基于REOF的珠江三角洲河网区水位时空变异特征分析EI北大核心CSCD

基于1962—2016年珠江三角洲河网区12个水文站的月平均水位资料,利用Mann-Kendall趋势检验法、旋转经验正交函数法(REOF)等方法分析了该地区平均水位的时间演变趋势和空间分布特征。结果表明:水位呈显著上升趋势的月份主要集中在1—3月和12月,水位呈显著下降趋势的月份主要集中在8—9月;珠江三角洲河网区平均水位分布特征可划分为4个典型空间异常型,第一空间异常型表现为旱季水位呈上升趋势,雨季水位呈下降趋势,第二、三、四空间异常型均表现为旱季和雨季水位均为先上升再下降的趋势。     

Supply efficiency of water ecological products and its influencing factors in Zhoushan City based on RSBM-DEA modelEI北大核心CSCD

Based on the construction of the evaluation index system for the supply efficiency of water ecological products in Zhoushan City, the evolutionary characteristics of the supply efficiency of water ecological products in Zhoushan City from 2000 to 2017 were analyzed by using the RSBM-DEA model based on time series data, and the influencing factors were analyzed. The results show that the value of water ecological services in Zhoushan City is mainly reflected in surface water storage and cultural services, showing a fluctuating upward trend. The supporting effect of water ecosystem on the sustainable development of Zhoushan's economy and society has been continuously enhanced. The supply efficiency of aquatic ecological products in Zhoushan City has maintained a fluctuating development trend at a high level, of which pure technical efficiency is the key factor. In 2003 and 2013, it experienced two “trough periods”, mainly caused by the impact of pure technical efficiency. Different factors have different influence directions and degrees on the supply efficiency of water ecological products in Zhoushan City. Among them, the level of science and technology, the construction of water conservancy facilities, industrial structure and the level of economic development have a very significant positive impact, while the annual average temperature and ground hardening rate have a negative impact on the ground hardening rate, and the ground hardening rate has a low impact © 2022, Editorial Board of Water Resources Protection. All rights reserved.     

粤港澳大湾区城市洪涝问题及其分析

近年来,粤港澳大湾区城市洪涝问题日趋严峻。本文梳理了大湾区典型城市洪涝事件,归纳了洪涝特征并分析了洪涝问题的主要驱动要素。结果表明,近100多年,大湾区年降雨量、降雨日平均雨量、暴雨日数及暴雨日降雨量占全年比例都波动增加,而降雨日数波动减少,降雨呈现增多且趋于集中的态势。大湾区降雨时空分布不均,近10年广州、东莞、惠州汛期降雨量占全年雨量的81%,广州龙舟水期间降雨量占全年约22%。虽然大湾区城市群呈现热岛效应,气温与城镇化率呈正相关,且100多年来各城市温度上升并与降雨量呈正相关;但受地理位置影响,各城市降雨量与其城镇化率的关系并不明显,而更下游的沿海城市面临更多的锋面雨和台风雨影响。近10年给大湾区带来暴雨以上降雨的台风有47场,发生在6—10月,其中恰逢天文大潮的有21场、有26场在大湾区以西登陆。近40年珠江口沿海海平面上升速率3.5 mm/a,高于全国平均水平,海平面的持续上升将使大湾区面临严重洪涝风险。对强降雨、台风暴潮、海平面变化等要素开展分析可为大湾区防灾减灾工作提供重要参考。     

A simplified isotropic damage model for concrete under bi-axial stress states

This paper presents a concrete model that is capable of describing the response of concrete under bi-axial loading, with the features of simplicity and avoidance of convergence problems, often seen in plasticity based models. The proposed model incorporates the failure of concrete into a conventional continuum damage mechanics framework, where particular emphasises are placed on highlighting the different responses of concrete under tension and compression, as well as the different contributions of hydrostatic and deviatoric stress components on concrete damage. A weighted damage parameter and a damage multiplier are introduced to eliminate potential convergence problems and to reduce the effect of hydrostatic pressure on damage, respectively. Finally, several examples are provided and compared with experimental data.     

广东省新型城镇化时期生活用水变化及驱动机制

运用多区域对数平均迪氏分解方法(logarithmic mean divisia index,LMDI)分解模型,从区域及时空变化角度,对比分析广东省21市人口变迁、城镇化等因素对生活用水变化的驱动效应,探究不同地区城镇化发展对于用水产生的影响机制。结果表明:研究期内,广东省生活用水总量稳中有增,其中城镇生活用水量逐年增加,年均增长率1.4%;新型城镇化建设以来,农村生活用水量降低,人均生活用水量呈逐年下降趋势;分区域看,各地区城镇生活用水量占生活用水总量比重不断增加,尤以粤北地区增加最为明显,城镇生活用水比重由2009年的43.8%增长至2018年的52.8%;人口变化效应是导致生活用水总量增加的最主要的正向驱动指标,其次为人口分布与城乡结构效应;而用水强度效应是负向驱动指标,延缓了生活用水总量的增加。城乡结构效应对珠三角城市群生活用水量增加呈正影响,而与非珠三角地区生活用水总量呈负影响。     

