Finite-Temperature Micromagnetics of Hysterisis for Misaligned Single Iron Nanopillars
温度传感器外文翻译
英文翻译Temperature humidity sensorThe sensor in type many sensors, the temperature sensor and applies two aspects in its output both is second to and with it correlation temperature is an important physical parameter, he affects all physical, chemistry and biomedicine process march, regardless of in the industry, the agriculture, the scientific research, the national defense and people's daily life each aspect, the temperature survey and the control all is the extremely important with the electronic technology and the materials science development, to each kind of new thermal element and the temperature sensor request structure advanced, the performance is stable, satisfies the more and more high request which proposed to the temperature survey and the control.Sensor classification carries on classified resistance type PN according to the manufacture temperature sensor material and the principle of work to tie the type thermoelectricity type radiation formular operating region is refers to the resistance value to have the remarkable change temperature sensor along with the temperature change, it may transform directly the temperature as the electrical the operating temperature scope, its resistance the which increases along with the temperature ascension is called positive temperature coefficient (PTC); Its resistance number the which reduces along with the temperature t ascension is called negative temperature (NTC); The negative temperature which reduces suddenly along with the temperature rise is called critical (CTR) in a warm area internal resistance.1. PTC principle of the PTC r usually to use the (BaTio3) ceramic material, the pure BaTio3 ceramics have the extremely high electronic resistivity under often the temperature, above 108Ω · m, therefore is the insulator.If carries on the doping in BaTio3, may cause the BaTio3 semiconductor, for example: Mixes by %% rare-earth element, but causes it to become has under the normal temperature----10Ω · m N line of semiconductors .Has electricity semiconductor BaTio3, when the temperature achieved when Curie temperature T, it transforms by the tetragonal system into the cubic system, this time its electronic resistivity leap increases several magnitudes ( times).Positive temperature coefficient the (PTC) acts according to this nature manufacture.After in semiconductor multi-crystal grain structure BaTio3, its crystal grain (general size small is approximately 3-10 µ m) the interior is the semiconductor nature; But the crystal boundary (has f e r r o electricity) for the high-resistance area. When type crystal external voltage, voltage majority of landings on high-resistance crystal boundary level, thus the crystal boundary has an effect to the material electric conductivity .The electron must pass through the crystal boundary barrier potential barrier from a crystal grain to be able to arrive another crystal grain .Below Curie temperature T c, BaTio3 is tetragonal system dielectric, the existence has the spontaneous polarized very strong internal electric field, enable the electron to have the high energy, thus the traversing crystal boundarypotential barrier is easy. But above Curie temperature T c, BaTio3 becomes the cubic system by the tetragonal system, polarizes vanishing spontaneously, internal electric field vanishing, the electricity is difficult in the traversing potential barrier, therefore above curie warm waste T c, electronic resistivity sharp increase. When two crystal grains contact mutually, crystal grain barrier potential barrier as shown in Figure is potential barrier le vel thickness, ø0 is the barrier height .According to the equation, the barrier height ø0 sticks the effective dielectric constant εe ff between with the crystal the relations is: In the formula, n0 is the density of donors; e is t he electronic electric quantity .ε0 is the vacuum coefficient of d i electrical loss. When the electronic overstepping potential barrier enters ø0, the electronic resistivity may write isWhen the temperature is l ower than Curie temperature TC, εe ff the value is approximately about 104, therefore ø0 very small, the ceramic electronic resistivity rho approaches in the volume resistivity ρv, after the temperature surpasses Curie temperature TC, the value drops suddenly, the A value increases, causes rho the value sharp increase, dopes BaTio3 and rho and between the temperature relational like chart .NTC t h r principle of work NTC the r s tor majority is by the transition family metal oxide compound (mainly is with M n, co, Ni, Fe and so on), the agglutination forms the semiconductor metal oxide compound under the controlled condition, they only have the P semiconductor characteristic .Regarding the common semiconducting material, the electronic resistivity mainly is relies on along with the warm waste change the current carrier number along with the temperature change, the temperature increment, the current carrier number increases, electric conduction ability enhancement. Thus electronic resistivity F falls. Regarding transition metal oxide compound semiconductor, for example Ni O, because its acceptor ionizing energy is very small, broad basic ionized completely in the room temperature, namely the current carrier density basically has nothing to do with