• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2006.11a
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• pp.262-265
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• 2006

In order to investigate characteristics of floor impact sound generated in the apartment buildings, questionnaire survey was conducted for respondents living in apartments in 200t. Questions in the surrey were on the characteristics of real impact sounds, subjective annoyance and satisfaction on the heavy and light impact sources. From the survey results, it was found that most annoying time of a day and the space were 8 p.m. to midnight at living room. It was also revealed that the main source of the floor impact sound from the upper floor is a child's jumping and running at from six to nine. More than half of people were not satisfied on the floor impact isolation performance of their own apartments. The percentage of residents who were annoyed by the heavy-weight impact sound such as children's jumping and adult's walking was $5{\sim}10%$ lower than by light-weight impact sound. In addition, females being responded more annoyed by floor impact sound than males.

• Geomechanics and Engineering
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• v.16 no.2
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• pp.169-176
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• 2018

An attempt has been made here to study the propagation of SH-type surface waves in an elastic medium, which is initially stressed and heterogeneous and has a point source inside the medium. The upper portion of the composite medium is a sandy layer. It is situated on an initially stressed heterogeneous half-space, whose density, rigidity and internal friction are function of depth. The analysis has been carried out by using Fourier transform and Green's function approach. The phase velocity has been investigated for several particular situations. It has been shown that the results of the study agree with those the case of Love wave propagation in a homogeneous medium in the absence of the sandy layer, when the initial stress is absent. In order to illustrate the validity of the analysis presented here, the derived analytical expression has been computed numerically, by considering an illustrative example and the variances of the concerned physical variables have been presented graphically. It is observed that the velocity of shear wave is amply influenced by the initial stress and heterogeneity parameters and the presence of the sandy layer. The study has an important bearing on investigations of different problems in the earth's interior and also in seismological studies.

• Journal of the korean society of oceanography
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• v.34 no.3
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• pp.133-143
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• 1999

We carried out simultaneous and long-time observations of currents across the western channel of the Korea Strait during the period of May, 1994 to September, 1996 in order to understand the spatial and temporal variability of tidal and nontidal currents in the Strait. Results show that currents in the Strait are quite variable in space and time, and they largely consist of mean current and diurnal and semidiurnal tidal currents of about equal magnitudes. The mean currents include the Tsushima Current and the Korea Strait Undercurrent at the center of the channel. The former occupies the upper two-thirds and the latter the lower one-third of the water column. The semidiurnal and diurnal currents are largely rectilinear in the direction of NE-SW and their amplitude variation across the channel appears to be small. However, the diurnal currents at some locations show rotational characteristics with significant nontidal effects. The station close to the Korean coast leads the phase and the phase difference of the semidiurnal current across the channel appears to be less than half an hour while that of the diurnal current is over five hours.

• Geophysics and Geophysical Exploration
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• v.5 no.4
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• pp.299-308
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• 2002

We have derived an analytical expression for the sensitivity of the frequency domain small-loop electromagnetic (EM) surveys over a two-layer earth in order to estimate the depth of investigation with an instrument having the source-receiver separation of about 2 m. We analyzed the sensitivities to the lower layer normalized by those to the upper half-space and estimated the depth of investigation from the sensitivity analyses and the mutual impedance ratio. The computational results showed that the in-phase components of the sensitivity to the lower layer dominates those to the upper layer when the thickness of the upper layer is less than 20 m, while the quadrature components are not sensitive to the lower layer over the entire frequency range. Hence we confirmed that the accurate measurement of the in-phase component is essential to increase the depth of investigation in the multi-frequency small-loop EM survey. When conductive basement of 10 ohm-m underlies the upper layer of 100 ohm-m, an accurate measurement of the in-phase components ensures the depth of the investigation more than 10 m even accounting a noise effect, from which we conclude that the small-loop EM survey is quite effective in imaging the conductive plume down to a considerable depth. On the other hand, in the presence of the resistive basement of 1,000 ohm-m, the depth of investigation may not exceed 5 m considering the instrumental accuracy, which implies that the application of the small-loop EM survey is not recommended over the resistive environment other than detecting the buried conductor.

