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HHT-based crack identification method for start-up rotor

Bing LI, Chunlin ZHANG, Zhengjia HE

《机械工程前沿（英文）》 2012年第7卷第3期页码 300-304 doi: 10.1007/s11465-012-0328-1

摘要：

This paper presents a crack identification method for start-up rotor based on the Hilbert-Huang transform (HHT). With this method, the instantaneous frequency (IF) of each intrinsic mode function is obtained through the Hilbert transform, and the spectrum of IF is calculated accordingly. The influence of acceleration and crack depth on the rotor is analyzed through experiments. HHT is employed to detect the shallower crack, and is then tested during the start-up process of the rotor. The results of the experiment show that HHT is a better tool for crack detection than fast Fourier transform.

关键词： cracked rotor start-up Hilbert-Huang transform (HHT)

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Acceleration of the particulate organic matter hydrolysis by start-up stage recovery and its original

Yanqing Duan, Aijuan Zhou, Xiuping Yue, Zhichun Zhang, Yanjuan Gao, Yanhong Luo, Xiao Zhang

《环境科学与工程前沿（英文）》 2021年第15卷第1期 doi: 10.1007/s11783-020-1304-3

摘要： Abstract • Carbon availability was partially solved by POM recovery and fermentation. • 12% carbon sources were regenerated by fermentation of the entrapped 35% TCOD. • The unique microbial communities facilitated the efficient hydrolysis of the POM. • Considerable economic benefits in aeration power and ECS dosage were anticipated. To address the availability of carbon sources for denitrification, the accelerated hydrolysis of the most abundant but low-availability fraction of particulate organic matter (POM) was investigated. Mesh sieves with different pore sizes were used as primary pretreatment at the start-up-stage of the biological process to separate some POM from the liquid system. The changes in soluble carbohydrates and proteins were monitored to investigate the hydrolysis performance of the sieved POM, with waste activated sludge (WAS) as the control test. The results showed that an average of 35% POM could be entrapped before filtrate mat development. In addition, benefiting from the high polysaccharides concentration, as well as the high availability due to the relatively loose physical structure, a 23% hydrolysis efficiency of POM was obtained, in contrast to that of WAS (3.4%), with a hydrolysis constant of 0.39 h−1. The prominent performance was also attributed to the unique microbial communities having been domesticated at a lower temperature, especially the cellulose-degrading bacteria Paraclostridium and psychrophile Psychrobacter, making up 6.94% and 2.56%, respectively. Furthermore, the potential benefits and application of improved POM hydrolysis by start-up stage recovery via mesh sieves combined with anaerobic fermentation were evaluated, including selective POM entrapment, alleviation of blockage and wear, and a reduction in aeration energy. By the proposed strategy, carbon availability for biological nutrient removal (BNR) processes is anticipated to be improved more economically than that can be achieved by primary clarifier elimination.

关键词： Particulate organic matter (POM) Hydrolysis Microbial community Mass balance

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Start-up of PN-anammox system under low inoculation quantity and its restoration after low-loading rate

Guoliang Zhang, Liang Zhang, Xiaoyu Han, Shujun Zhang, Yongzhen Peng

《环境科学与工程前沿（英文）》 2021年第15卷第2期 doi: 10.1007/s11783-020-1324-z

摘要： Abstract • PN-A was start-up under low inoculation amount and a higher NRR was achieved. • PN-anammox system was successfully restored by aggressive sludge discharge. • Increase in granular sludge was the important factor to rapid recovery. • Enrichment of AOB and AnAOB in granular sludge favors the stable operation. Partial nitritation (PN)-anaerobic ammonium oxidation (anammox) is a promising pathway for the biological treatment of wastewater. However, the destruction of the system caused by excessive accumulation of nitrate in long-term operation remains a challenge. In this study, PN-anammox was initialized with low inoculation quantity in an air-lift reactor. The nitrogen removal rate of 0.71 kgN/(m3·d) was obtained, which was far higher than the seed sludge (0.3 kgN/(m3·d)). Thereafter, excess nitrate build-up was observed under low-loading conditions, and recovery strategies for the PN-anammox system were investigated. Experimental results suggest that increasing the nitrogen loading rate as well as the concentration of free ammonium failed to effectively suppress the nitrite oxidation bacteria (NOB) after the PN-anammox system was disrupted. Afterwards, effluent back-flow was added into the reactor to control the up-flow velocity. As a result, an aggressive discharge of sludge that promoted the synergetic growth of functional bacteria was achieved, leading to the successful restoration of the PN-anammox system. The partial nitritation and anammox activity were in balance, and an increase in nitrogen removal rate up to 1.07 kgN/(m3·d) was obtained with a nitrogen removal efficiency of 82.4% after recovery. Besides, the proportion of granular sludge (over 200 mm) increased from 33.67% to 82.82%. Ammonium oxidation bacteria (AOB) along with anammox bacteria were enriched in the granular sludge during the recovery period, which was crucial for the recovery and stable operation of the PN-anammox system.

