Two-dimensional Body Research Articles

Diagnosis and Analysis of Vasa Previa Types With Flow HD Glass Body.

To explore the value of applying flow high definition (HD) glass body in prenatal diagnosis of vasa previa and to preliminarily discuss the types of vasa previa. Two-dimensional ultrasound, flow HD, and flow HD glass body were used to image the umbilical cord insertion site and placenta, observe the cervical internal os and surrounding areas, and retrospectively analyze cases of vasa previa. There were 15 cases of vasa previa, including 14 cases of singleton pregnancies and 1 case of twin pregnancy, with a total of 22 vasa previa, including 10 veins and 12 arteries. There was 1 case with 3 vessels, 5 cases with 2 vessels, and 9 cases with a single vessel. Among them, in 3 cases of vasa previa detected at 12, 14, and 24 weeks, respectively, the vasa previa were relocated to a normal position at 24, 29, and 35 weeks of gestation when re-examined. Routine 2-dimensional ultrasound examination in this group showed tubular or circular hypoechoic areas near the cervical internal os, but vasa previa could not be confirmed. Flow HD could display color blood flow at and near the cervical internal os in 15 cases, but it was difficult to continuously show the course and source of the blood vessels under the chorion. Flow HD glass body from multiple angles could display the relationship between 15 cases of 22 vasa previa and the placenta and cervix. Combined with color Doppler blood flow spectra, flow HD glass body could determine the types of vasa previa. Flow HD glass body imaging can clearly display vasa previa, showing their origin and the spatial relationship with the cervix and placenta in a 3-dimensional manner, displaying the course and attachment points of umbilical vessels under the chorion. It can observe the area of interest at any angle, and combined with color Doppler blood flow spectra, it can judge the vasa previa of the umbilical vein, providing a more definite imaging basis for clinical management.

Observation of multifunctional robust topological states based on asymmetric C4 photonic crystals

Recent advancements in high-order topological insulators have heralded new opportunities for the innovation and utilization of optical devices. This paper presents a composite asymmetric C4 photonic crystal to achieve multifunctional, robust topological states. Through detailed analysis of the fine changes in the topological bandgap induced by distortion parameters, we facilitate the realization of topological edge states in wavelength division multiplexing applications. We utilize both trivial and nontrivial properties of the topological bandgap to precisely manipulate zero-dimensional angular states, one-dimensional topological boundary states, and two-dimensional body states. Through simulations and experimental results, our advanced asymmetric C4 photonic crystal structure demonstrates superior robustness for the transmission of topological edge states. Our research paves the way for the deployment of more robust topological boundary state transmission systems and advances the application potential of higher-order topological states.

The starting vortices generated by bodies with sharp and straight edges in a viscous fluid

A two-dimensional body that moves suddenly in a viscous fluid can instantly generate vortices at its sharp edges. Recent work using inviscid flow theory, based on the Birkhoff–Rott equation and the Kutta condition, predicts that the ‘starting vortices’ generated by the sharp and straight edges of a body – i.e. the vortices formed immediately after motion begins – can be one of three distinct self-similar types. We explore the existence of these starting vortices for a flat plate and two symmetric Joukowski aerofoils immersed in a viscous fluid, using high-fidelity direct numerical simulations (DNS) of the Navier–Stokes equations. A lattice Green's function method is employed and simulations are performed for chord Reynolds numbers ranging from 5040 to 45 255. Vortices generated at the leading and trailing edges of the flat plate show agreement with the derived inviscid theory, for which a detailed assessment is reported. Agreement is also observed for the two symmetric Joukowski aerofoils, demonstrating the utility of the inviscid theory for arbitrary bodies. While this inviscid theory predicts an abrupt transition between the starting-vortex types, DNS shows a smooth transition. This behaviour occurs for all Reynolds numbers and is related to finite-time effects – there is a maximal time for which the (self-similar) starting vortices exist. We confirm the inviscid prediction that the leading-edge starting vortex of a flat plate can be suppressed dynamically. This has implications for the performance of low-speed aircraft such as model aeroplanes, micro air vehicles and unmanned air vehicles.

