Applied Mechanics and Materials Vol. 461

Abstract: Numerical simulation was used with SST turbulence model on the drag reduction characteristics of bionic jet surface, which clarified the reason that the bionic jet surface could reduce the frictional resistance and the control behavior to the flow field near the wall. Results show that when the area of the jet hole is constant, the higher the ratio of the length along the longitudinal direction of jet hole and that of jet surface is, the better the drag reduction effect is. With the jet speed and jet flux increasing, the drag reduction rate will increase gradually until the maximum of 35.97%. The frictional resistance of bionic jet surface will decrease by increasing the area of reverse flow and decreasing the velocity gradient of the wall; the control behavior of jet surface to boundary layer embodies the shear stress in the bottom of boundary layer caused by the reverse flow in the back flow surface is opposite to the main flow field direction when the shear flow near the wall converges the jet impedance, which causes the low speed reverse rotating vortex pair in the downstream of jet hole, the secondary vortex near the wall caused by the extent of reverse vortex towards the downstream can increase the boundary bottom layer thickness and decrease the velocity gradient and frictional resistance.

Abstract: Inspired by stripe shaped structure of owl wing feathers, V-ring surface was proposed in this paper to reduce the aerodynamic noise of a circular cylinder. The effects of V-ring surface on the aerodynamic and aeroacoustic performance of the cylinder were investigated by wind tunnel and numerical simulation. We tested the fluctuating pressure of the smooth cylinder and the V-ring surface cylinder by pulsating pressure sensor in FD-09 wind tunnel of China Academy of Aerospace Aerodynamics（CAAA）. At a wind speed of 42m/s, the Reynolds number is 1.62×10⁵ based on the cylinder diameter D of 58mm. The test results showed that the overall fluctuating pressure on the measurement points of the V-ring surface cylinder was significantly decreased compared with the smooth cylinder. The mechanisms of aerodynamic noise control of circular cylinder by V-ring surface were studied by the Large Eddy Simulation（LES）and the Ffowcs Williams and Hawkings （FW-H） equation. The numerical simulation results showed that the aerodynamic noise of the V-ring surface cylinder was reduced by 4.1dB compared to the smooth cylinder. The sound pressure of V-ring surface cylinder model is reduced when the lift fluctuation becomes lower. The V-ring surface is capable of reducing the frequency of the vortex shedding and controlling the fluctuating lift force induced by unstable vortices acting on the cylinder surface.

Abstract: This paper describes a method for visual reconstruction and analysis of the surface of earthworm in AVS/Express, Advanced Visual System's new visualization development tool. The digital measurements of surfaces of the earthworm were carried out using a three-dimensional laser scanner. Detailed information on the point clouds, the scanning digital data of the surface of the earthworm were obtained by importing and analyzing those point clouds in AVS/Express. Methods and results presented in this paper proved to be potentially useful for analyzing the feature of biological prototype, optimizing the mathematical model and affording deformable physical model to bionic engineering, this would have significant implications to the research of biological coupling theory and technological creation in bionic engineering.

Abstract: The soft surface of birds and aquatic organisms in the nature can effectively reduce the drag. Inspired by the fact,in this paper, an attempt is made to stick silicone rubber soft surface on the surfaces of NACA 4412 and NACA 6409 airfoils. The drags, lifts and lift-drag ratios of airfoils with soft and rigid surfaces in 5 different thickness were compared through wind tunnel test under the condition of α = 0 °. The results show that most of the bionic soft surfaces play the role of reducing the aerodynamic drag, and also increasing the lift at the same time, in which the soft surface of 0.6mm had the most significant effect of drag reduction and lift increasing.

Abstract: Initiation of insect’s optomotor reaction, researchers developed the element movement detector (EMD) in motion detection. The detector can estimate the motion parameters of the moving target quickly in 2-D spatial orientation, such as angular velocity and angular rotation. Based on the function of compound eyes, we promoted a fast positioning EMD model. It has the ability in positioning in 3-D spatial orientation with wide field of view (FOV). And then we did some experiments to verify that the positioning algorithm had higher estimation accuracy of position in time.