关键词： PN-anammox Granular sludge Excess nitrate build-up Recovery strategy for partial nitrification Aggressive discharge of sludge

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Performance and bioparticle growth of anaerobic baffled reactor (ABR) fed with low-strength domestic sewage

Jing FENG,Yili WANG,Xueyuan JI,Dongqin YUAN,Hui LI

《环境科学与工程前沿（英文）》 2015年第9卷第2期页码 352-364 doi: 10.1007/s11783-014-0638-0

摘要： We investigated the performance of a 15.3 L capacity anaerobic baffled reactor (ABR) toward the treatment of low-strength domestic wastewater. The start-up period of the ABR was finished within approximately 130 days at a temperature below 25°C. The average COD in the effluent was 165 mg·L , and the corresponding COD removal efficiency of the ABR was 52.3%. During the third stage (from day 130 to day 233) of ABR operation, the average COD in the effluent reached 71 mg·L , which meets the secondary discharge requirement of the Integrated Wastewater Discharge Standard (GB 18918-2002, China). Moreover, partial microbial separation was observed along the five ABR compartments through scanning electron microscopic images. The geometric mean diameter of bioparticles in the five compartments increased from 0.050 mm to 0.111, 0.107, 0.104, 0.110, and 0.103 mm during the start-up stage. After operation for 179 days, the corresponding diameters further increased to 0.376, 0.225, 0.253, 0.239, and 0.288 mm, respectively. The fractal dimensions of the bioparticles indicated that these particles have smoother surfaces and more compact structures during ABR operation. Morphological analysis of the bioparticle sections demonstrated that the bioparticles have a pore volume of 30%–55%. The highest porosity was observed for the bioparticles in the second ABR compartment, whereas the lowest fractal dimension of bioparticle section was observed in the fifth compartment.

关键词： low-strength domestic wastewater start-up bioparticles morphology anaerobic baffled reactor

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金属支撑型固体氧化物燃料电池研究进展

周永川,宋世栋,韩敏芳

《中国工程科学》 2013年第15卷第2期页码 27-32

摘要：

随着固体氧化物燃料电池(SOFC)向中低温发展，使得金属材料用于SOFC的关键组件成为可能。金属支撑型SOFC（MS-SOFC）是以金属或合金作为燃料电池支撑体的结构。相对于其他支撑型SOFC，MS-SOFC具有更好的导电能力和导热能力、较高的机械强度以及较低的成本，所以引起了研究人员的广泛关注。目前，MS-SOFC的结构呈多样化发展，支撑体、电极和电解质的材料及其制备工艺也不尽相同。本文介绍了不同结构的MS-SOFC的研究现状，评述了它们各自的制备工艺和存在的问题，并提出了目前MS-SOFC亟需解决的问题。

关键词：固体氧化物燃料电池金属支撑型SOFC 薄膜电解质热循环快速启动

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Effect of catalyst layer mesoscopic pore-morphology on cold start process of PEM fuel cells

Ahmed Mohmed DAFALLA, Fangming JIANG

《能源前沿（英文）》 2021年第15卷第2期页码 460-472 doi: 10.1007/s11708-021-0733-4

摘要： Water transport is of paramount importance to the cold start of proton exchange membrane fuel cells (PEMFCs). Analysis of water transport in cathode catalyst layer (CCL) during cold start reveals the distinct characteristics from the normal temperature operation. This work studies the effect of CCL mesoscopic pore-morphology on PEMFC cold start. The CCL mesoscale morphology is characterized by two tortuosity factors of the ionomer network and pore structure, respectively. The simulation results demonstrate that the mesoscale morphology of CCL has a significant influence on the performance of PEMFC cold start. It was found that cold-starting of a cell with a CCL of less tortuous mesoscale morphology can succeed, whereas starting up a cell with a CCL of more tortuous mesoscale morphology may fail. The CCL of less tortuous pore structure reduces the water back diffusion resistance from the CCL to proton exchange membrane (PEM), thus enhancing the water storage in PEM, while reducing the tortuosity in ionomer network of CCL is found to enhance the water transport in and the water removal from CCL. For the sake of better cold start performance, novel preparation methods, which can create catalyst layers of larger size primary pores and less tortuous pore structure and ionomer network, are desirable.

