Two-dimensional(2D) materials and their heterostructures have attracted a lot of attention due to their unique electronic and optical properties. MoS_2 as the most typical 2D semiconductors has great application poten...Two-dimensional(2D) materials and their heterostructures have attracted a lot of attention due to their unique electronic and optical properties. MoS_2 as the most typical 2D semiconductors has great application potential in thin film transistors, photodetector, hydrogen evolution reaction, memory device, etc. However, the performance of MoS_2 devices is limited by the contact resistance and the improvement of its contact quality is important. In this work, we report the experimental investigation of pressure-enhanced contact quality between monolayer MoS_2 and graphite by conductive atom force microscope(C-AFM). It was found that at high pressure, the contact quality between graphite and MoS_2 is significantly improved. This pressure-mediated contact quality improvement between MoS_2 and graphite comes from the enhanced charge transfer between MoS_2 and graphite when MoS_2 is stretched. Our results provide a new way to enhance the contact quality between MoS_2 and graphite for further applications.展开更多
In order to find out the contact pressure intensity distribution and its effects on the workepiece flatness error in plane polishing with retaining ring,the contact model and the boundary conditions are built up based...In order to find out the contact pressure intensity distribution and its effects on the workepiece flatness error in plane polishing with retaining ring,the contact model and the boundary conditions are built up based on the axial symmetric elastic contact theory.The pressure intensity distribution is calculated and analyzed with the help of the Hankel transform theory and the constructing solution method of Chebyshev orthogonal polynomials.And then,the effects of the dimensionless ring-workpiece gap,the load ratio of the retaining ring and the dimensionless ring width on the contact pressure intensity distribution are obtained.Finally,based on the distribution theory of material removal volume,the effects of the pressure intensity distributions on the flatness errors of polished workpiece are also investigated experimentally.The results show that the contact pressure intensity distribution becomes more uniform and the better profile of polished workpiece can also be obtained,if the dimensionless ring-workpiece gap is reduced,the load ratio is selected as 0.6 to 0.85,and the dimensionless ring width is taken as 0.13 to 0.40.展开更多
An atmospheric pressure plasma jet generated in Ar and O2/Ar mixtures has been investigated by specially designed equipment with double power electrodes at 20~32 kHz, and their effects on the cleaning of surfaces have...An atmospheric pressure plasma jet generated in Ar and O2/Ar mixtures has been investigated by specially designed equipment with double power electrodes at 20~32 kHz, and their effects on the cleaning of surfaces have been studied. Properties of the jet discharge are studied by electrical diagnostics, including the waveform of discharge voltage, discharge current and the Q-V Lissajous figures. The optical emission spectroscopy is used to measure the plasma parameters, such as the excitation temperature and the gas temperature. It is found that the consumed power and the excitation temperature increase with increase of the discharge frequency. On the other hand, at the same discharge frequency, these parameters in O2/Ar mixture plasma are found to be much larger. The effect on surface cleaning is studied from the changes in the contact angle. For Ar plasma jet, the contact angle decreases with increase of the discharge frequency. For O2/Ar mixture plasma jet, the contact angle decreases with increase of discharge frequency up to 26 kHz, however, further increase of discharge frequency does not show further decrease in the contact angle. At the same discharge frequency, the contact angle after O2/Ar mixture plasma cleaning is found to be much lower compared to the case of pure Ar. From the results of quadrupole mass-spectrum analysis, we can identify more fragment molecules of CO and H2O in the emitted gases after O2/Ar plasma jet treatment compared with Ar plasma jet treatment, which are produced by the decomposition of surface organic contaminants during the cleaning process.展开更多
