Soft Boundary Research Articles

SoftClusterMix: learning soft boundaries for empirical risk minimization

SoftClusterMix: learning soft boundaries for empirical risk minimization

Weakly supervised semantic segmentation for MRI: exploring the advantages and disadvantages of class activation maps for biological image segmentation with soft boundaries

Fully supervised semantic segmentation models require pixel-level annotations that are costly to obtain. As a remedy, weakly supervised semantic segmentation has been proposed, where image-level labels and class activation maps (CAM) can detect discriminative regions for specific class objects. In this paper, we evaluated several CAM methods applied to different convolutional neural networks (CNN) to highlight tissue damage of cod fillets with soft boundaries in MRI. Our results show that different CAM methods produce very different CAM regions, even when applying them to the same CNN model. CAM methods that claim to highlight more of the class object do not necessarily highlight more damaged regions or originate from the same high discriminatory regions, nor do these damaged regions show high agreement across the different CAM methods. Additionally, CAM methods produce damaged regions that do not align with external reference metrics, and even show correlations contrary to what can be expected.

The evolution of cavitation in narrow soft-solid wedge geometry mimicking periodontal and peri-implant pockets

In periodontology and implantology, laser-induced cavitation has not yet been used to treat biofilm-related problems. In this study we have checked how soft tissue affects the evolution of cavitation in a wedge model representing periodontal and peri-implant pocket geometry. One side of the wedge model was composed of PDMS mimicking soft periodontal or peri-implant biological tissue, the other side was composed of glass mimicking hard tooth root or implant surface, which allowed observations of the cavitation dynamics with an ultrafast camera. Different laser pulse modalities, PDMS stiffness, and irrigants were tested for their effect on the evolution of cavitation in the narrow wedge geometry. The PDMS stiffness varied in a range that corresponds to severely inflamed, moderately inflamed, or healthy gingival tissue as determined by a panel of dentists. The results imply that deformation of the soft boundary has a major effect on the Er:YAG laser-induced cavitation. The softer the boundary, the less effective the cavitation. We show that in a stiffer gingival tissues model, photoacoustic energy can be guided and focused at the tip of the wedge model, where it enables generation of secondary cavitation and more effective microstreaming. The secondary cavitation was absent in severely inflamed gingival model tissue, but could be induced with a dual-pulse AutoSWEEPS laser modality. This should in principle increase cleaning efficiency in the narrow geometries such as those found in the periodontal and peri-implant pockets and may lead to more predictable treatment outcomes.

Converging-diverging shock-driven instabilities along soft hydrogel surfaces.

Intense surface eruptions are observed along the curved surface of a confined cylindrical film of hydrogel subject to laser-induced converging-diverging shock loading. Detailed numerical simulations are used to identify the dominant mechanisms causing mechanical instability. The mechanisms that produce surface instability are found to be fundamentally different from both acoustic parametric instability and shock-driven Richtmyer-Meshkov instability. The time scale of observed and simulated eruption formation is much larger than that of a single shock reflection, in stark contrast to previously studied shock-driven instabilities. Moreover, surface undulations are only found along external, as opposed to internal, soft solid boundaries. Specifically, classic bubble surface instability mechanisms do not occur in our experiments and here we comment only on the new surface undulations found along the outer boundary of solid hydrogel cylinders. Our findings indicate a new class of impulsively excited surface instability that is driven by cycles of internal shock reflections.

Concept evolution detection based on noise reduction soft boundary

Concept evolution detection is an important but difficult task in streaming data analysis, and further the noise may seriously limit the detection performance gains. This paper proposed a concept evolution detection method based on noise reduction soft boundary (NRSB). To reduce the negative effect of noise samples near category boundary, the noise reduction soft boundaries are defined based on the introducing of extension distance, intension distance and corresponding noise reduction process. Then the sample space is divided into in-class, mixed-class and out-of-class areas corresponding to each category. For online new coming samples, three strategies of automatic labeling by model, active labeling by expert and multi-class collaborative labeling will be adopted respectively according to different areas they located in. Automatic model labeling does not need to update the model, which may improve the learning efficiency. Expert active labeling will help with difficult samples in mixed-class area. Multi-class collaborative labeling can change the sample label dynamically during online learning. The experimental results show that the proposed method can reflect the character of dynamic evolution of streaming data well and detect the concept evolution effectively.

