Sine Curve Research Articles

The Design and Experimental Research on a High-Frequency Rotary Directional Valve

A directional valve is a core component of the electro-hydraulic shakers in fatigue testing machines, controlling the cylinder or motor that drives the piston for reciprocating linear or rotary motion. In this article, a high-speed rotating directional valve with a symmetrical flow channel layout is designed to optimize the force on the valve core of the directional valve. A comparative analysis is conducted on the flow capacity of valve ports with different shapes. A steady-state hydrodynamic mathematical model is established for the valve core, the theoretical analysis results of which are verified through a Computational Fluid Dynamics (CFD) simulation of the fluid domain inside the directional valve. A prototype of the rotatory directional valve is designed and manufactured, and an experimental platform is built to measure the hydraulic force acting on the valve core to verify the performance of the valve. The displacement curves at different commutation frequencies are also obtained. The experimental results show that the symmetrical flow channel layout can significantly optimize the hydraulic force during the movement of the valve core. Under a pressure of 1 MPa, the hydraulic cylinder driven by the prototype can achieve a sinusoidal curve output with a maximum frequency of 60 Hz and an amplitude of 2.5 mm. The innovation of this design lies in the creation of a directional valve with a symmetric flow channel layout. The feasibility of the design is verified through modeling, simulation, and experimentation, and it significantly optimizes the hydraulic forces acting on the spool. It provides us with the possibility to further improve the switching frequency of hydraulic valves and has important value in engineering applications.

Rapid non-contact measurement of distance between two pins of flexspline in harmonic reducers based on standard/actual parts comparison

In order to achieve rapid and precise measurement of distance between two pins of flexspline in harmonic reducers, an rapid non-contact measurement strategy based on standard/actual parts comparison is proposed. Firstly, to eliminate the installation eccentricity error of flexspline fixture, a sine-quadrant eccentricity error elimination method is designed. The sinusoidal curve and quadrant of the measured fixture eccentricity error with respect to the fixture rotation angle is used to calculate the eccentric error components along x and y axes, which has the advantages of simplicity and rapidity. Secondly, a Gaussian-Harmonic Wavelet Filtering (GHWF) algorithm is proposed to filter out the noise in the measurement process, which can effectively suppress the Gibbs phenomenon in harmonic wavelet transformation and improve the signal-to-noise ratio. Finally, an experimental platform including baseplate, turntable, flexspline, moving platform and laser sensor is constructed, in order to verify the performances of error elimination, noise filtering and distance measuring. Experimental results show that the measurement error of the proposed strategy is less than 7 μm, which is consistent with the accuracy obtained by the commercial high-precision gear measuring instrument. The average measurement time is about 29.6 s, much less than the 5 min of the commercial instrument, showing great application potential for the efficient distance measurement of gears and flexsplines.

Superstatistical functions of modified shifted Morse potential for diatomic molecules

The application of the molecular potential model to the study of different thermodynamic systems has been a focus of interest in recent time due to its importance in molecular and chemical physics. Hence, the asymptotic iteration method and the Laguerre polynomials are employed to obtain the eigensolutions of the Schrödinger equation with the modified shifted Morse potential model. Vibrational energy results for different diatomic molecules have been presented numerically, and these results are compared with experimental data and other results from available literature. The variation of normalised wave function and probability density of modified shifted Morse potential for some selected diatomic molecules at the ground- and first-excited states have been considered. Results obtained show that the equally spaced sinusoidal wave curves and varying nodes depend on the level of electron concentrations in the diatomic molecules considered. Partition function and other superstatistical function expressions of modified shifted Morse potential for some diatomic molecules within the modified Dirac delta distribution are obtained, using the Poisson summation formula. The superstatistical plots show a high level of dependence on the temperature parameter, maximum vibrational quantum number and deformation parameter. The superstatistical functions for a deformation parameter of zero correspond to the conventional thermodynamic functions.

