两种能衡式蒸汽干度仪的研究

水蒸气干度是水蒸气的品质参数,在许多工业生产中需要实时测量与控制该参数。文中分析了现有蒸汽干度的测量方法和测量仪器,根据能量守恒原理以及混合式和凝结式蒸汽干度的测量原理,研制了两种能衡式干度测量仪,定量分析了它们的测量精度,并从实用稳定性的角度得出了凝结式蒸汽干度仪更佳。为了验证测量精度,建立了蒸汽干度实验台。实验不仅验证了能衡凝结式蒸汽干度仪的精度高达98%以上,而且还表明它具有稳定性、准确性和实用性。

冷凝式蒸汽干度仪的模拟与研制

蒸汽是重要的二次能源,为了安全、经济地使用蒸汽,许多工业生产中都需要实时测量控制湿蒸汽干度。根据能量守恒原理、质量守恒原理以及凝结法的测量原理,研制了冷凝式蒸汽干度仪,运用软件进行了模拟计算,并通过建立湿蒸汽干度检测台进行实验研究。研究表明该干度仪具有结构简单,成本低,精度高,测量范围宽等优点。

新型油田热采蒸汽流量干度计量仪

由于稠油的黏度大、流动性差、凝固点高等因素决定了稠油难以像稀油那样直接采出,因此在实际生产过程中,90%以上依靠蒸汽吞吐或蒸汽驱动进行稠油开采。但注入蒸汽的计量问题一直困扰着稠油生产,依靠人工经验计算的蒸汽注入量精度不高,因此在实际生产过程中造成蒸汽利用率低、浪费大等问题。新型油田热采蒸汽流量干度计量仪,采用分流分相式两相流体流量测量方法:从注汽管道提取一定比例的蒸汽,然后经过分离,分离出的蒸汽经过气体流量计进行计量,同时分离出的液体经过液体流量计,最终经过分离方程进行运算,计算出主管道蒸汽流量、干度、温度等一系列油田所需数据。此套计量仪所有计量参数精度可以达到5%以内。

Experimental research on modulation degree of refractive index in the SCLP/E_7/C_(60) polymer using a fiber Fabry-Perot Interferometer

Modulation degree of refractive index is an important parameter for information storage in photorefractive materials. Using the relationship between the refractive index and the wavelengths of laser and the order of interference, we introduce a new method to measure the modulation degree of refractive index in photorefractive materials through detecting the shift of the interference fringe in a fiber Fabry-Perot interferometer with a CCD. The measurement precision is also analyzed. With this method, the modulation degree of refractive index in our prepared SCLP/E7/C 60 photorefractive polymer is measured for different external voltages and the external voltage corresponding to the maximal modulation degree of refractive index is reported. The dynamic change of refractive index in the SCLP/E7/C 60 is also studied, which will be helpful to understand the reaction mechanism of photochemistry in the material.

Evaluation of an interferometric distance meter

This paper discussed the main parameters contributing to the measurement uncertainty of interferometric distance meter （IDM）. A simple and robust set-up is used to measure distance of about 12 cm with an expanded uncertainty （ k = 2） of ±16.4 μm. The measurement uncertainty is found to be limited by the wavelength measurement accuracy. This set-up can be used to measure distances up to 56 m. It also enables easy determination of the point of equal path difference between the measuring and the reference arms. LabVIEW program is used for counting of the fringes and applying fast Fourier transfor- mation （FFT） to perform frequency selective filtration to the noise. Although the reported uncertainty does not represent the state-of-art uncertainty reached for similar distance, the measurement provides traceable measurement to the unit of length, the meter.

A Novel Dynamic Stretching Solution to Eliminate Saturation Effect in NDVI and Its Application in Drought Monitoring

The normalized difference vegetation index(NDVI) is one of the key input variables for developing drought indices.However,the NDVI quickly saturates in high vegetation surfaces,and thus,the generalization of a drought index over different ecosystems becomes a challenge.This paper presents a novel,dynamic stretching algorithm to overcome the saturation effect in NDVI.A scaling transformation function to eliminate saturation effects when the vegetation fraction(VF) is large is proposed.Dynamic range adjustment is conducted using three coefficients,namely,the normalization factor(a),the stretching range controlling factor(m),and the stretching size controlling factor(e).The results show that the stretched NDVI(S-NDVI) is more sensitive to vegetation fraction than NDVI when the VF is large,ranging from 0.75 to 1.00.Moreover,the saturation effect in NDVI is effectively removed by using the S-NDVI.Further analysis suggests that there is a good linear correlation between the S-NDVI and the leaf area index(LAI).At the same time,the proposed S-NDVI significantly reduces or even eliminates the saturation effect over high biomass.A comparative analysis is performed between drought indices derived from NDVI and S-NDVI,respectively.In the experiment,reflectance data from the moderate resolution imaging spectroradiometer(MODIS) products and in-situ observation data from the meteorological sites at a regional scale are used.In this study,the coefficient of determination(R2) of the stretched drought index(S-DI) is above 0.5,indicating the reliability of the proposed algorithm with surface soil moisture content.Thus,the S-DI is suggested to be used as a drought index in extended regions,thus regional heterogeneity should be taken into account when applying stretching method.

