Influence of sewage culvert cover plate thickness on dynamic response and damage of the cover plate under gas explosion

In order to address the risk of combustible gas explosions in sewage culverts, a numerical model was established using ANSYS/LS-DYNA software. The model consisted of a culvert and a cover plate, and was used to study the effect of cover plate thickness (ranging from 0.08 m to 0.12 m) on the dynamic response and damage of the structure under explosive loads. The results indicated that, during the loading negative pressure stage, the equivalent stress peak value of the central monitoring unit of the cover plate first increased and then decreased with increasing cover plate thickness. Additionally, the maximum principal stress peak value first decreased and then increased, while the maximum shear stress peak value first increased and then decreased. During the loading positive pressure stage, the maximum principal strain peak value of the monitoring unit decreased overall with increasing cover plate thickness. However, the equivalent plastic strain peak value initially increased and then decreased gradually. The equivalent strain indicated that plastic damage occurred in the cover plate. Beyond a thickness of 0.11 m, increasing the cover thickness did not appear to enhance its resistance to plastic damage. The damage analysis revealed that as cover plate thickness increased, the peak displacement and velocity of the monitoring unit continued to decrease, while the overall stability and explosive resistance of the cover plate increased. Additionally, the number of damaged fragments decreased. However, once the cover plate thickness reached 0.11 m, the bonding performance of the reinforced concrete structure had been fully developed, increasing the thickness of the cover plate no longer had a significant impact on the explosive resistance of the cover plate.     

Assessing slope stability in unplanned settlements in developing countries

Unplanned housing in developing countries is often located on steep slopes. Frequently no building code is enforced for such housing and mains water is provided with no drainage provision. Both of these factors can be particularly significant in terms of landslide risk if, as is so often the case, such slopes lack any planned drainage provision. There is thus a need to develop a model that facilitates the assessment of slope stability in an holistic context, incorporating a wide range of factors (including surface cover, soil water topographic convergence, slope loading and point source water leakage) in order that appropriate advice can be given as to the general controls on slope stability in such circumstances. This paper outlines a model configured for this specific purpose and describes an application to a site in St. Lucia, West Indies, where there is active slope movement in an unplanned housing development on relatively steep topography. The model findings are in accord with the nature of the current failure at the site, provide guidance as to the significance of slope drainage and correspond to inferences drawn from an application of resistance envelope methods to the site. In being able to scenario test a uniquely wide range of combinations of factors, the model structure is shown to be highly valuable in assessing dominant slope stability process controls in such complex environments.     

Environmental risk perception, environmental concern and propensity to participate in organic farming programmes

This paper aims to identify the factors underlying farmers' propensity to participate in organic farming programmes in a Romanian rural region that confronts non-point source pollution. For this, we employ structural equation modelling with latent variables using a specific data set collected through an agri-environmental farm survey in 2001. The model includes one 'behavioural intention' latent variable ('propensity to participate in organic farming programmes') and five 'attitude' and 'socio-economic' latent variables ('socio-demographic characteristics', 'economic characteristics', 'agri-environmental information access', 'environmental risk perception' and 'general environmental concern'). The results indicate that, overall, the model has an adequate fit to the data. All loadings are statistically significant, supporting the theoretical basis for assignment of indicators for each latent variable. The significance tests for the structural model parameters show 'environmental risk perception' as the strongest determinant of farmers' propensity to participate in organic farming programmes.     