Employing stable isotopes to reveal temporal trajectories of water travelling through the soil–plant-atmosphere continuum

The spatiotemporal patterns of water travelling through the soil–plant-atmosphere continuum (SPAC) have received much attention due to the frequency of extreme weather and water scarcity. However, the interconnections and transboundary transport of specific compartments within the hydrologic cycle are poorly understood. We portrayed the propagation paths of water isotope signals by analyzing isotopes of precipitation, soil water, and xylem water. The isotope sine curves analysis method was improved to quantify water transfer efficiency, mean transmission time from precipitation to soil (MTT1), mean transmission time from soil to trees (MTT2), mean residence time within soil (MRTSW), and mean residence time within tree xylems (MRTXY). The temporal trajectory of water traveling through SPAC was depicted, and its influencing factors and intrinsic mechanisms were explored. Our results showed that (1) water isotopes were blocked when crossing water pools (precipitation, soil water, and xylem water) and the transfer efficiency was progressively weaker (85.5 %→13.5 %). (2) The MTT1 was significantly and positively correlated with soil porosity (Spearman correlation coefficient, 0.551). Its spatiotemporal pattern (0.8–15.9d) indicated that the transport and mixing of soil water involved two modes: displacement flow and bypass flow. The MTT2 (−13.2d–4.3d) of Platycadus orientalis was in general smaller than that of Quercus variabilis (−4.7d–11.5d). (3) The MRT (35.2d–343.8d) was influenced by a combination of soil physicochemical properties, root distribution, and tree morphological traits. Our study shows that connectivity between pools is better reflected with transfer efficiency. Comparing MTT and MRT of P. orientalis and Q. variabilis, tree hydrodynamic processes were quantified, and P. orientalis was more sensitive to seasonal moisture variability. Additionally, our study improved the understanding of the “black box” within the hydrological interface of plant-soil interactions.

Lift enhancement via leading edge vortex delay in flapping flight utilizing kinematic modifications

Flapping-winged micro aerial vehicles (MAVs) are an innovative approach to indoor flight, useful for reconnaissance. However, challenges remain in improving the maneuverability of these drones in low-speed flight, specifically using wing kinematics for different flight profiles. This work focuses on the plunge motion of the SD7003 airfoil in forward flight. Unsteady simulations are carried out at a Reynolds number of 10,000 in Ansys Fluent upon validation against experimental, theoretical, and numerical results from literature. Modification of the kinematics is performed by skewing the sinusoidal curve that dictates the effective angle of attack of the airfoil, leading to what is termed “peak-shifted” (PS) kinematics. The skewness of the curve is varied systematically to delay the peak of plunge velocity during the downstroke. Due to this, the leading edge vortex formation and shedding were also found to be delayed, with stronger vortex cores causing a surge in lift force. Results indicate that with the PS kinematics, mean lift increased by 4.5% and mean drag reduced by 7.9%, at the cost of an increase in power requirement of 42.9% compared to the baseline kinematics. Since lift augmentation and drag reduction are obtained with no change in plunge amplitude or frequency, this opens up opportunities in tail-less MAV design to use PS kinematics in short intervals for maneuvers or flight controls, including roll, pitch, and yaw.

Sudden cardiac death due to adrenal insufficiency masquerading as Brugada syndrome. Case report

