Dry Hollow Research Articles

Revealing the flashover mechanism of EP/GF composite insulation under DC combined harmonic voltage

Abstract In ultra-high voltage converter stations, the phenomenon of flashover along the outer insulation of dry hollow reactors made of epoxy/glass fiber composites poses a potential threat to the stability of the power system. To enhance its flashover performance under varying complex conditions, it is necessary to conduct in-depth research on the flashover mechanism of this material under different voltage forms. This study conducted tests on the flashover voltage, surface space charge distribution, and partial discharge parameters under varying AC-DC ratios and AC frequencies, and exploring their relationships. The results show that the DC content in the AC-DC ratio decreases, the flashover voltage decreases, the apparent total discharge of partial discharges increases, and the maximum surface space charge density decreases. The main influencing factor is the increase in the number of seed charges involved in gas ionization. Increasing the AC frequency, the flashover voltage decreases, the apparent total discharge increases significantly, and the surface charge density remains basically unchanged. The main reason is that the change in the number of alternating cycles further increases the number of seed charges. This study reveals the flashover mechanism of epoxy/glass fiber composites under different voltage forms, which provides theoretical support for subsequent material modification.

Habitat requirements of deadwood-dependent invertebrates that occupy tree hollows.

Tree hollows support a specialised species-rich fauna. We review the habitat requirements of saproxylic (= deadwood dependent) invertebrates which occupy tree hollows. We focus on studies quantifying relationships between species occurrence patterns and characteristics of tree hollows, hollow trees, and the surrounding landscape. We also explore the processes influencing species occurrence patterns by reviewing studies on the spatio-temporal dynamics of populations, including their dispersal and genetic structure. Our literature search in the database Scopus identified 52 relevant publications, all of which were studies from Europe. The dominant taxonomic group studied was beetles. Invertebrates in hollow trees were often more likely to be recorded in trees with characteristics reflecting a large amount of resources or a stable and warm microclimate, such as a large diameter, large amounts of wood mould (= loose material accumulated in the hollows mainly consisting of decaying wood), a high level of sun exposure, and with entrance holes that are large and either at a low or high height, and in dry hollows, with entrances not directed upwards. A stable microclimate is probably a key factor why some species of saproxylic invertebrates are confined to tree hollows. Other factors that are different in comparison to downed dead wood is the fact that hollows at a given height from the ground provide shelter from ground-living predators, that hollows persist for longer, and that the content of nutrients might be enhanced by the accumulation of dead leaves, insect frass, and remains from dead insects. Several studies have identified a positive relationship between species occupancy per tree and the amount of habitat in the surrounding landscape, with a variation in the spatial scale at which characteristics of the surrounding landscape had the strongest effect over spatial scales from 200 to 3000 m. We found empirical support for the extinction threshold hypothesis, which predicts that the frequency of species presence per tree is greater if a certain number of trees are aggregated into a few large clusters of hollow trees rather than distributed among many small clusters. Observed thresholds in species occurrence patterns can be explained by colonisation-extinction dynamics, with species occupancy per tree influenced by variation in rates of immigration. Consistent with this assumption, field studies suggest that dispersal rate and range can be low for invertebrates occupying tree hollows, although higher in a warmer climate. For one species in which population dynamics has been studied over 25 years (Osmoderma eremita), the observed population dynamics have characteristics of a "habitat-tracking metapopulation", as local extinctions from trees occur possibly because those trees become unsuitable as well as due to stochastic processes in small populations. The persistence of invertebrate fauna confined to tree hollows may be improved by prolonging the standing life of existing hollow trees. It is also important to recruit new generations of hollow trees, preferably close to existing larger groups of hollow trees. Thus, the spatio-temporal dynamics of hollow trees is crucial for the invertebrate fauna that rely upon them.

