高温下石灰岩膨胀特性和力学特性的试验研究

利用自行研制的岩石高温装置和RMT-150C岩石力学试验机,对石灰岩试件在200~700°C高温双向约束条件下的膨胀特性和力学特性进行了试验研究。结果表明:升温过程中,随着温度的升高,石灰岩试件两个约束方向的膨胀应力在600°C前逐渐增加,600°C或650°C以后出现减小现象;石灰岩垂直层理方向的热膨胀应力大于平行层理方向的热膨胀应力。恒温过程中,600°C以前的试件两方向膨胀应力曲线都随时间延长呈平稳上升,但曲线斜率远远小于升温过程;恒温一定时间后,膨胀应力趋于该温度的一个稳定值。700°C恒温结束后,石灰岩两方向的膨胀应力小于恒温前的值,说明到一定温度后石灰岩已膨胀到极限。在试验温度范围内,石灰岩峰值应力随温度升高而降低,700°C时,峰值强度值比常温下降低了58.92%,说明高温对岩石的强度会产生明显的弱化作用。石灰岩峰值应变随温度升高先增加后减少,500°C前峰值应变增加,之后逐渐减小。由于受约束条件限制,在过高温度后,石灰岩内部裂隙部分闭合,空隙数量减少,致使一定温度后其热膨胀应力和峰值应变可能减小,但具体原因有待进一步研究。     

Impact of varying soil structure on transport processes in different diagnostic horizons of three soil types

When soil structure varies in different soil types and the horizons of these soil types, it has a significant impact on water flow and contaminant transport in soils. This paper focuses on the effect of soil structure variations on the transport of pesticides in the soil above the water table. Transport of a pesticide (chlorotoluron) initially applied on soil columns taken from various horizons of three different soil types (Haplic Luvisol, Greyic Phaeozem and Haplic Cambisol) was studied using two scenarios of ponding infiltration. The highest infiltration rate and pesticide mobility were observed for the Bt₁ horizon of Haplic Luvisol that exhibited a well-developed prismatic structure. The lowest infiltration rate was measured for the Bw horizon of Haplic Cambisol, which had a poorly developed soil structure and a low fraction of large capillary pores and gravitational pores. Water infiltration rates were reduced during the experiments by a soil structure breakdown, swelling of clay and/or air entrapped in soil samples. The largest soil structure breakdown and infiltration decrease was observed for the Ap horizon of Haplic Luvisol due to the low aggregate stability of the initially well-aggregated soil. Single-porosity and dual-permeability (with matrix and macropore domains) flow models in HYDRUS-1D were used to estimate soil hydraulic parameters via numerical inversion using data from the first infiltration experiment. A fraction of the macropore domain in the dual-permeability model was estimated using the micro-morphological images. Final soil hydraulic parameters determined using the single-porosity and dual-permeability models were subsequently used to optimize solute transport parameters. To improve numerical inversion results, the two-site sorption model was also applied. Although structural changes observed during the experiment affected water flow and solute transport, the dual-permeability model together with the two-site sorption model proved to be able to approximate experimental data.     

亚临界水技术处理厨余垃圾的比较研究

在亚临界实验条件下,以淀粉、纤维素类物质为模型化合物,H₂O₂为氧化剂,研究了厨余垃圾（大米、白菜）在亚临界水中部分氧化获取小分子有机酸的过程中处理时间、处理温度、加氧量对有机酸（甲酸、乙酸）生成的影响。以碳转化率为评价指标,确定反应最佳条件。实验结果表明：淀粉和纤维素分别在处理时间1～1.5 min,加氧量70%～100%,温度280℃;处理时间1～2 min,加氧量70%～100%,温度280～300℃条件下,生成有机酸浓度最大,达到最佳工艺条件。     

水葫芦压榨液厌氧发酵及其发酵液对青菜种子发芽和生长的影响

研究了水葫芦压榨液厌氧发酵过程物质的变化,分析了水葫芦压榨液的发酵液(简称发酵液)对青菜种子发芽及后续生长的影响.结果表明,厌氧发酵能显著降低压榨液中的COD,在厌氧发酵结束时,COD从5 377.0mg/L下降到730.0mg/L,下降86.4%;TN从126.6 mg/L下降到79.7 mg/L,氮素流失37.0%,且主要发生在厌氧发酵初期;TP从31.1 mg/L下降到25.0 mg/L,下降19.6%;发酵液中悬浮物(SS)和可溶性固体(DS)分别下降到719、600 mg/L.分别用蒸馏水、水葫芦压榨液和各阶段的发酵液(发酵时间分别为6、20、27、30 d)进行青菜种子发芽试验(历时10 d),平均发芽率分别达到79%、54%、51%、82%、87%、89%.在10 d的青菜苗生长时间内,平均苗高与发酵时间呈显著正相关,说明发酵液具有作为植物液体肥料使用的潜力.     

高职食品工艺学实验室建设和教学方法的探讨

实验教学是高职教育中不可缺少的环节,多媒体课件的制作与演示性实验教学作为重要的教学方法可以应用于高职食品工艺学的辅助教学.本文介绍了食品工艺实验室设计及教学方法的要求和特点,为使食品工艺实验室实现可持续发展,该实验教学必须与其他学科结合,实验项目必须反映加工新技术,培养学生自发动手动脑能力.     

