Reduction Of Moment Research Articles

Squatting in adolescents with unilateral and bilateral hip dysplasia.

Adolescent hip dysplasia is a condition that often affects hip mechanics, leading to loss of function, pain, and early onset osteoarthritis. Objective literature investigating functional activities remains sparse within this population. A traditional body weight deep squat has translation to everyday tasks, is a clinical screening tool, and is also a common pre/rehabilitation exercise. However, the biomechanical approach and potential movement compensations have not been investigated in this population. Thirty patients diagnosed with dysplasia from a pediatric hip registry were included. Each patient completed 3D motion capture with minimal instructions during the squat. Wilcoxon signed-rank tests were conducted to compare differences between: affected and unaffected limbs, unilateral and bilateral patients, patients and controls. A Spearman correlation assessed the relationship between symptom severity (modified Harris Hip Score) and squat depth. Unilateral and bilateral patients demonstrated similar biomechanical movement patterns across both limbs (p>0.05). When compared to controls, dysplasia patients squatted with less sagittal plane range of motion throughout the lower extremities, reducing achievable squat depth (p<0.05). Upright trunk positioning was identified as a movement compensation that led to a reduction in the hip flexor moment. Symptom severity was not associated with squat depth (r=-0.282, p=0.058). An upright trunk compensation (i.e. knee dominant squat) may be utilized by adolescent hip dysplasia patients. When incorporating squats for targeted hip strengthening in this population, it may be advisable for clinicians to encourage greater trunk flexion to effectively engage the hip musculature.

Analysis of an Existing Box Culvert Structure with or Without Retrofiting Using Analysis Tool

The design and comparative analysis of box culverts subjected to vehicle loading are the main topics of this study. For the structural analysis and design of an old and a retrofitted culvert, STAAD Pro CONNECT Edition was used. Using STAAD Pro, a comprehensive 3D model with geometric and material properties was made for every culvert. A comparative study of the outcomes showed that the modified culvert had greatly improved. Significant reductions in axial force, shear force, bending moment, and torsion in comparison to the original structure are among the main findings. These improvements were ascribed to the extra reinforcement that was added in the course of the retrofitting. The modified culvert showed improved stiffness, overall structural integrity, and load-carrying capability. The study demonstrates how well STAAD Pro CONNECT Edition works for box culvert design and analysis.

Improving MRI turbulence quantification by addressing the measurement errors caused by the derivatives of the turbulent velocity field - Sequence development and in-vitro validation.

To improve the current method for MRI turbulence quantification which is the intravoxel phase dispersion (IVPD) method. Turbulence is commonly characterized by the Reynolds stress tensor (RST) which describes the velocity covariance matrix. A major source for systematic errors in MRI is the sequence's sensitivity to the variance of the derivatives of velocity, such as the acceleration variance, which can lead to a substantial measurement bias. We developed a Cartesian phase contrast sequence with fast velocity encoding and two separately measured partial echoes with opposite readout directions. This design aims to reduce the high-order gradient moments that are responsible for the described measurement error. Velocity encoding directions follow the ICOSA6 scheme to capture the full RST. Turbulence data is reconstructed using the intra-voxel phase dispersion (IVPD) technique. We validated this sequence in vitro using a periodic hill flow benchmark with highly anisotropic turbulence. MRI data underwent extensive averaging, with multiple velocity encoding values employed to reduce noise and isolate systematic effects. The RST data obtained from the new sequence agree well with the ground truth. Compared to a state-of-the-art sequence, the maximum errors were reduced by factor five. Simple adjustments to current MRI protocols can greatly enhance turbulence measurement accuracy through the reduction of high-order gradient moments. The proposed measures include applying fast velocity encoding, high readout bandwidth, and a highly asymmetric readout. Ringing artifacts due to the asymmetric readout can be removed via a second, inverted readout.

