The Effect of a Vibrating Serrated Slice and the Subsequent Paper Formation

Introduction Paper exhibits a wide range of physical and optical properties, all, in essence, can be said to depend on one property, its internal structure, more commonly known as its formation. Generally, the sheet structure is largely determined by the orientation and distribution of the fibers in the finished sheet, both across the sheet and through its thickness. Paper is like most other materials, it is only as strong as its weakest link. Because paper is a complex, heterogeneous material, it is extremely sensitive to the weak link concept. Higher headbox consistencies are being used by the industry to reduce overall water handling in the paper making process. High consistencies create problems with paper formation, pushing the use of various devices to improve the drainage, orientated shear and turbulence to the pulp on the wire. As a result, improvements in formation properties, as well as fiber orientation, can be expected. Slower machines are often equipped with a shake mechanism, which improves sheet formation, but has little effect on the fiber orientation. As the machines get faster, the shake effects decrease, due to the nearly instant setting of the pulp suspension. A stationary serrated slice mechanism, designed for the faster papermachines, causes stock ridges and valleys to occur in a controlled manner as the pulp suspension leaves the headbox. Collapsing of the stock ridges and valleys occur as water is pulled from the web by gravitation and suction forces from drainage elements. Phase changes cause ridges to form valleys and valleys to form ridges. Several phase changes occur as the pulp suspension travels down the machine, until a full collapse results. The collapsing action creates a shear and turbulence to the pulp suspension resulting in improved sheet formation and fiber orientation along the direction of the collapsed ridges. Vibrating the serrated slice mechanism causes the stock ridges and valleys to oscillate back and forth down the length of the machine. The intent of this thesis is to examine the effects the vibrating serrated slice has on paper formation and fiber orientation at above normal headbox consistencies

Relationship between habitat and ant communities in oak-dominated Appalachian forests treated with microbial pesticides.

Ants in the George Washington (Augusta Co. VA, USA) and Monongahela National Forests (Pocahontas Co. WV, USA) were studied using pitfall traps and bait traps to assess the effect of Bacillus thuringiensis var kurstaki (Foray 48F) and gypsy moth nuclear polyhedrosis virus (Gypchek) application on ant communities and the association of habitat characteristics with ants. Ant samples were also compared by forest, sampling year and season, sampling method, and sampling micro-habitat. Pitfall traps were operated for 45 weeks during summers of 1995 to 1997. Bait traps were set up and collected 42 times during the same period. A total of 31,732 ants were collected from pitfall traps and 54,694 ants were collected from bait traps. They belonged to 4 subfamilies, 17 genera, and 33 species. The ant species richness, diversity, abundance, and species composition did not change as a result of the treatments. Both ant abundance and species richness were correlated with soil moisture, elevation, and vegetation structure of the plots. The correlation was stronger for species richness than for abundance. More mesic and higher elevation plots had fewer ants and lower species richness. Ants from the two sampling methods showed different relative abundance and species richness. Pitfall traps caught more species than bait traps. There was no clear seasonal trend in overall ant activities during the sampling season. Comparisons between sampling years showed a very similar species composition and species evenness. There was a significant decrease in ant abundance in 1997, which may have been caused by over-trapping. Some rare species did not appear in the second and third year of sampling. Ant communities on ridges had one more species than those in valleys in the George Washington National Forest. The difference in ant species richness between ridges and valleys was more distinct in the Monongahela National Forest, which had 5 more species on ridges than in valleys. The ants in valleys were also distributed less evenly. The abundance of ants between ridges and valleys was similar

Spatial reasoning to determine stream network from LANDSAT imagery

In LANDSAT imagery, spectral and spatial information can be used to detect the drainage network as well as the relative elevation model in mountainous terrain. To do this, mixed information of material reflectance in the original LANDSAT imagery must be separated. From the material reflectance information, big visible rivers can be detected. From the topographic modulation information, ridges and valleys can be detected and assigned relative elevations. A complete elevation model can be generated by interpolating values for nonridge and non-valley pixels. The small streams not detectable from material reflectance information can be located in the valleys with flow direction known from the elevation model. Finally, the flow directions of big visible rivers can be inferred by solving a consistent labeling problem based on a set of spatial reasoning constraints

A topographic mechanism for arcing of dryland vegetation bands

Banded patterns consisting of alternating bare soil and dense vegetation have been observed in water-limited ecosystems across the globe, often appearing along gently sloped terrain with the stripes aligned transverse to the elevation gradient. In many cases these vegetation bands are arced, with field observations suggesting a link between the orientation of arcing relative to the grade and the curvature of the underlying terrain. We modify the water transport in the Klausmeier model of water-biomass interactions, originally posed on a uniform hillslope, to qualitatively capture the influence of terrain curvature on the vegetation patterns. Numerical simulations of this modified model indicate that the vegetation bands change arcing-direction from convex-downslope when growing on top of a ridge to convex-upslope when growing in a valley. This behavior is consistent with observations from remote sensing data that we present here. Model simulations show further that whether bands grow on ridges, valleys, or both depends on the precipitation level. A survey of three banded vegetation sites, each with a different aridity level, indicates qualitatively similar behavior.Comment: 26 pages, 13 figures, 2 table

