Symmetric Design Research Articles

Group Doubly Coupled Designs

Doubly coupled designs (DCDs) have better space-filling properties between the qualitative and quantitative factors than marginally coupled designs (MCDs) which are suitable for computer experiments with both qualitative and quantitative factors. In this paper, we propose a new class of DCDs, called group doubly coupled designs (GDCDs), and provide methods for constructing two forms of GDCDs, within-group doubly coupled designs and between-group doubly coupled designs. The proposed GDCDs can accommodate more qualitative factors than DCDs, when the subdesigns for the qualitative factors are symmetric. The subdesigns of qualitative factors are not asymmetric in the existing results on DCDs, and in this paper, we construct GDCDs with symmetric and asymmetric designs for the qualitative factors, respectively. Moreover, detailed comparisons with existing MCDs show that GDCDs have better space-filling properties between qualitative and quantitative factors. Finally, the methods are particularly easy to implement.

Multi-Objective Topology Optimization of Conjugate Heat Transfer Using Level Sets and Anisotropic Mesh Adaptation

This study proposes a new computational framework for the multi-objective topology optimization of conjugate heat transfer systems using a continuous adjoint approach. It relies on a monolithic solver for the coupled steady-state Navier–Stokes and heat equations, which combines finite elements stabilized by the variational multi-scale method, level set representations of the fluid–solid interfaces and immersed modeling of heterogeneous materials (fluid–solid) to ensure that the proper amount of heat is exchanged to the ambient fluid by solid objects in arbitrary geometry. At each optimization iteration, anisotropic mesh adaptation is applied in near-wall regions automatically captured by the level set. This considerably cuts the computational effort associated with calling the finite element solver, in comparison to traditional topology optimization algorithms operating on isotropic grids with a comparable refinement level. Given that we operate within the constraint of a specified number of nodes in the mesh, this allows not only to improve the accuracy of interface representation and motion but also to retain the high fidelity of the numerical solutions at the grid points just adjacent to the interface. Finally, the remeshing and resolution steps both run within a highly parallel environment, which makes it possible for the proposed algorithm to tackle large-scale problems in three dimensions with several tens of millions of state degrees of freedom. The developed solver is validated first by minimizing dissipation in a flow splitter device, for which the method delivers relevant optimal designs over a wide range of volume constraints and flow rate distributions over the multiple outlet orifices but yields better accuracy compared to reference data from literature obtained using uniform meshes (in the sense that the layouts are more smooth, and the solutions are better resolved). The scheme is then applied to a two-dimensional heat transfer problem, using bi-objective cost functionals combining flow resistance and thermal recoverable power. A comprehensive parametric study reveals a complex arrangement of optimal solutions on the Pareto front, with multiple branches of symmetric and asymmetric designs, some of them previously unreported. Finally, the algorithmic developments are substantiated with several three-dimensional numerical examples tackled under fixed weights for heat transfer and flow resistance, for which we show that the optimal layouts computed at low Reynolds number, that are intrinsically relevant to a broad range of microfluidic application, can also serve as smooth solutions to high-Reynolds-number engineering problems of practical interest.

Emergency Strategies for Gushing Water of Borehole and Numerical Simulation on Circular Diaphragm Wall Excavation with Ring-Beams

This study explores the underground structure and soil retention capabilities of a large-scale circular diaphragm wall (93.5 m in diameter) utilized as a soil retention strategy in deep excavation projects. The symmetrical design of the wall facilitates the use of an unsupported construction method, effectively resisting soil and water pressures. Using PLAXIS 3D 2017 software, this study simulates wall deformation and ground settlement, employing three different soil models to assess behavior under standard and emergency water gushing scenarios. The results show that the hardening soil (HS) model most accurately reflects the actual deformations and settlements. This study also finds that adjusting Young’s modulus for clay significantly impacts the accuracy of soil behavior predictions, while changes in the properties of sand have minimal effects. This research highlights the challenges posed by water gushing and suggests the need for model improvements to capture better the dynamic interactions between soil and water pressure, which could lead to wall tilting. Overall, this study offers innovative and practical value, providing crucial insights for designing and mitigating strategies in large-scale circular deep excavation projects, especially in regions such as Taiwan, where such constructions are rare and face unique challenges.

The Damietta Server: a comprehensive protein design toolkit.

