Artykuły w czasopismach: „Field defect”

1

Dzhala, R. M., V. R. Dzhala, M. I. Melnyk, B. I. Horon i O. I. Senyuk. "Influence of the pipe defect on its magnetic field". Information extraction and processing 2018, nr 46 (27.12.2018): 5–10. http://dx.doi.org/10.15407/vidbir2018.46.005.

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Foroozan, Rod, i Lawrence M. Buono. "Foggy visual field defect". Survey of Ophthalmology 48, nr 4 (lipiec 2003): 447–51. http://dx.doi.org/10.1016/s0039-6257(03)00051-1.

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Vaphiades, Michael S., i John Mason. "Foggy visual field defect". Survey of Ophthalmology 49, nr 2 (marzec 2004): 266–67. http://dx.doi.org/10.1016/j.survophthal.2003.12.004.

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Toriello, Helga V., John M. Opitz i James F. Reynolds. "The arhinencephaly field defect". American Journal of Medical Genetics 25, S2 (1986): 73–76. http://dx.doi.org/10.1002/ajmg.1320250611.

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CAUDRELIER, V. "ON A SYSTEMATIC APPROACH TO DEFECTS IN CLASSICAL INTEGRABLE FIELD THEORIES". International Journal of Geometric Methods in Modern Physics 05, nr 07 (listopad 2008): 1085–108. http://dx.doi.org/10.1142/s0219887808003223.

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We present an inverse scattering approach to defects in classical integrable field theories. Integrability is proved systematically by constructing the generating function of the infinite set of modified integrals of motion. The contribution of the defect to all orders is explicitely identified in terms of a defect matrix. The underlying geometric picture is that those defects correspond to Bäcklund transformations localized at a given point. A classification of defect matrices as well as the corresponding defect conditions is performed. The method is applied to a collection of well-known integrable models and previous results are recovered (and extended) directly as special cases. Finally, a brief discussion of the classical r-matrix approach in this context shows the relation to inhomogeneous lattice models and the need to resort to lattice regularizations of integrable field theories with defects.

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He, Shaobo, Liang Yang, Li Li i Xiao-Tao Zu. "The Electric Field Modulation by Hemisphere Damage Sites in Fused Silica Subsurface". Advances in Condensed Matter Physics 2014 (2014): 1–5. http://dx.doi.org/10.1155/2014/843261.

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The effect of defect density on the electric field modulation to incident laser is investigated in this work. Based on the actual defect distribution in fused silica subsurface, the three-dimension grid model of defect sites is constructed firstly. Then, the three-dimension finite-difference time-domain method is developed to solve the Maxwell equations. The electric field intensity in the vicinity of the defect sites located in front subsurface of fused silica is numerically calculated. The relationships between the maximal electric field intensity in fused silica and the geometry of the defect sites are given. The simulated results reveal that the modulation becomes more remarkable with the increase of defects density firstly and then decrease. Besides, the effect of the distribution mode of defects on modulation is discussed. Meanwhile, the possible physical mechanism is analyzed in detail.

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Xu, Wen Ji, Ji Shang Jiang, Xu Yue Wang i Wen Qing Song. "Temperature Field Model in Plasma Arc Forming of Laminated Clad Metal Sheets Containing Defects". Advanced Materials Research 97-101 (marzec 2010): 4160–63. http://dx.doi.org/10.4028/www.scientific.net/amr.97-101.4160.

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A FEM model, based on the structural characteristics of laminated clad metal sheets (LCMS) containing defects, was developed to study the variations of temperature field in the flexible forming using plasma arc. The typical LCMS Q235A/1Cr18Ni9Ti was selected as the sample, and the effects of different defects in the bonding interface on the temperature field were analyzed. The results show that the peak value of temperature containing defect is 107 oC higher than that without defect under the same processing parameters. The peak values of temperature and temperature difference increase with the increasing of defect size, but decrease when the location of defect is far away from the heating surface of LCMS. Compared with spherical defect, cubic defect has more power to impede heat conduction along the thickness direction of LCMS.

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Zhu, Wenfa, Yujie Zhang, Guopeng Fan, Haiyan Zhang i Shao Wei. "Time-domain topological energy imaging with ultrasonic Lamb waves considering multiple defects". Insight - Non-Destructive Testing and Condition Monitoring 62, nr 4 (1.04.2020): 208–15. http://dx.doi.org/10.1784/insi.2020.62.4.208.

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This study presents a fast imaging approach with ultrasonic Lamb waves based on time-domain topological energy to identify multiple defects with defect spacing smaller than the threshold of the Rayleigh criterion in terms of imaging resolution. The direct acoustical field and time-domain topological energy of the two fields are used as imaging functions when considering the calculation of direct and adjoint acoustical fields in a non-defective reference medium on the basis of topological theory. The functions are not limited by acoustic diffraction and can achieve super-resolution imaging with multiple defects. First, a 3D finite element model is established. Transient acoustic field diagrams at different moments are used to show the focusing process of direct and adjoint acoustical fields clearly with multiple defects, thereby revealing the physical mechanism of time-domain topological energy imaging. Second, the effectiveness of the proposed approach to characterise multiple defects when the defect spacing is smaller than the imaging resolution threshold is verified through numerical simulation. Finally, the feasibility of super-resolution imaging considering multiple defects is proven by conducting experiments on aluminium plate samples with multiple defects under different defect spacing conditions. Numerical simulation and experimental results show that the proposed approach can overcome the problem of multiple defects with defect spacing smaller than the imaging resolution threshold by breaking the Rayleigh criterion constraint, while the accuracy presented is higher than that of the traditional delay-and-sum method.

