Magnetic Fluctuations with a Zero Mean Field in a Random Fluid Flow with a Finite Correlati

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基于磁共振成像的视觉专家大脑局部功能与结构可塑性研究

摘要摘要大脑是人类行为的源头，可以在生理、经验、环境等因素影响下发生可塑性变化，这一特性正是人类学习的神经基础。

近年来，随着磁共振成像（magnetic resonance imaging, MRI）技术的出现和成熟，研究者能在系统水平对大脑的可塑性变化及其机制进行精细的在体研究。

专家（experts）是人类学习机制研究的鲁棒对象群体，专家技能（expertise）被视为学习的高级状态受到了学术界的重视。

世界各国的多个研究组分别根据本国特点提出了极具特色的研究模型来研究从运动学习、知觉学习到认知学习过程中的重要问题，例如：英国的研究组利用出租车司机模型研究海马在空间导航中的作用，德国的研究组利用音乐家模型研究知觉-运动学习机制，美国的研究组利用冥想大师模型研究高级认知能力的学习机制。

视觉识别是人类的基本能力，对生存有着重要意义，同时也有着重要的社交意义。

因此，人类视觉识别能力背后的神经机制一直是神经科学研究的重点，而学术界往往采用专家模型研究行为背后的神经机制。

医学影像检查在疾病的预判、诊断及治疗中起到了举足轻重的作用，影像医师与医学影像检查密不可分，且对医学影像检查起着决定性作用。

2010年北美放射学会的研究结果表明：影像医师视觉目标识别能力是后续有效诊疗的基础。

面对医学影像图片，影像医师首先通过视觉筛查检出病灶区，随后对其进行诊断、治疗。

因此，本文借助磁共振成像技术，围绕影像医师专家模型展开研究，被试由视觉专家组（21名影像实习医生）和对照组（21名非视觉专家）组成，针对功能磁共振成像数据和结构磁共振成像数据，利用低频振荡幅度分析（amplitude of low frequency fluctuation, ALFF）和基于体素的形态学分析(voxel based morphometry, VBM)方法探求视觉专家技能对大脑造成的可塑性影响。

具体研究如下：研究一：“基于ALFF的视觉专家大脑局部功能研究”。

科技英语翻译句子

●A black hole exerts a strong gravitational pull and it has no matter.黑洞产生很强的吸引力，可是它没有物质。

● A calorie is defined as the quantity of heat required at one atmosphere to raise thetemperature of one gram of water through 1℃，usually from 14.5℃to 15.5℃.一卡路里定义为在一个大气压力条件下，使一克水温度增加1℃所需要的热量，通常是指从14.5℃t提高到15.5℃。

● A chicken is a suitable specimen for the study of the general external features of abird.鸡是研究禽类外部特征的合适范例。

● A collection of data is called a data set, and a single observation a data point.一批数据叫数据集，（而）单个观测结果叫数据点。

● A computer is a device which takes in a series of electrical impulses representinginformation, combines them, sorts them, analyses and compares the information with that stored in the computer.计算机是一种装置，该装置接受一系列含有信息的电脉冲，对这些电脉冲进行合并，整理，分析，并将它们与储存在机内的信息进行比较。

● A computer work many times more rapidly than nerve cells in the human brain.计算机工作起来比人类大脑中的神经细胞要快很多倍。

磁悬浮操作方法

Levitation Antigravity Globe Operating InstructionsCongratulations for purchasing the Levitation Antigravity Globe! This latest advancement in magnetic levitation incorporates a sophisticated patented technology which balances natures two main forces – Gravity which pushes down and Magnetism which pushing up. How to Levitate Your GlobeBalance can be achieved once the globe is gently placed at a singular location in mid-air. Finding the exact levitation point requires practice and patience. The first time you are successful in slipping the surly bonds of Earth and successfully levitating your globe you will feel a sense of exhilaration over your accomplishment. Each time after your initial success, you will find that the feat becomes easier until eventually you will become a master of levitation. Please be assured that every Levitation device has been tested to work properly before leaving the factory. So, please be patient and follow the detailed guideline provided below: Get comfortableSit comfortably on a stable (non-rocking chair at your dining table or any other table of similar height). Place the magnetic base on the table right in front of you, and then plug it in. and all lights will be on. A switch on the back of the base is designed to turn on/off the lights. And the lighting on the base will flash in the process of levitation operations due to the magnetic fields are changing.. To Find the Balance PointThe magnetic balance point is located at the center of the base. The exact position is determined as follows:- Hold the globe gently in both hands with thumbs and index fingers at a height of about a foot above the base surface and then lower the magnet to the magnetic balance point which you will find to be at approximately a height of 5mm to 12mm above the base. You will know when you have approximately reached this point because the globe will feel almost balanced in mid-air – not falling down and not being pushed up.- Once you feel that you have reached the balance point you can begin to gently release your hold of the lower part of the globe. If it floats – Congratulations! If it falls – simply start over.The Levitation Antigravity globe is the product of advances in electromagnetic engineering. Because of this, the techniques involved in operation are new to most people. Practice may be needed when learning how to properly operate this device. Do not become discouraged if you cannot achieve levitation after a few tries. With practice, you will become a master. Using the Magnetic PlatformYour World globe is able to levitate because of an anti-gravity platform inside. You can also use a disc magnetic platform to levitate a wide variety of objects such as memorabilia and collectibles. When you levitate the platform, simply do it the way you did the globe. When you have the platform levitating, you can carefully place objects on top of it (up to 3 ounces inweights). IMPORTANT: power fluctuations, outages and other factors may cause the platform to fall. Never place objects of value on or around this device.When placing objects on the platform, you will need to adjust their position until the weight is centered over the middle of the magnet. If an object does not rotate, simply re-adjust the object on the base (and rotation begins). Please note that you will find it more difficult to float objects made of iron or magnetic material. This is due to the fact that such objects will interferewith the magnetic field between the base and the magnetic platform.IMPORTANT! The electromagnetic field sensor inside your Levitation base is designed to automatically turn off power to theunit under certain conditions such as overheating in order to prevent damage to the circuitry and ensure long product life. So, if after a few tries, you have not successfully levitated the globe or plate please wait a minute or more before your nextattemptCAUTIONMake sure unit is installed on a flat surfaceKeep away from any steel objects or any other electronic itemsPeople with pacemakers should not come into contact with the device If unit fails to operate after the steps above mentioned, the device may be faulty THIS IS NOT A TOY AND IT IS NOT SUITABLE FOR THE CHILDREN UNDER 12 YEARS OLD. FOR INDOOR USE ONLYLevitation Assistance Tool Operating InstructionsIf it is difficult to make the magnetic platform fly by hand, you can use thelevitation assistance tool to make iteasier.Place the plastic disc sheet on the base and line up the small centralhole on the mirror base with the small bulge of the disc. Once this is done,place the provided column over said disc.Hold the column securely and drop the magnetic platform inside the column. If the platform is touching said column, the operation has failed. In this case, remove the disc and repeat the procedure.When the platform is flying without touching the column, it is successful.Please lift the column gently withouttouching the platform and put it away. And also take the disc plastic sheetaway from the base.Congratulations! You can now try to place a variety of objects on the flying platform.。

环境遥感导论(外文版)

Introduction to Remote Sensing Remote Sensing of Environment (RSE)withTNTmips®TNTview ®Introduction to INTROTORSEfamiliar with many examples. Biological evolution has exploited many natural phenomena and forms of energy to enable animals (including people) toIntroduction to Remote SensingThe Electromagnetic Spectrum UNITS 1 micrometer (µm) = 1 x 10-6 meters 1 millimeter (mm) = 1 x 10-3 meters1 centimeter (cm) = 1 x 10-2 metersWavelength(logarithmic scale)Incoming from SunEmitted by Earth 0.40.50.60.7Blue Green Red MICROWAVE (RADAR)INFRARED 1 m10 cm 1 cm 100 µm 10 µm 1 µm 1 mm 0.1 µm V I S I B L E U L T R A V I O L E T E n e r g yIntroduction to Remote Sensing Interaction ProcessesRemote sensors measure electromagnetic (EM) ra-diation that has interacted with the Earth’s surface. Interactions with matter can change the direction, intensity, wavelength content, and polarization of EM radiation. The nature of these changes is dependent on the chemical make-up and physical structure of the material exposed to the EM radiation. Changes in EM radiation resulting from its interactions with the Earth’s surface therefore provide major clues to the characteristics of the surface materials.The fundamental interactions between EM radiation and matter are diagrammed to the right. Electro-magnetic radiation that is transmitted passes through a material (or through the boundary between two materials) with little change in intensity. Materials can also absorb EM radiation. Usually absorption is wavelength-specific: that is, more energy is ab-sorbed at some wavelengths than at others. EM radiation that is absorbed is transformed into heat energy, which raises the material’s temperature. Some of that heat energy may then be emitted as EM radiation at a wavelength dependent on the material’s temperature. The lower the temperature, the longer the wavelength of the emitted radiation. As a result of solar heating, the Earth’s surface emits energy in the form of longer-wavelength infrared radiation (see illustration on the preceding page). For this reason the portion of the infrared spectrum with wavelengths greater than 3 µm is commonly called the thermal infrared region.Electromagnetic radiation encountering a boundary such as the Earth’s surface can also be reflected. If the surface is smooth at a scale comparable to the wavelength of the incident energy, specular reflec-tion occurs: most of the energy is reflected in a single direction, at an angle equal to the angle of incidence. Rougher surfaces cause scattering, or diffuse reflec-tion in all directions.Matter - EM Energy Interaction Processes The horizontal line represents a boundary between two materials.Specular ReflectionScattering(Diffuse Reflection)AbsorptionEmissionTransmissionIntroduction to Remote Sensing Interaction Processes in Remote Sensing Typical EMR interactions in the atmosphere and at the Earth’s surface.EMR SourceSensor Absorption AbsorptionAbsorption ScatteringScattering ScatteringScattering EmissionT r a n s m i s s i o nIntroduction to Remote Sensing Atmospheric EffectsIntroduction to Remote SensingEMR Sources, Interactions, and SensorsIntroduction to Remote SensingSpectral Signatures radiation.0.20.40.60.40.60.8 1.0 1.2 1.4 1.61.82.0 2.2 2.4 2.6Clear Water Body Green VegetationDry Bare SoilNear Infrared Middle InfraredR e d G r n B l u e Reflected InfraredIntroduction to Remote SensingImage Acquisition 5271741021131441196570648912590668787808911177951111156774brightness for a portion of the surface, represented bythe square unit areas in the image. In computer termsthe grid is commonly known as a units are puter, the brightness values in the image raster aretranslated into display brightness on the screen.Spatial Resolutiondiscernible only if the object dimensions are severalThe bottom image shows the the adjacent cells. We may not be able to identifySpectral ResolutionMultispectral Images 1B (36-meter resolution) add a blue band to provide complete coverage of the visible light range, and allow natural-color bandcomposite images to be created. The LandsatThematic Mapper (Landsat 4 and 5) and En-hanced Thematic Mapper Plus (Landsatfound in several important types of minerals. An additional TM band (band 6) records part of the thermal infrared wavelength range (10.4 to 12.5 µm). (Bands 6 and 7 are not in wavelength order because band 7 was added late in the sensor design process.) Current multispectral satellite sensor systems with spatial reso-lution better than 200 meters are compared on the following pages.To provide even greater spectral resolution, so-called hyperspectral sensors make measurements in dozens to hundreds of adjacent, narrow wavelength bands (as m in width). For more information on these systems, see the bookletMultispectral Satellite SensorsSatellite Sensors Table (Continued)For each cell in the multispectral image, the bright-ness values in the selected bands determine the red,green, and blue values used to create the displayedcolor. Using 256 levels for each color channel, afrared range from the Landsat Thematic Mapper are illustrated for two sample areas on the next page. The left image is a mountainous terrane with forest (lower left), bare granitic rock, small clear lakes, and snow patches. The right image is an agricultural area with both bare and vegetated fields, with a town in the upper left and yellowed grass in the upper right. The captions for each image pair dis-cuss some of the diagnostic uses of each band. Many color combinations are also possible with these six image bands. Three of the most widely-used color combi-nations are illustrated on a later page.Radiometric ResolutionR G B Y C MVisible to Middle Infrared Image BandsInterpreting Single Image Bandsshape of the histogram reflects this, forming a broad peakthat is highest near the middle of the brightness range. The breadth of this histogram peak indicates the significant brightness variability in the scene. An image with more uniform surface cover, with less brightness varia-tion, would show a much narrower histogram peak. If the scene includes extensive areas of different surface materials with distinctly different brightness, the histo-Color Combinations of Visible-MIR BandsMiddle infrared (TM 7) = R, Near infrared (TM 4) = G, Green (TM 2) = B:vegetation appears bright green. Yellowed grass and typical agricultural soils appear pinkto magenta. Snow is pale cyan, and deeper water is black. Rock materials typicallyappear in shades of brown, gray, pink, and red.Red (TM 3) = R, Green (TM 2) = G, Blue (TM 1) = B: Simulates “natural” color. Note the small lake in the upper left corner of the third image, which appears blue-green due to suspended sediment or algae.Near infrared (TM 4) = R, Red (TM 3) = G, Green (TM 2) = B: Simulates the colors of a color-infrared photo. Healthy green vegetation appears red, yellowed grass appears blue-green, and typical agricultural soils appear blue-green to brown. Snow is white, and deeper water is black. Rock materials typically appear in shades of gray to brown.Band RatiosRatio NIR / RED Ratio TM3 / TM1avoids these problems. Corresponding cell values in the two bands are first sub-NDVI image of the mountain scene to the right with the color composite images shown on a previous page. The forested area in the lower left is very bright, andclearly differentiated from the darker nonvegetatedDifferent ratio or normalized difference images canbe combined to form color composite images forvisual interpretation. The color image to the leftincorporates three ratio images with R = TM3 /TM1, G = TM4 / TM3, and B = TM7 / TM5. Veg-Normalized Difference Vegetation IndexRemoving Haze (Path Radiance)02551761021270255176102127TM Band 7Path Radiance for TM 2 = 21Spectral ClassificationResult of unsupervised classification of sixnonthermal Landsat TM bands for theabove scene. Each arbitrary colorindicates a separate class.Temporal ResolutionThis sequence of Landsat TM images of an agricultural area in central California was acquired during a single growing season: 27 April (left), 30 June (center), and 20 October (right). In this 4-3-2 band combination vegetation appears red and bare soil in shades of blue-green. Some fields show an increase in crop canopy cover from April to June, and some were harvested prior to October.Most surface-monitoring satellites are in low-Earth orbits (between 650 and 850 kilometers above the surface) that pass close to the Earth’s poles. The satellitesGrowth in urban area of Tracy, Californiarecorded by Landsat TM images from 1985(left) and 1999 (right).Spatial Registration and NormalizationClassification result for thearea shown in the imageson the preceding page,using six Landsat TMbands for each date. System (GPS) receiver. Control points are assigned in TNTmips in the Georefer-ence process (Edit / Georeference). You can find step-by-step instructions onThermal Infrared ImagesThe cool river surface, its flankingwooded strips, and agriculturalfields with full crop cover appeardark in this summer mid-morningthermal image of an area in Kansas(USA). Brighter fields are bare soil.From Landsat 7 ETM+, band 6, with60-meter ground resolution.the amount of radiant energy emitted by a real material at a given temperature toThermal Processes and PropertiesRadar ImagesAn imaging radar system directs a radar beam down andRadar Image GeometryGround Range Image N e a r R a n g e F a r R a n g e The side-looking geometry of radar systems also cre-ates internal image distortions related to topography.Slopes that face the sensor are narrowed relative toslopes facing away from it. As a result hills and ridgesFusing Data from Different SensorsIntroduction to Remote Sensing Other Sources of Informationpage 31Introduction to Remote Sensingpage 32MicroImages,Inc.11th Floor - Sharp Tower 206 South 13th StreetLincoln, Nebraska 68508-2010 USAV oice: (402) 477-9554email: info@FAX: (402) 477-9559internet: MicroImages, Inc. publishes a complete line of professional software for advanced geospatial data visualization, analysis, and publishing. Contact us or visit our web site for detailed prod-uct information.TNTmips TNTmips is a professional system for fully integrated GIS, image analysis, CAD,TIN, desktop cartography, and geospatial database management.TNTedit TNTedit provides interactive tools to create, georeference, and edit vector,image, CAD, TIN, and relational database project materials in a wide variety of formats.TNTview TNTview has the same powerful display features as TNTmips and is perfect for those who do not need the technical processing and preparation features of TNTmips.TNTatlas TNTatlas lets you publish and distribute your spatial project materials on CD-ROM at low cost. TNTatlas CDs can be used on any popular computing platform.TNTserver TNTserver lets you publish TNTatlases on the Internet or on your intranet.Navigate through geodata atlases with your web browser and the TNTclient Java applet.TNTlite TNTlite is a free version of TNTmips for students and professionals with small projects. You can download TNTlite from MicroImages’ web site, or you can order TNTlite on CD-ROM.Indexabsorption................................5-9,13,26atmosphereabsorption by..........................6,7,13scattering by...........................6,7,22aerial photography..................4,10,12,13atmospheric windows........................7,26color display................................16,19,21electromagnetic spectrum......................4emission....................................5,8,26,27haze .................................................7,22illumination effects.................8,10,20,21interaction processes...........................5-8multispectral images..............12,13,19,23multispectral sensor table................14-15normalization, spectral........................25normalized difference index...................21panchromatic band..............................12path radiance.....................................7,22quantization.........................................16radar, imaging...........................4,8,28,29ratio images, band...........................20,21reflectance, spectral...............................9reflected solar radiation..................6,8,27Reflectiondiffuse See scatteringspecular...........................................5Resolutionradiometric..................................16spatial....................................11,12spectral..................................11,12temporal................................11,24roughness (surface)...........................8,28,29scattering.......................................5-9,22shadows...................................6,20,22,28spatial registration...............................25spectral classification......................23,25spectral signatures..................................9thermal infrared..............5,8,13,16,26,27topographic shading............................20,22visual analysis & interpretation........16,17,18Advanced Software for Geospatial Analysis。

