Pitfalls in Drawing Policy Conclusions from Retrospective Survey Data: The Case of Advertising and Underage Smoking

Measuring the impact of potentially controllable factors on the willingness of youth to undertake health risks is important to informed public health policy decisions. Typically the only data linking these factors with risk-taking behavior are retrospective. This study demonstrates, by means of a recent example, that there can be serious pitfalls in using even longitudinal retrospective data to draw conclusions about causal relations between potentially controllable factors and risk-taking behavior.     

9GLQ—2.1型割搂草机组的研制

本文主要论述了9GLQ－2．1型割搂草机组的结构、性能特点及工作原理．并对机组研制的技术关键和机组的性能作了简要分析．根据研究、设计的结构参数，试制了样机，经测试及200小时生产考核，证明设计思路正确，性能稳定．     

农机服务发展与粮食生产效率研究:2004—2016——基于变系数随机前沿分析

采用“两步法”研究了农机服务发展与中国粮食生产效率的关系.基于2004-2016年全国31省份粮食生产投入产出的面板数据,利用变系数随机前沿分析方法测算了中国粮食生产的技术变化、技术效率以及全要素生产率,然后构建农机服务发展影响粮食生产效率的OLS回归模型.结果表明:(1)31省份粮食生产的投入要素产出弹性和技术效率存在明显差异,2008年粮食技术变化最为明显,粮食全要素生产率的增长在2008年高达5%.(2)农机服务在2008年以后对粮食全要素生产率的增长具有显著的促进作用,农机服务对粮食TFP的作用存在一定的滞后效应.(3)农机服务发展与劳动产出弹性具有替代关系,与化肥和机械产出弹性具有互补关系.在三大粮食作物中,小麦机械化程度最高,水稻和玉米的机械化程度还有待提升.     

全球农机装备专利技术信息分析及启示

采用Innography专利检索与分析工具,从专利授权年度趋势、专利布局、主要创新机构竞争态势、技术研究热点、核心专利挖掘等维度进行专利信息分析.分析结果表明,美国、德国、法国在农机装备领域的技术实力较强,拥有各自独特的核心专利,并在全球进行广泛的策略性布局.中国虽然是该领域最大的技术来源国,但核心专利拥有量不多,海外专利申请也相对缺乏.目前农机装备领域技术研发集中在A01C7、A01B49、A01B33等IPC类别.法国库恩、美国迪尔、美国凯斯纽荷兰等大型跨国公司掌握了产业发展的制高点,中国农大、东北农大等单位技术实力强,但并不是该领域的领跑者.     

农机跨区作业——加速我国农业机械化进程的战略选择

我国农业机械化进程突飞猛进,农机跨区作业功不可没.在针对后者对前者影响的基础上进行定量分析,提出推动农机跨区作业,加速我国农业机械化进程建议,以实现我国农业机械化跨跃式超常规发展.     

《电机与拖动》课实验教学改革的探讨

实验教学是培养21世纪综合性、应用性复合人才的有效途径。为了适应高等教育发展和社会的需求,我们选择了对《电机与拖动》的实验教学进行了尝试性的改革,提出了实验教学的“四个目标”,以突出培养学生创新意识和创造能力为重点,从教学内容、方式、管理制度上进行了实验教学改革的实践和探讨。     

How do cohabiting couples with children spend their money?

Increasing rates of cohabitation in the United States raise important questions about how cohabitation fits in with the definition of family. Answers to this question depend in part upon the extent to which cohabitors’ behavior differs from that of other family types. Using data from the Consumer Expenditure Survey, we compare the expenditure patterns of cohabiting‐parent (n = 1,804), married‐parent (n = 33,159), divorced single‐parent (n = 7,641), and never‐married single‐parent (n = 2,893) families. We find that cohabiting‐parent families, compared to married‐parent families, spend a greater amount on 2 adult goods (alcohol and tobacco) and a smaller amount on education. Cohabiting‐parent families also differ in their spending patterns from divorced single‐parent families and from never‐married single‐parent families. Overall, our results show that cohabiting‐parent families allocate their budgets differently than do other families.     

割草机光刃动刀片磨损规律的研究

用不同材料和同一材料不同工艺制成的动刀片，在模拟割草机上进行割草试验．试验结果表明，割草机刀片与金属切削刀具及一般机件的磨损规律不同。除工作环境等因素外，刀片的几何条件（刃口曲率半径小）是造成区别的主要原因。     

Environmental Tobacco Smoke: Science vs. Rhetoric

After an extensive review and analysis of the scientific evidence on the respiratory health effects of passive smoking, the U.S. Environmental Protection Agency concluded that environmental tobacco smoke causes lung cancer in adult nonsmokers and increases the risk of a variety of non-cancer respiratory disorders, especially in children. This article is a response to claims in Dr. Gio Gori's article "Policy Against Science: The Case of Environmental Tobacco Smoke," appearing in the same issue of this journal, that such conclusions are unwarranted. This response focuses only on the respiratory health effects of environmental tobacco smoke.     

劳动力禀赋变化与生产条件差异下的农业技术选择——以中国水稻机插秧技术推广应用为例

农业生产要素禀赋状况变化与农业生产条件差异对农业技术进步有着重要的影响。通过23个水稻生产省（直辖市、自治区）2004—2015年的面板数据实证分析发现：随着水稻雇工工价不断上升和各地区水稻机插秧水平不断提高,各地区的农业生产条件也对水稻机插秧水平具有显著的影响,农业生产条件的差异是导致地区间水稻机插秧水平差异的重要原因。随着中国农业劳动力逐渐稀缺会诱致劳动节约型技术的不断出现和大量应用,但诱致性技术变迁机制的有效发挥还依赖于各地区农业生产条件。为进一步提高中国农业机械化水平,需要加大农业基础设施建设、改善农机作业条件和提高农机技术水平。