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Understanding the behavior of recycled aggregate concrete by using thermogravimetric analysis

Subhasis PRADHAN, Shailendra KUMAR, Sudhirkumar V. BARAI

《结构与土木工程前沿（英文）》 2020年 第14卷 第6期   页码 1561-1572 doi: 10.1007/s11709-020-0640-5

摘要： The physio-chemical changes in concrete mixes due to different coarse aggregate (natural coarse aggregate and recycled coarse aggregate (RCA)) and mix design methods (conventional method and Particle Packing Method (PPM)) are studied using thermogravimetric analysis of the hydrated cement paste. A method is proposed to estimate the degree of hydration ( ) from chemically bound water ( ). The PPM mix designed concrete mixes exhibit lower . Recycled aggregate concrete (RAC) mixes exhibit higher and after 7 d of curing, contrary to that after 28 and 90 d. The chemically bound water at infinite time ( ) of RAC mixes are lower than the respective conventional concrete mixes. The lower , Ca(OH) bound water, free Ca(OH) content and FT-IR analysis substantiate the use of pozzolanic cement in the parent concrete of RCA. The compressive strength of concrete and cannot be correlated for concrete mixes with different aggregate type and mix design method as the present study confirms that the degree of hydration is not the only parameter which governs the macro-mechanical properties of concrete. In this regard, further study on the influence of interfacial transition zone, voids content and aggregate quality on macro-mechanical properties of concrete is needed.

关键词： recycled aggregate concrete     Particle Packing Method     thermogravimetric analysis     chemically bound water     degree of hydration     Fourier transform infrared spectroscopy    

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Effects of environmental factors on the production and release of matrix-bound phosphine from lake sediments

GENG Jinju, WANG Qiang, WANG Xiaorong, NIU Xiaojun

《环境科学与工程前沿（英文）》 2007年 第1卷 第1期   页码 120-124 doi: 10.1007/s11783-007-0022-4

摘要： Effects of pH, temperature, and oxygen on the production and release of phosphine in eutrophic lake sediments were investigated under laboratory tests. Results indicated that the elimination of matrix-bound phosphine was accelerated under initial pH 1 or 12. Phosphine levels could reach maximum under initial pH 10. The contents of phosphine increased with the addition of alkali under pH 4 12. The rates of phosphine production and release from lake sediments varied with temperature. 20?C was the most favorable temperature for the production of matrix-bound phosphine. Oxygen showed little effect on matrix-bound phosphine. Matrix-bound phosphine concentrations in lake sediments were concluded to be dependent on a balance of natural generation and depletion processes.
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化学强化反冲洗缓解超滤处理含藻地表水的膜污染机制及调控——从小试到生产示范研究 Article

唐小斌, 郭铁城, 常海庆, 岳霄, 王金龙, 于海宽, 谢冰涵, 朱学武, 李圭白, 梁恒

《工程（英文）》 2022年 第19卷 第12期   页码 40-49 doi: 10.1016/j.eng.2021.01.013

摘要：

超滤（UF）工艺已广泛应用于饮用水处理中。然而，藻类及其分泌物会导致严重的膜污染，在实际生产过程中对超滤工艺构成巨大挑战。本文开发了一种简单实用的化学强化反冲洗（CEB）技术，考察了次氯酸钠（NaClO）、氯化钠（NaCl）、氢氧化钠（NaOH）、柠檬酸钠及其组合对藻源膜污染的控制效能。结果表明，化学清洗剂的类型是影响超滤膜水力不可逆膜污染（HIMF）的关键因素。其中，NaClO 对HIMF的控制效果最佳，其次是NaCl。此外，与单独使用NaClO相比，将NaClO与NaCl、NaOH或柠檬酸钠等组合使用对HIMF的控制效果并没有明显提升。NaClO 的最优投加量和投加方案为10 mg∙L−1，且最佳投加频次为每天两次。通过开展长周期的中试和生产实验进一步表明CEB技术可有效缓解藻源膜污染，尤其是HIMF。此外，与不添加化学药剂的常规水力反冲洗相比，CEB技术主要是通过氧化作用有效地去除包括生物聚合物、腐殖质和蛋白质类物质等在内的有机污染物，削弱有机污染物与膜表面之间的黏附力，从而显著降低HIMF。因此，CEB技术可在低药剂条件下有效地缓解藻源膜污染，是一种有效阻控超滤处理含藻地表水过程膜污染的方法。

