• Bulletin of the Korean Chemical Society
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• 제31권9호
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• pp.2618-2626
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• 2010

In this paper poly (4-methyl vinylpyridinium hydroxide)/SBA-15 composite was prepared as a highly efficient heterogeneous basic catalyst by in situ polymerization method for the first time. It was characterized by XRD, FT-IR, BET, TGA, SEM and back titration using NaOH. This catalyst exhibited the excellent catalytic activities for the Knoevenagel condensation of various aldehydes with ethyl cyanoacetate. Over this catalyst, ${\alpha},{\beta}$-unsaturated carbonyl compounds were obtained in the reasonable yield at $95^{\circ}C$ in 10 - 30 min in $H_2O$ as a solvent with a 100% selectivity to the condensation products. Catalyst could be easily recycled after the reaction and it could be reused without the significant loss of activity/selectivity performance. No by-product formation, high yields, short reaction times, mild reaction conditions and operational simplicity with reusability of the catalyst were the salient features of the present synthetic protocol. Presence of $H_2O$ as a solvent was also recognized as a "green method".

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2004년도 추계학술대회 논문집 Vol.17
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• pp.675-678
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• 2004

Ozone is usually generated from oxygen gas using a silent discharge apparatus and its concentration is less then 10 mol%. An ozone condensation system is constructed for metal oxide thin film fabrication. Ozone is condensed by the adsorption method, which is widely used for the growth of oxidation thin films such as superconductor. Highly condensed ozone is analyzed by three methods; ultraviolet absorption, thermal decomposition and Q-mass analyzing methods. Thermal decomposition method is most effective in the highly condensed ozone region and its method is superior to Q-mass analyzer for determining ozone concentration because of the simplicity of the method.

• 한국정밀공학회지
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• 제12권9호
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• pp.137-147
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• 1995

The unbalance response analysis is one of the essential area in the forced vibration analysis of rotor-bearing systems. Local bearing parameters in rotor-bearing systems are the major sources which give rise to a difficulty in unbalance response computation due to the complicated dynamic properties such as rotational speed dependency and anisotropy. In the present paper, an efficient method for unbalance responses is proposed so as to easily take into account bearing parameters in computation. An exact matrix condensation procedure is proposed which enables the present method to compute unbalance responses by dealing with condensed, small matrices. The proposed method causes no errors even though the computation procedure is based on the small matrices condensed from the full matrices. The present method is illustrated through a numerical example and compared with the conventional method.

• Restorative Dentistry and Endodontics
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• 제12권1호
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• pp.155-163
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• 1986

The purpose of this study was to measure penetration of dye stuff (2% Methylene blue, 2% Hematoxylin, 2% crystal violet and 2% safranin-O) on unfilled resin (Lang Dental MFG Co.) Hipol (Boopyung Dental Chemical Co. Macrocomposite resin) Durafill (Kulzer, Co. Microfilled Composite resin) and Heliosit (Vivadent Co. Microfilled Composite resin) The unfilled resin with dough stage was inserted into plastic tuble (5mm in diameter and 4mm in height) with condensation force of 1000 gr, 2000 gr and without condensation force. Hipol mixed on the mixed pad was inserted into the plastic tube by the same method as the unfilled resin. The microfilled resins which were Durafill and Heliosit were polymerized for 60 seconds with the visible light on each surface of the plastic tube which was upper and lower, under condensation force of 1000 gr, 2000 gr and without condensation force. All specimens were stored in the air for 24 hours, then specimens were immersed in the various kind of dye solution for different period of time (1 hour and 24 hours). These dye-treated specimens were polished horizontally until removing 0.5mm of each surface on the emery paper (#1000), and the dye penetration in the polished surface was measured under the digital microscope (Japan Fosuh). Following results were obtained 1. The penetration of dyes was the most excessive in Durafill and was not influenced on the condensation force and the period of immersion time. 2. All dyes were penetrated into Hipol, and Crystal violet was penetrated most excessively in all dyes. 3. The penetration of dye in all resins was not influenced by the period of immersion time and condensation force. 4. There was no evidence of dye penetration in unfilled resin.

