Advanced Mechanical Science and Technology for the Industrial Revolution 4.0

A novel ankle rehabilitation robotRehabilitation robot and its mechanism composition, were proposed. The 3D modeling of the proposed ankle rehabilitationAnkle Rehabilitation robot and the 3D modeling of the complete human body were established. The integration of the two 3D models was further proceeded by importing the robot models into the AnyBody simulation software. A driving function was also designed on the basis of the sine function; the inverse kinematic analysis and muscle force analysis of the integrated model are carried out. The driving function design was executed to determine the relationships of the movement of the angles for the proposed ankle rehabilitation robot with the activity and passive traction of the muscles. A rehabilitation strategy was also developed according to different motion amplitudes, velocity, and different external environments in dorsal flexion motion. This research would provide a reference for further design of the structure and control of rehabilitation robots.

In this study, a two wheeled guard robot (TWGR) system with visual ability is realized. The hardware of the TWGR includes a chassis carrying dc motors for wheels, the input/output (I/O) board connects the TWGR system to a personal computer (PC) and Personal Digital Assistant (PDA), driver circuits for the motors, the necessary sensors and filter circuit needed to measure system states. Moreover, camera system and image transmission module are also connected to the chassis. Moreover, based on Internet of Things (IoT)Internet of Things technology, all system state and real-time image from the visual system can be transmitted to the cloud server through the Internet. Administrator is able to access the cloud server to monitor each TWGR immediately. Finally, TWGRs can be controlled remotely to deal with any emergency situationSystem integration.

The purpose of this study is to complete the design, production and implementation of the machine animal of bionic bird. Objectives of this paper was on design and manufacture of small-scale flight mechanism with a pair of wings. The implementation of mechanical structure, system integrationSystem integration of the bionic robot bird platform and the design of controller has completed. It has flight, remote control, attitude feedback ability. The point of this paper, is to construct the image transmission system and integrates with the bionic robot bird platform. Based on the system platform we established above, adding the camera lens, image transmission and other modules to the fuselage. And the interface of the original system is integrated and compatible. Dynamic sensors are used to measure flight information of the bionic robot bird. Moreover, according to image transmission unit, the bionic robot bird has the ability of aerial photography. Finally, the remote images from the flying robot bird are provided to other platform by using the network of the ground control center, in purpose to integrate the function of theUnmanned aerial vehicle Internet of Things (IoT) Internet of Things.

This research has two main parts that are the use of different sensors to make quadcopterQuadcopter as a detective aircraft and the use of C++ and MATLAB on quadcopter software simulation. In order to maintain altitude holding in hostile environment, air pressure altimeter and optical flow are utilized. Ultrasonic sensors are used in autonomous obstacle avoidanceObstacle avoidance. In addition, Pixy (CMUcam5) camera is used to do image processing and image trackingImage tracking. The data caught by ultrasonic sensor and Pixy camera are processed in Arduino board. In software simulation, we use C++ programming to achieve Gyroplane pitch and roll angles of the rule table, combine images of feedback data tracking, and balance flight movement independently through their rules tables. MATLAB software simulations for PID and fuzzy control of a flying robot to meet independent verification tracking needs are given.

Service robots have already acquired the skills to execute explicit tasks. But service robots cannot deal with the situations where ambiguities exist. When the robot encounters ambiguities such as multiple objects belonging to a same category in the surrounding environment meeting needs of the user, the robot should provide options for the user to choose by communication. In order to address this problem, we fuse verbal languageVerbal language command and pointing gesturePointing gesture information to enable a robot to execute a vague task, such as “Give me the book”. In our work, we propose a progressive approach that allows robots to analyze the meaning of task assigned by the user and acquire direction information from human gestures. The conducted experiments show that a humanoid robot NAO can execute vague task by applying the proposed approach.

Aiming at extracting the finger vein patterns in low-quality vein images, a finger vein image pattern extraction algorithm based on Hessian matrix was proposed. Firstly, Hessian matrix was acquired by the convolution of all the second derivative of Gaussian filter and finger vein image. Subsequently, the Hessian matrix eigenvalues of each pixel were calculated and the pixels not belonging to finger vein region according to the requirement of the eigenvalues were filtered. Finally, the maximum of the eigenvalues at each pixel under different scales was chosen as the output, and a finger vein image was segmented effectively after image binarization and morphological filtering. The branching points of the refined finger vein pattern were found as the feature points. The results indicated that the algorithm performs well in separating the vein region from the non-vein region and in extracting the feature points.

