• Transactions of the Korean Society of Automotive Engineers
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• v.8 no.2
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• pp.9-18
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• 2000

Combustion and emission characteristics in a direct injection diesel engine is closely related to the intake port system. It is therefore important to understand the swirl flow characteristics formed by a helical intake port. However there are still many uncertainties. The purpose of this experimental study is to investigate the effects of the valve eccentricity ratio and the inlet flow conditions of a helical intake port on the characteristics of an in-cylinder swirl flow. A steady state flow test rig consisted of ISM(impulse swirl meter), LFM(laminar flow meter) and cylinder head with a helical intake port was used. The swirl ratio(Rs) and mean flow coefficient(Cf(mean)) with inlet flow conditions were measured. The results of these experiment can be summarized as follows. Swirl flow characteristics of a helical intake port are affected by the inlet flow conditions, and especially they are much affected by the length of a manifold runner and the rotational angle of a curved manifold runner.

• Proceedings of the Korea Institute of Fire Science and Engineering Conference
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• 2009.04a
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• pp.540-547
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• 2009

국내도로터널 화재안전성을 확보하기 위하여 FDS를 이용하여 ISO, 도로터널 방재시설기준, Runner Hammer 터널기준의 시나리오에 따라 콘크리트 터널구조물의 내부 열역학적 특성을 예측하였다. 화재로 인한 터널내부의 온도분포를 측정하기 위하여 화염원으로부터 터널입구 방향으로 5m 마다 터널 단면의 온도분포를 추출하였고, 터널의 중심을 지나는 길이방향 단면의 온도분포를 해석하였다. 해석결과 온도는 500${\sim}$950$^{\circ}C$까지의 분포를 나타내었고 가장 높은 온도영향을 받은 Runner Hammer 터널기준의 내부 열환경 조건에서는 터널 단면이 모두 화염에 직접적으로 노출 때문에 단면전체가 800${\sim}$950$^{\circ}C$까지 상승하였다. 특히 상부부분은 900$^{\circ}C$ 이상의 고온에 장시간 노출되고 있어 깊이 50mm 지점의 온도가 250$^{\circ}C$까지 상승하였다.

• Journal of Ecology and Environment
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• v.42 no.4
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• pp.150-154
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• 2018

In lotic wetlands, runner reed (Phragmites japonicus) plays a role as a pioneer, which helps other plant species to settle by making dense roots trapping floating-sediments. In lentic wetlands, on the other hand, P. japonicus could play a role as an invader threatening biodiversity by forming tall and dense stands. To conserve an abandoned paddy terrace in mountainous areas, a habitat of an endangered dragonfly species (Nannophya pygmaea), from the monotypic-occupation by P. japonicus, we applied three kinds of treatment: (1) hand-clipping in 2009, (2) mechanical excavating in 2012, and (3) planting of alternative vegetational unit in 2012. We have monitored vegetation changes in the wetland in 2008~2012 and 2017. Vegetation cover of P. japonicus sharply decreased from 43% in 2011 to 16% in 2012 by the mechanical excavation. After 5 years from applying the treatment, Schoenoplectiella mucronata that was utilized in the planting became the predominant species instead of P. japonicus and the number of wetland plant species increased from 16 to 25 with the shift in species composition. This study showed the utility of three control methods of P. japonicas in a lentic wetland.

• Journal of the Korean Society of Marine Environment & Safety
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• v.25 no.3
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• pp.373-380
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• 2019

In this paper, a pico hydro turbine employing low head circulation water at fish farms is designed and evaluated. Due to the advantages of simple structures, small head requirements, and low-cost investment, the constant thickness propeller turbine is considered as a feasible solution. The design process based on the free vortex method is presented in full detail, and a 4-blade runner is built using BladeGen. The turbine performance is analyzed both numerically and via experimental methods. Despite slight differences, the results show similar trends between CFD simulations and experiments carried out on factory test-rigs in a wide range of working conditions. At the design flow rate, the turbine achieves the best efficiency of 70 %, generating 3.5 kW power when rotating at 420 rpm. The internal flow field, as well as the turbine's behavior, are investigated through the distribution of blade streamlines, pressure, and velocity around the runner. Moreover, the pressure coefficient on the blade surface at 3 span positions is plotted while the head loss for each simulation domain is calculated and displayed by charts.

