General Configuration Research Articles

Analysis of rotorcraft ground resonance with generic inter-blade damper configurations

The paper investigates the effect of inter-blade dampers with generic in-plane and out-of-plane attachment offsets on ground resonance stability proneness. An analytical formulation, considering dampers with radial offsets only is initially proposed. Sensitivity analyses show that the increase of radial offset reduces the cyclic lead-lag damping and stiffness, providing a non-zero contribution to collective terms. The analytical formulation is suitable, in a preliminary design phase, to define the optimal location of the inter-blade attachment points to avoid ground resonance phenomena and to stabilize the engine drive-train dynamics. A more detailed numerical approach is then presented to consider generic in-plane and out-of-plane attachment offsets. Ground resonance stability analyses are performed also for cases with dissimilar dampers. It is found that out-of-plane offset leads to a modification on the blade pitch-lag coupling, acting on the helicopter stability margins. However, to capture these effects it is necessary to include the overall blade motions, considering flap, lag, and pitch dynamics, together with the corresponding generalized aerodynamics forces, usually neglected in classical ground resonance analysis. Finally, the periodic stability with one damper inoperative shows how, with the radial offsets, the hybridized lead-lag collective and cyclic modes may fall into resonance conditions due to super-harmonics.

Effective two-body approach to the hierarchical three-body problem: Quadrupole to 1PN

Many binary systems of interest for gravitational-wave astronomy are orbited by a third distant body, which can considerably alter their relativistic dynamics. Precision computations are needed to understand the interplay between relativistic corrections and three-body interactions. We use an effective field theory approach to derive the effective action describing the long time-scale dynamics of hierarchical three-body systems up to 1PN quadrupole order. At this level of approximation, computations are complicated by the backreaction of small oscillations on orbital time-scales as well as deviations from the adiabatic approximation. We address these difficulties by eliminating the fast modes through the method of near-identity transformations. This allows us to compute for the first time the complete expression of the 1PN quadrupole cross-terms in generic configurations of three-body systems. We numerically integrate the resulting equations of motion and show that 1PN quadrupole terms can affect the long term dynamics of relativistic three-body systems.

On polarization of spherical codes and designs

In this article we investigate the N-point min-max and max-min polarization problems on the sphere for a large class of potentials in Rn. We derive universal lower and upper bounds on the polarization of spherical designs of fixed dimension, strength, and cardinality. The bounds are universal in the sense that they are a convex combination of potential function evaluations with nodes and weights independent of the class of potentials. As a consequence of our lower bounds, we obtain the Fazekas-Levenshtein bounds on the covering radius of spherical designs. Utilizing the existence of spherical designs, our polarization bounds are extended to general configurations. As examples we completely solve the min-max polarization problem for 120 points on S3 and show that the 600-cell is universally optimal for that problem. We also provide alternative methods for solving the max-min polarization problem when the number of points N does not exceed the dimension n and when N=n+1. We further show that the cross-polytope has the best max-min polarization constant among all spherical 2-designs of N=2n points for n=2,3,4; for n≥5, this statement is conditional on a well-known conjecture that the cross-polytope has the best covering radius. This max-min optimality is also established for all so-called centered codes.

Micromagnetic frequency-domain simulation methods for magnonic systems

We present efficient numerical methods for the simulation of small magnetization oscillations in three-dimensional micromagnetic systems. Magnetization dynamics is described by the Landau–Lifshitz–Gilbert equation, linearized in the frequency domain around a generic equilibrium configuration, and formulated in a special operator form that allows leveraging large-scale techniques commonly used to evaluate the effective field in time-domain micromagnetic simulations. By using this formulation, we derive numerical algorithms to compute the free magnetization oscillations (i.e., spin wave eigenmodes) as well as magnetization oscillations driven by ac radio-frequency fields for arbitrarily shaped nanomagnets. Moreover, semi-analytical perturbation techniques based on the computation of a reduced set of eigenmodes are provided for fast evaluation of magnetization frequency response and absorption spectra as a function of damping and ac field. We present both finite-difference and finite-element implementations and demonstrate their effectiveness on a test case. These techniques open the possibility to study generic magnonic systems discretized with several hundred thousands (or even millions) of computational cells in a reasonably short time.

