Fin Weight Research Articles

Implementing Machine Learning approaches for accelerated prediction of bone strain in acetabulum of a hip joint

The Finite Element (FE) methods for biomechanical analysis involving implant design and subject parameters for musculoskeletal applications are extensively reported in literature. Such an approach is manually intensive and computationally expensive with longer simulations times. Although Artificial Intelligence (AI) based approaches are implemented to a limited extent in biomechanics, such approaches to predict bone strain in acetabulum of a hip joint, are hardly explored. In this context, the primary objective of this paper is to evaluate machine learning (ML) models in tandem with high-fidelity FEA data for the accelerated prediction of the biomechanical response in the acetabulum of the human hip joint, during the walking gait. The parameters used in the FEA study included the subject weight, number and distribution of fins on the periphery of the acetabular shell, bone condition and phases of the gait cycle. The biomechanical response has also been evaluated using three different acetabular liners, including pre-clinically validated HDPE-20% HA-20% Al2O3, highly-crosslinked ultrahigh molecular weight polyethylene (HC-UHMWPE) and ZrO2-toughened Al2O3 (ZTA). Such parametric variation in FEA analysis, involving 26 variables and a full factorial design resulted in 10,752 datasets for spatially varying bone strains. The bone condition, as opposed to subject weight, was found to play a statistically significant role in determining the strain response in the periprosthetic bone of the acetabulum. While utilising hyperparameter tuning, K-fold cross validation and statistical learning approaches, a number of ML models were trained on the FEA dataset, and the Random Forest model performed the best with a coefficient of determination (R2) value of 0.99/0.97 and Root Mean Square Error (RMSE) of 0.02/0.01 on the training/test dataset. Taken together, this study establishes the potential of ML approach as a fast surrogate of FEA for implant biomechanics analysis, in less than a minute.

A novel fin efficiency concept to optimize solid state hydrogen storage reactor

The process of heat-driven mass transfer involved in hydrogen storage within metal hydrides (MHs) demands implementing a heat transfer system (HTS) to facilitate faster hydrogen charging and discharging. One effective method to enhance heat transfer is utilizing an HTS equipped with fins and a cooling tube. Among the crucial factors for optimizing the reactor, fin efficiency (FE) plays a vital role, although it has not been explored in unsteady processes like the present one. This study introduces a novel FE technique to optimize fins in a conventional longitudinal finned tube MH reactor based on LaNi5. Due to the intricacies of the problem, making analytical estimation of FE challenging, the authors turned to the concept of reverse engineering. This approach utilizes simulated data's temporal temperature profiles to calculate the FE. The number of fins is varied from 4 to 12 while keeping the total fin weight constant. Heat transfer performance improved as the number of fins increased, but the FE deteriorated from 0.89 to 0.56 due to the reduction in fin thickness. A performance index (PI) that considers the number of fins is introduced to assess the overall performance. Its values are 0.58, 0.79, 0.96, 1.05, and 1.1 for configurations with 4, 6, 8, 10, and 12 fins, respectively. The configuration with 8 fins is deemed optimal because further increasing the number of fins led to only marginal improvements in PI value. Subsequent optimization of fin shape, precisely radial tapering, had a minimal impact on heat transfer performance. Finally, the desorption behavior was examined for the optimal configuration with 8 fins of constant thickness.

Genetic variation between hybrid (Labeo rohita ♂, Cirrhinus mrigala ♀ and Labeo rohita) by RAPD marker.