the temperature, this time, should mainly consider the transport ratio and the temperature relations .By the semiconductor physics knowledge, the transport ratio expresses by the equation below:In the formula: The d-- oxygen octahedron gap is away from (Ni O is the Na Cl structure); V0-- lattice vibration frequency; The Ei-- activation energy, indicated the electron jumps originally from one in the position the energy which needs to the neighboring atom site. Or rewriting Then the electronic resistivity is: 0Ne-Ei/kT If command, then type changes: rho =ρ0eEi/KT Obviously the metal oxide compound semiconductor electronic resistivity mainly has the transport ratio along with the temperature change to cause along with the temperature change .When temperature increment, the electronic resistivity drops, assumes the negative temperature coefficient characteristic. Critical temperature also belongs to the negative temperature coefficient. But in some critical temperature scope, its resistance number drops suddenly along with the temperature rise .Anti- as shown in Figure 4-4. In the chart the anti- r curve has aresistance number point of discontinuity, approximately for 68℃, resistance number point of discontinuity magnitude generally in 3~ carry on the adjustment based on the material ingredient, it is suitable specially in 65℃~75℃ between uses, this kind of resistor may make the constant temperature control and on-off element.The CTR r usually uses the glass semiconductor processing, take the vanadium as the main material. Mixes in certain materials and so on oxide compound like C a O, B a O, S O or P2O5, TiO2 becomes after the hot dissolve. temperature sensor basic characteristic in view of the fact that the temperature sensor type is many, moreover its work mechanism is also different. This mainly introduces t the hot sensitive diode and the hot sensitive transistor characteristic and the parameter. from the s the material and anti- and so on carry on the classification variously. According to structure shape classification: Laminated shape, gasket shape, rod-shaped, tubular, thin membrane, thick membranous and other shapes. Includes according to the anti- temperature ra classification: Normal temperature, high temperature and ultralow temperature hot sensitive resistor. Includes according to the anti- classification: Negative temperature coefficient r (NTC), switch temperature r (PTC); Slow aberration positive temperature coefficient r (PTC), the critical negative temperature coefficient, the platinum resistor limits the temperature curve like chart 4-4 curvature 1. 1st, resistance - temperature characteristic anti- is refers to between the actual resistance value and the resistance body temperature dependent relations, this is one of basic characteristics.PTC switch positive temperature coefficient anti- curve. value rises suddenly to some temperature nearby the maximizing.Through the doping .If dopes P b in BaTio3, may cause Tc to the high temperature traverse, mixes in elements and so on S r or S n after BaTio3, may cause TC to the low temperature traverse. May according to need to adjust t Curie temperature TC. The actual resistance number expressed with RT. Is under certain ambient temperature, uses causes the resistance number change not to surpass the resistance value which % survey power actual resistance value is called the zero energy resistance value, or is called does not give off heat the power resistance value (cold resistance value).The actual resistance value size is decided by the resistor material and the geometry shape. If the actual resistance number own temperature has the following relations: NTC In the formula: RT time 11 temperature T actual resistance value; R 1 and resistance geometry shape with material related constant B, A 11 material constants. For the easy to operate, usually takes the ambient temperature for 25℃ to take the reference temperature, then has: NTC puts the resistor hotly: RT/R25=exp[B(1/T-1/298)] PTC g change along with the temperatureT change, and is proportional with material constant B. Therefore, usually while gives the resistance temperature coefficient, must point out when the survey temperature, positive temperature coefficient t a T in value superior constant A. Slow aberration positive temperature coefficient value in %/℃ 110%/℃ between. But the switch(mutant) positive temperature co efficient T may achieve 60%/℃ or higher. Material constant B is uses for to describe the t material physical property - parameter. Also is called the thermal sensitivity target. In the operating region, the B value is not a strict constant, has slightly along with the temperature ascension increases .In general, the B value great electronic resistivity is also high. The different B value material has the different use, like ordinary negative temperature coefficient material constant B value between 2000yi5000 K. The negative temperature coefficient B value may according to the equation below computation: Positive temperature coefficient resistor, its A value according to equation below computation: In the formula, R1 R2 respectively is time thermodynamic temperature T1 and the T2 resistance value. 