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Novel technologies for the lost foam casting process

Wenming JIANG, Zitian FAN

《机械工程前沿（英文）》 2018年 第13卷 第1期   页码 37-47 doi: 10.1007/s11465-018-0473-2

摘要：

Lost foam casting (LFC) is a green precision casting process categorized as a near net forming technology. Yet, despite its popularity, it still suffers from some technological problems, such as poor filling ability of the castings, coarse and non-dense microstructure, low mechanical properties for the Al and Mg LFC processes, and defective carburization for the low carbon steel LFC process. These drawbacks restrict the development and widespread application of the LFC process. To solve these problems, the present study developed several novel LFC technologies, namely, LFC technologies under vacuum and low pressure, vibration solidification, and pressure solidification conditions; expendable shell casting techno- logy; and preparation technology of bimetallic castings based on the LFC process. The results showed that the LFC under vacuum and low pressure evidently improved the filling ability and solved the oxidization problem of the alloys, which is suitable for producing complex and thin-wall castings. The vibration and pressure solidifications increased the compactness of the castings and refined the microstructure, significantly improving the mechanical properties of the castings. The expendable shell casting technology could solve the pore, carburization, and inclusion defects of the traditional LFC method, obtaining castings with acceptable surface quality. Moreover, the Al/Mg and Al/Al bimetallic castings with acceptable metallurgical bonding were successfully fabricated using the LFC process. These proposed novel LFC technologies can solve the current technological issues and promote the technological progress of the LFC process.

关键词： LFC under vacuum and low pressure     vibration solidification     pressure solidification     expendable shell casting     bimetallic castings    

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Lateral displacement of soft ground under vacuum pressure and surcharge load

Chin-Yee ONG, Jin-Chun CHAI

《结构与土木工程前沿（英文）》 2011年 第5卷 第2期   页码 239-248 doi: 10.1007/s11709-011-0110-1

摘要： Surcharge load (e.g. embankment fill) will induce settlement and outward lateral displacement, while vacuum pressure will induce settlement and inward lateral displacement of a ground. Ideally, combination of surcharge load and vacuum pressure can reduce or minimize the lateral displacement. Laboratory large scale model (length: 1.50 m, width: ~0.62 m, height: 0.85 m) tests and finite element analyses (FEA) were conducted to investigate the main influencing factors on lateral displacement of a soft clayey ground under the combination of vacuum pressure and surcharge load. For the conditions investigated, the results indicate that the outward lateral displacement increases with the increase of the ratio of surcharge load to vacuum pressure ( ) and the loading rate of the surcharge load ( ). Also, it is shown that for a given and condition, lateral displacement reduces with the increase of the initial undrained shear strength ( ) of the ground. To predict the lateral displacement of a ground under the combination of surcharge load and vacuum pressure, the loading conditions in terms of and , and value of the ground have to be considered.

关键词： vacuum consolidation     lateral displacement     PVD     finite element analysis     surcharge load    

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Catalytic ozonation of reactive red X-3B in aqueous solution under low pressure: decolorization and OH

Hong SUN,Min SUN,Yaobin ZHANG,Xie QUAN

《环境科学与工程前沿（英文）》 2015年 第9卷 第4期   页码 591-595 doi: 10.1007/s11783-014-0694-5

摘要： Catalytic ozonation of Reactive Red X-3B in aqueous solution had been carried out in an ozone oxidation reactor where Mn-Fe-ceramic honeycomb was used as the catalysts. The presence of Mn-Fe-ceramic honeycomb catalyst could obviously improve the decoloration efficiency of Reactive Red X-3B and the utilization efficiency of ozone compared to the results from non-catalytic ozonation. Adsorption of Reactive Red X-3B had no obviously influence on the degradation efficiency. Addition of tert-butanol significantly decreased the degradation efficiency, indicating that the degradation of Reactive Red X-3B followed the mechanism of hydroxyl radical (OH·) oxidation. The operating variables such as reaction pressure and ozone supply had a positive influence on the degradation efficiency, mainly attributing to facilitate the ozone decomposition and OH· formation.

