Search

• 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]

• 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]

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]

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]

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]

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]

This paper studies chaotic control of a tethered satellite system (TSS) driven only by a momentum-exchange device during its attitude adjustment. In dealing with such the underactuated system, an extended time-delay autosynchronization (ETDAS) is employed to stabilize the chaotic motion to a periodic motion. To obtain the control domains of the ETDAS method, a stability analysis of the controlled tethered satellite system in elliptical orbit is implemented. According to the principle of dynamic similarity, then, ground-based experiment setups are proposed and designed to emulate the in-plane motions of the TSS. Representative experiments are presented to demonstrate the effectiveness of the ETDAS scheme in controlling the chaotic motion of the underactuated TSS. [ABSTRACT FROM AUTHOR]

In this paper, we discretized the ball motion in a horizontal planetary ball mill, the fundamental equation of the relative motion and the detaching trajectory were analyzed, and the impact time was approximately formulated. We performed experiments on impact comminution and observed that an equal impact potential energy causes an equal grinding effect. Based on theoretical analysis, comparing the horizontal planetary ball mill whose planetary factor is z with the traditional ball mill through dynamic similarity principles, the results show that when dynamic similarity exists and when the grinding outputs of each mill are equal to each other, the radius of horizontal planetary ball mill is z −1/4 times as the radius of a traditional ball mill. If the impact potential energies of the balls in these two mills are the same, the impact stress of the balls in a horizontal planetary ball mill is z times as in a dynamic similarity traditional ball mill. To determine the equal grinding effect, the energy consumption of a horizontal planetary ball mill is z −3/8 times as that of traditional ball mill. [ABSTRACT FROM AUTHOR]

The aim of this study was to assess the accuracy of a new dimensionless number associating Froude (Nfr) and Strouhal (Str) called Modela-w to induce walking dynamic similarity among humans of different sizes. Nineteen subjects walked in three experimental conditions: (i) constant speed, (ii) similar speed (Nfr) and (iii) similar speed and similar step frequency (Modela-w). The dynamic similarity was evaluated from scale factors computed with anthropometric, temporal, kinematic and kinetic data and from the decrease of the variability of the parameters expressed in their dimensionless form. Over a total of 36 dynamic parameters, dynamic similarity from scale factors was met for 11 (mean r = 0.51), 22 (mean r = 0.52) and 30 (mean r = 0.69) parameters in the first, the second and the third experimental conditions, respectively. Modela-w also reduced the variability of the dimensionless preceding parameters compared to the other experimental conditions. This study shows that the combination of Nfr and Str called Modela-w ensures dynamic similarity between different-sized subjects and allows scientists to impose similar experimental conditions removing all anthropometric effects. [ABSTRACT FROM AUTHOR]

Abstract: As a primary device of the S-lay technique, the stinger is used to protect the overbend section in a pipeline. It is difficult to determine the design loads acting on the rollers during the dynamic pipelaying condition using numerical methods alone. Instead, a test model is used to analyze this complex problem. This paper introduces some similarity criteria based on the dynamic similarity of a stinger, a pipeline, and a vessel. Then, the stinger of the first pipelaying crane vessel in China, “HYSY201”, is modeled with these similarity criteria. The loads for the stinger׳s structural design and movement mechanism in the off-design conditions are simulated, producing some useful conclusions and suggesting that local reinforcement of this stinger be performed. The vessel recently began its first deep-sea pipelaying project in Liwan in the South China Sea. Thus, the model method proposed in this paper is effective and could be used to design and test other articulated stinger structures rather than relying on engineering heuristics. [Copyright &y& Elsevier]

Abstract: To study transient mass transfers inside buildings equipped with ventilation systems, reduced-scale experiments have been performed by applying the scaling down methodology developed for studying isothermal airflows in a steady or a transient state [1]. Transient tests have been carried out both on simplified cases considered for the validation of the methodology and on two reference industrial configurations representative of real industrial facilities. In this article, focus is made on transient results obtained on simplified and reference industrial cases subjected to wind and internal overpressure effects. The main objectives are firstly to identify the internal transient airflow behaviour, compared with Helmholtz oscillated phenomena underlined from natural ventilation studies, secondly to analyse the pollutant containment of reference industrial configurations subjected to wind and/or internal overpressure effects due to an accident, and finally to check the ability of the SYLVIA code to model these transient phenomena. [Copyright &y& Elsevier]

