Towards the improvement of attenuation range and response time of electrochromic polymer-based variable optical attenuators

A solid–liquid electrochromic variable optical attenuator device consisting of a thin layer of LiClO₄-doped poly(3,4-ethylenedioxythiophene) (PEDOT) and ferrocene in propylene carbonate has been demonstrated to exhibit a large dynamic range of optical attenuation at the telecommunication wavelength of 1550 nm. Doping of PEDOT film with an electrolyte greatly improves the device performance in terms of optical attenuation or color efficiency at 1550 nm and response time. An optimized single-layer device consisting of LiClO₄-doped PEDOT film (440 nm) shows a 10-dB dynamic range of optical attenuation at 1550 nm, a low optical loss of 0.86 dB for the bleached state, and a response time of 5–7 s at the switching potential of 0–2 V.     

Influence of polarization on properties of 0–3 cement-based PZT composites

In this paper, studies on a new 0–3 type cement-based PZT (lead zirconate titanate) composite are presented. Using a normal mixing and compacting method, up to 50 vol.% PZT ceramic powder can be easily incorporated into the composites. The behaviors of the cement-based PZT composites under different polarizing conditions have been investigated on the piezoelectric properties both theoretically and experimentally. It shows that cement-based PZT composites have their own unique characteristics. There is a good potential for the application of 0–3 type cement based piezoelectric composites in civil engineering.     

Luminescent properties of a novel naphthalimide-fluorene molecule

A novel naphthalimide-fluorene molecule, 4-(N,N-dimethylamino)-N-(2′-fluorenyl)-1,8-naphthalimide (DFN), has been synthesized and characterized, and its luminescent properties have been studied. DFN has an absorption maximum at 420 nm and possesses solvent polarity dependent changes. The environmental sensitivity exhibited the characteristics of an excited state charge transfer complex. DFN also showed strong luminescence, good electron-affinity, and temperature independence of fluorescence. The application of DFN in organic light-emitting diodes (OLEDs) as an electron-transporting electroluminescent material was investigated. The OLED with a structure of ITO/N,N′-bis(3-methylphenyl)-N,N′-diphenyl-1,1′-biphenyl-4,4′-diamine/DFN/Al shows a yellow-green emission (chromaticity coordinates: x = 0.424, y = 0.543) with a brightness of 3563 cd/m². The external quantum efficiency and the highest luminous efficiency of the device reach 0.2% and 0.55 lm/W, respectively.     

Research into models and algorithms of artificial life

This paper deals with methodology and algorithms for artificial life. The paper is organized as follows. First we briefly present the background and general concept of A-life. Then we describe the methodology and problems of A-life, and modeling, coding, and rendering techniques are proposed. Finally we investigate the application of cellular automata for metal crystallization and some aspects of A-life in engineering and computer art.     

Effect of Hf and Hf-Ca substitution on the superconductivity of GdBa2Cu3O7 − δ

The structural and superconducting properties of (Gd_1−x−yCa_yHf_x)Ba₂Cu₃O_z samples are investigated using X-ray diffraction, resistivity, AC susceptibility and oxygen content measurements. The effect of increasing Hf concentration in (Gd_1−xHf_x)Ba₂Cu₃O_z lowers the oxygen content and decreases T_c which is attributed to hole filling by Hf. The substitution of Ca for Gd in (Gd_0.85−yCa_yHf_0.15)Ba₂Cu₃O_z provides proper matching between the ionic radius and valence of Gd³⁺ (0.94 Å) and the average ionic radius and valence of Hf⁴⁺ (0.78 Å) and Ca²⁺ (0.99 Å). As the Ca content increases, the T_c increases from 81 K (y = 0.05) to 86.5 K (y = 0.20, compensated oxide), closer to the value of 91 K for pure GdBa₂Cu₃O_7−δ due to the balance between the hole filling by Hf and hole doping by Ca. A comparative study of Hf doped samples of (R_1−xHf_x)Ba₂Cu₃O_z (R = Y, Er, Gd) indicates that the magnetic moment carried by R-ion plays an important role in the suppression of superconductivity and T_c.     

Electrochemical behaviour of multicomponent ZrTiVMnCrNi alloys in alkaline solution

The effect of the composition of multicomponent ZrTiVMnCrNi alloys on their hydrogen-storage capacity and on the rate of electrosorption/desorption of hydrogen was investigated under potentiodynamic as well as single-pulse and long-term galvanostatic conditions. The main characteristics of alloys and alloy electrodes were determined by their structural analysis by means of X-ray diffraction and scanning electron microscope, by specific surface are tests and by determination of the hydrogen absorption/desorption isotherms in the gas/solid phase system. It was found that only the alloys with a manganese content below a threshold could be used as electrode materials for NiMH batteries, whereas the modification of the electrode material by micro-encapsulation of alloy particles should limit the dissolution of manganese from the electrode material in a strong alkaline solution.     

Absorption of CO2 and H2S in aqueous alkanolamine solutions using a fixed-bed reactor with cocurrent downflow operation in the pulsing flow regime: Absorption von CO2 und H2S in wäßrigen alkanolamin-lösungen in einem Festbettreaktor bei abwärtsfließendem Gleichstrombetrieb und pulsierendem Arbeiten

Absorption rates of H₂S and CO₂ in several aqueous alkanolamines in a cocurrent downflow fixed-bed reactor operated in the pulse flow regime have been measured in order to obtain information on the potential selectivity and on the mass transfer parameters. From these experiments it can be concluded that this type of reactor seems to be very suitable for the selective removal of H₂S from acid gases.It was not possible to derive correlations which are always valid for the calculation of the mass transfer parameters in laboratory-scale contactors. The results of the present study in combination with the data published in the literature were correlated with only one unknown parameter in which the influence of the physical properties of the system and the shape and material of the packing were combined. This parameter has to be determined empirically.Small amounts of acid gases in aqueous alkanolamine solutions have a pronounced effect on the properties, such as the foaming behaviour, of the liquid phase. The pressure drops measured in the cocurrently operated fixed-bed reactor were affected substantially by small amounts of acid gases present in the aqueous alkanolamine solutions and up to now this effect could not be explained satisfactorily.For the design of contactors for industrial purposes, detailed scale-up rules are required. In the present study this aspect is not investigated.