• 수산해양기술연구
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• 제29권3호
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• pp.177-182
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• 1993

In order to estimate the mesh selectivity master curves and the optimum mesh size, experiments were made by the cover net method with the cod-ends of the five different the opening mesh sizes(51.2mm, 70.2mm, 77.6mm, 88.0mm and 111.3mm). After that 163 hauling were performed and there by investigated, on the training vessel Saebada in the Southern Korean Sea and East China Sea from June 1991 to August 1992. In this report, the mesh selectivity master curves were fitted by using logistic function(S=1/(1+exp super(-(aR+b))), R=(L-L sub(0))/(M-M sub(0)) and the optimum mesh sizes were estimated from each master curve. In this case, a and b are the selection parameters, M is the mesh size of each experimental cod-end. L is body length, L sub(0) and M sub(0) is the distance from the coordinate origine to intersection of linear regression between 25% and 50% selection length. The results obtained are summarized as follows; 1. Trachurus japonicus: Mesh selectivity master curve parameters: a and b were 2. 25, -4.73 respectively and optimum mesh size was estimated to be 79.3mm. 2. Trichiurus lepturus: Mesh selectivity master curve parameters: a and b were 0.81, -3.17 respectively and optimum mesh size was estimated to be 64.5mm. 3. Photololigo edulis: Mesh selectivity master curve parameters: a and b were 1.30m, -4.10 respectively and optimum mesh size was estimated to be 89.9mm. 4. Todarodes pacificus: Mesh selectivity master curve parameters: a and b were 1. 35, -3.45 respectively and optimum mesh size was estimated to be 89.4mm.

• 수산해양기술연구
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• 제30권2호
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• pp.86-96
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• 1994

In order to estimate the optimum harvesting mesh size of multispecies, the 24 species of catching data which were taken by fishing trial of trawl gear in Korean Southern Coast and East China Sea during 1991-1993 year were grouped and divided by the Cluster analysis method, considering first maturity length and body width, body height, body girth based on the first maturity length. With the same method, the above groups were subdivided by the potential escape such as possible escape index, range factor and selection factor. In case of the species devoid of selection parameters, these species were first subdivided by the use of possible escape index and length range factor. Next, the optimum harvesting mesh size of multispecies was properly classified according to the optimal mesh size of a fish estimated by first maturity length against selection factor. The results obtained are summarized as follows: 1. Each optimum harvesting mesh size of Psenopsis anomala, Priacanthus macra-canthus, Trachurus japonicus, Argyrosomus argentatus was 71.1-79.5mm, and Saurida undosquamis was 65.5mm. 2. Each optimum harvesting mesh size of Scomber japonicus, Pseudosciaena crosea, Pseudosciaena Polyactis, Sebastes thompsoni, Doderleinia berycoides was 78.5-85.6mm, and Bembras japonicus, Sphyraena pinguis was 48.4-51.3mm. 3. Each optimum harvesting mesh size of Zeus faber, Pampus argenteus, Zenopsis nebulosan was 118.4-124.1mm, and Caranx equula was 91.4mm, and Thamnaconus modestus was 131.2mm, and Pagrus major was 149.4mm. 4. Each optimum harvesting mesh size of Upeneus bensasi, Callanthias japonicus, Sardinops melanosticata, Konosirus punctatus was 36.8-42.8mm, and Acropoma japonicum was 21.2mm, and Apogon lineatus was 26.3mm.

• 대한기계학회논문집A
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• 제21권11호
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• pp.1950-1956
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• 1997

An engineering goal in vibration and noise professionals is to develope quiet machines at the preliminary design stage, and various numerical techniques such as FEM, SEA or BEM are one of the schemes toward the goal. In this paper, the research has been focused on the sensitivity effect of mesh sizes for FEM application so that the optimum size of the mesh that leads to engineering solution within acceptable computing time could be generated. In order to evaluate the mesh size effect, three important parameters have been examined : natural frequencies, number of modes and driving point mobility. First, several lower modes including the fundamental frequency of a 2-D plate structure have been calculated as mesh size changes. Since theoretical values of natural frequencies for a simple structure are known, the deviation between the numerical and theoretical values is obtained as a function of mesh size. The result shows that the error is no longer decreased if the mesh size becomes a quarter wavelength or smaller than that. Second, the mesh size effect is also investigated for the number of modes. For the frequency band up to 1.4 kHz, the structure should have 38 modes in total. As the mesh size reaches to the quarter wavelength, the total count in modes approaches to the same values. Third, a mobility function at the driving point is compared between SEA and FEM result. In SEA application, the mobility function is determined by the modal density and the mass of the structure. It is independent of excitation frequencies. When the mobility function is calculated from a wavelength to one-tenth of it, the mobility becomes constant if the mesh becomes a quarter wavelength or smaller. We can conclude that dynamic parameters, such as eigenvalues, mode count, and mobility function, can be correctly estimated, while saving the computing burden, if a quarter wavelength (.lambda./4) mesh is used. Therefore, (.lambda./4) mesh is recommended in structural vibration analysis.

