• Transactions of the Korean hydrogen and new energy society
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• v.15 no.2
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• pp.129-136
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• 2004

환경문제와 석유자원의 고갈이 많은 연구자들을 기존 탄화수소연료를 대체할수 있는 재생 가능한 연료를 구하는데 많은 노력을 기울이고 있다. 수소연료는 유해배기물질이 없는 연소와 또한 연소후에 재생 가능한 물성분만 배출하는 속성으로 미래의 청정에너지로 각광을 받고 있다. 이러한 이유로 수소연료는 수송기계의 연료로도 주목을 받고 있다. 따라서 수소연료기관 개발은 21세기에도 지속적으로 진행될 것이다. 이에대한 초기연구로 기체 LPG 연료가 아닌 액체 LPG 연료를 흡기관에 분사하여 기화된 LPG 연료를 엔진으로 흡입하는 LPi엔진에 수소연료를 과급하여 엔진에 성능을 연구하고자 하였다.

• Proceedings of the Korean Institute of Surface Engineering Conference
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• 2014.11a
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• pp.204-206
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• 2014

석탄 화력발전소에는 연소가스의 질소산화물(NOx) 저감을 위한 SCR(selective catalytic reduction)설비가 운전되고 있으며, SCR은 환원제인 암모니아($NH_3$)를 이용하여 연소가스 내에 질소산화물을 물과 질소로 분해하는 역할을 한다. 그러나, 연소가스 중의 일부 삼산화황($SO_3$)과 미반응 암모니아가 결합하여 황산암모늄염(Ammonium bisulfate; $NH_4HSO_4$)을 생성하며, 이는 후단 APH(air preheater)의 열소자에 점착된 후 분진들과 함께 성장하여 막힘을 야기한다. 막힘이 발생된 APH는 연소가스의 흐름을 방해하기 때문에 차압을 증가시키며, 이는 발전효율의 감소뿐만 아니라 급전정지를 초래한다. 이를 해결하기 위하여 $CO_2$ 드라이아이스 세정 방법을 적용하였으며, pilot-scale plant에서 실험을 수행하였다. 또한, 드라이아이스 공정변수인 분사압력과 분사시간을 제어하여 pilot-scale plant의 APH 열소자 표면에 생성되어있는 오염물질들의 제거효율을 관찰한 결과 95 %의 높은 제거효율을 보였다.

• Transactions of the Korean Society of Automotive Engineers
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• v.12 no.6
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• pp.96-102
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• 2004

The diesel particulate filter(DPF) is effective for particulate removal from diesel engine under a variety of conditions, and then the regeneration strategies is very important in the aspects of engine fuel consumption and engine durability. This paper addresses the changes of Peugeot 406 vehicle engine parameters(fuel injection timing, period, rail pressure, emissions exhaust temperature so on) during DPF regeneration. additionally, checked the soot loading mass with mileage and the change of fuel consumption and performance with ash accumulation.

• Proceedings of the Korean Institute of Electrical and Electronic Material Engineers Conference
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• 1999.11a
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• pp.471-474
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• 1999

본 논문에서는 열전소자(TEC모듈)를 이용한 에어컨의 개발에 대하여 검토한다. 사용한 TEC모듈의 개수와 TEC모듈의 발열부를 냉각하는 FAN냉각방식과 분사냉각방식에 따른 냉각능력을 평가하였다. 분사냉각방식의 경우에는 기존의 에어컨과 동등한 수준의 냉각능력을 갖는다는 것을 알 수 있었다. 급속냉각은 어렵지만 약 1시간 후부터는 충분히 사용 가능하며, 열전소자 한 개당 약 1평을 냉각할 수 있으며, 기존에어컨의 가격에 비해 약 50∼70%정도로 충분한 가격 경쟁력이 있다. 빙축열 방식 등을 적용하면, peak 쳐t등의 효용성으로 상품화 가능성이 매우 크다고 판단된다.

• Journal of the Korean Society of Fisheries and Ocean Technology
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• v.19 no.1
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• pp.40-45
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• 1983

The paper describes an experimental investigation of axisymmetric diesel spray and flame which is held in rapid compression machine (RCM) with electromagnetic single injection nozzle. The axisymmetric diesel spray and flame are taken with high speed photograph and analysis it with image processor. The data presented include fuel concentration of spray, flame temperature, soot concentration of flame in axial and radial direction at a moment and compared it with each other.

