Analysis of Absolute Stability for Time-delay Teleoperation Systems

In this paper, a new bilateral control algorithm based on absolute stability theory is put forward, which aims at the time-delay teleoperation system with force feedback from the slave directly. In the new control algorithm, the delay-dependent stability, instead of delay-independent stability, is taken as the aim of control design. It improves the transparency of the system at the price of unnecessary stability. With this algorithm, the time-delay teleoperation systems have good transparency and stability. A simulation system is established to verify the effect of this algorithm.

Use of a plane jet for flow-induced noise reduction of tandem rods

Unsteady wake from upstream components of landing gear impinging on downstream components could be a strong noise source.The use of a plane jet is proposed to reduce this flow-induced noise.Tandem rods with different gap widths were utilized as the test body.Both acoustic and aerodynamic tests were conducted in order to validate this technique.Acoustic test results proved that overall noise emission from tandem rods could be lowered and tonal noise could be removed with use of the plane jet.However,when the plane jet was turned on,in some frequency range it could be the subsequent main contributor instead of tandem rods to total noise emission whilst in some frequency range rods could still be the main contributor.Moreover,aerodynamic tests fundamentally studied explanations for the noise reduction.Specifically,not only impinging speed to rods but speed and turbulence level to the top edge of the rear rod could be diminished by the upstream plane jet.Consequently,the vortex shedding induced by the rear rod was reduced,which was confirmed by the speed,Reynolds stress as well as the velocity fluctuation spectral measured in its wake.This study confirmed the potential use of a plane jet towards landing gear noise reduction.

Experimental investigations of detonation initiation by hot jets in supersonic premixed flows

A new method to initiate and sustain the detonation in supersonic flow is investigated. The reaction activity of coming flow may influence the result of detonation initiation. When a hot jet initiates a detonation wave successfully, there may exist two types of detonations. If the detonation velocity is greater than the velocity of coming flow, there will be a normal detonation here. Because of the influence of boundary layer separation, the upstream detonation velocity is much greater than the Chapman-Jouguet （C J） detonation velocity. On the other hand, if the detonation velocity is less than the velocity of coming flow, an oblique detonation wave （ODW） will form. The ODW needs a continuous hot jet to sustain itself. If the jet pressure is lower than a certain value, the ODW will decouple. In contrast, the normal detonation wave can sustain itself without the hot jet.

Synthesis and characterization of polyaluminocarbosilane as SiC ceramic precursor

Polyaluminocarbosilane（PACS） was synthesized by the reaction of aluminum acetylacetonate（（Al（AcAc）3）） with polysilacarbosilane （PSCS）, which was prepared by thermolysis and condensation of polydimethylsilane （PDMS）. The sublimation of Al（AcAc）3 could be avoided by the use of PSCS as reactant. The empirical formula of PACS was SiC2.01H7.66O0.13Al0.02, which has the relative molecular mass of 2 265. When the reaction of PSCS with Al（AcAc）3 proceeds, an enormous decrease in the number of Si—H bonds in PSCS is observed, at the same time, gas acetylacetonate is a by-product of the reaction based on the ligands of Al（AcAc）3. The reaction mechanism is found to be related to the increase in the molecular mass of PACS by the cross-linking reaction of （Si—H） bonds in PSCS with Al（AcAc）3, which leads to the formation of Si—Al bonds.

Improvement on the wave absorbing property of a lossy frequency selective surface absorber using a magnetic substrate

An equivalent-circuit model is used to analyse the improvement of the wave absorbing performance of the lossy frequency selective surface（FSS） absorber by using a magnetic substrate,showing that it is possible to widen the wave absorbing bandwidth.Three pieces of magnetic substrates are prepared.According to the complex permittivity and permeability,the reflectivity of the corresponding absorber is calculated by the finite difference time-domain（FDTD） method,and the bandwidth of the reflectivity below 10 dB is optimized by genetic algorithm.The calculated results indicate that the wave absorbing performance is significantly improved by increasing the complex permeability of the substrate;the reflectivity bandwidth below 10 dB of the single layer FSS absorber can reach 3.6-18 GHz with a thickness of 5 mm,which is wider than that with a dielectric substrate.The density of the FSS absorber is only 0.92 g/cm 3.Additionally,the absorption band can be further widened by inserting a second lossy FSS.Finally,a double layer lossy FSS absorber with a magnetic substrate is fabricated based on the design result.The experimental result is consistent with the design one.

