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排序方式: 共有185条查询结果,搜索用时 15 毫秒
41.
Baris Binici 《钢结构》2008,23(9):85-86
建筑物中柱和桥墩的修复设计要求对结构变形能力进行精确预测。本文提出分析模型近似计算经纤维增强聚合物修复的钢筋混凝土柱的潜在塑性关键区的延展性。提出能够代表纤维增强聚合物混凝土响应的双线性应力一应变模型,该模型在低压下混凝土响应降低,在高压下混凝土响应增强。对于承受轴力和弯矩的圆柱,模型采用近似形式的组合分析,根据无量纲柱参数和纤维增强聚合物提供的约束压力来计算经纤维增强聚合物修复的截面延展性。通过比较组合分析的模型估计结果和试验结果,验证纤维增强聚合物修复柱延展性模型的精确性。随后,建立了循环桥柱纤维增强聚合物简单非重复抗震修复设计程序。最后,对不同轴向荷载、含筋率、纤维增强聚合物数量进行典型桥柱参数研究,计算结果以无量纲形式给出,有助于工程师采用纤维增强聚合物进行提高柱延展性的抗震修复设计。 相似文献
42.
Ayotte JD Nolan BT Nuckols JR Cantor KP Robinson GR Baris D Hayes L Karagas M Bress W Silverman DT Lubin JH 《Environmental science & technology》2006,40(11):3578-3585
We developed a process-based model to predict the probability of arsenic exceeding 5 microg/L in drinking water wells in New England bedrock aquifers. The model is being used for exposure assessment in an epidemiologic study of bladder cancer. One important study hypothesis that may explain increased bladder cancer risk is elevated concentrations of inorganic arsenic in drinking water. In eastern New England, 20-30% of private wells exceed the arsenic drinking water standard of 10 micrograms per liter. Our predictive model significantly improves the understanding of factors associated with arsenic contamination in New England. Specific rock types, high arsenic concentrations in stream sediments, geochemical factors related to areas of Pleistocene marine inundation and proximity to intrusive granitic plutons, and hydrologic and landscape variables relating to groundwater residence time increase the probability of arsenic occurrence in groundwater. Previous studies suggest that arsenic in bedrock groundwater may be partly from past arsenical pesticide use. Variables representing historic agricultural inputs do not improve the model, indicating that this source does not significantly contribute to current arsenic concentrations. Due to the complexity of the fractured bedrock aquifers in the region, well depth and related variables also are not significant predictors. 相似文献
43.
Molecular communication is a promising nanoscale communication paradigm that enables nanomachines to exchange information by using molecules as communication carrier. Up to now, the molecular communication channel between a transmitter nanomachine (TN) and a receiver nanomachine (RN) has been modeled as either concentration channel or timing channel. However, these channel models necessitate exact time synchronization of the nanomachines and provide a relatively low communication bandwidth. In this paper, the Molecular ARray-based COmmunication (MARCO) scheme is proposed, in which the transmission order of different molecules is used to convey molecular information without any need for time synchronization. The MARCO channel model is first theoretically derived, and the intersymbol interference and error probabilities are obtained. Based on the error probability, achievable communication rates are analytically obtained. Numerical results and performance comparisons reveal that MARCO provides significantly higher communication rate, i.e., on the scale of 100 Kbps, than the previously proposed molecular communication models without any need for synchronization. More specifically, MARCO can provide more than 250 Kbps of molecular communication rate if intersymbol time and internode distance are set to 2 μs and 2 nm, respectively. 相似文献
44.
Basak Yazgan Kokuoz Karn Serivalsatit Baris Kokuoz Olt Geiculescu Exley McCormick John Ballato 《Journal of the American Ceramic Society》2009,92(10):2247-2253
Nanoparticles of erbium-doped yttria (Er:Y2 O3 ) are important precursors to transparent ceramics for high-power solid-state lasers systems. As structure influences properties and, subsequently, performance the purpose of this work is to compare the morphological and chemical nature of the nanoparticles synthesized using two common methods: solution precipitation and combustion synthesis. A thorough characterization of as-prepared and calcined powders was performed using Fourier transform infrared spectroscopy, X-ray diffraction, conventional and high-resolution transmission electron microscopy, and Brunauer–Emmet–Teller methods. Solution precipitation was found to lead to two different precursor compositions (yttrium carbonate or yttrium hydroxide) depending on the precipitating reagent whereas combustion synthesis yielded only phase-pure, cubic Er:Y2 O3 . The hydroxide precipitation and combustion synthesis methods exhibited agglomerated particles with low surface area after calcining the precursors at 900°C. The addition of a small amount of ammonium sulfate during combustion synthesis was found to reduce the level of agglomeration, resultant particle size, and degree of crystallinity of the calcined Er:Y2 O3 nanoparticles. The amount of carbon dioxide (CO2 ) and water (H2 O) on the surface of the Er:Y2 O3 powders is dependent on the powder surface area, however, increasing levels of gas absorption on the particle surfaces do not have a detrimental effect on the sinterability. The sintered density increases with increasing surface area and decreasing agglomeration. 相似文献
45.
