• 소성∙가공
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• 제1권1호
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• pp.66-74
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• 1992

According to the variation of hydrostatic pressure on the central axis of deformable material, the V-shaped central bursting defect may be created in extrusion or drawing processes. The process factors which affect the generation of defects are semi-angle of die, reduction ratio of cross-sectional area, friction factor, material properties and so on. The combination of these factors can determine the possibility of defect creation and the shape of various round holes which have been created inside already. By the rigid plastic finite element method, this paper describes the observations of change in shape of round holes with process conditions such as semi-angle of die, reduction ratio of cross-sectional area and friction factor at the non-steady state of axisymmetrical extrusion process when the round hole is already existed inside the original billet. Also, the effects of process factors are investigated to prevent the possible defects.

• Structural Engineering and Mechanics
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• 제5권6호
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• pp.803-815
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• 1997

It is well understood that concentrated forces applied in the plane of a beam or panel (such as a wall or slab) lead to splitting forces developing within a disturbed region forming beyond the bearing zone. In a linearly elastic material the length of the disturbed region is approximately equal to the depth of the member. In concrete structures, however, the length of the disturbed region is a function of the orthotropic properties of the concrete-steel composite. In the detailing of steel reinforcement within the disturbed regions two limit states must be satisfied; strength and serviceability (in this case the serviceability requirement being acceptable crack widths). If the design requires large redistribution of stresses, the member may perform poorly at service and/or overload. In this paper the results of a plane stress finite element investigation of concentrated loads on reinforced concrete panels are presented. Two cases are examined (i) panels loaded concentrically, and (ii) panels loaded eccentrically. The numerical investigation suggests that the bursting force distribution is substantially different from that calculated using elastic design methods currently used in some codes of practice. The optimum solution for a uniformly reinforced bursting region was found to be with the reinforcement distributed from approximately 0.2 times the effective depth of the member ($0.2D_e$) to between $1.2D_e$ and $1.6D_e$. Strut and tie models based on the finite element analyses are proposed herein.

• 한국의류학회지
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• 제36권7호
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• pp.703-713
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• 2012

This study analyzed the physical properties and flame retardancy of Tencel FR/Cotton complex knit fabrics in order to satisfy two aspects of eco-friendliness and functionality. The flame retardant (FR) treatment of complex knit fabrics was applied by a pad-dry-cure method for additional functionality. Tensile strength, extension, bursting strength, LOI, and flame retardancy were measured by the KS (Korean Standard) K manual. The hand value knit fabrics were measured by KES-FB system. Subsequently, tensile strength and extension of wale and tensile strength of course increased in tandem with the Tencel FR yarn content. Tencel FR/Cotton complex knit fabrics were suitable for summer-weight and for baby clothes through the KES-FB system measurements. The bursting strength of Tencel FR/Cotton complex knit fabrics decreased as the contents of the Tencel FR increased; in addition, LOI increased as the contents of Tencel FR increased. This was due to the Tencel FR flame resistance function; however, the tensile strength decreased. The optimum fiber content of Tencel FR/cotton content was 1:1. The optimum conditions of flame retardant treatment were a treatment temperature $130^{\circ}C$ and the concentration of finishing agent and assistance binder (AR4260) was 35% and 1%, respectively.

• 한국포장학회지
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• 제4권2호
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• pp.3-11
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• 1998

산화전분을 골판지 구성원지인 표면라이너지와 이면라이너지에 각각 코팅하였으며 산화전분 코팅에 따른 골판지의 물성변화를 조사, 산화전분 코팅의 효과를 분석한 결과는 다음과 같았다. 산화전분의 코팅에 의해 골판지의 수직압축강도 뿐만아니라 파열강도도 동시에 개선될 수 있었다. 골판지의 파열강도는 구성 라이너지의 처리면에 관계없이 일정수준의 도공량에 도달할 때까지 크게 증가하다가 그 이상에서는 더 이상의 증가를 보이지 않았다. 표면라이너지에 처리한 골판지의 경우 도공하지 않은 골판지의 파열강도에 비해 도공량이 $2.32g/m^2$일 때 30.3%가 증가하였고 이면라이너지에 처리한 경우 도공량이 $4.84g/m^2$일 때 36.8%가 증가하였으며 표면라이너지와 이면라이너지 모두 처리한 경우 도공량이 $7.16g/m^2$일 때 39.9%가 증가하였다. 산화전분의 코팅은 골판지 원지의 섬유간 결합을 증가시키는데 기여하고 강직성을 개선시켜 골판지 수직압축강도의 개선을 가져왔다. 구성 라이너지의 처리면에 관계없이 골판지의 수직압축강도는 산화전분 도공에 의해 전반적으로 증가하였는데, 이면 라이너지에 처리한 경우 도공량이 $1.58g/m^2$일 때 11.3%가 증가하였고, 표면라이너지와 이면라이너지 모두 처리한 경우 도공량이 $2.99g/m^2$일 때 11.9%가 증가되어 소량의 산화전분 도공에 의해서도 수직압축강도가 크게 개선되었다.

