Substation system simulation models for transformer risk assessment analysis

This paper comprises a study which is carried out to investigate and evaluate the effect of lightning stresses on the 132 kV substation in the way to improve its reliability in the event of active lightning activities. The paper also detailed the modelling parameters of substation for this transient analysis in order to evaluate the performance and to recommend such configuration to optimize its design to be not only to withstand the stresses but to be more cost effective. The modelling and simulation are carried out using one of the most powerful power system simulations tools that is PSCAD-EMTDC and the substation layout design is adapted from 132/11 kV Simpang Renggam -- Ayer Hitam substation, courtesy of TNB. The model is based on single phase line model as it was suggested by the IEEE to be adequate to represent the substation in transient analysis simulation. The outcome of this paper would be the results of lightning stresses in term of voltage level measured at particular points in substation. The results are then compared with the suggested BIL for assessment of transformer failure

Erratum to: 36th International Symposium on Intensive Care and Emergency Medicine: Brussels, Belgium. 15-18 March 2016.

[This corrects the article DOI: 10.1186/s13054-016-1208-6.]

Association between smoking and anthropometric characteristics, biochemical markers, and dietary intake of Pakistani male adult population

Background/Objectives: A community-based study was conducted to compare the nutritional status between smokers and non-smokers in association with dietary, biochemical and socio- economic characteristics. Methods: A convenient sampling method was used to enroll 100 smokers and 99 non-smokers aged between 46 and 78 years from the urban and semi-urban areas of district Peshawar, Pakistan. Weight, height, waist and hip circumferences of the subjects were taken while body composition was determined by employing a Bodystat Analyzer. A blood sample was taken from each subject for the determination of serum vitamin A and zinc levels. Subjects were interviewed for a 24-hr dietary recall and demographic and socio-economic characteristics. Student’s t-test and bivariate analysis were conducted to compare the mean differences and examine the association between different variables of smoker and non-smoker groups. Results: The results revealed that there was no significant ( p>0.05) difference between the mean age, weight, height and body mass index of smokers and non smokers. However, the mean body fat, waist and hip circumference of the smokers were significantly (p <0.05) lower than the non-smokers. Conversely, the mean serum vitamin A (32.30±15.99 μg/dl) of smokers was significantly (p<0.05) higher than non-smokers (26.50±20.44 μg/dl) but the mean serum zinc concentration of smokers (99.76±27.42 μg/dl) was significantly lower than the non-smokers (108.25±32.20 μg/dl). Conclusions: The study concludes that anthropometric (body mass index), biochemical (vitamin A and zinc status), dietary (energy intake) and socio-economic (income, profession) characteristics failed to establish an association with smoking as most of the indicators of smokers are comparable to non-smokers

Ultrathin compound semiconductor on insulator layers for high performance nanoscale transistors

Over the past several years, the inherent scaling limitations of electron devices have fueled the exploration of high carrier mobility semiconductors as a Si replacement to further enhance the device performance. In particular, compound semiconductors heterogeneously integrated on Si substrates have been actively studied, combining the high mobility of III-V semiconductors and the well-established, low cost processing of Si technology. This integration, however, presents significant challenges. Conventionally, heteroepitaxial growth of complex multilayers on Si has been explored. Besides complexity, high defect densities and junction leakage currents present limitations in the approach. Motivated by this challenge, here we utilize an epitaxial transfer method for the integration of ultrathin layers of single-crystalline InAs on Si/SiO2 substrates. As a parallel to silicon-on-insulator (SOI) technology14,we use the abbreviation "XOI" to represent our compound semiconductor-on-insulator platform. Through experiments and simulation, the electrical properties of InAs XOI transistors are explored, elucidating the critical role of quantum confinement in the transport properties of ultrathin XOI layers. Importantly, a high quality InAs/dielectric interface is obtained by the use of a novel thermally grown interfacial InAsOx layer (~1 nm thick). The fabricated FETs exhibit an impressive peak transconductance of ~1.6 mS/{\mu}m at VDS=0.5V with ON/OFF current ratio of greater than 10,000 and a subthreshold swing of 107-150 mV/decade for a channel length of ~0.5 {\mu}m

Built-in and induced polarization across LaAlO3_3/SrTiO3_3 heterojunctions

Ionic crystals terminated at oppositely charged polar surfaces are inherently unstable and expected to undergo surface reconstructions to maintain electrostatic stability. Essentially, an electric field that arises between oppositely charged atomic planes gives rise to a built-in potential that diverges with thickness. In ultra thin film form however the polar crystals are expected to remain stable without necessitating surface reconstructions, yet the built-in potential has eluded observation. Here we present evidence of a built-in potential across polar \lao ~thin films grown on \sto ~substrates, a system well known for the electron gas that forms at the interface. By performing electron tunneling measurements between the electron gas and a metallic gate on \lao ~we measure a built-in electric field across \lao ~of 93 meV/\AA. Additionally, capacitance measurements reveal the presence of an induced dipole moment near the interface in \sto, illuminating a unique property of \sto ~substrates. We forsee use of the ionic built-in potential as an additional tuning parameter in both existing and novel device architectures, especially as atomic control of oxide interfaces gains widespread momentum.Comment: 6 pages, 4 figures. Submitted to Nature physics on May 1st, 201

Evaluation and assessment of transformer failure on 132kV substation

Insulation coordination models are an essential part of power system studies and are used to determine the expected overhead line back-flashover rate. A study is carried out to investigate and evaluate the effect of lightning stresses on the 132 kV substation in the way to improve its reliability in the event of active lightning activities. This paper also presents the modeling guidelines on substation for this transient analysis in order to evaluate the performance and to recommend such configuration to optimize its design to be not only to withstand the stresses but to be more cost effective. The modeling and simulation are carried out using one of the most powerful power system simulations tools that is PSCAD-EMTDC and the substation layout design is adapted from 132/11 kV Simpang Renggam-Ayer Hitam substation, courtesy of Tenaga Nasional Berhad, Malaysia (TNB). The model is based on single phase line model as it is suggested by the IEEE to be adequate to represent the substation in transient analysis simulation. The outcome of this paper will be the results of lightning stresses in term of voltage level measured at particular points in substation. The results are then compared with the suggested basic lightning insulation level (BIL) for assessment of transformer failure