• Elastomers and Composites
• /
• v.46 no.1
• /
• pp.60-69
• /
• 2011

The various types of PBA/PMMA composite latexes were prepared by $2.1\;{\mu}m$ PBA seeded batch and seeded semi-continuous dispersion polymerization. The morphology of the PBA/PMMA composite latexes by seeded batch process was found to be closely dependant on the weight ratios of methanol/water in polymerization medium and of PBA seed/MMA at the second stage. In general, egg, snowman, confetti, peanut-like nonspherical composite latex particles were formed with increasing amount of water and MMA as a result of the occurrence of the phase separation between PBA seed and PMMA. The morphology of the PBA/PMMA composite latexes by seeded semi-continuous process was controlled by the addition time of MMA, especially, spherical shaped core(PBA)/shell(PMMA) composite latex particles were prepared under the monomer-starved condition at the second stage.

• Journal of Adhesion and Interface
• /
• v.11 no.3
• /
• pp.112-119
• /
• 2010

Poly(methyl methacrylate)/poly(butyl acrylate) PMMA/PBA core-shell composite particles were prepared by the emulsion polymerization of MMA and BA in the presence of different concentration of sodium dodecyl benzene sulfonate (SDBS). The following conclusions are drawn from the measured conversion and particle size distribution, morphology, average molecular weight distribution, observation of film formation and particle formation, glass transition temperature and physical properties of polymerized core-shell composition particles for using adhesive binder. When the concentration of 0.03 wt% surfactant, the conversions of PMMA and PBA core polymerization are excellent as 95.8% for PMMA core and 92.3% for PBA core. Core-shell composite particles are obtained 90.0% for PMMA/PBA core-shell composite particles and 89.0% for PMMA/PBA core-shell composite particles. It is considered that the core and shell particles are polymerized to be confirmed FT-IR spectra and average molecular weight measured with a GPC, formation of the composite particles is confirmed by the film formation from normal temperature, and composition of inside and outside of the composite particle is confirmed by TEM photograph. The synthesized polymer has two glass transition temperatures, suggesting that the polymer is composed of core polymer and shell polymer unlike general copolymers. It is considered that each core-shell composite particle can be used as a high functionality adhesion binder by the measurement of tensile strength and elongation.

• Proceedings of the Korean Fiber Society Conference
• /
• 2002.04a
• /
• pp.207-210
• /
• 2002

PVDF는 측쇄에 C=O기를 갖는 고분자인 PMMA와 PVAc와의 블렌드 및 주쇄에 C=O기를 갖는 poly(1,4-butylene adipate) (PBA)와의 블렌드에서 PVDF의 융점보다 상당히 높은 온도에서 LCST거동을 보이고 있음이 알려져 있다. 그런데 PVDF/PMMA와 PVDF/PVAC 블렌드계에서는 LCST가 고분자의 열분해온도와 유사하여 LCST거동을 실험적으로 관찰하기 어려웠다. 그런데 PVDF/PBA 블렌드계에서는 실험적으로 측정할 수 있을 정도로 LCST가 낮아지긴 하였지만 PBA의 열분해를 완전히 배제하기엔 아직도 높은 온도이다.[1] (중략)

• Journal of KIISE:Computer Systems and Theory
• /
• v.36 no.2
• /
• pp.53-59
• /
• 2009

Simulation Based Acquisition(SBA) which pursues to use M&S in manner of integrated collaboration is being applied in defense acquisition. To accomplish SBA efficiently, reusability, reconfiguration and scalability of M&S components are important factors. To avoid constraints caused by coupling of components, PBA is designed to add and configure components easily by enabling independent interface and interaction among the components and provides common development infrastructure also. And PBA framework is implemented to support the development of a simulator which uses the PBA. It is expected that deployment of PBA framework as common development infrastructure can raise efficiency of M&S works.

• Polymer(Korea)
• /
• v.36 no.6
• /
• pp.727-732
• /
• 2012

Baroplastic poly(butyl acrylate) (PBA)/polystyrene (PS) blends were prepared by mixing PBA and PS emulsions synthesized by cationic and anionic surfactant, respectively. Interestingly, the heterocoagulation of nanoparticles have found to be affected strongly by emulsion concentration but the blends have been prepared with almost same compositions regardless of the amount of reactants. Utilizing this method, PBA/PS/Si hybrid nano-blends were prepared successfully via electrostatic attraction forces between PBA, PS and silica nanoparticles. The hybrid nano-blend having 2 or 5 wt% of silica was then processed to a semi-transparent film at $25^{\circ}C$ under 13.8 MPa for 10 min, which showed 3.0 MPa of tensile strength and 25 MPa of elastic modulus. Therefore, the heterocoagulation technique can be used for preparing baroplastics with uniform compositions of polymer and silica nanoparticles.

• The Journal of Korean Association of Computer Education
• /
• v.11 no.1
• /
• pp.1-10
• /
• 2008

Web-based Assessment System is needed for Process-Oriented Evaluation to integrate instructions into evaluation frequently in Informatics Education, and considered usability for supporting teachers to test more conveniently. First of all, we analyzed usability of traditional Web-based Assessment System, and proposed PBA(Paper-Based Assessment) model by extracting usability features of paper-pencil assessment in off-line. The evaluation system based on the PBA model controls the whole processes of tests; before-test, under-test, after-test. Especially, the system readily can change the target class, and control access to the test page during each step. Thus we can get high credibility about the test results. Moreover, students can login to the paper easily by using their grade, class, number and name. Finally, we designed and implemented the Web-based Assessment System for Informatics education on the basis of PBA model; PAS(PBA-based Assessment System).

