共检索到 542

Deep-rooted maize plants utilize water and nutrients more effectively, particularly in compacted soil. However, the mechanisms by which different maize genotypes adjust root angles in response to compaction remain underexplored. We conducted a two-year study (2021-2022) on silty loam soils in the North China Plain. We tested two genotypes of maize [one with naturally deep roots (DR) and another with shallow roots (SR)] in compacted (C) and non-compacted (NC) soil. Soil compaction impeded shoot growth in both genotypes; however, DR exhibited better growth than SR. Under compacted conditions, DR maintained steeper root angles and demonstrated superior mechanical strength with larger root cortex areas (increased by 60 %) and stele (increased by 92 %), as well as higher cellulose concentration (up to 146 %). Notably, PIEZO1 gene expression increased significantly (up to 242 %) in DR under compaction, suggesting its role in root structural enhancement, unlike in SR where it remained unchanged. These findings underscore the importance of genetic, anatomical, and biochemical adaptations in maize roots, facilitating their resilience to soil compaction. Such insights could inform the breeding of maize genotypes that are better adapted to diverse soil conditions, potentially boosting agricultural productivity.

期刊论文 2025-10-01 DOI: 10.1016/j.still.2025.106620 ISSN: 0167-1987

A series of large-scale (1:13) model tests of multi-stage loading and unidirectional multi-cycle loading were conducted on semi-rigid piles before and after cement-soil reinforcement in clay. The difference of ultimate bearing capacity between unreinforced and reinforced piles under different criterions is discussed, and their bending moment and displacement distribution rules are revealed. Meanwhile, the cyclic bearing behaviour of the unreinforced and reinforced piles are compared and analyzed, including cyclic load-displacement response, unloading stiffness, cumulative peak & residual displacement, peak & locked in moment. The test results show that the ultimate bearing capacity of the large diameter pile is increased by 34.4 % and the initial stiffness is increased by 56.8 % (reinforced width is 3D and depth is 1D) in the multistage loading test. Comparing the monotonic and cyclic load-displacement curves of unreinforced and reinforced piles obtained by multi-stage loading test and unidirectional multi-cycle loading test respectively, it is found that when the applied load is small, the curve obtained from multistage loading test is almost coincident with the first cycle envelope of all load levels in 1-way multi-cycle loading test, indicating that the cyclic effect is not significant. As the load increases, the difference between the curves becomes larger, indicating that the cyclic loading of higher amplitude causes greater soil disturbance. In addition, after applying cement-soil to the shallow soil around monopile, cement-soil reinforced pile exhibits a more rigid response, specifically manifested as an initial unloading stiffness of 1.76 times that of unreinforced pile, and a slower stiffness degradation rate. Meanwhile, the cyclic peak displacement & residual displacement accumulation of reinforced piles are smaller than that of the unreinforced pile, thereby reducing the development of the locked in moment.

期刊论文 2025-08-01 DOI: 10.1016/j.soildyn.2025.109421 ISSN: 0267-7261

The lunar base establishing is crucial for the long-term deep space exploration. Given the high costs associated with Earth-Moon transportation, in-situ resource utilization (ISRU) has become the most viable approach for lunar construction. This study investigates the sintering behavior of BH-1 lunar regolith simulant (LRS) in a vacuum environment across various temperatures. The sintered samples were characterized using X-ray diffraction (XRD) and scanning electron microscopy (SEM), along with nanoindentation, uniaxial compression, and thermal property tests to evaluate the microstructural, mechanical, and thermal properties. The results show that the sintering temperature significantly affects both the microstructure and mechanical strength of the samples. At a sintering temperature of 1100 degrees C, the compressive strength reached a maximum of 90 MPa. The mineral composition of the sintered samples remains largely unchanged at different sintering temperatures, with the primary differences observed in the XRD peak intensities of the phases. The plagioclase melting first and filling the intergranular pores as a molten liquid phase. The BH-1 LRS exhibited a low coefficient of thermal expansion (CTE) within the temperature range of - 150 degrees C to 150 degrees C, indicating its potential for resisting fatigue damage caused by temperature fluctuations. These findings provide technical support for the in-situ consolidation of lunar regolith and the construction of lunar bases using local resources.

