Magnetic Unit Research Articles

An AI approach to automated magnetic formation mapping beneath cover

SummaryMost regional scale magnetic maps are dominated by the magnetic characteristics of steeply dipping basement units truncated by an unconformity surface. It is easy to demonstrate that 80 to 90% of each total field magnetic anomaly is contributed by this intersecting surface. We approach this problem by mapping the boundaries between contrasting magnetic units along each line in the magnetic survey using the full precision of the line data and 3D information from the magnetic gradient tensor. Additionally, we derive the azimuth of each boundary, depth to the unconformity and magnetic properties of the anomalous units. The segments are overlain on any image such as existing geological maps, satellite imagery, gravity or magnetic imagery to provide a new geological interpretation concept. This method provides a new way to interpret new and old magnetic surveys.Eigenvector analysis of the magnetic tensor and normalised source strength (NSS) are combined with an artificial intelligence (AI) approach to estimate the basement properties. The method is applied to full tensor magnetic survey data or a grid of the total magnetic intensity data is processed using FFT transformations to derive the magnetic gradient tensor. These data are used as input to the pre-trained AI process for calculation of depth, width, azimuth, magnetic susceptibility and magnetisation direction. The rock properties and depth information can be used for 3D visualisation of the unconformity and 2D mapping of the magnetic lithology of the unconformity surface.

Accuracy of right ventricular volume and function assessed with cardiovascular magnetic resonance: comparison with echocardiographic parameters

BackgroundCardiac magnetic resonance imaging (MRI) is an essential imaging method used to assess patients with diseases of the left and right ventricles. Cardiac MRI is the gold standard for right ventricular measurements; however, the most suitable method for volumetric analysis of the right ventricle remains controversial. AimsTo compare the accuracy of the short axis and four-chamber view segmentation methods in assessing the right ventricle in cardiac MRI studies, to determine the reproducibility of cardiac MR measurements, and to correlate cardiac MR methods with frequently used echocardiographic methods. MethodsEighty patients with different clinical indications were studied using a 1.5-Tesla resonance magnetic unit. In all patients, the end-diastolic volume, end-systolic volume, and right ventricle ejection fraction were measured in the short axis and four-chamber views. Twenty-three patients also underwent echocardiography on the same day the cardiac MRI was completed. ResultsCardiac MRI revealed no statistically significant differences in the volume or function of the right ventricle, calculated by the two segmentation methods (p > 0.05). The correlation was excellent between both planes in the assessment of the volume (concordance correlation coefficient [CCC] = 0.97) and the ejection fraction (CCC = 0.90). The correlation was low between the right ventricular ejection fraction and the echocardiographic methods (CCC = 0.02 and CCC = 0.01). ConclusionRight ventricular function in normal ventricles and in dilated ventricles was appropriately measured by cardiac MRI using either of the two segmentation methods. Both methods were highly accurate. However, the correlation with echocardiographic methods was rather poor.

Magnetic properties and magnetic structures of Nd2TGe6 (T = Ni, Cu)

ABSTRACTThe magnetic properties and magnetic structures of Nd2TGe6 (T = Ni and Cu) were studied by magnetometric and neutron diffraction measurements. Both compounds have an orthorhombic crystal structure of the Ce2CuGe6-type and are antiferromagnetic with the Néel temperatures of 6.4 K (Nd2NiGe6) and 9.8 K (Nd2CuGe6). Based on the neutron diffraction data the magnetic structures were determined. In the investigated compounds all magnetic moments are localized on the Nd atoms and form a collinear commensurate magnetic structure with the magnetic unit cell equal to the crystal one. The moments are parallel to the b-axis (T = Ni) or to the c-axis (T = Cu). The obtained magnetic structures are discussed on the basis of competition between the RKKY-type interactions and influence of Crystalline Electric Field (CEF).

Characteristics of a Magnetic Field Sensor with a Concentrating-Conducting Magnetic Flux Structure.

