• Korean Chemical Engineering Research
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• v.50 no.5
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• pp.890-893
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• 2012

Gas hydrates are solid crystal structures formed by enclathration of gaseous guest species into 3-dimensional lattice structure of hydrogen-bonded water molecules. These compounds can be potentially used as an energy storage/transportation medium because they can hold a large amount of gas in a small volume of the solid phase. In addition, huge amount of natural gas, buried in seabeds or permafrost region in the form of the solid hydrate, is regarded as a future energy source. In this study, synthesized natural gas, whose composition is 90.0 mol% of methane, 7.0 mol% of ethane, and 3.0 mol% of propane, was used to identify formation behaviors of natural gas hydrates for the purpose of applying the gas hydrate to a storage/transportation medium of natural gas. According to the experimental results obtained by means of the solid-state NMR and high-resolution powder XRD methods, it is found that formed natural gas hydrates have crystal structure of the structure-II hydrate, and that methane occupies both small and large cages, while the others only occupy large ones. In addition, both the NMR spectroscopy and the gas chromatograph showed that there exists preferential occupation among the natural gas components during the hydrate formation. Compositional changes after the hydrate formation revealed that the preferential occupation is in order of propane, ethane, and methane (propane is the most preferential guest species when forming natural gas hydrates).

• Journal of the Korean Chemical Society
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• v.55 no.3
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• pp.472-477
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• 2011

The concentration of selenium in grain samples was determined using isotope dilution method in ORC-ICPMS. The experimental conditions were optimized to $H_2$ mode and the flow rate was $4.0\;mL\;min^{-1}$. ORC in $H_2$ mode proved to eliminate most of polyatomic interferences except $BrH^+$ when Br is present in sample matrix. Chemical removal of Br was very difficult and the mathematical correction was successfully employed. The fraction of $BrH^+$ generated from Br at the current experimental condition was 14.1%. The signal on m/z 82 was corrected and calculated for isotope dilution. The analytical reliability of the propose method was successfully evaluated by analyzing the certified standard reference material NIST SRM 1566 and 1567. The method was applied to real samples and the results are $0.034{\pm}0.001\;{\mu}g\;g^{-1}$ for white rice, $0.059{\pm}0.002_5\;{\mu}g\;g^{-1}$ for brown rice, $0.029{\pm}0.001_4\;{\mu}g\;g^{-1}$ for black rice, and $0.034{\pm}0.002\;{\mu}g \;g^{-1}$ for barley. The detection limits ($3\sigma$) for Se was $0.012\;ng\;g^{-1}$.

• Journal of dental hygiene science
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• v.6 no.3
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• pp.153-158
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• 2006

Bleaching of vital and nonvital teeth is becoming a more commonly used treatment in the dental office and at home. To improve appearance and remove discoloration, the teeth of specific patients are treated with a variety of bleaching agents. The typical bleaching agents contains carbamide or hydrogen peroxide as the active component. The purpose of the review article was to summarize and discuss the available information concerning the effect of peroxide releasing bleaching agent on dental restorative materials and restorations. Information from all original scientific full papers or reviews listed in PubMed or ISI Web Science were included in the review. Bleaching may exert a negative influence on restorations and restorative materials. Advice is provided based on the current literature to minimize the impact of bleaching treatment on restorative materials and restorations.

• Journal of dental hygiene science
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• v.12 no.4
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• pp.320-328
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• 2012