Sudden cardiac death in young people in 20% of cases is caused by cardiomyopathies and channelopathies. One of the forms of channelopathies is Brugada syndrome, a hereditary disease characterized by ST segment elevation in the right precordial leads (V1-V3) and an increased risk of sudden cardiac death in the absence of structural heart disease. Brugada phenocopies are also known – clinical situations that are manifested by electrocardiogram (ECG) patterns identical to true Brugada syndrome. They are caused by different clinical circumstances and form a group of heterogeneous conditions that are often difficult to distinguish from true congenital Brugada syndrome due to identical ECG patterns. The formation of Brugada phenocopy due to hyperkalemia is presented in the literature in various conditions: with renal failure, after extensive trauma, application of medications. The article presents a case report demonstrating a rare cause of sudden cardiac arrest in a young patient without a history of cardiovascular pathology: the occurrence of the Brugada pattern on the ECG due to severe hyperkalemia in adrenal insufficiency. The stages of the differential diagnostic search are described, which made it possible to verify the final diagnosis and prescribe effective hormone replacement therapy. Performing a provocative test with novocanamide allowed us to confirm that the patient had a phenocopy, and not Brugada syndrome. Differential diagnosis of phenocopies of Brugada syndrome – a series of often life-threatening cardiac and non-cardiac diseases and conditions, manifested by similar ECG changes in the form of a peculiar ST segment elevation in leads V1-V3, is often a difficult task. This case represents a phenocopy of Brugada in the setting of severe hyperkalemia with development of cardiac arrest due to adrenal insufficiency, which resolved with correction of electrolyte abnormalities and treatment of the underlying disease. Typical ECGs are presented: a graph of the Brugada phenomenon, hyperkalemia, a sinusoidal curve during cardiac arrest, recorded over time in a patient, and the pathogenetic mechanisms causing the formation of the Brugada pattern in adrenal insufficiency are explained.

Research on damage characteristics and contact interface evolution behavior of double-block ballastless track considering tunnel floor heave

Excessive railway tunnel floor heave (TFH) will reduce the durability of the track structure and jeopardize train operation safety. The TFH characteristics were fitted into cosine and bilinear curves according to the monitoring data. A nonlinear failure analysis model of double-block ballastless track under TFH was established. The deformation transfer law, structural damage mechanism and the interlayer bonding interface failure evolution of the track structure under different TFH characteristics were explored. The results show that the deformation of TFH can be well mapped to the track. The amplitude transfer ratio is less than 100 %. The maximum wavelength transfer ratio under the cosine and bilinear TFH is 129.3 % and 127.5 %, respectively. To avoid the damage of track structure, when the wavelength is 10 m, the amplitude of cosine and bilinear TFH should be controlled at 2.5 mm and 0.5 mm respectively. When the wavelength is greater than 10 m, the amplitude can be appropriately increased. To avoid interlayer bonding cracking, the cosine and bilinear amplitudes with a wavelength of 10 m should be controlled at 5 mm and 1.5 mm, respectively. The track-tunnel interlayer debonding failure under the cosine curve occurs at the edge of the TFH, while the bilinear curve occurs at the center and edge of the TFH. The gaps under the cosine and bilinear TFH exhibit double-peak and multi-peak shapes, respectively. This study can provide theoretical guidance for controlling the performance degradation of track structure caused by TFH.

Multi-layer topology optimization of dual-fluid convective heat transfer in printed circuit heat exchangers

Optimizing channel configurations in printed circuit heat exchangers is essential for enhancing heat transfer and minimizing pumping power. The present study aims to optimize channel configurations by developing a multi-layer topology optimization (TO) model that simultaneously optimizes the fin structures in both the cold and hot fluid layers. The TO model directly integrates the heat transfer rate as the target function while using the pressure drop from an airfoil structure as the constraint. Counterintuitive channel configurations are generated by the TO model under various Reynolds numbers (Re). The evaluation under both laminar and turbulent conditions demonstrates that the TO-designed channel configuration outperforms conventional channel configurations including empty, airfoil, heatric, louver, modified louver, sine curve, and S-shaped designs. Compared with the airfoil structure, at Re = 300, the optimized structure can reduce pumping power by 17.0 % while increasing heat transfer by 10.8 %, and at Re = 20000 it reduces pumping power by 52.0 % and enhances heat transfer by 1.2 %. The present study introduces a promising method for designing novel printed circuit heat exchangers.

