• Journal of Korea Water Resources Association
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• v.37 no.8
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• pp.623-630
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• 2004

In this paper, the hydraulic model tests are conducted for the hydraulic characteristics at channel junctions. The experiments are examined through the variation of approaching angle, discharge in the upstream main channel and the discharge ratio between the main channel and the tributary. The experiments are conducted in the channel model having the length of 450cm, the widths of 40cm and 32cm. Four water tanks and pumps are installed in the experimental channel. The length of stagnation zone is increased by Increasing of approaching angle and the discharge in the upstream channel. The length of stagnation increase with the discharge ratio between the main channel and the tributary. However, the variation of the stagnation zone near the channel junctions is little at the same approaching angles and the discharge ratioes between the main channel and tributary. However, the variation of the stagnation zone near the channel junctions is little at the same approaching angles and the discharge ratioes between the main channel and tributary. Accelerating zone of the velocity is occurred in the middle of the channel in the small approaching angle. However, the influence zone of the accelerating velocity is increased by increasing the approaching angle.

• Wind and Structures
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• v.23 no.3
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• pp.191-209
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• 2016

Wind tunnel tests of a 1/2200-scale mountainous terrain model have been carried out to investigate local wind characteristics at a bridge location in southeast Tibet, China. Flows at five key locations on the bridge at deck level were measured for 26 directions. It was observed that wind characteristics (including mean wind velocity and overall turbulence intensity) vary significantly depending on the approaching wind direction and measurement position. The wind inclination angle measured in the study fluctuated between $-18^{\circ}$ and $+16^{\circ}$ and the ratio of mean wind velocity to reference wind velocity was small when the wind inclination angles were large, especially for positive wind inclination angles. The design standard wind speed and the minimum critical wind speed for flutter rely on the wind inclination angle and should be determined from the results of such tests. The variation of wind speed with wind inclination angles should be of the asymmetry step type. The turbulence characteristics of the wind were found to be similar to real atmospheric flows.

• Journal of Korean Society on Water Environment
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• v.21 no.1
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• pp.79-83
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• 2005

Foraging behaviour of false dace, Pseudorasbora parva, was investigated in water flowing at various velocities with the existence of a cavity for rest. The pursuit comprised three succeeding processes such as, approaching, chasing and attacking. Angles between the fish body and the water flow direction and swimming speeds increased in the latter stages of approaching, chasing and attacking. All pursuit angles, swimming speeds and distances increased with flow velocity and peaked at the flow velocity of 7 cm/sec. At higher velocities, however, the fish avoided the use of much energy against the large drag force. The probability of capture and the feeding rate steadily decreased with increasing flow velocity. Under the fast flow, the fish adjusted their swimming speed to get the optimum velocity relative to the flowing water for the energetic budget. Fish spent more time in the cavity as flow velocity increased to avoid the energy expenditure necessitated by the high velocity.

• Education of Primary School Mathematics
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• v.27 no.2
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• pp.155-171
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• 2024

This study compared and analyzed students' reasoning processes and justification methods when introducing the concept of "the sum of angles in a triangle" in mathematics classes with a focus on both measurement and geometric aspects. To confirm this, the research was conducted in a 4th-grade class at H Elementary School in Suwon, Gyeonggi-do, South Korea. The conclusions drawn from this study are as follows. First, there is a significant difference when introducing "the sum of angles in a triangle" in mathematics classes from a measurement perspective compared to a geometric perspective. Second, justifying the statement "the sum of angles in a triangle is 180°" is more effective when explained through a measurement approach, such as "adding the sizes of the three angles gives 180°," rather than a geometric approach, such as "the sum of the angles forms a straight angle." Since elementary students understand mathematical knowledge through manipulative activities, the level of activity is connected to the quality of mathematics learning. Research on this reasoning process will serve as foundational material for approaching the concept of "the sum of angles in a triangle" within the "Geometry and Measurement" domain of the Revised 2022 curriculum.

• Journal of the Korean Society of Hazard Mitigation
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• v.6 no.1 s.20
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• pp.59-68
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• 2006

Flow separation of recirculation zone by increasing of flow and change of its direction at confluence results in backwater due to conveyance reduction. The hydraulic characteristics of flow separation are analysed by experimental results of flow ratios of tributary and main streams and approaching angles. The boundary of flow separation by dimensionless length and width is defined by the streamline of zero and this definition agrees well to the existing investigation. Because flow separation doesn't appear in small flow ratio and approaching angle of $30^{\circ}$, the equation of flow separation with flow ratio and approaching angle is provided. In flow separation consideration and comparing with previous results, the existing equations of dimensionless length and width ratios by function of approaching angle, flow ratio, and downstream Froude number are modified and also contraction coefficient and shape factor are analysed. Dimensionless length and width ratios are proportional to the flow ratio and approaching angle. In analysis of water surface profiles, the backwater effects are proportional to the flow ratio and approaching angle and the magnitude at outside wall is greater than that of inside wall of main stream. The length, $X_l$ from the beginning of confluence to downstream of uniform flow, where the depth is equal to uniform depth, is characterized by width of stream, flow ratio, approaching angle, and contraction coefficient. The ratios between maximum water depth by backwater and minimum depth at separation are analysed.

