• Journal of the Korean Society of Safety
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• v.27 no.5
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• pp.99-104
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• 2012

A turnelling work beneath roadways or railways in use is unsafe and dangerous. A turnelling method should be analytically and experimentally studied to verify stability and safety of excavating works by construction step. The conventionally analytical method was ineffective in computational time and cost, so the new analytical method named homogenuity method, was developed and verified compared with analytical results. That method was applied to parameterly study the effect of distance of steel supports and overburdening height of soil. It showed that the homogenuity method was very practical and effective in step-by-step analysis considering construction sequences. A measuring device was set at the construction field and mechanical behavior was monitored during construction. Measuring values are larger than analytical values because impact of inserting steel pipes, lowering level of underground water and vibration of passing vehicles affected soil density during construction, but those values were within allowable limits.

• Journal of the Korean housing association
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• v.11 no.3
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• pp.99-107
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• 2000

The purpose of this study was to identify the universal design characteristics in residential environments. The subjects were 135 physically disabled persons who lived in the rental multi-family housing apartments in Pusan. Interview method was used for this study. They were an average age of 51 years and 63% were male. They were low income families and lived in 12 pyung ($39.75\textrm{m}^2$) apartments. They were asked about what housing characteristics were constraints in their daily living. They pointed out that the constraints in their apartments were as follows: 1) the small amount of space in the bathroom, kitchen, bedroom, and the entrance area of housing unit, 2) the unflat floor level between the bathroom and the hallway, or the balcony and the bedroom, 3) the slippery floor finish in the bathroom, 4) lack of grab bars or handrails in the bathroom and the ramp, 5) the kitchen work centers and the electric switches at improper height, and 6) the steep ramp. Therefore, the universal design characteristics in residential environments were the adequate amount of space, flat floor level, non-slippery floor finish, grab bars or handrails, accessible height, and ramp.

• Coupled systems mechanics
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• v.7 no.4
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• pp.407-420
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• 2018

In solid-liquid two phase flow, the knowledge of how descending solid particles affected by the presence of downstream wall is important. This work studies at what interstitial distance the velocity of a vertically descending sphere is affected by a downstream wall as a consequence of wall-modified hydrodynamic forces through a validated dynamic model. This interstitial distance-the hydrodynamic coupling distance ${\delta}_c-is$ found to decay monotonically with the approach Stokes number St which compares the particle inertia to viscous drag characterized by the quasi-steady Stokes' drag. The scaling relation ${\delta}_c-St-1$ decays monotonically as literature below the value of St equal to 10. However, the faster diminishing rate is found above the threshold value from St=10-40. Furthermore, an empirical relation of ${\delta}_c-St$ shows dependence on the drop height which clearly indicates the non-negligible effect of unsteady hydrodynamic force components, namely the added mass force and the history force. Finally, we attempt a fitting relation which embedded the particle acceleration effect in the dependence of fitting constants on the diameter-scaled drop height.

• Wind and Structures
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• v.15 no.4
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• pp.313-329
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• 2012

There have existed for a number of years good practice guidelines for the use of Computational Fluid Dynamics (CFD) in the field of wind engineering. As part of those guidelines, details are given for the size of flow domain that should be used around a building of height, H. For low-rise buildings, the domain sizes produced by following the guidelines are reasonable and produce results that are largely free from blockage effects. However, when high-rise or tall buildings are considered, the domain size based solely on the building height produces very large domains. A large domain, in most cases, leads to a large cell count, with many of the cells in the grid being used up in regions far from the building/wake region. This paper challenges this domain size guidance by looking at the effects of changing the domain size around a tall building. The RNG ${\kappa}-{\varepsilon}$ turbulence model is used in a series of steady-state solutions where the only parameter varied is the domain size, with the mesh resolution in the building/wake region left unchanged. Comparisons between the velocity fields in the near-field of the building and pressure coefficients on the building are used to inform the assessment. The findings of the work for this case suggest that a domain of approximately 10% the volume of that suggested by the existing guidelines could be used with a loss in accuracy of less than 10%.

