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The omni-directional mobile manipulator robot (OMMR) is a class of a new robot with activating operating capability, which is composed of one or more manipulators mounted on a mobile platform. However, after the manipulator is installed on the mobile platform, the coupling effect between the manipulator and the mobile platform will significantly increase the complexity of the dynamic behavior of the whole system, involving the dynamic interaction between the ground and the mobile platform, the mobile platform and the manipulator, the manipulator and the operating environment, which brings great difficulties to the modeling of the system. Based on establishing the kinematics and statics models of OMMR, this study presents a simplified modeling approach of OMMR system dynamics. Based on this dynamic model, the vehicle-manipulator interaction model is established, and its interaction is analyzed. Simulation and experiments verify the correctness of the vehicle-manipulator interaction model, indirectly prove the rationality and effectiveness of the proposed OMMR system dynamics modeling approach, and provide model data for motion planning and control of robots.

A simplified three-dimensional brake model with crater structure is established by using the finite element software Abaqus, and the influence of the depth, diameters, degrees and types of craters on the temperature and stress of the brake disc is investigated by combining the thermal coupling theory and the orthogonal test method. On this basis, the temperature and stress fields of brake discs with different non-smooth surface forms are analyzed, and the influence of temperature with radius on non-smooth discs with different braking initial speeds and pressures during emergency braking is investigated under the optimal combination. The results show that the square pit brake disc with the pit depth of 5 mm, the diameter of 8 mm and the 20° interval between adjacent pits in the circumferential direction has the smallest temperature and stress by the orthogonal test method, which is the optimal combination. Among them, the square pit brake disc has the best heat dissipation performance. With the increase of the initial speed and pressure of braking, the temperature of this brake disc surface gradually increases, the highest temperatures of the brake disc all appeares in the brake disc radius of 136 mm.

Using the theory related to thermal coupling and heat transfer, the finite element software Abaqus is used to establish an orthogonal anisotropic C/SiC model of an automotive ventilated brake disc. Based on this model, different braking initial velocities, different braking pressures and different longitudinal expansion coefficients of the brake disc during emergency braking are simulated and analyzed. The results show that the temperature profile of the nodal unit of the brake disc exhibited "sawtooth" fluctuations under the effect of thermal coupling, and the thermal stresses mainly appeared in the middle region of the friction contact. The higher the braking pressure and initial speed during emergency braking are, the higher the temperature rise of the disc surface will be. However, the effect of different disc expansion coefficients on the maximum disc temperature is not significant.

The cable-driven parallel robot is a special flexible mechanism in parallel mechanism, the end-effector of which is driven by cables instead of rigid rods. It integrates the advantages of flexible robots and parallel robots. A three-degree-of-freedom (3-DOF) under-constrained parallel robot with variable cable mast heights is investigated in this study. The inverse kinematics model of the robot is established by using the vector closed-loop principle. The forward kinematics model of the robot is derived according to cable lengths. The dynamics model of the robot is established based on the Lagrange formula. The static equilibrium workspace (SEW) of the robot is studied using the Monte-Carlo method. Given the motion trajectory of the end-effector, the expected three cable lengths are obtained through the inverse kinematics model of the robot. Taking the expected three cable lengths as the experimental input, the experimental curves of cable lengths and cable tensions as well as the forward kinematics trajectory of the robot are obtained. The experimental results validate the correctness of the forward and inverse kinematics models and the dynamics model of the robot, as well as the effectiveness of the SEW.

Calcareous sand is widely observed in the foundation of off-shore infrastructure. Although a lot of research has been carried out on the mechanical properties of calcareous sand, study into the influence of the stress–strain path on the mechanical behaviour of calcareous sand is very limited. In this study, a series of triaxial tests were performed on calcareous sand under three different stress paths. The particle morphology of calcareous sand before and after the tests, the stress–strain relationship under different stress paths, and the characteristics of shear strength and deformation were investigated. The results show that the consolidation pressure and stress path have significant effects on the volume strain, strength, and particle breakage of calcareous sand. In addition, the underlying mechanisms of the different behaviours of calcareous sand observed in this study were discussed.

In the operation of civil aircraft at plateau airport, the climbing gradient is required to be high, and the load loss is serious.Therefore, it is of great significance to optimize the takeoff performance and increase the takeoff weight in terms of economic benefits.In this paper, based on theoretical analysis, the takeoff performance is optimized under the premise of meeting the airworthiness requirements by reducing the flap deflection or using the improved climb method, and the takeoff distances, acceleration stop distances, and takeoff weights of different flap configurations and different climb methods are calculated and analyzed.The results show that the effective optimization can significantly improve the takeoff weight and performance, also yield good economic returns.

