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Hai-Ying Chen,1,&ast; Ming-Chao Li,2,&ast; Dan Liao,1 Chi Li,1 Qiu-Ming Ji,1 Ping Guo,1 Zou Su,1 Yu-Hong Yang,1 Wen-Hao Xiao,1 Wen-Hui Zhai1 1Department of Psychiatry, Wuhan Wudong Hospital, Wuhan, People’s Republic of China; 2Department of Psychiatry, Wuhan Mental Health Center, Wuhan, People’s Republic of China&ast;These authors contributed equally to this workCorrespondence: Dan Liao; Chi Li, Department of Psychiatry, Wuhan Wudong Hospital, No. 46 of Wudong Street, Qingshan District, Wuhan, 430084, People’s Republic of China, Tel +86 27 5052 8367, Fax +86 27 8643 8247, Email danliaodr@21cn.comObjective: Our study aimed to investigate the effects of computer-assisted cognitive remediation therapy (CCRT) on cognitive function, social function and quality of life in patients with vascular dementia (VD).Methods: Ninety-eight patients with VD were treated with CCRT in four 45-minute sessions per week over a course of 40 sessions to exercise four cognitive functions, including flexibility, working memory, plan execution and social cognition. The Mini-Mental State Examination (MMSE), Social Disability Screening Schedule (SDSS), Personal and Social Performance Scale (PSP), and Generic Quality of Life Inventory-74 (GQOL-74) were used to assess before and after treatment.Results: (1) The scores of orientation (5.60 ± 1.35), calculation (2.20 ± 0.79), verbal ability (7.10 ± 0.36), spatial ability (0.78 ± 0.42), immediate memory (2.42 ± 0.53), short-term memory (1.17 ± 0.78) and MMSE (23.36 ± 2.98) were all improved after treatment (P < 0.05) compared with those before treatment; (2) The scores of SDSS, PSP and Activities of Daily Living (ADL) after treatment were 8.23 ± 0.94, 81.36 ± 14.23, and 32.7 ± 12.1, and all of which improved (P < 0.05); (3) The scores of physical health were 68.24 ± 7.44, mental health were 69.75 ± 7.15, social function were 69.08 ± 7.43, material life were 37.46 ± 4.85 and the total score were 230.79 ± 9.56, all of which improved (P < 0.05).Conclusion: For patients with VD, CCRT can improve their cognitive function, social function, daily life ability and quality of life.Keywords: computer-assisted cognitive remediation, vascular dementia, cognitive function, social function, daily life ability

The multiple autonomous underwater vehicles (AUV) sailing in a specific configuration can reduce resistance if properly using the hydrodynamic interactions. This paper investigated the resistance characteristics of a multi-AUV system with both experimental and numerical approaches. A center-beam-support bar structure was designed to conduct the experiment. Validation of our numerical method was carried out by comparing with the experimental data. Parametric studies were then performed on the distance, the speed and the number of AUVs. The numerical results showed that SST-transition model is more suitable for simulating the multi-AUV system at Reynolds numbers (Re) ranging from 2.46 × 106 to 6.69 × 106. At Re = 6.14 × 106, the largest reduction of resistance can be 35.14% at d/L = 0. In the meantime, there appears some undesirable interference area between d/L = 0.042 and d/L = 0.063 where the total resistance of the fleet increases sharply. Apart from that, higher reduction of resistance can be expected with the increase of the speed and the number of AUVs.

This paper presents a systematic work focused on the thrust generation and wake structures of two travelling-wavy foils with tandem, parallel and staggered arrangements, therein presenting essential information about actual schooling fish. The fluid dynamics around two identical foils arranged with a dimensionless horizontal gap, G x , and vertical gap, G y , are investigated at Reynolds number R e = 2 × 1 0 5 . The wake structures are classified into proximity interference, wake interference, proximity and wake interference, and no interference associated with thrust generation. Based on numerical computations, we find that G x significantly affects the re-organisation of the vortex shedding from the leading and following foils, resulting in various propulsive forces acting on the foils. Moreover, G y causes a result whereby the vortex shedding from the leading foil deflects towards the flow behind the following foil, leading to a slight change in the thrust generation for both travelling-wavy foils. This work is helpful for guiding the queue control of multiple bio-inspired underwater robots.

We numerically investigate the force generation and wake structures of a nonsinusoidal periodic pitching foil under a thickness-based Reynolds number of R e D = 255 . We consider various nonsinusoidal periodic trajectories of pitching motion, such as the sawtooth and square trajectories, using an adjustable parameter, K . Similar to previous studies on sinusoidal pitching foils, the present results for the nonsinusoidal pitching foil indicate that the transition from a Benard–von Karman wake to a reverse Be nard–von Karman wake precedes the actual drag–thrust transition. In addition, the symmetry breaking of a reverse Be nard–von Karman wake is observed. As K increases, the drag–thrust transition of the nonsinusoidal pitching foil advances gradually and it becomes easy to destabilize the wake structures produced by the oscillating foil. Since K physically describes how rapidly the foil reverses its pitching direction, we argue that the initial velocity of vortex shedding from the foil increases with K and results in the aforementioned phenomena. The present work provides helpful findings for better understanding the kinematic behaviour of actual animals and for designing bio-inspired robotics.

