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Articles de revues sur le sujet "High velocity - low amplitude technique (HVLA)"
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Flaum, Theodore B., Arfa Mirza, Frances Mary-Ann Rusnack, Theresa E. Apoznanski, Aida Munarova, Joseph Mazzie, Michael John Terzella et Sheldon C. Yao. « Palpatory and Ultrasound Assessment of Cervical Dysfunctions and the Effect of Cervical High-Velocity, Low-Amplitude (HVLA) Technique ». AAO Journal 27, no 3 (1 décembre 2017) : 9–16. http://dx.doi.org/10.53702/2375-5717-27.3.9.
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Abstract Background Ultrasound is commonly used to assess musculoskeletal abnormalities. High-velocity, low-amplitude (HVLA) is an osteopathic manipulative treatment technique commonly used by osteopathic physicians. The Shaw et al study has shown the reliability of ultrasound in measuring the improvement of rotational symmetry of lumbar somatic dysfunction (SD) after the use of HVLA. Objectives The purpose of this study was to evaluate the use of ultrasonography as a reference tool to quantitatively assess the rotational symmetry of cervical SD after the use of HVLA. Design The study was separated into 2 phases: 1) cervical diagnosis and pretreatment imaging and 2) HVLA or cranial vault hold (CVH) and post-treatment imaging. Method Two physicians independently diagnosed each participant (N = 51) with an SD between levels C2–C7; the key SD (the segment with the most posteriorly rotated articular pillar (AP)) was chosen. Ultrasound imaging was performed immediately after diagnosis. Next, the participants were randomly distributed into a treatment group, in which the participants were treated with HVLA, and a control group, in which a CVH was performed on the participant. Members of the HVLA group were then reassessed to confirm the key SD had resolved. Ultrasound imaging was immediately performed at the level of the segment with the key SD after HVLA reassessment or CVH completion. Results Physician reassessment confirmed SD resolution in 25 of 25 HVLA participants and 0 of 26 control participants. There was no significant change in ultrasound-measured AP rotation for the HVLA group (M=.05680 cm, P=.179) or control group (M=.02384 cm, P=.160). Conclusions Despite a palpatory resolution of the cervical SD, ultrasound was not able to determine a statistically significant change in AP rotation in either the HVLA or the control group.
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Hu, Annette, Thomas Motyka, Eric Gish et Godwin Dogbey. « Teaching and use of cervical high-velocity, low-amplitude manipulation at colleges of osteopathic medicine ». Journal of Osteopathic Medicine 121, no 3 (11 février 2021) : 265–70. http://dx.doi.org/10.1515/jom-2020-0120.
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Abstract Context Despite the documented effectiveness of high-velocity, low-amplitude (HVLA) treatment of the cervical spine, concerns about patient safety potentially limit didactic instruction and use in clinical practice. Understanding how cervical HVLA is taught and employed is of interest to osteopathic educators and clinicians. Objectives To characterize the perspectives of osteopathic manipulative medicine/osteopathic principles and practices (OMM/OPP) departments within colleges of osteopathic medicine (COMs) in the US regarding patterns of teaching and practice of HVLA treatment of the cervical spine. Methods A questionnaire was distributed on April 11, 2019 in paper format to OMM/OPP department chairs or designated faculty member attendees at the Educational Council on Osteopathic Principles biannual meeting. If the department chair was not available, the survey was provided to the faculty member designated to represent the Chair of the institution at ECOP. All respondents in this category returned the survey in paper before they left the meeting. The OMM/OPP department chairs who did not attend or send representatives to the ECOP meeting were sent the survey by email on April 11, 2019 and given three opportunities over 6 weeks at 2-week intervals to reply to this voluntary online survey. The survey was given or sent to a total of 51 OMM/OPP department chairs or representatives. Six questions elicited demographic information pertaining to status, age, gender, ethnicity, board-certified specialty, and COM affiliation. Nine questions examined perspectives related to the instruction of cervical HVLA manipulation and treatment. Results Of the 51 OMM/OPP department chairs surveyed, 38 (74.5%) responded, 32 to the paper survey at the ECOP meeting and six to the digital survey. Respondents were primarily dual Board-certified in Family Medicine and Neuromuscular Medicine (55.3%). At over 90% (35) of the COMs for which department chairs responded to the survey, cervical HVLA instruction occurs in the curriculum primarily during program years 1 and 2. Instruction in cervical HVLA to the 2nd through 7th cervical vertebral levels occurred in 97% (37), while 11% (4) of the COMs excluded the occipital-atlanto (OA) and atlanto-axial (AA) joints. A high percentage (81.6%; 31) of the OMM/OPP department chairs or representatives reported employing cervical HVLA techniques within their practice. Among the respondents, 40.5% (15) reported that 0–25% of their school’s medical school class could perform cervical HVLA competently upon graduation, whereas 27% (10) said that 51–75% of their class could perform cervical HVLA. Conclusions A majority of COMs provide education in their curricula related to cervical HVLA primarily in the first 2 years of medical education. However, instruction often excludes cervical HVLA to the upper regions of the cervical spine. At COMs where HVLA to the cervical spine is not taught, that decision is because the techniques are thought to be too difficult and the attendant medicolegal risk perceived to be too high. OMM/OPP department chairs expressed confidence in only a small proportion of their graduates having the ability to competently apply HVLA to the cervical spine immediately after completing their predoctoral medical training.
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Barnes, Precious L., Frank J. Casella, Hilda Lai, Olavi Airaksinen et Michael L. Kuchera. « Retention of tissue texture change after cervical muscle energy and high velocity low amplitude intervention : implications for treatment intervals ». Journal of Osteopathic Medicine 122, no 4 (24 janvier 2022) : 203–9. http://dx.doi.org/10.1515/jom-2021-0187.
