| 1. |
- Ge, Yue, et al.
(författare)
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Environmental OMICS: Current Status and Future Directions
- 2013
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Ingår i: JOURNAL OF INTEGRATED OMICS. - : Proteomass Scientific Society. - 2182-0287. ; 3:2, s. 75-87
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Tidskriftsartikel (refereegranskat)abstract
- Applications of OMICS to high throughput studies of changes of genes, RNAs, proteins, metabolites, and their associated functionsin cells or organisms exposed to environmental chemicals has led to the emergence of a very active research field: environmental OMICS.This developing field holds an important key for improving the scientific basis for understanding the potential impacts of environmentalchemicals on both health and the environment. Here we describe the state of environmental OMICS with an emphasis on its recent accomplishmentsand its problems and potential solutions to facilitate the incorporation of OMICS into mainstream environmental and healthresearch.Data sources: We reviewed relevant and recently published studies on the applicability and usefulness of OMICS technologies to the identificationof toxicity pathways, mechanisms, and biomarkers of environmental chemicals for environmental and health risk monitoring andassessment, including recent presentations and discussions on these issues at The First International Conference on Environmental OMICS(ICEO), held in Guangzhou, China during November 8-12, 2011. This paper summarizes our review.Synthesis: Environmental OMICS aims to take advantage of powerful genomics, transcriptomics, proteomics, and metabolomics tools toidentify novel toxicity pathways/signatures/biomarkers so as to better understand toxicity mechanisms/modes of action, to identify/categorize/prioritize/screen environmental chemicals, and to monitor and predict the risks associated with exposure to environmental chemicalson human health and the environment. To improve the field, some lessons learned from previous studies need to be summarized, aresearch agenda and guidelines for future studies need to be established, and a focus for the field needs to be developed.Conclusions: OMICS technologies for identification of RNA, protein, and metabolic profiles and endpoints have already significantly improvedour understanding of how environmental chemicals affect our ecosystem and human health. OMICS breakthroughs are empoweringthe fields of environmental toxicology, chemical toxicity characterization, and health risk assessment. However, environmental OMICS is stillin the data generation and collection stage. Important data gaps in linking and/or integrating toxicity data with OMICS endpoints/profilesneed to be filled to enable understanding of the potential impacts of chemicals on human health and the environment. It is expected thatfuture environmental OMICS will focus more on real environmental issues and challenges such as the characterization of chemical mixturetoxicity, the identification of environmental and health biomarkers, and the development of innovative environmental OMICS approachesand assays. These innovative approaches and assays will inform chemical toxicity testing and prediction, ecological and health risk monitoringand assessment, and natural resource utilization in ways that maintain human health and protects the environment in a sustainable manner.
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| 2. |
- Li, Zhiyuan, 1974, et al.
(författare)
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A comparative study of fatigue assessment of a container ship structure using various direct calculation approaches
- 2012
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Ingår i: Proceedings of The International Conference on Maritime Technology (ICMT 2012). ; , s. 405-409
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Konferensbidrag (refereegranskat)abstract
- Today, it is common practice to carry out fatigue assessments of ship structures using direct calculation procedures. Many numerical codes are available for these types of analyses. They could yield different values in a fatigue life prediction due to the different degrees of complexity as well as the large number of uncertainties in the computation of the ship’s response. In this investigation, a comparative study is carried out on a Panamax container ship in oblique waves using different typical direct calculation methods. The results of fatigue life prediction using these methods are compared with results obtained from full-scale measurements. It is found that the nonlinear time-domain method shows the best agreement with the full-scale measurements, and therefore, it is recommended to be used in fatigue predictions.
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| 3. |
- Li, Zhiyuan, 1974, et al.
