Longitudinal Moment Research Articles

A response surface equation for the drag polar for an airplane flying in the vicinity of wavy sea surface

The drag polar equation is the key issue to calculate the performance-based parameters during various flight phases and determine the optimum conditions. This is an essential feature to be included in airplane flight control system to manage the flight. The aircraft under certain emergency conditions are instructed to land on sea water. This underlines the combinational role of ground effect and the surface wave shape on airplane aerodynamic responses. Up to now, many investigations have described the airfoil and wing aerodynamic behaviors near the ground but none was devoted to an airplane flying near a wavy surface. In this paper, intensive numerical simulations have been carried out on a general aviation airplane flying near the water wavy surface. The effects of ground proximity as well as the wave amplitude have been investigated on airplane 2D longitudinal forces and moment. Some limited wind tunnel tests have also been performed on the same model, in the vicinity of water surface to validate the numerical calculations. A statistical quadratic equation based on Response Surface Model, RSM, has been proposed for the airplane flying in the vicinity of the wavy water in which, the wave shape deterioration due to both the airplane flowfield and the viscous dissipation has been taken into account. The statistical measures approve the model quality and accuracy in comparison to the numerical simulation data. The results show that the oscillations in aerodynamic forces are strong functions of the wave amplitude. The time variations of both CL and CD follow the shape of the surface wave while it does not have any remarkable effect on their mean values.

Influence of velocity pulse directivity on seismic response of cross-fault bridges

Pulse-type ground motions have special destructive effects on structures, and directivity is one of the fundamental characteristics of velocity pulses. In this paper, the impact of the velocity pulse directivity of seismic motions on both sides of the fault on the seismic response of fault-crossing bridges was quantified using the original records from the Chi-Chi earthquake in Taiwan. First, an automatic baseline correction method was applied to restore the permanent ground displacement, and the direction corresponding to the strongest pulse energy on both sides of the fault was identified based on continuous wavelet transformation. On this basis, the variability of the peak intensity of ground motions on the hanging wall and footwall in different directions, as well as the differences in pulse characteristics between the strongest pulse component and the two initial horizontal components, were analysed. Finally, a typical 5 × 30 m continuous girder bridge was considered as the research object to reveal the influence of the velocity pulse directivity on the seismic response of key parts on both sides of the fault. The results showed that the variability in the peak ground-motion intensity on the hanging wall of the fault was higher than that on the footwall. The displacement variability was up to 863 %, velocity was 262 %, and acceleration was 124 %. The pulse characteristics of the strongest pulse component were stronger than those of the parallel and vertical fault components, and its acceleration, velocity, and displacement response spectra were larger. The amplification effects of the velocity pulse directivity on the transverse bending moment, longitudinal bending moment, and torque of the pier bottom reached 1.3, 1.1, and 1.6, respectively. However, the amplification effect of the velocity pulse directivity on the relative displacement of the pier top, displacement of the main beam, and displacement of the bearing was more than 1.6 times, which was more significant than the internal force of the pier bottom.

Gamification as a Tool to Improve Vocabulary in English Language in High-School Students

Gamification has gained popularity among educators who perceive it as a useful tool for carrying out the teaching-learning process optimally. The lack of positive results in the learning of English as a foreign language has become one of the main challenges Mexico faces considered the language as a priority. English teachers know the importance of finding options to present new words to students in a way they could learn appropriately. Vocabulary is a meaningful key of language learning, based on it, other skills are developed. Trough unplugged gamification there has been determinate the relation between the strategy and academic results in written tests in vocabulary area, specifically nouns, among fourth-semester students in high-school education at Plantel Norte, Escuela de Bachilleres. The study follows a quantitative approach with a quasi-experimental design, correlational scope, and a longitudinal study moment when nouns have been measured based on tests administered before and after the development and use of these low-cost games.

Wilberforce-like Larmor Magnetic Moment and Spin Precession.