Abstract: This work presents the design and experimental evaluation of a cold-flow model, built to simulate a 100kW chemical-looping combustor for solid fuel. A theoretical background is provided, as well as some initial results using air as fluidization medium. The cold-flow model has been operated for about 10h and shows no indication of imbalances in the bed inventories. In the fuel and air reactors, the mass fluxes were found to be linear in the riser pressure drop and the corresponding measured mass flows were approximately proportional to the mass flows calculated from the riser pressure drop. From the study of mass flows, residence times in both the fuel and air reactor were obtained. From pressure profile investigations, it was found that the system remained stable to changes in the fluidization velocity. Thus, both the internal circulation in the fuel reactor, and the circulation between air and fuel reactor, could be varied in a large range with only minor impact on the solids inventories of the air and fuel reactors. [Copyright &y& Elsevier]

Previous experimental work in globe valves has mainly been conducted over a narrow range of laminar or turbulent flow. The work available in laminar flow has not been conducted in geometrically similar valves, hence dynamic similarity could not be established--a critical precursor to practical engineering hydraulic design. In this work various Newtonian and non-Newtonian fluids, including viscoplastic fluids, were tested in three globe valves (with circular plug disk) of 15 mm, 25mm and 40mm nominal diameters on a Balanced Beam Tube Viscometer (BBTV). A single constant was obtained in laminar flow to determine the loss coefficient for all the sizes of valves and types of fluids tested in the valve, indicating that dynamic similarity had been achieved. Consequently a correlation could be developed to determine the loss coefficient in globe valves in both the fully open and half open positions. Dynamic similarity was obtained using a Reynolds number that accounted for the fluid rheology, specifically the yield stress. [ABSTRACT FROM AUTHOR]

Abstract: The hydraulic jump is the sudden transition from a high-velocity open channel flow regime to a subcritical flow motion. The flow properties may be solved using continuity and momentum considerations. In this review paper, recent advances in turbulent hydraulic jumps are developed: the non-breaking undular hydraulic jump, the positive surge and tidal bore, and the air bubble entrainment in hydraulic jumps with roller. The review paper demonstrates that the hydraulic jump is a fascinating turbulent flow motion and the present knowledge is insufficient, especially at the scales of environmental and geophysical flows. [Copyright &y& Elsevier]

The mooring system needs to be truncated in physical model test to adapt to the limited dimensions of offshore basins. Especially, the drag force and inertial force are required to be included in the dynamic mooring truncation methods, and the method should be verified by model test comparison. Here an effective dynamic truncation method is proposed based on slender rod theory and multi-objective cuckoo search optimization algorithm. The line tensions in time domain are transferred into frequency domain to implement the dynamic similarity. The proposed process can promote optimization efficiency in a great extent. In order to demonstrate the accuracy of the proposed method, a horizontal truncation is carried out to an internal turret moored FPSO working in 420 m water depth. The model test in deep-water basin is performed with static tests and irregular wave tests. It can be found that model test and numerical results show consistence on the static stiffness characteristics and dynamic response. The comparison verifies the reliability and accuracy of the proposed truncation method well. • A new method is proposed to reach the dynamic similarity efficiently. • Model tests are performed to verify the rationality of the proposed method. [ABSTRACT FROM AUTHOR]

Abstract: Dynamic similarity is a widely used concept in the fluid mechanics field, and consists in placing two different-sized systems in equivalent experimental conditions. This enables removal of the effects of size and prediction of the behavior of a full size system from a scale model. The aim of this study was to test whether the Froude number (Nfr) or the Strouhal number (Str) could be used as a criterion for dynamic similarity during running. Fifteen male subjects ran barefoot on a runway in three experimental conditions (i) all subjects ran at the same speed V=3.5ms−1; (ii) the speed was determined from Nfr; (iii) the stride frequency was determined from Str. Antero-posterior (Fy) and vertical (Fz) ground reaction force components were assessed. The similarity between the subjects was analysed from scale factor sets computed from anthropometric and kinetic data. The use of Str implied strong inter-subject similarity for temporal parameters (mean r=0.96, time to Fz peak, time to Fy braking peak, Fy zero fore–aft shear, time to Fy propulsive peak) while Nfr induced fewer and lower similarities (mean r=0.75, Fy zero fore–aft shear, time to Fy propulsive peak, Fy braking impulse) that only concerned antero-posterior parameters. This study brought experimental evidence that neither Nfr nor Str were sufficient for dynamic similarity during running, but that each of them made its own contribution. These findings suggested that the concomitant use of Nfr and Str should be assessed to induce inter-subject dynamic similarity during running. [Copyright &y& Elsevier]

