Box Geometry Research Articles

Assessment of the Aerodynamic and Aeroelastic Performance of Long-Span Twin-Box Bridges Based upon Multidimensional Surrogate Models

Twin-box decks are being extensively used in the design of long-span bridges due to their superior flutter performance. Although the significant role played by the gap distance has been previously addressed in the frame of experimental studies, there is still a lack of understanding about the complex interplay between box geometry, gap distance and the aerodynamic force coefficients and flutter derivatives. In the present work, firstly, a surrogate model is developed, considering three design inputs for the geometry of the deck along with the angle of attack, providing the force coefficients as output. Afterwards, the work is then extended by developing another surrogate model, considering as inputs the reduced velocity and the same geometric variables of the deck, with the outputs being the flutter derivatives. The methodology, comprising the selection of the design domain, the definition of the samples, the CFD-based evaluation of the samples' response and the construction of the surrogate through the application of the neural network-based radial basis method, is reviewed. The surrogate models enable a quantitative description of the impact caused in the force coefficients and the flutter derivatives by modifications in the geometry of the twin-box deck. It has been found that flutter derivatives H1*, H2* and A2* are strongly dependent on the gap distance.

The LSU-Argonne conversion electron spectrometer: A new detector for the X-Array and SATURN decay station

A new conversion electron detector has been commissioned at the ATLAS/ CARIBU facility at Argonne National Laboratory. The LSU-Argonne Conversion Electron Spectrometer (LACES) is a LN2-cooled Si(Li) detector system designed to be incorporated into a decay station that comprises the dedicated HPGe clover array with a box geometry (X-Array) and the Scintillator and Tape Using Radioactive Nuclei (SATURN) device. This integration enables simultaneous measurements of conversion electrons and gamma-rays in decay experiments, yielding novel information on transition multipolarities, electric monopole transitions, and isomeric states that decay mostly via conversion electrons. A measurement of the energy resolution of LACES yielded 2.3-keV FWHM at 975 keV for electrons and 1.3-keV FWHM at 75 keV for X-rays. A detailed study of the absolute detection efficiency (at 5 mm from the source) was performed, where this quantity was determined experimentally in the range of electron transition energies between 25.5 keV and 1047.8 keV and subsequently simulated using the GEANT4 code. Measurement and simulations are found to be in excellent agreement. A precise characterization, for this type of detector system, of the absolute detection efficiency for such a wide energy range is reported for the first time.

An OrthoBoXY-method for various alternative box geometries.

We have shown in a recent contribution [Busch and Paschek, J. Phys. Chem. B, 2023 127, 7983-7987] that for molecular dynamics (MD) simulations of isotropic fluids based on orthorhombic periodic boundary conditions with "magical" box length ratios of Lz/Lx = Lz/Ly = 2.7933596497, the computed self-diffusion coefficients Dx and Dy in x- and y-direction become system size independent. They thus represent the true self-diffusion coefficient D0 = (Dx + Dy)/2, while the shear viscosity can be determined from diffusion coefficients in x-, y-, and z-direction, using the expression η = kBT·8.1711245653/[3πLz(Dx + Dy - 2Dz)]. Here we present a more generalized version of this "OrthoBoXY"-approach, which can be applied to any orthorhombic MD box of any shape. In particular, we would like to test, how the efficiency is affected by using a shape more akin to the cubic form, albeit with different box length ratios Lx/Lz ≠ Ly/Lz and Lx < Ly < Lz. We use NVT and NpT simulations of systems of 1536 TIP4P/2005 water molecules as a benchmark and explore different box geometries to determine the influence of the box shape on the computed statistical uncertainties for D0 and η. Moreover, another "magical" set of box length ratios is discovered with Ly/Lz = 0.57804765578 and Lx/Lz = 0.33413909235, where the self-diffusion coefficient in x-direction becomes system size independent, such that D0 = Dx.