Geological Assessment of Turonian - Coniacian terrestrial sedimentation records during climatic recovery, Moreno Hill Formation, Zuni Basin

Understanding of Upper Cretaceous terrestrial sediments within the Western Interior Basin is advancing; however, the Turonian–Coniacian transition remains enigmatic. Recent chronometry of the Moreno Hill Formation indicates that sediment deposition took place during this interval of geodynamic upheaval and climatic recovery immediately following the peak of the Cretaceous Thermal Maximum (CTM). To decipher these effects, the sedimentary record of the Moreno Hill Formation was reassessed near the type section, and near Quemado, New Mexico (USA) using facies analysis and architectural reconstruction. Seven facies types (thirteen lithofacies codes), eleven architectural elements, and three facies associations were identified. Sedimentation within the floodplain of the lower Moreno Hill Formation was affected by the east-migrating forebulge of the Western Interior Basin. Furthermore, increasingly bedload-rich multi-story channel complexes and a transition from near-coastal to alluvial coals reflect gradual climatic cooling and overall regression of the Western Interior Seaway (with interruption by a regional [T2–R2] transgressive-regressive sequence). This is consistent with more subaerial conditions indicative of continued regression reflected within the floodplain sediments of the upper Moreno Hill Formation. Whilst diversion of westerly fluvial feeder systems by ongoing forebulge migration also affected sediment transport and deposition, a return to more suspended-load-rich single-story channels and thin coals are tied to an intervening (T3) transgression. Repetitive paleosol sequences throughout the Moreno Hill Formation indicate groundwater fluctuation in response to these base level changes. Together with detrital zircon-based geochronology, these slight sedimentary differences support a revised subdivision from three into two members: lower and upper. Beyond feeding the seaward Gallup Delta, the newly defined lower member correlates to the Toreva, Straight Cliffs (Smoky Hollow member), Ferron Sandstone, Funk Valley and Frontier formations (Dry Hollow Member) and the upper member to the Wepo and Straight Cliffs (John Henry Member) formations within the Kaiparowits, Notom, Last Chance and Vernal fluvio-deltaic systems. Landward sediments of the Cardium Formation (Canada) correlate with the lower and upper members of the Moreno Hill Formation.

Periglacial gully erosion on the east European plain and its recent analog at the Yamal peninsula

The net of dry valleys, gullies and shallow hollows is typical for the East European Plain. Dense vegetation usually covers their bottoms and slopes, so the modern erosion there is negligible in the pristine conditions. This erosion landscape formed in periglacial conditions during the terminations of the last two glaciations. The same kind of the erosion landscape is typical for the Arctic regions, especially for the Yamal, Gydan, and Tazovsky peninsulas. The size and the density of such valleys and gullies are quite similar to those existing on the East European Plain, but these erosion features are active there, especially in the conditions of natural or anthropogenic deterioration of the vegetation cover. As the density of dry valley network is an indicator of hydrological conditions in the river basin, the landscapes of the Arctic regions can be used as the modern analogs of the territories with the past periglacial erosion.The recent hydrological characteristics of the west-central Yamal Peninsula were used to estimate the parameters of erosion network at the Khoper River basin, formed in periglacial conditions. For these purposes gully erosion and thermoerosion model GULTEM was verified and calibrated based on the observation of the modern processes on the Yamal Peninsula. The meteorological characteristics were taken from ERA-Interim Reanalysis grid. To calculate the flow characteristics a synthetic hydrological model was used. These verified and calibrated models were used to find the most suitable characteristics of climate and vegetation cover, which can explain the structure and density of the Perepolye dry valley in the Khoper River basin. This dry valley with the main trunk length of 6400 m was formed at the end of the Late Valdai Glaciation (MIS 2). The conditions required for the formation of a periglacial gully of such length were estimated with the GULTEM model. The critical velocity of erosion initiation was within the range 0.8-0.9 m/s, and the surface runoff depth was close to the recent one on the Yamal Peninsula (330 mm). The system of shallow hollows in the Perepolye catchment (the gullies formed at the end of the Moscow Glaciation, MIS 6) is denser and longer than the dry valley system, and the modelling estimates showed that the surface runoff during that period was almost 3.3 times more than the recent one on the Yamal Peninsula.

Study on the Influence Factors of Dry Hollow Parallel Reactor Loss

Reactor individual branch loss mutation is one of the important reasons leading to local temperature too high. In order to explore process deviation for dry type hollow shunt reactor loss amplification effect, this paper is establish a loss calculation model of dry-type air-core reactor as the tool, Comparative analysis relationship between the four common types of process deviation and the local branch loss. Calculation results show that the number of turns deviation are the main factor influencing the reactor partial loss, So the reactor production winding process should strengthen the control of the number of turns deviation.