Air-launched autonomous underwater vehicles (AUVs) are subjected to huge impact loads in the early stage of water entry, which may cause structural damage or failure of electronic components, especially in the case of high speed water entry. Therefore, it is very imperative to carry out experimental and numerical research on the impact loads of air-launched AUVs. An experimental study of the water entry of air-launched AUVs with different launch velocities and angles was conducted using high-speed photography and sensing technology. The axial and radial accelerations of AUVs under different working conditions at the early stage of water entry were obtained. Furthermore, a coupled finite element technique and the smooth particle hydrodynamics method (FEM-SPH) is employed to model the water entry process of air-launched AUVs. Numerical simulation results such as the peak of impact acceleration were compared with the presented experiment results. The good agreement between the experimental results and the numerical simulation results revealed the capability and accuracy of the numerical algorithm in solving the problem of AUV water entry.

In a two-autonomous underwater vehicle (AUV) system, the hydrodynamic interaction between the two vehicles can have both beneficial and harmful impact on the system. In an aim to investigate the fa...

We characterised the hydrodynamics of the two staggered swimming fish using vortex dynamic method. Based on the theoretical model, we showed that the horizontal spacing between the two fish plays a crucial role in affecting the fluid dynamics around two fish, while the vertical spacing between the two fish merely affects the value of propulsive force individually generated by the two fish. Furthermore, we revealed that there are two horizontal spacing thresholds for the holding and breaking of the spatial configurations of the two fish, indicating that two fish would swim at the stable status: the synchronous acceleration or deceleration.

The drag-thrust transition and wake structures of a pitching foil undergoing combinations of fast and slow pitching are systematically investigated. The foil locomotion having combinations of fast and slow pitching is made by setting a variable s defined as the fraction of the pitching time required on the upper side of the wake centerline. On the other hand, time 1-s is required for the foil to pitch on the lower side of the wake centerline. Compared to the symmetric pitching (s = 0.5) case, the time-mean thrust rapidly increases and the drag-thrust boundary advances with increasing |s − 0.5|. The Karman vortex street slants and produces thrust when |s − 0.5| is sufficiently large, which supersedes the previous thumb rule that only reverse Karman vortex street can produce thrust. The faster forward stroke determines the slant direction of the vortex street. The detailed wake structures produced by the pitching foil are discussed, showing how the combined pitching affects vortex dynamics, drag-thrust transition, slant direction, and wake jet. This work provides a physical basis for understanding the hydrodynamics of native swimmers which may be useful to design bio-inspired underwater robots.

A numerical study is carried out to investigate the energy harvesting from an inverted foil undergoing flow-induced pitching oscillation for reduced velocity Ur = 1–45 and damping ratio ζ = 0–0.295. The benchmark results with undamped foil (ζ = 0) indicate that the foil does not oscillate for Ur ≤ 27 but does oscillate with increasing amplitude for 27

The drag–thrusttransition and wake structures of a pitching foil undergoing asymmetric sinusoidal oscillation are numerically investigated for foil thickness-based Strouhal number St D = 0.1–0.3 and amplitude ratio A D = 0.5–2.0. The asymmetry in the oscillation is introduced by making one half-stroke (e.g. from the lower extreme to the upper extreme) faster than the other. The results reveal that the drag–thrust​ transition advances with increasing the pitching asymmetry because of enhanced thrust in the faster stroke. Similar to the reverse Karman wake generated from the symmetric oscillation, the P+S (paired and single vortices) wake identified in the case of the asymmetric oscillation can produce both drag and thrust, hence appearing around the drag–thrust transition boundary. The formation and evolution of wake structures produced by the asymmetrically oscillating foil are discussed, showing how the asymmetric oscillation affects fluid dynamics, drag–thrust transition, vortex strength, and wake jet. This work provides some new perspectives to understand the swimming and flying performance and some useful findings to design bio-inspired robots.

In this work, we present a systematical investigation to understand the hydrodynamic characteristics of the manta-inspired foil. At the Reynolds number of 200, the thrust acting on an active deforming foil is numerically studied. Based on the numerical results, we reveal that the propulsive force of the manta-inspired foil is increased with keeping increase of the kinematic frequency and amplitude of the foil. In addition, it is found that the flexibility of the foil also plays a key role in affecting the foil’s propulsive performance. This work provides helpful findings for designing the manta-inspired underwater robots.

In this paper, a theoretical study is conducted to investigate the propulsive performance of two flapping foils with the inline arrangement. At first, we consider the propulsive performance of two flapping foils when they are relative static to each other, that is, the horizontal gap between the foils is fixed. Then, we provide a model to consider the dynamic stability of the two-foil system when the relative movement between them has occurred, that is, the horizontal gap between the two foils can be changed depending on the propulsive force acting on the foil. This work provides helpful suggestions for managing the trajectories and energy cost of multiple bio-inspired robotics.

