Ice formation detection on road surfaces using infrared thermometry

Ice formation on roads causes hazardous conditions due to reduction of road surface friction. Forecasting, detecting and preventing ice formation are therefore of high importance for winter road maintenance personnel. Advanced sensors for detecting road ice exist, but there is a demand for more cost-effective technologies. A method for detection of road surface ice formation based on remote temperature measurements with infrared thermometers is presented. Freezing events were detected based on the temperature dynamics that result from the exothermic reaction as water freezes. Experimental measurements in a climate chamber and in field conditions showed that ice formation often causes a distinct temperature pattern, which could easily be identified and distinguished from other temperature fluctuations. The method is promising as a cost-effective technique suitable for several applications in cold regions where detection of ice formation is important.     

Effects of contacts on the electrical characterization of amorphous chalcogenide alloys

The comparison of the electrical parameters in amorphous chalcogenide, obtained using three different methods (electrical impedance, d.c. and the four-point resistivity measurements), has shown that impedance measurement is the most appropriate because it is able to separate the contributions of the bulk and contacts. For that reason, impedance measurements provide the real values for the electrical parameters of the material. In addition, the impedance measurements were able to detect the initial stages of the amorphous-to-crystalline phase transition.     

Numerical simulation of local ice loads in uniform and randomly varying ice conditions

The ice loading process has a clear stochastic nature due to variations in the ice conditions and in the icebreaking processes of ships. The statistical characteristics of local ice loads are typically studied on the basis of field measurements. In this paper, a numerical method was applied to simulate a ship moving forward in either uniform or randomly varying ice conditions, where the thickness and strength properties of the ice encountered by the ship were assumed to be constant or randomly generated using the Monte Carlo method. The purpose of this simulation is to show the origin of the statistical variation in ice loading, which is difficult to identify in field measurements. To validate the numerical results, an icebreaking tanker, MT Uikku, was then modeled in a simulation program, the ice loading process was stochastically reproduced and the calculated amplitude values of the ice-induced frame loads were compared with the field measurements.     

结构参数影响聚能杆式弹丸成型的数值模拟

应用LS-DYNA3D软件对聚能杆式弹丸的形成过程进行数值模拟,研究了药型罩外曲率半径、壳体厚度、外层炸药等因素对聚能杆式弹丸成型的影响规律,得出形成理想聚能杆式侵彻体的各参数之间的关系;并对比分析了钢壳和铝壳形成理想聚能杆式弹丸的条件差异;模拟结果可应用于轻型壳体的聚能杆式战斗部结构设计。     

青藏铁路冻土开挖爆破参数的研究

冻土爆破开挖是青藏铁路建设中的一大难题。通过现场球状药包和柱状药包漏斗爆破试验 ,初步确定冻土爆破的炸药单耗 ,在此基础上 ,利用三次深孔路堑开挖爆破试验 ,确定了高含冰量冻土开挖的最佳爆破参数。     

Comparison of galvanic displacement and electroless methods for deposition of gold nanoparticles on synthetic calcite

Gold nanoparticles have been deposited on synthetic calcite substrate by galvanic displacement reaction and electroless deposition methods. A comparative study has shown that electroless deposition is superior compared to galvanic displacement reaction for uniform deposition of gold nanoparticles on calcite. Characterization of the samples, prepared by two different deposition methods, was carried out by X-ray diffraction, transmission electron microscopy, field emission scanning electron microscopy (FE–SEM) and diffuse reflectance spectroscopy (DRS) measurements. FE–SEM studies prove that smaller nanoparticles of gold are deposited uniformly on calcite if electroless deposition method was employed and DRS measurements show the characteristic surface plasmon resonance of gold nanoparticles.     