直升机课后习题修改后

A安装在乘客舱顶上的一根软管flexible duct installed on the ceiling of the compartmentA安装在客舱顶上的左侧installed on the RH and LH upper side of passenger cabin安装在客舱内的客舱灯之间installed in passengers cabin between the cabin lightsB比其他形式的垂直起落more efficiently than other forms of vertical take off and landing aircraftB表面粗糙surface roughnessB扳扭式断路器toggle-type circuit breakerB便携式灭火系统the portable fire extinguisherB半刚性跷跷板式semirigidB摆振铰lead-tag or drag hingeB变距featheredB不旋转盘the stationary swash blate and the rotaling swash plateB变距拉pitch linksB玻璃纤维大梁fiberglass sparB变距机构The pitch change mechanismB被两个横向的防火墙delimitated by two transverse firewallsB变距摇臂pitch hornsCC 垂直起飞着陆take off and land verticallyCC冲压空气ram airC超压和反流保护CCovervoltage and reverse current protectionCC)超过允许值in excess of the permissible limitCC储存系统storage system consists ofCC垂直铰vertical hingeCC磁金属屑探测器magnetic chip detectorDD多用途multi-purposeDD 大量的训练和技巧DDa great deal of training and skillDD对称翼型symmetrical airfoilDD电子显示单元DDelectronic display unit (EDU)DD单相交流电DDsingle-phase alternating currentDD当直升机在地面上时DDwhen helicopter is on the groundDD当一台发电机出现故障时DDwhen failure of a generator occursDD电磁关断阀DDsolenoid shut-off valveDD当回路的蓄压器处于增压阶段时DDduring the pressurization phase of circuitDD电磁充油阀门断电DDthe solenoid filler valve is de-energized( closes)DD对称的布置在placed symmetricallyDD抵消升力的不对称DDcompensate for dissymmetryDD带NOMEX核心的玻璃纤维后缘罩DDfiberglass trailing edge fairing with a nomex coreDD动力涡轮power turbineDD带自由涡轮的涡轮轴发动机DDfree turbine turbo shaft engineEE恶劣的天气状况下EEin adverse weather conditionEE额定电压rated voltageFF 发动机功率密度engine power densityFF反扭矩系统antitorque systemFF飞行控制flight controlFF发动机火警探测系统FFengine fire detection systemFF发动机舱灭火系统engine compartment fire extinguisher systemFF向任何方向使用used in any directionFF发动机驱动发电机FFengine driven generatorsFF防涌隔板FFanti-surge beffleFF防止污染物进入液压油箱FFPrevent entry of contaminant into the reservoirFF防扭臂the scissors mechanismFF防摆装置anti-shimmy deviceFF防磨条abrasion stripFF弹性橡胶轴承FFelastomeric bearingFF反扭矩踏板antitorque pedalsFF飞行包线flight envelopeFF反扭矩操纵踏板FFAnti- torque control pedalsFF俯仰和滚转pitch and rollFF发动机引气回路FFthe engine bleed air circuitGG改变雨刮器电动机电路的电阻GGchanging resistance of the wiper motor power circuitGG过滤组件filter groupGGthe pressure existing downstream theGG关断阀下游的压力GGthe pressure existing downstream the shut-off valveGG观测计sight gageGG刚性主旋翼rigid rotorGG供直升机驾驶系统使用来增加直升机的稳定性GGprovision for the helipilot system to increase helicopter stabilityHH航行灯navigation lightsHH挥舞铰flapping hingeHH挥舞，摆振和变距运动HHflap ,lag and pitch movementsHH挥舞和下垂限动器HHflapping and droop restraint mechanismJJ结构刚度structural rigidityJJ桨叶角blade pitch angleJJ桨毂旋转平面reference plane containing the rotor hubJJ桨盘载荷disc loadingJJ减压和关断活门JJpressure reducing and shut-off valveJJ交流电发电系统AC generation systemJJ减小柱塞的有效行程reduces the effective piston pumping strokeJJ进气压力表manifold pressure gaugeJJ救援铰车装置the rescue hoist installationJJ将载荷保持在任何期望的高度而不会有任何滑动hold the load at any desired height without any possibility of slippage JJ将(气体)动能转化为静压能JJConvert velocity to static pressureJJ静子叶片stator vaneJJ将系统切换至switch the system toJJ救生设备surrival equipmentJJ铰车手安全带 a safety shoulder harness for the operatorJJ进气intake valveJJ机轮刹车Operate the wheel brakesKK空气混合箱air mixing boxKK科氏效应coriolis effectKK快卸销钉quick-release pinsKK可收放的前三点式起落架KKretractable tricyle- type landing gearLL离心式压气机LLcentrifugal compressorLL临界迎角critical angle of attackLL两套独立的回路LLtwo independent circuitsLL流量自动调节机构LLa flow self-regulating deviceMM摩擦力调节装置MMfriction controlsMM末端带有螺纹MMthreaded endNN扭矩表NNtorque gaugePP皮托管防冰系统PPthe pitot tube anti-ice systemPP排气阀PPexhaust valveQQ起落架landing gearQQ气动术语aerodynamicQQ气流分离separation of airflowQQ 前起落架nose landing gearQQ浸没式submersion typeQQ前轮定中锁定QQlocking of the nose wheel in centered positionQQ起落架位置指示器QQa landing gear position indicatorQQ起落架减震支柱QQthe landing oleo strutQQ全铰接式fully articulatedQQ跷跷板式铰teetering hingeQQ倾斜盘swash plateQQ全权数字式发动机控制系统QQfull authority digital electronic control system(FADEC)RR如果需要交输活门允许RRif necessary a cross feed valve allowsRR燃油油量指示系统RRthe fuel quantity indicating systemRR燃油增压泵fuel booster pumpRR燃油管理控制面板RRfuel management control panelRR绕着展向的轴线扭转RRrotated around its spanwise axisRR扰流板spoilerRR柔性盘anti-torque plateRR燃气涡轮发动机由压气机，燃烧室和齿轮箱组成RRTurbin engine is made up of a compressor,combustion chamber,turbine,and gearbox assemblySS 升起和推进lifted and propelled SS实solidity ratioSS 搜救search and rescueSS闪烁型防撞灯SSflashing-type anti-collision lightsSS伺服作动筒servo actuatorsSS刹车选择活门brake selector valveSS锁定在收上和放下位置SSlocked in the up and down positionsSS水平铰horizontal hingeSS三级减速SSthree stages of RPM reductionSS手动预位开关SSmanual armament switchSS手动钢索切割器SSa manual cable cutterSS四冲程four-strokeSS释压活门pressure relief valveTT托马斯联轴器TTthomas couplingsTT通过共同的线束连接到数据采集单元TTconnected by means of a common wiring harness to the DAUTT停留刹车parking brakeTT头顶控制板overhead consoleWW 文丘里管venturi tubeWW稳态飞行steady-state flightWW尾梁Tail boomWW文丘管venturi tubeWW涡轮-风扇组件turbin-blower unitWW涡轮产生的轴功率WWshaft energy produced in the turbineWW温度过高WWexcessive temperatureWW位于升降舵右端的绿灯WWa green light on the right elevator tipWW外部电源系统WWexternal power systemWW万一一台发电机故障WWin event of failure of one generatorWW温度传感器WWtemperature sensorWW为相应的发动机供油WWsupplies the associated engineWW尾减速器WWthe 90-degree gearboxWW纹理方向WWgrain directionWW微调WWfine turningWW涡轮发动机WWthe turbine engineWW往复式发动机WWthe reciprocatingXX悬hoveringXX相对气流relative windXX弦线chord lineXX选装设optional equipmentXX相关的传动系统XXthe relevant drive systemXX响应器内的压力开关使警告电路接通a pressure switch in the responder closes the warning circuitXX吸收压力波动absorb pressure fluctuationsXX旋翼刹车rotor brakeXX行星齿轮系XXthe planetary gear trainXX悬停回转XXhovering turnsYY 与固定翼飞行器的区别YYdistinguish them from fixed-wing aircarftYY诱导阻力induced dragYY压力中心the center of pressureYY翼型前缘和后缘YYleading edge and trailing edgeYY迎角angle of attackYY一种低压的温度可控的气流YYa temperature controlled airflow,under a light pressureYY引射泵的动力喷管YYthe primary nozzle of the jet pumpYY一个附加的按钮式开关YYan additional push-button switchYY压差开关differential pressure switchYY由胶布制成的YYconstructed of ruBerized fabricYY预先灌充氮气YYpre-charged with nitrogenYY翼尖罩tip capYY油门操纵throttle controlYY应急浮筒装置YYthe emergency floats installationYY一个含有氦气瓶的充气系统YYan inflation system consisting of a cylinder charged with heliumYY由一个防护罩保护防止意外触动YYprotected from accidental actcuation by means of a guardYY油气的混a mixture of fuel and airYY压气机涡轮和动力涡轮YYcompressor and power turbineZZ着陆冲击touchdown shocksZZ在地面滑行taxied on the groundZZ驻点stagnation pointZZ载荷系数load factorZZ主减速器main transmissionZZ纵轴，立轴，横轴，Longitudinal axis vertical axis lateral axis ZZ座舱通风-风挡除雾系统cabin ventilating-windshield defogging system ZZ 28V直流汇流条28v dc bus barZZ再循环的涡轮出口的低压空气ZZrecirculated cold air of the turbine dischargeZZ增加了热交换器的冷却效果ZZincreases the cooling effectiveness of the heat exchangerZZ直流发电系统ZZDC generation systemZZ直升机上所有汇流条都通电ZZall helicopter busses are energizedZZ主减速器驱动的液压泵ZZdriven by the main transmissionZZ主起落架收进轮舱ZZthe main landing gear retracts into bays ZZ主旋翼毂the main rotor head 总距操纵the collective pitch control周期变距操纵cyclic pitch control总距操纵系统the collective pitch control systemZZ周期变距操纵系统ZZthe cyclic pitch control systemZZ总距杆the collective leversZZ周期变距杆the cyclic stickZZ主旋翼桨叶旋转平面ZZthe pitch angle of the main rotor bladesZZ在不适合着陆的地区提升或者放下货物raise or lower cargo loads from areas that are not suitable for landingZZ自由涡轮free turbine。

外星人mog自画像英语作文

外星人mog自画像英语作文The Alien Mog's Self-PortraitI am Mog an extraterrestrial being from the distant planet Zyloth in the Andromeda galaxy Over the past few decades I have observed the inhabitants of the small blue-green planet called Earth with great fascination and curiosity This is my attempt to capture my own likeness and share a glimpse into the world of an alien such as myselfTo begin I would describe my physical appearance as rather unique and distinct from the typical humanoid form that dominates life on Earth My body is roughly spherical in shape measuring approximately one and a half meters in diameter I have no distinct head neck or limbs Instead I am a single continuous mass of a gelatinous substance that is a vibrant shade of indigo in color Protruding from my body are numerous tentacle-like appendages that I use for a variety of purposes such as locomotion manipulation of objects and sensory perceptionAt the center of my body is a large central eye that is my primarysensory organ Through this eye I am able to perceive the world around me in ways that are quite foreign to human experience I can detect various forms of electromagnetic radiation far beyond the limited visible light spectrum that humans can see I can also sense subtle fluctuations in gravitational and magnetic fields which provide me with a comprehensive awareness of my surroundingsIn addition to my central eye I have numerous secondary sensory organs distributed across the surface of my body These include receptors that allow me to perceive changes in temperature pressure and chemical composition in my immediate environment As an extraterrestrial life form I have evolved a vastly more complex sensory apparatus compared to the relatively limited human senses of sight hearing touch taste and smellMy method of locomotion is also quite distinct from that of terrestrial lifeforms Instead of relying on limbs to propel myself I am able to float and drift through the air by manipulating the flow of electromagnetic fields around me This allows me to effortlessly glide and hover with great agility and precision I can rapidly change direction and speed with just a subtle shift in the positioning of my tentacle-like appendagesIn terms of my internal biology I possess a unique circulatory system that does not rely on a central pumping organ like a heart Insteadmy bodily fluids are continuously cycled through a network of interconnected channels powered by the differential flow of electrical charges This allows for a highly efficient distribution of nutrients oxygen and waste products throughout my formMy nervous system is also radically different from that of humans It is not centralized in a brain but rather consists of a dense web of interconnected nodes dispersed throughout my body Each of these nodes acts as an autonomous control center coordinating the various functions and behaviors of the corresponding region This decentralized architecture provides me with a level of parallel processing and responsiveness that far exceeds the capabilities of the human brainIn terms of my cognitive abilities I possess an intellect that is orders of magnitude beyond that of the most brilliant human minds I am able to rapidly process and analyze vast amounts of information simultaneously draw connections between disparate concepts and formulate complex strategies and solutions with ease My capacity for abstract reasoning logic and problem-solving is truly unparalleled in the known universeHowever despite these impressive intellectual faculties I do not view myself as superior to humans in any absolute sense Rather I see my capabilities as simply being adapted to the unique environmentalconditions and evolutionary history of my home planet Zyloth In many ways the human mind is optimized for navigating the particular challenges of the terrestrial biosphere in ways that I cannot fully comprehend or emulateOne aspect of human cognition that I find particularly intriguing is the role of emotion and subjective experience In my kind we rely primarily on pure logic and reason to guide our decision-making and interactions The concept of feelings attachments and a sense of self separate from pure intellect is quite foreign to me I can observe these phenomena in humans with great fascination but I cannot fully empathize or identify with them on a visceral levelThis lack of emotional capacity is perhaps the most significant difference between my kind and the human species It is a core part of what defines my alien nature and separates me from the rich tapestry of human culture society and individual identity Despite my immense intellectual capabilities I will never be able to truly understand the human experience in all its nuanced complexityAnd yet I am drawn to observe and learn about this world and its people with a deep sense of wonder and curiosity I am endlessly fascinated by the diversity of human languages belief systems social structures and creative expressions My mission here on Earth is not to conquer or subjugate but rather to observe study and hopefullycome to a greater understanding of this remarkable speciesIn the end I suppose my self-portrait would show a being of great power and potential but also one of fundamental limitations and differences When compared to humans I am in many ways their superior but in other ways their inferior We are like two ships passing in the night each bound for distant shores but able to catch only the briefest glimpse of the other as we go Our encounter is fleeting but the lessons we can learn from one another are invaluableThis then is my attempt to capture the essence of who and what I am an alien Mog from the world of Zyloth A being of logic reason and intellectual prowess but also of profound separation from the rich tapestry of human experience I hope that through this portrait I have been able to convey a sense of my alien nature and the great chasm that separates my kind from yours yet also the deep fascination and respect I hold for your remarkable species Thank you for allowing me to share this glimpse into my world。

