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This paper presents an efficient multi-objective optimization method, focusing on aerodynamic optimization of a diverterless supersonic inlet (DSI) in transonic and supersonic flight conditions. The DSI inlet, through scrutinizing the Bump shape has potential to attain greater aerodynamic performance on exit plane of inlet. However, the high cost of computational fluid dynamic (CFD) simulations raises a significant challenge in the DSI optimization process. In order to obtain solution set in few numbers of objective function calls, a meta-model multi-objective particle swarm optimization (MOPSO) method is proposed based on a self-adaptive Kriging surrogate model, and applied to solve this kind of costly black-box optimization problem. The Kriging model is updated by using a dynamic expected hyper-volume improvement (EHVI) sample metric, which is developed by analyzing disadvantages of the original sample criterion. With the help of the dynamic sample metric, simulation results show that the surrogate-based MOPSO algorithm can obtain plenty enough non-dominated solutions and achieve high precision in the approximation of the Pareto front. In terms of DSI inlet optimization, the bump shape is parameterized by free form deformation (FFD) method, and the total pressure distortions of inlet exit plane are treated as two minimization objectives under transonic and supersonic flight conditions. A well distributed non-dominated solution set is generated by the proposed algorithm within the context of a small call number of cost evaluations, and optimized inlet configurated by the selected solution has better aerodynamic characteristics compared with the initial inlet.

This paper presents a disturbance observer-based adaptive sliding mode control (SMC) strategy for a quadrotor helicopter subject to multiple actuator faults, parametric uncertainties, and external disturbances. Unlike most of the existing control strategies for quadrotor helicopters, actuator faults, parametric uncertainties, and external disturbances can be simultaneously compensated within the proposed control scheme. Firstly, by employing the adaptive control parameters in both continuous and discontinuous control parts, the proposed control strategy can generate appropriate control signals to accommodate actuator faults and parametric uncertainties without merely relying on the robust discontinuous control strategy of SMC. Then, a nonlinear disturbance observer is designed and integrated to attenuate external disturbances while keeping the small value of the discontinuous control gain of SMC. In addition, the stability analysis of the proposed control strategy is given, showing that the presented controller can ensure system tracking performance and make the tracking errors arbitrarily small under the concerned situation. The effectiveness of the proposed control strategy is demonstrated through comparative numerical simulations and experimental tests of a quadrotor helicopter under different faulty and uncertain scenarios.

In this contribution, theoretical model of the induced vibration and energy harvesting performances of a piezoelectric tubular energy harvester is established and analyzed. Analytical solutions to the model are obtained with the help of a system of linear operator equations. A series of simulations are done to investigate the influences of mechanical and electrical load parameters upon output performances of the energy harvester. Analyses of the characteristic roots show possible way to simplify the problem with asymptotic method. Results for state variables in the piezoelectric tube show good linear dependence of elastic displacements upon radial coordinates. Simulations on output performances indicate that the external connected electrical circuits should be compatible with the intended working conditions of the piezoelectric tubular energy harvester. The model developed here is expect to be useful in the design for self-powered sensor networks in hydraulic piping systems.

The aerodynamic layout of the fixed-wing mode of Canard Rotor/Wing (CRW) aircraft is quite different from that of the conventional fixed-wing aircraft. This study will focus on the flight dynamics characteristics and control in the fixed-wing mode of the CRW aircraft. First, aiming at the complicated aerodynamic interference in the fixed-wing mode of CRW aircraft, the flight dynamics model of the fixed-wing mode is established by combining CFD and engineering estimation. Then, by trimming at the different forward flight speeds, it is found that the minimum thrust is required when only the canard control surface is operated for longitudinal control. The linearized results show that the stability of most modes are good, and nevertheless only the Dutch roll mode diverges. It is found that the Dutch roll mode divergence is results from the unique three-wing aerodynamic layout of CRW aircraft. Finally, an explicit model tracking control system is designed to enhance the stability of the fixed-wing mode of CRW aircraft, which contributes for the future engineering application.

