Error analysis of a new planar electrostatic gravity gradiometer for airborne surveys   总被引：1，自引：1，他引：0  

Karim Douch  Isabelle Panet  Gwendoline Pajot-Métivier  Bruno Christophe  Bernard Foulon  Marie-Françoise Lequentrec-Lalancette  Michel Diament 《Journal of Geodesy》2015,89(12):1217-1231

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Assessing the potential underestimation of sediment and nutrient loads to the Great Barrier Reef lagoon during floods     

Wallace J  Karim F  Wilkinson S 《Marine pollution bulletin》2012,65(4-9):194-202

Much of the sediment and nutrient load to the Great Barrier Reef (GBR) lagoon happens during over bank floods, when discharge can be significantly underestimated by standard river gauges. This paper assesses the potential need for a flood load correction for 28 coastal rivers that discharge into the GBR lagoon. For each river, daily discharge was divided into flows above and below a 'flood' threshold to calculate the mean annual percentage flow above this threshold. Most GBR rivers potentially need a flood load correction as over 15% of their mean annual flow occurs above the minor flood level; only seven rivers need little/no correction as their flood flows were less than 5% of the mean annual flow. Improved assessment of the true load of materials to the GBR lagoon would be an important contribution to the monitoring and reporting of progress towards Reef Plan and associated marine load targets.  相似文献   

Diagnosis, seismic analysis and reinforcement of an old building in El-Maleh, Algeria     

Nadir Boumechra  Fabio Casciati  Karim Hamdaoui 《地震工程与工程振动(英文版)》2010,9(4):577-586

The Northern part of Algeria is considered to be the most active seismogenic area in the Western Mediterranean region. This area has a rich history of seismicity and had experienced many destructive earthquakes such as the Chlef (1954), El-Asnam (1980), Beni-Chograne (1994), An-Temouchent (1999) and recently Boumerdes (2003) earthquakes. The earthquake of An-Temouchent on December 22, 1999, was of magnitude 5.7, killed at least 28 people and made thousands of families homeless. Consequent damage was seen in all the structures located in a radius of 30 km. In the city of El-Maleh, located 12 km northeast of An-Temouchent, the "The National Bank Branch" of El-Maleh suffered moderate damage, but enough to justify questions about its safety. The project of rehabilitating this building required a broad analysis of its static and dynamic, past and present behaviors. The study reported in this paper was a necessary preliminary step toward the development of an optimal retrofit solution.  相似文献   

Topographic reflection of the Socompa debris avalanche,Chile     

Karim Kelfoun  Tim Druitt  Benjamin van Wyk de Vries  Marie-Noëlle Guilbaud 《Bulletin of Volcanology》2008,70(10):1169-1187

One of the most remarkable features of the exceptionally well preserved 26 km³ Socompa debris avalanche deposit is the evidence for topographically driven secondary flow. The avalanche formed by sector collapse of Socompa stratovolcano and spread 40 km across a pre-existing basin, forming a sheet of ∼50 m average thickness. As the avalanche impinged on the western and northern margins of the basin, it was reflected back, forming a secondary flow that continued to travel 15 km down a gentle slope at an oblique angle to the primary flow, the front of the return wave being preserved frozen on the surface of the deposit as a prominent escarpment. Satellite images, aerial photos, digital elevation models and field observations were used to reconstruct the sequence of events during avalanche emplacement, and in particular during secondary flow. The avalanche sheet was divided into distinct terrane groups, each believed to have experienced a particular strain history during emplacement. Evidence for avalanche reflection includes clearly recognizable secondary slide masses, sub-parallel sets of curvilinear shear zones, headwall scarps separating the (primary) levée from the secondary terranes, extensional jigsaw breakup of surface lithologies during return flow, and cross cutting, or deflection, of primary flow fabrics by secondary terranes. Reflection off the basin margin took place in an essentially continuous manner, most major return motions being simultaneous with, or shortly following, primary flow. The secondary flow occurred as a wave that swept obliquely across the primary avalanche direction, remobilizing the primary material, which was first compressed, then stretched, as it passed over and rearward of the wave front. As return flow occurred, surface lithologies were rifted in a brittle manner, and the slabs were sheared pervasively as they glided and rotated back into the basin; some sank into the more fluidal interior of the avalanche, which drained out into a prominent distal lobe. Extension by factors of up to 1.8 took place during return flow. Secondary flow took place on slopes of only a few degrees, and the distal lobe flowed 8 km on a slope of ∼1°. Overall the avalanche is inferred to have slid into place as a fast-moving sheet of fragmental rock debris, with a leading edge and crust with near-normal friction and an almost frictionless, fluidal interior and base. The avalanche emplacement history deduced from field evidence is consistent with the results of a previously published numerical model of the Socompa avalanche.  相似文献   