(författare)
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A comparative study of fatigue assessments of container ship structures using various direct calculation approaches
- 2014
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Ingår i: Ocean Engineering. - : Elsevier BV. - 0029-8018 .- 1873-5258. ; 82:1, s. 65-74
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Tidskriftsartikel (refereegranskat)abstract
- It is common practice today to carry out fatigue assessments of ship structures using direct calculation procedures to compute fatigue loads. Many numerical codes are available for use in such fatigue load analyses. In addition to the various degrees of computation complexity associated with fatigue estimation methods, such methods also have large inherent uncertainties. In this investigation, a comparative study was carried out for two container ships using various typical direct fatigue calculation methods. The fatigue damage amounts calculated using these methods were compared with those obtained from full-scale measurements. Most of the direct calculation approaches investigated yielded similar fatigue damage estimates. The approach that employs nonlinear time-domain hydrodynamic analysis and the finite element method yields reasonable and conservative fatigue damage results and is therefore recommended. In addition, the results of this study confirm that various measures of wave environments and of the variation in wave models are important sources of uncertainty in fatigue life prediction.
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| 4. |
- Li, Zhiyuan, 1974, et al.
(författare)
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A comparison of direct calculation approaches applied on the fatigue strength assessment of a Panamax container ship
- 2012
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Ingår i: Proceedings of The ASME 2012 31st International Conference on Ocean, Offshore and Arctic Engineering (OMAE 2012). ; 2, s. 1-8
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Konferensbidrag (refereegranskat)abstract
- Today, it is common practice to carry out fatigue assessments of ship structures using direct calculation procedures. A direct calculation analysis of a ship’s fatigue strength involves hydrodynamic analysis, stress response evaluation followed by fatigue damage calculation. Many numerical codes are available for these types of analyses. They could yield different values in a fatigue life prediction because of the different degrees of complexity in the computation of the ship’s response. For example, hydrodynamic loads can be calculated using the strip theory or the panel method. The stress response to these loads can be computed using a beam theory or more advanced analyses, such as global and/or local finite element analyses. In a direct fatigue analysis for ship design, spectral methods have been dominating but there is a growing interest in time-domain fatigue damage calculation procedures. The objective of the current investigation is to compare four commonly used direct calculation methods against measurement data. The comparison is carried out by making a case study on a Panamax container ship on which full-scale measurements have been performed. The computational efforts involved in the application of the current direct calculation methods are compared and their applicability in ship fatigue design is discussed.
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| 5. |
- Li, Zhiyuan, 1974, et al.
(författare)
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An efficient direct calculation approach for fatigue assessment of container ships concerning bending and warping stresses
- 2014
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Ingår i: Proceedings of The 2014 ASME 33rd International Conference on Ocean, Offshore and Arctic Engineering (OMAE 2014). - 9780791845424 ; 4A, s. 1-9
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Konferensbidrag (refereegranskat)abstract
- Container ships are particularly susceptible to torsional loads. The distribution of torsion-induced warping stress in a container ship hull is more complicated and difficult to be expressed by beam theory formulas. In practice, finite element (FE) analysis is typically used to calculate the stress response to wave-loading conditions. However, it is time consuming to compute hull girder stresses for all relevant sea conditions through FE analyses. In this paper, an efficient and robust approach is proposed by combining beam theory and FE analyses in the determination of hull girder stresses. The parameters required by beam theory can be regressed through matching stress records from a FE analysis with the corresponding sectional and pressure loads from the hydrodynamic simulation. Stress records obtained using the proposed method are utilized in fatigue assessment of a case study container vessel. The results show that the accuracy of the regression approach is satisfactory compared with the full FE analyses.
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| 6. |
- Li, Zhiyuan, 1974, et al.
(författare)
-
Direct calculation of fatigue damage of ship structure details
- 2011
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Ingår i: Proceedings of The ASME 2011 30th International Conference on Ocean, Offshore and Arctic Engineering (OMAE 2011). - 9780791844342 ; 2, s. 551-558
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Konferensbidrag (refereegranskat)abstract
- Fatigue assessment of ships using the direct calculation approach has been investigated by numerous researchers. Normally, this approach is carried out as either a global model analysis, or as a local model structural analysis. The current investigation presents a case study of a container vessel where the global and local analyses procedures are combined. A nonlinear time-domain hydrodynamic analysis followed by a global FE analysis is employed to screen for the most severe locations of the global ship’s hull with regard to fatigue damage. Once these locations have been identified, a sub-modelling technique is employed to transfer global loads from the global FE model to local FE models that have high resolution of elements for local structure details.Results from a selection of local FE model simulations are presented. Stress concentration factors at four critical locations are calculated and compared with values recommended by classification guidelines. Results are presented from a short-term fatigue analysis which has been carried out using the rainflow counting method. Finally, a long-term fatigue analysis is performed in time-domain using a designed wave scatter diagram of representative sea states.
