庄河、光明山陨石的岩石矿物学研究

庄河陨石和光明山陨石是两个降落于同一地区的Ｈ５型普通球粒陨石．根据两辉石温度计求出这两个陨石的平衡温度＜ ５００℃；根据镍纹石的带宽与组成关系，获得光明山陨石在其母体中的冷却速率约为 １０－１０℃／Ｍａ，而庄河陨石中普遍出现均一的四方镍纹石表明其冷却速率更低．光明山陨石的冲击变质特征以硅酸盐颗粒破碎为主，其冲击相为Ｓ１；庄河陨石中硅酸盐矿物具明显的波状消光，并存在细小的冲击熔融脉，其冲击相划分为Ｓ２．

PCA-based 3D Shape Reconstruction of Human Foot Using Multiple Viewpoint Cameras

This paper describes a multiple camera-based method to reconstruct the 3D shape of a human foot. From a foot database, an initial 3D model of the foot represented by a cloud of points is built. The shape parameters, which can characterize more than 92% of a foot, are defined by using the principal component analysis method. Then, using ＂active shape models＂, the initial 3D model is adapted to the real foot captured in multiple images by applying some constraints （edge points＇ distance and color variance）. We insist here on the experiment part where we demonstrate the efficiency of the proposed method on a plastic foot model, and also on real human feet with various shapes. We propose and compare different ways of texturing the foot which is needed for reconstruction. We present an experiment performed on the plastic foot model and on human feet and propose two different ways to improve the final 3D shapers accuracy according to the previous experiments＇ results. The first improvement proposed is the densification of the cloud of points used to represent the initial model and the foot database. The second improvement concerns the projected patterns used to texture the foot. We conclude by showing the obtained results for a human foot with the average computed shape error being only 1.06 mm.

Root-Fusion Characteristic of Eucalyptus Trees Block Gully Development

Soil erosion by water resulting in gully formation is a common occurrence in western Kenya. Establishment of local and sustainable countermeasures to prevent gully development/expansion in western Kenya is an urgent issue. This study presents the proposal to prevent gully development/expansion by planting Eucalyptus trees in gully prone regions. A survey study was undertaken in Kenya from 2008 to 2011. Roots of adjacent Eucalyptus citriodora trees fused forming a dense network of closely woven mass of root system holding large amount of soil thereby checking erosion by water and hence gully development. The network of roots among adjacent Eucalyptus trees also supported the standing and normal growth of the other Eucalyptus trees whose root systems were completely free from soil. Recognizable aging and breakdown of root networks were not observed during the survey period.

3D FE Analysis of Effect of Ground Subsidence and Piled Spacing on Ultimate Bearing Capacity of Piled Raft and Axial Force of Piles in Piled Raft

The effects of ground subsidence and piled spacing on axial force of piles in squared piled rafts were investigated using numerical analysis. Two cases of piled rafts in soft clay including case 1 (s = 2d) and case 2 (s = 4d) with s and d were piled spacing and piled diameter respectively were considered in this study. Undrained (without ground water pumping) and drained (with ground water pumping) conditions were applied in each case in order to evaluate variations of ultimate bearing capacity of piled raft and axial force of the piles in piled raft. The results showed that ultimate bearing capacity increased about 25% for undrained condition and about 32% for drained condition when piled spacing increased from 2d to 4d. In the same piled spacing, axial force of the piles increased about 9% for piled spacing of 2d and 7% for piled spacing of 4d when drained condition was applied. When piled spacing increased 2 times (2d to 4d), the axial force of piles increased about 7% for undrained condition and about 5% for drained condition.

自然环境中T4型噬菌体g23基因多样性研究进展

过去的20多年,伴随着分子生物学技术在环境微生物研究中的应用,环境中细菌和真菌群落基因多样性及与其生存环境间的关系逐渐被揭示,但对于地球上广泛存在且数量巨大的生命体-噬菌体基因多样性研究还很少。本文以编码T4型噬菌体主要壳蛋白基因g23为目标,综述了近年来T4型噬菌体在海洋、湖泊和稻田中基因多样性的研究进展。研究结果表明T4型噬菌体g23基因分布与其生存环境关系很大,许多g23基因按获取环境不同划分为几个新类群。同时文中也指出了针对环境中T4型噬菌体g23基因研究应该注意的几点问题及未来的研究发展趋势。

不同自然环境下噬藻体g20基因多样性研究进展

随着分子生物学技术发展与病毒基因组测序的推进,对地球上数量最大且广泛存在的病毒及其基因多样性的研究备受科学家们关注。迄今为止,仍未发现类似于细菌16S rDNA和真菌18S rDNA的病毒通用分子标记,但利用病毒某些家族的保守氨基酸序列设计简并性引物可研究环境中病毒多样性,并取得了一系列突破性成果。本文以编码噬藻体壳组装蛋白基因g20为目标,综述了噬藻体在海洋、湖泊和稻田中噬藻体基因多样性的研究进展,讨论了噬藻体g20基因分布与生存环境的相关性,发现不同的自然环境中都存在着独特的类群。同时指出了针对环境中噬藻体g20基因研究存在的问题及未来研究发展的趋势。

Numerical investigation on arching effect surrounding deep cylindrical shaft during excavation process

