2,636 research outputs found

    Numerical Computation of Wind Turbine Flows and Fluid Problem by OpenFOAM and ANSYS

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    Wind energy is the mainstream source of clean and renewable energy and it is also the fastest-growing source of sustainable energy in the world. In the Global Wind Energy Council's report in 2014, wind industry grew 44% worldwide. In order to optimize the efficiency of wind farms, it is important to observe wake interactions among wind turbines. Computational mathematics and mechanics provide fundamental methods and tools for simulating physical processes. Numerical computation can offer important insights and data that are either difficult or expensive to measure or to perform tests experimentally. In this dissertation, we use Computational Fluid Dynamics (CFD) software OpenFOAM and ANSYS FLUENT to simulate the wake effect of Horizontal Axis Wind Turbines (HAWT) and related problems. Numerical simulation can also help us comprehend and control man-made disasters. Air craft crashworthiness and human survivability are of utmost concerns in any emergency landing situation. Motivated by the air incidents lately, the disappearance of Malaysia Airlines Flight MH370 in March 2014 and Germanwings Flight 9525 crash in March 2015, we use Computational Structural Dynamics (CSD) software ANSYS Explicit Dynamics and LS-DYNA to try different numerical simulations of Airbus A320 crashing into a wall and compare the results to the reality. We calculate three CFD problems in this dissertation: lid-driven problems, one turbine wake problem, and two serial turbines wake problem. We simulate a lid-driven flow in both two- (2D) and three-dimension (3D) to compare the simulation capability of the three turbulence modelings, i.e., Direct Numerical Simulation (DNS), Large Eddy Simulation (LES), and Reynolds-Averaged Navier-Stokes Equations Simulation (RANS) by OpenFOAM. Among these three turbulence models, we can find that LES is capable of capturing more details of turbulence flow. We simulate the airflow effect of one wind turbine with both fixed angular velocity and wind-driven case, run benchmark tests based on NRELs reports, and compare the numerical results under the same condition by OpenFOAM and FLUENT. For the fixed angular velocity case, we use wind speed 8 m/s and angular velocity of the wind turbine 75 deg/s. For the wind-driven case, we use wind speed 8 m/s and 16 m/s and the angular velocity of the wind turbine calculated by FLUENT converges faster than OpenFOAM case. We simulate the interactions of wake flow for two serial wind turbines by FLUENT. We use wind speed 8 m/s and angular velocity of the wind turbine 75 deg/s. The wake of former turbine affects the rear one and the diffusion of flow caused by two turbines can be seen clearly. For both one and two serial turbines problems, the turbulence model RANS kΔ is used. We calculate and simulate Airbus A320 crashing into a wall by ANSYS Explicit Dynamics and LS-DYNA. For ANSYS Explicit Dynamics, we use the angle of approach 0Âș, 15Âș, and 30Âș. For LS-DYNA, we only test the pitch angles 0Âș. For all cases, we use the speed of aircarft 200 m/s. The deformation of both aircraft and wall can be seen clearly. Numerical simulation can also help us comprehend and control man-made disasters. Air craft crashworthiness and human survivability are of utmost concerns in any emergency landing situation. Motivated by the air incidents lately, the disappearance of Malaysia Airlines Flight MH370 in March 2014 and Germanwings Flight 9525 crash in March 2015, we use Computational Structural Dynamics (CSD) software ANSYS Explicit Dynamics and LS-DYNA to try different numerical simulations of Airbus A320 crashing into a wall and compare the results to the reality. The demonstration of aircraft crash calculation by Explicit Dynamics and LS-DYNA, snapshots of aircraft crashing into a wall, and the links of animation videos can be seen in Chapter 5

    Assessment of design factory concept's transferability into the Chinese cultural context

