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This article presents a distributed, efficient, scalable, and real-time motion planning algorithm for a large group of agents moving in 2-D or 3-D spaces. This algorithm enables autonomous agents to generate individual trajectories independently with only the relative position information of neighboring agents. Each agent applies a force-based control that contains two main terms: 1) collision avoidance and 2) navigational feedback. The first term keeps two agents separate with a certain distance, while the second term attracts each agent toward its goal location. Compared with existing collision-avoidance algorithms, the proposed force-based motion planning (FMP) algorithm can find collision-free motions with lower transition time, free from velocity state information of neighboring agents. It leads to less computational overhead. The performance of proposed FMP is examined over several dense and complex 2-D and 3-D benchmark simulation scenarios, with results outperforming existing methods.

The number of Indonesian students in higher education has been increasing rapidly. However, many Indonesian university students report experiencing mental distress. Research on student wellbeing found that self-compassion (i.e., being kind towards oneself in challenging times) and academic engagement (i.e., a commitment and purposeful effort toward study) are essential to students’ mental wellbeing. With the present study, we aimed to assess the mental wellbeing of Indonesian students. A convenience sample of 156 Indonesian students completed self-report measures on mental wellbeing, self-compassion and academic engagement (consisting of vigour, dedication and absorption). To contextualise their mental wellbeing, data from Indonesian students were compared with those from 145 UK students using Welch t-tests. Correlation, regression and mediation analyses were then performed to examine the relationships among these variables. Indonesian students had higher levels of self-compassion and absorption and a lower level of dedication than UK students. Self-compassion and academic engagement explained 36% of variance in mental wellbeing. Self-compassion and vigour were identified as significant predictors of mental wellbeing, whereas self-compassion was the strongest predictor. Lastly, vigour did not mediate the pathway from self-compassion to mental wellbeing. Interventions to support self-compassion and academic engagement, especially vigour, in Indonesian students are recommended to support their mental wellbeing.

This article presents a novel guidance and control design for a parcel tethered to a drone in its delivery mission. The proposed proportional-navigation-based guidance, integrated with custom-built control, enables to achieve autonomous payload landing. The novelty of the proposed method lies in two aspects: 1) the guidance law allows for soft landing and 2) the path-following control ensures the swing-free payload transportation that sets the solid foundation for landing. The development is verified by extensive simulations and further demonstrated by flight experiments.

This article designs and tests a dominant region based strategy for a group of defenders to intercept an intruder before it enters a target area. The intruder is intelligent in the sense that it makes decisions based on the defenders’ strategies instead of following a predefined path, making the problem a differential game. When the intruder moves slower than the defenders, the optimal strategies are solved from a geometric concept called the dominant region. These strategies are then extended into the case where the intruder travels faster. Crazyflie 2.1 is used as an experimental platform to test the proposed strategy. For fixed defender locations, a barrier line can be found such that the intruder is guaranteed to be captured outside the target area if it starts beyond.

A path-following controller based on an uncertainty and disturbance estimator (UDE) for a quadrotor with a cable-suspended payload is proposed in this paper. The quadrotor and the payload are subject to unknown wind disturbances. The controller resembles a cascade architecture. For the outer loop, a UDE-based translational control law is proposed. The controller asymptotically stabilizes the quadrotor along a given path and estimates the lumped disturbances with a low-pass filter. For the inner loop, an attitude tracking controller is used to control the direction of the lift vector so that the actual lift force can asymptotically follow the reference force generated by the translational controller. The stability of the system with the translational controller and the attitude tracking controller has been shown to be asymptotically stable using the reduction theorem. With the help of the reduction theorem, the design of the translational and the attitude control can be decoupled, providing the flexibility of implementing different attitude controllers without redoing the stability analysis. As shown in the simulation, the control law can stabilize the quadrotor on the desired path under different wind disturbances.

