Search Coil Research Articles

Vertical vergence in nonhuman primates depends on horizontal gaze position

ABSTRACTThe goal of this study was to compare vertical fusion capability at different orbital eye positions in normal nonhuman primates and attempt to use this information to isolate the extraocular muscles (EOMs) that mediate vertical vergence. Scleral search coils were used to record movements of both eyes as two normal nonhuman primates (M1, M2) performed a vertical vergence task at different horizontal eye positions. In a control experiment, M1 was also tested at different angles of horizontal vergence. To elicit vertical vergence, a 50° x 50° stimulus comprising a central fixation cross and random dots elsewhere was presented separately to each eye under dichoptic viewing conditions. Vertical disparity was introduced by slowly displacing the stimulus for one eye vertically. Vertical fusion amplitude (maximum disparity that the monkey was able to fuse) and vertical vergence (maximum difference in vertical position of the two eyes) were measured. Vertical fusion capability differed at different orbital eye positions. Monkey M1 had significantly smaller vertical fusion capabilities when the right eye (RE) was abducted than left eye (LE) while M2 had significantly smaller vertical fusion capabilities when the RE was adducted and LE abducted. M1 also showed greater vertical fusion capability for near gaze. M1 data suggested that the vertical recti mediated vertical vergence in the RE and the oblique muscles in the LE while M2 data suggested that the oblique muscles mediated vertical vergence in the RE and the vertical recti in the LE. The variable results within the same animal and across animals suggest that EOM involvement during vertical fusional vergence is idiosyncratic and likely a weighted combination of multiple cyclovertical muscles.

Spectral descriptors and supervised classifier for ammonium nitrate detection in landmines by nuclear quadrupole resonance.

The high specificity of Nuclear Quadrupole Resonance (NQR) makes it very suited for the detection of antipersonnel mines, where the intensity of the signal spectrum around the resonance frequency of the target substance is the standard decision parameter; however, radiofrequency interference, soil effects on the search coil, landmine size, burial depth, and target temperature affect signal intensity. To overcome this, the use of spectral descriptors and a supervised classifier are proposed in this work, where an assembly of decision trees was trained with NQR data collected on places where a target filled with ammonium nitrate was present and where it was not. A statistical test, comparing the proposed classifier and the solution based solely on the intensity of the signal spectrum, showed with significant evidence that the proposed classifier outperforms the traditional solution. A final blind experiment was conducted in a rural region of Colombia, where five landmines of different size filled with ammonium nitrate were shallowly buried in an area of 1.9 × 1.52 m, and the system with the proposed classifier detected four of them with three false alarms. This work is also novel in detecting ammonium nitrate in antipersonnel mines, which are typical in Colombia, the second most mined country in the world.

Accurate Magnetic Characterization Based Model Development for Switched Reluctance Machine

High performance control and analysis of switched reluctance machines (SRMs) require accurate modeling of their magnetic characteristics. However, the doubly salient structure and deep magnetic saturation make it very complicated to accurately model SRMs. This paper presents a high fidelity model development for SRMs. The model is developed based on the experimental measurement of flux-linkage and torque characteristics. The introduced measurement noises / errors are investigated carefully. Then several post-processes are achieved to reduce these noises. The measurement accuracy is verified by three methods: finite element method (FEM), search coil comparison, and LCR meter. The measured data are employed after proper rearrangement to build a dynamic MATLAB simulation model for the tested 8/6 machine. The model accuracy and dependability is achieved experimentally.

Long-term mass flux assessment of a DNAPL source area treated using bioremediation

This study assessed the long-term effectiveness of bioremediation as a remedial strategy for a chlorinated, ethene dense, non-aqueous phase liquid (DNAPL) source area, consisting of a higher- and a lower-permeability zone at Alameda Point, California. The evaluation was performed over 3.7 years after cessation of active source area bioremediation using passive flux meters (PFMs), push-pull tracer tests, and soil cores. PFMs showed that total chlorinated ethene molar discharge emanating from the source area remained relatively unchanged pre-and post-bioremediation, but molar discharge compositions shifted from trichloroethene (TCE) and cis-1,2-dichloroethene (cis-DCE) to vinyl chloride (VC) and ethene dominated during post-remedial monitoring. First-order rate constants, derived from PFM data at the edge of the source area and describing the complete dechlorination of TCE at 3.7 years following active bioremediation, were approximately 1.05 yr−1, which was over three times lower than the rate 3.6 yr−1 determined using compound stable isotope analysis (CSIA). Soil cores and push-pull tracer test data showed that DNAPL volume estimates were relatively unchanged pre- and post-bioremediation due to the remaining presence of DNAPL in the lower-permeability zone. These data suggest biotransformation processes are continuing in the higher-permeability zone, whereas DNAPL in the lower-permeability zone continues to serve as a significant source of groundwater contamination. The results suggest that it will take many years under current conditions to attain the United States Environmental Protection Agency (EPA) Maximum Contaminant Levels (MCLs) cleanup objectives.