关键词： catalytic ozonation     reactive red X-3B     ceramic honeycomb     hydroxyl radical (OH·)    

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Experiments on the effect of the pressure on the mineral transformation of coal ash under the different

Nijie JING, Qinhui WANG, Zhongyang LUO, Tao JIE, Xiaomin LI, Kefa CEN

《化学科学与工程前沿（英文）》 2010年 第4卷 第4期   页码 394-399 doi: 10.1007/s11705-010-0505-x

摘要： This paper investigated the effect of the pressures, reaction atmospheres and coal ash species on the ash fusibility with high-pressure thermogravimetric analysis (PTGA) apparatus and X-ray diffraction (XRD) analysis. Each specimen analyzed by XRD was observed for the mineral conversion and formation of new minerals with the pressures under different atmospheres. These results indicate that the pressure restrains the transformation and decomposition of minerals. Many low-temperature minerals are still present under the elevated pressure. The different reaction atmospheres have different effects on the formation of coal ash minerals. Under the N atmosphere, the present microcline may decrease the melting temperature of coal ash. And later, it transforms into sanidine at high pressure; thus, the melting temperature of coal ash may increase. Under the CO atmosphere, the minerals such as microcline, lomonitite, geothite and illite are still present with the increase in pressure; this may reduce the melting temperature. While under the H O atmosphere, there are magnetite and anorthoclase, which may produce the low-temperature eutectics decreasing the melting temperature. The coal ash abundance in basic oxides or higher SiO , Fe O , K O and Na O has lower melting temperature. While the ash sample with more SiO and Al O and less Fe O and basic oxides may lead to higher melting temperature.

关键词： ash fusibility     XRD analysis     PTGA     low-temperature eutectic    

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低真空管道高速磁悬浮系统技术发展研究

冯仲伟,方兴,李红梅,程爱君,潘永杰

《中国工程科学》 2018年 第20卷 第6期   页码 105-111 doi: 10.15302/J-SSCAE-2018.06.017

摘要：

轮轨式是目前轨道交通技术体系的主流，但由于空气阻力、轮轨黏着、运行噪声等问题的限制，在现有的技术水平下，难以经济地实现运营速度大幅度提高。为满足更高经济运行速度的需求，在利用磁悬浮技术减少轮轨摩擦、振动的基础上，构建低真空运行环境以减小空气阻力和噪声是未来更高速度轨道交通技术发展的重要方向。本文阐述了发展低真空管道高速磁悬浮系统的意义，研究了其技术特点、发展现状，分析了低真空管道高速磁悬浮系统的科学问题和关键技术，并提出了在国家层面立项研究、建设试验线和国家级实验室的政策建议。

关键词： 轨道交通     低真空管道     高速磁悬浮     系统技术    

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Theoretical study of failure in composite pressure vessels subjected to low-velocity impact and internalpressure

Roham RAFIEE, Hossein RASHEDI, Shiva REZAEE

《结构与土木工程前沿（英文）》 2020年 第14卷 第6期   页码 1349-1358 doi: 10.1007/s11709-020-0650-3

摘要： A theoretical solution is aimed to be developed in this research for predicting the failure in internally pressurized composite pressure vessels exposed to low-velocity impact. Both in-plane and out-of-plane failure modes are taken into account simultaneously and thus all components of the stress and strain fields are derived. For this purpose, layer-wise theory is employed in a composite cylinder under internal pressure and low-velocity impact. Obtained stress/strain components are fed into appropriate failure criteria for investigating the occurrence of failure. In case of experiencing any in-plane failure mode, the evolution of damage is modeled using progressive damage modeling in the context of continuum damage mechanics. Namely, mechanical properties of failed ply are degraded and stress analysis is performed on the updated status of the model. In the event of delamination occurrence, the solution is terminated. The obtained results are validated with available experimental observations in open literature. It is observed that the sequence of in-plane failure and delamination varies by increasing the impact energy.

