液体的沸点与气压关系的实验

如图１连接好仪器．阀门Ｅ处于开启状态,使烧瓶与大气相通．用酒精灯给烧瓶加热．图　１Ａ——烧瓶　Ｂ——Ｔ形管　Ｃ——温度计Ｄ——Ｕ形压强计　Ｅ——阀门Ｆ——支架　Ｇ——酒精灯待水沸腾时观察温度计的示数和压强计两液面高度的变化（温度１００℃,压强计无变化）．关闭阀门Ｅ,向瓶内充气,观察此时水的沸腾情况、温度计的示数和压强计两端液面高度的变化（水停止沸腾,温度１００℃,瓶内压强大于ｐ０）．开启阀门Ｅ,使压强计两液面高度相同．撒去酒精灯,待水温降低些,关闭阀门Ｅ,向瓶外抽气至水沸腾．观察此时温度计示数和…     

温度与温标

一、引 言 人类对于冷热的感觉是在很早以前就有的.夏季的炎日,寒冬的冰河,早就作用于他们的感官并逐渐在人们的头脑里形成了概念.但是,使冷热的概念精确化、温度(数值)和温度计的出现,却是近三百年来的事情.1660年酒精温度计的出现是向冷热现象作探讨的重要一步.1714年华伦海脱(Fahrenheit)改良了水银温度计,大体上以当地冬季最冷的气温为0℃,以人的体温约为100°,这样一来,就造成了水的冰点为32°,水沸点为212°的华氏温度计.冰点和水沸点之间的温度划为180个等分,每一等分叫做华氏1°,温度数值的如此表示法,叫做华氏温标.虽然工业和科学…     

水沸腾实验的改进

初中物理关于汽化的教学涉及一个探究水沸腾的实验.此实验的过程是用酒精灯对烧杯中的水加热,将温度计插入水中,相隔一定时间读出温度计的即时读数;根据记录的结果画出一个温度随时间变化的图像,通过分析记录结果和图像来验证水沸腾时温度不变的汽化规律.     

关于液体蒸发时温度降低演示实验的改进

在温度计上包蘸酒精棉花做液体蒸发时温度降低的实验,较短的时间内温度计读数下降不够明显,如室温是10℃时,大约是两分钟温度计读数下降1℃。究其原因,显然是由于棉花吸收了较多的酒精,从而导致温度降低慢。因此,我在实验中用温度计蘸取酒精来代替包上酒精棉花,这样一来,既节省了酒精,还增强了实验效果,在室温11℃时     

低温铑铁电阻温度计

本文对研制的低温铑铁电阻温度计结构和制作工艺作了简要叙述.给出了该温度计在液氮、液氢和液氦中反复锻炼后在水三相点温度时的阻值的稳定性.试制的多数温度计年变化率≤8×10~(-6);温度计的主要性能与英国国家物理研究所制作的铑铁电阻温度计性能相比,前两项接近,后项相等.分度后可给出其不确定度为士0.004K.     

水的热膨胀的演示

利用某些物质溶解时的吸热现象来代替冰——例如按每克分子溶于水时NaNO_3吸热5.03大卡,K_2SO_4吸热6.38大卡,NH_4Cl吸热3.88大卡,只要将其中任何一种溶质溶解于水时,都能使温度降至0℃以下。我们掌握这一点,采用了工业常用的寒剂NH_4NO_3和NaNO_3分别做了实验,实验结果都成功。(一)实验步骤: ①用100c.c.的烧瓶装满纯净的冷水(蒸馏水),将橡皮塞穿两孔,分别插入温度计及内径很小长约15厘米的玻璃管(我们利用内径较大     

一道中考实验题的答案分析及教学启示

[题目]如图,在"观察水的沸腾"实验中 (1)水在沸腾时,温度计示数如图所示,此时水的沸点为____℃,表明当时的大气压强要比一个标准大气压____.     

