Accounting for dynamics in attribute-importance and for competitor performance to enhance reliability of BPNN-based importance-performance analysis

Importance-performance analysis (IPA) is a decision-support tool used in prioritizing quality improvements of products/services. Recently, back-propagation neural network (BPNN)-based approaches have been proposed to deal with the problem of asymmetric effects in customer satisfaction formation. Though reliability of IPA is increased by the integration of BPNN, shortcomings of the analytical framework remain that (a) it does not provide insight into forms and degrees of these asymmetric effects, (b) it does not account for differences between the relevance and determinance of quality attributes, and (c) it neglects the competitor dimension in attribute-prioritization. Since all these issues have important managerial implications, the authors of this study propose an extended BPNN-based IPA that uses a multidimensional operationalization of attribute-importance, and that considers competitive performance levels. Using data from an airline satisfaction survey, an empirical test reveals that the proposed approach significantly outperforms conventional BPNN-based IPA. In particular, conventional BPNN-IPA would mislead managerial action with regard to 3 out of 8 quality components (37.5%).     

The hydrothermal synthesis of super-paramagnetic barium hexaferrite particles

Superparamagnetic Ba-hexaferrite nanoparticles were prepared using modified hydrothermal synthesis. The precursor and hydroxide [OH⁻] concentrations were optimized and the synthesis temperature and time were drastically reduced. The size and the morphology of synthesized nanoparticles was confirmed by transmission electron microscopy (TEM) images. The crystal structure of the nanoparticles was characterized by X-ray diffraction data. Powders synthesized at 160 °C exhibit a bimodal particle size distribution while those synthesized at T_S = 150 °C show a monomodal particle size distribution. Zero-field-cooling (ZFC) and field-cooling (FC) magnetization measurements were performed using a superconducting quantum interference device magnetometer from 2 to 300 K to investigate the magnetic properties of nanoparticles. The FC/ZFC magnetization measurements showed a typical superparamagnetic behavior. The synthesized superparamagnetic particles exhibit a disc-like shape, in average 11 nm wide and 3 nm thick with a room temperature magnetization of approximately 10 Am²/kg at 5 T.     

Fabrication of porous mullite-based ceramic bricks from Al-rich water treatment sludge and kaolinitic-based clay

A large quantity of water treatment sludge (WTS) is generated yearly from Ghana's Weija water treatment plant. The sludge contains some heavy metals and other toxic chemicals, which must be managed to minimize environmental impact. In the current work, WTS was mixed with varying quantities of kaolinitic-based clays (kaolin and lithomargic clays) to produce porous mullite-based bricks. The bricks were fired at 1200°C for 1 h, and their properties were determined. Lithomargic clay-based mixtures had less dimensional variation and were suitable to produce near-net shape bricks compared to WTS-based bricks. The addition of WTS increased the linear firing shrinkage and apparent porosity whilst decreasing bulk density and compressive strength. Porous mullite-based bricks fabricated from lithomargic clay exhibited high compressive strength (6.3 MPa) at 10 wt.% WTS addition. The highest apparent porosity of 27% was attained at 40 wt.% WTS addition with compressive strength of 5.1 MPa and thermal conductivity of .5 W/m K.     

Improvement of ammonia removal in activated sludge process with feedforward-feedback aeration controllers.

In the paper three linear aeration controllers that can be easily implemented are presented and evaluated on the activated sludge process pilot plant. Controllers differ according to the information that is used about the process, which can be oxygen in the last aerobic reactor, ammonia in the last aerobic reactor and ammonia in the influent. The aeration controllers that are addressed are: oxygen cascade PI controller, ammonia cascade PI controller and ammonia feedforward-cascade PI controller. Experiments show that, in comparison with the oxygen cascade PI controller, the ammonia cascade PI controller allows better control of effluent ammonia and airflow savings of around 23%, while the ammonia feedforward-cascade PI controller gives the best reduction of ammonia peaks and can save up to 45% of the airflow.     

Telecommunication liberalization and economic development in European countries in transition

Developed and widely available telecommunications services are regarded as key enablers of a new economy. In Eastern European countries in transition, investment in telecommunications is generally perceived as a stimulus for economic growth. We investigate empirical correlation and Granger causality between certain indicators of telecommunications activity and economic growth. The indicators include total investment in the telecommunications sector and other parameters such as the penetration rate of services. We also propose additional indicators that may describe telecommunications sector development better than traditional, fixed, telephony-based measures. This is due to the migration of users from fixed to mobile networks, and from basic to broadband Internet access in the last few years. In the near future one also can expect broadband Internet users to move to mobile network infrastructure.     

Extended Defects in ZnO Ceramics Containing Bi4Ti3O12 Additive

Extended defects in ZnO ceramics containing, 6 wt% Bi₄Ti₃O₁₂ were studied by analytical electron microscopy. Apart from basal plane condensation stacking faults, which are also present in as-received ZnO, extended defects related to the presence of Bi₄Ti₃O₁₂ were observed. In samples sintered at 900°C they lie in the basal or in the prismatic     planes and they quite often form closed loops, whereas they form serpentine-shaped boundaries in samples sintered at 1200°C. Evidence is given that they are inversion boundaries. Their TEM image characteristics, as well as the unambiguous presence of Ti at the boundaries, suggest that they are formed due to the presence of 2-D coherent precipitates of Ti-rich (possibly Zn₂TiO₄-type spinel) phase.     

Electrochemical and AFM study of nickel nucleation mechanisms on vitreous carbon from ammonium sulfate solutions

Reaction and nucleation mechanisms of nickel in ammoniacal solutions have been investigated as a function of nickel concentration, solution pH, deposition potential, temperature and conditioning potential. Electrochemical mechanisms of nickel reduction were found to be pH dependent, while their kinetics was concentration dependent. A surface film formed by anodic oxidation passivates nickel clusters preventing their further oxidation. Nickel nucleation on vitreous carbon, which proceeds according to the progressive nucleation model, shows a large degree of inhibition at both pH 6 and pH 9. Cluster sizes were larger when electrodeposition was carried out from solutions with higher nickel concentrations. The clusters were also larger at more negative deposition potentials and at higher solution pH. Cluster population density increased with the increasing solution temperature. Different activation energies for the nickel-aquo and nickel-ammino complexes calculated from Arrhenius diagram indicate that electroreduction of nickel-ammino complex is energetically more demanding. All electrochemical results were further verified by the atomic force microscopy investigations.