An Improved UPFC Control for Oscillation Damping

This paper proposes a new control approach for a unified power flow controller (UPFC) for power system oscillation damping. This control is simple to implement, yet is valid over a wide range of operating conditions. It is also effective in the presence of multiple modes of oscillation. The proposed control is implemented in several test systems and is compared against a traditional PI control

An Improved Nonlinear STATCOM Control for Electric Arc Furnace Voltage Flicker Mitigation

Electric arc furnaces (EAFs) are prevalent in the steel industry to melt iron and scrap steel. EAFs frequently cause large amplitude fluctuations of active and reactive power and are the source of significant power-quality (PQ) disturbances. Static synchronous compensators (STATCOMs) provide a power-electronic-based means of embedded control for reactive power support and PQ improvement. This paper introduces a new nonlinear control for the STATCOM that provides significant reduction in EAF-induced aperiodic oscillations on the power system. This method is compared with traditional PI controls and has shown to have improved performance

THE INFLUENCE OF TRANSITION METALS ON THE PERFORMANCE OF Pt Rh Pd/γ-AL2O3 THREE WAY CATALYSTS FOR PURIFICATION OF AUTOMOTIVE EXHAUST GAS

The influences of transition metal oxides (Zr, Mn, Co, Cu, Mo) on the performance of Pt Rh Pd/γ-Al2O3 three way catalysts were studied. The characteristics of the catalysts are investigated by using XRD, TPD, TPR. Experimental results show that the addition of Zr, Mn, Co, and Cu promoters improved the activity of Pt Rh Pd/γ-Al2O3 catalyst remarkably for CO, CH and NOx conversion, respectively. The effective order of the promoters is CuO > ZrO2 > Co3O4 > MnO2. The addition of CuO improved the dispersion of the noble metal on the γ-Al2O3 support and increased the absorption of Pt Rh Pd/γ-Al2O3 catalyst for CO and O2, in addition, promoted the reduction of the noble metal. KEY WORDS: Purification of exhaust gas, Pt Rh Pd/γ-Al2O3 catalyst, Transition metals Bull. Chem. Soc. Ethiop. 2006, 20(1), 113-120

Selenium status and cardiovascular diseases: meta-analysis of prospective observational studies and randomized controlled trials

Background/Objectives: Selenium was thought to have a role in cardiovascular disease (CVD) owing to its antioxidant properties; however, evidence from observational studies and randomized controlled trials (RCTs) has been inconsistent and controversial. We thus conducted a meta-analysis to assess the discrepancies between observational and randomized trial evidence. Subjects/Methods: We searched MEDLINE and EMBASE for eligible prospective studies regarding the relationship between selenium and CVD up to 15 December 2013 and finally included 16 prospective observational studies and 16 RCTs. Random effects model was used to estimate the pooled relative risk (RR). Generalized least-squares trend test and restricted cubic spline model were performed to assess a linear and a nonlinear dose–response relationship. Results: Our meta-analysis of prospective studies showed a nonlinear relationship of CVD risk with blood selenium concentrations across a range of 30–165 μg/l and a significant benefit of CVD within a narrow selenium range of 55–145 μg/l. Our meta-analyses of RCTs showed that oral selenium supplements (median dose: 200 μg/day) for 2 weeks to 144 months significantly raised the blood selenium concentrations by 56.4 μg/l (95% confidence interval (CI): 40.9, 72.0 μg/l), whereas oral selenium supplements (median: 100 μg/day) for 6 to 114 months caused no effect on CVD (RR=0.91; 95% CI: 0.74, 1.10). Conclusions: Our meta-analysis in prospective studies demonstrated a significant inverse association between selenium status and CVD risk within a narrow selenium range and a null effect of selenium supplementation on CVD was observed in RCTs. These findings indicate the importance of considering selenium status, dose and safety in health assessment and future study design

Irreversible Investment with Regime Shifts

Under the real options approach to investment under uncertainty, agents formulate optimal policies under the assumption that firms’ growth prospects do not vary over time. This paper proposes and solves a model of investment decisions in which the growth rate and volatility of the decision variable shift between different states at random times. A value-maximizing investment policy is derived such that in each regime the firm’s investment policy is optimal and recognizes the possiblity of a regime shift. Under this policy, investment is intermittent and increases with marginal q. Moreover, the rate of investment typically is very small but exhibits some spurts of growth. Implications for marginal q and the user cost of capital are also examined.Investment; Capacity choice; Regime shifts

