Optical gradation for crushed limestone aggregates

The strength and durability of asphalt pavement is directly affected by the characteristics of its main ingredient, mineral aggregate. Besides material strength, research has shown that mixture properties such as particle shape and mixture gradation have a significant affect on the quality of the asphalt concrete. A standard called Superpave has been developed which sets forth specifications for material selection and methods for measurement of aggregate properties. These standards require monitoring of aggregate properties, particularly gradation. In this dissertation, the feasibility of developing an optically based method for determining aggregate gradation was explored. The physical system primarily consists of a standard monochrome CCD video camera and a computer with a frame grabber board. Software was developed to separate touching or overlapping particles in the image, and to detect the size and shape of each particle. Correlation to estimate each particle\u27s mass and to predict the sieving behavior for crushed limestone aggregates was developed and tested. Laboratory testing demonstrated the ability to measure gradation over a range of particle sizes from 4.75 mm to 25 mm with an accuracy of +/-3 in terms of percent-passing residual when compared with mechanical sieving

The dissolution of magnesium in strong acids and neutral solutions

The increasing demand for magnesium and magnesium- base alloys in the manufacture of aircraft has stimulated a great amount of research into the corrosion characteristics of these materials. The result of such research has been the development of suitable magnesium alloys and protective coatings to retard corrosion. The basic mechanism of the anodic dissolution of metals such as magnesium, zinc, and cadmium in salt solutions is not completely known. Several schools of investigators have proposed different and opposing theories to explain the discrepancies which often arise between coulometer data and the weight loss of metal electrodes in certain salt solutions. The purpose of this investigation was to study the anion effect on the dissolution and disintegration of magnesium. If anion adsorption is important in these processes, then varying the ionic species present should alter kinetic parameters for the dissolution reaction and the apparent valence for the disintegration. To this end, the self-dissolution was studied in hydrochloric, hydrobromic, and hydriodic acids and the anodic dissolution in one normal solutions of potassium sulfate, potassium chloride, potassium nitrate, potassium bromide, and potassium iodide --Introduction, page 1

Finite element analysis for the navier - stokes equations

The finite element method was employed to solve two-dimensional, unsteady, incompressible, viscous fluid flow problems. A practical computation procedure is presented. A complete finite element computer program has been developed. The numerical technique is based upon a general formulation for the Navier-Stokes equations making use of a combined variational principle finite element approach. Solution to the system of algebraic equations is approached by the Gaussian elimination scheme. The time-dependent Navier-Stokes equations are expressed in terras of a stream function equation and a transport equation. A variational functional of the stream function and a pseudo-variational functional of the vorticity of the respective boundary value problem is presented. The pressure distribution and velocity profile are determined from stream function. Two numerical examples are presented and compared with present papers. Some now ideas about the numerical method, obtained through numerical experiments, are presented and discussed

Parton Distributions in the Virtual Photon Target and Factorization Scheme Dependence

We investigate parton distributions in the virtual photon target, both polarized and unpolarized, up to the next-leading order (NLO) in QCD. Parton distributions can be predicted completely up to NLO, but they are factorization-scheme-dependent. We analyze parton distributions in several factorization schemes and discuss their scheme dependence. Particular attentions are paid to the axial anomaly effect on the first moments of the polarized quark parton distributions, and also to the large-$x$ behaviors of polarized and unpolarized parton distributions.Comment: 6 pages, LaTeX, 3 ps figures, uses npb.sty, Contribution to the Zeuthen Workshop on Elementary Particle Theory: Loops and Legs in Quantum Field Theory, Koenigstein-Weissig, Germany, April 200

Behavioral ecology of odometric memories in desert ants: acquisition, retention, and integration

Assuming that the acquisition and retention of memories have costs, properties of memories should fit the functional requirements for the system of memory. Based on a functional analysis of what path integration is meant to do, we predicted that odometric memories in desert ants should show (1) little improvement with repeated training: performance should be as good after one training trial as after six training trials, (2) decay of memory after 24 h, and (3) performance based solely on the most recent outbound trip, with no integration over multiple memories. Desert ants (Cataglyphis fortis) traveled in narrow straight plastic channels to forage for cookie crumbs in a feeder at 6- or 12-m distance. Each ant was tested once by being taken from the feeder and released 2 m from the end of a 32-m channel to run home. The distance at which the ant first turned back (first turn) constituted the data. In acquisition, groups trained one or six times before being tested had unsystematic scatter that did not differ significantly. In retention, ants tested after a 24-h delay showed larger unsystematic scatter than control animals tested after no delay. In integration, ants were trained five times at 6 or 12 m and then tested at 12 or 6 m, respectively. No evidence of integration of multiple odometric memories was found. The results show that the properties of odometric memories are indeed tailored to what the memory system is used fo

Landmarks or panoramas: what do navigating ants attend to for guidance?