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Abstract Context When choosing to incorporate osteopathic manipulative treatment (OMT) into a patient’s care, the risk-to-benefit ratio, the choice of treatment technique, as well as the frequency of treatments are always taken into consideration. This has been even more important during the COVID-19 pandemic, in which social distancing has been the best preventative measure to decrease exposure. By increasing treatment intervals, one could not only limit possible exposure/spread of viruses but also decrease the overall cost to the system as well as to the individual. This is an expansion of a previous study in which quantifiable changes in cervical hysteresis characteristics post-OMT were documented utilizing a durometer (Ultralign SA201®; Sigma Instruments; Cranberry, PA USA). This study compared two treatment modalities, muscle energy (ME) and high-velocity low-amplitude (HVLA) postcervical treatment. Subjects in this study were allowed to re-enroll, provided that they could be treated utilizing the alternate treatment modality. By allowing repeat subjects, analysis of the data for lasting effects of OMT could be observed. Objectives To determine whether a significant change in cervical hysteresis would be observed after each treatment regardless of a short treatment interval. Methods A total of 34 subjects were retrospectively noted to be repeat subjects from a larger, 213-subject study. These 34 subjects were repeat participants who were treated with two different direct-treatment modalities 7–10 days apart. Each subject was randomly assigned to receive a single-segmental ME or HVLA treatment technique directed toward a cervical (C) segment (C3–C5 only). Subjects were objectively measured pretreatment in all cervical segments utilizing the Ultralign SA201®, then treated with cervical OMT to a single segment, and finally reassessed at all cervical levels with the Ultralign SA201® posttreatment to assess for change in cervical hysteresis. Results Statistically significant or suggestive changes (p-values 0.01–0.08) with good clinical effect size (0.30 or greater) were noted in all four components of the Ultralign SA201® at multiple cervical levels after the first treatment, but only one component (frequency) had a statistically significant change after the second treatment (AA cervical level, p-value 0.01) with good clinical effect size (0.45). However, when comparing the post–first-treatment values to the pre–second-treatment values, no statistically significant differences (p-value 0.10 or higher) were observed between them. Conclusions Statistically significant changes were noted after the first treatment; however, when comparing cervical hysteresis changes after the first treatment to the cervical hysteresis values prior to the second treatment delivered 7–10 days later, there were no statistically significant or suggestive changes. This data suggest that several post-OMT changes noted after the first treatment were still in effect and may indicate that follow-up visits for direct manipulation may be deferred for a least two weeks.
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Price, James W. « A mixed treatment comparison of selected osteopathic techniques used to treat acute nonspecific low back pain : a proof of concept and plan for further research ». Journal of Osteopathic Medicine 121, no 6 (24 février 2021) : 571–82. http://dx.doi.org/10.1515/jom-2020-0268.
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Abstract Context Back injuries have a high prevalence in the United States and can be costly for both patients and the healthcare system at large. While previous guidelines from the American College of Physicians for the management of acute nonspecific low back pain (ANLBP) have encouraged nonpharmacologic management, those treatment recommendations involved only superficial heat, massage, acupuncture, and spinal manipulation. Investigation about the efficacy of spinal manipulation in the management of ANLBP is warranted. Objectives To compare the results in previously-published literature documenting the outcomes of osteopathic manipulative treatment (OMT) techniques used to treat ANLBP. The secondary objective of this study was to demonstrate the utility of using Bayesian network meta-analysis (NMA) to perform a mixed treatment comparison (MTC) of a variety of osteopathic techniques. Methods A literature search for randomized controlled trials (RCTs) of ANLBP treatments was performed in April 2020 according to PRISMA guidelines by searching MEDLINE/PubMed, OVID, Cochrane Central, PEDro, and OSTMED.Dr databases; scanning the reference lists of articles; and using the Canadian Agency for Drugs and Technologies in Health grey literature checklist. Each database was searched from inception to April 1, 2020. The following search terms were used: acute low back pain, acute low back pain plus physical therapy, acute low back pain plus spinal manipulation, and acute low back pain plus osteopathic manipulation. The validity of eligible trials was assessed by the single author using an adapted National Institute for Health and Care Excellence methodology checklist for randomized, controlled trials and an extraction form based on that checklist. The outcome measure chosen for this NMA was the Visual Analogue Scale of pain. The NMA were performed using the GeMTC user interface for automated NMA utilizing a Bayesian hierarchical model of random effects. Results The literature search initially found 483 unduplicated records. After screening and full text assessment, five RCTs were eligible for the MTC, yielding a total of 430 participants. Results of the MTC model suggested that there was no statistically significant decrease in reported pain when exercise, high-velocity low-amplitude (HVLA), counterstrain, muscle energy technique, or a mix of techniques were added to conventional treatment to treat ANLBP. However, the rank probabilities assessment determined that HVLA and the OMT mixed treatment protocol plus conventional care were ranked superior to conventional care alone for improving ANLBP. Conclusions While this study failed to provide definitive evidence upon which clinical recommendations can be based, it does demonstrate the utility of performing NMA for MTCs of osteopathic modalities used to treat ANLBP. However, to take full advantage of this statistical technique, future studies should be designed with consideration for the methodological shortcomings found in past osteopathic research.
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Shafqat, Sadaf. « EFFICACY OF HIGH-VELOCITY LOW-AMPLITUDE SPINAL MANIPULATION FOR NON SPECIFIC LOW BACK PAIN ». Pakistan Journal of Rehabilitation 3, no 1 (10 janvier 2014) : 4–14. http://dx.doi.org/10.36283/pjr.zu.3.1/009.
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BACKGROUND Back pain is one of the most frequently seen health problems, affecting 9 out of 10 people in a population at some point during their lives. The lower back is the region most commonly affected. Low-back pain can be debilitating, and it is often challenging to treat Low Back Pain. OBJECTIVE The objective of this review is to evaluate the efficacy of High-Velocity Low-Amplitude (HVLA) Spinal Manipulative Therapy (SMT) for Non Specific Low Back Pain (NSLBP). STUDY DESIGN Systemic review METHODS Only articles that had adult (18 years and above) participants were included in this review and studies that classified the intervention as HVLA spinal manipulation were included. Studies that included spinal manipulation other than HVLA or studies of spinal manipulation under anesthesia were excluded. RESULTS Eight full text papers and three systemic reviews justifying the inclusion criteria are reviewed which revealed that high velocity low amplitude spinal manipulative therapy have significant effect in alleviating low back pain. CONCLUSION Spinal manipulation therapy is a distinctive approach that considerably decreases nonspecific low back pain however there is need of further clinical trials into this subject focusing solely on high velocity low amplitude spinal manipulation.
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Haavik, Heidi, Imran Khan Niazi, Nitika Kumari, Imran Amjad, Jenna Duehr et Kelly Holt. « The Potential Mechanisms of High-Velocity, Low-Amplitude, Controlled Vertebral Thrusts on Neuroimmune Function : A Narrative Review ». Medicina 57, no 6 (27 mai 2021) : 536. http://dx.doi.org/10.3390/medicina57060536.