3-D scanned oven geometry improves the modeling accuracy of the solid-state microwave heating process

Solid-state-based microwave ovens are promising to mitigate the non-uniformity issue for their precise controlled microwave parameters. Multiphysics modeling is a useful tool for understanding complicated microwave heating processes. However, previous models using simple or manually measured oven geometry had challenges in accurately predicting the heating patterns. This study developed a 3-D scanning approach to characterize the accurate geometric details of the cavity and incorporate it in the multiphysics modeling of solid-state microwave heating. The effect of oven geometric details on modeling accuracy was evaluated for models using the simple box, manually measured, and 3-D scanned geometries at multiple microwave frequencies and port locations. A quantitative approach was also developed to replace the previously often-used qualitative approach to compare the spatial temperature profiles between the simulation and experiments. The Multiphysics-based models using 3-D scanned geometry showed significantly or considerably smaller RMSE values (1.57 to 4.11 °C) than the models with simple box geometry (1.73 to 6.33 °C) and manually measured geometry (1.48 to 4.66 °C) at most heating scenarios. The 3-D scanned approach can accurately incorporate the irregular geometric details of the oven cavity and can improve the prediction accuracy of microwave heating models for future food products and oven development.

OrthoBoXY: A Simple Way to Compute True Self-Diffusion Coefficients from MD Simulations with Periodic Boundary Conditions without Prior Knowledge of the Viscosity.

Recently, an analytical expression for the system size dependence and direction-dependence of self-diffusion coefficients for neat liquids due to hydrodynamic interactions has been derived for molecular dynamics (MD) simulations using orthorhombic unit cells. Based on this description, we show that for systems with a "magic" box length ratio of Lz/Lx = Lz/Ly = 2.7933596497 the computed self-diffusion coefficients Dx and Dy in the x- and y-direction become system-size independent and represent the true self-diffusion coefficient D0 = (Dx + Dy)/2. Moreover, by using this particular box geometry, the viscosity can be determined with a reasonable degree of accuracy from the difference of components of the diffusion coefficients in x-, y-, and z-directions using the simple expression η = kBT × 8.1711245653/[3πLz(Dx + Dy - 2Dz)], where kB denotes Boltzmann's constant and T represents the temperature. MD simulations of TIP4P/2005 water for various system sizes using both orthorhombic and cubic box geometries are used to test the approach.

DEM simulations on the influence of carbonate precipitation on liquefaction mitigation of sand

Microbially induced carbonate precipitation (MICP) is an effective method to mitigate liquefaction of sands under cyclic shear loading. In this paper, discrete element method (DEM)-based simulations of the cyclic direct simple shear (CyDSS) tests are carried out using a three-dimensional shear box geometry to evaluate the liquefaction resistance of untreated, MICP-cemented, and reconstituted sands. A six-parameter contact model previously used for undrained and drained triaxial tests on sand is used in the DEM analysis. Verification and validation of the DEM model is implemented through modeling of experimental CyDSS results on loose Fraser River sand at several values of cyclic stress ratios (CSR). The DEM model parameters for untreated and microbially treated Ottawa 20–30 sand are obtained by matching the simulated deviatoric stress and excess pore pressure from strain-controlled undrained isotopically consolidated triaxial compression tests. The DEM model is shown to be capable of accurately representing the cyclic strength curves for untreated, treated, and treated but reconstituted sand using parameters derived from the triaxial test data. The simulated stress path, shear strain evolution, and the evolution of coordination number are used to further examine the effect of MICP on liquefaction in CyDSS tests. The DEM model can be used to design cementation levels and develop cyclic strength curves for different types of sands to aid engineers in designing liquefaction mitigation strategies using MICP.

A Simplified Dynamic Strength Analysis of Cardboard Packaging Subjected to Transport Loads.

