• Journal of the Korean Wood Science and Technology
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• v.51 no.5
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• pp.419-430
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• 2023

In this study, the floor impact sound insulation performance of Korean domestic Cross-Laminated Timber (CLT) slabs was evaluated according to their joint types, species and thicknesses in laboratory experiments. The sound insulation performance of the CLT has not been investigated before, thus, this study was conducted to quantify basic data on floor impact sound insulation performance of CLT slabs. 5-ply and 150 mm thick CLT panels made of 2 species, Larix kaempferi and Pinus densiflora, were used for the study. The CLT panels were assembled by 3 types of inter-panel joints to form floor slabs: spline, butt and half-lap. And the 150 mm thick Larix CLT slabs were stacked to the thicknesses of 300 mm and 450 mm. The heavy-weight floor impact sound insulation performance of the 150 mm CLT slabs were evaluated to be 70 dB for the Larix slabs and 71.6 dB for the Pinus slabs, and the light-weight floor impact sound insulation performance, 78.3 dB and 79.6 dB, respectively. No significant difference in the sound insulation performance was found between the slabs of the 2 species or among the 3 types of joints. The reduction of 1 dB in the heavy-weight floor impact sound and 1.6 dB in the light-weight floor impact sound per 30 mm increase in thickness were confirmed through the experiments. This study can be viewed as the basic research for the evaluation of floor impact sound insulation performance of CLT.

• Earthquakes and Structures
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• v.23 no.2
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• pp.115-128
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• 2022

One common method to select input ground motions to predict dynamic behavior of structures subjected to seismic excitation requires spectral acceleration (S_a) match target mean response spectrum. However, dispersion of ground motions, which explicitly affects the structural response, is rarely discussed in this method. Generally, selecting ground motions matching target mean and variance has been utilized as an appropriate method to predict reliable seismic response. The goal of this paper is to investigate the impact of target spectra variance of ground motions on structural seismic response. Two sets of ground motions with different target variances (zero variance and minimum variance larger than inherent variance of the target spectrum) are selected as input to two different structures. Structural responses at different heights are compared, in terms of peak, mean and dispersion. Results show that increase of target spectra variance tends to increase peak floor acceleration, peak deformation and dispersions of response of interest remarkably. To short-period structures, dispersion increase ratios of seismic response are close to that of S_a of input ground motions at the first period. To long-period structures, dispersions of floor acceleration and floor response spectra increase more significantly at the bottom, while dispersion increase ratios of IDR and deformation are close to that of S_a of input ground motions at the first period. This study could further provide useful information on selecting appropriate ground motion to predict seismic behavior of different types of structures.

• The Proceeding of the Korean Institute of Electromagnetic Engineering and Science
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• v.2 no.3
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• pp.17-25
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• 1991

Magnetic leakage flux which is generated from the levitation magnets, linear induction motors, and guide magnets of a MagLev(Magnetic Levitation) system is directly related to inter - system EMI, intra - system EMI, and biological effects. In this paper, the magnetic leakage flux from MagLev vechicles designed by Korea Resarch Institute of Ships & Ocean Engineering was calculated considering the various parameters which influence ma- gnetic field intensity around the MagLev system. Based on the calculated field intensity, the thickness of shielding material and shielding position for MagLev floor and side walls are calculated, taking into account the shielding effectiveness of a shield with minimum weight. For the nonuniform shielding method derived from the above procedure, the weight of a shield con- sisting of floor and side walls shielding can be reduced to more 50% than uniform shielding method.

• Structural Engineering and Mechanics
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• v.20 no.5
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• pp.505-526
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• 2005

The influence of the inter-story structural pounding on the seismic behaviour of adjacent multistory reinforced concrete structures with unequal total heights and different story heights is investigated. Although inter-story pounding is a common case in practice, it has not been studied before in the literature as far as the authors are aware. Fifty two pounding cases, each one for two different seismic excitations, are examined. From the results it can be deduced that: (i) The most important issue in the inter-story pounding is the local effect on the external column of the tall building that suffers the impact from the upper floor slab of the adjacent shorter structure. (ii) The ductility demands for this column are increased comparing with the ones without the pounding effect. In the cases that the two buildings are in contact these demands appear to be critical since they are higher than the available ductility values. In the cases that there is a small distance between the interacting buildings the ductility demands of this column are also higher than the ones of the same column without the pounding effect but they appear to be lower than the available ductility values. (iii) It has to be stressed that in all the examined cases the developed shear forces of this column exceeded the shear strength. Thus, it can be concluded that in inter-story pounding cases the column that suffers the impact is always in a critical condition due to shear action and, furthermore, in the cases that the two structures are in contact from the beginning this column appears to be critical due to high ductility demands as well. The consequences of the impact can be very severe for the integrity of the column and may be a primary cause for the initiation of the collapse of the structure. This means that special measures have to be taken in the design process first for the critically increased shear demands and secondly for the high ductility demands.

• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2002.11b
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• pp.676-681
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• 2002

System Identification is carried out for a full scale five-story builing to design a vibration controller. Dynamic characteristics such as natural frequencies, damping ratios, and modes are obtained from the input/output information by both sine-sweep method and white noise method. The active mass driver installed on the five floor is applied as external loading to move the building and each floor acceleration is measured and processed for the system identification. The identified building will be experimentally investigated again with viscoelastic dampers installed at inter-stories to obtain the response behavior. Corresponding result will be presented soon.

• The Journal of the Acoustical Society of Korea
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• v.37 no.6
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• pp.428-436
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• 2018

The response to noise may differ depending on the respondent's noise sensitivity. In this study, it was investigated that the noise sensitivity, the annoyance and disturbance of floor impact noise and opinions on their neighbors. The questionnaire respondents were divided into two or three groups based on noise sensitivity, and annoyance and disturbance on floor impact sound were compared. The noise sensitivity questionnaire method was presented. The questionnaire survey was conducted on 233 residents of Seoul, Gyeonggi - do area. As a result of the questionnaire survey, when the sensitivity group was divided into three groups, it was found that there was a significant difference between the groups with the noise sensitivity and the disturbance reaction. As a result of the opinions on their neighbors, positive responses to neighbors increased with age. Also, it was found that there was a low perception of inter - floor noise and life disturbance of the group having positive feelings about neighbors.

• Journal of the Korean Institute of Telematics and Electronics
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• v.24 no.6
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• pp.1068-1073
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• 1987

Traditional circuit partitioning algorithm using the cluster development method, which is suitable for such applications as single chip floor planning or multiple layer PCB system placement, where the clusters are formed so that inter-cluster nets are localized within the I/O connector pins, may not be appropriate for the functiona block placement in truly 3-D electronic modules. 3-D hybrid IC is one such example where the inter-layer routing as well as the intra-layer routing can be maximally incorporated to reduce the overall circuit size, cooling requirements and to improve the speed performance. In this paper, we propose a new algorithm called MBE(Minimum Box Embedding) for the layer assignment of each functional block in 3-D hybrid IC design. The sequence of MBE is as follows` i) force-directed relaxation in 3-D space, ii) exhaustive search for the optimal orientation of the slicing plane and iii) layer assignment. The algorithm is first explaines for a 2-D reduced problem, and then extended for 3-D applications. An example result for a circuit consisting of 80 blocks has been shown.

• Journal of Korean Academy of Oral and Maxillofacial Radiology
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• v.6 no.1
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• pp.7-14
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• 1976

This study was done using the 45° oblique lateral old, 18 males and 27 females, with normal occlusion, premolars and molars on upper and lower jaws. Axial inclination to nasal floor, occlusal plane and inter-axial inclination were examined. In addition the position of each tooth was examined in height and depth in upper and lower jaws. The results were obtained as follows; 1. The inclination of long axis of upper 1st premolar was most nearly perpendicular, upper canine was tilted mesially, and 2nd premolar and molars were tilted distally. 2. The inclination of long axis of lowers molar were tilted mesially. 3. There were no severe variation on the inter-axial inclination of canine to mandibular plane, and 2nd molar.

• The Journal of Korean Institute of Communications and Information Sciences
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• v.24 no.6B
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• pp.1024-1031
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• 1999

In order to transmit high-speed wide band signals efficiently in multipath fading environments, M-ary QAM signalling combined with OFDM transmission technique is applied. In this paper, the effect of synchronization error caused by carrier frequency offset and SER(Symbol Error Rate) performance of OFDM-16QAM and OFDM-64QAM are theoretically analyzed. Our result shows that as the number of sub-carrier in OFDM system increases the frequency-offset caused inter-channel interference(ICI) increases significantly, and that an error floor occurs even at high SNR of OFDM system. For OFDM-64QAM, the error floor occurs at SER=1$\times$10-7 when a normalized frequency-offset is 0.001, in which the SNR degradation is much greater than that of OFDM-16QAM. From this study the maximum allowable frequency-offset of OFDM-16QAM and OFDM-64QAM systems can be determined to meet the specific SER requirement.

• Earthquakes and Structures
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• v.18 no.2
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• pp.233-248
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• 2020

In this article, one of the procedures to design viscous dampers proposed in literature is applied to 3D asymmetric-plan buildings, considering different distributions for the damping coefficients, which are assumed to be proportional to specific structural or response parameters. The main purpose was to investigate the effectiveness of different vertical and in-plan distributions of the damping coefficients of nonlinear viscous dampers for the seismic retrofit of existing buildings. For comparison purposes, all the distributions were applied utilizing both a simplified and an extended method for the 3D structures, where the simplified method takes into account only the translation in the seismic direction, and the extended method considers the translations along the two orthogonal directions together with the floor rotations. The proposed distributions were then applied to a typical case study involving an asymmetric-plan six-storey RC building. The effectiveness of the different distributions was examined through time-history analyses, assuming nonlinear behaviour for both the viscous dampers and the structural elements. The results of the nonlinear dynamic analyses were examined in terms of maximum and residual inter-storey drifts, peak floor accelerations and maximum damper forces.