Optimum Nitrogen and Density Allocation for Trade−Off Between Yield and Lodging Resistance of Winter Wheat

Increasing nitrogen and planting density can enhance crop yield, but it can reduce lodging resistance due to decreased lignin content. There is an urgent need to find feasible measures to balance these conflicting factors. We conducted a two-year field experiment in Tai’an, Shandong Province, China, evaluated SN23 (lodging resistant) and SN16 (lodging sensitive), under three nitrogen applications (120 kg/ha, N1; 240 kg/ha, N2; 360 kg/ha, N3) and four planting densities (75 plants/m2, D1; 225 plants/m2, D2; 375 plants/m2, D3; 525 plants/m2, D4), with N2D2 as the control, and measured lodging resistance related indexes and yield. N2D3 (SN23) increased internode length by 0.40 cm, reduced fresh weight by 0.09 g, resulting in a bending moment reduction of 0.39 g/cm. Lignin, cellulose, and hemicellulose decreased by 18.27, 16.48, and 16.22 mg/g DW, while S and G lignin subunits decreased by 118.09 and 127.34 μg/g DW, and H subunit increased by 23.59 μg/g DW. Eventually, the breaking strength was reduced by 1.74 g/cm resulting in a reduction of 0.09 in the lodging resistance index. The yield reached 10.17 t/ha due to an increase in spike number by 100.33 plants/m2, achieving an optimal balance between yield and lodging resistance in this experiment. This study provides a viable solution for balancing lodging resistance and yield in winter wheat.

Influence of soil hysteretic damping on lateral response of offshore wind turbine monopile in sandy soil

Damping plays an important role in the design of offshore wind turbine structures. The hysteretic damping of the seabed soil represents the energy dissipation caused by the soil-particle interaction and the nonlinear behavior of the soil under cyclic loading. However, the effect of sand damping on the lateral response of the monopile foundation of an offshore wind turbine is still unclear. In this paper, the effect of soil hysteretic damping on the lateral dynamic response of a monopile foundation in a sandy seabed is investigated using a subplastic soil constitutive model. The constitutive model response at the foundation level is verified by comparing the monotonic and cyclic responses of the monopile with the results of the 1g model test. The results show that when soil hysteretic damping is present in the monopile-soil system, the energy dissipation in the soil reduces the stress accumulation in the soil, resulting in a reduction in the bending moment and horizontal displacement of the monopile, compared with the case without soil hysteretic damping. The results are crucial for optimizing the monolithic design of offshore wind turbine structures.

Research on an Aerial Docking Strategy for Meta-UAVs Using Aerodynamic Data Surrogate Models

Meta-aircraft, in High-Altitude, Long-Endurance (HALE) unmanned aerial vehicle (UAV) applications, utilize a strategy of formation flying in the stratosphere and aerial docking in the troposphere to enhance flight range and gust resistance. This paper explores an aerial docking strategy for unmanned meta-aircraft using a surrogate model based on aerodynamic data. The study begins with an analysis of the aerodynamic characteristics and the establishment of a dynamic model, followed by the development of a surrogate model using the vortex lattice method and a BP neural network. This model accurately simulates aerodynamic changes near the wingtip. Optimization of the docking process, focusing on impulse and moment of impulse, is achieved using a greedy algorithm. The results show a reduction in drag impulse and rolling moment by 10.89% and 15.76%, respectively, thereby easing the burden on the control system of UAVs.

Robust optimization design of a blended wing-body drone considering influence of propulsion system

In contrast to conventional configurations, blended wing-body drones exhibit a pronounced coupling between their aerodynamic and propulsion system. While this configuration significantly enhances aerodynamic efficiency, perturbations in flight conditions substantially influence aerodynamic performance. To fully exploit the performance benefits inherent in this configuration, this paper integrates the calculation of the total pressure recovery coefficient and distortion coefficient into the flow field solution and achieves the gradient evaluation of these parameters. This allows the effects of the propulsion system to be considered in the gradient-based optimization. Additionally, utilizing the Gradient-enhanced polynomial chaos expansion (GPCE) method, we construct statistical moment related to the mean and variance and analytically compute the gradients of the moment with respect to the design variables. Consequently, a gradient-based uncertainty optimization framework that accounts for the effects of the propulsion system is established. The framework can accommodate large-scale deterministic design variables and several uncertain parameters. Using this framework, both deterministic and uncertainty-based optimizations that consider the effects of the propulsion system are performed. The objective functions include statistical moments accounting for flight conditions uncertainties. The comparison reveals a 11.89% reduction in statistical moment with robust optimization, highlighting the efficacy of the framework in future robust design optimization of propulsion-airframe integration.