Development ofLacuna pallidula(da Costa, 1778) from the White Sea (Caenogastropoda: Littorinimorpha) with emphasis on radula formation

ABSTRACTThe gastropod radula is highly diverse in structure in comparison with that of other mollusсs. The main radular types in the different phylogenetic groups of gastropods differ not only in the general morphology and configuration of the teeth but also in the mode of tooth synthesis and the ultrastructure of the formation zone. Previously, the formation and anlage of the radula in the ontogeny of radulae of all major phylogenetic gastropods groups have been studied, with the exception of the taenioglossan radula of Caenogastropoda. The data obtained in this study on the radular anlage and synthesis in one littorinimorph species Lacuna pallidula supplement the existing knowledge of diversity in gastropod radula formation. The radula is initially formed at the stage of the post-torsion veliger, with five teeth in each transverse row, and acquires the adult morphology before hatching from the egg mass. The larval radula is synthesized by a few morphologically uniform cells in the radular sac. Synthesis of the adult radula also occurs at the blind end of the radular sac, where groups of numerous odontoblasts each form one tooth, and membranoblasts, located on the ventral side, form the membrane. Characteristic features of the adult radular sac are an additional supporting cartilage-like structure at the radula curve in the middle of the radular sac, a well-defined proliferation zone in the zone of radula formation and the presence of an additional extracellular matrix around the teeth in the maturation zone.

Driven Tracer in the Symmetric Exclusion Process: Linear Response and Beyond.

Tracer dynamics in the symmetric exclusion process (SEP), where hard-core particles diffuse on an infinite one-dimensional lattice, is a paradigmatic model of anomalous diffusion. While the equilibrium situation has received a lot of attention, the case where the tracer is driven by an external force, which provides a minimal model of nonequilibrium transport in confined crowded environments, remains largely unexplored. Indeed, the only available analytical results concern the means of both the position of the tracer and the lattice occupation numbers in its frame of reference and higher-order moments but only in the high-density limit. Here, we provide a general hydrodynamic framework that allows us to determine the first cumulants of the bath-tracer correlations and of the tracer's position in function of the driving force, up to quadratic order (beyond linear response). This result constitutes the first determination of the bias dependence of the variance of a driven tracer in the SEP for an arbitrary density. The framework presented here can be applied, beyond the SEP, to more general configurations of a driven tracer in interaction with obstacles in one dimension.

Proposing a Small-Scale Digital Twin Implementation Framework for Manufacturing from a Systems Perspective

Due to the fourth industrial revolution, manufacturing companies are looking to implement digital twins in their factories to be more competitive. However, the implementation of digital twins in manufacturing systems is a complex task. Factories need a framework that can guide them in the development of digital twins. Hence, this article proposes a small-scale digital twin implementation framework for manufacturing systems. To build this framework, the authors gathered several concepts from the literature and designed a digital twin subsystem model using a model-based systems engineering (MBSE) approach and the systems engineering “Vee” model. The systems modelling defines the digital twin components, functionalities, and structure. The authors distribute most of these concepts throughout the framework configuration and some concepts next to this general configuration. This configuration presents three spaces: physical, virtual, and information. The physical space presents a physical layer and a perception layer. The information space has a single layer called middleware. Finally, the virtual space presents two layers: application and model. In addition to these layers, this framework includes other concepts such as digital thread, data, ontology, and enabling technologies. This framework could help researchers and practitioners to learn more about digital twins and apply it to different domains.

Multidisciplinary Optimization and Analysis of Stratospheric Airships Powered by Solar Arrays

Stratospheric airships have much potential in military and commercial applications. Design, analysis and optimization of stratospheric airships involves complex trade-off of different disciplines, and hence a multidisciplinary approach is essential. This paper describes a methodology coupling several disciplines and involving seven design variables to obtain the optimal design of a stratospheric airship powered by solar arrays. A numerical method is established to calculate the output power of the solar array in the optimization process. The optimal solutions are obtained using hybrid algorithms. The methodology can obtain the optimal envelope shape, solar array layout and other general configurations of subsystems. Results show that the methodology was able to achieve a solution with a 19.2% reduction in airship volume compared to the value being part of an arbitrary initial set of airship parameters. In addition, a comparative study is carried out to highlight the importance of considerations of solar array layouts and array circumferential location. Furthermore, detailed sensitivity analysis shows that operating parameters of latitudes, heading angles and average resisting wind speeds have significant effects on the airship design and solar array layouts.

