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28 December 2018, Volume 23 Issue Sup. 1 Previous Issue    Next Issue

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Research on Spatially Adaptive High-Order Total Variation Model for Weak Fluorescence Image Restoration MA Jin (马进), XUE Teng (薛腾), SHAO Quanquan (邵全全), HU Jie (胡洁), WANG Weiming (王伟明) 2018, 23 (Sup. 1):  1-7.  doi: 10.1007/s12204-018-2016-8 Abstract ( 620 )   Confocal laser scanning microscopy (CLSM) has emerged as one of the most advanced fluorescence cell imaging techniques in the field of biomedicine. However, fluorescence cell imaging is limited by spatial blur and additive white noise induced by the excitation light. In this paper, a spatially adaptive high-order total variation (SA-HOTV) model for weak fluorescence image restoration is proposed to conduct image restoration. The method consists of two steps: optimizing the deconvolution model of the fluorescence image by the generalized Lagrange equation and alternating direction method of multipliers (ADMM); using spatially adaptive parameters to balance the image fidelity and the staircase effect. Finally, an comparison of SA-HOTV model and Richardson-Lucy model with total variation (RL-TV model) indicates that the proposed method can preserve the image details ultimately, reduce the staircase effect substantially and further upgrade the quality of the restored weak fluorescence image. References | Related Articles | Metrics

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Catalytic Combustion of Lean Methane Assisted by Electric Field over Pd/Co3O4 Catalysts at Low Temperature LIU Ke (刘柯), LI Ke (李珂), XU Dejun (许得隽), LIN He (林赫), GUAN Bin (管斌), CHEN Ting (陈婷), HUANG Zhen (黄震) 2018, 23 (Sup. 1):  8-17.  doi: 10.1007/s12204-018-2017-7 Abstract ( 435 )   A series of Pd/Co3O4 catalysts were prepared by Self-Propagating High-Temperature Synthesis (SHS) method in this study, and electric field was applied for catalytic combustion of lean methane over Pd/Co3O4 catalysts at low temperature. When electric field was applied, the catalytic combustion performance of Pd/Co3O4 catalysts was greatly improved, and the application of electric field could reduce the load of active element Pd to some extent while maintaining the same efficiency. Based on experimental tests and the analysis results of X-ray diffraction (XRD), X-ray photoelectron spectroscopy (XPS), H2-temperature-programmed reduction (H2- TPR) and in-situ diffuse reflectance infrared Fourier transform spectroscopy (in-situ DRIFTS), the mechanism of catalytic oxidation of CH4 over Pd/Co3O4 catalysts in electric field was proposed. The catalytic combustion of CH4 occurs only when the temperature is higher than 250?C normally, but when electric field was applied, the whole process of CH4 oxidation was promoted significantly and the reaction temperature was reduced. Electric field could promote the reduction of the support Co3O4 to release the lattice oxygen, resulting in the increase of PdOx and the surface chemisorbed oxygen, which could provide more active sites for the low-temperature oxidation of CH4. Furthermore, electric field could accelerate the dehydroxylation of CoOOH to further enhance the activity of the catalysts. References | Related Articles | Metrics

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Study on Oxidation Activity of CuCeZrOx Doped with K for Diesel Engine Particles in NO/O2 WANG Kexin (王可欣), GUAN Bin (管斌), LI Ke (李珂), ZHAN Rijing (湛日景), LIN He (林赫), HUANG Zhen (黄震) 2018, 23 (Sup. 1):  18-27.  doi: 10.1007/s12204-018-2018-6 Abstract ( 352 )   CuCeZrOx and KCuCeZrOx catalysts were synthesized and coated on the blank diesel particulate filter (DPF) substrate and a particulate matter (PM) loading apparatus was used for soot loading. The catalytic performances of soot oxidation were evaluated by temperature programmed combustion (TPC) test and characterization tests were conducted to investigate the physicochemical properties of the catalysts. The reaction mechanism in the oxidation process was analyzed with diffuse reflectance infrared Fourier transform spectroscopy. The results demonstrated that CuCeZrOx catalyst exhibited high activities of soot oxidation at low temperature and the best results have been attained with Cu0.9Ce0.05Zr0.05Ox over which the maximum soot oxidation rate decreased to 410°C. Characterization tests have shown that catalysts containing 90% Cu have uniformly distributed grains and small particle sizes, which provide excellent oxidation activity by providing more active sites and forming a good bond between the catalyst and the soot. The low-temperature oxidation activity of soot could be further optimized due to the excellent elevated NO’s conversion rate by partially substituting Cu with K. The maximum particle oxidation rate can be easily realized at such a low temperature as 347°C. References | Related Articles | Metrics

