Subjects: Mechanical Engineering >> Other Disciplines of Mechanical Engineering submitted time 2024-04-02
Abstract: In this study, first, an orthopedic plate was 3D printed with Polylactic acid (PLA) and coated with polycaprolactone (PCL)/Akermanite (AKT) nano-fibers. The composition included 8 wt.% of PCL and 3 wt.% of nAKT, while diameter of the PCL/AKT nano-fibers was approximately 253 nm ± 33 nm. Thermomechanical properties such as pressure, three-point bending flexural, and thermal conductivity of coated and non-coated specimens were examined and compared. In the next step, the bioactivity of the coated samples was evaluated following a 28-day immersion in simulated body fluid (SBF). Further, scanning electron microscope (SEM) images were taken to assess morphology of nanofibers and apatite formation on samples. By adding PCL to PLA, the maximum pressure force is enhanced by 16.83%. Further by adding nAKT to PLA+PCL sample, the maximum pressure force is enhanced by 4.72%. Further, by adding PCL to PLA, the maximum bending flexural force is enhanced by 21.06%. Further by adding nAKT to PLA+PCL sample, the maximum bending flexural force is enhanced by 21.39%. The results of this study are used to improve modeling of the orthopedic plates.
Subjects: Mechanical Engineering >> Other Disciplines of Mechanical Engineering submitted time 2024-03-28
Abstract: Increasing the transfer (HT) coefficient used in thermal industries is very important. Various methods are used to improve the efficiency of thermal heat HT so that maximum HT takes place in a smaller space. Ethylene glycol (EG) is generally used as an agent for convective HT. EG obtains energy from a hot source and discharges it to the required location. At present, the most consumption of EG is to produce engine cooling fluid. In the upcoming research, the TB of EG fluid in two-dimensional microchannels (MCs) has been investigated using molecular dynamics (MD) simulations, and the effect of variables such as MC dimensions and MC wall temperature (Temp) on the TB of the simulated fluid has been investigated. The results revealed that by increasing the Temp difference of the MC wall from 10 to 50 K, the maximum temperature (Max-Temp) and velocity (Max-Vel) of the target sample increased to 640.94 K and 0.024 Å/ps. It can be concluded that the increase in the cross-sectional area and the wall Temp difference leads to an increase in the HT rate in the MC.
Subjects: Mechanical Engineering >> Other Disciplines of Mechanical Engineering Subjects: Computer Science >> Computer Software submitted time 2022-02-16
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Peer Review Status:Awaiting Review
Subjects: Electronics and Communication Technology >> Information Processing Subjects: Engineering and technical science >> Engineering General Technology Subjects: Mechanical Engineering >> Other Disciplines of Mechanical Engineering submitted time 2022-02-08
Abstract:The spectral leakage (SL) from windowing and the picket fence effect (PEF) from discretization have been among the standard contents in textbooks for many decades. The SL and PEF would cause the distortions in amplitude, frequency, and phase of signals, which have always been of concern, and attempts have been made to solve them. This paper proposes two novel decomposition theorems that can totally eliminate the SL and PEF, they could broaden the knowledge of signal processing. First, two generalized eigenvalue equations are constructed for multifrequency discrete real signals and complex signals. The two decomposition theorems are then proved. On these bases, exact decomposition methods for real and complex signals are proposed. For a noise-free multifrequency real signal with m sinusoidal components, the frequency, amplitude, and phase of each component can be exactly calculated by using just 4m1 discrete values and its second-order derivatives. For a multifrequency complex signal, only 2m1 discrete values and its first-order derivatives are needed. The numerical experiments show that the proposed methods have very high resolution, and the sampling rate does not necessarily obey the Nyquist sampling theorem. With noisy signals, the proposed methods have extraordinary accuracy.
Peer Review Status:Awaiting Review
Subjects: Mechanical Engineering >> Other Disciplines of Mechanical Engineering submitted time 2018-06-15 Cooperative journals: 《电气工程学报》
Abstract: In experimental advanced superconducting Tokamak (EAST) device, during the quench process of a superconducting coil, the voltage variation caused by change in coil resistance is so small that is submersed in the background noise. To solve the problem, the time-frequency characteristic of the coil voltage signals is analyzed by Fourier decomposition, then the coil voltage signals is decomposed into several intrinsic mode functions (IMF) and the remainder by empirical mode decomposition (EMD). The result shows that the energy of weak signal is distributed mainly in the remainder and the weak variation can be extracted from the noise by EMD.
