Letteratura scientifica selezionata sul tema "Leaf specimens"
Cita una fonte nei formati APA, MLA, Chicago, Harvard e in molti altri stili
Consulta la lista di attuali articoli, libri, tesi, atti di convegni e altre fonti scientifiche attinenti al tema "Leaf specimens".
Accanto a ogni fonte nell'elenco di riferimenti c'è un pulsante "Aggiungi alla bibliografia". Premilo e genereremo automaticamente la citazione bibliografica dell'opera scelta nello stile citazionale di cui hai bisogno: APA, MLA, Harvard, Chicago, Vancouver ecc.
Puoi anche scaricare il testo completo della pubblicazione scientifica nel formato .pdf e leggere online l'abstract (il sommario) dell'opera se è presente nei metadati.
Articoli di riviste sul tema "Leaf specimens"
1
Volkova, Polina A., Sof'ya A. Kasatskaya, Anna A. Boiko e Alexey B. Shipunov. "Stability of leaf form and size during specimen preparation of herbarium specimens". Feddes Repertorium 121, n. 5-6 (dicembre 2010): 219–25. http://dx.doi.org/10.1002/fedr.201000021.
Testo completo
2
Beauvais, Marie-Pierre, Stéphanie Pellerin, Jean Dubé e Claude Lavoie. "Herbarium specimens as tools to assess the impact of large herbivores on plant species". Botany 95, n. 2 (febbraio 2017): 153–62. http://dx.doi.org/10.1139/cjb-2016-0206.
Testo completoAbstract (sommario):
Herbarium specimens can be used to reconstruct spatiotemporal changes in plant morphology caused by environmental pressures. The reliability of herbarium-derived data requires evaluation, because specimen collection is subject to biases. We used herbarium and field data to investigate the impact of large herbivore browsing on the size of a forb. White trillium (Trillium grandiflorum (Michaux) Salisbury) was studied because the impacts of white-tailed deer (Odocoileus virginianus Zimmermann) browsing on this species are well-known. A total of 692 herbarium specimens collected in Quebec (Canada) were used to evaluate leaf area. Leaf area values of herbarium specimens were compared with those of modern (2013, 2014) specimens collected in sites either with >8 deer per square kilometre or without deer. Flowering individuals in modern sites with deer had a significantly lower leaf area than herbarium specimens and modern specimens collected in sites without deer. The distribution of white trillium individuals in deer sites was also skewed towards plants with a smaller leaf area. Herbarium specimens may offer unique and inexpensive data, compared with methods traditionally used to assess the impacts of herbivores on plants, such as exclosures or clipping experiments. Unfortunately, this rich data source is seriously jeopardized by the downtrend in specimen collecting.
3
Ahlstrand, Gilbert G., e Richard J. Zeyen. "Bulk Specimen Preparation For X-Ray Microanalysis of Plant Cells". Proceedings, annual meeting, Electron Microscopy Society of America 48, n. 2 (12 agosto 1990): 334–35. http://dx.doi.org/10.1017/s0424820100135277.
Testo completoAbstract (sommario):
Numerous plant pathological investigations have been published where pathologists determined elemental differences between diseased and healthy plant tissue using unfractured bulk specimens and energy dispersive x-ray microanalysis (EDX). In these studies effects of specimen preparation procedures were largely ignored (1). Our objective was to compare bulk specimen preparation procedures using healthy leaf epidermal (surface) cells of barley, Hordeum vulgare, (Fig. 1) to determine advantages and disadvantages of each procedure for reference to future pathological work using EDX. Three preparation procedures were compared: 1) Frozen-hydrated (FH) specimens to maintain soluble and insoluble elements in situ; 2) Freeze-dried (FD) specimens to maintain total soluble and insoluble elements and allow deeper beam penetration than does FH, and; 3) Formalin/acetic acid/ethanol (FAA) fixed specimens, dehydrated in ethanol, and critical point dried (CD) using CO2, for determination of elemental loss in liquid fixatives (2,3).Aluminum specimen stubs were colloidal graphite coated (leaf segments attached to graphite areas) leaving clean Al margins for calibration.
4
Corney, David P. A., Jonathan Y. Clark, H. Lilian Tang e Paul Wilkin. "Automatic extraction of leaf characters from herbarium specimens". TAXON 61, n. 1 (febbraio 2012): 231–44. http://dx.doi.org/10.1002/tax.611016.
Testo completo
5
Kim, Hyeree, XiaoXuan Du, Sungwook Kim, Pilun Kim, Ruchire Eranga Wijesinghe, Byoung-Ju Yun, Kyung-Min Kim, Mansik Jeon e Jeehyun Kim. "Non-Invasive Morphological Characterization of Rice Leaf Bulliform and Aerenchyma Cellular Regions Using Low Coherence Interferometry". Applied Sciences 9, n. 10 (22 maggio 2019): 2104. http://dx.doi.org/10.3390/app9102104.
Testo completoAbstract (sommario):
Non-invasive investigation of rice leaf specimens to characterize the morphological formation and particular structural information that is beneficial for agricultural perspective was demonstrated using a low coherence interferometric method called swept source optical coherence tomography (SS-OCT). The acquired results non-invasively revealed morphological properties of rice leaf, such as bulliform cells; aerenchyma, parenchyma, and collenchyma layer; and vascular bundle. Beside aforementioned morphologic characteristics, several leaf characteristics associated with cytological mechanisms of leaf rolling (leaf inclination) were examined for the pre-identification of inevitable necrosis and atrophy of leaf tissues by evaluating acute angle information, such as angular characteristics of the external bi-directional angles between the lower epidermis layer and lower mid-vein, and internal angle of lower mid-vein. To further assist the pre-identification, acquired cross-sections were employed to enumerate the small veins of each leaf specimen. Since mutants enlarge leaf angles due to increased cell division in the adaxial epidermis, healthy and abnormal leaf specimens were morphologically and quantitatively compared. Therefore, the results of the method can be used in agriculture, and SS-OCT shows potential as a rigorous investigation method for selecting mutant infected rice leaf specimens rapidly and non-destructively compared to destructive and time consuming gold-standard methods with a lack of precision.
6
Kirker, Grant T., Amy Bishell, Jed Cappellazzi, Jonathan Palmer, Nathan Bechle, Patricia Lebow e Stan Lebow. "Role of Leaf Litter in Above-Ground Wood Decay". Microorganisms 8, n. 5 (9 maggio 2020): 696. http://dx.doi.org/10.3390/microorganisms8050696.