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Pressure-Based Approach to Estimating the Injection Start and End in Single and Split Common Rail Injection Processes ZHAI Jiaqi (翟佳琦), DUAN Yaozong (段耀宗), HAN Dong (韩东) 2018, 23 (Sup. 1):  28-33.  doi: 10.1007/s12204-018-2019-5 Abstract ( 253 )   Fuel injection timing is an important control parameter for engine combustion optimization and emissions control. However, the actual fuel injection timing is different from the nominal one commanded by the electronic control unit, due to the system hydraulic lag or the possible communication malfunction. In this study, a simple estimate approach based on the injector inlet pressure is proposed to capture four critical characteristic instants at the start and end of injection. The critical characteristic moments estimated using this pressure-based approach are validated against those determined by the actual injection rate profiles, in the context of different single or split injection processes. The comparison revealed that the characteristic injection moments estimated by the injector inlet pressures and those determined by the actual injection rate profiles have a satisfactory agreement, certifying the broad applicability and reliability of this pressure-based approach in the detection of the real fuel injection start and end time. References | Related Articles | Metrics

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Error Analysis of Liquid Holdup Measurement in Gas-Liquid Annular Flow Through Circular Pipes Using High-Speed Camera Method LIU Li (刘莉), BAI Bofeng (白博峰) 2018, 23 (Sup. 1):  34-40.  doi: 10.1007/s12204-018-2020-z Abstract ( 268 )   Accurate measurement of gas-liquid phase fraction is essential for the proper modelling of the pressure drop, heat transfer coefficient, mass transfer rate and interfacial area in two-phase flows. In this paper, taking the issue of optical distortion into account, an analytical model was proposed to estimate and correct the liquid holdup in gas-liquid annular flow through a circular pipe using high-speed camera method. The error in the liquid holdup measurement generated from different refractive indices among transparent circular pipe, liquid film and air core was firstly theoretically analyzed based on the geometric optics. Experimental tests were then carried out to identify the difference as well as to validate the proposed model. Results indicated that the prediction of the liquid holdup has a good performance with the experimental data (i.e., mean relative error is 4.1%) and the measured liquid holdup is larger than the real one. It was found that the measured liquid holdup is larger than the real one. Generally, when the real liquid holdup gets smaller, the discrepancy between the measured liquid holdup by image and the real liquid holdup becomes more significant. Thus, after measuring the liquid holdup from the images, the value of the measured liquid holdup must be corrected by the present model in order to obtain the real liquid holdup. References | Related Articles | Metrics

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Performance Evaluation of Short Parabolic Trough Collectors Integrated with a Small-Scale Solar Power and Heating System ZHANG Guang (张光), LI Yong (李勇) 2018, 23 (Sup. 1):  41-49.  doi: 10.1007/s12204-018-2021-y Abstract ( 330 )   An investigation is presented on the performance of a small-scale solar power and heating system with short parabolic trough collectors (PTCs). The steady-state model of the short PTCs is evaluated with outside experiments. The model mainly contains the heat loss of the receiver, the peak optical efficiency and the incident angle factor consisting of incident angle modifier and end loss. It is found that the end loss effect is essential in this model when the length of the PTCs is less than 48 m, especially in the winter. The standard deviation of the steady-state model is 1.4%. Moreover, the potential energy efficiency ratio of the solar power and heating system is considerably larger than the coefficient of performance (COP) of general air-source heat pumps, and increases with the decrease of the condensation temperature. An overall system efficiency of 49% can be reached. Lastly, the existence of a water storage tank improves the flexibility of heating the building, and the volume of the water storage tank decreases with the increase of the heating water temperature. References | Related Articles | Metrics

