Search

Foodborne pathogenic bacteria detection is an important work, the traditional laboratory identification method, will cause irreversible damage to the sample, and the detection cycle is long. Compared with traditional biological detection methods, the greatest advantage of terahertz spectroscopy detection is that it can do non-destructive detection of samples, and terahertz spectroscopy technology, combined with computer systems, can reduce analysis time, improve recognition accuracy, and maximize the extraction and mining of effective information in the spectrum. This paper establishes an intelligent foodborne pathogenic bacteria terahertz spectroscopic recognition model, The results showed that the recognition accuracy of pathogens was 99.76%.

To improve energy storage performance of the multi-ring RCP flywheel comprised of inner hub, tungsten alloy ring and outer retainer, optimization design process for the radial thicknesses of components and interference fit assembly is demonstrated. Radial thicknesses of these components and magnitude of interference fit are set as design parameters to construct parametric analysis model. Design of experiments (DOE) technique is adopted to generate design matrix for sensitive analysis. Subsequently, radial basis function (RBF) approximation is employed to search for the optimal design considering structural integrity requirement. Finally, a proper range of the magnitude of interference fit is obtained which can not only prevent neither slippage nor separation between the inner hub and tungsten alloy ring but also ensure the safety of structural strength. In addition, it is found that to ensure a high moment of inertia and energy density, a reasonable large radial thickness of tungsten alloy ring and a reasonable small radial thickness of outer retainer are required.

Proton exchange membrane fuel cell (PEMFC) stack usually undergoes various vibrations during packing, transportation and serving time, in particular for those used in the automobiles and portable equipment. Based on the Miner fatigue damage theory, the fatigue lives of the fuel cell components are first assessed. Then the component fatigue life contours of the stack are obtained under four working conditions, i.e. the three single-axial (in X-, Y- and Z-axis separately) and multi-axial random vibrations. Accordingly, the component damage under various vibrations is evaluated. The stress distribution on the gasket and PEM will greatly affect their fatigue lives. Finally, we compare the fatigue lives of 4-bolt- and 6-bolt-clamping stacks under the same total clamping force, and find that increasing the bolt number could improve the bolt fatigue lives.

This paper considers the design of electrorheological (ER) particles. Multi-coated particles suspended in insulating (very weakly conducting) oil are recommended for obtaining high-performance ER suspensions. Only the outer two coatings determine the ER strength. The outermost coating should be a material with high dielectric constant, high electrical breakdown strength and a reasonable level of conductivity. The coating immediately below should be a highly conducting material. The inner coatings, including the core (which can be void), can be of any material having such a density that the composite particle has substantially the same density as the host liquid. Our analysis gives that multi-coated particles can have an ER shear strength as high as 29 kPa when the volume fraction of particles is 0.4 and the applied field is 5 kV . Results in the literature provide support for the concept and analysis.

The electrorheology of a zeolite/silicone oil suspension with direct current (dc) and alternating current (ac) electric fields was determined at room temperature. The shear yield stress changed only slightly with the field frequency, but the current density increased considerably. Good agreement occurs between the experimental results and those predicted by our model for both the shear yield stress and the current density. This study shows that there is a significant electrorheological (ER) effect over a large frequency range when a suspension has both a high conductivity ratio and a high dielectric ratio of the particles to the host oil.

Dielectric and conduction effects in electrorheological (ER) fluids with ohmic conductivity of the host liquids and with an applied AC electric field are considered. It is found that the conductivity ratio , the dielectric constant ratio and the applied field frequency f are three important parameters which determine the ER effect. If , a stronger ER response is obtained with a low applied field frequency than with a high frequency. If , the opposite occurs. Empirical equations are given for the attractive force between the particles in an ER fluid and for the shear yield stress. The calculated current density is independent of the applied field frequency when the frequency is smaller than a critical value, but becomes a linear function of the frequency beyond the critical value. The predicted attractive force of two nearly touching polymer spheres in mineral oil is in good agreement with that measured; also the predicted shear yield stress of some common ER suspensions is in accord with measurements.

A modified conduction model is proposed for predicting the maximum local electric field, current density and attractive force between two spherical particles in a host oil. The dependence of the conductivity of the host fluid on electric field is expressed by a simplified equation based on Onsager's theory. The model gives the ratio of the maximum local field to the applied field as , where and , A and are the conductivity parameters relating to the host fluid. is the conductivity of the particles and the applied field. Good agreement is found between the predicted and measured values of the current density and the yield stress of electrorheological (ER) suspensions. To obtain a strong ER effect, a high value of the combined conductivity parameter of the host fluid is desired.

It has long been recognized that woodpecker is an excellent anti-shock organism, as its head and brain can bear high deceleration up to 1500 g under fast pecking. To investigate the mechanism of brain protection of woodpecker, we built a finite element model of a whole woodpecker using computed topography scanning technique and geometry modeling. Numerical results show that the periodical changing Young's modulus around the skull affects the stress wave propagation in head and makes the stress lowest at the position of the brain. Modal analysis reveals the application of pre-tension force to the hyoid bone can increase the natural frequency of woodpecker's head. The large gap between the natural and working frequencies enable the woodpecker to effectively protect its brain from the resonance injury. Energy analyses indicate the majority of the impact energy (99.7%) is stored in the bulk of body and is utilized in the next pecking. There is only a small fraction of it enters into the head (0.3%). The whole body of the woodpecker gets involved in the energy conversion and forms an efficient anti-shock protection system for the brain.

The three-point bending Young's modulus (E) of nanowires was studied by a finite element method. It was found that the constraint conditions at the nanowire ends, the ratio of the suspended length of the wire to the wire diameter and the deflection of the wire all work together to contribute to the measurement errors of the Young's modulus. Yielding of the deposited material used to fix the nanowire ends leads to a decrease in the slope of the load–deflection curve. The three-point bending criteria for nanowires have been established. A modified equation for the measurement of the three-point bending Young's modulus of nanowires is proposed.