• Proceedings of the Korean Institute of Navigation and Port Research Conference
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• 2009.10a
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• pp.241-242
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• 2009

There are marry ships and marine structures and also has marry differences on according to the shape and the interval of hulls to the purpose. the multi-submerged body needs appropriate distance between the hulls because of the optimum hull form. thus, through this paper, the flow characteristics behind the multi-submerged body according os the distance ration between the hulls and various angles of attack was conducted.

• Journal of the Korean Society for Marine Environment & Energy
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• v.13 no.1
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• pp.12-17
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• 2010

Oscillating Water Column (OWC) device has been widely employed in the wave energy conversion. Wave Focusing Device (WFD) is proposed to be helpful for improving the operating performance of OWC chamber. In the present paper, a Numerical Wave Tank (NWT) using two-phase VOF model is utilized to simulate the generation and propagation of incident regular waves, water column oscillation inside the chamber. The NWT consists of the continuity equation, Reynolds-averaged Navier-Stokes equations and two-phase VOF functions. The standard k- turbulence model, the finite volume method, NITA-PISO algorithm and dynamic mesh technique are employed. Effects of WFD on the operating performance of OWC chamber are investigated numerically.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.23 no.3
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• pp.1-1
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• 1987

The accurate prediction of the ship wave resistance is very important to design ships which operate satisfactorily in a wave environment. Thus, work should continue on development and validation of methods to compute ship wave patterns and wave resistance. Research efforts to improve the prediction of ship waves and wavemaking resistance are categorized in two major areas. First is the development of higher-order theories to take account of the nonlinear effect of the free surface condition and improved analytical treatment of the body boundary condition. Second is the development of direct numerical methods aimed at solving body and free-surface boundary conditions as accurately as possible. A new formulation of the slender body theory for a ship with constant speed is developed by Maruo. It is quite different from the existing slender ship theory by Vossers, Maruo and Tuck. It may be regarded as a substitute for the Neumann-Kelvin approximation. In present work, the method of asymptotic expansion of the Kelvin source is applied to obtain a new wave resistance formulation in fluid of finite depth. It takes a simple form than existing theory.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.40 no.4
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• pp.460-472
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• 1995

This study was aimed to provide understanding on the eco-physiological response of barley tillers as affected by difference in seeding date. Yield and yield contribution rates of tillers were investigated with the data of field experiments in the former Wheat and Barley Research Institute of Suwon, Korea from September 1982 to July 1984. When barley was sowed 15 days earlier than or at the locally recommended sowing date (i.e. October 5), it produced more mainstem leaves than the that sowed 15 days later than the local recommendation. The effective tillers (i.e. ear-bearing tillers) were observed in concurrently occurring leaves up to 10/0 (abbreviation of the 10th mainstem leaf) from early and optimum sowed crops, while 9/0 from late sowed crops. Tillering followed the production rule of Gatayama(l952) which has the linear leaf appearance pattern. Early sowing produced more effective tillers, but the highest production of effective ears (i.e. ears heavier than 0.505g) was noticed in sowing at the recommended date. The tillers in the axil of first leaf in mainstem (abbreviated as 1) produced more effective ears than other mainstem tillers (i.e. primary tillers such as C, 2, 3 and 4). The tillers from the axil of first leaf, whether they were primary or secondary, always performed better in the production of effective tillers, grains per ear, grain weight, and grain yield per ear than those from the axil of coleoptile or prophyll. Other tillers from subsequent leaves were also inferior in production with the order of their appearance, thus making first leaf tillers as the best performer(e.g. 1 against C, 2, 3, 4 of primary tillers, 11 and 21 against 1P, 12, 13, 2P, 22 of secondary tillers). Even though the first leaf tiller from the first mainstem leaf(i.e. 11) emerged at a same time with the fourth mainstem leaf tiller(i.e. 4), it was always a better producer of ears and grains. The above observations of hierarchy among tillers were persistent irrespective of cropping conditions and treatments. Sowing at the recommended date produced more effective tillers and grains per ear than early or late sowing. In early and late sowings, more grains per effective ear were observed by early sowing, whereas more grains per ear were produced by late sowing. The order of performance in production of effective tillers and ears per plant was as follows: optimum > early > late sowings. In optimum sowing the mainstems were the highest in grain weight per ear, while the first leaf tillers were the ones in early sowing probably due to winter damage on mainstem ears. Yield contribution by the tillers was greater with the following order irrespective of sowing dates: mainstem, 1, 2, 3, C, 11, 12 and Cl. The contribution of CP, 2P, 21 and 31 varied with sowings.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.37 no.6
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• pp.514-520
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• 1992

