傅里叶变换静电场离子阱的离子入射条件优化研究

在推导傅里叶变换静电场离子阱离子运动规律的基础上,得出了离子的最佳入射条件。研究了离子在不同初始条件下进入离子阱后的运动状态,计算出了离子能够被离子阱束缚的入射动能范围。分析了入射动能范围与离子入射角度及入射位置之间的关系,给出了实现傅里叶变换静电场离子阱离子接口的离子初始条件。

振荡叶栅传播失速不稳定流场的离散旋涡法数值模拟

采用离散旋涡法对振荡叶栅传播失速不稳定流场进行了数值模拟。分片线性化与再校正技术节省了大量计算时间。进行了一系列数值试验包括:进气冲角对传播失速的定量影响;叶片振动频率与振幅的不同响应;随时间流谱与旋涡分布变化的分析,可以显示传播失速的时间与空间传播。本工作为叶片失速颤振气动弹性问题研究的一部分。

Impact of correlated private signals on continuous-time insider trading

A model of continuous-time insider trading in which a risk-neutral in-sider possesses two imperfect correlated signals of a risky asset is studied.By conditional expectation theory and filtering theory,we first establish three lemmas:normal corre-lation,equivalent pricing and equivalent profit,which can guarantee to turn our model into a model with insider knowing full information.Then we investigate the impact of the two correlated signals on the market equilibrium consisting of optimal insider trading strategy and semi-strong pricing rule.It shows that in the equilibrium,(1)the market depth is constant over time;(2)if the two noisy signals are not linerly correlated,then all private information of the insider is incorporated into prices in the end while the whole information on the asset value can not incorporated into prices in the end;(3)if the two noisy signals are linear correlated such that the insider can infer the whole information of the asset value,then our model turns into a model with insider knowing full information;(4)if the two noisy signals are the same then the total ex ant profit of the insider is increasing with the noise decreasing,while down to O as the noise going up to infinity;(5)if the two noisy signals are not linear correlated then with one noisy signal fixed,the total ex ante profit of the insider is single-peaked with a unique minimum with respect to the other noisy signal value,and furthermore as the noisy value going to O it gets its maximum,the profit in the case that the real value is observed.

三明市疟疾局部爆发点调查

1984～1986年我们对16个疟疾局部爆发点进行调查,结果如下。三明市1984～1986年疟疾发病率分别为2.93/1000,1.97/1000和0.83/1000。但3年间先后在梅列等4县(区)发现疟疾局部爆发点16个,爆发点均处已砍伐或正在砍伐的山地竹林区,13个点为临时工棚供从附近低疟区迁入的无免疫外来人员居住,工棚居住人数11～107人不等,另3个点为当地居民的自然村。 16个局部爆发点均发现嗜人按蚊,疟疾患病率为16.23％,带虫率为24.47％(表)。

Effects of Magnetic Stress on the Delayed Luminescence of Mung Bean Leaves

[Objective] The research aimed to study the effects of magnetic stress on the delayed luminescence of mung bean leaves.[Method]With mung bean leaves as the experimental materials,the delayed luminescence curve of mung bean leaves under the same magnetic field intensity at different processing time was measured by using BPCL-type weak luminescence measuring instrument.[Result] The absorption of the magnetic field stimulation within the leaves had its own rules.A certain magnetic field intensity and a certain...

Determination of wax pattern die profile for investment casting of turbine blades

In order to conform to dimensional tolerances, an efficient numerical method, displacement iterative compensation method, based on finite element methodology （FEM） was presented for the wax pattern die profile design of turbine blades. Casting shrinkages at different positions of the blade which was considered nonlinear thermo-mechanical casting deformations were calculated. Based on the displacement iterative compensation method proposed, the optimized wax pattern die profile can be established. For a A356 alloy blade, substantial reduction in dimensional and shape tolerances was achieved with the developed die shape optimization system. Numerical simulation result obtained by the proposed method shows a good agreement with the result measured experimentally. After four times iterations, compared with the CAD model of turbine blade, the total form error decreases to 0.001 978 mm from the orevious 0.515 815 mm.

爱的春天

隐隐约约地来了,沿着时光的跑道,象闪电、象奔马、象云雾、象彩霞、象丘比特的?,象拜伦的诗,象?宫的?,象莫余的画……云水一样的风度,松柏一样的气概,飘然而至,似云似雾,?衣长裙,洋洋洒洒!你是谦?的,亲切的,礼?的,充满魅力的.你用风儿吻我们的面颊,用百灵鸟的话语温暖我们的心窝,用绿叶编织的花环送来请帖,象维纳斯那样默默无语;你象一个纯真的孩子,更象一位聪慧的少年,理智的长者,充满活力的青年!

