Identification of Trend in Reference Evapotranspiration Series with Serial Dependence in Iran

Monitoring the temporal variations of reference evapotranspiration (ET_o) and quantifying any trends offer valuable information for regional hydrology, agricultural water requirements and water resources management. This study aimed to examine the temporal trends in the Penman–Monteith ET_o in the west and southwest of Iran by using the Kendall and Spearman tests after eliminating the influence of significant lag-1 serial correlation from the ET_o time series. The magnitudes and starting years of significant ET_o trends were determined by the Mann-Kendall rank statistic and the Theil–Sen’s estimator, respectively. For the study period of 1966–2005, a significant positive lag-1 serial correlation coefficient was observed at almost all the stations. The existence of the positive serial correlation in the ET_o series increased the possibility of the Kendall and Spearman tests to reject the null hypothesis of no trend while it is true. It was found that the Kendall test was more sensitive than the Spearman test to the existence of the positive serial correlation in the ET_o series. After removing the serial correlation effect with pre-whitening method, only three significant increasing ET_o trends were obtained at Khorram-Abad, Shahrekord and Zanjan stations at the rates of 0.16, 0.06 and 0.06 mm/day per decade, respectively. The significant increasing ET_o trends of Khorram-Abad, Zanjan and Shahrekord stations started in 1997, 1994 and 1998, respectively. The stepwise regression method showed that wind speed was the most dominating variable affecting on the significant changes of ET_o.     

The impacts of capabilities and constraints of generating units on simultaneous scheduling of energy and primary reserve

Frequency control, as an ancillary service, is usually provided by generation reserves. Modern generating units have special technical capabilities; e.g., their governor operation mode can be selected to be either active or passive, their ramp rate can be selected to be either normal or fast, etc. On the other hand, generating units have some technical constraints; e.g. some generating units cannot participate in primary frequency control at their capacity limits. In this paper, operational capabilities and constraints of generating units are incorporated in a “simultaneous scheduling of energy and primary reserve” problem. Furthermore, a heuristic iterative method (based on genetic algorithm) is proposed to obtain the optimal scheduling. The impacts of capabilities and constraints on scheduling are investigated through simulation studies. Simulation results depicts that taking these capabilities and constraints of generating units into account, not only reduces the total operational cost of generating units, but also will end up with a feasible solution for the system, even in cases where the previously proposed methods fail.     

An adaptive latency mitigation scheme for massively multiuser virtual environments

As massively multiuser virtual environments (MMVEs) expand in terms of size and user population, they tend toward using P2P architectures as a way to provide scalability without the need for large centralized resources. Distributed hash table (DHT)-based networks have been introduced as a promising option for overlay-based distributed massively multiuser virtual environment applications. However, overlay latency stretch seriously affects MMVE performance where QoS is crucial for real-time user collaboration. This work includes a series of efforts in the alleviation of such undesired latency. Our approach to latency mitigation consists of two phases. First, we propose a position-based ID assignment approach to minimize message hop-count by exploiting the clustered pattern of traffic exchange among MMVE users. Second, we introduce a new ant-based distributed neighbor selection scheme that can be used by MMVE users to select the best neighbors within their areas of interest. In order to evaluate the performance of this heuristic approach, we model the neighbor selection problem in the form of a network flow problem and use its solution as an optimality bound to compare the results. Simulation results demonstrate that the proposed algorithms will compensate for DHT latency stretch to a high extent and the performance of the resulting system would closely follow the optimal bound while communication overhead is negligible.     

An improved topology of electronic ballast with wide dimming range,PFC and low switching losses using PWM-controlled soft-switching inverter

This paper presents a novel improved topology of voltage-fed soft-switching LC_rC_dc series–parallel quasi-resonant inverter with a constant-frequency for electronic ballast applications. This new topology introduces a low-cost solution to reduce switching losses to achieve high-efficiency ballast. A symmetrical pulse wide modulation (PWM) control scheme is implemented to regulate a wide range of output power. Switching losses effect on ballast efficiency is discussed through experimental point of view. In this discussion, an improved topology in which accomplishes soft-switching operation over a wide power regulation range is proposed. Energy consumption of this new circuit is decreased by using reverse recovery attribute. Additionally, a power-factor correction (PFC) circuit is employed to make the line current follow naturally the sinusoidal line voltage waveform.     

