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Time reversal method for guided wave inspection in pipes

DENG Fei, WU Bin, HE Cunfu

《机械工程前沿（英文）》 2008年第3卷第3期页码 251-260 doi: 10.1007/s11465-008-0050-1

摘要： The application of the time reversal method in pipe-like structures based on finite element method (FEM) is investigated. A steel pipe model measuring 70 mm × 3.5 mm is used to analyze the reflection coefficient of the (0,2) mode with the time reversal process. Simulation results show that the time reversal array method is beneficial to the improvement of the signal-to-noise ratio of a guided wave inspection system. As the intercepting window is widened, more energy is included in re-emitted signals, which leads to a large reflection coefficient of the (0,2) mode. In parallel, a circumferential locating method based on the time reversal method is described. The time reversal process used for guided wave inspection leads to the temporal and spatial focusing. When the time reversal signals are re-emitted, the angular profile obtained at the axial location of the defect can be used to determine the circumferential location of the defect. Except for a pipe with one defect, the circumferential locating method has been verified on another pipe model with two defects. Meanwhile, the elements number of the time reversal array has been discussed for enhancing the discrimination of the defect circumferential location.

关键词： reversal process beneficial circumferential location energy number

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TiO supported IrO for anode reversal tolerance in proton exchange membrane fuel cell

《能源前沿（英文）》 2022年第16卷第5期页码 852-861 doi: 10.1007/s11708-021-0811-7

摘要： Fuel starvation can occur and cause damage to the cell when proton exchange membrane fuel cells operate under complex working conditions. In this case, carbon corrosion occurs. Oxygen evolution reaction (OER) catalysts can alleviate carbon corrosion by introducing water electrolysis at a lower potential at the anode in fuel shortage. The mixture of hydrogen oxidation reaction (HOR) and unsupported OER catalyst not only reduces the electrolysis efficiency, but also influences the initial performance of the fuel cell. Herein, Ti₄O₇ supported IrO_x is synthesized by utilizing the surfactant-assistant method and serves as reversal tolerant components in the anode. When the cell reverse time is less than 100 min, the cell voltage of the MEA added with IrO_x/Ti₄O₇ has almost no attenuation. Besides, the MEA has a longer reversal time (530 min) than IrO_x (75 min), showing an excellent reversal tolerance. The results of electron microscopy spectroscopy show that IrO_x particles have a good dispersity on the surface of Ti₄O₇ and IrO_x/Ti₄O₇ particles are uniformly dispersed on the anode catalytic layer. After the stability test, the Ti₄O₇ support has little decay, demonstrating a high electrochemical stability. IrO_x/Ti₄O₇ with a high dispersity has a great potential to the application on the reversal tolerance anode of the fuel cell.

关键词： proton exchange membrane fuel cell (PEMFC) fuel starvation cell reverse reversal tolerance anode oxygen evolution reaction

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Flow, thermal, and vibration analysis using three dimensional finite element analysis for a flux reversal

B. VIDHYA,K. N. SRINIVAS

《能源前沿（英文）》 2016年第10卷第4期页码 424-440 doi: 10.1007/s11708-016-0423-9

摘要： This paper presents the simulation of major mechanical properties of a flux reversal generator (FRG) viz., computational fluid dynamic (CFD), thermal, and vibration. A three-dimensional finite element analysis (FEA) based CFD technique for finding the spread of pressure and air velocity in air regions of the FRG is described. The results of CFD are mainly obtained to fine tune the thermal analysis. Thus, in this focus, a flow analysis assisted thermal analysis is presented to predict the steady state temperature distribution inside FRG. The heat transfer coefficient of all the heat producing inner walls of the machine are evaluated from CFD analysis, which forms the main factor for the prediction of accurate heat distribution. The vibration analysis is illustrated. Major vibration sources such as mechanical, magnetic and applied loads are covered elaborately which consists of a 3D modal analysis to find the natural frequency of FRG, a 3D static stress analysis to predict the deformation of the stator, rotor and shaft for different speeds, and an unbalanced rotor harmonic analysis to find eccentricity of rotor to make sure that the vibration of the rotor is within the acceptable limits. Harmonic analysis such as sine sweep analysis to identify the range of speeds causing high vibrations and steady state vibration at a mode frequency of 1500 Hz is presented. The vibration analysis investigates the vibration of the FRG as a whole, which forms the contribution of this paper in the FRG literature.

