• Journal of the Korean Geotechnical Society
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• v.26 no.1
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• pp.45-54
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• 2010

It is important to calculate the natural frequency of a piled structure in the design stage in order to prevent resonance-induced damage to the pile foundation and analyze the dynamic behavior of the piled structure during an earthquake. In this paper, a simple but relatively accurate method employing a mass-spring model is presented for the evaluation of the natural frequency of a pile-soil system. Greatly influencing the calculation of the natural frequency of a piled structure, the spring stiffness between a pile and soil was evaluated by using the coefficient of subgrade reaction, the p-y curve, and the subsoil elastic modulus. The resulting natural frequencies were compared with those of 1-g shaking table tests. The comparison showed that the natural frequency of the pile-soil system could be most accurately calculated by constructing a stiffness matrix with the spring stiffness of the Reese (1974) method, which utilizes the coefficient of the subgrade reaction modulus, and Yang's (2009) dynamic p-y backbone curve method. The calculated natural frequencies were within 5% error compared with those of the shaking table tests for the pile system in dry dense sand deposits and 5% to 40% error for the pile system in saturated sand deposits depending on the occurrence of excess pore water pressure in the soil.

• Journal of Korean Neurosurgical Society
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• v.65 no.3
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• pp.422-429
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• 2022

Objective : Extracranial supra-aortic dissections (ESADs) with severe stenosis, occlusion and/or pseudoaneurysm presents potential risk of stroke. Endovascular stenting to reconstruct non acute phase ESADs (NAP-ESADs) is an alternative to anticoagulant or antiplatelet therapy. However, its feasibility, safety and efficacy of stenting in NAP-ESADs is unclear. This study aims to investigate the long-term outcomes of the feasibility, safety and efficacy of stenting in NAP-ESADs. Methods : Seventy-four patients with 91 NAP-ESAD vessels with severe stenosis, occlusion and/or pseudoaneurysm presents potential risk of stroke who underwent stent remodeling were enrolled into this respective study from December 2008 to March 2020. Technical success rate, complications, clinical and angiographic results were harvested and analyzed. Results : Success rate of stent deployment was 99% (90/91) with no procedural mortality or morbidity. Transient ischemic attack occurred in three patients during operation (4.1%, 3/74). Asymptomatic embolisms of distal intracranial vessels were found in two patients (2.7%, 2/74). One hundred and forty-two stents deployed at 85 carotid (135 stents) and six vertebral (seven stents) vessels. Six stent types (Wingspan, 28/135, 20.7%; Solitaire, 10/135, 7.4%; Neuroform, 8/135, 5.9%; LVIS, 2/135, 1.5%; Precise, 75/135, 55.6%; Acculink, 12/135, 8.9%) were deployed at carotid arterial dissection while two types (Wingspan, 5/7, 71.4%; Solitaire 2/7, 28.6%) at vertebral arterial dissection. Digital subtracted angiography (56%, 51/91), computational tomography angiography (41.8%, 38/91) and high resolution magnetic resonance imaging (2.2%, 2/91) were adopted for follow up, with a mean time of 17.2±15.4 months (5-77). All patient modified Rankin Scale scores showed no increase at discharge or follow-up. Angiographically, dissections in 86 vessels in 69 patients (94.5%, 86/91) were completely reconstructed with only minor remnant dissections in four vessels in four patients (4.4%, 4/91). Severe re-stenosis in the stented segment required re-stenting in one patient (1.1%, 1/91). Conclusion : Stent remodeling technique provides feasible, safe and efficacious treatment of ESADs patients with severe stenosis, occlusion and/or pseudoaneurysm.

• Journal of Popular Narrative
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• v.25 no.2
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• pp.169-216
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• 2019

This study proposes the concept of Bachchin's Chronotope as a tool for analyzing coevolution between the genre of the epic and society. Bachchin says through the concept of chronotope, literary works are on the foundation on which the axs of time and space intersect, and the literary works standsuch intersections are always conversing with social and historical chronotopes and mutually penetrating. Thus, finding and analyzing chronotope in literary works and extended things such as films and dramas reveals how chronotope and chronotope of a society have created specific social realities through a process of resonance. To make analytical use of this concept, we proposed a "cronotope drama analysis method" and concretely analyzed the genre of Korean medical dramas. The naturalized categories of health care, health, and disease are socially constructed entities, and the analysis of public works that has a significant impact on this process of social construction is essential but was underperformed. According to the analysis, the Korean medical drama's "Chronotope" has evolved using "Chronotope of the school" and "Chronotope of the secret chamber". At this time, the genre of Chronotope was expanding spatially and converging in time. In other words, the influence of structures and systems within the genre has grown, and the capacity of individual actors has decreased. This change in chronotope was interpreted as resonating with the social reality of neo-liberalistic spatial expansion and simultaneous production. The neo-liberalistic trend that dominates Korean society has embraced the category of health care and was further influencing the chronotope of drama text. It can also be inferred that the popular understanding of health care produced by the medical drama genre has taken a break in the process of forming a social reality of health care again.

