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Among numerous approaches that have been presented for computational contact analysis, the node-to-segment (NTS) approach is widely adopted in industrial applications, particularly with the penalty method. However, the pure penalty-method-based NTS approach fails the patch test even with the area regularization (AR) technique. There have been relatively few solutions for this problem compared to those for Lagrange-multiplier-method-based NTS approaches. This paper presents an improved AR technique and attempts to make the penalty-method-based NTS approach pass the patch test. The proposed approach improves the accuracy without the need to introduce additional geometry to the conventional penalty-method-based NTS approach. The entire competence area of a slave node is not directly utilized as a penalty weighting factor. Instead, a part of the competence area is extracted in accordance with the projection from a master node to a slave segment. In a complementary manner, a two-pass algorithm is used for the selected master nodes to achieve segment-wise force/moment equivalence. The results obtained using the proposed approach are introduced in a two-dimensional frictionless context. It is observed that the proposed approach passes the patch test. Furthermore, a significant improvement in accuracy compared to the conventional NTS and NTS-AR approaches is observed. We aim to extend the approach to three-dimensional applications in the future work.

The goal of this paper is to examine the computational approaches for predicting both of the overall sound pressure level (OASPL) at a few locations and acceleration power spectral density (APSD) of surrounding thin plates due to the aero-acoustic pressure generated by a cold jet with M = 1.8. First, computational fluid dynamics (CFD), particularly delayed detached eddy simulation, are applied to predict the OASPL at the near-field and compute the acoustic properties. Second, the linearized boundary element method (BEM), that is, the Helmholtz-Kirchhoff method is utilized to propagate the pressure and obtain the OASPL at the far-field. Finally, the finite element method is implemented to predict the APSD for a clamped thin plate based on the optimal triangle membrane element, discrete Kirchhoff triangle plate bending element, and Newmark- β time integration scheme. Using the present CFD and BEM, the OASPLs are compared with the experimental results measured by microphones at both the near- and far-fields, respectively. Moreover, APSDs are compared with the experimental results obtained by an accelerometer at a few different locations. Although OASPLs are overestimated because of the coarse meshes in the higher-angle area and low order scheme of the present CFD analysis, the present integrated aero-vibro-acoustic analysis is capable of predicting the OASPL and APSD generated by a cold jet with M = 1.8.

The conventional representative volume element approach may not be accurate enough in examining stress distribution near singularity in a composite. However, enormous number of degrees of freedom (DOFs) is usually required to discretize the subcomponents within the composite structure; hence, it may not be handled in a single CPU. In this study, the finite element tearing and interconnecting algorithm, a domain decomposition method, is proposed to address the challenges posed by such enormous number of DOFs via parallel computation. Owing to the message passing interface, analyses in this study will be conducted on the parallel computing environment. Furthermore, the METIS algorithm is adopted to automatically divide the solid domain into certain number of subdomains. Consequently, the fiber-reinforced polymer which possesses either a crack or notch discretized by over 10 million DOFs will be readily analyzed. The computational time is reduced significantly compared against the original one. Also, the stress and stiffness predictions show good agreement with those by the other existing analyses or experiments. Therefore, this study is expected to be fast and accurate in analyzing composite structures with enormous number of DOFs.

Forced vibration analysis is an indispensable process for the design of a rotating component. However, rather expensive nonlinear static and linear frequency response analyses are usually accompanied by a frequency domain analysis. The traditional mode-superposition method (MSM) effectively reduces the cost of the frequency response analysis. However, the nonlinear static analysis of earlier processes remains as the computational bottleneck. In this paper, the application of the hyper-reduction method will be proposed along with the model order reduction (MOR) framework for rotating component forced vibration analysis. The energy-conserving sampling and weighting (ECSW) method will be employed for the nonlinear iterative computation. The pre-stressed stiffness matrix of the reduced finite elements (FEs) resulting from the ECSW will be used for the post computation stage. Also, a variety of MOR will be attempted for the performance comparison, including MSM, proper orthogonal decomposition (POD)-based reduced order model (ROM), and a hybrid approach. It is found that the present ECSW-combined MOR will significantly relieve the computational bottleneck, provide a minimal loss of accuracy, and be compatible with both nonlinear and linear analyses of the rotating component forced vibration analysis.