In a Wilberforce pendulum, two mechanical oscillators are coupled: one pertains to the longitudinal (tension) motion and the other to the rotational (twisting) motion. It is shown that the longitudinal magnetic moment of circular currents, and similarly the magnetic moment of a spin-chain, can exhibit a Wilberforce-like vibration. The longitudinal oscillation is related to the Langevin diamagnetism, while the twisting motion is superimposed on the magnetic moment and spin precession. The calculations show that the coupling term is nonlinear in this (longitudinal) vibrating and (magnetic moment) precession system. By increasing the strength of the coupling we arrive at a spectrum, where further vibrational modes can be associated with the rotation of the precession. This means that the extent of the change in coherence can be demonstrated. Since the coupling strength can be different due to local effects, this can be an important factor from the point of view of signal propagation and in preserving signal shapes. The amount specifying the dissipation is introduced to express the degree of deviation. A relationship exists between the parameter characteristic of the coupling strength and how its quantity influences decoherence and dissipation.

Modeling of the unsteady aerodynamic characteristics of the NACA 0015 airfoil from the data of numerical calculations of the flow

The possible application of the results of numerical modeling in developing an approximate phenomenological mathematical aerodynamic model applicable in solving the problems of dynamics is studied with reference to the example of the unsteady flow past the NACA 0015 airfoil oscillating in the angle of attackat different frequencies, amplitudes, and mean angles of attack. For this purpose, the Reynolds equations are solved in both steady and unsteady formulations, together with thek–ω-SST turbulence model. The results of the calculations are validated by means of comparing them with the experimental data. The model of the normal force and the longitudinal moment formulated within the frameworkof an approach introducing an internal dynamic variable is identified according to the data of calculations. The results of the modeling are compared with the numerical and experimental data. The comparison with the conventional approach to the modeling based on the linear unsteady model with the use of dynamic derivatives is also carried out.

The influence of flow field bottom effect and sand cloud effect on the hydrodynamic performance and stability of bottom trawling otter board under tilted attitudes

To explore how bottom and sand cloud effects influence the hydrodynamic performance and stability of bottom trawling otter board under tilted attitudes, this study combines numerical simulations by oval cambered otter board and flume tank experiments verification. By assessing drag and lift coefficients (CD,CL), center-of-pressure coefficients (Cpc, Cpb) and longitudinal moment (My) in different heel angles, the study evaluates the impact under the two effects on hydrodynamics and stability. Findings reveal that inward and outward tilting increases CD maximally under sand cloud effect, while minimizing it under broad-field only water conditions; CL is maximal under bottom effect and minimal under broad-field only water conditions. For forward and backward tilting, CD under sand cloud effect is greater than that under bottom effect, with minimal values in broad-field only water conditions; CL is maximal under bottom effect and minimal under broad-field only water conditions. Additionally, stability varies across different flow field conditions, deteriorating along the x-axis due to bottom and sand cloud effects, while maintaining relative stability along the y-axis and z-axis. This study demonstrates that the bottom effect and sand cloud effect alter the otter board's proximity to the seabed and the fluid viscosity, leading to differences in hydrodynamic performance and stability under inclined attitudes. The findings aim to provide insights for the use and design of bottom trawling otter boards, ensuring stability and safety under various operating conditions and attitudes.

Antiferromagnetic liquid-crystal suspensions of goethite nanorods: three mechanisms of magnetic field influence on orientational structure.

The study looks into magnetically induced orientational transitions in suspensions of goethite nanorods based on a nematic liquid crystal. The study considers magnetically compensated suspension, which is a liquid-crystal analogue of an antiferromagnet. Unlike conventional magnetic particles, goethite nanorods have a remanent magnetic moment directed along the long axis of the particle and also they have negative diamagnetic anisotropy. Thus, it can be claimed that liquid-crystal composites of goethite nanorods have three mechanisms of interaction with an external magnetic field. The first two mechanisms are originally quadrupolar and are related to diamagnetic susceptibility anisotropies of liquid-crystal matrix and impurity goethite nanorods. The third mechanism is a dipolar one and is due to a remanent longitudinal magnetic moment of each dispersed particle. The magnetic-field-induced birefringence is used to show that the presence of three competing orientational mechanisms of interaction with an external magnetic field can both increase and decrease the Fréedericksz transition threshold compared to a pure liquid crystal. Diagrams of orientational phases of the suspension were constructed, and cases of various orientational mechanism predominance were analysed. Besides, a representation of the free energy of the suspension near the Fréedericksz transition in the form of the Landau expansion was obtained. This made it possible to establish that the Fréedericksz transition can occur as a phase transition of both the first and second order.