Preliminary investigation of yaw stability in undulatory fish propulsion using stability derivatives

Fish are capable of maintaining a stable forward direction without yawing during long-distance movements. This long-term yaw stability has been investigated using static derivatives, revealing that undulatory locomotion is highly unstable. However, the present simulation of the perturbation development process shows that the yaw perturbation growth rate of the undulatory fish is an order of magnitude smaller than that of non-undulatory one. This study investigates the yaw stability of two-dimensional fish body undergoing the carangiform undulatory deformation by considering both the mean static and dynamic derivatives method. The results indicate that the yaw instability always occurs when the fish body is in undulatory propulsion or coasting model, and the undulation has stabilizing effect compared with the body straight in the uniform incoming flow. Analysis of the mean derivatives reveals that the stabilizing effect is due to the negative value of the dynamic derivative, which plays the role of damping, although the static derivative indicates that the yaw is unstable. Utilizing mean derivatives method can analyze qualitatively the linear stability at the equilibrium point, which cannot provide an assessment of overall stability.

Prediction of lower limb discomfort of elderly drivers based on key dimensions in the leg space

Significant difference exists in spatial fitness and perception between elderly and non-elderly drivers. However, due to dynamic and real-time changes in human subjective feelings and joint movements, two-dimensional human body templates and human-machine simulation software are not enough to obtain necessary space parameters. In this study, seven key dimensions of the legroom were measured thrice and averaged, in the situation that the seat and posture are comfortable. Such anthropometric data can reflect dynamic perception that may change due to personal emotions and environmental influences. Extreme learning machine (ELM) was adopted to build a prediction model of leg space discomfort degree, and the influence of the activation function and the number of hidden layer neurons on the prediction accuracy of the model were analyzed. In addition, a multiple linear regression (MLR) model was established with the discomfort score as the dependent variable and the seven key dimensions as the independent variables. The results indicated that the ELM model could effectively predict elderly drivers’ discomfort degree (MSE = 0.182, MRE = 9.364, R2 = 0.869) by learning the dimensions of the seven key positions. The MLR model (R2 = 0.861) did not perform as well as ELM. However, the regression coefficients could reflect the degree to which each dimension affects the discomfort degree of leg space for elderly drivers. The conclusions could function in elderly-oriented in-vehicle space arrangement and driving risk assessment of elderly people.

Added mass of oscillating bodies in stratified fluids

The concept of added mass is generalized to stratified fluids, accounting for the presence of internal waves. Once the added mass of a moving body is known, so is the hydrodynamic force exerted on it by the fluid, and the energy imparted by it to the fluid. As a function of frequency, added mass is complex. Its real part is associated with inertia and its imaginary part, only present in the frequency range of propagating waves, with wave damping. Owing to causality, these two parts satisfy Kramers–Kronig relations. The added masses of an elliptic cylinder of horizontal axis, typical of two-dimensional bodies, and a spheroid of vertical axis, typical of three-dimensional bodies, are deduced from their dipole strengths, themselves deduced from their representations as single layers. The wave power is shown to be a maximum, for fixed oscillation amplitude, at approximately $0.8$ times the buoyancy frequency. In the temporal domain, added mass appears as a new memory force taking the form of a convolution integral. The kernel of this integral combines algebraically decaying oscillations at the buoyancy frequency on the one hand; and an exponentially damped oscillation for the horizontal motion of the spheroid, implying short-term memory, an aperiodic algebraic decay for its vertical motion, implying long-term memory, and a constant for the motion of the cylinder, implying everlasting memory, on the other hand. A limitation of the study is its restriction to translational motion.

Development of equation of motion deciphering locomotion including omega turns of Caenorhabditis elegans.

Locomotion is a fundamental behavior of Caenorhabditis elegans (C. elegans). Previous works on kinetic simulations of animals helped researchers understand the physical mechanisms of locomotion and the muscle-controlling principles of neuronal circuits as an actuator part. It has yet to be understood how C. elegans utilizes the frictional forces caused by the tension of its muscles to perform sequenced locomotive behaviors. Here, we present a two-dimensional rigid body chain model for the locomotion of C. elegans by developing Newtonian equations of motion for each body segment of C. elegans. Having accounted for friction-coefficients of the surrounding environment, elastic constants of C. elegans, and its kymogram from experiments, our kinetic model (ElegansBot) reproduced various locomotion of C. elegans such as, but not limited to, forward-backward-(omega turn)-forward locomotion constituting escaping behavior and delta-turn navigation. Additionally, ElegansBot precisely quantified the forces acting on each body segment of C. elegans to allow investigation of the force distribution. This model will facilitate our understanding of the detailed mechanism of various locomotive behaviors at any given friction-coefficients of the surrounding environment. Furthermore, as the model ensures the performance of realistic behavior, it can be used to research actuator-controller interaction between muscles and neuronal circuits.