One of the major advantages of utilizing atmospheric pressure plasma processing （APPP） technology to fabricate ultra-precision optics is that there is no subsurface damage during the process. In APPP, the removal fo...One of the major advantages of utilizing atmospheric pressure plasma processing （APPP） technology to fabricate ultra-precision optics is that there is no subsurface damage during the process. In APPP, the removal footprint and removal rate are critical to the capability and efficiency of the figuring of the optical surface. In this paper, an atmospheric plasma torch, which can work in both remote mode and contact mode, is presented. The footprints and the removal rates of both modes are compared by profilometer measurements. The influences of process recipes and substrate thickness for both modes are investigated through a series of experiments. When the substrate is thinner than 12 mm, the removal rate in contact mode is higher. However, the removal rate and width of the footprint decrease dramatically as the substrate thickness increases in contact mode.展开更多
目的:分析飞秒激光小切口角膜基质透镜取出术(SMILE)后影响非接触式眼压(IOP_(NCT))测量值的部分因素,探讨SMILE术后IOP_(NCT)与角膜中央厚度(CCT)及角膜曲率之间的相关性,并构建相应的回归模型,为临床评估SMILE术后患者眼压真实状况提...目的:分析飞秒激光小切口角膜基质透镜取出术(SMILE)后影响非接触式眼压(IOP_(NCT))测量值的部分因素,探讨SMILE术后IOP_(NCT)与角膜中央厚度(CCT)及角膜曲率之间的相关性,并构建相应的回归模型,为临床评估SMILE术后患者眼压真实状况提供科学依据。方法:回顾性分析2023-06/2024-05在成都市第三人民医院眼科行SMILE的近视患者107例206眼和行飞秒激光原位角膜磨镶术(FS-LASIK)的近视患者107例201眼,收集患者术前,术后1、3 mo的IOP_(NCT)测量值、CCT、角膜曲率等资料,通过重复测量数据的方差分析、Pearson相关性分析对手术前后的IOP_(NCT)、CCT、角膜曲率进行分析,并构建多元线性回归模型评估术后IOP_(NCT)与CCT、角膜曲率变化值之间的关联性。结果:SMILE与FS-LASIK术后患者的IOP_(NCT)、CCT、角膜曲率在时间上均存在显著差异(均P<0.001),组间和交互比较无差异(均P>0.05),两组术后1、3 mo IOP_(NCT)、CCT、角膜曲率均显著低于术前(均P<0.05)。SMILE患者术后1、3 mo IOP_(NCT)与CCT之间呈正相关(r=0.261、0.267,均P<0.001),而与角膜曲率无显著相关(均P>0.05)。SMILE术后1 mo IOP_(NCT)与CCT、角膜曲率之间的回归方程为:Y=3.426+0.019X_(1)-0.058X_(2)(Y代表IOP_(NCT),X_(1)代表CCT,X_(2)代表角膜曲率),方程差异有统计学意义(F=7.654,P=0.001);术后3 mo的回归方程为:Y=2.056+0.020X_(1)-0.038X_(2)(Y代表IOP_(NCT),X_(1)代表CCT,X_(2)代表角膜曲率),方程差异有统计学意义(F=7.903,P<0.001)。SMILE术前术后IOP_(NCT)变化值(△IOP_(NCT))与术中切削角膜厚度(△CCT)、角膜曲率变化值在术后1 mo的回归方程为:Y=-2.252+0.008X_(1)+0.587X_(2)(其中Y代表△IOP_(NCT),X_(1)代表△CCT,X_(2)代表角膜曲率变化值),方程差异有统计学意义(F=17.550,P<0.001);术后3 mo的回归方程为:Y=-2.168+0.024X_(1)+0.281X_(2)(Y表示△IOP_(NCT),X_(1)表示△CCT,X_(2)表示角膜曲率变化值),方程差异有统计学意义(F=16.030,P<0.001)。结论:SMILE与FS-LASIK手术后,患者IOP_(NCT)值主要受CCT影响较术前降低,术后短期内使用激素类滴眼液氟米龙不会使眼压升高,且SMILE术后1 mo眼压校正公式Y=3.426+0.019X_(1)-0.058X_(2)(Y代表IOP_(NCT),X_(1)代表CCT,X_(2)代表角膜曲率)和术后3 mo眼压校正公式Y=2.056+0.020 X_(1)-0.038X_(2)(Y代表IOP_(NCT),X_(1)代表CCT,X_(2)代表角膜曲率)均可用于临床以评估SMILE术后患者的实际眼压并进行修正。展开更多
To obtain thermal contact resistance（TCR） between the vertical double-diffused metal-oxide-semiconductor（VDMOS） and the heat sink, we derived the relationship between the total thermal resistance and the contact f...To obtain thermal contact resistance（TCR） between the vertical double-diffused metal-oxide-semiconductor（VDMOS） and the heat sink, we derived the relationship between the total thermal resistance and the contact force imposed on the VDMOS. The total thermal resistance from the chip to the heat sink is measured under different contact forces, and the TCR can be extracted nondestructively from the derived relationship. Finally, the experimental results are compared with the simulation results.展开更多
基金Project supported by the National Key R&D Program,China(Grant No.2016YFA0300904)the Key Research Program of Frontier Sciences of the Chinese Academy of Sciences(Grant No.QYZDB-SSW-SLH004)+1 种基金the Strategic Priority Research Program(B)of the Chinese Academy of Sciences(Grant Nos.XDPB06 and XDB07010100)the National Natural Science Foundation of China(Grant Nos.61734001 and 51572289)