对在不同浓度的盐胁迫条件下,叶面喷施液态腐植酸和土壤施用腐植酸类物质对小麦作物生长和矿物营养吸收的影响进行了研究。通过添加不同量的NaCl得到不同的盐浓度环境。腐植酸类物质在作物种植前一个月施用,液态腐植酸在种苗发芽后20d和35d喷施于小麦叶面。腐植酸类物质的施用量为0、1g/kg、2g/kg,液态腐植酸的浓度为0、0.1%、0.2%。盐度对小麦生长具有负面影响,它会降低小麦对除Na、Mn以外的矿物营养的吸收,影响小麦干重。通过在土壤施用腐植酸类物质可以增加小麦对N的吸收,叶面施用腐植酸可增加其对P、K、Mg、Na、Cu和Zn的吸收。研究结果显示:在土壤中施用腐植酸类物质,不同盐浓度与施用量之间存在较好的相关性,但叶面喷施时盐度和喷施量之间相关性并不明显。在盐胁迫环境的影响下,叶面喷施腐植酸的初始浓度和土壤中施用的腐植酸类物质的初施量都增加了作物对营养元素的吸收。 相似文献
46.
47.
Sumengen B Manjunath BS 《IEEE transactions on pattern analysis and machine intelligence》2006,28(4):509-521
In this paper, we introduce new types of variational segmentation cost functions and associated active contour methods that are based on pairwise similarities or dissimilarities of the pixels. As a solution to a minimization problem, we introduce a new curve evolution framework, the graph partitioning active contours (GPAC). Using global features, our curve evolution is able to produce results close to the ideal minimization of such cost functions. New and efficient implementation techniques are also introduced in this paper. Our experiments show that GPAC solution is effective on natural images and computationally efficient. Experiments on gray-scale, color, and texture images show promising segmentation results. 相似文献
48.
Baris Sergi Ipek Bulut Ying Xia Dr. Zoë A. E. Waller Yasemin Yildizhan Dr. Ceyda Acilan Dr. Rianne M. Lord 《ChemMedChem》2021,16(15):2402-2410
To understand the potential in vitro modes of action of bis(β-diketonato) oxovanadium(IV) complexes, nine compounds of varying functionality have been screened using a range of biological techniques. The antiproliferative activity against a range of cancerous and normal cell lines has been determined, and show these complexes are particularly sensitive against the lung carcinoma cell line, A549. Annexin V (apoptosis) and Caspase-3/7 assays were studied to confirm these complexes induce programmed cell death. While gel electrophoresis was used to determine DNA cleavage activity and production of reactive oxygen species (ROS), the Comet assay was used to determine induced genomic DNA damage. Additionally, Förster resonance energy transfer (FRET)-based DNA melting and fluorescent intercalation displacement assays have been used to determine the interaction of the complexes with double strand (DS) DNA and to establish preferential DNA base-pair binding (AT versus GC). 相似文献
49.
Muhammad Waseem Ahmad Monjur Mourshed Baris Yuce Yacine Rezgui 《Building Simulation》2016,9(4):359-398
Buildings are responsible for 40% of global energy use and contribute towards 30% of the total CO2 emissions. The drive to reduce energy use and associated greenhouse gas emissions from buildings has acted as a catalyst in the development of advanced computational methods for energy efficient design, management and control of buildings and systems. Heating, ventilation and air-conditioning (HVAC) systems are the major source of energy consumption in buildings and ideal candidates for substantial reductions in energy demand. Significant advances have been made in the past decades on the application of computational intelligence (CI) techniques for HVAC design, control, management, optimization, and fault detection and diagnosis. This article presents a comprehensive and critical review on the theory and applications of CI techniques for prediction, optimization, control and diagnosis of HVAC systems. The analysis of trends reveals that the minimisation of energy consumption was the key optimization objective in the reviewed research, closely followed by the optimization of thermal comfort, indoor air quality and occupant preferences. Hardcoded Matlab program was the most widely used simulation tool, followed by TRNSYS, EnergyPlus, DOE-2, HVACSim+ and ESP-r. Metaheuristic algorithms were the preferred CI method for solving HVAC related problems and in particular genetic algorithms were applied in most of the studies. Despite the low number of studies focussing on multi-agent systems (MAS), as compared to the other CI techniques, interest in the technique is increasing due to their ability of dividing and conquering an HVAC optimization problem with enhanced overall performance. The paper also identifies prospective future advancements and research directions. 相似文献
50.
In the present paper, the performance and emission characteristics of a conventional four cylinder spark ignition (SI) engine operated on hydrogen and gasoline are investigated experimentally. The compressed hydrogen at 20 MPa has been introduced to the engine adopted to operate on gaseous hydrogen by external mixing. Two regulators have been used to drop the pressure first to 300 kPa, then to atmospheric pressure. The variations of torque, power, brake thermal efficiency, brake mean effective pressure, exhaust gas temperature, and emissions of NOx, CO, CO2, HC, and O2 versus engine speed are compared for a carbureted SI engine operating on gasoline and hydrogen. Energy analysis also has studied for comparison purpose. The test results have been demonstrated that power loss occurs at low speed hydrogen operation whereas high speed characteristics compete well with gasoline operation. Fast burning characteristics of hydrogen have permitted high speed engine operation. Less heat loss has occurred for hydrogen than gasoline. NOx emission of hydrogen fuelled engine is about 10 times lower than gasoline fuelled engine. Finally, both first and second law efficiencies have improved with hydrogen fuelled engine compared to gasoline engine. It has been proved that hydrogen is a very good candidate as an engine fuel. The obtained data are also very useful for operational changes needed to optimize the hydrogen fueled SI engine design. 相似文献