Testo completoAbstract (sommario):
The effects of leaf litter on moisture content and fungal decay development in above-ground wood specimens were assessed. Untreated southern pine specimens were exposed with or without leaf litter contact. Two types of leaf litter were evaluated; aged (decomposed) and young (early stages of decomposition). The moisture content of specimens was monitored, and specimens were periodically removed for visual evaluation of decay development. In addition, amplicon-based sequencing analysis of specimens and associated leaf litter was conducted at two time points. Contact with either type of leaf litter resulted in consistently higher moisture contents than those not in contact with leaf litter. Visually, evident decay developed most rapidly in specimens in contact with the aged leaf litter. Analysis of amplicon-based sequencing revealed that leaf litter contributes a significant amount of the available wood decay fungal community with similar communities found in the litter exposed wood and litter itself, but dissimilar community profiles from unexposed wood. Dominant species and guild composition shifted over time, beginning initially with more leaf saprophytes (ascomycetes) and over time shifting to more wood rotting fungi (basidiomycetes). These results highlight the importance of the contributions of leaf litter to fungal colonization and subsequent decay hazard for above-ground wood.
7
Petrulaitis, Lukas, e Zigmantas Gudžinskas. "What are We Conserving? A Case Study of Mentha longifolia and Allied Species from Lithuania". Botanica 24, n. 1 (1 giugno 2018): 3–14. http://dx.doi.org/10.2478/botlit-2018-0001.
Testo completoAbstract (sommario):
AbstractAssessment of the conservation status of a species, first, should be based on its clearly defined taxonomic identity. Insufficient knowledge of certain taxonomic groups may lead to misidentifications, misinterpretations and become an obstacle for conservation. Mentha longifolia, listed as a protected plant species of Lithuania since 1981, belongs to a taxonomically complex group of species. The aim of this research was to examine available herbarium specimens of M. longifolia and verify their identification, specify distribution of this species in Lithuania and evaluate its conservation status in the country. The study was based on the analysis of herbarium specimens and information provided in references and databases. We studied a total of 93 specimens initially identified as M. longifolia. Morphological features of 30 leaves (leaf length, leaf width, petiole length, distance from leaf base to the widest place, length of leaf tooth) of both M. longifolia and M. ×villosa were measured on herbarium specimens. After the revision of herbarium specimens, we revealed that 37.6% of specimens initially identified as M. longifolia belong to other species (mostly to M. ×villosa) and 29.0% of specimens cannot be identified precisely because of the early stage of development. Only 33.4% of M. longifolia specimens were identified precisely. Thus, M. longifolia, previously supposed as quite widespread in Lithuania, after the revision appeared to be restricted mainly to the southern and south-eastern parts of the country. Applying the IUCN criteria, M. longifolia was evaluated as data deficient (DD) species. Analysis of leaf morphological traits revealed that M. longifolia and M. ×villosa can be differentiated by the length and the width of leaf blade, the distance from leaf base to the widest part of leaf and by the ratio between the length and the width of middle cauline leaves. This study revealed that taxonomic revision of the genus Mentha in Lithuania is required. Distribution of species, ecology and state of populations, impact of alien species on native congeners should be estimated in the future.
8
Dacuan, Cecielle N., Virgilio Y. Abellana e Hana Astrid R. Canseco. "Assessment and Evaluation of Blended Cement Using Bamboo Leaf Ash BLASH Against Corrosion". Civil Engineering Journal 7, n. 6 (1 giugno 2021): 1015–35. http://dx.doi.org/10.28991/cej-2021-03091707.
Testo completoAbstract (sommario):
Concrete provides a high degree of protection against corrosion of embedded steel reinforcement. Owing to the harsh environmental conditions and the presence of aggressive elements from the marine environment, deteriorating corrosion affects the durability of reinforced concrete structures. This study evaluated the effectiveness of bamboo leaf ash BLASH as a supplementary cementing material or admixture with Portland cement to improve the durability of reinforced concrete structures. Specimens of 0, 10, 15, and 20% BLASH mixtures were prepared using 16, 20, and 25 mm steel reinforcements. A total of 100 cylindrical specimens were cast and used in this study. The specimens were accelerated by corrosion using impressed current techniques and a galvanostatic method in a simulated environment. The results show that specimens with a BLASH content of 10% exhibited superior performance and exhibited longer corrosion initiation and propagation times. It has a higher resistance to acid penetration and lower corrosion rates. The crack parameters of the specimen with BLASH admixtures, such as the crack width and crack frequency, were negligible. The use of BLASH as an admixture strengthens its durability and improves its residual strength and serviceability. Doi: 10.28991/cej-2021-03091707 Full Text: PDF
9
Koponen, T. "Taxonomic Results of the BRYOTROP Expedition to Zaire and Rwanda 21. Mniaceae". Bryophyte Diversity and Evolution 8, n. 1 (31 dicembre 1993): 189. http://dx.doi.org/10.11646/bde.8.1.22.
Testo completoAbstract (sommario):
The specimen represents a rather typical African form of this taxon. The marginal teeth of the leaf are small and the leaf cells near isodiametric, but on the basis of the clearly differentiated juxtacostal cells, the specimen belongs to var. rhynchophyrum. Two other tropical African species are Plagiomnium cuspidatum (Hedw.) T. Kop. and P. undulatum (Hedw.) T. Kop. which differ by having an acute or cuspidate leaf apex, which in P. rhynchophorum tends to be emarginate and apiculate, and having sharper and larger projecting marginal teeth on their leaves. The distribution of P. rhynchophyrum is mapped and African specimens listed in Koponen (1981).
10
Kozlov, Mikhail V., Irina V. Sokolova, Vitali Zverev e Elena L. Zvereva. "Changes in plant collection practices from the 16th to 21st centuries: implications for the use of herbarium specimens in global change research". Annals of Botany 127, n. 7 (9 febbraio 2021): 865–73. http://dx.doi.org/10.1093/aob/mcab016.
Testo completoAbstract (sommario):
Abstract Background and Aims Herbaria were recently advertised as reliable sources of information regarding historical changes in plant traits and biotic interactions. To justify the use of herbaria in global change research, we asked whether the characteristics of herbarium specimens have changed during the past centuries and whether these changes were due to shifts in plant collection practices. Methods We measured nine characteristics from 515 herbarium specimens of common European trees and large shrubs collected from 1558 to 2016. We asked botanists to rank these specimens by their scientific quality, and asked artists to rank these specimens by their beauty. Key Results Eight of 11 assessed characteristics of herbarium specimens changed significantly during the study period. The average number of leaves in plant specimens increased 3-fold, whereas the quality of specimen preparation decreased. Leaf size negatively correlated with leaf number in specimens in both among-species and within-species analyses. The proportion of herbarium sheets containing plant reproductive structures peaked in the 1850s. The scientific value of herbarium specimens increased until the 1700s, but then did not change, whereas their aesthetic value showed no systematic trends. Conclusions Our findings strongly support the hypothesis that many characteristics of herbarium specimens have changed systematically and substantially from the 16th to 21st centuries due to changes in plant collection and preservation practices. These changes may both create patterns which could be erroneously attributed to environmental changes and obscure historical trends in plant traits. The utmost care ought to be taken to guard against the possibility of misinterpretation of data obtained from herbarium specimens. We recommend that directional changes in characters of herbarium specimens which occurred during the past 150‒200 years, primarily in specimen size and in the presence of reproductive structures, are accounted for when searching for the effects of past environmental changes on plant traits.
