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Early Stage of Oxidation on Titanium Surface by Reactive Molecular Dynamics Simulation
Get PDFUnderstanding of metal oxidation is very critical to corrosion control, catalysis synthesis, and advanced materials engineering. Metal oxidation is a very complex phenomenon, with many different processes which are coupled and involved from the onset of reaction. In this work, the initial stage of oxidation on titanium surface was investigated in atomic scale by molecular dynamics (MD) simulations using a reactive force field (ReaxFF). We show that oxygen transport is the dominant process during the initial oxidation. Our simulation also demonstrate that a compressive stress was generated in the oxide layer which blocked the oxygen transport perpendicular to the Titanium (0001) surface and further prevented oxidation in the deeper layers. The mechanism of initial oxidation observed in this work can be also applicable to other self-limiting oxidation
A Novel Twist Deformation Model of Soft Tissue in Surgery Simulation
Get PDFReal-time performance and accuracy are two most challenging requirements in virtual surgery training. These difficulties limit the promotion of advanced models in virtual surgery, including many geometric and physical models. This paper proposes a physical model of virtual soft tissue, which is a twist model based on the Kriging interpolation and membrane analogy. The proposed model can quickly locate spatial position through Kriging interpolation method and accurately compute the force change on the soft tissue through membrane analogy method. The virtual surgery simulation system is built with a PHANTOM OMNI haptic interaction device to simulate the torsion of virtual stomach and arm, and further verifies the real-time performance and simulation accuracy of the proposed model. The experimental results show that the proposed soft tissue model has high speed and accuracy, realistic deformation, and reliable haptic feedback
On the Privacy-Preserving Outsourcing Scheme of Reversible Data Hiding over Encrypted Image Data in Cloud Computing
Get PDFAdvanced cloud computing technology provides cost saving and flexibility of services for users. With the explosion of multimedia data, more and more data owners would outsource their personal multimedia data on the cloud. In the meantime, some computationally expensive tasks are also undertaken by cloud servers. However, the outsourced multimedia data and its applications may reveal the data owner’s private information because the data owners lose the control of their data. Recently, this thought has aroused new research interest on privacy-preserving reversible data hiding over outsourced multimedia data. In this paper, two reversible data hiding schemes are proposed for encrypted image data in cloud computing: reversible data hiding by homomorphic encryption and reversible data hiding in encrypted domain. The former is that additional bits are extracted after decryption and the latter is that extracted before decryption. Meanwhile, a combined scheme is also designed. This paper proposes the privacy-preserving outsourcing scheme of reversible data hiding over encrypted image data in cloud computing, which not only ensures multimedia data security without relying on the trustworthiness of cloud servers, but also guarantees that reversible data hiding can be operated over encrypted images at the different stages. Theoretical analysis confirms the correctness of the proposed encryption model and justifies the security of the proposed scheme. The computation cost of the proposed scheme is acceptable and adjusts to different security levels
Dynamical Interaction Between Information and Disease Spreading in Populations of Moving Agents
Get PDFConsidering dynamical disease spreading network consisting of moving individuals, a new double-layer network is constructed, one where the information dissemination process takes place and the other where the dynamics of disease spreading evolves. On the basis of Markov chains theory, a new model characterizing the coupled dynamics between information dissemination and disease spreading in populations of moving agents is established and corresponding state probability equations are formulated to describe the probability in each state of every node at each moment. Monte Carlo simulations are performed to characterize the interaction process between information and disease spreading and investigate factors that influence spreading dynamics. Simulation results show that the increasing of information transmission rate can reduce the scale of disease spreading in some degree. Shortening infection period and strengthening consciousness for self-protection by decreasing individual’s scope of activity both can effectively reduce the final refractory density for the disease but have less effect on the information dissemination. In addition, the increasing of vaccination rate or decreasing of long-range travel can also reduce the scale of disease spreading
An Evidence Combination Method based on DBSCAN Clustering
Get PDFDempster-Shafer (D-S) evidence theory is a key technology for integrating uncertain information from multiple sources. However, the combination rules can be paradoxical when the evidence seriously conflict with each other. In the paper, we propose a novel combination algorithm based on unsupervised Density-Based Spatial Clustering of Applications with Noise (DBSCAN) density clustering. In the proposed mechanism, firstly, the original evidence sets are preprocessed by DBSCAN density clustering, and a successfully focal element similarity criteria is used to mine the potential information between the evidence, and make a correct measure of the conflict evidence. Then, two different discount factors are adopted to revise the original evidence sets, based on the result of DBSCAN density clustering. Finally, we conduct the information fusion for the revised evidence sets by D-S combination rules. Simulation results show that the proposed method can effectively solve the synthesis problem of high-conflict evidence, with better accuracy, stability and convergence speed