The present work was to study the genetic variability between the major carps Labeo rohita and Cirrhinus mrigala and their hybrids of L. rohita (male♂) and C. mrigala (female♀). Genetic variability was studied by employing RAPD molecular markers. 25 samples of each target species having different sizes with the same age group for the determination of interspecific variation were collected. The morphometric parameters such as body weight, total length, tail length, and lengths of dorsal and anal fins of each individual were recorded and results showed that wet body weight, total length, dorsal fin, anal fin, and tail fin length are positively correlated and then the DNA was extracted using the inorganic salt-based method and conformed by Gel electrophoresis. Twenty-four arbitrary decamer primers were used to get species-specific RAPD analysis Distinct and highly reproducible RAPD profiles with significant genetic variability was detected among species. Only five primers showed amplification. The RAPAD primer OPB-05 produced a total of seven bands out of these 5 monomorphic and 2 polymorphic, so in this case, the percentage polymorphism was 28.57%. The Hybrid show more than a 50% difference from the Labeo rohita. This shows that the Hybrid more resembles C.mrigala. Phylogenetic analysis demonstrated that hybrid (L. rohita ♂ X Cirrhinus mrigala ♀) is the closest to C. mrigala and the farthest from L. rohita. Overall data are presented concerning the applications of RAPD markers for hybrid identification, genetic diversity assessment, and studying taxonomic relationships at a molecular level.

Pectoral Fin Morphometry of Nile Tilapia (Oreochromis niloticus) Cultivated in Different Aerator and Filter

The anomaly of the pectoral fin is caused by an inappropriate amount of oxygen and ammonia within the water, which is expected to be resolved by the combination usage of an aerator and filter. This study aimed to analyze the combination usage of an aerator and filter with different amounts toward the growth of Nile tilapia’s pectoral fin. This study used a 2×2 factorial completely randomized design consisting of 4 treatments (ANF, AANF, AF, and AAF) with 6 replications. The measurement variable of the pectoral fin includes length, width, weight, and the ratio of the pectoral fin’s length with the total size of the fish. The measurement was analyzed using two way-ANOVA and continued with the LSD test. The results of the combination usage of the aerator and filter revealed a significant effect (P0.05) on the pectoral fin length, pectoral fin width, pectoral fin weight, and ratio of pectoral fin length to total body length. The research’s conclusion was the combination of usage aerator and filter had a positive impact on the growth of Nile tilapia’s pectoral fin. The study’s novelty is the combination usage of an aerator and filter with a different number to promote the growth of the cell within the pectoral fin of Nile tilapia. This research would benefit people through the discovery of the combination usage of an aerator and filter to improve the growth of Nile tilapia’s pectoral fin.

Numerical Analysis of Tube Heat Exchanger with Trimmed Star-Shaped Fins

In some engineering applications, it is very desirable that the heat exchanger is as light as possible while maintaining the heat transfer rate at an acceptable level. In this context, the possibility of reducing the weight of the heat exchanger with the star-shaped fins by cutting off the thermally least efficient part of the fin was investigated. For this purpose, the rear part of the fins was trimmed to Ø28, Ø31 and Ø34 mm. Numerical analysis was used to determine the influence of each variant on the flow characteristics in the air–water heat exchanger and on heat transfer for the range of 2300 < Re < 16,000. The best results were obtained by trimming the rear part of the fin to Ø28 mm. With a 5.53% reduction in fin weight, heat transfer can be increased by up to 8.12% compared to the star-shaped fins without trimming. The pressure drop can be reduced by up to 0.92%. The trimmed fins were also compared with perforated star-shaped fins (perforation Ø2). At approximately the same weight, the trimmed fins increase the heat transfer coefficient by up to 5.75% with a reduction in pressure drop of up to 0.76% compared to the perforated fins.

The effect of using circular fins with a V-shaped cut on the weight reduction and the overall performance of a finned tube heat exchanger

In this work, we have investigated the use of circular fins with a V-shape cut in place of regular circular fins. This study was carried out numerically in a natural convection heat transfer in order to understand the effect of creating a V-shape cut on circular fins. We performed this study for a 3D model in a laminar flow containing a single finned tube heat exchanger. The result of this study shows us that, using circular fins with a V-shape cut instead of regular circular fins can significantly improve weight reduction. For fins with a large diameter and a high thermal conductivity, the weight reduction can reach up to 27.8%. On the other hand, for the same fin weight, we can improve the total heat transfer rate by up to 41.6% by using fins with a V-shaped cut in the place of regular ones.