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Konik, Robert, i André LeClair. "Purely transmitting defect field theories". Nuclear Physics B 538, nr 3 (styczeń 1999): 587–611. http://dx.doi.org/10.1016/s0550-3213(98)00712-3.

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Larner, A. J. "A developing visual field defect". Postgraduate Medical Journal 78, nr 916 (1.02.2002): 106. http://dx.doi.org/10.1136/pmj.78.916.106.

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Mathura, Jeevan R., i Lee M. Jampol. "Medical Mystery — Visual-Field Defect". New England Journal of Medicine 355, nr 15 (12.10.2006): 1592. http://dx.doi.org/10.1056/nejmicm040399.

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Johnson, Virginia P. "Holoprosencephaly: A developmental field defect". American Journal of Medical Genetics 34, nr 2 (październik 1989): 258–64. http://dx.doi.org/10.1002/ajmg.1320340228.

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Hegde, Hardally R., i Alexander K. C. Leung. "Acro-pectoro-renal field defect". Pediatric Nephrology 18, nr 3 (25.02.2003): 307–8. http://dx.doi.org/10.1007/s00467-002-1026-8.

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Покровский, Aleksey Pokrovskiy, Новиков, Ilya Novikov, Хвостов i Andrey Khvostov. "Field Topography of Defects in Magnetic Non-Destructive Testing". NDT World 19, nr 4 (15.12.2015): 53–56. http://dx.doi.org/10.12737/23510.

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The defect parameters can be evaluated by defect induced magnetic field topography using Hall sensor. Investigations were carried out on specially prepared samples with artificial defects. According to calculations and tests tangential component of magnetic field strength extremes were detected values on either side of the defect in the surface layer l only. But this effect can not be detected by Hall sensors or Foerster probes due to their sizes. The normal component of the magnetic field strength provides a sufficiently accurate determination of the fault location, where this component becomes zero between the two extreme values located quite close to each other. The results of the study showed that at distances available to Hall transducers one can confine to the experimental research, whereas computational methods shall be used to study the topography of field defects at very small distances from the surface. This could open the prospects for testing at small distances from the surface of the object.

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15

Gao, Xiangdong, Xinxin Dai, Xiaohu Zhou, Yanfeng Li, Deyong You, Yanxi Zhang i Nanfeng Zhang. "Elucidation of magnetic flux leakage for welding defect detection at different magnetic field directions through alternating magnetic field measurement". Insight - Non-Destructive Testing and Condition Monitoring 61, nr 12 (1.12.2019): 720–28. http://dx.doi.org/10.1784/insi.2019.61.12.720.

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Alternating current field measurement (ACFM) is a technology for detecting magnetic flux leakage (MFL) using a magnetic sensor and is often used to detect welding defects. An alternating magnetic field was generated under the excitation of an alternating electric field. The magnetic field direction of an alternating magnetic field changes with time and the size and direction of the leakage magnetic field on the weldment also change periodically. In order to verify this rule, the distribution of the leakage magnetic field in different magnetisation directions was analysed through simulation and experiment. The simulation results show that when sinusoidal excitation is applied to the coil, the direction of magnetisation changes with time and the magnetic field density (B) gradually changes periodically on the weldment. This was verified through related experiments. When the surface of the weldment had welding defects, the dynamic magneto-optical image was captured in different magnetisation directions. Welding defects have different magneto-optical images in different frames, which can present more information for the same defect. In addition, in the experiment, the correlation between the grey-level co-occurrence matrix (GLCM) of magneto-optical images in different magnetisation directions and that of the leakage magnetic field in the corresponding direction was analysed. Simulations and experiments were performed on different types of welding defect. It was found that the trend of characteristics for the leakage magnetic fields was similar to that of the characteristics for the grey-level co-occurrence matrix of the magneto-optical images. The results show that the characteristics of the leakage magnetic field can reflect the texture features of the welding defect.

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16

BAJNOK, Z., i A. GEORGE. "FROM DEFECTS TO BOUNDARIES". International Journal of Modern Physics A 21, nr 05 (20.02.2006): 1063–77. http://dx.doi.org/10.1142/s0217751x06025262.

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In this paper we describe how relativistic field theories containing defects are equivalent to a class of boundary field theories. As a consequence previously derived results for boundaries can be directly applied to defects, these results include reduction formulas, the Coleman–Thun mechanism and Cutcosky rules. For integrable theories the defect crossing unitarity equation can be derived and defect operator found. For a generic purely transmitting impurity we use the boundary bootstrap method to obtain solutions of the defect Yang–Baxter equation. The groundstate energy on the strip with defects is also calculated.

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Zhao, Xiao Fang, i A. K. Soh. "Phase Field Simulation of Ferroelectrics with Cracks". Key Engineering Materials 462-463 (styczeń 2011): 710–15. http://dx.doi.org/10.4028/www.scientific.net/kem.462-463.710.

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By employing a dipole defect model, two-dimensional phase field simulations of domain switching in the crack tip vicinity of a crack embedded in a relaxor ferroelectric single crystal, which was subjected to mechanical loading and electric field, have been carried out. The interaction between the dipole defects and crack, the influence of the dipole defect concentration density on the switching process, and the coupling effect of mechanical stress and electric field on domain switching in the vicinity of the crack tip have been studied. Comparing the results obtained from relaxor ferroelectrics with those of normal ferroelectrics, the former showed that, due to the interaction between the dipole defects and crack, polarization switching in the vicinity of the crack tip was suppressed. Moreover, the coupling between applied mechanical stress and electric field can either promote or suppress domain switching in the vicinity of a crack.

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Guo, Li, Yu Liao, Hongying Yao, Jinhao Chen i Manran Wang. "An Electrical Insulator Defects Detection Method Combined Human Receptive Field Model". Journal of Control Science and Engineering 2018 (3.07.2018): 1–9. http://dx.doi.org/10.1155/2018/2371825.

