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Patients with high-risk neuroblastoma have a poor prognosis; new therapeutic agents are therefore required. We investigated the antitumor effects of OBP-801, a novel histone deacetylase inhibitor, its underlying mechanism, and its potential as a therapeutic agent for patients with neuroblastoma.The study included five human neuroblastoma cell lines: IMR32, GOTO, KP-N-RTBM, SK-N-AS, and SH-SY5Y. We investigated cell proliferation, cell cycle status, protein expression patterns, and apoptosis in neuroblastoma cells after OBP-801 treatment in vitro. Cell survival rate and cell cycle were analyzed using the WST-8 assay and flow cytometry, respectively. Apoptosis was detected using annexin V staining, and the expression of apoptosis-related proteins was investigated by western blotting. The antitumor activity of OBP-801 was examined in an in vivo xenograft mouse model.Dose-effect curve analysis showed that the mean half-maximal inhibitory concentration value was 5.5 ± 5.9 nM for the MYCN-amplified cell lines (IMR32, GOTO, and KP-N-RTBM) and 3.1 ± 0.7 nM for the MYCN-nonamplified cell lines (SK-N-AS and SH-SY5Y). OBP-801 inhibited cell proliferation and growth in all the cell lines. It induced G2/M phase arrest through the p21 (CDKN1A) pathway, increasing histone H3 levels and, subsequently, apoptosis in human neuroblastoma cells. OBP-801 suppressed the growth of neuroblastoma cells in the mouse xenograft model.Overall, OBP-801 induces M-phase arrest and apoptosis in neuroblastoma cells via mitotic catastrophe. Our results indicate that OBP-801 is a promising therapeutic agent with fewer adverse effects for patients with neuroblastoma.

The magnetic field of vortices in anisotropic superconducting films is considered in the framework of anisotropic London approach. It is found that at distances large relative to the core size, the magnetic field normal to the film surface may change sign. We find that the magnetic field attenuates at large distances as $1/r^3$ as it does in isotropic films, but the anisotropy induces an angular dependence to the supercurrents which causes the sign of the field to change for anisotropy parameters $\gamma=\lambda_2/\lambda_1>\sqrt{2}$ in some parts of the $(x,y)$ plane., Comment: 8 pages, 12 figures

Moving vortices in thin superconducting films are considered within the time-dependent London description. The dissipation due to out-of-core normal excitations for two vortices moving together turns out to have a minimum for the separation vector $\bm a$ parallel to the velocity and equal to $a_m \approx 2.2\, \Lambda$, where $\Lambda $ is the Pearl length. The minimum entropy production suggests that moving vortices should have a tendency to form chains along the velocity with a period of the order $a_m$., Comment: 4 pages, 4 figures

We take account of normal currents that emerge when vortices move. Moving Abrikosov vortices in the bulk and Pearl vortices in thin films are considered. Velocity dependent distributions of both normal and persistent currents are studied in the frame of time-dependent London equations. In thin films near the Pearl vortex core, these distributions are intriguing in particular., Comment: 8 pages,10 figures. arXiv admin note: text overlap with arXiv:2102.00073

This paper presents a model-based study of undesirable signal loss problems, often encountered by eddy current inspections of tight cracks. Possible current leakage through a portion of the crack face is the focus here as the principal mechanism of signal reduction. Two problematic types of cracking conditions are studied particularly, i.e., a surface-smeared crack and a crack under compressive stress. With a newly developed model and its numerical results, the paper shows quantitative analyses of the signal loss for the above two cases, compared to the response of a pristine surface-breaking crack in the similar geometrical configuration.

Although paternally expressed IGF2 is known to play a critical role in placental and body growth, only a single mutation has been found in IGF2. We identified, through whole-exome sequencing, a de novo IGF2 indel mutation leading to frameshift (NM_000612.5:c.110_117delinsAGGTAA, p.(Leu37Glnfs*31)) in a patient with Silver-Russell syndrome, ectrodactyly, undermasculinized genitalia, developmental delay, and placental hypoplasia. Furthermore, we demonstrated that the mutation resided on the paternal allele by sequencing the long PCR product harboring the mutation- and methylation-sensitive SmaI and SalI sites before and after SmaI/SalI digestion. The results, together with the previous findings in four cases from a single family with a paternally inherited IGF2 nonsense mutation and those in patients with variable H19 differentially methylated region epimutations leading to compromised IGF2 expression, suggest that the whole phenotype of this patient is explainable by the IGF2 mutation, and that phenotypic severity is primarily determined by the IGF2 expression level in target tissues.

