Residual Field Research Articles

Maximum spherical mean value filtering for whole-brain QSM.

To develop a tissue field-filtering algorithm, called maximum spherical mean value (mSMV), for reducing shadow artifacts in QSM of the brain without requiring brain-tissue erosion. Residual background field is a major source of shadow artifacts in QSM. The mSMV algorithm filters large field-magnitude values near the border, where the maximum value of the harmonic background field is located. The effectiveness of mSMV for artifact removal was evaluated by comparing existing QSM algorithms in numerical brain simulation as well as using in vivo human data acquired from 11 healthy volunteers and 93 patients. Numerical simulation showed that mSMV reduces shadow artifacts and improves QSM accuracy. Better shadow reduction, as demonstrated by lower QSM variation in the gray matter and higher QSM image quality score, was also observed in healthy subjects and in patients with hemorrhages, stroke, and multiple sclerosis. The mSMV algorithm allows QSM maps that are substantially equivalent to those obtained using SMV-filtered dipole inversion without eroding the volume of interest.

Objective Lagrangian Vortex Cores and their Visual Representations.

The numerical extraction of vortex cores from time-dependent fluid flow attracted much attention over the past decades. A commonly agreed upon vortex definition remained elusive since a proper vortex core needs to satisfy two hard constraints: it must be objective and Lagrangian. Recent methods on objectivization met the first but not the second constraint, since there was no formal guarantee that the resulting vortex coreline is indeed a pathline of the fluid flow. In this paper, we propose the first vortex core definition that is both objective and Lagrangian. Our approach restricts observer motions to follow along pathlines, which reduces the degrees of freedoms: we only need to optimize for an observer rotation that makes the observed flow as steady as possible. This optimization succeeds along Lagrangian vortex corelines and will result in a non-zero time-partial everywhere else. By performing this optimization at each point of a spatial grid, we obtain a residual scalar field, which we call vortex deviation error. The local minima on the grid serve as seed points for a gradient descent optimization that delivers sub-voxel accurate corelines. The visualization of both 2D and 3D vortex cores is based on the separation of the movement of the vortex core and the swirling flow behavior around it. While the vortex core is represented by a pathline, the swirling motion around it is visualized by streamlines in the correct frame. We demonstrate the utility of the approach on several 2D and 3D time-dependent vector fields'.

Improving the Uniformity of the Residual Magnetic Field in the MSR Using Independent Coils Compensation Method

Improving the Uniformity of the Residual Magnetic Field in the MSR Using Independent Coils Compensation Method

Temperature control of atomic gas chamber using a nonmagnetic heating chip fabricated on quartz substrate

Nonmagnetic electrical heating and temperature sensing chip fabricated on quartz substrate is developed, and a high-precision digital temperature control system is designed based on this chip. The heating resistance and temperature sensing resistance are prepared by depositing two layers of Ti/Pt alloy electrodes on quartz substrate through magnetic field cancellation design. The temperature coefficient of fabricated Ti/Pt temperature sensing resistance is +0.197%/℃. The simulation results show that the residual magnetic field generated by the heating current in the atomic gas chamber closely adjacent to the chip is less than 0.1 nT. Temperature control in the range of 100~150 ℃ is realized, and the temperature stability is about 0.02 ℃. Due to the high light transmittance of quartz glass, this heating chip has significant advantages for optical integration and miniaturization of atomic magnetometers.

Physical-Layer Network Coding Based on Residual Field of Algebraic Integers in OFDM-VLC Two-Way Relay Networks

Physical-Layer Network Coding Based on Residual Field of Algebraic Integers in OFDM-VLC Two-Way Relay Networks

Variation of color of magnetic noise in Er3+ molecular magnets contacting metal surface in ferromagnetic composite

Interaction between single molecule magnets (SMMs) and metal surface is a hot topic promising controllable deposition of SMMs, programmable frequency of magnetic relaxation and addressed reading of information. In this paper, we develop strategy of the Er3+ based SMM functionalization by its penetration inside the arrays of Ferromagnetic Micro Particles (FMPs). We show that predictable residual magnetic field of the FMPs arrays is an effective tool for regulation of the frequency maximum of imaginary magnetic susceptibility. We analyzed color of magnetic noise in respect to physical origin of magnetic relaxation. An additional channel for control over spin noise is formation of chemical bonds between SMM and the FMPs surface. Oxidation of an Er complex transforms 20 ± 5 % of the initial 10-coordinated SMM complex to the 9-coordinated complex with reduced relaxation time. Memorized residual magnetization of the composite material allows one to set desirable relaxation frequency in the individual micronized cells to create a sound frequency register. The proposed compaction of SMMs of different types in ferromagnetic composites provides engineering of the chemically designed spin interface on ferromagnetic surface for spintronics and quantum computing.