• 한국의류학회지
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• 제41권4호
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• pp.633-645
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• 2017

This study examined the effects of the number of Dakji layer (a layer, two layers), the time of Jumchichigi (20, 40 and 60 minutes) and the type of Choji method making Dakji (Oebal-teugi, Ssangbal-teugi) on five strength properties of Jumchi-Hanji. As a result, the number of Dakji layer and the time of Jumchichigi influenced the five strength properties (tensile, wet tensile, tearing, bursting, and folding strengths). Jumchi-Hanjis made with two layers of Dakijis had higher properties than Jumchi-Hanjis with a layer of Dakji in the strength properties. The more the time for Jumchichigi is spent, the more the five strength properties of Jumchi-Hanji increased. The type of Choji was related to only three strength properties. The tearing strength of Jumchi-Hanjis with one and two layers, and the wet tensile and the folding strengths of Jumchi-Hanjis with two layers depended on the type of Choji. The differences of Jumchi-Hanji and Dakji were also identified in the strength properties. All Jumchi-Hanjis had low tensile and wet tensile strengths when compared to Dakjis. However, Jumchi-Hanjis, made by sixty minute Jumchchigi, had generally higher tearing, bursting, and folding strengths than the Dakjis. In conclusion, the strength properties of Jumchi-Hanji could be improved by controlling the number of Dakji layers and the time of Jumchichigi.

• 한국의류학회지
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• 제45권6호
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• pp.1035-1051
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• 2021

This study compares the strength properties of Jumchi-Hanjis dyed with 70% and 100% persimmon juice concentrations and undyed Jumchi-Hanjis. The Juumchi-Hanjis were made from Dakjis (mulberry papers), which were mixed with different ratios of fibers from paper mulberries originating in Korea and Thailand, including wood pulp from Canada. Research results showed that tensile, wet tensile, and bursting strengths of Jumchi-Hanjis dyed with 70% concentration were higher than those of undyed Jumchi-Hanjis. However, the tearing strengths of the dyed Jumchi-Hanjis were lower than those of undyed Jumchi-Hanjis. The wet tensile strengths of Jumchi-Hanjis dyed with 100% concentration were higher than those of dyed with 70% concentration. The increase and decrease of tensile, tearing, and bursting strengths depending on persimmon juice dyeing differed as per the mixing ratio of the raw materials of Jumchi-Hanjis. Dyeing with 100% persimmon juice concentration tends to be more useful than 70% to increase the tensile (MD) and wet tensile strengths of Jumchi-Hanjis containing only Korean mulberry fibers (90%) and wood pulp (10%) as raw materials. Dyeing with 100% concentration tends to be less useful than 70% to increase the tensile, tearing and bursting strengths of Jumchi-Hanjis with high proportions (90% or 60%) of mulberry fibers from Thailand.

• 한국포장학회지
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• 제3권2호
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• pp.17-23
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• 1996