• Journal of the Korean Society of Manufacturing Process Engineers
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• v.20 no.2
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• pp.86-92
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• 2021

Usually, the die-cast components used in small mobile devices require finishing processes, such as computer numerically controlled coating. In such cases, porosity is the most important defect. The shape of the molten aluminum that passes through the runner and gate in a mold is the one of the factors that influences gas porosity. To define the spurt index, which numerically indicates the shape of molten aluminum after the gate, Reynolds number and Ohnesorge number are used. Before die fabrication, computer-aided engineering analysis is performed to optimize the filling pattern. Finally, X-ray and surface inspection are performed after casting and machining to evaluate how the spurt index affects porosity and other product parameters. Based on the results obtained herein, a new gating system design process is suggested.

• Journal of Bio-Environment Control
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• v.31 no.4
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• pp.497-503
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• 2022

This study was conducted to investigate the horticultural media + decomposed granite + reused rock wool in the following mixing ratio: Control = 100:0, M1 = 80:0:20, M2 = 60:30:10, M3 = 40:30:30, M4 = 30:40:30, M5 = 0:50:50 (reused rockwool : decomposed granite : horticultural media) and develop the physicochemical properties and the growth of 'Sulhyang' strawberry runner plant. In the physical aspect of the horticultural media, statistical differences were recognized that the bulk density and particle density were lower in the control and M1. But the bulk density and particle density were high in the M3, M4, and M5, because it had high mixing ratio between recycled rock wool and decomposed granite. EAW and WBC showed a similar tendency. The air porosity and total porosity were higher in control and M1 than M3, M4, M5. Exchangeable cation (K⁺, Ca²⁺, Na⁺, Mg²⁺) and base replacement capacity (CEC) were higher in control and M1, than M2, M3, M4, and M5. As a result of the cultivation of 'Sulhyang' runner plant, the plant length was long in M2, 32.1 cm and smaller than M5 to 28.4 cm. However, if the crown diameter, which is the growth indicator of the runner plant, all 6 treatments were formed 11.23 mm-12.03 mm, which is considered to be suitable for the growth of the runner plant. There wasn't a statistical difference between the weight and dry weight of the root. As a result, the growth difference of the seedlings by the horticulture media was similar. Therefore, considering the physical properties of the horticultural media, it was judged that the air porosity and total porosity would be improved when the recycled rock wool and the decomposed granite were properly mixed rather than the use of the horticultural media as a single medium, which would be advantageous for irrigation management.

• Korean journal of applied entomology
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• v.47 no.1
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• pp.101-105
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• 2008

Effects of different application of nematicides (fosthiazate 5% G, ethoprophos 5% G, and diazinon 34% EC) for the control of Aphelenchoides fragariae in strawberry were evaluated in a greenhouse experiments. Mother strawberry (Fragaria grandiflora) cv. Yeohong were dipped in solution of nematicides (fosthiazate or ethoprophos at 2.5 g a.i./liter in $20^{\circ}C\;or\;46^{\circ}C$) for 10 min. and planted in a greenhouse for dipping treatment. For the compare, mother strawberry were dipped in hot water for 10 min. without chemicals. For soil treatment, fosthiazate or ethoprophos at 3 kg a.i./ha were mixed into soil. For foliar spray, diazinon at 3.4 g a.i./liter was sprayed at foliage until runoff. At 40, 80, and 100 days after planting, runners were harvested from each treatment and the rate of nematode infestation and the number of nematodes per plant were examined. After 100 days of planting, mother strawberry plants dipped in fosthiazate solution (2.5 g a.i./liter, $20^{\circ}C$) for 10 min. produced more number of healthy runners and reduced % of infected runner as much as 90% and also had fewer nematodes per runner. Fosthiazate was more effective than ethoprophos. Foliar application of diazinon was reduced A. fragariae populations only in early season. Hot water treatment and nematicide soil treatment were less effective.