Microbial conversion of androst‐1,4‐dien‐3,17‐dione by Mucor racemosus to hydroxysteroid‐1,4‐dien‐3‐one derivatives

BACKGROUND: A large number of bacterial, fungal and microalgal species are able to bio‐transform steroid compounds. Among them, fungi from the Mucor genus have been shown to mediate hydroxylation, oxidation, and desaturation by the double bond formation and epoxidation of various steroid substances. Mucor racemocus has not been studied for its ability to modify androst‐1,4‐dien‐3,17‐dione, a pharmaceutically important steroid precursor. RESULTS: The filamentous fungus M. racemosus was applied for bioconversion of androst‐1,4‐dien‐3,17‐dione (ADD, I ) in a 5‐day fermentation. Microbial metabolites were purified chromatographically and identified on the basis of their spectral data as 17β‐hydroxyandrost‐1,4‐dien‐3‐one ( II ), 14α‐hydroxyandrost‐1,4‐dien‐3,17‐dione ( III ), 15α‐hydroxyandrost‐1,4‐dien‐3,17‐dione ( IV ), 15α,17β‐dihydroxyandrost‐1,4‐dien‐3‐one ( V ), 14α,17β‐dihydroxyandrost‐1,4‐dien‐3‐one ( VI ), and 6β,17β‐dihydroxyandrost‐1,4‐dien‐3‐one ( VII ). CONCLUSION: Observed modifications included hydroxylation at C‐6β, C‐14α, C‐15α positions and 17‐carbonyl reduction. The best fermentation conditions for production of hydroxysteroid‐1,4‐dien‐3‐one derivatives were found to be 25 °C at 150 rpm for 5 days with a substrate concentration of 0.5 g L^?1. Copyright © 2009 Society of Chemical Industry     

Empirical evaluation of river basin sustainability affected by inter‐basin water transfer using composite indicators

In this study, a practical approach to evaluate the sustainability of river basins subjected to an inter‐basin water transfer project is developed. Selection of appropriate evaluation indicators is pivotal to such approach. To make use of huge amount of data, composite indicators of sustainability (CIS) should be utilised. The proposed approach relies on 15 sustainability indicators (SI) that cover three major criteria namely (economic, social and environmental), and aggregates them into eight different types of sustainability indices for a more robust outcome. Two scenarios were considered within the source and recipient basins. Furthermore, multivariate principal component analysis (PCA) was applied to determine principal and non‐principal indicators for the two river basins. The ability of CIS and PCA methods were verified via correlation and simple regression methods respectively. The results demonstrated that inter‐basin water transfer may improve sustainability, provided that a proper water resource management is enforced.     

Kinetic study of styrene atom transfer radical polymerization from hydroxyl groups of graphene nanoplatelets: Heterogeneities in chains and graft densities

Confinement effect of graphene nanoplatelets on the kinetics of styrene atom transfer radical polymerization was studied by a “grafting from” reaction. Graphene oxide was modified by different amounts of (3‐aminopropyl) triethoxysilane and then alpha‐bromoisobutyryl bromide from the hydroxyl groups. Polymerization of styrene in the presence of modified graphene and free initiator, ethyl alpha‐bromoisobutyrate, was accomplished at 110°C. Then, effect of various graft densities and different graphene loadings on the heterogeneous graft and free polystyrene chains characteristics and also kinetics of polymerization was studied by gas and gel permeation chromatographies. Efficiency of grafting reactions along with the graft contents was studied by X‐ray photoelectron spectroscopy, elemental analysis, and thermogravimetric analysis. Confinement effects of graphene on the relaxation behavior of polystyrene chains and also morphology of the graphenes were studied by differential scanning calorimetry and transmission electron microscopy, respectively. POLYM. ENG. SCI., 55:1720–1732, 2015. © 2014 Society of Plastics Engineers     

Optimization of Ozonation Process for a Composting Leachate-Contaminated Soils Treatment Using Response Surface Method

The ozonation process has become one of the most favorable processes among soil remediation technologies nowadays. Ozone, which has an oxidation potential of 2.07 V and acts as a powerful oxidizer, is capable of degrading organic pollutants of soil in a short period of time without producing any toxic residuals. In this study the capability of ozone, as an ex-situ method of soil treatment, in remediating the leachate-contaminated soil has been investigated. To maximize the removal efficiency of organic content of soil, design of experiments using the response surface method (RSM) and central composite design (CCD) have been employed. To select the range of effective parameters several experiments were performed at laboratory scale. Results showed a range of effective parameters on the ozonation process, including pH, humidity, and initial soil pollution. Present research shows that acid-washed ozone greatly enhanced the removal efficiency. According to the developed model, the maximum removal efficiency using acid-washed ozone was obtained by setting the parameters as pH = 10.8, humidity of 5% and initial organic content of soil to be 7720 mg/kg. Confirmation experiments showed that RSM could be effectively utilized for the optimization of the ozonation process. Analysis of variance also showed that pH was the most significant factor affecting removal efficiency.     

Rapid determination of soil unconfined compressive strength using reflectance spectroscopy

Bulletin of Engineering Geology and the Environment - Understanding the physical and especially mechanical properties of forest soils is very important in forest engineering operations including...