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Nondestructive inspection of electrical insulators subjected to the high electrical stress and environmental damage is fundamental for reliable operation of a transmission lines. The breakage and defect of the insulator have great influence on the safe of transmission lines, and insulator defect detection with difference types is a complex work. This paper proposed an insulator defect detection method inspired by human receptive field model, which meets the requirements for detecting defect insulator in a simple background. In this method, the defect detection combined human receptive field model of human visual system is constructed and applied on the different insulators, so as to achieve accurate detection of the insulator defected parts. Experimental results show that the method can accurately and robustly detect the defect (such as cracks and damage) of electrical insulator in case of noise affect.

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19

Liu, Han Wu, Rui Hua Dong i Han Xun Lv. "Numeral Simulation Study on Pipeline Corrosion Defects under Different Sizes and Pressures Based on FEM". Applied Mechanics and Materials 215-216 (listopad 2012): 1154–57. http://dx.doi.org/10.4028/www.scientific.net/amm.215-216.1154.

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Finite element analysis software ANSYS is used to establish a three-dimensional finite element model of the pipeline corrosion defects by applying the boundary conditions of square wave excitation to simulate the distributions of current and induced magnetic field in the pipeline under various defect volumes. The results of the study show: When there is no corrosion defect in the pipeline, the electric current in the pipeline is basically even distribution. The magnetic field is distributed for the symmetrical vortex shape from head to foot, and it has not obviously gather phenomenon. When there are some corrosion defects in the pipeline, the electric current forms partial symmetrical vortex shape in both sides of the corrosion defect, and it is obviously assembled in the defect place. The simulation results of the different size defects show that the maximum magnetic field strength and the maximum current value increase with the defect depth increasing, while the output voltage decreases with the defect depth increasing. For the analysis of the stress distributions of the pipeline corrosion defect with certain size under different pressures, it was found that the maximum stress is 596 MPa when the bearing limit work pressure of the pipeline is 7 MPa, which is smaller than the yield strength with ensuring the safely running of the pipelines with defects.

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Yu, Caberry W., i Jonathan A. Micieli. "Monocular Visual Field Defect on Humphrey 24-2 SITA-Fast Testing Later Identified as a Highly Incongruous Homonymous Defect on Humphrey 30-2 SITA-Fast Testing". Case Reports in Ophthalmology 12, nr 2 (11.06.2021): 507–12. http://dx.doi.org/10.1159/000516663.

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Monocular visual field defects generally localize at or anterior to the optic chiasm, while homonymous hemianopias localize to the retrochiasmal visual pathway. Highly incongruous visual field defects may be difficult to identify on 24-2 Humphrey visual field testing, and this case demonstrates the value of optical coherence tomography (OCT) ganglion cell-inner plexiform layer (GCIPL) in rapidly localizing the lesion. A 54-year-old woman was found on routine examination to have an isolated superonasal quadrant visual field defect respecting the vertical meridian in the left eye only on Humphrey 24-2 SITA-Fast testing. She had a remote history of significant head trauma. Visual acuity, anterior segment, and fundus examination were normal. OCT revealed a bow-tie atrophy of the retinal nerve fiber layer in the right eye (OD), and binocular homonymous hemi-macular atrophy of OCT GCIPL, confirming the localization was the left retrochiasmal visual pathway. A repeat Humphrey 30-2 SITA-Fast visual field demonstrated that the visual field defect was also present in the OD in a highly incongruous manner. Magnetic resonance imaging of the brain with contrast showed mild atrophy of the left optic tract. This case demonstrates that highly incongruous visual field defects may be difficult to identify on Humphrey 24-2 SITA-Fast visual fields, and OCT GCIPL serves as a rapid way to localize the lesion. More detailed visual field testing including 30-2 programs should be considered in these cases.

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Jin, Hyung Nam, Yeon Soo Kang, Mi Sun Sung i Sang Woo Park. "Characteristics of Visual Field Defects in Korean Advanced Glaucoma". Journal of the Korean Ophthalmological Society 62, nr 8 (15.08.2021): 1105–15. http://dx.doi.org/10.3341/jkos.2021.62.8.1105.

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Purpose: We investigated the clinical characteristics of visual field (VF) defects in Korean advanced glaucoma patients.Methods: The present study included 109 eyes of 109 advanced glaucoma patients whose mean deviation (MD) is under -12 dB. The subjects were classified into primary open angle glaucoma (POAG) and normal tension glaucoma (NTG) group. Average numeric decibel in each VF points were visualized with color topographic image and dot graph image using python 3.5. VF was divided into four quadrants or two half fields, and the differences in the degree of VF defects in each locations were assessed with raw decibel data. Additionally, mean sensitivity of central 12 points were compared between the two groups.Results: Generally the features of VF defects were severely depressed VF sensitivity at the superonasal quadrant and relatively preserved central area and inferotemporal quadrant in both of the glaucoma groups. But we found the extent of deflection for VF defect in the NTG eyes was higher than that of the POAG eyes (p < 0.05). The POAG eyes tended to show more diffuse and evenly distributed VF defect, whereas NTG eyes tended to have more severely depressed VF at the superonasal quadrant and relatively preserved VF at the inferotemporal quadrant. There was no significant difference in the degree of central VF defects between the two groups.Conclusions: The characteristics of VF defect in Korean advanced glaucoma revealed different features based on the glaucoma diagnosis. The POAG eyes tended to show diffuse VF defects, whereas NTG eyes tended to have more severely depressed VF sensitivity at the superonasal quadrant and relatively preserved VF at the inferotemporal quadrant.