A magnetic field sensor with a new concentrating-conducting magnetic flux structure (CCMFS) is proposed in this paper, using a silicon-on insulator (SOI) Hall element fabricated by complementary metal oxide semiconductor (CMOS) technology as a magnetic sensitive unit. By fixing the CCMFS above the Hall element packaged on a printed circuit board (PCB) based on inner-connect wire bonding technology, a non-magnetized package can subsequently be obtained. To analyze the inner magnetic field vector distribution of the CCMFS, a simulation model was built based on a finite element software, where the CCMFS was processed using Ni-Fe alloys material by a low speed wire-cut electric discharge technology. The test results showed that the measurement of magnetic fields along a sensitive and a non-sensitive axis can be achieved when VDD = 5.0 V at room temperature, with magnetic sensitivities of 122 mV/T and 132 mV/T in a testing range from −30 mT to 30 mT, respectively. This study makes it possible to not only realize the detection of magnetic field, but also to significantly improve the sensitivity of the sensor along a non-sensitive axis.

Upper limb joint kinematics using wearable magnetic and inertial measurement units: an anatomical calibration procedure based on bony landmark identification

The estimate of a consistent and clinically meaningful joint kinematics using wearable inertial and magnetic sensors requires a sensor-to-segment coordinate system calibration. State-of-the-art calibration procedures for the upper limb are based on functional movements and/or pre-determined postures, which are difficult to implement in subjects that have impaired mobility or are bedridden in acute units. The aim of this study was to develop and validate an alternative calibration procedure based on the direct identification of palpable anatomical landmarks (ALs) for an inertial and magnetic sensor-based upper limb movement analysis protocol. The proposed calibration procedure provides an estimate of three-dimensional shoulder/elbow angular kinematics and the linear trajectory of the wrist according to the standards proposed by the International Society of Biomechanics. The validity of the method was assessed against a camera-based optoelectronic system during uniaxial joint rotations and a reach-to-grasp task. Joint angular kinematics was found as characterised by a low-biased range of motion (<−2.6°), a low root mean square deviation (RMSD) (<4.4°) and a high waveform similarity coefficient (R2 > 0.995) with respect to the gold standard. Except for the cranio–caudal direction, the linear trajectory of the wrist was characterised by a low-biased range of motion (<11 mm) together with a low RMSD (8 mm) and high waveform similarity (R2 > 0.968). The proposed method enabled the estimation of reliable joint kinematics without requiring any active involvement of the patient during the calibration procedure, complying with the metrological standards and requirements of clinical movement analysis.

IMPROVING THE PERFORMANCE OF COMPOST EXTRACTION SYSTEM USING MAGNETIC TREATMENT

The compost extract is primarily a liquid fertilizer, brewed by immersing organic compost in water in specified proportions and allowing the nutrients to leak as aerobic fermentation process. It is used as foliar fertilizer and soil amendment to supply the plant with water-soluble nutrients as well as to improve soil structure and water holding capacity. The aim of the research was to construct and evaluate the performance of a compost extract system to reach the optimum production parameters. Farm animal wastes were used as compost source. The performance of the manufactured system was studied under the different magnetic pumping period of (6,12,24 h/day);three dilution ratios of (1:10,1:15,1:20) ,different aeration period of (6,12,24 h/day).It has also been evaluated taking into consideration the following indicators: system productivity and specific energy requirements as well as physicochemical properties of compost extract. The experimental results showed that the highest value of unit productivity was 13.45 kg.day-1 with 1.29 kWh.Kg-1 specific energy. Based on the results, it can be concluded that the best dilution ratio is 1:20 and the preferable operating parameters for the compost extract production is 12 hours of aeration or magnetic pumping time. Furthermore, using a magnetic unit during pumping lead to improve the values of nutrients concentration N, P, and K. They were 1100, 97.86 and 5544 ppm, respectively compared with no magnetic treatment.

