• Journal of Chest Surgery
• /
• v.29 no.1
• /
• pp.73-78
• /
• 1996

From June 1989 to May 1994, 23 patients with myasthenia gravis underwent thymectomy in the Department of Thoracic Surgery, Asan Medical Center. For the evaluation of the effect of thymectomy, clinical analysis including age and sex distribution, preoperative disease severity, duration of the symptoms, thymic pathology, and postoperative clinical improvement was performed. The mean follow-up period was 15 mon hs(range : 5∼60mon1hs). The effectiveness of thymectomy according to the postoperative symptoms and drug dose was graded as follow : a) complete remission in 5 cases (21.7%), b) clinical improvement with dose reduction in II cases (47.9%), c) clinical improvement without dose reduction in 3 cases(13.0%), 4) unchanged in 2 cases (8.8%), e) early death in 1 case(4.3%) and f) recurrence in 1 case(4.3%). According to the preoperative disease stage by Modified Osserman classification, 6(66.7%) of the 9 patients in stage I and 13 (92.9%) of 14 patients in stage II were clinically improved after thymectomy. although there was no significant statistical differences between these two groups (p> 0.05). According to the thymic pathology, 4 (100%) of 4 cases with normal thymus were clinically improved. Ten (90.9%) of 11 cases with thymic hyperplasia and 5 (62.5%) of 8 cases with thymoma were clinically improved, but there was no significant statistical differences in these three groups (p> 0.05 . The thymectomy resulted in dramatic clinical improvement in 19 (82.5%) out of 23 patients. According to the preoperative disease stage by Modified Osserman classification or the thymic pathology, there was no significant statistical differeneces in the effect of thyinectomy (p> 0.05).

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.18 no.1
• /
• pp.69-83
• /
• 2006

A Level 3 reliability analysis has been performed for wave run-up and overtopping on a sloping seawall. A Monte-Carlo simulation was performed considering the uncertainties of various variables affecting the wave overtopping event. The wave overtopping probability was evaluated from the individual wave run-up by using the wave-by-wave method, while the mean overtopping rate was calculated directly from the significant wave height. Using the calculated overtopping probability and mean overtopping rate, the maximum overtopping volume was also calculated on the assumption of two-parameter Weibull distribution of individual wave overtopping volume. In addition, by changing wave directions, depths, and structure slopes, their effects on wave overtopping were analyzed. It was found that, when the variability of wave directions is considered or the water depth decreases toward shore, wave height become smaller due to wave refraction, which yields smaller mean overtopping rate, overtopping probability and maximum overtopping volume. For the same mean overtopping rate, the expected overtopping probability increases and the expected maximum overtopping volume decreases as approaching toward shore inside surfzone.

• Journal of Korean Society of Coastal and Ocean Engineers
• /
• v.27 no.4
• /
• pp.246-257
• /
• 2015

The progressive degradation paths of structures have quantitatively been tracked by using stochastic processes, such as Wiener process, gamma process and compound Poisson process, in order to consider both the sampling uncertainty due to the usual lack of damage data and the temporal uncertainty associated with the deterioration evolution. Several important features of stochastic processes which should carefully be considered in application of the stochastic processes to practical problems have been figured out through assessing cumulative damage and lifetime distribution as a function of time. Especially, the Wiener process and the gamma process have straightforwardly been applied to armors of rubble-mound breakwaters by the aid of a sample path method based on Melby's formula which can estimate cumulative damage levels of armors over time. The sample path method have been developed to calibrate the related-parameters required in the stochastic modelling of armors of rubble-mound breakwaters. From the analyses, it is found that cumulative damage levels of armors have surely been saturated with time. Also, the exponent of power law in time, that plays a significant role in predicting the cumulative damage levels over time, can easily be determined, which makes the stochastic models possible to track the cumulative damage levels of armors of rubble-mound breakwaters over time. Finally, failure probabilities with respect to various critical limits have been analyzed throughout its anticipated service life.

