We have calculated the longitudinal acoustic phonon limited electron mobility of 14 twvo-dimensional semiconductors with composition of MX2, where M （= Mo, W, Sn, Hf, Zr and Pt） is the transition metal, and X is S, ...We have calculated the longitudinal acoustic phonon limited electron mobility of 14 twvo-dimensional semiconductors with composition of MX2, where M （= Mo, W, Sn, Hf, Zr and Pt） is the transition metal, and X is S, Se and Te. We treated the scattering matrix by the deformation potential approximation. We found that out of 14 compounds, MoTe2, HfSe2 and ZrSe2 are promising regarding to their possible high mobility and finite band gap. The phonon limited mobility can be above 2,500 cm^2·V^-1·s^-1 at room temperature.展开更多
In order to solve the bad low frequency sound absorption of the Micro-Perforated panel （MPP） absorber, mechanical impedance was introduced in the back of the MPP absorber to form a composite structure. According to ...In order to solve the bad low frequency sound absorption of the Micro-Perforated panel （MPP） absorber, mechanical impedance was introduced in the back of the MPP absorber to form a composite structure. According to the same particle vibration velocity on both sides of a plate, the mechanical impedance plate transfer matrix could be obtained. The units of the mechanical impedance, cavity and MPP were connected in series with the use of the transfer matrix method, thus creating the composite structure＇s theoretical calculation model. The qual- ity factor affecting absorption bandwidth was analyzed. Bandwidth is inversely proportional to the mechanical impedance plate mass. During the experiments, when at close to 400 Hz, the composite structure reached an absorption peak with a coefficient of above 0.8. Experimen- tal results concurred with theoretical calculations. Mechanical resonance is added based on the traditional MPP resonance sound absorption mechanism. Through this, the performance of low frequency sound absorption can be improved without increasing the thickness of the structure. The frequency band can be broadened by reducing the mechanical impedance plate mass and controlling its boundary-damping coefficient.展开更多
目的：观察 Solitaire AB 型支架取栓术治疗血栓栓塞造成的急性大脑中动脉闭塞或合并颈内动脉闭塞的效果。方法因急性血栓栓塞造成的单纯大脑中动脉闭塞患者5例、大脑中动脉闭塞合并同侧颈内动脉不同节段闭塞患者8例。13例患者在发病6 h...目的：观察 Solitaire AB 型支架取栓术治疗血栓栓塞造成的急性大脑中动脉闭塞或合并颈内动脉闭塞的效果。方法因急性血栓栓塞造成的单纯大脑中动脉闭塞患者5例、大脑中动脉闭塞合并同侧颈内动脉不同节段闭塞患者8例。13例患者在发病6 h 内接受了取栓治疗，利用 Solitaire AB 型支架取栓。结果13例患者中，10例闭塞血管再通、3例闭塞血管部分再通；出院时美国国立卫生研究院卒中量表（NIHSS）评分（中位数）为6（4）分，较术前 NIHSS 评分（中位数）19（4．5）分明显下降（P ＜0．01）。10例闭塞血管再通患者中，4例恢复良好（mRS 评分0～2分）、4例残疾（mRS 评分≥3分）、1例死于原发性肾病、1例死于心力衰竭；3例闭塞血管部分再通患者中，1例术后第90天随访 mRS 评分4分，2例因大面积脑梗死死亡。13例患者中，8例术后24 h 颅脑 CT 扫描示脑梗死灶内出血。结果 Solitaire AB 型支架取栓术治疗血栓栓塞造成的急性大脑中动脉闭塞或合并颈内动脉闭塞可获得较高的血管再通率，临床效果较好。展开更多
The first-principles density functional calculation is used to investigate the electronic structures and magnetic properties of Mn-doped and N-co-doped ZnO nanofilms.The band structure calculation shows that the band ...The first-principles density functional calculation is used to investigate the electronic structures and magnetic properties of Mn-doped and N-co-doped ZnO nanofilms.The band structure calculation shows that the band gaps of ZnO films with 2,4,and 6 layers are larger than the band gap of the bulk with wurtzite structure and decrease with the increase of film thickness.However,the four-layer ZnO nanofilms exhibit ferromagnetic phases for Mn concentrations less than 24% and 12% for Mn-doping performed in the whole layers and two layers of the film respectively,while they exhibit spin glass phases for higher Mn concentrations.It is also found,on the one hand,that the spin glass phase turns into the ferromagnetic one,with the substitution of nitrogen atoms for oxygen atoms,for nitrogen concentrations higher than 16% and 5% for Mn-doping performed in the whole layers and two layers of the film respectively.On the other hand,the spin-glass state is more stable for ZnO bulk containing 5% of Mn impurities,while the ferromagnetic phase is stable by introducing the p-type carriers into the bulk system.Moreover,it is shown that using the effective field theory for ferromagnetic system,the Curie temperature is close to the room temperature for the undamped Ruderman-Kittel-Kasuya-Yoshida（RKKY） interaction.展开更多
文摘We have calculated the longitudinal acoustic phonon limited electron mobility of 14 twvo-dimensional semiconductors with composition of MX2, where M （= Mo, W, Sn, Hf, Zr and Pt） is the transition metal, and X is S, Se and Te. We treated the scattering matrix by the deformation potential approximation. We found that out of 14 compounds, MoTe2, HfSe2 and ZrSe2 are promising regarding to their possible high mobility and finite band gap. The phonon limited mobility can be above 2,500 cm^2·V^-1·s^-1 at room temperature.
