Another Look at Measures of Forecast Accuracy

We discuss and compare measures of accuracy of univariate time series forecasts. The methods used in the M-competition and the M3-competition, and many of the measures recommended by previous authors on this topic, are found to be inadequate, and many of them are degenerate in commonly occurring situations. Instead, we propose that the mean absolute scaled error become the standard measure for comparing forecast accuracy across multiple time series.Forecast accuracy, Forecast evaluation, Forecast error measures, M-competition, Mean absolute scaled error.

Towards electron transport measurements in chemically modified graphene: The effect of a solvent

Chemical functionalization of graphene modifies the local electron density of the carbon atoms and hence electron transport. Measuring these changes allows for a closer understanding of the chemical interaction and the influence of functionalization on the graphene lattice. However, not only chemistry, in this case diazonium chemistry, has an effect on the electron transport. Latter is also influenced by defects and dopants resulting from different processing steps. Here, we show that solvents used in the chemical reaction process change the transport properties. In more detail, the investigated combination of isopropanol and heating treatment reduces the doping concentration and significantly increases the mobility of graphene. Furthermore, the isopropanol treatment alone increases the concentration of dopants and introduces an asymmetry between electron and hole transport which might be difficult to distinguish from the effect of functionalization. The results shown in this work demand a closer look on the influence of solvents used for chemical modification in order to understand their influence

On Reasonable and Forced Goal Orderings and their Use in an Agenda-Driven Planning Algorithm

The paper addresses the problem of computing goal orderings, which is one of the longstanding issues in AI planning. It makes two new contributions. First, it formally defines and discusses two different goal orderings, which are called the reasonable and the forced ordering. Both orderings are defined for simple STRIPS operators as well as for more complex ADL operators supporting negation and conditional effects. The complexity of these orderings is investigated and their practical relevance is discussed. Secondly, two different methods to compute reasonable goal orderings are developed. One of them is based on planning graphs, while the other investigates the set of actions directly. Finally, it is shown how the ordering relations, which have been derived for a given set of goals G, can be used to compute a so-called goal agenda that divides G into an ordered set of subgoals. Any planner can then, in principle, use the goal agenda to plan for increasing sets of subgoals. This can lead to an exponential complexity reduction, as the solution to a complex planning problem is found by solving easier subproblems. Since only a polynomial overhead is caused by the goal agenda computation, a potential exists to dramatically speed up planning algorithms as we demonstrate in the empirical evaluation, where we use this method in the IPP planner

Tutor Effectiveness of Student-Athletes at a Division I University

Peer tutoring services are a vital aspect to collegiate athletic support services to ensure that the academic needs of its student-athletes are being met. Collegiate student-athletes hail from a variety of academic backgrounds and everyone may not be ready for the rigors of college. Student-athletes also devote many hours to their specific sport in the form of practice, weight training, watching film, hosting recruits, doing volunteer services, and competing in athletic contests. Athletic contests may require student-athletes to miss class, which makes tutorial services even more crucial for student-athletes. In addition to these time consuming athletic activities, are a wide array of National Collegiate Athletic Association (NCAA) academic eligibility rules that student-athletes must abide by in order to remain eligible for their respective sport (Meyer, 2005). This places a higher importance on tutorial services not only for students, but also for coaches, athletic academic advisors, and the support services that serve student-athletes. While many campuses have tutorial services for the overall student body, tutorial services for athletes differ by catering to the busy schedules of its student-athletes. The goal of this study was to determine what internal factors (e.g., motivation of a student) influence an effective tutor as well as determine the extrinsic factors (e.g., nutrition/eating habits) that influence effective tutoring. Understanding these research questions will assist the hiring practice of tutor coordinators as well as provide valuable insight in the external factors that may affect tutoring

Bipolar Nickel-hydrogen Batteries for Aerospace Applications

A bipolar nickel-hydrogen battery which effectively addresses all key requirements for a spacecraft power system, including long-term reliability and low mass, is discussed. The design of this battery is discussed in the context of system requirements and nickel-hydrogen battery technology in general. To achieve the ultimate goal of an aerospace application of a bipolar Ni-H2 battery several objectives must be met in the design and development of the system. These objectives include: maximization of reliability and life; high specific energy and energy density; reasonable cost of manufacture, test, and integration; and ease in scaling for growth in power requirements. These basic objectives translate into a number of specific design requirements, which are discussed

ANALYSIS OF PROPORTIONS FROM SPLIT-PLOT AND REPEATED MEASURES EXPERIMENTS

Several methods for analyzing proportions from split-plot and repeated measures experiments are illustrated and compared. One approach simply uses analysis of variance for the usual linear mixed model fit to split-plot and repeated measures experiments. Alternatively, logistic regression analysis is considered and a so-called robust estimate of the covariance matrix is used to adjust for possible correlations among responses. Finally, a quasi-likelihood approach to logistic regression analysis that requires more explicit specification of the covariance structure for the observed proportions is considered. These methods are illustrated with the analyses of data from a repeated measures study of acorn consumption by blue jays and a study of the effects of several environmental factors on nest predation for ground nesting birds