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Wood debris are an important component of mangrove marine environments. Current knowledge of the ecological role of wood falls is limited by the absence of information on metazoan colonization processes over time. The aim of this study was to provide insights to their temporal dynamics of wood eukaryotic colonization from a shallow water experiment in a mangrove swamp. Combined in situ chemical monitoring and biological surveys revealed that the succession of colonizers in the mangrove swamp relates with the rapid evolution of sulfide concentration on the wood surface. Sulfide-tolerant species are among the first colonizers and dominate over several weeks when the sulfide content is at its maximum, followed by less tolerant opportunistic species when sulfide decreases. This study supports the idea that woody debris can sustain chemosynthetic symbioses over short time-scale in tropical shallow waters. 相似文献
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A novel smart control system based on genetic algorithms (GAs) is proposed in this paper. The system is comprised of three parts: the fiber Bragg grating (FBG) sensor‐based sensing network for structural health monitoring, the GA‐based location optimizer for sensor arrangement, and the GA‐based controller for vibration mitigation under external excitation. To evaluate the performance of the proposed system, an eight‐story steel structure was designed specifically to represent a structure with large degrees of freedom. In total 16 FBG sensors were deployed on the structure to implement the concept of a reliable sensing network, and to allow the structure to be monitored precisely under any loading. The advantage of applying a large amount of information from the sensing system is proven theoretically by the GA‐based location optimizer. This result greatly supports the recent tendency of distributing sensors around the structure. Two intuitive GA‐based controllers are then proposed and demonstrated numerically. It is shown that the structure can be controlled more effectively by the proposed GA‐strain controller than by the GA‐acceleration controller, which represents the traditional control method. A shaking table test was carried out to examine the entire system. Experimental verification has demonstrated the feasibility of using this system in practice. Copyright © 2008 John Wiley & Sons, Ltd. 相似文献
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The Smart Sediment Particle(SSP) instrumented with multiple sensors to obtain tri-axial linear accelerations is used for studying the mechanism of coarse grain entrainment. Three bed arrangements are tested to examine their influences on entrainment processes and the threshold force and impulse conditions. The SSP shows satisfactory precision to capture the imperceptible movement tendencies immediately(e.g., 0.15 s) after the dislodgement. The experimental results show that bed packing can signi... 相似文献
96.
A new electrochemical voltammetric sensor, Langmuir–Blodgett (LB) film of 25,27‐dimethoxy‐26‐(N‐trichloroacetyl)carbamoyloxy‐p‐tert‐butylcalix[4]arene (DCA) modified GCE (LBDCA–GCE), was designed and successfully used for recognition and determination of trace amounts of Ag+ in water. Under the optimum experimental conditions, the lowest detectable concentration of Ag+ reached 1 × 10?9 mol L?1. Moreover, LBDCA–GCE exhibited a well‐defined response relating to the Ag+ with good sensitivity, selectivity, reproducibility, and long stability. The recognizing mechanism of LBDCA–GCE for silver ion in aqueous solution was also discussed. The results show that the size of calixarene cavity may be the predominate factor affecting recognition of calixarene for silver ions. 相似文献
97.
Athanasios N. 《国际泥沙研究》2009,24(1):1-15
A recent acoustic instrument (Gravel Transport Sensor, GTS) was tested for predicting sediment transport rate (bed load rate) in gravel bed streams. The GTS operation is based on the particle collision theory of submerged obstacles in fluids. When particles collide with the GTS cylinder their momentum is recorded in the form of ping rates. The GTS is attractive for further consideration here because of its potential to provide continuous unattended local bed load measurements, especially in areas found in streams that access may be difficult under extreme conditions. Laboratory experiments coupled with numerical simulations for the same flow conditions were performed in order to determine the conditions under which particles of different size will hit the GTS cylinder and be able to register a ping rate. The GTS was able to detect the number of particles with diameter in the range of 15.9 to 25.4 mm, with reasonable accuracy, if the applied Shields effective stress τ*e = τ* - τ*cr was in the range of 0.006 to 0.015. A drawback of the tested prototype GTS, however, was that it exerted increased resistance on the incoming particles. The added drag effects increased the overall resistance that was exerted by the flow on particles and thus increased the likelihood that particles will rest in the ambient region of the cylinder instead of hitting it. Numerical simulation of the flow around the GTS cylinder revealed that changing the prototype geometry from cylindrical to ellipsoid or rhomboid will increase the likelihood of the particles hitting the instrument under the same flow conditions failed by the original tested GTS cylinder. 相似文献
98.
Ying Lei Anne S. Kiremidjian K. Krishnan Nair Jerome P. Lynch Kincho H. Law 《地震工程与结构动力学》2005,34(6):555-573
Dense networks of wireless structural health monitoring systems can effectively remove the disadvantages associated with current wire‐based sparse sensing systems. However, recorded data sets may have relative time‐delays due to interference in radio transmission or inherent internal sensor clock errors. For structural system identification and damage detection purposes, sensor data require that they are time synchronized. The need for time synchronization of sensor data is illustrated through a series of tests on asynchronous data sets. Results from the identification of structural modal parameters show that frequencies and damping ratios are not influenced by the asynchronous data; however, the error in identifying structural mode shapes can be significant. The results from these tests are summarized in Appendix A. The objective of this paper is to present algorithms for measurement data synchronization. Two algorithms are proposed for this purpose. The first algorithm is applicable when the input signal to a structure can be measured. The time‐delay between an output measurement and the input is identified based on an ARX (auto‐regressive model with exogenous input) model for the input–output pair recordings. The second algorithm can be used for a structure subject to ambient excitation, where the excitation cannot be measured. An ARMAV (auto‐regressive moving average vector) model is constructed from two output signals and the time‐delay between them is evaluated. The proposed algorithms are verified with simulation data and recorded seismic response data from multi‐story buildings. The influence of noise on the time‐delay estimates is also assessed. Copyright © 2004 John Wiley & Sons, Ltd. 相似文献
99.
Nicolas Baghdadi Olivier Cerdan Mehrez Zribi Véronique Auzet Frédéric Darboux Mahmoud El Hajj Rania Bou Kheir 《水文研究》2008,22(1):9-20
Synthetic aperture radar (SAR) sensors are often used to characterize the surface of bare soils in agricultural environments. They enable the soil moisture and roughness to be estimated with constraints linked to the configurations of the sensors (polarization, incidence angle and radar wavelength). These key soil characteristics are necessary for different applications, such as hydrology and risk prediction. This article reviews the potential of currently operational SAR sensors and those planned for the near future to characterize soil surface as a function of users' needs. It details what it is possible to achieve in terms of mapping soil moisture and roughness by specifying optimal radar configurations and the precision associated with the estimation of soil surface characteristics. The summary carried out for the present article shows that mapping soil moisture is optimal with SAR sensors at low incidence angles (<35 ). This configuration, which enables an estimated moisture accuracy greater than 6% is possible several times a month taking into account all the current and future sensors. Concerning soil roughness, it is best mapped using three classes (smooth, moderately rough, and rough). Such mapping requires high‐incidence data, which is possible with certain current sensors (RADARSAT‐1 and ASAR both in band C). When L‐band sensors (ALOS) become available, this mapping accuracy should improve because the sensitivity of the radar signal to Soil Surface Characteristics (SSC) increases with wavelength. Finally, the polarimetric mode of certain imminent sensors (ALOS, RADARSAT‐2, TerraSAR‐X, etc.), and the possibility of acquiring data at very high spatial resolution (metre scale), offer great potential in terms of improving the quality of SSC mapping. Copyright © 2007 John Wiley & Sons, Ltd. 相似文献
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