• Transactions of the Korean Society of Mechanical Engineers B
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• v.28 no.9
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• pp.1042-1050
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• 2004

Theoretical study has been conducted to clarify pressure characteristics of KTX(Korea Train eXpress) in tunnel. The severe pressure change in tunnel may give rise to the ear-discomfort for passenger and fatigue for car body. The external and internal pressure of rolling stock have been measured by using the running test with atmospheric pressure sensors and portable data acquisition system in high speed train. In this study, the tunnels from 200m to 4000m in length have been chosen for the investigation of tunnel length effects. We found that there are similar patterns of external pressure change for each critical tunnel length. The critical tunnel lengths are governed by train speed, train length and sonic velocity. And, the patterns of pressure wave in tunnel are classified into eight groups.

• Proceedings of the KSME Conference
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• 2004.04a
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• pp.1655-1660
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• 2004

Theoretical study has been conducted to clarify pressure characteristics of KTX(Korea Train eXpress) in tunnel. The external and internal pressure of rolling stock have been measured by using the atmospheric pressure sensors and portable data acquisition system on Seoul-Busan high speed railroad line. These pressure change may give rise to the ear-discomfort for passenger and fatigue for car body. In this study, the tunnels from 200m to 4000m in length have been chosen for the investigation of tunnel length effects. From the results of experiment, the pattern of pressure change generally agrees to RTRI's experimental result for Shinkansen. We found that there are similar patterns of external pressure variation for each critical tunnel length. The critical tunnel lengths are governed by train speed, train length and sonic velocity.

• Journal of the Korean Society for Railway
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• v.7 no.1
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• pp.26-31
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• 2004

A study is conducted to clarify internal and external pressure variation of passenger cabin for KTX. These pressure variation may give rise to the ear-discomfort for passenger and fatigue for carbody. In this study, the pressure variation of interior, gangway and exterior of KTX passenger car is measured by using the atmospheric pressure sensors and portable data acquisition system. The tunnel from 4000m to 200m in length are chosen far the investigation of tunnel length effects. From the results of experiment, the pressure variation of interior per second is under the ear-discomfort limitation in all of tunnel. And, We found that there are similar patterns of exterior pressure variation for each critical tunnel length. These results generally agree to RTRI's experimental result fur Shinkansen.

• The Journal of Asian Finance, Economics and Business
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• v.7 no.12
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• pp.283-292
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• 2020

The implementation of physical or social distancing during the Covid-19 pandemic has an implication on the shifting of conventional to online business activities. This study aims to explore how financial support, perceived benefits, external pressure determine social media marketing as well as understanding the role of internet and e-business technology (IEBT) that occurs in this relationship. This study adopted a quantitative study with Structural Equation Modeling (SEM)-based variance Partial Least Square (PLS), which aims to enhance understanding of the relationship between variables. The surveyed population of this study came from 123 small- and medium-sized enterprise (SME) owners in East Java of Indonesia, using an online survey and selected with the convenience random sampling method. The findings of this study indicated that the perceived benefits and external pressure have a positive effect on the adoption of IEBT. However, financial support failed in explaining SMEs' adoption of IEBT. This study confirmed that the adoption of IEBT has successfully mediated the influence of financial support, perceived benefits, and external pressure on social media marketing. Despite the samples solely collected from East Java, this study is the first step in research related to the social media marketing in SMEs in Indonesia.

• Journal of Korean Association for Spatial Structures
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• v.10 no.1
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• pp.59-66
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• 2010

Among the protected horticulture facilities in Korea, 99.2% are pipe-framed green houses and most of them are structurally vulnerable single-span type green houses. This study examined peak external pressure coefficient for the roof surface of a green house group composed of single-span and a multiple-span green houses. According to the results of the experiment, the distribution of peak external pressure coefficient was around 30% higher in the single-span greenhouse than in the multi-span ones. The external pressure coefficient for the roof surface of the vinyl house group was, in all of the three vinyl houses, was around 20%-30% higher than that for single-span greenhouses.