关键词： composite pressure vessel     low-velocity impact     failure     theoretical solution     progressive damage modeling    

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A biofilter model for simultaneous simulation of toluene removal and bed pressure drop under varied inlet

Jinying XI,Insun KANG,Hongying HU,Xian ZHANG

《环境科学与工程前沿（英文）》 2015年 第9卷 第3期   页码 554-562 doi: 10.1007/s11783-014-0671-z

摘要： In this study, a biofiltration model including the effect of biomass accumulation and inert biomass growth is developed to simultaneously predict the Volatile Organic Compounds (VOCs) removal and filter bed pressure drop under varied inlet loadings. A laboratory-scale experimental biofilter for gaseous toluene removal was set up and operated for 100 days with inlet toluene concentration ranging from 250 to 2500 mg?m . According to sensitivity analysis based on the model, the VOCs removal efficiency of the biofilter is more sensitive to Henry’s constant, the specific surface area of the filter bed and the thickness of water layer, while the filter bed pressure drop is more sensitive to biomass yield coefficient and original void fraction. The calculated toluene removal efficiency and bed pressure drop satisfactorily fit the experimental data under varied inlet toluene loadings, which indicates the model in this study can be used to predict VOCs removal and bed pressure drop simultaneously. Based on the model, the effect of mass-transfer parameters on VOCs removal and the stable-run time of a biofilter are analyzed. The results demonstrate that the model can function as a good tool to evaluate the effect of biomass accumulation and optimize the design and operation of biofilters.

关键词： Volatile Organic Compounds (VOCs)     biofilters     modelling     biomass accumulation     pressure drop    

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Ionic strength directed self-assembled polyelectrolyte single-bilayer membrane for low-pressure nanofiltration

《化学科学与工程前沿（英文）》 2022年 第16卷 第5期   页码 699-708 doi: 10.1007/s11705-021-2093-3

摘要： Layer-by-layer assembly is a versatile technique for fabricating nanofiltration membranes, where multiple layers of polyelectrolytes are usually required to achieve reasonable separation performance. In this work, an ionic strength directed self-assembly procedure is described for the preparation of nanofiltration membranes consisting of only a single bilayer of poly(diallyldimethylammoniumchloride) and poly(sodium-4-styrenesulfoate). The influence of background ionic strength as well as membrane substrate properties on the formation of single-bilayer membranes are systematically evaluated. Such a simplified polyelectrolyte deposition procedure results in membranes having outstanding separation performance with permeating flux of 14.2 ± 1.5 L∙m–2∙h–1∙bar–1 and Na2SO4 rejection of 97.1% ± 0.8% under a low applied pressure of 1 bar. These results surpass the ones for conventional multilayered polyelectrolyte membranes. This work encompasses an investigation of ionic strength induced coiling of the polyelectrolyte chains and emphasizes the interplay between-polyelectrolyte chain configuration and substrate pore profile. It thus introduces a new concept on the control of membrane fabrication process toward high performance nanofiltration.

关键词： layer-by-layer self-assembly     single bilayer     nanofiltration membrane     desalination    

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Using mRNA to investigate the effect of low-pressure ultraviolet disinfection on the viability of

Chao Yang, Wenjun Sun, Xiuwei Ao

《环境科学与工程前沿（英文）》 2019年 第13卷 第2期 doi: 10.1007/s11783-019-1111-x

摘要：

UV can induce damages on mRNA consistently among different genes.

SOS response was more active after UV treatment.

Programmed cell death was not found to be more active after UV treatment.

