• Structural Engineering and Mechanics
• /
• v.18 no.6
• /
• pp.745-757
• /
• 2004

Lateral-torsional buckling moment resistances of I-shaped stepped beams with continuous lateral top-flange bracing under a single point load on the top flange and negative end moments were investigated. Stepped beam factors and a moment gradient correction factor suggested by Park et al. (2003, 2004) were used to develop new lateral buckling formula for beam designs. From the investigation of finite element analysis (FEA), new lateral buckling formula of beams with singly or doubly stepped member changes and with continuous lateral top-flange bracing subjected to a single point load on top flange and end moments were developed. The new design equation includes the length-to-height ratio factor to account for the increase of lateral-torsional buckling moment resistance as the increase of length-to-height ratio of stepped beams. The calculation examples for obtaining lateral-torsional buckling moment resistance using the new design equation indicate that engineers should easily determine the buckling capacity of the stepped beams.

• Proceedings of the KSME Conference
• /
• 2008.11a
• /
• pp.1427-1432
• /
• 2008

This paper describes the locomotion of a water jumping robot which attempts to emulate the fishing spider’s ability to jump on the water surface. While previous studies of the robots mimicking arthropods living on water were focused on recreating their horizontal skating motions, here we aim to achieve a vertical jumping motion. The robot jumps by pushing the water surface with rapidly released legs which were initially bent. The motion is triggered with a latch driven by the shape memory alloy actuator. The robot is capable of jumping to the maximum height of 26mm. Jumping efficiency, defined the maximum jumping height on water over the maximum jumping height on rigid ground, is 0.26 This work represents a first step toward robots that can locomote on water with superior versatility including skating and jumping.

• Journal of the Korean Society of Industry Convergence
• /
• v.7 no.1
• /
• pp.63-68
• /
• 2004

There are a lot of manholes such as for water supply, sewage, telecommunication cable, traffic sign, electricity supply, and rainwater, etc. Conventional manholes installed on a road are impossible to adjust height, so that they should be entirely excavated to reinstall or repair. This entire excavation of a manhole causes too much time-consuming work, waste of resources, and obstruction of traffic. In this study, in order to solve the above mentioned problems, a cover, outer and inner parts of a manhole are integrated by gear-shaped parts located between outer and inner parts of a manhole. Mechanical design is performed to determine dimension of gear-shaped parts by Taguchi orthogonal array table. Cast molds for a gear-shaped manhole are also manufactured.

• Journal of the Ergonomics Society of Korea
• /
• v.15 no.2
• /
• pp.51-62
• /
• 1996

This research utilized the psychophysical methodology, where secrw drivers are used, to determine the effects of i) the location and orientation of work objects, and ii) wearing gloves, on ratings of perceived exertion at various body parts. The validity of the psychophysical methodology in determining a preferred work pace was also studied. The subjects drove screws with a screw driver into thick wooden sheet at three vertical and three horizontal locations. They drove serews for 3 minutes at each location and assessed the condition using the psychophysical scale. The results showed that only the vertical location was a significant factor in determining the discomfort ratings. Driving screws at elbow height on the vertical surface and with the lower arm close to the body on the horizontal surface were the work locations with the smallest ratings of perceived discomfort. Wearing gloves had significant effects on reducing the pain of the hand. From the experiment in which a comfortable work pace was identified using 20 minute psychophysical adjustment, it was found that the psychophysical method is sensitive to workers perception of the physical stress when the upper limbs are employed. This was confirmend by the high correlation between the psychophysical results and EMG measurement.

• Transactions of Materials Processing
• /
• v.1 no.1
• /
• pp.42-51
• /
• 1992

The ring compression test has been widely employed as an experimental means to determine the friction factor. The calibration curves are obtained by the rigid-plastic finite element analysis for various work-hardening exponent and strain-rate hardening exponent. The effects of work-hardening exponent and strain-rate hardening exponent are thoroughly studied and discussed from the finite element computation. The change of friction factor during height reduction in ring compression is also discussed. Then, the method to estimate the change of friction factor during ring compression is proposed.

• Journal of the Korea Fashion and Costume Design Association
• /
• v.19 no.4
• /
• pp.123-137
• /
• 2017

The purpose of this study is to suggest sleeve cap height with a satisfying wearing sensation and appearance on jackets for women in their twenties so that high-consumer demand jackets can be produced. Five experimental jackets with sleeve cap heights of [(AH/3)-1cm], [(AH/3)-0.5cm], [AH/3], [(AH/3)+0.5cm] and [(AH/3)+0.8cm] were made for 30 subjects to try on after which the subjects were then surveyed for their assessment of appearance, wearing sensation and preference. On the basis of the results, the optimum height of the sleeve cap has been proposed along with the following contents and results of this research. 1. [AH/3] [(AH/3)+0.8cm] of sleeve cap height was assessed to beof desirable appearance. 2. [AH/3] of sleeve cap height garnered a high opinion in terms of intuitive wearing sensation, while [(AH/3)-1cm] [AH/3] were the heights with overall satisfaction of intuitive and movement wearing sensations. If discomfort in the upper sleeve at 'straight arm' posture can be tolerated, the sleeve cap height can be set to [(AH/3)-1cm]~[(AH/3)+0.5cm]. 3. [AH/3] and [(AH/3)+0.5cm] were found to have a high preference among wearers, which indicated that the women in their twenties prefer a slim type of sleeve, putting appearance above wearing sensation. Consequently, [AH/3] is desirable when appearance, wearing sensation and preference are considered, [(AH/3)+0.5cm] is fit for business uniform for static duties or formal dress focused on aesthetic impression and [(AH/3)-1cm]~[AH/3] are desirable for work clothes when considering active duties.

