临近空间高超声速飞行器作战应用研究

临近空间高超声速飞行器是21世纪武器系统的重要组成部分,是未来联合作战的重要作战平台。分析了临近空间高超声速飞行器的作战任务,研究了高超声速飞行器的作战样式,并对高超声速飞行器的对未来联合作战产生的影响进行了讨论,总结了对抗高超声速技术的一些策略。

等离子体流动控制在高超声速飞行器中的应用研究

采用等离子体流动控制改善飞行器气动推进性能是近年来流动控制领域研究的热点。以临近空间高超声速飞行器的应用为背景,分析了等离子体流动控制的机理,详细介绍了等离子体流动控制的国外研究现状、风洞试验技术以及等离子体气动激励建模仿真方法。

临近空间高超声速飞行器发展现状及其跟踪技术

临近空间高超声速飞行器是未来超远程精确打击和战略威慑的重要手段,受到了世界武器装备发达国家的高度重视。对国外临近空间高超声速试飞器的发展现状进行了介绍,提出了对临近空间高超声速飞行器跟踪方法的一些思考。

Trigonometric Regularization and Continuation Method Based Time-Optimal Control of Hypersonic Vehicles

Aiming at the time-optimal control problem of hypersonic vehicles(HSV)in ascending stage,a trigonometric regularization method(TRM)is introduced based on the indirect method of optimal control.This method avoids analyzing the switching function and distinguishing between singular control and bang-bang control,where the singular control problem is more complicated.While in bang-bang control,the costate variables are unsmooth due to the control jumping,resulting in difficulty in solving the two-point boundary value problem(TPBVP)induced by the indirect method.Aiming at the easy divergence when solving the TPBVP,the continuation method is introduced.This method uses the solution of the simplified problem as the initial value of the iteration.Then through solving a series of TPBVP,it approximates to the solution of the original complex problem.The calculation results show that through the above two methods,the time-optimal control problem of HSV in ascending stage under the complex model can be solved conveniently.

ADRC FRACTIONAL ORDER PID CONTROLLER DESIGN OF HYPERSONIC FLIGHT VEHICLE

Active disturbance rejection controller（ADRC）uses tracking-differentiator（TD）to solve the contradiction between the overshoot and the rapid nature.Fractional order proportion integral derivative（PID）controller improves the control quality and expands the stable region of the system parameters.ADRC fractional order（ADRFO）PID controller is designed by combining ADRC with the fractional order PID and applied to reentry attitude control of hypersonic vehicle.Simulation results show that ADRFO PID controller has better control effect and greater stable region for the strong nonlinear model of hypersonic flight vehicle under the influence of external disturbance,and has stronger robustness against the perturbation in system parameters.

ANALYSIS OF INTERNAL WAVERIDER INLET AND TYPICAL SIDEWALL COMPRESSION INLET PERFORMANCE

A new internal waverider inlet with a rectangular shape of entrance and exit in front view is designed at Ma=6.0.The design is based on a better basic flowfield ICFC than traditional one and derived with the technology of stream tracing and shock cutting.Comparison between the newly designed inlet and a typical sidewall compression inlet is given.The design Mach number and entrance shape of this new inlet are chosen according to the sidewall compression inlet.Numerical results show that most of the performance parameters of the internal waverider inlet are a bit higher than the sidewall inlet,such as the flow capture coefficient,total pressure recovery and the kinetic efficiency.The performances of these two inlets at off-design points are compared.The internal waverider inlet can capture more than 91% of incoming flow under all simulated conditions.Results show that internal waverider inlet using 3-D compression and high flow capture coefficient is a kind of fixed-geometry inlet with better performance.

MODAL FREQUENCY CHARACTERISTICS OF AXIALLY MOVING BEAM WITH SUPERSONIC/HYPERSONIC SPEED

The vibration characteristics of transverse oscillation of an axially moving beam with high velocity is in- vestigated. The vibration equation and boundary conditions of the free-free axially moving beam are derived using Hamilton＇s principle. Furthermore, the linearized equations are set up based on Galerkinl s method for the ap- proximation solution. Finally, three influencing factors on the vibration frequency of the beam are considered： （1） The axially moving speed. The first order natural frequency decreases as the axial velocity increases, so there is a critical velocity of the axially moving beam. （2） The mass loss. The changing of the mass density of some part of the beam increases the beam natural frequencies. （3） The thermal effect.＇ The temperature increase will decrease the beam elastic modulus and induce the vibration frequencies descending.

