금강 용담댐 하류의 어류군집 특성과 조사어구별 채집어종의 차이, 멸종위기어종의 서식양상을 밝히기 위해 2023년 5월부터 8월까지 족대와 투망, 일각망, 통발을 이용하여 5개 지점을 2회 조사하였다. 조사결과 11과 35종 2,010개체가 채집되었으며, 우점종은 참갈겨니(Zacco koreanus, 비교풍부도 30.1%), 아우점종은 돌고기(Pungtungia herzi, 11.9%), 그 다음으로 칼납자루(Acheilognathus koreensis, 8.6%), 긴몰개(Squalidus gracilis majimae, 7.4%), 눈동자개 (Pseudobagrus koreanus, 6.0%) 등의 순으로 우세하였다. 출현종 중 환경부지정 멸종위기야생생물은 I급의 감돌고기 (Pseudopungtungia nigra), II급의 돌상어(Gobiobotia brevibarba), 꺽저기(Coreoperca kawamebari) 등 3종이 출현하였고, 한국고유종은 칼납자루, 줄납자루(A. yamatsutae), 감돌고기, 쉬리(Coreoleuciscus splendidus), 참중고기(Sarcocheilichthys variegatus wakiyae), 긴몰개, 돌상어, 돌마자(Microphysogobio yaluensis), 참갈겨니, 참종개(Iksookimia koreensis), 눈동자 개, 금강자가사리(Liobagrus geumgangensis), 꺽지(C. herzi), 동사리(Odontobutis platycephala), 얼록동사리(O. interrupta) 등 15종(고유화율 42.9%)이, 외래어종은 생태계교란 생물로 지정된 배스(Micropterus salmoides)와 블루길(Lepomis macrochirus) 2종이 출현하였다. 군집분석 결과, 비교적 우점도(0.38~0.57)와 균등도(0.66~0.78)는 낮고 종 다양도 (2.01~2.52), 종 풍부도(2.98~3.94)는 높게 나타났다. 하천건강성평가(FAI)는 지점별 87.5~100.0으로 모두 매우좋음(A)으로 평가되었다. 어구별 출현결과를 보면 족대는 8과 23종 294개체, 투망은 6과 19종 627개체, 일각망은 8과 25종 824개체, 통발은 9과 20종 265개체로 나타나, 종수와 개체수는 일각망이 가장 높았고, 종수는 투망이, 개체수는 통발이 가장 적었다. 어구별 채집 특성을 보면, 투망은 표층성 유영어류가, 족대는 소형 저서성 어류가 많이 채집되었고 일각망은 종수와 개체수가 가장 풍부하게 채집된 어구이며, 통발은 이입어종인 꺽저기가 많이 채집되어 주목되었다. 출현 어류 중 멸종위기종 I급인 감돌고기는 비교적 안정적으로 서식하고 있었고, II급의 돌상어는 소수 서식이 확인되었으며, 꺽저기는 국내도입종으로 많은 개체가 서식하고 있어 주목되었다. 교란요인으로 조사기간 중 일부 구간이 하천공사로 어류 서식지가 교란되고 있었고, 생태계교란생물로 지정된 배스와 블루길이 각각 17개체 출현하여 우려되었다. 따라서 본 구간에서 안정적인 어류 서식을 위해서는 무분별한 하천공사는 지양해야 하고, 배스와 블루길의 개체수를 감소시킬 수 있는 구제방안이 필요하며, 최근 도입된 꺽저기의 서식범위 및 양상, 생태계에 미치는 영향 등에 대한 연구가 요구되었다.