• Journal of the Korean Society for Aeronautical & Space Sciences
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• v.36 no.10
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• pp.954-961
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• 2008

An experimental study has been conducted to investigate the flow field around the wing having a circular damage hole. The damage was represented by a circular hole passing through the model with 10% airfoil chord diameter and normal to the chord. The hole was centered at quarter or half chord. The PIV flow fields and static pressure measurements on the wing upper and lower surface were carried out at Rec=2.85×105 based on the chord length. The PIV results showed the two types of flow structures around a damage hole were formed. The first one was a weak jet that formed an attached wake behind the damage hole. The second one resulted from increased incidence; this was a strong jet where the flow through the hole penetrates into the free-stream resulting in extensive separation of oncoming boundary layer flow and development of a separated wake with reverse flow. The surface pressure data showed a big pressure alteration near the circular damage hole. The severity of pressure alteration was increased as a damage hole located nearer to the leading edge.

• Journal of Korean Tunnelling and Underground Space Association
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• v.22 no.5
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• pp.543-561
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• 2020

This paper is the result of the study on the effect of the support structure of the tunnel steel rib. In tunnel excavation, the top and bottom half excavation methods result in subsidence of steel rib reinforcement due to insufficient support of steel rib reinforcement when the ground is poor after excavation. The foundation of the steel rib installed in the upper half excavates the bottom part of the base, causing the subsidence to occur due to various effects such as internal load and lateral pressure. As a result, the tunnel is difficult to maintain and its safety is problematic. To solve these problems, steel rib support structures have been developed. For the purpose of verification, the behavior of the supporting structure is verified by model experiments reduced to shotcrete and steel rib material similarity, the numerical analysis of ΔP and ΔP generated by bottom excavation by Terzaghi theoretical equation. As a result, it was found that the support structure of 20.100~198.423 kN is required for the 10~40 m section of the depth for each soil of weathered soil~soft rock. In addition, as a result of the reduced model experiment, a fixed level of 50% steel rib deposit of steel rib support structure was installed. The study shows that the installation of steel rib support structures will compensate for uncertainties and various problems during construction. It is also thought that the installation of steel rib support structure will have many effects such as stability, economy, and air reduction.

• The Korean Journal of Pain
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• v.2 no.2
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• pp.135-144
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• 1989

Celiac plexus block is recommended in patients with intractable upper abdominal cancer pain. The success rate of a celiac plexus block is variable among the authors. One of the causes of this is the anatomical variations of the celiac plexus. There has not been a study concerning anatomical observations of the celiac plexus in Korean cadavers. So, anatomical dissections were performed and observations were made of the celiac plexus and related structures in Korean cadavers. The results were as follows: 1) The subjects were 21 male bodies and 5 female bodies. The mean age at death was $69.9{\pm}15.5$ years (range 37~93). The mean height was $155.5{\pm}8.3\;cm$ (range 143~172). 2) The number of celiac ganglia ranged from 1~4. The mean numbers were $2.3{\pm}1.9$ in the right plexus and $1.9{\pm}0.8$ in the left, and the mean sizes were $18.9{\pm}7.7{\times}8.0{\pm}3.8\;mm^2$ and $18.5{\pm}8.3{\times}9.5{\pm}3.9\;mm^2$ respectively. 3) Celiac ganglia were most frequently located at the level of the upper third and middle third of L1 in both sides (65.5% in right, 64.0% in left). The vertical range of celiac ganglia ranged from 1 space, which is one third the height of one vertebral body, to 4 spaces. Mean vertical ranges were $1.5{\pm}0.6$ spaces in the right plexus and $1.6{\pm}0.7$ spaces in the left. The celiac ganglia located at the level of the upper third of L1 in the right and the lower third of L1 in the left side, had the largest vertical ranges respectively ($1.8{\pm}0.5$ spaces in right, $2.3{\pm}0.6$ spaces in left) 4) Right side celiac ganglia were located near the midline of the vertebrae compared to the left ones (mean 5.0 mm) The horizontal dimension was greater in the right ganglia ($24.2{\pm}9.2\;mm$) than in the left ganglia ($l8.8{\pm}7.0\;mm$). 5) There was no vertebral level difference between both celiac ganglia in most cases (60%). However, of the 40% of cases at different levels, in half of these (20%) the right ganglia were located higher than the left ganglia; and in the other 20%, this was reversed. 6) The origin sites of the celiac artery were most frequently in the upper third and middle third of L1 (61.6%). The celiac ganglia were usually located at the same level as the site of origin of the celiac artery (61.6% in right, 52.0% in left). 7) The vertebral level of the splanchnic nerves piercing the abdominal surface of the diaphragm was most frequently in the upper third and middle third of L1 (66.6% in right, 66.7% in left). 8) The level of the origin of diaphragmatic crura from the anterior surface of the vertebral bodies varied from the L1-L2 interspace to the L3-L4 interspace. Right crura most frequently originated at the level of the lower third of L2 to the upper third of L3 (57.6%), while left crura originated from the level of the L2-L3 interspace to the middle third of L3 (69.3%). From the above results, we realized that there were some anatomical variations of the celiac plexus and its relations to adjacent structures in Korean bodies. However, when the needle point is behind the anterior margin of the upper third of L1, it is possible to perform a successful retrocrural splanchnic nerve block.

