Adaptive Regulation of the Flying Height Based on Hybrid Actuator in Near-field Optical Disk Drives

In the next generation near-field optical data storage systems, higher data transfer rate and higher data density require the optical pickup head to maintain a constant sub-micrometer flying height above the rotating disk surface without any collisions. However, suspension vibration and force disturbance, as well as disk vibration make it difficult to maintain the desired flying height during disk operation in the near-field optical disk drives (ODD). It is proposed in this paper to design a hybrid actuator system which combines both advantages of the flying slide used in hard disk drives and the voice coil actuator used in optical disk drives. Then based on the developed model of the hybrid actuator, an adaptive regulation approach is proposed to regulate the flying height at its desired value, despite the unknown vibrations and the unknown force disturbance. The performance of the proposed approach is analyzed and simulation results are presented to illustrate the capability of the proposed adaptive regulation approach to achieve and maintain the desired flying height

Effect of blade number on rotor efficiency and noise emission at hovering condition

The configuration of rotors significantly impacts the aerodynamic efficiency and noise emission of multicopters. To date, there are no general guidelines regarding how many blades a rotor should use for optimal aerodynamic performance and minimum noise emission. From the perspectives of aerodynamics and acoustics during the hovering condition, two key parameters, i.e., figure of merit (FM) and overall sound pressure level (OASPL), are evaluated to determine the optimal blade number (BN). The number of blades chosen in this study is BN = 2–6, which is largely observed in commercial multicopters. A genetic algorithm was developed to optimize blade design for each BN-rotor configuration. The individuals are evaluated by steady computational fluid dynamics (CFD) simulations and acoustic analogy for optimizations, and the detailed analyses of optimal ones are further explored by unsteady CFD simulations. The planform of the baseline blade is maintained, and the radial distribution of twist angles is the parameter for optimization. While generating the same thrust, the value of FM keeps increasing as the number of blades increases from 2 to 4, after which the FM value reaches a plateau. The value of OASPL keeps decreasing as the number of blades increases. The reason for the FM and OASPL value trends vs blade number is explained with the numerical simulation results, and a general design rule is suggested at the end

Rapeseed Seedling Stand Counting and Seeding Performance Evaluation at Two Early Growth Stages Based on Unmanned Aerial Vehicle Imagery

The development of unmanned aerial vehicles (UAVs) and image processing algorithms for field-based phenotyping offers a non-invasive and effective technology to obtain plant growth traits such as canopy cover and plant height in fields. Crop seedling stand count in early growth stages is important not only for determining plant emergence, but also for planning other related agronomic practices. The main objective of this research was to develop practical and rapid remote sensing methods for early growth stage stand counting to evaluate mechanically seeded rapeseed (Brassica napus L.) seedlings. Rapeseed was seeded in a field by three different seeding devices. A digital single-lens reflex camera was installed on an UAV platform to capture ultrahigh resolution RGB images at two growth stages when most rapeseed plants had at least two leaves. Rapeseed plant objects were segmented from images of vegetation indices using typical Otsu thresholding method. After segmentation, shape features such as area, length-width ratio and elliptic fit were extracted from the segmented rapeseed plant objects to establish regression models of seedling stand count. Three row characteristics (the coefficient of variation of row spacing uniformity, the error rate of the row spacing and the coefficient of variation of seedling uniformity) were further calculated for seeding performance evaluation after crop row detection. Results demonstrated that shape features had strong correlations with ground-measured seedling stand count. The regression models achieved R-squared values of 0.845 and 0.867, respectively, for the two growth stages. The mean absolute errors of total stand count were 9.79 and 5.11% for the two respective stages. A single model over these two stages had an R-squared value of 0.846, and the total number of rapeseed plants was also accurately estimated with an average relative error of 6.83%.Moreover, the calculated row characteristics were demonstrated to be useful in recognizing areas of failed germination possibly resulted from skipped or ineffective planting. In summary, this study developed practical UAV-based remote sensing methods and demonstrated the feasibility of using the methods for rapeseed seedling stand counting and mechanical seeding performance evaluation at early growth stages

臼歯陶材焼付鋳造冠におけるメタルフレーム形態の力学的検討(英文)

Objectives: The purpose of this study was to find an ideal shape of the metal frame (coping) in the porcelain fused to metal (PFM) crown. The stress distribution was assessed by the load-to-fracture values and a three-dimensional finite element analysis. Methods: Three kinds of coping designs were tested; Design I: Conventional type as control (traditional frame). Design II: 1.0 mm lower than occlusal surface of coping (butterfly frame). Design III: Straight type (flat frame). The load-to-fracture value consisted of three groups (Design I, II and III) of five samples each. The loading location is selected at the area where mesial and distal of the metal frame will coincide with the projection of the occlussal surface. All samples were loaded to fracture at the rate of 0.1 mm/min using a universal-testing machine. The stress distribution was assessed in a three-dimensional finite element model, which consisted of the abutment tooth, cement, metal coping and porcelain. The loading position is the projection point ofbuccal-lingual transitional part of the frame mesial and distal proximal surface on the occlusal surface towards the median, in which the load is in constant value. Loading direction is vertically downward along tooth axis with a load of 2000 N. Results: The mean load-to-fracture value for each group is as follows: Group A (Design I)=1823.0 N±132.7 (S.D.), Group B (Design II)=1940.4 N±147.4 (S.D.), Group C (Design III)=2333.9 N±180.9 (S.D.). The results of the three-dimensional finite element analysis showed that the maximum tensile stress of 84.5 MPa occurred in Design I. The maximum tensile stress in design II and III were 53.8 MPa and 53.3 MPa, respectively, which were the lower than Design I. Conclusions: The results indicated that the butterfly and flat frame designs will increase metal support on proximal porcelain, thus effectively change the stress distribution within the coping and porcelain, optimizing stress distribution in PFM crown under perpendicular load, and enhance structural strength of porcelain of PFM crown

