Solar rejection in laser based underwater communication systems

This article provides a numerical study of the expected improvements in an underwater optical system given by a single-mode laser diode operating within a Fraunhofer line in a coastal water type. The system performance is examined for a silicon PIN direct-detection receiver in the euphotic zone. The solar irradiance, modelled as white noise, is evaluated when using a lithium niobate interference and a birefringent filter with different field-of-view (FOV) characteristics in a clear sky situation. The results of this analysis show the inverse dependence of the signal-to-noise (SNR) on the FOV, along with the significant improvement in the receiver sensitivity given by a narrow optical bandpass filter (OBPF)

Operational criteria used by professional social workers to assess relationship

Thesis (M.S.)--Boston Universit

Laser Based Underwater Communication Systems

We report on recent progress in the field of visible light communications including direct modulation of blue laser devices at data rates beyond 10 Gbit/s, and the transmission of 2.5 Gbit/s OOK data through water. We also discuss the advantages of operating with single mode laser devices and matched filtering at the receiver in the context of applications with significant solar background. The system performance for two types of direct-detection receivers, a PIN detector and less conventional silicon Photomultiplier technology will be presented

Optimizing the trade-off between number of cops and capture time in Cops and Robbers

The cop throttling number $th_c(G)$ of a graph $G$ for the game of Cops and Robbers is the minimum of $k + capt_k(G)$, where $k$ is the number of cops and $capt_k(G)$ is the minimum number of rounds needed for $k$ cops to capture the robber on $G$ over all possible games in which both players play optimally. In this paper, we construct a family of graphs having $th_c(G)= \Omega(n^{2/3})$, establish a sublinear upper bound on the cop throttling number, and show that the cop throttling number of chordal graphs is $O(\sqrt{n})$. We also introduce the product cop throttling number $th_c^{\times}(G)$ as a parameter that minimizes the person-hours used by the cops. This parameter extends the notion of speed-up that has been studied in the context of parallel processing and network decontamination. We establish bounds on the product cop throttling number in terms of the cop throttling number, characterize graphs with low product cop throttling number, and show that for a chordal graph $G$, $th_c^{\times}=1+rad(G)$.Comment: 19 pages, 3 figure

Preservice teachers’ beliefs in the context of teaching mathematics to English learners in the United States

This study examines the beliefs of fourteen preservice teachers in the Southeast United States about mathematics and language in the context of teaching mathematics to English learners. Qualitative interviews were conducted using survey items as a starting point for the questioning. Speer’s (2008) construct of collections of beliefs was used to understand the preservice teachers’ belief system and the interaction of beliefs. Three primary beliefs emerged: mathematics is universal, mathematical language, and language barrier. Their belief about mathematics being universal was grounded in their view that mathematics was mostly about symbols and equations. The preservice teachers believed that there was some language in mathematics, though these features were not as pervasive as the symbolic form. Most of them also believed that the English learners were recent immigrants to the country and that English was a barrier for the students in the mathematics classroom. The beliefs interacted in three ways as they responded to the items: dominance, tension, and convergence

Scarlet & Silver Jubilee

Program listing performers and works performe

Towards a formative assessment of classroom competencies (FACCs) for postgraduate medical trainees

Background An assumption of clinical competency is no longer acceptable or feasible in routine clinical practice. We sought to determine the feasibility, practicability and efficacy of undertaking a formal assessment of clinical competency for all postgraduate medical trainees in a large NHS foundation trust. Methods FY1 doctors were asked to complete a questionnaire to determine prior experience and self reported confidence in performing the GMC core competencies. From this a consensus panel of key partners considered and developed an 8 station Objective Structured Clinical Examination (OSCE) circuit to assess clinical competencies in all training grade medical staff... The OSCE was then administered to all training grade doctors as part of their NHS trust induction process. Results 106 (87.6% of all trainees) participated in the assessment during the first 14 days of appointment. Candidates achieved high median raw percentage scores for the majority of stations however analysis of pre defined critical errors and omissions identified important areas for concern. Performance of newly qualified FY1 doctor was significantly better than other grades for the arterial blood gas estimation and nasogastric tube insertion stations. Discussion Delivering a formal classroom assessment of clinical competencies to all trainees as part of the induction process was both feasible and useful. The assessment identified areas of concern for future training and also served to reassure as to the proficiency of trainees in undertaking the majority of core competencies