Letteratura scientifica selezionata sul tema "Pressure time integrals"
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Articoli di riviste sul tema "Pressure time integrals"
1
Claisse, Penny J., Jodi Binning e Julia Potter. "Effect of Orthotic Therapy on Claw Toe Loading". Journal of the American Podiatric Medical Association 94, n. 3 (1 maggio 2004): 246–54. http://dx.doi.org/10.7547/0940246.
Testo completoAbstract (sommario):
This study demonstrates the effect of orthotic therapy for toe deformity on toe and metatarsal head pressures using a new analysis method facilitated by an in-shoe pressure-measurement system’s ability to export detailed data. Plantar pressure–time integrals in 11 individuals (22 feet) with claw deformity of the lesser toes were measured with and without toe props. Differences in pressure–time integrals at every individual sensor unit were then calculated for the two conditions, and significance was tested using the paired t-test. Plantar surface charts with contours of equal significant pressure–time integral change showed significant reduction under 17 second toes (77%), 22 third toes (100%), 15 fourth toes (68%), 13 second metatarsal heads (59%), 16 third metatarsal heads (73%), and 16 fourth metatarsal heads (73%). All 22 feet showed increases under the prop in the area of the third toe sulcus. This innovative approach to plantar pressure analysis could improve access to data that show significant pressure–time integral changes and, therefore, could advance the clinical application of plantar pressure measurement. (J Am Podiatr Med Assoc 94(3): 246–254, 2004)
2
Naraghi, Reza, Linda Slack-Smith e Alan Bryant. "Plantar Pressure Measurements and Geometric Analysis of Patients With and Without Morton’s Neuroma". Foot & Ankle International 39, n. 7 (11 aprile 2018): 829–35. http://dx.doi.org/10.1177/1071100718766553.
Testo completoAbstract (sommario):
Background: The purpose of this research was to see if there were any differences in peak pressure, contact time, pressure-time integrals, and geometric variables such as forefoot width, foot length, coefficient of spreading, and arch index between subjects with Morton’s neuroma (MN) and control subjects. Methods: Dynamic peak plantar pressure, contact time, pressure-time integral, and geometric data were extracted using the EMED-X platform in 52 subjects with MN and 31 control subjects. Differences in peak pressure, contact time, pressure-time integral, and geometric data between participants with and those without MN were determined using independent-samples t tests. There were no significant differences in age, weight, height, and body mass index between patients with MN and control subjects. Results: There were no significant differences in the peak pressures of all masked areas and pressure-time integrals under metatarsal 2 to 4 heads between patients with MN and control subjects. In addition, no significant differences were observed between patients with MN and control subjects in geometric measurements of forefoot length, width, coefficient of spreading, foot progression angle, and arch index. Conclusion: No relationship was found in this study between peak pressure, contact time, and pressure-time integral under the metatarsal heads, forefoot width, foot length, coefficient of spreading, and foot progression angle in a symptomatic MN group compared with a control group. The need to perform osteotomies to treat MN not associated with other lesser metatarsal phalangeal joint pathologies is questionable. Level of Evidence: Level III, Case-Control Study
3
Tong, Jasper W. K., U. Rajendra Acharya, Kuang C. Chua e Peck H. Tan. "In-shoe Plantar Pressure Distribution in Nonneuropathic Type 2 Diabetic Patients in Singapore". Journal of the American Podiatric Medical Association 101, n. 6 (1 novembre 2011): 509–16. http://dx.doi.org/10.7547/1010509.
Testo completoAbstract (sommario):
Background: We sought to establish the in-shoe plantar pressure distribution during normal level walking in type 2 diabetic patients of Chinese, Indian, and Malay descent without clinical evidence of peripheral neuropathy. Methods: Thirty-five patients with type 2 diabetes mellitus without loss of tactile sensation and foot deformities and 38 nondiabetic individuals in a control group had in-shoe plantar pressures collected. Maximum peak pressure and peak pressure-time integral of each foot were analyzed as separate variables and were masked into 13 areas. Differences in pressure variables were assessed by analysis of covariance, adjusting for relevant covariates at the 95% confidence interval. Results: No significant differences were noted in maximum peak pressures after adjusting for sex, race, age, height, and body mass. However, patients with diabetes mellitus had significantly higher mean ± SD pressure-time integrals at the right whole foot (309.50 ± 144.17 kPa versus 224.06 ± 141.70 kPa, P < .05) and first metatarsal (198.65 ± 138.27 kPa versus 121.54 ± 135.91 kPa, P < .05) masked areas than did those in the control group after adjustment. Conclusions: Patients without clinical observable signs of foot deformity (implying absence of motor neuropathy) and sensory neuropathy had similar in-shoe maximum peak pressures as controls. This finding supported the notion that either component of neuropathy needs to be present before plantar pressures are elevated. Patients with diabetes mellitus demonstrated greater pressure-time integrals, implying that this variable might be the first clinical sign observable even before peripheral neuropathy could be tested. (J Am Podiatr Med Assoc 101(6): 509–516, 2011)
4
Borg, Iona, Stephen Mizzi e Cynthia Formosa. "Plantar Pressure Distribution in Patients with Diabetic Peripheral Neuropathy and a First-Ray Amputation". Journal of the American Podiatric Medical Association 108, n. 3 (1 maggio 2018): 225–30. http://dx.doi.org/10.7547/16-021.
Testo completoAbstract (sommario):
Background: Elevated dynamic plantar pressures are a consistent finding in diabetic patients with peripheral neuropathy, with implications for plantar foot ulceration. This study aimed to investigate whether a first-ray amputation affects plantar pressures and plantar pressure distribution patterns in individuals living with diabetes and peripheral neuropathy. Methods: A nonexperimental matched-subject design was conducted. Twenty patients living with diabetes and peripheral neuropathy were recruited. Group 1 (n = 10) had a first-ray amputation and group 2 (n = 10) had an intact foot with no history of ulceration. Plantar foot pressures and pressure-time integrals were measured under the second to fourth metatarsophalangeal joints, fifth metatarsophalangeal joint, and heel using a pressure platform. Results: Peak plantar pressures under the second to fourth metatarsophalangeal joints were significantly higher in participants with a first-ray amputation (P = .008). However, differences under the fifth metatarsophalangeal joint (P = .734) and heel (P = .273) were nonsignificant. Pressure-time integrals were significantly higher under the second to fourth metatarsophalangeal joints in participants with a first-ray amputation (P = .016) and in the heel in the control group (P = .046). Conclusions: Plantar pressures and pressure-time integrals seem to be significantly higher in patients with diabetic peripheral neuropathy and a first-ray amputation compared with those with diabetic neuropathy and an intact foot. Routine plantar pressure screening, orthotic prescription, and education should be recommended in patients with a first-ray amputation.
5
Štefan, Lovro, Mario Kasović e Martin Zvonar. "Association between the levels of physical activity and plantar pressure in 6-14-year-old children". PeerJ 8 (14 febbraio 2020): e8551. http://dx.doi.org/10.7717/peerj.8551.