Influence of inter-river water diversion on estuary pollution control: A case study of Liaodong Bay

Long-term mass transport processes in offshore seas are controlled by seasonal residual currents. The Euler residual mass transport velocity field was calculated form seasonal residual current patterns in shallow sea area, comparing with polluted water changes in typical years. The following conclusions were made: closed local large loops of the Euler residual mass transport led to polluted waters in the northeast Liaodong Bay, and the bay's optimal physical self-purification occurred in winter (Euler residual mass transport diffuses polluted water masses) and spring (overall self-purification capacity of the bay plays a role after winter). The central waters were clean while pollutants were discharged into near-shore waters, leading to perennial pollution in some near-shore waters. Pollution in Liaodong Bay could be alleviated or eliminated via diversion of water from the Daliaohe River (flowing into the northeast corner of Liaodong Bay and carrying > 65% of the total amount of pollutants discharged into the top of the bay) into the Liaohe River and Daling River. The percentage of inorganic nitrogen carried by 10% of the flux of the Daliaohe River was 5.70% of that discharged into Liaodong Bay. If 10% of the flux of the Daliaohe River was discharged into the Daling River, the annual total environmental carrying capacity of inorganic nitrogen increased 4.48%. Many bays in the world have adjacent river flows, such as Gulf of Mexico, Gulf of Guinea, and Bay of Bengal. Based on the Euler residual mass transport field, the water transfer between adjacent rivers could make better use of the Euler residual mass transport capacity to mitigate the water pollution of the estuaries.

The Koszulness of numerical semigroup rings of minimal multiplicity

Let R = k [H] be a numerical semigroup ring over a field k and grm (R) is the associated graded ring of R. In this paper, we show that grm (R) is a Cohen-Macaulay ring, provided H has minimal multiplicity. As a consequence, we conclude that the numerical semigroup ring R = k [H] of minimal multiplicity is a Koszul ring, i.e., the residue field k has a grm (R) – linear free resolution.

Strongly divisible lattices and crystalline cohomology in the imperfect residue field case

Strongly divisible lattices and crystalline cohomology in the imperfect residue field case

A degree bound for rings of arithmetic invariants

Consider a Noetherian domain R and a finite group G⊆Gln(R). We prove that if the ring of invariants R[x1,…,xn]G is a Cohen-Macaulay ring, then it is generated as an R-algebra by elements of degree at most max⁡(|G|,n(|G|−1)). As an intermediate result we also show that if R is a Noetherian local ring with infinite residue field then such a ring of invariants of a finite group G over R contains a homogeneous system of parameters consisting of elements of degree at most |G|.

Re-Distribution of Welding Residual Stress in Fatigue Crack Propagation Considering Elastic–Plastic Behavior

The welding residual stress re-distribution behavior during fatigue crack propagation in butt-welded high-strength steel plates for ship construction is investigated based on experimental test results and numerical analyses. The specimens’ initial welding residual stresses are obtained from X-ray for middle tensile (MT) specimens cut from butt-welded high-strength steel plates. Then, fatigue crack propagation experiments on MT specimens are conducted, and a strain gauge is used to measure the residual stress re-distribution field around cracks. A practical fatigue crack propagation simulation procedure is developed with a dynamic update of in-situ welding residual stress, where the residual stress intensity factor Kres of the MT specimen is deduced. The stress ratio effect on Kres during fatigue crack propagation is analyzed and a good agreement between experimental and numerical results is achieved.

