基于变更平衡表的土地利用演化信息提取与预测方法研究——以苏州市为例

变更平衡表为国土资源管理部门历年实地调查、汇总所得,精度高,目前的研究中对其深入的应用较少,基于变更平衡表的应用方法研究可为区域土地利用演变信息提取与预测提供帮助。推导了由连续年份的年度变更平衡表求多年周期的平衡表的方法,提出了基于土地利用综合动态度分析土地利用有序程度的思路,探讨了利用连续年份的变更平衡表预测任意年份土地利用结构的方法,并基于传统方法进行了改进,提出了利用矩阵开方法求预测概率矩阵。应用苏州市一定时期的连续年份的年度变更平衡表对上述方法进行了验证,结果表明:提出的信息提取方法有效,预测结果可信;在分析期内(1998~2008年),苏州市耕地大量减少的去向是各类建设用地增加的来源,区域土地利用有序程度较高;预测显示至2020年土地利用结构变化仍将维持农用地、耕地不断减少和建设用地总量不断增加的趋势,但转化的速率将有所放缓;对变更平衡表的深入应用有一定的借鉴意义。     

长江源区基于坡面尺度的土壤水热过程模拟研究

长江源多年冻土区土壤水热传输过程机理与模拟,是广泛关系到高原生态环境保护恢复和区域水文过程的关键科学问题。因此,以GEOtop模型为研究平台,以长江源不同植被盖度下（裸地、30%、65%和92%）高寒草甸的观测数据为基础,检验模型对土壤水热迁移过程的描述与模拟精度。总体而言,GEOtop模型需要率定的参数较少,从而减少模型模拟的不确定性,提高了模拟精度。对不同植被盖度下土壤温度、水分和实际蒸散发模拟的NSE 系数基本达到08,表明模型能准确模拟高寒生态系统土壤的水热传输过程,可以作为长江源区土壤水热过程的有效模拟工具     

污水处理过程水温变化模型构建与验证

污水处理是一个复杂的生物、物理及化学反应过程.污水水温直接影响到污染物生物处理效果,并对污水处理运行能耗产生重要影响.另一方面,污水中也蕴含着相当热能,是潜在可以回收的低品位能源,加以利用则有望实现污水处理碳中和运行.然而,现有研究很少涉及 污水处理厂污水进、出水水温变化及其影响因素;工程中也只强调冬季保温,并无法从微观角度认识处理过程水温变化规律.为此,研究尝试构建污水处理过程水温变化热量衡算模型,涵盖污水生化反应、机械传热、环境热传递和水蒸发热损失等4个主要涉热过程.与此同时,收集北京某污水处理厂实际水温、气温数据,借助热量平衡图来模拟污水处理过程中水温变化,并对理论模型参数进行校验和修正.通过参数敏感性分析,可以评价不同参数对水温热量的影响程度.基于这些工作,一个污水温度变化模型被构建成功,可用于指导实际污水处理厂水温控制或余温热能回收过程,可助力污水处理厂节能降耗、甚至实现碳中和目标.     

非农就业与土地流转对农户耕地撂荒行为的影响——以闽赣湘山区为例

耕地撂荒是世界各国长期普遍存在的一种土地利用变化现象。基于闽赣湘山区640户农户调查数据,运用Tobit和IV-Tobit模型回归分析得出：农户家庭非农就业每提升10%,耕地撂荒占比会增加1.11%;小规模农户土地转入会提升其耕地撂荒规模,此时扩大经营规模对耕地撂荒的减缓作用甚微,而土地转出会降低非农就业对耕地撂荒的正向影响。此外,农户的劳动力、土地与农业机械等要素投入,以及灌溉条件和地块数等均稳健影响其耕地撂荒行为。农业机械化和土地流转是缓解山区耕地撂荒的重要举措,政府在推动经营规模扩大的同时,应着重提高地块规模,鼓励留村务农劳动力换工,并提升农机社会化服务水平,以及拓宽农户家庭多元化的收入机会。     

基于可疑筛查技术研究有机磷阻燃剂V6转化规律

运用Orbitrap高分辨质谱仪,评估了人体肝微粒体(HLM)代谢V6的转化规律.除5种已被报道过的O-脱烷基、氧化性去磷酸化和氧化脱氯产物外,首次发现了6种新型产物.基于其MS/MS质谱图,该6种代谢产物被鉴定为醛基和羧基产物.其中,5种代谢物生成量随孵育时间呈线性增加趋势,具有累积性.此外,推导的代谢途径表明,脱烷基化和羟基化代谢物进一步转化为次级代谢物,即醛和羧基代谢物.     