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Rowe, Fiona J., Carmel Noonan i Melanie Manuel. "Comparison of Octopus Semi-Automated Kinetic Perimetry and Humphrey Peripheral Static Perimetry in Neuro-Ophthalmic Cases". ISRN Ophthalmology 2013 (15.07.2013): 1–8. http://dx.doi.org/10.1155/2013/753202.

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Aim. To compare semikinetic perimetry (SKP) on Octopus 900 perimetry to a peripheral static programme with Humphrey automated perimetry. Methods. Prospective cross-section study comparing Humphrey full field (FF) 120 two zone programme to a screening protocol for SKP on Octopus perimetry. Results were independently graded for presence/absence of field defect plus type and location of defect. Results. 64 patients (113 eyes) underwent dual perimetry assessment. Mean duration of assessment for SKP was 4.54 minutes ±0.18 and for FF120 (). 80% of results were correctly matched for normal or abnormal visual fields using the I4e target versus FF120, and 73.5% were correctly matched using the I2e target versus FF120. When comparing Octopus results with combined I4e and I2e isopters to the FF120 result, a match for normal or abnormal fields was recorded in 87%. Conclusions. Humphrey perimetry test duration was generally longer than Octopus SKP. In the absence of kinetic perimetry, peripheral static suprathreshold programme options such as FF120 may be useful for detection of visual field defects. However, statokinetic dissociation may occur. Octopus SKP utilising both I4e and I2e targets provides detailed information of both the defect depth and size and may provide a more representative view of the actual visual field defect.

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Xu, Li, i Jianzhong Hu. "A Method of Defect Depth Recognition in Active Infrared Thermography Based on GRU Networks". Applied Sciences 11, nr 14 (10.07.2021): 6387. http://dx.doi.org/10.3390/app11146387.

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Active infrared thermography (AIRT) is a significant defect detection and evaluation method in the field of non-destructive testing, on account of the fact that it promptly provides visual information and that the results could be used for quantitative research of defects. At present, the quantitative evaluation of defects is an urgent problem to be solved in this field. In this work, a defect depth recognition method based on gated recurrent unit (GRU) networks is proposed to solve the problem of insufficient accuracy in defect depth recognition. AIRT is applied to obtain the raw thermal sequences of the surface temperature field distribution of the defect specimen. Before training the GRU model, principal component analysis (PCA) is used to reduce the dimension and to eliminate the correlation of the raw datasets. Then, the GRU model is employed to automatically recognize the depth of the defect. The defect depth recognition performance of the proposed method is evaluated through an experiment on polymethyl methacrylate (PMMA) with flat bottom holes. The results indicate that the PCA-processed datasets outperform the raw temperature datasets in model learning when assessing defect depth characteristics. A comparison with the BP network shows that the proposed method has better performance in defect depth recognition.

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Fromme, Paul. "Guided wave sensitivity prediction for part and through-thickness crack-like defects". Structural Health Monitoring 19, nr 3 (9.12.2019): 953–63. http://dx.doi.org/10.1177/1475921719892205.

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Guided waves allow for the efficient structural health monitoring of large structures using phased or distributed arrays of sensors. The sensitivity for specific defects can be improved by accounting for the angular scattering pattern. The scattering of the fundamental anti-symmetric guided wave mode (A0 Lamb mode) at through-thickness and part-through crack-like defects was studied experimentally and from three-dimensional finite element simulations. Experimentally, the scattered field around manufactured notches of different depths and lengths in an aluminium plate was measured using a laser interferometer. The scattered field was extracted by taking the complex difference in the frequency domain between baseline measurement and measurements around the defect. Good agreement was found between measurements and three-dimensional finite element simulations, and the amplitude and directionality pattern of the scattered field can be predicted accurately. The angular directionality pattern of the scattered field depending on the direction of the incident wave relative to the crack-like defect orientation, depth and length relative to the wavelength was investigated. For short and part-thickness defects, the main scattering effect is a reduction of the (forward) wave propagating past the defect with very limited backscattered amplitude. Significant energy scattered back towards the incident wave direction was only found for perpendicular incidence on long and deep defects. Even for large defects, almost no energy is scattered in certain directions from the defect, possibly complicating defect detection. Based on the predicted amplitude and angular dependency of the scattered guided waves, the sensitivity for defect detection using localized and distributed structural health monitoring sensor array systems can be quantified.

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Tonomura, Akira. "Application Of Field-Emission Tem To Investigating Flux Pinning Mechanism In Superconductors". Microscopy and Microanalysis 4, S2 (lipiec 1998): 686–87. http://dx.doi.org/10.1017/s1431927600023552.

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Magnetic vortices in superconductors have become directly and dynamically observable[l] by Lorentz microscopy in our 300 kV field-emission TEM[2]. Since material defects can also be observed simultaneously though the images are defocused, the microscopic flux pinning mechanism can be directly observed. Using this technique, we observed when and how vortices trapped at artificial defects were depinned.Artificial point defects were produced by the irradiation of a focused Ga ion beam. Electron microscopy revealed that the defect consisted of a pit 300 Å in radius surrounded by entangled dislocations. The depth of a pit increased with the ion dose.We first investigated the pinning force of individual defect: by observing the depinning of vortices from defects produced with various ion-doses. When a force was exerted on vortices trapped at the defects by changing the magnetic field and increased, we found that the pinning force of defects increased with the ion doses.

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NAZAROV, VLADIMIR, i RISHAT SHAFEEV. "INFLUENCE OF AN EXTERNAL MAGNETIC FIELD ON THE DYNAMICS OF A NEW-PHASE NUCLEUS IN THE VICINITY OF THE FIRST-ORDER PHASE TRANSITION IN MAGNETS WITH DEFECTS PRESENT". Modern Physics Letters B 26, nr 28 (8.10.2012): 1250183. http://dx.doi.org/10.1142/s0217984912501837.

