Flat Conditions Research Articles

A three-dimensional kinematic analysis of bipedal walking in a white-handed gibbon (Hylobates lar) on a horizontal pole and flat surface.

Gibbons, a type of lesser ape, are brachiators but also walk bipedally and without forelimb assistance, not only on the ground but also on tree branches. The arboreal bipedal walking strategy of the gibbons has been studied in previous studies in relation to two-dimensional (2D) kinematic analysis. However, because tree branches and the ground differ greatly in width, leading to a constrained foot contact point on the tree branches, gibbons must adjust their 3D joint motions of trunk and hindlimb on the tree branches. Furthermore, these motor adjustments could help minimize the center of mass (CoM) mediolateral displacement. This study investigated the kinematic adjustment mechanism necessary to enable a gibbon to walk bipedally on an arboreal-like substrate using 3D measurements. Trials were recorded with eight video cameras that were placed around the substrate. The CoM position on the body, the Cardan angles of the hindlimb joints and trunk, and spatiotemporal parameters were calculated. Asymmetry of thorax, pelvis, trunk, and left and right hindlimb joint motion was observed in the pole and flat conditions. In the pole condition, the narrower step width and the smaller range of motion of the mediolateral CoM displacement were observed with increased hip adduction and knee eversion angles. These kinematic adjustments might place the knee and foot directly under the body during the single support phase, producing a reduced step width and the amount of the mediolateral CoM displacement of a gibbon.

Dual‐Mode Flexible Parylene‐C‐Based In‐Memory Tactile Sensory Device with CMOS Compatibility

AbstractThe artificial tactile memory system enables electronic skin (e‐skin) electronics to detect and record tactile sensations like natural skin, significantly expanding the applications of flexible electronics in wearable devices, human‐computer interaction, and healthcare. However, current tactile memory electronics still face challenges such as complex structures and high hardware costs, limiting further high‐density integration. Herein, an in‐memory tactile sensory (IMTS) device with a simple structure is experimentally demonstrated, which can achieve pressure information detecting, storage, and erasure in a single device. Due to the chemical stability of the parylene‐C and its compatibility with standard photolithography, the device can be manufactured on advanced CMOS process platforms, showing potential for high‐density integration. Additionally, the device demonstrates excellent mechanical properties, maintaining outstanding electrical performance in both flat and bending conditions. Furthermore, pressure distribution can be detected and recorded with the IMTS arrays, providing new avenues for developing high‐performance tactile memory systems in human‐computer interaction and wearable electronics.

Comparative performance investigation of rectangular microstrip antennas utilizing polydimethylsiloxane (PDMSCNT) and polycaprolactone (PCL-CNT) composites at 2.4 GHz and 5.8 GHz

ABSTRACT Current research efforts are directed towards utilizing polymers and biodegradable materials to develop innovative wireless devices for emerging applications within the sub-6 GHz spectrum. This study seeks to enhance the electrical and radiation characteristics of antennas while ensuring favorable environmental properties such as flexibility and Specific Absorption Rate (SAR). To this end, a comparative analysis of two flexible rectangular microstrip antennas constructed from novel polymer-based substrates is presented. One antenna uses a flexible composite substrate of polydimethylsiloxane (PDMS) embedded with carbon nanotubes (CNT), while the other employs a biodegradable polymer composite substrate made of polycaprolactone (PCL) reinforced with CNT. Results indicate that the PCL-CNT antenna surpasses the PDMS-CNT antenna in performance, in both flat and bent conditions. Specifically, at 2.4 GHz, the PCL-CNT antenna achieved a gain of 4.46 dBi and an efficiency of 0.70, compared to a gain of 3.94 dBi and an efficiency of 0.61 for the PDMS-CNT antenna. Furthermore, the superior performance of the PCL-CNT biodegradable polymer composite antenna suggests its potential for IoT applications and wireless communications, combining effective on-body usage with minimal environmental impact.

