基于双还原体系与膜进样质谱快速测定15N加富水样中15NO3-的方法

海洋中的氮循环是海洋生物地球化学研究的热点领域之一,而硝化过程是氮循环的关键一环,准确获取硝化速率对于丰富海洋氮循环的认识至关重要。¹⁵N标记同位素技术是目前国际上最为广泛使用的硝化速率测定方法,该方法的核心在于准确测定¹⁵N加富样品产生的¹⁵NO₂^-和¹⁵NO₃^-的含量,但目前的方法普遍存在测试时间较长、测试成本较高、所需样品体积较大或者检测限较高等问题。研究以低成本的膜进样质谱作为¹⁵N加富样品测试设备,建立了基于镉柱与氨基磺酸双还原体系测定¹⁵N加富样品中¹⁵NO₃^-含量的方法。经条件优化实验确定的具体方法:采用1 mol/L HCl配制15 mmol/L的氨基磺酸（SA）作为反应试剂除去样品原有的NO₂^-,然后利用镉柱将¹⁵NO     

藏东地区斜坡土壤冻融侵蚀力学机制及敏感性分析

冻融侵蚀是青藏高原草甸覆盖区的主要侵蚀方式,以气候条件一致的藏东地区斜坡表层土壤侵蚀为对象,基于区域地质条件和土体赋存特征,分析了土壤剥蚀输移的力学过程,探索了缓变的隐性因子和灾变的显性因子对冻融侵蚀的作用机制.结果表明:①地表冻融侵蚀是自基岩风化和土壤演化起始,经历冻融拉裂破坏与沙土输移,到重新裸露基岩的一个循环演化...     

Contribution of waves and currents to sediment resuspension in the Yellow River Delta

The objective of this study was to investigate that the effects of different hydrodynamic conditions on sediment resuspension on a tidal mudflat in the Yellow River Estuary. A field experiment was conducted on an intertidal flat of the Yellow River Delta, China. The sediment resuspension concentrations and hydrodynamic conditions were obtained in the field from September 2–7, 2013. The resuspended sediment concentrations induced by wave loading were compared with those induced by coupled wave–current actions in Yellow River Delta. The results were as follows: (1) when the wave height was higher than 10?cm and the shear stress induced by the waves was greater than the critical stress of the seabed sediments, the surface seabed was eroded and sediment was resuspended. In addition, 60% of the significant wave heights were larger than 10?cm on the intertidal flat of the Yellow River Delta. (2) The contribution of waves to sediment resuspension was greater than 30% when the significant wave height is higher than 10?cm, and the average contribution of waves to sediment resuspension was 51%. The mechanism of wave-induced sediment resuspension and processes of sediment resuspension were described in this paper.     

Uncertainty estimation of a CFD-methodology for the performance analysis of a collective and cyclic pitch propeller

Estimation and analysis of the uncertainty introduced by using a numerical model for the investigation and study of any type of flow problem have become common industry practice. Through understanding and evaluation of the uncertainty introduced by a numerical model, the accuracy and applicability of the model itself are evaluated. In this paper, the numerical uncertainty of a CFD-methodology developed to analyse the hydrodynamic performance of a collective and cyclic pitch propeller (CCPP) is estimated and analysed. The CCPP is a novel propulsion and manoeuvring concept for autonomous underwater vehicles, aimed to generate both propulsion and manoeuvring forces through advanced control of the propeller's blade pitch. The numerical uncertainty is established for three performance parameters, the generated propulsive force, the side-force magnitude, and the side-force orientation, by conducting a grid and time-step refinement study over three operational conditions. Additionally, the influence of the oscillatory uncertainty, introduced by the periodic nature of the problem, is investigated although shown to have a minimal effect when properly monitored. Based on a least-squares regression analysis of the refined simulation results, the numerical uncertainty is proven to be dominated by the introduced discretisation errors. In the case of the propulsive and side-force magnitude, the total uncertainty is dictated by the time discretisation uncertainty under bollard pull conditions, while the total uncertainty of the captive cases is mainly a result of the spatial discretisation uncertainty. The total uncertainty in the side-force orientation is observed to be primarily a consequence of the time discretisation uncertainty for all simulated cases. Overall, the total uncertainty for captive cases can be considered satisfactory for all three performance parameters, while further work is needed to reduce the observed uncertainty of the simulations under bollard pull conditions.     