关键词： cold start energy conversion fuel cells mesoscale morphology tortuosity water management

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氢能列车投入运营

Chris Palmer

《工程（英文）》 2022年第11卷第4期页码 9-11 doi: 10.1016/j.eng.2022.02.003

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汽油压燃发动机低负荷燃烧稳定性和冷机着火性能的试验研究 Article

周磊, 华剑雄, 卫海桥, 韩义勇

《工程（英文）》 2019年第5卷第3期页码 558-567 doi: 10.1016/j.eng.2018.12.010

摘要：

汽油压燃（GCI）是一种极具发展前景的低排放、高效率燃烧技术。然而，低负荷燃烧稳定性和冷启动是GCI燃烧面临的两大挑战。为了解决这些问题，研究人员提出了负气门重叠角（NVO）、喷油策略优化、燃油重整和进气预热等策略，然而，冷启动难题却仍然有待解决。本文的目标正是研究实现GCI发动机冷启动的切实可行的方法。本研究结合了NVO、缸内燃油重整和进气预热，以实现在冷机和冷边界条件下GCI发动机的着火和随后的热机工况。结果表明，喷油开始时刻（SOI）在进气冲程时具有最佳的燃油经济性；SOI在压缩冲程期间可有效拓展发动机小负荷极限；SOI在NVO期间则可实现发动机在冷进气和冷却液未预热条件下的稳定燃烧。考虑到NVO喷油策略具有未燃混合气活性强、缸内热积累速度快的特点，该策略非常适合用于实现GCI的冷机着火。在冷启动过程中，实现GCI发动机的着火还需要一些辅助措施，如进气加热，以启动第一个着火循环。通过NVO策略、缸内燃油重整和进气预热的组合，本文实现了GCI发动机在5个燃烧循环内的成功着火。启动过程结束后，发动机无需再采用进气预热即可实现稳定运行。

关键词：汽油压燃冷起动热机工况喷油策略燃烧稳定性

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Structure controlling and process scale-up in the fabrication of nanomaterials

Chunzhong LI,

《化学科学与工程前沿（英文）》 2010年第4卷第1期页码 18-25 doi: 10.1007/s11705-009-0305-3

摘要： Nanotechnology is already having a significant commercial impact, and will very certainly have a much greater impact in the future. The research on process engineering and scale-up will be very important for the commercial production and application of nanomaterials, because the properties and structure of nanomaterials are not only determined by the nucleation and growth process, but also strongly affected by the engineering properties, such as the mixing, the heat and mass transfer, and also the distribution of temperature, concentration, etc. This paper will present some research work in our laboratory on the fabrication of nanomaterials. Based on the chemical engineering principle and methods, many kinds of novel nanomaterials can be synthesized and their structure can be easily controlled through adjusting the parameters of the fluid mixing, and the distribution of temperature, residence time and concentration, etc. By using the micro-mixing, heat and mass transfer and reaction control methods, the host-guest nanocomposites have been assembled and assumed as the novel electroanalytical sensing nanobiocomposite materials. Based on the principles of chemical engineering, the manufacturing technologies for magnetic powders, calcium carbonate, and titanium dioxide have been developed for commercial-scale production, and the largest production scale has reached 15 kt/year.

关键词： scale-up significant commercial electroanalytical engineering laboratory

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BUEES: a bottom-up event extraction system

Xiao DING,Bing QIN,Ting LIU

《信息与电子工程前沿（英文）》 2015年第16卷第7期页码 541-552 doi: 10.1631/FITEE.1400405

摘要： Traditional event extraction systems focus mainly on event type identification and event participant extraction based on pre-specified event type paradigms and manually annotated corpora. However, different domains have different event type paradigms. When transferring to a new domain, we have to build a new event type paradigm and annotate a new corpus from scratch. This kind of conventional event extraction system requires massive human effort, and hence prevents event extraction from being widely applicable. In this paper, we present BUEES, a bottom-up event extraction system, which extracts events from the web in a completely unsupervised way. The system automatically builds an event type paradigm in the input corpus, and then proceeds to extract a large number of instance patterns of these events. Subsequently, the system extracts event arguments according to these patterns. By conducting a series of experiments, we demonstrate the good performance of BUEES and compare it to a state-of-the-art Chinese event extraction system, i.e., a supervised event extraction system. Experimental results show that BUEES performs comparably (5% higher -measure in event type identification and 3% higher -measure in event argument extraction), but without any human effort.

