受限透视角度下超声波CT温度场诊断技术

超声波CT一种热测量方法,具有不接触、对温度场不干扰的优点。本文发展一种新的超声波CT再现方法,用于解决受限透视角度所产生的信息量不足的问题。新的超声波CT再现算法建立在逆矩阵变换的基础上,它不同于通常的采用SL过滤器的所谓FBPCT再现方式。论文中描述了三种CT迭代再现算法,用计算机模拟结果和三维温度场测量实验数据验证了再现算法的可靠性。同时根据计算和实验结果,建议在受限的透视角度情况下,迭代方法采用修正的正则最小二乘法CGM是合适的。     

Modelling the conversion of Colombian lowland ecosystems since 1940: drivers, patterns and rates

In biologically mega-diverse countries that are undergoing rapid human landscape transformation, it is important to understand and model the patterns of land cover change. This problem is particularly acute in Colombia, where lowland forests are being rapidly cleared for cropping and ranching. We apply a conceptual model with a nested set of a priori predictions to analyse the spatial and temporal patterns of land cover change for six 50-100 km(2) case study areas in lowland ecosystems of Colombia. Our analysis included soil fertility, a cost-distance function, and neighbourhood of forest and secondary vegetation cover as independent variables. Deforestation and forest regrowth are tested using logistic regression analysis and an information criterion approach to rank the models and predictor variables. The results show that: (a) overall the process of deforestation is better predicted by the full model containing all variables, while for regrowth the model containing only the auto-correlated neighbourhood terms is a better predictor; (b) overall consistent patterns emerge, although there are variations across regions and time; and (c) during the transformation process, both the order of importance and significance of the drivers change. Forest cover follows a consistent logistic decline pattern across regions, with introduced pastures being the major replacement land cover type. Forest stabilizes at 2-10% of the original cover, with an average patch size of 15.4 (+/-9.2)ha. We discuss the implications of the observed patterns and rates of land cover change for conservation planning in countries with high rates of deforestation.     

近似Rayleigh地震波作用下地下综合管廊响应分析

地下综合管廊是一种重要的生命线基础设施,目前对其抗震性能的研究还处于起步阶段。由于属于浅埋地下结构,故地震波中的面波、尤其是Rayleigh波可能会成为地下综合管廊破坏的控制因素。本文根据简谐Rayleigh波的特点,提出了近似Rayleigh地震波的概念,并在假定已知Rayleigh波水平分量的情况下,利用傅里叶变换求得近似Rayleigh地震波场。采用三维有限元模型,对地下管廊结构进行了地震响应分析。分析结果表明:本文建议方法可以有效地模拟波动的传播过程;地下综合管廊结构的变形以整体弯曲变形为主;结构顶面应变约为对应底面位置应变的两倍,与Rayleigh波沿深度衰减的规律相类似。     

Earth stewardship: Shaping a sustainable future through interacting policy and norm shifts

Transformation toward a sustainable future requires an earth stewardship approach to shift society from its current goal of increasing material wealth to a vision of sustaining built, natural, human, and social capital—equitably distributed across society, within and among nations. Widespread concern about earth’s current trajectory and support for actions that would foster more sustainable pathways suggests potential social tipping points in public demand for an earth stewardship vision. Here, we draw on empirical studies and theory to show that movement toward a stewardship vision can be facilitated by changes in either policy incentives or social norms. Our novel contribution is to point out that both norms and incentives must change and can do so interactively. This can be facilitated through leverage points and complementarities across policy areas, based on values, system design, and agency. Potential catalysts include novel democratic institutions and engagement of non-governmental actors, such as businesses, civic leaders, and social movements as agents for redistribution of power. Because no single intervention will transform the world, a key challenge is to align actions to be synergistic, persistent, and scalable.     