Experimental study on eccentric compression of the prefabricated columns with a new type of column-column connection node

An assembled building is defined by a construction methodology wherein prefabricated components are fabricated off-site and subsequently assembled at the construction site. This methodology confers cost efficiency, expedites construction timelines, and enhances the quality of the prefabricated components. Furthermore, it mitigates a range of environmental concerns inherent to conventional poured-in-place construction methods. This paper introduces a novel assembled column-column connection node that utilizes a new adhesive potted rebar lap joint. The research was divided into two principal components. Firstly, 18 specimens of adhesive potted rebar lap joints were tested under tension, with the lap length being the variable parameter. Secondly, eccentric compression experiments were conducted on one poured-in-place column and six assembled columns, varying parameters such as stirrup configuration and the length of the post-poured section. The failure modes of the columns, as well as their bearing capacities, deflection, rebar strains, and concrete strains, were analyzed and recorded. The test results revealed the existence of two different failure modes in the tensile tests of adhesive potted rebar lap joints. It was found that the reasonable lap length of the specimen should be no less than 14 times the diameter of the rebar (d). Eq. (15) was employed to estimate the suitable lap length for specimens with different sleeve and rebar diameters. In the failure sections of the prefabricated columns, all failures occurred outside the nodes. Moreover, the mechanical properties of small eccentrically compressed columns were comparable to those of the poured-in-place column. The use of spiral stirrups enhances the bearing capacity of the specimen, and an increase in the length of the post-poured section corresponds to a greater bearing capacity. The lateral deflection of the poured-in-place column generally follows a sinusoidal curve, while the lateral deflection of prefabricated columns in the later stages of loading does not exhibit a sinusoidal pattern. Both align with the assumption of a flat section. The stress performance of adhesive potted rebar lap joints in eccentric columns meets the strength requirements. The inclusion of tenons minimally affects the stress distribution in the node, fulfilling construction specifications. The stress performance of the assembled column nodes is reliable. The proposed adhesive potted rebar lap joint technology, along with the novel prefabricated column-column node, provides significant insights into engineering design and construction applications.

Research on design and control methods of a lightweight upper limb joint isokinetic rehabilitation training equipment.

Isokinetic exercise can improve joint muscle strength and stability, making it suitable for early rehabilitation of stroke patients. However, traditional isokinetic equipment is bulky and costly, and cannot effectively avoid external environmental interference. This paper designed a lightweight upper limb joint isokinetic rehabilitation training equipment, with a control system that includes a speed planning strategy and speed control with disturbance rejection. Based on the established human-machine kinematic closed-loop model between the equipment and the user, a dynamic evaluation method of torque at the joint level was proposed. To validate the effectiveness of the equipment, experiments were conducted by manually applying random disturbances to the equipment operated at an isokinetic speed. The results showed that the root mean square error between the observed torque curve of the second-order linear extended state observer used in this paper and the actual disturbance curve was 0.52, and the maximum speed tracking error of the speed control algorithm was 1.27%. In fast and slow sinusoidal speed curve tracking experiments, the root mean square errors of the speed tracking results for this algorithm were 9.65 and 5.27, respectively, while the tracking errors for the PID speed control algorithm under the same environment were 19.94 and 12.11. The research results indicate that compared with traditional PID control method, the proposed control strategy demonstrates superior performance in achieving isokinetic control and suppressing external disturbances, thereby exhibiting significant potential in promoting upper limb rehabilitation among patients.

Control and prediction of bedding-parallel fractures in fine-grained sedimentary rocks: A case from the Permian Lucaogou Formation in Jimusar Sag, Junggar Basin, Western China

