Abstract:In order to solve the problems about slow speed and low accuracy on the online roughness recognition of the grinding workpiece, an online measurement system for surface roughness was developed based on DSP. In this system, the surface scattered images based on the light scattering principle were captured by an industrial camera, then these images were preprocessed and their feature parameters were extracted by the DSP chip. Finally, these images with different surface roughness were classified by the multi-class support vector machine model. Experimental results show that it takes about 0.5 s for the entire identification process and the recognition rate can be up to 96% or more on this hardware platform, so this designed system can effectively identify the level of the surface roughness and realize the online testing of surface roughness.

Abstract:The influence of surface roughness in the difficult-to-polished blade regions, such as blade tip, blade fillet and hub, on the aerodynamic performance of the compressor rotor was investigated in order to define the required roughness in these regions for blade polishing. How the roughness in the above-mentioned regions of the rotor affects pressure loss coefficient and outlet total pressure on conditions of 98% choke mass flow in different design speeds was analyzed with the numerical aerodynamic calculation of rotor 37 based on computational fluid dynamics (CFD) tools. The results show that the rotor losses increase with the roughness in the difficult-to-vlished regions of the blade, and the outlet total pressure increases with the roughness of blade tip but decreases with the roughness of blade fillet and hub. The surface roughness value 15 μm is considered as a turning point, because it affects the aerodynamic performance more significantly when it is greater than 15 μm. The aerodynamic performance is most affected by the hub roughness. The hub roughness reduces the rotor losses at 60% of the design speed, but increases the rotor losses at 80%, 100% of the design speed.

Abstract:Aiming at the die wear problem of ultra high strength steel stamping forming, an effective and fast method was proposed for predicting die wear and working life. The method adopted Archard wear theory in order to obtain mould wear data after stamping forming. Die wear was mainly concentrated in the die round corners. The factors affecting die wear were analyzed systematically. These factors include die hardness, stamping speed and die material. The results showed that the die wear decreased effectively when the die hardness reached 60~65 HRC. The die wear was positively correlated with the stamping speed. Wear cumulation method was used to predict the service life of die， which had stamped 7500 times. the difference between die wear calculated by simulation and test data was only 1.47%, which showed that the method was feasible. The method has an important practical value in determining reasonable stamping process and designing die structure.

Abstract:A disc rubber vibration isolator with quasi-zero stiffness (QZS) was designed, and the characteristics of vibration isolation were studied. The QZS isolator was devised by assembling a reinforced disc rubber with negative stiffness in parallel with a vertical rubber cylinder with positive stiffness. By using Finite Element Analysis (FEA), the geometrical parameters of the reinforced disc rubber and the vertical rubber cylinder were achieved to ensure that the isolator's stiffness is close to zero at the static equilibrium position. And then, the characteristics of restoring force were analyzed, and the expression of restoring force was given as a polynomial only having cubic item by fitting the FEA simulations data. Moreover, the equation of motion of the vibration isolation system was obtained, and the isolation performance was evaluated theoretically based on Harmonic Balanced method, which was compared with that by using dynamic FEA. The results have shown that the QZS isolator significantly outperforms the corresponding linear one.

Abstract:With different materials of gaskets, friction coefficient between reeds is also different, so performance analysis result is not accurate when contact friction between steels is only considered in the design process. The VonMises stress and stiffness characteristics of leaf spring were analyzed with the nonlinear contact function of ANSYS software, and the stress distribution and load-deformation curve were obtained. Meanwhile, the test of taper-leaf spring was performed. The results have shown that the difference of stress between calculated and tested value is relatively small, and the calculated values of stiffness basically agree well with tested one, and the relative error is less than 5%. This indicates that finite element analysis(FEA) can accurately simulate the contact and friction and reflect the forces and deformations, and can be used to discuss the influence of different coefficients of friction between spring leaves on the equivalent stress and the average stiffness of the taper-leaf spring.

Abstract:To study the temperature field distribution of engine cylinder head more precisely, based on the Euler multi-phase model, a new two-phase flow model combining the Rohsenow core boiling heat transfer model was established, which can be used for the numerical simulation of subcooled boiling. Applying BDL and Rohsenow transfer models separately, the cylinder head fluid-solid coupling heat transfer system was simulated and analyzed with the CFD technology. The results have shown that the Rohsenow core boiling heat transfer model is more precise than the BDL model in calculating the temperature field of engine cylinder head. The highest temperature of the cylinder head is 192.22 ℃, and the maximum of stress is 235 MPa, both of which can meet the strength requirements of cylinder head materials.

Abstract:Based on low utilization rate of energy and high fuel consumption, the energy losses in the hydraulic excavator during typical working condition were analyzed, and the major directions of the energy saving research for the hybrid power system were derived. A parallel hydraulic & electric configuration for hybrid excavator was proposed based on capacitor and motor. For the hybrid power system based on SUNWARD 20T hybrid excavator, the paper established simulation model, and the effect of the power coupling characteristics, the control strategy, the capacitor’s State Of Charge on the hybrid excavator were studied by contrast calculation and simulation. And the key parameters were optimized and matched. At last the energy saving effect was studied by building test platform of hybrid system, and found that adopting the parallel hydraulic & electric system, selecting the appropriate parameters in power coupling, instantaneous optimization of control strategy, compensating parameter of capacitor SOC are helpful to improve the energy saving effect of hybrid excavator, and the energy saving efficiency can reach above 20%.

