碳汇营林技术推广的认知基础测度与实证研究

基于文献回顾与理论假设,设计了一套用于测评农户对碳汇营林技术推广过程中内在认知基础的量表体系,并根据调研数据对该量表测度效果进行了实证检验。检验最终结果显示:在碳汇营林技术推广过程中,农户关于碳汇营林技术推广的交易成本与权利损失认知、农户关于碳汇营林技术推广的社会生态与经济收益认知、农户关于碳汇营林技术推广的组织参与认知等,都将对推广过程的实现度与满意度产生显著性影响。这一结果说明,本研究所提出的影响农户对碳汇营林技术推广的认知基础测度框架大体趋于合理并可以接受,这就为更进一步进行碳汇营林技术推广相关管理制度的设计与构建,提供了一个主观数据设置方面的实证支持。     

土壤腐殖物质形成转化与结构特征研究进展

土壤有机质(SOM)是极为重要和复杂的天然有机物,从化学本质出发,SOM包括腐殖物质(HS)和非腐殖物质两个主要部分。HS是土壤SOM的主体,在土壤养分循环和碳截获方面具有重要作用。SOM的重要性和复杂性共存,这是激励研究者勇于探索的不竭动力。为了能够更好地了解土壤HS,本文对HS及其组分的形成转化及稳定性(包括形成顺序、相互转化、驱动因素、同位素分异、热力学稳定性等),化学组成和结构特征(包括HS组分的提取、分组、纯化、结构表征等),人为措施响应规律(包括耕作、施肥、土地利用的影响)的研究现状进行了回顾和总结,同时提出今后HS研究中要进一步应用先进技术、重新重视HS化学分组研究、进一步认识HS结构特征,以及探索HS形成转化机制及其与农业措施的关系。     

A validated mechanistic model of carrot (Daucus carota L.) growth

A mechanistic model of carrot vegetative and root development was constructed. This model determined canopy photosynthesis over a day, assimilates were then partitioned into either roots or leaves via temperature dependent partitioning coefficients. Assimilates were lost via terms describing growth and maintenance respiration. The model was calibrated on data from four different carrot cultivars, originating from the UK (Autumn King), Syria (Carrot_S), Poland (Dolanka) and Russia (Hibinskaja), grown in controlled environment glasshouse compartments at one of six temperatures (9–30 °C) repeated over three sowing dates. Calibration of the model showed that it could account for between 83 and 95% of the variance in carrot plant and root dry weights. The model was then validated using independent data from the same cultivars of carrots grown in the field at Reading. In this instance, the model accounted for 75 and 79% of the variance in plant and root weight, respectively. Two other independent data sets were used to validate the model, including carrot of a different cultivar (Panther) grown in phytotrons at temperatures between 9 and 21 °C, at two different locations and over a three sowing dates. In this instance, the model accounted for between 63 and 69% of the variance in root weight. The model also predicted that if ambient carbon dioxide levels increased from 348 to 551 μmol mol⁻¹, root dry weight would increase by 12%, which is within the margin of error of the experimental value of 16% reported in the literature. The model can therefore be used to study the potential impacts of global climate change on carrot production, as well as to rapidly predict whether germplasm is suited to any particular environment.     

Relationship of percolation stability of soil aggregates to land use, selected properties, structural indices and simulated rainfall erosion

Simple tests of structural stability are needed for evaluating the ease with which soils slake and erode when in contact with water. In a laboratory study, we related the percolation stability (PS) of 22 Nigerian soils to land use, soil properties, structural stability indices and simulated rainfall erosion. All measurements were carried out with the 1–2 mm diameter air-dry aggregates. Land use influenced PS more than the type of soil. Forest soils, bush fallows, mulched, minimally tilled plots and pasture lands had rapid PS (>250 ml/10 min) values, whereas mulched conventionally tilled plots, bare fallows and continuously cultivated plots from where residues were removed by burning had relatively slow to moderate PS values (34–241 ml/10 min). The single most important soil property that correlated positively with PS is organic matter (OM) (r = 0.55^*) followed by total Fe + Al (r = 0.52^*). The significant inverse relationship (r = −0.49^*) between log (PS) and log (pH/OM) indicates a decrease in PS of these acidic, low-OM soils with increasing pH levels. The percent water-stable aggregate (WSA) >0.20 mm diameter, aggregated clay index (AC) and clay dispersion ratio (CDR) correlated weakly with PS. Conversely, the sealing index (SI) (i.e. the ratio of saturated hydraulic conductivity of an uncrusted to that of a crusted soil) had a strong, inverse relationship with PS (r = −0.97^***). These relationships indicate that PS measures the slakability (and not dispersibility) of soils. The relationship between PS and erosion (E) was an exponential decay form, E = 102 e^−0.0043PS (r² = 0.98) and showed that high interrill erosion rates would be expected on soils with PS < 250 ml/10 min. The PS which is simple to measure, is, therefore, a good indicator of structural stability for assessing the potential of these soils to erode.     