Analytical investigation on the rotational behavior of dovetail mortise–tenon joints between beams and columns in traditional Chinese timber frames

We theoretically analyzed the rotational behavior of beam–column dovetail joints in traditional Chinese timber frames in this study. An analytical model of dovetail joints at both the column head and body was designed by clarifying the moment generation mechanism and effect of rotational embedment yielding in timber perpendicular to the grain on the rotational behavior of joints. An asynchronous manifestation of rotational embedment deformation across the column surface, tenon cheeks, and upper and lower surfaces of the tenon head was analyzed, and the corresponding characteristic yield points and consequent reduction in rotational stiffness were derived in the model. The Inayama embedment theory was used to clarify the effect of rotational embedment with varying end lengths on the movement of the joint rotation center and asymmetric moment generated in different rotation directions of the column head joint. The precision of the analytical model was validated through a comparative analysis by involving nine sets of experimental data, for estimating the initial stiffness, post-yield stiffness, and identified yield points. The implications of the parameters, including the initial gap between the tenon and mortise, geometric dimensions of the dovetail tenon, and friction coefficient, were also discussed. Controlling the ratio of the initial gap and tenon height within 0.01 to ensure a certain rotational resistance of dovetail beam–column joints within the collapse limits of traditional timber frames is recommended considering the significant effect of the initial gap on the initial sliding angle and moment reduction.

Single-molecule Magnets (SMM) spin channels connecting FeMn antiferromagnet and NiFe ferromagnetic electrodes of a tunnel junction

The integration of single-molecule magnets (SMMs) into magnetic tunnel junctions (MTJs) offers significant potential for advancing molecular spintronics, particularly for next-generation memory devices, quantum computing, and energy storage technologies such as solar cells. In this study, we present the first demonstration of SMM-induced spin-dependent properties in an antiferromagnet-based MTJ molecular spintronic device (MTJMSD). We engineered cross-junction-shaped devices comprising FeMn/AlOx/NiFe MTJs. The AlOx barrier thickness where the exposed junction edges meet was comparable to the SMM length, facilitating the incorporation of SMM molecules as spin channels for spin-dependent transport. The SMM channels enabled long-range magnetic moment ordering around molecular junctions, which were precisely engineered via fabrication processes. The SMM, composed of a [Mn6(μ3-O)2(H2N-sao)6(6-atha)2(EtOH)6] (H2N-saoH = salicylamidoxime, 6-atha = 6-acetylthiohexanoate) complex, featured thioester groups at the ends that upon hydrolysis they form bonds with the magnetic electrodes. SMM-treated junctions demonstrated a significant current enhancement, reaching up to 7 μA at an input voltage of 60 mV. Furthermore, SMM-doped junctions exhibited current stabilization in the μA range at lower temperatures, whereas the bare electrodes showed current suppression to the picoampere range. Magnetization measurements conducted at 55 K and 300 K on pillar-shaped devices revealed a reduction in magnetic moment at low temperatures. Additionally, Kelvin probe atomic force microscopy (KPAFM) measurements confirmed that SMM integration transformed the electronic properties over long ranges.These findings are attributed to the spin channels formed between magnetic metal electrodes, which enhance spin polarization at each magnetic electrode. Our research highlights the potential of using antiferromagnetic materials, characterized by minimal stray fields and zero net magnetization, to transform MTJMSD devices.

Doping effects in strontium hexaferrite: Theoretical and experimental analysis

Hexagonal ferrites based on SrFe12O19 (SFO) are vital materials in the field of permanent magnets, valued for their cost-effectiveness and reliable magnetic properties, making them a more affordable alternative to rare-earth permanent magnets. This study focuses on understanding the doping effects of commonly used elements in SFO system. DFT calculation results show that doping La or La-Co can enhance the phase stability of SFO, in which Co has a preference for the 4f1 sites of Fe. The total magnetic moment was observed to slightly decrease with La doping, whereas it exhibited an increasing trend with La-Co and La-Ca-Co co-doping and the largest increase of 6.5 % can be obtained in Sr2LaCaFe44Co4O76 (SLCFCO). The increase in the total magnetic moment is mainly attributed to the smaller antiferromagnetic moment of Co than that of Fe on 4f1 sites, as well as the reduction in the antiferromagnetic Fe moments at 4f1 and 4f2 sites. The total density of states indicates a transition from semiconductor behavior to a metallic character both in the La-Co and La-Ca-Co doped versions. The experimental results validate the theoretical predictions, confirming enhancements in magnetic performance. The saturation magnetization increased from 63.86 Am2/kg in SrFe11.7O19 (SFO) to 67.53 Am2/kg in Sr0.4La0.4Ca0.2Fe10.5Co0.5O19 composition. These findings provide a vital understanding of tuning the magnetic and electronic properties in doped SFO, which will enable the development of advanced applications in magnetic materials.

