• 한국콘크리트학회:학술대회논문집
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• 한국콘크리트학회 2005년도 추계 학술발표회 제17권2호
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• pp.715-718
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• 2005

The purpose of this paper is to investigate on hydration, setting time and compressive strength properties of cement paste mixed alkali-free accelerator using aluminum sulfate for shotcrete. The experimental focus is to variouse added element with alkali-free accelerator for shotcrete using aluminum sulfate. When diethanolamine was used as a component of alkali-free accelerator, alkali-free accelerator contributed to increasing early hydration, setting time and compressive strength properties of cement paste and mortar.

• Preventive Nutrition and Food Science
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• 제5권1호
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• pp.7-9
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• 2000

Variouss concentrationss of free malonaldehyde were prepared from 1,1,3,3-tetraethoxy propane (TEP). Spectrophoto-metric determination and HPLC analysis of free malonaldehyde instead of malonaldehyde-thiobaribituric acid (MA-TBA) complex were conducted. Malonaldehyde was well separated on a $\mu$Bondapak C18 column. The absorbances at 254 nm and the HPLC peak areas of free malonaldehyde increased with the increase in its concentration. The correlation coefficient between absorbances and peak areas was 0.998. The total time elapsed to conduct the whole procedure was less than 15 minutes. This method directly measured the amount of free malonaldehyde in a short period of time successfully. This procedure is expected to be used as a rapid, accurate and specific means to de-termine the development of lipid oxidation in food.

• 제어로봇시스템학회논문지
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• 제8권11호
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• pp.970-975
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• 2002

We suggests an effective method to construct time-varying C-obstacles in the 3-dimensional configuration space (C-space) using free arc. The concept of free arc was defined mathematically and the procedure to find free arc in the case off-dimensional C-space was derived in [1]. We showed that time-varying C-obstacles can be constructed efficiently using this concept, and presented simulation results for two SCARA robot manipulators to verify the efficacy of the proposed approach. In this paper, extensions of this approach to the 3-dimensional C-space is introduced since nearly all industrial manipulators are reasonably treated ill the too or three dimensional C-space f3r collision avoidance problem The free arc concept is summarized briefly and the method to find lice arc in the 3-dimensional f-space is explained. To show that this approach enables us to solve a practical collision avoidance problem simulation results f3r two PUMA robot manipulators are presented.

• 한국생산제조학회지
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• 제20권2호
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• pp.187-192
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• 2011

UBM(Under Bump Metallurgy) is very important for successful realization of Flip-Chip technology. In this study, it is investigated the interfacial reactions between various Sn-Ag solder alloys and Ni-P/Au UBM and Cu plate finish. It is also evaluated the shear strength by using the micro shear-punch test method for Sn-37Pb alloy, binary and ternary alloys of environment-friendly Pb-free solder alloys which are applied in the electronic packages. In terms of interfacial microstructure, the Pb-free solder joints have thicker IMCs than the Sn-Pb solder joints. The thickness of IMC is related to Reflow time. The IMC has been observed to grow with the increase in Reflow time. As a result of the shear test, in case of Max. shear strength, Pb-free solder showed the highest strength value and Sn-37Pb showed the lowest strength value 10 be generally condition of Reflow time.

• Journal of the Optical Society of Korea
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• 제15권2호
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• pp.161-167
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• 2011

In this paper, we propose an in-plane switching (IPS) mode for liquid crystal displays (LCDs) that, in principle, is free of retardation of the LC cell. Basically, the optical configuration of the LC cell consists of an A-plate and an LC layer for switching between the dark and bright states. We could achieve a fast response time compared with the conventional in-plane LC cell because the free retardation condition of the proposed LC cell enables us to reduce the cell gap even by quarter-wave retardation without any change of the optimized LC material in the transmissive mode. Experiments for verification of the proposed in-plane switching LC cells have shown a significant reduction of the rising time and falling time simultaneously due to the small cell gap. Furthermore, we also proposed an optical configuration for wide viewing property of the retardation free IPS LCD by applying the optical films. We proved the wide-view property of the retardation free IPS LCD by comparing its optical luminance with the calculated optical property of the conventional IPS LCD.

• Archives of Plastic Surgery
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• 제49권5호
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• pp.696-700
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• 2022

We performed distal bypass and free flap transfer in a single-stage operation to repair an extensive soft tissue defect in an ischemic foot of an 84-year-old woman. The nutrient artery of the free flap was anastomosed to the bypass graft in an end-to-side manner. Subsequently, the bypass graft became occluded on several occasions. Although intravascular and surgical interventions were performed each time, the bypass graft eventually became completely occluded. However, despite late occlusion of the nutrient artery, the free flap has remained viable and the patient is ambulatory. The time required for a transplanted free flap to become completely viable without a nutrient artery is likely longer for an ischemic foot compared with a healthy foot. However, the exact period of time required is not known. A period of month was required in our patient. We report this case to help clarify the process by which a free flap becomes viable when applied to an ischemic foot.

• 동력기계공학회지
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• 제18권3호
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• pp.73-78
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• 2014

Recently, Free cooling system usage has increased at many buildings in intermediate and winter season. Free cooling system is used to reduce the energy consumption of refrigeration in that season. Free cooling system is refrigeration system using cooled water. In general, this system is applied with the building having refrigeration load at all time such as a data center. In this study, energy consumption of a data center taking free cooling system in Ulsan was evaluated by the software HYSYS. the main result is as in the following : free cooling system is effective from January to April and from November to December. In case of Ulsna in 2013, using free coolng system is able to spend refrigeration energy of about 15% less than existing system. According to this result, it is appropriated that free cooling system is used in building having refrigeration load at all time such as data center.