Testo completoAbstract (sommario):
Background The main purpose of the study was to determine whether lower levels of physical activity were associated with higher plantar pressure generated under each foot. Methods In this cross-sectional study, we recruited 641 children aged 6–14 years (agemean ± SD = 9.7 ± 2.4 years; heightmean ± SD = 143.6 ± 15.3 cm, weightmean ± SD = 37.6 ± 13.4 kg; body-mass indexmean ± SD = 17.6 ± 3.2 kg/m2; 44.2% girls). We used EMED –XL pressure platform to measure force time integral, pressure-time integral, contact-time and contact area, peak plantar pressure and mean plantar pressure of the right and the left foot during the gait analysis. The level of physical activity was measured by using The Physical Activity Questionnaire for Older Children (PAQ–C). The associations were calculated by using generalized estimating equations with linear regression models. Results Lower levels of physical activity were associated with higher force- and pressure-time integrals, longer contact time and higher peak and mean plantar pressures in both feet. Conclusion Our study shows that the level of physical activity is strongly and inversely associated with plantar pressure in a sample of 6–14 year olds.
6
Chang, An-Hsiung, Ziad U. Abu-Faraj, Gerald F. Harris, Joe Nery e Michael J. Shereff. "Multistep Measurement of Plantar Pressure Alterations Using Metatarsal Pads". Foot & Ankle International 15, n. 12 (dicembre 1994): 654–60. http://dx.doi.org/10.1177/107110079401501205.
Testo completoAbstract (sommario):
Metatarsal pads are frequently prescribed for nonoperative management of metatarsalgia due to various etiologies. When appropriately placed, they are effective in reducing pressures under the metatarsal heads on the plantar surface of the foot. Despite the positive clinical reports that have been cited, there are no quantitative studies documenting the load redistribution effects of these pads during multiple step usage within the shoe environment. The objective of this study was to assess changes in plantar pressure metrics resulting from pad use. Ten normal adult male subjects were tested during a series of 400-step trials. Pressures were recorded from eight discrete plantar locations at the hindfoot, midfoot, and forefoot regions of the insole. Significant increases in peak pressures, contact durations, and pressure-time integrals were noted at the metatarsal shaft region with pad use ( P ≤ .05). Statistically significant changes in metric values were not seen at the other plantar locations, although metatarsal pad use resulted in mild decreases in mean peak pressures at the first and second metatarsal heads and slight increases laterally. Contact durations decreased at all metatarsal head locations, while pressure-time integrals decreased at the first, second, third, and fourth metatarsal heads. A slight increase in pressure-time integrals was seen at the fifth metatarsal head. The redistribution of plantar pressures tended to relate not only to the dimensions of the metatarsal pads, but also to foot size, anatomic foot configuration, and pad location. Knowledge of these parameters, along with careful control of pad dimensions and placement, allows use of the metatarsal pad as an effective orthotic device for redistributing forefoot plantar pressures.
7
Prats, Michael, Lidia Lucely Meneses-P., Fernando Samaniego-V. e Ricardo Pacheco-V. "Pressure Buildup in a Well Produced at Constant Pressure". SPE Journal 25, n. 04 (20 maggio 2020): 1578–98. http://dx.doi.org/10.2118/201111-pa.
Testo completoAbstract (sommario):
Summary Dimensionless analytic expressions of the well-pressure buildup resulting from shutting in a well after producing it at constant pressure were obtained, in both Laplace space and time, using different mathematical approaches to solve the pertinent differential equations, including the effects of both wellbore storage and skin damage. Such a pressure response is said to have been obtained at constant-pressure-buildup (CPBU) conditions. The well, represented by a cylindrical source of nonzero radius, produces a single compressible fluid from an infinite and homogeneous reservoir. For a vertical well, the reservoir flow is always radial and horizontal. For the first approach in Laplace space, the pressure distribution in the reservoir at the shut-in time was used as the initial condition to obtain the transient pressure response upon shutting in the well. In the second approach, the solution in Laplace space was inverted analytically, yielding an expression containing infinite integrals. Duhamel's principle was used in the third approach, yielding the same integrals as the second approach. Subject to the inherent numerical errors in the integration and inversion algorithms, all solutions gave the same numerical results over a wide range of the production period, the elapsed time since the well was shut in, the storage coefficients, and the skin damage. As required by material balance, all pressures are restored to the value of the initial reservoir pressure as the infinite reservoir eventually completely recharges the amount of fluid produced before the well being shut in. The pressure response divided by the production rate at the time the well is shut in is denoted as the specific pressure response and has the same units as the pressure response under constant rate buildup (CRBU) conditions. It is thus not surprising that the general trends of the specific pressure response and the specific pressure increment are somewhat similar for both producing conditions, and that a number of interpretation procedures developed for CRBU conditions using the exponential integrals are applicable under CPBU conditions, including use of Horner plots. The Laplace-space procedure used to obtain numerically inverted values of the pressure response under CPBU conditions can be formally extended to provide expressions for the shut-in pressure response for any rate or pressure history during the production period. Although the emphasis is on the description of the well pressure and the specific-well-pressure buildup after shut-in, and of their time derivatives, the paper also presents analytic Laplace-space expressions for the pressure and radial flow within the reservoir after the well is shut in.
8
Maiwald, Christian, Stefan Grau, Inga Krauss, Marlene Mauch, Detlef Axmann e Thomas Horstmann. "Reproducibility of Plantar Pressure Distribution Data in Barefoot Running". Journal of Applied Biomechanics 24, n. 1 (febbraio 2008): 14–23. http://dx.doi.org/10.1123/jab.24.1.14.
Testo completoAbstract (sommario):
The aim of this study was to provide detailed information on rationales, calculations, and results of common methods used to quantify reproducibility in plantar pressure variables. Recreational runners (N = 95) performed multiple barefoot running trials in a laboratory setup, and pressure variables were analyzed in nine distinct subareas of the foot. Reproducibility was assessed by calculating intraclass correlation coefficients (ICC) and the root mean square error (RMSE). Intraclass correlation coefficients ranged from 0.58 to 0.99, depending on the respective variable and type of ICC. Root mean square errors ranged between 2.3 and 3.1% for relative force–time integrals, between 0.07 and 0.23 for maximum force (Fmax), and between 107 and 278 kPa for maximum pressure (Pmax), depending on the subarea of the foot. Force–time integral variables demonstrated the best within-subject reproducibility. Rear-foot data suffered from slightly increased measurement error and reduced reproducibility compared with the forefoot.
9
Rome, Keith, David George Survepalli, Maria Lobo, Nicola Dalbeth, Fiona McQueen e Peter J. McNair. "Evaluating Intratester Reliability of Manual Masking of Plantar Pressure Measurements Associated with Chronic Gout". Journal of the American Podiatric Medical Association 101, n. 5 (1 settembre 2011): 424–29. http://dx.doi.org/10.7547/1010424.
Testo completoAbstract (sommario):
Background: Plantar pressure measurements are commonly used to evaluate foot function in chronic musculoskeletal conditions. However, manually identifying anatomical landmarks is a source of measurement error and can produce unreliable data. The aim of this study was to evaluate intratester reliability associated with manual masking of plantar pressure measurements in patients with gout. Methods: Twenty-five patients with chronic gout (mean disease duration, 22 years) were recruited from rheumatology outpatient clinics. Patients were excluded if they were experiencing an acute gout flare at the time of assessment, had lower-limb amputation, or had diabetes mellitus. Manual masking of peak plantar pressures and pressure-time integrals under ten regions of the foot were undertaken on two occasions on the same day using an in-shoe pressure measurement system. Test-retest reliability was assessed by using intraclass correlation coefficients, SEM, 95% limits of agreement, and minimal detectable change. Results: Mean peak pressure intraclass correlation coefficients ranged from 0.92 to 0.97, with SEM of 8% to 14%. The 95% limits of agreement ranged from−150.3 to 133.5 kPa, and the minimal detectable change ranged from 30.8 to 80.6 kPa. For pressure-time integrals, intraclass correlation coefficients were 0.86 to 0.94, and SEM were 5% to 29%, with the greater errors observed under the toes. The 95% limits of agreement ranged from −48.5 to 48.8 kPa/sec, and the minimal detectable change ranged from 6.8 to 21.0 kPa/sec. Conclusions: These findings provide clinicians with information confirming the errors associated with manual masking of plantar pressure measurements in patients with gout. (J Am Podiatr Med Assoc 101(5): 424–429, 2011)
10
Coates, P. D., e R. G. Speight. "Towards Intelligent Process Control of Injection Moulding of Polymers". Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 209, n. 5 (ottobre 1995): 357–67. http://dx.doi.org/10.1243/pime_proc_1995_209_095_02.
