Variable area surveys are used in large geographic regions to estimate the density of birds distributed over a region. If some birds go undetected, a measure of the effective area surveyed, the amount of area occupied by the birds detected, is needed. The effective area surveyed is determined by observational, biological, and environmental factors relating to detectability. It has been suggested that density estimates are inaccurate, and that it is risky to compare bird populations intraspecifically over time and space, since factors influencing bird counts will vary. There have been several controversial studies where variable area survey density estimates were evaluated using density estimates calculated from spot mapping as the standard for comparison. Spot mapping itself is an unproven estimator that the previously mentioned factors also influence. Without a known population density, determining how the different density estimators perform is difficult to access. Variable area surveys of inanimate objects whose densities were known have been conducted under controlled circumstances with results generally supporting the variable area survey method, but time and inability to control for all factors limit the application of this type of study. A simulation program that distributes over a region vegetation and a known density of birds, and then simulates the process of gathering bird detection data is one tool accessible to evaluate variable area density estimates. Within such a simulation study various observational, biological, and environment factors could be introduced. This thesis introduces such a simulation program, VABS, that was written with the objectives of identifying factors that influence bird counts and determining the limitations of the variable area survey. Within this thesis are discussions concerning the several factors that have been identified as influencing bird counts and the effects that these factors had on the Fourier series, exponential power series, and Cum-D density estimates when these factors were simulated in VABS. Critical assumptions of the variable area survey are identified, and the ability of the variable area survey to estimate density for different detectability curve is examined. Also included are discussions on the topics of pooling data gathered under different detectabilities and monitoring population trends. / Graduation date: 1994

Thesis (doctoral)--Helsingfors universitet, 1990. / Summary in English. Includes bibliographical references (p. [141]-145).

Disc golf is one of the fastest growing sports in Sweden and the countrywide playerbase is steadily growing. In order to meet this increased demand, municipalities and sports associations alike have built new courses all around the country, which all require maintenence. Without an accurate way of determining course usage, it's difficult to guage how much money should be put towards maintaining and developing additional courses. The aim of this project was to design and test a people-counting system for disc golf couses which could provide this information to both players and course owners. Computer vision, wireless communication and sensor technologies were core topics explored during the development of the working prototype.

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An ultrametric field is a field that is locally compact as a metric space with respect to a non-archimedean absolute value. The main topic of this dissertation is to study roots of polynomials over such fields. If we have a univariate polynomial with coefficients in an ultrametric field and non-vanishing discriminant, then there is a bijection between the set of roots of the polynomial and classes of roots of the same polynomial in a finite ring. As a consequence, there is a ball in the polynomial space where all polynomials in it have the same number of roots. If a univariate polynomial satisfies certain generic conditions, then we can efficiently compute the exact number of roots in the field. We do that by using Hensel's lemma and some properties of Newton's polygon. In the multivariate case, if we have a square system of polynomials, we consider the tropical set which is the intersection of the tropical varieties of its polynomials. The tropical set contains the set of valuations of the roots, and for every point in the tropical set, there is a corresponding system of lower polynomials. If the system satisfies some generic conditions, then for each point w in the tropical set the number of roots of valuation w equals the number roots of valuation w of the lower system. The last result enables us to compute the exact number of roots of a polynomial system where the tropical set is finite and the lower system consists of binomials. This algorithmic method can be performed in polynomial-time if we fix the number of variables. We conclude the dissertation with a discussion of the feasibility problem. We consider the problem of the p-adic feasibility of polynomials with integral coefficients with the prime number p as a part of the input. We prove this problem can be solved in nondeterministic polynomial-time. Furthermore, we show that any problem, which can be solved in nondeterministic polynomial-time, can be reduced to this feasibility problem in randomized polynomial-time.

A distributed system consists of a set of N processor nodes and a finite set of communication channels. It is frequently described as a directed graph in which each vertex represents a processor node and the edges represent the communication channels. A global snapshot of a distributed system consists of the local states of all the processor nodes and all of the in-transit messages of a distributed computation. This is meaningful as it corresponds to the global state where all the local states and communication channels of all the processor nodes in the system are recorded simultaneously. A classic example where snapshots are utilized is in the scenario of some failure where the system can restart from the last global snapshot. This is an important application of global snapshot algorithms as it forms the basis for fault-tolerance in distributed programs and aids in serviceability as a distributed program debugging mechanism. Another important application includes checkpointing and monitoring systems where a set of continuous global snapshots are employed to detect when a certain number of triggers have been received by the system. When the distributed system is scaled in terms of an increase in the number of processor nodes and an increase in the number of expected triggers the message complexity increases and impacts the total overhead for the communication and computation of the global snapshot algorithm. In such a large distributed system, an optimal algorithm is vital so that the distributed application program that is employing the snapshots does not suffer from performance degradation as the size of the distributed system continues to grow over time. We are interested in global snapshot algorithms that offer lower bound message complexity and lower bound MaxLoad messages for large values of N processor nodes and large values of W expected triggers. In this report we study and simulate the Centralized, Grid based, Tree Based, and LayeredRand global snapshot algorithms then evaluate the algorithms for total number of messages (sent and received) and MaxLoad messages (sent and received) for the trigger counting problem in distributed computing. The report concludes with simulation results that compare the performance of the algorithms with respect to the total number of messages and MaxLoad messages required by each algorithm to detect when the number of W triggers have been delivered to the distributed system. / text

Thesis (M.S.)--University of Michigan, 1959. / Project completed in 1958. Degree awarded in 1959.

Microchannel plate (MCP) detectors have been the detector of choice for ultraviolet (UV) instruments onboard many NASA missions. These detectors have many advantages, including high spatial resolution (<20 mu m), photon counting, radiation hardness, large formats (up to 20 cm), and ability for curved focal plane matching. Novel borosilicate glass MCPs with atomic layer deposition combine extremely low backgrounds, high strength, and tunable secondary electron yield. GaN and combinations of bialkali/alkali halide photocathodes show promise for broadband, higher quantum efficiency. Cross-strip anodes combined with compact ASIC readout electronics enable high spatial resolution over large formats with high dynamic range. The technology readiness levels of these technologies are each being advanced through research grants for laboratory testing and rocket flights. Combining these capabilities would be ideal for UV instruments onboard the Large UV/Optical/IR Surveyor (LUVOIR) and the Habitable Exoplanet Imaging Mission (HABEX) concepts currently under study for NASA's Astrophysics Decadal Survey.

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