Ricci curvature bounded below and uniform rectifiability

We prove that Ahlfors-regular RCD spaces are uniformly rectifiable and satisfy the Bilateral Weak Geometric Lemma with Euclidean tangents–a quantitative flatness condition. The same is shown for Ahlfors regular boundaries of non-collapsed RCD spaces. As an application we deduce a type of quantitative differentiation for Lipschitz functions on these spaces.

Analysis and Design of a Multistorey Building on Sloped and Flat Grounds (Stilt + Ground + 4)

This project focuses on the planning, static analysis, and structural design of a (Stilt + Ground + 4) residential building, located on both sloping and flat ground, using ETABS software. The primary goal is to study the impact of ground conditions on the structural behavior and design considerations of the building. The project incorporates planning principles to create a functional and efficient layout, ensuring compliance with Indian Standard codes for beams, columns, slabs, and other structural elements. Key aspects such as load distribution, stability, reinforcement detailing, and member sizing are thoroughly examined to ensure the building's safety and adherence to IS guidelines. A comparative analysis between sloping and flat ground conditions highlights the differences in design parameters, such as member forces, moments, and reinforcement requirements, with particular attention to the unique challenges posed by sloping ground. The findings of the study aim to offer insights into cost- effective and optimized design strategies that cater to different site conditions. By exploring these variations, the study contributes to the development of advanced modeling techniques for structural analysis and design. It also emphasizes the importance of adaptable strategies to ensure safe, resilient, and efficient residential buildings, regardless of topography. This research enhances the understanding of how varying ground conditions influence the design process and promotes the development of residential structures that are both safe and cost-efficient across diverse terrains. Keywords: Residential Building Design, Sloping Ground, Flat Ground, ETABS, Static Analysis, Structural Components, Indian Standards, Comparative Study, Planning Principles, Reinforcement Detailing.

Series-Fed Microstrip Patch Antenna Array with Additive-Manufactured Foldable Honeycomb-Shaped Substrate.

This paper presents a novel foldable S-band microstrip patch antenna array operating in the 2.4-2.45 GHz band. The substrate is designed to allow the array to be folded and arranged in tiles, forming a versatile, reconfigurable antenna array. Additive manufacturing is used to fabricate the substrate for ease of fabrication and flexibility in its design. The major challenge in this type of design is creating a proper method of feeding the elements while maintaining the array's optimal performance. A novel hinge design that can hold a coaxial cable for the series-fed array is introduced. The hinge provides the capability of folding the array from a flat orientation into various folded orientations. In this paper, a 2 × 1 microstrip array unit is presented as proof of concept. The antenna was fabricated and measured, and the results of the measurements are in close agreement with the simulations. The antenna can provide a gain as high as 7.72 dBi in flat conditions.

Flatness constraints in the estimation of GNSS satellite antenna phase center offsets and variations

Accurate information on satellite antenna phase center offsets (PCOs) and phase variations (PVs) is indispensable for high-precision geodetic applications. In the absence of consistent pre-flight calibrations, satellite antenna PCOs and PVs of global navigation satellite systems are commonly estimated based on observations from a global network, constraining the scale to a given reference frame. As part of this estimation, flatness and zero-mean conditions need to be applied to unambiguously separate PCOs, PVs, and constant phase ambiguities. Within this study, we analytically investigate the impact of different boresight-angle-dependent weighting functions for PV minimization, and we compare antenna models generated with different observation-based weighting schemes with those based on uniform weighting. For the case of the GPS IIR/-M and III satellites, systematic differences of 10 mm in the PVs and 65 cm in the corresponding PCOs are identified. In addition, new antenna models for the different blocks of BeiDou-3 satellites in medium Earth orbit are derived using different processing schemes. As a drawback of traditional approaches estimating PCOs and PVs consecutively in distinct steps, it is shown that different, albeit self-consistent, PCO/PV pairs may result depending on whether PCOs or PVs are estimated first. This apparent discrepancy can be attributed to potentially inconsistent weighting functions in the individual processing steps. Use of a single-step process is therefore proposed, in which a dedicated constraint for PCO-PV separation is applied in the solution of the normal equations. Finally, the impact of neglecting phase patterns in precise point positioning applications is investigated. In addition to an overall increase of the position scatter, the occurrence of systematic height biases is illustrated. While observation-based weighting in the pattern estimation can help to avoid such biases, the possible benefit depends critically on the specific elevation-dependent weighting applied in the user’s positioning model. As such, the practical advantage of such antenna models would remain limited, and uniform weighting is recommended as a lean and transparent approach for the pattern estimation of satellite antenna models from observations.