Precision medicine strategies for treating rhabdomyosarcoma (RMS), a childhood malignancy, have not been developed. We examined the effect of CH5126766, a potent selective dual RAF/MEK inhibitor, on RMS cell lines. Among the eleven cell lines studied, one NRAS and two HRAS mutated cell lines were detected. CH5126766 inhibited the proliferation and growth in all of the RAS-mutated RMS cell lines, while it induced G1 cell cycle arrest in two of them. G1 cell cycle arrest was accompanied by p21 up-regulation and RB dephosphorylation. CH5126766 also suppressed the in vivo growth of RAS-mutated RMS tumor, and the mice showed improved survival. Thus, our results demonstrate that CH5126766 is an effective RAF/MEK inhibitor in RAS-mutated RMS. This study not only shows that in RMS, mutations in the RAS pathway can be a target for precision medicine, but also demonstrates that the evaluation of the gene mutation status is important in childhood malignancies.

Lipoblastoma is a rare benign adipose tissue tumor that occurs mostly in infants and children. Histological diagnosis of lipoblastoma is sometimes difficult because it closely resembles other lipomatous tumors. The detection of PLAG1 gene rearrangement is useful for the diagnosis of lipoblastoma. Four PLAG1 fusion partner genes are known in lipoblastoma: HAS2 at 8q24.1, COL1A2 at 7q22, COL3A1 at 2q32, and RAB2A at 8q12. Herein, we describe a novel fusion gene in a case of lipoblastoma of left back origin. We identified a potential PLAG1 fusion partner using 5′ rapid amplification of cDNA ends, and sequence analysis revealed the novel fusion gene, BOC-PLAG1. The BOC-PLAG1 fusion transcript consists of the first exon of the BOC gene fused to exon 2 or exon 3 of the PLAG1 gene. PLAG1 expression was found to be 35.7 ± 2.1 times higher in the tumor specimen than in human adipocytes by qRT-PCR. As a result of the translocation, the constitutively active promoter of BOC leads to PLAG1 overexpression. The identification of the BOC-PLAG1 fusion gene will lead to more accurate diagnosis of lipoblastoma.

Eddy current inspection is widely used in nondestructive evaluation to detect cracks in metal structures. The impedance plane measurement response, collected using our motion controlled eddy current inspection system, is used in the analysis. A scalar reduction from the impedance plane response is used to minimize human-factor variation. We apply a noise interference model to the data from a large-scale experiment taking measurements on fastener rivet holes in multilayer structures with fatigue cracks, and estimate the probability of detection (POD). The estimates of POD as a function of crack size will be valuable for future model-assisted POD studies.

This paper reports on Hall Effect measurements on nickel-base superalloys and their stress dependency. The work is motivated by the desire to develop a nondestructive method of characterizing the near-surface protective residual stress in metals. Our approach is based on the assumption that the Hall coefficient deviates under the stress. It is anticipated that stress measurements based on the Hall Effect are less contaminated by cold work and other effects than conductivity-based measurements such as eddy current. The paper focuses on the two superalloys, Inconel 718 and Inconel 600. The challenge is that Hall coefficients are small in metals, and the stress-induced changes are even smaller. To measure the small effect, the lock-in technique was used, with AC injected current and AC magnetic field. It was found that the Hall coefficients indeed vary proportionally to the stress. The proportionality coefficients are significantly larger than what are estimated from the volumetric effect in a free carrier gas model. The temperature and injected current dependences of the Hall coefficients were also measured, while no dependence on the magnetic flux density was observed.

