Oxidation of Zircaloy-4 by oxygen and the production of water

The interaction of isotopic oxygen (¹⁸O₂) with Zircaloy-4 (Zry-4) at 150 and 300 K has been studied using Auger electron spectroscopy (AES) and temperature-programmed desorption (TPD) methods. AES reveals the oxidation of the Zry-4 surface, reflected in shifts of the Zr(MNV) and Zr(MNN) features by about 5.5 and 3.0 eV, respectively, for both adsorption temperatures. The O(KLL)/Zr(MNN) Auger peak-to-peak height ratios as a function of exposure show the same trends at both temperatures. Following ¹⁸O₂ adsorption at 150 or 300 K, TPD experiments show hydrogen desorption near 400 K that is attributed to the presence of a surface-stabilized form of hydrogen. Additionally, water (H₂¹⁸O and H₂¹⁶O) desorption below 200 K and above 700 K is observed after 150 K oxygen adsorption. However, after oxygen adsorption at 300 K the only significant desorption features are from isotopic water (H₂¹⁸O). These findings indicate that mass transport involving the near-surface region contributes to the observed desorption, and that this behavior is dependent on the original adsorption temperature. Charging experiments using D₂ prior to and after ¹⁸O₂ adsorption were also performed and support our conclusions about the role of surface–subsurface mass transport in this system.     

Optical Spectroscopy of Er^3＋ and Er^3＋/Yb^3＋ Co-doped Bi2O3-GeO2-B2O3-ZnO Glasses

The （60 - x）Bi2O3 - xGeO2-30B2O3-10ZnO （x = 5, 10, 20, 30 molar percent） glasses doped with Er^3＋ and Er^3＋/Yb^3＋ were fabricated using the melting method. The thermal stability of the glasses was studied with their DTA curves. The results show that the difference between the glass transition temperature and the crystallization onset temperature increases with the increase of GeO2 content, indicating that the thermal stability of the glass has become better. The absorption spectra were recorded and the stimulated emission cross sections were calculated using the McCumber theory. The Ω2, O4, and Ω6 parameters,the transition probability, the radiative lifetime, and the fluorescence branch ratio of Er^3＋ for optical transition were calculated from their absorption spectra in terms of reduced matrix U^（t）（λ = 2, 4, 6） character for optical transitions. The infrared emission of Er^3＋ was measured upon excitation with 970 nm light and the full width at half-maximum （FWHM） was estimated from the emission spectra. The pumping efficiency and the intensity of the emission at the 1.54 μm band of Er^3＋ were enhanced considerably by co-doping Yb^3＋ .     

Actively Q-switched fiber lasers: Switching dynamics and nonlinear processes

The Q-switching characteristics of actively Q-switched fiber lasers, especially the inconsistency of experimental observations with traditional Q-switching theory, are reviewed first in this paper. Based on a few typical high-power Q-switched rare-earth-doped fiber lasers, the switching dynamics in the linear and ring fiber cavities is then systematically illustrated under different fiber, pumping and switching conditions by using the traveling wave method, which leads to a new understanding of Q-switched fiber lasers. In particular, the switching-induced perturbation and its influence on the Q-switched outputs are emphasized, and some experimental demonstrations are shown for the purpose of comparison. Nonlinearity is an important concern in these lasers due to the high-power optical pulses confined in small fiber cores. In the second part of this paper, some nonlinear effects, such as self-phase modulation (SPM), four-wave mixing (FWM), stimulated Raman scattering (SRS) and stimulated Brillouin scattering (SBS), in Q-switched fiber lasers are discussed. In particular, their temporal and spectral influences on the Q-switched outputs are analyzed experimentally and theoretically. These theoretical analyses and experimental demonstrations provide a complete picture of the switching dynamics and optical nonlinear processes in Q-switched fiber lasers, and are hence important for laser optimization and control.     

Fuzzy logic-based pre-classifier for tropical wood species recognition system

Classifying tropical wood species poses a considerable economic challenge and failure to classify the wood species accurately can have significant effects on timber industries. The problem of wood recognition is compounded with the nonlinearities of the features among the similar wood species. Besides that, large wood databases presented a problem of large processing time especially for online wood recognition system. In view of these problems, we propose the use of fuzzy logic-based pre-classifier as a means of treating uncertainty to improve the classification accuracy of tropical wood recognition system. The pre-classifier serve as a clustering mechanism for the large database simplifying the classification process making it more efficient. The use of the fuzzy logic-based pre-classifier has managed to increase the accuracy of the wood recognition system by 4 % and reduce the processing time for training and testing by more than 75 % and 26 % respectively.     

Quality evaluation of floss projects: Application to ERP systems

ContextThe selection and adoption of open source software can significantly influence the competitiveness of organisations. Open source software solutions offer great opportunities for cost reduction and quality improvement, especially for small and medium enterprises that typically have to address major difficulties due to the limited resources available for selecting and adopting a new software system.ObjectiveThis paper aims to provide support for selecting the open source software that is most suitable to the specific needs of an enterprise from among the options offering equivalent or overlapping functionality.MethodThis paper proposes a framework for evaluating the quality and functionality of open source software systems. The name of the framework is EFFORT (Evaluation Framework for Free/Open souRce projecTs). It supports the evaluation of product quality, community trustworthiness and product attractiveness. The framework needs to be customised to the analysis of software systems for a specific context.ResultsThe paper presents the customisation of EFFORT for evaluating Enterprise Resource Planning (ERP) open source software systems. The customised framework was applied to the evaluation and comparison of five ERP open source software systems. The results obtained permitted both the refinement of the measurement framework and the identification of the ERP open source software system that achieved the highest score for each chosen characteristic.ConclusionEFFORT is a useful tool for evaluating and selecting an open source software system. It may significantly reduce the amount of negotiation conducted among an enterprise’s members and reduce the time and cost required for gathering and interpreting data. The EFFORT framework also considers the users’ opinions by introducing relevance markers associated with the metrics and questions in the data aggregation process.     