• 연구논문집
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• s.28
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• pp.73-87
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• 1998

A pneumatic control system of compressed air as a working fluid has a variety of advantages such as low price, high respondence, non-explosion and good control performance and thus has many applications in the field of automobile, electronic and semiconductor industry. However, it has a difficulty in contolling a precise position due to quick response of system and compressibility of working fluid and. in particular, shock stress may occur due to an external load, resulting in fracture of a cylinder cap unless cushion device is equipped in the linear actuator. To avoid this, a cushion device should be installed for damping effect of the external load and the supply pressure as well as for decreasing shock stress and vibration caused by high speed rotation. Previous studies include dimensionless analyses and computer simulations of cushion capability and experiments of horizontally-mounted cylinder performances. A new attempt is experimentally made in this study using a vertically-mounted cylinder under an operation condition of 4, 5 and 6 (bar) as supply pressure and 40, 70 and 100 (kgf) as external load. It turns out that the cushion pressure is mainly a function of the external load rather than the supply pressure. The cushion characteristics was also revealed in the meter-in circuit.

• Journal of Korean Society of Steel Construction
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• v.21 no.3
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• pp.245-255
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• 2009

The low-rise buildings with gable roofs are commonly used in a number of industries. In order to study the characteristics of peak external pressure coefficient on low-rise buildings with gable roofs, wind-tunnel test have been carried out. Wind-induced pressures were measured simultaneously at many points on wind-pressure models, typical of simple low-rise buildings with gable roofs, which have seven different roof slope with constant width(D), height(H), and length(D). The pressure measurements were made in one kind of turbulent boundary layer, which simulated the natural winds over typical suburban terrains at a geometric scale of 1/150. The results indicate that peak external pressure coefficient on the roof and wall edges were increased. The results compared with wind standard of KBC-2005 and standards of various nations. The comparative resultant, experimental result appeared very similar at AIJ-2004. But the results were somewhat larger then wind standard of KBC-2005.

• Transactions of the Society of Information Storage Systems
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• v.8 no.2
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• pp.72-77
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• 2012

The demand for the laptop computer has been increased day by day and most of users ask quiet computer and devices to work in comfortable environment. One of the devices which generate acoustic noise is an external ODD. Unlike the internal ODD, the external ODD is easy to emit noise because it runs outside of the computer and also it is packed with a thin plastic covers. As the disk rotates, vortex flow is generated inside of the cavity due to various and complicated mold parts of the cover. In addition, there is a gap between the disk tray and the upper/lower cases, through which the air flows as well as the noise leaks. In this study, we have proposed how to reduce the acoustic noise of an external ODD using numerical and experimental analysis. The pressure fluctuations and turbulent kinetic energy distributions are calculated for the developed model. The results show that the sound pressure level is reduced by 2.3dB through simple modifications of ribs of the top cover, which remove or suppress flow instabilities inside of the cavity.

• Wind and Structures
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• v.28 no.6
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• pp.389-404
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• 2019

In coastal regions, it is common to witness significant damages on low-rise buildings caused by hurricanes and other extreme wind events. These damages start at high pressure zones or weak building components, and then cascade to other building parts. The state-of-the-art in experimental and numerical aerodynamic load evaluation is to assume buildings with intact envelopes where wind acts only on the external walls and correct for internal pressure through separate aerodynamic studies. This approach fails to explain the effect of openings on (i) the external pressure, (ii) internal partition walls; and (iii) the load sharing between internal and external walls. During extreme events, non-structural components (e.g., windows, doors or rooftiles) could fail allowing the wind flow to enter the building, which can subject the internal walls to lateral loads that potentially can exceed their load capacities. Internal walls are typically designed for lower capacities compared to external walls. In the present work, an anticipated damage development scenario is modelled for a four-story building with a stepped gable roof. LES is used to examine the change in the internal and external wind flows for different level of assumed damages (starting from an intact building up to a case with failure in most windows and doors are observed). This study demonstrates that damages in non-structural components can increase the wind risk on the structural elements due to changes in the loading patterns. It also highlights the load sharing mechanisms in low rise buildings.

• Journal of the Society of Disaster Information
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• v.11 no.1
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• pp.1-8
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• 2015

This paper presents finite element (FE) analyses to clarify the effects of external pressure on the residual stresses in a girth-welded steel pipe. At first, FE simulation of the girth welding process is carried out to obtain the weld-induced residual stresses employing sequentially coupled three-dimensional (3-D) thermo-mechanical FE formulation. Then, 3-D elastic-plastic FE analyses incorporating the residual stresses and plastic strains obtained from the preceding FE simulation are performed to investigate the residual stress behavior in the girth-welded pipe under external pressure. The FE analysis results show that the hoop compressive stresses induced by the external pressure significantly alter the hoop residual stresses in the course of the mechanical loading.