• Environmental and Resource Economics Review
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• v.16 no.2
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• pp.213-237
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• 2007

Discussions on regionalization of the world crude oil markets have provided important implications for the establishment of national energy policies. In particular, due to arbitrage trading, if these markets are regionalized, Korea who imports approximately 80% of the annual oil consumption from a single region may be faced with a crucial problem. Therefore, in this study, we analyzed regionalization of the world crude oil markets using causality analysis as well as cointegration method to consider temporal relationship and time lags. To analyze regionalization, we chose Dubai price for the Middle East market, Brent for the European, WTI for the U.S., and Tapis for the East Asian. For the case that long-run equilibrium existed between market prices, we used vector error correction model to analyze causal relationship, and for the case that equilibrium did not exist, we used Hsiao (1981)'s framework that can consider asymmetric time lags in the model for causality analysis. By the results of cointegration analysis, there did not exist long-run equilibrium among Dubai price and the other prices. However, we found the causal relationship among Dubai price and the other prices with one to four weeks time lags. Therefore, in effect, we could conclude that the world crude oil markets are unified supporting Adelman (1984)'s hypothesis.

• The korean journal of orthodontics
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• v.41 no.2
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• pp.87-97
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• 2011

Objective: Facial asymmetry is usually evaluated from the difference in length and angulation of the maxilla and mandible. However, asymmetric position or shape of the condyle can also affect the expression of asymmetry. The purpose of this study was to evaluate the correlation between condylar asymmetry and chin point deviation in facial asymmetry. Methods: Cone-beam CT images of fifty adult skeletal Class III patients were studied. Thirty patients who had more than 4 mm menton deviation were categorized in the asymmetric group. Twenty patients with less than 4 mm menton deviation were assigned to the symmetric group. Anteroposterior and transverse condyle positions were evaluated from the cranial base. The greatest mediolateral diameter (GMD) of the condyle in the axial plane and angulation to the coronal plane were measured. The height and volume of the condyles were evaluated. Results: The symmetric group had no statistical difference between both condyles in position, angulation, GMD, height and volume. In the asymmetric group, the non-deviated side condyle was larger in GMD, height and volume than the deviated side. There was no statistical difference in condyle position and angulation. The GMD, height difference and condylar volume ratio (non-deviated/deviated) were positively correlated with chin deviation. From the linear regression analysis, condylar volume ratio was a significant factor affecting chin deviation. Conclusions: These findings suggests that the non-deviated side condyle is larger than the deviated side. In addition, condylar asymmetry can affect the expression of facial asymmetry.

• Proceedings of the Membrane Society of Korea Conference
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• 1999.07a
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• pp.39-42
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• 1999

Perfluoropolymers represent the ultimate resistance to hostile chemical environments and high service temperature, attributed to the presence of fluorine in the polymer backbone, i.e. to the high bond energy of C-F and C-C bonds of fluorocarbons. Copolymers of Tetrafluoroethylene (TEE) and 2, 2, 4Trifluoro-5Trifluorometoxy- 1, 3Dioxole (TTD), commercially known as HYFLON AD, are amorphous perfluoropolymers with glass transition temperature (Tg)higher than room temperature, showing a thermal decomposition temperature exceeding 40$0^{\circ}C$. These polymer systems are highly soluble in fluorinated solvents, with low solution viscosities. This property allows the preparation of self-supported and composite membranes with desired membrane thickness. Symmetric and asymmetric perfluoropolymer membranes, made with HYFLON AD, have been prepared and evaluated. Porous and not porous symmetric membranes have been obtained by solvent evaporation with various processing conditions. Asymmetric membranes have been prepared by th wet phase inversion method. Measure of contact angle to distilled water have been carried out. Figure 1 compares experimental results with those of other commercial membranes. Contact angles of about 120$^{\circ}$for our amorphous perfluoropolymer membranes demonstrate that they posses a high hydrophobic character. Measure of contact angles to hexandecane have been also carried out to evaluate the organophobic character. Rsults are reported in Figure 2. The observed strong organophobicity leads to excellent fouling resistance and inertness. Porous membranes with pore size between 30 and 80 nanometers have shown no permeation to water at pressures as high as 10 bars. However high permeation to gases, such as O2, N2 and CO2, and no selectivities were observed. Considering the porous structure of the membrane, this behavior was expected. In consideration of the above properties, possible useful uses in th field of gas- liquid separations are envisaged for these membranes. A particularly promising application is in the field of membrane contactors, equipments in which membranes are used to improve mass transfer coefficients in respect to traditional extraction and absorption processes. Gas permeation properties have been evaluated for asymmetric membranes and composite symmetric ones. Experimental permselectivity values, obtained at different pressure differences, to various single gases are reported in Tab. 1, 2 and 3. Experimental data have been compared with literature data obtained with membranes made with different amorphous perfluoropolymer systems, such as copolymers of Perfluoro2, 2dimethyl dioxole (PDD) and Tetrafluorethylene, commercialized by the Du Pont Company with the trade name of Teflon AF. An interesting linear relationship between permeability and the glass transition temperature of the polymer constituting the membrane has been observed. Results are descussed in terms of polymer chain structure, which affects the presence of voids at molecular scale and their size distribution. Molecular Dyanmics studies are in progress in order to support the understanding of these results. A modified Theodoru- Suter method provided by the Amorphous Cell module of InsightII/Discover was used to determine the chain packing. A completely amorphous polymer box of about 3.5 nm was considered. Last but not least the use of amorphous perfluoropolymer membranes appears to be ideal when separation processes have to be performed in hostile environments, i.e. high temperatures and aggressive non-aqueous media, such as chemicals and solvents. In these cases Hyflon AD membranes can exploit the outstanding resistance of perfluoropolymers.

