• Proceedings of the Korean Society of Propulsion Engineers Conference
• /
• 2010.11a
• /
• pp.265-270
• /
• 2010

This paper presents the rocket motor support structure to position solid rocket engine within a missile fuselage. When the rocket motor is mounted inside a missile fuselage, fuselage structure must be designed to withstand various structural problems resulting from inserted rocket motor such as axial thrust force, shock/vibration, axial deformation of the rocket motor tank in addition to the flight loads. The motor support structure system proposed in this paper proved to be very simple and efficient while satisfying all the design requirements.

• Proceedings of the Korean Society of Machine Tool Engineers Conference
• /
• 2003.04a
• /
• pp.484-487
• /
• 2003

In designing AMBs (active magnetic bearings) for high-speed spindle system, the shaft is usually assumed as a rigid rotor. For automatic tool change process, there should be a tool clamping system with drawbar using spring or hydraulic force, and the drawbar in the spindle can be in various condition of support during design and manufacturing error. In this paper, the modal characteristics of drawbar in high-speed milling spindle system due to supporting stiffness between drawbar and shaft are analyzed by numerical method. The result shows enough stiff supports must be provided between shaft and drawbar to prevent occurring drawbar vibration lower than the natural frequency of 1$\^$st/ bending mode of spindle.

• Geomechanics and Engineering
• /
• v.25 no.3
• /
• pp.233-243
• /
• 2021

Rib spalling is a major issue affecting the safety of steeply inclined coal seam. And the failure coal face and support system can be affected with each other to generate a vicious cycle along with inducing large-scale collapse of surrounding rock in steeply inclined coal seam. In order to analyze failure mechanism and propose the corresponding prominent control measures of steeply inclined coal working face, mechanical model based on coal face-support-roof system and mechanical model of coal face failure was established to reveal the disaster mechanism of rib spalling and the sensitive analysis of related factors was performed. Furthermore, taking 3402 working face of Chen-man-zhuang coal mine as engineering background, numerical model by using FLAC3D was built to illustrate the propagation of displacement and stress fields in steeply inclined coal seam and verify the theory analysis as mentioned in this study. The results show that the coal face slide body in steeply inclined working face can be observed as the failure height of upper layer smaller than that of lower layer exhibiting with an irregular quadrilateral pyramid shape. Moreover, the cracks were originated from the upper layer of sliding body and gradually developed to the lower layer causing the final rib spalling. The influence factors on the stability of coal face can be ranked as overlying strata pressure (P) > mechanical parameters of coal body (e.g., cohesion (c), internal fraction angle (φ)) > support strength (F) > the support force of protecting piece (F') > the false angle of working face (Θ). Moreover, the corresponding control measures to maintain the stability of the coal face in the steeply inclined working face were proposed.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.11 no.10
• /
• pp.3658-3665
• /
• 2010

As the population of elderly people and disabled people are increased, various demands for human welfare using robot system are raised. Especially autonomous rehabilitation system using robot could reduce the human effort while maintaining the its intrinsic efficacy. This study deals with mobile gait rehabilitation system which combined with BWS (Body Weight Support) for training of elderly and handicapped people who suffer the muscle force weakness of lower extremity. BWS which is designed by kinematic analysis of body lifting characteristics and walking guide system are integrated with main control system and wheeled platform. This mobile platform is operated by UCS (User Command System) and autonomous trajectory planning algorithm. Finally, through the EMG (Electromyography) signal measuring and its analysis for subject, performance and feasibility of developed system is verified.

• Korean Journal of Applied Biomechanics
• /
• v.12 no.2
• /
• pp.393-405
• /
• 2002

When our body is immersed in water, we experience weightlessness. The degree of weightlessness that we experience varies depending on the proportion of the body immersed in water, being governed by the relationship between the weight of body and the buoyant force acting on the body. Human body during the performance of swimming in no exception to these influences. Swimmers body is subject to a time and position dependent force system. Even the magnitude of the buoyant force acting on the swimmers body at every given instant and the corresponding position of the CB change continuously. The findings of this study support the following conclusions. The buoyancy torque was the primary source of bodyroll exhibited by front crawl swimmers performing at distance pace, accounting for 88 % of the bodyroll. Faster swimmers used buoyancy more effectively to generate bodyroll, partially supporting the postulation that an effective use of buoyancy for bodyroll may reduce the generated hydrodynamic forces to be wasted in non-propulsive directions and maximize forward propulsion.

