• 콘크리트학회논문집
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• 제24권4호
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• pp.361-368
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• 2012

보수 보강재는 강도, 안정성, 내구성, 모재와의 부착력 등 많은 특성이 필요하며, 최근 변형경화형 시멘트 복합체(strain-hardening cement-based composite, SHCC)가 기존의 재료를 대체할 수 있는 성능으로 많은 연구가 이루어지고 있다. 팽창형 SHCC는 팽창재를 이용하여 수축이 발생하는 SHCC의 단점을 보완하여 성능을 개선시킨 복합체로 이를 이용해 보강재의 성능을 만족시키면서 동시에 강도 증진 효과를 가져올 수 있을 것으로 예상된다. 따라서 이 연구에서는 SHCC 보강재의 강도, 팽창재 대체 여부 및 보강 두께를 변수로 하여 휨 성능을 평가하였으며, 실제 보강에 적용 시 기초 자료로 활용하고자 한다.

• Journal of the Korean Wood Science and Technology
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• 제18권3호
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• pp.42-52
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• 1990

In this study, thick 24mm glulams were composed of thick. 3, 4, 6, 8mm Larch laminas to study that the theoretical analysis and the experimental analysis regarding the location of neutral axis of the glulams were compared, and to study on the effect of location of neutral axis on mechanical properties of glulam. The variation of location of neutral axis after proportional limit(or elastical limit) was studied to offer basic data to make the better composition method of glulam. The result obtained can be summarized as follows: 1. The theoretical neutral axis was 0.547 in solid wood, and also 0.547 in glulams because glulams were composed of only Larch laminas. 2. In solid wood, the deviation of the theoretical and the experimental neutral axis location was 0.1%, But in glulams, the deviation from-12.2% to + 7.8% showed nonuniform pattern but no large deviation. Because laminas was only of Larch and so the mechanical properties of laminas were monotonous. 3. The neutral axis exerted no influance on the elasticity of glulam, which meaned that the maximum shear strength in the neutral axis showed no influance on elasticity limit. 4. The only minutely lower elasticities of glulam than that of solid wood were shown. This was because of influance of glue lines of glulam on the elasticlties. 5. The failure type of glulam was wholly simple tension failure and the horizontal shear failure near neutral axis was not taken place, which was that glue line was complete in bonding and the strength of the lamina was not various but uniform. 6. The ratio of tension strain($^{\varepsilon}t$) I compression strain($^{\varepsilon}c$) initially showed uniform level After the elasticity limit. the ratio was increased with the flow of time and so the tension strain was more increased than compression strain. So this proved tension lamination technique, which is that the mechanical properties of glulam could be improved, if the lamina of more superior strength would he added on the bottom side of the glulam.

• 한국미생물·생명공학회지
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• 제44권3호
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• pp.349-354
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• 2016

누룩으로부터 44℃에서 성장할 수 있는 효모 균주를 분리하고 상대적으로 성장속도가 가장 우수한 MBY/L1569 균주를 선별하였다. MBY/L1569 균주는 Pichia farinosa로 동정되었으며, 대조구인 P. farinosa KCTC27412 균주에 비하여 내열성, 내산성 및 내알칼리성이 월등히 우수하였다. P. farinosa MBY/L1569 균주는 46℃에서 0.37 ± 0.05 h⁻¹의 비성장속도를 나타내었으며, 배양온도 37℃, 초기 pH 7.0, 포도당 농도 50 g/l 조건에서 0.50 ± 0.02 h⁻¹의 가장 빠른 비성장속도를 나타내었다. 최적 호기적 배양조건에서 P. farinosa MBY/L1569 균주는 50 g/l 포도당으로부터 19.66 ± 0.68 g/l 에탄올을 생산하여 약 40%의 수율을 나타냈다. P. farinosa MBY/L1569 균주는 한국미생물자원센터에 KCTC27753 균주로 기탁하였다.

