• Journal of the Korean Society for Precision Engineering
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• v.10 no.3
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• pp.97-106
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• 1993

This is the study on fracture life under the interaction of creep and fatigue. It is difficult to explain the interaction of the creep and fatigue with indication of frequency but the dependency of the time should be considered. The formulation of material varieties causing by interaction of creep and fatigue is required in the accumulative damage method. The strain range partition method requires some of modification corresponding to the changes in temperature and load. All of other method also comprehended with above mentioned problems. Generally, in this field, the variety of stress-strain and suitable parameter is required and connective study between the macro and micro results seems to be insufficient. The linear damage rule is acquiring the support generally but it requires modification in the hgigh temperature instruments. The variety of stress effecting on crack and variety of stress on the metallurgical side are considered to be problems in the future days.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.40 no.5
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• pp.497-503
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• 2016

In this study, we formulate an acoustical topology optimization problem to optimally design a partition layout inside the expansion chamber of a muffler. The lower-limit insertion loss value at a target frequency is constrained, and the partition volume is selected as an object function. In this study, we calculate the insertion loss outside the duct, while to determine the noise-attenuation performance, we use the insertion loss value calculated inside the duct or transmission loss value obtained in a previous study. We employ the finite-element model for acoustical analysis, and we determine the transmission of an incident acoustic wave through each finite element using the functions of design variables that change continuously between "0" and "1." The rigid body elements, which totally reflect incident waves, build up partitions. Finally, we compare optimal topologies that depend on the target frequency and the allowed lower-limit value of insertion loss.

• Journal of the Korean Institute of Telematics and Electronics S
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• v.36S no.10
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• pp.1-9
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• 1999

In this paper, a subblock partition scheme for reduction of computational complexity in partial transmit sequence which reduces the peak-to-average power ratio in orthogonal frequency division multiplexing (OFDM) is proposed. In this scheme, complex signals are assigned into partial subbands randomly and signals in a partial subband are duplicated and concatenated repetitively to make a subblock. By modulation of active subbands which have almost interleaved pattern, computational complexity can be reduced. As results of computer simulation, the proposed shows almost same peak to average power ratio reduction performance as compared to the conventional one. However, computational complexity required to transmit a partial transmit sequence OFDM symbol has been reduced extensively.

• The Journal of the Acoustical Society of Korea
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• v.22 no.8
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• pp.670-679
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• 2003

This paper deals with application of wavelet transform, which is known to be good for time-frequency analysis, in order to detect the underwater transient signals embedded in ambient noise. A new detector of acoustic transient signals is presented. It combines two detection tools: wavelet analysis and higher-order statistics. Using both techniques, the detection of the transient signal is possible in low signal to noise ratio condition. The proposed algorithm uses the wavelet transform of a partition of the signal on frequency domain, and then higher-order statistics tests the Gaussian nature of the segments.

• Journal of Information Processing Systems
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• v.10 no.3
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• pp.384-394
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• 2014

The femtocell overlaid cellular network (FOCN) has been used to enhance the capacity of existing cellular systems. To obtain the desired system performance, both cross-tier interference and co-tier interference in an FOCN need to be managed. This paper proposes an interference management scheme that adaptively constructs a femtocell cluster, which is a group of femtocell base stations that share the same frequency band. The performance evaluation shows that the proposed scheme can enhance the performance of the macrocell-tier and maintain a greater signal to interference-plus-noise ratio than the outage level can for about 99% of femtocell users.

• Journal of Power Electronics
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• v.14 no.6
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• pp.1147-1156
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• 2014

This study proposes a quasi-fixed-frequency hysteresis current tracking control strategy for modular multilevel converters (MMCs) on the basis of voltage partition principle. First, by monitoring the grid voltage and the deviation between the output and reference currents, the output voltage is determined, thus prompting the output current to quickly and efficiently track the given current. Second, the voltages of the upper/lower capacitor of the arm and the voltages between the upper and lower arms are balanced by combining these arms with virtual loop mapping and arm voltage balance control, respectively. In particular, the proposed method is designed for any level and number of sub-modules. The validity of the proposed method is verified by simulations and experimental results of a five-level MMC prototype.