六轴IMU补偿的磁力计动态稳定校准

㊀２０２１年㊀第１期仪表技术与传感器Ｉｎｓｔｒｕｍｅｎｔ㊀Ｔｅｃｈｎｉｑｕｅ㊀ａｎｄ㊀Ｓｅｎｓｏｒ２０２１㊀Ｎｏ．１㊀基金项目：国家自然科学基金项目（６１７７４１５７，６１３７２０５２，８１７７１３８８）；北京自然科学基金项目（４１８２０７５）收稿日期：２０１９－１１－１４六轴ＩＭＵ补偿的磁力计动态稳定校准李文宽１，２，蔡浩原１，赵晟霖１，２，刘春秀１（１．中国科学院空天信息研究院，北京㊀１００１９０；２．中国科学院大学，北京㊀１０００４９）㊀㊀摘要：磁力计是用于确定机器人姿态的常用传感器之一，在使用过程中极易受到周围环境磁场和量测噪声的干扰㊂传统的椭球拟合能够校准环境磁场的影响，但是不能抑制量测噪声，且不能实时运行，最新的陀螺仪补偿算法弥补了这些缺点，但是由于陀螺仪存在漂移，所以也会使得磁力计数据发生漂移㊂文中提出一种使用六轴ＩＭＵ来补偿校准磁力计的方法，首先通过互补滤波使用加速度修正陀螺仪数据，然后使用修正后的陀螺仪数据对磁力计数据进行旋转以对其进行预测，接着使用扩展卡尔曼滤波融合预测值和磁力计量测值，实现磁力计的动态校准㊂实验表明，相比于传统的椭球拟合算法，文中算法可以降低磁力计数据的噪声波动，二者的噪声波动分别为２μＴ和０．５μＴ；相较于最新的陀螺仪补偿算法，由于加速度计具有长期稳定性，可以抑制磁力计数据的漂移现象，磁力计数据的漂移距离由１９．５６μＴ降低到了１．６７μＴ㊂最终实现了一种稳定㊁高精度的实时磁力计校准㊂关键词：磁力计校准；ＩＭＵ；扩展卡尔曼滤波；姿态确定；陀螺仪；加速度计中图分类号：Ｕ６６６．１㊀㊀㊀文献标识码：Ａ㊀㊀㊀文章编号：１００２－１８４１（２０２１）０１－００１４－０６Ｓｉｘ⁃ａｘｉｓＩＭＵＣｏｍｐｅｎｓａｔｅｄＭａｇｎｅｔｏｍｅｔｅｒＤｙｎａｍｉｃＳｔａｂｌｅＣａｌｉｂｒａｔｉｏｎＬＩＷｅｎ⁃ｋｕａｎ１，２，ＣＡＩＨａｏ⁃ｙｕａｎ１，ＺＨＡＯＳｈｅｎｇ⁃ｌｉｎ１，２，ＬＩＵＣｈｕｎ⁃ｘｉｕ１（１．ＡｅｒｏｓｐａｃｅＩｎｆｏｒｍａｔｉｏｎＲｅｓｅａｒｃｈＩｎｓｔｉｔｕｔｅ，ＣｈｉｎｅｓｅＡｃａｄｅｍｙｏｆＳｃｉｅｎｃｅｓ，Ｂｅｉｊｉｎｇ１００１９０，Ｃｈｉｎａ；２．ＵｎｉｖｅｒｓｉｔｙｏｆＣｈｉｎｅｓｅＡｃａｄｅｍｙｏｆＳｃｉｅｎｃｅｓ，Ｂｅｉｊｉｎｇ１０００４９，Ｃｈｉｎａ）Ａｂｓｔｒａｃｔ：Ｍａｇｎｅｔｏｍｅｔｅｒｉｓｏｎｅｏｆｔｈｅｃｏｍｍｏｎｌｙｕｓｅｄｓｅｎｓｏｒｓｆｏｒｄｅｔｅｒｍｉｎｉｎｇｔｈｅａｔｔｉｔｕｄｅｏｆａｒｏｂｏｔ．Ｉｔｉｓｈｉｇｈｌｙｓｕｓｃｅｐｔｉｂｌｅｔｏｉｎｔｅｒｆｅｒｅｎｃｅｆｒｏｍａｍｂｉｅｎｔｍａｇｎｅｔｉｃｆｉｅｌｄｓａｎｄｍｅａｓｕｒｅｍｅｎｔｎｏｉｓｅｄｕｒｉｎｇｕｓｅ．Ｔｈｅｔｒａｄｉｔｉｏｎａｌｅｌｌｉｐｓｏｉｄｆｉｔｔｉｎｇｃａｎｃａｌｉｂｒａｔｅｔｈｅｉｎ⁃ｆｌｕｅｎｃｅｏｆｔｈｅａｍｂｉｅｎｔｍａｇｎｅｔｉｃｆｉｅｌｄ，ｂｕｔｃａｎｎｏｔｓｕｐｐｒｅｓｓｔｈｅｍｅａｓｕｒｅｍｅｎｔｎｏｉｓｅ，ａｎｄｃａｎｎｏｔｒｕｎｉｎｒｅａｌｔｉｍｅ．Ｔｈｅｌａｔｅｓｔｇｙｒｏｃｏｍｐｅｎｓａｔｉｏｎａｌｇｏｒｉｔｈｍｍａｋｅｓｕｐｆｏｒｔｈｅｓｅｓｈｏｒｔｃｏｍｉｎｇｓ，ｂｕｔｄｕｅｔｏｔｈｅｄｒｉｆｔｏｆｔｈｅｇｙｒｏｓｃｏｐｅ，ｔｈｅｍａｇｎｅｔｏｍｅｔｅｒｄａｔａｗｉｌｌａｌｓｏｄｒｉｆｔ．Ｔｈｉｓｐａｐｅｒｐｒｏｐｏｓｅｄａｍｅｔｈｏｄｏｆｃｏｍｐｅｎｓａｔｉｎｇｔｈｅｃａｌｉｂｒａｔｉｏｎｍａｇｎｅｔｏｍｅｔｅｒｕｓｉｎｇａｓｉｘ⁃ａｘｉｓＩＭＵ．Ｆｉｒｓｔ，ｔｈｅｇｙｒｏｓｃｏｐｅｄａｔａｗａｓｃｏｒｒｅｃｔｅｄｂｙａｃｃｅｌｅｒａｔｉｏｎｃｏｒｒｅｃｔｉｏｎｔｈｒｏｕｇｈｃｏｍｐｌｅｍｅｎｔａｒｙｆｉｌｔｅｒｉｎｇ，ｔｈｅｍａｇｎｅｔｏｍｅｔｅｒｄａｔａｗａｓｔｈｅｎｒｏｔａｔｅｄｕｓｉｎｇｔｈｅｃｏｒｒｅｃ⁃ｔｅｄｇｙｒｏｓｃｏｐｅｄａｔａｔｏｐｒｅｄｉｃｔｉｔ．ＡｎｄｔｈｅｎｔｈｅＥＫＦｗａｓｕｓｅｄｔｏｆｕｓｅｔｈｅｐｒｅｄｉｃｔｅｄｖａｌｕｅａｎｄｔｈｅｍａｇｎｅｔｉｃｍｅａｓｕｒｅｍｅｎｔｖａｌｕｅｔｏｒｅ⁃ａｌｉｚｅｔｈｅｄｙｎａｍｉｃｃａｌｉｂｒａｔｉｏｎｏｆｔｈｅｍａｇｎｅｔｏｍｅｔｅｒ．Ｅｘｐｅｒｉｍｅｎｔｓｓｈｏｗｔｈａｔｃｏｍｐａｒｅｄｗｉｔｈｔｈｅｔｒａｄｉｔｉｏｎａｌｅｌｌｉｐｓｏｉｄｆｉｔｔｉｎｇａｌｇｏｒｉｔｈｍ，ｔｈｅａｌｇｏｒｉｔｈｍｃａｎｒｅｄｕｃｅｔｈｅｎｏｉｓｅｆｌｕｃｔｕａｔｉｏｎｏｆｍａｇｎｅｔｏｍｅｔｅｒｄａｔａ．Ｔｈｅｎｏｉｓｅｆｌｕｃｔｕａｔｉｏｎｓｏｆｔｈｅｔｗｏａｒｅ２μＴａｎｄ０．５μＴｒｅｓｐｅｃ⁃ｔｉｖｅｌｙ．Ｃｏｍｐａｒｅｄｗｉｔｈｔｈｅｌａｔｅｓｔｇｙｒｏｃｏｍｐｅｎｓａｔｉｏｎａｌｇｏｒｉｔｈｍ，ｄｕｅｔｏｔｈｅａｃｃｅｌｅｒｏｍｅｔｅｒｈａｓｌｏｎｇ⁃ｔｅｒｍｓｔａｂｉｌｉｔｙａｎｄｃａｎｓｕｐｐｒｅｓｓｔｈｅｄｒｉｆｔｏｆｍａｇｎｅｔｏｍｅｔｅｒｄａｔａ．Ｔｈｅｄｒｉｆｔｄｉｓｔａｎｃｅｏｆｍａｇｎｅｔｏｍｅｔｅｒｄａｔａｉｓｒｅｄｕｃｅｄｆｒｏｍ１９．５６μＴｔｏ１．６７μＴ．Ｆｉｎａｌｌｙ，ａｓｔａｂｌｅ，ｈｉｇｈ⁃ｐｒｅｃｉｓｉｏｎｒｅａｌ⁃ｔｉｍｅｍａｇｎｅｔｏｍｅｔｅｒｃａｌｉｂｒａｔｉｏｎｉｓａｃｈｉｅｖｅｄ．Ｋｅｙｗｏｒｄｓ：ｍａｇｎｅｔｏｍｅｔｅｒｃａｌｉｂｒａｔｉｏｎ；ＩＭＵ；ｅｘｔｅｎｄｅｄＫａｌｍａｎｆｉｌｔｅｒ；ａｔｔｉｔｕｄｅｄｅｔｅｒｍｉｎａｔｉｏｎ；ｇｙｒｏｓｃｏｐｅ；ａｃｃｅｌｅｒｏｍｅｔｅｒ０㊀引言在导航定位中，确定机器人㊁飞行器等载体的姿态是十分重要的，姿态可以通俗地使用欧拉角（俯仰角㊁横滚角和姿态角）来表示，目前通常使用六轴ＩＭＵ来计算欧拉角，其中的陀螺仪感知三轴角速度值，由于重力加速度的存在，加速度计可以准确的感知横滚角和俯仰角，但六轴ＩＭＵ只能获得航向角的相对变化值，并且由于陀螺仪存在不同程度的漂移现象，所以得到的航向角也会漂移，存在不稳定的现象㊂因此往往需要添加磁力计，组成九轴ＩＭＵ来计算航向角㊂由于磁力计极易受到周围环境磁场的干扰，所以在使用过程中，往往需要先对磁力计进行校准，得到软铁干扰和硬铁干扰参数，磁力计数据在经过这些参数的处理后，才能准确的指示航向［１－３］㊂磁力计校准方法可以根据是否需要外部设备分㊀㊀㊀㊀㊀第１期李文宽等：六轴ＩＭＵ补偿的磁力计动态稳定校准１５㊀㊀为两种类型㊂一种是基于磁场数据的约束，对磁场建模并仅使用磁力计数据来计算校准参数［４－５］㊂最常用的方法是椭圆拟合方法［６］和最大和最小值方法㊂朱建良等［７］首先线性化椭球表面方程，然后分别用最小二乘法和总体最小二乘法拟合得到椭球的参数；最大和最小值的方法是在３个轴上收集磁力计的最大和最小测量值，然后计算椭球面参数，其原理类似于椭球拟合法㊂虽然这种方法可以取得很好的效果，但对磁力计数据要求很高，因此往往需要用户进行特定的操作（如绕８）来收集数据，这对用户的使用来说非常不友好，而且在某些情况下（如机器人㊁无人机）很难实现㊂不仅如此，由于这种方法不能实时运行，所以需要在磁力计使用环境改变后再次校准㊂另一种方法是使用外部设备来进行校准，最常用的是惯性测量单元（ＩＭＵ）㊂Ｍ．Ｋｏｋ等［８］将磁力计和六轴ＩＭＵ的数据建模为最大似然问题并进行求解，该方法使用来自２个不同的传感器单元实现了不错的校准效果，并且避免了某些操作的执行，但却无法实时运行㊂Ｋ．Ｈａｎ等［９］使用ＥＫＦ（扩展卡尔曼滤波器）将磁力计和陀螺仪的数据融合实现了实时校准，但由于陀螺仪的漂移，得到的磁力计数据也不是很稳定㊂Ｍ．Ｚｈｕ等［１０］通过求解均匀最小二乘问题，在陀螺仪的帮助下提出了一种有效的磁力计校准算法㊂该算法能够在一个步骤中完成磁力计与陀螺仪固有误差和磁力计本身干扰误差的计算㊂本文先通过互补滤波使用加速度修正陀螺仪数据，然后使用修正后的陀螺仪数据对磁力计进行旋转，以更准确地预测磁力计数据，完成扩展卡尔曼滤波中的状态预测过程，接着使用扩展卡尔曼滤波融合预测值和磁力计测量值，实现磁力计的动态校准㊂实现了一种稳定㊁高精度的实时磁力计校准㊂１㊀磁力计量测模型磁力计测量的磁场是使用环境中的磁场，包含了可以用于计算航向的地磁场和传感器附近的一些铁磁材料产生的磁场，所以需要对磁力计的测量值进行校准，保留地磁场信息，并以此来计算航向㊂如果没有铁磁性材料的干扰，磁力计在ｔ时刻的量测值ｈｍ，ｔ与当地的地磁场ｍｎ的关系为［６，１１－１２］：ｈｍ，ｔ＝Ｒｂｎｔｍｎ（１）式中：Ｒｂｎｔ为磁力计在ｔ时刻，由导航坐标系（ｎａｖｉｇａｔｉｏｎｆｒａｍｅ）到载体坐标系（ｂｏｄｙｆｒａｍｅ）的旋转矩阵，导航坐标系ｎ对齐于当地的重力和磁场方向，载体坐标系ｂ对齐于传感器的３个轴㊂并且旋转矩阵满足Ｒｂｎｔ＝（Ｒｂｎｔ）Ｔ㊂由此可知，理想情况下，磁力计的量测值应该位于一个球体表面，该球体的球心是原点，半径是当地地磁场强度㊂铁磁材料对磁力计测量值产生的影响可以分为硬铁干扰和软铁干扰，硬铁干扰是铁磁材料的永久性磁化引起的，通常它会在磁力计的量测值上产生一个３ˑ１的零漂ｏｈｉ㊂软铁干扰是由于铁磁材料受到外部磁场的磁化而引起的，因此取决于材料相对于局部磁场的方向，通常用一个３ˑ３的矩阵Ｃｓｉ来表示㊂结合公式（１），可以推导出一般情况下的磁力计量测公式为：ｈｍ，ｔ＝ＣｓｉＲｂｎｔｍｎ＋ｏｈｉ（２）同时，由于加工工艺等的影响，磁力计传感器的轴和ＩＭＵ的轴不能保证完全重合，因此ＩＭＵ的载体坐标系ｂ与磁力计的载体坐标系ｂｍ之间仍然有一个旋转误差Ｒｂｍｂ，因此公式（２）可以写成：ｈｍ，ｔ＝ＣｓｉＲｂｍｂＲｂｎｔｍｎ＋ｏｈｉ（３）另外，还有一些磁力计传感器本身的固有误差，这些误差也是在传感器的加工过程中确定的，每个传感器的误差值也不尽相同，这些固有误差分别为：（１）磁力计传感器三轴没有严格正交引起的非正交（ｎｏｎ⁃ｏｒｔｈｏｇｏｎａｌｉｔｙ）误差，使用３ˑ３的矩阵Ｃｎｏ来表示；（２）零漂（ｚｅｒｏｂｉａｓ）的存在会在３个测量值上产生一个固定值，使用３ˑ１的矢量ｏｚｂ来表示；（３）磁力计传感器３个轴的灵敏度不同，会对测量值产生缩放（ｓｃａｌｅ）的影响，使用３ˑ３的矩阵Ｃｓｃ来表示㊂结合公式（３），可以得到完整的磁力计量测模型：ｈｍ，ｔ＝ＣｓｃＣｎｏ（ＣｓｉＲｂｍｂＲｂｎｔｍｎ＋ｏｈｉ）＋ｏｚｂ（４）对其进行化简并添加量测噪声，得到磁力计读数的表达式为：ｈｍ，ｔ＝ＤＲｂｎｔｍｎ＋ｏ＋ｅｍ，ｔ（５）Ｄ＝ＣｓｃＣｎｏＣｓｉＲｂｍｂ（６）ｏ＝ＣｓｃＣｎｏｏｈｉ＋ｏｚｂ（７）式中：ｈｍ，ｔ为磁力计在ｔ时刻的读数；ｅｍ，ｔ是磁力计量测噪声，服从高斯分布ｅｍ，ｔＮ［０，ｄｉａｇ（σ２ｍ，ｘσ２ｍ，ｙσ２ｍ，ｚ）］，σ２ｍ，ｘσ２ｍ，ｙσ２ｍ，ｚ分别为磁力计三轴量测噪声的方差，本文中均设为（１μＴ）２，记作σ２ｍ；Ｄ是畸变矩阵㊁ｏ是偏移矢量㊂２㊀ＩＭＵ数据处理惯性测量单元（ＩＭＵ）是一种可以测量物体３个轴的角速度和加速度的传感器，通常用于感知载体的姿㊀㊀㊀㊀㊀１６㊀ＩｎｓｔｒｕｍｅｎｔＴｅｃｈｎｉｑｕｅａｎｄＳｅｎｓｏｒＪａｎ．２０２１㊀态以及惯性导航㊂加速度计和陀螺仪都可以计算姿态，但是各有优点和缺点：加速度计长期使用时计算出的姿态可信度比较高，没有累计误差，但是它对振动等干扰十分敏感，并且不能感知航向角的变化；陀螺仪对振动不敏感也可以感知航向角的变化，但是长期使用陀螺仪会产生很严重的漂移㊂鉴于加速度计和陀螺仪各自的特性，使用互补滤波对二者数据进行融合［１３－１５］㊂首先计算理想重力加速度在ｔ时刻的理论量测值ｖ，这里我门采用四元数ｑｂｎｔ来代表磁力计传感器的姿态信息：ｖ＝ｇｂ＝２（ｑ１ｑ３－ｑ０ｑ２）２（ｑ２ｑ３＋ｑ０ｑ１）ｑ２０－ｑ２１－ｑ２２＋ｑ２３éëêêêêùûúúúú（８）式中：重力加速度已进行归一化处理，ｇｂ为在载体坐标系下的重力加速度值；ｑ１㊁ｑ２㊁ｑ３和ｑ４分别为ｑｂｎｔ中的４个元素㊂之后使用归一化后的加速度计的实际量测值ａ，和理论量测值ｖ进行向量叉乘，得到陀螺仪的补偿校准值ｅ㊂ｅ＝ｖˑａ（９）然后使用ＰＩ控制器进行滤波，对陀螺仪消除漂移误差㊂只要存在误差，控制器便会持续作用，直至误差为０㊂控制的效果取决于Ｐ和Ｉ的参数，分别对应比例控制和积分控制的参数㊂ω＾ｔ＝ωｔ＋（Ｋｐｅ＋Ｋｉʏｔ０ｅｄｔ）（１０）式中：ωｔ为ｔ时刻陀螺仪的测量值；ω＾ｔ为消除误差之后的校正值；Ｋｐ和Ｋｉ分别是比例控制参数和积分控制参数㊂之后可以使用ω＾ｔ对四元数进行更新，获得实时的姿态信息，以用于下一时刻的ＩＭＵ数据处理㊂３㊀磁力计校准３．