Optimization and Mechanical Accuracy Reliability of a New Type of Forging Manipulator

Researches on forging manipulator have enormous influence on the development of the forging industry and national economy.Clamp device and lifting mechanism are the core parts of forging manipulator,and have been studied for longer time.However,the optimization and mechanical accuracy reliability of them are less analyzed.Based on General Function(G_F)set and parallel mechanism theory,proper configuration of 10t forging manipulator is selected firstly.A new type of forging manipulator driven by cylinders is proposed.After solved mechanical analysis of manipulator’s core mechanisms,expressions of force of cylinders are carried out.In order to achieve smaller force afforded by cylinders and better mechanical characteristics,some particular sizes of core mechanisms are optimized intuitively through the combined use of the genetic algorithms(GA)and GUI interface in MATLAB.Comparing with the original mechanisms,optimized clamp saves at least 8 percent efforts and optimized lifting mechanism 20 percent under maximum working condition.Finally,considering the existed manufacture error of components,mechanical accuracy reliability of optimized clamp,lifting mechanism and whole manipulator are demonstrated respectively based on fuzzy reliability theory.Obtained results show that the accuracy reliability of optimized clamp is bigger than 0.991 and that of optimized lifting mechanism is 0.995.To the whole manipulator under maximum working condition,that value exceeds 0.986 4,which means that optimized manipulator has high motion accuracy and is reliable.A new intuitive method is created to optimize forging manipulator sizes efficiently and more practical theory is utilized to analyze mechanical accuracy reliability of forging manipulator precisely.     

Exploring the deep biosphere

Over the past two decades, scientific drilling into sediments and rocks in the ocean and the continent has revealed the presence of physiologically and phylogenetically complex microbial life in the deep subsurface. Microorganisms, most of which have no cultured or known relatives in the surface biosphere, have been discovered in sediments and rock at depth as deep as 1 km below the seafloor and more than 3 km deep in the continent. The deep biosphere probably represents the most voluminous part of the glob...     

Stress arch bunch and its formation mechanism in blocky stratified rock masses

Stress arch is a common phenomenon occurring in continuous materials and has also been proved to have great influences on the self-stabilization of soils or rock masses after excavation.In this paper,based on UDEC simulation,stress redistribution after excavation is investigated for a kind of special discontinuous material,i.e.blocky stratified rock mass.A layered stress arch system is observed with each stress arch lying over another.This special phenomenon is defined herein as "stress arch bunch".Effects of dip angle of bedding plane,lateral pressure and joint offset on this stress arch bunch are studied.Its formation mechanism is also discussed based on voussoir beam theory.     

Effect of Solidifcation Rate on Grain Structure Evolution During Directional Solidifcation of a Ni-based Superalloy

The effect of solidification rate on grain structure evolution during directional solidification(DS) of a Ni-based superalloy was explored.It was found that a high solidification rate led to sharper <001> texture and smaller grain size in the DS samples.One of the most important findings in this work was that such result was not in accordance with the general concept,and the sharper <001> texture was accompanied by the larger grain size.To explain the contradiction,the modeling samples with five grains were produced and the effect of solidification rate on the evolution of grain texture was illustrated based on the modeling samples.     

High Hole Mobility of GaSb Relaxed Epilayer Grown on GaAs Substrate by MOCVD through Interfacial Misfit Dislocations Array

The structural property of GaSb epilayers grown on semi-insulator GaAs (001) substrate by metalorganic chemical vapor deposition (MOCVD) using Triethylgallium (TEGa) and trimethylantimony (TMSb),was investigated by variation of the Sb:Ga (V/III) ratio.An optimum V/III ratio of 1.4 was determined in our growth conditions.Using transmission electron microscopy (TEM),we found that there was an interfacial misfit dislocations (IMF) growth mode in our experiment,in which the large misfit strain between epilayer and substrate is relaxed by periodic 90 deg.IMF array at the hetero-epitaxial interface.The rms roughness of a 300 nm-thick GaSb layer is only 2.7 nm in a 10 μm×10 μm scan from atomic force microscopy (AFM) result.The best hole density and mobility of 300 nm GaSb epilayer are 5.27×10 6 cm 3 (1.20×10 6) and 553 cm 2 ·V 1 ·s 1 (2340) at RT (77 K) from Hall measurement,respectively.These results indicate that the IMF growth mode can be used in MOCVD epitaxial technology similar to molecular beam epitaxy (MBE) technology to produce the thinner GaSb layer with low density of dislocations and other defects on GaAs substrate for the application of devices.     