Subjects: Mechanical Engineering >> Other Disciplines of Mechanical Engineering submitted time 2018-06-15 Cooperative journals: 《电气工程学报》
Abstract: In the paper, the comprehensive evaluation index system of distribution grid is established with renewable energy on the basis of comprehensive evaluation on traditional distribution grid. This index system can make evaluation on distribution grid more comprehensively from equipment operational condition, power distribution reliability, power quality, economical efficiency and environmental protection property, highlighting the characteristics of distribution grid with renewable energy different from the traditional distribution network. The comprehensive evaluation method based on extensional analytic hierarchy process is also put forward. Considering vagueness in human judgment based on traditional analytic hierarchy process, this method is easier to meet the requirement for consistency in judgment matrix. At last, the comprehensiveness of index system and adaptability of evaluation method are verified through analysis of examples.
Subjects: Mechanical Engineering >> Other Disciplines of Mechanical Engineering submitted time 2018-06-15 Cooperative journals: 《电气工程学报》
Abstract: Through the analysis of the transient process of single phase to ground fault in distribution network, a new method is presented to study fault line,which decomposes transient grounding capacitive current through the wavelet packet, the maximum energy band is extracted using the energy method, and the modulus maxima and signal singularity theory are used for the characteristic frequency band of each line , and finally which is the fault line is determined.The line selection principle are introduced as well as the line selection basis. Finally, the simulation experiments show that the proposed method is accurate, reliable and strongly adaptive, and it has an important application value.
Subjects: Mechanical Engineering >> Other Disciplines of Mechanical Engineering submitted time 2018-06-15 Cooperative journals: 《电气工程学报》
Abstract: Solid-state transformer has the function of conversion and isolation in different voltage grade as the important equipment of energy internet, and it can integrate distributed renewable energy effectively, but also has some imbalance problem in voltage. At first,the SVPWM of single-phase solid-state transformer cascaded by arbitrary number of H bridge and the principle of voltage balance control are studied in the paper. Then, a control strategy which control one of H bridge's voltage through solid-state transformer voltage control loop is proposed, and this strategy control other H bridge's voltage to follow master H bridge by adding a new control loop in the SVPWM which control the vector pulse width of each slave H bridge. Finally, the simulation verifies the correctness of strategy proposed.
Subjects: Mechanical Engineering >> Other Disciplines of Mechanical Engineering submitted time 2018-06-15 Cooperative journals: 《电气工程学报》
Abstract: On the problem of large-scale probabilistic power flow problems with random variables, if the Gram-Charlier series expansion was used to approximate the cumulative distribution of random variables, the amount of calculation was large. In order to reduce the computational complexity of higher order expansion by using the recurrence of Hermite orthogonal matrix of edgeworth, a probabilistic power flow model considering the randomness of wind power output and load fluctuation is established. According to the method of high-order series transform is eliminated the influence of calculation accuracy, the method of multiple linear systems by uniform division of the total active power is used to reduce the truncation error caused by the large variation range of the input random variables due to linearization of the power flow equation. Simulation results of IEEE 39 system verify the effectiveness of the proposed method.
Subjects: Mechanical Engineering >> Other Disciplines of Mechanical Engineering submitted time 2018-06-15 Cooperative journals: 《电气工程学报》
Abstract: The devices which need time synchronization are numerous and distributed broadly in nuclear power station, and there are different requirements of precision and mode among different devices. Therefore several time synchronizing systems exist in nuclear power station at present. The modes of time adjustment, precision and transmission channel are discussed in this paper, and in order to solute the problem which time synchronizing systems are not unified and mounted repeatedly, a optimal time synchronizing network is presented which has unique time source. This time synchronizing system has high availability and precision because of its main clock and GPS/China compass dual-mode satellite antenna. The main clock and sub-clock is connected through optical fiber and transmission delay is set to improve system precision. Analysis result indicates that the optimal time synchronizing network has higher reliability and precision, and it also realize the optimization of technology and economy.
Subjects: Mechanical Engineering >> Other Disciplines of Mechanical Engineering submitted time 2018-06-15 Cooperative journals: 《电气工程学报》
Abstract: Hall sensor is the specific switchposition sensor of bypass-switch in UHV system, and it is important to the process of deblock the single valve group while the anothervalve group is operating in the same pole. In this paper a valve group deblock failure caused by the Hall sensor fault is analized, and the improvement suggestions are proposed to regularly test on Hall sensor.