Lysine effect on the characterization of fillet, by-products, residues, and morphometry of tambaqui Colossoma macropomum (Cuvier, 1818)

This study aimed to evaluate the yields of by-products and residues and the morphometry of juvenile tambaqui Colossoma macropomum undernutrition with different levels of lysine. Diets were elaborated containing 6.60, 9.72, 12.84, 15.96, 19.08, and 22.20 g kg -1 of total lysine, and these were fed to fish distributed in 18 tanks (310 L each one) for 90 days. Morphometric analysis, measurements of whole fish, by-products, and residues were taken and compared to each other. All variables were validated using ANOVA, Tukey's test, and quadratic regression analysis ( P < 0.05). No differences were found for the morphometric variables ( P > 0.05). The ratio between morphometric data for the standard and total length showed significance at levels of 9.72 and 15.96 g kg -1 ( P = 0.03). The gutted fish and fillets, the protein and lipid contents of the fillets, and the weights and lengths of the intestines did not change ( P > 0.05). Moisture was modified with lysine at levels of 22.20 g kg -1 ( P = 0.00), and minerals, between 6.60 and 22.20 g kg -1 ( P = 0.01). The increase in lysine levels in the diet led to an increase in fin weight ( P = 0.00). It was concluded that the addition of lysine in the diet did not directly influence the morphometry and yields of the fish in the juvenile phase, but it did affect the fin waste and the skin by-product.

Sexual dimorphism and biology of the large deepwater mastigoteuthid squid Idioteuthis cordiformis (Cephalopoda, Mastigoteuthidae) off Tasmania, Australia

AbstractThis study provided biological information on 146 specimens of the poorly known deepwater mastigoteuthid squid Idioteuthis cordiformis. Mantle length ranged from 200–500 mm for males and 270–702 mm for females. The largest female weighed just under 12 kg. The majority of males were mature and all females were immature. The fins were larger and thicker than the mantle. Mantle weight of males and females was 44.8% and 55.2% of fin weight, respectively, and were significantly different. There was a significant sex effect on mantle length, total weight, mantle weight and fin weight, with females having greater values in all categories. There was a small season effect for mantle weight and fin weight. There was little ingested prey material except fluid and oil in the caecum that was typically bright orange or red. Total fluid volume ranged from 23–230 ml and 20–550 ml for males and females, respectively. The per cent oil component of total fluids in the caecum ranged from 6.9–50% and 10.8–50% for males and females, respectively, with no significant difference in per cent oil between males and females. There was a significant positive relationship between total weight and oil volume for females, and for males and females combined. The function of the oil is uncertain. While this study provided information on sex differences in the body size, sexual dimorphism and caecum oil content, information is still incomplete regarding reproduction due to the lack of any mature females captured in this study.

Morphometric Analysis and Proximate Nutrition several Commercial Fish Species from Mesangat wetland, Muara Ancalong, Kutai Timur, East Kalimantan, Indonesia

Mesangat wetland has a high diversity of fish, which is traded for consumption by the community. The types of fish consumed have different sizes with unknown morphometric analysis and nutritional content. The purpose of this study was to determine the morphometric measurement (total weight and length, weight of visceral, fin, head, bone, fillet, and gills) and evaluate the proximate content of several commercial fish species from the Mesangat wetland, Muara Ancalong, Kutai Timur. The method used was direct sampling from the field for morphometric measurement, while fish was sampled for further proximate analysis and the results was compared to Standard National Indonesia (SNI). The results found that several species of fish used as consumption have a size that was classified as not in a good growth pattern, namely Channa striata, Notopterus chitala, Pangasiodon hypopthalmus, and Hemibagrus nemurus. Meanwhile, Channa micropeltes, Anabas testudineus, and Helostoma temminckii were found in a good growth pattern category. Furthermore, proximate analysis for sampled fish were in standard such as water content, protein, fat, and fibre. However, ash content was not in a standard. In conclusion, several sampled fish for consumption which was found in the Mesangat wetland are in a good growth condition and nutrition composition.