In this paper, an adaptive fault-tolerant control strategy is proposed for a quadrotor helicopter in the presence of actuator faults and model uncertainties by integrating sliding mode control and radial basis function neural network. By assuming knowledge of the bounds on external disturbances, a baseline sliding mode control is first designed to achieve the desired system tracking performance and retain insensitive to disturbances. Then, regarding actuator faults and model uncertainties of the quadrotor helicopter, neural adaptive control schemes are constructed and incorporated into the baseline sliding mode control to deal with them. Finally, a series of simulation tests are conducted to validate the effectiveness of the proposed control strategy where a quadrotor helicopter is subject to inertial moment variations and different level of actuator faults. The capability of the proposed control strategy is confirmed and verified by the demonstrated results.

With the increasing demand for unmanned aerial vehicles (UAVs) in both military and civilian applications, critical safety issues need to be specially considered in order to make better and wider use of them. UAVs are usually employed to work in hazardous and complex environments, which may seriously threaten the safety and reliability of UAVs. Therefore, the safety and reliability of UAVs are becoming imperative for development of advanced intelligent control systems. The key challenge now is the lack of fully autonomous and reliable control techniques in face of different operation conditions and sophisticated environments. Further development of unmanned aerial vehicle (UAV) control systems is required to be reliable in the presence of system component faults and to be insensitive to model uncertainties and external environmental disturbances. This thesis research aims to design and develop novel control schemes for UAVs with consideration of all the factors that may threaten their safety and reliability. A novel adaptive sliding mode control (SMC) strategy is proposed to accommodate model uncertainties and actuator faults for an unmanned quadrotor helicopter. Compared with the existing adaptive SMC strategies in the literature, the proposed adaptive scheme can tolerate larger actuator faults without stimulating control chattering due to the use of adaptation parameters in both continuous and discontinuous control parts. Furthermore, a fuzzy logic-based boundary layer and a nonlinear disturbance observer are synthesized to further improve the capability of the designed control scheme for tolerating model uncertainties, actuator faults, and unknown external disturbances while preventing overestimation of the adaptive control parameters and suppressing the control chattering effect. Then, a cost-effective fault estimation scheme with a parallel bank of recurrent neural networks (RNNs) is proposed to accurately estimate actuator fault magnitude and an active fault-tolerant control (FTC) framework is established for a closed-loop quadrotor helicopter system. Finally, a reconfigurable control allocation approach is combined with adaptive SMC to achieve the capability of tolerating complete actuator failures with application to a modified octorotor helicopter. The significance of this proposed control scheme is that the stability of the closed-loop system is theoretically guaranteed in the presence of both single and simultaneous actuator faults.

The bis(imino)pyridine iron complex, for the first time, is developed as an effective metal carbene catalyst for carbene transfer reactions of donor-acceptor diazo compounds. Its broad catalytic capability is demonstrated by a range of metal carbene reactions, from cyclopropanation, cyclopropenation, epoxidation, and Doyle-Kirmse reaction to O-H insertion, N-H insertion, and C-H insertion reactions. The asymmetric cyclopropanation of styrene and methyl phenyldiazoacetate was successfully achieved by the new chiral bis(imino)pyridine iron catalyst, which delivers a new gateway for the development of chiral iron catalysis for metal carbene reactions.

ATP-sensitive K+ (KATP) channels are expressed in gastrointestinal smooth muscles, and their activity is regulated by muscarinic receptor stimulation. However, the physiological significance and mechanisms of muscarinic regulation of KATP channels are not fully understood. We examined the effects of the KATP channel opener cromakalim and the KATP channel blocker glibenclamide on electrical activity of single mouse ileal myocytes and on mechanical activity in ileal segment preparations. To explore muscarinic regulation of KATP channel activity and its underlying mechanisms, the effect of carbachol (CCh) on cromakalim-induced KATP channel currents ( IKATP) was studied in myocytes of M2 or M3 muscarinic receptor-knockout (KO) and wild-type (WT) mice. Cromakalim (10 µM) induced membrane hyperpolarization in single myocytes and relaxation in segment preparations from WT mice, whereas glibenclamide (10 µM) caused membrane depolarization and contraction. CCh (100 µM) induced sustained suppression of IKATP in cells from both WT and M2KO mice. However, CCh had a minimal effect on IKATP in M3KO and M2/M3 double-KO cells. The Gq/11 inhibitor YM-254890 (10 μM) and PLC inhibitor U73122 (1 μM), but not the PKC inhibitor calphostin C (1 μM), markedly decreased CCh-induced suppression of IKATP in WT cells. These results indicated that KATP channels are constitutively active and contribute to the setting of resting membrane potential in mouse ileal smooth muscles. M3 receptors inhibit the activity of these channels via a Gq/11/PLC-dependent but PKC-independent pathways, thereby contributing to membrane depolarization and contraction of smooth muscles. NEW & NOTEWORTHY We systematically investigated the regulation of ATP-sensitive K+ channels by muscarinic receptors expressed on mouse ileal smooth muscles. We found that M3 receptors inhibit the activity of ATP-sensitive K+ channels via a Gq/11/PLC-dependent, but PKC-independent, pathway. This muscarinic suppression of ATP-sensitive K+ channels contributes to membrane depolarization and contraction of smooth muscles.

