Ultrafast transverse thermoelectric response in c‐axis inclined epitaxial La0.5Sr0.5CoO3 thin films

Ultrafast transverse thermoelectric voltage response has been observed in c‐axis inclined epitaxial La_0.5Sr_0.5CoO₃thin films. Voltage signals with the rise time of 7 ns have been detected under the irradiation of pulse laser with duration of 28 ns. A concept, named response rate ratio, has been proposed to evaluate the intrinsic response rate, and this ratio in La_0.5Sr_0.5CoO₃is smaller than that in other reported materials. The low resistivity is thought to be responsible for the ultrafast response, as low resistivity induces small optical penetration depth, and response time has a monotonous increasing relationship with this depth.

     

Investigations on the g factors of the ground and excited states for Cu2+ ions in ZnO crystal

The g factors g _// and g _⊥ of the ground Γ₆(² T ₂) and excited Γ_4,5(² E), Γ₆(² E) states for trigonal Cu²⁺ centres in ZnO crystals are calculated from three theoretical methods, the complete diagonalization (of the energy matrix) method, the second-order perturbation method (PTM-I) and the simplified second-order perturbation method (PTM-II, this method was described in an earlier paper). These methods are based on the cluster approach in which the spin-orbit coupling parameters ζ, ζ′ and the orbital reduction factors k, k′ are calculated from a semi-empirical molecular orbital method. The crystal-field parameters used in the calculations are obtained from the superposition model and so the defect structure of Cu²⁺ centres in ZnO can be acquired. The calculated g factors from the three methods are in reasonable agreement with the experimental values and the defect structure of Cu²⁺ centres in ZnO is acquired. It appears that in some cases the approximate PTM can be applied in the studies of g factors of various states. The conditions that the PTM are ineffective are discussed.     

Temperature evolution associated with dynamic phase transformation in shape-memory TiNi alloys

In this paper, temperature evolution in shape-memory TiNi alloys was in situ measured in the process of phase transition under shock loading tests. It was shown that the temperature increased during loading, while unloading, it would keep the maximum value constant or decreased, depending on the strain rate. The corresponding dynamic response indicated that the hardening property is related to phase transition strain and the transformation path has remarkable strain-rate effect. The reason for this phenomenon is essentially due to the temperature dependence of the phase transformation stress. Moreover, the evolution of temperature was consistent with the change of stress, suggesting that this dynamic phase transition deformation is uniform. The theoretical calculation shows that the mechanism of temperature evolution results from the release of latent heat and the hysteresis dissipated energy. The results of this investigation provide insight into intriguing strain-rate-dependent phenomena intrinsic of TiNi alloys.     

Mössbauer study of the vibrational anisotropy and of the light-induced population of metastable states in single-crystalline guanidinium nitroprusside

M?ssbauer studies were performed on single crystals of guanidinium nitroprusside with different orientations of their principal crystallographic axes (a, b, c) with respect to the incident radiation. The markedly anisotropic Lamb-M?ssbauer factor f _LM , i.e. f _LM ^(a) = 0.118(8), f _LM ^(b) = 0.174(8), f _LM ^(c) = 0.202(8) is in contrast to that of nitroprussides with inorganic anions. The observed anisotropy is ascribed to the anisotropic vibrational mean-square displacement of the nitroprusside anions as a whole which is due to the specific packing of both, anions and cations, as well as the very weak chemical bonding between the ions, typical only for guanidinium nitroprusside. The vibrational anisotropy of iron atoms in barium nitroprusside that has been observed by X-ray structural investigations has a different origin and therefore does not result in an anisotropic Lamb-M?ssbauer factor. We have also investigated metastable states in guanidinium nitroprusside that have been populated by means of incoherent irradiation from light-emitting diodes. With a specific orientation of the guanidinium nitroprusside single crystal a population of the metastable states up to 26% could be achieved. Populations of comparable size on lithium, sodium and potassium nitroprussides have only been reached using coherent laser irradiation. Received 15 December 1998 and Received in final form 3 March 1999     

Circularly Polarized Luminescence of Free Complex Molecules in a Constant Magnetic Field

It is shown that the magnetic fieldinduced optical activity in the luminescence of complex molecules in vapors in the presence of rotational anisotropy in the ensemble of luminescent molecules provides information also on the intramolecular orientation of the initiating dipole moments of transitions, including borrowed ones. The relationships between the rotational force of the optical activity and this orientation in the case of anisotropy induced by a linearly polarized exciting light are obtained.     