关键词： flux reversal generator air velocity computation fluid dynamics thermal analysis vibration analysis finite element analysis

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The effects of festivals and special events on city image design

LIU Yuan, CHEN Chong

《结构与土木工程前沿（英文）》 2007年第1卷第2期页码 255-259 doi: 10.1007/s11709-007-0032-0

摘要： City marketing provides a good vehicle to strengthen a city in competition. On the analysis of the important roles of events and city image in the context of city marketing, this paper suggests that holding festivals or special events is an effective approach to enhance city marketing. The positive impacts of festivals and special events, such as the identification of city image, the promotion of the transmission of city image, and the reversal of the negative image of the city, are discussed. The negative impacts of festivals and special events are also talked about. The unique image of the city could be identified by the City Mind Identity, the City Visual Identity and the City Behavior Identity concerned with festivals and special events.

关键词： Visual Identity reversal transmission marketing Behavior Identity

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A logic-based controller for the mitigation of ventilation air methane in a catalytic flow reversal reactor

Zhikai LI, Zhangfeng QIN, Yagang ZHANG, Zhiwei WU, Hui WANG, Shuna LI, Mei DONG, Weibin FAN, Jianguo WANG

《化学科学与工程前沿（英文）》 2013年第7卷第3期页码 347-356 doi: 10.1007/s11705-013-1347-0

摘要： The control system of a catalytic flow reversal reactor (CFRR) for the mitigation of ventilation air methane was investigated. A one-dimensional heterogeneous model with a logic-based controller was applied to simulate the CFRR. The simulation results indicated that the controller developed in this work performs well under normal conditions. Air dilution and auxiliary methane injection are effective to avoid the catalyst overheating and reaction extinction caused by prolonged rich and lean feed conditions, respectively. In contrast, the reactor is prone to lose control by adjusting the switching time solely. Air dilution exhibits the effects of two contradictory aspects on the operation of CFRR, i.e., cooling the bed and accumulating heat, though the former is in general more prominent. Lowering the reference temperature for flow reversal can decrease the bed temperature and benefit stable operation under rich methane feed condition.

关键词： ventilation air methane reverse flow reactor lean methane combustion logic-based controller mathematical modeling

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线性分配方法的逆序问题研究

章玲,周德群

《中国工程科学》 2008年第10卷第2期页码 50-53

摘要：

指出了线性分配方法的决策结果可能产生逆序，然后提出排序向量和相对分配比的概念，以分析线性分配方法决策结果产生逆序的原因，并在此基础上构建顺序线性分配方法，最后通过算例验证顺序线性分配方法决策结果的保序性。

关键词：决策分析线性分配方法逆序保序

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应用规范化公式的MCDM保序研究

章玲,周德群,李洪伟,朱佩枫

《中国工程科学》 2006年第8卷第12期页码 85-88

摘要：

规范化公式的应用会破坏方案之间的独立性，导致逆序的产生。提出了两种改进规范化公式的方法以消除逆序，并以加权算术平均（WAA）集结算子的多属性决策分析(MCDM)为例验证了所提出方法的合理性和有效性。改进后的规范化公式不仅可以应用于WAA算子，还可以应用到其他类似的决策算子中。改进后规范化公式的应用可以降低和消除规范化公式对无关方案独立性的影响，使得MCDM决策过程更加合理、科学。

关键词： MCDM决策规范化公式无关方案独立性保序逆序

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Applications of the crystallization process in the pharmaceutical industry

Sohrab ROHANI

《化学科学与工程前沿（英文）》 2010年第4卷第1期页码 2-9 doi: 10.1007/s11705-009-0297-z

摘要： The applications of the crystallization technique in the pharmaceutical industry as a purification and separation process for the isolation and synthesis of pure active pharmaceutical ingredients (API), co-crystals, controlled release pulmonary drug delivery, and separation of chiral isomers are briefly discussed using a few case studies. The effect of process variables and solvent on the polymorphism and morphology of stavudine is discussed. The implementation of external control in the form of feedback and real-time optimal control using cooling and antisolvent crystallization of paracetamol in water-isopropyl alcohol is introduced. Two methods to prepare micron-sized drug particles, namely, micro-crystallization and polymer-coated API-loaded magnetic nanoparticles for pulmonary drug delivery, are discussed. The significance of co-crystals in drug administration is highlighted using the theophylline-nicotinamide co-crystal system. Resolution of chloromandelic acid derivatives, a racemic compound, is achieved using direct crystallization and diastereomeric salts crystallization. The crystal structures of diastereomeric salts of chloromandelic acid and phenylethylamine are determined. The structure comparison between the less soluble and more soluble salts shows that weak interactions such as CH/π interactions and van der Waals forces contribute to chiral recognition when the hydrogen bonding patterns are similar.