A study of stable wormhole solution with non-commutative geometry in the framework of linear f(R,Lm,T) gravity

This research delves into the potential existence of traversable wormholes (WHs) within the framework of modified, curvature based gravity. The modification includes linear perturbations of the matter Lagrangian and the trace of the energy-momentum tensor with specific coupling strengths α and β and can thus be viewed as a special case of linear f(R, T)-gravity with a variable matter coupling or as the simplest additively separable f(R,Lm,T)-model. A thorough examination of static WH solutions is undertaken using a constant redshift function; therefore, our work can be regarded as the first-order approximation of WH theories in f(R,Lm,T). The analysis involves deriving WH shape functions based on non-commutative geometry, with a particular focus on Gaussian and Lorentzian matter distributions ρ. Constraints on the coupling parameters are developed so that the shape function satisfies both the flaring-out and asymptotic flatness conditions. Moreover, for positive coupling parameters, violating the null energy condition (NEC) at the WH throat r0 demands the presence of exotic matter. For negative couplings, however, we find that exotic matter can be avoided by establishing the upper bound β+α/2<-1ρr02-8π. Additionally, the effects of gravitational lensing are explored, revealing the repulsive force of our modified gravity for large negative couplings. Lastly, the stability of the derived WH solutions is verified using the Tolman–Oppenheimer–Volkoff (TOV) formalism.

Insights of BDAPbI4-Based Flexible Memristor for Artificial Synapses and In-Memory Computing.

Inspired by brain-like spiking computational frameworks, neuromorphic computing-brain-inspired computing for machine intelligence promises to realize artificial intelligence (AI) while reducing the energy requirements of computing platforms. In this work, we show the potential of advanced learnings of butane-1,4-diammonium based low-dimensional Dion-Jacobson hybrid perovskite (BDAPbI4) memristor devices in the realm of artificial synapses and neuromorphic computing. Memristors validate Hebbian learning rules with various spike-dependent plasticity within a 10 ± 2 ms time frame, reminiscent of the human brains under flat and bending conditions (∼5 mm radium). A high recognition accuracy of ∼94% of handwritten images from the MNIST database via an artificial neural network (ANN) is achieved with only 50 epochs. An efficient demonstration of second-order memristors and the Pavlovian dog experiment exhibit significant promise in expediting learning and memory consolidation. To showcase the in-memory computing potential, a flexible 4 × 4 crossbar array is designed with measured data retention up to ∼103 s along with 26 multilevel resistance states. The crossbar array is successfully programmed for the facile configurability of image "Z". In conclusion, the integration of supervised, unsupervised, and associative learning holds great promise across a spectrum of future technologies, ranging from the realm of spiking neural networks to neuromorphic computing, brain-machine interfaces, and adaptive control systems.

Numerical simulation on the influence of artificial island on reef hydrodynamics

The construction of artificial island can greatly change the reef hydrodynamics, leading to increased water level and wave height as well as changes in flow field distribution. These alterations can affect sediment transport on the reef, and increase the risk of overtopping and structure instability. A numerical model based on the Reynolds Averaged Navier-Stokes (RANS) equations and k-ε turbulence closure model was developed to investigate the influence of artificial island on reef hydrodynamics. The numerical model was validated against the experimental results of wave height, mean water level, and wave breaking morphology. Detailed flow field, wave height, and wave set-up in front of artificial island were further analyzed based on the validated model. After building the reef-top structure, the wave breaking and offshore currents at reef edge were amplified. The flow stratification and increase of the wave set-up were also found on the reef flat. Furthermore, we found the relationship between maximum flow velocities on the reef flat and incoming wave conditions could be characterized by two non-dimensional parameters: |u¯|max/g(η¯+hr), (η¯+hr)/Hi.

