• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2020년도 가을 학술논문 발표대회
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• pp.169-170
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• 2020

The purpose of this study is to explore the possibility of estimating optimum surface finish time of the fresh concrete placed at the job site by applying a surface hardness test meter(Durometer). Tests are carried out by measuring and comparing the Penetration resistance test and hardness test by Durometer. Penetration resistance tester and improved Durometer are similar, but the higher the temperature, the higher the setting time, and the higher the correlation was shown. When the hardness value of the improved Durometer is about 50 HD, it is found that the initial and 80 HD represent the end. It is expected that this will be useful in determining the finish time of the surface at the actual site.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2023년도 가을학술발표대회논문집
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• pp.17-18
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• 2023

This study aims to compare the hardness value development characteristics according to the water-cement ratio during a series of experiments to develop a setting estimator for an AI-based concrete finishing automation system. For the test variables, water-cement ratios are varied with 30, 40 and 50%. Proctor penetration test and surface hardness test by setting time estimator are conducted to estimate the setting time. For the effect of water-cement ratios, they did not affect the surface hardness either, while initial set time and final set time are not constant with water-cement ratios.

• 한국해양공학회지
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• 제3권2호
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• pp.138-144
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• 1989

It has been very important in various industry fields to improve the fatigue strength characteristics of bearings such as bearing life, fatigue limit, etc., because such poor properties could result in shortening the machinery life as well as in decreasing the accuracy. However, no successful heat treatment criterion seems to be available at present. In this study, the effect of the $170^{\circ}C\times120min$ tempering cycles repeated after $380^{\circ}C\times80min$ oil quenching for $800^{\circ}C$ spheroidizing-annealed bearing steel (STB2) as base metal on the $120^{\circ}C$ high temperature rotary bending fatigue strength characteristics were investigated, including the effects on hardness, Charpy impact value and micro-structure, in order to seek for the best heat treatment condition finally. The important results obtained are as follows : 1) The optimal cycle of tempering so that the fatigue strength .sigma. could become the highest was the 4th cycle. And it is confirmed that this $\sigma_{F}$ is about 6 times more increased than that of base metal, and about 1.3 times more increased than the case of the 1 cycle tempered. 2) As a result of the investigation for the effects of tempering cycles on hardness, the hardness at the tempering number of 2 thru 5 cyles was not decreased severely ; only about 10% decrease from those of the quenched and 1 cycle tempered case. Such hardness is equivalent to $H_{R}$/C61-62 with no bad effect on anti-abrasion of bearing steel. 3) In the case of 2 thru 5 cycle tempering as well as 1 cycle tempering, the impact value was not so improved comparing with the case of quenching, but an increase of 5 to 10% could be expected at least. 4) It was experimentally confirmed that the control of the mechanical properties improvement such as fatigue strength and fatigue life for bearing steels could be possible by the number of tempering cycles.

• 한국해양공학회지
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• 제3권2호
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• pp.638-638
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• 1989

It has been very important in various industry fields to improve the fatigue strength characteristics of bearings such as bearing life, fatigue limit, etc., because such poor properties could result in shortening the machinery life as well as in decreasing the accuracy. However, no successful heat treatment criterion seems to be available at present. In this study, the effect of the $170^{\circ}C\times120min$ tempering cycles repeated after $380^{\circ}C\times80min$ oil quenching for $800^{\circ}C$ spheroidizing-annealed bearing steel (STB2) as base metal on the $120^{\circ}C$ high temperature rotary bending fatigue strength characteristics were investigated, including the effects on hardness, Charpy impact value and micro-structure, in order to seek for the best heat treatment condition finally. The important results obtained are as follows : 1) The optimal cycle of tempering so that the fatigue strength .sigma. could become the highest was the 4th cycle. And it is confirmed that this $\sigma_{F}$ is about 6 times more increased than that of base metal, and about 1.3 times more increased than the case of the 1 cycle tempered. 2) As a result of the investigation for the effects of tempering cycles on hardness, the hardness at the tempering number of 2 thru 5 cyles was not decreased severely ; only about 10% decrease from those of the quenched and 1 cycle tempered case. Such hardness is equivalent to $H_{R}$/C61-62 with no bad effect on anti-abrasion of bearing steel. 3) In the case of 2 thru 5 cycle tempering as well as 1 cycle tempering, the impact value was not so improved comparing with the case of quenching, but an increase of 5 to 10% could be expected at least. 4) It was experimentally confirmed that the control of the mechanical properties improvement such as fatigue strength and fatigue life for bearing steels could be possible by the number of tempering cycles.