The cable-driven parallel robot is a special type of parallel robots whose end-effector is driven by cables instead of rigid rods. A three-degree-of-freedom (3-DOF) under-constrained parallel robot with variable cable mast angle is studied. The inverse kinematics model of the robot is established by using the vector closed-loop principle. According to the Lagrange equation, the dynamics model of the robot is established. Based on the robot PD control theory of model compensation, a PD controller of the robot is designed. Given a motion trajectory of the end-effector of the robot, the pose change of the end-effector is transformed into cable length change through the inverse kinematics of the robot. The cable length is used as the input of the control system. The experimental results verify the correctness of the inverse kinematics and dynamics model of the robot and the effectiveness of the control method.

As the voltage level is relatively low under medium and low voltage distribution network,the number of modular multilevel converter (MMC) sub-modules is also small. Therefore,the modulation mode of MMC with small quantities of sub-modules has an important influence on the performance of the MMC system. In order to improve the output quality and output capability of the MMC with small quantities of sub-modules,a hybrid modulation strategy suitable for MMC with small quantities of sub-modules based on level step switching at a high modulation degree is proposed. On the basis of the nearest level modulation (NLM),the MMC is controlled to switch between NLM and the carrier phase shift pulse width modulation (CPS-PWM) at the output level step point in real time. At the same time,the circulation control and the sub-module voltage equalization control are combined to further ensure the normal operation of MMC with small quantities of sub-modules under the hybrid modulation. Then,the simulation model of MMC hybrid modulation with four sub-modules is established,and a simulation study is carried out on the MMC hybrid modulation strategy of the MMC with small quantities of sub-modules. The results show that the proposed hybrid modulation strategy not only takes into account the characteristics of low output harmonics and low switching loss,but also improves its output quality. And its operation in high-profile system increases the DC voltage utilization rate and improves the output capacity of the MMC with small quantities of sub-modules.

In order to solve the stability problem of large section top coal roadway in No.4 coal seam of Longquan Coal Mine, taking the return airway of 4203 working face of Longquan Coal Mine as the research object, the roadway stability is studied by the combination of theoretical analysis, numerical simulation and field measurement. Firstly, the mechanical analysis model of roadway rock stability is established, the calculation formula of top coal crushing position is deduced, and the main factors affecting top coal failure are determined. Secondly, UDEC-Trigon model is used to analyze the stress, plastic zone and surrounding rock displacement of roadway under different top coal thickness. The results show that the shear failure of roadway roof is related to the internal friction angle of rock and the friction angle between rock blocks(surfaces), and the failure position is at the shoulder angle of two sides of roadway. By comparing the supporting effects of supporting schemes under different top coal thickness, the comprehensive control technology of surrounding rock for timely supporting roadways with high pre-stress and high strength bolt and cable in return airway of 4203 working face was proposed. The optimized support scheme was applied in the field, and the measured maximum deformation of roof and floor was 104 mm, and the maximum deformation of two sides was 86 mm, and the implementation effect was significantly improved.

In the new energy power generation system,the inverter is connected to the grid in parallel,which expands the grid capacity. In addition,due to the existence of grid impedance,the stability of the inverter is reduced and the difficulty of power quality governance in the load increases. The problem of power quality governance of parallel inverter in weak current network is studied. Firstly,H repetitive control combined with voltage feedforward is used as the current inner loop control strategy and the stability performance of single and multiple parallel inverters in weak current network is analyzed. The composite strategy of feedforward channel series complex filter and forward channel series lead correction link is adopted to improve the stability of inverter. Secondly,the current detection algorithm is used to separate the unbalanced,harmonic and reactive currents in the load,which solves the governance of power quality problems caused by unbalanced,nonlinear and reactive loadd. Finally,the simulation experiment is carried out in Simulink. The simulation results show that the power quality problems of multiple loads under the condition of weak power grid can be solved by parallel inverter.

Shale oil is mainly extracted by fracturing. However, it is difficult to determine the optimum construction parameters to obtain maximum productivity. In this paper, a fuzzy comprehensive production evaluation model for fractured shale oil horizontal wells based on random forest algorithm and coordinated principal component analysis is proposed. The fracturing parameters of the target wells are optimized by combining this model with an orthogonal experimental design. The random forest algorithm was used to calculate the importance of data sample factors. The main controlling factors of the production of fractured horizontal wells in shale oil were obtained. To reduce the noise of the sample data, principal component analysis was used to reduce the dimensions of the main control factors. Furthermore, the random forest algorithm was used to determine the weight of the principal components after reducing the dimensionality. The membership function of the main control factors after reducing dimensionality was established by combining the fuzzy statistics and assignment methods. In addition, the membership matrix of the effect prediction of fractured horizontal wells in shale oil was determined. The fuzzy comprehensive evaluation method is used to score and evaluate the effect of fractured horizontal wells. Combined with the orthogonal experimental design method, the optimized parameter design of a fractured horizontal well considering the comprehensive action of multiple parameters is realized. After construction according to the optimized parameters, production following fracturing increases significantly. This verifies the rationality of the optimization method that is proposed in this paper.