Abstract:Failure analysis is an important part of realizing the growth of machining center reliability level, so it is important to improve the accuracy of failure analysis. In view of this, this paper first considered the relationship and influence among failure subsystem elements of machining center, constructed the hierarchical structure model based on ISM method, made clear the class of interrelated failure subsystem, found out the deep failure subsystem elements and determined the weak link in the reliability improvement. Secondly, it analyzed the subsystem with FMECA, and determined the critical failure modes of the subsystem and laid a foundation for improving the reliability of machining center. Finally, it did the case study based on the field failure data of a series of machining center. The result has proved that the above method is accurate and effective in the failure analysis of machining center.

Abstract:A finite element model of a water-lubricated bearing at low speeds, and heavy loads was established. The Explicit module of Abaqus was used to analyze the influence regularity of transient performance on the water-lubricated bearing with different friction factors, loadings and revolving speeds, and the vibrational frequency and acceleration RMS of the bearing were obtained. Finally, the results were validated with experiments. The results have indicated that the stability of the system reduces and more vibrational noises rise with the increase in friction coefficient, the vibration response of the bearing system increases with the increase in loading within a certain range, but there is less impact from revolving speeds on the vibration frequency of the bearing. However, the accelerated speed of the system is getting higher with the increase of revolving speed, and the simulation analysis results are consistent with the experiment results, and it provides a theoretical basis for the study of the vibrational noise mechanism of water-lubricated bearings.

Abstract:With plenty of distributed generators connected to distribution system, island operation can be used as a new fault recovery approach to ensure the power supply of critical loads. A heuristic islanding algorithm based on distance-weight was proposed, taking the maximum recovered critical load as the main target, considering the pact of various operation constraints and uncontrolled loads of the distribution networks, introducing distance-weight which represents the distance between the objective load and the island to find out which load is the nearest to the current island and should be recovered first. The initial island is composed of all the DGs and some branches between them, and then enlarged by merging the nearest load among all the considered loads. Finally, it will get security assessment and be regulated. Simulation results have demonstrated that the proposed algorithm can generate a reasonable islanding scheme after a fault occurs.

Abstract:AC supply and DC supply coexist in electrified railway in some countries, such as South Africa. When a locomotive runs to a railway section powered by DC, its transformer is usually used as a filter reactor. In this paper, the electromagnetic characteristics of a locomotive transformer in DC system were studied with a geometry of "C-core" core-type and four high voltage windings and four low voltage windings symmetrically arranged on two core limbs respectively. When a locomotive is powered by DC, the four high voltage windings of a transformer are connected in parallel and in open circuit, and the two low voltage windings on a limb are connected in series and used as the filter reactor. There are two DC powered circuits in a locotomotive and one of them can work alone or the two work together. In this paper, the magnetic field of the transformer was analyzed and the inductances were calculated, in which different connections of the four low voltage windings were considered. Moreover the characteristics of inductances with changes of the currents in the windings were studied, and the inductance computation was proved with tests for that in which a DC circuit works alone. Then, a proper connection of the low voltage windings in DC system was proposed according to the above analysis. Finally, some investigation was done to increase the inductance when a DC circuit works alone and an improved design was presented.

Abstract:The key function of adaptive reclosing is to correctly identify fault nature and quickly capture the transient fault arc extinction time. Based on the analysis of the waveform complexity of fault terminal voltage after circuit breaker tripping under transient fault and permanent fault, this paper presented an adaptive reclosing overall implementation by combining local mean decomposition (LMD), approximate entropy and support vector machine (SVM). After getting the PF components of fault signal by using LMD decomposition, the approximate entropy of the first three PF components is calculated, which constitutes a three-dimensional feature vector as the input of SVM to identify fault nature and to capture arc extinguishing moment. Simulation results verify that this method can intelligently distinguish the transient fault from permanent fault, and capture transient fault extinction time with a strong anti-noise ability.

Abstract:Annual energy output of a candidate site in its life span is an important reference criterion of wind farm macro siting. A regional information fusion method， which allows the use of multiple reference wheather stations with a long history of wind speed and wind direction measurements, was proposed to improve the annual energy output prediction accuracy. Firstly, the correlation model was established between the short-term wind data of a single reference wheather station and the candidate wind farm, and the multiple long-term wind speeds of candidate site based on different reference stations were predicted by using the model. Then, the multiple prediction results were integrated by neural network to obtain the final long-term hourly wind speed data, and the annual energy output was subsequently determined on the basis of the knowledge of these wind speeds. The simulation results show that, by using the proposed method, the error reduction up to 11.32% has been achieved in the relative error of the average annual power output, with respect to the case of using a single reference wheather station method.