Airfoil Design Optimization of Blended Wing Body for Various Aerodynamic and Stealth Stations

The airfoil is the foundation of an aircraft, and its characteristics have a significant impact on those of the aircraft. Conventional airfoil design mainly focuses on improving aerodynamic performance, while flying wing airfoil designs should also consider layout stability and stealth performance. The design requirements for an airfoil vary with its position on the flying wing layout aircraft based on corresponding spanwise flow field characteristics. By analyzing the spanwise flow characteristics of the flying wing, partition design models for flying wing airfoils were established in this study, and a series of flying wing airfoil designs that consider aerodynamics and aerodynamic/stealth were implemented. Then, the designed airfoils were configured on a three-dimensional X-47B layout for testing and verification. The results showed that the aerodynamic design and the aerodynamic/stealth design exhibited significant improvements in terms for aerodynamic and longitudinal trimming characteristics. However, the cruise drag performance of the aerodynamic/stealth design was slightly worse than that of the aerodynamic design, although the longitudinal moment trimming characteristics were basically the same. The stealth characteristics of the aerodynamic/stealth design had significant advantages, indicating that there were weak contradictions between the aerodynamic, stealth, and trimming requirements in the design of the flying wing.

Fatigue life prediction of corroded hangers with parallel steel wire in a network arch bridge under vehicle-bridge interaction based on a novel noniterative simplified method

Fatigue damage is a main concern during the life-cycle maintenance of bridges with corroded hangers under vehicle-bridge interaction (VBI). In this study, a novel noniterative simplified method for VBI is proposed to analyze the responses of hangers in a network arch bridge, considering the effects of vehicle types, driving lanes, and road surface roughness. Furthermore, the fatigue life of corroded hangers is investigated, considering the actual traffic flow and uneven distribution of stress in the hanger’s cross-section. The results show that longitudinal and transverse bending moments of the hanger significantly affect the stress of steel wires in one hanger but have limited influence on stress amplitudes. The fatigue lives of steel wires are considerably reduced when subjected to both uniform and pitting corrosion. The fatigue life of steel wires is reduced under deteriorating road surface conditions. Moreover, as the fatigue life of steel wires in the hangers declines, the variations in fatigue life among individual steel wires within a single hanger gradually decrease. Consequently, this trend leads to a heightened likelihood of continuous wire breakage.

Coordinated torque control for enhanced steering and stability of independently driven mobile robots

PurposeMobile robots with independent wheel control face challenges in steering precision, motion stability and robustness across various wheel and steering system types. This paper aims to propose a coordinated torque distribution control approach that compensates for tracking deviations using the longitudinal moment generated by active steering.Design/methodology/approachBuilding upon a two-degree-of-freedom robot model, an adaptive robust controller is used to compute the total longitudinal moment, while the robot actuator is regulated based on the difference between autonomous steering and the longitudinal moment. An adaptive robust control scheme is developed to achieve accurate and stable generation of the desired total moment value. Furthermore, quadratic programming is used for torque allocation, optimizing maneuverability and tracking precision by considering the robot’s dynamic model, tire load rate and maximum motor torque output.FindingsComparative evaluations with autonomous steering Ackermann speed control and the average torque method validate the superior performance of the proposed control strategy, demonstrating improved tracking accuracy and robot stability under diverse driving conditions.Research limitations/implicationsWhen designing adaptive algorithms, using models with higher degrees of freedom can enhance accuracy. Furthermore, incorporating additional objective functions in moment distribution can be explored to enhance adaptability, particularly in extreme environments.Originality/valueBy combining this method with the path-tracking algorithm, the robot’s structural path-tracking capabilities and ability to navigate a variety of difficult terrains can be optimized and improved.

