At Pyropia farms, organic acid treatments have enhanced productivity and quality by removing pest algae (such as Ulva spp. and diatoms) and reducing the occurrence of diseases. Ulva spp. attaches to the Pyropia nets competing for inorganic nutrients & space and diminishing productivity. Additionally, the presence of attached contaminants (such as diatoms and middy particles) on the Pyropia nets negatively affects the quality of Pyropia. This study investigated the effects of removing Ulva linza and washing the Pyropia yezoensis nets using an activating treatment agent (organic acid and highly saline solution) with an air bubble device. The results of measuring the dead cell ratios after treatment under different conditions showed that the dead cell ratio of U. linza did not significantly increase when the air bubble device combined the activating treatment agent with the activating treatment agent alone. When washing the P. yezoensis nets, the air bubble device was about 19-37% more effective than the activating treatment agent alone. The findings of this study suggest that the air bubble device enhances the efficacy of the activating treatment agent, resulting in the effective cleaning of the Pyropia nets.
최근 양식기법이 보급되어 어가의 양식이 활발해진 감태 (Ecklonia cava Kjellman)는 향후 다양한 품종개발이 예상되고, 이들의 구분을 위한 신품종 심사기준 (특성조사요 령) 작성과 기초자료가 되는 자연 개체군의 변이 폭과 지역적 형태 변이에 관한 연구 필요성은 더욱 커지고 있다. 본 연구는 감태 양식 개체군과 국내 연안 16개소에서 채집한 자연개체군의 형태를 비교하고, 주요 형태 형질의 특성과 변이 폭을 규명하고자 하였다. 감태의 품종 구분에 적합한 형질은 1차엽과 2차엽, 줄기에 대한 주요 형태와 특 징에 관한 14개 측정 형질과 4개 비율 형질, 총 18개 특성을 선정하였다. 군집 분석에서 전체 19개 개체군 중, 자연 개체군인 장길 (E4), 소록 (S7)은 동일 지역 개체군들과 유의한 차이를 보였고, 동해와 남해의 나머지 자연 개체군은 양식 2년생인 수유 (Q6, Q8, Q10)를 포함한 2개 집단으로 구분되었고, 제주의 3개 개체군은 별도의 집단을 이루어 지역적으로 구분되었다. 주성분 분석에서도 군집 분석에서 집단을 이룬 동해와 남해 개체군을 중심으로 양식 개체군은 중앙에 모여 나타났고, 장길 (E4), 소록 (S7)과 제주 개체군들은 주성분 1 (PC1)과 주성분 2 (PC2)에 연관된 2 차엽 지수, 줄기의 길이와 직경, 줄기 길이/1차엽 길이, 1차엽 길이와 너비, 2차엽 수, 2차엽 길이와 너비의 형질에 의해 각 축에 따라 구분되어 나타났다. 이상의 결과로 본 연구에서 조사한 18개 형질은 각 해역에서 유의한 차이를 보이는 개체군 구분을 위한 기준으로 유용성이 확인되었으 며, 감태의 각 지역 개체군은 향후 신품종 개발 후보 종으로 가능성이 클 것으로 기대되었다.
The macroalgal community structure was examined at the subtidal zones of six study sites, on the Southern coast of Korea from between May and August 2015. A total of 132 seaweeds, comprising 10 green, 28 brown and 94 red Seaweed, were identified. The seaweed biomass was 80.32 g dry wt. m-2 in average, and it was maximal at Geomundo (166.94 g dry wt. m-2) and minimal at Byeongpungdo (14.52 g dry wt. m-2). On the basis of the biomass, the Ecklonia cava was a representative species, distributed widely in the subtidal zone of the three islands (Yeoseodo, Geomundo, Baekdo). Also, the Sargassum sp. was dominant at Sejondo and Hongdo. The turbidity and light transmittance was divided into two groups. The seaweed community structure of group A (Byeongpungdo, Sejondo, Geomundo) was characterized by high turbidity, low light transmittance and a lower habitat depth than were observed in group B (Hongdo, Baekdo, Yeoseodo). As the water depth increased, the biomass decreased due to the lowered light transmittance. In Byeongpungdo and Sejondo, which showed high turbidity and low light transmittance, the degree of seaweed coverage was decreased with the depth of water. The ESGⅡ ratio of the Ecological Status Group was higher than fourty percentage in Byeongpungdo and Baekdo. Community indices were as follows: dominance index (DI) 0.35-0.90, richness index (R) 7.03-17.93, evenness index (J′) 0.22-0.60, and diversity index (H′) 0.79-2.18. The Macroalgal zonation of the subtidal zone was calculated by the Ecklonia cava and Brown algal population on five islands (Byeongpungdo, Yeoseodo, Geomundo, Beakdo, Hongdo). On the other hand, Undaria pinnatifida and Sargassum sp. dominated at Sejondo. Additionally, the biomass ratio and the species richness of green algae was lower in group A. These differences in the seaweed community structure may have resulted from the effects of turbidity and light transmittance.