Development of equation of motion deciphering locomotion including omega turns of Caenorhabditis elegans

Locomotion is a fundamental behavior of Caenorhabditis elegans (C. elegans). Previous works on kinetic simulations of animals helped researchers understand the physical mechanisms of locomotion and the muscle-controlling principles of neuronal circuits as an actuator part. It has yet to be understood how C. elegans utilizes the frictional forces caused by the tension of its muscles to perform sequenced locomotive behaviors. Here, we present a two-dimensional rigid body chain model for the locomotion of C. elegans by developing Newtonian equations of motion for each body segment of C. elegans. Having accounted for friction-coefficients of the surrounding environment, elastic constants of C. elegans, and its kymogram from experiments, our kinetic model (ElegansBot) reproduced various locomotion of C. elegans such as, but not limited to, forward-backward-(omega turn)-forward locomotion constituting escaping behavior and delta-turn navigation. Additionally, ElegansBot precisely quantified the forces acting on each body segment of C. elegans to allow investigation of the force distribution. This model will facilitate our understanding of the detailed mechanism of various locomotive behaviors at any given friction-coefficients of the surrounding environment. Furthermore, as the model ensures the performance of realistic behavior, it can be used to research actuator-controller interaction between muscles and neuronal circuits.

Active flow control for bluff body drag reduction using reinforcement learning with partial measurements

Active flow control for drag reduction with reinforcement learning (RL) is performed in the wake of a two-dimensional square bluff body at laminar regimes with vortex shedding. Controllers parametrised by neural networks are trained to drive two blowing and suction jets that manipulate the unsteady flow. The RL with full observability (sensors in the wake) discovers successfully a control policy that reduces the drag by suppressing the vortex shedding in the wake. However, a non-negligible performance degradation ( $\sim$ 50 % less drag reduction) is observed when the controller is trained with partial measurements (sensors on the body). To mitigate this effect, we propose an energy-efficient, dynamic, maximum entropy RL control scheme. First, an energy-efficiency-based reward function is proposed to optimise the energy consumption of the controller while maximising drag reduction. Second, the controller is trained with an augmented state consisting of both current and past measurements and actions, which can be formulated as a nonlinear autoregressive exogenous model, to alleviate the partial observability problem. Third, maximum entropy RL algorithms (soft actor critic and truncated quantile critics) that promote exploration and exploitation in a sample-efficient way are used, and discover near-optimal policies in the challenging case of partial measurements. Stabilisation of the vortex shedding is achieved in the near wake using only surface pressure measurements on the rear of the body, resulting in drag reduction similar to that in the case with wake sensors. The proposed approach opens new avenues for dynamic flow control using partial measurements for realistic configurations.

Adhesive contact between two-dimensional anisotropic elastic bodies

Adhesion plays a vital role in the design of smart and intelligent high-tech devices such as modern optical, microelectromechanical, and biomedical systems. However, in the literature, adhesive contact is mostly considered for contact of rigid substrates and transversely isotropic and isotropic elastic materials. The composite materials are increasingly used in the mart and intelligent high-tech devices. Since the composite materials are generally anisotropic and contact bodies are all deformable, it is more practical to consider the adhesive contact of two anisotropic elastic materials. In this paper, an adhesive contact model of anisotropic elastic bodies is established, and the closed-form solutions for two-dimensional adhesive contact of two anisotropic elastic bodies are derived. The full-field solutions and the relation for the contact region and applied force are developed using the Stroh complex variable formalism, the analytical continuation method, and concepts of the JKR adhesive model. We will show that the frictionless contact of two anisotropic elastic materials is just a special case of the present contact problem, and its solutions can be obtained by setting the work of adhesion equal to zero. In addition, we also show that our present solutions are valid for the problems of indentation by a rigid punch on an elastic half-space through a proper placement of the contact radius and the corresponding material constant. Numerical results are provided to demonstrate the accuracy, applicability, and versatility of the developed solutions.