Development of the aeromagnetic space debris deorbiting system

The study has considered the possibility of creating an aeromagnetic system for removing space debris from low Earth orbits. The peculiarity of the design of the aeromagnetic deorbiting system is the use of magnetic controls for the relative position of the aerodynamic element with permanent rotary magnets that are shielded with the help of special screen capsules with shutters. It should be noted that this system is offered for aerodynamically unstable spacecraft. Besides, to analyse the performance and benefits of using permanent magnet aeromagnetic input systems, a corresponding discrete law is proposed to control the magnetic parts. The control of the relative position of the aerodynamic element in the orbital coordinate system is carried out in order to orient and stabilize it perpendicular to the dynamic incident atmospheric flow. A mathematical simulation has been performed for the orbital motion of a spacecraft during its removal with the help of a permanent magnet aeromagnetic system from different orbits. It has been determined that when stabilizing the aerodynamic element perpendicular to the vector of the incident dynamic atmospheric flow, the withdrawal time is reduced by 25 % compared with the non-oriented passive deorbiting. However, this advantage during the removal time is peculiar only to aerodynamic elements whose midsection area is much larger than a quarter of the total surface area. It is noteworthy that the design of aeromagnetic evacuation systems is only appropriate using aerodynamically deployable sail elements and is not effective at all for large inflatable elements. Thus, the development of an aeromagnetic space debris removal system with permanent magnet controls extends the boundaries of effective use of aerodynamic sailing systems. The use of permanent magnet units provides a new direction for further research on the orientation of large-scale space systems with minimal fuel and onboard energy consumption

Human Activities and Postures Recognition: From Inertial Measurements to Quaternion-Based Approaches.

This paper presents two approaches to assess the effect of the number of inertial sensors and their location placements on recognition of human postures and activities. Inertial and Magnetic Measurement Units (IMMUs)—which consist of a triad of three-axis accelerometer, three-axis gyroscope, and three-axis magnetometer sensors—are used in this work. Five IMMUs are initially used and attached to different body segments. Placements of up to three IMMUs are then considered: back, left foot, and left thigh. The subspace k-nearest neighbors (KNN) classifier is used to achieve the supervised learning process and the recognition task. In a first approach, we feed raw data from three-axis accelerometer and three-axis gyroscope into the classifier without any filtering or pre-processing, unlike what is usually reported in the state-of-the-art where statistical features were computed instead. Results show the efficiency of this method for the recognition of the studied activities and postures. With the proposed algorithm, more than 80% of the activities and postures are correctly classified using one IMMU, placed on the lower back, left thigh, or left foot location, and more than 90% when combining all three placements. In a second approach, we extract attitude, in term of quaternion, from IMMUs in order to more precisely achieve the recognition process. The obtained accuracy results are compared to those obtained when only raw data is exploited. Results show that the use of attitude significantly improves the performance of the classifier, especially for certain specific activities. In that case, it was further shown that using a smaller number of features, with quaternion, in the recognition process leads to a lower computation time and better accuracy.

Ab initio study of magnetic nanopatterning of a hybrid transition metal dichalcogenides/Ir(111) system via magnetic clusters

In this theoretical study we scrutinized how the interaction between a magnetic cluster made of three Fe atoms and a ${\mathrm{MoS}}_{2}$ monolayer adsorbed on Ir(111) reciprocally modifies their structural, electronic, and magnetic properties. From the structural point of view, the sulfur atom directly coordinated by the Fe cluster is pulled out of ${\mathrm{MoS}}_{2}$ on Ir(111) while this behavior is not present for a freestanding ${\mathrm{MoS}}_{2}$ single layer. Interestingly, this observation implies that Ir(111) catalyzes such a structural change in ${\mathrm{MoS}}_{2}$ upon the magnetic cluster adsorption. Besides this, from the magnetic point of view, the sulfur atom lifted from the transition metal dichalcogenide (TMD) monolayer acquires a small magnetic moment and forms together with the Fe atoms a reactive local heterogeneous chalcogene--transition metal magnetic unit that can be employed to functionalize TMD-based hybrid systems.