关键词： 超滤     膜污染     水力不可逆的膜污染     化学强化反冲洗（CEB）     含有藻类的地表水    

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Upper bound solution to seismic active earth pressure of submerged backfill subjected to partial drainage

《结构与土木工程前沿（英文）》 2021年 第15卷 第6期   页码 1480-1493 doi: 10.1007/s11709-021-0776-y

摘要： In waterfront geotechnical engineering, seismic and drainage conditions must be considered in the design of retaining structures. This paper proposes a general analytical method to evaluate the seismic active earth pressure on a retaining wall with backfill subjected to partial steady seepage flow under seismic conditions. The method comprises the following steps: i) determination of the total head, ii) upper bound solution of seismic active earth thrust, and iii) deduction for the earth pressure distribution. The determination of total head h(x,z) relies on the Fourier series expansions, and the expressions of the seismic active earth thrust and pressure are derived by using the upper bound theorem. Parametric studies reveal that insufficient drainage and earthquakes are crucial factors that cause unfavorable earth pressure. The numerical results confirm the validity of the total head distribution. Comparisons indicate that the proposed method is consistent with other relevant existing methods in terms of predicting seismic active earth pressure. The method can be applied to the seismic design of waterfront retaining walls.

关键词： seismic active earth pressure     partial seepage flow     pore pressure     anisotropy     upper bound theorem    

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Effect of undercut on the lower bound stability of vertical rock escarpment using finite element and

Shuvankar DAS; Debarghya CHAKRABORTY

《结构与土木工程前沿（英文）》 2022年 第16卷 第8期   页码 1040-1055 doi: 10.1007/s11709-022-0841-1

摘要： In the present study, the stability of a vertical rock escarpment is determined by considering the influence of undercut. Lower bound finite element limit analysis in association with Power Cone Programming (PCP) is applied to incorporate the failure of rock mass with the help of the Generalized Hoek-Brown yield criterion. The change in stability due to the presence of undercut is expressed in terms of a non-dimensional stability number (σci/γH). The variations of the magnitude of σci/γH are presented as design charts by considering the different magnitudes of undercut offset (H/vu and wu/vu) from the vertical edge and different magnitudes of Hoek-Brown rock mass strength parameters (Geological Strength Index (GSI), rock parameter (mi,), Disturbance factor (D)). The obtained results indicate that undercut can cause a severe stability problem in rock mass having poor strength. With the help of regression analysis of the computed results, a simplified design equation is proposed for obtaining σci/γH. By performing sensitivity analysis for an undisturbed vertical rock escarpment, we have found that the undercut height ratio (H/vu) is the most sensitive parameter followed by GSI, undercut shape ratio (wu/vu), and mi. The developed design equation as well as design charts can be useful for practicing engineers to determine the stability of the vertical rock escarpment in the presence of undercut. Failure patterns are also presented to understand type of failure and extent of plastic state during collapse.

关键词： undercut     vertical escarpment     stability     Hoek-Brown yield criterion     PCP    

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A comparative study of the mechanical properties, fracture behavior, creep, and shrinkage of chemically

Mahdi AREZOUMANDI, Mark EZZELL, Jeffery S VOLZ

《结构与土木工程前沿（英文）》 2014年 第8卷 第1期   页码 36-45 doi: 10.1007/s11709-014-0243-0

摘要： This study presents the results of an experimental investigation that compares the mechanical properties, fracture behavior, creep, and shrinkage of a chemically-based self-consolidating concrete (SCC) mix with that of a corresponding conventional concrete (CC) mix. The CC and SCC mix designs followed conventional proportioning in terms of aggregate type and content, cement content, air content, water-cementitiuos materials ( / ) ratio, and workability. Then, using only chemical admixtures, the authors converted the CC mix to an SCC mix with all of the necessary passing, filling, flowability, and stability requirements typically found in SCC. The high fluidity was achieved with a polycarboxylate-based high-range water-reducing admixture, while the enhanced stability was accomplished with an organic, polymer-based viscosity-modifying admixture. The comparison indicated that the SCC and CC mixes had virtually identical tensile splitting strengths, flexural strengths, creep, and shrinkage. However, the SCC mix showed higher compressive strengths and fracture energies than the corresponding CC mix.