Recent studies have shown the possibility of exploiting the eddy current (EC) method for nondestructive characterization of near-surface residual stresses in surface-treated nickel-base superalloy components. The method involves measuring swept frequency EC signals to obtain near-surface electrical conductivity depth profiles, which can be converted into residual stress profiles using the empirical piezoresistivity relationship. However, the relationship between EC responses and residual stress profiles appears to depend on the microstructure. This paper reports on a systematic study of microstructural effects on the EC responses and near-surface conductivity deviation profiles induced by shot peening, using a series of heat-treated Inconel 718 samples with different secondary phase contents and thus a variety of hardness levels. Calibrated EC signals from 100 kHz to 50 MHz were measured from aged and unaged samples, before and after shot peening at various Almen intensities. Strong dependence of the EC responses on the sample hardness and microstructure has been observed. A procedure is introduced to convert the EC signals into shot-peening-induced conductivity deviation profiles where the microstructure dependency is suppressed. The resulting estimates of the conductivity changes are larger than expected, indicating that characterization of shot-peening-induced residual stresses by EC requires further understanding of the material responses beyond the empirical piezoresistivity relationship. Other mechanisms that could contribute to the observed conductivity changes are discussed.

A boundary integral equation (BIE) is developed for the eddy-current (EC) problems with Dirichlet boundary condition by considering the difference between the field without cracks and the one with cracks. Once the field and its normal derivative are given for the structure in the absence of cracks, normal derivative of the scattered field on the surface can be calculated by solving this integral equation numerically. For infinite-domain problems, this equation is more efficient than the conventional BIE due to a smaller computational region needed. Four kinds of two-dimensional EC problems have been solved using this integral equation. The surface impedance for different cases is presented in this paper. Numerical results are compared with analytical solutions and published numerical results. There are good agreements between them. Also, this concept can be extended to three-dimensional problems with other boundary conditions.

Eddy current (EC) measurements have shown promise toward becoming a nondestructive method of residual stress characterization, particularly for nickel-base superalloys. However, previous studies on shot-peened materials have shown apparent discrepancies between directly measured residual stress profiles and those determined from EC data. Here, we report a study of the inter-relationship among electrical conductivity deviation, residual stress and texture of shot peened materials, in order to improve understanding of the piezoresistivity effect that is essential to the on-going efforts to make EC measurements a viable technique for residual stress assessment. Specifically, we develop a macroscopic piezoresistivity theory for polycrystalline materials influenced by texture. The theory was applied to analyze the swept high frequency eddy current data obtained from a shot peened Inconel 718 sample, which was found to exhibit shot-induced texture in the near surface region using X-ray diffraction (XRD) and orientation imaging microscopy (OIM). The residual stress profile of the peened sample was inverted from EC data using a physics model-based approach, and was found to agree with the residual stress profiles measured independently using the standard layer removal XRD technique.

This paper reports on the Hall Effect and their stress dependence, observed experimentally on the superalloy Inconel® 718. The work is motivated by the desire to develop a nondestructive method of characterizing the near-surface protective residual stress in metals. Our approach is based on Hall Effect measurements, because it is anticipated that these measurements are less contaminated by cold work and other effects than conductivity-based measurements such as eddy current. The challenge is that, in metals, the Hall coefficient is very small. To achieve the required sensitivity, the Hall coefficient was measured with an AC injected current and an AC magnetic field. The measurements were performed on a thin film sample. The Hall coefficient was found to be positive, and varies proportionally to the applied tension. The proportionality coefficient is significantly larger than estimated from the volumetric effect in a free carrier model.

This paper describes a model-based investigation of inspection standards being developed as a recommended practice for eddy current (EC) NDT of aerospace structures for surface cracks. Compared to experimental investigations that can be laborious and expensive, model-based approach provides cost-effective and quantitative verifications of the recommended practice that covers wide ranges of materials, probes, instruments, frequencies, and test conditions. Probe signals for a number of specified standard notches are predicted and the expected amplitudes and phase-angle ranges are determined for various test conditions, in order to examine the influence of material electrical conductivity, frequency, and probe types. For a few selected situations, the model predictions are validated against experimental data. This study verifies the adequacies of the recommended specifications, especially of the reference notch selections and their response amplitudes for various test conditions, as well as confirming the suitability of using vertical amplitude alone for all the test situations. The influence of probe cable and the issue of three-point calibration are also discussed specifically in this investigation.

