• Journal of the Korean Society of Marine Environment & Safety
• /
• v.20 no.2
• /
• pp.172-178
• /
• 2014

This study suggests the minimum critical external forces based on the assessment of anchoring safety to single anchor situation for representative 8 number of ships in E-group anchorage of Ulsan port. Assessment of anchoring safety is compared holding powers of anchor with external forces of wind, wave and current. Holding powers was reflected materials of seabed, equipment numbers regarding anchor and chain weight, also external forces acting on a hull was calculated considering projected wind area and wetted surface area to the full and ballast conditions respectively. The results of anchoring safety assessments to single anchor showed that the minimum criteria of dragging anchor is a little different from ship's type, size and loading conditions. Bulk carrier can be dragged over the 15m/s of winds and Tanker can be dragged over the 13m/s of winds in case of less than 2knots of currents speed.

• Smart Structures and Systems
• /
• v.21 no.3
• /
• pp.257-262
• /
• 2018

Vibrational problems in the domestic Small Horizontal Axis Wind Turbines (SHAWT) are due to flap wise vibrations caused by varying wind velocities acting perpendicular to its blade surface. It has been reported that monitoring the structural health of the turbine blades requires special attention as they are key elements of a wind power generation, and account for 15-20% of the total turbine cost. If this vibration problem is taken care, the SHAWT can be made as commercial success. In this work, Shape Memory Alloy (SMA) wires made of Nitinol (Ni-Ti) alloys are embedded into the Glass Fibre Reinforced Polymer (GFRP) wind turbine blade in order to reduce the flapwise vibrations. Experimental study of Nitinol (Ni-Ti) wire characteristics has been done and relationship between different parameters like current, displacement, time and temperature has been established. When the wind turbine blades are subjected to varying wind velocity, flapwise vibration occurs which has to be controlled continuously, otherwise the blade will be damaged due to the resonance. Therefore, in order to control these flapwise vibrations actively, a non-linear current controller unit was developed and fabricated, which provides actuation force required for active vibration control in smart blade. Experimental analysis was performed on conventional GFRP and smart blade, depicted a 20% increase in natural frequency and 20% reduction in amplitude of vibration. With addition of active vibration control unit, the smart blade showed 61% reduction in amplitude of vibration.

• Nuclear Engineering and Technology
• /
• v.26 no.2
• /
• pp.197-204
• /
• 1994

In a PWR rod cluster control assembly(RCCA) for shutdown is released upon action of control rod drive mechanism and falls down through the guide thimble by its weight. Drop time and impact velocity of the RCCA are two key parameters with respect to reactivity insertion time and the mechanical integrity of fuel assembly. Therefore, the precise control of drop time and impact velocity is prerequisite to modifying the existing design features of the RCCA and guide thimble or newly designing them. During its falling down into the core, the RCCA is retarded by various forces acting on it such as fluid resistance caused by the RCCA movement, buoyance and mechanical friction caused by contacting inner surface of the guide thimble, etc. However, complicated coupling of the various forces makes it difficult to derive an analytical dynamic equation for the drop time and impact velocity. This paper deals with the development of a computer program containing an analytical dynamic equation applicable to the Korean Fuel Assembly(KOFA). The computer program is benchmarked with an available single control rod drop tests. Since the predicted values are in good agreement with the test results, the computer program developed in this paper can be employed to modify the exiting design features of the RCCA and guide thimble and to develope their new design features for advanced nuclear reactors.

• Journal of the Korean Geophysical Society
• /
• v.4 no.3
• /
• pp.197-203
• /
• 2001

The vertical distribution of pore water pressure in the highly saturated sand layer under the oscillating water pressure (water wave) us studied theoretically and experimentally. By the experiments it is shown that the water pressure acting on the sand surface propagates into the sand layer with the damping in amplitude and the lag in phase, and that the liquefaction, the state that the effective stress become zero, occurs under certain conditions. These experimental results are explained fairly well by the same theoretical tearment as for ground water problems in the elastic aquifer. The main characteristics of liquefaction clarified by the analysis are as follows: 1) The depth of the liquified layer increases with the increase of the amplitude and the frequency of the oscillating water pressure. 2) The increase of the volume of the air in the layer increases the liquified depth. Especially the very small amount of the air affects the liquefaction significantly. 3) The liquefied depth decrese rapidly with the increase of the compressibility coefficient of the sand. 4) In the range beyond a certain value of the permeability coefficient the liquified depth decrease with the increase of the coefficient.

• Transactions of the Korean Society of Mechanical Engineers
• /
• v.16 no.5
• /
• pp.873-882
• /
• 1992

The study is concerned with the rigid-plastic element analysis for axisymmetric hydromechanical deep drawing in which the fluid flow influences the metal deformation. Due to the fluid pressure acting on the sheet material hydromechanical deep drawing is distinguished from the conventional deep drawing processes. In considering the pressure effect, the governing equation for fluid pressure is solved and the result is reflected on the global stiffness matrix. The solution procedure consists of two stages ; i.e., initial bulging of the sheet surface before the initiation of steady fluid flow in the flange and fluid-lubricated stage. The problem is decoupled between fluid analysis and analysis of solid deformation by deformation by iterative feedback of mutual computed results. The corresponding experiments are carried out for axisymmetric hydro-mechanical deep drawing of annealled aluminium sheet as well as for deep drawing. It has been shown from the experiments that the limit drawing ratio for hydro-mechanical deep drawing is improved as compared with deep drawing. The computed results are in good agreement with the experiment for variation of punch head and chamber pressure with respect to the punch travel and for distribution of thicknees strain. It is thus shown that the present method of analysis can be effectively applied to the analysis of axisymmetric hydro-mechanical deep drawing processes.

