Data rectification and detection of trend shifts in jet engine path measurements using median filters and fuzzy logic

Filtering methods are explored for removing noise from data while preserving sharp edges that many indicate a trend shift in gas turbine measurements. Linear filters are found to be have problems with removing noise while preserving features in the signal. The nonlinear hybrid median filter is found to accurately reproduce the root signal from noisy data. Simulated faulty data and fault-free gas path measurement data are passed through median filters and health residuals for the data set are created. The health residual is a scalar norm of the gas path measurement deltas and is used to partition the faulty engine from the healthy engine using fuzzy sets. The fuzzy detection system is developed and tested with noisy data and with filtered data. It is found from tests with simulated fault-free and faulty data that fuzzy trend shift detection based on filtered data is very accurate with no false alarms and negligible missed alarms.

Electrical characterization of Ba(Zr0.1Ti0.9)O-3 thin films grown by pulsed laser ablation technique

In situ annealed thin films of ferroelectric Ba(Zr0.1Ti0.9)O-3 were deposited on platinum substrates by pulsed laser ablation technique. The as grown films were polycrystalline in nature without the evidence of any secondary phases. The polarization hysteresis loop confirmed the ferroelectricity, which was also cross-checked with the capacitance-voltage characteristics. The remnant polarization was about 5.9 muC cm(-2) at room temperature and the coercive field was 45 kV. There was a slight asymmetry in the hysteresis for different polarities, which was thought to be due to the work function differences of different electrodes. The dielectric constant was about 452 and was found to exhibit low frequency dispersion that increased with frequency, This was related to the space-charge polarization. The complex impedance was plotted and this exhibited a semicircular trace, and indicated an equivalent parallel R - C circuit within the sample. This was attributed to the grain response. The DC leakage current-voltage plot was consistent with the space-charge limited conduction theory, but showed some deviation, which was explained by assuming a Poole-Frenkel type conduction to be superimposed on to the usual space-charge controlled current. (C) 2002 Elsevier Science B.V. All rights reserved.

An assessment of creep deformation and fracture behavior of 2.25Cr-1Mo similar and dissimilar weld joints

The evaluation of the creep deformation and fracture behavior of a 2.25Cr-1Mo steel base metal, a 2.25Cr-1Mo/2.25Cr-1Mo similar weld joint, and a 2.25Cr-1Mo/Alloy 800 dissimilar weld joint at 823 K over a stress range of 90 to WO MPa has been carried out. The specimens for creep testing were taken from single-V weld pads fabricated by a shielded metal arc-welding process using 2.25Cr-1Mo steel (for similar-joint) and INCONEL 182 (for dissimilar-joint) electrodes. The weld pads were subsequently given a postweld hear treatment (PWHT) of 973 K for I hour. The microstructure and microhardness of the weld joints were evaluated in the as-welded, postweld heat-treated, and creep-tested conditions. The heat-affected zone (HAZ) of similar weld joint consisted of bainite in the coarse-prior-austenitic-grain (CPAG) region near the fusion line, followed by bainite in the fine-prior-austenitic-grain (FPAG) and intercritical regions merging with the unaffected base metal. In addition to the HAZ structures in the 2.25Cr-1Mo steel, the dissimilar weld joint displayed a definite INCONEL/2.25Cr-1Mo weld interface structure present either as a sharp line or as a diffuse region. A hardness trough was observed in the intercritical region of the HAZ in both weld joints, while a maxima in hardness was seen at the weld interface of the dissimilar weld joint. Both weld joints exhibited significantly lower rupture lives compared to the 2.25Cr-1Mo base metal. The dissimilar weld joint exhibited poor rupture life compared to the similar weld joint, at applied stresses lower than 130 MPa. In both weld joints, the strain distribution across the specimen gage length during creep testing varied significantly. During creep testing, localization of deformation occurred in the intercritical HAZ. In the similar weld joint, at all stress levels investigated, and in the dissimilar weld joint, at stresses greater than or equal to 150 MPa, the creep failure occulted in the intercritical HAZ. The fracture occurred by transgranular mode with a large number of dimples. At stresses below 150 MPa, the failure in the dissimilar weld joint occurred in the CPAG HAZ near to the weld interface. The failure occurred by extensive intergranular creep cavity formation.