Tesi sul tema "Leaf specimens"
1
Tipping, Claudia, of Western Sydney Hawkesbury University, of Science Technology and Agriculture Faculty e School of Horticulture. "Morphological and structural investigations into C3 C4 and C3/C4 members of the genus Panicum grown under elevated CO2 concentrations". THESIS_FSTA_HOR_Tipping_C.xml, 1996. http://handle.uws.edu.au:8081/1959.7/329.
Testo completoAbstract (sommario):
Three perennial tropical Panicum species were grown under ambient and elevated (900 ppm) carbon dioxide concentrations in especially designed microclimate chambers. The study aimed to investigate the influence of high carbon dioxide concentrations on morphology/anatomy with physiological change among three closely related species possessing distinctly different photosynthetic pathways. The anatomy of the leaf was investigated using light microscopy (LM), transmission electron microscopy (TEM), and graphics image analysis. A suitable schedule for fixation, dehydration and embedding of leaf specimens for both forms of microscopy was developed. The anatomy of the species investigated did not change qualitatively, but there were detectable changes in leaf thickness and tissue proportions of the epidermis, mesophyll and thickened tissues (sclerenchyma, bundle sheath, vascular elements) that differed with species. This study is also relevant to the investigation of the evolution of C4, although species, and the progression involved in plants with characteristics intermediate between those of C3 and C4 species. These intermediate species have been mainly characterized by CO2 exchange and biochemical analysis, but they also display anatomical characteristics in between those of C3 and C4 plants. The evolutionary progression of the C3 to C4 species remains unsolved, although current studies indicate that the evolutionary step was from the C3 plant to the C4. Thus the intermediate C3/C4 plants may not be intermediate in an evolutionary sense and they could be seen as a simple hybridization between a C3 plant and C4 plant. In most of the parameters measured the C3/C4 P. decipiens resembled either the C3 P. tricanthum or the C4 P. antidotale. It may therefore be likened to a physiological chimera rather than to a true intermediate formDoctor of Philosophy (PhD)
2
Thambi, Joel Luther [Verfasser], Klaus-Dieter [Akademischer Betreuer] Lang, Klaus-Dieter [Gutachter] Lang, Ulrich [Gutachter] Tetzlaff e Bernhard [Gutachter] Wunderle. "Reliability assessment of lead- free solder joint, based on high cycle fatigue & creep studies on bulk specimen / Joel Luther Thambi ; Gutachter: Klaus-Dieter Lang, Ulrich Tetzlaff, Bernhard Wunderle ; Betreuer: Klaus-Dieter Lang". Berlin : Technische Universität Berlin, 2018. http://d-nb.info/1162540451/34.
Testo completo
3
Tipping, Claudia. "Morphological and structural investigations into C3 C4 and C3/C4 members of the genus Panicum grown under elevated CO2 concentrations". Thesis, 1996. http://handle.uws.edu.au:8081/1959.7/329.
Testo completoAbstract (sommario):
Three perennial tropical Panicum species were grown under ambient and elevated (900 ppm) carbon dioxide concentrations in especially designed microclimate chambers. The study aimed to investigate the influence of high carbon dioxide concentrations on morphology/anatomy with physiological change among three closely related species possessing distinctly different photosynthetic pathways. The anatomy of the leaf was investigated using light microscopy (LM), transmission electron microscopy (TEM), and graphics image analysis. A suitable schedule for fixation, dehydration and embedding of leaf specimens for both forms of microscopy was developed. The anatomy of the species investigated did not change qualitatively, but there were detectable changes in leaf thickness and tissue proportions of the epidermis, mesophyll and thickened tissues (sclerenchyma, bundle sheath, vascular elements) that differed with species. This study is also relevant to the investigation of the evolution of C4, although species, and the progression involved in plants with characteristics intermediate between those of C3 and C4 species. These intermediate species have been mainly characterized by CO2 exchange and biochemical analysis, but they also display anatomical characteristics in between those of C3 and C4 plants. The evolutionary progression of the C3 to C4 species remains unsolved, although current studies indicate that the evolutionary step was from the C3 plant to the C4. Thus the intermediate C3/C4 plants may not be intermediate in an evolutionary sense and they could be seen as a simple hybridization between a C3 plant and C4 plant. In most of the parameters measured the C3/C4 P. decipiens resembled either the C3 P. tricanthum or the C4 P. antidotale. It may therefore be likened to a physiological chimera rather than to a true intermediate form
4
HUANG, WEN-CHIN, e 黃文錦. "Facilitating Surgical Pathology Specimens Management Using Smart Information Technology: Applying Lean Principles". Thesis, 2018. http://ndltd.ncl.edu.tw/handle/kt4794.
Testo completoAbstract (sommario):
碩士嘉南藥理大學
醫務管理系
106
The collection and inspection of surgical pathology specimens is a key medical task in the operating room (OR). Such specimens provide physicians with a referential basis for diagnosis and treatment. The collection of surgical pathology specimens is an invasive procedure, during which patients are at risk of bleeding, infection, and even death. The integrity of surgical pathology specimen inspection is crucial to patients’ safety, and any missing links may affect their diagnosis and treatment. Furthermore, reexamination of missing specimens puts patients at greater risks related to invasive examination. The incomplete inspection of pathology specimens increases human resource usage. Thus, medical care requires the introduction of stricter norms; establishment and practice of correct collection, storage, and transportation of surgical pathology specimens; elimination of mistakes in the process; reduction of specimen rejection rates; and reduction of treatment risks. Current OR processes are characterized by multiple risks, a high level of wastage, and ineffective actions. Therefore, a proven method must be used to address existing problems. It is thus necessary for lean thinking—normally used in the manufacturing industry—to be implemented in medical care to address methods that are risky and cause process waste. Accordingly, this study explored the use of lean healthcare in surgical pathology specimen inspection implemented through smart technologies. The research objective was the use of lean healthcare by a medical center for surgical pathology specimen inspection. In-depth interviews, field observations, and relevant secondary data collection methods were used to explore informatization and the application of surgical pathology specimen inspection from the perspective of lean healthcare, as well as benefits and obstacles in systematic development. Data were analyzed and discussed using the content analysis method. The data analysis results can be summarized according to five lean principles: 1.Specify value: The value of treatment activities related to surgical pathology specimens is patient safety, which must be ensured and protected in the process of relevant inspection. The correct actions and timing can reduce delay- and mistake-related risks. 2.Identify the value stream: The confirmation of the value stream, including the informatization of the surgical pathology specimen inspection process, can contribute to cooperation within surgical teams and reduce complications related to traditional manual processes, paper waste, and other waste and errors. Information management tasks include the informatization of all operations related to list compilation, pathology specimen collection, and inspection completion. On-the-job education and systematic testing can be provided to ensure the effective collection, delivery, and management of information in the overall process. This can reduce process-related waste and increase the safety of operational processes because of an absence of man-made mistakes, thereby transforming the current unfavorable situation into a more ideal value stream. 3.Flow: Three core steps exist in flow establishment. The first is to perform an overall examination of the design of surgical pathology specimen inspection from beginning to completion in order to determine problems influencing the flow. The second step is to solve current issues and conduct on-the-job education regarding the informatization of the inspection process. A quality management center performs problem analyses, proposes improvement methods and problems occurring in the intervention of information seeds, and determines specimens for 30-minute laboratory registration and inspection. The safety protection mechanism used in specimen inspection includes a careful examination of inspection operations, which transforms the service line into a continuous flow. The final step involves rethinking specific work methods and tools to exclude repetitive and canceled processes. Thus, necessary technologies, special pathology-related facilities, and operational process norms can be established according to relevant informatization needs to avoid process waste. 4.Custom pull: The matching processes to patient needs include the coordination of patients’ pathological reports from various departments and adjustment of the specimen stream. Processing of surgical pathology accounting must be adjusted according to emergency outpatient and inpatient needs to ensure the integrity of the specimen inspection accounting procedures. 5.Continuous improvement: Problems related to the informatization of pathology specimen inspection must be addressed and solved by individual units through continuous monitoring of surgical pathology specimen quality. The practical application of lean principles in this study effectively reduced process-related waste. Smart technologies were effectively used to monitor patient safety. The use of lean thinking was explored to improve the quality of surgical pathology specimens without increasing the use of human resources as well as to avoid process waste. The results can provide a reference for organizations currently or prospectively engaged in developing lean healthcare.
