• Journal of Korean Society on Water Environment
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• v.32 no.3
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• pp.271-280
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• 2016

The aim of this study was to analyze spatial and temporal patterns of bacterial pollution levels and the relationship between bacterial pollutants and environmental parameters at the main stream and tributaries of Nakdong River. Water quality data including total coliform and fecal coliform were compiled from a total of 50 monitoring sites (30 at the main stream and 20 at the tributaries) along with rainfall and discharge data for three consecutive years from 2012 to 2014. During the study periods, the geometric mean values of total coliforms and fecal coliforms in the main stream were 74 (22~465) CFU/100 mL and 8 (3~42) CFU/100 mL, respectively. The geometric mean values of total coliforms and fecal coliforms in the tributaries were 275 (36~5,145) CFU/100 mL and 6 (1~1,352) CFU/100 mL, respectively. High concentrations of fecal coliforms were observed at Gumi (M 10), Hyeonpung (M 19), Hapcheon (M 23), and Namji (M 25) in the main stream, whereas Gamcheon (T 6), Bakcheon (T 7), Geumho-gang (T 8), and Gyeseongcheon (T 16) were identified as pollution hot spots in the tributaries. Although bacterial pollution levels showed complex behavior across monitoring sites and time, the highest coliform concentrations were routinely observed in the monsoon season between July and September of each year, indicating that the pollution levels were strongly dependent on precipitation in addition to other physiochemical parameters. Statistically significant correlations were found between fecal coliform concentrations and precipitation (r=0.403, p<0.01), followed by SS (r=0.425, p<0.01), nutrient TP (r=0.388, p<0.01), organic matter COD (r=0.322, p<0.01), and PO₄-P (r=0.317, p<0.01) in the main stream in the order of correlation coefficient from high to low.

• Journal of Korea Water Resources Association
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• v.42 no.10
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• pp.891-896
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• 2009

The puff models have been developed to simulate the advection-diffusion processes of dredging suspended solids, either alone or in combination with Eulerian models. Computational efficiency and accuracy are of prime importance in designing these hybrid approaches to simulate a pollutant discharge, and we characterize two relatively simple Lagrangian techniques in this regard: forward Gaussian puff tracking (FGPT), and backward Gaussian puff tracking (BGPT). FGPT and BGPT offer dramatic savings in computational expense, but their applicability is limited by accuracy concerns in the presence of spatially variable flow or diffusivity fields or complex no-flux or open boundary conditions. For long simulations, particle and/or puff methods can transition to an Eulerian model if appropriate, since the relative computational expense of Lagrangian methods increases with time for continuous sources. Although we focus on simple Lagrangian models that are not suitable to all environmental applications, many of the implementation and computational efficiency concerns outlined herein would also be relevant to using higher order particle and puff methods to extend the near field.

• Journal of Korean Society of Transportation
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• v.21 no.5
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• pp.97-110
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• 2003

The sight distance at unsignalized intersections is the one of the fundamental geometric design elements, and can ensure safety and efficient operations. Despite its importance, little research attention has been directed in Korea compared to developed countries such as European countries, the United States, and Japan. AASHTO ISD policies have been applied to the intersection design in Korea without any revise, which can produce unrealistic and unadoptable design values. Those values are emerged from several reasons because the AASHTO ISD has been calibrated based on the local data. Therefore the ISD hardly takes into account the local characteristics of Korea such as driving behavior. vehicular movement and roadway conditions. The objective of this study is to calculate the appropriate ISD values for unsignalized intersections in the urban area in Korea. In this study, we employed the ISD model of AASHTO(2001), which is based on gap acceptance theory and can account for and take the driving and roadway conditions in Korea into consideration. The approach can also consider the complex driving maneuvers at the intersections in a proper and simple manner. The results in this study show that the ISD design criteria currently used in Korea are more conservative(safer) than those of the USA. In other words, the ISD using field data collected in this study has generally smaller values than those in USA.