An assessment of creep deformation and fracture behavior of 2.25Cr-1Mo

The evaluation of the creep deformation and fracture behavior of a 2.25Cr-1Mo steel base metal, a 2.25Cr-1Mo/2.25Cr-1Mo similar weld joint, and a 2.25Cr-1Mo/Alloy 800 dissimilar weld joint at 823 K over a stress range of 90 to WO MPa has been carried out. The specimens for creep testing were taken from single-V weld pads fabricated by a shielded metal arc-welding process using 2.25Cr-1Mo steel (for similar-joint) and INCONEL 182 (for dissimilar-joint) electrodes. The weld pads were subsequently given a postweld hear treatment (PWHT) of 973 K for I hour. The microstructure and microhardness of the weld joints were evaluated in the as-welded, postweld heat-treated, and creep-tested conditions. The heat-affected zone (HAZ) of similar weld joint consisted of bainite in the coarse-prior-austenitic-grain (CPAG) region near the fusion line, followed by bainite in the fine-prior-austenitic-grain (FPAG) and intercritical regions merging with the unaffected base metal. In addition to the HAZ structures in the 2.25Cr-1Mo steel, the dissimilar weld joint displayed a definite INCONEL/2.25Cr-1Mo weld interface structure present either as a sharp line or as a diffuse region. A hardness trough was observed in the intercritical region of the HAZ in both weld joints, while a maxima in hardness was seen at the weld interface of the dissimilar weld joint. Both weld joints exhibited significantly lower rupture lives compared to the 2.25Cr-1Mo base metal. The dissimilar weld joint exhibited poor rupture life compared to the similar weld joint, at applied stresses lower than 130 MPa. In both weld joints, the strain distribution across the specimen gage length during creep testing varied significantly. During creep testing, localization of deformation occurred in the intercritical HAZ. In the similar weld joint, at all stress levels investigated, and in the dissimilar weld joint, at stresses greater than or equal to 150 MPa, the creep failure occulted in the intercritical HAZ. The fracture occurred by transgranular mode with a large number of dimples. At stresses below 150 MPa, the failure in the dissimilar weld joint occurred in the CPAG HAZ near to the weld interface. The failure occurred by extensive intergranular creep cavity formation.

Tailoring of Structural Morphology of Silver Nanowires in Electrochemical Growth

Noble metal such as Ag normally exists in an fcc crystal structure. However as the size of the material is decreased to nanometer lengthscales, a structural transformation from that of its bulk state can be expected with new atomic arrangements due to competition between internal packing and minimization of surface energy. In many previous studies, it has been shown that silver nanowires (AGNWs) grown inside anodic alumina (AAO) templates by ac or dc electrochemical deposition from silver salts or complexes, adopt fcc structure and below some critical diameter ∼ 20 nm they may acquire hcp structure at low temperature. This is, however, critically dependant on the nature of confinement, as AgNWs grown inside nanotube confinement with subnanometer diameter have been reported to have fcc structure. Hence the question of the crystal structure of metal nanowires under combined influence of confinement, temperature and deposition condition remains open. In this abstract we show that the alternative crystal structures of AGNWs at room temperature can be achieved with electrochemical growth processes under specific conditions determined by the deposition parameters and nature of confinement. We fabricated AgNWs of 4H hexagonal structure with diameters 30 – 80 nm inside polycarbonate (PC) templates with a modified dc electrodeposition technique, where the nanowires were grown at deposition potentials as low as 10 mV in 2 M silver nitrate solution[1]. We call this low-potential electrodeposition (LPED) since the electrodeposition process occurs at potential much less than the standard Nernst potential (770 mV) of silver. Two types of electrodes were used – stainless steel and sputtered thin Pt film, neither of which had any influence on the crystal structure of the nanowires. EDS elemental analysis showed the nanowires to consist only of silver. Although the precise atomic dynamics during the LPED process is unclear at present, we investigated this with HRTEM (high-resolution transmission electron microscopy) characterization of nanowires grown over various deposition times, as well as electrical conductivity measurements. These experiments indicate that nanowire growth does not occur through a three-dimensional diffusion controlled process, as proposed for conventional over-potential deposition, but follow a novel instantaneous linear growth mechanism. Further experiments showed that, (a) conventional electrochemical growth at a small over-potential in a 2 mM AgNO3 solution yields nanowires with expected fcc structure inside the same PC templates, and (2) no nanowire was observed under the LPED conditions inside hard AAO templates, indicating that LPED-growth process, and hcp structure of the corresponding nanowires depend on deposition parameters, as well as nature of confinement.