This paper proposes a novel adaptive sliding-mode-based control allocation scheme for accommodating simultaneous actuator faults. The proposed control scheme includes two separate control modules with virtual control part and control allocation part, respectively. As a low-level control module, the control allocation/reallocation scheme is used to distribute/redistribute virtual control signals among the available actuators under fault-free or faulty conditions, respectively. In the case of simultaneous actuator faults, the control allocation and reallocation module may fail to meet the required virtual control signal, which will degrade the overall system stability. The proposed online adaptive scheme can seamlessly adjust the control gains for the high-level sliding mode control module and reconfigure the distribution of control signals to eliminate the effect of the virtual control error and maintain the stability of the closed-loop system. In addition, with the help of the boundary layer for constructing the adaptation law, the overestimation of control gains is avoided, and the adaptation ceases once the sliding variable is within the boundary layer. A significant feature of this study is that the stability of the closed-loop system is guaranteed theoretically in the presence of simultaneous actuator faults. The effectiveness of the proposed control scheme is demonstrated by experimental results based on a modified unmanned multirotor helicopter under both single and simultaneous actuator faults conditions with comparison to a conventional sliding mode controller and a linear quadratic regulator scheme.

Based on the refined dynamic equation of stretching plates, the elastic tension–compression wave scattering and dynamic stress concentrations in the thick plate with two cutouts are studied. In view of the problem that the shear stress is automatically satisfied under the free boundary condition, the generalized stress of the first-order vanishing moment of shear stress is considered. The numerical results indicate that, as the cutout is thick, the maximum value of the dynamic stress factor obtained using the refined dynamic theory is 19% higher than that from the solution of plane stress problems of elastic dynamics.

Sliding mode control (SMC) is known as a robust control method to maintain system performance and keep it insensitive to system uncertainties. To achieve this objective, the knowledge of the uncertainty bound is usually needed, but sometimes it could be a hard task. Hence, the adaptive technology is introduced to be synthesized with SMC. In this paper, a novel adaptive SMC (ASMC) scheme is proposed to accommodate system uncertainties caused by actuator faults. An integral sliding mode controller is used as the baseline controller. When actuator faults occur, there is no need to know the exact bound of the uncertainties in control effectiveness matrix. The post-fault control effectiveness matrix can be estimated by the proposed adaptive control scheme, and the control inputs will be changed accordingly. In such a way, the robustness of the controller to actuator faults is improved. With the help of adaptive change of both continuous and discontinuous control parts, a minimum value of the discontinuous control gain can be guaranteed. In this case, the resulting control effort is reduced accordingly to avoid control chattering effect. Owing to the minimized control effort to accommodate uncertainties compared to the conventional SMC, the proposed ASMC can still maintain the system performance when severer faults occur. The effectiveness of the developed algorithm is demonstrated by the simulation results based on an unmanned quadrotor helicopter under various faulty conditions.

This paper proposes an adaptive sliding mode control allocation scheme for accommodating simultaneous actuator fault/failure. A control allocation and re-allocation scheme is synthesized to redistribute the control signals among the working actuators. In the case of the desired virtual control not being achieved, the proposed on-line adaptive scheme can seamlessly adjust the control gain to stabilize the overall system. The effectiveness of the proposed algorithm is demonstrated by the simulation results based on a modified unmanned multirotor helicopter under simultaneous actuator fault/failure conditions.

