The technique of creep feed grinding is most suitable for geometrical shaping, and therefore has been expected to improve effectively material removal rate and surface quality of components with complex profile. This ...The technique of creep feed grinding is most suitable for geometrical shaping, and therefore has been expected to improve effectively material removal rate and surface quality of components with complex profile. This article studies experimentally the effects of process parameters （i.e. wheel speed, workpiece speed and depth of cut） on the grindability and surface integrity of cast nickel-based superalloys, i.e. K424, during creep feed grinding with brazed cubic boron nitride （CBN） abrasive wheels. Some important factors, such as grinding force and temperature, specific grinding energy, size stability, surface topography, microhardhess and microstructure alteration of the sub-surface, residual stresses, are investigated in detail. The results show that during creep feed grinding with brazed CBN wheels, low grinding temperature at about 100 ℃ is obtained though the specific grinding energy of nickel-based superalloys is high up to 200-300 J/mm^3. A combination of wheel speed 22.5 m/s, workpiece speed 0.1 m/min, depth of cut 0.2 mm accomplishes the straight grooves with the expected dimensional accuracy. Moreover, the compressive residual stresses are formed in the bum-free and crack-free ground surface.展开更多
目的:探讨词联导航训练法(word association navigation training,WANT)结合经颅直流电刺激(tDCS)改善慢性非流畅性失语症患者言语功能的治疗方案。方法:16例非流畅性失语症患者随机分为真刺激组(8例)和伪刺激组(8例)。真刺激组tDCS阳...目的:探讨词联导航训练法(word association navigation training,WANT)结合经颅直流电刺激(tDCS)改善慢性非流畅性失语症患者言语功能的治疗方案。方法:16例非流畅性失语症患者随机分为真刺激组(8例)和伪刺激组(8例)。真刺激组tDCS阳极置于左侧Broca区,阴极置于对侧肩部,电流强度为1.0mA,2次/天,20min/次,连续10d。伪刺激组每次tDCS刺激30s后停止。两组同时实施WANT训练。治疗前后进行西方失语症成套测试(WAB)、训练图片和未训练图片命名测试。结果:治疗前后两组WAB失语商(WAB-AQ)和图片命名测试得分均有显著提高(P<0.05)。治疗后真刺激组训练图片命名得分和WAB中言语流畅度得分显著提高(P<0.01)。未训练图片命名测试得分和WAB-AQ较伪刺激组改善明显(P<0.05)。结论:词联导航训练法结合tDCS能更显著地改善慢性非流畅性失语症患者的言语流畅度和命名能力。展开更多
基金National Basic Research Program of China (2009CB724403)Program for Changjiang Scholars and Innovative Research Team in University (IRT0837)Program for New Century Excellent Talents in University from Ministry of Education of China (NCET-07-0435)
文摘The technique of creep feed grinding is most suitable for geometrical shaping, and therefore has been expected to improve effectively material removal rate and surface quality of components with complex profile. This article studies experimentally the effects of process parameters （i.e. wheel speed, workpiece speed and depth of cut） on the grindability and surface integrity of cast nickel-based superalloys, i.e. K424, during creep feed grinding with brazed cubic boron nitride （CBN） abrasive wheels. Some important factors, such as grinding force and temperature, specific grinding energy, size stability, surface topography, microhardhess and microstructure alteration of the sub-surface, residual stresses, are investigated in detail. The results show that during creep feed grinding with brazed CBN wheels, low grinding temperature at about 100 ℃ is obtained though the specific grinding energy of nickel-based superalloys is high up to 200-300 J/mm^3. A combination of wheel speed 22.5 m/s, workpiece speed 0.1 m/min, depth of cut 0.2 mm accomplishes the straight grooves with the expected dimensional accuracy. Moreover, the compressive residual stresses are formed in the bum-free and crack-free ground surface.
文摘目的:探讨词联导航训练法(word association navigation training,WANT)结合经颅直流电刺激(tDCS)改善慢性非流畅性失语症患者言语功能的治疗方案。方法:16例非流畅性失语症患者随机分为真刺激组(8例)和伪刺激组(8例)。真刺激组tDCS阳极置于左侧Broca区,阴极置于对侧肩部,电流强度为1.0mA,2次/天,20min/次,连续10d。伪刺激组每次tDCS刺激30s后停止。两组同时实施WANT训练。治疗前后进行西方失语症成套测试(WAB)、训练图片和未训练图片命名测试。结果:治疗前后两组WAB失语商(WAB-AQ)和图片命名测试得分均有显著提高(P<0.05)。治疗后真刺激组训练图片命名得分和WAB中言语流畅度得分显著提高(P<0.01)。未训练图片命名测试得分和WAB-AQ较伪刺激组改善明显(P<0.05)。结论:词联导航训练法结合tDCS能更显著地改善慢性非流畅性失语症患者的言语流畅度和命名能力。
