• 한국환경과학회지
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• 제29권12호
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• pp.1261-1274
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• 2020

The characteristics of ammonia-nitrogen (NH4+-N) adsorption by a zeolitic material synthesized from Jeju scoria using the fusion and hydrothermal method was studied. The synthetic zeolitic material (Z-SA) was identified as a Na-A zeolite by X-ray diffraction, X-ray fluorescence analysis and scanning electron microscopy images. The adsorption of NH4+-N using Jeju scoria and different types of zeolite such as the Z-SA, natural zeolite, and commercial pure zeolite (Na-A zeolite, Z-CS) was compared. The equilibrium of NH4+-N adsorption was reached within 30 min for Z-SA and Z-CS, and after 60 min for Jeju scoria and natural zeolite. The adsorption capacity of NH4+-N increased with approaching to neutral when pH was in the range of 3-7, but decreased above 7. The removal efficiency of NH4+-N increased with increasing Z-SA dosage, however, its adsorption capacity decreased. For initial NH4+-N concentrations of 10-200 mg/L at pH 7, the adsorption rate of NH4+-N was well described by the pseudo second-order kinetic model than the pseudo first-order kinetic model. The adsorption isotherm was well fitted by the Langmuir model. The maximum uptake of NH4+-N obtained from the Langmuir model decreased in the order of Z-CS (46.8 mg/g) > Z-SA (31.3 mg/g) > natural zeolite (5.6 mg/g) > Jeju scoria (0.2 mg/g).

• 한국마린엔지니어링학회:학술대회논문집
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• 한국마린엔지니어링학회 2001년도 추계학술대회 논문집(Proceeding of the KOSME 2001 Autumn Annual Meeting)
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• pp.112-119
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• 2001

Parameter tuning methods by Ziegler-Nickels for control systems are generally classified into Z-N(1) and Z-N(2). The purpose of this paper is to describe what relations exist between methods of Z-N(1) and Z-N(2), or how Z-N(1) method can be originated from Z-N(2) method by analyzing one loop control system of P or PI controller and time delay process. The formulas of Z-N(1) consist of process parameters, L(time delay), $K_m$(gain) and $T_m$(time constant), but Z-N(2) method is based only on the ultimate gain $K_u$ and the ultimate period $T_u$ acquired normally by practical trial without any parameters of Z-N(1). In this paper, for the first step to seek mutual relations, the simple formulas of Z-N(2) are transformed into the formulas composed of the same parameters as Z-N(1) which is derived from the analysis of frequency characteristics. Then, the approximation of the actual ultimate frequency is proposed as important premise in the translation between Z-N(1) and (2). Such equalization and approximation brings a simple approximated formula which can explain how Z-N(1) is originated from the Z-N(2) in the form of formula. And a model system is adopted to compare the approximated formula to Z-N(1) and Z-N(2) methods, the results of which show the effectiveness of the proposals.

• 환경영향평가
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• 제22권6호
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• pp.591-607
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• 2013

본 연구에서는 생물학적 바이오마커, 물리적 서식지 지표 및 화학적 수질지표를 종합하여 12-메트릭 생태평가 모형을 확립하였고, 도심하천에 적용하여 수생태계 평가를 실시하였다. 생태모형 적용을 위해 도심하천의 상류역의 대조군 지역($C_Z$), 중류의 전이대($T_Z$) 및 하류역의 오염지역(IZ)을 선정한 후, 모델값에 대한 계절별 변이특성을 분석하였다. DNA 손상도 분석은 혈액을 이용한 단세포 전기영동법(Single-cell gel electrophoresis, SCGE)인 Comet assay 지표에 의거한 생지표 메트릭으로 이용되었고, Tail moment, Tail DNA(%) 및 Tail length(${\mu}m$)값이 분석되었다. DNA의 손상은 하류역의 오염지역($I_Z$)에서 분명하게 나타났지만, 대조군($C_Z$) 지역에서는 그렇지 않았다. 개체군 지표로서 비만도 지수인 $C_F$ 값 분석, 체장빈도 분포 지표 및 개체 이상도(Abnormality) 지표가 생물지표로서 이용되었다. 물리적 서식지 지표는 QHEI 모델을 이용하였고, 4개 메트릭이 분석되었다. 화학적 수질지표는 부영양화 지표인 인(P)/질소(N), 화학적 산소요구량 및 전기전도도 지표가 이용되었다. 본 연구를 종합해보면, 12-메트릭 생태모형의 생지표 속성은 대조군($C_Z$)지역에 비해 오염지역($I_Z$)에서 화학적 스트레스 지표(부영양화 지표)에 아주 민감하게 반응 하는 것으로 나타났으며, 또한 이들은 부분적으로 서식지 평가지표에 의해 영향 받는 것으로 분석되었다.