2. thermal properties (1) dissipation constant H dissipation constant H defined as the temperature each increase once diffusion power .It uses for when describes work, the resistance element and the external environment carry on the hot conversation a physical quantity. Dissipation constant H and dissipated power P .The temperature increment AT relations are The H size and the t structure, locates the environment medium type, the velocity of movement, the pressure and the heat conduction performance and so on related, when ambient temperature change, H has the change. (2) capacity and the time-constant r appliance has certain calorific capacity C, therefore it has certain warm. Also is the temperature change needs certain time. When the is heated up the T2 temperature, puts to the temperature is in the T0 environment, does not add the electric power, the starts to decrease temperature, its temperature T is the time t function, in △t time. The may indicate to the environment diffusion quantity of heat is: H(T-T0)△t, this part of quantity of heat is provides by the temperature decrease. Its value for - C△T, therefore has:Expressed in the environment atmosphere the steam content physical quantity is a y. The humidity expression method has two kinds, namely absolute humidity and relative h um (RH).The absolute humidity is refers to in the atmosphere the water content absolute value, the relative humidity is refers to in the atmosphere the steam to press with the identical temperature under ratio of the saturated steam tension, expressed with the percentage. The humidity sensor or the dew cell are refer to the paraphrase to the humidity sensitive part, it may be the wet sensitive resistor, also may be the wet sensitive capacitor or other dew cells. The humidity sensor classification classifies according to the feeling wet physical quantity, the humidity sensor may divide into three big kinds, namely wet sensitive resistor, wet sensitive capacitor and wet sensitive transistor. The humidity resistor makes which according to the use different material may divide into: Metal oxide compound semiconductor ceramics wet sensitive resistor, for example: MgCr2O4 series, ZnO-Cr2O3 series; Element material wet sensitive resistor, for example: Semiconductor G e, Si, Se and C element; Compound wet sensitive resistor, for example: Li Cl, CaSO4, and fluoride and iodide and so on; High polymer wet sensitive resistor and so on. The wet sensitive capacitor mainly is the porous Al2O3material makes as the medium. The wet sensitive transistor divides into the wet sensitive diode and the wet sensitive three levels of tubes. The wet sensitive resistor principle of work and the characteristic 1, the metal oxide compound semiconductor ceramics wet sensitive resistor (1) principle of work porous metal oxide compound semiconductor ceramics, in the crystal plane and the crystal boundary place, very easy to adsorb t drone. Because the water is one strong polar dielectric medium, nearby the h y drone hydrogen atom has the very strong electric field, has the very big electron affinity. When h y drone adheres to stick cohere when the semiconductor ceramics surface, will form the energy level very deep attachment surface acceptor condition, but from semiconductor ceramics surface capture electron, but will form the bound state in the ceramic surface the negative space charge, correspondingly will appear the hole in the near surface layer to accumulate, thus will cause the semiconductor ceramics electronic resistivity depression.Moreover, according to the ion electric conductance principle, the structure not compact semiconductor ceramics crystal grain has certain crevice, reveals the porous capillarity tubular .The drone may adsorbs through this kind of pore between various crystal grains surface and the crystal grain, because adsorbs the e separable relieves the massive electric conduction ion, these ions are playing the electric charge transportation role in the water adsorbed layer. along with humidity increase, material electronic resistivity drop. oxide compound semiconductor ceramics wet sensitive resistor principal variety and structure The metal oxide compound semiconductor ceramics wet sensitive resistor typical product includes: MgCr2O4 - TiO2 wet sensitive resistor, ZnO-Cr2O3 wet sensitive resistor, ZnO-Li2O3-V2O5 wet sensitive resistor and so on. For example: The ZnO-Li2O3-V2O5 wet sensitive resistance, is take Zn O as the main material, is joining a price, two prices, three prices and so on other metal oxide compound burns the ceramics semiconducting material, the survey humidity scope is 5%~100%RH, the measuring accuracy is 2%, is one kind of more ideal dew cell, and may make the miniaturization, the structure is simple. 2nd, element material wet sensitive resistor kind of wet sensitive resistor is a part which the element semiconducting material or the element material make.The carbon wet sensitive resistor is one resistance - humidity characteristic is the dew cell. With the organic matter polypropylene plastic piece or the stick are substrates, spreads cloth one to include the conductive carbon granule organic textile fiber constitution. This kind of wet sensitive resistor craft is simple, is advantageous for the uses the organic material absorption of moisture, the volume expansion, between the carbon granule distance increases, thus the resistance value increases principle. The element semiconductor, have on the honeycomb electrode ceramic substrate, is composed [granule diameter by the characteristic in the Fe3O4 colloid by the particle approximately for (100~250)×10-8m], each pellet only then a magnetic domain, therefore, the co current pellet attracts the union mutually, thus does not need the highpolymer material to make the colloid bond, but can obtain the good performance and the long service life. Figure 4-1 is the Fe3O4 colloid wet sensitive resistor structure drawing. Figure 4-2 is the Fe3O4 wet sensitive resistor resistance humidity characteristic curve, displays for the negative feeling wet characteristic. 4th, the wet sensitive resistor characteristic (1) resistance - humidity characteristic wet sensitive resistor resistance number along with the humidity change is generally the index relations change.温度传感器在种类繁多的传感器中，温度传感器在其产量和应用两方面都是数一数二的。