• Restorative Dentistry and Endodontics
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• 제21권2호
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• pp.517-529
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• 1996

The purpose of this study was to evaluate the apical sealing ability of the Thermafil endodontic obturation technique and to compare it with lateral condensation technique. 42 straight canals from extracted human anterior teeth and 42 curved canals(> $25^{\circ}$) from maxillary and mandibular molar teeth were selected. And 80 of them were divided into four groups, 20 canals respectively. The teeth in prior two groups had straight canals and the other two groups had curved canals. The rest of four canals served as positive and negative controls. After resecting anatomical crowns, all canals were prepared using a standard step-back technique. Lateral condensation was used to obturate two groups, one group of straight ones the other curved. And Thermafil obturators were also used in the same two groups. Obturated teeth were infiltrated by India ink for a week, decalcified and cleared with 5% nitric acid and methyl salicylate. The apical leakage and the frequency of filled lateral and accessory canals were measured with stereomicroscope and also apical extrusion of sealer and gutta-percha and obturation time were checked and the data were analyzed statistically(one-way ANOVA, t-test, Chi-square test). The results were as follows : 1. There was no significant difference in the degree of dye penetration between Thermafil and lateral condensation groups(p>0.05). 2. Apical extrusion of sealer and gutta-percha occurred significantly more often with Thermafil obturators in straight canals(p<0.05), but not significantly different in curved canals(p>0.05). 3. Canal obturation time with Thermafil obturators was significantly faster than lateral condensation (p<0.05). 4. The Thermafil groups showed a higher frequency of filled lateral and accessory canals than in the lateral condensation groups. But the difference was not statistically significant (p>0.05).

• 한국수소및신에너지학회논문집
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• 제33권4호
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• pp.413-418
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• 2022

This paper presents two-phase condensation heat transfer and pressure drop characteristics of R32 and R454B as an alternative refrigerant to R410A in a 9.52 mm OD microfin tube. The test facility has a straight, horizontal test section with an active length of 2.0 m and is cooled by cold water circulated in a surrounding annular space. The heat transfer coefficients of the annular space were obtained using the modified Wilson plot method. Average condensation heat transfer coefficient and pressure drop data are presented at the condensation temperature of 35℃ for the range of mass flux 100-400 kg/m²s. The average condensation heat transfer coefficients of R32 refrigerant are 35-47% higher than R410A at the mass flux considered in the study, while R454B data are similar to R410A. The average pressure drop of R32 and R454B are much higher than R410A and they are 134-224% and 151-215% of R410A, respectively. R32 and R454B have relatively low GWP and high heat transfer characteristics, so they are suitable as alternatives for R410A.

• Restorative Dentistry and Endodontics
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• 제19권2호
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• pp.461-472
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• 1994

The purpose of this study was to evaluate the sealing ability according to types of spreader and compatibility of accessory cone used in lateral condensation method. 120 plastic blocks with canal preformed were instrumented with K-,H-files and Gates-Gllidden bur. Shaped plastic blocks were divided into six experimental groups according to spreader and accessory cone used in lateral condensation. Then they were obturated by lateral condensation method without -sealer. Six experimental groups were as follows: Group 1 : Filling with #30 spreader & #25 gutta-percha cone Group 2 : Filling with #30 spreader & Fine accessory cone Group 3 : Filling with #3 spreader & #25 gutta-percha cone Group 4 : Filling with #3 spreader & Fine accessory cone Group 5 : Filling with #20,#30 spreader & #25 gutta-percha cone Group 6 : Filling with #2, #3 spreader & Fine accessory cone All the blocks were stored in 100% humidor at room temperature for 2 days. Each block was placed in centrifuged for 20 minutes at 3,000 rpm. Apical leakage was mesured from the apical foramen to the most coronal level of- dye leakage in millimeter under a stereoscope. The data were analysed by ANOVA. The obtained results were as follows; 1. In groups using two spreaders(Group 5,6), the linear leakage was less than one spreader using groups(Group 1-4). 2. Tn groups using two spreaders(Group 5,6), there was no significant difference in linear leakage between standardized -spreader group and non standardized group (p>0.01). 3. When one spreader was used(Group 1-4), standardized-spreader groups showed less linear leakage than nonstandardized spreader groups(P<0.01). 4. In case of using same spreader(Groupl,2 & Group 3,4), there was no significant difference in linear leakage according to accessory cone type. 5. It needs to use one more spreaders to increase apical sealability.