• The Korean Journal of Applied Statistics
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• v.27 no.1
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• pp.123-132
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• 2014

Inflation uncertainty is known to have deleterious effects on facilities investment by disturbing the corporate decision on the opportunity cost of investment. In this paper, we test the validity of this hypothesis in Korea by estimating the inflation uncertainty with both a time-varing parameter model with GARCH disturbances and the relative price volatility and then, estimate the facilities investment equation which includes those uncertainty indicators. The uncertainty indexes estimated by the above-mentioned methods continue to fluctuate even after the inflation rate has dropped dramatically reflecting the structural changes of Korea's economy since the financial crisis in 1997. As a result of estimation of the investment equation by both OLS and GMM, we find the inflation uncertainty has a negative effect on facilities investment with a statistical significance. Moreover, by means of Markov-switching regression model utilized to verify the non-linearity of this relationship, we draw a conclusion that this negative effect of inflation uncertainty heightens asymmetrically during the downturn periods of business cycle.

• Bulletin of the Korean Chemical Society
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• v.27 no.9
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• pp.1297-1304
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• 2006

A systematic study of the structure, energetics and spectral characteristics of substituted aminoketenes $R(NH_2)$C=C=O (R = H, $CH_3$, $NH_2$, OH, $OCH_3$, CH=$CH_2$, C$\equiv$CH, CN, CHO, NO, $NO_2$) which are highly reactive and transient intermediates in synthesis has been conducted by ab initio calculations at the MP2/6- 31G*//MP2/6-31G* level. Twenty four stable isomers of the eleven substituted aminoketenes having dihedral angles $\phi NH_2\sim120{^{\circ}}$ and $60^{\circ}$ have been identified and their optimized geometries and energies obtained. Electrostatic and steric effects on the molecular geometries have been analyzed. While the $\pi$-acceptor groups lead to planar conformations, the electron-donor groups give rise to non-planar conformations. Isodesmic substituent stabilization energies relative to alkenes have been calculated and correlation with group electronegativities established. Role of induction effect by the substituent groups and resonance effects in charge distribution in the molecules has been analyzed. An analysis of the asymmetric stretching frequencies and intensities of the C=C=O group shows that affect of non-$\pi$ acceptor substituents on the frequency is determined by the field effect (F) and resonance effect (R) parameters, the calculated intensities I (km/mol.) are correlated to group electronegativities $x$ of the substituents by the relationship I = 640.2–100.1 $x$ (r = 0.92). The $\pi$-acceptor substituents increase the intensity which may be explained in terms of their delocalizing effect on the negative charge at the $C_{\beta}$ atom.

• Korean Journal of Materials Research
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• v.29 no.12
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• pp.774-780
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• 2019

The performance of Li-ion hybrid supercapacitors (asymmetric-type) depends on many factors such as the capacity ratio, material properties, cell designs and operating conditions. Among these, in consideration of balanced electrochemical reactions, the capacity ratio of the negative (anode) to positive (cathode) electrode is one of the most important factors to design the Li-ion hybrid supercapacitors for high energy storing performance. We assemble Li-ion hybrid supercapacitors using activated carbon (AC) as anode material, lithium manganese oxide as cathode material, and organic electrolyte (1 mol L^-1 LiPF₆ in acetonitrile). At this point, the thickness of the anode electrode is controlled at 160, 200, and 240 ㎛. Also, thickness of cathode electrode is fixed at 60 ㎛. Then, the effect of negative and positive electrode ratio on the electrochemical performance of AC/LiMn₂O₄ Li-ion hybrid supercapacitors is investigated, especially in the terms of capacity and cyclability at high current density. In this study, we demonstrate the relationship of capacity ratio between anode and cathode electrode, and the excellent electrochemical performance of AC/LiMn₂O₄ Li-ion hybrid supercapacitors. The remarkable capability of these materials proves that manipulation of the capacity ratio is a promising technology for high-performance Li-ion hybrid supercapacitors.