Abstract: This study aimed to highlight a new dimensionless number from mechanical energy transfer occurring at the centre of gravity (Cg) during running. We built two different-sized spring–mass models (SMM #1 and SMM #2). SMM #1 was built from the previously published data, and SMM #2 was built to be dynamically similar to SMM #1. The potential gravitational energy (E P), kinetic energy (E K), and potential elastic energy (E E) were taken into account to test our hypothesis. For both SMM #1 and SMM #2, N Mo–Dela=(E P+E K)/E E reached the same mean value and was constant (4.1±0.7) between 30% and 70% of contact time. Values of N Mo–Dela obtained out of this time interval were due to the absence of E E at initial and final times of the simulation. This phenomenon does not occur during in vivo running because a leg muscle''s pre-activation enables potential elastic energy storage prior to ground contact. Our findings also revealed that two different-sized spring–mass models bouncing with equal N Mo–Dela values moved in a dynamically similar fashion. N Mo–Dela, which can be expressed by the combination of Strouhal and Froude numbers, could be of great interest in order to study animal and human locomotion under Earth''s gravity or to induce dynamic similarity between different-sized individuals during bouncing gaits. [Copyright &y& Elsevier]

Abstract: Dimensionless variables are proposed to guide the experimental study of flow in a small-scale solar chimney: a solar power plant for generating electricity. Water and air are the two working fluids chosen for the modeling study. Computational fluid dynamics (CFD) methodology is employed to obtain results that are used to prove the similarity of the proposed dimensionless variables. The study shows that air is more suitable than water to be the working fluid in a small-scale solar chimney model. Analyses of the results from CFD show that the models are dynamically similar to the prototype as suggested by the proposed dimensionless variables. [Copyright &y& Elsevier]

Abstract: The pharmaceutical industry is looking for new technology that is easy to scale up from analytical to process scale and is cheap and reliable to operate. Large scale counter-current chromatography is an emerging technology that could provide this advance, but little was known about the key variables affecting scale-up. This paper investigates two such variables: the rotor radius and the tubing bore. The effect of rotor radius was studied using identical: length, β-value, helix angle and tubing bore coils for rotors of different radii (50mm, 110mm and 300mm). The effect of bore was researched using identical: length, helix angle and mean β-value coils on the Maxi-DE centrifuge (R =300mm). The rotor radius results show that there is very little difference in retention and resolution as rotor radius increases at constant bore. The tubing bore results show that good retention is maintained as bore increases and resolution only decrease slightly, but at the highest bore (17.5mm) resolution can be maintained at very high flow rates making it possible for process scale centrifuges to be designed with throughputs exceeding 25kg/day. [Copyright &y& Elsevier]

Abstract: The purpose of this study was to determine if using similar walking velocities obtained from fractions of the Froude number (N Fr ) and leg length can lead to kinematic and kinetic similarities and lower variability. Fifteen male subjects walked on a treadmill at 0.83 (VS1) and 1.16ms−1 (VS2) and then at two similar velocities (V Sim27 and V Sim37) determined from two fractions of the N Fr (0.27 and 0.37) so that the average group velocity remained unchanged in both conditions (). N Fr can theoretically be used to determine walking velocities proportional to leg lengths and to establish dynamic similarities between subjects. This study represents the first attempt at using this approach to examine plantar pressure. The ankle and knee joint angles were studied in the sagittal plane and the plantar pressure distribution was assessed with an in-shoe measurement device. The similarity ratios were computed from anthropometric parameters and plantar pressure peaks. Dynamically similar conditions caused a 25% reduction in leg joint angles variation and a 10% significant decrease in dimensionless pressure peak variability on average of five footprint locations. It also lead to heel and under-midfoot pressure peaks proportional to body mass and to an increase in the number of under-forefoot plantar pressure peaks proportional to body mass and/or leg length. The use of walking velocities derived from N Fr allows kinematic and plantar pressure similarities between subjects to be observed and leads to a lower inter-subject variability. In-shoe pressure measurements have proven to be valuable for the understanding of lower extremity function. Set walking velocities used for clinical assessment mask the effects of body size and individual gait mechanics. The anthropometric scaling of walking velocities (fraction of N Fr ) should improve identification of unique walking strategies and pathological foot functions. [Copyright &y& Elsevier]

