• Transactions of the Korean Society for Noise and Vibration Engineering
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• v.17 no.7 s.124
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• pp.596-604
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• 2007

This article investigates the effects of geometric configuration on the vibro-acoustic characteristics of in-plane vibration of a thick annular disc. Disc thickness and outer radius for a given inner radius are selected as independent variables having reasonable ranges. Variations in structural eigensolutions for radial modes are investigated using pre-developed analytical method. Based on these data, far-field sound pressure distributions due to the modal vibrations for a given geometry are also calculated using an analytical solution. Modal sound powers and radiation efficiencies are calculated from the far-field sound pressure distributions and vibratory velocity distributions on the radial surfaces. Based on the results explained above, the geometric configuration that minimizes modal sound radiations in a given frequency range is determined. Finally sound power and radiation efficiency spectra for a unit harmonic force from the selected geometric configuration are obtained from structural and acoustic modal data using the modal expansion technique. Multi-modal sound radiations of the optimized disc that are obtained using proposed analytical methods are confirmed with numerical results. Using the procedure introduced in this article, sound radiation due to in-plane modes within a specific frequency range can be minimized by the disc geometry modifications in a comprehensive and convenient manner.

• The Journal of Internal Korean Medicine
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• v.22 no.4
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• pp.589-599
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• 2001

Objective: This study was carried out to investigate the effects of Hyangsayukgunja-tang extract on indomethacin-induced gastric mucosal lesions of mice. Methods: To evaluate the effects of Hyangsayukgunja-tang extract and Misoprostol, the morphology of gastric mucosa, and the distribution of mucose cells, PNA(Peanut Agglutinin), ICAM(intercellular adhesion molecule), and apoptotic cells were observed. Hyangsayukgunja-tang extract and Misoprostol were intragastric injected to the test groups at hour 72 before and just before indomethacin treatment(HYT-J, HYT-72, M-J, M-72), while the INDO group was injected only with indomethacin and the control group was subcutaneously injected only with saline. Results: The gastric mucosal lesions incresed in the fundus and body of INDO group, but softened in HYT group and M group, the effects were more excellent in the HYT-72, M-72 groups than the HYT-J, M-J groups and in the HYT group than M group. The disappearance of surface and neck mucose cells were shown in INDO group, but softened in HYT group and M group. The mucosal configuration of HYT-72 group was the same as control group. The numerical increase of PNA positive reaction in cytoplasm of perietal cells were appeared in INDO group. The PNA positive reaction in HYT group and Miso-group were shown in surface mucous cells and microvilli of apical surface in chief cells as control group, and were the same as control group in all mucosa of HYT-72 group. The distribution of ICAM positive cells, increased in INDO group, but decreased in M-72 group, and were the same as control group in HYT-72 group. The apoptotic cells, increased noticeably in gastric mucosa of INDO group, decreased in HYT group and M group, and decreased noticeably in HYT-72 group. Conclusions: Hyangsayukgunja-tang extract had excellent effects on indomethacin-induced gastric mucosal lesions.

• The Journal of Internal Korean Medicine
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• v.38 no.6
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• pp.1085-1095
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• 2017

Objectives: The purpose of this study was to investigate the efficacy of Lijin-tang-gamibang on refractory gastroesophageal reflux disease (GERD). Methods: This before-and-after study compared the first medical examination and examination at the end of medical treatment. Twelve refractory GERD patients who visited the Department of Digestive Diseases of Kyung Hee University Korean Medicine Hospital from August 14th, 2017 to October 14th, 2017, were treated with Lijin-tang-gamibang for four consecutive weeks. The clinical characteristics of refractory GERD and the efficacy of herbal medical treatment was assessed by questionnaires, the Nepean Dyspepsia Index-Korean version (NDI-K), the Korean Gastrointestinal Symptom Rating Scale (KGSRS), the Numerical Rating Scale (NRS), the Korean version of the Perceived Stress Scale (KPSS-10), the Qi Stagnation Questionnaire (QSQ), the Spleen Qi Deficiency Questionnaire (SQDQ), and the Patient Global Impression of Change (PGIC). Prolonged effects were reported upon the follow-up telephone survey two weeks after treatment. Results: After treatment with the herbal medicine Lijin-tang-gamibang, the clinical characteristics of 12 refractory GERD patients were improved, especially in terms of the most common symptoms of acid regurgitation and heartburn. Each symptom score of NDI-K, KGSRS, NRS, SQDQ, and PGIC showed significant advances. Prolonged effects were reported in NDI-K, NRS and PGIC questionnaires two weeks after treatment. Conclusions: These results suggest that Lijin-tang-gamibang is an effective treatment for refractory GERD.

