• Proceeding of EDISON Challenge
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• 2016.03a
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• pp.256-261
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• 2016

In this paper, Shape optimal design for a chair with 4 legs and 2 stretchers consisting of stainless steel was conducted. The shape was transformed by identifying stress and deformation for the part of leg and stretcher. In addition, load condition and mesh was designed using Hypermesh. The stress analysis was carried out using CSD_Elast that is one of EDISON program. In seat test, Maximum equivalent stress was showed at the contact part between seat and legs. As a result, a leg cross-section with rectangular and arch was designed. And optimal height of stretcher was found to reduce a deformation. Also, maximum deformation was reduced by designing a stretcher with ellipse cross-section. So, Optimal chair having 4 legs with rectangular cross section and 2 stretchers with ellipse cross section was shown to satisfy the safety ratio.

• Journal of the Korean Society of Physical Medicine
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• v.10 no.4
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• pp.107-112
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• 2015

PURPOSE: This study investigated the effects of lower limb and trunk muscles activation on seat angle and height during sit to stand and stand to sit. METHODS: Subjects were instructed to sit and stand on different angles and heights; $0^{\circ}$(43cm), $5^{\circ}$(48cm), $10^{\circ}$(51cm) and $15^{\circ}$(58cm). Measurements were conducted from sit to stand and stand to sit for external oblique, transversus abdominis, rectus femoris, vastus medialis, vastus lateralis, tibialis anterior and gastrocnemius muscle activation by surface EMG. The muscle activation was measured three times for five seconds in each posture, and the %RVC value was calculated after the exclusion of one second before and after this measurement. This calculation standardized the data from each participant so it could be comparatively analyzed. RESULTS: The external oblique, tibialis anterior, and erector spinae muscles showed significant difference in $10^{\circ}$(51cm), $15^{\circ}$(58cm) and $0^{\circ}$(43cm), rectus femoris, in $15^{\circ}$(58cm) and $0^{\circ}$(43cm)(p<.05) during sit to stand. The external oblique, tibialis anterior, and rectus femoris muscles showed significant difference in $0^{\circ}$(43cm) and $15^{\circ}$(58cm), erector spinae and vastus medialis muscles showed significant difference in $10^{\circ}$(51cm), $15^{\circ}$(58cm) and $0^{\circ}$(43cm)(P<.05) during stand to sit. CONCLUSION: The present study findings indicate that the toilet seat angle and height could affect muscle activities of the lower limb and trunk.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 2003.07b
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• pp.946-949
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• 2003

This paper reports on the fluid flow simulation results of a multilayer type piezoelectric valve. The mechanical and fluidic analysis are done by finite element method. The designed structure is normally closed type using buckling effect, which is consist of three separate structures; a valve seat die, an actuator die and a MLCA(Multilayer Type Ceramic Actuator). It is confirmed that the complete laminar flow and the lowest flow leakage are strongly depend on the valve seat geometry. In addition, turbulent flow was occurs in valve outlet according to increase seat dimension, height and inlet pressure. From this, we was deducts the optimum geometry of the valve seat and diaphragm deflection that have an great influence fluid flow in valve. Thus, it is expected that our simulation results would be apply for piezoelectric applications such as valve and pump, fluidic control systems.

• The Journal of the Convergence on Culture Technology
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• v.6 no.4
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• pp.753-760
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• 2020

In this study, the structural safety of the bearing support was analysed by applying the vertical load (bearing design load) and horizontal load (horizontal force generated during an earthquake) using a precise three-dimensional numerical model. The results of stress and displacement of newly-poured concrete and welded rebars were confirmed numerically. Numerical results show that the increase in the horizontal force and the height of the beam causes the concrete cracking and the stress increase of the rebar connections due to the increase of the stress at the new concrete interface. Therefore, it was analyzed that the increase in the height of bearing support is directly related to the horizontal force and it is necessary to apply the bearing support height appropriate for the bearing support capacity. It was proposed that a method of setting the height of the bearing support suitable for the bearing capacity and determining the reinforcement by presenting the guideline with the correlation between the horizontal force acting on the bearing support and its height.

• Proceedings of the Korean Society of Precision Engineering Conference
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• 2012.05a
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• pp.125-126
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• 2012

• Tribology and Lubricants
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• v.35 no.1
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• pp.37-43
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• 2019

This paper presents an optimization method to determine the shoulder height of an angular contact ball bearing by 3D contact analysis using nondimensional-shaped variables. The load analysis of the ball bearing is performed to calculate the internal load distributions and contact angles of each rolling element. From the results of bearing load analysis and the contact geometry between the ball and inner/outer raceway, 3D contact analyses using influence function are conducted. The nondimensional shoulder height and nondimensional load are defined to give the generalized results. The relationship between the shoulder height and radius of curvature of the shoulder under various loading conditions is investigated in order to propose a design method for the two design parameters. Using nondimensional parameters, the critical shoulder heights are optimized with loads, contact angles, and conformity ratios. We also develop contour maps of the critical shoulder height as functions of internal loads and contact angles for the different contact angles using nondimensional parameters. The results show that the dimensionless shoulder height increased as the contact angle and dimensionless load increased. Conversely, when the conformity ratio increased, the critical shoulder height decreased. Therefore, if the contact angle is reduced and the conformity ratio is increased within the allowable range, it will be an efficient design to reduce the shoulder height of ball bearings.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.12
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• pp.253-260
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• 2020

