TY - CONF TI - Power Electronics Packaging AU - Hopkins, Douglas C. T2 - 14th Annual IEEE Conference on Applied Power Electronics Conference and Exposition (APEC) C2 - 1999/3/14/ C3 - 14th Annual IEEE Conference on Applied Power Electronics Conference and Exposition (APEC) CY - Dallas, TX DA - 1999/3/14/ PY - 1999/3/14/ ER - TY - CONF TI - On the Validation of a Watershed Model AU - Vogel, R.M. AU - Sankarasubramanian, A. T2 - International Union of Geodesy and Geophysics C2 - 1999/8// CY - University of Buckingham, Buckingham, United Kingdom DA - 1999/8// PY - 1999/8// ER - TY - CONF TI - Comparisons of Climate Elasticity of Streamflow in the United States AU - Vogel, Richard M. AU - Sankarasubramanian, A. AU - Limbrunner, James F. AU - Wilson, Ian T2 - 29th Annual Water Resources Planning and Management Conference AB - The sensitivity of streamflow to climate is investigated by calculating precipitation and potential evapotranspiration elasticity of streamflow for 1,447 watersheds in the United States. A unique dataset of streamflow and climate time-series is constructed which accounts for the complex spatial variations in climate across the U.S. Average annual values of streamflow, precipitation, temperature, and potential evapotransiration are used to estimate climate elasticity of the long-term mean streamflow using a nonparametric (databased) approach, a regional regression approach and a water balance modeling approach. Comparisons are provided with nine previous climate change studies based on monthly water balance models and soil moisture accounting models Our results suggest that streamflow is more sensitive to changes in precipitation than to changes in potential evapotranspiration. Streamflow is particularly sensitive to both precipitation and potential evapotranspiration in the midwestern regions of the U.S. Difficulties with both the concept of elasticity and with its estimation are discussed and ongoing research is summarized. Climate elasticities derived from detailed monthly simulation experiments agree nicely with the simpler annual approaches outlined in this study. C2 - 1999/6/3/ C3 - WRPMD'99 DA - 1999/6/3/ DO - 10.1061/40430(1999)251 PB - American Society of Civil Engineers SN - 9780784404300 UR - http://dx.doi.org/10.1061/40430(1999)251 DB - Crossref ER - TY - JOUR TI - Investigation and comparison of sampling properties of L-moments and conventional moments AU - Sankarasubramanian, A. AU - Srinivasan, K. T2 - Journal of Hydrology AB - The first part of this article deals with fitting of regression equations for the sampling properties, variance of L-standard deviation (l2), and bias and variance of L-skewness (t3), based on Monte-Carlo simulation results, for generalised Normal (Lognormal-3) and Pearson-3 distributions. These fitted equations will be useful in formulating goodness-of-fit test statistics in regional frequency analysis. The second part presents a comparison of the sampling properties between L-moments and conventional product moments for generalised Normal, generalised Extreme Value, generalised Pareto and Pearson-3 distributions, in a relative form. The comparison reveals that the bias in L-skewness is found to be insignificant up to a skewness of about 1.0, even for small samples. In case of higher skewness, for a reasonable sample size of 30, L-skewness is found to be nearly unbiased. However, the conventional skewness is found to be significantly biased, even for a low skewness of 0.5 and a reasonable sample size of 30. The overall performance evaluation in terms of “Relative-RMSE in third moment ratio” reveals that conventional moments are preferable at lower skewness, particularly for smaller samples, while L-moments are preferable at higher skewness, for all sample sizes. This point is illustrated through an application that seeks to obtain an appropriate regional flood frequency distribution for the 98 catchment areas located in the central region of India, spread over six hydrometeorologic subzones. DA - 1999/5// PY - 1999/5// DO - 10.1016/s0022-1694(99)00018-9 VL - 218 IS - 1-2 SP - 13-34 J2 - Journal of Hydrology LA - en OP - SN - 0022-1694 UR - http://dx.doi.org/10.1016/s0022-1694(99)00018-9 DB - Crossref KW - sampling methods KW - generalised normal KW - Pearson distributions KW - L-moments KW - L-skewness ER - TY - JOUR TI - Line harmonics reduction in high-power systems using square-wave inverters-based dominant harmonic active filter AU - Cheng, P.