Pre-Construction Progress of Giant Steerable Science Mirror for TMT

The Changchun Institute of Optics, Fine Mechanics and Physics (CIOMP) team is developing the Giant Steerable Science Mirror (GSSM) for Thirty Meter Telescope (TMT) which will enter the preliminary design phase in 2016. The GSSM is the tertiary mirror of TMT and consists of the world’s largest flat telescope mirror (approximately 3.4m X 2.4 m X 100mm thick) having an elliptical perimeter positioned with an extremely smooth tracking and pointing mechanism in a gravity-varying environment. In order to prepare for developing this unique mirror system, CIOMP has been developing a 1/4 scale, functionally accurate version of the GSSM prototype during the pre-construction phase of GSSM. The prototype will incorporate the same optomechanical system and servo control system as the GSSM. The size of the prototype mirror is 898.5mm×634mm×12.5mm with an elliptical perimeter. The mirror will be supported axially by an 18 point whiffletree and laterally with a 12 point whiffletree. The main objective of the preconstruction phase includes requirement validation and risk reduction for GSSM and to increase confidence that the challenge of developing the GSSM can be met. The precision mechanism system and the optical mirror polishing and testing have made good progress. CIOMP has completed polishing the mirror, the prototype mechanism is nearly assembled, some testing has been performed, and additional testing is being planned and prepared. A dummy mirror is being integrated into the cell assembly prototype to verify the design, analysis and interface and will be used when testing the prototype positioner tilt and rotation motions. The prototype positioner tilt and rotator structures have been assembled and tested to measure each subsystem’s jitter and dynamic motion. The mirror prototype has been polished and tested to verify the polishing specification requirement and the mirror manufacturing process. The complete assembly, integration and verification of the prototype will be soon finished. Final testing will verify the prototype requirements including mounted mirror surface figure accuracy in 5 different orientations; rotation and tilt motion calibration and pointing precision; motion jitter; and internally generated vibrations. CIOMP has scheduled to complete the prototype by the end of July 2016. CIOMP will get the sufficient test results during the pre-construction phase to prepare to enter the preliminary design for GSSM

Nonuniform Correction of Ground-Based Optical Telescope Image Based on Conditional Generative Adversarial Network

Ground-based telescopes are often affected by vignetting, stray light and detector nonuniformity when acquiring space images. This paper presents a space image nonuniform correction method using the conditional generative adversarial network (CGAN). Firstly, we create a dataset for training by introducing the physical vignetting model and by designing the simulation polynomial to realize the nonuniform background. Secondly, we develop a robust conditional generative adversarial network (CGAN) for learning the nonuniform background, in which we improve the network structure of the generator. The experimental results include a simulated dataset and authentic space images. The proposed method can effectively remove the nonuniform background of space images, achieve the Mean Square Error (MSE) of 4.56 in the simulation dataset, and improve the target’s signal-to-noise ratio (SNR) by 43.87% in the real image correction

Design and Experiment of Gripper for Greenhouse Plug Seedling Transplanting Based on EDM

Many plug seedling grippers have a complex structure and bulky volume in design. They have poor performance in holding substrate and keeping a high integrity rate. In this paper, a new multi-needle seedling gripper is proposed. Based on the elasto-plastic contact model (ECM) in the EDEM, numerous particles with different material properties are modeled to simulate real seedling substrate and to study the interaction between steel needle and growing substrate. Taking the medium integrity rate as an evaluation index, explore the influence of different needle diameters, insertion depths, and insertion and grabbing speeds on the substrate integrity through the response surface method. The optimized technical parameters of the gripper was obtained through Design-Expert. The results show that the insertion depth of needles has a significant effect on the integrity of the raising medium, and the optimal depth is 40 mm. Insertion and grasping speed and depth have an interaction effect, while other factors have no significant influence on substrate integrity. Optimization results imply that when the diameter of the needle was 3 mm, the insertion depth was 40 mm, and the insertion and grabbing speed was 1 m/s, the growing medium integrity rate was the highest, reaching 89.10%. Under these parameters, prototype tests were conducted, and the highest medium integrity rate was 87.34%, which increased by an average of 7.25% compared with existing studies. The research has reference value for improving the operation quality of the plug seedling transplanter and the design of the seedling gripper. It also shows that solving problems of needle-discrete substrate interaction based on the discrete element method is feasible

Cobalt–Graphene Catalyst for Selective Hydrodeoxygenation of Guaiacol to Cyclohexanol