The attitude synchronization for multiple three-degree-of-freedom helicopters in the presence of system uncertainties and time-varying actuator faults is investigated. A fault-tolerant cooperative control algorithm based on robust adaptive control is proposed to synchronize attitudes of multiple helicopter systems in the case where some of the helicopters are subjected to both partial losses of control effectiveness and additive actuator faults. The proposed design is a distributed control method that allows each vehicle to track external reference signals merely in light of its neighborhood information. With the proposed design, time-varying actuator faults are tolerated without sacrificing the attitude synchronization performance. The effectiveness of the proposed control method is verified via a comparative experimental study.

Coronavirus disease 2019 (COVID-19) is spreading worldwide. The onset of severe COVID-19 could lead to multiple organ damage and even death. It is worth paying attention to the warning index of the onset for severe COVID-19 so that patients can be identified and monitored carefully.The report is a retrospective study that describes and analyzes the clinical features during the treatment of COVID-19. Four patients with COVID-19 were involved in this study, who were father-and-son pairs from two families. All patients were treated with the same combination of anti-microbial and anti-viral agents for 10-14 days, adjusting for the disease status. The primary outcome measure was SARS-CoV-2 detection using RT-qPCR with oropharyngeal swabs. Chest CT imaging served as a secondary outcome measure.One of the four patients progressed to severe disease, while the remaining patients recovered with the same treatment. A persistent decrease in the lymphocyte ratio and increase in the C-reactive protein (CRP) level were observed in the severe patient, along with other typical symptoms of COVID-19.The cases we described indicate that blood cell and CRP tests could be useful risk warnings of severe onset of COVID-19.

Accumulating evidence verified that microRNAs (miRNAs) participate in the development of several cancers.The levels of miR-138-5p and forkhead box c1 (FOXC1) were examined using quantitative Real-time PCR (qRT-PCR). Cell Counting Kit-8 (CCK-8), colony formation, migration, and Transwell invasion assays were conducted to examine the impact of miR-138-5p on hepatocellular carcinoma (HCC) cells. The protein expression of FOXC1 was detected using Western blotting assay. The tumor growth of HCC cell in vivo was analyzed using transplanted tumor model. The expressions of FOXC1 and Ki67 in vivo were assessed using immunohistochemistry (IHC) assay.We testified that miR-138-5p was down-expressed in HCC and the low level of miR-138-5p was related to the poor clinical outcome of patient with HCC. Moreover, miR-138-5p repressed the growth and metastatic phenotypes of HCC cells. Consistent with the results in vitro investigations, we revealed that miR-138-5p served as a suppressive miRNA in the growth of HCC cell in vivo. By using the luciferase assay and immunoblotting, we validated that FOXC1 was a potential downstream gene of miR-138-5p. Finally, our results showed that re-expression of FOXC1 rescued the growth and metastatic-related traits of HCC cell inhibited by miR-138-5p.Altogether, our observations imply that miR-138-5p restrains the aggressive phenotypes of HCC cell via modulating FOXC1.

To uncover the role of miRNA-1246 in influencing the proliferative and migratory capacities of RCC by binding CXCR4 and downregulating its level.Relative levels of miRNA-1246 and CXCR4 in 40 paired RCC tissues and adjacent normal tissues were determined. The binding relationship between miRNA-1246 and CXCR4 was confirmed by Dual-Luciferase reporter assay. Proliferative and migratory abilities of RCC regulated by miRNA-1246 and CXCR4 were assessed.MiRNA-1246 was downregulated in RCC tissues and cell lines. Overexpression of miRNA-1246 attenuated proliferative and migratory capacities of 786-O and 769-P cells. CXCR4 was the direct target of miRNA-1246 and its level was negatively regulated by miRNA-1246. Silence of CXCR4 inhibited RCC to proliferate and migrate.MiRNA-1246 attenuates proliferative and migratory abilities of RCC by downregulating CXCR4. MiRNA-1246/CXCR4 axis could be potential therapeutic target for RCC.

Wildfires play an important role in forest management, while an accurate assessment of current wildfire status is imperative for fire management. In this paper, a Kalman filter-based methodology is proposed to estimate the wildfire progress with online measurements that are collected by a system of unmanned aerial vehicles. The method is developed to estimate the wildfire propagation behavior as well as fire front contour. It is enabled by developing a scalar field wildfire model and utilizing the Kalman filter to estimate the parameters of the model. In addition, an uncertainty function is developed to describe the performance of the estimation results. The effectiveness of the algorithm is demonstrated in an independent fire simulation environment.

