A Zig-Zag Transformer and Three-leg VSC Based DSTATCOM for a Diesel Generator Based Microgrid

AbstractThe distribution systems are facing severe power quality problems due to the uncontrolled use of different types of linear and non-linear loads such as solid state controllers which will draw harmonics and reactive currents from ac mains. It may lead to poor power quality at ac sources such as sag, swell, notch, flicker, unbalance etc. The installation of the diesel generator set is widely used in practice to feed power to some crucial equipments and in remote areas. DG sets used for these purposes may be loaded with unbalanced, reactive and non-linear loads such as power supplies in telecommunication system and medical equipments. A Zig-Zag Transformer and three-leg VSC based DSTATCOM is used here to compensate the neutral current, harmonic current, reactive power and unbalanced load. The insulated gate bipolar transistor (IGBT) based VSC is supported by a capacitor and is controlled for the compensation required in the load current. The dc bus voltage of the VSC is regulated during varying load conditions. In this paper, a Synchronous Reference Frame (SRF) controlled three-leg voltage source converter (VSC) based DSTATCOM with a Zig-Zag transformer is used for reactive power, harmonics, unbalanced load current and neutral current compensation in grid connected and islanded mode

Estimation of Economic Returns to Soil and Water Conservation Research – An Ex Ante Analysis

The economic returns to investment made in soil and water conservation research have been analyzed. Technologies such as conservation furrow, residue incorporation have been found to be economically viable under farmers’ conditions. The study has covered four locations, viz. Agra and Varanasi in Uttar Pradesh, Kota in Rajasthan and Jabalpur in Madhya Pradesh. The economic surplus analysis has revealed that when adopted on a large scale, soil and water conservation technologies generate significant economic surplus as reflected in high NPV and BC ratio. The share of producer surplus has been found to be higher in the total economic surplus generated from technology adoption. Thus, investments in generation and transfer of soil and water conservation technologies have been found be justified in terms of economic benefits. However, various constraints that hamper adoption of these technologies are to be addressed so that the potential benefits could be realized by both farmer and consumer.Agricultural and Food Policy,

Soil and Water Conservation Works through National Rural Employment Guarantee Scheme (NREGS) in Andhra Pradesh — An Analysis of Livelihood Impact

The impact of National Rural Employment Guarantee Scheme (NREGS) has been studied on rural livelihoods and the nature of soil and water conservation (SWC) works. NREGS is under implementation in almost all the rural districts of the country with the major objective of enhancing livelihoods through productive works. Rajasthan, Andhra Pradesh and Madhya Pradesh are the three states leading in scheme implementation with a large number of works, expenditure and employment. In Andhra Pradesh, soil and water conservation (SWC) works have accounted for over 80 per cent. The share of labour wages under the scheme has been 80 per cent with only 20 per cent for material, which is well within the prescribed norm of 40 per cent for the latter. The field study in the Ananthapur district has indicated that almost two-thirds of the beneficiaries are farmers. The scheme has brought down the migration levels from about 27 per cent to only 7 per cent in the study villages. The linear regression function has brought out that the number of family members participating in the NREGS is significantly influenced by income from other sources, family size and landholding. The NREGS earnings are being used mainly for food, education and health security. Although the scheme provides opportunity for 100 days of wage guarantee, the actual average employment is only for 25 days per household. Ideally, this gap needs to be bridged at least in the distress districts. The study has observed that SWC works in agricultural lands, especially in the rainfed areas need to be continued. However, some works require structural modifications for a better impact.Agricultural and Food Policy,

Spatial heterogeneity and irreversible vegetation change in semi-arid grazing systems

Recent theoretical studies have shown that spatial redistribution of surface water may explain the occurrence of patterns of alternating vegetated and degraded patches in semiarid grasslands. These results implied, however, that spatial redistribution processes cannot explain the collapse of production on coarser scales observed in these systems. We present a spatially explicit vegetation model to investigate possible mechanisms explaining irreversible vegetation collapse on coarse spatial scales. The model results indicate that the dynamics of vegetation on coarse scales are determined by the interaction of two spatial feedback processes. Loss of plant cover in a certain area results in increased availability of water in remaining vegetated patches through run-on of surface water, promoting within-patch plant production. Hence, spatial redistribution of surface water creates negative feedback between reduced plant cover and increased plant growth in remaining vegetation. Reduced plant cover, however, results in focusing of herbivore grazing in the remaining vegetation. Hence, redistribution of herbivores creates positive feedback between reduced plant cover and increased losses due to grazing in remaining vegetated patches, leading to collapse of the entire vegetation. This may explain irreversible vegetation shifts in semiarid grasslands on coarse spatial scales

