• Tunnel and Underground Space
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• v.24 no.1
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• pp.46-54
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• 2014

Direct shear tests have been initiated to understand the characteristics of joints which crucially affect the stability of rock mass. In this research, numerical approach in direct shear tests has been initiated using 3DEC on the basis of 3D distinct element method. Normal loads were altered in four different levels on artificial joint tests depending on the sawtooth angle and strengths on constant normal stress conditions, measuring the peak shear strength according to the direct shear tests under laboratory condition. Also results obtained from mechanical properties through laboratory test were used to perform numerical modeling, and shear strength obtained from the modeling was used to compare with laboratory direct shear test. As a result numerical analysis from distinct element method can simulate well on the shear behavior of rockmass.

• Tunnel and Underground Space
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• v.25 no.6
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• pp.515-526
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• 2015

Predicting and measuring tunnel convergence is very crucial for estimating tunnel stability and economical construction of NATM tunnels. The method to estimate the tunnel convergence that occurs before and after construction is proposed based on literature reviews. The total displacement occurring related to tunnel construction is determined to be about 2.5 times that of measured displacements. The results of displacement measurements at two tunnels constructed with similar rock types are examined for the investigation of factors affecting the tunnel convergence. The average convergence of Gyungju A Tunnel is about 6.7 times bigger than that of Daejeon B Tunnel. The possible causes of the large convergence in Gyungju A Tunnel are suggested. In order to predict the convergence of tunnels, careful investigation of the geological structures in the ground surface and the influence of external conditions as well as careful face mapping of the tunnel face should be conducted.

• Tunnel and Underground Space
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• v.19 no.5
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• pp.388-396
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• 2009

Rock bolt is one of the most important supports for tunnelling to prevent excessive ground relaxation at the primary tunnel excavation stage. It forms a ground arch band by confining the ground around a tunnel. Rock bolt has various effects, such as support or hanging effect, internal pressure effect, arching effect, ground improvement effect etc. Most studies on rock bolt focused on the concept of support, but only a few researches on the ground reinforcing effect by pre-tensioning a rock bolts. In this study, large scale model tests are performed to investigate the ground reinforcing effect of rock bolts for regularly jointed rocks. Simple beam model was built to find out the reinforcing effect of jointed rocks, which was reinforced by pre-tensioned rock bolts. Settlement of model beam was analyzed through measuring its sagging for various installation intervals.

• Tunnel and Underground Space
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• v.27 no.6
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• pp.406-421
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• 2017

This study describes a precise numerical analysis process by adopting the real image of mine openings obtained by LIDAR, which can produce a point cloud data by measuring the target surface numerically. Research area is a section of underground limestone mine which is used hybrid room-and-pillar method for improving the production rate. From the application of LIDAR to this section several results were deduced, that is, the central axis of upper and lower vertical safety pillars is distorted to the direction of NW and the section area of lower vertical safety pillar is $34m^2$ smaller than the designed area of $100m^2$. The results of precise measurement in geometrical shape of mine openings and precise simulation in numerical analysis confirms that LIDAR techniques can be suggested as a valuable tool for stability analysis in underground mine by configuring the mine opening shape.

• Tunnel and Underground Space
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• v.27 no.6
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• pp.357-365
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• 2017

The mine subsidence prevention technology has been promoted based on the field test for design, construction, automation measurement and monitoring optimized for investigation, design and mine-filling efficiency customized in Korean mining environment. Based on the R&D roadmap ('07~'16) of the 1st and 2nd stage, mine reclamation technology development has been focused on developing method of evaluating subsidence stability, development of filling material and optimum filling technology, and development of measuring instrument. In the future, in order to systematic management for the subsidence risk areas, we intend to enhance technological capabilities and strengthen the technological infrastructure for business promotion in parallel with the discovery and introduction of new technology to prevent subsidence in the 4th Industrial Revolution era.

• Journal of Korean Society of Rural Planning
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• v.21 no.1
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• pp.117-127
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• 2015

This study evaluated properties and items for selecting on a forest healing village. In order to assign a weight value-between factors, this study was conducted the primary survey first and then the secondary survey for measuring the importance of items. Experts'surveys were conducted on 3 items on level 1, 9 items on level 2, 35 items on level 3 with use of AHP technique. In level 1, the main analysis result was that physical resource properties(0.387) indicated the highest importance. in level 2, healing resources of physical properties(0.402), community participation of human resource properties(0.425), and business competency in part of vision(-.438) showed the highest importance. The analysis result of 35 items on level 3 was that in physical resources properties, securing public land in the village(0.220), possessing recreation space(0.440) and resources available for link with healing(0.413) showed the highest importance. In part of human resources properties, the average age of residents(0.465), commitment to the promotion of the villagers(0.367) and support of local leaders(0.318) showed the highest importance. Adequacy of development plan(0.274), forest work experience-related(0.293), and building profit sharing system(0.282) were also evaluated to have a relatively high importance.