• 대한기계학회논문집A
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• 제24권3호
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• pp.777-785
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• 2000

The low-cycle fatigue behaviors of cast AI-Si alloy and composite with reinforcement of SIC particles were compared with those of extruded unreinforced matrix alloy and composite in order to investigate the influence of cast and extrusion processes on the cyclic deformation and fatigue life. Generally, both cast and extruded composites including the unreinforced alloy exhibited cyclic hardening behaviour, with more pronounced strain-hardening for the composites with a higher volume fraction of the SiC particles. However, cast composite under a low applied cyclic strain showing no observable plastic strain exhibited cyclic softening behavior due to the cast porosities. The elastic modulus and yield strength of the cast composite were found to be quite comparable to those of the extruded composite, however, the extrusion process considerably improved the ductility and fracture strength of the composite by effectively eliminating the cast porosities. Low-cycle fatigue lives of the cast alloy and composite were shorter than those of the extruded counterparts. Large difference in life between cast and extruded composites was attributed to the higher influence of the cast porosities on the fatigue life of the composite than that of the unreinforced alloy material. A fatigue damage parameter using strain energy density effectively represented the inferior life in the low-cycle regime and superior life in the high-cycle regime for the composite, compared to the unreinforced alloy.

• Journal of Pharmaceutical Investigation
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• 제36권1호
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• pp.31-38
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• 2006

Using a Rheometries Dynamic Analyzer (RDA II), the dynamic viscoelastic properties of a semi-solid ointment base (vaseline) in large amplitude oscillatory shear flow fields were measured over a temperature range of $25{\sim}45^{\circ}C$ and the linear viscoelastic behavior in small amplitude oscillatory shear flow fields was investigated over a wide range of angular frequencies. In this article, the nonlinear viscoelastic behavior was reported from the experimentally obtained data and the effect of temperature on this behavior was discussed in detail. In addition, the angular frequency and temperature dependencies of a linear viscoelastic behavior were explained. Finally, the applicability of a time-temperature superposition principle originally developed for polymeric materials was examined using a shift factor. Main results obtained from this study can be summarized as follows : (1) At very small strain amplitude region, vaseline shows a linear viscoelastic behavior independent of the imposed deformation magnitudes. Above a critical strain amplitude $({\gamma}_{0}=0.1{\sim}0.2%)$, however, vaseline exhibits a nonlinear viscoelastic behavior ; indicating that both the storage modulus and dynamic viscosity are sharply decreased with increasing deformation magnitude. (2) In large amplitude oscillatory shear flow fields, an elastic behavior (storage modulus) has a stronger strain amplitude dependence and begins to show a nonlinear behavior at a smaller strain amplitude region than does a viscous behavior (dynamic viscosity). (3) In small amplitude oscillatory shear flow fields, the storage modulus as well as the loss modulus are continuously increased as an increase in angular frequency and an elastic nature is always superior to a viscous behavior over a wide range of angular frequencies. (4) A time-temperature superposition principle can successfully be applicable to vaseline. This finding allows us to estimate the dynamic viscoelastic behavior of vaseline over an extraordinarily extended range (11 decades) of angular frequencies inaccessible from the experimentally measured range (4 decades).

• Journal of Welding and Joining
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• 제19권2호
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• pp.182-190
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• 2001

