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Short-term effect of temperature variation on the competition between PAOs and GAOs during acclimation period of an EBPR system

Nanqi REN, Han KANG, Xiuheng WANG, Nan LI

《环境科学与工程前沿（英文）》 2011年第5卷第2期页码 277-282 doi: 10.1007/s11783-010-0226-x

摘要： Sequencing batch reactor (SBR) for enhanced biological phosphorus removal (EBPR) processes was used to investigate the impact of the temperature shock on the competition between phosphorus-accumulating organisms (PAOs) and glycogen accumulating organisms (GAOs) in start-up stage. During the 34 days operation, SBR was set with temperature variation(0–5 d, 22±1°C; 6–13 d, 29±1°C; 14–34 d, 14±1°C). PAOs and GAOs were analyzed by fluorescent in situ hybridization (FISH), and intracellular polyphosphate granules were stained by Neisser-stain. The results showed that the influence of temperature shock on PAOs’ abundance was more serious than that on GAOs in the enriching process. Under sudden and substantially temperature variation, from 22±1°C to 29±1°C and then to 14±1°C, the domination of PAOs was deteriorated. After temperature shock, PAOs’ competitive advantages at low temperature that concluded in other study did not appear in our study. As mesophilic, GAOs (indicated by and ) were more temperature adaptive and better grew and took the domination at 14±1°C in the end. In the competition process, organisms of tetrad forming organisms (TFOs)-like shape which were considered as typical GAOs, were observed. With the evidence of poly-P granules containing by Neisser-straining and result of FISH, these organisms of TFOs-like shape were better to be assumed as adaption state or a special self-protecting shape of PAOs.

关键词： fluorescent in situ hybridization (FISH) tetrad forming organisms (TFOs) temperature variation enhanced biological phosphorus removal (EBPR)

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Finite element simulations of sheet metal forming under complex strain paths

CHEN Wei, YANG Jichang, WU Xiaofeng, LU Dun, GUO Weigang

《机械工程前沿（英文）》 2007年第2卷第4期页码 399-403 doi: 10.1007/s11465-007-0069-8

摘要： Fracture is a common defect in sheet metal forming and it is essentially caused by tensile instability. This paper analyzes some experiments and theories for building forming limit diagrams of sheet metal and points out the advantages and disadvantages of current experiments and theories. According to this, a method that integrates the finite element simulation and experiment was used to research the forming limit diagrams of the sheet metal under complex strain paths. Taking the rear hanger that undergoes twice stamping as an example, the strain paths of the dangerous point of the rear hanger is investigated. Finally, the forming method of the rear hanger is confirmed. Results indicate that finite element method (FEM) can achieve the complex strain paths and different strain paths will have great impacts on the result of the sheet metal forming.

关键词： dangerous forming method different hanger forming

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Digital high-efficiency print forming method and device for multi-material casting molds

Zhongde SHAN, Zhi GUO, Dong DU, Feng LIU, Wenjiang LI

《机械工程前沿（英文）》 2020年第15卷第2期页码 328-337 doi: 10.1007/s11465-019-0574-6

摘要： Sand mold 3D printing technology based on the principle of droplet ejection has undergone rapid development in recent years and has elicited increasing attention from engineers and technicians. However, current sand mold 3D printing technology exhibits several problems, such as single-material printing molds, low manufacturing efficiency, and necessary post-process drying and heating for the manufacture of sand molds. This study proposes a novel high-efficiency print forming method and device for multi-material casting molds. The proposed method is specifically related to the integrated forming of two-way coating and printing and the short-flow manufacture of roller compaction and layered heating. These processes can realize the high-efficiency print forming of high-performance sand molds. Experimental results demonstrate that the efficiency of sand mold fabrication can be increased by 200% using the proposed two-way coating and printing method. The integrated forming method for layered heating and roller compaction presented in this study effectively shortens the manufacturing process for 3D-printed sand molds, increases sand mold strength by 63.8%, and reduces resin usage by approximately 30%. The manufacture of multi-material casting molds is demonstrated on typical wheeled cast-iron parts. This research provides theoretical guidance for the engineering application of sand mold 3D printing.

