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1.
Fatigue reliability analysis of deep water rigid marine risers associated with Morison-type wave loading 总被引：1，自引：0，他引：1
Muddassir Nazir Faisal Khan Paul Amyotte 《Stochastic Environmental Research and Risk Assessment (SERRA)》2008,22(3):379-390
This work presents a simple and efficient framework for the fatigue reliability assessment of a vertical top-tensioned rigid
riser. The fatigue damage response is considered as a narrow-band Gaussian stationary random process with a zero mean for
the short-term behavior of a riser. Non-linearity in a response associated with Morison-type wave loading is accounted for
by using a factor, which is the ratio of expected damage according to a non-linear probability distribution to the expected
damage according to a linear method of analysis. Long-term non-stationary response is obtained by summing up a large number
of short-term stationary responses. Uncertainties associated with both the strength and stress parts of the limit state function
are quantified by a lognormal distribution. A closed form reliability analysis is carried out, which is based on the limit
state function formulated in terms of Miner’s cumulative damage rule. The results thus obtained are compared with the well-documented
lognormal format of reliability analysis based on time to fatigue failure. The validity of using the lognormal hazard rate
function in predicting the fatigue life is discussed. A Monte Carlo simulation technique is also used as a reliability assessment
method. A simple algorithm is used to reduce the uncertainty associated with direct sampling at small probability of failure
values and a small number of simulations. Simulation results are compared with closed form solutions. A worked example is
included to show the practical riser design problem based on reliability analysis. 相似文献
2.
Sumira Malik Shristi Kishore Jutishna Bora Vishal Chaudhary Anjali Kumari Preeti Kumari Lamha Kumar Abhaya Bhardwaj 《洁净——土壤、空气、水》2023,51(3):2200044
In the past few years, microalgae have gained huge recognition from the scientific community due to their potential applications in the production of a broad array of bio-based products varying from biofuels to nanoparticles. Due to their elevated growth rate, high tolerance to various types of abiotic stresses, and complex metabolic capacity, microalgae can be used as promising tools for the attainment of a circular bioeconomy. Moreover, they can simply utilize nutrients from wastewater for biorefinery purposes, resulting in resource recovery coupled with wastewater treatment. However, due to their sub-optimal yields and high production costs, microalgae-based bio-products have not yet been commercialized. This review provides insights into the employment of microalgae as an efficient bioresource for the treatment of wastewater with simultaneous enactment as a biorefinery to produce biofuels, biochar, bioplastic, fertilizers, and other high-value bioproducts. Furthermore, the application of microalgal nanoparticles in wastewater treatment and prospects for genetic modification of microalgae for enhanced biorefinery capabilities have also been briefly highlighted. 相似文献
3.
Ramli Nazir Hossein Moayedi Rozaimi Bin Mohd Noor Soheil Ghareh 《Arabian Journal of Geosciences》2016,9(20):741
The attenuation equation for far field earthquake is important because the earthquake occurring in neighboring countries can be felt in Malaysia. In this study, a new attenuation was generated using the regression method. It was developed to calculate the peak ground acceleration (PGA) onsite (offshore platform). The database consisting of more than 150 PGAs from 9 events of earthquakes recorded by the Seismology Station in Malaysia was used to develop the relationship. In addition, attenuation relationships for subduction mechanisms from previous researchers are then compared with the newly generated ones in this research. The new attenuation equation was also validated and used to calculate the acceleration for far field earthquake in a case study of offshore platform at a Terengganu seaside. The result of PGA from the new generated attenuation relationship was in a good match with previous attenuation equations. 相似文献
4.