期刊论文 2025-07-01 DOI: 10.1016/j.cscm.2024.e04132 ISSN: 2214-5095

This study investigated seasonal changes in litter and soil organic carbon contents of deciduous and coniferous forests at two altitudes (500 and 1000 m a.s.l.), which were used as proxies for temperature changes. To this aim, adjacent pine (P500 and P1000) and deciduous forests (downy oak forest at 500 m a.s.l. and beech forest at 1000 m a.s.l., D500 and D1000, respectively) were selected within two areas along the western slope of a calcareous massif of the Apennine chain (central Italy). Periodic sampling was carried out within each site (a total of 19 sampling dates: 6 in autumn, 4 in winter and spring, and 5 in summer), taking each time an aliquot of the upper mineral soil horizon and measuring litter thickness and CO2 emission from the soil. The samples were then analyzed for their content of organic C, total N, water-soluble organic C and N (WEOC and WEN, respectively), and the natural abundance of 13C and 15N. Soil and litter C and N stocks were calculated. The chemical and isotopic data suggested that organic C and N transformations from litter to the upper mineral soil horizon were controlled not only by temperature but also by the quality (i.e. C:N ratio) of the plant material. In particular, the more the temperature decreased, the more the quality of the organic matter would influence the process. This was clearly showed by the greater 13C fractionation from litter to soil organic matter (SOM) in D1000 than in P1000, which would indicate a higher degree of transformation under the same thermal condition of the plant residues from the deciduous forest, which were characterized by a more balanced C:N ratio than the pine litter. However, while at 500 m altitude a significant SOM 13C fractionation and a parallel increase in soil CO2 emissions occurred in the warmer seasons, no seasonal delta 13C variation was observed at 1000 m for both forests, despite the different quality of SOM derived from deciduous and coniferous forests. Our findings suggested that organic C and N transformations from litter to the upper soil mineral horizon were greatly controlled by the quality of the plant residues, whereas soil temperature would seem to be the major driver for the seasonal evolution of SOM. This study, by considering two different vegetation types (deciduous and coniferous), allowed to evaluate the combined interactions between the plant residue quality and temperature in controlling litter and SOM mineralisation/accumulation processes.