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Simulation Research on Solutions to 66kV Vertical SVC Switching Overvoltage and the Implementation

The dry hollow reactor has the features of good inductance linearity and heat dissipation and is not easy to produce ferromagnetic resonance with capacitive load in the system. Therefore, the phase controlled reactor in TCR-type SVC is usually a dry hollow reactor. According to years’ actual operating condition, the phase controlled reactor in 35kV SVC or SVC at a lower level operates stably while tree discharge or breakdown failure frequently happens to the phase controlled reactor in the 66kV vertical SVC, which seriously affects the stable operation of the equipment. This paper puts forward a method of installing arrester on the phase controlled reactors to relieve the SVC switching overvoltage impulse and protect the phase controlled reactors. Besides, it uses PSCAD to conduct a simulation and verifies the feasibility of this method.

Fabrication of hydrophilic and sponge-like PVDF/brush-like copolymer blend membranes using triethylphosphate as solvent

Porous PVDF blend membranes with good hydrophilicity and a symmetric structure were prepared by the phase inversion method using amphiphilic brush-like copolymers, P(MMA-r-PEGMA), as hydrophilic additive and triethylphosphate (TEP) as solvent. P(MMA-r-PEGMA) was synthesized by radical polymerization in TEP. Then the obtained amphiphilic copolymer solution was mixed with PVDF and TEP to prepare the dope solution. The effects of P(MMA-r-PEGMA) content and coagulation composition on membrane morphologies were investigated using scanning electron microscopy (SEM). The results demonstrated that, even blended with amphiphilic copolymers, a symmetric structure can be formed. Hollow fiber membranes with a mainly symmetric structure were also fabricated. The dry hollow fiber membranes showed good hydrophilicity, high flux and good rejection performance because of their hydrophilic surface and pores wall.

Environmental and Vegetation Drivers of Seasonal CO2 Fluxes in a Sub-arctic Forest–Mire Ecotone

Unravelling the role of structural and environmental drivers of gross primary productivity (GPP) and ecosystem respiration (R eco) in highly heterogeneous tundra is a major challenge for the upscaling of chamber-based CO2 fluxes in Arctic landscapes. In a mountain birch woodland-mire ecotone, we investigated the role of LAI (and NDVI), environmental factors (microclimate, soil moisture), and microsite type across tundra shrub plots (wet hummocks, dry hummocks, dry hollows) and lichen hummocks, in controlling net ecosystem CO2 exchange (NEE). During a growing season, we measured NEE fluxes continuously, with closed dynamic chambers, and performed multiple fits (one for each 3-day period) of a simple light and temperature response model to hourly NEE data. Tundra shrub plots were largely CO2 sinks, as opposed to lichen plots, although fluxes were highly variable within microsite type. For tundra shrub plots, microsite type did not influence photosynthetic parameters but it affected basal (that is, temperature-normalized) ecosystem respiration (R 0). PAR-normalized photosynthesis (P 600) increased with air temperature and declined with increasing vapor pressure deficit. R 0 declined with soil moisture and showed an apparent increase with temperature, which may underlie a tight link between GPP and R eco. NDVI was a good proxy for LAI, maximum P 600 and maximum R 0 of shrub plots. Cumulative CO2 fluxes were strongly correlated with LAI (NDVI) but we observed a comparatively low GPP/LAI in dry hummocks. Our results broadly agree with the reported functional convergence across tundra vegetation, but here we show that the role of decreased productivity in transition zones and the influence of temperature and water balance on seasonal CO2 fluxes in sub-Arctic forest–mire ecotones cannot be overlooked.

Calibration of in-reactor detectors and determination of the computational error of the RBMK-1000 SKALA-mikro information measuring system