• Journal of the Korean Orthopaedic Association
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• v.52 no.1
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• pp.65-72
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• 2017

Purpose: The purpose of this study was to evaluate the radiologic features of juxtafacet cyst and determine the correlation between these features and clinical outcome. Materials and Methods: We analyzed a total of 23 patients. The degree of facet joint degeneration was classified using the Fujiwara method. The facet joint angles were measured with an magnetic resonance imaging to determine whether there was a difference between the cystic lesion that was occupied and the cystic lesion that was not occupied. Disc degeneration was measured by the Pfirrmann classification method. The clinical result was evaluated using the Oswestry disability index score and visual analogue scale. Results: The L4-5 level of juxtafacet cyst was mostly affected, as found in previous studies. Facet joint arthritis was more severe within the side with the cystic lesion. Significant correlation was found between disc degeneration and juxtafacet joint cyst. All patients underwent wide decompression and fusion. Clinical result was excellent. No patients had signs of recurrence during the follow-up periods. Conclusion: Juxtafacet cyst has a significant correlation with facet joint degeneration. Therefore, aggressive surgical treatment-not just simple cyst excision-should be considered as the treatment option for juxtafacet cyst associated with degenerative lumbar disease.

• The Bulletin of The Korean Astronomical Society
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• v.46 no.2
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• pp.38.2-39
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• 2021

I will presents the analysis of the gas properties of the protoplanetary disk surrounding the young low-mass (about 1.2M_sun) triple star, GG Tau A. This work makes use of ALMA observations of rotational lines of CO (¹²CO, ¹³CO and C¹⁸O) together NOEMA observations of a few dozens of other molecules. While the CO emission gives information on the molecular layer close to the disk atmosphere, its less abundant isotopologues ¹³CO and C¹⁸O bring information much deeper in the molecular layer. I will present the analysis of the morphology and kinematics of the gas disk using the CO isotopologues. A radiative transfer model of the ring in CO isotopologues will also be presented. The subtraction of this model from the original data reveals the weak emission of the molecular gas lying inside the cavity. Thus, I am able to evaluate the properties of the gas inside the cavity, such as the gas dynamics, excitation conditions, and the amount of mass in the cavity. High angular resolution observations of CO reveals sprials induced by embedded planet(s) located near the 3:2:1 mean-motion resonance that help to explain the special morphology of the circumbinary disk. I also discuss some chemical properties of the GG Tau A disk. I report the first detection of H2S and C₂S in a protoplanetary disk. The molecule abundance relative to ¹³CO of about twenties other molecules will also be given. In GG Tau A, the detections of rare molecules such as H₂S and C₂S have been probably possible because the disk is more massive (a factor about 3-5) than other disks where the molecules was searched. Such a large disk mass makes the system suitable to detect rare molecules and to study cold-chemistry in protoplanetary disks.

• Journal of Life Science
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• v.33 no.7
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• pp.574-585
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• 2023

Sarcopenia is a leading cause of increased medical and nursing care costs among the elderly. In Korea, preventive measures for sarcopenia are mostly targeted toward the general elderly population without specific diseases. However, it is also necessary to implement measures for elderly individuals living in nursing homes and hospitals, where the prevalence of sarcopenia is high. Currently, computed tomography and/or magnetic resonance imaging are considered standard diagnostic tools. However, their complexity and time-consuming nature make them unsuitable for clinical use. The exact pathophysiological mechanisms of sarcopenia are unclear, as they involve various molecular biological pathways, including decreased exercise, protein and nutrient intake, changes in testosterone and growth hormone, and inflammation. Sarcopenia symptoms can lead to several diseases, such as osteoporosis, fractures, dementia, diabetes, and cardiovascular disease. Vitamin B deficiency is a significant factor in sarcopenia induction, with B vitamins being directly involved in energy and protein metabolism and nerve function. Vitamin B deficiency can lead to neuromuscular and neurogenic disorders, which often overlap with sarcopenia. Suboptimal intake of B vitamins, malabsorption, and anorexia are common among the elderly. This study aims to provide information on the role of water-soluble B vitamins in preventing and controlling muscle mass loss and deterioration among the elderly with sarcopenia. In addition, we discuss the potential of myokines from the B vitamin family in modulating sarcopenia.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.1B
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• pp.89-100
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• 2010

The performance evaluation of a conventional Wave Resonator at the entrance of harbors against solitary wave has been performed using 3D numerical wave flume. A wave resonator has been designed for the attenuation of the transmitted wave energy by trapping the short periodic incident waves only. In this study, however, the controlled performance of the wave resonator by its various widths has been numerically investigated for solitary waves. Source distribution method based on the Green function and the 3D one-field Model for immiscible TWO-Phase flows (TWOPM-3D) using 3D numerical wave flume were used for the short-periodic waves and the solitary waves, respectively, and these models were verified through the comparisons with the previous experimental and numerical results by other researchers. It was confirmed that the wave resonator is effective enough to control the solitary waves as well as the periodic waves when it compares with the case of no resonance system. Further, it was found that there is the optimal width of a wave resonator to attenuate the target solitary waves.