• Strategy21
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• s.41
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• pp.108-152
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• 2017

This paper aims to analyze hegemonic competition and the role of naval power. To this end the paper is composed of four chapters titled introduction, the role of naval power in the hegemonic competition, the role of naval power in the East Asia, and the lessons and implications for the Korean Peninsula. Since the modern era, the hegemonic competition in the East Asian region has been the intrusion and struggle process between the world system and the East Asian regional system, and the ocean between these two systems has become the goal and means of supremacy(hegemony). Currently, the hegemonic competition between the US and China consists of systemic competition at the global level and marine competition at the regional level. When South Korea is forced to make strategic choices in the course of the US-China hegemonic competition, naval power will be the first factor to be considered. The ROK is asymmetrically maintaining a deep dependency relationship with the United States in terms of security and China in relation to the economy. And while the ROK's national economic power is acquired from the ocean, the ROK's military power is imbalanced because it is centered on the ground forces. These international relations and asymmetric-unbalanced resources distribution will not be able to effectively cope with the hegemonic competition between the US and China in the future, and will limit Korea's strategic choice. Since naval power and forces are the prerequisites for the hegemonic competition or the maintenance of supremacy we must construct balanced naval forces(naval power) that are not subordinate to the ground forces at the national strategic level for the future of the country.

• Journal of the Korean Data and Information Science Society
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• v.23 no.6
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• pp.1127-1135
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• 2012

Association rule mining is the method to quantify the relationship between each set of items in a large database. One of the well-studied problems in data mining is exploration for association rules. There are three primary quality measures for association rule, support and confidence and lift. We generate some association rules using confidence. Confidence is the most important measure of these measures, but it is an asymmetric measure and has only positive value. Thus we can face with difficult problems in generation of association rules. In this paper we apply the similarity measures by probabilistic interestingness measure to find a solution to this problem. The comparative studies with support, two confidences, lift, and some similarity measures by probabilistic interestingness measure are shown by numerical example. As the result, we knew that the similarity measures by probabilistic interestingness measure could be seen the degree of association same as confidence. And we could confirm the direction of association because they had the sign of their values.

• Maxillofacial Plastic and Reconstructive Surgery
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• v.19 no.1
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• pp.1-13
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• 1997

Preoperative and postoperative TMJ symptoms were observed in mandibular prognathism of 30 patients operated on by Le Fort I osteotomy and intraoral vertical ramus osteotomy. The alterations of TMJ symptoms were investigated and the relationship between changes of TMJ symptoms and some cephalometric values including occlusal plane angle, mandibular plane angle, posteior ramal height and a degree of deviation of mandibular incisor midline to facial midline were observed. The results are as follows. The incidence of patient with TMJ symptoms before orthognathic surgery was 40% and after orthognathic surgery was 20%. The most frequetly encountered symptoms in orthognathic TMJ dysfunction patients were TMJ pain and/or clicking. After surgery 66% of the preoperative symptomatic patients reported improvement TMJ symptoms. On the orther hand 2 patient (6%) of the preoperative asymptomatic patients developed TMJ symptoms after surgery. Preoperatively, 60% of the facial asymmetric patients with mandibular prognathism had TMJ symptomas. The more severe facial asymmetry was, the higher incidence of TMJ symptoms was. The alteration of occlusal plane angle and mandibular plane angle seems to be one of the contributing factors which make to change TMJ symptoms in orthognathic patients. But its amount seems to be low significance. Increase or decrease of posterior ramal height have influence on the change of TMJ symptoms.

• Journal of the Korean Association of Oral and Maxillofacial Surgeons
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• v.31 no.3
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• pp.266-273
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• 2005

Purpose: To assess the relationship between soft tissue reference line and hard tissue reference line using the standardized photographs and the posteroanterior cephalometric radiographs(P-A)in facial asymmetric patients and to compare the differences of angular measurement between normal group and asymmetry group. Methods: Normal group consisted of 44 persons with normal occlusion and normal facial morphology. Asymmetry group consisted of 90 patients with facial asymmetry. Standardized facial photographs and P-A were taken in all subjects. The horizontal reference lines were bipupillary line in photographs and latero-orbitale line in P-A respectively. The vertical reference line were the line from the midpoint of horizontal reference line perpendicularly. Angular measurement of otobasion canting, lip canting, nose deviation, chin deviation, and maxillary deviation were compared and analyzed in photographs. And angular measurement of mastoid canting, mandibular canting, nose deviation, chin deviation, and maxillary deviation were compared and analyzed in P-A. Results: 1. The variables of photographs and P-A were significantly related in the asymmetry group. 2. Significant differences between all variables except for PT2 and PA2 were shown in the asymmetry group and between PT1 and PA1, PT3 and PA3 in the normal group respectively. 3. Comparison measurement scores of angular difference between control group and experimental group concerning each variable showed significant difference except for PA1. Conclusions: Soft tissue components may not compensate for underlying skeletal imbalance in nose deviation and chin deviation. The horizontal reference lines in photographs were significant related with the P-A, but angular variables between the two studies show significant differences. Therefore, we do not recommend use photography in the assessment the facial asymmetry as complemented in the P-A.