General Configuration Research Articles

Estimation of the Curie Temperature of Nickel Using a Simple Thermodynamic Analysis

An activity is described that uses simple materials and an easy-to-perform protocol to estimate the Curie temperature of nickel, which is the temperature at which nickel loses its ferromagnetism. To do so, an object made of nickel metal is heated with a lighter until it loses its ferromagnetism. The metal is allowed to drop into a beaker that contains a known amount of water at a known temperature. Thermodynamic analysis of the exchange of energy between the metal, water, and beaker allows for an estimate of the Curie temperature of nickel. The activity provides students with the opportunity to explore concepts commonly found in introductory and general chemistry curricula, including thermodynamics and electronic configurations of the elements.

Prediction of wall-pressure fluctuations for separating/reattaching flows applied to space launchers using zonal detached eddy simulation-based convolutional neural networks

Convolutional neural networks (CNNs) are used to predict the fluctuating wall-pressure coefficient and associated single-point pressure spectra in the separating/reattaching flow region around a generic space launcher configuration in the transonic regime. The neural networks are trained on a generic axisymmetric afterbody configuration. A Zonal Detached Eddy Simulation of a semi-realistic launcher geometry [NASA (National Aeronautics and Space Administration) model 11 hammerhead] is performed and validated using available experimental results. This configuration is used as a testing case for the trained models. It is shown that the CNNs are able to identify flow features related to physical phenomena of the flow. From this feature identification, the models are able to predict the evolution of fluctuating wall quantities and locate the regions of high pressure fluctuations. A scaling procedure is proposed to retrieve correct levels of the predicted quantities for a given unknown configuration having different free stream conditions. We also demonstrate that the present models perform well applied on Reynolds-Averaged Navier–Stokes mean flow fields, paving the way for a significant reduction in the computational cost for predicting wall-pressure fluctuations around space launchers.

Numerical Investigations on Low-Speed Aerodynamic Characteristics of Generic Unmanned Combat Aerial Vehicle Configurations

The leading-edge sweep angle significantly influences the flight performance of swept wings. The vortex flow structures affect the flow behavior of the moderate to highly swept wings, which form at low angles of attack because of leading-edge flow separation. This topic of investigation gained momentum due to its application to unmanned combat aerial vehicle (UCAV) configurations that are significantly affected by flow separation at high angles of attack. The present work investigates the flowfield and low-speed aerodynamic characteristics of the generic UCAV models with a constant and nonconstant leading-edge sweep for a wide range of angles of attack. The open-source computational fluid dynamics code OpenFOAM 8.0 is employed for the numerical simulations. The present numerical simulation results agree well with the experimental data in the literature. It is demonstrated that the lift and drag characteristics of the UCAV are sensitive to the leading-edge sweep angle, and a nonconstant leading-edge sweep angle variant exhibits delayed stall and enhanced aerodynamic performance.

DeapSea: Workflow-Supported Serious Game Design for Stroke Rehabilitation

The design and development of a serious game are complex due to different and often numerous stakeholders involved. Different guidelines for general best practices exist, but those are not specific and often do not include therapists or patients as essential stakeholders especially in the context of individualisation of a serious games. Although there are a lot of serious games in the area of (stroke) rehabilitation, design guidelines and indications of what is important are quite scarce. Identifying individualisation possibilities to adapt a serious game to the specific needs of patients was identified to support and improve the design and outcome of serious game development. A literature research and the analysis of previously designed serious games created the foundation for this research. The identified configuration possibilities, additional requirements, and the developed workflow were then evaluated with the gathered insights of therapists trough an online survey. 20 generic configuration possibilities for therapists, as well as seven requirements, were identified and are presented, which can be used when designing a serious game in the context of stroke. In addition a workflow, called “DeapSea” is proposed for supporting the design as well. These results should be used as an addition to already established design recommendations to deliver an adaptable and flexible serious game in the area of stroke—helping to fulfill individual patient needs from the point of therapists and other involved medical stakeholders within the rehabilitation process.