Impact of Superconducting Magnetic Energy Storage Unit on Doubly Fed Induction Generator Performance During Various Levels of Grid Faults

Since 2004, Doubly Fed Induction Generator (DFIG) has become the most admired wind turbine generator type that is widely installed worldwide. The popularity of DFIG is due to its capability to extract more energy than fixed speed wind turbine generator type. Moreover, a DFIG requires only one-third of the full converter size used by type-4 wind turbine generator which in turn reduces the total cost of DFIG installation. The main weakness of DFIG is its vulnerability to grid faults such as voltage dip and swell. Grid faults may have adverse impacts on the overall performance of the DFIG including the voltage at the point of common coupling that, at certain fault levels, may violate the permissible margins of the grid codes established by the transmission line operators. This paper investigates the application of Superconducting Magnetic Energy Storage (SMES) unit to improve the fault ride-through capability of a DFIG during grid faults. Results show that the connection of a SMES unit at the point of common coupling between the DFIG and the grid can enhance the overall performance of the DFIG during such faults events.

Qualitative aeromagnetic interpretation over Ikogosi Warm Spring, southwestern Nigeria

In this paper, lineaments of Ikogosi warm spring and its environs have been delineated using qualitative methods. Boundary structures or lineaments between magnetic units were delineated using the first horizontal derivative map and skeletonization of derivative-based data. Also, the residual anomaly contour map was digitized into ten profiles, profiles’ plots were made and used for interpretation. Dominant lineaments suspected were elongated features trending North East-South West direction and are housed by the shallow basements beneath the study area and surroundings.

Alignment of heavy ion therapy center vertical terminal

ABSTRACTWuwei heavy ion therapy center is the first Chinese heavy ion accelerator facility developed for cancer therapy, in which four terminals are distributed and the height of the vertical terminal is up to 18 m. Installation units of vertical terminal are diverse and complex, moreover, these units present poor alignment visibility. Thereby, it is difficult to perform the alignment among these components. Based on the laser tracker and high precision three-dimensional surveying control network, this paper proposes an efficient alignment method using multiple conversion of magnet fiducial data and pre-alignment of complex magnet unit. All the components are successfully aligned, and meanwhile the installation efficiency of vertical terminals is improved. Alignment accuracy of magnets is less than 0.1 mm. Error analysis presents that this alignment method achieves its goal.

Structural and magnetic properties of 3d transition metal oxide chains on the (001) surfaces of Ir and Pt

We present a survey of the structural and magnetic properties of submonolayer transition metal dioxides on the (001) surfaces of the heavy face-centered cubic (fcc) noble metals Ir and Pt performed by spin-averaged scanning tunneling microscopy (STM) and spin-polarized (SP-)STM. Our STM results confirm that deposition of Co, Fe, Mn, and Cr on the (2 {\times} 1) oxygen-reconstructed Ir(001) surface leads to the formation of quasi one-dimensional chains with a (3 {\times} 1) unit cell. As recently predicted by density functional theory [Ferstl et al., Phys. Rev. Lett. 117, 046101 (2016)], our SP-STM images of FeO2 and MnO2 on Ir(001) show a two-fold periodicity along the chains which is characteristic for an antiferromagnetic coupling along the chains. In addition, these two materials also exhibit spontaneous, permanent, and long-range magnetic coupling across the chains. Whereas we find a ferromagnetic inter-chain coupling for FeO2/Ir(001), the magnetic coupling of MnO2 on Ir(001) appears to be a non-collinear 120{\deg} spin spiral, resulting in a (9 {\times} 2) magnetic unit cell. On Pt(001) patches of (3 {\times} 1)-reconstructed oxide chains could only be prepared by transition metal (Co, Fe, and Mn) deposition onto the cold substrate and subsequent annealing in an oxygen atmosphere. Again SP-STM on MnO2/Pt(001) reveals a very large, (15 {\times} 2) magnetic unit cell which can tentatively be explained by a commensurate 72{\deg} spin spiral. Large scale SP-STM images reveal a long wavelength spin rotation along the MnO2 chain.

