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Assessment of zonal isolation risk to changes in design parameters
The Well Containment Screening Tool (WCST) focuses on well integrity evaluation after well control incident. The WCST favors a greater wall thickness and, hence, a narrower cementing annulus, potentially increasing the risk of cement loss. We develop a structured and systematic physical model to simulate and track formation damage. A simulation process is conducted to assess the sensitivity of zonal isolation risk as design parameters are changed. In this paper, a physical model involving wellbore, casing and cement fluid is developed to understand the interaction between cement fluid and the formation. Two failure metrics are defined that provide a comprehensive understanding of the zonal isolation risk. Quantitative risk assessment is implemented with Monte Carlo simulation to assess the risk of zonal isolation problems when design parameters are changed. Models of production casing and intermediate casing are studied to verify the generality of this analysis. Taking both failure metrics into consideration, sensitivity analysis for models of production casing and intermediate casing present common observations regarding changes of design parameters. Our analysis suggests that minor increases (within 0.05â) in casing thickness, due to increased outer diameter, has little influence on the risk of cement loss, as does slight decreases in mean open hole diameter (within 0.05â). To verify the generality of this approach, in addition to casing and wellbore parameters, the sensitivity to cement fluid flow rate is analyzed. We find that risk is not significantly affected by small increase of flowrate (e.g. from 40 to 100 gpm). This paper applies a novel quantitative risk analysis to assess the influence of different design parameters on zonal isolation problems. This approach, if well implemented, can help to assess the impact of changes in design parameters (e.g., casing length and depth, mud density and cement fluid density, etc.) on drilling safety. It can also help to inform drilling decisions by providing forecasts of zonal isolation risk for particular geological condition.Mechanical Engineerin
Perhaps the 1970s FOMC did what it said it did
Briefing forecasts prepared for the Federal Open Market Committee (FOMC) are used to estimate changes in the design of US monetary policy and in the implied policy target for inflation from 1970 through 1997. Both estimated policy rate responses and FOMC transcripts are consistent with intermediate targeting of monetary aggregates throughout the Great Inflation of the 1970s. The unpublished FOMC targets for M1 growth are tabulated. Empirical results support an effective inflation target of roughly 7% in the 1970s and 3% thereafter. A notable difference in the 1970s monetary policies of the US and Germany is the absence of explicit public objectives for US long-run inflation
System thermal-hydraulic modelling of the phénix dissymmetric test benchmark
Phénix is a French pool-type sodium-cooled prototype reactor; before the definitive shutdown, occurred in 2009, a final set of experimental tests are carried out in order to increase the knowledge on the operation and the safety aspect of the pool-type liquid metal-cooled reactors. One of the experiments was the Dissymmetric End-of-Life Test which was selected for the validation benchmark activity in the frame of SESAME project. The computer code validation plays a key role in the safety assessment of the innovative nuclear reactors and the Phénix dissymmetric test provides useful experimental data to verify the computer codes capability in the asymmetric thermal-hydraulic behaviour into a pool-type liquid metal-cooled reactor. This paper shows the comparison of the outcomes obtained with six different System Thermal-Hydraulic (STH) codes: RELAP5-3D©, SPECTRA, ATHLET, SAS4A/SASSYS-1, ASTEC-Na and CATHARE. The nodalization scheme of the reactor was individually achieved by the participants; during the development of the thermal-hydraulic model, the pool nodalization methodology had a special attention in order to investigate the capability of the STH codes to reproduce the dissymmetric effects which occur in each loop and into pools, caused by the azimuthal asymmetry of the boundary conditions. The modelling methodology of the participants is discussed and the main results are compared in this paper to obtain useful guide lines for the future modelling of innovative liquid metal pool-type reactors
Regime mapping and the role of the intermediate region in wall-coated microreactors
Operation of a wall-coated microreactor can occur in several mass transfer-reaction regimes. We define these regimes analytically in several planes of a multi-parametric map, taking into account the different degrees of concentration profile development, as well as the influence of non-unity orders of reaction and reactant inhibition in the kinetic law. It was found that the regions where conversion can be calculated from simplified mass transfer models are not discriminated by common results for entrance-length. We also illustrate the trade-offs that exist across this operating map concerning the catalyst design (costs associated with loading and volume) and overall system performance (evaluated in terms of reactant conversion, flow efficiency and microreactor effectiveness). It is shown that under certain conditions, the existence of moderate mass transfer resistance can be advantageous (even if internal limitations cannot be avoided), clarifying the role of the intermediate transport-reaction region
Guidelines for data collection and monitoring for asset management of New Zealand road bridges
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Timing of Pathogen Adaptation to a Multicomponent Treatment
The sustainable use of multicomponent treatments such as combination
therapies, combination vaccines/chemicals, and plants carrying multigenic
resistance requires an understanding of how their population-wide deployment
affects the speed of the pathogen adaptation. Here, we develop a stochastic