Thermal stability of a two-dimensional multilayer diffusion-reaction problem

Multilayer diffusion-reaction problems appear commonly in heat and mass transfer analysis, including in thermal management of Li-ion batteries, drug delivery and reacting systems. Thermal stability of diffusion-reaction problems is of much interest due to the potential for thermal runaway in such systems. While there is some past work on investigating thermal instability in a one-dimensional multilayer body, practical systems such as Li-ion cells are often two- or even three-dimensional. Therefore, it is important to develop a theoretical understanding of when a two-dimensional multilayer diffusion-reaction system may be thermally unstable. This work addresses this important question by deriving a solution for the transient temperature field in this problem, followed by pole analysis in the Laplace domain. An explicit threshold for thermal stability of the system is determined on the basis of the determinants associated with a set of algebraic equations. The impact of key non-dimensional numbers on thermal stability is determined, including those associated with heat generation and boundary cooling, as well as ratios of thermal properties of the layers. Good agreement with past papers for special cases of the general problem considered here is shown. A stability curve that separates stable and unstable regions in the thermal design space of a two-dimensional two-layered body, such as a stack of Li-ion cells is presented. This work extends the state-of-the-art in the theoretical understanding of thermal stability, and may also contribute towards design for safety of practical engineering systems.

Investigation of the influence of the bluff-body temperature on a lean premixed DME/air flame approaching blowoff

In flames stabilized by a two-dimensional (2D) bluff body, the lean blowoff (LBO) limit can be extended by increasing the bluff-body temperature, which is verified experimentally in premixed dimethyl ether (DME)/air flames in this work. Two bluff-body temperatures of 573 K and 773 K are tested, respectively. High-speed OH* chemiluminescence (CL) imaging is applied to record the spatial distribution of the heat release. Particle image velocimetry (PIV) and OH planar laser-induced fluorescence (PLIF) are performed simultaneously to explore the flow field and the combustion characteristics. Based on the results of OH*-CL, the heat release of the area near the bluff body is strengthened in the case of higher bluff-body temperature, and the enhanced chemical reactivity will further influence the downstream area. The turbulent flame speed obtained by OH-PLIF is increased in the entire area of interest. Due to the higher velocity gradient adjacent to the bluff body in the upstream region (y < 35 mm), the flame surface density (FSD), brush thickness, and flame wrinkling ratio are not sensitive to the bluff-body temperature. However, in the downstream region (y > 35 mm), a noticeable change can be found in these three parameters due to a higher turbulent flame speed and a much lower velocity gradient. Based on the PIV results, a limited effect on the velocity field by increasing the bluff-body temperature by 200 K. Furthermore, the probability density functions (PDF) of the vorticity and strain rate on the flame front are computed. The results indicate that the enhanced flame stability leads to a more pronounced overlapping between the flame front and the high-vorticity region, further increasing the values of these two parameters.

A computational approach to heat transfer and ablation in space capsule insulation

In this article, the heat transfers and ablation phenomena of thermal insulations utilized in manned space capsules are investigated. In this regard, by collecting and solving the equations related to ablation insulations, a computer program has been developed that is able to predict the thermal response of these insulations under various operating conditions. This approach considers mass and heat transfer equations in two-dimensional solid bodies. To solve these equations, finite volume method and implicit formulation for time dependence have been used. The reaction equation, written in the form of Arrhenius, is solved using the Runge-Kutta method, and the density and the flux of the gas produced at each step are obtained. Furthermore, a practical model with low computational requirements and execution time and execution time is presented to consider the regression rate based on determining the identifier for destroyed cells, charred cells, and virgin material. The research results demonstrate that increasing the thickness of the layers, the heat of decomposition and ablation, the intensity of the reaction, and reducing the thermal diffusion coefficient, density of char, and temperature of ablation enhance the efficiency of thermal insulation. Validation of the model with experimental results in silica-phenolic insulation reveals a good agreement between simulation and experimental observations. Additionally, it was shown that for a carbon-phenolic insulation with a thickness of 5 mm in the specified space capsule under the given conditions, the maximum recession rate is 1.9 mm at a maximum temperature of 1000 K and 4.9 mm at a maximum temperature of 1300 K.

