• 대한약리학회지
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• 제19권2호
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• pp.9-16
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• 1983

현재 사용되고 있는 강심제로는 디지탈리스 배당체가 유일한 약물이지란 그 안전역이 대단히 좁아서 보다 안전한 강심제의 개발이 요구되고 있다. 최근 강심작용이 현저할 뿐 아니라 안전역이 비교적 넓을 것으로 인정되는 higenamine이 개발되어 그 작용기전을 밝히려는 시도가 많이 있었다. 본 연구에서는 higenamine의 강심작용 기전을 규명하기 위한 연구의 일환으로 수축빈도-수축력 상관관계(interval-strength relationship)에 있어서 1) Rested-state수축력 2) Positive inotropic effect of activation(PIEA) 3) Negative inotropic effect of activation(NIEA)에 대한 higenamine의 영향을 $Ca^{++}$및 epinephrine과 비교 분석하였다. 실험결과 칼슘은 PIEA를 증가시키기 보다는 오히려 NIEA의 소멸을 촉진함으로써 강심작용을 나타내며 epinephrine 및 higenamine은 PIEA를 증가시키고 NIEA에는 거의 영향을 미치지 않았다.

• Geomechanics and Engineering
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• 제19권6호
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• pp.533-542
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• 2019

Geosynthetic reinforced soil method in coarse-grained soils has been widely used in last decades. Two effective factors on soil-geosynthetic interaction are confining stresses and loading rate in clay. In terms of methodology, one pull-out test with four different strain rates, namely 0.75, 1.25, 1.75 and 2.25 mm/min, and three different normal stresses equal to 20, 50, and 80 kg have been performed on specimens with dimensions of 30×30×17 cm in the saturated, consolidated condition. The obtained results have demonstrated that activation of geosynthetic strength at contact surface depends on the applied stress. In addition, the increase in normal stress would increase the shear strength at contact surface between clay and geogrid. Moreover, it is concluded that the strain rate increment would increase the shear strength.

• 한국건축시공학회:학술대회논문집
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• 한국건축시공학회 2008년도 춘계 학술논문 발표대회
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• pp.61-65
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• 2008

This study, having combined and displaced blast furnace slag("BS" hereinafter) known as admixture material that delays hydration reaction with coarse particle cement("CC" hereinafter) collected in particle classification method during ordinary portland cement("OPC" hereinafter), reviewed the hydration heat characteristics affecting the concrete. To reduce hydration heat, the study plain-mixed which used 100% OPC for W/B 50% level 1, displaced CC at level 3 of 25%, 50% and 75% for OPC, and by displacing BS with admixture material at level 5 of 0%, 20%, 40%, 60% and 80% for cement(OPC+CC), experimented totally 16 batches. As a result of experiment, in the case of flow, the more CC displacement rate increased, the more it tended to decrease, and the more BS displacement rate increased, the more it decreased. Also, as for simple adiabatic temperature rise by the CC and BS displacement rates, it decreased as displacement rate increased, and particularly in the case of displaced BS of 80%, It showed temperature reduction effect of about 63% companing with plain. Compressive strength decreased in proportion to displacement rate, however strength reduction increment was shown to decrease with age progress.

• 한국세라믹학회지
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• 제33권7호
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• pp.771-778
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• 1996

Utilization of fly ash by-produced from coal fired power plants and classified as general waste became very important problem to solve in the environmental protection and recycling of waste materials. The possibility of large scale substitution of fly ash as a raw material for bricks and wet tiles was highly expected because the chemical compositions of fly ash were mostly Al2O3 and SiO2 and the properties of it were very similar with clay. Accordingly in order to investigate the substitutional limit these specimens were substituted from 0 to 100 wt% fly ash by 20wt% increment for clay. Fly ash-clay bodies were fired at 1200, 1250 and 130$0^{\circ}C$ and then their properties were measured, It was found that these specimens sintered at 125$0^{\circ}C$ had a good bending strength. Especially when these sintered bodies were added to 20, 40 and 60 wt% fly ash the bending strength of those were 201 , 205 and 191kg.cm2 respectively with the water absorption below 1%, This showed that fly ash could be substituted ab 60 wt% in this experiment.