The impact of aging and environmental conditions on the effective thermal conductivity of several foam materials

The thermal conductivity, a fundamental property for insulating materials, is often advertised using a single value implied to be constant. However, research shows that the effective thermal conductivity changes as a result of material aging and the environmental parameters, including temperature and moisture content levels. In recent years, linear temperature-dependent laws have been occasionally proposed for inorganic fibrous materials, although there is increasing awareness of the fact that foam insulating materials have less regular temperature-dependent behaviours. This depends on the fact that the equilibrium among the different gasses in the material changes over time. In this paper, several polyurethane and polyisocyanurate foams are analysed in order to determine how the effective thermal conductivity is altered after accelerated aging obtained by exposing them to high temperature, high relative humidity levels, and freeze-thaw cycling. For each material, and after each aging exposure condition, measurements of the thermal conductivity were collected over a large temperature range from −20 °C to +40 °C using a Heat Flux Meter. These experimental results allow to build 3-D plots showing the effective thermal conductivity as a function of temperature and moisture content for both pristine and aged materials. Then, the measured results are used in hygrothermal simulations performed inputting the measured temperature- and moisture-dependent thermal conductivity in order to determine the effective performance of the considered insulating materials in both pristine and aged conditions. Results show that the aging of the foams and the operating temperatures have higher impacts on the insulating performance of polyisocyanurates than on polyurethanes. Additionally, high moisture levels contribute to lower performance in all foam materials, with open cell foams experiencing the greatest thermal resistance reduction. The increase in the energy fluxes across the insulating layer with respect to the constant thermal conductivity assumption was significantly higher once the effective thermal conductivity of aged materials was considered, especially when polyisocyanurate foams were modelled in cold and humid conditions.

A novel calibration system for heat flow meters: Experimental and numerical analysis

The estimation and the reduction of thermal transmittance of building envelope components is crucial.Heat Flux Meters (HFMs), instruments devoted to this aim, unfortunately not always are provided with metrological traceability due to the lack of suitable reference standards, especially at critical conditions, such as in the low heat flux regime and low conductivity values.In this paper, the authors propose a novel calibration standard for heat flux meters and discuss the metrological performance of this apparatus operating at critical conditions. Besides experiments, a detailed numerical analysis has been conducted, validating obtained results against measurements. A validated numerical model has then been employed to design, improve and analyze the calibration system in different operating conditions, also through a parametric analysis. Numerical results enabled us to improve and define the required heat flux uniformity in a specific sub-region of the measuring section.

Design and commissioning of Brav measurement system for SC200 superconducting cyclotron

The SC200 proton therapy superconducting cyclotron was developed by ASIPP (Hefei, China) and JINR (Dubna, Russia). A measurement system was designed to assess the average radial component of the magnetic field (Brav) with 15 search coils in the median plane. The winding differences of the search coils affect the measurement accuracy of the Brav. Based on the electromagnetic induction principle, to measure the Brav accurately, this paper focuses on the design and commissioning of the Brav measurement system. The preliminary results confirm that the system design is reasonable and suitable. After testing the search coil at different speeds, the optimal speed was determined as 2.5 mm/s. The relative error was approximately 0.1% under the maximum radial component of the magnetic field Br of 7 G. The measurement precision was up to 1.0 × 10−3, which can provide the required measurement tolerance of 3–7 G for Br in the median plane. The commissioning of the Brav measurement system is an important step for Br measurement. It can check and adjust the asymmetry of the superconducting coils (SCs).

Experimental and numerical analysis in heat flow sensors calibration

The 2010/31/CE directive has highlighted the necessity to improve the energy efficiency in buildings, since they are responsible for 40% of energy consumption and 36% of CO2 emissions in the EU. In situ measurements of envelope components are needed for estimating the thermal transmittance of existing buildings in order to perform the energy certification. The instruments devoted to this aim, the heat flux meters (HFMs), are unfortunately not always provided with metrological traceability, and the appropriate reference standards are not available. The calibration systems currently adopted present different limits related to low performances at low and constant heat fluxes, non-uniformity of the heat flux in the measurement section and impossibility to control the heat flux at different temperatures. In this paper, the authors discuss the metrological behaviour of an existing HFM reference standard. A numerical model is employed to analyse the calibration system in different operating conditions (low and moderate heat fluxes), to improve it and to design a new prototype presenting high performances also in the presence of the HFM under calibration. In particular, the numerical tool is applied to investigate the heat flux uniformity and the metrological performances in a specific sub-region of the measuring section where the HFM under calibration is applied. A detailed experimental analysis is also conducted with the objective to validate the adopted numerical tool. Moreover, a metrological characterization of the system affords a combined standard uncertainty of better than 6% at low heat flows.

