Satellite radar remote sensing of seasonal growing seasons for boreal and subalpine evergreen forests

We evaluated whether satellite radar remote sensing of landscape seasonal freeze-thaw cycles provides an effective measure of active growing season timing and duration for boreal and subalpine evergreen forests. Landscape daily radar backscatter measurements from the SeaWinds scatterometer on-board the QuikSCAT satellite were evaluated across a regional network of North American coniferous forest sites for 2000 and 2001. Radar remote sensing measurements of the initiation and length of the growing season corresponded closely with both site measurements and ecosystem process model (BIOME-BGC) simulations of these parameters because of the sensitivity of the K_u-band scatterometer to snow cover freeze-thaw dynamics and associated linkages between growing season initiation and the timing of seasonal snowmelt. In contrast, remote sensing estimates of the timing of growing season termination were either weakly or not significantly associated with site measurements and model simulation results, due to the relative importance of light availability and other environmental controls on stand phenology in the fall. Regional patterns of estimated annual net primary production (NPP) and component photosynthetic and autotrophic respiration rates for the evergreen forest sites also corresponded favorably with remote sensing estimates of the seasonal timing of spring thaw and associated growing season length, indicating the importance of these parameters in determining spatial and temporal patterns of NPP and the potential utility of satellite radar remote sensing for regional monitoring of the terrestrial biosphere.     

Execution History Guided Instruction Prefetching

The increasing gap in performance between processors and main memory has made effective instructions prefetching techniques more important than ever. A major deficiency of existing prefetching methods is that most of them require an extra port to I-cache. A recent study by Rivers et al. [19] shows that this factor alone explains why most modern microprocessors do not use such hardware-based I-cache prefetch schemes. The contribution of this paper is two-fold. First, we present a method that does not require an extra port to I-cache. Second, the performance improvement for our method is greater than the best competing method BHGP [23] even disregarding the improvement from not having an extra port. The three key features of our method that prevent the above deficiencies are as follows. First, late prefetching is prevented by correlating misses to dynamically preceding instructions. For example, if the I-cache miss latency is 12 cycles, then the instruction that was fetched 12 cycles prior to the miss is used as the prefetch trigger. Second, the miss history table is kept to a reasonable size by grouping contiguous cache misses together and associated them with one preceding instruction, and therefore, one table entry. Third, the extra I-cache port is avoided through efficient prefetch filtering methods. Experiments show that for our benchmarks, chosen for their poor I-cache performance, an average improvement of 9.2% in runtime is achieved versus the BHGP methods [23], while the hardware cost is also reduced. The improvement will be greater if the runtime impact of avoiding an extra port is considered. When compared to the original machine without prefetching, our method improves performance by about 35% for our benchmarks.     

Citywide: Supporting Interactive Digital Experiences Across Physical Space

The Citywide project is exploring ways in which technology can provide people with rich and engaging digital experiences as they move through physical space, including historical experiences, performances and games. This paper describes some initial results and experiences with this project based upon two prototype demonstrators. In the first, we describe an application in which a search party explores an archaeological site, uncovering enacted scenes within the virtual world that are of a historical relevance to their particular physical location. In the second, we describe a museum experience where participants explore an outdoors location, hunting for buried virtual artifacts that they then bring back to a museum for a more detailed study. Our demonstrators employ a varied set of devices, including mobile wireless interfaces for locating hotspots of virtual activity when outdoors, to give different experiences of the virtual world depending upon location, task, available equipment and accuracy of tracking. We conclude by discussing some of the potential advantages of using an underlying shared virtual world to support interactive experiences across extended physical settings.     

Formal methods for verification and validation of partial specifications: A case study

This paper describes our work exploring the suitability of formal specification methods for independent verification and validation (IV&V) of software specifications for large, safety-critical systems. An IV&V contractor often has to perform rapid analysis on incomplete specifications, with no control over how those specifications are represented. Lightweight formal methods show significant promise in this context, as they offer a way of uncovering major errors without the burden of full proofs of correctness. We describe a case study of the use of partial formal models for IV&V of the requirements for Fault Detection Isolation and Recovery on the space station. We conclude that the insights gained from formalizing a specification are valuable, and it is the process of formalization, rather than the end product, that is important. It was only necessary to build enough of the formal model to test the properties in which we were interested. Maintenance of fidelity between multiple representations of the same requirements (as they evolve) is still a problem, and deserves further study.     

Investigation of HgCdTe p-n device structures grown by liquid-phase epitaxy

The microstructure of p-n device structures grown by liquid-phase epitaxy (LPE) on CdZnTe substrates has been evaluated using transmission electron microscopy (TEM). The devices consisted of thick (∼21-μm) n-type layers and thin (∼1.6-μm) p-type layers, with final CdTe (∼0.5 μm) passivation layers. Initial observations revealed small defects, both within the n-type layer (doped with 8×10¹⁴/cm³ of In) and also within the p-type layer but at a much reduced level. These defects were not visible, however, in cross-sectional samples prepared by ion milling with the sample held at liquid nitrogen temperature. Only isolated growth defects were observed in samples having low indium doping levels (2×10¹⁴/cm³). The CdTe passivation layers were generally columnar and polycrystalline, and interfaces with the p-type HgCdTe layers were uneven. No obvious structural changes were apparent in the region of the CdTe/HgCdTe interfaces as a result of annealing at 250°C.     

Producing mind

Those who support a computationalist view of the mind tend to hold that it must apply to all aspects of mentality. This view is called computational universalism. An apparently opposed perception-phenomenal universalism-is that consciousness is at the root of all mental processes. Computationalists tend to cognitivize, or otherwise play down, phenomenal consciousness. The recent book by David Chalmers proposes one way to take both computation and phenomenal consciousness seriously. A different way is explored here, which avoids the commitment to a non-materialist ontology of consciousness in Chalmers' position. This alternative approach rejects universalism of both the computational and the phenomenal kinds. Instead a pluralistic view of mind is proposed. Cognitive and phenomenal aspects of mind are to be taken as equally fundamental and as complementary. Cognitive or productive aspects of mind have their own kind of reality which is independent of consciousness. Semantic content may well result from the combination of cognitive productivity and consciousness. The view proposed offers solutions to old problems affecting computational accounts.     

Aesthetic 3D model evolution

A new research frontier for evolutionary 2D image generation is the use of mathematical models of aesthetics, with the goal of automatically evolving aesthetically pleasing images. This paper investigates the application of similar models of aesthetics towards the evolution of 3-dimensional structures. We extend existing models of aesthetics used for image evaluation to the 3D realm, by considering quantifiable properties of surface geometry. Analyses used include entropy, complexity, deviation from normality, 1/f noise, and symmetry. A new 3D L-system implementation promotes accurate analyses of surface features, as well as productive rule sets when used with genetic programming. Multi-objective evaluation reconciles multiple aesthetic criteria. Experiments resulted in the generation of many models that satisfied multiple criteria. A human survey was conducted, and survey takers showed a statistically significant preference for high-fitness highly-evolved models over low-fitness unevolved ones. This research shows that aesthetic evolution of 3D structures is a promising new research area for evolutionary design.