Optimizing rectangular fins for natural convection cooling using CFD

Efficient heat transfer from finned-surfaces under natural convection is a critical consideration in the design of heat sinks for microelectronics and thermal devices. Previous experimental studies on natural convection from rectangular fins on horizontal surfaces have shown that maximum heat transfer per unit base area occurs within a narrow range of fin spacing in tall fins, and over a wider range of fin spacing in shallow fins. However, the heat transfer and flow characteristics of optimum fin configurations and the combined effects of fin geometrical parameters have not been sufficiently scrutinized in the literature. This work is primarily focused on characterizing the optimum heat transfer and flow patterns using three-dimensional, steady-state, laminar, conjugate heat transfer simulations, which serve as the fundamental basis for determining optimum fins. The main fin design parameters are the fin spacing, height, and length. Multi-parametric computational fluid dynamics (CFD) optimization was conducted to determine the combined effects of fin spacing, height, and length on heat transfer. To find a global optimum fin design, we performed a multi-parametric optimization using the dynamic-Q algorithm, rather than through a single parameter variation as is commonly done in previous studies. It was found that the fin spacing, height, and length strongly affect the flow through the fin channel ends, and hence the temperature gradient and heat transfer rate from the fin surfaces. The results demonstrate that the dynamic-Q optimization could efficiently find the global optimum CFD solutions for the design objectives: the maximum heat transfer per unit base area and the maximum heat transfer per unit base area and fin weight. The results are validated through the experimental results available for typical fin designs, as well as an experimental measurement of an example fin design in this work.

Improvement of heat transfer through fins: A brief review of recent developments

AbstractFins or extended surfaces are generally used in heat exchangers to enhance heat transfer between the main surface and ambient fluid. Various types of simple‐shaped fins, namely, rectangular, square, annular, cylindrical, and tapered, have been used with different geometrical combinations. To satisfy industrial demand, different trials have also been carried out for designing optimized fins. The optimization of fins can be performed either by enhancing heat dissipation at an exact fin weight or by diminishing the weight of the fin by precise heat dissipation. Recently a notable amount of work on some typical fins, like, porous fins and perforated fins, has also been carried out. This paper presents a brief review on heat transfer enhancement using fins of different types considering variable thermophysical and geometric parameters, which will also be useful for future use of geometrical modifications of extended surfaces, based on the cost and availability of space.

Shape optimisation of air-cooled finned-tube heat exchangers

The use of annular fins in air-cooled heat exchangers is a well-known solution, commonly used in air-conditioning and heat-recovery systems, for enhancing the air-side heat transfer. Although associated with additional material and manufacturing costs, custom-designed finned-tube heat exchangers can be cost-effective. In this article, the shape of the annular fins in a multi-row air heat exchanger is optimised in order to enhance performance without incurring a manufacturing cost penalty. The air-side heat transfer, pressure drop and entropy generation in a regular, four-row heat exchanger are predicted using a steady-state turbulent CFD model and validated against experimental data. The validated simulation tool is then used to perform model-based optimisation of the fin shapes. The originality of the proposed approach lies in optimising the shape of each fin row individually, resulting in a non-homogenous custom bundle of tubes. Evidence of this local-optimisation potential is first provided by a short preliminary study, followed by four distinct optimisation studies (with four distinct objective functions), aimed at addressing the major problems faced by designers. Response-surface methods – namely, NLPQL for single-objective and MOGA for multi-objective optimisations – are used to determine the optimum configuration for each optimisation strategy. It is shown that elliptical annular-shaped fins minimise the pressure drop and entropy generation, while circular-shaped fins at the entrance region (i.e., first row) can be employed to maximise heat transfer. The results also show that, for the scenario in which the total heat transfer rate is maximised and the pressure drop minimised, the pressure drop is reduced by up to 31%, the fin weight is reduced up to 23%, with as little as a 14% decrease in the total air-side heat transfer, relative to the case in which all the fins across the tube bundle are circular. Moreover, in all optimised cases, the entropy generation rate is also reduced, which shows a thermodynamic improvement in tube bundle performance.

