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The beam-plate coupled structure is a typical structure in spacecraft solar wings, and the prediction of its mechanical environment is crucial for overall design, structure and mechanism subsystem design. However, it is usually difficult to perform ground simulation tests on spacecraft solar wings with full-size structure. Therefore, a scaled model is established based on similarity theory to forecast the dynamic response of the full-size structure. In this article, finite element (FE) and hybrid finite element-statistical energy analysis (FE-SEA) models of the beam-plate coupled structure are established according to the band division principle. Finite element model allows for detailed analysis of structural behaviour, while hybrid models incorporate statistical energy analysis to account for high-frequency dynamics. By integrating these approaches, a comprehensive understanding of the coupled structure's response can be achieved, facilitating efficient design and optimisation processes. The scaling laws of the dynamic response are obtained by combining the dimensional analysis and equation analysis methods, respectively. The scaled models are designed for verification, and the natural characteristics and vibration responses predicted by the scaled models are basically consistent with those of the prototype. The findings indicate that the prediction accuracy derived from the FE-SEA model is higher, which provides a novel approach for the dynamic similarity of complicated structures such as the solar wings of spacecraft. [ABSTRACT FROM AUTHOR]

Due to the diversity of image sources, content-based multi-source image fusion and retrieval have shown promising capabilities in computer vision tasks, and especially when applied in Computer-Aided Diagnosis (CAD) to automate and improve the accuracy of medical image analysis. The combination of computer vision and CAD systems has the potential to revolutionize healthcare by augmenting the expertise of clinicians, improving overall diagnostic accuracy and helping experts in the clinical decision-making process by classifying and retrieving similar annotated clinical images to a given query. In the context of multi-view mammography interpretation, the concept of multi-view feature fusion has recently been studied to improve retrieval performance while effectively guaranteeing the complementarity of both MLO and CC views. However, conventional multi-view feature fusion makes descriptors long and lacks to take into consideration the relationship between descriptors. To deal with this issue, we propose two hierarchical multi-view feature fusion methods, for multi-view mammogram retrieval, based on the Canonical Correlation Analysis (CCA), which is the most commonly used multivariate parametric test. In fact, we have adapted CCA to determine the relationship between two descriptors by processing latent correlation factors. Moreover, after extracting descriptors for each view, a comparative study of texture and shape fusion descriptors is proposed in order to identify the more discriminative features for multi-view mammogram retrieval. Then, a query-dependent distance metric preserving both visual resemblance and semantic similarity is carried out to dynamically determine the more appropriate distance measure for each query image. Extensive experiments on the challenging Curated Breast Imaging Subset of Digital Database for Screening Mammography (CBIS-DDSM) have demonstrated the effectiveness of the proposed hierarchical multi-view feature fusion for mammogram retrieval, which outperforms the performance achieved either by conventional fused information or by single view information. To improve the transparency of our paper, the source code of the proposed method and the related dataset (including readme files) are publicly accessible through the following GitHub link: https://github.com/ABDERRAHIMMAR/Multi-View-Feature-Fusion-for-Mammogram-Retrieval. This open-access resource empowers researchers and practitioners to delve deeper into our methodology, fostering collaboration and advancements in the field of computer-aided diagnosis and medical image analysis. [ABSTRACT FROM AUTHOR]

Due to the diversity of image sources, content-based multi-source image fusion and retrieval have shown promising capabilities in computer vision tasks, and especially when applied in Computer-Aided Diagnosis (CAD) to automate and improve the accuracy of medical image analysis. The combination of computer vision and CAD systems has the potential to revolutionize healthcare by augmenting the expertise of clinicians, improving overall diagnostic accuracy and helping experts in the clinical decision-making process by classifying and retrieving similar annotated clinical images to a given query. In the context of multi-view mammography interpretation, the concept of multi-view feature fusion has recently been studied to improve retrieval performance while effectively guaranteeing the complementarity of both MLO and CC views. However, conventional multi-view feature fusion makes descriptors long and lacks to take into consideration the relationship between descriptors. To deal with this issue, we propose two hierarchical multi-view feature fusion methods, for multi-view mammogram retrieval, based on the Canonical Correlation Analysis (CCA), which is the most commonly used multivariate parametric test. In fact, we have adapted CCA to determine the relationship between two descriptors by processing latent correlation factors. Moreover, after extracting descriptors for each view, a comparative study of texture and shape fusion descriptors is proposed in order to identify the more discriminative features for multi-view mammogram retrieval. Then, a query-dependent distance metric preserving both visual resemblance and semantic similarity is carried out to dynamically determine the more appropriate distance measure for each query image. Extensive experiments on the challenging Curated Breast Imaging Subset of Digital Database for Screening Mammography (CBIS-DDSM) have demonstrated the effectiveness of the proposed hierarchical multi-view feature fusion for mammogram retrieval, which outperforms the performance achieved either by conventional fused information or by single view information. To improve the transparency of our paper, the source code of the proposed method and the related dataset (including readme files) are publicly accessible through the following GitHub link: https://github.com/ABDERRAHIMMAR/Multi-View-Feature-Fusion-for-Mammogram-Retrieval. This open-access resource empowers researchers and practitioners to delve deeper into our methodology, fostering collaboration and advancements in the field of computer-aided diagnosis and medical image analysis.

