A sandwiched denitrifying biocathode in a microbial fuel cell for electricity generation and waste minimization     

A. Al-Mamun  O. Lefebvre  M. S. Baawain  H. Y. Ng 《International Journal of Environmental Science and Technology》2016,13(4):1055-1064

A denitrifying biocathode in a microbial fuel cell was developed to investigate the replacement of the costly Pt-coated abiotic cathodes for electricity generation. The denitrifying biocathode was sandwiched between the dual-anode systems. The study investigated the performance for simultaneous treatment of wastewater on the anode, biological denitrification on the cathode and the potential recovery of electrical energy. Autotrophic biofilms performed denitrification on the cathode using supplied electrons by the biodegradation of organics on the anode. Graphite granules were used as electrodes for biofilm attachment, and nafion membranes were used as separators between electrodes. The system achieved a volumetric power of 7 ± 0.4 W m^?3 net cathodic compartment (NCC) with the simultaneous removal of 229.5 ± 18 mg L^?1 COD on anode and 88.9 g m^?3 NCC day^?1 nitrogen on cathode, respectively. The columbic efficiency for cathodic and anodic reactions was 98.9 ± 0.57 and 23.54 ± 0.87 %, respectively. This is a combined study for domestic wastewater treatment and biological denitrification in a compact MFC reactor. Further optimization of the system is desired to improve its performance and applicability.  相似文献   

Urban heat islands in Hong Kong: statistical modeling and trend detection     

Weiwen Wang  Wen Zhou  Edward Yan Yung Ng  Yong Xu 《Natural Hazards》2016,83(2):885-907

  相似文献   

Performance of ethylene-vinyl acetate foam as cushioning material for rigid debris-resisting barriers     

Carlos Lam  Julian S. H. Kwan  Y. Su  Clarence E. Choi  Charles W. W. Ng 《Landslides》2018,15(9):1779-1786

This paper reports an investigation on the performance of ethylene-vinyl acetate (EVA) foam when used as a cushion layer for rigid barriers used to resist debris flow. Large-scale pendulum impact tests were conducted to study the effects of layer thickness on cushion performance under six successive impacts. Results show that for the first impact at 70 kJ, the peak contact force with the EVA foam thickness of 500 mm is about twice larger compared to that of 1000 mm. Results also reveal that the cushion mechanism of elastic collapse of cell walls in the EVA foam results in peak contact forces and maximum transmitted loads that are up to 30 and 50% lower compared to gabions for the first impact at 70 kJ, respectively. The elastic behavior of EVA foam provides consistent cushioning efficiency. Furthermore, EVA foam is found to be susceptible to degradation by ultraviolet light so that a suitable coating layer is required for outdoor use. Polyurea was identified as a suitable coating material and a small-scale coating trial was performed to confirm this. Findings presented in this paper will have direct implications on the future design of cushion layers for rigid barriers used to intercept debris flows.  相似文献   

Geophysical flows impacting a flexible barrier: effects of solid-fluid interaction     

D. Song  C. E. Choi  C. W. W. Ng  G. G. D. Zhou 《Landslides》2018,15(1):99-110

Flexible barriers undergo large deformation to extend the impact duration, and thereby reduce the impact load of geophysical flows. The performance of flexible barriers remains a crucial challenge because there currently lacks a comprehensive criterion for estimating impact load. In this study, a series of centrifuge tests were carried out to investigate different geophysical flow types impacting an instrumented flexible barrier. The geophysical flows modelled include covered in this study include flood, hyperconcentrated flow, debris flow, and dry debris avalanche. Results reveal that the relationship between the Froude number, Fr, and the pressure coefficient α strongly depends on the formation of static deposits called dead zones which induce static loads and whether a run-up or pile-up impact mechanism develops. Test results demonstrate that flexible barriers can attenuate peak impact loads of flood, hyperconcentrated flow, and debris flow by up to 50% compared to rigid barriers. Furthermore, flexible barriers attenuate the impact load of dry debris avalanche by enabling the dry debris to reach an active failure state through large deformation. Examination of the state of static debris deposits behind the barriers indicates that hyperconcentrated and debris flows are strongly influenced by whether excessive pore water pressures regulate the depositional process of particles during the impact process. This results in significant particle rearrangement and similar state of static debris behind rigid barrier and the deformed full-retention flexible barrier, and thus the static loads on both barriers converge.  相似文献   

Particle shape effect on macro‐ and micro‐behaviors of monodisperse ellipsoids     

Tang‐Tat Ng 《国际地质力学数值与分析法杂志》2009,33(4):511-527

The microscopic and macroscopic behaviors of assemblages of monodisperse ellipsoids with different particle shapes were studied using the discrete element method. Four samples were created with 1170 identical prolate ellipsoids. The samples were compressed isotropically to 100 kPa. Then triaxial compression tests were carried out to very large strains until the ultimate state was reached. This paper presents typical macroscopic result including stress–strain relationship and volumetric behavior. In addition, the fabric of the samples was examined at the initial state, at the peak shear strength state, and at the ultimate state. We studied the evolution of three vector‐typed micromechanical arguments with strain including the particle orientation, branch vector, and normal contact force. The normal contact force (micromechanical argument) was found to have a direct relationship with the principal stress ratio (macroscopic parameter). The angles between these vectors were also investigated. The maximum angle between vectors is related to particle shape. The results indicate that the distributions and the maximum values of these angles do not change with loading. Copyright © 2008 John Wiley & Sons, Ltd.  相似文献   