Aeroelastic analysis of cantilever non-symmetric FG sandwich plates under yawed supersonic flow

In this paper, a numerical solution is presented for supersonic flutter analysis of cantilever non-symmetric functionally graded (FG) sandwich plates. The plate is considered to be composed of two different functionally graded face sheets and an isotropic homogeneous core made of ceramic. Based on the first order shear deformation theory (FSDT) and linear piston theory, the set of governing equations and boundary conditions are derived. Dimensionless form of the governing equations and boundary conditions are derived and solved numerically using generalized differential quadrature method (GDQM) and critical velocity and flutter frequencies are calculated. For various values of the yaw angle, effect of different parameters like aspect ratio, thickness of the plate, power law indices and thickness of the core on the flutter boundaries are investigated. Numerical examples show that wings and tail fins with larger length and shorter width are more stable in supersonic flights. It is concluded for FG sandwich plates made of Al-Al2O3 that increase in volume fraction of ceramic (Al2O3) increases aeroelastic stability of the plate. Presented study confirms that improvement of aeroelastic behavior and weight of wings and tail fins of aircrafts are not consistent items. It is shown that value of the critical yaw angle depends on aspect ratio of the plate and other parameters including thickness and variation of properties have no considerable effect on it. Results of this paper can be used in design and analysis of wing and tail fin of supersonic airplanes.

FILLETING YIELD, BODY CHARACTERISTICS AND LENGTH WEIGHT RELATIONSHIP OF FOUR FISH SPECIES FROM LOWER RIVER BENUE MAKURDI NIGERIA

Fillet yield , length-weight relationship and condition factor of four commercial fish species including: Protopterus annectens, Labeo coubie, Auchenoglanis occidentalis and Mormyrus rume from lower river Benue Makurdi Nigeria were determined. A total of 600 fish samples were used, 50 individuals regarding each species for the period of three months. Fish samples were collected and transported to the University of Agriculture Makurdi, Department of Fisheries and Aquaculture laboratory where data were recorded on: The Total weight (TW), Total length (TL), Standard length (ST), Visceral weight (VW), Head length (HL), Weight of bones (WB), Weight of fins (WF) and Weight of fillet (WF) from the four fish species. Large differences in the fillet yield were observed among the species studied. L abeo cuobie had the highest fillet percentage yield (65.51 %) while Auchenoglanis occidentalis had the lowest fillet percentage yield (56.85 %). There was a linear relationship between fish length and fillet, also, significant correlation was found between fillet yield and body measurements (weight and length).

Biogeophysical and physiological processes drive movement patterns in a marine predator