A theoretical method is developed to study the magnetoelastic coupled wave and dynamic stress intensity around a cylindrical aperture in exponential graded piezomagnetic materials. By employing the decoupling technique, the coupled magnetoelastic governing equations are decomposed. Then the analytic solutions of elastic wave fields and magnetic fields are presented by using the wave function expansion method. By satisfying the boundary conditions of the aperture, the mode coefficients, and the analytic solutions of dynamic stress intensity factors are determined. The numerical examples of the dynamic stress intensity factor near the aperture are presented. The numerical results indicate that the incident wave number, the piezomagnetic properties, and the nonhomogeneous parameter of materials highly influence the dynamic stress around the aperture.

FOXO3a belongs to a family of transcription factors characterized by a conserved forkhead box DNA-binding domain. It has been known to regulate various cellular processes including cell proliferation, apoptosis and differentiation. Post-translational modifications of FOXO3a and their roles in the regulation of FOXO3a activity have been well-documented. FOXO3a can be phosphorylated, acetylated and ubiquitinated, however, the ISGylation of FOXO3a has not been reported. Protein overexpression, ISGylation and half-life were measured to determine the post-translational modification of FOXO3a. Human fibroblast cells were treated with transforming growth factor (TGF)-β1 to determine the role of FOXO3a ISGylation in TGF-β1 signaling. FOXO3a's half-life is around 3.7 hours. Inhibition of the proteasome, not lysosome, extends its half-life. ISGylation, but not ubiquitination of FOXO3a, is increased in the presence of the proteasome inhibitor. Overexpression of ISG15 increases FOXO3a degradation, while overexpression of USP18 stabilizes FOXO3a through de-ISGylation. These results suggest that FOXO3a is degraded in the ISGylation and proteasome system, which can be reversed by USP18, an ISG15-specific deubiquitinase. This study reveals a new molecular mechanism by which ISGylation regulates FOXO3a degradation. Furthermore, we show that the overexpression of FOXO3a attenuated TGF-β1-induced fibronectin expression in human lung fibroblast cells without altering Smad2/3 expression and activation. FOXO3a can be ISGylated, which can regulate FOXO3a stability. USP18/FOXO3a pathway is a potential target for treating TGF-β1-mediated fibrotic diseases such as idiopathic pulmonary fibrosis.

Examining the 1959 film Five Golden Flowers (Wuduo jinhua), this chapter claims that eulogistic comedy propagates the principle of national unity in ethnic diversity by rallying popular passion and joy, and that a new comic aesthetic arose in Mao’s era from an understanding of the dignity of labor. The new comedy challenges the shopworn dichotomy between the official and unofficial, the ethnic and the national, the lighthearted and the serious. In the 1950s through 1960s, far from being in opposition to the official, the comic is to bridge the gap between ethnic diversity and the emergent nation-state in search of socialist identity in the international arena. Rather than defined by ethnicity and culture, film comedy encourages men and women’s equal participation in socialist labor and the fun-filled ordinary life of love and work. The socialist concept of the Chinese people offers the image of an inclusive world where different ethnic groups can live together and mingle without domination.

With the application to engineering practice, the study of the scattering of thermal waves using innovative and comprehensive methods is becoming increasingly important. The thermal wave scattering by an elliptic subsurface hole in a block with two boundaries is discussed based on the non-Fourier heat conduction equation, employing the complex function method and the conformal mapping method, and a general solution for the thermal wave scattering is given. The numerical results of temperature distributions around a subsurface hole are presented and the effects of geometrical and physical parameters on the temperature distributions were analyzed. The wave number, the shape and position of the hole, the scale of the block, and the frequency of the heat load were found to have great effects on distributions and variations of temperature. The findings of this study could be helpful in providing better understandings of infrared thermal wave imaging, the physical inverse problem, and the evaluation of internal holes in materials.