关键词： admixture     conventional concrete (CC)     creep     fracture mechanic     mechanical Properties     self-consolidating concrete (SCC)     shrinkage    

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Multi-objective optimization in a finite time thermodynamic method for dish-Stirling by branch and bound

Mohammad Reza NAZEMZADEGAN, Alibakhsh KASAEIAN, Somayeh TOGHYANI, Mohammad Hossein AHMADI, R. SAIDUR, Tingzhen MING

《能源前沿（英文）》 2020年 第14卷 第3期   页码 649-665 doi: 10.1007/s11708-018-0548-0

摘要： There are various analyses for a solar system with the dish-Stirling technology. One of those analyses is the finite time thermodynamic analysis by which the total power of the system can be obtained by calculating the process time. In this study, the convection and radiation heat transfer losses from collector surface, the conduction heat transfer between hot and cold cylinders, and cold side heat exchanger have been considered. During this investigation, four objective functions have been optimized simultaneously, including power, efficiency, entropy, and economic factors. In addition to the four-objective optimization, three-objective, two-objective, and single-objective optimizations have been done on the dish-Stirling model. The algorithm of multi-objective particle swarm optimization (MOPSO) with post-expression of preferences is used for multi-objective optimizations while the branch and bound algorithm with pre-expression of preferences is used for single-objective and multi-objective optimizations. In the case of multi-objective optimizations with post-expression of preferences, Pareto optimal front are obtained, afterward by implementing the fuzzy, LINMAP, and TOPSIS decision making algorithms, the single optimum results can be achieved. The comparison of the results shows the benefits of MOPSO in optimizing dish Stirling finite time thermodynamic equations.

关键词： dish-Stirling     finite time model     branch and bound algorithm     multi-objective particle swarm optimization (MOPSO)    

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Particle-bound polycyclic aromatic hydrocarbons in typical urban of Yunnan-Guizhou Plateau: Characterization

《环境科学与工程前沿（英文）》 2022年 第16卷 第9期 doi: 10.1007/s11783-022-1535-6

摘要：

• The sampling was conducted in city on the Yunnan-Guizhou Plateau for one year.

关键词： Particle-associated PAHs     Fine particle     Source appointment     Group analysis     Risk assessment     Biomass burning    

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Correction to: Effect of undercut on the lower bound stability of vertical rock escarpment using finite

《结构与土木工程前沿（英文）》 doi: 10.1007/s11709-023-0035-5

摘要： Correction to: Effect of undercut on the lower bound stability of vertical rock escarpment using finite element and power cone programming

关键词： finite element power     stability rock escarpment    

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Bearing and uplift capacities of under-reamed piles in soft clay underlaid by stiff clay using lower-bound

Mantu MAJUMDER, Debarghya CHAKRABORTY

《结构与土木工程前沿（英文）》 2021年 第15卷 第2期   页码 537-551 doi: 10.1007/s11709-021-0708-x

摘要： Ensuring a safe foundation design in soft clay is always a challenging task to engineers. In the present study, the effectiveness of under-reamed piles in soft clay underlaid by stiff clay is numerically studied using the lower-bound finite element limit analysis (LB FELA). The bearing and uplift capacities of under-reamed piles are estimated through non-dimensional factors and , respectively. These factors increased remarkably and marginally compared to and of the piles without bulbs when the bulb is placed in stiff and soft clay, respectively. For a given ratio of undrained cohesion of stiff to soft clay ( / ), the factors and moderately increased with the increase in the length-to-shaft-diameter ratio ( / ) and adhesion factors in soft clay ( ) and stiff clay ( ). The variation of radial stress along the pile–soil interface, distribution of axial force in the under-reamed piles, and state of plastic shear failure in the soil are also studied under axial compression and tension. The results of this study are expected to be useful for the estimation of the bearing and uplift capacities of under-reamed piles in uniform clay and soft clay underlaid by stiff clay.