碳纳米管的新应用--最小的温度计

最近 ,来自日本材料科学国家研究院的Ｇａｏ等人将液态金属Ｇａ装入碳纳米管 ,制成了世界上最小的温度计 .碳纳米管的直径只有 75ｎｍ ,长度约 10μｍ .它在 2 0— 5 0 0℃的温度范围内可以保持其内径不变 ,其线膨胀系数仅为 - 1× 10 -6/℃ .金属Ｇａ在2 9 78— 2 4 0 3℃的温区内呈液态 ,并且具有极低的蒸气压 .因此 ,在特定温度下 ,纳米温度计中Ｇａ液柱的高度由Ｇａ的总体积惟一地决定 .Ｇａｏ等人对准一维液态Ｇａ的实测表明 :其体积随温度线性变化 ,即Ｖ=Ｖ0 [1+α(ｔ-ｔ0 ) ],其中ｔ0 和Ｖ0 是参考点的温度和体积 .在 30— 977℃之间…     

恒温器径向温度不均匀性对低温温度计精密校验影响的估计

在分析低温温度计的校验误差时,需要估计温度不均匀性的影响.本文提出一个估计这种影响的方法.若使用同一型号的两支电阻温度计进行测试,则径向温度理想均匀的必要条件是两温度计的电阻比不因温度起伏而变化,充分条件是两温度计所处部位之间无同步温差.分析测试数据对这两个条件的偏离,就可以估计出温度不均匀性的影响.文中给出方法应用实例,并对实验条件进行讨论.     

测量液体膨胀系数的新方法

液体膨胀系数是指温度每改变1摄氏度时,其体积的变化和它在0℃时体积之比。本文自组了测量液体膨胀系数的实验装置,将毛细管与感温泡组装成实验用的感温液体的容器,再用恒温水浴锅作为改变液体温度的设备,记录实验数据,处理数据,得出水和乙醇的膨胀系数。实验结论对温度计的设计与校准有重要的参考作用。实验结果与标准值相比较误差分别为2.9%和3.0%,相对误差小,说明该实验方案可行。     

Guided-Wave Two-Dimensional Acousto-Optic Scanner Using Proton-Exchanged Lithium Niobate Waveguide

Two-dimensional scanning of a 0.6328 mum guided-light beam has been realized using noncolinear acousto-optic (AO) coplanar Bragg diffraction together with colinear AO guided-mode to substrate radiation-mode conversion in a Z-cut Xpropagation LiNbO3 proton-exchanged (PE) waveguide. The two surface acoustic (SAW) waves utilized are at the center frequencies of 500 and 200 MHz, propagating in the Y and X axes, respectively. Two-dimensional scanning of approximately 720 resolvable light beam spots, namely, 18 40 (horizontal vertical) scanning, has been demonstrated using a light beam of 1.0 mm aperture. The total number of resolvable beam spots can be greatly increased from 720 by simply utilizing SAW transducers of larger bandwidth and a light beam of greater aperture. It should also be possible to significantly increase the diffraction efficiency from 3 % by optimizing the parameters of the PE waveguide and the SAWs.     

Hybrid Wavelength and Code Division Multiple Access in Optical Networks

A review of schemes for multiple access in fiber optic networks shows that a hybrid of wavelength and code division multiple access (WCDMA) combines the best features of both. In particular, the hybrid scheme retains the large information carrying capacity of wavelength division multiple access (WDMA) and flexibility of code division multiple access (CDMA). In this paper WDMA, optical CDMA (OCDMA), and WCDMA networks are discussed. In OCDMA networks, concept of incoherent and coherent coding including inverse decoding and matched filter is introduced. The delay performance of both WDMA and WCDMA networks, under the simple suboptimum access protocols based on cyclic search, is computed. It has been shown quantitatively that tuning delay significantly affects the delay performance of both WDMA and WCDMA networks. Futhermore, delay performance of WCDMA networks is always better than the WDMA networks for the same tuning delay, load, and number of users.     

Effect ofγ-radiation on the spectral luminescence characteristics of impure cadmium tungstate crystals

Results of a study of the effect of γ-radiation on the spectral luminescence properties of cadmium tungstate crystals doped with silver, bismuth, and molybdenum cations are presented. Spectral characteristics of the nondnnnoped crystals are briefly described. Absorption and photo and X-ray luminescence spectra of the crystals taken before and after exposure to γ-radiation (5.5·10⁴ Gy) are compared. It is found that the spectral characteristics of the crystals doped with silver, bismuth, and molybdenum cations do not change markedly after the exposure. The relation between the type of impurity-induced defects, individual characteristics of the impurity cations, and the character of the effect of γ-radiation on the spectral luminescence properties of impure crystals is analyzed (preliminarily). Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 1, pp. 55–60, January–February, 1997.     