An improved nonintrusive parametric model order reduction (pMOR) approach is proposed for the flow field interpolation regarding fluid–structure interaction (FSI) objects. Flow field computation using computational fluid dynamics (CFD) requires excessive computational time and memory. Nonintrusive and data-driven MOR schemes have been proposed to overcome such limitations. The present methodology is implemented by both proper orthogonal decomposition (POD) and a modified Nouveau variational autoencoder (mNVAE). POD attempts to reduce the number of degrees of freedom (DOFs) on the precomputed series of the full-order model parametric result. The reduced DOF yields parametrically independent reduced bases and dependent coefficients. Then, mNVAE is employed for the interpolation of POD coefficients, which will be combined with POD modes for parametrically interpolated flow field generation. The present approach is assessed on the benchmark problem of a two-dimensional plunging airfoil and the highly nonlinear FSI phenomenon of the limit cycle oscillation. The comparison was executed against other POD-based generative neural network approaches. The proposed methodology demonstrates applicability on highly nonlinear FSI objects with improved accuracy and efficiency.

A Phase I clinical trial is currently underway to test Nelmastobart (hSTC810), an antibody targeting butyrophilin 1A1 (BTN1A1), a novel immune checkpoint protein. This Phase I clinical trial is using a standard 3 + 3 escalation design to (i) explore safety, tolerability, dose-limiting toxicities, and pharmacokinetics, (ii) define a recommended Phase II dose, and (iii) evaluate preliminary efficacy in patients with advanced solid tumors. The current dose range for the clinical trial is 0.3 mg/kg to 15 mg/kg. Currently, all the dose levels have been completed without any dose-limiting toxicity having been observed. Here, we provide an update on the clinical trial data shown previously. First, we provide the results of the pharmacokinetics study of these patients for the selected doses and dosing intervals, including the peak plasma concentration (Cmax), the time to reach Cmax (tmax), and the average plasma concentration of hSTC810 over the dosing interval in steady state (Cavg). The change in cytokine expression and immune cell concentrations in patient blood samples were also analyzed. Specifically, a panel of cytokines was measured including IFN- γ, IL-2, IL-4, IL-6, IL-10, TNF-α, MCP-1, and TGF- β, while flow cytometry was used to detect a panel of immunological marker proteins including CD3, CD4, CD8, CD19, CD14, CD16, CD56, CD25, CD45. For pharmacokinetic studies, the concentrations of hSTC810 and anti-hSTC810 antibodies were quantified. Immunohistochemistry was performed on patient tumor biopsies that were stained for PD-L1, CD3, CD4, CD8, and BTN1A1 expression. The resultant slides were analyzed for PD-L1 tumor proportional score (TPS), PD-L1 combined positive score (CPS), BTN1A1 scoring, the percentage of CD3+ lymphocytes, CD4+ lymphocytes, CD8+ lymphocytes, tumor-infiltrating lymphocytes, and necrosis. Citation Format: Stephen Sunghan Yoo, Soohyeon Lee, Sangjoon Shin, Hyunjin Jung, David S. Hong. Pharmacokinetic analyses and immunophenotyping of patients treated with Nelmastobart (hSTC810), a novel immune checkpoint inhibitor [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2023; Part 2 (Clinical Trials and Late-Breaking Research); 2023 Apr 14-19; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2023;83(8_Suppl):Abstract nr CT238.

In this paper, the finite element tearing and interconnecting (FETI) method and proper orthogonal decomposition-based reduced order model (POD-ROM) are suggested as fast and novel computational approaches for multi-scale and multi-physics analysis. FETI is one of non-overlapping domain decomposition methods, facilitating the parallel computation. POD-ROM reduces the number of degrees of freedom (DoFs) to several representative POD modes which completely describe the behavior of the full order model. The computational time for the analyses using large number of DoFs can be decreased by using the previously mentioned methods. The present FETI-local and POD-ROM are found to reduce computational time significantly in each example.

