Phase and amplitude scintillations of microwave signals over an elevated atmospheric path

Phase and amplitude scintillations of microwave signals over elevated atmospheric path for obtaining atmospheric density profile

Movements Around Transit Tunnels in Mixed Ground

This paper describes the ground movements measured at a Test Section during construction of twin rapid transit tunnels in Cambridge, Massachusetts. The Test Section was located in an area of rock, soft ground and mixed face tunneling, with the alignment of the twin tunnels approximately 100 feet below ground surface. Overburden soils consist primarily of a very dense, saturated glacial till containing cobbles and boulders, with a weakly metamorphosed, fractured shale bedrock below. Instrumentation at the Test Section was installed in three cross-sections: one with the tunnel headings entirely in rock, a second with the tunnel headings in soft ground, and a third in a mixed face area. The field measurements are analyzed to show the effects of ground losses at the tunnel headings vs. distance away from headings, the effects of single vs. twin tunnel construction, and the effects of mixed face vs. rock and soft ground tunneling on ground movements

Ground Driven Powered Tillage

A ground driven powered tillage device is described which utilizes a passive rolling coulter propelled through the soil by a prime mover. The reaction torque imparted by the soil to the coulter is delivered via a torque transfer unit to a powered tillage blade. The tillage blade rotates counter to the direction of the passive rolling coulter and prepares a tilled furrow of some predetermined depth for seed placement and coverage. Analysis is presented in which the torque developed by a passive rolling coulter engaging the soil is predicted. A relationship is presented for determining the velocity ratio between the coulter and tillage blade. Finally, the shape and number of teeth a tillage blade has is expressed in terms of tillage depth and speed of the tillage blade

Observations of the 8 December 1987 occultation of AG+40 deg 0783 by 324 Bamberga

The occultation of AG+40 deg 0783 by 324 Bamberga on 8 December 1987 was observed at 13 sites in the United States, Japan, and China. At four sites the event was observed photoelectrically; the other observations were visual. A least-squares fit of a circular limb profile to the data gives a diameter of 227.6 + or - 1.9 km. However, this solution is inconsistent with a negative visual observation near the northern edge of the ground track. The inconsistency cannot be removed by assuming an elliptical profile. The data suggest that Bamberga, despite its low-amplitude lightcurve, may depart significantly from a spherical or ellipsoidal shape. The asteroid also appears to be at least 10 percent smaller than indicated by infrared radiometry

Nonlinear Analysis of Irregular Variables

The Fourier spectral techniques that are common in Astronomy for analyzing periodic or multi-periodic light-curves lose their usefulness when they are applied to unsteady light-curves. We review some of the novel techniques that have been developed for analyzing irregular stellar light or radial velocity variations, and we describe what useful physical and astronomical information can be gained from their use.Comment: 31 pages, to appear as a chapter in `Nonlinear Stellar Pulsation' in the Astrophysics and Space Science Library (ASSL), Editors: M. Takeuti & D. Sasselo

Enhancing Classroom Interaction in Distance Education Utilizing the World Wide Web

study utilized the World Wide Web and a Class Page to evaluate interaction strategies in a distance education setting. Participants were primarily elementary school teachers (n= 47 graduate students) who completed survey instruments concerning their participation on the Class Page , interactions with both the instructor and other students, and utilization of linked Web resources. An initial survey regarding students’ computer literacy skills and usage proficiencies was followed by seven additional surveys which focused upon Page ” use and interaction patterns. Among the findings were: student views regarding the value of getting to know fellow classmates shifted from zero percent (Week 2) to 88 percent (Week 15); students judging they were able freely to express their views went from 11 percent (Week 2) to 91 percent (Week 15). Increases were also noted concerning student out-of-class participation, enjoyment using the Internet, use of e-mail, and appreciation of the distance environment tools for encouraging involvement and interaction. Although many students questioned the usefulness of the Page at the beginning of the semester, the final survey found all students viewed the Page as beneficial. Analysis of the data found both interaction and class involvement were greatly enhanced through the Class Page and the Web based tools which supported the “Page” in this distance education environment

