Decomposition of Electromagnetic Q and P Media

Two previously studied classes of electromagnetic media, labeled as those of Q media and P media, are decomposed according to the natural decomposition introduced by Hehl and Obukhov. Six special cases based on either non-existence or sole existence of the three Hehl-Obukhov components, are defined for both medium classes.Comment: 18 page

Electromagnetic Boundary Conditions Defined in Terms of Normal Field Components

A set of four scalar conditions involving normal components of the fields D and B and their normal derivatives at a planar surface is introduced, among which different pairs can be chosen to represent possible boundary conditions for the electromagnetic fields. Four such pairs turn out to yield meaningful boundary conditions and their responses for an incident plane wave at a planar boundary are studied. The theory is subsequently generalized to more general boundary surfaces defined by a coordinate function. It is found that two of the pairs correspond to the PEC and PMC conditions while the other two correspond to a mixture of PEC and PMC conditions for fields polarized TE or TM with respect to the coordinate defining the surface

Structural analysis of a bolted joint concept for the space shuttle's solid rocket motor casing

The Space Shuttle Challenger accident is thought to have been caused by the failure of one of the tang-clevis joints joining together the casing segments of the Solid Rocket Motors (SRM). Excessive displacement between the tang and clevis, possibly unseating the O-ring seals, may have initiated the resulting accident. An effort was made at NASA Langley Research Center to design an alternative concept for mating the casing segments. A bolted flange joint concept was designed and analyzed to determine if the concept would effectively maintain a seal while minimizing joint weight and controlling stress levels. It is shown that under the loading conditions analyzed the seal area of the joint remains seated. The only potential stress problem is a stress concentration in the flange at the edge of the bolt hole, which is highly localized. While heavier than the existing joint, this concept does have some advantages making the bolted joint an attractive alternative

Negative reflections of electromagnetic waves in chiral media

We investigate the reflection properties of electromagnetic/optical waves in isotropic chiral media. When the chiral parameter is strong enough, we show that an unusual \emph{negative reflection} occurs at the interface of the chiral medium and a perfectly conducting plane, where the incident wave and one of reflected eigenwaves lie in the same side of the boundary normal. Using such a property, we further demonstrate that such a conducting plane can be used for focusing in the strong chiral medium. The related equations under paraxial optics approximation are deduced. In a special case of chiral medium, the chiral nihility, one of the bi-reflections disappears and only single reflected eigenwave exists, which goes exactly opposite to the incident wave. Hence the incident and reflected electric fields will cancel each other to yield a zero total electric field. In another word, any electromagnetic waves entering the chiral nihility with perfectly conducting plane will disappear.Comment: 5 pages, 5 figure

Supporting Farmer Adoption of Sustainable Bird Management Strategies

Pest birds cause substantial and costly damage to crops. Managing birds is complex because (1) they are highly mobile, (2) they habituate quickly to many deterrents, (3) some species provide benefits to farmers by deterring and consuming pest insects, rodents, and other birds, and (4) birds are highly valued by many people. Thus, farmers have many issues to consider when developing bird management strategies. Here I discuss recent work indicating that farmer adoption of sustainable agricultural practices is more likely when practices are effective, clear guidelines for implementation are available, implementation is relatively easy, and when practices are linked, in farmers’ minds and logistically, with other farm management practices. This manuscript draws together information about these factors for common bird management tactics to aid in the development of sustainable bird management strategies by farmers and the development of education programs for farmers by extension personnel and researchers. Such strategies will necessarily involve combinations of tactics, following the framework of Integrated Pest Management

Connecting students' homework to their participation in a course-based social network

