Applicability of moisture transfer parameters estimated by correlation between Biot number and lag factor (Bi–G correlation) for convective drying of eggplant slices

Accurate values of the moisture transfer parameters are necessary to study heat and mass transfer, particularly for the efficient design of both process and equipment. However, these parameters obtained from empirical equations or analytical solutions of Fick’s second diffusion law are generally different from each other. In order to make simulation more accurate and closer to the fact, it is necessary to perform theoretical analysis and test of available empirical equations in literatures. In this work, such efforts were made: firstly, moisture transfer parameters were evaluated by Bi–G correlation; then, the obtained parameters were substituted to Fick’s second law of diffusion model, and the model was numerically calculated with convective boundary condition. The results show that although the exponential equation fits the experimental data well, the data predicted from Fick’s second law deviate far from the experimental data. This implicates that Bi–G correlation need be further improved to obtain better accurate moisture transfer parameters.     

Finite-time synchronization of switched stochastic R?ssler systems

This paper presents the finite-time synchronization between switched stochastic R?ssler systems accompanied by a time-driven switching law. Based on the Ito formula and Lyapunov stability theory, the finite-time synchronization of switched stochastic master-slave R?ssler systems and the finite-time stability for the mean of error states are developed with the proposed feedback controller. Numerical simulations demonstrate the effectiveness of the proposed methods.     

Dielectric Loss Suppression of Silver/Poly(vinylidene fluoride) Composite Films with Polydopamine

The preparation and dielectric properties of silver-polydopamine/poly(vinylidene fluoride) (Ag-PDOP/PVDF) composite films with suppressed dielectric loss are reported. The dielectric loss tangents of the composite films were found to be rather low similar to that of pure PVDF over the frequency range 100 Hz to 30 kHz, almost regardless of the Ag content, and even lower than that of pristine PVDF in the relatively high frequency region. The nanoscale structure comprised of Ag nanoparticles (Ag NPs), isolated by the PDOP coating and the PVDF matrix, hindered the formation of percolative networks, resulting in the decreased conduction loss in the composite films, even at a high filler loading. The strong interfacial interaction between the Ag@PDOP particles and the PVDF matrix also contributed to the restrained interfacial loss. Consequently, these composite films had higher permittivity and smaller dielectric loss than the PVDF matrix at relatively high frequencies, and would thus be attractive for physically small capacitor applications in electronics and electric power systems.     

First-Principles Investigation of Mechanical and Thermodynamic Properties of Nickel Silicides at Finite Temperature

First-principles calculations are performed to investigate lattice parameters, elastic constants and 3D directional Young’s modulus E of nickel silicides (i.e., β-Ni₃Si, δ-Ni₂Si, θ-Ni₂Si, ε-NiSi, and θ-Ni₂Si), and thermodynamic properties, such as the Debye temperature, heat capacity, volumetric thermal expansion coefficient, at finite temperature are also explored in combination with the quasi-harmonic Debye model. The calculated results are in a good agreement with available experimental and theoretical values. The five compounds demonstrate elastic anisotropy. The dependence on the direction of stiffness is the greatest for δ-Ni₂Si and θ-Ni₂Si, when the stress is applied, while that for β-Ni₃Si is minimal. The bulk modulus B reduces with increasing temperature, implying that the resistance to volume deformation will weaken with temperature, and the capacity gradually descend for the compound sequence of β-Ni₃Si > δ-Ni₂Si > θ-Ni₂Si > ε-NiSi > θ-Ni₂Si. The temperature dependence of the Debye temperature ΘD is related to the change of lattice parameters, and ΘD gradually decreases for the compound sequence of ε-NiSi > β-Ni₃Si > δ-Ni₂Si > θ-Ni₂Si > θ-Ni₂Si. The volumetric thermal expansion coefficient αV, isochoric heat capacity and isobaric heat capacity C _p of nickel silicides are proportional to T³ at low temperature, subsequently, αV and C _p show modest linear change at high temperature, whereas C_v obeys the Dulong-Petit limit. In addition, β-Ni₃Si has the largest capability to store or release heat at high temperature. From the perspective of solid state physics, the thermodynamic properties at finite temperature can be used to guide further experimental works and design of novel nickel–silicon alloys.