Rotorcraft composite structures are required to satisfy desired reliability levels when analyzing the scatter of material properties at coupon and element levels in accordance with the Federal Aviation Regulations “FAR 29.573” and the Advisory Circular “AC 29.573”. By estimating the strength and life shape parameters from static and fatigue test results, load enhancement factors can be obtained. Thus, the uncertainties from the scatter of composite properties can be analyzed. However, depending on the Weibull parameter estimation and scatter analysis methods, the load enhancement factors may differ. Therefore, in this paper, improved Weibull parameter estimation and scatter analysis methods have been proposed. Baseline static and fatigue tests are conducted, and the test data are pooled to generate reliable shape parameters. The static-strength shape and fatigue-life shape parameters are evaluated for eight Weibull parameter estimation and three scatter analysis methods. Moreover, based on the strategies of the Weibull parameter estimation and scatter analysis methods, the load enhancement factors are evaluated as a function of test duration. Finally, the consequences of model selection on distribution fitting and the scatter analysis along with the effect of life factors and strength parameters on the load enhancement factors are discussed. As a result, more conservative load enhancement factors are obtained by applying various Weibull parameter estimation methods for the scatter analysis.

In this study, a numerical analysis of pogo instability in liquid propulsion rockets was conducted and an optimization of the pogo suppressor was attempted. Pogo analysis was carried out using nume...

Designing the structure of a wind turbine blade is a nontrivial task. Nowadays, finite element software is widely applied for its design and computation. However, huge computational resources and t...

With regard to the parameterized projection-based reduced-order model, it is significant to consider the computational efficiency as well as its capability for the parametric variation. The proposed approach is based on the online adaptive procedure to improve the accuracy and stability of the reduced-order model. Achieving efficient computation in online adaptation, a matrix version of the discrete empirical interpolation method is employed to approximate the nonlinear finite element matrix, independently. The proposed approach is applied to analysis of a structure with geometric and material nonlinearities. As a result, the computational efficiency during the offline/online steps of the proposed approach is significantly improved, compared to other existing approaches. Moreover, within the present numerical examinations, it is found that the proposed approach is capable of accurately addressing broad parametric variations by using only ten percent of the number of data used in the conventional ROM from the preliminary computation.

This paper proposes a nonlinear finite-element analysis for slender composite structures with anisotropic material properties using the mixed geometrically exact beam formulation and exponential map finite rotation. Rodrigues finite rotation expression used in the existing mixed-variational formulation of the geometrically exact beam is further improved by replacing it with the exponential map finite rotation, which is free of singularities. As a result, the existing mixed-variational formulation is further simplified by the matrix arithmetic, so that numerical implementation of the resulting equations may become more compact. Using the present beam formulation, nonlinear static displacements of a straight beam, twisted straight beam, and initially curved beam are precisely predicted within smaller number of iterations compared to the existing formulations. In addition, the present eigenmode analysis is capable of providing the rotating natural frequencies for a full-scale realistic rotor blade accurately. As a result, the present analysis is applicable for large deflection behavior of a composite structure without the singularities in a better convergence.

While Community participation has been considered as an essential determi nant in enhancing the level of quality of life (QOL), few have systemically tested the mediating impact of community participation between physical Environments, social Relationships, social conflicts, and QOL. Using the 2015 Korean’ Conflicts and Cooperation Survey, which is randomly sampled by gender, age, and regions, this research aims to analyzes the mediating effect of community participation between physical Environments, social Re lationships, social conflicts, and QOL. The analysis results show that com munity participation plays a mediating role in increasing the level of QOL among many people with experiences with social conflict. The individuals’ satisfaction with their physical environment and interpersonal relationships directly affects their level of QOL, while their experiences of social conflict does not have an impact on the level of QOL. The findings of this study suggest that the activation of communities can offset negative experiences resulting from social conflicts and improve the level of QOL of individuals in the South Korean context. This research contributes to methodological and theoretical topics in the field of quality of life.

