TiB2增强Al2O3陶瓷刀具高速干切削摩擦磨损性能

采用TiB2增强Al2O3陶瓷刀具对淬硬钢进行高速干切削试验,利用切削高温作用下的摩擦化学反应,在刀具表面原位生成具有润滑作用的反应膜,从而实现Al2O3/TiB2陶瓷刀具的自润滑.结果表明:低速干切削时,Al2O3/TiB2陶瓷刀具的磨损机制主要表现为粘着磨损和磨料磨损;而在高速干切削时,刀具的磨损机制主要表现为氧化磨损,刀具表面经由氧化反应生成具有润滑作用的反应膜而起到固体润滑作用,从而使刀具的耐磨性能提高,随着TiB2含量和切削速度的增加,反应膜的减摩抗磨作用增强;而在切削区通入氮气时,由于刀具表面氧化膜形成受阻,刀具的抗磨能力有所降低.     

轧辊用高钒高速钢的滚-滑动磨损性能及失效行为研究

在高应力滚-滑动(滑动率约10%)条件下,利用自制的磨损试验机研究了高钒高速钢的磨损性能,并利用电子显微镜分析了失效行为.结果表明:高钒高速钢的相对耐磨性是高铬铸铁(Cr20)的2倍以上.磨损失效形式为显微切削与疲劳剥落的复合,兼有碳化物碎裂.碳化物对磨损失效有重要作用,高铬铸铁中的杆状M7C3型碳化物易于弯曲、碎裂而在其内部形成大量裂纹,促进磨损表面产生大块的疲劳剥落;高钒高速钢中团块状VC硬度高、形态好、具有精细亚结构、不易碎裂,可有效地抵御显微切削和疲劳剥落,是高钒高速钢耐磨性优良的原因.     

New fabrication approach to develop a high birefringence photo-crosslinked film based on a sulfur-containing liquid crystalline molecule with large temperature dependence of birefringence

ABSTRACT

We present a new fabrication approach to achieve a high birefringence film by means of photopolymerization based on an alkylthio-containing rod-like liquid crystalline molecule exhibiting large temperature dependence of birefringence. We designed a new reactive mesogen having alkylthio linkages (BPM–S). It was found that BPM–S had a larger increment of birefringence with decreasing temperature, relative to commercially available alkoxy analog LC242. This result could be thought to be due to enhanced intermolecular attractive interaction for an alkylthio mesogen implied by the proximity of laterally neighboring molecules and cybotactic nematic tendency based on wide-angle X-ray measurement. The uniaxially-aligned photo-polymerized film for BPM–S showed higher birefringence than that for LC 242.     

偶氮四唑叠氮基甲脒AFZT高压物性的第一性原理计算

偶氮四唑叠氮基甲脒AFZT的爆轰性能表现优异,在高能炸药领域中具有广阔的应用前景.本文采用基于密度泛函理论的第一性原理方法计算了AFZT在0～50 GPa压力下的晶体结构、电子性质以及氢键相互作用,并分析了这些性质在压力下的变化规律.在压力的作用下,AFZT晶体在5 GPa下发生了结构转变并伴随着电子结构中带隙值的突变,其带隙先减小后增大再减小,总态密度的峰值随着压力的增加而减小.结构中叠氮甲脒阳离子上的N8-N9与N9-N10键在压力下表现得最稳定,N-H^…N类型的氢键在所有相互作用中占据主导地位.此外,AFZT结构沿不同晶轴压缩的难易程度与此方向上氢键相互作用分布的疏密有关,并且其氢键主要沿xz平面分布而在y轴上分布极少,这导致了它沿y轴方向最易被压缩.     