Control of light scattering by nanoparticles with optically-induced magnetic responses

Conventional approaches to control and shape the scattering pattems of light generated by different nanostructures are mostly based on engineering of their electric response due to the fact that most metallic nanostructures support only electric resonances in the optical frequency range. Recently, fuelled by the fast development in the fields of metamaterials and plasmonics, artificial optically-induced magnetic responses have been demonstrated for various nanostructures. This kind of response can be employed to provide an extra degree of freedom for the efficient control and shaping of the scattering patterns of nanoparticles and nanoantennas. Here we review the recent progress in this research direction of nanoparticle scattering shaping and control through the interference of both electric and optically-induced magnetic responses. We discuss the magnetic resonances supported by various structures in different spectral regimes, and then summarize the original results on the scattering shaping involving both electric and magnetic responses, based on the interference of both spectrally separated （with different resonant wavelengths） and overlapped dipoles （with the same resonant wavelength）, and also other higher-order modes. Finally, we discuss the scattering control utilizing Fano resonances associated with the magnetic responses.

Preparation and properties of continuous Al-containing silicon carbide fibers

Continuous SiC(OAl) fibers, named KD-A fibers, were prepared by the melt-spinning of ceramic precursor polyaluminocarbosilane, air-curing, and pyrolizing at 1 300 ℃. These fibers contained small amount of aluminum and 7%- 9% oxygen. The KD-A fibers were converted into sintered SiC(Al) fibers, named KD-SA, by sintering at 1 800 ℃. The fibers were characterized by chemical analysis, tensile strength test, SEM and XRD. The tensile strength, elastic modulus and diameter of the KD-A fibers are 2.6 GPa, 210 GPa, 12 - 14 μm, respectively. The KD-A fibers have higher thermal stability, more excellent oxidation resistance than the Nicalon fibers. The properties of the KD-A fibers have reached the level of Hi-Nicalon fibers. The tensile strength, elastic modulus and diameter of the KD-A fibers are 2.1 GPa, 405 GPa, 10 - 12 μm, respectively. The KD-SA fibers with nearly stoichiometric component have stable performance at high temperature, and better creep resistance than the Tyranno SA fibers.

Investigation of an S-Band Tapered Magnetically Insulated Transmission Line Oscillator

We present an improved structure of the tapered magnetically insulated transmission fine oscillator （MILO）. Simulation results show that this structure can obtain more microwave power with higher efficiency. Studies indicate that the distance between the load support legs and the last vane can affect the operation characteristics of this device. In the experiments, we obtain microwave with peak power of 2 GW, frequency of 2.63 GHz, and mode TMol. The beam to microwave power efficiency is 11%.

Simulation and Experimental Research of a Novel Vircator

A new configuration of an axially-extracted vircator with three resonant cavities is put forward and optimized by simulation with the PIC code. The output power of over 1 GW is obtained at around 4.1 GHz in the experiment, in agreement well with the PIC simulation results. The beam to wave power conversion efficiency is more than 6.6%.

Interactions of Microwave with Plasmas

When plasma size scale is comparable with the wavelength of electromagnetic waves, W.K.B. solution isn't applicable. In this paper a new numerical solution technique to investigate interactions of microwave with plasmas is presented by using Runge-Kutta method. The results of numerical solution coincide with that of analytical solution while the model is linear electron density profile in calculated accuracy.