A marine structural material was well known to have high tensile strength, good weldability and proper corrosion resistance. Cu-containing high strength low alloy(HSLA) steel was recently developed for their purposes mentioned above. And the steel is free about preheating for welding, therefore it is reported that shipbuilding cost by using it can be saved more or less. However the marine structural materials like Cu-containing HSLA steel are being generally adopted with cathodic protection method in severe corrosive environment like natural sea water but the high strength steel may give rise to Hydrogen Embrittlement due to over protection at high cathodic current density for cathodic protection. In this study Cu-containing HSLA steel using well for marine atructure was investigated about the susceptibility of Hydrogen Embrittlement as functions of tensile strength, strain ratio, fracture time, and fracture mode, etc. and an optimum cathodic protection potential by slow strain rate test(SSRT) method as well as corrosion properties in natural sea water. And its corrosion resistance was superior to SS400 steel, but Hydrogen Embrittlement susceptibility of Cu-containing HSLA steel was higer than that of SS400 steel. However Hydrogen Embrittlement of its steel by SSRT method was showed with pheonomena such as decreasing of fracture time, strain ratio and fracture mode of QC(quasi-cleavage). Eventually it is suggested that an optimum cathodic protection potential not presenting Hydrogen Embrittlement of Cu-containing of HSLA steel by SSRT method was from-770mv(SCE) to - 900mV(SCE)under natural sea water.

• 한국가금학회지
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• 제13권2호
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• pp.187-195
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• 1986

본 연구는 상용종계 모계통으로 이용되고 있는 White Plymouth Rock종에서 부화시간에 따른 체중과 체척치의 차이를 구명하기 위하여 실시하였다. 종웅계 60수와 종빈계 300수를 교배하여 생산된 종란을 부화하여 발생된 초생추중 "C"계통 551수와 "D"계통 424수등 총 975수를 육성하여 조사한 성적과 부화시간을 479시간부터 3시간 간격으로 521시간까지 14회 조사하여 얻은 자료에 근거하여 실시하였다. 본 연구에서 얻은 결과를 요약하면 다음과 같다. 1. 부화시간별 체중 및 체척치 : 4, 6주 및 8주령 체중, 흉골장 및 정강이 길이의 평균치는 부화시간이 경과함에 따라 낮아지는 경향을 뚜렷이 볼 수 있었다. 수탉에 있어 부화시간의 효과는 대부분의 형질에 대하여 고도의 통계적인 유의성(P〈.01)을 보였고, 6주 및 8주령 흉골장은 유의차가 없었으나 부화시간이 경과함에 따라서 흉골장이 뚜렷하게 짧아지는 경향을 보였다. 암탉에 있어 부화시간의 효과는 주령별 모든 형질에 대하여 통계적 유의성이 있었고, 수탉에서와 마찬가지로 부화시간이 증가할수록 각 주령별 체중이 현저하게 작아지는 경향을 나타냈다. 2. 계통별 체중 및 체척치 : 계통별 부화시간에 따른 평균능력 중 부화시간은 "D"계통이 "C"계통보다 수탉이 7.4시간, 암탉은 7.2시간이 더 길었으며, 산육능력에서는 "C" r계통이 모든 형질에서 더 우수하였다.

• 한국해양공학회지
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• 제30권4호
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• pp.268-276
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• 2016

This paper presents a study on the crashworthiness of the scaled-down stiffened panels used on a Korean icebreaker. In order to validate the crashworthiness of the panels, this paper provides various mechanical properties such as the results of a CVN test, quasi-static tensile test, and high-speed tensile test at arctic temperatures. Two types of steels (EH32 and FH32) were chosen for the material tests. CVN tests revealed that the two steels were equivalent up to −60℃ in terms of their impact energy absorption capacity. However, the toughness of FH32 was significantly superior to that of EH32. EH32 showed slightly higher flow stresses at all temperature levels compared to FH32. The improvement ratios of the yield strengths, tensile strengths, plastic hardening exponents, etc. for FH32, which were obtained from quasi-static tensile tests, showed an apparent ascending tendency with a decrease in temperature. Dynamic tensile test results were obtained for the two temperatures levels of 20℃ and −60℃ with two plastic strain rate levels of 1 s⁻¹ and 100 s⁻¹. A closed form empirical formula proposed by Choung et al. (2011;2013) was shown to be effective at predicting the flow stress increase due to a strain rate increase.