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    The purpose of this study was threefold. First, to understand what are the core elements that Aalto Design Factory is comprised of in order to examine Design Factory concept’s transferability across cultural boundaries. Second, to explain the cultural challenges in localizing Design Factory concept into China. Third, provide managerial suggestions in order to improve the management of Aalto-Tongji Design Factory. Case study approach was selected for this qualitative research. The research process was conducted by using an abductive approach in two phases. In the first phase, five semi-structured thematic interviews on key informants were conducted in order to induce a theoretical construct for modeling Design Factory concept, which resulted six core elements: 1) physical space, 2) equipments and materials, 3) activities, 4) people, 5) leadership, and 6) philosophy. In the second phase, four semi-structured thematic interviews and one open interview were conducted in order to evaluate the transferability of the theoretical construct’s six core elements into the Chinese cultural context. The theoretical reference for these two phases is comprised of literature review from fields such as creativity, motivation, co-creation, organizational culture, and organizational culture in China, “guanxi” (Chinese concept for social relationships), “lian” (Chinese concept of dignity), and change management. The research findings suggest that it seems rather unfeasible to localize the Finnish Design Factory concept into China as the way it is in Finland due to the strong prevailing Confucian values that are guiding people’s minds. There appears to be some changes in the air, although, the existence of Design Factory’s experience seems to be missing at Sino-Finnish Centre’s Aalto-Tongji Design Factory. However, this research suggests that with careful planning, strong governmental support, a motivated Chinese leader and a committed management team could make the impossible possible

    Modeling of minimum void ratio for sand–silt mixtures

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    Minimum void ratio or maximum packing density is an important soil property in geotechnical engineering. It correlates to the volume change tendency, the pore fluid conductivity, and the shear strength of the soil. In geotechnical engineering, it often requires to estimate the minimum void ratio for a sand–silt mixture with any amount of fines content, based only on few laboratory test results. The minimum void ratio for soil mixtures is usually estimated by methods based on, to some extent, an empirical approach, for example, the AASHTO coarse particle correction method. In this paper, based on a more fundamental approach using the concept of dominant particle network, we aim to develop a mathematical model that can predict the minimum void ratio for sand–silt mixtures with any amount of fines content. The developed model only requires two parameters for the prediction of minimum void ratios of soil mixtures with various fines contents. The developed model is evaluated by the experimental results on 33 types of soil mixtures available in the literature, including mixtures of sands (Ottawa sand, Nevada sand, Toyoura sand, Hokksund sand, etc), and silts (ATC silt, Nevada fines, crushed silica fines, grind Toyoura fines, etc). Comparisons of the results are discussed

    Three-dimensional structure and cytokine distribution of platelet-rich fibrin

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    OBJECTIVES: Previous reports have revealed that several cytokines (including platelet-derived growth factor-BB, transforming growth factors-ÎČ1 and insulin-like growth factor-1) can enhance the rate of bone formation and synthesis of extracellular matrix in orthopaedics or periodontology. This study aimed to determine the concentration of cytokines within platelet-rich fibrin microstructures and investigate whether there are differences in the different portions of platelet-rich fibrin, which has implications for proper clinical use of platelet-rich fibrin gel. METHODS: Whole blood was obtained from six New Zealand rabbits (male, 7 to 39 weeks old, weight 2.7-4 kg); it was then centrifuged for preparation of platelet-rich fibrin gels and harvest of plasma. The resultant platelet-rich fibrin gels were used for cytokine determination, histological analyses and scanning electron microscopy. All plasmas obtained were subject to the same cytokine determination assays for the purpose of comparison. RESULTS: Cytokines platelet-derived growth factor-BB and transforming growth factor-ÎČ1 formed concentration gradients from high at the red blood cell end of the platelet-rich fibrin gel (p=1.88×10-5) to low at the plasma end (p=0.19). Insulin-like growth factor-1 concentrations were similar at the red blood cell and plasma ends. The porosities of the platelet-rich fibrin samples taken in sequence from the red blood cell end to the plasma end were 6.5% ± 4.9%, 24.8% ± 7.5%, 30.3% ± 8.5%, 41.4% ± 12.3%, and 40.3% ± 11.7%, respectively, showing a gradual decrease in the compactness of the platelet-rich fibrin network. CONCLUSION: Cytokine concentrations are positively associated with platelet-rich fibrin microstructure and portion in a rabbit model. As platelet-rich fibrin is the main entity currently used in regenerative medicine, assessing cytokine concentration and the most valuable portion of PRF gels is essential and recommended to all physicians