With the increasing applications of robots in complex environment, the dynamic behaviors of the unknown environment are the major factors which affect the robot system’s performance. In robot community, one of the most efficient methods is reasonably modeling the environment to achieve robot force control or safety. Meanwhile, an efficient online parameters estimation method is required in the robot system. Since the parameters of the analytical models are simple and easy to use mathematical formula to describe, a review and comparison of the online identification methods are presented in this paper, according to the linear and nonlinear model type of the analytical models. Moreover, we summarized their application fields and their advantages and disadvantages, and then made a conclusion and the future scopeRobotic system.

A general stiffness modeling methodology for tripod parallel kinematic machines (PKMs)Parallel kinematic machine with prismatic actuators is proposed in this paper. With the technique of substructure synthesis, the whole system of a tripod is divided into a platform, a base and three kinematic limb substructures. Each limb assemblage is modeled as a spatial beam constrained by two sets of six degree-of-freedom (6-DOF) virtual lumped springs with equivalent stiffness at their geometric centers. The equilibrium equation of each individual limb assemblage is derived through finite element formulation, while that of the platform is derived with the Newton’s 2nd law. The governing stiffness matrix is synthesized by introducing the deformation compatibility conditions between the platform and the limbs. By extracting a 6x6 block matrix from the inversion of the governing compliance matrix, a stiffness matrix of the platform is formulated. Taking the Sprint Z3 Head and the A3 Head as examples, the distributions of stiffness values of these two types of PKM modules are predicted and discussed. It is worth mentioning that the proposed methodology of stiffness modeling can further be applied to other types of PKMs for evaluating the global rigidity performance over entire workplace efficiently with minor revisions.

Magnetic memory detection technology was applied to detect the fillet weld of boiler tube. Through the summary and analysis of the magnetic field intensity and the graphical distribution for each fillet weld of boiler tube, we could find out the more serious stress concentration problem of nozzle fillet weld, which provides the basis for the inspection of fillet weld of boiler tube.

During the decades, the application of fringe projection techniques for rebuilding the three-dimensional(3D) surface has become more useful. The fringe projection techniques can measures the 3D surface as small as MEMS components, and as large as large panel (2.5 m × 0.45 m). The technique can also be applied in versatile fields, such as 3D intra-oral dental measurements [1], non-invasive 3D imaging and monitoring of vascular wall deformations [2], industrial and scientific applications such as characterization of MEMS components [3, 4]. Aiming to measure the small size of object, we have designed a system which can measure the object minimized to 2.5 cm × 2.5 cm × 2.5 cm. The components in the system were the computer, mini protector and the camera which were used to generate different phases of fringe patterns, project the patterns on the object, and record the fringe patterns quickly. The data were processed by filtering, phase-shifting, and unwrapping algorithms. Finally, the object’s 3D surface profile has been rebuilt from the phase data. It’s no need to use extra device to produce shifted phase images; therefore, it can shorten the time of measurement.

A rule of the effect between the output of a single load cellSingle load cell and a combinatorial structure was proposed by changing the sensitivity of the single load cell. The relevant relationship between the sensitivity of single load cell and the variation of total output of the combinatorial structure was analyzed by the numerical derivation method and experimental validation. In the cases, the output of a single load cell is linear or nonlinear, when the same load was acted on the combinatorial structure. The results showed that the effect was limited and the influence quantity is due to the accuracy and number of load cell. However, it must be controlled in a certain range to avoid additional measurement errors to the combinatorial structure. Moreover, the rule provides an evaluation method with improving the measurement accuracy for the combinatorial structure. Consequently, the rule can be employed as a useful guidance for the product quality when this evaluation method is applied to the load cell selection for the electronic truck scales.