Integrated AGC Approach for Balancing the Thickness Dynamic Response and Shape Condition of a Hot Strip Rolling Control System

Thickness and shape are two significant indices in the tandem hot strip rolling process. Excessive thickness correction can cause rolling force imbalance, leading to deteriorated shape conditions. Aiming at this problem, we propose a new monitor automatic gauge control (M-AGC) with consideration of the rolling force distribution to not only keep the shape condition but also improve the robustness of the rolling process. First, the M-AGC with the Smith predictor control structure was studied. Second, based on the rolling force and thickness correction redistribution algorithm, shape balance automatic gauge control (SB-AGC), the phenomenon of rolling force imbalance was improved. Third, the transient response was improved by adding a command prefilter to the upstream stands, which is asynchronous shape balance automatic gauge control (ASB-AGC). The proposed algorithms can be applied to all steel grades and are easy to implement. Finally, cross-validation was conducted through numerical simulations and application results, confirming the alignment between the theoretical derivation and practical implementation. The simulation results show improvements in both the rolling force balance and the thickness response. The practical application results also confirm that better flatness conditions and thickness response can be achieved, significantly reducing the amount of head-end cutoff losses.

Synthesis and properties of flexible supercapacitor based on zinc-aluminum layered doubled hydroxide

A flexible, effective supercapacitor using zinc-aluminum-layered double hydroxides (Zn-Al LDHs) as an electrode material is reported. Nanosheets of Zn-Al LDHs were synthesized using a chemical bath deposition method, and they were present in a well-standing shape covering the complete area of the Al foil. The imaging of these nanosheets showed that their average thickness is between 60 and 80 nm, with a width and length average of 1.3 and 0.6 μm, respectively. These dimensions help to create the connection arrangements of sheets with a high specific surface area of 88 m2/g which increased electrochemical active sites for charge storage. The X-ray diffraction further approves the structural properties of the prepared material. The flexibility of the supercapacitor was examined by bending and folding up the device to 180° with little mechanical deformation. The highest capacitance value is found to be ∼597F/g in the case of the flat condition. The capacitance value decreased to ∼387F/g after folding the device 30°, and these values drooped slightly after more increasing the folding angle. The energy density (ED) remains nearly constant at any folding angle (ED=3.39Wh/kg at 30° and ED=3.7Wh/kg at 135°), and similarly, the power density (PD) remains nearly constant (PD=27 kW/kg at 30° and 135°). The aforementioned approves the flexibility of the Zn-Al LHD because it provides lifelong stability (87 % retaining after 2000 charge/discharge cycles) and stable efficiency after different bending and twisting conditions. The impedance measurements along with the obtained equivalent circuits confirm the electrical characteristics of the as-prepared electrodes with low equivalent series resistances, ensuing the promising conductive path in the supercapacitor device.

Bendable non-silicon RISC-V microprocessor.

Semiconductors have already had a very profound effect on society, accelerating scientific research and driving greater connectivity. Future semiconductor hardware will open up new possibilities in quantum computing, artificial intelligence and edge computing, for applications such as cybersecurity and personalized healthcare. By nature of its ethos, open hardware provides opportunities for even greater collaboration and innovations across education, academic research and industry. Here we present Flex-RV, a 32-bit microprocessor based on an open RISC-V (ref. 1) instruction set fabricated with indium gallium zinc oxide thin-film transistors2 on a flexible polyimide substrate, enabling an ultralow-cost bendable microprocessor. Flex-RV also integrates a programmable machine learning (ML) hardware accelerator inside the microprocessor and demonstrates new instructions to extend the RISC-V instruction set to run ML workloads. It is implemented, fabricated and demonstrated to operate at 60 kHz consuming less than 6 mW power. Its functionality when assembled onto a flexible printed circuit board is validated while executing programs under flat and tight bending conditions, achieving no worse than 4.3% performance variation on average. Flex-RV pioneers an era of sub-dollar open standard non-silicon 32-bit microprocessors and will democratize access to computing and unlock emerging applications in wearables, healthcare devices and smart packaging.