The fine-grained sedimentary rocks have numerous bedding-parallel fractures that are essential for the migration, enrichment, and efficient development of oil and gas. However, because of their variety and the complexity of the factors that affect them, their spatial prediction by the industrial community becomes challenging. Based on sample cores, thin sections, and well-logging and seismic data, this study employed a multi-scale data matching approach to quantitatively predict the development of bedding-parallel fractures and investigate their spatial distribution. Bedding-parallel fractures in the Lucaogou Formation in Jimusar Sag frequently occur along preexisting bedding planes and lithological interfaces. Unfilled bedding-parallel fractures inside or near source-rocks exhibit enhanced oil-bearing capacity. They were identified on micro-resistivity scanning images by the presence of regularly continuous black or nearly black sinusoidal curves. Overall, the developmental degree of bedding-parallel fractures was positively related to the brittle mineral and total organic carbon contents and negatively related to single reservoir interval thickness. The maintained porosity of the reservoir matrix contributed to a thorough response to factors affecting the development of bedding-parallel fractures. Here, an effective and objective method was proposed for predicting the development and distribution of bedding-parallel fractures in the fine-grained sedimentary rocks. The method was based on the matched reservoir interval density, reservoir interval density, and matched sweet spot density of bedding-parallel fractures. The prediction method integrated the significant advantages of high vertical resolution from logging curves and strong lateral continuity from seismic data. The average relative prediction error was 8% in the upper sweet spot in the Lucaogou Formation, indicating that the evaluation parameters for bedding-parallel fractures in fine-grained sedimentary rocks were reasonable and reliable and that the proposed prediction method has a stronger adaptability than the previously reported methods. The workflow based on multi-scale matching and stepwise progression can be applied in similar fine-grained sedimentary rocks, providing reliable technological support for the exploration and development of hydrocarbons.

A simple sinusoidal curve‐based one‐dimensional periodic leaky‐wave antenna for high‐gain continuous beam scanning

AbstractA novel technique is presented based on a sinusoidal curve‐shaped one‐dimensional periodic leaky‐wave antenna to eliminate open stopband (OSB) and enhance gain. The radiating stub is inspired by a sinusoidal curve showing zero phase constant at a single broadside frequency (9 GHz) and ripple‐free attenuation constant. The technique is first used on a unit cell with half‐cycle sinusoidal‐curved radiating stub to achieve uniform gain and OSB suppression. Subsequently, to further improve the gain, a unit cell with a full‐cycle sinusoidal‐curved radiating stub with an offset introduced at the centerline is applied. Finally, the full‐cycle sinusoidal stub is modified by introducing a pair of inclined “branching” half‐cycle sinusoidal stubs at an angle θ° from the centerline to further enhance the gain. A 4.65 dB gain improvement is observed along with complete OSB elimination for the proposed design.

Comprehensive Understanding of TGO Morphology Effect on the Thermal Barrier Coatings Failure Under Free Edges

Abstract The growth stresses induced by the thermally grown oxide (TGO) will be amplified at the free-edge site, making the free-edge site a weak part of the thermal barrier coatings (TBCs). In this study, the TBCs failure behavior is investigated based on different TGO morphologies under free edges. The thermomechanical model is established by creating straight lines and simplified sinusoidal curves, respectively. Dynamic TGO growth is realized by the secondary development of the subroutine. The cohesive element is inserted at the TC/TGO interface to simulate the delamination. The stress evolution near different TGO morphologies under the influence of the free edge are examined. In addition, the interfacial cracking behavior near the free edge is also explored. The results show that the appearance of the free edge will deteriorate the stress condition in the nearby area, change the preferred cracking area, and induce the earlier failure behavior. The straight line morphology has the most “friendly” stress distribution. The sinusoidal curves have peaks and valleys, and different areas of the TGO shape are different under the influence of the free edge, but all of them have the effect of stress “convergence”. These results can provide significant guidance to develop the next-generation advanced TBCs.

The Characteristics of Long-Wave Irregularities in High-Speed Railway Vertical Curves and Method for Mitigation.