Several methods are used to calibrate in-reactor detectors or to determine their sensitivity to the power of the fuel assemblies at zero burnup. For a long time, the most widely used method was axial scanning of the fuel assemblies of assembly 49 with a dry hollow casing by detector Dt.6 or Dt.4 with an HfO 2 detector and long sensitive part, whose length equals the core height [1]. The power of a fuel channel with an in-reactor detector, reconstructed from the scan results and calculated using the signals from the detector, was used to determine its sensitivity taking account of the burnup of the fuel assembly and detector. The rms deviation of the error in this calibration is 3‐4%. Subsequently, an adjacent reference sample was used to calibrate the sensitive part of the detector, since the amount of HfO 2 per unit length of the sensitive part varies very little along the sensor cable. The rms deviation of the ratio of the HfO 2 amount to the sensitive part of the in-reactor detector and two reference samples, placed at the ends of the detector, is about 1%. The sensitivity of each reference sample was determined in the IRT reactor at the Moscow Engineering Physics Institute and extended to the corresponding sensitive part of the in-reactor detector. However, this method was time-consuming and expensive. It was improved by determining the dependence of the sensitivity of the calibrated reference samples on HfO 2 content of each per unit length. The amount of HfO 2 was determined by measuring the resistivity and length of emitter shell of the reference sample, making it possible to determine the mass of the emitter shell, and weighing the emitter in the inner shell after the outer shell and sensor cable insulation were removed. This calibration requires about 10 min. The sensitivity of an in-reactor detector is calculated from the relation η = ƒ(m), (1) where m is the mass of the emitter material. The unit (current) chosen for the sensitivity to the number of neutrons captured by a hafnium nucleus in 1 sec makes it possible to eliminate the effect of the neutron spectrum on it. The ratio of the rms deviation of the measurements of the sensitivity of the reference samples and the calculation with the (1) fit was obtained on the basis of the expressions in [2]. The result was the rms error in determining the sensitivity using Eq. (1), equal to about 1%. The procedure described also made it possible to determine the mass of the outer shell and insulation of the emitter, having included them in the expression for the sensitivity calculation. Since the positive gain in the rms error of calibration is negligible (it is 1.1 times less with 1.3‐1.5 times larger costs), dependence (1) is used in practice. The procedure described is termed the factory calibration.

Application of Effective Media Theory for Determination of Thermal Properties of Hollow Bricks as a Function of Moisture Content

The effective thermal conductivity and effective specific heat capacity of hollow brick blocks are investigated as a function of moisture content. While the effective specific heat capacity as a heat storage parameter is calculated using the linear theory of mixtures, the effective thermal conductivity as a heat transport parameter is analyzed using the effective media theory. At first, the effective thermal conductivity of the dry hollow brick block is calculated using a combination of properties of the brick body and air cavities, and verified using experimental data. Then, the effective thermal conductivity of the brick body is analyzed as a function of moisture content both theoretically and experimentally, and appropriate homogenization formulas are identified. Finally, the effective thermal conductivity of the whole hollow bricks is expressed as a function of moisture content from the dry state to water saturation.

Water-dispersible PVA-based dry microballoons with potential for biomedical applications

This paper reports on the preparation and characterization of stable poly(vinyl alcohol) (PVA)-based dry hollow microparticles, readily convertible to gas-filled microballoons (MBs) in water suspension. The rehydrated MBs can be used as ultrasound contrast agents and for targeted drug delivery, while the dry MBs are suitable for encapsulation of biologically active gases. The MBs powder material is obtained by freeze-drying the as-prepared telechelic PVA-shelled MBs aqueous dispersion. The microstructure of the lyophilized MBs as well as of the starting and the reconstituted MBs in water suspension was examined using transmission electron microscopy (TEM), scanning electron microscopy (SEM), scanning transmission X-ray microspectroscopy (STXM) and confocal laser scanning microscopy (CLSM). STXM observations below and above the oxygen K-edge reveal that 80% of the MBs originating from the lyophilized particles are gas-filled. Moreover, local carbon K near-edge X-ray absorption fine structure spectroscopy (NEXAFS) measurements evidenced that the chemical composition of the polymeric shell is preserved during the freeze-drying process and subsequent shelf storage for at least more than one year.

Removal of Benzene/Toluene from Water by Vacuum Membrane Distillation in a PVDF Hollow Fiber Membrane Module

Asymmetric polyvinylidene fluoride (PVDF) hollow fiber membranes were prepared by a phase inversion method using dimethylacetamide (DMAc) and a mixture of water/LiCl as solvent and a nonsolvent additive, respectively. The prepared membranes were characterized by scanning electron microscopy (SEM) for observing its microstructures and by a gas permeation method for measuring its surface porosity, pore size, and pore size distribution. Wetting pressures of the dry hollow fiber membranes were also measured. Using the prepared PVDF hollow fiber membranes, a membrane module was fabricated for removal of benzene/toluene from water. Effects of various operating parameters such as downstream vacuum levels, feed temperatures, and feed flow rates on performances of the module were investigated experimentally. The benzene/toluene removal was achieved over 99% under an optimal operating condition. Mass transfer of benzene or toluene removal is controlled not only by the liquid phase resistance but also by the membrane and gas phase resistances. Benzene and toluene can be removed from water simultaneously with no adverse coupling effects.