Abstract Background Ventilator-induced lung injury (VILI) is a common complication in the treatment of respiratory diseases with high morbidity and mortality. ETS-domain containing protein (Elk1) and Matrix metalloproteinase (MMP) 9 are involved in VILI, but the roles have not been fully elucidated. This study examined the mechanisms of the activation of MMP-9 and Elk1 regulating barrier function in VILI in vitro and in vivo. Methods For the in vitro study, Mouse lung epithelial cells (MLE-12) were pre-treated with Elk1 siRNA or MMP-9 siRNA for 48 h prior to cyclic stretch at 20% for 4 h. For the in vivo study, C57BL/6 mice were pre-treated with Elk1 siRNA or MMP-9 siRNA for 72 h prior to 4 h of mechanical ventilation. The expressions of Elk1, MMP-9, Tissue inhibitor of metalloproteinase 1 (TIMP-1), E-cadherin, and occludin were measured by Western blotting. The intracellular distribution of E-cadherin and occludin was shown by immunofluorescence. The degree of pulmonary edema and lung injury were evaluated by Hematoxylin–eosin (HE) staining, lung injury scores, Wet/Dry (W/D) weight ratio, total cell counts, and Evans blue dye. Results 20% cyclic stretch and high tidal volume increases the expressions of Elk1, MMP-9, and TIMP-1, increases the ratio of MMP-9/TIMP-1, decreases the E-cadherin and occludin level. Elk1 siRNA or MMP-9 siRNA reverses the degradations of E-cadherin, occludin, and the ratio of MMP-9/TIMP-1 caused by cyclic stretch. Elk1 siRNA decreases the MMP-9 level with or not 20% cyclic stretch and high tidal volume. Conclusions The results demonstrate mechanical stretch damages the tight junctions and aggravates the permeability in VILI, Elk1 plays an important role in affecting the tight junctions and permeability by regulating the balance of MMP-9 and TIMP-1, thus indicating the therapeutic potential of Elk1 to treat VILI.

The knowledge of Technological Pedagogical Content Knowledge (TPACK) is a new definition of the knowledge structure of higher vocational college teachers in the era of information society. This study investigated the prominent problems in TPACK training of teachers in higher vocational college of arts in our city by sampling. Firstly, in the professional training of provincial or municipal teachers, emphasis was placed on “theory or method propaganda” rather than “guidance of technology integration training”; Secondly, focus on “discipline knowledge”, “teaching knowledge” and “technical knowledge” of a single module of training, but lack of “integration and deep integration of the three”; In view of the above problems, it is suggested that educational administrative departments or universities should pay attention to the training of “subject teaching with technology integration” in the professional training of teachers, and pay attention to the deep integration of “Content knowledge”, “Pedagogical knowledge” and “ Technological knowledge” in the training process. In order to effectively improve the TPACK knowledge structure of the teachers in higher vocational college of arts, promote the high-quality development of vocational education in our city.

Aiming at vehicles will produce shocks and vibrations for various reasons in the process of transportation and handling, any shock and vibration that exceeds the regulations would cause damage to the nuclear fuel being transported. In order to monitor and analyze the shock and vibration data scientifically, a monitoring system based on MEMS acceleration sensor technology is developed to measure shocks and vibrations. The measured result involves some noise caused by the sensitivity of the sensor and the electrical noise, and a digital filter mathematical modelling is introduced to reduce noise and improve the measured result accuracy. In order to verify the effectiveness of the device designed in this paper, the device and the high-precision seismic acceleration sensor AC73 are, respectively, used for field tests; the results show that the test precision of the designed device can meet the requirements, and also, the designed shock and vibration monitoring system can record and store the three-axis acceleration, temperature, humidity, pressure, time, and other parameters that exceed the set threshold during nuclear fuel transportation in real time and complete the fuel assembly transportation status assessment and promptly remind the transportation personnel to take safety precautions and treatment measures. Therefore, it can be widely used in the monitoring, recording, and postevent data analysis of the transportation process of important products such as nuclear fuel.

Lithium-rich manganese-based materials have attracted much attention because of their high charge-discharge capacity. In order to solve the problems of low coulombic efficiency, poor cycling performance and poor rate capability, lithium-ion conductor Li2ZrO3 with three-dimensional Li+ channel was employed to coat lithium-rich manganese-based cathode material Li[Li0.2Ni0.2Mn0.6]O2. According to the structure and morphological analysis, different amounts of Li2ZrO3 were successfully coated on the surface of the sample. When the thickness of the coating layer is 3 nm (1% coating amount, mass fraction), the electrochemical performance of the composite material is significantly improved. The first discharge specific capacity is 271.5 mAh·g-1 and the first coulombic efficiency is 72.4%. The first irreversible capacity loss is obviously reduced. The discharge specific capacity at 0.5 C is 191.5 mAh·g-1 and the capacity retention is 89.5%. The specific capacity at 5 C is 75 mAh·g-1 and the rate performance is improved. The results show that a uniform thickness of Li2ZrO3 coating layer can form a core-shell structure on the surface of the sample to make the sample more stable. It can reduce surface side reactions and prevent the formation of thicker SEI films. All of these results benefit from the high conductivity, high electrochemical stability and good lithium ion conductivity of Li2ZrO3 coating layer.