High-Resolution Bistatic Spotlight SAR Imagery With General Configuration and Accelerated Track

High-Resolution Bistatic Spotlight SAR Imagery With General Configuration and Accelerated Track

Wing rock mode and its mechanism of a flying-wing aircraft

The flying wing is an aerodynamic configuration with high efficiency, but the lack of lateral-directional stability has always been an obstacle that limits its application. In this study, the wing rock motion of a 65° swept flying-wing aircraft is studied via wind tunnel experiments and numerical simulations at a low speed, and various unsteady motion phenomena are focused on. Both the experimental and numerical results show that the flying wing has a bicyclic ${C_l}$ – $\phi $ hysteresis loop during its wing rock, different from the slender delta wing, rectangular wing, generic aircraft configuration, etc., which have a tricyclic hysteresis loop. This form of hysteresis loop implies a different energy exchange manner of the flying wing in the wing rock oscillation. Further analysis shows that the flying wing forms a unilateral leading-edge vortex (LEV) under a high roll angle, with its wing rock oscillation driven by the ‘vortex–shear-layer’ structure, which is different from that of slender and non-slender delta wings. Moreover, the quantitative dynamic hysteresis characteristics of the LEV's strength and location for the flying wing and the slender delta wing are also different. These results have proven the existence of a wing rock mode which is different from previous investigations, which enriches the understanding of self-induced oscillation. Present discoveries are also conducive to the aerodynamic shape design and flight manipulation of a flying-wing aircraft, which is significant for its wider application.

Noise Prior Knowledge Informed Bayesian Inference Network for Hyperspectral Super-Resolution.

Well-known deep learning (DL) is widely used in fusion based hyperspectral image super-resolution (HS-SR). However, DL-based HS-SR models have been designed mostly using off-the-shelf components from current deep learning toolkits, which lead to two inherent challenges: i) they have largely ignored the prior information contained in the observed images, which may cause the output of the network to deviate from the general prior configuration; ii) they are not specifically designed for HS-SR, making it hard to intuitively understand its implementation mechanism and therefore uninterpretable. In this paper, we propose a noise prior knowledge informed Bayesian inference network for HS-SR. Instead of designing a "black-box" deep model, our proposed network, termed as BayeSR, reasonably embeds the Bayesian inference with the Gaussian noise prior assumption to the deep neural network. In particular, we first construct a Bayesian inference model with the Gaussian noise prior assumption that can be solved iteratively by the proximal gradient algorithm, and then convert each operator involved in the iterative algorithm into a specific form of network connection to construct an unfolding network. In the process of network unfolding, based on the characteristics of the noise matrix, we ingeniously convert the diagonal noise matrix operation which represents the noise variance of each band into the channel attention. As a result, the proposed BayeSR explicitly encodes the prior knowledge possessed by the observed images and considers the intrinsic generation mechanism of HS-SR through the whole network flow. Qualitative and quantitative experimental results demonstrate the superiority of the proposed BayeSR against some state-of-the-art methods.

Impact of Malfunction Load Cell and Mechanical actuator Sensor to Performance of Ship Stability General Cargo Simulator at Unit Laboratorium and Workshop STIP Jakarta

Ship Stability General Cargo Simulator (SSTS) is a laboratory to provide training on the configuration and procedures for maintaining ship stability as a training facility for cadets in the engineering field. The Ship Stability General Cargo Simulator configuration at STIP Marunda Jakarta describes a general cargo ship configuration in which it has equipment to simulate cargo loading and ship ballast filling, which serves to simulate ship conditions when loading cargo. Maintenance and repair are activities carried out to improve, maintain, and return equipment in good and ready-to-use condition. In relation to the maintenance of laboratory equipment, maintenance is intended as a preventive effort or prevention so that the equipment is not damaged or is maintained in good condition, ready to operate. Besides that, maintenance is also intended as an effort to adjust or repair laboratory equipment that has already been damaged or is not feasible so that it becomes ready to be used for practical activities for students or cadets. Some of the maintenance that needs to be done on this Ship Stability Simulator are: Electrical system, Filling System, Drain System, Actuator System, Measurement Level System. Research purposes: The research objectives of this paper that make this is to obtain solutions so that maintenance and repairs can operate properly, viability of laboratory facilities as training infrastructure in the STIP Marunda Jakarta environment, always in a state of optimal use.

Controlling a combined polymer fuel cell and directional battery system maintaining efficiency at the optimum point

In this paper, a hybrid polymer fuel cell system with a lead-acid battery has been explored, so that the battery is designed to support the fuel cell system in providing the power needed for the load as well as storing additional energy. The battery is used to maintain the efficiency of the SOC battery. From a constant power strategy for a fuel cell and managing the fuel at the optimum operating point, to reducing the voltage load on the battery and reducing the instantaneous current load on the fuel cell in use. The general configuration of the hybrid system includes a polymer fuel cell followed by a boost converter, as well as a lead-acid battery pack, after which a bidirectional converter to control the power of the battery in charge and discharge mode. It's in the system. According to the simulation, it has been observed that the power contribution between the fuel cell and the battery is well suited to load changes, and the fuel cell always produces a constant power to charge the battery and power the load. It is protected from any kind of load fluctuation and interference.

