• Journal of Environmental Science International
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• v.20 no.5
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• pp.555-564
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• 2011

This study examines the potential restoration of abandoned channels of the Mangyeong River in South Korea. To analyze the morphological changes and equilibrium conditions, a flow duration analysis was performed to obtain the discharge of 255 m3/s with a recurrence interval of 1.5 year. It is a gravel-bed stream with a median bed diameter of 36 mm. The reach-averaged results using HEC-RAS showed that the top width is 244 m, the mean flow depth is 1.11 m, the width/depth ratio is very high at 277, the channel velocity is 1.18 m/s, and the Froude number is also high at 0.42. The hydraulic parameters vary in the vicinity of the three sills which control the bed elevation. The total sediment load is 6,500 tons per day and the equivalent sediment concentration is 240 mg/l. The Engelund-Hansen method was closer to the field measurements than any other method. The bed material coarser than 33 mm will not move. The methods of Julien-Wargadalam and Lacey gave an equilibrium channel width of 83 m and 77 m respectively, which demonstrates that the Mangyeong River is currently very wide and shallow. The planform geometry for the Mangyeong River is definitely straight with a sinuosity as low as 1.03. The thalweg and mean bed elevation profiles were analyzed using field measurements in 1976, 1993 and 2009. The measured profiles indicated that the channel has degraded about 2 m since 1976. The coarse gravel material and large width-depth ratio increase the stability of the bed material in this reach.

• Journal of Environmental Health Sciences
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• v.36 no.3
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• pp.182-190
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• 2010

We examined the association of particulate matter with an aerodynamic diameter < $10\;{\mu}m$ ($PM_{10}$) with asthma-related hospitalization, stratified by socioeconomic status (SES), among children less than 15 years of age in Seoul, Korea, between 2003 and 2005. In addition, we estimated the reduction in the number of asthma-related hospitalizations that would result from implementing the World Health Organization (WHO) guideline. SES was defined based on data concerning health insurance premium grades, and grouped into two levels: lower-income group and control group. The lower-income group was classified as having an accumulated income which did not exceed the 50th percentile of the median income. Time-series analysis was performed to evaluate the association between $PM_{10}$ and asthma-related hospitalization. The Environmental Benefits Mapping and Analysis Program was used to analyze the impact on children's health. Based upon an increase of $10\;{\mu}g/m^3$ of $PM_{10}$, the asthma-related hospitalization risk for the lower-income group was increased by 1.78% (95% confidence intervals (CI) = 0.79-2.78%), while the risk for the control group was increased by 0.83% (95% CI = 0.34-1.32%). Attaining the WHO guideline, relative to the concentration in 2007, would result in a reduction in asthma-related hospitalizations of 18 cases per 100,000 of the children population in the lower-income group, and 7 cases in the control group. The health benefits of improved air quality for children in the lower-income group were thus 2.5 times greater than for children in the control group. Our results show that the lower-income group is disproportionately burdened with asthma-related hospitalization arising from air pollution. Therefore, biologically- and socioeconomically-disadvantaged populations should be considered in public health interventions in order to protect the children's health.

• Journal of Korea Water Resources Association
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• v.44 no.5
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• pp.417-427
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• 2011

The open-channel flow with submerged vegetation shows distinct features in two separate regions, namely upper and vegetation layers. In the upper layer, the flow is akin to the open-channel flow, while the flow in the vegetation layer is relatively uniform with suppressed turbulence due to vegetation stems. This paper presents laboratory experiments to investigate the characteristics of turbulent flows and suspended sediment transport in open-channel flows with submerged vegetation. An open-channel facility, 0.5 m wide and 12 m long, was used for laboratory experiments. Various discharges were employed with depth ratios of 2~3, and wooden cylinders were used for vegetation. To make equilibrium suspension, sediment particles of median diameter of 75 ${\mu}M$ were fed until capacity condition. Laser Doppler velocimeter was used to measure instantaneous velocity, and direct sampling with vinyl tube was used to measure the concentration of suspended sediment. Using the sampled data, the mean flow and turbulence structures were provided and characteristics of suspended sediment concentration with Rouse number were presented.

