• 한국세라믹학회지
• /
• 제34권11호
• /
• pp.1187-1197
• /
• 1997

Dry gel composed of primary particles more homogeneous than starting boehmite powder was prepared by dispersing and gelling the boehmite powder. The transformation temperatures of boehmite powder, dry gel seeded with 0, 1, 3, 5 wt% $\alpha$-Al2O3, and ball milled gel were 1192$^{\circ}C$, 1184$^{\circ}C$, 1141$^{\circ}C$, 1119$^{\circ}C$, 1117$^{\circ}C$, and 1106$^{\circ}C$, respectively. Sintering behavior of dry gel without seed was similar to that of boehmite powder, but the sintered density of dry gel was improved as much as 10%~15% than boehmite powder. In the case of dry gel seeded with 5 wt% $\alpha$-Al2O3, sintering behavior was much improved. The relative density of the gel seeded with 5 wt% $\alpha$-Al2O3 was 96% when sintered at 140$0^{\circ}C$ for 1h. On the other hand, ball milling of the non-seeded sol for 48h resulted in the relative density of 97% when sintered at 130$0^{\circ}C$ for 1h. The size and amount of $\alpha$-Al2O3 particles added by ball milling were 0.107 ${\mu}{\textrm}{m}$ and 0.5 wt%.

• 한국식품과학회지
• /
• 제27권5호
• /
• pp.690-696
• /
• 1995

수분함량(12.6, 18.4, 24.4%)이 다른 벼를 각각 도정하여 pin mill로 분쇄한 건식쌀가루와 물에 침지후 roll mill로 분쇄한 습식쌀가루의 특성을 비교하였다. 벼수분 24%에서 건식제조된 쌀가루에서는 지방과 회분함량이 다른 건식쌀가루에 비하여 낮았다. 벼의 수분함량이 많을수록 건식쌀가루는 미세하게 분쇄되었고 전분입자가 떨어져나간 흔적이 쉽게 관찰되었다. 또한 백색도와 수분흡수지수가 높았고, 수분용해도지수는 낮았다. 벼수분이 많을수록 amylogram에서의 setback값은 낮았다. 건식제분된 쌀가루들은 gel consistency와 gel strength에서 차이가 없었으나 습식제분된 쌀가루에서보다 덜 consistent하였고, gel strength는 낮았다. 호화후 $7{\sim}14$일 저장하였을 때 노화gel을 재호화시키는 데 필요한 enthalphy는 벼수분이 많은 건식쌀가루일수록 높았고, 습식쌀가루의 경우는 건식쌀가루보다 낮았다.

• 대한간호학회지
• /
• 제43권3호
• /
• pp.305-311
• /
• 2013

Purpose: The purpose of this study was to compare the effect of alcohol gel according to the amount and drying time in health personnel hand hygiene and to promote in their practice adequate and effective hand hygiene. Methods: The crossover experimental study was performed with 14 volunteers. Hands were artificially contaminated with 5 mL of $10^8$ CFU/mL of Serratia marcescens (ATCC 14756) and four different alcohol gel hand hygiene methods varying by the amount of alcohol gel (2 mL vs. 1 mL) and drying time (complete vs. incomplete) were compared. Samples were collected by glove juice sampling procedures. Results: Mean log reduction values of the four different hand hygiene methods were $2.22{\pm}0.36$, $1.26{\pm}0.53$, $1.49{\pm}0.60$, $0.89{\pm}0.47$ respectively for the 4 groups: adequate amount (2mL) and complete dry (30 seconds rubbing followed by 2 min air-dry), inadequate amount (1 mL) and complete dry, adequate amount and incomplete dry (15 seconds rubbing and no air-dry), and inadequate amount and incomplete dry. The difference was statistically significant in the adequate amount and complete dry group compared to other three groups (p<.001). Conclusion: Only alcohol gel hand hygiene with adequate amount and complete drying was satisfactory by U.S. FDA-TFM efficacy requirements for antiseptic hand hygiene products.