TWO ASYMMETRICAL PERMIAN GRANITIC BELTS IN THE SOUTHEAST CAOB AND THEIR IMPLICATIONS

There has been much discussion about the evolution of the Southeastern CAOB in the past two decades [Tang, 1990; Hong et al., 1994; Xiao et al., 2003; Li, 2006; Chen et al., 2009; Jian et al., 2010]. Most people believed that the Palaeozoic Asia ocean was closed along the Solonker suture at Permian with two-direction subduction models [Xiao et al., 2003; Jian et al., 2010]. Three EW subparallel Permian granitic belts took place both side of the Solonker suture, including Erlian-Uliastai belt on north side of the Erlian-Hegengshan ophiolite, south Mongolia-Xilinhot belt the Erlian-Hegengshan ophiolite on the north and the Solonker suture on the south, and the Baotou-Chifeng belt along the north margin of North China Carton on the south of the Solonker suture. Most Permian granitoids in the ErlianUliastai belt and Mongolia-Xilinhot belt were intruded in Early-Middle Permian.There has been much discussion about the evolution of the Southeastern CAOB in the past two decades [Tang, 1990; Hong et al., 1994; Xiao et al., 2003; Li, 2006; Chen et al., 2009; Jian et al., 2010]. Most people believed that the Palaeozoic Asia ocean was closed along the Solonker suture at Permian with two-direction subduction models [Xiao et al., 2003; Jian et al., 2010]. Three EW subparallel Permian granitic belts took place both side of the Solonker suture, including Erlian-Uliastai belt on north side of the Erlian-Hegengshan ophiolite, south Mongolia-Xilinhot belt the Erlian-Hegengshan ophiolite on the north and the Solonker suture on the south, and the Baotou-Chifeng belt along the north margin of North China Carton on the south of the Solonker suture. Most Permian granitoids in the ErlianUliastai belt and Mongolia-Xilinhot belt were intruded in Early-Middle Permian

Comparative Analysis on Energy Consumption of Commercial Buildings Based on Sub-metered Data

With energy use growing rapidly around the world, building energy conservation is becoming a great concern especially for large commercial buildings. Therefore, it is of great significance to develop appropriate methods for energy use assessment of commercial buildings. In recent years, energy monitoring system (EMS) has been applied in some large-scale commercial buildings, which has laid the foundation for exhaustive and authentic evaluation. However, most of the current studies are only focused on annual or monthly aggregated energy consumption. Though end-use data are monitored in some buildings, only major categories or equipment are included. Little has been done to analyze the energy performance of numerous buildings with detailed hourly end-use data. With the access to hourly sub-metered data of detailed end uses, this study aims to introduce a comparing method to evaluate building energy performance through a case study. Information on selected buildings in the case was introduced. The research intends to compare energy use intensity (EUI) of the 19 malls based on a uniform energy data model, from total energy to detailed end-uses. It was shown that there is a significant discrepancy on the total energy use among these buildings, mainly due to HVAC (Heating, Ventilation and Air Conditioning) and public lighting. Then an in-depth comparative study was conducted on the energy consumption of public lighting and HVAC respectively. An unexpectedly remarkable discrepancy was illustrated on the EUI of public lighting. Thus the daily and hourly energy of public lighting were compared to identify the discrepancy in management mode. The study on HVAC was focused on the comparison of daily and hourly EUI in terms of four subordinate end uses (chillers, chilled water pumps, fans and cooling systems). The result showed that chillers accounts for larger proportions of total energy use, and the daily and hourly data were compared between buildings with similar climate. At last, the methods were summarized and challenges were discussed

From Control to Competition: Trust Institution in E-Business

Global economy has formed a huge challenge to the trust of traditional business. It’s a important problem of all enterprise how to build a effective trust institution in the new economy. The rapid development of E-business is bringing a turning point of trust institution. In traditional trust institution, trust means that principal controls the agent in fact. The evolution of trust institution was closely related to the development of technology because of control. This paper presents, with the innovation of technology and system, precondition of trust through the method of controlling has already been out of the existence. The development of E-business will have influence on the evolution of trust institution, Advantages of E-business can promote monitor from man-made to market-made, from control to competition. It will build an effectual trust institution