Testo completoAbstract (sommario):
Steps towards process control of the complex, multi-variable injection moulding process are presented. In-process measurements, in particular melt and hydraulic pressures in the primary injection stage, are shown to provide a sensitive means of monitoring changes in the process and changes in the polymer feedstock. Correlations have been observed between real time process measurements, in the form of specific time integrals of melt and hydraulic pressure, and product quality measures, such as product weight or dimensions. The research has been validated in both scientific laboratory and factory studies, and for a range of polymers, injection moulding technologies and complexities of product. Such correlations, and the specific integrals upon which they are based, can therefore form the basis of meaningful statistical process control for injection moulding or a viable closed-loop control strategy.
Tesi sul tema "Pressure time integrals"
1
Duffin, Anthony C., University of Western Sydney, of Science Technology and Environment College e of Science Food and Horticulture School. "Structural and functional changes in the feet of young people with Type 1 diabetes mellitus". THESIS_CSTE_SFH_Duffin_A.xml, 2002. http://handle.uws.edu.au:8081/1959.7/408.
Testo completoAbstract (sommario):
Diabetes can affect the structure and function of the foot, resulting in severe limitation of mobility and reduction of life expectancy. Early warning signs include limited joint mobility (LJM), soft tissue changes, high plantar pressure (HPP), high pressure time integrals (P/TI) and plantar callus. These abnormalities were examined in 216 young people with diabetes and 57 controls. The fingers, toes, ankle subtalar and first metatarsophalangeal joints shows reduced motion and the plantar aponeurosis was thicker in diabetic subjects. Skin thickness was the same for diabetic and control subjects. LJM in the feet was more common in males and older subjects. Subtalar and finger LJM was associated with early sensory nerve changes and finger LJM was associated with retinopathy and higher HbAtc. Thicker plantar aponeurosis was associated with male gander and larger feet. High peak pressure, high P/TI and callus were no more common in diabetic subjects than controls. However, high P/TI and callus were associated with early sensory nerve changes in young people with diabetes. Diabetic subjects with callus were significantly older than those without callus. Those with HPP had higher body mass index and less motion at the first MTP joints than those without HPP. Although plantar callus, HPP and high P/TI were no more common in young people with diabetes these abnormailities may be complicated by diabetes. Cushioning, custom orthoses or both in combination significantly reduced peak pressure and P/TI in diabetic subjects.Doctor of Philosophy (PhD)
2
Duffin, Anthony C. "Structural and functional changes in the feet of young people with Type 1 diabetes mellitus". Thesis, 2002. http://handle.uws.edu.au:8081/1959.7/408.
Testo completoAbstract (sommario):
Diabetes can affect the structure and function of the foot, resulting in severe limitation of mobility and reduction of life expectancy. Early warning signs include limited joint mobility (LJM), soft tissue changes, high plantar pressure (HPP), high pressure time integrals (P/TI) and plantar callus. These abnormalities were examined in 216 young people with diabetes and 57 controls. The fingers, toes, ankle subtalar and first metatarsophalangeal joints shows reduced motion and the plantar aponeurosis was thicker in diabetic subjects. Skin thickness was the same for diabetic and control subjects. LJM in the feet was more common in males and older subjects. Subtalar and finger LJM was associated with early sensory nerve changes and finger LJM was associated with retinopathy and higher HbAtc. Thicker plantar aponeurosis was associated with male gander and larger feet. High peak pressure, high P/TI and callus were no more common in diabetic subjects than controls. However, high P/TI and callus were associated with early sensory nerve changes in young people with diabetes. Diabetic subjects with callus were significantly older than those without callus. Those with HPP had higher body mass index and less motion at the first MTP joints than those without HPP. Although plantar callus, HPP and high P/TI were no more common in young people with diabetes these abnormailities may be complicated by diabetes. Cushioning, custom orthoses or both in combination significantly reduced peak pressure and P/TI in diabetic subjects.
3
Okeng'o, Geoffrey Onchongâa. "A theoretical study of stellart pulsations in young brown dwarfs". Thesis, 2011. http://etd.uwc.ac.za/index.php?module=etd&action=viewtitle&id=gen8Srv25Nme4_4946_1308548503.
Testo completoAbstract (sommario):
This thesis reports the results of a twofold study on the recently proposed phenomenon of &lsquo
stellar pulsations&rsquo
in young brown dwarfs by the seminal study of Palla and Baraffe (2005) (PB05, thereafter). The PB05 study presents results of a non-adiabatic linear stability analysis showing that young brown dwarfs should become pulsationally unstable during the deuterium burning phase of their evolution.
Libri sul tema "Pressure time integrals"
1
Read, Matthew, e Christopher V. Maani. Procedures in the Adult and Neonatal Intensive Care Units. Oxford University Press, 2018. http://dx.doi.org/10.1093/med/9780190495756.003.0028.
Testo completoAbstract (sommario):
Bedside procedures in the ICU are an integral component of critical care medicine. Anesthesiologists who are assigned to the ICU must adapt principles of safe and effective anesthesia practice to this novel outside-of-the-operating-room environment. There are several reasons for surgical procedures to sometimes be performed at the bedside in the ICU, such as the avoidance of transporting unstable patients from the ICU to the OR, or the lack of adequate time to mobilize resources to perform an urgent procedure in the OR. Readiness of the entire ICU team is essential to avoid compromising care due to production pressure or lack of standards routine to the OR environment. This chapter discusses the types of procedures performed in the ICU and reviews the requirements of performing them successfully.
2
Roche, Benjamin, Hélène Broutin e Frédéric Simard, a cura di. Ecology and Evolution of Infectious Diseases. Oxford University Press, 2018. http://dx.doi.org/10.1093/oso/9780198789833.001.0001.
Testo completoAbstract (sommario):
During the last thirty years, the ecology and evolution of infectious diseases has been studied extensively. Understanding how pathogens are transmitted in time and space, how they are evolving according to different selective pressures, and how the environment can influence their transmission, has paved the way for new approaches to the study of host/pathogen interactions. At the same time, pathogen control in low-income countries (LIC) has tended to remain largely inspired and informed by classical epidemiology, where the objective is to treat as many people as possible, despite recent findings in ecology and evolutionary biology suggesting new opportunities for improved disease control in the context of limited economic resources. The need to integrate the scientific developments in ecology and evolution of infectious diseases with public health strategy in low-income countries is clearly as important today as it has ever been. In this book, the authors provide an up to date, authoritative, and challenging review of the ecology and evolution of infectious diseases focusing on low-income countries for effective public health applications and outcomes. Accessible to students and researchers working on evolutionary ecology of infectious diseases and public health scientists working on their control in low-income countries, this book combines chapters exposing fundamental concepts in evolutionary ecology with others exploring the most recent advances in the field as well as highlighting how they can provide new innovative approach on the field. This work is concluded by an integrative chapter signed by all the authors highlighting the key missing points to improve this connection between evolutionary ecology and public health in low-income countries.