A Class of Fractional Stochastic Differential Equations with a Soft Wall

In this paper we are interested in fractional stochactic differential equations (SDEs) with a soft wall. What do we mean by such a type of equation? It has been established that SDE with reflection can be imagined as equations having a hard wall. Now, by introducing repulsion instead of reflection, one obtains an SDE with a soft wall. In contrast to the SDE with reflection, where the process cannot pass the hard wall, the soft wall is repulsive but not impenetrable. As the process crosses the soft wall boundary, it experiences the force of a chosen magnitude in the opposite direction. When the process is far from the wall, the force acts weakly. We find conditions under which SDE with a soft wall has a unique solution and construct an implicit Euler approximation with a rate of convergence for this equation. Using the example of the fractional Vasicek process with soft walls, we illustrate the dependence of the behaviour of the solution on the repulsion force.

Resource Estimation in Multi-Unit Mineral Deposits Using a Multivariate Matérn Correlation Model: An Application in an Iron Ore Deposit of Nkout, Cameroon

Modeling the spatial dependence structure of metal grades in the presence of soft boundaries between geological domains is challenging in any mineral resource estimation strategy. The aim of this work was to propose a structural model adapted to this type of geological boundary, based on a multivariate Matérn model that fits the observed direct (within domain) and cross (between domains) correlation structures of metal grades. The methodology was applied to a case study of an iron deposit located in southern Cameroon. Cross-validation scores show that accounting for the grade correlation across domain boundaries improved the traditional workflow, where the grade was estimated in each domain separately. The scores were significantly better when we also ensured that the mean grade was locally invariant from one domain to another to reflect the grade continuity across the domain boundary.

Mission, governance, and accountability of benefit corporations: Toward a commitment device for achieving commercial and social goals

AbstractBenefit corporations (BCs) are profit‐with‐purpose organizations regulated by a legal framework for establishing explicit commitments in terms of multi‐stakeholder governance and accountability structures. We comprehensively analyze the theoretical alignment of four concepts (ownership, mission, governance, and accountability) to explain the legal rationale for BCs' unique corporate form. However, the boundaries of BC legislation are blurry, leaving them open to top‐down governance arrangements and weak accountability. To explore this ambiguity, this paper investigates whether BCs implement a de facto (i.e., beyond the letter of the law) multi‐stakeholder structure with governance models and downward accountability mechanisms that balance different stakeholders' interests, instead of focusing only on shareholder profits. This further highlight the soft boundaries imposed by the BC regulatory framework and suggests that more work is needed to explore the relationship between governance models that differently balance stakeholders' claims and the firm's social performance.

Крайова задача з м’якими межами для рівнянь параболічного типу з операторами Бесселя — Ейлера — Лежандра на сегменті кусково-однорідної полярної осі

Composite materials are widely used in a variety of technological process-es, building, energy saving, in connection with which there is a need to pose and solve problems of thermal conductivity in environments that are heteroge-neous in their structure (multilayer bodies). At the same time, the heterogeneity of the medium leads to the consideration of boundary value problems with piecewise continuous or piecewise constant coefficients [3] and differential op-erators of the Bessel, Euler, Legendre, and Fouriertype, which model the het-erogeneity of the medium in terms of a geometric variable.In the classical setting, the processes of heat propagation were studied under the assumption that the boundary of the medium is rigid in relation to the reflection of waves. However, if we assume that wave absorption can occur at the boundary of the medium (soft boundary), we obtain a boundary value problem containing a time derivative in the operators of boundary conditions and conjugation conditions of the form (1).The analytical solution of the corresponding boundary value problem can be obtained using integral transformations with a spectral parameter, which work for problems with soft boundaries according to the same logi-cal scheme as integral transformations without a spectral parameter in problems with hard boundaries.This paper is devoted to the construction of one class of such hybrid in-tegral transformations generated by a hybrid differential operator of the Bessel-Euler-Legendre type on the polar axis.In this article an integral image of the exact analytical solution of a mixed problem for parabolic equations on a three-complex segment of the polar axis with soft boundaries is obtained by the method of a hybrid inte-gral transformation of the Bessel-Euler-Legendre type under the assump-tion that the boundary conditions and conjugation conditions contain a de-rivative with respect to the time variable

Three-dimensional effects of cascade perforations on rotor–stator interaction noise