-T. AU - Bhattacharya, S. AU - Divan, D.D. T2 - IEEE Transactions on Power Electronics AB - This paper presents a dominant harmonic active filter (DHAF) scheme using small-rated square-wave inverters for supply line harmonic current reduction for high-power nonlinear loads in the range of 10 MW and above to meet IEEE 519 harmonic standard. The active filter inverters are connected in series with the fifth and seventh L-C tuned filters, respectively. A synchronous reference frame-based controller which achieves harmonic isolation for the dominant fifth and seventh harmonic load currents in the presence of supply voltage harmonic distortion is presented. Impact of mistuned passive filters on the operation and rating of the square-wave active filter inverters is examined. Simulation results validate the proposed harmonic isolation controller under mistuned fifth and seventh L-C tuned filter conditions and supply voltage harmonic distortion. The proposed scheme is general and applicable for high-power 6- or 12-pulse rectifier loads. The use of small-rated square-wave inverters (approximately 2% of load kilovoltampere rating) increases the cost effectiveness of the DHAF system for high-power applications. DA - 1999/// PY - 1999/// DO - 10.1109/63.750179 VL - 14 IS - 2 SP - 265-272 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0033097168&partnerID=MN8TOARS KW - active filter KW - harmonic filtering KW - harmonic isolation KW - square-wave inverter ER - TY - JOUR TI - Experimental comparison of motor bearing currents with PWM hard- and soft-switched voltage-source inverters AU - Bhattacharya, S. AU - Resta, L. AU - Divan, D.M. AU - Novotny, D.W. T2 - IEEE Transactions on Power Electronics AB - This paper compares motor bearing currents due to pulsewidth modulation (PWM) hard- and soft-switched inverters. The mechanisms for bearing currents are first identified using an approach based on direct small-signal excitation of the motor bearing with sinusoidal and square-wave signals to characterize the bearings. It is shown that many of the motor models that have been proposed in the literature to explain bearing currents do not adequately explain the observed higher frequency effects. The paper also outlines some of the important phenomena which need to be considered for a more complete description of bearing currents. Finally, the paper compares the performance of hard and soft-switched inverters with respect to bearing currents and shaft voltage. Experimental results are provided for PWM hard- and soft-switched insulated gate bipolar transistor (IGBT) inverters which have exactly the same power circuit layout, identical chassis, and rating of 70 kVA. DA - 1999/// PY - 1999/// DO - 10.1109/63.761699 VL - 14 IS - 3 SP - 552-562 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0032629348&partnerID=MN8TOARS ER - TY - JOUR TI - Application of dominant harmonic active filter system with 12 pulse nonlinear loads AU - Cheng, P.-T. AU - Bhattacharya, S. AU - Divan, D.M. T2 - IEEE Transactions on Power Delivery AB - Harmonic filtering is required for 12 pulse rectifier-utility interface to meet IEEE 519 harmonic current limits. Passive filter techniques employ tuned L-C filters at dominant 11th and 13th harmonic frequencies. However, they also require 5th and 7th tuned filters to avoid series and parallel resonance conditions. State of the art active filtering solutions require high bandwidth and relatively large rating PWM inverters for harmonic filtering of 12 pulse rectifier loads. Thus existing passive and active harmonic filtering solutions are not cost-effective for high power 12 pulse rectifier loads. Dominant harmonic active filter (DHAF) based on square-wave inverters is proposed to cost-effectively meet IEEE 519 harmonic current limits for 12 pulse rectifier loads. The proposed DHAF system employs square-wave inverters switching at 5th and 7th harmonic frequencies, which are transformer coupled in series with 11th and 13th passive filters respectively. The square-wave inverters are controlled to provide 'harmonic isolation' between the supply and load at 5th and 7th harmonic frequencies. The square-wave inverters are rated 1%-2% of the load kVA rating. The proposed DHAF system eliminates the need for large kVAR rated and bulky 5th and 7th passive filters, delivers superior harmonic filtering performance, and provides cost-effective harmonic filtering solution. Simulation results are given to validate the 'harmonic isolation' feature at 5th and 7th harmonic frequencies, and also demonstrate harmonic filtering required to meet IEEE 519 harmonic current limits. DA - 1999/// PY - 1999/// DO - 10.1109/61.754112 VL - 14 IS - 2 SP - 642-647 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0033116513&partnerID=MN8TOARS KW - active filter KW - square-wave inverter KW - harmonic isolation KW - 12 pulse rectifier KW - passive filter KW - HVDC ER - TY - JOUR TI - Determination of [13C]Pyrene Sequestration in Sediment Microcosms Using Flash Pyrolysis−GC−MS and13C NMR AU - Guthrie, Elizabeth A. AU - Bortiatynski, Jaqueline M. AU - van Heemst, Jasper D. H. AU - Richman, Jack E. AU - Hardy, Kristine S. AU - Kovach, Eugene M. AU - Hatcher, Patrick G. T2 - Environmental Science & Technology AB - In this study, the use of a 