Leachability and Microstructural Analysis of Clay and Lime Stabilized/Solidified Polluted Sediment – Long-Term Performance

The objective of this study is to enable a better understanding of the effectiveness of solidification/stabilization (S/S) technique in treating polluted sediment, and provide the much needed validation of the longevity of the technology. In this research kaolinite and montmorillonite, with a certain proportion of lime, were used for S/S treatment of sediment polluted with metals. Leachability of metals was examined using the toxicity characteristic leaching procedure (TCLP) and the German standard leaching test (DIN 3841-4 S4) prescribed in national legislative. Results indicated successful S/S treatment using both clays and lime, from the aspect of all leached metals even with pH variations over time and slight changes in structural integrity of specimens. X-ray diffraction (XRD), scanning electron microscope (SEM) analyses and porosity measurement were also performed on the prepared monolithic matrices. XRD qualitative and semi-quantitative analysis proved hydration and pozzolanic product formation with increase in their content and finer crystallites formation over time. SEM analysis confirmed the presence of morphologically dense and stable structures while pore size distribution indicated on mesoporous matrices with ongoing compaction over time. Generally, structural microanalysis indicated the formation of hardened matrices over time and hydration process has been fully completed and further carbonation took place. Unconfined compressive strength measurement gave the satisfying results and matured monolite with 30 % of montmorillonite and 10 % of lime can be considered potentially applicable as non-load-bearing material. In summary, all results indicated that this kind of S/S treatment can achieve satisfactory durability and represent reliable and economically feasible technique for long-term remediation of metal polluted sediment.

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The Importance of Variables and Parameters in Radiolytic Chemical Kinetics Modeling

MRS Proceedings ◽

10.1557/proc-127-905 ◽

1988 ◽

Vol 127 ◽

Author(s):

M. G. Piepho ◽

P. J. Turner ◽

P. W. Reimus

Keyword(s):

Chemical Kinetics ◽

Rate Constants ◽

Transient Species ◽

Geologic Repository ◽

Species Concentration ◽

Waste Package ◽

Long Term Performance ◽

Term Performance ◽

Over Time

ABSTRACTRadiolysis may significantly affect the long-term performance of nuclear waste packages in a geologic repository. Radiolysis of available moisture and air in an unsaturated or saturated environment will create transient species that can significantly change the pH and/or Eh of the available moisture. These changes can influence rates of containment corrosion, waste form dissolution, and radionuclide solubilities and transport.Many of the pertinent radiochemical reactions are not completely understood, and most of the associated rate constants are poorly characterized. To help identify the important radiochemical reactions, rate constants, species, and environmental conditions, an importance theory code, SWATS (Sensitivity With Adjoint Theory-Sparse version)-LOOPCHEM, has been developed for the radiolytic chemical kinetics model in the radiolysis code LOOPCHEM. The LOOPCHEM code calculates the concentrations of various species in a radiolytic field over time. The SWATS-LOOPCHEM code efficiently calculates: 1) the importance (relative to a defined response of interest) of each species concentration over time, 2) the sensitivity of each parameter of interest, and 3) the importance of each equation in the radiolysis model. The calculated results will be used to guide future experimental and modeling work for determining the importance of radiolysis on waste package performance. A demonstration (the importance of selected concentrations and the sensitivities of selected parameters) of the SWATS-LOOPCHEM code is provided for illustrative purposes, and no attempt is made at this time to interpret the results for waste package performance assessment purposes.

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The reinforcement effect of vegetation on live cribwalls

10.5194/egusphere-egu21-5858 ◽

2021 ◽

Author(s):

Alejandro Gonzalez Ollauri ◽

Slobodan Mickovski ◽

Rohinton Emmanuel ◽

Albert Sorolla Edo

Keyword(s):

Numerical Model ◽

Native Vegetation ◽

Empirical Knowledge ◽

Reinforcement Effect ◽

Proposed Model ◽

Multi Level ◽

Long Term Performance ◽

Term Performance ◽

Over Time

Live cribwalls are Nature-based solutions consisting of timber-based structures acting as retention walls at the toe of slopes and embankments subjected to instability and erosion events. The structure of live cribwalls resembles a multi-level crib made of timber logs from different plant species (e.g. pine, spruce, hazelnut, etc.). The crib structure is then backfilled with earth materials in which locally-available plant cuttings and/or saplings are inserted to establish a dense cover of native vegetation, providing added reinforcement and stability to the cribwall over time; particularly after the complete decay of the timber structure is reached. However, the effect of vegetation on the reinforcement of live cribwalls has not been examined systematically. Information on how vegetation can contribute to reinforce cribwalls hydrologically and mechanically is essential to evaluate the long-term performance of these Nature-based solutions against hydro-meteorological hazards. In this study, we propose a novel conceptual, numerical model based on empirical knowledge to evaluate the reinforcement effect of vegetation on live cribwalls over time. We also demonstrate how the proposed model can be applied to other Nature-based solutions concerned with slope protection and erosion control, such as live gratings or palisades.