Abstract: This paper presents a method of how to improve the accuracy of the ultrasonic detecting for drainage pipeline. The method is composed of two parts. One is the hardware, which provides a multiplexer that gradually amplifies the echo signal. The other is the software, decreasing the reference voltage step by step at a fixed value as the microprocessor controls. With the cooperation of the hardware and the software, signal is continuously amplified and reference voltage is ceaselessly reduced till they approach to each other within the given limit. Through this method, accurate measurement is available.

Abstract: We describe a novel mobile visual search system based on the saliencymechanism and sparse coding principle of the human visual system (HVS). In the featureextraction step, we first divide an image into different regions using thesaliency extraction algorithm. Then scale-invariant feature transform (SIFT)descriptors in all regions are extracted while regional identities arepreserved based on their various saliency levels. According to the sparsecoding principle in the HVS, we adopt a local neighbor preserving Hash functionto establish the binary sparse expression of the SIFT features. In the searchingstep, the nearest neighbors matched to the hashing codes are processed accordingto different saliency levels. Matching scores of images in the database arederived from the matching of hashing codes. Subsequently, the matching scoresof all levels are weighed by degrees of saliency to obtain the initial set of results. In order to further ensure matching accuracy, we propose an optimized retrieval scheme based on global texture information. We conduct extensive experiments on an actual mobile platform in large-scale datasets by using Corel-1000. The resultsshow that the proposed method outperforms the state-of-the-art algorithms on accuracyrate, and no significant increase in the running time of the feature extractionand retrieval can be observed.

Abstract: To detect the freshness of chicken quickly and accurately with non-destructive, in this paper, the gas-sensitive sensor array has been optimized according to the odor of chicken and the sensor experiment. gas sensors combinations of TGS2600 TGS2610 TGS2611 TGS2620 and TGS2442 were selected and combined to establish new sensor array,The outcome of biological olfactory research has been used to design a bionic gas collection chamber. We have also adopted RBF neural network as a pattern recognition method. The fact that the accuracy of chicken freshness detection using the system is physically and chemically proved to be 96% demonstrates the feasibility of making use of artificial olfactory system to detect chicken freshness.

Abstract: In order to fabricate biosensors with high sensitivity, the diatom Coscinodiscus excentricus was cultured on a microfluidic chip made with polydimethylsiloxane (PDMS), then the organic matter of diatom cells was removed and only diatom frustules were left, after which the cleaned frustules were bonded onto the bottom of the PDMS micro chamber by ultraviolet irradiation. The overview and the detailed morphology of the frustules in the chamber were analyzed by SEM, and the ultraviolet irradiation bonding mechanism of diatom with PDMS was discussed. Finally, the diatom based microfluidic chip was tested with the fluorescein-labeled protein; and the result showed that the fluorescence intensity of the diatom is 4 times stronger compared with that of the blank regions.

Abstract: This study is aiming at the practical problem of meat freshness evaluation. Since meat putrefaction is a complex process that is influenced by many factors, it is necessary to have a comprehensive investigation of the various indicators to determine the freshness of meat. This research integrated information from a multisensory system to reduce uncertainty of evaluation. According to the odor mechanism model of rotten chicken, six types of sensors were chosen, which were combined as array for olfactory experiments. WDW-20 electronic universal testing machine (UTM) was adopted as tactile sensing device. As a bionic tactile test part, the UTM head is to obtain pressure characteristic curves of the meat. According to the odor model and elastic mechanics parameters of the chicken, the mechanical parameters were analyzed under the condition of cold storage, as well as time-varying results of fingerprint odor signal and salt base nitrogen volatile signal. Then, established the meat odor, elastic mechanics and freshness parameters, which were integrated into a fusion system and combined with the data through the experimental test. Eventually, established the mathematical model among meat odor, elastic mechanics parameters and meat freshness. This study provides theory reference for the evaluation of meat freshness, and delivers new thought and method for the design of multiphase bionic intelligent electrical measuring equipment.