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Hydrodynamic characteristics of knotted and knotless purse seine netting panels as determined in a flume tank.

ABSTRACT: Nylon (PA) netting is widely used in purse seines and other fishing gears due to its high strength and good sinking performance. However, hydrodynamic properties of nylon netting of different characteristics are poorly understood. This study investigated hydrodynamic characteristics of nylon netting of different knot types and solidity ratios under different attack angles and flow velocities. It was found that the hydrodynamic coefficient of netting panels was related to Reynolds number, solidity ratio, attack angle, knot type and twine construction. The solidity ratio was found to positively correlate with drag coefficient when the netting was normal to the flow (CD90), but not the case when the netting was parallel to the flow (CD0). For netting panels inclined to the flow, the inclined drag coefficient had a negative relationship with the solidity ratio for attack angles between 0° and 50°, but a positive relationship for attack angles between 50° and 90°. The lift coefficient increased with the attack angle, reaching the culminating point at an attack angle of 50°, before subsequent decline. We found that the drag generated by knot accounted for 15-25% of total drag, and the knotted netting with higher solidity ratio exhibited a greater CD0, but it was not the case for the knotless netting. Compared to knotless polyethylene (PE) netting, the drag coefficients of knotless PA netting were dominant at higher Reynolds number (Re>2200).

SUBMITTER: Tang H

PROVIDER: S-EPMC5805286 | biostudies-literature | 2018

REPOSITORIES: biostudies-literature

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Hydrodynamic characteristics of knotted and knotless purse seine netting panels as determined in a flume tank.

Tang Hao H Xu Liuxiong L Hu Fuxiang F

PloS one 20180208 2

Nylon (PA) netting is widely used in purse seines and other fishing gears due to its high strength and good sinking performance. However, hydrodynamic properties of nylon netting of different characteristics are poorly understood. This study investigated hydrodynamic characteristics of nylon netting of different knot types and solidity ratios under different attack angles and flow velocities. It was found that the hydrodynamic coefficient of netting panels was related to Reynolds number, solidit ...[more]

PMID: 29420569

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Project description:Purpose:To determine the cost-effectiveness of knotted (KT) versus knotless (KL) methods for rotator cuff surgical repair and to assess differences in patients' outcomes. Methods:We retrospectively identified all patients who underwent arthroscopic rotator cuff repair at 1 institution by 1 surgeon over 2 6-month periods of time (KT technique from August 1, 2013, through January 31, 2014; and KL technique from December 1, 2014, through May 31, 2015) to calculate the direct and indirect costs associated with arthroscopic KT or KL suture bridge rotator cuff repair. Patient demographics, number of anchors used, tendons repaired, procedure time, operative time, and clinical results were also evaluated. We used univariate generalized linear models with a Gaussian distribution for assessment scores and total and implant cost data. Results:We identified 87 patients for inclusion during the 2 time frames (35 KT, 54 KL). After excluding patients for tear size < 4 cm2 (n = 42), ? 3 anchors (n = 5), revision surgery (n = 1), and those in whom additional procedures were performed (n = 2), 37 eligible subjects remained (nKT = 15, nKL = 22). Median implant costs were statistically significantly higher in the KL group than in the KT group (MKL = $2,127, MKT = $1,520, ? = 413.7, 95% CI: 242.8, 584.6, P < .01), and more anchors were used in the KL group, with KT requiring a median of 4 anchors (IQR: 4, 5) and KL requiring a median of 5 anchors (IQR: 5, 5, P = .02). Procedure time was cut in half with KL repair (estimated 43.5 minutes) versus KT repair (80 minutes) (? = 0.5, 95% CI: 0.4, 0.6, P < .001). Operating room time also was reduced by approximately 40% (79.5 minutes for KL; 121 minutes for KT [? = 0.6, CI: 0.6, 0.7, P < .001]). Once operating room costs were considered, median costs were found to be significantly lower in the KL group (MKL = $3788.40, MKT = $4262.90, ? = -492.1, 95% CI: -840.0, -144.1, P < .01). No statistically significant differences were found between groups in mean preoperative, postoperative or postpreoperative differences in the visual analog scale, Simple Shoulder Test, American Shoulder and Elbow Surgeons, or University of California at Los Angeles scores (P > 0.05 for all). Conclusions:Despite using more anchors and incurring higher implant costs, the KL technique for rotator cuff repair required less surgical procedure time and cost less overall than the KT technique and resulted in equivalent clinical results. Level of Evidence:Level IV Economic and Decision Analyses.