Physiographic Features of Faulting in Southern California

The abundance and variety of faults in southern California provide good opportunity for study of landforms created directly by faulting or indirectly by other processes acting upon faulted materials. High-angle gravity faults, high- and low-angle thrusts, and faults with large strike-slip displacement are present (see Chapter IV). Furthermore, all degrees and dates of activity are represented. Landforms created by faulting can be classed as primary and secondary, or as original and subsequent (Lahee, 1952, p. 248). Primary features are those formed by actual fault displacement. They are nearly always modified by erosion, but should be classed as primary until completely effaced. Secondary or fault-line features are those formed solely by other processes acting upon faulted materials. Further subdivision into initial and modified primary forms and into erosional and depositional secondary forms would be possible, but it is not urged

Predicting evolution and visualizing high-dimensional fitness landscapes

The tempo and mode of an adaptive process is strongly determined by the structure of the fitness landscape that underlies it. In order to be able to predict evolutionary outcomes (even on the short term), we must know more about the nature of realistic fitness landscapes than we do today. For example, in order to know whether evolution is predominantly taking paths that move upwards in fitness and along neutral ridges, or else entails a significant number of valley crossings, we need to be able to visualize these landscapes: we must determine whether there are peaks in the landscape, where these peaks are located with respect to one another, and whether evolutionary paths can connect them. This is a difficult task because genetic fitness landscapes (as opposed to those based on traits) are high-dimensional, and tools for visualizing such landscapes are lacking. In this contribution, we focus on the predictability of evolution on rugged genetic fitness landscapes, and determine that peaks in such landscapes are highly clustered: high peaks are predominantly close to other high peaks. As a consequence, the valleys separating such peaks are shallow and narrow, such that evolutionary trajectories towards the highest peak in the landscape can be achieved via a series of valley crossingsComment: 12 pages, 7 figures. To appear in "Recent Advances in the Theory and Application of Fitness Landscapes" (A. Engelbrecht and H. Richter, eds.). Springer Series in Emergence, Complexity, and Computation, 201

Feature Lines for Illustrating Medical Surface Models: Mathematical Background and Survey

This paper provides a tutorial and survey for a specific kind of illustrative visualization technique: feature lines. We examine different feature line methods. For this, we provide the differential geometry behind these concepts and adapt this mathematical field to the discrete differential geometry. All discrete differential geometry terms are explained for triangulated surface meshes. These utilities serve as basis for the feature line methods. We provide the reader with all knowledge to re-implement every feature line method. Furthermore, we summarize the methods and suggest a guideline for which kind of surface which feature line algorithm is best suited. Our work is motivated by, but not restricted to, medical and biological surface models.Comment: 33 page

Application of shuttle imaging radar to geologic mapping

Images from the Shuttle Imaging Radar - B (SIR-B) experiment covering the area of the Panamint Mountains, Death Valley, California, were examined in the field and in the laboratory to determine their usefulness as aids for geologic mapping. The covered area includes the region around Wildrose Canyon where rocks ranging in age from Precambrian to Cenozoic form a moderately rugged portion of the Panamint Mountains, including sharp ridges, broad alluviated upland valleys, and fault-bounded grabens. The results of the study indicate that the available SIR-B images of this area primarily illustrate variations in topography, except in the broadly alluviated areas of Panamint Valley and Death Valley where deposits of differing reflectivity can be recognized. Within the mountainous portion of the region, three textures can be discerned, each representing a different mode of topographic expression related to the erosion characteristics of the underlying bedrock. Regions of Precambrian bedrock have smooth slopes and sharp ridges with a low density of gullies. Tertiary monolithologic breccias have smooth, steep slopes with an intermediate density of gullies with rounded ridges. Tertiary fanglomerates have steep rugged slopes with numerous steep-sided gullies and knife-sharp ridges. The three topographic types reflect the consistancy and relative susceptibility to erosion of the bedrock; the three types can readily be recognized on topographic maps. At present, it has not been possible to distinguish on the SIR-B image of the mountainous terrain the type of bedrock, independent of the topographic expression

The contrasting fission potential-energy structure of actinides and mercury isotopes

Fission-fragment mass distributions are asymmetric in fission of typical actinide nuclei for nucleon number $A$ in the range $228 \lnsim A \lnsim 258$ and proton number $Z$ in the range $90\lnsim Z \lnsim 100$. For somewhat lighter systems it has been observed that fission mass distributions are usually symmetric. However, a recent experiment showed that fission of $^{180}$Hg following electron capture on $^{180}$Tl is asymmetric. We calculate potential-energy surfaces for a typical actinide nucleus and for 12 even isotopes in the range $^{178}$Hg--$^{200}$Hg, to investigate the similarities and differences of actinide compared to mercury potential surfaces and to what extent fission-fragment properties, in particular shell structure, relate to the structure of the static potential-energy surfaces. Potential-energy surfaces are calculated in the macroscopic-microscopic approach as functions of fiveshape coordinates for more than five million shapes. The structure of the surfaces are investigated by use of an immersion technique. We determine properties of minima, saddle points, valleys, and ridges between valleys in the 5D shape-coordinate space. Along the mercury isotope chain the barrier heights and the ridge heights and persistence with elongation vary significantly and show no obvious connection to possible fragment shell structure, in contrast to the actinide region, where there is a deep asymmetric valley extending from the saddle point to scission. The mechanism of asymmetric fission must be very different in the lighter proton-rich mercury isotopes compared to the actinide region and is apparently unrelated to fragment shell structure. Isotopes lighter than $^{192}$Hg have the saddle point blocked from a deep symmetric valley by a significant ridge. The ridge vanishes for the heavier Hg isotopes, for which we would expect a qualitatively different asymmetry of the fragments.Comment: 8 pages, 9 figure