Analysis of near-interface cracks in three-dimensional anisotropic multi-materials by efficient BIEM

This paper presents the full analysis of near-interface cracks in three-dimensional linear elastic multimaterial bodies by a weakly singular boundary integral equation method (BIEM). The proposed technique was implemented in a general framework that allowed the treatment of finite cracked bodies with general configurations, material anisotropy, and mode-mixity. A system of integral equations governing unknown data on the boundary, crack surface, and material interface was established using a pair of weakly singular weak-form displacement and traction integral equations together with continuity along the material interface. A symmetric Galerkin boundary element method along with the finite element technique were implemented to solve the governing integral equations. In addition, the special near-front interpolation was employed to enhance the approximation of the relative crack-face displacement in the neighborhood of the crack front. The solved crack-face data were used directly to post-process the stress intensity factors and T-stresses along the crack front. An extensive numerical study was carried out not only to demonstrate the accuracy, convergence, and capability of the proposed technique, but also to explore the influence of material stiffness and distance to the material interface on fracture data along the crack front.

A Review on Photonic Sensing Technologies: Status and Outlook.

In contemporary science and technology, photonic sensors are essential. They may be made to be extremely resistant to some physical parameters while also being extremely sensitive to other physical variables. Most photonic sensors may be incorporated on chips and operate with CMOS technology, making them suitable for use as extremely sensitive, compact, and affordable sensors. Photonic sensors can detect electromagnetic (EM) wave changes and convert them into an electric signal due to the photoelectric effect. Depending on the requirements, scientists have found ways to develop photonic sensors based on several interesting platforms. In this work, we extensively review the most generally utilized photonic sensors for detecting vital environmental parameters and personal health care. These sensing systems include optical waveguides, optical fibers, plasmonics, metasurfaces, and photonic crystals. Various aspects of light are used to investigate the transmission or reflection spectra of photonic sensors. In general, resonant cavity or grating-based sensor configurations that work on wavelength interrogation methods are preferred, so these sensor types are mostly presented. We believe that this paper will provide insight into the novel types of available photonic sensors.

Towards a Hybrid Design Approach of Anchored Drapery Systems

Anchored drapery meshes represent a worldwide adopted protective solution against rockfall. The mechanical performance of a wire mesh is evaluated through laboratory procedures in which the boundary conditions strongly differ from the ones typical of field applications. This shows that the laboratory characterization is, in general, not representative of the field behavior. In this work, referring to a double-twisted wire mesh, a simple approach allowing the extension of the laboratory characteristic values to field conditions is proposed. The approach is based on the definition of analytical relations for evaluating the effects of both the mesh’s system geometry and the loading condition on the force–displacement response. These relations are derived from previously calibrated laboratory tests and are extended to different configurations on the basis of a large number of discrete element simulations. A master curve allowing the prediction of the entire force–displacement response of a general configuration of the drapery system is then defined. The results of this study can provide useful information for designing anchored drapery systems and can be easily associated with standard limit equilibrium calculations to move toward a hybrid design approach that couples forces with mesh deformations.

Continuous cross-modal hashing

Generally, multimodal data with new classes arrive continuously in the real world. While advanced cross-modal hashing (CMH) focuses primarily on batch-based data with previously observed classes (ASCs), it disregards the effect of newly arriving classes (ANCs) on hash-code conflicts. In addition, class-level continuous hashing scenarios do not suit themselves well with the generic CMH configuration. To solve the aforementioned issues, we propose a novel framework, called CT-CMH, for the new task of continuous cross-modal hashing. For dealing with ANCs, CMH models require the ability of continuous learning, i.e. they can preserve the knowledge of previously observed data and, more crucially, they can be adapted to unseen data with ANCs. Specifically, we introduce the adaptive weight importance updating (AWIU) mechanism to alleviate the catastrophic forgetting problem of CMH and a new hash-code divergence (HCD) method to eliminate hash-code conflicts between ASCs and ANCs. When CT-CMH is equipped with both AWIU and HCD, it can consistently achieve high retrieval performance. The experiment results and visualization analyses validate the effectiveness of our approach. To the best of our knowledge, we are the first to introduce and implement the task of CCMH for ANCs.

High responsivity mid-infrared indirect detection based on nonlinear crystal BaGa4Se7

Currently, non-oxide BaGa4Se7 crystal has been demonstrated as a superior nonlinear medium for both coherent mid-infrared (MIR) generation and up-conversion detection. By bridging the desired MIR region to the well-developed near-infrared devices, the latter addresses the drawbacks of traditional direct detection. Based on our recent report, a comprehensive study is conducted on the nonlinear optical up-conversion process to achieve high responsivity. An analytical model is developed and verified through experiment. Their measurement and calculation cover the relationship between the up-converted signal and the two input lights, the acceptable angle of detection crystal, and the responsivities at a wavelength ranging from 3 to 8 µm. The dependence of responsivity on experimental factors is indicated by the model. The present study provides a theoretical reference for the calibration and optimal design of this detection system, which can also be applied to other general MIR up-conversion configurations.

