• Macromolecular Research
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• v.17 no.8
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• pp.616-622
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• 2009

In-depth understanding of the influence of hot pressing and melt processing on the properties of thermoplastic polyurethane (TPU) is critical for effective mechanical recycling of TPU scraps. Therefore, this study focused on the effects of hot pressing and melt mixing on molecular weight (MW), polydispersity index (PDI), melt index (MI), characteristic IR peaks, hardness, thermal degradation and mechanical properties of TPU. The original TPU pellet (o-TPU) showed two broad peaks at lower and higher MW regions. However, four TPU film samples, TPU-0 prepared only by hot pressing of o-TPU pellet and TPU-1, TPU-2 and TPU-3 obtained by hot pressing of melt mixed TPUs (where the numbers indicate the run number of melt mixing), exhibited only a single peak at higher MW region. The TPU-0 film sample had the highest $M_n$ and the lowest PDI and hardness. The TPU-1 film sample had the highest $M_w$ and tensile modulus. As the run number of melt mixing increased, the peak-intensity of hydrogen bonded C=O stretching increased, however, the free C=O peak intensity, tensile strength/elongation at break and average MW decreased. All the samples showed two stage degradations. The degradation temperatures of TPU-0 sample (359 $^{\circ}C$ and 394 $^{\circ}C$)were higher than those of o-TPU (342 $^{\circ}C$ and 391 $^{\circ}C$). While all the melt mixed samples degraded at almost the same temperature (365 $^{\circ}C$ and 381 $^{\circ}C$). The first round of hot pressing and melt mixing was found to be the critical condition which led to the significant changes of $M_n$/$M_w$/PDI, MI, mechanical property and thermal degradation of TPU.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.187-190
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• 1999

An experimental study is carried out to estimate the way of applying the granulated blast furnace slag[GBFS] to the lean concrete base of concrete pavement. According to the test results, this application seems promising. For this application, mixing percent of GBFS ranging from 30 to 50 is recommendable at this stage. And performance of base mixed with GBFS is greatly affected by the curing and placing condition. As long as all requirements for application of GBFS to the base is satisfied, better performance is expected.

• Journal of the Korean Mathematical Society
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• v.53 no.1
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• pp.57-72
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• 2016

We establish maximal moment inequalities of partial sums under ${\psi}$-weak dependence, which has been proposed by Doukhan and Louhichi [P. Doukhan and S. Louhichi, A new weak dependence condition and application to moment inequality, Stochastic Process. Appl. 84 (1999), 313-342], to unify weak dependence such as mixing, association, Gaussian sequences and Bernoulli shifts. As an application of maximal moment inequalities, a functional central limit theorem is developed for linear processes with ${\psi}$-weakly dependent innovations.

• 제어로봇시스템학회:학술대회논문집
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• 1994.10a
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• pp.725-730
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• 1994

A sodium chloride crystallizer shows oscillatory and nonlinear characteristics under its nucleating and growing process. Because these characteristics vary with operational condition, we can't control the product crystal size exactly with a PID controller or a sequence controller. Then, we make a model with threefold neural networks for the laboratory equipment that is a jet mixing crystallizer. We try to control the product crystal size with its neuro-model, and we reach the conclusion that our neuro-model is applicable to the practical crystallizer.

• Journal of ILASS-Korea
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• v.2 no.4
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• pp.36-46
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• 1997

The present study investigated the effects of MTV(Manifold Throttle Valve) on the fuel distribution and the flame stability in a SI engine at cold, idling condition. For the quantitative measurement of fuel distribution with PLIF method, compensating techniques of various factors such as laser beam nonuniformity, background image and local OTF nonuniformity were developed. As a result, it was found that MTV had a positive effect on the air-fuel mixing and flame stability.

• 한국전산유체공학회:학술대회논문집
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• 2002.05a
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• pp.134-139
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• 2002

This study is focused on investigating the characteristics of internal flow of the polymer reactor and its effect on the polymer quality. Four types of polymer reactor which have different kind of impeller, baffle and operation condition were calculated by CFD. Fluent 6 have been used to simulate mixing phenomena of reactor. According to the comparison of computational results and SEM photographs of polymer particle, distribution of turbulent dissipation rate greatly influences on the quality of polymer. So, distribution of turbulent dissipation rate to be important criterion to predict polymer quality.

• Journal of the Korean Society of Combustion
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• v.7 no.2
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• pp.7-14
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• 2002

The probability density functions (PDF) of temperature were measured by coherent anti-Stokes Raman Spectroscopy (CARS) in flames of gas turbine combustor sector rig of an aero-engine. The combustor was operated at simulated ground idle conditions with standard kerosene fuel. Temperature PDFs had been measured near fuel nozzle with change of rotation of a swirler and existence of a prefilmer. The characteristic features of temperature PDFs showed the variation of combustion configurations at four experimental conditions. Without a prefilmer, large recirculation of high temperature gas was expected in the co-flow condition and un vaporized fuel fragments were detected in the counter-flow condition. With a prefilmer, the enhanced mixing increased combustion intensity near fuel nozzle in the counter-flow condition and the flame was attached far from the fuel nozzle in the co-flow condition.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2012.11a
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• pp.207-208
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• 2012

This study is aimed to utilize for basic material of concrete quality management through evaluate properties of fresh and hardened concrete with the aggregate quality. As a result, fine aggregate's slump change of between one grade was 8~82% and in case of coarse aggregate, slump change of between one grade was 2~22% on same mixing condition. The unit water for same workability condition, unit water was increased 16kg/㎥ with decreasing of one grade for fine aggregate and unit water was increased 5kg/㎥ with decreasing of one grade for coarse aggregate.

• Proceedings of the KSME Conference
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• 2001.06c
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• pp.287-292
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• 2001

Under the condition of variable density and specific heat, maximum pressure, maximum temperature, bearing load, friction and side leakage in high-speed journal bearing operation are examined. The results are compared with the calculation results under the conditions of constant density and specific heat, and variable density and constant specific heat. It is found that the condition of variable density and specific heat play important roles in determining friction and load of journal bearing at high speed operation.

• International Journal of Aeronautical and Space Sciences
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• v.7 no.2
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• pp.50-55
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• 2006

Currently, a gas fueled diffusion flame is used for the relay torch system. It could be burned cleanly but should be stable at severe weather condition such as rain of up to 55 mm/h, winds of up to 70 km/h and also produce a highly bright yellow visible flame. This paper presents torch diffusion flame characteristics on the various wind speeds and rainfall conditions. From the results, flame lengths are controlled by the momentum flux ratio of fuel and ambient air flow and flame stability is much influenced by the mixing characteristics with air flow. Flame is fluctuated above than 200 mm/h rainfall and blow out is occurred about 300 mm/h rainfall condition.