粪便与生活垃圾混合堆肥氮转化与腐熟度

采用静态仓强制通风进行粪便和生活垃圾混合堆肥,以玉米秸和石灰为调理剂,考察堆肥过程的氮转化与腐熟度。试验结果表明:堆肥中氮的损失量为26%～49%,堆体高温期持续时间长,导致氮的损失增加。添加石灰使堆肥前期的氮损失率增加,但加快了堆肥过程,总氮的损失没有加大。水溶性氨氮含量在堆肥升温期出现峰值5.61mg/gdw,堆肥结束时氨氮含量小于0.34mg/gdw;堆肥中硝态氮主要在降温期和腐熟期形成,达到1.84～4.05mg/gdw。氨氮和硝态氮之比小于0.16和水溶态有机碳与总氮之比小于1.10,较适合作为粪便与垃圾的混合堆肥腐熟指标。     

焦化废水中细菌质粒的研究

细菌质粒中常带有一些可编码降解特殊有毒物质酶的基因,为了研究质粒对有毒物质CN^-的降解的意义,主要调查了焦化废水中好氧异养菌的质粒分布特点。从山西省焦化企业公司生化站、太原煤气公司焦化厂生化站中筛选出53株细菌,利用琼脂糖凝胶电泳法,采用GDS-8000型凝胶电泳分析仪进行拍照,同时测定各菌株降氰、降酚能力,CN^-采用异烟酸-毗唑啉酮法,酚采用4-氨基安替比林法测定。结果表明,质粒的存在与降氰力有一定的关系,但对降酚力的影响差异不显著。同时,通过对其中11^*号菌株进行了质粒转化和消除实验,证明质粒稳定,不可用十二烷基磺酸钠(SDS)消除掉,用E．cbli DHI作受体菌,用11^#菌株作供体菌。作转化实验,但由于种种原因,没有筛洗到转化子。     

圆冲头压入半无限体的组合解析法

将圆冲头压入半无限体变形区,模拟成实心圆盘与空心圆环压缩的组合,将R_f/R_ο=θ设为特定参量.以上界定理对定冲压力解析解,给出了最小上界值及相对应的变形区形状.     

Fate of herbicides and nonylphenol in soil–plant–water systems amended with contaminated sewage sludge

We studied the fate of sludge spiked with ¹⁴C-labelled diuron, glyphosate and nonylphenol applied to the soil by the way of contaminated sewage sludge in the soil-plant-water system. Here we show that the mineralization of the chemicals in mixture is reduced by 40–80% by comparison with a direct soil contamination. The persistence of the chemicals in soils is increased in the presence of sludge. We showed also that the chemicals present in the sludge are mobile and partly transferred to soil leachates and plant seedlings. These results allow postulating that these compounds may induce an ecotoxicological impact on the soil ecosystem.     

Fate of the veterinary medicine ivermectin in soil

We investigated the fate of the drug ivermectin in the soil. We found that ivermectin was transformed solely by photos, leading to the formation of two ivermectin isomers. We indeed failed to detect any biotransformation reaction of the chemical either in the soil or in fungal liquid cultures. According to its limited water solubility, the bioavailability of ivermectin was very low in the soil solution. Here, we show that ivermectin, transferred to the soil from faeces of drug-treated cattle, could be stored for long periods in the soil.     

Anaerobic testosterone degradation in Steroidobacter denitrificans - Identification of transformation products

The transformation of the androgenic steroid testosterone by gammaproteobacterium Steroidobacter denitrificans was studied under denitrifying conditions. For the first time, growth experiments showed that testosterone was mineralized under consumption of nitrate and concurrent biomass production. Experiments with cell suspensions using [4-¹⁴C]-testosterone revealed the intermediate production of several transformation products (TPs). Characterisation of ten TPs was carried out by means of HPLC coupled to high resolution mass spectrometry with atmospheric pressure chemical ionization as well as ¹H and ¹³C NMR spectroscopy. 3β-hydroxy-5α-androstan-17-one (trans-androsterone) was formed in the highest amount followed by 5α-androstan-3,17-dione. The data suggests that several dehydrogenation and hydrogenation processes take place concurrently in ring A and D because no consistent time-resolved pattern of TP peaks was observed and assays using 2 TPs as substrates resulted in essentially the same TPs. The further transformation of testosterone in S. denitrificans seems to be very efficient and fast without formation of detectable intermediates.