Nest site selection by ants in a flooded Mexican mangrove, with special reference to the epiphytic orchid Myrmecophila christinae

The distribution of the arboreal ant community plus a termite species of the genus Nasutitermes was inventoried on 938 red mangrove, Rhizophora mangle L., trees in a completely flooded mangrove forest of the Sian Ka'an Biosphere Reserve, Quintana Roo, Mexico. Colonies sheltered in dry hollow branches of the trees and the pseudobulbs of the epiphytic orchid, Myrmecophila christinae. Two size classes of dry hollow tree branches were categorized in order to test differences in ant distribution. As some trees remained unoccupied by either an ant or a termite colony, we deduced that the competition for nesting sites was low. Differences in the composition of the ant community corresponded to the nature of the shelters (i.e. diameter of the hollow branches or orchid pseudobulbs). The ant fauna was richer in the large dry hollow branches of R. mangle than in the smaller ones, with certain ant species belonging to the subfamilies Ponerinae and Formicinae being significantly more frequent in the large dry hollow branches than in the small ones. Cephalotes and Pseudomyrmex were the most frequent ant genera inhabiting the dry branches of R. mangle, while Dolichoderus bispinosus was the most frequent ant species inhabiting the orchid pseudobulbs. Arboreal Nasutitermes sp. selected mostly the orchid pseudobulbs and thus indirectly interfered with ant nest-site selection. Our results highlight niche differentiation through the selection of nest sites among different types of shelter.

Response of Forest to Climatic Events and Human Management at Fort Leavenworth, Kansas

Characteristics and temporal changes in forest cover from 1987 to 1997 were documented on the basis of remote sensing for two study forests at Fort Leavenworth, northeastern Kansas. Eight Landsat 5 Thematic Mapper (TM) datasets from the month of July cover the study period, which included a major drought in 1988-1989 and flooding along the Missouri River in 1993. Other data sources included kite aerial photographs, digital orthophotos, tree-ring cores, climatic records, and ground observations. Three study areas were evaluated from Landsat TM datasets: (1) the entire Fort Leavenworth area; (2) an upland, hardwood forest composed mainly of oaks; and (3) a bottomland, softwood forest dominated by cottonwood. Normalized Difference Vegetation Index (NDVI) values were derived from these three study sets and subjected to image differencing and principal-component analysis. The TM band 5:4 ratio was also analyzed for the two study forests. Values and trends derived from Landsat imagery were compared to data on tree-ring growth in upland oaks and regional climatic events.
 Annual growth of tree rings in upland oaks is tied closely to precipitation and the Palmer Drought Severity Index (PDSI); however, changes in NDVI values lag one to two years behind the onset of climatic events, particularly drought episodes. During the first year of drought (1988), vegetation cover in the upland and bottomland forests reacted in different ways: with a slight decline in the upland forest and a slight increase in the bottomland forest. The increased vegetation in the bottomland forest presumably resulted from more understory growth in dry hollows and potholes. In the second year of drought (1989), both forests suffered a marked decline in vegetation cover. NDVI values reached their minima for all categories (whole area, upland forest, and bottomland forest) in 1990, even though precipitation and tree-ring growth increased substantially that year. We conclude that changes in Landsat-derived NDVI values are out of phase with climatic events and variations in tree-ring growth for both upland and bottomland forests in northeastern Kansas and northwestern Missouri.
 Overall change (1987 to 1997) for NDVI values is down slightly for all categories of evaluation. This probably reflects reduced precipitation throughout the study period compared to the long-term average. Changes in vegetation took place mainly on the forest margins. Such changes are thought to result from microclimatic stress at forest edges. The bottomland study forest also was impacted by severe flooding in 1993. Routine human activities may have resulted in minor changes along the margins of both study forests. The bottomland forest was affected by intentional burning of the adjacent prairie in April 2000. Cottonwood trees at the forest edge were killed or injured by the prairie fire, which penetrated the forest understory some distance.

