稳恒电场对小晶面晶体生长的影响

本文选用NH4Cl和H2O过饱和二元溶体为研究对象,研究其在稳恒电场作用下溶体中游离晶的重熔规律及晶体生长规律.利用显微镜感光器件(CCD)及智能通讯测温仪表,对实验过程进行实时照片拍摄和实时温度记录.结果表明:电场的Joule Heat效应为决定性因素,使得NH4Cl溶体温度场显著变化,导致糊状区的游离晶重熔明显;N...     

Liquid crystal infiltrated photonic crystal fibers for electric field intensity measurements

The application of nematic liquid crystal infiltrated photonic crystal fiber as a sensor for electric field intensity measurement is demonstrated. The device is based on an intrinsic sensing mechanism for electric fields. The sensor probe, which consists of a 1 cm infiltrated section of photonic crystal fiber with a lateral size of ～125 μm, is very compact with small size and weight. A simple all-fiber design for the sensor is employed in an intensity based measurement scheme. The transmitted and reflected power of the infiltrated photonic crystal fiber is shown to have a linear response with the applied electric field. The sensor is operated in the telecommunication window at 1550 nm. The temperature dependence of the device at this operating wavelength is also experimentally studied and discussed. These structures can be used to accurately measure electric field intensity and can be used for the fabrication of all-fiber sensors for high electric field environments as both an in-line and reflective type point sensor.     

Influence of a magnetic field on quartz crystal resonators

The magnetic sensitivity of quartz crystal resonators is a consequence of the ferromagnetic properties of the metal used as support for the vibrating plate. Various magneto-mechanic interactions can contribute to the overall sensitivity, the most important of which is shown to be the change in Young's modulus of the spring material submitted to a magnetic field, which in turn modifies the stress in the quartz plate and then induces a change in the crystal resonant frequency. The experimental setup and procedure are described and a large number of experimental results obtained with resonators of different technologies are presented and discussed. A comparison between the magnetic behavior of identical resonators mounted with different materials definitely proves the responsibility of the supports in the magnetic sensitivity of resonators and gives interesting information on its reduction     

Polymer dispersed liquid crystal fiber optic electric field probe

Polymer dispersed liquid crystal inserted between two multimode optical fiber end faces forms the basis of an electric field probe. This probe has an active volume of about 0.001 mm³ and approximates a point measurement. The linear relation between detector output and electric field in the 600 V/cm to 800 V/cm range is adequate for most electric power distribution systems. As the contrast ratio of this transducer is large, it can also be used as a safety on-off detector for high-voltage equipment     

Validation of predicted 3D electromagnetic field distributions due to vehicle-mounted antennas against measured 2D external electric field mapping

Predicted 3D electromagnetic field distributions from TLM models of two vehicle-mounted antenna installations are compared with 2D measurements for similar systems over four horizontal planes. Sample qualitative (visual) comparisons provide useful insights into the sources of some of the differences between the models and the measurements. Quantitative measures show that these differences are within the measurement uncertainty for more than 83% of the points for a roof-mounted antenna, and for more than 70% for a wing-mounted case. These results are considered to be excellent, given the known disparities between the measured and simulated systems     

取向聚氯乙烯/液晶复合膜表面形态特征研究

模仿生物膜表面的液晶态结构,将有序的、流动的胆甾醇液晶与基质材料聚氯乙烯共混,通过在成膜过程中施加不同强度的电场,制成取向聚氯乙烯/液晶复合膜,作为抗凝血生物材料.通过各种测试手段,考察不同取向条件下复合膜表面液晶畴的取向性能、尺寸、表面形态及其与电场强度、液晶含量的相关关系.结果表明:取向聚氯乙烯/液晶复合膜表面呈现出的形态特征是液晶含量、电场强度和基质材料大分子链诱导作用等综合因素影响的结果;电场强度可以调控液晶畴的体积和取向性;通过适当调节电场强度和液晶含量可获得具有一定相分离程度和有序性的复合膜.     

取向聚氨酯／液晶复合膜血液相容性材料的表面形态表征

模仿生物膜的表面结构形态,将有序的、流动的胆甾醇液晶(LC)与基质材料聚氨酯(PU)共混,在不同强度的电场条件下制成取向PU/LC复合膜,作为抗凝血生物材料.表征了不同取向条件下复合膜表面液晶畴取向性、体积、形状及其与电场强度、液晶含量的相关关系.结果表明:复合膜表面呈现出的形态特征是液晶含量、电场强度综合影响的结果;电场可以调控指状液晶畴的体积、分布,通过电场调控可获得具有适宜相分离程度和有序性的复合膜.     