The influence of cryostructure on the creep behavior of ice-rich permafrost

Unconfined constant stress creep (CSC) tests were performed in order to look at the influence of cryostructure on the creep behavior of ice-rich undisturbed permafrost soils and remolded frozen soils within the temperature range from − 1 °C to − 2 °C. Undisturbed ice-rich permafrost soils were sampled from a Pleistocene age yedoma or “ice-complex” permafrost deposit in Interior Alaska. Cryostructure or the pattern of ice inclusions within a frozen soil is a direct indicator of the geologic and cryogenic genesis of permafrost soils. The data indicate that cryostructure influences the creep behavior of permafrost soils. Undisturbed soils with massive cryostructure showed higher induced creep strains and minimum strain rates than the more ice-rich undisturbed soils. Remolded soils with massive cryostructure experienced significantly lower creep strains and lower strain rates than the undisturbed soils. Deformation rates increase rapidly above a threshold stress value for remolded soils. From an engineering viewpoint, use of creep rates from remolded soils is non conservative and under predicts the creep rates of undisturbed soils. The orientation of ice lenses can facilitate motion along the ice lens–soil contact. Similarly, folding of ice lenses may occur, thus inducing anisotropic lateral strains. The ice facies tested indicate that for the temperature and stress range tested, ice creeps at a slower rate than frozen soils.     

Field dielectric measurements of frozen silt using VHF pulses

Radiowave propagation experiments utilizing short pulses in the VHF band were conducted in the permafrost tunnel at Fox, Alaska. The purpose was to measure dielectric properties of this naturally occurring, perennially frozen organic silt which is common to much of interior Alaska and for which ice content varies between about 54 and 79% by volume. Transmissions across a septum dividing two drifts gave relative dielectric permittivity values between 3.9 and 7.3. The low values resulted when transmission was predominantly through an ice wedge. Propagation along the septum gave values of 3.3 and 5.0 depending on antenna polarization. This propagation was influenced by the dry, surface silts, as was propagation along a ceiling section, which also gave an approximate value of 3.3. The data from attempted transmissions from the ground surface directly above the tunnel to the tunnel ceiling (approximately 12 m distance) are ambiguous, as signals that propagated indirectly along the transmitter cable through a nearby ventilation shaft may or may not have masked direct transmission through the permafrost. The results agree with previous laboratory investigations conducted at temperatures well below that of naturally occurring materials in interior Alaska suggesting that winter refrigeration of the tunnel by circulated outside air greatly affected the natural conditions at this site.     

Detection of differences in sea ice crystal structure using cross-borehole DC resistivity tomography

Cross-borehole DC resistivity tomography measurements on first-year Antarctic sea ice show a decrease in the horizontal component of resistivity below 0.8 m in depth which is not related to changes in either temperature or brine volume fraction. Microstructural models derived from the resistivity data suggest that this change is related to an increased degree of horizontal connectivity in the brine microstructure of the ice. Comparison of the resistivity data with crystallographic measurements shows that this correlates with a change in ice structure from columnar ice to ice which contains an increasing fraction of platelet ice. It is thus demonstrated that not only can resistivity measurements track the temporal evolution of sea ice microstructure due to changes in temperature, but are also able to distinguish different ice types. This suggests that the dependence of sea ice properties on the distribution of brine inclusions can be studied in-situ through the use of resistivity measurements, providing a non-destructive technique for examining permeability–porosity relations in sea ice.     

铁磁层/导电层/铁磁层多层膜中巨磁阻抗效应理论*

采用经典电磁理论,对铁磁层／导电层／铁磁层（M／C／M）多层膜中出现的巨磁阻抗效应进行了理论分析。对于单轴横向磁各向异性多层膜,理论计算结果表明：高频阻抗在某一外加磁场（近似等于等效各向异性场）下出现最大值,铁磁层和导电层电阻率相关较大的多层膜中将出现较强的巨磁阻抗效应。多层膜在1MHz附近即可出现远大于单层膜的阻抗变化比。多层膜理论计算与实验结果能够较好地符合。     

Continuous monitoring of river surface ice during freeze-up using upward looking sonar