Module performance of anion-exchange porous hollow-fiber membranes for high-speed protein recovery

A laboratory-scale module was fabricated by housing eight anion-exchange porous hollow-fiber membranes with an effective length of 8 cm in parallel to each other in a cartridge. The hollow fibers were prepared by radiation-induced graft polymerization of glycidyl methacrylate and subsequent chemical modifications using diethylamine and ethanolamine. The resultant hollow fibers had diethylamino and ethanolamino group densities of 2.1 and 1.2 mmol/g of the dry hollow fiber, respectively, with inner and outer diameters of 2.8 and 4.4 mm, respectively, in a wet state. A low operating pressure of 0.1 MPa in the module provided a flow-rate of 100 ml/min for a bovine serum albumin solution. The dynamic binding amount of bovine serum albumin for the module was 270 mg, irrespective of the flow-rate, for rates ranging from 10 to 100 ml/min. The dynamic binding amount for the module was equivalent to eight times that of a single hollow fiber with an identical effective length, which indicates a linear relationship between the module and the number of single fibers for dynamic binding amount.

Synorogenic Sedimentation of Upper Cretaceous Frontier Formation Conglomerates and Associated Strata, Wyoming-Idaho-Utah Thrust Belt

The Dry Hollow Member of the Upper Cretaceous (Turonian) Frontier Formation in the Wyoming-Idaho-Utah thrust belt is comprised predominantly of fluvial deposits. In northeastern Utah, these strata include massive cobble conglomerates, horizontally-stratified very coarse sandstones, planar cross-stratified pebbly sandstones, and rare siltstones. Farther eastward in southwestern Wyoming, the Dry Hollow Member contains sandstone lenses which possess basal conglomeratic (pebble) lenses and fine upward to medium-grained, trough cross­ stratified sandstones interbedded shales, coals, and thin, fine-grained, ripple-drift cross-laminated sandstones account for much of the Dry Hollow Member. Regional variations in stratification styles, grain size, and geometry of the sandstone units are interpreted as a consequence of downslope variations in channel pattern. These variations represent a change from near-source braided streams in northeastern Utah to distal meandering streams in southwestern Wyoming.

Pore Pressure Buildup in Resonant Column Tests

Resonant column tests were performed on fully saturated and dry hollow cylindrical and fully saturated solid cylindrical specimens of Monterey No. 0 sand of 60% relative density subjected to 96 kPa confining pressure. The hollow specimens were tested by torsional excitation and the solid specimens by longitudinal excitation. It was observed that the threshold shear strain amplitude below which no pore water pressure buildup occurs is approximately 1.5 x 10\u-³ for specimens which were not previously shaken. Between the approximate shear strain amplitudes of 1.5 x 10\u-³ and 8.5 x 10\u-³% there was a cyclic strain hardening effect which increased the threshold strain amplitude for specimens which were previously shaken, and caused the pore water pressure of virgin specimens subjected to cyclic strain to stabilize at a predictable level (liquefaction did not occur). All specimens, whether previously shaken or not, liquefied at the threshold strain of 1.2 x10\u-²% which was previously identified to be the shear strain below which gross particle displacement is frictionally blocked. The effect of previous shaking on damping ratios and shear moduli was also investigated.

Depositional Environment of Dry Hollow Member, Upper Cretaceous Frontier Formation, Southwestern Wyoming: ABSTRACT

The Dry Hollow Member of the Frontier Formation in southwestern Wyoming consists of alluvial deposits that accumulated along part of the western margin of the Western Interior Cretaceous seaway. Typically, the lower part of the Dry Hollow Member contains sandstone bodies 4 to 15 m thick that fine upward and possess basal conglomeratic lenses. These units are interpreted as channel deposits of meandering streams, with the conglomerates having formed as channel-lag deposits. Commonly, silicified wood, plant fragments, freshwater gastropods, and intraformational shale clasts are present in these deposits. Medium-scale trough cross-stratification is dominant and indicates a general west to east paleocurrent direction. The upper part of the Dry Hollow Member is dominated by interbedded shales, coals, and thin (0.2 to 1 m) fine-grained sandstones. The shales contain abundant carbonaceous plant material, silicified wood, and lignitic layers. Root horizons are commonly preserved within large (0.3 to 1 m) concretions that formed in the shales. The interbedded fine-grained sandstones are typically small-scale trough cross-stratified and contain abundant plant material. These sandstones are interpreted as near-channel overbank deposits that accumulated during periods of stream flooding, while the shales and coals represent vertical accretion deposits of interchannel swamps and lowlands that accumulated farther from the stream channels. Analysis of these deposits suggests that a wet, poorly-drained fluvial lowland dominated by meandering streams and coal swamps existed along the Western Interior Cretaceous seaway during deposition of the bulk of the Dry Hollow Member of the Frontier Formation. End_of_Article - Last_Page 987------------