• Korean Chemical Engineering Research
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• v.61 no.1
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• pp.80-88
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• 2023

Ensuring safety in the designing of manufacturing and handling facilities for low-density polyethylene (LDPE) is difficult because there are no standards for the dust explosion characteristics of LDPE. In this study, a dust explosion test was performed on two dust samples collected from a bag filter (LDPE 1) during the LDPE manufacturing process and sedimentary dust (LDPE 2) leaked outside a facility such as a silo, and the LDPE 2 explosion test results were summarized. Particle size analysis showed that the volume-based particle diameter (median) was 95.04 ㎛ and the number density was 0-1 ㎛. The maximum explosion pressure (P_max) was 6.6 bar, and the maximum rate of explosion pressure rise was 366 [bar/s] at 1500 g/m³. Accordingly, the dust explosion index (K_st) was 99.4 bar·m/s, which was confirmed as ST-1 grade. Moreover, the minimum ignition energy and minimum ignition temperature was 10 mJ and 450 ℃, respectively. Currently, manufacturing and handling design is based on the characteristic values of high-density polyethylene (HDPE). However, as the test results show that LDPE 2 dust has a higher risk than HDPE (particle diameter 61.6 ㎛), caution is required when using the HDPE design criteria in the LDPE manufacturing process.

• Toxicological Research
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• v.29 no.2
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• pp.121-127
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• 2013

Nanotoxicological research has shown toxicity of nanomaterials to be inversely related to particle size. However, the contribution of agglomeration to the toxicity of nanomaterials has not been sufficiently studied, although it is known that agglomeration is associated with increased nanomaterial size. In this study, we prepared aerosols of nano-sized carbon black by 2 different ways to verify the effects of agglomeration on the toxicity and deposition of nano-sized carbon black. The 2 methods of preparation included the carbon black dispersion method that facilitated clustering without sonication and the carbon black dispersion method involving sonication to achieve scattering and deagglomeration. Male Sprague-Dawley rats were exposed to carbon black aerosols 6 hr a day for 3 days or for 2 weeks. The median mass aerodynamic diameter of carbon black aerosols averaged $2.08{\mu}m$ (for aerosol prepared without sonication; group N) and $1.79{\mu}m$ (for aerosol prepared without sonication; group S). The average concentration of carbon black during the exposure period for group N and group S was $13.08{\pm}3.18mg/m^3$ and $13.67{\pm}3.54mg/m^3$, respectively, in the 3-day experiment. The average concentration during the 2-week experiment was $9.83{\pm}3.42mg/m^3$ and $9.08{\pm}4.49mg/m^3$ for group N and group S, respectively. The amount of carbon black deposition in the lungs was significantly higher in group S than in group N in both 3-day and 2-week experiments. The number of total cells, macrophages and polymorphonuclear leukocytes in the bronchoalveolar lavage (BAL) fluid, and the number of total white blood cells and neutrophils in the blood in the 2-week experiment were significantly higher in group S than in normal control. However, differences were not found in the inflammatory cytokine levels (IL-$1{\beta}$, TNF-${\alpha}$, IL-6, etc.) and protein indicators of cell damage (albumin and lactate dehydrogenase) in the BAL fluid of both group N and group S as compared to the normal control. In conclusion, carbon black aerosol generated by sonication possesses smaller nanoparticles that are deposited to a greater extent in the lungs than is aerosol formulated without sonication. Additionally, rats were narrowly more affected when exposed to carbon black aerosol generated by sonication as compared to that produced without sonication.

• Journal of Korea Water Resources Association
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• v.44 no.1
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• pp.65-72
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• 2011

Natural streams meander, forming pools at the outer part of bend and riffles at the crossing. Pools are deep at a lower flow velocity, and riffles are shallow at a higher flow velocity. Attentions are being paid to pool-riffle sequences in meandering streams because pool-riffle sequences tend to increase biodiversity of the stream ecosystem. This study investigates the characteristics of distribution of bed sediment particles in the upstream reach of the Gap Stream, which is a tributary of the Geum River in Korea. The upstream part of the Gap Stream, the study reach, is a gravel-bed stream, showing a pool and three riffles due to meandering. The reach also includes pools at the upstream and downstream parts of the weir. The characteristics of bed sediment particles sampled at the wetland and in the side channel are studied, revealing that the median particle diameter in the riffle is about four times larger than that in the pool. In addition, flow simulations are carried out for ordinary discharge and design flood, and such parameters important to sediment transport as velocity, shear stress, dimensionless shear stress (or Shields number), and dimensionless shear velocity are provided to see the mobility of sediment particles in the pool-riffle sequence.