Capitoli di libri sul tema "Pressure time integrals"
1
Horng, J., XC Liu, J. Thometz, C. Tassone e A. Duey-Holtz. "Evaluation of plantar pressures and center of pressure trajectories in Adolescent Idiopathic Scoliosis". In Studies in Health Technology and Informatics. IOS Press, 2021. http://dx.doi.org/10.3233/shti210451.
Testo completoAbstract (sommario):
Adolescent idiopathic scoliosis (AIS) has been postulated to affect gait patterns and postural stability due to its effect on center of body mass. 1) Determine the correlation between Cobb angle and COP in the anterior-posterior (AP) direction, COP in the medial-lateral (ML) direction, COP oscillation (COP-O) from midline walking, peak pressures, and pressure-time integrals (loading) at 10 anatomic foot segments; 2) Determine the differences in COP-AP, COP-ML, COP-O, and peak plantar pressures at 10 anatomic foot segments between the normal group and the AIS group. All patients wore a gown to expose the posterior trunk and underwent evaluation with Formetric 4D (DIERS International GmbH, Schlangenbad, Germany) while walking on the treadmill at 2 km/hour for 15 seconds. A total of 24 pressure metrics at 10 anatomic foot segments were evaluated. We then analyzed the data using t-test and linear regression analyses.16 patients were assigned to a normal group (Cobb angle 10° or less, n=4) or AIS group (Cobb greater than 10°, n=12). Of note, AIS patients had statistically significant lower max. pressures at the hallux and the 2nd, 4th, 5th metatarsal head compared to the normal group. Additionally, there was a statistically significant linear association between Cobb angle and both hallux max. pressure and hallux pressure-time integral (P<0.05). Reduced peak plantar pressures before the toe-off phase of gait cycle indicate that AIS patients may lean backwards and have posterior postural sway, which may be associated with hypokyphosis during walking.
2
Koussios, Sotiris. "Integral Design for Filament Winding—Materials, Winding Patterns, and Roving Dimensions for Optimal Pressure Vessels". In Composite Filament Winding, 19–34. ASM International, 2011. http://dx.doi.org/10.31399/asm.tb.cfw.t52860019.
Testo completoAbstract (sommario):
Abstract This chapter outlines a methodology for the design of cylindrical pressure vessels, with emphasis on the establishment of winding patterns and the interaction between the real fiber bed geometry (finite roving dimensions) and the theoretical one. To highlight the materials-shape/pattern-roving interaction, an outline of the basic principles of pressure vessel design is provided. After a short section on laminate thickness approximation techniques (essential for establishing a range of acceptable roving dimensions), the chapter concludes with an example demonstrating the methodology from an initial set of design parameters up to the final stage, including patterns, roving dimensions, and production time minimization.
3
Buckley, Benjamin J. R., e Stephanie J. Finnie. "Non-pharmacological management of hypertension". In Hypertension (Oxford Cardiology Library) 3E, a cura di Sunil K. Nadar e Gregory Y. H. Lip, 115–24. 3a ed. Oxford University PressOxford, 2022. http://dx.doi.org/10.1093/med/9780198870678.003.0013.
Testo completoAbstract (sommario):
Abstract The importance of a healthy lifestyle is well understood for primary and secondary prevention of cardiovascular disease. Numerous studies have emphasized the importance of lifestyle changes as an important component of lowering blood pressure in both patients with hypertension and pre-hypertension. Non-pharmacological interventions are an integral part of not only preventing and managing hypertension, but also reducing cardiovascular mortality and morbidity. The importance of physical activity, exercise training, and a healthy diet need to be re-emphasized as powerful primary and secondary preventive tools. Therefore, physicians and other healthcare practitioners must allow time with patients to discuss patient goals related to non-pharmacological and lifestyle modifications.
4
Rose'Meyer, Roselyn, e Indu Singh. "Introduction and Current Status of Technology in Teaching and Learning of Allied Healthcare Students". In Emerging Technologies and Work-Integrated Learning Experiences in Allied Health Education, 1–11. IGI Global, 2018. http://dx.doi.org/10.4018/978-1-5225-3850-9.ch001.
Testo completoAbstract (sommario):
Allied healthcare professionals are an integral part of multidisciplinary healthcare teams requiring highly skilled and competent members from every discipline. Clinical and allied health education in Australia is challenged by increasing student numbers, changing healthcare practices, and service pressures impacting the clinical training of students. There is a need to optimise the effectiveness and efficiency of the way students develop their professional skills. New technological approaches deliver student-centered education involving work-integrated learning. This chapter covers different strategies developed and implemented over time, merging various technologies in an innovative manner providing better standardized skills and competencies to more students within limited resources to prepare them for a global inter-professional multidisciplinary healthcare team providing efficient service to society. It will also provide future directions to adapt technology from the non-healthcare industry to healthcare training and share some strategies of bringing the workplace to the classroom.
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McKercher, Bob, e Bruce Prideaux. "Sustainability". In Tourism Theories, Concepts and Models. Goodfellow Publishers, 2020. http://dx.doi.org/10.23912/9781911635352-4730.
Testo completoAbstract (sommario):
During the early 1980s, it became apparent that major global environmental changes were occurring suddenly and silently and were only beginning to be recognized as an emerging threat by the global scientific community. Scholars and an increasing number of citizens became aware that there was a growing element of uncertainty and risk from human activities on global environments The establishment of the Intergovernmental Panel on Climate Change (IPCC) in 1988 by the World Meteorological Organization (WMO) and the United Nations Environmental Programme (UNEP) and endorsed later by the General Assembly of the United Nations was a major step in focusing the global community’s attention to the problem. At that time, moderate environmentalists were wrestling with the idea that we can live in a world where economic development and economic pressures for both developing and developed countries would continue. Short- term pressures to develop national economies (along with the social benefits that derive from it) were considered by policy makers to outweigh long-term potential impacts from that development process. In other words, we failed to ask the question of how can a sustainable economy be developed that integrates both industrial and ecological needs? More recently, advocates of degrowth suggest a more radical change to how the global economy functions. While it is unrealistic to suggest that the solution to our environmental woes would be to wind back the global economy, growing concerns about sea level rise, ecosystem collapse and the emergence of other global ecological crises challenge the idea that it is possible to promote economic growth while maintaining environmental protection. This chapter explores a range of issues related to sustainable development in general and sustainable tourism in particular. It begins with an overview of the concept of sustainable development before moving onto a discussion of sustainable tourism. The chapter then discusses the range of models and concepts that have been developed to monitor asustainability.
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Parlance, J. Y., e T. S. Steenhuis. "Soil Properties and Water Movement". In Vadose Zone Hydrology. Oxford University Press, 1999. http://dx.doi.org/10.1093/oso/9780195109900.003.0008.