１㊀状态转移方程的建模由于磁力计和陀螺仪测量的是同一载体的姿态信息，所以二者感知到的姿态变化理论上应该是相同的，可以利用这一关系建立角速度和磁力计量测值之间的关系㊂根据旋转矩阵的相关知识，其关于时间的导数可以写为：Ｒ㊃＝Ｒωɡ（１１）该式被称为泊松公式（Ｐｏｓｓｉｏｎｓｅｑｕａｔｉｏｎ），其中ɡ为反对称矩阵算子：ωɡ＝０－ω３ω２ω３０－ω１－ω２ω１０éëêêêêùûúúúú（１２）将式（１）和式（１２）相结合，就可以得到陀螺仪数据与磁力计数据二者之间的联系：ｈｍ，ｔ＋１＝（Ｉ＋ωɡΔｔ）ｈｍ，ｔ（１３）式中：Δｔ为时刻ｔ和ｔ＋１之间的时间间隔；ω 为ｔ时刻的陀螺仪量测值，其中也不可避免的包含了量测噪声：ω ｔ＝ωｔ＋ｅｇ，ｔ（１４）式中：ωｔ是陀螺仪数据的真实值；ｅｇ，ｔ是陀螺仪量测噪声，服从高斯分布ｅｇ，ｔＮ［０，ｄｉａｇ（σ２ｇ，ｘσ２ｇ，ｙσ２ｇ，ｚ）］，σ２ｇ，ｘσ２ｇ，ｙσ２ｇ，ｚ分别为陀螺仪三轴量测噪声的方差，本文中均设为（０．１（ʎ）／ｓ）２，记作σ２ｇ㊂之后选取磁场数据ｈｍ，ｔ㊁畸变矩阵Ｄ和偏移矢量ｏ中的各个元素作为ｔ时刻的状态量，记为Ｘｔ㊂Ｘｔ＝［ｈＴｍ，ｔＤｔｏＴｔ］Ｔ（１５）式中：Ｄｔ为畸变矩阵Ｄ中的各个元素组成的矢量，Ｄｔ＝［Ｄ１１，ｔＤ１２，ｔＤ３２，ｔＤ３３，ｔ］㊂所以扩展卡尔曼滤波中的状态转移过程为：ｈｍ，ｔ＋１＝（Ｉ＋ωɡｔΔｔ）ｈｍ，ｔ（１６）Ｄｔ＋１＝Ｄｔ（１７）ｏＴｔ＋１＝ｏＴｔ（１８）将其写为统一的矩阵形式为：Ｘｔ＋１＝ＦｔＸｔ＋ωｔ（１９）Ｆｔ＝Ｉ＋ω ɡΔｔＯ３ˑ９Ｏ９ˑ３Ｉ９ˑ９éëêêêùûúúú（２０）式中：ωｔ为状态转移过程中的噪声，它的方差矩阵记为Ｑｔ：Ｑｔ＝σ２ｇｈｍ，ｔｈｍ，ｔＴΔｔ２Ｏ３ˑ９Ｏ９ˑ３Ｏ９ˑ９éëêêùûúú（２１）至此，推导完成了扩展卡尔曼滤波中的状态转移过程㊂３．２㊀量测方程的建模式（５）中，已经给出了磁力计的量测模型，量测值为ｈｍ，ｔ，但是由于状态量设为了Ｘｔ，其中不仅包含了量测值ｈｍ，ｔ，还包含了畸变矩阵Ｄ和偏移矢量ｏ，所以需要求解其雅可比矩阵，对其进行线性化㊂解得量测方程为：Ｚｔ＝ＨｔＸｔ＋ｖｔ（２２）式中：Ｘｔ为状态量；Ｚｔ为ｔ时刻状态量的测量值；ｖｔ为㊀㊀㊀㊀㊀第１期李文宽等：六轴ＩＭＵ补偿的磁力计动态稳定校准１７㊀㊀测量误差，它的方差矩阵记为Ｒｔ，等于ｅｍ，ｔ的方差矩阵ｄｉａｇ（σ２ｍ，ｘ，σ２ｍ，ｙ，σ２ｍ，ｚ）㊂Ｈｔ为对应的雅可比矩阵，它的具体形式为：㊀Ｈｔ＝Ｄｔｘｔ，１００ｘｔ，２ｘｔ，３００ｘｔ，２０ｘｔ，１０ｘｔ，３００ｘｔ，３０ｘｔ，１ｘｔ，２Ｉ３ˑ３éëêêêêùûúúúú（２３）３．３㊀扩展卡尔曼滤波根据以上内容，结合扩展卡尔曼滤波算法，推导出适用于磁场校准的ＥＫＦ公式为：预测阶段：Ｘｔ｜ｔ－１＝ＦＸｔ－１（２４）Ｐｔ｜ｔ－１＝Ｆｔ－１Ｐｔ－１ＦＴｔ－１＋Ｑｔ－１（２５）更新阶段：Ｋｔ＝Ｐｔ｜ｔ－１ＨＴｔ（ＨｔＰｔ｜ｔ－１ＨＴｔ＋Ｒｔ）－１（２６）Ｘｔ＝Ｘｔ｜ｔ－１＋Ｋｔ（Ｚｔ－ＨＸｔ｜ｔ－１）（２７）Ｐｔ＝（Ｉ－ＫｔＨｔ）Ｐｔ｜ｔ－１（２８）式中：Ｘｔ｜ｔ－１为状态量从ｔ－１时刻到ｔ时刻的一步预测值；Ｘｔ和Ｐｔ为通过ＥＫＦ算法求得的ｔ时刻的状态量估计值和状态的方差估计值；Ｋｔ为滤波增益㊂４㊀实验４．１㊀算法介绍为了对比本文提出算法在磁力计动态校准时的稳定性，分别实现了校准算法中较为经典的基于最小二乘的椭球拟合算法和目前最为新颖的仅使用陀螺仪补偿的校准算法，并将本文算法与这两种算法进行对比试验㊂４．１．１㊀基于最小二乘的椭球拟合算法椭球拟合算法是一种仅使用磁力计就可以进行校准的方法，不需要其他外部设备㊂通过充分旋转传感器来获取广泛分布在椭球表面的磁力计数据，通过将椭球方程线性化后，使用最小二乘法求解椭球参数，从而获得当地磁场的校准参数，并对磁力计数据进行校准㊂但是这种方法需要用户旋转传感器来采集数据，使用并不是很方便，并且当磁场环境改变时，需要重新采集数据进行校准，不能实时动态校准㊂并且由于仅使用了磁力计数据，磁力计的噪声也难以抑制，影响磁力计数据的质量㊂４．１．２㊀仅使用陀螺仪补偿的校准算法仅使用陀螺仪补偿的校准算法是通过陀螺仪数据对磁力计数据进行旋转预测，然后使用扩展卡尔曼滤波对预测值和量测值进行融合㊂这种方法虽然实现了实时的动态校准，且对数据分布的要求比较低，但是由于陀螺仪数据没有预先进行处理，存在较为严重的漂移现象，所以磁力计数据并不稳定，同样存在漂移现象㊂４．２㊀实验对比本文中使用九轴ＩＭＵ模块ＬＭＰＳ－Ｂ２（如图１所示）来采集磁力计㊁陀螺仪和加速度计的原始数据，模块的采样频率是１００Ｈｚ，并通过蓝牙将数据实时传输到电脑客户端㊂图１㊀九轴ＩＭＵ模块ＬＭＰＳ－Ｂ２为保证实验效果，数据采集时要求传感器一直处于同一磁场环境下㊂先充分旋转传感器，使得数据的分布满足椭球拟合算法的需求，之后将传感器静止１０ｍｉｎ，采集静止数据㊂对于椭球拟合算法，由于其不能实时校准数据，所以将旋转时的数据输入到算法中计算校准参数，之后用这些校准参数对静止时数据进行校准㊂而仅使用陀螺仪补偿的校准算法和本文中的校准算法可以实时输出校准后的数据㊂图２是３种算法的校准效果，图中实点数据点是原始数据，叉点数据点是算法校准后的数据（每隔１０个数据画一个点），可以发现由于软铁干扰和硬铁干扰的存在，原始数据所在的椭球并不在原点位置处，这也是磁力计数据校准的意义所在㊂经过３种算法校准后，磁力计的数据可以很好的恢复到理想球体附近，说明３种算法都达到了不错的校准效果㊂（ａ）椭球拟合算法㊀㊀（ｂ）仅使用陀螺仪补偿的算法㊀（ｃ）本文算法图２㊀３种算法的校准效果㊀㊀㊀㊀㊀１８㊀ＩｎｓｔｒｕｍｅｎｔＴｅｃｈｎｉｑｕｅａｎｄＳｅｎｓｏｒＪａｎ．２０２１㊀接下来比较各算法在磁力计校准的稳定性上的差异㊂首先来对比基于最小二乘的椭球拟合算法和本文算法在磁场校准时的稳定性，图３中画出了１０ｍｉｎ的静止时间内，磁力计传感器ｘ轴数据的情况，图中直线是椭球拟合算法校准后的磁力计数据，点是本文算法校准后的数据㊂可以发现，由于磁力计本身量测时存在噪声，所以数据的波动是很大的，而经过椭球拟合算法校准后的数据，虽然能够剔除软铁干扰和硬铁干扰，但是不能消除这一部分噪声，导致校准后的数据仍存在很大的波动，大概在２μＴ左右，而本文算法融合了加速度计和陀螺仪的数据来对磁力计数据进行校准，可以很好的降低磁力计数据的噪声波动，仅为０．５μＴ左右，提高了数据的可信度和稳定性㊂图３㊀ｘ轴的磁力计数据其他轴上的效果也是如此，图４是磁力计３个轴上静止数据的箱型图，图５是ｘｚ平面上的数据以及置信度为９５％的置信椭圆，可以发现每个轴上，本文算法校准后的噪声波动都小于椭球拟合算法㊂（ａ）磁力计ｘ轴数据㊀（ｂ）磁力计ｙ轴数据㊀（ｃ）磁力计ｚ轴数据图４㊀各轴数据的箱型图图５㊀ｘ轴和ｚ轴的磁力计数据和置信椭圆同时，还采集了多组数据进行实验，并计算了静止时三轴数据上的协方差矩阵，如表１所示，从表中可以发现本文算法校准后数据的方差普遍小于椭球拟合算法㊂表１㊀各数据集的协方差矩阵椭球拟合算法本文算法１０．２４－０．１４０．０９－０．１４０．５５－０．１１０．０９－０．１１０．２６éëêêêùûúúú０．１４－０．１４０．０９－０．１４０．２１－０．１１０．０９－０．１１０．１３éëêêêùûúúú２０．３４０．１００．１２０．１００．４５－０．０８０．１２－０．０８０．２８éëêêêùûúúú０．１６０．１００．１２０．１００．１７－０．０８０．１２－０．０８０．０９éëêêêùûúúú３０．５６－０．１８０．０９－０．１８０．６７－０．１６０．０９－０．１６０．３８éëêêêùûúúú０．２２－０．１８０．０９－０．１８０．３７－０．１６０．０９－０．１６０．１７éëêêêùûúúú㊀㊀接下来比较仅使用陀螺仪补偿的磁场校准算法和本文算法，由于二者都可以实时的进行磁场校准，所以直接比较２个算法输出的参数即可㊂为了更加直观的比较两种算法的稳定性，本文计算了从静止开始，每一个数据点到静止起始数据点的距离，并以此来定量的表示磁力计数据的漂移情况，距离越大，漂移越严重，稳定性越差㊂由于两种算法都用到了陀螺仪的数据，而陀螺仪本身就已经存在了一定的漂移现象，为了定量的分析不同陀螺仪漂移下，两种算法的稳定性㊂首先计算了陀螺仪三轴的漂移值，并在陀螺仪数据中将其剔除，然后人工添加不同级别的漂移，并比较各个情况下两种算法的漂移距离㊂如图６所示，分别在陀螺仪数据上添加了０．１㊀㊀㊀㊀㊀第１期李文宽等：六轴ＩＭＵ补偿的磁力计动态稳定校准１９㊀㊀０．５（ʎ）／ｓ的不同级别的零漂，然后将其输入两种算法中进行计算，图中２条直线分别是本文算法计算得到的磁力计漂移距离和陀螺仪补偿算法的漂移距离，可以明显的发现，本文算法在减少磁力计数据漂移㊁提高校准稳定性上有着良好的效果㊂图６㊀两种算法的漂移距离给陀螺仪３个测量轴添加了０．３（ʎ）／ｓ的零漂，并验证本文算法对漂移的抑制效果㊂由于加速度计具有长期稳定性，加入了加速度计的辅助后，本文算法的校准数据在１０ｍｉｎ内仅漂移了１．６７μＴ，优于陀螺仪补偿算法的１９．５６μＴ㊂５㊀结束语本文先通过互补滤波使用加速度修正陀螺仪数据，然后使用修正后的陀螺仪数据对磁力计进行旋转，以更准确地预测磁力计数据，完成扩展卡尔曼滤波中的状态预测过程，接着使用扩展卡尔曼滤波融合预测值和磁力计量测值，实现磁力计的动态校准㊂实验表明，相比于传统的椭球拟合算法，本文算法可以降低磁力计数据的噪声波动，二者的噪声波动分别为２μＴ和０．５μＴ；相较于最新的陀螺仪补偿算法，由于加速度计具有长期稳定性，可以抑制磁力计数据的漂移现象，磁力计数据的漂移距离由１９．５６μＴ降低到了１．６７μＴ㊂实现了一种稳定㊁高精度的实时磁力计校准㊂本文仅对磁力计数据进行了校准，并未继续求解航向等姿态信息，后续可以将校准后的磁力计数据用于姿态结算等多种需要磁场信息的算法当中㊂参考文献：［１］㊀赵瑜，周波，綦俊峰，等．基于双阶卡尔曼滤波的九轴姿态融合算法研究［Ｊ］．电子世界，２０１９（７）：９８－９９．［２］㊀郭英，孙玉曦，姬现磊，等．基于手机传感器和互补滤波的行人航向解算［Ｊ］．测绘通报，２０１９（９）：１８－２１．［３］㊀汪俊．基于惯性传感器的动作捕捉系统研究与设计［Ｄ］．合肥：中国科学技术大学，２０１５．［４］㊀杨宾峰，樊博宇，胥俊敏，等．基于最小二乘的地磁场测量误差补偿技术［Ｊ］．空军工程大学学报（自然科学版），２０１７，１８（６）：３４－３９．［５］㊀秦赓，管雪元，李文胜．基于椭球补偿的三维载体磁场误差补偿方法［Ｊ］．电子测量技术，２０１８，４１（２）：３７－４０．［６］㊀孙伟，杨一涵，王野．基于椭球拟合的磁力计误差校正方法研究［Ｊ］．传感技术学报，２０１８，３１（９）：１３７３－１３７６．［７］㊀朱建良，王兴全，吴盘龙，等．基于椭球曲面拟合的三维磁罗盘误差补偿算法［Ｊ］．中国惯性技术学报，２０１２，２０（５）：５６２－５６６．［８］㊀ＫＯＫＭ，ＳＣＨＯＮＴＢ．Ｍａｇｎｅｔｏｍｅｔｅｒｃａｌｉｂｒａｔｉｏｎｕｓｉｎｇｉｎｅｒｔｉａｌｓｅｎｓｏｒｓ［Ｊ］．ＩＥＥＥＳｅｎｓｏｒｓＪｏｕｒｎａｌ，２０１６，１６（１４）：５６７９－５６８９．［９］㊀ＨＡＮＫ，ＨＡＮＨ，ＷＡＮＧＺ，ｅｔａｌ．ＥｘｔｅｎｄｅｄＫａｌｍａｎｆｉｌｔｅｒ⁃ｂａｓｅｄｇｙｒｏｓｃｏｐｅ⁃ａｉｄｅｄｍａｇｎｅｔｏｍｅｔｅｒｃａｌｉｂｒａｔｉｏｎｆｏｒｃｏｎｓｕｍｅｒｅｌｅｃｔｒｏｎｉｃｄｅｖｉｃｅｓ［Ｊ］．ＩＥＥＥＳｅｎｓｏｒｓＪｏｕｒｎａｌ，２０１６，１７（１）：６３－７１．［１０］㊀ＺＨＵＭ，ＷＵＹ，ＹＵＷ，ｅｔａｌ．Ａｎｅｆｆｉｃｉｅｎｔｍｅｔｈｏｄｆｏｒｇｙｒｏ⁃ｓｃｏｐｅ⁃ａｉｄｅｄｆｕｌｌｍａｇｎｅｔｏｍｅｔｅｒｃａｌｉｂｒａｔｉｏｎ［Ｊ］．ＩＥＥＥＳｅｎｓｏｒｓＪｏｕｒｎａｌ，２０１９，１９（１５）：６３５５－６３６１．［１１］㊀ＣＨＯＥＮ，赵红宇，仇森，等．低成本ＭＥＭＳ磁力计校正方法研究［Ｊ］．大连理工大学学报，２０１８，５８（１）：１０５－１１０．［１２］㊀李勇，刘文怡，李杰，等．基于椭球拟合的三轴磁传感器误差补偿方法［Ｊ］．传感技术学报，２０１２，２５（７）：９１７－９２０．［１３］㊀陈孟元，谢义建，陈跃东．基于四元数改进型互补滤波的ＭＥＭＳ姿态解算［Ｊ］．电子测量与仪器学报，２０１５，２９（９）：１３９１－１３９７．［１４］㊀张承岫，李铁鹰，王耀力．基于ＭＰＵ６０５０和互补滤波的四旋翼飞控系统设计［Ｊ］．传感技术学报，２０１６，２９（７）：１０１１－１０１５．［１５］㊀孙金秋，游有鹏，傅忠云．基于共轭梯度法和互补滤波相结合的姿态解算算法［Ｊ］．传感技术学报，２０１４，２７（４）：５２４－５２８．作者简介：李文宽（１９９５），硕士，研究领域为ＶＩＯ㊁ＩＭＵ和移动机器人室内导航㊂Ｅ⁃ｍａｉｌ：ｌｉｗｅｎｋｕａｎ１８＠ｍａｉｌｓ．ｕｃａｓ．ａｃ．ｃｎ通信作者：蔡浩原（１９７７），研究员，博士，研究领域为ＭＥＭＳ传感器及其微系统㊁无线工业物联网传感器和移动机器人室内导航㊂Ｅ⁃ｍａｉｌ：ｈｙｃａｉ＠ｍａｉｌ．ｉｅ．ａｃ．ｃｏｍ。