Morphological transformations of vesicles with confined flexible filaments

A fundamental understanding of cell shaping with confined flexible filaments, including microtubules, actin filaments, and engineered nanotubes, has been limited by the complex interplay between the cell membrane and encapsulated filaments. Here, combining theoretical modeling and molecular dynamics simulations, we investigate the packing of an open or closed filament inside a vesicle. Depending on the relative stiffness and size of the filament to the vesicle as well as the osmotic pressure, the vesicle could evolve from an axisymmetric configuration to a general configuration with a maximum of three reflection planes, and the filament could bend in or out of plane or even coil up. A plethora of system morphologies are determined. Morphological phase diagrams predicting conditions of shape and symmetry transitions are established. Organization of actin filaments or bundles, microtubules, and nanotube rings inside vesicles, liposomes, or cells are discussed. Our results provide a theoretical basis to understand cell shaping and cellular stability and to help guide the development and design of artificial cells and biohybrid microrobots.

Network Interface Program for Actuator Controllers for Pseudo-Dynamic Hybrid Simulation

ABSTRACT A network interface program for controllers (NICON) for pseudo-dynamic hybrid simulations is presented. The program is implemented as an independent program residing between the simulation model and an actuator controller with various functions necessary for hybrid simulations, such as communication, coordinate transformation, error compensation. These functions are generalized to allow for a generic configuration of actuator setup theoretically with any number of control points and control degrees of freedom. Application examples of NICON to hybrid simulations of civil infrastructures subjected to earthquakes or fire are presented.

Aerodynamic Drag of Road Vehicles in Close Lateral Proximity

<div class="section abstract"><div class="htmlview paragraph">Aerodynamic interaction between vehicles on a roadway can modify the fuel use and greenhouse gas emissions of the vehicle relative to their performance under isolated, uniform-wind conditions. A comprehensive wind-tunnel study was undertaken to examine changes to the aerodynamic drag experienced by vehicles in close proximity, in adjacent lanes. Wind-load measurements were conducted for two general configurations: 15%-scale testing with light-duty-vehicle (LDV) models, and 6.7%-scale testing with a heavy-duty vehicle (HDV) model. For the LDV study, a DrivAer model was tested with a proximate AeroSUV model or an Ahmed model at lateral distances representing 75%, 100%, and 125% of a typical highway lane spacing, and for longitudinal distances up to 2 vehicle lengths forward and back. Commensurate measurements were conducted for the AeroSUV model with the proximate DrivAer or Ahmed model. For the HDV study, a tractor-trailer model was tested with a single or combination of adjacent-lane models. Measurements were conducted over a range of yaw angles, permitting wind-averaged-drag evaluations.</div><div class="htmlview paragraph">Changes in drag coefficient on the order of 25% or more were observed, relative to isolated-vehicle conditions. Adjacent-lane proximity-vehicle effects can increase or decrease the drag of a vehicle, with the strongest effects being an increase when vehicle models are side-by-side or when an HDV has its aft end coincident with another vehicle. The LDV-model pairing demonstrated that, for a two-vehicle arrangement, the increased drag on one vehicle can be offset by the decrease in drag on the other, and that proximity-vehicle effects should be examined in the context of the overall vehicle-system performance.</div></div>

Simulation of Rotorcraft Fuselage with Rotor Effects Using An Immersed Boundary Method

Computational fluid dynamics simulations of the flow around the ROtor Body INteraction (ROBIN)-mod7 fuselage with pressure-sensitive paint rotor are conducted using an immersed boundary method and an actuator surface model in OpenFOAM. The ROBIN-mod7 fuselage is represented by the immersed boundary method, while the unsteady rotor is modeled using the actuator surface model. A comprehensive analysis of the generic helicopter configuration is carried out for the hovering flight condition; the isolated fuselage is simulated to provide its baseline aerodynamics, and the isolated rotor and rotor–fuselage cases are studied to measure the rotor performance in hover and the fuselage effect on the performance. The validation of each test case is conducted against both experimental measurements and computational data from the literature. The surface pressure data from the isolated fuselage case shows good agreement with the experimental measurements. Also, the rotor performance predicted on the isolated and installed rotors (rotor–fuselage) has excellent agreement with the reference data; in particular, the performance data on the installed rotor agree with the experimental data better than the previous numerical study does. The fuselage effect has been analyzed by comparing the isolated rotor and rotor–fuselage datasets. The computational effort for different grid levels of each test case is provided. Overall, the results have demonstrated an equivalent level of accuracy compared to the previous high-fidelity simulation results at their fraction of setup and computational expenses.