基金supported by the Scientific Research Foundation for Senior Professional of Jiangsu University(11JDG096)the Project Funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions((2011)6)
文摘In order to solve the bad low frequency sound absorption of the Micro-Perforated panel （MPP） absorber, mechanical impedance was introduced in the back of the MPP absorber to form a composite structure. According to the same particle vibration velocity on both sides of a plate, the mechanical impedance plate transfer matrix could be obtained. The units of the mechanical impedance, cavity and MPP were connected in series with the use of the transfer matrix method, thus creating the composite structure＇s theoretical calculation model. The qual- ity factor affecting absorption bandwidth was analyzed. Bandwidth is inversely proportional to the mechanical impedance plate mass. During the experiments, when at close to 400 Hz, the composite structure reached an absorption peak with a coefficient of above 0.8. Experimen- tal results concurred with theoretical calculations. Mechanical resonance is added based on the traditional MPP resonance sound absorption mechanism. Through this, the performance of low frequency sound absorption can be improved without increasing the thickness of the structure. The frequency band can be broadened by reducing the mechanical impedance plate mass and controlling its boundary-damping coefficient.
文摘目的：观察 Solitaire AB 型支架取栓术治疗血栓栓塞造成的急性大脑中动脉闭塞或合并颈内动脉闭塞的效果。方法因急性血栓栓塞造成的单纯大脑中动脉闭塞患者5例、大脑中动脉闭塞合并同侧颈内动脉不同节段闭塞患者8例。13例患者在发病6 h 内接受了取栓治疗，利用 Solitaire AB 型支架取栓。结果13例患者中，10例闭塞血管再通、3例闭塞血管部分再通；出院时美国国立卫生研究院卒中量表（NIHSS）评分（中位数）为6（4）分，较术前 NIHSS 评分（中位数）19（4．5）分明显下降（P ＜0．01）。10例闭塞血管再通患者中，4例恢复良好（mRS 评分0～2分）、4例残疾（mRS 评分≥3分）、1例死于原发性肾病、1例死于心力衰竭；3例闭塞血管部分再通患者中，1例术后第90天随访 mRS 评分4分，2例因大面积脑梗死死亡。13例患者中，8例术后24 h 颅脑 CT 扫描示脑梗死灶内出血。结果 Solitaire AB 型支架取栓术治疗血栓栓塞造成的急性大脑中动脉闭塞或合并颈内动脉闭塞可获得较高的血管再通率，临床效果较好。
文摘The first-principles density functional calculation is used to investigate the electronic structures and magnetic properties of Mn-doped and N-co-doped ZnO nanofilms.The band structure calculation shows that the band gaps of ZnO films with 2,4,and 6 layers are larger than the band gap of the bulk with wurtzite structure and decrease with the increase of film thickness.However,the four-layer ZnO nanofilms exhibit ferromagnetic phases for Mn concentrations less than 24% and 12% for Mn-doping performed in the whole layers and two layers of the film respectively,while they exhibit spin glass phases for higher Mn concentrations.It is also found,on the one hand,that the spin glass phase turns into the ferromagnetic one,with the substitution of nitrogen atoms for oxygen atoms,for nitrogen concentrations higher than 16% and 5% for Mn-doping performed in the whole layers and two layers of the film respectively.On the other hand,the spin-glass state is more stable for ZnO bulk containing 5% of Mn impurities,while the ferromagnetic phase is stable by introducing the p-type carriers into the bulk system.Moreover,it is shown that using the effective field theory for ferromagnetic system,the Curie temperature is close to the room temperature for the undamped Ruderman-Kittel-Kasuya-Yoshida（RKKY） interaction.
