External-Memory Algorithms for Processing Line Segments in Geographic Information Systems

In the design of algorithms for large-scale applications it is essential to consider the problem of minimizing I/O communication. Geographical information systems (GIS) are good examples of such large-scale applications as they frequently handle huge amounts of spatial data. In this paper we develop efficient external-memory algorithms for a number of important problems involving line segments in the plane, including trapezoid decomposition, batched planar point location, triangulation, red--blue line segment intersection reporting, and general line segment intersection reporting. In GIS systems the first three problems are useful for rendering and modeling, and the latter two are frequently used for overlaying maps and extracting information from them.     

Milk production, health, behavior, and endocrine responses of cows exposed to electrical current during milking

Six cows were exposed during milkings to electrical current to assess its effects on behavior, health, milking performance, and endocrine responses. Three treatments (0, 4, and 8 mA) were applied in a changeover design over three consecutive 1-wk periods. A cow received the same current treatment during 14 consecutive milkings, beginning with the evening milking (d 1) and ending with the morning milking (d 8). Treatments began 5 min before milking and continued until milking unit removal. Treatments consisted of 60 Hz square wave current of 5-s duration applied every 30 s from udder to hooves. Milk accumulation curves provided information about milk yields, milking times, peak milk flow rates, and times of peak milk flow. Residual milk yields also were measured. Milk was analyzed for protein, fat, and somatic cells. Blood samples from 60 min before to 60 min after treatment were collected, and oxytocin, prolactin, and cortisol concentrations were measured. Behavioral responses to current decreased with time. Changes of milking performance and milk composition were not significant. Changes of milking related cortisol responses during 8-mA current stimulation were significant. Oxytocin release was delayed during 8-mA treatments. Current treatments did not affect prolactin.     

Life table study of Aedes aegypti (Diptera: Culicidae) in Puerto Rico fed only human blood versus blood plus sugar

Life table studies were performed in 1996 with Aedes aegypti (L.) during the low (cool/dry) and high (hot/rainy) dengue virus transmission seasons in Puerto Rico. Mated adult females from field-collected pupae were placed individually in cages and divided into 2 treatment groups: one was fed only human blood and the other human blood plus a 10% sucrose solution. Survival and number of eggs laid were recorded daily for each female. During both seasons, age specific survivorship was higher for the blood plus sugar group, groups fed only human blood had higher reproductive outputs (mx), and net replacement rates (Ro) for blood only groups were higher than for those fed blood plus sugar. Intrinsic rates of growth (r) were the same for both treatments during the low (cool/dry) transmission season, but higher for the blood-only treatment during the high (hot/rainy) transmission season. Our results indicate that feeding on only human blood provides an evolutionary advantage to Ae. aegypti females in Puerto Rico. These results are similar to those from an earlier study carried out with Ae. aegypti in Thailand; the advantage of feeding on human blood does not seem to be restricted to a particular geographic region. We also found that the benefits associated with human feeding persist through epidemiologically different times of the year. We conclude that feeding on human blood is reproductively beneficial for Ae. aegypti, which may increase their contact with human hosts, and therefore may influence their vectorial capacity for dengue viruses through frequent feeding on blood.     

Real-time evaluation and visualization of learner performance in a mixed-reality environment for clinical breast examination

We investigate the efficacy of incorporating real-time feedback of user performance within mixed-reality environments (MREs) for training real-world tasks with tightly coupled cognitive and psychomotor components. This paper presents an approach to providing real-time evaluation and visual feedback of learner performance in an MRE for training clinical breast examination (CBE). In a user study of experienced and novice CBE practitioners (n = 69), novices receiving real-time feedback performed equivalently or better than more experienced practitioners in the completeness and correctness of the exam. A second user study (n = 8) followed novices through repeated practice of CBE in the MRE. Results indicate that skills improvement in the MRE transfers to the real-world task of CBE of human patients. This initial case study demonstrates the efficacy of MREs incorporating real-time feedback for training real-world cognitive-psychomotor tasks.     

The volume integral method of eddy-current modeling: Verification

The volume integral method of eddy-current modeling represents a flaw in metal as a set of electric dipoles located within volume elements or cells defining the flaw volume. Given this dipole distribution, impedance changes may be computed. The electric field of the dipole distribution is determined by an integral equation relating, by means of the electric field Green's tensor, the electric field due to the source to the total electric field in the flaw. The integral equation is solved by assuming that the total electric field is constant in each volume element, resulting in a matrix equation. The method has been programmed for use on a microcomputer. The method and computer program are verified using the analytical solution for a small spherical flaw and three sets of measured impedance data, measured by air-core coils along profiles overlying both surface-breaking and buried simulated flaws of known dimensions. Operating frequencies ranged between 900 and 4000 Hz. Generally agreement is good at lower frequencies ( 1000 Hz). At higher frequencies ( 4000 Hz), the agreement is not as good. This is thought to be due to the inability of the constant electric field approximation to model the steep electric field gradients present in the host metal at high frequency. The results are also sensitive to the method of computation of the electric field due to the source. Some improvements can and should be made to the method.     

Attenuation of second sound in bulk flowing He II

New measurements of second sound attenuation in bulk flowing He II are reported which extend to a region of higher Reynolds number. An expression for the attenuation explicitly containing the quantum vortex line density is developed which allows comparison with vortex line density data taken by other means. A bellows driven experimental apparatus is used to produce bulk flow velocities of 0 to 1 m/sec in a channel of 4.064 mm square internal cross section. Second sound pulses are produced by applying a square voltage pulse 200 s width and variable height to a strain gauge heater. The second sound pulses are detected with thin film sensors mounted 56 and 119 mm downstream. The velocity-dependent attenuation, measured as a function of bulk flow velocity at 1.5, 1.8, and 2.0 K, is compared with data from other researchers. The attenuation, and thus the vortex line density, appears to follow a gradual transition from laminar to turbulent behavior. Current theories do not account for the presence of quantized vortices in bulk flowing He II, where (v _n–v _s), and thus do not explain the observed second sound attentuation in this regime.     

Higher-Order and Modal Logic as a Framework for Explanation-Based Generalization

Certain tasks, such as formal program development and theorem proving, fundamentally rely upon the manipulation of higher-order objects such as functions and predicates. Computing tools intended to assist in performing these tasks are at present inadequate in both the amount of knowledge they contain (i.e., the level of support they provide) and in their ability to learn (i.e., their capacity to enhance that support over time). The application of a relevant machine learning technique—explanation-based generalization (EBG)—has thus far been limited to first-order problem representations. We extend EBG to generalize higher-order values, thereby enabling its application to higher-order problem encodings.Logic programming provides a uniform framework in which all aspects of explanation-based generalization and learning may be defined and carried out. First-order Horn logics (e.g., Prolog) are not, however, well suited to higher-order applications. Instead, we employ Prolog, a higher-order logic programming language, as our basic framework for realizing higher-order EBG. In order to capture the distinction between domain theory and training instance upon which EBG relies, we extend Prolog with the necessity operator of modal logic. We develop a meta-interpreter realizing EBG for the extended language, Prolog, and provide examples of higher-order EBG.     

A Universal Method of Scientific Inquiry

A paradigm of scientific discovery is defined within a first-order logical framework. Within this paradigm, the concept of successful scientific inquiry is formalized and investigated. Among other results, it is shown that a simple method of scientific inquiry is universal in the sense that it leads to success on every problem for which success is in principle possible.