• Economic and Environmental Geology
• /
• v.33 no.2
• /
• pp.91-100
• /
• 2000

It has been more than ten years since Dukun mine was abandoned. Tailings of waste deposits and slime dumps in the abandoned Dukum mine have been left to be deserted for fifty years. The results of fifty years of neglecting are nothing short of major environmental problems. Slime dumps have been exposed to air and water in the mine over ten years and then soil profile has been formed well. Soil in the upper layer (A horizon) is the light gray color due to the leaching of cations. Soil in the lower layer (A2 horizon, 0.2∼0.3m)is tinted with reddish brown and yellowish brown color due to the development of iron oxides and iron hydroxides. Soil in the lower part of B horizon of (1.0∼3.0m) with the growth of copper and zinc oxides exposes to the bluish green, light blue, and dark gray. Ranging from 3m to 8m in depth, 85 samples were taken from 22 sampling sites with 50m intervals located on the slime dump area with hand auger and trench (open cut). As tailings was distributed, heavy metal elements extracted by the process of surface water and ground water move and disperse in to the hydrosphere. Waste dumps were distributed in and around the mine and water draining from those dumps be a potential source of contamination. Soils, thus, can be dispersed into downslope and downstream through wind and water by clastic movement. These materials may be deposited in another horizon if the water is withdrawn, or if the materials are precipitated as a result of differences in pH, or other conditions in deeper horizons. These were primarily associated with acid mine drainage. The characteristics and rate of release of acid mine drainage are influenced by various chemical and biological reactions at the source of acid generations. Prolonged extration of heavy metal elements has a detrimental effect on the agricultural land and residental area. Twenty soil samples were collected from the agricultural land in the area (0∼30 cm). Seventeen samples were also taken from the sediment in the stream running alongside the dumps. The dispersion patterns of heavy metal elements are as follows: The content of As ranged 2∼6 ppm in a horizon, 20∼125 ppm in B horizon with large amount of clay mineral is concentrated and the content of Cd ranged 1∼2 ppm in A horizon, 4∼22 ppm in B horizon. Like Cd, the content of As, Cu, Zn, Pb in B horizon is higher than that in A horizon (approximately 5∼100 times). When soil formation proceeds in stages, it is necessary to investicate the B horizon with the concentration of heavy metal and preventive measures will have to established.

• Economic and Environmental Geology
• /
• v.51 no.2
• /
• pp.113-120
• /
• 2018

Radioactive cesium($^{137}Cs$) can be released into the environment through severe nuclear accidents such as the Chernobyl and Fukushima, The $^{137}Cs$ is one of major monitoring radionuclides due to its chemical toxicity, ${\gamma}$ radiation and long half-life($t_{1/2}=30.2yrs$). It has been known well that illite adsorb selectively and strongly the cesium due to frayed edge sites. The quantity of the FES in the illite could be controlled by weathering processes. Therefore, this study was modified illite samples through artificial weathering in the laboratory to increase sorption efficiency for cesium. Abundant interlayer cations(i.e., K, Ca) were eluted within 1 day, while Si and Al were gradually released from the crystal structure. In addition, broad peaks of XRD indicated the occurrence of chemical weathering. The cesium sorption distribution coefficients increased up to approximately 2 times after the weathering. These results suggested that sorption capacity of illite could be enhanced for cesium through artificial weathering under low temperature.

• Asian Journal of Atmospheric Environment
• /
• v.9 no.1
• /
• pp.66-77
• /
• 2015

In order to survey the seasonal variation of the chemical composition of particulate matter of $2.5{\mu}m$ or less ($PM_{2.5}$), $PM_{2.5}$ was sampled from 8 February 2013 to 31 March 2014 in an industrial area of Chiba Prefecture, Japan. Chemical measurements of the sample included: ionic components ($Na^+$, $NH_4{^+}$, $Ca^{2+}$, $Mg^{2+}$, $K^+$, $Cl^-$, $NO_3{^-}$ and $SO_4{^{2-}}$), carbonaceous components - organic carbon (OC) and elemental carbon (EC), and water-soluble organic carbon (WSOC). Also, secondary organic carbon (SOC) was measured based using the EC tracer method, and char-EC and soot-EC were calculated from the analytical results. The data obtained were interpreted in terms of temporal variation. Of the overall mean value of $PM_{2.5}$ mass concentration obtained during the study period, ionic components, OC and EC accounted for 45.3%, 19.7%, and 8.0%, respectively. $NO_3{^-}$ showed a unique seasonal distribution pattern due to a dependence on temperature and absolute humidity. It was estimated that an approximate temperature of $14^{\circ}C$, and absolute humidity of $7g/m^3$ were critical for the reversible reaction of $NH_4NO_3(p){\leftrightharpoons}NH_3(g)+HNO_3(g)$. The amount of OC and EC contributing to the monthly $PM_{2.5}$ mass concentration was higher in autumn and winter compared to spring and summer. This result could be attributed to the impact of burning biomass, since WSOC and the ratio of char-EC/soot-EC showed a similar pattern during the corresponding period. From the comparison of monthly WSOC/OC values, a maximum ratio of 83% was obtained in August (summer). The WSOC and estimated SOC levels derived from the EC tracer method correlated (R=0.77) in summer. The high occurrence of WSOC during summer was mainly due to the formation of SOC by photochemical reactions. Through long-term observation of $PM_{2.5}$ chemical components, we established that the degree to which the above-mentioned factors influence $PM_{2.5}$ composition, fluctuates with seasonal changes.