Performance of direct seeded paddy rice in ridged dry soil was evaluated at different seeding methods (broadcasting, drilling, and seeding in group) and seeding rates (4, 6, and 8kg /10a). The number of maximum tillers at broadcasting and drilling of seeds was higher than that at seeding in group. At broadcasing and drilling the number of maximum tillers at seeding rate of 6kg /10a was greater than that at 4 or 8kg /10a, but at seeding in group the number of maximum tillers increased with seeding rates. Among the seeding methods there were no differences in the number of seedlings per unit area, culm and panicle lengths, and productive tiller ratio, but heading date at seeding in group was delayed by a day compared with broadcasting or drilling. At heading stage leaf area index(LAI) and dry matter production at broadcasting of seeds were higher compared with drilling and seeding in group, but light transmission ratio at drilling and seeding in group was higher than that at broadcasting of seeds. Although the number of seedlings increased with seeding rates, LAI and dry matter production at heading stage, culm and panicle lengths, and productive tiller ratio were not different among the seeding rates. There were no differences in the number of panicles and spikelets per unit area, 1,000 grain weight, yield, and harvest index among the seeding methods. The number of spikelets per panicle at seeding in group was higher, but percent ripened grains was lower compared with broadcasting and drilling. There were no significant differences in the number of panicles and spikelets per panicle and unit area, percent ripened grains, and harvest index among the seeding rates, but yield at seeding rate of 6kg /10a was higher than at 4 or 8kg /10a. There were no significant differences in tiller length, bending moment, and fresh weight of tiller among the seeding methods. Breaking strength was lower in the order of seeding in group, drilling, and broadcasting of seeds. However, lodging index was similar among the seeding rates and lodging was not occurred in the field. There was a significant interaction in the cellulose, hemicellulose, and lignin contents of culm base between seeding methods and seeding rates.

• Journal of Bio-Environment Control
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• v.17 no.1
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• pp.60-65
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• 2008

For autumn field cutting of Sedum sarmentosum, the effects of cutting site (distal, middle, and proximal) and planting method (space drill seeding, drill seeding, and broadcast seeding) on survival rate and growth characteristics were investigated at pre- and post-winter season. Plant height root length, stem number per plant, number of branch per plant, fresh weight of shoot, and dry weight of shoot were significantly superior in distal site at pre-wintering (40 days after cutting). At post-wintering (May 10th), stem number per plant, fresh weight and dry weight per $m^2$ in cutting of distal site showed a significant increasement compared to the cutting of proximal site. At pre-wintering (40 days after cutting), the growth in space drill seeding was well than that in drill seeding and broadcast seeding, and fresh weight and dry weight per $m^2$ in space drill seeding were high in order of space drill seeding, broadcast seeding, and drill seeding. At post-wintering (May 10th), stem number per plant, fresh weight and dry weight per $m^2$ in space drill seeding were significantly increased than those in drill seeding. Accordingly, the cutting using distal site of stem in autumn field cutting was desirable for the growth and shoot yield. The space drill seeding showed the highest yield potential among three seeding methods, but broadcast seeding was favorable in saving of labor, because the fresh weight of shoot in broadcast seeding was similar in the space drill seeding at post-wintering.