• Horticultural Science & Technology
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• v.29 no.2
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• pp.95-101
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• 2011

The influence of physicochemical properties of root substrates on the growth of mother plants and occurrence of daughter plants in 'Seolhyang' strawberry propagation were investigated through plastic bag cultivation. Six different formulations of root substrates were coir dust + perlite (5:5, A), coir dust + perlite (6:4, B), coir dust + perlite (7:3, C), coir dust + coconut chip (7:3, D), coir dust + coconut chip (6:4, E), and peatmoss + vermiculite (5:5, v/v; F). The total porosities (TP) and container capacities (CC) of all root substrates were higher than 85% and 55%, respectively, indicating that all substrates were in the acceptable range. But the TP and CC of F substrate were 91.5% and 60%, respectively, which were the highest among the root substrates tested. In the soil chemical properties analyzed before planting and after harvesting of 'Seolhyang' strawberry mother plants, the root substrates of A, B, C, and F had higher electrical conductivity and $NO_3$-N concentrations than those of D and F. The root substrates of A, B, C, and F had heavier runner fresh and dry weights, longer runner lengths, and more daughter plant occurrence than those of D and F. The treatment F had higher tissue N content than any other treatments at 120 days after the transplanting of 'Seolhyang' strawberry and statistical differences were not observed among remained 5 substrates. The treatment of F also had the higher tissue contents of other nutrients except N analyzed at 120 days after transplanting. These results indicated that soil chemical properties rather than physical properties severely influenced the growth of runners and occurrence of daughter plants.

• Tribology and Lubricants
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• v.35 no.1
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• pp.44-51
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• 2019

The paper presents the rotordynamic performance measurements and model predictions of a fuel cell electric vehicle (FCEV) air compressor supported on gas foil bearings (GFBs). The rotor has an impeller on one end and a thrust runner on the other end. The front (impeller side) and rear (thrust side) gas foil journal bearings (GFJBs) are located between the impeller and thrust runner to support the radial loads, and a pair of gas foil thrust bearings are located on both sides of the thrust runner to support the axial loads. The test GFJBs have a partial arc shim foil installed between the top foil and bump strip layers to enhance hydrodynamic pressure generation. During the rotordynamic performance tests, two sets of orthogonally installed eddy-current displacement sensors measure the rotor radial motions at the rotor impeller and thrust ends. A series of speed-up and coast-down tests to 100k rpm demonstrates the dominant synchronous (1X) rotor responses to imbalance masses without noticeable subsynchronous motions, which indicates a rotordynamically stable rotor-GFB system. Finite element analysis of the rotor determines the rotor free-free (bending) natural modes and frequencies well beyond the maximum rotating frequency. The predicted damped natural frequencies and damping ratios of the rotor-GFB system reveal rotordynamic stability over the speeds of interest. The imbalance response predictions show that the predicted critical speeds and rotor amplitudes strongly agree with the test measurements, thus validating the developed rotordynamic model.

• 한국신재생에너지학회:학술대회논문집
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• 2005.06a
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• pp.443-446
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• 2005

The Kaplan turbine model has been tested and analyzed. The blade angle and the guide vane opening of the turbine model were designed to be varied according to the best combination of guide vane and runner blade opening. When the changes in head and output were comparatively large, the efficiency drop were small, so the efficiency characteristics and stability of the entire operating condition were maintained in good condition. These results showed that the developed model in this study will be suitable for small hydro power stations with large changes in head and load.