Lithium-rich manganese-based materials have attracted much attention because of their high charge-discharge capacity. In order to solve the problems of low coulombic efficiency, poor cycling performance and poor rate capability, lithium-ion conductor Li2ZrO3 with three-dimensional Li+ channel was employed to coat lithium-rich manganese-based cathode material Li[Li0.2Ni0.2Mn0.6]O2. According to the structure and morphological analysis, different amounts of Li2ZrO3 were successfully coated on the surface of the sample. When the thickness of the coating layer is 3 nm (1% coating amount, mass fraction), the electrochemical performance of the composite material is significantly improved. The first discharge specific capacity is 271.5 mAh·g-1 and the first coulombic efficiency is 72.4%. The first irreversible capacity loss is obviously reduced. The discharge specific capacity at 0.5 C is 191.5 mAh·g-1 and the capacity retention is 89.5%. The specific capacity at 5 C is 75 mAh·g-1 and the rate performance is improved. The results show that a uniform thickness of Li2ZrO3 coating layer can form a core-shell structure on the surface of the sample to make the sample more stable. It can reduce surface side reactions and prevent the formation of thicker SEI films. All of these results benefit from the high conductivity, high electrochemical stability and good lithium ion conductivity of Li2ZrO3 coating layer.

Soil’s water-physical properties support essential soil water retention functions for driving water distribution and availability, which is vital for plant growth and biogeochemical cycling. However, the question concerning how tree compositions and their interactions with other abiotic factors modulate soil’s water-physical properties in disturbed forests remains poorly understood. Based on observational data from nine permanent forest sites (18,747 trees and 210 plots) in the northeast of China, where forests once undergone three different levels of anthropogenic logging disturbance, we evaluated how multiple biotic (i.e., tree diversity and functional trait composition) and abiotic (soil texture and soil organic carbon) factors influence water-physical properties (i.e., in terms of soil capillary water retention (WC) and soil saturated water retention (WS)) in temperate forests. We found that the impacts of logging disturbance on soil water-physical properties were associated with improved tree diversity, acquisitive functional traits, and SOC. These associated attributes were also positively related to WC and WS, while there was no significant effect from soil texture. Moreover, disturbance indirectly affected soil water-physical properties mainly by functional traits and SOC, as acquisitive functional traits significantly mediate the effect from disturbance on WC and SOC mediates the influence from disturbance on WS. Finally, our results emphasize the potential relationships of tree composition with SOC and soil water retention as compared with soil texture and hence suggest that plants can actively modulate their abiotic contexts after disturbance, which is meaningful for understanding forest health and resistance.

A better elucidation of molecular mechanisms underlying drug-membrane interaction is of great importance for drug research and development. To date, different biochemical and biophysical methods have been developed to study biological membranes at molecular level. This review focuses on the recent applications and achievements of modern analytical techniques in the study of drug interactions with lipid membranes, including chromatography, spectrometry, calorimetry, and acoustic sensing. The merits and limitations of these techniques were compared and critically discussed. Moreover, various types of biomimetic model membranes including liposomes, lipid monolayers, and supported lipid monolayers/bilayers were described. General mechanisms underlying drug-membrane interaction process were also briefly introduced.

Let p3(n) denote the number of 3-component multipartitions of n. Recently, using a 3-dissection formula for the generating function of p3(n), Baruah and Ojah proved that for n ≥ 0, p3(9n + 5) ≡ 0 (mod 33) and p3 (9n + 8) ≡ 0 (mod 34). In this paper, we prove several congruences modulo powers of 3 for p3(n) by using some theta function identities. For example, we prove that for n ≥ 0, p3 (243n + 233) ≡ p3 (729n + 638) ≡ 0 (mod 310).

Chain drive relying on the sprocket teeth meshing with the chain link to transmit motion and power,it is one of the most important transmission mode in the modern machinery manufacturing industry,and the application of roller chain is most.As the chain drive is a disturbing movement,its assembly relationships and movement characteristic are complex.By using Creo 2.0software and taking single row roller chain as example,the a single chain link modeling,assembly are carried out.Through the guide curve,all the chain links are imported for assembly,and its motion simulation is carried out,a reference for the design of modern mechanical chain drive parametric modeling and motion simulation is provided.