The growing importance of protein design to various research disciplines motivates the development of integrative computational platforms that enhance the accessibility and interoperability of different design tools. To this end, we describe a web-based toolkit that builds on the Damietta protein design engine, which deploys a tensorized energy calculation framework. The Damietta Server seamlessly integrates different design tools, in addition to other tools such as message-passing neural networks and molecular dynamics routines, allowing the user to perform multiple operations on structural models and forward them across tools. The toolkit can be used for tasks such as core or interface design, symmetric design, mutagenic scanning, or conformational sampling, through an intuitive user interface. With the envisioned integration of more tools, the Damietta Server will provide a central resource for protein design and analysis, benefiting basic and applied biomedical research communities.The toolkit isavailable with no loginrequirement through https://damietta.de/.

Broadband Janus-Helmholtz transducer with various liquid cavity resonances

To enhance the radiation capacity of the Janus-Helmholtz transducer (JHT) and achieve a broadband transmitting response, an asymmetric dual-cavity JHT is proposed and a broadband symmetric multi-cavity JHT design is introduced. Firstly, the vibration characteristics of the cylindrical liquid cavity are analyzed and two liquid cavities with different dimensions are utilized to construct the asymmetric dual-cavity JHT. The operating principles of both the typical JHT and the asymmetric dual-cavity JHT are revealed. Furthermore, an equivalent circuit model (ECM) for the asymmetric dual-cavity JHT is proposed by combining the ECMs of the Janus transducer and the liquid cavities. To validate the accuracy and generality of the ECM for the asymmetric dual-cavity JHT, four JHTs are fabricated and tested, and the finite element method (FEM) is also employed to predict their electroacoustic performance. The admittance obtained from ECM, FEM and experiment (EXPT) exhibit good agreement. Additionally, the radial transmitting voltage response (rTVR) calculated by FEM aligns well with the experimental results. Experimental results demonstrate that the asymmetric dual-cavity JHT, compared to its typical counterpart of the same dimensions, exhibits a significantly increased rTVR within the low-frequency band. Moreover, the directivity of the typical JHT and the asymmetric dual-cavity JHT are compared by FEM and the causes of radial response fluctuations in the asymmetric dual-cavity JHT are analyzed. Finally, a symmetric multi-cavity JHT with a lower resonant frequency and a wider operating bandwidth is designed through FEM, verifying the effectiveness of the multi-mode coupling design principle. The ECM for the dual-cavity JHT offers valuable theoretical support for optimizing JHT designs and the symmetric multi-cavity JHT design serves as inspirations for modifying resonant frequency, enhancing emission capability and advancing operating bandwidth of the JHTs.

Low-rank matrices, tournaments, and symmetric designs

Let a=(ai)i≥1 be a sequence in a field F, and f:F×F→F be a function such that f(ai,ai)≠0 for all i≥1. For any tournament T over [n], consider the n×n symmetric matrix MT with zero diagonal whose (i,j)th entry (for i<j) is f(ai,aj) if i→j in T, and f(aj,ai) if j→i in T. It is known [3] that if T is a uniformly random tournament over [n], then rank(MT)≥(12−o(1))n with high probability when char(F)≠2 and f is a linear function.In this paper, we investigate the other extremal question: how low can the ranks of such matrices be? We work with sequences a that take only two distinct values, so the rank of any such n×n matrix is at least n/2. First, we show that the rank of any such matrix depends on whether an associated bipartite graph has certain eigenvalues of high multiplicity. Using this, we show that if f is linear, then there are real matrices MT(f;a) of rank at most n2+O(1). For rational matrices, we show that for each ε>0 we can find a sequence a(ε) for which there are matrices MT(f;a) of rank at most (12+ε)n+O(1). These matrices are constructed from symmetric designs, and we also use them to produce bisection-closed families of size greater than ⌊3n/2⌋−2 for n≤15, which improves the previously best known bound given in [5].

Numerical and experimental analysis of 3D printer hot ends

The design of the hot end plays a critical role in additive manufacturing, especially in material extrusion. Yet the melt flow behavior within the hot end assembly has not been explicitly presented regarding the hot end design. The present study intends to fill this knowledge gap by employing a two-phase approach to investigate the melt dynamics through three commercially available hot ends. The hot ends considered are E3D v6 Standard, v6 Gold, and Revo Six, which were chosen based on brand, design, and functionality. In Phase 1, an experimental apparatus was developed to assess the impact of feeding rate and extrusion temperature on the outlet temperature, outlet velocity, and under-extrusion percentage of extruded polymer. In Phase 2, the polymer flow through each hot end is explored utilizing a computational fluid dynamics model, which was validated using data obtained in Phase 1. It was determined that the filament feeding rate is the most influential parameter in polymer extrusion and that Revo Six’s symmetrical design affects the stability of extrusion. It was also revealed that the thermal evolution of the melted filament within the hot end assembly is directly affected by the length of the heating region and the polymer's material properties. The experimental and numerical procedures developed in this investigation can be useful to 3D printing users and manufacturers in selecting a hot end assembly based on application requirements.

