Efficient Algorithms for Scheduling Moldable Tasks

We study the problem of scheduling $n$ independent moldable tasks on $m$ processors that arises in large-scale parallel computations. When tasks are monotonic, the best known result is a $(\frac{3}{2}+\epsilon)$-approximation algorithm for makespan minimization with a complexity linear in $n$ and polynomial in $\log{m}$ and $\frac{1}{\epsilon}$ where $\epsilon$ is arbitrarily small. We propose a new perspective of the existing speedup models: the speedup of a task $T_{j}$ is linear when the number $p$ of assigned processors is small (up to a threshold $\delta_{j}$) while it presents monotonicity when $p$ ranges in $[\delta_{j}, k_{j}]$; the bound $k_{j}$ indicates an unacceptable overhead when parallelizing on too many processors. For a given integer $\delta\geq 5$, let $u=\left\lceil \sqrt[2]{\delta} \right\rceil-1$. In this paper, we propose a $\frac{1}{\theta(\delta)} (1+\epsilon)$-approximation algorithm for makespan minimization with a complexity $\mathcal{O}(n\log{\frac{n}{\epsilon}}\log{m})$ where $\theta(\delta) = \frac{u+1}{u+2}\left( 1- \frac{k}{m} \right)$ ($m\gg k$). As a by-product, we also propose a $\theta(\delta)$-approximation algorithm for throughput maximization with a common deadline with a complexity $\mathcal{O}(n^{2}\log{m})$

Effectiveness of textually-enhanced captions on Chinese high-school EFL learners’ incidental vocabulary learning

This study employed mixed-methods approach to investigate the impact of textually-enhanced captions on EFL learners’ incidental vocabulary gains and learners’ perceptions of the captioning usefulness in a multi-modal learning environment. 133 Chinese EFL high school learners of the low-intermediate level were randomly assigned to English captions with highlighted target words and L1 gloss (ECL1), Chinese and English captions (CEC), Chinese and English captions with highlighted target words (CECGW), and no captions (NC). Our quasi-experimental findings did not detect any significant differences among the caption types on vocabulary form recognition while ECL1 was found the most effective in meaning recall and recognition. Captioning types and learners’ language proficiency exerted medium-to-large effects on meaning recall and meaning recognition. Our qualitative data suggested the participants generally viewed captioned videos positively, with variability in perceptions of concurrent presentation of information. The saliency of L1 gloss could direct the viewers’ attention to the semantic features of a word and reinforce sound-form-meaning connections. Videos lacking L1 glosses of target words had relatively little effect on learners’ vocabulary learning while more textual inputs might not necessarily result in vocabulary gains. Pedagogical implications are proposed for teachers’ adoption of L1 in captioned videos to enhance learners’ learning effectiveness.Este estudio investigó el impacto y las percepciones de los estudiantes de los subtítulos mejorados textualmente en las ganancias incidentales de vocabulario de los estudiantes de inglés como lengua extranjera en un entorno de aprendizaje multimodal. 133 estudiantes chinos de inglés como lengua extranjera de nivel intermedio bajo fueron asignados aleatoriamente a subtítulos en inglés con palabras objetivo resaltadas y brillo L1 (ECL1), subtítulos en chino e inglés (CEC), subtítulos en chino e inglés con palabras objetivo resaltadas (CECGW), y sin subtítulos (NC). Nuestros hallazgos cuasi-experimentales no detectaron diferencias significativas entre los tipos de subtítulos en el reconocimiento de formas de vocabulario, mientras que ECL1 resultó ser el más efectivo para recordar y reconocer significados. Nuestros datos cualitativos sugirieron que los participantes generalmente veían los videos subtitulados de manera positiva, con variabilidad en las percepciones de la presentación simultánea de información. La prominencia del brillo L1 podría dirigir la atención de los espectadores a las palabras objetivo y reforzar las conexiones de la forma del sonido y el significado

Influence of coastal groundwater salinization on the distribution and risks of heavy metals

Coastal groundwater quality significantly affects the regional sustainable development, due to the water resource shortage in coastal zone. Current studies on coastal groundwater have mainly focused on saline water intrusion and over-extraction. Information on the heavy metal pollution of coastal groundwater with salinization trend is limited. This study investigated heavy metals in groundwater from a typical coastal region with intensive anthropogenic activities and saline water intrusion. The southwestern coastal plains of the study area showed significant groundwater salinization trend. Heavy metals in the coastal groundwater mainly originated from anthropogenic activities and groundwater salinization according to principal component analysis. Relative high concentrations of As, Co, Cr, Cu, Fe, Mn, and Ni occurred in the southwestern coast of the study area with high TDS level, indicating that the concentrations of these heavy metals in shallow aquifer of the study area might be influenced by the groundwater salinization. Average concentrations of heavy metals in groundwater of the study area ranged from 0.03 (Cd) to 686.92 (Fe) mu g/L. Fe was the dominant heavy metal in groundwater with the maximal concentration of 2333.76 mu g/L and exceeding-standard rate reaching 98.23%. Approximately 13.27% of sampling sites showed moderate or higher heavy metal pollution of groundwater based on heavy metal pollution index. Heavy metals in groundwater exerted low ecological risks. Elements Fe, Ni, and As were the main contributors for ecological risks. Cancer risks of heavy metals for both adults and children were high at all sampling sites. Non-cancer risks for adults and children were unacceptable at 4.42% and 17.70% of sampling sites, respectively. The salinization of the coastal groundwater could also lead to the increase in the ecological and health risks of heavy metals in coastal groundwater. These findings provide initial and important information on heavy metals pollution in coastal aquifer with saline water intrusion. (C) 2018 Elsevier B.V. All rights reserved