关键词： multi-material casting mold 3D printing efficient print forming method

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Formation mechanism and modeling of surface waviness in incremental sheet forming

《机械工程前沿（英文）》 2022年第17卷第2期 doi: 10.1007/s11465-022-0679-1

摘要： Improving and controlling surface quality has always been a challenge for incremental sheet forming (ISF), whereas the generation mechanism of waviness surface is still unknown, which impedes the widely application of ISF in the industrial field. In this paper, the formation mechanism and the prediction of waviness are both investigated through experiments, numerical simulation, and theoretical analysis. Based on a verified finite element model, the waviness topography is predicted numerically for the first time, and its generation is attributed to the residual bending deformation through deformation history analysis. For more efficient engineering application, a theoretical model for waviness height is proposed based on the generation mechanism, using a modified strain function considering deformation modes. This work is favorable for the perfection of formation mechanism and control of surface quality in ISF.

关键词： surface waviness incremental sheet forming numerical simulation formation mechanism deformation history

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FEM-based strain analysis study for multilayer sheet forming process

Rongjing ZHANG,Lihui LANG,Rizwan ZAFAR

《机械工程前沿（英文）》 2015年第10卷第4期页码 373-379 doi: 10.1007/s11465-015-0371-9

摘要：

Fiber metal laminates have many advantages over traditional laminates (e.g., any type of fiber and resin material can be placed anywhere between the metallic layers without risk of failure of the composite fabric sheets). Furthermore, the process requirements to strictly control the temperature and punch force in fiber metal laminates are also less stringent than those in traditional laminates. To further explore the novel method, this study conducts a finite element method-based (FEM-based) strain analysis on multilayer blanks by using the 3A method. Different forming modes such as wrinkling and fracture are discussed by using experimental and numerical studies. Hydroforming is used for multilayer forming. The Barlat 2000 yield criteria and DYNAFORM/LS-DYNA are used for the simulations. Optimal process parameters are determined on the basis of fixed die-binder gap and variable cavity pressure. The results of this study will enhance the knowledge on the mechanics of multilayer structures formed by using the 3A method and expand its commercial applications.

关键词： finite element method (FEM) strain analysis multilayer sheet forming

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Hybrid forming mechanism of patternless casting and laser cladding

Zhongde SHAN, Fuzhen SUN, Yang LIU

《机械工程前沿（英文）》 2019年第14卷第4期页码 393-401 doi: 10.1007/s11465-019-0550-1

摘要： In accordance with the requirement of manufacturing dies quickly and economically, a hybrid forming method of stamping dies for automobile panels is proposed. The method combines digital patternless casting and high-power laser cladding. An experimental study is conducted on the hybrid forming process and its trial production and application in the manufacturing of stamping dies for typical panels. Results prove that the laser cladding layer exceeds HRC60 (Rockwell hardness) and thus meets the production efficiency requirement of automobile dies. The rate of defects is well controlled. Compared with traditional technology, this technology has remarkable advantages and advancement.

关键词： patternless casting laser cladding hybrid forming rapid tooling

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Highlight yield forming and innovative technologies in tropical crops

Wenquan WANG

《农业科学与工程前沿（英文）》 2016年第3卷第4期页码 283-284 doi: 10.15302/J-FASE-2016128

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Properties and effect of forming sewage sludge into lightweight ceramics

Min YUE, Qinyan YUE, Yuanfeng QI, Baoyu GAO, Hui YU

《环境科学与工程前沿（英文）》 2012年第6卷第1期页码 117-124 doi: 10.1007/s11783-010-0220-3

摘要： In this work we investigated the chemical, thermal and toxic properties of dried sewage sludge (DSS), the preparation and properties of lightweight sludge ceramic (LSC) and the mechanisms of action of the organic and inorganic foaming agents (OFAs and IFAs). The chemical components and thermal properties of the raw materials were studied by Energy Dispersive X-ray Detection (EDX) and Thermogravimetric Analysis and Differential Scanning Calorimetry (DSC/TGA). The mineral phases of the raw materials and the formed ceramics were determined by X-ray Diffraction (XRD). The leaching characteristics of heavy metals were investigated with Inductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES). Different ratios of DSS and clay were mixed and pressed into raw pellets. After drying and preheating treatment, the raw pellets were sintered at 1150°C for 10 min. The physical properties of LSC (50 wt% DSS added) were tested. The results showed that when the addition of DSS was above 50 wt%, LSC began to shrink, and a maximum density occurred. The environmental safety of LSC was satisfactory. XRD showed that some new mineral phases formed in the LSC. Observation of the microstructure by Scanning Electron Microscope (SEM) indicated that the body of LSC was porous.