• 수산해양기술연구
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• 제43권3호
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• pp.169-175
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• 2007

To examine the mesh selectivity and optimum mesh size of gill nets for silver promfret Pampus argenteus, the field experiments were carried out during June 27th to July 3rd, 2005 at the coastal area of Imja island. The experimental gill nets for silver promfret were used in two set, which one set was consisted of 12 sheets, and each set was connected alternatively four defferent sheets those were 141mm, 148mm, 155mm and 164mm in mesh size. The analysis of mesh selectivity curve was done by Kitahara's method. The total number of fishes caught by experimental fishing of gill nets for silver promfret was 1,409, and it was consisted of 1,022 silver promfrets(72.5%), 123 croakers(8.7%), 70 red tongue soles(5.0%), 67 blue crabs(4.8%), 22 red seabreams(1.6%), and 105 other fishes(7.4%). The number of fishes caught by the mesh size was 244 at mesh 141mm(mean 6.8/sheet), 261 at mesh 148mm(mean 7.3/sheet), 295 at mesh 155mm(mean 8.2/sheet) and 222 at mesh 164mm(mean 6.2/sheet). The body weight of fishes caught by the mesh size was 102.1kg at mesh 141mm(mean 2.8kg/sheet), 112.9kg at mesh 148mm(mean 3.1kg/sheet), 132.8kg at mesh 155mm(mean 3.7kg/sheet), and 100.4kg at mesh 164mm(mean 2.8kg/sheet). The value of maximum l/m on mesh selectivity curve and the value of l/m on the selection range of 50% was estimated at 1.91 and from 1.63 to 2.23, respectively. Therefore, the optimum mesh size of gill nets for silver promfret was estimated 135mm, and the total length at the selection range of 50% was from 220mm to 301mm. But, it will be useful to use the mesh size of gill nets which is about 10-15% larger than the estimated optimum mesh size of gill nets considering the number of fishes caught, body length and body weight etc.

• 한국수산과학회지
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• 제30권6호
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• pp.916-922
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• 1997

This paper attempted to estimate mesh selectivity of gill nets for neon flying squid in the north Pacific Ocean. The 11 linear regressions, (P<0.05) were obtained using the data on catch ratios derived from mesh size combinations between two slightly different mesh sizes of 12 kinds of research gillnet (namely 33, 37, 42, 48, 55, 63, 72. 76, 86, 96, 105 and 115 mm in stretched mesh size). There was an increase in the optimum length with the increase in mesh size but standard deviation showed somewhat increase with the increase in the mesh size. The selectivity curves were well fitted to the length frequency distributions obtained from samples for the mesh sizes from 48 mm through 86 mm. For the mesh sizes of 33, 37 and 42 mm the DML (Dorsal Mantle Length) compositions were distributed towards the right hand-limb of the curves. The DML distributions from the 96 mm and larger meshes showed a trend towards the left hand-limb of the curves. The selectivity curves for different mesh sizes indicate that large mesh sizes catch a greater size range of squid, and the gill net fishery in the north Pacific Ocean captures effectively neon flying squid within the range of $9\~43cm$ DML.