The purpose of this study was to evaluate the tooth whitening and properties of an enamel surface after treatments with tooth bleaching agents that contained dicalcium phosphate dihydrate (DCPD) and hydrogen peroxide (HP). Thirty specimens were obtained from fifteen premolar and were randomly divided into three groups (n=10): 1, 3.5% HP + 0 g DCPD; 2, 3.5% HP + 0.1 g DCPD; 3. 3.5% HP + 1 g DCPD. All groups were bleached 8 hours per day for 14 days. With increasing DCPD concentration, the pH values in the agents increased, making it less acidic. However, there was no statistically significant difference (p>.05). As the concentration of DCPD was increased, the concentration of Ca and P was also increased. In all groups, after the tooth whitening, the tooth color was found to have a value of $L^*$ (p<.05). All groups showed significantly decreased enamel microhardness compared to their baseline (p<.05). The percentage microhardness loss (PML) of the group A1 and A2 were significantly lower than that of group A3. The obvious variation of morphology was observed on enamel surfaces in group A1. Following an analysis of the constituents of enamel surface after bleaching, as DCPD content was increased, the amount of Ca and P was increased. In this study, the experimental results suggest that DCPD/HP agent less demineralization changes such as the erosion morphology and hardness loss without compromising whitening efficiency.

• Korean Journal of Soil Science and Fertilizer
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• v.18 no.1
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• pp.38-49
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• 1985

The water soluble organic fractions (WSOF) from an agricultural soil (W), a soil treated with sludge for 6 years ($WS_6$), a sludge-soil mixture incubated for one week ($WS_1$), and sewage sludge (SS) were extracted, purified, and characterized by elemental analysis, functional group determinations, infrared, UV-visible, and proton nuclear magnetic resonance spectrosocpy. The SS was characterized by higher organic H, N, and P contents, a higher H/C ratio, and a lower C/N ratio than W. Total acidity carboxyl and phenolic hydroxyl group contents were generally highest in SS, intermediate in $WS_6$ and $WS_1$, and lowest in W. Overall aromatic character and aromatic carboxyl group contents were highest in W, and lowest in SS. Aliphatic proton, aliphatic carboxyl, and phenolic hydroxyl group contents were highest in SS, and lowest in W. Protein decomposition products were the pronounced components in SS, and decreased in concentration as the sludge component in the mixtures decreased. The $^1H$-NMR spectra suggested that the SS-protons were bound to a wider range of functional groups than W-protons. Structural complexities around the aromatic protons followed the following order: SS>$WS_1$>$WS_6$>W.

• Proceedings of the Korean Society of Propulsion Engineers Conference
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• 2000.04a
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• pp.4-4
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• 2000