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Prediction of Bearing Lifetime Demands by Considering the Bridge Design and Location Parameters

IABSE Congress, New York, New York 2019: The Evolving Metropolis ◽

10.2749/newyork.2019.1398 ◽

2019 ◽

Author(s):

Minesh K. Patel ◽

Georgios P. Balomenos

Keyword(s):

Bridge Design ◽

Traffic Loading ◽

Location Parameters ◽

Long Term Performance ◽

Term Performance ◽

Long Term Behavior ◽

Bridge Bearings ◽

Bearing Behavior ◽

Over Time

The long-term performance and safety of bridges is of paramount importance. Researchers have placed significant focus on the degradation and deterioration of bridge materials such as steel and concrete, but significantly less is known about the long-term behavior of bridge bearings. Uncertainty in the bearing behavior over time leads to challenges about when the bearings should be inspected and potentially replaced. However, bearing demands vary greatly based on the design of the bridge (e.g. differences in bridge material, girder type, span, height, and location). This paper finds trends in lifetime bearing demands from seismic, thermal, and traffic loading when the bridge design and location parameters are considered. These results can be used to identify which of the parameters have the greatest influence on the lifetime bearing demands which can then be used, in turn, to evaluate bearing long-term performance.

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Long-Term Performance of Utah Slanted Electrode Arrays and Intramuscular Electromyographic Leads Implanted Chronically in Human Arm Nerves and Muscles

10.1101/2020.03.30.016683 ◽

2020 ◽

Cited By ~ 1

Author(s):

Jacob A. George ◽

David M. Page ◽

Tyler S. Davis ◽

Christopher C. Duncan ◽

Douglas T. Hutchinson ◽

...

Keyword(s):

Receptive Field ◽

Signal To Noise Ratio ◽

Electrode Arrays ◽

Neural Recordings ◽

Long Term Performance ◽

Term Performance ◽

Recording Electrodes ◽

Over Time ◽

Field Location

AbstractObjectiveWe explore the long-term performance and stability of seven percutanous Utah Slanted Electrode Arrays (USEAs) and intramuscular recording leads (iEMGs) implanted chronically in the residual arm nerves and muscles of three human amputees as a means to permanently restore sensorimotor function after upper-limb.ApproachWe quantify the number of functional recording and functional stimulating electrodes over time. We also calculate the signal-to-noise ratio of USEA and iEMG recordings and quantify the stimulation amplitude necessary to evoke detectable sensory percepts. Furthermore, we quantify the consistency of the sensory modality, receptive field location, and receptive field size of USEA-evoked percepts.Main ResultsIn the most recent subject, involving USEAs with technical improvements, neural recordings persisted for 502 days (entire implant duration) and the number of functional recording electrodes for one USEA increased over time. However, for six out of seven USEAs the number of functional recording electrodes decreased within the first two months after implantation. The signal-to-noise ratio of neural recordings and electromyographic recordings stayed relatively consistent over time. Sensory percepts were consistently evoked over the span of 14 months, were not significantly different in size, and highlighted the nerves’ fascicular organization. The percentage of percepts with consistent modality or consistent receptive field location between sessions (~1 month apart) varied between 0–86.2% and 9.1–100%, respectively. Stimulation thresholds and electrode impedances increased initially but then remained relatively stable over time.SignificanceThis work demonstrates improved performance of USEAs, and provides a basis for comparing the longevity and stability of USEAs to that of other neural interfaces. Although USEAs provide a rich repertoire of neural recordings and sensory percepts, performance still generally declines over time. Future work should leverage the results presented here to further improve USEA design or to develop adaptive algorithms that can maintain a high level of performance.

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Material state changes as a basis for prognosis in aeronautical structures

The Aeronautical Journal ◽

10.1017/s0001924000003444 ◽

2009 ◽

Vol 113 (1150) ◽

pp. 789-798 ◽

Cited By ~ 18

Author(s):

K. L. Reifsnider ◽

P. Fazzino ◽

P. K. Majumdar ◽

L. Xing

Keyword(s):

High Performance ◽

Structural Integrity ◽

Future Performance ◽

Material State ◽

History Of ◽

Small Set ◽

History Of Use ◽

Long Term Performance ◽

Term Performance

Abstract The long-term performance of aeronautical structures is typically discussed in terms of concepts such as structural integrity, durability, damage tolerance, fracture toughness, etc. These familiar concepts are usually addressed by considering balance equations, crack growth relationships, and constitutive equations with constant material properties, and constant or cyclically applied load conditions. Loading histories are represented by changing stress (or strain) states, only. But for many situations, especially associated with high performance aircraft, the local state of the material may also change during service, so that the properties used in those equations are functions of time and history of applied conditions. For example, local values of stiffness, strength, and conductivity are altered by material degradation to create ‘property fields’ that replace the global constants, and introduce time and history into the governing equations. The present paper will examine a small set of such problems and offer a construct for using related solutions to estimate future performance based on history of use and current material state, a concept typically called prognosis.