Interferometry observations of low-latitude E-region irregularity patches using the Sanya VHF radar

Interferometry plays an important role in revealing fine-scale structures of ionospheric irregularity.By placing an additional receiving array of four 5-element Yagi antennas in the north of the main East-West array of the Sanya VHF radar,multiple interferometry baselines with components parallel and perpendicular to the magnetic meridian are formed.These baselines allow us to study the three-dimensional(3D)behavior of low-latitude ionospheric field-aligned irregularity(FAI)over Sanya.Using multiple non-collinear receiving baselines,an experiment for which the Sanya VHF radar operated as an interferometer was performed on 10 July 2013.Ionospheric E-region FAI echoes with periods of several minutes were observed during 0745-0915 UT;mean Doppler velocity was around -30 m/s with spectral widths of about 50 m/s.The interferometry results show fine-scale structures of E-region FAI with a zonal scale size of 15 km or less.In addition,we found that the periodic variations of echo intensity shown in radar range-time-intensity(RTI)maps were produced by spatially separated E-region irregularity patches.The patches drifted westward with a velocity of about 40-60 m/s and could be associated with propagating gravity waves.These results provide a clearer picture of the characteristics of FAI and thus help to investigate the generation and dynamics of low-latitude ionospheric irregularities in the Chinese sector.

Temperature Insensitive Bending Sensor Based on In-Line Mach-Zehnder Interferometer

A simple and compact fiber bending sensor based on the Maeh-Zehnder interferometer was proposed. A photonic crystal fiber （PCF） with a length of 10mm was spliced by collapsing air holes with two conventional single mode fibers to consist of an all fiber bending sensor. The sensitivity of 0.53nm/m-1 was obtained at 1586nm for the curvature range from 0 to 8.514 m-1. The temperature sensitivity was very low. The measurement error due to the temperature effect was about 8.68x10-3 m-1/℃, and the temperature effect in the curvature measurement could be ignored. This device can avoid the cross sensitivity of the temperature in the curvature measurement.

All fiber sensor based on Mach-Zehnder interferometer for simultaneous measurement of temperature and refractive index

In this paper, we propose and experimentally demonstrate a compact optical fiber sensor based on a Mach-Zehnder in- terferometer （MZI） cascaded with fiber Bragg grating （FBG） for simultaneous measurement of refractive index （RI） and temperature. In order to get a proper spectrum, we discuss the effects of different structure parameters of MZI. Using the resonant wavelength of the FBG （DipFBG） and the interference dip of the MZI （Dipl）, the RI and tempera- ture of the surrounding medium can be determined. The sensor has good operation linearity. The experimental results show that the distinctive spectral sensitivities are 0.071 75 nm/℃and -91.766 67 nm/RIU （refraction index unit） for Dip1 and 0.009 09 nm/℃ for DipFBG.

Micro-Structured Fiber Interferometer as Sensitive Temperature Sensor

We report on a fast and sensitive temperature sensor using a micro-structured or photonic crystal fiber interferometer with a high germanium doped fiber core. The wavelength sensitivity for temperature variation was as high as △λ/△T= 78 pm/℃ up to 500℃, which was 6 times more sensitive than the fiber Bragg grating temperature sensitivity of △λ/△TT= 13pm/℃ at 1550nm. The sensor device was investigated conceming the sensitivity characteristics and response time.

Temperature Measurement of Small Objects by Mach-Zehnder Interferometer

A Mach-Zehnder Interferometer incorporated with image processing has been set up to study the temperature field of small objects.Small objects with width to height ratios ranging from 0.33 to 1.0 subjected to natural convection are used to simulate the condition at which the end effects are significant. Interferogram representing the temperature gradient is captured,digitized,and image processed with the aid of an image processing unit.A simple correction model is proposed to treat the stored interferometric data.The interference data are found to compare well with those provided by the thermocouples.

Miniature Fabry-Perot interferometric sensor for temperature measurement based on photonic crystal fiber

A novel miniature Fabry-Perot interferometric(FPI) temperature sensor is proposed and demonstrated experimentally. The modal interferometer is fabricated by just splicing a section of photonic crystal fiber(PCF) with a single-mode fiber(SMF). The air holes of the PCF are fully collapsed by the discharge arc during the splicing procedure to enhance the reflection coefficient of the splicing point. The transmission spectra with different temperatures are measured, and the experimental results show that the linear response of 11.12 pm/°C in the range of 30–80 °C is obtained. This sensor has potential applications in temperature measurement field.