일반적인 액체추진제 로켓엔진의 연소는 분사제트의 미립화, 액적의 증발, 기상 추진제의 혼합, 화학반응 등, 일련의 물리적 과정들로 이루어지고, 여기서 특성속도 효율은 크게 분사특성 및 연소의 두 단계에서 결정되게 된다. 액체추진제 로켓엔진에 사용되는 여러 분무형태 중, 동축형 분사기에서는 액상과 기상 제트의 운동량 차에 의해 미립화가 이루어지며, 분무 액적들의 전개와 더불어 분사기 출구를 포함한 전 영역에서 연소가 발생되므로 매우 복잡한 물리적 특성들을 포함하게 된다. 본 연구에서는 기상 연료-액상 산화제의 동축형 분무연소를 JANNAF의 방법을 사용하여 수식화 하였으며, 이를 바탕으로 분무특성과 연소성능 예측을 위한 프로그램을 작성, 분사조건에 의한 분무특성과 그에 따른 연소성능을 계산하였다. 연속, 운동량, 에너지 및 혼합비 방정식의 지배방정식들을 바탕으로 기상 유동을 수식화 하였으며, 별도로 액적의 소산 및 연소과정을 모사하기 위한 별도의 수식들이 추가되었고, 이 식들을 결합하여 액적의 크기, 분포를 포함하는 액체 제트의 미립화 정도를 공간적으로 계산하였다. 미립화 모델의 검증을 위하여 계산 결과를 Reitz의 실험과 Giridharan의 모델 등과 비교하였으며 잘 일치하는 경향을 나타내었다. 또한 동축형 분사기에서의 분무 특성을 예측하기 위해 액체 산소, 기체 수소를 추진제 조합으로 하는 동축형 분무 연소장에서의 제트 길이, 액적의 크기, 액체 제트의 속도를 계산하였다. 계산 결과 액체 제트의 접촉길이는 분사공의 지름이 증가할수록 웨버수가 증가되므로 짧아지는 것으로 관찰되었으며 액적의 크기도 분사공의 지름이 증가할수록 작아지는 경향을 나타내었다. 액체 제트의 속도는 처음에는 일정하게 유지되다가 운동량을 보존하기 위해 가스로부터 운동량을 받아 점차 가속되어지는 것으로 나타났다.본 규격은 키, 총장, 어깨길이, 등길이, 머리길이, 머리둘레, 진동둘레, 목둘레, 가슴둘레, 허리둘레, 배둘레, 엉덩이둘레, 앞품, 뒤품, drop치를 포함하고 있고, 각 규격에서 호칭간 치수 간격도 함께 제시하고 있다. 본 연구 결과에서 보듯, 현행 8규격의 무진복의 각 호칭간 적정 허용범위를 고려해 합리적인 치수체계를 정립한다면 치수에 대한 적합도가 상당히 증가할 뿐 아니라 생산비용도 상당히 감축할 것으로 생각된다.나타났다. 4) 호감적 서비스능력 차원에서 세 독립변수간에 유의한 3원 상호작용이 존재하는 것으로 나타나( $F_{2,228}$=15.62, P<.001) 20대에 적합한 의복 착용시( $F_{2,228}$=3.98, P<.05)와 60대에 적합한 의복 착용시( $F_{2,228}$=16.55, P<.001) 점포유형과 격식차림간에는 유의한 상호작용이 존재하는 것으로 나타났다. 5) 호감을 구성하는 세 요인들이 구매의도에 미치는 영향을 조사한 결과 호감적 인상차원은 29%(P<.001), 호감적 서비스능력차원은 6%(P<.001)의 구매의도를 설명해 주는 것으로 나타났다. 본 연구결과 노년 소비자에게 호감을 주는 판매원의 외모는 구매의도에 영향을 주어 실버의류산업의 이익증대와 밀접한 연관을 갖는 서비스품질의 중요한 요인으로 밝혀졌다.중요한 요인으로 밝혀졌다.로운 단백질 EPSPS가 다른 여러 식물에 이미 존재하고 있는 단백질로서 우리가 이미 이러한 식품을 섭취할 때 이 단백질도 같이 섭취해오고 있었다는 점, 둘째. 이 단백질이 소화액 분해 실험에서 짧은 시간내에 분해가 되었다는 점, 셋째. 재조합 된 콩과 자연 콩이 성분 분석에서 차이를 나타내지 않았다는 점, 네 번째. 쥐를 통한 다양섭취 실험에서 아무런 이상 반응이 없었

• Applied Biological Chemistry
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• v.33 no.3
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• pp.231-238
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• 1990

The structure-antifungal activity correlations between the structure of fourteen new 1-(phenoxymethyl)benzotriazoles (I) (Y=0), 1-(thiophenoxymethyl)benzotriazoles (ll) (Y=S) and 1-(azidomethyl)benzotriazole (III) derivatives were synthesized, and their activity, fifty percent inhibition of mycelial growth($pI_{50}$), in vitro against Pyricularia oryzae, Fusarium axysporum f.sp sesami, Valsa ceratosperma and Botrytis cinerea were investigated using a generalized QSAR method. The activity of (I) was superior In those of (II) and (III). The effect of the substituents (X) on the phenoxy group (I) was rationalized by a parabolic function of electronic (${\sigma}$), steric ($B_1$) and hydrophobic parameter(${\pi}$), and hydrogen bonding (HB). Where the optimal values of substituent on the fungicidal activity againt P. oryzae and F. axysporum f.sp.sesami are $B_1=1.40A;(H)$ and ${\pi}=0.07{\sim}0.15;(H)$, and those of substituent on the fungicidal activity against V. ceratosperma and B. cinerea are ${\sigma}=0.23{\sim}0.28;\;(C1),\;{\pi}=0.70;$ (C1), respectively. The most effective compound ( I a) and ( I d) were examined in this study.