The article presents a simplified method for determining the strength of corrugated board packaging subjected to dynamic transport loads. The proposed algorithm consists of several calculation steps: (1) a static analysis of the compressive strength of the package, (2) an analysis of random vibrations in the frequency domain used to determine the resonance frequencies and (3) a dynamic analysis of the package loaded with computed resonant frequencies. For this purpose, numerical models of the static compression test of the packaging before and after the dynamic analysis of the package subjected to general transport loads were developed. In order to validate the model, laboratory packaging compression tests were also performed for samples of boxes using three-layer cardboard. Due to this, it was possible to verify the numerical simulation results of the compression tests for several box geometries. This, in turn, allowed for the development of a method based on dynamic and post-dynamic (static) numerical analyses, permitting a high-accuracy determination of the resistance of the selected packaging to vibrations and dynamic loads. The results of the (experimentally validated) numerical analysis proved the usefulness of the simplified method presented herein for precise estimation of the load capacity of various packages dynamically loaded during transport.

82‐3: Rapid AR/VR Device Eye‐Box Measurement Using a Wide‐FOV Lens

We present a method to rapidly and accurately measure the eye box of Augmented Reality (AR) and Virtual Reality (VR) eyewear. We demonstrate that this rapid method measures the eye box with a fidelity comparable to slower, traditional methods. The presented rapid method uses a lens that mimics the human eye in core aspects like pupil position, pupil size and field of view to get an impression of the eyewear performance as it appears to a human user with single image capture. By combining as few as three such image captures with such a lens, one can rapidly and accurately measure the entire eye box geometry of any given AR or VR eyewear. We further demonstrate the advantages of adopting this new method by referencing the display metrology industry, where this method has already been adopted as the new metrology standard.

FixBox: A General Algorithm to Fix Molecular Systems in Periodic Boxes.

Periodic boundary conditions (PBCs) are a standard feature of molecular simulations, and their mathematical and computational aspects are well-understood and relatively straightforward. However, they can in practice be a nuisance when simulating heterogeneous systems, especially when different types of molecules change their relative positions during the simulation. Although the translation required to fix a broken molecular complex of interest can in most cases be easily inferred by visual inspection, it typically depends on the type of system, its configuration, and the box geometry, making automated procedures problematic. We present here a general algorithm, named FixBox, that can fix a molecular complex of interest from a minimal set of definitions of its assembling parts and intended arrangement in the simulation box. It uses a unified triclinic framework for the box geometric periodicity, does not require a full molecular topology, and is applicable to various types of systems and configurations, making it possible to fully and easily automate the fixing of a broken molecular complex. The performance of the algorithm is illustrated with problematic configurations of various types of simulated systems. The presented formal framework can generally be useful for algorithms that need to perform geometrical transformations on systems with PBCs.

Desain Iterasi Dudukan Pelat Pengukur Gaya Pada RIG Alat Uji Jatuh Bebas Menggunakan Optimasi Topology

Abstract -. This research was conducted based on data obtained during testing at LAPAN (Lembaga Antariksa dan Penerbangan Nasional), where there was a case that became a concern. The test is about the free fall test, which results in a deflection that is considered too large. From these results it was decided to investigate further. This free fall test uses impact testing where a material is measured for its shock load resistance. Impact testing simulates the operating conditions of a material where the loading that occurs is not only in static conditions but also occurs in dynamic conditions. In the free fall test, a test was carried out to measure and see the resistance of the landing gear and crash box in receiving dynamic loads, when the aircraft landed. The main purpose of simulating this tool is for research and development of the free fall test equipment itself, as well as the design of the landing gear of the LSU (Lapan Survaillance UAV) drone in the future. The impact platform on the free fall test equipment plays an important role in impact testing, where the deformation of the plate holder will be converted by the load cell, into a signal received by the acquisition system. So it is designed to fit the existing needs. In this test equipment, the test object is given a load (50 kg and 200 kg), height (4.72 m and 1,204 m), so that it reaches a velocity (9,623 m/s and 4,861 m/s) with impactor crash box geometry and main landing gear as well as plate holder design based tools in the field. Based from testing, impact, and analysis using the finite element method in this study, it was found that the deflection value was 1.771 mm which reduced 94.61% for the crash box case and the deflection value was 2.696 mm with a reduction value of 87.85 % for the main landing gear case from the existing initial design.&#x0D; Keywords: Free fall test equipment, impact platform, landing gear, plate mount, main landing gear, crash box, finite element method, LSU.