5
Han, Ching Ju, e 韓晴如. "A Research of Improving Correctness on the Specimen Delivery in Laboratory Testing by Using Lean Thinking Methodology". Thesis, 2009. http://ndltd.ncl.edu.tw/handle/73242251561332763345.
Testo completoAbstract (sommario):
碩士長庚大學
資訊管理學研究所
97
Laboratory medicine is a clinic advisory service that is based on scientific empirical evidence. It includes providing various clinical tests which are used by physicians to determine the most appropriate treatments. However, the current process for laboratory testing is very complex, involving many procedures -- including request for testing, sample collection, sample transportation, sample analysis, and return results to the physicians. If any mistake exists in any of these procedures, the final test result will be affected, which in turn may cause the physician to make erroneous diagnosis and treatment. Such errors will result in wasting medical resources and endangering patient safety. The term “Lean” came from the concept of Lean Production, and it focuses on streamlining the production process through continuous improving current processes and quality, identifying core value processes, and to resolve unnecessary waste and mistakes. This study applies the “lean” concept on the laboratory testing procedures in hospitals. Literatures have listed seven primary wastes in Lean Production, which include: Overproduction, Waiting, Transportation, Inventory, Motion, Over Processing, and Defects. Combined with Service Oriented Architecture and RFID technologies, these waste classifications are used to help classify laboratory testing procedures to design an information system for resolving current problems. The purpose is to strengthen the sample quality, sample safety, and to improve the quality of healthcare.
Libri sul tema "Leaf specimens"
1
Speirs, Gill. The green leaf. Racine, Wis: Western Pub. Co., 1995.
Cerca il testo completo
2
Ehlert, Lois. Leaf Man. Orlando, Fla: Harcourt, Inc., 2005.
Cerca il testo completo
3
Leaf Man. Orlando, Fla: Harcourt, 2005.
Cerca il testo completo
4
Gillingham, Sara. On my leaf. San Francisco, Calif: Chronicle Books, 2012.
Cerca il testo completo
5
Phitzer, Juniper Von. Leaf: A play on a word. [San Francisco]: Juniper Von Phitzer Press, 1994.
Cerca il testo completo
6
Wakeman, Geoffrey. A leaf history of British printing: From 1610 to 1774. Oxford [Oxfordshire]: Plough Press, 1986.
Cerca il testo completo
7
Delamar, Gloria T. Wishing: Shooting stars, four-leaf clovers, and other wonders to wish upon. Philadelphia: Running Press Book Publishers, 1996.
Cerca il testo completo
8
David, Butcher. Pages from presses: Kelmscott, Ashendene, Doves, Vale, Eragny & Essex House. Risbury, Herefordshire: Whittington Press, 2006.
Cerca il testo completo
9
Locatelli, Boneto. A leaf from Biblia Latina: With commentary by Nicolai de Lyra ; printed in Venice in 1489 by Bonetus Locatellus. Sacramento, Calif: Sacramento Book Collectors Club and the California State Library Foundation, 1995.
Cerca il testo completo
10
Press, Kazui. Type faces, the Kazui Press: Specimen of twentysix soldiers of lead. Tokyo: Kazui Press, 1993.
Cerca il testo completoCapitoli di libri sul tema "Leaf specimens"
1
Casey, Francis. "Specimen Critical Analysis". In King Lear by William Shakespeare, 82–85. London: Macmillan Education UK, 1986. http://dx.doi.org/10.1007/978-1-349-08342-8_5.
Testo completo
2
Peng, Chengwei, e Wenlong Lv. "Experimental Study on Mechanical Properties of the Damaged Hoop Head Mortise-Tenon Joint". In Advances in Frontier Research on Engineering Structures, 397–407. Singapore: Springer Nature Singapore, 2023. http://dx.doi.org/10.1007/978-981-19-8657-4_35.
Testo completoAbstract (sommario):
AbstractDamage is a common condition in ancient timber structures, whose influence on the mechanical properties of structures cannot be ignored. To study the mechanical properties of damaged hoop head mortise-tenon joint, four specimens with shrinkage gauge, including one intact joint specimen and three artificial simulated damaged joint specimens, are designed, and fabricated in this paper by regarding the global damage degree and column axial force as the variation of parameters. The failure mode, hysteresis curve, skeleton curve, ductility, and energy dissipation capacity of the specimens are studied by low-cyclic reversed loading tests. The results show that the failure pattern is randomly manifested as parallel-to-grain tensile cracking failure or vertical splitting failure of the beam tenon. When the global damage degree increases, the two types of damage are more likely to appear simultaneously. The global damage degree has a significant influence on the ultimate bending moment and energy dissipation capacity of hoop head mortise-tenon joints, and 2.4% of the global damage degree can lead to a significant decrease in both. The column axial force can affect the ultimate bending moment, ductility, and energy dissipation capacity of hoop head mortise-tenon joints. When the column axial force increases, the ultimate bending moment and energy dissipation capacity will increase, while the ductility will decrease.
3
Tavares, T. M. "The Role of Lead and Cadmium Reference Samples in an Epidemiological Case Study at Santo Amaro, Bahia, Brazil". In Specimen Banking, 89–98. Berlin, Heidelberg: Springer Berlin Heidelberg, 1992. http://dx.doi.org/10.1007/978-3-642-77197-2_10.