A Symmetric Sixth-Order Step-Up Converter with Asymmetric PWM Achieved with Small Energy Storage Components

This research explores an improved operation of a recently studied converter, the so-called two-phase sixth-order boost converter (2P6OBC). The converter consists of a symmetric design of power stations followed by an LC filter; its improved operation incorporates an asymmetric pulse width modulation (PWM) scheme for transistor switching, sometimes known as an interleaved PWM approach. The new operation leads to improved performance for the 2P6OBC. Along with studying the 2P6OBC, one of the contributions of this research is providing design equations for the converter and comparing it versus the interleaved (or multiphase) boost converter, known for its competitiveness and advantages; the single-phase boost topology was also included in the comparison. The comparison consisted of a design scenario where all converters must achieve the same power conversion with an established maximum switching ripple, and then the stored energy in passive components is compared. Although the 2P6OBC requires a greater number of components, the total amount of stored energy is smaller. It is known that the stored energy is related to the size of the passive components. Still, the article includes a discussion of this topic. The new operation of the converter offers more streamlined, cost-effective, and efficient alternatives for a range of applications within power electronics. The final design of the 2P6OBC required only 68% of the stored energy in inductors compared to the multiphase boost converter, and 60% of the stored energy in capacitors. This result is outstanding, considering that the multiphase boost converter is a very competitive topology. Experimental results are provided to validate the proposed concept.

12-mJ 1-kHz cryogenically cooled rod Yb:YAG regenerative amplifier

We report on a continuous-wave (CW) pumped cryogenically cooled rod Yb:YAG regenerative amplifier delivering uncompressed 12-mJ, 90-ps, 1030-nm pulses at a 1-kHz repetition rate. The amplifier demonstrates an efficiency of 31.7%. A symmetric cavity design was utilized to compensate for the substantial thermal lensing effect, yielding a final measured beam quality of 1.1 in both horizontal and vertical directions. After significant gain narrowing, the measured spectra exhibit a bandwidth of 0.3 nm corresponding to an approximately 5 ps transform-limited pulse.

Compensating thermal bending of the runner disk in hydrodynamic thrust bearings: Simple approach for passively improving the performance of gas bearings

This paper presents a method for passively compensating thermal bending distortions of the thrust disk in gas thrust bearings by passive approaches. Thermal bending displays a prominent problem in hydrodynamic thrust bearings, especially in connection with air bearings. Axial temperature gradients cause the rotor disk to dish which in turn diminishes the lubricating gap topology and reduces the load capacity of the bearing. Consequently, the bearing performance is decreased and the bearing may even fail. The here proposed straightforward solutions are small changes in the rotor and runner disk design and are therefore rather simple and inexpensive to adopt. They comprise asymmetric mass distributions, recesses, disk cuts, and dual-material rotor disks. In order to show the benefit for the thrust bearing performance, detailed multiphysical numerical simulations of a representative rotor assembly with a foil thrust bearing are presented. The fully coupled finite element model calculates the deformations of the foil package (2D Reissner–Mindlin type shell equations), lubricating air film pressure (2D compressible Reynolds equation), air film temperatures (3D energy equation), and thermo-elastic deformations of the rotor and rotor disk (2D Navier-Lamé equations including centrifugal forces and thermal stresses). When the proposed design changes are applied, the model predicts reduced thermal bending, marked improvements in load capacity as well as decreased temperatures. The load capacity increase ranges up to 43% for an optimized design when compared against a standard symmetric design. Also, the sensitivity of different design parameters is discussed in detail. The suggested disk design changes may be applied to a broad variety of rotor-bearing systems. However, the design has to be tailored to the specific and individual machine operating conditions.

Towards a fiber barrel detector for next-generation high-pressure gaseous xenon TPCs

The NEXT (Neutrino Experiment with a Xenon TPC) project is an international collaboration aimed at finding evidence of neutrinoless double beta decay using gaseous xenon. The current phase of the project involves the construction and operation of NEXT-100, which is designed to hold 100 kg of xenon at 15 bar and is expected to start commissioning in the first quarter of 2024. NEXT-HD will be a tonne scale experiment following NEXT-100 and will incorporate a symmetric design, with one cathode and two anodes. For this detector, the collaboration is considering to implement a barrel of wavelength-shifting fibers read-out by silicon photomultipliers to measure the energy of the particles interacting in the gaseous xenon. In this document, we will discuss the characteristics of this approach and provide an update on the related R&D efforts.