Design of ECC based Secured Cloud Storage Mechanism for Transaction Rich Applications
Get PDFCloud computing is the highly demanded technology nowadays. Due to the service oriented architecture, seamless accessibility and other advantages of this advent technology, many transaction rich applications are making use of it. At the same time, it is vulnerable to hacks and threats. Hence securing this environment is of at most important and many research works are being reported focusing on it. This paper proposes a safe storage mechanism using Elliptic curve cryptography (ECC) for the Transaction Rich Applications (TRA). With ECC based security scheme, the security level of the protected system will be increased and it is more suitable to secure the delivered data in the portable devices. The proposed scheme shields the aligning of different kind of data elements to each provider using an ECC algorithm. Analysis, comparison and simulation prove that the proposed system is more effective and secure for the Transaction rich applications in Cloud
Numerical Solutions of Unsteady MHD Flow Heat Transfer Over a Stretching Surface with Suction or Injection
Get PDFThe objective of the present problem is to investigate a two-dimensional unsteady flow of a viscous incompressible electrically conducting fluid over a stretching surface taking into account a transverse magnetic field of constant strength. Applying the similarity transformation, the governing boundary layer equations of the problem converted into nonlinear ordinary differential equations and then solved numerically using fourth order Runge-Kutta method with shooting technique. The effects of various parameters on the velocity and temperature fields as well as the skin-friction coefficient and Nusselt number are presented graphically and discussed qualitatively
Numerical Investigation of Combined Surface Radiation and Free Convection in a Square Enclosure with an Inside Finned Heater
Get PDFThe study goes further to investigate a two-dimensional numerical model coupling free convection and surface radiation in an air-filled cavity containing a heated thin finned plate. The square enclosure is subjected to isothermal and insulated boundary conditions while the heating element location is varied from the horizontal position (HPFU, HPFD) to the vertical position (VPFL). The dimensionless governing equations under Boussinesq approximations are coupled with a radiative model through the boundaries conditions and solved by the Finite Volume Method. The effects of the pertinent parameters, namely, Rayleigh number (103≤Ra≤106), fin length (0.125≤La≤0.875), fin position (0.25≤Ha≤0.75) and wall emissivity (0≤ε≤1) are investigated for a constant plate length (A=0.5). Results discussed in terms of streamlines, isotherms, convective and radiative Nusselt numbers highlighted the condition of the heat transfer improvement within the cavity which show an optimal thermal performance for a VPFL case (Ha=0.75 and La=0.875). Correlations are also developed for convective and Nusselt numbers for Ha=0.25 and La=0.5 with a maximum deviation less than 4%
On the InGaAs-based Photodetection Circuit for Scanning Near-Infrared Signal in the Wavelength Range of 1.0-2.0μm
Get PDFDetection of scanning long wave near-infrared (NIR) signal is critical in numerous applications spanning the fields of military, industry, agriculture, environment, and medicine. In this paper, we present a low cost, high performance InGaAs-based photoelectric conversion and amplification circuit for detecting scanning NIR signal in the wavelength range of 1.0-2.0 μm. With a special focus on reducing the influence of dark current and dark current noise for improved detector efficiency and precision, this proposed circuit features a photovoltaic preamplifier, a low-pass filter, and a temperature control unit; the signal gain, the bandwidth and the noise of the entire circuit is tuned for the signal spectrum of interest. In particular, to make the InGaAs detector operate at the target temperature with little fluctuation, a low-cost closed-loop temperature control circuit is designed that delivers temperature control accuracy of ±0.1°C. Both simulation and experimental results have confirmed that the proposed detection circuit meets the specific performance requirements for its intended use in spectrometer
Observing Wave/Particle Duality of Light Using Topological Charge
Get PDFWave particle duality, also called complementarity, is deeply rooted in the heart of quantum theory. It is fully exemplied in the famous Wheeler’s delayed choice experiment where the choice of the wave nature (ability to interfere) or the particle like behavior (path distinguishability) is introduced a posteriori. We perform here a delayed choice experiment in a Mach-Zehnder interferometer, using a classical laser beam and twisted light in a given mode. We entangle the polarization and the twisted internal degrees of freedom, with the which-path-information external degree of freedom of the beam. The particle behavior of light arises from the quantization of the orbital angular momentum. It is demonstrated from torque and light power measurements within 10% accuracy. We then experimentally evidence that the particle or wave behavior of light can be chosen a posteriori, even after the light has left the interferometer, at the moment of the detection