Flat Conditions Research Articles

Tribological Evaluation of Coatings in Fuel Environments

Abstract To enhance the durability and reliability of high-pressure fuel system components operating with low-viscosity fuels, an analysis of the tribological performance of potential coating material candidates was conducted. This study focuses on evaluating the friction and wear characteristics of various coatings widely used by industry for surface protection, including carbides, nitrides, diamond-like carbon (DLC), and solid lubricants, under accelerated reciprocating ball on flat conditions intended to provide information on longer term operation in fuel pumps. The tribological performance of these coatings in fuels of varying chemistry and viscosity, including ethanol, decane, dodecane, and aviation fuel (F-24), was compared to the mechanical properties of materials, such as hardness and elastic modulus. Results indicate that carbides show the lowest friction and wear values across different fuel environments. CrN-based coatings demonstrate a decrease in friction and wear in comparison to other nitrides. This comprehensive investigation lays the groundwork for informed design decisions in developing high-performance coatings tailored to withstand the challenges of low-viscosity fuel environments.

Geometry from geodesics: fine-tuning Ehlers, Pirani, and Schild

Ehlers, Pirani, and Schild argued that measurements of null and timelike geodesics yield Weyl and projective connections, respectively, with compatibility in the lightlike limit giving an integrable Weyl connection. Their conclusions hold only for a 4-dim representation of the conformal connection on the null cone, and by restricting reparameterizations of timelike geodesics to yield a torsion-free, affine connection. An arbitrary connection gives greater freedom. A linear connection for the conformal symmetry of null geodesics requires the SO(4,2) representation. The enlarged class of projective transformations of timelike geodesics changes Weyl’s projective curvature, and we find invariant forms of the torsion and nonmetricity, along with a new, invariant, second rank tensor field generalizing the dilatational curvature without requiring a metric. We show that either projective or conformal connections require a monotonic, twice differentiable function on a spacetime region foliated by order isomorphic, totally ordered, twice differentiable timelike curves in a necessarily Lorentzian geometry. We prove that the conditions for projective and conformal Ricci flatness imply each other and gauge choices within either can reduce the geometry to the original Riemannian form. Thus, measurements of null and timelike geodesics lead to an SO(4,2) connection, with no requirement for a lightlike limit. Reduction to integrable Weyl symmetry can only follow from the field equations of a gravity theory. We show that the simplest quadratic spacetime action leads to this reduction.

Optimizing the graft size in the Evans osteotomy to minimize the calcaneocuboid joint pressure by highly realistic in-silico analysis

This contribution details a new high-fidelity finite element analysis (FEA) methodology for the investigation of the effect of the graft size on the pressure distribution developing at the calcaneocuboid joint after the Evans osteotomy procedure. The FEA model includes all 28 bones of the foot up to the distal end of fibula and tibia as well as soft tissues, tendons, and muscles. The developed FEA model was validated by comparing the in-vivo pressure distribution on the foot plantar with the in-silico results, resulting in a low deviation equal to 7.8%, and with the deformed foot shape caused by the body weight in static standing position measured by a high-precision lidar scanning, for an average shape error of 5.3%. The developed FEA was then employed to investigate the effect of the graft size on the calcaneocuboid joint pressure and improvement in the medial-longitudinal arch for a flat foot patient, where the soft and hard tissues’ geometries were acquired by a CT scan. The results quantitatively demonstrated that the maximum pressure at the calcaneocuboid joint follows a quadratic trend where the minimum point also represents the best compromise to alleviate the flat foot condition while avoiding excessive pressure.

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.