• Development and Reproduction
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• v.4 no.2
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• pp.161-173
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• 2000

The aim of this study was to assess the effect of the frequency of the L$N_2$ infusion on the ultrastructure, metabolism and development of the embryo after freezing and thawing by computerized cell freezer. Two-cell embryos of ICR mouse were randomly allocated into fresh (control), high-frequency freezing (group 1) and low-frequency freezing (group 2). For fresh and frozen-thawed intact 2-cell embryos, total ceil number in the blastocyst was counted by fluorescent microscope after Hoechst 33258 staining. Relative amount of $H_2O$$_2$ was measured by DCHFDA. Intracellular location and membrane potential of the mitochondria were evaluated by staining with rhodamine 123 and JC-1. The structure of actin filament was also evaluated by confocal microscope. DNA fragmentation was assessed by TUNEL method after development into blastocyst. The survival rate of intact embryo was higher in group 1 than group 2 (50.7％ vs. 34.6％ respectively, p<0.05). The blastocyst developmental rate was significantly low in group 2 (86.7％, 76.7％ vs. 44.0％ for control, group 1 and group 2 respectively, p<0.05). Total cell number in the blastocyst was also significantly lower in group 2 than control (79.5$\pm$12.9, 71.6$\pm$8.0, and 62.5$\pm$4.7 for control, group 1 and group 2 respectively, p<0.05). The relative amount of $H_2O$$_2$ was higher in group 2 than other groups (15.3$\pm$3.0, 16.6$\pm$1.6 vs. 23.4$\pm$1.8, p<0.05). After JC-1 staining, relative intensity of mitochondria with high membrane potential was significantly lower in group 2 than control and group 1 (17.2$\pm$3.8, 17.4$\pm$1.3 vs. 13.2$\pm$2.0, p<0.05). In group 2, partial deletion and aggregation of the actin filament was found. DNA fragmentation rate was also hieher for group 2 versus other groups (30.8％, 36.0％ vs. 65.6％, p<0.05). The frequency of the L$N_2$ infusion is an important factor for the development of frozen-thawed mouse embryo. High-frequency infusion may prevent damages of cytoskeleton and mitochondria in the embryo probably by preventing the temperature fluctuation during dehydration phase. We speculate that the application of high-frequency infusion method in human embryo may be promising.

• The Journal of Korean Academy of Prosthodontics
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• v.61 no.3
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• pp.179-188
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• 2023

Purpose. The purpose of this study was to evaluate the effect of surface treatments on the shear bond strength of two types of zirconia (3-TZP and 5Y-PSZ) with resin cement. Materials and methods. Two different types of zirconia specimens with a fully sintered size of 14.0×14.0×2.0 mm³ were prepared, polished with 400, 600, and 800 grit silicon carbide paper, and buried in epoxy resin. They were classified into four groups each control, sandblasting, primer, and sandblasting & primer. Cylindrical resin adhered to the surface-treated zirconia with resin cement. It was stored in distilled water (37℃) for 24 hours, and a shear bond strength test was performed. The normality of the experimental group was confirmed with the Kolmogorov-Smirnov & Shapiro-Wilk test. The interaction and statistical difference were analyzed using a two-way ANOVA. A post-hoc analysis was performed using Dunnett T3. Results. As a result of two-way ANOVA, there was no significant difference in shear bonding strength between zirconia types (P > .05), but there was a significant correlation in the sandblasting, primer, and alumina sandblasting & primer group (P < .05). Dunnett T3 post-test showed that, regardless of the type of zirconia, shear bonding strength was sandblasting & primer > Primer > sandblasting > control group (P < .05). Conclusion. There was no difference in shear bond strength between the types of zirconia. The highest shear bond strength was shown when the mechanical and chemical treatments of the zirconia surface was performed simultaneously.