• Journal of Korean Neurosurgical Society
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• v.60 no.5
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• pp.584-590
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• 2017

Objective : Traumatic brain injury (TBI) in children under age 24 months has characteristic features because the brain at this age is rapidly growing and sutures are opened. Moreover, children this age are completely dependent on their parents. We analyzed the demographic data and risk factors for outcomes in TBI patients in this age group to elucidate their clinical characteristics. Methods : We retrospectively reviewed the medical records and radiological films of children under 24 months who were admitted to Kyungpook National University Hospital from January 2004 to December 2013 for TBI. Specifically, we analyzed age, cause of injury, initial Glasgow coma scale (GCS) score, radiological diagnosis, seizure, hydrocephalus, subdural hygroma, and Glasgow outcome scale (GOS) score, and we divided outcomes into good (GOS 4-5) or poor (GOS 1-3). We identified the risk factors for post-traumatic seizure (PTS) and outcomes using univariate and multivariate analyses. Results : The total number of patients was 60, 39 males and 21 females. Most common age group was between 0 to 5 months, and the median age was 6 months. Falls were the most common cause of injury (n=29, 48.3%); among them, 15 were falls from household furniture such as beds and chairs. Ten patients (16.7%) developed PTS, nine in one week; thirty-seven patients (61.7%) had skull fractures. Forty-eight patients had initial GCS scores of 13-15, 8 had scores of 12-8, and 4 had scored 3-7. The diagnoses were as follows : 26 acute subdural hematomas, 8 acute epidural hematomas, 7 focal contusional hemorrhages, 13 subdural hygromas, and 4 traumatic intracerebral hematomas larger than 2 cm in diameter. Among them, two patients underwent craniotomy for hematoma removal. Four patients were victims of child abuse, and all of them had PTS. Fifty-five patients improved to good-to-moderate disability. Child abuse, acute subdural hematoma, and subdural hygroma were risk factors for PTS in univariate analyses. Multivariate analysis found that the salient risk factor for a poor outcome was initial GCS on admission. Conclusion : The most common cause of traumatic head injury in individuals aged less than 24 months was falls, especially from household furniture. Child abuse, moderate to severe TBI, acute subdural hematoma, and subdural hygroma were risk factors for PTS. Most of the patients recovered with good outcomes, and the risk factor for a poor outcome was initial mental status.

• Korean Journal of Fisheries and Aquatic Sciences
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• v.17 no.2
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• pp.151-156
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• 1984

The Chili fish, one of the most common species of the freshwater fishes, is distributed in the river basins of the western coast of Korea. However, any studies on this fish, especially its development or life history, have not been made so far. The authors, therefore, carried out an experiment to reveal some characteristics of egg develoment and fry in this fish. For accomplshing this study, we caught some adult Chili fish by means of a casting net at raceway in the vicinity of Kunsan in June and July, 1983; then, we injected 0. 1 cc Gonadotrophic hormone 1,000 unit solution (Puberogen) in order to induce the spawning on the abdominal cavity of male and female respectively, Approximately 12 hours after injection, the artificially fertilized eggs by using of the dry method and the naturally fertilized eggs were observed simultaneously in the aquarium ($30{\times}50{\times}70cm$). The fertilized eggs, in spherical shape, were sperative, demersel, adhesive nature and $1.38{\sim}1.59\;mm$ in diameter. The light yellow yolk was opaque and $1.17{\sim}l.27\;mm$ in diameter. The hatching of eggs took place at 29.5 hours after fertilization under the condition of $23.5{\sim}25.0^{\circ}C$ water temperature. Basically there were not found so many different aspects in comparison with the common species of Cyprinidae in the development process of eggs : however, there were a few noticable characteristics, that is, pigment cells, eye balls and blood circulation are invisible, or the velocity of egg development is rapid, seemed similar to the Loach's egg. Newly hatched larvae with the yolk sac (2.39 mm in size) were $3.87{\sim}3.99\;mm$ in total length and their myotome number was expressed as 28+15=43. About 20 hours after hatching, a caudal and a pectoral fin as well as an anus began to orgin. In addition, a few malanophore showed on the upper regin of the yolk sac of the larvae whose size was 4.73 mm in total length. The larvae developed about 5.02 mm in total length, and the median fin fold in the abdomen extended forward to two thirds or beyond of the yolk sac at 50 hours after hatching. Simultaneously, the eye balls and mouth also appeared. After 3 days, the yolk sac nearly disappeared, and the larvae (5.4 mm in total length) with perfect eye balls began to swim for themselves for the first time. Also, the specialization between the gill arches and the ailmentary canal, the development of each fins except dorsal fin as well as the blood circulation obviously distinguished in this stage. The larvae whose total length was 5.68 mm was very brisk: also, the development of the dorsal fin rudiment, nearly perfect formation of each organs and the function of the upper and lower jaws were noticeably observed 5 days after hatching.