This paper describes an algorithm that has been developed to process field data from two upward looking sonars, one high (546 kHz) and one low (235 kHz) frequency, a 2 MHz current profiler and a monitoring station, to measure surface ice characteristics on the North Saskatchewan River in the north east of Edmonton, AB, Canada, during the 2009/2010 freeze-up season. The algorithm used to calculate pans/rafts drafts and lengths, and the surface ice concentration is described. The validity and the accuracy of this technique were tested and computed surface ice conditions are presented. For the purpose of examining the effects of hydro-meteorological conditions on measured pan characteristics, the freeze-up period was divided into three distinct stages depending on the measured surface ice concentration. Pan/raft drafts were found to range from 0.1 to 1.0 m and pan/raft lengths from 0.6 to 8.0 m. The sonar proved to be very accurate in detecting the exact surface ice conditions locally above the sonar beam. However, interpretation of the results can sometimes be challenging, especially when physical processes such as bridging affect local ice conditions. Therefore, additional visual observations (e.g. time lapse photography) of surface ice conditions are recommended to aid in the interpretation of sonar measurements.     

A method for simultaneously measuring resistivity and permeabilitywith a multilayer solenoid coil

A formula is given for a more accurate estimate of either the resistivity and permeability of a cylindrical magnetic material or the resistivity and penetration depth of a cylindrical superconductor, using the difference in the complex impedance between a circular multilayer solenoid coil having a conductor and a similar coil without a conductor. In comparison with the conventional method which uses a single-layer solenoid coil, it is shown experimentally that a multilayer solenoid coil is more effective for a short sample conductor because a larger difference in the complex impedance is obtained without increasing the width of the solenoid coil. The results of measurements of magnetic and superconductive materials are included     

Irreversible change of surface impedance of high-Tc thin films due to D.C. magnetic field commutation

The magnetic field dependence of the surface impedance (resistance and reactance) of high-T _c thin films is found employing measurements of the quality factor and the frequency of the parallel plate resonator in a dc magnetic field up to 500 Oe at 10 GHz.c-Oriented YBa₂Cu₃O₇ thin films are examined. Enhancement of surface resistance and inductance with increase of magnetic field is observed. The effect of irreversible increase of surface impedance as compared to its initial values after a cycle of magnetic field commutation is found. A qualitative explanation of the observed effects based on the picture of magnetic vortex penetration and accumulation in the film due to strong pinning is presented.     

Fourier-based magnetic induction tomography for mapping resistivity

Magnetic induction tomography is used as an experimental tool for mapping the passive electromagnetic properties of conductors, with the potential for imaging biological tissues. Our numerical approach to solving the inverse problem is to obtain a Fourier expansion of the resistivity and the stream functions of the magnetic fields and eddy current density. Thus, we are able to solve the inverse problem of determining the resistivity from the applied and measured magnetic fields for a two-dimensional conducting plane. When we add noise to the measured magnetic field, we find the fidelity of the measured to the true resistivity is quite robust for increasing levels of noise and increasing distances of the applied and measured field coils from the conducting plane, when properly filtered. We conclude that Fourier methods provide a reliable alternative for solving the inverse problem.     

Investigation of rock and ice loss in a recently deglaciated mountain rock wall using terrestrial laser scanning: Gemsstock, Swiss Alps

Monitoring of permafrost phenomena is an integral part of the investigation of Alpine natural environments. The sensitivity of permafrost to climate change and the resulting destabilization of slopes are of particular interest at present. Rock walls react rapidly to changing climate conditions and the consequences can be hazardous. Temporally and spatially resolved monitoring of the terrain surface using terrestrial laser scanning can contribute towards improved process understanding and the prevention and management of natural hazards. The advantages and disadvantages of two scan systems used to monitor a recently deglaciated permafrost rock wall at Gemsstock in the central Swiss Alps are analyzed here and the optimization of referencing methods and accuracy analyses are discussed. Mass movements of around 1800 m³ were detected and quantified over a period of 4 years and mean erosion rates of 6.5 mm year^− 1were determined. Volumetric changes caused by rock fall and melting ice could be defined with an accuracy of 4%-10% of their surface area in cubic meters in the direction of projection.     