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Design and Combustion Characteristic Analysis of Free Piston Stirling Engine External Combustion System JIN Xudong (金旭东), Lü Tian (吕田), YU Guoyao (余国瑶), LIU Jiawei (刘佳伟), HUANG Xiaoyu (黄晓宇) 2018, 23 (Sup. 1):  50-55.  doi: 10.1007/s12204-018-2022-x Abstract ( 411 )   The free piston Stirling engine external combustion system was simulated to investigate the diesel-air combustion characteristics in order to demonstrate its feasibility by computational fluid dynamics (CFD). The different effects on combustion were distinguished by analyzing the combustion burner, the injection position of diesel oil, the front tube arrangement of Stirling heater head and the back fin. The results show that the tilted front tube arrangement of the heater head with the back fin is the best practicable technology while the distance between the diesel nozzle position and the swirler top is 0. Its total heat flux is 15.6 kW, and the average heat transfer coefficients of the front and back tubes are 127W/(m2 ·K) and 192W/(m2 ·K), respectively. The heat transfer is mainly through convection, and the proportion of radiative heat transfer is only 16.9%. The best combustion efficiency of the free piston Stirling engine external combustion system is 86%. References | Related Articles | Metrics

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Cyclostationary Modeling of Surface Electromyography Signal During Gait Cycles and Its Application for Cerebral Palsy Diagnosis YU Liang (余亮), YAN Li (严莉), CHEN Mengjie (陈梦婕), DONG Liangchao (董良超) 2018, 23 (Sup. 1):  56-61.  doi: 10.1007/s12204-018-2023-9 Abstract ( 378 )   Cerebral palsy (CP) is a group of permanent movement disorders that appear in early childhood. The electromyography (EMG) signal analysis and the gait analysis are two most commonly used methods in the clinic. In this paper, a cyclostationary model of the EMG signal is proposed. The model can combine the aforementioned two methods. The EMG signal acquired during the gait cycles is assumed to be cyclostationary due to the physiological characteristics of the EMG signal production. Then, the spectral correlation density is used to analyze the cyclic frequency (corresponding to the gait cycles) and spectral frequency (the frequency of EMG signal) in a waterfall representation of the two kinds of frequencies. The experiments show that the asymptomatic (normal) subjects and symptomatic subjects (with CP) can be distinguished from the spectral correlation density in a range of cyclic frequencies. References | Related Articles | Metrics

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Research on Morlet Wavelet Based Lamb Wave Spatial Sampling Signal Optimization Method LIU Bin (刘彬), LIU Tingzhang (刘廷章), MENG Fanqin (孟凡芹) 2018, 23 (Sup. 1):  62-69.  doi: 10.1007/s12204-018-2024-8 Abstract ( 341 )   In recent years, Lamb wave and piezoelectric transducers (PZTs) array based wavenumber filtering technique for damage estimation has been gradually studied. Compared with the time domain and frequency domain analysis of the Lamb wave signals, the wavenumber domain analysis is an effective approach to distinguish wave propagating direction and wave modes. However, the spatial resolution sampled by the PZTs is lower than that sampled by scanning laser Doppler vibrometer. As for the diameter of the PZT, it cannot be very small. In this paper, a new Lamb wave spatial sampling signal optimization method based on Morlet wavelet is proposed. Firstly, the frequency band parameter of the Morlet mother wavelet function is calculated by the Lamb wave excitation signal. Then, the sum of squared errors between the Lamb wave spatial sampling signal and the Morlet wavelet function fitting waveform at each scale factor and time factor is calculated. Finally, the scale factor and time factor corresponding to the least sum of squared errors can be judged to be the best match scale factor and time factor respectively, and the Morlet wavelet function fitting waveform in that scale factor and time factor can be seen as the optimized Lamb wave spatial sampling signal. The validation experiment performed on a glass fiber epoxy composite plate shows that the proposed method can improve the spatial resolution and length of the Lamb wave spatial sampling signal, and the sum of squared errors of this method is no more than 0.2. References | Related Articles | Metrics