Track geometry measurements (TGMs) are a critical methodology for assessing the quality of track regularities and, thus, are essential for ensuring the safety and comfort of high-speed railway (HSR) operations. TGMs also serve as foundational datasets for engineering departments to devise daily maintenance and repair strategies. During routine maintenance, S-shaped long-wave irregularities (SLIs) were found to be present in the vertical direction from track geometry cars (TGCs) at the beginning and end of a vertical curve (VC). In this paper, we conduct a comprehensive analysis and comparison of the characteristics of these SLIs and design a long-wave filter for simulating inertial measurement systems (IMSs). This simulation experiment conclusively demonstrates that SLIs are not attributed to track geometric deformation from the design reference. Instead, imperfections in the longitudinal profile's design are what cause abrupt changes in the vehicle's acceleration, resulting in the measurement output of SLIs. Expanding upon this foundation, an additional investigation concerning the quantitative relationship between SLIs and longitudinal profiles is pursued. Finally, a method that involves the addition of a third-degree parabolic transition curve (TDPTC) or a full-wave sinusoidal transition curve (FSTC) is proposed for a smooth transition between the slope and the circular curve, designed to eliminate the abrupt changes in vertical acceleration and to mitigate SLIs. The correctness and effectiveness of this method are validated through filtering simulation experiments. These experiments indicate that the proposed method not only eliminates abrupt changes in vertical acceleration, but also significantly mitigates SLIs.

Quantum entanglement and classical correlation have the same form

In agreement with the data, the quantum correlation between spins violates Bell’s inequality by following a cosine curve when one analyzer is rotated relative to the other. In contrast, the linear correlation attributed to hidden variables has never been observed. Besides these well-established facts, we show here that classical covariance, Pearson correlation, between spins projected as up or down on the analyzer axes also follows the cosine form hitherto uniquely ascribed to the quantum mechanical expectation value. The common cause for the classical correlation is the conservation of intrinsic angular momentum that aligns the two spins antiparallel at the breakup. Thus, as long as the spins retain their orientations relative to each other, the measurement of one spin in a chosen frame of reference also discloses the opposite orientation of the other in that frame. Realizing that classical correlation has the same functional form as quantum entanglement sheds light on the foundations of modern physics and quantum computing.

Circadian Rhythms in Tongue Features.

(1) Background: The aim of this study was to investigate the circadian rhythms of tongue features according to the effects of physiological phases over a 24 h period. (2) Methods: Fifteen healthy participants aged 20 to 69 years were recruited. The participants did not have current chronic diseases or past diseases and had to meet the inclusion and exclusion criteria. The participants stayed at the Gil Hospital for a duration of 2 nights and 3 days. On the first day, at 18:00, they consumed their allocated portions of food and water and then completed a questionnaire. At approximately 21:00, their tongue images were acquired using a computerized tongue image acquisition system, following which they slept for 8 h, commencing at 23:00. Measurements were taken from 07:00 through 21:00 on the second day, and the final acquisition was taken at 07:00 on the following morning, resulting in a total of eight images. The circadian rhythm was authenticated and quantified utilizing the single cosinor analysis, a technique for periodic regression analysis for fitting a 24 h cosine curve. (3) Results: Cosinor analysis revealed that all tongue features were significantly related to circadian rhythm. (4) Conclusions: The results of this study may be important for considering the time of day at which the tongue is observed and tongue status is evaluated.

Influence of 3D surface irregularities on the performance of hydrostatic rectangular tilted thrust pad bearing configurations

Tribological behavior of tribo-pairs is strongly dependent on the surface topography. Further, the structural deformation, manufacturing, and assembly errors cause the hydrostatic thrust pad bearings to tilt slightly. The work in this article is aimed to study the effect of tilt and three-dimensional (3D) surface irregularities on the performance of hydrostatic rectangular thrust pad bearings (HRTPB) compensated with capillary restrictors. The 3D surface irregularities are assumed to follow cosine curve. To perform the analysis, a source code has been developed in MATLAB and the Finite Element Method has been used to solve the governing Reynold's equation. The numerical simulation results indicate that the effect of tilt reduces the value of fluid film reaction, fluid film stiffness, and fluid film damping coefficients. The study reveals that 3D surface irregularities results in a higher value of fluid film stiffness and damping coefficient as compared to that of smooth-bearing surfaces.