Marketing-driven channel coordination with revenue-sharing contracts under price promotion to end-customers

This paper explores the equilibrium behavior of a basic supplier-retailer distribution channel with and without revenue-sharing contracts under price promotion to end-customers. Three types of promotional demand patterns characterized by different features of dynamic price sensitivity are considered to rationalize price promotional effects on end-customer demands. Under such a retail price promotion scheme, this work develops a basic model to investigate decentralized channel members’ equilibrium decisions in pricing and logistics operations using a two-stage Stackelberg game approach. Extending from the basic model, this work further derives the equilibrium solutions of the dyadic members under channel coordination with revenue-sharing contracts. Analytical results show that under certain conditions both the supplier and retailer can gain more profits through revenue-sharing contracts by means of appropriate promotional pricing strategies. Moreover, the supplier should provide additional economic incentives to the retailer. Furthermore, a counter-profit revenue-sharing chain effect is found in the illustrative examples. Such a phenomenon infers that the more the retailer requests to share from a unit of sale the more it may lose under the revenue-sharing supply chain coordination scheme.     

Direct Fabrication Methods of Surface Relief Electro-Optic Gratings in Azo-Polymer Films

Two fabrication methods of surface relief electro-optic (EO) gratings in azo-polymer films are described: surface deformation by a continuous wave laser and laser ablation by a pulse laser. In the fabrication process, the periodic intensity modulation of laser beams is formed by an interference fringe or a phase mask. The surface relief EO grating is fabricated by poling the surface relief grating (SRG) after the SRG fabrication process. The linear dependence of an applied voltage in the modulation efficiency of the first-order diffraction beam is observed. The proposed methods are effective for highly-efficient surface relief EO grating fabrication.     

Spin fluctuation effects in substituted CeRu2Si2 and YbPd2Si2 alloys

Effects of chemical substitution in CeRu₂Si₂, a well-studied heavy fermion system and YbPd₂Si₂ have been investigated through magnetic susceptibility and x-ray diffraction in the systems CeRu _x Si₂, CeRu_2−x Os _x Si₂, CeRu₂Si_2−x Ge _x and YbPd₂Si_2−x Ge _x . Replacing silicon by germanium generates normal chemical pressure effect, namely, Ce and Yb atoms in CeRu₂Si₂ and YbPd₂Si₂ became more and less magnetic respectively. With increasing Ge concentration, CeRu₂Si_2−x Ge _x exhibits larger susceptibility at low temperature, goes to an antiferromagnetic state and finally becomes ferromagnetic. In YbPd₂Si_2−x Ge _x , increasing Ge concentration drives Yb atoms to more divalent state. Electronic effects are more pronounced in CeRu_2−x Os _x Si₂ though CeRu₂Si₂ and CeOs₂Si₂ have very nearly the same lattice parameters. It is conjectured that CeRu₂Si_2−x Ge _x may be the first Ce-based heavy fermion having a magnetic ground state. The authors felicitate Prof. D S Kothari on his eightieth birthday and dedicate this paper to him on this occasion.     

Effects of low-LET radiations on CR-39 track detector

The effects of Co-60 gamma-rays and about 25-MeV pulsed electrons have been investigated on CR-39 plastic nuclear track detector. The bulk etch rate was measured as a function of the absorbed dose under three different irradiation conditions; gamma-ray exposure in air at the dose rate of 6 kGy/h, that in vacuum and electron shower in air at 126 kGy/h on average. It was found that the bulk etch rate (V) increased nearly exponentially with the dose (D); V=V₀exp(kD), and the characteristic parameter (k) was 35, 9 and 12 MGy⁻¹, respectively. It is considered that a lack of oxygen in damage formation processes could occur momentarily during a short electron pulse, just similarly to the vacuum effect of reduction in track etch rates in outgassed CR-39 plastic.     

稀磁半导体Cd_（1－x）Fe_xTe的磁光光谱

在７０－３００Ｋ温度范围内测量了组分ｘ为０．０１和０．０４的Ｃｄ１－ｘＦｅｘＴｅ及ＣｄＴｅ的法拉第效应随入射光子能量的变化，首次获得了Ｃｄ１－ｘＦｅｘＴｅ在布里渊区Γ点和Ｌ点的有效ｇ因子及其与温度的关系。给出了Ｆｅ２＋离子与载流子间的ｓｐ－ｄ交换作用常数Ｎ０（β－α）＝（－１．５７±０．０３）ｅＶ。