• KSTLE International Journal
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• v.3 no.1
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• pp.49-53
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• 2002

Inconel 690 for nuclear steam generator tube has more chromium than the conventionally used Inconel 600 in order to increase the corrosion resistance. TD evaluate the tribological characteristics under fretting condition the fretting tests as well as sliding tests were carried out in elevated temperature water environment. Fretting tests of the cross-cylinder type were done under various vibrating amplitudes and applied normal loads in order to measure the friction forces and wear volumes. Also, the conventional sliding tests of pin-en-disk type were carried out to compare the test results. In fretting, the friction was very sensitive to the load and the amplitude. The friction coefficient decreased with increasing load and decreasing amplitude. Also, the wear of Inconel 690 can be predictable using the work rate model. Depending on normal loads and vibrating amplitudes, distinctively different wear mechanisms and of ten drastically different wear rates can occur. It was fecund that the fretting wear coefficients in water were increased as increasing the temperature of water.

• Journal of the Korean Society for Precision Engineering
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• v.8 no.2
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• pp.106-113
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• 1991

A diamond grinding wheel is generally used to grind hard and brittle materials, such as advanced ceramics. It is, however, quite difficult to dress a diamond grinding wheel efficiently because of its high degree of hardness. In this study, some investigations are carried out to increase dressing efficiecy of resinoid bonded diamond grinding wheel. Dressing forces are measured over a wide range of dressing conditions, and SEM observation of a grinding wheel is carried out. Special attention is paid to comparison between stick method and rotary brake method. Results obtained in this study provide useful information determining reguired dressing time, and for choosing efficient dressing condition for diamond grinding wheel.

• International Journal of Automotive Technology
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• v.5 no.1
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• pp.61-67
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• 2004

This paper suggests two simple two-degree-of-freedom models to describe the dynamical interaction between the pad and the disc of a disc brake system. Separate models for in-plane and out -of-plane vibration are described. Although a brake pad and disc have many modes of vibration, the interaction between a single mode of each component is considered as this is thought to be crucial for brake noise. For both models, the pad and the disc are connected by a sliding friction interface having a velocity dependent friction coefficient. In this paper, it is shown that this friction model acts as negative damping in the system that describes the in-plane vibration, and as negative stiffness in system that describes the out-of-plane vibration. Stability analysis is performed to investigate the conditions under which the systems become unstable. The results of the stability analysis show that the damping is the most important parameter for in-plane vibration, whereas the stiffness is the most important parameter for the out-of-plane vibration.

• Journal of Korean Society of Industrial and Systems Engineering
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• v.42 no.4
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• pp.69-75
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• 2019

Remotely Piloted Aircraft (RPA) controls as a type of unmanned aerial vehicle (drone) is growing rapidly and its flight controller stick disposition is required standardization. We should standardize RPA drone flight control disposition because the flight pilot of RPA is hard to be trained so the flight controller stick differences impairs safety and wastes time and effort of flight controller industry. So this study researches the on-going standardization of RPA drone flight control disposition in Korea and foreign countries. Also this paper analyzes and researches of expert about RPA drone flight controller function and application of flight control mode. I accomplished expert research about standardization plan of unmanned flight control mode and confirm the necessity. Nowadays mode1 and 2 are mostly used in Korea so I carried out preference investigation for two modes. There were 4 preferences choices of RPA drone control mode necessity (importance) and recommendation of standardization modes. They answered that necessity of standardization is important considering pilot training, flight safety and positive development of drone industry. The result of standardization mode preference is that they prefer mode 2 (drone maker 86%, training facilities and research facilities 58%, government bureau 60%). Overall preference result shows that mode 1 24%, mode 1&2 16%, mode 2 60%. So they preferred mode 2 by 60%. The differences between two modes are the direction of throttle and pitch. Direction of throttle and pitch operate opposite way. They prefer mode 2 because mode 2 has similarities of manned flight control mode. Significance of this study is that it showed the necessity of standardization and flight control preference in a quantitative way. It will help drone standardization in related industries and development direction near future.