关键词： UV disinfection     Viability     mRNA     SOS response     Programmed cell death    

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Study of the robustness of a low-temperature dual-pressure process for removal of CO

Stefania Moioli, Laura A. Pellegrini, Paolo Vergani, Fabio Brignoli

《化学科学与工程前沿（英文）》 2018年 第12卷 第2期   页码 209-225 doi: 10.1007/s11705-017-1688-1

摘要： The growing use of energy by most of world population and the consequent increasing demand for energy are making unexploited low quality gas reserves interesting from an industrial point of view. To meet the required specifications for a natural gas grid, some compounds need to be removed from the sour stream. Because of the high content of undesired compounds (i.e., CO ) in the stream to be treated, traditional purification processes may be too energy intensive and the overall system may result unprofitable, therefore new technologies are under study. In this work, a new process for the purification of natural gas based on a low temperature distillation has been studied, focusing on the dynamics of the system. The robustness of the process has been studied by dynamic simulation of an industrial-scale plant, with particular regard to the performances when operating conditions are changed. The results show that the process can obtain the methane product with a high purity and avoid the solidification of carbon dioxide.

关键词： CO2 capture     innovative process     cryogenic distillation     dynamic simulation     solid-liquid-vapor equilibrium    

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Simulation of flow excursion and thermal siphon under natural circulation condition with lower pressure

WANG Jianjun, YANG Xingtuan, JIANG Shengyao

《能源前沿（英文）》 2008年 第2卷 第2期   页码 169-173 doi: 10.1007/s11708-008-0044-z

摘要： The simulation of flow excursion was conducted under HRTL-5 condition. The mechanism analysis and the simulation of thermal siphon process were also performed. The result shows that the computer code can be used to simulate the static instability of a natural circulation system and the simulation of flow excursion almost conforms to the experiment result.

关键词： HRTL-5     experiment     circulation     simulation     thermal    

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Simultaneous nitrification and denitrification in activated sludge system under low oxygen concentration

ZHANG Peng, ZHOU Qi

《环境科学与工程前沿（英文）》 2007年 第1卷 第1期   页码 49-52 doi: 10.1007/s11783-007-0009-1

摘要： Simultaneous nitrification and denitrification (SND), which is more economical compared with the traditional method for nitrogen removal, is studied in this paper. In order to find the suitable conditions of this process, a mixed flow activated sludge system under low oxygen concentration is investigated, and some key control parameters are examined for nitrogen removal from synthetic wastewater. The results show that SND is accessible when oxygen concentration is 0.3 0.8 mg/L. The nitrogen removal rate can be obtained up to 66.7% with solids retention time (SRT) of 45 d, C/N value of 10, and F/M ratio of 0.1 g COD/(g MLSS·d). Theoretical analysis indicates that SND is a physical phenomenon and governed by oxygen diffusion in flocs.

关键词： synthetic wastewater     accessible     Simultaneous nitrification     MLSS·d     diffusion    

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Spray characteristics of high-pressure swirl injector fueled with alcohol

WANG Xibin, CHEN Wansheng, GAO Jian, JIANG Deming, HUANG Zuohua

《能源前沿（英文）》 2007年 第1卷 第1期   页码 105-112 doi: 10.1007/s11708-007-0012-z

摘要： The spray characteristics of methanol and ethanol with high-pressure swirl injector were explored experimentally and numerically. Experimental results show that the spray characteristics of methanol and ethanol had displayed the same trends as that of gasoline. Under the low back-pressure ambient conditions, the spray behavior exhibited a hollow cone with wide spray angle and initial spray slug at the tip, while the spray presented a solid cone in the case of high back-pressure. Vortexes in the opposite direction existed in the rear part of the spray under low back-pressure ambient conditions while the vortexes formed in the middle part under high back-pressure ambient conditions. Experiments also showed that methanol had the largest cone angle, while ethanol and gasoline presented almost the same cone angle. Simulation results indicated that methanol and ethanol had a slightly larger Sauter mean diameter (SMD) than that of gasoline with swirl injector. The SMD profile of methanol coincided well with that of ethanol under low back-pressure ambient conditions, but displayed a slightly larger value under high back-pressure due to fuel evaporation. Numerical simulation could successfully demonstrate the spray characteristics of high-pressure swirl injector for methanol and ethanol fuels.

