Place‐based action in Wollongong: the role of union–community alliances in constructing labour geographies of steel

Place‐based action (PBA) features prominently in labour geographies, particularly in restructuring politics, and is consistently employed as an enduring union tactic, yet it remains relatively undervalued in steel restructuring accounts, with common approaches emphasising the class instability and limitations of such action. In contrast, and to redress the apparent imbalance, this paper argues the merit of recognising PBA as a distinct movement‐based politic with specific forms of representation and empowerment. Such an approach should lead to greater recognition and appreciation of the impact that PBA has had historically. To illustrate this, a case study is presented of how local groups used place‐based action in Wollongong to shape steel restructuring politics and industry policy during the 1980s. Although powerful, the influence of PBA diminished at the policy writing stage. Rather than devaluing all benefits from PBA due to such limitations, it is suggested that the constraints on PBA at this point suggests the need for other forms of intervention. It is concluded that the approach suggested here highlights when other tactics are required, strengthening real‐world tactical analysis.     

Potential promoted productivity and spatial patterns of medium- and low-yield cropland land in China

With a continuously increasing population and better food consumption levels, improving the efficiency of arable land use and increasing its productivity have become fundamental strategies to meet the growing food security needs in China. A spatial distribution map of medium- and low-yield cropland is necessary to implement plans for cropland improvement. In this study, we developed a new method to identify high-, medium-, and low-yield cropland from Moderate Resolution Imaging Spectroradiometer (MODIS) data at a spatial resolution of 500 m. The method could be used to reflect the regional heterogeneity of cropland productivity because the classification standard was based on the regionalization of cropping systems in China. The results showed that the proportion of high-, medium-, and low-yield cropland in China was 21%, 39%, and 40%, respectively. About 75% of the low-yield cropland was located in hilly and mountainous areas, and about 53% of the high-yield cropland was located in plain areas. The five provinces with the largest area of high-yield cropland were all located in the Huang-Huai-Hai region, and the area amounted to 42% of the national high-yield cropland area. Meanwhile, the proportion of high-yield cropland was lower than 15% in Heilongjiang, Sichuan, and Inner Mongolia, which had the largest area allocated to cropland in China. If all the medium-yield cropland could be improved to the productive level of high-yield cropland and the low-yield cropland could be improved to the level of medium-yield cropland, the total productivity of the land would increase 19% and 24%, respectively.     

不同种植方式下柽柳光合生理参数光响应特性研究

为选择合适的间套模式,在塔干沙漠南缘绿洲外围利用Li-6400光合作用仪对四种种植模式(行间混交、带状混交、块状混交、块状套作)下多年生多枝柽柳(Tamarix ramasissima ledeb.)的光合水分生理指标对有效光辐射(PAR)的响应进行测定。结果表明:(1)柽柳具有高光饱和点(679~822μmol·m^-2·s^-1)和高光补偿点(50.0~61.1μmol·m^-2·s^-1)。(2)不同的光照强度和种植方式对柽柳净光合速率有明显的影响(p<0.01),当0< PAR< 1500μmol·m^-2·s^-1,除胞间CO₂浓度(Ci)外柽柳的各项生理指标均随光照的增强而增加。(3) PAR>1500μmol·m^-2·s^-1后,块状套作和块状混交气孔导度(Gs)下降,行间混交和带状混交Gs则随光强增加而递增;带状混交下胞间CO₂浓度(Ci)和蒸腾速率(Tr)均随光强增加而递增,其他3种种植方式下Ci和Tr均呈递减或平稳趋势。(4) 4种种植方式下柽柳光响应曲线的特征参数存在着差异(P<0.05),带状混交下的光饱和速率、光饱和点、表观量子效率均最高,块状混交的暗呼吸速率最大,水分利用效率(WUE)随着光强的增强而逐步增大,依次表现为带状混交>块状混交>行间混交>块状套作。通过4种种植方式柽柳光响应特征的综合分析可知,带状混交下的柽柳具有高光合和高水分利用效率的特点,对于极端干旱的塔南地区而言,该种植方式下的柽柳生理特征表现出最好的适应性。     

Advances in studies on concrete durability and countermeasures against freezing-thawing effects

This paper is a meta-analysis of recent domestic and foreign research on freezing-thawing effects on concrete durability. The main theories on the mechanisms of freeze-thaw damage to concrete are introduced： the hydrostatic pressure theory, the osmotic pressure theory, the critical water saturation degree theory, the dual mechanism theory, and the micro-ice-crystal lens model theory. The influence laws of freezing-thawing on the mechanical properties of concrete are summarized, and countermeasures to improve concrete durability in freezing-thawing circumstances are presented. This work provides valuable references for future engineering constructions in cold regions.     