Motivated by a design of a vertical axis wind turbine, we present a theory of dynamical similarity for mechanical systems consisting of interacting elastic solids, rigid bodies and incompressible fluids. Throughout, we focus on the geometrically nonlinear case. We approach the analysis by analyzing the equations of motion: we ask that a change of variables take these equations and mutual boundary conditions to themselves, while allowing a rescaling of space and time. While the disparity between the Eulerian and Lagrangian descriptions might seem to limit the possibilities, we find numerous cases that apparently have not been identified, especially for stiff nonlinear elastic materials (defined below). The results appear to be particularly adapted to structures made with origami design methods, where the tiles are allowed to deform isometrically. We collect the results in tables and discuss some particular numerical examples. [ABSTRACT FROM AUTHOR]

• A similarity analysis method of the planetary gear transmission system is proposed. • Hierarchical rules for planetary gear transmission systems are established. • The structural similarity and functional similarity conditions are put forward. • The ability of the scale model to predict the dynamic characteristics is verified. Large high-power gear transmission systems, especially complex gear systems, have problems such as high processing costs, long manufacturing cycles, and difficult testing, resulting in the inability to implement performance evaluation and structural optimization of gear systems. To solve this problem, the similarity and vibration signal prediction method of planetary gear transmission system (PGTS) is studied based on hierarchical analysis. The similarity relationship analysis is completed based on the similarity theory of complex systems. According to the hierarchical idea, the PGTS can be divided into subsystems at different levels from top to bottom, which can be divided into the component layer at least. The concepts of functional similarity and structural similarity are proposed, and the similarity conditions of each subsystem are formulated. Based on the equation analysis method, the dynamic similarity relationship of the PGTS is deduced. Furthermore, the parameter design and working condition design of the scale model is completed. The scale model can predict the time and frequency domain curves of each vibration signal of the prototype. Under different working conditions, the scale model can accurately predict the vibration signal and floating amount of the prototype. The similarity analysis method applicable to PGTSs has been verified. [ABSTRACT FROM AUTHOR]

For the aero-engine rotor system with complex vibration responses, a simplified model based dynamic similarity is proposed to study the vibration characteristics of that. On the basis of the principle of dynamic similarity, a simplified model of the combustion-driven rotor is obtained, with the criteria of the same critical speed of each order and similar vibration modes, while keeping the layout of the structure unchanged. By comparing the vibration characteristics of the actual rotor with those of the simplified model through theoretical analysis, there is less than 2.59 % error between the simplified model and the actual rotor. The rationality of the research method, which is developing the simplified model based on dynamic similarity to study the vibration response law of the original rotor, is demonstrated. Then, the unbalance response law of the rotor with a squeeze film damper is explored expanding on the produced model, and the study shows that the unbalanced excitation can significantly reduce the response. Finally, the influence law of the phase of unbalance excitation is experimentally verified on the test rotor. The results show that the simplified model of the actual rotor based on dynamic similarity can well reflect the vibration characteristics of the original rotor, and the proposed analysis method has an important reference role in studying the vibration mechanism of the aero-engine rotor system.

A low-temperature high-pressure helium compressor is one of the key components in a hypersonic air-breath engine cycle. Its aerodynamic performance is the basis of engine cycle design and control. The low-temperature and high-pressure conditions make it difficult in a laboratory environment to conduct a compressor performance experiment, thus constraining the engine cycle design. An alternative method is to test the compressor with other gas at a reference operation condition and then calculate the helium compressor performance according to the test results using transformation laws. This paper investigates the transformation method based on the dynamic similarity principle and derives transformation equations. CFD simulations performed on the compressors validate the equations. Eventually, the study analyzes the alternative experimental cycles. [ABSTRACT FROM AUTHOR]

This paper concerns a hybrid vibration reduction system (HVRS) equipped with a linear electrodynamic motor (LM). The objective of the study was to implement the HVRS in a scaled vehicle suspension and reveal the benefits of its application in the system. First, a mathematical model of a quarter-vehicle suspension with the HVRS was formulated. Next, the dynamic similarity method was employed to conduct numerical simulations of the passive vibration reduction system (PVRS). Subsequently, an algorithm for HVRS controlling was developed. Then, the system was investigated experimentally under deterministic and random excitations. The results confirmed the effectiveness and applicability of the proposed HVRS. [ABSTRACT FROM AUTHOR]

With the continuous enrichment of traffic Internet-of-Things data acquisition methods, more and more spatiotemporal data on road networks is collected in real time by various sensors and multimedia devices. The data-driven deep learning approach can make full use of real-time data from a road network to predict future traffic status. By mining the spatiotemporal relationships between road units, the ability to predict network evolutionary behaviors is improved, which provides a new method of traffic management. There are strong semantic relations between road intersections or road sections in terms of traffic evolution. Modeling the network only from a shallow spatial topological perspective ignores the important intrinsic association of the dynamic network. In this paper, we propose a semantic associative neural network (SANN) for traffic evolution analysis by modeling the propagation effects and similarity patterns between road units. Considering the inadequacy of the fixed adjacent matrix, graph convolution is used to encode the semantic features of a road network and embed them in a bidirectional recurrent neural network for sequence prediction. Finally, the experiments are conducted based on speed data sets to prove the effectiveness of the proposed method. The model achieved a well-predicted accuracy of 95.33% and 84.08% on Pems-Bay and Los Angeles data sets. [ABSTRACT FROM AUTHOR]