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Theoretically, with the aid of a soliton model, the evolution of a new-phase nucleus near the first-order spin-reorientation phase transition in magnets has been investigated in an external magnetic field. The influence of an external field and one-dimensional defects of magnetic anisotropy on the dynamics of such nucleus has been demonstrated. The conditions for the localization of the new-phase nucleus in the region of the magnetic anisotropy defect and for its escape from the defect have been determined. The values of the critical fields which bring about the sample magnetization reversal have been identified and estimated.

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Wein, Francine, i Neil R. Miller. "An Unusual Homonymous Visual Field Defect". Survey of Ophthalmology 44, nr 4 (styczeń 2000): 324–28. http://dx.doi.org/10.1016/s0039-6257(99)00116-2.

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Kumar, V. "Artefactual uniocular altitudinal visual field defect". British Journal of Ophthalmology 86, nr 12 (1.12.2002): 1442–43. http://dx.doi.org/10.1136/bjo.86.12.1442.

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Comaish, I. F. "Visual field defect associated with vigabatrin". BMJ 320, nr 7246 (20.05.2000): 1403. http://dx.doi.org/10.1136/bmj.320.7246.1403.

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Khan, A. A., R. J. Kelly i Z. I. Carrim. "Flashes, floaters, and a field defect". BMJ 347, nr 04 1 (4.11.2013): f6496. http://dx.doi.org/10.1136/bmj.f6496.

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Wilkie, M. D., i R. Al-Mahfoudh. "Acute headache and visual field defect". BMJ 344, apr04 1 (4.04.2012): e2229-e2229. http://dx.doi.org/10.1136/bmj.e2229.

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Robertson, Craig. "Folding defect affine Toda field theories". Journal of Physics A: Mathematical and Theoretical 47, nr 18 (17.04.2014): 185201. http://dx.doi.org/10.1088/1751-8113/47/18/185201.

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Sika, Robert, Michał Rogalewicz, Paweł Popielarski, Dorota Czarnecka-Komorowska, Damian Przestacki, Katarzyna Gawdzińska i Paweł Szymański. "Decision Support System in the Field of Defects Assessment in the Metal Matrix Composites Castings". Materials 13, nr 16 (12.08.2020): 3552. http://dx.doi.org/10.3390/ma13163552.

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This paper presented a new approach to decision making support of defects assessment in metal matrix composites (MMC). It is a continuation of the authors’ papers in terms of a uniform method of casting defects assessment. The idea of this paper was to design an open-access application (follow-up system called Open Atlas of Casting Defects (OACD)) in the area of industry and science. This a new solution makes it possible to quickly identify defect types considering the new classification of casting defects. This classification complements a classical approach by adding a casting defect group called structure defects, which is especially important for metal matrix composites. In the paper, an application structure, and the possibility of its use in casting defects assessment were introduced.

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ZHOU, CHUNFENG, PENGTAO YUE i JAMES J. FENG. "The rise of Newtonian drops in a nematic liquid crystal". Journal of Fluid Mechanics 593 (23.11.2007): 385–404. http://dx.doi.org/10.1017/s0022112007008889.

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We simulate the rise of Newtonian drops in a nematic liquid crystal parallel to the far-field molecular orientation. The moving interface is computed in a diffuse-interface framework, and the anisotropic rheology of the liquid crystal is represented by the Leslie–Ericksen theory, regularized to permit topological defects. Results reveal interesting coupling between the flow field and the orientational field surrounding the drop, especially the defect configuration. The flow generally sweeps the point and ring defects downstream, and may transform a ring defect into a point defect. The stability of these defects and their transformation are depicted in a phase diagram in terms of the Ericksen number and the ratio between surface anchoring and bulk elastic energies. The nematic orientation affects the flow field in return. Drops with planar anchoring on the surface rise faster than those with homeotropic anchoring, and the former features a vortex ring in the wake. These are attributed to the viscous anisotropy of the nematic. With homeotropic anchoring, the drop rising velocity experiences an overshoot, owing to the transformation of the initial surface ring defect to a satellite point defect. With both types of anchoring, the drag coefficient of the drop decreases with increasing Ericksen number as the flow-alignment of the nematic orientation reduces the effective viscosity of the liquid crystal.

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Li, Tang, Zhang, Guo, Li, Su, Li i Yun. "Nanoscale Characterization of V-defect in InGaN/GaN QWs LEDs using Near-Field Scanning Optical Microscopy". Nanomaterials 9, nr 4 (18.04.2019): 633. http://dx.doi.org/10.3390/nano9040633.

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The size of the V-defects in the GaN/InGaN-based quantum wells blue light-emitting diode (LED) was intentionally modified from 50 nm to 300 nm. High resolution photoluminescence and electroluminescence of a single large V-defect were investigated by near-field scanning optical microscopy. The current distribution along the {10-11} facets of the large defect was measured by conductive atomic force microscopy. Nearly 20 times the current injection and dominant emission from bottom quantum wells were found in the V-defect compared to its vicinity. Such enhanced current injection into the bottom part of quantum wells through V-defect results in higher light output power. Reduced external quantum efficiency droops were achieved due to more uniform carrier distribution. The un-encapsulated fabricated chip shows light output power of 172.5 mW and 201.7 mW at 400 mA, and external quantum efficiency drop of 22.3% and 15.4% for the sample without and with large V-defects, respectively. Modified V-defects provide a simple and eﬀective approach to suppress the efficiency droop problem that occurs at high current injection, while improving overall quantum efficiency.

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Liu, Han Wu, Shan Ping Zhan, Yun Hui Du i Peng Zhang. "Study on Pulsed Eddy Current Nondestructive Testing Technology for Pipeline Corrosion Defects Based on Finite Element Method". Applied Mechanics and Materials 120 (październik 2011): 36–41. http://dx.doi.org/10.4028/www.scientific.net/amm.120.36.

