Optimization of Geoscience Laser Altimeter System waveform metrics to support vegetation measurements

The Geoscience Laser Altimeter System (GLAS) has collected over 250 million measurements of vegetation height over forests globally. Accurate vegetation heights can be determined using waveform metrics that include vertical extent and extent of the waveform's trailing and leading edges. All three indices are highly dependent upon the signal strength, background noise and signal-to-noise ratio of the waveform, as the background noise contribution to the waveforms has to be removed before their calculation. Over the last six years, GLAS has collected data during thirteen observation periods using illumination from three different lasers. The power levels of these lasers have changed over time, resulting in variable signal power and noise characteristics. Atmospheric conditions vary continuously, also influencing signal power and noise.To minimize these effects, we optimized a noise coefficient which could be constant or vary according to observation period or noise metric. This parameter is used with the mean and standard deviation of the background noise to determine a noise level threshold that is removed from each waveform. An optimization analysis was used with a global dataset of waveforms that are near-coincident with waveforms from other observation periods; the goal of the optimization was to minimize the difference in vertical extent between spatially overlapping GLAS observations. Optimizations based on absolute difference in height led to situations in which the total extent was minimized as well; further optimizations reduced a normalized difference in height extent. The simplest optimizations were based on a constant value to be applied to all observations; noise coefficients of 2.7, 3.2, 3.4 and 4.0 were determined for datasets consisting of global forests, global vegetation, forest in the legal Amazon basin and boreal forests respectively. Optimizations based on the power level or the signal-to-noise ratio of waveforms best minimized differences in waveform extent, decreasing the percent root mean squared height difference by 25-54% over the constant value approach. Further development of methods to ensure temporal consistency of waveform indices will be necessary to support long-term satellite lidar missions and will result in more accurate and precise estimates of canopy height.     

基于Lotus Notes的分布式信息商函系统的设计与实现

设计并实现了一种基于Ｌｏｔｕｓ Ｎｏｔｅｓ的分布式信息邮政商业信函系统,并研究了系统实现过程中的两个关键技术。     

The Automatic Acquisition, Evolution and Reuse of Modules in Cartesian Genetic Programming

This paper presents a generalization of the graph- based genetic programming (GP) technique known as Cartesian genetic programming (CGP). We have extended CGP by utilizing automatic module acquisition, evolution, and reuse. To benchmark the new technique, we have tested it on: various digital circuit problems, two symbolic regression problems, the lawnmower problem, and the hierarchical if-and-only-if problem. The results show the new modular method evolves solutions quicker than the original nonmodular method, and the speedup is more pronounced on larger problems. Also, the new modular method performs favorably when compared with other GP methods. Analysis of the evolved modules shows they often produce recognizable functions. Prospects for further improvements to the method are discussed.     

Who Are You? The Trade-Off between Information Utility and Privacy

There's no doubt that personal information can be valuable to companies. People are willing to give up information about themselves not because they're stupid or because they're being tricked by evil corporations, but because it can sometimes be in their best interests to do so. From this perspective, the important questions are how users can provide or limit access to that information, what benefits they might receive in exchange for a bit of information, and how they perceive the value of those benefits.     

A methodology for measuring in situ lattice strain of bulk polycrystalline material under cyclic load

The material response of polycrystalline materials under cyclic loading is not fully understood. Even during uniaxial loading, individual grains embedded within the polycrystalline material can experience complicated strain histories. By quantifying the deformation state at the crystal level, we can begin to understand the conditions that lead to fatigue failure. An in situ powder diffraction method was developed and employed at the Cornell High Energy Synchrotron Source to measure the aggregate crystal response at various points in a material's life using synchrotron x ray. A set of experiments was conducted using a load frame capable of exerting cyclic uniaxial loads on a specimen. A high speed x-ray shutter was developed to synchronize the x-ray beam and the loading cycle. Using the high speed shutter, the evolution of the lattice strains for the families of crystallographic planes was measured while the aggregate was under cyclic uniaxial loading, thus monitoring a live evolution of lattice strain in a cyclically loaded specimen. The methodology is demonstrated using uniaxial cyclic specimens machined from oxygen free conductivity (OFHC) copper sheet.     