Control of coal and gas outbursts in Huainan mines in China: A review

Coal extraction in Huainan area is basically characterized by one of typical multi-seam mining conditions observed in China, where coal is mined in soft seams characterized by high gas content, high stress, low permeability and difficult geological conditions. The average mining depth in Huainan area is 875 m and continues to increase by 15-25 m annually. The rise in mining depth increases the risk of coal and gas outbursts and makes it more difficult to control outburst risk in Huainan coalmines. This paper reviews the main achievements(e.g. theories, technologies and equipment) in outburst control in Huainan, and tries to analyze some key challenging issues, and to present associated strategies to address these issues.It suggests that the outburst control in Huainan must take a combination approach of both regional and localized control in which the former plays a dominant role. Other outburst prevention principles include(1) non-outburst seams protecting outburst seams,(2) less outburst-prone seams protecting strong outburst-prone seams,(3) stress-releasing mining, and(4) the combination of ground and underground gas drainage(the model is dubbed as "walking on two legs"). The paper concludes that we should conduct fundamental researches on outburst mechanism, and develop outburst control technologies and equipment to ensure safe and efficient coal mining of deep coal resources in Huainan area.     

Modeling tree root diameter and biomass by ground-penetrating radar

Roots play a key role in ecosystem functioning as they transfer water and nutrients from soil to plants.Traditional methods for measuring roots are labor-intensive and destructive in nature,which limits quantitative and repeatable assessments in longterm research.Ground-penetrating radar(GPR) provides a non-destructive method to measure plant roots.Based on the superiority of GPR with 2 GHz frequency,we developed a new,practical method to estimate root biomass.First,average root matter density was measured ...     

Mantle dynamics of the reactivating North China Craton:Constraints from the topographies of the 410-km and 660-km discontinuities

The topographies of the 410-km and 660-km discontinuities have important implications for mantle dynamics.Here we present high-resolution seismic imaging of the 410-km and 660-km discontinuities beneath the North China Craton (NCC) employing the receiver function method.Depth anomalies (deeper or shallower than the global average depths) at both discontinuities were detected by introducing a three-dimensional regional velocity model.The depressions of the 410-km discontinuity are mostly located in the easte...     

Loop reduction techniques for reachability analysis of linear hybrid automata

The problem of reachability analysis of linear hybrid automata(LHA) is very difficult.This paper considers to improve the efficiency of the reachability analysis by optimizing the structures of LHA.We identify two types of loops called the flexible loops and the zero loops,and present the techniques to replace the repetitions of those loops in the behavior of LHA with finite sequences of locations and in the meantime simplify the associated constraints.The techniques work not only for the polyhedral computing based algorithms but also for the bounded model checkers.     

Study on the Mechanisms for Baeyer-Villiger Oxidation of Cyclohexanone with Hydrogen Peroxide in Different Systems

The green and effective Baeyer-Villiger oxidation reaction of cyclohexanone for preparing ε-caprolactone is of particular importance in the synthesis of new polymer materials. We have discussed here several mechanism types of Baeyer-Villiger oxidation of cyclohexanone with H2O2 in different reaction systems. Five main types have been addressed, i. e.: (1) the non-catalyzed reaction type, where the C=O of ketones is activated by H+, which is electrolytically dissociated from H2O2 and H2O, to improve the capability of C=O group for accepting the electron pairs; (2) the thermally activated radical reaction type, where the Criegee intermediate is produced via two steps of radical reaction with ·OH attack, with much more hydroxyl radicals being excited in the presence of TS-1 zeolite; (3) the Brnsted acid catalysis reaction type, where both O-O moiety and C=O group could be activated by Brnsted acid; (4) the solid Lewis acid catalyzed C=O of the substrate activation reaction type through enhancing the donor-acceptor interaction between the antibonding π*C=O orbital of cyclohexanone and HOMO of Sn-containing zeolites; and (5) the solid Lewis acid catalyzed H2O2 to form Me-OOH oxidative species by converting the highest occupied molecular orbital (HOMO) of Ti-OOH into a singly occupied molecular orbital (SOMO), making the O-O group highly electrophilic to attack the C=O of cyclohexanone during the Baeyer-Villiger oxidation process. In the end, we have also compared the different mechanisms and put forward our opinions on the development direction of catalytic materials aiming at eco-friendly Baeyer-Villiger oxidation of cyclohexanone in the years to come.