Collective spin dynamics of Z2 vortex crystals in triangular Kitaev-Heisenberg antiferromagnets

We show that the mesoscopic incommensurate $\mathbb{Z}_2$ vortex crystals proposed for layered triangular anisotropic magnets can be most saliently identified by two distinctive signatures in dynamical spin response experiments: The presence of pseudo-Goldstone `phonon' modes at low frequencies $\omega$, associated with the collective vibrations of the vortex cores, and a characteristic multi-scattered intensity profile at higher $\omega$, arising from a large number of Bragg reflections and magnon bandgaps. These are direct fingerprints of the large vortex sizes and magnetic unit cells and the solitonic spin profile around the vortex cores.

A Robust Pedestrian Dead Reckoning System Using Low-Cost Magnetic and Inertial Sensors

Pedestrian dead reckoning (PDR) using inertial and magnetic measurement unit (IMMU) is a current research hotspot that can be used to provide location-based services. The main challenges of the self-contained sensor-based PDR method are mainly sensor errors and orientation estimation errors. In this paper, a novel orientation estimation algorithm and gait phase detection algorithm with strong adaptability are proposed. The variance and magnitude of the angular rate are adopted to detect the gait. The experimental results show that the gait phase detection method can accurately distinguish the swing phase and the stance phase of the foot even under running conditions. By reasonable assumptions, the attitude angles calculated in the swing phase can be calibrated while the attitude angles are in the stance phase. The calibration of velocity not only uses the zero velocity updates method but also makes reasonable assumptions about the bias error of the accelerometer, so that the velocity calculated during the whole swing phase can be calibrated. Experimental results demonstrate that the proposed self-contained IMMU is capable of providing consistent beacon-free PDR in different scenarios, achieving less than 1.2% average distance error and average end-to-end position error.

Changes in shock absorption and kinematics during a Half Marathon as measured with inertial magnetic measurement units

Changes in shock absorption and kinematics during a Half Marathon as measured with inertial magnetic measurement units

Analysis and Design of a Novel Magnetic Levitation Gravity Compensator With Low Passive Force Variation in a Large Vertical Displacement

This paper presents a novel magnetic levitation gravity compensator and its design philosophy by which the nearly constant levitation force performance within a relatively large vertical displacement can be easily obtained. Generally, the absolute levitation is desired in many ultraprecision positioning systems, because the vibration disturbance can be effectively isolated. However, it is very difficult to obtain the low stiffness performance due to the serious nonlinearity of the passive force between two permanent magnets. The proposed magnetic levitation gravity compensator is combined with two passive magnetic levitation units owning the opposite levitation force characteristics. Based on the design principle of stiffness counteraction, the two levitation forces from the two units are superimposed but the resultant levitation force variation is very low. The stiffness counteraction effect is finally verified by experiments. The prototype testing data shows that the maximum levitation force variation of the proposed magnetic levitation gravity compensator within ±5 mm is only 0.72 N, which is 2.4% of the rated passive levitation force 30 N.

The First Conducting Spin‐Crossover Compound Combining a MnIII Cation Complex with Electroactive TCNQ Demonstrating an Abrupt Spin Transition with a Hysteresis of 50 K