Water quality parameter estimation in steady-state distribution system

The maintenance of chlorine residual is needed at all the points in the distribution system supplied with chlorine as a disinfectant. The propagation and level of chlorine in a distribution system is affected by both bulk and pipe wall reactions. It is well known that the field determination of wall reaction parameter is difficult. The source strength of chlorine to maintain a specified chlorine residual at a target node is also an important parameter. The inverse model presented in the paper determines these water quality parameters, which are associated with different reaction kinetics, either in single or in groups of pipes. The weighted-least-squares method based on the Gauss-Newton minimization technique is used for the estimation of these parameters. The validation and application of the inverse model is illustrated with an example pipe distribution system under steady state. A generalized procedure to handle noisy and bad (abnormal) data is suggested, which can be used to estimate these parameters more accurately. The developed inverse model is useful for water supply agencies to calibrate their water distribution system and to improve their operational strategies to maintain water quality.

Adaptive Filtering Technique and DSP Based Implementation for High-Speed Distance Protection

The paper presents an adaptive Fourier filtering technique and a relaying scheme based on a combination of a digital band-pass filter along with a three-sample algorithm, for applications in high-speed numerical distance protection. To enhance the performance of above-mentioned technique, a high-speed fault detector has been used. MATLAB based simulation studies show that the adaptive Fourier filtering technique provides fast tripping for near faults and security for farther faults. The digital relaying scheme based on a combination of digital band-pass filter along with three-sample data window algorithm also provides accurate and high-speed detection of faults. The paper also proposes a high performance 16-bit fixed point DSP (Texas Instruments TMS320LF2407A) processor based hardware scheme suitable for implementation of the above techniques. To evaluate the performance of the proposed relaying scheme under steady state and transient conditions, PC based menu driven relay test procedures are developed using National Instruments LabVIEW software. The test signals are generated in real time using LabVIEW compatible analog output modules. The results obtained from the simulation studies as well as hardware implementations are also presented.

Direct Infrared Absorption Spectroscopy of Benzene Dimer

The direct infrared (IR) absorption spectrum of benzene dimer formed in a free-jet expansion was recorded in the 3.3 mu m region for the first time. This has led to the observation of the C H stretching fundamental mode nu(13) (B(1u)), which is both IR and Raman forbidden in the monomer. Moreover, the IR forbidden and Raman allowed nu(7) (E(2g)) mode has been observed as well. These two modes were found to be red-shifted along with the IR allowed nu(20) (E(1u)) mode, as previously reported by Erlekam et al. [Erlekam; Frankowski; Meijer; Gert von Helden J. Chem. Phys. 2006, 124, 171101], using ion-dip spectroscopy, contrary to the blue-shift predicted earlier by theoretical studies. The observation of the nu(13) band indicates that the symmetry is reduced in the dimer, confirming the T-shaped structure observed by Erlekam et al. Our experimental results have not provided any direct evidence for the presence of the parallel displaced geometry, the main objective of the present work, as predicted by theoretical calculations.

