Guide Modeling Efforts Research Articles

Variability in surge levels in communities adjacent to the Houston Ship Channel industrial Corridor to changes in Hurricane characteristics

ABSTRACT The sensitivity of hurricane-driven storm surge in the Houston Ship Channel Industrial Corridor to variations in storm characteristics is studied. Hurricane surge from Hurricane Ike from 2008 was simulated using the Delft3D Flexible Mesh model. Use of the HURDAT2 wind parameter database allowed alteration of relevant hurricane characteristics to develop these alternate scenarios. Moving the actual landfall location of Ike toward the southwest at a distance of 50 km yielded a 123% increase at Manchester relative to observations during the storm. Relocation of the landfall location 200 km further southwest caused a 40% decrease in water level at the Galveston Bay entrance relative to observed values, but with a corresponding 50% water level increase at Manchester. Reduction of the storm forward speed to 25% of the actual speed over the nearshore led to a 25% increase in water level in Manchester over recorded values, while a 57% reduction of the storm forward speed over land increased water levels in Manchester by 30%. Incorporating river flow also identified locations where Galena Park’s residual floodwater is likely to remain after flooding. The results of this work can be used to guide modeling efforts of storm impacts on areas with narrow waterways.

Gas Separation Membrane Module Modeling: A Comprehensive Review.

Membrane gas separation processes have been developed for diverse gas separation applications that include nitrogen production from air and CO2 capture from point sources. Membrane process design requires the development of stable and robust mathematical models that can accurately quantify the performance of the membrane modules used in the process. The literature related to modeling membrane gas separation modules and model use in membrane gas separation process simulators is reviewed in this paper. A membrane-module-modeling checklist is proposed to guide modeling efforts for the research and development of new gas separation membranes.

Laboratory Investigation of Hydraulic Fracture Growth in Zimbabwe Gabbro

AbstractDirect measurement of the apparent toughness evolution during hydraulic fracture growth remains challenging in rocks due to the difficulty of measuring the time evolution of the fracture geometry. We report hydraulic fracturing tests performed in 250 × 250 × 250 mm Zimbabwe gabbro under different confining stress. Using time‐lapse active acoustic surveys, we reconstruct the fracture front and fracture width using scattered and transmitted waves. After verifying that hydraulic fracture growth is dominated by the energy dissipated in fracture creation such that the fluid pressure can be considered spatially uniform in the fracture (negligible viscous flow energy dissipation), we estimate the apparent fracture toughness, using the theory of linear hydraulic fracture mechanics, by combining fracture geometry and pressure data. The apparent fracture energy is higher than that measured from semicircular bending tests. The created fractures evolve in a planar and radial geometry at the macroscopic scale, but we observe overlapping segments and bridges at the millimetric scale. This complex segmentation at a scale on par with the rock grain size is likely responsible for the observed higher fracture energy at centimetric scale. Such fracture segmentation and bridging will necessarily occur when encountering heterogeneities and result in a further increase of fracture energy at a larger scale even if the overall macroscopic geometry remains planar. The experimental data set reported here should guide modeling efforts necessary to better predict hydraulic fracture growth in rock masses.

Hydrogenase Enzymes and Their Synthetic Models: The Role of Metal Hydrides.

Hydrogenase enzymes efficiently process H2 and protons at organometallic FeFe, NiFe, or Fe active sites. Synthetic modeling of the many H2ase states has provided insight into H2ase structure and mechanism, as well as afforded catalysts for the H2 energy vector. Particularly important are hydride-bearing states, with synthetic hydride analogues now known for each hydrogenase class. These hydrides are typically prepared by protonation of low-valent cores. Examples of FeFe and NiFe hydrides derived from H2 have also been prepared. Such chemistry is more developed than mimicry of the redox-inactive monoFe enzyme, although functional models of the latter are now emerging. Advances in physical and theoretical characterization of H2ase enzymes and synthetic models have proven key to the study of hydrides in particular, and will guide modeling efforts toward more robust and active species optimized for practical applications.

Bayesian model selection framework for identifying growth patterns in filamentous fungi

This paper describes a rigorous methodology for quantification of model errors in fungal growth models. This is essential to choose the model that best describes the data and guide modeling efforts. Mathematical modeling of growth of filamentous fungi is necessary in fungal biology for gaining systems level understanding on hyphal and colony behaviors in different environments. A critical challenge in the development of these mathematical models arises from the indeterminate nature of their colony architecture, which is a result of processing diverse intracellular signals induced in response to a heterogeneous set of physical and nutritional factors. There exists a practical gap in connecting fungal growth models with measurement data. Here, we address this gap by introducing the first unified computational framework based on Bayesian inference that can quantify individual model errors and rank the statistical models based on their descriptive power against data. We show that this Bayesian model comparison is just a natural formalization of Occam׳s razor. The application of this framework is discussed in comparing three models in the context of synthetic data generated from a known true fungal growth model. This framework of model comparison achieves a trade-off between data fitness and model complexity and the quantified model error not only helps in calibrating and comparing the models, but also in making better predictions and guiding model refinements.

