Gear Restrictions Research Articles

Protective Modifications in Ophthalmology Practice during COVID-19 Pandemic: Challenges and Lessons Learned.

Ophthalmology is a specialty which involves close contact with patients. Personal protective equipment (PPE) along with modifications in examination techniques and equipment are needed to avoid spread of coronavirus infectious disease (COVID-19) to health professionals. This communication aims to highlight and critically analyse the measures suggested to control this spread. We also highlighted our experience with protective gear modifications. As with any practice, triage is cornerstone. Use of disinfectants, good personal hygiene practices and PPE for patients and staff, must be adopted for safe ophthalmology practices. Key Words: COVID-19, Ophthalmology, Personal protective equipment (PPE).

Protective Modifications in Ophthalmology Practice during COVID-19 Pandemic: Challenges and Lessons Learned.

Ophthalmology is a specialty which involves close contact with patients. Personal protective equipment (PPE) along with modifications in examination techniques and equipment are needed to avoid spread of coronavirus infectious disease (COVID-19) to health professionals. This communication aims to highlight and critically analyse the measures suggested to control this spread. We also highlighted our experience with protective gear modifications. As with any practice, triage is cornerstone. Use of disinfectants, good personal hygiene practices and PPE for patients and staff, must be adopted for safe ophthalmology practices. Key Words: COVID-19, Ophthalmology, Personal protective equipment (PPE).

Gillnet illumination as an effective measure to reduce sea turtle bycatch

The growing demand for fish around the world is an immediate threat to marine megafauna that are unintentionally captured in commercial and artisanal fishery operations. Bycatch mitigation strategies, such as turtle excluder devices, circle hooks, and net illumination, have successfully reduced this risk in some fisheries. We explored the effectiveness of gillnet illumination to reduce sea turtle captures in 2 artisanal fisheries (Mankoadze and Winneba, Ghana) under normal fishing conditions. We first quantified sea turtle bycatch in Ghana's artisanal gillnet fishery from 15 boats for 12 months. We then quantified catch of targeted species and sea turtle bycatch from 20 boats for 15 months (7427 net sets). For 10 of these boats, we placed a Centro Economy green light (1 LED) at each 10-m interval on the net. We also quantified target catch and sea turtle bycatch from 30 boats for 8 months (2250 net sets). In 15 of these boats, a Centro Deluxe green light (3 LEDs) was installed at 15-m intervals. Boats with economy lights and those with deluxe lights both exhibited an 81% decrease in sea turtle captures (W = 1, p < 0.001, n = 20; W = 215, p < 0.001, n = 30, respectively) compared with control boats without lights. Illuminated nets resulted in fewer turtle catches for leatherback (Dermochelys coriacea), olive ridley (Lepidochelys olivacea), and green sea turtles (Chelonia mydas) (p < 0.05 for all species). Target catch (mass) (W = 53, p = 0.853 n = 20; W = 76, p = 0.449, n = 23) and value (W = 50, p = 1, n = 20; W = 69, p = 0.728, = 23) were not different across treatments. Our study affirms net illumination can reduce capture rates of 3 species of sea turtles, including the imperiled leatherback. Gear modification methods can successfully reduce bycatch if they are affordable and have broad applications for multiple species in different fisheries.

Beyond the boundaries: How regulation-centered marine protected area information improves ocean protection assessments

Comprehensive, spatially explicit data that include regulatory information are essential for evaluating the level of protection that marine protected areas (MPAs) and other marine managed areas (MMAs) provide to marine life, and to inform progress towards ocean protection targets. An analysis based on the ProtectedSeas database, which includes information on regulated activities, found that 85% of U.S. waters are in managed areas that restrict living resource extraction at some level above generally applicable regulations, with 52% managed at a low level of protection and 3% managed as highly protected no-take areas. States with the most state waters area in no-take MPAs are Hawaii (~25%), California (~9%), and Oregon (~3%). The majority of highly protected areas in U.S. waters exist in low-populated areas of the Pacific, such as the Papahānaumokuākea and Pacific Remote Islands Marine National Monuments. Under a quarter of U.S. waters are closed to bottom trawling, with the West Coast and Alaska each contributing one-third of trawl closures by area. Bottom trawling is prohibited in nearly 90% of West Coast waters. Focusing on waters off California showed that overlapping management and fishing gear restrictions can increase overall protection. In state waters, no-take MPAs account for roughly 9% of the area, while restricted take MPAs of different types cover 27% of the area. About 40% of California state waters are in some kind of MPA, while 13.4% of state waters have a high level of protection from fishing impacts. In federal waters off California, under one percent are in no-take areas while nearly all waters are subject to some kind of fishery restriction. Capturing regulatory information at the individual MPA and MMA level will improve assessments of current protection, inform planning of new protections, and provide ocean users a more accessible way to increase compliance through awareness.