Atom probe tomography characterization of solute segregation to dislocations

The extent and level of solute segregation to individual dislocations may be quantified by atom probe tomography. The technique is best applied to materials with high dislocation densities, such as cold worked, mechanically alloyed, or neutron-irradiated materials. Dislocations may be observed in field ion images by a change of the normal concentric atom terraces at crystallographic poles to spirals. Solute segregation is evident in field ion images by brightly imaging atoms near the core of the dislocation. Dislocations are evident in atom maps in the three-dimensional atom probe by linear regions of enhanced solute concentration. The maximum separation envelope and tracer methods may be used to quantify the levels of solute at the dislocation at the subnanometer scale. Examples of interstitial and substitutional element segregation in a mechanically alloyed, oxide dispersion strengthened ferrite steel and phosphorus segregation to dislocations in neutron-irradiated pressure vessel steels are presented.     

A parallel algorithm for approximate regularity

Spatial regularity amidst a seemingly chaotic image is often meaningful. Many papers in computational geometry are concerned with detecting some type of regularity via exact solutions to problems in geometric pattern recognition. However, real-world applications often have data that is approximate, and may rely on calculations that are approximate. Thus, it is useful to develop solutions that have an error tolerance.

A solution has recently been presented by Robins et al. [Inform. Process. Lett. 69 (1999) 189–195] to the problem of finding all maximal subsets of an input set in the Euclidean plane that are approximately equally-spaced and approximately collinear. This is a problem that arises in computer vision, military applications, and other areas. The algorithm of Robins et al. is different in several important respects from the optimal algorithm given by Kahng and Robins [Patter Recognition Lett. 12 (1991) 757–764] for the exact version of the problem. The algorithm of Robins et al. seems inherently sequential and runs in O(n^5/2) time, where n is the size of the input set. In this paper, we give parallel solutions to this problem.     

Prophylactic efficacy of tilmicosin for bovine respiratory tract disease

The prophylactic administration of injectable tilmicosin for pneumonia in weaned beef calves was investigated in 1,806 animals. Comparisons were made among calves receiving an "on-arrival" injection of tilmicosin, calves receiving a single injection of long-acting oxytetracycline, and calves receiving no prophylaxis. Morbidity and mortality attributable to pneumonia, morbidity and mortality attributable to all causes, and case fatality were significantly lower in the group of calves that received tilmicosin, compared with calves that received long-acting oxytetracycline and calves that received no prophylactic antibiotic. Mean time to initial pneumonia treatment was significantly extended in calves that received prophylaxis, compared with those that received no antibiotic on arrival at the feedlot. Calves that received tilmicosin gained significantly more weight than calves that received oxytetracycline. Calves that were not treated for pneumonia during the trial period gained significantly more weight than did those calves that were treated for pneumonia regardless of experimental group. The majority of mortalities were attributable to fibrinous pneumonia (31/34). Important bacterial isolates (Pasteurella spp, Haemophilus somnus, Actinomyces pyogenes) obtained at necropsy did not have resistance to tilmicosin in association with administration of tilmicosin as prophylaxis for pneumonia. However, bacterial resistance to trimethoprim/sulfonamide and to oxytetracycline were commonly found in these postmortem isolates.     

The continuing dilemma concerning medical versus surgical management of patients with acute type B dissections

In the free-running circadian rhythms of 14 human subjects (4 females, 10 males) who lived singly in an isolation unit without temporal clues, locomotor activity was recorded by means of contact plates installed below the carpet in the main room. During sleep, movements in bed were picked up by spring contacts attached to the mattress. In all subjects, the hourly means of locomotion during wakefulness (alpha) were negatively correlated with the duration of alpha to such an extent that the total amount of locomotion per cycle remained constant when alpha varied from 14 to 23 hr. The hourly values of movements in bed were independent of the duration of sleep (rho), so that the total number of movements was almost proportional to rho. The "homeostatic control" of locomotion during wake time is considered as a means to conserve energy when the duration of wakefulness increases.