• Environmental Engineering Research
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• v.22 no.2
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• pp.203-209
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• 2017

Innovations in the biofiltration process can provide effective solutions to overcome crucial water pollution problems. The elimination of pollutants is a result of the combined effects of biological oxidation, adsorption and filtration processes. This research aims to evaluate the performance of quartz sand biofiltration for removing total suspended solids, turbidity, color, organic matter, and ammonium from polluted river water and develop an empirical model for designing quartz sand biofilters for the treatment of polluted river water. Experiments were conducted using two biofilter units filled with quartz sand as filter media. A set of experiments were performed to evaluate the effect of hydraulic retention time on biofilter performance in removing water contaminants. The kinetics of organic matter removal were also determined to describe the performance of the biofilter. The results show that biofiltration can significantly remove river water pollutants. Removal efficiency depends on the applied hydraulic retention time. At a hydraulic retention time of two hours, removal efficiencies of total organics, ammonium and total suspended solids were up to 78%, 82%, and 91%, respectively. A model for designing quartz sand biofiltration has been developed from the experimental data.

• Restorative Dentistry and Endodontics
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• v.38 no.2
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• pp.65-72
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• 2013

Objectives: To evaluate the inhibitory effect of ursolic acid (UA)-containing composites on Streptococcus mutans (S. mutans) biofilm. Materials and Methods: Composite resins with five different concentrations (0.04, 0.1, 0.2, 0.5, and 1.0 wt%) of UA (U6753, Sigma Aldrich) were prepared, and their flexural strengths were measured according to ISO 4049. To evaluate the effect of carbohydrate source on biofilm formation, either glucose or sucrose was used as a nutrient source, and to investigate the effect of saliva treatment, the specimen were treated with either unstimulated whole saliva or phosphate-buffered saline (PBS). For biofilm assay, composite disks were transferred to S. mutans suspension and incubated for 24 hr. Afterwards, the specimens were rinsed with PBS and sonicated. The colony forming units (CFU) of the disrupted biofilm cultures were enumerated. For growth inhibition test, the composites were placed on a polystyrene well cluster, and S. mutans suspension was inoculated. The optical density at 600 nm ($OD_{600}$) was recorded by Infinite F200 pro apparatus (TECAN). One-way ANOVA and two-way ANOVA followed by Bonferroni correction were used for the data analyses. Results: The flexural strength values did not show significant difference at any concentration (p > 0.01). In biofilm assay, the CFU score decreased as the concentration of UA increased. The influence of saliva pretreatment was conflicting. The sucrose groups exhibited higher CFU score than glucose group (p < 0.05). In bacterial growth inhibition test, all experimental groups containing UA resulted in complete inhibition. Conclusions: Within the limitations of the experiments, UA included in the composite showed inhibitory effect on S. mutans biofilm formation and growth.

• Journal of Adhesion and Interface
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• v.20 no.4
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• pp.155-161
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• 2019

Understanding charge transport anisotropy at the interface of conjugated nanostructures basically gives insight into structure-property relationship in organic field-effect transistors (OFET). Here, the anisotropy of the field-effect mobility at the interface between 6,13-bis(triisopropylsilylethynyl) pentacene (TIPS-pentacene) single crystal with cofacial molecular stacks in a-b basal plane and SiO gate dielectric was investigated. A solvent exchange method has been used in order for TIPS-pentacene single crystals to be grown on the surface of SiO₂ thin film, corresponding to the charge accumulation at the interface in OFET structure. In TIPS-pentacene OFET, the anisotropy ratio between the highest and lowest measured mobility is revealed to be 5.2. By analyzing the interaction of a conjugated unit in TIPS-pentacene with the nearest neighbor units, the mobility anisotropy can be rationalized by differences in HOMO-level coupling and hopping routes of charge carriers. The theoretical estimation of anisotropy based on HOMO-level coupling is also consistent with the experimental result.

• Journal of the Korean Association of Geographic Information Studies
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• v.20 no.4
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• pp.15-23
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• 2017

The WGS conversion project of cadastral drawing (promoted by the Ministry of Land) is not able to reflect the cadastral registration due to subtle differences such as area and location. When converting the digital cadastral region to the world geodetic system, the boundary point coordinates must be changed to the legal coordinate units. However, there is a phenomenon that occurs in which the minute area changes do not coincide with the area registered in the cadastral registration when the coordinate unit is changed. In this study, we have developed a method to adjust many parcels collectively by applying a passive fine-tuning method used in cadastral resurvey project to solve these problems. Total 1, total 2+1, interval 1, interval 2+1, etc. were classified based on the number of parcels that need to be considered for the range of adjustment and the area condition. The analysis of the experimental area (after developing SW for comparison of each method) showed that the total 2+1 method is suitable for the location accuracy and the interval 2+1 method is suitable for the temporal efficiency.

• Bulletin of the Korean Chemical Society
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• v.31 no.6
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• pp.1704-1710
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• 2010

The structure of a 2D grid-like copper(II) complex [Cu$(NCO)_2$(pyz)](pyz=pyrazine) (1) consists of 1D chains of Cu-pyz units connected by double end-on (EO) cyanato bridges. Each Cu(II) ion has a distorted octahedral coordination, completed by the four EO cyanato and two pyrazine ligands. Magnetic interactions through EO cyanato and pyrazine bridges in 1 are discussed on the basis of DFT broken-symmetry calculations at the B3LYP level. For model dicopper(II) complexes I (bridged by cyanato) and II (bridged by pyrazine), electronic structure calculations reproduce very well the experimental couplings for the S = 1/2 ferromagnetic and antiferromagnetic exchange-coupled 2D system: the calculated exchange parameters J are +1.25 $cm^{-1}$ and -3.07 $cm^{-1}$ for I and II, respectively. The $\sigma$ orbital interactions between the Cu $x^2-y^2$ magnetic orbitals and the nitrogen lone-pair orbitals of pyrazine are analyzed from the viewpoint of through-bond interaction. The energy splitting of 0.106 eV between two SOMOs indicates that the superexchange interaction should be antiferromagnetic in II. On the other hand, there are no bridging orbitals that efficiently connect the two copper(II) magnetic orbitals in I because the HOMOs of the basal-apical NCO bridge do not play a role in the formation of overlap interaction pathway. The energy separation in the pair of SOMOs of I is calculated to be very small (0.054 eV). This result is consistent with the occurrence of weakly ferromagnetic properties in I.