The political economy of certificates for land use in Germany – experimental evidence

Certificate trading schemes have been discussed as a cost-efficient means of reducing urban land consumption in Germany by capping and reallocating permissions to conduct building projects. However, in contrast to the established cap & trade systems for emissions, reputation-seeking politicians would be in charge of buying and trading certificates – an aspect not considered to date. We thus present a laboratory experiment that captures politicians’ incentives connected to electoral cycles in a cap & trade scheme for land consumption, whereby tradable certificates are auctioned and grandfathered in equal shares. We find the cap & trade system to be efficient at large; yet, there are several politically relevant distortions that are aggravated by self-serving incentives. We thus identify potential problems to a cap & trade system for urban land consumption that could substantially reduce both its assumed superior efficiency and its political feasibility.     

Do exurban communities want more development?

Most land-use surveys of exurban residents focus on eliciting preferences for residential development and open space conservation. This article, in contrast, reports on a stated preference study of exurban residents that assesses the relative attractiveness of a variety of commercial and recreational land uses. Focus group participants and town planners proclaimed a demand for certain commercial services such as modern grocery stores and fine-dining restaurants, but survey respondents generally exhibit a strong preference for no additional development beyond the current rate of development. Results show that if additional development is to occur, then recreational services are generally preferred over more traditional commercial development. Combining two commercial services in a single development project are strongly preferred to stand-alone developments. Our approach illustrates how planners may uncover misconceptions about and priorities for land conversion through examining residents’ preferences.     

Sorption and desorption of glyphosate,MCPA and tetracycline and their mixtures in soil as influenced by phosphate

Phosphate fertilizers and herbicides such as glyphosate and MCPA are commonly applied to agricultural land, and antibiotics such as tetracycline have been detected in soils following the application of livestock manures and biosolids to agricultural land. Utilizing a range of batch equilibrium experiments, this research examined the competitive sorption interactions of these chemicals in soil. Soil samples (0-15 cm) collected from long-term experimental plots contained Olsen P concentrations in the typical (13 to 20 mg kg^?1) and elevated (81 to 99 mg kg^?1) range of build-up phosphate in agricultural soils. The elevated Olsen P concentrations in field soils significantly reduced glyphosate sorption up to 50%, but had no significant impact on MCPA and tetracycline sorption. Fresh phosphate additions in the laboratory, introduced to soil prior to, or at the same time with the other chemical applications, had a greater impact on reducing glyphosate sorption (up to 45%) than on reducing tetracycline (up to 13%) and MCPA (up to 8%) sorption. The impact of fresh phosphate additions on the desorption of these three chemicals was also statistically significant, but numerically very small namely < 1% for glyphosate and tetracycline and 3% for MCPA. The presence of MCPA significantly reduced sorption and increased desorption of glyphosate, but only when MCPA was present at concentrations much greater than environmentally relevant and there was no phosphate added to the MCPA solution. Tetracycline addition had no significant effect on glyphosate sorption and desorption in soil. For the four chemicals studied, we conclude that when mixtures of phosphate, herbicides and antibiotics are present in soil, the greatest influence of their competitive interactions is phosphate decreasing glyphosate sorption and the presence of phosphate in solution lessens the potential impact of MCPA on glyphosate sorption. The presence of chemical mixtures in soil solution has an overall greater impact on the sorption than desorption of individual organic chemicals in soil.     

Heterogeneity of farmers' preferences towards agri-environmental schemes across different agricultural subsystems

Specialised literature on the uptake of agri-environmental schemes (AES) has paid little attention to how this can be influenced by the different types of agricultural systems. This paper analyses the heterogeneity of farmers' preferences towards these schemes, distinguishing between different subsystems within the same agricultural system. We use the choice experiment method to analyse the case study of three olive grove subsystems in southern Spain, with the subsystems ranging from extensive to intensive. The results reveal inter- and intra-subsystem heterogeneity of farmers' preferences towards AES, both in general and specifically related to scheme attributes. A variety of factors appear to lie behind inter-subsystem heterogeneity, especially those associated with subsystem specificities (principally, the type of joint production). Likewise, numerous factors play a role in intra-subsystem heterogeneity, most of them related to farm/farmer socio-economic and physical characteristics. These findings will help in the design of more efficient AES.     

污泥生物沥滤工艺优化和重金属分配研究

为了得到嗜酸硫细菌沥滤污泥中重金属的最佳工艺参数,对沥滤过程进行3因素4水平的正交实验研究。3种影响因素的水平设置分别为:污泥浓度35、25、15和5 g/L,单质硫投加量15、10、5和1 g/L,接种量15、10、5和3 g/L。对沥滤过程污泥中7种重金属(As、Cd、Cr、Cu、Ni、Pb和Zn)的去除率进行极差分析,提出了因素影响程度依次为单质硫投加量污泥浓度接种量,且最佳工艺条件为:污泥浓度25 g/L,单质硫投加量10 g/L,接种量为5%。采用超声波-离心方法,分步提取污泥胞外聚合物(EPS)的2种形态:松散结合态(LB)和紧密结合态(TB)。分析其中的重金属浓度,提出沥滤后重金属在污泥EPS的赋存以LB为主。