• Bulletin of the Korean Chemical Society
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• v.32 no.9
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• pp.3295-3305
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• 2011

Thermal behavior of poly (methyl methacrylate) was analyzed in the presence of tin (IV) chloride. Five different proportions - polymer to additive - were selected for casting films from common solvent. TG, DTG and DTA were employed to monitor thermal degradation of the systems. IR and py-GC-MS helped identify the decomposition products. The blends start degrading at a temperature lower than that of the neat polymer and higher than that of the pure additive. Complex formation between tin of additive and carbonyl oxygen (pendent groups of MMA units) was noticed in the films soon after the mixing of the components in the blends. The samples were also heated at three different temperatures to determine the composition of residues left after the expulsion of volatiles. The polymer, blends and additive exhibited a one step, two-step and three-step degradation, respectively. $T_0$ is highest for the polymer, lowest for the additive and is either $60^{\circ}C$ or $70^{\circ}C$ for the blends. The amount of residue increases down the series [moving from blend-1 (minimum additive concentration) to blend-5 (maximum additive concentration)]. For blend-1, it is 7% of the original mass whereas it is 16% for blend-5. $T_{max}$ also goes up as the concentration of additive in the blends is elevated. The complexation appears to be the cause of observed stabilization. Some new products of degradation were noted apart from those reported earlier. These included methanol, isobutyric acid, acid chloride, etc. Molecular-level mixing of the constituents and "positioning effect" of the additive may have brought about the formation of new compounds. Routes are proposed for the appearance of these substances. Horizontal burning tests were also conducted on polymer and blends and the results are discussed. Activation energies and reaction orders were calculated. Activation energy is highest for the polymer, i.e., 138.9 Kcal/mol while the range for blends is from 51 to 39 Kcal/mol. Stability zones are highlighted for the blends. The interaction between the blended parts seems to be chemical in nature.

• Journal of the HCI Society of Korea
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• v.13 no.2
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• pp.31-44
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• 2018

In the IoT environment, various things could be connected. Those connected things learn and operate themselves, by acquiring data. As human being, they have self-learning and self-operating systems. In the field of IoT study, therefore, the key issue is to design communication system connecting both of the two different types of subjects, human being(user) and the things. With the advent of the IoT environment, much research has been done in the field of UI design. It can be seen that research has been conducted to take complex factors into account through keywords such as multi-modality and interusability. However, the existing UI design method has limitations in structuring or testing interaction between things and users of IoT environment. Therefore, this paper suggests a new UI prototyping method. In this paper, the major analysis and studies are as follows: (1) defined what is the behavior process of the things (2) analyzed the existing IoT product (3) built a new framework driving personality types (4) extracted three representative personality models (5) applied the three models to the smart home service and tested UI prototyping. It is meaningful with that this study can confirm user experience (UX) about IoT service in a more comprehensive way. Moreover, the concept of the personality of things will be utilized as a tool for establishing the identity of artificial intelligence (AI) services in the future.

• Journal of the Korean Geotechnical Society
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• v.30 no.4
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• pp.35-45
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• 2014

Limit equilibrium methods of slope stability analysis have been widely adopted mainly due to their simplicity and applicability. However, the conventional methods may not give reliable and convincing results for various geological conditions such as nonhomogeneous and anisotropic soils. Also, they do not take into account soil slope history nor the initial state of stress, for example excavation or fill placement. In contrast to the limit equilibrium analysis, the analysis of deformation and stress distribution by finite element method can deal with the complex loading sequence and the growth of inelastic zone with time. This paper proposes a technique to determine the critical slip surface as well as to calculate the factor of safety for shallow failure on partially saturated soil slope. Based on the effective stress field in finite element analysis, all stresses are estimated at each Gaussian point of elements. The search strategy for a noncircular critical slip surface along weak points is appropriate for rainfall-induced shallow slope failure. The change of unit weight by seepage force has an effect on the horizontal and vertical displacements on the soil slope. The Drucker-Prager failure criterion was adopted for stress-strain relation to calculate coupling hydraulic and mechanical behavior of the partially saturated soil slope.

• Korea Journal of Hospital Management
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• v.25 no.2
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• pp.45-56
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• 2020