New insights into folding tape-spring

The tape-spring is widely used in aerospace, mechanical, and civil engineering due to its unique mechanical properties and compact size. This paper aims to establish a new analytical model to more accurately predict the folding behavior of the tape-spring, including the geometric configuration, folding moment versus longitudinal curvature curve, peak moment, and propagation moment. This model comprehensively considers the influence of stretching strain energy and bending strain energy on the total strain energy, and determines the folding behavior of the tape-spring through the minimum energy principle. The proposed analytical model was compared with Wuest’s model, Yee’s model, and Yao’s model. Experiments of tape-springs made from two different materials were utilized for validation. The study shows that the proposed model has the highest prediction accuracy compared with the classical models, with the error of approximately 10%. The reason for the significant difference in the prediction results between the proposed model and Yao’s model was given, and the relationship between stretching strain energy and bending strain energy during the folding process of the tape-spring was analyzed. The proposed model has broader applicability than classical models and provides new insights and solutions for accurate prediction of the folding behavior of the tape-spring.

A design approach to obtaining highly polar liquid crystal dimers

ABSTRACT The synthesis and characterisation of 10 members of the [4[(E)-[4-[4-[ω-(4-cyanophenyl)phenoxy]alkyloxy]-3-nitrophenyl]methylideneamino]phenyl] 2,4-dimethoxybenzoates is reported in which the number of methylene units in the flexible spacer is increased from three to twelve. The mesogenic units are based on cyanobiphenyl and 3-nitrobenzylideneaniline benzoate and linked by the spacer such that their dipoles are parallel giving rise to a large longitudinal dipole moment. All 10 members of the series show a nematic phase, and the nematic-isotropic transition temperatures, TNI, and associated entropy changes show a strong dependence on the length and parity of the spacer. This behaviour is attributed to the average shapes of the molecules and their flexibility. The heptyl member was further characterised using dielectric spectroscopy revealing a high value of dielectric permittivity reflecting the large dipole moment of the molecules and possibly indicating local short-range ferroelectric order. The synthesis and characterisation of two members of the [4[(E)-[4-[4-[3-(ω-cyanophenyl)phenoxy]alkyloxy]-4-nitrophenyl]methylideneamino]phenyl] 2,4-dimethoxybenzoates are also described for which the difference in shape between odd and even members is reduced. Both dimers are exclusively nematogenic and the difference between TNI for the odd and even member is smaller reflecting the more similar molecular shapes. The potential for developing dimers that exhibit the ferroelectric nematic phase is discussed.

Liquid sloshing in a tank vehicle: A numerical and experimental investigation with baffle configurations

A three-dimensional numerical model based on VOF (Volume of Fluid) method is established to investigate anti-sloshing effects of various baffle configurations, proposed in this paper, on liquid sloshing in a partially filled tank vehicle. A series of experiments were conducted in a scaled clean-bore or baffled tank. The liquid surface deformations obtained from the numerical model exhibit good agreement with the experimental results at each moment, demonstrating the validity of the numerical model. The validated numerical model was further used to investigate the anti-sloshing effect of different baffle configurations in full-size tank vehicles. The results imply that the addition of baffles can decrease longitudinal force and pitch moment to some extent, in terms of peak value or mean value. Moreover, the addition of baffles may elevate the fundamental sloshing frequency by 50% to 200%, mitigating the risk of resonance phenomena in tank vehicles.

Exploring the Impact of Linkage Structure in Ferroelectric Nematic and Smectic Liquid Crystals.

The liquid crystal molecule 3-fluoro-4-(3,4,5-trifluorophenyl)phenyl 2,6-difluoro-4-(trans-5-n-propyl-1,3-dioxane-2-yl)benzoate (DIO) has attracted considerable interest owing to its unique ferroelectric nematic phase and extraordinarily high dielectric constant. To expand the DIO series, novel analogs with 1,3-dioxane units converted to ester units (EST analogs) were synthesized, and their physical properties were characterized. The EST analogs exhibited ferroelectric phases similar to those of the corresponding DIO analogs. Interestingly, an EST analogue featuring a defluorinated benzoate unit exhibited a ferroelectric smectic A phase, despite its smaller longitudinal dipole moment of 6.9 D. This result diverges from the common knowledge that the formation of large longitudinal dipoles is traditionally effective in the emergence of ferroelectric phases. Unlike the DIO series, the EST analogs can be readily obtained without the formation of undesired geometric isomers, which is advantageous for practical applications. The results of this study provide valuable insights into the design of liquid-crystalline materials expressing ferroelectric phases.