• The Korean Journal of Physiology and Pharmacology
• /
• v.10 no.5
• /
• pp.251-254
• /
• 2006

Schizandrae Fructus has been used for controlling respiratory allergic or inflammatory diseases in folk medicine and their components, schizandrin, schizandrin-A and gomisin-A were reported to have diverse biological effects. In this study, we investigated whether schizandrin, schizandrin-A and gomisin-A affect adenosine triphosphate (ATP)-induced mucin secretion from cultured airway epithelial cells. Confluent primary hamster tracheal surface epithelial (HTSE) cells were metabolically radio labeled using $^{3}H-glucosamine$ for 24 h and chased for 30 min in the presence of varying concentrations of each agent to assess the effects on $^{3}H-mucin$ secretion. The results were as follows: 1) schizandrin significantly inhibited ATP-induced mucin secretion; 2) However, schizandrin-A and gomisin-A did not affect ATP-induced mucin secretion, significantly. We conclude that schizandrin can inhibit ATP-induced mucin secretion by directly acting on airway mucin-secreting cells. Therefore, schizandrin should further be investigated for the possible use as mucoregulators in the treatment of inflammatory airway diseases.

• The Korean Journal of Physiology and Pharmacology
• /
• v.10 no.6
• /
• pp.317-321
• /
• 2006

In this study, we investigated whether glycyrrhizin, prunetin and morroniside affect mucin secretion from cultured airway epithelial cells and compared the possible activities of these agents with the inhibitory action on mucin secretion by poly-L-lysine (PLL) and the stimulatory action by adenosine triphosphate (ATP). Confluent primary hamster tracheal surface epithelial (HTSE) cells were metabolically radiolabeled using $^{3}H-glucosamine$ for 24 h and chased for 30 min in the presence of varying concentrations of each agent to assess the effects on $^{3}H-mucin$ secretion. The results were as follows: 1) glycyrrhizin and morroniside increased basal mucin secretion from airway; 2) prunetin did not affect basal mucin secretion; 3) glycyrrhizin did not inhibit ATP-induced mucin secretion. We conclude that glycyrrhizin and morroniside can increase basal mucin secretion, by directly acting on airway mucin-secreting cells and suggest that two compounds be further investigated for the possible use as mild expectorants during the treatment of inflammatory airway diseases.

• Journal of the Korea institute for structural maintenance and inspection
• /
• v.22 no.2
• /
• pp.43-50
• /
• 2018

In this study, to investigate the shear connection material for the composite of steel plate and bottom plate, design standards and research cases for shear connectors in various countries around the world were analyzed and shear tests were performed on the Push-out specimens with a shear connection, which transmits the horizontal shear force developed on the contact surface between the steel plate and the concrete slab due to various vertical loads acting on the bridge deck. Through Push-out tests of shear studs, of which FRP bar instead reinforcement is placed, the shear stud evaluation formula of the steel strap bottom plate was suggested. The suggested equation suggested in this study has the safety factor of approximately three times compared to allowable strength of highway bridge design criteria. In addition, compared to existing DIN standards and Viest assessment equation, the results showed similar values(approximately, 5% error).

• The Journal of Engineering Research
• /
• v.4 no.1
• /
• pp.125-135
• /
• 2002

The vertical distribution of pore water pressure in the highly saturated sand layer under the oscillating water pressure (water wave) is studied theoretically and experimentally. By experiments it is shown that the water pressure acting on the sand surface propagates into the sand layer with the damping in amplitude and the lag in phase, and that the liquefaction, the state that the effective stress becomes zero, occurs under certain conditions. These experimental results are explained fairly well by the same theoretical treatment as for the ground water problems in the elastic aquifer. The main characteristics of liquefaction clarified by the analysis are as follows: 1) The depth of the liquefied layer increases with the increase of the amplitude and the frequency of the oscillating water pressure. 2) The increase of the volume of the water and the air in the layer increases the liquefied depth. Especially the very small amount of the air affects the liquefaction significantly. 3) The liquefied depth decrease rapidly with the increase of the compressibility coefficient of the sand. 4) In the range beyond a certain value of the permeability coefficient the liquefied depth decrease with the increase of the coefficient.

• Biomolecules & Therapeutics
• /
• v.14 no.4
• /
• pp.202-206
• /
• 2006

Angelicae Dahiricae Radix has been used for controlling inflammatory respiratory diseases in oriental medicine and their components, phellopterin, isoimperatorin and byakangelicol were reported to have various biological effects. In this study, we investigated whether phellopterin, isoimperatorin and byakangelicol affect adenosine triphosphate(ATP)-induced mucin secretion from cultured airway epithelial cells. Confluent primary hamster tracheal surface epithelial(HTSE) cells were metabolically radiolabeled using $^3H$-glucosamine for 24 h and chased for 30 min in the presence of varying concentrations of each agent to assess the effects on $^3H$-mucin secretion. The results were as follows: 1) phellopterin significantly inhibited ATP-induced mucin secretion; 2) However, isoimperatorin and byakangelicol did not affect ATP-induced mucin secretion, significantly. This result suggests that phellopterin can regulate 'mucin secretion induced by ATP'-a phenomenon simulating mucus overproduction from inflamed airway epithelial cells-by directly acting on airway mucin-secreting cells. Therefore, phellopterin should further be investigated for the possible use as mucoregulators in the treatment of inflammatory airway diseases.