Testo completoAbstract (sommario):
For all spatial scales, from pore through local and field, to a watershed, interaction of the land surface with the atmosphere will be one of the crucial topics in hydrology and environmental sciences over the forthcoming years. The recent lack of water in many parts of the world shows that there is an urgent need to assess our knowledge on the soil moisture dynamics. The difficulty of parameterization of soil hydrological processes lies not only in the nonlinearity of the unsaturated flow equation but also in the mismatch between the scales of measurements and the scale of model predictions. Most standard measurements of soil physical parameters provide information only at the local scale and highlight the underlying variability in soil hydrological characteristics. The efficiency of soil characteristic parameterization for the field scale depends on the clear definition of the functional relationships and parameters to be measured, and on the development of possible methods for the determination of soil characteristics with a realistic use time and effort. The soil’s hydraulic properties that affect the flow behavior can be expressed by a soil water retention curve that describes the relation between volumetric water content, θ(L3L3), and soil water pressure, h(L), plus the relation between volumetric water content and hydraulic conductivity, K(L/T). In the next section, the determination of soil hydraulic parameters is first discussed for local and field scale. Then, we show how the pore-scale processes can be linked to soil hydraulic properties. These properties are then used in some of the modern methods that use integral and superposition solutions of Richards’ equation for infiltration and water flow problems for both stable and preferential types of flows. Finally, some practical aspects for watersheds are discussed to highlight the difficulties encountered when large-scale predictions are needed.
7
Rahman, Hakikur. "Network Deployment for Social Benefits in Developing Countries". In Encyclopedia of Multimedia Technology and Networking, Second Edition, 1048–54. IGI Global, 2009. http://dx.doi.org/10.4018/978-1-60566-014-1.ch141.
Testo completoAbstract (sommario):
For many reasons, the establishment of technology is crucial to socio-economic development, as well as increasing democratization of a nation. The technology is pervasive in nature, but the cost benefit together with the national urgency for its introduction through various applications mostly depends on the grass roots awareness and utilization of computers (interconnected computers) for the common people. Hence, the transferability and applicability of e-applications (e-learning, e-commerce, e-governance, e-health, etc.) must assured to be applied at their consistent state and best obtained by the congenial atmosphere at all levels of the policy making. The essential issues are that developing countries, faced with enormous social and economic pressures, must start to confirm consistent economic growth and at the same time accelerate broad-based technology deployment. In this aspect, low-ranking developing countries had to utilize every benefit of it in order to compete with others for a dominant share of the global ICT contribution. In order to realize this vision more efficiently and cost effectively, and to integrate increased human participation within the technology, governments must be proactive in prioritizing limited resources by appropriate planning: build the foundation for a rational expansion of the ICT sector into higher value-added services. In addition, the drive to transform countries into “knowledge-based” societies will necessitate intergovernmental, interagencies, intersocietal, as well as private sector cooperation, commitment, dedication, and partnership in the context of an overall framework for the logical development of the ICT sector. The positioning of suitable foundations requires a comprehensive national strategic vision with elaborate plans. They should ensure seamless interlinkages among all sectors and meaningful participation of all citizens in meeting the challenges to transform the human capital through establishment of various e-applications. At the same time, pervasive education/skill development and the provision for life long learning has to be interlaced within all sectors. As the technology is ever renewing, especially in developing countries, the inadequacy of proper management structure and the scarcity of suitably trained managers deserve immediate attention. This article emphasizes broad-based utilization of ICT applications for social developments, focuses on issues and challenges of their implementations with various usages, and provides a brief discussion on a few cases on networked applications.
8
Potts, Charlotte R. "The decoration of early shrines and temples". In Religious Architecture in Latium and Etruria, c. 900-500 BC. Oxford University Press, 2015. http://dx.doi.org/10.1093/oso/9780198722076.003.0011.
Testo completoAbstract (sommario):
An integral part of the transition from ‘huts’ to ‘houses’ in the seventh and early sixth century BC was the adoption of a new roofing system using wooden beams and terracotta tiles instead of traditional thatch. The two elements of the new system formed an integrated unit, with special tiles designed and positioned to protect the perishable wooden beams from rain, wind, and fire; many also carried painted and moulded decorations that have encouraged study of their iconography as well as function. The disappearance of wooden trusses and supporting mud-brick walls from the archaeological record means that thousands of these durable tiles and architectural terracottas now comprise the primary evidence for the size, form, and decoration of many early Etruscan and Latial superstructures. Excavations in the last seventy years have yielded new information about the distribution of the decorative elements of these roofs in Etruria and Latium, and in particular about the different types of buildings on which they appeared. It is clear that architectural terracottas were initially placed on a wide variety of buildings, unlike their Greek counterparts, but gradually became the preserve of religious architecture. This chapter will examine the nature and location of these roofs, their imagery, and explanations for their increasingly limited use. As such it will offer a detailed analysis of the process by which terracottas became a means of differentiating religious buildings from vernacular architecture during the sixth century BC. Tile production appears to have begun in central Italy by the middle of the seventh century BC and can be associated with significant changes in society and economy. With an approximate weight of 60 kilograms per square metre for tiles and up to 85 kilograms per square metre for the supporting roof beams, the downward and outward pressure of tiled roofs had to be countered with strong, preferably stonebased, walls following rectangular or square plans, the careful selection of timbers to span greater distances, and specialized craftsmen to make, fit, and repair the roofs. All of these factors imply more sedentary communities than hut architecture, growing technical infrastructure, and an ability and readiness to invest in the greater capital expense of a tiled roof.
9
Daly, Blánaid, Paul Batchelor, Elizabeth Treasure e Richard Watt. "Planning dental services". In Essential Dental Public Health. Oxford University Press, 2013. http://dx.doi.org/10.1093/oso/9780199679379.003.0028.
Testo completoAbstract (sommario):
Planning is an integral part of dental care provision that can operate at many different levels. At a national level, government NHS policy impacts upon dental services in different ways. For example, in the General Dental Service, patient charge bands in England are currently set by the government. In the future, at the national level, the National Health Service Commissioning Board (NHSCB) will determine national policy and national delivery requirements. The NHSCB will be responsible for commissioning primary dental services and contractual arrangements with dentists. At the Health and Wellbeing Board (HWB) level in England, planners (in conjunction with general medical practioner (GMP) consortia/clinical care commissioning groups (CCGs)) will make decisions over the priorities for local services, and the types and range of services offered locally. Within a dental practice, dental practitioners and their team members may develop a range of practice policies aimed at improving the services provided. Finally, every day clinicians develop treatment plans for individual patient care based upon their oral health needs. All these activities are planning in action. This chapter will examine the basic principles of planning, and review the different steps in the planning process. At the most basic level, planning aims to guide choices so that decisions are made in the best manner to reach the desired outcomes. Planning provides a guide and structure to the process of decision-making to maximize results within the limited resources available. Is planning really necessary when there are so many other demands on practitioners’ time? Planning can be justified for the following reasons: . . . ● It provides an opportunity to be proactive in decision-making rather than constantly reacting to pressures and demands. . . . . . . ● It enables priorities to be set. . . . . . . ● It identifies where resources can be directed to have the greatest impact. . . . Various planning models have been proposed to act as a guide to the different steps in the planning process. The rational planning model provides a basic guide to the process (McCarthy 1982), and involves the following steps: . . . 1 Assessment of need: e.g. identification of the oral health problems and concerns of the population. . . . . . . 2 Identifying priorities: agreeing the target areas for action. . . .
10
"Propagated Fish in Resource Management". In Propagated Fish in Resource Management, a cura di JAMES R. JACKSON, JEFF C. BOXRUCKER e DAVID W. WILLIS. American Fisheries Society, 2004. http://dx.doi.org/10.47886/9781888569698.ch10.
