Recent Advances of SnO2-Based Sensors for Detecting Fault Characteristic Gases Extracted From Power Transformer Oil

Tin oxide SnO2-based gas sensors have been widely used for detecting typical fault characteristic gases extracted from power transformer oil, namely, H2, CO, CO2, CH4, C2H2, C2H4, and C2H6, due to the remarkable advantages of high sensitivity, fast response, long-term stability, and so on. Herein, we present an overview of the recent significant improvement in fabrication and application of high performance SnO2-based sensors for detecting these fault characteristic gases. Promising materials for the sensitive and selective detection of each kind of fault characteristic gas have been identified. Meanwhile, the corresponding sensing mechanisms of SnO2-based gas sensors of these fault characteristic gases are comprehensively discussed. In the final section of this review, the major challenges and promising developments in this domain are also given

Development of sensors for the on-site monitoring of dry-type electrical machines

L'abstract è presente nell'allegato / the abstract is in the attachmen

Predictive Maintenance Of Railway Transformer Oil Based On Periodic Content Analysis

The high frequency of operation of commuter trains, due to passenger demand as well as the selection of railway as the mode of daily transportation for commuting on weekdays, increases the usage of on-board power, especially for a train’s traction system. As maintenance is rarely performed on transformer oil, it deteriorates and negatively affects transformer performance, increases heat, and may damage the transformer as well. This will result in significantly costly maintenance expenses for train operators. Therefore, this paper proposes a predictive maintenance schedule for transformer oil. The recommendations are based upon an analysis of transformer oil contents and its properties over a 90-month period of operation. A linear correlation between the properties of the oil and the train’s period of operation yielded a predictive maintenance schedule, primarily reclamation and filtration, for the oil at the threshold of each property. Major oil changes are to be considered when all properties are approaching their thresholds. As oil deterioration increases over time, a specific maintenance schedule was suggested. This was tested and observed on several transformer units. The content analysis of each oil is also discussed. Based on the results, this predictive maintenance schedule can be used on other trains with the same transformer model or other trains using the same type of insulating oil

Spectroscopic detection of volatile fluorides following gas chromatographic separation

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The Biology Instrument for the Viking Mars Mission

Two Viking spacecraft have successfully soft landed on the surface of Mars. Each carries, along with other scientific instruments, one biology laboratory with three different experiments designed to search for evidence of living microorganisms in material sampled from the Martian surface. This 15.5-kg biology instrument which occupies a volume of almost 28.3 dm3 is the first to carry out an in situ search for extraterrestrial life on a planet. The three experiments are called the pyrolytic release, labeled release, and gas exchange. The pyrolytic release experiment has the capability to measure the fixation of carbon dioxide or carbon monoxide into organic matter. The labeled release experiment detects metabolic processes by monitoring the production of volatile carbon compounds from a radioactively labeled nutrient mixture. The gas exchange experiment monitors the gas changes in the head space above a soil sample which is either incubated in a humid environment or supplied with a rich organic nutrient solution. Each experiment can analyze a soil sample as it is received from the surface or, as a control, analyze a soil which has been heated to above 160C. Each instrument has the capability to receive four different soils dug from the Martian surface and perform a number of analysis cycles depending on the particular experiment. This paper describes in detail the design and operation of the three experiments and the supporting subsystems

Analytical-Toxicological Studies of Environmental Importance.

