• Progress in Medical Physics
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• v.17 no.3
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• pp.153-158
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• 2006

The purpose of this study was to improve the technique so as to develop an advanced sensitive RF surface coil for investigating the sensitivities of the multi-spiral surface coils, and we eventually wanted to achieve high resolution of the microscopic MR images and MR spectra. The magnetic field inhomogeneity and shape of a surface coil were statistically estimated by simulation of the magnetic field distribution. On the basis of the experimental results with single, 3 and S-turned spiral RF surface coils, we found that the 3-turned coil had the highest sensitivity. The present study showed that the sensitivity of the RF surface coil was improved by increasing the number of spiral coil turns, and also the SNR of the RF surface coil was dependent upon the number of spiral coil turns. However, we found, rather strikingly, that the sensitivity of excessive turns of the coils was decreased due to the rise of the coil's Impedance. Thus, the present results demonstrated that the sensitivity was not proportional to the number of a spiral RF coil's turns, and the number of spiral coil turns should be optimized for obtaining the highest sensitivity and SNR.

• Investigative Magnetic Resonance Imaging
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• v.11 no.2
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• pp.127-132
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• 2007

Sinonasal neuroendocrine carcinoma is a rare disease, and reports focusing on the MR imaging findings of sinonasal neuroendocrine carcinoma are extremely rare. Threrefore we intend to report 2 cases of histologically confirmed neuroendocrine carcinoma. A 62-year-old man and a 74-year-old man are both presented with nasal bleeding. Computed tomography(CT) images of the 2 patients showed large, ill-defined masses in sinonasal cavities with adjacent bony destructions. MR images showed masses with isosignal intensity on Tl-weighted images and mixed iso- and high signal intensity on T2-weighted images. Post-contrast MR images showed heterogenous enhancement of masses with necrosis. Adjacent bony destructions were also noted on MR images. In both cases, peritumoral cystic lesions or mucoceles with high signal intensity on T1-weighted images were noted in sphenoid sinus. Both of the CT and MR imaging findings of the 2 patients were nonspecific which are usually seen in malignant tumor. But further study is needed for the significance of the peritumoral cystic areas adjacent the tumors.

• The Journal of Engineering Geology
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• v.27 no.1
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• pp.91-101
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• 2017

Fault materials has various properties depending on their areas, rock types, and components because they are formed by heterogeneous and complicated mechanisms. In this study, to understand the physical and mechanical properties of fault materials, 109 fault materials distributed in South Korea were collected to conduct various laboratory tests with them and analyze their physical and mechanical properties (unit weight, specific gravity, porosity, gravel content, silt/clay content, clay mineral content, friction angle, and cohesion) according to areas, rock types, and components. As for the physical and mechanical properties by rock type, gneiss shows the highest medians in the unit weight ($17.1kN/m^3$) and specific gravity (2.73), granite does so in the porosity (45.5%), schist does so in the gravel content (20.0 wt.%) and cohesion (38.1 kPa), and phyllite does so in the silt/clay content (54.4 wt.%), clay mineral content (30.1 wt.%), and friction angle ($38.2^{\circ}$). With regard to the physical and mechanical properties by component, fault gouge was shown to have lower values than cataclasite and damage zones in all factors other than porosity and silt/clay contents.

• Economic and Environmental Geology
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• v.39 no.3 s.178
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• pp.269-284
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• 2006

Aquifer responses to the river stage fluctuations were analyzed between the groundwater level and the river stage in an alluvial aquifer. The auto-correlation and cross-correlation as a time series analysis were applied. Study site is a floodplain in the Mangyeong river. Groundwater levels in each depth representing the silt and sand(SS), gravel and sand(GS), and weathered zone(WZ) layer were monitored. The groundwater levels were more sensitive to the river stage fluctuations than rainfall. Since the river stages are influenced by the gate operations downstream and tide, show periodic patterns, and the correlation coefficients with rainfall is low. Cross-correlation function between groundwater level in each depth do not show any delay time, then response time is very short to each depth. Cross-correlation analysis were performed to estimate the response time of groundwater levels to river stage fluctuations. Groundwater levels respond to the river stage within 30 minutes to 1 hour in wells near the stream. Short time lag between groundwater level and river stage indicates the quick response. A different response time imply the hydraulic inhomogeneity of the site, and a probable high permeability zone between river and aquifer can be inferred. Mangyeong-river in study site is a gaining stream normally, and river stage rising by gate operation or floods makes river water flow into groundwater. The auto-correlation and cross-correlation functions as a time series analysis can be a good tool to interpret the aquifer responses to stream stage fluctuation