This paper presents an aerodynamic model-based robust adaptive control algorithm for close formation flight. The leader aircraft is assumed to be at level and straight flight which characterizes the most common scenario for close formation flight. The formation aerodynamic effects are assumed to be unknown, but an online formation aerodynamic model is available to predict those effects. In light of the online formation aerodynamic model, a robust adaptive control algorithm is thereafter developed on the follower aircraft to counteract the unknown formation aerodynamic effects and obtain highly accurate formation tracking performance. The proposed control algorithm is composed of a baseline controller and an integrator-augmented robust adaptive controller, which can efficiently deal with both matched and mismatched formation aerodynamic effects and external disturbances. The major advantage of the proposed design is that it can achieve at least ultimate bounded tracking control with certain transient performance guaranty. The efficiency and robustness of the proposed control design are eventually validated via numerical simulations of close formation flight at two different scenarios.

The distributed cooperative control strategy is proposed to make the networked nonlinear 3-DOF helicopters achieve the attitude synchronization in the presence of actuator faults and saturations. Based on robust adaptive control, the proposed control method can both compensate the uncertain partial loss of control effectiveness and deal with the system uncertainties. To address actuator saturation problem, the control scheme is designed to ensure that the saturation constraint on the actuation will not be violated during the operation in spite of the actuator faults. It is shown that with the proposed control strategy, both the tracking errors of the leading helicopter and the attitude synchronization errors of each following helicopter are bounded in the existence of faulty actuators and actuator saturations. Moreover, the state responses of the entire group would not exceed the predesigned performance functions which are totally independent from the underlaying interaction topology. Simulation results illustrate the effectiveness of the proposed control scheme.

In this paper, a new fault diagnosis method is presented for the sensors in the vertical direction of a quadrotor. Different from the existing methods that treat the inertial sensors and the measurement sensors separately, the presented method is capable of dealing with both the z -axis accelerometer and the barometer. The knowledge of the thrust model is used to generate an analytical redundancy based fault diagnosis approach for altitude estimation. The filter design, fault detection, isolation, and recovery problems are addressed. An improved chi-test method is used for fault detection. Real-flight data is used to validate the proposed approaches, showing that the faults of the z -axis accelerometer and the barometer can both be detected and the thrust model of a quadrotor can be used to replace the faulty z -axis accelerometer.

A novel computationally efficient close formation aerodynamic model is presented using the lifting-line theory based on an elliptical lift distribution assumption. Formation aerodynamic effects ind...

Application of light-emitting diodes (LEDs) in frequency-domain fluorescence lifetime imaging microscopy (FLIM) has been limited by the trade-off between modulation frequency and illumination intensity of LEDs, which affects the signal-to-noise ratio in fluorescence lifetime measurements. To increase modulation frequency without sacrificing output power of LEDs, we propose to use LEDs with multiple dice connected in series. The LED capacitance was reduced with series connection; therefore, the frequency response of multidie LED was significantly increased. LEDs in visible light, including blue, green, amber and red, were all applicable in FLIM. We also present a homogenizing optics design, so that multidie LEDs produced uniform illumination on the same focal spot. When the homogenizing optics was combined with multicolour emitters, it provides multiple colour selection in a compact and convenient design.

In this paper, a fault-tolerant control design that can gain schedule with the airspeed is developed for a flexible aircraft with actuator saturation and stuck control surface faults. First, a flex...