Guotao Zhang Peng Cui Yanzhou Yin Dingzhu Liu Wen Jin Hao Wang Yan Yan Bazai Nazir Ahmed Jiao Wang 《水文研究》2019,33(25):3195-3212
Synchronously and accurately estimating the flood discharges and dynamic changes in the fluid density is essential for hydraulic analysis and forecasting of flash floods, as well as for risk assessment. However, such information is rare for steep mountain catchments, especially in regions that are hotspots for earthquakes. Therefore, six hydrological monitoring sites were established in the main stream and tributaries of the 78.3‐km2 Longxi River catchment, an affected region of the Wenchuan earthquake region in China. Direct real‐time monitoring equipment was installed to measure the flow depths, velocities, and fluid total pressures of the flood hydrographs. On the basis of field measurements, real‐time mean cross‐sectional velocities during the flood hydrographs could be derived from easily obtainable parameters: cross‐sectional maximum velocities and the calibrated dimensionless parameter Kh . Real‐time discharges were determined on the basis of a noncontact method to establish the effective rating curves of this mountainous stream, ranging from 1.46 to 386.34 m3/s with the root mean square errors of ≤10.22 m3/s. Compared with the traditional point‐velocity method and empirical Manning's formula, the proposed noncontact method was reliable and safe for monitoring whole flood hydrographs. Additionally, the real‐time fluid density during the flood hydrographs was calculated on the basis of the direct monitoring parameters for fluid total pressures and water depths. During the flood hydrograph, transient flow behaviour with higher fluid density generally occurred downstream during the flood peak periods when the flow was in the supercritical flow regime. The observed behaviour greatly increased the threat of damage to infrastructure and human life near the river. Thus, it is important to accurately estimate flood discharge and identify for fluid densities so that people at risk from an impending flash flood are given reliable, advanced warning. 相似文献
5.
Mushtaq A. Wani J. A. Wani M. A. Bhat N. A. Kirmani Zahid M. Wani Shaista Nazir Bhat 《Journal of the Indian Society of Remote Sensing》2013,41(2):319-329
Soil nutrient maps based on intensive soil sampling are useful to adopt site-specific management practices. Geostatistical methods have been widely used to determine the spatial correlation and the range of spatial dependence at different sampling scales. If spatial dependence is detected, the modeled semivariograms can then be used to map the interested variable by kriging, an interpolation method that produces unbiased estimates with minimal estimation variance. The objectives of this paper were to examine and map the spatial distribution of the soil micronutrients Cu, Zn, Fe and Mn on an agricultural area in Kupwara, J&K, under temperate climatic conditions. The ordinary kriging was first used to determine the values for the non-sampled locations, and then the indicator approach was used to transform the micronutrient content values into binary values having the mean values of each nutrient as the threshold content. All four elements analyzed showed spatial dependence using the indicator semivariograms. The strength of spatial dependence was assessed using the values of nugget effect and range from the semivariogram, the fitted range values decreased in the order Zn > Cu > Mn > Fe. The spatial dependence of the combination of two or more of the studied micronutrients was also examined using indicator semivariograms. In opposition to spatial analysis of individual microelements, indicator semivariograms obtained for the binary coding of the variables showed a great nugget effect value or a low proportion of sill. The maps for each nutrient obtained using indicator kriging showed some similarity in the spatial distribution, suggesting the delimitation of uniform management areas. 相似文献
6.
青藏高原处于东亚季风、印度季风和西风环流交互作用区.末次冰消期以来,太阳辐射对该地区的古气候环境产生了重要影响,湖泊随着季风系统的变化发生了明显的水位升降,对湖岸阶地的形成起到了直接作用.本项研究重建了青藏高原东北缘冬给错纳湖湖岸阶地记录的湖面波动历史,试图了解青藏高原季风系统演变过程.通过湖泊北岸265 cm厚湖岸阶地沉积物粒度、碳酸盐、矿物、元素和介形虫古环境指标,结合OSL年代模式,分析表明在约10. 2 ka B. P.之前水体较浅;约10. 2~9. 0 ka B. P.湖面开始上升,气候凉湿;9. 0~8. 5 ka B. P.为印度季风强盛期,湖面明显上升,降雨量增高、温度上升;8. 5~7. 9 ka B. P.湖面降低与气候变冷有关;7. 9~7. 0 ka B. P.印度季风开始减弱,气温、降雨下降,但有效湿度较大,湖面降低;7. 0~6. 1 ka B. P.湖面上升可能与低蒸发作用有关,印度季风仍然影响该地区;6. 1~5. 2 ka B. P.,印度季风衰退,气候逐渐变冷、降雨量减小、水体变浅;5. 2~4. 6 ka B. P.气候冷干,有效湿度减小,湖面进一步下降;4. 6 ka B. P.至今气候干冷,东亚季风衰退,湖面下降,期间也可能受西风环流影响而有短暂的降雨增加时期. 相似文献
7.