期刊论文 2025-07-01 DOI: 10.1016/j.geoderma.2025.117382 ISSN: 0016-7061

Despite the complexity of real earthquake motions, the incident wavefield excitation for soil-structure interaction (SSI) analysis is conventionally derived from one-dimensional site response analysis (1D SRA), resulting in idealized, decoupled vertically incident shear and compressional waves for the horizontal and vertical components of the wavefield, respectively. Recent studies have revealed potentially significant deviation of the 1D free-field predictions from the actual three-dimensional (3D) site response and obtained physical insights into the mechanistic deficiencies of this simplified approach. Particularly, when applied to vertical motion estimation, 1D SRA can lead to consistent overprediction due to the refraction of inclined S waves in the actual wavefield that is not correctly accounted for in the idealized vertical P wave propagation model. However, in addition to the free-field site response, seismic demands on structures and non-structural components are also influenced by the dynamic characteristics of the structure and SSI effects. The extent to which the utilization of vertically propagating waves influences the structural system response is currently not well understood. With the recent realization of high-performance broadband physics-based 3D ground motion simulations, this study evaluates the impact of incident wavefield modeling on SSI analysis of representative building structures based on two essential ingredients: (1) realistic spatially dense simulated ground motions in shallow sedimentary basins as the reference incident motions for the local SSI model and (2) high-fidelity direct modeling of the soil-structure system that fully honors the complexity of the incident seismic waves. Numerical models for a suite of archetypal two-dimensional (2D) multi-story building frames were developed to study their seismic response under the following incident wavefield modeling conditions: (1) SSI models with reference incident waves from the 3D earthquake simulation, (2) SSI models with idealized vertically incident waves based on 1D SRA, and (3) conventional fixed-base models with base translational motions from 1D SRA. The impact of these modeling choices on various structural and non-structural demands is investigated and contrasted. The results show that, for the horizontal direction, the free-field linear and nonlinear site amplification and subsequent dynamic filtering of the base motions within the structure can be reasonably captured by the assumed vertically propagating shear waves. This leads to generally fair agreements for structural demands controlled by horizontal motions, including peak inter-story drifts and yielding of structural components. In contrast, vertical seismic demands on structures are overpredicted in most cases when using the 1D wavefields and can result in exacerbated structural damage. Special attention should be given to the potentially severe vertical floor accelerations predicted by the 1D approach due to the combined effects of fictitious free-field site amplification and significant vertical dynamic amplification along the building height. This can pose unrealistic challenges to seismic certification of acceleration-sensitive secondary equipment necessary for structural and operational functionality and containment barrier design of critical infrastructures. It is also demonstrated that vertical SSI effects can be more significant than those in the horizontal direction due to the large vertical structural stiffness and should be considered in vertical floor acceleration assessments, especially for massive high-rise buildings.

期刊论文 2025-07-01 DOI: 10.1002/eqe.4350 ISSN: 0098-8847

本文基于两幅Sentinel-1雷达卫星影像,利用像素偏移追踪技术提取出普若岗日冰川及4条典型冰川的表面流速信息并绘制冰川流速场,以研究普若岗日冰川在2023年9—10月的表面流速和流速分布特征。利用像素偏移追踪技术对两幅SAR影像进行精确配准,得到同名像元在水平方向的像素偏移量,从而获取冰川表面流速。基于冰川流速场对普若岗日冰川表面流速和流速分布特征进行分析,结果表明,普若岗日冰川的表面流速整体上较缓慢,平均流速约为0.05 m/d,普若岗日西北部、东北部、中部和西南部4条典型冰川主要流动区域的平均流速分别约为0.20、0.19、0.15和0.04 m/d。研究发现,普若岗日冰川空间位置分布不同的区域,其流速特征也有所不同,主要表现为普若岗日东北部典型冰川比西南部典型冰川的流速更快。

期刊论文 2025-06-20 DOI: 10.13474/j.cnki.11-2246.2025.0509

本文基于两幅Sentinel-1雷达卫星影像,利用像素偏移追踪技术提取出普若岗日冰川及4条典型冰川的表面流速信息并绘制冰川流速场,以研究普若岗日冰川在2023年9—10月的表面流速和流速分布特征。利用像素偏移追踪技术对两幅SAR影像进行精确配准,得到同名像元在水平方向的像素偏移量,从而获取冰川表面流速。基于冰川流速场对普若岗日冰川表面流速和流速分布特征进行分析,结果表明,普若岗日冰川的表面流速整体上较缓慢,平均流速约为0.05 m/d,普若岗日西北部、东北部、中部和西南部4条典型冰川主要流动区域的平均流速分别约为0.20、0.19、0.15和0.04 m/d。研究发现,普若岗日冰川空间位置分布不同的区域,其流速特征也有所不同,主要表现为普若岗日东北部典型冰川比西南部典型冰川的流速更快。

