Study on Doppler characteristics of underwater bistatic reverberation

Active sonar has two typical types of geometry configuration respectively named monostatic and bistatic like a radar system. In the monostatic scenario, co-located underwater transducers transmit and receive sound energy, while in a bistatic situation the transducers are physically separated. Both object detection and identification can be significantly enhanced through utilization of the additional dimension provided by a bistatic geometry. So, more people care about bistatic scattering characteristics of underwater objects as well as bistatic reverberation in recent years. In this paper, Doppler characteristics of bistatic reverberation generated by moving transmitter and receiver are studied. Theoretical formulism for receiving frequency of bistatic reverberation is derived in case of a tone signal being transmitted. Further analysis shows bistatic reverberation is more complicated than monostatic reverberation when Doppler is concerned. In monostatic case, the Doppler frequency shift of reverberation relates to centre frequency of the tone signal, velocity of the transmitter as well as the arriving direction. While in bistatic situation, it varies not only with the above factors, but also the locations, moving directions, velocities of both transmitter and receiver, and also the arriving time of the reverberation, which makes extraction and utilization of Doppler information more difficult

Bionic Design and Parameter Optimization of Rotating and Fixed Stem- and Leaf-Cutting Devices for Carrot Combine Harvesters

To solve the problems of the high rhizome damage and low net cutting during carrot combine harvesting, the following research was performed. The designed carrot stem- and leaf-cutting device was taken as the research object, and a bionic design idea was adopted. MATLAB software was used to extract and optimize the tibial curve of the mantis forelimb, and its shape was applied to the cutting edges of a single-disc rotating cutter and a straight fixed cutter, whose key structural parameters were determined. The kinematic and dynamic models of the cutter, stems, and leaves were established to explore the critical conditions of smooth cutting. A single-factor experiment was performed. The results show that the rhizome damage and the stems and leaf net cutting increased when the rotation speed of the clamping conveyor pulley increased. The flatness of the cutting surface first increased and subsequently decreased. At a speed of 102 r/min, the rhizome damage was 2.86%, the net cutting of stems and leaves was 92.82%, and the flatness of the cutting surface was 85.39%. The net cutting of stems and leaves and the flatness of the cutting surface increased as the disc cutter speed increased, while the rhizome damage decreased. When the rotation speed reached 165 r/min, the rhizome damage, the net cutting of stems and leaves, and the flatness of the cutting surface were 1.97%, 89.59%, and 91.48%, respectively. The bench test and field experiment results showed that the cutting performance of the optimized bionic cutter group is significantly better than that of the conventional knife group. The rhizome damage, net cutting of stems and leaves, and flatness of the cutting surface were 4.01%, 92.05%, and 84.05%, respectively, which meet the agronomic requirements for carrot harvesting

Evaluation of Physical Characteristics of Typical Maize Seeds in a Cold Area of North China Based on Principal Component Analysis

The physical properties of maize seeds are closely related to food processing and production. To study and evaluate the characteristics of maize seeds, typical maize seeds in a cold region of North China were used as test varieties. A variety of agricultural material test benches were built to measure the maize seeds’ physical parameters, such as thousand-grain weight, moisture content, triaxial arithmetic mean particle size, coefficient of static friction, coefficient of rolling friction, angle of natural repose, coefficient of restitution, and stiffness coefficient. Principal component and cluster comprehensive analyses were used to simplify the characteristic parameter index used to judge the comprehensive score of maize seeds. The results showed that there were significant differences in the main physical characteristics parameters of the typical maize varieties in this cold area, and there were different degrees of correlation among the physical characteristics. Principal component analysis was used to extract the first three principal component factors, whose cumulative contribution rate was over 80%, representing most of the information of the original eight physical characteristic parameters, and had good representativeness and objectivity. According to the test results, the classification standard of the evaluation of the physical characteristics of 15 kinds of maize seeds were determined, and appropriate evaluations were conducted. The 15 kinds of maize seeds were clustered into four groups by cluster analysis, and the physical characteristics of each groups were different. This study provides a new idea for the evaluation and analysis of the physical properties of agricultural materials, and provides a new method for the screening and classification of food processing raw materials

