189 research outputs found
A propósito de la distinción "humano-no humano" en el análisis de la práctica científica
En el presente trabajo analizo algunas de las implicancias de la distinción humano-no humano en relación con la pretensión de los enfoques poshumanistas de trascender al constructivismo social
Implementation of high slurry concentration and sonication to pack high-efficiency, meter-long capillary ultrahigh pressure liquid chromatography columns
Slurry packing capillary columns for ultrahigh pressure liquid chromatography is complicated by many interdependent experimental variables. Previous results have suggested that combination of high slurry concentration and sonication during packing would create homogeneous bed microstructures and yield highly efficient capillary columns. Herein, the effect of sonication while packing very high slurry concentrations is presented. A series of six, 1 m × 75 μm internal diameter columns were packed with 200 mg/mL slurries of 2.02 μm bridged-ethyl hybrid silica particles. Three of the columns underwent sonication during packing and yielded highly efficient separations with reduced plate heights as low as 1.05
Dc track edge interactions
Includes bibliographical references.We have developed an experimental method for investigating the interaction between two dc track edges by studying the track edge noise. We conclude that two edges do not interact when they are several micrometers apart, but the noise reduces nearly to zero when their separation is less than about half a micrometer. There is a transition region that exists between these two limits. The net track edge noise power from two dc edges is quantized, implying that in our experiment track edges interact around the complete revolution of the disk or not at all.This work was supported in part by NSF Grant No. ECS-880470 and NSF Presidential Young Investigator Award (Indeck) ECS-89-5714
On the association of terrestrial gamma-ray bursts with lightning and implications for sprites
Includes bibliographical references (page [1020]).Measurements of ELF/VLF radio atmospherics (sferics) at Palmer Station, Antarctica, provide evidence of active thunderstorms near the inferred source regions of two different gamma-ray bursts of terrestrial origin [Fishman et al., 1994]. In one case, a relatively intense sferic occurring within ±1.5 ms of the time of the gamma-ray burst provides the first indication of a direct association of this burst with a lightning discharge. This sferic and many others launched by positive cloud-to-ground (CG) discharges and observed at Palmer during the periods studied exhibit 'slow tail' waveforms, indicative of continuing currents in the causative lightning discharges. The slow tails of these sferics are similar to those of sferics originating in positive CG discharges that are associated with sprites
Learning from Power Signals: An Automated Approach to Electrical Disturbance Identification Within a Power Transmission System
As power quality becomes a higher priority in the electric utility industry,
the amount of disturbance event data continues to grow. Utilities do not have
the required personnel to analyze each event by hand. This work presents an
automated approach for analyzing power quality events recorded by digital fault
recorders and power quality monitors operating within a power transmission
system. The automated approach leverages rule-based analytics to examine the
time and frequency domain characteristics of the voltage and current signals.
Customizable thresholds are set to categorize each disturbance event. The
events analyzed within this work include various faults, motor starting, and
incipient instrument transformer failure. Analytics for fourteen different
event types have been developed. The analytics were tested on 160 signal files
and yielded an accuracy of ninety-nine percent. Continuous, nominal signal data
analysis is performed using an approach coined as the cyclic histogram. The
cyclic histogram process will be integrated into the digital fault recorders
themselves to facilitate the detection of subtle signal variations that are too
small to trigger a disturbance event and that can occur over hours or days. In
addition to reducing memory requirements by a factor of 320, it is anticipated
that cyclic histogram processing will aid in identifying incipient events and
identifiers. This project is expected to save engineers time by automating the
classification of disturbance events and increase the reliability of the
transmission system by providing near real time detection and identification of
disturbances as well as prevention of problems before they occur.Comment: 18 page
Prototype Cryospheric Experimental Synthetic Aperture Radiometer (CESAR)
Present satellite microwave radiometers typically have a coarse spatial resolution of several kilometers or more. This is only adequate only over homogenous areas. Significantly enhanced spatial resolution is critically important to reduce the uncertainty of estimated cryospheric parameters in heterogeneous and climatically-sensitive areas. Examples include: (1) dynamic sea ice areas with frequent lead and polynya developments and variable ice thicknesses, (2) mountainous areas that require improved retrieval of snow water equivalent, and (3) melting outlet glacier or ice shelf areas along the coast of Greenland and Antarctica. For these situations and many others, an Earth surface spot size of no more than 100 m is necessary to retrieve the information needed for significant new scientific progress, including the synthesis of field observations with satellite observations with high confidence
Retrieval of atmospheric attenuation using combined ground-based and airborne 95-GHz cloud radar measurements
Includes bibliographical references (page 1353).Cloud measurements at millimeter-wave frequencies are affected by attenuation due to atmospheric gases, clouds, and precipitation. Estimation of the true equivalent radar reflectivity, Ze, is complicated because extinction mechanisms are not well characterized at these short wavelengths. This paper discusses cloud radar calibration and intercomparison of airborne and ground-based radar measurements and presents a unique algorithm for attenuation retrieval. This algorithm is based on dual 95-GHz radar measurements of the same cloud and precipitation volumes collected from opposing viewing angles. True radar reflectivity is retrieved by combining upward-looking and downward-looking radar profiles. This method reduces the uncertainty in radar reflectivity and attenuation estimates, since it does not require a priori knowledge of hydrometeors' microphysical properties. Results from this technique are compared with results retrieved from the Hitschfeld and Bordan algorithm, which uses single-radar measurements with path-integrated attenuation as a constraint. Further analysis is planned to employ this dual-radar algorithm in order to refine single-radar attenuation retrieval techniques, which will be used by operational sensors such as the CloudSat radar
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