关键词： feedback morphology pulmonary paracetamol recognition

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Degradation of refractory organics in concentrated leachate by the Fenton process: Central compositedesign for process optimization

Senem Yazici Guvenc, Gamze Varank

《环境科学与工程前沿（英文）》 2021年第15卷第1期 doi: 10.1007/s11783-020-1294-1

摘要： Abstract • 90% total COD, 95.3% inert COD and 97.2% UV254 were removed. • High R2 values (over 95%) for all responses were obtained with CCD. • Operational cost was calculated to be 0.238 €/g CODremoved for total COD removal. • Fenton oxidation was highly-efficient method for inert COD removal. • BOD5/COD ratio of leachate concentrate raised from 0.04 to 0.4. The primary aim of this study is inert COD removal from leachate nanofiltration concentrate because of its high concentration of resistant organic pollutants. Within this framework, this study focuses on the treatability of leachate nanofiltration concentrate through Fenton oxidation and optimization of process parameters to reach the maximum pollutant removal by using response surface methodology (RSM). Initial pH, Fe2+ concentration, H2O2/Fe2+ molar ratio and oxidation time are selected as the independent variables, whereas total COD, color, inert COD and UV254 removal are selected as the responses. According to the ANOVA results, the R2 values of all responses are found to be over 95%. Under the optimum conditions determined by the model (pH: 3.99, Fe2+: 150 mmol/L, H2O2/Fe2+: 3.27 and oxidation time: 84.8 min), the maximum COD removal efficiency is determined as 91.4% by the model. The color, inert COD and UV254 removal efficiencies are determined to be 99.9%, 97.2% and 99.5%, respectively, by the model, whereas the total COD, color, inert COD and UV254 removal efficiencies are found respectively to be 90%, 96.5%, 95.3% and 97.2%, experimentally under the optimum operating conditions. The Fenton process improves the biodegradability of the leachate NF concentrate, increasing the BOD5/COD ratio from the value of 0.04 to the value of 0.4. The operational cost of the process is calculated to be 0.238 €/g CODremoved. The results indicate that the Fenton oxidation process is an efficient and economical technology in improvement of the biological degradability of leachate nanofiltration concentrate and in removal of resistant organic pollutants.

关键词： Concentrated leachate Fenton oxidation Central composite design Biodegradability Inert COD

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Review on mechanism and process of surface polishing using lasers

Arun KRISHNAN, Fengzhou FANG

《机械工程前沿（英文）》 2019年第14卷第3期页码 299-319 doi: 10.1007/s11465-019-0535-0

摘要： Laser polishing is a technology of smoothening the surface of various materials with highly intense laser beams. When these beams impact on the material surface to be polished, the surface starts to be melted due to the high temperature. The melted material is then relocated from the ‘peaks to valleys’ under the multidirectional action of surface tension. By varying the process parameters such as beam intensity, energy density, spot diameter, and feed rate, different rates of surface roughness can be achieved. High precision polishing of surfaces can be done using laser process. Currently, laser polishing has extended its applications from photonics to molds as well as bio-medical sectors. Conventional polishing techniques have many drawbacks such as less capability of polishing freeform surfaces, environmental pollution, long processing time, and health hazards for the operators. Laser polishing on the other hand eliminates all the mentioned drawbacks and comes as a promising technology that can be relied for smoothening of initial topography of the surfaces irrespective of the complexity of the surface. Majority of the researchers performed laser polishing on materials such as steel, titanium, and its alloys because of its low cost and reliability. This article gives a detailed overview of the laser polishing mechanism by explaining various process parameters briefly to get a better understanding about the entire polishing process. The advantages and applications are also explained clearly to have a good knowledge about the importance of laser polishing in the future.

关键词： laser polishing surface roughness process parameters mechanism

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Tool path strategy and cutting process monitoring in intelligent machining

Ming CHEN, Chengdong WANG, Qinglong AN, Weiwei MING

《机械工程前沿（英文）》 2018年第13卷第2期页码 232-242 doi: 10.1007/s11465-018-0469-y

摘要：

Intelligent machining is a current focus in advanced manufacturing technology, and is characterized by high accuracy and efficiency. A central technology of intelligent machining—the cutting process online monitoring and optimization—is urgently needed for mass production. In this research, the cutting process online monitoring and optimization in jet engine impeller machining, cranio-maxillofacial surgery, and hydraulic servo valve deburring are introduced as examples of intelligent machining. Results show that intelligent tool path optimization and cutting process online monitoring are efficient techniques for improving the efficiency, quality, and reliability of machining.

