• Applied Chemistry for Engineering
• /
• v.29 no.1
• /
• pp.49-55
• /
• 2018

In this study, we investigated the cellular protective effects and mechanisms of nicotiflorin and its aglycone kaempferol isolated from Annona muricata. The protective effect of these components against $^1O_2$-induced cell damage was also studied by using L-ascorbic acid and (+)-${\alpha}$-tocopherol as controls. Kaempferol exhibited the most potent protective effect, followed by (+)-${\alpha}$-tocopherol and nicotiflorin. L-Ascorbic acid did not exhibit any cellular protective effects. To elucidate the mechanism underlying protective effects, the quenching rate constant of the singlet oxygen, free radical-scavenging activity, ROS-scavenging activity, and uptake ratio of the erythrocyte membrane were measured. The results showed that the cell membrane penetration is a key factor determining the cellular protective effect of kaempferol and its glycoside nicotiflorin. The result from L-ascorbic acid demonstrated that the cellular protective effect of a compound depends on its ability to penetrate the cell membrane and is independent of its antioxidant capacity. In addition, it is suggested that cellular protective effects of kaempferol and (+)-${\alpha}$-tocopherol depend not only on the cell permeability, but also on free radical- and ROS-scavenging activities. These results indicate that the cell permeability and free radical- and ROS- scavenging activities of antioxidants are major factors affecting the protection of cell membranes against the oxidative damage induced by photosensitization reaction.

• Journal of the Korea Convergence Society
• /
• v.9 no.1
• /
• pp.405-418
• /
• 2018

This paper was carried out to provide basic data for career search of the free school system. Putting the goal of career education into cultivating expertise, the review was made on the results of the previous studies on the requirements of professional practice. However, As the controversy over the requirements of professional practice has not been solved, so the core elements related to expert performance were examined as a whole through a fundamental cognitive mechanism from which diverse human cognitive characteristics appear. The results show that expert domains consists of content and representation that can exist in an integrated to a great variety of combinations between the two or independent manner, and each domain or field expert performance require different levels of the elements such as intelligence, internal thinking, curiosity (motivation), and obsession (task commitment); and the birth of 1% experts in a domain or field is determined by the obsession. Based on the results, this paper discusses issues related to professionalism and provides a concrete approach to career search during the free semester.

• Informatization Policy
• /
• v.31 no.1
• /
• pp.72-82
• /
• 2024

The presence of traditional media content on online platforms is one of the critical issues nowadays, and Article 17 of the European Media Freedom Act (EMFA) seeks to regulate this. However, it can be seen that the current version of the text is not yet free of flaws: both its harmonisation with the Digital Services Regulation, its use of definitions and the media fast track mechanism it contains would require careful legislative scrutiny before the final text is adopted. The article examines if the self-declaration procedure envisaged by the EMFA would create a loophole for rogue media actors and bring confusion at both the European and horizontal levels or if it would fit the original goal of the EMFA, which is to improve the functioning of the internal European media market and to reinforce the independent media.

• Journal of the Korean Society for Aeronautical & Space Sciences
• /
• v.46 no.1
• /
• pp.41-51
• /
• 2018

Downwash from helicopter rotor blades and external winds from various maneuvering make an unguided rocket change its trajectory and range. For the prediction of the trajectory and range, it is essential to consider the downwash effect. In this study, an algorithm was developed to calculate 6-Degree-Of-Freedom(6 DOF) forces and moments exerting on the rocket, and total flight trajectory of a 2.75-inch unguided rocket in a helicopter downwash flow field. Using Actuator Disk Model(ADM) analysis result, the algorithm could analyze the entire trajectory in various initial launch condition such as launch angle, launch velocity, and external wind. The algorithm that considered the interference between a fuselage and external winds could predict the trajectory change more precisely than inflow model analysis. Using the developed algorithm, the attitude and trajectory change mechanism by the downwash effect were investigated analyzing the effective angle of attack change and characteristics of pitching stability of the unguided rocket. Also, the trajectory and range changes were analyzed by considering the downwash effect with external winds. As a result, it was concluded that the key factors of the rocket range change were downwash area and magnitude which effect on the rocket, and the secondary factors were the dynamic pressure of the rocket and the interference between a fuselage and external winds. In tailwind case which was much influential on the range characteristics than other wind cases, the range of the rocket rose as increasing the tailwind velocity. However, there was a limit that the range of the rocket did not increase more than the specific tailwind velocity.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.35 no.12
• /
• pp.1585-1591
• /
• 2011

In this paper, we present a new exoskeleton-type data glove that can sense the movement of the human finger and reflect the force to the finger. The data glove is designed on the basis of the skeletal structure of the human hand, and the finger module has 1 degree-of-freedom because it includes three four-bar mechanism joints in series and a wire-coupling mechanism. In addition, the transmission ratio of the finger module is maintained at 1:1.4:1 over the entire movement range, and hence, the module can perform both extension and flexion. In addition, to enable adduction/abduction motion of the human hand, a unique MCP joint is designed by using two universal joints. To validate the feasibility of the data glove, master-slave control experiments based on force-position control between the data glove and the robot hand are conducted.