EFFECT OF TIP CLEARANCE ON PERFORMANCE AND FLOW FIELD OF SMALL SIZED HIGH SPEED CENTRIFUGAL FAN

A centrifugal fan with the high speed and compact dimensions is studied numerically and experimentally. The centrifugal fan consists of a shrouded impeller rotating at 34 000 r/min with a small tip clearance 0.7 mm to the fixed outer casing. Computational models with/without the tip clearance are built and the κ-ω shear stress transport （SST） turbulence model and the unstructured mesh are applied to the numerical simulation for unsteady solutions. The overall performance is measured on a standard experimental bench and the major flow feature of each component inside the centrifugal fan is numerically investigated. In the presence of the tip clearance due to the difference of static pressure between leading and trailing edges of the clearance, i. e. , leading and trailing edges of the impeller, a strong return flow exists inside the clearance passage and re-circulates the main stream inside the impeller passage, and produces the strong flow interaction, thus changing the flow field and influencing the overall performance.

Flow Field Around Rushton Turbine in Stirred Tank by Particle Image Velocimetry Measurement

In this paper, particle image velocimetry (PIV) was used to measure the mean and root meansquare(RMS) velocity in the stirred tank with six-flat blade Rushton turbine and with no baffles. Two typesof motion patterns were studied. One was that the impeller runs at constant speed, the other was that the impellerruns at time-dependent speed and in a periodic way. The emphasis of the paper was on the comparison of meanand RMS velocity vector maps and profiles between these two types of motion patterns, and especial attention waspaid to the comparison of the mean velocity, time-averaged RMS velocity, phase averaged RMS velocity betweenthe constant 3 RPS (revolution per second) and time-dependent operation. The Reynolds number was between 763and 1527. The study explained the mechanism that time-dependent RPS is more efficient for mixing than that ofconstant RPS.

CFD Prediction of Mean Flow Field and Impeller Capacity for Pitched Blade Turbine

This work focused on exploring a computational fluid dynamics(CFD)method to predict the macromixing characteristics including the mean flow field and impeller capacity for a 45° down-pumping pitched blade turbine(PBT)in stirred tanks. Firstly, the three typical mean flow fields were investigated by virtue of three components of liquid velocity. Then the effects of impeller diameter(D)and off-bottom clearance(C)on both the mean flow field and three global macro-mixing parameters concerning impeller capacity were studied in detail. The changes of flow patterns with increasing C/D were predicted from these effects. The simulation results are consistent with the experimental results in published literature.

Study on three dimensional electromagnetic model for permanent magnet linear synchronous motor

In this paper, with the non-salient pole permanent magnet linear synchronous motor (PMLSM)being cited, by using Fourier transform method and "slot-by-slot", "pole -by-pole" current approach, a 3D electromagnetic field model of PMLSM is established. Special attention is paid to its structure and the influence of longitudinal and transverse end effect. The distribution of electromagnetic field of PMLSM can be obtained directly and promptly by using FFT algorithm. It can also be used for the analysis of other LSM.

人工大叶藻场构建的关键技术研究与应用

近年来的海岸资源调查结果表明，我国海草资源不断衰退，直接导致近海环境恶化，生态失衡，海湾的自净能力下降，海水透明度降低等。针对这些问题，该项目以大叶藻（Zostera marina）为主要研究对象，首先对烟台和威海海域的大叶藻场资源分布进行了调查，选定特定海区对其生长和繁殖规律进行了跟踪监测，以此为基础，开展了大叶藻种子的采集、保存、萌发以及幼苗培育技术，播种技术，幼苗和成体移栽技术的研究，经进一步优化、集成，建立了人工大叶藻场构建的关键技术体系，并先后应用该技术体系成功构建人工大叶藻场总计约14500平米，形成了一定规模的可通过营养繁殖自我维持的大叶藻种群。

Effects of stator bending on pressure field and loss of transonic turbine stage

To study effects of the upstream flow field changing on the downstream flow field of transonic turbine, different three-dimensional bowed blades, which are the stator blades of transonic turbine stage, were designed in this paper. And then numerical calculations were carried out. The effects on downstream flow field were studied and analyzed in detail. Results show that, at the middle of stator blades, although the increasing Maeh number causes the increase of shock-wave strength and friction, the middle flow field of downstream rotors is improved obviously. It is an important change in transonic condition. This causes the loss of the rotor＇ s middle part decreased greatly. Correspondingly, efficiency of the whole transonic stage can be increased.

Effect of Guazuma Leaves （Guazuma ulmifolia） Inclusion as Protein Source on Growing Calves

The present work was undertaken in a cattle ranch of the north of Puebla state, Mexico. The aim was to incorporate Guazuma leaves （Guazuma ulmifolia） in the diet of growing calves and evaluate its effect on weight gain. Twenty-four Cebu × Swiss calves （approximately live weight 250 kg） were used during all the experimental period （64 d）. They were assigned to a completely randomized design under two treatments （n = 12 for each treatment）： control （T1） consisted of commercial feed based on 15% crude protein （CP） ＋ cut Taiwan grass and the treatment （T2） consisted of a formulated diet containing 14.7% CP including Guazuma. The composition of the formulated diet consisted of： Guazuma （60%）, rolled corn （12%）, ground sorghum （9%）, oats in grain （7%）, wheat bran （9%） and vitamins and minerals. The feed was offered twice a day at a rate of 3% of live weight for 64 d. The mean daily gain for T1 and T2 was 1.15 g/animal and 1.52 g/animal, respectively （p 〈 0.05）. Results indicate that Guazuma-based supplements resulted in greater productive yield in growing calves.