• Journal of Korean Tunnelling and Underground Space Association
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• v.12 no.4
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• pp.295-306
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• 2010

Contrary to an intact rock, the jointed rock mass shows strain-dependent deformation characteristics (elastic modulus and damping ratio). The maximum elastic modulus of a rock mass can be obtained from an elastic wave-based exploration in a small strain level and applied to seismic analyses. However, the assessment and application of the non-linear characteristics of rock masses in a small to medium strain level ($10^{-4}{\sim}0.5%$) have not been carried out yet. A non-linear dynamic analysis module is newly developed for FLAC3D to simulate strain-dependent shear modulus degradation and damping ratio amplification characteristics. The developed module is verified by analyzing the change of the Ricker wave propagation. Strain-dependent non-linear characteristics are obtained from disks of cored samples using a rock mass dynamic testing apparatus which can evaluate wave propagation characteristics in a jointed rock column. Using the experimental results and the developed non-linear dynamic module, seismic analyses are performed for the intersection of a shaft and an inclined tunnel. The numerical results show that vertical and horizontal displacements of non-linear analyses are larger than those of linear analyses. Also, non-linear analyses induce bigger bending compressive stresses acting on the lining. The bending compressive stress concentrates at the intersection part. The fundamental understanding of a strain-dependent jointed rock mass behavior is achieved in this study and the analytical procedure suggested can be effectively applied to field designs and analyses.

• Journal of Korean Tunnelling and Underground Space Association
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• v.11 no.1
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• pp.71-83
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• 2009

Shotcrete is an important primary support for tunnelling in rock. The quality control of shotcrete is a core issue in the safe construction and maintenance of tunnels. Although shotcrete may be applied well initially onto excavated rock surfaces, it is affected by blasting, rock deformation and shrinkage and can debond from the excavated surface, causing problems such as corrosion, buckling, fracturing and the creation of internal voids. This study suggests an effective non-destructive evaluation method of the tunnel shotcrete bonding state applied onto hard rocks using the impact-echo (IE) method and ground penetration radar (GPR). To verify previous numerical simulation results, experimental study carried out. Generally, the bonding state of shotcrete can be classified into void, debonded, and fully bonded. In the laboratory, three different bonding conditions were modeled. The signals obtained from the experimental IE tests were analyzed at the time domain, frequency domain, and time-frequency domain (i.e., the Short- Time Fourier transform). For all cases in the analyses, the experimental test results were in good agreement with the previous numerical simulation results, verifying this approach. Both the numerical and experimental results suggest that the bonding state of shotcrete can be evaluated through changes in the resonance frequency and geometric damping ratio in a frequency domain analysis, and through changes in the contour shape and correlation coefficient in a time-frequency analysis: as the bonding state worsens in hard rock condition, the autospectral density increases, the geometric damping ratio decreases, and the contour shape in the time-frequency domain has a long tail parallel to the time axis. The correlation coefficient can be effectively applied for a quantitative evaluation of bonding state of tunnel shotcrete. Finally, the bonding state of shotcrete can be successfully evaluated based on the process suggested in this study.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.6A
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• pp.535-542
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• 2010

Precise estimation of a structure's dynamic characteristics is indispensable for ensuring stable dynamic responses during lifetime especially for the structures which can experience resonance such as railway bridges. In this paper, the results of forced vibration tests of different excitation methods (vibration exciter and impact hammer) are compared to examine the differences and the cause of differences of extracted natural frequencies. Consequently a natural frequency modification method is suggested to eliminate effects of non-structural disturbance factors. Also, sequential forced vibration tests are performed before and after track construction according to the construction stage of a railway bridge, and the variation of natural frequencies are examined. Effect of added mass of vibration exciter and variation of support condition due to the level of excitation force are concluded as the major cause of natural frequency differences. Thus eliminating these effects can enhance the reliability of the extracted natural frequencies. Construction of track affects not only the mass of structure but also the stiffness of the structure. Also, the amount of increase in stiffness varies according to the level of structural deflection. Therefore, reasonable estimation of the level of structural response during operation is important for precise natural frequency calculation at design phase.