Income and Pollutant Emissions in the ObjECTS MiniCAM Model

This article examines the relationship between income and pollutant emissions in the Obj ECTS Mini Climate Assessment Model (MiniCAM) to determine how historical analysis can best guide modeling efforts. Future scenarios for energy-related emissions of nitrous oxide (NOx ) and sulfur dioxide (SO2 )are presented along with the methodology used. A pseudo-Kuznets approach is used where the level of emission control is assumed to vary with per capita income. Emission results depend on the assumptions for when emission controls are implemented and the stringency of those controls. Historical analysis of the relationship between income and emission controls might be particularly useful in informing the parameterization of when emission controls are implemented. However, historical analysis is likely to be less helpful in informing the selection of parameters for the future levels of control, particularly at future times when parameter values are well outside the range of historical experience.

Experiments on collapsing cylindrical flames

This article is concerned with the effect of curvature on laminar flame dynamics. This topic is of fundamental interest and it has practical implications in turbulent combustion. It is shown that highly curved premixed flames may be obtained by operating a standard axisymmetric burner in a specific pulsed mode. Collapsing cylindrical flames are observed by submitting the burner to suitably tuned plane pulsations of the flow velocity. The cylindrical flame pattern collapses in an essentially radial motion. In these circumstances the flame cylinder separates unburned inner gases from the burned outer flow. The temporal evolution of the flame may be monitored using schlieren images while the inner flow velocity is determined from particle image velocimetry (PIV). It is shown that these data yield the stretched laminar burning velocity up to very small radii. Models of the stretched laminar burning velocity as a function of curvature are compared to experimental data and Markstein lengths are deduced. These experiments indicate how laminar flames respond to large curvature values. The data gathered may be used to guide modeling efforts in the area of turbulent combustion.

Seasonal Habitat Use by Sitka Black-Tailed Deer on Admiralty Island, Alaska

We measured seasonal habitat use by 30 radio-collared Sitka black-tailed deer (Odocoileus hemionus sitkensis) on northern Admiralty Island in southeastern Alaska from February 1979 to July 1982. Habitat use varied seasonally as deer moved from low-elevation ( 600 m) summer ranges in open canopy subalpine and alpine habitats. Deer used oldgrowth forest almost exclusively during winter and spring, and high-volume old growth (>74 mbf/ha) was used in much greater proportion than its abundance. To minimize the impacts of timber harvesting on deer populations, emphasis should be placed on maintaining stands of high-volume old growth on low-elevation deer winter ranges. J. WILDL. MANAGE. 54(3):371-378 The Sitka black-tailed deer in southeastern Alaska occurs at the northern limit of its natural range (Wallmo 1981). This subspecies inhabits a densely forested coastal environment where deep winter snows are the major factor limiting population size (Klein and Olson 1960). In high snowfall regions of the Pacific Northwest and in southeastern Alaska, low-elevation old-growth forest has been identified as essential deer winter range (Bloom 1978, Wallmo and Schoen 1980, Bunnell and Jones 1984). The 6.8 million-ha Tongass National Forest encompasses over 80% of the land area of southeastern Alaska. Approximately 7,000 ha of old growth on National Forest lands, as well as additional thousands on state and private lands, are scheduled for harvest annually (U.S. For. Serv. [USFS] 1988). Converting old-growth forests to younger seral forests in Alaska will reduce forage availability and consequently deer carrying capacity (Wallmo and Schoen 1980, Alaback 1982). In southeastern Alaska, the old-growth forest is variable in structure and composition on a fine-grained (<1 ha) scale (Schoen et al. 1984). Timber harvesting in this region has been concentrated in the most economically valuable oldgrowth stands, specifically on low-elevation, high-volume sites (Hutchison and LaBau 1975, Schoen et al. 1988). An understanding of the seasonal habitat use of deer, including their use within the forest mosaic, will help managers identify important habitats and guide modeling efforts aimed at predicting the effects of timber harvesting on deer populations in southeastern Alaska. We assume that current habitat preferences are indicative of long-term habitat requirements or needs (Fagen 1988, Ruggiero et al. 1988). Our objectives were to determine seasonal habitat use of radio-collared deer and to describe the implications of harvesting timber on deer populations in southeastern Alaska. Our project was supported by the Alaska Department of Fish and Game through Federal Aid in Wildlife Restoration Project W-17, W-21, and W-22, and the U.S. Forest Service, Pacific Northwest Forest and Range Experiment Station. We recognize the late O. C. Wallmo for his cooperation, advice, and encouragement during the initial stages of this study; G. G. Fisch, L. R. Beier, L. H. Holton, L. J. Johnson, and J. W. Lentfer for their assistance during this study; and D. A. Anderson, R. W. Flynn, L. M. McManus, and W. L. Regelin for reviewing this manuscript. D. R. McCullough and an anonymous reviewer offered valuable editorial suggestions.