• Radiation Oncology Journal
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• v.20 no.4
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• pp.303-308
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• 2002

Purpose : To determine the optimal radiation dose in a localized non-Hodgkin's lymphoma of the head and neck in the treatment setting for combined chemoradiotherapy. Materials an Methods :Fifty-three patients with stage I and II diffuse large ceil non-Hodgkin's lymphoma of the head and neck, who were treated with combined chemoradiotherapy between 1985 and 1998 were retrospectively reviewed. The median age was 49 years, and the male-to-female ratio was approximately 1.6. Twenty-seven patients had stage 1 disease and 26 had stage II. Twenty-three patients had bulky tumors $(\geq5\;cm)$ and 30 had non-bulky tumors (<5 cm). The primary tumors arose mainly from an extranodal organ $(70\%)$, most cases involving Waldeyer's ring $(90\%)$. All patients except one were initially treated with $3\~6$ cycles of chemotherapy, which was followed by radiotherapy. Radiation was delivered either to the primary tumor area alone $(9\%)$ or to the primary tumor area plus the bilateral neck nodes $(91\%)$ with a minimum dose of 30 Gy $(range\;30\~60\;Gy)$. The failure patterns according to the radiation field were analyzed, and the relationship between the dose and the in-field recurrence was evaluated. Results : The 10-year overall survival and the 10-year disease free survival rates were similar at $75\%\;and\;76\%$, respectively. A complete response (CR) after chemotherapy was achieved in 44 patients $(83\%)$. Subsequent radiotherapy showed a CR in all patients. Twelve patients $(23\%)$ had a relapse of the lymphoma after the initial treatment. Two of these patients had a recurrence inside the radiation field. No clear dose response relationship was observed and no significant prognostic factors for the in-field recurrences were identified because of the small number of in-field recurrences. However, for patients with tumors <5 cm in diameter, there were no in-field recurrences after a radiation dose 30 Gy. The 2 in-field recurrences encountered occurred in patients with a tumor $\geq5\;cm$. Conclusion .A dose of 30 Gy is sufficient for local control in patients with a non-bulky (<5 cm), localized, diffuse large cell non-Hodgkin's lymphoma when combined with chemotherapy. An additional boost dose in the primary site is recommended for patients with bulky tumors $(\geq5\;cm)$.

• Restorative Dentistry and Endodontics
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• v.32 no.1
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• pp.19-27
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• 2007

The purpose of this study is to develope new dental color-space system. Twelve kinds of dental composites and one kind of dental porcelain were used in this study. Disk samples (15 mm in diameter, 4 mm in thickness) of used materials were made and sample's CIE $L^*a^*b^*$ value was measured by Spectrocolorimeter (MiniScan XE plus, Model 4000S, diffuse/$8^{\circ}$ viewing mode, 14.3 mm Port diameters, Hunter Lab USA) The range of measured color distribution was analyzed. All the data were applied in the form of T### which is expression unit in CNU Cons Dental Color Chart. The value of $L^*$ lies between 80.40 and 52.70. The value of $a^*$ are between 10.60 and 3.60 and $b^*$ are between 28.40 and 2.21. The average value of $L^*$ is 67.40, and median value is 67.30. The value of $a^*$ are 2.89 and 2.91 respectively. And for the $b^*$, 14.30 and 13.90 were obtained. The data were converted to T### that is the unit count system in CNU-Cons Dental Color Chart. The value of $L^*$ is converted in the first digit of the numbering system. Each unit is 2.0 measured values. The second digit is the value of $a^*$ and is converted new number by 1.0 measured value. For the third digit $b^*$ is replaced and it is 2.0 measured unit apart. T555 was set to the value of $L^*$ ranging from 66.0 to 68.0, value of $a^*$ ranging from 3 to 4 and $b^*$ value ranging from 14 to 16.