Source identification of nitrous oxide on autotrophic partial nitrification in a granular sludge reactor

Emission of nitrous oxide (N₂O) during biological wastewater treatment is of growing concern since N₂O is a major stratospheric ozone-depleting substance and an important greenhouse gas. The emission of N₂O from a lab-scale granular sequencing batch reactor (SBR) for partial nitrification (PN) treating synthetic wastewater without organic carbon was therefore determined in this study, because PN process is known to produce more N₂O than conventional nitrification processes. The average N₂O emission rate from the SBR was 0.32 ± 0.17 mg-N L⁻¹ h⁻¹, corresponding to the average emission of N₂O of 0.8 ± 0.4% of the incoming nitrogen load (1.5 ± 0.8% of the converted NH₄⁺). Analysis of dynamic concentration profiles during one cycle of the SBR operation demonstrated that N₂O concentration in off-gas was the highest just after starting aeration whereas N₂O concentration in effluent was gradually increased in the initial 40 min of the aeration period and was decreased thereafter. Isotopomer analysis was conducted to identify the main N₂O production pathway in the reactor during one cycle. The hydroxylamine (NH₂OH) oxidation pathway accounted for 65% of the total N₂O production in the initial phase during one cycle, whereas contribution of the NO₂⁻ reduction pathway to N₂O production was comparable with that of the NH₂OH oxidation pathway in the latter phase. In addition, spatial distributions of bacteria and their activities in single microbial granules taken from the reactor were determined with microsensors and by in situ hybridization. Partial nitrification occurred mainly in the oxic surface layer of the granules and ammonia-oxidizing bacteria were abundant in this layer. N₂O production was also found mainly in the oxic surface layer. Based on these results, although N₂O was produced mainly via NH₂OH oxidation pathway in the autotrophic partial nitrification reactor, N₂O production mechanisms were complex and could involve multiple N₂O production pathways.     

Effect of different parameters on the in situ thermal conductance evaluation

In the last years many studies have been carried out on the possible improvements of the in situ thermal conductance measurement; as well known, this has to be derived by recorded values of temperatures and heat fluxes. A big effort has been addressed in the implementation and comparison of different analysis methods. The aim of this paper is to widen the existent literature in the study of the influence of different kinds of input data on the final result. First the problem of analysing input data with significant drift in temperature is considered, adopting both nominal clean and noise affected data. Then the effect due to the presence of the Heat Flux Meter (HFM) on the thermal field of the testing element has been analysed, as well as the possibility of recording HFM surface temperature. These studies are based on Finite Element Method (FEM) simulations; both nominal clean and noise affected data have been considered as input. Finally, a difference in emissivity between the heat flux meter and internal plaster surface has been analysed by means of FEM simulations based on nominal clean data. An overall estimation of the occurred deviations in the different cases is shown.     

基于都市发展阶段论的城市居住隔离研究

本文归纳并总结我国居住隔离研究的现状,从研究成果及应用性、研究层面及针对性和规划对策三方面评述居住隔离研究存在的问题,在此基础上引入并剖析都市发展阶段论与居住隔离的内在关联,结合我国城市化特点构建基于都市发展阶段论的居住隔离研究框架,探讨我国居住隔离问题的应对策略,并着重论述框架中各类居住隔离问题的混居措施。     

Bolt length requirement in underground openings

A parametric study has been carried out using the numerical analysis code FLAC^3D to obtain the influence of various shapes of underground openings on the maximum induced boundary stress. Five shapes—viz. circular, horseshoe, rectangular, elongated D-shape and elliptical—have been considered. For each shape, four tunnel depths and five horizontal in situ stress models have been taken for the study of induced boundary stresses.The values of maximum and minimum induced boundary stresses in the roof and wall have been obtained from the analyses. This data has subsequently been used to develop correlations to estimate the normalized maximum and minimum boundary stresses, which have been subsequently compared with the strength of the rock mass obtained from the Sheorey's non-linear failure criterion for three rock masses represented by three values of Bieniawski's RMR and three values of crushing strength of intact rock material. The values of minimum factor of safety at the roof and the wall have been collected from all the plots. Using these data sets, different correlations have been developed to estimate the minimum factor of safety (f_min) in the roof and wall.Since the bolt length should be normalized with the opening size, some more computer models have been run with varying tunnel width of 5 and 20 m besides the earlier 10 m size to obtain the correlations for estimating the bolt length. The depth of factor of safety contour of 1.5 from the opening periphery has been picked up from all these models and the correlations have been developed for estimating the roof and wall bolt length for the five shapes of underground openings. The correlations for bolt length show that in addition to the shape of underground openings and in situ stress, the bolt length also varies with the rock mass type. These correlations have been verified for field cases of elongated D-shape openings.     