This study aimed to compare the effects of sit-to-stand training, or training to stand up from sitting positions at various seat heights, on the balance recovery among stroke patients. This study included 20 stroke patients who were randomly divided into two groups. Each group was trained for six weeks, three times a week from March to June 2019. Static balance and dynamic balance were measured, and the variations were analyzed using the paired t-test and the independent t-test. There were significant changes observed in both static and dynamic balance (p<.05) before and after training. However, no significant changes were seen in the static balance in the standing posture with eyes closed (p>.05). This study confirmed that there was a significant effect of training on the balance of stroke patients, especially when progressively lower seat heights were used during the training. This suggests new directions for treatment during rehabilitation for balance recovery of stroke patients. Further studies will need to apply this training to a larger number of subjects, and use various training methods such as randomization of seat height to enable the generalization of the results of this study and application in clinical practice.

• Journal of rehabilitation welfare engineering & assistive technology
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• v.8 no.3
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• pp.205-211
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• 2014

The purpose of this document is to provide basic data helpful in selecting seating device material by examining the affects of polyurethane foam material on seating pressure. In order to achieve this study objective, four seats, 6cm in height, were produced in hardness of: 13, 28, 25, and $45kg/cm^2$. To measure the sitting pressure distribution (depending on the characteristics of the produced seats), 10 healthy subjects participated in the experiment. XSENSOR was used a measuring device, and each seat was mounted on a wheelchair simulation. By analyzing the obtained data with Average Pressure(AP), Peak Pressure(PP,), and Contact Area(CA), the sitting pressure was measured for five minutes on each seat. This experiment showed the following results: There were significant differences between the AP, PP, and CA in the seat material (p<0.5). While the hardness of $18kg/cm^2$ showed low pressure, the hardness of $45kg/cm^2$ showed high pressure. This study also showed that seat material made of polyurethane should be considered when selecting seats. If polyurethane foam is used in seat recommendations, it will be recommended to use $18kg/cm^2$ for the proper hardness of the seat material.

• Archives of design research
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• v.12 no.3
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• pp.73-80
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• 1999

Many domestic users complain about severe pain to the waist, neck, and shoulder as well as work performance because the domestic chair design was developed with western anthropometry dimension and design criteria. Ergonomic design standards are needed for office chair design to reduce stress and poor physical posture for various user body types. In this study, we have suggested design dimensions recommended from previous studies and Korean anthropometry data. We also have reviewed users' preference dimension through measured subjects and analyzed differences between users' preference dimension and the previous design criteria to verify physical appropriateness. We evaluated general office chairs and adjustable chairs which can adjust to fit each person. we also analyzed how each design dimension was reached and affected the human body by evaluation of physical discomfort and comfort. We have found seat height is very important in a workstation. If the seat height is high, it effects the thigh. If width, height, and angle of the backrest are wrong, fatigue to the shoulder, neck, and waist, etc.. As a result of this experiment, we suggested that the height of a seat for Koreans be 425mm for the fixed type and 365-484mm for the adjustable type. Also other design recommendations were suggested in the thesis. In conclusion, our research will be very important in the database because it provides adjustable ranges to fit user's body types in the various design fields.

• Journal of the Korean Society for Library and Information Science
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• v.11
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• pp.3-42
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• 1984

This is to establish a model of the standardization of shelving, chairs, tables and card cabinets for college and university libraries in Korea. The size of furniture was measured on the base of the analysis of the human factors, such as the standard size of human bodies of the college students in Korea, the scope of work area, the moving degree of muscles, the limit of the visual field, etc. The results of this study are as follows: 1. It is desirable that the standard shelf length should be 800mm. and the maximum . shelving height should not exceed 1,803mm. And it is desirable that the bottom shelf has a ground clearance of about $210\~390mm$. 2. It is advisable that the sloped shelving has the slope from about 1,000mm, or 930mm, and the gradient should be $19^{\circ}$ from the above mentioned sloping position and the bottom of each shelf. And it is desirable that the slope height of each shelf should be 77mm. 3. It is advisable that the seat area for users should be $410\~420\times420mm$, and the seat height should be $390\~0400mm$. 4. It is desirable that the table size per user should exceed $490\times880\~890mm$, and the table height should be $680\~690mm$. 5. It is advisable that each tray of the card cabinet should hold about 740 cards, and the depth should exceed 430mm. And it is desirable that the maximum height of card cabinets should be as follows: 60du(drawer units)-$1,400\~1,460mm$, 30du-1, 300mm, 15du-1,100mm. In addition, it is advisable that the 30du cabinet should accomodate 5 trays vertically and 6 trays horizontally for avoiding the worst working position rather than 6 trays vertically and 5 trays horizontally. 6. It is desirable that the height of sliding reference shelves in card cabinets, or consultation tables should be 900mm. But in the case of the sliding shelves, it is desirable to be as follows: 15du-900mm when the card cabinet height is more than 1,100, mm, but unnecessary when less than 1,100mm high, 30du-1,000mm, or 1,100mm in the case of $5\times6du$, but 900mm in the case of $6\times5du$, $60du-900\~950mm$ when the card cabinet height is $1,400\~1,460mm$.