A non-contact and non-invasion method to measure lens curvature radius was proposed. In the experiment, we developed a homemade Line Field Spectral Domain Optical Coherence Tomography (LF-OCT)Optical coherence tomography System to measure lens curvature and focal length, using a broadband super luminescent diode (SLD) light source having a center wavelength of 830 nm. By using the methods of spectrum correction, the frequency, phase and amplitude can be corrected automatically and we can reach a higher accuracy. The result demonstrated that the LF-OCT has high accuracy and reliability and therefore it could be recommended to use in optical lens measurement due to its non-contact and non-invasion in nature.

Stationary wavelet transform (SWT)Stationary wavelet transform and the Artificial Neural NetworksNeural network (ANN) Algorithm were proposed for continuous measurement of blood pressure. A total number of 26,900 photoplethysmographyPhotoplethysmography (PPG) signals from Mimic Database were analyzed using SWT decomposition. The fifth layer high frequency coefficient was employed to reconstruct the signals. Ten characteristic parameters obtained from the reconstructed signals, as ANN input vector, and the PPG corresponding to the systolic blood pressure (SBP) and diastolic blood pressure (DBP), as the ANN vector output, were used to train the ANN model. The averaging error between the systolic pressure estimated by the proposed method and actual pressure value is 3.98 mmHg, and the standard deviation is 3.32 mmHg. The averaging error between the diastolic pressure estimated by the proposed method and actual pressure value is 3.81 mmHg, and the standard deviation is 3.63 mmHg. These results satisfy the American National Standards of the Association for the Advancement of Medical Instrumentation.

TerahertzTerahertz wave (λ = 30 μm–3 mm@f = 0.1–10 THz) is such a band of electromagnetic wave that locates between light and microwave. Many chiral biomolecules, such as protein and amino acid, have their own unique structure vibrating frequencies at Terahertz region, therefore they have the “fingerprint” terahertz absorption spectrum. It is meaningful to study the chirality of chiral macromolecules through their terahertz circular dichroism (CD)Circular dichroism response which is defined as the differential absorption of two opposite chiral terahertz wave. In the present work, we used the Finite-element-method (FEM) to investigate terahertz spoof surface plasmon polariton (SSPP)Surface plasmon polariton wave propagating on the helically grooved metal wire. Different from the metal wire decorated by the periodic grooves the helically grooved metal wire can support a kind of chiral SSPP surface mode. Due to the chirality of helical grooves, the normal degenerate HE1 SSPP mode on helically grooved metal wire decompose into two opposite chiral modes, i.e., HE−1 and HE+1 SSPP surface modes. Mode analysis showed that the dispersion curves of HE+1 mode deviated from that of HE−1 modes, and thus form a broad frequency band where the chiral HE+1 mode could exists exclusively. Super-chiral terahertz field concentration that may be achieved on the helically grooved metal wire through chiral HE+1 mode can find important applications in near-field circular dichroism spectroscopy in terahertz frequencies.

TerahertzTerahertz detection of multilayer marine protective coatingsMarine protective coating on a steel substrate using terahertz pulsed imaging (TPI)Terahertz pulsed imaging system in reflection mode was investigated. The multilayered anticorrosive/antifouling paint on steel substrate with different coating structures were produced as experimental samples for terahertz wave detection. The modeling and numerical simulation to calculate the propagation of THz radiation from marine protective coatings was studied by the finite difference time domain (FDTD) method. The reflected radiation properties in both simulation and experimentation were recorded for further analysis, such as the identification of the defect beneath coating. The results showed that it was able to provide much more detailed information on the position of the defect beneath the coating, such as detachment of large areas where adhesion has failed, or the blistering defect beneath the coating. Therefore, the developed model combined with the experimental analysis was effective and feasible for the detection and structure characterization of marine protective coatings and will provide timely and reliable information for ship maintenance work.