Synthesis of carbon molecular sieves from palm shell by carbon vapor deposition

A series of experiments were conducted to produce carbon molecular sieves (CMS) through carbon deposition from a locally available palm shell of Tenera type for separating gaseous mixtures. The process involves three stages; carbonization, physical activation with steam, and carbon deposition by using benzene cracking technique. Carbonization of the dried palm shells was occurred at 900°C for duration of 1 h followed by steam activation at 830°C for 30–420 min to obtain activated carbons with different degree of burn-offs. The highest micropore volume of activated carbon obtained at 53.2% burn-off was used as a precursor for CMS production. Subsequent carbon deposition of the activated sample at temperature range from 600 to 900°C for 30 min has resulted in a series of CMSs with different selectivities of CO₂/CH₄ and O₂/N₂. The kinetic adsorption isotherm of CO₂, CH₄, O₂ and N₂ at room temperature also presented in this work.     

Response Surface Modeling of Processing Parameters for the Preparation of Phytosterol Nanodispersions Using an Emulsification–Evaporation Technique

The purpose of this study was to optimize the production parameters for water-soluble phytosterol nanodispersions. Response surface methodology (RSM) was employed to model and optimize three of the processing parameters: mixing time (t) by conventional homogenizer (1–20 min), mixing speed (v) by conventional homogenizer (1,000–9,000 rpm) and homogenization pressure (P) by high-pressure homogenizer (0.1–80 MPa). All responses [i.e., mean particle size (PS), polydispersity index (PDI) and phytosterols concentration (Phyto, mg/l)] fitted well to a reduced quadratic model by multiple regressions after manual elimination. For PS, PDI and Phyto, the coefficients of determination (R ²) were 0.9902, 0.9065 and 0.8878, respectively. The optimized processing parameters were 15.25 min mixing time, 7,000 rpm mixing speed and homogenization pressure 42.4 MPa. In the produced nanodispersions, the corresponding responses for the optimized preparation conditions were a PS of 52 nm, PDI of 0.3390 and a Phyto of 336 mg/l.     

Potential application of renewable energy for rural electrification in Malaysia

Energy poverty and lack of electricity in rural areas exacerbate the poverty of the developing countries. In Malaysia, 3.8% of the population lives below the poverty line and most of them are settled in rural areas. The electricity coverage in poor states is about 79% in comparison with 99.62% in Peninsular Malaysia. The renewable energy sources can be considered the best alternative to reduce the energy poverty of the rural areas where the grid extension through a difficult terrain and thick jungle is not possible or economic. In this study, the potential for applying renewable sources – solar, wind and hydropower – for rural electrification is investigated, especially in the poorest States. A comparative study on rural electrification policies, in order to have community approval, appropriate siting and financial benefits for the rural community, while considering the three categories of social, institutional and economic issues, is also examined. Finally, the Malaysian policies of rural electrification by applying renewable sources are explained. It is found that in Malaysia, with a maximum solar radiation of about 6.027 kWh/m² per day in Sabah and 5.303 kWh/m² per day in Sarawak, the potential for applying solar energy for electrification is too high. However, the potential for micro-hydropower in Sabah and Sarawak is found to be 3182 kW and 6317 kW through 18 and 22 sites, respectively.     

Optical tomography hardware development for solid gas measurement using mixed projection

The ability to implement fan beam projection in parallel view in an optical tomography setup is one of the novelties of this research. This design involves a sensor jig specifically designed for parallel applications that does not involve a collimator. Therefore, the fan beam projections can also be implemented in the same sensor jig without difficulty. This method is a very practical solution for overcoming the disadvantages of parallel beam projection. Although the fan beam has its own disadvantages, combining the fan beam approach with the parallel beam approach is expected to further enhance the optical tomography image quality. The image quality can be measured using the Peak Signal-to-Noise Ratio (PSNR) and the Normalized Mean-Square Error (NMSE) parameters. The combination of the two approaches also eliminates the unwanted noise that appears when using parallel beam projection alone.     

Influence of the dissolved oxygen content on corrosion of the ferritic–martensitic steel P92 in supercritical water

The corrosion of the ferritic–martensitic steel P92 exposed to supercritical water at 550 °C under 25 MPa with the dissolved oxygen contents of 100, 300 and 2000 ppb was investigated. The results indicated that the weight gain increased with the dissolved oxygen content. The oxide scale with a typical dual-layered structure including a Fe-rich outer magnetite layer and a Cr-rich inner layer was formed on all samples in spite of different dissolved oxygen. Finally, the possible explanations for the influence of the dissolved oxygen content on the weight gain and exfoliation of oxide scale were given.