Asymmetric Implant Design for Posterolateral Overhang of the Femoral Component in Total Knee Arthroplasty: A Retrospective Computed Tomography-Based Study.

Introduction During total knee arthroplasty (TKA), also referred to as total knee replacement (TKR), patients may experience pain in the posterolateral knee. One possible cause is the impingement between the popliteus tendon and the femoral components. The purpose of this study was to analyze the posterolateral overhang of the femoral component using 3D template software. Methods Preoperative CT scan images of 50 knees (11 males and 39 females) with osteoarthritis of grade 2 or lower according to the Kellgren-Lawrence classification were analyzed. The mean age of the subjects was 73.8±7.6 years (range 52-84 years). The Athena (Soft Cube Co., Ltd., Osaka, Japan) knee 3D image-matching software was used for the analysis. The positions of the two femoral components (symmetrical and asymmetrical) were simulated. In the coronal plane, the component overhang was measured between the resected lateral part of the posterior femur and its corresponding component size, and the two designs were compared in three zones (proximal, central, and distal). Results In the simulated femoral component, the asymmetric design had a significantly lower component overhang than the symmetric design in the proximal zone of the lateral posterior condyle (0.2±1.9 mm vs. 3.5±1.6 mm, p<0.01). In the proximal zone, significant overhang (>3 mm) was observed in 30 knees (60.0%) with the symmetric design, but only three knees (6.0%) had asymmetric designs (p<0.01). Conclusions The posterolateral overhang of the lateral posterior condyle occurs when a symmetrical prosthesis is used. The use of an asymmetric implant with a small, rounded proximal portion of the lateral posterior condyle improves this overhang and is expected to decrease problems such as impingement of the popliteus tendon and improve patient satisfaction.

A 4-Element UWB MIMO Antenna System with High Isolation Performance

This paper proposes a 4-element multiple-input multiple-output (MIMO) antenna system, which is intended for ultra-wideband (UWB) applications. The antenna has a dimension of 92 × 70 × 1.6 mm3. It achieves element isolation via the defected ground structure (DGS) and symmetric E-shaped branch structures design. The realized operating bandwidth is from 3 GHz to 18 GHz, with 15 dB isolation within the whole wide band. The envelope correlation coefficient (ECC) is less than 0.01 with diversity gain (DG) greater than 9.95. The prototype is fabricated and measured to verify its potential applications for UWB MIMO communication.

Dumbbell shaped structure loaded modified circular ring resonator based perfect metamaterial absorber for S, X and Ku band microwave sensing applications

In this paper, a new metamaterial absorber (MMA) is presented that exhibits peak absorptions at 3.26 GHz, 11.6 GHz, and 17.13 GHz within S, X, and Ku bands. The unit cell of the proposed MMA is constructed on an FR4 substrate having an electrical dimension of 0.144λ × 0.144λ, where wavelength, λ is calculated at the lowest absorption frequency. The unique structural design of the unit cell consists of two concentric copper rings with which dumbbell-shaped structures are attached. The rotating symmetrical structural design of this MMA provides around 93.8%, 96.47%, and 99.95% peak absorptance in the mentioned frequencies, which is invariable with the change of incident angle as well as polarization angle. The metamaterial properties of the proposed absorber are studied along with the surface current analysis. The MMA shows single negative behaviour and it also exhibits high-quality factors (Q factor) of 21.73, 41.42, and 51.90 at maximum absorptance frequencies. The MMA is analysed by it's equivalent circuit to understand the resonance phenomenon, which is verified through simulation in Advanced Design Systems (ADS) software. The testing is done on the developed prototype of the proposed MMA. Measurement results are in close proximity to the simulation results. Due to its high Q factor, high EMR, and insensitivity to polarization and angle of incidence, it can be utilized as a part of miniaturized microwave device. In addition, the proposed MMA can exhibit high sensing performance and flexibility to differentiate different oils in S, X, and Ku bands.

Polarized and Unpolarized Emission from a Single Emitter in a Bullseye Resonator

AbstractPolarized , and unpolarized emission from a single emitter embedded in a single, cylindrically symmetric device design is presented. The polarization stems from a position offset of the single emitter with respect to the cavity center, which breaks the cylindrical symmetry, and a position‐dependent coupling to the frequency degenerate eigenmodes of the resonator structure is shown. The experimental results are interpreted by using numerical simulations and by experimental mapping of the polarization‐resolved far‐field emission patterns. The findings can be generalized to any nanophotonic structure where two orthogonal eigenmodes are not fully spatially overlapping.

