ANALYSIS OF COUPLING INFLUENCES OF LABYRINTH SEAL PARAMETERS ON CROSS COUPLED STIFFNESS AND DIRECT DAMPING COEFFICIENT

Labyrinth seal can cause steam-exciting, the structural and operating parameters of labyrinth seal have effect on stability of rotor-system. For investigating the coupling influences of the structure and operating parameters of labyrinth seals on dynamic coefficients, a model of calculating dynamic coefficients of labyrinth seals is presented using a two control volume model. The coupling influences of parameters on cross-coupled stiffness and direct damping of labyrinth seal are discussed. In the conclusion, a reference of preventing steam-exciting vibration and optimum determination of design parameters of labyrinth seals are provided.

Double Position Servo Synchronous Drive System Based on Cross-Coupling Integrated Feedforward Control for Broacher

Synchronization errors directly deteriorate the machining accuracy of metal parts and the existed method cannot keep high synchronization precision because of external disturbances. A new double position servo synchronous driving scheme based on semi-closed-loop cross- coupling integrated feedforward control is proposed. The scheme comprises a position error cross-coupling feedfor-ward control and a load torque identification with feed- forward control. A digital integrated simulation system for the dual servo synchronous drive system is established. Using a 20 t servo broacher, performance analysis of the scheme is conducted based on this simulation system and the simulation results show that systems with traditional parallel or single control have problems when the work- table works with an unbalanced load. However, the system with proposed scheme shows good synchronous perfor- mance and positional accuracy. Broaching tests are performed and the experimental results show that the maximum dual axis synchronization error of the system is only 8μm during acceleration and deceleration processes and the error between the actual running position and the given position is almost zero. A double position servo synchronous driving scheme is presented based on crosscoupled integrated feedforward compensation control, which can improve the synchronization precision.

Cross-coupling integral adaptive robust posture control of a pneumatic parallel platform

A pneumatic parallel platform driven by an air cylinder and three circumambient pneumatic muscles was considered. Firstly, a mathematical model of the pneumatic servo system was developed for the MIMO nonlinear model-based controller designed. The pneumatic muscles were controlled by three proportional position valves, and the air cylinder was controlled by a proportional pressure valve. As the forward kinematics of this structure had no analytical solution, the control strategy should be designed in joint space. A cross-coupling integral adaptive robust controller(CCIARC) which combined cross-coupling control strategy and traditional adaptive robust control(ARC) theory was developed by back-stepping method to accomplish trajectory tracking control of the parallel platform. The cross-coupling part of the controller stabilized the length error in joint space as well as the synchronization error, and the adaptive robust control part attenuated the adverse effects of modelling error and disturbance. The force character of the pneumatic muscles was difficult to model precisely, so the on-line recursive least square estimation(RLSE) method was employed to modify the model compensation. The projector mapping method was used to condition the RLSE algorithm to bound the parameters estimated. An integral feedback part was added to the traditional robust function to reduce the negative influence of the slow time-varying characteristic of pneumatic muscles and enhance the ability of trajectory tracking. The stability of the controller designed was proved through Laypunov's theory. Various contrast controllers were designed to testify the newly designed components of the CCIARC. Extensive experiments were conducted to illustrate the performance of the controller.

Photo-induced reductive cross-coupling of aldehydes, ketones and imines with electron-deficient arenes to construct aryl substituted alcohols and amines

Umpolung reactions of C=X bonds(X=O,N)are valuable ways of constructing new C–C bonds,which are sometimes difficult to be constructed using traditional synthetic pathways.Classical polarity inversion of C=X bonds(X=O,N)usually requires air or moisture‐sensitive and strong reducing agents,which limit the feasibility of substrate scope.Herein we describe a photo‐induced reductive cross‐coupling reaction of aldehydes,ketones and imines with electron‐deficient arenes(aromatic nitriles)using fac‐Ir(ppy)3as a photocatalyst and diisopropylethylamine(DIPEA)as a terminal reductant under visible light irradiation.Mild conditions and high yields mean that this new polarity inversion strategy can be used with aryl‐substituted alcohols and amines.Spectroscopic studies and control experiments have demonstrated the oxidative quenching of Ir(ppy)3*by electron‐deficient arenes involved in the key step for the C–C bond formation.

