干部培训非得出国吗?

据《中国青年报》7月7日报道,目前,党内中高层正悄然兴起境外学习热潮,该报把这股热潮的特点概括为:级别越来越高,学习针对性强.甘肃省的说法是:"级别越来越高,时间越来越短,质量越来越高.经过培训的干部,回来后80%都得到了提升."

FAST IMPLEMENTATION OF CONVOLUTION BACKPROJECTION ALGORITHM IN SPOTLIGHT SAR

A fast implementation of the convolution backprojection（CBP）algorithm in spotlight synthetic aperture radar（SAR）is presented based on the fast Fourier transform（FFT）.Traditionally,the computation of the ＇backprojection＇ process is expensive,since resampling in the process is implemented by using the interpolation operation.By analyzing the relative location relationship among different pixels,the algorithm realizes the ＇backprojection＇ using a series of FFTs instead of the interpolation operation.The point target simulation validates that the new algorithm accelerates the CBP algorithm,and the computational rate increases about 85%.

Using Luseweilei insecticide to control Dendrolimus superans T.

Luseweilei is an easily-bursted microcapsule insecticide. A test of effectiveness of the insecticide to control the larvae of Dendrolimus superans T. was carried out in larch forest in Baoan Forest Farm of Nehe City, Heilongjiang Province, in April 2001. The solutions of different concentrations (1:150, 1:250, 1:350, and 1:450 Luseweilei : water) were sprayed on the larch trunk before the overwintering larvae climbing on trees and the spraying lengths (height) designed were 1.0, 2.5, and 3.5 m high from ground. The control result showed that spraying 150-, 250-, and 350-fold solutions of the insecticide all produced a good control result, with a mortality rate of 97%, but the 450-fold solution only produced 70% mortality. It is concluded that this insecticide can be used as a kind of good insecticide to control the overwintering larvae of D. superans in spring. Spraying 350-fold solution of easy-burst microcapsule insecticide and one meter spraying length are recommended for the future application..

清初茂明安部叛逃事件二则史料辨析

本文以文本解读方法,对《满文原档》所载天聪十年二、三月的二则原始记录做了语文学研究,并结合《清太宗实录》及其他相关记载,揭示了天聪九年茂明安部众叛逃事件发生的时间、逃亡的目的地以及阿赖达尔汉奉命追赶的时间、参与追击的外藩蒙古部落及其兵丁数目、对俘获人畜的瓜分情况,并对顺路俘获的喀木尼汉首领叶雷的最初信息做了分析。

Transition Modelling Implications in the CFD Analysis of a Turbine Nozzle Vane Cascade Tested Over a Range of Mach and Reynolds Numbers

The aerodynamic performance of a gas turbine nozzle vane cascade was investigated over a range of Mach and Reynolds numbers.The work is part of a vast research project aimed at the analysis of fluid dynamics and heat transfer phenomena in cooled blades.In this paper computed results on the"solid vane"(without cooling devices)are presented and discussed in comparison with experimental data.Detailed measurements were provided by the University of Bergamo where the experimental campaign was carried out by means of a subsonic wind tunnel.The impact of boundary layer transition is investigated by using a novel laminar kinetic energy transport model and the widely used Langtry-Menterγ-Reθ,t model.The comparison between calculations and measurements is presented in terms of blade loading distributions,total pressure loss coefficient contours downstream of the cascade,and velocity/turbulence-intensity profiles within the boundary layer at selected blade surface locations at mid-span.It will be shown how transitional calculations compare favorably with experiments.

Design and Optimization of a Single Stage Centrifugal Compressor for a Solar Dish-Brayton System

According to the requirements of a solar dish-Brayton system,a centrifugal compressor stage with a minimum total pressure ratio of 5,an adiabatic efficiency above 75% and a surge margin more than 12% needs to be designed.A single stage,which consists of impeller,radial vaned diffuser,90° crossover and two rows of axial stators,was chosen to satisfy this system.To achieve the stage performance,an impeller with a 6:1 total pressure ratio and an adiabatic efficiency of 90% was designed and its preliminary geometry came from an in-house one-dimensional program.Radial vaned diffuser was applied downstream of the impeller.Two rows of axial stators after 90° crossover were added to guide the flow into axial direction.Since jet-wake flow,shockwave and boundary layer separation coexisted in the impeller-diffuser region,optimization on the radius ratio of radial diffuser vane inlet to impeller exit,diffuser vane inlet blade angle and number of diffuser vanes was carried out at design point.Finally,an optimized centrifugal compressor stage fulfilled the high expectations and presented proper performance.Numerical simulation showed that at design point the stage adiabatic efficiency was 79.93% and the total pressure ratio was 5.6.The surge margin was 15%.The performance map including 80%,90% and 100% design speed was also presented.

Profile and Secondary Flow Losses in a High-Lift LPT Blade Cascade at Different Reynolds Numbers under Steady and Unsteady Inflow Conditions

The aerodynamic flow field downstream of a Low-Pressure High-Lift(HL)turbine cascade has been experimentally investigated for different Reynolds numbers under both steady and unsteady inflows,in order to analyse the cascade performance under real engine operating conditions.The Reynolds number has been varied in the range 100000<Re<300000,where lower and upper limits are typical of cruise and take-off/landing conditions,respectively.The effects induced by the incoming wakes at the reduced frequency f+=0.62 on both profile and secondary flow losses have been investigated.Total pressure,velocity and secondary kinetic energy distributions at the downstream tangential plane have been measured by means of a miniaturized 5-hole probe.These quantities provide information on both blade wake and secondary flow structures(passage and horse-shoe vortices).The analysis of the results allows the evaluation of the aerodynamic performance of the HL front-loaded blade in terms of both profile and secondary losses.

