24 research outputs found
Output-only Structural Health Monitoring of a Riveted Steel Railway Bridge utilizing Proper Orthogonal Decomposition, Artificial Neural Network, and Strain Measurements
No full textThis study presents a new scheme for autonomous health monitoring of railroad infrastructure using a continuous stream of structural health monitoring data. The study utilized measured strains from an optimized sensor set deployed on a double track, steel, railway, truss bridge located in central Nebraska. The most common failure mode for the superstructure of this structural system is the stringer-to-floor beam connection failure, which was the focus of this study. However, the proposed methodology could be used to assess the condition of a wide range of structural elements and details. The damage feature adopted in this framework was the variations of Proper Orthogonal Modes (POMs) of the measured structural response. To automatically detect the occurrence, location, and intensity of deficiencies from the POMs, Artificial Neural Networks (ANN) were adopted. POM variations, which are traditionally input (load) dependent, were ultimately utilized as damage indicators. To alleviate the variability of POMs due to non-stationarity of the train loads, a preset windowing of measured output was completed in conjunction with automated peak-picking. Furthermore, input variability necessitated implementing ANNs to help decouple POM changes due to load variations from those caused by deficiencies, changes that would render the proposed framework input independent; a significant advancement. Damage “scenarios” were artificially introduced into select output (strain) datasets recorded while monitoring train passes across the selected bridge. This information, in turn, was used to train ANNs using MATLAB’s Neural Net Toolbox. Trained ANNs were tested against monitored loading events and artificial damage scenarios. Applicability of the proposed, output-only framework was investigated via studies of the bridge under operational conditions. To account for the effects of potential deficiencies at the stringer-to-floor beam connections, measured signal amplitudes were artificially decreased at select locations. Finally, to validate the applicability of the proposed method using low-cost measurement devices, the measured signals were corrupted by high levels of white, Gaussian noises featuring spatial correlations. It was concluded that the proposed framework could successfully identify 20 damage indices, which were artificially imposed on measured signals under operational conditions
Full Scale Bridge Damage Detection Using Sparse Sensor Networks, Principal Component Analysis, and Novelty Detection
No full textOver the decades, visual inspection has been adopted as a means to monitor infrastructure health. While visual inspection provides insights on a bridge’s condition, it has been generally agreed that it is insufficient and inefficient. This has called for the creation of autonomous, robust, continuous, and quantitative structural health monitoring (SHM) systems to detect potential deficiencies in an early stage, and monitor future condition. Various methods have been explored that associate changes in condition with changes in the structure’s vibration characteristics. These methods have been mostly tested on laboratory specimens experiencing simulated damage. There is need for extending validation of these SHM methods on in-situ structures experiencing real damage under operational and environmental conditions. This paper summarizes a full-scale experiment exploring bridge damage detection effectiveness under variable traffic loads. Three different types of damage were introduced into a full-scale, bridge deck mock-up. These included crash-induced bridge barrier damage, controlled barrier damage, and damage to the deck slab. At the end of each introduced damage case, the bridge’s response to the multiple passages was recorded using specific vehicles specifications. Data was extracted and analyzed to identify damage using principal component analysis (PCA) and independent component analysis (ICA) as damage-sensitive features. The extracted damage features were thereafter used as input for unsupervised learning (novelty detection). One interesting observation was how PCA revealed possibly significant damage after a crash, which under visual inspection appeared to be minor. Novelty detection using PCA as its damage feature was shown to provide robust damage detection irrespective of load, speed variation, and signal noise levels
ANATOMICAL, PHYSICOCHEMICAL, PHYTOCHEMICAL, ANTIOXIDANT AND ANTIMICROBIAL INVESTIGATIONS OF TAGETES MINUTA L. AERIAL PARTS
