高职《建筑力学》教学改革与实践

《建筑力学》是建筑工程类专业的专业基础课程,内容覆盖面广、难度大,一直是高职院校建筑工程类专业教学中的一个重点和难点。文章分析了传统的建筑力学教学中存在的问题,结合近些年的教学经验,介绍了已经实行的改革措施,希望能提高建筑力学的教学质量,提高学生用力学知识解决实际问题的能力。     

碳源对氮素在不同潜流带介质中的迁移转化规律研究

通过室内土柱实验模拟氮素在不同沉积物的潜流带中迁移转化途径,选取粗砂、细砂、粉砂三种介质,以浓度为65.5mg/L的硝酸钾溶液为原水,研究硝态氮在不同沉积物的潜流带中的环境行为;再通过补充碳源,研究碳源对氮的迁移转化过程的影响。实验结果表明,在不同的沉积物介质中,氮的迁移转化不同,主要受介质孔隙度和介质中有机质的制约。由于粉砂介质中孔隙度较小,有利于微生物的附着,且有机质含量较多,反硝化作用和异化还原作用强烈,所以硝酸盐氮下降的最多,而在粗砂介质中孔隙度相对较大,不利于微生物附着,且有机质含量相对较低,反硝化作用和异化还原作用较弱,硝酸盐氮下降的较少。而添加碳源后,反硝化作用和异化还原作用增强,三根柱子中的硝酸盐氮都降到很低的值,说明碳源对潜流带中硝态氮的去除起着重要的作用。     

参与PPP能否减轻企业税负——基于准自然实验的证据

政府与社会资本合作（PPP）模式在解决公共服务供给不足问题的同时,也给社会资本方的经营带来影响。企业参与PPP与政府建立良好合作关系是否有助于其税负的减轻？基于PPP概念股上市公司数据,本文采用准自然实验框架实证研究了企业参与PPP对其税负的影响。研究结果表明：企业参与PPP提高了其避税程度,降低了税负水平。分行业看,建筑业效应在统计上最为显著,而电力、热力等市政建设类项目企业参与PPP后税负不降反升。分区域看,东部和中部地区企业参与PPP对其税负有显著的降低,而西部地区并不显著。政策启示是在严格执行显性税收优惠的同时,规范PPP项目中政府与企业之间的利益关系。     

政府研发补贴促进企业创新了吗

政府补贴能否促进企业创新一直存在争议。与以往从资源视角探讨政府补贴与企业创新关系的研究不同,基于信号理论视角,以2012—2016年沪深A股非金融类上市公司为研究样本,通过剔除非研发补贴的噪音并控制样本自选择偏误,实证检验中国转型经济背景下,政府研发补贴对企业创新的微观政策效应,以及企业层面制度因素（产权性质）和区域层面制度因素（制度环境）对该效应的调节作用。研究发现,政府研发补贴释放的积极信号能够帮助企业获取外部创新资源,有效促进企业创新;相比于国有企业,政府研发补贴对非国有企业创新的激励效应更强;制度环境越好,政府研发补贴对企业创新的激励效应越强。研究理论丰富了科技创新政策有效性和信号理论相关研究。同时,研究发现,政府应继续加大对企业创新活动的补贴额度,不断深化所有制改革,为企业创新营造良好的外部制度环境;另外,企业还应充分发挥政府研发补贴信号的杠杆效应,拓宽外部创新资源获取渠道。     

Risk Behaviours and Grazing Land Management: A Framed Field Experiment and Linkages to Range Land Condition

We use a framed field experiment considering hypothetical stocking rate decisions made by grazing enterprise managers and estimate non‐linear multinomial logit models for a range of nested non‐expected utility and expected utility models. The risk and decision‐bias parameters for five models estimated for individual responses are shown to be significantly related to land condition but in ways which suggest behavioural aspects of decision making are critical in understanding land management and stocking rate decisions. Our results show that individual heterogeneity in decision making amongst farming groups is likely to be a significant source of variation in farming intensity and technology adoption decisions. This heterogeneity does not appear to be a reflection of socio‐demographic characteristics. Furthermore, decision functions appear to be biased toward selection of simpler representative functions (e.g. Expected Utility) for sample averages. This suggests that experimental findings that Expected Utility is representative for actual decisions may be due to sample averaging rather than reflect actual behaviour.     