One novel trend in reducing aero-engine noise is to utilize the silent flight mechanism of owls by applying perforations on fan stator vanes. Consequently, the establishment of relevant theoretical models is of particular interest. The current efforts made in this regard are just targeting the features based on two-dimensional models without including the three-dimensionality. In this paper, we present a three-dimensional solution for acoustic scattering by annular perforated cascades, and the dipole source corresponding to the unsteady pressure loading on the vanes is identified as the dominant sound source. By the singularity method, the acoustic response is obtained with the soft boundary condition applied on the vane surfaces. It is found that considerable noise reduction can be achieved for rotor–stator interaction with a modest uniform porosity, and accordingly two mechanisms are proposed to understand the effect of porosity on propagating sound. The first is that the perforations allowing a normal velocity across the vane reduce the unsteady loading induced by the incident disturbances. The second is that the three-dimensional interactions among the dipole sources at different positions are also dampened by the soft boundaries, thus the distribution of the unsteady pressure loading on the vanes will also change significantly compared to hard-vane cases. Non-uniform distributions of porosity are investigated further, indicating that perforations in the vane upstream area are more effective in reducing propagating noise. Our method is fully three-dimensional and capable of investigating non-uniform porosity, and thus is able to provide useful guidance for future soft vane designs.

Acoustic energy flux analysis of the bifurcated waveguide by varying outlet boundaries

This communication is devoted to the analysis of the energy flux of a two-dimensional waveguide with planar and non-planar surfaces. The main goal is to analyze the effects of reflected and transmitted energy fluxes of the bifurcated waveguide by varying the different types of outlet boundaries. The upper and lower boundaries of the inlet are taken as flexural in nature, whilst the outlet of the duct is varied by soft, rigid and impedance boundary conditions. The benchmark Mode-Matching (MM) technique is applied to solve the underlying boundary value problem (BVP). The system is excited with two types of incident forcing: fluid-borne incident and structure-borne incident. For a flexible inlet bounded by a membrane, the obtained eigenfunctions are linearly dependent and non-orthogonal in character. For sake of this, generalized orthogonality relations (OR) are developed. Additionally, the application of generalized OR led to the appearance of some dependent sums that are tackled using the fixed membrane edge conditions. The application of edge conditions led to the unique solution of the BVP. In the end, the expressions of reflected and transmitted energy fluxes are obtained and analyzed graphically against frequencies for different structural properties of the waveguide. Furthermore, it is shown that the conserved energy flux is valid, and reconstructed matching conditions are found in good accord.

Amplitude reflections and interaction solutions of linear and nonlinear acoustic waves with hard and soft boundaries

In this study, the propagation of a fundamental plane mode in a bifurcated waveguide structure with soft–hard boundaries is analyzed by using the Helmholtz equation. The explicit solution is given to this bifurcated spaced waveguide problem by means of matching the potential across the boundary of continuity. Amplitudes of the reflected field in all those regions have been evaluated, and the energy balance has been derived. We have observed the reflection of the acoustic wave against the wavenumber and shown its variation with the duct width. Convergence of the problem has been shown graphically. In our analysis, we notice that the reflected amplitude decreases as the duct spacing increases; as a result, the acoustic energy will increase as the duct spacing increases. It is expected that our analysis could be helpful to give better understanding of wave reflection in an exhaust duct system. We then reduce the linear acoustic wave equation to the Kadomtsev–Petviashvili (KP) equation. Multiple-periodic wave interaction solutions of the KP nonlinear wave equation are investigated, and the energy transfer mechanism between the primary and higher harmonics is explained, which, to the best of our knowledge, is overlooked.

