Revisiting Y2Si2O7 and Y2SiO5 polymorphic structures by Y MAS-NMR spectroscopy

This paper describes the ⁸⁹Y MAS-NMR spectra for all the established polymorphs of Y₂Si₂O₇ (y, α, β, γ and δ) and Y₂SiO₅ (X1 and X2). The combination of our spectroscopic data with the structural information published up to now from diffraction data permits the revision and correction of mistakes which appear in the literature. Finally, the influence of different structural factors, such as yttrium coordination number and Y-O distances on the ⁸⁹Y NMR isotropic chemical shift is analyzed.     

Formation and Reactivity of an Aluminabenzene Ligand at Pentadienyl‐Supported Rare‐Earth Metals

The half‐open rare‐earth‐metal aluminabenzene complexes [(1‐Me‐3,5‐tBu₂‐C₅H₃Al)(μ‐Me)Ln(2,4‐dtbp)] (Ln=Y, Lu) are accessible via a salt metathesis reaction employing Ln(AlMe₄)₃ and K(2,4‐dtbp). Treatment of the yttrium complex with B(C₆F₅)₃ and tBuCCH gives access to the pentafluorophenylalane complex [{1‐(C₆F₅)‐3,5‐tBu₂‐C₅H₃Al}{μ‐C₆F₅}Y{2,4‐dtbp}] and the mixed vinyl acetylide complex [(2,4‐dtbp)Y(μ‐η¹:η³‐2,4‐tBu₂‐C₅H₄)(μ‐CCtBu)AlMe₂], respectively.     

基于PWM的数字电位差计设计简

设计利用AT89C2051单片机内部所带的定时器,通过软件设计产生PWM信号。该信号经滤波后形成相应的直流补偿电压,再用该单片机自带的精密模拟比较器检测该电压与待测的未知电压的完全补偿。     

Lifetime measurement in 74Kr and 76Kr

Lifetimes of excited states in the ground-state bands of ⁷⁴Kr and ⁷⁶Kr were measured using the recoil-distance Doppler-shift and the differential decay curve methods. The states were populated in the ⁴⁰Ca(⁴⁰Ca, α2p) and ⁴⁰Ca(⁴⁰Ca, 4p) reactions. Gamma rays were detected with the GASP array which was coupled to the Cologne Plunger device. The results resolve discrepancies between earlier lifetime measurements and a recent Coulomb excitation experiment. Experimental transition rates are compared to theoretical calculations. The results support a strong mixing between prolate and oblate configurations for the low-spin states, and represent an important basis for the interpretation and understanding of the shape coexistence phenomenon in this mass region.     

基于安卓手机的无线重力感应控制智能小车

无线智能小车不仅在侦查、防爆、防辐射等特殊危险环境中应用广泛,在玩具行业也有很大的应用前景。安卓智能终端在全球拥有很大的市场占有率,通过对安卓手机的重力感应器、蓝牙和小车蓝牙模块HC06、电机驱动模块L298N、单片机等硬件平台进行详细设计和分析,实现了一种新型无线控制智能小车的方法,与传统的遥控器相比,设计的软硬件更为方便和灵活,软件经过不同手机测试,功能和界面都具有良好的适用性和可靠性,体验感也较强,达到了预定目标。     

The category of commutative HopfC *-algebras

In this paper, we first continue our study of group duality, and prove that the duality we established earlier is natural. Then we use this naturality to study the category of commutative, cocommutative HopfC ^*-algebras, and show that the category of compact Abelian semigroups and the category of commutative, cocommutative HopfC ^*-algebras with units are isomorphic. By using this result, we show that the category of commutative, cocommutative quantum groups is Abelian. This is a generalization of a result of Grothendieck about the catrgory of finite-dimensional commutative, cocommutative Hopf algebras with antipodes.     

Haar measures on HopfC *-algebras

In this paper, we first use Markov-Kakutani's fixed point theorem to prove the existence and uniqueness of Haar measures on cocommutative HopfC ^*-algebras. Also we show that in the commutative case, there exists a natural one-to-one correspondence between the Haar measure on a given HopfC ^*-algebra and Haar measures on the associated semigroup. Finally, we show that for HopfC ^*-algebras with Peter-Weyl property, they have Haar measures.Work supported in part by the NSF.     

On fractional powers of generators of fractional resolvent families

We show that if −A generates a bounded α-times resolvent family for some α∈(0,2], then −Aβ generates an analytic γ-times resolvent family for and γ∈(0,2). And a generalized subordination principle is derived. In particular, if −A generates a bounded α-times resolvent family for some α∈(1,2], then −A1/α generates an analytic C₀-semigroup. Such relations are applied to study the solutions of Cauchy problems of fractional order and first order.