ANALYTICAL SOLUTION OF FLOW OF SECOND-ORDER NON-NEWTONIAN FLUIDS THROUGH ANNULAR PIPES

This paper presents an analytical solution to the unsteady flow of the second-order non-Newtonian fluids by the use of intergral transformation method. Based on the numerical results, the effect of non-Newtonian coefficient Hc and other parameters on the flow are analysed. It is shown that the annular flow has a shorter characteristic time than the general pipe flow while the correspondent velocity, average velocity have a ... nailer value for a given Hc. Else, when radii ratio keeps unchanged, the shear stress of inner wall of annular flow will change with the inner radius -compared with the general pipe flow and is always smaller than that of the outer wall.

Data-driven Methods to Predict the Burst Strength of Corroded Line Pipelines Subjected to Internal Pressure

A corrosion defect is recognized as one of the most severe phenomena for high-pressure pipelines,especially those served for a long time.Finite-element method and empirical formulas are thereby used for the strength prediction of such pipes with corrosion.However,it is time-consuming for finite-element method and there is a limited application range by using empirical formulas.In order to improve the prediction of strength,this paper investigates the burst pressure of line pipelines with a single corrosion defect subjected to internal pressure based on data-driven methods.Three supervised ML(machine learning)algorithms,including the ANN(artificial neural network),the SVM(support vector machine)and the LR(linear regression),are deployed to train models based on experimental data.Data analysis is first conducted to determine proper pipe features for training.Hyperparameter tuning to control the learning process is then performed to fit the best strength models for corroded pipelines.Among all the proposed data-driven models,the ANN model with three neural layers has the highest training accuracy,but also presents the largest variance.The SVM model provides both high training accuracy and high validation accuracy.The LR model has the best performance in terms of generalization ability.These models can be served as surrogate models by transfer learning with new coming data in future research,facilitating a sustainable and intelligent decision-making of corroded pipelines.

THE UNIVERSAL DUAL COMODULE OF MODULE IN HOPF ALGEBRAS

The purpose of this paper is to present some dual properties of dual comodule. It turns out that dual comodule has universal property (cf.Theorem 2). Since (( )*,()°) is an adjoint pair (cf.Theorem 3), some nice properties of functor ( )° are obtained. Finally Theoram 4 provides that the cotensor product is the dual of the tensor product by (M (?)A N)°≌M°□A°N°. Moreover, the result Hom(M,JV)≌ComA°(N°,M°) is proved for finite related modules M, N over a reflexive algebra A.

Trade-Off between Efficiency and Effectiveness: A Late Fusion Multi-View Clustering Algorithm

Late fusion multi-view clustering(LFMVC)algorithms aim to integrate the base partition of each single view into a consensus partition.Base partitions can be obtained by performing kernel k-means clustering on all views.This type of method is not only computationally efficient,but also more accurate than multiple kernel k-means,and is thus widely used in the multi-view clustering context.LFMVC improves computational efficiency to the extent that the computational complexity of each iteration is reduced from Oen3T to OenT(where n is the number of samples).However,LFMVC also limits the search space of the optimal solution,meaning that the clustering results obtained are not ideal.Accordingly,in order to obtain more information from each base partition and thus improve the clustering performance,we propose a new late fusion multi-view clustering algorithm with a computational complexity of Oen2T.Experiments on several commonly used datasets demonstrate that the proposed algorithm can reach quickly convergence.Moreover,compared with other late fusion algorithms with computational complexity of OenT,the actual time consumption of the proposed algorithm does not significantly increase.At the same time,comparisons with several other state-of-the-art algorithms reveal that the proposed algorithm also obtains the best clustering performance.