Sustainable electrochemical cross‐dehydrogenative coupling of4‐quinolones and diorganyl diselenides

An environmentally friendly method for the synthesis of 3‐organylselenyl quinolones through theelectrochemical cross‐dehydrogenative coupling of 4‐quinolones and diorganyl diselenides wasdeveloped.As a green,atom economic and self‐separating process,the present reaction requiresneither external oxidants nor electrolytes,forming a recyclable catalytic system.

Unveiling inverse vulcanized polymers as metal-free,visible-light-driven photocatalysts for cross-coupling reactions

Inverse vulcanized polymers(IVPs) that generated from elemental sulfur and smaller amounts of alkenes have found broad promising applications such as cathode materials for Li-S batteries, dynamic and repairable materials, optics applications, and metal sorption. However, their exploration in organic synthesis is still unprecedented. Here we first report the application of inverse vulcanized polymers in catalysis for organic transformations. A biomass-derived inverse vulcanized polymer(IVP-EAE) is found to be capable of catalyzing cross-coupling reactions in a transition-metal-free fashion under visible light.This method allows the direct C–H functionalization of pyrroles and N-arylacrylamides with(hetero)aryl halides, respectively, leading to the formation of two sets of structurally important scaffolds including pyrrole-containing biaryls and 3,3-disubstituted oxindoles with high selectivity. We anticipate this study will not only unveil the new potential of IVPs, but also offer a distinct type of catalysts for organic transformations.

The Influence of Convergence Movement on Turbulent Transportation in the Atmospheric Boundary Layer

Classical turbulent K closure theory of the atmospheric boundary layer assumes that the vertical turbulent transport flux of any macroscopic quantity is equivalent to that quantity's vertical gradient transport flux. But a cross coupling between the thermodynamic processes and the dynamic processes in the atmospheric system is demonstrated based on the Curier-Prigogine principle of cross coupling of linear thermodynamics. The vertical turbulent transportation of energy and substance in the atmospheric boundary layer is related not only to their macroscopic gradient but also to the convergence and the divergence movement. The transportation of the convergence or divergence movement is important for the atmospheric boundary layer of the heterogeneous underlying surface and the convection boundary layer. Based on this, the turbulent transportation in the atmospheric boundary layer, the energy budget of the heterogeneous underlying surface and the convection boundary layer, and the boundary layer parameterization of land surface processes over the heterogeneous underlying surface are studied. This research offers clues not only for establishing the atmospheric boundary layer theory about the heterogeneous underlying surface, but also for overcoming the difficulties encountered recently in the application of the atmospheric boundary layer theory.

CuI/Proline-catalyzed N-Arylation of Nitrogen Heterocycles

Ma＇s CuI/proline procedure for the catalytic cross coupling between nitrogen heterocycles and aryl halides was markedly improved. The key finding was that K3PO4 was a much better base than K2CO3 for the reaction. With this new reaction condition the cross coupling with aryl iodides could be accomplished in 1,4-dioxane instead of DMSO. This reactin also could be carried out in DMF. Furthermore, the coupling yields under the new conditions are usually higher than in Ma＇s original methods.

Synthesis of α-Arylated Esters from Aryl Halides

An operationally simple and inexpensive catalyst system was developed for the cross coupling of aryl iodides and bromides with ethyl acetoacetate by using CuI as catalyst and Nmethyl glycine as ligand. The reaction represents a novel Cu-catalyzed C-C cross coupling reaction. This procedure is applicable to the preparation of pharmaceutically important α- arylalkanoic acids.

