Search Results (15)

Using COMSOL finite element software, a three-dimensional numerical transient model of an underground tunnel collapse vertical freezing repair project was established. The model was altered to change the head difference, allowing for analysis of the development of the permafrost curtain, the time of intersection circles, and the freezing temperature field cloud diagram. The results indicated that, without seepage, development of the upstream and downstream permafrost curtains was stable and uniform. However, under seepage conditions, development of the upstream and downstream permafrost curtains became increasingly uneven with increasing seepage velocity. The downstream side of the soil body began freezing earlier than the upstream side, and the final temperature was lower. The intersection time of the freezing wall was an important indicator of development of the permafrost curtain, and the freezing time of the freezing wall was the most critical indicator. A hydraulic head difference of 1 m was found to significantly impact the development of the freezing wall, with less influence from seepage velocity on the overall permafrost curtain intersection time. However, the intersection time of the isotherm increased significantly with increasing seepage flow rate. The findings from this project provide a theoretical reference for future restoration design. Full article

We re-examine the internal structure of bimerons, which are stabilized in easy-plane chiral magnets and represent coupled states of two merons with the same topological charge $|1/2|$ but with opposite vorticity and the polarity. We find that, in addition to the vortices and antivortices, bimerons feature circular regions which are located behind the anti-vortices and bear the rotational sense opposite to the rotational sense chosen by the Dzyaloshinskii–Moriya interaction. In an attempt to eliminate these wrong-twist regions with an excess of positive energy density, bimerons assemble into chains, and as such exhibit an attracting interaction potential. As an alternative to chains, we demonstrate the existence of ring-shaped bimeron clusters of several varieties. In some rings, bimeron dipoles are oriented along the circle and swirl clockwise and/or counterclockwise (dubbed “roundabouts”). Moreover, a central meron encircled by the outer bimerons may possess either positive or negative polarity. In other rings, the bimeron dipoles point towards the center of a ring and consequently couple to the central meron (dubbed “crossings”). We point out that the ringlike solutions for baryons obtained within the Skyrme model of pions, although driven by the same tendency of the energy reduction, yield only one type of bimeron rings. The conditions of stability applied to the described bimeron rings are additionally extended to bimeron networks when bimerons fill the whole space of two-dimensional samples and exhibit combinations of rings and chains dispersed with different spatial density (dubbed bimeron “polymers”). In particular, bimeron crystals with hexagonal and the square bimeron orderings are possible when the sides of the unit cells represent chains of bimerons joined in intersections with three or four bimerons, respectively; otherwise, bimeron networks represent disordered bimeron structures. Moreover, we scrutinize the inter-transformations between hexagonal Skyrmion lattices and disordered bimeron polymers occuring via nucleation and mutual annihilation of merons within the cell boundaries. Our theory provides clear directions for experimental studies of bimeron orderings in different condensed-matter systems with quasi-two-dimensional geometries. Full article

Ship detection is an important topic in the task of understanding remote sensing images. One of the challenges for ship detection is the large length–width ratio of ships, which may weaken the feature extraction ability. Simultaneously, ships inclining in any direction is also a challenge for ship detection in remote sensing images. In this paper, a novel Oriented Ship detection method is proposed based on an intersecting Circle and Deformable region of interest (OSCD-Net), which aims at describing the characteristics of a large length–width ratio and arbitrary direction. OSCD-Net is composed of two modules: an intersecting circle rotated detection head (ICR-head) and a deformable region of interest (DRoI). The ICR-head detects a horizontal bounding box and an intersecting circle to obtain an oriented bounding box. DRoI performs three RoIAlign with different pooled sizes for each feature candidate region. In addition, the DRoI module uses transformation and deformation operations to pay attention to ship feature information and align feature shapes. OSCD-Net shows promising performance on public remote sensing image datasets. Full article

A three-dimensional numerical investigation of turbulent heat transfer and fluid flow characteristics of the new heat exchanger and self-support of a rectangular converging-diverging (SS-RCD) tube bundle heat exchanger with different inserts was performed. The values of the Reynolds number varied from 27,900 to 41,900. The baseline case (without an insert) was compared with two enhanced configurations: one circular hole in the baffle plate (one-circle case) and a rectangular hole in the baffle plate (one-rectangle case). Compared with the baseline case, the airside Nusselt number (Nu) of the enhanced cases improved by 39.6~48.0% and 36.2~40.2% and had an associated friction factor (f) penalty increase of 53.9–66.7% and 60.7–77.8%, respectively. The baseline case was compared with three enhanced configurations: one-circle case, two-circle case, and three-circle case baffle plate. Compared with the baseline case, Nu of the enhanced cases improved by 39.6–48.0%, 36.2–45.4%, and 35.0–44.2%, with f penalty increases of 53.9–66.7%, 44.9–60.0%, and 43.8–60.0%, respectively. The overall performance was conducted by heat transfer enhancement factor (η). It was found that the one circle case obtained the best overall performance. The numerical results were analyzed from the viewpoint of the field synergy principle. It was found that the reduction in the average intersection angle between the velocity vector and the temperature gradient (θ) was one of the essential factors influencing heat transfer performance. Full article