• 한국정밀공학회지
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• 제18권12호
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• pp.167-176
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• 2001

The effects of heat treatments and testing temperatures on the mechanical properties of Invar materials were investigated through experiments, which call influence the formability in metal forming fields. Annealing temperatures were changed from $900^{\circ}C$ to $1200^{\circ}C$ with an increment of $100^{\circ}C$ under two different furnace atmosphere(vacuum and H$_2$gas). Microstructure and hardness tests were performed for annealed specimens at room temperature(RT) and tensile tests were also performed by changing annealing temperatures as well as testing temperatures from RT to $300^{\circ}C$. The grain size of annealed materials increased with increasing annealing temperature, while micro-hardness distributions showed almost same hardness values regardless of annealing temperatures. Strength ratio (tensile/yield strength), which influences the forming characteristics of sheet metal, remained almost constant for various experimental conditions in case of unannealed specimens. However, it showed increasing tendency with increasing both annealing and testing temperatures, particularly at the testing temperature higher than $200^{\circ}C$. Therefore it can be concluded that press formability of fully-annealed Invar material can be improved by warm forming technique.

• Computers and Concrete
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• 제7권2호
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• pp.159-167
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• 2010

This paper demonstrates numerical techniques for complex large-scale modeling with microplane constitutive theories for reinforced high strength concrete, which for these applications, is defined to be around the 7000 psi (48 MPa) strength as frequently found in protective structural design. Applications involve highly impulsive loads, such as an explosive detonation or impact-penetration event. These capabilities were implemented into the authors' finite element code, ParaAble and the PRONTO 3D code from Sandia National Laboratories. All materials are explicitly modeled with eight-noded hexahedral elements. The concrete is modeled with a microplane constitutive theory, the reinforcing steel is modeled with the Johnson-Cook model, and the high explosive material is modeled with a JWL equation of state and a programmed burn model. Damage evolution, which can be used for erosion of elements and/or for post-analysis examination of damage, is extracted from the microplane predictions and computed by a modified Holmquist-Johnson-Cook approach that relates damage to levels of inelastic strain increment and pressure. Computation is performed with MPI on parallel processors. Several practical analyses demonstrate that large-scale analyses of this type can be reasonably run on large parallel computing systems.

• Advances in concrete construction
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• 제7권4호
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• pp.241-247
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• 2019

In this paper the effect of bedding layer on the failure mechanism of rock in direct shear test has been investigated using particle flow code, PFC. For this purpose, firstly calibration of pfc2d was performed using Brazilian tensile strength. Secondly direct shear test consisting bedding layer was simulated numerically. Thickness of layers was 10 mm and rock bridge length was 10 mm, 40 mm and 60 mm. In each rock bridge length, bedding layer angles changes from $0^{\circ}$ to $90^{\circ}$ with increment of $15^{\circ}$. Totally 21 models were simulated and tested. The results show that two types of cracks develop within the model. Shear cracks and tensile cracks. Also failure pattern is affected by bridge length while shear strength is controlled by failure pattern. It's to be noted that bedding layer has not any effect on the failure pattern because the layer interface strength is too high.

• Structural Engineering and Mechanics
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• 제88권2호
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• pp.179-188
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• 2023

The mechanical behaviours of biopolymer-treated soil depend on the formation of soil-biopolymer matrices. In this study, various biopolymers(e.g., xanthan gum (XG), locust bean gum (LBG), sodium alginate (SA), agar gum (AG), gellan gum (GE) and carrageenan kappa gum (KG) are selected to treat three types of natural soil at different concentrations (e.g., 1%, 2% and 3%) and curing time (e.g., 4-365 days), and reveal the reinforcement effect on natural soil by using unconfined compression tests. The results show that biopolymer-treated soil obtains the maximum unconfined compressive strength (UCS) at curing 14-28 days. Although the UCS of biopolymer-treated soil has a 20-30% reduction after curing 1-year compared to the maximum value, it is still significantly larger than untreated soil. In addition, the UCS increment ratio of biopolymer-treated soil decreases with the increase of biopolymer concentration, and there exists the optimum concentration of 1%, 2-3%, 2%, 1% and 2% for XG, SA, LBG, KG and AG, respectively. Meanwhile, the optimum initial moisture content can form uniformly biopolymer-soil matrices to obtain better reinforcement efficiency. Furthermore, the best performance in increasing soil strength is XG following SAand LBG, which are significantly better than AG, KG and GE.