• International Journal of Vascular Biomedical Engineering
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• v.1 no.1
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• pp.13-23
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• 2003

Backgrounds: The present study in angulated coronary stenosis was to evaluate the influence of velocity and wall shear stress (WSS) on coronary atherosclerosis, the changes of hemodynamic indices following coronary stenting, as well as their effect of evolving in-stent restenosis using human in vivo hemodynamic parameters and computed simulation quantitatively and qualitatively. Methods: Initial and follow-up coronary angiographies in the patients with angulated coronary stenosis were performed (n=80). Optimal coronary stenting in angulated coronary stenosis had two models: < 50 % angle changed(model 1, n=43), > 50% angle changed group (model 2, n=37) according to percent change of vascular angle between pre- and post-intracoronary stenting. Flow-velocity wave obtained from in vivo intracoronary Doppler study data was used for in vitro numerical simulation. Spatial and temporal patterns of velocity vector and recirculation area were drawn throughout the selected segment of coronary models. WSS of pre/post-intracoronary stenting were calculated from three-dimensional computer simulation. Results: Follow-up coronary angiogram demonstrated significant difference in the percent of diameter stenosis between two groups (group 1: $40.3{\pm}30.2$ vs. group 2: $25.5{\pm}22.5%$, p<0.05). Negative WSS area on 3D simulation, which is consistent with re-circulation area of velocity vector, was noted on the inner wall of post-stenotic area before stenting. The negative WSS was disappeared after stenting. High spatial and temporal WSS before stenting fell into within physiologic WSS after stenting. This finding was prominent in Model 2 (p<0.01) Conclusions: The present study suggests that hemodynamic forces exerted by pulsatile coronary circulation termed as WSS might affect on the evolution of atherosclerosis within the angulated vascular curvature. Moreover, geometric change, such as angular difference between pre / post-intracoronary stenting might give proper information of optimal hemodynamic charateristics for vascular repair after stenting.

• Journal of Biomedical Engineering Research
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• v.28 no.1
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• pp.8-16
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• 2007

Finite element analysis (FEA) is an effective means for the analysis of bioelectromagnetism. It has been successfully applied to various problems over conventional methods such as boundary element analysis and finite difference analysis. However, its utilization has been limited due to the overwhelming computational load despite of its analytical power. We have previously developed a novel mesh generation scheme that produces FE meshes that are content-adaptive to given MR images. MRI content-adaptive FE meshes (cMeshes) represent the electrically conducting domain more effectively with far less number of nodes and elements, thus lessen the computational load. In general, the cMesh generation is affected by the quality of feature maps derived from MRI. In this study, we have tested various feature maps created based on the improved differential geometry measures for more effective cMesh head models. As performance indices, correlation coefficient (CC), root mean squared error (RMSE), relative error (RE), and the quality of cMesh triangle elements are used. The results show that there is a significant variation according to the characteristics of specific feature maps on cMesh generation, and offer additional choices of feature maps to yield more effective and efficient generation of cMeshes. We believe that cMeshes with specific and improved feature map generation schemes should be useful in the FEA of bioelectromagnetic problems.

• Smart Structures and Systems
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• v.4 no.3
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• pp.343-365
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• 2008

In this study, the frequency domain method which utilizes the evaluation of changes in the structural mode shape is adopted to identify regions which contain localized damages. Frequency response function (FRF) values corresponding to the modal frequency, analogous to the mode shape coefficients, are used since change in natural frequency of the system is usually insignificant for localized damage. This method requires only few sensors to obtain the dynamic response of the structure at specific locations to determine the FRF via fast-Fourier transform (FFT). Numerical examples of an aluminum plate, which includes damages of varying severity, locations and combinations of multiple locations, are presented to demonstrate the feasibility of the method. An experimental verification of the method is also done using an aluminum plate with two different degrees of damage, namely a half-through notch and a through notch. The inconsistency in attaining the FRF values for practical applications due to varying impact load may be overcome via statistical averaging, although large variations in the loading in terms of the contact duration should still be avoided. Nonetheless, this method needs special attention when the damages induce notable changes in the modal frequency, such as when the damages are of high severity or cover more extensive area or near the boundary where the support condition is modified. This is largely due to the significant decrease in the frequency term compared to the increase in the vibration amplitude. For practical reasons such as the use of limited number of sensors and to facilitate automation, extending the resolution of this method of identification may not be efficient. Hence, methods based on wave propagation can be employed as a complement on the isolated region to provide an accurate localization as well as to trace the geometry of the damage.