Template free synthesis of vacancy tailored, highly mesoporous one-dimensional δ-MnO2 for energy storage applications

This work involves the synthesis of highly conducting, ultra-thin, mesoporous manganese dioxide, nanotubes and nanowires, using a sol–gel technique. This is a template-free method for preparing mesoporous (3.3 to 5.4 nm) nanotubes and nanowires of 10–15 nm radius with surface area (221.19 m2/g-102.09 m2/g). In the MnO2 lattice, oxygen and cationic vacancies are tailored by changing the reducing agent for improved energy storage. X-ray photoelectron spectroscopic studies are conducted to quantify the oxygen and cationic vacancies. The tailored one-dimensional δ-MnO2 is used as an electrode material for symmetric and asymmetric supercapacitor designs. A non-toxic, less volatile aqueous neutral electrolyte is used for the supercapacitive measurement, giving a specific capacitance of 460.75 F g−1 at 2 mV s−1 with symmetric mode at 1 V. With activated carbon, this material can also produce asymmetric supercapacitors with a specific capacitance of 107.38 F g−1 at 10 mV s−1 at 1.7 V.

Optimal design of prestressed bolt thread

The design of bolt and nut thread comes in many variations, typically the designs are specified in standards like the metric ISO thread. The thread design is important for the connection strength, and bolted connections are used for many applications. In the present paper focus is on the strength of prestressed bolts, that is, where the preload is typically more than 75% of the proof strength. The objective is in the present work to reduce the stress concentration in the thread. The stress is found numerically using a full 3D finite element model, and a simplified 2D axisymmetric model. It is shown that the 2D model is sufficient for evaluating the maximum stress. Applying a symmetric design it is shown that a reduction in the maximum stress in the thread of 14% can be achieved. Allowing for an unsymmetrical thread design the maximum stress is reduced by 33%. With the unsymmetrical design some of the stress reduction is due to a more evenly load distribution along the thread. geometrically, all optimized designs are such that they can be manufactured by the same methods as a standard ISO thread.

Symmetric elastic wave cloak design for underground protective structures based on multi-center coordinate transformation

Symmetric elastic wave cloak design for underground protective structures based on multi-center coordinate transformation

Electrochemical Ionic Synapses with Mg2+ as the Working Ion

AbstractDynamic doping by electrochemical ion intercalation is a promising mechanism for modulating electronic conductivity, allowing for energy‐efficient, brain‐inspired computing hardware. While proton‐based devices have achieved success in terms of speed and efficiency, the volatility and environmental pervasiveness of hydrogen (H) might limit the robustness of devices during fabrication, as well as the long‐term retention of devices after programming. This motivates the search for alternative working ions. In this work, a proof‐of‐concept is demonstrated for electrochemical ionic synapses (EIS) based on intercalation of Mg2+ ions. The reported device has a symmetric design, with MgxWO3 used as both the gate and channel material. Increasing the Mg fraction, x, in WO3 increases the electronic conductance in a continuum over a large range (80 nS − 2 mS). Ex situ characterization of the channel confirms that modulation of channel conductance is due to Mg2+ intercalation. Unlike H‐EIS which rapidly loses programmed conductance states over a few seconds when exposed to air, Mg‐EIS can be operated and has good retention in air, with no sign of degradation after 1 h. Mg2+ as a working ion with WO3 as the channel is a promising material system for EIS with long‐term retention and low energy consumption.

Crushing performance of a novel tetra-missing rib honeycomb: Experimental and numerical studies

Based on the unique monoclinic characteristics of the plastic deformation of the tetra-missing rib honeycomb, the symmetrical design of the whole and subunits of the tetra-missing rib honeycomb was carried out in this paper, and two new types of tetra-missing rib honeycomb with symmetrical structural characteristics were obtained. First, quasi-static compression was performed on three structures, including a conventional tetra-missing rib honeycomb, and the experimental results showed that both symmetrical designs could effectively improve the plastic deformation of the conventional tetra-missing rib honeycomb. At the same time, round holes were introduced into the three honeycomb structures, and the mechanical properties and deformation modes of the three structures under quasi-static loads were explored. The results of two sets of experiments were compared, and it was found that the introduction of round holes could improve the structural stiffness of the honeycomb. Second, Abaqus/Explicit was used to construct a finite element numerical model in the later stage, and the accuracy of the model was verified. The number of honeycomb cells was determined for the three honeycomb structures, and finally, the dynamic Poisson's ratio of the honeycomb structure in plastic deformation was determined, and the negative Poisson's ratio (NPR) effect of the three honeycombs was compared.