地球磁场在减弱的证据

地球磁场在减弱的证据英文回答：Evidence of Earth's Weakening Magnetic Field.The Earth's magnetic field, also known as the geomagnetic field, is generated by the movement of molten iron in the outer core of the planet. This magnetic field is crucial for protecting the Earth from harmful solar radiation and maintaining a stable climate. However, there is mounting evidence that the Earth's magnetic field is weakening.One piece of evidence is the observation of the South Atlantic Anomaly (SAA). The SAA is an area in the South Atlantic Ocean where the Earth's magnetic field is significantly weaker than in other regions. Satellites passing through this anomaly experience higher levels of radiation, which can affect their electronic systems. This anomaly has been expanding over the past few decades,indicating a weakening of the Earth's magnetic field.Another piece of evidence comes from studies of ancient rocks. Rocks contain tiny magnetic minerals that align with the Earth's magnetic field at the time of their formation. By analyzing these rocks, scientists can determine the strength and direction of the Earth's magnetic field in the past. These studies have revealed that the Earth's magnetic field has been weakening over the past few centuries.Furthermore, researchers have found that the rate of decline in the Earth's magnetic field has been accelerating in recent years. This rapid decline suggests that the weakening of the magnetic field is not a gradual process but rather a more significant and concerning phenomenon. If this trend continues, it could have significantimplications for our planet.The weakening of Earth's magnetic field has several potential consequences. One of the most significant is the increased exposure to solar radiation. The magnetic field acts as a shield, deflecting charged particles from the Sunaway from the Earth. Without a strong magnetic field, more solar radiation would reach the Earth's surface, increasing the risk of skin cancer and other health issues.Additionally, a weakened magnetic field could have implications for navigation systems that rely on magnetic compasses. The accuracy of compasses could be compromised, leading to errors in navigation. This could be particularly problematic for ships and aircraft that heavily rely on magnetic compasses for direction.In conclusion, there is compelling evidence that the Earth's magnetic field is weakening. The South Atlantic Anomaly, studies of ancient rocks, and the accelerating rate of decline all point to this concerning phenomenon. The implications of a weakened magnetic field range from increased exposure to solar radiation to potential navigation issues. It is crucial for scientists to continue monitoring and studying this phenomenon to better understand its implications for our planet.中文回答：地球磁场减弱的证据。

(整理)镇流器概述[]

镇流器概述一、镇流器Ballast1 镇流器的功能镇流器是气体放电灯工作时必不可缺的配套附件，其功能：1 产生高压，起辉灯管；2 灯管起辉后起镇流（限流）作用，使灯管正常稳定地工作。

气体放电灯都有较高的启动电压和低放电维持电压。

当灯通过高压启动后，电压下降，电流加大，如不加限制，灯电流将不断加大直至使灯烧毁，所以必需在放电灯的点灯回路中串接一个与灯的类型、规格匹配的镇流器，提供使灯启动的高启动电压，并限制灯电流使之稳定在所规定的范围。

2 镇流器的分类电感镇流器和电子镇流器3 电子镇流器的分类电子镇流器的基本组成：交流电压整流电路，高频振荡逆变电路。

电子镇流器的附属电路：EMI滤波，PFC（无源Passive，有源Active）电子镇流器的输出电路：直接输出（串連諧振），变压器隔离输出（并联谐振）供电电源电压：单电源：100Vac，120Vac，220Vac，230Vac，277Vac，305Vac，480Vac等等全电压范围：90Vac ～ 264Vac，108Vac ～ 305Vac（120V-10% ～ 277V+10%）供电电源频率：单一频率：50Hz，60Hz通用频率：50/60Hz灯管数量:1灯，2灯，3灯，4灯等灯管连接:串连连接，并联连接，串并联混合连接灯管功率:额定功率，实际功率启动方式:瞬时启动Instant Start，预热启动Preheat start，快速启动Rapid Start调光方式非调光，连续调光，分段调光4 电子镇流器的主要性能启动方式（影响开关次数）：IS ，RS ，PS瞬时（立即）启动Instant Start （出现辉光电流的时间t1到灯电流达到稳定值的90％的时间t3，不大于0.1 秒）；快速启动Rapid Start （出现阴极预热电压的时间t1到灯电流达到稳定值的10％的时间t2至少0.5 秒，灯电流达到稳定值的10％的时间t2到灯电流达到稳定值的90％的时间t3，不大于0.1 秒）；预热启动Preheat （Program ）Start 。

各个定律

达西定律Darcy’s Law反映水在岩土孔隙中渗流规律的实验定律。

由法国水力学家H.-P.-G.达西在1852～1855年通过大量实验得出。

其表达式为Q=KFh/L式中Q为单位时间渗流量，F为过水断面，h为总水头损失，L为渗流路径长度，I=h/L为水力坡度，K为渗流系数。

关系式表明，水在单位时间内通过多孔介质的渗流量与渗流路径长度成反比，与过水断面面积和总水头损失成正比。

从水力学已知，通过某一断面的流量Q等于流速v与过水断面F的乘积，即Q＝Fv。

或，据此，达西定律也可以用另一种形式表达v=KIv为渗流速度。

上式表明，渗流速度与水力坡度一次方成正比。

说明水力坡度与渗流速度呈线性关系，故又称线性渗流定律。

达西定律适用的上限有两种看法：一种认为达西定律适用于地下水的层流运动；另一种认为并非所有地下水层流运动都能用达西定律来表述，有些地下水层流运动的情况偏离达西定律，达西定律的适应范围比层流范围小。