Numerical investigation of AdBlue film formation and NH3 conversion in generic SCR system using Eulerian stochastic fields method

In this paper, the Eulerian stochastic fields (ESF) method in a LES framework is applied to a generic selective catalytic reduction (SCR) configuration in order to retrieve seamlessly the effect of turbulence–chemistry interaction on the NH3-conversion and AdBlue film formation. The ESF method is based on the transport equation of a joint scalar filtered density function. The injection of AdBlue and relevant spray dynamics are modeled by the Lagrange-particle description where a computational parcel represents a cluster of real AdBlue droplets. Owing to the low injection pressure, weak atomization of AdBlue leads to intense droplet wall-impingement and film formation on the SCR duct wall and/or on the mixer elements, if present. A 2-D thin film approach is adopted to model the film formation and dynamics in combination with multi-regimes droplet–wall interaction model. After verification tasks against the reference data for simple gas phase reactive cases, the verified ESF method is coupled with a one-equation based LES turbulence model together with the Lagrange particle-tracking which is combined with the 2-D thin film approach to simulate the AdBlue injection and the film formation in the generic SCR configuration. At first, the assessment of the adopted LES mesh is carried out in terms of the so-called LES quality of index to determine the optimal mesh resolution. Next, to ensure the convergence with respect to the number of required ESF and mesh resolution, SCR simulations are performed by using various (2, 4, 6, 8, 12 and 16) stochastic fields and also with refined mesh. Thereby, the sensitivity of the predictive capability of the numerical tool is evaluated for the production of NH3 and HNCO with and without ESFs. This clearly indicates the importance of an accurate description of the turbulence–chemistry interaction to retrieve reliably the conversion of NH3. Finally, the film dynamics especially the evolution of the film thickness described with six required ESF and without ESF is compared with experimental data from the generic SCR configurations. To further demonstrate the potential of suggested numerical approach, a detailed numerical analysis is provided in terms of spray-impingement dynamics, scalar uniformity index, droplet life time and characteristics of the droplets prone to form solid deposits in the monolith channel.

A Linear Hypergraph Extension of Turán's Theorem

An $r$-uniform hypergraph is linear if every two edges intersect in at most one vertex. Given a family of $r$-uniform hypergraphs $\mathcal{F}$, the linear Turán number ex$_r^{lin}(n,\mathcal{F})$ is the maximum number of edges of a linear $r$-uniform hypergraph on $n$ vertices that does not contain any member of $\mathcal{F}$ as a subgraph.
 Let $K_l$ be a complete graph with $l$ vertices and $r\geq 2$. The $r$-expansion of $K_l$ is the $r$-graph $K_l^+$ obtained from $K_l$ by enlarging each edge of $K_l$ with $r-2$ new vertices disjoint from $V(K_l)$ such that distinct edges of $K_l$ are enlarged by distinct vertices. When $l\geq r \geq 3$ and $n$ is sufficiently large, we prove the following extension of Turán's Theorem $$ex_{r}^{lin}\left(n, K_{l+1}^{+}\right)\leq |TD_r(n,l)|,$$ with equality achieved only by the Turán design $TD_r(n,l)$, where the Turán design $TD_r(n,l)$ is an almost balanced $l$-partite $r$-graph such that each pair of vertices from distinct parts are contained in one edge exactly. Moreover, some results on linear Turán number of general configurations are also presented.

Destination imagination: Development of the octomodal mental imagery (OMI) scale

This article introduces and develops a comprehensive scale named Octomodal Mental Imagery (OMI) to measure various aspects of imagination and prospection. OMI is developed and validated by conducting three rigorous studies and six data collections. In the first study, using the phenomenology approach, a detailed internal experience of the imagination process was carefully recorded. In the second study, the potential manifest variables to measure imagination/prospection were developed and a general configuration of the questionnaire was determined. In the third study, through three data collections, two versions of long (original) and short OMI were thoroughly screened, refined, and validated. Furthermore, from the measurement and structural perspectives, the conceptualization of imagination was compared to prospection. Our results substantiate OMI as a reliable and valid scale to be used in and out of hedonic consumption contexts.