This wind tunnel study was conducted to investigate the similarity laws involved in the reasonable simulation of the wake characteristics of a full-scale wind turbine. A 5 MW scaled wind turbine model was designed using an optimization method based on the blade element momentum (BEM) theory. Subsequently, wind tunnel tests were carried out on the geometrically similar model and the thrust-optimized model, with different yaw angles and under various upstream flow conditions. The results indicated that the wake development of the wind turbine model was closely related to the thrust forces of the wind turbine, and both kinematic and dynamic similarity laws should be observed to achieve wake characteristics that are reasonably similar to those of a full-scale wind turbine. This study investigated the aerodynamic similarity principles of small-scale wind turbine models to develop a more effective method for simulating full-scale turbine wake characteristics in wind tunnel tests. The outcomes of this study revealed the limitations of the anomalously low thrust coefficients in geometrically similar wind turbine models and present reasonable model design methodologies for small-scale wind turbine models in wind tunnel tests. [ABSTRACT FROM AUTHOR]

• The proposed scaling strategy ensures dynamic similarity by optimizing structural parameters of rotor systems. • The distance between disk and bearing has significant influence on the first-order critical speed in optimization process. • Increasing the weighing coefficient of a certain order of critical speed effectively reduces the deviation in optimization. • The optimized GDSM rotor predicts the prototype more accurately than the SSM rotor. • Such scaling strategy practically guides the design and manufacturing of experimental rotor systems. It is difficult to perform practical experiments on working gas turbine rotors due to the factors of safety and implementability etc. Therefore, it is of great importance to design a well-scaled test rig that can accurately predict the dynamic characteristics of a prototype rotor. In this paper, a design method for scaled rotor systems considering dynamic similarity and restricted support stiffness is proposed. The structural similarity coefficients of the strictly scaled model (SSM) in a rotor system are obtained based on the similarity theory and scaling law. Key optimization parameters and ranges are determined through sensitivity analysis. By genetic algorithm, the geometrically distorted scaled model (GDSM) in rotor system with dynamic similarity is established to modify the SSM rotor. Moreover, modal experiments are carried out to verify the validity of the proposed scaling design method. Results show that the type, number and accuracy of optimized parameters are important in optimization design. The critical speed of the first three orders of the GDSM rotor are very close to ones in the prototype, and the maximum percentage deviation is 1.18%. Experimental results show that the rotor developed by the geometrically distorted scaling method is able to reflect the dynamic properties of prototype accurately despite the slightly distorted partial structural parameters. Such proposed design method can provide a highlight in the design and manufacturing of the key components of gas turbine rotors for laboratory. [ABSTRACT FROM AUTHOR]

Dimensional analysis has been very helpful in experimentation of very large or small-scale engineering systems. A good example would be experimentation on the aircrafts and ships, which was made cost-effective and simple by dimensional analysis. The history of dimensional analysis mentioned in the introduction section of the present document includes many of such applications. Automotive industry, however, never felt the need as the price or the size of land vehicles did not make experimentation so far-fetched; therefore, there are many crash tests which every new vehicle has to go through before mass production This changed with the imminent introduction of autonomous vehicles, which brought all the risks involved in experimenting with them. Many cost-effective experimental platforms are introduced, such as QCar or laboratories, such as Scaled Autonomous Vehicles Indoor (SAVI) . The present study will enable the results taken from such platforms to be translated to real-sized vehicles, enabling researchers to study dynamics of various vehicles. Classical vehicle equations of motion including constant velocity, accelerating bicycle model and roll model have been made dimensionless. The case of steady-state responses is also calculated in a dimensionless form. Some practical numerical examples are also mentioned as a proof of theory. [ABSTRACT FROM AUTHOR]

With the development of deep-sea oil and gas resources, the aspect ratio of deep-sea flexible riser has reached the order of 102–103, which makes the experimental model of the equal scale of deep-sea flexible risers challenging to achieve under typical experimental conditions. Alternatively, the non-scale experiment is sometimes used. However, the dynamic response of the prototype may not be exactly modeled. To solve the problem, this paper expands the distortion similarity method to consider the pretension and designs a distortion model of the deep-sea flexible riser based on the improved distortion similarity method. Applying the governing equation and dimensional analysis method to analyze the prototype and experimental model, the design method of the distortion model is obtained. In the numerical analysis, the design of the distortion model of a top tensioned riser (TTR) is carried out, and the selection criteria and range of the aspect ratio are proposed. The three parts of the natural frequency similarity, the pretension non-satisfaction similarity, and the error analysis are studied. This analytical study indicates that the transverse direction of the distortion model satisfies the similarity of the dynamics, and the longitudinal direction satisfies the static similarity. The selection of the aspect ratio of the distortion model should satisfy three factors. [ABSTRACT FROM AUTHOR]