13C-labeled pollutant probe, [13C]pyrene, and the application of flash pyrolysis−GC−MS and CPMAS 13C NMR provided analytical capabilities to study pyrene interactions with soluble and insoluble compartments of sedimentary organic matter (SDOM) during whole sediments incubations in aerated microcosms. Surface sediments were collected from a site of previous hydrocarbon contamination in New Orleans, LA. Over a period of 60 days, humic acid and humin fractions of SDOM accumulated increasing amounts of pyrene that were resistant to exhaustive extraction with organic solvents. The sequestered pyrene was evident in CPMAS 13C NMR spectra of humin fractions. The amount of sequestered pyrene in humic materials was quantified by flash pyrolysis−GC−MS, a technique that destroys the three-dimensional structure of macromolecular SDOM. Noncovalent binding of pyrene to humic materials in SDOM was greater in sediments incubated with biological activity than biocide-treated sediments. The combined analytical approaches demonstrate that the sequestered pyrene, or bound residue, is noncovalently associated with SDOM and has not undergone structural alteration. Implications of these data are discussed in reference to SDOM diagenesis and long-term availability of bound pollutant residues in sediments. DA - 1999/1// PY - 1999/1// DO - 10.1021/es980515e VL - 33 IS - 1 SP - 119-125 J2 - Environ. Sci. Technol. LA - en OP - SN - 0013-936X 1520-5851 UR - http://dx.doi.org/10.1021/es980515e DB - Crossref ER - TY - JOUR TI - Methods for characterizing variability and uncertainty: Comparison of bootstrap simulation and likelihood-based approaches AU - Frey, H.C. AU - Burmaster, D.E. T2 - Risk Analysis DA - 1999/// PY - 1999/// DO - 10.1023/A:1006962412150 VL - 19 IS - 1 SP - 109-130 UR - http://www.scopus.com/inward/record.url?eid=2-s2.0-0032940312&partnerID=MN8TOARS KW - variability KW - uncertainty KW - maximum likelihood KW - bootstrap simulation KW - Monte Carlo simulation ER - TY - JOUR TI - Evaporative air conditioning in a manufacturing facility AU - Brown, CD AU - Leach, JW AU - Terry, SD T2 - ENERGY ENGINEERING AB - ABSTRACT A case study evaluates the economics of installing a staged evaporative cooling system in a factory in the southeastern USA. The effective temperature at the plant floor is predicted for each working hour from typical meteorological year data. The analysis accounts for internal loads and moisture evaporated by the manufacturing process. Worker productivity is estimated from the effective temperature. Several building loads and evaporative cooling system designs are considered. The results show that evaporative air conditioning can improve worker productivity and profit margins in manufacturing facilities that have high internal loads, high ventilation requirements, or other plant-specific conditions that would make conventional air conditioning uneconomical. DA - 1999/// PY - 1999/// DO - 10.1080/01998595.1999.10530467 VL - 96 IS - 4 SP - 40-58 SN - 0199-8595 ER - TY - JOUR TI - Transformer derating for harmonic currents: A wide-band measurement approach for energized transformers AU - Kelley, AW AU - Edwards, SW AU - Rhode, JP AU - Baran, ME T2 - IEEE TRANSACTIONS ON INDUSTRY APPLICATIONS AB - Power system transformers must often be derated when supplying harmonic currents to nonlinear loads. IEEE Recommended Practice C57.110 extrapolates transformer loss for harmonic frequencies based on DC winding resistance and rated eddy-current loss. This paper describes an improved derating technique based on direct measurements performed at fundamental and harmonic frequencies. The measurements can be performed regardless of whether the transformer is energized and in service or deenergized and out of service. For energized transformers, the measurement can be performed regardless of whether the transformer is fully loaded or unloaded. Measurements of several distribution transformers show the improvement of this method over C57.110. DA - 1999/// PY - 1999/// DO - 10.1109/28.806061 VL - 35 IS - 6 SP - 1450-1457 SN - 0093-9994 KW - harmonics KW - impedance measurement KW - power quality KW - transformer derating ER - TY - JOUR TI - A transaction assessment method for allocation of transmission services AU - Baran, ME AU - Banunarayanan, V AU - Garren, KE T2 - IEEE TRANSACTIONS ON POWER SYSTEMS AB - This paper presents a power flow based method for an accurate assessment of the impact of a transaction on an area/utility. The method determines, for each transaction, the following: the flowpath of the transaction (both real and reactive power components); generator reactive power support from each area/utility; and real power loss support from each area/utility. The proposed method is tested extensively on a real-life system. Results indicate that the method is very accurate in allocating the above transmission services