The spatial difference of hydrate dissociation by depressurization was investigated in an L-shape hydrate simulator to enhance the exploitation efficiency of natural gas hydrates. Hydrates were found to dissociate slower near the mining well than far from the mining well due to the higher water saturation. The mass transfer rate of methane molecules in the water phase was much slower than that in the gas phase. In both vertical and horizontal directions, pore water migrated from the location far from the mining well to that near the mining well in the hydrate reservoir under the pressure difference. This led to a lower dissociation rate for the hydrate distributed at the location near the mining well, which was different from the results in gas/petroleum reservoirs and numerical simulations. The spatial difference was more pronounced in the vertical direction than in the horizontal direction. Gravity caused more water migration in the vertical direction, which led to more uneven dissociation of the hydrates. Sediments with higher permeability and lower mining pressure could result in more pronounced spatial differences. These findings can provide deep insights into the spatial evolution of multiple fields during the exploitation of natural gas hydrates.

In order to improve the strength and toughness of 95CrMo steel and explore a short flow process, a direct rolling process was employed, and the effect of finishing rolling process on microstructure and mechanical properties was investigated. The results show that, with the decrease of finishing rolling temperature, inter-lamellar spacing increases, the strength as well as hardness has a general increase, and secondary cementite is distributed uniformly but represents a remarkable decrease in size. Based on Hall-Petch type equation, an effective relationship of yield strength and pearlite structure parameters was established. The correlation coefficients between the measured and calculated strength were more than 0. 95, which indicated a high reliability of the relationship. By analyzing the individual strength contributions of pearlite structures, yield strength was found to have a more great dependence on pearlite inter-lamellar spacing than colony size.

Several recent studies have suggested seemingly contrasting roles of SIRT2 in inflammation: Our previous cell culture study has indicated that SIRT2 siRNA-produced decrease in SIRT2 levels can lead to significant inhibition of lipopolysaccharides (LPS)-induced activation of BV2 microglia, suggesting that SIRT2 is required for LPS-induced microglial activation. In contrast, some studies have suggested that SIRT2 deficiency can lead to increased inflammation. In our current study, we used a mouse model of neuroinflammation to determine the roles of SIRT2 in LPS-induced inflammation. We found that administration of SIRT2 inhibitor AGK2 can significantly decrease LPS-induced increases in CD11b signals and the mRNA of TNF-α and IL-6. We further found that AGK2 can block LPS-induced nuclear translocation of NFκB. In addition, our study has shown that AGK2 can decrease not only LPS-induced increase in TUNEL signals-a marker of apoptosis-like damage, but also LPS-induced increases in the levels of active Caspase-3 and Bax. Collectively, our current in vivo study, together with our previous cell culture study, has suggested that SIRT2 is required for LPS-induced neuroinflammation and brain injury.

In order to control the growth of space debris, a novel tethered space robot (TSR) was put forward. After capture,the platform, tether, and target constituted a tethered combination system. General nonlinear dynamics of the tethered combination system in the post-capture phase was established with the consideration of the attitudes of two spacecrafts and the quadratic nonlinear elasticity of the tether. The motion law of the tethered combination in the deorbiting process with different disturbances was simulated and discussed on the premise that the platform was only controlled by a constant thrust force. It is known that the four motion freedoms of the tethered combination are coupled with each other in the deorbiting process from the simulation results. A noticeable phenomenon is that the tether longitudinal vibration does not decay to vanish even under the large tether damping with initial attitude disturbances due to the coupling effect. The approximate analytical solutions of the dynamics for a simplified model are obtained through the perturbation method. The condition of the inter resonance phenomenon is the frequency ratio λ1=2. The case study shows good accordance between the analytical solutions and numerical results, indicating the effectiveness and correctness of approximate analytical solutions.

Two kinds of steels (YP960 and YP690) with low carbon bainite structure were designed, and their flow stress and strain hardening exponents were studied. The results showed that, when Hollomon relation was applied to describe the flow stress, there were significant errors between the experimental and calculated points in specimens tempered below 400 °C, while a high precision was observed in samples tempered above 400 °C. Whereas, the modified Voce relation could effectively predict the flow stress as well as the strain hardening exponent at different tempering temperatures, which was verified by unbiased estimators such as maximum relative error (MRXE) and average absolute relative error (AARE). Besides, the modified Voce relation was also applied to estimate the maximum uniform strain, and the correlation coefficients (R) between the experimental data and calculated maximum uniform strain were more than 0.91. The high correlation coefficients indicated that the modified Voce relation could effectively predict the uniform deformation ability of high strength steels with low carbon bainite structure at different tempering temperatures.