Cu(Ⅰ)-catalyzed cascade reaction of N-tosylhydrazones with 3-butyn-1-ol:A new synthesis of tetrahydrofurans

The Cu(I)‐catalyzed cascade coupling/cyclization reaction of N‐tosylhydrazones with 3‐butyn‐1‐ol has been explored. This new strategy represents a simple platform for the synthesis of tetrahydrofurans in moderate to good yields.

CuI-catalyzed Synthesis of Aryl Thiocyanates from Aryl Iodides

An operationally simple and inexpensive catalyst system was developed for the cross coupling of potassium thiocyanate with aryl iodides by using CuI as catalyst, 1, 10-phenanthroline as ligand, and tetraethylammonium iodide as activator. The procedure is applicable for the synthesis of diverse aryl thiocyanates without any exotic, poisonous reagents.

Cu-catalyzed arylation of phosphinic amide facilitated by (±)-trans-cyclohexane-1,2-diamine

Cu-catalyzed cross coupling between phosphinic amides and aryl halides was accomplished for the first time by using (±)-trans-cyclohexane-1,2-diamine as the ligand. This reaction provided a novel approach for synthesizing arylated phosphinic amides. Both kinetic measurement and theoretical calculation indicated that phosphinic amides were much less reactive than amides by about 10 times in Cu-catalyzed cross coupling.

Copper-mediated synthesis of N,N'-diarylhydrazines from boronic acids

N,N＇-Diarylhydrazines have been prepared via the reaction of N-Boc-aryl hydrazines with boronic acids mediated by copper acetate. This mild reaction condition tolerates the presence of a variety of functional groups.

Modeling and Simulation of Two Axes Gimbal Using Fuzzy Control

The application of the guided missile seeker is to provide stability to the sensor’s line of sight toward a target by isolating it from the missile motion and vibration.The main objective of this paper is not only to present the physical modeling of two axes gimbal system but also to improve its performance through using fuzzy logic controlling approach.The paper is started by deriving the mathematical model for gimbals motion using Newton’s second law,followed by designing the mechanical parts of model using SOLIDWORKS and converted to xml file to connect dc motors and sensors using MATLAB/SimMechanics.Then,a Mamdani-type fuzzy and a Proportional-Integral-Derivative(PID)controllers were designed using MATLAB software.The performance of both controllers was evaluated and tested for different types of input shapes.The simulation results showed that self-tuning fuzzy controller provides better performance,since no overshoot,small steady-state error and small settling time compared to PID controller.

Research and Design of Coordinated Control Strategy for Smart Electromechanical Actuator System

In order to improve the frequency response and anti-interference characteristics of the smart electromechanical actuator(EMA)system,and aiming at the force fighting problem when multiple actuators work synchronously,a multi input multi output(MIMO)position difference cross coupling control coordinated strategy based on double‑closed-loop load feedforward control is proposed and designed.In this strategy,the singular value method of return difference matrix is used to design the parameter range that meets the requirements of system stability margin,and the sensitivity function and the H_(∞)norm theory are used to design and determine the optimal solution in the obtained parameter stability region,so that the multi actuator system has excellent synchronization,stability and anti-interference.At the same time,the mathematical model of the integrated smart EMA system is established.According to the requirements of point-to-point control,the controller of double-loop control and load feedforward compensation is determined and designed to improve the frequency response and anti-interference ability of single actuator.Finally,the 270 V high-voltage smart EMA system experimental platform is built,and the frequency response,load feedforward compensation and coordinated control experiments are carried out to verify the correctness of the position difference cross coupling control strategy and the rationality of the parameter design,so that the system can reach the servo control indexes of bandwidth 6 Hz,the maximum output force 20000 N and the synchronization error≤0.1 mm,which effectively solves the problem of force fighting.

