Modal analysis of micro wind turbine blade using COSMOSWorks

In this paper, vibration modal analysis of a horizontal axis micro wind turbine blade of different rotational speeds was carried out by using the finite element analysis software COSMOSWorks. The dynamic stiffening phenomenon and its effect on the vibration mode of the wind turbine blade were taken into account. Numerical results were analyzed and compared. The analysis can help not only to ensure the reliability of system operation but also to improve the structural performance

Water invasion performance of complex fracture-vuggy gas reservoirs based on classification modeling

   The complexity of the pore structure, spatial development, fractures, and pore distribution of fractured-vuggy carbonate reservoirs influences the water invasion dynamics of gas reservoirs, which is crucial in the dynamic research of strongly heterogeneous reservoirs. In this study, the collocation relationship of pore-vuggy fractures is described by the quantitative characterization of their attribute parameters. The discrete fracture network model is used to match and construct the fractures in different modes. The distribution classification method is used to model three-dimensional geological reservoirs in terms of their geometric and attribute characteristics. Bottom-water and edge-water gas reservoirs are constructed separately using numerical simulation, and the dynamic characteristics of water invasion are described. The results show that the proposed method is suitable for the geological modeling of fractured-vuggy gas reservoirs with strong heterogeneity and complexity. The modeling accuracy is improved because the gas reservoir heterogeneity and water invasion’s dynamic characteristics can be described accurately. Six stages of water invasion are identified from the numerical simulation of water invasion. This method provides theoretical guidance for the study of heterogeneous gas reservoirs with water.Cited as: Han, X., Tan, X., Li, X., Pang, Y., Zhang, L. Water invasion performance of complex fracture-vuggy gas reservoirs based on classification modeling. Advances in Geo-Energy Research, 2021, 5(2): 222-232, doi: 10.46690/ager.2021.02.1

The study on magnetism and solid coupling vibration and its electromagnetic force characteristics in stator system of electrical machine

The air-gap electromagnetic force is not the unique excitation which excites magnetism and solid coupling vibration on stator system of asynchronous machine. Besides, there should be a ponderomotive force as an internal electromagnetic excitation in stator core. Therefore, the magnetism and solid coupling vibration equation with both of the forces was obtained for the electromagnetically excited vibration on stator system of electrical machine. Based on Maxwell equations and the electromagnetic constitutive relation, the expressions of the electromagnetic field and force were derived by solving the eddy equation and the boundary conditions. With numerical calculation, the influences of geometric parameters on the electromagnetic field and forces were analyzed. The electromagnetic excitations of magnetism and solid coupling vibration on stator system were improved by the analysis of ponderomotive force in the stator core. Furthermore, the conclusions provide a theoretical basis for the electromagnetic design of asynchronous machine

The new method on gas-water two phase steady-state productivity of fractured horizontal well in tight gas reservoir

Based on a large number of tight gas exploration and development literature researches, it is found that the horizontal drilling technology and fracturing operation are usually used in the tight gas reservoir for its low permeability. Three tasks have been done in this paper. First, we described the characteristics and the flow mechanism of the tight gas reservoirs which are different from the conventional ones and gave a new definition of two phase pseudo pressure. Second, formation stress sensitivity, starting pressure gradient and the interaction of fractures are considered. Equivalent flow resistance was used to establish a model of tight gas steady flow, and a new productivity formula of fractured horizontal well in tight gas reservoir derived by the new flow model. Third, the productivity influence research has been done, which gives the influence degree of different parameters. It is signified that the productivity will increase with the addition of the permeability modulus and decrease with the increase of the water-gas volume ratio. The influence of starting pressure gradient was not very clear and the fractures parameters showed the opposite situation. Therefore optimization design of tight gas reservoir development mode can be improved by the productivity formula and research.Cited as: Li, X., Liang, J., Xu, W., et al. The new method on gas-water two phase steady-state productivity of fractured horizontal well in tight gas reservoir. Advances in Geo-Energy Research, 2017, 1(2): 105-111, doi: 10.26804/ager.2017.02.0