Methane hydrate exploitation via depressurization for a reservoir with a bottom gas-rich zone was simulated using a large-sized three-dimensional hydrate simulator. A single vertical well system and a system with a combination of vertical and horizontal wells were employed to elucidate the different effects of horizontal and vertical wells on the exploitation process. The results showed that effect of promoting gas production using a horizontal well is not obvious for a high permeability reservoir. A large exploitation temperature drop may lead to ice blockage in the pipelines, and fracturing technology was introduced to solve this blockage problem. Experiments performed above and below the freezing point inferred that the decomposition of the hydrate in different areas of the reactor was not simultaneous, according to analysis of the temperature distribution of the entire reactor during the exploitation process. For exploitation above the freezing point, temperatures in the bottom of the reactor tend to maintain a low level and work against hydrate decomposition. However, for exploitation below the freezing point, the low-temperature area in the bottom of the reactor preferentially converts to ice. Heat release and salt precipitation promoted hydrate decomposition, and the decomposition rate was significantly accelerated.

This paper proposes an active fault-tolerant control strategy for a quadrotor helicopter against actuator faults and model uncertainties while explicitly considering fault estimation errors based on adaptive sliding mode control and recurrent neural networks. Firstly, a novel adaptive sliding mode control is proposed. In virtue of the proposed adaptive schemes, the system tracking performance can be guaranteed in the presence of model uncertainties without stimulating control chattering. Then, due to the fact that model-based fault estimation schemes may fail to correctly estimate fault magnitudes in the presence of model uncertainties, a fault estimation scheme is proposed by designing a parallel bank of recurrent neural networks. With the trained networks, the severity of actuator faults can be precisely estimated. Finally, by synthesizing the proposed fault estimation scheme with the developed adaptive sliding mode control, an active fault-tolerant control mechanism is established. Moreover, the issue of actuator fault estimation error is explicitly considered and compensated by the proposed adaptive sliding mode control. The effectiveness of the proposed active fault-tolerant control strategy is validated through real experiments based on a quadrotor helicopter subject to actuator faults and model uncertainties. Its advantages are demonstrated in comparison with a model-based fault estimator and a conventional adaptive sliding mode control.

This paper presents a dual adaptive fault-tolerant control strategy for a quadrotor helicopter based on adaptive sliding mode control and adaptive boundary layer. Within the proposed adaptive control strategy, both model uncertainties and actuator faults can be compensated without the knowledge of the uncertainty bounds and fault information. By virtue of the proposed adaptive control scheme, the minimum discontinuous control gain is adopted, which significantly reduces the control chattering effect. As compared to the existing adaptive sliding mode control schemes in the literature, larger actuator faults can be tolerated by employing the proposed control scheme while suppressing control chattering. Moreover, boundary layer is used to smoothen control discontinuity and further eliminate control chattering. Nevertheless, the choice of boundary layer thickness is a trade-off between system stability and tracking accuracy. By explicitly considering this fact, an adaptive boundary layer is developed and synthesized with the proposed adaptive control framework to ensure stability and tracking accuracy of the considered system. When the control parameter tends to be overestimated, the thickness of boundary layer can be appropriately adjusted to avoid control parameter overestimation. Simulation and experimental tests of a quadrotor helicopter are both conducted to validate the effectiveness of the proposed control scheme. Its advantages are demonstrated in comparison with a conventional adaptive sliding mode control scheme.

To improve the stratum mechanical properties and prevent the geological disaster, we present a new approach by executing CH4 hydrate exploitation and CO2 sequestration below the freezing point of water to maintain the stratum stiffness during and after hydrate exploitation. An experimental method to clearly show the evolution of the stratum mechanical properties was built and a series of experiments were conducted to simulate the CH4 exploitation and CO2 sequestration process below and above the freezing point of water. The stratum stiffness was found to be maintained during the whole hydrate exploitation process when below the freezing point. Moreover, the presence of ice improves the stratum stiffness due to cementing the sandy grain. The CO2 injection into the hydrate-bearing sediments would further enhance the mechanical properties and realize a CO2 geological sequestration. Compared with hydrate exploitation above the freezing point, the CH4 recovery efficiency is a little lower when under below the freezing point and it decreased with the increased hydrate saturation due to the CH4 hydrate being surrounded by the generation of ice from hydrate dissociation. This phenomenon could be modified by injecting CO2, from which the CH4 recovery efficiency obviously improved for hydrate exploitation below the freezing point.