Fishing and trade of devil rays (Mobula spp.) in the Bay of Bengal, Bangladesh: Insights from fishers’ knowledge

Abstract Devil rays (Mobula spp.) are globally threatened cartilaginous fishes that have attracted global conservation concern owing to their high extinction risk and lack of protection in many countries. Limited resources and data on threatened marine species, including devil rays, impede conservation actions, particularly in developing countries, many of which have high biodiversity. Devil ray catch is a component of artisanal fisheries in Bangladesh, but data on their fisheries and trade are limited. To characterize devil ray fishing practices, fishers’ perception and trade, 230 fishers and traders were interviewed between 4 June 2018 and 22 June 2019, in four areas of south‐east Bangladesh. Catch data were also opportunistically collected at landing sites. Six devil ray species were documented, caught in an array of gill nets, set‐bag nets and longlines. All interviewed fishers reported life‐long devil ray bycatch in some numbers, and also noted a decline in catch over the last decade. Bottom trawling, increased bycatch levels, increased demand for devil ray products and, in some cases, ecosystem changes were identified by fishers as threats to devil ray populations. Unregulated and undocumented trade and retained bycatch, especially by gill nets and set‐bag nets, are fuelled by local consumption of devil ray meat and international trade in meat and gill rakers. Compliance with international trade control treaties for all Mobula spp. or the Bangladeshi law protecting Mobula mobular was low, with the majority of fishers (87%, n = 174) unaware of their existence. To manage devil ray fisheries, and prevent possible population declines, we propose a combination of legally enforced gear modifications, and catch and trade control through community‐owned implementation strategies. Additionally, we propose the simultaneous implementation of inclusive, community‐based awareness and stewardship projects in conjunction with a coast‐wide ray monitoring programme. Finally, we emphasize that more research and action rooted in a sustainable fishery model is urgently needed to protect Bangladeshi devil ray populations.

Are Cloth Tarpaulin Mounted Nets Effective for Discard Reduction in Trammel Nets?

Discarding is a significant problem due to net damage and labour loss in trammel net fisheries. In this study, the effects of 15, 25, and 35 cm high cloth tarpaulin rigged between the lead line and the net were investigated in reducing the discard amount of trammel nets for red mullet (Mullus barbatus) in the south-eastern Black Sea. During the study, twenty fishing trips were carried out on-board a commercial vessel between May 11 and June 20, 2018. Results showed that there were no significant differences in the amount of discards between the commercial and experimental nets (P&gt;0.05) However, cloth tarpaulin mounted nets (CTMN) were found to be significantly successful to reduce the amount of shore crab (Liocarcinus depurator) and the veined rapa whelk (Rapana venosa) (P&lt;0.05). Although it is insignificant, a decline of capture was also observed in the amount of target species in CTMN compared to the commercial net (CN). Finally, the advantages and concerns of this gear modification, and potential reasons for the reduction of target and discard species are discussed.

Technical and tactical measures to reduce unwanted catches in mixed fisheries: Do the opinions of Irish fishers align with management advice?