Contouring error modeling and simulation of a four-axis motion control system

A layered modeling method is proposed to resolve the problems resulting from the complexity of the error model of a multi-axis motion control system. In this model, a low level layer can be used as a virtual axis by the high level layer. The first advantage of this model is that the complex error model of a four-axis motion control system can be divided into several simple layers and each layer has different coupling strength to match the real control system. The second advantage lies in the fact that the controller in each layer can be designed specifically for a certain purpose. In this research, a three-layered cross coupling scheme in a four-axis motion control system is proposed to compensate the contouring error of the motion control system. Simulation results show that the maximum contouring error is reduced from 0.208 mm to 0.022 mm and the integration of absolute error is reduced from 0.108 mm to 0.015 mm, which are respectively better than 0.027 mm and 0.037 mm by the traditional method. And in the bottom layer the proposed method also has remarkable ability to achieve high contouring accuracy.

Nickel-catalyzed umpolung C-S radical reductive cross coupling of S-(trifluoromethyl)arylsulfonothioates with alkyl halides

A new cooperative nickel reductive catalysis and N,N-dimethylformamide-mediated strategy for umpolung C–S radical reductive cross coupling of S-(trifluoromethyl)arylsulfonothioates with alkyl halides to produce alkyl aryl thioethers is described. This reaction features excellent selectivity, wide functionality tolerance, broad substrate scope, and facile late-stage modification of biologically relevant molecules.Mechanistic studies recognize initial generation of an amidyl radical anion via thermoinduced reduction of DMF with Sn, followed by umpolung reduction and single electron transfer of the nucleophilic sulfonyl moiety to form a sulphydryl radical and engage the Ni^(0)/Ni^(Ⅰ)/Ni^(Ⅲ)/Ni^(I) catalytic cycle.

Single-atom Pd catalyst anchored on Zr-based metal-organic polyhedra for Suzuki-Miyaura cross coupling reactions in aqueous media

The challenge for single-atom catalysts in various C-C cross coupling reaction exists in the development of solid supporting materials.It has been desired tofind a supporting material designed in molecular level to anchor a single-atom catalyst and provide high degree of dispersion and substrate access in aqueous media.Here,we prepared discrete cages of metal-organic polyhedra anchoring single Pd atom(MOP-BPY(Pd))and successfully performed a Suzuki-Miyaura cross coupling reaction with various substrates in aqueous media.It was revealed that each tetrahedral cage of MOP-BPY(Pd)has 4.5 Pd atoms on average and retained its high degree of dispersion up to 3 months in water.The coupling efficiencies of the Suzuki-Miyaura cross coupling reaction exhibited more than 90.0%for various substrates we have tested in the aqueous media,which is superior to those of the molecular Pd complex and metal-organic framework(MOF)anchoring Pd atoms.Moreover,MOP-BPY(Pd)was successfully recovered and recycled without performance degradation.

Iron-mediated cross dehydrogenative coupling(CDC) of terminal alkynes with benzylic ethers and alkanes

Iron-mediated sp-sp3 C-C bond formation through the cross dehydrogenative coupling(CDC) of terminal alkynes with benzylic ethers or alkanes has been developed.The inexpensive iron salt is used as the catalyst to make this transformation environmentally benign.Iron-mediated sp-sp3 C-C bond formation through the cross dehydrogenative coupling(CDC) of terminal alkynes with benzylic ethers or alkanes has been developed.The inexpensive iron salt is used as the catalyst to make this transformation environmentally benign.

Efficient Synthesis of Unsymmetrical Heteroaryl Ethers by a Transition Metal-Free C--O Cross-Coupling Reaction of Activated and Unactivated Heteroaryl Chlorides with Alcohols and Phenols

By optimizing the reaction conditions via a careful screening of the bases and solvents, we developed an efficient transition metal-free method for C--O cross-coupling of activated and unactivated heteroaryl chlorides with primary and secondary alcohols and phenols, providing a simple, efficient, and practical method for synthesis of the useful unsymmetrical heteroaryl alkyl and heteroaryl aryl ethers.