This paper presents an experimental study of the broadband energy harvesting and dynamic responses of an L-shaped piezoelectric cantilever beam.Experimental results show that the L-shaped piezoelectric beam generates ...This paper presents an experimental study of the broadband energy harvesting and dynamic responses of an L-shaped piezoelectric cantilever beam.Experimental results show that the L-shaped piezoelectric beam generates two optimal voltage peaks when the horizontal beam size is similar to the vertical beam size.Several optimized L-shaped piezoelectric cantilever beam structures are proposed.Power generation using the inverted bistable L-shaped beam is better.It is observed experimentally that the inverted bistable L-shaped beam structure shows obvious bistable characteristics and hard spring characteristics.Furthermore,the corresponding relationship between the bistable phase portrait and the potential energy curve is found in the experiment.This is the first time that a phase portrait for stiffness hardening of an L-shaped beam has been found experimentally.These results can be applied to analysis of new piezoelectric power generation structures.展开更多
To investigate the control effect and flow mechanism of the L-shaped endwall groove on corner separation in the real compressor stage,a single stage axial flow compressor is selected as the research object and the L-s...To investigate the control effect and flow mechanism of the L-shaped endwall groove on corner separation in the real compressor stage,a single stage axial flow compressor is selected as the research object and the L-shaped grooves are introduced on the stator casing side.First,the experimental measurement is conducted on the optimal L-shaped groove obtained through a full factorial experimental design,and the results demonstrate that the optimal groove has a great control over the endwall flow.Moreover,the peak efficiency is improved by 0.9%and the stall margin is increased by 4.46%.Then,the flow field visualization of numerical results and analysis of variance method are employed to analyze the control mechanism and parameter control law of the L-shaped groove.It is found that the L-shaped groove can guide the skewed inlet endwall boundary layer towards the streamwise direction due to its confinement effect,thereby delaying the onset of corner separation and reducing the size of ring vortex.As a result,the aerodynamic performance of the compressor is enhanced.Furthermore,the groove depth and groove width play a significant role in controlling endwall flow among the three L-shaped groove design parameters.The larger groove depth and smaller groove width enhance the capability of the streamwise groove to constrain the endwall boundary layer,leading to a greater reduction in endwall loss.展开更多
目的：回顾性分析 Tile C 型骨盆骨折患者死亡相关的危险因素。方法2010年1月至2014年12月我院收治的 Tile C 型骨盆骨折患者139例,收集资料包括术前一般情况、伤后就诊时间、休克指数、各类创伤评分、最低氧合指数、伤后6 h 乳酸清除率...目的：回顾性分析 Tile C 型骨盆骨折患者死亡相关的危险因素。方法2010年1月至2014年12月我院收治的 Tile C 型骨盆骨折患者139例,收集资料包括术前一般情况、伤后就诊时间、休克指数、各类创伤评分、最低氧合指数、伤后6 h 乳酸清除率等,采用多因素 Logistic 回归分析死亡相关危险因素。结果入院后死亡41例（29.5%）,其中入院后48 h 内死亡36例（25.9%）。多因素回归分析显示,休克指数＆gt;2（OR=2.591,95%CI 1.041~4.216）、损伤严重程度评分（ISS）≥25分（OR=47.96,95%CI 15.89~147.23）、改良创伤评分（RTS）≤8分（OR=6.917,95%CI 1.147-13.862）、格拉斯哥昏迷评分（GCS）〈9分（OR=4.172,95%CI 2.962~6.268）、最低氧合指数〈200（OR=117.016,95%CI 51.011~176.032）、伤后6 h 乳酸清除率〈10%（OR=2.785,95%CI 1.191~4.892）,以及合并头部损伤（OR=6.302,95%CI 2.270~13.175）或胸部损伤（OR=12.233,95%CI 5.193~33.985）是骨盆骨折患者死亡相关危险因素（P 〈0.01）。早期行血管栓塞治疗有助于降低死亡风险（OR=0.887,95%CI 0.875~0.899）。结论创伤评分高,出现严重休克、昏迷、氧合指数下降和6 h 乳酸清除率降低,合并头部和胸部损伤是导致 Tile C 型骨盆骨折患者死亡的危险因素。展开更多
基金supported by the National Natural Science Foundation of China(Grants 11772008,11172009,11372015,11232009,10872010,11290152,10732020)the Tianjin Natural Science Foundation(Grant 19JCZDJC32300).