纳米管制作皮肤感应器 翻译 中英
最后译文：纳米管弹性制作出皮肤般的感应器美国斯坦福大学的研究者发现了一种富有弹性且透明的导电性能非常好的薄膜，这种薄膜由极易感触的碳纳米管组成，可被作为电极材料用在轻微触压和拉伸方面的传感器上。
“这种装置也许有一天可以被用在被截肢者、受伤的士兵、烧伤方面接触和压迫的敏感性的恢复上，也可以被应用于机器人和触屏电脑方面”，这个小组如是说。
鲍哲南和他的同事们在他们的弹透薄膜的顶部和底部喷上一种碳纳米管的溶液形成平坦的硅板，覆盖之后，研究人员拉伸这个胶片，当胶片被放松后，纳米管很自然地形成波浪般的结构，这种结构作为电极可以精准的检测出作用在这个材料上的力量总数。
事实上，这种装配行为上很像一个电容器，用硅树脂层来存储电荷，像一个电池一样，当压力被作用到这个感应器上的时候，硅树脂层就收紧，并且不会改变它所储存的电荷总量。
这个电荷是被位于顶部和底部的硅树脂上的纳米碳管测量到的。
当这个复合膜被再次拉伸的时候，纳米管会自动理顺被拉伸的方向。
薄膜的导电性不会改变只要材料没有超出最初的拉伸量。
事实上，这种薄膜可以被拉伸到它原始长度的2.5倍，并且无论哪种方向不会使它受到损害的拉伸它都会重新回到原始的尺寸，甚至在多次被拉伸之后。
当被充分的拉伸后，它的导电性喂2200S/cm，能检测50KPA的压力，类似于一个“坚定的手指捏”的力度，研究者说。
“我们所制作的这个纳米管很可能是首次可被拉伸的，透明的，肤质般感应的，有或者没有碳的纳米管”小组成员之一Darren Lipomi.说。
这种薄膜也可在很多领域得到应用，包括移动设备的屏幕可以感应到一定范围的压力而不仅限于触摸；可拉伸和折叠的几乎不会毁坏的触屏感应器；太阳能电池的透明电极；可包裹而不会起皱的车辆或建筑物的曲面；机器人感应装置和人工智能系统。
其他应用程序“其他系统也可以从中受益—例如那种需要生物反馈的—举个例子，智能方向盘可以感应到，如果司机睡着了，”Lipomi补充说。
外文翻译(英文)用氧化物粉末制NTC热敏电阻的微观结构与导电性能的关系(外文)
Correlation between Microstructure andConductance in NTC Thermistors Produced from Oxide PowdersG.D.C.Csete de Gyo rgyfalva,*A.N.Nolte and I.M.ReaneyDepartment of Engineering Materials,Sir Robert Had®eld Building,University of She eld,She eld,S13JD,UKAbstractA detailed study of spinel-structured Ni 1Àx Mn 2+x O 4formed by a mixed oxide route has shown that when x %0a high proportion of NiO is residual in the sin-tered ceramic.Wickham (Wickham,D.G.,Solid phase equilibria in the system NiO±Mn 2O 3±O 2.J.Inorg.Chem.,1964,26,1369±1377)demonstrated that the spinel phase decomposes in air above 900 C.Sintering in this system is usually per-formed around 1200 C.Decomposition of the spi-nel phase is therefore inevitable.The e ect of decomposition on the microstructure and electrical properties of Ni 1Àx Mn 2+x O 4based ceramics is discussed.#1999Elsevier Science Limited.All rights reservedKeywords :microstructure,electrical conductivity,spinels,thermistors.1IntroductionNegative temperature coe cient (NTC)thermistors are found in an ever increasing number of electrical and electronic products.Ni 1Àx Mn 2+x O 4,where x denotes the deviation from the stoichiometric 1:1NiO:Mn 2O 3ratio,o ers a range of properties that are suitable for most temperature sensing applications.When x =0,(nickel manganite,NiMn 2O 4),the solid solution has an inverse cubic spinel structure,based on a 2Â2Â2array of face centred cubic (fcc)oxygen subunits.When x =1,Mn 3O 4is present which is a tetragonally distorted spinel.The properties routinely used to characterise NTC thermistors are resistance,R 1and R 2,at 25 C (T 1)and 85 (T 2)and a B value (with units of tem-perature in Kelvin)which is a measure of the sensi-tivity of the device over a given temperature range:BT 1T 2T 2ÀT 1ln R 1R 2IThe exact mode of conduction in nickel manga-nite is poorly understood,but several modelsinvoke the small polaron theory.1,2Small polaron conduction is sometimes referred to as a `hopping'mechanism,as it involves the transfer of polarisa-tion from one cation to another.In the nickel manganite system,it has been postulated that the mixed valence,Mn 4+,Mn 3+cations present on the octahedral sites give rise to these small polaron pathways.1The octahedral cations in the spinel structure lie in chains along some <110>direc-tions.These vectors represent the smallest inter-cationic distances within the unit cell.Another important parameter when considering applications for Ni 1Àx Mn 2+x O 4ceramics is their thermal stability or aging characteristics (changes in conductance over long periods,i.e.lifetime of the component).Reports indicate that better ther-mal stability is found in tetragonal ceramics rather than cubic materials though the conductivity of the latter is 10to 100times higher.2,3This could be explained by a reduction in the concentration of Mn 4+compared to Mn 2+and Mn 3+or possibly by the presence of planar defects such as ferroelas-tic domain walls.4Ni 1Àx Mn 2+x O 4ceramics have been prepared by the carbonate and oxalate methods,in addi-tion to the more conventional mixed oxide route.5Irrespective of the preparation route,sintering (typically around 1200 C)is always carried out above the decomposition temperature in air for the system ($900 C)as discussed by Wickham.5Con-sequently,ceramics ®red using conventional pro-cessing will contain multiple phases,e.g.NiO fromJournal of the European Ceramic Society 19(1999)857±860#1999Elsevier Science LimitedPrinted in Great Britain.All rights reservedP I I :S 0955-2219(98)00331-80955-2219/99/$-see front matter857*To whom correspondence should be addressed.Fax:+44-(0)114-222-5943;e-mail:mtp96gdc@she the decomposed spinel and Mn-rich regions,3,6,7in accordance with the equation:xiwn III2y43x xiy 