Herein, cobalt-reduced graphene oxide (rGO) catalyst was synthesized with a practical impregnation–calcination approach for the selective hydrodeoxygenation (HDO) of guaiacol to cyclohexanol. The synthesized Co/rGO was characterized by transmission electron microscopy (TEM), high-angle annular dark-field scanning TEM (HAADF-STEM), X-ray photoelectron spectroscopy (XPS), Raman spectroscopy, X-ray diffraction (XRD), and H2 temperature-programmed reduction (H2-TPR) analysis. According to the comprehensive characterization results, the catalyst contains single Co atoms in the graphene matrix and Co oxide nanoparticles (CoOx) on the graphene surface. The isolated Co atoms embedded in the rGO matrix form stable metal carbides (CoCx), which constitute catalytically active sites for hydrogenation. The rGO material with proper amounts of N heteroatoms and lattice defects becomes a suitable graphene material for fabricating the catalyst. The Co/rGO catalyst without prereduction treatment leads to the complete conversion of guaiacol with 93.2% selectivity to cyclohexanol under mild conditions. The remarkable HDO capability of the Co/rGO catalyst is attributed to the unique metal–acid synergy between the CoCx sites and the acid sites of the CoOx nanoparticles. The CoCx sites provide H while the acid sites of CoOx nanoparticles bind the C-O group of reactants to the surface, allowing easier C-O scission. The reaction pathways were characterized based on the observed reaction–product distributions. The effects of the process parameters on catalyst preparation and the HDO reaction, as well as the reusability of the catalyst, were systematically investigated

Design and Experiment of Gripper for Greenhouse Plug Seedling Transplanting Based on EDM

Many plug seedling grippers have a complex structure and bulky volume in design. They have poor performance in holding substrate and keeping a high integrity rate. In this paper, a new multi-needle seedling gripper is proposed. Based on the elasto-plastic contact model (ECM) in the EDEM, numerous particles with different material properties are modeled to simulate real seedling substrate and to study the interaction between steel needle and growing substrate. Taking the medium integrity rate as an evaluation index, explore the influence of different needle diameters, insertion depths, and insertion and grabbing speeds on the substrate integrity through the response surface method. The optimized technical parameters of the gripper was obtained through Design-Expert. The results show that the insertion depth of needles has a significant effect on the integrity of the raising medium, and the optimal depth is 40 mm. Insertion and grasping speed and depth have an interaction effect, while other factors have no significant influence on substrate integrity. Optimization results imply that when the diameter of the needle was 3 mm, the insertion depth was 40 mm, and the insertion and grabbing speed was 1 m/s, the growing medium integrity rate was the highest, reaching 89.10%. Under these parameters, prototype tests were conducted, and the highest medium integrity rate was 87.34%, which increased by an average of 7.25% compared with existing studies. The research has reference value for improving the operation quality of the plug seedling transplanter and the design of the seedling gripper. It also shows that solving problems of needle-discrete substrate interaction based on the discrete element method is feasible

Nonuniform Correction of Ground-Based Optical Telescope Image Based on Conditional Generative Adversarial Network

Ground-based telescopes are often affected by vignetting, stray light and detector nonuniformity when acquiring space images. This paper presents a space image nonuniform correction method using the conditional generative adversarial network (CGAN). Firstly, we create a dataset for training by introducing the physical vignetting model and by designing the simulation polynomial to realize the nonuniform background. Secondly, we develop a robust conditional generative adversarial network (CGAN) for learning the nonuniform background, in which we improve the network structure of the generator. The experimental results include a simulated dataset and authentic space images. The proposed method can effectively remove the nonuniform background of space images, achieve the Mean Square Error (MSE) of 4.56 in the simulation dataset, and improve the target’s signal-to-noise ratio (SNR) by 43.87% in the real image correction

A Novel Estimation Method of Water Surface Micro-Amplitude Wave Frequency for Cross-Media Communication

Cross-media communication underpins many vital applications, especially in underwater resource exploration and the biological population monitoring domains. Water surface micro-amplitude wave (WSAW) frequency detection is the key to cross-media communication, where the WSAW frequency can invert the underwater sound source frequency. However, extracting the WSAW frequency information encounters many challenges in a real environment, such as low precision and symbol synchronization, leading to inaccurately estimating the WSAW frequency. Thus, this paper proposed a WSAW frequency estimation method based on an improved RELAX algorithm, incorporating two improvements. First, adding a nonlinear filter to the RELAX kernel function compensates for the filtered gain and enhances the WSAW frequency precision. Second, the improved RELAX kernel function is combined with the generalized inner product method to obtain the time distribution of the non-stationary signals, which is convenient for decoding. Several simulations and experiments applying our method on a Ka-band frequency modulated continuous wave (FMCW) radar demonstrate that our algorithm attains a better performance than traditional methods, e.g., periodogram and the RELAX algorithm. Using the improved algorithm affords to extract the frequency information of the WSAW signal accurately with a short sampling duration, further improving the performance indicators of the communication system, such as communication rate