Analysis and Experiment on the Seed Metering Mechanism of Multi-Grain Cluster Air Suction Type Rice (<i>Oryza sativa</i> L.) Hill Direct Seed Metering Device

This paper aims to solve the problem of high reseeding rates and mis-seeding rates in the rice multi-grain hole direct seeding process. A multi grain cluster air suction type rice hill direct seed metering device was developed, and its seeding mechanism was analyzed. Based on CFD-DEM coupling simulation and bench tests, this study explored and optimized the performance of the seed metering device, and carried out the seeding adaptability test. The simulation results were as follows: when the negative pressure was −5 kPa, the static pressure, dynamic pressure and velocity of the flow field reached the maximum. When the negative pressure was −4 kPa, the qualification index was 89.62%, the reseeding index was 4.36%, and the mis-seeding index was 6.02%. The results of the orthogonal rotation combination test of three factors and five levels showed that when the rotation speed, negative pressure and the length of stirring brush were 20.70 rpm, −4.0 kPa and 10.50 mm respectively, the seed metering performance was the best, the qualification index was 90.85%, the reseeding index was 4.41% and the mis-seeding index was 4.74%. The seed metering device had strong adaptability to the sowing of different rice varieties, and met the agronomic requirements of direct seeding and seeding in rice holes

Loss of the ER membrane protein complex subunit Emc3 leads to retinal bipolar cell degeneration in aged mice.

The endoplasmic reticulum (ER) membrane protein complex (EMC) is a conserved protein complex involved in inserting the transmembrane domain of membrane proteins into membranes in the ER. EMC3 is an essential component of EMC and is important for rhodopsin synthesis in photoreceptor cells. However, the in vivo function of Emc3 in bipolar cells (BCs) has not been determined. To explore the role of Emc3 in BCs, we generated a BC-specific Emc3 knockout mouse model (named Emc3 cKO) using the Purkinje cell protein 2 (Pcp2) Cre line. Although normal electroretinography (ERG) b-waves were observed in Emc3 cKO mice at 6 months of age, Emc3 cKO mice exhibited reduced b-wave amplitudes at 12 months of age, as determined by scotopic and photopic ERG, and progressive death of BCs, whereas the ERG a-wave amplitudes were preserved. PKCa staining of retinal cryosections from Emc3 cKO mice revealed death of rod BCs. Loss of Emc3 led to the presence of the synaptic protein mGLuR6 in the outer nuclear layer (ONL). Immunostaining analysis of presynaptic protein postsynaptic density protein 95 (PSD95) revealed rod terminals retracted to the ONL in Emc3 cKO mice at 12 months of age. In addition, deletion of Emc3 resulted in elevated glial fibrillary acidic protein, indicating reactive gliosis in the retina. Our data demonstrate that loss of Emc3 in BCs leads to decreased ERG response, increased astrogliosis and disruption of the retinal inner nuclear layer in mice of 12 months of age. Taken together, our studies indicate that Emc3 is not required for the development of BCs but is important for long-term survival of BCs

Development of essential oils as skin permeation enhancers: penetration enhancement effect and mechanism of action

Context: Essential oils (EOs) have shown the potential to reversibly overcome the stratum corneum (SC) barrier to enhance the skin permeation of drugs. Objective: The effectiveness of turpentine, Angelica, chuanxiong, Cyperus, cinnamon, and clove oils were investigated for the capacity and mechanism to promote skin penetration of ibuprofen. Materials and methods: Skin permeation studies of ibuprofen across rat abdominal skin with the presence of 3% w/v EOs were carried out; samples were withdrawn from the receptor compartment at 8, 10, 22, 24, 26, 28, 32, 36, and 48 h and analyzed for ibuprofen content by the HPLC method. The mechanisms of penetration enhancement of EOs were further evaluated by attenuated total reflection-Fourier transform infrared spectroscopy (ATR-FTIR) analysis and determination of the properties of EOs. Moreover, the toxicities of EOs on skin cells were also measured. Results: The enhancement ratio (ER) values of turpentine, Angelica, chuanxiong, Cyperus, cinnamon, clove oils and azone were determined to be 2.23, 1.83, 2.60, 2.49, 2.63 and 1.97, respectively. Revealed by ATR-FTIR analysis, a linear relationship (r = 0.9045) was found between the ER values and the total of the shift of peak position of SC lipids. Furthermore, the results of HaCaT skin cell toxicity evaluation revealed that the natural EOs possessed relatively lower skin irritation potential. Conclusion: Compared with azone, the investigated EOs possess significantly higher penetration enhancement effect and lower skin toxicity. EOs can promote the skin permeation of ibuprofen mainly by disturbing rather than extracting the SC lipids