BackgroundBlue sharks (Prionace glauca) are among the most abundant and widely distributed of oceanic elasmobranchs. Millions are taken annually in pelagic longline fisheries and comprise the highest component of auctioned fin weight in the international shark fin trade. Though studies of blue sharks outnumber those of other large pelagic sharks, the species’ complicated and sexually segregated life history still confound current understanding of Atlantic movement patterns. Lack of detailed information regarding movement and vertical behavior continues to limit management efforts that require such data for stock assessment and sustainable catch modeling. Therefore, this study aims to describe behavioral and ecological patterns distinct to aggregating and migrating blue sharks, and compare the findings to existing Atlantic movement models.ResultsData collected from 23 blue sharks instrumented with pop-up satellite archival tags were used in statistical predictive regression models to investigate habitat use during a localized aggregation in the northwest Atlantic, while undergoing seasonal migrations, and with respect to environmental variables. Deployment durations ranged from 4 to 273 days, with sharks inhabiting both productive coastal waters and the open ocean, and exhibiting long-distance seasonal movements exceeding 3700 km. While aggregating on the continental shelf of the northwest Atlantic, blue sharks displayed consistent depth use independent of sex and life stage, and exhibited varied response to environmental (temperature and chlorophyll a) factors. As sharks dispersed from the aggregation site, depth use was influenced by bathymetry, latitude, demography, and presence in the Gulf Stream. Mature females were not observed at the New England tagging site, however, two mature females with recent mating wounds were captured and tagged opportunistically in The Bahamas, one of which migrated to the Mid-Atlantic Ridge.ConclusionsVertical behaviors displayed by blue sharks varied greatly among locales; depth use off the continental shelf was significantly greater, and individuals exhibited a greater frequency of deep-diving behavior, compared to periods of aggregation on the continental shelf. Sexual segregation was evident, suggesting mature and immature males, and immature females may be subjected to high levels of anthropogenic exploitation in this region during periods of aggregation. Analysis of the spatio-temporal tracks revealed that nine individuals traveled beyond the United States EEZ, including a mature female captured in The Bahamas that migrated to the Mid-Atlantic Ridge. These results reflect and augment existing Atlantic migration models, and highlight the complex, synergistic nature of factors affecting blue shark ecology and the need for a cooperative management approach in the North Atlantic.

Growth and reproduction of the squid Illex coindetii Verany, 1839 in the central Mediterranean Sea

Life span, growth and cost of reproduction of Illex coindetii were examined for the first time in the southern Adriatic Sea, central Mediterranean Sea. Age and growth were investigated through statoliths reading. Cost of reproduction was explored by studying the relative investment between somatic and gonad growth. The life span of I. coindetii was less than nine months in both sexes. Females (128-234 days) showed longer life span than males (124-178 days). In both sexes the linear model best described the mantle length-at age data, while the exponential model provided the best fit to the total weight-at-age data. In terms of mantle length, females grew faster than males (average growth rate was 1.33 mm day- 1 in females and 1.00 mm day-1 in males). In terms of total weight, no significant differences were highlighted between growth curves of males and females. Mantle length, total weight, mantle weight and fin weight increased up to the latest maturity stage in both sexes. Immature and maturing individuals showed poorer body condition than mature counterparts in both sexes. Some evidences of a reproductive strategy more similar to a multiple-spawning than to a single-spawning species were found.

Study on the heat transfer and fluid flow characteristics in V-shaped corrugated composite fin

The study on the composite fin with louver and slit is performed numerically to enhance fin performance. It is confirmed that the performance of V-shaped corrugated composite fin is better than that of plate fin, which shows that flow vorticity is stronger due to interaction between corrugate, slit and louver. Slit dimensions optimized in fin performance are drawn by numerical analysis for key parameters of slit using Response Surface Methods (RSM). It is also numerically confirmed that JF-factor of the specification with optimized composite fin is higher than that of X-shaped slit fin by 6.1% on average. Part-level performance test is conducted with heat exchanger samples including the V-shaped fin and X-shaped fin respectively, and confirmed that the heat exchanger with X-shaped fin of 1.5mm fin pitch could be replaced by that with V-shaped composite fin of 1.7mm fin pitch resulting in the reduction of fin weight by 11.7%.