Theoretical analysis and simulation of conjugate heights for dual-conjugate AO system in lidar

A multi-conjugate adaptive optics （MCAO） can offer a possibility of widening field of view （FOV） characterized by the isoplanatic angle, and the choose of conjugate height becomes a basic problem for MCAO, which influences the size of iosplanatic angle. Considering the application of lidar, the isoplanatic angle＇s expressions of two deformable mirrors （DMs） MCAO for uplink and downlink are deduced. The effects of conjugate heights for dual-conjugate AO are thoughtfully discussed, and the isoplanatic angles are further analyzed. The results show that the isopanatic angle varies with the conjugate height and reaches the maximum as the conjugate height is at the optimal altitude. Moreover, the optimal conjugate height changes with the propagation distance.     

Quick single-photon detector with many avalanche photo diodes working on the time division

Due to the limit of response speed of the present single-photon detector, the code rate is still too low to come into practical use for the present quantum key distribution (QKD) system.A new idea is put up to design a quick single-photon detector.This quick single-photon detector is composed of a multi-port optic-fiber splitter and many avalanche photo diodes (APDs).Au of the ports with APDs work on the time division and cooperate with a logic discriminating and deciding unit driven by the clock signal.The operation frequency lies on the number N of ports, and can reach N times of the conventional single-photon detector.The single-photon prompt detection can come true for high repetition-rate pulses.The applying of this detector will largely raise the code rate of the QKD, and boost the commercial use.     

Research on beamforming method for dual-line array with space mismatch between the two line arrays

The performance of port/starboard discrimination of dual-line array will be seriously degraded when the space between the two line arrays of the dual-line array is mismatched. The directivity function of the delay-sum and delay-subtract beamforming is deduced and the port/starboard discrimination of the delay-sum and delay-subtract beamforming is also studied both under the ideal status and the status under which the space between the two line arrays of the dual-line array is mismatched. Analysis results show the delay-subtract beamforming has better performance of port/starboard discrimination. At last, the sea trial results demonstrate the theoretical results.     

Retrieval of ultraviolet skylight radiances and O3 slant column densities from balloon-borne limb spectrometer

With a novel light-weight and absolutely calibrated ultraviolet （UV） spectrometer, UV skylight radiances and O3 slant column densities are measured by balloon-borne limb measurements in Xinjiang area, China. UV skylight radiances measured at the height of 31 km are compared with the results from Modtran in the wavelength range from 290 to 420 nm. O3 slant column densities are derived from radiance spectra in the Huggins bands （320 - 335 nm） using differential optical absorption spectroscopy method. And the parameter exhibits a good correlation with the same value simulated by radiative transfer model （Tracy）. The O3 profile simultaneously measured by an O3 sonde is used as input in Tracy calculations. The O3 sonde is launched on the same balloon.     

Design optimization of highly sensitive LSPR enhanced surface plasmon resonance biosensors with nanoholes

For breaking through the sensitivity limitation of conventional surface plasmon resonance (SPR) biosensors, novel highly sensitive SPR biosensors with Au nanoparticles and nanogratings enhancement have been proposed recently.But in practice, these structures have obvious disadvantages.In this study, a nanohole based sensitivity enhancement SPR biosensor is proposed and the influence of different structural parameters on the performance is investigated by using rigorous coupled wave analysis (RCWA).Electromagnetic field distributions around the nanohole are also given out to directly explain the performance difference for various structural parameters.The results indicate that significant sensitivity increase is associated with localized surface plasmons (LSPs) excitation mediated by nanoholes.Except to outcome the weakness of other LSP based biosensors, larger resonance angle shift, reflectance amplitude, and sharper SPR curves' width are obtained simultaneously under optimized structural parameters.     

Polymer gratings based on photopolymerization for low-order distributed feedback polymer lasers

Novel polymer distributed feedback(DFB)gratings are fabricated based on photopolymerization to reduce lasing threshold of polymer lasers.A photopolymer formulation sensitive to 355-nm ultraviolet(UV)light is proposed for the fabrication of polymer gratings and it can be used to form polymer films by spin-coating process.A very low surface-relief depth ranging from 12.5 to about 1.0 nm has been demonstrated with a refractive-index modulation of about 0.012.The experimental results indicate that such polymer gratings have promising potentials for the fabrication of low-order DFB organic semiconductor lasers.