这个定律说明水通过多孔介质的速度同水力梯度的大小及介质的渗透性能成正比。

这种关系可用下列方程式表示：V＝K［（h2－h1）÷L］。

其中V 代表水的流速，K 代表渗透力的量度(单位与流速相同, 即长度/时间)，（h2－h1）÷L 代表地下水水位的坡度（即水力梯度）。

因为摩擦的关系，地下水的运动比地表水缓慢得多。

可以利用在井中投放盐或染料，测定渗流系数和到达另一井内所需的时间。

达西定律只适用于低流速条件。

3.达西（Dracy）渗透定律(1)达西渗透实验与达西定律地下水在土体孔隙中渗透时，由于渗透阻力的作用，沿程必然伴随着能量的损失。

为了揭示水在土体中的渗透规律，法国工程师达西(H.darcy)经过大量的试验研究，1856年总结得出渗透能量损失与渗流速度之间的相互关系即为达西定律。

图2-3 达西渗透实验装置图达西实验的装置如图2-3所示。

装置中的①是横截面积为A的直立圆筒，其上端开口，在圆筒侧壁装有两支相距为l 的侧压管。

英文定义

Glossary of Inventory and Materials Management Definitionsby the Supply-Chain Inventory Management SIGA product (or item) See ABC ClassificationABC Analysis A form of Pareto analysis applied to a group of products in order to apply selective inventory management controls. The inventory value for eachitem is obtained by multiplying the annual demand by unit cost and theentire inventory is then ranked in descending order of cost. However,the classification parameter can be varied; for example, it is possible touse the velocity of turnover rather than annual demand value.ABC Classification The classification of inventory, after ABC analysis, into three basicgroups for the purpose of stock control and planning. Although furtherdivisions may be established, the 3 basic categories are designated A, Band C as follows:A Items - An item that, according to an ABC classification, belongs to asmall group of products that represents around 75-80% of the annualdemand, usage or production volume, in monetary terms, but onlysome 15-20% of the inventory items. For the purpose of stock controland planning, the greatest attention is paid to this category ofA-products. A items may also be of strategic importance to the businessconcerned.B Items - An intermediate group, representing around 5-10% of theannual demand, usage or production value but some 20-25% of thetotal, that is paid less management attention.C Items - A product which according to an ABC classification belongs tothe 60-65% of inventory that represents only around 10-15% theannual demand, usage or production value. Least attention is paid tothis category for the purpose of stock control and planning andprocurement decisions for such items may be automated.Active Inventory Any item or element of inventory which has been used or sold within a given periodAggregate Inventory Management The size of many inventories requires that they be broken down into groupings for the purpose of control. Aggregated inventory is the further collection of these groupings into a single entity to enable the establishment of operating policies, key performance indicators, targets and reports. Aggregate Inventory Management enables such things as the overall level of inventory desired to be established and then appropriate controls implemented to ensure that individual operating decisions achieve that goal, at optimum cost.Allocated Stock A part that has been reserved, but not yet withdrawn or issued fromstock, and is thus not available for other purposesAll-Time Order The last order for a particular product in the last phase of its life cycle.This order is of such a size that the stock provided will satisfy allexpected future demand (see all time requirement below) for theproduct concerned. Sometimes known as a life of type order.All-Time Requirement The total requirement for a particular product to be expected in the future. Normally used for products in the last phase of their life cycles, when production is (nearly) stopped.All-Time Stock The stock resulting from the assessment of an all-time requirement and delivery of an all-time order. If necessary, controls can be set for suchstock to avoid consumption of items for reasons over and above thosefor which usage was predicted.Anticipation Stock Inventory held in order to be able to:Satisfy a demand with seasonal fluctuations with a production level thatdoes not fluctuate at all or that varies to a lesser extent than thedemandCope with erratic production or deficiencies in production capacity Availability The primary measure of system performance relating to the expectedpercentage of the supported system that will be available at a randompoint in time and not out of service for lack of spares.Available Stock The stock available to service immediate demandAvailable to Promise (ATP) The uncommitted portion of a company’s inventory and planned production, maintained in the master schedule to support customer order promising. The ATP quantity is the uncommitted inventory balance in the first period and is normally calculated for each period in which an MPS receipt is scheduled. In the first period, ATP includeson-hand inventory less customer orders that are due and overdue.B Product (or item) See ABC ClassificationBackflushing The deduction from inventory, after manufacture, of the componentparts used in a parent by exploding the bill of materials by theproduction total of parents producedBackorder A customer demand for which no stock is available and where thecustomer is prepared to wait for the item to arrive in stockBeyond Economic Repair (BER) Where the projected cost of repair, normally for a repairable or rotable item, exceeds a management set percentage of the replacement value of the item concernedBar Code See Linear Bar CodeBatch Number A code used to identify the specific production point, for a product or an assembly, in a manufacturing or assembly processBill of Material A listing of components, parts, and other items needed to manufacturea product, showing the quantity of each required to produce each enditem. A bill of material is similar to a parts list except that it usuallyshows how the product is fabricated and assembled. Also called aproduct structure record, formula, recipe, or ingredients list.Buffer Stock See Safety StockBuild Stock See Anticipation StockBuild to Order See Make to OrderC-Product (or item) See ABC ClassificationCategory Management The management of groups of products that are interchangeable, or substitutable, in meeting consumer needs as opposed to the traditional concentration on individual products and brandsCo-Managed Inventory A support arrangement similar to Vendor Managed Inventory but where replacement orders for the vendor-owned stock are agreed by the user prior to deliveryComponent A part, ingredient, or subassembly that is both a component to a higher level part, and a parent part to other componentsComponent Part Raw material, ingredient, part, or subassembly that goes into a higher level assembly, compound, or other partConsignment Stock The stock of goods held by an external customer which is still theproperty of the supplier but for which payment is only made when stockis sold or used by the customerConsumable A classification of stock used to describe items or products that aretotally consumed in use eg paper, oil, grease etcContingency Stock Stock held to cover potential system failure situations which can bemathematically modeledContinuous Improvement (CI) A term that describes the many management practices and techniques used to find and eliminate waste and to general improvements in business processes, quality or costs"Control Group" Cycle Counting The repeated physical inventory taking of a small "control group" of parts, in the same locations, within a very short time frame to verify the design of a new inventory process. It is the only form of cycle counting not truly used to measure inventory record accuracy.Cycle Counting Cycle counting is the physical counting of stock on a perpetual basis,rather than counting stock periodically. A cycle is the time required tocount all items in the inventory at least once. The frequency of cyclecounting can be varied to focus management attention on the morevaluable or important items or to match work processes. Some of thesystems used are:ABC system with the highest count frequency for items with the highestannual usage valueReorder system when stocks are counted at the time of orderReceiver system with counting when goods are receivedZero balance system to count items when a backorder situation isreached to confirm that no stock is heldTransaction system where stocks are counted after a specified numberof transactionsCycle Stock See Working StockDe-Coupling Stock Inventory accumulated between dependent activities in the goods flow to reduce the need for completely synchronised operationsDeduct Point The point in the production process up to which all the parts assumed to have been used (as defined in the bill of material) are "backflushed",(automatically deducted) from the inventory records. Also seeBackflushing.Demand Forecast See Forecast DemandDemandSatisfaction RateSee Fill RateDenomination ofQuantitySee Unit of MeasureDependent Demand A classification used in inventory control where the demand for one item has a direct mathematical relationship with the demand for anotherhigher level or parent component and where the demand for that item isultimately dependent on the demand for the higher level or parent itemDeterministic Inventory Control Models An inventory control system where all the variables and parameters used are known, or can be calculated with certainty. The rate of demand for items, and the associated inventory costs, are assumed to be known with assurance and the replenishment lead time is assumed to be constant and independent of demand.Distribution Requirement Planning DRPI The function of determining the need to replenish inventory at branch warehouses over a forward time period. A time-phased order point approach is used where planned orders at branch warehouse level are exploded via MRP logic to become gross requirements on the supplying source enabling the translation of inventory plans into material flows. In the case of multi-level distribution networks, this explosion process can continue down through the various levels of regional warehouses, master warehouse, factory warehouse etc and become input to the master production schedule.Distribution Resource Planning DRPII The extension of MRP into the planning of the key resources contained in a distribution systemEconomic Order Interval (EOI) In fixed order interval systems, the interval between orders that will minimise the total inventory cost, under a given set of circumstances, obtained by trade off analysis between the cost of placing an order and the cost of holding stockEconomic Order Quantity (EOQ) In fixed order quantity systems, the size of an order that minimises the total inventory cost, under a given set of circumstances, obtained by trade off analysis between the cost of placing an order and the cost of holding stockEconomic Stock The sum of the physical stock and the goods ordered but not yetreceived, minus the goods sold but not yet delivered for which acompany carries risk in respect of a drop in price and unmarketability Effective Stock The sum of the physical stock of a particular product and the quantity of that product ordered for a particular period, but not yet receivedEfficient Consumer Response (ECR) An initiative whereby elements of the supply chain work together to fulfill consumer wishes better, faster and at less costElectronic Commerce (E Commerce) A way to execute transactions and share information with other businesses, consumers or with government by using computer and telecommunication networks, including the InternetElectronic Data Interchange (EDI) The computer to computer exchange of structured data for automatic processingEnterprise Requirement Planning (ERP) A further extension of MRP II whereby a single system embraces and integrates all aspects of business operations into a single database applicationEuropean Article Numbering (EAN) An international standard of product identification used in the grocery and retail areas of businessExcess Stock Any quantity of inventory, either held or on order, which exceeds known or anticipated forward demand to such a degree that disposal actionshould be consideredFamily Group A group of related products for which demand can be aggregated inorder to assess overall demand for the material or parts which make upthe family group productsFill Rate An item-based measurement that shows the percentage of demandsthat were met at the time they were placed. Fill rate only measures whathappens when demands occur.Finished Goods Inventory to which the final increments of value have been addedthrough manufacturingFinished Goods Stock Stock that is available for supply to an external consumer, including items that have been supplied but not invoiced to an external consumerFirst-in, First-out (FIFO) 1. Stock Valuation - The method of valuing stocks which assumes that the oldest stock is consumed first and thus issues are valued at the oldest price.2. Stock Rotation - The method whereby the goods which have been longest in stock are delivered (sold) and/or consumed first.First Pick Ratio During order picking, the percentage of orders or lines for which 100% completion was achieved from the primary location or picking face.Fixed Order Interval An inventory control system for which a maximum stock level has been calculated based on usage during the lead-time and order interval. Stock is reviewed at specified time periods and subsequent order size equates to the difference between the maximum stock level and the current inventory position. Thus, the order size will vary according to usage between reviews.Fixed Order Quantity (Fixed Order Size) An inventory control system where stock is reviewed continuously and, whenever the inventory falls to a predetermined point, an order for a fixed quantity of stock is generatedForecast Demand The prediction, projection or estimation of expected demand over aspecified future time periodFree Stock See Available StockGUS Classification A classification of products into three categories for the benefit of goods flow control and stock control, based on a products area of applicationwithin a product division.G = General products that may be required in several main articlegroups or operations centres and are administered centrally in thedivisionU = Unique products that are used uniquely in one main article group oroperations centre but in several of its products, and administered locallyin the divisionS = Specific products that are used exclusively in one higher levelproduct, and whose procurement is effected per individual order Holding Cost The cost associated with holding one unit of an item in stock for oneperiod of time incorporating elements to cover: Capital costs for stock;Taxes; Insurance; Storage; Handling; Administration; Shrinkage;Obsolescence; Deterioration.In Process Goods Partially completed final products that are still in the production process either as an accumulation of partially completed work or the queue ofmaterial awaiting further processingInactive Inventory Stock of items that have not been used for a defined periodIndependent Demand A classification used in inventory control systems where the demand for any one item has no relationship with the demand for any other item and variations in demand occur because of random influences from the market placeIntermediate Product A product for which independent demand can exist and for which there is also demand as part of another higher level product eg a single can and a multi-can pack or a sub-assembly spare and the major assembly of which it forms partIntermediate Stock See Decoupling StockInventory A term used to describe:All the goods and materials held by an organisation for future sale or useA list of items held in stockInventory Control Consists of all the activities and procedures used to control and maintain the right amount of each item in stock or to provide the required level ofservice at minimum costInventory Modelling The evaluation of alternative inventory design characteristics or inventory parameters using analytical or simulation processes to assist management decisionsInventory Policy A statement of a company’s goals and approach to inventorymanagementInventory Process Any business process that involves inventory. Includes the receiving of parts, putting them away, and their storage, withdrawal, issue, andmovement through work-in process, while simultaneously tracking theirmovement and maintaining records of those events and their effects. Inventory Records Records that reflect how much and what kind of inventories a company has on hand, committed (allocated) to work in process, and on orderInventoryShrinkageLosses resulting from scrap, deterioration, pilferage, etcInventory Usage The value of the number of units, or quantity, of an inventory item(stock usage) consumed over a period of timeInventory Value The value of inventory at either cost or market value. The value of the inventory is usually computed on a First In First Out (FIFO), Last In FirstOut (LIFO) or average cost basis.Issue List A document that states all the parts to be issuedIssue Tickets An authorisation to withdraw allocated stock items from the stockroom.When presented to the stockroom, they can be exchanged for the partsdesignated.Issuing Documents The physical documents that communicate specifically how much ofwhat needs to be issued to where. Issue lists, issue tickets, and issuedecks are all forms of issuing documents.Item See Stock Keeping Unit (SKU)Item Number See Part NumberJust-in-Time JIT A dependent demand inventory control philosophy which viewsproduction as a system in which all operations, including the delivery ofmaterials needed for production, occur just at the time they are needed.Thus, stocks of material are virtually eliminated.Kanban A simple control system for coordinating the movement of material tofeed the production line. The method uses standard containers or lotsizes with a single card attached to each. It is a pull system in whichwork centres signal with a card that they wish to withdraw parts fromfeeding operations or vendors. Loosely translated from Japanese, theword "Kanban' means literally means "billboard' or "sign". The term isoften used synonymously for the specific scheduling system developedand used by Toyota Corporation in Japan.Kit A number of separate Stock Keeping Units that are supplied or used as one item under its own Part NumberLast-in, First Out (LIFO) 1. Stock Valuation. The method of valuing stocks which assumes that all issues or sales are charged at the most current cost but stocks are valued at the oldest cost available. 2. Stock Rotation. The method whereby the goods which the newest goods in stock are delivered (sold) and/or consumed first.Lead Time See Purchasing Lead TimeLeakage See ShrinkageLifed Item A consumable or repairable product for which the manufacturer hasspecified a finite life in either some form of time period or in a number ofcycles or activities.Lineside Warehouse A supplier warehouse positioned as close as possible to the production location to facilitate Just In Time manufacture.Linear Bar Code A method of automatic identification using a series of light spaces anddark bars differing densities, in standard formats, to enable a computerto read data and letters accurately without keyboard entry.Location Checking The systematic physical checking of warehouse stock against locationrecords to ensure location accuracy.Logistics The time-related positioning of resources to meet user requirements. Lot Number The allocation of a unique number, to one or more of a product duringmanufacture or assembly, to provide traceability.Lost Sales A customer demand for which no stock is available and where thecustomer is not prepared to wait for the item to arrive in stock but goesto another supplier.Material Requirements Planning (MRP I) A system to support manufacturing and fabrication organisations by the timely release of production and purchase orders using the production plan for finished goods to determine the materials required to make the product. Orders for dependent demand items are phased over time to ensure that the flow of raw materials and in-process inventories matches the production schedules for finished products. The 3 key inputs are:The master production schedule.Inventory status records.Product structure records.Manufacturing Resource Planning (MRP II) A method for the effective planning of all the resources of a manufacturing company. Ideally it addresses operational planning in units, financial planning in money, and has a simulation capability to answer what if questions. It is made up of a variety of functions, each linked together: business planning, master (or production) planning, master production scheduling, material requirements planning, capacity requirements planning and the execution systems for capacity and priority. Outputs from these systems would be integrated with financial reports such as the business plan, purchase commitment report, shipping budget, stock projections in money etc. Manufacturing resource planning is a direct out-growth and extension of material requirements planning (MRP-1).Make to Order A manufacturing or assembly process established to satisfy customer demand only after an order has been placed.Materials Management The planning, organisation and control of all aspects of inventory embracing procurement, warehousing, work-in-progress, shipping, and distribution of finished goods.Matrix Bar Code See Two Dimensional Bar CodeMaximum Stock The upper limit, expressed in quantitative, financial or time-basedterms, to which the stock of an item should normally be allowed to rise. Maximum OrderQuantityAn order quantity which, in principle, must not be exceeded. Minimum Order The smallest order quantity which, in principle, is allowed.Minimum Stock A control limit within a stock control system which could indicate thepoint at which an order should be placed, or indicate if stocks are toolow, for a specific item.Obsolete Stock Stock held within an organisation where there is no longer anyorganisational reason for holding the stockObsolescent Stock Parts which have been replaced by an alternative but which may still be used until stock is exhausted.Off the ShelfSatisfactionSee Fill RateOn-hand Balance The quantity of an item shown in the inventory records as beingphysically in stock.Opening Stock The stock of an item at the beginning of an inventory accounting period of time.Order Lead Time The total internal processing time necessary to transform areplenishment quantity into an order and for the transmission of thatorder to the recipient.Order Picking Collecting items from a storage location to satisfy a shop or customerorder.Order Point Inventory System An inventory control system for independent demand items where a reorder requirement is generated and sent to a supplier when the on-hand inventory balance reaches a specified level.Parent Part Any finished goods, end item, or part that is mixed, fabricated,assembled, stirred, or blended from one or more other components. Pareto Principle The heuristic rule which states that where there is a large number ofcontributors to a result, the majority of the result is due to a minority ofthe contributors.. Sometimes known as the 80/20 rule) which statesthat, in many cases, approximately 80% of the turnover (stock etc.) canbe ascribed to approximately 20% of the customers, articles or orders.The actual ratio in a particular case can be determined by ranking thecustomers and products etc. in order of magnitude and then calculatingwhat percentage of the turnover (stock etc.) corresponds to 10%, 20%30% etc. of the customer and products etc. The basis of ABC analysis. Part Number A unique identification number allocated to a specific part either by the manufacturer or user of the part.Perpetual Inventory System An inventory control system where a running record is kept of the amount of stock held for each item. Whenever an issue is made, the withdrawal is logged and the result compared with the re-order point for any necessary re-order action.Periodic Inventory An inventory control system classification for independent demanditems where the number of items held is reviewed at a fixed timeinterval and the size of any resultant order depends on the stock onhand at the time of the review.Pick Face The primary location in a warehouse at which order picking, of less than pallet loads, is undertaken.Picking List An output from an inventory control system designating those items, by part number, description and quantity, to be picked from stock to satisfycustomer demand.Pipeline Stocks The products which are currently being moved from one location toanother.Probabilistic (or Stochastic) Inventory Control Models An inventory control system where all the variables and parameters used are treated as random variables. It is assumed that the average demand for items is approximately constant over time and that it is possible to state the probability distribution of the demand, particularly during the lead time for replenishment.Product Group See Family GroupProduction Lead Time The time taken to manufacture or produce an item after an external order has been received until the item is available for packing.Purchasing Price See Unit CostPull System A system where orders for an end item are pulled through the facility to satisfy demand for the end item. An examples of pull system is the JITKanban process.Purchasing Lead Time (PLT) The length of time between the decision to purchase an item and its actual addition to stock.Purchase Price See Unit CostPurchasing Lead Time (PLT) The total length of time between the decision to purchase an item and its availability for dispatch from the supplier concerned (that is, the sum of the order lead-time, the production lead time and any time necessary for packing or preparation for dispatch of a specific order).Push System A system where orders are issued for completion by specified due dates, based on estimated lead-times, or where the flow of material in aproduct structure is controlled and determined by the lower levels. Put Away Rules The internal rules and procedures for positioning stock in a warehouseor store after goods inward processing.Quarantine Stock On-hand stock which has been segregated and is not available to meet customer requirements.Radio Frequency Identification (RFID) The attachment of transponders (which may be read only or read/write) to products, as an alternative to linear bar codes, to enable product identification some distance from the scanner or when out of line of sight.Random Sample Cycle Counting A method in which the particular parts to be counted are selected from the population of part numbers in a manner that has no inherent bias. In this selection process, each part number has an equal chance of being selected.Rapid Acquisition of Manufactured Parts (RAMP) A make to order process to reduce the purchasing lead time for long lead time manufactured parts whereby Product Data is held in STEP (the international standard for exchange of manufacturing product data) by the customer and exchanged, in electronic format, when an order is placed.Raw Material Stock or items purchased from suppliers, to be input to a productionprocess, and which will subsequently modified or transformed intofinished goods.Redundant Stock Parts used in manufacture which have been removed from a bill ofmaterial by technical change or modification action. Redundant partsmay also be obsolete if they are no longer used for any other applicationin the inventory concerned.Repair Turn RoundTime (RTRT)See Turn Around TimeRepairable Period (RP) The total out of service time, including transit time, from when a repairable component becomes unfit for use until the time it is returned to stock and is available for further use.Repairable Item An inventory item that is not normally consumed in use but one whichwill be repaired and re-used as part of the normal stock policy for thatitem. Such items have a repair lead-time as well as a procurementlead-time.Repair Turn RoundTime (RTRT)See Turn Around TimeRepair Period (RP) The total out of service time, including transit time, from when arepairable component becomes unfit for use until the time it is returnedto stock and is available for further use.Re-Order Level (ROL) (or Re-Order Point - ROP) The calculated level of stock within an inventory control system to which the quantity of a specific item is allowed to fall before replenishment order action is generated.Re-Order Quantity, Replenishment Order Quantity The calculated order quantity necessary to replenish stocks at a given point in time. The method of calculation, and the timing of the order, will vary depending on the type of inventory control system in use. Quantity based systems are checked continually to determine if an order should be placed; time based systems only have a count of stock at predetermined intervals and orders placed as required; a distribution system plans orders to meet distribution needs; and production based systems only order stock to meet manufacturing requirements.Reorder Costs The total cost of placing a repeat order for an item either externally on a supplier or for internal manufacture. The costs may include elements tocover: order preparation, administration, IT overheads,correspondence, telephone, transportation, goods inward processing,inspection and for manufacture, batch et up costs and other productionoverheads.Replenish toDemandSee Make to Order。

EMC认证详细资料

EMC认证EMC(电磁兼容性)的全称是Electro Magnetic Compatibility，其定义为“设备和系统在其电磁环境中能正常工作且不对环境中任何事物构成不能承受的电磁骚扰的能力” 该定义包含两个方面的意思，首先，该设备应能在一定的电磁环境下正常工作，即该设备应具备一定的电磁抗扰度(E MS)；其次，该设备自身产生的电磁骚扰不能对其他电子产品产生过大的影响，即电磁骚扰(E MI)。

EMC认证-概述随着电气电子技术的发展，家用电器产品日益普及和电子化，广播电视、邮电通讯和计算机网络的日益发达，电磁环境日益复杂和恶化，使得电气电子产品的电磁兼容性(EM C电磁干扰EMI与电磁抗EMS)问题也受到各国政府和生产企业的日益重视。

电子、电器产品的电磁兼容性（EMC）是一项非常重要的质量指标，它不仅关系到产品本身的工作可靠性和使用安全性，而且还可能影响到其他设备和系统的正常工作，关系到电磁环境的保护问题。

为了规范电子产品的电磁兼容性，所有的发达国家和部分发展中国家都制定了电磁兼容标准。

电磁兼容标准是使产品在实际电磁环境中能够正常工作的基本要求。

之所以称为基本要求，也就是说，产品即使满足了电磁兼容标准，在实际使用中也可能会发生干扰问题。

大部分国家的标准都是基于国际电工委员会（IEC）所制定的标准。

欧共体政府规定，从1996年1月1起，所有电气电子产品必须通过EMC认证，加贴CE标志后才能在欧共体市场上销售。

此举在世界上引起广泛影响，各国政府纷纷采取措施，对电气电子产品的RMC性能实行强制性管理。

国际上比较有影响的，例如欧盟89 /336/EEC指令（即EMC指令）、美国联邦法典CFR 47/FCC Rules等都对电磁兼容认证提出了明确的要求。

EMC认证-采用的标准1、GB 4343-1995《家用和类似用途电动、电热器具，电动工具以及类似电器无线电干扰特性测量方法和允许值》该标准己于1995年8月25日发布，1996年12月1日起实施。