Robust design assessment of automotive crash box structures through model order reduction

The research work is focused on a comprehensive study of crashworthiness parameters associated with widely used crash box components of passenger cars. The finite-element models representing the automotive crash box structure were procured from full-car digital models issued by NHTSA. From the full car model, the crash box geometry is extracted for the crash analysis and further design optimizations. The crashworthiness parameters such as energy absorption, crush force efficiency, specific energy absorption is studied in detail with analytical and finite-element solutions for each variant and are further enhanced using multi-objective design optimization through RSM-based DOE methods. For guiding engineers in real- time design exploration and other parametric assessments, a reduced-order model for each of the variants was developed by using the sPGD (sparse Proper Generalised Decomposition) method. The developed reduced order models of the crash boxes were able to accurately capture the non-linearities associated with them and delivered accuracy of 90%. On undergoing robust design assessment with crash box designs, taking into account of all variants, an average of 34.33% in energy absorption capacity was achieved. The heavier crash box variants which had good SEA capacity are performed for successful mass reduction of 18.91% without affecting their crash performance. For the explicit crash simulations, the virtual performance solution finite-element solver from the ESI group is utilized.

Soil-Structure Interaction of Flexible Temporary Trench Box: Parametric Studies Using 3D FE Modelling

This paper presents the results of two parametric finite-element studies that were carried out using the PLAXIS-3D finite element (FE) computer code. The following objectives and corresponding parameters were considered: (i) to evaluate the soil pressure on the steel trench box shield; the parameters studied were related to soil type and material, and the study considered till, dry sand, wet sand, and sensitive clay soil; (ii) to assess the effect of trench box material and geometry on earth pressure; the parameters studied were related to trench box material (steel versus aluminum) as well as geometry (plate thickness and strut diameter). These studies included simulation of two steel (or aluminum) trench box shields stacked upon each other to cover the total 6 m (20 ft) deep trench. A Mohr-Coulomb (MC) constitutive material model was chosen for FE analysis (FEA). The FEA results were compared to empirical apparent earth pressure diagrams for a sensitive clay. Comparisons showed that the parameters related to the soil and the trench box have a significant influence on earth pressures.

Influence of Cavity Geometry on the Fracture Strength of Dental Restorations: Finite Element Study

The main purpose of this work was to analyze the stress distribution in premolars restored with indirect IPS Empress® CAD onlays or inlays. The three-dimensional geometry of a human first premolar was created using modeling software. The tooth fixation system was simulated through box geometry, comprising a cortical bone layer with 2 mm of thickness over a layer of trabecular bone with 15 mm of thickness. The tooth had the following approximated crown dimensions: 10.35 mm buccolingual length; 7.1 mm mesiodistal width; and 7.0 mm cervico-occlusal height. The mesio-occluso-distal (MOD) cavity preparations followed the suggestions available in the literature. The cement geometry was modified to include cohesive zone models (CZM) to perform the adhesive joint’s strength prediction. The loading body was created assuming contact between the food bolus and the tooth surface. Numerical solutions were obtained by performing static analysis and damage analysis using the finite element method. Von Mises stress values generated in the ceramic inlay restoration ranged from 1.39–181.47 MPa, which were on average 4.4% higher than those of the onlay ceramic restoration. The fracture strength of the onlay restoration was about 18% higher than that of the inlay restoration. The onlay design seems to contribute to higher homogenization of the adhesive resin cement strain and higher tooth structure protection.

Two-dimensional electronic spectroscopy with active phase Management

Two-dimensional electronic spectroscopy (2DES) is a powerful method to probe the coherent electron dynamics in complicated systems. Stabilizing the phase difference of the incident ultrashort pulses is the most challenging part for experimental demonstration of 2DES. Here, we present a tutorial review on the 2DES protocols based on active phase managements which are originally developed for quantum optics experiments. We introduce the 2DES techniques in box and pump-probe geometries with phase stabilization realized by interferometry, and outline the fully collinear 2DES approach with the frequency tagging by acoustic optical modulators and frequency combs. The combination of active phase managements, ultrashort pulses and other spectroscopic methods may open new opportunities to tackle essential challenges related to excited states.