This paper concerns a hybrid vibration reduction system (HVRS) equipped with a linear electrodynamic motor (LM). The objective of the study was to implement the HVRS in a scaled vehicle suspension and reveal the benefits of its application in the system. First, a mathematical model of a quarter-vehicle suspension with the HVRS was formulated. Next, the dynamic similarity method was employed to conduct numerical simulations of the passive vibration reduction system (PVRS). Subsequently, an algorithm for HVRS controlling was developed. Then, the system was investigated experimentally under deterministic and random excitations. The results confirmed the effectiveness and applicability of the proposed HVRS.

The present paper addresses the problem of creating a dynamically and elastically scaled blade of a helicopter main rotor model. The issues of scaling the geometric, elastic and mass characteristics of the full-scale blade, are considered. A sequential design approach of constructing the structure section to attain the required elastic and mass characteristics of the blade, is described. Numerical verification is conducted for the results obtained. [ABSTRACT FROM AUTHOR]

This wind tunnel study was conducted to investigate the similarity laws involved in the reasonable simulation of the wake characteristics of a full-scale wind turbine. A 5 MW scaled wind turbine model was designed using an optimization method based on the blade element momentum (BEM) theory. Subsequently, wind tunnel tests were carried out on the geometrically similar model and the thrust-optimized model, with different yaw angles and under various upstream flow conditions. The results indicated that the wake development of the wind turbine model was closely related to the thrust forces of the wind turbine, and both kinematic and dynamic similarity laws should be observed to achieve wake characteristics that are reasonably similar to those of a full-scale wind turbine. This study investigated the aerodynamic similarity principles of small-scale wind turbine models to develop a more effective method for simulating full-scale turbine wake characteristics in wind tunnel tests. The outcomes of this study revealed the limitations of the anomalously low thrust coefficients in geometrically similar wind turbine models and present reasonable model design methodologies for small-scale wind turbine models in wind tunnel tests.

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GPU-based DEM is used to study large-scale particle mixing in bladed mixers. A bladed mixer is scaled-up to three different sizes by maintaining the geometric similarity. Four Froude numbers are selected as the main operating conditions of bladed mixers with different sizes. The results demonstrated that the mixing quality across different mixer sizes is similar at the same Froude number, but it requires a longer mixing time to achieve similar mixing performances as the mixer becomes larger. Correlations to predict the mixing rate, average particle velocity, average total forces, average contact forces and average blade torque as functions of the scale-up ratio and Froude number (or rotation speed) are proposed. A similarity study shows that maintaining the dynamic or kinematic similarity does not produce a similar mixing performance, while maintaining the mixing rate produces a similar mixing performance across all mixers. Unlabelled Image • A bladed mixer is scaled up by maintaining its geometric similarity. • Mixing properties are correlated with scale-up ratio and Froude number. • Maintaining average total forces does not produce similar mixing performances. • Maintaining average particle velocity does not produce similar mixing performances. • Maintaining the mixing rate has successfully produced similar mixing performances. [ABSTRACT FROM AUTHOR]

A similitude is proposed for the dynamic response analysis of a satellite solar array. It is defined by invoking the wave coupling hybrid finite element–statistical energy analysis method which is considered as an effective way to solve the wide frequency (especially middle-frequency) vibration response of complex structures. The scaling laws are then derived by looking for equalities in the structural responses. A numerical case involving an assembly of two plates is discussed to verify the proposed scaling laws. Moreover, the new similitude is applied to a simplified satellite solar array model. If the analysis frequency step is selected appropriately, it is shown that a complete similitude can be defined: it allows predicting the vibration response of satellite solar array and provides the possibility for the model test of complex structures. [ABSTRACT FROM AUTHOR]

Many phenomena related to motor behaviour in animals are spatially and temporally periodic, making them accessible for transformation to the frequency domain via Fourier Series. Although this has been applied previously, it had not been noticed that the characteristic arrangement of Fourier coefficients in their complex-valued representation resembles landmarks in geometric morphometrics. We define a superimposition procedure in the frequency domain, which removes affine differences (mean, amplitude, phase) to reveal and compare the shape of periodic kinematic measures. This procedure is conceptually linked to dynamic similarity, which can thereby be assessed on the level of individual limb elements. We demonstrate how to make intralimb coordination accessible for large-scale, quantitative analyses. By applying this to a dataset from terrestrial ungulates, dominant patterns in forelimb coordination during walking are identified. This analysis shows that typical strides of these animals differ mostly in how much the limbs are lifted in the presence or absence of obstructive substrate features. This is shown to be independent of morphological features. Besides revealing fundamental characteristics of ungulate locomotion, we argue that the suggested method is generally suitable for the large-scale quantitative assessment of coordination and dynamics in periodic locomotor phenomena. [ABSTRACT FROM AUTHOR]