신갈호의 어류군집 특징 및 어구별 채집 효과를 밝히기 위해 2020년 8월부터 2021년 10월까지 조사를 실시하였다. 채집 어구는 호소에서 일반적으로 사용되고 있는 족대와 투망, 자망, 정치망을 사용하였다. 조사결과, 조사기간 동안 채집된 어류는 7과 18종 3,501개체, 생체량 117,670g이었다. 개체수비 우점종은 참붕어(Pseudorasbora parva, 29.9%), 아우점종은 피라미(Zacco platypus, 25.1%), 다음으로 배스(Micropterus salmoides, 19.3%), 붕어(Carassius auratus, 9.1%), 밀어(Rhinogobius brunneus, 6.1%), 블루길(Lepomis macrochirus, 4.2%) 등의 순으로 우세하였으며, 생체량비 우점종은 붕어(45.1%), 아우점종은 잉어(Cyprinus carpio, 17.4%), 그 다음으로 배스(14.3%), 피라미(7.7%), 떡붕어(C. cuvieri, 7.4%), 참붕어(3.9%) 등의 순으로 우세하였다. 출현종 중 한국고유종은 몰개(Squalidus japonicus coreanus), 점줄종개(Cobitis nalbanti), 얼록동사리(Odontobutis interrupta) 3종이었으며, 외래어종은 배스, 블루길, 떡붕어, 향어 (Cyprinus carpio nudus type) 4종으로 이중 배스와 블루길은 생태계교란 생물로 지정된 종이다. 주요종의 평균 체장과 체중을 조사한 결과, 우점종인 참붕어는 체장 60±24.1㎜, 체중 4.4±3.42g이었고, 아우점종인 피라미는 체장 82±17.6㎜, 체중 10.4±7.27g, 우세종 배스는 체장 96±25.1㎜, 체중 24.9±96.02g, 붕어는 체장 125±77.3㎜, 체중 168±336.5g이었 다. 어구별 조사결과, 족대로 채집된 어류는 3과 8종 302개체 생체량 1,269g, 투망으로 채집된 어류는 4과 11종 948개체 생체량 31,343g, 자망으로 채집된 어류는 4과 13종 682개체 생체량 69,695g, 정치망으로 채집된 어류는 7과 15종 1,569개체, 생체량 15,362g으로 나타났다. 어구별 조사결과를 요약하면, 정치망은 종수와 개체수가, 삼중자망은 생체량 이 가장 많았으며, 투망은 연안지대의 종수와 개체수를 채집하는데 강점이 있었으며, 족대는 종수와 개체수, 생체량 모두 가장 적었으나 연안지대의 저서성 소형어류를 채집하는데 강점을 보였다.

기어의 구조 안정성 및 치물림 성능을 분석하기 위하여 유한요소해석이 널리 사용된다. 본 연구에서는 스퍼 기어의 유한요소 모델 링 조건이 해석 결과 및 간소화 효과에 미치는 영향을 분석하였다. 기어 구조 해석의 간소화 방법으로 기어 몸체 및 잇수 간소화, 요소 망 생성 방식, 접촉 및 마찰 조건, 해석 조건 등을 선정하였다. 기어의 성능해석 지표로써 1주기의 기어 치물림 사이클 동안의 정전달 오차를 계산하였고, 간소화 지표로써 해석 소요 시간을 측정하였다. 유한요소해석을 통해 치물림 주기에 따른 접촉 응력 분포 및 변화 양상을 확인하였다. 모델링 조건에 따라 최대 전달 오차와 해석 소요 시간에 차이를 확인하고 원인을 분석하였다.

Sampling gears for collecting fish are diverse, and the community of fish varies according to the selection and characteristics of the sampling gears. The present study compared the characteristics of fish communities in Yedang reservoir using four sampling gears (kick net, cast net, gill net, and fyke net). The kick net and cast net were inefficient in collecting the number of individuals. However, they increased the species diversity of fish inhabiting the waterfront. Although not many individuals were collected, the gill net mainly collected large fish. The largest number of individuals was collected in the fyke net, and the dominance was high due to the high species selectivity. Through Self-Organizing Map (SOM) analysis, large fish were collected in the gill net, whereas small fish were collected in the fyke net. The characteristics and efficiency of the fish differed depending on the sampling gears. It is expected that researchers will need to use it appropriately according to the characteristics of the sampling gears when investigating the fish community.