샥스핀 가공 중 사용된 메타규산나트륨 분석

메타규산나트륨은 우리나라 식품첨가물공전에 등록되어 있는 품목으로 식용유지류의 여과보조제의 목적 이외에는 사용할 수 없으며, 최종식품 완성 전에 제거하도록 규정되어 있다. 그러나 최근 샥스핀 등 수산물에 중량 증량의 목적으로 메타규산나트륨을 불법 사용하는 사례가 지속적으로 발생함에 따라 메타규산나트륨의 사용 여부를 판별할 수 있는 분석법의 필요성이 대두되고 있다. 그러나 메타규산나트륨의 수용액은 강알칼리성용액으로 식품에 첨가되면 해리되어 그 자체로 분석할 수 없으며, 규소 양의 측정을 통해 간접적인 방법으로 추정할 경우 시료 자체에 천연적으로 존재하는 규소와 구분해야 하는 어려움이 있다. 따라서 본 연구에서는 메타규산나트륨의 첨가 여부를 판별하기 위한 기초 자료 확보를 위해 메타규산나트륨 수용액에 가공되지 않은 상어지느러미를 침지하여 중량의 증가, pH 및 규소 함량 변화를 측정하였고, 이를 모니터링 결과와 비교하였다. 그러나 Robberecht 등(7)의 연구결과 6종의 어류에서 규소가 1.77-84.19 mg/kg의 범위에서 검출된 결과에서 알 수 있듯이, 수산물의 종류와 개체 간에 규소 함량의 편차가 크게 나타날 수 있기 때문에 향후 샥스핀의 규소 함량 모니터링을 지속적으로 수행하여 데이터베이스를 좀 더 보강할 필요가 있을 것으로 판단되며, 그 이후에 대조군과 pH, 수분 및 규소 함량 비교를 통해 메타규산나트륨 사용여부를 유추해 볼 수 있을 것으로 생각된다. According to the Korea Food Additives Code, sodium metasilicate is permitted for use as a filtering agent for edible oils and fats. Sodium metasilicate is currently used as a food additives to increase the weight of shark fins. In this study, we developed an analytical method to quantify sodium metasilicate in food. Sodium metasilicate content was estimated by measuring the moisture content, pH and silicon content of shark fins. Silicon content was analyzed using inductively coupled plasma-optical emission spectrometry (ICP-OES) following microwave-assisted digestion with <TEX>$HNO_3$</TEX> (65%) and <TEX>$H_2O_2$</TEX> (30%). Shark fin total silicon content was <TEX>$7.17{\pm}8.92mg/kg$</TEX>, while the soluble silicon content was <TEX>$2.34{\pm}3.80mg/kg$</TEX>. After soaking raw shark fin in an aqueous solution of sodium metasilicate, fin weight, pH and silicon content were measured. These results would be used as the basic information for shark fins safety management.

Variation in whole-, landed- and trimmed-carcass and fin-weight ratios for various sharks captured on demersal set-lines off eastern Australia

Sharks are important apex predators in marine systems but many populations have experienced large declines, which has resulted in adverse effects on marine food webs. Sharks are also economically important, as their fins are valued in Asian markets. In response to concerns about declining shark populations, a number of nations, including Australia, have developed national plans of action for their conservation and management. As part of New South Wales’ (NSW) efforts to understand the characteristics of their shark fishery, data were collected on the depth of capture, species, sex, body length and weight, fin weight, and reproductive status of individuals caught in the NSW commercial ‘large shark’ demersal set-line fishery. We created models of the relationship between fin to body weight and wastage (discarded or low value portions of the carcass) and compared the ratios of whole, landed, trimmed, and fin weight to determine the relationship between fin weight and wastage to length by species. Our results indicate that length, sex, and the interactions between length with species and sex account for differences in the relative fin weight of sharks; whereas species, length, and their interaction account for differences in the proportion of a shark carcass that is wasted. The data reveal that catching smaller sharks will increase relative fin weight and decrease wastage. Given these results, we recommend that managers consider weight ratio data information in their decision making to promote a sustainable and profitable shark fishery.

Directional Stability Study of Torpedo Anchors

After a torpedo anchor is released into water during its installation, the directional stability of this anchor is an important factor for its penetration performance. In this paper, a CFD method is used to simulate the falling behavior of the anchor, and detailed parametric studies are conducted to analyze the effects of various parameters to the directional stability. The results show that some parameters like weight, gravity center, and aspect ratio of fin have significant influence on the directional stability.