Rotating black holes at future colliders: Greybody factors for brane fields

We study theoretical aspects of the rotating black hole production and evaporation in the extra dimension scenarios with TeV scale gravity, within the mass range in which the higher dimensional Kerr solution provides good description. We evaluate the production cross section of black holes taking their angular momenta into account. We find that it becomes larger than the Schwarzschild radius squared, which is conventionally utilized in literature, and our result nicely agrees with the recent numerical study by Yoshino and Nambu within a few percent error for higher dimensional case. In the same approximation to obtain the above result, we find that the production cross section becomes larger for the black hole with larger angular momentum. Second, we derive the generalized Teukolsky equation for spin 0, 1/2 and 1 brane fields in the higher dimensional Kerr geometry and explicitly show that it is separable in any dimensions. For five-dimensional (Randall-Sundrum) black hole, we obtain analytic formulae for the greybody factors in low frequency expansion and we present the power spectra of the Hawking radiation as well as their angular dependence. Phenomenological implications of our result are briefly sketched.Comment: Typo in basic equation corrected; Following calculations and results unchange

Assessing L2 Academic Speaking Ability: The Need for a Scenario-based Assessment Approach

The conceptualization of L2 proficiency has evolved to include a broader range of knowledge, skills, and abilities, prompting L2 testers to embrace new approaches to defining and assessing L2 speaking ability. This review discusses the evolution of L2 proficiency and speaking ability, and suggests scenario-based assessment (SBA) as a promising practice to designing language assessments that can provide a more comprehensive interpretation of one’s L2 speaking ability. An example of an online scenario-based academic speaking assessment is illustrated to demonstrate SBA’s efficacy and potential

Strategic Competence and L2 Speaking Assessment

Assessing second language speaking has long been an important part of language testing in both large-scale assessment settings and in smaller scale classroom-based assessments. Accordingly, researchers in the second language (L2) assessment field have made efforts to establish a better understanding of the nature of speaking ability and its underlying competences. With speaking tests increasingly involving test takers’ performances on certain tasks, test takers are required to utilize their language knowledge by means of their strategic competence (i.e., skills necessary to put language knowledge into use), which has been considered an integral component of communicative language ability (e.g., Bachman & Palmer, 1996) and L2 speaking ability (e.g., Bygate, 1987; Fulcher, 2003). However, what strategic competence in speaking entails remains unclear, as its definition has varied greatly across different theoretical models and empirical studies. This paper provides a brief overview of the varying approaches to defining strategic competence, and reports on major empirical findings related to the conceptualization of this important facet of speaking ability, surveying the extensive literature in the broader fields of applied linguistics and L2 assessment in particular. The paper starts with (1) a review of the applied linguistics literature on the major influential approaches to understanding oral strategic competence, followed by (2) an in-depth review of how the L2 assessment literature has conceptualized strategic competence in relation to different theoretical models, and lastly, (3) a discussion of empirical studies examining strategic competence in the context of speaking test performance. The paper concludes with directions for future research

The Teacher’s Role in Classroom-based Language Assessment

Different from large-scale language tests aiming to measure general proficiency and often administered in specific highly-controlled test settings, classroom-based language assessment is embedded in the teaching and learning cycle of a classroom and has multiple “identities” (Rea-Dickins, 2001, p. 451) due to its wide range of uses or purposes. Classroom-based language assessment is an integral part of language instruction where the teachers, as “agents” (Rea-Dickins, 2004), are the ones responsible for facilitating student learning and obtaining information about their progress and achievement, hence, also earning the name teacher assessment. From planning what to assess and how, through implementing assessment procedures and monitoring students’ performances to recording students’ attainment and progress, the teacher is constantly making decisions on how to keep track of students’ progress and attainment (Rea-Dickins, 2001). Either accomplished through a formal assessment procedure or through informal daily monitoring and observation, the teacher’s knowledge of the students guides him/her to make subsequent pedagogical decisions and push learning further

Assessing L2 Academic Speaking Ability: The Need for a Scenario-based Assessment Approach

The conceptualization of L2 proficiency has evolved to include a broader range of knowledge, skills, and abilities, prompting L2 testers to embrace new approaches to defining and assessing L2 speaking ability. This review discusses the evolution of L2 proficiency and speaking ability, and suggests scenario-based assessment (SBA) as a promising practice to designing language assessments that can provide a more comprehensive interpretation of one’s L2 speaking ability. An example of an online scenario-based academic speaking assessment is illustrated to demonstrate SBA’s efficacy and potential

Commentaries on Computer based Language Assessment

The rapid change and use of computer technology has had a profound influence in the field of language teaching and assessment, and the changes that computer and technology has brought to language assessment in particular are not only in the delivery method, but also in the scoring systems (Chapelle & Douglas, 2006). For instance, a wide variety of tasks be given as a test online worldwide, and scores can be available immediately to the test takers. However, along with such advances come potential problems and concerns

Commentaries on Validity Issues in Foreign and Second Language Assessment

In empirical applied linguistics research, the primary goal and concern is to operationalize key variables (i.e., measured constructs) in a valid and reliable way, generate scores for the measured variables through quantitative and/or qualitative means (e.g., various kinds of pre- or posttests, surveys, or coded observations), treat those scores appropriately, and allow for proper hypothesis testing of the research questions under investigation (Purpura, Brown, & Schoonen, 2015, p. 37). If the consequences of the research are “low stakes” in that the participants in the study are generally not directly impacted by the results (i.e., decisions are not made on the results to either advance or demote them in some way), the research can be published, our knowledge and understanding of the phenomenon in question deepened, and the story can essentially end there. But if there are important “high stakes” decisions to be made about the participants based on the results, decisions that can potentially impact their lives directly, it becomes imperative that our procedures and theoretical constructs have been thoroughly examined and are valid. That is why in the subfield of second and foreign language assessment, where high stakes decisions such as university admission or classification as an English language learner (ELL) in the U.S. K-12 public school system do take place based on the various test results, a higher standard needs to be adhered to in the development and implementation of the test instruments, potential interpretations of the results, and any possible subsequent uses of the results. Consequently, in second and foreign language testing, validation frameworks have been thoroughly developed and discussed to ensure that best measurement practices and high professional standards are followed (American Educational Research Association [AERA], American Psychological Association [APA], and the National Council on Measurement in Education [NCME], 1985, 2014), and that is why second/foreign language testers subject test scores to rigorous validity evaluation so that claims made about the measured constructs can be deemed meaningful and appropriate for their intended purpose(s), and their intended use and interpretation in decision making can also be justified (Purpura et al., 2015)