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The current COVID-19 pandemic has necessitated the need to find healthcare solutions that boost or support immunity. There is some evidence that high-velocity, low-amplitude (HVLA) controlled vertebral thrusts have the potential to modulate immune mediators. However, the mechanisms of the link between HVLA controlled vertebral thrusts and neuroimmune function and the associated potential clinical implications are less clear. This review aims to elucidate the underlying mechanisms that can explain the HVLA controlled vertebral thrust--neuroimmune link and discuss what this link implies for clinical practice and future research needs. A search for relevant articles published up until April 2021 was undertaken. Twenty-three published papers were found that explored the impact of HVLA controlled vertebral thrusts on neuroimmune markers, of which eighteen found a significant effect. These basic science studies show that HVLA controlled vertebral thrust influence the levels of immune mediators in the body, including neuropeptides, inflammatory markers, and endocrine markers. This narravtive review discusses the most likely mechanisms for how HVLA controlled vertebral thrusts could impact these immune markers. The mechanisms are most likely due to the known changes in proprioceptive processing that occur within the central nervous system (CNS), in particular within the prefrontal cortex, following HVLA spinal thrusts. The prefrontal cortex is involved in the regulation of the autonomic nervous system, the hypothalamic–pituitary–adrenal axis and the immune system. Bi-directional neuro-immune interactions are affected by emotional or pain-related stress. Stress-induced sympathetic nervous system activity also alters vertebral motor control. Therefore, there are biologically plausible direct and indirect mechanisms that link HVLA controlled vertebral thrusts to the immune system, suggesting HVLA controlled vertebral thrusts have the potential to modulate immune function. However, it is not yet known whether HVLA controlled vertebral thrusts have a clinically relevant impact on immunity. Further research is needed to explore the clinical impact of HVLA controlled vertebral thrusts on immune function.
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Karason, Agust B., et Ian P. Drysdale. « Somatovisceral response following osteopathic HVLAT : a pilot study on the effect of unilateral lumbosacral high-velocity low-amplitude thrust technique on the cutaneous blood flow in the lower limb ». Journal of Manipulative and Physiological Therapeutics 26, no 4 (mai 2003) : 220–25. http://dx.doi.org/10.1016/s0161-4754(02)54110-5.
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King, Alicia A., Jayme Cox, Shalini Bhatia et Karen T. Snider. « Characteristics and treatment of geriatric patients in an osteopathic neuromusculoskeletal medicine clinic ». Journal of Osteopathic Medicine 121, no 5 (19 février 2021) : 503–11. http://dx.doi.org/10.1515/jom-2020-0220.
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Abstract Context Osteopathic manipulative medicine (OMM) is an adjunctive treatment approach available to geriatric patients, but few studies provide details about presenting conditions, treatments, and response to osteopathic manipulative treatment (OMT) in that patient population. Objectives To provide descriptive data on the presentation and management of geriatric patients receiving OMT at an outpatient osteopathic neuromusculoskeletal medicine (ONMM) clinic. Methods Data were retrospectively collected from electronic health records (EHR) at a single outpatient clinic for clinical encounters with patients over 60 years of age who were treated with OMT between July 1, 2016, and June 30, 2019. Records were reviewed for demographic information, insurance type, presenting concerns, assessments, regions treated, OMT techniques used, and treatment response. Results There were 9,155 total clinical encounters with 1,238 unique patients found during the study period. More women than men were represented for overall encounters (6,910 [75.4%] vs. 2,254 [24.6%]) and unique patients (850 [68.7%] vs. 388 [31.3%]; both p<0.001). The mean (standard deviation, SD) number of encounters per patient per year was 4.5 (4.0) and increased with increasing age by decade (p<0.001). Medicare was the most common primary insurance (7,246 [79.2%]), with private insurance the most common secondary insurance (8,440 [92.2%]). The total number of presenting concerns was 12,020, and back concerns were most common (6,406 [53.3%]). The total number of assessments was 18,290; most were neuromusculoskeletal (17,271 [94.5%]) and in the thoracolumbar region (7,109 [38.9%]). The mean (SD) number of somatic dysfunction assessments per encounter was 5 (1.7); the thoracic region was the most documented and treated (7,263 [15.8%]). With up to 19 technique types per encounter, the total number of OMT techniques documented across all encounters was 43,862, and muscle energy (7,203 [16.4%]) was the most documented. The use of high-velocity, low-amplitude (HVLA) declined as age increased (p<0.001). The overall treatment response was documented in 7,316 (79.9%) encounters, and most indicated improvement (7,290 [99.6%]). Conclusions Our results showed that geriatric patients receiving OMT at our clinic were predominately presenting for neuromusculoskeletal concerns associated with back, neck, and extremity conditions, consistent with national epidemiological data for this population. The most common OMT techniques were also consistent with those used nationally by osteopathic medical students and practicing physicians. Future longitudinal studies are needed to determine the length of time improvement persists and the overall health impact experienced by geriatric patients receiving OMT.
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Shannon, Zacariah K., Robert D. Vining, Maruti Ram Gudavalli et Ron J. Boesch. « High-velocity, low-amplitude spinal manipulation training of prescribed forces and thrust duration : A pilot study ». Journal of Chiropractic Education 34, no 2 (5 avril 2019) : 107–15. http://dx.doi.org/10.7899/jce-18-19.
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Objective High-velocity, low-amplitude spinal manipulation (HVLA-SM) may generate different therapeutic effects depending on force and duration characteristics. Variability among clinicians suggests training to target specific thrust duration and force levels is necessary to standardize dosing. This pilot study assessed an HVLA-SM training program using prescribed force and thrust characteristics. Methods Over 4 weeks, chiropractors and students at a chiropractic college delivered thoracic region HVLA-SM to a prone mannequin in six training sessions, each 30 minutes in duration. Force plates embedded in a treatment table were used to measure force over time. Training goals were 350 and 550 Newtons (N) for peak force and ≤150 ms for thrust duration. Verbal and visual feedback was provided after each training thrust. Assessments included 10 consecutive thrusts for each force target without feedback. Mixed-model regression was used to analyze assessments measured before, immediately following, and 1, 4, and 8 weeks after training. Results Error from peak force target, expressed as adjusted mean constant error (standard deviation), went from 107 N (127) at baseline, to 0.2 N (41) immediately after training, and 32 N (53) 8 weeks after training for the 350 N target, and 63 N (148), −6 N (58), and 9 N (87) for the 550 N target. Student median values met thrust duration target, but doctors' were >150 ms immediately after training. Conclusion After participation in an HVLA-SM training program, participants more accurately delivered two prescribed peak forces, but accuracy decreased 1 week afterwards. Future HVLA-SM training research should include follow-up of 1 week or more to assess skill retention.
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Reed, William R., Dong-Yuan Cao, Cynthia R. Long, Gregory N. Kawchuk et Joel G. Pickar. « Relationship between Biomechanical Characteristics of Spinal Manipulation and Neural Responses in an Animal Model : Effect of Linear Control of Thrust Displacement versus Force, Thrust Amplitude, Thrust Duration, and Thrust Rate ». Evidence-Based Complementary and Alternative Medicine 2013 (2013) : 1–12. http://dx.doi.org/10.1155/2013/492039.