We present herein the synthesis, crystal structure, and electric and magnetic properties of the spin-crossover salt [Mn(5-Cl-sal-N-1,5,8,12)]TCNQ1.5 ⋅2 CH3 CN (I), where 5-Cl-sal-N-1,5,8,12=N,N'-bis(3-(2-oxy-5-chlorobenzylideneamino)propyl)-ethylenediamine, containing distinct conductive and magnetic blocks along with acetonitrile solvent molecules. The MnIII complex with a Schiff-base ligand, [Mn(5-Cl-sal-N-1,5,8,12)]+ , acts as the magnetic unit, and the π-electron acceptor 7,7,8,8-tetracyanoquinodimethane (TCNQ- ) is the conducting unit. The title compound (I) exhibits semiconducting behavior with room temperature conductivity σRT ≈1×10-4 ohm-1 cm-1 and activation energy Δ ≈0.20 eV. In the temperature range 73-123 K, it experiences a hysteretic phase transition accompanied by a crossover between the low-spin S=1 and high-spin S=2 states of MnIII and changes in bond lengths within the MnN4 O2 octahedra. The pronounced shrinkage of the basal Mn-N bonds in I at the spin crossover suggests that the d orbital is occupied/deoccupied in this transition. Interestingly, the bromo isomorphic counterpart [Mn(5-Br-sal-N-1,5,8,12)]TCNQ1.5 ⋅2 CH3 CN (II) of the title compound evidences no spin-crossover phenomena and remains in the high-spin state in the temperature range 2-300 K. Comparison of the chloro and bromo compounds allows the thermal and spin-crossover contributions to the overall variation in bond lengths to be distinguished. The difference in magnetic behavior of these two salts has been ascribed to intermolecular supramolecular effects on the spin transition. Discrete hydrogen bonding exists between cations and cations and anions in both compounds. However, the hydrogen bonding in the crystals of II is much stronger than in I. The relatively close packing arrangement of the [Mn(5-Br-sal-N-1,5,8,12)]+ cations probably precludes their spin transformation.

Catalytic self-folding of 2D structures through cascading magnet reactions.

While thousands of proteins involved in development of the human body are capable of self-assembling in a distributed manner from merely 20 types of amino acid, macroscopic products that can be assembled spontaneously from ‘alive’ components remains an aspiration in engineering. To attain such a mechanism, a major challenge lies in understanding which attributes from the bio-molecular realm must be leveraged at the macro-scale. Inspired by protein folding, we present a centimetre-size 1D tile chain whose self-folding processes are directed by structure-embedded magnetic interactions, which can theoretically self-assemble into convex 2D structures of any size or shape without the aid of a global ‘controller’. Each tile holds two magnets contained in paths designed to control their interactions. Once initiated by a magnetic unit (termed Catalyst), the chain self-reconfigures by consuming magnetic potential energy stored between magnet pairs, until the final 2D structure is reached at an energetic minimum. Both simulation and experimental results are presented to illustrate the method’s efficacy on chains of arbitrary length. Results demonstrate the promise of a physically implemented, bottom-up, and scalable self-assembly method for novel 2D structure manufacturing, bridging the bio-molecular and mechanical realms.

Validity of MRI Measurements in Lumbar Spinal Canal Stenosis

Background:Lumbar spinal canal stenosis results from compression of spinal cord and/or nerves at any level of lumbar vertebra. The relationship between clinical features of the patients and the degree of stenosis is not clear and there is no accepted “gold standard” for the diagnosis of lumbar stenosis. Objective:To evaluate the relationship between the degree of radiologically confirmed stenosis and the severity of Oswestry disability Index and to assess the most valid parameter for the diagnosis of the lumbar stenosis. Methods;A cross-sectional study conducted on randomly selected patients with lumbar stenosis at Magnetic Resonance Image Unit of Al-Imamein Al-Kadhimein Medical City in Baghdad from May to September 2018. All patients filled Oswestry disability Index questionnaire and underwent examination using 1.5 Tesla magnetic resonance unit (Avanto, SIEMENS). Results:A total of 41 patients were included (51.46±12.62) years of age. The measurements of spinal canal including the cross-sectional area of dural sac at intervertebral levels, stenosis ratio, and depth of lateral recesses are found to be correlated significantly with the level of disability assessed by Oswestry disability Index. At all levels, neither the cross-sectional area of the lateral recesses nor Ligamentous interfacet distance correlated significantly to the level of disability. Conclusion:Magnetic resonance image measurements of spinal canal correlated to the level of disability. Stenosis ratio and cross-sectional area of dural sac at intervertebral disc were more sensitive measurements for lumbar stenosis than other parameters. Keywords: Oswestry disability Index, Spinal stenosis, magnetic resonance image Citation: Al-Jaberi HKH, Shakir BK, Hjazeen AA. Validity of MRI measurements in lumbar spinal canal stenosis. Iraqi JMS. 2019; 17(2): 126-134. doi: 10.22578/IJMS.17.2.6