Based on the gravitational red shift, which is a prediction of Einstein's general relativity theory, of broad optical emission lines in active galactic nuclei (AGNs), a new method is proposed to estimate the virial factors f in measuring black hole massesM(RM) by the reverberation mapping of AGNs. The factors f can be measured based on two physical quantities, i.e. the gravitational red shifts z(g) and the full widths at half maxima vFWHM of broad lines. In the past, it has been difficult to determine the factors f for individual AGNs. We apply this new method to several reverberation- mapped type 1 Seyfert galaxies. There is a correlation between f and the radius of the broad-line region (BLR) r(BLR), f = 5.4r(BLR)(0.3), for the gravitationally red-shifted broad lines He II, HeI, H beta and H alpha in the narrow-line type 1 Seyfert galaxy (NLS1) Mrk 110. This correlation results from the influence of the radiation pressure of the accretion disc on the BLR clouds. This influence seems to be more important than usually thought so in AGNs. Mrk 110 has f approximate to 8-16, distinctly larger than the mean (f) approximate to 1 usually used to estimate M-RM for v(FWHM.) NGC 4593 and NLS1 Mrk 486 have f approximate to 3 and f approximate to 9, respectively. Higher f values of several tens are derived for three other NLS1s. There is a correlation between f and accretion rate U-f=1, f = 6.8M(f= 1)(0.4) for five objects, where U-f=1 = M-center dot/L-Edd(c-2) as f = 1 is assumed when estimating MRM used in the Eddington luminosity L-Edd, M-center dot is the mass accretion rate, and c is the speed of light. These larger f values will produce higher MRM values and lower Eddington ratios.

In this article, we present a framework to use an autonomous multirotor unmanned aerial system UAS for cyanobacterial harmful algal blooms CHABs monitoring. The requirements of CHABS monitoring, and the factors are analysed. Formulae are developed to describe the relation between the image qualities and the UAS performance. Experiments are designed to investigate the influences of the flight parameters the flight altitude, the flight speed and the shutter time of the camera on the image resolution. CHABs detection experiments were carried out at Kingston, Canada. Experimental results show that the autonomous UAS is a promising enabling technology to contribute to a novel CHABs detection method.

In this paper, an active fault tolerant control (FTC) approach based on transient performance index is proposed for the attitude control systems of unmanned aerial vehicle (UAV) with actuator fault. The nonlinear attitude control system model for UAV with actuator faults is given, which represents the dynamic characteristics of UAV. A fault diagnosis component is used for fault detection and estimation. According to the fault estimation information obtained during the fault diagnosis, the fault tolerant control scheme is developed by adopting the adaptive dynamic surface control technique, which guarantees the asymptotic output tracking and ultimate uniform boundedness of the closed-loop attitude control systems of UAV in actuator faulty case. Further, a prescribed transient performance of the FTC attitude control systems is considered which characterizes the convergence rate and maximum overshoot of the attitude tracking error. Finally, simulation results are shown that the attitude control system states remain bounded and the output tracking errors converge to a neighborhood of zero.

Carbon fibre reinforced plastic is graphite fibre or carbon fibre reinforced composite material. It is easy to generate cemented carbide tool wear in the process of drilling. Diamond-coated tools have good cutting performance in drilling super hard materials, and they have potential application in the drilling of carbon fibre reinforced plastic materials. This paper presents the preparation of chemical vapour deposition diamond-coated tools used and tests of their performance in the drilling of carbon fibre reinforced plastic materials. The results indicate that chemical vapour deposition diamond-coated tools offer better drilling performance than cemented carbide cutting tools do when applied to the drilling of carbon fibre reinforced plastic materials. In addition, it was shown that the lifespan of diamond-coated tool is longer than that of cemented carbide tool during the drilling of carbon fibre reinforced plastic materials.

The second-order consensus tracking problem of multiple 3-degree-of-freedom laboratory helicopters is studied on directed communication topologies in this paper. The laboratory helicopters are subjected to nonlinearity, model uncertainty, and equipped only with angular position sensors. We present a decentralized consensus controller that includes a nonlinear uncertainty and disturbance estimation (UDE) term to compensate the model uncertainties and disturbances in each vehicle and its neighborhood. The UDE term consists of a second-order auxiliary system and a discontinuous term, neither the measurement of angular velocity nor its asymptotic estimation is required. Convergence of the tracking error is analyzed using invariance-like theorems. It is also proved that the UDE term will converge to the actual uncertainties and disturbances. Experimental results show that a group of four vehicles reach second-order consensus tracking using the proposed method, on a one-direction communication topology where only one vehicle can reach the reference signal.