This paper considers the use of on-line structural health monitoring in advanced nuclear power systems such as IRIS. The motivation for the on-line health monitoring is to prevent routine maintenance from interrupting long-term continuous reactor operation. However, the outcome of the on-line monitoring implementation has a broader impact, and amounts to a paradigm shift in maintenance strategy from outage-based maintenance to continuous real-time monitoring of operational and structural integrity. Indeed, on-line health monitoring data will provide a foundation for diagnostics and prognostics (i.e., predictive) capabilities that will detect component degradation prior to failure, thus allowing for proactive rather than reactive maintenance strategies. Specifically, this paper briefly reports on our studies on (1) on-line monitoring strategy and its benefits, (2) candidate reactor components where on-line monitoring provides maximum benefits, (3) applicable on-line NDE sensor methodologies and conceptual sensor designs, and (4) model-based sensor performance estimations.

All current gravitational wave detectors use test masses coated with alternating layers of two different dielectric materials to form highly reflective mirrors. The thermal noise from mechanical dissipation associated with such coatings may be significant for future detectors such as advanced LIGO. We have measured the mechanical dissipation of a number of types of coatings formed from SiO2 (silica) and Ta2O5 (tantala). The frequency dependence of the dissipation has been determined, taking into account the contribution of thermoelastic loss.

Magnetic particle inspection (MPI) is a nondestructive evaluation technique used with ferromagnetic materials. Although the application of this method may appear straightforward, MPI combines the complicated nature of electromagnetics, metallurgical material effects, fluid-particle motion dynamics, and physiological human factors into a single inspection. To fully appreciate industry specifications such as ASTM E-1444, users should develop a basic understanding of the many factors that are involved in MPI. We have developed a series of MPI training modules that are aimed at addressing this requirement. The modules not only offer qualitative explanations, but also show quantitative explanations in terms of measurement and numerical simulation data in many instances. There are five modules in all. Module ♯1 shows characteristics of waveforms and magnetizing methods. This allows MPI practitioners to make optimum choice of waveform and magnetizing method. Module ♯2 explains how material properties relate to the magnetic characteristics. Module ♯3 shows the strength of the excitation field or the flux leakage from a crack and how it compares to the detectability of a crack by MPI. Module ♯4 shows how specimen status may influence defect detection. Module ♯5 shows the effects of particle properties on defect detection.

Interferometric gravitational wave detectors use mirrors whose substrates are formed from materials of low intrinsic mechanical dissipation. The two most likely choices for the test masses in future advanced detectors are fused silica or sapphire (Rowan S et al 2000 Phys. Lett. A 265 5). These test masses must be coated to form mirrors, highly reflecting at 1064 nm. We have measured the excess mechanical losses associated with adding dielectric coatings to substrates of fused silica and calculated the effect of the excess loss on the thermal noise in an advanced interferometer.

This paper presents a nonlinear theory of eddy current NDE response, applicable to EC measurements involving ferromagnetic materials. The theory treats the nonlinearity at the lowest nontrivial order. At this lowest order, the well-known Rayleigh relation exists, describing the non-linear hysteretic B-H relation, except that it is restricted to the case where the B and H fields are unidirectional and parallel to each other. Prototypical EC NDE problems require extension of Rayleigh's formula for vector-valued B and H fields. The paper examines a vector Preisach model, and points out that the vector extension of the Rayleigh relation is obtainable by the choice of a constant weight function. The given Preisach-Rayleigh model is amenable to explicit harmonic analysis, through which NLEC problems are soluble in Born approximation.

The boundary integral equations (BIE) method is a numerical computational method of solving linear partial differential equations which have been formulated as integral equations. It can be applied in many areas of engineering and science including fluid mechanics, acoustics, electromagnetics, and fracture mechanics. The eddy current problem is formulated by the BIE and discretized into matrix equations by the method of moments (MoM) or the boundary element method (BEM). The three dimensional arbitrarily shaped objects are described by a number of triangular patches. The Stratton-Chu formulation is specialized for the conductive medium. The equivalent electric and magnetic surface currents are expanded in terms of Rao-Wilton-Glisson (RWG) vector basis function while the normal component of magnetic field is expanded in terms of the pulse basis function. Also, a low frequency approximation is applied in the external medium. Additionally, we introduce Auld’s impedance formulas to calculate impedance variati...