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High velocity low amplitude spinal manipulation (HVLA-SM) is used frequently to treat musculoskeletal complaints. Little is known about the intervention’s biomechanical characteristics that determine its clinical benefit. Using an animal preparation, we determined how neural activity from lumbar muscle spindles during a lumbar HVLA-SM is affected by the type of thrust control and by the thrust's amplitude, duration, and rate. A mechanical device was used to apply a linear increase in thrust displacement or force and to control thrust duration. Under displacement control, neural responses during the HVLA-SM increased in a fashion graded with thrust amplitude. Under force control neural responses were similar regardless of the thrust amplitude. Decreasing thrust durations at all thrust amplitudes except the smallest thrust displacement had an overall significant effect on increasing muscle spindle activity during the HVLA-SMs. Under force control, spindle responses specifically and significantly increased between thrust durations of 75 and 150 ms suggesting the presence of a threshold value. Thrust velocities greater than 20–30 mm/s and thrust rates greater than 300 N/s tended to maximize the spindle responses. This study provides a basis for considering biomechanical characteristics of an HVLA-SM that should be measured and reported in clinical efficacy studies to help define effective clinical dosages.
Thèses sur le sujet "High velocity - low amplitude technique (HVLA)"
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Platania, Gabriele. « Efficacia delle manipolazioni thrust nel trattamento del low back pain in fase acuta e in fase cronica. Revisione della letteratura ». Bachelor's thesis, Alma Mater Studiorum - Università di Bologna, 2018. http://amslaurea.unibo.it/16914/.
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Background
Il low back pain è un disturbo comune nella società occidentale ed un fardello economico non indifferente. Si definisce come una condizione di dolore e disagio che si localizza al di sotto del margine costale e al di sopra della piega glutea inferiore, a cui si può associare o meno un dolore irradiato riferito all’arto inferiore. Le tecniche utilizzate per fare fronte a questa patologia sono molteplici, di queste la manipolazione thrust è una delle più comuni e popolari, utilizzata dai professionisti di tutto il mondo.
Obiettivo:
Valutare,attraverso le evidenze scientifiche presenti in letteratura, l’effetto delle tecniche manipolative di tipo Thrust sul Low Back Pain in fase acuta e cronica.
Metodi:
I dati sono stati ottenuti attraverso la ricerca all’interno di banche dati come PUBMED, COCHRANE e PEDRO.
Sono stati inclusi studi clinici randomizzati con restrizioni riguardanti il tempo di pubblicazione, il linguaggio, la reperibilità del full-text, la tipologia di pazienti e l’outcome primario.
Risultati
In base ai criteri di inclusione sono risultati eleggibili 4 studi e 2 revisioni Cochrane. Le evidenze non sono univoche nello schierarsi a favore di questa tecnica, visto che vari studi non sono riusciti a rilevare differenze significative tra le manipolazioni thrust e altre tecniche. In altri le ricerche hanno invece verificato come i pazienti trattati con thrust manipulation abbiano ottenuto miglioramenti degni di nota negli outcomes soprattutto a breve termine.
Conclusioni
La manipolazione thrust rimane una delle tecniche di elezione nel trattamento del Low Back Pain, se questa tecnica sia più efficace rispetto ad altre non è chiaro e spesso dipende da molti fattori. Si consiglia quindi di utilizzarla all’interno di un programma terapeutico emerso dal confronto del ragionamento clinico del singolo professionista con le preferenze del paziente, in base alle risorse disponibili.
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Eriksson, Andreas. « Finns det evidens för att höghastighetsmanipulation av nacken kan orsaka stroke ? » Thesis, Linnéuniversitetet, Institutionen för kemi och biomedicin (KOB), 2020. http://urn.kb.se/resolve?urn=urn:nbn:se:lnu:diva-98971.
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Höghastighetsmanipulation av nacken är en manuell behandlingsteknik mot smärta i framförallt nacken och skuldrorna. Tekniken har enligt flera källor visats hänga samman med risken för att drabbas av skador på de kärl som försörjer hjärnan med blod, med bland annat stroke som följd. Andra källor har å andra sidan visat att de är en teknik som är säker att utföra. Den här litteraturstudien har sammanställt och utvärderat forskning som på olika sätt söker utreda om det påstådda sambandet är kausalt eller inte. Metoden som valdes var att genom en av SBU färdigställd mall värdera forskningsartiklar och sedan sortera dem efter relevans, för att på så sätt avgöra huruvida sambandet kan ses som kausalt eller inte. Studieresultatet visade att frågan är för komplex för att kunna besvaras i en enskild studie, och att mer forskning behövs inom flera delområden innan frågan kan besvaras fullt ut. Orsaken till detta är att det finns flera orsaksmekanismer, och flera riskgrupper, för denna typ av skada, där flera ännu är okända. Detta gör att en fullständig kartläggning av samband i frågan ännu inte är möjlig. Däremot är det sannolikt att tekniken kan verka som en utlösande faktor, en trigger, hos vissa personer i riskgrupperna. Därför kan det sägas finnas en risk med tekniken rent praktiskt, oavsett om ett kausalt samband mellan tekniken och stroke i sig existerar eller inte.High Velocity Manipulation of the cervical spine is a manual treatment technique against pain in foremost the neck, shoulders. The technique has according to multiple sources been connected to the risk of injury to the blood vessels that supply the brain with blood, with among others stroke as a consequence. Other sources have on the other hand shown it the technique to be safe to perform. This literature study has compiled and evaluated research that in various ways tries to find out if said connection is causal The method used was to evaluate articles through a pre-made form from SBU, and then to sort them according to relevance to see if the connection is causal or not. The result showed that the question is too complex to be answered in a single study, and that more research is needed to answer the question in full. This is due to the fact that there are multiple mechanisms behinds this form om injury, that the risk seems to exists in certain groups, and that some of these are not yet identifiable. On the other hand there is a high probability that the technique might act as an activating factor in these groups. Because of this there can be said that a risk exists with the technique in practice, no matter if there is a casual connection between the technique and stroke in itself or not.
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Williams, Kevin. « An investigation of the lasting effects of thoracic manipulation and rib raising on spirometric measurements of asymptomatic participants ». Thesis, 2003. https://vuir.vu.edu.au/933/.
