A multi-phase mesoscopic simulation model for the long-term chloride ingress and electrochemical chloride extraction

The potentially detrimental side-effects of prawn trawling are coming under increasing scrutiny in Australian waters, particularly in such ecologically sensitive areas as Queensland's Great Barrier Reef, and various restrictive measures are being suggested. Before changes are imposed on the prawning industry, the effects of trawling on the target prawn species and the long-term management of these effects need to be fully understood. Using a simulation model of a simplified prawn fishery, this paper describes the basis for the current regulatory mechanisms for Australian's prawn fisheries, in particular the manipulation of both the level and pattern of fishing effort. It is shown that even in moderately fished stocks, the fishery manager has several options, such as seasonal and nursery area closures, that are consistent with the goal of minimizing the impact of prawn trawling, while in no way penalizing the industry economically. With these in mind, possible ways of resolving or reducing the conflict with groups outside the prawning industry are discussed.

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Instant performance verification after electrochemical chloride extraction by enhanced corrosion testing

MATEC Web of Conferences ◽

10.1051/matecconf/201928903009 ◽

2019 ◽

Vol 289 ◽

pp. 03009

Author(s):

Ulrich Schneck

Keyword(s):

Treatment Time ◽

Performance Testing ◽

Chloride Content ◽

Corrosion Current ◽

Concrete Cover ◽

Chloride Ingress ◽

Corrosion Activity ◽

Multi Stage ◽

Chloride Profile ◽

Electrochemical Chloride Extraction

Electrochemical chloride extraction (ECE) is meant to re-establish the corrosion protection of concrete for the embedded reinforcement by removing chloride non-destructively and by enhancing the alkalinity of the rebar surrounding concrete. Both effects depend on various parameters, such as concrete cover, rebar spacing, chloride profile (especially if chloride ingress is deeper than the outside rebar layer) and concrete permeability. Often these parameters require long or multi-stage treatments, which basically can achieve any desired target level of chloride profile and impressed charge, but become a costly solution after a while. The acceptance criteria mentioned in CEN TS 14038-2 clause 8.6 refer to the achieved chloride content and to the amount of impressed charge, which are the conventional, easy measurable, but not direct parameters for evaluating the corrosion activity. A third parameter – the re-measurement of potentials for assessing (intended) low potential gradients and more positive average potentials – requires some weeks to months of depolarization and evaporation of water, before such a measurement can be applied successfully. A promising approach for an instant performance testing after an ECE treatment has been made on several occasions with follow-up measurements of electrolyte resistance, polarization resistance and corrosion current. Convincing changes towards significantly lower corrosion activity could be obtained (and compared to known classified values) – regardless of sometimes high residual chloride and very wet concrete. These data could be verified when re-assessed after some weeks, so enhanced corrosion measurements seem to be a useful tool for either establishing that the designed treatment time has been sufficient or to check on possible earlier termination of the treatment during a running ECE.

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Comparison Between DEXA and Finite Element Studies in the Long-Term Bone Remodeling of an Anatomical Femoral Stem

Journal of Biomechanical Engineering ◽

10.1115/1.3072888 ◽

2009 ◽

Vol 131 (4) ◽

Cited By ~ 16

Author(s):

A. Herrera ◽

J. J. Panisello ◽

E. Ibarz ◽

J. Cegoñino ◽

J. A. Puértolas ◽

...

Keyword(s):

Finite Element ◽

Bone Density ◽

Bone Mass ◽

Simulation Model ◽

Load Transfer ◽

Fe Simulation ◽

Femoral Stem ◽

Mineral Density ◽

Biomechanical Behavior

The implantation of a cemented or cementless femoral stem changes the physiological load transfer on the femur producing an effect on the bone called adaptative remodeling. The patterns of this remodeling are attributed to mechanical and biological factors, and those changes in bone mineral density have been determined in long-term densitometry studies. This technique has proved to be a useful tool able to quantify small changes in bone density in different femoral areas, and it is considered to be ideal for long-term studies. On the other hand, the finite element (FE) simulation allows the study of the biomechanical changes produced in the femur after the implantation of a femoral stem. The aim of this study was to contrast the findings obtained from a 5 year follow-up densitometry study that used a newly designed femoral stem (73 patients were included in this study), with the results obtained using a finite element simulation that reproduces the pattern of load transfer that this stem causes on the femur. In this study we have obtained a good comparison between the results of stress of FE simulation and the bone mass values of the densitometry study establishing a ratio between the increases in stress (%) versus the increases in bone density (%). Hence, the changes in bone density in the long term, compared with the healthy femur, are due to different load transfers after stem implantation. It has been checked that in the Gruen zone 7 at 5 years, the most important reduction in stress (7.85%) is produced, which coincides with the highest loss of bone mass (23.89%). Furthermore, the simulation model can be used with different stems with several load conditions and at different time periods to carry out the study of biomechanical behavior in the interaction between the stem and the femur, explaining the evolution of bone density in accordance to Wolff’s law, which validates the simulation model.

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A Generic Simulation Model of the Relative Cost-Effectiveness of ICU Versus Step-Down (IMCU) Expansion

Journal of Intensive Care Medicine ◽

10.1177/0885066617737303 ◽

2017 ◽

Vol 35 (2) ◽

pp. 191-202

Author(s):

Amin Mahmoudian-Dehkordi ◽

Somayeh Sadat

Keyword(s):

Intensive Care ◽

Cost Effectiveness ◽

Simulation Model ◽

Cost Effective ◽

Capacity Expansion ◽

Baseline Scenario ◽

Relative Cost ◽

Relative Cost Effectiveness ◽

Step Down

Background: Many jurisdictions are facing increased demand for intensive care. There are two long-term investment options: intensive care unit (ICU) versus step-down or intermediate care unit (IMCU) capacity expansion. Relative cost-effectiveness of the two investment strategies with regard to patient lives saved has not been studied to date. Methods: We expand a generic system dynamics simulation model of emergency patient flow in a typical hospital, populated with empirical evidence found in the medical and hospital administration literature, to estimate the long-term effects of expanding ICU versus IMCU beds on patient lives saved under a common assumption of 2.1% annual increase in hospital arrivals. Two alternative policies of expanding ICU by two beds versus introducing a two-bed IMCU are compared over a ten-year simulation period. Russel equation is used to calculate total cost of patients’ hospitalization. Using two possible values for the ratio of ICU to IMCU cost per inpatient day and four possible values for the percentage of patients transferred from ICU to IMCU found in the literature, nine scenarios are compared against the baseline scenario of no capacity expansion. Results: Expanding ICU capacity by two beds is demonstrated as the most cost-effective scenario with an incremental cost-effectiveness ratio of 3684 (US $) per life saved against the baseline scenario. Sensitivity analyses on the mortality rate of patients in IMCU, direct transfer of IMCU-destined patients to the ward upon completing required IMCU length of stay in the ICU, admission of IMCU patient to ICU, adding two ward beds, and changes in hospital size do not change the superiority of ICU expansion over other scenarios. Conclusions: In terms of operational costs, ICU beds are more cost effective for saving patients than IMCU beds. However, capital costs of setting up ICU versus IMCU beds should be considered for a complete economic analysis.

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