In Situ Measurement of Nitrate Flux and Attenuation Using a Soil Passive Flux Meter.

This work enhances our understanding of catchment-scale N budgets by demonstrating the modification and application of a simple method for direct in situ measurements of vadose zone nitrate leaching and attenuation. We developed a soil passive flux meter (SPFM) to measure solute leaching based on a modified design of ion-exchange resin columns, and we tested the design in numerical simulations, laboratory experiments, plot-scale field experiments, and a catchment-scale field deployment. Our design minimized flow divergence around the resin column to attain nearly 100% capture of surface applied tracers in plot- and catchment-scale deployments. We found that mixing resin with native soil and extending the column height 10 cm above the resin layer minimized divergence of soil water around the column, resulting in a field-measured convergence factor (χ) of 1.3 that was consistent with numerical simulations. For catchment-scale testing, SPFMs were used at nine sites in three dominant land uses (crop, pasture, and turf) with known N inputs in two deployments, one during the 4-mo wet season and an additional set during the 8-mo dry season, to obtain integral annual measures of soil nitrate fluxes. In situ measured nitrate leaching determined from the SPFMs was positively correlated with known N inputs ( = 0.55, < 0.05) and attenuation averaged 67% (± 24% SD) of inputs across all sites. Although N inputs explain a large portion of the variability, our results emphasize the importance of both inter- and intra-land use variability in landscape-scale N budgets.

Assessment of CH4 oxidation in macroinvertebrate burrows of tidal flats

In tidal flats that lack plants, methane (CH4) fluxes are both positive (gas emission) and negative (gas “sinking”) in nature. The levels of methanotroph populations significantly affect the extent of CH4 sinking. This preliminary study examined CH4 flux in tidal flats using a circular closed-chamber method to understand the effects of macroinvertebrate burrowing activity. The chamber was deployed over decapods (mud shrimp, Laomedia astacina and crab, Macrophthalmus japonicus) burrows for ~ 2 h, and the CH4 and CO2 concentrations were continuously monitored using a closed, diffuse CH4/CO2 flux meter. We found that Laomedia astacina burrow (which is relatively long) site afforded higher-level CH4 production, likely due to diffusive emission of CH4 in deep-layer sediments. In addition, the large methanotrophic bacteria population found in the burrow wall sediments has CH4 oxidation (consumption) potential. Especially, nitrite-driven anaerobic oxidation of methane (AOM) may occur within burrows. The proposed CH4-oxidation process was supported by the decrease in the δ13C of headspace CO2 during the chamber experiment. Therefore, macroinvertebrate burrows appear to be an important ecosystem environment for controlling atmospheric CH4 over tidal flats.

Method to assess the mismatch between the measured and nominal parameters of transcranial magnetic stimulation devices

BackgroundSmall variations in TMS parameters, such as pulse frequency and amplitude may elicit distinct neurophysiological responses. Assessing the mismatch between nominal and experimental parameters of TMS stimulators is essential for safe application and comparisons of results across studies. New methodA search coil was used to assess exactness and precision errors of amplitude and timing parameters such as interstimulus interval, the period of pulse repetition, and intertrain interval of TMS devices. The method was validated using simulated pulses and applied to six commercial stimulators in single-pulse (spTMS), paired-pulse (ppTMS), and repetitive (rTMS) protocols, working at several combinations of intensities and frequencies. ResultsIn a simulated signal, the maximum exactness error was 1.7% for spTMS and the maximum precision error 1.9% for ppTMS. Three out of six TMS commercial devices showed exactness and precision errors in spTMS amplitude higher than 5%. Moreover, two devices showed amplitude exactness errors higher than 5% in rTMS with parameters suggested by the manufactures. Comparison with existing methodsCurrently available tools allow characterization of induced electric field intensity and focality, and pulse waveforms of a single TMS pulse. Our method assesses the mismatch between nominal and experimental values in spTMS, ppTMS and rTMS protocols through the exactness and precision errors of amplitude and timing parameters. ConclusionThis study highlights the importance of evaluating the physical characteristics of TMS devices and protocols, and provides a method for on-site quality assessment of multiple stimulation protocols in clinical and research environments.