• 한국전기전자재료학회:학술대회논문집
• /
• 한국전기전자재료학회 2001년도 하계학술대회 논문집
• /
• pp.315-318
• /
• 2001

The optical and dielectric properties of TiO$_2$ thin films prepared with mixtures of Epoxy, bits-(4, 4'-p-toluenesulfonylacidic isoproplylidene)-cyclohexadiol and UVI 6990 in dry sol-gel process were investigated. The absorption peak of the films was showed at 360nm. Photocurrent of the thin films doped with 50 wt% of TiO$_2$was higher than that of nondoped thin films. Energy gap was lowered from 3.6 to 3.3 eV with increasing amount of TiO$_2$. Relative dielectric constants of samples were 1.5 to 3 and showed a characteristics of lower dielectric materials.

• 한국세라믹학회지
• /
• 제30권7호
• /
• pp.535-542
• /
• 1993

It was investigated in this study that a preparation method, activation energy, surface area, pore volume, pore size distribution and DTA analysis of the dry gel in process of producing monolithic porous gel in Li2O-Al2O3-TiO2-SiO2 system by the sol-gel technique using metal alkoxides. Activation energy for gellation according to the variation of water concentration and the kind of catalysts ranged from 10 to 20kcal/mole. Monolithic dry gels were prepared after drying at 9$0^{\circ}C$ when the amount of water for gellation was 4~8 times more than the stoichiometric amount, that was necessary for the full hydrolysis of the mixed metal alkoxide. The specific surface area, the pore volume, the average pore radius of the dried gel at 18$0^{\circ}C$ according to the various kinds of catalyst were about 348~734$m^2$/g, 0.35~0.70ml/g and 10~35$\AA$, respectively. It showed that the dry gels were porous body. As a result ofthe analysis of DTA, it was confirmed that the exothermaic peaks at 715$^{\circ}C$ and 77$0^{\circ}C$ was clue to the crystallization of dried gel.

• 한국미생물·생명공학회지
• /
• 제20권1호
• /
• pp.79-84
• /
• 1992

Rhodopseudomonas sphaeoides B6 세포를 agar gel 중에 고정했을 때, 수소생산을 위한 최적 agar 농도는 2(w/v)였다. B6의 2% agar gel 고정화균체(300ml gel: 2.85 mg dry cells/ml)와 비고정세포(1l culture: 0.87 mg dry cells/ml)에 있어서 초기의 최고 수소 생산활성은 각각 47.5 및 48.0ml/hr/culture로 거의 같았다. 그러나, 수소생산이 거의 정지된 배양후기에는 lactate의 제한공급( 10 mmole)에 의한 비고정세포의 활성회복은 50% 이하로 감소되었지만, 고정화세포의 활성은 거의 초기상태로 회복되었다. B6의 고정화균체를 이용하여 12시간 주기의 광조사조건으로, 매 1l의 수소생산시 마다 그에 소비된 만큼의 기질에 상당하는 9.3mmole의 DL-lactate와 1.86mmole의 L-glutamate 함유 기본배지를 주기적으로 공급한 결과, 228시간의 배양기간 동안 명암의 반복조건에도 불구하고 평균 510 ml/day/300m/ gel(2.9mg dry cells/ml)의 속도로 수소생산이 지속되었다. 이 결과는 광합성세균에 의한 수소생산에 있어서, 보다 효율적 기질공급과 가변적인 태양광 이용 조건에 대응되는 자동배양 시스템의 구성 가능성을 시사한다.