关键词： intelligent machining tool path strategy process optimization online monitoring

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Seasonal and treatment-process variations in invertebrates in drinking water treatment plants

Zhiling Wu, Xianchun Tang, Hongbin Chen

《环境科学与工程前沿（英文）》 2021年第15卷第4期 doi: 10.1007/s11783-020-1354-6

摘要： Abstract • Seasonal and treatment-process variations in invertebrates in a DWTP were analyzed. • The propagation and leakage of invertebrates in BAC filter were the most serious. • Invertebrates can survive and reproduce in chlorine disinfected clear water tanks. • Proportions of endogenous invertebrates increased along the treatment process. Problems associated with excessive propagation and leakage of invertebrates in drinking water have received increasing attention in recent years. We performed a monthly survey of invertebrate abundance and taxa in the effluent of each treatment stage in a drinking water treatment plant between May 2015 and April 2016 and analyzed seasonal and treatment-process variations in invertebrates. The results showed that invertebrate abundances in raw water, effluent of the biological activated carbon (BAC) filter, and finished water significantly correlated with water temperature, whereas no correlation was observed between water temperature and invertebrate abundance in the effluents of the sedimentation tank and sand filter. The dominant taxa in the effluent of each treatment stage were rotifers, nematodes, and crustaceans. The sedimentation tank could efficiently remove invertebrates with an annual average removal rate of 92%. The propagation and leakage of invertebrates occurred in the sand and BAC filters but more seriously in the latter. The average reproduction rate in the BAC filter was 268.8% with rotifers as the taxon that leaked the most. Invertebrate survival and reproduction were also observed in the chlorine-disinfected clean water reservoir with an average reproduction rate of 41.9%. Owing to differences in chlorine resistance, the reproduction ability of the dominant taxa was in the order nematodes>crustaceans>rotifers. The proportion of endogenous invertebrates gradually increased along the treatment process. The average proportion of endogenous invertebrates in the finished water was higher than 79.0%. Our findings suggested that waterworks should pay more attention to endogenous invertebrate growth.

关键词： Invertebrates Drinking water Seasonal variations Treatment process

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Special issue on “Green chemical process and intensification”

《化学科学与工程前沿（英文）》 2022年第16卷第11期页码 1533-1535 doi: 10.1007/s11705-022-2263-y

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Sulfate digestion process for high purity TiO

T. A. LASHEEN

《化学科学与工程前沿（英文）》 2009年第3卷第2期页码 155-160 doi: 10.1007/s11705-009-0005-z

摘要： A titania slag product of Rosetta ilmenite assaying 72% TiO is treated by the sulfate process option of the pigmentary TiO manufacture. The relevant factors of acid concentration, particle size, slag/acid ratio besides the reaction temperature, and time have been studied. After dissolving the cured mass in dilute acid and clarification, the obtained solution was subjected to hydrolysis of its titanium content. The final product was bleached under reducing conditions to redissolve the residual coloring impurities before being dewatered and calcinated. The obtained results indicated that a leaching efficiency of about 92% was realized due to the presence of some refractory components in the working slag material, namely, rutile and magnesium iron titanate. The obtained white pigment assay attained up to 99.85% TiO , while the analyzed impurities involve 77 ppm Mn and only 14 and 7 ppm of total iron and V, respectively.

关键词： titania slag sulfate process pigment

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矿山微震震源定位研究进展与展望 Review

程久龙,宋广东,孙晓云,温来福,李飞

《工程（英文）》 2018年第4卷第5期页码 653-660 doi: 10.1016/j.eng.2018.08.004

摘要：

震源定位是微震监测技术的核心要素，微震震源定位的准确性关系到微震技术的应用效果。针对矿山微震波场特征，分析了矿山微震定位的特点，指出了基于到时的经典定位方法用于矿山微震定位存在的不足。介绍了近几年来在矿山微震定位方面的研究进展，主要包括Geiger 方法与线性方法联合定位、联合微震事件定位、相对定位法优化、无需预先测速的定位方法、无需拾取初至到时的定位方法，分析各方法的优缺点和可行条件。分析了检波器布置、初至到时拾取、波速模型对微震震源定位的影响，提出了应对措施。解决上述问题的方法包括采用新型融合、组合优化已有的方法、创建新方法以实现高精度微震震源定位。提出了矿山微震精确定位的发展方向，即速度模型优化、逆时成像、被动时间反转镜法、相对干涉成像法等新方法的应用，有望大大提高矿山微震震源定位精度。同时，探讨了多方法多参数信息融合和深度学习在矿山微震定位中的应用前景。这些创新性的微震震源定位方法具有广阔的发展前景。

关键词：微震震源定位影响因素逆时成像研究进展发展前景