Determination of the Orientation of an Artificial Satellite from Magnetic Field Data in Orbit

Geomagnetism and Aeronomy - At present, the determination of the position of satellite axes from data obtained via measurement of the magnetic field in orbit is an urgent task. This task is...     

Field test of an intelligent stiffener for bridges at the I-35 Walnut Creek bridge

The addition of controllable hardware to structures to mitigate vibration that results from dynamic loads is an emerging area of technological development. The paper describes the results of a research project that was conducted to test a relatively new approach to structural control: an adjustable semi-active hydraulic actuation system that was attached to an in service interstate bridge. The system, which is powered by a 12-volt automative battery, has been tested over a 2- year period. Data indicates that the system reduces truck induced peak stresses by over 50 per cent, and calculations, per NCHRP 299, indicate that the safe life of the structure is increased by approximately 50 yr. The installed cost of the system represents less than 10 per cent of the cost to replace the bridge. Copyright © 1999 John Wiley & Sons, Ltd.     

Monitoring Evapotranspiration in an Agricultural Field and Determination of Irrigation Rates and Dates by Automated Mobile Field Agrometeorological Complex

An automated mobile field agrometeorological complex was designed and constructed to study the evapotranspiration in agricultural fields and to determine the rates and dates of irrigation. The complex collects, stores, and processes data on meteorological parameters: air temperature and humidity, atmospheric pressure, wind speed, and the temperature and net radiation of land surface. The meteorological characteristics and data on agricultural plants are used to evaluate the evapotranspiration, the rates and dates of irrigation in real-time regime. All measured and calculated parameters are accumulated in an inner database in the complex during the measurement period. The mobility of the complex enables its operation on fields with different crops. Field studies were carried out in 2013–2014 in different climatic zones.     

Experimental Studies of Brine Migration through Unsaturated Zone at an Oil Field

The problem of unsaturated zone pollution by highly mineralized field brines is considered. The results of experiments with field brines and tracer solutions were used to establish the migration mechanism of brines and tracer solutions at the first stages of their spreading with allowance made for the difference between their densities and chemical compositions. Salt transfer parameters are determined for the case of an ion not subject to sorption.     

Barrier Layer and Relevant Variability of the Salinity Field in the Equatorial Pacific Estimated in an Ocean Reanalysis Experiment

This paper investigates the feasibility of an ocean data assimilation system to analyze the salinity variability associated with the barrier layer in the equatorial Pacific. In order to validate reproducibility of the temperature and salinity fields, we perform an assimilation run where some temperature and salinity observations by TRITON buoys and Argo floats are withheld. The assimilation run reproduces interannual variability of salinity in the equatorial Pacific exhibited in the data that are withheld. Statistics shows that salinity values and variations in the assimilation run are closer to the data than the climatology and in the model free run. We also confirm that zonal currents in the equatorial Pacific in the reanalysis, where all available temperature and salinity data are assimilated, are consistent with an observation-based mapping and the data of the Acoustic Doppler Current Profiler mounted on TAO buoys. Variability of the barrier layer and relevant salinity field in the reanalysis is consistent with former studies. A thick barrier layer area generally exists west of the equatorial salinity front and is displaced zonally with the migration of the front in the response to El Niño-Southern Oscillation, although the area moved to the east over the front in the 1997 El Niño. It is confirmed that the barrier layer thickness is closely correlated with the near-surface temperature in the equatorial Pacific.     

Field line resonances in discretized magnetospheric models: an artifact study

For more than two decades numerical models of the Earths magnetosphere have been used success- fully to study magnetospheric dynamic features such as the excitation of ULF pulsations and the mechanism of field line resonance. However, numerical formulations simplify important properties of the real system. For instance the Alfveén continuum becomes discrete because of a finite grid size. This discretization can be a possible source of numerical artifacts. Therefore a careful interpretation of any observed features is required. Examples of such artifacts are presented using results from a three dimensional dipole model of the magne tosphere, including an inhomogeneous distribution of the Alfveé n velocity.     

Environmental Condition of Water Bodies in the Territory of an Oil–Gas Condensate Field (the Pechora Delta)

Chemical characteristics of the surface water and algae in lakes in the Seduiyakha River basin are presented. Specific features of components of limnetic ecosystems under the influence of anthropogenic factors in the territory of an oil–gas condensate field are shown. Ambiguous response of algal communities to changes in the aquatic environment is revealed.     

Taylor Polynomial Model of the Geomagnetic Field in an Underground Gas Storage Area

Geomagnetism and Aeronomy - The study of normal geomagnetic background fields is the premise and basis for obtaining local geomagnetic anomalies caused by changes in underground pressure during gas...     

Human-induced Changes in the Groundwater Chemical Composition within an Oil Field Area

The effect of highly saline oil-field water on soils and potable groundwater is considered. Three phases of the hydrochemical evolution of groundwater quality affected by transborder pollution and field development that has deteriorated potable groundwater in the two topmost aquifers are identified.     