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| 7. |
- Li, Zhiyuan, 1974
(författare)
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Direct Calculation of Wave-Induced Loads and Fatigue Damage of Container Vessels
- 2011
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Licentiatavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Container ships and their rules for fatigue design are in several ways differentcompared with other types of commercial ships such as tankers and bulk carriers. Forexample, most modern container ships have a pronounced bow flare and an overhangstern. This unique hull form, in combination with high service speed, gives rise to largeship motions that require nonlinearity in wave loads must be taken into account.Another important characteristic of container ships is that the U-shaped cross sectionsdue to the large deck openings make the ship structure sensitive to wave-inducedtorsion, especially in high waves. A consequence of the open cross section is lowtorsion rigidity of the ship hull, which, together with the high service speed and largeship motions, demands new stricter requirements for fatigue design of the futurecontainer ships.The objective of the current thesis was to review the design methodology in currentship design regarding wave-induced structural loads and fatigue strength assessment.The outcome and contribution to both industrial and scientific relevance of theresearch work is a novel and comprehensive calculation procedure on the directcalculation of wave-induced loads and fatigue damage assessment with the targetapplication of container ships. It comprises hydrodynamic analysis, finite element (FE)analysis followed by fatigue assessments.A 4400TEU Panamax container ship is used for case study in the thesis. The waveloads and ship structural responses are based on the nonlinear time-domainhydrodynamic analysis, with particular attention to wave-induced torsion. Togetherwith full-scale measurement data, the nonlinear vertical bending moments fromhydrodynamic simulations are employed for the extreme hogging and saggingprediction. Global and local FE models of the ship are designed and used in thestructural analysis. A procedure for calculation of the stress concentration factor (SCF)for local details is proposed which compares the ranges of the hot spot stress and thenominal stress. The results from the FE analysis are used in a fatigue assessmentprocedure. Fatigue damages in two structure details are calculated using the rainflowcounting approach. Additionally, a designed wave scatter diagram for the NorthAtlantic was introduced for the computation of a long-term fatigue damageaccumulation.The approach and models presented in the thesis have been validated against full-scalemeasurements of ship motions and stress responses. In addition, a numerical code forfatigue route planning and monitoring is presented, which will be further developed infuture work. Finally, it is believed that the numerical procedure proposed contributesto enhanced accuracy in the estimation of fatigue damage of container ships.