Capillarity-driven Stokes flow: the one-phase problem as small viscosity limit

We consider the quasistationary Stokes flow that describes the motion of a two-dimensional fluid body under the influence of surface tension effects in an unbounded, infinite-bottom geometry. We reformulate the problem as a fully nonlinear parabolic evolution problem for the function that parameterizes the boundary of the fluid with the nonlinearities expressed in terms of singular integrals. We prove well-posedness of the problem in the subcritical Sobolev spaces Hs(R)\\documentclass[12pt]{minimal} \\usepackage{amsmath} \\usepackage{wasysym} \\usepackage{amsfonts} \\usepackage{amssymb} \\usepackage{amsbsy} \\usepackage{mathrsfs} \\usepackage{upgreek} \\setlength{\\oddsidemargin}{-69pt} \\begin{document}$$H^s(\\mathbb {R})$$\\end{document} up to critical regularity, and establish parabolic smoothing properties for the solutions. Moreover, we identify the problem as the singular limit of the two-phase quasistationary Stokes flow when the viscosity of one of the fluids vanishes.

Life-size telepresence using holographic display

Despite massive advancements in the telecommunications industry over the last few decades, telepresence video-based teleconferencing is still far from giving a physical co-presence experience. Applications like Skype, Zoom and WebEx are constrained as it is only able to display the head and shoulders of the users on one monitor. It offers the user flat two-dimensional (2D) upper body imageries, a fixed viewpoint, inconsistent gaze direction, and restriction. Therefore, the problem arises when video-based teleconferencing is unable to support effective communication in telepresence. Thus, this research aims to propose life-size telepresence by using a projector-based holographic display. To actualize the aim, there are three phases have been proposed in this research. The first phase is to enable the tracking technique using the Kinect sensor. The second phase is to enable networking using Agora.io. The last phase is to set up the holographic display using a projector before the evaluation phase. Based on the evaluation results, the life-size telepresence using holographic display application has succeeded in achieving the project aim and shown the life-size display increases the co-presence experience of the users and increases the efficient communication between the users.

Equilibrium problem for an inhomogeneous two-dimensional elastic body with two interacting thin rigid inclusions

A new nonlinear mathematical model is proposed that describes an equilibrium of a two-dimensional elastic body with two interacting thin rigid inclusions. Thin rigid inclusions are defined by straight line segments. In the initial state of the body, both inclusions are in contact at one breaking point. Both inclusions can move, subject to the conditions in the form of systems of inequalities describing a possible contact of the inclusions. These three systems of inequalities for infinitesimal rigid displacements correspond to three possible cases of mutual configurations of inclusions in equilibrium state. Inclusions exfoliate near the breaking point from the elastic matrix, in other words, there are cracks of a given length on both sides of thin inclusions. Nonpenetration conditions of the Signorini type are imposed on the curves defining the cracks. On a part of the outer boundary, clamping conditions are prescribed. The problem is formulated as a minimization of an energy functional over a non-convex set of possible displacements defined in an appropriate Sobolev space. The existence of a solution to the problem is proved. Optimality conditions of the solution have been obtained under the condition of sufficient smoothness of the solution.

Can AI-based body composition assessment outperform body surface area in predicting dose-limiting toxicities for colonic cancer patients on chemotherapy?

Gold standard chemotherapy dosage is based on body surface area (BSA); however many patients experience dose-limiting toxicities (DLT). We aimed to evaluate the effectiveness of BSA, two-dimensional (2D) and three-dimensional (3D) body composition (BC) measurements derived from Lumbar 3 vertebra (L3) computed tomography (CT) slices, in predicting DLT in colon cancer patients. 203 patients (60.87 ± 12.42 years; 97 males, 47.8%) receiving adjuvant chemotherapy (Oxaliplatin and/or 5-Fluorouracil) were retrospectively evaluated. An artificial intelligence segmentation model was used to extract 2D and 3D body composition measurements from each patients' single mid-L3 CT slice as well as multiple-L3 CT scans to produce a 3D BC report. DLT was defined as any incidence of dose reduction or discontinuation due to chemotherapy toxicities. A receiver operating characteristic (ROC) analysis was performed on BSA and individual body composition measurements to demonstrate their predictive performance. A total of 120 (59.1%) patients experienced DLT. Age and BSA did not vary significantly between DLT and non-DLT group. Females were significantly more likely to experience DLT (p = 4.9 × 10-3). In all patients, the predictive effectiveness of 2D body composition measurements (females: AUC = 0.50-0.54; males: AUC = 0.50-0.61) was equivalent to that of BSA (females: AUC = 0.49; males: AUC = 0.58). The L3 3D skeletal muscle volume was the most predictive indicator of DLT (AUC of 0.66 in females and 0.64 in males). Compared to BSA and 2D body composition measurements, 3D L3 body composition measurements had greater potential to predict DLT in CRC patients receiving chemotherapy and this was sex dependent.