ProcessingIn situ measurement steel plate is the major step during the ship construction processes. In order to maintain more accurate control of the ship plate bending and reduce technical training time and cost, we developed a computer program for calculating the difference between the geometry of the manufactured curve plate with the design blue print. In the developed program, the coordinate rotation matrix and Euler angles (Deakin in Surv. Land Inf. Sys. 58:223–234, [1]; Lehmann in J. Geodesy 88:1117–1130, [2]; Shimizu in Evaluation of Three Dimensional Coordinate Measuring Methods for Production of Ship Hull Blocks. Kitakyushu, Japan, pp. 348–351 [3]) are applied to unify the coordinate system between the measured 3D data with the ship coordinate system. The program is written under the MATLAB coding environment. In our research, the most time consuming task is to determine which sets of rotation axes that can be used to transform the measuring coordinate to the design coordinate with the minimum error. Therefore, the least squares method is used to find the optimum Euler angle based on the minimization of error between the measured and design data. We have built an iterative scheme to search the most suitable set of rotation axes and the Euler angles, which spends about 30 s or less, and it has been tested for the in situ application. The program has the potential to speed up the plate processing time and aid the automated manufacturing capability of the ship yard.

A suspended doped grapheneGraphene monolayer based terahertz (THzTerahertz) plasmonicsPlasmonics gaseous sensor using Otto prism-coupling attenuated total reflection configuration was presented. The finite element method (FEM)Finite element method software COMSOL MULTIPHYSICS is used to combine Maxwell’s equation and Druse-Lorentz’s dispersion model into a 2D simulations to investigate the performance of the sensor in terms of detection accuracy with different refractive indexRefractive index gaseous sample. The sensitivity was also acquired by using the dispersion relation analysis. Preliminary results showed good agreement between simulation and theoretical analysis, as well as supporting previously literature reported calculation result. This method also can be used to computationally explore and design graphene based plasmonics sensor with more complex geometries compared with current sensor.

Much emphasis has been given to research and development of manufacturing systems to produce machine products, such as automotive and machine tools, with high accuracy and quality since the first industrial revolution in 18th Centuries. Industry 4.0 initiated by Germany also deals with the advanced manufacturing systems, which have the capability called “Plug and Produce”, by applying such recent information and communication technologies as CPS (Cyber Physical Systems)Cyber Physical Systems and IoTs (Internet of Things) Internet of Things. The paper deals with the new manufacturing systems called HMS (Holonic Manufacturing Systems)Holonic manufacturing system, which was proposed by an international collaborations for the advanced manufacturing systems under the recent ICT (Information and Communication Technologies) environment.

The number of small boilers using city natural gas, heavy oil (HO), and waste oils has been increasing annually in Japan, and more stringent regulations for nitrogen oxides (NO_x) emission are being anticipated to reduce environmental NO_x concentration. Taking this into consideration, it is envisioned that a suitable flue gas treatment system for small boilers will be required. The author proposed a plasma–chemical hybrid clean technology, consisting of an indirect nonthermal plasma process and a wet-chemical treatment. The tested flue tube boiler has an original rotary burner for gas and/or oil and is operated using city natural gas, biomass oil, or HO. The boiler has a steam generation rate of 2.5 ton/h, and for the clean technology, two sets of silent discharge-type plasma ozonizers are employed to generate ozone. Using the combination of ozone injection and chemical scrubber for flue gas, NO_x can be effectively decomposed to nitrogen and oxygen, thus purifying the resulting effluent. The amount of nitrogen monoxide (NO) removed is almost the same as the amount of the corresponding ozone required to oxidize NO to nitrogen dioxide (NO₂) (1:1 stoichiometric ratio). Previously reported experimental data are also discussed in the paper. A NO_x removal efficiency of more than 85% was achieved over an operating time of 23 h using city natural gas as fuel. Based on the concept of carbon neutrality, ~80% carbon dioxide (CO₂) reduction or fuel saving is also possible using waste vegetable oil (WVO)/HO mixed fuels. This low-emission boilerBoiler emission system can be used in industry.Pollution control

In order to obtain synthetically advantages from the independent multiple-motors-driven system and the centralized single-motor-driven system, a novel centralized dual-motor-coupling powertrain (DMCP) system with a single row double pinions gear train for electric vehicle (EV)Electric vehicle is proposed. By means of changing the drive modes, the proposed powertrain can satisfy the demands of different running conditions with high energy utilization efficiency. In this paper, the analyses on the mechanism structure and operating principles of the proposed powertrain are carried out firstly. Then, for further improving the operating efficiency and providing the effective ways for optimal matching design of the novel DMCP, the parameters sensitivity analysis is studied under the certain tested driving cycle based on a systematic simulation model. The simulation result shows that the energy consumption is increased by 3% as compared to the result of automobile test with the single motor powertrain.

