• 대한치과기공학회지
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• 제30권1호
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• pp.17-23
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• 2008

Gypsum products are used for the preparation of stone casts of oral and maxillofacial structures and as important adjuncts to dental laboratory operations involved in the production of dental prosthesis. Accuracy and dimensional stability over time are properties of concern in fixed prothodontics. Gypsum products used in denstry are a form calcium sulfate hemihydrate and are classified as 1 of 5 types according to International Standard Organization(ISO) 6873. All die materials exhibit some dimensional change during setting, but expansion and contraction during setting and dimensional changes in response to varations in temperature and the water-powder ratio must be minimal. Although numerous investigators have studied the properties of die materials, several products have been introduced recently with manufacturer claims of superior dimensional stalility. The aim of this study was to determine the surface properties using various separating materials of dental gypsum products The results were as follows 1. In the comparison of first and second plaster distances before separation in different separating agent, there was no significant difference except using Trio separating agent. The interface using Trio separating agent forms like to pores. 2. In the comparison of first and second plaster distances after separation in different separating agent, there was significant difference. The interface of plasters using WD-40, Trio and Vaseline was showed some gaps. Each they were measured at average 7.97 $\pm$ 2.07 ${\mu}m$, 63.09 $\pm$ 23.25 ${\mu}m$, 27.59 $\pm$ 4.19 ${\mu}m$. 3. In the comparison of the surface, the surface of control sample(using none seperating agent) showed irregular properties and the surface using Trio and Vaseline become wrinkled. Specially the surface using Vaseline was showed shiny properties. But the surface using MAGIC SEP, Plaster seperating agent, WD-40 showed regular properties.

• 한국자기학회지
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• 제3권2호
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• pp.87-93
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• 1993

질화철(Fe-N) 박막을 DC magenetron sputtering 방법으로 증착하였다. 스퍼터링 기체중의 질소유량비와 스퍼터링 power가 박막의 구조와 조성, 자기적 특성에 미치는 영향을 조사하였다. 증착 박막중의 질소원자 함유량은 박막의 구조, 생성상 및 자기적 특성을 결정짓는 지배적인 인자이다. 낮 은 질소 유량비에서 증착하였을 경우 박막은 질소 침입형 $\alpha$-Fe 결정구조를 갖으며, 질소원자 함유량에 비례하여 격자변형은 증가하고 포화자화값은 감소하였다. 격자변형이 어느 정도 심하게 일어 나면 주상정으로의 성장이 억제되어 평탄한 표면형상과 균일한 미세구조를 갖게되며, 자구벽의 이동이 용이하게 되어 보자력의 급격한 감소를 가져왔다. 질소유량비가 증가하여 박막내의 질소함유량이 15 at.%가 되면 격자정수 d(110)이 5% 증가하게 되며 이때 $Fe_{2-3}N$ 상으로의 상변화가 일어나 포화 자화값은 급격히 감소한다.

• 한국지역사회생활과학회지
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• 제28권3호
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• pp.365-375
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• 2017

The purpose of this study was to investigate the maximal elongation rate and area expansion ratio of human skin in various postures. Five males and five females (male: $23{\pm}2yr$ in age, $177.9{\pm}4.8cm$ in height, $76.7{\pm}8.8kg$ in body weight, $24.2{\pm}2.5$ in BMI, $16.2{\pm}3.4%$ in body fat; female: $22{\pm}1yr$, $163.2{\pm}3.6cm$, $51.4{\pm}2.7kg$, $19.3{\pm}1.6$, $27.4{\pm}6.7%BF$) participated in this study. Measurements were conducted using a pen and tape on the elbow, knee, wrist, shoulder, and neck. Subjects held postures so that each joint of the body regions was bent at its maximal level. The results were as follows: 1) The maximal elongation rate of skin showed a significant difference among the regions: $16.6{\pm}3.4%$ for the wrist, $22.4{\pm}5.5%$ for the neck (back), $37.6{\pm}11.3%$ for the shoulder, $42.6{\pm}10.0%$ for the knee, and $43.9{\pm}4.0%$ for the elbow (p<0.05). 2) The maximal expansion rate of the body surface area had the greatest values on the elbow ($93.7{\pm}6.4%$) and knee ($74.8{\pm}10.8%$). 3) No significant difference was found between males and females. In summary, maximal values of skin elongation and expansion rates in vivo were greater than in vitro values known from previous reports. These results can be applied to develop electronic fibers or textiles for wearable tight fit work clothing as well as fitness wear.