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Micro-Grinding Performance of Hard-Brittle Chip Materials in Precision Micro-Grinding Microgroove ZHANG Long (张龙), XIE Jin (谢晋), ZHU Limin (朱利民), LU Yanjun (鲁艳军) 2018, 23 (Sup. 1):  70-76.  doi: 10.1007/s12204-018-2025-7 Abstract ( 371 )   The micro-structure on hard-brittle chip materials (HBCMs) surface can produce predominant functions and features. The micro-grinding with diamond wheel micro-tip is an efficient method to machine microstructure on HBCMs. However, different HBCMs and crystal orientation may have a significant influence on the micro-grinding performance. In this paper, the micro-grinding performance along different crystal orientation of HBCMs is investigated. First, a dressed 600# diamond grinding wheel is used to micro-grind micro-structure on HBCMs. Then, the experiment of micro-grinding force test is completed. Finally, the quality of microgroove, the grinding ratio and the micro-grinding force are investigated and they are related to the crystal orientation of HBCMs. It is shown that the stronger resistance to the micro-crack propagation has the best quality of microgroove and the smallest grinding ratio. Moreover, the hardest single-crystal SiC has the best machinability and the micro-grinding force is 38.9%, 10.8% and 46.8% less than the one of sapphire, single-crystal Si and quartz glass, respectively. The direction to micro-grind easily is the crystal orientation 10ˉ10 for single-crystal SiC and sapphire. In addition, the micro-grinding force increases with the increase of the micro-grinding depth and feed rate and decreases with the increase of the grinding wheel speed. References | Related Articles | Metrics

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Opportunistic Replacement Optimization for Multi-Component System Based on Programming Theory XIAO Lei (肖雷), XIA Tangbin (夏唐斌) 2018, 23 (Sup. 1):  77-84.  doi: 10.1007/s12204-018-2026-6 Abstract ( 307 )   It is widely accepted that too excessive or too insufficient maintenance actions on a system are consumptive or potentially risky. This paper focuses on the optimization of opportunistic replacement for a multicomponent system in which no failure or suspension histories can be used for prediction of all the critical components in the system. Firstly, the remaining useful life (RUL) is predicted using the real-time sensor data, which is based on an “individual-based lifetime inference” method. Then a failure risk estimation method is introduced, which is based on the degradation extent and service time of components. Subsequently, the possible replacement combinations of components are compared, which is based on a proposed current-term cost rate. Finally, the best replacement scheduling is selected. The proposed framework is validated by the simulation dataset and PHM-2012 competition bearing dataset. Group replacement and individual replacement are conducted for comparison, and sensitivity analysis is discussed. References | Related Articles | Metrics

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Remaining Useful Life Prediction of Turbofan Engine Using Hybrid Model Based on Autoencoder and Bidirectional Long Short-Term Memory SONG Ya (宋亚), SHI Guo (石郭), CHEN Leyi (陈乐懿), HUANG Xinpei (黄鑫沛), XIA Tangbin (夏唐斌) 2018, 23 (Sup. 1):  85-94.  doi: 10.1007/s12204-018-2027-5 Abstract ( 451 )   Turbofan engine is a critical aircraft component with complex structure and high-reliability requirements. Effectively predicting the remaining useful life (RUL) of turbofan engines has essential significance for developing maintenance strategies and reducing maintenance costs. Considering the characteristics of large sample size and high dimension of monitoring data, a hybrid health condition prediction model integrating the advantages of autoencoder and bidirectional long short-term memory (BLSTM) is proposed to improve the prediction accuracy of RUL. Autoencoder is used as a feature extractor to compress condition monitoring data. BLSTM is designed to capture the bidirectional long-range dependencies of features. A hybrid deep learning prediction model of RUL is constructed. This model has been tested on a benchmark dataset. The results demonstrate that this autoencoder-BLSTM hybrid model has a better prediction accuracy than the existing methods, such as multi-layer perceptron (MLP), support vector regression (SVR), convolutional neural network (CNN) and long short-term memory (LSTM). The proposed model can provide strong support for the health management and maintenance strategy development of turbofan engines. References | Related Articles | Metrics