Optimization of bridges with short gap streamlined twin-box decks considering structural, flutter and buffeting performance

While it is well known that the gap between twin-box decks is a key design variable that impacts the onset flutter velocity of a bridge, further research is required to ascertain how modifications in several bridge design variables affect other aeroelastic responses. This paper utilizes aero-structural optimization techniques for the design of long-span bridges with short gap twin-box decks considering simultaneously structural, flutter and buffeting constraints. The optimization helps to reduce the material volume of the structure while maintaining all the performance and safety requirements below the imposed thresholds. It has been found that the geometry of the individual box cross-section is an important feature for the control of the buffeting response, particularly the vertical acceleration. On the other hand, flutter and torsional buffeting constraints require designs with larger gap distance and alternative box geometries, leading to a trade-off between conflicting design demands. Hence, depending on the expected wind load conditions and the specific requirements of a particular project, an optimum aero-structural bridge design with a particular deck shape can be identified. The framework presented in this study is an effective tool to achieve sustainable and safe bridge designs that seeks a most efficient balance between all the design constraints.

TAP-Net

We introduce the transport-and-pack (TAP) problem, a frequently encountered instance of real-world packing, and develop a neural optimization solution based on reinforcement learning. Given an initial spatial configuration of boxes, we seek an efficient method to iteratively transport and pack the boxes compactly into a target container. Due to obstruction and accessibility constraints, our problem has to add a new search dimension, i.e., finding an optimal transport sequence , to the already immense search space for packing alone. Using a learning-based approach, a trained network can learn and encode solution patterns to guide the solution of new problem instances instead of executing an expensive online search. In our work, we represent the transport constraints using a precedence graph and train a neural network, coined TAP-Net, using reinforcement learning to reward efficient and stable packing. The network is built on an encoder-decoder architecture, where the encoder employs convolution layers to encode the box geometry and precedence graph and the decoder is a recurrent neural network (RNN) which inputs the current encoder output, as well as the current box packing state of the target container, and outputs the next box to pack, as well as its orientation. We train our network on randomly generated initial box configurations, without supervision , via policy gradients to learn optimal TAP policies to maximize packing efficiency and stability. We demonstrate the performance of TAP-Net on a variety of examples, evaluating the network through ablation studies and comparisons to baselines and alternative network designs. We also show that our network generalizes well to larger problem instances, when trained on small-sized inputs.

Design and measurement of Trans-PET basic detector module II using 6× 6 SiPM array for small-animal PET

Silicon photomultiplier (SiPM) coupled scintillation detectors, are considered as promising tools for basic design of imaging instrumentation for the next generation PET, PET/MRI, SPECT and autoradiography scanners. The precise technical knowledge is inadequate, and still some challenges need to be addressed in order to successfully implement the SiPM technology in high resolution PET systems. Firstly, the advantages of SiPM pixel array 1:1 coupled crystal detector were obvious, and has minimized the position resolution errors of charge sharing in multiplexing circuits. However, in the system level, too many electronic channels have perplexed with complications, such as complex, messy electronics or dedicated ASIC chips. Multiplexing circuits were usually used to lower the complexity and cost of electronics, which has resulted in gradual deterioration of the performances of the detectors. Secondly, the light guide has become a necessity in high-resolution preclinical PET detectors. For a complete SiPM detector block, the light yield of outermost two rows/columns crystals were blurred due to the edge effects. In order to avoid this edge deterioration effect, crystal array size was reduced than that of the SiPM array in many PET detectors. The PET system built by these detectors had big gaps between the detector modules, which has largely affected the quality of reconstructed images. In order to solve these key problems, the Trans-PET basic detection module (BDM) II was designed and implemented in this study. This module was a flexible, easy to upgrade, simple, box geometry, small animal PET scanner. A better balance could be achieved by this detector, while reducing the electronic channels, and could simultaneously enhance the position resolution and time performance. A specially customized semi-cutting light guide had been designed, which could be optically multiplexed and diffused to optimize the effect of edge deterioration, so that both the outermost and inner crystals could be clearly distinguished. Specifically, in this PET module, two type crystal arrays with different crystal size had been designed, 13× 13 crystal array with 1.89 mm width and 18× 18 crystal array with 1.2 mm width, based on the same 6× 6 SiPM array and frond-end electronics. The total area of 6× 6 SiPM was 25.0× 25.0 mm2, which was similar to Hamamatsu PSPMT R8900. The area of the SiPM array was slightly smaller than the size of the crystal array, in order to reduce the gap of the PET system built by this detector. The purpose of this study was to evaluate the performance of this detector module, including position profile quality, energy resolution, timing resolution in different operating environment. Based on this detector module, PET scanners can easily be designed with different shapes such as, quadrilaterals, hexagonals, octagonals, dodecagonals, twenty-four-sides, and other shapes.