This paper presents a comparison between students' efforts on homework (problem sets delivered and completed online using WebAssign) and their participation on a course-focused social media site. The social media platform, CourseNetworking (CN), has many features typical of Learning Management Systems (LMSs), but is distinct in several important ways. The interface is far more "student centric" than traditional LMSs, and is designed to increase engagement; most of the CN window is devoted to student-authored content. Also, the site measures and "gamifies" participation, using an algorithm that includes posts, completion of surveys, comments on other students' posts, and other actions. The setting for our efforts was an introductory calculus-based mechanics class enrolling approximately 150 students, most of whom were engineering majors. Course exams, problem sets, and labs followed a traditional model. Social media participation was not required, but it was encouraged and students could earn a small extra-credit bonus. We investigated correlations between social media "micropoints" and three variables associated with the homework: time on task, points earned, and assignments skipped. Our results show small to moderate correlations and statistical significance in all three cases. Pearson's correlation coefficients are r = 0.286, 0.444, and -0.436 for time on task, points earned, and assignments skipped, respectively. The associated p values are 1.2 × 10-3 for time on task, and p < 10-5 for the other two variables. Because the variables we measure are not normally distributed, we verify these results by also calculating Kendall's tau statistic. This analysis confirms both the size and significance of the correlations we observe. We do not suggest a causal connection; rather, our conclusion is that participation in the social network is a form of engagement with the class comparable to traditional measures of engagement such as homework effort and outcome. © American Society for Engineering Education, 2017

Consumers favor “right brain” training: The dangerous lure of neuromarketing

Over the past decade the neuromarketing of educational products has become increasingly common. Researchers have however expressed concern about the misapplication of neuroscience to education marketing, fearing that consumers may be deceived into investing in apparently “brain-based” products under the misapprehension that they will be more effective. This study provides the first demonstration that these fears are justified. We presented 180 participants with one of four advertisements for an identical educational program, named either “Right Brain” or “Right Start” Training; the advertisements either did, or did not, include an MRI brain image in one corner. Results demonstrated that “Right Brain” training was deemed more interesting, educationally valuable, and scientifically strong than an identical product named “Right Start” training. Advertisements including an unrelated brain image enhanced ratings of scientific rationale. These results confirm that by implying a strong scientific basis, “brain-based” product names are remarkably effective in implicitly manipulating consumer opinion

Making Cereal Box Dioramas of Native American Historic Homes and Culture

Hands-on projects such as creating a three-dimensional diorama are among the most memorable of positive elementary school experiences, yet they are generally uncommon because these complex projects are daunting to undertake. Therefore, it is important to prepare preservice teachers with the skills to lead children in creating these types of projects. This document is a compilation of preservice teacher work completed during a social studies methods class that assists instructors in teaching students to create unique dioramas. After the preservice teachers had constructed dioramas and assisted elementary students in making their own, they reflected on previous social studies projects from their childhoods and considered the learning outcomes of the current project. Eighty preservice teachers enrolled in a social studies methods course participated in the study. These college students created their own Native American dioramas along with images for furnishing and finishing dioramas of the Native American group on which they focused. The five Native American groups explored through dioramas include the Iroquois of the northeastern United States, the Seminole of the Southeast, the Lakota of the Central Plains, Hopi (and Navajo) of the American Southwest and the Haida of the Northwest Coast. This document provides photoillustrated examples and steps of how to create an intricate diorama from a cereal box, recycled copy paper, white craft glue, paints, images, and common craft items. The cereal box base is cut to open like a book and a model of a Native American home made of recycled cardboard is affixed over a cut-out hole in the cover so that the box opens to reveal the interior of the home. All surfaces are covered with a layer of torn recycled copy paper that is securely glued, coated with white gesso base paint, and then decorated with acrylic craft paints. In the facing inside enclosure, a ceremony scene is displayed. The back of the cereal box features crafts of the Native American group, while the other cereal box exterior sides show foods, clothing, and other cultural Reflection data indicate that preservice teachers recognized the large amount of time and patience necessary to complete a quality diorama and the valuable amount of in-depth learning that results, including a deeper respect for Native American people and greater confidence in teaching these concepts. Therefore, we recommend diorama projects in teaching about diverse cultures (2 tables, 5 figures, 2 photo-illustrated appendices)