    Role of CD8+ cells in the progression of murine adriamycin nephropathy

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    Role of CD8+ cells in the progression of murine adriamycin nephropathy.BackgroundMany studies have shown that interstitial inflammation in human and experimental renal disease is characterized by T-cell infiltration, but published data on the involvement of inflammatory cell subsets in progressive tubulointerstitial lesions are often conflicting. A previous study suggested a role for cytotoxic T lymphocytes in the damaging effect of CD4+ T-cell depletion in murine adriamycin (ADR) nephropathy, a model of focal segmental glomerulosclerosis (FSGS), and tubulointerstitial inflammation. The aim of this study was to investigate the role of CD8+ cells in this model.MethodsMale BALB/c mice were treated with five intraperitoneal injections of anti-CD8 monoclonal antibody (mAb), beginning from five days after ADR treatment, when overt proteinuria was established. Seven mice in each of groups A (ADR + mAb), B (ADR only), and C (saline treated, age matched) were sacrificed at week 6. Changes in renal function and histopathological features were assessed. Tubulointerstitial inflammation and glomerular inflammation were examined immunohistochemically.ResultsmAb treatment reduced CD8+ cell levels to <2% of normal in spleen. Proteinuria in group A was no different from that in group B at week 6, but was markedly higher than in group C. Creatinine clearance was significantly ameliorated by anti-CD8 treatment (71.8 ± 4.9 ΌL/min vs. 29.2 ± 2.8 in group B and 81.9 ± 3.7 in group C). Morphometric analysis showed less FSGS in group A compared with group B (6.5 ± 1.9 vs. 13.0 ± 2.8, P < 0.001), as well as less tubular atrophy (indicated by increased ratio of tubule cell height to tubular diameter, 0.25 ± 0.24 in group A vs. 0.04 ± 0.02 in group B, P < 0.05). CD8 depletion also reduced interstitial expansion (6.3 ± 2.2% vs. 16.4 ± 3.1 in group B, P < 0.001) and fibrosis (P < 0.01). Macrophage infiltration in tubulointerstitium was less in group A than in group B (P = 0.052). The number of interstitial CD4+ cells appeared to increase after anti-CD8 treatment, but was not statistically different between groups A and B.ConclusionAnti-CD8 treatment protects against renal functional and structural injury in this murine model of chronic proteinuric renal disease

    Effects of Childhood Adversity and Resilience on Taiwanese Youth Health Behaviors

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    Adverse childhood experiences (ACEs) can leave negative impacts on one\u27s health behaviors or social functioning later in life. Resilient characteristics have been shown to mitigate effects against risk behaviors in developing adolescents. However, clinical and research attention has rarely been given to jointly consider the effects of ACEs and resilient characteristics on health behaviors in Taiwanese youth. Method: A total of 200 individuals aged 15–22 years were recruited from primary care settings, communities, and schools. Participants completed questionnaires assessing their ACEs, resilient characteristics, and health behaviors. Univariate analysis was firstly used to describe the correlates of ACEs and resilient characteristics. Further multivariate logistic regression analysis was used to examine the association of both factors with health behaviors. Results: More than half (61.5%) of those surveyed had been exposed to at least one category of ACE. Verbal (37%) and physical (21%) abuses were the most common types of ACEs. The counts in the ACE categories were associated with being involved in physical fights (odds ratio 1.28 [confidence interval 1.01–1.63]), property damage (1.29 [1.03–1.61]), running away from home (1.30 [1.05–1.60]), bullying victimization (1.37 [1.16–1.61]), and sleep problems/tiredness (1.25 [1.03–1.52]). Meanwhile, resilience scores were associated with decreased odds of infrequent seatbelt use (0.47 [0.23–0.97]), low fruit and vegetable intake (0.42 [0.21–0.86]) unsatisfied body image (0.46 [0.22–0.97]), and sleep problems/tiredness (0.37 [0.18–0.79]). Conclusions: ACEs and resilience characteristics play a significant role in shaping youth health behaviors. Further research should be undertaken to identify ways to build resilience against health risks in youth with prior ACE exposure

    THE KINEAMTIC ANALYSIS OF THREE TAEKWONDO KICKING MOVEMENTS

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    The purpose of this study was to compare and describe the kinematic characteristics of the lower limb joints of three kicking movements in Taekwondo. Five elite female athletes served as subjects in this study. Two Peak high-speed cameras (120Hz) were synchronized to record three kicking movements. The maximum foot velocity duration of movement and the minimum knee angle in these three kicking movements have significant differences. Back round-kick and Back-kick are not whip-like movements. As for the curve of foot velocity, there is twin peak in Back round-kick. It is also notably different from the other kicking movements
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