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为促进各向同性热解石墨的精密/超精密加工技术的发展,采用压痕试验的方法研究了其在纳米/微米尺度上的尺寸效应.在确立压痕试验中使用载荷可行性域的基础上,对不同载荷作用条件下存在的尺寸效应进行了研究.结果表明,为提高尺寸效应分析的准确性,本试验条件下所施加的载荷应大于450 μN,且各向同性热解石墨压痕试验中硬度及弹性模量均存在一定的尺寸效应.同时,尺寸效应主要是由各向同性热解石墨表面附近球形单元内部的位错运动引起的.位错滑移阻碍较小时产生的尺寸效应较明显,位错滑移阻碍较大时产生的尺寸效应并不显著. 相似文献
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为了研究各向同性热解石墨切削过程中单晶金刚石刀具磨损及其对加工质量的影响,对各向同性热解石墨材料进行了切削试验.观测了刀具磨损形貌的演变过程,分析了刀具磨损机理以及刀具磨损对加工表面质量的影响.研究结果表明,在切削距离逐渐增加的情况下,单晶金刚石刀具后刀面磨损区域逐渐增大,磨损形貌分为平行沟槽和微细网状两种.切削过程中产生的颗粒状切屑和交变应力分别是导致磨粒磨损和解理磨损的主要原因.切削距离300 m内,试件加工表面粗糙度值Ra在0.2~0.4 μm之间波动,切削距离达到l000 m以后,试件加工表面粗糙度值明显增大,但是保持了相对稳定,表面粗糙度值Ra约为0.8μm. 相似文献
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Squeezed states belong to the most prominent non-classical resources. They have compelling applications in precise measurement, quantum computation, and detection. Here, we report on the direct measurement of 13.8 d B squeezed vacuum states by improving the interference efficiency and gain of balanced homodyne detection. By employing an auxiliary laser beam, the homodyne visibility is increased to 99.8%. The equivalent loss of the electronic noise is reduced to 0.05% by integrating a junction field-effect transistor(JFET) buffering input and another JFET bootstrap structure in the balanced homodyne detector. 相似文献
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用激光二极管(LD)抽运Nd YAG晶体,采用四镜环行腔,腔内放置TGG晶体和λ/2波片,组成光学单向器,利用LBO晶体内腔倍频技术,实现单频946 nm红外光和473 nm蓝光输出.最大单频蓝光输出12 mW,红外光输出13 mW,光束x方向的M2为1.02,Y方向的M2为1.14.腰斑的不对称性为1.062.自由运转情况下,功率波动小于±1.5%,频率稳定性优于±5.4 MHz. 相似文献
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Suppressing the preferential o-polarization oscillation in a high power Nd:YVO4 laser with wedge laser crystal 下载免费PDF全文
We observe the phenomenon of priority oscillation of the unexpected a-polarization in high-power Nd:YVO4 ring laser. The severe thermal lens of the a-polarized lasing, compared with the n-polarized lasing, is the only reason for the phenomenon. By designing a wedge Nd:YVO4 crystal as the gain medium, the unexpected a-polarization is completely suppressed in the entire range of pump powers, and the polarization stability of the expected zc-polarized output is enhanced. With the output power increasing from threshold to the maximum power, no a-polarization lasing is observed. As a result, 25.3 W of stable single-frequency laser output at 532 nm is experimentally demonstrated. 相似文献
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Suppressing the preferential σ-polarization oscillation in a high power Nd:YVO_4 laser with wedge laser crystal 下载免费PDF全文
We observe the phenomenon of priority oscillation of the unexpected σ -polarization in high-power Nd:YVO 4 ring laser. The severe thermal lens of the σ -polarized lasing, compared with the π-polarized lasing, is the only reason for the phenomenon. By designing a wedge Nd:YVO 4 crystal as the gain medium, the unexpected σ -polarization is completely suppressed in the entire range of pump powers, and the polarization stability of the expected π-polarized output is enhanced. With the output power increasing from threshold to the maximum power, no σ -polarization lasing is observed. As a result, 25.3 W of stable single-frequency laser output at 532 nm is experimentally demonstrated. 相似文献
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为研究石墨转移膜在刀具表面形成的可能性和演变规律及形成机理,采用聚晶金刚石(PCD)刀具进行了各向同性热解石墨切削试验.对刀具磨损区域形貌、表面加工质量和切削力进行了分析.根据试验结果分析表明:切削过程中PCD刀具后刀面上形成了一层石墨转移膜.石墨转移膜的形成机理以物理吸附作用和摩擦挤压为主.石墨晶体结构特性、石墨晶体缺陷和环境氛围是影响石墨转移膜形成的三个主要因素.刀具磨损、表面加工质量和切削力的变化情况与石墨转移膜的动态变化过程具有较高的一致性,石墨转移膜的形成可以有效地降低刀具磨损速度,提高表面加工质量,降低切削力. 相似文献