The introduction of the Landing Obligation in Europe has increased the need for fishers to adopt more selective fishing practices, to avoid unwanted catches that would previously have been legally discarded. Modelling, experiments and trials have been conducted by scientists, often in collaboration with industry, to determine how gear modifications, changes in fishing tactics, and alterations to spatio-temporal exploitation patterns can assist in reducing unwanted catches. Yet voluntary uptake of resultant recommendations is often poor or slow. During semi-structured interviews with fishers and industry representatives from the Irish demersal fishing industry we discussed their views with regard to the effectiveness of such measures in reducing unwanted catches. Opinions varied between respondents. There was broad agreement that larger mesh sizes are vital for reducing discards, which aligns with current management advice. Other selectivity devices were viewed less favourably due to the difficulties associated with correctly setting up and maintaining gear to ensure effective operation. The benefits of spatio-temporal solutions were recognised despite a lack of formal management advice with regards to such measures. A lack of trust between fishers, as well as fear of providing additional information to authorities which could be used against them, led to a guarded response for resources such as more formal information sharing schemes. While our results indicate individuals have their own tactics and preferences to reduce unwanted catches, understanding broad industry perspectives towards technical and tactical measures to reduce discards is important if scientists and policy makers are to best support industry to increase selectivity.

Mortality and serious injury of northern right whales (Eubalaena glacialis) in the western North Atlantic Ocean

Northern right whales in the western North Atlantic number about 300 animals and have shown little sign of recovery in recent decades.Mortality and serious injury due to human activities, particularly commercial fishing and shipping, are thought to be significant factorslimiting their recovery. From 1970-1999, 45 right whale deaths were reliably documented. Sixteen of these fatalities (35.5%) were due toship collisions, and three (6.7%) were due to entanglement in fishing gear. The remainder were neonates (13; 28.9%) and ‘unknown cause’mortalities (13; 28.9%). Criteria for defining serious injuries and mortalities from entanglement or ship strikes were developed and includeany animal carrying fishing gear, cuts from entanglement or ship strike deeper than 8cm, swelling or necrosis, evidence of poor health fromsuch interactions, and, in carcasses, evidence of haematoma, haemorrhaging or broken bones. A total of 56 animals fitting the definedcriteria were documented from 1970-1999: 31 (55.4%) from entanglement and 25 (44.6%) from ship strikes. Nineteen were fatal (16 shipstrikes, 3 entanglements), 10 were possibly fatal (2 ship strikes, 8 entanglements) and 27 were non-fatal (7 ship strikes, 20 entanglements).The breakdown of potentially serious injuries by age and sex reveals no difference in levels between sexes but shows a 3.3:1 higher levelof interaction in juveniles and calves versus adults. The data show that ship strikes are more immediately lethal, but entanglements can resultin long term deterioration of an animal and may be responsible for higher levels of mortality than previously thought. Considering that someanimals become entangled, drown and never return to the surface, even these levels may be underestimated. Between 1986 and 1999, 84animals were presumed dead based on a lack of resightings for six years. There were 32 confirmed deaths during this time period suggestingthat at least as many unreported deaths occurred as carcasses were reported. Definitive actions need to be taken to reduce the level andseverity of anthropogenic injuries and deaths. Actions could include continued disentanglement efforts, gear modifications, seasonalclosures for fisheries, mandatory ship reporting, ships’ routing measures and speed restrictions for commercial shipping.

When large marine predators feed on fisheries catches: Global patterns of the depredation conflict and directions for coexistence

AbstractThe sustainable mitigation of human–wildlife conflicts has become a major societal and environmental challenge globally. Among these conflicts, large marine predators feeding on fisheries catches, a behaviour termed “depredation,” has emerged concomitantly with the expansion of the world’s fisheries. Depredation poses threats to both the socio‐economic viability of fisheries and species conservation, stressing the need for mitigation. This review synthesizes the extent and socio‐ecological impacts of depredation by sharks and marine mammals across the world, and the various approaches used to minimize it. Depredation was reported in 214 fisheries between 1979 and 2019 (70% post‐2000) and affected fleets from 44 countries, in all sectors (commercial, artisanal and recreational), and in all major fishing techniques (nets, traps and hook‐and‐lines). A total of 68 predator species were involved in depredation (20 odontocetes, 21 pinnipeds and 27 sharks), and most (73%) were subject to either by‐catch and/or retaliatory killing from fishers when interacting with gear. Impacts on fishers were primarily associated with catch losses and gear damage but often lacked assessments. Deterrence was a major mitigation approach but also the least effective. Gear modifications or behavioural adaptation by fishers were more promising. This review highlights the need for improved monitoring, and interdisciplinary and integrated research to quantify the determinants and impacts of depredation in the socio‐ecological dimension. More importantly, as the conflict is likely to escalate, efforts directed towards changing perceptions and integrating knowledge through adaptive co‐management are raised as key directions towards coexistence between fisheries and large marine predators.