• Genomics & Informatics
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• 제19권2호
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• pp.15.1-15.7
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• 2021

The direction of evolution can estimate based on the variation among nonsynonymous to synonymous substitution. The simulative study investigated the nucleotide sequence of closely related strains of respiratory syndrome viruses, codon-by-codon with maximum likelihood analysis, z selection, and the divergence time. The simulated results, dN/dS > 1 signify that an entire substitution model tends towards the hypothesis's positive evolution. The effect of transition/transversion proportion, Z-test of selection, and the evolution associated with these respiratory syndromes, are also analyzed. Z-test of selection for neutral and positive evolution indicates lower to positive values of dN-dS (0.012, 0.019) due to multiple substitutions in a short span. Modified Nei-Gojobori (P) statistical technique results also favor multiple substitutions with the transition/transversion rate from 1 to 7. The divergence time analysis also supports the result of dN/dS and imparts substantiating proof of evolution. Results conclude that a positive evolution model, higher dN-dS, and transition/transversion ratio significantly analyzes the evolution trend of severe acute respiratory syndrome coronavirus 2, severe acute respiratory syndrome coronavirus, and Middle East respiratory syndrome coronavirus.

• 한국결정학회지
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• 제15권2호
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• pp.83-87
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• 2004

유기금속 착화합물 $Me_2Pt(PPh_2CH_2C(t-Bu)=N-N=CMe(2-py)-\kappa^2N,P)$을 phosphino hydrazone $Ph_2PCH_2C(t-Bu)=NNH_2$와 2-acetylpyridine와 $[PtMe2({\mu}-SMe_2)]_2$를 사용하여 합성하였다. X-선 회절법을 이용하여 이 화합물의 분자 구조를 규명하였다. 이 백금 화합물의 결정학적 자료는 monoclinic, space group $P2_1/n,\;a=11.6926(7)\;{\AA},\;b=15.6607(19)\;{\AA},\; c=14.6125(6)\;{\AA},\;\beta=93.018(4)^{\circ},\;Z=4,\;V=2672.0(4)\;{\AA}^3$이다. 결정 구조는 직접법으로 해석하였으며, 5238개의 회절 반점에 대하여 최종 신뢰도 인자 R=0.0363인 분자 모형을 구하였다.

• Geomechanics and Engineering
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• 제35권4호
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• pp.367-383
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• 2023

The present paper examines the natural frequency responses of the bi-directional (n_x-n_y, n_y-n_z and n_z-n_x) and multidirectional (n_x-n_y-n_z) functionally graded (FG) plate and curved structures with and without porosity. The even and uneven kind of porosity pattern are considered to observe the influence of porosity type and porosity index. The numerical findings have been obtained using a higher order shear deformation theory (HSDT) based isometric finite element (FE) approach generated in a MATLAB platform. According to the convergence and validation investigation, the proposed HSDT based FE model is adequate to predict free vibrational responses of multidirectional porous FG plates and curved structures. Further a parametric analysis is carried out by taking various design parameters into account. The free vibrational behavior of bidirectional (2D) and multidirectional (3D) perfect-imperfect FGM structure is examined against various power law index, support conditions, aspect, and thickness ratio, and for the curvature of curved structures. The results indicate that the maximum non-dimensional fundamental frequency (NFF) value is observed in perfect FGM plates and curved structures compared to porous FGM plates and curved structures and it is maximum for FGM plates and curved structures with uneven kind of porosity than even porosity.

• Bulletin of the Korean Chemical Society
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• 제21권9호
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• pp.882-890
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• 2000

