Coherent Acoustic Phonon and Its Chirping in Dirac Semimetal Cd_3As_2

Ultrafast optical spectroscopy of a single crystal of a Dirac semimetal Cd_3As_(2 )is carried out.An acoustic phonon(AP)mode with central frequency f=0.037 THz(i.e.,1.23 cm~(-1)or 0.153 meV)is unambiguously generated and detected,which we attribute to laser-induced thermal strain.An AP chirping(i.e.,variation of the phonon frequency)is clearly detected,which is ascribed to heat capacity variation with time.By comparing our experimental results and the theoretical model,we obtain a chirping time constant,which is 31.2 ps at 6 K and 19.8 ps at 300 K,respectively.Significantly,we identify an asymmetry in the AP frequency domain peak and find that it is caused by the chirping,instead of a Fano resonance.Moreover,we experimentally demonstrate that the central frequency of AP is extremely stable with varying laser fluence,as well as temperature,which endows Cd_3As_2application potentials in thermoelectric devices.     

相对论重离子碰撞手征电荷分离效应的研究

相对论重离子碰撞的拓扑荷作用破坏作用平面两侧不同手征性的夸克数目的平衡,从而引起P和CP破坏特征。本工作主要分析RHIC和LHC能区的手征电荷分离作用,分析手征电荷分离随碰撞中心度、碰撞能量和核屏蔽等依赖关系。并未发现手征电荷分离效应与碰撞能量大小有非常紧密的依赖关系,但发现核屏蔽效应对手征电荷分离有重要的影响,与不考虑屏蔽效应相比,考虑屏蔽效应会使手征分离效应明显压低,由于屏蔽效应出现,使得a₊₊（a_--）的分布与a_+-（a_-+）分布并不对称。并且还发现手征分离效应主要发生在碰撞参量较大的周边碰撞,越接近中心碰撞,手征分离效应几乎可以忽略。The topological charge interactions in relativistic heavy ion collisions cause quark chirality imbalance, resulting in charge separation under the strong magnetic field and local P and CP violation. In this paper, the chiral charge separation at RHIC and LHC energies is systematically analyzed as functions of the collision centrality, the collision energy and the nuclear shielding factor. It is found that there is not a very close dependence of the chiral charge separation effect on the collision energies, but that has an important dependence on nuclear shielding factor. Compared with the non-shielding effect, the shielding effect can reduce the chiral separation effect obviously. Due to the shielding effect, the distribution of a₊₊(a_--) and the distribution of a_+-(a_-+) are asymmetric. One also finds that chiral separation effect, which is almost negligible when more close to the central collision, occurs mainly in the peripheral collision for larger impact parameter.     

大数据背景下电力行业数据应用研究

随着SG—ERP的建设推进,业务应用数据正以前所未有的速度增长,大数据时代正式到来。通过对大数据内涵和外延的深入理解,结合公司数据现状和业务需求,研究并提出了“电力大数据”的概念。为了预测公司业务趋势,挖掘电力大数据的数据价值,提取公司三集五大两中心业务大数据分析典型应用场景,利用数据集成管理、数据存储、数据计算、分析挖掘等方面核心关键技术,实现面向典型业务场景的模式创新及应用提升。电力大数据的应用将推动公司业务发展和管理水平提升,有效支撑公司三集五大两中心深入建设。     

Numerical Analysis of Characterized Back Interface Traps of SOI Devices by R-G Current

SOI technology is based on the complicated fabrication process of ultra- thin siliconfilm on Si O2 insulation layer.The key of improving the performance of SOI- based devicesand circuits is to reduce the density of electron- hole reco...     

t →cγ and t →cg in Local Gauged Baryon and Lepton Numbers

In this paper, we calculate the top quark rare decays t →cγ and v in an extension of the standard model, where baryon number and lepton number are local gauge symmetries. Adopting reasonable assumptions on the parameter space, we find that the branching ratios of t →cγ and t →cg can reach 10^-6 and 10^-5 respectively, which can be detected in near future.     

