电气设备监测装置选择和应用中应注意的问题

针对近年来一些电力设备的监测装置运行不可靠、寿命短、提前报废或退出运行的问题,对监测装置的可靠性、安全性、运行总成本以及电气设备的故障规律进行综合分析。结果表明当监测装置结构过于复杂时将导致可靠性下降,并有可能造成运行总成本不合理,而被监测设备某些类型的故障发生规律如果与监测装置的寿命配合不当时将造成监测装置的无效投运。建议引进新的监测技术先从小规模开始,当监测装置的运行总成本不合理时就没有必要投入,当监测装置的有效工作时间不适应设备故障率的变化规律时,应选择合适的安装时机使监测装置能够充分发挥作用。     

Estimation of mercury vapor flux from natural substrate in Nevada

The contribution of mercury to the atmosphere from natural sources is not well-quantified, particularly at the regional scale. This modeling study employed a Geographic Information Systems (GIS) approach to estimate mercury flux from substrate in Nevada, which lies within one of the global belts of geologic Hg enrichment. In situ mercury flux measurements were taken from a variety of substrate types with a wide range of mercury concentrations. This empirical data forms the basis of equations applied to a database of over 71,000 rock and soil samples used in scaling mercury flux for Nevada. The GIS was employed to spatially model estimated flux values according to sample type, geology, presence/absence of hydrothermal alteration, and meteorological conditions. The area average flux calculated for Nevada adjusted for meteorological conditions is 4.2 +/- 1.4 ng m-2 h-1, which corresponds to a approximately 29 kg daily emission of mercury. Areas of hydrothermal alteration emit 12.9 +/- 3.6 ng m-2 h-1, accounts for 22% of net mercury emissions yet represents only 7% of the area of Nevada. Unaltered geologic units have low fluxes (3.5 +/- 1.2 ng m-2 h-1) but, because of their large area, emit 78% of the total mercury.     

Rapid,simple, and accurate method for measurement of VFA and carbonate alkalinity in anaerobic reactors

This paper presents a new simple, rapid, and accurate method suitable for on-site measurement of volatile fatty acids (VFA) and carbonate alkalinity in anaerobic reactors. This titrimetric method involves eight pH observations, and typically, the full procedure takes approximately 15 min. An important feature of the method is a built-in quality control mechanism allowing the user a rapid means of assessing the reliability of the experimental procedure. To evaluate the accuracy of the method, both laboratory-made waters and industrial UASB effluent were tested. High accuracy for both VFA and carbonate alkalinity measurements (error within 2% and 1%, respectively) plus good repetition (average standard deviation of 6.7% and 1.45%, respectively) was obtained. The method takes into account the effects of the phosphate, ammonium, and sulfide weak acid subsystems. Appraisal of the effect of an input error in these subsystems revealed that VFA measurement is fairly insensitive to phosphate and ammonium concentrations. It is, however, sensitive to H2S loss during titration where the sulfide concentration is higher than approximately 10 mg/Las S. With regard to the carbonate alkalinity measurement, error in concentration of either phosphate or sulfide or H2S loss might result in a significant error. Short guidelines for correct execution of the method are given in an appendix.     

Prevalence of Escherichia coli associated with a cabbage crop inadvertently irrigated with partially treated sewage wastewater

Preharvest contamination of field crops may have many sources, including feces, soil, and irrigation water. In March 2000, a sewage spill released unchlorinated tertiary-treated effluent into a creek used to irrigate commercial produce. A field of young cabbage transplants was irrigated with creek water as the contaminated water flowed past this land. Cabbage samples were taken from plots within this field, and Escherichia coli was isolated from the roots of these plants but not from the edible portion of the cabbage. No E. coli was isolated from water samples or from control samples taken from a nearby cabbage field watered with chlorinated municipal water. The cabbage field under study had not been fertilized with manure for at least 2 years prior to the contamination incident. Six different E. coli serotypes were identified, although none of them proved to be pathogenic. These serotypes were separated into five groups by a RiboPrinter; the resulting groups correlated well with the serotypes and the locations in the field from which these strains were isolated. We previously found that certain nonpathogenic E. coli strains displayed lower levels of adherence to lettuce seedling roots in a hydroponic adherence assay. The E. coli field strains displayed variable patterns of adherence to lettuce seedlings: strain MW421 showed significantly lower root and shoot adherence levels than did the other field strains, while strains MW423 and MW425 showed significantly higher root and shoot adherence levels. These data suggest that water quality is of paramount importance for the food safety of growing crops.     

Baseline resolution of isobaric phosphorylated and sulfated peptides and nucleotides by electrospray ionization FTICR ms: another step toward mass spectrometry-based proteomics

Electrospray ionization broadband FTICR mass spectrometry at a mass resolving power, m/delta m50% > or = 400,000 has achieved the first direct mass spectral resolution of phosphorylated and sulfated peptides (or nucleotides) of the same nominal mass. The elemental composition difference in each case is PH versus S (9.5 mDa), requiring a minimum mass resolving power ((m2 - m1)/ml) of 118,000 (C terminal amidated cholecystekinin fragment 26-33 (CCK-8), DY(PO3H2)MGWMDF-NH2 versus DY(SO3H)MGWMDF-NH2) or 65,400 (adenosine triphosphate vs 3-phosphoadenosine 5'-phosphosulfate). The isobaric mass doublets were detected in broadband mode (400 < m/z <1400) in the presence of dozens of other species. It is therefore now possible to distinguish phosphorylated from sulfated peptides, even when both species are present at the same time in a protein digest.     