Preparation and wear properties of TiB_2/Al-30Si composites via in-situ melt reactions under high-energy ultrasonic field

TiB2/Al-30Si composites were fabricated via in-situ melt reaction under high-energy ultrasonic field. The microstructure and wear properties of the composite were investigated by XRD, SEM and dry sliding testing. The results indicate that TiB2 reinforcement particles are uniformly distributed in the aluminum matrix under high-energy ultrasonic field. The morphology of the TiB2 particles is in circle-shape or quadrangle-shape, and the size of the particles is 0.1-1.5μm. The primary silicon particles are in quadrangle-shape and the average size of them is about 10μm. Hardness values of the Al-30Si matrix alloy and the TiB2/Al-30Si composites considerably increase as the high energy ultrasonic power increases. In particular, the maximum hardness value of the in-situ composites is about 1.3 times as high as that of the matrix alloy when the ultrasonic power is 1.2 kW, reaching 412 MPa. Meanwhile, the wear resistance of the in-situ TiB2/Al-30Si composites prepared under high-energy ultrasonic field is obviously improved and is insensitive to the applied loads of the dry sliding testing.

PARALLEL COMPUTATION OF 3-D HYPERSONIC FLOWS ON UNSTRUCTURED HYBRID MESHES

A parallel virtual machine （PVM） protocol based parallel computation of 3-D hypersonic flows with chemical non-equilibrium on hybrid meshes is presented. The numerical simulation for hypersonic flows with chemical non-equilibrium reactions encounters the stiffness problem, thus taking huge CPU time. Based on the domain decomposition method, a high efficient automatic domain decomposer for three-dimensional hybrid meshes is developed, and then implemented to the numerical simulation of hypersonic flows. Control equations are multicomponent N-S equations, and spatially discretized scheme is used by a cell-centered finite volume algorithm with a five-stage Runge-Kutta time step. The chemical kinetic model is a seven species model with weak ionization. A point-implicit method is used to solve the chemical source term. Numerical results on PC-Cluster are verified on a bi-ellipse model compared with references.

Ultrasonic method for measuring water holdup of low velocity and high-water-cut oil-water two-phase flow

Oil reservoirs with low permeability and porosity that are in the middle and late exploitation periods in China＇s onshore oil fields are mostly in the high-water-cut production stage.This stage is associated with severely non-uniform local-velocity flow profiles and dispersed-phase concentration（of oil droplets） in oil-water two-phase flow,which makes it difficult to measure water holdup in oil wells.In this study,we use an ultrasonic method based on a transmission-type sensor in oil-water two-phase flow to measure water holdup in lowvelocity and high water-cut conditions.First,we optimize the excitation frequency of the ultrasonic sensor by calculating the sensitivity of the ultrasonic field using the finite element method for multiphysics coupling.Then we calculate the change trend of sound pressure level attenuation ratio with the increase in oil holdup to verify the feasibility of the employed diameter for the ultrasonic sensor.Based on the results,we then investigate the effects of oildroplet diameter and distribution on the ultrasonic field.To further understand the measurement characteristics of the ultrasonic sensor,we perform a flow loop test on vertical upward oilwater two-phase flow and measure the responses of the optimized ultrasonic sensor.The results show that the ultrasonic sensor yields poor resolution for a dispersed oil slug in water flow（D OS/W flow）,but the resolution is favorable for dispersed oil in water flow（D O/W flow） and very fine dispersed oil in water flow（VFD O/W flow）.This research demonstrates the potential application of a pulsed-transmission ultrasonic method for measuring the fraction of individual components in oil-water two-phase flow with a low mixture velocity and high water cut.