Field observations of an evolving rip current on a meso-macrotidal well-developed inner bar and rip morphology

The Aquitanian Coast (France) is a high-energy meso-macrotidal environment exhibiting a highly variable double sandbar system. The inner and the outer bar generally exhibit a bar and rip morphology and persistent crescentic patterns, respectively. In June 2007, an intense five-day field experiment was carried out at Biscarrosse Beach. A large array of sensors was deployed on a well-developed southward-oriented bar and rip morphology. Daily topographic surveys were carried out together with video imaging to investigate beach morphodynamic evolution. During the experiment, offshore significant wave height ranged from 0.5 to 3 m, with a persistent shore-normal angle. This paper identifies two types of behavior of an observed rip current: (1) for low-energy waves, the rip current is active only between low and mid tide with maximum mean rip current velocity reaching 0.8 m/s for an offshore significant wave height (H_s) lower than 1 m; (2) for high-energy waves (H_s≈ 2.5–3 m), the rip current was active over the whole tide cycle with the presence of persistent intense offshore-directed flows between mid and high tide. For both low and high-energy waves, very low-frequency pulsations (15–30 min) of the mean currents are observed on both feeder and rip channels.A persistent slow shoreward migration of the sandbar was observed during the experiment while no significant alongshore migration of the system was measured. Onshore migration during the high-energy waves can be explained by different sediment transport processes such as flow velocity skewness, wave asymmetry or bed ventilation. High-frequency local measurements of the bed evolution show the presence of significant (in the order of 10 cm) fluctuations (in the order of 1 h). These fluctuations, observed for both low- and high-energy waves, are thought to be ripples and megaripples, respectively and may play an important but still poorly understood role in the larger scale morphodynamics. The present dataset improves the knowledge of rip dynamics as well as the morphological response of strongly alongshore non-uniform meso-macrotidal beaches.     

Field reconnaissance of the 2007 Niigata-Chuetsu Oki earthquake

As part of the 2007 Tri-Center Field Mission to Japan, a reconnaissance team comprised of fourteen graduate students and three faculty members from three U.S. earthquake engineering research centers, namely, Multidisciplinary Center for Earthquake Engineering Research (MCEER), Mid-America Earthquake Center (MAE), and Pacifi c Earthquake Engineering Research Center (PEER), undertook a reconnaissance visit to the affected area shortly after the 2007 Niigata- Chuetsu Oki earthquake. This mission provided an opportunity to review the nature of the earthquake damage that occurred, as well as to assess the signifi cance of the damage from an educational perspective. This paper reports on the seismological characteristics of the earthquake, preliminary fi ndings of geotechnical and structural damage, and the causes of the observed failures or collapses. In addition, economic and socio-economic considerations and experiences to enhance earthquake resilience are presented.     

Parallel Electric Field and Electron Acceleration: an Advanced Model

A kinetic theory is necessary to explain the electron flows forming strong field-aligned currents in the auroral region. Its construction in this paper is based on the following propositions. (a) In the equatorial region, the arrival of electrons through the lateral surface of the magnetic flux tube is compensated for by their escape along the magnetic field. This is provided by action of the pitch-angle diffusion mechanism in the presence of plasma turbulence concentrated in this region. (b) Outside the equatorial region, the distribution functions of trapped and precipitating particles become “frozen.” The distributions and particle concentrations are calculated there in a model with conservation of the total energy and the magnetic moment. (c) The quasi-neutrality condition yields a large-scale parallel electric field, which contributes to the conserved total energy. In this field, the electron acceleration occurs, causing strong field-aligned currents directed upward from the ionosphere.     

Variations in the Intensity of the Earth's Magnetic Field

The Earth's main magnetic field can be approximated by an axial, geocentric dipole. The remaining non-dipole field is much smaller and is a regional rather than a global feature – quite large changes can occur in a few ka. This review is concerned with changes in the dipole component of the geomagnetic field, and one of the problems is in separating the non-dipole from the dipole contributions to the field. Unlike the many determinations of the direction of the Earth's magnetic field in the past (which have led to fundamental contributions to our understanding of plate tectonics and shown that the field can on occasion reverse its polarity), estimates of the intensity of the field are comparatively few, especially before the Holocene. This is mainly the result of experimental difficulties in obtaining reliable measurements of the field. These problems are discussed in some detail and are followed by a short account of archaeomagnetic intensities and results from Hawaii where many of the first determinations were obtained. Measurements for the last 100 ka from both lavas and lacustrine and oceanic sediments are reviewed and results from different areas compared. An asymmetric saw-tooth pattern has been observed in some of the records over the last few Ma, and this rather controversial question is discussed. Finally an account is given of the far more limited data on palaeointensities in earlier times.A short discussion is given of the interpretation of coherent short wavelength variations which are observed in many marine magnetic profiles. Although short reversals of the field may be responsible for some of these tiny wiggles, it is more likely that in general they are the result of changes in the strength of the Earth's magnetic field.     

