基于USB和蓝牙的单片机温度监测系统的设计

介绍一种基于USB和蓝牙的单片机温度监测系统,以单片机芯片AT89S52为核心,结合外围USB芯PDIUSBD12、蓝牙芯片BC4、温度监测芯片DS18B20等,实现了对温度的监测。系统采用蓝牙无线通信协议,实现数据的无线传输。具体阐述了软硬件的设计并给出了部分硬件电路图和程序流程图。     

时段式教室照明节能控制器的设计

介绍了一种可预设定时间的照明节能控制器的研发.该控制器硬件以AT98S52单片机为控制芯片,DS12C887时钟芯片为时钟计时,软件采用MCS-51单片机汇编语言,可在每天预定的3个时间段内对教室、车间等公共场合的照明灯进行集中控制,实现在该3个时段内当房间无人时关断照明,房间有人时开启照明并适时延长照明时间的节能控制.该控制器时钟运行不受市电停电影响,时钟年误差小于10 min.     

At-Risk High School Students Recovering Course Credits Online: What We Know and Need to Know

The majority of American high school students enrolling in online education are doing so in credit recovery courses. These are online courses specifically for students who previously failed a face-to-face version of the course. Despite the popularity of credit recovery courses, the literature on online learning largely ignores credit recovery courses and students. Assuming credit recovery students are similar to other online learners can be misleading. In this article, the existing literature on credit recovery is reviewed in 3 specific areas: the proliferation of credit recovery courses, the student experience in credit recovery courses, and outcomes and impacts of credit recovery. Suggestions are given for how to advance the credit recovery literature in future research of online learning.     

微波促进杂多酸催化双氧水氧化环已酮制备己二酸

本文研究了微波促进杂多酸催化剂催化双氧水氧化环己酮制备己二酸的反应,考察了5种催化剂以及催化剂用量、反应原料、微波辐射功率和辐射时间对己二酸产率的影响.反应的优化条件为：3.5ml环己酮、0.5g钨酸钠、0.5g磺基水杨酸、15ml30%双氧水,在微波辐射功率为400W下反应50min,其产率达72.37%,产物经红外光谱表征.     

Class size and achievement in introductory economics: Evidence from the TUCE III data

Does class size affect achievement in introductory economics? This paper addresses this question using a national economic education data base (TUCE III), consolidating these data so that each observation represents a single class rather than a single student, thereby alleviating several estimation problems that plague empirical work in this area. Our results indicate that class size does not affect student achievement, and further, that class characteristics over which instructors or department chairs have control also do not influence achievement. These results are remarkably robust to different specifications, so long as students' Scholastic Aptitude Test (SAT) scores are used to control for ability and account is taken of whether the TUCE test result counted toward the students' final grade.     

美国K-12阶段技术教育:背景、现状与启示

着当代技术的高速发展,技术教育得到了世界各国的广泛重视。美国K-12阶段技术教育以技术素养的培养为目标,在课程内容设置上具有多样性,技术课堂教学强调技术设计,并重视技术教师培养和培训。美国K-12阶段技术教育的许多经验可为我国中小学技术教育提供借鉴。     

美国《CSTA K—12计算机科学课程标准(2017年修订版)》的解读与启示

普及信息技术教育,是我国国家战略和教育发展改革的重要组成部分,扎根于课堂教学是有效落实的根本。《CSTA K-12计算机科学课程标准(2017年修订版)》基于全纳教育的教育理念、计算机科学的学科本质、面向未来的教育需求和实践可操作的教学标准进行研制和表达,其学科概念结构化体系、普及计算机科学教育、将计算思维作为思维方式和教学目标融于多学科教学中、系统进阶的结构化表述与呈现方式等方面的设计,对我国信息技术学科课程建设、课程标准内容的设计、面向每个学生的课堂教学的推进,提供了有益的参考和借鉴。     

从第12届全运会探析新周期我国女子体操竞技实力

通过录像观察、问卷调查、专家访谈和数理统计等方法,对参加第12届全运会女子体操比赛运动员的情况进行调查研究,并全面分析了新周期我国女子竞技体操四个项目的竞技实力。结果显示,当前我国女子体操专业队运动员年龄偏大、数量不足、伤病严重,且"青黄不接",缺乏领军人物;跳马难度有所提高,但完成质量总体不高;高低杠有所突破和提高,具备较高实力,但缺乏顶尖人才;平衡木表现平平;自由体操在难度和质量上均无明显突破。     

Are returns to education on the decline in Venezuela and does Mission Sucre have a role to play?

Anecdotal evidence points to a falling standard of living for the educated in Venezuela. During this same period, President Hugo Chávez implemented several education reforms. We focus on a major university education reform known as Mission Sucre and its potential impact on returns to university education. First, we show that returns to education decreased significantly in Venezuela from 2002 to 2008. Subsequently, we explore the impact of the program on non-program participants and provide evidence that a substantial part of the falling returns at the tertiary level can be linked to Mission Sucre. Our results suggest that the reform created a negative externality on students who did not participate in the program, leading to a 2.7 percentage point decline in returns to university education for non-Mission Sucre students in the 23–28 age cohort.     

Study of Serum Homocysteine, Folic Acid and Vitamin B12 in Patients with Preeclampsia

The present study was carried out to evaluate the occurrence of association between homocysteine, folic acid and vitamin B(12) in patients with preeclampsia. Fifty preeclamptic patients from gynecology ward were studied for estimation of serum homocysteine, folic acid and vitamin B(12) over a period of October 2007 to June 2010. Serum homocysteine and folic acid, and vitamin B(12) were determined by means of Immulite 1000 analyzer. The statistical analysis of study group of preeclampsia compared with normotensive control group, showed significant alterations in serum homocysteine, folic acid and vitamin B(12) concentrations in preeclampsia. Inverse association between serum homocysteine and folic acid, and vitamin B(12) levels were observed in preeclampsia. The present study found hyperhomocysteinemia and deficiency of folic acid and vitamin B(12) along with increased blood pressure as a risk factor for cardiovascular disease (CVD) in preeclampsia.