Tool path active design for tooth modification of face-hobbed spiral bevel gears

An advanced design and manufacturing method called tool path active design for face-hobbed spiral bevel gears is mainly discussed in this paper. The method bases on the forming mechanism of extended epicycloids and utilizes an integrated cutter head without tilting, meanwhile, all its controlled parameters can be directly calculated according to the given meshing performances and modified conditions. Starting with the cutting principle of face-hobbing method, a tooth flank mending plan of altering tool path is developed, which detailed expressions are also given in functions. Then, the meshing performances which are used to determine the modification parameters are introduced and their formulas are also derived. Finally, the proposed method is validated by a numerical example of tooth contact analysis for a face-bobbed hypoid gear pair. As a further explanation, a numerical example of tooth contact analysis is done to validate the feasibility of the proposed method.

Mitigation of Elasmobranch Bycatch in Trawlers: A Case Study in Indian Fisheries

Bycatch poses a significant threat to marine megafauna, such as elasmobranchs. India has one of the highest elasmobranch landings globally, through both targeted catch and bycatch. As elasmobranchs contribute to food and livelihood security, there is a need for holistic approaches to bycatch mitigation. We adopt an interdisciplinary approach to critically assess a range of hypothetical measures for reducing elasmobranch capture in a trawler fishery on India�s west coast, using a risk-based mitigation hierarchy framework. Data were collected through landing surveys, interviews and a literature review, to assess the following potential management options for their technical effectiveness and socio-economic feasibility: (1) spatio-temporal closures; (2) net restrictions; (3) bycatch reduction devices (BRDs); and (4) live onboard release. Our study provides the first evidence-based and nuanced understanding of elasmobranch bycatch management for this fishery, and suggestions for future conservation and research efforts. Onboard release may be viable for species like guitarfish, with moderate chances of survival, and was the favored option among interview respondents due to minimal impact on earnings. While closures, net restrictions and BRDs may reduce elasmobranch capture, implementation will be challenging under present circumstances due to the potentially high impact on fisher income. Interventions for live release can therefore be used as a step toward ameliorating bycatch, while initiating longer-term engagement with the fishing community. Participatory monitoring can help address critical knowledge gaps in elasmobranch ecology. Spatio-temporal closures and gear restriction measures may then be developed through a bottom-up approach in the long term. Overall, the framework facilitated a holistic assessment of bycatch management to guide decision-making. Scaling-up and integrating such case studies across different species, fisheries and sites would support the formulation of a meaningful management plan for elasmobranch fisheries in India. © Copyright © 2020 Gupta, Booth, Arlidge, Rao, Manoharakrishnan, Namboothri, Shanker and Milner-Gulland.

Study on 3-D modification for reducing vibration of helical gear based on TCA technology, LTCA technology and system dynamics

Vibration and noise of gear meshing come from the dynamic working conditions, therefore, combining gear modification and dynamic characteristic analysis may offer reliable basis for the modification. Compared with profile modification and axial modification, 3-D modification is more comprehensive. The existing problems in current gear modification includes: (1) The ideal force under static or quasi-static conditions is used to replace the transient dynamic meshing force, so the effect of modification is not obvious in the middle and high speed gear transmission. (2) Though the modification is completed according to the dynamic performance, the dynamic characteristic analysis is not well combined with the gear meshing performance. Tooth contact analysis (TCA) and loaded tooth contact analysis (LTCA) can simulate the meshing process of gear and provide precise tooth surface geometric analysis data for later dynamic characteristic analysis. Therefore, combining TCA technology, LTCA technology and dynamic performance of gear, a 3-D modification method for reducing vibration of helical gear is proposed. Two application examples are given and good vibration reduction effects have been obtained. The biggest highlight of the paper is to use TCA technology, LTCA technology and dynamic characteristic analysis of gear to complete the 3-D modification of helical gear.