Testo completoAbstract (sommario):
<em>Abstract.</em>—The use of cultured fishes by fisheries agencies is a long-standing management technique. In recent decades, however, potential negative impacts of fish stocking programs have received increased attention, particularly as they affect native fish communities and the genetic integrity of wild fish populations. In 1994, a facilitated workshop was organized to develop recommended procedures for the use of cultured fishes that would be compatible with these broader environmental concerns. We administered a survey to state and provincial fisheries management agencies in the United States and Canada to determine the current status of fish culture and stocking programs and assess progress toward adoption of these procedures. With 54 of 62 agencies reporting, our results indicated that stocking programs continue to be an integral part of management programs, but that substantial progress has been made toward addressing concerns about potential negative effects of cultured fishes. The percentage of responding agencies reporting use of management plans in which stocking was considered as part of a larger management program more than doubled in the years since 1980. Consistent with this finding, agency emphasis on alternative management approaches was evidenced by a twofold greater increase in expenditures on habitat management programs relative to culture programs in six agencies that provided budget figures. The percentage of responding agencies evaluating appropriateness of stocking through the use of formal criteria on at least half the waters where cultured fish were used tripled since 1980, and decisions not to stock due to potential impacts on biodiversity or the genetic integrity of recipient fish communities were reported to be four times more likely today than in 1980. Emphasis on the use of native fishes in stocking programs since 1980 was reported to have increased for more than half the agencies responding to our survey, and the number of agencies reporting development of broodstock plans for at least some of the species they cultured also doubled since 1980. Agency perceptions of angler attitudes concerning the importance of stocking indicated that the percentage of anglers who believed that stocking was the primary or only solution to low fish abundance remained high, at 61%, a decline of only 27% from reported attitudes in 1980. While positive strides have been made by agencies toward more careful evaluation of the appropriateness of stocking for achieving management objectives and in the institution of programs to minimize impacts of cultured fishes, these policies have not been adopted by all agencies, nor are they routinely used on all stocked waters by the agencies that have them. To make continued progress, agencies may be required to make difficult decisions regarding allocation of funding, and a more concerted effort to educate anglers and reduce public pressure for stockings will be needed to create an atmosphere where reduced emphasis on stocking is possible. The American Fisheries Society should play a continuing role in providing opportunities for scientists and policy makers to interact and discuss prevailing and emerging issues relative to the use of propagated fishes in resource management.
Atti di convegni sul tema "Pressure time integrals"
1
Gommerstadt, B. Y. "The J and M Integrals for a Cylindrical Cavity in a Time-Harmonic Wave Field". In ASME 2013 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/imece2013-65353.
Testo completoAbstract (sommario):
The invariant integrals are being widely used in the study of defects and fracture mechanics, mostly in elastostatics. However, the properties and the interpretation of these integrals in elastodynamics, especially in the case of time-harmonic excitation, have remained unexplored. Their study has a variety of engineering and geophysical implications, in particular, for the further development of non-destructive evaluation techniques. This contribution is focused on the derivation of the time average J integral for a cylindrical inhomogeneity and M integral for a cylindrical cavity placed in a monochromatic plane elastic wave of arbitrary wavelength. It is shown in the context of antiplane linear elasticity, that the J integral or the material force acting on the inhomogeneity resembles the radiation pressure force exerted on a dielectric cylinder by the normally incident electromagnetic wave. Based on the existing solution of this electrodynamic problem and the corresponding acoustic problem, the J integral is expressed as a function of the nondimensional wave number in the form of the partial wave expansion of the scattering theory. Employing the same classical method as for the J integral, the closed-form solution for the time average M integral for a traction-free cavity is also obtained as a function of the nondimensional wave number. The M integral, i.e., the expansion moment per unit length on an infinitely long circular cavity, is represented in terms of the scattering phase shifts as in the case of the J integral. Rather different expressions for the cavity are also derived for both integrals, which can be used more conveniently for numerical calculations, and these calculations are carried out for J and M integrals in a wide spectrum of frequencies. Asymptotic approximations of both integrals for low and high frequencies are presented. The long wavelength approximation, including the monopole and dipole contributions, has been provided for the J integral in the form of simple analytical expression. The value of M integral in the vanishing frequency limit is also presented. In the opposite short wavelength limit, the corresponding asymptotic values are derived for both integrals. These solutions which are valid for the empty cavity are extended to the case of inviscid fluid-filled cavity. The obtained results can be used in the area of non-destructive evaluation for the flaw characterization by ultrasonic scattering methods. The derived frequency dependence of the J and M integral can be related to the measurable far-field scattering amplitudes. This relationship is relevant to the inverse-scattering approach, which can be applied to the characterization of materials in an attempt to infer geometrical characteristics of flow structures.
2
Apte, Shrinivas G., e Brian H. Dennis. "Pseudo Compressible Mixed Interpolation Finite Element Method for Solving Three Dimensional Navier-Stokes Equations". In ASME 2013 International Design Engineering Technical Conferences and Computers and Information in Engineering Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/detc2013-13484.
Testo completoAbstract (sommario):
A pseudo compressible finite element method for solving three dimensional incompressible Navier-Stokes equations is presented. A physical problem discretized using tetrahedral elements with linear and quadratic interpolation functions for pressure and velocity variables respectively is then marched in time by using implicit time marching scheme based on finite differencing. The possible formation of indefinite matrix due to incompressibility constraint is avoided by inserting an artificial/pseudo time dependent term (Chorin, 1974) into the continuity equation that is eliminated when steady state is reached. This definite matrix system can then be solved using standard pre-conditioners and iterative solvers. Solutions for pressure driven flows obtained using this method are validated with the ones obtained from a standard problem of flow over a cylinder and also with numerical benchmark case of a 3-D laminar flow around an obstacle. An object oriented C++ program was developed which uses exact integrals of shape functions in its calculations rather than numerical integrations. This program was tested with different values of artificial compressibility factor (β), Reynolds numbers (Re) and grid sizes (number of Elements) and time steps (dt). The effect of these parameters on the the number of linear solver iterations required for convergence is studied efficiently using the non-dimensional numbers Pseudo Compressibility Number (PCN) and Elemental Reynolds Number (ERe). Although the relationship between the linear solver performance and these two non dimensional numbers remain complicated, it is found that there exists an optimum range of PCN as a function of ERe for which the solution convergence can be obtained with the minimum number of iterations.
3
Toyoshima, Manabu, e Chikahiro Minowa. "Discussion on Two Times Integral Displacements of Strong Ground Motion Records and Shaking Table Data". In ASME 2003 Pressure Vessels and Piping Conference. ASMEDC, 2003. http://dx.doi.org/10.1115/pvp2003-1821.
Testo completoAbstract (sommario):
In this paper, two times integral of acceleration record was discussed by the use of strong earthquake motion data; recorded in the 1999 Kocaeli (Turkey) Earthquake data. Usually, the two times integral displacements of horizontal seismic acceleration records will diverge. It was estimated for the integral displacement to diverge by the baseline shift caused on sensor tilting during quake. The data was simulated in 3 dimensional and 6 freedom shaking table. The divergent process of seismic data and shaking table data were studied.
4
Funai, Madoka, Osamu Watanabe e Akihiro Matsuda. "Inelastic FE Analysis for J-Integral of Center-Cracked Plate in Creep-Fatigue Range". In ASME 2014 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/pvp2014-28605.