3Àx3xi II 3À3x a 3Àxwn II 2x a 3Àx wn III2O4 x6O2PIt is the intention of this paper to demonstrate how the degree of decomposition from single phase in¯uences conductivity and,in particular,aging. X-ray di raction and transmission electron micro-scopy will be used to monitor the degree of decomposition and accelerated aging tests(470 C) will be performed.2Experimental ProcedureThe NiO and Mn2O3powders in a1:1Mn2O3:NiO molar ratio were weighed out using an electronic balance( 0.01g)and transferred to a poly-propylene vessel with a charge of ZrO2milling media(the weight of ZrO2varied with the weight of the batch being processed).The batch was mil-led for6h to reduce particle size distribution to a mean of6"m and a maximum of12"m then drawn through a suction®lter.The resulting slurry was dried in a70 C oven overnight.The dried powder was calcined in a mullite crucible at900 C for16h and subjected to a further6h milling under the above conditions.One one cm diameter pellets were pressed from the powders and sintered at 1250 C,achieving densities better than95%. Microstructural and structural characterisation were carried out using transmission electron microscopy(TEM)and X-ray di raction(XRD), respectively.XRD was performed on solid cera-mics and loose powders using a Phillips PW1050 di ractometer with a Cu K source.A0.02 step size was used at a scan rate of0.5 minÀ1.TEM samples were prepared by grinding the ceramic to a thickness of20"m and ion beam milling to per-foration.Images were obtained using JEOL200CX and3010TEMs:the latter was equipped with a LINK energy dispersive X-ray detector. Accelerated aging tests were carried out using a non-induction wound furnace held at470 C.Tem-perature¯ux was monitored in the furnace using a thermocouple mounted immediately adjacent to the test piece.Platinum wires leading to a high precision HP4284A LCR meter were used to make contact to the electroded surface of the cera-mic.Changes in the resistance of the leads and contacts as a function of temperature were taken into account by performing a closed circuit run.Typically,temperature varied within a 0.2 C range over10h.3Results and DiscussionWickham,5in his study of the Ni1Àx Mn2+x O4solid solution,demonstrated that above900 C decom-position occurs resulting in the formation of NiO and a Mn-rich spinel phase.The higher the tem-perature above the onset of the decomposition reaction,the more rapid the rate.In order to study the decomposition reaction in more detail and its potential e ect on electrical properties,single phase ceramics(within the sensitivity of conventional XRD)were fabricated,as demonstrated in Fig.1. Figure2shows a series of XRD traces from single phase samples heat treated at1000,1100and 1200 C for1h.The evolution of peaks corres-ponding to NiO can be observed in accordance with the predictions of Wickham.6The relative intensities of the NiO peaks(marked)increase with increasing temperature.Figure3is a bright®eld(BF)TEM image showing a typical region of spinel grains in single phase material.The grain boundaries and interiors are free from second phase.Inset in Fig.3is a <110>zone axis di raction pattern(ZADP)from one of the spinel grains in the image.Figure4isaFig.1.XRD trace of single phase ceramic.Note absence ofNiOpeaks.Fig.2.XRD spectra of samples held at1000,1100,1200 c for1h.NiO peaks are marked.858G.D.C.Csete de GyoÈrgyfalva et al.BFTEM image obtained from a sample decom-posed for9h at1250 C.Inset is a<110>ZADP pattern from the imaged region.The fundamental re¯ections can be indexed according to a<110> zone axis from rock salt structured NiO.The weak re¯ections at half integer positions arise from regions of spinel phase,observed as dark contrast. Rock salt(NiO)and spinel structured compounds invariably exhibit a cube//cube orientation rela-tionship.Oxides with the rock salt structure are based around single fcc oxygen subunits whereas spinel structured compounds have a2Â2Â2fcc oxygen sublattice.In order to study the aging characteristics of the ceramics as a function of decomposition,con-ductance measurements were performed over10h at470 C 0.2 C.Figure5shows the change in conductance normalised to the initial value,against time at470 C for(A)single phase spinel and(B) `partially'decomposed spinel(heat treated for9h at1250 C).The single phase sample showed a negligible drift in resistivity over the test period, whereas the`partially'decomposed sample exhib-ited a steady decline in conductance.Di erences in the absolute starting values can be attributed to small variations in the dimensions of the samples. Figures6and7are XRD traces showing the samples before and after the accelerated aging experiments.Figure6,which corresponds to Fig.5(A)(decomposed),shows a reduction intheFig.4.BFTEM image of spinel regions in a NiO matrix.Insetis a<110>ZADP from the NiO.Faint re¯ections are presentat half integer positions arising from the dark regions ofspinel.Fig.5.Graph showing normalised conductance versus time at470 C for(A)single phase and(B)decomposed(9h at1250 C)material.Fig.6.XRD spectra of single phase sample(A)before and(B)after acceleratedaging.Fig.7.XRD spectra of decomposed sample(A)before and(B)after acceleratedaging.Fig.3.BFTEM image of spinel grains in single phase mate-rial.Inset is a<110>zone axis di raction pattern(ZADP)from a spinel grain.NTC thermistors produced from oxide powders859intensity