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| 8. |
- Li, Zhiyuan, 1974
(författare)
-
Fatigue Assessment of Container Ships – a Contribution to Direct Calculation Procedures
- 2013
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Within the field of marine structural engineering, the introduction of new materials and material classes, the development of production techniques and new design, and new requirements imposed by authorities are examples which justify a need for continuous revisit and update of fatigue assessment methodologies of marine structures. This thesis contributes to the development and improvement of fatigue assessment methodology for ship structures. Although the work is demonstrated using container vessels here, the methodology provides good insight into the direct calculation procedure of fatigue in general.A practical time-domain procedure is proposed that utilises more sophisticated numerical tools to take account for realistic sea conditions and actual operational profiles in the direct calculation of fatigue damage in ship structures. The feasibility and sensitivity of this time-domain procedure were investigated through case studies. In-depth studies are presented for nonlinear wave loads and their influence on fatigue damage estimation in the deck, bilge, and side-shell structures of container ships. The proposed time-domain procedure provides reasonable and conservative fatigue life estimations in comparison with the fatigue methodologies in widespread use.A method is proposed to derive local stress for fatigue calculation from the ship’s global nominal stress. The idea behind this method is that a stress concentration factor should be based on realistic loadings. This method utilises stress ranges extracted from the stress history, which is particularly suitable for time-domain fatigue analyses. Nonlinear finite element (FE) analyses are carried out to investigate the cyclic material response during severe wave loading conditions. The results indicate that the amount of accumulated plastic strain is often low and that the material exhibits an elastic shakedown response after repeated cyclic loadings. It was therefore concluded that elastic FE analyses followed by stress-based fatigue assessments can be successfully employed, at least for the studied cases.Furthermore, important influencing factors causing uncertainties in fatigue analyses are identified and quantified by comparing fatigue damages estimated using various numerical methods. Uncertainties connected with the wave environment are also studied through the comparison of fatigue assessment using different wave descriptions for a specific sea condition and different distributions of the long-term wave environment. In addition, concerning that the girder stresses occur as a combination of torsion, horizontal and vertical bending moment loadings, an analytical derivation for the separation of wave-induced girder stresses is presented. As a result, it was possible to identify the contribution to fatigue damage, in various locations of containership structures, from stress components that are caused by these different loading modes. The practical usefulness of the results is demonstrated in an example of ship fatigue routing between Europe and North America.
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| 9. |
- Li, Zhiyuan, 1974, et al.
(författare)
-
Fatigue damage assessment of container ships concerning wave-induced torsion
- 2010
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Ingår i: Proceedings of the ASME 29th International Conference on Ocean, Offshore and Arctic Engineering (OMAE 2010) in Shanghai, China, June 6-11, 2010. - 9780791849101
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Konferensbidrag (refereegranskat)abstract
- The traditional method to assess fatigue damage of ship structures assumes moderate wave amplitudes and linear responses. This method can be questioned when applied on container ships that are characterized by large deck openings, because the low torsion rigidity of this type of ship makes it sensitive to oblique waves. In this paper, the 3D hydrodynamic code WASIM is used to simulate a 4400 TEU container ship operating in the North Atlantic Ocean. Nonlinear wave loads are utilized for direct calculation of the stress histories under severe sea states. The warping stress from wave-induced torsion is separated from the stress components from vertical and horizontal bending. The contribution to fatigue damage accumulation from warping stresses is evaluated. For comparison, the results from the numerical simulations and fatigue calculations are verified with full-scale measurements made on a similar type of container vessel.
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| 10. |
- Li, Zhiyuan, 1974, et al.
(författare)
-
Fatigue routing of container ships – assessment of contributions to fatigue damage from wave-induced torsion and horizontal and vertical bending
- 2012
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Ingår i: Ships and Offshore Structures. - : Informa UK Limited. - 1754-212X .- 1744-5302. ; 7:2, s. 119-131
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Tidskriftsartikel (refereegranskat)abstract
- The traditional method for assessing fatigue damage of ship structures assumes moderate wave amplitudes and linear responses. This method can be questioned when applied on container ships which are characterized by large deck openings that cause low torsion rigidity of the structure. Depending on the heading of the vessel in relation to wave encounter direction, container ships can therefore be sensitive to, for example, oblique waves. In the current investigation, the SESAM software with the three-dimensional hydrodynamic code WASIM is used to simulate a 4400 TEU container ship operating in the North Atlantic. Nonlinear wave loads are utilized for direct calculation of stress histories under severe sea states using the finite element software in SESAM. A method for the separation of normal stress components in an arbitrary cross section and location of the ship is proposed: warping stress from wave-induced torsion, and stress components from horizontal and vertical bending. The strain (stress) response calculated using the models in one location is verified against full-scale measurements made on a similar type of container vessel in the same location. A case study is presented for fatigue damage assessment in two cross sections of the container ship. The contributions to fatigue damage from wave-induced torsion and horizontal and vertical bending are calculated and presented in a fatigue damage routing tool by means of polar diagrams, which includes the effects of heading and ship speed on fatigue damage.
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