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Although research has been undertaken into the effects of manual intervention on common respiratory conditions, very little research has been undertaken into whether manual therapy can produce a significant improvement in the respiratory function of asymptomatic volunteers one week after the manual intervention. To test whether a relationship exists between the effects of thoracic HVLA and rib raising (RR) on the pulmonary function of asymptomatic volunteers one week after the manual intervention, 38 participants (males = 25, females = 13) were randomly assigned to either a HVLA (n=11), RR (n=14) or a HVLA + RR group (n=13). Statistically significant increases were observed in both FVC (p=0.005) and FEV1 (p=0.002) within each of the three groups over time (pre-test, post-test, 1 week). However, no significant increases were found neither in the chest diameter values within the three treatment groups with respect to time nor between the three groups at any of the three time periods. The greatest increases in percentage change occurred in FEV1 and FVC values at the 1 week time period, particularly for the HVLA + RR and the RR group in which respective FEV1 increases of 10.5% and 7.41% occurred. The results of this study suggest that HVLA and rib raising ought to be equally effective in improving the pulmonary function of asymptomatic individuals , given that no statistically significant difference was found between the mean FEV1 and FVC values within the 3 groups over time. Since previous research shows that rib raising produces within subject increases in both FEV1 and FVC over time that are statistically significant in asthmatics, it may be possible to infer that HVLA may be as useful an adjunct as rib raising in the long-term management of stable asthma.
This minor thesis was written by a post-graduate student as part of the requirements of the Master of Health Science (Osteopathy) program.
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Hamilton, Luke. « The effect of high-velocity, low-amplitude manipulation on suboccipital tenderness ». Thesis, 2005. https://vuir.vu.edu.au/821/.
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High-velocity, low-amplitude (HVLA) manipulation is commonly advocated by manual therapists to relieve spinal pain and dysfunction. The aim of this controlled, single blinded study was to investigate whether HVLA manipulation of the occipito-atlantal (OA) joint had any lasting effect on pressure pain thresholds (PPT) in the suboccipital musculature in an asymptomatic population.
HVLA manipulation of the OA joint did not significantly change the PPT of the suboccipital muscles in asymptomatic participants. HVLA produced a greater mean increase in PPT and effect size compared to the control group over both time intervals, and therefore investigation of the effect of this technique with a symptomatic population is warranted.
This minor thesis was written by a post-graduate student as part of the requirements of the Master of Health Science (Osteopathy) program.
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Buttigieg, Della. « Forces generated in high velocity, low amplitude manipulations of both the dominant and non-dominant rib 1 costotransverse joints : a pilot study ». Thesis, 2004. https://vuir.vu.edu.au/758/.
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Objective: To determine the force/time characteristics of prone rib 1 High Velocity, Low Amplitude (HVLA) manipulations.
Conclusions: Preload and peak thrust force closely related to each other and the production of a joint cavitation. No significant differences between the force/time characteristics of thrusts to dominant and non-dominant sides, other than post-thrust dip. The practical relevance of this parameter however, is questionable.
This minor thesis was written by a post-graduate student as part of the requirements of the Master of Health Science (Osteopathy) program.
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Nawrocki, Simon. « A comparison between muscle energy technique and high velocity low amplitude thrust technique on gross trunk rotation range of motion ». Thesis, 2004. https://vuir.vu.edu.au/854/.
Texte intégralRésumé :
Muscle energy technique (MET) and high velocity low amplitude (HVLA) thrust technique are two techniques commonly used by osteopaths and other musculoskeletal therapists. Despite their widespread use, there has been very limited research to compare the efficacy of HVLA and MET for increasing gross trunk rotation range of motion (ROM). Ninety volunteers (age range 18-40) were randomly assigned to either treatment (MET or HVLA) or control groups, and blinded pre-, immediately post- and thirty minutes post-active trunk rotation measures were recorded using a reliable measuring device. Volunteers in the treatment groups received a single application of either thoracolumbar MET or HVLA in the direction of the side (right or left), with the least ROM. Although demonstrating a statistically significant difference in gross trunk ROM immediately and 30 minutes following a single application of MET or HVLA, this was meaningless as it was within the error range of the test equipment. Overall this study failed to show a significant benefit in the use of these osteopathic treatment techniques in increasing gross trunk rotation ROM.
This minor thesis was written by a post-graduate student as part of the requirements of the Master of Health Science (Osteopathy) program.
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Nawrocki, Simon. « A comparison between muscle energy technique and high velocity low amplitude thrust technique on gross trunk rotation range of motion ». 2004. http://eprints.vu.edu.au/854/1/Nawrocki_et.al_2004.pdf.
Texte intégralRésumé :
Muscle energy technique (MET) and high velocity low amplitude (HVLA) thrust technique are two techniques commonly used by osteopaths and other musculoskeletal therapists. Despite their widespread use, there has been very limited research to compare the efficacy of HVLA and MET for increasing gross trunk rotation range of motion (ROM). Ninety volunteers (age range 18-40) were randomly assigned to either treatment (MET or HVLA) or control groups, and blinded pre-, immediately post- and thirty minutes post-active trunk rotation measures were recorded using a reliable measuring device. Volunteers in the treatment groups received a single application of either thoracolumbar MET or HVLA in the direction of the side (right or left), with the least ROM. Although demonstrating a statistically significant difference in gross trunk ROM immediately and 30 minutes following a single application of MET or HVLA, this was meaningless as it was within the error range of the test equipment. Overall this study failed to show a significant benefit in the use of these osteopathic treatment techniques in increasing gross trunk rotation ROM. This minor thesis was written by a post-graduate student as part of the requirements of the Master of Health Science (Osteopathy) program.
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Fuller, Luke. « The effect of thoracolumbar high velocity low amplitude manipulation on gross trunk range of motion : is the direction of thrust important ? » Thesis, 2004. https://vuir.vu.edu.au/813/.
Texte intégralRésumé :
High Velocity Low Amplitude (HVLA) is a form of spinal manipulation commonly used by Osteopaths and other manual medicine practitioners. Despite its widespread use, there is little experimental evidence that supports the efficacy of HVLA in the thoracolumbar region or whether the direction of thrust is important in altering rotation range of motion (ROM). This study investigated whether a single application of thoracolumbar HVLA, either into or away from the restrictive rotation barrier, could significantly increase an asymptomatic volunteer's gross trunk rotation ROM.
Thoracolumbar HVLA performed either into or away from the restrictive rotation barrier, had no significant effect on active, seated trunk rotation in asymptomatic volunteers with no fixed asymmetry.
This minor thesis was written by a post-graduate student as part of the requirements of the Master of Health Science (Osteopathy) program.
Chapitres de livres sur le sujet "High velocity - low amplitude technique (HVLA)"
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Bose, Tanmoy, N. S. V. N. Hanuman et Subhankar Roy. « Non-Destructive Testing of Carbon Fibre Reinforced Polymer (CFRP) Composite Using Thermosonic Technique ». Dans Handbook of Research on Developments and Trends in Industrial and Materials Engineering, 348–65. IGI Global, 2020. http://dx.doi.org/10.4018/978-1-7998-1831-1.ch015.
