• Proceedings of the Korean Society for Noise and Vibration Engineering Conference
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• 2004.11a
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• pp.178-183
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• 2004

This paper presents phenomena of vibration and noise due to acoustic resonance in tube bank of a large fossil power plant. The phenomena of acoustic resonance may arise when the vortex shedding frequency coincides with the acoustic natural frequency. In this system dominant frequency of vibration and noise was 37.5Hz. The $3^{rd}$ acoustic natural frequency calculated was 37.2 Hz. When the difference of vortex shedding frequency and acoustic natural frequency is within ${\pm}20%$, acoustic resonance could occur. If system is the state of acoustic resonance, vibration and noise become large. In order to prevent acoustic resonance, anti-noise baffle should be installed in the tube bank. In the case of installing baffle, we should consider the number of baffle and the effect of acoustic mode due to baffle extension length. To do this, we did acoustic mode analysis. After installing anti-noise baffle, acoustic resonance was disappeared and vibration magnitude and noise level was reduced dramatically.

• The Korean Journal of Zoology
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• v.20 no.1
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• pp.1-8
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• 1977

Several hundred flies of Drosophila melanogaster collected in Anyang City were selected for positive, negative and neutral directions during 15 generations. The population responded effectively to the artificial selection. The realized heritability estimated for the first 10 generations was $2 \\sim 4%$ per generation in the positive and negative phototaxis. The results of diallel crosses among selected populations indicated that some polygenes showing a negative phototaxis were partially dominant over polygenes controlled the positive phototaxis, and the dominant effect became greater in later generations. The populations selected for positive and negative phototaxis were relaxed after 15 generations of selection, and their phototactic responses were completely returned to their original states. Such phenomena would be explained by the genetic homeostasis resulted from an action of natural selection. It seems reasonable to assume that the phototactic neutrality of a natural population was maintained as an adaptive trait under natural environment.

• Phonetics and Speech Sciences
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• v.11 no.3
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• pp.1-7
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• 2019

Korean (L1)-English (L2) bilingual adults' and children's production of Korean and English stops was examined to determine the age effects and L2 experience on the development of L1 and L2 stop contrasts. Four groups of Seoul Korean speakers (experienced and inexperienced adult and child groups) and two groups of age-matched native English speakers participated. The overall results of voice onset time (VOT) and fundamental frequency (F0) of phrase-initial stops in Korean and word-intial stops in English showed a delay in the acquisition of L1 due to the dominant exposure to L2. Significantly longer VOT and lower F0 for aspirated stops as well as high temporal variability across repetitions of lenis stops were interpreted to indicate a strong effect of English on Korean stop contrasts for bilingual children. That is, the heavy use of VOT for Korean stop contrasts shows bilingual children's attention to the acoustic cue that are primarily employed in the dominant L2. Furthermore, inexperienced children, but not adults, were shown to create new L2 categories that are distinctive from the L1 within 6 months of L2 experience, suggesting greater independence between the two phonological systems. The implications of bilinguals' age at the time of testing to the degree and direction of L1-L2 interaction are further discussed.

• The Journal of Internal Korean Medicine
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• v.42 no.4
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• pp.707-717
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• 2021

Objectives: The aim of this study was to introduce the normalization effects of stimulation of both ST36 and CV11, 12, 13 meridian points on the abnormal gastric myoelectrical activity in two cases of functional dyspeptic patients with gastric dysmotility. Methods: Gastric myoelectrical activity was recorded by electrogastrography every two weeks until their gastric myoelectrical activity finally reached the normality. Dominant frequency of gastric slow waves in the fasting and postprandial periods and a dominant power ratio were obtained on each occasion. Patients were treated three times each day: 9 am, 1 pm, and 7 pm. The first treatment consisted of manual and immersion stimulation on all used meridian points for 20 min. In the second and third treatments, electrical stimulation of both ST36 was added. It was conducted for 20 min at a strength intensity of 1.2 times the pain threshold at a frequency of 3 Hz. Results: Stimulation of the above meridian points normalized abnormal gastric myoelectrical activity. The time taken to return from abnormal gastric myoelectrical activity to normal was 16-19 weeks. Conclusion: Stimulation of both ST36 and CV11, 12, 13 meridian points normalized the abnormal gastric myoelectrical activity in the functional dyspepsia of gastric dysmotility.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.163-177
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• 2021

