The hydrocarbons in the Isla Vista marine seep environment     

Daniel H. Stuermer  Robert B. Spies  Paul H. Davis  Douglas J. Ng  Clarence J. Morris  Sharon Neal 《Marine Chemistry》1982,11(5):413-426

Hydrocarbon analyses on samples of sediment, interstitial water, and dissolved and particulate fractions of the water column from the vicinity of the Isla Vista seep near Santa Barbara, California, are presented. The results demonstrate that a very heterogeneous distribution of hydrocarbon composition and concentration exists in the seep environment and that the life-style and feeding habits of the organisms in this environment will have a dramatic effect on their hydrocarbon exposure.  相似文献   

The propagation of solar cosmic-ray bursts     

C. K. Ng  L. J. Gleeson 《Solar physics》1971,20(1):166-185

A model is presented in which we show analytically the three phases of anisotropy which occur during solar cosmic-ray events observed in the 7.5 MeV to 21 MeV kinetic-energy interval and reported by McCracken et al. (1971): (i) a highly anisotropic, near field-aligned, initial phase, (ii) a convective phase, and (iii) a late-time phase in which the anisotropy is approximately perpendicular to the mean interplanetary magnetic field. The model is based on the cosmic-ray particles being convectively transported out from the Sun, undergoing anisotropic diffusion along the interplanetary magnetic-field lines, and losing energy by adiabatic deceleration or by collision processes. The event is seen simply as a pulse moving outward from the Sun after a cosmic-ray burst with a negative density-gradient in front of it and a positive gradient behind. The convective phase (ii) occurs as the spatial peak moves past the observer and has a propagation speed V _d associated with it; the anisotropy vector late in the decay phase (iii) is the result of a residual balance between the radial outward convection and the inward radial component of the anisotropic diffusion. The mathematical solutions are based upon a diffusion coefficient proportional to heliocentric radius and independent of energy and are thus rather special. However they yield formulae for the propagation speed of the convective phase and the direction in space of the long-time anisotropy which are useful as a guide to the dependence of these quantities on the solar wind speed V, the diffusion coefficient and the spectral index . In this model V _d increases with V, , and ; and , the angle between the anisotropy vector at infinite time and the outward radial direction increases with /V and decreases as is increased. These predictions of the dependence of and V _d upon V, , and are open to observational verification.  相似文献   

Laboratory simulation to understand translational soil slides and establish movement criteria using wireless IMU sensors     

Prapti Giri  Kam Ng  William Phillips 《Landslides》2018,15(12):2437-2447

Landslide monitoring and warning using inertial measurement units (IMUs) has shown the potential for remote and real-time applications. However, the studies conducted using the IMU sensors are limited to rainfall-induced landslide detection using soil moisture sensors and accelerometers for predicting slide and measuring tilt, respectively. The tilting of the slope might not occur during a slow-moving translational slide, and it may not always be possible to accurately record the soil moisture condition. The use of raw acceleration data, which is the combination of linear and gravitational accelerations, for calculating tilt or motion is another drawback of the existing studies. Hence, there is a need for a better approach to monitor slides. This paper presents two methods to define movement thresholds and criteria to identify the translational soil slides based on our understanding of the sensor data recorded during the two laboratory experiments. BNO055 sensor devices (IMU sensors) with 3-axis accelerometers and 3-axis gyroscopes were selected for this study. The linear accelerations, gravitational accelerations, and angular velocities were utilized to understand the translational soil slides by correlating the sensor behavior to that of the slope. The interpretation of the movements during the failure at each sensor location was further verified by referring to the videos recorded by two pi-cameras. The outcomes of this study confirm the applicability of the proposed IMU sensor system and the movement thresholds for effective and reliable monitoring and warning of translational soil slides.  相似文献   

Morphology and evolution of supraglacial hummocks on debris-covered Himalayan glaciers     

Oliver T. Bartlett  Felix S.L. Ng  Ann V. Rowan 《地球表面变化过程与地形》2021,46(3):525-539

Thick supraglacial debris layers often have an undulating, hummocky topography that influences the lateral transport of debris and meltwater and provides basins for supraglacial ponds. The role of ablation and other processes associated with supraglacial debris in giving rise to this hummocky topography is poorly understood. Characterizing hummocky topography is a first step towards understanding the feedbacks driving the evolution of debris-covered glacier surfaces and their potential impacts on mass balance, hydrology and glacier dynamics. Here we undertake a geomorphological assessment of the hummocky topography on five debris-covered glaciers in the Everest region of the central Himalaya. We characterize supraglacial hummocks through statistical analyses of their vertical relief and horizontal geometry. Our results establish supraglacial hummocks as a distinct landform. We find that a typical hummock has an elongation ratio of 1.1:1 in the direction of ice flow, length of 214 ± 109 m and width of 192 ± 88 m. Hummocky topography has a greater amplitude across-glacier (15.4 ± 10.9 m) compared to along the glacier flow line (12.6 ± 8.3 m). Consequently, hummock slopes are steeper in the across-glacier direction (8.7 ± 4.3°) than in the direction of ice flow (5.6 ± 4.0°). Longer, wider and higher-amplitude hummocks are found on larger glaciers. We postulate that directional anisotropy in the hummock topography arises because, while the pattern of differential ablation driving topography evolution is moderated by processes including the gravitational redistribution of debris across the glacier surface, it also inherits an orientation preference from the distribution of englacial debris in the underlying ice. Our morphometric data inform future efforts to model these interactions, which should account for additional factors such as the genesis of supraglacial ponds and ice cliffs and their impact on differential ablation.  相似文献   