福建紫金山高硫型铜金矿采矿境界面生态修复技术研究

露天采矿对区域生态环境会带来一定程度的损害,实施生态修复工程是保障生产型矿山资源开发利用与生态环境和谐共处的必然途径。本研究以福建紫金山高硫型铜金矿采矿境界面为对象,应用松散堆渣边坡土壤改良、岩质边坡原位固化阻隔、立体近自然植被群落恢复3种生态修复技术,使得修复区浅表土壤pH值自2.78~5.05上升至8.21~8.6,由酸性转为弱碱性,有效抑制了土壤酸化,同时磷（P）、钾（K）、钙（Ca）、镁（Mg）等矿质营养元素含量明显增加。紫金矿业采用矿山环境治理和景观资源融合的生态修复模式,打造了一个集矿业开发、森林景观、科普研学为一体的近郊型国家矿山公园。研究成果为有色金属矿山采矿境界面高陡边坡生态修复治理提供借鉴。     

Application of wave equation theory to improve dynamic cone penetration test for shallow soil characterisation

Among the geotechnical in situ tests,the dynamic penetration test(DPT)is commonly used around the world.However,DPT remains a rough technique and provides only one failure parameter:blow count or cone resistance.This paper presents an improvement of the dynamic cone penetration test(DCPT)for soil characterisation based on the wave equation theory.Implemented on an instrumented lightweight dynamic penetrometer driving with variable energy,the main process of the test involves the separation and reconstruction of the waves propagating in the rods after each blow and provides a dynamic cone load-penetration(DCLT)curve.An analytical methodology is used to analyse this curve and to estimate additional strength and deformation parameters of the soil:dynamic and pseudo-static cone resistances,deformation modulus and wave velocity.Tests carried out in the laboratory on different specimens(wood,concrete,sand and clay)in an experimental sand pit and in the field demonstrated that the resulting DCLT curve is reproducible,sensitive and reliable to the test conditions(rod length,driving energy,etc.)as well as to the soil properties(nature,density,etc.).Obtained results also showed that the method based on shock polar analysis makes it possible to evaluate mechanical impedance and wave velocity of soils,as demonstrated by the comparisons with cone penetration test(CPT)and shear wave velocity measurements made in the field.This technique improves the method and interpretation of DPT and provides reliable data for shallow foundation design.     

The foundation of a 40-storey tower in jointed basalt

A 132.70-m-high tower (above foundation) has been successfully completed at Tenerife Island. The foundation of the tower, a 2-m-thick reinforced concrete slab, is supported by jointed, vesicular and weathered basalt, and scoria. A three-dimensional, elastic finite element program has permitted to calculate the displacements of the tower and the stresses in the slab. The installation of rod extensometers at different depths below the slab and clinometers at the lower basement has provided comparison between measured and calculated displacements, and the estimation of in situ deformation moduli. A first stage prediction (before construction) has allowed establishment of an upper limit, based upon pressuremeter modulus, and a lower limit, based upon Bieniawski's equation [The geomechanics classification in rock engineering applications. In: Proceedings of the fourth cong. ISRM congress, Montreux, vol. 2. 1979. p. 41–48], of the settlements of the tower slab. The geometric mean of these values comes close to the measured settlement. The moduli deduced from the simple empirical equation proposed by Gokceoglu et al. [Predicting the deformation modulus of rock masses: a comparative study. Int J Rock Mech Min Sci 2003;40:701–10], and Hoek and Brown [Practical estimates of rock mass strength. Int J Rock Mech Min Sci 1997;40:701–10] as a function of GSI provide a good fit with the measured settlements in this type of rock. A good correlation is also obtained with the empirical equation presented by Verman et al. [Effect of tunnel depth on modulus of deformation of rock mass. Rock Mech Rock Eng 1997;30(3):121–7] that incorporates the influence of the confining stress in the deformation modulus.     

湿陷性黄土地区桩基础的应用分析

本文通过实例 ,对湿陷性黄土地区常见的桩基础从施工工艺、设计计算、桩基检测、适用范围、常见问题及对策和经济指标各个方面进行分析论述 ,总结该地区桩基础选型原则及其发展趋势     

白沙广场高层异形柱框架结构设计

主要介绍了白沙广场高层异形柱框架 剪力墙的结构设计及有关计算的理论 ,重点讨论了基础选型、异形柱框架 剪力墙结构体系的布置与计算。通过采用各种技术措施 ,提高了结构的安全性和抗震性能 ,整个工程设计的特点、构思和创新情况可供类似工程设计时参考     

生料空气搅拌库的设计

本文根据生料空气搅拌库中物料的均化原理和动水力学理论提出了物料作用于仑壁和仓底的水平压力和竖向压力的计算公式,并综合介绍了生料空气搅拌库的结构设计,可供设计人员参考。     