Electromagnetic and mechanical characterization of a flexible coil for transcranial magnetic stimulation

Transcranial magnetic stimulation is a painless and noninvasive method for treating brain disorders. The coil-geometries that match the head topologies achieve more effective stimulation, however it is difficult for a rigid coil to fit the skulls of all patients. We propose and develop a rubber-like flexible coil that can be shaped into different geometries to reduce the inter-individual variabilities in its clinical use. The main challenge is attributed to the fact that the external bending and induced Lorentzian forces cause coil deformation and fatigue. Herein, we investigated the influence of bending on the electromagnetic characteristics of the flexible coil. The magnetic field distribution was calculated and measured using a search coil. The induced Lorentzian force was calculated and the induced eddy current density was simulated using the scalar potential finite difference (SPFD) method. For a mechanical characterization, we fixed the center of the coil, and external bending forces were applied on the two wings of the coils, while Lorentzian forces were applied in a direction normal to the side wall of the wire groove. Fatigue analyses of these forces were also conducted. The results show that the eddy current density induced in the brain by the flexible coil was significantly higher compared to that of the figure-eight and butterfly coils. Fatigue analyses show that the bending force required to achieve a close coil fit on the human head and the generated Lorentzian force would not lead to fatigue problem.

High-Sensitivity Real-Time Tracking System for High-Speed Pipeline Inspection Gauge.

Real-time tracking of pipeline inspection gauges (PIGs) is an important aspect of ensuring the safety of oil and gas pipeline inline inspections (ILIs). Transmitting and receiving extremely low frequency (ELF) magnetic signals is one of the preferred methods of tracking. Due to the increase in physical parameters of the pipeline including transportation speed, wall thickness and burial depth, the ELF magnetic signals received are short transient (1-second duration) and very weak (10 pT), making the existing above-ground-marker (AGM) systems difficult to operate correctly. Based on the short transient very weak characteristics of ELF signals studied with a 2-D finite-element method (FEM) simulation, a data fusion model was derived to fuse the envelope decay rates of ELF signals by a least square (LS) criterion. Then, a fast-decision-tree (FDT) method is proposed to estimate the fused envelope decay rate to output the maximized orthogonal signal power for the signal detection through a determined topology and a fast calculation process, which was demonstrated to have excellent real-time detection performance. We show that simulation and experimental results validated the effectiveness of the proposed FDT method, and describe the high-sensitivity detection and real-time implementation of a high-speed PIG tracking system, including a transmitter, a receiver, and a pair of orthogonal search coil sensors.

A Low-cost Electromagnetic Docking Guidance System for Micro Autonomous Underwater Vehicles

As important observational platforms for the Smart Ocean concept, autonomous underwater vehicles (AUVs) that perform long-term observation in fleets are beneficial because they provide large-scale sampling data with a sufficient spatiotemporal resolution. Therefore, a large number of low-cost micro AUVs with docking capability for power recharge and data transmission are essential. This study designed a low-cost electromagnetic docking guidance (EMDG) system for micro AUVs. The EMDG system is composed of a transmitter coil located on the dock and a three-axial search coil magnetometer acting as a receiver. The search coil magnetometer was optimized for small sizes while maintaining sufficient sensitivity. The signal conditioning and processing subsystem was designed to calculate the deflection angle (β) for docking guidance. Underwater docking tests showed that the system can detect the electromagnetic signal and successfully guide AUV docking. The AUV can still perform docking in extreme positions, which cannot be realized through normal optical or acoustic guidance. This study is the first to focus on the EM guidance system for low-cost micro AUVs. The search coil sensor in the AUV is inexpensive and compact so that the system can be equipped on a wide range of AUVs.

Quicker Measurement of Walls’ Thermal Resistance Following an Extension to ISO 9869 Average Method

Determination of the thermo-physical characteristics of the buildings’ components is crucial to illustrate their thermal behavior and therefore their energy consumption. Along the same line, accurate determination of the thermal resistance of the building walls falls into one the most important targets. Following the difference between in-lab, and on site thermal performance of walls, in-situ measurements have been highly recommended. The most well-known practice for in-situ measurement of walls’ thermal resistance is the Average Method of ISO 9869, using one heat flux meter and two thermocouples. The method, in comparison with other existing methods is quite straight-forward and therefore, is applied widely in large scale. Despite its simplicity, this method usually needs a relatively long time to reach an acceptable result. The current paper deals with a modification to the ISO 9869 method, making it in many situations much quicker than its original state. Through simulation of walls of different typologies, it is shown in which cases the measurement period becomes longer than expected. It is demonstrated how the addition of a heat flux meter to the aforementioned equipment can lead to a much quicker achievement of the thermal resistance, following the rest of the instructions of the standard method.

