• 한국식품과학회지
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• 제28권2호
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• pp.393-395
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• 1996

배추조직의 연화방지를 위해 0.05 M $CaCI_2$ 용액중에서 배추의 예비열처리와 pectinesterase 주입전처리 및 효소의 침투를 용이하게 하기 위한 감압처리의 효과를 조사하였다. $CaCI_2$ 용액중 예비열처리에 의해 줄기는 약 50% 이상 경도가 증가하였고, 잎사귀의 경우는 약 4-5배 증가하였으며, PE 효소를 첨가한 경우 줄기 및 잎사귀 모두에서 경도가 더욱 증가하여 상승효과를 나타내었다. 배추를 감압처리한 후 효소를 주입 처리한 경우. 잎사귀 부분에서는 별다른 변화가 없었으나 줄기 부분의 경우 감압처리후 효소주입처리한 시료들은 모두 경도가 증가하였으며, 저장시험에 따르면 김치제조 4일째까시 경도유지 효과가 있었으나 그 후 점차 감하였다.

• 한국재료학회지
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• 제12권1호
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• pp.48-53
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• 2002

$Al_2O_3-SiC$ and $Al_2O_3-SiC$-TiC composite powders were prepared by SHS process using $SiO_2,\;TiO_2$, Al and C as raw materials. Aluminum powder was used as reducing agent of $SiO_2,\;TiO_2$ and activated charcoal was used as carbon source. In the preparations of $Al_2O_3-SiC$, the effect of the molar ratio in raw materials, compaction pressure, preheating temperature and atmosphere were investigated. The most important variable affecting the synthesis of $Al_2O_3-SiC$ was the molar ratio of carbon. Unreactants remained in the product among all conditions without compaction. The optimum condition in this reaction was $SiO_2$: Al: C=3: 5: 5.5, 80MPa compaction pressure under Preheating of $400^{\circ}C$ with Ar atmosphere. However there remains cabon in the optimum condition. The effect of $TiO_2$ as additive was investigated in the preparations of $Al_2O_3-SiC$. As a result of $TiO_2$ addition, $Al_2O_3-SiC$-TiC composite powder was prepared. The $Al_2O_3$ powder showed an angular type with 8 to $15{\mu}m$, and the particle size of SiC powder were 5~$10{\mu}m$ and TiC powder were 2 to $5{\mu}m$.

• 한국결정성장학회지
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• 제10권3호
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• pp.252-257
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• 2000

성장 전 GaAs기판의 열에칭 온도 변화에 따른 ZnS 에피층의 특성을 최초로 조사하기 위하여 450~$660^{\circ}C$로 열에칭한 기판 위에 hot wall epitaxy법으로 ZnS 에피층을 성장하였다. ZnS 에피층의 이중결정요동곡선의 반치폭은 기판의 열에칭 온도가 50$0^{\circ}C$와 $600^{\circ}C$일 때 가장 작았다. 그러나 ZnS 에피층의 photoluminescence(PL)특성은 기판의 열에칭 온도가 $500^{\circ}C$ 보다는 $600^{\circ}C$에서 더 양호하였다. 그러므로 고품질의 ZnS 에피층을 성장하기 위한 GaAs기판의 최적 열에칭 온도는 $600^{\circ}C$임을 알았다. 이러한 결과로부터 GaAs 기판의 열에칭은 $600^{\circ}C$에서 ZnS 에피층의 결정성과 PL특성에 좋은 영향을 주는 것으로 확인되었다.

• Restorative Dentistry and Endodontics
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• 제44권4호
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• pp.41.1-41.13
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• 2019

Objectives: This paper presents a systematic review and meta-analysis of the effect of preheating on the hardness of nanofilled, nanoceramic, nanohybrid, and microhybrid resin composites. Materials and Methods: An electronic search of papers on MEDLINE/PubMed, ScienceDirect, and EBSCOhost was performed. Only in vitro studies were included. Non-English studies, case reports, clinical trials, and review articles were excluded. A meta-analysis of the reviewed studies was conducted to quantify differences in the microhardness of the Z250 microhybrid resin composite using the Comprehensive Meta-Analysis software. Results: Only 13 studies met the inclusion criteria for this systematic review. The meta-analysis showed that there were significant differences between the non-preheated and preheated modes for both the top and bottom surfaces of the specimens (p < 0.05). The microhardness of the Z250 resin composite on the top surface in the preheated mode (78.1 ± 2.9) was higher than in the non-preheated mode (67.4 ± 4.0; p < 0.001). Moreover, the microhardness of the Z250 resin composite on the bottom surface in the preheated mode (71.8 ± 3.8) was higher than in the non-preheated mode (57.5 ± 5.7, p < 0.001). Conclusions: Although the results reported in the reviewed studies showed great variability, sufficient scientific evidence was found to support the hypothesis that preheating can improve the hardness of resin composites.