Advances in Wall Interference Corrections for Two-Dimensional Lifting Bodies

A novel approach to correcting the effects of wall interference has been developed for low-speed closed-wall wind tunnels using a nonlinear least-squares optimization process independent of the model geometry. Potential flow singularities are used to represent the test object, and the method of images is used to represent the tunnel walls. Trust-region reflective optimization enables the locations and strengths of singularities to be determined iteratively with only wall pressure measurements as independent inputs. Results are obtained from a range of two-dimensional and three-dimensional airfoil test cases using both computational fluid dynamics simulations and wind tunnel experiments, including a NACA 0012 with deployed spoiler, a NACA 0015, a NACA 4415, and a McDonnell Douglas 30P30N high-lift configuration. The nonlinear least-squares wall-correction method is shown to demonstrate a considerable improvement over the conventional two-variable technique.

Numerical simulation of lateral jet interaction with rarefied hypersonic flow over a two-dimensional blunt body

Reaction Control System (RCS) is a direct force control system that successfully adjusts a craft's attitude or orbit using the reaction force created by jet flow. RCS is frequently employed in the management of near-space vehicles due to its properties of fast response time and effective control efficiency. When the near-space vehicle is navigating at high altitude in a low density atmosphere, the Navier–Stokes equation is no longer applicable. The numerical approach utilized in this study is known as the Conserved Discrete Unified Gas Kinetic Scheme, and the governing equation is the Boltzmann equation, which is not constrained by the continuum hypothesis. In velocity space, an unstructured mesh is utilized, which minimizes the amount of discrete velocity points and considerably increases computation efficiency. The numerical results are in good agreement with the direct simulation Monte Carlo code DS2V when modeling large Knudsen number lateral jet flow. The interaction flow field between hypersonic free stream and lateral jet is then simulated at altitudes of 60–90 km using argon as the working gas and a two-dimensional blunt cone with lateral jet as the study object. Under a fixed jet pressure ratio, preliminary research was conducted on the variation of the lateral jet interference flow field characteristics with the freestream Knudsen number and angle of attack. The differences in surface pressure and heat flux caused by jet opening and shutting are compared. Under rarefied atmospheric conditions, the variation of the force/moment amplification coefficient is given. The numerical results show that when the angle of attack is 0°, the separation area in front of the nozzle and a pair of opposite vortices, which are common in the jet interference flow field, gradually disappear with increasing altitude, but the separation vortex reappears when the angle of attack of the freestream is increased. The high-pressure region generated upstream of the nozzle is the primary cause of the extra force/moment. The density of the main flow decreases as altitude increases, various shock wave patterns of the interference flow field gradually dissipate and the force/moment amplification factor changes considerably. The rarefied gas effect has a significant effect on the lateral jet interference flow.

Simulation of sports training recognition system based on internet of things video behavior analysis

The video behavior analysis of the Internet of Things is the apparent characteristics and continuous state of the two-dimensional human body in the time dimension. The patterns representing human behavior can be divided into states based on human body structure, forms based on common features and forms based on temporal features, local spaces, and behaviors based on deep learning. Applying IoT video behavior analysis to sports training will have a huge impact. Physical training is the process of training people to improve their physical fitness, increase courage and endurance, and acquire practical skills. It is the basis of various training courses and an important way to improve human physical fitness. The motion recognition system is a DTW pattern matching method, which uses a finite state to describe the spatial characteristics of the angle between the joint points. This method can accurately meet the low-delay requirements of the motion recognition of each frame and the standard motion. It can match and eliminate the influence of individual differences on motion recognition. At the same time, it can also effectively expand the pattern matching method to recognize newly filled motions, and it is a powerful composite general motion recognition system.