• 생물환경조절학회지
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• 제19권4호
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• pp.366-371
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• 2010

예냉(2, 4, $8^{\circ}C$)과 저장온도(4, 8, $10^{\circ}C$)가 수출용 딸기 '매향'과 '수경'의 저장성에 미치는 영향을 알아보고자 본 연구를 수행하였다. 2010년 3월 16일에 숙도 70%의 과실을 진주지역 온실에서 수확하였다. 농가의 예냉기에서 3시간 동안 예냉한 딸기를 30분만에 실험실로 수송하였고, 즉시 챔버에 저장하였다. 예냉을 위해 농가 현장에 설치되어 있는 간이 예냉기를 이용하였다. 저장하는 동안 딸기의 무게변화, 경도, 색도, 당도, 잿빛곰팡이병 발생율을 이틀 간격으로 3월 16일부터 3월 30일까지 조사하였다. 두 품종 모두 경도, 당도, 색도는 '매향'보다 '수경'이 높았고, $4^{\circ}C$에 저장 하였을 때 경도와 당도함량이 가장 높았다. 숙도가 진행됨에 따라 경도와 당도는 감소하는 경향을 보였다. 또한 모든 온도처리에서 저장기간이 경과함에 따라 무게의 변화가 감소하였다. 잿빛곰팡이병은 $10^{\circ}C$에 저장하였을 때 발생율이 가장 높았다. 따라서 딸기의 신선도를 장기간 유지하기 위해서는 두 품종 모두 $2^{\circ}C$에 예냉하여 $4^{\circ}C$에 저장하는 것이 효과적인 것으로 판단된다.

• 한국식품조리과학회지
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• 제30권1호
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• pp.64-75
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• 2014

Freeze-drying process was used for 10 major protein foods referred by the Korea Health Statistics 2011 as follows; chicken, pork, beef, eggs, tofu, squid, soybean, mackerel, anchovy, and pollack/frozen pollack. Boiled samples and re-hydrated samples after freeze-drying were prepared for analysis. The weight variation, the chromaticity, the mechanical texture and sensory properties by eight trained panelists were measured. In the ratio of re-hydration, the anchovy showed the highest value(89.40%), followed by eggs, and squid showed the lowest value(35.51%). Changes of Hunter color value were observed among all samples. For rates on changes of hardness, every sample was increased except for eggs(p<.05). Among the 9 samples, except for eggs, chicken showed the lowest rate of increase in hardness(125.44%) while squid showed the highest rate of increase in hardness(1335.1%). Except for eggs and pork, eight samples represented differences in sensory properties, especially in juiciness and tenderness(p<.05). As a result, we found that egg is the most suitable for freeze-drying among 10 protein sources followed by pork and chicken.

• 한국버섯학회지
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• 제8권2호
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• pp.51-58
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• 2010

Total eight different winter mushroom (Flammulina velutipes) strains were characterized by comparisons of fruiting body morphology, hardness and color after growing at different temperature. Although variations depending on the strains were observed, in general, both stipe length and pilus diameter were shorter while pilus thickness was bigger as growing temperatures were decreased. No significant differences in stipe thickness were observed. The ASI4065 and 4151 had the tallest stipe and the ASI4021 had the shortest stipe. The ASI4103 strain had the biggest pilus diameter. The ASI4153 had most thick pilus, while the ASI 4021 had least thick pilus. Also, the ASI4166 had the most thick stipe and the ASI4065 had the most thin stipe. The hardness of white mushrooms were increased by decreasing growth temperatures, while no relationships between the hardness of brown mushrooms. In most strains, stipe were much stronger than pilei and white mushrooms were harder than brown ones. The strain having most strong stipe was ASI4021. Both ASI 4021 and ASI4166 had the most strong pilus. The color of pilus has much lighter than that of stipe. White mushrooms had high brightness value ranging from 70-90, while brown mushrooms showed low brightness value from 30-70. Saturation value was higher in brown mushrooms. Based on our study, it was shown that environmental conditions had some effects on winter mushrooms, but genetic differences among strains were more important factors to determine most characteristics of winter mushrooms.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2012년도 추계학술대회 논문집
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• pp.280-285
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• 2012