• Journal of Korean Elementary Science Education
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• v.39 no.3
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• pp.449-463
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• 2020

This study was to analysis teaching strategies, types of inquiry activities and the relationship between science concepts and inquiry activities presented in science textbooks. As a result of the study, first, the inquiry-based teaching strategies presented in science textbooks were experiment, simulation, demonstration, and field study. Second, there were 53 inquiry activities presented in 8 units related to the earth science area of science textbooks, and the types of inquiry activities were experimental observation (EO) 18, mock activity (SA) 20, investigation discussion and presentation (IP). It was analyzed as 12, data interpretation (ID) 2, and express (EX) 1 piece. Third, the relationship between inquiry activities and science concepts presented in science textbooks was analyzed. As a result of the analysis, out of a total of 42 inquiry activities, 21 inquiry activities corresponded to EA (explicit activities), in which the result of inquiry activities was directly and explicitly linked to science concepts. And IA (implicit activities), which is an implicit inquiry activity in which science concepts must be inferred using the results of inquiry activities, were analyzed as 21. In particular, IA (implicit activities), which is an implicit inquiry activity, can be said to be the result of reflecting the characteristics of earth science areas where many simulated activities (SA) are used. This is considered to be a matter to be considered in the process of developing various elementary science textbooks in the future.

• The Journal of the Acoustical Society of Korea
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• v.35 no.6
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• pp.491-500
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• 2016

The present study describes the acoustical characteristics of the new noise barriers which can control not only noise but also wind pressure by allowing air flow through barriers. In order to investigate the sound reduction index of the air transparent noise barrier, 17 models in total were examined with various size of openings and the volume of the resonators. As a result, it was found that the sound reduction index varies with the volume of the resonator and the area of the openings. Also, it was revealed that double layer of units has more sound reduction index than the single layer of unit at the frequency band from 400 Hz to 1250 Hz. This denoted that physical features of openings and resonators affect the sound reduction index of the air transparent noise barrier.

• Korean Journal of Air-Conditioning and Refrigeration Engineering
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• v.16 no.11
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• pp.1051-1059
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• 2004

Two phase thermosyphone loop for electronics cooling are designed and manufactured to test its performance under the partial load and low environment temperature conditions. The thermosyphone device has six evaporators connected parallel for the purpose of cooling six power amplifier units (PAU) independently. The heater modules for simulating PAUs are adhered with thermal pad to the evaporator plates to reduce the contact resistance. There are unbalanced distributions of liquid refrigerant in the differently heated evaporators due to the vapor pressure difference. To reduce the vapor pressure differences caused by partial heating, two evaporators are connected each other using the copper tube. The pressure regulation tube successfully reduces these unbalances and it is good candidates for a field distributed systems. Under the low environment temperature operating condition, such as $-30^{\circ}C$, there may be unexpected subcooling in condenser. It leads the very low saturation pressure, and under this condition there exists explosive boiling in evaporator. The abrupt pressure rise due to the explosive boiling inhibits the supplement of liquid refrigerant to the evaporator for continuous cooling. Finally the cooling cycle will be broken. For the normal circulation of refrigerant there may be an optimum cooling air flow rate in condenser to adjust the given heat load.

• The KIPS Transactions:PartB
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• v.18B no.1
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• pp.45-50
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• 2011

Unknown morpheme errors in Korean morphological analysis are divided into two types: The one is the errors that a morphological analyzer entirely fails to return any morpheme sequences, and the other is the errors that a morphological analyzer returns incorrect combinations of known morphemes. Most previous unknown morpheme estimation techniques have been focused on only the former errors. This paper proposes a unknown morpheme estimation method which can handle both of the unknown morpheme errors. The proposed method detects Eojeols (Korean spacing units) that may include unknown morpheme errors using SVM (Support Vector Machine). Then, using CRFs (Conditional Random Fields), it segments morphemes from the detected Eojeols and annotates the segmented morphemes with new POS tags. In the experiments, the proposed method outperformed the conventional method based on the longest matching of functional words. Based on the experimental results, we knew that the second type errors should be dealt with in order to increase the performance of Korean morphological analysis.

• Journal of the Institute of Convergence Signal Processing
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• v.4 no.3
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• pp.34-40
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• 2003

The paper presents a method to detect dissolve shots of video scene change detections in an MPEG compressed domain. The proposed algorithm uses color-R DCT coefficients of Ⅰ, P-frames for a fast operation and accurate detection and a minimum decoding process in MPEG sequences. The paper presents a method to detect dissolve shot for three-dimensional visualization and analysis of Image in order to recognize easily in computer as a human detects accurately shots of scene change. First, Color-R DCT coefficients for 8*8 units are obtained and the features are summed in a row. Second, Four-step analysis are Performed for differences of the sum in the frame sequences. The experimental results showed that the algorithm has better detection performance, such as precision and recall rate, than the existing method using an average for all DC image by performing four step analysis. The algorithm has the advantage of speed, simplicity and accuracy. In addition. it requires less amount of storage.