<p>Abstract</p> <p>Background</p> <p>Insects are known to rely on terrestrial landmarks for navigation. Landmarks are used to chart a route or pinpoint a goal. The distant panorama, however, is often thought not to guide navigation directly during a familiar journey, but to act as a contextual cue that primes the correct memory of the landmarks.</p> <p>Results</p> <p>We provided <it>Melophorus bagoti </it>ants with a huge artificial landmark located right near the nest entrance to find out whether navigating ants focus on such a prominent visual landmark for homing guidance. When the landmark was displaced by small or large distances, ant routes were affected differently. Certain behaviours appeared inconsistent with the hypothesis that guidance was based on the landmark only. Instead, comparisons of panoramic images recorded on the field, encompassing both landmark and distal panorama, could explain most aspects of the ant behaviours.</p> <p>Conclusion</p> <p>Ants navigating along a familiar route do not focus on obvious landmarks or filter out distal panoramic cues, but appear to be guided by cues covering a large area of their panoramic visual field, including both landmarks and distal panorama. Using panoramic views seems an appropriate strategy to cope with the complexity of natural scenes and the poor resolution of insects' eyes. The ability to isolate landmarks from the rest of a scene may be beyond the capacity of animals that do not possess a dedicated object-perception visual stream like primates.</p

Lab Retriever: a software tool for calculating likelihood ratios incorporating a probability of drop-out for forensic DNA profiles.

BackgroundTechnological advances have enabled the analysis of very small amounts of DNA in forensic cases. However, the DNA profiles from such evidence are frequently incomplete and can contain contributions from multiple individuals. The complexity of such samples confounds the assessment of the statistical weight of such evidence. One approach to account for this uncertainty is to use a likelihood ratio framework to compare the probability of the evidence profile under different scenarios. While researchers favor the likelihood ratio framework, few open-source software solutions with a graphical user interface implementing these calculations are available for practicing forensic scientists.ResultsTo address this need, we developed Lab Retriever, an open-source, freely available program that forensic scientists can use to calculate likelihood ratios for complex DNA profiles. Lab Retriever adds a graphical user interface, written primarily in JavaScript, on top of a C++ implementation of the previously published R code of Balding. We redesigned parts of the original Balding algorithm to improve computational speed. In addition to incorporating a probability of allelic drop-out and other critical parameters, Lab Retriever computes likelihood ratios for hypotheses that can include up to four unknown contributors to a mixed sample. These computations are completed nearly instantaneously on a modern PC or Mac computer.ConclusionsLab Retriever provides a practical software solution to forensic scientists who wish to assess the statistical weight of evidence for complex DNA profiles. Executable versions of the program are freely available for Mac OSX and Windows operating systems

Challenges and responses : the impact of classification methods of policies on first-generation college students in China and the US

In China and the United States, with the expansion of higher education, more and more people have become the first-generation of college students in their families. However, while gaining opportunities for social upward mobility, they also face many challenges, and the formation of these challenges is related to their multiple identities. In China, these challenges are more related to regional development differences, while in the United States, they are more impacted by identities such as immigrants and ethnic minorities. At the same time, the governments, universities, and society of both countries have introduced various policies to support first-generation college students, typical formats of which include admission preference, financial support, and intervention program. These policies have different audiences’ classification methods. In China, most of them are classified based on income levels, regional conditions, and ethnic identities. However, in the United States, many policies are specifically conducted for the first-generation college students. Combining primary and secondary data, this study will conduct a thematic analysis on the challenges of first-generation college students in China and the United States as well as the response effects of relevant policies. Through the comparison between the two cases, implications for policy classification methods will also be proposed