Echoes of the hexagon: Remnants of hexagonal packing inside regular polygons

We provide evidence that for regular polygons with σ = 6 j sides (with j = 2 , 3 , …), N ( k ) = 3 k ( k + 1 ) + 1 (with k = 1 , 2 , …) congruent disks of appropriate size can be nicely packed inside these polygons in highly symmetrical configurations, which apparently have maximal density for N sufficiently small. These configurations are invariant under rotations of π / 3 and are closely related to the configurations with perfect hexagonal packing in the regular hexagon and to the configurations with curved hexagonal packing (CHP) in the circle found a long time ago by Graham and Lubachevsky [“Curved hexagonal packings of equal disks in a circle,” Discrete Comput. Geometry 18(2), 179–194 (1997)]. The packing fraction, i.e., the portion of accessible volume (area) occupied by multiple solid objects, has a role in determining the properties of granular materials and fluids. At the basis of our explorations are the algorithms that we have devised, which are very efficient in producing the CHP and more general configurations inside regular polygons. We have used these algorithms to generate a large number of CHP configurations for different regular polygons and numbers of disks; a careful study of these results has made it possible to fully characterize the general properties of the CHP configurations and to devise a deterministic algorithm that completely ensembles a given CHP configuration once an appropriate input is specified.

A data-based reduced-order model for dynamic simulation and control of district-heating networks

This study concerns the development of a data-based compact model for the prediction of the fluid temperature evolution in district heating (DH) pipeline networks. This so-called “reduced-order model” (ROM) is obtained from reduction of the conservation law for energy for each pipe segment to a semi-analytical input–output relation between the pipe outlet temperature and the pipe inlet and ground temperatures that can be identified from training data. The ROM basically is valid for generic pipe configurations involving 3D unsteady heat transfer and 3D steady flow as long as heat-transfer mechanisms are linearly dependent on the temperature field. Moreover, the training data can be generated by physics-based computational “full-order” models (FOMs) yet also by (calibration) experiments or field measurements. Performance tests using computational training data for a single-pipe configuration demonstrate that the ROM (i) can be successfully identified and (ii) can accurately describe the response of the outlet temperature to arbitrary input profiles for inlet and ground temperatures. Application of the ROM to two case studies, i.e. fast simulation of a small DH network and design of a controller for user-defined temperature regulation of a DH system, demonstrate its predictive ability and efficiency also for realistic systems. Dedicated cost analyses further reveal that the ROM may significantly reduce the computational costs compared to FOMs by (up to) orders of magnitude for higher-dimensional pipe configurations. These findings advance the proposed ROM as a robust and efficient simulation tool for practical DH systems with a far greater predictive ability than existing compact models.

Optimising General Configuration of Wing-Sailed Autonomous Sailing Monohulls Using Bayesian Optimisation and Knowledge Transfer

Wing-sailed autonomous sailing monohulls are promising platforms used in various scenarios to provide data for marine science research. These platforms need to operate long-term in changing seas; their general configurations (size matching between sail, hull, and keel) necessitate careful trade-offs to balance safety and efficiency. Since autonomous sailboats are often designed for different observation missions, scientific pay-loads and target areas, their design space is considerably large. It is also challenging to obtain prior performance estimation from historical designs. Therefore, traditional offline surrogate-based simulation-driven design frameworks suffer from a large amount of sampling required, the computational cost of which remains too expensive for such ad hoc design tasks. This paper proposes an innovative, generalised simulation-driven framework combining Bayesian optimisation and knowledge transfer. It allows for high-quality, low-cost optimisation of autonomous sailing monohulls’ general configuration without initial design and prior performance estimation. The proposed optimisation framework has been used to optimise the ‘Seagull’ prototype within the design constraints. The optimised design exhibits significant performance improvements. At the same time, the results show that the present method is significantly superior to traditional offline methods. The authors believe that the proposed framework promises to provide the autonomous sailing community with a solution for a general design methodology.