Enhancing hydrological insight: isotopic methods revealing groundwater–surface water interactions in the Lower Quang Tri River Group, Vietnam

ABSTRACT The Lower Quang Tri River Group, situated in central Vietnam, faces a myriad of challenges, notably the decline in groundwater levels and the salinisation of both groundwater and surface water, significantly impacting water availability for domestic, agricultural, and industrial purposes. To address these pressing concerns, this study adopts a comprehensive methodology integrating hydrogeological measurements, isotopic techniques, and chemical analyses of various water sources, including local precipitation, surface water bodies, reservoirs, and groundwater samples. Utilising the deuterium and oxygen-18 signatures (δ 2H and δ 18O) in water molecules as environmental tracers for the assessment of base flow and water sources enables a nuanced understanding of the intricate interaction between surface water and groundwater. Research findings elucidate that during the dry season, groundwater recharge primarily stems from water in the reservoirs over approximately seven months. Base flow contributes between 80 and 85 % of streamflow during the rainy season, escalating to 100 % during the dry season. The mean travelling time of the base flow is estimated at 120 ± 10 days using the sine curve model developed by Rodgers et al. The insights gleaned from this study are poised to play a pivotal role in guiding the local water resources managers in licensing for the exploitation of a right quantities of groundwater as sustainable management strategies in the region.

Compliant mechanism design of combined aircraft wing for stable separation

Abstract Stable separation is a crucial condition that must be met in order for combined aircraft to successfully engage in cooperative flight. In order to achieve the desired fast and controlled separation, this paper proposes a novel design for a torque-driven compliant separation mechanism. By taking into account the compliance characteristics of a sinusoidal acceleration function curve, a mechanical model for the separation mechanism is developed. By utilising the Coulomb friction law, an accurate determination of the aerodynamic load distribution under various conditions is achieved. Subsequently, the relationship between the unlocking moment and the aerodynamic load is derived based on these findings. Through the utilisation of the finite element method, a model of the separation mechanism is generated. To ensure the safety and reliability of the compliant separation mechanism, the mechanical properties of the structural materials are thoroughly analysed under the maximum aerodynamic load. Subsequently, the separation mechanism structure is constructed and subjected to testing in order to showcase the compliance characteristics. In addition, this paper conducts a simulation to analyse the impact of flight speed and angle-of-attack on the separation process. By doing so, the optimal conditions for separation are determined. The methods and findings presented in this study have the potential to contribute valuable insights to the design of combined aircraft.

An Analysis of the Kinematics and Dynamics Performance of a New Type of Three-Pronged Sliding Universal Coupling

The three-pronged sliding universal coupling is a new kind of three-pronged coupling. The purpose of this study is to demonstrate that, compared with a traditional unequal angular velocity universal coupling (such as the Hooke universal coupling), the universal coupling has the superior characteristics of constant angular speed transmission, simple structure and strong transmission capacity by performing kinematic and dynamic analysis of the new three-pronged sliding constant angular velocity universal coupling. It provides a broad prospect for applications in automotive and other fields. To study its kinematic and dynamic characteristics, directional cosine matrices are utilized as tools to analyze the coordinate systems by establishing simplified geometric models and corresponding motions. Through the analysis of the motions of the input and output shafts and employing the method of single-force element, a set of equilibrium equations for the forces acting on the output shaft and the input shaft are formulated for solution analysis. The research indicates that during the rotation process, there exists a small angular difference between the input shaft and the intermediate shaft, demonstrating the quasi-constant angular velocity characteristics of the new tripod sliding universal coupling. The curves of the forces and force moment acting on each component of the coupling approximate sinusoidal curves. The optimal operating angle range for the new tripod universal coupling is at angle , during which the system exhibits good transmission and mechanical performance. It can be widely used in the automobile industry, tie steel industry and other occasions that require angular transmission. It is especially used in high-speed operation and large transmission capacity.