| 1. |
- Dong, Shichang, et al.
(författare)
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Mechanistic critical heat flux model development for subcooled flow boiling based on superheated liquid sublayer depletion
- 2022
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Ingår i: Progress in nuclear energy (New series). - : Elsevier BV. - 0149-1970 .- 1878-4224. ; 153, s. 104445-
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Tidskriftsartikel (refereegranskat)abstract
- Critical heat flux (CHF) refers to the limit of boiling transfer systems, and crossing this limit may jeopardize system safety. However, a clear understanding of the physical mechanisms of CHF is still lacking. In this study, a new CHF prediction model based on superheated sublayer depletion was established for subcooled flow boiling in an upward vertical tube at low pressure. The model is characterized by its developed determination of the superheated liquid sublayer thickness, net vapor generation location, forced convection heat transfer and liquid supplement caused by bubble turbulent fluctuations. The proposed CHF model was validated by a database covering the low pressure subcooled operational ranging over P = 0.1-2.15 MPa, G = 0.7-35 Mg/m2s, Delta Tin = 11-183.16 K, D = 0.7-12 mm, L/D = 4.2-115.55, and xeqout = -0.2673-0.0843. The model can accurately predict the trend of thermal-hydraulic and geometric factors' effects on the CHF. The prediction results have good prediction accuracy with an root-mean-square error (RMSE) of 15.21%, and overall error of +/- 25%. The proposed model also shows good adaptation to a non-water (refrigerant 113 and liquid nitrogen) system.
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| 2. |
- Dong, Shichang, et al.
(författare)
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Theoretical model for subcooled upward flow boiling heat transfer and critical heat flux for an inclined downward heated surface
- 2023
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Ingår i: International Journal of Heat and Mass Transfer. - : Elsevier BV. - 0017-9310 .- 1879-2189. ; 213
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Tidskriftsartikel (refereegranskat)abstract
- The in-vessel retention system and ex-vessel retention system are very important to the safety of nu-clear power plants under severe accidents. While the success of such safety systems relies on well un-derstanding the corresponding physical mechanisms of boiling heat transfer and critical heat flux (CHF). Challenges till remain in accurately predicting the subcooled flow boiling curve especially in the low-pressure and low-flow conditions due to its complex boiling phenomenon. The present study introduces a theoretical model to predict the boiling curve and critical heat flux for subcooled flow boiling in in-clined downward heated rectangular channel. The proposed model well estimates the transition from forced convection, isolated bubble nucleate boiling to fully developed boiling regime by considering the growth and interaction of bubbles. Through probability analysis of bubbles' interaction, the proportion of heat flux in different boiling regimes is determined. In addition, the flow boiling CHF is predicted based on the probability analysis of dry spots. The new model is validated by the subcooled flow boil-ing experiments with vertical single-side heated channel under low-pressure and low-flow conditions. The predicted boiling curves are consistent with experimental results corresponding to different thermal-hydraulic parameters, such as pressure, mass flux, inlet subcooling and wall wettability (hydrophilic and hydrophobic), and the prediction error of CHF is within & PLUSMN;15%. Furthermore, the inclination effect on CHF is validated by the subcooled flow boiling experiments in inclined channel with the inclination angle varying from 0 & DEG; to 90 & DEG;, which shows the good applicability of the developed model.
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| 3. |
- Dong, Yidan, et al.
(författare)
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Association between long-term static postures exposure and musculoskeletal disorders among university employees : A viewpoint of inflammatory pathways
- 2022
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Ingår i: Frontiers in Public Health. - : FRONTIERS MEDIA SA. - 2296-2565. ; 10
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Tidskriftsartikel (refereegranskat)abstract
- BackgroundMusculoskeletal disorders (MSDs) are critical occupational and social problems. With the improvement of production mechanization and automation, and the widespread application of computers, more occupations are exposed to static postures and load. This study explored the role of inflammation in the association between static postures exposure and MSDs. MethodsThis study adopted a prospective nested case-control design in which 66 lower back MSDs cases and 66 healthy controls were selected from a cohort study of university employees. The personal information, postural load, musculoskeletal symptoms, pressure pain thresholds (PPTs), and inflammatory cytokines were collected. Logistic and linear regressions were used to investigate the association among postural load, inflammatory cytokines, and lower back MSDs. Mediation analysis was used to calculate the mediation effect. ResultsThe results of logistic and linear regressions showed that postural load and inflammatory cytokines were positively associated with lower back MSDs (P < 0.05), and postural load was positively associated with inflammatory cytokines (P < 0.05). Further, mediation analysis showed that the mediation effect of postural load on the lower back MSDs through TNF-alpha was 0.073 (95%CI: 0.025-0.128), and the mediation effect of posture load on the lower back MSDs through IL-6 was 0.098 (95%CI: 0.041-0.179), respectively. ConclusionStatic postures were associated with the occurrence of MSDs through inflammatory cytokines, and low-level inflammation may be a critical early event in the generation of MSDs. This study may help bridge the gap of potential mechanisms linking static postures to increased risks of MSDs, and provide new evidence for targeted protection against the global increasing MSDs.
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| 4. |
- Dong, Yidan, et al.