Ethnobotany of the Monpa ethnic group at Arunachal Pradesh, India

Background: The present paper documents the uses of plants in traditional herbal medicine for human and veterinary ailments, and those used for dietary supplements, religious purpose, local beverage, and plants used to poison fish and wild animals. Traditional botanical medicine is the primary mode of healthcare for most of the rural population in Arunachal Pradesh. Materials and methods: Field research was conducted between April 2006 and March 2009 with randomly selected 124 key informants using semi-structured questionnaire. The data obtained was analyzed through informant consensus factor (F(IC)) to determine the homogeneity of informant's knowledge on medicinal plants. Results: We documented 50 plants species belonging to 29 families used for treating 22 human and 4 veterinary ailments. Of the medicinal plants reported, the most common growth form was herbs (40%) followed by shrubs, trees, and climbers. Leaves were most frequently used plant parts. The consensus analysis revealed that the dermatological ailments have the highest F(IC) (0.56) and the gastro-intestinal diseases have F(IC) (0.43). F(IC) values indicated that there was high agreement in the use of plants in dermatological and gastro-intestinal ailments category among the users. Gymnocladus assamicus is a critically rare and endangered species used as disinfectant for cleaning wounds and parasites like leeches and lice on livestocks. Two plant species (Illicium griffithii and Rubia cordifolia) are commonly used for traditional dyeing of clothes and food items. Some of the edible plants recorded in this study were known for their treatment against high blood pressure (Clerodendron colebrookianum), diabetes mellitus (Momordica charantia), and intestinal parasitic worms like round and tape worms (Lindera neesiana, Solanum etiopicum, and Solanum indicum). The Monpas of Arunachal Pradesh have traditionally been using Daphne papyracea for preparing hand-made paper for painting and writing religious scripts in Buddhist monasteries. Three plant species (Derris scandens, Aesculus assamica, and Polygonum hydropiper) were frequently used to poison fish during the month of June-July every year and the underground tuber of Aconitum ferrox is widely used in arrow poisoning to kill ferocious animals like bear, wild pigs, gaur and deer. The most frequently cited plant species; Buddleja asiatica and Hedyotis scandens were used as common growth supplements during the preparation of fermentation starter cultures. Conclusion: The traditional pharmacopoeia of the Monpa ethnic group incorporates a myriad of diverse botanical flora. Traditional knowledge of the remedies is passed down through oral traditions without any written document. This traditional knowledge is however, currently threatened mainly due to acculturation and deforestation due to continuing traditional shifting cultivation. This study reveals that the rural populations in Arunachal Pradesh have a rich knowledge of forest-based natural resources and consumption of wild edible plants is still an integral part of their socio-cultural life. Findings of this documentation study can be used as an ethnopharmacological basis for selecting plants for future phytochemical and pharmaceutical studies.

The oxygen potential of the systems Fe+FeCr2O4+ Cr2O3 and Fe+FeV2O4+ V2O3 in the temperature range 750 1600o C

From electromotive force (emf) measurements using solid oxide galvanic cells incorporating ZrOz-CaO and ThOz-YO~.s electrolytes, the chemical potentials of oxygen over the systems Fe + FeCrzO 4 + Cr20 ~ and Fe + FeV204 + V203 were calculated. The values may be represented by the equations: 2Fe(s, I) + Oz(g) + 2Cr2Oa(s) -- 2FeCr204 (s)Akto2 = - 151,400 + 34.7T (• cal= -633,400 + 145.5T(• J (750 to 1536~ A~tO2 = -158,000 + 38.4T(• cal= -661,000 + 160.5T(*1250) J (1536 to 1700~2Fe (s, I) + O2 (g) + 2V203 (s) -- 2FeV204 (s) A/~Oz = - 138,000 + 29.8T(+300) cal= - 577,500 + 124.7T (• J (750 to 1536~A/IO2 = -144,600 + 33.45T(-300) cal = -605,100 + 140.0T(~-1250) J (1536 to 1700~At the oxygen potentials corresponding to Fe + FeCrzO a + Cr203 equilibria, the electronic contribution to the conductivity of ZrO2-CaO electrolyte was found to affect the measured emf. Application of a small 60 cycle A.C. voltage with an amplitude of 50 mv across the cell terminals reduced the time required to attain equilibrium at temperatures between 750 to 9500C by approximately a factor of two. The second law entropy of iron chromite obtained in this study is in good agreement with that calculated from thermal data. The entropies of formation of these spinel phases from the component oxides can be correlated to cation distribution and crystal field theory.