• Journal of Drive and Control
• /
• v.12 no.4
• /
• pp.15-20
• /
• 2015

Unlike a typical metal spring, a gas spring uses compressed gas contained in a cylinder and compressed by a piston to exert a force. A common application includes automobiles where gas spring are incorporated into the design of open struts that support the weight of tail gate. They are also used in furniture such as office chairs, and in medical and aerospace applications. The gas spring works by the application of pressurized gas (nitrogen) contained in a cylinder. The internal pressure of the gas spring greatly exceeds atmospheric pressure. This differential in pressure exists at any rod position and generates an outward force on the rod, making the gas spring extend. In this paper, we investigated the dynamic characteristics of a gas spring on an automotive tail gate system.

• Women's Health Nursing
• /
• v.30 no.2
• /
• pp.140-152
• /
• 2024

Purpose: Social support is essential for postpartum well-being, but little is known about the postpnatal social support preferred by primiparous women. This study aimed to comprehensively understand and describe the meaning of postnatal social support experience in primiparous women. Methods: The participants were seven primiparous women who were within 1 year after childbirth, recruited through purposive and snowball sampling from an online parenting community. The data were collected through in-depth interviews from November 14 to 28, 2022. Participants were interviewed face-to-face or via phone or online platform, according to their choice. Colaizzi's phenomenological qualitative research method was applied to analyze the meaning of the participants' experience. Results: Five theme clusters and fourteen themes were identified from the data. The five theme clusters are as follows: (1) Shortcomings of the childbirth and postpartum care system I learned through my experience; (2) Government policies focusing on childbirth and child-rearing rather than postpartum recovery; (3) Driving force of postpartum recovery: Shared childbirth process; (4) Childcare on my own; and (5) Conflicted between being a stay-at-home mom and a working mom under inadequate maternity protection policies. Conclusion: Despite postpartum support from the government that was perceived as inadequate, first-time mothers regained confidence and motivation for parenting with the help of family, peers, and social networks. First-time mothers need support from professionals and reliable online communities for postpartum recovery and parenting.

• Journal of Agricultural Extension & Community Development
• /
• v.25 no.3
• /
• pp.161-173
• /
• 2018

The study aims to explore the policy directions for young farmers within Korean agricultural context, particularly in Chung-nam Province. In order to accomplish this, young farmers were classified into three categories: successors, new farmers, potential farmers. The importance of young farmers is becoming more of a focus due to decline of population numbers in rural communities as well as the aging of agriculture population. In order to address these two problems, it is necessary to create and implement policy to support each category of young farmer. Rather than the current focus on nurturing young farmers as a labor force, the role of young farmers in maintaining local communities should be expanded in current agricultural system. The local community should provide appropriate conditions for young farmers in Chung-nam Province for the various purposes they have and the roles they fill. In conclusion, it is necessary to provide a 'space' where young farmers can meet base on the community. For this, the role of the community based intermediate support organization for the integrated support system is of great significance.

• The Journal of the Korean dental association
• /
• v.53 no.5
• /
• pp.307-317
• /
• 2015

Although the long-term success of osseointegrated endosseous implants for the support of fixed dental prostheses has been reported, the increasingly widespread use of implant-supported prostheses has led to problems associated with their structural integrity. The most common biomechanical complications observed in dental implant treatment are fracture and screw loosening. The nature of loosening or fracture of dental implant components is complex, since it involves fatigue, fitness, and varied chewing patterns and loads. To assess the service life of the components of the prosthetic system, a knowledge of the loads transmitted through the system is necessary. Design of the final restoration and occlusion in relation to the geometry of a prosthetic restoration has a great influence on the mechanical loading of the implant. It is proposed that control of force in oral cavity may play a larger role in failures than previously believed. Based on theoretic consideration and clinical experiences with dental implant, this article gives simple guidelines for controlling these loads.

• Proceedings of the Korean Society of Precision Engineering Conference
• /
• 1997.10a
• /
• pp.303-306
• /
• 1997

Magnetic bearings have been adopted to support the rotor by electromagnetic force without mechanical contact and have many advantages. The application of the magnetic bearings have become more and more widespread in recent years. But magnetic bearings require feedback control for stable operation because they are inherently open loop unstable systems. In this study, H infinity controller has been applied for rotor-magnetic bearing system for vibration control. The result showed that H infinity controller has better performance than PID controller through simulations.