北京城市绿地对大气PM_(2.5)的削减作用

PM2.5导致的大气污染已经成为中国经济快速发展地区共同面临的问题。城市绿地对削减大气PM2.5具有一定的作用。本研究基于NDVI数据模拟北京城市绿地叶面积指数,再利用干沉降模型模拟区域绿地PM2.5削减量,最后根据大气PM2.5存量计算了绿地对大气PM2.5的去除效果。研究结果显示,2000年、2005年和2010年北京城市绿地PM2.5削减总量分别为1 861t、2 987t和3 852t,单位面积削减量分别为22.71kg/hm2、24.64kg/hm2和33.36kg/hm2,可分别将研究区内PM2.5削减0.07%、0.12%和0.19%。苗圃与果园、社区林和路旁林的PM2.5削减总量较高,而针阔混交林、灌木林和针叶林的单位面积削减量较高。五环以外绿地的PM2.5削减总量、单位面积削减量和大气PM2.5去除率都高于五环以内绿地。本研究可以为北京城市规划中更好发挥绿地缓解大气PM2.5作用提供决策依据。     

Exploring School Principals’ Leadership Styles and Learners’ Educational Performance: A Perspective from High- and Low-Performing Schools

School leadership is fundamental to the educational functioning of schools and their improvements of results. The study employed a qualitative approach to explore school principals’ leadership styles and the educational performance of learners in high- and low-performing schools in Vhembe District, Limpopo, South Africa. The participants were purposefully selected from 10 secondary schools in terms of their performance. Focus group interviews were conducted with five teachers from each school. The interview data was transcribed and analysed, and identical patterns of coded data were grouped together under emerging themes. The overall results of the study indicated that the democratic leadership style together with the transformational leadership style contribute to high educational performance of learners. School principals from high- and low-performing schools employ a democratic leadership style and differ only in the sense that the latter are permissive or lenient towards learners’ behaviours or conduct. The study recommends that school principals engage teachers as members of a disciplinary committee in order to deal with those learners whose conduct is not conducive to successful teaching and learning. It is recommended that school principals from low-performing schools strengthen their democratic leadership by not being lenient to learners’ behaviour which is not conducive to successful teaching and learning.     

Establishing the overall service quality of engineering education: fuzzy logic approach

Measuring overall service quality (OSQ) is gaining prominence in higher education due to the increased competition among engineering education institutions (EEIs) and growing awareness about value for money among the public. Determination of OSQ on certain institutional aspects is done by various agencies throughout the world. Each system uses a different set of weighted indicators to measure the overall service quality of institutions. Five service quality factors, namely professionalism, integrated education, facilities, responsiveness and empathy are considered in the study. Trapezoidal fuzzy numbers are used to determine the aggregate weights of the factors to handle the vagueness present in the linguistic values of the stakeholders’ subjective opinions. Final weights of the factors are assessed by taking the distances of each factor between Fuzzy Positive Ideal Rating and Fuzzy Negative Ideal Rating. An illustrative study is presented to determine the OSQ of EEIs. The results help to focus on the factors which need immediate attention to enhance the quality of EEIs.     

Direction of arrival tracking for signals with known waveforms based on block least squares techniques

In this paper, we address the problem of tracking DOA of multiple moving targets with known signal source waveforms and unknown gains in the presence of Gaussian noise using a nonuniform linear array. Herein, we make use of the fact that the output of each sensor can be described as a linear regression model whose coefficients each contain a pair of DOA and gain information corresponding to one target. These coefficients are determined by solving a linear least squares (LS) problem and then updated recursively based on a block QR decomposition recursive least squares (QRD-RLS) technique or a block regularized LS technique. Since the coefficients from different sensors have the same amplitude but variable phase information for the same signal, along with simple algebraic manipulations the well-known generalized least squares (GLS) are used to obtain an asymptotically-optimal DOA estimate without requiring a search over a large region of the parameter space. Computer simulations show that the proposed DOA tracking techniques when applied to a sparse antenna array can provide a better tracking performance than some of the existing methods do.     

Work–Life Balance Among Community College Faculty Members: Generational and Life Course Theory Lenses

Generational and life course theory lenses were placed upon one finding of a large-scale qualitative interview-based study focused on if and how community college faculty members construct work–life balance. Twenty-eight interviews with faculty members at a midwestern community college were conducted. Differences regarding to work-life balance approaches between Baby Boomer (n = 15) and Generation X (n = 13) faculty and as mediated by position within the life course are elucidated. We termed this finding tides of life, which is comprised of three subfindings: roles, tenure, and gender performance. Practical implications of this finding are put forward. Better understanding of the nuanced ways in which community college faculty construct work–life balance can inform policy decisions that impact faculty work. Moreover, better understanding of faculty life in a general sense is critical as community college leaders craft policies and refine practices related to faculty employment contracts, work environments, support mechanisms, professional development, and mentoring.