• Journal of the Mineralogical Society of Korea
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• v.28 no.2
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• pp.109-126
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• 2015

Because fault gouge developed at the center of fault is recognized as one of the most important weak sites, it is evident that clay mineralogy and physical properties greatly affect the rock stability. The purpose of this study is to establish the relationship of mineralogy and physical factors that control rock stability in fault zones. We analyzed a total of 51 samples from 16 main faults which were selected from a Korea fracture map, using XRD, SEM, and physical analyses like unit weight, friction and cohesion properties. Though it is considered that the most common clay minerals comprising fault gouge are kaolinite, illite and smectite, clay mineralogy slightly varies depending on lithology: illite > smectite > kaolinite and chlorite in volcanic rocks, kaolinite and chlorite > illite > smectite in sedimentary rocks, and illite > smectite > kaolinite and chlorite in abundance, respectively. Friction angle decreases with increasing clay content. Cohesion increases with increasing clay content below the 45 % region while it decreases with increasing clay content at the region higher than 45%, with some scatters in the data. It is likely that these results are ascribed to the physical heterogeneity of fault gouges with varying content of different clay minerals.

• Journal of the Korean Geotechnical Society
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• v.17 no.6
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• pp.15-24
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• 2001

In order to evaluate undrained shear strength of clayey soils using Piezocone Penetration Test (CPTu), piezoncone factor is utilized. Commonly, piezoncone factors determined by empirical basis were preferred, which were established by correlation between measurements of piezocone test and undrained strengths obtained from other shearing tests. However, previous studies on the empirical piezocone factors were site-specific and there have been no systematic investigations on the effect of both engineering characteristics of clayey soils and soil non-homogeneity on the piezocone factor. Accordingly, the direct application of the previous results to Korean clayey soils without verification may be inappropriate. In this study, empirical piezocone factors are evaluated by comparing 46 CPTu results of 10 test sites with undrained shear strength obtained from Field Vane Test (FVT) and laboratory triaxial tests. Their reliabilities are investigated by the comparison with the previous piezocone factors and the deviation of data distribution from the mean values. And the effects of referencing test methods and typical engineering characteristics of clayey soils such as overconsolidation ratio (OCR) and plastic Index (I$_{p}$) are examined. Because piezocone factors obtained for various soil conditions are widely distributed, it is not appropriate to use the mean value as a representative. Instead, it is recommended to apply the piezocone factors with OCR, which is found to be a major factor in deriving piezocone factor. The necessitated piezocone factors are presented.d.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.21 no.11
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• pp.870-877
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• 2020

A suction bucket foundation, especially useful at depths of more than 20m, is a method of construction. The method first places an empty upturned bucket at the target site. Then, the bucket is installed by sucking water or air into it to create negative pressure. For stability, it is crucial to secure the verticality of the bucket. However, inclination by the bucket may occur due to sea-bottom conditions. In general, a repeated intrusion-pulling method is used for securing verticality. However, it takes a long time to complete the job. In this paper, we propose a real-time suction bucket verticality monitoring system. Specifically, the system consists of a sensor unit that collects raw verticality data, a controller that processes the data and wirelessly transmits the information, and a display unit that shows verticality information of a circular steel pipe. The system is implemented using an inclination sensor and an embedded controller. Experimental results show that the proposed system can efficiently measure roll/pitch information with a 0.028% margin of error. Furthermore, we show that the system properly operates in a suction bucket-based model experiment.