This paper proposes a robust attitude tracking controller for a table-mounted experimental helicopter that has three rotational degrees-of-freedom and only equips angular position sensors. The proposed controller can achieve output-feedback attitude tracking of the pitch and elevation channels of the helicopter. The experimental platform is subjected to model uncertainties, coupling effects, and equips with an independent active disturbance system, which have effectively examined the robustness of proposed controller. The control law includes a second-order auxiliary system to generate filtered error signals, and a discontinuous uncertainty and disturbance estimation (UDE) term to compensate the model uncertainties and external disturbances. A Lyapunov-based stability analysis shows the semiglobal asymptotic tracking ability of the proposed controller. The experimental results further demonstrate that the proposed method can achieve equivalent dynamic and static performance compared to other high-performance state-feedback methods, and even when the initial position is away from design point, it also gives more consistent responses than other linear methods.

This paper is concerned with the fault detection filter design problem for linear time-invariant systems subject to disturbance and possible faults. To make a tradeoff between fault sensitivity and disturbance sensitivity, frameworks such as ? - / ? ∞ , ? 2 / ? ∞ , and ? ∞ / ? ∞ are considered. It is shown that for ? - / ? ∞ and ? ∞ / ? ∞ frameworks, all optimal fault detection filters can be characterized by an envelope besieged by the special solutions serving as upper and lower bounds. Furthermore, the explicit parametrization is given in terms of a free contractive system/parameter. This free parameter provides freedom to emphasize fault and disturbance sensitivities at different frequency ranges, which can be used to construct new optimal fault detection filter. The results are also extended to the optimization over finite frequency range, for which the upper and/or lower bound of the optimal solution set may not be rational. On the other hand, it is shown that the solution set of ? 2 / ? ∞ problem is unique up to square inner system. Finally, examples are given to illustrate the results.

This paper proposes a cooperative nonlinear filter to estimate the states of a maneuvering target with unknown dynamics and bounded acceleration using multiple mobile sensors. The proposed filter is applied to a vision-based estimation task in which multiple unmanned aerial vehicles equipped with monocular cameras are employed to estimate the position and velocity of a maneuvering target. Its performance is validated through extensive numerical simulations.

In this paper a nonlinear time-domain aeroservoelastic model is developed to study stall flutter and design flutter suppression control systems. A novel state-space model description enables for both aeroelastic analysis and control design. As a case study, limit cycle oscillations and bifurcation behavior of a NACA 0012 airfoil undergoing stall flutter are investigated. The results agree well with experimental results reported in the literature. Further, to demonstrate the model capability for control design, an output feedback controller is employed to suppress stall flutter and to stabilize the system at different incoming flow speeds to expand the flutter envelope. Closed-loop simulations confirm the improvement of the flutter envelope.

Multiple experimental three-degrees-of-freedom (three-DOF) helicopters that are equipped with active disturbance systems constitute an attractive platform to validate robust control strategies. In this paper, a distributed synchronization controller is developed for such a platform, where each helicopter is subjected to unknown model uncertainties and external disturbances, and the desired trajectories are generated online, communicated through a network and not accessible by all helicopters. The controller is composed of a continuous tracker and a continuous uncertainty and disturbance estimator (UDE). The tracker makes the nominal closed-loop system globally asymptotically stable, and the UDE output is used to reject total uncertainties. The conditions that ensure zero-error tracking for each helicopter are identified; for the case with nonzero error, explicit relationship inequalities between the involved design parameters and the ultimate bound of error are revealed. Experimental results of four cases demonstrate improved tracking and synchronization accuracy of using the UDE with small parameters.

This paper presents a steady-state concept model for studying the thermal behavior of a greased aircraft landing gear lower slider bearing. Structural damage has been reported as a consequence of excessive heat generated by the high loads induced by rough runways on the bearings, and by the high sliding velocities of the piston. The goal of the model is to enable fundamental understanding of the frictional heat generation. The governing equations are adapted for grease flow and special attention is given to the underlying algorithm of the developed numerical framework used to efficiently solve the governing equations. The developed numerical code is validated against existing results. Numerical results indicate fundamental differences in fluid flow behavior between greased and oil-lubricated bearings.