The characteristics of stress distribution and fatigue life have been investigated in the road mower head system using FEM(Finite Element Method). There is high stress distribution around the coupling part with non-uniform load from the irregular road surface. Maximum equivalent stress especially occurs in the fixed plate and the pillar of the head device with maximum deformation at the rotation axis frame of the mower system. Fatigue life tests were also performed with SAE bracket history, SAE transmission, and sample history conditions. SAE bracket history and SAE transmission predicted the possibility of high damage while Sample history showed a stable trend. These results will be applicable in optimal design for various systems equipped with mower head system.
In this study, natural frequency characteristics of road mower head system are investigated through experiment and numerical analysis. ANSYS workbench 14.5 is used to calculate the frequency analysis in the mower system. Compared the natural frequency using the modal test and computerized analysis. When compared with the experimental results, a 5% error rate has occurred. Simulation results showed that vibration mode shape has directional characteristics, especially to the right and left. These results will be helpful in optimal design for road mower head systems.
Seawater flow characteristics around deep-sea sediment resuspension system was analyzed using CFD simulation. Seawater flow is influenced by migration velocity of DSSRS and the resuspension system with disturbance device. Especially complicated flow field is generated with discharged flow in the vertical direction, and there is large variation of seawater velocity near the system with vortex flow. Turbulent kinetic energy near the system increases 2～6 times, and its variation is also affected by the operation condition of the disturbance device. The results of this study are expected to be useful in evaluating the environmental effects of the suspended solid matters which are generated in the deep sea sediment disturbance process.
Numerical analysis was performed to analysis the structural characteristics of the head device in the road mower system. The head device connects mower system with the boom of the special vehicle. The system with various road surface conditions is subjected to continuous vibration and repeated load. Especially, the maximum equivalent stress occurs in the pillar of the head device, and the maximum equivalent strain also occurs in the fixed plate that supports the mower system. Fatigue analysis results show that the upper end of the pillar is very vulnerable. This analysis results can be used as basic data for optimal road mower head system design.
In this study, temperature variation characteristics in a flat plate with sheath heater are investigated through experiment and numerical analysis. ANSYS fluent is used to calculate the temperature distribution in the heating plate system. Transient condition is applied to observe temperature variation with the sheath heater operation, and thermal resistance on the contacted surfaces is also considered. Experimental data agree well with numerical results obtained for heat generation rate from sheath heater, Local temperature variation on the surface of flat plate is also predicted through this simulation. There is large temperature variation in the air surrounded flat plate, especially at the top of flat plate with natural convective heat transfer. These results will be helpful in optimal design for various systems equipped with sheath heater.
Numerical analysis was carried out to investigate the variation of stress and strain characteristics for the rail device in stone board cutting system. The maximum equivalent stress and strain from the vertical load acting on the device decrease as the load moves forward. Also, the maximum equivalent stress appears near the end of left, and the equivalent force of right rail device was about 1.8 times higher than that of left rail device. The variation of stress and strain distributions was remarkable at the edge of the device, and it has a strong influence on the bottom and column. These results can be applicable to optimal design of the stone board cutting device for the system safety.