期刊论文 2025-06-20 DOI: 10.13474/j.cnki.11-2246.2025.0509

本文基于两幅Sentinel-1雷达卫星影像,利用像素偏移追踪技术提取出普若岗日冰川及4条典型冰川的表面流速信息并绘制冰川流速场,以研究普若岗日冰川在2023年9—10月的表面流速和流速分布特征。利用像素偏移追踪技术对两幅SAR影像进行精确配准,得到同名像元在水平方向的像素偏移量,从而获取冰川表面流速。基于冰川流速场对普若岗日冰川表面流速和流速分布特征进行分析,结果表明,普若岗日冰川的表面流速整体上较缓慢,平均流速约为0.05 m/d,普若岗日西北部、东北部、中部和西南部4条典型冰川主要流动区域的平均流速分别约为0.20、0.19、0.15和0.04 m/d。研究发现,普若岗日冰川空间位置分布不同的区域,其流速特征也有所不同,主要表现为普若岗日东北部典型冰川比西南部典型冰川的流速更快。

期刊论文 2025-06-20 DOI: 10.13474/j.cnki.11-2246.2025.0509

本文基于两幅Sentinel-1雷达卫星影像,利用像素偏移追踪技术提取出普若岗日冰川及4条典型冰川的表面流速信息并绘制冰川流速场,以研究普若岗日冰川在2023年9—10月的表面流速和流速分布特征。利用像素偏移追踪技术对两幅SAR影像进行精确配准,得到同名像元在水平方向的像素偏移量,从而获取冰川表面流速。基于冰川流速场对普若岗日冰川表面流速和流速分布特征进行分析,结果表明,普若岗日冰川的表面流速整体上较缓慢,平均流速约为0.05 m/d,普若岗日西北部、东北部、中部和西南部4条典型冰川主要流动区域的平均流速分别约为0.20、0.19、0.15和0.04 m/d。研究发现,普若岗日冰川空间位置分布不同的区域,其流速特征也有所不同,主要表现为普若岗日东北部典型冰川比西南部典型冰川的流速更快。

期刊论文 2025-06-20 DOI: 10.13474/j.cnki.11-2246.2025.0509

Lunar soil-based polymers, created using lunar soil as a precursor combined with highly automated 3D printing construction methods, hold great potential for lunar base construction. However, technical challenges such as ambiguities in characterizing rheological behavior and difficulties in regulation limit their 3D printing workability. To address these issues, the applicability of the Bingham model, Herschel-Bulkley (H-B) model, and a modified Bingham model to TJ-1 simulated lunar soil-based polymer was investigated by analyzing the fluidity variation. The effects of the solid-liquid ratio, Ca(OH)2, and Hydroxypropyl Methyl Cellulose ether (HPMC) on the 3D printing performance of the simulated lunar soil-based polymer were explored through one-way tests and standard deviation analysis. The results show that the modified Bingham model more accurately describes the rheological properties of TJ-1 simulated lunar soil-based polymer. HPMC proved to be an effective thixotropic agent for adjusting the 3D printing performance of the polymer. The yield stress and plastic viscosity of the polymer doped with 0.15 % HPMC were 3.577 Pa and 0.733 Pa s, respectively, meeting the requirements for printability. The yield stress and plastic viscosity of the simulated lunar soil polymers ranged from 1.84 to 3.58 Pa and 0.23-0.73 Pa s, respectively. Moreover, the compressive and flexural strengths of the simulated lunar soil polymers were significantly improved by adding Ca(OH)2. The optimal ratios for 3Dprinted simulated lunar soil polymers are a water-cement ratio of 0.30, 10 % NaOH, 8 % Na2SiO3, 6 % Ca(OH)2, and 0.10 % HPMC. Under these conditions, the 28-day compressive strength and flexural strength were 19.5 MPa and 6.9 MPa, respectively, meeting the strength standards of ordinary sintered bricks.The research results could provide a theoretical basis for the subsequent optimization of the simulated lunar soil base polymer mixing ratios for 3D printing.

期刊论文 2025-06-15 DOI: 10.1016/j.jobe.2025.112256
  • 首页
  • 1
  • 2
  • 3
  • 4
  • 5
  • 末页
  • 跳转
当前展示1-10条  共542条,55页