• 한국식품저장유통학회지
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• 제19권3호
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• pp.361-367
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• 2012

소맥분에 생강분말을 첨가한 물리적 특성은 Falling number는 생강분말의 첨가비율이 증가할수록 falling number 값이 증가하였다. Farinogram에서 consistency는 생강분말 첨가구 중 3% 이상 첨가구에서 커지는 현상이 나타났다. 흡수율은 생강분말의 첨가량이 많아질수록 흡수율도 증가하였지만 유의적인 차이를 보이지는 않았다. 반죽의 안정도는 생강분말첨가량이 많아질수록 증가하였지만, 모든 시료 간에 유의적인 차이를 보이지는 않았다. MTI 값은 생강 분말을 첨가 할수록 증가하였고 Farinograph quality number는 대조구와 생강분말 첨가구간에 유의적인 차이를 보이지 않았다. 호화 개시온도는 대조구가 가장 높았으며, 생강분말 첨가량이 많아질수록 낮아졌다. 최고점도는 생강 분말의 첨가량이 많아질수록 높아졌다. 최고점도 후에 나타나는 최저 점도인 holding strength는 생강분말 첨가량에 따라 유의적인 차이가 나타나지 않았다. Breakdown 값은 생강분말 첨가량이 많아질수록 높아져, 생강분말을 첨가할 경우 호화된 전분의 안정도는 떨어지는 것으로 나타났다. 최종 점도는 생강분말 첨가량이 많아질수록 높아졌으며, setback 값은 5% 첨가 시 가장 높은 값이 나온 것으로보아 생강분말 첨가는 노화 방지를 할 수 없는 것으로 예측할 수 있었다. Alveogram의 $P_{max}$ 값은 1%와 5% 첨가구에서는 감소하였으며, 신장성을 나타내는 L값은 생강분말 첨가량이 증가할 수록 글루텐 형성이 저해되어 감소하였다. 부피를 예측할 수 있는 G값은 생강분말 첨가량에 따라 감소하였다. 이는 생강분말을 많이 넣을수록 파운드 케이크의 부피는 작아지고, 밀도는 커짐을 예측할 수 있었다. W(반죽의 탄력에 대한 저항성)값도 생강분말 첨가량이 증가할수록 감소하였다.

• Fisheries and Aquatic Sciences
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• 제17권2호
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• pp.203-207
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• 2014

The present study was conducted to elucidate effects of heat, salt and hydrocolloid treatments on flying fish Cypselurus agoo roe analogs prepared using calcium alginate gel. The changes in size, sphericity and rupture strength of the analogs as affected by treatments of heat, sodium chloride and hydrocolloids were investigated. The size (mm), sphericity (%), and rupture strength (kPa) of the analogs were $2.2{\pm}0.1$, $98.2{\pm}0.2$, and $74.7{\pm}1.7$, respectively. When the analogs were heated at $95^{\circ}C$ in water, the size was slightly decreased. The rupture strength by curing with 2% sodium chloride was slightly increased. Sphericity didn't show significant differences by sodium chloride and heat treatment. The rupture strength of the analogs was slightly decreased by heat treatment, whereas remarkably decreased by curing with sodium chloride. In order to prevent a remarkable decrease in rupture strength of the analogs by curing with sodium chloride, the analogs were treated with hydrocolloids such as xanthan gum, gum guar, glucomannan, pectin and gelatin. The hydrocolloids treated analogs showed an increment in size and no significant changes in sphericity. On the other hand, the rupture strength of the hydrocolloids treated analogs exhibited remarkable increase than that of untreated ones.