Numerical simulations of the Vortex-Induced Vibration (VIV) about a large-scale flexible pipe subject to shear flow were carried out in this paper. Efficiency verification was performed firstly, validating that the proposed fluid-structure interaction solution strategy is competent in predicting the VIV response. Then, the VIV characteristics related to multi-mode and spanwise hybrid waveform about the flexible pipe attributed to shear flow were investigated. When inflow velocity rises, higher vibration modes are apt to be excited, and the spanwise waveform easily convertes from a standing-wave-dominated status to a hybrid standing-traveling wave status. The multi-mode or even multiple-dominant-mode is prone to occur, that is, the dominant mode is often followed by several apparent subordinate modes with considerable vibration energy. Hence, the shedding frequencies no longer obey Strouhal law, and vibration trajectories become intricate. According to the motion analysis concerning the coupled cross-flow and in-line vibrations, as well as the corresponding wake patterns, a tight coupling interaction exists between the structural deformation and the wake flow behind the flexible pipe. In addition, the evolution of the vortex tube along the pipe span and a strong 3D effect are observed due to the slenderness of the flexible pipe and the variability of the vortex shedding attributed to the shear flow.

• International Journal of Naval Architecture and Ocean Engineering
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• v.13 no.1
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• pp.223-235
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• 2021

The Vortex-Induced Vibration (VIV) test system on deepwater riser based on Bare Fiber Bragg Grating (BFBG) sensor technology was designed. Meanwhile, a riser VIV response numerical model was established based on the work-energy principle. The results show that the first-order vibration frequency dominates the vibration of the riser, and as the velocity increases, the dominant frequency of the riser gradually increases under the effect of different top tensions. At the same velocity, as the top tension increases step by step, the dominant frequency and fatigue damage at the same position along the axial length of the riser both gradually decreases. The model test and numerical simulation show a relatively consistent change, maintaining a high degree of agreement. The process control system based on BFBG of model test has excellent performance, and FBG sensors have great advantages in VIV test of a vertical riser in water.

• Food Science of Animal Resources
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• v.43 no.3
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• pp.441-453
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• 2023

The objective of this study was to investigate the physicochemical and microbiological characteristics of round of Hanwoo by vacuum packaging film materials, polyvinylidene chloride (PVDC) and ethylene vinyl alcohol (EVOH). The packaged beef samples were stored in refrigerated conditions (2±1℃) for 12 weeks. Physicochemical analysis with pH, surface color, thiobarbituric acid reactive substances (TBARS) values, and volatile basic nitrogen (VBN) values and microbiological analysis with aerobic plate count (APC) and metagenomic analysis of packaged beef samples were performed. The pH and surface color did not change substantially during the 12 weeks and EVOH-packaged beef tended to be lower than those of PVDC-packaged beef. PVDC- and EVOH-packaged samples showed low TBARS and VBN values below standard limits. APC did not exceed 7 Log CFU/g for both samples during storage. In metagenomic analysis, Firmicutes and Lactobacillaceae were dominant phylum and family of the PVDC- and EVOH-packaged beef. In both packaged samples, Dellaglioa algida was the dominant species during storage, with the notable difference being the presence of Lactococcus piscium. Therefore, this study provided the information on the quality of vacuum-packaged beef according to different vacuum films for long-term refrigerated storage.