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According to the principle and the type of the oil pipeline corrosion, we use the square wave of wide spectrum, strong signal transmission capability and a certain duty ratio as the excitation source of the pulsed eddy current. The finite element analysis software ANSYS is used to establish a three-dimensional finite element model of the pipeline corrosion defects by applying the boundary conditions of square wave excitation to simulate the distributions of current and induced magnetic field in the pipeline under various defect volumes. It can solve the induced voltage variation with time on detection coil, and can accomplish the finite element analysis and the nondestructive testing about the pipeline internal corrosion defects with the insulation layer and the protection layer. The results of the study show: When there is no corrosion defect in the pipeline, the electric current in the pipeline is basically even distribution. The magnetic field is distributed for the symmetrical vortex shape from head to foot, and it has not obviously gather phenomenon. When there are some corrosion defects in the pipeline, the electric current forms partial symmetrical vortex shape in both sides of the corrosion defect, and it is obviously assembled in the defect place. The simulation results of the different size defects show that the maximum magnetic field strength and the maximum current value increase with the defect depth increasing, while the output voltage decreases with the defect depth increasing. By extracting the induced voltage signals on the detection coil in a certain excitation condition, the quantitative detection of the pipeline corrosion defects can be achieved.

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Hua, Jun, Peng Yun Jin, Li Bing Zheng, Hua Chao Fang, Chun Lei Wang, Li Han i Ping Song. "Design of the Temperature Field Test System of Power Electronic Packaging Modules". Advanced Materials Research 875-877 (luty 2014): 1929–33. http://dx.doi.org/10.4028/www.scientific.net/amr.875-877.1929.

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The defects of material, packaging process and layout in power electronic packaging modules can affect the temperature distribution. Defects such as the voids of the welding and the unreasonable layout will cause uneven distribution of the temperature field in the internal surface and the local hot spots will emerge. If the hot spots continued, the module will be damaged. In order to achieve the defect analysis based on the temperature field, a test system is designed. The infrared camera is used to measure the temperature distribution in the system. The system can test the temperature field distribution characteristics with different loads. The study provided a strong basis of defect analysis standards based on temperature field.

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Handley, Siân E., Maja Šuštar i Manca Tekavčič Pompe. "What can visual electrophysiology tell about possible visual-field defects in paediatric patients". Eye 35, nr 9 (16.07.2021): 2354–73. http://dx.doi.org/10.1038/s41433-021-01680-1.

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AbstractRecognising a potential visual-field (VF) defect in paediatric patients might be challenging, especially in children before the age of 5 years and those with developmental delay or intellectual disability. Visual electrophysiological testing is an objective and non-invasive technique for evaluation of visual function in paediatric patients, which can characterise the location of dysfunction and differentiate between disorders of the retina, optic nerve and visual pathway. The recording of electroretinography (ERG) and visual-evoked potentials (VEP) is possible from early days of life and requires no subjective input from the patient. As the origins of ERG and VEP tests are known, the pattern of electrophysiological changes can provide information about the VF of a child unable to perform accurate perimetry. This review summarises previously published electrophysiological findings in several common types of VF defects that can be found in paediatric patients (generalised VF defect, peripheral VF loss, central scotoma, bi-temporal hemianopia, altitudinal VF defect, quadrantanopia and homonymous hemianopia). It also shares experience on using electrophysiological testing as additional functional evidence to other tests in the clinical challenge of diagnosing or excluding VF defects in complex paediatric patients. Each type of VF defect is illustrated with one or two clinical cases.

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Tosi, Gian Marco, Gianluca Martone, Angelo Balestrazzi, Alex Malandrini, Marco Alegente i Patrizia Pichierri. "Visual Field Loss Progression after Macular Hole Surgery". Journal of Ophthalmology 2009 (2009): 1–3. http://dx.doi.org/10.1155/2009/617891.

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Purpose. To report a patient who experienced visual field loss progression after vitrectomy for an idiopathic stage II macular hole.Methods. Case report. A 68-year-old woman, with no history of glaucoma or any neuroophthalmological diseases, underwent a vitrectomy for a macular hole.Results. The patient showed macular hole closure and a resulting central visual acuity of 20/20. However, two months after surgery, she developed an inferotemporal visual field defect. Moreover, seven months after surgery, the patient noticed an enlargement of the temporal blind area: a nearly complete temporal defect was confirmed on visual field testing.Conclusions. Although the beneficial results of successfully treated macular holes are unquestionable, this report raises the possibility that visual field defects following macular hole surgery may be progressive.

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SOCHICHIU, CORNELIU. "ON DEFECT INDUCED GAUGE AND YUKAWA FIELDS IN GRAPHENE". International Journal of Modern Physics B 26, nr 05 (20.02.2012): 1250055. http://dx.doi.org/10.1142/s0217979212500555.

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We consider lattice deformations (both continuous and topological) of the hexagonal lattice model describing the electronic wave function of graphene in the tight binding approximation. The deformation involves operators with the range up to next-to-neighbor. In the low energy limit, we find that these deformations give rise to couplings of the electronic Dirac field to an external scalar (Yukawa) and gauge fields. The fields are expressed in terms of original defects. As a by-product we establish that the next-to-nearest order is the minimal range of deformations which produces the complete gauge and scalar fields. We consider an example of Stone–Wales defect, and find the associated gauge field.

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Baev, A. R., N. V. Levkovich, A. L. Mayorov i M. V. Asadchaya. "Scattering of Elastic Waves by an Inhomogeneous Boundary in the Acoustic Testing of Permanent Joints". Devices and Methods of Measurements 10, nr 4 (12.12.2019): 360–72. http://dx.doi.org/10.21122/2220-9506-2019-10-4-360-372.