• 한국유기농업학회지
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• 제26권4호
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• pp.649-660
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• 2018

Colletotrichum acutatum에 의해 발생하는 고추탄저병을 방제하기 위해 토양 근권으로부터 분리한 미생물 중 길항효과가 있는 미생물을 선발하여 주요 작물병원균에 대한 항균활성 효과와 포장에서의 방제효과를 검정하였다. 기내 대치배양법을 이용한 길항력을 검정하였을 때, CAB13001 균주는 고추 탄저병을 일으키는 Colletotrichum acutatum을 포함한 식물 병원균 Sclerotinia cepivorum, Sclerotinia sclerotium, Botrytis cinerea에 대한 뛰어난 항균활성 효과를 보였다. 또한 풋고추를 이용한 생체 검정에서 선발균주는 고추 탄저병의 병반진전 억제효과가 우수하였으며, 포장에서의 방제가 역시 무처리 대비 82.4%로 매우 우수하였다. 이러한 결과로 볼 때 CAB13001 균주는 공기 전염을 하는 고추 탄저병의 생물적 방제제로 매우 유용할 것으로 판단된다. 한편, 본 연구에 사용된 길항미생물 CAB13001 균주는 16s rRNA gene의 계통학적 위치를 분석한 결과 Burkholderia lata로 동정하였다.

• Journal of Pharmaceutical Investigation
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• 제39권3호
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• pp.185-199
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• 2009

Using a strain-controlled rheometer [Advanced Rheometric Expansion System (ARES)], the steady shear flow properties and the dynamic viscoelastic properties of $Antiphlamine-S^{(R)}$ lotion have been measured at $20^{\circ}C$ (storage temperature) and $37^{\circ}C$ (body temperature). In this article, the temperature dependence of the linear viscoelastic behavior was firstly reported from the experimental data obtained from a temperature-sweep test. The steady shear flow behavior was secondly reported and then the effect of shear rate on this behavior was discussed in detail. In addition, several inelastic-viscoplastic flow models including a yield stress parameter were employed to make a quantitative evaluation of the steady shear flow behavior, and then the applicability of these models was examined by calculating the various material parameters. The angular frequency dependence of the linear viscoelastic behavior was nextly explained and quantitatively predicted using a fractional derivative model. Finally, the strain amplitude dependence of the dynamic viscoelastic behavior was discussed in full to elucidate a nonlinear rheological behavior in large amplitude oscillatory shear flow fields. Main findings obtained from this study can be summarized as follows : (1) The linear viscoelastic behavior is almostly independent of temperature over a temperature range of $15{\sim}40^{circ}C$. (2) The steady shear viscosity is sharply decreased as an increase in shear rate, demonstrating a pronounced Non-Newtonian shear-thinning flow behavior. (3) The shear stress tends to approach a limiting constant value as a decrease in shear rate, exhibiting an existence of a yield stress. (4) The Herschel-Bulkley, Mizrahi-Berk and Heinz-Casson models are all applicable and have an equivalent validity to quantitatively describe the steady shear flow behavior of $Antiphlamine-S^{(R)}$ lotion whereas both the Bingham and Casson models do not give a good applicability. (5) In small amplitude oscillatory shear flow fields, the storage modulus is always greater than the loss modulus over an entire range of angular frequencies tested and both moduli show a slight dependence on angular frequency. This means that the linear viscoelastic behavior of $Antiphlamine-S^{(R)}$ lotion is dominated by an elastic nature rather than a viscous feature and that a gel-like structure is present in this system. (6) In large amplitude oscillatory shear flow fields, the storage modulus shows a nonlinear strain-thinning behavior at strain amplitude range larger than 10 % while the loss modulus exhibits a weak strain-overshoot behavior up to a strain amplitude of 50 % beyond which followed by a decrease in loss modulus with an increase in strain amplitude. (7) At sufficiently large strain amplitude range (${\gamma}_0$>100 %), the loss modulus is found to be greater than the storage modulus, indicating that a viscous property becomes superior to an elastic character in large shear deformations.