Estimation of gross primary production in wheat from in situ measurements

Gross primary production (GPP) is a parameter of significant importance for carbon cycle and climate change research. Remote sensing combined with other climate and meteorological data offers a convenient tool for large scale GPP estimation. This paper presents a study of GPP estimation using three methods with in situ measurements of canopy reflectance, LAI, and the photosynthetically active radiation (PAR). First, because LAI is considered as an indicator of the factor of absorbed PAR (f_APAR), it provides reasonable estimates of GPP for all types of wheat with coefficient of determination R² of 0.7353. The second method uses four kinds of vegetation indices (VIs) to estimate GPP because these indices are suggested to be reliable candidates in the estimation of light use efficiency (LUE). Good determination coefficients were acquired in estimating GPP with R² ranging from the lowest of 0.7604 for NDVI to the highest of 0.8505 for EVI. A new method was proposed for the estimation of GPP following the Monteith logic, which considering GPP as a product of VI × VI × PAR. Results indicated that this method can provide the best estimates of GPP as determination coefficient R² increased largely compared to the other two methods. EVI × EVI × PAR was demonstrated to be the most suitable for the estimation of GPP with the highest R² of 0.9207, which was about 10% larger as compared to GPP estimated from the single EVI. These results will be helpful for the development of new models of GPP estimation with all remote sensing inputs.     

永年地震台伸缩仪EW向张性异常分析

针对河北永年地震台伸缩仪EW分量2015年5月11日起出现的加速拉张变化,从仪器工作状态、洞室环境、气象条件和外界环境干扰等方面,进行调查分析。利用3种荷载模型计算道路施工荷载变化可能引起的应变变化量,并结合其他形变测项变化特征进行论证,认为永年伸缩仪张性变化是区域应力场调整的结果。     

Rainfall interception by tree crown and leaf litter: An interactive process

Rainfall interception research in forest ecosystems usually focuses on interception by either tree crown or leaf litter, although the 2 components interact when rainfall occurs. A process‐based study was conducted to jointly measure rainfall interception by crown and litter and the interaction between the 2 interception processes for 4 tree species (Platycladus orientalis and Pinus tabulaeformis represented needle‐leaf species, and Quercus variabilis and Acer truncatum represented broadleaf species) at 3 simulated rainfall intensities (10, 50, and 100 mm hr^?1). Results indicated that (a) crown and litter interception processes incorporated 3 phases: the dampening phase, the steady saturation phase, and the postrainfall drainage phase, but the dampening phase for litter interception usually lasted 30 min longer than for crown interception; (b) the maximum and minimum interception storage (C _max and C _min ) for the crown were 0.63 and 0.36 mm on average, and litter C _max and C _min were 5.38 and 2.36 mm, respectively; (c) generally, crown and litter C _max and C _min increased when gross precipitation increased significantly (p  < .05) from 10 to 100 mm; and (4) crown C _max and C _min for needle‐species were 1.8 and 1.2 times larger than broadleaf species, whereas broadleaf litter showed the opposite, its C _max and C _min were 2.0 and 1.6 times larger than needle‐leaf litter on average; however, no significant differences were observed in crown and litter C _max and C _min between species on per leaf area and litter thickness basis. Results were normalized by total leaf area and litter thickness to provide a way to scale up from young trees to mature forests. Overall, rainfall interception was affected by biotic and abiotic factors together and could be quantified via multiple linear regression functions.     

Ultradeep diamonds originate from deep subducted sedimentary carbonates

Diamonds are renowned as the record of Earth’s evolution history. Natural diamonds on the Earth can be distinguished in light of genetic types as kimberlitic diamonds (including peridotitic diamonds and eclogitic diamonds), ultrahigh-pressure metamorphic diamonds and ophiolitic diamonds. According to the inclusion mineralogy, most diamonds originated from continental lithospheric mantle at depths of 140–250 km. Several localities, however, yield ultradeep diamonds with inclusion compositions that require a sublithospheric origin (>~250 km). Ultradeep diamonds exhibit distinctions in terms of carbon isotope composition, N-concentration, mineral inclusions and so on. The present study provides a systematic compilation concerning the features of ultradeep diamonds, based on which to expound their genesis affinity with mantle-carbonate melts. The diamond-parental carbonate melts are proposed to be stemmed from the Earth’s crust through subduction of oceanic lithosphere. Ultradeep diamonds are classified into a subgroup attaching to kimberlitic diamonds grounded by formation mechanism, and present connections in respect of carbon origin to eclogitic diamonds, ultrahigh-pressure metamorphic diamonds and ophiolitic diamonds.     

Using a global reference sample set and a cropland map for area estimation in China

A technically transparent and freely available reference sample set for validation of global land cover mapping was recently established to assess the accuracies of land cover maps with multiple resolutions. This sample set can be used to estimate areas because of its equal-area hexagon-based sampling design. The capabilities of these sample set-based area estimates for cropland were investigated in this paper. A 30-m cropland map for China was consolidated using three thematic maps (cropland, forest and wetland maps) to reduce confusion between cropland and forest/wetland. We compared three area estimation methods using the sample set and the 30 m cropland map. The methods investigated were: (1) pixel counting from a complete coverage map, (2) direct estimation from reference samples, and (3) model-assisted estimation combining the map with samples. Our results indicated that all three methods produced generally consistent estimates which agreed with cropland area measured from an independent national land use dataset. Areas estimated from the reference sample set were less biased by comparing with a National Land Use Dataset of China (NLUD-C). This study indicates that the reference sample set can be used as an alternative source to estimate areas over large regions.     