• Journal of Korean Tunnelling and Underground Space Association
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• v.6 no.3
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• pp.183-197
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• 2004

The introduction of geodetic methods of absolute displacement monitoring in tunnels has significantly improved the value of the measurements. Structurally controlled behavior and influences of an anisotropic rock mass can be determined, and the excavation and support adjusted accordingly. Three-dimensional finite element simulations of different weakness zone properties, thicknesses, and orientations relative to the tunnel axis were carried out and the function parameters were evaluated from the results. The results were compared to monitoring results from Alpine tunnels in heterogeneous rock. The good qualitative correlation between trends observed on site and numerical results gives hope that by a routine determination of the function parameters during excavation the prediction of rock mass conditions ahead of the tunnel face can be improved. Implementing the rules developed from experience and simulations into the monitoring data evaluation program allows to automatically issuing information on the expected rock mass quality ahead of the tunnel.

• Structural Engineering and Mechanics
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• v.75 no.4
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• pp.415-424
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• 2020

Recently, many structural damage detection (SDD) methods have been proposed to monitor the safety of structures. As an important modal parameter, mode shape has been widely used in SDD, and the difference of vectors was adopted based on sensitivity analysis and mode shapes in the existing studies. However, amplitudes of mode shapes in different measured points are relative values. Therefore, the difference of mode shapes will be influenced by their amplitudes, and the SDD results may be inaccurate. Focus on this deficiency, a multi-strategy SDD method is proposed based on the included angle of vectors and sparse regularization in this study. Firstly, inspired by modal assurance criterion (MAC), a relationship between mode shapes and changes in damage coefficients is established based on the included angle of vectors. Then, frequencies are introduced for multi-strategy SDD by a weighted coefficient. Meanwhile, sparse regularization is applied to improve the ill-posedness of the SDD problem. As a result, a novel convex optimization problem is proposed for effective SDD. To evaluate the effectiveness of the proposed method, numerical simulations in a planar truss and experimental studies in a six-story aluminum alloy frame in laboratory are conducted. The identified results indicate that the proposed method can effectively reduce the influence of noises, and it has good ability in locating structural damages and quantifying damage degrees.

• The Korean Journal of Pain
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• v.11 no.1
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• pp.41-46
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• 1998

Background: Preoperative analgesia may prevent nociceptive inputs generated during surgery from sensitizing central neurons and therefore may preempt postoperative pain. Although preemptive analgesia has shown to decrease postinjury pain in animals, studies in human are not consistent. We studied whether epidural morphine injection before surgical incision could affect postoperative pain and analgesic demands, compared with injection after removal of specimen. Methods: Forty patients scheduled for radical subtotal gastrectomy were randomly assigned to one of two groups for prospective study in a double-blind manner. Group 1 received an epidural injection of 3 mg of morphine in 8 ml of 0.9% saline before surgical incision, and Group 2 after removal of specimen. Postoperative pain relief was provided with I.V. patient controlled analgesia (PCA) system. Numerical rating scales for pain and mood, Prince Henry Hospital scores for pain, cumulative PCA analgesic consumptions, and incidence of side effects were assessed at 2, 6, 12, 24, 48 hours after operation. Results: Cumulative PCA analgesic consumption in group 1 was significantly less than in group 2 at 2, 6 hours after surgery. Pain scores and the incidence of side effects were similar in both groups. Conclusions: Preoperative analgesia with epidural morphine showed little difference in patient controlled analgesic consumption after upper abdominal surgery compaired to intraoperative morphine.

• The Korean Journal of Pain
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• v.22 no.3
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• pp.234-240
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• 2009

Background: The purpose of this study was to compare the analgesic effect of 0.25% and 0.5% levobupivacaine for real time ultrasound guided single-injection femoral nerve block for the patients who are undergoing bilateral total knee arthroplasty (TKA). Methods: Femoral nerve block was done to all patients with 20 ml of 0.9% normal saline on one leg and 20 ml of 0.25% levobupivacaine on the other leg for group I (n = 16) and 0.5% levobupivacaine for group II (n = 15) with 1:200,000 epinephrine and using real-time ultrasound and a nerve stimulator. The data concerning the verbal numerical rating scale (VNRS) for each leg, the consumption of the intravenous patient-controlled analgesia (IV PCA) and the demands for the additional analgesics was collected at 0, 1, 6, 12, 24 and 48 hours after the operation. Results: The legs on which femoral nerve block was done with levobupivacaine showed a lower VNRS score than the legs with normal saline in either group I or group II. The VNRS scores between the two legs, the consumption of the IV PCA and the demand for additional analgesics showed no significant differences between the groups. Conclusions: Our results demonstrate that single-injection femoral nerve block using real-time ultrasound with either 0.25% levobupivacaine or 0.5% levobupivacaine 20 ml provides a good effect for the postoperative pain control after TKA.