Electrochemical oxidation of herbicide bifenox acid in aqueous medium using diamond thin film electrode

The electrochemical oxidation of bifenox acid was studied at a boron-doped diamond thin film by cyclic voltammetry and galvanostatic electrolysis. The course of the electrolysis was monitored by measurement of chemical oxygen demand (COD) and by gas chromatography/mass spectrometry (GC / MS) analysis. It was found that exhaustive electrolysis leads to degradation and, ultimately, to mineralization of the starting herbicide. The degradation intermediates were identified showing that the oxidation process begins with the fragmentation of the molecule followed by reactions involving the hydroxyl radical, which is generated by the discharge of water. The study of the effect of current density and concentration showed that the degradation efficiency increases with decreasing current densities and increasing concentrations. The whole results were interpreted in a mechanistic scheme involving two oxidation pathways, the first is a direct oxidation at the electrode and the second uses hydroxyl radical as mediator of the oxidation. Finally, a kinetic study based on spectrophotometric measurements showed that the degradation process is pseudo first order.     

农村土地流转影响因素的理论与实证研究——基于农民阶层分化与产权偏好的视角

随着我国经济的发展和社会转型,农民群体逐渐分化为不同职业的农民阶层,由于职业选择的不同以及生活环境的变化,农民在经济收入、产权偏好等方面都出现了巨大的差异,这导致他们对土地流转意愿与决策行为的选择也出现分化,因此,研究由于农民职业分化导致的产权偏好不同及对土地流转的影响就具有重要现实意义.本文利用笔者对江苏省实地问卷调查所得的数据,在理论分析与研究假说的基础上,运用Lagistic模型对农民职业分化、产权偏好与农村土地流转的关系进行了实证分析.研究结果表明:文化程度、职业类别、非农收入比重、是否具有非农就业技能、是否拥有转让权、地权稳定性、地区虚拟变量对土地流转有正向影响,年龄则对土地流转有负向影响,而农业劳动力人数、土地的养老保障作用和是否具有抵押权则对土地流转决策没有显著影响.基于上述研究结论,本文提出了应强化土地产权、完善产权结构、大力发展非农产业和提供非农就业机会、提高农村劳动力职业技术素质、逐步建立和完善农村社会保障体系等政策建议.     

钢铁企业工作场所煤气泄漏扩散规律的研究

以钢铁企业管网煤气泄漏为研究对象,以煤气泄漏扩散规律为研究主题,在确定煤气泄漏相似于浮力射流的基础上,建立煤气泄漏扩散的数学模型。采用CFD软件PHOENICS数值模拟气体泄漏过程的速度场及其浓度分布。在已有煤气泄漏检测系统的基础上,选择性实验模拟煤气泄漏浓度与扩散时间、扩散方向的变化。数值模拟和实验模拟表明,虽然两种方法所得结果存在一定差异,从定性分析角度而言,却能够反映工作场所煤气泄漏后在有限空间内运移扩散的一般规律。     

Strategies for improving the photocatalytic performance of metal-organic frameworks for CO2 reduction: A review

Photocatalytic CO₂ reduction is an appealing strategy for mitigating the environmental effects of greenhouse gases while simultaneously producing valuable carbon-neutral fuels. Numerous attempts have been made to produce effective and efficient photocatalysts for CO₂ reduction. In contrast, the selection of competitive catalysts continues to be a substantial hindrance and a considerable difficulty in the development of photocatalytic CO₂ reduction. It is vital to emphasize different techniques for building effective photocatalysts to improve CO₂ reduction performance in order to achieve a long-term sustainability. Metal-organic frameworks (MOFs) are recently emerging as a new type of photocatalysts for CO₂ reduction due to their excellent CO₂ adsorption capability and unique structural characteristics. This review examines the most recent breakthroughs in various techniques for modifying MOFs in order to improve their efficiency of photocatalytic CO₂ reduction. The advantages of MOFs using as photocatalysts are summarized, followed by different methods for enhancing their effectiveness for photocatalytic CO₂ reduction via partial ion exchange of metal clusters, design of bimetal clusters, the modification of organic linkers, and the embedding of metal complexes. For integrating MOFs with semiconductors, metallic nanoparticles (NPs), and other materials, a number of different approaches have been also reviewed. The final section of this review discusses the existing challenges and future prospects of MOFs as photocatalysts for CO₂ reduction. Hopefully, this review can stimulate intensive research on the rational design and development of more effective MOF-based photocatalysts for visible-light driven CO₂ conversion.