Assessment of water body change and sedimentation rate in Moulay Bousselham wetland,Morocco, using geospatial technologies     

Mounir Karim  Mehdi Maanan  Mohamed Maanan  Hassan Rhinane  Henri Rueff  Lahssen Baidder 《国际泥沙研究》2019,34(1):65-72

Coastal lagoons have significant biodiversity and ecologic and socio-economic interest. Several resident and migratory birds live in coastal lagoons as well as fish and other aquatic biota. Over the years, lagoons worldwide have been subject to considerable sediment deposition coming especially from soil erosion due of agricultural activities, and the lagoon's inflows have resulted in an accelerated sedimentation which can drastically affect the aquatic ecosystem balance. A new, fast, and cost-effective approach was developed, using water surface change as a proxy, to evaluate the sediment deposition rate. In the current research, this methodology was applied in the Moulay Bousselham Lagoon in Morocco, and a combination of Landsat 8 and Landsat 5 imagery acquired at four points in time over 30 years(1985-2015) was used. Following geometric correction and enhancement, the interpretation of the acquired images provided important insight on the current conditions of the water surface change using the Normalized Difference Water Index(NDWI). Several iterations were done to determine a suitable threshold for effective water surface detection. In order to validate the automatically extracted water surface features, many band combinations of Landsat and Sentinel 2 were used as references to run the accuracy assessment. The results show that the Moulay Bousselham Lagoon lost 17.60%(106 ha) of its water surface area, and 530,000 m^3 to 1,060,000 m^3 of its water volume during the last three decades.Converting water surface loss into sedimentation returned a rate of 0.58 cm/yr. These results have been confirmed by previous field work using sedimentological approaches. Proper management should be applied to sustain the vitality of this lagoon environment.  相似文献   

Correlation properties of integral ground-motion intensity measures from Italian strong-motion records     

Chen Huang  Karim Tarbali  Carmine Galasso 《地震工程与结构动力学》2020,49(15):1581-1598

This study investigates the correlation properties of integral ground-motion intensity measures (IMs) from Italian strong-motion records. The considered integral IMs include 5–95% significant duration, Housner intensity, cumulative absolute velocity, and Arias intensity. Both IM spatial correlation and the correlation between different integral and amplitude-based IMs (i.e., cross-IM correlation) are addressed in this study. To this aim, a new Italian ground-motion model (GMM) with spatial correlation for integral IMs is first introduced. Based on the newly developed GMM, the empirical correlation coefficients from interevent and intraevent residuals are investigated and various analytical correlation models between integral IMs and amplitude-based IMs are proposed. The effective range parameter representing spatial correlation properties and the trend in the cross-IM correlations are compared with existing models in the literature. The variability of the effective range parameters with respect to event-specific features is also discussed. Modeling ground-motion spatial and cross-IM correlations is an important step in seismic hazard and risk assessment of spatially distributed systems. Investigating region-specific correlation properties based on Italian strong-motion records is of special interest as several correlation models have been developed based on global datasets, often lacking earthquakes in extensional regions such as Italy.  相似文献   

Countermeasure of river bend scour using a combination of submerged vanes and riprap     

