Weedpatch syndrome II: an examination of the wildflower movement in North America

This paper describes the origin, strengths and shortcomings of the wildflower movement in North America. At present, the wildflower industry needs to improve the longevity of seed mixes and provide mixes that are more applicable to a wider variety of site conditions and regions. In addition, some alien wildflowers should not be introduced to the North American landscape; in contrast, the potential of some native species regarded s weeds is being overlooked. The present situation in North America for the implementation and a management of landscapes with wildflowers can be described as an integrated design approach.     

Ptex: Per‐Face Texture Mapping for Production Rendering

Explicit parameterization of subdivision surfaces for texture mapping adds significant cost and complexity to film production. Most parameterization methods currently in use require setup effort, and none are completely general. We propose a new texture mapping method for Catmull‐Clark subdivision surfaces that requires no explicit parameterization. Our method, Ptex, stores a separate texture per quad face of the subdivision control mesh, along with a novel per‐face adjacency map, in a single texture file per surface. Ptex uses the adjacency data to perform seamless anisotropic filtering of multi‐resolution textures across surfaces of arbitrary topology. Just as importantly, Ptex requires no manual setup and scales to models of arbitrary mesh complexity and texture detail. Ptex has been successfully used to texture all of the models in an animated theatrical short and is currently being applied to an entire animated feature. Ptex has eliminated UV assignment from our studio and significantly increased the efficiency of our pipeline.     

Non-linear characteristics of engineering soils

The paper deals with the non-linear stress-strain characteristics of engineering soils and investigates some of the more important factors relating to the elasto-plastic behaviour. A review of previous literature describes some of the work already performed in this area of study, and discusses the applicability of the theories proposed, most of which have been established using results obtained from a standard tri-axial test. A non-linear stress-strain theory is formulated, using results from a true tri-axial test, which also takes into account the behaviour of the soil during unloading and subsequent reloading. This behaviour is shown to depend on the stress levels attained in the unloading/reloading hysteresis loop in which the reloading portion of the loop is closely linearly elastic. Finally, the suitability of the proposed equations in typical engineering calculations is discussed and a worked example is included which demonstrates how the proposed incremental stress-strain equations may be applied in analysis.

List of symbols

The notation used in the theoretical work is as follows: E modulus of elasticity of soil - H vertical depth of cavity - K ₀ coefficient of earth pressure at rest assumed constant with depth - K _r Rankine ratio=(1 – sin )/(1 + sin ) - K, K ₁,K ₂,f ₁,f ₂,g, m, n constants found experimentally - k R ₀ ²/R₁ ² - p _h stress in any horizontal direction whenp _x =P _z =P _h - p _r radial stress - p _x stress inx-direction - p _y vertical stress - p _z stress in z-direction - p _xi ,p _yi ,p _zi stress levels in co-ordinate directions at commencement of unloading/reloading cycle - p _xf ,p _yf ,p _zf stress levels in co-ordinate directions at end of unloading portion of unloading/reloading cycle - p circumferential stress - p _u ultimate pressure in cavity - R ₀ initial radius of cavity - R ₁ ultimate radius of cavity - R ₂ radius of plastic zone - r a radial distance from centre of cavity to typical element in elastic or plastic zone - r ₁,r ₂,r ₃ stress ratiosp _x (ultimate)/p _xi ,p _y (ultimate)/p _yi ,p _z (ultimate)/p _zi respectively - t step length - w radial displacement of elastic zone - soil density - average volumetric strain of plastic zone - _r volumetric strain of increment of plastic zone - _pr , _r , etc. a small increment of the quantity concerned - _r radial strain - _x strain inx-direction - _y vertical strain - _z strain inz-direction - circumferential strain - _xyi etc strain in thex-direction due to loading in-direction at commencement of unloading/reloading cycle, etc. - _xyf , etc strain in thex-direction due to loading in-direction at end of unloading portion of unloading/ reloading cycle, etc. - Poisson's ratio - angle of internal friction of soil     

Sorted Deferred Shading for Production Path Tracing

Ray‐traced global illumination (GI) is becoming widespread in production rendering but incoherent secondary ray traversal limits practical rendering to scenes that fit in memory. Incoherent shading also leads to intractable performance with production‐scale textures forcing renderers to resort to caching of irradiance, radiosity, and other values to amortize expensive shading. Unfortunately, such caching strategies complicate artist workflow, are difficult to parallelize effectively, and contend for precious memory. Worse, these caches involve approximations that compromise quality. In this paper, we introduce a novel path‐tracing framework that avoids these tradeoffs. We sort large, potentially out‐of‐core ray batches to ensure coherence of ray traversal. We then defer shading of ray hits until we have sorted them, achieving perfectly coherent shading and avoiding the need for shading caches.     

Surface analysis of poor printability PVC films

Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS) were employed to analyze the surfaces of PVC films with poor printability. FTIR indicated that, independent of formulation, the migrating species were metal carboxylates. Different techniques penetrate the surface to different depths allowing examination of a range of surface layers. XPS indicated that, in the worst case, the upper surface layer was comprised almost exclusively of a mixed metal carboxylate. Atom percentages obtained by XPS indicated hydrolysis of the mixed metal carboxylate at the vinyl surface.     

High-density support matrices: Key to the deep borehole disposal of spent nuclear fuel

Deep (4-5 km) boreholes are emerging as a safe, secure, environmentally sound and potentially cost-effective option for disposal of high-level radioactive wastes, including plutonium. One reason this option has not been widely accepted for spent fuel is because stacking the containers in a borehole could create load stresses threatening their integrity with potential for releasing highly mobile radionuclides like ¹²⁹I before the borehole is filled and sealed. This problem can be overcome by using novel high-density support matrices deployed as fine metal shot along with the containers. Temperature distributions in and around the disposal are modelled to show how decay heat from the fuel can melt the shot within weeks of disposal to give a dense liquid in which the containers are almost weightless. Finally, within a few decades, this liquid will cool and solidify, entombing the waste containers in a base metal sarcophagus sealed into the host rock.     

Photolytic Behavior of Silver Iodide

Silver iodide exposed to high intensity radiation in the visible light spectrum was found to yield a powder X-ray diffraction pattern showing marked deviations from ideality. It was found possible to correlate these with a decrease in primary extinction, indicating a constant progress from an ideal to a mosaic type crystallinity. Large single crystals showed pronounced asterism in transmission Laue photographs under similar experimental conditions. Small amounts of colloidal silver were detected. A mechanism for this process in silver iodide is proposed, in general agreement with the theory of the photographic process. The primary difference from the other silver halides appears to be a considerably slower rate, permitting the observation of a two step process in detail.     

Modelling dispersive optical fibres with a circuit simulator

The authors describe a new approach to modelling the optical electric field envelope function using a standard circuit simulator, show application to the calculation of dispersive linear propagation in a uniform single-mode optical fibre, and demonstrate that such a model can be integrated with an existing model of a semiconductor laser