Seasonal movement and groundwater flow mechanism in an unsaturated saprolitic hillslope   总被引：4，自引：4，他引：0  

Anthony Kwan Leung  Charles Wang Wai Ng 《Landslides》2013,10(4):455-467

Numerous field monitoring programs have been conducted to investigate the performance of an unsaturated soil slope subjected to rainfalls in wet seasons. Most case histories focus on the response of matric suction, which is one of the two stress-state variables governing unsaturated soil behaviour. However, effects due to another variable, net normal stress, are often ignored. Also, slope performance under alternative wet and dry seasons is rarely reported and analysed. In this study, a saprolitic hillslope situated in Hong Kong was instrumented heavily to investigate its seasonal movement due to changes of the two variables and also groundwater flow mechanism. Two-year seasonal variations of matric suction and net normal stress were monitored by tensiometers together with heat dissipation matric water potential sensors and earth pressure cells, respectively. During heavy rainstorms in wet season, there was a substantial recharge of the main groundwater table, causing a significant increase of positive pore-water pressure in deeper depths. Rupture surface likely developed at depths between 5.5 and 6 m, hence resulting in a “deep-seated” mode of downslope movement. The downslope movement resulted in a peak increase of horizontal stress. In dry seasons, matric suction of up to 190 kPa was recorded, and the associated soil shrinkage led to substantial upslope rebounds. The stress built up in wet seasons hence reduced. After monitoring period of 2 years, downslope ratcheting is identified. Up to 40 % of the downslope displacements were recovered by the upslope rebounds.  相似文献   

Performance of Tropical Vertical Subsurface Flow Constructed Wetlands at Different Hydraulic Loading Rates          下载免费PDF全文

G.M.P.R. Weerakoon  K.B.S.N. Jinadasa  G.B.B. Herath  M.I.M. Mowjood  Dongqing Zhang  Soon Keat Tan  Ng Wun Jern 《洁净——土壤、空气、水》2016,44(8):938-948

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Short-term survival of severe propeller strike injuries and observations on wound progression in a bottlenose dolphin     

SL Dwyer  L Kozmian-Ledward  KA Stockin 《新西兰海洋与淡水研究杂志》2013,47(2):294-302

Until recently, vessel collisions with small cetaceans were presumed rare, mainly as a consequence of limited reporting. Observations on dolphin wound healing from propeller strike injuries also remain scarce. We present an extreme case of a bottlenose dolphin (Tursiops truncatus) with multiple propeller wounds, including a penetration to the bone, where survival was possible for at least 23 days post injury. We used photographic records in conjunction with field observations to describe wound progression in the absence of treatment. Considering the severity of the wounds, it was surprising that the injuries were not immediately fatal. A practical solution remains to be found for the problem of odontocete vessel collisions, in particular for small highly mobile species using neritic waters. In view of the ongoing problem in the Hauraki Gulf and, indeed, worldwide, we recommend continued evaluation of cases and reporting of incidents, in addition to investigations into mechanisms that may reduce the risk of occurrence of vessel collisions with cetaceans.  相似文献   

Effects of leaf toughness and nitrogen content on litter breakdown and macroinvertebrates in a tropical stream     

Aggie O. Y. Li  Lily C. Y. Ng  David Dudgeon 《Aquatic Sciences - Research Across Boundaries》2009,71(1):80-93

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带裙房高层建筑地震反应控制振动台试验研究   总被引：1，自引：1，他引：0  

瞿伟廉  陈静  徐幼麟  C.L.Ng 《地震工程与工程振动》2004,24(3):64-72

2002年9月在香港理工大学成功地进行了带裙房高层建筑地震反应控制试验研究。设计和制作的结构模型是带3层裙房的12层高楼剪切模型,在裙房顶层与主楼之间安装单MR阻尼器形成MR阻尼器耦联结构模型。MR阻尼器采用美国LORD公司摩擦型MR阻尼器,并且选用其配套产品计算机电流控制器对其进行控制,控制系统采用德国dSPACE公司实时控制系统。对独立主楼、独立裙房和原结构模型的动力特性进行了辨识;对结构模型进行了El Centro地震动作用下的地震反应振动台试验;以作者提出的MR阻尼器半主动逻辑控制算法,对MR阻尼器耦联的结构模型进行了地震反应振动台试验。试验结果表明：用MR阻尼器耦联主楼与裙房,采用半主动逻辑控制方法进行控制,能有效抑制主楼的鞭梢效应并使主楼和裙房的地震反应减小。  相似文献   

Erratum to: Velocity attenuation of debris flows and a new momentum-based load model for rigid barriers     

R. C. H. Koo  J. S. H. Kwan  C. W. W. Ng  C. Lam  C. E. Choi  D. Song  W. K. Pun 《Landslides》2017,14(2):631-631

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