Background formation of lower levels of reactive oxygen species by neutrophils after hypomagnetic field exposure is not accompanied by the impairment of chemiluminescence response of neutrophils to respiratory-burst stimuli

This study shows that the background formation of lower levels of reactive oxygen species in mouse peritoneal neutrophils after short-term (40 minutes) exposure to hypomagnetic fields with ~10 nT residual field at physiological temperatures, which has been detected by use of lucigenin-dependent chemiluminescence, is not accompanied by the impairment of chemiluminescence response of neutrophils to respiratory-burst stimuli: the formylated tripeptide N-formyl-Met-Leu-Phe (fMLF) and phorbol ester phorbol-12-myristate-13-ace-tate (PMA). These results were obtained with lucigenin or luminol-enhanced activated chemiluminescence and various combinations of reactive oxygen species production stimuli (phorbol-12-myristate-13-acetate and/or N-formyl-Met-Leu-Phe). Based on the results of the present work as well as on those of previous studies, this study reveal that the systems that control the respiratory burst in neutrophils can be excluded from a list of main targets and acceptors that respond to short-term deprivation of the magnetic field.

Correlation between Residual Sensitivity in the Central Inferior Nasal Visual Field and Visual Function in Chronic Leber Hereditary Optic Neuropathy Patients

Introduction: Leber hereditary optic neuropathy (LHON) is a maternally inherited, acute or subacute, optic neuropathy. The typical symptoms include reduced visual acuity and central scotoma. Despite the presence of deep central scotoma, some patients with LHON are able to perform daily activities. This study aimed to investigate the correlation between the residual visual field and visual acuity, critical flicker frequency, and fixation ellipse in patients with chronic LHON. Methods: Residual visual function (defined as sensitivity points where patients sensed the size V stimulus) of both eyes was evaluated in 10 patients with LHON carrying the m.11778 mitochondrial DNA mutation and with median age of onset and disease duration of 29 and 16.5 years, respectively. The central visual field was measured as static perimetry using the Humphrey visual field testing 30-2 program with the size III or V stimulus. Moreover, best-corrected visual acuity, critical flicker frequency, and the correlation between fixation ellipse and residual central visual fields were determined. The analysis was performed through a linear mixed-effects model. Results: The residual visual sensitivity in the inferior nasal visual field was significantly correlated with the logMAR (p < 0.05). The fixation ellipse fell within the residual visual field region with higher sensitivity. Conclusions: Patients with chronic LHON tended to retain the sensitivity detectable with the size V stimulus at the central inferior nasal visual field regions, where the fixation ellipse fell. Visual acuity, which influences daily activity, was spatially correlated with residual visual sensitivity.

Effect of defects on flux expulsion of pure niobium superconducting radio frequency cavities via spatial temperature gradient

Since flux vortices are easily pinned by defects in superconducting radio frequency (SRF) cavities, trapped magnetic flux increases the surface resistance of the SRF cavity. It has been experimentally demonstrated that trapped magnetic flux can be expelled by cooling down a superconducting cavity under a large spatial temperature gradient. In this paper, we use the time-dependent Ginzburg–Landau (TDGL) theory to theoretically investigate the effect of defects on the flux expulsion ability of pure niobium superconducting cavities with an applied spatial temperature gradient. It is shown that the residual flux vortex density displays a notable stepwise decreasing trend with increasing temperature gradient at smaller residual fields, while it shows a stepwise rising with increasing defect size. Both larger defect number and size make vortices difficult to be expelled. Moreover, long cooling time is beneficial for vortices to be expelled, and the cooling time has nearly no significant effect on flux expulsion under conditions of large cooling times. The results in this paper provide some theoretical guidelines for improving the performance of superconducting cavities in practical situations.

Domain patterning in nonpolar cut PMN–PT by focused ion beam

The formation of the ferroelectric domain structure as a result of irradiation by focused ion beam of [100]-cut 0.61Pb(Mg[Formula: see text]Nb[Formula: see text]O3–0.39PbTiO3 (PMN–PT) single crystals covered by surface artificial dielectric layer and with free surface was investigated. The dot irradiation resulted in formation of the wedge-like domains grown along [00[Formula: see text]] direction. For irradiation of the free surface, the domains are mainly located under the surface, while at the irradiated surface with an artificial dielectric layer the domains are located at the surface. It was shown that the subsurface wedge-shaped part of the domain is unstable and completely disappears after a month due to spontaneous backswitching under the action of the residual depolarization field. The revealed nonlinear dose dependence of the domain sizes was attributed to the distribution of the electric field using the point charge model. The domain interaction for the distance between irradiated dots below 30[Formula: see text][Formula: see text]m has been revealed in all samples. It was shown that the decrease of the distance between irradiated dots in the created domain row leads to an increase in the length of the central domains, which is explained by the contribution of all injected charges to the switching field.