Novel tubing microreactor for monitoring chemical reactions

There is an expanding interest in small-scale methods to evaluate catalysts and chemical reactions at a variety of conditions, ranging up to 6.9 MPa (1000 psig) and 300 degrees C. Multiwell parallel batch techniques are most commonly applied in high-throughput screening systems. In contrast, we describe here a rapid, serial, highly controllable method based on LC-type steel tubing rated for high pressures. The tube, containing a variety of flowing ingredients, such as carrier solvents, catalyst formulations, and reactants, is self-heated ohmically using electrical current from a power supply monitored and regulated with a precision of 0.01%. An array of voltage taps arranged along its length serves to sense the real-time temperature profile of the tube. Reactions are seen as temperature pulses progressing through the reactor, in zones of 200 microL each, and tracked with a temperature precision of 0.1 degrees C. A unique pressure controller was devised to maintain constant reactor pressures despite effluent viscosity fluctuations due to polymerization. Several chemical reaction systems have been characterized to date, including decomposition reactions of di-tert-butyl peroxide, polymerizations of styrene, formation of polyethylene from ethylene, and copolymerization of ethylene with 1-octene. For ethylene polymerization, the amount of mass of polymer formed is proportional to the responses observed.     

Species-specific isotope dilution-based calibration for trace element speciation and its combined uncertainty evaluation: determination of tributyltin in sediment by HPLC-ICPMS

A method is described for the determination of tributyltin (TBT) in NRCC sediment CRM PACS-2 by isotope dilution (ID) analysis using HPLC-ICPMS. Reverse spike ID analysis was performed to determine the accurate concentration of a 117Sn-enriched TBT spike using a well-characterized natural abundance TBT standard. The accuracy of the latter is critical for obtaining reliable results. A unique approach, using hydride generation GC/MS, was developed to quantify the inorganic Sn and dibutyltin impurities in the natural abundance TBT standard. The true natural abundance TBT standard concentration was obtained following correction for these impurities. The total Sn concentration in the natural abundance TBT standard was determined by ID analysis using an enriched inorganic 117Sn following closed vessel mixed-acid digestion. Calibration of the enriched inorganic 117Sn standard was achieved by reverse ID analysis against a natural abundance inorganic tin standard prepared from the high-purity metal. An overall uncertainty associated with the present method was estimated, to which the uncertainties arising from measurement of the natural abundance TBT concentration, from the measurement of the isotope ratio in the spiked sample and in the reverse ID calibration solutions, and from estimation of the extraction efficiency were the main contributors. A concentration of 1.018 +/- 0.054 mg kg(-1) (expanded uncertainty, k = 2) as tin was obtained for TBT in PACS-2 using the present method, in excellent agreement with the certified value of 0.98 +/- 0.13 mg kg(-1) (95% confidence interval). A TBT concentration of 0.97 +/- 0.11 mg kg(-1) (expanded uncertainty, k = 2) as tin in PACS-2 was determined using the standard additions technique. Much smaller expanded uncertainty was obtained with ID, clearly demonstrating its superiority in providing more accurate and precise results over the method of additions. A detection limit (3sigma) of 0.02 mg kg(-1) for TBT, based on a 0.5-g subsample, was obtained.     

Assessment of the Wiener-Retinex process

We assess the performance of the Retinex transformation, the Wiener restoration, and the combined Wiener-Retinex process in the context of the end-to-end model of color visual-communication channels for near-surface acquisition. We extend the formulations of panchromatic imaging for the nonlinear Retinex transformation and the linear Wiener and Wiener-Retinex restoration filters to color imaging. We further assess the accuracy by which colors are restored in the cases of uniform and spatially varying irradiance levels, and the shadow depth for which color consistency is still possible with reasonable accuracy. Finally, we assess the sensitivity of these processes to perturbations in the visual channel, including the image-gathering design and the spatial support of the Retinex transformation.     

Exercise training-induced changes in sensitivity to endothelin-1 and aortic and cerebellum lipid profile in rats

The purpose of this work was to study whether exercise training induces changes in the lipid profile of rat aorta and nervous system and in the in vitro intrinsic responsiveness of these tissues to endothelin-1 (ET-1) treatment. The exercise program performed successfully produced the characteristic metabolic alterations of the trained state. Exercise training induced a large and significant increase in the levels of both aortic ethanolamine plasmalogens (PlasEtn) and glucosylceramides. In contrast, a decrease of aortic ceramide and cholesterol levels was evoked by exercise training. ET-1 increased PlasEtn content only in sedentary animals. An exercise-induced increase in cerebellum levels of ceramides and ceramide monohexosides was found. The cerebellum ceramide content was increased by FT-1 more noticeably in sedentary rats than in trained animals. In contrast, cerebral cortex was observed to be largely insensitive to both exercise training and ET-1 treatment. It was concluded that exercise training (i) induces changes in both vascular and cerebellar lipid profiles, the former being much more pronounced than the latter, and (ii) diminishes the aortic and cerebellar sensitivity to ET-1 action.     

Data dependent systems technique: a methodology with an application to human systems

The objective of this paper is to introduce the application of Data Dependent Systems (DDS) methodology to the field of ergonomics. Many current techniques in ergonomics utilize static models, which can have significant limitations. DDS is a stochastic modelling and analysis technique that can be used to capture the dynamics of a system through quantitative analysis of the available data. DDS has been successfully applied to the analysis of manufacturing processes and the surfaces generated by those processes. In this research, DDS was used to analyse time-based hand-skin temperature data for the evaluation of two types of glove liners to be used underneath latex gloves. DDS was able to capture the differences between the two glove liners and the two subjects. The implications of the results and the potential of the DDS methodology are discussed.