• Journal of Korean Society of Environmental Engineers
• /
• v.31 no.12
• /
• pp.1161-1168
• /
• 2009

This research was conducted on characteristic of offensive odors in Shihwa industrial complex. Result of blocks distribution of TVOC indicates that mechanic block, site D, was the highest concentration (74 ppb). Chemistry block, site A, was the second highest concentration (50 ppb). Also, mixed blocks, metal blocks and park etc. were measured almost similar concentration about 30 ppb, but mixed block, site F, was the place where concentrations were the smallest. Average of TVOC was shown about 35 ppb concentration. Aldehydes including acetaldehyde, butyraldehyde and hydrogen sulfide concentrations were prevalent among offensive odors in Shihwa industrial complex. Comparing the offensive odor intensity mostly about acetaldehyde, butyraldehyde and hydrogen sulfide which contain high offensive odor intensity showed results that sites A, B (chemistry block) and site D, I (mechanic block) site H (metal block) have showed the intensity over 1. In the case of acetaldehyde, relatively the high odor intensities over '2' were able to obtain in many cases. The correlation coefficient (r) for hydrogen sulfide was 0.91, so that high positive correlation exists between offensive odor intensity and the hydrogen sulfide element. Butyraldehyde also showed high positive correlation coefficient, as 0.82. Correlation coefficient of acetaldehyde that had the highest value as offensive odor substance was 0.62, had somewhat correlation with offensive odor intensity.

• Journal of the Korean association of regional geographers
• /
• v.12 no.5
• /
• pp.614-630
• /
• 2006

Improved estimates of populations at risk for quick and effective response to natural and man-made disasters require spatial disaggregation of zonal population data because of the spatial mismatch problem in areal units between census and impact zones. This paper implements a dasymetric surface model to facilitate spatial disaggregation of the population of a census block group into populations associated with each constituent pixel and evaluates the performance of the surface-based spatial disaggregation model visually and statistically. The surface-based spatial disaggregation model employed geographic information systems (GIS) to enable dasymetric interpolation to be guided by satellite-derived land use and land cover data as additional information about the geographic distributor of population. In the spatial disaggregation, percent cover based empirical sampling and areal weighting techniques were used to objectively determine dasymetric weights for each grid cell. The dasymetric population surface for the Atlanta metropolitan area was generated by the surface-based spatial disaggregation model. The accuracy of the dasymetric population surface was tested on census counts using the root mean square error (RMSE) and an adjusted RMSE. The errors related to each census track and block group were also visualized by percent error maps. Results indicate that the dasymetric population surface provides high-precision estimates of populations as well as the detailed spatial distribution of population within census block groups. The results also demonstrate that the population surface largely tends to overestimate or underestimate population for both the rural and forested and the urban core areas.

• Journal of the Korean association of regional geographers
• /
• v.17 no.1
• /
• pp.17-39
• /
• 2011

As recent inflows of foreign immigrants to relatively advanced countries in Northeast Asia have rapidly increased, Japan in particular uses 'multicultural coexistance' as a key concept for developing both discourse and policies on them. This paper is first of all to suggest a new typology of multicultural societies in the world ill order to differentiate the case of Northeast Asian countries from those of Western countries. And this paper is to suggest that foreign immigrants in Japan have different positions in labor markets and living experiences according to historical and social backgrounds as well as their nationality. The transformation process towards multicultural society is not only historical and social but also geographical and spatial, as foreign immigrants have made different spatial distribution and regional segregation in types. In order to control this socio-spatial process towards multicultural society, Japan has developed the concept of 'multicultural coexistence' similar with that of multiculturalism in Western countries. This concept seems to be quite significant as it has been initiated by local communities for symbiotic relationship between foreign immigrants and native Japanese dwellers. But it can be regarded as a strategic ideology to control foreign immigrants as it targets mainly on Nikkeijin, and is usually concerned with the cultural aspect. Seen from a theoretical point of view, this concept can be seen as closed with liberal multiculturalism as opportunity equity, but far from corporative multiculturalism as outcome equity, and it is on the process transferring from the first stage of tolerance to the second stage of legislation of nondiscrimination, while being distant from the third stage of legislation paradigmization of recognition, and hence appears to be easily reverted to assimilationism.

• Journal of Conservation Science
• /
• v.30 no.2
• /
• pp.169-179
• /
• 2014

After occurrence of Cyanobacteria in 1997, Songsan-ri tombs located in Gonju have been investigated to monitor for biological damage. The room temperature of Tomb No.6 was $18.6{\sim}19.8^{\circ}C$ and the relative humidity was 94.3~99.9%. The temperature of Royal Tomb of King Muryeong was $17.3{\sim}18.53^{\circ}C$ and the relative humidity was 73.2~96.45%. The variation of relative humidity increased after setting up air vents. If the outside temperature increases, dew condensation occurs on the floor and the north side. When conditioning equipment operates, the maximum temperature differences between walls is $2.8^{\circ}C$. Bacteria from the air of the tomb and on the surface of the walls outnumbered fungi. 20 species of fungi including Alternaria sp., Aspergillus sp., Penicillium sp., and 19 species of bacteria including Pseudomonas sp., Arthrobacter sp., are identified. Microbes in the tombs may damage cultural heritage. The growth possibility of microbes should be estimated because the microbes in the tombs may damage mural painting. The interrelation between microenvironmental condition and biological damage of mural painting should be researched to come up with an long-term conservation method.