Memory Effects in High-Dimensional Systems Faithfully Identified by Hilbert–Schmidt Speed-Based Witness

A witness of non-Markovianity based on the Hilbert–Schmidt speed (HSS), a special type of quantum statistical speed, has been recently introduced for low-dimensional quantum systems. Such a non-Markovianity witness is particularly useful, being easily computable since no diagonalization of the system density matrix is required. We investigate the sensitivity of this HSS-based witness to detect non-Markovianity in various high-dimensional and multipartite open quantum systems with finite Hilbert spaces. We find that the time behaviors of the HSS-based witness are always in agreement with those of quantum negativity or quantum correlation measure. These results show that the HSS-based witness is a faithful identifier of the memory effects appearing in the quantum evolution of a high-dimensional system with a finite Hilbert space.     

同轴虚阴极振荡器实验研究

介绍了中国工程物理研究院应用电子学研究所关于同轴虚阴极振荡器实验的最新进展。实验结果表明,带阳极反射板结构的同轴虚阴极振荡器比不带阳极反射板结构的同轴虚阴极振荡器输出微波功率更高,频谱更纯。在二极管电压350 kV,电流23 kA条件下,输出微波峰值功率500 MW,能量转换效率约6.2%,工作频率为3.3 GHz。对实验结果进行了理论分析。     

基于Z箍缩装置的实验室天体物理研究

大型高功率脉冲装置广泛应用于高能量密度物理的实验室中,随着诊断技术和流体力学模拟技术水平的提高,基于此类装置,实验室天体物理方向取得一些新的重要进展,文章主要介绍帝国理工大学Z箍缩结构的MAGPIE 脉冲功率装置上开展的关于磁重联和喷流的实验进展,在磁重联实验中,发现重联电流片中电子温度和离子温度远高于入流等离子体的温度,必然有其他效应导致电子和离子的异常高温;喷流实验中观察到弓形激波和锥形激波的产生。最后对Z 箍缩装置实验室天体物理学的未来发展做一些展望。     

强激光加载下高压液氘材料的电导率

液氘在高压下有丰富的电学光学性质。利用反射率和相对介电函数关系并从广义极化角度出发初步建立了计算低Z材料电导率的简易模型;在神光-Ⅱ装置上利用第九路激光冲击加载液氘材料并测量了其在强激光冲击下的高压状态参数和反射率。结合上述理论模型和实验,研究了高压下液氘的电离度和电导率。结果表明,液氘在约70 GPa时的电导率约为2.87105 (Wm)-1,已呈现出较为明显的金属电导特性。显然,冲击加载下液氘从绝缘分子态开始电离并向金属氘转变发生在更低的压强。     

低场磁共振系统的低噪声前置放大器研究设计

噪声前置放大器是磁共振射频接收子系统中的重要组件,它的性能优劣直接决定了最终磁共振图像的好坏.目前市场上的低噪声前置放大器大多基于中高场磁共振系统开发,而针对低场磁共振系统的很少;另外,商用低场磁共振系统的低噪声前置放大器价格相对较贵,并且多采用两级放大结构,结构复杂、调试难度大、成本相对较高.在此背景下,针对0.5 T低场磁共振设备利用Keysight公司的先进设计系统（ADS）软件对低噪声前置放大器进行研究设计,采用一级放大结构,探索电路设计与布局对放大器性能的影响.实测结果表明自主设计的低噪声前置放大器在21 MHz共振频率附近噪声系数为0.5 dB左右,增益达到了30 dB,能够满足低场磁共振应用的要求.     

Quantum speedup via engineering multiple environments

Evolution speed of an open quantum system is vividly influenced by the structure of environments. The strong system‐environment coupling is found to be able to accelerate quantum evolution. In this work, we propose a different method of governing the quantum speedup via engineering multiple environments. It is shown that, with a judicious choice of the number of coupling environments, the quantum speedup of an open system can be achieved even under weak system‐environment coupling conditions. The mechanism for the speedup is due to the switch between Markovian and non‐Markovian regions by manipulating the number of the surrounding environments. In addition, we verify the above phenomena by using quantum dots embedded in a planar photonic crystal under current technologies. These results provide a new degree of freedoms to accelerate quantum evolution of open systems. The strong system‐environment coupling can speed up the quantum evolution process. This work shows that, via engineering multiple environments, one can speed up the evolution process even under weak coupling conditions.