Koncepcija i eksperiment sa inovativnim detektorom minerala i metala ispitivanjem elektromagnetnih talasa koje emituje i prima helikoidna antena

This paper discusses the simulation and experimentation of innovative minerals and metals detector to improve the performances of old systems. Indeed, actual detectors are limited concerning depth, sensitivity and selectivity. We propose here to implant helical antenna on shell points of two coils to boost detection process by increasing directivity gain and reflexion coefficient. The system uses the principle of electromagnetic induction and beat frequency oscillator (BFO) and contains search coil to detect metals and minerals at appropriate range and gives an auditory and vibratory indication once the element is detected. The search coil forms part of an LC oscillation circuit linked to added helical antenna. The activation frequency of the LC oscillator is primarily determined by the value of involved inductor and capacitor to recover the large gamme of frequencies and detect more kind of materials.

Comparison of the thermal performance between conventional and cob building

The appliance of sustainable development approach in building has urged construction industry to adopt proper measurements to protect environment and reduce residential building energy consumption and CO2 emissions. Thus, an increasing interest in alternative building materials has developed including the use of bio-based materials such as cob which is studied in this paper. In the previous work, many experimental and numerical studies have been carried out to characterize thermal behaviour of earth buildings, reduce its thermal conductivity and water content. In this paper, an experimental study is carried out to determine the thermal properties and energy performance of cob building. Cob samples within different soil and fiber contents are studied using an experimental set up instrumented with flux meters and micro-thermocouples in order to evaluate the local heat flux and thermal conductivity during stationary regime. The results are analysed and compared to deduce the performant mixes in terms of thermal behaviour while respecting the French thermal regulation. A static thermal simulation based on RT 2012 calculation method (the official French calculation method for the energy performance of new residential and commercial buildings according to France thermal regulation) is used to compare energy performance between conventional and cob building using the French climate data base .

Measurements of X-ray radiation of the Sun on the heliogeophysical measuring equipment of spacecraft of the Russian Hydrometheorological Service

The characteristics of the equipment for monitoring X-ray solar radiation onboard geostationary satellites. A reference base for X-ray flux meters of the DIR-E was developed and experimental studies of the characteristics on the technological sample of the device were carried out. The calibration procedure of DIR-E for use in measurements on perspective space vehicles was also developed.

Localization of a Mobile Platform Equipped With a Rotating Magnetic Dipole Source

In this paper, we propose a method for indoor localization based on quasi-static magnetic fields. High penetration ability and absence of multipath effects make it advantageous over other indoor localization techniques based on electromagnetic or acoustic waves. Moreover, the circular rotating magnetic field’s specific structure enables it to be distinguished from common magnetic interferences, which generally lack this feature. A dual-axis search-coil magnetometer is placed at a known location with a known orientation and it is used to localize the mobile platform equipped with a source of a rotating magnetic field. We have carried out a theoretical analysis obtaining closed-form expressions for the bearing and distance. The analytical expressions allow calculations without high computational complexity as often required by the numerical analysis methods. The localization method has been tested using a computer simulation in order to evaluate its performance. We have developed a system prototype that has been successfully tested in our laboratory. In a test area of 7 m $\times7$ m, the experimental results yield a mean localization error of 0.11 m and a maximal localization error of less than 0.29 m. The high accuracy of the method and the absence of resource-intensive calculations allow low-power, real-time implementation.

Compensation of Hysteresis in Hybrid Reluctance Actuator for High-Precision Motion

In hybrid reluctance actuators for high precision motion control, the magnetic hysteresis in the ferromagnetic stator and mover usually affects the precision. Therefore, this paper proposes magnetic flux estimation and control to compensate for the hysteresis. To measure the magnetic flux at various frequencies, the output signal of a search coil is combined with that of the current monitor of the employed current amplifier in a magnetic flux estimator. Finally, a magnetic flux controller is designed and implemented. For evaluation of the hysteresis compensation, the performance of the hybrid reluctance actuator is compared with both flux and current control. Experimental results show that flux control successfully compensates for some of the nonlinearities of the hybrid reluctance actuator, as the hysteresis is reduced by up to a factor 8.2 and the phase lag of the mover position is reduced by up to 6 deg in comparison with the case of current control.