A human listening to monophonic sound through headphones perceives the sound to emanate from a point inside the head at the auditory centre at effectively zero range. The extent to which this is predicted by synthetic-aperture calculation performed in response to head rotation is explored. The instantaneous angle between the auditory axis and the acoustic source, lambda, for the zero inter-aural time delay imposed by headphones is 90°. The lambda hyperbolic cone simplifies to the auditory median plane, which intersects a spherical surface centred on the auditory centre, along a prime meridian lambda circle. In a two-dimensional (2-D) synthetic-aperture computation, points of intersection of all lambda circles as the head rotates constitute solutions to the directions to acoustic sources. Geometrically, lambda circles cannot intersect at a point representing the auditory centre; nevertheless, 2-D synthetic aperture images for a pure turn of the head and for a pure lateral tilt yield solutions as pairs of points on opposite sides of the head. These can reasonably be interpreted to be perceived at the sums of the position vectors of the pairs of points on the acoustic image, i.e., at the auditory centre. But, a turn of the head on which a fixed lateral tilt of the auditory axis is concomitant (as in species of owl) yields a 2-D synthetic-aperture image without solution. However, extending a 2-D synthetic aperture calculation to a three-dimensional (3-D) calculation will generate a 3-D acoustic image of the field of audition that robustly yields the expected solution. Full article

Objectives: Deep learning methods have achieved impressive diagnostic performance in the field of radiology. The current study aimed to use deep learning methods to detect caries lesions, classify different radiographic extensions on panoramic films, and compare the classification results with those of expert dentists. Methods: A total of 1160 dental panoramic films were evaluated by three expert dentists. All caries lesions in the films were marked with circles, whose combination was defined as the reference dataset. A training and validation dataset (1071) and a test dataset (89) were then established from the reference dataset. A convolutional neural network, called nnU-Net, was applied to detect caries lesions, and DenseNet121 was applied to classify the lesions according to their depths (dentin lesions in the outer, middle, or inner third D1/2/3 of dentin). The performance of the test dataset in the trained nnU-Net and DenseNet121 models was compared with the results of six expert dentists in terms of the intersection over union (IoU), Dice coefficient, accuracy, precision, recall, negative predictive value (NPV), and F1-score metrics. Results: nnU-Net yielded caries lesion segmentation IoU and Dice coefficient values of 0.785 and 0.663, respectively, and the accuracy and recall rate of nnU-Net were 0.986 and 0.821, respectively. The results of the expert dentists and the neural network were shown to be no different in terms of accuracy, precision, recall, NPV, and F1-score. For caries depth classification, DenseNet121 showed an overall accuracy of 0.957 for D1 lesions, 0.832 for D2 lesions, and 0.863 for D3 lesions. The recall results of the D1/D2/D3 lesions were 0.765, 0.652, and 0.918, respectively. All metric values, including accuracy, precision, recall, NPV, and F1-score values, were proven to be no different from those of the experienced dentists. Conclusion: In detecting and classifying caries lesions on dental panoramic radiographs, the performance of deep learning methods was similar to that of expert dentists. The impact of applying these well-trained neural networks for disease diagnosis and treatment decision making should be explored. Full article

The time of arrival (TOA) trilateration is one of the representative location detection technologies (LDT) that determines the true location of a mobile station (MS) using a unique intersection point of three circles based on three radii corresponding to distances between MS and base stations (BSs) and center coordinates of BSs. Since the distance between MS and BS is estimated by using the number of time delays, three circles based on the estimated radii are generally increased and they may not meet at a single point, resulting in the location estimation error. In order to compensate this estimation error and to improve estimation performance, we present two advanced TOA trilateration localization algorithms with detail mathematical expressions. The considered algorithms are the shortest distance algorithm, which calculates an average of three interior intersection points among an entire six intersection points from three intersecting circles, and the line intersection algorithm, which calculates an intersection point of three lines connecting two intersection points of two circles among the three circles, as the estimated location of the MS. In this paper, we present both algorithms with detailed mathematical expressions. The computer simulation results are provided to compare the location estimation performance of both algorithms. In addition, in this paper, mathematical analysis is provided to indicate the relation between the line intersection algorithm and the shortest distance algorithm. In this analysis, we verify that line equations based on the intersection points obtained from the shortest distance algorithm are identical to those obtained from the line intersection algorithm. Full article