Corrosion behaviour in concrete of three differently galvanized steel bars

The increasing use of galvanized steel reinforcements in concrete structures submitted to aggressive environments induces research into innovative zinc coatings with higher corrosion resistance. In this work, several cylindrical concrete specimens were manufactured with two cements of different alkalinity and reinforced with different hot-dip galvanized bars obtained from the “traditional” Zn–Pb bath and from two “modified baths”: Zn–Ni–Bi and Zn–Ni–Sn–Bi. The corrosion rate and corrosion potential of the bars were monitored during the air curing period and during wet–dry exposure both in tap water and in a 5% sodium chloride solution. The results showed that the coatings obtained from Zn–Ni–Sn–Bi bath have the highest corrosion rates, when the aggressiveness of the concrete matrix is determined mainly by its alkalinity. On the contrary, when the corrosion process is determined mainly by the penetration of chlorides (concrete manufactured with cement having a low alkali content) Zn–Ni–Sn–Bi was attacked only when the chloride concentration at the concrete cover depth reached the threshold of 4.02% (by weight of cement), which is higher than those necessary for the attack of the other coatings studied (1.36% for Zn–Ni–Bi, 1.73% for Zn–Pb).     

Principal component and multiple regression analysis in modelling of ground-level ozone and factors affecting its concentrations

Data on the concentrations of seven environmental pollutants (CH₄, NMHC, CO, CO₂, NO, NO₂ and SO₂) and meteorological variables (wind speed and direction, air temperature, relative humidity and solar radiation) were employed to predict the concentration of ozone in the atmosphere using both multiple linear and principal component regression methods. Separate analyses were carried out for day light and night time periods. For both periods the pollutants were highly correlated, but were all negatively correlated with ozone. Multiple regression analysis was used to fit the ozone data using the pollutant and meteorological variables as predictors. A variable selection method based on high loadings of varimax rotated principal components was used to obtain subsets of the predictor variables to be included in the regression model of the logarithm of the ozone data. It was found that while high temperature and high solar energy tended to increase the day time ozone concentrations, the pollutants NO and SO₂ being emitted to the atmosphere were being depleted. Night time ozone concentrations were influenced predominantly by the nitrogen oxides (NO+NO₂), with the meteorological variables playing no significant role. However, the model did not predict the night time ozone concentrations as accurately as it did for the day time. This could be due to other factors that were not explicitly considered in this study.     

Catalytic reforming of biomass primary tar from pyrolysis over waste steel slag based catalysts

Steel slag (SS) contains high amounts of metal oxides and could be applied as the catalyst or support material for the reforming of biomass derived tar. In this research, steel slag supported nickel catalysts were prepared by impregnation of a small amount of nickel (0–10 wt%) and calcination at 900 °C, and then tested for the catalytic reforming of biomass primary tar from pine sawdust pyrolysis. The steel slag after calcination was mainly composed of Fe₂O₃ and MgFe₂O₄, and granular NiO particles was formed and highly dispersed on the surface of nickel loaded steel slag which lead to a porous structure of the catalysts. The steel slag showed good activity on converting biomass primary tar into syngas, and its performance can be further enhanced by the loading of nickel. The yield of H₂ increased significantly with the increase of nickel loading amount, while excessive nickel loading resulted in the decrease in CO and CH₄ yields and significant increase in CO₂ yield. The presence of steam contributed to enhancing the tar steam reforming as well as reactions between steam and produced gases, while decrease the contact probability between the reactants and the active sites of catalysts, leading to a little decrease in tar conversion efficiency but significant increase in syngas yield. The iron and nickel oxides were reduced by the syngas (CO and H₂) from the biomass pyrolysis, and stable and porous structure was formed on the surface of the nickel loaded catalysts during tar reforming.     

Deciphering the meaning and mechanism of migrants' and locals' neighborhood attachment in Chinese cities: Evidence from Guangzhou

The rising fluidity of the society in contemporary China has led to a restructuring of people's cognition and emotion toward their place of residence. Although a growing body of literature has attempted to identify place-based factors that influence residents' attachment to their neighborhoods in Chinese large cities, little effort has been devoted to unraveling the migrant-local distinction regarding the meaning and mechanism of neighborhood attachment. Using both questionnaire survey data and in-depth interview data collected in 23 neighborhoods of Guangzhou, China, this paper aims to explore the meaning and mechanism of neighborhood attachment through the combination of both structure equation modelling and qualitative analysis. The novelties of this study relate to the focus of migrant-local distinction and to the breakdown of place attachment into its social and functional dimensions. Results from structure equation modelling show that local residents have stronger attachment to their neighborhoods than migrants. Migrants' neighborhood attachment is more related to its social dimension, as measured by social contact and social trust, and locals' neighborhood attachment is more linked to its functional dimension, as measured by satisfaction with living environment of the neighborhood. This paper enhances our understanding of the nature of place attachment by taking into account the effects of institutional constraints and migration experiences.