农业土地利用转变对土壤团聚体组成及碳、氮含量的影响

为探究农业土地利用转变对土壤团聚体组成、稳定性及有机碳（SOC）、全氮（TN）含量变化的影响,选取玉米地、玉米地转变为姜地、稻田和稻田转变为姜地4种农业土地利用类型为研究对象,对土壤水稳性团聚体的组成、稳定性及SOC、TN含量进行测定与分析.结果表明： ①玉米地转变为姜地后,>0.25 mm粒级的大团聚体减少21.48%（p<0.01）,>0.25 mm稳定性团聚体的含量（DR_0.25）显著降低53.39%;稻田转变为姜地后,大团聚体差异不显著,<0.053 mm粒级的粉黏团聚体增加8.93%（p<0.01）;冗余分析和相关分析表明,土壤含水量是团聚体组成和 稳定性的重要影响因素;②玉米地转变为姜地后,0.25~1 mm粒级团聚体中SOC、TN含量分别减少52.68%、50.98%,粉黏团聚体（<0.053 mm）中SOC和TN含量增加约2倍（p<0.01）;稻田转变为姜地后,>0.25 mm的大团聚体和0.053~0.25 mm的微团聚体中的SOC、TN含量均减少（p<0.05）,其中,大团聚体碳氮比与团聚体组成和稳定性存在相关关系（p<0.05）;③所有处理均为大团聚体SOC、TN贡献率最高,转变后的姜地较玉米地、稻田的土壤粉黏团聚体的SOC、TN贡献率显著增加,尤其是较玉米地的粉黏团聚体SOC、TN贡献率增加3倍（p<0.01）;④平均质量 直径（MWD）和几何平均直径（GMD）与大团聚体的SOC、TN含量呈显著正相关（p<0.05）,分形维数（D）与MWD及1~2 mm粒级大团聚体的SOC、TN含量呈显著负相关（p<0.01）,DR_0.25与大团聚体的SOC、TN含量呈显著正相关（p<0.01）.总体上,玉米地和稻田两种用地转变为姜地后,土壤团聚体的组成发生较大变化,团聚体稳定性变化虽不显著,但大团聚体中SOC、TN含量降低,粉黏团聚体中SOC、TN含量增加.本研究的开展对农田科学管理和可持续生产具有重要的指导意义.     

基于函数极值条件下的中国碳达峰碳中和情景分析

基于函数极值条件提出了碳达峰出现时间和需要满足的理论条件,并对主要发达国家作了验证,同时对中国现状做了分析,最后采用了基准和强化两种情景分析了中国实现2030年碳达峰后进入2060年碳中和时期的二氧化碳排放量。研究结果显示：（1）根据IPAT恒等式将碳排放函数分解成人口、人均GDP和碳强度三个因素时,碳峰值出现时间为三个因素年增长率之和由正转负的正数值年度,发达国家的历史数据证实了这一条件。（2）中国三个因素年增长率之和自2003年起已经开始降低,最近几年一直在0.01~0.02徘徊,表明总体上朝着有利于碳达峰的方向发展,同时按照三个因素的预期发展目标计算得出中国2030年碳排放峰值的上限为112.2亿t,若2021—2035年保持相同的人均GDP年均复合增长率,碳强度年均复合增长率的绝对值需要比人均GDP年均复合增长率高0.14个百分点。（3）在能源消费总量逐渐回落的前提条件下,2060年基准情景下非化石能源占比约为65%,产生的二氧化碳量约为31.4亿t,强化情景下非化石能源占比约为70%,二氧化碳排放约为26.6亿t,而碳汇和CCUS等固碳技术还存在不确定性,碳中和任务依然艰巨。实现碳达峰碳中和最终需要控制能源消费,践行低碳消费行为。     

包埋硫铁生物填料的制备及自养反硝化性能

采用包埋固定化技术制备了包埋硫铁生物填料(ESI Filler),基于升流式自养反硝化反应器开展动态实验研究,通过改变水力停留时间(HRT)、pH值、溶解氧(DO)等运行条件,探究ESI Filler反应器的脱氮效果及微生物群落结构组成。结果表明,当进水硝酸盐氮(NO₃^--N)浓度为30mg/L,HRT为10h时,NO₃^--N去除率不断上升至99.80%。当HRT缩短为2.5h时,NO₃^--N去除率降至61.35%。ESI Filler反应器对pH值和DO的改变具有较高的稳定性,NO₃^--N平去除率可维持在82.5%以上。但对低温的耐受性较差,当温度从35℃降低至15℃时,NO₃^--N平均去除率由90.12%降低至68.80%。运行164d后,球体未出现破裂散落的现象,表现出较长的使用寿命。通过扫描电镜发现,填料表面疏松多孔,附着大量杆状细菌,已成为微生物的良好载体。高通量测序结果表明,包埋颗粒中优势菌属为典型的自养反硝化功能菌Thiobacillus,丰度为80.79%。     

Daily Bank Erosion Rates in the Lower Yellow River Before and After Dam Construction