on a transaction basis. DA - 1999/8// PY - 1999/8// DO - 10.1109/59.780904 VL - 14 IS - 3 SP - 920-927 SN - 0885-8950 KW - transmission services KW - transmission flowpath KW - transmission ancillary services ER - TY - JOUR TI - Methods for characterizing variability and uncertainty: Comparison of bootstrap simulation and likelihood-based approaches AU - Frey, H. Christopher AU - Burmaster, D. E. T2 - Risk Analysis AB - Variability arises due to differences in the value of a quantity among different members of a population. Uncertainty arises due to lack of knowledge regarding the true value of a quantity for a given member of a population. We describe and evaluate two methods for quantifying both variability and uncertainty. These methods, bootstrapsimulation and a likelihood‐based method, are applied to three datasets. The datasetsinclude a synthetic sample of 19 values from a Lognormal distribution, a sample of nine values obtained from measurements of the PCB concentration in leafy produce, and asample of five values for the partitioning of chromium in the flue gas desulfurization system of coal‐fired power plants. For each of these datasets, we employ the two methods to characterize uncertainty in the arithmetic mean and standard deviation, cumulative distribution functions based upon fitted parametric distributions, the 95th percentile of variability, and the 63rd percentile of uncertainty for the 81st percentile of variability. The latter is intended to show that it is possible to describe anypoint within the uncertain frequency distribution by specifying an uncertainty percentile and a Variability percentile. Using the bootstrap method, we compare results based upon use of the method of matching moments and the method of maximum likelihood for fitting distributions to data. Our results indicate that with only 5‐19 data pointsas in the datasets we have evaluated, there is substantial uncertainty based upon random sampling error. Both the boostrap and likelihood‐based approaches yield comparable uncertainty estimates in most cases. DA - 1999/// PY - 1999/// DO - 10.1111/j.1539-6924.1999.tb00393.x VL - 19 IS - 1 SP - 109–130 ER - TY - JOUR TI - Volt/var control at distribution substations AU - Baran, ME AU - Hsu, MY T2 - IEEE TRANSACTIONS ON POWER SYSTEMS AB - This paper proposes new methods to improve the performance of the current volt/VAr control schemes at distribution substations. The approach makes use of the new measurement and computer resources that are now available at the substations. The paper shows that new supervisory type control schemes can be developed to improve the performance of both the voltage regulator controllers and also the substation capacitor controllers that are used at the substations for volt/VAr control. The new voltage regulator controller makes use of the voltage drop characteristics of the feeders it regulates. The capacitor controller uses local real and reactive power measurements for power factor control at the substation. DA - 1999/2// PY - 1999/2// DO - 10.1109/59.744549 VL - 14 IS - 1 SP - 312-318 SN - 0885-8950 KW - distribution systems KW - feeder voltage regulation KW - substation power factor correction ER - TY - JOUR TI - Optimal nitrate concentration for the biodegradation of n-heptadecane in a variably-saturated sand column AU - Boufadel, MC AU - Reeser, P AU - Suidan, MT AU - Wrenn, BA AU - Cheng, J AU - Du, X AU - Huang, THL AU - Venosa, AD T2 - ENVIRONMENTAL TECHNOLOGY AB - Bioremediation of oil spills on beaches commonly involves the addition of nutrients (especially nitrogen and phosphorus) to stimulate the growth of indigenous oil-degrading bacteria. Very little information is available regarding the relationship between nutrient concentration and the rate of oil biodegradation. This information is necessary to design an appropriate nutrient delivery technology. We used continuous-flow beach microcosms containing heptadecane-coated sand (2.0 g per kg of dry sand) to evaluate the effect of nitrate concentration on the hydrocarbon biodegradation rate. Heptadecane biodegradation was determined by monitoring oxygen consumption and carbon dioxide production in the microcosms. The maximum biodegradation occurred at 2.5 mg nitrate-N l−1. Nitrogen recycling by the biomass was evidenced by the presence of microbial activity at zero influent nitrate concentration. DA - 1999/2// PY - 1999/2// DO - 10.1080/09593332008616808 VL - 20 IS - 2 SP - 191-199 SN - 0959-3330 KW - bioremediation KW - oil KW - nutrient KW - beaches KW - shores ER - TY - CONF TI - Covered anaerobic lagoon system for swine waste treatment and energy recovery AU - Cheng, J. AU - Roos, K. F. AU - Saele, L. M. C2 - 1999/// C3 - 1999 ASAE/CSAE-SCGR annual international meeting : emerging technologies for the 21st century ; Toronto, Ontario, Canada, July 18-21, 1999 DA - 1999/// VL - 994048 ER -