Physical characteristics of anisotropic solutions in f(Q,T) gravity under the vanishing complexity, embedding class one, conformally flat and conformally Killing conditions

The foundation of this paper is to present a comparative study of the properties of anisotropic solutions for compact stars in the framework of modified f(Q,T) gravity for the first time under the schemes of vanishing complexity, embedding class one, conformally flat and conformally Killing, where Q is the nonmetricity scalar and T is the trace of the energy-momentum tensor. The model f(Q,T)=ϕQ+αQn+1−γ(1−e−Q/γ)+βT is chosen in order to compare the results of the various forms f(Q,T) and f(Q) gravity theories. The f(Q,T) and f(Q) gravities in this model are then further simplified to depend on parameters ϕ,α,γ&β. Then, we discussed several approaches to determining the spherically symmetric spacetime components. Schwarzschild geometry represents the exterior spacetime, while a Tolman-Kuchowiz spacetime is used to examine the spherically symmetric spacetime inside the interior geometry. Many properties of compact stars are investigated, like energy density, energy conditions, pressure profiles, sound speeds, gradients, adiabatic index, TOV equation, mass function, compactness, and redshift function are all carefully examined in order to complete the analysis. We have compiled results for both stable and unstable scenarios, derived from gravity theories categorized into various cases, with solutions considered under different frameworks such as Tolman-Kuchowiz spacetime, embedding class 1 spacetime, the vanishing complexity condition, the conformally flat condition, and the conformal Killing vector condition.

Analytical solutions to Einstein field equations for spherically symmetric anisotropic matter: a comparative study using Tolman VII metric potential

In this paper, we present analytical solutions to the Einstein field equations for spherically symmetric anisotropic matter distributions using the well-established Tolman VII metric potential, chosen for its strong physical and mathematical foundations. Our solutions are derived using three distinct approaches: the vanishing complexity factor condition (VCC), the embedding class I condition (ECC), and the conformally flat condition (CFC). We conduct a comprehensive comparative analysis of these three approaches. By ensuring a smooth match between the interior spacetime metric and the exterior Schwarzschild metric, and applying the condition of vanishing radial pressure at the boundary, we determine the model parameters. We graphically assess the model’s stability by examining conditions such as causality, the adiabatic index, equations of state, and the generalized Tolman–Oppenheimer–Volkov (TOV) equation, considering the forces acting within the system. Additionally, the effects of anisotropy on the stars’ physical characteristics are investigated through graphical representations.

Neuromorphic learning and recognition in WO3−x thin film-based forming-free flexible electronic synapses

In pursuing advanced neuromorphic applications, this study introduces the successful engineering of a flexible electronic synapse based on WO3-x, structured as W/WO3-x/Pt/Muscovite-Mica. This artificial synapse is designed to emulate crucial learning behaviors fundamental to in-memory computing. We systematically explore synaptic plasticity dynamics by implementing pulse measurements capturing potentiation and depression traits akin to biological synapses under flat and different bending conditions, thereby highlighting its potential suitability for flexible electronic applications. The findings demonstrate that the memristor accurately replicates essential properties of biological synapses, including short-term plasticity (STP), long-term plasticity (LTP), and the intriguing transition from STP to LTP. Furthermore, other variables are investigated, such as paired-pulse facilitation, spike rate-dependent plasticity, spike time-dependent plasticity, pulse duration-dependent plasticity, and pulse amplitude-dependent plasticity. Utilizing data from flat and differently bent synapses, neural network simulations for pattern recognition tasks using the Modified National Institute of Standards and Technology dataset reveal a high recognition accuracy of ∼95% with a fast learning speed that requires only 15 epochs to reach saturation.

