Factors and options for improved frequency regulation: Case study of utility scale solar in Nigeria

This paper presents the structure, tuning, and evaluation of a model for power system frequency response in Nigeria. We demonstrate that a 100MW utility scale solar farm is unlikely to degrade frequency performance, and we quantify the effect of several possible interventions to improve frequency regulation. The Nigerian system already experiences wide frequency variations due to steel mill loads and load rejection during storms, and this often necessitates manual intervention and load management. The model is one of several employed in grid-integration evaluations of proposed large utility-scale solar farms. The model is intended to support ongoing discussions on how grid code and market policies should specify ancillary services supplied by participants

Exact Solutions in Five-Dimensional Axi-dilaton Gravity with Euler-Poincare Term

We examine the effective field equations that are obtained from the axi-dilaton gravity action with a second order Euler-Poincare term and a cosmological constant in all higher dimensions. We solve these equations for five-dimensional spacetimes possessing homogeneity and isotropy in their three-dimensional subspaces. For a number of interesting special cases we show that the solutions fall into two main classes: The first class consists of time-dependent solutions with spherical or hyperboloidal symmetry which require certain fine-tuning relations between the coupling constants of the model and the cosmological constant. Solutions in the second class are locally static and prove the validity of Birkhoff's staticity theorem in the axi-dilaton gravity. We also give a special class of static solutions, among them the well-known black hole solutions in which the usual electric charge is superseded by an axion charge.Comment: New formulas and references adde

Observations of the views of university students on agricultural production

In this study, an attempt was made to examine the perspective of university students and their family members on the agricultural sector, the value they attach to agriculture and their own lands, the level of knowledge and awareness of the agricultural sector where they are engaged in production activities and make a living, and the importance they attribute to the sustainability of agriculture. In addition, the production activities of farmers and their membership in cooperatives or unions were also examined. The surveys conducted by interviewing a total of 200 participants representing university students and their family members within the scope of the research constituted the target material of this study. The obtained survey data were examined and tables containing frequency and percentage parameters were prepared and tried to be interpreted. According to the results of the research, a significant majority of the participants attribute importance to the integrity of the land and believe that agriculture is indispensable. Besides, considering the importance of the agricultural sector and the existing agricultural land, there is a substantial proportion of participants who do not see any harm in non-agricultural use of their lands and state that they will give up their lands in a possible situation

Data protection, safeguarding and the protection of children's privacy: exploring local authority guidance on parental photography at school events

Should parents be allowed to take photographs at school events? Media reports suggest that increasingly schools are answering no to this question, either prohibiting or imposing stringent restrictions upon such photography. The legal justifications for such restrictions are, however, unclear. Accordingly, in 2013 freedom of information requests were sent to local education authorities across England, Scotland and Wales, the aim being to determine what advice local education authorities provide to schools in relation to parental photography at school events, and to identify how education authorities’ understandings of the law influence the advice they offer. That research reveals that local education authorities’ understandings of the law vary significantly and that where authorities do not fully appreciate the extent of the legal obligations arising this may have significant repercussions for the children concerned

The geometrical form for the string space-time action

In the present article, we derive the space-time action of the bosonic string in terms of geometrical quantities. First, we study the space-time geometry felt by probe bosonic string moving in antisymmetric and dilaton background fields. We show that the presence of the antisymmetric field leads to the space-time torsion, and the presence of the dilaton field leads to the space-time nonmetricity. Using these results we obtain the integration measure for space-time with stringy nonmetricity, requiring its preservation under parallel transport. We derive the Lagrangian depending on stringy curvature, torsion and nonmetricity.Comment: 13 page

Backflow air and pressure analysis in emptying a pipeline containing an entrapped air pocket