Texte intégralRésumé :
Composite materials are often subjected to low velocity impacts which leads to delamination in subsequent layers. Linear ultrasound-based approaches are not accurate enough to detect it properly. The local defect resonance (LDR) based thermosonic is proved to be an efficient candidate for detection of such defects. LDR frequency excitation leads to high amplitude vibration which raises defect temperature drastically, detectable by an infrared camera. In this chapter, a numerical investigation of LDR frequency excited ultrasound thermography is carried out on delaminated carbon fibre reinforced polymer (CFRP) plate. The location and size of the delamination can be easily understood from thermal signature. The temperature gradient variation is found to be high at first and then it decreases due to higher heat conduction rate. The delamination in CFRP plate is detected by standard phased array ultrasound testing (PAUT) using flat bottom hole in aluminium plate as a case study. Delamination detection by PAUT is found to be very time consuming process compared with thermosonic technique.
Actes de conférences sur le sujet "High velocity - low amplitude technique (HVLA)"
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Gudavalli, Maruti Ram, Ting Xia, Vijay Goel, Yi-Xian Qin, Randall Sozio et Joel G. Pickar. « Development of Experimental Set-Up to Simulate High Velocity Low Amplitude Spinal Manipulations to Validate Finite Element Models ». Dans ASME 2013 Conference on Frontiers in Medical Devices : Applications of Computer Modeling and Simulation. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/fmd2013-16030.
Texte intégralRésumé :
The authors have developed experimental set-up to simulate chiropractic high velocity low amplitude spinal manipulations (HVLA SM) used for treating low back pain. The experimental set-up was used to test fresh unembalmed lumbar spinal specimens Our experimental-set-up simulated HVLA SM manipulations such as doctors hand contact, anatomical locations of load application, durations of load, magnitudes of load. The results from the experimental set-up are used to validate finite element models that simulated HVLA SM.
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Balusamy, Saravanan, et Simone Hochgreb. « Comparison of Acoustic Velocity Perturbation Measurements Using PIV vs. Two-Microphone Technique ». Dans ASME 2013 Gas Turbine India Conference. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/gtindia2013-3512.
Texte intégralRésumé :
Understanding combustion instabilities requires accurate measurements of the acoustic velocity perturbation into injectors. This is often accomplished via the use of the two microphone technique, as this only requires two pressure transducers. However, measurements of the actual velocities emerging from the injectors are not often taken, leaving questions regarding the assumptions about the acoustic velocity. A comparison of velocity measured at downstream of the injector with that of two-microphone technique can show the accuracy and limitations of two-microphone technique. In this paper, velocity measurements are taken using both particle image velocimetry (PIV) and the two-microphone technique in a high pressure facility designed for aeroengine injector measurements. The flow is excited using an area modulation device installed on the choked end of the combustion chamber, with PIV measurements enabled by optical access downstream of the injector through a quartz tube and windows. Acoustic velocity perturbations at the injector are determined by considering the Fourier transformed pressure fluctuations for two microphones installed at a known distance upstream of the injector. PIV measurements are realized by seeding the air flow with micrometric water particles under 2.5 bar pressure at ambient temperature. Phase locked velocity fields are realized by synchronizing the acquisition of PIV images with the revolution of the acoustic modulator using the pressure signal measured at the face of injector. The mean velocity fluctuation is calculated as the difference between maximum and minimum velocities, normalized by the mean velocity of the unforced case. Those values are compared with the peak-to-peak velocity fluctuation amplitude calculated by the two-microphone technique. Although the ranges of velocity fluctuations for both techniques are similar, the variation of fluctuation with forcing frequencies diverges significantly with frequency. The differences can be attributed to several limitations associated with of both techniques, such as the quality of the signal, the signal/noise ratio, the accuracy of PIV measurements and the assumption of isentropic flow of the particle velocity from the plenum through the injector. We conclude that two-microphone methods can be used as a reference value for the velocity fluctuation in low order applications such as flame transfer functions, but not for drawing conclusions regarding the absolute velocity fluctuations in the injector.
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Mundla, V., J. R. Kadambi, S. Sastry, C. Deng et Y. Zhou. « Measurement of Liquid Layer Thickness Using Ultrasound Technique ». Dans ASME 2005 International Mechanical Engineering Congress and Exposition. ASMEDC, 2005. http://dx.doi.org/10.1115/imece2005-80022.
Texte intégralRésumé :
The use of ultrasound technique to obtain the liquid film thickness was investigated. Ultrasound imaging is a technique that uses high frequency sound waves to produce precise images of structures. Ultrasound imaging is based on the same principle as SONAR (Sound Navigation and Ranging) during which a transducer capable of generating and receiving high frequency sound waves, sends pulses of sound waves into the interrogation area and the sound reflected back (echo) form any interface (such as water air interface) within the interrogation plane is obtained by the transducer. The time taken for the sound wave to travel from the transducer surface to the water air interface is obtained from the delay of the echo signal with regard to the transmitted signal; this time is used to compute the distance of the interface knowing the velocity of sound in medium. An experiment was set up to measure the depth of water in a container using ultrasound technique. A-mode (amplitude-mode) scanning was used where a pulsed ultrasound wave is directed into the interrogation region and echoes generated at various interfaces are detected. It is observed that levels as low as 0.55 mm were measured.
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Tang, Deman, et Earl H. Dowell. « Effects of Steady Angle of Attack on Nonlinear Flutter of a Delta Wing Plate Model ». Dans ASME 2000 International Mechanical Engineering Congress and Exposition. American Society of Mechanical Engineers, 2000. http://dx.doi.org/10.1115/imece2000-1004.
Texte intégralRésumé :
Abstract Limit cycle oscillations (LCO) have been observed in flight for certain modern high performance aircraft. The nonlinear physical mechanism responsible for the LCO is still in doubt, even to the point of it not yet being determined whether the nonlinearity is principally in the flexible elastic structure of the aircraft or due to the fluid behavior in the surrounding aerodynamic flow field. One observation from flight tests is that by changing the angle of attack of aircraft, the flight velocity at which LCO begins may be raised or lowered and that the amplitude of the LCO may be reduced. It has been suggested that this sensitivity to angle of attack indicates the nonlinearity is in the fluid rather than in the structure. In the present paper we show that such effects of an angle of attack change can be the result of a structural nonlinearity. Specifically an investigation to determine the effects of a steady angle of attack on nonlinear flutter and limit cycle oscillation of a delta wing-plate model in low subsonic flow has been made. A three-dimensional time domain vortex lattice aerodynamic model and a reduced order aerodynamic technique are used and the structure is modeled using von Karman plate theory that allows for geometric strain-displacement nonlinearities in the delta wing structure. The results provide new insights into nonlinear aeroelastic phenomena not previously widely appreciated, i.e. limit cycle oscillations (LCO) for low aspect ratio wings that have a plate-like nonlinear structural behavior. The effects of a steady angle of attack on both the flutter boundary and the LCO are found to be significant. For a small steady angle of attack, α0 ≤ 0.1°, the flutter onset velocity increases, while for larger α0 it decreases. Moreover, as α0 increases, the maximum LCO amplitude decreases substantially. Such effects have been observed by Bunton and Denegri in flight flutter experiments. It is noted that the present theoretical results do not prove that the LCO phenomena observed in flight are due to structural nonlinearities; however, the results of the present analysis are consistent with those observed in flight and do show that a structural nonlinearity can give rise to the observed effects of angle of attack on LCO.