Systematic errors in diffusion coefficients from long-time molecular dynamics simulations at constant pressure.

In molecular dynamics simulations under periodic boundary conditions, particle positions are typically wrapped into a reference box. For diffusion coefficient calculations using the Einstein relation, the particle positions need to be unwrapped. Here, we show that a widely used heuristic unwrapping scheme is not suitable for long simulations at constant pressure. Improper accounting for box-volume fluctuations creates, at long times, unphysical trajectories and, in turn, grossly exaggerated diffusion coefficients. We propose an alternative unwrapping scheme that resolves this issue. At each time step, we add the minimal displacement vector according to periodic boundary conditions for the instantaneous box geometry. Here and in another paper [J. T. Bullerjahn, S. von Bülow, and G. Hummer, J. Chem. Phys. 153, 024116 (2020)], we apply the new unwrapping scheme to extensive molecular dynamics and Brownian dynamics simulation data. We provide practitioners with a formula to assess if and by how much earlier results might have been affected by the widely used heuristic unwrapping scheme.

Transport properties of coupled Majorana bound states in the Coulomb blockade regime

Topologically protected qubits based on nanostructures hosting Majorana bound states (MBSs) hold great promise for fault-tolerant quantum computing. We study the transport properties of nanowire networks hosting MBSs with a focus on the effects of the charging energy and the overlap between neighboring MBSs in short mesoscopic samples. In particular, we investigate structures hosting four MBSs such as T-junctions and Majorana boxes. Using a master equation in the Markovian approximation, we discuss the leading transport processes mediated by the MBSs. Single-electron tunneling and processes involving creation and annihilation of Cooper pairs dominate in the sequential tunneling limit. In the cotunneling regime the charge in the MBSs network is fixed and transport is governed by transitions via virtual intermediate states. Our results show that four-terminal measurements in the T-junction and Majorana box geometries can be useful tools for the characterization of the properties of MBSs with finite overlaps and charging energy.

Effects of simulation system on the phase transition behavior of liquid film: A molecular dynamics study

In the present study, the effects of liquid film thickness and simulation box geometry on the molecular dynamics simulation studies of phase transition are investigated. Results show that the simulation system has significant impacts on phase transition behaviors of the liquid film because of the applications of periodic boundary and reflecting boundary. The evaporation and bubble nucleation phenomena happen on the substrate with a temperature of 140 K. If the heated liquid film is thin or the height of the simulation box is low, the evaporated liquid atoms from the interface of vapor-liquid cause a high vapor pressure and prevent the happening of bubble nucleation in the vicinity of the substrate, and only evaporation phenomenon happens. When the substrate temperature is raised to 150 K, a bubble nucleus turns up on the substrate. If the length of the simulation box is short, the bubble nucleus converts into a vapor film quickly under the joint effects of liquid film lifting and high-temperature liquid vaporization, and the explosive boiling phenomenon happens. However, with the increase of the length of the simulation box, a distinct bubble nucleation and growth process are observed. The present study can provide a reference for researchers in the molecular dynamics simulation studies of phase transition.