• Tunnel and Underground Space
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• v.11 no.1
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• pp.30-35
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• 2001

Focusing on the bench length, this paper presents the results of 3-dimensional elafto-plastic FE Analysis un tunnels of full face, mini-bench and short bench excavated in weathered rock. Influences of unsupported span, horizontal to vertical stress ratio, thickness of shotcrete on the behavior of rock and support were a1so studied. Results showed that displacements of mini-bench tunnels responded more sensitively to bench lengths than those of short bench. The effects of bench excavation on upper half displacement increased with longer unsupported span. Horizontal to vertical stress ratio showed a greater influence on displacement and preceding displacement ratio or sidewall rather than those of crown and invert.

• Tunnel and Underground Space
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• v.23 no.2
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• pp.110-119
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• 2013

It is generalized to measure the arch settlement and convergence during tunnel construction for monitoring its mechanical stability. The initial convergence rate a day is defined from the first convergence measurement and the final convergence defined as the convergence measured lastly. The initial and the final tunnel arch settlement are defined like the preceding convergence. In the study, the relations between the initial and final displacements of a shallow tunnel are analyzed. The measurements were performed in the tunnel of subway 906 construction site in Seoul. The overburden is 10-20 m and the tunnel goes through weathered soil/rock. The width and height of the tunnel are about 11.5 m, 10m, respectively. So this is a shallow tunnel in weak rock. The length of tunnel is about 1,820 m and the tunnel was constructed in 2 stages, dividing upper and lower half. The numbers of measurement locations of arch settlement and convergence are 184 and 258, respectively. As a result, the initial displacement rate and the final displacement are comparatively larger in the section of weathered soil.

• Korean Journal of Applied Biomechanics
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• v.23 no.3
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• pp.209-218
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• 2013

This study was to perform the kinetic analysis of forward $1\frac{1}{2}$ somersault on the platform diving. Six men's diving players of the Korea national reserve athletes participated in this study. The variables were analyzed response time, velocity, center of mass (COM), angle, center of pressure (COP) and ground reaction force (GRF) of motion. For measure and analysis of this study, used to synchronized to 4 camcorder and 1 force plate, used to the Kwon3D XP (Ver. 4.0, Visol, Korea) and Kwon GRF (Ver. 2.0, Visol, Korea) for analyzed of variables. The results were as follows; Time factor were observed in maximum knee flexion depending on the extent of use at phase 1 of take-off to execute the somersault. This enabled the subject to secure the highest possible body position in space at the moment of jumping to execute the somersault and prepare for the entry into the water with more ease. Regarding the displacement of COM, all subjects showed rightward movement in the lateral displacement during technical execution. Changes in forward and downward movements were observed in the horizontal and vertical displacements, respectively. In terms of angular shift, the shoulder joint angle tended to decrease on average, and the elbow joints showed gradually increasing angles. This finding can be explained by the shift of the coordinate points of body segments around the rotational axis in order to execute the half-bending movement that can be implemented by pulling the lower limb segments toward the trunk using the upper limb segments. The hip joint angles gradually decreased; this accelerated the rotational movement by narrowing the distance to the trunk. Movement-specific shifts in the COP occurred in the front of and vertical directions. Regarding the changes in GRF, which is influenced by the strong compressive load exerted by the supporting feet, efficient aerial movements were executed through a vertical jump, with no energy lost to the lateral GRF.