• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
• /
• v.4 no.1
• /
• pp.77-85
• /
• 2006

A demonstration facility for an advanced spent fuel conditioning process (ACP) is under construction at KAERI. In this hotcell facility, the rear door is frequently used since all process equipment and materials are taken in and out only through the rear door. Therefore , both the structural safety and stability of the door are essentially required for the safety of ACP facility. In this paper, the finite element analysis has been performed to investigate the structural safety under the impact condition between the rear door and the door frame. Also the possibility of the rear door being tumbled over by the impact force or the inertia force under a sudden stop conditon has been evaluated. The analysis results demonstrate that the structural safety and stability of the rear door are sufficiently assured for both the impact and the accidential stop conditions.

• Journal of KSNVE
• /
• v.6 no.1
• /
• pp.107-114
• /
• 1996

The damping characteristics of a cylindrical structure containing oil and bearing balls is investigated for external bending forces. The experimental data obtained through the use of bearing balls with viscous oil in a column is given and analyzed. The viscous action of the oil and inertia effects of the balls on the inside of column create a drag force. The drag force dampens the vibration of the column. This study aims to search for an optimum combination of oil and balls which would produce maximum damping. Machining oils of various viscosities along with ball bearings of various sizes place inside cantilevered aluminium tubes of various diameters to create a rig on which the damping properties of the oil and balls can be studied. The contileved tubes are studied in both horizontal and vertical positions in order to gauge the effect of gravity on the system. The actions of the ball in the column and damping characteristics are investigated according to the dimensionless terms. The Buckingham theorem is used to reduce the variables and to predict the damping of an oil ball column. Though the damping ratio remains fairly constant in the horizontal position of column, the damping ratio begins to increase as the ratio of the number of balls and column length rise above 0.28 in the vertical position of oil ball column. The ratio of the ball diameter to column diameter influences the damping ratio with an optimum diameter ratio. Slenderness ratio and gravity effects on the damping ratio ane investigated.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.8
• /
• pp.642-648
• /
• 2019

This paper presents a fast back-type transfer device for snack food processing that uses the inertia of transferred material. A conventional conveying system is a drive system that uses a belt conveyor and mechanical crank, which generate noise and vibration and cause environmental pollution. Vibration and noise are reduced in the proposed fast back feeding device by using a counterweight. The crank drive unit was replaced with a linear servomotor, and an equilibrium device was designed to balance the force due to acceleration. This makes it is possible to adjust the forward and backward speed and acceleration through PLC control. A vibration damper device offsets the vibration force of the periodic shock form. The main cause of the vibration was identified through vibration analysis, and reduction measures were established. We verified the effectiveness of the vibration by making a prototype and performing about 10 vibration tests. Because no mechanical transducer is needed, energy loss, noise, and vibration do not occur, and the operating speed is not limited.

• Journal of The Korean Association For Science Education
• /
• v.26 no.3
• /
• pp.317-329
• /
• 2006

In this research, a questionnaire was developed to investigate high school students' viewpoints, originating from science history, on 'motion of on object', the subjects were seventy- five 10th grade students and sixty-five 11th grade students. Results found that the highest percentage among the types of 10th grade students' thoughts was related to the Middle Ages 'Impetus' viewpoints. Percentages of 11th grade students' thoughts were highest for Middle Ages and Newton views. These results provided proof that the development of student thoughts' based on science history' are consistent with school year. Furthermore, student thought regarding 'object motion' under the conditions of no force, vacuum, or air under a weightless stage were related to progressive viewpoints on science history. However, the percentage of thoughts related to earlier viewpoints were considerable. Student thoughts on parabolic motion, circle motion, and conservation amount of motion were found to be highly significant in similarity to the viewpoints of Galilei, Descartes, and Huygens; view cultivated before Newton. Consequently, this study determined that educational efficiency could be raised by providing historically more progressive views to cope with conflictory student thoughts-thoughts related to past views in science history.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.34 no.10
• /
• pp.1385-1391
• /
• 2010