Ab initio calculations are carried out on protonation equilibria of 5-memberedheteroaromatic aldehydes (5MHAs;heteroatom Y = NH, O, PH,and S and substituentZ = NH2, OCH3, SCH3, CH3, H, Cl, CHO, CN,NO2) at the $MP2}6-31G*$ level. Naturalbond orbital (NBO) analyses show that the optimal localized natural Lewis structures of the protonated aldehydes,(P), are ortho (C3) protonated (for Y = O, PH and S) and N-pro-tonated (for Y = NH) forms in contrast to the standard structural Lewis formula for aldehydes, (R). The delo-calizability of ${\pilone}-pairon$ the heteroatom $(n{\pi}(Y))$ is in the order Y = NH > O > S > PH. The transmission efficiency of (Z) substituent effects to the carbonyl moiety run parallel to the delocalizability of $n{\pi}(Y)$ for R,but is dominantly influenced by the cationic charge on $C{\alpha}(C{\alpha}+)$ for P, which is in the reverse order of thede-localizability of $n{\pi}(Y).$ The Hammett ${\rho}values$ for variation of Z in the protonation are determined by the dif-ference in the transmission efficiencies between Pand R stateat simple interpretation of their magnitude is not warranted. However,the magnitude of the gas-phase ${\rho}z+$ values decreases as the level ofcomputation is raised from RHF/3-21G* to RHF/6-31G* and to $MP2}6-31G*$ but increases again at the MP4SDQ/6-31G* level. Further decrease occurs when solvent effect (water) is accounted for by the SCRF method. Comparison of the SCRF ${\rho}z+values$ with those determined in the aqueous acid solution for Y = S and CHCH shows inadequacy of accounting for the solvent effects on the ${\rho}values$ by a continuum model. It is noteworthy that semiempirical calculations, especially theAM1 method, give even lower magnitude of the gas-phase ${\rho}values.

• 한국치위생학회지
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• 제13권2호
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• pp.351-360
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• 2013

Objectives : The purpose of this study was to evaluate the effects of tooth bleaching agent contained 15% carbamide peroxide on the color, microhardness and surface roughness of tooth-colored restorative materials by using pH cycling model. Methods : Four types of tooth-colored restorative materials, including a composite resin(Filtek Z350 ; Z350), a flowable composite resin(Filtek P60 : P60), a compomer(Dyract$^{(R)}$ AP ; DY), and a glass-ionomer cement(KetacTM Molar Easymix ; KM). were used in the study. Eighty-eight specimens of each material were fabricated, randomly divided into two groups(n=44): experimental group(15% carbamide peroxide) and control group(distilled water). These groups were then divided into four subgroups(n=11). All groups were bleached 4 hours per day for 14 days using pH cycling model. The authors measured the color, microhardness, and roughness of the specimens before and after bleaching. The data were analyzed with ANOVA and T-test. Results : Z350 and P60 showed a slight color change(${\Delta}E^*$), whereas DY and KM showed significantly color change(p<0.05). Among them, the greatest color change was observed in DY. Percentage microhardness loss(PML) of the distilled water group was 1.8 to 5.1%, and 15% peroxide peroxide group was 5.0 to 25.2%. Microhardness of DY and KM showed a statistically significant decrease(p<0.05). Roughness was increased in all groups after bleaching. Z350 and P60 does not have a significant difference(p>0.05), however DY and KM significantly increased more than the 0.2 ${\mu}m$(p<0.05). Conclusions : The effects of bleaching on restorative materials were material dependent. It is necessary to consider the type of the material before starting the treatment.

• 전기학회논문지
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• 제56권9호
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• pp.1626-1631
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• 2007

This paper presents a new modeling method using lamp output power and the modeling coefficients of the lamp. The proposed method utilizes the lamp modeling coefficients such as equivalent impedance Z(p), coupling coefficient of the transformer k(p), turns ratio of the transformer n(p), and plasma resistance Rp(p) as a function of lamp output power. The equivalent impedance Z(p) was developed from the equivalent resistance Req(p) and equivalent inductance Leq(p) of the lamp. Simulation and experimental results of the proposed model are presented in order to validate the proposed method. The modeling method can use to design an impedance matching circuit for a Class-D inverter.

• 한국결정학회지
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• 제4권1호
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• pp.1-5
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• 1993

니클로사미드 일수화물의 결정구조는 흑연으로 단색화된 Mo-Ka 방사선을 사용하는 자동 CAD4 회절 기로 측정된 1976개의 독립반점을 이용하여 결정되었다. 결정계는 단사정계이며, 공간군은 P211c이고, 293k에서 단위세포 상수는 a=11.331(3), b=6.964 (2), c=7.347(4)A, p=98.20(3)°, Z=4이다. 구조는 ggg Parity군에 속하는 반불변수를 이용하는 직접법으로 해석하였으며, 완전행렬 최소자승법으로 정밀화하여 최종 신뢰도 R=0.046인 모형을 구하였다. 분자 모양은 ab평면상에 평행하게 놓이는 평면성 구조를 나타낸다.