Fenotipado proteómico de Líneas Celulares de Cáncer Humano

Comunicaciones a congreso

Effects of a nanoscopic filler on the structure and dynamics of a simulated polymer melt and the relationship to ultra-thin films

We perform molecular dynamics simulations of an idealized polymer melt surrounding a nanoscopic filler particle to probe the effects of a filler on the local melt structure and dynamics. We show that the glass transition temperature $T_g$ of the melt can be shifted to either higher or lower temperatures by appropriately tuning the interactions between polymer and filler. A gradual change of the polymer dynamics approaching the filler surface causes the change in the glass transition. We also find that while the bulk structure of the polymers changes little, the polymers close to the surface tend to be elongated and flattened, independent of the type of interaction we study. Consequently, the dynamics appear strongly influenced by the interactions, while the melt structure is only altered by the geometric constraints imposed by the presence of the filler. Our findings show a strong similarity to those obtained for ultra-thin polymer films (thickness $\lesssim 100$ nm) suggesting that both ultra-thin films and filled-polymer systems might be understood in the same context

Synthetic aperture radar and optical remote sensing image fusion for flood monitoring in the Vietnam lower Mekong basin: a prototype application for the Vietnam Open Data Cube

Flood monitoring systems are crucial for flood management and consequence mitigation in flood prone regions. Different remote sensing techniques are increasingly used for this purpose. However, the different approaches suffer various limitations, including cloud and weather effects (optical data), and low spatial resolution and poor colour presentation (synthetic aperture radar data). This study fuses two data types (Landsat and Sentinel-1) to overcome these limitations and produce better quality images for a prototype flood application in the Vietnam Open Data Cube (VODC). Visual and quantitative evaluation of fused image quality revealed improvement in the images compared with the original scenes. Ground-truth data was used to develop the study flood extraction algorithm and we found a good agreement between our results and SERVIR Mekong (a joint initiative by the US agency for International Development (USAID), National Aeronautics and Space Administration (NASA), Myanmar, Thailand, Cambodia, Laos and Vietnam) maps. While the algorithm is run on a personal computer (PC), it has a clear potential to be developed for application on a big data system

Influence of intensive melt shearing on the microstructure and mechanical properties of an Al-Mg alloy with high added impurity content

The official published version can be accessed from the link below - Copyright @ The Minerals, Metals & Materials Society and ASM International 2011We have investigated the influence of melt conditioning by intensive shearing on the mechanical behavior and microstructure of Al-Mg-Mn-Fe-Cu-Si alloy sheet produced from a small book mold ingot with high added impurity content. The melt conditioned ingot has fine grains throughout its cross section, whereas a conventionally cast ingot, without melt shearing, has coarser grains and shows a wider variation of grain size. Both needle-shaped and coarse Chinese script iron bearing intermetallic particles are found in the microstructure at the center of the conventionally processed ingot, but for the melt conditioned ingot, only fine Chinese script intermetallic particles are observed. In addition to the iron bearing intermetallics, Mg2Si particles are also observed. The ingots were rolled to thin sheet and solution heat treated (SHT). During rolling, the iron-based intermetallics and Mg2Si particles are broken and aligned along the rolling direction. Yield strength (YS), ultimate tensile strength (UTS), and elongation of the intensively melt sheared and processed sheet are all improved compared to the conventionally cast and processed sheet. Fractographic analysis of the tensile fracture surfaces shows that the clustered and coarse iron bearing intermetallic particles are responsible for the observed reduction in mechanical properties of the conventionally cast sheet. We have shown that by refining the initial microstructure of the ingot by intensive shear melt conditioning, it is possible to achieve improved mechanical properties at the final sheet gage of an AlMgMn alloy with a high content of impurities.This study is under the Technology Strategy Board funded REALCAR projec