Purpose: The purpose of this study is to investigate medical care behaviors influencing accuracy of the payment based New diagnosis-related groups (DRG) compared to fee for service (FFS) in hospitalized patients with medical illness. Methodology: In order to estimate the difference in medical costs between New DRG and FFS depending on medical care behaviors, medical records and hospital claims data (n=4,232) were utilized, which were collected from a single public hospital during the first-half of 2018. Data were analyzed by descriptive statistics, t-test, chi-square test, and multivariate binary logistic regression. Findings: The average difference in medical costs between New DRG and FFS were KRW 506,711±13,945 with incentives and KRW -51,506±12,979 without incentives, respectively. Forty-four point two percent (44.2%, n=1,872) of total subjects were shown to have negative compensation in overall medical costs with New DRG compared to the costs with FFS. Medical care behaviors that affected on the negative compensation were the presence of severe bed sores on admission, medical consultations, death, operations, medications and laboratory or imaging tests with unit price over KRW 100,000, hospital-acquired complications or underlying comorbidities, elderly patients (≧65 years), and hospitalized for more than average inpatient days defined by New DRG (p<0.001). The difference in average medical cost between New DRG and FFS for a group with mild illness was KRW -11,900±10,544, whereas it was KRW -196,800±46,364 for a group with severe illness (p<0.0001). Practical Implications: These findings suggest that New DRG payment model without incentives may incompletely cover the variation of medical costs in real clinical practice. Therefore, policy makers need to consider that the current New DRG reimbursement should be focused and refined to improve accuracy of payment on medical care resources utilized in severe and complex medical conditions.

• Journal of the korean academy of Pediatric Dentistry
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• v.43 no.3
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• pp.327-333
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• 2016

Tourette's syndrome is a chronic neuropsychiatric disorder characterized by the presence of vocal and multiple motor tics. Tics are defined as brief, intermittent, repetitive, unpredictable, purposeless, and stereotyped movements or sounds. Some patients experience physical pain from intense and complex tics. In addition, motor tics can result in self-injury which is a common feature of Tourette's syndrome. A 9-year-old boy was referred by the department of neuropsychiatry because of a severe tongue laceration. His parents reported that he had been biting his tongue irregularly for 2 months before referral and suffered from an intense burning sensation. The repeated biting resulted in ulcers on the tongue, which quickly worsened and led to progressive difficulty chewing and swallowing food. We offered to give him a two-piece removable appliance to limit tongue biting; it was made of soft silicone and fitted to both the maxillary and mandibular arches. As we emphasized that the device could help alleviate his pain, he agreed to accept it and adapted well. Just 3 weeks later, his tongue lesions had healed significantly.

• Journal of the Korean GEO-environmental Society
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• v.18 no.5
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• pp.55-60
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• 2017

It is critical for Korea to make effective use of limited space as it has dense population and high traffic volume compared to its terrestrial area. To resolve this issue, diverse types of underground structures have increasingly been applied so far, and one of the most representative structures is double-deck tunnel. It has upper and lower roads separated by middle slab that shows dynamic behavior according to the vehicle and earthquake loads. In case of the characteristics of earthquake response, it is necessary to have exploratory study as it has high loads, complex working mechanism, and difficult theoretical approach. In order to understand the characteristics of earthquake response based on the supporting conditions of middle slab in double-deck tunnel, this study conducts indoor shaking table test with 3 test cases: (1) fix both brackets, (2) free and fix at each bracket and (3) free at both brackets for 2 seismic waves of artificial and Gyeongju earthquake. The result shows if the middle slab is free at both brackets, the acceleration response is reduced 41% for artificial earthquake and 60% for Gyeongju earthquake compared to the one with fix at both brackets.

• Korean Chemical Engineering Research
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• v.50 no.6
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• pp.1056-1063
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• 2012

Recent rapidly growth in nanotechnolgies is promised novel benefits through the exploitation of their unique industrial and biomedical applications. With increasing utilization of nanomaterials in consumer products, the potential release of nanomaterials into the environment and their impacts on the ecosystem and human health have been the issues of concern. Nanomaterials that was exposed unintentionally in environment might be accumulated in various environmental media, and finally it will be influenced to human and ecosystems. Therefore, it is important to understand the fate and behavior of nanoparticles for understanding effects on environmental media (air, water, and soil phase). Therefore, in this work, we investigated the several cases for environmental exposure of nanomaterials and suggested the direction of further research. In workplace, exposure to air media is dominant, but finally waste and wastewater was moved to the water and soil phase. In addition, we found the existing sewage treatment plant was not suitable to remove completely nanomaterials in wastewater flow. To deeper study, environmental monitoring tool must be developed additionally and we suggested the several analyzing method for aged and pristine physicochemical properties of nanomaterials exposed into environmental media. This review for nanomaterials' exposure to environmental media will be helpful to investigate the environmental fate of nanomaterials and define the suitable treatment method for nano-waste.