Predicting the inner displacements of deep vertical shafts during the excavation process has been a difficult task considering the geological,structural,and constructional influences.In fact,the two-dimensional(2D)analytical solution based on the retaining wall model remains insufficient for understanding the actual behavior during an excavation.This is because the deformation of vertical shafts becomes complicated due to the unexpected arching effect brought about by the three-dimensional(3D)flexible displacements occurring in the excavation process.Previous analytical solutions only considered the limit equilibrium.Therefore,the present study deals with a 3D soil-structure simulation by considering the displacements of a cylindrical shaft and the mechanical behavior of the surrounding soil as well as the geometry of the cylindrical structure.Moreover,this mechanical behaviors of the surrounding soil and shaft are controlled by the shaft stiffness;hence,the relationships among the shaft stiffness,mechanical behavior of the surrounding soil(in terms of earth pressure coefficient),and shaft displacement were investigated.A cylindrical model,120 m in depth and 20 m in diameter,was positioned at the center of a sand domain,and each excavation step was performed at an interval depth of 20 m.A 3D finite difference method analysis was applied using the modified Cam-Clay(MCC)model to represent the soil behavior.As a result,the present study provides a new normalized lateral earth pressure theory for excavated shafts by considering the 3D arching effect obtained from parametric studies using various levels of shaft stiffness.From a comparison with the analytical solutions of previous studies(Terzaghi,1943a;Prater,1977;Cheng&Hu,2005),it is found that the previous studies underestimated the earth pressure acting on the cylindrical shaft because they did not consider the accurate arching effect.

Evaluation of seismic behavior of box culvert buried in the ground through centrifuge model tests and numerical analysis

Japan has yet to establish a seismic design for road box culverts(RBCs)because past major earthquakes did not damage them.In recent years,structures with enlarged sectional dimensions(the purpose of which is to optimize the internal space in RBCs)have become common.However,the unknown seismic strength of such large RBCs makes RBC seismic designs increasingly necessary.Several seismic design methods have been developed for and applied to rectangular underground structures,e.g.,cut-and-cover tunnels,which are structurally similar to RBCs.Although these methods are applicable to RBCs,it is uncertain whether they can be applied directly because there are currently no evaluation results from model tests on RBCs,which have unique structural features,e.g.,no haunch at the bottom of the sidewalls.Therefore,we verify a seismic behavior of an RBC and develop a method for evaluating it in order to establish a seismic design for RBCs.We conducted centrifuge model tests subjected to seismic force and a numerical analysis using an elastoplastic finite analysis method,in addition,we validated this analysis by comparing the test and analytical results.The test results show RBCs will most likely develop rocking rotation when the ground strain exceeds approximately 0.08%.A comparison of the numerical and experimental results shows that this analysis can estimate the shear deformation behavior with approximately 90%accuracy in square cross-section cases.Meanwhile,this analysis has tendency to underestimate the axial forces in each case and to overestimate the bending moments of some members in the case of wide cross-sections.

For holistic control of reactive N:Regional,national and global perspectives

Reactive N is closely related to the global issues of climate change and regional pollutions. Nitrous oxide (N2O), the fourth important gas among greenhouse gases, is produced as an intermediate in nitrification and denitrification processes. As methane (CH4) is the end product in the anoxic decomposition of organic materials, mitigation options of N2O emission are different from those of CH4 emission. Nitrate is another reactive N bringing about the eutrification of aqueous environments and the hazard of drinking water. Mitigation of NO3 problem also relates closely to the N2O emission. Therefore, holistic approaches are necessary for solving the problems of Earth warming and environmental eutrification by reactive N at the same time. In this paper, the deforestation in the tropics, and the present situations of food supply and sustainable agriculture in Japan are re-evaluated in terms of N2O emission and NO3 discharge from the agricultural sector. The magnitude of N2O emission by deforestation in the tropics may fall within the similar order of magnitude by N fertilization. As more N is imported as foods and fodder than the amount of fertilized N in Japan, more attention should be paid to the phases of their consumption and waste treatment. Sole attention to the production stage is not enough for the total mitigation of various environmental problems by reactive N in relation to agriculture. Parameters holistically evaluating the impact of reactive N on the Earth and respective regions are urgently necessary.

Discussion on the mechanism of ground improvement method at the excavation of shallow overburden tunnel in difficult ground

Tunnel construction opportunities involving shallow overburdens under difficult(e.g.,soft,unconsolidated)grounds have been increasing in Japan.Various auxiliary methods for excavating mountain tunnels have been developed and can satisfy stringent construction requirements.The ground improvement method,which is one of the auxiliary methods for shallow overburden tunnels,has demonstrated its ability to effectively control the amount of settlement under soft ground.However,the mechanism of the ground improvement method has not been clarified,nor has a suitable design code been established for it.Therefore,because the strength of the improved ground and the suitable length and width of the improved area have not been fully understood,an empirical design has been applied in every case.In this paper,the mechanical behavior during the excavation,including that of the stabilized ground,is evaluated through trapdoor experiments and numerical analyses.In addition,the enhancement of tunnel stability resulting from the application of the ground improvement method is discussed.

Deformation behavior and acting earth pressure of three-hinge precast arch culvert in construction process

The three-hinge precast arch culvert consists of two segmental precast units and three hinge points.It harnesses the passive resistance of an embankment by permitting deflection,resulting in a mechanically stable structure.However,the design of the three-hinge precast arch culvert differs from that of a conventional culvert,prompting the mechanical behavior of the culvert to become an important issue.In this study,therefore,1/5 scale model tests were conducted on a three-hinge precast arch culvert to measure the changes in the inside width and earth pressure acting on the culvert at each step in order to investigate the culvert’s mechanical behavior at each construction stage.Moreover,the deflection measurement of the culvert was obtained at the in-situ construction site.The results indicate that the arch members were displaced according to the embankment depth in a similar manner to the design load.Therefore,the horizontal earth pressure,which was larger than the earth pressure at rest,acted on the culvert at the end of its construction.