TWO EXAMPLES CONCERNING EXISTENTIAL UNDECIDABILITY IN FIELDS

Abstract We construct an existentially undecidable complete discretely valued field of mixed characteristic with existentially decidable residue field and decidable algebraic part, answering a question by Anscombe–Fehm in a strong way. Along the way, we construct an existentially decidable field of positive characteristic with an existentially undecidable finite extension, modifying a construction due to Kesavan Thanagopal.

Gravity evidence for a heterogeneous crust of Mercury

We modeled gravity data to explore Mercury’s internal structure and show the presence of crustal heterogeneities in density. We first evaluated the lithospheric flexure occurring in the spherical harmonic degree range 5–80, according to the flexural isostatic response curve. We thus estimated a mean elastic lithosphere thickness of about 30 pm 10 km and modeled the crust-mantle interface, which varies from 19 to 42 km depth, according to a flexural compensation model. The isostatic gravity anomalies were then obtained as the residual field with respect to the contributions from topography and lithospheric flexure. Isostatic anomalies are mainly related to density variations in the crust: gravity highs mostly correspond to large-impact basins suggesting intra-crustal magmatic intrusions as the main origin of these anomalies. Isostatic gravity lows prevail, instead, above intercrater plains and may represent the signature of a heavily fractured crust.

Non-admissible irreducible representations of 𝑝-adic 𝐺𝐿_{𝑛} in characteristic 𝑝

Let p &gt; 3 p&gt;3 and F F be a non-archimedean local field with residue field a proper finite extension of F p \mathbb {F}_p . We construct smooth absolutely irreducible non-admissible representations of G L 2 ( F ) \mathrm {GL}_2(F) defined over the residue field of F F extending the earlier results of the authors for F F unramified over Q p \mathbb {Q}_{p} . This construction uses the theory of diagrams of Breuil and Pašk u ¯ \bar {\mathrm {u}} nas. By parabolic induction, we obtain smooth absolutely irreducible non-admissible representations of G L n ( F ) \mathrm {GL}_n(F) for n &gt; 2 n&gt;2 .

Hybrid Method for Reducing the Residual Field in the Magnetic Shielding Room

This study proposes a hybrid method for improving the magnetic shielding performance of a magnetic shielding room (MSR) with few permalloy layers. In this method, two types of compensating coils are combined, one placed outside the MSR and the other placed inside. The coupling effect between the outside coil and the permalloy layer is used to adjust the residual field distribution characteristics of the MSR, and the inside coil is used to compensate for the adjusted residual field. This method has been verified with an MSR with two permalloy layers and an inner space of 1.3 m × 1.3 m × 2.2 m. According to the result, the residual field was reduced to less than 2.5 nT in a cube with a 0.4-m side length, which is seven times lower than that without compensation, and the inner space utilization rate was also improved by two times compared with existing MSRs with a comparable space size. The proposed method is of great significance in the development of magnetic shielding technology.

Deep Learning Approach for Multi-class Semantic Segmentation of UAV Images

Image understanding plays a very crucial role in remote sensing applications. For this, image semantic segmentation is one of the approaches where each pixel of an image is assigned to particular classes based on various features. Aerial semantic segmentation suffers from the class imbalance problem. Proper differentiation of least represented categories is challenging and a goal for the state-of-art approach. In this work, we present a novel deep learning method to perform this task. We proposed a lightweight encoder-decoder network residual depth separable UNet (RDS-UNet) and conditional random field for effective segmentation on very high-resolution aerial images. We proposed patch-with-multi-class sampling to handle the class imbalance problem without increasing the computational overhead during the training process. We created a semi-precise annotated UAV dataset named NESAC UAV Seg for the aerial semantic segmentation task. We demonstrated the efficacy of our model using the publicly available benchmark Drone Deploy dataset and our NESAC UAV Seg dataset. Our model required approximately half the number of trainable parameters and floating point operations compared to other methods. A detailed ablation study is presented to showcase the effectiveness of various modules utilized in our network.