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Real-Time Fault Diagnosis for Gas Turbine Blade Based on Output-Hidden Feedback Elman Neural Network ZHUO Pengcheng (卓鹏程), ZHU Ying (朱颖), WU Wenxuan (邬雯喧), SHU Junqing (舒俊清), XIA Tangbin (夏唐斌) 2018, 23 (Sup. 1):  95-102.  doi: 10.1007/s12204-018-2028-4 Abstract ( 360 )   In order to remotely monitor and maintain large-scale complex equipment in real time, China Telecom plans to create a total solution that integrates remote data collection, transmission, storage, analysis and prediction. This solution can provide manufacturers with proactive, systematic, integrated operation and maintenance service, and the data analysis and health forecasting are the most important part. This paper conducts health management for the turbine blades. Elman neural network, and improved Elman neural network, i.e., outputhidden feedback (OHF) Elman neural network are studied as the main research methods. The results verify the applicability of OHF Elman neural network. References | Related Articles | Metrics

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Residual Chart with Hidden Markov Model to Monitoring the Auto-Correlated Processes LI Yaping (李亚平), HUANG Mengdie (黄梦蝶), PAN Ershun (潘尔顺) 2018, 23 (Sup. 1):  103-108.  doi: 10.1007/s12204-018-2029-3 Abstract ( 337 )   Autocorrelations exist in real production extensively, and special statistical tools are needed for process monitoring. Residual charts based on autoregressive integrated moving average (ARIMA) models are typically used. However, ARIMA models need a quite amount of experience, which sometimes causes inconveniences in the implementation. With a good performance under less experience or even none, hidden Markov models (HMMs) were proposed. Since ARIMA models have many different performances in positive and negative autocorrelations, it is interesting and essential to study how HMMs affect the performances of residual charts in opposite autocorrelations, which has not been studied yet. Therefore, we extend HMMs to negatively auto-correlated observations. The cross-validation method is used to select the relatively optimal state number. The experiment results show that HMMs are more stable than Auto-Regressive of order one (AR(1) models) in both cases of positive and negative autocorrelations. For detecting abnormalities, the performance of HMMs approach is much better than AR(1) models under positive autocorrelations while under negative autocorrelations both methods have similar performances. References | Related Articles | Metrics

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Effects of Heat Intensity and Inflow Wind on the Reactive Pollution Dispersion in Urban Street Canyon XIE Xiaomin (谢晓敏), ZHU Zhongwei (朱中伟) 2018, 23 (Sup. 1):  109-116.  doi: 10.1007/s12204-018-2030-x Abstract ( 393 )   This paper investigates the impacts of heating intensity and inflow wind speed on the characteristics of reactive pollutant dispersion in street canyons using the computational fluid dynamic (CFD) model that includes the transportation of NO, NO2, and O3 coupled with NO-NO2-O3 photochemistry. The results indicated that the heat intensity and inflow wind speed have a significant influence on the flow field, temperature field and the characteristics of reactive pollutant dispersion in and above the street canyon. With the street canyon bottom heating intensity increasing, NO, NO2 and O3 concentrations in street canyon are decreased. The O3 concentration reductions are even more than the NO and NO2 concentrations. Improving the inflow wind speed can significantly reduce the NO and NO2 concentrations within street canyons. But the O3 concentrations have a slight rise with wind speed increasing. The results would be useful for understanding the interrelation among reactive vehicle emissions, and provide references for urban planners. References | Related Articles | Metrics

