Seismic detection of sonic booms

The pressure signals from a sonic boom will produce a small, but detectable, ground motion. The extensive seismic network in southern California, consisting of over 200 sites covering over 50 000 square kilometers, is used to map primary and secondary sonic boom carpets. Data from the network is used to analyze three supersonic overflights in the western United States. The results are compared to ray-tracing computations using a realistic model of the stratified atmospheric at the time of the measurements. The results show sonic boom ground exposure under the real atmosphere is much larger than previously expected or predicted by ray tracing alone. Finally, seismic observations are used to draw some inferences on the origin of a set of "mystery booms" recorded in 1992–1993 in southern California

E-Learning in Postsecondary Education

Over the past decade postsecondary education has been moving increasingly from the class room to online. During the fall 2010 term 31 percent of U.S. college students took at least one online course. The primary reasons for the growth of e-learning in the nation\u27s colleges and universities include the desire of those institutions to generate new revenue streams, improve access, and offer students greater scheduling flexibility. Yet the growth of e-learning has been accompanied by a continuing debate about its effectiveness and by the recognition that a number of barriers impede its widespread adoption in higher education

Self-Assessments of Knowledge: Where Do We Go From Here?

[Excerpt] In this paper, we argue that there remain several unanswered questions surrounding self-assessments of knowledge that must be addressed before we can reach a more definitive conclusion on the viability of these measures. The answers to these questions may provide further evidence that self-assessments should not be used as an indicator of learning or they may serve to qualify the conditions under which self-assessments can be used with reasonable confidence. In either case, addressing these issues is critical if work in this area is to influence how researchers and practitioners evaluate trainees’ learning

AN ANALYSIS OF ALTERNATIVE NET PRESENT VALUE CAPITAL INVESTMENT DECISION MODELS

We have found that the disagreement between Returns-to-Assets (RTA) and Returns-to-Equity (RTE) proponents is not confined to agricultural economics. Depending on the course they are taking and the accompanying text, students are likely to learn that there is a "right" way to calculate Net Present Values (NPVs), either by the RTA method or the RTE method. In most cases, only one of the two methods is discussed and illustrated with numerical examples. Less common are texts that compare the two methods, discuss their underlying assumptions, or show how the NPVs from the two methods can be reconciled. The paper is organized as follows. The first section of the main body of the paper provides a comparative overview of the RTA and RTE methods; the second section discusses our textbook survey; the final section offers our conclusions. Appendix A contains a brief history of the theoretical development of discounted cash flow (DCF) concepts. Appendix B contains additional details on defining components of NPV models. Finally, Appendix C is a listing of some additional references.Research Methods/ Statistical Methods,

HANDLING DURABLE AND NONDURABLE FARM INPUT DECISIONS USING A SINGLE THEORETICAL FRAMEWORK

Students in economics are taught that the optimal usage of a nundurable input occurs when the value of its marginal product (VMP) equals its marginal cost (MC). However, this fundamental condition has rarely been extended to durable inputs. Even advanced textbooks have done little to compare and contrast the optimality conditions for durables versus nondurables. This paper outlines and compares a common VMP-MC decision for (1) nondurables in a single-period time horizon, (2) durables in a finite planning horizon, and (3) durables in an infinite planning horizon.Agricultural Finance,