• 수산해양기술연구
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• 제29권4호
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• pp.247-259
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• 1993

The fishing experiment was carried out by the training ship Saebada in order to analyse the mesh selectivity for trawl cod-end, in the Southern Korea Sea and the East China Sea from June. 1991 through August, 1992. The trawl cod-end used in this experiment has the trouser type of cod-end with cover net. and the mesh selectivity was examined for the five kinds of the opening of mesh in its cod-end part. A total of 163 hauls, of which having mesh size 51.2mm ; A 89, 70.2mm ; B 54, 77.6mm ; C 55, 88.0mm ; D 52 and 111.3mm ; E 20 were used respectively. Selection curves and selection parameters were calculated by using a logistic function, S=1/(1+exp super(-(aL+b)) ). The mesh election master curves were estimated by S=1/(1+exp super(-[a(L/M)+$\beta$]) ). and the optimum mesh size were calculated with (L/M) sub(50) of master curve. In these cases 'a' and '$\alpha$' are slope, 'b' and '$\beta$' are intercept. 'L' is body length of the target species of fishes, 'M' is the mesh size, and 'S' denotes mesh selectivity. In this report, the four species of compressed form fishes were taken analized according to fish shape, and 'S' denotes mesh selectivity. In this report, the four species of compressed form fishes were taken analized according to fish shape, and the results obtained are summarized as follows: 1. Red seabream Pagrus major(Temminct et Schlegel) and yellow porgy Dentex tumifrons(Temminct et Schlegel) ; Selection rate in each mesh size of A, B, C, D and E were 99.7%, 97.5%, 91.4%, 76.7% and 57.8% respectively. Selection parameters 'a' and 'b' of mesh sizes C, D and E were 2.65 and -28.62, 4.40 and -77.73, 2.31 and -46.99, and their selection factors were 1.39, 2.10, 1.83 respectively. Selection parameters of master curve '$\alpha$' and '$\beta$' were 3.05 and -5.65 respectively, and (L/M) sub(50) was 1.85. The optimum mesh size of Red seabream was 141mm. 2. Filefish Thamnaconus modestus (Gunther) ; Selection rate in each mesh size of A, B, C, D and E were 99.6%, 98.3%, 91.2%, 80.0% and 48.6% respectively. Selection parameters 'a' and 'b' of mesh sizes C, D and E were 5.82 and -55.10, 2.92 and -36.90, 3.91 and -63.09, and their selection factors were 1.35, 1.44, 1.45 respectively. Selection parameters of master curve '$\alpha$' and '$\beta$' were 3.02 and -4.32 respectively, and (L/M) sub(50) was 1.43. The optimum mesh size was 129mm. 3. Target dory Zeus faber Valenciennes ; Selection rate in each mesh size of A, B, C, D and E were 99.7%, 100%, 83.2%, 91.6% and 65.0% respectively. Selection parameters 'a' and 'b' of mesh sizes C, D and E were 3.85 and -32.46, 4.19 and -57.38, 2.45 and -40.03, and their selection factors were 1.09, 1.56, 1.47 respectively. Selection parameters of master curve '$\alpha$' and '$\beta$' were 2.64 and -3.53 respectively, and (L/M) sub(50) was 1.34. The optimum mesh size was 127mm. 4. Butterfish Psenopsis anomala (Temminct et Schlegel) ; Selection rate in each mesh size of A, B, C, D and E were 99.2%, 34.1%, 46.5%, 14.3% and 2.4% respectively. Selection parameters 'a' and 'b' of mesh sizes B, C and D were 5.35 and -71.70, 5.07 and -69.25, 3.31 and -62.06 and their selection factors were 1.91, 1.75, 2.13 respectively. Selection parameters of master curve '$\alpha$' and '$\beta$' were 3.16 and -6.24 respectively, and (L/M) sub(50) was 1.98. The optimum mesh size was 71mm.

• 수산해양기술연구
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• 제41권1호
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• pp.27-34
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• 2005

붕장어에 대한 스프링형 그물통발의 망목선택성 및 적정망목을 추정하기 위한 시험조업은 경남 거제시 능포 인근해역에서 2002년 9월25일${\sim}$9월27일에 실시되었다. 시험어구는 현용어구인 15mm, 20mm 및 시험을 위해 제작한 25mm, 30mm 그리고 수산자원보호령에서 규정하고 있는 35mm와 대조어구로써 통수공 6.7mm의 플라스틱 통발을 각각 50개씩 제작하여 사용하였다. 망목선택성은 Kitahara(1968)와 Fujimori(1996)의 방법을 사용하여 분석하였고, 적정망목은 어체 동주와 체장과의 관계 그리고 망목선택성 Master Curve를 사용하여 추정하였다. 그 결과를 요약하면 다음과 같다. 1. 시험조업 결과 총어획미수는 835미로, 붕장어 537미(64.4%), 게류 225미(26.9%), 기타 73미(8.7%)였다. 2. 망목선택성 곡선의 Master Curve에서 최대 전장/망목(max. 1/m)의 값은 23.9로 추정되었다. 3. 붕장어 스프링 통발의 적정망목은 34.0mm로 추정되었다.