Objective Percutaneous cervical nucleoplasty (PCN) is used to treat cervical disc herniation. Radiological imaging studies, including plain radiography, computed tomography (CT), and magnetic resonance imaging (MRI), have been used to make early predictions of cervical spinal surgery outcomes. However, simple radiological studies do not provide sufficiently detailed information; moreover, CT and MRI are highly expensive. Herein, we aimed to elucidate the usefulness of digital infrared thermography imaging (DITI) as an outcome marker after cervical nucleoplasty by correlating the changes in thermal difference (ΔTD) with the changes in pain intensity after PCN expressed as visual analogue scale (ΔVAS) scores. Methods For this study, 255 patients treated with PCN at Thomas Hospital between March 2012 and August 2014 were included. For each patient, demographic and clinical data, including preoperative MRI results, ΔVAS, ΔTD at the disc level treated with PCN, subjective symptom improvement, procedure-related discomfort, overall satisfaction, and adverse effects, were collected and evaluated for up to 3 months retrospectively. Results Thermal difference (TD) and VAS scores improved after PCN (p

Flapping wing micro-air vehicles are biologically inspired by nature flyers, specifically insects and birds. Specifically, insect wings generally consist of veins and membrane components. In this study, a structural analysis considering the vein/membrane components of an insect-like flapping wing is presented. Co-rotational (CR) finite elements are adopted in order to consider the complex wing configuration including both vein and membrane. The CR beam elements with warping degrees of freedom are employed for veins and CR shell elements for the wing membrane. The present structural analysis is verified against the analytical results obtained by an existing software, and it is validated by comparison to existing results from the literature. A fluid–structure interaction analysis is then performed. In the procedure, an aerodynamic analysis based on three-dimensional preconditioned Navier–Stokes equations is employed. Finally, a comparative study with respect to the structural characteristics is conducted. As a result, an efficiency of the present structural analysis is confirmed by comparing with the existing software. It is found that the present FSI results are in good agreement with the existing experimental and numerical results. Moreover, the passive wing twist may have a significant influence on the hover performance.

In this paper, we present a computational aeroelastic analysis of flexible flapping wings in the vicinity of solid walls. The wall effects change the aerodynamic forces and moments of the wings, and thus the aeroelastic behavior. The numerical simulation is carried out using a fluid–structure interaction framework by coupling the computational fluid dynamics and computational structural dynamics. A preconditioned Navier–Stokes solver based on a finite volume method is used for the aerodynamic analysis. The structural analysis is performed using a nonlinear structural model based on a geometrically exact beam formulation. The method is validated using previous numerical and experimental results. The aeroelastic characteristics of the flexible wings with and without the walls are computed and compared.

The pogo phenomenon is a type of instability that arises when the longitudinal modes of a space launch vehicle fuselage resonate with the pressure modes of the feedline in its propulsion system, with such resonance re-exciting the fuselage structure. To analyze this phenomenon, this paper specifically focuses on an analysis of the pressure modes in the space shuttle interpump line included in the LOX engine system. Because the interpump line is connected to pipes in different cross-sectional areas, the pressure modes are analyzed as a nonuniform cross-sectional pipe. Further, by applying a pogo suppressor in the feedline system, the possibility of preventing the pogo phenomenon is demonstrated. In order to design the suppressor, the resistive accumulator inertance, compliance, and resistance are considered as variables. Resistive accumulator compliance and inertance are determined and the pressure perturbation of the engine is prevented by lowering the inlet pressure amplitude of the high-pressure oxidizer pump (HPOP) in the space shuttle LOX system interpump line. When the resistive accumulator resistance is increased, the pressure frequencies of the interpump line gradually decrease, avoiding the resonance region with the fuselage. As a result, the resonance region with the fuselage is prevented by varying the pressure amplitude and natural frequencies of the interpump line. In this way, the capability of the present pogo suppression is evaluated.