关键词： sludge foaming agents ceramics preheating process

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Transient performance comparison of grid-forming converters with different FRT control strategies

《能源前沿（英文）》 2023年第17卷第2期页码 239-250 doi: 10.1007/s11708-022-0856-2

摘要： Grid-forming converters (GFMs) are faced with the threat of transient inrush current and synchronization instability issues when subjected to grid faults. Instead of disconnecting from the grid unintentionally, GFMs are required to have fault ride through (FRT) capability to maintain safe and stable operation in grid-connected mode during grid fault periods. In recent studies, different FRT control strategies with distinguishing features and that are feasible for different operation conditions have been proposed for GFMs. To determine their application scope, an intuitive comparison of the transient performance of different FRT control strategies is presented in this paper. First, three typical FRT control strategies (virtual impedance, current limiters, and mode-switching control) are introduced and transient mathematical models are established. A detailed comparison analysis on transient inrush current and transient synchronization stability is then presented. The results will be useful for guiding the selection and design of FRT control strategies. Finally, simulation results based on PSCAD/EMTDC are considered to verify the correctness of the theoretical analysis.

关键词： grid-forming converters (GFMs) fault ride through (FRT) transient stability transient inrush current transient modeling

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Isolation and application of predatory

Ran Yu, Shiwen Zhang, Zhoukai Chen, Chuanyang Li

《环境科学与工程前沿（英文）》 2017年第11卷第1期 doi: 10.1007/s11783-017-0900-3

摘要： Indigenous predatory BALO strains were successfully isolated from activated sludge. Sludge SRF and CST were significantly reduced by BALOs induced biolysis process. The increase of BALO input dosage promoted the sludge biolysis efficiency. Sludge biolysis disintegrated flocs and lysed cells for internal water release. The optimal sludge biolysis time was 24 h and no pH adjustment was needed. -and-like organisms (BALOs) are a group of ubiquitous and obligate predatory bacteria and commonly used as biocontrol agents. In this study, an efficient, environmental-friendly, and convenient BALOs encouraged municipal waste sludge biolysis pretreatment technique was developed and investigated for dewaterability enhancement of excess waste sludge. The indigenous predatory BALOs were successfully isolated from the sludge for biolysis treatment. Without any chemical addition or pH adjustment, the sludge specific resistance (SRF) and capillary suction time (CST) were significantly reduced by as high as 53.4% and 23.8%, respectively within 24 h’s treatment, which would further be lowered with the increase of BALOs input dosage. However, the continuous extension of reaction time would worsen the sludge dewaterability. The decreases of SRF and CST accompanied with the increases of sludge disintegration degree and soluble chemical oxygen demand, nitrogen, and phosphorus concentrations all emphasized the contributions of BALOs’ predation activities to sludge disturbance, cell lysis, and consequently the release of sludge intracellular water to finally effectively improve the sludge dewaterability and disposal efficiency.

关键词： Bdellovibrio-and-like organisms (BALOs) Biolysis Activated sludge Dewaterability Predation

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复杂曲面薄壁构件流体压力成形理论与技术研究进展 Review

苑世剑

《工程（英文）》 2021年第7卷第3期页码 358-366 doi: 10.1016/j.eng.2020.08.014

摘要：

面向航空航天、汽车和高速列车等工业领域迫切需求的管、板和壳三类典型结构以及难变形材料构件，新一代流体压力成形技术得到迅速发展。本文系统介绍了管类构件低载荷液压成形、板类构件双向加压成形、椭球壳体无模液压成形和难变形材料双调热介质成形理论与工艺的最新研究进展，重点阐述了变形行为、应力调控、缺陷控制和典型应用。此外，本文还展望了流体压力成形技术的未来发展方向，包括超大尺度非均质构件超低载荷成形、金属间化合物和高熵合金构件精密成形、智能化流体压力成形工艺与装备，以及非均质强各向异性薄壳的精确有限元仿真。