Proton exchange membrane fuel cell (PEMFC) is regarded as one of the most promising power solutions for driving electric vehicle (EV) depending on its high efficiency, high energy density, low operation temperature, as well as zero emission. The limitations of wide application and commercialization of PEMFC in EV are low power density, unidirectional energy flow that cannot meet EV transient operating condition as well as store regenerating energy. Moreover, the transient load of EV may cause PEMFC lifetime dramatically degrade. Lithium-ion battery (LIB) is considered used in this study to hybridize with PEMFC to supply transient power demand as well as to save extra energy. To distribute power and to extend PEMFC lifetime, power management strategy based on the PEMFC operation point fixing is designed and implemented. The proposed hybrid PEMFC/LIB power system comprised by PEMFC, LIB, boost converter as well as bidirectional converter is modeled in Matlab/Simulink. Subsequently, the coordinated current-voltage control and cascade current-voltage control power splitting methods are developed to regulate DC bus voltage and PEMFC stack current. The fixed PEMFC stack current can lead to PEMFC operate in a suitable condition even the external load variations. The simulation and experimental results demonstrate that the designed power management strategy can balance the load demand and protect PEMFC.

A vision-based measurement systemVision-based measurement system for vibrationVibration monitoring was proposed by using a non-projection fringe pattern. The designed artificial fringe pattern was similar to the interferogram of 2D-OCVT system, which was named as quasi-interferogram fringe pattern (QIFP) and pasted on the surface of a vibrating structure. A high-speed CMOS camera worked as a detector was used to capture the image sequence of the fringe pattern during the structural vibration. The period density of the imaged QIFP changes due to the structural vibration, from which the vibration information of the structure could be obtained. The change of the dynamics parameters of a cracked structure was analyzed by Finite Element Method (FEM), traditional accelerometer-based method and the proposed method using a roving auxiliary mass, from which the frequency shiftFrequency shift curves can be obtained. The crack position information can be achieved confidently from the discontinuity of the frequency shift curves owing to the auxiliary mass effect when the mass was located at the crack position. The results demonstrated that the proposed method was an effective and accurate technique to measure structural vibrationStructural vibration monitoring without introducing extra mass on the tested structure. Significant advantages of the proposed method making the measurement system suitable for vibration monitoring of engineering structures and damage detectionDamage detection of beam structures.

Industry 4.0 has become an inexorable trend. To increase the efficiency of testing screen on smartphone, we design a system which includes a 5 degrees-of-freedom robotic arm to smartphone automatic test. The coordinate conversion is important for the operation between robot and camera. We use an algorithm named improved back propagation (BP) neural networkNeural network on the robot arm to solve the coordinate conversion problem. First, the neural network is used to fix the error of coordinate difference between robot and camera. Then the improved BP algorithm will train the network through the error. For the machine vision, we use a video camera to catch the patterns on the screen of tested smartphone. The control scheme calculates angle of motor through image processing and fuzzy control. When robot arm cannot press buttons correctly, fuzzy system will fix the error. Experimental results show that the proposed control scheme is capable of drive the robotic arm by DH model to press the desired positions on the tested smartphone.

This paper presents a two-vectors-based model-free predictive current control Current Control(TVB-MFPCC) for a voltage source inverterVoltage source inverter (VSI). In a single-vector-based model predictive current control (SVB-MPCC), the VSI can generate one out of the eight voltage vectors during each fixed sampling period. To increase the number of the available voltage vectors up to fourteen, two voltage vectors are synthesized as new ones for current prediction. Moreover, unlike the SVB-MPCC that requires the system model and load parameters, the proposed TVB-MFPCC is based on measuring the load currents, such that any system model or system parameter is not required. Both the TVB-MFPCC and the SVB-MPCC are realized on a 16-bit microcontroller, TMS320F28335, and they are applied to a VSI for testing and comparing their current-tracking performances.