Testo completo
4
Visinoni, Franco. "Towards the Lean lab: The Industry Challenge". In Pre-Analytics of Pathological Specimens in Oncology, 119–33. Cham: Springer International Publishing, 2015. http://dx.doi.org/10.1007/978-3-319-13957-9_12.
Testo completo
5
Telang, Adwait U., e Thomas R. Bieler. "Dislocation Activity and Slip Analysis Contributing to Grain Boundary Sliding and Damage during Thermomechanical Fatigue in Dual Shear Lead-Free Solder Joint Specimens". In Solid State Phenomena, 219–26. Stafa: Trans Tech Publications Ltd., 2005. http://dx.doi.org/10.4028/3-908451-09-4.219.
Testo completo
6
Perlongo, Alessandro, Nicolas Goujard, Mahsa Mozayan e Farid Benboudjema. "Development of a Thermo-Hydro-Mechanical Model of the Containment Vessel Vercors to Study Its Aging and Leak Tightness, Based on Specimen Tests and In Situ Measurements". In RILEM Bookseries, 289–300. Cham: Springer International Publishing, 2022. http://dx.doi.org/10.1007/978-3-031-07746-3_29.
Testo completo
7
Kleinfeller, Nikolai, Christopher M. Gehb, Maximilian Schaeffner, Christian Adams e Tobias Melz. "Assessment of Model Uncertainty in the Prediction of the Vibroacoustic Behavior of a Rectangular Plate by Means of Bayesian Inference". In Lecture Notes in Mechanical Engineering, 264–77. Cham: Springer International Publishing, 2021. http://dx.doi.org/10.1007/978-3-030-77256-7_21.
Testo completoAbstract (sommario):
AbstractDesigning the vibroacoustic properties of thin-walled structures is of particularly high practical relevance in the design of vehicle structures. The vibroacoustic properties of thin-walled structures, e.g., vehicle bodies, are usually designed using finite element models. Additional development effort, e.g., experimental tests, arises if the quality of the model predictions are limited due to inherent model uncertainty. Model uncertainty of finite element models usually occurs in the modeling process due to simplifications of the geometry or boundary conditions. The latter highly affect the vibroacoustic properties of a thin-walled structure. The stiffness of the boundary condition is often assumed to be infinite or zero in the finite element model, which can lead to a discrepancy between the measured and the calculated vibroacoustic behavior. This paper compares two different boundary condition assumptions for the finite element (FE) model of a simply supported rectangular plate in their capability to predict the vibroacoustic behavior. The two different boundary conditions are of increasing complexity in assuming the stiffness. In a first step, a probabilistic model parameter calibration via Bayesian inference for the boundary conditions related parameters for the two FE models is performed. For this purpose, a test stand for simply supported rectangular plates is set up and the experimental data is obtained by measuring the vibrations of the test specimen by means of scanning laser Doppler vibrometry. In a second step, the model uncertainty of the two finite element models is identified. For this purpose, the prediction error of the vibroacoustic behavior is calculated. The prediction error describes the discrepancy between the experimental and the numerical data. Based on the distribution of the prediction error, which is determined from the results of the probabilistic model calibration, the model uncertainty is assessed and the model, which most adequately predicts the vibroacoustic behavior, is identified.
8
Lee, Liz. "A New Leaf". In Biologically-Inspired Computing for the Arts, 278–88. IGI Global, 2012. http://dx.doi.org/10.4018/978-1-4666-0942-6.ch016.
Testo completoAbstract (sommario):
The author and artist, Liz Lee discusses her latest digital image series, “A New Leaf Series,” within the context of early photographic imaging and its connection to science and biology by investigating and connecting to the work of Thomas Wedgewood, William Henry Fox-Talbot, and the early pioneers of photographic technologies. Hippolyte Bayard’s “Arrangement of Specimens” and Anna Atkins’ “Photographs of British Algae: Cyanotype Impressions” serve as early examples of the scientific fundamentals of photography; the technological advances of the medium still draw on the same subject matter to reveal the basic structure of conceptual and aesthetic investigation. The author discusses how contemporary electronic imaging has returned to its photographic origins through nature-related subject matter.
9
Ewers, Ulrich, Martina Turfeld e Erich Jermann. "Chapter 18 Lead". In Trace Element Analysis in Biological Specimens, 371–84. Elsevier, 1994. http://dx.doi.org/10.1016/s0167-9244(08)70160-4.
Testo completo
10
Krishnan, Kannan M. "Probes: Sources and Their Interactions with Matter". In Principles of Materials Characterization and Metrology, 277–344. Oxford University Press, 2021. http://dx.doi.org/10.1093/oso/9780198830252.003.0005.
Testo completoAbstract (sommario):
Probes are generated using laboratory sources, or in large user facilities. Photon sources include incandescence and plasma discharge lamps. Electron beams are generated using thermionic or field-emission sources. RF plasma sources generate ions that are accelerated and used for scattering experiments. Specimens should be probed first with light, as it causes the least damage. Electron interaction with matter causes beam broadening, atomic displacements, sputtering, or radiolysis leading to mass loss and local contamination. Neutrons are heavier than electrons, penetrate more deeply in materials, and require more sample for analysis. Protons (positive charge, heavier than electrons) go a longer way in the specimen without significant broadening. Ions in solids undergo kinematic collisions with conservation of energy and momentum; they also lose energy continuously as they propagate. In the back-scattering geometry, they form important methods of Rutherford backscattering spectroscopy (RBS) and low-energy ion scattering spectroscopy (LEISS). Medium energy ions generate secondary ions by sputtering that can be analyzed by mass spectrometers to determine specimen composition (SIMS). Alternatively, its composition is analyzed (ICP-MS), by creating an aqueous dispersion and converting it to a plasma. Finally, interaction of high-energy ions with core electrons can lead to inner shell ionization and characteristic X-ray emission (PIXE).
Atti di convegni sul tema "Leaf specimens"
1
Singh, Gurdit, Nitin Aggarwal, Kanika Gupta e Devendra Kumar Misra. "Plant Identification Using Leaf Specimen". In 2020 11th International Conference on Computing, Communication and Networking Technologies (ICCCNT). IEEE, 2020. http://dx.doi.org/10.1109/icccnt49239.2020.9225683.
Testo completo
2
Nakamura, Izumi, e Naoto Kasahara. "Improved Model Tests to Investigate the Failure Modes of Pipes Under Beyond Design Basis Earthquakes". In ASME 2018 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2018. http://dx.doi.org/10.1115/pvp2018-84424.