• Tunnel and Underground Space
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• v.28 no.2
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• pp.156-169
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• 2018

The relationship between the mechanical and textural properties of sedimentary rocks has been studied for decades. However, inconsistencies in the results have arisen from both the inhomogeneity of natural rocks and the difficulties encountered in controlling just one textural factor of interest in each experiment. This work produced artificial sedimentary rocks to enable control of every independent parameter at all times. Their homogeneity lowered the deviation of the results, and thus they produced clearer correlations than for natural rocks. The samples were made by mixing bassanite powder with water and silica sand, which produced rocks consisting of sand and gypsum cement. The effect of grain content and size on mechanical properties such as uniaxial compressive strength, Young's modulus, and seismic velocity was estimated. Increasing grain content lowered the compressive strength but raised Young's modulus and seismic velocity. Overall, grain size did not linearly affect the mechanical properties of the samples, but affected them in some way. In future, these results can be compared and integrated with similar experiments using different cement or grain types. This should allow comparison of the effects of the rock constituents themselves and their interactions, with applicability to all kinds of sedimentary rocks.

• Journal of Korea Soil Environment Society
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• v.5 no.1
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• pp.13-23
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• 2000

The effects of operating condition of soil vapor extraction system and the characteristics of site on the remediation of oil contaminated soil were investigated. Thorough investigation showed that the site was contaminated with gasoline leaked from underground storage tank and the maximum concentration of BTEX and TPH were 1,081 ppm and 5,548 ppm respectively. The leaked gasoline were diffused to 6m deep and the area and volume of the polluted soil were assumed to 170$m^2$ and 1,000$\textrm{m}^3$respectively. The site were consisted of three different vertitical layers, the top reclaimed sandy soil between the earth surface and 3~4m deep, middle silty sand between 3~4m and 6m deep, and the bottom bedrock below the 6m deep. The air pemeability of soil was measured to 1.058-1.077$\times$10$^{-6}$ $\textrm{mm}^2$ by vacuum pump tests. The groundwater which level was 3~4m deep was observed in some areas of this site. The soil vapor extraction system which had 7.5 HP vacuum pump and 8 extraction wells was constructed in this site and operated at 8 hrs/day for 100 days. The BTEX was removed with above 90% efficiency where no groundwater and silty sand were observed. On the contrary, the efficiency of BTEX and TPH were dramatically decreased where groundwater and silty sand were observed. The flow rate of soil air induced by soil vapor extraction system was reduced in deeper soil.

• Journal of Chest Surgery
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• v.39 no.5 s.262
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• pp.376-381
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• 2006

Background: The Ki-67 protein is a biomarker associated with cell proliferation and a valuable negative prognostic factor in non-small cell lung cancer. We investigated the Ki-67 protein expression in resected non-small cell lung cancer to evaluate the impact on clinicopathological characteristics and postoperative prognosis. Material and Method: Using monoclonal antibody Ki-67, we immunohistochemically examined 38 surgically resected non-small ceil lung cancers to determine Ki-67 Labeling Index (LI). We analysed the differences of clinicopathological characteristics and postoperative recurrence and survival between High Ki-67 Group $(LI{\ge}20%)$ and Low Ki-67 Group (LI<20%). Result: The Ki-67 LIs were heterogenous and a mean values was $20.0{\pm}20.05%$. There were no significant differences in age, sex, smoking, TNM stage, and vascular invasion between High Ki-67 Group and Low Ki-67 Group. A High Ki-67 Group was significantly associated with squamous cell type, poor differentiation, and lymphatic invasion $(p{\le}0.05)$. High Ki-67 Group showed a trend of lower survival (median 47.2 vs. 90.5 months, p=0.312) and lower disease-free survival (median 18.2 vs. 72.3 months, p=0.327) than Low Ki-67 Group. Conclusion: These results indicate that increased Ki-67 protein expression may be a negative prognostic factor and showed a trend of shortened survival and disease-free survival. To evaluate the pivotal role of Ki-67 protein expression, a long-term follow-up and further study are required.