文摘Two-dimensional(2D) materials and their heterostructures have attracted a lot of attention due to their unique electronic and optical properties. MoS_2 as the most typical 2D semiconductors has great application potential in thin film transistors, photodetector, hydrogen evolution reaction, memory device, etc. However, the performance of MoS_2 devices is limited by the contact resistance and the improvement of its contact quality is important. In this work, we report the experimental investigation of pressure-enhanced contact quality between monolayer MoS_2 and graphite by conductive atom force microscope(C-AFM). It was found that at high pressure, the contact quality between graphite and MoS_2 is significantly improved. This pressure-mediated contact quality improvement between MoS_2 and graphite comes from the enhanced charge transfer between MoS_2 and graphite when MoS_2 is stretched. Our results provide a new way to enhance the contact quality between MoS_2 and graphite for further applications.
基金Sponsored by the National Nature Science Foundation of China (50875179)
文摘In order to find out the contact pressure intensity distribution and its effects on the workepiece flatness error in plane polishing with retaining ring,the contact model and the boundary conditions are built up based on the axial symmetric elastic contact theory.The pressure intensity distribution is calculated and analyzed with the help of the Hankel transform theory and the constructing solution method of Chebyshev orthogonal polynomials.And then,the effects of the dimensionless ring-workpiece gap,the load ratio of the retaining ring and the dimensionless ring width on the contact pressure intensity distribution are obtained.Finally,based on the distribution theory of material removal volume,the effects of the pressure intensity distributions on the flatness errors of polished workpiece are also investigated experimentally.The results show that the contact pressure intensity distribution becomes more uniform and the better profile of polished workpiece can also be obtained,if the dimensionless ring-workpiece gap is reduced,the load ratio is selected as 0.6 to 0.85,and the dimensionless ring width is taken as 0.13 to 0.40.
基金supported by National Natural Science Foundation of China(Nos.51077008 and 11247239)
文摘An atmospheric pressure plasma jet generated in Ar and O2/Ar mixtures has been investigated by specially designed equipment with double power electrodes at 20~32 kHz, and their effects on the cleaning of surfaces have been studied. Properties of the jet discharge are studied by electrical diagnostics, including the waveform of discharge voltage, discharge current and the Q-V Lissajous figures. The optical emission spectroscopy is used to measure the plasma parameters, such as the excitation temperature and the gas temperature. It is found that the consumed power and the excitation temperature increase with increase of the discharge frequency. On the other hand, at the same discharge frequency, these parameters in O2/Ar mixture plasma are found to be much larger. The effect on surface cleaning is studied from the changes in the contact angle. For Ar plasma jet, the contact angle decreases with increase of the discharge frequency. For O2/Ar mixture plasma jet, the contact angle decreases with increase of discharge frequency up to 26 kHz, however, further increase of discharge frequency does not show further decrease in the contact angle. At the same discharge frequency, the contact angle after O2/Ar mixture plasma cleaning is found to be much lower compared to the case of pure Ar. From the results of quadrupole mass-spectrum analysis, we can identify more fragment molecules of CO and H2O in the emitted gases after O2/Ar plasma jet treatment compared with Ar plasma jet treatment, which are produced by the decomposition of surface organic contaminants during the cleaning process.