[EN] The prediction of the pressure inside the air pocket in water pipelines has been the topic for a lot of research works. Several aspects in this field have been discussed, such as the filling and the emptying procedures. The emptying process can affect the safety and the efficiency of water systems. Current research presents an analysis of the emptying process using experimental and computational results. The phenomenon is simulated using the two-dimensional computational fluid dynamics (2D CFD) and the one-dimensional mathematical (1D) models. A backflow air analysis is also provided based on CFD simulations. The developed models show good ability in the prediction of the sub-atmospheric pressure and the flow velocity in the system. In most of the cases, the 1D and 2D CFD models show similar performance in the prediction of the pressure and the velocity results. The backflow air development can be accurately explained using the CFD model.This work was supported by the Fundação para a Ciência e a Tecnologia (FCT), Portugal under grant number PD/BD/114459/2016.Besharat, M.; Coronado-Hernández, OE.; Fuertes-Miquel, VS.; Viseu, MT.; Ramos, HM. (2018). Backflow air and pressure analysis in emptying a pipeline containing an entrapped air pocket. Urban Water Journal. 15(8):769-779. https://doi.org/10.1080/1573062X.2018.1540711S769779158Benjamin, T. B. (1968). Gravity currents and related phenomena. Journal of Fluid Mechanics, 31(2), 209-248. doi:10.1017/s0022112068000133Besharat, M., Teresa Viseu, M., & Ramos, H. (2017). Experimental Study of Air Vessel Behavior for Energy Storage or System Protection in Water Hammer Events. Water, 9(1), 63. doi:10.3390/w9010063Besharat, M., Tarinejad, R., & Ramos, H. M. (2015). The effect of water hammer on a confined air pocket towards flow energy storage system. Journal of Water Supply: Research and Technology-Aqua, 65(2), 116-126. doi:10.2166/aqua.2015.081Besharat, M., Tarinejad, R., Aalami, M. T., & Ramos, H. M. (2016). Study of a Compressed Air Vessel for Controlling the Pressure Surge in Water Networks: CFD and Experimental Analysis. Water Resources Management, 30(8), 2687-2702. doi:10.1007/s11269-016-1310-1Coronado-Hernández, O., Fuertes-Miquel, V., Besharat, M., & Ramos, H. (2017). Experimental and Numerical Analysis of a Water Emptying Pipeline Using Different Air Valves. Water, 9(2), 98. doi:10.3390/w9020098Coronado-Hernández, O. E., Fuertes-Miquel, V. S., Besharat, M., & Ramos, H. M. (2018). Subatmospheric pressure in a water draining pipeline with an air pocket. Urban Water Journal, 15(4), 346-352. doi:10.1080/1573062x.2018.1475578Edmunds, R. C. (1979). Air Binding in Pipes. Journal - American Water Works Association, 71(5), 272-277. doi:10.1002/j.1551-8833.1979.tb04348.xEscarameia, M. (2007). Investigating hydraulic removal of air from water pipelines. Proceedings of the Institution of Civil Engineers - Water Management, 160(1), 25-34. doi:10.1680/wama.2007.160.1.25Izquierdo, J., Fuertes, V. S., Cabrera, E., Iglesias, P. L., & Garcia-Serra, J. (1999). Pipeline start-up with entrapped air. Journal of Hydraulic Research, 37(5), 579-590. doi:10.1080/00221689909498518Kader, B. A. (1981). Temperature and concentration profiles in fully turbulent boundary layers. International Journal of Heat and Mass Transfer, 24(9), 1541-1544. doi:10.1016/0017-9310(81)90220-9Laanearu, J., Annus, I., Koppel, T., Bergant, A., Vučković, S., Hou, Q., … van’t Westende, J. M. C. (2012). Emptying of Large-Scale Pipeline by Pressurized Air. Journal of Hydraulic Engineering, 138(12), 1090-1100. doi:10.1061/(asce)hy.1943-7900.0000631Leon, A. S., Ghidaoui, M. S., Schmidt, A. R., & Garcia, M. H. (2010). A robust two-equation model for transient-mixed flows. Journal of Hydraulic Research, 48(1), 44-56. doi:10.1080/00221680903565911Martins, N. M. C., Delgado, J. N., Ramos, H. M., & Covas, D. I. C. (2017). Maximum transient pressures in a rapidly filling pipeline with entrapped air using a CFD model. Journal of Hydraulic Research, 55(4), 506-519. doi:10.1080/00221686.2016.1275046Martins, S. C., Ramos, H. M., & Almeida, A. B. (2015). Conceptual analogy for modelling entrapped air action in hydraulic systems. Journal of Hydraulic Research, 53(5), 678-686. doi:10.1080/00221686.2015.1077353Pozos, O., Gonzalez, C. A., Giesecke, J., Marx, W., & Rodal, E. A. (2010). Air entrapped in gravity pipeline systems. Journal of Hydraulic Research, 48(3), 338-347. doi:10.1080/00221686.2010.481839Ramezani, L., Karney, B., & Malekpour, A. (2016). Encouraging Effective Air Management in Water Pipelines: A Critical Review. Journal of Water Resources Planning and Management, 142(12), 04016055. doi:10.1061/(asce)wr.1943-5452.0000695Richards, R. T. (1962). Air Binding in Water Pipelines. Journal - American Water Works Association, 54(6), 719-730. doi:10.1002/j.1551-8833.1962.tb00883.xTijsseling, A. S., Hou, Q., Bozkuş, Z., & Laanearu, J. (2015). Improved One-Dimensional Models for Rapid Emptying and Filling of Pipelines. Journal of Pressure Vessel Technology, 138(3). doi:10.1115/1.4031508Triki, A. (2015). Water-hammer control in pressurized-pipe flow using an in-line polymeric short-section. Acta Mechanica, 227(3), 777-793. doi:10.1007/s00707-015-1493-1Vasconcelos, J. G., & Wright, S. J. (2008). Rapid Flow Startup in Filled Horizontal Pipelines. Journal of Hydraulic Engineering, 134(7), 984-992. doi:10.1061/(asce)0733-9429(2008)134:7(984)Wang, H., Zhou, L., Liu, D., Karney, B., Wang, P., Xia, L., … Xu, C. (2016). CFD Approach for Column Separation in Water Pipelines. Journal of Hydraulic Engineering, 142(10), 04016036. doi:10.1061/(asce)hy.1943-7900.0001171Zhou, F., Hicks, F. E., & Steffler, P. M. (2002). Transient Flow in a Rapidly Filling Horizontal Pipe Containing Trapped Air. Journal of Hydraulic Engineering, 128(6), 625-634. doi:10.1061/(asce)0733-9429(2002)128:6(625)Zhou, L., Liu, D., & Karney, B. (2013). Investigation of Hydraulic Transients of Two Entrapped Air Pockets in a Water Pipeline. Journal of Hydraulic Engineering, 139(9), 949-959. doi:10.1061/(asce)hy.1943-7900.0000750Zhou, L., Liu, D., & Ou, C. (2011). Simulation of Flow Transients in a Water Filling Pipe Containing Entrapped Air Pocket with VOF Model. Engineering Applications of Computational Fluid Mechanics, 5(1), 127-140. doi:10.1080/19942060.2011.11015357Zhou, L., Wang, H., Karney, B., Liu, D., Wang, P., & Guo, S. (2018). Dynamic Behavior of Entrapped Air Pocket in a Water Filling Pipeline. Journal of Hydraulic Engineering, 144(8), 04018045. doi:10.1061/(asce)hy.1943-7900.0001491Zukoski, E. E. (1966). Influence of viscosity, surface tension, and inclination angle on motion of long bubbles in closed tubes. Journal of Fluid Mechanics, 25(4), 821-837. doi:10.1017/s002211206600044