Testo completoAbstract (sommario):
In order to estimate crack growth rate, it is necessary to use increments of the J-integral for both of time-independent fatigue process and time-dependent creep process. Many researchers and methodologies use C* to characterize creep crack growth and ΔJ or ΔK for fatigue crack growth, suggested are the following Refs.[1,2] This paper shows the fundamental features of J-integral in elastic, plastic and creep range. The path dependency is studied for center-cracked plate by using path integral from the large path to the small path near crack tip. The inelastic FE analysis is carried out for creep-fatigue loading, where the tensile strain is held constant to receive creep damage, and this paper shows the J-integral according to the loading histories. Also discussed are effects of the strain rate in fatigue process to affect the successive creep behavior.
5
Mohamed, Bassel Y., e Tamer I. Eid. "Analytical Comparison Between Separate Reinforcement Nozzle and Integral Reinforcement Nozzle Behaviors Under Cyclic Loading". In ASME 2016 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2016. http://dx.doi.org/10.1115/pvp2016-63318.
Testo completoAbstract (sommario):
ASME code explicitly addresses design for fatigue due to pressure or temperature cycles. Protection against fatigue failure due to cyclic external mechanical loads (e.g. piping loads) is not tackled in depth. This paper provides a less-tedious yet fit-for-purpose approach to evaluate the effect of cyclic external mechanical loads as well as the pressure fluctuations — as a result of piping slug flow — on nozzles fatigue life. The evaluation compares between two types of nozzles construction (configuration); separate reinforcement nozzle and readily radiographed (lip type) integrally reinforced nozzle. Within the analysis, a unity fatigue damage ratio or exceeding the ratcheting allowable limits was selected as the indication for the inadequacy of the reinforcement configuration. COMPRESS® FEA software results comprehensively predict that the separate reinforcement nozzles can’t withstand the imposed cyclic loads since the accumulated fatigue damage are greater than 1 (one) implying that the nozzle will experience fatigue failure before the end of its life time. COMPRESS® FEA results were examined at four locations, namely “shell next to nozzle”, “nozzle next to shell”, “nozzle thickness transition” and “shell away from nozzle”. The maximum stress of the four locations was always at “shell next to nozzle”. These results have been verified against SOLIDWORKS® simulation FEA results. The results show that the separate reinforcement nozzle construction, although adequate for static loadings, has less fatigue life compared to the integral reinforcement nozzle construction. Moreover, progressive distortion of the non-integral (separate) reinforcement connection is predicted showing that the mating members may become loose at the end of each complete operating cycle which could eventually cause disengagement. Additionally, the results support ASME 2004, VIII-2 para. 5-112 recommendations in prohibiting fillet welds in joints of category D for components subject to fatigue service. The paper concludes the advantage of integral reinforced readily radiographed nozzle construction in protection against fatigue failure and ratcheting and also provides a roadmap for simplified fatigue analysis using commercially available software.
6
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.
7
Funai, Madoka, Osamu Watanabe e Akihiro Matsuda. "Estimation of Crack Growth Rate by J-Integral Range for Type SUS304 Stainless Steel Plate in Creep-Fatigue Tests at High Temperature". In ASME 2014 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/pvp2014-28598.
Testo completoAbstract (sommario):
In structures having stress concentration under cyclic loading, a small crack initiates and it grows and propagates. Evaluating crack growth is important to estimate the remaining life of cracked components. The present paper shows the estimation of crack growth rate under creep-fatigue loading with some patterns of strain holding times. Creep-fatigue tests of the perforated plate having initial crack were conducted with the different strain holding time under strain-controlled loading at 550°C. The crack growth was observed from the photographs taken at each cycle. The crack growth per one cycle of creep-fatigue loading was evaluated by the creep-fatigue crack propagation law which used increment J-integral range. Comparing the crack growth rates of experimental with those of predicted, the crack growth rates were predicted by using increment J-integral range with the accuracy was factor of 2.
8
Chang, Shuenn-Yih, e Chiu-Li Huang. "Time Integration Method With Structure-Dependent Difference Equations". In ASME 2013 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/pvp2013-97044.
Testo completoAbstract (sommario):
A novel family of structure-dependent integration method is proposed for time integration. This family method can have the possibility of unconditional stability, second-order accuracy and the explicitness of each time step. Since it can integrate the most important advantage of an implicit method, unconditional stability, and that of an explicit method, the explicitness of each time step, a lot of computational efforts can be saved in solving an inertial type problem, where the total response is dominated by low frequency modes and high frequency responses are of no interest.
9
Orynyak, Igor, e Andrii Oryniak. "Computational Aspect of Nonlinear Fracture Mechanics Application". In ASME 2015 Pressure Vessels and Piping Conference. American Society of Mechanical Engineers, 2015. http://dx.doi.org/10.1115/pvp2015-45838.
Testo completoAbstract (sommario):
The development of powerful commercial computer programs made the concept of J-integral as computational parameter of fracture mechanics to be a very attractive one. It is equivalent to SIF in linear case, it converges in numerical calculation and the same results are obtained by different codes (programs). Besides, it is widely thought that elastic-plastic analysis gives bigger values than elastic SIF ones what is good from regulatory point of view. Such stand was reflected in the recommended by IAEA TECDOC 1627 (February 2010) devoted to pressurized thermal shock analysis of reactor pressure vessels, where the embedded crack in FEM mesh, elastic-plastic analysis with simultaneous determination of J-integral was stated as the best option of analysis. But at that time all the most widely used software were not able to treat the residual stresses, the thermal stresses in case of two different materials. Such a contradiction between requirements and the possibilities made a lot of problems for honest contractors especially in countries where the regulator had no own experience in calculation and completely relied on the authority of international documents. This means that at that time the said recommendations were harmful. The main reason of such a situation was the absence of the carefully elaborated examples. Now the capabilities and accuracy of such software are increasing. Nevertheless, some principal ambiguities and divergences of computations results in various J-integral contours around the crack tip still exist. They are exhibited when the large plastic zone emerges at the crack tip. Other problem is influence of the history of loading and the specification of the time of crack insertion in the mesh including the time of emergence of residual stress. This paper is invitation for discussion of the accuracy and restriction of computational J-integral. With this aim the detailed analysis of some simplified 2D examples of calculation of elastic -plastic J-integral for surface crack with accounting for residual stress, thermal stress and inner pressure are performed and commented. The attainment of consensus among the engineering society for treating the outcome results is the prerequisite for practical application of computational elastic plastic J-integral.
10
Oh, Chang-Young, Tae-Kwang Song e Yun-Jae Kim. "An Estimation of C(t) of Transient Creep Under Combined Mechanical and Thermal Stresses". In ASME 2010 Pressure Vessels and Piping Division/K-PVP Conference. ASMEDC, 2010. http://dx.doi.org/10.1115/pvp2010-25372.
Testo completoAbstract (sommario):
In this paper, a prediction of C(t), a crack tip parameter for the transient creep condition, for the circumferential cracked pipe under combined mechanical and thermal stresses are presented. The estimation formulae for C(t)-integral of the cracked component operating under mechanical load alone have been provided for decades [1–6]. However, high temperature structures usually work under combined mechanical and thermal load. And the interactions between mechanical and thermal loads make the relaxation rate different from those produced under mechanical load alone. In this study, 3-dimensional finite element analyses are conducted to calculate the C(t)-integral under combined mechanical and thermal load. As a result, redistribution time for the crack under combined mechanical and thermal load is re-defined to quantify the C(t)-integral. The estimation of C(t)-integral using this proposed redistribution time agrees well with FE results.