文摘This paper presents an experimental study of the broadband energy harvesting and dynamic responses of an L-shaped piezoelectric cantilever beam.Experimental results show that the L-shaped piezoelectric beam generates two optimal voltage peaks when the horizontal beam size is similar to the vertical beam size.Several optimized L-shaped piezoelectric cantilever beam structures are proposed.Power generation using the inverted bistable L-shaped beam is better.It is observed experimentally that the inverted bistable L-shaped beam structure shows obvious bistable characteristics and hard spring characteristics.Furthermore,the corresponding relationship between the bistable phase portrait and the potential energy curve is found in the experiment.This is the first time that a phase portrait for stiffness hardening of an L-shaped beam has been found experimentally.These results can be applied to analysis of new piezoelectric power generation structures.
基金financially supported by the National Natural Science Foundation of China(No.52176045)the National Science and Technology Major Project of China(No.J2019-I-0011-0011)。
文摘To investigate the control effect and flow mechanism of the L-shaped endwall groove on corner separation in the real compressor stage,a single stage axial flow compressor is selected as the research object and the L-shaped grooves are introduced on the stator casing side.First,the experimental measurement is conducted on the optimal L-shaped groove obtained through a full factorial experimental design,and the results demonstrate that the optimal groove has a great control over the endwall flow.Moreover,the peak efficiency is improved by 0.9%and the stall margin is increased by 4.46%.Then,the flow field visualization of numerical results and analysis of variance method are employed to analyze the control mechanism and parameter control law of the L-shaped groove.It is found that the L-shaped groove can guide the skewed inlet endwall boundary layer towards the streamwise direction due to its confinement effect,thereby delaying the onset of corner separation and reducing the size of ring vortex.As a result,the aerodynamic performance of the compressor is enhanced.Furthermore,the groove depth and groove width play a significant role in controlling endwall flow among the three L-shaped groove design parameters.The larger groove depth and smaller groove width enhance the capability of the streamwise groove to constrain the endwall boundary layer,leading to a greater reduction in endwall loss.
文摘目的：回顾性分析 Tile C 型骨盆骨折患者死亡相关的危险因素。方法2010年1月至2014年12月我院收治的 Tile C 型骨盆骨折患者139例,收集资料包括术前一般情况、伤后就诊时间、休克指数、各类创伤评分、最低氧合指数、伤后6 h 乳酸清除率等,采用多因素 Logistic 回归分析死亡相关危险因素。结果入院后死亡41例（29.5%）,其中入院后48 h 内死亡36例（25.9%）。多因素回归分析显示,休克指数＆gt;2（OR=2.591,95%CI 1.041~4.216）、损伤严重程度评分（ISS）≥25分（OR=47.96,95%CI 15.89~147.23）、改良创伤评分（RTS）≤8分（OR=6.917,95%CI 1.147-13.862）、格拉斯哥昏迷评分（GCS）〈9分（OR=4.172,95%CI 2.962~6.268）、最低氧合指数〈200（OR=117.016,95%CI 51.011~176.032）、伤后6 h 乳酸清除率〈10%（OR=2.785,95%CI 1.191~4.892）,以及合并头部损伤（OR=6.302,95%CI 2.270~13.175）或胸部损伤（OR=12.233,95%CI 5.193~33.985）是骨盆骨折患者死亡相关危险因素（P 〈0.01）。早期行血管栓塞治疗有助于降低死亡风险（OR=0.887,95%CI 0.875~0.899）。结论创伤评分高,出现严重休克、昏迷、氧合指数下降和6 h 乳酸清除率降低,合并头部和胸部损伤是导致 Tile C 型骨盆骨折患者死亡的危险因素。