Tooth Surface Modeling and Stress Analysis of 3-DOF Spherical Gear

A new type of spherical gear is proposed, which is formed by combining the tooth profile of the plane involute annular tooth surface and spherical involute spherical cone tooth surface. 3-DOF of pitch, deflection and rotation can be realized without principle error transmission. Based on the forming principle of plane involute and spherical involute, the equations of annular tooth surface and spherical cone tooth surface are derived by coordinate transformation theory; Combined with MATLAB and Pro/E, the 3D accurate model of 3-DOF spherical gear was obtained, and the contact stress of tooth surface was analyzed based on the finite element method. The simulation results show that the stress concentration always occurs at the tooth root and the tooth top of the spherical and conical tooth surface under the condition of constant spherical distance and the same torque but different coaxial intersection angle, which can provide reference for the tooth surface modification and optimization of spherical gear.

Simulation analysis of the tooth modification about wind power gearbox based on Romax software

At present, the gearboxes are faced with the problems of high failure rate, large vibration and noise, short service life etc. Gear modification is an effective means to reduce vibration and noise, extend life, which has been proved by practical experience at home and abroad for many years. With the introduction of some professional gear software or wind turbine analysis software from abroad, the work efficiency has been improved greatly and the extra cost due to experimental verification has also been reduced. With the use of Romax WIND excellent load distribution analysis function on the basis of the theory of gear modification, the static simulation analysis of the gearbox through the Romax WIND software was carried out under the equivalent loads. According to the load distribution on the tooth surface of gear, transmission errors and other parameters, the length, amount and curve of axial modification and the tooth profile of the high-speed pinion gear were analyzed and determined in the end. Conclusions can provide reference for gear modification.

Impact of Spatial Management on Nontarget Species in an Oceanic Penaeid Trawl Fishery

AbstractTrawling is generally an unselective fishing method that is employed to harvest a number of species. Capture of nontarget species that are subsequently discarded is an important issue for trawl fisheries, especially penaeid trawl fisheries. While gear modifications are a common approach to manage this issue, maintaining areas that are closed to trawling may also have a positive impact on these nontarget species. This study systematically examined the diversity and abundance of nontarget species across a network of areas closed to trawling (trawl closure areas) relative to adjacent areas that were open to trawling. Analysis of nontarget species from 209 trawls and 72,787 animals (across 216 taxa) revealed some impact on both abundance and diversity within trawl closure areas. Latitude was a key variable that was driving differences in the taxonomic assemblage among locations. Within locations, there were inconsistent impacts for different nontarget species in trawl closure areas. Length distributions showed size truncation of abundant nontarget species in fished areas relative to adjacent trawl closure areas. While the impact of trawl closure areas varied among species, it was clear that the spatial management in the fishery provided some refuge for a diversity of nontarget species, observed in patterns of species richness, abundance, and population size structure. Latitudinal breadth appears to be an essential component of the trawl closure network, but localized effects may be important for maintaining reproductive capacity for nontarget species. These data highlight the broader utility of trawl closure networks as a management tool for trawl fisheries.

Dynamic Meshing Characteristics of Elliptic Cylinder Gear Based on Tooth Contact Analysis

As the most important working area of gear, teeth play the role of transmitting load and power. Tooth line and tooth profile are the two main characteristics of the tooth surface, which affect the shape of the tooth surface, tooth meshing characteristics and contact characteristics. Taking the elliptical cylinder gear pair in the reversing device of a new type of drum pumping unit as the research object, the dynamic meshing process of the gear is simulated by LS-PREPOST software based on loaded tooth contact analysis (LTCA) technology. The distribution law of the effective plastic strain, effective stress and tooth surface pressure in the direction of the tooth line and tooth profile as well as the tooth meshing force under different speed conditions are obtained. The results show that the effective plastic strain, effective stress and tooth surface pressure will decrease with the transition of the center position of the elliptical contact area on the tooth surface to both sides. The distribution of stress and strain in the direction of tooth line will change with the location of the teeth, and the rotational speed has a certain influence on the meshing force of the teeth. The results of this research can provide a theoretical basis for the subsequent analysis of the dynamic meshing characteristics and modification of non-circular gear.

