Notes on piecewise-Koszul algebras

The relationships between piecewise-Koszul algebras and other “Koszul-type” algebras are discussed. The Yoneda-Ext algebra and the dual algebra of a piecewise-Koszul algebra are studied, and a sufficient condition for the dual algebra A ^! to be piecewise-Koszul is given. Finally, by studying the trivial extension algebras of the path algebras of Dynkin quivers in bipartite orientation, we give explicit constructions for piecewise-Koszul algebras with arbitrary “period” and piecewise-Koszul algebras with arbitrary “jump-degree”.     

非晶硅界面缓冲层对非晶硅锗电池性能的影响

针对非晶硅锗电池本征层高锗含量时界面带隙失配以及高界面缺陷密度造成电池开路电压和填充因子下降的问题,通过在PI界面插入具有合适带隙的非晶硅缓冲层,不仅有效缓和了带隙失配,降低界面复合,同时也通过降低界面缺陷密度改善内建电场分布,从而提高了电池的收集效率. 进一步引入IN界面缓冲层以及对非晶硅锗本征层进行能带梯度设计,在仅采用Al背电极时,单结非晶硅锗电池转换效率达8.72%. 关键词： 非晶硅缓冲层 非晶硅锗薄膜太阳电池 带隙 界面     

A novel orthogonally linearly polarized Nd:YVO4 laser

<正>We presented a novel orthogonally linearly polarized Nd:YVO₄ laser.Two pieces of a-cut grown-together composite YVO₄/Nd:YVO₄ crystals were placed in the resonant cavity with the c-axis of the two crystals orthogonally.The polarization and power performance of the orthogonally polarized laser were investigated.A 26.2-W orthogonally linearly polarized laser was obtained.The power ratio between the two orthogonally polarized lasers was varied with the pump power caused by the polarized mode coupling.The longitudinal modes competition and the corresponding variable optical beats were also observed from the orthogonally polarized laser.We also adjusted the crystals with their c-axis parallele to each other,and a 40.7-W linearly polarized TEMoo laser was obtained,and the beam quality factors were M_x²=1.37 and M_y² =1.25.     

层次ω-开集及其应用

首先在L-保序算子空间中引入层次ω-开集,讨论了它的一些基本性质;其次用层次ω-开集刻画了（ω_1,ω_2）-连续序同态和（ω_1,ω_2）-开序同态的一些新的特征性质.     

Ln2Sn2O7：Er3+纳米晶的制备及发光性能研究

采用溶胶-凝胶法合成Ln₂Sn₂O₇:Er³⁺(Ln=La,Gd,Y)纳米晶。通过X射线衍射和场发射扫描电子显微镜测试了样品的晶体结构和形貌,同时对样品的上转换发光性能进行了测试。结果表明:在980 nm连续激发光的激发下,样品主要表现为绿光发射。发射中心在528,549 nm的绿光和672 nm处的红光发射分别对应Er³⁺离子的⁴S_3/2→⁴I_15/2、²H_11/2→⁴I_15/2和 ⁴F_9/2→⁴I_15/2跃迁。以La₂Sn₂O₇:Er³⁺纳米晶为例,Er³⁺离子的摩尔分数为7%、退火温度为1 150℃是其制备的最佳条件,此时其各个发射峰的强度最高。对La₂Sn₂O₇:Er³⁺的发光强度与激发功率关系的研究表明,其绿光和红光发射均为双光子过程。激发光吸收和能量转移是La₂Sn₂O₇:Er³⁺纳米晶上转换发光的主要机制。     