of the NiO peaks(A)before and(B)after the experiment.However,Fig.7,which corre-sponds to Fig.5(B)(single phase),shows traces that are identical(A)before and(B)after.It is thought that the accelerated aging at470 C leads to NiO being re-absorbed into the ceramic during the lifetime of the experiment.It is proposed that the decomposition reaction occurs homogeneously throughout the ceramic,and the NiO is intimately mixed with the spinel phase,as evidenced by Fig.4. The reverse process may therefore occur relatively quickly because of the short di usion distances involved(of the order of nm according to Fig.4). However,it should be noted that aging at room temperature may be related to di erent phenomena than suggested by these accelerated tests.4Conclusions.The reaction between NiO and Mn2O3pro-ceeds forwards slowly at temperatures less than900 C,but will reverse as temperature increases above this value..The rate of decomposition increases with increasing temperature resulting in amicrostructure of intimately mixed NiO and Mn-rich spinel..Initial investigations indicate that a single phase ceramic gives rise to substantial improvements in thermal stability under accelerated aging.References1.Brabers,V.A.M.and Terhell,J.,Electrical conductivityand cation valencies in nickel manganite.Phys.Stat.Sol.(a),1982,69,325±332.2.Dorris,S.E.and Mason,T.O.,Electrical properties andcation valences in Mn3O4.J.Am.Ceram.Soc.,1988, 71(5),379±385.3.Rousset,A.,Larange,A.,Brieu,M.,Couderc,J.andLegros,R.,In¯uence de la microstructure sur la stabilite electrique des thermistance.C.T.N Journ.de Phys.III, 1992,4,833±845.4.Macklen,E.D.,Electric conductivity and cation distribu-tion in nickel manganite.J.Phys.Chem.Solids,1986, 47(11),1073±1079.5.Wickham,D.G.,Solid phase equilibria in the systemNiO±Mn2O3±O2.J.Inorg.Chem.,1964,26,1369±1377.6.Feltz,A.,Topfer,J.and Schirrmeister,F.,Conductivitydata and preparation routes for NiMn2O4thermistor ceramics.J.Eur.Ceram.Soc.,1992,9,187±191.7.Jung,J.,Topfer,J.,Murbe,J.and Feltz,A.,Micro-structure and phase development in NiMn2O4spinel ceramics during isothermal sintering.J.Europ.Ceram.Soc.,1990,6,351±359.860G.D.C.Csete de GyoÈrgyfalva et al.。
聚释氟乙烯的耐高温度点
聚释氟乙烯的耐高温度点英文回答：Polytetrafluoroethylene (PTFE), commonly known as Teflon, is a synthetic fluoropolymer with excellent thermal stability. Its high-temperature resistance is one of its key properties, making it suitable for various high-temperature applications. The melting point of PTFE is around 327°C (621°F), and it can withstand continuous use at temperatures up to 260°C (500°F). At higher temperatures, PTFE undergoes gradual degradation, releasing toxic fumes. Therefore, it is generally recommended to use PTFE below 260°C (500°F) for optimal performance and safety.PTFE's high-temperature resistance can be attributed to several factors. Firstly, the strong carbon-fluorine bonds in the PTFE molecule provide excellent thermal stability. The fluorine atoms have a high electronegativity, which draws electrons away from the carbon atoms, creating astrong and rigid molecular structure. Secondly, the non-polar nature of the PTFE molecule reduces intermolecular forces, allowing the polymer chains to slide past eachother easily. This reduces the coefficient of friction and prevents the material from sticking or melting at high temperatures.The high-temperature resistance of PTFE makes itsuitable for various applications, including:Aerospace components: PTFE is used as seals, gaskets, and insulation in aircraft and spacecraft due to itsability to withstand extreme temperatures and harsh environments.Chemical processing equipment: PTFE is used in linings, gaskets, and seals for chemical processing equipment due to its resistance to corrosive chemicals and high temperatures.Electrical insulation: PTFE is used as insulation for electrical wires and cables due to its high dielectric strength and resistance to heat.Semiconductor manufacturing: PTFE is used as a protective layer in semiconductor manufacturing due to its resistance to high temperatures and chemicals.Medical devices: PTFE is used in medical devices, such as catheters and implants, due to its biocompatibility and resistance to high temperatures.中文回答：聚四氟乙烯（PTFE），俗称特氟龙，是一种具有优异耐热稳定性的合成氟聚合物。
温湿度传感器英语单词
温湿度传感器英语单词Temperature and humidity are critical factors that influence our daily lives, and their monitoring isfacilitated by a device known as a "hygrometer."This instrument is essential in various settings, from homes to laboratories, ensuring that the environment is comfortable and conducive for various activities.A hygrometer measures the amount of moisture in the air, which is expressed as "relative humidity." It helps in understanding the atmospheric conditions that can affect health and well-being.In addition to humidity, a hygrometer often includes a thermometer to gauge the "ambient temperature." This dual functionality makes it a versatile tool for maintaining optimal living and working conditions.For accurate readings, it's crucial to place the hygrometer in a well-ventilated area, away from direct sunlight or heat sources, which can skew the temperature readings.Understanding the hygrometer's readings can help in making informed decisions, such as adjusting the thermostat or using a dehumidifier to achieve a balanced environment.In summary, a hygrometer is an indispensable tool for anyone looking to monitor and control the temperature and humidity levels in their surroundings.。