Companies nowadays strive to gain public recognition through corporate social responsibility (CSR) activities. However, what are consumers’ cognition and evaluations of these CSR efforts, and can they be explained by the concentric circle model, the pyramid model, the intersecting circles model, or by a combination of all three? The novelty of this study is to reexamine the traditional theoretical models in order to find an empirical answer and offer it as a reference to companies. First, we specified the causal relationships of the principles using the modified decision-making trial and evaluation laboratory (DEMATEL)-based analytic network process (ANP) (DANP); then we identified and examined consumers’ cognition and evaluation of these CSR efforts by importance-performance analysis (IPA). The research result demonstrates that, in a Taiwanese community, consumers’ cognition and evaluation of companies’ CSR rarely follows one single model. On basic economic and legal levels, consumers indicate characteristics of the intersecting circles model. On higher ethical and philanthropic levels, they exhibit characteristics of the pyramid/concentric circles models. Notably, consumers’ demands and expectations of companies have reached an ethical level but have not yet placed great value on a philanthropic level. Moreover, the actual phenomenon may be interpreted by a combination of the above-mentioned models. Low- and high-level CSRs reveal different characteristics; therefore, companies should cultivate various communication strategies to improve effectiveness. Full article

This work proposes a model starting from the Three-Circle Model, based on the reality of the small and medium-sized family business sector in the Mexico City Metropolitan Area. The present paper proposes a new model that was built based on the Three Circle Model, but it is based on the reality of the Small and Medium Mexican family business sector. The model does not include the Ownership Subsystem, but it includes the Environment Subsystem, a subsystem that has a vital influence on the life and performance of an organization of that size. These three subsystems intersect in common elements such as culture, economy or company vision, triggering the success or failure of the company itself. The methodology used was a mixed methodology, with both qualitative and quantitative elements. First, the Delphi method was used on a scale that was applied to 25 owners of Small and Medium Enterprises and then, to make an additional confirmation, hypothesis testing, factorial analysis and the technique of structural equations were used. It was seen that the ownership subsystem has a lower weight than the business, environment and family subsystems, is the least relevant. Full article

The ever-growing mobile station (MS) localization technologies provide an increasingly important role in all aspects of the wireless cellular systems and Internet of Things (IoT). The accurate MS location information is the basis in connection of different devices in IoT. The MS localization techniques based on time of arrival (TOA) trilateration algorithm, which determines the location of MS using an intersection point of three circles based on distances between MS and base stations (BS) and coordinates of BSs, have been actively studied. In general, the distance between the MS and BS is calculated by counting the number of delay samples or measuring the power of the received signal. Since the estimated distance (radius of a circle) between MS and BS is commonly increased, three circles may not meet at a single point, resulting in the estimation error of MS localization. In order to improve this problem, in this paper, we propose the hybrid TOA trilateration algorithm based on the line intersection algorithm for the general case for intersection of three circles and the comparison approach of intersection distances for the specific case where a small circle is located inside the area of two large circles. The line intersection algorithm has an excellent location estimation performance in the general case, but it does not work in the specific case. The comparison approach of intersection distances has good performance only for the specific case. In addition, we propose the mode selection algorithm to efficiently select a proper mode between the general and specific cases. The representative computer simulation examples are provided to verify the localization performance of the proposed algorithm. Full article

Let $q\ge 2$ be a positive integer and let $\left(a_j\right)$ , $\left(b_j\right)$ , and $\left(c_j\right)$ (with j a non-negative integer) be three given $\mathbb{C}$ -valued and q-periodic sequences. Let $A\left(q\right):=A_{q-1}\cdots A_0$ , where $A_j$ is as is given below. Assuming that the “monodromy matrix” $A\left(q\right)$ has at least one multiple eigenvalue, we prove that the linear scalar recurrence $x_{n+3}=a_n{x}_{n+2}+b_n{x}_{n+1}+c_n{x}_n,n\in {\mathbb{Z}}_{+}$ is Hyers-Ulam stable if and only if the spectrum of $A\left(q\right)$ does not intersect the unit circle $\mathsf{\Gamma }:=\{w\in \mathbb{C}:|w|=1\}$ . Connecting this result with a recently obtained one it follows that the above linear recurrence is Hyers-Ulam stable if and only if the spectrum of $A\left(q\right)$ does not intersect the unit circle. Full article