The scarcity of data available on the best approach for pulmonary fetal valve replacement or implantation necessitate an investigation on whether practices using adult transcatheter valves could be translated to fetal applications. The objective of this study is to evaluate the hemodynamic characteristics and the turbulent properties of a fetal sized trileaflet transcatheter pulmonary valve in comparison with an adult balloon-expandable valve in order to assess the possibility of designing valves for fetal applications using dynamic similarity. A 6 mm fetal trileaflet valve and a 26 mm SAPIEN 3 valve were assessed in a pulse duplicator. Particle image velocimetry was performed. Pressure gradient (ΔP), effective orifice area (EOA), regurgitant fractions (RF), pinwheeling indices (PI) and turbulent stresses were evaluated. ΔP was 8.56 ± 0.139 and 7.76 ± 0.083 mmHg with fetal valve and SAPIEN respectively (p < 0.0001); EOA was 0.10 ± 0.0007 and 2.1 ± 0.025 cm2 with fetal valve and SAPIEN respectively (p < 0.0001); RF with the fetal valve was 2.35 ± 1.99% and with SAPIEN 10.92 ± 0.11% (p < 0.0001); PI with fetal valve was 0.404 ± 0.01 and with SAPIEN 0.37 ± 0.07; The flow regime with the fetal valve was turbulent and Reynolds numbers reached about 7000 while those with the SAPIEN reached about 20,000 at peak velocity. Turbulent stresses were significantly higher with fetal valve compared with SAPIEN. Instantaneous viscous shear stresses with fetal valve were 5.8 times higher than those obtained with SAPIEN and Reynolds shear stresses were 2.5 times higher during peak systole. The fetal valve implantation leads to a turbulent flow (specific to this particular type and design of valve) regime unlike what is expected of a small valve with different flow properties compared to adult valves. [ABSTRACT FROM AUTHOR]

Wind flow through urban areas is studied either by wind tunnel scale experiments or via computational fluid dynamics simulations through full-scale actual models. The large difference between the Reynolds numbers based on the geometries of actual cities and wind tunnel scale cities makes the dynamic similarity between the two models uncertain. In this study, the mean and turbulent flow parameters were investigated using a large eddy simulation for two models i.e. the actual urban area model and the wind tunnel scale (1:1000) model. Kuala Lumpur City Centre, Malaysia, was considered as the case study of an urban area. Vertical velocity profiles were plotted at five locations representing different building packing densities. The results of wind tunnel scale model largely agreed with the actual model with some discrepancies in the building vicinity and wakes. The dissimilarity of the wake patterns due to the large difference in Re was responsible for the deviations. Largest discrepancies were found in the lateral and wall-normal velocity components and turbulence stresses. The results casted a shadow on the applicability of the conclusions derived from the simulations on wind tunnel scale models to the actual urban environments they represented. The deviation between the two models should be assessed before proceeding with experimental or numerical simulations on small-sized models.

This paper discusses the scaling laws of the flow structures around geometrically similar fire whirls, an insight that will be necessary when applying laboratory-scale data to real-scale fire whirls in urban or wildland fires. A fixed-frame-type fire-whirl generator is used to form geometrically similar fire whirls of three different scales. A particle image velocimetry (PIV) technique is used to measure the tangential (rotational) and the radial velocity components around the fire whirls. Scaling analysis is then conducted to derive two pi numbers, namely, the Reynolds number and the Froude number. Measured tangential velocity distributions are nearly uniform in the vertical direction when the height from the floor is greater than ~1 cm, where the velocity profiles are found to be well correlated using the Froude number, suggesting that viscosity plays only a minor role. Near the floor, on the other hand, the magnitude of tangential velocity is reduced, leading to an enhanced radial inflow toward the flame, a phenomenon similar to the Ekman layer. This inflow layer pushes the flame toward the fuel surface, increasing the heat input from the flame to the fuel and hence the burning rate. It is found that the Froude number can also correlate the radial velocity distributions near the floor.

The study of animal locomotion can be logistically challenging, especially in the case of large or unhandleable animals in uncontrolled environments. Here we demonstrate the utility of a low cost unmanned aerial vehicle (UAV) in measuring two-dimensional running kinematics from free-roaming giraffes (Giraffa camelopardalis giraffa) in the Free State Province, South Africa. We collected 120 Hz video of running giraffes, and calibrated each video frame using metatarsal length as a constant object of scale. We tested a number of methods to measure metatarsal length. The method with the least variation used close range photography and a trigonometric equation to spatially calibrate the still image, and derive metatarsal length. In the absence of this option, a spatially calibrated surface model of the study terrain was used to estimate topographical dimensions in video footage of interest. Data for the terrain models were collected using the same equipment, during the same study period. We subsequently validated the accuracy of the UAV method by comparing similar speed measurements of a human subject running on a treadmill, with treadmill speed. At 8 m focal distance we observed an error of 8% between the two measures of speed. This error was greater at a shorter focal distance, and when the subject was not in the central field of view. We recommend that future users maximise the camera focal distance, and keep the subject in the central field of view. The studied giraffes used a grounded rotary gallop with a speed range of 3.4–6.9 ms−1 (never cantering, trotting or pacing), and lower duty factors when compared with other cursorial quadrupeds. As this pattern might result in adverse increases in peak vertical limb forces with speed, it was notable to find that contralateral limbs became more in-phase with speed. Considering the latter pattern and the modest maximal speed of giraffes, we speculate that tissue safety factors are maintained within tolerable bounds this way. Furthermore, the angular kinematics of the neck were frequently isolated from the pitching of the body during running; this may be a result of the large mass of the head and neck. Further field experiments and biomechanical models are needed to robustly test these speculations.