• 한국식품영양학회지
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• 제21권4호
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• pp.448-456
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• 2008

In this study, domestic wheat white breads were prepared with the substitution of 1.5, 3.0, 4.5, and 6.0% Nelumbo nucifera G. tea powder(NNTP). The samples and a control were then compared with regard to quality characteristics, including pH, total titratable acidity, fermentation power of dough expansion, specific volume, baking loss, moisture content, color, textural characteristics, external and internal surface appearances, and sensory qualities in order to determine the optimal ratio of NNTP in the formulation. As the NNTP contents increased, the pH of dough and bread, baking loss, and lightness decreased, whereas the total titratable acidity of dough and bread increased. The fermentation power of dough expansion increased with increasing incubation time. The NNTP samples evidenced significantly higher specific volume, greenness, yellowness, resilience, and crumb consistency than were observed in the control group. However, hardness and fracturability evidenced the opposite effect. The water content and uniformity of the crumb pores were highest at a substitution level of 1.5%, and were lowest at a level of 4.5%. Crumb color, flavor, and delicious taste decreased with increasing NNTP contents, whereas lotus leaf flavor, astringency, bitterness, and off-flavor increased. Density of the crumb pore and crumb springiness were not significantly different among the samples. Softness, chewiness, and overall acceptability were maximal with the 1.5% substitution, and were minimal in the 6.0% group. In conclusion, our results demonstrate that $1.5{\sim}3.0%$ NNTP may prove quite useful as a substitute for domestic wheat flour in the production of white bread, and may evidence favorable nutritional and functional properties.

• 한국식품영양학회지
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• 제23권2호
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• pp.178-185
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• 2010

Barley leaves tea white bread were prepared by the addition of 0.005, 0.010, 0.015, and 0.020% hemicellulase to flour of the basic formulation. The experiments and control were then compared in terms of quality characteristics, including pH, total titratable acidity, fermentation power of dough expansion, specific volume, baking loss, moisture content, color, textural characteristics, internal surface appearances, and sensory qualities in order to determine the optimal ratio of hemicellulase in the formulation. There were no significant differences in pH and total titratable acidity of dough and bread among the experiments. Fermentation power of dough expansion were increased as incubation time increased. Bread made by the addition of hemicellulase had significantly higher specific volume than the control group. However, lightness and yellowness showed the reverse effect. Greenness was not significantly different among the samples. Baking loss was the highest at the 0.020% addition level, and moisture content was maximal with the 0.010% addition, while the lowest in the control bread samples. As hemicellulase contents increased, harness and fracturability decreased. Resilience was maximal with the 0.015% addition, and was minimal in the 0.005% group. In the sensory evaluation, color, flavor, softness, overall acceptability, barley leaves flavor, delicious taste, astringency, bitterness, and off-flavor were not significantly different among the samples. In coclusion, the results indicate that adding 0.010% hemicellulase in barley leaves tea white bread is optimal for quality and provides a product with reasonably high overall acceptability.

• 한국식품조리과학회지
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• 제27권5호
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• pp.507-522
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• 2011

In this study, samples of wheat flour and dough were prepared by adding of 1, 3, or 5% branched dextrin, which is produced from the amylopectin of waxy corn starch using a cyclization reaction with a branching enzyme. The samples were then evaluated qualitatively in terms of farinogram, viscogram, and extensogram characteristics. The fermentation power of dough expansion, extensogram characteristics, specific volume, baking loss, external/internal surface appearance, and sensory qualities were also examined after 4 weeks of storage at -20$^{\circ}C$ to determine the effect on freeze-thaw stability and quality improvement of branched dextrins in the soft roll bread formulation. Furthermore, the samples along with a control were compared regarding their quality characteristics, including changes in moisture content, water activity, color, and textural characteristics during a storage period of 4 days at 20$^{\circ}C$ to determine the effect on preventing retrogradation of the branched dextrin. As the branched dextrin content increased, area and extensibility increased, whereas water absorption, fermentation power of dough expansion, resistance/extensibility ratio, baking loss, and brownness of the crust decreased. However, the control group presented significantly higher peak viscosity, resistance, specific volume, taste, overall acceptability, moisture content, water activity, springiness, cohesiveness, and resilience values than those of the branched dextrin samples, whereas lightness, hardness, and chewiness showed the reverse effect. As the storage period increased, lightness, hardness, and chewiness increased, whereas cohesiveness decreased. In conclusion, the results indicate that adding 1~3% branched dextrin into a soft roll bread formulation from frozen dough had no positive effect on freeze-thaw stability or preventing retrogradation but may provide good nutritional properties.