• Journal of Korean Society of Occupational and Environmental Hygiene
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• v.21 no.4
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• pp.209-214
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• 2011

Objectives: To assess the risk of pushing or pulling the yarn-carrying cart, the survey was performed in some fiber manufacturing factories. Methods: We selected 6 fiber-twisting factories which agreed to in-site survey of their workplace. To measure both initial and sustained forces of the push-pull tasks, Chatillon CSD500 dynamometer(2004, Ametek, USA) was used. The mean of 3 tests for the same cart was adopted as the measured forces. Height and width of cart, weight of spooled yarns, and distance of movement were also measured. Inspection of cart wheel, moving path, and the actual hand position while moving was done. Results: More than one pushing or pulling task exceeded the push-pull force limits of design goal in 5 factories. Though the cart was not loaded the heaviest weight in the factory, the measured push or pull force exceeded the limits several times. A few cart wheels were worn out and tangled with pieces of yarn. It was also observed some holes in the moving path. Conclusions: While the push-pull task is not included in the 11 scopes of over-burdened work notified by Korean government, it should be recognized as risk factor of work-related musculoskeletal disorders. The maintenance work such as regular change and frequent cleaning of cart wheel, the use of fitting wheel, and flattening of bumpy floor through the moving path should be advised importantly in the worksite management of work-related musculoskeletal disorders.

• Proceedings of the KSME Conference
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• 2007.05b
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• pp.2378-2383
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• 2007

Direct Numerical Simulation was carried out to predict mass transfer in turbulent flow around a rotating stepped cylinder. This investigation is a follow-up study of Nesic et al. [Corrosion, Vol. 56, No. 10, pp. 1005 - 1014] The original motivation of this work stemmed from the efforts to design a simple device which can generate flows of high turbulence intensity at low cost for corrosion researchers. Two cases were considered; Sc=1 and 10 both at Re=335. Here, Sc and Re stand for Schmidt number and Reynolds number, respectively, based on the step height and the surface speed of the cylinder upstream the step. Main focus was placed on the correlation between turbulent fluctuation and concentration field. The spatio-temporal evolution of concentration field is discussed. The numerical results are qualitatively compared with those of the experiment conducted with the same flow configuration.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.27 no.1
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• pp.17-24
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• 2003

A mathematical model of the hydrodynamic and heat transfer performances of two-phase flow (gas-liquid) in thin film region of micro channel is proposed. For the formulation of modeling, the flow of the vapor phase and the shear stress at the liquid-vapor interface are considered. In this work, disjoining pressure and capillary force which drive the liquid flow at the liquid-vapor interface in thin film region are adopted also. Using the model, the effects of the variations of channel height and heat flux on the flow and heat transfer characteristics are investigated. Results show that the influence of variation of vapor pressure on the liquid film flow is not negligible. The heat flux in thin-film region is the most important operation factor of micro cooler system.

• Transactions of the Korean Society of Mechanical Engineers B
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• v.31 no.9
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• pp.799-806
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• 2007

Direct Numerical Simulation was carried out to predict mass transfer in turbulent flow around a rotating stepped cylinder. This investigation is a follow-up study of DNS of turbulent flow in Nesic et al. [Corrosion, Vol. 56, No. 10, pp. 1005 - 1014] The original motivation of this work stemmed from the efforts to design a simple device which can generate flows of high turbulence intensity at low cost for corrosion researchers. Two cases were considered; Sc=1 and 10 both at Re=335. Here, Sc and Re stand for Schmidt number and Reynolds number, respectively, based on the step height and the surface speed of the cylinder upstream of the step. Main focus was placed on the correlation between turbulence and mass transfer. The spatio-temporal evolution of concentration field is discussed. The numerical results are qualitatively compared with those of the experiment conducted with a similar flow configuration.

• Journal of the Korean Society of Safety
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• v.10 no.2
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• pp.113-119
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• 1995

Many studies have been done to determine the magnitudes of force a man can exert on the objects. However, very little attention has been paid to those In postures on slopes. This paper was aimed to evalute how human work postures would affect the push/pull force and to grasp the relationships between the rectified EMG(REMG) measured at the trunk muscles and force exerted on upward slopes. Two subjects participated in the experiment. The results showed no lineal relationship between the REMG and exerted force at handle. But as the slope and handle height increased, exerted force and muscular stress on erector spinae or rectus abdominis were generally increased. It was notified that since ANOVA did not detect any statistical significance in REMG variation due to dominant muscles, careful application and interpretation of the REMG should be required in analyzing maximal force exertions.

• Journal of the Korean Society of Safety
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• v.36 no.5
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• pp.36-42
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• 2021

Portable ladders are widely used as ascend and descend pathways and platforms for works at height at residential and industrial sites. In the last 10 years, 267 fatalities and 36,571 accidents related to portable ladders have been reported, suggesting a need to develop countermeasures to prevent such accidents. In this study, an in-depth focus group interview (FGI) was conducted with various stakeholders of portable ladders to survey the current usage and requirements for improving work safety. A new portable ladder called active platform ladder was developed based on the requirements suggested by the FGI. A stability test confirmed that the developed ladder is more stable than conventional ones, suggesting that it can reduce the fall accidents.