• Polymer(Korea)
• /
• v.38 no.1
• /
• pp.80-84
• /
• 2014

Polymer nanoparticles with cross-linked core and PBA/PS double-shell were synthesized and their baroplastic properties were characterized. PBA/PS, the inner and outer shell with cross-linked core consisting of St and DVB were synthesized by three-stage emulsion polymerization. The obtained materials exhibited pressure-induced mixing of their components and could be processed at $25^{\circ}C$ by compression molding which means there was no effect of the presence of cross-linked core. Interestingly, the Young's modulus of molded objects has found to be affected strongly by the size of double-shell nanoparticles. Furthermore, the molded object of higher PBA content was successfully recycled 5 times at $25^{\circ}C$ and showed 0.55 MPa of modulus and 1.81 MPa of strength at break.

• Journal of the Korea Academia-Industrial cooperation Society
• /
• v.20 no.12
• /
• pp.535-545
• /
• 2019

The PBA of ship weapon system should be installed and operated under harsh environmental conditions and so it should be highly reliable to endure the mission profiles during its entire lifetime. In the case of PBA failure during operation, rapid maintenance is highly likely to be difficult due to problems such as supply of parts, which can have a devastating effect on the mission. In order to validate the reliability of PBA, a series of tests are performed with PBA samples, but they require time, testing facilities, samples, expenses and failure analysis if failed. The reliability of PBA is predicted on the basis of specifications such as MIL-HDBK-217F, but this specification does not take into account failure mechanisms for specific design details, environment and usage, interconnects and its characteristics that drive many failures of PBA in the field. Therefore, this study predicts the reliability of PBA using an RPA tool and proposes the RPA methodology as a validation process at the design stage. With RPA, it is now possible to achieve design validation including inherent failure mechanism, identification of weakest link, alternative design options, and test plan development.

• The Korean Journal of Pesticide Science
• /
• v.11 no.2
• /
• pp.87-94
• /
• 2007

Pyrethroid insecticide have widely been used for agricultural sector and residential environments. To assess the exposure of insecticide which is absorbed through skin the analysis of urinary metabolite is essential. At present, the urinary 3-PBA was analyzed using liquid-phase extraction. But LPE have many limitations, such as long pre-treatment time and low recovery. So, this study was conducted to determine the optimum conditions for analysing 3-PBA in urine using solid phase extraction. Furthermore, this study intend to investigate the relation of concentrations of pyrethroid, deltamethrin in air and 3-PBA in urine. The optimum condition for hydrolysis was found to be done with hydrochloric acid for one hour. The recovery rates of 3-PBA were $84.6%{\pm}1.2%$, $54.8{\pm}0.9%$, $99.8{\pm}1.2%$ with XAD-2, XAD-7, XAD-16 using as the aborbents and acetone as eluents respectively. But acetonitrle and methanol gave low recovery rate and methyl cellosolve could not elute the compound. The amount of acetone for elution were 6mL, 9mL, 3mL for XAD-2, XAD-7, XAD-16 as absorbents respectively. The non-absorbed rates was $0.8{\pm}0.5%$, and $0.7{\pm}0.3%$ under XAD-16, mesh size 140-200, amount of resin 1.4g and the flow rate of eluent was 0.1mL/min. In the concentration process, we obtained 11 times higher concentration of material. The amounts of urinary 3-PBA were. The LODs of 3-PBA and deltamethrin were 0.004 mg/L, 0.038 mg/L, respectively. The further research of minute monitoring which include spray pattern, environmental condition is needed And more research about the relation between total pyrethroid exposure and urinary various metabolite are also necessary.

• Journal of Science Education
• /
• v.44 no.2
• /
• pp.133-144
• /
• 2020

As a part of the second-year monitoring study on the implementation of the 2015 revised science curriculum in middle schools, this study focuses more on examining middle school science teachers' perceptions on the process-based assessment (PBA). A total of 105 middle school science teachers (44 teachers from science leading schools, 61 teachers from ordinary schools) responded to the survey questionnaire, and 16 teachers participated in interviews. The results include teachers' perceptions on the changes in their teaching and assessment methods, some challenges of implementing PBA, and educational implications of PBA. Survey results indicate that the teachers perceived themselves using more PBA methods after the 2015 revised science curriculum was launched. The teachers in science-leading schools present statistically higher average scores to the items on the PBA utilization than the ones in ordinary schools. However, the teachers felt confused in conceptually differentiating PBA from prior performance-based assessment. They also experienced some conflicts when implementing PBA under the achievement-oriented school atmospheres. In addition, they often faced difficulties in securing objectivity and reliability of PBA and felt the burden of evaluating individual students. This study suggests the necessity of giving more authority and trust to science teachers regarding PBA, constructing more supportive environment to cultivate teacher competency as evaluation experts, and the need to reduce task burden. However, some teachers who actively implemented PBA express some level of satisfaction as observing students' positive reaction to PBA.