CFD(Computational Fluid Dynamics) analysis was carried out to analysis the air flow characteristics of vertical axis wind turbine system with accelerating device. Geometric arc angle of the accelerating device affects the air flow characteristics in the turbine with the effect of Coanda generated from the curved surface. Air velocity distributions with the device angle variation are compared. Flow velocity increases with the device length, and the accelerating device plays a key role in decreasing the air velocity in the wake flow region. Maximum air velocity variation becomes reduced with the accelerating device, and it is largely affected by the arc angle. These results are expected to be utilized in various ways to determine the shape of accelerating device for wind power generation system.
The characteristics of temperature variation for laser diode welding system have been analyzed with numerical investigation. The laser diode is assembled with a cap and stem by projection welding. Resistance heat, in this process, is generated by electric current at the contact surface between cap and stem within a very short time. Temperature variation of laser diode is largely affected by the welding time and the heat generated from the surface. Maximum temperature of each component in the laser diode should be lower than the melting point except for cap and stem in order to prevent welding defect. Temperature distribution of each component in the laser diode is also affected by thermal conduction mechanism. Welding defect near the insulator occurs when the resistance heat is high. Appropriate resistance heat supply to the laser diode was about 400W. The results from this study could be applicable for optimal design of laser diode welding system.
In this study, center marking process is numerically analyzed to investigate the characteristics of deformation of aluminium alloy bracket by the pin load. The proper size of groove which are required for marking system and the pressure of cylinder are predicted through the analyse of stress and strain fields of the plate. The results of this study show that von Mises stress is a maximum when the maximum of reaction force.
In this study, flow characteristic of small vertical-axis wind turbine was performed to analysis the numerical analysis. Blade geometry in the wind turbine is NACA 6512-43, and various degrees of the wind turbine accelerator were adopted. Numerical models are used for the analysis with CFD program of Ansys fluent and RNG k-e turbulence model was used. Rotational speed value of the wind turbine in analysis condition were obtained by the experiment. When the wind turbine accelerator is equipped, exit velocity of wind turbine accelerator tended to increases. Also RPM of wind turbine is increase. And maximum RPM appeared that wind turbine accelerator in degree 60° is equipped.
In this study, temperature variation characteristics in the stone board cutting device with sheath heater were analyzed through numerical investigation. Four 2kW sheath heaters whose length and diameter are 1800mm, 11mm are installed, and the initial temperature is -5℃. Also Transient condition is used for temperature variations with the operating time of sheath heater. From the analysis, transient temperature variations of cutting device after operating the sheath heater were predicted. Temperature variations were predicted that mainly appears in part contacted with the sheath heater. The result will be helpful in optimal design for various system equipped with sheath heater.
독도 해역의 해조류는 2013년 5월과 7월에 14개 정점에서 정성채집 하였으며, 대황의 생태학적 역할을 확인하기 위하여 7월과 11월에 23개체를 채집하여 부착기에 서식하는 해조류와 동물을 동정하였다. 대황의 줄기길이와 무게의 회귀식으로 생물량을 측정하였다. 해조류는 녹조류 18종, 갈조류 35종과 홍조류 75종을 포함하여 총 128종이 관찰되었으며, 성긴분기형이 47.66%로 가장 우점하였고 안정된 환경에 서식하는 ESG I그룹에 속하는 종이 91종(71.09%)이었다. 또한, R/P, C/P, (R+C)/P는 2.14, 0.51과 2.66으로 온대성과 혼합성 해조상을 보였다. 대황의 생물량은 23.74kg m-2이고 밀도는 64 fronds m-2로 확인되었다. 한편, 대황의 부착기에서 해조류 12종과 동물 83종(환형 15종, 연체 25종, 절지 34종, 극피 3종, 기타 6종)의 1,248개체가 동정되어 생태학적으로 매우 중요한 핵심종으로 확인되었으며, 넓은마디육질꼬리옆새우붙이가 538개체(43.11%)로 가장 우점하였다. 본 연구 결과 독도의 해조류 출현종수는 이전 연구에 비해 증가하였고 성긴분기형과 ESG I 해조류가 우점하는 것으로 나타나 현재까지 독도 연안의 환경은 매우 안정된 상태라고 판단된다.