Experiment Research on Deformation Mechanism of CNT Film Material

Nanometer composite usually has multilevel structure, and deformation mechanism of its multilevel structure is the hot spot at present. The paper studies deformation mechanism of multilevel structure of CNT film material under tension loading and its influence on film mechanical properties by jointing multiscale experiment methods such as tensile test, digital image correlation, SEM observation, and in situ micro-Raman spectroscopy. The result shows that, during film loading process, the deformation of CNTs inside the film endures elastic elongation and glide successively, with very small axial elongation, which is about 7% of film deformation; the deformation of CNT bundle network structure endures deformation mechanism such as CNT bundle extension, rotation, and glide, and this structure deformation occupies about 93% of film deformation that large structure deformation makes CNT film have good toughness; during film loading process, the formation of CNT bundle long chain and glide mechanism in the chains help to improve film strength and toughness

Turnover intention and coping strategies among older nursing assistants in China: a qualitative study

IntroductionWith the increasing aging population, older nursing assistants have made significant contributions to institutional eldercare. However, there is a high turnover rate among these workers, and it is crucial to address this issue and find ways to stabilize the workforce. This study aimed to explore the factors influencing turnover intention and coping strategies among older nursing assistants, in order to provide targeted assistance and guidance to reduce their intention to resign and ultimately lower the turnover rate.MethodsQualitative research methods were employed to conduct semi-structured interviews with older nursing assistants in Changsha. The data obtained from these interviews were then analyzed using a phenomenological analysis approach and NVIVO (QSR International, Doncaster, Australia) software version 11.0.ResultsIt is found that several factors influence turnover intention among older nursing assistants. Which include work pay, work environment, professional identity, external motivation, and work pressure. Additionally, the coping strategies employed by these individuals in relation to their intention to resign include self-regulation, seeking support, self-improvement, and exploring motivation.DiscussionIt is also evident from our study that reducing the turnover intention of older nursing assistants requires a collaborative effort from older adult care institutions, functional departments, and eldercare nursing assistants themselves. By addressing the factors influencing turnover intention and providing support and resources for coping strategies, we can work towards stabilizing the workforce and improving institutional eldercare

A Versatile Surface Bioengineering Strategy Based on Mussel-Inspired and Bioclickable Peptide Mimic

In this work, we present a versatile surface engineering strategy by the combination of mussel adhesive peptide mimicking and bioorthogonal click chemistry. The main idea reflected in this work derived from a novel mussel-inspired peptide mimic with a bioclickable azide group (i.e., DOPA4-azide). Similar to the adhesion mechanism of the mussel foot protein (i.e., covalent/noncovalent comediated surface adhesion), the bioinspired and bioclickable peptide mimic DOPA4-azide enables stable binding on a broad range of materials, such as metallic, inorganic, and organic polymer substrates. In addition to the material universality, the azide residues of DOPA4-azide are also capable of a specific conjugation of dibenzylcyclooctyne- (DBCO-) modified bioactive ligands through bioorthogonal click reaction in a second step. To demonstrate the applicability of this strategy for diversified biofunctionalization, we bioorthogonally conjugated several typical bioactive molecules with DBCO functionalization on different substrates to fabricate functional surfaces which fulfil essential requirements of biomedically used implants. For instance, antibiofouling, antibacterial, and antithrombogenic properties could be easily applied to the relevant biomaterial surfaces, by grafting antifouling polymer, antibacterial peptide, and NO-generating catalyst, respectively. Overall, the novel surface bioengineering strategy has shown broad applicability for both the types of substrate materials and the expected biofunctionalities. Conceivably, the “clean” molecular modification of bioorthogonal chemistry and the universality of mussel-inspired surface adhesion may synergically provide a versatile surface bioengineering strategy for a wide range of biomedical materials