基于GIS的地震现场应急指挥管理信息系统研制

基于GIS的地震现场应急指挥管理信息系统(MapEFMIS 2007 for Windows)是“十五”中国数字地震观测网络地震应急指挥分项中的一部分。主要为地震现场指挥部应急指挥和现场灾害损失调查与评估、科学考察等工作提供公用数据管理和信息服务,提高地震现场工作的实效性,本文介绍了该系统的设计思路和主要功能。     

Field investigation of the groundwater contribution to baseflow in an urban stream from a Quaternary aquifer with a leaky base

Groundwater contributions to baseflow in Minnehaha Creek, a creek located in a highly developed watershed in the Minneapolis-St. Paul metropolitan area, from the watershed's Quaternary aquifer were quantified as part of an effort to manage low flow conditions in the creek. Considerable uncertainty exists with any single method used to quantify groundwater contributions to baseflow; therefore, a “weight of evidence” approach in which methods spanning multiple spatial scales was utilized. Analyses conducted at the watershed-scale (streamflow separation and stable isotope analyses) were corroborated with site-scale measurements (piezometer, seepage meter, and streambed temperature profiles) over a multi-year period to understand processes and conditions controlling connectivity between the stream, its shallow aquifer system and other flow sources. In the case of Minnehaha Creek, groundwater discharge was found to range from 6.2 to 23 mm year⁻¹, which represented only 5 to 11% of annual streamflow during the study period. From the weight of evidence, it is conjectured that regional-scale hydrogeological conditions control groundwater discharge in Minnehaha Creek. Implications of these results with regard to possible augmentation of baseflow by increasing groundwater recharge with infiltration of stormwater are discussed.     

Weibel Instability and Deformation of an External Magnetic Field in the Region of Decay of a Strong Discontinuity in a Plasma with Hot Electrons

Geomagnetism and Aeronomy - In this paper, for a number of significantly different parameters of a localized plane layer of collisionless electron–proton plasma and an external magnetic field...     

Magnetic Field Feedback Circuit for Geomagnetic Field Compensation Control

In the current state of geomagnetic instrument testing, some aspects of geomagnetic instrument performance are difficult to test in the laboratory. If laboratory test results are inadequate, the instrument will have multiple problems while operating in the field, where a geomagnetic instrumentation test platform with a stable natural magnetic field is critical. Here, the magnetic field feedback circuit for geomagnetic field compensation control is studied in detail. That is, the magnetic field measured by the feedback magnetic sensor and the required working magnetic field are compared as input to the system, and the electric signal is transmitted to the feedback coil through an analog circuit to form a closed loop control, which provides compensation to control the magnetic field. Compared with the existing magnetic shielding method, the analog control circuit can achieve the realization of any working magnetic field, and it is not limited to a null magnetic field. The experimental result shows that the system compensates the earth''s magnetic field of 10,000nT with an average error of 10.6nT and average compensation error of 0.106%, providing a high compensation accuracy. The system also shows high sensitivity and excellent stability. The feedback circuit has achieved effective compensation control for the earth''s magnetic field.     

Field tests of an improved sediment tracer including non-intrusive measurement of burial depth

Radio-frequency identification (RFID) transponders are now widely used to track sediment in a variety of environments. A recent innovation placed the transponder inside of a rotating inner mechanism that is designed to minimize missed detections due to burial and shielding or ‘signal collision’ effects between tracers, while also allowing a rapid measurement of the burial depth of the particle. Here we test a developed protocol for burial depth measurement and deploy the ‘Wobblestone’ tracers in the field for the first time. Results show that new tracers can be reliably positioned in the horizontal plane (median error ± 0.03 m) and that the burial depth can be accurately measured (~0.02 m maximum error). The field study was characterized by high mobility and travel lengths, and ~20% of the tracers were buried at depths up to 0.15 m. A comparison of exponential distributions for travel length of surface deposited and buried tracers indicate that the buried tracers on average traveled farther and earlier in the flood event. Tracers that did not move were also buried at one site as a result of sediment transport from upstream. Overall the technique has great potential for characterizing vertical mixing and understanding this rarely considered control on sediment transport. © 2020 John Wiley & Sons, Ltd.     

电磁干扰实验研究

本文分析了地电、地磁同台观测中出现的干扰问题，并针对地电观测对地磁场测量的影响进行了研究。通过实地测量和对长直导线产生的磁场模拟计算，得出不同距离（20～120m）的感应磁场强度值，由此判断通电导线对周围地磁场的影响。结果表明：电流为2A时，单根导线距地磁场观测点距离应大于150m；导线两侧在相等距离处对地磁总场的干扰并不遵循“数值相等，方向相反”的规律，而是一侧增加量大于另一侧减少量。这项实验研究为地磁、地电同台观测及排除干扰提供了有价值的依据。