Thermal conductivity of reinforced soils: A literature review

This paper aims a review of the literature related to soil reinforcements to achieve lower soil thermal conductivity （2）. The use of various natural and synthetic fibers, polymers, geosynthetics, agricultural waste/materials, and nanoclays is discussed and existing prediction models that have been thought to affect low thermal conductivity are presented.     

Laboratory and field performance of recycled aggregate base in a seasonally cold region

The objective of this project was to characterize the freeze-thaw properties of recycled concrete (RCA) and asphalt (RAP) as unbound base and to assess how they behaved in the field for nearly 8 years. This paper includes an examination of existing information, laboratory studies of freeze-thaw behavior, and evaluation of data from MnROAD field-test sections in a seasonally cold region, i.e., in Minnesota, USA. Test sections were constructed using recycled materials in the granular base layers at the MnROAD test facility. One test section included 100% RAP, another 100% RCA, a third one a 50/50 blend of RCA/natural aggregate, and a fourth one only natural aggregate (Class 5) as a control. The stiffness (i.e., elastic modulus) was monitored during construction and throughout the pavement life by the Minnesota Department of Transportation, along with the variation of temperatures and moisture regimes in the pavement to determine their effects on pavement performance. The resilient modulus of each material was determined by bench-scale testing in accordance with NCHRP 1-28a, as well as by field-scale tests incorporating a falling-weight deflectometer. Specimens were subjected to as many as 20 cycles of freeze-thaw in the laboratory, and the change in their resilient modulus was measured. In the field-test sections constructed with the same materials as the base course, temperature, moisture, and field modulus (from falling-weight deflectometer tests) were monitored seasonally for nearly 8 years. From the temperatures in the base course layer, the number of freeze-thaw cycles experienced in the field was determined for each test section. Inferences were made relative to modulus change versus freeze-thaw cycles. Conclusions were drawn for long-term field performances of the recycled base (RAB) in comparison to natural aggregate.     

轻量砂变形及强度特性三轴试验研究

通过三轴试验系统研究了新型土工材料--轻量砂的变形及强度特性。结果表明,不同的配比、龄期使轻量砂具有不同的原生结构强度,围压使不同原生结构强度的土样处于剪胀或剪缩状态,导致发生应变硬化、应变软化以及相应状态下孔压的3种对应形态变化。变形模量随EPS（发泡聚苯乙烯）球粒掺入比的增大而线性减小,随水泥掺入比、龄期增大而线性增大,相同配比的土样变形模量与围压关系不大;三轴抗压强度随EPS球粒掺入比增大而呈负指数关系减小,随水泥掺入比、龄期、围压增大而线性增大,存在水泥掺入比阀值;土骨架转换效应对于土样强度的影响很大,造成了土体单轴、三轴抗压强度分带,高水泥掺入比能够大大弱化EPS颗粒的土骨架效应。结合前人成果,系统地研究了轻量砂密度、无侧限抗压强度的影响因素,引入材料学中比强的概念,提出了单价比强图结合配方公式的方法,对轻量土砂进行配方优化。分析了轻量土砂应力-应变关系转型问题,提出采用无侧限抗压强度来表征不同配比、龄期轻量土砂的原生结构强度。通过试验与数理统计,建立临界围压与原生结构强度的关系,为数值模拟计算与建立本构模型奠定了基础。     

多遍冲击碾压混凝土路面时路基的动力响应分析

采用三维动力弹塑性有限元,考虑冲击压路机沿面板纵向中线及板边行驶来冲击碾压破碎旧水泥混凝土板,对路基在不同冲击遍数下的变形、受力等力学响应进行了分析。研究发现,土基在3个方向均承受压应力,板角荷载作用位置路基竖向变形最大,板中最小。板中路线路基竖向变形总体小于板边路线。随着距冲击点距离减小,土体竖向变形逐渐增大,并存在有明显的波动滞后现象和残余变形。随着冲击遍数的增加,土基最大竖向变形逐渐变大;第3遍冲击完后已出现明显的塑性区;随着冲击遍数的增加,土基中土压力逐渐增大,但渐趋稳定。虽然冲击遍数增加,但土压力增大范围仅限于土基一定深度内。     

北京市南水北调工程水工隧洞初期支护方案研究

水工隧洞应用日趋广泛,如何确定水工隧洞初期支护方案是设计中的重点课题。以北京市南水北调配套工程南干渠工程为背景,通过现场试验确定水工隧洞支护施工配合比,然后对网喷混凝土支护及钢纤维喷射混凝土两种初期支护结构进行数值模拟研究,并结合现场监测及现场施工效果,进行浅埋水工隧洞支护方案研究。研究结果表明：采用钢纤维喷射混凝土支护与网喷混凝土支护相比,钢纤维喷射混凝土支护更能保证施工安全。研究成果对于类似隧洞设计及施工具有借鉴和参考价值。