Subjects: Mechanical Engineering >> Other Disciplines of Mechanical Engineering submitted time 2018-06-15 Cooperative journals: 《电气工程学报》
Abstract: An three-phase line-voltage-cascaded high-frequency link matrix rectifier (LVC-HLFMR) topology applied in high-voltage situations is proposed in the paper. The topology consists of three-phase line voltage cascaded converter which based on HLFMR unit module, high frequency link transformer, single-phase rectifier,and it can be directly connected to a three-phase system. It has the advantages of few switch quantity, omit the dc energy storage link, compact structure, etc. The HLFMR modulation strategy is analyzed, on this basis an improved commutation strategy is proposed according to the three-phase bridge direct cascade structure characteristics. The problem of open load when using the conventional commutation strategy and the instantaneous short circuit problem when converter work status switch to zero vector are solved. The simulation and experimental results verify the validity of the proposed topology and the effectiveness of the improvement commutation strategy.
Subjects: Mechanical Engineering >> Other Disciplines of Mechanical Engineering submitted time 2018-06-15 Cooperative journals: 《电气工程学报》
Abstract: According to the IEEE SSR first benchmark system, proposed to suppress sub synchronous resonance controllable series compensation (TCSC) scheme. By using PSCAD/EMTDC simulation software, the establishment of TCSC and its control simulation model, simulation study can suppress sub synchronous resonance with controllable series compensation and fixed series compensation combination scheme. By using open loop impedance control strategy of TCSC the performance of inhibiting sub synchronous resonance simulation.
Subjects: Mechanical Engineering >> Other Disciplines of Mechanical Engineering submitted time 2018-06-15 Cooperative journals: 《电气工程学报》
Abstract: In view of the local overheating and the higher temperature rise of the inductance in the power factor correction (PFC) circuit of the inverter air conditioner during operation, the electromagnetic coupling simulation is adopted to optimize the design of the inductor. The three-dimensional electromagnetic thermal field simulation model of PFC inductor is established by the finite element analysis method. The power loss of each component of the reactor is calculated by electromagnetic simulation, and the thermal field is simulated as a heat source. By changing the number of turns and the size of the magnetic core, four different design schemes are simulated. The magnetic field thermal coupling analysis is carried out, and the optimal design scheme is given. The actual operation shows that the optimized PFC inductor effectively reduces the temperature rise and loss, and the design method is of reference value for the design of other inductors.
Subjects: Mechanical Engineering >> Other Disciplines of Mechanical Engineering submitted time 2018-06-15 Cooperative journals: 《电气工程学报》
Abstract: In order to improve the recognition rate of wind turbine blade fault diagnosis, the nonlinear relationship between fault diagnosis and characteristic parameters of wind turbine blade is established by using support vector machine. In the Cauchy artificial bee colony algorithm, a dynamic Cauchy factor is introduced to dynamically adjust the search step in the optimization process of the colony, to improve the perturbation ability of the colony algorithm, and to avoid the colony into the local search. A dynamic support vector machine model for dynamic Cauchy bee colony optimization is established. The model is trained and diagnosed by four conditions of a wind farm in the south. The results show that the support vector machine model can be improved based on the dynamic Cauchy artificial bee colony algorithm. Wind turbine generator fault recognition rate, with a certain engineering reference significance.
Subjects: Mechanical Engineering >> Other Disciplines of Mechanical Engineering submitted time 2018-06-15 Cooperative journals: 《电气工程学报》
Abstract: Vacuum circuit breakers (VCBs) are widely used in power systems to control and protect power lines and power equipments under the conditions of normal, overload, short circuit and other faults. Once a VCB is unable to interrupt or make a current as designed, especially for the short circuit current, heavy losses would be brought about to both the power system and the consumers. In order to reduce the number of accidents and prevent possible troubles due to the failures of VCBs, one valid way is to monitor their performance and condition on-line. Based on the understanding and development of condition based maintenance (CBM) of high-voltage circuit breakers, the authors give some general introduction to electrical endurance on-line condition monitor for VCBs, in which the stress put on the non-intrusive method and device for determination of the arcing duration. The principle and configuration for arcing duration detect are emphatically expounded in our research, in which the electromagnetic induction theory is adopted for the arcing initialization and duration detect. The simulation and experimental results of the arcing detect device are provided in detail. The accuracy and stability of the arcing detect device have been demonstrated and it can distinguish co-existing arc signals in three-phase of circuit breakers. In the end, an algorithm for the electrical endurance of vacuum circuit breakers on-line condition monitoring system is proposed, which based on TMS320F2812 one type of DSP281X series produced by texas instruments semiconductor. The universally accepted approach of accumulative breaking current of high voltage circuit breaker contact to diagnose electrical endurance is used in the high-voltage circuit breakers electrical endurance on-line monitor system.