Impact of dyke and vegetation on fluid force and moment reduction under sub and supercritical flow conditions

Flooding is the most common natural disaster throughout the world and requires efficient management. Therefore, the current investigation aimed to explore the impact of a composite defense system comprising dyke and vegetation on flow dynamics and velocity reduction. Experiments were conducted in an open channel setup with an adjustable bed slope and transparent sidewalls, and the vegetation model was replicated as real trees such as Eucalyptus trees. The study involved calculating several parameters, including flow velocity, reduction of fluid force index (RFI%), reduction in moment index (RMI%), and hydrostatic and hydrodynamic forces. These calculations were done by changing the channel bed slope and keeping the flow rate (discharge) constant while considering both subcritical and supercritical flow conditions. Moreover, regression analysis was performed for the prediction of RFI% and RMI% under various flow conditions. Also, statistical analyses were performed to assess the effectiveness of the defense system in reducing fluid force and moment indices. The result of the current investigation indicates that the highest values of RFI% and RMI% under subcritical flow conditions were 79% and 88%, while under supercritical flow conditions they were 94% and 78%, respectively. Moreover, a velocity reduction of 69% was observed under subcritical flow, while 84% was observed under supercritical flow conditions. Under subcritical flow conditions, RFI% and RMI% enhanced by enhancing Froude number (Fr) because of an increase in velocity reduction and hydraulic jump formation. Similar trends were observed under supercritical flow conditions, with effective mitigation of high-velocity flows by the composite system. The finding of current research helps in providing effective techniques for flood management.

Influence of Walking Modification Strategies on Frontal Plane Hip Joint Moment and Gait Naturalness in Healthy Adults

OBJECTIVE: To evaluate the effects of lateral trunk lean and step width modification on hip adduction moment in healthy participants and examine their influence on walking naturalness. METHODS: Ten healthy participants underwent gait analysis under 4 walking conditions: natural walking, large trunk lean, doubled step width, and combined modification with slight trunk lean and 1.5 times step width. Early stance and late stance hip adduction moment were analyzed and compared using repeated-measures analysis of variance. Subjective naturalness of gait was also recorded. RESULTS: We observed a significant effect of walking condition on the hip adduction moment during early stance (F3,36 = 6.665, P = .001) and gait naturalness (F3,36 = 30.519, P&lt;.001), but not hip adduction moment during late stance ( P = .733). Pairwise comparison indicated significantly reduced hip adduction moment during early stance with large trunk lean when compared to natural walking (36.7% less, P = .002, Cohen’s d = −1.41). Both combined and doubled step width modifications did not yield the expected hip adduction moment reduction ( P&gt;.296). The perceived naturalness of the doubled step width modification was most comparable to natural walking ( P = .529), while the trunk lean modification was significantly less natural than natural walking and the least natural modification overall (81.1% less, P&lt;.001, Cohen’s d = −4.34). CONCLUSION: Although trunk lean modification effectively reduces hip joint loading, it is perceived as the least natural pattern. Step width was more challenging to modify than trunk lean. JOSPT Open 2024;2(4):306-314. Epub 7 August 2024. doi:10.2519/josptopen.2024.0463

A Hinge Moment Alleviation Control Strategy for Morphing Tail Aircraft Based on a Data-Driven Method

Morphing airplane technology is currently a focal point of research. For morphing airplanes, besides effective morphing strategies and control schemes, the hinge moment at the root of the vertical tail during morphing is a critical factor influencing flight safety. To prevent failure in tail morphing due to excessive hinge moments, this paper analyzes the hinge moment characteristics of the variable vertical tail structure in high-speed flight, based on a flying wing model from the China Aerodynamics Research and Development Center. The proposed adaptive morphing tail hinge moment reduction (AMTHR) method is model-free, utilizing real-time data to dynamically adjust the rudder and reduce hinge moments without requiring prior knowledge of system dynamics. This method utilizes the concept of extremum-seeking control by introducing periodic perturbations to the system and adjusting the control input based on their impact on the output. This approach drives the output toward an extremum point, enabling real-time reduction of the vertical tail hinge moment. Finally, the simulation analysis is carried out under the conditions of no wind and gust disturbance, and the effect of this method on the load reduction of the tail hinge moment is verified.