Vertical launching system (VLS) is useful in operating and sheltering high-speed rockets. The aft closure in the plenum plays a significant role in protecting the interiors from the exhaust gas induced by the ignition of adjacent or in-positioned canisters. During the aft opening/closing event, a complex flow is propagated into the VLS. By presence of such structural components, it is necessary to analyze the interaction between the deforming aft closure and a highly pressurized plume. This paper presents a two-dimensional fluid–structure interaction (FSI) simulation under high pressure loading condition for preliminary design of VLS. A quadrilateral 9-node element based on co-rotational (CR) framework is used to predict the geometrically/materially nonlinear deformation of the aft closure while supersonic impinging jet plume is predicted by fully Eulerian modeling. A contact mechanism is also utilized to apply reaction forces between the structures and inclined plenum using a penalty term. The interface and boundary conditions are obtained by the hybrid particle level-set method via the Ghost framework. Furthermore, a parametric study is conducted by changing the thickness of the aft closure and the inclined angle of the plenum. It is expected that the magnitudes of pressure and temperature can be decreased by the introduction of appropriate thickness of the aft closure and inclined angle in the plenum.

This paper proposes a framework to analyze the capacity of a launch vehicle systematically. Important mission requirements and flight parameters that influence the payload capacity of a given launch vehicle configuration are identified. The response surface models (RSM; the “analyzer”) for the launch capacity, coasting/burning arcs, and the velocity increment elements are developed. A series of trajectory optimization results, which are obtained with the “optimizer”, are used to determine the coefficients of the models. The case study to analyze the capacity of a low Earth orbit (LEO) launch vehicle configuration is conducted to demonstrate the validity of the proposed framework.

This paper investigated associations between COVID‐19 responses in social welfare facilities and the psychological state of social workers together with the potential mediating role of satisfaction with the government. During the COVID‐19 pandemic, following government guidelines, social workers have continued to provide social services to the vulnerable groups. However, no research has been conducted focusing on their psychological state. A cross‐sectional survey was carried out in Incheon Metropolitan City, South Korea. Data from 332 participants were analyzed using structural equation modeling. Supplementary in‐depth interviews were conducted with social workers. Analysis results show that higher levels of preventive measures against COVID‐19 directly worsen levels of well‐being, but this negative effect is offset by the satisfaction with the government (β = .383, p

A real-time flight simulation for multirotor unmanned aerial vehicles (UAV) is performed in combination with dynamic inflow aerodynamics. The present combination procedure includes rotor/fuselage aerodynamics and trim analysis. The rotor aerodynamics is based on dynamic inflow aerodynamics, which is appropriate for the analysis of multirotor UAVs. The present simulation uses an appropriate formulation for fuselage aerodynamics. Trim analysis was conducted for climb and forward flight to determine the physical constraints of the UAV. Based on this procedure, a simulation was performed and validated against the flight test. It was found that the accuracy of flight simulation increased if the simulation is performed in combination with dynamic inflow aerodynamics. Using this methodology, the dynamic characteristics that affect the performance of UAVs were investigated.

A linear quadratic Gaussian (LQG) controller for active vibratory loads reduction in helicopters is proposed based on a revisited higher harmonic control (HHC) input by active trailing-edge flaps (ATEFs). Conventional individual blade control (IBC) input is redefined using N − 1/rev interblade phase lead, N/rev collective, and N + 1/rev interblade phase lag signals where 1/rev frequency modulation originates from the multiblade coordinate (MBC) transform. A Mach-scaled flap blade is designed and analyzed by the multibody dynamics analysis DYMORE. A linear time-invariant representation is identified from N/rev envelopes of the input and output responses obtained by DYMORE analysis. A matlab/simulink closed-loop control simulation is designed using the identified state-space realization. The N/rev vibratory loads are reduced up to 52% with flap deflections and the linear control results match well with the nonlinear responses obtained from DYMORE. Furthermore, the multivariable closed-loop stability estimated by the loop transfer functions using disk margin analysis reveals sufficient gain and phase margins.