The 1st assessment (performance test) was applied to assure the floor impact sound performance for developing the dry double- floor with the change of rubber hardness of the upper panel's support and the ceiling structure of the sub-floor. Depends on the change of the rubber hardness in substructure, the heavy-weight sound impact value is improved up to 3 dB, and the light-weight sound impact value is moved up to 21 dB, comparing with the bare-slab. Also, the improved value for the floor impact sound conjugating with the sub-floor's ceiling was 5dB. Based on this result, the 2nd assessment (performance test) was made the state that the rubber hardness of the sub-floor support was ranged between 50 and 70 for considering the stability of walking patients. In addition to this process, the assessment was carried out with a variety of ceiling structure applied to the dry doublefloor structure with the air flow system on the sub-floor's ceiling. The result for the 2nd assessment proved that TYPE-11 had the better sound reduction performance in the heavy-weight impact sound test than other types, and also for the light-weight impact sound TYPE-11 had the 29 dB sound reduction performance overall. Henceforth, based on the result the research for the sound reduction performance from the floor impact sound shall be ongoing process as well as the development of a double-dry floor and a sound reduction ceiling to suitable on the field.

• 열처리공학회지
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• 제30권5호
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• pp.215-221
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• 2017

The effect of austenitizing temperature on the degree of carbides re-solutionizing, mean graine size, hardness and the volume fraction of retaind austenite ($V_{\gamma}$) etc., has been studied by means of metallography, X-ray diffractometry and hardness measurement in STD 11 tool steel. As austenitizing temperature increases, the amount of alloying elements which is re-dissolved into matrix increases, resulting in increase of $V_{\gamma}$, due to the chemical stabilization of austenite. The Vickers hardness value decreases with increasing austenitizing temperature, which is attributed to grain size as well the volume fractions of $V_{\gamma}$ and carbides. Theoretical diffraction intensity of (200) ${\alpha}^{\prime}$, (211) ${\alpha}^{\prime}$ (200) ${\gamma}$ and (220) ${\gamma}$ peaks obtained by $CuK_{\alpha}$ chracteristics X-ray (${\lambda}=0.15429nm$) was calculated, and quantitative analysis of $V_{\gamma}$ could be carried out by X-ray diffraction method. The resultant value is well coincided with the value obtained by image analysis method. When the quenched specimen is tempered above $200{\sim}400^{\circ}C$ for 30 min, the transition carbides i.e., MC and $M_2C$ in the size of about 20 nm begin to precipitate at $300^{\circ}C$.

• 한국식품조리과학회지
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• 제31권6호
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• pp.781-790
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• 2015

Germinated brown rice (GBR) flour (0%, 25%, 50%, 75% and 100%) was added to brown rice (BR) and white rice (WR) flours and the densities of pound cake batters, morphology, color value, textural properties, sensory preference test, and hardness during storage were investigated, in order to develop health functional gluten-free rice pound cakes with high nutritional value. The rice was milled with the newly developed rice milling method. The entire shape and cross section of all cakes were symmetrical and desirable. The density of pound cake batter and weight of cake increased with addition of increasing GBR. Specific volume was not significantly different (2.1-2.4 mL/g). Textural properties of cakes between WR-GBR and BR-GBR showed different trends with adding GBR. On the sensory test, overall quality of rice pound cake did not significantly differ between rice flour types. Hardness of rice pound cakes and brittleness decreased with increasing addition of GBR flour. The hardness and the peak intensity at $2{\theta}=17^{\circ}$ decreased with increasing addition of GBR. The results, that addition of GBR flour improved the nutrition value and functionality of gluten free rice pound cakes and prevented staling of rice pound cakes during storage.