Investigation of the thermal stiffness and thermal tooth profile modification of spur gears

This paper first proposed the concept of thermal stiffness of gears and then calculated thermal stiffness using the finite element method and the analytical method, respectively. After that, based on the thermal stiffness, the thermal tooth profile modification of gears was studied. The results showed that the meshing thermal stiffness of tooth pair under the thermo-elastic coupling is a serial connection of elastic stiffness and modified thermal expansion stiffness. In addition, the meshing thermal stiffness of tooth pair decreases compared with the meshing elastic stiffness in the entire meshing region. There is only one intersection point of the distribution curves of the single tooth thermal stiffness and elastic stiffness along the meshing line. In the tooth root side of the intersection point, the thermal stiffness is larger than the elastic stiffness, and it is opposite in the tip side of the intersection point. It can be concluded from the thermal tooth profile modification parameters that the maximum amount of profile modification is the thermo-elastic coupling deformation of point B or D, with the modification index being 1.33.

A New Tooth Profile Modification Method of Cycloidal Gears in Precision Reducers for Robots

The tooth profile modification of cycloidal gears is important in the design and manufacture of precision reducers or rotary vector (RV) reducers for robots. The traditional modification design of cycloidal gears is mainly realized by setting various machining parameters, such as the size and center position of the grinding wheel. The traditional modification design has some disadvantages such as complex modification calculation, uncontrollable tooth profile curve shape and unstable meshing performance. Therefore, a new tooth profile modification method is proposed based on the consideration of the comprehensive influences of pressure angle distribution, meshing backlash, tooth tip and root clearance. Taking the pressure angle and modifications of tooth profile as the parameters of the modification function and the meshing backlash of gear teeth as constraints, the mathematical model for tooth profile modifications is built. The modifications are superimposed on the normal direction of the theoretical profile—the force transmission direction. The mathematical relationship between the modifications and the pressure angle distribution, which determines the force transmission performance, is established. Taking the straight line method, cycloid method and catenary method as examples, by means of the tooth contact analysis technology, the transmission error and minimum meshing backlash, which reflects the lost motion, of the newly modified profile are analyzed and verified. This proposed method can flexibly control the shape change of the modification profile and accurately pre-control the transmission accuracy of the cycloid-pin gear. It avoids the disadvantages of traditional modification methods, such as uncontrollable tooth profile shape and unstable meshing accuracy. The method allows good meshing characteristics, high force transmission performance and more precise tooth profile curve. The study provides a new design method of the modified profile of cycloidal gears.

An Elastic Transmission Error Compensation Method for Rotary Vector Speed Reducers Based on Error Sensitivity Analysis

An elastic transmission error (TE) compensation method for a rotary vector (RV) speed reducer is proposed to improve its transmission accuracy based on error sensitivity analysis. Elastic and geometric TEs of the RV speed reducer can be compensated by tooth surface modification of cycloidal gears. Error coefficients of the TE of the RV speed reducer are derived to determine error factors with positive effects on TEs based on error sensitivity analysis. A total TE, including the elastic TE, is obtained by using Adams. The elastic TE compensation method is developed to calculate modification values of error factors with positive effects on the TE to decrease the elastic TE of the RV speed reducer. TE simulation results show that the elastic TE accounts for 25.28% of the total TE, and calculation results show that the maximum contact force and normal deformation of the modified prototype are obviously improved. The feasibility and accuracy of the proposed elastic TE compensation method for RV speed reducers were verified by TE experiments. TE experiment results showed that the TE of the modified RV speed reducer is 47.22% less than that of the initial RV speed reducer.

Optimal Design of Traction Gear Modification of High-Speed EMU Based on Radial Basis Function Neural Network

The dynamic characteristics of the traction gear transmission system have a great influence on the safety, comfort, and reliability of EMU (electric multiple units). Combining the methods of theoretical analysis, numerical simulation, and optimization design theory, establishing a parameterized gear modification model. Meanwhile, designing reasonable shape modification schemes and parameters. The dynamic characteristics, vibration response characteristics, and acoustic response characteristics of gear meshing of CRH380A high-speed EMU under continuous traction conditions are analyzed. The corresponding relationship between gear modification parameters and gear transmission radiation noise is approximated by finite element simulation data and RBF (radial basis function) neural network. Using a multi-island genetic algorithm to optimize gear modification parameters to minimize gear transmission noise, further seeking to meet the low-noise modification design of high-speed train traction helical gear transmission system under continuous operating conditions method.