Determination of contents of 10-Hydroxycamptothecin in Camptotheca acuminata by high-performance liquid chromatogram

The determination method of 10-hydroxycamptothecin in Camptotheca acuminata fruits by high-performance liquid chromatogram (HPLC) was studied. The HPLC analysis was performed on a HIQ sil C18(4.6×250 mm) column with mobile phase of acetonitrilewater (3:7, V:V), flow rate 1 mLmin-1 and UV detective wavelength 266 nm. Extracting 10-hydroxycamptothecin by ultrasonic method from fruits of C. acuminata to prepare samples for analysis was systematically discussed. The optimal extraction condition was carried out by 60% alcohol solution at 60℃ for 50 minutes.

High frequency components in avian vocalizations

Ultrasonic communication in vertebrates is attracting increasing research interest.To determine if ultrasonic vocalization is common in birds,we recorded their vocalizations with ultrasound detectors in the Dongzhai National Nature Reserve of Henan Province,China.We found varying degrees of high frequency components in the vocalizations of 14 species and in several of these species,the frequency of harmonics was up to the range of ultrasound.We suggest that more studies are required to determine whether the high frequency components in avian vocalizations have functions and what these functions are.In addition,the ability of birds to hear sounds in the high frequency range also requires re-examination.

21世纪的“超级武器”

随着科学技术的巨大发展,武器装备变革日新月异.其中新概念武器的研制和发展占有一席之地.所谓的新概念武器就是利用声、光、电磁、计算机病毒或化学物质等手段,使敌方武器装备或人员丧失战斗能力的武器.这类武器不会致人于死地,不会造成武器装备"硬件"的损坏,但却能对人员或武器的"软件"造成巨大的"制约",可以起到严重削弱对方战斗力的效果.目前,正在探索和发展中的典型新概念武器,主要有以下几种:

Positioning planning of high-intensity-focused ultrasound surgery platform using Bezier curve

A positioning volume ellipsoid method is proposed to represent tumor volume in the workspace of a high-intensity-focused ultrasound (HIFU) surgery platform during the platform's positioning motion. To this simplified tumor model, a nearest neighbor search method is used to determine intermediate configuration and goal configuration, which the treatment head and ultrasound focus must pass in their localization to target volume. Based on the decided configurations, the continuity condition of combined Bezier curve in Euclidean space and De Casteljau algorithm on Lie group SO(3) are integrated to construct a combined Bezier positioning path of C2 continuity at junctional configuration, and an illustration of different positioning path planning is analyzed based on a liver tumor case.

Application of high temperature heat pipe in hypersonic vehicles thermal protection

In order to develop further the application of high temperature heat pipe in hypersonic vehicles thermal protection, the principles and characteristics of high temperature heat pipe used in hypersonic vehicles thermal protection were introduced. The methods of numerical simulation, theory analysis and experiment research were utilized to analyze the frozen start-up and steady state characteristic of the heat pipe as well as the machining improvement for fabricating irregularly shaped heat pipe which is suitable for leading edge of hypersonic vehicles. The results indicate that the frozen start-up time of heat pipe is long （10 min） and there exists large temperature difference along the heat pipe （47 ℃/cm）, but the heat pipe can reduce the temperature in stagnation area of hypersonic vehicles from 1 926 to 982 ℃ and work normally during 1 000-1 200℃. How to improve the maximum heat transfer capability and reduce the time needed for start-up from frozen state of the heat pipe by optimizing thermostructure such as designing of a novel wick with high performance is the key point in hypersonic vehicles thermal protection of heat pipe.