Current progress in sparse signal processing applied to radar imaging

Sparse signal processing is a signal processing technique that takes advantage of signal’s sparsity,allowing signal to be recovered with a reduced number of samples.Compressive sensing,a new branch of the sparse signal processing,has become a rapidly growing research field.Sparse microwave imaging introduces the sparse signal processing theory to radar imaging to obtain new theories,new systems and new methodologies of microwave imaging.This paper first summarizes the latest application of sparse microwave imaging,including Synthetic Aperture Radar(SAR),tomographic SAR and inverse SAR.As sparse signal processing keeps evolving,an avalanche of results have been obtained.We also highlight its recent theoretical advances,including structured sparsity,off-grid,Bayesian approaches,and point out new research directions in sparse microwave imaging.

Experimental and Numerical Investigation on Compressor Cascade Flows with Tip Clearance at a Low Reynolds Number Condition

High flow rate aeroengines typically employ axial flow compressors, where aerodynamic loss is predominantly due to secondary flow features such as tip leakage and comer vortices. In very high altitude missions, turbo- machinery operates at low density ambient atmosphere, and the recent trend toward more compact engine core inevitably leads to the reduction of blade size, which in turn increases the relative height of the blade tip clearance. Low Reynolds number fiowfield as a result of these two factors amplifies the relative importance of secondary flow effects. This paper focuses on the behavior of tip leakage flow, investigating by use of both experimental and numerical approaches. In order to understand the complex secondary flow behavior, cascade tests are usually conducted using intrusive probes to determine the loss. However relatively few experimental studies are pub- lished on tip leakage flows which take into account the interaction between a rotating blade row and its casing wall. Hence a new linear cascade facility has been designed with a moving belt casing in order to reproduce more realistic flowfield as encountered by a rotating compressor row. Numerical simulations were also performed to aid in the understanding of the complex flow features. The experimental results indicate a significant difference in the flowfield when the moving belt casing is present. The numerical simulations reveal that the leakage vortex is pulled by the shearing motion of the endwall toward the pressure side of the adjacent blade. The results highlight the importance of casing wall relative motion in analyzing leakage flow effects.

Computational Investigation of Blade Slotting on a High-Load Low-Pressure Turbine Profile at Various Reynolds Numbers:Part Ⅱ——Optimization of Slotting Position

The concept of using blade slotting to suppress the large boundary layer separation of high aerodynamic loading low pressure turbine profile has been developed in Part 1.Calculated results highlight the inability performance accompanied with un-proper blade slotting at high Reynolds number,blade slotting optimization seems like compulsory.Meanwhile,to further dignify the rational for use of blade slotting,slotting position and its geometry needed to be optimized.Comparison of different slotting scheme calculation results promised that blade slotting parameter like outlet angle and outlet position are the most important parameters which must be investigated to satisfy the design purpose.

Computational Investigation of Blade slotting on a High-Load Low-Pressure Turbine Profile at various Reynolds Numbers:Part Ⅰ——Slotting Scheme's Verification

Boundary layer separation and reattachment is often an unavoidable feature of low pressure (LP) turbine,one of the main causes of this phenomenon is the high altitude low Reynolds number experienced by the modern LP turbine stage in aero-engine.Although an excellent turbine airfoil design can avoid flow separation on certain extent,but within flight envelope,LP turbine's characteristic Reynolds number may varied greatly,so it will be still under the risk of the presence of separation bubble.In this two parts paper a new concept of slotted-blade was raised to testify the gain of the blade slotting.A high aerodynamic loading LP turbine blade IET-LPTA was under investigated with different Reynolds number.Computational results reveal that the blade slotting could be a way of choice to suppress separation bubble and reduce profile loss under the condition of low Reynolds number,although its position and geometry need to be further investigated.

Effects of Freestream Turbulence on Bypass Transition of Separated Boundary Layer on Low-Pressure Turbine Airfoils

This paper presents experimental studies on bypass transition of separated boundary layer on low-pressure turbine airfoils,focusing on the effects of freestream turbulence on the transition process.Hot-wire probe measurements are performed on the suction side of an airfoil in the low-pressure linear turbine cascade at several Reynolds number conditions.Freestream turbulence is enhanced by use of turbulence grid located upstream of the cascade.The results of this experimental study show that the location of boundary layer separation does not strongly de-pend on the freestream turbulence level.However,as the freestream turbulence level increases,the size of separa-tion bubble becomes small and the location of turbulent transition moves upstream.The size of separation bubble becomes small as the Reynolds number increases.At low freestream turbulence intensity,the velocity fluctuation due to Kelvin-Helmholtz instability is observed clearly in the shear layer of the separation bubble.At high frees-tream turbulence intensity,the streak structures appear upstream of the separation location,indicating bypass transition of attached boundary layer occurs at high Reynolds number.