Transcriptome pathways unique to dehydration tolerant relatives of modern wheat

Among abiotic stressors, drought is a major factor responsible for dramatic yield loss in agriculture. In order to reveal differences in global expression profiles of drought tolerant and sensitive wild emmer wheat genotypes, a previously deployed shock-like dehydration process was utilized to compare transcriptomes at two time points in root and leaf tissues using the Affymetrix GeneChip(R) Wheat Genome Array hybridization. The comparison of transcriptomes reveal several unique genes or expression patterns such as differential usage of IP(3)-dependent signal transduction pathways, ethylene- and abscisic acid (ABA)-dependent signaling, and preferential or faster induction of ABA-dependent transcription factors by the tolerant genotype that distinguish contrasting genotypes indicative of distinctive stress response pathways. The data also show that wild emmer wheat is capable of engaging known drought stress responsive mechanisms. The global comparison of transcriptomes in the absence of and after dehydration underlined the gene networks especially in root tissues that may have been lost in the selection processes generating modern bread wheats

Titanium, Sinusitis, and the Yellow Nail Syndrome

Yellow nail syndrome is characterized by nail changes, respiratory disorders, and lymphedema. In a yellow nail patient with a skeletal titanium implant and with gold in her teeth, we found high levels of titanium in nail clippings. This study aims to examine the possible role of titanium in the genesis of the yellow nail syndrome. Nail clippings from patients with one or more features of the yellow nail syndrome were analyzed by energy dispersive X-ray fluorescence. Titanium was regularly found in finger nails in patients but not in control subjects. Visible nail changes were present in only half of the patients. Sinusitis with postnasal drip and cough was the most common complaint. The dominant source of titanium ions was titanium implants in the teeth or elsewhere. The titanium ions were released through the galvanic action of dental gold or amalgam or through the oxidative action of fluorides. In other patients the titanium was derived from titanium dioxide in drugs and confectionary. Stopping galvanic release of titanium ions or canceling exposure to titanium dioxide led to recovery. In one patient with a titanium implant, the symptoms recurred after renewed exposure to titanium. Yellow nail syndrome is caused by titaniu