关键词：流体压力成形液压成形热介质压力成形薄壁构件应力状态

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汽车轻量化技术：铝/镁合金及其成型技术发展动态

付彭怀,彭立明,丁文江

《中国工程科学》 2018年第20卷第1期页码 84-90 doi: 10.15302/J-SSCAE-2018.01.012

摘要：

为了推动我国汽车工业轻量化进程，文章从新材料、成型新技术、新应用三个方面对铝合金、镁合金两类轻金属材料的国内外研究动态进行了回顾，分析了两类轻金属材料在汽车工业应用的阻力，提出了我国汽车工业铝/镁合金可能的发展建议。

关键词：汽车轻量化铝合金镁合金成型技术发展动态

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excessive anaerobic reaction time on anaerobic metabolism of denitrifying polyphosphate- accumulating organisms

Gang GUO, Yayi WANG, Chong WANG, Hong WANG, Mianli PAN, Shaowei CHEN

《环境科学与工程前沿（英文）》 2013年第7卷第4期页码 616-624 doi: 10.1007/s11783-013-0505-4

摘要： The short-term effect of anaerobic reaction time (AnRT) (i.e., 90, 120 and 150 min) on the denitrifying phosphorus (P) removal performance and N O production was examined using a denitrifying enhanced biologic phosphorus removal (EBPR) sludge acclimatized with mixed acetate (HAc) and propionate (Pro) (in the molar ratio 3∶1) as carbon sources. The results showed that when the AnRT was prolonged from 90 to 150 min, the anaerobic polyhydroxyalkanoate (PHA) synthesis was decreased by 15.3%. Moreover, the ineffective PHA consumption occurred in anaerobic phases and contributed to an increased accumulation and higher free nitrous acid (FNA) concentrations (≥0.001–0.0011 mg HNO -N/L) in the subsequent anoxic phases, causing a severe inhibition on anoxic P-uptake and denitrification. Accordingly, the total nitrogen (TN) and total phosphorus (TP) removal efficiencies dropped by approximately 6.3% and 85.5%, respectively; and the ratio of anoxic N O-N production to TN removal increased by approximately 3.8%. The fluorescence in situ hybridization (FISH) analysis revealed that the sludge was mainly dominated by (62.0% (SE = 1.5%)). In conclusion, the short-term excessive anaerobic reaction time negatively impacted denitrifying P removal performance and stimulated more N O production, and its effect on P removal was more obvious than that on nitrogen removal.

关键词： Denitrifying phosphorus removal anaerobic reaction time nitrous oxide polyhydroxyalkanoate free nitrous acid fluorescence in-situ hybridization

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材料塑性成形与热处理一体化工程的理论基础

徐祖耀

《中国工程科学》 2004年第6卷第1期页码 16-21

摘要：

材料塑性成形与热处理一体化工程的理论基础，主要为应力—相变—形变间冶金交互作用和力学交互作用的机制、建模以及组织与性能变化的模拟。以钢为例，介绍了应力下铁素体、珠光体相变的文献工作，并提出0.38C-Cr-Mo钢在应力下铁素体形成和珠光体相变的动力学模型以及组织变化的计算机模拟；讨论了Scheil相加性原则的不足及其修正途径；略述应力对钢中贝氏体相变及马氏体相变的影响；简介相场理论及其应用。对材料在应力下相变理论、建模与组织模拟的后续研究工作提出了展望。

关键词：塑性成形—热处理应力下相变相变建模组织模拟 Scheil原则相场理论

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金属板料激光喷丸成形新技术

周建忠,张兴权,王广龙,杨超君,张永康

《中国工程科学》 2005年第7卷第11期页码 94-97

摘要：

激光喷丸塑性成形金属板料是从激光强化发展起来的新技术。当激光诱导冲击波的峰值超过材料的动态屈服极限时，板料冲击区的表层发生微观塑性变形，导致了板料厚度方向上不均勻应力分布，使板料发生宏观变形。不同的激光脉冲参数在板料内部产生不同的残余应力，不同的残余应力使板料发生不同的变形，通过控制喷丸的工艺参数来控制板料内部应力场的精确分布，就可实现板料的精确变形。其显著特点是成形精确，且表层留有有益的残余压应力。

关键词：激光喷丸成形金属板料残余应力