Rapporti di organizzazioni sul tema "Pressure time integrals"
1
Delwiche, Michael, Boaz Zion, Robert BonDurant, Judith Rishpon, Ephraim Maltz e Miriam Rosenberg. Biosensors for On-Line Measurement of Reproductive Hormones and Milk Proteins to Improve Dairy Herd Management. United States Department of Agriculture, febbraio 2001. http://dx.doi.org/10.32747/2001.7573998.bard.
Testo completoAbstract (sommario):
The original objectives of this research project were to: (1) develop immunoassays, photometric sensors, and electrochemical sensors for real-time measurement of progesterone and estradiol in milk, (2) develop biosensors for measurement of caseins in milk, and (3) integrate and adapt these sensor technologies to create an automated electronic sensing system for operation in dairy parlors during milking. The overall direction of research was not changed, although the work was expanded to include other milk components such as urea and lactose. A second generation biosensor for on-line measurement of bovine progesterone was designed and tested. Anti-progesterone antibody was coated on small disks of nitrocellulose membrane, which were inserted in the reaction chamber prior to testing, and a real-time assay was developed. The biosensor was designed using micropumps and valves under computer control, and assayed fluid volumes on the order of 1 ml. An automated sampler was designed to draw a test volume of milk from the long milk tube using a 4-way pinch valve. The system could execute a measurement cycle in about 10 min. Progesterone could be measured at concentrations low enough to distinguish luteal-phase from follicular-phase cows. The potential of the sensor to detect actual ovulatory events was compared with standard methods of estrus detection, including human observation and an activity monitor. The biosensor correctly identified all ovulatory events during its testperiod, but the variability at low progesterone concentrations triggered some false positives. Direct on-line measurement and intelligent interpretation of reproductive hormone profiles offers the potential for substantial improvement in reproductive management. A simple potentiometric method for measurement of milk protein was developed and tested. The method was based on the fact that proteins bind iodine. When proteins are added to a solution of the redox couple iodine/iodide (I-I2), the concentration of free iodine is changed and, as a consequence, the potential between two electrodes immersed in the solution is changed. The method worked well with analytical casein solutions and accurately measured concentrations of analytical caseins added to fresh milk. When tested with actual milk samples, the correlation between the sensor readings and the reference lab results (of both total proteins and casein content) was inferior to that of analytical casein. A number of different technologies were explored for the analysis of milk urea, and a manometric technique was selected for the final design. In the new sensor, urea in the sample was hydrolyzed to ammonium and carbonate by the enzyme urease, and subsequent shaking of the sample with citric acid in a sealed cell allowed urea to be estimated as a change in partial pressure of carbon dioxide. The pressure change in the cell was measured with a miniature piezoresistive pressure sensor, and effects of background dissolved gases and vapor pressures were corrected for by repeating the measurement of pressure developed in the sample without the addition of urease. Results were accurate in the physiological range of milk, the assay was faster than the typical milking period, and no toxic reagents were required. A sampling device was designed and built to passively draw milk from the long milk tube in the parlor. An electrochemical sensor for lactose was developed starting with a three-cascaded-enzyme sensor, evolving into two enzymes and CO2[Fe (CN)6] as a mediator, and then into a microflow injection system using poly-osmium modified screen-printed electrodes. The sensor was designed to serve multiple milking positions, using a manifold valve, a sampling valve, and two pumps. Disposable screen-printed electrodes with enzymatic membranes were used. The sensor was optimized for electrode coating components, flow rate, pH, and sample size, and the results correlated well (r2= 0.967) with known lactose concentrations.
2
Wideman, Jr., Robert F., Nicholas B. Anthony, Avigdor Cahaner, Alan Shlosberg, Michel Bellaiche e William B. Roush. Integrated Approach to Evaluating Inherited Predictors of Resistance to Pulmonary Hypertension Syndrome (Ascites) in Fast Growing Broiler Chickens. United States Department of Agriculture, dicembre 2000. http://dx.doi.org/10.32747/2000.7575287.bard.
Testo completoAbstract (sommario):
Background PHS (pulmonary hypertension syndrome, ascites syndrome) is a serious cause of loss in the broiler industry, and is a prime example of an undesirable side effect of successful genetic development that may be deleteriously manifested by factors in the environment of growing broilers. Basically, continuous and pinpointed selection for rapid growth in broilers has led to higher oxygen demand and consequently to more frequent manifestation of an inherent potential cardiopulmonary incapability to sufficiently oxygenate the arterial blood. The multifaceted causes and modifiers of PHS make research into finding solutions to the syndrome a complex and multi threaded challenge. This research used several directions to better understand the development of PHS and to probe possible means of achieving a goal of monitoring and increasing resistance to the syndrome. Research Objectives (1) To evaluate the growth dynamics of individuals within breeding stocks and their correlation with individual susceptibility or resistance to PHS; (2) To compile data on diagnostic indices found in this work to be predictive for PHS, during exposure to experimental protocols known to trigger PHS; (3) To conduct detailed physiological evaluations of cardiopulmonary function in broilers; (4) To compile data on growth dynamics and other diagnostic indices in existing lines selected for susceptibility or resistance to PHS; (5) To integrate growth dynamics and other diagnostic data within appropriate statistical procedures to provide geneticists with predictive indices that characterize resistance or susceptibility to PHS. Revisions In the first year, the US team acquired the costly Peckode weigh platform / individual bird I.D. system that was to provide the continuous (several times each day), automated weighing of birds, for a comprehensive monitoring of growth dynamics. However, data generated were found to be inaccurate and irreproducible, so making its use implausible. Henceforth, weighing was manual, this highly labor intensive work precluding some of the original objectives of using such a strategy of growth dynamics in selection procedures involving thousands of birds. Major conclusions, solutions, achievements 1. Healthy broilers were found to have greater oscillations in growth velocity and acceleration than PHS susceptible birds. This proved the scientific validity of our original hypothesis that such differences occur. 2. Growth rate in the first week is higher in PHS-susceptible than in PHS-resistant chicks. Artificial neural network accurately distinguished differences between the two groups based on growth patterns in this period. 3. In the US, the unilateral pulmonary occlusion technique was used in collaboration with a major broiler breeding company to create a commercial broiler line that is highly resistant to PHS induced by fast growth and low ambient temperatures. 4. In Israel, lines were obtained by genetic selection on PHS mortality after cold exposure in a dam-line population comprising of 85 sire families. The wide range of PHS incidence per family (0-50%), high heritability (about 0.6), and the results in cold challenged progeny, suggested a highly effective and relatively easy means for selection for PHS resistance 5. The best minimally-invasive diagnostic indices for prediction of PHS resistance were found to be oximetry, hematocrit values, heart rate and electrocardiographic (ECG) lead II waves. Some differences in results were found between the US and Israeli teams, probably reflecting genetic differences in the broiler strains used in the two countries. For instance the US team found the S wave amplitude to predict PHS susceptibility well, whereas the Israeli team found the P wave amplitude to be a better valid predictor. 6. Comprehensive physiological studies further increased knowledge on the development of PHS cardiopulmonary characteristics of pre-ascitic birds, pulmonary arterial wedge pressures, hypotension/kidney response, pulmonary hemodynamic responses to vasoactive mediators were all examined in depth. Implications, scientific and agricultural Substantial progress has been made in understanding the genetic and environmental factors involved in PHS, and their interaction. The two teams each successfully developed different selection programs, by surgical means and by divergent selection under cold challenge. Monitoring of the progress and success of the programs was done be using the in-depth estimations that this research engendered on the reliability and value of non-invasive predictive parameters. These findings helped corroborate the validity of practical means to improve PHT resistance by research-based programs of selection.