• Journal of Dental Rehabilitation and Applied Science
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• v.29 no.1
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• pp.69-79
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• 2013

The aim of this study was to evaluate the effect of surface conditioning on the shear bond strength of zirconium-oxide ceramic to resin cement. A total of 120 disk-shaped zirconium-oxide ceramic blocks(3-TZP, Kyoritsu, Tokyo, Japan) were treated as follows: (1) no treatment; (2) sandblasting with 110 ${\mu}m$ aluminum-oxide(Al2O3); (3) particles tribochemical silica coating(RocatecTM, 3M ESPE). Then zirconium-oxide ceramic blocks were divided into six groups(10 for each group) and bonded with resin cement(Rely X U-200, 3M ESPE). (1) No treatment / No treatment (2) No treatment / Sandblasting with 110 ${\mu}m$ aluminum-oxide particles (3) No treatment / Silica coating (4) Sandblasting with 110 ${\mu}m$ aluminum-oxide particles / Sandblasting with 110 ${\mu}m$ aluminum-oxide particles (5) Sandblasting with 110 ${\mu}m$ aluminum-oxide particles / Silica coating (6) Silica coating / Silica coating. Each group was tested in shear bond strengths by UTM. Data analysis included one-way analysis of variance(ANOVA) and the Tukey Honestly Significant Difference test (P=0.05). Group that bonded two silica coated specimen showed a highest bond strength(P<0.05). Two silica coated surface conditioning group and air-abrasion and silica coated surface conditioning group showed significantly difference with other groups(P<0.05). Other groups had no significantly difference each other. Within the limitation of this study, Surface conditioning with Rocatec treatment to each side of specimen provided the highest bond strength.

• Journal of Bio-Environment Control
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• v.23 no.1
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• pp.26-30
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• 2014

Purpose of this study was a development of a sprayer arm auto control system that could be operated according to distance from pear trees for automation of pest control. Auto control system included two parts, hardware and software. First, controller was made with an MCU and relay switches. Two types of ultra-sonic sensors were installed to measure distance from pear trees: one on/off type that detect up to 3 m, and the other continuous type providing 0~5 V output corresponding to distance of 0~3 m. Second, an auto control algorithm was developed to control. Each spraying arm was controlled according to the sensor-based distance from the pear trees. And it could dodge obstacles to protect itself. Max and min signal values were eliminated, when five sensor signals was collected, and then signals were averaged to reduce sensor's noises. According to results of field experiment, auto control test result was better than non auto control test result. Spraying rates were 69.25% (left line) and 98.09% (right line) under non auto control mode, because pear trees were not planted uniformly. But, auto control test's results were 92.66% (left line) and 94.64% (right line). Spraying rate was increased by maintaining distance from tree.

• Journal of radiological science and technology
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• v.26 no.4
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• pp.21-26
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• 2003

To evaluate the newly designed gastroduodenal coil catheter:in-vitro test. The coil catheter that we made in our laboratory was 150 cm. The coil that is made of stainless steel wire was composed 1.3 mm inner diameter and this coil spring was covered with heat-shrinkable polyethylene tube. To measure the length under fluorocopy, 8 radiopaque marks were attached at 5 cm, 10 cm, 11 cm, 12 cm, 13 cm, 14 cm, 15 cm, 20 cm apart from distal end of the catheter and 6, 2, 1 pores were made at 7 cm, 13 cm, 19 cm apart from the distal end. Radio-opacity and the amount of injected contrast was investigated in formerly used 5 Fr. vessel catheter, which is possible in measuring length, and newly designed coil catheter. Film density was tested for radio-opacity with autodensitometer. For measuring the volume of injected salin, the catheter was located in the acryl box(26 cm, 3 cm, 16 cm) that divided into 4 chambers. After injection 50 cc of contrast with autoinjector, the contrast's quantity in each chamber was measured with and without over the guide wire. Radio-opacity was 0.51 in 5 Fr. vessel catheter, 0.31 in newly made catheter. The amount of injected contrast was measured. In case of 5 Fr. vessel catheter, the amount was 99.5% from the distal part, there was no difference between with and without the guide wire. Otherwise, using a coil catheter, the pacentage the ejected saline was 1.17%, 18.8%, 41.8%, 38.2% from the distal part with the guide wire, 19.5%, 32.6%, 27.7%, 20.3% without the guide wire. Compare with formerly established catheter, this new coil catheter is easy to measure the length thanks to easy confirming under fluoroscopy and excellent in injecting contrast. Therefore, newly designed gastrointestinal catheter seems to be useful in gastrointestinal intervention procedure.