model describing the emergence of a mutant pathogen and its dynamics in a
heterogeneous host population split into various types by the management
strategy. Based on a multi-type Markov birth and death process, the model can
be used to provide a basic understanding of how the life-cycle parameters of
the pathogen population, and the controllable parameters of a management
strategy affect the speed at which a pathogen adapts to a multicomponent
treatment. Our results reveal the importance of coupling stochastic mutation
and migration processes, and illustrate how their stochasticity can alter our
view of the principles of managing pathogen adaptive dynamics at the population
level. In particular, we identify the growth and migration rates that allow
pathogens to adapt to a multicomponent treatment even if it is deployed on only
small proportions of the host. In contrast to the accepted view, our model
suggests that treatment durability should not systematically be identified with
mutation cost. We show also that associating a multicomponent treatment with
defeated monocomponent treatments can be more durable than associating it with
intermediate treatments including only some of the components. We conclude that
the explicit modelling of stochastic processes underlying evolutionary dynamics
could help to elucidate the principles of the sustainable use of multicomponent
treatments in population-wide management strategies intended to impede the
evolution of harmful populations.Comment: 3 figure
Adaptive Multicast of Multi-Layered Video: Rate-Based and Credit-Based Approaches
Network architectures that can efficiently transport high quality, multicast
video are rapidly becoming a basic requirement of emerging multimedia
applications. The main problem complicating multicast video transport is
variation in network bandwidth constraints. An attractive solution to this
problem is to use an adaptive, multi-layered video encoding mechanism. In this
paper, we consider two such mechanisms for the support of video multicast; one
is a rate-based mechanism that relies on explicit rate congestion feedback from
the network, and the other is a credit-based mechanism that relies on
hop-by-hop congestion feedback. The responsiveness, bandwidth utilization,
scalability and fairness of the two mechanisms are evaluated through
simulations. Results suggest that while the two mechanisms exhibit performance
trade-offs, both are capable of providing a high quality video service in the
presence of varying bandwidth constraints.Comment: 11 page
Heterogeneous and rate-dependent streptavidin-biotin unbinding revealed by high-speed force spectroscopy and atomistic simulations
Receptor-ligand interactions are essential for biological function and their
binding strength is commonly explained in terms of static lock-and-key models
based on molecular complementarity. However, detailed information of the full
unbinding pathway is often lacking due, in part, to the static nature of atomic
structures and ensemble averaging inherent to bulk biophysics approaches. Here
we combine molecular dynamics and high-speed force spectroscopy on the
streptavidin-biotin complex to determine the binding strength and unbinding
pathways over the widest dynamic range. Experiment and simulation show
excellent agreement at overlapping velocities and provided evidence of the
unbinding mechanisms. During unbinding, biotin crosses multiple energy barriers
and visits various intermediate states far from the binding pocket while
streptavidin undergoes transient induced fits, all varying with loading rate.
This multistate process slows down the transition to the unbound state and
favors rebinding, thus explaining the long lifetime of the complex. We provide
an atomistic, dynamic picture of the unbinding process, replacing a simple
two-state picture with one that involves many routes to the lock and
rate-dependent induced-fit motions for intermediates, which might be relevant
for other receptor-ligand bonds.Comment: 21 pages, 4 figure
Quality of Service over Specific Link Layers: state of the art report
The Integrated Services concept is proposed as an enhancement to the current Internet architecture, to provide a better Quality of Service (QoS) than that provided by the traditional Best-Effort service. The features of the Integrated Services are explained in this report. To support Integrated Services, certain requirements are posed on the underlying link layer. These requirements are studied by the Integrated Services over Specific Link Layers (ISSLL) IETF working group. The status of this ongoing research is reported in this document. To be more specific, the solutions to provide Integrated Services over ATM, IEEE 802 LAN technologies and low-bitrate links are evaluated in detail. The ISSLL working group has not yet studied the requirements, that are posed on the underlying link layer, when this link layer is wireless. Therefore, this state of the art report is extended with an identification of the requirements that are posed on the underlying wireless link, to provide differentiated Quality of Service
Optimal predictive control of water transport systems: ArrĂȘt-DarrĂ©/Arros case study
This paper proposes the use of predictive optimal control as a suitable methodology to manage efficiently transport water networks. The predictive optimal controller is implemented using MPC control techniques. The ArrĂȘt-DarrĂ©/Arros dam-river system located in the Southwest region of France is proposed as case study. A high-fidelity dynamic simulator based on the full Saint-Venant equations and able to reproduce this system is developed in MATLAB/SIMULINK to validate the performance of the developed predictive optimal control system. The control objective in the ArrĂȘt-DarrĂ©/Arros dam-river system is to guarantee an ecological flow rate at a control point downstream of the ArrĂȘt-DarrĂ© dam by controlling the outflow of this dam in spite of the unmeasured disturbances introduced by rainfalls incomings and farmer withdrawals
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