小黑头热敏电阻制作流程
小黑头热敏电阻制作流程英文回答：To make a thermistor, also known as a thermal resistor, you will need a few basic materials and follow a simple process. First, you will need a ceramic or metal oxide material that has a high temperature coefficient of resistance. This means that the resistance of the material changes significantly with temperature. Common materials used for thermistors include nickel oxide, manganese oxide, and cobalt oxide.Next, you will need to mix the chosen material with a binder, such as epoxy or glass, to form a paste. This paste is then applied to a substrate, such as a ceramic disc or a metal plate, using a screen printing technique. The substrate acts as the base for the thermistor and provides mechanical support.After the paste has been applied, the substrate isfired in a kiln at high temperatures to sinter the material and binder together. This process helps to form a solid, uniform film on the substrate. The firing temperature and time are crucial to ensure the thermistor's performance and stability.Once the film has been sintered, electrodes are added to the thermistor to allow for electrical connections. These electrodes are typically made of a conductive material like silver or platinum and are attached to the film using a bonding process.Finally, the thermistor is encapsulated in a protective casing to shield it from external factors like moisture and mechanical damage. The casing can be made of materials like epoxy resin or glass to ensure the longevity of the thermistor.Overall, the process of making a thermistor involves careful selection of materials, precise manufacturing techniques, and quality control measures to produce a reliable and accurate temperature-sensitive resistor.中文回答：制作热敏电阻（thermistor），也称为热敏电阻器，需要一些基本材料和简单的工艺。
设把一块牛肉当作厚2δ的无限大平板
Bi数的物理意义是什么？Bi→0和Bi→∞分 别表示了怎样的换热条件？
本节重点词汇
unsteady heat conduction 非稳态导热 non-regular regime 非正规状况阶段 regular regime 正规状况阶段
25.6
例题3-2
一温度计的水银泡呈圆柱形，长20mm，内径 为4mm，初始温度为t0，今将其插入到温度较 高的储气罐中测量气体温度。设水银泡同气 体间对流换热系数为h=11.63W/(m2·K)，水银 泡一层薄玻璃的作用可以忽略不计.水银的物 性参数：λ=10.36W/(m·K);ρ=13110kg/m3; c=0.138kJ/(kg·K) 试计算此条件下温度计的时间常数，并确定 插入5分钟后温度计读数的过余温度为初始过 余温度的百分之几？
0＜Bi＜∞ a large roast in a oven
Example
现代微波炉加热物体的原理是利用高频电磁波使物 体中的分子极化产生震荡，其结果是相当于物体中 产生了一个接近于均匀分布的内热源；而一般烘箱 是从物体的外表面进行接近于恒热流的加热，设把 一块牛肉当作厚２δ的无限大平板， 试定性画出采用微波炉及烘箱对牛肉加热过程中的 温度分布曲线(开始加热,加热过程中,及终了时刻)
[Solution]
t
τ2 τ1 τ0
x microwave
t
τ2 τ1 τ0
x baker
求解非稳态问题的简化 方法，很重要！
3-2 Lumped-heat-capacity method
集中参数法
本节要注意的问题
集中参数法的物理概念及数学上处理的特点
什么是时间常数？它与哪些参数有关？
THD2FE非接触前额温度计说明书
THD2FE Non-contact Forehead Thermometer⇔The device setting with buzzer is on, you can set buzzer on/off under Mute mode.beep sounds. You can also use the same process to turn off the Mute function.Use of the thermometerNote: If there is any temperature difference between the places where the device is stored and where you are going to measure, subject and the device should stay in the same room for at least 15 minutes before measurement.1. Always make sure the probe lens is clean without any damage and the forehead is clean. Warning: Choking from swallowing small parts and batteries by children or pets is possible, please keep small parts and batteries at places wherechildren and pets can’t reach.2. Power on:Press the “ON/MEM ” button (see figure 1).3. Measuring body temperature on the forehead:Indications for use: The Non-contact Clinical Thermometer, Model THD2FE is an infrared thermometer intended for the intermittent measurement of human body temperature in people of all ages.Ref No.：032020Press the “ON/MEM” button to power on the device. Forehead mode is the default mode. You can see the icon on the screenand hear two beep sounds (see figure 1). In this mode, you can hold the thermometer within 1.5 inch from the central forehead (Fig. 2) andpressthe "START" button to get the forehead measurement. The time consuming for measurement might be 1 second. After each foreheadmeasurement, wait icon stop flashing to be ready for next measurement.Figure 2 Points for attention:a. Forehead temperature is displayed in oral mode. This mode converts the forehead temperature to display its “oral-equivalent” value.b. Before the measurement, the subject should stay in a stable environment for 5 minutes and avoid exercise, bath for 30mins.c. Remember to keep the forehead area clean and away from sweat, cosmetics and scar while taking temperature.d. The “Clinical Bias” is -2.5 ~ -3.1°F (-1.4 ~ -1.7°C).e. The “Limits of Agreement” is 0.98.f. The "Repeatability" is 0.36°F (0.20°C)4. Measuring surface temperature:4.1 After power on, press and hold the “ON/MEM” button, and press the “START” button one time for “Infrared thermometer” mode to see icon on your LCDdisplay. In this mode, you can get the target surface temperature.4.2 When you press the “START” button, you will get the real time temperature immediately. If you press and hold the “START” button, the reading of measurement willbe continuously updated.4.3 Applications include temperature measurements for water, milk, cloth, skin or other objects.* Note: This mode shows the actual and unadjusted surface temperature which is different from the body temperature.5. Power off:5.1 Device will automatically shut off if left idle for more than 1 minute to extend battery life.ProblemWarranty:Warranty: 12 monthsManufacture Date: as the serial number (please open the battery cover, it is shown on the inside of the device.)Ex.SN:E512A000001, the first “E” is External, the second number “5” is the last number of manufacture year, the third and the fourth number “12” is the manufacture Note: The thermometer is calibrated at the time of manufacture. If you question calibration mode, the accuracy of temperature measurements or unexpected events at any time, please contact the dealers or nearest service address.Warning: No modification of this equipment is allowed.Please read the instructions for use BF type applied partMetris instrument east, IIcAdd: 25 Long Meadow PlaceSouth Setauket, NY USA 11720Figure 1 Figure 2 Figure 3IP220,120,23 FM c)±5 kHz deviation1 kHz sine。