신문고지에 볏짚펄프를 혼합하였을 때 그 혼합비율이 포장 트레이의 물성에 미치는 영향을 조사하였다. 포장 트레이의 밀도는 볏짚펄프의 혼합비율이 증가됨에 따라 전반적으로 증가하는 경향을 보였다. 파열강도는 볏짚펄프의 혼합비율이 40%에 달할 때까지는 약간 감소하다가 그 이상의 혼합비율에서 점차 증가하는 경향을 보였으며 특히 볏짚펄프 단독으로 제조할 경우 트레이의 파열강도는 급격히 증가하였다. 포장 트레이의 압축강도는 볏짚펄프의 혼합비율이 40-80%되는 구간에서 비교적 낮게 나타난 반면 20%와 100% 수준에서는 비교적 높게 나타났다. 볏짚펄프의 혼합이 이루어진 처음 20% 수준에서 투기 시간은 급격히 감소하여 80%에 이를 때까지 약간 감소하다가 100% 수준에서 투기 시간이 증가하는 현상을 나타내었다. 볏짚펄프의 혼합에 따라 트레이 표면의 L값은 약간 낮아지고 b값은 뚜렷하게 증가하여 황색으로 변화함을 알 수 있었다.

• 한국생물물리학회:학술대회논문집
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• 한국생물물리학회 2003년도 정기총회 및 학술발표회
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• pp.38-38
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• 2003

The electrical properties of neurons are produced by the coordinated activity of ion channels (Hille, 1992). $K^{+}$ channels play a key role in shaping action potentials and in determining neural firing patterns. Small conductance $Ca^{2+}$-activated $K^{+}$ (S $K_{Ca}$ ) channels are involved in modulating the slow component of afterhyperpolarization (AHP) (Kohler et al., 1996). Here we examine whether rat type 2 S $K_{Ca}$ (rSK2) channels can affect the shape of the action potential and the neural firing pattern, by overexpressing rat SK2 channels in Aplysia neuron R15. Our results show that rSK2 overexpression decreased the intraburst frequency and changed the regular bursting activity of neurons to an irregular bursting or beating pattern in R15, Furthermore, the overexpression of rSK2 channels increased AHP and reduced the duration of the action potential. Thus, our results suggest that ectopic S $K_{Ca}$ channels play an important role in regulating the filing pattern and the shape of the action potential.ntial.

• The Korean Journal of Physiology and Pharmacology
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• 제4권1호
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• pp.1-8
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• 2000

To investigate the contributions of intrinsic membrane properties to the spontaneous activity of medial vestibular nucleus (MVN) neurons, we assessed the effects of blocking large and small calcium-activated potassium channels by means of patch clamp recordings. Almost all the MVN neurons recorded in neonatal $(P13{\sim}P17)$ rat were shown to have either a single deep after-hyperpolarization (AHP; type A cells), or an early fast and a delayed slow AHP (type B cells). Among the recorded MVN cells, immature action potential shapes were found. Immature type A cell showed single uniform AHP and immature B cell showed a lack of the early fast AHP, and the delayed AHP was separated from the repolarization phase of the spike by a period of isopotentiality. Application of apamin and charybdotoxin (CTX), which selectively block the small and large calcium-activated potassium channels, respectively, resulted in significant changes in spontaneous firings. In both type A and type B cells, CTX (20 nM) resulted in a significant increase in spike frequency but did not induce bursting activity. By contrast, apamin (300 nM) selectively abolished the delayed slow AHP and induced bursting activity in type B cells. Apamin had no effect on the spike frequency of type A cells. These data suggest that there are differential roles of apamin and CTX sensitive potassium conductances in spontaneous firing patterns of MVN neurons, and these conductances are important in regulating the intrinsic rhythmicity and excitability.

• 한국의류학회지
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• 제29권9_10호
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• pp.1274-1284
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• 2005

Effect of fixation methods and relaxation treatment on the dimensional stability and physical properties of MDPPA/HMM treated cotton knitted fabrics were studied. Combination of four different fixation methods - relaxation, swelling agent treatment, pad dry cure fixation, and wet fixation - were applied to flame retardant finish of 4 kinds of cotton knitted fabric with MDPPA/HMM. Then these fabrics were washed 10 times. As a result, In swelling treatment on 10G showed relatively higher value of length shrinkage than 14G. Length and width shrinkage were increased by initial washing treatment and no further change was shown after 6 washing cycles. After 10 washing cycles, length and width shrinkage decreased. The KES standardized basic value of B/W, 2HB/W and bursting strength of interlock were relatively larger than those of single jersey. The values of B/W and 2HB/W of cotton knitted fabrics were increased by relaxation and washing treatment but were decreased by swelling treatment. In addition, the bursting strength of the cotton knitted fabrics was decreased after fusing, washing and relaxation treatment.