关键词： bearing capacity     uplift capacity     under-reamed pile     clay     limit analysis    

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Chemically triggered life control of “smart” hydrogels through click and declick reactions

《化学科学与工程前沿（英文）》 2022年 第16卷 第9期   页码 1399-1406 doi: 10.1007/s11705-022-2149-z

摘要： The degradation of polymeric materials is recognized as one of the goals to be fulfilled for the sustainable economy. In this study, a novel methodology was presented to synthesize multiple highly cross-linked polymers (i.e., hydrogels) through amine–thiol scrambling under mild conditions. Amine-terminated poly(ethylene glycol) (PEG-NH2) was reacted with the representative conjugate acceptors to synthesize hydrogels in organic and aqueous solutions, respectively. The materials above exhibited high water-swelling properties, distributed porous structures, as well as prominent mechanical strengths. It is noteworthy that the mentioned hydrogels could be degraded efficiently in hours to release the original coupling partner, which were induced by ethylene diamine at ambient temperature through amine-amine metathesis. The recovered PEG-NH2 reagent could be employed again to regenerate hydrogels. Due to the multiple architectures and functions in polymeric synthesis, degradation and regeneration, a new generation of “smart” materials is revealed.

关键词： hydrogels     degradation     synthesis     regeneration    

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基于非关联流动法则的滑移线场及上限法研究

郑颖人,邓楚键,王敬林

《中国工程科学》 2010年 第12卷 第8期   页码 56-69

摘要：

当前岩土材料的滑移线场理论及上限法中都广泛采用经典塑性理论中的关联流动法则，由此得出应力特征线与速度滑移线一致的结论。而试验得知，岩土材料并不服从关联流动法则，因而应力特征线与速度滑移线不可能重合。文章分析了基于关联流动法则的滑移线场及上限法中存在的问题，根据广义塑性理论推导了基于非关联流动法则的滑移线场及上限法，消除了现行滑移线场理论及上限法理论中的种种矛盾。

关键词： 滑移线场     上限法     关联流动法则     非关联流动法则     广义塑性理论    

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Chemically reactive solute transfer in a boundary layer slip flow along a stretching cylinder

Swati Mukhopadhyay

《化学科学与工程前沿（英文）》 2011年 第5卷 第3期   页码 385-391 doi: 10.1007/s11705-011-1101-4

摘要： This paper presents the distribution of a solute undergoing a first order chemical reaction in an axisymmetric laminar boundary layer flow along a stretching cylinder. Velocity slip condition at the boundary is used instead of no-slip condition. Similarity transformations are used to convert the partial differential equations corresponding to momentum and concentration into highly nonlinear ordinary differential equations. Numerical solutions of these equations are obtained by the shooting method. The velocity decreases with increasing slip parameter. The skin friction as well as the mass transfer rate at the surface is larger for a cylinder than for a flat plate.

关键词： boundary layer     stretching cylinder     partial slip     mass transfer     similarity solution    

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Occurrence and removal of

Lin WANG,Yongmei LI,Xiaoling SHANG,Jing SHEN

《环境科学与工程前沿（英文）》 2014年 第8卷 第4期   页码 519-530 doi: 10.1007/s11783-013-0610-4

摘要： Six wastewater treatment plants (WWTPs) were investigated to evaluate the occurrence and removal of -nitrosodimethylamine (NDMA), NDMA formation potential (FP) and four specific NDMA precursors, dimethylamine (DMA), trimethylamine (TMA), dimethylformamide (DMFA) and dimethylaminobenzene (DMAB). DMA and tertiary amines with DMA functional group commonly existed in municipal wastewater. Chemically enhanced primary process (CEPP) had no effect on removal of either NDMA or NDMA FP. In WWTPs with secondary treatment processes, considerable variability was observed in the removal of NDMA (19%–85%) and NDMA FP (16%–76%), moreover, there was no definite relationship between the removal of NDMA and NDMA FP. DMA was well removed in all the six surveyed WWTPs; its removal efficiency was greater than 97%. For the removal of tertiary amines, biologic treatment processes with nitrification and denitrification had better removal efficiency than conventional activated sludge process. The best removal efficiencies for TMA, DMFA and DMAB were 95%, 68% and 72%, respectively. CEPP could remove 73% of TMA, 23% of DMFA and 36% of DMAB. After UV disinfection, only 17% of NDMA was removed due to low dosage of UV was applied in WWTP. Although chlorination could reduce NDMA precursors, NDMA concentration was actually increased after chlorination.