微波场对(Ba,Sr)3MgSi2O8：Eu2+,Mn2+荧光粉中Mn2+ 660 nm红光能量传递的影响

研究了2.45 GHz微波灼烧(Ba,Sr)₃MgSi₂O₈：Eu²⁺,Mn²⁺荧光粉的非热效应对Mn²⁺离子660 nm红光发射强度的影响。在相同的加热温度条件下,增加微波场的输出功率,微波非热效应导致Eu²⁺离子蓝光的跃迁概率增加,Eu²⁺通过(Ba,Sr)₃MgSi₂O₈基质晶格把能量传递给Mn²⁺,进而使Mn²⁺的跃迁概率增加,导致红光发射增强。提出了一种微波场非热效应对能量传递影响的新观点,认为在微波加热过程中强微波磁场可能会对像Mn²⁺这样具有顺磁性的激活剂离子的能级结构和能量传递性质产生干扰作用。     

Enhancement of green emission by the codoping U . 3＋ A＋ （A - Li, Na, K） in Ca2 O3CI.Tb phosphor

Tb3＋-doped Ca2BO3C1 compounds with different charge compensation approaches are synthesized by a hightemperature solid-state reaction method, and the luminescent properties and Commission Internationale de l＇Eclairage （CIE） chromaticity coordinates are systematically characterized. Ca2BO3Cl：Tb3＋ can produce green emission under 376 nm radiation excitation. With codoped A＋ （A = Li, Na, K） as charge compensators, the relative emission intensities of Ca2BO3Cl：Tb3＋ are enhanced by about 1.61, 1.97, and 1.81 times compared with those of the direct charge balance, which is considered to be due to the effect of the difference in ion radius on the crystal field. The CIE chromaticity coordinates of Ca2BO3CI：Tb3＋, A＋ （A = Li, Na, K） are （0.335, 0.584）, （0.335, 0.585）, and （0.335, 0.585）, corresponding to the hues of green. Therefore, A＋ （A = Li, Na, K） may be the optimal charge compensator for Ca2BO3Cl：Tb3＋.     

Optical spectroscopy studies on FeTelxSex and AxFe2uSe2 （A = K, Rb, Cs）： A brief overview

In this short overview, we summarize the optical spectroscopy FeTezxSex and AxFe2-ySe2. We elaborate that optical spectroscopy band structure evolution across the AFM phase transition temperature, studies on iron selenide superconducting systems measurements yield fruitful information about the the electronic correlation effect, the superconduct- ing pairing energy gap, the condensed carrier density or penetration depth, the inhomogeneity and the nanoscale phase separation between superconductivity and antiferromagnetism in those systems.     

Influences of Mg^2＋ ion on dopant occupancy and upconversion luminescence of Ho^3＋ ion in LiNbO3 crystal

The effects of a Mg^2＋ ion on the dopant occupancy and upconversion luminescence of a Ho^3＋ ion in LiNbO3 crystal are reported. The birefringence gradient of the crystal is measured to investigate the optical homogeneity. The X-ray powder diffraction spectrum and the upconversion luminescence are used to investigate defect structure and spectroscopic properties of Mg,Ho：LiNbO3. Under 808-nm excitation, blue, red, and very intense yellow-green bands are observed. Based on the energy levels of Ho^3＋ in LiNbO3, and the pump intensity dependence of the observed emission, an excitation scheme is presented. The upconversion emission spectra reveal an enhancement of upconversion intensity when the Mg^2＋ ions are introduced into Ho：LiNbO3. The main upconversion mechanism is discussed in this work.     

高功率准连续波腔内和频全固态黄光激光器

报道了高功率准连续波腔内和频全固态黄光激光器的研究结果.为获得高功率的黄光输出,首先,激光器采用准连续方式运转,在保持抽运水平的条件下降低热效应,从而提高光束质量和光光转换效率;第二,采用热近非稳腔腔型设计,双棒串接补偿热致双折射技术,获得大基模体积高光束质量的基频光;第三,通过优化腔型,采用L型共折叠臂平-凹对称腔,使两束基频光达到空间重合且满足功率配比.通过这些方法,得到了输出功率7.6W,重复频率1.1kHz的准连续波黄光输出.据我们所知,这是目前腔内和频方案所获得的最高功率全固态黄光输出. 关键词： 黄光激光 腔内和频 Nd：YAG激光 全固态激光器