• 한국환경과학회지
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• 제23권7호
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• pp.1367-1373
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• 2014

This study was conducted to evaluate the effects of heating hatching eggs on the number of day-old chicks, egg temperature and egg weight during extended storage, and to provide basic information for improving hatchability to livestock producers. Eggs (Hy-line) were subjected to the following treatments: "control": eggs were maintained in an incubator after storage for 8 days; "T1": eggs were preheated for 8 hours at $23.9^{\circ}C$ after storage for 8 days in a hatchery; "T2": eggs were initially heated for 8 hours at $37.8^{\circ}C$ in an incubator and then preheated for 8 hours at $23.9^{\circ}C$ in a hatchery after storage for 8 days. The results were as follows: First, at the end of the experiment, the total number of day-old chicks was higher in T1, followed by T2 and then the control. This indicated that chick hatchability may be improved when eggs are preheated. Second, compared with the control, the number of day-old female chicks was expected to be higher in treatments with pre-heating; however, the results indicated the opposite effect. Third, as storage time lengthened, the factor that influenced preheating (the main effect and interactions) was not egg weight but egg temperature measured in the upper, middle and bottom parts of incubator. The temperatures recorded in all treatments ranged from 37.97 to $38.40^{\circ}C$ in the upper parts of incubator, 37.80 to $38.26^{\circ}C$ in the middle parts of incubator, and 37.94 to $38.59^{\circ}C$ in the bottom parts of incubator over storage. In conclusion, preheating was very effective in improving hatchability, and egg temperature was the main factor affecting preheating and hatchability.

• 산업기술연구
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• 제17권
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• pp.233-239
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• 1997

The effects of preheating the gas stream on deposition characteristics of ultrafine $SiO_2$ particles were investigated theoretically. The model equations such as mass and energy balance equations and aerosol dynamic equations were solved to predict the particle growth and deposition. The gas temperatures, $SiCl_4$ concentrations, $SiO_2$ particle volumes, $SiO_2$ particle sizes and deposition efficiencies of $SiO_2$ particles were calculated for various preheating temperatures. As the preheater setting temperature increases, the $SiO_2$ particle size distribution becomes more uniform, because the effect of $SiCl_4$ diffusion decreases.

• 한국해양공학회지
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• 제17권2호
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• pp.14-20
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• 2003

In this paper, a practical design criteria for judgement of crack occurrence in weldments is presented as a function of typical welding parameters, such as diffusible hydrogen, restraint intensity, and preheating temperature. The elastic analyses using the finite element techniques are employed in order to quantify the restraint intensities, numerically. Systematic experiments are also conducted in order to investigate the propensity of crack to typical welding parameters. The results of numerical estimation using the proposed method for the experimental specimens show the usefulness as a practical tool in welding induced crack problems with extensive uncertainties. Systematic experiments are also conducted in order to investigate the propensity of crack to typical welding parameters. The results of numerical estimation using the proposed method for the experimental specimens show the usefulness as a practical tool in welding induced crack problems with extensive uncertainties.

• 한국정밀공학회:학술대회논문집
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• 한국정밀공학회 2012년도 추계학술대회 논문집
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• pp.681-682
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• 2012

• 대한용접접합학회:학술대회논문집
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• 대한용접접합학회 2006년 추계학술발표대회 개요집
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• pp.144-146
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• 2006

• 한국주조공학회지
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• 제17권6호
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• pp.608-614
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• 1997

The effect of mold preheating temperature on the microstructure such as grain size, eutectic silicon morphology was investigated for the Al-7wt%Si-0.3wt%Mg alloy. Microstructural variations have been characterized as a function of Sr addition and cooling rate during solidification. Microstructures were correlated with cooling rate, local solidification time and eutectic nucleation temperature, etc. In this study, Sr addition caused increase of local solidification time, undercooling and reduction of eutectic plateau temperature. In logarithmic scale, local solidification time was in inverse proportion to cooling rate. Eutectic nucleation temperature was in inverse proportion to cooling rate of logarithmic scale. Increasing the cooling rate refined dendrite arm spacing and eutectic silicon. Dendrite arm spacing was logarithmically in inverse proportion to cooling rate. Without modifier addition, eutectic silicon was modified at cooling rate of $7^{\circ}C/s$ or higher.