湘潭富瑶天下·礼宾府设计

富瑶天下.礼宾府以混合居住的规划手法,体现土地最大化价值。塑造内部环境,追求人与自然和谐共生,打造一个充满小镇浪漫生活气息的、高品质的绿色国际社区。     

A case study in evaluating the status of consolidation of a soft soil deposit by incomplete piezocone dissipation tests using laboratory and field data

By using the piezocone penetration test (PCPT or CPTu), one can develop not only a better understanding of the soil stratification, but also an understanding of soil behavior parameters related to soil compressibility, as well as soil strength. This paper describes a case study that utilizes incomplete piezocone dissipation test to estimate status of consolidation of a soil deposit. Incomplete pore pressure dissipation record of PCPT is extrapolated on an inverse time scale (1/t method) to estimate the “in situ” pore pressure and “residual excess” pore pressure. No case study has been reported in open literature where this methodology has been utilized to estimate the status of consolidation of the soil deposit. In this paper, the 1/t method was verified using dissipation data from rigorous calibration chamber tests and field test data.     

开口截面钢-混凝土组合梁受扭的试验分析

为研究钢-混凝土组合梁在不同加载方式下的受扭性能,完成了6根钢-混凝土组合梁的弯扭试验和纯扭试验,其中2根梁的扭矩直接作用于工字钢梁上,其余4根梁则由钢梁和混凝土翼缘板作为整体共同受扭。试验结果表明,当扭矩直接作用于钢梁上时,混凝土翼缘板通过栓钉对钢梁的扭转提供约束,从而使钢梁的抗扭承载力比纯钢梁的提高2倍以上。在试验参数相同时,混凝土翼缘板和钢梁作为整体复合受扭时组合梁的开裂扭矩及极限抗扭承载力比扭矩直接作用于钢梁时的分别提高86%和39%。分析了两种不同加载方式下钢-混凝土组合梁受扭和受弯承载力的变化。建立了扭矩直接作用于钢梁上时极限扭矩的计算模型及计算公式。对整体受扭时组合梁的弯矩相关性进行了分析,并建立了相关曲线公式。计算结果与实测值吻合较好。     

Preconsolidation, structural strength of soil, and its effect on subsoil upper structure interaction

When constructing a building, manufactured materials are used. That is the reason for their excellent material properties. In the case of the foundation, the natural condition of the soils must mostly always be respected. The geostatical stress plays a significant role on the subsoil behavior because it is the de facto natural form of the soil compaction. The soil has a memory of the highest stress that has ever been loaded on it. The soil can be considered incompressible if the magnitude of a surcharge is lower. In engineering practice the construction of higher buildings is founded in a deeper hole so that the depth of the influence zone achieves an acceptable value for the future surcharge of the upper structure. For very tall buildings, the deep hole foundation must be prolonged by piles. In particular, this article deals with laboratory testing that provides the preconsolidation. In Czech, we term it the structural strength of soil. The test provides the initial void ratio as well as the initial coefficient of fully saturated hydraulic conductivity. The isotropic consolidation test with the triaxial test apparatus and consequent knowledge of the pore pressure course was chosen to determine the initial soil properties, including the preconsolidation level. Derived theory together with the genetic algorithms provide an efficient tool for the determining parameters. Good knowledge of the influence zone is crucial when solving soil structure interaction. The progress of the influence zone was considered from the extensive research carried out at the University of Brasília, Brazil. Thus, using the measurements, the preconsolidation and its effect were verified in situ. The derived formulas and presented graphs for influence zone depth estimation have considerable importance for civil engineering practice. The Kantorovich method together with the strategy of convolution was used to reach dimensional reduction when deriving analytical formulas. Recommended results and formulas were verified against FEM code ADINA.     

风冷热泵机组冬季运行的可靠性

分析了造成风冷热泵机组在长江流域地区冬季运行不可靠的原因,提出了对机组除霜控制技术和管路设计方面的改进意见,并就机组布置提出了新的看法。     

梅山铁矿地应力测量结果及其分析

梅山铁矿地应力测量采用应力解除法和改进型空心包体应力计，测量获得矿区３个水平８个测点的三维地应力大小和方向，并通过统计分析得出矿区地应力场分布的基本规律。实测结果与依据构造线推测的矿区构造应力场状态基本一致。     

Flora_Flex: In Search of Synthetic Immortality

Evan Douglis performs alchemy, bringing to life from theinaminate ‘the natural’ with his genetically inspired Flora_flex prefab modular building system. He demonstrates the beauty, intricacy and opulence inherent in pursuing flowering plant morphology as a model for surface variation. Copyright © 2008 John Wiley & Sons, Ltd.