A general formula and a computational scheme for estimating the power spectrum of the displacement correlation function of suspended test masses such as those used in interferometric gravitational wave detectors are presented. Unlike previous mode-summation approaches, the fluctuation-dissipation theorem has been applied directly to the displacement correlation. The resulting formula expresses the correlation in terms of material damping parameters and mechanical Green’s functions, and provides an efficient and flexible method to compute thermally induced surface displacements of arbitrarily shaped anisotropic elastic bodies. The formula can be used for optimizing the shape and size of test masses in gravitational wave receivers. A simple one-dimensional example is included to clarify the relationship with the modal expansion approach and to illustrate the advantage of the Green’s function method. This paper presents the theoretical formulation; numerical evaluations of the formula will be presented elsew...

This paper reports on a feasibility study of using eddy current (EC) and magnetic flux leakage (MFL) methods to detect corrosion damage in rebars that anchor concrete barrier rails to the road deck of bridge structures. EC and MFL measurements were carried out on standalone rebars with and without artificial defects of 25% and 50% material loss, using a commercial EC-based rebar locator and a MFL system that was developed using giant magnetoresistance sensors to detect leakage fluxes from the defects. Both techniques can readily detect the defects at a distance of 2.5″ (63.5 mm). The amplitudes of the EC and MFL signals vary monotonically with the amount of material loss, indicating the potential of using the techniques to quantify material loss of standalone rebars.

This paper reports on a study of the effects of cold work induced by surface enhancement treatment on conductivity profiles in nickel-base superalloys, as part of the on-going efforts aimed at evaluating the feasibility of characterizing near-surface residual stress profiles in peened engine components using a swept frequency eddy current (SFEC) technique. The approach is based on the empirical piezoresistivity effect that correlates conductivity changes with residual stress, but recent studies have shown that conductivity changes induced by peening processes are also influenced by metallurgical factors such as cold work. In this study, conductivity deviation profiles were obtained by model-based inversion of SFEC signals from a set of aged Inconel 718 samples, which were either shot peened or laser shock peened to produce different residual stress and cold work profiles. The laser shock peened samples exhibit a larger increase in surface conductivity and deeper conductivity profiles, which are attributed to a smaller amount of surface cold work and deeper residual stress profiles created by laser shock peening than by shot peening.

Applications of the boundary integral equation method to real world problems often require that field values should be obtained near boundary surfaces. A numerical difficulty is known to arise in this situation if one attempts to evaluate near-boundary fields via the conventional Green's formula. The present work addresses this particular issue. Namely, a stable computational scheme for both fields and gradients in the near-boundary region has been formulated. This approach starts with the conventional Green and Maue representations of fields and gradients written inside and outside of the defining volume. Then, a new set of integral representations that have weaker kernel singularities is derived by canceling the most singular terms between the conventional formulas of the two sides. The principal contribution of this work is the explicit construction of the improved representations for the fields and gradients. Also presented are several numerical results that demonstrate the superiority of the new representations over the conventional ones.

This paper reports on a microstructural study of a nickel-base superalloy, Inconel 718, with a focus on quantifying precipitate density and their effects on conductivity variations. The study is motivated by eddy current (EC) characterization of residual stresses, where observed EC signals are attempted to correlate with stress profiles of shot peened superalloy surfaces. It has been observed that the correlation is less universal than anticipated, and in fact strongly influenced by the material hardness, or the aging conditions. For example, the soft sample surface exhibits significantly stronger EC signals than the fully hardened sample when both are shot peened at the same Almen intensity. Thus, the objective of the present study is to examine this complex material response against aging and shot peening treatments at the microstructure scale, by the use of techniques such as transmission electron microscopy (TEM) and scanning electron microscopy (SEM). We will describe preparations of a series of Inconel 718 samples that was aged and shot peened at various conditions, and present microstructural data obtained from SEM and TEM images such as precipitate densities, correlated with bulk properties such as the hardness and conductivity.

