• International journal of steel structures
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• v.18 no.5
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• pp.1754-1760
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• 2018

The present article showcases a temperature dependent cohesive zone model (CZM)-based fi nite element simulation of drop weight tear test (DWTT), to analyse fracture behavior of pipeline steel (PS) at different temperatures. By co-relating the key CZM parameters with known mechanical properties of PS at varying temperature, a temperature dependent CZM for PS is proposed. A modified form of Johnson and Cook model has been used for the true stress-strain behavior of PS. The numerical model, using Abaqus/CAE 6.13, has been validated by comparing the predicted results with load-displacement curves obtained from test data. During steady-state crack propagation, toughness parameters (such as CTOA and CTOD) were found to remain fairly constant at a given temperature. These toughness parameters, however, show an exponential increase with increase in temperature. The present paper offers a plausible approach to numerically analyze fracture behavior of PS at varying temperature using a temperature dependent CZM.

• The Journal of Information Systems
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• v.19 no.4
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• pp.65-85
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• 2010

The importance of communities of practice(CoP) as an organizational informal unit for fostering knowledge transfer and sharing gains a lot of attention from KM researchers and practitioners. Since most of CoPs are formulated online these days, the credibility or trustworthiness of knowledge contents circulated within a certain CoP should be considered thoroughly for them to be fully utilized safely. Here comes the need for an appropriate trust measuring methodology to determine the true value of knowledge given by unknown people through an online channel. In this paper, an improved trust measuring method is proposed using new trust variables such as level of degrees derived from the relationships among community users. In addition, activeness, relevance, and usefulness of the knowledge contents themselves, which are calculated automatically using a text categorization technique, are also used for trust measurement. The proposed framework incorporates fuzzy set and calculation concepts to help build trust matrices and models, which are used to measure the level of trust involved in specific knowledge artifacts concerned.

• 프린팅코리아
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• v.12 no.3
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• pp.96-97
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• 2013

한국후지제록스(대표 우에노 야스아키, www.fujixerox.co.kr)는 지난 2월 14일 서울시 중구 정동에 위치한 한국후지제록스 본사에서 '2013 PS(Production System) 월드 페어' 행사를 개최하고 신제품 누베라 157와 누베라 314를 포함한 디지털 인쇄기 전 제품과 솔루션을 소개했다. 이번 행사에는 200여명이 참가해 성황을 이루며 디지털 인쇄에 대한 시장의 큰 관심을 드러냈다.

• Journal of the Korean Ceramic Society
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• v.32 no.5
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• pp.608-616
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• 1995

Porous silicon (PS) was prepared under different anodization conditions and the photoluminescence (PL) was measrued. In addition PL of the naturally and thermally oxidized PS was measured. It was found that the PL peak was shifted to shorter wavelength as the anodization current density and the extent of the oxidation increased. The absence of correlation between the PL behavior and the surface hydrogen species (Si-H2, Si-H) implies that the mechanism of PL of PS is not likely related to the surface hydrogen species effect but to the quantum confinement effect.

• Macromolecular Research
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• v.15 no.5
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• pp.403-411
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• 2007

Monodisperse micron-sized polystyrene (PS) spheres were successfully obtained using a single stage soap-free emulsion method in aqueous media mixed with ethanol (co-solvent) containing NaCI as the electrolyte. The optimum conditions for preparing the monodisperse PS microspheres, using soap-free emulsion polymerization in a water/ethanol mixture with an electrolyte, were studied. The presence of the co-solvent and electrolyte controlled the particle dispersion stability during the polymerization. The microspheres formed using PS, with a weight-average diameter of $2.6{\mu}m$, coefficient of variation of 5.3% and zeta potential of -15.1 eV, were successfully obtained in the presence of 0.1 wt% NaCI, 10 wt% monomer, 0.1 wt% initiator and 95/5 (g/g) of a water/ethanol mixture reacted at $70^{\circ}C$ for 24 h.

• Proceedings of the KIEE Conference
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• 2004.07c
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• pp.1661-1663
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• 2004

The effect of the triblock copolymer poly[styrene-b-(ethylene-co-butylene)-b-styrene](SEBS) on the formation of space charge of immiscible low density polyethylene/polystyrene(LDPE/PS) blends was investigated. The amount of charge accumulated in the 70/30(wt%) LDPE/PS blends decreased when the SEBS content increased up to 10 wt%. For compatibilzed and uncompatibilized blend, morphological observation showed that the addition of SEBS results in the domain size reduction of the dispersed PS phase and a better interfacial adhesion between LDPE and PS phases. The location of SEBS at a domain interface enables charges to migrate from one phase to the other via domain interface and therefore, results in a significant decrease in the amount of space charge for the LDPE/PS blends with SEBS.