Subjects: Mechanical Engineering >> Other Disciplines of Mechanical Engineering submitted time 2018-06-15 Cooperative journals: 《电气工程学报》
Abstract: In the traditional system of ICPT, to calculate the optimal ratio of the receiving coils(Rx) of loosely coupled transformer coil and the distance between the transmitting coil (Tx) and the receiving coil (Rx), That is, radius-center distance ratio γ , usually by system modeling to project the mutual inductance value between the Tx and the Rx and supplemented by a large number of experiments. It not only lack theoretical basis but also waste manpower and material resources in this way. Pointing to this problem, this paper proposes a design method, using by simulating and observing the change rules of current density, to obtain the optimal radius-center distance ratio γ . Firstly, the system decoupling equivalent circuit model, that primary and secondary coils are in parallel compensation (PP) structure of the single switch inverter ICPT system, is used to derive the relationship among the current density, mutual inductance (M), system transmission power. Through the formula analysis, the ratio of the Rx inductance (L1) to the Tx inductance (L2) and the value of the coupling coefficient λ of the system are determined, and to determine the values of L1 and L2 at different frequencies. The simulation model is established in this way and using the finite element simulation software to study the optimal value of γ . Compared with the method of optimizing the coil through the coil mutual inductance value, the current density in this paper can be directly observed by software, vivid, save time and cost, and improve the design efficiency effectively. The simulation results show that the optimal radius-center distance ratio (γ ) of loosely coupled coils is consistent with the empirical values summed up by the enterprise experiments.
Subjects: Mechanical Engineering >> Other Disciplines of Mechanical Engineering submitted time 2018-06-15 Cooperative journals: 《电气工程学报》
Abstract: Line-start permanent magnet synchronous motor (LSPMSM) with nonuniform air gap structure is proposed for reducing torque ripple, high electromagnetic noise caused by the complex harmonic distortion rate of air gap magnetic field of common LSPMSM. The demagnetization condition of the permanent magnet of the structure is different from that of the ordinary motor. In this paper, based on the principle that magnetic field vector in permanent magnet is almost the same, the magnetic flux density of the permanent magnet is characterized by the magnetic density of inner point of the magnet. Theoretical study and finite element simulation of line-start permanent magnet synchronous motor with non-uniform air gap structure are carried out. This article has analyzed the influence factors of the motor demagnetization, and relationship between load characteristic and demagnetization of permanent magnet has also been studied. In this paper, the variation law of permanent magnet working point during steady state operation and starting process is obtained, and research method of obtaining the minimum working point of permanent magnet is proposed.
Subjects: Mechanical Engineering >> Other Disciplines of Mechanical Engineering Subjects: Computer Science >> Computer Application Technology submitted time 2017-12-26
Abstract: There are some shortcomings in the existing methods of fault diagnosis of planetary gearbox: First, the traditional methods are complex and can not effectively diagnose the planetary gearbox faults. Second, the methods based on convolution neural network mostly diagnose gearbox faults and rarely are used to diagnose planetary gearbox. In order to effectively diagnose complex faults and variable working conditions, fault tree structure, working condition parallel structure and multi-SoftMax convolution neural network are proposed for the first time. Fault tree structure can handle a variety of complex faults and see the diagnosis effect of each node. The parallel structure can handle variable conditions, and predict speed and load. A series of experiments are carried out using the vibration data of ours laboratory planetary gearbox, which indicated that the method can accurately diagnose the complex faults and variable working conditions of the planetary gearbox, and the accuracy is 97%. It is verified that the multi-SoftMax convolution neural network has strong generalization ability, and the advantages of the fault tree structure.
Peer Review Status:Awaiting Review
Subjects: Mechanical Engineering >> Other Disciplines of Mechanical Engineering Subjects: Computer Science >> Computer Application Technology submitted time 2017-12-26
Abstract: The existing methods of bearing diagnosis have some disadvantages: The conventional method has complex mathematical calculation and poor diagnosis effect. It generally only diagnoses the fault location and irrespective of the load and the fault size. The existing convolutional neural network method use the traditional convolution neural network. A network can only output a property and can not simultaneously diagnose multiple properties. In order to simultaneously diagnose the fault location, fault size and load, for the first time put forward a multi-attributes convolution neural network (MACNN) and applied to the bearing fault diagnosis. The multi-attribute convolution neural network is trained using one-dimensional vibration signal training . The advantages lies in overcoming the shortcomings of the traditional method: the diagnosis result of any combination of the fault attributes can be obtained, the network parameters are less, the method is simple, the generalization ability is strong and the accuracy rate is high. A series of tests have been carried out using the bearing data of Case Western Reserve University. The results show that the proposed method can accurately diagnose several properties of bearing faults with high accuracy and good generalization ability.
Peer Review Status:Awaiting Review