This paper studies the spinning stability of a triangular tethered satellite formation that flies on a low earth orbit. The spinning around the center of mass at a constant angular rate gives rise to a periodic motion in the non-inertial orbital frame. Floquet theory is used to analyze the stability of the periodic motion. A dynamic similarity between the on-orbit dynamics and ground experimental models is built to construct an equivalent ground experiment to verify the stability analysis. The analytical and experimental results show that a stable periodic motion can be guaranteed if the spinning angular rate of the system exceeds a critical value. [ABSTRACT FROM AUTHOR]

Abstract We develop the approach to simulate the experiments with surface and underwater vehicles in towing tanks for Reynolds numbers Re, corresponding to sea trials, using discrete injection of polymer additives. The complete dynamic similarity between full-scale and tank tests is possible if both Froude number and Re are equal for a ship and its model. In traditional experiments, the first condition is only satisfied and the viscous and wave resistances are independently studied. The Toms effect is widely used in marine engineering, e.g., to reduce energy cost. In this work, it is applied quite differently. Re is higher and the skin friction coefficient c f is hence less for sea trials than for towing tanks. Injection of polymer additives allows decreasing c f on ship model to full-scale values, providing the complete similarity and reproducing sea trials in that way. We report the selected results of such novel approach that, in particular, include velocity profiles and c f for sea trial, towing tank and pipe experiments, plane boundary layer and 3D flow around propeller, rough and smooth surfaces. The data for full-scale and tank experiments agree well with each other. Highlights • Novel approach in both application of Toms effect and marine engineering to simulate sea trials. • Complete dynamic similarity for sea trials and towing tank tests using polymer drag reduction. • Сoinciding data on viscous and total resistances of ships for full-scale and model experiments. [ABSTRACT FROM AUTHOR]

Abstract The passive truncation model called DyTrunMoor is proposed to realize the dynamic similarity of mooring line in this paper. The nonlinear inertial forces and drag forces are integrated with Morison model within elastic rod model to reserve dynamic response of mooring line. The mooring line parameters of truncated line are figured out with the optimization algorithm NSGA-II for the static and dynamic simulation. The fitness function for NSGA-II is constructed with tension amplitudes corresponding to limited frequencies, which are fetched from tension history with Fast Fourier Transform algorithm. A single mooring line is discussed in detail with truncation from 1500 m to 1050 m water depth. The feasibility and accuracy of the truncation method is verified with harmonic forced motion, which shows a consistent nonlinearity in the dynamic response of the original and the truncated mooring line. Truncation design is also carried out to a Semi-submersible platform mooring system truncated from 1200 m to 700 m. The static and dynamic characteristics are compared, which verifies the validity of the proposed method. Highlights • The slender rod model and NSGA-II are used to create a new method for dynamic truncation of mooring line for model test. • An innovative fitness function is created in frequency domain by transferring mooring forces from time domain. • All 3 segments of one mooring line can be evaluated with the proposed method. • The complete nonlinearity consistence makes the truncated line has almost the same performance with the original line. [ABSTRACT FROM AUTHOR]

Abstract Granular shear flows in chambers with rotating shafts are ubiquitous in manufacturing processes for numerous industries such as pharmaceuticals, food, and cereal processing, wherein flow homogeneity is critical to maintain product quality. In this work, Discrete Element Modeling (DEM) was used to study flow behaviors of rice particles using the special stirred chambers. The non-geometric similar chambers equipped with a regular polygon sieve and a roller shaft are used as simulated stirred chambers. This work's goal was to establish a similarity rule of the particle flow behaviors among these chambers. The gap between the shaft and the sieve periodically varies from maximum to minimum when the chamber is in work, which forms the gap curve. The kinematic flow behavior evaluated in this work were normalised velocity, normalised tangential velocity, radial velocity and radial distance distribution of particles. The dynamic flow behavior evaluated in this work was the particle collision energy. The DEM results were used to compare the kinematic and dynamic flow behaviors for the different chambers. The results indicated that both kinematic and dynamic flow behaviors were similar among chambers with the same gap curve. From these results and analysis, an empirical similarity rule of particle flow behavior, that is, the constant gap curve, was developed. Meanwhile, the effectiveness of the proposed similarity rule is experimentally confirmed. These findings are useful to understand and control the operational performance of the similar stirred chambers. Graphical abstract Unlabelled Image Highlights • Similarities of particle behavior in stirred chambers were numerically analyzed. • Kinematic and dynamic characteristics were used to express behavior similarity. • The constant gap curve can be used as a similarity rule for particle flow behavior. • Flow behavior similarity is easier to be achieved under gentle change rate of gap. • Large change rate of gap is beneficial to milling rate of the stirred chamber. [ABSTRACT FROM AUTHOR]