• Safety and Health at Work
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• v.12 no.1
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• pp.66-73
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• 2021

Background: The objective was to assess the knowledge level, attitude, and practice of health care workers towards standard precautions, and to identify the related factors. Furthermore, it was attempted to identify the proportion of having the experience of needle stick injuries (NSIs) and associated factors among participants. Methods: A cross-sectional study was conducted in a teaching hospital among 233 health workers using a self-administrated questionnaire. The questionnaire included eight knowledge items, seven practice items, and five attitude items. Based on the mean score of each category, responses were grouped into "satisfactory" and "unsatisfactory". Univariate, bivariate, and multivariable logistic regression analyses were done. Results: The mean age of the participants 32.95 (SD ± 9.70) and 62.2% of them were women. 57.5% of the staff had a satisfactory level of correct knowledge (>5 correct answers), 37.3% had a satisfactory positive attitude (>3 correct answers), and 30.9% had a satisfactory practice (>3 correct answers) towards standard precautions. The occupation was one of the predictors as doctors were less likely to have satisfactory knowledge and practice compared to nurses (OR = 0.269, 95% CI: 0.10-0.70 and OR = 0.248, 95% CI: 0.08-0.77, respectively). Out of 174 participants, 31.6% of them reported experiencing NSIs and support staff were 71% less likely to experience NSIs compared to nurses & paramedics. Conclusion: The findings revealed a substandard adherence of standard precautions among participants, which highlighted the necessity of the provision of a periodic, tailored training program based on the occupation and risk exposure.

• Geomechanics and Engineering
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• v.34 no.6
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• pp.637-648
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• 2023

When an earth pressure balance (EPB) shield machine bores a tunnel in gravelly sand stratum, the excavated natural soil is normally transformed using foam and water to reduce cutter wear and the risk of direct muck squeezing out of the screw conveyor (i.e., muck spewing). Understanding the undrained shear behavior of conditioned soils under pressure is a potential perspective for optimizing the earth pressure balance shield tunnelling strategies. Owing to the unconventional properties of conditioned soil, a pressurized vane shear apparatus was utilized to investigate the undrained shear behavior of foam-conditioned gravelly sands under normal pressure. The results showed that the shear stress-displacement curves exhibited strain-softening behavior only when the initial void ratio (e₀) of the foam-conditioned sand was less than the maximum void ratio (e_max) of the unconditioned sand. The peak and residual strength increased with an increase in normal pressure and a decrease in foam injection ratio. A unique relation between the void ratio and the shear strength in the residual stage was observed in the e-ln(τ) space. When e₀ was greater than e_max, the fluid-like specimens had quite low strengths. Besides, the stick-slip behavior, characterized by the variation coefficient of measured shear stress in the residual stage, was more evident under lower pressure but it appeared to be independent of the foam injection. A comparison between the results of pressurized vane shear tests and those of slump tests indicated that the slump test has its limitations to characterize the chamber muck fluidity and build the optimal conditioning parameters.

• Journal of the Korean Applied Science and Technology
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• v.35 no.1
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• pp.205-213
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• 2018

The purpose of this study was to investigate the effect of somatosensory input on the gait ability and equilibrium sensory of elderly women. The subjects who participated in this study were 31 elderly women with a mean age of 75 years or older who no using a walking stick and had no abnormality in otolaryngology. The control group consisted of 30 elderly women who did not exercise regularly more than twice a week. Dependent variables consisted of 2.44m timed up and go test, 10m usual gait, 10m fast gait and 6minute gait. The equilibrium sensory test was performed using EquiTest (NeuroCom, USA). The results of the study on gait ability were not statistically significant for 2.44m timed up and go test, and 10m usual gait. However, 10m fast gait (P<.001) and 6min gait (P<.05) showed significant differences. According to the results of the study on equilibrium sensory ability, there was no significant difference between Condition 1 and Condition 5 however Condition 2 (P<.01), Condition 3 (P<.01), Condition 4(P<.01) and Condition 6 (P<.05) showed statistically significant differences. In conclusion, walking stick have beneficial effects on walking and equilibrium sensation, and elderly women need to actively use walking stick when going out and walking.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.34 no.6
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• pp.731-742
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• 2010