Analysis and Experiment on the Seed Metering Mechanism of Multi-Grain Cluster Air Suction Type Rice (Oryza sativa L.) Hill Direct Seed Metering Device

This paper aims to solve the problem of high reseeding rates and mis-seeding rates in the rice multi-grain hole direct seeding process. A multi grain cluster air suction type rice hill direct seed metering device was developed, and its seeding mechanism was analyzed. Based on CFD-DEM coupling simulation and bench tests, this study explored and optimized the performance of the seed metering device, and carried out the seeding adaptability test. The simulation results were as follows: when the negative pressure was &minus;5 kPa, the static pressure, dynamic pressure and velocity of the flow field reached the maximum. When the negative pressure was &minus;4 kPa, the qualification index was 89.62%, the reseeding index was 4.36%, and the mis-seeding index was 6.02%. The results of the orthogonal rotation combination test of three factors and five levels showed that when the rotation speed, negative pressure and the length of stirring brush were 20.70 rpm, &minus;4.0 kPa and 10.50 mm respectively, the seed metering performance was the best, the qualification index was 90.85%, the reseeding index was 4.41% and the mis-seeding index was 4.74%. The seed metering device had strong adaptability to the sowing of different rice varieties, and met the agronomic requirements of direct seeding and seeding in rice holes

Research on the operation strategies of the solar assisted heat pump with triangular solar air collector

The solar-assisted heat pump (SAHP) is considered to be one of the efficient and promising clean heating technologies, while the research on its operation strategy is insufficient. In this study, a novel triangular solar air collector assisted air source heat pump (TSAHP) for rural residence heating is presented. Three working modes of the TSAHP including preheating, series and parallel modes were investigated, and corresponding mathematical models were established and verified. The effects of solar irradiance, outdoor temperature, indoor temperature, south wall covered area of the TSAC and the heating load on the performances of the three working modes were analyzed. The distribution diagram of the optimal working mode was designed, and the equations that define the boundaries between operating modes were fitted. Finally, the performances of the TSAHP under typical meteorological parameters were compared and analyzed based on the modified boundary equations. Results indicate that the TSAHP can sufficiently utilize solar energy. With the increase of solar irradiance, the optimal working mode is shifted from the preheating to series and parallel. Compared with the traditional air source heat pump system, the COP of the TSAHP under the optimal working modes could be increased by 64.4%

Multi-component yttrium aluminosilicate (YAS) fiber prepared by melt-in-tube method for stable single-frequency laser

The multi-component glass fibers have demonstrated their unique advantages in the application of single-frequency lasers due to their higher solubility of rare-earth ions and thus a higher gain per unit length in a compact fiber laser cavity. In this study, multi-component yttrium aluminosilicate (YAS) fiber with high doping concentration of Yb3+ was prepared by the "melt-in-tube" (MIT) method. A unit-length gain of 3 dB/cm was obtained in a 4.4 cm-long YAS fiber, the laser output slope efficiency reached 23.8% in a 10 cm-long Yb:YAS fiber. Single-frequency laser operation was achieved in a 1.7-cm-long Yb:YAS active fiber. To the best of our knowledge, this is the first demonstration of single-frequency laser with this YAS glass fiber as gain medium. The novel multi-component YAS fiber can be applied as a new gain material to realize single-frequency fiber laser