Elimination of current non-uniformity in carbon nanotube field emitters

Activation of abnormal emitting sites in Carbon Nano Tube (CNT) field emitters and their elimination is reported. CVD grown, patterned CNT was used as cathode for field emission studies. We encountered the problem of current non-uniformity in CNT cathode. This non-uniformity was attributed to abnormally active emitting sites during voltage ramp-up. The sudden increase in current resulted in region of positive slope in F–N curve, which can’t be explained by conventional F–N theory. Also the grown CNTs can be a mixture of metallic and semi conducting nature, which may cause deviation from the conventional F–N theory. We could eliminate abnormally active sites by electric field treatment, thereby increasing current uniformity and stability. The work is underway to understand the deviation in FN curve at high fields.     

Transmission planning for Indian power grid: a mixed integer programming approach

The paper presents a modeling framework to analyze some important issues associated with operation planning of a power system. Major activities involved in operations planning of large integrated power systems are considered simultaneously to ensure optimal utilization of generation and transmission capacity. The model also examines optimal transmission expansion plans vis-à-vis fuel supply issues. A mixed integer programming model is developed for this purpose and the Indian power system considered. Specific emphasis is on spatial transmission expansion plan for the existing Indian inter-state transmission grid and new transmission links, coordinated operation of the isolated regional grids and system benefits accruing from transmission expansion, enhanced fuel production and supply rescheduling to ensure efficient operation of various generating stations.     

Selectivity sequences and sorption capacities of phosphatic clay and humus rich soil towards the heavy metals present in zinc mine tailing

Sorption efficacy of phosphatic clay and humus rich soil alone and on combination were tested towards heavy metals present in zinc mine tailing (Zawar Zinc Mine), Udaipur (India). Characterization of the zinc mine tailing sample indicated the presence of Pb, Cu, Zn and Mn in the concentration of 637, 186, 720 and 577microg(-1), respectively. For sorption efficacy, the zinc mine tailing soil were properly amended with phosphatic clay and humus rich soil separately and in combination and leachability study was performed by batch experiment at different pH range from 3 to 9. The data showed that the percent leachability of heavy metal in non-amended soil was 75-90%. After amendment with phosphatic clay percent leachability of heavy metals became 35-45%. Further, the addition of humus soil to phosphatic clay decreased the percent leachability up to 5-15% at all tested pH. Column leachability experiment was performed to evaluate the rate of leachability. The shape of cumulative curves of Pb, Cu, Zn and Mn showed an increase in its concavity in following order: PbCu>Zn>Mn. Further, Langmuir isotherms applied for the sorption studies indicated that phosphatic clay in the presence of humus soil had high affinity for Pb followed by Cu, Zn and Mn, with sorption capacities (b) 139.94, 97.02, 83.32 and 67.58microgg(-1), respectively.     

Tata钢厂改进铸机对铸坯质量的改善

2002年,Tata钢厂改进了它的一台六流铸机,改进内容包括在结晶器中加入电磁搅拌器(EMS)和在中间包和结晶器之间使用浸入式水口(SEN)以能提供一种封闭式浇注工艺.改进的目标是提高铸坯的现行质量并且开发其生产多种高附加值钢材品种的能力,以丰富产品种类.改进的铸机投入生产后,要生产出合乎质量要求的铸坯就必须对铸机的一些操作参数进行优化.本文讨论了Tata钢厂依据不同的优化方法使用改进的铸机所取得的一些经验.     

Big Board: Teleconferencing Over Maps for Shared Situational Awareness

Collaborative technologies for information sharing are an invaluable resource for emergency managers to respond to and manage highly dynamic events such as natural disasters and other emergencies. However, many standard collaboration tools can be limited either because they provide passive presentation and dissemination of information, or because they are targeted towards highly specific usage scenarios that require considerable training to use the tools. We present a real-time gather and share system called “Big Board” which facilitates collaboration over maps. The Big Board is an open-source, web based, real time visual collaborative environment that runs on all modern web browsers and uses open-source web standards developed by the Open Geospatial Consortium (OGC) and WorldWideWeb Consortium (W3C). An evaluation of Big Board was conducted by school representatives in North Carolina for use in situational understanding for school closure decisions during winter weather events. The decision to close schools has major societal impacts and is one that is usually made based on how well a teenage driver could handle wintry precipitation on a road. Collecting information on the conditions of roads is especially critical, however gathering and sharing of this information within a county can be difficult. Participants in the study found the Big Board intuitive and useful for sharing real time information, such as road conditions and temperatures, leading up to and during a winter storm scenario. We have adapted the Big Board to manage risks and hazards during other types of emergencies such as tropical storm conditions.     

Study of molecular structure and vibrational spectra of poly (β,-l-malic acid) [PMLA] using DFT approach

Poly (β-L-malic acid) (PMLA) is a biodegradable polymer and it has various important applications in the biomedical field. In the present work the structural and spectral characteristics of PMLA have been studied by methods of infrared, Raman spectroscopy and quantum chemistry. Electrostatic potential surface, optimized geometry, harmonic vibrational frequencies, infrared intensities and activities of Raman scattering were calculated by density functional theory (DFT) using oligomeric approach employing B3LYP with complete relaxation in the potential energy surface using 6-311++G (d, p) basis set. Based on results, we have discussed the correlation between the vibrational modes and the structure of the PMLA. A complete analysis of the experimental infrared and Raman spectra has been reported on the basis of wavenumber of the vibrational bands and potential energy distribution. The calculated HOMO and LUMO energies shows that charge transfer occur within the molecule. The calculated infrared and the Raman spectra of the polymer based on DFT calculations show reasonable agreement with the experimental results.     

A Study of Linear Friction Weld Microstructure in Single Crystal CMSX-486 Superalloy

The microstructure of linear friction welds in single crystal (SX) CMSX 486 superalloy was studied. Gleeble thermomechanical simulation of the welding process was also performed in order to understand the microstructural changes induced in the alloy during the joining process. Microstructural analysis of the welded and Gleeble-simulated specimens showed that extensive liquation occurred in the alloy during joining, which is in contrast to the general assumption that linear friction welding (LFW) occurs exclusively in the solid state. The study revealed the application of the compressive load during the forging stage of LFW induced rapid solidification of the resultant metastable liquid phase. Nevertheless, part of the liquid resulted in a continuous Hf-base oxide phase along the weld line. Possible ways of preventing the formation of the potentially deleterious oxide film and, thus, improve the prospect of applying LFW for the joining of CMSX-486 superalloy are suggested.