• Journal of Korean Society of Coastal and Ocean Engineers
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• v.27 no.1
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• pp.38-49
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• 2015

Past study of tsunami heavily relied on the numerical modelling using 2D Boussinesq Eq. and Solitary wave. Lately, based on the fact that numerically simulated run up heights based on solitary wave are somewhat smaller than the measured one, Leading Depression N (LDN) Wave has been elaborated, which can account the advancement of a shore line before tsunami strikes a shore. Thereafter it is reported that more accurate simulation can be possible once LDN is deployed. On the other hand, there were numerous reports indicating that stable LDN wave can't be sustained in the hydraulic model test. These conflicts between the hydraulic model tests and numerical results have their roots on the assumption made in the derivation of Boussinesq type wave model such as that wave nonlinearity is equally balanced with wave dispersiveness. Hence, in the numerical simulation based on the Boussinesq type wave model, wave dispersiveness is inevitably underestimated, especially in deep water. Based on this rationale, we developed the modified methodology for the generation of stable LDN wave in the 3D numerical wave flume, and proceeded to numerically analyze the depression effect of Hybrid Breaker on the run up height due to tsunami using the Navier Stoke Equation. The verification of newly proposed wave model in this study was carried out using the run up height from the hydraulic model test. It was shown that Hybrid Breaker consisting of three water chamber and slope at its front can reduce 13% of run up height for H = 5m, and 10% of run up height for H = 6m.

• Journal of the Korean Society for Marine Environment & Energy
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• v.17 no.3
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• pp.182-188
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• 2014

In an oscillating water column (OWC)-type wave energy conversion system, the performance of the OWC chamber depends on the chamber shape, as well as the incident wave direction and pressure drop produced by the turbine. Although the previous studies on OWC chambers have focused on wave absorbing performance in ideal operating conditions, incident waves do not always arrive normally to the OWC chamber in real sea conditions, especially in fixed devices. The present study deals with experiments and numerical calculations to investigate the effects of wave direction on the performance of the OWC chamber. The experiments were carried out in a three-dimensional wave basin for five different wave directions, including the effect of turbine using the corresponding orifice. The wave elevation inside the chamber was measured at the center point under various incident wave conditions. The numerical study was conducted by using a numerical wave tank-based volume-of-fluid model to compare the results with experimental data and to reveal the detailed flows around the chamber.

• Journal of the Society of Naval Architects of Korea
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• v.33 no.3
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• pp.35-47
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• 1996

A surface panel method treating a boundary-value problem of the Dirichlet type is presented to design a three dimensional body with free surface corresponding to a prescribed pressure distribution. An integral equation is derived from Green's theorem, giving a relation between total potential of known strength and the unknown local flux. Upon discretization, a system of linear simultaneous equations is formed including free surface boundary condition and is solved for an assumed geometry. The pseudo local flux, present due to the incorrect positioning of the assumed geometry, plays a role f the geometry corrector, with which the new geometry is computed for the next iteration. Sample designs for submerged spheroids and Wigley hull and carried out to demonstrate the stable convergence, the effectiveness and the robustness of the method. For the calculation of the wave resistance, normal dipoles and Rankine sources are distributed on the body surface and Rankine sources on the free surface. The free surface boundary condition is linearized with respect to the oncoming flow. Four-points upwind finite difference scheme is used to compute the free surface boundary condition. A hyperboloidal panel is adopted to represent the hull surface, which can compensate the defects of the low-order panel method. The design of a 5500TEU container carrier is performed with respect to reduction of the wave resistance. To reduce the wave resistance, calculated pressure on the hull surface is modified to have the lower fluctuation, and is applied as a Dirichlet type dynamic boundary condition on the hull surface. The designed hull form is verified to have the lower wave resistance than the initial one not only by computation but by experiment.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.31 no.4
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• pp.434-439
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• 1986

This experiment was conducted to explore the cultural method capable of raising of picked cotton ratio and more high-yielding in the middle part of Korea where growth period of cotton is short. By early vinyl-mulching culture, emergence date was earlier, flowering and boll opening were shorter than non-mulching, especially boll opening date was earlier about 8 to 15 days. Plant height was longer by vinyl-mulching, fruiting branches and number of bolls per plant at vinyl-mulching of the 10th April produced more twice than non-mulching of the 10th May. Picked cotton ratio was 79% at non-mulching of the 10th May, while viny-mulching of the 10th April produced most of picked cotton as picked cotton ratio 99%. At vinyl-mulching of the 10th April, lint yield increased more 76-90% than non-mulching. Staple length was some longer and also content of linolenic acid of cotton seed oil was higher than non-mulching.