• International Journal of Ocean Engineering and Technology Speciallssue:Selected Papers
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• 제3권1호
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• pp.40-48
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• 2000

The term "deep holes" is used to describe the machining of holes with a relatively large length to diameter ratio. The main feature of BTA deep hole drilling is the stabilization of cutting force necessary for the self guidance of the drill head. An additional feature is the cutting tool edges that are unsymmetrically placed on the drill head. There is an increasing necessity to predict the hole geometry and other dynamic stability behavior of deep hole drilling guidance. In this study, the effects of BTA deep hole drilling conditions on the hole profile machined piece are analyzed using domain analysis technique. The profile of deep hole drilled work piece is related to cutting speed, feed rate, chip flow, tool wear, and so on. This study deals with the experimental results obtained during the BTA drilling on SM45C, SM55C carbon steels and SCM440 steels under various cutting conditions, and these results are compared with analytical evaluations.aluations.

• KEPCO Journal on Electric Power and Energy
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• 제7권1호
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• pp.167-169
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• 2021

In this study, monodispersive silica nanoparticles with double mesoporous shells were synthesized, and the pore size of synthetic mesoporous silica nanoparticles was controlled. Cetyltrimethylammonium chloride (CTAC), N, N-dimethylbenzene, and decane were used as soft template and induced to form outer mesoporous shell. The resultant double mesoporous silica nanoparticles were consisted of two layers of shells having different pore sizes, and it has been confirmed that outer shells with larger pores (Mean pore size > 2.5 nm) are formed directly on the surface of the smaller pore sized shell (Mean pore size < 2.5 nm). It was confirmed that the regulation of the molar ratio of pore expansion agents plays a key role in determining the pore size of double mesoporous shells.

• 태양에너지
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• 제9권1호
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• pp.53-61
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• 1989

In the present investigation, experiments on the melting of a phase change material were performed to research heat transfer phenomena generated by means of conduction and natural convection in the vertical tube at inward melting. The phase change material used in the experiments is 99 percent pure n-Docosane paraffin which is measured melting temperature of $42.5^{\circ}C$, latent heat of 37.5 cal/g, heat conductivity of $0.1505W/m^{\circ}C$. Experiments were performed both in the no-subcooling which is initiating it at melting temperature of phase change material, and in the subcooling which means to initiate it under melting temperature of phase change material, in order to compare and investigate the horizontal temperature history, vertical temperature history, ratio of melting and melted mass, figure of the melting front in the vertical tube. In the experimental results, heat transfer from tube wall to phase change material were due to conduction at early stage and due to natural convection with the passage of time, and then occurred melting downward from surface by volumetric expansion. Natural convection affects temperature distribution in the tube, ratio of melting and melted mass, figure of the melting front and then progress rapidly in case of nosubcooling compared to subcooling.

• Preventive Nutrition and Food Science
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• 제6권3호
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• pp.163-169
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• 2001

To produce expanded, minimally hard extrudates from blends of raw pork meat (20%), defatted soy flour (25%), and corn starch using a single-screw extruder, various combinations of feed moisture, process temperature, and screw speed were evaluated. First series of extrusion runs were conducted according to a central composite rotatable design/response surface methodology (RSM). Upon assessing the full model for each response, insignificant terms were eliminated to determine final response surface models. Screw speed within the range evaluated was found to have no significant effect on expansion ratio (ER) or shear force (SF) of extrudates. Since examinations of the response surfaces and their generated grids of predicted values indicated that maximum ER and minimum SF were likely to be attained with a moisture-temperature combination outside the RSM experimental range, the second series of extrusion runs were conducted with several selected combinations of moisture and temperature to determine a practical optimum extrusion condition. The combination of 22.78% feed moisture, 16$0^{\circ}C$ process temperature, and 170 rpm screw speed was chosen as such a condition, and used in the final extrusion. The final product required less force to break than did commercial pretzel sticks.