significantly affected particle's flow behaviors at the lower zone of the riser, while the PSD effects were negligible in the upper part of the riser. This is meaningful for the industrial riser reactors since most of the reaction and transport process occur in this lower zone of the riser. Besides, the simulation results showed that wider PSD dramatically weaken the particle's back-mixing behaviors in the riser. The significant effects of PSD predicted by the CPFD method imply that large errors will be introduced if the mono-disperse assumption is adopted to simulate the experimental CFB riser handling particles with broad size distribution.
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•We used the CPFD method to study the effects of particle size distribution (PSD).•The PSD significantly affects the particle flow behaviors.•Wider PSD is helpful to reduce the extent of solids back-mixing.
We investigate optimal decay rates for higher–order spatial derivatives of strong solutions to the 3D Cauchy problem of the compressible viscous quantum magnetohydrodynamic model in the
×
×
...framework, and the main novelty of this work is three–fold: First, we show that fourth order spatial derivative of the solution converges to zero at the
, which is same as one of the heat equation, and particularly faster than the
in Pu–Xu Z. Angew. Math. Phys., 68:1, 2017 and the
, in Xi–Pu–Guo Z. Angew. Math. Phys., 70:1, 2019. Second, we prove that fifth–order spatial derivative of density
converges to zero at the
, which is same as that of the heat equation, and particularly faster than ones of Pu–Xu Z. Angew. Math. Phys., 68:1, 2017 and Xi–Pu–Guo Z. Angew. Math. Phys., 70:1, 2019. Third, we show that the high-frequency part of the fourth order spatial derivatives of the velocity
and magnetic
converge to zero at the
, which are faster than ones of themselves, and totally new as compared to Pu–Xu Z. Angew. Math. Phys., 68:1, 2017 and Xi–Pu–Guo Z. Angew. Math. Phys., 70:1, 2019.
With the booming of Internet of Things (IoT), smart health (s-health) is becoming an emerging and attractive paradigm. It can provide an accurate prediction of various diseases and improve the ...quality of healthcare. Nevertheless, data security and user privacy concerns still remain issues to be addressed. As a high potential and prospective solution to secure IoT-oriented s-health applications, ciphertext policy attribute-based encryption (CP-ABE) schemes raise challenges, such as heavy overhead and attribute privacy of the end users. To resolve these drawbacks, an optimized vector transformation approach is first proposed to efficiently transform the access policy and user attribute set into respective vectors of shorter length while other approaches result in redundant and longer vectors. Our transformation approach can greatly relieve the costly overheard of key generation, encryption, and decryption phases. Then, based on the transformation approach and the offline/online computation technology, we propose a lightweight policy-hiding CP-ABE scheme for the IoT-oriented s-health application. With our proposed scheme, data users in the s-health system can perform lightweight encryption and decryption without leaking any sensitive privacy about the attributes of the user. Finally, the formal security analysis, the theoretic performance evaluation and experiment results indicate that the solution is secure and efficient.
In this work a coupled (LDG-CFEM) method for singularly perturbed Volterra integro-differential equations with a smooth kernel is implemented. The existence and uniqueness of the coupled solution is ...given, provided that the source function and the kernel function are sufficiently smooth. Furthermore, the coupled solution achieves the optimal convergence rate
p
+
1
in the
L
2
norm and a superconvergence rate 2
p
at nodes for the numerical solution
U
ˆ
N
with the one-sided flux inside the boundary layer region under layer-adapted meshes uniformly with respect to the singular perturbation parameter
ϵ
.
In order to get the optimal profile of cycloid gear after sectional modification, a multi-objective optimization design method is proposed that considers both the modification parameters and ...macro-parameters of the cycloid gear. An algorithm of meshing force, meshing efficiency and anti-gluing ability between the cycloid gear and the pin gear was derived, and the related independent parameters were extracted as optimization variables. Taking high efficiency, high strength and light weight as the objective, the mathematical models of double-objective and three-objective optimization were established, and the influence of key design variable on the objective function was analyzed, and NSGA-II multi-objective genetic algorithm was used to solve the Pareto optimal solution of the optimization mathematical model. Results show that the optimized parameters can significantly improve the meshing efficiency, reduce the volume and meet the design requirements of high strength, high efficiency and lightweight on the premise of ensuring the strength of cycloid gear surface.
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