During the period of water impoundment and sediment detention of the Sanmenxia Reservoir, riverbank erosion processes played a key role in the channel evolution of the Lower Yellow River (LYR). However, research into bank erosion rates of the LYR has been neglected due to the lack of direct field monitoring. In this study, an indirect method is proposed to determine bank erosion rates at daily time scales by outlining a detailed calculation procedure using measured hydrological data. A total of 810 data points of daily bank erosion rates before and after the construction of Sanmenxia Dam was calculated at seven hydrometric sections along the LYR, with the corresponding values of the bank stability coefficient and the width‐to‐depth ratio also being calculated. Empirical relations were then developed to estimate the daily bank erosion rates, using these parameters at the sections. Temporal and spatial variability in daily bank erosion rates in the LYR before and after dam construction were also investigated, revealing that: (1) the bank erosion rates had a mean value of 16.7‐29.1 m/day in the braided reach, with a maximum value of 290.0 m/day, while they were relatively low in the meandering reach, with a mean value of 2.5 m/day; (2) the erosion rates before dam construction were slightly greater than those after dam construction, with the difference reaching 5‐10 m/day in the braided reach, decreasing in the transitional reach gradually, and being slight in the meandering reach.     

Household income,living and working conditions of dumpsite waste pickers in Bantar Gebang: Toward integrated waste management in Indonesia

This paper clarifies household income, living and working conditions of dumpsite waste pickers at Bantar Gebang final disposal site for municipal solid waste generated in Jakarta, and investigates the feasibility of integrating the informal sector into formal waste management in Indonesia. The first author did fieldwork for totally 16 months at the site and quantitative field surveys were conducted twice during the period. All respondents in the first round quantitative survey (n = 1390) were categorized as follows: waste pickers, family workers, wage labors, bosses, family of the bosses, housewives, pupils/students, preschoolers, the unemployed, and others. Based on the results of the second round quantitative survey (n = 69 households), their average household income was estimated to be approximately US 216 dollars per month (n = 59 households), which was virtually equivalent to the minimum wage in Jakarta in 2013. Living conditions of scavengers at the site were horrible, and their working conditions were dangerous due to medical waste and other sharp waste. Polluted groundwater was one of the serious environmental problems at the site. Despite the social, health and environmental problems, they were attracted to the freedom of entering the informal recycling system in Bantar Gebang and withdrawing from the system, in which a lot of opportunities were provided for the people having few marketable skills to obtain cash earnings. The freedom of their choice should be guaranteed as a prerequisite before integrating the informal sector into formal waste management. Furthermore, special attentions are required when incomes of scavengers are the same level as minimum wages and the national economy is rapidly growing, because scavengers cannot easily change their jobs due to few marketable skills. Indonesian national waste laws and regulations should be properly applied to facilitate a socialization process at final disposal sites. Measures need to be taken to prevent children from working as informal recycling actors, especially for waste pickers aged 15 or younger.     

对定标用标准紫外辐射光源性能指标的探讨

紫外辐射是模拟环境条件测试的重要组成部分,对紫外辐射强度、剂量等的定标对于老化耐久实验数据的准确性和可靠性具有重要意义。本文通过实验手段对目前常见的定标用紫外标准光源的技术指标进行分析,同时对该类光源的性能指标未来的改进方向进行探讨,并提出了改进设计方案。     

Erosional Consequence of Saltcedar Control

Removal of nonnative riparian trees is accelerating to conserve water and improve habitat for native species. Widespread control of dominant species, however, can lead to unintended erosion. Helicopter herbicide application in 2003 along a 12-km reach of the Rio Puerco, New Mexico, eliminated the target invasive species saltcedar (Tamarix spp.), which dominated the floodplain, as well as the native species sandbar willow (Salix exigua Nuttall), which occurred as a fringe along the channel. Herbicide application initiated a natural experiment testing the importance of riparian vegetation for bank stability along this data-rich river. A flood three years later eroded about 680,000 m³ of sediment, increasing mean channel width of the sprayed reach by 84%. Erosion upstream and downstream from the sprayed reach during this flood was inconsequential. Sand eroded from channel banks was transported an average of 5 km downstream and deposited on the floodplain and channel bed. Although vegetation was killed across the floodplain in the sprayed reach, erosion was almost entirely confined to the channel banks. The absence of dense, flexible woody stems on the banks reduced drag on the flow, leading to high shear stress at the toe of the banks, fluvial erosion, bank undercutting, and mass failure. The potential for increased erosion must be included in consideration of phreatophyte control projects.