A novel boundary integral equation (BIE) is developed for eddy‐current nondestructive evaluation problems with surface crack under a uniform applied magnetic field. Once the field and its normal derivative are obtained for the structure in the absence of cracks, normal derivative of scattered field on the conductor surface can be calculated by solving this equation with the aid of method of moments (MoM). This equation is more efficient than conventional BIEs because of a smaller computational domain needed.

We present a new method for characterizing the performance of eddy current probes by mapping their electromagnetic fields. The technique is based on the photoinductive effect, the change in the impedance of an eddy current probe induced by laser heating of the material under the probe. The instrument we developed maps a probe's electric field distribution by scanning an infrared laser beam over a thin film of gold lying underneath the probe. Measurements of both photoinductive signals and flaw signals for a series of similar probes demonstrate that the impedance change caused by an electrical-discharge-machined (EDM) notch or a fatigue crack is proportional to the strength of the photoinductive signal. Thus, photoinductive measurements can supplant the use of artifact standards to calibrate eddy current probes. Furthermore, the shape and symmetry of the probe's field pattern can reveal defects in probe construction. By combining photoinductive measurements of a probe's field strength with a theor...

Eddy current nondestructive evaluation (NDE) of airframe structures involves the detection of electromagnetic field irregularities due to non‐conducting inhomogeneities in an electrically conducting material, which often treats with complicated geometrical features such as cracks, fasteners, sharp corners/edges, multi‐layered structures, etc. The eddy‐current problem can be formulated by the boundary integral equations (BIE) and discretized into matrix equations by the method of moments (MoM) or the boundary element method (BEM). This paper introduces the implementation of Stratton‐Chu formulation for the conductive medium, in which the induced electric and magnetic surface currents are expanded in terms of Rao‐Wilton‐Glisson (RWG) vector basis function and the normal component of magnetic field is expanded in terms of pulse basis function. Also, a low frequency approximation is applied in the external medium, that is, free space in our case. Computational tests are presented to demonstrate the accuracy a...

This paper discusses the acquisition and processing of experimental data collected using a low frequency eddy current sliding probe to inspect aluminum, simulated airframe structure for inner layer cracks. This effort is part of a model‐assisted probability of detection (MAPOD) study aimed at complex structure. Since the experimental data will be compared to idealized model‐generated data, an automated scanning setup in the laboratory was used to produce results with minimal human factor variables and low measurement uncertainty. While good reproducibility of the data was achieved, the inherent nature of the multilayer, riveted structure resulted in significant scatter in the data. This scatter required special statically processing techniques to produce a meaningful POD curve, which will be discussed in an accompanying paper.

Nondestructive evaluation (NDE) of airframe structures may involve finding eddy‐current distributions in complicated geometrical features including cracks, fasteners, sharp corners/edges, multi‐layered structures, complex ferrite‐cored probes, etc. The eddy‐current problem can be formulated in terms of boundary integral equations (BIE), which can be discretized into matrix equations by the method of moments (MoM) or the boundary element method (BEM). The Fast Multipole Method (FMM) is a well‐established and effective method for accelerating numerical solutions of the matrix equations. Accelerated by the FMM, the BIE method can now solve large‐scale electromagnetic wave propagation and diffusion problems. The traditional BIE method requires O(N2) operations to compute the system of equations and another O(N3) operations to solve the system using direct solvers, with N being the number of unknowns; in contrast, the BIE method accelerated by the two‐level FMM can potentially reduce the operations and memory ...