Testo completoAbstract (sommario):
In order to investigate the failure modes of piping systems under the beyond design basis seismic loads, the authors proposed an experimental approach to use pipes made of the simulation material instead of steel pipes in the previous study. Though the ratchet-collapse (ratchet and subsequent collapse) was successfully obtained as the failure mode through the shaking table test using the pure lead (Pb) pipes as the simulation material pipe specimens, there was concern that characteristics of pure lead was somewhat extreme considering the analogy with the stress-strain relationship of steel. In order to resolve such concern, a modified experimental procedure has been developed. In the modified procedure, lead-antimony (Pb-Sb) alloy is used as the simulation material. Through the shaking table tests on single elbow pipe specimens made of Pb-Sb alloy, it is found that the typical failure mode is the ratchet and subsequent collapse, as same as the results by the shaking table tests of the Pb pipe specimens. The results indicate that the lower input frequency than the specimen’s natural frequency is prone to cause failure to the specimen, while the higher input frequency hardly causes the failure. The tendency of the global behavior of specimens is similar each other between the Pb pipe specimens and the Pb-Sb alloy specimens, but the strength of self-weight collapse of the Pb-Sb alloy pipe specimen is much higher than that of the Pb pipe specimen. Due to such higher strength of Pb-Sb alloy pipes, a prospect to conduct an excitation test on a more complicated piping system model is obtained.
3
Williams, Bruce W., William R. Tyson, C. Hari M. Simha e Bogdan Wasiluk. "Specimen Curvature and Size Effects on Crack Growth Resistance From Compact Tension Specimens of CANDU Pressure Tubes". In ASME 2019 Pressure Vessels & Piping Conference. American Society of Mechanical Engineers, 2019. http://dx.doi.org/10.1115/pvp2019-93318.
Testo completoAbstract (sommario):
Abstract CSA Standard N285.8 requires leak-before-break and fracture protection for Zr-2.5Nb pressure tubes in operating CANDU reactors. In-service deuterium uptake causes the formation of hydrides, which can result in additional variability and reduction of fracture toughness. Pressure tube fracture toughness is assessed mainly through rising pressure tube section burst tests. Given the length of the ex-service pressure tubes required for burst testing and the requirement to increase the hydrogen content of irradiated ex-service pressure tubes, only a limited number of burst tests can be performed. Using small-scale compact tension, C(T), specimens are advantageous for obtaining a statistically significant number of fracture toughness measurements while using less ex-service pressure tube material. This work focuses on the study of C(T) geometry designs in order to obtain crack growth resistance and fracture toughness closer to those deduced from burst tests. Because C(T) specimens must be machined from pressure tubes of about 100 mm in diameter and 4 mm in wall thickness, they are out-of-plane curved. As well, they undergo significant tunnelling during crack extension. These two factors can result in a violation of the ASTM standard for fracture toughness testing. The current work examined the influence of specimen curvature and tunnelled crack front on the crack growth resistance curve, or J-R curve. Finite element (FE) models using stationary and growing cracks were used in a detailed numerical investigation. To capture crack tunnelling in the FE models, a damage mechanics approach was adopted, with the critical strain to accumulate damage being a function of crack front stress triaxiality. The J-integral numerically estimated from the domain integral approach was compared to the J-integral calculated from the analytical equations in the ASTM E-1820 standard. In most cases, the difference between the numerical and the standard estimations was less than 10%, which was considered acceptable. It was found that at higher load levels of load-line-displacement, specimen curvature influenced the J-integral results. Crack tunnelling was shown to have a small influence on the estimated J-integrals, in comparison with the straight crack fronts. A modest number of experiments were carried out on unirradiated Zr-2.5Nb pressure tube material using three designs of curved C(T) specimens. It was found that the specimens of both designs that featured a width of 34 mm had more than twice the crack extension of the specimens of the 17-mm width design. The 17-mm width specimens are used mainly to assess the small-scale fracture toughness of pressure tube material. Additionally, the applied J-integral at the maximum load was about 1.4 times higher for the larger-width C(T) specimens. These C(T) specimens also produced J-R curves with greater crack extensions, which were closer to those obtained from the pressure tube section burst tests. Artificially hydrided pressure tube material was not considered in the current work, to avoid any potential source of experimental variability; however, it should be considered in future work.
4
ŠVADLENA, Jan, Kristýna Charlotte STRACHOTOVÁ, Tomáš PROŠEK e Milan KOUŘIL. "Evaluation of corrosivity of indoor museum atmospheres using lead specimens". In METAL 2020. TANGER Ltd., 2020. http://dx.doi.org/10.37904/metal.2020.3631.
Testo completo
5
Seo, Young Ho, Tae Goo Kang, Young-Ho Cho, Seong-A. Kim, Geun Ho Kim e Jong Uk Bu. "Locally Heated Low Temperature Wafer Level MEMS Packaging With Closed-Loop AuSn Solder-Lines". In ASME 2002 International Mechanical Engineering Congress and Exposition. ASMEDC, 2002. http://dx.doi.org/10.1115/imece2002-39267.
Testo completoAbstract (sommario):
In this paper, locally heated closed-loop AuSn solder-line bonding method was proposed and evaluated for a low-temperature, high strength, and hermetic MEMS packaging. We fabricated two different test specimens including substrate-heated specimen and locally heated specimen in order to verify the performance of locally heated method. In air tightness test, the substrate-heated specimen and locally heated specimen show the maximum leak rate of 13.5±9.8×10−10mbar-l/s and 18.8±9.9×10−10mbar-l/s with the same internal volume of 6.89±0.2×10−6l, respectively. In the critical pressure test, any fracture was not found in the bonded specimens at applied pressure of 10±2bar. From these results, we approximately extracted the bonding strength of the proposed bonding process of 3.53±0.07MPa. By EDS (Energy Dispersive X-ray Spectrometer) analysis at bonded interface, we found that bonded interface (between AuSn solder and Ti/Au layer) of substrate-heated specimen was stronger than that of locally heated specimen.
6
Kathikeyan, J., C. C. Berndt, A. Ristorucci e H. Herman. "Ceramic Impregnation of Plasma Sprayed Thermal Barrier Coatings". In ITSC 1996, a cura di C. C. Berndt. ASM International, 1996. http://dx.doi.org/10.31399/asm.cp.itsc1996p0477.
Testo completoAbstract (sommario):
Abstract Reducing the pore size and pore volume can lead to improved mechanical properties and enhanced corrosion resistance of plasma sprayed thermal barrier coatings. In this work, plasma sprayed 8 wt.% yttria stabilized zirconia coatings were removed from the substrate and machined to obtain 25x5x1 mm test specimens. These specimens were vacuum impregnated with alumina sol, calcined at 873 K for an hour and then heat treated at 1273 K for an hour to produce ceramic impregnated specimens. As-sprayed and impregnated specimens were investigated using optical microscopy, XRD, SEM, mercury intrusion porosimetry and electron microprobe analysis. This technique can impregnate the entire thickness of the specimens. Pores in the as-sprayed specimens were impregnated with α alumina grains, resulting in microstructural variations and reduction of the size and volume of the specimen pores.