Part One. Acidity and chemical composition of precipitation in Baton Rouge, Louisiana; The synergistic effects of acidity and aluminum on fish. Acid precipitation which consists of both wet precipitation and dry deposition has recently become a significant environmental problem. It has been shown that the effects of acid rain are deleterious to soil, vegetation, aquatic life and buildings. Wet-precipitation-only samplers were used to collect acid rainfalls in the vicinity of Louisiana State University, Baton Rouge and subjected to appropriate chemical analysis for the purpose of characterization of general composition and acidity. About 50% of precipitation is within pH range of 4.0-5.0. Acidity is largely due to the presence of sulfuric and nitric acid. There is seasonal variation in acidity of precipitation, namely rain water is more acidic in summer than winter. Study of pH of rainfall versus wind directions indicated no correlation between average pH and any specific local wind directions. Light showers yielded much higher values of conductance than did large storms. The concentration of the major anions (SO\sb4\sp{-2}, NO\sb3\sp-, Cl\sp{-}) and major cations (Na\sp{+}, NH\sb4\sp{+}, K\sp{+}) were measured utilizing ion chromatography. Inductively coupled plasma was utilized in determination of minor trace metals in the precipitation. Addition of aluminum ion to acidified waters caused increased toxicity to aquatic life, especially in the pH range of 4.5-5.0. Part Two. Electrochemical preconcentration of trace mercury on carbon fiber for atomic absorption analysis; Capillary GC-AA for speciation of mercury compounds. Speciation is critically important in assessing the potential toxic effects of a specific element on susceptible organisms and ecosystems. Mercury and its compounds are highly toxic and organomercury compounds are far more toxic than elemental or inorganic mercury. A capillary gas chromatographic interfaced atomic absorption unit has been developed and used for the speciation and determination of volatile mercury compounds in environmental samples. Use of AA as a specific detector for GC combines the high resolving power of chromatography with specificity, selectivity and sensitivity of AA for the determination of organometallic compounds in environmental samples. Mercuric chloride, methyl mercuric chloride, and dimethyl mercury were separated. Resolution was excellent and reproducibility is within 5-10%. 100 pg of mercury can easily be detected. (Abstract shortened with permission of author.)

An assessment of the performance of semiconductor gas sensors as gas chromatographic detectors.

Four types of commercially available n-type semiconductor gas sensors (three tin oxide types: T.G.S.711, T.G.S.812 and International Sensor Technology methane sensor, and one ferric oxide type: Matsushita L.P.G. sensor) were evaluated as gas chromatographic detectors in the G.C. analysis of mine air samples. A 1.5 meter x 4 millimeter stainless steel column packed with active carbon type 208C (60-72 B.S.mesh) at 40 G was used; to separate hydrogen, carbon monoxide and methane using purified air as carrier gas. Optimum operating conditions for the T.G.S.711 sensor: heater voltage 6.5 volts DC, purified air carrier gas at 20 cnrminuteand operational amplifer circuitry (LM 741), provided good sensitivity and acceptable peak symmetry, although some skewness of peaks was still evident. A preliminary assessment of the performance of these sensors was made for the analysis of some lower hydrocarbon gases (C[1]-C[3]) using a 1.5 meter x 4 millimeter stainless steel column packed with activated alumina (60-80 B.S.mesh) at 60 C. Lower limits of detection achieved were 0.002 ppm for hydrogen and 0.01 ppm for other gases, with a useful working range up to 100 ppm. An interesting finding was that carrier gases containing lower levels of oxygen gave an enhanced response in terms of peak height. It was concluded that the use of semiconductor gas sensors as G.C. detectors provided a simple and convenient method of assessing the characteristics of this type of sensor and might be employed to elucidate the mechanism of response, which is still in question

Abstracts of Papers Presented at the 2005 Pittsburgh Conference

To attend or not to attend, that is the question. The Pittsburgh Conference continues to pose this conundrum to conferees and exhibitors alike. This year's conference was the first to be presented without a set of paper abstracts—a good thing some would say but this old codger always used the paper abstracts to select papers of interest to our readership and to seek a full publication. The exhibit took its usual format but it seemed that there were less manufacturers present. The information presented to the attendees was also lacking and many companies' details were missing from the final program book, an omission no doubt on their behalf—my company was one of these—however I feel sure that past Pittcon organizers would have been more persistent in getting the required details for the audience. As is now the norm, many of the presentations take the form of posters displayed within the exhibition area. Without a driver to get the audience there, the traffic was slow, to say the least. Lecture presentations were also attended in a mixed fashion. So the Pittsburgh Conference show moves on, and again next year it will be held in Orlando from 12 March to 17 March 2006. No doubt I will be there making it a straight 31 in a row; in Pittsburgh Conference terms I am just a beginner with many of the attendees making more shows in a run than that. Selected abstracts dealing with topics of interest to the readers of this journal follow—hopefully many of these groups will be willing to publish their work either within this journal or elsewhere

Atomic fluorescence spectroscopy

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Cumulative Index to NASA Tech Briefs, 1963 - 1966

Cumulative index of NASA Tech Briefs dealing with electrical and electronic, physical science and energy sources, materials and chemistry, life science, and mechanical innovation