绥中36-1油田D27井氮气泡沫分流酸化效果研究

砂岩储层酸化技术是油田生产中一项重要的增产措施。针对层间矛盾突出、近井地带污染较为严重的油层采用常规酸化效果不佳的实际状况,氮气泡沫分流酸化技术能够有效封堵相对较高渗透层,使酸液转向分流进入相对较低渗透层,达到全面酸化的目的。从油藏角度对首次在海洋油田应用的SZ36-1-D27井氮气泡沫分流酸化的效果进行评价。结果表明：SZ36-1-D27井氮气泡沫分流酸化后吸水能力显著增强,达到了常规酸化视吸水指数的要求;酸化解除了高渗层堵塞,并且使得Iu油组和Id油组的吸水剖面得到显著改善,达到了分流及剖面调整效果;酸化后,该井组内的D21油井和F2油井见效明显。现场实践证明,氮气泡沫分流酸化能够有效地增加中低渗透层吸酸量,扩大了酸化范围,提高了酸化效果,具有广阔的应用前景。     

Poro‐elasto‐plastic response of an unconsolidated formation confined with stiff seal rocks under radial injection

In this article, we evaluate geomechanics of fluid injection from a fully penetrating vertical well into an unconsolidated formation confined with stiff seal rocks. The coupled behavior of an isotropic, homogeneous sand layer is studied under injection pressures that are high enough to induce plasticity yet not fracturing. Propagation of the significant influence zone surrounding the injection borehole, quantified by the extent of the plastic domain in the elasto‐plastic model, is examined for the first time. First, a new fully coupled axisymmetric numerical model is developed. A comprehensive assessment is performed on pore pressures, stresses/strains, and failure planes during the entire transient period of an injection cycle. Results anticipate existence of five distinctive zones in terms of plasticity state: liquefaction at wellbore; two inner plastic domains surrounding the wellbore, where failure occurs along two planes and major principal stress is in vertical direction; remaining of the plastic domain, where formation fails along one plane and major principal stress is in radial direction; and a non‐plastic region. Failure mechanism at the wellbore is found to be shear followed by liquefaction. Next, a novel methodology is proposed based on which new weakly coupled poro‐elasto‐plastic analytical solutions are derived for all three stress/strain components. Unlike previous studies, extension of the plastic zone is obtained as a function of injection pressure, incorporating plasticity effects on the subsequent elastic domain. Solutions, proven to be a good approximation of numerical simulations, offer a huge advantage as the run time of coupled numerical simulations is considerably long. Copyright © 2016 John Wiley & Sons, Ltd.     

Continuum large cracking in a rate‐dependent plastic–damage model for cyclic‐loaded concrete structures

Formulation and algorithmic treatment of a rate‐dependent plastic–damage model modified to capture large tensile cracking in cyclic‐loaded concrete structures are presented in detail for a three‐dimensional implementation. The plastic–damage model proposed by Lee and Fenves in 1998 was founded based on isotropic damaged elasticity in combination with isotropic multi‐hardening plasticity to simulate cracking and crushing of concrete under cyclic or dynamic loadings. In order that the model can capture large crack opening displacements, which are inevitable in plain concrete structures, the excessive increase in plastic strain causing unrealistic results in cyclic behaviors is prevented when the tensile plastic–damage variable controlling the evolution of tensile damage is larger than a critical value. In such a condition, the crack opening/closing mechanism becomes similar to discrete cracking. The consistent tangent operator required to accelerate convergence rate is also formulated for the large cracking state including viscoplasticity. The validation and performance of the modified algorithm implemented in a special finite element program is exemplified through several single‐element tests as well as three structural applications. The last example examines the model in the seismic fracture analysis of Koyna dam as a benchmark problem and the resulting crack profile is compared with the available experiment. The numerical experimentations well demonstrate that the developed model whose modification is necessary to properly simulate the cyclic behavior of plain concrete subjected to large tensile strains is robust and reasonably accurate. Copyright © 2012 John Wiley & Sons, Ltd.     

温、湿控制生土三轴试验装置的研制与应用

为研究温度和湿度对生土力学特性的影响,自主研发了温、湿控制生土三轴试验装置。基于常规三轴压力室,借助电涡流非接触位移传感器搭建高精度变形测试系统,实现环境变化下生土应变的连续性捕捉。针对法国里昂地区生土材料,开展不同湿度、围压和温度作用下生土三轴循环加载-卸载试验,实测生土在不同工况下的三轴剪切破坏强度、应力-应变曲线及体积变化,通过分析滞回曲线,研究弹性模量和残余应变随应力水平的演化特征;同时进行了变湿度条件下生土气态水迁移效应试验。结果表明：该装置能够稳定控制生土环境变化条件,模拟再现生土单元体实际服役工况,精确测量试验过程中生土力学指标及湿度、温度与压力等环境指标,初步检验了装置性能的可靠性和准确性。相关成果可为荷载-湿-热耦合作用下非饱和生土变形机制的研究与本构模型的建立提供技术支撑。     

注浆注胶技术在治理铁路轨道板下沉病害中的应用

唐包铁路线白草鞍隧道无砟轨道上行线局部线段轨道板渗水、翻浆,在列车动荷载作用下发生不均匀下沉。对轨道板下沉病害进行了注浆、注胶整治施工：向下沉悬空轨道板线段仰拱下0.5 m垂深破碎岩层压注速凝水泥浆以达到密实和固化拱底破碎岩层改善和提高仰拱基底岩石承载能力,向已下沉的轨道板底压注新型高强度发泡树脂4.75^#双液胶体以提升整体轨道板直至恢复其原位。经注浆、注胶技术处理,该线段垂向下沉量达到了设计稳定值,恢复无砟轨道运载能力。