Trawl fishing is a fishing method in which a large, motorized trawler tows a bag-shaped net to catch fish living at the bottom or middle layers. For a trawl gear, it is of utmost importance to select the gear size and towing speed suitable for the effective horsepower (EHP) of the trawler in the design stage. In general, the power required to move an object is proportional to the product of the object speed and resistance; therefore, there are various choices for the gear resistance and towing speed given the effective horsepower of the trawler. However, there have been few studies on the gear design of an appropriate scale for the towing speed given the effective horsepower of the trawler. In this study, the resistance and shape of three types of midwater trawl gears were analyzed using SimuTrawl, a computer simulation tool. In addition, the relationship between the propulsion force and speed of the ship was clarified when the size and effective horsepower of the trawler were determined. Finally, we suggested the relationship between the towing speed and the resistance of the gear when the trawler towed the net was investigated, and a specific method of selecting the gear size according to the towing speed.

The accurate estimation of fish assemblages is highly dependent on the sampling gear used for sampling. We used data from 15 sampling sites along the Nakdong River, which is a large river in South Korea, to identify differences in assemblages and sizes of freshwater fishes collected with either cast nets or gill nets, the two most commonly used sampling gear in South Korea. The two gears differed in the fish assemblages they captured, with more species caught by gill nets. Further, due to its tighter mesh size, the cast net caught significantly smaller fishes than the gill nets (independent t-test, p<0.05). We found the cast net to be appropriate for species that inhabit shallow (less than 2 m) and open water, but inappropriate for deep water, habitats with plant beds, and nocturnal species. Thus, cast net sampling is not efficient in a large river environment, and a combination of sampling methods is more suitable for understanding fish assemblages in such habitats. In general, appropriate selection of fishing methods to specific habitats is necessary to improve data quality and minimize the misrepresentation of environmental conditions.

This study was carried out to compare the regional fishing gears and catches of the gape net with wings used in Jeonnam, Korea. The total length of the gear used in Yeosu, Wando and Jindo was 107.0m, 64.0m, 52.8m, and the size of codend was 4.3mm. 7.8mm. 9.8mm, respectively. The total number of bycatch species from anchovy (Engraulis japonicus) catches in Yeosu, Wando, and Jindo during the survey period were 21, 13, and 13 species. A total of individuals of anchovy accounted for over 90% out of total catches in all survey areas. The proportion of anchovy individuals was constantly high up to October in Yeosu, but it showed a sharp reduction to 18% in October in Wando with the increase of the individuals of Kammal thryssa (Thryssa kammalensis) and Big eyed herring (Sardinella zunasi). In Jindo, individuals of anchovy occupied over 99.8% out of total catches up to August. Since August, the number of individuals of Big eyed herring (Sardinella zunasi), Kammal thryssa (Thryssa kammalensis), and Slimy (Leiognathus nuchalis) has increased while the number of anchovy individuals were decreased.

A novel PM (powder metallurgy) steel for automotive power-train gear components was developed to reduce manufacturing cost, while meeting application requirements. The high-density PM steel was manufactured by mixing using special Cr-Mo atomized iron powders, high-pressure compaction, and sintering. Tensile strength, charpy impact, bending fatigue, and contact fatigue tests for the PM steel were carried out and compared to conventional forged steel. Pinion gears for auto-transmission were also manufactured by helical pressing, sintering, and surface densification process. In order to evaluate the durability of the PM parts, auto-transmission durability tests were performed using dynamometer tests. Results showed that the PM steel fulfilled the requirements for pinion gears indicating suitable tensile, bending fatigue, contact fatigue strengths and improved gear tooth profile. The PM gears also showed good performance during the transmission durability tests. As a result, the PM gears showed significant potential to replace the conventional forged steel gears manufactured by tooth machining (hobbing, shaving, and grinding) processes.