Spatial Distribution of Solar Energetic Particles in the Inner Heliosphere     

Donald V. Reames  Chee K. Ng  Allan J. Tylka 《Solar physics》2013,285(1-2):233-250

We study the spatial distribution of solar energetic particles (SEPs) throughout the inner heliosphere during six large SEP events from the period 1977 through 1979, as deduced from observations on the Helios 1 and 2, IMP 7 and 8, ISEE 3, and Voyager 1 and 2 spacecraft. Evidence of intensity maxima associated with the expanding shock wave is commonly seen along its central and western flanks, although the region of peak acceleration or “nose” of the shock is sometimes highly localized in longitude. In one event (1 January 1978) a sharp peak in 20?–?30 MeV proton intensities is seen more strongly by Voyager at ～?2 AU than it is by spacecraft at nearby longitudes at ～?1 AU. Large spatial regions, or “reservoirs,” often exist behind the shocks with spatially uniform SEP intensities and invariant spectra that decrease adiabatically with time as their containment volume expands. Reservoirs are seen to sweep past 0.3 AU and can extend out many AU. Boundaries of the reservoirs can vary with time and with particle velocity, rather than rigidity. In one case, a second shock wave from the Sun reaccelerates protons that retain the same hard spectrum as protons in the reservoir from the preceding SEP event. Thus reservoirs can provide not only seed particles but also a “seed spectrum” with a spectral shape that is unchanged by a weaker second shock.  相似文献   

利用雷达差分干涉测量技术获取汶川MS 8.0地震形变场     

董玉森  Ge Lin-lin  Alex Hay-Man Ng  张奎 《地质科技情报》2009,28(6)

利用ENVISAT/ASAR和ALOS/PALSAR数据,结合两路差分干涉测量技术获得了汶川地震的同震形变信息和震前、震后地面在卫星视线(light of sight,简称LOS)方向上的形变特征。结果表明,汶川地震引起的地面形变范围广,程度大,地震形变沿断层向北北东向扩展,所形成的差分干涉条纹明显。地面的形变特征对于推断断层的性质,研究地震形变和地震发育特征具有重要的参考价值。另外,将同震雷达差分干涉测量的结果与利用USGS发布的汶川地震有限元断层模型(finite fault model)反演的LOS方向的形变进行了对比验证,发现二者在断裂带的上盘具有较好的一致性,但在下盘却有较大的误差。通过不同传感器干涉结果的对比发现,L波段的雷达干涉结果更能够反映汶川大地震在龙门山断裂带附近的地面形变信息。  相似文献   

Simulation of wave propagation over a submerged bar using the VOF method with a two-equation k– turbulence modeling     

Y. M. Shen  C. O. Ng  Y. H. Zheng 《Ocean Engineering》2004,31(1):87-95

A two-equation k– turbulence model is used in this paper to simulate the propagation of cnoidal waves over a submerged bar, where the free surface is handled by the volume-of-fluid (VOF) method. Using a VOF partial-cell variable and a donor–acceptor method, the model is capable of treating irregular boundaries, including arbitrary bottom topography and internal obstacles, where the no-slip condition is satisfied. The model also allows the viscous sublayer to be modeled by a wall function approximation implemented in the grid nodes that are immediately adjacent to a wall boundary. The numerical model applied to the propagation of cnoidal waves over a submerged bar can produce results that are in general agreement with some laboratory measurements. Some remarks arising from the comparison between the computational and experimental results are presented.  相似文献   

Seismic response control of a building complex utilizing passive friction damper: experimental investigation     

Chi‐Lun Ng  You‐Lin Xu 《地震工程与结构动力学》2006,35(6):657-677

Multi‐storey main buildings constructed with a low‐rise podium structure possess some architectural merits but the setback features of such a building complex may lead to seismic response enlargement of the main buildings. This paper explores the possibility of using passive friction dampers to connect the podium structure to the main buildings to prevent their seismic response enlargement without violating the architectural features. A series of shaking table tests were carried out on one 3‐storey and one 12‐storey building models in fully‐separated, rigidly connected, and friction damper‐linked configurations. Four sets of seismic ground motions were selected as inputs to the shaking table. The control competence of two buildings linked with friction damper was evaluated by comparison of their responses with those from fully‐separated and rigidly connected cases. Experimental results showed that unfavourable seismic response amplification did occur in the building complex in the rigidly connected case. By contrast, friction damper showed effectiveness in reducing absolute acceleration and interstorey drift responses of both buildings if friction force level was appropriately applied. Copyright © 2005 John Wiley & Sons, Ltd.  相似文献   

Characterization of Distributional Forms for Compositional Data and Associated Distributional Tests     

John Aitchison  Gloria Mateu-Figueras  Kai W. Ng 《Mathematical Geology》2003,35(6):667-680

A variety of approaches to the testing of distributional forms for compositional data has appeared in the literature, all based on logratio or Box–Cox transformation techniques and to a degree dependent on the divisor chosen in the formation of ratios for these transformations. This paper, recognizing the special algebraic–geometric structure of the standard simplex sample space for compositional problems, the use of the fundamental simplicial singular value decomposition, and an associated power-perturbation characterization of compositional variability, attempts to provide a definitive approach to such distributional testing problems. Our main consideration is the characterization and testing of additive logistic–normal form, but we also indicate possible applications to logistic skew normal forms once a full range of multivariate tests emerges. The testing strategy is illustrated with both simulated data and applications to some real geological compositional data sets.  相似文献