Influence of strain and external electric field on the performance of PC6/MoSe2 heterostructure

Journal of Materials Science - In this work, the structural, electronic and optical performances of PC6/MoSe2 heterostructure are investigated using first principles calculations based on density...     

The use of 2D non-uniform electric field to enhance in situ bioremediation of 2,4-dichlorophenol-contaminated soil

In situ bioremediation is a safe and cost-effective technology for the cleanup of organic-contaminated soil, but its remediation rate is usually very slow, which results primarily from limited mass transfer of pollutants to the degrading bacteria in soil media. This study investigated the feasibility of adopting 2D non-uniform electric field to enhance in situ bioremediation process by promoting the mass transfer of organics to degrading bacteria under in situ conditions. For this purpose, a 2D non-uniform electrokinetic system was designed and tested at bench-scale with a sandy loam as the model soil and 2,4-dichlorophenol (2,4-DCP) as the model organic pollutant at two common operation modes (bidirectional and rotational). Periodically, the electric field reverses its direction at bidirectional mode and revolves a given angle at rotational mode. The results demonstrated that the non-uniform electric field could effectively stimulate the desorption and the movement of 2,4-DCP in the soil. The 2,4-DCP was mobilized through soil media towards the anode at a rate of about 1.0 cmd(-1)V(-1). The results also showed that in situ biodegradation of 2,4-DCP in the soil was greatly enhanced by the applied 2D electric field upon operational mode. At the bidirectional mode, an average 2,4-DCP removal of 73.4% was achieved in 15 days, and the in situ biodegradation of 2,4-DCP was increased by about three times as compared with that uncoupled with electric field, whereas, 34.8% of 2,4-DCP was removed on average in the same time period at the rotational mode. In terms of maintaining remediation uniformity in soil, the rotational operation remarkably excelled the bidirectional operation. In the hexagonal treatment area, the 2,4-DCP removal efficiency adversely increase with the distance to the central electrode at the bidirectional mode, while the rotational mode generated almost uniform removal in soil bed.     

Effect of cathode emissivity on runaway electron beam formation in gas-filled diode with inhomogeneous electric field

Mechanisms of the formation of runaway electron beams at the initial stage of breakdown in a gasfilled diode with sharply inhomogeneous electric field have been studied by numerical simulations using a specially developed PIC/MC code. It is established that a beam of runaway electrons can be generated either immediately at the cathode or at a discharge plasma boundary. The obtained dependence of the runaway electron beam current on the state of the cathode surface (emissivity) has the characteristic shape.     

Influence of the external electric field on propagation of Lamb waves in piezoelectric plates

The influence of the electric field on the properties of the Lamb and SH-waves in piezoelectric Bi(12)GeO(20) and La(3)Ga(5)SiO1(4) crystal plates has been investigated. Using basic equations and boundary conditions, the formulas for computer simulation have been obtained. The effect of acoustic modes hybridization has been considered.     

Influence of an external electric field on the propagation of ultrasound in electrorheological suspensions

The influence of a constant external electric field on the velocity and attenuation of ultrasound in electrorheological suspensions is studied experimentally.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 48, No. 2, pp. 219–224, February, 1985.     

Preparation of vertically aligned ZnO crystal rods in aqueous solution at external electric field

In this study, an external electric field was used to facilitate the growth of vertically aligned ZnO crystal rods on the surface of indium tin oxide (ITO) glass substrates in an aqueous solution. We used Zn(NO₃) and C₆H₁₂N₄ as precursor and reagent. We found that the external electric field generated by DC potential of 5 kV between two electrodes that were placed outside the bottle could facilitate the growth of homogeneous, high density and vertically aligned ZnO crystal rods. Position of the substrate during the growth of crystal was found to be important to obtain well aligned crystal. The crystals that were grown near the negative electrode had the best properties. Photoluminescence measurement at room temperature revealed sharp peaks at around 360 and 380 nm and a broad peak around 420 nm that indicated good properties of ZnO crystals grown with external electric field.     

