Growing technical problems with the maintenance of precast concrete housing stock result in the search for efficient repair methods. The paper analyses the effects of flaws in the design concept and assembly accuracy ...Growing technical problems with the maintenance of precast concrete housing stock result in the search for efficient repair methods. The paper analyses the effects of flaws in the design concept and assembly accuracy of integrated AAC （autoclaved aerated concrete） panel walls, type GWO （Gazobetonowa Wielka P｜yta Ostonowa which means large cover panel from aerated concrete in English）, used as curtain walls in a system of precast concrete housing blocks erected in Lublin. The results of in-situ observations and laboratory tests of the panel walls have been described, and the opinion on the further use of these elements has been presented. As for the analysed case, there is no possibility of replacing damaged elements, thus, additional reinforcement with steel tendons has been proposed as a repair measure.展开更多
The aim of this study was to analyze the effects of mechanical perforation of a golf course grassy sward, subject to maintenance machinery traffic and golf players trampling on its compaction and density. The evolutio...The aim of this study was to analyze the effects of mechanical perforation of a golf course grassy sward, subject to maintenance machinery traffic and golf players trampling on its compaction and density. The evolution of soil compaction state after aeration was also conducted in four stages of measurement. This operation aims to improve the structure and soil texture, which is also called ＂perforation＂ or ＂coring＂. The taken cores leaving on the soil holes of adjustable depth and density （350 holes/mE） are made with an aerator machine called Vertidrain. Soil resistance to penetration and density were determined at the initial state before aeration as well as 10, 20, and 30 days after aeration. Compared to the initial state, the results show that mechanical aeration greatly affects the grassy sward ground by reducing its resistance to penetration as 35% and 43% decrease in penetration resistance were noticed at 5 cm depth l0 and 20 days after aeration, respectively. Also, resistance to penetration decreased by 41% and 48% at 15 cm depth during the same two periods of time with a relatively constant moisture content. However, soil resistance to penetration at 5 and 15 cm depths only decreased by 21% and 26%, respectively. Regarding the soil density measured after aeration, a significant improvement at the 1% level with the method of variance analysis was observed compared to that at the initial state （e.g. 1.33 g·cm^-3） Indeed, the density was 1.29, 1.26 and 1.30 gcm^-3 10, 20 and 30 days after aeration, respectively.展开更多
One of the most important and effective hardware elements for improvement of efficiency and power density of proton exchange membrane fuel cells is the flow field plate. The design and the pattern of the flow field pl...One of the most important and effective hardware elements for improvement of efficiency and power density of proton exchange membrane fuel cells is the flow field plate. The design and the pattern of the flow field plate have a considerable effect on the effectiveness of mass transport as well as on the electrochemical reactions inside the cell. The configuration of the flow field plate aims at ensuring a low pressure-drop over all channels in the stack. In this work, a FPFFP （fractal parallel flow field plate）, with bio-inspired configuration by insertion of fractals in a classic PFFP （parallel flow field plate）, is proposed, increasing the flow area of the hydrogen at anode side without increasing the section＇s area of the flow field plate. By simulating was observed that, the use of channels in fractal shape can increase the hydrogen flow area without occuring pressure loss in the cell. The fluid dynamic behavior in the FPFFP at smaller scales was replicated in the same plate, with better advantage of the active area of the electrode. Increasing the hydrogen flow area without causing pressure loss could be a good tactic to increase the power density of fuel cells, and consequently improving the cell performance.展开更多
文摘Growing technical problems with the maintenance of precast concrete housing stock result in the search for efficient repair methods. The paper analyses the effects of flaws in the design concept and assembly accuracy of integrated AAC （autoclaved aerated concrete） panel walls, type GWO （Gazobetonowa Wielka P｜yta Ostonowa which means large cover panel from aerated concrete in English）, used as curtain walls in a system of precast concrete housing blocks erected in Lublin. The results of in-situ observations and laboratory tests of the panel walls have been described, and the opinion on the further use of these elements has been presented. As for the analysed case, there is no possibility of replacing damaged elements, thus, additional reinforcement with steel tendons has been proposed as a repair measure.
文摘The aim of this study was to analyze the effects of mechanical perforation of a golf course grassy sward, subject to maintenance machinery traffic and golf players trampling on its compaction and density. The evolution of soil compaction state after aeration was also conducted in four stages of measurement. This operation aims to improve the structure and soil texture, which is also called ＂perforation＂ or ＂coring＂. The taken cores leaving on the soil holes of adjustable depth and density （350 holes/mE） are made with an aerator machine called Vertidrain. Soil resistance to penetration and density were determined at the initial state before aeration as well as 10, 20, and 30 days after aeration. Compared to the initial state, the results show that mechanical aeration greatly affects the grassy sward ground by reducing its resistance to penetration as 35% and 43% decrease in penetration resistance were noticed at 5 cm depth l0 and 20 days after aeration, respectively. Also, resistance to penetration decreased by 41% and 48% at 15 cm depth during the same two periods of time with a relatively constant moisture content. However, soil resistance to penetration at 5 and 15 cm depths only decreased by 21% and 26%, respectively. Regarding the soil density measured after aeration, a significant improvement at the 1% level with the method of variance analysis was observed compared to that at the initial state （e.g. 1.33 g·cm^-3） Indeed, the density was 1.29, 1.26 and 1.30 gcm^-3 10, 20 and 30 days after aeration, respectively.
文摘One of the most important and effective hardware elements for improvement of efficiency and power density of proton exchange membrane fuel cells is the flow field plate. The design and the pattern of the flow field plate have a considerable effect on the effectiveness of mass transport as well as on the electrochemical reactions inside the cell. The configuration of the flow field plate aims at ensuring a low pressure-drop over all channels in the stack. In this work, a FPFFP （fractal parallel flow field plate）, with bio-inspired configuration by insertion of fractals in a classic PFFP （parallel flow field plate）, is proposed, increasing the flow area of the hydrogen at anode side without increasing the section＇s area of the flow field plate. By simulating was observed that, the use of channels in fractal shape can increase the hydrogen flow area without occuring pressure loss in the cell. The fluid dynamic behavior in the FPFFP at smaller scales was replicated in the same plate, with better advantage of the active area of the electrode. Increasing the hydrogen flow area without causing pressure loss could be a good tactic to increase the power density of fuel cells, and consequently improving the cell performance.