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Improving the reliability and testing performance of permanent joints оf different materials made by welding, spraying, gluing, soldering and other methods is an important production task, for which the ultrasonic method is the simplest and most effective. The purpose of this work was to expand the technical possibilities and increase the sensitivity of ultrasonic testing of adhesion defects of materials joints based on the establishment of laws governing the formation of a scattering field of elastic waves from an inhomogeneous boundary in three-dimensional space and issuing recommendations for the development of suggested method.For the first time, in the framework of classical concepts, the scattering fields of elastic waves of an acoustic beam with a circular cross section moving across the boundary of a semi-infinite defect are calculated. It is proposed to use a phase shift between the waves reflected from the indicated surfaces, which varies in the range of π/4–π, as an important parameter of the material joint's defect. It has a significant effect on the field pattern and its angular amplitude extrema — minima and maxima of different orders when the defect boundary is moved relative to the center of the acoustic beam spot.The features of the evolution of the structure of the scattering field are established, which make it possible to identify optimal conditions for the detection of weakly reflective defects in sound. It is shown that it is possible in principle to estimate the defect's area by measuring a change in the amplitude of the primary maximum of the radiation pattern of the scattered waves.Specific examples show the effectiveness of using the proposed method for a number of practical applications.

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Jian, Chuan Xia, Jian Gao i Xin Chen. "A Review of TFT-LCD Panel Defect Detection Methods". Advanced Materials Research 734-737 (sierpień 2013): 2898–902. http://dx.doi.org/10.4028/www.scientific.net/amr.734-737.2898.

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TFT-LCD panel defect detection has been one of the difficulties in this field because of fuzzy defect boundary, low contrast between defects and background, and low detection speed. The structure of TFT-LCD panels and classification are introduced. Through the analysis of panel defect features, current detection methods for the TFT-LCD panel defects are reviewed. The key technologies of feature extraction and defect classification are analyzed in the defect image recognition of TFT-LCD panel. Meanwhile the methods of fuzzy boundary defect segmentation, image subtraction and image filtering are also discussed. Finally, the characteristics and advantages of these detection methods are concluded, and several key issues for the TFT-LCD defect detection have been proposed for future development.

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Kuerten, David, Konstantin Kotliar, Matthias Fuest, Peter Walter, Muriel Hollstein i Niklas Plange. "Does hemispheric vascular regulation differ significantly in glaucoma patients with altitudinal visual field asymmetry? A single-center, prospective study". International Ophthalmology 41, nr 9 (19.05.2021): 3109–19. http://dx.doi.org/10.1007/s10792-021-01876-0.

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Abstract Purpose Vascular risk factors and ocular perfusion are heatedly discussed in the pathogenesis of glaucoma. The retinal vessel analyzer (RVA, IMEDOS Systems, Germany) allows noninvasive measurement of retinal vessel regulation. Significant differences especially in the veins between healthy subjects and patients suffering from glaucoma were previously reported. In this pilot-study we investigated if localized vascular regulation is altered in glaucoma patients with altitudinal visual field defect asymmetry. Methods 15 eyes of 12 glaucoma patients with advanced altitudinal visual field defect asymmetry were included. The mean defect was calculated for each hemisphere separately (−20.99 ± 10.49 profound hemispheric visual field defect vs −7.36 ± 3.97 dB less profound hemisphere). After pupil dilation, RVA measurements of retinal arteries and veins were conducted using the standard protocol. The superior and inferior retinal vessel reactivity were measured consecutively in each eye. Results Significant differences were recorded in venous vessel constriction after flicker light stimulation and overall amplitude of the reaction (p < 0.04 and p < 0.02 respectively) in-between the hemispheres. Vessel reaction was higher in the hemisphere corresponding to the more advanced visual field defect. Arterial diameters reacted similarly, failing to reach statistical significance. Conclusion Localized retinal vessel regulation is significantly altered in glaucoma patients with asymmetric altitudinal visual field defects. Veins supplying the hemisphere concordant to a less profound visual field defect show diminished diameter changes. Vascular dysregulation might be particularly important in early glaucoma stages prior to a significant visual field defect.

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Roshanzamir-Nikou, M., i H. Goudarzi. "Magnetization of disclinated graphene in nonuniform magnetic field". International Journal of Modern Physics B 31, nr 04 (6.02.2017): 1750013. http://dx.doi.org/10.1142/s0217979217500138.

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Two-dimensional disclinated atomic graphene layer in curved space–time is exactly discussed, and the explicit dependence of Landau levels on the topological defect and external magnetic field are obtained in the presence of nonuniform magnetic field. It is worth mentioning that the presence of topological defect reduces the degeneracy of energy levels. The persistent current, magnetization, susceptibility and the magnetoresistance of structure are investigated. It can be shown that the curvature of the conical surface affects the pattern of oscillations of persistent current and, of course, corresponding magnetoresistance. The behavior of the above physical quantities as a function of magnetic flux is explicitly found for various defects. We observe that increasing magnetic field leads to a aperiodic oscillation. The large Aharonov–Bohm flux gives rise to vanish the magnetization oscillations.

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Filev, Veselin G. "Hot defect superconformal field theory in an external magnetic field". Journal of High Energy Physics 2009, nr 11 (30.11.2009): 123. http://dx.doi.org/10.1088/1126-6708/2009/11/123.

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Singh, Pranisha, i AP Rijal. "Pattern of Visual Field Defects in Newly Diagnosed Primary Open Angle Glaucoma Patients Attending Tertiary Care Hospital, Kathmandu, Nepal". Nepal Medical College Journal 22, nr 4 (31.12.2020): 203–10. http://dx.doi.org/10.3126/nmcj.v22i4.34181.