A sliding mode terminal guidance strategy is developed for an unpowered reusable launch vehicle (RLV) during the terminal area energy management (TAEM) phase. The main idea is to use the finite-time reaching phase of the sliding mode method to solve the three-dimensional (3D) guidance problem with multiple flight constraints. Firstly, the mathematical model of a RLV in the altitude domain is provided, based on which a new sliding surface is constructed to account for multiple constraints on terminal conditions and dynamic pressure profile. Subsequently, a second-order sliding mode guidance law is constructed to ensure the reaching of the sliding surface at a specific altitude. Finally, the effectiveness of the proposed guidance strategy in both nominal case and the case of bank limitations is illustrated by the numerical simulations.

A sliding mode guidance strategy is developed for an unpowered reusable launch vehicle (RLV) during the terminal area energy management (TAEM) phase. The 3-DOF guidance model of a RLV in the domain of altitude is firstly provided, based on which a new sliding surface is constructed to account for multiple constraints on terminal conditions and dynamic pressure profile during flight. A second-order sliding mode guidance law is then developed to ensure the reaching of the sliding surface at a specific altitude. The simulation results confirm the effectiveness of the proposed method.

In order to investigate the effects of SKF96365 (SKF), which is a non-selective cationic channel blocker, on K(+) channel currents, we recorded currents through ATP sensitive K(+) (IKATP), voltage-gated K(+) (IKv) and Ca(2+) activated K(+) channels (IBK) in the absence and presence of SKF in single small intestinal myocytes of mice with patch-clamp techniques. SKF (10 µM) reversibly abolished IKATP that was induced by cromakalim (10 µM), which is a selective ATP sensitive K(+) channel opener. These inhibitory effects were induced in a concentration-dependent and voltage-independent manner. The 50% inhibitory concentration (IC50) was 0.85 µM, which was obviously lower than that reported for the muscarinic cationic current. In addition, SKF (1 µM ≈ the IC50 value in IKATP suppression) reversibly inhibited the IKv that was induced by repetitive depolarizing pulses from -80 to 20 mV. However, the extent of the inhibitory effects was only ~30%. In contrast, SKF (1 µM) had no significant effects on spontaneous transient IBK and caffeine-induced IBK. These results indicated that SKF inhibited ATP sensitive K(+) channels and voltage-gated K(+) channels, with the ATP sensitive K(+) channels being more sensitive than the voltage-gated K(+) channels. These inhibitory effects on K(+) channels should be considered when SKF is used as a cationic channel blocker.

In order to promote the tolerance and controllability of the multi-degree-of-freedom (M-DOF) ultrasonic motor, a novel two-degree-of-freedom (2-DOF) spherical ultrasonic motor using three traveling-wave type annular stators was put forward. Firstly, the structure and working principle of this motor were introduced, especially a spiral spring as the preload applied component was designed for adaptive adjustment. Then, the friction drive model of 2-DOF spherical motor was built up from spatial geometric relation between three annular stators and the spherical rotor which was used to analyze the mechanical characteristics of the motor. The optimal control strategy for minimum norm solution of three stators’ angular velocity was proposed, using Moore-Penrose generalized inverse matrix. Finally, a 2-DOF prototype was fabricated and tested, which ran stably and controllably. The maximum no-load velocity and stall torque are 92 r/min and 90 mN·m, respectively. The 2-DOF spherical ultrasonic motor has compact structure, easy assembly, good performance and stable operation.