The geoindicators of land degradation such as erosion, vegetation change and wetland loss were identified in the Kashmir Himalayan region using a geospatial model. Geomatics techniques were used to generate information on landuse/landcover, NDVI, slope and the lithological formations that form inputs to map the erosion risk. The results of erosion analysis revealed that 48.27?% of the area is under very high erosion risk. The Middle Himalayan watersheds were found to be under high erosion risk compared to the Greater Himalayan watersheds. Pohru and Doodhganga watersheds of the Middle Himalayas were found to be under very high erosion risk. These two watersheds were studied in detail from 1992 to 2001 for vegetation change and wetland loss. In Pohru watershed, significant change was found in the dense forest with 10?% decrease. Wular lake, an important wetland in the Pohru watershed, has shrunk by 2.7?km2 during the last decade. The vegetation change analysis of the Doodhganga watershed revealed that there has been 9.13?% decrease in the forest, 7?% increase in built up and the largest wetland in the Doodhganga, Hokarsar, has reduced by 1.98?km2 from 1992 to 2001. Field studies showed that anthropogenic activities and chemically deficit soil (Karewa) along Pir Panjal ranges are the main factors responsible for high land degradation in the area. The assessment of these geoindicators provided valuable information for identifying causes and consequences of the land degradation and thus outlining potential hazard areas and designing remedial measures. 相似文献
8.
Cosmic energy equation is an important equation for studying the gravitational galaxy clustering in the expanding universe.
We derive the distribution function for fluctuations in particle number by using the cosmic energy equation for extended structures
(galaxies with halos). From spatial distribution function, containing particle fluctuations, we derive the velocity distribution
function to understand the influence of particle fluctuations on the velocities of galaxies.With the help of cosmic energy
equation we try to find out the physical constraints for the application of quasi-equilibrium approximation. 相似文献
9.
Hossein Moayedi Mansour Mosallanezhad Ramli Nazir Sina Kazemian Bujang Kim Huat 《Geotechnical and Geological Engineering》2014,32(4):933-947
Peat is known as soft soil with low shear strength and high compressibility. Electrokinetic injection technique is being used by applying a direct electrical potential across the soil specimens to improve physicochemical characteristics of the peat. Such applications cause electrochemical effects on the soil, leading to changes in the soil’s chemical, physical, and mechanical properties. This paper presents the results of the undrained shear strength, pH, water content across the electrokinetic box after injecting the cationic grouts. Four cationic grouts namely; calcium chloride, calcium oxide, Aluminum hydroxide, and sodium silicates were selected as grout. The microstructures of the stabilized peats were investigated by scanning electron microscopy and energy dispersive X-ray spectrometer analysis. The result showed that the cationic stabilizer injected by the electrokinetic technique could significantly increase the peat soil’s shear strength. Furthermore, the result showed that the effect of calcium oxide was the highest on the shear strength of peat due to its physico-chemical properties. The shear strength, pH and moisture content of peats across the electrokinetic box also altered depending on the used electrolytes and time. 相似文献
10.
Peat has been considered as an organics remnant that suffers decomposition process throughout times under overburden pressure. Composition of peats normally consists of organics materials which sometimes exceed 75% specifically from woods that grows in marshes and places in conditions where deficiencies of oxygen exist. Usually peat area related with swampy and normally a low shear strength region. High compressibility is significant and often related to problematic soil for construction purposes. In this article, extensive number of studies are reviewed to understand the behavior of the peat after being stabilized. New findings indicated that the peat contents differs from one location to another, thus inevitably gives different behavior. Many improvisation methods have been put forward such as chemical stabilization, cement stabilization, deep mixing and fiber reinforcement to name a few to enhance the strength properties of the peat. This is mainly for construction reliability purposes. However, the suitability of the ground improvement for peat thus depend on its fundamental properties and cost involve for any dedicated ground construction work. This paper review the properties of peat in Malaysia and reviewed recent development in the peaty soil stabilization in Malaysia. It is also compared the materials used for the peat stabilization and the expansive clay soils as the main two problematic soils. 相似文献