Project description:Tuna fisheries catch over three million tonnes of skipjack tuna (Katsuwonus pelamis) each year, the majority of which come from purse-seine vessels targeting fish associated with man-made fish aggregating devices (FADs). A significant challenge for fisheries management is to maximize the efficiency of skipjack tuna catches whilst minimizing the bycatch of small and immature bigeye (Thunnus obesus) and yellowfin (T. albacares) tuna, for which long-term sustainability is uncertain in 75% of the world's stocks. To better manage the issues common with this fishing method, an improved understanding of tuna behaviour around FADs is necessary. We probabilistically classified the vertical behavioural patterns of 50 bigeye and 35 yellowfin tuna (mean fork length 72cm and 70cm, respectively) electronically tagged throughout the western and central Pacific Ocean into shallow and deep states, using a state-space modelling approach. The occurrence of surface-association behaviours, defined as an individual remaining in a shallow state for 24-hours, was examined in relation to known capture events and FAD density. In general, surface-association events for both species were short and lasted on average less than three days, although events as long as 28 days were observed, and were more common in yellowfin when in archipelagic waters. Events were longest immediately following tagging in 62% and 17% of bigeye and yellowfin, respectively. Surface-association behaviour was not generally estimated just prior to recapture, being either non-existent or shorter than two days for 85% of bigeye and 74% of yellowfin. Current management measures in purse-seine tuna fisheries involve periodic or spatial closures for FAD use. If the chief benefit to purse-seine fishers of surface-association around floating objects is in locating schools in horizontal space at short-term time-scales, rather than holding fish near the surface for extended periods, controlling the number of sets made on FADs should be explored further as an additional management tool.

Project description:PurposeTo compare clinical failure, recurrent instability, patient-reported outcome measures (PROMs), and return to sport (RTS) between knotted and knotless fixation methods in arthroscopic posterior labral repair for isolated posterior shoulder instability (PSI).MethodsMultiple databases were queried according to Preferred Reported Items for Systematic Reviews and Meta-Analyses guidelines for clinical studies with Level I to IV evidence, including knotted and knotless suture anchors for arthroscopic posterior labral repair. Combined anterior and posterior instability, multidirectional instability, SLAP injuries, unspecified repair techniques, majority open procedures, and revision surgery were excluded.ResultsScreening yielded 17 full-text articles reporting on 852 shoulders undergoing posterior labral repair. Recurrent instability ranged from 0% to 21%, and the rate of revision surgery ranged from 0% to 11% in knotted only, 0% in knotless only, and 2.0% to 8.1% in knotted and knotless studies. Six studies with both pre- and postoperative visual analog scale scores and 7 studies with both pre- and postoperative American Shoulder and Elbow Score scores all showed improvement in scores after intervention regardless of repair technique. Thirteen studies reported RTS or duty rates with a minimum of 79%.ConclusionsOverall recurrent instability after posterior labral repair for isolated PSI was low with improvement in PROMs and favorable RTS rates regardless of fixation method. There was no clear difference in recurrent instability or revision surgery between knotted and knotless fixation methods for isolated posterior labral repair. However, the current literature is predominantly limited by Level III and IV evidence. The quality of literature and lack of standardization on the definition of clinical failure and recurrent instability among surgeons preclude any definitive conclusion regarding one clinically superior fixation method.Level of evidenceLevel IV, systematic review of Level III and IV studies.

Dataset Information

Hydrodynamic characteristics of knotted and knotless purse seine netting panels as determined in a flume tank.

Publications

Hydrodynamic characteristics of knotted and knotless purse seine netting panels as determined in a flume tank.

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