It has been a routine practice to draw a clear line between two parts of historical discourse. The history of historians is taken to be archival and narrative labor seeking to discover new data and to register an objective concatenation of occurrences in the past. The other part is theoretical labor, which expounds the principles and models for explaining historical change. Some historians complain that all too often in modern Chinese historiography theoretical labor has tended to get the upper hand of empirical work. Yu Ying-shih remarks that Chinese historians in the Mainland have often gone too far in pursuing theoretical models in historical inquiry, privileging a Hegelian or Marxist style of abstract discourse at the cost of objectivity. 1 Susanne Weigelin-Schwiedrzik uses the familiar distinction of lun and shi to define two parts of history writing in socialist China. While in premodern China the discussion of the dao, or principles that inform change, never ceased to animate the literati, in the twentieth century Chinese historians have embarked on theoretical pursuits with greater urgency. 2 Wang Hui gives credit to this pursuit with the observation that the development of modern Chinese historiography lies not in the accumulation of knowledge about the past, but rather in the constantly renewed efforts to explain historical changes and reformulate historical outlooks. 3

Sliding mode control is known as a robust control approach to maintain system performance and keep it insensitive to disturbances. This paper proposes an integral sliding mode based adaptive robust control for a quadrotor helicopter with parametric uncertainties and disturbances. With the help of the synthesized on-line adaptive scheme, the uncertain parameters can be accurately estimated without the knowledge of the uncertainty bounds. In this case, there is no need to increase the discontinuous control gain, which may stimulate control chattering effect, to maintain the robustness of the controller. The effectiveness of the proposed control strategy is validated through a simulation of the payload transportation application. Compared to the commonly used linear quadratic regulator (LQR) approach, the proposed adaptive robust control strategy can maintain the tracking performance during the whole flight phase.

This paper proposes an adaptive robust tracking control strategy for a quadrotor helicopter with parametric uncertainties and external disturbances based on sliding mode control. The inner loop of the control strategy is concerned about the attitude and altitude control of the quadrotor helicopter, while the outer loop is employed to track the desired horizontal positions. By assuming knowledge of the bounds on external disturbances, an integral sliding mode control is designed to maintain system performance and keep it insensitive to disturbances. For parametric uncertainties (e.g., total mass and moments of inertia) of the quadrotor helicopter, an on-line adaptive scheme is proposed and incorporated into the nominal sliding mode control to deal with it. With this adaptive scheme, there is no need to know the parametric uncertainty bounds. A guaranteed transient and steady-state tracking performance can be obtained with the adaptive robust sliding mode controller. The effectiveness of the proposed control strategy is validated through a simulation on a quadrotor helicopter subject to parametric uncertainties and external disturbances.

This paper proposes a fuzzy adaptive sliding mode control for accommodating large actuator fault and maintaining system stability. Boundary layer is employed to smooth control discontinuity and eliminate control chattering. However, if the thickness of boundary layer is chosen too big, the tracking accuracy will be degraded. Whereas, if the boundary layer thickness is too small, control chattering will be stimulated and system stability will also be affected. With this consideration, a fuzzy logic based boundary layer is designed together with the proposed adaptive control scheme to maintain system stability. The on-line adaptive control scheme can seamlessly change control gains to make a compensation in the presence of actuator fault. When there is a trend to overestimate the control gain, the fuzzy boundary layer will be triggered to enlarge boundary layer thickness to ensure system stability. In such a way, larger actuator fault can be accommodated within the proposed control scheme. The effectiveness of the proposed control strategy is validated through a simulation based on a quadrotor helicopter under two different fault scenarios.

Motion trajectory is the fundamental basis for the design and research of parachute. The fall state, the minimum safe altitude and airborne site are closely associated with the motion trajectory. Particularly due to rapid changes in these parameters such as canopy shape, velocity, dynamic load of the parachute, it is very difficult to determine the motion trajectory of parachute inflation process. Currently, the trajectory is mainly obtained by airdrop tests or wind tunnel tests. The tests are very expensive. Based on the force analysis and mathematical model of a certain type of parachute, we used the computer system to study the motion trajectory of parachute.

During his tenure in the Lu Xun Academy in Yan'an, the center of the Chinese Revolution, the novelist Zhou Libo ran a seminar on world literature. While teaching masterpieces of European novelists, Zhou developed a theory of the novel that inherited themes of liberal humanism and appropriated them for a burgeoning revolutionary culture. In his teaching notes, Zhou upholds the people as the transformative engine for social progress: they are authors of their own culture, the political subjects of popular democracy, and in solidarity with the working classes of the world. This essay considers Zhou's fiction theory as a part of the transition from the old democratic revolution led by the Chinese bourgeoisie to the new democratic cultural initiative carried out by the enlightened intelligentsia and progressive working people.