No full textيستخدم نبات الرنجس (.Tagetesminuta L) الذي ينمو في مناطق مختلفة من اليمن لعلاج أمراض الجلد ولم تتم دراسته بشكل كافٍ، لذا فإن الهدف من البحث الحالي هو تقييم خصائصه التشريحية، الفيزيكيميائية النباتية، مضادات الأكسدة ومضادات الميكروبات لأجزائه العلوية باستخدام طرق قياسية مقبولة. تم تحديد المعايير المجهرية والفيزيكيميائية. تم إجراء التحليل الكيميائي النباتي على مستخلصات البترول الإيثرية والميثانول بنسبة 80% والماء، حيث وجد فيهما الكربوهيدرات والفينولات والفلافونويدات والعفص والتربينات والستيرولات. تم تحديد أن المحتوى الفينولي الكلي 205.14 و 91.2 ملغ / غرام مكافئ حمض الجاليك ووجد أن المحتوى الفلافونويدي الكلي 106.46 و 18.15 ملغ / غرام مكافئ كيورسيتين للمستخلص الجاف للميثانول بنسبة 80 % والمستخلصات المائية على التوالي. تم تحديد النشاط المضاد للأكسدة باستخدام طريقة DPPH في المختبر. وجد أن قيم IC50 للكويرسيتين، إيثير البترول، 80 % مستخلصات الميثانول والمائية كانت 13.54، 151.04، 21.36 و 47.31 ميكروجرام/مل على التوالي، لذا أظهر المستخلص الميثانولي 80% نشاطًا مضادًا للأكسدة مرتفعًا جدًا مقارنة بالكويرسيتين. تم اختبار النشاط المضاد للميكروبات باستخدام طريقة الانتشار البئري، أظهرت جميع التركيزات المستخدمة للمستخلص الميثانولي 80% نشاطًا مضادًا للبكتيريا مرتفعًا جدًا ضد Pseudomonas aeruginosa , Staphylococcus aureus و Proteus vulgaris، بينما أظهرت منطقة تثبيط كبيرة ضد Klebsilla pneumoniae, و Candid albican. أظهرت جميع التركيزات المستخدمة في المستخلص المائي ظهور منطقة تثبيط ضد Pseudomonas aeruginosa وStaphylococcus aureus، في حين لم يظهر أي تأثير ضد Klebsiella pneumoniae وproteus vulgaris وCandid albicans. تشير النتائج المذكورة أعلاه إلى أن الأجزاء الهوائية من نبات الرنجس (Tagetes minuta) يمكن أن تكون مضادة للأكسدة ومضادة للبكتيريا بشكل طبيعي، ويمكن استخدامها لمزيد من الدراسات على النبات.Tagetes minuta L., which grows in different regions of Yemen, is used to treat skin diseases and has not been adequately studied, so the aim of the present research is to evaluate its anatomical, physicochemical, phytochemical, antioxidant and antimicrobial properties of its aerial parts, using accepted standard methods. The microscopic and physicochemical parameters were determined. Phytochemical analysis was performed on petroleum ether, 80% methanol and water extracts, and carbohydrates, phenols, flavonoids, tannins, terpenes and sterols were identified. The total phenolic content was found to be 205.14 and 91.2 mg/g gallic acid equivalent and the total flavonoid content was found to be 106.46 and 18.15 mg/g quercetin equivalent of the dry extract of 80% methanol and aqueous extracts, respectively. The antioxidant activity was determined by using in vitro DPPH method. The IC50 values of quercetin, petroleum ether, 80% methanolic and water extracts were found to be 13.54, 151.04, 21.36 and 47.31 µg/ml respectively, so the 80% methanolic extract showed very high antioxidant activity compared to quercetin. The antimicrobial activity was tested by using well diffusion method, all concentrations used for the 80% methanolic extract showed very high antibacterial activity against Pseudomonas aeruginosa, Staphylococcus aureus and Proteus vulgaris, while they showed significant of inhibition zone against Klebsilla pneumoniae, and Candid albicans. All concentrations used for the aqueous extract showed appearance of inhibition zone against Pseudomonas aeruginosa, Staphylococcus aureus, while no effect was shown against the Klebsiella pneumoniae, proteus vulgaris and Candid albicans. The above results indicate that the aerial parts of Tagetes minuta could be a useful natural antioxidant and antibacterial agent, and may be used for further study on the plant
Modeling Dense Particle Flow in Multistage and Obstructed Flow Receivers Using High Fidelity Simulations
No full textParticles are a leading contender for next-generation, concentrating solar power technologies, and the design of the particle receiver is critical to minimize the levelized cost of electricity. Falling particle receivers (FPRs) are a viable receiver concept, but many new designs feature complex particle obstructions that include dense discrete phase flows. This creates additional challenges for modeling as particle-to-particle interactions (i.e., collisions) and particle drag become more complex. To improve upon existing modeling strategies, a CFD-DEM simulation capability was created by coupling two independent codes: Sierra/Fuego and LAMMPS. A suitable receiver model was then defined using a traditional continuum-based model for the air and a granular model for the particle curtain. A sensitivity study was executed using this model to determine the relevance of different granular model inputs on important quantities of interest in obstructed flow FPRs: the particle velocity and curtain opacity. The study showed that the granular model inputs had little effect on the particle velocity magnitude and curtain opacity after an obstruction
Arab attributions for the attack on America: The case of Lebanese subelites
No full textThere are at least two major ways of understanding the attributions that Arab young people used to explain the September 11 th attack on the World Trade Center: (a) in terms of a so-called clash of civilizations or an inherent conflict between Muslim and Western values or (b) in terms of an antidominance reaction to perceived American and Israeli oppression of Arabs in general and Palestinians in particular. The authors compare the relative validities of these two framings using a sample of Lebanese students from the American University of Beirut. The results from analysis of variance, regression, and structural equation modeling showed strong, clear, and consistent support for the antidominance attributions and essentially no support for the clash-of-civilizations attributions.Chomsky N., 2001, 9 11; DEYOUNG K, 2002, WASH POST 0911, pA13; DUMONT L, 1980, HOMO HEIARCHICUS CAS; HENRY PJ, 2002, UNPUB SOCIAL DOMINAN; Herting J. R., 1985, CAUSAL MODELS SOCIAL, P263; HUNTINGTON SP, 1993, FOREIGN AFF, V72, P22, DOI 10.2307-20045621; HUSSIEN AD, 2001, J MUSLIM MINORITY AF, V21, P25; JORESKOG KG, 1993, LISREL 8 USERS MANUA; Lewis Bernard, 1990, ATLANTIC MONTHLY, V266, P47; MARGALIT A, 2002, NEW YORK REV BOOKS; PRATTO F, 1994, J PERS SOC PSYCHOL, V67, P741, DOI 10.1037-0022-3514.67.4.741; RAGEH R, 2002, ASS PRESS 1113; SAID EW, 2000, COMMENCEMENT SPEECH; Scott James C., 1990, DOMINATION ARTS RESI; Sidanius J., 2001, SOCIAL DOMINANCE INT; 2002, BBC NEWS 033015101