Effect of high intensity ultrasound on the allergenicity of shrimp

The tropomyosin fraction of shrimp proteins is potentially responsible for allergic reaction in individuals with genetic predisposition to allergy. However, there are no efficient and safe methods to reduce its allergenicity. High intensity ultrasound is known to change the structure of proteins. This study is aimed at assessing high intensity ultmsound＇s effect on the allergenicity of shrimp allergen. Shrimp and purified shrimp allergen were treated with high intensity ultrasound for 30-180 min. Extracts of treated samples were analyzed by enzyme-linked immunosorbent assay （ELISA） with pool serum of shrimp allergy patients and polyclonal anti-allergen antibodies and by immunoblotting after polyacrylamide gel electrophoresis. Shrimp treated with high intensity ultrasound showed a decrease in allergenicity measured with ELISA. A linear relationship between the immune response induced by treated shrimp allergen and the applied treatment time was observed. The decrease in allergenicity was confirmed by immunoblot assays with shrimp allergic patients serum. Allergenicity of shrimp allergen extracted from treated shrimp was higher than that of purified shrimp allergen with the same treatment time. Gel-filtration HPLC was applied for analysis of shrimp allergen after treatment with high intensity ultrasound. Some fractions were appeared with increasing treatment time. The results suggested that high intensity ultrasound could be used to reduce the allergenicity of shrimp.

Robust tracking control design for a flexible air-breathing hypersonic vehicle

A nonlinear robust controller was presented to improve the tracking control performance of a flexible air-breathing hypersonic vehicle(AHV) which is subjected to system parametric uncertainties and unknown additive time-varying disturbances.The longitudinal dynamic model for the flexible AHV was used for the control development.High-gain observers were designed to compensate for the system uncertainties and additive disturbances.Small gain theorem and Lyapunov based stability analysis were utilized to prove the stability of the closed loop system.Locally uniformly ultimately bounded tracking of the vehicle's velocity,altitude and attack angle were achieved under aeroelastic effects,system parametric uncertainties and unknown additive disturbances.Matlab/Simulink simulation results were provided to validate the robustness of the proposed control design.The simulation results demonstrate that the tracking errors stay in a small region around zero.

Right liver lobe/albumin ratio:Contribution to non-invasive assessment of portal hypertension

AIM： To study the value of biochemical and ultrasonographic parameters in prediction of presence and size of esophageal varices.METHODS： The study includes selected cirrhotic patients who underwent a complete biochemical workup, upper digestive endoscopic and ultrasonographic examinations. Albumin/right liver lobe diameter and platelet count/spleen diameter ratios were calculated. The correlation between calculated ratio and the presence and degree of esophageal varices was evaluated.RESULTS： Ninety-four subjects （62 males, 32 females）, with a mean age of 52.32 ± 13.60 years, were studied. Child-Pugh class A accounted for 42.6%, class 13 37.2%, whereas class C 20.2%. Esophageal varices （OE） were not demonstrated by upper digestive endoscopy in 24.5%, while OE grade Iwas found in 22.3% patients, grade Ⅱ in 33.0%, grade m in 16.0%, and grade iV in 4.3%. The mean value of right liver lobe diameter/ albumin ratio was 5.51± 1.82 （range from 2.76 to 11.44）, while the mean platelet count/spleen diameter ratio was 1017.75 ± 729.36 （range from 117.39 to 3362.50）, respectively. Statistically significant correlation was proved by Spearman＇s test between OE grade and calculated ratios. The P values were 0.481 and -0.686, respectively.CONCLUSION： The right liver lobe diameter/albumin and platelet count/spleen diameter ratios are noninvasive parameters providing accurate information pertinent to determination of presence of esophageal varices, and their grading in patients with liver cirrhosis.

In situ(Mg_2Si+MgO)/Mg composites fabricated from AZ91-Al_2(SiO_3)_3 with assistance of high-energy ultrasonic field

In situ （Mg2Si＋MgO）/Mg composites fabricated from AZ91-A12（SiO3）3 under high-energy ultrasonic field were investigated by XRD, DSC and SEM. The results indicate that the size, morphology and distribution of the in situ Mg2Si particles are greatly optimized with the assistance of the high-energy ultrasonic field. The amounts of the in situ Mg2Si particles are increased, the sizes are refined, the distributions become uniform, and the morphologies are changed to smooth olive-shape or spherical shape. The amounts of brittle fl-Mgl7All2 phases are decreased and the morphologies are granulated. The values of the tensile strength ab and HB hardness are increased. These are due to the cavitation effects and acoustic streaming effects induced by the high-energy ultrasonic field.