三值FPRM电路极性间转换算法及其在面积优化中的应用

通过对三值FPRM(Fixed-polarity Reed-Muller)展开式和四值列表技术的研究,提出了一种三值FPRM电路极性间转换算法,并将其应用于电路面积优化.首先根据四值RM(Reed Muller)逻辑多项式系数的计算方法,推导出三值FPRM展开式极性间系数转换算法;然后利用该算法,结合三值模代数特点以及电路面积估计模型,沿非循环格雷码极性遍历路径进行三值FPRM电路面积最佳极性搜索,得到面积最优的FPRM电路.最后对8个MCNC基准电路进行测试,结果表明：与0极性Reed-Muller电路相比,三值FPRM电路的面积平均减少56.2%.     

碳结构锯齿形边缘对SO2的催化氧化机制研究

利用多孔碳实现SO2脱除和高值资源化具有耗水少、吸附剂可循环等优点,是当前重要技术方向,探究SO2在碳材料纳米空间中的吸附转化机制是该技术的理论基础。前期研究表明O2存在的条件下,碳材料中SO2会被催化氧化形成SO3,但具体的吸附催化位点和氧化路径有待进一步研究。本文采用密度泛函理论计算了SO2碳材料锯齿形不饱和碳原子处的吸附和催化氧化路径,发现:SO2和O2在不饱和碳原子处发生化学吸附。当O2在不饱和碳原子处优先吸附时,SO2会与活化的O2反应生成SO3和化学吸附态的O;当SO2在不饱和碳原子处优先吸附时,O2会在S原子附近活化,活化后的O2会与SO2反应生成气相SO3、化学吸附态SO3。本文计算结果为用于硫资源化的高性能碳材料合成提供了理论指导。     

一套高效、实用的编辑系统

虽然全数字化是电视制作设备的发展方向,但模拟设备短期内不会被全部淘汰,模拟设备与数字设备共存还会持续一段相当长的时间。目前,中、小电视台用于电视节目制作的设备主要以索尼ＶＯ,９字头ＳＰ系列,Ｂｅｔａｃａｍ－ＳＰ,ＤＶＣＰＲＯ系列为主,播出设备有ＶＯ－９字头系列、Ｂｅｔａｃａｍ一ＳＰ系列和大１／２系列。节目制作的播出带要以３／４带为主,向中央台（省台）送节目或进行节目交换时要用Ｂｅｔａｃａｍ带,故这种多种带源并存给后期节目制作带来了许多麻烦。对于中、小电视台来讲,由于资金所限,不可能购买太多的制作…     

包含无关项逻辑函数的固定极性转换

通过对Boolean逻辑和RM((Reed-Muller)逻辑的研究,针对Boolean逻辑函数SOP(Sum-of-Products)展开式中无关项取舍不确定的特点,结合快速列表技术,提出一种包含无关项逻辑函数的固定极性转换方法。该方法首先求出最小项和无关项的相关与项,然后生成最小项索引表以及无关项索引表,最后搜索无关项取舍,得到最佳固定极性RM(Fixed-Polarity Reed-Muller,FPRM)展开式。通过对10个MCNC Benchmark电路进行测试,结果表明:与不考虑无关项的极性转换方法相比,该方法能有效简化FPRM展开式。     

Mach-Zehnder Interferometers with Asymmetric Modulation Arms in Applications of High Speed Silicon-on-Insulator Based Optical Switches

Modulation arms with different widths are introduced to Mach-Zehnder interferometers （MZIs） to obtain improved performance. Theoretical analysis and numerical simulation have shown that when tile widths of tile two arms are properly designed to achieve an inherent mπ/2 （m is an odd integer） optical phase difference between the arms, the asymmetric MZI presents higher modulation speed. Furthermore, the carrier-absorption induced divergence of insertion losses in silicon-on-insulator （SOI） based MZI optical switches can be obviously improved.