The main purpose of this study is to understand the marketing approaches and strategies that are used to disseminating biodegradable fishing gears and distinguish the cognition and the non-cognition group's attitudes on the product. We used a technology acceptance model for analyzing product attributes and its impacts on fishers' purchase. The result of this research shows that 'perceived usefulness and easiness of use' have positive effect on 'purchase intention,' and then give impacts on 'purchase intention' for the entire respondents. For the cognitive respondents these factors have influence on 'attitude' but they do not affect 'purchase decision.' However, 'perceived usefulness and easiness of use' have much positive impact on 'purchase intention.' In the non-cognition group, the 'perceived intention' and 'company and country of manufacturers' have direct positive effect on 'purchase intention' through 'attitude' and also 'on 'purchase intention.' This research provides some meaningful policy implications on further development and technology marketing of biodegradable fishing gears.

The processes of P/M affect the properties of sintered gears. The different techniques of P/M lead to the different properties of sintered gears. This paper summarizes new progress in powder metallurgy for sintered gears. These progresses include warm compaction, high velocity compaction, sinter hardening, high temperature sintering, infiltration, CNC powder press and surface densification etc.

Highly compressible Ni-Mo steels are attractive materials for PM due to high sinter density and ease of processing. Extra-fine Ni admixed PM steels have demonstrated improved mechanical properties and rolling contact fatigue resistance due to a more uniform microstructure and increased Ni diffusion during sintering. Sinter densities of single press single sinter XF Ni-Mo steels can approach at moderate compaction pressures. Leaner alloys based on extra-fine Ni powder are possible depending on the performance requirements of the PM steel part. Extra-fine Ni steels are particularly attractive for the growing market of high performance PM gears and sprockets.

1987년 9월중에 남부해역에서 부산수산대학 실습선 402호와 403호를 이용하여 통발 어구로써 어획한 붕장어 Astroconger myriaster의 전장「체중 및 굵기 등의 상호관계와 어체 크기와 어구망목과의 관계를 분석한 결과를 요약하면 다음과 같다. 1. 전장 L, 체중 W 및 굵기 D의 상호관계는 W=3.58×10 상(-4) L 상(3.38) (r=0.99). D=0.07 L-0.59 (r=0.99). W=10.38 D 상(2.76) (r=1.00). W=1/2×D 상(2)「L 과 같이 표현된다. 2. 붕장어를 어획하는 통발 어구의 그물코 크기와 구멍의 직경은 각각 29.2mm, 18.6mm이상 되어야 한다.

In order to improve the net-mouth height of dragged gears, the authors devised models of floatingcollars of nylon cloth instead of floats and experimented with 4 types-A type (length 65em, breadth 3em), B type (length 65em, breadth 4em), C type (length 65em, breadth 5em) and D type (length 65 em, breadth 6em) attached respectively to the front edge of square of a model net after preliminary experimentation. These various types of floating collars were experimented in a circulating water channel to evaluate the characteristics of net-mouth height and hydrodynamic resistance and the effect of the length of bridles were also examined. The results obtained were as follows: 1. In case of attaching floats, the model net-mouth height reduced from 80 em to 20 em when current velocity was increased from 0.25m/see to 1m/sec. 2. In case of attaching floating collars, the model net-mouth heights were maintained 70 em, 71 em, 80 em, 78 em in maximum and 55 em, 63 em, 69 em, 73 em in minimum respectively even the current volocity was increased from 0.25 m/see to 1 m/see. 3. The model net-mouth height was reduced to 10 em maximum according to the current velocity and types of floating collars when the bridles were shortened 3~4 mm in length. 4. Hydrodynamic resistance of D type only was increased to 700 g in maximum and those of A, B, C type were reduced to 460 g in maximum at current velocity beyond 0.5 m/ see when bridles were shortened 3-4 mm in length. 5. But the model net-mouth heights became higher in accordance with breadth of floating coliars, B type was the best for this model net in case that hydrodynamic resistance was taken into account.