• Journal of the Korean Geophysical Society
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• v.6 no.1
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• pp.25-29
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• 2003

We suggest a method that vectorially composes 3-component earthquake records in the frequency domain, to reduce the uncertainties in the analysis of the Fourier amplitude spectrum. The use of the Fourier amplitude spectrum composed from 3 components has two advantages. First, it provides a more accurate estimate of seismic moment by eliminating the vector-partition term that appears in individual component. Second, it provides more accurate estimates of seismic moment, corner frequency, high-frequency decay constant($χ$) .etc., by enhancing the shape of the Fourier amplitude spectrum. The latter is especially useful in the analysis of small earthquakes with low signal-to-noise ratios.

• Korean Institute of Interior Design Journal
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• v.25 no.2
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• pp.30-40
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• 2016

This study analyzed the attention concentration tendencies of one(1) subject who showed convergent exploratory acts actively through the gaze-brainwave measurement experiment of cafe space images and our research findings are as follows. First, the areas of interest (AOIs) that the subject gazed visually by paying attention to it and concentrating on it at a cafe space include counter&menu area, sign area, partition area, image wall area, stairs area, and movable furniture area, and built-in furniture area: seven areas in total. Second, conscious gaze frequency appeared the highest in counter&menu area, and conscious gaze appeared more later than in initial times. Third, conscious gaze pattern was divided into the zone that explored various areas dispersely (distributed exploratory zone) and the zone that explored between particular areas concentratedly (intensive exploratory zone). Fourth, as a result of analyzing the brainwave attention concentration, it was found that the attention concentration in prefrontal lobe (Fp1, Fp2) and frontal lobe (F3, F4) rose to a higher level in the zone of 15 to 16 seconds and this time zone was considered to be a zone where gazing at counter&menu area was very active. In addition, the attention concentration appeared higher in the initial zone than in the later zone, among the entire experimental time zones. Finally, as a result of analyzing the changes in activation by brain portion of the SMR wave expressed when maintaining the arousal and attention concentration, it was found that the right prefrontal lobe and the frontal lobe became activated in the time zone when the intensive exploration of "counter&menu area" and "movable furniture${\leftrightarrow}$built-in furniture area" had occurred and the time zone when the intensive exploration of "image wall${\leftrightarrow}$partition area" and "counter&menu${\leftrightarrow}$sign area" had occurred.

• Journal of the Institute of Electronics Engineers of Korea SP
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• v.44 no.4 s.316
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• pp.93-100
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• 2007

In this paper, a novel approach based on wavelet transform is proposed to process the scraped character which is represented on digital image. The basis idea is that the scraped character is described by its textured neighborhood, and it is decomposed into multiresolution features at different levels with its background region. The image is first decomposed into sub bands by applying Daubechies wavelets. Character features are extracted from the low frequency sub-bands by partition, FCM clustering and area-based region process. High frequency ones are activated by applying local energy density over a moving mask. Features are synthesized in order to reconstruct the original image state through inverse wavelet transform Background region is eliminated and character is extracted. The experimental results demonstrate the effectiveness of the proposed method.

• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.23 no.4
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• pp.372-378
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• 2013

An acoustical shape optimization problem is formulated for optimal design of a perforated reactive muffler with offset inlet/outlet. The mean transmission loss value in a target frequency range is maximized for an allowed pressure drop value between an inlet and an outlet. Partitions in the chamber are divided into several sub-partitions, whose lengths are selected as design variables. Each sub-partition has the same number of holes, whose sizes are equal. A finite element model is employed for acoustical and flow analyses. A gradient-based optimization algorithm is used to obtain an optimal muffler. The acoustical and fluidic characteristics of the optimal muffler are compared with those of a reference muffler. Validation experiment is carried out to support the effectiveness of our suggested method.