The purpose of this paper is to provide guidance for AUV manoeuvering of two vehicles missions. In this paper, the numerical simulation of interaction between two vehicles with different size is conducted using CFD code. Mesh independence is tested and then validated with experimental results in previous paper. In an aim to predict the factors that influence the hydrodynamic performance, the simulation is then investigated in different longitudinal and lateral distances, drift angles and depth from the water surface.

The drag–thrust transition of a symmetric foil undergoing pitching oscillation in a uniform flow is numerically studied in the present work. Under a certain thickness-based Reynolds number R e D = 255 , the fluid dynamics around the oscillated foil at a series of values for the chord-based Reynolds number, R e c , are investigated. The various values of R e c are obtained by keeping the maximum thickness of the foil fixed while rhythmically changing the chord length of the foil. Depending on the numerical results, we uncover a scaling relation that links the amplitude-based Strouhal number S r A to the R e c at the drag–thrust transition boundary, which is briefly expressed as S r A ∼ R e c − 1 . Through analysing the velocity field of the foil, it is found that the drag–thrust transition of the pitching foil is closely associated with the critical velocity of the latest vortex produced by the foil. These findings helps in understanding the kinematic behaviour of aquatic animals and designing bio-inspired underwater robots.

The optimal aquatic locomotion has previously been associated with a narrow St(= fA/u) number range of 0.2–0.4. We present how animals tune their Strouhal (St) number to this range to reveal the mechanisms influencing efficiency. The self-propelled swimming of a 2D swimmer is simulated using an immersed boundary method. The locomotion kinematics is controlled by two variables, [Formula: see text] and frequency f. We show that only when animals constrain their [Formula: see text] = 0.125–0.25, their St number can fall into the optimal St range. When [Formula: see text] Hz, the St number is independent with frequency. Although different combinations of f and [Formula: see text] can achieve a same cruising velocity, high-f and low-[Formula: see text] motions are more efficient. This can be linked to its larger lateral velocity component in the proto-vortex region and the transition of the tail vortices into small eddies.

The effects of the Reynolds number (Re) and thickness on an undulatory self-propelled foil were numerically investigated using the immersed boundary method. Re varied from 50 to 2 × 105, which encompasses the viscous, intermediate, and inertial regimes using a NACA 0012 airfoil. An investigation of the thickness was performed on NACA airfoils with maximum thicknesses of 0.04 ∼ 0.24 at two Re values (5 × 104 and 500). The results indicated that the foil can achieve a higher forward velocity, perform less work, and exhibit a higher propulsive efficiency with increasing Re. However, the effect of Re is asymptotic beyond 5 × 104. Four types of vortex structures exist, and the transition from one regime to another is closely related to hydrodynamic changes. In the thickness study, thinner foils outperformed thicker foils in terms of the forward velocity and input power at both Re values. However, the efficiency related to the conversion of input power into kinetic energy for NACA 0004 was the lowest. An optimum thickness exists that depends on Re. At higher Re, the vortical structure differs for each thickness with the deflection angle, whereas at low Re, the location of the separation point strongly influences the hydrodynamics.

The unsteady ground effect on a self-propelled undulatory foil is numerically investigated in this paper. The situation can be widely found in nature especially for fish swimming near the ground. In this study, frequency varies from 0.1 Hz to 2 Hz and distance from the ground varies from 0.2 L to 1 L. Under most kinematics, the ground has a negative effect on the performance of the foil. The swimming velocity slows down, power spend increases and swimming economy reduces. The higher frequency can produce a larger negative effect. Only at the low frequencies f = 0.1 Hz, 0.25 Hz and 0.5 Hz with distance of 0.2 L the velocity can be enhanced by 18%, 6%, 0.8%, respectively. The lift production is found to be increased. The link between the performance and the wake dynamics is also established by studying the vortex structures.

To understand the interaction between the oscillated body and oncoming vortex, some numerical studies have been conducted on a system including two parallel D-cylinder and one oscillated foil in this paper. It is found that the distance between parallel D-cylinder and oscillated foil would play a key role in affecting the change regulation of thrust generation of oscillated foil, and the kinematics of oscillated foil would determine the value of propulsive thrust, the gap between two parallel D-cylinder would only affect the hydrodynamic performance of oscillated foil at intermediate conditions.

The effect of size and kinematics difference between two tandem flexible foils on drag reduction have been numerically studied. Compared with single foil, it is found that the kinematics difference between two foils would not play a significant role in reducing drag, while the size difference between two foils significantly affects the drag reduction in this two foil system. For leading foil, it always enjoys drag reduction and the highest drag reduction can be observed at bigger size difference and gap distance between two foil as 22%. For trailing foil, it suffers drag increase when the gap distance between two foils is smaller, while it enjoys drag decrease when the size difference between two foils is bigger enough. The hydrodynamic interaction between such actively undulated foils also has been uncovered and used to explain the mechanisms of drag reduction.