Recently, studies on the control and aerodynamics of multirotor unmanned aircraft system (UAS) have been performed. However, some studies depend on methods that require significant computin...

The purpose of this paper is to develop a six degree-of-freedom flight simulation while considering the flexibility of an aircraft with high aspect ratio wings using by new quasi-steady temporal coupling scheme named ‘snapshot method’. The simulation was based on the quasi-steady temporal coupling scheme for the flow field, elastic structure, and rigid body motion problem. A full three-dimensional finite-element model of unmanned aerial vehicles was used. The object aircraft has main wings with an aspect ratio over 20 and a flight for long endurance in high altitude. To consider the flexibility of these aircraft, the present snapshot method was developed that combines ‘aerodynamic—structural dynamics—flight dynamics’ to analyze dynamic response. By applying this method, MATLAB/SIMULINK, which analyzes the rigid body motion, and MSC FlightLoads, which is responsible for aeroelastic trim analysis, was tightly linked into the present simulation framework. Using the present simulation, aircraft response under various maneuver conditions was simulated. First, the trim analysis for the level cruise was performed. Trim parameters, stability derivative coefficients, and the moment of inertia were also determined. Based on these results, the flight dynamics of the aircraft was simulated according to the operation of the rudder and the aileron control surface. The effect of the rigid and flexible body assumptions was also confirmed. In addition, these results were compared with other existing simulation results based on the multibody dynamics under the same conditions. To predict the response of the aircraft under the gust, the simulation was performed by applying the two-dimensional 1-cosine discrete gust profile. The important aspects, such as numerical prediction methods during stages of the highly flexible aircraft design process for a countermeasure to various challenging problems, were shown.

Wing flexibility affects the flight performance of flapping-wing micro air vehicles. In this paper, we present a computational approach for the aeroelastic analysis of realistic insect-like flexible flapping wings with hovering and forward-flight modes. A three-dimensional preconditioned Navier–Stokes solver is used with a deforming mesh technique for the aerodynamic analysis of a flapping wing. For the structural analysis, co-rotational (CR) finite elements and CR shell elements are used. As seen from the numerical analysis, wing flexibility leads to thrust increments with the increasing flapping frequency. The advance ratio, however, is the cause of the thrust decrease for flexible flapping wings with high flapping-frequency motions.

This paper introduces the comprehensive design of a thin piezoelectric-driven fin. Because of its hinge and flexible spar component having a low torsional stiffness with a thin composite actuator, ...

We develop a combined Lagrangian–Eulerian method for transient fluid–structure interaction problems. Based on the ghost fluid framework for improving interface tracking accuracy between a fluid (ho...

Purpose The purpose of this paper is to present the design, analysis and experiments of the active trailing-edge flap (Seoul National University Flap, SNUF) for vibration reduction in the helicopter rotor prior to the small-scale blades planned to test in a whirl tower. Design/methodology/approach The predictions of the hinge moment in both steady and unsteady flows were obtained through computational fluid dynamics calculations. When compared with the results originated from analytical formulations, the proposed method showed improved prediction capabilities. To validate the deflection of the flap under the centrifugal load by rotating, static analysis was conducted using both contact and rotating condition of MSC NASTRAN. The corresponding experiment also was performed using the vertical frame for simulating the effect of the centrifugal force. Findings The hinge moment of the flap is predicted through unsteady analysis in the actuation frequency of 3/rev. The material of the guide in the flap mechanism was selected through static analysis under both contact and rotating condition. Finally, reduction of the deflection occurred because of the load in the axial direction of the hinge like the centrifugal load. Practical implications The important aspects, such as design, analysis, and experiments for the active trailing-edge flap were shown. Originality/value This paper showed the relationship of the displacement, block force and voltage of the piezo-actuator, combined with the hinge moment predicted. The methodology and the experiment were presented for simulating the centrifugal force acting on the flap.