| 121651. |
- Jeltsov, Marti, 1985-, et al.
(författare)
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Risk of sloshing in the primary system of a lead cooled fast reactor
- 2014
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Ingår i: PSAM 2014 - Probabilistic Safety Assessment and Management.
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Konferensbidrag (refereegranskat)abstract
- Pool-type designs of Lead-cooled Fast Reactor (LFR) aim for commercial viability by simplified engineering solutions and passive safety systems. However, such designs carry the risks related to heavy coolant sloshing in case of seismic event. Sloshing can cause (i) structural damage due to fluid-structure interaction (FSI) and (ii) core damage due to void induced reactivity insertion or due to local heat transfer deterioration. The main goal of this study is to identify the domain of seismic excitation characteristics at the reactor vessel level that can lead to exceedance of the safety limits for structural integrity and core damage. Reference pool-type LFR design used in this study is the European Lead-cooled SYstem (ELSY). Liquid lead sloshing is analyzed with Computational Fluid Dynamics (CFD) method. Outcome of the analysis is divided in two parts. First, different modes of sloshing depending on seismic excitation are identified. These modes are characterized by wave shapes, loads on structures and entrapped void. In the second part we capitalize on the framework of Integrated Deterministic-Probabilistic Safety Assessment (IDPSA) to quantify the risk. Specifically, statistical parameters pertaining to mechanical loads and void transport are quantified and combined with the deterministically obtained data about consequences.
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| 121652. |
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| 121653. |
- Jeltsov, Marti, et al.
(författare)
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Validation of a CFD Code Star-CCM+ for Liquid Lead-Bismuth Eutectic Thermal-Hydraulics Using TALL-3D Experiment
- 2014
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Konferensbidrag (refereegranskat)abstract
- The engineering design, performance analysis and safety assessment of Generation IV heavy liquid metal cooled nuclear reactors calls for advanced and qualified numerical tools. These tools need to be qualified before used in decision making process. Computational Fluid Dynamics (CFD) codes provide detailed means for thermal-hydraulics analysis of pool-type nuclear reactors. This paper describes modeling of a forced to natural flow experiment in TALL-3D experimental facility using a commercial CFD code Star-CCM+. TALL-3D facility is 7 meters high LBE loop with two parallel hot legs and a cold leg. One of the hot legs accommodates the 3D test section, a cylindrical pool where the multi-dimensional flow conditions vary between thermal mixing and stratification depending on the mass flow rate and the power of the heater surrounding the pool. The pool outlet temperature which affects the natural convection flow rates in the system is governed by the flow structure in the pool. Therefore, in order to predict the dynamics of the TALL-3D facility it is crucial to resolve the flow inside the 3D test section. Specifically designed measurement instrumentation set-up provides steady state and transient data for calibration and validation of numerical models. The validity of the CFD model is assessed by comparing the computational results to experimental results.
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| 121654. |
- Jemaa, Syrine, et al.
(författare)
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Green Supplier Evaluation and Selection: An Updated Literature Review
- 2020
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Ingår i: Operational Research in Agriculture and Tourism. - Cham : Springer. ; , s. 169-196
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Konferensbidrag (refereegranskat)abstract
- Green supply chain management is concerned with the integration of environmental criteria and sustainability issues in the management of the supply chain. Within this framework, firms applying internally green strategy have, naturally, the interest to pressure purchases of goods and services from suppliers that are themselves green, at least to a certain extent. Thus, Supplier Evaluation and Selection is crucial due to its big impact on business function. The prospect of applying green principles has consequently become an important feature of a supplier’s overall performance. Hence, green supplier selection and evaluation, although a relatively new research subject, has grown quite rapidly. It develops and studies the decision and evaluation models based on environmental criteria. Its main tools are based on multi-criteria decision making approaches. Our objective, in this paper, is to review journal articles published in the period 2012–2019 on this topic, in order to identify the most widely applied approaches for green supplier evaluation and selection and the most cited green criteria.Our research methodology in inducing the present review has been based on several criteria for the selection of the appropriate articles relevant to the subject. The analysis of those papers has led to an extended classification with respect to the multi-criteria decision making approaches, as well as with respect to the adopted green criteria.We conclude that the majority of applied approaches are based on integrated fuzzy models and that the most popular criteria are “Environmental management system” and “Green design”.
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| 121655. |
- Jemander, S.T., et al.
(författare)
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Surface structure of Si(100) with submonolayer coverages of C
- 2002
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Ingår i: Metallurgical and materials transactions. B, process metallurgy and materials processing science. - : Elsevier. - 1073-5615 .- 1543-1916. ; 89:1-3, s. 415-419
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Konferensbidrag (refereegranskat)abstract
- We report a combined STM, LEED and AES study of Si(100) surfaces prepared by coevaporation from two MBE-sources with Si and SiC, respectively. The flux from the SiC source contains 10% C, enabling studies of deposited layers with C-concentrations in the range 0-10%. After room temperature deposition, the structures have been annealed at 600 °C to generate a c(4 × 4) reconstruction. This has previously been reported to contain from 0.0 to 0.5 monolayers (ML) of C. Annealing at 800 °C irreversibly transforms the c(4 × 4) surface to a 2 × 1-reconstructed surface that contains precipitates of SiC. Since only 0.07 ML of C is needed to have 98% of the surface covered with the c(4 × 4) reconstruction, we conclude that the c(4 × 4) reconstruction is impurity-induced rather than having C-atoms in well defined positions within each unit cell. The c(4 × 4) reconstruction is attributed to a basic structure containing buckled parallel ad-dimers, which in approximately 50% of the reconstructed unit cells is decorated with perpendicular dimers. © 2002 Elsevier Science B.V. All rights reserved.
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| 121656. |
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| 121657. |
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| 121658. |
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| 121659. |
- Jena, Ayesha, et al.
(författare)
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Chaos to Control : Human Assisted Scene Inspection
- 2023
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Ingår i: HRI 2023 - Companion of the ACM/IEEE International Conference on Human-Robot Interaction. - New York, NY, USA : ACM. - 2167-2148. - 9781450399708 ; , s. 491-494
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Konferensbidrag (refereegranskat)abstract
- We are working towards a mixed reality-based human-robot collaboration interface using gaze and gesture as methods of communicating intent in a search and rescue scenario to optimize the operation. The lack of mature algorithms and control schemes for autonomous systems makes it still difficult for them to operate safely in high-risk environments. We are approaching the problem through symbiosis while utilizing humans' intuition of the environment and robots' capability to travel through unknown environments for optimal performance in a given time.
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| 121660. |
- Jena, Ajit K., et al.
(författare)
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Application Layer Tracing for Performance Evaluation
- 2002
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Konferensbidrag (refereegranskat)abstract
- The paper reports on a set of non-intrusive tools that can be used for the performance evaluation of "classical" Internet applications such as Email, WWW, and FTP. At the application layer, key factors influencing the events are stochastic aspects of user behavior, protocol characteristics and sizes of contents transferred. A multi pronged approach involving application log analysis, direct probe of the WWW pages, and network flow analysis has been used. The measurement infrastructure is presented and diverse software tools for gathering of application layer properties are described in detail. The motivation is to build stochastic models for the key elements of application layer that can be further used to build up an integrated end-to-end performance testbed for conducting traffic engineering experiments.
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