It is fascinating to think that the ideas of two 19th century naval architects could offer useful insights for 21st century scientists contemplating the exploration of our planetary system or monitoring the long-term effects of a neurosurgical procedure on gait. The Froude number, defined as Fr=v2/gL, where v is velocity, g is gravitational acceleration and L is a characteristic linear dimension (such as leg length), has found widespread application in the biomechanics of bipedal locomotion. This review of two parameters, Fr and dimensionless velocity β=(Fr)1/2, that have served as the criterion for dynamic similarity, has been arranged in two parts: (I) historical development, including the contributions by William Froude and his son Edmund, two ship designers who lived more than 130 years ago, the classic insights of D’Arcy Wentworth Thompson who, in his magnum opus On Growth and Form, espoused the connection between mathematics and biology, and the pioneering efforts of Robert McNeill Alexander, who popularised the application of Fr to animal locomotion; and (II) selected applications, including a comparison of walking for people of different heights, exploring the effects of different gravitational fields on human locomotion, establishing the impact of pathology and the benefits of treatment, and understanding the walking patterns of bipedal robots. Although not all applications of Fr to locomotion have been covered, the review offers an important historical context for all researchers of bipedal gait, and extends the idea of dimensionless scaling of gait parameters. [Copyright &y& Elsevier]

The adjustment of the leg during running was addressed using a spring-mass model with a fixed landing angle of attack. The objective was to obtain periodic movement patterns. Spring-like running was monitored by a one-dimensional stride-to-stride mapping of the apex height to identify mechanically stable fixed points.We found that for certain angles of attack, the system becomes self-stabilized if the leg stiffness was properly adjusted and a minimum running speed was exceeded. At a given speed, running techniques fulfilling a stable movement pattern are characterized by an almost constant maximum leg force. With increasing speed, the leg adjustment becomes less critical. The techniques predicted for stable running are in agreement with experimental studies.Mechanically self-stabilized running requires a spring-like leg operation, a minimum running speed and a proper adjustment of leg stiffness and angle of attack. These conditions can be considered as a movement criterion for running. [Copyright &y& Elsevier]

An investigation was conducted to evaluate the effectiveness of a passive gust alleviation device (PGAD) installed in a flying-wing aircraft of 62.3 m wing span at large swept back angle. It was performed by numerical analysis and validated by wind-tunnel test of a 1:25 reduced scale physical model of dynamic similarity to the full-scale aircraft. The 1- cosine gust model with a range of gust parameters specified in the airworthiness regulation CS-23 was taken in the gust response analysis that led to 7 ∼ 9 % gust alleviation results by employing the PGAD. The gust response dominated by the first three modes of the aircraft was most critical in the frequency close to the first bending mode of the wing. The wind-tunnel test model was designed and manufactured based on dynamic scaling law, and proved to be of excellent dynamic similarity by the deviation of less than 5.5% between the first three modes of the physical model measured by vibration test and the full-scale aircraft model. The wind tunnel test results show that the gust response of the model in the specified range was reduced by 8.3 ∼ 14.3 % according to the measured wing tip deflection associated with the PGAD oscillation amplitude at 4.0 ∘ ∼ 15.5 ∘. The present study shows that the numerical analysis of gust response and alleviation of a full-scale aircraft installed with PGAD can be validated by wind tunnel test of a scaled physical model with dynamic similarity. [ABSTRACT FROM AUTHOR]

• Introduction of the Multi-View Information Fusion (MVIF) in the Content-Based Mammogram Retrieval (CBMR) context. • Assisting in radiological decision-making. • Optimization of the computational time of retrieving relevant images using the coupled index based on a hashing technique. • The imitation of the radiologists' analyses using a dynamic similarity assessment. Content-Based Mammogram Retrieval (CBMR) methods using Multi-View Information Fusion (MVIF) have triggered a growing interest in the last years given their ability to help radiologists make the right breast-cancer related decision. To further improve the retrieval performance, this paper introduces an efficient MVIF-CBMR method based on late fusion that combines retrieval result-level of Medio-Lateral Oblique (MLO) and Cranio-Caudal (CC) views. The proposed method adopts a coupled multi-index with a dynamic distance to evaluate the similarity between mammograms, which allows to fully exert the discriminative power of the complementary of MLO-CC features. Furthermore, the ROI dataset signature indexing step uses a hashing technique to optimize the computational time for retrieving relevant images. Thus, the proposed method takes two query ROIs corresponding to two different views (MLO and CC) as input and displays the most similar ROIs to each view using a dynamic similarity assessment. The retrieved ROIs can therefore be analyzed according to their clinical cases for the final decision-making relative to the query ROIs. The experiments realized on the challenging Digital Database for Screening Mammography (DDSM) dataset have proved the effectiveness and the efficiency of the proposed method. [ABSTRACT FROM AUTHOR]