• Journal of agriculture & life science
• /
• v.53 no.4
• /
• pp.113-124
• /
• 2019

In this study, the operational characteristics of a cam-type vegetable transplanter which usually used in domestic was analyzed and operating mechanism of a transplanting device was analyzed. The main components and power path of the transplanter were analyzed. The maximum and minimum control cycles according to the moving speed and the plant spacing were analyzed. 3D modeling and simulation were performed to derive the trajectory of the bottom end of the transplanting hopper and the plant spacing at the each operating condition. The simulation results were verified by the field tests. As main findings of this study, the transplanting device has one degree of freedom (DOF) which consist of 13 links, 17 rotating joints and 1 half joint, and each part has composite structure with cam and links. By continuous and repetitive motion of the structures of transplanting device, the transplanting hopper plants the seedling in the ground with a vertical direction, and the seedling was planted stably. The power is transmitted to the driving part and transplanting device from the engine, and the maximum and minimum plant spacing of the transplanting device were about 900 mm and 350 mm, respectively.

• Journal of Aerospace System Engineering
• /
• v.13 no.5
• /
• pp.94-101
• /
• 2019

The dynamic characteristics of the composite reflector panels are numerically and experimentally investigated. A dynamics model of the panel is analytically developed based on a deployment mechanism of the antenna. The deployment is passively activated using elastic energy of a spring with two rotational degrees of freedom. Using the flexible multi-body dynamic analysis ADAMS, dynamic behavior of the panels such as velocities, deformations, as well as reaction forces during the deployment, are investigated in the gravity and zero-gravity cases. The reflector panel is manufactured using carbon fiber reinforced plastics (CFRPs) and its deployment characteristics are experimentally observed using a zero-gravity deployment test. The impact response and vibration problems that occur during deployment of the antenna panel have been identified and reliably deployed using dampers.

• Journal of the Korea Society for Simulation
• /
• v.19 no.1
• /
• pp.13-22
• /
• 2010

This paper describes tagline PD control for reduction of motion for the heavy cargo(load) suspended by a floating crane. The equations of motion are set up considering the 6-degree-of-freedom floating crane and the 6-degree-of-freedom load based on multi-body system dynamics. The tagline mechanism is applied to floating crane to control motion of the heavy cargo(load). The winch, mounted on the deck of floating crane, is used to control the tension of tagline. To generate control force, PD control algorithm is applied. Numerical simulation and experiment is executed to verify the tagline control mechanism. The numerical simulation and experiment shows that the tagline control mechanism reduces the motion of the load suspended by a floating crane.

• Transactions of the Korean Society of Pressure Vessels and Piping
• /
• v.12 no.1
• /
• pp.134-140
• /
• 2016

The Control Rod Assembly (CRA) controls the reactor power by adjusting its position in the reactor core during normal operation and should be quickly inserted into the reactor core by free drop under scram condition to shut down chain reactions. Therefore, the drop time of the CRA is one of important factors for the safety of the nuclear reactor and must be experimentally verified. This study presents the drop performance test of the CRA which has been conceptually designed for the Proto-type Generation IV Sodium-cooled Fast Reactor. During the test, the CRA was free dropped from a height of 1 m under different flow rate conditions and its drop time was measured. The results showed that the drop time of the CRA increased as the flow rate increased; the average drop times of the CRA were approximately 1.527 seconds, 1.599 seconds and 1.676 seconds at 0%, 100% and 200% of design flow rates, respectively.

• Transactions of the Korean Society of Mechanical Engineers A
• /
• v.36 no.1
• /
• pp.73-79
• /
• 2012

Kiosks are widely used in drive-thru systems in parking lots or on the highway to provide various services to drivers. However, the driver must stop at an exact location to access the kiosk, since its panel is fixed. In order to improve the kiosk accessibility, in this study we developed a manipulator that can adjust the position of the kiosk panel. The number of active joints was minimized to lower the cost, whereas a parallelogram mechanism and passive joints were adopted to increase its convenience for the users. Furthermore, a safety mechanism using springs and a cam was designed to ensure the safety of the user in the case of an emergency. The performance of the position controller and the safety mechanism were verified through various tests. In addition, the proposed collision reaction strategy improved the safety performance of the kiosk system.