一叶知秋

题目所说的“一叶”,不是说飘落的黄叶,是说茶叶。中国素有茶叶古国,茶叶大国之称,但“老外”敢于班门弄斧,英国的立顿红茶已从广州打到上海,是不是已经进了北京,还不清楚。早年的英国,并不是出产茶叶的国家。英国人甚至不知茶为何物?17世纪初,荷兰人在澳门贩茶。

认识中国的大数据产业

我是贵州大学国际贸易专业硕士研究生。贵州大学国际教育学院举办了＂感知中国＂活动,使我有机会认识中国的大数据产业与茶文化。我们参加了题为＂Enter the era of Big Data：Big Data industry application in Guizhou＂的讲座。讲座人龚兰蕴老师介绍了什么是大数据,它的来源,以及未来的趋势和挑战。

Experimental Study of Effects of Tip Geometry on the Flow Field in a Turbine Cascade Passage

This study investigates the effects of blade tip geometry on the flow field of a turbine cascade at the incidence angle of 0 degree experimentally. The tests were performed in a low-speed turbine cascade wind tunnel. The Reynolds number based on the blade chord was about 172300 at the exit. Traverses of the exit flow field were made in order to measure the overall performance. The effects of using fiat tip and grooved tip with a chord-wise channel were studied. The case with the flat tip is referenced as the baseline. The tip clearances are all 1 mm measuring 0.84 percent of the blade span. The depth of channel is 2mm.The flow field at 10% chord downstream from the cascade trailing edge was measured at 38 span-wise positions and 26 pitch-wise positions using a mini five-hole pressure probe. The static pressure distribution on the tip end wall is measured at 16 pitch-wise stations and 17 chord-wise stations. Results show that there exists great pressure gradient in the pressure side for the fiat tip and the pressure side squealer tip, which means strong leakage flow. The pressure gradient from the pressure side to the suction side is greatly decreased for the grooved tip, and the resulting leakage flow is weaker. The core of the leakage vortex moves closer to the suction side for the pressure side squealer tip and farther away from the suction side for the suction side squealer tip. The pressure side squealer has little advantages over the fiat tip in improving the flow capacity and reducing the overall losses. The suction side squealer tip and grooved tip can effectively decrease the intensity of the tip leakage vortex, improve the flow capacity and reduce loss of the turbine cascade passage and the grooved tip performs the best.

Experimental Investigation of the Internal Flow Field of Rotating Impeller Passage with Inlet Box

Using PDA and its measurement system, the flow fields at the different peripheral locations of rotating impeller passage of a diagonal fan with inlet box are measured. The results are compared with the flow field of the rotating impeller passage of the same fan without inlet box. The differences of the flow characteristics of the rotating passage at the different peripheral locations are revealed. The effects of the complex flow in the inlet box on the internal flow of the rotating impell passage are investigated.

Effects of Airfoil-probe Tubes on the Flow Field of a Compressor Cascade

To explore the effects of airfoil-probe tubes and its installment position on the flow field of the compressor cas- cade, and find out the mechanism that how the airfoil-probes affect the aerodynamic characteristics of the com- pressor cascade, this paper performed both numerical and experimcntal works on the same compressor cascade. The experiment mainly focused on the cases of low Mach number （Ma = 0.1）, and cases with different Mach numbers （0.1, 0.3, 0.7） and different incidence angles （-5, 0, 5） are investigated by the numerical method. The case without the airfoil-probe tube was referenced as the baseline, and other three cases with the airfoil-probe tubes installed in different chordwise positions O0%, 50%, 70% of the chord length） were studied. The diameter of the airfoil-probe tube is 3ram, which is configured as 300% amplification of some particular airfoil-probe ac- cording to the geometrical similarity principle. The results show that the airfoil-probe tubes have a negative in- fluenc~ on the flow capacity of the cascade at all investigation points. The separations and the large scale stream- wise vortices that induced by the airfoil-probe tube on the pressure side cause most the losses at the high Mach number. The influence of the airfoil-probe tube on the flow field in the vicinity of the pressure side surface is lo- cal separation at the low Mach number. The airfoil-probe tubes also have a clearly effect on the leakage flow. It decreases the mass flow of the leakage flow and weakens the intensity of the leakage vortex, but enlarges the in- fluence area. The total pressure loss of the case that the tube is installed at the half chordwise position is generally lower than other cases especially at the high Mach number, it can even decrease the losses compared with the ba- sic case.

Investigations on the Flow Field in an Unshrouded Pump Impeller Geometry

Transient CFD simulations are performed to investigate the flow behaviour inside an unshrouded pump using the SAS method. Two blade designs are compared at two different tip clearances and the results are validated by measurements. The detected vortex structure is visualized by the normalized helicity, further discussed regarding its development and behaviour and finally implicated to the efficiency of the two different blade designs.