关键词： low back-pressure     diameter     initial spray     hollow     middle    

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Experimental study and product analysis of lignocellulosic biomass hydrolysis under extremely low acids

WANG Shurong, LUO Zhongyang, CEN Kefa, ZHUANG Xinshu

《能源前沿（英文）》 2008年 第2卷 第3期   页码 268-272 doi: 10.1007/s11708-008-0046-x

摘要： Using our self-designed facility for lignocellulosic biomass hydrolysis under extremely low acid, and under the optimal reaction conditions of hemicellulose and cellulose determined by xylan and quantitative filter paper as the model, two-step dilute acid hydrolysis was carried out in detail on pine, fast-growing poplar and maize straw. The corresponding conversion ratio is 41.78%, 57.84% and 53.44% and the total reducing sugar conversion ratio is 39.28%, 42.83% and 23.82% respectively. Simultaneously, sugar component analysis of the products was performed by high performance liquid chromatography (HPLC) and monosaccharide and oligosaccharide content were compared. Finally, poplar hydrolysis residues were analyzed by proximate and ultimate analysis.

关键词： HPLC     oligosaccharide     lignocellulosic     chromatography     reducing    

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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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标题 作者 时间 类型 操作

Novel technologies for the lost foam casting process

Wenming JIANG, Zitian FAN

期刊论文

Lateral displacement of soft ground under vacuum pressure and surcharge load

Chin-Yee ONG, Jin-Chun CHAI

期刊论文

Catalytic ozonation of reactive red X-3B in aqueous solution under low pressure: decolorization and OH

Hong SUN,Min SUN,Yaobin ZHANG,Xie QUAN

期刊论文

Experiments on the effect of the pressure on the mineral transformation of coal ash under the different

Nijie JING, Qinhui WANG, Zhongyang LUO, Tao JIE, Xiaomin LI, Kefa CEN

期刊论文

低真空管道高速磁悬浮系统技术发展研究

冯仲伟,方兴,李红梅,程爱君,潘永杰

期刊论文

Theoretical study of failure in composite pressure vessels subjected to low-velocity impact and internalpressure

Roham RAFIEE, Hossein RASHEDI, Shiva REZAEE

期刊论文

A biofilter model for simultaneous simulation of toluene removal and bed pressure drop under varied inlet

Jinying XI,Insun KANG,Hongying HU,Xian ZHANG

期刊论文

Ionic strength directed self-assembled polyelectrolyte single-bilayer membrane for low-pressure nanofiltration

期刊论文

Using mRNA to investigate the effect of low-pressure ultraviolet disinfection on the viability of

Chao Yang, Wenjun Sun, Xiuwei Ao

期刊论文

Study of the robustness of a low-temperature dual-pressure process for removal of CO

Stefania Moioli, Laura A. Pellegrini, Paolo Vergani, Fabio Brignoli

期刊论文

Simulation of flow excursion and thermal siphon under natural circulation condition with lower pressure

WANG Jianjun, YANG Xingtuan, JIANG Shengyao

期刊论文

Simultaneous nitrification and denitrification in activated sludge system under low oxygen concentration

ZHANG Peng, ZHOU Qi

期刊论文

Spray characteristics of high-pressure swirl injector fueled with alcohol

WANG Xibin, CHEN Wansheng, GAO Jian, JIANG Deming, HUANG Zuohua

期刊论文

Experimental study and product analysis of lignocellulosic biomass hydrolysis under extremely low acids

WANG Shurong, LUO Zhongyang, CEN Kefa, ZHUANG Xinshu

期刊论文

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

期刊论文