Measurement of high-dynamic temperature field using high-speed quadriwave lateral shearing interferometer

An approach to measure a high-dynamic two-dimensional(2 D) temperature field using a high-speed quadriwave lateral shearing interferometer(QWLSI) is proposed. The detailed theoretical derivation to express the wavefront reconstruct principle of the proposed method is presented. The comparison experiment with thermocouples shows that the temperature field measurement using QWLSI has a precision of ±0.5 °C. An experiment for measuring the highdynamic temperature field generated by an electrical heater is carried out. A 200 frame rate temperature field video with 512 × 512 resolution is obtained finally. Experimental results show that the temperature field measurement system using a QWLSI has the advantage of high sensitivity and high resolution.

Non-invasive human extremely weak pulse wave measurement based on a high-precision laser self-mixing interferometer

In this paper, a technique based on laser self-mixing effect for acquiring pulse wave profile is proposed and demonstrated. For the characteristics of extremely weak vibration in human pulse waves, a method of multiple reflections with external cavity is designed to improve the measurement accuracy to λ/4. Based on the fringe counting algorithm, one period of pulse wave is successfully reconstructed. The measurement results show that the root mean square error(RMSE) of the reconstructed pulse wave is 0.912 μm at sampling rate of 8 k Hz. Besides, the correlation coefficients and heart beats of this method and the traditional photoplethysmography(PPG) measurement are analyzed.

Interferometer Based on a D-shape Chaotic Optical Fiber for Measurement of Multiparameters

An interferometer based on a D-shape chaotic optical tiber tor measurement ot multiparameters was proposed. The sensing structure relied on a D-shape fiber section spliced in between two singlemode fibers and interrogated in transmission. The optical spectrum was composed by multiple interference loss peaks, which were sensitive to the refractive index, temperature and strain-maximum sensitivities of 95.2 nm/RIU, 10.5 pm/℃ and -3.51 pm/με, respectively, could be achieved.

Quantum Fisher Information of Entangled Coherent States in a Lossy Mach–Zehnder Interferometer

We give an analytical result for the quantum Fisher information of entangled coherent states in a lossy Mach-Zehnder interferometer recently proposed by Joo et al., [Phys. Rev. Lett. 107 （2011） 083601]. For small loss of photons, we find that the entangled coherent state can surpass the Heisenberg limit. Phrthermore, the formalism developed here is applicable to the study of phase sensitivity of multipartite entangled coherent states.

A hybrid magnetometer towards femtotesla sensitivity under ambient conditions

Detecting magnetic field is of great importance for many applications,such as magnetoencephalography and underground prospecting.There have been many magnetometers being widely used since the age of Hall magnetometer.One of the magnetometers,the superconducting quantum interference device,is capable of measuring femtotesla magnetic fields at cryogenic temperature.However,a solid-state magnetometer with femtotesla sensitivity under ambient conditions remains elusive.Here we present a hybrid magnetometer based on the ensemble nitrogen-vacancy centers in diamond with the sensitivity of(195±60)fT/Hz^(1/2)under ambient conditions,which can be further advanced to 11 fT/Hz^(1/2)at 100 Hz with cutting-edge fabrication technologies.Our method will find potential applications in biomagnetism and geomagnetism.

A novel three-component hybrid-integrated optical accelerometer based on a Mach-Zehnder interferometer with a LiNbO_3 photoelastic waveguide

An investigation of the properties ofa LiNbO3 photoelastic waveguide via the acceleration-induced effect is presented. A novel three-component hybrid-integrated optical accelerometer based on a Mach-Zehnder interferometer with a LiNbO3 photoelastic waveguide has been designed, which is capable of detecting seismic acceleration in high-accuracy seismic exploration. The Mach-Zehnder interferometer was successfully fabricated and a lighting test used to check its quality. The frequency response characteristic of the accelerometer was measured2 The accelerometer with a resonant frequency of 3549 Hz was demonstrated to show good linear frequency responding characteristics in the range of 100-3000 Hz. The accelerometer also shows good stability and consistency. Experimental results indicate that the outputs of the on- and cross-axis are 147 and 21.3 mV, respectively.

Plasma density evolution in plasma opening switch obtained by a time-resolved sensitive He-Ne interferometer

To understand the formation process of vacuum gap in coaxial microsecond conduction time plasma opening switch(POS),we have made measurements of the line-integrated plasma density during switch operation using a time-resolved sensitive He-Ne interferometer.The conduction current and conduction time in experiments are about 120 kA and 1 s,respectively.As a result,more than 85%of conduction current has been transferred to an inductive load with rise time of 130 ns.The radial dependence of the density is measured by changing the radial location of the line-of-sight for shots with the same nominal POS parameters.During the conduction phase,the line-integrated plasma density in POS increases at all radial locations over the gun-only case by further ionization of material injected from the guns.The current conduction is observed to cause a radial redistribution of the switch plasma.A vacuum gap forms rapidly in the plasma at 5.5 mm from the center conductor,which is consistent with the location where magnetic pressure is the largest,allowing current to be transferred from the POS to the load.