7
Ma, Hongtao, Jeffrey C. Suhling, Pradeep Lall e Michael J. Bozack. "Evolution of Lead Free Solder Material Behavior During Isothermal Aging". In ASME 2006 International Mechanical Engineering Congress and Exposition. ASMEDC, 2006. http://dx.doi.org/10.1115/imece2006-15491.
Testo completoAbstract (sommario):
Solder materials demonstrate evolving microstructure and mechanical behavior that changes significantly with environmental exposures such as isothermal aging and thermal cycling. These aging effects are greatly exacerbated at higher temperatures typical of thermal cycling qualification tests for harsh environment electronic packaging. In the current study, mechanical measurements of thermal aging effects and material behavior evolution of lead free solders have been performed. Extreme care has been taken so that the fabricated solder uniaxial test specimens accurately reflect the solder materials present in actual lead free solder joints. A novel specimen preparation procedure has been developed where the solder uniaxial test specimens are formed in high precision rectangular cross-section glass tubes using a vacuum suction process. The tubes are then sent through a SMT reflow to re-melt the solder in the tubes and subject them to any desired temperature profile (i.e. same as actual solder joints). Using specimens fabricated with the developed procedure, isothermal aging effects and viscoplastic material behavior evolution have been characterized for 95.5Sn4.0Ag-0.5Cu (SAC405) and 96.5Sn-3.0Ag-0.5Cu (SAC305) lead free solders, which are commonly used as the solder ball alloy in lead free BGAs and other components. Analogous tests were performed with 63Sn-37Pb eutectic solder samples for comparison purposes. In our total experimental program, samples have been solidified with both reflowed and water quenching temperature profiles, and isothermal aging has been performed at room temperature (25 °C) and elevated temperatures (100 °C, 125 °C and 150 °C). In this paper, we have concentrated on reporting the results of the room temperature aging experiments. Variations of the temperature dependent mechanical properties (elastic modulus, yield stress, ultimate strength, creep compliance, etc.) were observed and modeled as a function of room temperature aging time. Microstructural changes during. room temperature aging have also been recorded for the solder alloys and correlated with the observed mechanical behavior changes.
8
Cryderman, Robert, Finn Bamrud, Tareq Eddir e Robert Goldstein. "Influence of Specimen Design on Maximum Heating Rate and Temperature Variation During Induction Heating in an 805L Dilatometer". In HT2021. ASM International, 2021. http://dx.doi.org/10.31399/asm.cp.ht2021p0138.
Testo completoAbstract (sommario):
Abstract Commercially, carbon steels are induction heated at heating rates on the order of 100 to 1,000 °C·s-1 for surface hardening. The high precision DIL 805L dilatometer employs induction heating and is often used to study transformation characteristics and prepare test specimens for metallurgical analysis. However, heating the commonly used 4 mm diameter by 10 mm long specimens at rates above 50 °C·s-1 results in non-linear heating rates during transformation to austenite and large transient temperature variations along the specimen length. These limitations in heating rate and variances from ideal uniform heating can lead to inaccurate characterization of the transformation behavior compared to commercial induction hardening practices. In this study it is shown that changing the specimen design to a thin wall tube allows faster heating rates up to 600 °C·s-1 and modifies the pattern of temperature variations within the test sample. The response of selected specimen geometries to induction heating in the dilatometer is characterized by modelling and tests using multiple thermocouples are used to verify the models. It is demonstrated that the use of properly designed tubular test specimens can aid in more accurately establishing transformation characteristics during commercial induction hardening.
9
Park, Soo, Sang-soo Yoo, Jun-ki Min, Jae-Mean Koo e Chang-Sung Seok. "Evaluation of Fracture Toughness Characteristic for Nuclear Piping Using Various Types of Specimens". In ASME 2010 Pressure Vessels and Piping Division/K-PVP Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/pvp2010-25540.
Testo completoAbstract (sommario):
The leak-before-break (LBB) concept is based on the fracture resistance curve obtained by J-R tests on various types of specimens. But it has been also known that the fracture toughness data by various types of specimens are different each other. For example, the estimates for fracture toughness of standard specimens are conservative when compared to the fracture toughness of real pipes owing to the difference of the constraint effect between real pipes and standard specimens. Therefore for estimating the integrity of real pipes on the basis of elastic-plastic fracture mechanics, we have to first establish the relations among real pipes, standard CT specimens and curved CT specimens. In this study, we performed the fracture toughness tests for nuclear piping material by various types of specimen. And each J-R curve considered in the constraint effect was compared.
10
Sato, Nobuhisa, Takashi Nakayama, Takashi Kaneko, Seiji Nagata, Tetsuo Imaoka, Keisuke Kurihara, Hideo Hirai, Ko Mizutani e Yoshito Umeki. "Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities: Part 8 — Fundamental Properties of Full-Scale Lead Rubber Bearings Based on Breaking Test". In ASME 2014 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/pvp2014-29006.
Testo completoAbstract (sommario):
This paper provides a part of the series “Development of an Evaluation Method for Seismic Isolation Systems of Nuclear Power Facilities.” This part shows the fundamental properties of full-scale lead rubber bearings with 1600 mm diameter based on break tests. The following results are mainly obtained. One: The deformations and the acting loads of the full-scale specimens were accurately obtained up to break by the measurement system for the break tests. Two: The fundamental properties for the full-scale lead rubber bearings with a large-diameter lead plug were obtained by the basic property tests. The load-displacement relations were stable and similar basic properties were obtained among the specimens. Three: The result of shear break tests showed that the hardening property of the specimens had a certain harmony with the hardening stiffness model which was used in the seismic response analysis to investigate the safety margin for severe earthquakes beyond design basis earthquakes of nuclear power facilities. The effect of axial pressure on hardening property was not specifically observed. The evaluated linear strain limit was larger than 250% for every specimen. Four: The softening property of the specimens was obtained from the tensile break tests. The axial stress of tensile yield was approx. 1.4 MPa and the axial stress did not show any negative gradient at least up to approx. 10% axial strain after the tensile yield even with offset shear strains. Five: The tensile force acting on the bolts which secure the specimen to the testing machine was lower than the estimated tensile force at shear break, which indicates tensile force was conservatively calculated to maintain safety in the design for foundation of lead rubber bearings.
Rapporti di organizzazioni sul tema "Leaf specimens"
1
Whisler, Daniel, Rafael Gomez Consarnau e Ryan Coy. Novel Eco-Friendly, Recycled Composites for Improved CA Road Surfaces. Mineta Transportation Institute, luglio 2021. http://dx.doi.org/10.31979/mti.2021.2046.
