Optical properties of PMMA doped with erbium(III) and ytterbium(III) complexes

In this article, we report the fabrication and optical/spectroscopic properties of polymethylmethacrylate (PMMA) doped with rare earth (RE) (Er³⁺ and Er³⁺/Yb³⁺) ions. Infrared spectroscopy revealed only very weak O? H stretching vibration peaks in the samples, which is important if satisfactory photoluminescence is to be observed at 1530 nm. Measurement of transmission spectra in the wavelength ranges from 300 to 700 nm for Er³⁺‐doped samples and from 900 to 1050 nm for Yb³⁺‐doped samples enabled us to observe the ⁴G_11/2 (377 nm) and ²H_11/2 (519 nm) transmission bands typical for Er³⁺‐doped samples, as well as the ²F_5/2 (975 nm) band typical for Yb³⁺‐doped samples. Under excitation at 980 nm, at room temperature, the characteristic Er³⁺ emission at 1530 nm was also observed with improving trend when the higher RE concentrations were applied. The results indicate that the PMMA reveals very low tendency to the RE clustering, which together with low cost and easy fabrication make it a material with a great potential in the active photonics devices. POLYM. ENG. SCI., 2009. © 2009 Society of Plastics Engineers     

Preparation of Transparent 3Y‐TZP Nanoceramics with No Low‐Temperature Degradation

The progresses of the relative density, average grain size (GS), and maximum pore size entering into the final sintering stage are investigated in 3 mol% yttria‐stabilized tetragonal zirconia polycrystals (3Y‐TZP) compacts in the range of 87%~99% theoretical density. It is found that during conventional pressureless sintering, the pores in the compact enlarged dramatically, which appears to be the major obstacle for preparing fully dense nanoceramics. Transparent 3Y‐TZP nanoceramics with an average GS of 87 nm were prepared by exploiting microstructural refinement on nanoscale. The yields a maximal optical transmittance of 67% and shows no noticeable low‐temperature degradation after 100 h aging at 134°C under a hydrothermal pressure of two bars.     

Transonic instability in entrance part of mixing chamber of high-speed ejector

Introduction The research of flow structure in the entrance part of the mixing chamber of two-dimensional supersonic ejector[1,2] shows, how this structure depends both on stagnation pressure ratio of streams p01/p02[3] and on back pressure ratio pb/p02 [4]. It was found out that the structure of shock waves is not stable, but it oscillates less or more. For the high back pressure ratio a terminal shock wave is in the mixing chamber and due to this shock wave the mixing processes change quali…     

Techno-economic comparison of three technologies for pre-combustion CO2 capture from a lignite-fired IGCC

This paper compares the techno-economic performances of three technologies for CO₂ capture from a lignite-based IGCC power plant located in the Czech Republic: (1) Physical absorption with a Rectisol-based process; (2) Polymeric CO₂-selective membrane-based capture; (3) Low-temperature capture. The evaluations show that the IGCC plant with CO₂ capture leads to costs of electricity between 91 and 120 €·MWh⁻¹, depending on the capture technology employed, compared to 65 €·MWh⁻¹ for the power plant without capture. This results in CO₂ avoidance costs ranging from 42 to 84 €·t_CO2,avoided⁻¹ , mainly linked to the losses in net power output. From both energy and cost points of view, the low-temperature and Rectisol based CO₂ capture processes are the most efficient capture technologies. Furthermore, partial CO₂ capture appears as a good mean to ensure early implementation due to the limited increase in CO₂ avoidance cost when considering partial capture. To go beyond the two specific CO₂-selective membranes considered, a cost/membrane property map for CO₂-selective membranes was developed. This map emphasise the need to develop high performance membrane to compete with solvent technology. Finally, the cost of the whole CCS chain was estimated at 54 €·t_CO2,avoided⁻¹ once pipeline transport and storage are taken into consideration.     

Effect of mobilizing agents on mycoremediation and impact on the indigenous microbiota

BACKGROUND: Mobilizing agents (MAs) have been suggested to improve the fungal degradation of polycyclic aromatic hydrocarbons (PAHs) in soil. Three different MAs (Tween 20, Tween 80 and soybean oil) were investigated for their ability to stimulate contaminant degradation by either Phlebia sp. DABAC 9 or Allescheriella sp. DABAC1 in a soil spiked with a mixture of PAHs. RESULTS: Phlebia sp. and Allescheriella sp. markedly differed in their growth capabilities under non‐sterile conditions and without MAs (3.0 versus 0.1 µg ergosterol g^?1 soil, respectively). However, soybean oil led to a 35‐fold increase of Allescheriella sp. growth. Contaminant degradations by Phlebia sp. DABAC 9 and Allescheriella sp. DABAC 1 were best supported by soybean oil and Tween 20, respectively. Enumeration of cultivable bacteria and denaturing gradient gel electrophoresis (DGGE) analysis of PCR‐amplified 16S rRNA showed that microbial density and biodiversity were positively affected by the mycoremediation especially with Allescheriella sp., the use of which led to an evident detoxification. CONCLUSIONS: Allescheriella sp. DABAC 1 appears to be a promising strain in the remediation of PAH‐contaminated soils. The different response of the two fungi to MAs addition confirms the stringent need for a preliminary lab‐scale assessment of fungus/MA combinations prior to application. Copyright © 2009 Society of Chemical Industry     