• Applied Biological Chemistry
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• v.50 no.3
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• pp.147-153
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• 2007

To search for a molecular design of a new breast cancerous inhibitory active compound, 2D-QSAR and HQSAR between the substituents of flavopiridol analogues as substrates and their breast cancerous inhibitory activities against MCF-7 cell were analyzed and discussed quantitatively. It was found that the dispersion with molecule and steric hindrance with substituents will have a tremendous impact on the inhibitory activities from the 2D-QSAR model (1). Also, MR constant is better than that of MS constant as animportant factor. The inhibitory activities from 2D-QSAR model (2) were dependent upon the optimum MR constant (MR = 126 $Cm^3/mol$). Optimized HQSAR model (V) exhibited the best predictability of the inhibitory activities based on the cross-validated $r^2_{cv}$($q^2$= 0.583) and non-cross-validated conventional coefficient ($r^2_{ncv}$= 0.982). From the contribution maps, the inhibitory activity by the imino group on $C_9$ atom was higher than that of the hydroxyl group of $C_8$ atom on the A ring in molecule. Therefore, we can confirm that the dispersion by substituents in molecule is the most important factor in inhibitory activities against MCF-7 cell.

• KOREAN JOURNAL OF CROP SCIENCE
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• v.46 no.3
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• pp.195-201
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• 2001

Sowing date experiments were carried out by employing a rice variety "Kwanganbyeo" in both field and phytotron with natural daylength. In phytotron, temperatures were controlled at daily mean of 21$^{\circ}C$ and 24$^{\circ}C$. The responses of final leaf number and beading date were analyzed in relation to daylength during photo-sensitive period (PSP). Based on the component models predicting the final leaf number and leaf appearance rate, a rice phenology model was established and verified. Days from sowing to flowering (DSF) were shortened and final number of leaves (FNL) increased as sowing dates were delayed from 25 April to 5 June in field and phytotron. The increased leaf appearance rate (LAR) and the reduced FNL, respectively, due to the higher temperature and the shorter daylength in delayed sowings in the field brought about greater shortening of DSF than in the phytotron where only FNL was reduced by shorter daylength in delayed sewings. FNL showed very close relationship with the average daylength during PSP of six-leaf stage to panicle initiation, being well fitted to the following rational function ($R^2$=0.98):(equation omitted) where D is daylength and a, b, and c are the constants that were estimated as 14.694, -0.992, and -0.068 in Kwanganbyeo, respectively. The rice phonology model, which was composed of two component models for LAR and FNL, predicted DSF very accurately. The differences between the observed and predicted DSF was less than two days in the sewing date field experiments in 1999 and 2000 of which data were not used for the model construction.struction.

• Journal of the Korean Society of Radiology
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• v.9 no.4
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• pp.187-195
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• 2015

The active transport characteristics of anions of cell membrane model which irradiated by $^{60}Co\;{\gamma}-ray$ was investigated. The cell membrane model used in this experiment was a sulfonated copolymerized membrane of poly(1-methyl-4-vinylpyridiniumiodide-co-divinylbenzene : MeVP-DVBI). First, the initial flux of $OH^-$ and $Cl^-$, $Na^+$ of membrane which was not irradiated was decreased with increase of thickness of membrane $80-200{\mu}m$, increased with increase of NaOH concentration 0-0.5mol/L and MeVP-DVBI concentration 20-80% was increased with initial flux of $OH^-$ and $Cl^-$, decreased with initial flux of $Na^+$. Second, the initial flux of membrane which was irradiated was less than that. And the driving force of pH of irradiated membrane was significantly increased more than membrane which was not irradiated. The initial flux of the $OH^-$ ion was decreased with increase of $H^+$ ion concentration. As selective transport of $OH^-$ and $Cl^-$ of cell membrane model were abnormal, cell damages were appeared at cell.