Observation of increased ion cyclotron resonance signal duration through electric field perturbations

Ion motion in Fourier transform ion cyclotron resonance mass spectrometry (FTICR-MS) is complex and the subject of ongoing theoretical and experimental studies. Two predominant pathways for the loss of ICR signals are thought to include damping of cyclotron motion, in which ions lose kinetic energy and radially damp toward the center of the ICR cell, and dephasing of ion coherence, in which ions of like cyclotron frequency become distributed out of phase at similar cyclotron radii. Both mechanisms result in the loss of induced ion image current in FTICR-MS measurements and are normally inseparable during time-domain signal analysis. For conventional ICR measurements which take advantage of ion ensembles, maximization of the ion population size and density can produce the desired effect of increasing phase coherence of ions during cyclotron motion. However, this approach also presents the risk of coalescence of ion packets of similar frequencies. In general, ICR researchers in the past have lacked the tools necessary to distinguish or independently control dephasing and damping mechanisms for ICR signal loss. Nonetheless, the ability to impart greater phase coherence of ions in ICR measurements will allow significant advances in FTICR-MS research by improving the current understanding of ICR signal loss contributions of dephasing and damping of ion ensembles, increasing overall time-domain signal length, and possibly, resulting in more routine ultrahigh resolution measurements. The results presented here demonstrate the ability to employ a high density electron beam to perturb electric fields within the ICR cell during detection of cyclotron motion, in an approach we call electron-promoted ion coherence (EPIC). As such, EPIC reduces ICR signal degradation through loss of phase coherence, and much longer time-domain signals can be obtained. Our results demonstrate that time-domain signals can be extended by more than a factor of 4 with the implementation of EPIC, as compared to conventional experiments with otherwise identical conditions. The application of EPIC has also been observed to reduce the appearance of peak coalescence. These capabilities are not yet fully optimized nor fully understood in terms of the complex physics that underlies the enhancement. However, the enhanced time-domain signals can result in improved resolution in frequency-domain signals, and as such, this result is important for more efficient utilization of FTICR-MS. High resolution and accurate mass analysis are prime motivating factors in the application of advanced FTICR technology. We believe the approach presented here and derivatives from it may have significant benefit in future applications of advanced FTICR technology.     

A method for applying strong electric fields in electron paramagnetic resonance at low temperatures

A method is described for studying epr spectra in crystals under the action of an external electric field which is applicable to a RE-1301 spectrometer, in the resonator of which a quartz cryostat extension is housed. A viscous electrically insulating grease is used, making it possible to carry out investigations in electric fields up to 700 kV cm^?1 at T = 77 and 4.2 K.     

Determination of the sign of the electric field gradient in indium by nuclear resonance

We have studied the temperature dependence of two of the four magnetic-field perturbed NQR lines in indium. Our results indicate that the sign of the internal electric field gradient (EFG) is positive, in accord with the recent heat capacity measurements of the ISSP group and one recent theoretical prediction. We also discuss the implications of the sign of the EFG on the use of indium as an absolute thermometer below 1 mK.     

电场对改性煤沥青中间相形成的影响

在氮气保护和高压电场作用下,以中温煤沥青为原料,采用带程序升温的管式炉进行热转化实验,制备出煤沥青中间相。采用偏光显微镜、X射线衍射仪(XRD)、红外光谱仪(FT-IR)和热重分析仪(TG)等测试手段对其形貌和结构进行了分析表征。研究了原料改性和电场对煤沥青中间相形成的影响。研究结果表明,原料改性对中间相的形成有促进作用。电场强度控制在20kV/m,在420℃开始引入电场,有利于生成具有各向异性的中间相组织。     

Bound electron states in a system of coupled quantum waveguides in a transverse electric field

It is shown that a bound electron state exists in a system of quantum waveguides laterally coupled via a small window and placed in a transverse electric field. A field-induced shift of the eigenvalue is estimated using a variational method.     

Liquid crystal order in colloidal suspensions of spheroidal particles by direct current electric field assembly

DC electric fields are used to produce colloidal assemblies with orientational and layered positional order from a dilute suspension of spheroidal particles. These 3D assemblies, which can be visualized in situ by confocal microscopy, are achieved in short time spans (t < 1 h) by the application of a constant voltage across the capacitor-like device. This method yields denser and more ordered assemblies than had been previously reported with other assembly methods. Structures with a high degree of orientational order as well as layered positional order normal to the electrode surface are observed. These colloidal structures are explained as a consequence of electrophoretic deposition and field-assisted assembly. The interplay between the deposition rate and the rotational Brownian motion is found to be critical for the optimal ordering, which occurs when these rates, as quantified by the Peclet number, are of order one. The results suggest that the mechanism leading to ordering is equilibrium self-assembly but with kinetics dramatically accelerated by the application of the DC electric field. Finally, the crystalline symmetry of the densest structure formed is determined and compared with previously studied spheroidal assemblies.