Motivations to grow energy crops: the role of crop and contract attributes

Perennial energy crops are a promising source of bioenergy whose production involves production risks, long‐term commitment of land and need for crop‐specific investments without the coverage of crop insurance potentially available for conventional crops. We conduct a choice experiment in five states in the Midwestern and South‐central regions of the U.S. to examine the effect of crop‐contract attributes on the joint discrete‐continuous choice decisions to adopt an energy crop and convert acres to it from a status quo use, while controlling for the effect of various farmers’ risk and time preferences, sociodemographic characteristics, and availability of crop insurance for conventional crops. We find robust evidence that high discount rates, high upfront establishment costs and need for crop‐specific investments create disincentives for adoption and allocation of land to energy crop production. The effects of riskiness of returns and risk aversion are less robust across specifications. The effect of conventional crop insurance on the energy crop adoption decision differs across types of insurance; in particular, farmers with revenue insurance are statistically significantly less likely to adopt an energy crop. Our results have implications for the design of effective contracts and policy incentives to induce the production of energy crops.     

Valuation of ecosystem services provided by irrigated rice agriculture in Thailand: a choice experiment considering attribute nonattendance

This research investigates how the public of a middle‐income country, Thailand, values ecosystem services associated with irrigated rice agriculture using a choice experiment. The results show a significant willingness to pay for services such as drought mitigation, water quality and the environment and maintenance of rural lifestyles and rice landscapes. The iterative procedure developed to fully analyze the incidence of attribute nonattendance (ANA) improved the model fit when compared with a multinomial logit model or an ANA model with potentially only one attribute ignored at a time (ANA‐1). Moreover, the inferred probability of the class of respondents having attended all attributes was 45%, compared to 9% with ANA‐1 model. However, it also suggests that 55% of the respondents made their choices by considering only two of the five attributes. Finally, this research also suggests that failing to consider ANA does not change the public ranking of scenarios contrasted by the services they would provide but would overestimate the WTP for these scenarios.     

Forecasting the Adoption of GM Oilseed Rape: Evidence from a Discrete Choice Experiment in Germany

This paper explores farmers’ willingness to adopt genetically modified (GM) oilseed rape prior to its commercial release and estimates the ‘demand’ for the new technology. The analysis is based upon choice experiments with 202 German arable farmers. A multinomial probit estimation reveals that GM attributes such as gross margin, expected liability from cross pollination, or flexibility in returning to conventional oilseed rape significantly affect the likelihood of adoption. Neighbouring farmers’ attitudes towards GM cropping and a number of farmer and farm characteristics were also found to be significant determinants of prospective adoption. Demand simulations suggest that adoption rates are very sensitive to the profit difference between GM and non‐GM rape varieties. A monopolistic seed price would substantially reduce demand for the new technology. A monopolistic seed supplier would reap between 45% and 80% of the GM rent, and the deadweight loss of the monopoly would range between 15% and 30% of that rent. The remaining rent for farmers may be too small to outweigh possible producer price discounts resulting from the costs of segregating GM and non‐GM oilseed rape along the supply chain.     

Myopia and saliency in renewable resource management

An important challenge in managing renewable resources is to understand why owners and managers sometimes make decisions that deplete resources and future earnings, such as when graziers allow pastures and land condition to be degraded. In this paper, we test two potential reasons for unsustainable management practices, myopia and salience, with each explaining why resource managers may exhibit impatience in harvest decisions. Myopia is associated with decision makers placing lower weight on future outcomes than would be implied by their pure time preference. Salience is associated with overweighting of consumption ‘now’, implying inconsistency in time preferences. To test for these effects on renewable resource management, an incentivised, dynamic field experiment was carried out with rangeland grazing enterprise owners in north‐eastern Australia that related management choices with uncertain rainfall events to both profits and land condition over time. Results demonstrate that respondents exhibiting myopia/salience in their choices tended to achieve lower cumulative scores in the experiment, as well as lower land conditions on their properties as measured with remote sensing data. Our results explain why there may be persistent optimisation failures by resource owners that reduce both profits and environmental outcomes.     

Country of origin labeling for complex supply chains: the case for labeling the location of different supply chain links

We investigate the value of a country of origin label (COOL) that separately identifies the geographic location of different stages in a food product's supply chain. We estimate the willingness‐to‐pay (WTP) of U.S. consumers for a packaged cereal product where the key grain ingredient may be grown in one country and processed in a second country (multicountry supply chain) and compare it to equivalent products that have both stages located in a single country. We find consumer WTP for products with single‐country and multicountry supply chains are statistically different, meaning that simplifying a multicountry label by listing only the country where the ingredients are grown or only the country where the ingredients are processed can result in different consumer values. We also find that for countries with a poor quality reputation, consumers respond more negatively when that country has the “last touch” than when that country's involvement is limited to upstream supply chain links.