基金supported by National Natural Science Foundation of China(Nos.51175123 and 51105112)National Science and Technology Major Project of China(No.2013ZX04006011-205)
文摘One of the major advantages of utilizing atmospheric pressure plasma processing （APPP） technology to fabricate ultra-precision optics is that there is no subsurface damage during the process. In APPP, the removal footprint and removal rate are critical to the capability and efficiency of the figuring of the optical surface. In this paper, an atmospheric plasma torch, which can work in both remote mode and contact mode, is presented. The footprints and the removal rates of both modes are compared by profilometer measurements. The influences of process recipes and substrate thickness for both modes are investigated through a series of experiments. When the substrate is thinner than 12 mm, the removal rate in contact mode is higher. However, the removal rate and width of the footprint decrease dramatically as the substrate thickness increases in contact mode.
文摘目的:分析飞秒激光小切口角膜基质透镜取出术(SMILE)后影响非接触式眼压(IOP_(NCT))测量值的部分因素,探讨SMILE术后IOP_(NCT)与角膜中央厚度(CCT)及角膜曲率之间的相关性,并构建相应的回归模型,为临床评估SMILE术后患者眼压真实状况提供科学依据。方法:回顾性分析2023-06/2024-05在成都市第三人民医院眼科行SMILE的近视患者107例206眼和行飞秒激光原位角膜磨镶术(FS-LASIK)的近视患者107例201眼,收集患者术前,术后1、3 mo的IOP_(NCT)测量值、CCT、角膜曲率等资料,通过重复测量数据的方差分析、Pearson相关性分析对手术前后的IOP_(NCT)、CCT、角膜曲率进行分析,并构建多元线性回归模型评估术后IOP_(NCT)与CCT、角膜曲率变化值之间的关联性。结果:SMILE与FS-LASIK术后患者的IOP_(NCT)、CCT、角膜曲率在时间上均存在显著差异(均P<0.001),组间和交互比较无差异(均P>0.05),两组术后1、3 mo IOP_(NCT)、CCT、角膜曲率均显著低于术前(均P<0.05)。SMILE患者术后1、3 mo IOP_(NCT)与CCT之间呈正相关(r=0.261、0.267,均P<0.001),而与角膜曲率无显著相关(均P>0.05)。SMILE术后1 mo IOP_(NCT)与CCT、角膜曲率之间的回归方程为:Y=3.426+0.019X_(1)-0.058X_(2)(Y代表IOP_(NCT),X_(1)代表CCT,X_(2)代表角膜曲率),方程差异有统计学意义(F=7.654,P=0.001);术后3 mo的回归方程为:Y=2.056+0.020X_(1)-0.038X_(2)(Y代表IOP_(NCT),X_(1)代表CCT,X_(2)代表角膜曲率),方程差异有统计学意义(F=7.903,P<0.001)。SMILE术前术后IOP_(NCT)变化值(△IOP_(NCT))与术中切削角膜厚度(△CCT)、角膜曲率变化值在术后1 mo的回归方程为:Y=-2.252+0.008X_(1)+0.587X_(2)(其中Y代表△IOP_(NCT),X_(1)代表△CCT,X_(2)代表角膜曲率变化值),方程差异有统计学意义(F=17.550,P<0.001);术后3 mo的回归方程为:Y=-2.168+0.024X_(1)+0.281X_(2)(Y表示△IOP_(NCT),X_(1)表示△CCT,X_(2)表示角膜曲率变化值),方程差异有统计学意义(F=16.030,P<0.001)。结论:SMILE与FS-LASIK手术后,患者IOP_(NCT)值主要受CCT影响较术前降低,术后短期内使用激素类滴眼液氟米龙不会使眼压升高,且SMILE术后1 mo眼压校正公式Y=3.426+0.019X_(1)-0.058X_(2)(Y代表IOP_(NCT),X_(1)代表CCT,X_(2)代表角膜曲率)和术后3 mo眼压校正公式Y=2.056+0.020 X_(1)-0.038X_(2)(Y代表IOP_(NCT),X_(1)代表CCT,X_(2)代表角膜曲率)均可用于临床以评估SMILE术后患者的实际眼压并进行修正。
基金Project supported by the National Natural Science Foundation of China(Grant No.61204081)
文摘To obtain thermal contact resistance（TCR） between the vertical double-diffused metal-oxide-semiconductor（VDMOS） and the heat sink, we derived the relationship between the total thermal resistance and the contact force imposed on the VDMOS. The total thermal resistance from the chip to the heat sink is measured under different contact forces, and the TCR can be extracted nondestructively from the derived relationship. Finally, the experimental results are compared with the simulation results.