Equilibrium states for the massive Sine-Gordon theory in the Lorentzian signature

In this paper we investigate the massive Sine-Gordon model in the ultraviolet finite regime in thermal states over the two-dimensional Minkowski spacetime. We combine recently developed methods of perturbative algebraic quantum field theory with techniques developed in the realm of constructive quantum field theory over Euclidean spacetimes to construct the correlation functions of the equilibrium state of the Sine-Gordon theory in the adiabatic limit. First of all, the observables of the Sine-Gordon theory are seen as functionals over the free configurations and are obtained as a suitable combination of the S−matrices of the interaction Lagrangian restricted to compact spacetime regions over the free massive theory. These S−matrices are given as power series in the coupling constant with values in the algebra of fields over the free massive theory. Adapting techniques like conditioning and inverse conditioning to spacetimes with Lorentzian signature, we prove that these power series converge when evaluated on a generic field configuration. The latter observation implies convergence in the strong operator topology in the GNS representations of the considered states. In the second part of the paper, adapting the cluster expansion technique to the Lorentzian case, we prove that the correlation functions of the interacting equilibrium state at finite temperature (KMS state) can be constructed also in the adiabatic limit, where the interaction Lagrangian is supported everywhere in space.

A transference principle for systems of linear equations, and applications to almost twin primes

The transference principle of Green and Tao enabled various authors to transfer Szemer\'edi's theorem on long arithmetic progressions in dense sets to various sparse sets of integers, mostly sparse sets of primes. In this paper, we provide a transference principle which applies to general affine-linear configurations of finite complexity. We illustrate the broad applicability of our transference principle with the case of almost twin primes, by which we mean either Chen primes or "bounded gap primes", as well as with the case of primes of the form $x^2+y^2+1$. Thus, we show that in these sets of primes the existence of solutions to finite complexity systems of linear equations is determined by natural local conditions. These applications rely on a recent work of the last two authors on Bombieri-Vinogradov type estimates for nilsequences.

Conditions of the Formation and Evolution of the Tjörnes Transform Zone on the Basis of Physical Modelling

The Tjörnes Transform Zone (TZ) is on the northern margin of Iceland, mostly in the shelf zone. It connects the Kolbeinsey spreading ridge and the Northern Rift Zone (RZ) of Iceland. The zone is complexly structured and comprises several heterochronous sections that evolved in various geodynamic conditions. The geodynamic conditions of the formation and evolution of the Tjörnes TZ were reconstructed by means of physical modelling. The models measured the thickness of the model lithosphere, displacement, and the overlapping between the spreading segments. Results of the modelling show that the Tjörnes TZ formed successively, in two stages. The first stage was the formation of the general configuration of the area of interaction of the extension centres of the Kolbeinsey Ridge and the Northern RZ of Iceland in the form of a small overlap of the spreading centres with a rotating block between them. At the second stage, one of the formed transtensional fault zones between the spreading centres became the feeder channel for a magma pulse of the Iceland Plume, which led to the formation of the Grímsey Oblique Rift (OR). Standing alone is the Húsavík-Flatey fault zone that might have formed under the influence of two at a time spreading segments, with the domination of the more magmatically active Northern Rift Zone.

An optimization framework for analyzing dual‐donor organ exchange

We study an optimal matching problem in the context of dual‐donor organ exchange, where a portion of two living donors' organs are transplanted to a single patient. This dual‐donor transplant technique is becoming more widespread for lung and liver transplants. However, multiple medical compatibility criteria pose a serious challenge for matching a patient with two compatible donors. In the United States and many other countries, laws prohibit commercial (for‐profit) deals for human organs, so donor exchanges are run by nonprofit organizations connecting donors with people in need of organs, with the goal of increasing transplant matches. We propose a simple chain mechanism in dual‐donor organ exchange to increase the number of patient–dual‐donor matches, which would maximize the number of patients receiving transplants. Based on this objective, we propose a general simple chain optimization framework for finding the maximum patient matching, taking into account multiple compatibility criteria (e.g., blood type and weight), and determine the complexity status of the problem. We provide theoretical results on the structures of simple chains, as well as a polynomial time algorithm to obtain the maximum patient matching simple chain with blood type compatibility. Through a numerical study for multiple compatibility criteria, we show that in many scenarios, a simple chain substantially increases the number of patients matched with dual donors for transplants, as opposed to exchange cycles. We also address the problem of maximizing the number of patients matched for dual‐donor organ transplants via two‐way and three‐way exchange cycles, subject to donors' and recipients' medical compatibility criteria, along with a discussion of their computational complexity. Finally, we characterize the general configurations of large n‐way exchange cycles and provide theoretical insights for their structural properties. Our findings provide general optimization models for dual‐donor organ exchange operators to increase the number of patients matched for transplant, given multiple compatibility criteria. In addition, we show how exchange operators, using simple chains, can increase patient matches and reduce simultaneous surgical resource requirements over exchange cycles.