In this study, we present small-size, low-power, and high-speed electromagnetic flapping shutters for phone cameras. These shutters are composed of trapezoidal twin blades suspended by H-type torsional springs. The existing electrostatic rolling and flapping shutters need high input voltage, while the existing electromagnetic rotating shutters are too big to be used for phone cameras. To achieve low-power and high-speed angle motion for small-size electromagnetic flapping shutters for camera phones, low-inertia trapezoidal twin blades, each suspended by the low-stiffness H-type torsional springs, are employed. The electromagnetic flapping shutters used in this experimental study have steady-state rotational angles of $48.8{\pm}1.4^{\circ}$ and $64.4{\pm}1.0^{\circ}$ in the magentic fields of 0.15 T and 0.30 T, respectively, for an input current of 60 mA; the maximum overshoot angles are $80.2{\pm}3.5^{\circ}$ and $90.0{\pm}1.0^{\circ}$ in the magentic fields of 0.15 T and 0.30 T, respectively. The rising/settling times of the shutter while opening are 1.0 ms/20.0 ms, while those while closing are 1.7 ms/10.3 ms. Thus, we experimentally demonstrated that the smallsize (${\sim}8{\times}8{\times}2\;mm^3$), low-power (${\leq}60\;mA$), and high-speed (~1/370 s) electromagnetic flapping shutters are suitable for phone cameras.

• Journal of Advanced Marine Engineering and Technology
• /
• v.39 no.7
• /
• pp.709-715
• /
• 2015

Underwater gliders do not typically have separate propellers for forward motion. They generate propulsive forces based on the difference between their buoyancy and gravity. They can control the volume from the buoyancy engine to adjust the propulsive force. In addition, the attitude of the underwater glider is controlled by a rubberless motion controller. The motion controller can change the mass center and moment of inertia of the inner moving mass. Owing to the change in these parameters, the attitude of the underwater glider is changed. In this study, we derive nonlinear, six degree of freedom (DOF) mathematical models for the motion controller and buoyancy engine. Using these equations, we perform dynamic simulations of the proposed underwater glider, and verify the suitability of the design and dynamic performances of the proposed underwater glider. We then perform the motion control simulation for the pitch and roll angle, and analyze the dynamic performance according to the pitch and roll angles.

• Journal of Advanced Marine Engineering and Technology
• /
• v.41 no.3
• /
• pp.202-208
• /
• 2017

The recently developed marine engines for propulsion of ships have higher torsional exciting force than previous engines to improve the propulsion efficiency and to reduce specific fuel oil consumption. As a result, a viscous damper or viscous-spring damper is installed in front of marine engine to control the torsional vibration. In the case of viscous damper, it is supposed that there is no elastic connection in the silicon oil, which is filled between the damper housing and inertia ring. However, In reality, the silicon oil with high viscosity possesses torsional stiffness and has non-linear dynamic characteristics according to the operating temperature and frequency of the viscous damper. In this study, the damping characteristics of a viscous damper used to control the torsional vibration of the shafting system have been reviewed and the characteristics of torsional vibration of the shafting system equipped with a corresponding viscous damper have been examined. In addition, it is examined how to interpret the theoretically optimal dynamic characteristics of a viscous damper for this purpose, and the optimum design for the propulsion shafting system has been suggested considering the operating temperature and aging. when the torsional vibration of the shafting system is controlled by a viscous damper filled with highly viscous silicon oil.

• Journal of National Security and Military Science
• /
• s.5
• /
• pp.1-45
• /
• 2007