Piya Biswas  Abdul Karim Barbhuiya 《国际泥沙研究》2018,33(4):478-492

A series of laboratory flume experiments were done in a large-scale 180° bend with non-cohesive sediment to find optimal or effective protection works at a bend. Detailed study of the scour and flow field dynamics with and without protection works was done. Spatially dense, high frequency velocity data were collected and analyzed to describe the pattern and magnitude of three-dimensional(3 D)velocity throughout the bend. Characterizing the role of flow field dynamics on the pattern of deposition and erosion through experimental measurements provided valuable data about how such flow features contribute to scour and about the performance of the protection works. From the experimental results, it is revealed that for a perennial river it is not possible to protect from scour either with riprap or with submerged vanes alone. Protection from scour at a bend can be achieved with proper combination of these two works. First, submerged vanes can protect the toe, and, second, riprap can protect the upper part of the slope if it is not damaged through toe erosion. The experiments convincingly demonstrate the efficiency of this bank protection technique.  相似文献   

Estimation of inelastic displacement ratio for base‐isolated structures          下载免费PDF全文

Saman Yaghmaei‐Sabegh  Sina Safari  Karim Abdolmohammad Ghayouri 《地震工程与结构动力学》2018,47(3):634-659

This study develops a straightforward approximate method to estimate inelastic displacement ratio, C₁ for base‐isolated structures subjected to near‐fault and far‐fault ground motions. Taking into account the inelastic behavior of isolator and superstructure, a 2 degrees of freedom model is employed. A total of 90 earthquake ground motions are selected and classified into different clusters according to the frequency content features of records represented by the peak ground acceleration to peak ground velocity ratio, A_p/V_p. A parametric study is conducted, and effective factors in C₁ (i.e., fundamental vibration period of the superstructure, T_s; postyield stiffness ratio of the superstructure, α_s; strength reduction ratio, R; vibration period of the isolator, T_b; strength of the isolator, Q; ratio of superstructure mass to total mass of the system, γ_m) are recognized. The results indicate that the practical range of C₁ values could be expected for base‐isolated structures. Subsequently, effective parameters are included in simple predictive equations. Finally, the accuracy of the proposed approximate equations is evaluated and verified through error measurement, and comparisons are made in the analyses.  相似文献   

Comparison of the antioxidant defense system in Crassostrea rhizophorae and Crassostrea gigas exposed to domestic sewage discharges     

Zanette J  Nunes FF  Medeiros ID  Siebert MN  Mattos JJ  Lüchmann KH  Rodrigues de Melo CM  Bainy AC 《Marine environmental research》2008,66(1):196-198

Oysters Crassostrea rhizophorae and Crassostrea gigas were kept for fourteen days at four sites in S?o José, SC, Brazil, chosen according to a sewage discharge contamination gradient. Enzymatic activities of CAT, GST, G6PDH and GR were evaluated in gills and digestive glands. Higher CAT activity was observed in tissues of C. rhizophorae in response to sewage contamination possibly indicating peroxisome proliferation induction. C. gigas showed elevated G6PDH activity in digestive gland, and GR in gills, after domestic sewage exposure. In conclusion, C. rhizophorae and C. gigas showed different biochemical responses after in situ exposure to domestic sewage. However, C. rhizophorae showed more significant changes in CAT suggesting that this organism could be a better monitor to this kind of effluent.  相似文献   

基于Ecopath模型的孟加拉国孟加拉湾海域营养结构和能量流动分析     

Karim Ehsanul  刘群  薛莹  Hasan Shanur Jahedul  Hoq M Enamul  Mahmud Yahia 《海洋学报(英文版)》2019,38(10):27-42

依据现有研究提供的信息,在孟加拉国孟加拉湾（BoB）新划定的超过90 000 km²的海域基于Ecopath方法利用2016年7月至2017年6月的数据构建了该生态系统的营养通道模型。对食物网中营养级从1（主要生产者和碎屑）到3.45（鲨鱼）的各功能群之间的营养相互作用进行评估,所研究的共19个功能群被认为代表了其中所有的营养级。大多数消费者的生态营养转换效率（EE）超过0.80;表明这是一个被高度利用的生态系统,并且从低营养级到高营养级有较高的能量转换效率。此外,整个生态系统的净效率（0.0018）和能量转换效率（11.12%）标志着当前这一"正在发展中的生态系统"已趋向成熟。生态系统的冗余度（64.6）和聚合度（35.4）也表明了这一生态系统的稳定性。因此,本研究认为这一海域具有显著的后备力量面对压力情况并有能力快速恢复到初始状态。  相似文献