• Journal of the Korea Safety Management & Science
• /
• v.16 no.4
• /
• pp.371-378
• /
• 2014

Manual materials handling tasks are the main risk factors for the work-related musculoskeletal disorders. Many assistant tools for manual materials handling are being used in various kind of industries. One of them is a 4-wheeled cart which is widely used in manufacturing factories, hospitals, etc. The major force required to control the 4-wheeled cart is pushing and pulling. There are two types of handles being used for the 4-wheeled cart : vertical type (two vertical handles), and horizontal type (one horizontal handle). This study tried to investigate the pushing forces and subjective discomforts (hand/writst, shoulder, low back, and overall) of the two handle types with different handle height and distance conditions. Twelve healthy male students (mean age = 23.4 years) participated in the experiment. The independent variables were handle angle (horizontal, vertical), handle height (low, medium, high), and handle distance (narrow, medium, wide). The full factorial design was used for the experiment and the maximum pushing forces were measured in 18 different conditions ($2{\times}3{\times}3$). Analysis of variance (ANOVA) procedure was conducted to test the effects of the independent variables on the pushing force and discomfort levels. Handle height and angle were found to be the critical design factors that affect the maximal pushing forces and subjective discomfort. In the middle height, subjects exerted higher pushing forces, and experience lower discomfort levels compared to the high, and low height. There was no statistical influence of the handle distance to the pushing forces and subjective discomfort levels. It was found out that the effects of the handle angle (horizontal and vertical) on both pushing force and subjective discomfort were statistically significant (p < 0.05). The vertical handle revealed higher pushing force and lower discomfort level than the horizontal handle. The reason for that was thought to be the different postures of the hand when grasping the handles. The horizontal handle induced pronaton of the hand and made hand posture more deviated from the neutral position.

• Journal of Preventive Medicine and Public Health
• /
• v.26 no.1 s.41
• /
• pp.37-48
• /
• 1993

This study was conducted to investigate the prevalence rate of low back pain during past one year and its risk factors. The data were collected from 1,384 manufacturing factory workers from March 1, 1992 to August 30, 1992. The results obtained were as follows: 1. The one year prevalence rate of low back pain by manufacturing company was 38.4% in textile manufacturing, 35.2% in concrete reenforcement, 31.0% in cigarette and 26.1% in metal part(P<0.01). 2. In textile manufacturing, age groups with high prevalence rate of low back pain were 30's(36.8%) and 40's(36.4%) (P<0.05), and the one year prevelence rates of low back pain by marital state were 34.9% in married workers and 28.5% in unmarried(P=0.0511). 3. The one year prevelence rates of low back pain by job part are 35.0% in labor workers and 26.1% in clerical(P<0.05), and by work hour per day it was 34.9% in 9 or more and 28.9% in 8 or less(P<0.05). 4. The highest group of low back pain by work posture was 43.5% in 'lifting and transfering materials', and it by fitness of chair was 56.0% in uncomfortable one, and by height of working board was 33.6% in low working one. 5. In logistic regression analysis, significant determinants with low back pain were marital state(p<0.05), work hour per day(P<0.05), height of working board(P<0.01), and work posture(P<0.01).

• Safety and Health at Work
• /
• v.6 no.4
• /
• pp.279-288
• /
• 2015

Background: In this study, the measurement of job stress of electric overhead traveling crane operators and quantification of the effects of operator and workplace characteristics on job stress were assessed. Methods: Job stress was measured on five subscales: employee empowerment, role overload, role ambiguity, rule violation, and job hazard. The characteristics of the operators that were studied were age, experience, body weight, and body height. The workplace characteristics considered were hours of exposure, cabin type, cabin feature, and crane height. The proposed methodology included administration of a questionnaire survey to 76 electric overhead traveling crane operators followed by analysis using analysis of variance and a classification and regression tree. Results: The key findings were: (1) the five subscales can be used to measure job stress; (2) employee empowerment was the most significant factor followed by the role overload; (3) workplace characteristics contributed more towards job stress than operator's characteristics; and (4) of the workplace characteristics, crane height was the major contributor. Conclusion: The issues related to crane height and cabin feature can be fixed by providing engineering or foolproof solutions than relying on interventions related to the demographic factors.

• Journal of Information Processing Systems
• /
• v.18 no.2
• /
• pp.223-234
• /
• 2022

The evaluation of the print quality of 3D printing has traditionally relied on manual work using dimensional measurements. However, the dimensional measurement method has an error value that depends on the person who measures it. Therefore, we propose the design of a new print quality measurement method that can be automatically measured using the field-of-view (FOV) model and the intersection over union (IoU) technique. First, the height information of the modeling is acquired from a camera; the output is measured by a sensor; and the images of the top and isometric views are acquired from the FOV model. The height information calculates the height ratio by calculating the percentage of modeling and output, and compares the 2D contour of the object on the image using the FOV model. The contour of the object is obtained from the image for 2D contour comparison and the IoU is calculated by comparing the areas of the contour regions. The accuracy of the automated measurement technique for determining, which derives the print quality value was calculated by averaging the IoU value corrected by the measurement error and the height ratio value.