• 한국세라믹학회지
• /
• 제30권3호
• /
• pp.169-174
• /
• 1993

The porous silica glass prepared by the sol-gel method from the mixed solution of Si(OCH3)4, H2O, HCl and CH3OH with HCONH2 as a DCCA (Drying Control Chemical Additives). For investigation the characteristics of gels and glasses, we examined gels and glasses using TG-DTA, XRD, IR, SEM and porosimeter. The more content of formamide in the mixed solution increased, the more pore size and porosity of gel increased. In the excess formamide added gel, the properties of pore of gel were not so changed. The porous silica glass was prepared from the dry gel after heat treatment at 75$0^{\circ}C$. Porosity and mean pore size of the porous silica glass was 17~25% and 40~60$\AA$ relatively.

• 생명과학회지
• /
• 제9권3호
• /
• pp.268-275
• /
• 1999

고저화된 Rp.palustris균을 이용한 양식장 폐수주으이 질산염 제거를 위하여 Rp.palustris균의 고정화를 위한 담체를 조사하였는데, 탈질능력과 내구성을 실험한 결과 agar,k-carrageenan,그리고 PVA 3종의 담체주우 3% agar가 가장 적합한 담체이었다.Agar bead 내부로의 기질 이동 및 sheer stress를 고려해볼 때 최적 bead 크기는 직경 4mm 였고,접종되는 세포의 양은 25mg dry $cells/cm^2$gel 이었다. 탄소원으로 ethanol이 가장 적합하였고,최적 C:N ratio는 1.5이며,온도와 pH는 각각$31^{\circ}C$,PH 6 이었다. 이러한 조건에서의 최대 탈질율은 인공합성폐수의 경우 $345{\MU}{\ell};N_2/Cm^3 gel{\cdot}hr;이었으며,;modifed MYC 배지의; 경우는; 450{\MU}{\ell}};N_2/Cm^3 gel{\cdot}hr $이었다.

• 한국세라믹학회지
• /
• 제49권1호
• /
• pp.72-77
• /
• 2012

In the preparation of a hydroxyapatite [HAp]/gelatin [GEL] nanocomposite, the GEL matrix in aqueous solution of $H_3PO_4$ was modified by the introduction of aspartic acid [Asp], asparagine [Asn], and glycine [Gly]. The addition of Asp, Asn and Gly greatly affected the slurry formation of HAp/GEL nanocomposite and the resulting dry body showed variations in toughness with the addition of the different amino acids. The introduction of Asn into HAp/GEL nanocomposite was effective for producing the organic-inorganic interaction between HAp and GEL, and caused the increase of toughness. The formation reaction of the modified HAP/GEL nanocomposites was investigated by using XRD and FT-IR. The organic-organic interaction between the GEL matrix and the additives of Asp, Asn and Gly was confirmed from FT-IR analysis, and the organic-inorganic interaction between HAp nanocrystallites and the modified GEL matrix was also discussed, using FT-IR spectra patterns. Nanocrystallites of HAp were covalently bound with the GEL macromolecules and differently influenced by the modification species of Asp, Asn, and Gly.

• 한국세라믹학회지
• /
• 제35권1호
• /
• pp.66-78
• /
• 1998

the microstructure and mechanical properties of seeded and ball-milled dry gels prepared by boehmite sol-gel method were discussed. The densification of seeded gels was improved with increasing seed content namely the number of seed The number of seed was 1.09, 3.35, 5.72${\times}$1012/cm3 boehmite when seeded with 1, 3, 5wt% respectively The ball milled gel contained about 0.5wt% seed and the number of seed was 4.72${\times}$1012/cm3 boehmite. The sintered density of 5wt% seeded gel was below 80% when sintered at 1300$^{\circ}C$ for 1h. On the other hand that of ball milled gel was very improved and reached to 97% In the case of 3wt% seeded gels the density over 97% was attained when sintered at 1500$^{\circ}C$for 1h. and the grain of the sintered body was several micrometers in size. However the sintered body of ball milled gel showed grain size of submicrometer when sintered at 1300$^{\circ}C$ for 1h. And this specimen showed highest harness value of 1900kg/mm2 The fracture toughness increased with increasing sintering temperature. The sintered body of ball milled gel showed the largest grain size and the highest fracture toughness without regard to sint-ering temperature.