Research on thermal-solid coupling behavior of drum brake under emergency braking on slopes

Abstract When a truck makes emergency braking while driving on a slope, the transient impact force generated can easily cause personal injury to passengers and damage the vehicle’s braking system. In order to study the working state of the brake under this working condition, the ANSYS finite element thermal-solid coupling transient analysis method was used to establish the mechanical model and finite element model of the vehicle and brake under the slope emergency braking state, showing the temperature field and stress field distribution rules and interactions of the drum brake under this working condition, and compared with the flat road emergency braking condition. The results show that the maximum temperature of the brake reaches 184.26°C during emergency braking, and the stress field and temperature field are strongly coupled in two directions, which can easily lead to uneven wear of the linings and a reduction in the fatigue life of the brake.

Spherically symmetric configurations in the quadratic f(R) gravity

We study spherically symmetric configurations of the quadratic f(R) gravity [f(R)=R−R2/6μ2]. In the case of a purely gravitational system, we have fully investigated the global qualitative behavior of all static solutions satisfying the conditions of asymptotic flatness. These solutions are proved to be regular everywhere except for a naked singularity at the center; they are uniquely determined by the total mass M and the “scalar charge” Q characterizing the strength of the scalaron field at spatial infinity. The case Q=0 yields the Schwarzschild solution, but an arbitrarily small Q≠0 leads to the appearance of a central naked singularity having a significant effect on the neighboring region, even when the space-time metric in the outer region is practically insensitive to the scalaron field. Approximation procedures are developed to derive asymptotic relations near the naked singularity and at spatial infinity, and the leading terms of the solutions are presented. We have investigated the linear stability of the static solutions with respect to radial perturbations satisfying the null Dirichlet boundary condition at the center and numerically estimate the range of parameters corresponding to stable/unstable configurations. In particular, the configurations with sufficiently small Q turn out to be linearly unstable. Published by the American Physical Society 2024

A Moment-Sum-of-Squares Hierarchy for Robust Polynomial Matrix Inequality Optimization with Sum-of-Squares Convexity

We study a class of polynomial optimization problems with a robust polynomial matrix inequality (PMI) constraint where the uncertainty set itself is also defined by a PMI. These can be viewed as matrix generalizations of semi-infinite polynomial programs because they involve actually infinitely many PMI constraints in general. Under certain sum-of-squares (SOS)-convexity assumptions, we construct a hierarchy of increasingly tight moment-SOS relaxations for solving such problems. Most of the nice features of the moment-SOS hierarchy for the usual polynomial optimization are extended to this more complicated setting. In particular, asymptotic convergence of the hierarchy is guaranteed, and finite convergence can be certified if some flat extension condition holds true. To extract global minimizers, we provide a linear algebra procedure for recovering a finitely atomic matrix-valued measure from truncated matrix-valued moments. As an application, we are able to solve the problem of minimizing the smallest eigenvalue of a polynomial matrix subject to a PMI constraint. If SOS convexity is replaced by convexity, we can still approximate the optimal value as closely as desired by solving a sequence of semidefinite programs and certify global optimality in case that certain flat extension conditions hold true. Finally, an extension to the nonconvexity setting is provided under a rank 1 condition. To obtain the above-mentioned results, techniques from real algebraic geometry, matrix-valued measure theory, and convex optimization are employed. Funding: This work was supported by the National Key Research and Development Program of China [Grant 2023YFA1009401] and the National Natural Science Foundation of China [Grants 11571350 and 12201618].

New Embedded Wormhole Solutions in Ricci Inverse Gravity

AbstractIn this work, two new embedded WH solutions are obtained by using the Class‐I approach in the background of newly fourth‐order Ricci inverse gravity. It is shown that the combination of these newly calculated shape functions and Ricci inverse gravity provides us with the possibility of obtaining traversable wormholes. All the required wormhole properties are discussed, along with flaring out and flatness conditions. The embedded diagrams within the scope of upper and lower universes are provided under the effect of both newly calculated embedded shape functions. All the energy conditions are explored with valid and negative regions. The presence of exotic matter is confirmed due to the negative region in all the energy conditions, specifically in the null energy condition. The Doppler effect through the red‐blue shifts function is also discussed. Several key findings from the current research are described that demonstrate the validity of these wormhole solutions in Ricci inverse gravity.