Experimental Characterization of Contact Stiffness for Fixture Design

When cutting flexible metal workpieces, the mechanical characteristics of the fixture play a crucial role in suppressing deformation and vibration. Previously, the influence of fixture design elements on workpiece vibration has been studied with the aim of gaining a fundamental understanding of the phenomenon. Meanwhile, there has been limited research on the contact area between the fixture and workpiece, and there is a need for further research to understand the phenomenon and establish design guidelines for fixtures. In this paper, an experimental approach is proposed to characterize the relationship between stress on the contact surface and the resulting displacement. The main goal is to analyze the influence of contact surface shape and material on the deformation (or vibration) of the fixture and the workpiece. To this end, an on-machine measurement device was introduced. This device was used to obtain displacement-load curves without setup errors for materials such as PTFE, MC nylon, and aluminum alloy, as well as contact surface shapes such as flat or conical. From the obtained curves, the repeatability stability of the fixture was qualitatively evaluated. When using MC nylon, the plastic deformation was minimal even when loads were applied multiple times under flat conditions or conical conditions with a tip angle of 170° or more. This indicates that these contact conditions are stable as fixtures. On the other hand, when using PTFE, buckling occurred due to its low Young’s modulus, and the workpiece was damaged when using aluminum alloy. This suggests that these materials are not suitable for use as fixtures in this paper. For a more quantitative evaluation, an assessment based on contact stiffness was conducted. The displacement-load curves were modeled using a power-law function, following existing elastoplastic models. The contact stiffness was calculated from the slope of the tangent line to the displacement-load curve at maximum load. When using MC nylon as the material, the contact stiffness was found to be a maximum of 6×106 N/m. Furthermore, the rate of change of contact stiffness during loading and unloading was used to quantitatively evaluate the fixture stability.

Unsteady Loading on a Tidal Turbine Due to the Turbulent Wake of an Upstream Turbine Interacting with a Seabed Ridge

Tidal sites can present uneven seabed bathymetry features that induce favourable or adverse pressure gradients and are sources of turbulence, and so are likely to affect the operation, performance, and wake recovery dynamics of deployed tidal-stream turbines. Large-eddy simulations are conducted to analyse the unsteady loading of a tidal turbine subjected to the wake of an upstream turbine that interacts with a two-dimensional ridge located between the two turbines. Relative to an isolated turbine, blade fatigue loading is increased by up to 43% when subject to the wake of a turbine located 8 turbine diameters upstream interacting with a ridge located 2 turbine diameters upstream, whereas for the same spacing, the turbine wake led to a limited 6% reduction in loading and the ridge wake only caused a 79% increase. For larger spacings, the trends were similar, but the magnitude of difference reduced. Predictions of fatigue loads with a blade element momentum model (BEMT) provided a good agreement for flat bed conditions. However, the ridge-induced pressure gradient drives rapid spatial change of coherent flow structures, which limits the applicability of Taylor’s frozen turbulence hypothesis adopted in the BEMT. Reasonable prediction of rotor loading with BEMT was found to be obtained using the turbulent onset flow field at a plane one-diameter upstream of the turbine. This is more accurate than use of the planes at the rotor plane or two-diameters upstream, as coherent structures represent those modified by wake recovery and rotor induction in the approach flow to the turbine.

Time Domain and Qualitative Analysis of a Compact Asymmetrically Fed Circular UWB Antenna for WBAN Scenarios

This article presents about the design, time domain analysis and qualitative analysis of a circular monopole Ultra Wideband (UWB) antenna for Wireless Body Area Networks (WBAN) applications. The size of the proposed antenna is 30 x 30 x 1 mm3. The proposed antenna provides Ultra wide bandwidth from 2 – 10 GHz and also complies with IEEE C95.3 safety standards. The simulated and measured results are close to each other with minimum deviations. To ensure proper and less distorted communication in real time scenarios, time domain analysis was done for free space, on body and off body conditions. The magnitude and phase of transmission coefficient (S21) were found to be consistent. The group delay was analyzed under free space, on &off body conditions whose variations are less than 0.5 ns in the entire UWB range. Fidelity factor was also analyzed for flat and bent conditions to ensure pulse similarity. Also to ensure the communication link quality, the obtained minimum path loss of 51.10 dB and maximum Received Signal Power of 0.17 dBm were found to be satisfactory warranting a good transmission and reception characteristics of the proposed antenna

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

Numerical simulation on the influence of artificial island on reef hydrodynamics

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

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

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

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