• Journal of the Korean Institute of Landscape Architecture
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• v.21 no.4
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• pp.101-111
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• 1994

This study deals with the degree of enclosure on the Court Space in 'Suh-Won' that has warious perceptual composition elements. 1. The size of Court Space in which we can read the complexion of others and easily understand every behavior of them is similar to that of the 'Madang' in the Korean traditional houses. 2. The angles of elevation are within the range of suitable enclosure as going from the center of the court Space to 'Kang-Dang' and the space -from the center of the Court Space to 'Kang-Dang'- is restricted and surrounded. It is also within the range of the least enclosure as going from the center of the Court Space to the 'Mun-Ru'. 3. The degrees of enclosure based on the horizontal angle are within the degree we can perceive the objects of structure easily. 4. The degree of enclosure based on the ratio D/H is increased as approaching from 'Mun-Ru' to 'Kang-Dang'. The distance as approaching from 'Mun-Ru' to 'Kang-Dang' is changed from social distance to personal distance. To conclude this the Court Space in 'Suh-Won' represents the hierarchical system with variety and the degree of enclosure and the size of space are within the range of human scale.

• Korean Journal of Hydrosciences
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• v.6
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• pp.23-37
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• 1995

In this experimental paper, the maximum scour depth at pier was student. The model of the pier of San Gye bridge in the Bocheong stream was set for the experimental studies. Several model verification processes were conducted through the roughness comparisons between model and prototype, pursuing scour depth variations with time depending upon channel bed variation, the comparison of the ratios between falling velocities and shear velocities in the model and prototype, and the comparison of pier scour depths between experimental data and field measuring data. The experiments were conducted in the free flow conditions and pressure flow conditions. The maximum scour depth at piers in the pressure flow conditions is almost twice as much as compared to the free flow conditions. Also, the maximum scour depth variations are indicated in the figures based on the Froude numbers, opening ratios, water depths and approaching angles in the free surface flow conditions.

• Journal of the Korean Institute of Navigation
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• v.17 no.1
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• pp.17-29
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• 1993

The new flexible controlling method integrated with some existing maneuvers of reducing a great head way during approaching a pilot station or anchor berth, namely , Super Rudder (Woo) controlling method originally was developed. The conclusions of this paper are drawn. 1) Super Rudder (Woo) controlling method has the shortest distance along base course and distance off base course among all reducing maneuvers including Rudder Cycling. 2) This new method is flexibly adjustable to a range of yaw angles 5-35 degrees either ship's side depending on traffic situations, 3) This new method is versatile controlling maneuver enabling shipandlers to reduce or stop a ship's headway and to adjust the proper courses to a pilot station or anchor berth.

• Solar Energy
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• v.19 no.3
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• pp.115-123
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• 1999

An experimental study was carried out to investigate the flow characteristics of a stationary blade for six kinds of measuring angles of attack, $0^{\circ},\;10^{\circ},\;20^{\circ}\;and\;30^{\circ}$ at Reynolds number of $5.8{\times}10^4$. Instant simultaneous velocity vectors around blade were measured by 2-D PIV system where laser-based illumination and two-frame grey-level cross correlation algorithm were adopted. Velocity profiles show uniform approaching flow from the straightening equipment, and experimental results reveal that separation phenomena occur and the separation point moves upstream with increasing angle of attack.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.14 no.2
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• pp.97-112
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• 1978

The rule 15, 16 and 17 of International Regulations for Preventing collisions at Sea direct actions to avoid collision when two power-driven vessels are crossing. But these rules do not present the safety minimum approaching distances outside which a give- way vessel deeps out of the way of a stand-on vessel. In this paper, the author analyzed the ship's collision avoiding actions from a viewpoint of ship kinematics as the method to calculate this distance. The author worked out mathematic formulas for calculating the safety minimum approaching distances outside which the give-way vessel takes the actions to avoid collisions in accordance with the cross angles of the crossing vessels' courses. Figuring out actually the values of maneuvering indices of the M. S. Koan Ack San (GT: 224tons), the training ship of the National Fisheries University of Busan and the M. S. Golden Clover (GT: 101, 235tons) of the Eastern Shipping Co., Ltd. through their Z test, the author applied these values to the calculating formulas and calculated the safety minimum approaching distances. The results of calculations are as follows; 1. The greatest distance is to be kept by the give-way vessel to avoid collision when the cross angle of courses is 90$^{\circ}$ or near it. In such case the safety minimum approaching distance of a small vessel must be more than 5 times of her own length and that of a large vessel more than 11 times of her own length. 2. Collision danger is greater when crossing angle is obtuse than in an acute angle, therefore greater distance is to be kept by the give-way vessel to avoid collision in the case of the obtuse angle. 3. The actions to be taken to avoid collisions by the give-way vessel in Rule 16 and by the stand-on vessel in Rule 17(a)(ii) of International Regulations for Preventing Collisions at Sea, must be done outside the above safety minimum approaching distance. When inevitably such actions are to be taken within the safety minimum approaching distance, they should be accompanied with engine motions.