The axial flow fan is the only actuator that simultaneously responses for delivering oxygen and cooling system. In this study, oxygen mass flow rate flowing across cathode channels is regarded as the control variable of the open-cathode fuel cell system. Air flow regulation based on a set of optimal oxygen excess ratios was analyzed in different stack currents. The motor voltage of the axial fan is controlled by the PWM circuit to regulate the air flow speed of the air supply subsystem. The destination of the control strategy centralizes on power optimal and over-temperature protection at the same time while the fuel cell system is running. Based on the fuel cell system model, an integral time absolute error (ITAE) criterion is employed to determine the PI gains of the controller. The verified experiments were implemented on the experiment platform consisted of NI devices.Control-oriented model

In view of the engineering significance of piezoelectric bodies with D_∞ symmetry, such as bulk wood and film or fibers made of poly-L-lactic acid, an analytical technique is constructed for general solutions to electroelastic problems in these bodies. First, the constitutive equations which describe the symmetry are presented. Then, the displacement and electric field are expressed in terms of two types of displacement potential functions and the electric potential function, and their governing equations are obtained using the fundamental equations for the electroelastic field. As a result, the electroelastic field quantities are found to be expressed in terms of three functions, namely an elastic displacement potential functions and two piezoelastic displacement potential functions, and the former is found to satisfy a fourth-order differential equation and the latter to satisfy a Laplace equation with respect to the appropriately transformed spatial coordinates.

Supply chain Supply chain network management has been studied for controlling material flow and information flow among different manufacturing companies. The recent research trends on supply chain management have been toward flexible and dynamic supply chains. In the dynamic supply chain environments, different organizations, such as law material suppliers, parts suppliers, and assembly manufacturers, can change business partners for finding suitable business partners and entering into profitable contracts. This paper reviews a basic dynamic supply chain model and discusses a minimum model for multi-layered dynamic supply chainsGenetic algorithm.

A theoretical approach is proposed to characterize the sample tilt by the tilt angle and the rotation angle, which can be calculated by the residual imprint morpholo-gy of Vickers indenter that is ideal with its axis along the vertical direction as well as the loading direction. Unique solutions of the three components of the local normal can be obtained by solving the equations with the projected contact lengths of Vickers indenter edges measured from the residual imprint after Vickers indentation. The tilt angle and the rotation angle can be calculated from compo-nents of the normal defined in Cartesian coordinate system. It is found both the tilt angle and the measured hardness have a Gaussian distribution, while the rota-tion angle has a random distribution. The measured hardness is found to linearly increase with the tilt angle, while independent of the rotation angle.

An accurate [aut]Kazuhiko, Sugaand robust lattice Boltzmann method for calculating turbulent flowsTurbulent flows by direct and large eddy simulation is developed. For the discrete velocity model, the D3Q27 model is proven to be desirable for turbulent flow simulation and then a multiple relaxation time (MRT) form is derived. To avoid unphysical kinks in turbulent quantities at grid interfaces by local mesh refinement, a correction method is developed. Coupling this imbalance correction (IBC) mesh refinement method with the D3Q27 MRT LBM, large scale turbulence simulation is effectively performed.

The multi-objective particle swarm optimization (MOPSO) is tested by the four ZDT problems. According to the simulation, the MOPSO can locate the global Pareto front (PF) on any instance. Moreover, a three-objective mathematical model is established to verify the ability of MOPSO when solving the practical engineering problems. The simulations show that, compared with the NSGA-II, the MOPSO is able to obtain better optimization results in a short period.

Nanoresonators based on graphenes have attracted worldwide attentions for applications in the field of modern microelectronics and nanoelectronics devices and sensors, due to their high stiffness and outstanding electrical properties. As a graphene-like quasi-two-dimensional (2D) nanomaterials, single-layer molybdenum disulfide (SLMoS₂)Molybdenum disulfide has the direct bandgap electric property, which is superior than the indirect bandgap of graphene. Compared with the extensive interests on the vibrationVibration of graphene nanoresonators with molecular dynamicsMolecular Dynamics simulations (MDs), there is lack of knowledge about the vibration of SLMoS₂ nanoresonators. Here, we carry out a set of MDs to investigate the fundamental resonant frequency of SLMoS₂ nanoresonators under different boundary conditions. Three types of beams, including simply supported beam, clamped-clamped beam, and fixed-fixed beam, are considered in our simulations. The effects of beam length, boundary conditions, and single S point vacancy defects on the fundamental resonant frequency of SLMoS₂ are mainly discussed. The interatomic interaction potentials of reactive empirical bond-order (REBO) is adopted in our simulations, after compared with the Stillinger-Weber (SW) potentials. It is found that the calculated frequencies with REBO potentials are higher than that using SW potentials. The resonant frequencies of clamped-clamped beams are found to be greater than other two types of beams. The resonant frequency is found to be inversely proportional to the square of beam length, i.e. decreasing with the increase of beam length, which is in line with the classical vibration theory of continuum beams. The existence of single S point vacancy defects will lead to the drift of resonance frequencies and motivate a new resonance modality.