Study and Analysis of the Relationship between Longitudinal Moment Coefficient and Angle of Attack or Lift Coefficient based on the Stability and Controllability of the ekranoplan

The ekranoplan, as a special type of vessel, combines the performance of an aircraft and a ship. It boasts high speed, low radar visibility, good maneuverability, excellent amphibious capabilities, and a unique feature that sets it apart from other vessels: it is immune to torpedo and mine attacks. This article aims to introduce the main component design of the ekranoplan, the composition of its power system, and analyze its stability and controllability. Through graphical analysis, the relationship between the longitudinal moment coefficient, attack angle, and lift coefficient of an aircraft was studied. The results indicate that ensuring stability for the ekranoplan is more challenging compared to an aircraft. The paper provides a good basis for subsequent seakeeping experiments on ground-effect winged vehicles, which is of great significance.

The influence of molecular shape and electronic properties on the formation of the ferroelectric nematic phase

ABSTRACT The synthesis and characterisation of two series of ferroelectric nematogens based on RM734 having an additional methoxy group on the central phenyl ring are reported, the 3-methoxy-4-((4-nitrophenoxy)carbonyl)phenyl 2-alkoxy-4-alkoxybenzoates (7-m-n) and the 3-methoxy-4-((3-fluoro-4-nitrophenoxy)carbonyl)phenyl 2-alkoxy-4-alkoxybenzoates (8-m-n). In order to compare the behaviour of these series to those of the corresponding materials that do not contain the methoxy group on the central phenyl ring, we also report the synthesis and characterisation of 4-[(4-nitrophenoxy)carbonyl]phenyl 4-methoxybenzoate (11-0-1), 4-[(3-fluoro-4-nitrophenoxy)carbonyl]phenyl 4-methoxybenzoate (12-0-1) and 4-[(3-fluoro-4-nitrophenoxy)carbonyl]phenyl 2,4-diethoxybenzoate (12-2-2). Two compounds in which a lateral ethoxy chain is attached to the central ring, 3-ethoxy-4-[(4-nitrophenoxy)carbonyl]phenyl 2,4-dimethoxybenzoate (18-2-1) and 3-ethoxy-4-[(3-fluoro-4-nitrophenoxy)carbonyl]phenyl 2,4-dimethoxybenzoate (19-2-1), are also described. The behaviour of these materials shows that the relative stabilities of the ferroelectric nematic, NF, and conventional nematic, N, phases are governed by a subtle interplay of steric and electronic factors. Furthermore, the electronic factors are better understood in terms of isolated regions of electron density rather than by a single large longitudinal dipole moment. In terms of molecular shape, to observe the NF phase it appears that the molecular structure must include one or more lateral substituents that enhance molecular biaxiality and destabilise the N phase.

Influence of erosion voids and traffic loads on buried large-diameter reinforced concrete pipes

Geotechnical centrifuge tests were conducted to examine the influence of invert voids and surface traffic loads on 1400 mm diameter reinforced concrete pipes buried with a shallow soil cover depth of 700 mm. Void formation beneath the pipe was simulated during centrifuge testing. The test results revealed that before void formation, the surface load directly above the middle of the pipe caused a significant increase in not only the circumferential bending moments but also the longitudinal bending moments, the latter of which was considerable and could not be ignored. Void formation beneath the middle of the pipe led to a reduction in both the circumferential bending moments and longitudinal bending moments at all measuring positions, i.e., crown, springline, and invert. The most significant reduction occurred at the invert, and there was even a reversal in the sign of the invert longitudinal bending moment. A comparison was made between centrifuge tests with erosion voids and surface loads at different horizontal positions, which had a marked influence even when the positions differed by half a pipe length. Joint rotation played an important role in relieving large bending moments of pipe barrels in a jointed pipeline when the void and surface load were located at the joint.

