In the present report the authors propose the method to estimate the minimum breakdown voltages of surface flashovers initiated from the triple junction at which a solid insulator, SF6 gas and a metal electrode come in contact.Using four kinds of test samples, we have measured the flashover voltages Vf. The voltages Vf become lower than the theoretical voltages Vs of streamer inception in the case of the test sample with the large electrode area at the triple junction. To understand the phenomena quantitatively, we estimated the real partial discharge voltages Vc from the voltages Vf, and investigated the relationship between the voltages Vc and the theoretical values Vs. The values of Vs/Vc, which characterize the properties of the partial discharges, can be shown by the product λ S90%EavP of the following parameters; (1) coefficient λ representing the surface roughness of electrode at the triple junction, (2) effective area S90% of the electrode, (3) average field Eav at the area S90%, and (4) gas pressure P. The minimum surface flashover voltages in the insulators for coaxial electrode systems can be estimated precisely, considering the properties of Vs/Vc.
When RC columns reach near-collapse and undergo axial shortening following shear failure, some of axial load sustained by the columns transfer to neighboring columns and axial load of the columns becomes lower than the initial one. This study was intended to examine the effect of the decreased axial load on the collapse behavior. Full-scale column specimens with shear failure mode were tested under decreased axial load or constant axial load until they collapse. The effect of varied rates of the axial load decrease on the column collapse drift is studied and the comparison of computed collapse drifts and observed ones are also discussed.
SiC-based nonlinear resistive material has been used for end-turn stress grading (SG) of turbogenerators over decades. In order to reduce power dissipations and avoid thermal breakdown of the SG material, high-voltage class generators adopt multiple-layer SG system, at which two SG materials with different nonlinear resistivity are used. With increasing capacity and efficiency of the apparatus, electrical, and especially thermal stresses at the system may become problematic, hence higher reliable SG system is required. For suppressing the local heating effectively, an optimization method of the multiple-layer system was investigated, where a new combination of the two SG materials was proposed and length of the SG layer in the longitudinal direction along a coil was optimized by using analytical approximations of the power dissipation. The optimized SG system showed 20% lower power dissipation and also 15% higher flashover voltage than those of the conventional one. Consequently, the effectiveness of the optimization method proposed was successfully confirmed.
Interprofessional collaboration (IPC) is vital to primary care. Improving IPC requires cooperation between medical and other healthcare professionals. Transprofessional role plays can enhance the quality of IPC; thus, in this study, we conducted transprofessional role plays, based on existing theories regarding IPC and medical education, with healthcare professionals in primary care. As a study design, the realist approach was used to clarify the effectiveness of transprofessional role plays. Five Likert-scale questionnaires regarding the competency of IPC were used to assess the change in perception of medical and care professionals through educational intervention. The realist approach was employed for the clarification of contexts, mechanisms and outcomes of transprofessional role play using one-on-one interview data. Sixty-two medical care professionals participated in the transprofessional role plays, and 31 participants were interviewed. The difference in the score of the competency scale of IPC was statistically significant in all six competencies (p-value <0.001). Three context, mechanism and outcome theories were clarified from the qualitative analysis of the interviews: reflection on others, realisation of own roles and driving humanistic relationship. Additionally, contextual factors, the mechanisms that facilitated them and the clarified outcomes were identified. Ultimately, in this realist evaluation transprofessional role plays proved to be effective in driving IPC in primary care through improving compassion and reliability across professions. The constant provision of the role play and mutual discussion of each professional's role can facilitate effective IPC in primary care.