• 수산해양기술연구
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• 제30권3호
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• pp.172-181
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• 1994

The mesh selectivity of diamond and suare mesh cod-ends at the Southern Korean Sea and the East China Sea were compared for Pampus argenteus, Trachurus japonicus, Trichiurus lepturus. Selection trials were carried out using diamond and square mesh cod-end by trouser type cod-end with cover net. of which the mesh cod-end has four types : A(51.2mm), B(70.2mm), C(77.6mm), D(88.0mm). Selection curves and selection parameters were calculated using a logistic model. The results obained are summarized as follows : 1. Harvest fish : In B. C and D type selection range and fifty percent selection length of the square mesh were about 21mm, 11mm : 12mm, 18mm and 34mm, 5mm higher than those of the diamond mesh, respectively. Selection factor of master curve for the diamond mesh was 1.54 and for the square mesh was 1.68. The optimum mesh size for the diamond mesh was 97.4mm and for the square mesh was 89.3mm, the difference was 8.1mm. 2. Horse mackerel : In A type, selection range was nearly the same for the diamond and the square mesh, but fifty percent selection length of the square mesh was 43mm higher than the diamond mesh. In B. C and D type, selection range and fifty percent selection length of the square mesh were about 6mm, 3mm : 24mm, 21mm and 11mm, 42mm higher than those of the diamond mesh, respectively. Selection factor of master curve for the diamond mesh was 2.37, for the square mesh was 2.77. The optimum mesh size for the diamond mesh was 78.1mm and for the square mesh was 66.8mm, the difference was 11.3mm. 3. Hair tail : In A, B and C type, selection range of the square mesh was about 34mm, 8mm, 60mm higher than those of the diamond mesh. Fifty percent selection length for the diamond mesh was about 5mm, 7mm, 8mm higher than that of the square mesh. Selection factor of master curve for the diamond mesh was 3.11, for the square mesh was 3.48. The optimum mesh size for the diamond mesh was 64.3mm and for the square mesh was 57.5mm, the difference was 6.8mm.

• 수산해양기술연구
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• 제49권3호
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• pp.200-207
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• 2013

This paper presents the mesh selectivity of a net pot for common octopus Octopus minor for the sustainable resources management of common octopus. The filed experiments were carried out the total 10 times in the southern part of coastal sea in Korea from March to May in 2010 using net pots of five different mesh sizes (16, 18, 20, 22 and 26mm). The test of size selectivity, indicated a 50% selection value on the logistic master curve of 3.195, whereby 50% of individuals with a mantle size of approximately 70.3mm selected a mesh size of 22mm. Considering that 50% of common octopus entering sexual maturity have a mantle size of 70.6mm, the optimum mesh size should be equal to, or larger than 22mm.

• 수산해양교육연구
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• 제25권4호
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• pp.928-936
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• 2013

This thesis is the fundamental study on the adaptation of escape device for reducing small fishes in set-net. The escape devices for experiments were made the mesh-type devices with three different mesh sizes (60.6, 75.8 and 120.0mm). The experiments of size selectivity on escape devices were conducted by using two kinds of species as black rockfish (Sebastes schlegeli) and sea perch (Lateolabrax maculatusi) in the experimental tank. The size selectivity curve was fitted by using a logistic function and the parameters of selectivity curve were estimated by a maximum likelihood method. In the results; 50% selection ranges for the mesh-type escape devices with three different mesh sizes were; a black rockfish was 18.99 in mesh size 60.6mm and 21.96 in mesh size 75.8mm (120mm could not estimate). A sea perch was 22.02 in mesh 60.6mm and 24.46 in mesh size 75.8mm (120mm could not estimate). The 50% selection range of a black rockfish was wilder than a sea perch about 1.1~.2 time. Therefore, the small fishes are able to reduce by using the mesh type escape device. However, the optimum mesh size should be decided to consider the size of target species and economics of catches.