(författare)
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Derived patterns of musculoskeletal symptoms and their relationships with ergonomic factors among electronic assembly workers : A latent class analysis
- 2022
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Ingår i: Journal of Safety Research. - : Elsevier BV. - 0022-4375 .- 1879-1247. ; 82, s. 293-300
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Tidskriftsartikel (refereegranskat)abstract
- Introduction: Multi-site musculoskeletal symptoms (MSS) are considered to be more common and have more serious consequences than single-site MSS. This study aimed to determine whether derived patterns of MSS may be identified in electronic assembly workers and if extracted MSS classes are associated with personal and work-related factors. Method: A cross-sectional questionnaire study was performed with 700 participating electronic assembly workers. The questionnaire included individual factors, psychosocial and physical exposures, and MSS. The derived patterns of MSS and their relationships with ergonomic factors were analyzed using latent class analysis (LCA) and multinomial logistic regression models (MLRM). Results: The 1-year prevalence of MSS affecting only one body site or two or more body sites was 14.9% and 32.7%, respectively. The results of LCA showed three distinct classes of MSS patterns, which were labelled 'MSS in most sites' (5.0%), 'MSS in neck and shoulder' (27.0%), and 'MSS in one or no site' (68.0%). The results of MLRM showed that the 'MSS in neck and shoulder' was associated with job tenure (OR 5.579, 95% CI 2.488-12.511), excessive dynamic and static loads (OR 3.868, 95% CI 1.702- 8.793 and OR 5.270, 95% CI 2.020-13.747, respectively); while the 'MSS in most sites' was associated with high job demands (OR 4.528, 95% CI 1.647-12.445) and excessive dynamic loads (OR 111.554, 95% CI 4.996-2490.793). Conclusions: The results showed unique patterns of MSS among electronic assembly workers that were associated with personal and work-related factors. Practical applications: The findings highlight that the high prevalence of multi-site MSS in this group should be a focus. It also provides further evidence that LCA considering the number and location of anatomical sites involving MSS can be used to determine distinct classes of MSS patterns, which is of great significance for the epidemiological study and management of MSS in the future.
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| 5. |
- Dong, Yidan, et al.
(författare)
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Study on the Associations of Individual and Work-Related Factors with Low Back Pain among Manufacturing Workers Based on Logistic Regression and Structural Equation Model
- 2021
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Ingår i: International Journal of Environmental Research and Public Health. - : MDPI. - 1661-7827 .- 1660-4601. ; 18:4
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Tidskriftsartikel (refereegranskat)abstract
- Work-related musculoskeletal injuries are one of the major occupational health issues of the workers, especially low back pain (LBP). The aim of this study was to survey the prevalence of LBP among manufacturing workers and to identify associations of individual and work-related factors with LBP. A cross-sectional questionnaire study was performed with 1173 participating manufacturing workers. The questionnaire included individual factors, psychosocial and physical exposures, and musculoskeletal discomfort. It was analyzed by logistic regression and structural equation modeling (SEM). The 1-year prevalence of LBP among Chinese manufacturing workers was 33.6%. Logistic regression analysis showed that job tenure, awkward postures, vibration and job demand were positively-while social support and job control were negatively associated with LBP (p < 0.05). The SEM results indicated that, as shown in other studies, job types, job tenure, postural load, high job demand, low job control and vibration were directly associated with LBP, but also that job types, high job demand, low social support and vibration may have indirect effects on LBP-mediated by postural load.
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| 6. |
- Jin, Xu, et al.
(författare)
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Prevalence and associated factors of lower extremity musculoskeletal disorders among manufacturing workers : a cross-sectional study in China
- 2022
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Ingår i: BMJ Open. - : BMJ. - 2044-6055. ; 12:2
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Tidskriftsartikel (refereegranskat)abstract
- Objective To survey the prevalence of lower extremity musculoskeletal disorders (MSDs) among Chinese manufacturing workers, and to identify the associated factors. Design Observational study with cross-sectional design. Setting A self-administered questionnaire survey was conducted in four manufacturing factories in China. Participants 7908 manufacturing workers were included in this study after excluding non-conforming personnel. Outcome measures Individual and work-related information, and MSDs in the whole leg and knee region were measured by the anonymous self-administered questionnaire. Individual and work-related factors associated with MSDs and their effects were identified through multivariate logistic regression. Results Of all respondents, 3241 (41.0%) reported having had lower extremity MSDs in the recent 12 months, and for the knees, ankles/feet and hips/thighs were 29.5%, 23.9% and 16.7%, respectively. After confounder-adjusted single-factor analysis, 22 variables (of 24) were significantly related to the disorders. Factors like always kneeling/squatting for long periods, always standing for long periods and often lifting in an uncomfortable position were shown to have higher risks, with ORs of 2.77 (95% CI: 2.33 to 3.30), 2.30 (1.96 to 2.69) and 2.25 (2.04 to 2.47). Comparable results were found on knee disorders. The final model included 15 variables of demography, biomechanics and work organisation. The following factors showed increased risks of lower extremity MSDs: being female, being older, longer working years, higher body mass index (BMI), keeping the same posture for a long time, awkward position, shift work and monotonous work. Whereas having enough breaks reduced the risk. Conclusion The prevalence of lower extremity MSDs among Chinese manufacturing workers is high. The most commonly affected body regions were the knees and ankles/feet. Multiple factors were found associated with lower extremity MSDs including age, BMI, work experience, work organisations, physical ergonomics exposures, etc.
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