空气中激光烧蚀Cu产生等离子体发射光谱的研究

利用Q-开关Nd:YAG激光器产生的1.06 μm、10 ns的脉冲激光聚焦在空气中的Cu靶上,观测了激光诱导的Cu等离子体发射光谱.采用不同的激光能量,分析了波长范围为440 nm到540 nm的空间分辨发射光谱.在局部热力学平衡(LTE)条件近似下,根据谱线的相对强度,得到了等离子体电子温度约在104 K以上,给出了靶面附近电子温度的空间演化规律,并探讨了N(Ⅱ)500.52 nm谱线的谱线强度和半高全宽随激光能量的变化规律.     

Non-Analyticity and the van der Waals Limit

We study the analyticity properties of the free energy f _γ (m) of the Kac model at points of first order phase transition, in the van der Waals limit γ↘0. We show that there exists an inverse temperature β ₀ and γ ₀>0 such that for all β≥β ₀ and for all γ∈(0,γ ₀), f _γ (m) has no analytic continuation along the path m↘m ^* (m ^* denotes spontaneous magnetization). The proof consists in studying high order derivatives of the pressure p _γ (h), which is related to the free energy f _γ (m) by a Legendre transform.     

Random-cluster representation of the ashkin-teller model

We show that a class of spin models, containing the Ashkin-Teller model, admits a generalized random-cluster (GRC) representation. Moreover, we show that basic properties of the usual representation, such as FKG inequalities and comparison inequalities, still hold for this generalized random-cluster model. Some elementary consequences are given. We also consider the duality transformations in the spin representation and in the GRC model and show that they commute.     

Coexistence of hydrogen-bonded loop and extended tetrapeptide conformations

The conformations of a protected tetrathiopeptide have been analysed by isotope labelling and two-dimensional infrared spectroscopy (2D-IR). It has been found that Boc-Ala-Gly(=S)-Ala-Aib-OMe in acetonitrile, as well as its oxopeptide analogue, can adopt a hydrogen-bonded loop conformation in coexistence with less restricted structures. The two types of conformations interconvert too quickly to be resolved on the nuclear magnetic resonance (NMR) timescale, but give rise to different cross peaks in two-dimensional infrared spectra. The hydrogen bond between the Boc terminal group and the amide proton of Aib can be broken by photoisomerisation of the thioamide bond.     

Highly spatially resolved velocity measurements of a turbulent channel flow by a fiber-optic heterodyne laser-Doppler velocity-profile sensor

Velocity measurements with a high spatial resolution are important in turbulent flow research. In this paper, we report on the development of a new fiber-optic laser-Doppler velocity-profile sensor exhibiting a spatial resolution of up to 5 μm and its application to turbulent boundary layers. The sensor developed in the present work employs a frequency-division-multiplexing technique in order to separate two measurement signals from the two fringe systems. Velocity measurements close to zero at the solid wall were realized using heterodyne technique. The use of fiber optics improved a robustness of the sensor. The measurement accuracy of the sensor was experimentally investigated with respect to the spatial resolution and velocity. Universal velocity profile of a turbulent flow was obtained in a fully developed channel flow. Mean and fluctuating velocity are presented with a high spatial resolution.     

Taylor–Couette flow with independently rotating end plates

Results are presented from a combined numerical and experimental study of steady bifurcation phenomena in a modified Taylor–Couette geometry where the end plates of the flow domain are allowed to rotate independently of the inner cylinder. The ends rotate synchronously and the ratio between the rate of rotation of the ends _e and the inner cylinder _i defines a control parameter :=_e/_i. Stationary ends favour inward motion along the end walls whereas rotating walls promote outward flow. We study the exchange between such states and focus on two-cell flows, which are found in the parameter range between =0 and =1 for =2. Hence is used as an unfolding parameter. A cusp bifurcation is uncovered as the organizing centre for the stability exchange between the two states. Symmetry breaking bifurcations, which lead to flows that break the mid-plane symmetry are also revealed. Overall, excellent agreement is found between numerical and experimental results. PACS 47.20, 47.11, 47.54     

Bias-temperature treatment on mos capacitors irradiated with 1 MeV electrons

The fading behaviour of TLD-900 has been investigated up to 140 davs. An high post irradiation annealing temperature allows a high stability of the stored TL signal over a period of 100 hours.     

Enhancement of hole drift velocity in amorphous As2Se3 by iodine doping

The addition of ～ 0.6 at.% iodine to approximately stoichiometric a-As₂Se₃ enhances the hole drift velocity by more than a decade but does not affect its field, thickness and temperature dependence or the degree of disorder. It is speculated that iodine reduces the ratio of trapping to hopping states in the trap-controlled hopping process which recently has been proposed for a-As₂Se₃.     

Charge transport and photogeneration in molecularly doped polymers

Room temperature studies of hole transport and photogeneration efficiency are reported for N-isopropyl carbazole (NIPC) molecularly dispersed in a polycarbonate polymer as a function of NIPC concentration. These provide independent confirmation of the recently proposed stochastic hopping model for transport in disordered solids.