Preparation,structure and hydrothermal stability of alternative (sodium silicate-free) geopolymers

In this contribution, we present the preparation and structural characterization of a new type of alternative (sodium silicate-free) geopolymer system. A new procedure of geopolymer synthesis based on the preparation of a reactive geopolymer precursor by direct calcinations of low-quality kaolin with Na/K hydroxides is introduced. The subsequent formation of geopolymer matrix does not require activation by alkaline silicate solution. The compact and hardened material was prepared only by adding a small amount of water. Besides the introduction of a new synthetic procedure, we focused also on the systematic study of chemical structure, mineralogical composition and hydrothermal stability of the prepared geopolymer systems as seen by solid-state NMR spectroscopy and powder X-ray diffraction (XRD). An important part of our contribution is the demonstration of structural and mineralogical changes induced by hydrothermal treatment and long-term aging of the prepared geopolymers. It was found that redistribution of basic structural units (SiO₄⁴⁻ and AlO₄⁵⁻) and gradual formation of zeolite fractions can be related to the observed changes in mechanical properties. Up to a certain level, the presence of zeolites enhances the mechanical properties of the prepared geopolymer systems. However, the additional formation of a new generation of zeolite fractions, occurring over the long-term period causes an inversion of this trend and a dramatic reduction of mechanical strength. Nevertheless, formation of the geopolymer matrix by alkaline and thermal activation of low-quality kaolin has the potential to be used in ecological problems solving (solidification of powdered and dangerous waste materials).     

Approximate Inverses of Operators

Inverting a nonlinear operator is usually a difficult problem. Consequently, approximation methods are useful. In this paper, we study the relationship between the set of approximate inverses of a given operator N and the invertibility of N.     

Enhancements of SDR-Based FPGA System for V2X-VLC Communications

This pilot study focuses on a real measurements and enhancements of a software defined radio-based system for vehicle-to everything visible light communication (SDR-V2X-VLC). The presented system is based on a novel adaptive optimization of the feed-forward software defined equalization (FFSDE) methods of the least mean squares (LMS), normalized LMS (NLMS) and QR decomposition-based recursive least squares (QR-RLS) algorithms. Individual parameters of adaptive equalizations are adjusted in real-time to reach the best possible results. Experiments were carried out on a conventional LED Octavia III taillight drafted directly from production line and universal software radio peripherals (USRP) from National Instruments. The transmitting/receiving elements used multistate quadrature amplitude modulation (M-QAM) implemented in LabVIEW programming environment. Experimental results were verified based on bit error ratio (BER), error vector magnitude (EVM) and modulation error ratio (MER). Experimental results of the pilot study unambiguously confirmed the effectiveness of the proposed solution (longer effective communication range, higher immunity to interference, deployment of higher state QAM modulation formats, higher transmission speeds etc.), as the adaptive equalization significantly improved BER, MER and EVM parameters. The best results were achieved using the QR-RLS algorithm. The results measured on deployed QR-RLS algorithm had significantly better Eb/N0 (improved by approx. 20 dB) and BER values (difference by up to two orders of magnitude).     

Study on lead–bismuth droplets'' generation and their removal by an electrostatic precipitator

The applicability of the electrostatic precipitator for the removal of lead–bismuth droplets generated in the direct-contact boiling lead–bismuth cooled fast reactor is investigated. A small apparatus in which argon gas bubbles through the pool of lead–bismuth and an electrode mounted in the test section is used. The ESP operating voltage was 1000 V. It was found that the removal efficiency of the electrostatic precipitator increases with time up to 96.5%. It appears that the probability of droplet removal is almost independent of the droplet size. There is a small increase in this probability for larger droplets, which is caused likely by the fact that the larger droplets travel at lower velocities. Otherwise the effect of velocity on the removal efficiency is negligible. The electrostatic precipitator current was decreasing during the experiment, which is probably caused by the reduction of the number of droplets in the test section as the electrostatic precipitator was getting more efficient. The electrostatic precipitator current was on the order of 7 μA. The experiment demonstrated the applicability of the electrostatic precipitator for removal of lead–bismuth droplets.     

When is the stability of a nonlinear input-output system robust?

We consider a general nonlinear input-output system governed by operator equations that relate the system's input, state, and output, all of which are in extended spaces. It is assumed that the system variables are separated. Our results give conditions under which the stability of the nominal system is robust; i.e., it is not destroyed by any sufficiently small admissible perturbation of the system. Theorem 1 deals with the case when by stability we mean theincremental stability. Theorem 3 concerns the^*-stability; i.e., the case when the stability is essentially the boundedness of the transmission operator. Moreover, in Theorem 2 it is shown that, under certain conditions, the incremental stability of the nominal system implies insensitivity. Basically, our results show that if the operators describing the nominal system are well behaved, and the transition from the nominal system to the perturbed system is not abrupt, then the nominal system stability is robust. The applications of the results are illustrated by several examples.