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ERC Center for Computational Sciences, Mississippi State Univ., Mississippi State, MS, USA Department of Physics and Astronomy, Mississippi State Univ., Mississippi State, MS, USA 3 Center for Computational Sciences, Oak Ridge National Lab, Oak Ridge, TN, USA 4 School for Computational Science and Information Technology, Florida State University, Tallahassee, FL, USA 5 Center for Materials Research and Technology and Department of Physics, Florida State University, Tallahassee, FL, USA
2.
METHODS AND MODELS
2.1
Coherent Rotation
Given a single-domain particle with uniaxial anisotropy, it is possible to find the quasi-static equilibrium position of the magnetization when a magnetic field is applied at some angle to the easy axis. It is assumed that the magnetization can be represented by a single vector, M , with constant amplitude, MS. The energy density is then E = K sin2θ – MSH cos(φ−θ), (1) where K is the uniaxial anisotropy constant, H is the magnetic field applied at an angle φ to the easy axis and θ is the angle the magnetization makes with the easy axis. Stoner and Wohlfarth showed that the critical transition curve for the coherent reversal of the magnetization is given by,1 2/3 2/3 (2) hAX + h AY =1 where hAX and hAY are the components of the magnetic field along the easy and hard axes respectively. Equation (2) is the well-known equation of a hypocycloid of four cusps, also known as an astroid.
(5)
where H T (ri ) is the total local field at the i-th position, γ0 is the gyromagnetic ratio (1.76x107 rad/Oe-s), and α is a dimensionless phenomenological damping term which determines the rate of energy dissipation. The first term represents the precession of each spin around the local field, while the second term is a dissipative term that drives the motion of the magnetization towards equilibrium. For the sign of the undamped precession term, we follow the convention of Brown.3 The total local field, H T (ri ) , may include contributions from the applied field (Zeeman term), the crystalline anisotropy (set to zero in our model), the dipole field, and exchange interactions. At nonzero temperatures, thermal fluctuations also contribute a term to the local field in the form of a stochastic field which is assumed to fluctuate independently for each spin. The fluctuations are assumed Gaussian, with zero mean and (co)variance given by the fluctuation- dissipation theorem.5 While the stochastic thermal field requires careful treatment of the numerical integration in time, the most computationally intensive part of the calculation involves the dipole term. For systems with more than a few hundred spins, it is necessary to use a more advanced algorithm. We use the Fast Multipole Method (FMM), the implementation of which is discussed elsewhere.5 In this paper, we examine two model systems. The first is a nanopillar with dimensions of 5.2 nm x 5.2 nm x 88.4 nm. The cross-sectional dimensions are small enough (about 2 exchange lengths) that the assumption is made that the only significant inhomogeneities in the magnetization occur along the long axis6 (z-direction). The particles in this model, discussed previously,5 are therefore discretized into a linear chain of 17 spins along the long axis of the pillar. The second model system consists of a single nanopillar with dimensions 9 nm x 9 nm x 150 nm. The dimensions were chosen to correspond to arrays of Fe nanopillars fabricated by Wirth, et al.7 In this model, the system is discretized into 4949 sites (7 x 7 x 101) on the computational lattice. Material properties in both systems were chosen to correspond to bulk Fe. The saturation magnetization is 1700 emu/cm3 and the exchange length (the length over which the magnetization can change appreciably) is 3.6 nm.
Abstract:
We present micromagnetic results for the hysteresis of a single magnetic nanopillar that is misaligned with respect to the applied magnetic field. We provide results for both a one-dimensional stack of magnetic rotors and of full micromagnetic simulations. The results are compared with the StonerWohlfarth model. hysteresis, micromagnetics, nanomagnets
Key words:
1.
INTRODUCTION
Although hysteresis in single-domain nanomagnets has been known for many decades, there is currently much interest in looking anew at this phenomenon. This is partly driven by recent experiments on singledomain nanomagnets, in which the hysteresis and magnetization reversal of a single single-domain nanomagnet can be measured. It is also driven by the applications of nanomagnets, in particular to magnetic recording.