Study of the optimum discrete structure configuration in obstructed flow particle heating receivers
No full textVulnerability of Thermal Energy Storage Lining Material to Erosion Induced by Particulate Flow in Concentrated Solar Power Tower Systems
No full textResearchers from all around the world have been paying close attention to particle-based power tower technologies. On the King Saud University campus in the Kingdom of Saudi Arabia, the first integrated gas turbine–solar particle heating hybrid system has been realized. In this study, two different types of experiments were carried out to examine how susceptible prospective liner materials for thermal energy storage tanks were to erosion. An accelerated direct-impact test with high particulate temperature was the first experiment. A low-velocity mass-flow test was the second experiment, and it closely mimicked the flow circumstances in a real thermal energy storage tank. The tests were conducted on bare insulating fire bricks (IFBs) and IFBs coated with Tuffcrete 47, Matrigun 25 ACX, and Tuffcrete 60 M. The latter three lining materials were high-temperature-resilient materials made by Allied Mineral Products Inc. (AMP) (Columbus, OH, USA). The results showed that although IFBs coated with AMP materials worked well in this test, the accelerated direct-impact test significantly reduced the bulk of the bare IFB. As a result, lining substances must be added to the surface of IFBs to increase their strength and protection because they cannot be used in situations where particles directly impact their surface. On the other hand, the findings of the 60 h cold-particle mass-flow test revealed that the IFBs were not significantly eroded. Additionally, it was discovered that the degree of erosion on the samples of bare IFB was unaffected by the height of the particle bed
Integrated CSP-PV hybrid solar power plant for two cities in Saudi Arabia
No full textSolar energy has the potential to provide most of the electricity needed by mankind sustainably into the indefinite future. Concentrated Solar Power (CSP) has conventionally been considered more applicable than photovoltaic (PV) for baseload power since thermal storage is far cheaper than battery storage. However, the solar fields for CSP are relatively expensive. On the other hand, PV plants without storage deliver electric power at a much lower cost than CSP plants of comparable capacity without storage. Integrating both technologies is an attractive approach towards solar baseload power with affordable levelized cost of energy (LCOE). This study, which investigates the two cities of Saudi Arabia, consists of simulation and optimization in three main parts: The first part is a simulation of the CSP parabolic trough (CSP-PT) standalone plant and integrating the output parameters with an economic model to calculate the LCOE. The second part is the simulation of combined CSP-PT with PV, with a design strategy of utilizing all PV power for daytime use, and supplementing the PV output with thermal power as needed to maintain baseload operation in the daytime. The third part is the simulation of combined CSP-PT with a design strategy of providing all or nearly all daytime power with PV, with the utilization of excess energy from PV to supply heat to the thermal storage system. The results show that for a target capacity factor of 79%, the CSP plant alone requires a solar multiple of 6 in Riyadh and 3.5 in Tabuk. For both locations, the introduction of the hybrid concept substantially reduced the solar multiple. In Riyadh, the solar multiple ranged from 2.9 to 3 with the PV portion of the plant having a nameplate capacity equal to that of the CSP portion and 1.95 for a case with the PV nameplate capacity 60% greater than the CSP portion. For these same cases in Tabuk, the solar multiples were 1.78–1.85 and 1.6 simultaneously. Generally, hybridization is of greater benefit in Riyadh than in Tabuk owing to the greater fraction of solar resource in the form of diffuse sunlight which can be collected by the PV plant but not by the CSP plant. The LCOE was reduced by hybridization in both locations, but again the benefit was greater for Riyadh. Clearly, from a technological perspective, it is important to study the hybridization for an individual city based on its weather data as the incorporation of PV into CSP plant designs should be considered for all locations in order to reduce the cost to provide baseload power from solar energy, and the application of the hybridization concept can extend the applicability of CSP technology to regions with less direct sunlight than would be economically feasible with CSP alone