In this work, the 18Cr–2Mo ferritic stainless steel was treated with and without warm rolling at 573 K with 66.5% reduction after conventional hot rolling process. It was shown that ductile-to-brittle transition behaviour could be closely related to deformation twinning and parameters affecting critical temperature for twinning would also inevitably affect ductile-to-brittle transition temperature. This correlation between ductile-to-brittle transition behaviour and twinning was in good agreement with the Cottrell–Petch model. A lowered transition temperature and an improved toughness after introducing warm rolling process and corresponding annealing process could be mainly explained in terms of refining the recrystallised grains and reducing the volume fraction of grains having orientations favourable for twinning, which decrease the critical temperature at which twins form.

This paper studies a persistent tracking problem, which is to design a control strategy for a unicycle-type mobile vehicle to track a moving target and to maintain the tracking distance within a detection range all the time, regardless of the target's motion. In a proposed framework based on the game theory, a bounded and closed region encircling the tracking vehicle is identified to enable persistent tracking and a tracking algorithm is constructed accordingly. The proposed approach is successfully verified through experiments using two ground vehicles, one serving as the autonomous tracking vehicle and the other as the target vehicle.

S5 0716+714 is a typical BL Lacertae object. In this paper we present the analysis and results of long-term simultaneous observations in the radio, near-infrared, optical, X-ray, and gamma-ray bands, together with our own photometric observations for this source. The light curves show that the variability amplitudes in gamma-ray and optical bands are larger than those in the hard X-ray and radio bands and that the spectral energy distribution (SED) peaks move to shorter wavelengths when the source becomes brighter, which is similar to other blazars, i. e., more variable at wavelengths shorter than the SED peak frequencies. Analysis shows that the characteristic variability timescales in the 14.5 GHz, the optical, the X-ray, and the gamma-ray bands are comparable to each other. The variations of the hard X-ray and 14.5 GHz emissions are correlated with zero lag, and so are the V band and gamma-ray variations, which are consistent with the leptonic models. Coincidences of gamma-ray and optical flares with a dramatic change of the optical polarization are detected. Hadronic models do not have the same natural explanation for these observations as the leptonic models. A strong optical flare correlating a. -ray flare whose peak flux is lower than the average flux is detected. The leptonic model can explain this variability phenomenon through simultaneous SED modeling. Different leptonic models are distinguished by average SED modeling. The synchrotron plus synchrotron selfCompton (SSC) model is ruled out because of the extreme input parameters. Scattering of external seed photons, such as the hot-dust or broad-line region emission, and the SSC process are probably both needed to explain the gamma-ray emission of S5 0716+714.

A methodology for characterizing the thermo-tribomechanical response of an aircraft landing gear shock absorber is presented. Structural damage has been reported as a consequence of heat generated by high loads induced by rough runways on the shock absorber bearings and by the high sliding velocities of the shock absorber piston. Therefore, a model that reveals the characteristics of the thermal behavior, and identifies heat sources and sinks in the landing gear shock absorber is developed. The thermo-tribomechanical model framework is presented with representative development of each component. In addition, a sensitivity study of the maximum heat flux to variations of key input parameters is investigated. The numerical results indicate that the runway amplitude dominates the landing gear thermal response.

The texture development and γ-fibre recrystallisation texture formation mechanism of ferritic stainless steels under different rolling processes were investigated. It was shown that the surface texture development was absolutely different from the centre texture development. In conventional rolled band, strong α-fibre was formed at the centre layer and it was weakened after hot band annealing; after cold rolling, the centre texture was characterised by sharp α-fibre and weak γ-fibre with a peak at {111} , and non-uniform γ-fibre recrystallisation texture was developed. By contrast, in warm rolled band, the centre texture consisted of weakened α-fibre and sharpened γ-fibre, and {111} became the prominent component after hot band annealing. The α-fibre and γ-fibre with a peak at {111} were intensified at the centre texture after cold rolling, resulting in the formation of uniform γ-fibre recrystallisation texture. It was indicated that the formation mechanism of γ-fibre recrystallisati...