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Sherwood, Joseph, Jonathan Dusting, Efstathios Konstantinidis et Stavroula Balabani. « Flow-Induced Streamwise Vibration of a Flexibly-Mounted Cantilevered Cylinder in Steady and Pulsating Crossflow ». Dans ASME 2009 Pressure Vessels and Piping Conference. ASMEDC, 2009. http://dx.doi.org/10.1115/pvp2009-77293.
Texte intégralRésumé :
This paper describes an experimental study of the response of a freely vibrating cylinder with low mass ratio and high damping to steady and pulsating crossflow for Reynolds numbers in the range 120–2900. A rigid circular cylinder was cantilevered by means of a plate spring allowing it to oscillate in the stream-wise direction only. A camera-based technique was employed for tracking the cylinder vibration while the wake fluctuations were measured by a laser-Doppler system. The results show that the forced excitation from pulsating flow can take over control of the wake and/or the cylinder oscillations in a complex manner. The overall response depends strongly on two main parameters: the ratios of the pulsation frequency to the structural frequency and to the vortex shedding frequency from a fixed cylinder in steady flow. When the excitation frequency from both the wake and the external pulsation coincided with the natural frequency of the structure, the r.m.s. amplitude of the cylinder vibration increased up to 400% compared to that for the same reduced velocity in steady flow. In this case, maximum end displacements exceeded 35% of the cylinder diameter.
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Martínez, D. S., E. Pescini, F. Marra, M. G. De Giorgi et A. Ficarella. « Analysis of the Performance of Plasma Actuators Under Low-Pressure Turbine Conditions Based on Experiments and URANS Simulations ». Dans ASME Turbo Expo 2017 : Turbomachinery Technical Conference and Exposition. American Society of Mechanical Engineers, 2017. http://dx.doi.org/10.1115/gt2017-64867.
Texte intégralRésumé :
The present work is focused on the investigation of an alternate current driven single dielectric barrier discharge plasma actuator (AC-SDBDPA) for the control of separated flow at Reynolds numbers up to 2·104. Laminar boundary layer separation typically occurs on the suction surface of the low pressure turbines (LPT) blades when operating at high altitude cruise conditions, as the Reynolds number can drop below 2.5·104. In this context, the implementation of an active boundary layer control system able to operate in suppressing separation — only at the critical Reynolds numbers — is of great interest. The SDBDPA was manufactured by means of the photolithographic technique, which ensured a thin metal deposition with high manufacturing reliability control. Actuator operation under sinusoidal voltage at 8 kV amplitude and 2 kHz frequency was considered. Investigations were performed in a closed loop wind tunnel. A curved plate with a shape designed to reproduce the suction surface of a LPT was mounted directly over the bottom wall of the test section. The SDBDPA was inserted in a groove made at the middle of the curved plate, located at the front side of the adverse pressure gradient region. The flow pattern and velocities in absence of actuation were experimentally measured by a two-dimensional (2-D) particle image velocimetry (PIV) system and a laser Doppler velocimetry (LDV) system. PIV measurements were performed in presence of actuation. Simultaneously to the velocity measurements, the voltage applied to the AC-SDBDPA and the discharge current flowing through the circuit were acquired in order to determine the power dissipated by the device. The experimental data were supported by computational fluid dynamics (CFD) simulations based on the finite volume method. In order to deeply investigate the effect of flow separation control by the AC-SDBDPA on the LPT blade performances, the viscous and unsteady Reynolds-averaged Navier-Stokes equations were solved to predict the characteristics of the flow with and without actuation. The actuation effect was modelled as a time-constant body force calculated prior to the fluid flow simulations by using the dual potential algebraic model. The experimental data were used to calibrate and successfully validate the numerical model. An unsteady RANS (URANS) approach, using the k-ω Lam and Bremhorst Low-Reynolds turbulence model was employed, accounting with the main transient flow structures. Results showed that the mixing action of the streamwise fluid with higher momentum and the boundary layer fluid with the lower momentum -due to the AC-SDBDPA-led, depending on the tested Reynolds number, to the alleviation or suppression of the boundary layer flow separation which occurred on the suction surface of the LPT blade. The validated numerical model will allow expanding the study of the actuation effect including different locations and multiple devices, saving considerably experimental efforts.
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Ohuchida, S., T. Kawakubo et H. Tamaki. « Experimental Study of Rotating Stall in Vaneless Diffuser of a Centrifugal Compressor ». Dans ASME Turbo Expo 2013 : Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2013. http://dx.doi.org/10.1115/gt2013-95468.
Texte intégralRésumé :
In this study, with a focus on the rotating stall phenomenon in the vaneless diffuser of a centrifugal compressor, 2D-PIV is conducted to better understand the flow structure. Although many studies have reported concerning this problem, most data is obtained through experiments under lower speed conditions, using a simplified model or equipment. Unlike such studies, a ship board turbocharger compressor with a higher impeller rotation speed is selected as an application for the present measurement. In the measurement, an ensemble-averaged phase locking technique is also selected to compensate for the lack of time resolution of the PIV system. Since rotating stall in vaneless diffuser results in a huge amplitude of pressure fluctuation, the trigger signal for the ensemble-averaged measurement was constructed from diffuser wall pressure. The equipment layout for PIV is set to a cross sectional measurement of constant span height in the diffuser passage. PIV is conducted through a sight glass mounted on the diffuser shroud wall, the field of view of which is limited by its size. To obtain the whole flow structure of the diffuser passage, the measurement is repeated for different cyclic phases of the phenomenon. Five different span heights ranging from diffuser hub to shroud were selected as velocity measurement planes. The result obtained at the mid span indicates a typical pattern of the flow field containing containing low and high-velocity regions mutually in a circumferential direction. Considering other results obtained at different span heights, the whole flow structure is visualized and utilizing this data, both a wall separation pattern and a stall propagation mechanism are considered.
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Mahgoub, Mohamed, Guillaume Cambois, James Cowell et Suaad Khoori. « Benefits of Ultra-Dense 3D Spatial Sampling for Seismic Processing and Interpretation ». Dans Abu Dhabi International Petroleum Exhibition & Conference. SPE, 2021. http://dx.doi.org/10.2118/207719-ms.