Screening and Antiscreening Effects in Endohedral Nanotubes.

Recently we investigated from first-principles screening properties in systems where small molecules, characterized by a finite electronic dipole moment, are encapsulated in different nanocages. The most relevant result was the observation of an antiscreening effect in alkali-halide nanocages characterized by ionic bonds: in fact, due to the relative displacement of positive and negative ions, induced by the dipole moment of the encapsulated molecule, these cages act as dipole-field amplifiers, different from what is observed in carbon fullerene nanocages, which exhibit instead a pronounced screening effect. Here we extend the study to another class of nanostructures: the nanotubes. Using first-principles techniques based on density functional theory, we studied the properties of endohedral nanotubes obtained by encapsulation of a water molecule or a linear HF molecule. A detailed analysis of the effective dipole moment of the complexes and of the electronic charge distribution suggests that screening effects crucially depend not only on the nature of the intramolecular bonds but also on the size and the shape of the nanotubes and on the specific encapsulated molecule. As observed in endohedral nanocages, screening is maximum in covalent-bond carbon nanotubes, while it is reduced in partially ionic nanotubes, and an antiscreening effect is observed in some ionic nanotubes. However, in this case, the scenario is more complex than in corresponding ionic nanocages. In fact the specific geometric structure of alkali-halide nanotubes turns out to be crucial for determining the screening/antiscreening behavior: while nanotubes with octagonal transversal section can exhibit an antiscreening effect, which quantitatively depends on the number of layers in the longitudinal direction, instead nanotubes with dodecagonal section are always characterized by a reduction of the total dipole moment so that a screening behavior is observed. Our results show that, even in nanotube structures, in principle one can tune the dipole moment and generate electrostatic fields at the nanoscale without the aid of external potentials.

A data-driven computational optimization framework for designing thin-walled lenticular deployable composite boom with optimal load-bearing and folding capabilities

The thin-walled lenticular deployable composite boom (LDCB) is promising for aerospace engineering applications due to its lightweight and compact nature, but its mechanical behaviors are the main challenges limiting its practical application. Here, the axial compression and folding behaviors of LDCB were numerically simulated and the simulation results were verified according to the experimental data in the literature. Then, a new double chains quantum genetic algorithm (DCQGA)-gaussian process regression (GPR) model and data-driven computational optimization framework were proposed and the new model was trained using a database with 400 simulation results, the superiority of which was demonstrated by prediction accuracy evaluation. Additionally, benchmarking five state-of-the-art algorithms found that the coupling technology of DCQGA-GPR-non-dominated sorting genetic algorithm III (NSGA-III) is an excellent optimization strategy to obtain a well-designed structure of LDCB that maximizes the effectiveness of the material while satisfying the lightweight. The optimized LDCB design exhibits a significant performance improvement, with a 26.3 % reduction in the folding moment, a 34.2 % reduction in the maximum Tsai-Hill failure index, a 43.6 % increase in the critical load, and an 11 % reduction in linear density of mass compared to the initial design.

Enhancement of the structural behavior of elevated water tanks using X-plate dampers

This study aims at utilizing of X-plate dampers to effectively address vibrations and minimize the possible structural harm to water tank facilities, and also at utilizing a finite element methodology to simulate and analyze the structural reactions. A non-linear time history analysis is employed to assess the effectiveness of X-plate dampers when subjected to different blast-induced ground motions. The efficiency of dampers was evaluated by conducting a comparative analysis of liquid storage structures with and without dampers using 50 m3 and 1500 m3 tanks in empty and full conditions. X – plate dampers are installed in a variety of bracing schemes, such as diagonal, X, V, Inverted V, and K bracing subjected to underground blast loads to improve the resilience of the selected elevated water tanks. The results showed the X-bracing pattern is the most effective configuration for X-plate dampers in mitigating blast loads in a 50 m3 elevated tank without water, resulting in a reduction of displacement, shear force, and bending moment by 43%, 15%, and 22%, in case of elevated tank with water reduced by 39% 25% and 33% respectively. In 1500 m3 elevated tank without water, the K-bracing is determined to be the most effective type of bracing, reducing the displacement, shear force, and bending moment by 50%, 70%, and 70%, in case of elevated tank with water reduced by 53%, 52%, and 54% respectively. The current study makes a significant contribution to the field of structural engineering by providing useful insights into raised water tank construction.