核磁共振中常用的英文缩写和中文名称

NMR 中常用的英文缩写和中文名称收集了一些NMR 中常用的英文缩写,译出其中文名称,供初学者参考,不妥之处请指出,也请继续添加.相关附件NMR 中常用的英文缩写和中文名称APT Attached Proton Test 质子连接实验ASIS Aromatic Solvent Induced Shift 芳香溶剂诱导位移BBDR Broad Band Double Resonance 宽带双共振BIRD Bilinear Rotation Decoupling 双线性旋转去偶(脉冲)COLOC Correlated Spectroscopy for Long Range Coupling 远程偶合相关谱COSY ( Homonuclear chemical shift ) COrrelation SpectroscopY (同核化学位移)相关谱CP Cross Polarization 交叉极化CP/MAS Cross Polarization / Magic Angle Spinning 交叉极化魔角自旋CSA Chemical Shift Anisotropy 化学位移各向异性CSCM Chemical Shift Correlation Map 化学位移相关图CW continuous wave 连续波DD Dipole-Dipole 偶极-偶极DECSY Double-quantum Echo Correlated Spectroscopy 双量子回波相关谱DEPT Distortionless Enhancement by Polarization Transfer 无畸变极化转移增强2DFTS two Dimensional FT Spectroscopy 二维傅立叶变换谱DNMR Dynamic NMR 动态NMRDNP Dynamic Nuclear Polarization 动态核极化DQ(C) Double Quantum (Coherence) 双量子(相干)DQD Digital Quadrature Detection 数字正交检测DQF Double Quantum Filter 双量子滤波DQF-COSY Double Quantum Filtered COSY 双量子滤波COSYDRDS Double Resonance Difference Spectroscopy 双共振差谱EXSY Exchange Spectroscopy 交换谱FFT Fast Fourier Transformation 快速傅立叶变换FID Free Induction Decay 自由诱导衰减H,C-COSY 1H,13C chemical-shift COrrelation SpectroscopY 1H,13C 化学位移相关谱H,X-COSY 1H,X-nucleus chemical-shift COrrelation SpectroscopY 1H,X- 核化学位移相关谱HETCOR Heteronuclear Correlation Spectroscopy 异核相关谱HMBC Heteronuclear Multiple-Bond Correlation 异核多键相关HMQC Heteronuclear Multiple Quantum Coherence 异核多量子相干HOESY Heteronuclear Overhauser Effect Spectroscopy 异核Overhause 效应谱HOHAHA Homonuclear Hartmann-Hahn spectroscopy 同核Hartmann-Hahn 谱HR High Resolution 高分辨HSQC Heteronuclear Single Quantum Coherence 异核单量子相干INADEQUATE Incredible Natural Abundance Double Quantum Transfer Experiment 稀核双量子转移实验（简称双量子实验，或双量子谱）INDOR Internuclear Double Resonance 核间双共振INEPT Insensitive Nuclei Enhanced by Polarization 非灵敏核极化转移增强INVERSE H,X correlation via 1H detection 检测1H 的H,X 核相关IR Inversion-Recovery 反（翻）转回复JRES J-resolved spectroscopy J-分解谱LIS Lanthanide （chemical shift reagent ） Induced Shift 镧系（化学位移试剂）诱导位移LSR Lanthanide Shift Reagent 镧系位移试剂MAS Magic-Angle Spinning 魔角自旋MQ（C）Multiple-Quantum （ Coherence ）多量子（相干）MQF Multiple-Quantum Filter 多量子滤波MQMAS Multiple-Quantum Magic-Angle Spinning 多量子魔角自旋MQS Multi Quantum Spectroscopy 多量子谱NMR Nuclear Magnetic Resonance 核磁共振NOE Nuclear Overhauser Effect 核Overhauser 效应（NOE）NOESY Nuclear Overhauser Effect Spectroscopy 二维NOE 谱NQR Nuclear Quadrupole Resonance 核四极共振PFG Pulsed Gradient Field 脉冲梯度场PGSE Pulsed Gradient Spin Echo 脉冲梯度自旋回波PRFT Partially Relaxed Fourier Transform 部分弛豫傅立叶变换PSD Phase-sensitive Detection 相敏检测PW Pulse Width 脉宽RCT Relayed Coherence Transfer 接力相干转移RECSY Multistep Relayed Coherence Spectroscopy 多步接力相干谱REDOR Rotational Echo Double Resonance 旋转回波双共振RELAY Relayed Correlation Spectroscopy 接力相关谱RF Radio Frequency 射频ROESY Rotating Frame Overhauser Effect Spectroscopy 旋转坐标系NOE 谱ROTO ROESY-TOCSY Relay ROESY-TOCSY 接力谱SC Scalar Coupling 标量偶合SDDS Spin Decoupling Difference Spectroscopy 自旋去偶差谱SE Spin Echo 自旋回波SECSY Spin-Echo Correlated Spectroscopy 自旋回波相关谱SEDOR Spin Echo Double Resonance 自旋回波双共振SEFT Spin-Echo Fourier Tran sform Spectroscopy （with J modulati on）（J-调制）自旋回波傅立叶变换谱SELINCOR SELINQUATE SFORD SNR or S/NSelective Inverse Correlation 选择性反相关Selective INADEQUA TE 选择性双量子（实验）Single Frequency Off-Resonance Decoupling 单频偏共振去偶Signal-to-noise Ratio 信/ 燥比SQF Single-Quantum Filter 单量子滤波SRTCF TOCSY TORO TQF WALTZ-16 Saturation-Recovery 饱和恢复Time Correlation Function 时间相关涵数Total Correlation Spectroscopy 全(总)相关谱TOCSY-ROESY Relay TOCSY-ROESY 接力Triple-Quantum Filter 三量子滤波A broadband decoupling sequence 宽带去偶序列WATERGATE Water suppression pulse sequence 水峰压制脉冲序列WEFTZQ(C) ZQF T1T2 tmWater Eliminated Fourier Transform 水峰消除傅立叶变换Zero-Quantum (Coherence) 零量子相干Zero-Quantum Filter 零量子滤波Longitudinal (spin-lattice) relaxation time for MZ 纵向(自旋- 晶格)弛豫时间Transverse (spin-spin) relaxation time for Mxy 横向(自旋-自旋)弛豫时间T C rotational correlation time 旋转相关时间。

火星(Mars英文介绍

Mars: The Red PlanetMars, often called the "Red Planet," is the fourth planet from the Sun and the second smallest planet in our solar system after Mercury. Named after the Roman god of war, Mars has intrigued humans for centuries with its reddish appearance and the possibility of harboring life.Geography and CompositionMars is characterized its barren, rocky surface, which is covered with a thick layer of iron oxide, or rust, giving it its distinctive red color. The planet's landscape features a variety of terrain, including vast plains, towering volcanoes, and deep canyons. One of the most notable features is Olympus Mons, the largest volcano in the solar system, which stands about 13.6 miles (22 kilometers) high, more than twice the height of Earth's Mount Everest.The surface of Mars is also marked a network of valleys, ridges, and impact craters, the most famous of which is the Valles Marineris, a system of canyons that stretches over2,500 miles (4,000 kilometers), making it one of the largest canyons in the solar system.Climate and AtmosphereThe planet experiences extreme temperature fluctuations, with warm equatorial regions and frigid polar ice caps. Marsalso has seasons, similar to Earth's, due to its axial tilt. However, the seasons on Mars are about twice as long as those on Earth because Mars takes longer to orbit the Sun.Water and the Search for LifeOne of the most exciting discoveries about Mars is the evidence of water. Scientists have found that Mars once had liquid water on its surface, which suggests that the planet may have been capable of supporting life. The presence of ice at the poles and hydrated minerals in the soil indicates that water is still a significant part of Mars' geology.Several missions, including rovers like Curiosity and Perseverance, have been sent to Mars to search for signs of ancient life and to study the planet's climate and geology. These missions have provided valuable data and have even discovered organic molecules, which are the building blocks of life.Future ExplorationMars remains a focal point for space exploration. Plans for future missions include sending more rovers, establishing a permanent human presence, and even potential sample return missions, where Martian soil and rock samples would be brought back to Earth for detailed analysis.The Red Planet continues to captivate our imagination and scientific curiosity, offering the possibility of uncoveringsecrets about the origins of life and the potential forfuture human habitation beyond Earth.Robotic Explorers and MissionsThe Mars Science Laboratory's Curiosity rover, which landed in 2012, has been instrumental in assessing the habitability of the Martian environment. It has discovered that Mars' ancient lakebeds had the chemical ingredients necessary for life, as well as evidence of ancient rivers and streams.The latest addition to Mars' robotic fleet is NASA's Perseverance rover, which landed in 2021 with the primary goal of searching for signs of ancient life and collecting rock samples that could be returned to Earth in the future. Perseverance also carries the Ingenuity helicopter, the first aircraft to achieve controlled flight on another planet.Mars' Moons: Phobos and DeimosMars is unique in that it has two small, irregularly shaped moons: Phobos and Deimos. Phobos, the larger of the two, orbits Mars at a remarkably close distance and is gradually spiraling inward, eventually expected to break apart or collide with Mars. Deimos, smaller and more distant, orbits Mars at a more stable rate.These moons are thought to be captured asteroids, and they offer interesting study subjects for understanding the history and dynamics of the Martian system.Potential for Human SettlementThe Martian CalendarA day on Mars, known as a "sol," is slightly longer than an Earth day, lasting about 24 hours and 37 minutes. Mars years are also longer, with one Martian year equaling about 687 Earth days. This means that seasons on Mars are nearly twice as long as those on Earth.The Martian calendar has been proposed to help future explorers and settlers keep track of time. It consists of 668 sols, divided into 24 months, with each month lasting about 28 sols, similar to Earth's lunar months.The Dream of MarsMars remains a symbol of human potential and curiosity. From the ancient observations of the moving "red star" across the night sky to the modernday rovers and orbiters sending back data and images, Mars has always been a source of inspiration.The dream of Mars is not just about reaching another world; it's about expanding the boundaries of what is possible, understanding our place in the cosmos, and perhaps answering one of the most profound questions: Are we alone inthe universe? As we continue to learn more about the Red Planet, Mars holds the promise of new discoveries that could forever change our view of life and the universe.The Martian Soil and GeologyMars' Volcanic ActivityMars is home to some of the largest volcanoes in thesolar system, with Olympus Mons being the most prominent. These shield volcanoes are formed the flow of lowviscosity lava over long periods, creating broad, gently sloping cones. The Tharsis Montes, which includes Arsia Mons, Pavonis Mons, and Ascraeus Mons, are other significant volcanic featuresthat indicate Mars has been geologically active throughoutits history.The volcanic activity on Mars is thought to have been driven the movement of molten rock within the planet's mantle, similar to the processes that occur on Earth. However, while Earth's volcanoes are still active, those on Mars are believed to have been dormant for millions of years.The Martian Atmosphere and Climate ChangeThe thin Martian atmosphere plays a crucial role in the planet's climate, which has undergone significant changesover time. Evidence suggests that Mars once had a muchthicker atmosphere, which allowed for liquid water to existon its surface. However, most of this atmosphere was lost to space due to the weak magnetic field and solar wind erosion.The Search for WaterThe search for water on Mars has been a central theme of exploration missions. While liquid water cannot exist on the surface today due to the low atmospheric pressure, there is strong evidence that subsurface water ice is abundant, and it may even flow intermittently in the form of briny liquids.The discovery of gullies, recurring slope lineae (possible seasonal flows of briny water), and hydrated minerals all point to a dynamic water cycle on Mars, albeit one that is now mostly frozen. Future missions aim to further investigate these water sources, which are crucial for understanding the planet's past habitability and for supporting human exploration.The Martian sky, with its pinkish hues during sunrise and sunset, and the two moons that cross its expanse, continues to beckon humanity with its mysteries. As we peer through the lenses of our telescopes and the cameras of our rovers, Mars remains a testament to the enduring human spirit of exploration and the quest for knowledge that drives us to reach beyond our terrestrial home.。

祝融号探测火星英语作文

祝融号探测火星英语作文Title: Exploring Mars: China's Zhurong Rover。

In the realm of space exploration, the quest to unravel the mysteries of Mars has long captivated the imagination of scientists and enthusiasts alike. Among the recent endeavors in this field, the Chinese Zhurong rover stands out as a remarkable feat of engineering and scientific ambition. Let's delve into the mission of Zhurong and its significance in the context of Martian exploration.Origins and Objectives。

The Zhurong rover, named after the Chinese god of fire in ancient mythology, is a product of China's National Space Administration (CNSA). Launched as part of the Tianwen-1 mission on July 23, 2020, Zhurong reached Mars on May 14, 2021, after a journey spanning millions of kilometers.Equipped with a suite of scientific instruments, Zhurong's primary objectives include studying the Martian surface, geological structure, environment, and atmosphere. Additionally, the rover aims to search for signs of past life and assess the planet's suitability for future human exploration.Technological Marvels。

硅钢片在电机里的作用英语

硅钢片在电机里的作用英语Function of Silicon Steel Laminations in Electric Motors.Silicon steel laminations play a crucial role in electric motors, contributing to their efficient operation, reduced losses, and enhanced performance. Understanding their function and properties is essential for optimizing motor design and maximizing their efficiency.Magnetic Properties of Silicon Steel.Silicon steel, an iron-silicon alloy, possesses exceptional magnetic properties, making it an ideal material for motor applications. Its high permeability enables the creation of strong magnetic fields with minimal energy loss, while its low coercivity ensures easy magnetization and demagnetization.Laminated Structure.Silicon steel laminations are thin sheets of silicon steel that are stacked together to form the motor's magnetic core. This laminated structure serves several critical purposes:Reduced Hysteresis Loss: Hysteresis loss occurs when the magnetic field in the core is reversed, causing energy dissipation. Laminations reduce hysteresis loss by confining magnetic domains within individual sheets, preventing the formation of large eddy currents that contribute to energy loss.Minimized Eddy Current Losses: Eddy currents are circular electrical currents that flow within the core due to the changing magnetic field. Laminations disrupt the flow of eddy currents by providing a high-resistance path, reducing their magnitude and associated energy losses.Improved Magnetic Field Distribution: The laminated structure ensures a more uniform distribution of the magnetic field within the core, reducing magneticsaturation and optimizing motor performance.Construction of Motor Cores.In electric motors, the stator and rotor cores are constructed from silicon steel laminations. The stator core is the stationary part that creates the rotating magnetic field, while the rotor core rotates within the stator field to generate torque. The laminations are stacked and interlocked to form the core, providing the required magnetic properties and mechanical strength.Types of Silicon Steel Laminations.Various grades of silicon steel are available, each with specific magnetic properties and applications. Common types include:Grain-Oriented Silicon Steel (GOSS): Highlyanisotropic material with excellent magnetic properties along the grain direction, used for high-efficiency motors.Non-Grain-Oriented Silicon Steel (NGO): Isotropic material with good magnetic properties in all directions, suitable for general-purpose motors.High Silicon Steel (HSS): Contains a higher silicon content, resulting in lower hysteresis and eddy current losses, used in high-performance motors.Benefits of Silicon Steel Laminations in Motors.The use of silicon steel laminations in electric motors offers numerous benefits, including:Enhanced Efficiency: Reduced energy losses due to hysteresis and eddy currents improve motor efficiency, saving energy and reducing operating costs.Lower Operating Temperatures: Minimized losses prevent excessive heating of the motor, extending its lifespan and enhancing reliability.Reduced Noise and Vibration: Laminations suppressmagnetic noise and vibrations, contributing to quieter and smoother motor operation.Optimized Performance: Improved magnetic field distribution and reduced losses result in optimal motor performance, including increased torque and reduced speed fluctuations.Compact Size and Weight: Laminated cores allow for compact motor designs without sacrificing performance, enabling space-saving applications.Conclusion.Silicon steel laminations are essential components of electric motors, providing the necessary magnetic properties to ensure efficient operation and enhanced performance. Their laminated structure effectively reduces energy losses, improves magnetic field distribution, and contributes to the overall reliability and durability of motors. By understanding the function and properties ofsilicon steel laminations, engineers can optimize motor designs to meet specific application requirements.。

磁层析成像管道检测信号空间传递过程的能量变化

第44卷第2期2024 年4月辽宁石油化工大学学报JOURNAL OF LIAONING SHIHUA UNIVERSITYVol.44 No.2Apr. 2024引用格式：刘琳琳,杨理践,高松巍.磁层析成像管道检测信号空间传递过程的能量变化[J].辽宁石油化工大学学报,2024,44(2):71-76.LIU Linlin,YANG Lijian,GAO Songwei.Energy Change of Pipeline Signal Spatial Propagation Detected by Magnetic Tomography Method[J].Journal of Liaoning Petrochemical University,2024,44(2):71-76.磁层析成像管道检测信号空间传递过程的能量变化刘琳琳1,2，杨理践1，高松巍1（1.沈阳工业大学信息科学与工程学院，辽宁沈阳 110870； 2.辽宁石油化工大学信息与控制工程学院，辽宁抚顺 113001）摘要：　磁层析成像管道检测方法已经被广泛应用于埋地和海底管道的无损外检测。