Giraffes (Giraffa camelopardalis) possess specialised anatomy. Their disproportionately elongate limbs and neck confer recognised feeding advantages, but little is known about how their morphology affects locomotor function. In this study, we examined the stride parameters and ground reaction forces from three adult giraffes in a zoological park, across a range of walking speeds. The patterns of GRFs during walking indicate that giraffes, similar to other mammalian quadrupeds, maintain a forelimb-biased weight distribution. The angular excursion of the neck has functional links with locomotor dynamics in giraffes, and was exaggerated at faster speeds. The horizontal accelerations of the neck and trunk were out of phase compared with the vertical accelerations, which were intermediate between in and out of phase. Despite possessing specialised morphology, giraffes' stride parameters were broadly predicted from dynamic similarity, facilitating the use of other quadrupedal locomotion models to generate testable hypotheses in giraffes. [ABSTRACT FROM AUTHOR]

The transport and deposition of micro/nanoparticles in the lungs under respiration has an important impact on human health. Here, we presented a real-scale alveolar chip with movable alveolar walls based on the microfluidics to experimentally study particle transport in human lung alveoli under rhythmical respiratory. A new method of mixing particles in aqueous solution, instead of air, was proposed for visualization of particle transport in the alveoli. Our novel design can track the particle trajectories under different force conditions for multiple periods. The method proposed in this study gives us better resolution and clearer images without losing any details when mapping the particle velocities. More detailed particle trajectories under multiple forces with different directions in an alveolus are presented. The effects of flow patterns, drag force, gravity and gravity directions are evaluated. By tracing the particle trajectories in the alveoli, we find that the drag force contributes to the reversible motion of particles. However, compared to drag force, the gravity is the decisive factor for particle deposition in the alveoli.

Coupling between aero-acoustic noise and structural vibration under high-speed open cavity flow-induced oscillation may bring about severe random vibration of the structure, and even cause structure to fatigue destruction, which threatens the flight safety. Carrying out the research on vibro-acoustic experiments of scaled down model is an effective means to clarify the effects of high-intensity noise of cavity on structural vibration. Therefore, in allusion to the vibro-acoustic experiments of cavity in wind tunnel, taking typical elastic cavity as the research object, dimensional analysis and finite element method were adopted to establish the similitude relations of structural inherent characteristics and dynamics for distorted model, and verifying the proposed similitude relations by means of experiments and numerical simulation. Research shows that, according to the analysis of scale-down model, the established similitude relations can accurately simulate the structural dynamic characteristics of actual model, which provides theoretic guidance for structural design and vibro-acoustic experiments of scaled down elastic cavity model. [ABSTRACT FROM AUTHOR]

An improved truncation method for a deepwater mooring system based on the dynamic similarity of the mooring line in the time domain is proposed in this paper. The optimisation algorithm NSGA-II (nondominated sorting genetic algorithm) is combined with the slender rod model to optimise the mooring line parameters in the static and dynamic analysis of the truncated system. A reliable fitness function is created in the frequency domain by transferring the mooring forces from the time domain with FFT, which makes the dynamic similarity between the truncated and full-depth mooring systems available and effective. An floating production storage and offloading unit (FPSO) mooring system working in 1500 m water depth is truncated to 1050 m and 700 m. The harmonic forced motions as well as the global response and mooring forces of the mooring system under irregular waves are consistent with each other across different water depths, thereby validating the proposed truncation method. [ABSTRACT FROM AUTHOR]

ABSTRACT: Fluid flow is an important regulator of cell function and metabolism in many tissues. Fluid shear stresses have been used to level the mechanical stimuli applied in vitro with what occurs in vivo. However, these experiments often lack dynamic similarity, which is necessary to ensure the validity of the model. For interstitial fluid flow, the major requirement for dynamic similarity is the Reynolds number (Re), the ratio of inertial to viscous forces, is the same between the system and model. To study the necessity of dynamic similarity for cell mechanotransduction studies, we investigated the response of osteocyte‐like MLO‐Y4 cells to different Re flows at the same level of fluid shear stress. Osteocytes were chosen for this study as flows applied in vitro and in vivo have Re that are orders of magnitude different. We hypothesize that osteocytes’ response to fluid flow is Re dependent. We observed that cells exposed to lower and higher Re flows developed rounded and triangular morphologies, respectively. Lower Re flows also reduced apoptosis rates compared to higher Re flows. Furthermore, MLO‐Y4 cells exposed to higher Re flows had stronger calcium responses compared to lower Re flows. However, by also controlling for flow rate, the lower Re flows induced a stronger calcium response; while degradation of components of the osteocyte glycocalyx reversed this effect. This work suggests that osteocytes are highly sensitive to differences in Re, independent of just shear stresses, supporting the need for improved in vitro flow platforms that better recapitulate the physiological environment. © 2017 Orthopaedic Research Society. Published by Wiley Periodicals, Inc. J Orthop Res 36:663–671, 2018. [ABSTRACT FROM AUTHOR]