• 한국전산구조공학회논문집
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• 제21권3호
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• pp.281-285
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• 2008

축소시스템 기법은 전체 구조의 거동을 나타내는 저차 고유모드를 근사화한다. 지난 연구에서 축소시스템을 구축하기 위한 2단계 축소기법을 제안하였다. 또, 기존의 2단계 축소기법을 반복적 IRS기법을 통해 중간 주파수 대역의 고유모드에 대한 해의 정확도를 높이는 방안에 대해 연구가 제안되었다. 본 연구에서는 기존의 향상된 2단계 축소기법에 다단계 부구조화 기법을 적용하는 기법을 제안한다. 첫 단계에서는 전체 시스템을 그래프 분할을 통해 계층적으로 부구조로 분할되고, 두 번째 단계에서는 각각의 부구조를 개선된 2단계 축소기법을 이용하여 축소한다. 각각의 축소된 분절화된 고유치문제의 조합을 총해 최종적 축소시스템을 구축하고 이렇게 구한 축소된 고유치 문제를 란초스 기법(ARPACK)을 통해 해석한다. 최종적으로 제안된 기법의 성능을 수치 예제를 통해 검증한다.

• 한국전기전자재료학회:학술대회논문집
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• 한국전기전자재료학회 2002년도 추계학술대회 논문집 Vol.15
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• pp.272-275
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• 2002

An ozone condensation system is evaluated in the viewpoint of an ozone supplier for oxide thin film growth. Ozone is condensed by the adsorption and distillation method. Then their concentrations are analyzed by three methods; ultraviolet absorption, thermal decomposition and Q-mass analyzing methods. Thermal decomposition method is found to be available to the concentration evaluation from dilution to highly condensed ozone. The highest ozone concentration condensed by the adsorption method is evaluated to be 96 mol%. The ozone is supplied for a sufficiently long time to grow oxide thin films.

• Restorative Dentistry and Endodontics
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• 제27권5호
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• pp.521-529
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• 2002

The purpose of this study was to compare the shaping time of two shaping methods and the leakage of three different obturation techniques. Ninty three canaled human molar teeth were used, which were randomly divided into two groups of forty teeth each and ten control teeth. After working length determination, the one group was prepared crown-down technique using rotary root canal instruments of GT rotary files .12/20, .10/20, .08/20 and .06/20 taper(Maillefer Instrument SA. Switzerland). The other group was instrumented with Gates Glidden burs(#1, #2, and #3) to coronal preparation and GT rotary files .08/20 and .06/30 taper to apical preparation. Shaping time was measured. After root canals were instrumented, they were divided to three subgroups and obturated as follows : Subgroup 1, obturated with single cone method Subgroup 2, obturated with lateral condensation : Subgroup 3, obturated with continuous wave technique. Three subgroups were obturated using non-standardized gutta-percha cone(Diadent, Korea, .06 or .08 taper) and AH-26(Dentsply DeTrey, Germany) as a root canal cement. Ten unobturated teeth served as positive and negative controls. After immersion in 2% methylene blue solution for 1 month, the teeth were washed during 24h. The teeth were demineralized in 10% nitric acid and dehydrated by immersion in 80, 90 and 100% ethyl alcohol. The teeth were finally cleared and stored in 100% methylsalicylate, and apical dye penetration was evaluated under stereomicroscope(Leica M420, LC, U.S.A)at $\times$8.75 magnification. Liner measurement of dye penetration was assessed with the use of digitalized image analysing system (analySIS, GmbH, Germany) The data were analysed statistically using independent T-test and Two-way ANOVA and Tukey test. The result were as follows 1. In canal prepared with GT$^{TM}$ rotary file, shaphing time taked more than the group of using Gates Glidden drill to coronal preparation without statistical significance (p>0.05) 2. The group of single cone obturation using canal preparation of GT$^{TM}$ rotary files showed significantly more apical leakage than those of lateral condensation and continuous wave technique regardless of shaping method (p<0.05). 3 The group of single cone obturation using canal preparation of GT$^{TM}$ rotary files and Gates Glidden drill showed significantly more apical leakage than those of continuous wave technique regardless of shaping method (p<0.05). 4. Regardless of shaping method, The group of continuous wave obturation showed less apical leakage than those of lateral condensation without statistical significance (p>0.05). 5. The group of single cone obturation using canal preparation of GT$^{TM}$ rotary files and Gates Glidden drill showed more apical leakage than the group of lateral condensation using same shaping method with-out statistical significance (p＞0.05).