Effective energy storage and conversion technologies are indispensable for developing advanced rechargeable batteries. Rechargeable Mg batteries have attracted increasing research interest as potential alternative to lithium-ion batteries, due to high energy capability, earth abundant, good operational safety, environmental friendliness, and low cost. Since monolayer MoS₂ have been synthesized through various methods, MoS₂ nanostructures have been applied to enhance the energy storage in the alkali-ion batteries. However, few works focus on the theoretical investigation of the Mg-ion batteries based on 1H-MoS₂ monolayer. In this paper, we conducted the first-principles calculations to investigate the Mg ions adsorption on and diffusion through the 1H-MoS₂ monolayer. Three adsorption sites, including top of S atom, top of Mo atom, and hole site (centre of hexagonal lattice), were considered for measuring the binding energy of Mg-ions. Result show that the binding energy at the top of Mo atom is the larger than those at the other adsorption sites, which indicates the possibly stable absorption configuration. Energy barriers of Mg-ions passing through and diffusing over the MoS₂ monolayer are also calculated. It was found that the Mg-ion has a largest energy barrier to pass through the 1H-MoS₂ layer and a smallest energy barrier to diffuse above the 1H-MoS₂ layer. The band structures and density of states of MoS₂ before and after Mg-ion absorption were also calculated and discussed.

With the development of world economy and the growing population, the shortage of water resources has become a major issue which affects survival and development of human beings. Hence, water-saving toilet is promoted and considered as the most effective way to solve this problem. In this paper, a new two-fluid approach was introduced to simulate the gas-liquid flow in the siphon pipeline. In the meantime, the VOF (Volume of Fluid) method and the RNG k-ε model were adopted to analyze the relative factors such as volume fraction, pressure and velocity magnitude, and thus the diagram of curves was produced accordingly. The study also shows that the negative pressure and velocity magnitude effect the siphon action directly which is formed by high-speed flow from the jet. Furthermore, the pressure gradient caused by jet and outlet confirmed the stability of the siphon. Additionally, it has not only approved the feasibility of applying the two-fluid method to siphon pipeline, but also provided the theory foundation for improving the performance of water-saving toilet.

The single-layer molybdenum disulfide (SLMoS₂)Molybdenum disulfide belongs to a graphene-like layered two-dimensional (2D) nanocrystal, consisting of S-Mo-S sandwich structure. The pristine SLMoS₂ holds unique properties due to its intrinsic direct bandgap of ~1.8 eV and high elastic modulus of ~0.2 TPa, which attracts extensive applications on 2D nanodevices. Since Lee’s pioneering work on graphene, the nanoindentationNanoindentation experiment based on the elastic membrane theory is routinized for obtaining the in-plane elastic modulus of other 2D nanomaterials, including SLMoS₂. Compared with the widely investigation of graphene nanoindentation with molecular dynamicsMolecular Dynamics simulations (MDs), only few studies focus on nanoindentation MDs of SLMoS₂. In the present work, we perform MDs for the SLMoS₂ nanoindentation to investigate the effects of indenter radius, loading speeds, and single S vacancies point defects on its mechanical response. Typical indentation load–displacement curves are obtained and fitted to deduce the elastic modulus of SLMoS₂ and the pre-tension. It is found that the extracted elastic modulus and pre-tension of defect-free SLMoS₂ increases with the indenter radius. Faster the indentation loading is extremely higher the elastic modulus of SLMoS₂ presents. The elastic modulus of SLMoS₂ with S point defects has the tendency to increase as the defect concentration varying from 0.1% to 1.0%, which is more obvious as the indenter radius becomes small.