This paper shows the procedure followed to design and manufacture a scaled railroad vehicle to be used in a scaled railroad track for the development and validation of computational models. The purpose of this work is to address the background experienced by the authors from the ideal concept to the assembly one, and serve as a guideline for future railroad prototype designs. This specific vehicle, in which different inertial, guiding, recording and monitoring devices are installed, is mainly designed to be used in a 5-in. gauge railroad track for the validation of computational models and, as much as possible, designed with physical similarity with respect to a real railroad vehicle. The commitment between the imperative design requirements and the desired dynamic behavior is managed from the CAD design to its final assembly. [ABSTRACT FROM AUTHOR]

This paper investigates the vibration patterns, i.e. rigid motions of shaft and elastic deformation of support structures, of fan rotor system in aero-engine, which differs from traditional flexible rotor systems, and together with its shaft transverse motions due to unbalanced mass. The fan rotor system commonly is composed of one rigid shaft and two flexible support structures (such as squirrel cages), which is effective to decrease the critical speeds avoiding serious shaft vibration due to unbalance. Scaled test rig for realistic fan rotor system is set up according to similarity principles, governing differential equations of which are deduced by means of Lagrangian approach with four degrees of freedom. In contrast to modeling a traditional flexible rotor system, the system stiffness is not determined by the shaft but the two flexible support structures. The rigid shaft only contributes to the inertial items of the governing equations. Parameter values of dynamic model are identified from measurements on the scaled test rig, the modal shapes and the modal energy distributions are calculated. These modal characteristics of the fan rotor system are quite different from those of a traditional flexible rotor system whose stiffness mainly contributed by its elastic shaft even the system values are consistent. The obtained modal characteristics are compared and confirmed by using the simulation results of a corresponding finite element model, in which shaft is built by rotating beam elements and its flexible structures are built by equivalent spring elements. Campbell diagrams of the fan rotor system are used to illustrate the gyroscopic effect with the increasing speeds. And then the unbalance responses are calculated through the deduced analytical formula rapidly and comparisons, including the response spectrum and orbits, the amplitude and phase frequency response curves, and operating deflection shapes, are carried out in the sub- and super-critical range. [ABSTRACT FROM AUTHOR]

A tidal bore is a positive surge or compression wave formed in an estuarine system during the early flood tide under macro-tidal conditions. A series of physical experiments were conducted in a large facility to investigate the unsteady free-surface properties, velocity characteristics and Reynolds shear stresses. Both instantaneous and ensemble-averaged measurements were performed. The results demonstrated the intense turbulence and turbulent mixing under breaking and undular tidal bores. A range of dimensionless unsteady turbulent properties were carefully compared based upon both Froude and Morton similitudes with two different Reynolds number ranges. The data showed that several parameters were affected by scale effects, including velocity and Reynolds stress fluctuations during the bore propagation. The finding implies that laboratory study data might not be up-scaled to prototype conditions without some form of scale effects. [ABSTRACT FROM AUTHOR]

A Lunar crewed vehicle (LCV) is an indispensable detection tool that can not only transport astronauts a long distance from the Lunar module but also ensure their safety when moving around the Lunar surface. Accurate ground simulation of LCVs on Earth is crucial for vehicle testing and astronaut training prior to launch deployment. This study proposes a novel methodology to simulate the dynamic behavior of an LCV on the Lunar surface, that combines dimensional analysis with vehicle active suspension compensation to simulate an LCV experiment without an external compensator. Using dimensional analysis, vehicle parameters can be scaled based on ground experiment requirements and astronaut sensory consistency constraints. A scaled vehicle compensation model was developed that considers variation in the gravity field, and active suspensions were regulated to compensate for gravitational effects using an optimal force distribution strategy. Finally, dynamic simulations were conducted to verify the proposed method, and the results revealed that the prototype vehicle under Earth gravity could effectively approximate the same body dynamic response of a crewed Lunar rover in the Lunar gravity environment. • A ground simulation method for a lunar crewed vehicle is proposed. • A dynamic modeling and a similitude-based scaling for proposed rover is presented. • Analysis of gravity variation effects on the scaled vehicle on Earth is provided. • Compensate the gravity effects by active actuators with forces distribution strategy. [ABSTRACT FROM AUTHOR]

In order to explore the dynamic similarity model test method different from atmospheric boundary layer wind tunnel and shaking table model test, in accordance with dynamic similar theory, an elastic model of a transmission tower with 1/35 scale and 5.2m height has been designed and manufactured with thin-walled circular pipes of high-density polyethylene. The model has been tested in the laboratory for time and frequency domain responses under suddenly unloading, essential dynamic characteristic of the scale model is also analysed and compared with that of its prototype tower, the dynamic similarity of the two is confirmed. By the mathematical deduction of Wigner-Ville Distribution (WVD) signal terms of structural free vibration response, the new damage detection index with clear physical signification is forwarded for damage detection for transmission tower, the damage detection test of the scale model of transmission tower is then carried out, totally three damage cases, related with chord rod weakening, flank rods failure, different damage degrees and positions, are tested to validate the proposed damage detection index.