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Intelligent Vehicle Human-Simulated Steering Characteristics Access and Control Strategy HUA Yiding (华一丁), GONG Jinfeng (龚进峰), RONG Hui (戎辉), WANG Wenyang (王文扬), GUO Peng (郭蓬), HE Jia (何佳) 2018, 23 (Sup. 1):  117-123.  doi: 10.1007/s12204-018-2031-9 Abstract ( 370 )   As the traditional control algorithm is over-dependent on accurate vehicle model in intelligent vehicle steering control, a human-simulated intelligent control method is proposed based on experienced driver steering characteristics. Intelligent vehicle unmanned steering system dynamics model and the driver model are set up. Through experienced drivers’ trial run experiment, the analysis is mainly conducted on the double lanes condition. After the transformation of coordinates on global positioning system (GPS) derivative, the path information of local coordinates is accessed. The ideal driver steering path is obtained through fuzzy C-means clustering algorithm. The human-simulated intelligent controller is designed. Characteristic model is established according to the ideal and practical steering angle deviation and the deviation rate. Besides, the corresponding control rules and control modality set are designed. The joint simulation under CarSim joint/Simulink environment shows that the humanoid steering controller designed in this paper has better tracking performance than the model predictive control. References | Related Articles | Metrics

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Effect of Needle Coke on Gas Permeability of Ceramic Casting Molds WANG Fei (王飞), ZHU Guoliang (祝国梁), LI Fei (李飞), SUN Baode (孙宝德) 2018, 23 (Sup. 1):  124-131.  doi: 10.1007/s12204-018-2032-8 Abstract ( 357 )   The permeability of a new investment casting mold system prepared by adding needle cokes has been investigated in this work. The permeability tests of the molds were carried out at the temperature of 25—1 200 ?C. The results showed that the addition of needle cork could significally increase the permeability of the molds by a factor of about 4 because the burning of needle cokes increased the porosities of the molds. Meanwhile, the needle coke modified molds exhibited higher green strength and greater thickness both on flat section and at sharp edges compared with the full fused silica mold. Taking account of the mold thickness, the needle coke modified molds had increased adjusted fracture load (AFL) by a factor of about 2 at the test temperature of 25—1 200 ?C. The addition of needle coke significally improved the permeability of the molds during both autoclaving and casting, and optimized the correlation between the permeability and green strength of the molds. References | Related Articles | Metrics

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Poly(Dimethylbenzimidazolium) Iodide Assisted Dispersion of Multiwalled Carbon Nanotubes and Their Palladium Nanoparticle Hybrid ZHANG Yanli (张燕黎), YU Ping (宇平), PAN Lijing (潘丽静), XUE Minzhao (薛敏钊), WANG Wei (王巍), HU Zuming (胡祖明) 2018, 23 (Sup. 1):  132-136.  doi: 10.1007/s12204-018-2033-7 Abstract ( 262 )   The multi walled carbon nanotubes (MWNTs) have always been as the catalyst supporting materials, but for high-performance composite catalysts, the dispersion and functionalization of MWNTs are important challenging problems. In this paper, Electrocatalytically active palladium nanoparticles (Pd NPs) on MWNTs with the high-performance and excellent solubility polymer, poly(dimethylbenzimidazolium) iodide (P(DMBI)-I?) as modifier and glue was first discussed. The results of transmission electron microscopy (TEM) demonstrate a better dispersion of MWNTs with the assist of P(DMBI)-I?. The Raman spectra indicate a strong π-π interaction between MWNTs and P(DMBI)-I?. Taking advantages of the coordination effect of imidazole groups and the electrostatic attraction to Pd NPs, the prepared Pd/MWNTs-P(DMBI)-I?(Pd/MPDI?) hybrid is of well electrocatalytic activity to the ethanol fuel cells by electrochemical measurements. So it is believed that P(DMBI)-I?can be further applied in the dispersion of different carbon-based materials and metal nanoparticles for fabricating more novel composites for catalyst and electrode material. References | Related Articles | Metrics