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The purpose of this study was to evaluate the location and pattern of visual field defects as measured by Humphrey Field Analyzer (HFA 24-2) in newly diagnosed primary open angle glaucoma (POAG) attending tertiary care hospital. This was a cross sectional, descriptive study. One hundred and four eyes of 52 patients who fulfilled the inclusion criteria during one year were included. They were classified as mild, moderate and severe glaucoma according to severity. Paracentral scotoma in superotemporal and superonasal region was the most frequent visual field defect observed in mild glaucoma. Superior arcuate defect and double arcuate defect was commonly seen among moderate and severe stages of POAG respectively. There was a significant association between severity of glaucoma and pattern of visual field defect (p=0.000). The superior hemifield was affected twice more than the inferior hemifield in newly diagnosed cases of POAG.

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Tanoko, Ivana, i Fifin L. Rahmi. "Visual Field Examination in Glaucoma Patients : Humphrey Visual Field Analysis vs Amsler Grid". Ophthalmologica Indonesiana 43, nr 2 (5.05.2017): 124. http://dx.doi.org/10.35749/journal.v43i2.152.

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Introduction and Objective: Glaucoma is the leading cause of global irreversible blindness, signed by glaucomatous optic neuropathy related to visual field defect. The purpose of the study is comparing visual field defect examination using HVFA to Amsler Grid in glaucoma patient at dr. Kariadi Hospital. Methods: This is a cross-sectional study. Amsler Grid were performed to the patients who have reliable HVFA at last 6 months and presented as descriptive analytic results. Result: There were 40 eyes involved in this study from 27 patients (15 men, 12 women), 26-68 years old and visual acuity 1/60-6/6. Seventeen eyes showed visual field defect in HVFA and Amsler Grid had average MD - 24.97 dB, CDR 0.89 and RNFL thickness 51.74. We found that 11 eyes didn’t showed in both of examination had average MD -8.06, CDR 0.63 and RNFL thickness 103.23 and those parameters are significantly different to the 17 eyes before (p<0.05). Data from 12 eyes that showed visual field defect only one of examination (9 only in HVFA and 3 in Amsler Grid) didn’t show difference statistically each other. Conclusion: HFVA and Amsler Grid seemed to be comparable in detecting visual field defect in advanced glaucoma.

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Xu, Zhiyuan, Xiang Wang i Yiming Deng. "Rotating Focused Field Eddy-Current Sensing for Arbitrary Orientation Defects Detection in Carbon Steel". Sensors 20, nr 8 (20.04.2020): 2345. http://dx.doi.org/10.3390/s20082345.

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This paper presents a rotating focused field eddy-current (EC) sensing technique, which leverages the advantages of magnetic field focusing and rotating magnetic field, for arbitrary orientation defects detection. The sensor consists of four identical excitation coils orthogonally arranged in an upside-down pyramid configuration and a giant magneto-resistive (GMR) detection element. The four coils are connected to form two figure-8-shaped focusing sub-probes, which are fed by two identical harmonic currents with 90 degrees phase difference. A finite element model-based study of arbitrary orientation defects detection was performed to understand the probe operational characteristics and optimize its design parameters. Probe prototyping and experimental validation were also carried out on a carbon steel plate specimen with four prefabricated surface-breaking defects. In-situ spot inspection with the probe rotating above the defect and a manual line-scan inspection were both conducted. Results showed that the probe has the capability of detecting defects with any orientations while maintaining the same sensitivity and the defect depth can be quantitatively evaluated by using the signal amplitude. Compared with the existing rotating field probes, the presented probe does not require additional excitation adjustment or data fusion. Meanwhile, due to its focusing effect, it can generate a strong rotating magnetic field at the defect location with a weak background noise, thus yielding superior signal-to-noise ratio.

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Mostovoy, S. D., i O. V. Pavlovsky. "Particle-like behavior of defects near a defect line in 2D Ising model: Defect–antidefect pair production and interaction". International Journal of Modern Physics B 33, nr 12 (10.05.2019): 1950117. http://dx.doi.org/10.1142/s0217979219501170.

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The aim of this work is to investigate Casimir effect in a system comprising of a defect line along with isolated defects (vacancies) in 2D Ising model. We have found out that the interaction energy has a decaying exponent with distance between defects. We are interested in an analogy between Casimir behavior of this defect structure and quantum field theory. The simplest deformation of a defect line (a defect’s position change) can be treated as defect–“antidefect” pair creation. Single defect is attracted to a defect line. By means of Monte Carlo simulation, the energy of pair creation and Casimir interaction potential are calculated. The interaction turned out that a Yukawa potential turns to the Coulomb’s one at phase transition point.

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Abdul Amir, Haider F. "Stopping Power and Range of Cesium-137 Gamma Rays in Gallium Arsenide Field Effect Transistor (GaAsFET)". Solid State Phenomena 263 (wrzesień 2017): 170–75. http://dx.doi.org/10.4028/www.scientific.net/ssp.263.170.

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In this paper, the defect generated in the interaction of gamma ray resulting from cesium ion (Cs-137) and GaAs as a main portion of gallium arsenide field effect transistor (GaAsFET) is simulated using SRIM (Stopping and Range of Ions in Matter). The induced defects are in the form of vacancies, defect clusters and dislocations. Besides, the defect is found influencing the kinetic processes that occur both inside and outside the cascade volume. The radiation tolerance between the conventional scale and nanoscale thickness of GaAs layer is also being compared. From the findings, it is observed that when the thickness of GaAs layer is scaled down, defect that induced by the energy deposition of gamma radiation is significantly lesser. This means that nanoscale GaAs layer features improved radiation robustness towards the deposition of energetic ions.

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