     

Synthesis and self‐assembled mechanism of CuO peony‐flowers by a composite hydroxide‐mediated approach at low temperature

A composite‐hydroxide mediated (CHM) method was utilized for the synthesis of CuO peony‐flower nanostructures under temperatures ranging between 25 and 160 °C. The CHM mechanism was confirmed through X‐ray Powder Diffraction (XRD) and a Thermo‐Gravimetric Differential Scanning Calorimeter (TG‐DSC). Cu(NO₃)₂ was shown to transform into Cu(OH)₂ in the mixed alkalis (NaOH/KOH); the reaction was facilitated by the solvent properties of the mixed alkalis. Cu(OH)₂ subsequently consumed H₂O in the adsorption of the mixed alkalis at 25∼65 °C. At higher reaction temperatures (>65 °C), the Cu(OH)₂ was seen to decompose at an accelerated rate. Therefore, crystalline CuO could be obtained not only above 65 °C but also at 25 °C. The crystal morphology and structure of CuO were examined through Filed Emission Scanning Electron Microscopy (FE‐SEM) and Transmission Electron Microscopy (TEM). It was determined that the CuO peony‐flower had a polycrystalline structure composed of single crystalline CuO petals. Using the Selected Area Electron Diffraction (SAED) results, the rings were indexed as (002), (111), (112), (202) and (−113), which was in agreement with the XRD results. With increasing temperature, the CuO flower petals self‐assembled through random aggregation and gathered CuO nanorod parts, which led to incomplete CuO flower petals through orientated aggregation. Prolonged reaction time led to the growth of CuO flower petals in the direction of [001]. An ideal CuO flower structure was observed through TEM observation.     

The analysis of system performance of WDM/OCDMA-PON based on DQPSK

The paper proposes an OCDM/WDM PON system solution based on DQPSK which has passed theoretical and simulative tests. This solution can realize the effective integration between OCDMA technology and DWDM system. Compared with the traditional OCDMA/WDM system, this solution saves a large number of OCDMA decoders/encoders, effectively reduces the complexity of the system integration process, and accomplishes seamless integration and upgrade. The results show that compared with the OCDM/WDM PON system based on OOK, the OCDM/WDM PON system based on DQPSK has advantages as follows: higher sensitivity for the receiving system; better system security and wider system noise margin. These advantages provide the DQPSK-based OCDM/WDM PON system solution with a better application prospect.     

A robust edge detection method with sub-pixel accuracy

In this paper, a new edge detection approach combining gray-moments operator with smoothing spline algorithm is proposed, which is invariant to additive and multiplicative noises in the image. This approach consists of two steps: firstly, a continuous blurred edge model is obtained using the smoothing spline algorithm in the edge region detected by Sobel operator; then a gray-moment solution is derived for both the one- and two-dimensional situations using the blurred edge model. Testing of this new detection approach demonstrates more robustness against the white Gaussian noise and speckle noise, and run time very close to the gray-moment and space-moment operators. The above advantages indicate this approach is very suitable for on-line accurate detection.     

Investigations into the mid-infrared Christiansen effect of the dispersive materials

The mid-infrared Christiansen effect was found to occur in the KBr pellets in which powder of the dispersive material -SiC was dispersed. The KBr pellet technique is commonly used for infrared transmission (or absorption) spectroscopy of powders, and when we dispersed in KBr powder a moderate amount of a dispersive material, such as -SiC, and pressed them into a pellet, a transmission spectrum with a sharp peak was obtained. The phenomenon is very interesting, and can be explained with the well-known Lorentz dispersion model accurately. Also, it is very useful for making a new type of mid-infrared band-pass filter, e.g. a mid-infrared Christiansen filter. After performing combinations of some other dispersive materials, such as MgO, with some transparent refractive index matching matrices, such as KCl etc, another aspect of the application of this important classical effect is shown, that is, determining the refractive indices of some mid-infrared transparent materials accurately.