Student Perspectives: Responses to Internet Opportunities in a Distance Learning Environment

This qualitative study examined student responses toward an interactive Internet site supplementing a multimedia graduate level distance learning course at Ball State University. The course, Elementary School Curriculum, was taught in a studio classroom and transmitted to five distant sites in Indiana. Technology included two-way audio signals and one-way video signals for in-class interaction and an Internet World Wide Web site for out-of-class interaction. Qualitative evidence collection techniques included focus group interviews, telephone interviews, and eight survey instruments. Analysis of students’ responses to the Internet site focused on coping strategies developed by students to manage the stresses and benefits of their computer involvement. Students reported strategies for managing personal resources, the computer environment, self, and others. Predominant themes in student reactions included concerns associated with communication issues, with computer involvement, and with computer and Internet access. Benefits most frequently identified were the sense of empowerment and the satisfaction of sharing a space with fellow classmates. Implications drawn include the value of moderator leadership, the importance of a face-to-face encounter, the challenge of the on-line text-based medium, the influence of learning and temperament styles, and the development of computer-supported collaborative learning opportunities

Enhancing Elementary Curricula through Internet Technology

Radical advancements in Internet technology over the last decade have created endless opportunities to expand the realm of the elementary classroom. The World Wide Web (WWW), e-mail, Newsgroups, and Internet Relay Chat (IRC) are four of the most prominent utilizations of Internet technology. This paper demonstrates how one mid-western, suburban elementary classroom has enhanced its curriculum and improved classroom interaction by maximizing Internet technology. In addition to reviewing the merits of this case study, the reader will also: (a) be presented with a rationale for utilizing Internet technology with existing curricula, (b) examine the current debate on the issue of networking schools, (c) compare and contrast the pros and cons of utilizing Internet technology in elementary classrooms, and (d) consider the coalescence of curriculum and technology. An overview regarding the current application of Internet technology in an elementary setting highlights its true benefits: students conducting research on a topic of interest, communication and collaborative projects between students around the world, and the opportunity for students to publish original work

Five questions to consider before conducting a stepped wedge trial.

Researchers should consider five questions before starting a stepped wedge trial. Why are you planning one? Researchers sometimes think that stepped wedge trials are useful when there is little doubt about the benefit of the intervention being tested. However, if the primary reason for an intervention is to measure its effect, without equipoise there is no ethical justification for delaying implementation in some clusters. By contrast, if you are undertaking pragmatic research, where the primary reason for rolling out the intervention is for it to exert its benefits, and if phased implementation is inevitable, a stepped wedge trial is a valid option and provides better evidence than most non-randomized evaluations. What design will you use? Two common stepped wedge designs are based on the recruitment of a closed or open cohort. In both, individuals may experience both control and intervention conditions and you should be concerned about carry-over effects. In a third, continuous-recruitment, short-exposure design, individuals are recruited as they become eligible and experience either control or intervention condition, but not both. How will you conduct the primary analysis? In stepped wedge trials, control of confounding factors through secular variation is essential. 'Vertical' approaches preserve randomization and compare outcomes between randomized groups within periods. 'Horizontal' approaches compare outcomes before and after crossover to the intervention condition. Most analysis models used in practice combine both types of comparison. The appropriate analytic strategy should be considered on a case-by-case basis. How large will your trial be? Standard sample size calculations for cluster randomized trials do not accommodate the specific features of stepped wedge trials. Methods exist for many stepped wedge designs, but simulation-based calculations provide the greatest flexibility. In some scenarios, such as when the intracluster correlation coefficient is moderate or high, or the cluster size is large, a stepped wedge trial may require fewer clusters than a parallel cluster trial. How will you report your trial? Stepped wedge trials are currently challenging to report using CONSORT principles. Researchers should consider how to demonstrate balance achieved by randomization and how to describe trends for outcomes in both intervention and control clusters