关键词： N-nitrosodimethylamine     NDMA precursors     NDMA formation potential     biological treatment process     chemically enhanced primary process    

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Acidogenic sludge fermentation to recover soluble organics as the carbon source for denitrification in wastewater treatment: Comparison of sludge types

Lin Lin, Ying-yu Li, Xiao-yan Li

《环境科学与工程前沿（英文）》 2018年 第12卷 第4期 doi: 10.1007/s11783-018-1043-x

摘要：

CEPS sludge was compared with conventional primary and secondary sludge for the VFAs yield.

Fe-based CEPS sludge exhibited the highest efficiency of organic recovery.

Fermented CEPS sludge liquor provided a sufficient carbon source for denitrification.

99% of nitrate removal was achieved based on the Fe-CEPS and sludge fermentation.

关键词： Sewage sludge     Chemically enhanced primary sedimentation (CEPS)     Acidogenic fermentation     Organic carbon recovery     Nitrogen removal    

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标题 作者 时间 类型 操作

Understanding the behavior of recycled aggregate concrete by using thermogravimetric analysis

Subhasis PRADHAN, Shailendra KUMAR, Sudhirkumar V. BARAI

期刊论文

Effects of environmental factors on the production and release of matrix-bound phosphine from lake sediments

GENG Jinju, WANG Qiang, WANG Xiaorong, NIU Xiaojun

期刊论文

化学强化反冲洗缓解超滤处理含藻地表水的膜污染机制及调控——从小试到生产示范研究

唐小斌, 郭铁城, 常海庆, 岳霄, 王金龙, 于海宽, 谢冰涵, 朱学武, 李圭白, 梁恒

期刊论文

Upper bound solution to seismic active earth pressure of submerged backfill subjected to partial drainage

期刊论文

Effect of undercut on the lower bound stability of vertical rock escarpment using finite element and

Shuvankar DAS; Debarghya CHAKRABORTY

期刊论文

A comparative study of the mechanical properties, fracture behavior, creep, and shrinkage of chemically

Mahdi AREZOUMANDI, Mark EZZELL, Jeffery S VOLZ

期刊论文

Multi-objective optimization in a finite time thermodynamic method for dish-Stirling by branch and bound

Mohammad Reza NAZEMZADEGAN, Alibakhsh KASAEIAN, Somayeh TOGHYANI, Mohammad Hossein AHMADI, R. SAIDUR, Tingzhen MING

期刊论文

Particle-bound polycyclic aromatic hydrocarbons in typical urban of Yunnan-Guizhou Plateau: Characterization

期刊论文

Correction to: Effect of undercut on the lower bound stability of vertical rock escarpment using finite

期刊论文

Bearing and uplift capacities of under-reamed piles in soft clay underlaid by stiff clay using lower-bound

Mantu MAJUMDER, Debarghya CHAKRABORTY

期刊论文

Chemically triggered life control of “smart” hydrogels through click and declick reactions

期刊论文

基于非关联流动法则的滑移线场及上限法研究

郑颖人,邓楚键,王敬林

期刊论文

Chemically reactive solute transfer in a boundary layer slip flow along a stretching cylinder

Swati Mukhopadhyay

期刊论文

Occurrence and removal of

Lin WANG,Yongmei LI,Xiaoling SHANG,Jing SHEN

期刊论文

Acidogenic sludge fermentation to recover soluble organics as the carbon source for denitrification in wastewater treatment: Comparison of sludge types

Lin Lin, Ying-yu Li, Xiao-yan Li

期刊论文