Complex aluminum forgings can have engineering properties which vary with position due to changes in the underlying local metal microstructure. Consequently, the material properties may be in compliance with production requirements in some regions of the forging, but out of compliance in others. One conical Al‐7050 forging of interest was found to have elongation properties which failed required tests in certain regions. NDE measurements sensitive to microstructural changes were carried out to search for correlations with elongation properties. The results of a set of initial feasibility experiments will be reported. Both ultrasonic and eddy current NDE methods were used, with the goal being to determine which properties were sensitive to the elongation. Ultrasonic testing included the measurement of longitudinal and shear‐wave velocity, longitudinal wave attenuation, and longitudinal and shear‐wave backscattered grain noise. All tests were performed with the sonic beam entering through the coupon face that would be adjacent to the outer surface of the forging. Only modest differences in wave speed and attenuation values were seen among the suite of coupons, but significant differences were seen in backscattered noise levels. These appeared to indicate changes in grain structure but only exhibited partial correlation with elongation. The eddy current measurements were designed to be sensitive to the electrical resistivity. Included were a number of measurement configurations and frequencies. The signals exhibited a significant correlation with elongation.

The Fast Multipole Method (FMM) is a well‐established and effective method for accelerating numerical solutions of the boundary integral equations (BIE). The BIE method, accelerated by the FMM, can solve large‐scale electromagnetic wave propagation and diffusion problems with up to a million unknowns on a personal computer. The conventional BIE method requires O(N2) operations to compute the system of equations and another O(N2) operations to solve the system using iterative solvers, with N being the number of unknowns; in contrast, the BIE method accelerated by the two‐level FMM can potentially reduce the operations and memory requirement to O(N3/2). This paper introduces the procedure of the FMM accelerated BIE method, which is not only efficient in meshing complicated geometries, accurate for solving singular fields or fields in infinite domains, but also practical and often superior to other methods in solving large‐scale problems. The two‐dimensional Helmholtz equation with a complex wave number for ...

This paper presents an element‐free boundary integral equation method for modeling eddy‐current nondestructive evaluation problems. Using the moving least squares algorithm, the proposed method effectively discretizes boundary integral equations for electromagnetic fields entirely in terms of distributed nodes without imposing the element structure that additionally requires node connectivity. The method retains the dimensionality advantage of the conventional boundary element method while adding the element‐free attribute of the moving least squares algorithm. By solving three‐dimensional eddy current problems for various prototypical geometries, we explicitly demonstrate that the method has the potential to achieve higher accuracy than the conventional boundary element method for similar numbers of nodes while alleviating meshing tasks and retaining the dimensionality advantage of the boundary element method. It is anticipated that similar computational advantages, flexibilities and accuracies will mani...

The purpose of this study is to develop a simple and flexible sensor to measure the torque and its change with respect to time, acting at human knee during standing-up from and sitting-down on the chair. The outer diameter of the leg increases when people bend their leg due to muscle power. Therefore, the muscle power, torque applied at the knee can be estimated if the diameter is measured. A thin rubber sheet, on which strain gauges were mounted, was equipped in a conventional wearable supporter for human legs. The sensor equipped supporter is flexible and expanded if the muscle becomes thick. The expansion of the rubber sheet is expected to reflect the nearest muscle stretch. However, every portion of the leg/muscles does not show enough change in its diameter/stretch. The location where the sensor equipped supporter was banded onto the leg was altered place to place from the top of the leg to the end in order to find the most appropriate location for estimating the precise torque applied at the knee. We introduced a new index called MAI (muscle activity index) defined by: MAI=1/(t2-t1)intt1 t2|f(t)|dt.Here, f(f) is the strain history of the rubber sheet while t is time. t1 and t2 are the times when the subject starts and finishes the motion, respectively. The relationship between sensor location and MAI effect was revealed. The standing-up and sitting-down tests were conducted under the condition of over-bending, which was considered to simulate the motion of the elderly with pain. The isometric joint torque in the sagittal plane was calculated by multiplying the isometric force defined as the initial force keeping the subject's posture and the length of moment arm at the knee. The tests result showed that the clear responses in diameter change of the muscle and distinctive MAI were found at several locations of the leg. When the subject moved with over-bending, the MAI calculated from the strain of the rubber sheet on the m. rectus femoris was significantly different from those at other locations. The correspondence was also shown between the knee joint torque and the observed strain, when the sensor was put on the m. rectus femoris. This paper concluded that the flexible strain sensor currently developed was applicable to evaluate the standing-up and sitting- down motions as well as to estimate the torque at the knee.