Modeling of rubber for design or analysis often requires confusing or complex work because there are a large number of constitutive models to be considered. Some models have few material constants, while others have many. Researchers have to prepare and fit extensive experimental data with caution and discretion. In this paper, we first compared some typical rubber models in which deformation was carried out by stretching up to around eight times the original size. We conclude that continuum-based models and chain molecular models can be used in the study of the small deformation in most engineering applications, but chain molecular models are preferred in the study of the large deformations in most biomaterial applications. As discrimination problems, Treloar's patch and cylindrical balloon stick are tested theoretically and numerically for studying bifurcation. In the case of Treloar's patch, by using the Kearsley's equation, we show that bifurcation exists for continuum-based models but not for chain molecular models. Both models show bifurcation in the cylindrical balloon stick. Therefore, in the analysis of the bifurcation of rubber showed that its existence also depends on the constitutive model selected.

• Journal of Veterinary Clinics
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• v.19 no.1
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• pp.28-36
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• 2002

These studies were carried out to develop some easy-checking thermometers instead of taking temperature of ectum for the farmers to detect easily a diseased animal with fever. Thermometers such as pincher-type, hood-type, raser-type, stick-type, and wrap-type were devised for the experiments. The experimental animals were cattle, horse, swine, aprine, and canine. Temperature-taking parts of the body were ear, shoulder, axilla, gluteal part, and coccygeal part according o the devised thermometer. Rectal temperature was taken at the same time for the comparison of temperature between rectum nd the certain part. The difference of temperature between rectum and shoulder part using eraser-type thermometer for the domestic animals were $3.37^{\circ}C$ for cattle, $1.94^{\circ}C$ for horses, $2.04^{\circ}C$ for swine, $1.27^{\circ}C$ for caprine, $0.9^{\circ}C$ for canine. The difference of temperature between rectum and gluteal part using eraser-type thermometer for domestic animals were $3.46^{\circ}C$ for cattle, $1.98^{\circ}C$ for horses, $2.22^{\circ}C$ for swine, and $1.1^{\circ}C$ for canine. The difference of intra-individual temperature taken by eraser-type thermometer of shoulder and gluteal part were 0.3 and $0.8^{\circ}C$ for cattle, 0.7 and $1.1^{\circ}C$ for horses, 0.6 and $0.7^{\circ}C$ for swine, 0.9 and $1.1^{\circ}C$ for canine. The difference of temperature between rectum and shoulder part taken by hood-type thermometer for cattle was $3.93^{\circ}C$ and the difference of intra-individual temperature was $0.8^{\circ}C$. The difference of temperature between rectum and gluteal part taken by stick-type thermometer for cattle was $3.7^{\circ}C$ and the difference of intra-individual temperature was $0.8^{\circ}C$. The other types of thermometers than the above three were not proved to be reliable to detect temperature of domestic animals. It was concluded that hood-type, stick-type and eraser-type thermometers are recommendable devices of thermometer to detect easily the status of body temperature and that the eraser-type was proved to be a practical one of the thermometers used in this study.

• Journal of the Korean Institute of Educational Facilities
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• v.14 no.4
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• pp.53-65
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• 2007

The present research has been conducted on the arranged form, the number and kinds, the area, the location of the rooms and the variation on exterior designs, based on a layout and a ground plan of each step, which are general plan, VE proposal and the final negotiation, for 11 elementary and middle and high schools that are designed in the way of BTL project. In consequence, it has been found out that there are some changes in the number and position of the rooms. However, the changes are not exceeding the overall arrangement form. This could not have led to the original aim, which is to induce creativity by PFI. It can be supposed that it is because the BTL system is stick to the old process, the method of financial investment and it is true to say that there needs to be solution for that.