Design of 8-like Non-planar Cavity

For eliminating the negative effects of lock-in region and optical elements in cavity,the non-planar structure is strongly needed in laser gyro. In this paper,the theoretical formula of rotatory effect in non-planar cavity is presented deducing from basic light propagating law. Based on the 8-like plane cavity,a novel non-planar structure is designed and numerically calculated. The results show that for obtaining the required rotatory angle,it just needs to adjust the structural parameters of the original 8-like plane cavity. The four-frequency-differential laser gyro which adopts the non-planar 8-like structure has the same advantages as those with the planar 8-like structure,such as the gain region locates at one leg,the position of Faraday rotator has better spatial symmetry and the coating films of the output mirror is easily designed.

Numerical Investigation of Thermal Effect in Plasma Electrode Pockels Cell for High Average Power

The average power of a Pockels cell is limited by thermal effects arising from the optical absorption of the laser pulse. These thermal effects can be managed by configuring the switch as a plasma-electrode thin plate Pockels ceil, which works under heat-capacity operation. Simulation results show that, based on KD＊P （in thickness 0.5 cm） at an average power loading of 1 kW, the aperture integrated depolarization loss at 1.06 um is less than 10% in 5min working time.

Temperature-related performance of Yb^3＋：YAG disc lasers and optimum design for diamond cooling

In this paper the temperature-related performances of the Yb^3＋：YAG disc laser has been investigated based on quasi-three level rate equation model. A compact diamond window cooling scheme also has been demonstrated. In this cooling scheme, laser disc is placed between two thin discs of single crystal synthetic diamond, the heat transfer from Yb^3＋：YAG to the diamond, in the direction of the optical axis, and then rapidly conducted radically outward through the diamond to the cooling water at the circumference of the diamond/Yb^3＋ ：YAG assembly. Simulation results show that increasing the thickness of the diamond and the overlap-length （between diamond and water） decreases the disc temperature. Therefore a 0.3-0.5 mm thick diamond window with the overlap-length of 1.5 2.0 mm will provide acceptable cost effective cooling, e.g., with a pump intensity of 15 kW/cm^2 and repetitive rate of 10 Hz, to keep the maximum temperature of the lasing disc below a reasonable value （310K）, the heat exchange coefficient of water should be about 3000 W/m^2K.

Propagation of Four-Petal Gaussian Beams in Turbulent Atmosphere

An analytical expression for the average intensity of four-petal Gaussian beams in turbulent atmosphere is derived. Studies show that in turbulent atmosphere, the contour lines of four-petal Gaussian beams with lower order N evolve into a number of petals with the increase in propagation distance, the contour lines with higher order N can reserve four-petal distribution at longer propagation distance than that with lower order N. These properties are similar to those in free space. However, with further increases of the propagation distance, the contours lines in turbulent atmosphere are different from those in free space.

Spin Polarization Electrons of Elastically Scattered from Hg Atom

Calculations on differential cross sections and spin polarization parameters of elastical electron scattering with Hg atoms are performed for electrons in the energy range from 0.5 to 150eV.Dirac equation is used to describe the motion of scattered electrons in the target field,which includes static,exchange and correlation-polarization interactions.The agreement between theory and experiment is generally good.

High resolution spectroscopy of Rb in magnetic field by far-detuning electromagnetically induced transparency

We have presented a high resolution spectroscopy of Rb in magnetic field by far-detuning electromagnetically induced transparency(EIT).The EIT spectrum in theΞ-type configuration is usually companied by a double resonance optical pumping(DROP)due to the strong optical coupling between the two upper states,leading to the spectral lines seriously deformed and widely broadened for complex relaxation processes in DROP.Here we demonstrate a high resolution spectroscopy by far-detuning EIT for^(87)Rb 5S_(1/2)→5P_(3/2)→5D_(5/2)in magnetic fields.The method of far-detuning eliminates the relaxation in DROP to the most extent and decreases the spectral linewidth from more than 20 MHz down to its natural linewidth limit(6 MHz).The deformation of the spectral lines also disappears and the observed spectra are well in accordance with the theoretical calculation.Our work shows that far-detuning EIT is a reliable high resolution spectroscopic method when the relaxation in DROP cannot be neglected,especially for the case of transition to low excited states.