Analyzing the impact of the size of fluoro and chloro substituents on induced mesomorphism in hydrogen bonded liquid crystals.

Synthesis of new supramolecules with specific properties and realistic applications requires a sound knowledge of the structure-property relationships of the synthesized molecules. Non-covalent interaction like hydrogen bonding is conducive in realizing mesomorphism. The induction of the liquid crystalline character is associated with the strength of hydrogen bonds formed between the interacting components, which are affected by the change of polarity and polarizability of both components upon change in their terminal polar substituents. When the polar substituents are similar in their reactivity, how does the size of the polar substituent influence the mesomorphism? New hydrogen bonded liquid crystals are synthesized with fluorine and chlorine as substituents, and the mesomorphic behaviour is studied with the size of the substituent as a critical parameter. The chemical characterization is carried out by FTIR measurements, the phase characterization by polarizing optical microscopy and the thermal characterization by differential scanning calorimetry. The DFT method utilizing wb97x-D theory along with the cc-pVTZ basis set were used for the calculations. The hybrid functional B3LYP-D3 and Gaussian type basis set 6-31G(d,p) were used for studying the orientation of the molecules. It is observed that the ortho substituents reduce the co-planarity, meta substituents lead to the molecular broadening while para substituents exhibited highest mesomorphism by enhancing longitudinal dipole moment. Fluoro substituted compounds are exhibiting higher mesomorphism while the bulky chloro substituents are helping to better stack the molecules possessing longer chain lengths.

Research on simplified tire finite element modeling and simulation method

A simplified tire finite element model modeling and simulation method with high efficiency and accuracy is proposed to address the issues of poor efficiency and low accuracy in tire finite element simulation. Firstly, the detailed finite element model of the tire is established, and the viscoelastic material parameters are determined through theoretical analysis and simulation verification. Then, the Hyperelastic material parameters are obtained through cyclic Tensile testing, and finally, the static tire condition test verification is completed. Based on the established detailed finite element model of the tire, the influence of different rubber materials on the dynamic characteristics of the tire is studied. On this basis, simplified friction and structure models are proposed to complete the establishment of a simplified tire finite element model. The simulation results of lateral and longitudinal slip conditions are compared with experimental data by implanting a finite element friction model that considers slip velocity and contact pressure. Through simulation analysis, it was found that the tread compound has a significant impact on the dynamic characteristics of the tire, while other compounds have a relatively small impact. Simplifying the tire finite element model can significantly improve the efficiency of finite element simulation and reduce convergence issues. The comparison accuracy between the finite element model simulation results and experimental data is relatively high, with the average accuracy of longitudinal force, lateral force, and correction moment reaching 89%, 95%, and 81%, respectively. This verifies the correctness and effectiveness of the simplified tire finite element model modeling and simulation method. This method provides certain reference significance for improving the efficiency of tire finite element simulation and providing virtual matching between tires and the entire vehicle.

A Strain Fitting Strategy to Eliminate the Impact of Measuring Points Failure in Longitudinal Bending Moment Identification

The identification of longitudinal bending moments is a critical component in the health monitoring of ship structures. This study examines the effect of the failure of measurement points on the accuracy of bending moment identification and presents a solution using an XGboost fitting method. The impact of failure point position and quantity on strain fitting accuracy and bending moment identification was investigated by performing a four-point bending experiment in typical failure scenarios. Further numerical analysis was conducted to identify potential sources of errors in the measurement process. Additionally, several XGBoost-based fitting schemes were tested under practical conditions to provide reliable fitting suggestions. The results indicated that the XGboost strain fitting method outperforms conventional methods for removing failed measurement points, resulting in improved accuracy of identification. When the most critical failure condition occurs (i.e., the deck plate measurement points and deck stiffener measurement points fail), the XGboost method can still estimate the strain at the failure points with acceptable accuracy. These results also hold in complex load scenarios. Moreover, in the practical measurement conditions, the arrangement of measuring points includes two sections that are sufficient to support the fitting of failed measurement points by using the XGboost method. The XGboost strain fitting method exhibits promising potential in strain fitting applications.