Rapeseed Seedling Stand Counting and Seeding Performance Evaluation at Two Early Growth Stages Based on Unmanned Aerial Vehicle Imagery

The development of unmanned aerial vehicles (UAVs) and image processing algorithms for field-based phenotyping offers a non-invasive and effective technology to obtain plant growth traits such as canopy cover and plant height in fields. Crop seedling stand count in early growth stages is important not only for determining plant emergence, but also for planning other related agronomic practices. The main objective of this research was to develop practical and rapid remote sensing methods for early growth stage stand counting to evaluate mechanically seeded rapeseed (Brassica napus L.) seedlings. Rapeseed was seeded in a field by three different seeding devices. A digital single-lens reflex camera was installed on an UAV platform to capture ultrahigh resolution RGB images at two growth stages when most rapeseed plants had at least two leaves. Rapeseed plant objects were segmented from images of vegetation indices using typical Otsu thresholding method. After segmentation, shape features such as area, length-width ratio and elliptic fit were extracted from the segmented rapeseed plant objects to establish regression models of seedling stand count. Three row characteristics (the coefficient of variation of row spacing uniformity, the error rate of the row spacing and the coefficient of variation of seedling uniformity) were further calculated for seeding performance evaluation after crop row detection. Results demonstrated that shape features had strong correlations with ground-measured seedling stand count. The regression models achieved R-squared values of 0.845 and 0.867, respectively, for the two growth stages. The mean absolute errors of total stand count were 9.79 and 5.11% for the two respective stages. A single model over these two stages had an R-squared value of 0.846, and the total number of rapeseed plants was also accurately estimated with an average relative error of 6.83%. Moreover, the calculated row characteristics were demonstrated to be useful in recognizing areas of failed germination possibly resulted from skipped or ineffective planting. In summary, this study developed practical UAV-based remote sensing methods and demonstrated the feasibility of using the methods for rapeseed seedling stand counting and mechanical seeding performance evaluation at early growth stages

Development and characterization of magnetron sputtered self-lubricating Au-Ni/a-C nano-composite coating on CuCrZr alloy substrate

Compounding Au-Ni with carbon (C) lubricants is a feasible approach to improve its mechanical properties and wear performance. In this study, 3.5 μm-thick Au-Ni/C nanocomposite coatings with a low residual stress on CuCrZr substrates by magnetron sputtering were developed. Face-centered cubic and hexagonal close-packed stacking structures were both confirmed in the composite coatings based on transmission electron microscopy and X-ray diffraction analyses. Amorphous C (a-C) was confirmed to be the structure of C in the composite coatings, and its graphitization transition with an increase in the C content was validated by X-ray photoemission spectra and Raman spectroscopy. By compounding 0.88 wt% a-C, the hardness of the Au-Ni/a-C coating reached 400 HV, which is twice higher than that of the Au-Ni coating. The electrical resistivity of the Au-Ni/a-C coating is relatively stable with an increase in the a-C content. As graphitization occurred on the wear track, the produced composite coatings showed a minimum wear rate of 2.2 × 10−6 mm3/N·m under atmospheric conditions, which is half that of the Au-Ni reference coating. Under vacuum, the wear performance of the produced Au-Ni/a-C composite coatings was similar to that of the Au-Ni reference coating

Surfactant-assisted electrodeposition of Au–Co/WS2 self-lubricating coating from WS2 suspended cyanide electrolyte

In this study, Triton X-100 was used as the WS2 dispersion agent in the Au–Co cyanide electrolyte to deposit Au–Co/WS2 composite coatings. Probe sonication was applied to exfoliate the commercial WS2 powders to produce thinner and smaller WS2 flakes, which improved the stability of the WS2 particles in the electrolyte. According to the electrochemical analyses, the effects of adding Triton X-100 and WS2 particles to the electroplating process were investigated. Through material characterizations, WS2 particles were proved to be compounded into the Au–Co matrix and showed clearly {002} preferred orientation due to their flake structures. Tribological tests were performed under dry condition in 10−3 Pa vacuum against stainless steel 316L balls with diameters of 3 mm and a normal contact force of 2 N. The Au–Co/WS2 composite coatings that developed showed the minimum coefficient of friction and wear rate of 0.05 and 8 × 10−6 mm3/N·m, which are 5 times and 3 times lower than the Au–Co reference coating, respectively

Recent progress on improving ICRF coupling and reducing RF-specific impurities in ASDEX Upgrade

The recent scientific research on ASDEX Upgrade (AUG) has greatly advanced solutions to two issues of Radio Frequency (RF) heating in the Ion Cyclotron Range of Frequencies (ICRF): (a) the coupling of ICRF power to the plasma is significantly improved by density tailoring with local gas puffing; (b) the release of RF-specific impurities is significantly reduced by minimizing the RF near field with 3-strap antennas. This paper summarizes the applied methods and reviews the associated achievements