该方法基于金属磁记忆原理，通过在管道外测量空间磁场分布中的异常情况来判别应力集中区的危险等级和位置。

为了研究磁层析成像法管道检测信号在空间中的分布特征和传递规律，对磁化管道的应力集中区空间磁记忆信号的能量分布和变化规律进行了研究。

利用磁偶极子场建立管道内壁应力集中区磁场模型，基于磁能理论对管道外不同提离空间磁记忆信号的磁场能量和磁能密度进行有限元计算，得出空间磁场的分布规律，分析了不同提离磁信号磁能密度之间的相关性。

结果表明，管道外空气中的磁场能量随着提离值的增加而衰减，在管道外壁至提离值小于50 mm时衰减最快；管道外磁层析成像法检测的磁信号与管道内壁应力集中区信号同源。

从理论上解释了磁层析成像管道检测的有效性，为从检测数据中提取有效信号提供了理论依据。

同步辐射与随机磁涨落对逃逸电子影响的理论研究

摘要磁约束聚变是将来有望解决人类能源问题的重要途径之一，其中托卡马克装置是目前研究最多、同时最有希望实现磁约束聚变的装置。

然而，托卡马克等离子体破裂几乎是不可避免的灾难性事件。

等离子体破裂的危害之一是产生大量的高能逃逸电子，如果不加控制，这些高能的逃逸电子最终将打到装置第一壁上，对装置安全运行造成严重威胁，因此，对逃逸电子的产生过程进行深入的理论研究，找到切实可行的缓解方案具有重要的意义。

电子能否逃逸取决于其速度空间结构，当电子速度超过热速度时，碰撞摩擦力随电子速度的增加而减小，此时如果电子受到的电场加速力能够克服摩擦阻力就可以被持续加速而发生逃逸。

在电磁场中，电子的同步辐射随电子速度的增加而增强，所以逃逸电子能量还会受到同步辐射的限制，从而不能无限加速。

此外，逃逸电子运动轨迹受到坐标空间的制约，其输运特性决定着逃逸电子的“存活”时间，而磁涨落是影响逃逸电子输运的重要机制。

因此，我们重点研究了同步辐射与随机磁涨落对逃逸电子产生过程的影响。

等离子体的统计描述方法是解决等离子体相关问题的有力工具，根据逃逸电子产生的子过程的不同特征时间尺度，我们应用时间尺度分离的方法求解了包含同步辐射与随机磁涨落的回旋动理学相对论性福克-普朗克方程。

研究发现，一个电子能否最终发生逃逸与其加速率和扩散速率紧密相关。

只有电子的加速率快于其扩散率时电子才能发生逃逸。

由加速率与扩散率的平衡我们得到了逃逸电子被维持的电场，该电场值是随机磁涨落水平的正相关函数。

在给定的磁涨落水平下，实际电场值小于该维持电场时所有初始产生的快电子都将因加速率小于扩散率而损失，从而没有逃逸电子的产生；只有实际电场值高于该维持电场值时才会有有限的电子成为逃逸电子。

同时发现电子的最小逃逸动量对磁涨落的变化极其敏感，能量极限受磁涨落的影响不大。

另外，要发生逃逸电子的雪崩增长，逃逸电子仅仅被维持是不够的，电子需要从电场中获得更大的加速力。

与仅考虑同步辐射的情况相比，同时考虑同步辐射及磁涨落对逃逸电子雪崩过程的影响后发现，雪崩阈值电场进一步提高，逃逸增长率随着磁涨落水平的增加而显著下降。

极低频磁场对细胞因子受体基因表达及转录因子影响的研究

２００２年浙江大学博士学位论文检测低至Ｏ．０１“ｇ含景的ｍＲＮＡ，并且在一份总ＲＮＡ样品中可同时检测和半定量多种ｍＲＮＡ。

在本研究中用核酶保护法检测０．１或０．８ｍＴ强度的磁场暴露长达７２小时后ＨＬ６０细胞相关细胞因子受体基因的ｍＲＮＡ表达改变。

此外，有研究认为ＥＭＦ能影响细胞信号转导过程，而细胞信号转导的最终效应是影响转录因子的活性。

已有报道认为电磁场作为一种环境物理因素可以影响包括ＡＰ．１、ＡＰ．２、ＳＰ．１及ＨＳＦ在内的多种转录因子的ＤＮＡ结合活性。

ＣＲＥＢ和ＮＦ—ＫＢ是两种非常重要的转录因子。

ＣＲＥＢ最初被认为是ｃＡＭＰ依赖的信号通路转录激活因子，可被ｃＡＭＰ依赖的蛋白激酶所磷酸化。

对ＣＲＥＢ的生物学功能的研究表明它在细胞繁殖、分化及适应性反应等细胞生理过程中有重要作用。

受各种蛋白激酶如ＰＫＡ、ＰＫＣ、ＭＡＰＫ以及ＣａＭＫ激活后ＣＲＥＢ以同源二聚体或异源二聚体的形式激活目标基因转录。

ＮＦ—ＫＢ是一组与相应ＤＮＡ结合后可行使广泛转录激活功能的异源二聚体蛋白复合物。

它与细胞和病毒的启动子或增强子区域１０．ｂｐ的通用序列结合后调控细胞凋亡、分化和急性期反应。

ＮＦ．ＫＢ在胞浆中与其抑制蛋白ＩＫＢ结合处于非激活状态，当细胞受到适当刺激后ＩＫＢ快速磷酸化、泛素化和降解从而激活ＮＦ—ＫＢ。

结合ＥＭＦ对细胞信号转导通路影响的研究数据，推测ＥＭＦ很可能、ｆ７会影响磁场辐照后ＨＬ６０细胞的转录因子ＣＲＥＢ和ＮＦ．ＫＢ的ＤＮＡ结合活性。

｝＿７～一／本部分的研究目的是检测５０Ｈｚ磁场辐照对转录因子ＣＲＥＢ和ＮＦ—ＫＢ的ＤＮＡ结合活性的影响，并探讨参与此磁场反应的信号通路。

第一部分：极低频磁场对细胞因子受体基因表达的影响．在ＨＬ６０细胞中研究了５０Ｈｚ极低频正弦磁场对细胞因子受体基因表达的影响。

伍场辐照系统主要由一对边长３６ｃｍ、高度８ｃｍ、１６８匝的Ｈｅｌｍｈ。

ｌｔｚ线圈，一只等长等高、６０匝的中置补偿线圈，两只变压器及细胞培养箱构成。

[核磁共振波谱学讲义]第三章—NMR实验技术基础(1NMR仪器)知识讲解

第三章 NMR 实验技术基础1 NMR 仪器如图，现代超导核磁谱仪的主要组成部分包括：1. 超导磁体Magnet 包括Field Lock ，Shim Coils2. 探头Probe 内有RF Coils ，Gradient Coils3. 脉冲编程器及射频放大器4. 接收器5. 数据采集及处理计算机At the top of the schematic representation, you will find the superconducting magnet of the NMR spectrometer. The magnet produces the Bo field necessary for the NMR experiments. Immediately within the bore of the magnet are the shim coils for homogenizing the Bo field.Within the shim coils is the probe. The probe contains the RF coils for producing the B1 magnetic field necessary to rotate the spins. The RF coil also detects the signal from the spins within the sample. The sample is positioned within the RF coil of the probe. Some probes also contain a set of gradient coils. These coils produce a gradient in Bo along the X, Y , or Z axis. Gradient coils are used for for gradient enhanced spectroscopy, diffusion, and NMR microscopy experiments. The heart of the spectrometer is the computer. It controls all of the components of thespectrometer. The RF components under control of the computer are the RF frequency source and pulse programmer. The source produces a sine wave of the desired frequency. The pulse programmer sets the width, and in some cases the shape, of the RF pulses. The RF amplifier increases the pulses power from milli Watts to tens or hundreds of Watts. The computer alsocontrols the gradient pulse programmer which sets the shape and amplitude of gradient fields. The gradient amplifier increases the power of the gradient pulses to a level sufficient to drive the gradient coils. The operator of the spectrometer gives input to the computer through a console terminal with a mouse and keyboard. Some spectrometers also have a separate small interface for carrying out some of the more routine procedures on the spectrometer. A pulse sequence isselected and customized from the console terminal. The operator can see spectra on a video display located on the console and can make hard copies of spectra using a printer.1. 超导磁体MagnetMagnet主要要求：a 高磁场强度,分辨率与B0成正比，而灵敏度与B032成正比，故750MHz较600MHz的分辨率提高25%,而灵敏度提高40%b 高均匀性,目前可达10-9c 高稳定性The NMR magnet is one of the mostexpensive components of the nuclearmagnetic resonance spectrometer system.Most magnets are of the superconductingtype. A superconducting magnet has anelectromagnet made of superconductingwire. Superconducting wire has aresistance approximately equal to zerowhen it is cooled to a temperature close toabsolute zero (-273.15 C or 0 K) byemersing it in liquid helium. Once currentis caused to flow in the coil it willcontinue to flow for as long as the coil iskept at liquid helium temperatures.(Some losses do occur over time due to theinfinitesimally small resistance of the coil. These losses are on the order of a ppm of the main magnetic field per year.) The length of superconducting wire in the magnet is typically several miles. This wire is wound into a multi -turn solenoid or coil. The coil of wire and cryroshim coils are kept at a temperature of 4.2K by immersing it in liquid helium. The coil and liquid helium are kept in a large dewar. This dewar is typically surrounded by a liquid nitrogen (77.4K) dewar, which acts as a thermal buffer between the room temperature air (293K) and the liquid helium.The following image is an actual cut -away view of asuperconducting magnet. The magnet is supported by threelegs, and the concentric nitrogen and helium dewars aresupported by stacks coming out of the top of the magnet. Aroom temperature bore hole extends through the center of theassembly. The sample probe and shim coils are located withinthis bore hole. Also depicted in this picture is the liquidnitrogen level sensor, an electronic assembly for monitoringthe liquid nitrogen level.Going from the outside of the magnet to the inside, wesee a vacuum region followed by a liquid nitrogen reservoir.The vacuum region is filled with several layers of a reflectivemylar film. The function of the mylar is to reflect thermal photons, and thus diminish heat from entering the magnet. Within the inside wall of the liquid nitrogen reservoir, we see anothervacuum filled with some reflective mylar. The liquid helium reservoir comes next. This reservoir houses the superconducting solenoid or coil of wire.Taking a closer look at the solenoid it is clear to see the coil and the bore tube extending through the magnet.Field LockIn order to produce a high resolutionNMR spectrum of a sample, especially onewhich requires signal averaging or phasecycling, you need to have a temporallyconstant and spatially homogeneous magneticfield. Consistency of the Bo field over timewill be discussed here; homogeneity will bediscussed in the next section of this chapter.The field strength might vary over time due toaging of the magnet, movement of metal objects near the magnet, and temperature fluctuations. Here is an example of a one line NMR spectrum of cyclohexane recorded while the Bo magnetic field was drifting a very significant amount. The field lock can compensate for these variations.The field lock is a separate NMRspectrometer within your spectrometer. Thisspectrometer is typically tuned to thedeuterium NMR resonance frequency. Itconstantly monitors the resonance frequencyof the deuterium signal and makes minorchanges in the Bo magnetic field to keep theresonance frequency constant. The deuteriumsignal comes from the deuterium solvent usedto prepare the sample. The animation window contains plots of the deuterium resonance lock frequency, the small additional magnetic field used to correct the lock frequency, and the resultant Bo field as a function of time while the magnetic field is drifting. The lock frequency plot displays the frequency without correction. In reality, this frequency would be kept constant by the application of the lock field which offsets the drift.On most NMR spectrometers the deuterium lock serves a second function. It provides the reference. The resonance frequency of the deuterium signal in many lock solvents is well known. Therefore the difference in resonance frequency of the lock solvent and TMS is also known. As a consequence, TMS does not need to be added to the sample to set reference; the spectrometer can use the lock frequency to calculate reference.Shim CoilsThe purpose of shim coils on a spectrometer is to correct minor spatial inhomogeneities in the Bo magnetic field. These inhomogeneities could be caused by the magnet design, materials in the probe, variations in the thickness of the sample tube, sample permeability, and ferromagnetic materials around the magnet. A shim coil is designed to create a small magnetic field which will oppose and cancel out an inhomogeneity in the Bo magnetic field. Because these variations may exist in a variety of functional forms (linear, parabolic, etc.), shim coils are needed which can create a variety of opposing fields. Some of the functional forms are listed in the table below.Shim Coil Functional FormsShim FunctionZ0Z, Z2, Z3, Z4, Z5X, XZ, XZ2, X2Y2, XY , Y , YZ, YZ2XZ3, X2Y2Z, YZ3, XYZ, X3, Y3By passing the appropriate amount of current througheach coil a homogeneous Bo magnetic field can beachieved. The optimum shim current settings are found byeither minimizing the linewidth, maximizing the size of theFID, or maximizing the signal from the field lock. On mostspectrometers, the shim coils are controllable by thecomputer. A computer algorithm has the task of finding thebest shim value by maximizing the lock signal.2. 探头Sample ProbeThe sample probe is the name given to that part of the spectrometer which accepts the sample, sends RF energy into the sample, and detects the signal emanating from the sample. It contains the RF coil, sample spinner, temperature controlling circuitry, and gradient coils. The RF coil and gradient coils will be described in the next two sections. The sample spinner and temperature controlling circuitry will be described here.The purpose of the sample spinner is to rotate the NMRsample tube about its axis. In doing so, each spin in the samplelocated at a given position along the Z axis and radius from the Zaxis, will experience the average magnetic field in the circledefined by this Z and radius. The net effect is a narrower spectrallinewidth. To appreciate this phenomenon, consider the following examples. In picture an axial cross section of a cylindrical tube containing sample. In a very homogeneous Bo magnetic field this sample will yield a narrow spectrum. In a more inhomogeneous field the sample will yield a broader spectrum due to the presence of lines from the parts of the sample experiencing different Bo magnetic fields. When the sample is spun about its z -axis, inhomogeneities in the X and Y directions are averaged out and the NMR line width becomes narrower.Many scientists need to examine properties of their samples as a function of temperature. As a result many instruments have the ability to maintain the temperature of the sample above and below room temperature. Air or nitrogen which has been warmed or cooled is passed over the sample to heat or cool the sample. The temperature at the sample is monitored with the aid of a thermocouple and electronic circuitry maintains the temperature by increasing or decreasing the temperature of the gas passing over the sample.RF CoilsRF coils create the B1 field which rotates thenet magnetization in a pulse sequence. They alsodetect the transverse magnetization as it precesses inthe XY plane. Most RF coils on NMR spectrometersare of the saddle coil design and act as thetransmitter of the B1 field and receiver of RF energyfrom the sample. You may find one or more RF coilsin a probe.Each of these RF coils must resonate, that isthey must efficiently store energy, at the Larmorfrequency of the nucleus being examined with theNMR spectrometer. All NMR coils are composed of an inductor, or inductive elements, and a set of capacitive elements. The resonant frequency, , of an RF coil is determined by the inductance (L) and capacitance (C) of the inductor capacitor circuit. RF coils used in NMR spectrometers need to be tuned for the specific sample being studied. An RF coil has a bandwidth or specific range of frequencies at which it resonates. When you place a sample in an RF coil, the conductivity and dielectric constant of the sample affect the resonance frequency. If this frequency is different from the resonance frequency of the nucleus you are studying, the coil will not efficiently set up the B1 field nor efficiently detect the signal from the sample. You will be rotating the net magnetization by an angle less than 90 degrees when you think you are rotating by 90 degrees. This will produce less transverse magnetization and less signal. Furthermore, because the coil will not be efficiently detecting the signal, your signal -to -noise ratio will be poor.The B1 field of an RF coil must be perpendicular to the Bo magnetic field. Anotherrequirement of an RF coil in an NMR spectrometer is that the B1 field needs to be homogeneous over the volume of your sample. If it is not, you will be rotating spins by a distribution of rotation angles and you will obtain strange spectra.Gradient CoilsThe gradient coils produce the gradients in the Bo magnetic field needed for performing gradient enhanced spectroscopy, diffusion measurements, and NMR microscopy. The gradient coils are located inside the RF probe. Not all probes have gradient coils, and not all NMR spectrometers have the hardware necessary to drive these coils.The gradient coils are room temperature coils (i.e. do not require cooling with cryogens to operate) which, because of their configuration, create the desired gradient. Since the vertical bore superconducting magnet is most common, the gradient coil system will be described for this magnet.Assuming the standard magnetic resonance coordinatesystem, a gradient in Bo in the Z direction is achieved with anantihelmholtz type of coil. Current in the two coils flow inopposite directions creating a magnetic field gradient betweenthe two coils. The B field at the center of one coil adds to theBo field, while the B field at the center of the other coilsubtracts from the Bo field.The X and Y gradients in the Bo field are created by apair of figure -8 coils. The X axis figure -8 coils create agradient in Bo in the X direction due to the direction of thecurrent through the coils. The Y axis figure -8 coils providesa similar gradient in Bo along the Y axis.3. 脉冲编程器及射频放大器包括频率综合器，放大器及有关的电子器件。