Let $q\ge 2$ be a positive integer and let $\left(a_j\right),\left(b_j\right)$ and $\left(c_j\right)$ (with j nonnegative integer) be three given $\mathbb{C}$ -valued and q-periodic sequences. Let $A\left(q\right):=A_{q-1}\cdots A_0,$ where $A_j$ is defined below. Assume that the eigenvalues $x,y,z$ of the “monodromy matrix” $A\left(q\right)$ verify the condition $(x-y)(y-z)(z-x)\ne 0.$ We prove that the linear recurrence in $\mathbb{C}$ $x_{n+3}=a_n{x}_{n+2}+b_n{x}_{n+1}+c_n{x}_n,n\in {\mathbb{Z}}_{+}$ is Hyers–Ulam stable if and only if $\left(\right|x|-1)\left(\right|y|-1)\left(\right|z|-1)\ne 0,$ i.e., the spectrum of $A\left(q\right)$ does not intersect the unit circle $\mathsf{\Gamma }:=\{w\in \mathbb{C}:|w|=1\}.$ Full article

Investigating the characteristics of urban expansion is helpful in managing the relationship between urbanization and the ecological and environmental issues related to sustainable development. The Defense Meteorological Satellite Program/Operational Line-scan System (DMSP/OLS) collects visible and near-infrared light from the Earth’s surface at night without moonlight. It generates effective time series data for mapping the dynamics of urban expansion. As a major urban agglomeration in the world, the Yangtze River Delta Urban Agglomeration (YRDUA) is an important intersection zone of both the “Belt and Road Initiative” and the “Yangtze River Economic Belt” in China. Therefore, this paper analyses urban expansion characteristics of the YRDUA for 1993–2012 from urban extents extracted from the DMSP/OLS for 1993, 1997, 2002, 2007, and 2012. First, calibration procedures are applied to DMSP/OLS data, including intercalibration, intra-annual composition, and inter-annual series correction procedures. Spatial extents are then extracted from the corrected DMSP/OLS data, and a threshold is determined via the spatial comparison method. Finally, three models are used to explore urban expansion characteristics of the YRDUA from expansion rates, expansion spatial patterns, and expansion evaluations. The results show that the urban expansion of the YRDUA occurred at an increasing rate from 1993–2007 and then declined after 2007 with the onset of the global financial crisis. The Suxichang and Ningbo metropolitan circles were seriously affected by the financial crisis, while the Hefei metropolitan circle was not. The urban expansion of the YRDUA moved from the northeast to the southwest over the 20-year period. Urban expansion involved internal infilling over the first 15 years and then evolved into external sprawl and suburbanization after 2007. Full article

A solution to binaural direction finding described in Tamsett (Robotics 2017, 6(1), 3) is a synthetic aperture computation (SAC) performed as the head is turned while listening to a sound. A far-range approximation in that paper is relaxed in this one and the method extended for SAC as a function of range for estimating range to an acoustic source. An instantaneous angle $\lambda$ (lambda) between the auditory axis and direction to an acoustic source locates the source on a small circle of colatitude (lambda circle) of a sphere symmetric about the auditory axis. As the head is turned, data over successive instantaneous lambda circles are integrated in a virtual field of audition from which the direction to an acoustic source can be inferred. Multiple sets of lambda circles generated as a function of range yield an optimal range at which the circles intersect to best focus at a point in a virtual three-dimensional field of audition, providing an estimate of range. A proof of concept is demonstrated using simulated experimental data. The method enables a binaural robot to estimate not only direction but also range to an acoustic source from sufficiently accurate measurements of arrival time/level differences at the antennae. Full article

In a wireless communication system, wireless location is the technique used to estimate the location of a mobile station (MS). To enhance the accuracy of MS location prediction, we propose a novel algorithm that utilizes time of arrival (TOA) measurements and the angle of arrival (AOA) information to locate MS when three base stations (BSs) are available. Artificial neural networks (ANN) are widely used techniques in various areas to overcome the problem of exclusive and nonlinear relationships. When the MS is heard by only three BSs, the proposed algorithm utilizes the intersections of three TOA circles (and the AOA line), based on various neural networks, to estimate the MS location in non-line-of-sight (NLOS) environments. Simulations were conducted to evaluate the performance of the algorithm for different NLOS error distributions. The numerical analysis and simulation results show that the proposed algorithms can obtain more precise location estimation under different NLOS environments. Full article