Evaluation of assumptions in foot and ankle biomechanical models

BackgroundA variety of biomechanical models have been used in studies of foot and ankle disorders. Assumptions about the element types, material properties, and loading and boundary conditions are inherent in every model. It was hypothesized that the choice of these modeling assumptions could have a significant impact on the findings of the model. MethodsWe investigated the assumptions made in a number of biomechanical models of the foot and ankle and evaluated their effects on the results of the studies. Specifically, we focused on: (1) element choice for simulation of ligaments and tendons, (2) material properties of ligaments, cortical and trabecular bones, and encapsulating soft tissue, (3) loading and boundary conditions of the tibia, fibula, tendons, and ground support. FindingsOur principal findings are: (1) the use of isotropic solid elements to model ligaments and tendons is not appropriate because it allows them to transmit unrealistic bending and twisting moments and compressive forces; (2) ignoring the difference in elastic modulus between cortical and trabecular bones creates non-physiological stress distribution in the bones; (3) over-constraining tibial motion prevents anticipated deformity within the foot when simulating foot deformities, such as progressive collapsing foot deformity; (4) neglecting the Achilles tendon force affects almost all kinetic and kinematic parameters through the foot; (5) the axial force applied to the tibia and fibula is not equal to the ground reaction force due to the presence of tendon forces. InterpretationThe predicted outcomes of a foot model are highly sensitive to the model assumptions.

The application of multiple metrics in deformable image registration for target volume delineation of breast tumor bed.

For postoperative breast cancer patients, deformable image registration (DIR) is challenged due to the large deformations and non-correspondence caused by tumor resection and clip insertion. To deal with it, three metrics (fiducial-, region-, and intensity-based) were jointly used in DIR algorithm for improved accuracy. Three types of metrics were combined to form a single-objective function in DIR algorithm. Fiducial-based metric was used to minimize the distance between the corresponding point sets of two images. Region-based metric was used to improve the overlap between the corresponding areas of two images. Intensity-based metric was used to maximize the correlation between the corresponding voxel intensities of two images. The two CT images, one before surgery and the other after surgery, were acquired from the same patient in the same radiotherapy treatment position. Twenty patients who underwent breast-conserving surgery and postoperative radiotherapy were enrolled in this study. For target registration error, the difference between the proposed and the conventional registration methods was statistically significant for soft tissue (2.06 vs. 7.82, p=0.00024<0.05) and body boundary (3.70 vs. 6.93, p=0.021<0.05). For visual assessment, the proposed method achieved better matching result for soft tissue and body boundary. Comparing to the conventional method, the registration accuracy of the proposed method was significantly improved. This method provided a feasible way for target volume delineation of tumor bed in postoperative radiotherapy of breast cancer patients.

Binary black hole merger rates in AGN discs versus nuclear star clusters: loud beats quiet

ABSTRACT Galactic nuclei are promising sites for stellar origin black hole (BH) mergers, as part of merger hierarchies in deep potential wells. We show that binary black hole (BBH) merger rates in active galactic nuclei (AGNs) should always exceed merger rates in quiescent galactic nuclei (nuclear star clusters, NSCs) around supermassive black holes (SMBHs) without accretion discs. This is primarily due to average binary lifetimes in AGNs that are significantly shorter than those in NSCs. The lifetime difference comes from rapid hardening of BBHs in AGNs, such that their semimajor axes are smaller than the hard–soft boundary of their parent NSC; this contrasts with the large average lifetime to merger for BBHs in NSCs around SMBHs, due to binary ionization mechanisms. Secondarily, merger rates in AGNs are enhanced by gas-driven binary formation mechanisms. Formation of new BHs in AGN discs is a minor contributor to the rate differences. With the gravitational wave detection of several BBHs with at least one progenitor in the upper mass gap, and signatures of dynamical formation channels in the χeff distribution, we argue that AGNs could contribute $\sim 25{\!-\!}80{{\ \rm per\ cent}}$ of the LIGO–Virgo measured rate of $\sim 24\, \rm {Gpc}^{-3} \rm {yr}^{-1}$.

Geological control for in-situ and recoverable resources assessment: A case study on Sarcheshmeh porphyry copper deposit, Iran

The incorporation of geological controls is essential for an accurate assessment of the in-situ and recoverable resources in an ore deposit, directly impacting the downstream stages of mining projects. Commonly, the mineral resources evaluation is carried out hierarchically, considering the definition of geological domains first and then predicting or simulating the metal grades within each domain. Nevertheless, this approach assumes a weak correlation between the metal grades across the domain boundaries, which could not be suitable when gradual variations of the grades are observed across these boundaries. To account for the latter scenario known as soft boundaries, we compare three approaches: (i) a hierarchical prediction of the geological domain indicators and the grade within each domain, (ii) a direct prediction of partial grades, defined as the product of the grade and a geological domain indicator, and (iii) a joint simulation of the grade and geological domain indicators. A porphyry copper deposit in which the copper grade is controlled by mineralogical and rock type domains is used as a case study. When compared with production data, the proposed approaches generate more precise predictions than the traditional approach consisting in accounting for the hard boundaries between mineralogical domains but ignoring the soft boundaries between rock types. The joint simulation approach provides more realistic grade variations across the rock type boundaries, allows for an unbiased prediction of the recoverable resources, and quantifies the uncertainty on these resources based on multiple grade outcomes. Ultimately, we emphasize that identifying the geological controls and the nature (hard or soft) of the geological boundaries, and then defining the proper approaches to account for them is necessary to accurately assess the in-situ and recoverable resources.