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Strength Behavior of Lateritic Soil Treated with Alccofine

International Journal of Engineering and Advanced Technology - Regular Issue ◽

10.35940/ijeat.a9530.109119 ◽

2019 ◽

Vol 9 (1) ◽

pp. 1995-1999

Keyword(s):

Shear Strength ◽

Structural Integrity ◽

Soil Stabilization ◽

Engineering Properties ◽

Lateritic Soil ◽

Weak Soil ◽

The Stability ◽

Long Term Performance ◽

Term Performance

One of the factors that affect the long term performance of a structure is the strength of the underlying soil strata. Presence of weak soil strata beneath the structure will affect the structural integrity. So, enhancing the engineering properties of the weak soil results in the betterment of bearing capacity of the soil. Nowadays, for improving the stability of the weak soil, various soil stabilization techniques are adopted. This paper presents an investigation of using alccofine as a soil stabilizing agent. Variation in shear strength parameters and compaction parameters of the soil is studied by adding different percentages of alccofine 1101 such as 1%, 2%, 3%, 4%, and 5%. Test results revealed that at the optimal rate of alccofine 1101, the shear strength characteristic is increased by 53.71% after a curing period of 3 days.

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Long-term performance of stabilised/solidified polluted sediment in terms of metal leachability and matrix characterization

Zastita materijala ◽

10.5937/zasmat1704556r ◽

2017 ◽

Vol 58 (4) ◽

pp. 556-563

Author(s):

Dunja Radjenovic ◽

Djurdja Kerkez ◽

Dragana Pilipovic-Tomasevic ◽

Sebastian Balos ◽

Aleksandar Dosic ◽

...

Keyword(s):

Polluted Sediment ◽

Long Term Performance ◽

Term Performance

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Identification of Top Performing Economies

Vikalpa The Journal for Decision Makers ◽

10.1177/0256090920040204 ◽

2004 ◽

Vol 29 (2) ◽

pp. 39-54

Author(s):

Ravindra H Dholakia ◽

Akhilesh S Kumar

Keyword(s):

Economic Performance ◽

Past Performance ◽

Top Performers ◽

High Inflation ◽

Overall Performance ◽

Per Capita ◽

Long Term Performance ◽

Term Performance ◽

Over Time

In the era of globalization and liberalization, important investment and business decisions have to carefully consider long-term performance and prospects of different national economies. National governments would also compete with one another on the strength of their economic performance and policies. Several organizations make regular efforts to evaluate prospects and rank countries for different purposes but research identifying the top performing economies considering different dimensions of their long-term performance is conspicuous by its absence. Using seven indicators of economic performance of 187 countries, this paper identifies the top 50 performers during the decades of 1981-90 and 1991-2000. Five of these indicators are the trend rates of growth over a decade in imports, foreign direct investment (FDI), capital formation, per capita income, and forex reserves. Average inflation rate and Human Development Index (HDI) are the remaining indicators. The selected indicators are very distinct from one another not only during the decade of eighties but also during the nineties. It is found that economic performance of countries, which was already specialized in a few dimensions, is becoming more specialized and focused during the nineties when compared to the eighties. This paper also examines the inter-relationship among the indicators over time. This study has generated findings for national policy making and for businesses to assess macroeconomic prospects. There are 26 common countries in the two sets of top 50 performers during the eighties and the nineties. High performance on the consumer inflation and/or human development front has emerged practically as a pre-condition for consistently good overall performance. On this count, it appears that a large number of the new entrants to the club of 50 top performers during the nineties are not likely to hold on to their position in the coming decade. Such emerging economies may prove to be risky. The experience of the eighties and the nineties suggests that high inflation during a decade does not deter the solid real economic performance on other dimensions during the same decade but may create problems of maintaining consistency of relative performance over time, if not checked. For predicting the overall performance of countries, past performance does not help in general. However, three indicators, viz., growth of per capita income, growth of FDI, and HDI can be predicted to some extent through past performance on various dimensions. The findings suggest the following: A trade-off exists between high inflation and future high growth and between high inflation and future high HDI. Long-term growth of investment may negatively affect the future long-term growth of output and long-term growth of forex reserves may negatively affect future long-term growth of FDI in a country. Growth causes human capital and not vice-versa. Based on the prediction of partial performance, the study identifies 15 economies likely to be among the top 50 performers in the first decade of the 21st century. Since four of the seven performance indicators do not depend on past performance, the remaining 35 top performers may spring genuine surprises. Economic environment and policies of countries during the decade would decide their relative performance.

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