A simplified design method for metallic dampers used in the transverse direction of cable-stayed bridges

The aseismic design of cable-stayed bridges in the transverse direction with newly proposed metallic dampers that can accommodate both longitudinal and transverse movement of the deck has recently been considered. This work focuses on developing a simplified method to design an appropriate metallic damper. The seismic performance of cablestayed bridges with different damper stiffness, main span lengths, tower shapes and types of deck in the transverse direction are investigated. The transverse displacement of the deck of a cable-stayed bridge increases significantly with the increment of the damper stiffness, which proves that the design of the damper stiffness is crucial. A simplified model considering the damper stiffness, cable system and tower in the transverse direction is developed to evaluate the period and lateral displacement of a complicated cable-stayed bridge. Based on the simplified model, a design method is proposed and assessed using two cable-stayed bridges as examples. The results show that metallic dampers can be designed with high efficiency, and the optimal ductility of the damper can be selected.     

Study of seismic behavior of PHC piles with partial normal-strength deformed bars

Nine PHC piles with partial normal-strength deformed bars were prepared in present study, and cyclic loading tests were implemented to evaluate these piles’ seismic performance. The influence of the axial compression ratio and the amount of normal-strength deformed bars on failure modes, crack patterns, strength, stiffness, and ductility were examined. The test findings indicate that the change of axial compression ratio has a noticeable influence on the failure mode of PHC piles. A larger axial compression ratio results in a higher cracking bending resistance, ultimate bending resistance, and initial stiffness, but the propagation heights of flexural cracks decrease as the axial compression ratio increases. Furthermore, increasing the amount of normal-strength deformed bars causes a slight decrease in ductility. Finally, a calculation formula was proposed to predict the flexural capacity of PHC piles with partial normal-strength deformed bars.     

蒙古国南戈壁省二叠系岩性组合特征及其与内蒙古银额盆地的对比

蒙古国南戈壁省中蒙边界地区分布多个二叠系大型—特大型煤矿,为一套以砾岩为主的粗碎屑岩和含煤系地层夹火山岩建造。银额盆地周缘地表剖面揭示,二叠系发育一套以海相沉积为主的碎屑岩+碳酸盐岩+火山岩建造。银额盆地希热哈达—赛汗桃来地区的钻井资料揭示其为一套粗碎屑岩+含煤系地层夹火山岩岩性组合,与盆地周缘地表剖面各时代地层的岩性组合均存在巨大差异,而与蒙古国南戈壁省二叠系的岩性组合特征相同。通过中蒙边界地区二叠系地层层序与岩性组合特征的对比,明确了银额盆地希热哈达—赛汗桃来地区钻井资料发现的含煤系地层时代为二叠纪,结合沉积充填特征,对银额盆地二叠纪沉积演化与沉积相平面展布有了新的认识,为银额盆地及邻区石炭纪—二叠纪构造演化的研究提供了新的证据。     

青藏高原重大冻土工程的基础研究

青藏高原是我国乃至世界高海拔多年冻土区的典型代表。伴随着青藏铁路的建成通车,西藏自治区迎来了新一轮经济发展,迫切需要新建高速公路、输变电线路、输油气管道工程等。这些拟建工程与已建的青藏公路、青藏铁路、格拉输油管道、兰西拉光缆等工程均聚集于宽度不足10km范围内的青藏工程走廊。在这狭长的冻土工程走廊内,已修建或拟建的各种冻土构筑物相互影响,多因素耦合叠加,加速区域内的冻土退化,而冻土融化必将影响到工程的稳定性和生态环境退化。再加上全球气候变化的影响,其变化程度更加剧烈。面对国家需求,国家重点基础研究发展项目"青藏高原重大冻土工程的基础研究"于2012年4月正式启动。该项目旨在揭示气候变化与人类工程活动加剧背景下冻土变化及灾害时空演化规律,建立冻土工程稳定性和服役性能评价体系,提出冻土工程灾害防治理论与控制对策,为冻土构筑物群灾害应急预案和重大冻土工程建设提供科学决策依据。     

保安煤矿西翼3煤层开采安全性研究

通过对矿区水文地质条件的分析,认为开采3煤层时的主要充水含水层为顶板砂岩裂隙水和底板奥灰水,以奥灰水最为突出。采用突水系数法及阻水系数法计算煤矿西翼3煤层开采的有效隔水层厚度为37.6m,运用大井法计算工作面开采过程中最大涌水量为98.3m3/h。研究认为：工作面可以进行带压开采,在巷道和工作面开拓中必须在井下施工探放水孔,在富水区进行疏水降压,达到安全开采的目的;开采F20、F35断层附近时应留足防水煤柱,并对奥灰进行疏水降压,以免发生突水事故。