• Physical Therapy Rehabilitation Science
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• v.12 no.1
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• pp.19-25
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• 2023

Objective: Patients with scoliosis complain of various symptoms such as muscle imbalance, dysfunction, back pain, abnormal posture and gait abnormality. The most basic treatment for scoliosis is to observe the progress based on conservative treatment. Therefore, in this case report, the effect of cytoskeletal manual therapy (CMT), a soft tissue mobilization technique, on pain intensity, muscle thickness, and pressure pain threshold (PPT) in a patient with scoliosis was investigated. Design: A case report Methods: A 25-year-old male diagnosed with scoliosis visited the Neuromusculoskeletal Science Laboratory with chronic back pain. In the laboratory, scoliosis was confirmed through the X-ray image used for his diagnosis, and it was confirmed again through Adam's forward bending test. Pain, pressure pain threshold and muscle thickness were measured to compare the immediate effects of CMT applied in the laboratory for 40 minutes. Treatments were visited two weeks after the first visit and outcome measures were assessed after a total of two visits. Results: After receiving CMT up to the second session, the pain intensity decreased by 4 points and the screening angle decreased by 15 degrees. Muscle thickness decreased in all but 10 mm on the dominant side of the thoracic spine. All of the PPTs increased, and the greatest increase was 3.1 lb on the dominant side of the thoracic spine. Conclusions: CMT showed positive improvement in pain during trunk flexion, spinal curvature, muscle imbalance, and pressure pain, which is considered as an ancillary treatment option for scoliosis management.

• Nuclear Engineering and Technology
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• v.55 no.2
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• pp.780-791
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• 2023

To study oscillation characteristic of steam and non-condensable gas direct contact condensation through multi-hole sparger at low mass flux, a series of experiments of pure steam and mixture gas condensation have been carried out under the conditions of steam mass flux of 20-120kg/m²s, water temperature of 20-95 ℃ and mass fraction of non-condensable gas of 0-5%. The regime map of pure steam condensation through multi-hole sparger is divided into steam chugging, separated bubble, aggregated bubble and escaping aggregated bubble. The bubbles behavior of synchronization in the same hole columns and desynchronized excitation between different hole columns can be found. The coalescence effect of mixture bubbles increases with water temperature and non-condensable gas content increasing. Pressure oscillation intensity of pure steam condensation first increases and then decreases with water temperature increasing, and increases with steam mass flux increasing. Pressure oscillation intensity of mixture gas condensation decreases with water temperature and non-condensable gas content increasing, which is significantly weaker than that of pure steam condensation. The oscillation dominant frequency decreases with the rise of water temperature and non-condensable gas content. The correlations for oscillation intensity and dominant frequency respectively are developed in pure steam and mixture gas condensation at low mass flux.

• Structural Engineering and Mechanics
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• v.86 no.6
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• pp.751-764
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• 2023

In practical engineering such as aerial refueling pipes, the boundary of the fluid-conveying pipe is difficult to be completely immovable. Pipes under movable and immovable boundaries are controlled by different dominant nonlinear factors, where the boundary mobility will affect the nonlinear dynamic characteristics, which should be focused on for adopting different strategies for vibration suppression and control. The nonlinear dynamic instability characteristics of functionally graded fluid-conveying pipes lying on a viscoelastic foundation under movable and immovable boundary conditions are systematically studied for the first time. Nonlinear factors involving nonlinear inertia and nonlinear curvature for pipes with a movable boundary as well as tensile hardening and nonlinear curvature for pipes with an immovable boundary are comprehensively considered during the derivation of the governing equations of the principal parametric resonance. The stability boundary and amplitude-frequency bifurcation diagrams are obtained by employing the two-step perturbation- incremental harmonic balance method (TSP-IHBM). Results show that the movability of the boundary of the pipe has a great influence on the vibration amplitude, bifurcation topology, and the physical meanings of the stability boundary due to different dominant nonlinear factors. This research has guidance significance for nonlinear dynamic design of fluid-conveying pipe with avoiding in the instability regions.