Potentiometric determination of the Gibbs free energy of formation of cadmium and magnesium chromites

The standard Gibbs free energy of formation of magnesium and cadmiumchromites have been determined by potentiometric measurements on reversiblesolid-state electrochemical cells [dformula (Au-5%Cd, , Au-5%Cd; Pt, + , CaO-ZrO[sub 2], + ,Pt; CdO, , CdCr[sub 2]O[sub 4] + Cr[sub 2]O[sub 3])] in the temperature range 500°–730°C, and [dformula Pt, Cr + Cr[sub 2]O[sub 3]/Y[sub 2]O[sub 3]-ThO[sub 2]/Cr + MgCr[sub 2]O[sub 4] + MgO, Pt] in the temperature range 800°–1200°C. The temperature dependence of the freeenergies of formation of the ternary compounds can be represented by theequations [dformula CdO(r.s.) + Cr[sub 2]O[sub 3](cor) --> CdCr[sub 2]O[sub 4](sp)] [dformula Delta G[sup 0] = - 42,260 + 7.53T ([plus-minus]400) J] and [dformula MgO(r.s.) + Cr[sub 2]O[sub 3](cor) --> MgCr[sub 2]O[sub 4](sp)] [dformula Delta G[sup 0] = - 45,200 + 5.36T ([plus-minus]400) J] The entropies of formation of these spinels are discussed in terms of cationdisorder and extent of reduction of Cr3+ ions to Cr2+ ions. Thermodynamicdata on the chromates of cadmium and magnesium are derived by combiningthe results obtained in this study with information available in the literatureon high temperature, high pressure phase equilibria in the systems CdO-Cr2O3-O2 and MgO-Cr2O3-O2.

Solubility and activity of oxygen in liquid nickel in equilibrium with -Al2O3 and NiO.(1+x)Al2O3

The limiting solubility of oxygen in liquid nickel in equilibrium withα-alumina and nickel aluminate has been measured by inert gas fusion analysis of suction samples in the temperature range 1730 to 1975 K. The corresponding oxygen potential has been monitored by a solid electrolyte cell consisting of calcia stabilized zirconia as the electrolyte and Mo + MoO2 as the reference electrode. The results can be summarized by the following equations: log(at. pct O) = \frac - 10,005T + 4.944 ( ±0.015)log(atpctO)=T−10005+4944(0015) % MathType!MTEF!2!1!+-% feaafiart1ev1aaatCvAUfeBSjuyZL2yd9gzLbvyNv2CaerbuLwBLn DmO2 /4.606RT = log P O2 1/2 = \frac - 13,550T + 4.411 ( ±0.009)O24606RT=logPO212=T−13550+4411(0009) From simultaneous measurements of the potential and concentration of oxygen in melts, not in thermodynamic equilibrium with alumina and aluminate phases, information on the composition dependence of the activity coefficient and the standard free energy of solution of oxygen is obtained. For the reaction, $\frac{1}{2} O_2 \to \underset{\raise0.3em\hbox{$Missing close brace ΔG o = -72,930 - 7.11T (±840) J gr.at.–1 = + 0.216 at. pct OlogfO=T−500+0216atpctO where the standard state for dissolved oxygen is that which makes the value of activity equal to the concentration (in at. pct) in the limit as concentration approaches zero. The oxygen solubility in liquid nickel in equilibrium with solid NiO, evaluated from thermodynamic data, is compared with information reported in the literature. Implications of the results to the deoxidation equilibria of aluminum in nickel are discussed.

Damping and synchronising torques contributed by a voltage regulator to a synchronous generator: a quantitative assessment

In the paper, the total damping and synchronising torques, which determine the dynamic stability of a synchronous generator in a power system, have been traced to their origin. The positive and negative components released or consumed by the voltage regulator, and by the various windings of the machine, have been isolated, with the object of making a quantitative assessment of the effects of various gains and time constants on the dynamic stability of a synchronous machine under different operating conditions. The analysis is based on the properties of quadratic invariance in tensor calculus. An alternative solution by network analysis has also been provided to establish the validity of the tensor approach.

Time delay to firing of a triggered vacuum gap with barium titanate in trigger gap

The time delay to the firing of a triggered vacuum gap (t.v.g.) containing barium titanate in the trigger gap is investigated as a function of the main gap voltage, main gap length, trigger pulse duration, trigger current and trigger voltage. The time delay decreases steadily with increasing trigger current and trigger voltage until it reaches saturation. The effect of varying the main gap length and voltage on the time delay is not strong. Before `conditioning�¿ the t.v.g. two groups of time delays, long (>100�¿s) and short (<10�¿s), are simultaneously observed when a large number of trials are conducted. After conditioning, only the group of short time delays are present. This is attributed to the marked reduction of the resistance of the trigger gap across the surface of the solid dielectric resulting directly from the conditioning effect.