Testo completoAbstract (sommario):
The continued use of structural plastics in consumer products, industry, and transportation represents a potential source for durable, long lasting, and recyclable roadways. Costs to dispose of reinforced plastics can be similar to procuring new asphalt with mechanical performance exceeding that of the traditional road surface. This project examines improved material development times by leveraging advanced computational material models based on validated experimental data. By testing traditional asphalt and select carbon and glass reinforced composites, both new and recycled, it is possible to develop a finite element simulation that can predict the material characteristics under a number of loads virtually, and with less lead time compared to experimental testing. From the tested specimens, composites show minimal strength degradation when recycled and used within the asphalt design envelopes considered, with an average of 49% less wear, two orders of magnitude higher compressive strength, and three orders for tensile strength. Predictive computational analysis using the validated material models developed for this investigation confirms the long-term durability.
2
Wu, Yingjie, Selim Gunay e Khalid Mosalam. Hybrid Simulations for the Seismic Evaluation of Resilient Highway Bridge Systems. Pacific Earthquake Engineering Research Center, University of California, Berkeley, CA, novembre 2020. http://dx.doi.org/10.55461/ytgv8834.
Testo completoAbstract (sommario):
Bridges often serve as key links in local and national transportation networks. Bridge closures can result in severe costs, not only in the form of repair or replacement, but also in the form of economic losses related to medium- and long-term interruption of businesses and disruption to surrounding communities. In addition, continuous functionality of bridges is very important after any seismic event for emergency response and recovery purposes. Considering the importance of these structures, the associated structural design philosophy is shifting from collapse prevention to maintaining functionality in the aftermath of moderate to strong earthquakes, referred to as “resiliency” in earthquake engineering research. Moreover, the associated construction philosophy is being modernized with the utilization of accelerated bridge construction (ABC) techniques, which strive to reduce the impact of construction on traffic, society, economy and on-site safety. This report presents two bridge systems that target the aforementioned issues. A study that combined numerical and experimental research was undertaken to characterize the seismic performance of these bridge systems. The first part of the study focuses on the structural system-level response of highway bridges that incorporate a class of innovative connecting devices called the “V-connector,”, which can be used to connect two components in a structural system, e.g., the column and the bridge deck, or the column and its foundation. This device, designed by ACII, Inc., results in an isolation surface at the connection plane via a connector rod placed in a V-shaped tube that is embedded into the concrete. Energy dissipation is provided by friction between a special washer located around the V-shaped tube and a top plate. Because of the period elongation due to the isolation layer and the limited amount of force transferred by the relatively flexible connector rod, bridge columns are protected from experiencing damage, thus leading to improved seismic behavior. The V-connector system also facilitates the ABC by allowing on-site assembly of prefabricated structural parts including those of the V-connector. A single-column, two-span highway bridge located in Northern California was used for the proof-of-concept of the proposed V-connector protective system. The V-connector was designed to result in an elastic bridge response based on nonlinear dynamic analyses of the bridge model with the V-connector. Accordingly, a one-third scale V-connector was fabricated based on a set of selected design parameters. A quasi-static cyclic test was first conducted to characterize the force-displacement relationship of the V-connector, followed by a hybrid simulation (HS) test in the longitudinal direction of the bridge to verify the intended linear elastic response of the bridge system. In the HS test, all bridge components were analytically modeled except for the V-connector, which was simulated as the experimental substructure in a specially designed and constructed test setup. Linear elastic bridge response was confirmed according to the HS results. The response of the bridge with the V-connector was compared against that of the as-built bridge without the V-connector, which experienced significant column damage. These results justified the effectiveness of this innovative device. The second part of the study presents the HS test conducted on a one-third scale two-column bridge bent with self-centering columns (broadly defined as “resilient columns” in this study) to reduce (or ultimately eliminate) any residual drifts. The comparison of the HS test with a previously conducted shaking table test on an identical bridge bent is one of the highlights of this study. The concept of resiliency was incorporated in the design of the bridge bent columns characterized by a well-balanced combination of self-centering, rocking, and energy-dissipating mechanisms. This combination is expected to lead to minimum damage and low levels of residual drifts. The ABC is achieved by utilizing precast columns and end members (cap beam and foundation) through an innovative socket connection. In order to conduct the HS test, a new hybrid simulation system (HSS) was developed, utilizing commonly available software and hardware components in most structural laboratories including: a computational platform using Matlab/Simulink [MathWorks 2015], an interface hardware/software platform dSPACE [2017], and MTS controllers and data acquisition (DAQ) system for the utilized actuators and sensors. Proper operation of the HSS was verified using a trial run without the test specimen before the actual HS test. In the conducted HS test, the two-column bridge bent was simulated as the experimental substructure while modeling the horizontal and vertical inertia masses and corresponding mass proportional damping in the computer. The same ground motions from the shaking table test, consisting of one horizontal component and the vertical component, were applied as input excitations to the equations of motion in the HS. Good matching was obtained between the shaking table and the HS test results, demonstrating the appropriateness of the defined governing equations of motion and the employed damping model, in addition to the reliability of the developed HSS with minimum simulation errors. The small residual drifts and the minimum level of structural damage at large peak drift levels demonstrated the superior seismic response of the innovative design of the bridge bent with self-centering columns. The reliability of the developed HS approach motivated performing a follow-up HS study focusing on the transverse direction of the bridge, where the entire two-span bridge deck and its abutments represented the computational substructure, while the two-column bridge bent was the physical substructure. This investigation was effective in shedding light on the system-level performance of the entire bridge system that incorporated innovative bridge bent design beyond what can be achieved via shaking table tests, which are usually limited by large-scale bridge system testing capacities.
3
OVERHANG EFFECT ON WEB CRIPPLING CAPACITY OF COLDFORMED AUSTENITIC STAINLESS STEEL SHS MEMBERS: AN EXPERIMENTAL STUDY. The Hong Kong Institute of Steel Construction, agosto 2022. http://dx.doi.org/10.18057/icass2020.p.343.
Testo completoAbstract (sommario):
This paper studies the overhang effects on ultimate bearing capacities of cold-formed austenitic stainless steel square hollow section (SHS) members undergoing web crippling between EndTwo-Flange (ETF) and Interior-Two-Flange (ITF) loading conditions. A total of 16 web crippling tests were conducted with specimens covering various overhang lengths. Tensile coupon tests were performed to obtain the material properties of the test specimens. The web crippling capacities obtained from the tests were compared with the nominal capacities predicted by the SEI/ASCE 8-22 Specification for the design of cold-formed stainless steel structural members. It is shown that the SEI/ASCE 8-22 Specification leads to overly conservative web crippling capacity predictions for the tubular specimens with overhangs. The applicability of the overhang effect enhancement factor codified in the AISI S100- 16 Specification to the studied stainless steel specimens was evaluated. It is revealed that the accuracy and consistency of the web crippling capacity predictions can be enhanced by employing the enhancement factor codified in the AISI S100-16 Specification, yet such a treatment still leads to rather scatter predictions and can lead to unconservative capacity estimations. An extended investigation is currently underway to propose improved design rules for cold-formed stainless steel tubular members with overhangs under ETF loading condition.