Design of a Robot for Inspecting the Multishape Pipeline Systems

Aiming at the question that most of the existing pipeline robots can only move in parts of common pipeline environments, in this study, we introduce a novel pipeline robot configuration with excellent environmental adaptability and obstacle avoidance capability for inspecting a more complex pipeline system. To ensure adaptability and mobility, the pipeline robot's general configuration was divided into three parts: the head, waist, and tail, with axisymmetric and planar symmetric structural distributions. Two active articulated joints connect the three sections of the pipeline robot, driving the head and tail to complete yaw and roll motions and allowing the pipeline robot to avoid raised obstacles and broken gaps. Furthermore, the pipeline robot can travel through annular gaps, straight pipelines with different diameters, and funnel-type pipelines due to the combination of scissor mechanism legs and a caterpillar track. Finally, a pipeline robot with the configuration and test bed with six common pipeline environments was built, and the obstacle avoidance ability and environmental adaptation experiments were conducted to evaluate the movement effectiveness. According to the experimental results, the pipeline robot can navigate smoothly within a complex pipeline environment. The pipeline robot in this setup has considerable potential in the real world.

The travelling salesman problem with positional consistency constraints: An application to healthcare services

In this paper we study the Consistent Traveling Salesman Problem with positional consistency constraints (CTSP), where we seek to generate a set of routes with minimum cost, in which all the clients that are visited in several routes require total positional consistency, that is, they need to appear in the same relative position in all the routes they are visited in. This problem was motivated by a scheduling application in healthcare. We present several compact formulations for the CTSP, which have been adapted from models known from the Time-dependent TSP (TDTSP) literature, and propose a new model, which is an aggregated version of a model adapted from the TDTSP. A preliminary computational experiment allowed us to identify the three most competitive models. These models were then evaluated in more detail, first through a set of instances with 2, 3 or 5 routes and characteristics that derive from an healthcare application; and second through a set of tests with 5 routes and seven different and more general consistency configurations. The computational results show that for consistency configurations in which the consistent nodes appear in all, or most, of the routes, the new aggregated model can outperform the best model adapted from the literature. For the cases where the consistent nodes appear in fewer routes or less frequently, the original time-dependent model is more efficient.

Research Initiative for Numerical and Experimental Studies on High-Speed Stall of Civil Aircraft

The aerodynamics of transport aircraft at the borders of the flight envelope is characterized by complex interactions and nonlinear, unsteady flow phenomena. The underlying physical mechanisms are not fully understood, and a prediction of aerodynamic properties, transient loads, and aeroelastic behavior is a major challenge that requires the use of sophisticated numerical models and dedicated experiments. A new research initiative investigates the three-dimensional buffet mechanisms at high-speed stall, the interaction of the wing wake with the empennage, and the influence of ultra-high-bypass-ratio-type engines on these phenomena. It comprises unsteady pressure-sensitive paint surface pressure and time-resolved particle image velocimetry flowfield measurements carried out in the cryogenic European Transonic Windtunnel. The experiments are conducted at different Mach numbers and cover a broad Reynolds number regime up to using the generic Airbus XRF1 configuration as a reference. This paper explains the rationale of the research initiative, introduces the planned test entries and test conditions, and presents selected results of the first measurement campaign and associated numerical analyses by means of the computational fluid dynamics code TAU, including usage of locally scale resolving simulations. An analysis of numerical and experimental results is presented for a high incidence transonic condition that serves to discuss the topology of wing root flow separation, the evolution of the associated wake, and its interaction with the empennage.

Orientation Workspace Analysis and Parameter Optimization of 3-RRPS Parallel Robot for Pelvic Fracture Reduction

Abstract For parallel robots with general configuration, it is difficult to achieve the large rotation range requirement for pelvic fracture reduction. Application-based workspace optimization is important. In this paper, a 3-revolute-revolute-prismatic-spherical (3-RRPS) parallel robot with optimized parameters is studied, which can offer a large orientation workspace and relatively compact configuration. The inverse kinematics of the robot is analyzed by the closed-loop vector method. The cylindrical coordinate searching algorithm and boundary extraction method are adopted to calculate the orientation workspace. Defining the comprehensive branch length (CBL) to express robot’s compactness under the premise of satisfying the required orientation workspace. The genetic algorithm (GA) is adopted to optimize structural parameters of the robot with CBL as the objective function. The optimization results show that when the orientation angles of the moving platform are limited to not less than 28 deg, the CBL of the robot is 291 mm. Finally, the virtual prototype simulation verification shows that the orientation angles of the moving platform around x-axis and y-axis can reach ±28 deg, the orientation angle around z-axis can reach ±40 deg, which meets the requirements of the rotational range for pelvic fracture reduction surgery.