冲击载荷下永磁式电涡流减振器设计及动态特性分析

为研究轮式车辆的电涡流减振器在行进间冲击载荷下的动态特性,结合电涡流理论设计了一种永磁式电涡流减振器,并基于等效磁路模型和麦克斯韦方程分析了其导体筒表面空气间隙处磁感应强度与阻尼力之间的关系;同时,利用有限元法对永磁式电涡流减振器的静、动态磁场分布进行了研究,并分析了不同结构参数对其阻尼特性的影响及不同运动速度下的示功特性曲线。通过建立1/4车辆悬架动力学模型和基于高斯滤波白噪声的随机路面激励模型,对车辆行进间冲击载荷下永磁式电涡流减振器的动态特性进行了分析。结果表明：永磁式电涡流减振器的磁场在动态条件下会发生退磁以及磁感线趋速聚集现象,各结构参数对其阻尼特性的影响较大;永磁式电涡流减振器的响应速度快,压缩、复原阻尼力恒定且平稳,可以高效、快速地消除轮式车辆越野时受到的路面激励和车载武器射击时的冲击载荷,能够有效抑制车体振动。研究结果对提高轮式车辆的越野机动性以及车载武器的射击精度具有重要意义。     

Thickness dependent structural, magnetic and transport properties of nanostructured cobalt thin films

This paper presents structural, magnetic, and transport properties measurements carried out on Co thin film as a function of thickness. The structure of the Co thin film changes from amorphous to nano-crystalline with the increase in film thickness. The corresponding magnetic and transport measurements show drastic changes in coercivity, saturation field and resistivity value as a function of Co film thickness. Observed magnetization and resistivity behaviour is mainly attributed to the (i) Change in crystal structure, (ii) stress relaxation, (iii) grain growth as revealed by X-ray diffraction (XRD), and atomic force microscopy (AFM) measurements.     

Induction Hardened Layer Characterization and Grinding Burn Detection by Magnetic Barkhausen Noise Analysis

The quality of the ball screw shafts used in the aeronautical sector has to be controlled and certified with the most advanced non-destructive techniques. The capacity of magnetic Barkhausen noise (MBN) as a non-destructive technique to control the quality of ball screw shafts by assuring the appropriate induction hardened layer depth and detecting local overheated regions, known as grinding burns, which may occur during grinding processes is shown in the present work. Magnetic Barkhausen noise measurements were made with a system designed and implemented by the authors and the derived parameters were compared with microhardness measurements made at various depths after the different induction hardening treatments and the grinding processes were applied. A multiparametric study of the MBN signal as a function of the magnetic field in the surface of the sample is done in order to estimate the thickness of the hardened layer and to detect the grinding burns produced during grinding processes. The hardened layer thickness can be characterized with an error of ±200 \(\upmu \)m in the range between 150 and 2500 \(\upmu \)m by the position of the first peak of the MBN envelope in terms of the tangential magnetic field measured at the surface and the grinding burns can be detected with the position of the second peak of the MBN envelope in terms of the tangential magnetic field measured at the surface.     

Validation of a Time-Harmonic Numerical Model for Solving Magnetic Field in End Region of a Radial-Flux Machine

We present an analysis of the magnetic field in the end region of a radial-flux rotating machine. In numerical simulations, we used three familiar boundary conditions to replace the modeling of the end shields and frame. We made measurements for comparison, and the simulation results were quite consistent with the measurements. Our analysis shows that the eddy current in the end shields and frame influences the magnetic field in the end region slightly and that the use of a homogeneous Neumann boundary condition or a standard impedance boundary condition (SIBC) to replace the end shields and frame can solve the magnetic field in the end region more accurately than a homogeneous Dirichlet boundary condition. Validation by the measurements demonstrates that 3-D current-driven time-harmonic model with suitable boundary conditions can be used to solve the magnetic field in the end region quite accurately.      

An experimental investigation of liquid metal flow past a cylinder in longitudinal magnetic field

The distribution of pressure on the surface of a cylinder is obtained as a result of experimental investigation; this distribution significantly varies with increasing magnetic induction compared to the flow past a cylinder in the absence of magnetic field. In so doing, the pressure drag coefficient of the cylinder significantly increases. The measurements of velocity profiles reveal that the extent of the region of stagnant flow before the cylinder (the so-called “leading” wake) increases with magnetic induction. The dependence of axial defect of velocity on the MHD interaction parameter is obtained; this dependence under conditions of flow in a strong magnetic field is unaffected by the shape of the body subjected to flow, as is confirmed by the results of experiment involving the flow past a plate.