Ultrahigh Q surface lattice resonance supported by a U-shaped resonant ring nanoarray.

We achieved an ultrahigh Q surface lattice resonance (SLR) using a conventional U-shaped split ring resonator (U-SRR) array. Numerical results confirmed by semi-analytical analysis show that with the transmission resonance amplitude up to 0.8, the Q-factor of the SLR can still surpass 104. The physical mechanisms of the ultrahigh Q-factor were also investigated. Besides the radiation suppression provided by conventional SLR, the unique geometry of the U-SRR can further offer dual radiation suppression mechanisms: reduction of the dipole moment and excitation of the in-plane quadrupole. We expect that the proposed ultrahigh Q SLR platform will be explored for more flexible and advanced nanoscale devices.

Interatomic correlations moments in graphene monolayer

This study investigated the interatomic correlation moments within a graphene monolayer using the correlative approach based on an unsymmetrized self-consistent field (CUSF) method. This analysis encompassed various approximations, such as the harmonic, quasi-harmonic, and weakly anharmonic models. Numerical evaluations for low temperatures were conducted employing the parametric interatomic potential specifically developed for graphene by Tewary and Yang. The findings revealed a notable reduction in the interatomic correlation moments with increased interatomic distance. Moreover, the correlations between the transverse atomic displacements were less pronounced than those between the longitudinal displacements. Additionally, the significance of anharmonicity was duly validated. Comparatively, the longitudinal atomic displacements in the graphene lattice exhibited a stronger correlation than the square and hexagonal lattices.

Mitigation of crosswind effects on high-speed trains using vortex generators

Vortex generators can enhance the operational safety of high-speed trains and offer effective anti-rolling performance. This paper investigates the influence of vortex generator installation angles on the aerodynamic characteristics of trains. The Improved Delayed Detached Eddy Simulation method is used to analyze the leeward side vortex structure. It is found that when the angle between the vortex generators and the relative wind is 30°, the rolling moment of the train is minimized, as it significantly reduces side forces while preventing excessive growth of lift force inducing rolling moment. The reduction in rolling moment of the train by vortex generators is attributed to the suppression of leeward side trailing vortices of the train, which delays flow separation at the roof of the train, inducing a downward trend in the separated flow. Dynamic Mode Decomposition reveals that vortex generators do not alter the stability of near-body trailing vortices but enhance the pulsatile characteristics of far-body trailing vortices, which do not affect the pressure distribution on the leeward side of the train.

Effects of shear on the lateral torsional buckling of singly-symmetric I-beams

This paper presents an investigation on the negative effects of shear on the lateral torsional buckling (LTB) of singly-symmetric I-shaped beams due to web distortion associated with shear. Results from a parametric FEA study including eigenvalue buckling analyses and large-displacement analyses were utilized considering both stiffened and unstiffened webs to consider the impact of shear on the LTB resistance. Moment gradients caused by constant shear and a shear gradient were considered. The FEA solutions demonstrate that shear can significantly reduce the lateral-torsional buckling resistance. The FEA results were used to develop design equations that account for the reduction in the LTB capacity from shear. The solutions were compared with conventional methods proposed by Winter to account for the effects of web distortion on girders with slender webs. Results from the study show that (i) the average flange area should be used to account for the effects of shear of singly-symmetric beams; (ii) post-buckling strength has limited impact on the shear effects with regards to the LTB resistance; and, (iii) compared to Winter's approach, the proposed method can capture the variation of the moment reduction factor with the shear force in the unbraced length, and is able to predict moment resistances with reasonable accuracy compared to refined FEA solutions using both eigenvalue analysis and large-displacement analysis. Design examples are provided to demonstrate the calculation procedure.