• Journal of Sensor Science and Technology
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• v.18 no.4
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• pp.294-300
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• 2009

Cardiopulmonary resuscitation(CPR) is performed by artificial ventilation and thoracic compression for the patient under emergent situation to maintain at least the minimum level of respiration and blood circulation for life survival. Quality of the pre-hospital CPR not only significantly affects the patient's survival rate but also minimizes side effects caused by CPR. Good quality CPR requires monitoring respiration, however, traditional respiratory air flow transducers cannot be used because the transducer elements are located on the flow axis. The present study developed a new technique with no physical object on the flow stream but enabling the air flow measurement and easily incorporated with the CPR devices. A turbulence chamber was formed in the middle of the respiratory tube by locally enlarging the cross-sectional area where the flow related turbulence was generated inducing energy loss which was in turn converted into pressure difference. The turbulence chamber was simply an empty enlarged air space, thus no physical object was placed on the flow stream, but still the flow rate could be evaluated. Both inspiratory and expiratory flows were obtained with symmetric measurement characteristics. Quadratic curve fitting provided excellent calibration formula with a correlation coefficient>0.999 (P<0.0001) and the mean relative error<1 %. The present results can be usefully applied to accurately monitor the air flow rate during CPR.

• Journal of Trauma and Injury
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• v.22 no.1
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• pp.1-4
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• 2009

Purpose: This study was conducted to evaluate the length of the catheter used in a needle thoracostomy for emergency decompression of a tension pneumothorax by measuring the chest wall thickness (CWT) in patients with chest trauma Methods: A retrospective review of 201 patients with chest trauma who had been transported the emergency department in a tertiary university hospital in a metropolitan area between 1 January and 31 February 2007 was performed. The average CWT at the second intercostal space (ICS) in the midclavicular line (MCL) was measured by using a chest computed tomography scan. Results: As the left and the right mean CWTs were $3.4{\pm}1.0cm$ and $3.4{\pm}1.0cm$, respectively, there was no significant statistical difference between them. The mean CWT of female patients was significantly higher than that of male patients (p=0.001). The mean CWT of patients under the age of 65 years was significantly thicker than that of the patients over the age of 65 years (p<0.001). Of the studied patients, 12 (6.0%) a CWT > 5 cm. Conclusion: A 5 cm-length catheter in a needle thoracostomy may be insufficient for emergency decompression of a tension pneumothorax, so a catheter longer than 5 cm in length is needed.

• Transactions of the Korean Society of Automotive Engineers
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• v.5 no.2
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• pp.50-59
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• 1997

When a front head of train enters a tunnel at a high speed, compression wave is generated at tunnel entrance due to the confinement effect and propagated along the tunnel with sound of speed. The propagated compression wave is reflected at tunnel exit due to abrupt pressure change at passage. The reflected wave is expansion pressure wave. And when the rear head of train goes through the tunnel entrance, another expansion pressure wave is generated and propagated along the tunnel. The pressure drop occurs seriously around train when the two expansion pressure waves come cross on train in the tunnel. In order to reduce the pressure drop, the compression wave front must be controlled because the intensity and magnitude of pressure drop is nearly proportional to that of compression wave at tunnel entrance. This study relates to reduction of the pressure wave gradient with respect to tunnel entrance shape change with various kind of angle and rounding. The results show characteristics of wave propagation in tunnel, usefulness of characteristic curve to estimate proper time domain size in numerical study and measuring time in actual experiment. Also rounding is contributed to improve pressure wave front even if its radius is very small at tunnel entrance. In order to improve of pressure wave front at tunnel entrance, proper angle is prefered to rounding with big radius and an angle of around 14$^{\circ}$ is recommended according to this simulations, And it is expected to reduce additional pressure drop in tunnel when the location and the size of the internal space for attendant equipment are considered in advance.

• The Plant Pathology Journal
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• v.29 no.3
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• pp.350-355
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• 2013

Plants protect themselves from diverse potential pathogens by induction of the immune systems such as systemic acquired resistance (SAR). Most bacterial plant pathogens thrive in the intercellular space (apoplast) of plant tissues and cause symptoms. The apoplastic leaf exudate (LE) is believed to contain nutrients to provide food resource for phytopathogenic bacteria to survive and to bring harmful phytocompounds to protect plants against bacterial pathogens. In this study, we employed the pepper-Xanthomonas axonopodis system to assess whether apoplastic fluid from LE in pepper affects the fitness of X. axonopodis during the induction of SAR. The LE was extracted from pepper leaves 7 days after soil drench-application of a chemical trigger, benzothiadiazole (BTH). Elicitation of plant immunity was confirmed by significant up-regulation of four genes, CaPR1, CaPR4, CaPR9, and CaCHI2, by BTH treatment. Bacterial fitness was evaluated by measuring growth rate during cultivation with LE from BTH- or water-treated leaves. LE from BTH-treatment significantly inhibited bacterial growth when compared to that from the water-treated control. The antibacterial activity of LE from BTH-treated samples was not affected by heating at $100^{\circ}C$ for 30 min. Although the antibacterial molecules were not precisely identified, the data suggest that small (less than 5 kDa), heat-stable compound(s) that are present in BTH-induced LE directly attenuate bacterial growth during the elicitation of plant immunity.