Field of study choice by community college students in Canada

Community college education is a key component of Canadian postsecondary education, with 21% of the population aged 25–64 having college credentials. In order to understand educational decisions at this level, we estimate a model of choice of field of study and analyze, among other things, the effect of earnings on this choice. In this way, we exploit two cross-sections (and cohorts) of young workers who completed community college (Cegeps in Quebec) in 1990 and 1995 from the Canadian National Graduate Survey. Structural estimates indicate that the probability of selecting a specific community college field of study depends significantly upon anticipated earnings in this field relative to other fields. Our results also show that women put less weight on earnings compared to men when choosing a field of study, and that students who were employed prior to starting community college are more sensitive to earnings variations across fields of study than students with no prior work experience.     

基于GSM短信的仓库监控报警系统的设计与实现

为满足实时无线监控和安防需求,以STC89C52RC单片机为核心,结合西门子公司的TC35i通信模块和HC-SR501人体红外传感器,运用C语言和AT指令,设计了一个基于GSM短信的仓库监控报警系统。经过了联机调试,系统工作正常,实现了对企业仓库的全天候远程无线监控和短信报警功能,达到了预期目标。     

美丽中国“35目标”和“50愿景”情景模拟

全面建成美丽中国，实现人与自然和谐共生的现代化，是未来30年中国生态文明建设的总目标。总目标包含“35目标”和“50愿景”共2个阶段性目标。文章首先从生态系统要素、结构、过程和功能角度，阐述了对美丽中国目标的理解，继而构建了刻画目标的指标体系，并采用情景模拟方法，模拟了气候变化、人口下降、经济增长趋势下美丽中国“35目标”和“50愿景”。结果表明，至2035年，全国总人口14.4亿人，国内生产总值（GDP）为200万亿元，进入中等发达国家行列。全国森林覆盖率达26%，草原综合植被覆盖度达60%，沙化土地治理率达75%；地表水水质达到Ⅲ类以上，近海海域水质达到Ⅱ类以上；城市空气质量达到国家优良标准。至2050年，全国总人口13.65亿人，GDP为380万亿元，迈入高收入国家行列。森林覆盖率30%，草原综合植被覆盖度65%，沙化土地全部得到有效治理；地表水和近海海域水质均达到Ⅱ类标准；城市空气质量达到发达国家水平。现实状况与目标愿景尚存在明显差距，如期实现美丽中国目标愿景，未来需大力推进减污、降碳、扩绿、增粮和绿色发展。