关键词： Event extraction Unsupervised learning Bottom-up

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新企业寻求加快核聚变商业化

Mitch Leslie

《工程（英文）》 2022年第8卷第1期页码 6-8 doi: 10.1016/j.eng.2021.11.006

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Working Up Green, and Living Up Green

Ji-shan He

《工程管理前沿（英文）》 2014年第1卷第1期页码 2-2 doi: 10.15302/J-FEM-2014002

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Jack up reliability analysis: An overview

Ahmad IDRIS, Indra Sati Hamonangan HARAHAP, Montasir Osman Ahmed ALI

《结构与土木工程前沿（英文）》 2018年第12卷第4期页码 504-514 doi: 10.1007/s11709-017-0443-5

摘要： Jack up is a mobile unit used for oil and gas exploration and production in offshore fields. On demand, the unit is moved and installed in a given location and used for a period up to 12 months before being un-installed and moved to another location. Due to its mobility and re-usability, when the unit is offered for use in a given offshore location, its suitability in terms of safe operation is evaluated in accordance with the guidelines of Site Specific Assessment (SSA) of jack up. When the unit failed safety assessment criteria, the guideline recommended that it is re-assessed by increasing the complexity of the assumptions and methods used. Reliability analysis theories are one of the frameworks recommended for the safety assessment of the units. With recent developments in uncertainty and reliability analysis of structures subject to stochastic excitation, this study aims at providing a review on the past developments in jack up reliability analysis and to identify possible future directions. The results from literature reviewed shows that failure probabilities vary significantly with analysis method used. In addition, from the variants of reliability analysis approach, the method of time dependent reliability for dynamic structures subject to stochastic excitation have not been implemented on jack ups. Consequently, suggestions were made on the areas that need further examination for improvement of the efficiency in safety assessment of the units using reliability theories.

关键词： jack up reliability analysis uncertainty analysis review of jack up

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Performance of a novel bent-up bars system not interacting with concrete

Aydin SHISHEGARAN, Mohammad Reza GHASEMI, Hesam VARAEE

《结构与土木工程前沿（英文）》 2019年第13卷第6期页码 1301-1315 doi: 10.1007/s11709-019-0552-4

摘要： Increasing the bending and shear capacities of reinforced concrete members is an interesting issue in structural engineering. In recent years, many studies have been carried out to improve capacities of reinforced concrete members such as using post and pre-tensioning, Fiber Reinforced Polymer and other techniques. This paper proposes a novel and significant technique to increase the flexural capacity of simply supported reinforced concrete beams. The proposed method uses a new reinforcement bar system having bent-up bars, covered with rubber tubes. This technique will avoid interaction of bent-up bars with concrete. They are located in the zone where compressive and tensile forces act against one another. The compressive force in the upper point of the bent-up bars is exerted to the end point of these bars located under neutral axis. Moreover, the tensile stress is decreased in reinforcements located under the neutral axis. This will cause the Reinforced Concrete (RC) beam to endure extra loading before reaching yield stress. These factors may well be considered as reasons to increase bending capacity in the new system. The laboratory work together with finite element method analysis were carried out in this investigation. Furthermore, bending capacity, ductility, strength, and cracking zone were assessed for the new proposed system and compared with the conventional model. Both the FEM simulation and the experimental test results revealed that the proposed system has significant impact in increasing the load bearing capacity and the stiffness of the RC beams. In the present study, an equation is formulated to calculate bending capacity of a new reinforcement bar system beam.

关键词： bending capacity rubber tube stress transfer bent-up bars ductility cracking

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Scale up of reactors for carbon dioxide reduction

《化学科学与工程前沿（英文）》 2023年第17卷第1期页码 116-122 doi: 10.1007/s11705-022-2178-7

摘要： In recent times there has been a great deal of interest in the conversion of carbon dioxide into more useful chemical compounds. On the other hand, the translation of these developments in electrochemical reduction of carbon dioxide from the laboratory bench to practical scale remains an underexplored topic. Here we examine some of the major challenges, demonstrating some promising strategies towards such scale-up, including increased electrode area and stacking of electrode pairs in different configurations. We observed that increasing the electrode area from 1 to 10 cm² led to only a 4% drop in current density, with similarly small penalties realised when stacking sub-cells together.

关键词： CO₂ reduction electrochemical cell electrosynthesis upscaling