Reserved forces of ROKA are in charge of replacement of TOE in the wartime and mission of rear area operation. But there is institutional inertia in the law and organization oriented to fill human resources rather than take mission. We need to prepare for the investment and arrangement of reserved forces as military power that would be replaced standing forces. In this portion, to reinforce reserve forces elite, First, efficient mobilization regulations and systems are suggested. I covered a maintenance of relevant mobilization ordinances which need to legislated and approved by national assembly for wartime and development of mobilization system which might lose the appropriate time for mobilization due to complicated declaration procedures and measures to overcome the panic at the initial stage of the war and organization and employment of nationwide transportation system and mobilization center. To ensure efficient resource management and mobilization of reserve forces with a number of approximately 3 million, there's a necessity of organization for integration and conciliation. To make it real, I suggested establishing and employing the mobilization center, on first phase, employ the mobilization center focusing on homeland divisions, on second phase, it is advisable to convert to national level mobilization system and develop to central mobilization center focusing on national emergency planning committee. During peacetime, in conjunction with Mobilization Cell, mobilization center can conduct resource survey and integrate and manage mobilization resources and take charge of mobilization training of subordinate units, and during wartime, in conjunction with mobilization coordination team and Cell, can ensure the execution of mobilization. Second, Future oriented reserve forces management system such as service system of reserve forces and support system of homeland defense operations. Current service and trainings of reserve forces by the year have very low connection, as it is very complex to manage the resources and trainings, and service and training lack the equity, re-establishment of service system is required. Also in an aspect of CSS and cultivation support for reserve forces, as the scope and limitation of responsibility between the armed forces and autonomous organization is obscure, conditions to conduct actual-fighting exercises are limited. Concentrated budgetting is extremely difficult because reserve forces training fields are scattered nationwide, and facilities and equipments are rapidly getting older. To improve all these, I suggest the organization of homeland defense battalion with a unit of "City-Gun-District" and supporting the local reserve forces. Conduct unit replacement or personal replacement for those who have finished their 1 or 2 years and homeland defense operation duty for those with 3-5 years for consistency and simplification. Third, I suggest Future oriented Reserved Training(FRT) and Training Center oriented training management to establish a reliable reserve training. Reserves carry out expansion of unit, conventional combat mission, homeland defense and logistics support during wartime, and actual-fighting exercise, and disaster relief, peace keeping activities. Despite diverse activities and roles, their training condition still stays definitely poor. For these reasons, Modernization of weapons and facilities through gradual replacement and procurement is essential to enhance mobilization support system.

• Journal of The Korean Association For Science Education
• /
• v.16 no.4
• /
• pp.340-350
• /
• 1996

Knowledge is composed through the interaction between the concept structure already held by students and their experience, and learning can be said to be the active process of solving the cognitive conflict caused by this interaction. Therefore, this study consists in showing the effective learning method and finding out the elements which the teacher has to own, through examining several forms of pre-conception or mis-conception of the inertia, the force-equilibrium, the action and reaction, the heat, and the electric current, and then finding out their solution and studying student's change in science concepts. For this study, the types of concept on the five above-mentioned materials which students have were examined through the concept-classifying question paper, and the classes to which the class mode for the change of concepts applied, were practised in each different classroom by each different instructor - a professor, a scientist, a teacher, and two students, respectively. And the effect of the teaching strategy based on these classes, and each different instructor' influence on the change of concept in students. were examined. The result of my study is as follows; 1. Students have various types of pre-conception which are different from science concept, and these types of pre-conception tend to last even after learning in class. 2. The thoughts on the correct science concept of the high school third-grade students who learned the physics in the traditional teaching method, and the second grade students who don't learn the physics yet, were nearly equal those of the second grade students by receiving the physics class through the cognitive conflict course were greatly changed especially that students showed the distinct change on mechanics and electric current. 3. Students didn't show the remarkable change of the science concept on the five materials in the four kinds of experimental classes by each different instructor but in the part of mechanics, there was the distinct change between the class by professor and those by the students. This was due to the difference of the authority and the attitude of the concept demonstrator. 1) The authority, the kind attitude, and the responsibility of the expert played an important role in the correct concept-formation of mechanics part - especially in the case of the mis-conception caused by the intuitive belief. 2) In the class by instructor with the democratic teaching method, the change of concept took place more easily, because in his class students could discuss the subject freely, so that they might experience the thought course to give them the confidence on the science concept.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.21 no.1
• /
• pp.208-215
• /
• 2020

This study investigated the relationship among gait variables and physical fitness variables for Korean elderly people. Two hundred elderly people aged 65 to 85, (100 men and 100 women) participated in this study. They performed senior fitness test consisting of 6 tests, 3 additional physical tests (vertical jump, one leg stand, and grip force), body composition measures, and gait test. The gait test used shoes having an inertia measurement device in the outer-soles. The results indicated that the stride length, 6-min walking, lean body mass, and dumbbell curls were significantly affected by age (the above 75 group vs. the below 75 group). Among 33 measured parameters, the principal component analysis (PCA) revealed five PCs such as gait characteristics, physical features, gait variability, and fitness levels. In addition, the correlation analysis showed that the preferred walking speed was significantly, positively associated with stride length and single support time, whereas it was negatively associated with double support time and gait variability.(Ed note: please confirm my modification) In conclusion, sarcopenia should be avoided in elderly people, and resistance exercise is highly recommended to help elderly people maintain their gait ability.