• 한국환경과학회지
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• 제17권2호
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• pp.211-224
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• 2008

Characteristics of the esterification reaction between free fatty acid in rice bran oil and methanol was investigated in the presence of catalysts, such as PTS(p-toluene sulfonic acid), Amberlyst 15 dry and SCX(silica gel based strong cation exchange resin). While reaction temperature was kept constant at $65^{\circ}C$, initial feed content of free fatty acid was varied from 100% to 1% by addition of pure free fatty acid which was previously made from rice bran oil. Also, the effect of mole ratio of methanol to fatty acid on the final conversion was examined. When esterification of pure free fatty acid was catalyzed by several acids, final conversions were increased in order of Amberlyst 15 dry, SCX and PTS. Using PTS catalyst, initially the reaction proceeded in homogeneous 2nd oder reaction mechanism. However, phase of reaction mixture changed from homogeneous to heterogeneous along the reaction time and then reaction rate was retarded by mass transfer resistance of methanol. Final conversion of free fatty acid in reaction mixture was depended on initial feed content of free fatty acid, and had maximum value at 30% of initial feed free fatty acid content for all kinds of catalysts used. And the final conversion was increased with mole ratio of methanol by the improvement of reaction rate. When initial feed free fatty acid content below 10% and the reaction was catalyzed by PTS, concentration of free fatty acid in reaction mixture was increased in the middle of reaction time by hydrolysis of triglyceride in reaction mixture. Also, if silica gel was added into the reaction mixture which had initial feed free fatty acid content below 50%, final conversion was increased by the adsorption of moisture produced. The SCX catalyst made the esterification reaction of free fatty acid to progress like in case of PTS catalyst. However, when initial feed free fatty acid content below 10%, concentration of free fatty acid in. reaction mixture was decreased monotonically and not increased in the middle of reaction time on the contrary to the case of PTS. Thus, SCX catalyst accomplished more high value of final conversion than PTS catalyst for the initial feed fatty acid content range from 50% to 5% In case of initial feed free fatty acid content of 1% and mole ratio of methanol was 2, concentration of free fatty acid in reaction mixture increased over the initial feed free fatty acid content for all kind of catalysts used. Although SCX catalyst was added into reaction mixture which had 1% of initial feed fatty acid content, final conversion was hardly raised by mole ratio of methanol.

• 한국인터넷방송통신학회논문지
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• 제18권6호
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• pp.133-137
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• 2018

아두이노는 소형 마이컴으로 다양한 산업에 사용되고 있으며 특히, 오픈소스 하드웨어 IoT 디바이스로 널리 사용되고 있다. 아두이노의 멀티태스킹 방식은 크게 수퍼루프 타이밍과 RTOS 쓰레드 방식으로 나뉘며 수퍼루프 타이밍 방식은 구현이 단순하고 이해하기 쉽다는 장점이 있지만 하나의 작업이 길어지면 다음 작업의 실행에 영향을 줄 수 있다는 단점을 가진다. 또 RTOS 쓰레드 방식은 다른 작업시간에 영향을 받지 않고 실행할 수 있다는 장점을 갖지만 소형 마이컴인 아두이노는 쓰레드의 개수가 늘어나면 쓰레드의 컨텍스트 스위칭타임으로 수퍼루프 타이밍 방식에는 없는 부가 시간이 발생하는 단점이 있다. 본 논문은 이와 같은 서로 다른 특징들을 분석하기 위하여 아두이노 우노 R3와 FreeRTOS를 사용하였으며 실험을 위한 태스크는 빌트인 LED 포트에 8000번의 디지털 신호를 보내도록 작성하였다. 같은 크기의 태스크를 두 방식으로 실행하면 수퍼루프 방식이 FreeRTOS 멀티태스킹 보다 3ms 빠른 실행을 보인다. 여러 개의 태스크를 동시에 실행하면 수퍼루프 방식의 태스크는 순차 실행으로 첫 태스크와 마지막 태스크의 실행시간 차가 크게 나타나며 FreeRTOS 방식은 모두 중첩되어 동시에 실행 가능하지만 30ms 정도의 컨텍스트 스위칭타임의 실행 시간지연이 발생한다.

• 한국식품저장유통학회지
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• 제14권6호
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• pp.624-632
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• 2007

가을울금과 봄울금의 채취시기에 따른 일반성분, 아미노산, 유리당 및 환원당 및 비타민 C와 $B_1$ 등의 함량을 비교분석 하였다. 가을울금과 봄울금의 수분, 조회분, 조단백 및 조지방 함량은 채취시기가 늦을수록 증가하였고, 가용성무질소분 함량은 채취시기가 늦을수록 감소하는 경향을 보였다. 구성아미노산은 채취시기가 늦을수록 아미노산의 함량이 증가하다가 다음해인 1월말에는 약간 감소하였으며, 총 아미노산에 대한 필수아미노산의 비율도 증가하였다. 유리 아미노산의 경우는 주된 성분은 구성아미노산과 비슷하였으나, 채취시기가 늦을수록 아미노산의 함량은 계속 증가 하였으며 총 아미노산에 대한 필수아미노산의 비율은 감소하였다. 구성아미노산과 유리아미노산 모두 가을울금이 더 높은 함유량을 보였다. 울금의 유리당 중 fructose는 채취시기가 늦어질수록 점차 증가하였으나, glucose와 sucrose는 감소하였으며, 총 함량은 채취시기가 늦어질수록 점차 감소하는 경향을 보였다. 유리당과 환원당 모두 가을울금이 더 높은 함유량을 보였다. 비타민 C와 $B_1$은 채취시기가 늦어질수록 그 함량이 가을울금은 감소하였으나 봄울금은 증가하였으며, 비타민 C는 가을울금이 더 높았으나 $B_1$의 경우는 봄울금이 더 높게 나타나 유의적인 차이를 보였다(p<0.05).