Texte intégralRésumé :
Abstract The advances in seismic acquisition systems, especially onshore nodes, have made it possible to acquire ultra-dense 3D surveys at a reasonable cost. This new design enables accurate processing sequences that deliver higher resolution images of the subsurface. These images in turn lead to enhanced structural interpretation and better prediction of rock properties. In 2019, ADNOC and partners acquired an 81 square kilometer ultra-high density pilot survey onshore Abu Dhabi. The receivers were nimble nodes laid out on a 12.5x12.5m grid, which recorded continuously and stored the data on a memory chip. The sources were heavy vibrators sweeping the 2-110 Hz frequency range in 14 seconds on a 12.5x100m grid. 184 million traces per square kilometers did make such small area, the densest 3D seismic survey ever recorded. The single sensor data were expectedly very noisy and the unconstrained simultaneous shooting required elaborate deblending, but we managed these steps with existing tools. The dense 3D receiver grid actually enabled the use of interferometry-based ground-roll attenuation, a technique that is rarely used with conventional data due to inadequate sampling, but that resulted in increased signal-to-noise ratio. The data were migrated directly to depth using a velocity model derived after five iterations of tomographic inversion. The final image gathers were made of 18 reciprocal azimuths with 12.5m offset increment, resulting in 5,000 fold on a 6.25x6.25m grid. The main structural interpretation was achieved during the velocity model building stage. Key horizons were picked after the tomographic iterations and the velocity model was adjusted so that their depth matched the well markers. Anisotropic parameters were adjusted to maintain gather flatness and the new model was fed to the next iteration. This ultimately resulted in flat image gathers and horizons that tied to the wells. The final high-resolution data provided a much crisper image of the target clinoforms and faults. This resulted in a more detailed interpretation of the reservoirs. The data was subjected to pre-stack stratigraphic inversion. The availability of low frequency signal (down to 3 Hz) means that less well constraints are needed for the inversion. Preliminary results are particularly encouraging. Amplitude variations with azimuth have yet to be analyzed but data density bodes very well for the process. Ultra-dense 3D seismic acquisition is feasible and results in a step change in image quality. Structural and stratigraphic interpretation provided a more detailed image of faults and clinoforms. Stratigraphic inversion benefited from the low frequencies of the vibrator source and the increased spatial resolution.
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Varea, Emilien, Stephan Kruse, Heinz Pitsch, Thivaharan Albin et Dirk Abel. « Actuation Studies for Active Control of Mild Combustion for Gas Turbine Application ». Dans ASME Turbo Expo 2014 : Turbine Technical Conference and Exposition. American Society of Mechanical Engineers, 2014. http://dx.doi.org/10.1115/gt2014-27138.
Texte intégralRésumé :
MILD combustion (Moderate or Intense Low Oxygen Dilution) is a well known technique that can substantially reduce high temperature regions in burners and thereby reduce thermal NOx emissions. This technology has been successfully applied to conventional furnace systems and seems to be an auspicious concept for reducing NOx and CO emissions in stationary gas turbines. To achieve a flameless combustion regime, fast mixing of recirculated burnt gases with fresh air and fuel in the combustion chamber is needed. In the present study, the combustor concept is based on the reverse flow configuration with two concentrically arranged nozzles for fuel and air injections. The present work deals with the active control of MILD combustion for gas turbine applications. For this purpose, a new concept of air flow rate pulsation is introduced. The pulsating unit offers the possibility to vary the inlet pressure conditions with a high degree of freedom: amplitude, frequency and waveform. The influence of air flow pulsation on MILD combustion is analyzed in terms of NOx and CO emissions. Results under atmospheric pressure show a drastic decrease of NOx emissions, up to 55%, when the pulsating unit is active. CO emissions are maintained at a very low level so that flame extinction is not observed. To get more insights into the effects of pulsation on combustion characteristics, velocity fields in cold flow conditions are investigated. Results show a large radial transfer of flow when pulsation is activated, hence enhancing the mixing process. The flame behavior is analyzed by using OH* chemiluminescence. Images show a larger distributed reaction region over the combustion chamber for pulsation conditions, confirming the hypothesis of a better mixing between fresh and burnt gases.
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Yamamoto, Cassio T., Rodrigo A. Fregonesi, Julio R. Meneghini et Fabio Saltara. « Numerical Simulations of the Flow Around Flexible Cylinders ». Dans ASME 2002 21st International Conference on Offshore Mechanics and Arctic Engineering. ASMEDC, 2002. http://dx.doi.org/10.1115/omae2002-28154.
Texte intégralRésumé :
In the offshore industry fluids are conveyed from the seabed to the platform through slender structures named risers. These risers are subject to shear and oscillatory flows due to currents and waves respectively, flows with a very high degree of complexity, with changes of intensity and direction the deeper the water depth. The main purpose of this work is to investigate the hydroelastic interactions which take place between flexible cylinders and fluid forces. The cylinders are subject to uniform flow, and the hydrodynamic forces are estimated by CFD, in a quasi three-dimensional fashion. This article presents the results of an investigation being carried out at the University of Sa˜o Paulo and sponsored by the Brazilian Oil Company Petrobras. In this research a discrete vortex method is used to simulate the flow around a flexible cylinder. A description of this method can be found at Yamamoto et al. (OMAE 2001). A finite element structural model based on the Euler-Bernoulli beam theory was developed. In order to evaluate the dynamic response, a general equation of motion is solved through a numerical integration scheme in the time domain. The hydrodynamic forces are evaluated in two-dimensional strips. The technique used is the Discrete Vortex Method, which is a Lagrangian numerical scheme to simulate an incompressible and viscous fluid flow. The calculations are compared with experiments of a cantilever flexible cylinder immersed in a current, see Fujarra [6]. The reduced velocity vs. non-dimensional amplitude curve obtained in our calculations is compared with the experimental results. Visualizations of the wake indicate a hybrid mode of vortex shedding along the span. A 2S mode is found in regions of low amplitudes, changing to a 2P mode in the regions o larger amplitudes. The position of the transition of the modes varies with the reduced velocity. A practical case of marine risers is also presented. In this case the results for various uniform currents acting on a single, flexible cylinder, representing a riser of 120m with 100m under water, are shown. Envelopes of maximum and minimum in-line and transverse displacements are presented.
Rapports d'organisations sur le sujet "High velocity - low amplitude technique (HVLA)"
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Wideman, Jr., Robert F., Nicholas B. Anthony, Avigdor Cahaner, Alan Shlosberg, Michel Bellaiche et 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, décembre 2000. http://dx.doi.org/10.32747/2000.7575287.bard.
Texte intégralRésumé :
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.