影响浅海网箱养殖鱼类生长的因素分析_解析结构模型法的应用

ｒｅｔｔ［１９７９］认为影响养殖鱼类生长的因素中,食量大小不是影响生长率和总效率的唯一因素。生物的与非生物的环境因素,经新陈代谢也会影响鱼类的活动与生长。Ｆｒｙ［１９４７,１９７１］认为有四种非生物的环境因素：①控制因子如温度,控制代谢反应发生的速率;②限制因子如溶解氧,限制某些生化变化发生的速率;③潜伏因子如盐度,会对代谢系统强加一个额外负担,因而阻碍了代谢系统对温度变化的充分反应;④直接因子如光线,会引起代谢系统以适当方式反应,白天长度变化会激发腺成熟。Ｂｒｅｔｔ［１９７９］与Ｂｒｅｔｔ和Ｇ…     

Experimental Study on the Beam Bars Detail in Exterior Short Pier Shear Wall Joints

By experiment of the beam bars in exterior short pier shear wall joints,the anchorage performance of the beam bars in joints on the action of low cyclic load have been studied to attest if the beam bars in exterior short pier shear wall joints can sufficed with the demanding of anchorage intensity and anchorage rigidity, when the anchorage of beam bars satisfy the requirement of the code.     

新生代农民工择业行为及影响因素实证分析——基于结构方程模型

基于对新生代农民工的问卷调查数据,运用结构方程模型探讨影响新生代农民工择业行为的各种因素以及因素之间的关系和强度。结果表明:新生代农民工择业行为体现出明显的主观意识,外界影响因素对个人因素产生不同程度的影响,并通过个人因素对最终职业选择产生影响。     

Seismic Load Tests on Reinforced Concrete Beam-Column Sandwich Joints with High Shear Stress

Seven reinforced concrete Beam-Column sandwich joint specimens were tested under cyclic load. The performances of these specimens consisting of loads resistance, deflection, ductility, displacement, energy dissipation could satisfy the requirement of structures for seismic design. The phenomena that concrete in joint region was crushed by axial load or eccentric load were never observed,and final failure for a multitude of specimens occurred by shear force. Though a few of performances such as beam bar anchorage capacity were not as well as those of traditional joints ,it is feasible for sandwich joints used while establishing structures.     

规模养猪场户清洁生产认知与行为的影响因素及其作用机理——基于山东省509家规模养猪场户的调查数据

生猪养殖是重要的环境污染源,规模养猪场户实施清洁生产行为是防治生猪养殖污染的重要途径。为从根本上降低生猪养殖污染,避免废弃物末端治理带来的弊端,实现环境效益与经济效益相统一。依据计划行为理论,利用山东省17地市509份问卷调查数据,运用结构方程模型,实证研究了规模养猪场户清洁生产认知与行为的影响因素及其作用机理。结果表明,由如何看待清洁生产和对生猪养殖污染熟悉度组成的规模养猪场户清洁生产态度,以及由年龄、受教育年限和生猪养殖出栏量组成的规模养猪场户禀赋特征对清洁生产认知具有显著的正向影响;由政府对清洁生产支持力度和经营组织对清洁生产的要求组成的外部规范对清洁生产认知有正向影响,但并不显著;规模养猪场户清洁生产认知对源头预防行为、过程控制行为和末端治理行为有显著的正向影响;规模养猪场户清洁生产态度、禀赋特征及外部规范约束对清洁生产行为有间接影响。其作用机理为：规模养猪场户清洁生产行为受制于认知程度,而认知程度又是行为主体态度、外部规范和主体自身禀赋特征共同作用的结果,而三者产生的作用条件又归因于外界环境（政府机构、经营组织、上下游企业等）与行为主体间的不断沟通。可见,规模养猪场户清洁生产行为作用机理并非单个因素间简单的线性作用,而是全产业链参与者与其所处环境间相互作用的结果。因此,应当根据认知与行为的影响因素和作用机理,提高规模养猪场户对清洁生产的积极态度,加强外部规范性,强化主体自身良好的禀赋,通过较高的认知水平正向作用于行为的形成和完善,并最终从根本上降低生猪养殖污染,实现经济效益与环境效益相统一。     

明式家具用料与结构的剖析

明式家具在用材上大部分选用的是重量适宜、材质均匀致密而且坚韧、色泽柔和纹理美观、切削面光滑、耐久性较强的散孔材。在家具结构上,根据各零部件接合部位的要求不同,设计的各种榫接合形式是合乎科学道理的。且加工制作精度高,配合严密,结构强度好。这些说明明式家具在当时无论在造型上或者在用料、结构和制作工艺上都达到了相当高的水平。