• Journal of Korean Society of Steel Construction
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• v.30 no.2
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• pp.77-85
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• 2018

A through diaphragm is often used to ensure their stiffness for moment-resisting connections using rectangular steel-tube column and H-shaped beam. The through-diaphragm connections, however, have some difficulties for their applicabilities to the field due to the complexity of the fabrication and construction processes. This study thus proposes a new modular system of steel structures assembled only using bolts without welding, by bringing a connection module composed of rectangular steel-tube column, H-shaped beam and oneway bolt onto the site. An experimental study to evaluate the seismic performance of the proposed connection details based on the new modular system is then conducted. The length and type of the inner reinforcement plate are considered as the primary design parameters, and the strength, stiffness, ductility and energy dissipation capability of the new connections are experimentally analyzed by comparison to those of conventional through diaphragm connections.

• Macromolecular Research
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• v.17 no.7
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• pp.483-490
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• 2009

Stable poly(styrene-co-divinylbenzene) [P(St-co-DVB)] micro spheres with narrow size distribution were synthesized in the presence of 2,2'-azobis(2,4-dimethyl valeronitrile) (V-65) and co-initiator in an acetone/water mixture in the precipitation polymerization at $53^{\circ}C$ for 24 h. Potassium peroxodisulfate (KPS), ammonium peroxodisulfate (APS) and sodium peroxodisulfate (NaPS) were used as co-initiators. The optimum ratio of acetone to water for the formation of a narrow distribution of P(St-co-DVB) particles was 49:11 (g/g). The optimum co-initiator compositions for narrow distribution were 9:1 (g/g) for V-65 to KPS, 11:1 for V-65 to APS and 6:1 for V-65 to NaPS. The yield for these compositions was $54{\sim}57%$ and the largest particle size was obtained with the lowest zeta-potential and CV values. From the XPS measurements, the charge density was increased but the zeta potential decreased with increasing sulfur content, implying that the sulfate group provides the electrostatic stabilization on the particle surface. This suggested that the self-crosslinking between styrene and DVB, the electrostatic stabilization of initiators, and the balanced hydrophobic and hydrophilic properties of the solvents are responsible for the formation of stable P(St-co-DVB) spherical particles with narrow size distribution.

• Polymer(Korea)
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• v.32 no.6
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• pp.573-579
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• 2008

PBA/PS core-shell polymer nanoparticles were synthesized by two stage emulsion polymerization and hybridized with silica nanoparticle by simple mixing in emulsion state and following precipitation into water/methanol mixture dissolving $Na_2CO_3$. The stress-strain curve revealed that the elastic modulus was increased with increasing molecular weight of polymer and silica weight fraction but decreased with increasing size of core-shell nanoparticle. Especially, there was a rapid increase of elastic modulus with silica blending. As a result, 6 times higher elastic modulus was observed in PBA/PS core-shell baroplastic sample processed at 25$^\circ$C under 13.8 MPa for 5 min by blending with 13.0 wt% of silica nanoparticle.

• Journal of Dental Anesthesia and Pain Medicine
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• v.22 no.2
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• pp.129-143
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• 2022

Background: Patient-controlled analgesia (PCA) has been widely used as an effective medical treatment for pain and for postoperative analgesia. However, improper dose errors in intravenous (IV) administration of narcotic analgesics from a PCA infusion pump can cause patient harm. Furthermore, opioid overdose is considered one of the highest risk factors for patients receiving pain medications. Therefore, accurate delivery of opioid analgesics is a critical function of PCA infusion pumps. Methods: We designed a microbalance method that consisted of a closed acrylic chamber containing a layer and an oil layer with an electronic balance. A commercially available infusion analyzer (IDA-5, Fluke Co., Everett, WA, USA) was used to measure the accuracy of the infusion flow rate from a commercially available smart PCA infusion pump (PS-1000, UNIMEDICS, Co., Ltd., Seoul, Korea) and compared with the results of the microbalance method. We evaluated the uncertainty of the flow rate measurement using the ISO guide (GUM:1995 part3). The battery life, delay time of the occlusion alarm, and bolus function of the PCA pump were also tested. Results: The microbalance method was good in the short-term 2 h measurement, and IDA-5 was good in the long-term 24 h measurement. The two measurement systems can complement each other in the case of the measurement time. Regarding battery performance, PS-1000 lasted approximately 5 days in a 1 ml/hr flow rate condition without recharging the battery. The occlusion pressure alarm delays of PS-1000 satisfied the conventional alarm threshold of occlusion pressure (300-800 mmHg). Average accuracy bolus volume was measured as 63%, 95%, and 98.5% with 0.1 ml, 1 ml, and 2 ml bolus volume presets, respectively. A 1 ml/hr flow rate measurement was evaluated as 2.08% of expanded uncertainty, with a 95% confidence level. Conclusion: PS-1000 showed a flow accuracy to be within the infusion pump standard, which is ± 5% of flow accuracy. Occlusion alarm of PS-1000 was quickly transmitted, resulting in better safety for patients receiving IV infusion of opioids. PS-1000 is sufficient for a portable smart PCA infusion pump.