Measuring temperature dependence of photoelectric conversion efficiency with dye-sensitized solar cells

It’s well known that the drift velocity of electrons in conductors depends on temperature in accordance with thermodynamics, which influences also photoelectric conversion efficiency of solar cells. The article presents experimental data for studying temperature influence of photoelectric conversion efficiency with dye-sensitized solar cells (DSSCs). The measured DSSCs were built in three layers, the photoelectrode, the electrolyte, and the counter electrode, which were made in the CCT laboratory, National Taipei University of Technology, Taiwan. The photoelectrode is coated by using ? = 21 nm nano TiO₂ and dye as well as the counter electrode using ? = 5 nm nano carbon black on their individual ITO glass. The fluidic electrolyte is used in this work due to its good ionic drift property. In process, the DSSC was waterproof and immersed in the constant temperature water tank for temperature adjusting. The measured temperature range was from ca. 5 °C to 80 °C at an interval of ca. 10 °C. The results show the higher temperature, the lower photoelectric conversion efficiency of DSSCs.     

Two-step hydrothermal synthesis of Ru-Sn oxide composites for electrochemical supercapacitors

A two-step hydrothermal process was developed to synthesize hydrous 30RuO₂-70SnO₂ composites with much better capacitive performances than those fabricated through the normal hydrothermal process, co-annealing method, or modified sol-gel procedure. A very high specific capacitance of RuO₂ (C_S,Ru), ca. 1150 F g⁻¹, was obtained when this composite was synthesized via this two-step hydrothermal process with annealing in air at 150 °C for 2 h. The voltammetric currents of this annealed composite were found to be quasi-linearly proportional to the scan rate of CV (up to 500 mV s⁻¹), demonstrating its excellent power property. From Raman, UV-vis spectroscopic and TEM analyses, the reduction in mean particulate size is clearly found for this two-step oxide composite, attributable to the co-precipitation of (Ru_δSn_1−δ)O₂·xH₂O onto partially dissolved SnO₂·xH₂O and the formation of (Ru_δSn_1−δ)O₂·xH₂O crystallites in the second step. This effect significantly promotes the utilization of RuO₂ (i.e., very high C_S,Ru). The excellent capacitive performances, very similar to that of RuO₂·xH₂O, suggest the deposition of RuO₂-enriched (Ru_δSn_1−δ)O₂·xH₂O onto SnO₂·xH₂O seeds as well as the individual formation of (Ru_δSn_1−δ)O₂·xH₂O crystallites in the second hydrothermal step.     

Analysis of dynamic voltage collapse mechanism for a three-bus power system

The phenomenon of voltage collapse is reconstructed based on a three-bus power system with dynamic on-load tap-changers (OLTC). Utilizing nonlinear stability techniques, the monotonic fall of bus voltages is derived from instability of the dynamic system. The exact stability region of the system is constructed which demonstrates the concept of voltage stability region as a tool for the prevention of voltage collapse.     

MicroRNA-Regulated Protein-Protein Interaction Networks and Their Functions in Breast Cancer

MicroRNAs, which are small endogenous RNA regulators, have been associated with various types of cancer. Breast cancer is a major health threat for women worldwide. Many miRNAs were reported to be associated with the progression and carcinogenesis of breast cancer. In this study, we aimed to discover novel breast cancer-related miRNAs and to elucidate their functions. First, we identified confident miRNA-target pairs by combining data from miRNA target prediction databases and expression profiles of miRNA and mRNA. Then, miRNA-regulated protein interaction networks (PINs) were constructed with confident pairs and known interaction data in the human protein reference database (HPRD). Finally, the functions of miRNA-regulated PINs were elucidated by functional enrichment analysis. From the results, we identified some previously reported breast cancer-related miRNAs and functions of the PINs, e.g., miR-125b, miR-125a, miR-21, and miR-497. Some novel miRNAs without known association to breast cancer were also found, and the putative functions of their PINs were also elucidated. These include miR-139 and miR-383. Furthermore, we validated our results by receiver operating characteristic (ROC) curve analysis using our miRNA expression profile data, gene expression-based outcome for breast cancer online (GOBO) survival analysis, and a literature search. Our results may provide new insights for research in breast cancer-associated miRNAs.     

Fabrication of diamond nanopowder using microwave plasma torch technique

This article presents a manufacturing process for diamond nanopowder by using a microwave plasma torch technique in a laboratory at near atmospheric pressure. The unique technique utilized in the arrangement is the hybrid plasma torch which was patented in 1997 by Dr. Cheng-Ming Wu in Taiwan. It has the advantage of working at near atmospheric pressure and does not require an extreme vacuum system, which is a necessary condition for fabrication of a large amount of nanoparticles. The applied constituents of gas mixtures for synthesizing diamond nanopowder in the process are CH₄ with AR and CH₄ with N₂, where AR and N₂ serve as catalysts. In processing the reaction chamber, it is first pumped to varied pressures from 40–300 Torr to induce plasma; then, the input reactive gas CH₄ is fixed at a constant flow rate of 0.6 l/min and mixed up with varied input flow rate of the catalysts Ar and N₂ from 0.6–1.2 l/min. The particle size of synthesized diamond nanopowder is within about 25--50 nm diameter, which mainly depends on flow rate of CH₄:AR and CH₄:N₂.     

Characterization of pistachio shell-derived carbons activated by a combination of KOH and CO2 for electric double-layer capacitors

The micropores and surface oxygen functional groups of KOH-activated carbons were respectively extended and desorbed by the gasification of CO₂ during the activation process of chars derived from pistachio shells. These activated carbons (ACs) were found to exhibit ideal capacitive performances (i.e., a rectangular shape of CVs at a wide range of scan rates, high power property, and excellent reversibility) in aqueous electrolytes for electric double-layer capacitors. Although the specific capacitance of these ACs measured at a low scan rate (25 mV s⁻¹) is decreased with reducing the density of surface functional groups, the ideal capacitive characteristics can be maintained at a much higher scan rate (300 mV s⁻¹) when the CO₂ gasification time is equal to or longer than 30 min because of the relatively high proportion of mesopores.     

Risk assessment in energy trading

This paper provides a state-of-the-art summary of risk assessment in energy trading. Techniques from financial engineering are needed by electric energy companies to manage price risk. These tools are needed by suppliers, distributors, and traders in a competitive electric power marketplace. Tools that have been adapted to the specific environment of the electric power system include portfolio analysis and hedging instruments. This paper provides a comprehensive critical literature survey of what has been applied to date in the power markets and which areas continue to need additional research. One example market scenario is used throughout the paper to demonstrate the usefulness of the risk assessment methods.     

Bounding the computation time of forward-chaining rule-based systems

For real-time applications of expert systems, success depends on the computational efficiency of the implementation. In this study, we propose an analytical method for evaluating the processing time of forward-chaining rule-based systems. An upper bound based on this system model is developed. If the upper bound stays within the time available for planning the operational or control task, the expert system would be able to complete the rule-processing in time. To compute the upper bound, the worst case working memory element sets are obtained for each functional step of the matching procedure. The worst case time for rule selection in the conflict resolution step is also derived. The maximal number of firings for each rule is considered in order to arrive at a bound for total processing time. Numerical examples are presented which point out the importance of rule and data structures in the efficient implementation of rule-based systems.