Low-frequency waterborne sound insulation by an acoustic metascreen with a metal chiral structure

Low sound speed or low-density materials can be used as soft acoustic boundaries in water, potentially as low-frequency underwater sound insulation. This study uses a chiral structure to construct an acoustic metascreen with deep subwavelength thickness. The results show that the transmission coefficient of the metascreen decreases noticeably in the low-frequency range when adjusting the chiral structure. The displacement pattern and the effective acoustic impedance are used to investigate the sound insulation mechanism. Low sound speed and effective acoustic impedance are found in the anisotropic chiral structure, and an extensive range of quasi-longitudinal wave phase velocities from 116.70 m/s to 3935.48 m/s can be obtained by adjusting the structural parameters without changing the filling rate. Finally, the effect of the oblique incidence angle on the sound insulation of the metascreen is investigated.

Comparing the functional range of English to be to German sein: a test of the boundary permeability hypothesis

Abstract The boundary permeability hypothesis views language as a system of categories which are more or less rigidly separated from one another. In previous work on grammatical categories, English was characterized as a soft boundary and German as a strict boundary language. This project presents a test of the prediction that English to be has a wider functional range than its German counterpart sein. The range of these verbs is determined on the basis of a bidirectional translation study. English to be is translated by a larger variety of lexical verbs in German while sein is translated by a smaller number of lexical verbs in English. In fact, the translation equivalents of sein form a subset of those of to be. Moreover, to be plays a much larger role in constructions such as there is and it is than sein does. The boundary permeability hypothesis views this structural difference and the wider semantic range of to be as two sides of the same coin. It is suggested that English is a more speaker-friendly language than German.

Bullet jet as a tool for soft matter piercing and needle-free liquid injection.

The collapse of a laser-induced vapor bubble near a solid boundary usually ends in a liquid jet. When the boundary is from a soft material the jetting may pierce the liquid-solid interface and result in the injection of liquid into it. A particular impulsive jet flow can be generated when a laser pulse is focused just below the free surface of a thin liquid layer covering a gelatin sample used as a surrogate of biological tissue. Here, a downwards jet forms from a liquid splash at the free surface and then penetrates through the liquid layer into the soft boundary. In the present manuscript we report on the use of this novel jet, termed "bullet" jet, to pierce soft materials and we explore its potential to become an optical needle-free injection platform. The dynamics and depth of the injection is studied as a function of the elasticity of the solid and the liquid properties. Injections of up to 4 mm deep into 4 %w/w gelatin within 0.5 ms are observed. The advantages of the bullet jet over other kinds of impulsively generated jets with lasers are discussed.

A High-Gain Multilevel dc–dc Converter for Interfacing Electric Vehicle Battery and Inverter

An isolated multilevel bidirectional dc–dc converter is presented in this article to interface the low-voltage (LV) battery and the high-voltage (HV) propulsion inverter in electric vehicles. The proposed topology achieves a HV step-up ratio in the motoring mode by reconfiguring two split capacitor half-bridge circuits in series/parallel through the symmetrical modulation of a voltage bidirectional, two quadrant switch. This reconfiguration generates a high-frequency multilevel voltage output at the dc-bus side of the inverter, which reduces the output filter volume. The dc-bus voltage is regulated by the duty cycle modulation of the intermediary switch in the motoring mode, simplifying the sensing and control. During regenerative braking, the converter is operated with phase shift modulation between the HV half bridges and the LV full bridge to regulate the battery voltage. The presented modulation strategies achieve zero voltage switching for the full-bridge devices over a wide load range. A comprehensive analysis of the proposed multilevel converter in motoring and braking modes along with the design constraints and soft switching boundary conditions is presented in this article. Detailed experimental results on a 1.5-kW laboratory prototype are presented to verify the design approach and illustrate the converter performance.