Abstract:The arbiter architecture of the ring bus was studied, and a novel extensible pipelined design was proposed, which can allocate the communication buffers and links simultaneously. Three characteristics have been found in the proposed design. Firstly, the arbiter is fair for each node, only with a 5% difference of the hit number. The communicated nodes were found in the simulation when the arbiter in an interconnect system was modeled with 14 nodes. Secondly, compared with the crossbar design, the worst time delay of our synthesis RTL design with Chartered 65 nm Technology was reduced by 36.8%. Furthermore, as the number of the nodes has less effect on the key circuit, the arbiter has certain scalability.

Abstract:Quadrature VCO is one of the key components in high speed data link. High Q on-chip inductance and capacitance integration is a key fact, which highly affects the performance of Voltage Controlled Oscillator. In order to fully compact the traditional digital CMOS process, we have designed on-chip inductance and capacitance with ultra-deep submicron digital CMOS process, based on which a capacitive coupling quadrature VCO is implemented. According to the simulation, the center frequency of QVCO is 16.12GHz, with 10% frequency tuning range, -112dBc@ 1MHz phase noise and 0.39°phase error.

Abstract:Large data RDMA (Remote Data Memory Access) transport is the most commonly used parallel communication mode for parallel computers, which has great impact on the whole system performance. As the system size increases, the fault-tolerate architecture design faces new challenges. The interconnection network usually uses the adaptive routing mode and becomes more unreliable. This paper proposed a fast RDMA offload method for unreliable interconnection networks, which can be efficiently implemented on the NIC hardware and provides reliable RDMA communication for upper driver and programs. Compared with the traditional approaches, the hardware overhead is greatly reduced. Another benefit is that it can partially retransmit the fault data, which greatly reduces the whole RDMA delay. Simulation results show that the RDMA delay is greatly reduced, compared with the traditional methods.

Abstract:LTE-based (Long Term Evolution) satellite mobile communication system combines 3GPP LTE standards and satellite communication technology and has important significance for the global coverage of mobile communication at a high speed. However, the problem of high bit error rate and bandwidth asymmetry in satellite communication constitutes a great challenge for the wireless resource scheduling and QoS (Quality of Service) guarantee in satellite mobile communication. Based on the semi-persistent scheduling mechanism in LTE, we proposed an uplink wireless resource scheduling scheme named VoSPS (Voice service Semi-persistent Scheduling). We added an access permission mechanism and a truncation mechanism based on uplink channel quality to VoSPS, reducing the waste of uplink resources. We also introduced a speech coding rate adjustment algorithm based on voice service satisfaction, which increased the user capacity of the system. The results of the simulation show that VoSPS can increase user satisfaction and the voice service capacity of the system effectively.

Abstract:This paper proposed a density based parallel clustering algorithm to mine the feature of large scale spatial data. The proposed PClusterdp algorithm is based on the cluster-dp algorithm. First, we introduced a data object count based RDD partition algorithm for balancing the working load of each compute node in computing cluster. Second, we redefined the local density for each data point to suit the parallel computing. Meanwhile, in order to get rid of original algorithm's decision graph, we proposed a method to automatically determine the center point for each cluster. Finally, we discussed the cluster merge stratagem to combine the partially clustered data together to generate the final clustering result. We implemented our Resilient Distributed Dataset (RDD) based algorithm on Spark. The experiment result shows that the proposed algorithm can cluster large scale spatial data effectively, and meanwhile, the method has better performance than the traditional density clustering methods and can achieve the rapid clustering of massive spatial data.

Abstract:Considering the large positioning error and high energy consumption concerning irregular and complex 3D plane with obstacles, this paper put forward a new strategy to locate the unknown nodes. This policy divides the complex three-dimensional plane into different logic layers and labels each layer node it belongs to. Then, sub-regions are divided and merged in horizontal layers. Finally, the positioning of 3D complex plane is possible by calculating the location coordinate of unknown nodes after atmospheric pressure sensor ranging. Compared with SV and COLA, the 3D-CCD positioning strategy in the average positioning error is 5% less than SV and 8% less than COLA． Its positioning precision increases more than 6.5%， and the energy consumption reduces 2.7% than SV and COLA. The 3D-CCD has great advantages in terms of positioning error, accuracy and energy.

Abstract:In the existing study of user roles, many scholars have defined the number and characteristics of roles，which have achieved good results in a particular dataset. But there are two problems: 1) the generality is poor,i.e., it must be reanalyzed if the dataset has been replaced; 2) in the real world, user's behavior and relationships are complicate and user roles are varied． So it's very difficult to describe and identify them with the artificial definition. So, this article proposed a user role found algorithm based on the tensor decomposition model. This algorithm can not only set the number of roles automatically, but also reflect the behavior characteristics of the role in specified period of time. Furthermore, this article extended user role to community roles and raised a community evolution analysis method based on the distance of community roles and the node overlapping. The experiment results indicate that the behavior characteristics of the identified roles are consistent with the fact, and the community evolution analysis method proposed has better effect than comparison algorithms.